.\" copyright (c) 2008 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th timerfd_create 2 2021-03-22 linux "linux programmer's manual" .sh name timerfd_create, timerfd_settime, timerfd_gettime \- timers that notify via file descriptors .sh synopsis .nf .b #include .pp .bi "int timerfd_create(int " clockid ", int " flags ); .pp .bi "int timerfd_settime(int " fd ", int " flags , .bi " const struct itimerspec *" new_value , .bi " struct itimerspec *" old_value ); .bi "int timerfd_gettime(int " fd ", struct itimerspec *" curr_value ); .fi .sh description these system calls create and operate on a timer that delivers timer expiration notifications via a file descriptor. they provide an alternative to the use of .br setitimer (2) or .br timer_create (2), with the advantage that the file descriptor may be monitored by .br select (2), .br poll (2), and .br epoll (7). .pp the use of these three system calls is analogous to the use of .br timer_create (2), .br timer_settime (2), and .br timer_gettime (2). (there is no analog of .br timer_getoverrun (2), since that functionality is provided by .br read (2), as described below.) .\" .ss timerfd_create() .br timerfd_create () creates a new timer object, and returns a file descriptor that refers to that timer. the .i clockid argument specifies the clock that is used to mark the progress of the timer, and must be one of the following: .tp .b clock_realtime a settable system-wide real-time clock. .tp .b clock_monotonic a nonsettable monotonically increasing clock that measures time from some unspecified point in the past that does not change after system startup. .tp .br clock_boottime " (since linux 3.15)" .\" commit 4a2378a943f09907fb1ae35c15de917f60289c14 like .br clock_monotonic , this is a monotonically increasing clock. however, whereas the .br clock_monotonic clock does not measure the time while a system is suspended, the .br clock_boottime clock does include the time during which the system is suspended. this is useful for applications that need to be suspend-aware. .br clock_realtime is not suitable for such applications, since that clock is affected by discontinuous changes to the system clock. .tp .br clock_realtime_alarm " (since linux 3.11)" .\" commit 11ffa9d6065f344a9bd769a2452f26f2f671e5f8 this clock is like .br clock_realtime , but will wake the system if it is suspended. the caller must have the .b cap_wake_alarm capability in order to set a timer against this clock. .tp .br clock_boottime_alarm " (since linux 3.11)" .\" commit 11ffa9d6065f344a9bd769a2452f26f2f671e5f8 this clock is like .br clock_boottime , but will wake the system if it is suspended. the caller must have the .b cap_wake_alarm capability in order to set a timer against this clock. .pp see .br clock_getres (2) for some further details on the above clocks. .pp the current value of each of these clocks can be retrieved using .br clock_gettime (2). .pp starting with linux 2.6.27, the following values may be bitwise ored in .ir flags to change the behavior of .br timerfd_create (): .tp 14 .b tfd_nonblock set the .br o_nonblock file status flag on the open file description (see .br open (2)) referred to by the new file descriptor. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .tp .b tfd_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .pp in linux versions up to and including 2.6.26, .i flags must be specified as zero. .ss timerfd_settime() .br timerfd_settime () arms (starts) or disarms (stops) the timer referred to by the file descriptor .ir fd . .pp the .i new_value argument specifies the initial expiration and interval for the timer. the .i itimerspec structure used for this argument contains two fields, each of which is in turn a structure of type .ir timespec : .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; struct itimerspec { struct timespec it_interval; /* interval for periodic timer */ struct timespec it_value; /* initial expiration */ }; .ee .in .pp .i new_value.it_value specifies the initial expiration of the timer, in seconds and nanoseconds. setting either field of .i new_value.it_value to a nonzero value arms the timer. setting both fields of .i new_value.it_value to zero disarms the timer. .pp setting one or both fields of .i new_value.it_interval to nonzero values specifies the period, in seconds and nanoseconds, for repeated timer expirations after the initial expiration. if both fields of .i new_value.it_interval are zero, the timer expires just once, at the time specified by .ir new_value.it_value . .pp by default, the initial expiration time specified in .i new_value is interpreted relative to the current time on the timer's clock at the time of the call (i.e., .i new_value.it_value specifies a time relative to the current value of the clock specified by .ir clockid ). an absolute timeout can be selected via the .i flags argument. .pp the .i flags argument is a bit mask that can include the following values: .tp .b tfd_timer_abstime interpret .i new_value.it_value as an absolute value on the timer's clock. the timer will expire when the value of the timer's clock reaches the value specified in .ir new_value.it_value . .tp .br tfd_timer_cancel_on_set if this flag is specified along with .b tfd_timer_abstime and the clock for this timer is .br clock_realtime or .br clock_realtime_alarm , then mark this timer as cancelable if the real-time clock undergoes a discontinuous change .rb ( settimeofday (2), .br clock_settime (2), or similar). when such changes occur, a current or future .br read (2) from the file descriptor will fail with the error .br ecanceled . .pp if the .i old_value argument is not null, then the .i itimerspec structure that it points to is used to return the setting of the timer that was current at the time of the call; see the description of .br timerfd_gettime () following. .\" .ss timerfd_gettime() .br timerfd_gettime () returns, in .ir curr_value , an .ir itimerspec structure that contains the current setting of the timer referred to by the file descriptor .ir fd . .pp the .i it_value field returns the amount of time until the timer will next expire. if both fields of this structure are zero, then the timer is currently disarmed. this field always contains a relative value, regardless of whether the .br tfd_timer_abstime flag was specified when setting the timer. .pp the .i it_interval field returns the interval of the timer. if both fields of this structure are zero, then the timer is set to expire just once, at the time specified by .ir curr_value.it_value . .ss operating on a timer file descriptor the file descriptor returned by .br timerfd_create () supports the following additional operations: .tp .br read (2) if the timer has already expired one or more times since its settings were last modified using .br timerfd_settime (), or since the last successful .br read (2), then the buffer given to .br read (2) returns an unsigned 8-byte integer .ri ( uint64_t ) containing the number of expirations that have occurred. (the returned value is in host byte order\(emthat is, the native byte order for integers on the host machine.) .ip if no timer expirations have occurred at the time of the .br read (2), then the call either blocks until the next timer expiration, or fails with the error .b eagain if the file descriptor has been made nonblocking (via the use of the .br fcntl (2) .b f_setfl operation to set the .b o_nonblock flag). .ip a .br read (2) fails with the error .b einval if the size of the supplied buffer is less than 8 bytes. .ip if the associated clock is either .br clock_realtime or .br clock_realtime_alarm , the timer is absolute .rb ( tfd_timer_abstime ), and the flag .br tfd_timer_cancel_on_set was specified when calling .br timerfd_settime (), then .br read (2) fails with the error .br ecanceled if the real-time clock undergoes a discontinuous change. (this allows the reading application to discover such discontinuous changes to the clock.) .ip if the associated clock is either .br clock_realtime or .br clock_realtime_alarm , the timer is absolute .rb ( tfd_timer_abstime ), and the flag .br tfd_timer_cancel_on_set was .i not specified when calling .br timerfd_settime (), then a discontinuous negative change to the clock (e.g., .br clock_settime (2)) may cause .br read (2) to unblock, but return a value of 0 (i.e., no bytes read), if the clock change occurs after the time expired, but before the .br read (2) on the file descriptor. .tp .br poll "(2), " select "(2) (and similar)" the file descriptor is readable (the .br select (2) .i readfds argument; the .br poll (2) .b pollin flag) if one or more timer expirations have occurred. .ip the file descriptor also supports the other file-descriptor multiplexing apis: .br pselect (2), .br ppoll (2), and .br epoll (7). .tp .br ioctl (2) the following timerfd-specific command is supported: .rs .tp .br tfd_ioc_set_ticks " (since linux 3.17)" .\" commit 5442e9fbd7c23172a1c9bc736629cd123a9923f0 adjust the number of timer expirations that have occurred. the argument is a pointer to a nonzero 8-byte integer .ri ( uint64_t *) containing the new number of expirations. once the number is set, any waiter on the timer is woken up. the only purpose of this command is to restore the expirations for the purpose of checkpoint/restore. this operation is available only if the kernel was configured with the .br config_checkpoint_restore option. .re .tp .br close (2) when the file descriptor is no longer required it should be closed. when all file descriptors associated with the same timer object have been closed, the timer is disarmed and its resources are freed by the kernel. .\" .ss fork(2) semantics after a .br fork (2), the child inherits a copy of the file descriptor created by .br timerfd_create (). the file descriptor refers to the same underlying timer object as the corresponding file descriptor in the parent, and .br read (2)s in the child will return information about expirations of the timer. .\" .ss execve(2) semantics a file descriptor created by .br timerfd_create () is preserved across .br execve (2), and continues to generate timer expirations if the timer was armed. .sh return value on success, .br timerfd_create () returns a new file descriptor. on error, \-1 is returned and .i errno is set to indicate the error. .pp .br timerfd_settime () and .br timerfd_gettime () return 0 on success; on error they return \-1, and set .i errno to indicate the error. .sh errors .br timerfd_create () can fail with the following errors: .tp .b einval the .i clockid is not valid. .tp .b einval .i flags is invalid; or, in linux 2.6.26 or earlier, .i flags is nonzero. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enodev could not mount (internal) anonymous inode device. .tp .b enomem there was insufficient kernel memory to create the timer. .tp .b eperm .i clockid was .br clock_realtime_alarm or .br clock_boottime_alarm but the caller did not have the .br cap_wake_alarm capability. .pp .br timerfd_settime () and .br timerfd_gettime () can fail with the following errors: .tp .b ebadf .i fd is not a valid file descriptor. .tp .b efault .ir new_value , .ir old_value , or .i curr_value is not valid a pointer. .tp .b einval .i fd is not a valid timerfd file descriptor. .pp .br timerfd_settime () can also fail with the following errors: .tp .b ecanceled see notes. .tp .b einval .i new_value is not properly initialized (one of the .i tv_nsec falls outside the range zero to 999,999,999). .tp .b einval .\" this case only checked since 2.6.29, and 2.2.2[78].some-stable-version. .\" in older kernel versions, no check was made for invalid flags. .i flags is invalid. .sh versions these system calls are available on linux since kernel 2.6.25. library support is provided by glibc since version 2.8. .sh conforming to these system calls are linux-specific. .sh notes suppose the following scenario for .br clock_realtime or .br clock_realtime_alarm timer that was created with .br timerfd_create (): .ip (a) 4 the timer has been started .rb ( timerfd_settime ()) with the .br tfd_timer_abstime and .br tfd_timer_cancel_on_set flags; .ip (b) a discontinuous change (e.g., .br settimeofday (2)) is subsequently made to the .br clock_realtime clock; and .ip (c) the caller once more calls .br timerfd_settime () to rearm the timer (without first doing a .br read (2) on the file descriptor). .pp in this case the following occurs: .ip \(bu 2 the .br timerfd_settime () returns \-1 with .i errno set to .br ecanceled . (this enables the caller to know that the previous timer was affected by a discontinuous change to the clock.) .ip \(bu the timer .i "is successfully rearmed" with the settings provided in the second .br timerfd_settime () call. (this was probably an implementation accident, but won't be fixed now, in case there are applications that depend on this behaviour.) .sh bugs currently, .\" 2.6.29 .br timerfd_create () supports fewer types of clock ids than .br timer_create (2). .sh examples the following program creates a timer and then monitors its progress. the program accepts up to three command-line arguments. the first argument specifies the number of seconds for the initial expiration of the timer. the second argument specifies the interval for the timer, in seconds. the third argument specifies the number of times the program should allow the timer to expire before terminating. the second and third command-line arguments are optional. .pp the following shell session demonstrates the use of the program: .pp .in +4n .ex .rb "$" " a.out 3 1 100" 0.000: timer started 3.000: read: 1; total=1 4.000: read: 1; total=2 .br "\(haz " " # type control\-z to suspend the program" [1]+ stopped ./timerfd3_demo 3 1 100 .rb "$ " "fg" " # resume execution after a few seconds" a.out 3 1 100 9.660: read: 5; total=7 10.000: read: 1; total=8 11.000: read: 1; total=9 .br "\(hac " " # type control\-c to suspend the program" .ee .in .ss program source \& .ex .\" the commented out code here is what we currently need until .\" the required stuff is in glibc .\" .\" .\"/* link with \-lrt */ .\"#define _gnu_source .\"#include .\"#include .\"#include .\"#if defined(__i386__) .\"#define __nr_timerfd_create 322 .\"#define __nr_timerfd_settime 325 .\"#define __nr_timerfd_gettime 326 .\"#endif .\" .\"static int .\"timerfd_create(int clockid, int flags) .\"{ .\" return syscall(__nr_timerfd_create, clockid, flags); .\"} .\" .\"static int .\"timerfd_settime(int fd, int flags, struct itimerspec *new_value, .\" struct itimerspec *curr_value) .\"{ .\" return syscall(__nr_timerfd_settime, fd, flags, new_value, .\" curr_value); .\"} .\" .\"static int .\"timerfd_gettime(int fd, struct itimerspec *curr_value) .\"{ .\" return syscall(__nr_timerfd_gettime, fd, curr_value); .\"} .\" .\"#define tfd_timer_abstime (1 << 0) .\" .\"//////////////////////////////////////////////////////////// #include #include #include #include /* definition of priu64 */ #include #include #include /* definition of uint64_t */ #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) static void print_elapsed_time(void) { static struct timespec start; struct timespec curr; static int first_call = 1; int secs, nsecs; if (first_call) { first_call = 0; if (clock_gettime(clock_monotonic, &start) == \-1) handle_error("clock_gettime"); } if (clock_gettime(clock_monotonic, &curr) == \-1) handle_error("clock_gettime"); secs = curr.tv_sec \- start.tv_sec; nsecs = curr.tv_nsec \- start.tv_nsec; if (nsecs < 0) { secs\-\-; nsecs += 1000000000; } printf("%d.%03d: ", secs, (nsecs + 500000) / 1000000); } int main(int argc, char *argv[]) { struct itimerspec new_value; int max_exp, fd; struct timespec now; uint64_t exp, tot_exp; ssize_t s; if ((argc != 2) && (argc != 4)) { fprintf(stderr, "%s init\-secs [interval\-secs max\-exp]\en", argv[0]); exit(exit_failure); } if (clock_gettime(clock_realtime, &now) == \-1) handle_error("clock_gettime"); /* create a clock_realtime absolute timer with initial expiration and interval as specified in command line. */ new_value.it_value.tv_sec = now.tv_sec + atoi(argv[1]); new_value.it_value.tv_nsec = now.tv_nsec; if (argc == 2) { new_value.it_interval.tv_sec = 0; max_exp = 1; } else { new_value.it_interval.tv_sec = atoi(argv[2]); max_exp = atoi(argv[3]); } new_value.it_interval.tv_nsec = 0; fd = timerfd_create(clock_realtime, 0); if (fd == \-1) handle_error("timerfd_create"); if (timerfd_settime(fd, tfd_timer_abstime, &new_value, null) == \-1) handle_error("timerfd_settime"); print_elapsed_time(); printf("timer started\en"); for (tot_exp = 0; tot_exp < max_exp;) { s = read(fd, &exp, sizeof(uint64_t)); if (s != sizeof(uint64_t)) handle_error("read"); tot_exp += exp; print_elapsed_time(); printf("read: %" priu64 "; total=%" priu64 "\en", exp, tot_exp); } exit(exit_success); } .ee .sh see also .br eventfd (2), .br poll (2), .br read (2), .br select (2), .br setitimer (2), .br signalfd (2), .br timer_create (2), .br timer_gettime (2), .br timer_settime (2), .br epoll (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" inspired by a page written by walter harms. .\" .th getfsent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getfsent, getfsspec, getfsfile, setfsent, endfsent \- handle fstab entries .sh synopsis .nf .b #include .pp .b "int setfsent(void);" .b "struct fstab *getfsent(void);" .b "void endfsent(void);" .pp .bi "struct fstab *getfsfile(const char *" mount_point ); .bi "struct fstab *getfsspec(const char *" special_file ); .fi .sh description these functions read from the file .ir /etc/fstab . the .ir "struct fstab" is defined by: .pp .in +4n .ex struct fstab { char *fs_spec; /* block device name */ char *fs_file; /* mount point */ char *fs_vfstype; /* filesystem type */ char *fs_mntops; /* mount options */ const char *fs_type; /* rw/rq/ro/sw/xx option */ int fs_freq; /* dump frequency, in days */ int fs_passno; /* pass number on parallel dump */ }; .ee .in .pp here the field .i fs_type contains (on a *bsd system) one of the five strings "rw", "rq", "ro", "sw", "xx" (read-write, read-write with quota, read-only, swap, ignore). .pp the function .br setfsent () opens the file when required and positions it at the first line. .pp the function .br getfsent () parses the next line from the file. (after opening it when required.) .pp the function .br endfsent () closes the file when required. .pp the function .br getfsspec () searches the file from the start and returns the first entry found for which the .i fs_spec field matches the .i special_file argument. .pp the function .br getfsfile () searches the file from the start and returns the first entry found for which the .i fs_file field matches the .i mount_point argument. .sh return value upon success, the functions .br getfsent (), .br getfsfile (), and .br getfsspec () return a pointer to a .ir "struct fstab" , while .br setfsent () returns 1. upon failure or end-of-file, these functions return null and 0, respectively. .\" .sh history .\" the .\" .br getfsent () .\" function appeared in 4.0bsd; the other four functions appeared in 4.3bsd. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br endfsent (), .br setfsent () t} thread safety t{ mt-unsafe race:fsent t} t{ .br getfsent (), .br getfsspec (), .br getfsfile () t} thread safety t{ mt-unsafe race:fsent locale t} .te .hy .ad .sp 1 .sh conforming to these functions are not in posix.1. several operating systems have them, for example, *bsd, sunos, digital unix, aix (which also has a .br getfstype ()). hp-ux has functions of the same names, that however use a .ir "struct checklist" instead of a .ir "struct fstab" , and calls these functions obsolete, superseded by .br getmntent (3). .sh notes these functions are not thread-safe. .pp since linux allows mounting a block special device in several places, and since several devices can have the same mount point, where the last device with a given mount point is the interesting one, while .br getfsfile () and .br getfsspec () only return the first occurrence, these two functions are not suitable for use under linux. .sh see also .br getmntent (3), .br fstab (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ctime.3 .\" copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_spin_lock 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_spin_lock, pthread_spin_trylock, pthread_spin_unlock \- lock and unlock a spin lock .sh synopsis .nf .b #include .pp .bi "int pthread_spin_lock(pthread_spinlock_t *" lock ); .bi "int pthread_spin_trylock(pthread_spinlock_t *" lock ); .bi "int pthread_spin_unlock(pthread_spinlock_t *" lock ); .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_spin_lock (), .br pthread_spin_trylock (): .nf _posix_c_source >= 200112l .fi .sh description the .br pthread_spin_lock () function locks the spin lock referred to by .ir lock . if the spin lock is currently unlocked, the calling thread acquires the lock immediately. if the spin lock is currently locked by another thread, the calling thread spins, testing the lock until it becomes available, at which point the calling thread acquires the lock. .pp calling .br pthread_spin_lock () on a lock that is already held by the caller or a lock that has not been initialized with .br pthread_spin_init (3) results in undefined behavior. .pp the .br pthread_spin_trylock () function is like .br pthread_spin_lock (), except that if the spin lock referred to by .i lock is currently locked, then, instead of spinning, the call returns immediately with the error .br ebusy . .pp the .br pthread_spin_unlock () function unlocks the spin lock referred to .ir lock . if any threads are spinning on the lock, one of those threads will then acquire the lock. .pp calling .br pthread_spin_unlock () on a lock that is not held by the caller results in undefined behavior. .sh return value on success, these functions return zero. on failure, they return an error number. .sh errors .br pthread_spin_lock () may fail with the following errors: .tp .b edeadlock .\" not detected in glibc the system detected a deadlock condition. .pp .br pthread_spin_trylock () fails with the following errors: .tp .b ebusy the spin lock is currently locked by another thread. .sh versions these functions first appeared in glibc in version 2.2. .sh conforming to posix.1-2001. .sh notes applying any of the functions described on this page to an uninitialized spin lock results in undefined behavior. .pp carefully read notes in .br pthread_spin_init (3). .sh see also .ad l .nh .\" fixme . .br pthread_mutex_lock (3), .br pthread_spin_destroy (3), .br pthread_spin_init (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man2/process_vm_readv.2 .so man3/ctime.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-24 by rik faith .\" modified 1996-10-22 by eric s. raymond .\" modified 2004-06-23 by michael kerrisk .\" modified 2005-01-09 by aeb .\" .th uselib 2 2021-03-22 "linux" "linux programmer's manual" .sh name uselib \- load shared library .sh synopsis .nf .b #include .pp .bi "int uselib(const char *" library ); .fi .pp .ir note : no declaration of this system call is provided in glibc headers; see notes. .sh description the system call .br uselib () serves to load a shared library to be used by the calling process. it is given a pathname. the address where to load is found in the library itself. the library can have any recognized binary format. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors in addition to all of the error codes returned by .br open (2) and .br mmap (2), the following may also be returned: .tp .b eacces the library specified by .i library does not have read or execute permission, or the caller does not have search permission for one of the directories in the path prefix. (see also .br path_resolution (7).) .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoexec the file specified by .i library is not an executable of a known type; for example, it does not have the correct magic numbers. .sh conforming to .br uselib () is linux-specific, and should not be used in programs intended to be portable. .sh notes this obsolete system call is not supported by glibc. no declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an abi for this system call. therefore, in order to employ this system call, it was sufficient to manually declare the interface in your code; alternatively, you could invoke the system call using .br syscall (2). .pp in ancient libc versions (before glibc 2.0), .br uselib () was used to load the shared libraries with names found in an array of names in the binary. .\" .pp .\" .\" libc 4.3.1f - changelog 1993-03-02 .\" since libc 4.3.2, startup code tries to prefix these names .\" with "/usr/lib", "/lib" and "" before giving up. .\" .\" libc 4.3.4 - changelog 1993-04-21 .\" in libc 4.3.4 and later these names are looked for in the directories .\" found in .\" .br ld_library_path , .\" and if not found there, .\" prefixes "/usr/lib", "/lib" and "/" are tried. .\" .pp .\" from libc 4.4.4 on only the library "/lib/ld.so" is loaded, .\" so that this dynamic library can load the remaining libraries needed .\" (again using this call). .\" this is also the state of affairs in libc5. .\" .pp .\" glibc2 does not use this call. .pp since linux 3.15, .\" commit 69369a7003735d0d8ef22097e27a55a8bad9557a this system call is available only when the kernel is configured with the .b config_uselib option. .sh see also .br ar (1), .br gcc (1), .br ld (1), .br ldd (1), .br mmap (2), .br open (2), .br dlopen (3), .br capabilities (7), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_mutexattr_setrobust.3 .\" copyright 2001 john levon .\" based on mkstemp(3), copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and gnu libc documentation .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .th mkdtemp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mkdtemp \- create a unique temporary directory .sh synopsis .nf .b #include .pp .bi "char *mkdtemp(char *" template ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mkdtemp (): .nf /* since glibc 2.19: */ _default_source || /* glibc 2.19 and earlier: */ _bsd_source || /* since glibc 2.10: */ _posix_c_source >= 200809l .fi .sh description the .br mkdtemp () function generates a uniquely named temporary directory from \fitemplate\fp. the last six characters of \fitemplate\fp must be xxxxxx and these are replaced with a string that makes the directory name unique. the directory is then created with permissions 0700. since it will be modified, .i template must not be a string constant, but should be declared as a character array. .sh return value the .br mkdtemp () function returns a pointer to the modified template string on success, and null on failure, in which case .i errno is set to indicate the error. .sh errors .tp .b einval the last six characters of \fitemplate\fp were not xxxxxx. now \fitemplate\fp is unchanged. .pp also see .br mkdir (2) for other possible values for \fierrno\fp. .sh versions available since glibc 2.1.91. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mkdtemp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function is present on the bsds. .\" as at 2006, this function is being considered for a revision of posix.1 .\" also in netbsd 1.4. .sh see also .br mktemp (1), .br mkdir (2), .br mkstemp (3), .br mktemp (3), .br tempnam (3), .br tmpfile (3), .br tmpnam (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .so man3/printf.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_overview 7 2020-06-09 "linux" "linux programmer's manual" .sh name sem_overview \- overview of posix semaphores .sh description posix semaphores allow processes and threads to synchronize their actions. .pp a semaphore is an integer whose value is never allowed to fall below zero. two operations can be performed on semaphores: increment the semaphore value by one .rb ( sem_post (3)); and decrement the semaphore value by one .rb ( sem_wait (3)). if the value of a semaphore is currently zero, then a .br sem_wait (3) operation will block until the value becomes greater than zero. .pp posix semaphores come in two forms: named semaphores and unnamed semaphores. .tp .b named semaphores a named semaphore is identified by a name of the form .ir /somename ; that is, a null-terminated string of up to .bi name_max \-4 (i.e., 251) characters consisting of an initial slash, .\" glibc allows the initial slash to be omitted, and makes .\" multiple initial slashes equivalent to a single slash. .\" this differs from the implementation of posix message queues. followed by one or more characters, none of which are slashes. .\" glibc allows subdirectory components in the name, in which .\" case the subdirectory tree must exist under /dev/shm, and .\" the fist subdirectory component must exist as the name .\" sem.name, and all of the subdirectory components must allow the .\" required permissions if a user wants to create a semaphore .\" object in a subdirectory. two processes can operate on the same named semaphore by passing the same name to .br sem_open (3). .ip the .br sem_open (3) function creates a new named semaphore or opens an existing named semaphore. after the semaphore has been opened, it can be operated on using .br sem_post (3) and .br sem_wait (3). when a process has finished using the semaphore, it can use .br sem_close (3) to close the semaphore. when all processes have finished using the semaphore, it can be removed from the system using .br sem_unlink (3). .tp .b unnamed semaphores (memory-based semaphores) an unnamed semaphore does not have a name. instead the semaphore is placed in a region of memory that is shared between multiple threads (a .ir "thread-shared semaphore" ) or processes (a .ir "process-shared semaphore" ). a thread-shared semaphore is placed in an area of memory shared between the threads of a process, for example, a global variable. a process-shared semaphore must be placed in a shared memory region (e.g., a system v shared memory segment created using .br shmget (2), or a posix shared memory object built created using .br shm_open (3)). .ip before being used, an unnamed semaphore must be initialized using .br sem_init (3). it can then be operated on using .br sem_post (3) and .br sem_wait (3). when the semaphore is no longer required, and before the memory in which it is located is deallocated, the semaphore should be destroyed using .br sem_destroy (3). .pp the remainder of this section describes some specific details of the linux implementation of posix semaphores. .ss versions prior to kernel 2.6, linux supported only unnamed, thread-shared semaphores. on a system with linux 2.6 and a glibc that provides the nptl threading implementation, a complete implementation of posix semaphores is provided. .ss persistence posix named semaphores have kernel persistence: if not removed by .br sem_unlink (3), a semaphore will exist until the system is shut down. .ss linking programs using the posix semaphores api must be compiled with .i cc \-pthread to link against the real-time library, .ir librt . .ss accessing named semaphores via the filesystem on linux, named semaphores are created in a virtual filesystem, normally mounted under .ir /dev/shm , with names of the form .ir \fbsem.\fpsomename . (this is the reason that semaphore names are limited to .bi name_max \-4 rather than .b name_max characters.) .pp since linux 2.6.19, acls can be placed on files under this directory, to control object permissions on a per-user and per-group basis. .sh notes system v semaphores .rb ( semget (2), .br semop (2), etc.) are an older semaphore api. posix semaphores provide a simpler, and better designed interface than system v semaphores; on the other hand posix semaphores are less widely available (especially on older systems) than system v semaphores. .sh examples an example of the use of various posix semaphore functions is shown in .br sem_wait (3). .sh see also .br sem_close (3), .br sem_destroy (3), .br sem_getvalue (3), .br sem_init (3), .br sem_open (3), .br sem_post (3), .br sem_unlink (3), .br sem_wait (3), .br pthreads (7), .br shm_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-11.7 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswcntrl 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswcntrl \- test for control wide character .sh synopsis .nf .b #include .pp .bi "int iswcntrl(wint_t " wc ); .fi .sh description the .br iswcntrl () function is the wide-character equivalent of the .br iscntrl (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "cntrl". .pp the wide-character class "cntrl" is disjoint from the wide-character class "print" and therefore also disjoint from its subclasses "graph", "alpha", "upper", "lower", "digit", "xdigit", "punct". .pp for an unsigned char .ir c , .i iscntrl(c) implies .ir iswcntrl(btowc(c)) , but not vice versa. .sh return value the .br iswcntrl () function returns nonzero if .i wc is a wide character belonging to the wide-character class "cntrl". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswcntrl () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswcntrl () depends on the .b lc_ctype category of the current locale. .sh see also .br iscntrl (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getcwd.3 .so man3/sigvec.3 .so man3/exec.3 .\" copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th signal-safety 7 2021-03-22 "linux" "linux programmer's manual" .sh name signal-safety \- async-signal-safe functions .sh description an .i async-signal-safe function is one that can be safely called from within a signal handler. many functions are .i not async-signal-safe. in particular, nonreentrant functions are generally unsafe to call from a signal handler. .pp the kinds of issues that render a function unsafe can be quickly understood when one considers the implementation of the .i stdio library, all of whose functions are not async-signal-safe. .pp when performing buffered i/o on a file, the .i stdio functions must maintain a statically allocated data buffer along with associated counters and indexes (or pointers) that record the amount of data and the current position in the buffer. suppose that the main program is in the middle of a call to a .i stdio function such as .br printf (3) where the buffer and associated variables have been partially updated. if, at that moment, the program is interrupted by a signal handler that also calls .br printf (3), then the second call to .br printf (3) will operate on inconsistent data, with unpredictable results. .pp to avoid problems with unsafe functions, there are two possible choices: .ip 1. 3 ensure that (a) the signal handler calls only async-signal-safe functions, and (b) the signal handler itself is reentrant with respect to global variables in the main program. .ip 2. block signal delivery in the main program when calling functions that are unsafe or operating on global data that is also accessed by the signal handler. .pp generally, the second choice is difficult in programs of any complexity, so the first choice is taken. .pp posix.1 specifies a set of functions that an implementation must make async-signal-safe. (an implementation may provide safe implementations of additional functions, but this is not required by the standard and other implementations may not provide the same guarantees.) .pp in general, a function is async-signal-safe either because it is reentrant or because it is atomic with respect to signals (i.e., its execution can't be interrupted by a signal handler). .pp the set of functions required to be async-signal-safe by posix.1 is shown in the following table. the functions not otherwise noted were required to be async-signal-safe in posix.1-2001; the table details changes in the subsequent standards. .pp .ts lb lb l l. function notes \fbabort\fp(3) added in posix.1-2001 tc1 \fbaccept\fp(2) \fbaccess\fp(2) \fbaio_error\fp(3) \fbaio_return\fp(3) \fbaio_suspend\fp(3) see notes below \fbalarm\fp(2) \fbbind\fp(2) \fbcfgetispeed\fp(3) \fbcfgetospeed\fp(3) \fbcfsetispeed\fp(3) \fbcfsetospeed\fp(3) \fbchdir\fp(2) \fbchmod\fp(2) \fbchown\fp(2) \fbclock_gettime\fp(2) \fbclose\fp(2) \fbconnect\fp(2) \fbcreat\fp(2) \fbdup\fp(2) \fbdup2\fp(2) \fbexecl\fp(3) t{ added in posix.1-2008; see notes below t} \fbexecle\fp(3) see notes below \fbexecv\fp(3) added in posix.1-2008 \fbexecve\fp(2) \fb_exit\fp(2) \fb_exit\fp(2) \fbfaccessat\fp(2) added in posix.1-2008 \fbfchdir\fp(2) added in posix.1-2008 tc1 \fbfchmod\fp(2) \fbfchmodat\fp(2) added in posix.1-2008 \fbfchown\fp(2) \fbfchownat\fp(2) added in posix.1-2008 \fbfcntl\fp(2) \fbfdatasync\fp(2) \fbfexecve\fp(3) added in posix.1-2008 \fbffs\fp(3) added in posix.1-2008 tc2 \fbfork\fp(2) see notes below \fbfstat\fp(2) \fbfstatat\fp(2) added in posix.1-2008 \fbfsync\fp(2) \fbftruncate\fp(2) \fbfutimens\fp(3) added in posix.1-2008 \fbgetegid\fp(2) \fbgeteuid\fp(2) \fbgetgid\fp(2) \fbgetgroups\fp(2) \fbgetpeername\fp(2) \fbgetpgrp\fp(2) \fbgetpid\fp(2) \fbgetppid\fp(2) \fbgetsockname\fp(2) \fbgetsockopt\fp(2) \fbgetuid\fp(2) \fbhtonl\fp(3) added in posix.1-2008 tc2 \fbhtons\fp(3) added in posix.1-2008 tc2 \fbkill\fp(2) \fblink\fp(2) \fblinkat\fp(2) added in posix.1-2008 \fblisten\fp(2) \fblongjmp\fp(3) t{ added in posix.1-2008 tc2; see notes below t} \fblseek\fp(2) \fblstat\fp(2) \fbmemccpy\fp(3) added in posix.1-2008 tc2 \fbmemchr\fp(3) added in posix.1-2008 tc2 \fbmemcmp\fp(3) added in posix.1-2008 tc2 \fbmemcpy\fp(3) added in posix.1-2008 tc2 \fbmemmove\fp(3) added in posix.1-2008 tc2 \fbmemset\fp(3) added in posix.1-2008 tc2 \fbmkdir\fp(2) \fbmkdirat\fp(2) added in posix.1-2008 \fbmkfifo\fp(3) \fbmkfifoat\fp(3) added in posix.1-2008 \fbmknod\fp(2) added in posix.1-2008 \fbmknodat\fp(2) added in posix.1-2008 \fbntohl\fp(3) added in posix.1-2008 tc2 \fbntohs\fp(3) added in posix.1-2008 tc2 \fbopen\fp(2) \fbopenat\fp(2) added in posix.1-2008 \fbpause\fp(2) \fbpipe\fp(2) \fbpoll\fp(2) \fbposix_trace_event\fp(3) \fbpselect\fp(2) \fbpthread_kill\fp(3) added in posix.1-2008 tc1 \fbpthread_self\fp(3) added in posix.1-2008 tc1 \fbpthread_sigmask\fp(3) added in posix.1-2008 tc1 \fbraise\fp(3) \fbread\fp(2) \fbreadlink\fp(2) \fbreadlinkat\fp(2) added in posix.1-2008 \fbrecv\fp(2) \fbrecvfrom\fp(2) \fbrecvmsg\fp(2) \fbrename\fp(2) \fbrenameat\fp(2) added in posix.1-2008 \fbrmdir\fp(2) \fbselect\fp(2) \fbsem_post\fp(3) \fbsend\fp(2) \fbsendmsg\fp(2) \fbsendto\fp(2) \fbsetgid\fp(2) \fbsetpgid\fp(2) \fbsetsid\fp(2) \fbsetsockopt\fp(2) \fbsetuid\fp(2) \fbshutdown\fp(2) \fbsigaction\fp(2) \fbsigaddset\fp(3) \fbsigdelset\fp(3) \fbsigemptyset\fp(3) \fbsigfillset\fp(3) \fbsigismember\fp(3) \fbsiglongjmp\fp(3) t{ added in posix.1-2008 tc2; see notes below t} \fbsignal\fp(2) \fbsigpause\fp(3) \fbsigpending\fp(2) \fbsigprocmask\fp(2) \fbsigqueue\fp(2) \fbsigset\fp(3) \fbsigsuspend\fp(2) \fbsleep\fp(3) \fbsockatmark\fp(3) added in posix.1-2001 tc2 \fbsocket\fp(2) \fbsocketpair\fp(2) \fbstat\fp(2) \fbstpcpy\fp(3) added in posix.1-2008 tc2 \fbstpncpy\fp(3) added in posix.1-2008 tc2 \fbstrcat\fp(3) added in posix.1-2008 tc2 \fbstrchr\fp(3) added in posix.1-2008 tc2 \fbstrcmp\fp(3) added in posix.1-2008 tc2 \fbstrcpy\fp(3) added in posix.1-2008 tc2 \fbstrcspn\fp(3) added in posix.1-2008 tc2 \fbstrlen\fp(3) added in posix.1-2008 tc2 \fbstrncat\fp(3) added in posix.1-2008 tc2 \fbstrncmp\fp(3) added in posix.1-2008 tc2 \fbstrncpy\fp(3) added in posix.1-2008 tc2 \fbstrnlen\fp(3) added in posix.1-2008 tc2 \fbstrpbrk\fp(3) added in posix.1-2008 tc2 \fbstrrchr\fp(3) added in posix.1-2008 tc2 \fbstrspn\fp(3) added in posix.1-2008 tc2 \fbstrstr\fp(3) added in posix.1-2008 tc2 \fbstrtok_r\fp(3) added in posix.1-2008 tc2 \fbsymlink\fp(2) \fbsymlinkat\fp(2) added in posix.1-2008 \fbtcdrain\fp(3) \fbtcflow\fp(3) \fbtcflush\fp(3) \fbtcgetattr\fp(3) \fbtcgetpgrp\fp(3) \fbtcsendbreak\fp(3) \fbtcsetattr\fp(3) \fbtcsetpgrp\fp(3) \fbtime\fp(2) \fbtimer_getoverrun\fp(2) \fbtimer_gettime\fp(2) \fbtimer_settime\fp(2) \fbtimes\fp(2) \fbumask\fp(2) \fbuname\fp(2) \fbunlink\fp(2) \fbunlinkat\fp(2) added in posix.1-2008 \fbutime\fp(2) \fbutimensat\fp(2) added in posix.1-2008 \fbutimes\fp(2) added in posix.1-2008 \fbwait\fp(2) \fbwaitpid\fp(2) \fbwcpcpy\fp(3) added in posix.1-2008 tc2 \fbwcpncpy\fp(3) added in posix.1-2008 tc2 \fbwcscat\fp(3) added in posix.1-2008 tc2 \fbwcschr\fp(3) added in posix.1-2008 tc2 \fbwcscmp\fp(3) added in posix.1-2008 tc2 \fbwcscpy\fp(3) added in posix.1-2008 tc2 \fbwcscspn\fp(3) added in posix.1-2008 tc2 \fbwcslen\fp(3) added in posix.1-2008 tc2 \fbwcsncat\fp(3) added in posix.1-2008 tc2 \fbwcsncmp\fp(3) added in posix.1-2008 tc2 \fbwcsncpy\fp(3) added in posix.1-2008 tc2 \fbwcsnlen\fp(3) added in posix.1-2008 tc2 \fbwcspbrk\fp(3) added in posix.1-2008 tc2 \fbwcsrchr\fp(3) added in posix.1-2008 tc2 \fbwcsspn\fp(3) added in posix.1-2008 tc2 \fbwcsstr\fp(3) added in posix.1-2008 tc2 \fbwcstok\fp(3) added in posix.1-2008 tc2 \fbwmemchr\fp(3) added in posix.1-2008 tc2 \fbwmemcmp\fp(3) added in posix.1-2008 tc2 \fbwmemcpy\fp(3) added in posix.1-2008 tc2 \fbwmemmove\fp(3) added in posix.1-2008 tc2 \fbwmemset\fp(3) added in posix.1-2008 tc2 \fbwrite\fp(2) .te .pp notes: .ip * 3 posix.1-2001 and posix.1-2001 tc2 required the functions .br fpathconf (3), .br pathconf (3), and .br sysconf (3) to be async-signal-safe, but this requirement was removed in posix.1-2008. .ip * if a signal handler interrupts the execution of an unsafe function, and the handler terminates via a call to .br longjmp (3) or .br siglongjmp (3) and the program subsequently calls an unsafe function, then the behavior of the program is undefined. .ip * posix.1-2001 tc1 clarified that if an application calls .br fork (2) from a signal handler and any of the fork handlers registered by .br pthread_atfork (3) calls a function that is not async-signal-safe, the behavior is undefined. a future revision of the standard .\" http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt is likely to remove .br fork (2) from the list of async-signal-safe functions. .\" .ip * 3 asynchronous signal handlers that call functions which are cancellation points and nest over regions of deferred cancellation may trigger cancellation whose behavior is as if asynchronous cancellation had occurred and may cause application state to become inconsistent. .\" .ss errno fetching and setting the value of .i errno is async-signal-safe provided that the signal handler saves .i errno on entry and restores its value before returning. .\" .ss deviations in the gnu c library the following known deviations from the standard occur in the gnu c library: .ip * 3 before glibc 2.24, .br execl (3) and .br execle (3) employed .br realloc (3) internally and were consequently not async-signal-safe. .\" https://sourceware.org/bugzilla/show_bug.cgi?id=19534 this was fixed in glibc 2.24. .ip * .\" fixme . https://sourceware.org/bugzilla/show_bug.cgi?id=13172 the glibc implementation of .br aio_suspend (3) is not async-signal-safe because it uses .br pthread_mutex_lock (3) internally. .sh see also .br sigaction (2), .br signal (7), .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .\" copyright (c) 1995 martin schulze .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1995-10-18 martin schulze .\" * first released .\" 2002-09-22 seth w. klein .\" * protocol numbers are now assigned by the iana .\" .th protocols 5 2012-08-05 "linux" "linux programmer's manual" .sh name protocols \- protocols definition file .sh description this file is a plain ascii file, describing the various darpa internet protocols that are available from the tcp/ip subsystem. it should be consulted instead of using the numbers in the arpa include files, or, even worse, just guessing them. these numbers will occur in the protocol field of any ip header. .pp keep this file untouched since changes would result in incorrect ip packages. protocol numbers and names are specified by the iana (internet assigned numbers authority). .\" .. by the ddn network information center. .pp each line is of the following format: .pp .rs .i protocol number aliases ... .re .pp where the fields are delimited by spaces or tabs. empty lines are ignored. if a line contains a hash mark (#), the hash mark and the part of the line following it are ignored. .pp the field descriptions are: .tp .i protocol the native name for the protocol. for example .ir ip , .ir tcp , or .ir udp . .tp .i number the official number for this protocol as it will appear within the ip header. .tp .i aliases optional aliases for the protocol. .pp this file might be distributed over a network using a network-wide naming service like yellow pages/nis or bind/hesiod. .sh files .tp .i /etc/protocols the protocols definition file. .sh see also .br getprotoent (3) .pp .ur http://www.iana.org\:/assignments\:/protocol\-numbers .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th mbsrtowcs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mbsrtowcs \- convert a multibyte string to a wide-character string .sh synopsis .nf .b #include .pp .bi "size_t mbsrtowcs(wchar_t *restrict " dest ", const char **restrict " src , .bi " size_t " len ", mbstate_t *restrict " ps ); .fi .sh description if .i dest is not null, the .br mbsrtowcs () function converts the multibyte string .i *src to a wide-character string starting at .ir dest . at most .i len wide characters are written to .ir dest . the shift state .i *ps is updated. the conversion is effectively performed by repeatedly calling .i "mbrtowc(dest, *src, n, ps)" where .i n is some positive number, as long as this call succeeds, and then incrementing .i dest by one and .i *src by the number of bytes consumed. the conversion can stop for three reasons: .ip 1. 3 an invalid multibyte sequence has been encountered. in this case, .i *src is left pointing to the invalid multibyte sequence, .i (size_t)\ \-1 is returned, and .i errno is set to .br eilseq . .ip 2. .i len non-l\(aq\e0\(aq wide characters have been stored at .ir dest . in this case, .i *src is left pointing to the next multibyte sequence to be converted, and the number of wide characters written to .i dest is returned. .ip 3. the multibyte string has been completely converted, including the terminating null wide character (\(aq\e0\(aq), which has the side effect of bringing back .i *ps to the initial state. in this case, .i *src is set to null, and the number of wide characters written to .ir dest , excluding the terminating null wide character, is returned. .pp if .ir dest is null, .i len is ignored, and the conversion proceeds as above, except that the converted wide characters are not written out to memory, and that no length limit exists. .pp in both of the above cases, if .i ps is null, a static anonymous state known only to the .br mbsrtowcs () function is used instead. .pp the programmer must ensure that there is room for at least .i len wide characters at .ir dest . .sh return value the .br mbsrtowcs () function returns the number of wide characters that make up the converted part of the wide-character string, not including the terminating null wide character. if an invalid multibyte sequence was encountered, .i (size_t)\ \-1 is returned, and .i errno set to .br eilseq . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br mbsrtowcs () t} thread safety t{ mt-unsafe race:mbsrtowcs/!ps t} .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br mbsrtowcs () depends on the .b lc_ctype category of the current locale. .pp passing null as .i ps is not multithread safe. .sh see also .br iconv (3), .br mbrtowc (3), .br mbsinit (3), .br mbsnrtowcs (3), .br mbstowcs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th request_key 2 2021-08-27 linux "linux key management calls" .sh name request_key \- request a key from the kernel's key management facility .sh synopsis .nf .b #include .pp .bi "key_serial_t request_key(const char *" type ", const char *" description , .bi " const char *" callout_info , .bi " key_serial_t " dest_keyring ");" .fi .pp .ir note : there is no glibc wrapper for this system call; see notes. .sh description .br request_key () attempts to find a key of the given .i type with a description (name) that matches the specified .ir description . if such a key could not be found, then the key is optionally created. if the key is found or created, .br request_key () attaches it to the keyring whose id is specified in .i dest_keyring and returns the key's serial number. .pp .br request_key () first recursively searches for a matching key in all of the keyrings attached to the calling process. the keyrings are searched in the order: thread-specific keyring, process-specific keyring, and then session keyring. .pp if .br request_key () is called from a program invoked by .br request_key () on behalf of some other process to generate a key, then the keyrings of that other process will be searched next, using that other process's user id, group id, supplementary group ids, and security context to determine access. .\" david howells: we can then have an arbitrarily long sequence .\" of "recursive" request-key upcalls. there is no limit, other .\" than number of pids, etc. .pp the search of the keyring tree is breadth-first: the keys in each keyring searched are checked for a match before any child keyrings are recursed into. only keys for which the caller has .i search permission be found, and only keyrings for which the caller has .i search permission may be searched. .pp if the key is not found and .i callout is null, then the call fails with the error .br enokey . .pp if the key is not found and .i callout is not null, then the kernel attempts to invoke a user-space program to instantiate the key. the details are given below. .pp the .i dest_keyring serial number may be that of a valid keyring for which the caller has .i write permission, or it may be one of the following special keyring ids: .tp .b key_spec_thread_keyring this specifies the caller's thread-specific keyring (see .br thread\-keyring (7)). .tp .b key_spec_process_keyring this specifies the caller's process-specific keyring (see .br process\-keyring (7)). .tp .b key_spec_session_keyring this specifies the caller's session-specific keyring (see .br session\-keyring (7)). .tp .b key_spec_user_keyring this specifies the caller's uid-specific keyring (see .br user\-keyring (7)). .tp .b key_spec_user_session_keyring this specifies the caller's uid-session keyring (see .br user\-session\-keyring (7)). .pp when the .i dest_keyring is specified as 0 and no key construction has been performed, then no additional linking is done. .pp otherwise, if .i dest_keyring is 0 and a new key is constructed, the new key will be linked to the "default" keyring. more precisely, when the kernel tries to determine to which keyring the newly constructed key should be linked, it tries the following keyrings, beginning with the keyring set via the .br keyctl (2) .br keyctl_set_reqkey_keyring operation and continuing in the order shown below until it finds the first keyring that exists: .ip \(bu 3 .\" 8bbf4976b59fc9fc2861e79cab7beb3f6d647640 the requestor keyring .rb ( key_reqkey_defl_requestor_keyring , since linux 2.6.29). .\" fixme .\" actually, is the preceding point correct? .\" if i understand correctly, we'll only get here if .\" 'dest_keyring' is zero, in which case key_reqkey_defl_requestor_keyring .\" won't refer to a keyring. have i misunderstood? .ip \(bu the thread-specific keyring .rb ( key_reqkey_defl_thread_keyring ; see .br thread\-keyring (7)). .ip \(bu the process-specific keyring .rb ( key_reqkey_defl_process_keyring ; see .br process\-keyring (7)). .ip \(bu the session-specific keyring .rb ( key_reqkey_defl_session_keyring ; see .br session\-keyring (7)). .ip \(bu the session keyring for the process's user id .rb ( key_reqkey_defl_user_session_keyring ; see .br user\-session\-keyring (7)). this keyring is expected to always exist. .ip \(bu the uid-specific keyring .rb ( key_reqkey_defl_user_keyring ; see .br user\-keyring (7)). this keyring is also expected to always exist. .\" mtk: are there circumstances where the user sessions and uid-specific .\" keyrings do not exist? .\" .\" david howells: .\" the uid keyrings don't exist until someone tries to access them - .\" at which point they're both created. when you log in, pam_keyinit .\" creates a link to your user keyring in the session keyring it just .\" created, thereby creating the user and user-session keyrings. .\" .\" and david elaborated that "access" means: .\" .\" it means lookup_user_key() was passed key_lookup_create. so: .\" .\" add_key() - destination keyring .\" request_key() - destination keyring .\" keyctl_get_keyring_id - if create arg is true .\" keyctl_clear .\" keyctl_link - both args .\" keyctl_search - destination keyring .\" keyctl_chown .\" keyctl_setperm .\" keyctl_set_timeout .\" keyctl_instantiate - destination keyring .\" keyctl_instantiate_iov - destination keyring .\" keyctl_negate - destination keyring .\" keyctl_reject - destination keyring .\" keyctl_get_persistent - destination keyring .\" .\" will all create a keyring under some circumstances. whereas the rest, .\" such as keyctl_get_security, keyctl_read and keyctl_revoke, won't. .pp if the .br keyctl (2) .br keyctl_set_reqkey_keyring operation specifies .br key_reqkey_defl_default (or no .br keyctl_set_reqkey_keyring operation is performed), then the kernel looks for a keyring starting from the beginning of the list. .\" .ss requesting user-space instantiation of a key if the kernel cannot find a key matching .ir type and .ir description , and .i callout is not null, then the kernel attempts to invoke a user-space program to instantiate a key with the given .ir type and .ir description . in this case, the following steps are performed: .ip a) 4 the kernel creates an uninstantiated key, u, with the requested .i type and .ir description . .ip b) the kernel creates an authorization key, v, .\" struct request_key_auth, defined in security/keys/internal.h that refers to the key u and records the facts that the caller of .br request_key () is: .rs .ip (1) 4 the context in which the key u should be instantiated and secured, and .ip (2) the context from which associated key requests may be satisfied. .re .ip the authorization key is constructed as follows: .rs .ip * 3 the key type is .ir """.request_key_auth""" . .ip * the key's uid and gid are the same as the corresponding filesystem ids of the requesting process. .ip * the key grants .ir view , .ir read , and .ir search permissions to the key possessor as well as .ir view permission for the key user. .ip * the description (name) of the key is the hexadecimal string representing the id of the key that is to be instantiated in the requesting program. .ip * the payload of the key is taken from the data specified in .ir callout_info . .ip * internally, the kernel also records the pid of the process that called .br request_key (). .re .ip c) the kernel creates a process that executes a user-space service such as .br request\-key (8) with a new session keyring that contains a link to the authorization key, v. .\" the request\-key(8) program can be invoked in circumstances *other* than .\" when triggered by request_key(2). for example, upcalls from places such .\" as the dns resolver. .ip this program is supplied with the following command-line arguments: .rs .ip [0] 4 the string .ir """/sbin/request\-key""" . .ip [1] the string .i """create""" (indicating that a key is to be created). .ip [2] the id of the key that is to be instantiated. .ip [3] the filesystem uid of the caller of .br request_key (). .ip [4] the filesystem gid of the caller of .br request_key (). .ip [5] the id of the thread keyring of the caller of .br request_key (). this may be zero if that keyring hasn't been created. .ip [6] the id of the process keyring of the caller of .br request_key (). this may be zero if that keyring hasn't been created. .ip [7] the id of the session keyring of the caller of .br request_key (). .re .ip .ir note : each of the command-line arguments that is a key id is encoded in .ir decimal (unlike the key ids shown in .ir /proc/keys , which are shown as hexadecimal values). .ip d) the program spawned in the previous step: .rs .ip * 3 assumes the authority to instantiate the key u using the .br keyctl (2) .br keyctl_assume_authority operation (typically via the .br keyctl_assume_authority (3) function). .ip * obtains the callout data from the payload of the authorization key v (using the .br keyctl (2) .br keyctl_read operation (or, more commonly, the .br keyctl_read (3) function) with a key id value of .br key_spec_reqkey_auth_key ). .ip * instantiates the key (or execs another program that performs that task), specifying the payload and destination keyring. (the destination keyring that the requestor specified when calling .br request_key () can be accessed using the special key id .br key_spec_requestor_keyring .) .\" should an instantiating program be using key_spec_requestor_keyring? .\" i couldn't find a use in the keyutils git repo. .\" according to david howells: .\" * this feature is provided, but not used at the moment. .\" * a key added to that ring is then owned by the requester instantiation is performed using the .br keyctl (2) .br keyctl_instantiate operation (or, more commonly, the .br keyctl_instantiate (3) function). at this point, the .br request_key () call completes, and the requesting program can continue execution. .re .pp if these steps are unsuccessful, then an .br enokey error will be returned to the caller of .br request_key () and a temporary, negatively instantiated key will be installed in the keyring specified by .ir dest_keyring . this will expire after a few seconds, but will cause subsequent calls to .br request_key () to fail until it does. the purpose of this negatively instantiated key is to prevent (possibly different) processes making repeated requests (that require expensive .br request\-key (8) upcalls) for a key that can't (at the moment) be positively instantiated. .pp once the key has been instantiated, the authorization key .rb ( key_spec_reqkey_auth_key ) is revoked, and the destination keyring .rb ( key_spec_requestor_keyring ) is no longer accessible from the .br request\-key (8) program. .pp if a key is created, then\(emregardless of whether it is a valid key or a negatively instantiated key\(emit will displace any other key with the same type and description from the keyring specified in .ir dest_keyring . .sh return value on success, .br request_key () returns the serial number of the key it found or caused to be created. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces the keyring wasn't available for modification by the user. .tp .b edquot the key quota for this user would be exceeded by creating this key or linking it to the keyring. .tp .b efault one of .ir type , .ir description , or .ir callout_info points outside the process's accessible address space. .tp .b eintr the request was interrupted by a signal; see .br signal (7). .tp .b einval the size of the string (including the terminating null byte) specified in .i type or .i description exceeded the limit (32 bytes and 4096 bytes respectively). .tp .b einval the size of the string (including the terminating null byte) specified in .i callout_info exceeded the system page size. .tp .b ekeyexpired an expired key was found, but no replacement could be obtained. .tp .b ekeyrejected the attempt to generate a new key was rejected. .tp .b ekeyrevoked a revoked key was found, but no replacement could be obtained. .tp .b enokey no matching key was found. .tp .b enomem insufficient memory to create a key. .tp .b eperm the .i type argument started with a period (\(aq.\(aq). .sh versions this system call first appeared in linux 2.6.10. the ability to instantiate keys upon request was added .\" commit 3e30148c3d524a9c1c63ca28261bc24c457eb07a in linux 2.6.13. .sh conforming to this system call is a nonstandard linux extension. .sh notes glibc does not provide a wrapper for this system call. a wrapper is provided in the .ir libkeyutils library. (the accompanying package provides the .i header file.) when employing the wrapper in that library, link with .ir \-lkeyutils . .sh examples the program below demonstrates the use of .br request_key (). the .ir type , .ir description , and .ir callout_info arguments for the system call are taken from the values supplied in the command-line arguments. the call specifies the session keyring as the target keyring. .pp in order to demonstrate this program, we first create a suitable entry in the file .ir /etc/request\-key.conf . .pp .in +4n .ex $ sudo sh # \fbecho \(aqcreate user mtk:* * /bin/keyctl instantiate %k %c %s\(aq \e\fp \fb> /etc/request\-key.conf\fp # \fbexit\fp .ee .in .pp this entry specifies that when a new "user" key with the prefix "mtk:" must be instantiated, that task should be performed via the .br keyctl (1) command's .b instantiate operation. the arguments supplied to the .b instantiate operation are: the id of the uninstantiated key .ri ( %k ); the callout data supplied to the .br request_key () call .ri ( %c ); and the session keyring .ri ( %s ) of the requestor (i.e., the caller of .br request_key ()). see .br request\-key.conf (5) for details of these .i % specifiers. .pp then we run the program and check the contents of .ir /proc/keys to verify that the requested key has been instantiated: .pp .in +4n .ex $ \fb./t_request_key user mtk:key1 "payload data"\fp $ \fbgrep \(aq2dddaf50\(aq /proc/keys\fp 2dddaf50 i\-\-q\-\-\- 1 perm 3f010000 1000 1000 user mtk:key1: 12 .ee .in .pp for another example of the use of this program, see .br keyctl (2). .ss program source \& .ex /* t_request_key.c */ #include #include #include #include #include #include int main(int argc, char *argv[]) { key_serial_t key; if (argc != 4) { fprintf(stderr, "usage: %s type description callout\-data\en", argv[0]); exit(exit_failure); } key = request_key(argv[1], argv[2], argv[3], key_spec_session_keyring); if (key == \-1) { perror("request_key"); exit(exit_failure); } printf("key id is %jx\en", (uintmax_t) key); exit(exit_success); } .ee .sh see also .ad l .nh .br keyctl (1), .br add_key (2), .br keyctl (2), .br keyctl (3), .br capabilities (7), .br keyrings (7), .br keyutils (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7), .br request\-key (8) .pp the kernel source files .ir documentation/security/keys/core.rst and .ir documentation/keys/request\-key.rst (or, before linux 4.13, in the files .\" commit b68101a1e8f0263dbc7b8375d2a7c57c6216fb76 .ir documentation/security/keys.txt and .\" commit 3db38ed76890565772fcca3279cc8d454ea6176b .ir documentation/security/keys\-request\-key.txt ). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gethostbyname.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswprint 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswprint \- test for printing wide character .sh synopsis .nf .b #include .pp .bi "int iswprint(wint_t " wc ); .fi .sh description the .br iswprint () function is the wide-character equivalent of the .br isprint (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "print". .pp the wide-character class "print" is disjoint from the wide-character class "cntrl". .pp the wide-character class "print" contains the wide-character class "graph". .sh return value the .br iswprint () function returns nonzero if .i wc is a wide character belonging to the wide-character class "print". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswprint () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswprint () depends on the .b lc_ctype category of the current locale. .sh see also .br isprint (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getgid.2 .so man2/rename.2 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_getvalue 3 2021-03-22 "linux" "linux programmer's manual" .sh name sem_getvalue \- get the value of a semaphore .sh synopsis .nf .b #include .pp .bi "int sem_getvalue(sem_t *restrict " sem ", int *restrict " sval ); .fi .pp link with \fi\-pthread\fp. .sh description .br sem_getvalue () places the current value of the semaphore pointed to .i sem into the integer pointed to by .ir sval . .pp if one or more processes or threads are blocked waiting to lock the semaphore with .br sem_wait (3), posix.1 permits two possibilities for the value returned in .ir sval : either 0 is returned; or a negative number whose absolute value is the count of the number of processes and threads currently blocked in .br sem_wait (3). linux adopts the former behavior. .sh return value .br sem_getvalue () returns 0 on success; on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b einval .i sem is not a valid semaphore. (the glibc implementation currently does not check whether .i sem is valid.) .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_getvalue () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the value of the semaphore may already have changed by the time .br sem_getvalue () returns. .sh see also .br sem_post (3), .br sem_wait (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_close 3 2021-03-22 "linux" "linux programmer's manual" .sh name mq_close \- close a message queue descriptor .sh synopsis .nf .b #include .pp .bi "int mq_close(mqd_t " mqdes ); .fi .pp link with \fi\-lrt\fp. .sh description .br mq_close () closes the message queue descriptor .ir mqdes . .pp if the calling process has attached a notification request (see .rb ( mq_notify (3)) to this message queue via .ir mqdes , then this request is removed, and another process can now attach a notification request. .sh return value on success .br mq_close () returns 0; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b ebadf the message queue descriptor specified in .i mqdes is invalid. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mq_close () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes all open message queues are automatically closed on process termination, or upon .br execve (2). .sh see also .br mq_getattr (3), .br mq_notify (3), .br mq_open (3), .br mq_receive (3), .br mq_send (3), .br mq_unlink (3), .br mq_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/des_crypt.3 .\" this man page is copyright (c) 1999 andi kleen , .\" copyright (c) 2008-2014, michael kerrisk , .\" and copyright (c) 2016, heinrich schuchardt .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" modified, 2003-12-02, michael kerrisk, .\" modified, 2003-09-23, adam langley .\" modified, 2004-05-27, michael kerrisk, .\" added sock_seqpacket .\" 2008-05-27, mtk, provide a clear description of the three types of .\" address that can appear in the sockaddr_un structure: pathname, .\" unnamed, and abstract. .\" .th unix 7 2021-03-22 "linux" "linux programmer's manual" .sh name unix \- sockets for local interprocess communication .sh synopsis .nf .b #include .b #include .pp .ib unix_socket " = socket(af_unix, type, 0);" .ib error " = socketpair(af_unix, type, 0, int *" sv ");" .fi .sh description the .b af_unix (also known as .br af_local ) socket family is used to communicate between processes on the same machine efficiently. traditionally, unix domain sockets can be either unnamed, or bound to a filesystem pathname (marked as being of type socket). linux also supports an abstract namespace which is independent of the filesystem. .pp valid socket types in the unix domain are: .br sock_stream , for a stream-oriented socket; .br sock_dgram , for a datagram-oriented socket that preserves message boundaries (as on most unix implementations, unix domain datagram sockets are always reliable and don't reorder datagrams); and (since linux 2.6.4) .br sock_seqpacket , for a sequenced-packet socket that is connection-oriented, preserves message boundaries, and delivers messages in the order that they were sent. .pp unix domain sockets support passing file descriptors or process credentials to other processes using ancillary data. .ss address format a unix domain socket address is represented in the following structure: .pp .in +4n .ex .\" #define unix_path_max 108 .\" struct sockaddr_un { sa_family_t sun_family; /* af_unix */ char sun_path[108]; /* pathname */ }; .ee .in .pp the .i sun_family field always contains .br af_unix . on linux, .i sun_path is 108 bytes in size; see also notes, below. .pp various systems calls (for example, .br bind (2), .br connect (2), and .br sendto (2)) take a .i sockaddr_un argument as input. some other system calls (for example, .br getsockname (2), .br getpeername (2), .br recvfrom (2), and .br accept (2)) return an argument of this type. .pp three types of address are distinguished in the .i sockaddr_un structure: .ip * 3 .ir pathname : a unix domain socket can be bound to a null-terminated filesystem pathname using .br bind (2). when the address of a pathname socket is returned (by one of the system calls noted above), its length is .ip offsetof(struct sockaddr_un, sun_path) + strlen(sun_path) + 1 .ip and .i sun_path contains the null-terminated pathname. (on linux, the above .br offsetof () expression equates to the same value as .ir sizeof(sa_family_t) , but some other implementations include other fields before .ir sun_path , so the .br offsetof () expression more portably describes the size of the address structure.) .ip for further details of pathname sockets, see below. .ip * .ir unnamed : a stream socket that has not been bound to a pathname using .br bind (2) has no name. likewise, the two sockets created by .br socketpair (2) are unnamed. when the address of an unnamed socket is returned, its length is .ir "sizeof(sa_family_t)" , and .i sun_path should not be inspected. .\" there is quite some variation across implementations: freebsd .\" says the length is 16 bytes, hp-ux 11 says it's zero bytes. .ip * .ir abstract : an abstract socket address is distinguished (from a pathname socket) by the fact that .ir sun_path[0] is a null byte (\(aq\e0\(aq). the socket's address in this namespace is given by the additional bytes in .ir sun_path that are covered by the specified length of the address structure. (null bytes in the name have no special significance.) the name has no connection with filesystem pathnames. when the address of an abstract socket is returned, the returned .i addrlen is greater than .ir "sizeof(sa_family_t)" (i.e., greater than 2), and the name of the socket is contained in the first .ir "(addrlen \- sizeof(sa_family_t))" bytes of .ir sun_path . .ss pathname sockets when binding a socket to a pathname, a few rules should be observed for maximum portability and ease of coding: .ip * 3 the pathname in .i sun_path should be null-terminated. .ip * the length of the pathname, including the terminating null byte, should not exceed the size of .ir sun_path . .ip * the .i addrlen argument that describes the enclosing .i sockaddr_un structure should have a value of at least: .ip .nf offsetof(struct sockaddr_un, sun_path)+strlen(addr.sun_path)+1 .fi .ip or, more simply, .i addrlen can be specified as .ir "sizeof(struct sockaddr_un)" . .pp there is some variation in how implementations handle unix domain socket addresses that do not follow the above rules. for example, some (but not all) implementations .\" linux does this, including for the case where the supplied path .\" is 108 bytes append a null terminator if none is present in the supplied .ir sun_path . .pp when coding portable applications, keep in mind that some implementations .\" hp-ux have .i sun_path as short as 92 bytes. .\" modern bsds generally have 104, tru64 and aix have 104, .\" solaris and irix have 108 .pp various system calls .rb ( accept (2), .br recvfrom (2), .br getsockname (2), .br getpeername (2)) return socket address structures. when applied to unix domain sockets, the value-result .i addrlen argument supplied to the call should be initialized as above. upon return, the argument is set to indicate the .i actual size of the address structure. the caller should check the value returned in this argument: if the output value exceeds the input value, then there is no guarantee that a null terminator is present in .ir sun_path . (see bugs.) .\" .ss pathname socket ownership and permissions in the linux implementation, pathname sockets honor the permissions of the directory they are in. creation of a new socket fails if the process does not have write and search (execute) permission on the directory in which the socket is created. .pp on linux, connecting to a stream socket object requires write permission on that socket; sending a datagram to a datagram socket likewise requires write permission on that socket. posix does not make any statement about the effect of the permissions on a socket file, and on some systems (e.g., older bsds), the socket permissions are ignored. portable programs should not rely on this feature for security. .pp when creating a new socket, the owner and group of the socket file are set according to the usual rules. the socket file has all permissions enabled, other than those that are turned off by the process .br umask (2). .pp the owner, group, and permissions of a pathname socket can be changed (using .br chown (2) and .br chmod (2)). .\" however, fchown() and fchmod() do not seem to have an effect .\" .ss abstract sockets socket permissions have no meaning for abstract sockets: the process .br umask (2) has no effect when binding an abstract socket, and changing the ownership and permissions of the object (via .br fchown (2) and .br fchmod (2)) has no effect on the accessibility of the socket. .pp abstract sockets automatically disappear when all open references to the socket are closed. .pp the abstract socket namespace is a nonportable linux extension. .\" .ss socket options for historical reasons, these socket options are specified with a .b sol_socket type even though they are .b af_unix specific. they can be set with .br setsockopt (2) and read with .br getsockopt (2) by specifying .b sol_socket as the socket family. .tp .b so_passcred enabling this socket option causes receipt of the credentials of the sending process in an .b scm_credentials ancillary message in each subsequently received message. the returned credentials are those specified by the sender using .br scm_credentials , or a default that includes the sender's pid, real user id, and real group id, if the sender did not specify .b scm_credentials ancillary data. .ip when this option is set and the socket is not yet connected, a unique name in the abstract namespace will be generated automatically. .ip the value given as an argument to .br setsockopt (2) and returned as the result of .br getsockopt (2) is an integer boolean flag. .tp .b so_passsec enables receiving of the selinux security label of the peer socket in an ancillary message of type .br scm_security (see below). .ip the value given as an argument to .br setsockopt (2) and returned as the result of .br getsockopt (2) is an integer boolean flag. .ip the .b so_passsec option is supported for unix domain datagram sockets .\" commit 877ce7c1b3afd69a9b1caeb1b9964c992641f52a since linux 2.6.18; support for unix domain stream sockets was added .\" commit 37a9a8df8ce9de6ea73349c9ac8bdf6ba4ec4f70 in linux 4.2. .tp .br so_peek_off see .br socket (7). .tp .b so_peercred this read-only socket option returns the credentials of the peer process connected to this socket. the returned credentials are those that were in effect at the time of the call to .br connect (2) or .br socketpair (2). .ip the argument to .br getsockopt (2) is a pointer to a .i ucred structure; define the .b _gnu_source feature test macro to obtain the definition of that structure from .ir . .ip the use of this option is possible only for connected .b af_unix stream sockets and for .b af_unix stream and datagram socket pairs created using .br socketpair (2). .tp .b so_peersec this read-only socket option returns the security context of the peer socket connected to this socket. by default, this will be the same as the security context of the process that created the peer socket unless overridden by the policy or by a process with the required permissions. .ip the argument to .br getsockopt (2) is a pointer to a buffer of the specified length in bytes into which the security context string will be copied. if the buffer length is less than the length of the security context string, then .br getsockopt (2) returns \-1, sets .i errno to .br erange , and returns the required length via .ir optlen . the caller should allocate at least .br name_max bytes for the buffer initially, although this is not guaranteed to be sufficient. resizing the buffer to the returned length and retrying may be necessary. .ip the security context string may include a terminating null character in the returned length, but is not guaranteed to do so: a security context "foo" might be represented as either {'f','o','o'} of length 3 or {'f','o','o','\\0'} of length 4, which are considered to be interchangeable. the string is printable, does not contain non-terminating null characters, and is in an unspecified encoding (in particular, it is not guaranteed to be ascii or utf-8). .ip the use of this option for sockets in the .b af_unix address family is supported since linux 2.6.2 for connected stream sockets, and since linux 4.18 .\" commit 0b811db2cb2aabc910e53d34ebb95a15997c33e7 also for stream and datagram socket pairs created using .br socketpair (2). .\" .ss autobind feature if a .br bind (2) call specifies .i addrlen as .ir sizeof(sa_family_t) , .\" i.e., sizeof(short) or the .br so_passcred socket option was specified for a socket that was not explicitly bound to an address, then the socket is autobound to an abstract address. the address consists of a null byte followed by 5 bytes in the character set .ir [0\-9a\-f] . thus, there is a limit of 2^20 autobind addresses. (from linux 2.1.15, when the autobind feature was added, 8 bytes were used, and the limit was thus 2^32 autobind addresses. the change to 5 bytes came in linux 2.3.15.) .ss sockets api the following paragraphs describe domain-specific details and unsupported features of the sockets api for unix domain sockets on linux. .pp unix domain sockets do not support the transmission of out-of-band data (the .b msg_oob flag for .br send (2) and .br recv (2)). .pp the .br send (2) .b msg_more flag is not supported by unix domain sockets. .pp before linux 3.4, .\" commit 9f6f9af7694ede6314bed281eec74d588ba9474f the use of .b msg_trunc in the .i flags argument of .br recv (2) was not supported by unix domain sockets. .pp the .b so_sndbuf socket option does have an effect for unix domain sockets, but the .b so_rcvbuf option does not. for datagram sockets, the .b so_sndbuf value imposes an upper limit on the size of outgoing datagrams. this limit is calculated as the doubled (see .br socket (7)) option value less 32 bytes used for overhead. .ss ancillary messages ancillary data is sent and received using .br sendmsg (2) and .br recvmsg (2). for historical reasons, the ancillary message types listed below are specified with a .b sol_socket type even though they are .b af_unix specific. to send them, set the .i cmsg_level field of the struct .i cmsghdr to .b sol_socket and the .i cmsg_type field to the type. for more information, see .br cmsg (3). .tp .b scm_rights send or receive a set of open file descriptors from another process. the data portion contains an integer array of the file descriptors. .ip commonly, this operation is referred to as "passing a file descriptor" to another process. however, more accurately, what is being passed is a reference to an open file description (see .br open (2)), and in the receiving process it is likely that a different file descriptor number will be used. semantically, this operation is equivalent to duplicating .rb ( dup (2)) a file descriptor into the file descriptor table of another process. .ip if the buffer used to receive the ancillary data containing file descriptors is too small (or is absent), then the ancillary data is truncated (or discarded) and the excess file descriptors are automatically closed in the receiving process. .ip if the number of file descriptors received in the ancillary data would cause the process to exceed its .b rlimit_nofile resource limit (see .br getrlimit (2)), the excess file descriptors are automatically closed in the receiving process. .ip the kernel constant .br scm_max_fd defines a limit on the number of file descriptors in the array. attempting to send an array larger than this limit causes .br sendmsg (2) to fail with the error .br einval . .br scm_max_fd has the value 253 (or 255 in kernels .\" commit bba14de98753cb6599a2dae0e520714b2153522d before 2.6.38). .tp .b scm_credentials send or receive unix credentials. this can be used for authentication. the credentials are passed as a .i struct ucred ancillary message. this structure is defined in .i as follows: .ip .in +4n .ex struct ucred { pid_t pid; /* process id of the sending process */ uid_t uid; /* user id of the sending process */ gid_t gid; /* group id of the sending process */ }; .ee .in .ip since glibc 2.8, the .b _gnu_source feature test macro must be defined (before including .i any header files) in order to obtain the definition of this structure. .ip the credentials which the sender specifies are checked by the kernel. a privileged process is allowed to specify values that do not match its own. the sender must specify its own process id (unless it has the capability .br cap_sys_admin , in which case the pid of any existing process may be specified), its real user id, effective user id, or saved set-user-id (unless it has .br cap_setuid ), and its real group id, effective group id, or saved set-group-id (unless it has .br cap_setgid ). .ip to receive a .i struct ucred message, the .b so_passcred option must be enabled on the socket. .tp .b scm_security receive the selinux security context (the security label) of the peer socket. the received ancillary data is a null-terminated string containing the security context. the receiver should allocate at least .br name_max bytes in the data portion of the ancillary message for this data. .ip to receive the security context, the .b so_passsec option must be enabled on the socket (see above). .pp when sending ancillary data with .br sendmsg (2), only one item of each of the above types may be included in the sent message. .pp at least one byte of real data should be sent when sending ancillary data. on linux, this is required to successfully send ancillary data over a unix domain stream socket. when sending ancillary data over a unix domain datagram socket, it is not necessary on linux to send any accompanying real data. however, portable applications should also include at least one byte of real data when sending ancillary data over a datagram socket. .pp when receiving from a stream socket, ancillary data forms a kind of barrier for the received data. for example, suppose that the sender transmits as follows: .pp .rs .pd 0 .ip 1. 3 .br sendmsg (2) of four bytes, with no ancillary data. .ip 2. .br sendmsg (2) of one byte, with ancillary data. .ip 3. .br sendmsg (2) of four bytes, with no ancillary data. .pd .re .pp suppose that the receiver now performs .br recvmsg (2) calls each with a buffer size of 20 bytes. the first call will receive five bytes of data, along with the ancillary data sent by the second .br sendmsg (2) call. the next call will receive the remaining four bytes of data. .pp if the space allocated for receiving incoming ancillary data is too small then the ancillary data is truncated to the number of headers that will fit in the supplied buffer (or, in the case of an .br scm_rights file descriptor list, the list of file descriptors may be truncated). if no buffer is provided for incoming ancillary data (i.e., the .i msg_control field of the .i msghdr structure supplied to .br recvmsg (2) is null), then the incoming ancillary data is discarded. in both of these cases, the .br msg_ctrunc flag will be set in the .i msg.msg_flags value returned by .br recvmsg (2). .\" .ss ioctls the following .br ioctl (2) calls return information in .ir value . the correct syntax is: .pp .rs .nf .bi int " value"; .ib error " = ioctl(" unix_socket ", " ioctl_type ", &" value ");" .fi .re .pp .i ioctl_type can be: .tp .b siocinq for .b sock_stream sockets, this call returns the number of unread bytes in the receive buffer. the socket must not be in listen state, otherwise an error .rb ( einval ) is returned. .b siocinq is defined in .ir . .\" fixme . http://sources.redhat.com/bugzilla/show_bug.cgi?id=12002, .\" filed 2010-09-10, may cause siocinq to be defined in glibc headers alternatively, you can use the synonymous .br fionread , defined in .ir . .\" siocoutq also has an effect for unix domain sockets, but not .\" quite what userland might expect. it seems to return the number .\" of bytes allocated for buffers containing pending output. .\" that number is normally larger than the number of bytes of pending .\" output. since this info is, from userland's point of view, imprecise, .\" and it may well change, probably best not to document this now. for .b sock_dgram sockets, the returned value is the same as for internet domain datagram sockets; see .br udp (7). .sh errors .tp .b eaddrinuse the specified local address is already in use or the filesystem socket object already exists. .tp .b ebadf this error can occur for .br sendmsg (2) when sending a file descriptor as ancillary data over a unix domain socket (see the description of .br scm_rights , above), and indicates that the file descriptor number that is being sent is not valid (e.g., it is not an open file descriptor). .tp .b econnrefused the remote address specified by .br connect (2) was not a listening socket. this error can also occur if the target pathname is not a socket. .tp .b econnreset remote socket was unexpectedly closed. .tp .b efault user memory address was not valid. .tp .b einval invalid argument passed. a common cause is that the value .b af_unix was not specified in the .i sun_type field of passed addresses, or the socket was in an invalid state for the applied operation. .tp .b eisconn .br connect (2) called on an already connected socket or a target address was specified on a connected socket. .tp .b enoent the pathname in the remote address specified to .br connect (2) did not exist. .tp .b enomem out of memory. .tp .b enotconn socket operation needs a target address, but the socket is not connected. .tp .b eopnotsupp stream operation called on non-stream oriented socket or tried to use the out-of-band data option. .tp .b eperm the sender passed invalid credentials in the .ir "struct ucred" . .tp .b epipe remote socket was closed on a stream socket. if enabled, a .b sigpipe is sent as well. this can be avoided by passing the .b msg_nosignal flag to .br send (2) or .br sendmsg (2). .tp .b eprotonosupport passed protocol is not .br af_unix . .tp .b eprototype remote socket does not match the local socket type .rb ( sock_dgram versus .br sock_stream ). .tp .b esocktnosupport unknown socket type. .tp .b esrch while sending an ancillary message containing credentials .rb ( scm_credentials ), the caller specified a pid that does not match any existing process. .tp .b etoomanyrefs this error can occur for .br sendmsg (2) when sending a file descriptor as ancillary data over a unix domain socket (see the description of .br scm_rights , above). it occurs if the number of "in-flight" file descriptors exceeds the .b rlimit_nofile resource limit and the caller does not have the .br cap_sys_resource capability. an in-flight file descriptor is one that has been sent using .br sendmsg (2) but has not yet been accepted in the recipient process using .br recvmsg (2). .ip this error is diagnosed since mainline linux 4.5 (and in some earlier kernel versions where the fix has been backported). .\" commit 712f4aad406bb1ed67f3f98d04c044191f0ff593 in earlier kernel versions, it was possible to place an unlimited number of file descriptors in flight, by sending each file descriptor with .br sendmsg (2) and then closing the file descriptor so that it was not accounted against the .b rlimit_nofile resource limit. .pp other errors can be generated by the generic socket layer or by the filesystem while generating a filesystem socket object. see the appropriate manual pages for more information. .sh versions .b scm_credentials and the abstract namespace were introduced with linux 2.2 and should not be used in portable programs. (some bsd-derived systems also support credential passing, but the implementation details differ.) .sh notes binding to a socket with a filename creates a socket in the filesystem that must be deleted by the caller when it is no longer needed (using .br unlink (2)). the usual unix close-behind semantics apply; the socket can be unlinked at any time and will be finally removed from the filesystem when the last reference to it is closed. .pp to pass file descriptors or credentials over a .br sock_stream socket, you must send or receive at least one byte of nonancillary data in the same .br sendmsg (2) or .br recvmsg (2) call. .pp unix domain stream sockets do not support the notion of out-of-band data. .\" .sh bugs when binding a socket to an address, linux is one of the implementations that appends a null terminator if none is supplied in .ir sun_path . in most cases this is unproblematic: when the socket address is retrieved, it will be one byte longer than that supplied when the socket was bound. however, there is one case where confusing behavior can result: if 108 non-null bytes are supplied when a socket is bound, then the addition of the null terminator takes the length of the pathname beyond .ir sizeof(sun_path) . consequently, when retrieving the socket address (for example, via .br accept (2)), .\" the behavior on solaris is quite similar. if the input .i addrlen argument for the retrieving call is specified as .ir "sizeof(struct sockaddr_un)" , then the returned address structure .i won't have a null terminator in .ir sun_path . .pp in addition, some implementations .\" i.e., traditional bsd don't require a null terminator when binding a socket (the .i addrlen argument is used to determine the length of .ir sun_path ) and when the socket address is retrieved on these implementations, there is no null terminator in .ir sun_path . .pp applications that retrieve socket addresses can (portably) code to handle the possibility that there is no null terminator in .ir sun_path by respecting the fact that the number of valid bytes in the pathname is: .pp strnlen(addr.sun_path, addrlen \- offsetof(sockaddr_un, sun_path)) .\" the following patch to amend kernel behavior was rejected: .\" http://thread.gmane.org/gmane.linux.kernel.api/2437 .\" subject: [patch] fix handling of overlength pathname in af_unix sun_path .\" 2012-04-17 .\" and there was a related discussion in the austin list: .\" http://thread.gmane.org/gmane.comp.standards.posix.austin.general/5735 .\" subject: having a sun_path with no null terminator .\" 2012-04-18 .\" .\" fixme . track http://austingroupbugs.net/view.php?id=561 .pp alternatively, an application can retrieve the socket address by allocating a buffer of size .i "sizeof(struct sockaddr_un)+1" that is zeroed out before the retrieval. the retrieving call can specify .i addrlen as .ir "sizeof(struct sockaddr_un)" , and the extra zero byte ensures that there will be a null terminator for the string returned in .ir sun_path : .pp .in +4n .ex void *addrp; addrlen = sizeof(struct sockaddr_un); addrp = malloc(addrlen + 1); if (addrp == null) /* handle error */ ; memset(addrp, 0, addrlen + 1); if (getsockname(sfd, (struct sockaddr *) addrp, &addrlen)) == \-1) /* handle error */ ; printf("sun_path = %s\en", ((struct sockaddr_un *) addrp)\->sun_path); .ee .in .pp this sort of messiness can be avoided if it is guaranteed that the applications that .i create pathname sockets follow the rules outlined above under .ir "pathname sockets" . .sh examples the following code demonstrates the use of sequenced-packet sockets for local interprocess communication. it consists of two programs. the server program waits for a connection from the client program. the client sends each of its command-line arguments in separate messages. the server treats the incoming messages as integers and adds them up. the client sends the command string "end". the server sends back a message containing the sum of the client's integers. the client prints the sum and exits. the server waits for the next client to connect. to stop the server, the client is called with the command-line argument "down". .pp the following output was recorded while running the server in the background and repeatedly executing the client. execution of the server program ends when it receives the "down" command. .ss example output .in +4n .ex $ \fb./server &\fp [1] 25887 $ \fb./client 3 4\fp result = 7 $ \fb./client 11 \-5\fp result = 6 $ \fb./client down\fp result = 0 [1]+ done ./server $ .ee .in .ss program source \& .ex /* * file connection.h */ #define socket_name "/tmp/9lq7bnbnbycd6nxy.socket" #define buffer_size 12 /* * file server.c */ #include #include #include #include #include #include #include "connection.h" int main(int argc, char *argv[]) { struct sockaddr_un name; int down_flag = 0; int ret; int connection_socket; int data_socket; int result; char buffer[buffer_size]; /* create local socket. */ connection_socket = socket(af_unix, sock_seqpacket, 0); if (connection_socket == \-1) { perror("socket"); exit(exit_failure); } /* * for portability clear the whole structure, since some * implementations have additional (nonstandard) fields in * the structure. */ memset(&name, 0, sizeof(name)); /* bind socket to socket name. */ name.sun_family = af_unix; strncpy(name.sun_path, socket_name, sizeof(name.sun_path) \- 1); ret = bind(connection_socket, (const struct sockaddr *) &name, sizeof(name)); if (ret == \-1) { perror("bind"); exit(exit_failure); } /* * prepare for accepting connections. the backlog size is set * to 20. so while one request is being processed other requests * can be waiting. */ ret = listen(connection_socket, 20); if (ret == \-1) { perror("listen"); exit(exit_failure); } /* this is the main loop for handling connections. */ for (;;) { /* wait for incoming connection. */ data_socket = accept(connection_socket, null, null); if (data_socket == \-1) { perror("accept"); exit(exit_failure); } result = 0; for (;;) { /* wait for next data packet. */ ret = read(data_socket, buffer, sizeof(buffer)); if (ret == \-1) { perror("read"); exit(exit_failure); } /* ensure buffer is 0\-terminated. */ buffer[sizeof(buffer) \- 1] = 0; /* handle commands. */ if (!strncmp(buffer, "down", sizeof(buffer))) { down_flag = 1; break; } if (!strncmp(buffer, "end", sizeof(buffer))) { break; } /* add received summand. */ result += atoi(buffer); } /* send result. */ sprintf(buffer, "%d", result); ret = write(data_socket, buffer, sizeof(buffer)); if (ret == \-1) { perror("write"); exit(exit_failure); } /* close socket. */ close(data_socket); /* quit on down command. */ if (down_flag) { break; } } close(connection_socket); /* unlink the socket. */ unlink(socket_name); exit(exit_success); } /* * file client.c */ #include #include #include #include #include #include #include #include "connection.h" int main(int argc, char *argv[]) { struct sockaddr_un addr; int ret; int data_socket; char buffer[buffer_size]; /* create local socket. */ data_socket = socket(af_unix, sock_seqpacket, 0); if (data_socket == \-1) { perror("socket"); exit(exit_failure); } /* * for portability clear the whole structure, since some * implementations have additional (nonstandard) fields in * the structure. */ memset(&addr, 0, sizeof(addr)); /* connect socket to socket address. */ addr.sun_family = af_unix; strncpy(addr.sun_path, socket_name, sizeof(addr.sun_path) \- 1); ret = connect(data_socket, (const struct sockaddr *) &addr, sizeof(addr)); if (ret == \-1) { fprintf(stderr, "the server is down.\en"); exit(exit_failure); } /* send arguments. */ for (int i = 1; i < argc; ++i) { ret = write(data_socket, argv[i], strlen(argv[i]) + 1); if (ret == \-1) { perror("write"); break; } } /* request result. */ strcpy(buffer, "end"); ret = write(data_socket, buffer, strlen(buffer) + 1); if (ret == \-1) { perror("write"); exit(exit_failure); } /* receive result. */ ret = read(data_socket, buffer, sizeof(buffer)); if (ret == \-1) { perror("read"); exit(exit_failure); } /* ensure buffer is 0\-terminated. */ buffer[sizeof(buffer) \- 1] = 0; printf("result = %s\en", buffer); /* close socket. */ close(data_socket); exit(exit_success); } .ee .pp for examples of the use of .br scm_rights , see .br cmsg (3) and .br seccomp_unotify (2). .sh see also .br recvmsg (2), .br sendmsg (2), .br socket (2), .br socketpair (2), .br cmsg (3), .br capabilities (7), .br credentials (7), .br socket (7), .br udp (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, 2014, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created sat aug 21 1995 thomas k. dyas .\" modified tue oct 22 22:09:03 1996 by eric s. raymond .\" 2008-06-26, mtk, added some more detail on the work done by sigreturn() .\" 2014-12-05, mtk, rewrote all of the rest of the original page .\" .th sigreturn 2 2021-03-22 "linux" "linux programmer's manual" .sh name sigreturn, rt_sigreturn \- return from signal handler and cleanup stack frame .sh synopsis .nf .bi "int sigreturn(...);" .fi .sh description if the linux kernel determines that an unblocked signal is pending for a process, then, at the next transition back to user mode in that process (e.g., upon return from a system call or when the process is rescheduled onto the cpu), it creates a new frame on the user-space stack where it saves various pieces of process context (processor status word, registers, signal mask, and signal stack settings). .\" see arch/x86/kernel/signal.c::__setup_frame() [in 3.17 source code] .pp the kernel also arranges that, during the transition back to user mode, the signal handler is called, and that, upon return from the handler, control passes to a piece of user-space code commonly called the "signal trampoline". the signal trampoline code in turn calls .br sigreturn (). .pp this .br sigreturn () call undoes everything that was done\(emchanging the process's signal mask, switching signal stacks (see .br sigaltstack "(2))\(emin" order to invoke the signal handler. using the information that was earlier saved on the user-space stack .br sigreturn () restores the process's signal mask, switches stacks, and restores the process's context (processor flags and registers, including the stack pointer and instruction pointer), so that the process resumes execution at the point where it was interrupted by the signal. .sh return value .br sigreturn () never returns. .sh conforming to many unix-type systems have a .br sigreturn () system call or near equivalent. however, this call is not specified in posix, and details of its behavior vary across systems. .sh notes .br sigreturn () exists only to allow the implementation of signal handlers. it should .b never be called directly. (indeed, a simple .br sigreturn () .\" see sysdeps/unix/sysv/linux/sigreturn.c and .\" signal/sigreturn.c in the glibc source wrapper in the gnu c library simply returns \-1, with .i errno set to .br enosys .) details of the arguments (if any) passed to .br sigreturn () vary depending on the architecture. (on some architectures, such as x86-64, .br sigreturn () takes no arguments, since all of the information that it requires is available in the stack frame that was previously created by the kernel on the user-space stack.) .pp once upon a time, unix systems placed the signal trampoline code onto the user stack. nowadays, pages of the user stack are protected so as to disallow code execution. thus, on contemporary linux systems, depending on the architecture, the signal trampoline code lives either in the .br vdso (7) or in the c library. in the latter case, .\" see, for example, sysdeps/unix/sysv/linux/i386/sigaction.c and .\" sysdeps/unix/sysv/linux/x86_64/sigaction.c in the glibc (2.20) source. the c library's .br sigaction (2) wrapper function informs the kernel of the location of the trampoline code by placing its address in the .i sa_restorer field of the .i sigaction structure, and sets the .br sa_restorer flag in the .ir sa_flags field. .pp the saved process context information is placed in a .i ucontext_t structure (see .ir ). that structure is visible within the signal handler as the third argument of a handler established via .br sigaction (2) with the .br sa_siginfo flag. .pp on some other unix systems, the operation of the signal trampoline differs a little. in particular, on some systems, upon transitioning back to user mode, the kernel passes control to the trampoline (rather than the signal handler), and the trampoline code calls the signal handler (and then calls .br sigreturn () once the handler returns). .\" .ss c library/kernel differences the original linux system call was named .br sigreturn (). however, with the addition of real-time signals in linux 2.2, a new system call, .br rt_sigreturn () was added to support an enlarged .ir sigset_t type. the gnu c library hides these details from us, transparently employing .br rt_sigreturn () when the kernel provides it. .\" .sh see also .br kill (2), .br restart_syscall (2), .br sigaltstack (2), .br signal (2), .br getcontext (3), .br signal (7), .br vdso (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .so man3/malloc_hook.3 .\" %%%license_start(public_domain) .\" this page is in the public domain .\" %%%license_end .\" .th zdump 8 2020-04-27 "" "linux system administration" .sh name zdump \- timezone dumper .sh synopsis .b zdump [ .i option \&... ] [ .i timezone \&... ] .sh description .ie '\(lq'' .ds lq \&"\" .el .ds lq \(lq\" .ie '\(rq'' .ds rq \&"\" .el .ds rq \(rq\" .de q \\$3\*(lq\\$1\*(rq\\$2 .. .ie \n(.g .ds - \f(cw-\fp .el ds - \- the .b zdump program prints the current time in each .i timezone named on the command line. .sh options .tp .b \*-\*-version output version information and exit. .tp .b \*-\*-help output short usage message and exit. .tp .b \*-i output a description of time intervals. for each .i timezone on the command line, output an interval-format description of the timezone. see .q "interval format" below. .tp .b \*-v output a verbose description of time intervals. for each .i timezone on the command line, print the time at the lowest possible time value, the time one day after the lowest possible time value, the times both one second before and exactly at each detected time discontinuity, the time at one day less than the highest possible time value, and the time at the highest possible time value. each line is followed by .bi isdst= d where .i d is positive, zero, or negative depending on whether the given time is daylight saving time, standard time, or an unknown time type, respectively. each line is also followed by .bi gmtoff= n if the given local time is known to be .i n seconds east of greenwich. .tp .b \*-v like .br \*-v , except omit the times relative to the extreme time values. this generates output that is easier to compare to that of implementations with different time representations. .tp .bi "\*-c " \fr[\filoyear , \fr]\fihiyear cut off interval output at the given year(s). cutoff times are computed using the proleptic gregorian calendar with year 0 and with universal time (ut) ignoring leap seconds. cutoffs are at the start of each year, where the lower-bound timestamp is exclusive and the upper is inclusive; for example, .b "\*-c 1970,2070" selects transitions after 1970-01-01 00:00:00 utc and on or before 2070-01-01 00:00:00 utc. the default cutoff is .br \*-500,2500 . .tp .bi "\*-t " \fr[\filotime , \fr]\fihitime cut off interval output at the given time(s), given in decimal seconds since 1970-01-01 00:00:00 coordinated universal time (utc). the .i timezone determines whether the count includes leap seconds. as with .br \*-c , the cutoff's lower bound is exclusive and its upper bound is inclusive. .sh "interval format" the interval format is a compact text representation that is intended to be both human- and machine-readable. it consists of an empty line, then a line .q "tz=\fistring\fp" where .i string is a double-quoted string giving the timezone, a second line .q "\*- \*- \fiinterval\fp" describing the time interval before the first transition if any, and zero or more following lines .q "\fidate time interval\fp", one line for each transition time and following interval. fields are separated by single tabs. .pp dates are in .ir yyyy - mm - dd format and times are in 24-hour .ir hh : mm : ss format where .ir hh <24. times are in local time immediately after the transition. a time interval description consists of a ut offset in signed .ri \(+- hhmmss format, a time zone abbreviation, and an isdst flag. an abbreviation that equals the ut offset is omitted; other abbreviations are double-quoted strings unless they consist of one or more alphabetic characters. an isdst flag is omitted for standard time, and otherwise is a decimal integer that is unsigned and positive (typically 1) for daylight saving time and negative for unknown. .pp in times and in ut offsets with absolute value less than 100 hours, the seconds are omitted if they are zero, and the minutes are also omitted if they are also zero. positive ut offsets are east of greenwich. the ut offset \*-00 denotes a ut placeholder in areas where the actual offset is unspecified; by convention, this occurs when the ut offset is zero and the time zone abbreviation begins with .q "\*-" or is .q "zzz". .pp in double-quoted strings, escape sequences represent unusual characters. the escape sequences are \es for space, and \e", \e\e, \ef, \en, \er, \et, and \ev with their usual meaning in the c programming language. e.g., the double-quoted string \*(lq"cet\es\e"\e\e"\*(rq represents the character sequence \*(lqcet "\e\*(rq.\"" .pp .ne 9 here is an example of the output, with the leading empty line omitted. (this example is shown with tab stops set far enough apart so that the tabbed columns line up.) .nf .sp .if \n(.g .ft cw .if t .in +.5i .if n .in +2 .nr w \w'1896-01-13 'u+\n(.i .ta \w'1896-01-13 'u +\w'12:01:26 'u +\w'-103126 'u +\w'hwt 'u tz="pacific/honolulu" - - -103126 lmt 1896-01-13 12:01:26 -1030 hst 1933-04-30 03 -0930 hdt 1 1933-05-21 11 -1030 hst 1942-02-09 03 -0930 hwt 1 1945-08-14 13:30 -0930 hpt 1 1945-09-30 01 -1030 hst 1947-06-08 02:30 -10 hst .in .if \n(.g .ft .sp .fi here, local time begins 10 hours, 31 minutes and 26 seconds west of ut, and is a standard time abbreviated lmt. immediately after the first transition, the date is 1896-01-13 and the time is 12:01:26, and the following time interval is 10.5 hours west of ut, a standard time abbreviated hst. immediately after the second transition, the date is 1933-04-30 and the time is 03:00:00 and the following time interval is 9.5 hours west of ut, is abbreviated hdt, and is daylight saving time. immediately after the last transition the date is 1947-06-08 and the time is 02:30:00, and the following time interval is 10 hours west of ut, a standard time abbreviated hst. .pp .ne 10 here are excerpts from another example: .nf .sp .if \n(.g .ft cw .if t .in +.5i .if n .in +2 tz="europe/astrakhan" - - +031212 lmt 1924-04-30 23:47:48 +03 1930-06-21 01 +04 1981-04-01 01 +05 1 1981-09-30 23 +04 \&... 2014-10-26 01 +03 2016-03-27 03 +04 .in .if \n(.g .ft .sp .fi this time zone is east of ut, so its ut offsets are positive. also, many of its time zone abbreviations are omitted since they duplicate the text of the ut offset. .sh limitations time discontinuities are found by sampling the results returned by localtime at twelve-hour intervals. this works in all real-world cases; one can construct artificial time zones for which this fails. .pp in the .b \*-v and .b \*-v output, .q "ut" denotes the value returned by .br gmtime (3), which uses utc for modern timestamps and some other ut flavor for timestamps that predate the introduction of utc. no attempt is currently made to have the output use .q "utc" for newer and .q "ut" for older timestamps, partly because the exact date of the introduction of utc is problematic. .sh see also .br tzfile (5), .br zic (8) .\" this file is in the public domain, so clarified as of .\" 2009-05-17 by arthur david olson. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)fclose.3 6.7 (berkeley) 6/29/91 .\" .\" converted for linux, mon nov 29 15:19:14 1993, faith@cs.unc.edu .\" .\" modified 2000-07-22 by nicolás lichtmaier .\" .th fclose 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fclose \- close a stream .sh synopsis .nf .b #include .pp .bi "int fclose(file *" stream ); .fi .sh description the .br fclose () function flushes the stream pointed to by .i stream (writing any buffered output data using .br fflush (3)) and closes the underlying file descriptor. .sh return value upon successful completion, 0 is returned. otherwise, .b eof is returned and .i errno is set to indicate the error. in either case, any further access (including another call to .br fclose ()) to the stream results in undefined behavior. .sh errors .tp .b ebadf the file descriptor underlying .i stream is not valid. .\" this error cannot occur unless you are mixing ansi c stdio operations and .\" low-level file operations on the same stream. if you do get this error, .\" you must have closed the stream's low-level file descriptor using .\" something like close(fileno(stream)). .pp the .br fclose () function may also fail and set .i errno for any of the errors specified for the routines .br close (2), .br write (2), or .br fflush (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fclose () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. .sh notes note that .br fclose () flushes only the user-space buffers provided by the c library. to ensure that the data is physically stored on disk the kernel buffers must be flushed too, for example, with .br sync (2) or .br fsync (2). .sh see also .br close (2), .br fcloseall (3), .br fflush (3), .br fileno (3), .br fopen (3), .br setbuf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2012 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" see also https://lwn.net/articles/519085/ .\" .th getauxval 3 2021-08-27 "gnu" "linux programmer's manual" .sh name getauxval \- retrieve a value from the auxiliary vector .sh synopsis .nf .b #include .pp .bi "unsigned long getauxval(unsigned long " type ); .fi .sh description the .br getauxval () function retrieves values from the auxiliary vector, a mechanism that the kernel's elf binary loader uses to pass certain information to user space when a program is executed. .pp each entry in the auxiliary vector consists of a pair of values: a type that identifies what this entry represents, and a value for that type. given the argument .ir type , .br getauxval () returns the corresponding value. .pp the value returned for each .i type is given in the following list. not all .i type values are present on all architectures. .tp .br at_base the base address of the program interpreter (usually, the dynamic linker). .tp .br at_base_platform a pointer to a string (powerpc and mips only). on powerpc, this identifies the real platform; may differ from .br at_platform "." on mips, .\" commit e585b768da111f2c2d413de6214e83bbdfee8f22 this identifies the isa level (since linux 5.7). .tp .br at_clktck the frequency with which .br times (2) counts. this value can also be obtained via .ir sysconf(_sc_clk_tck) . .tp .br at_dcachebsize the data cache block size. .tp .br at_egid the effective group id of the thread. .tp .br at_entry the entry address of the executable. .tp .br at_euid the effective user id of the thread. .tp .br at_execfd file descriptor of program. .tp .br at_execfn a pointer to a string containing the pathname used to execute the program. .tp .br at_flags flags (unused). .tp .br at_fpucw used fpu control word (superh architecture only). this gives some information about the fpu initialization performed by the kernel. .tp .br at_gid the real group id of the thread. .tp .br at_hwcap an architecture and abi dependent bit-mask whose settings indicate detailed processor capabilities. the contents of the bit mask are hardware dependent (for example, see the kernel source file .ir arch/x86/include/asm/cpufeature.h for details relating to the intel x86 architecture; the value returned is the first 32-bit word of the array described there). a human-readable version of the same information is available via .ir /proc/cpuinfo . .tp .br at_hwcap2 " (since glibc 2.18)" further machine-dependent hints about processor capabilities. .tp .br at_icachebsize the instruction cache block size. .\" .tp .\" .br at_ignore .\" .tp .\" .br at_ignoreppc .\" .tp .\" .br at_notelf .tp .\" kernel commit 98a5f361b8625c6f4841d6ba013bbf0e80d08147 .br at_l1d_cachegeometry geometry of the l1 data cache, encoded with the cache line size in bytes in the bottom 16 bits and the cache associativity in the next 16 bits. the associativity is such that if n is the 16-bit value, the cache is n-way set associative. .tp .br at_l1d_cachesize the l1 data cache size. .tp .br at_l1i_cachegeometry geometry of the l1 instruction cache, encoded as for .br at_l1d_cachegeometry . .tp .br at_l1i_cachesize the l1 instruction cache size. .tp .br at_l2_cachegeometry geometry of the l2 cache, encoded as for .br at_l1d_cachegeometry . .tp .br at_l2_cachesize the l2 cache size. .tp .br at_l3_cachegeometry geometry of the l3 cache, encoded as for .br at_l1d_cachegeometry . .tp .br at_l3_cachesize the l3 cache size. .tp .br at_pagesz the system page size (the same value returned by .ir sysconf(_sc_pagesize) ). .tp .br at_phdr the address of the program headers of the executable. .tp .br at_phent the size of program header entry. .tp .br at_phnum the number of program headers. .tp .br at_platform a pointer to a string that identifies the hardware platform that the program is running on. the dynamic linker uses this in the interpretation of .ir rpath values. .tp .br at_random the address of sixteen bytes containing a random value. .tp .br at_secure has a nonzero value if this executable should be treated securely. most commonly, a nonzero value indicates that the process is executing a set-user-id or set-group-id binary (so that its real and effective uids or gids differ from one another), or that it gained capabilities by executing a binary file that has capabilities (see .br capabilities (7)). alternatively, a nonzero value may be triggered by a linux security module. when this value is nonzero, the dynamic linker disables the use of certain environment variables (see .br ld\-linux.so (8)) and glibc changes other aspects of its behavior. (see also .br secure_getenv (3).) .tp .br at_sysinfo the entry point to the system call function in the vdso. not present/needed on all architectures (e.g., absent on x86-64). .tp .br at_sysinfo_ehdr the address of a page containing the virtual dynamic shared object (vdso) that the kernel creates in order to provide fast implementations of certain system calls. .tp .br at_ucachebsize the unified cache block size. .tp .br at_uid the real user id of the thread. .sh return value on success, .br getauxval () returns the value corresponding to .ir type . if .i type is not found, 0 is returned. .sh errors .tp .br enoent " (since glibc 2.19)" .\" commit b9ab448f980e296eac21ac65f53783967cc6037b no entry corresponding to .ir type could be found in the auxiliary vector. .sh versions the .br getauxval () function was added to glibc in version 2.16. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getauxval () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a nonstandard glibc extension. .sh notes the primary consumer of the information in the auxiliary vector is the dynamic linker, .br ld\-linux.so (8). the auxiliary vector is a convenient and efficient shortcut that allows the kernel to communicate a certain set of standard information that the dynamic linker usually or always needs. in some cases, the same information could be obtained by system calls, but using the auxiliary vector is cheaper. .pp the auxiliary vector resides just above the argument list and environment in the process address space. the auxiliary vector supplied to a program can be viewed by setting the .b ld_show_auxv environment variable when running a program: .pp .in +4n .ex $ ld_show_auxv=1 sleep 1 .ee .in .pp the auxiliary vector of any process can (subject to file permissions) be obtained via .ir /proc/[pid]/auxv ; see .br proc (5) for more information. .sh bugs before the addition of the .b enoent error in glibc 2.19, there was no way to unambiguously distinguish the case where .i type could not be found from the case where the value corresponding to .i type was zero. .sh see also .br execve (2), .br secure_getenv (3), .br vdso (7), .br ld\-linux.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-13.7 .\" copyright 1995 yggdrasil computing, incorporated. .\" written by adam j. richter (adam@yggdrasil.com), .\" with typesetting help from daniel quinlan (quinlan@yggdrasil.com). .\" and copyright 2003, 2015 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified by david a. wheeler 2000-11-28. .\" applied patch by terran melconian, aeb, 2001-12-14. .\" modified by hacksaw 2003-03-13. .\" modified by matt domsch, 2003-04-09: _init and _fini obsolete .\" modified by michael kerrisk 2003-05-16. .\" modified by walter harms: dladdr, dlvsym .\" modified by petr baudis , 2008-12-04: dladdr caveat .\" .th dlopen 3 2021-03-22 "linux" "linux programmer's manual" .sh name dlclose, dlopen, dlmopen \- open and close a shared object .sh synopsis .nf .b #include .pp .bi "void *dlopen(const char *" filename ", int " flags ); .bi "int dlclose(void *" handle ); .pp .b #define _gnu_source .br .b #include .pp .bi "void *dlmopen(lmid_t " lmid ", const char *" filename ", int " flags ); .fi .pp link with \fi\-ldl\fp. .sh description .ss dlopen() the function .br dlopen () loads the dynamic shared object (shared library) file named by the null-terminated string .i filename and returns an opaque "handle" for the loaded object. this handle is employed with other functions in the dlopen api, such as .br dlsym (3), .br dladdr (3), .br dlinfo (3), and .br dlclose (). .pp if .i filename .\" fixme on solaris, when handle is null, we seem to get back .\" a handle for (something like) the root of the namespace. .\" the point here is that if we do a dlmopen(lm_id_newlm), then .\" the filename==null case returns a different handle than .\" in the initial namespace. but, on glibc, the same handle is .\" returned. this is probably a bug in glibc. .\" is null, then the returned handle is for the main program. if .i filename contains a slash ("/"), then it is interpreted as a (relative or absolute) pathname. otherwise, the dynamic linker searches for the object as follows (see .br ld.so (8) for further details): .ip o 4 (elf only) if the calling object (i.e., the shared library or executable from which .br dlopen () is called) contains a dt_rpath tag, and does not contain a dt_runpath tag, then the directories listed in the dt_rpath tag are searched. .ip o if, at the time that the program was started, the environment variable .b ld_library_path was defined to contain a colon-separated list of directories, then these are searched. (as a security measure, this variable is ignored for set-user-id and set-group-id programs.) .ip o (elf only) if the calling object contains a dt_runpath tag, then the directories listed in that tag are searched. .ip o the cache file .i /etc/ld.so.cache (maintained by .br ldconfig (8)) is checked to see whether it contains an entry for .ir filename . .ip o the directories .i /lib and .i /usr/lib are searched (in that order). .pp if the object specified by .i filename has dependencies on other shared objects, then these are also automatically loaded by the dynamic linker using the same rules. (this process may occur recursively, if those objects in turn have dependencies, and so on.) .pp one of the following two values must be included in .ir flags : .tp .b rtld_lazy perform lazy binding. resolve symbols only as the code that references them is executed. if the symbol is never referenced, then it is never resolved. (lazy binding is performed only for function references; references to variables are always immediately bound when the shared object is loaded.) since glibc 2.1.1, .\" commit 12b5b6b7f78ea111e89bbf638294a5413c791072 this flag is overridden by the effect of the .b ld_bind_now environment variable. .tp .b rtld_now if this value is specified, or the environment variable .b ld_bind_now is set to a nonempty string, all undefined symbols in the shared object are resolved before .br dlopen () returns. if this cannot be done, an error is returned. .pp zero or more of the following values may also be ored in .ir flags : .tp .b rtld_global the symbols defined by this shared object will be made available for symbol resolution of subsequently loaded shared objects. .tp .b rtld_local this is the converse of .br rtld_global , and the default if neither flag is specified. symbols defined in this shared object are not made available to resolve references in subsequently loaded shared objects. .tp .br rtld_nodelete " (since glibc 2.2)" do not unload the shared object during .br dlclose (). consequently, the object's static and global variables are not reinitialized if the object is reloaded with .br dlopen () at a later time. .tp .br rtld_noload " (since glibc 2.2)" don't load the shared object. this can be used to test if the object is already resident .rb ( dlopen () returns null if it is not, or the object's handle if it is resident). this flag can also be used to promote the flags on a shared object that is already loaded. for example, a shared object that was previously loaded with .b rtld_local can be reopened with .br rtld_noload\ |\ rtld_global . .\" .tp .br rtld_deepbind " (since glibc 2.3.4)" .\" inimitably described by ud in .\" http://sources.redhat.com/ml/libc-hacker/2004-09/msg00083.html. place the lookup scope of the symbols in this shared object ahead of the global scope. this means that a self-contained object will use its own symbols in preference to global symbols with the same name contained in objects that have already been loaded. .pp if .i filename is null, then the returned handle is for the main program. when given to .br dlsym (3), this handle causes a search for a symbol in the main program, followed by all shared objects loaded at program startup, and then all shared objects loaded by .br dlopen () with the flag .br rtld_global . .pp symbol references in the shared object are resolved using (in order): symbols in the link map of objects loaded for the main program and its dependencies; symbols in shared objects (and their dependencies) that were previously opened with .br dlopen () using the .br rtld_global flag; and definitions in the shared object itself (and any dependencies that were loaded for that object). .pp any global symbols in the executable that were placed into its dynamic symbol table by .br ld (1) can also be used to resolve references in a dynamically loaded shared object. symbols may be placed in the dynamic symbol table either because the executable was linked with the flag "\-rdynamic" (or, synonymously, "\-\-export\-dynamic"), which causes all of the executable's global symbols to be placed in the dynamic symbol table, or because .br ld (1) noted a dependency on a symbol in another object during static linking. .pp if the same shared object is opened again with .br dlopen (), the same object handle is returned. the dynamic linker maintains reference counts for object handles, so a dynamically loaded shared object is not deallocated until .br dlclose () has been called on it as many times as .br dlopen () has succeeded on it. constructors (see below) are called only when the object is actually loaded into memory (i.e., when the reference count increases to 1). .pp a subsequent .br dlopen () call that loads the same shared object with .b rtld_now may force symbol resolution for a shared object earlier loaded with .br rtld_lazy . similarly, an object that was previously opened with .br rtld_local can be promoted to .br rtld_global in a subsequent .br dlopen (). .pp if .br dlopen () fails for any reason, it returns null. .\" .ss dlmopen() this function performs the same task as .br dlopen ()\(emthe .i filename and .i flags arguments, as well as the return value, are the same, except for the differences noted below. .pp the .br dlmopen () function differs from .br dlopen () primarily in that it accepts an additional argument, .ir lmid , that specifies the link-map list (also referred to as a .ir namespace ) in which the shared object should be loaded. (by comparison, .br dlopen () adds the dynamically loaded shared object to the same namespace as the shared object from which the .br dlopen () call is made.) the .i lmid_t type is an opaque handle that refers to a namespace. .pp the .i lmid argument is either the id of an existing namespace .\" fixme: is using dlinfo() rtld_di_lmid the right technique? (which can be obtained using the .br dlinfo (3) .b rtld_di_lmid request) or one of the following special values: .tp .b lm_id_base load the shared object in the initial namespace (i.e., the application's namespace). .tp .b lm_id_newlm create a new namespace and load the shared object in that namespace. the object must have been correctly linked to reference all of the other shared objects that it requires, since the new namespace is initially empty. .pp if .i filename is null, then the only permitted value for .i lmid is .br lm_id_base . .ss dlclose() the function .br dlclose () decrements the reference count on the dynamically loaded shared object referred to by .ir handle . .pp if the object's reference count drops to zero and no symbols in this object are required by other objects, then the object is unloaded after first calling any destructors defined for the object. (symbols in this object might be required in another object because this object was opened with the .br rtld_global flag and one of its symbols satisfied a relocation in another object.) .pp all shared objects that were automatically loaded when .br dlopen () was invoked on the object referred to by .i handle are recursively closed in the same manner. .pp a successful return from .br dlclose () does not guarantee that the symbols associated with .i handle are removed from the caller's address space. in addition to references resulting from explicit .br dlopen () calls, a shared object may have been implicitly loaded (and reference counted) because of dependencies in other shared objects. only when all references have been released can the shared object be removed from the address space. .sh return value on success, .br dlopen () and .br dlmopen () return a non-null handle for the loaded object. on error (file could not be found, was not readable, had the wrong format, or caused errors during loading), these functions return null. .pp on success, .br dlclose () returns 0; on error, it returns a nonzero value. .pp errors from these functions can be diagnosed using .br dlerror (3). .sh versions .br dlopen () and .br dlclose () are present in glibc 2.0 and later. .br dlmopen () first appeared in glibc 2.3.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dlopen (), .br dlmopen (), .br dlclose () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001 describes .br dlclose () and .br dlopen (). the .br dlmopen () function is a gnu extension. .pp the .br rtld_noload , .br rtld_nodelete , and .br rtld_deepbind flags are gnu extensions; the first two of these flags are also present on solaris. .sh notes .ss dlmopen() and namespaces a link-map list defines an isolated namespace for the resolution of symbols by the dynamic linker. within a namespace, dependent shared objects are implicitly loaded according to the usual rules, and symbol references are likewise resolved according to the usual rules, but such resolution is confined to the definitions provided by the objects that have been (explicitly and implicitly) loaded into the namespace. .pp the .br dlmopen () function permits object-load isolation\(emthe ability to load a shared object in a new namespace without exposing the rest of the application to the symbols made available by the new object. note that the use of the .b rtld_local flag is not sufficient for this purpose, since it prevents a shared object's symbols from being available to .i any other shared object. in some cases, we may want to make the symbols provided by a dynamically loaded shared object available to (a subset of) other shared objects without exposing those symbols to the entire application. this can be achieved by using a separate namespace and the .b rtld_global flag. .pp the .br dlmopen () function also can be used to provide better isolation than the .br rtld_local flag. in particular, shared objects loaded with .br rtld_local may be promoted to .br rtld_global if they are dependencies of another shared object loaded with .br rtld_global . thus, .br rtld_local is insufficient to isolate a loaded shared object except in the (uncommon) case where one has explicit control over all shared object dependencies. .pp possible uses of .br dlmopen () are plugins where the author of the plugin-loading framework can't trust the plugin authors and does not wish any undefined symbols from the plugin framework to be resolved to plugin symbols. another use is to load the same object more than once. without the use of .br dlmopen (), this would require the creation of distinct copies of the shared object file. using .br dlmopen (), this can be achieved by loading the same shared object file into different namespaces. .pp the glibc implementation supports a maximum of .\" dl_nns 16 namespaces. .\" .ss initialization and finalization functions shared objects may export functions using the .b __attribute__((constructor)) and .b __attribute__((destructor)) function attributes. constructor functions are executed before .br dlopen () returns, and destructor functions are executed before .br dlclose () returns. a shared object may export multiple constructors and destructors, and priorities can be associated with each function to determine the order in which they are executed. see the .br gcc info pages (under "function attributes") .\" info gcc "c extensions" "function attributes" for further information. .pp an older method of (partially) achieving the same result is via the use of two special symbols recognized by the linker: .b _init and .br _fini . if a dynamically loaded shared object exports a routine named .br _init (), then that code is executed after loading a shared object, before .br dlopen () returns. if the shared object exports a routine named .br _fini (), then that routine is called just before the object is unloaded. in this case, one must avoid linking against the system startup files, which contain default versions of these files; this can be done by using the .br gcc (1) .i \-nostartfiles command-line option. .pp use of .b _init and .br _fini is now deprecated in favor of the aforementioned constructors and destructors, which among other advantages, permit multiple initialization and finalization functions to be defined. .\" .\" using these routines, or the gcc .\" .b \-nostartfiles .\" or .\" .b \-nostdlib .\" options, is not recommended. .\" their use may result in undesired behavior, .\" since the constructor/destructor routines will not be executed .\" (unless special measures are taken). .\" .\" void _init(void) __attribute__((constructor)); .\" .\" void _fini(void) __attribute__((destructor)); .\" .pp since glibc 2.2.3, .br atexit (3) can be used to register an exit handler that is automatically called when a shared object is unloaded. .ss history these functions are part of the dlopen api, derived from sunos. .sh bugs as at glibc 2.24, specifying the .br rtld_global flag when calling .br dlmopen () .\" dlerror(): "invalid mode" generates an error. furthermore, specifying .br rtld_global when calling .br dlopen () results in a program crash .rb ( sigsegv ) .\" https://sourceware.org/bugzilla/show_bug.cgi?id=18684 if the call is made from any object loaded in a namespace other than the initial namespace. .sh examples the program below loads the (glibc) math library, looks up the address of the .br cos (3) function, and prints the cosine of 2.0. the following is an example of building and running the program: .pp .in +4n .ex $ \fbcc dlopen_demo.c \-ldl\fp $ \fb./a.out\fp \-0.416147 .ee .in .ss program source \& .ex #include #include #include #include /* defines libm_so (which will be a string such as "libm.so.6") */ int main(void) { void *handle; double (*cosine)(double); char *error; handle = dlopen(libm_so, rtld_lazy); if (!handle) { fprintf(stderr, "%s\en", dlerror()); exit(exit_failure); } dlerror(); /* clear any existing error */ cosine = (double (*)(double)) dlsym(handle, "cos"); /* according to the iso c standard, casting between function pointers and \(aqvoid *\(aq, as done above, produces undefined results. posix.1\-2001 and posix.1\-2008 accepted this state of affairs and proposed the following workaround: *(void **) (&cosine) = dlsym(handle, "cos"); this (clumsy) cast conforms with the iso c standard and will avoid any compiler warnings. the 2013 technical corrigendum 1 to posix.1\-2008 improved matters by requiring that conforming implementations support casting \(aqvoid *\(aq to a function pointer. nevertheless, some compilers (e.g., gcc with the \(aq\-pedantic\(aq option) may complain about the cast used in this program. */ .\" http://pubs.opengroup.org/onlinepubs/009695399/functions/dlsym.html#tag_03_112_08 .\" http://pubs.opengroup.org/onlinepubs/9699919799/functions/dlsym.html#tag_16_96_07 .\" http://austingroupbugs.net/view.php?id=74 error = dlerror(); if (error != null) { fprintf(stderr, "%s\en", error); exit(exit_failure); } printf("%f\en", (*cosine)(2.0)); dlclose(handle); exit(exit_success); } .ee .sh see also .br ld (1), .br ldd (1), .br pldd (1), .br dl_iterate_phdr (3), .br dladdr (3), .br dlerror (3), .br dlinfo (3), .br dlsym (3), .br rtld\-audit (7), .br ld.so (8), .br ldconfig (8) .pp gcc info pages, ld info pages .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-2.7 .\" copyright (c) 2020 stephen kitt .\" and copyright (c) 2021 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th close_range 2 2021-08-27 "linux" "linux programmer's manual" .sh name close_range \- close all file descriptors in a given range .sh synopsis .nf .b #include .pp .bi "int close_range(unsigned int " first ", unsigned int " last , .bi " unsigned int " flags ); .fi .sh description the .br close_range () system call closes all open file descriptors from .i first to .i last (included). .pp errors closing a given file descriptor are currently ignored. .pp .i flags is a bit mask containing 0 or more of the following: .tp .br close_range_cloexec " (since linux 5.11)" set the close-on-exec flag on the specified file descriptors, rather than immediately closing them. .tp .b close_range_unshare unshare the specified file descriptors from any other processes before closing them, avoiding races with other threads sharing the file descriptor table. .sh return value on success, .br close_range () returns 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b einval .i flags is not valid, or .i first is greater than .ir last . .pp the following can occur with .b close_range_unshare (when constructing the new descriptor table): .tp .b emfile the number of open file descriptors exceeds the limit specified in .ir /proc/sys/fs/nr_open (see .br proc (5)). this error can occur in situations where that limit was lowered before a call to .br close_range () where the .b close_range_unshare flag is specified. .tp .b enomem insufficient kernel memory was available. .sh versions .br close_range () first appeared in linux 5.9. library support was added in glibc in version 2.34. .sh conforming to .br close_range () is a nonstandard function that is also present on freebsd. .sh notes .ss closing all open file descriptors .\" 278a5fbaed89dacd04e9d052f4594ffd0e0585de to avoid blindly closing file descriptors in the range of possible file descriptors, this is sometimes implemented (on linux) by listing open file descriptors in .i /proc/self/fd/ and calling .br close (2) on each one. .br close_range () can take care of this without requiring .i /proc and within a single system call, which provides significant performance benefits. .ss closing file descriptors before exec .\" 60997c3d45d9a67daf01c56d805ae4fec37e0bd8 file descriptors can be closed safely using .pp .in +4n .ex /* we don't want anything past stderr here */ close_range(3, ~0u, close_range_unshare); execve(....); .ee .in .pp .b close_range_unshare is conceptually equivalent to .pp .in +4n .ex unshare(clone_files); close_range(first, last, 0); .ee .in .pp but can be more efficient: if the unshared range extends past the current maximum number of file descriptors allocated in the caller's file descriptor table (the common case when .i last is ~0u), the kernel will unshare a new file descriptor table for the caller up to .ir first , copying as few file descriptors as possible. this avoids subsequent .br close (2) calls entirely; the whole operation is complete once the table is unshared. .ss closing files on \fbexec\fp .\" 582f1fb6b721facf04848d2ca57f34468da1813e this is particularly useful in cases where multiple .rb pre- exec setup steps risk conflicting with each other. for example, setting up a .br seccomp (2) profile can conflict with a .br close_range () call: if the file descriptors are closed before the .br seccomp (2) profile is set up, the profile setup can't use them itself, or control their closure; if the file descriptors are closed afterwards, the seccomp profile can't block the .br close_range () call or any fallbacks. using .b close_range_cloexec avoids this: the descriptors can be marked before the .br seccomp (2) profile is set up, and the profile can control access to .br close_range () without affecting the calling process. .sh examples the program shown below opens the files named in its command-line arguments, displays the list of files that it has opened (by iterating through the entries in .ir /proc/pid/fd ), uses .br close_range () to close all file descriptors greater than or equal to 3, and then once more displays the process's list of open files. the following example demonstrates the use of the program: .pp .in +4n .ex $ \fbtouch /tmp/a /tmp/b /tmp/c\fp $ \fb./a.out /tmp/a /tmp/b /tmp/c\fp /tmp/a opened as fd 3 /tmp/b opened as fd 4 /tmp/c opened as fd 5 /proc/self/fd/0 ==> /dev/pts/1 /proc/self/fd/1 ==> /dev/pts/1 /proc/self/fd/2 ==> /dev/pts/1 /proc/self/fd/3 ==> /tmp/a /proc/self/fd/4 ==> /tmp/b /proc/self/fd/5 ==> /tmp/b /proc/self/fd/6 ==> /proc/9005/fd ========= about to call close_range() ======= /proc/self/fd/0 ==> /dev/pts/1 /proc/self/fd/1 ==> /dev/pts/1 /proc/self/fd/2 ==> /dev/pts/1 /proc/self/fd/3 ==> /proc/9005/fd .ee .in .pp note that the lines showing the pathname .i /proc/9005/fd result from the calls to .br opendir (3). .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include #include #include /* show the contents of the symbolic links in /proc/self/fd */ static void show_fds(void) { dir *dirp = opendir("/proc/self/fd"); if (dirp == null) { perror("opendir"); exit(exit_failure); } for (;;) { struct dirent *dp = readdir(dirp); if (dp == null) break; if (dp\->d_type == dt_lnk) { char path[path_max], target[path_max]; snprintf(path, sizeof(path), "/proc/self/fd/%s", dp\->d_name); ssize_t len = readlink(path, target, sizeof(target)); printf("%s ==> %.*s\en", path, (int) len, target); } } closedir(dirp); } int main(int argc, char *argv[]) { for (int j = 1; j < argc; j++) { int fd = open(argv[j], o_rdonly); if (fd == \-1) { perror(argv[j]); exit(exit_failure); } printf("%s opened as fd %d\en", argv[j], fd); } show_fds(); printf("========= about to call close_range() =======\en"); if (syscall(__nr_close_range, 3, \(ti0u, 0) == \-1) { perror("close_range"); exit(exit_failure); } show_fds(); exit(exit_failure); } .ee .sh see also .br close (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sigset.3 .so man3/fmod.3 .so man3/toupper.3 .so man3/sigset.3 .so man3/getspnam.3 .so man3/lgamma.3 .\" copyright 2001 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th lround 3 2021-03-22 "" "linux programmer's manual" .sh name lround, lroundf, lroundl, llround, llroundf, llroundl \- round to nearest integer .sh synopsis .nf .b #include .pp .bi "long lround(double " x ); .bi "long lroundf(float " x ); .bi "long lroundl(long double " x ); .pp .bi "long long llround(double " x ); .bi "long long llroundf(float " x ); .bi "long long llroundl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions round their argument to the nearest integer value, rounding halfway cases away from zero, regardless of the current rounding direction (see .br fenv (3)). .pp note that unlike the .br round (3) and .br ceil (3), functions, the return type of these functions differs from that of their arguments. .sh return value these functions return the rounded integer value. .pp if .i x is a nan or an infinity, or the rounded value is too large to be stored in a .i long .ri ( "long long" in the case of the .b ll* functions), then a domain error occurs, and the return value is unspecified. .\" the return value is -(long_max - 1) or -(llong_max -1) .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is a nan or infinite, or the rounded value is too large .\" .i errno .\" is set to .\" .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .pp these functions do not set .ir errno . .\" fixme . is it intentional that these functions do not set errno? .\" bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6797 .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br lround (), .br lroundf (), .br lroundl (), .br llround (), .br llroundf (), .br llroundl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br ceil (3), .br floor (3), .br lrint (3), .br nearbyint (3), .br rint (3), .br round (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:51:06 1993 by rik faith (faith@cs.unc.edu) .th ctermid 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ctermid \- get controlling terminal name .sh synopsis .nf .b #include .\" posix also requires this function to be declared in , .\" and glibc does so if suitable feature test macros are defined. .pp .bi "char *ctermid(char *" "s" ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br ctermid (): .nf _posix_c_source .fi .sh description .br ctermid () returns a string which is the pathname for the current controlling terminal for this process. if .i s is null, a static buffer is used, otherwise .i s points to a buffer used to hold the terminal pathname. the symbolic constant .b l_ctermid is the maximum number of characters in the returned pathname. .sh return value the pointer to the pathname. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ctermid () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh bugs the returned pathname may not uniquely identify the controlling terminal; it may, for example, be .ir /dev/tty . .pp it is not assured that the program can open the terminal. .\" in glibc 2.3.x, x >= 4, the glibc headers threw an error .\" if ctermid() was given an argument; fixed in 2.4. .sh see also .br ttyname (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 2006 jens axboe .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th tee 2 2020-06-09 "linux" "linux programmer's manual" .sh name tee \- duplicating pipe content .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "ssize_t tee(int " fd_in ", int " fd_out ", size_t " len \ ", unsigned int " flags ); .fi .\" return type was long before glibc 2.7 .sh description .\" example programs http://brick.kernel.dk/snaps .\" .\" .\" add a "tee(in, out1, out2)" system call that duplicates the pages .\" (again, incrementing their reference count, not copying the data) from .\" one pipe to two other pipes. .br tee () duplicates up to .i len bytes of data from the pipe referred to by the file descriptor .i fd_in to the pipe referred to by the file descriptor .ir fd_out . it does not consume the data that is duplicated from .ir fd_in ; therefore, that data can be copied by a subsequent .br splice (2). .pp .i flags is a bit mask that is composed by oring together zero or more of the following values: .tp 1.9i .b splice_f_move currently has no effect for .br tee (); see .br splice (2). .tp .b splice_f_nonblock do not block on i/o; see .br splice (2) for further details. .tp .b splice_f_more currently has no effect for .br tee (), but may be implemented in the future; see .br splice (2). .tp .b splice_f_gift unused for .br tee (); see .br vmsplice (2). .sh return value upon successful completion, .br tee () returns the number of bytes that were duplicated between the input and output. a return value of 0 means that there was no data to transfer, and it would not make sense to block, because there are no writers connected to the write end of the pipe referred to by .ir fd_in . .pp on error, .br tee () returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b eagain .b splice_f_nonblock was specified in .ir flags or one of the file descriptors had been marked as nonblocking .rb ( o_nonblock ) , and the operation would block. .tp .b einval .i fd_in or .i fd_out does not refer to a pipe; or .i fd_in and .i fd_out refer to the same pipe. .tp .b enomem out of memory. .sh versions the .br tee () system call first appeared in linux 2.6.17; library support was added to glibc in version 2.5. .sh conforming to this system call is linux-specific. .sh notes conceptually, .br tee () copies the data between the two pipes. in reality no real data copying takes place though: under the covers, .br tee () assigns data to the output by merely grabbing a reference to the input. .sh examples the example below implements a basic .br tee (1) program using the .br tee () system call. here is an example of its use: .pp .in +4n .ex $ \fbdate |./a.out out.log | cat\fp tue oct 28 10:06:00 cet 2014 $ \fbcat out.log\fp tue oct 28 10:06:00 cet 2014 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include int main(int argc, char *argv[]) { int fd; int len, slen; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } fd = open(argv[1], o_wronly | o_creat | o_trunc, 0644); if (fd == \-1) { perror("open"); exit(exit_failure); } do { /* * tee stdin to stdout. */ len = tee(stdin_fileno, stdout_fileno, int_max, splice_f_nonblock); if (len < 0) { if (errno == eagain) continue; perror("tee"); exit(exit_failure); } else if (len == 0) break; /* * consume stdin by splicing it to a file. */ while (len > 0) { slen = splice(stdin_fileno, null, fd, null, len, splice_f_move); if (slen < 0) { perror("splice"); break; } len \-= slen; } } while (1); close(fd); exit(exit_success); } .ee .sh see also .br splice (2), .br vmsplice (2), .br pipe (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gethostbyname.3 .so man3/memchr.3 .so man2/getxattr.2 .so man3/rint.3 .\" copyright (c) 2013, peter schiffer .\" and copyright (c) 2014, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th memusage 1 2021-03-22 "gnu" "linux user manual" .sh name memusage \- profile memory usage of a program .sh synopsis .nf .br memusage " [\fioption\fr]... \fiprogram\fr [\fiprogramoption\fr]..." .fi .sh description .b memusage is a bash script which profiles memory usage of the program, .ir program . it preloads the .b libmemusage.so library into the caller's environment (via the .b ld_preload environment variable; see .br ld.so (8)). the .b libmemusage.so library traces memory allocation by intercepting calls to .br malloc (3), .br calloc (3), .br free (3), and .br realloc (3); optionally, calls to .br mmap (2), .br mremap (2), and .br munmap (2) can also be intercepted. .pp .b memusage can output the collected data in textual form, or it can use .br memusagestat (1) (see the .b \-p option, below) to create a png file containing graphical representation of the collected data. .ss memory usage summary the "memory usage summary" line output by .b memusage contains three fields: .rs 4 .tp \fbheap total\fr sum of \fisize\fr arguments of all .br malloc (3) calls, products of arguments (\finmemb\fr*\fisize\fr) of all .br calloc (3) calls, and sum of \filength\fr arguments of all .br mmap (2) calls. in the case of .br realloc (3) and .br mremap (2), if the new size of an allocation is larger than the previous size, the sum of all such differences (new size minus old size) is added. .tp .b "heap peak" maximum of all \fisize\fr arguments of .br malloc (3), all products of \finmemb\fr*\fisize\fr of .br calloc (3), all \fisize\fr arguments of .br realloc (3), .i length arguments of .br mmap (2), and \finew_size\fr arguments of .br mremap (2). .tp .b "stack peak" before the first call to any monitored function, the stack pointer address (base stack pointer) is saved. after each function call, the actual stack pointer address is read and the difference from the base stack pointer computed. the maximum of these differences is then the stack peak. .re .pp immediately following this summary line, a table shows the number calls, total memory allocated or deallocated, and number of failed calls for each intercepted function. for .br realloc (3) and .br mremap (2), the additional field "nomove" shows reallocations that changed the address of a block, and the additional "dec" field shows reallocations that decreased the size of the block. for .br realloc (3), the additional field "free" shows reallocations that caused a block to be freed (i.e., the reallocated size was 0). .pp the "realloc/total memory" of the table output by .b memusage does not reflect cases where .br realloc (3) is used to reallocate a block of memory to have a smaller size than previously. this can cause sum of all "total memory" cells (excluding "free") to be larger than the "free/total memory" cell. .ss histogram for block sizes the "histogram for block sizes" provides a breakdown of memory allocations into various bucket sizes. .sh options .tp .bi \-n\ name \fr,\ \fb\-\-progname= name name of the program file to profile. .tp .bi \-p\ file \fr,\ \fb\-\-png= file generate png graphic and store it in .ir file . .tp .bi \-d\ file \fr,\ \fb\-\-data= file generate binary data file and store it in .ir file . .tp .b \-u\fr,\ \fb\-\-unbuffered do not buffer output. .tp .bi \-b\ size \fr,\ \fb\-\-buffer= size collect .i size entries before writing them out. .tp .b \-\-no\-timer disable timer-based .rb ( sigprof ) sampling of stack pointer value. .tp .b \-m\fr,\ \fb\-\-mmap also trace .br mmap (2), .br mremap (2), and .br munmap (2). .tp .b \-?\fr,\ \fb\-\-help print help and exit. .tp .b \-\-usage print a short usage message and exit. .tp .b \-v\fr,\ \fb\-\-version print version information and exit. .tp the following options apply only when generating graphical output: .tp .b \-t\fr,\ \fb\-\-time\-based use time (rather than number of function calls) as the scale for the x axis. .tp .b \-t\fr,\ \fb\-\-total also draw a graph of total memory use. .tp .bi \fb\-\-title= name use .i name as the title of the graph. .tp .bi \-x\ size \fr,\ \fb\-\-x\-size= size make the graph .i size pixels wide. .tp .bi \-y\ size \fr,\ \fb\-\-y\-size= size make the graph .i size pixels high. .sh exit status the exit status of .br memusage is equal to the exit status of the profiled program. .sh bugs to report bugs, see .ur http://www.gnu.org/software/libc/bugs.html .ue .sh examples below is a simple program that reallocates a block of memory in cycles that rise to a peak before then cyclically reallocating the memory in smaller blocks that return to zero. after compiling the program and running the following commands, a graph of the memory usage of the program can be found in the file .ir memusage.png : .pp .in +4n .ex $ \fbmemusage \-\-data=memusage.dat ./a.out\fp \&... memory usage summary: heap total: 45200, heap peak: 6440, stack peak: 224 total calls total memory failed calls malloc| 1 400 0 realloc| 40 44800 0 (nomove:40, dec:19, free:0) calloc| 0 0 0 free| 1 440 histogram for block sizes: 192\-207 1 2% ================ \&... 2192\-2207 1 2% ================ 2240\-2255 2 4% ================================= 2832\-2847 2 4% ================================= 3440\-3455 2 4% ================================= 4032\-4047 2 4% ================================= 4640\-4655 2 4% ================================= 5232\-5247 2 4% ================================= 5840\-5855 2 4% ================================= 6432\-6447 1 2% ================ $ \fbmemusagestat memusage.dat memusage.png\fp .ee .in .ss program source .ex #include #include #define cycles 20 int main(int argc, char *argv[]) { int i, j; size_t size; int *p; size = sizeof(*p) * 100; printf("malloc: %zu\en", size); p = malloc(size); for (i = 0; i < cycles; i++) { if (i < cycles / 2) j = i; else j\-\-; size = sizeof(*p) * (j * 50 + 110); printf("realloc: %zu\en", size); p = realloc(p, size); size = sizeof(*p) * ((j + 1) * 150 + 110); printf("realloc: %zu\en", size); p = realloc(p, size); } free(p); exit(exit_success); } .ee .sh see also .br memusagestat (1), .br mtrace (1), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .so man7/system_data_types.7 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th mbsnrtowcs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mbsnrtowcs \- convert a multibyte string to a wide-character string .sh synopsis .nf .b #include .pp .bi "size_t mbsnrtowcs(wchar_t *restrict " dest ", const char **restrict " src , .bi " size_t " nms ", size_t " len \ ", mbstate_t *restrict " ps ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mbsnrtowcs (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br mbsnrtowcs () function is like the .br mbsrtowcs (3) function, except that the number of bytes to be converted, starting at .ir *src , is limited to at most .ir nms bytes. .pp if .i dest is not null, the .br mbsnrtowcs () function converts at most .i nms bytes from the multibyte string .i *src to a wide-character string starting at .ir dest . at most .i len wide characters are written to .ir dest . the shift state .i *ps is updated. the conversion is effectively performed by repeatedly calling .i "mbrtowc(dest, *src, n, ps)" where .i n is some positive number, as long as this call succeeds, and then incrementing .i dest by one and .i *src by the number of bytes consumed. the conversion can stop for three reasons: .ip 1. 3 an invalid multibyte sequence has been encountered. in this case, .i *src is left pointing to the invalid multibyte sequence, .i (size_t)\ \-1 is returned, and .i errno is set to .br eilseq . .ip 2. the .i nms limit forces a stop, or .i len non-l\(aq\e0\(aq wide characters have been stored at .ir dest . in this case, .i *src is left pointing to the next multibyte sequence to be converted, and the number of wide characters written to .i dest is returned. .ip 3. the multibyte string has been completely converted, including the terminating null wide character (\(aq\e0\(aq) (which has the side effect of bringing back .i *ps to the initial state). in this case, .i *src is set to null, and the number of wide characters written to .ir dest , excluding the terminating null wide character, is returned. .pp according to posix.1, if the input buffer ends with an incomplete character, it is unspecified whether conversion stops at the end of the previous character (if any), or at the end of the input buffer. the glibc implementation adopts the former behavior. .pp if .ir dest is null, .i len is ignored, and the conversion proceeds as above, except that the converted wide characters are not written out to memory, and that no destination length limit exists. .pp in both of the above cases, if .i ps is null, a static anonymous state known only to the .br mbsnrtowcs () function is used instead. .pp the programmer must ensure that there is room for at least .i len wide characters at .ir dest . .sh return value the .br mbsnrtowcs () function returns the number of wide characters that make up the converted part of the wide-character string, not including the terminating null wide character. if an invalid multibyte sequence was encountered, .i (size_t)\ \-1 is returned, and .i errno set to .br eilseq . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br mbsnrtowcs () t} thread safety t{ mt-unsafe race:mbsnrtowcs/!ps t} .te .hy .ad .sp 1 .sh conforming to posix.1-2008. .sh notes the behavior of .br mbsnrtowcs () depends on the .b lc_ctype category of the current locale. .pp passing null as .i ps is not multithread safe. .sh see also .br iconv (3), .br mbrtowc (3), .br mbsinit (3), .br mbsrtowcs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2009-2015 michael kerrisk, .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 00:06:00 1993 by rik faith .\" modified wed jan 17 16:02:32 1996 by michael haardt .\" .\" modified thu apr 11 19:26:35 1996 by andries brouwer .\" modified sun jul 21 18:59:33 1996 by andries brouwer .\" modified fri jan 31 16:47:33 1997 by eric s. raymond .\" modified sat jul 12 20:45:39 1997 by michael haardt .\" .\" .th read 2 2021-03-22 "linux" "linux programmer's manual" .sh name read \- read from a file descriptor .sh synopsis .nf .b #include .pp .bi "ssize_t read(int " fd ", void *" buf ", size_t " count ); .fi .sh description .br read () attempts to read up to .i count bytes from file descriptor .i fd into the buffer starting at .ir buf . .pp on files that support seeking, the read operation commences at the file offset, and the file offset is incremented by the number of bytes read. if the file offset is at or past the end of file, no bytes are read, and .br read () returns zero. .pp if .i count is zero, .br read () .i may detect the errors described below. in the absence of any errors, or if .br read () does not check for errors, a .br read () with a .i count of 0 returns zero and has no other effects. .pp according to posix.1, if .i count is greater than .br ssize_max , the result is implementation-defined; see notes for the upper limit on linux. .sh return value on success, the number of bytes read is returned (zero indicates end of file), and the file position is advanced by this number. it is not an error if this number is smaller than the number of bytes requested; this may happen for example because fewer bytes are actually available right now (maybe because we were close to end-of-file, or because we are reading from a pipe, or from a terminal), or because .br read () was interrupted by a signal. see also notes. .pp on error, \-1 is returned, and .i errno is set to indicate the error. in this case, it is left unspecified whether the file position (if any) changes. .sh errors .tp .b eagain the file descriptor .i fd refers to a file other than a socket and has been marked nonblocking .rb ( o_nonblock ), and the read would block. see .br open (2) for further details on the .br o_nonblock flag. .tp .br eagain " or " ewouldblock .\" actually eagain on linux the file descriptor .i fd refers to a socket and has been marked nonblocking .rb ( o_nonblock ), and the read would block. posix.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities. .tp .b ebadf .i fd is not a valid file descriptor or is not open for reading. .tp .b efault .i buf is outside your accessible address space. .tp .b eintr the call was interrupted by a signal before any data was read; see .br signal (7). .tp .b einval .i fd is attached to an object which is unsuitable for reading; or the file was opened with the .b o_direct flag, and either the address specified in .ir buf , the value specified in .ir count , or the file offset is not suitably aligned. .tp .b einval .i fd was created via a call to .br timerfd_create (2) and the wrong size buffer was given to .br read (); see .br timerfd_create (2) for further information. .tp .b eio i/o error. this will happen for example when the process is in a background process group, tries to read from its controlling terminal, and either it is ignoring or blocking .b sigttin or its process group is orphaned. it may also occur when there is a low-level i/o error while reading from a disk or tape. a further possible cause of .b eio on networked filesystems is when an advisory lock had been taken out on the file descriptor and this lock has been lost. see the .i "lost locks" section of .br fcntl (2) for further details. .tp .b eisdir .i fd refers to a directory. .pp other errors may occur, depending on the object connected to .ir fd . .sh conforming to svr4, 4.3bsd, posix.1-2001. .sh notes the types .i size_t and .i ssize_t are, respectively, unsigned and signed integer data types specified by posix.1. .pp on linux, .br read () (and similar system calls) will transfer at most 0x7ffff000 (2,147,479,552) bytes, returning the number of bytes actually transferred. .\" commit e28cc71572da38a5a12c1cfe4d7032017adccf69 (this is true on both 32-bit and 64-bit systems.) .pp on nfs filesystems, reading small amounts of data will update the timestamp only the first time, subsequent calls may not do so. this is caused by client side attribute caching, because most if not all nfs clients leave .i st_atime (last file access time) updates to the server, and client side reads satisfied from the client's cache will not cause .i st_atime updates on the server as there are no server-side reads. unix semantics can be obtained by disabling client-side attribute caching, but in most situations this will substantially increase server load and decrease performance. .sh bugs according to posix.1-2008/susv4 section xsi 2.9.7 ("thread interactions with regular file operations"): .pp .rs 4 all of the following functions shall be atomic with respect to each other in the effects specified in posix.1-2008 when they operate on regular files or symbolic links: ... .re .pp among the apis subsequently listed are .br read () and .br readv (2). and among the effects that should be atomic across threads (and processes) are updates of the file offset. however, on linux before version 3.14, this was not the case: if two processes that share an open file description (see .br open (2)) perform a .br read () (or .br readv (2)) at the same time, then the i/o operations were not atomic with respect updating the file offset, with the result that the reads in the two processes might (incorrectly) overlap in the blocks of data that they obtained. this problem was fixed in linux 3.14. .\" http://thread.gmane.org/gmane.linux.kernel/1649458 .\" from: michael kerrisk (man-pages gmail.com> .\" subject: update of file offset on write() etc. is non-atomic with i/o .\" date: 2014-02-17 15:41:37 gmt .\" newsgroups: gmane.linux.kernel, gmane.linux.file-systems .\" commit 9c225f2655e36a470c4f58dbbc99244c5fc7f2d4 .\" author: linus torvalds .\" date: mon mar 3 09:36:58 2014 -0800 .\" .\" vfs: atomic f_pos accesses as per posix .sh see also .br close (2), .br fcntl (2), .br ioctl (2), .br lseek (2), .br open (2), .br pread (2), .br readdir (2), .br readlink (2), .br readv (2), .br select (2), .br write (2), .br fread (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) and .\" and copyright 2002 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified fri jan 31 16:26:07 1997 by eric s. raymond .\" modified fri dec 11 17:57:27 1998 by jamie lokier .\" modified 24 apr 2002 by michael kerrisk .\" substantial rewrites and additions .\" 2005-05-10 mtk, noted that lock conversions are not atomic. .\" .\" fixme maybe document lock_mand, lock_rw, lock_read, lock_write .\" which only have effect for samba. .\" .th flock 2 2021-03-22 "linux" "linux programmer's manual" .sh name flock \- apply or remove an advisory lock on an open file .sh synopsis .nf .b #include .pp .bi "int flock(int " fd ", int " operation ); .fi .sh description apply or remove an advisory lock on the open file specified by .ir fd . the argument .i operation is one of the following: .rs 4 .tp 9 .b lock_sh place a shared lock. more than one process may hold a shared lock for a given file at a given time. .tp .b lock_ex place an exclusive lock. only one process may hold an exclusive lock for a given file at a given time. .tp .b lock_un remove an existing lock held by this process. .re .pp a call to .br flock () may block if an incompatible lock is held by another process. to make a nonblocking request, include .b lock_nb (by oring) with any of the above operations. .pp a single file may not simultaneously have both shared and exclusive locks. .pp locks created by .br flock () are associated with an open file description (see .br open (2)). this means that duplicate file descriptors (created by, for example, .br fork (2) or .br dup (2)) refer to the same lock, and this lock may be modified or released using any of these file descriptors. furthermore, the lock is released either by an explicit .b lock_un operation on any of these duplicate file descriptors, or when all such file descriptors have been closed. .pp if a process uses .br open (2) (or similar) to obtain more than one file descriptor for the same file, these file descriptors are treated independently by .br flock (). an attempt to lock the file using one of these file descriptors may be denied by a lock that the calling process has already placed via another file descriptor. .pp a process may hold only one type of lock (shared or exclusive) on a file. subsequent .br flock () calls on an already locked file will convert an existing lock to the new lock mode. .pp locks created by .br flock () are preserved across an .br execve (2). .pp a shared or exclusive lock can be placed on a file regardless of the mode in which the file was opened. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not an open file descriptor. .tp .b eintr while waiting to acquire a lock, the call was interrupted by delivery of a signal caught by a handler; see .br signal (7). .tp .b einval .i operation is invalid. .tp .b enolck the kernel ran out of memory for allocating lock records. .tp .b ewouldblock the file is locked and the .b lock_nb flag was selected. .sh conforming to 4.4bsd (the .br flock () call first appeared in 4.2bsd). a version of .br flock (), possibly implemented in terms of .br fcntl (2), appears on most unix systems. .sh notes since kernel 2.0, .br flock () is implemented as a system call in its own right rather than being emulated in the gnu c library as a call to .br fcntl (2). with this implementation, there is no interaction between the types of lock placed by .br flock () and .br fcntl (2), and .br flock () does not detect deadlock. (note, however, that on some systems, such as the modern bsds, .\" e.g., according to the flock(2) man page, freebsd since at least 5.3 .br flock () and .br fcntl (2) locks .i do interact with one another.) .pp .br flock () places advisory locks only; given suitable permissions on a file, a process is free to ignore the use of .br flock () and perform i/o on the file. .pp .br flock () and .br fcntl (2) locks have different semantics with respect to forked processes and .br dup (2). on systems that implement .br flock () using .br fcntl (2), the semantics of .br flock () will be different from those described in this manual page. .pp converting a lock (shared to exclusive, or vice versa) is not guaranteed to be atomic: the existing lock is first removed, and then a new lock is established. between these two steps, a pending lock request by another process may be granted, with the result that the conversion either blocks, or fails if .b lock_nb was specified. (this is the original bsd behavior, and occurs on many other implementations.) .\" kernel 2.5.21 changed things a little: during lock conversion .\" it is now the highest priority process that will get the lock -- mtk .ss nfs details in linux kernels up to 2.6.11, .br flock () does not lock files over nfs (i.e., the scope of locks was limited to the local system). instead, one could use .br fcntl (2) byte-range locking, which does work over nfs, given a sufficiently recent version of linux and a server which supports locking. .pp since linux 2.6.12, nfs clients support .br flock () locks by emulating them as .br fcntl (2) byte-range locks on the entire file. this means that .br fcntl (2) and .br flock () locks .i do interact with one another over nfs. it also means that in order to place an exclusive lock, the file must be opened for writing. .pp since linux 2.6.37, .\" commit 5eebde23223aeb0ad2d9e3be6590ff8bbfab0fc2 the kernel supports a compatibility mode that allows .br flock () locks (and also .br fcntl (2) byte region locks) to be treated as local; see the discussion of the .i "local_lock" option in .br nfs (5). .ss cifs details in linux kernels up to 5.4, .br flock () is not propagated over smb. a file with such locks will not appear locked for remote clients. .pp since linux 5.5, .br flock () locks are emulated with smb byte-range locks on the entire file. similarly to nfs, this means that .br fcntl (2) and .br flock () locks interact with one another. another important side-effect is that the locks are not advisory anymore: any io on a locked file will always fail with .br eacces when done from a separate file descriptor. this difference originates from the design of locks in the smb protocol, which provides mandatory locking semantics. .pp remote and mandatory locking semantics may vary with smb protocol, mount options and server type. see .br mount.cifs (8) for additional information. .sh see also .br flock (1), .br close (2), .br dup (2), .br execve (2), .br fcntl (2), .br fork (2), .br open (2), .br lockf (3), .br lslocks (8) .pp .i documentation/filesystems/locks.txt in the linux kernel source tree .ri ( documentation/locks.txt in older kernels) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright i2007, 2012, 2018, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:00:59 1993 by rik faith (faith@cs.unc.edu) .\" clarification concerning realloc, iwj10@cus.cam.ac.uk (ian jackson), 950701 .\" documented malloc_check_, wolfram gloger (wmglo@dent.med.uni-muenchen.de) .\" 2007-09-15 mtk: added notes on malloc()'s use of sbrk() and mmap(). .\" .\" fixme . review http://austingroupbugs.net/view.php?id=374 .\" to see what changes are required on this page. .\" .th malloc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name malloc, free, calloc, realloc, reallocarray \- allocate and free dynamic memory .sh synopsis .nf .b #include .pp .bi "void *malloc(size_t " "size" ); .bi "void free(void " "*ptr" ); .bi "void *calloc(size_t " "nmemb" ", size_t " "size" ); .bi "void *realloc(void " "*ptr" ", size_t " "size" ); .bi "void *reallocarray(void " "*ptr" ", size_t " nmemb ", size_t " "size" ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br reallocarray (): .nf since glibc 2.29: _default_source glibc 2.28 and earlier: _gnu_source .fi .sh description the .br malloc () function allocates .i size bytes and returns a pointer to the allocated memory. .ir "the memory is not initialized" . if .i size is 0, then .br malloc () returns either null, .\" glibc does this: or a unique pointer value that can later be successfully passed to .br free (). .pp the .br free () function frees the memory space pointed to by .ir ptr , which must have been returned by a previous call to .br malloc (), .br calloc (), or .br realloc (). otherwise, or if .i free(ptr) has already been called before, undefined behavior occurs. if .i ptr is null, no operation is performed. .pp the .br calloc () function allocates memory for an array of .i nmemb elements of .i size bytes each and returns a pointer to the allocated memory. the memory is set to zero. if .i nmemb or .i size is 0, then .br calloc () returns either null, .\" glibc does this: or a unique pointer value that can later be successfully passed to .br free (). if the multiplication of .i nmemb and .i size would result in integer overflow, then .br calloc () returns an error. by contrast, an integer overflow would not be detected in the following call to .br malloc (), with the result that an incorrectly sized block of memory would be allocated: .pp .in +4n .ex malloc(nmemb * size); .ee .in .pp the .br realloc () function changes the size of the memory block pointed to by .i ptr to .i size bytes. the contents will be unchanged in the range from the start of the region up to the minimum of the old and new sizes. if the new size is larger than the old size, the added memory will .i not be initialized. if .i ptr is null, then the call is equivalent to .ir malloc(size) , for all values of .ir size ; if .i size is equal to zero, and .i ptr is not null, then the call is equivalent to .i free(ptr) (this behavior is nonportable; see notes). unless .i ptr is null, it must have been returned by an earlier call to .br malloc (), .br calloc (), or .br realloc (). if the area pointed to was moved, a .i free(ptr) is done. .pp the .br reallocarray () function changes the size of the memory block pointed to by .i ptr to be large enough for an array of .i nmemb elements, each of which is .i size bytes. it is equivalent to the call .pp .in +4n realloc(ptr, nmemb * size); .in .pp however, unlike that .br realloc () call, .br reallocarray () fails safely in the case where the multiplication would overflow. if such an overflow occurs, .br reallocarray () returns null, sets .i errno to .br enomem , and leaves the original block of memory unchanged. .sh return value the .br malloc () and .br calloc () functions return a pointer to the allocated memory, which is suitably aligned for any built-in type. on error, these functions return null. null may also be returned by a successful call to .br malloc () with a .i size of zero, or by a successful call to .br calloc () with .i nmemb or .i size equal to zero. .pp the .br free () function returns no value. .pp the .br realloc () function returns a pointer to the newly allocated memory, which is suitably aligned for any built-in type, or null if the request failed. the returned pointer may be the same as .ir ptr if the allocation was not moved (e.g., there was room to expand the allocation in-place), or different from .ir ptr if the allocation was moved to a new address. if .i size was equal to 0, either null or a pointer suitable to be passed to .br free () is returned. if .br realloc () fails, the original block is left untouched; it is not freed or moved. .pp on success, the .br reallocarray () function returns a pointer to the newly allocated memory. on failure, it returns null and the original block of memory is left untouched. .sh errors .br calloc (), .br malloc (), .br realloc (), and .br reallocarray () can fail with the following error: .tp .b enomem out of memory. possibly, the application hit the .br rlimit_as or .br rlimit_data limit described in .br getrlimit (2). .sh versions .br reallocarray () first appeared in glibc in version 2.26. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br malloc (), .br free (), .br calloc (), .br realloc () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br malloc (), .br free (), .br calloc (), .br realloc (): posix.1-2001, posix.1-2008, c89, c99. .pp .br reallocarray () is a nonstandard extension that first appeared in openbsd 5.6 and freebsd 11.0. .sh notes by default, linux follows an optimistic memory allocation strategy. this means that when .br malloc () returns non-null there is no guarantee that the memory really is available. in case it turns out that the system is out of memory, one or more processes will be killed by the oom killer. for more information, see the description of .ir /proc/sys/vm/overcommit_memory and .ir /proc/sys/vm/oom_adj in .br proc (5), and the linux kernel source file .ir documentation/vm/overcommit\-accounting.rst . .pp normally, .br malloc () allocates memory from the heap, and adjusts the size of the heap as required, using .br sbrk (2). when allocating blocks of memory larger than .b mmap_threshold bytes, the glibc .br malloc () implementation allocates the memory as a private anonymous mapping using .br mmap (2). .b mmap_threshold is 128\ kb by default, but is adjustable using .br mallopt (3). prior to linux 4.7 allocations performed using .br mmap (2) were unaffected by the .b rlimit_data resource limit; since linux 4.7, this limit is also enforced for allocations performed using .br mmap (2). .pp to avoid corruption in multithreaded applications, mutexes are used internally to protect the memory-management data structures employed by these functions. in a multithreaded application in which threads simultaneously allocate and free memory, there could be contention for these mutexes. to scalably handle memory allocation in multithreaded applications, glibc creates additional .ir "memory allocation arenas" if mutex contention is detected. each arena is a large region of memory that is internally allocated by the system (using .br brk (2) or .br mmap (2)), and managed with its own mutexes. .pp susv2 requires .br malloc (), .br calloc (), and .br realloc () to set .i errno to .b enomem upon failure. glibc assumes that this is done (and the glibc versions of these routines do this); if you use a private malloc implementation that does not set .ir errno , then certain library routines may fail without having a reason in .ir errno . .pp crashes in .br malloc (), .br calloc (), .br realloc (), or .br free () are almost always related to heap corruption, such as overflowing an allocated chunk or freeing the same pointer twice. .pp the .br malloc () implementation is tunable via environment variables; see .br mallopt (3) for details. .ss nonportable behavior the behavior of .br realloc () when .i size is equal to zero, and .i ptr is not null, is glibc specific; other implementations may return null, and set .ir errno . portable posix programs should avoid it. see .br realloc (3p). .sh see also .\" http://g.oswego.edu/dl/html/malloc.html .\" a memory allocator - by doug lea .\" .\" http://www.bozemanpass.com/info/linux/malloc/linux_heap_contention.html .\" linux heap, contention in free() - david boreham .\" .\" http://www.citi.umich.edu/projects/linux-scalability/reports/malloc.html .\" malloc() performance in a multithreaded linux environment - .\" check lever, david boreham .\" .ad l .nh .br valgrind (1), .br brk (2), .br mmap (2), .br alloca (3), .br malloc_get_state (3), .br malloc_info (3), .br malloc_trim (3), .br malloc_usable_size (3), .br mallopt (3), .br mcheck (3), .br mtrace (3), .br posix_memalign (3) .pp for details of the gnu c library implementation, see .ur https://sourceware.org/glibc/wiki/mallocinternals .ue . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@cantor.informatik.rwth-aachen.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1993-07-25 by rik faith (faith@cs.unc.edu) .\" modified 1995-02-26 by michael haardt .\" modified 1996-07-20 by michael haardt .\" modified 1997-07-02 by nicolás lichtmaier .\" modified 2004-10-31 by aeb, following gwenole beauchesne .th utmp 5 2021-03-22 "linux" "linux programmer's manual" .sh name utmp, wtmp \- login records .sh synopsis .nf .b #include .fi .sh description the .i utmp file allows one to discover information about who is currently using the system. there may be more users currently using the system, because not all programs use utmp logging. .pp .b warning: .i utmp must not be writable by the user class "other", because many system programs (foolishly) depend on its integrity. you risk faked system logfiles and modifications of system files if you leave .i utmp writable to any user other than the owner and group owner of the file. .pp the file is a sequence of .i utmp structures, declared as follows in .ir (note that this is only one of several definitions around; details depend on the version of libc): .pp .in +4n .ex /* values for ut_type field, below */ #define empty 0 /* record does not contain valid info (formerly known as ut_unknown on linux) */ #define run_lvl 1 /* change in system run\-level (see \fbinit\fp(1)) */ #define boot_time 2 /* time of system boot (in \fiut_tv\fp) */ #define new_time 3 /* time after system clock change (in \fiut_tv\fp) */ #define old_time 4 /* time before system clock change (in \fiut_tv\fp) */ #define init_process 5 /* process spawned by \fbinit\fp(1) */ #define login_process 6 /* session leader process for user login */ #define user_process 7 /* normal process */ #define dead_process 8 /* terminated process */ #define accounting 9 /* not implemented */ #define ut_linesize 32 #define ut_namesize 32 #define ut_hostsize 256 struct exit_status { /* type for ut_exit, below */ short e_termination; /* process termination status */ short e_exit; /* process exit status */ }; struct utmp { short ut_type; /* type of record */ pid_t ut_pid; /* pid of login process */ char ut_line[ut_linesize]; /* device name of tty \- "/dev/" */ char ut_id[4]; /* terminal name suffix, or inittab(5) id */ char ut_user[ut_namesize]; /* username */ char ut_host[ut_hostsize]; /* hostname for remote login, or kernel version for run\-level messages */ struct exit_status ut_exit; /* exit status of a process marked as dead_process; not used by linux init(1) */ /* the ut_session and ut_tv fields must be the same size when compiled 32\- and 64\-bit. this allows data files and shared memory to be shared between 32\- and 64\-bit applications. */ #if __wordsize == 64 && defined __wordsize_compat32 int32_t ut_session; /* session id (\fbgetsid\fp(2)), used for windowing */ struct { int32_t tv_sec; /* seconds */ int32_t tv_usec; /* microseconds */ } ut_tv; /* time entry was made */ #else long ut_session; /* session id */ struct timeval ut_tv; /* time entry was made */ #endif int32_t ut_addr_v6[4]; /* internet address of remote host; ipv4 address uses just ut_addr_v6[0] */ char __unused[20]; /* reserved for future use */ }; /* backward compatibility hacks */ #define ut_name ut_user #ifndef _no_ut_time #define ut_time ut_tv.tv_sec #endif #define ut_xtime ut_tv.tv_sec #define ut_addr ut_addr_v6[0] .ee .in .pp this structure gives the name of the special file associated with the user's terminal, the user's login name, and the time of login in the form of .br time (2). string fields are terminated by a null byte (\(aq\e0\(aq) if they are shorter than the size of the field. .pp the first entries ever created result from .br init (1) processing .br inittab (5). before an entry is processed, though, .br init (1) cleans up utmp by setting \fiut_type\fp to \fbdead_process\fp, clearing \fiut_user\fp, \fiut_host\fp, and \fiut_time\fp with null bytes for each record which \fiut_type\fp is not \fbdead_process\fp or \fbrun_lvl\fp and where no process with pid \fiut_pid\fp exists. if no empty record with the needed \fiut_id\fp can be found, .br init (1) creates a new one. it sets \fiut_id\fp from the inittab, \fiut_pid\fp and \fiut_time\fp to the current values, and \fiut_type\fp to \fbinit_process\fp. .pp .br mingetty (8) (or .br agetty (8)) locates the entry by the pid, changes \fiut_type\fp to \fblogin_process\fp, changes \fiut_time\fp, sets \fiut_line\fp, and waits for connection to be established. .br login (1), after a user has been authenticated, changes \fiut_type\fp to \fbuser_process\fp, changes \fiut_time\fp, and sets \fiut_host\fp and \fiut_addr\fp. depending on .br mingetty (8) (or .br agetty (8)) and .br login (1), records may be located by \fiut_line\fp instead of the preferable \fiut_pid\fp. .pp when .br init (1) finds that a process has exited, it locates its utmp entry by .ir ut_pid , sets .i ut_type to .br dead_process , and clears .ir ut_user , .ir ut_host , and .i ut_time with null bytes. .pp .br xterm (1) and other terminal emulators directly create a \fbuser_process\fp record and generate the \fiut_id\fp by using the string that suffix part of the terminal name (the characters following \fi/dev/[pt]ty\fp). if they find a \fbdead_process\fp for this id, they recycle it, otherwise they create a new entry. if they can, they will mark it as \fbdead_process\fp on exiting and it is advised that they null \fiut_line\fp, \fiut_time\fp, \fiut_user\fp, and \fiut_host\fp as well. .pp .br telnetd (8) sets up a \fblogin_process\fp entry and leaves the rest to .br login (1) as usual. after the telnet session ends, .br telnetd (8) cleans up utmp in the described way. .pp the \fiwtmp\fp file records all logins and logouts. its format is exactly like \fiutmp\fp except that a null username indicates a logout on the associated terminal. furthermore, the terminal name \fb\(ti\fp with username \fbshutdown\fp or \fbreboot\fp indicates a system shutdown or reboot and the pair of terminal names \fb|\fp/\fb}\fp logs the old/new system time when .br date (1) changes it. \fiwtmp\fp is maintained by .br login (1), .br init (1), and some versions of .br getty (8) (e.g., .br mingetty (8) or .br agetty (8)). none of these programs creates the file, so if it is removed, record-keeping is turned off. .sh files .i /var/run/utmp .br .i /var/log/wtmp .sh conforming to posix.1 does not specify a .i utmp structure, but rather one named .ir utmpx , with specifications for the fields .ir ut_type , .ir ut_pid , .ir ut_line , .ir ut_id , .ir ut_user , and .ir ut_tv . posix.1 does not specify the lengths of the .i ut_line and .i ut_user fields. .pp linux defines the .i utmpx structure to be the same as the .i utmp structure. .ss comparison with historical systems linux utmp entries conform neither to v7/bsd nor to system v; they are a mix of the two. .pp v7/bsd has fewer fields; most importantly it lacks \fiut_type\fp, which causes native v7/bsd-like programs to display (for example) dead or login entries. further, there is no configuration file which allocates slots to sessions. bsd does so because it lacks \fiut_id\fp fields. .pp in linux (as in system v), the \fiut_id\fp field of a record will never change once it has been set, which reserves that slot without needing a configuration file. clearing \fiut_id\fp may result in race conditions leading to corrupted utmp entries and potential security holes. clearing the abovementioned fields by filling them with null bytes is not required by system v semantics, but makes it possible to run many programs which assume bsd semantics and which do not modify utmp. linux uses the bsd conventions for line contents, as documented above. .pp .\" mtk: what is the referrent of "them" in the following sentence? .\" system v only uses the type field to mark them and logs .\" informative messages such as \fb"new time"\fp in the line field. system v has no \fiut_host\fp or \fiut_addr_v6\fp fields. .sh notes unlike various other systems, where utmp logging can be disabled by removing the file, utmp must always exist on linux. if you want to disable .br who (1), then do not make utmp world readable. .pp the file format is machine-dependent, so it is recommended that it be processed only on the machine architecture where it was created. .pp note that on \fibiarch\fp platforms, that is, systems which can run both 32-bit and 64-bit applications (x86-64, ppc64, s390x, etc.), \fiut_tv\fp is the same size in 32-bit mode as in 64-bit mode. the same goes for \fiut_session\fp and \fiut_time\fp if they are present. this allows data files and shared memory to be shared between 32-bit and 64-bit applications. this is achieved by changing the type of .i ut_session to .ir int32_t , and that of .i ut_tv to a struct with two .i int32_t fields .i tv_sec and .ir tv_usec . since \fiut_tv\fp may not be the same as \fistruct timeval\fp, then instead of the call: .pp .in +4n .ex gettimeofday((struct timeval *) &ut.ut_tv, null); .ee .in .pp the following method of setting this field is recommended: .pp .in +4n .ex struct utmp ut; struct timeval tv; gettimeofday(&tv, null); ut.ut_tv.tv_sec = tv.tv_sec; ut.ut_tv.tv_usec = tv.tv_usec; .ee .in .\" .pp .\" note that the \fiutmp\fp struct from libc5 has changed in libc6. .\" because of this, .\" binaries using the old libc5 struct will corrupt .\" .ir /var/run/utmp " and/or " /var/log/wtmp . .\" .sh bugs .\" this man page is based on the libc5 one, things may work differently now. .sh see also .br ac (1), .br date (1), .br init (1), .br last (1), .br login (1), .br logname (1), .br lslogins (1), .br users (1), .br utmpdump (1), .br who (1), .br getutent (3), .br getutmp (3), .br login (3), .br logout (3), .br logwtmp (3), .br updwtmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005 robert love .\" and copyright, 2006 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2005-07-19 robert love - initial version .\" 2006-02-07 mtk, various changes .\" .th inotify_add_watch 2 2021-03-22 "linux" "linux programmer's manual" .sh name inotify_add_watch \- add a watch to an initialized inotify instance .sh synopsis .nf .b #include .pp .bi "int inotify_add_watch(int " fd ", const char *" pathname ", uint32_t " mask ); .fi .sh description .br inotify_add_watch () adds a new watch, or modifies an existing watch, for the file whose location is specified in .ir pathname ; the caller must have read permission for this file. the .i fd argument is a file descriptor referring to the inotify instance whose watch list is to be modified. the events to be monitored for .i pathname are specified in the .i mask bit-mask argument. see .br inotify (7) for a description of the bits that can be set in .ir mask . .pp a successful call to .br inotify_add_watch () returns a unique watch descriptor for this inotify instance, for the filesystem object (inode) that corresponds to .ir pathname . if the filesystem object was not previously being watched by this inotify instance, then the watch descriptor is newly allocated. if the filesystem object was already being watched (perhaps via a different link to the same object), then the descriptor for the existing watch is returned. .pp the watch descriptor is returned by later .br read (2)s from the inotify file descriptor. these reads fetch .i inotify_event structures (see .br inotify (7)) indicating filesystem events; the watch descriptor inside this structure identifies the object for which the event occurred. .sh return value on success, .br inotify_add_watch () returns a watch descriptor (a nonnegative integer). on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces read access to the given file is not permitted. .tp .b ebadf the given file descriptor is not valid. .tp .b eexist .i mask contains .b in_mask_create and .i pathname refers to a file already being watched by the same .ir fd . .tp .b efault .i pathname points outside of the process's accessible address space. .tp .b einval the given event mask contains no valid events; or .i mask contains both .b in_mask_add and .br in_mask_create ; or .i fd is not an inotify file descriptor. .tp .b enametoolong .i pathname is too long. .tp .b enoent a directory component in .i pathname does not exist or is a dangling symbolic link. .tp .b enomem insufficient kernel memory was available. .tp .b enospc the user limit on the total number of inotify watches was reached or the kernel failed to allocate a needed resource. .tp .b enotdir .i mask contains .b in_onlydir and .i pathname is not a directory. .sh versions inotify was merged into the 2.6.13 linux kernel. .sh conforming to this system call is linux-specific. .sh examples see .br inotify (7). .sh see also .br inotify_init (2), .br inotify_rm_watch (2), .br inotify (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2015 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:41:09 1993 by rik faith (faith@cs.unc.edu) .th memcpy 3 2021-03-22 "" "linux programmer's manual" .sh name memcpy \- copy memory area .sh synopsis .nf .b #include .pp .bi "void *memcpy(void *restrict " dest ", const void *restrict " src \ ", size_t " n ); .fi .sh description the .br memcpy () function copies \fin\fp bytes from memory area \fisrc\fp to memory area \fidest\fp. the memory areas must not overlap. use .br memmove (3) if the memory areas do overlap. .sh return value the .br memcpy () function returns a pointer to \fidest\fp. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memcpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes failure to observe the requirement that the memory areas do not overlap has been the source of significant bugs. (posix and the c standards are explicit that employing .br memcpy () with overlapping areas produces undefined behavior.) most notably, in glibc 2.13 .\" glibc commit 6fb8cbcb58a29fff73eb2101b34caa19a7f88eba a performance optimization of .br memcpy () on some platforms (including x86-64) included changing the order .\" from forward copying to backward copying in which bytes were copied from .i src to .ir dest . .pp this change revealed breakages in a number of applications that performed copying with overlapping areas. .\" adobe flash player was the highest profile example: .\" https://bugzilla.redhat.com/show_bug.cgi?id=638477 .\" reported: 2010-09-29 02:35 edt by jchuynh .\" bug 638477 - strange sound on mp3 flash website .\" .\" https://sourceware.org/bugzilla/show_bug.cgi?id=12518 .\" bug 12518 - memcpy acts randomly (and differently) with overlapping areas .\" reported: 2011-02-25 02:26 utc by linus torvalds .\" under the previous implementation, the order in which the bytes were copied had fortuitously hidden the bug, which was revealed when the copying order was reversed. in glibc 2.14, .\" glibc commit 0354e355014b7bfda32622e0255399d859862fcd a versioned symbol was added so that old binaries (i.e., those linked against glibc versions earlier than 2.14) employed a .br memcpy () implementation that safely handles the overlapping buffers case (by providing an "older" .br memcpy () implementation that was aliased to .br memmove (3)). .sh see also .br bcopy (3), .br bstring (3), .br memccpy (3), .br memmove (3), .br mempcpy (3), .br strcpy (3), .br strncpy (3), .br wmemcpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/nextup.3 .\" copyright (c) tom bjorkholm & markus kuhn, 1996 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-04-01 tom bjorkholm .\" first version written .\" 1996-04-10 markus kuhn .\" revision .\" modified 2004-05-27 by michael kerrisk .\" .th sched_setparam 2 2021-03-22 "linux" "linux programmer's manual" .sh name sched_setparam, sched_getparam \- set and get scheduling parameters .sh synopsis .nf .b #include .pp .bi "int sched_setparam(pid_t " pid ", const struct sched_param *" param ); .bi "int sched_getparam(pid_t " pid ", struct sched_param *" param ); .pp \fbstruct sched_param { ... int \fisched_priority\fb; ... }; .fi .sh description .br sched_setparam () sets the scheduling parameters associated with the scheduling policy for the thread whose thread id is specified in \fipid\fp. if \fipid\fp is zero, then the parameters of the calling thread are set. the interpretation of the argument \fiparam\fp depends on the scheduling policy of the thread identified by .ir pid . see .br sched (7) for a description of the scheduling policies supported under linux. .pp .br sched_getparam () retrieves the scheduling parameters for the thread identified by \fipid\fp. if \fipid\fp is zero, then the parameters of the calling thread are retrieved. .pp .br sched_setparam () checks the validity of \fiparam\fp for the scheduling policy of the thread. the value \fiparam\->sched_priority\fp must lie within the range given by .br sched_get_priority_min (2) and .br sched_get_priority_max (2). .pp for a discussion of the privileges and resource limits related to scheduling priority and policy, see .br sched (7). .pp posix systems on which .br sched_setparam () and .br sched_getparam () are available define .b _posix_priority_scheduling in \fi\fp. .sh return value on success, .br sched_setparam () and .br sched_getparam () return 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval invalid arguments: .i param is null or .i pid is negative .tp .b einval .rb ( sched_setparam ()) the argument \fiparam\fp does not make sense for the current scheduling policy. .tp .b eperm .rb ( sched_setparam ()) the caller does not have appropriate privileges (linux: does not have the .b cap_sys_nice capability). .tp .b esrch the thread whose id is \fipid\fp could not be found. .sh conforming to posix.1-2001, posix.1-2008. .sh see also .ad l .nh .br getpriority (2), .br gettid (2), .br nice (2), .br sched_get_priority_max (2), .br sched_get_priority_min (2), .br sched_getaffinity (2), .br sched_getscheduler (2), .br sched_setaffinity (2), .br sched_setattr (2), .br sched_setscheduler (2), .br setpriority (2), .br capabilities (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getgrnam.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:55:27 1993 by rik faith (faith@cs.unc.edu) .th memcmp 3 2021-03-22 "" "linux programmer's manual" .sh name memcmp \- compare memory areas .sh synopsis .nf .b #include .pp .bi "int memcmp(const void *" s1 ", const void *" s2 ", size_t " n ); .fi .sh description the .br memcmp () function compares the first \fin\fp bytes (each interpreted as .ir "unsigned char" ) of the memory areas \fis1\fp and \fis2\fp. .sh return value the .br memcmp () function returns an integer less than, equal to, or greater than zero if the first \fin\fp bytes of \fis1\fp is found, respectively, to be less than, to match, or be greater than the first \fin\fp bytes of \fis2\fp. .pp for a nonzero return value, the sign is determined by the sign of the difference between the first pair of bytes (interpreted as .ir "unsigned char" ) that differ in .i s1 and .ir s2 . .pp if .i n is zero, the return value is zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memcmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes do not use .br memcmp () to compare security critical data, such as cryptographic secrets, because the required cpu time depends on the number of equal bytes. instead, a function that performs comparisons in constant time is required. some operating systems provide such a function (e.g., netbsd's .br consttime_memequal ()), but no such function is specified in posix. on linux, it may be necessary to implement such a function oneself. .sh see also .br bcmp (3), .br bstring (3), .br strcasecmp (3), .br strcmp (3), .br strcoll (3), .br strncasecmp (3), .br strncmp (3), .br wmemcmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" and copyright (c) 1998 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2006, 2007, 2008, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-21 by rik faith .\" modified 1996-07-09 by andries brouwer .\" modified 1996-11-06 by eric s. raymond .\" modified 1997-05-18 by michael haardt .\" modified 2004-06-23 by michael kerrisk .\" 2007-07-08, mtk, added an example program; updated synopsis .\" 2008-05-08, mtk, describe rules governing ownership of new files .\" (bsdgroups versus sysvgroups, and the effect of the parent .\" directory's set-group-id mode bit). .\" .th chown 2 2021-08-27 "linux" "linux programmer's manual" .sh name chown, fchown, lchown, fchownat \- change ownership of a file .sh synopsis .nf .b #include .pp .bi "int chown(const char *" pathname ", uid_t " owner ", gid_t " group ); .bi "int fchown(int " fd ", uid_t " owner ", gid_t " group ); .bi "int lchown(const char *" pathname ", uid_t " owner ", gid_t " group ); .pp .br "#include " "/* definition of at_* constants */" .b #include .pp .bi "int fchownat(int " dirfd ", const char *" pathname , .bi " uid_t " owner ", gid_t " group ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fchown (), .br lchown (): .nf /* since glibc 2.12: */ _posix_c_source >= 200809l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* glibc <= 2.19: */ _bsd_source .fi .pp .br fchownat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description these system calls change the owner and group of a file. the .br chown (), .br fchown (), and .br lchown () system calls differ only in how the file is specified: .ip * 2 .br chown () changes the ownership of the file specified by .ir pathname , which is dereferenced if it is a symbolic link. .ip * .br fchown () changes the ownership of the file referred to by the open file descriptor .ir fd . .ip * .br lchown () is like .br chown (), but does not dereference symbolic links. .pp only a privileged process (linux: one with the .b cap_chown capability) may change the owner of a file. the owner of a file may change the group of the file to any group of which that owner is a member. a privileged process (linux: with .br cap_chown ) may change the group arbitrarily. .pp if the .i owner or .i group is specified as \-1, then that id is not changed. .pp when the owner or group of an executable file is changed by an unprivileged user, the .b s_isuid and .b s_isgid mode bits are cleared. posix does not specify whether this also should happen when root does the .br chown (); the linux behavior depends on the kernel version, and since linux 2.2.13, root is treated like other users. .\" in linux 2.0 kernels, superuser was like everyone else .\" in 2.2, up to 2.2.12, these bits were not cleared for superuser. .\" since 2.2.13, superuser is once more like everyone else. in case of a non-group-executable file (i.e., one for which the .b s_ixgrp bit is not set) the .b s_isgid bit indicates mandatory locking, and is not cleared by a .br chown (). .pp when the owner or group of an executable file is changed (by any user), all capability sets for the file are cleared. .\" .ss fchownat() the .br fchownat () system call operates in exactly the same way as .br chown (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br chown () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br chown ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp the .i flags argument is a bit mask created by oring together 0 or more of the following values; .tp .br at_empty_path " (since linux 2.6.39)" .\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d if .i pathname is an empty string, operate on the file referred to by .ir dirfd (which may have been obtained using the .br open (2) .b o_path flag). in this case, .i dirfd can refer to any type of file, not just a directory. if .i dirfd is .br at_fdcwd , the call operates on the current working directory. this flag is linux-specific; define .b _gnu_source .\" before glibc 2.16, defining _atfile_source sufficed to obtain its definition. .tp .b at_symlink_nofollow if .i pathname is a symbolic link, do not dereference it: instead operate on the link itself, like .br lchown (). (by default, .br fchownat () dereferences symbolic links, like .br chown ().) .pp see .br openat (2) for an explanation of the need for .br fchownat (). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors depending on the filesystem, errors other than those listed below can be returned. .pp the more general errors for .br chown () are listed below. .tp .b eacces search permission is denied on a component of the path prefix. (see also .br path_resolution (7).) .tp .b ebadf .rb ( fchown ()) .i fd is not a valid open file descriptor. .tp .b ebadf .rb ( fchownat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b efault .i pathname points outside your accessible address space. .tp .b einval .rb ( fchownat ()) invalid flag specified in .ir flags . .tp .b eio .rb ( fchown ()) a low-level i/o error occurred while modifying the inode. .tp .b eloop too many symbolic links were encountered in resolving .ir pathname . .tp .b enametoolong .i pathname is too long. .tp .b enoent the file does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of the path prefix is not a directory. .tp .b enotdir .rb ( fchownat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b eperm the calling process did not have the required permissions (see above) to change owner and/or group. .tp .b eperm the file is marked immutable or append-only. (see .br ioctl_iflags (2).) .tp .b erofs the named file resides on a read-only filesystem. .sh versions .br fchownat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br chown (), .br fchown (), .br lchown (): 4.4bsd, svr4, posix.1-2001, posix.1-2008. .pp the 4.4bsd version can be used only by the superuser (that is, ordinary users cannot give away files). .\" chown(): .\" svr4 documents einval, eintr, enolink and emultihop returns, but no .\" enomem. posix.1 does not document enomem or eloop error conditions. .\" fchown(): .\" svr4 documents additional einval, eio, eintr, and enolink .\" error conditions. .pp .br fchownat (): posix.1-2008. .sh notes .ss ownership of new files when a new file is created (by, for example, .br open (2) or .br mkdir (2)), its owner is made the same as the filesystem user id of the creating process. the group of the file depends on a range of factors, including the type of filesystem, the options used to mount the filesystem, and whether or not the set-group-id mode bit is enabled on the parent directory. if the filesystem supports the .b "\-o\ grpid" (or, synonymously .br "\-o\ bsdgroups" ) and .b "\-o\ nogrpid" (or, synonymously .br "\-o\ sysvgroups" ) .br mount (8) options, then the rules are as follows: .ip * 2 if the filesystem is mounted with .br "\-o\ grpid" , then the group of a new file is made the same as that of the parent directory. .ip * if the filesystem is mounted with .br "\-o\ nogrpid" and the set-group-id bit is disabled on the parent directory, then the group of a new file is made the same as the process's filesystem gid. .ip * if the filesystem is mounted with .br "\-o\ nogrpid" and the set-group-id bit is enabled on the parent directory, then the group of a new file is made the same as that of the parent directory. .pp as at linux 4.12, the .br "\-o\ grpid" and .br "\-o\ nogrpid" mount options are supported by ext2, ext3, ext4, and xfs. filesystems that don't support these mount options follow the .br "\-o\ nogrpid" rules. .ss glibc notes on older kernels where .br fchownat () is unavailable, the glibc wrapper function falls back to the use of .br chown () and .br lchown (). when .i pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir dirfd argument. .ss nfs the .br chown () semantics are deliberately violated on nfs filesystems which have uid mapping enabled. additionally, the semantics of all system calls which access the file contents are violated, because .br chown () may cause immediate access revocation on already open files. client side caching may lead to a delay between the time where ownership have been changed to allow access for a user and the time where the file can actually be accessed by the user on other clients. .ss historical details the original linux .br chown (), .br fchown (), and .br lchown () system calls supported only 16-bit user and group ids. subsequently, linux 2.4 added .br chown32 (), .br fchown32 (), and .br lchown32 (), supporting 32-bit ids. the glibc .br chown (), .br fchown (), and .br lchown () wrapper functions transparently deal with the variations across kernel versions. .pp in versions of linux prior to 2.1.81 (and distinct from 2.1.46), .br chown () did not follow symbolic links. since linux 2.1.81, .br chown () does follow symbolic links, and there is a new system call .br lchown () that does not follow symbolic links. since linux 2.1.86, this new call (that has the same semantics as the old .br chown ()) has got the same syscall number, and .br chown () got the newly introduced number. .sh examples the following program changes the ownership of the file named in its second command-line argument to the value specified in its first command-line argument. the new owner can be specified either as a numeric user id, or as a username (which is converted to a user id by using .br getpwnam (3) to perform a lookup in the system password file). .ss program source .ex #include #include #include #include int main(int argc, char *argv[]) { uid_t uid; struct passwd *pwd; char *endptr; if (argc != 3 || argv[1][0] == \(aq\e0\(aq) { fprintf(stderr, "%s \en", argv[0]); exit(exit_failure); } uid = strtol(argv[1], &endptr, 10); /* allow a numeric string */ if (*endptr != \(aq\e0\(aq) { /* was not pure numeric string */ pwd = getpwnam(argv[1]); /* try getting uid for username */ if (pwd == null) { perror("getpwnam"); exit(exit_failure); } uid = pwd\->pw_uid; } if (chown(argv[2], uid, \-1) == \-1) { perror("chown"); exit(exit_failure); } exit(exit_success); } .ee .sh see also .br chgrp (1), .br chown (1), .br chmod (2), .br flock (2), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2009 intel corporation, author andi kleen .\" some sentences copied from comments in arch/x86/kernel/msr.c .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th msr 4 2021-03-22 "linux" "linux programmer's manual" .sh name msr \- x86 cpu msr access device .sh description .i /dev/cpu/cpunum/msr provides an interface to read and write the model-specific registers (msrs) of an x86 cpu. .i cpunum is the number of the cpu to access as listed in .ir /proc/cpuinfo . .pp the register access is done by opening the file and seeking to the msr number as offset in the file, and then reading or writing in chunks of 8 bytes. an i/o transfer of more than 8 bytes means multiple reads or writes of the same register. .pp this file is protected so that it can be read and written only by the user .ir root , or members of the group .ir root . .sh notes the .i msr driver is not auto-loaded. on modular kernels you might need to use the following command to load it explicitly before use: .pp .in +4n .ex $ modprobe msr .ee .in .sh see also intel corporation intel 64 and ia-32 architectures software developer's manual volume 3b appendix b, for an overview of the intel cpu msrs. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fopen.3 .so man3/rpc.3 .\" copyright 1993 giorgio ciucci .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" added correction due to nick duffek , aeb, 960426 .\" modified wed nov 6 04:00:31 1996 by eric s. raymond .\" modified, 8 jan 2003, michael kerrisk, .\" removed eidrm from errors - that can't happen... .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" added notes on /proc files .\" .th msgget 2 2021-03-22 "linux" "linux programmer's manual" .sh name msgget \- get a system v message queue identifier .sh synopsis .nf .b #include .pp .bi "int msgget(key_t " key ", int " msgflg ); .fi .sh description the .br msgget () system call returns the system\ v message queue identifier associated with the value of the .i key argument. it may be used either to obtain the identifier of a previously created message queue (when .i msgflg is zero and .i key does not have the value .br ipc_private ), or to create a new set. .pp a new message queue is created if .i key has the value .b ipc_private or .i key isn't .br ipc_private , no message queue with the given key .i key exists, and .b ipc_creat is specified in .ir msgflg . .pp if .i msgflg specifies both .b ipc_creat and .b ipc_excl and a message queue already exists for .ir key , then .br msgget () fails with .i errno set to .br eexist . (this is analogous to the effect of the combination .b o_creat | o_excl for .br open (2).) .pp upon creation, the least significant bits of the argument .i msgflg define the permissions of the message queue. these permission bits have the same format and semantics as the permissions specified for the .i mode argument of .br open (2). (the execute permissions are not used.) .pp if a new message queue is created, then its associated data structure .i msqid_ds (see .br msgctl (2)) is initialized as follows: .ip \(bu 2 .i msg_perm.cuid and .i msg_perm.uid are set to the effective user id of the calling process. .ip \(bu .i msg_perm.cgid and .i msg_perm.gid are set to the effective group id of the calling process. .ip \(bu the least significant 9 bits of .i msg_perm.mode are set to the least significant 9 bits of .ir msgflg . .ip \(bu .ir msg_qnum , .ir msg_lspid , .ir msg_lrpid , .ir msg_stime , and .i msg_rtime are set to 0. .ip \(bu .i msg_ctime is set to the current time. .ip \(bu .i msg_qbytes is set to the system limit .br msgmnb . .pp if the message queue already exists the permissions are verified, and a check is made to see if it is marked for destruction. .sh return value on success, .br msgget () returns the message queue identifier (a nonnegative integer). on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces a message queue exists for .ir key , but the calling process does not have permission to access the queue, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b eexist .b ipc_creat and .br ipc_excl were specified in .ir msgflg , but a message queue already exists for .ir key . .tp .b enoent no message queue exists for .i key and .i msgflg did not specify .br ipc_creat . .tp .b enomem a message queue has to be created but the system does not have enough memory for the new data structure. .tp .b enospc a message queue has to be created but the system limit for the maximum number of message queues .rb ( msgmni ) would be exceeded. .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh notes .b ipc_private isn't a flag field but a .i key_t type. if this special value is used for .ir key , the system call ignores everything but the least significant 9 bits of .i msgflg and creates a new message queue (on success). .pp the following is a system limit on message queue resources affecting a .br msgget () call: .tp .b msgmni system-wide limit on the number of message queues. before linux 3.19, .\" commit 0050ee059f7fc86b1df2527aaa14ed5dc72f9973 the default value for this limit was calculated using a formula based on available system memory. since linux 3.19, the default value is 32,000. on linux, this limit can be read and modified via .ir /proc/sys/kernel/msgmni . .ss linux notes until version 2.3.20, linux would return .b eidrm for a .br msgget () on a message queue scheduled for deletion. .sh bugs the name choice .b ipc_private was perhaps unfortunate, .b ipc_new would more clearly show its function. .sh see also .br msgctl (2), .br msgrcv (2), .br msgsnd (2), .br ftok (3), .br capabilities (7), .br mq_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014, red hat, inc .\" written by alexandre oliva .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th attributes 7 2021-03-22 "linux" "linux programmer's manual" .sh name attributes \- posix safety concepts .sh description .\" .\" .ir note : the text of this man page is based on the material taken from the "posix safety concepts" section of the gnu c library manual. further details on the topics described here can be found in that manual. .pp various function manual pages include a section attributes that describes the safety of calling the function in various contexts. this section annotates functions with the following safety markings: .tp .i mt-safe .i mt-safe or thread-safe functions are safe to call in the presence of other threads. mt, in mt-safe, stands for multi thread. .ip being mt-safe does not imply a function is atomic, nor that it uses any of the memory synchronization mechanisms posix exposes to users. it is even possible that calling mt-safe functions in sequence does not yield an mt-safe combination. for example, having a thread call two mt-safe functions one right after the other does not guarantee behavior equivalent to atomic execution of a combination of both functions, since concurrent calls in other threads may interfere in a destructive way. .ip whole-program optimizations that could inline functions across library interfaces may expose unsafe reordering, and so performing inlining across the gnu c library interface is not recommended. the documented mt-safety status is not guaranteed under whole-program optimization. however, functions defined in user-visible headers are designed to be safe for inlining. .\" .tp .\" .i as-safe .\" .i as-safe .\" or async-signal-safe functions are safe to call from .\" asynchronous signal handlers. .\" as, in as-safe, stands for asynchronous signal. .\" .\" many functions that are as-safe may set .\" .ir errno , .\" or modify the floating-point environment, .\" because their doing so does not make them .\" unsuitable for use in signal handlers. .\" however, programs could misbehave should asynchronous signal handlers .\" modify this thread-local state, .\" and the signal handling machinery cannot be counted on to .\" preserve it. .\" therefore, signal handlers that call functions that may set .\" .i errno .\" or modify the floating-point environment .\" .i must .\" save their original values, and restore them before returning. .\" .tp .\" .i ac-safe .\" .i ac-safe .\" or async-cancel-safe functions are safe to call when .\" asynchronous cancellation is enabled. .\" ac in ac-safe stands for asynchronous cancellation. .\" .\" the posix standard defines only three functions to be ac-safe, namely .\" .br pthread_cancel (3), .\" .br pthread_setcancelstate (3), .\" and .\" .br pthread_setcanceltype (3). .\" at present the gnu c library provides no .\" guarantees beyond these three functions, .\" but does document which functions are presently ac-safe. .\" this documentation is provided for use .\" by the gnu c library developers. .\" .\" just like signal handlers, cancellation cleanup routines must configure .\" the floating point environment they require. .\" the routines cannot assume a floating point environment, .\" particularly when asynchronous cancellation is enabled. .\" if the configuration of the floating point .\" environment cannot be performed atomically then it is also possible that .\" the environment encountered is internally inconsistent. .tp .ir mt-unsafe \" ", " as-unsafe ", " ac-unsafe .ir mt-unsafe \" ", " as-unsafe ", " ac-unsafe functions are not safe to call in a multithreaded programs. .\" functions are not .\" safe to call within the safety contexts described above. .\" calling them .\" within such contexts invokes undefined behavior. .\" .\" functions not explicitly documented as safe in a safety context should .\" be regarded as unsafe. .\" .tp .\" .i preliminary .\" .i preliminary .\" safety properties are documented, indicating these .\" properties may .\" .i not .\" be counted on in future releases of .\" the gnu c library. .\" .\" such preliminary properties are the result of an assessment of the .\" properties of our current implementation, .\" rather than of what is mandated and permitted .\" by current and future standards. .\" .\" although we strive to abide by the standards, in some cases our .\" implementation is safe even when the standard does not demand safety, .\" and in other cases our implementation does not meet the standard safety .\" requirements. .\" the latter are most likely bugs; the former, when marked .\" as .\" .ir preliminary , .\" should not be counted on: future standards may .\" require changes that are not compatible with the additional safety .\" properties afforded by the current implementation. .\" .\" furthermore, .\" the posix standard does not offer a detailed definition of safety. .\" we assume that, by "safe to call", posix means that, .\" as long as the program does not invoke undefined behavior, .\" the "safe to call" function behaves as specified, .\" and does not cause other functions to deviate from their specified behavior. .\" we have chosen to use its loose .\" definitions of safety, not because they are the best definitions to use, .\" but because choosing them harmonizes this manual with posix. .\" .\" please keep in mind that these are preliminary definitions and annotations, .\" and certain aspects of the definitions are still under .\" discussion and might be subject to clarification or change. .\" .\" over time, .\" we envision evolving the preliminary safety notes into stable commitments, .\" as stable as those of our interfaces. .\" as we do, we will remove the .\" .i preliminary .\" keyword from safety notes. .\" as long as the keyword remains, however, .\" they are not to be regarded as a promise of future behavior. .pp other keywords that appear in safety notes are defined in subsequent sections. .\" .\" .\" .ss unsafe features .\" functions that are unsafe to call in certain contexts are annotated with .\" keywords that document their features that make them unsafe to call. .\" as-unsafe features in this section indicate the functions are never safe .\" to call when asynchronous signals are enabled. .\" ac-unsafe features .\" indicate they are never safe to call when asynchronous cancellation is .\" .\" enabled. .\" there are no mt-unsafe marks in this section. .\" .tp .\" .\" .i code .\" functions marked with .\" .i lock .\" as an as-unsafe feature may be .\" .\" interrupted by a signal while holding a non-recursive lock. .\" if the signal handler calls another such function that takes the same lock, .\" the result is a deadlock. .\" .\" functions annotated with .\" .i lock .\" as an ac-unsafe feature may, if canceled asynchronously, .\" fail to release a lock that would have been released if their execution .\" had not been interrupted by asynchronous thread cancellation. .\" once a lock is left taken, .\" attempts to take that lock will block indefinitely. .\" .tp .\" .i corrupt .\" functions marked with .\" .\" .i corrupt .\" as an as-unsafe feature may corrupt .\" data structures and misbehave when they interrupt, .\" or are interrupted by, another such function. .\" unlike functions marked with .\" .ir lock , .\" these take recursive locks to avoid mt-safety problems, .\" but this is not enough to stop a signal handler from observing .\" a partially-updated data structure. .\" further corruption may arise from the interrupted function's .\" failure to notice updates made by signal handlers. .\" .\" functions marked with .\" .i corrupt .\" as an ac-unsafe feature may leave .\" data structures in a corrupt, partially updated state. .\" subsequent uses of the data structure may misbehave. .\" .\" .\" a special case, probably not worth documenting separately, involves .\" .\" reallocing, or even freeing pointers. any case involving free could .\" .\" be easily turned into an ac-safe leak by resetting the pointer before .\" .\" releasing it; i don't think we have any case that calls for this sort .\" .\" of fixing. fixing the realloc cases would require a new interface: .\" .\" instead of @code{ptr=realloc(ptr,size)} we'd have to introduce .\" .\" @code{acsafe_realloc(&ptr,size)} that would modify ptr before .\" .\" releasing the old memory. the ac-unsafe realloc could be implemented .\" .\" in terms of an internal interface with this semantics (say .\" .\" __acsafe_realloc), but since realloc can be overridden, the function .\" .\" we call to implement realloc should not be this internal interface, .\" .\" but another internal interface that calls __acsafe_realloc if realloc .\" .\" was not overridden, and calls the overridden realloc with async .\" .\" cancel disabled. --lxoliva .\" .tp .\" .i heap .\" functions marked with .\" .i heap .\" may call heap memory management functions from the .\" .br malloc (3)/ free (3) .\" family of functions and are only as safe as those functions. .\" this note is thus equivalent to: .\" .\" | as-unsafe lock | ac-unsafe lock fd mem | .\" .\" @sampsafety{@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}} .\" .\" .\" .\" check for cases that should have used plugin instead of or in .\" .\" addition to this. then, after rechecking gettext, adjust i18n if .\" .\" needed. .\" .tp .\" .i dlopen .\" functions marked with .\" .i dlopen .\" use the dynamic loader to load .\" shared libraries into the current execution image. .\" this involves opening files, mapping them into memory, .\" allocating additional memory, resolving symbols, .\" applying relocations and more, .\" all of this while holding internal dynamic loader locks. .\" .\" the locks are enough for these functions to be as-unsafe and ac-unsafe, .\" but other issues may arise. .\" at present this is a placeholder for all .\" potential safety issues raised by .\" .br dlopen (3). .\" .\" .\" dlopen runs init and fini sections of the module; does this mean .\" .\" dlopen always implies plugin? .\" .tp .\" .i plugin .\" functions annotated with .\" .i plugin .\" may run code from plugins that .\" may be external to the gnu c library. .\" such plugin functions are assumed to be .\" mt-safe, as-unsafe and ac-unsafe. .\" examples of such plugins are stack unwinding libraries, .\" name service switch (nss) and character set conversion (iconv) back-ends. .\" .\" although the plugins mentioned as examples are all brought in by means .\" of dlopen, the .\" .i plugin .\" keyword does not imply any direct .\" involvement of the dynamic loader or the .\" .i libdl .\" interfaces, .\" those are covered by .\" .ir dlopen . .\" for example, if one function loads a module and finds the addresses .\" of some of its functions, .\" while another just calls those already-resolved functions, .\" the former will be marked with .\" .ir dlopen , .\" whereas the latter will get the .\" .ir plugin . .\" when a single function takes all of these actions, then it gets both marks. .\" .tp .\" .i i18n .\" functions marked with .\" .i i18n .\" may call internationalization .\" functions of the .\" .br gettext (3) .\" family and will be only as safe as those .\" functions. .\" this note is thus equivalent to: .\" .\" | mt-safe env | as-unsafe corrupt heap dlopen | ac-unsafe corrupt | .\" .\" .\" @sampsafety{@mtsafe{@mtsenv{}}@asunsafe{@asucorrupt{} @ascuheap{} @ascudlopen{}}@acunsafe{@acucorrupt{}}} .\" .tp .\" .i timer .\" functions marked with .\" .i timer .\" use the .\" .br alarm (3) .\" function or .\" similar to set a time-out for a system call or a long-running operation. .\" in a multi-threaded program, there is a risk that the time-out signal .\" will be delivered to a different thread, .\" thus failing to interrupt the intended thread. .\" besides being mt-unsafe, such functions are always .\" as-unsafe, because calling them in signal handlers may interfere with .\" timers set in the interrupted code, and ac-unsafe, .\" because there is no safe way to guarantee an earlier timer .\" will be reset in case of asynchronous cancellation. .\" .\" .ss conditionally safe features for some features that make functions unsafe to call in certain contexts, there are known ways to avoid the safety problem other than refraining from calling the function altogether. the keywords that follow refer to such features, and each of their definitions indicates how the whole program needs to be constrained in order to remove the safety problem indicated by the keyword. only when all the reasons that make a function unsafe are observed and addressed, by applying the documented constraints, does the function become safe to call in a context. .tp .i init functions marked with .i init as an mt-unsafe feature perform mt-unsafe initialization when they are first called. .ip calling such a function at least once in single-threaded mode removes this specific cause for the function to be regarded as mt-unsafe. if no other cause for that remains, the function can then be safely called after other threads are started. .\" .\" functions marked with .\" .i init .\" as an as-unsafe or ac-unsafe feature use the gnu c library internal .\" .i libc_once .\" machinery or similar to initialize internal data structures. .\" .\" if a signal handler interrupts such an initializer, .\" and calls any function that also performs .\" .i libc_once .\" initialization, it will deadlock if the thread library has been loaded. .\" .\" furthermore, if an initializer is partially complete before it is canceled .\" or interrupted by a signal whose handler requires the same initialization, .\" some or all of the initialization may be performed more than once, .\" leaking resources or even resulting in corrupt internal data. .\" .\" applications that need to call functions marked with .\" .i init .\" as an as-safety or ac-unsafe feature should ensure .\" the initialization is performed .\" before configuring signal handlers or enabling cancellation, .\" so that the as-safety and ac-safety issues related with .\" .i libc_once .\" do not arise. .\" .\" .\" we may have to extend the annotations to cover conditions in which .\" .\" initialization may or may not occur, since an initial call in a safe .\" .\" context is no use if the initialization doesn't take place at that .\" .\" time: it doesn't remove the risk for later calls. .tp .i race functions annotated with .i race as an mt-safety issue operate on objects in ways that may cause data races or similar forms of destructive interference out of concurrent execution. in some cases, the objects are passed to the functions by users; in others, they are used by the functions to return values to users; in others, they are not even exposed to users. .\" .\" we consider access to objects passed as (indirect) arguments to .\" functions to be data race free. .\" the assurance of data race free objects .\" is the caller's responsibility. .\" we will not mark a function as mt-unsafe or as-unsafe .\" if it misbehaves when users fail to take the measures required by .\" posix to avoid data races when dealing with such objects. .\" as a general rule, if a function is documented as reading from .\" an object passed (by reference) to it, or modifying it, .\" users ought to use memory synchronization primitives .\" to avoid data races just as they would should they perform .\" the accesses themselves rather than by calling the library function. .\" standard i/o .\" .ri ( "file *" ) .\" streams are the exception to the general rule, .\" in that posix mandates the library to guard against data races .\" in many functions that manipulate objects of this specific opaque type. .\" we regard this as a convenience provided to users, .\" rather than as a general requirement whose expectations .\" should extend to other types. .\" .\" in order to remind users that guarding certain arguments is their .\" responsibility, we will annotate functions that take objects of certain .\" types as arguments. .\" we draw the line for objects passed by users as follows: .\" objects whose types are exposed to users, .\" and that users are expected to access directly, .\" such as memory buffers, strings, .\" and various user-visible structured types, do .\" .i not .\" give reason for functions to be annotated with .\" .ir race . .\" it would be noisy and redundant with the general requirement, .\" and not many would be surprised by the library's lack of internal .\" guards when accessing objects that can be accessed directly by users. .\" .\" as for objects that are opaque or opaque-like, .\" in that they are to be manipulated only by passing them .\" to library functions (e.g., .\" .ir file , .\" .ir dir , .\" .ir obstack , .\" .ir iconv_t ), .\" there might be additional expectations as to internal coordination .\" of access by the library. .\" we will annotate, with .\" .i race .\" followed by a colon and the argument name, .\" functions that take such objects but that do not take .\" care of synchronizing access to them by default. .\" for example, .\" .i file .\" stream .\" .i unlocked .\" functions .\" .rb ( unlocked_stdio (3)) .\" will be annotated, .\" but those that perform implicit locking on .\" .i file .\" streams by default will not, .\" even though the implicit locking may be disabled on a per-stream basis. .\" .\" in either case, we will not regard as mt-unsafe functions that may .\" access user-supplied objects in unsafe ways should users fail to ensure .\" the accesses are well defined. .\" the notion prevails that users are expected to safeguard against .\" data races any user-supplied objects that the library accesses .\" on their behalf. .\" .\" .\" the above describes @mtsrace; @mtasurace is described below. .\" .\" this user responsibility does not apply, however, .\" to objects controlled by the library itself, .\" such as internal objects and static buffers used .\" to return values from certain calls. .\" when the library doesn't guard them against concurrent uses, .\" these cases are regarded as mt-unsafe and as-unsafe (although the .\" .i race .\" mark under as-unsafe will be omitted .\" as redundant with the one under mt-unsafe). .\" as in the case of user-exposed objects, .\" the mark may be followed by a colon and an identifier. .\" the identifier groups all functions that operate on a .\" certain unguarded object; users may avoid the mt-safety issues related .\" with unguarded concurrent access to such internal objects by creating a .\" non-recursive mutex related with the identifier, .\" and always holding the mutex when calling any function marked .\" as racy on that identifier, .\" as they would have to should the identifier be .\" an object under user control. .\" the non-recursive mutex avoids the mt-safety issue, .\" but it trades one as-safety issue for another, .\" so use in asynchronous signals remains undefined. .\" .\" when the identifier relates to a static buffer used to hold return values, .\" the mutex must be held for as long as the buffer remains in use .\" by the caller. .\" many functions that return pointers to static buffers offer reentrant .\" variants that store return values in caller-supplied buffers instead. .\" in some cases, such as .\" .br tmpname (3), .\" the variant is chosen not by calling an alternate entry point, .\" but by passing a non-null pointer to the buffer in which the .\" returned values are to be stored. .\" these variants are generally preferable in multi-threaded programs, .\" although some of them are not mt-safe because of other internal buffers, .\" also documented with .\" .i race .\" notes. .tp .i const functions marked with .i const as an mt-safety issue non-atomically modify internal objects that are better regarded as constant, because a substantial portion of the gnu c library accesses them without synchronization. unlike .ir race , which causes both readers and writers of internal objects to be regarded as mt-unsafe,\" and as-unsafe, this mark is applied to writers only. writers remain\" equally mt-unsafe\" and as-unsafe to call, but the then-mandatory constness of objects they modify enables readers to be regarded as mt-safe\" and as-safe (as long as no other reasons for them to be unsafe remain), since the lack of synchronization is not a problem when the objects are effectively constant. .ip the identifier that follows the .i const mark will appear by itself as a safety note in readers. programs that wish to work around this safety issue, so as to call writers, may use a non-recursive read-write lock associated with the identifier, and guard .i all calls to functions marked with .i const followed by the identifier with a write lock, and .i all calls to functions marked with the identifier by itself with a read lock. .\" the non-recursive locking removes the mt-safety problem, .\" but it trades one as-safety problem for another, .\" so use in asynchronous signals remains undefined. .\" .\" .\" but what if, instead of marking modifiers with const:id and readers .\" .\" with just id, we marked writers with race:id and readers with ro:id? .\" .\" instead of having to define each instance of 'id', we'd have a .\" .\" general pattern governing all such 'id's, wherein race:id would .\" .\" suggest the need for an exclusive/write lock to make the function .\" .\" safe, whereas ro:id would indicate 'id' is expected to be read-only, .\" .\" but if any modifiers are called (while holding an exclusive lock), .\" .\" then ro:id-marked functions ought to be guarded with a read lock for .\" .\" safe operation. ro:env or ro:locale, for example, seems to convey .\" .\" more clearly the expectations and the meaning, than just env or .\" .\" locale. .tp .i sig functions marked with .i sig as a mt-safety issue .\" (that implies an identical as-safety issue, omitted for brevity) may temporarily install a signal handler for internal purposes, which may interfere with other uses of the signal, identified after a colon. .ip this safety problem can be worked around by ensuring that no other uses of the signal will take place for the duration of the call. holding a non-recursive mutex while calling all functions that use the same temporary signal; blocking that signal before the call and resetting its handler afterwards is recommended. .\" .\" there is no safe way to guarantee the original signal handler is .\" restored in case of asynchronous cancellation, .\" therefore so-marked functions are also ac-unsafe. .\" .\" .\" fixme: at least deferred cancellation should get it right, and would .\" .\" obviate the restoring bit below, and the qualifier above. .\" .\" besides the measures recommended to work around the .\" mt-safety and as-safety problem, .\" in order to avert the cancellation problem, .\" disabling asynchronous cancellation .\" .i and .\" installing a cleanup handler to restore the signal to the desired state .\" and to release the mutex are recommended. .tp .i term functions marked with .i term as an mt-safety issue may change the terminal settings in the recommended way, namely: call .br tcgetattr (3), modify some flags, and then call .br tcsetattr (3), this creates a window in which changes made by other threads are lost. thus, functions marked with .i term are mt-unsafe. .\" the same window enables changes made by asynchronous signals to be lost. .\" these functions are also as-unsafe, .\" but the corresponding mark is omitted as redundant. .ip it is thus advisable for applications using the terminal to avoid concurrent and reentrant interactions with it, by not using it in signal handlers or blocking signals that might use it, and holding a lock while calling these functions and interacting with the terminal. this lock should also be used for mutual exclusion with functions marked with .ir race:tcattr(fd) , where .i fd is a file descriptor for the controlling terminal. the caller may use a single mutex for simplicity, or use one mutex per terminal, even if referenced by different file descriptors. .\" .\" functions marked with .\" .i term .\" as an ac-safety issue are supposed to .\" restore terminal settings to their original state, .\" after temporarily changing them, but they may fail to do so if canceled. .\" .\" .\" fixme: at least deferred cancellation should get it right, and would .\" .\" obviate the restoring bit below, and the qualifier above. .\" .\" besides the measures recommended to work around the .\" mt-safety and as-safety problem, .\" in order to avert the cancellation problem, .\" disabling asynchronous cancellation .\" .i and .\" installing a cleanup handler to .\" restore the terminal settings to the original state and to release the .\" mutex are recommended. .\" .\" .ss other safety remarks additional keywords may be attached to functions, indicating features that do not make a function unsafe to call, but that may need to be taken into account in certain classes of programs: .tp .i locale functions annotated with .i locale as an mt-safety issue read from the locale object without any form of synchronization. functions annotated with .i locale called concurrently with locale changes may behave in ways that do not correspond to any of the locales active during their execution, but an unpredictable mix thereof. .ip we do not mark these functions as mt-unsafe,\" or as-unsafe, however, because functions that modify the locale object are marked with .i const:locale and regarded as unsafe. being unsafe, the latter are not to be called when multiple threads are running or asynchronous signals are enabled, and so the locale can be considered effectively constant in these contexts, which makes the former safe. .\" should the locking strategy suggested under @code{const} be used, .\" failure to guard locale uses is not as fatal as data races in .\" general: unguarded uses will @emph{not} follow dangling pointers or .\" access uninitialized, unmapped or recycled memory. each access will .\" read from a consistent locale object that is or was active at some .\" point during its execution. without synchronization, however, it .\" cannot even be assumed that, after a change in locale, earlier .\" locales will no longer be used, even after the newly-chosen one is .\" used in the thread. nevertheless, even though unguarded reads from .\" the locale will not violate type safety, functions that access the .\" locale multiple times may invoke all sorts of undefined behavior .\" because of the unexpected locale changes. .tp .i env functions marked with .i env as an mt-safety issue access the environment with .br getenv (3) or similar, without any guards to ensure safety in the presence of concurrent modifications. .ip we do not mark these functions as mt-unsafe,\" or as-unsafe, however, because functions that modify the environment are all marked with .i const:env and regarded as unsafe. being unsafe, the latter are not to be called when multiple threads are running or asynchronous signals are enabled, and so the environment can be considered effectively constant in these contexts, which makes the former safe. .tp .i hostid the function marked with .i hostid as an mt-safety issue reads from the system-wide data structures that hold the "host id" of the machine. these data structures cannot generally be modified atomically. since it is expected that the "host id" will not normally change, the function that reads from it .rb ( gethostid (3)) is regarded as safe, whereas the function that modifies it .rb ( sethostid (3)) is marked with .ir const:hostid , indicating it may require special care if it is to be called. in this specific case, the special care amounts to system-wide (not merely intra-process) coordination. .tp .i sigintr functions marked with .i sigintr as an mt-safety issue access the gnu c library .i _sigintr internal data structure without any guards to ensure safety in the presence of concurrent modifications. .ip we do not mark these functions as mt-unsafe,\" or as-unsafe, however, because functions that modify this data structure are all marked with .i const:sigintr and regarded as unsafe. being unsafe, the latter are not to be called when multiple threads are running or asynchronous signals are enabled, and so the data structure can be considered effectively constant in these contexts, which makes the former safe. .\" .tp .\" .i fd .\" functions annotated with .\" .i fd .\" as an ac-safety issue may leak file .\" descriptors if asynchronous thread cancellation interrupts their .\" execution. .\" .\" functions that allocate or deallocate file descriptors will generally be .\" marked as such. .\" even if they attempted to protect the file descriptor .\" allocation and deallocation with cleanup regions, .\" allocating a new descriptor and storing its number where the cleanup region .\" could release it cannot be performed as a single atomic operation. .\" similarly, .\" releasing the descriptor and taking it out of the data structure .\" normally responsible for releasing it cannot be performed atomically. .\" there will always be a window in which the descriptor cannot be released .\" because it was not stored in the cleanup handler argument yet, .\" or it was already taken out before releasing it. .\" .\" it cannot be taken out after release: .\" an open descriptor could mean either that the descriptor still .\" has to be closed, .\" or that it already did so but the descriptor was .\" reallocated by another thread or signal handler. .\" .\" such leaks could be internally avoided, with some performance penalty, .\" by temporarily disabling asynchronous thread cancellation. .\" however, .\" since callers of allocation or deallocation functions would have to do .\" this themselves, to avoid the same sort of leak in their own layer, .\" it makes more sense for the library to assume they are taking care of it .\" than to impose a performance penalty that is redundant when the problem .\" is solved in upper layers, and insufficient when it is not. .\" .\" this remark by itself does not cause a function to be regarded as .\" ac-unsafe. .\" however, cumulative effects of such leaks may pose a .\" problem for some programs. .\" if this is the case, .\" suspending asynchronous cancellation for the duration of calls .\" to such functions is recommended. .\" .tp .\" .i mem .\" functions annotated with .\" .i mem .\" as an ac-safety issue may leak .\" memory if asynchronous thread cancellation interrupts their execution. .\" .\" the problem is similar to that of file descriptors: there is no atomic .\" interface to allocate memory and store its address in the argument to a .\" cleanup handler, .\" or to release it and remove its address from that argument, .\" without at least temporarily disabling asynchronous cancellation, .\" which these functions do not do. .\" .\" this remark does not by itself cause a function to be regarded as .\" generally ac-unsafe. .\" however, cumulative effects of such leaks may be .\" severe enough for some programs that disabling asynchronous cancellation .\" for the duration of calls to such functions may be required. .tp .i cwd functions marked with .i cwd as an mt-safety issue may temporarily change the current working directory during their execution, which may cause relative pathnames to be resolved in unexpected ways in other threads or within asynchronous signal or cancellation handlers. .ip this is not enough of a reason to mark so-marked functions as mt-unsafe, .\" or as-unsafe, but when this behavior is optional (e.g., .br nftw (3) with .br ftw_chdir ), avoiding the option may be a good alternative to using full pathnames or file descriptor-relative (e.g., .br openat (2)) system calls. .\" .tp .\" .i !posix .\" this remark, as an mt-safety, as-safety or ac-safety .\" note to a function, .\" indicates the safety status of the function is known to differ .\" from the specified status in the posix standard. .\" for example, posix does not require a function to be safe, .\" but our implementation is, or vice-versa. .\" .\" for the time being, the absence of this remark does not imply the safety .\" properties we documented are identical to those mandated by posix for .\" the corresponding functions. .tp .i :identifier annotations may sometimes be followed by identifiers, intended to group several functions that, for example, access the data structures in an unsafe way, as in .i race and .ir const , or to provide more specific information, such as naming a signal in a function marked with .ir sig . it is envisioned that it may be applied to .i lock and .i corrupt as well in the future. .ip in most cases, the identifier will name a set of functions, but it may name global objects or function arguments, or identifiable properties or logical components associated with them, with a notation such as, for example, .i :buf(arg) to denote a buffer associated with the argument .ir arg , or .i :tcattr(fd) to denote the terminal attributes of a file descriptor .ir fd . .ip the most common use for identifiers is to provide logical groups of functions and arguments that need to be protected by the same synchronization primitive in order to ensure safe operation in a given context. .tp .i /condition some safety annotations may be conditional, in that they only apply if a boolean expression involving arguments, global variables or even the underlying kernel evaluates to true. .\" such conditions as .\" .i /hurd .\" or .\" .i /!linux!bsd .\" indicate the preceding marker only .\" applies when the underlying kernel is the hurd, .\" or when it is neither linux nor a bsd kernel, respectively. for example, .i /!ps and .i /one_per_line indicate the preceding marker only applies when argument .i ps is null, or global variable .i one_per_line is nonzero. .ip when all marks that render a function unsafe are adorned with such conditions, and none of the named conditions hold, then the function can be regarded as safe. .sh see also .br pthreads (7), .br signal\-safety (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getdomainname.2 .so man2/listxattr.2 .so man3/stdarg.3 .\" this man page is copyright (c) 1999 claus fischer. .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" 990620 - page created - aeb@cwi.nl .\" .th fifo 7 2017-11-26 "linux" "linux programmer's manual" .sh name fifo \- first-in first-out special file, named pipe .sh description a fifo special file (a named pipe) is similar to a pipe, except that it is accessed as part of the filesystem. it can be opened by multiple processes for reading or writing. when processes are exchanging data via the fifo, the kernel passes all data internally without writing it to the filesystem. thus, the fifo special file has no contents on the filesystem; the filesystem entry merely serves as a reference point so that processes can access the pipe using a name in the filesystem. .pp the kernel maintains exactly one pipe object for each fifo special file that is opened by at least one process. the fifo must be opened on both ends (reading and writing) before data can be passed. normally, opening the fifo blocks until the other end is opened also. .pp a process can open a fifo in nonblocking mode. in this case, opening for read-only succeeds even if no one has opened on the write side yet and opening for write-only fails with .b enxio (no such device or address) unless the other end has already been opened. .pp under linux, opening a fifo for read and write will succeed both in blocking and nonblocking mode. posix leaves this behavior undefined. this can be used to open a fifo for writing while there are no readers available. a process that uses both ends of the connection in order to communicate with itself should be very careful to avoid deadlocks. .sh notes for details of the semantics of i/o on fifos, see .br pipe (7). .pp when a process tries to write to a fifo that is not opened for read on the other side, the process is sent a .b sigpipe signal. .pp fifo special files can be created by .br mkfifo (3), and are indicated by .ir "ls\ \-l" with the file type \(aqp\(aq. .sh see also .br mkfifo (1), .br open (2), .br pipe (2), .br sigaction (2), .br signal (2), .br socketpair (2), .br mkfifo (3), .br pipe (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/__ppc_set_ppr_med.3 .so man3/rint.3 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" $id: getsockopt.2,v 1.1 1999/05/24 14:57:04 freitag exp $ .\" .\" modified sat jul 24 16:19:32 1993 by rik faith (faith@cs.unc.edu) .\" modified mon apr 22 02:29:06 1996 by martin schulze (joey@infodrom.north.de) .\" modified tue aug 27 10:52:51 1996 by andries brouwer (aeb@cwi.nl) .\" modified thu jan 23 13:29:34 1997 by andries brouwer (aeb@cwi.nl) .\" modified sun mar 28 21:26:46 1999 by andries brouwer (aeb@cwi.nl) .\" modified 1999 by andi kleen . .\" removed most stuff because it is in socket.7 now. .\" .th getsockopt 2 2021-03-22 "linux" "linux programmer's manual" .sh name getsockopt, setsockopt \- get and set options on sockets .sh synopsis .nf .b #include .pp .bi "int getsockopt(int " sockfd ", int " level ", int " optname , .bi " void *restrict " optval ", socklen_t *restrict " optlen ); .bi "int setsockopt(int " sockfd ", int " level ", int " optname , .bi " const void *" optval ", socklen_t " optlen ); .fi .sh description .br getsockopt () and .br setsockopt () manipulate options for the socket referred to by the file descriptor .ir sockfd . options may exist at multiple protocol levels; they are always present at the uppermost socket level. .pp when manipulating socket options, the level at which the option resides and the name of the option must be specified. to manipulate options at the sockets api level, .i level is specified as .br sol_socket . to manipulate options at any other level the protocol number of the appropriate protocol controlling the option is supplied. for example, to indicate that an option is to be interpreted by the .b tcp protocol, .i level should be set to the protocol number of .br tcp ; see .br getprotoent (3). .pp the arguments .i optval and .i optlen are used to access option values for .br setsockopt (). for .br getsockopt () they identify a buffer in which the value for the requested option(s) are to be returned. for .br getsockopt (), .i optlen is a value-result argument, initially containing the size of the buffer pointed to by .ir optval , and modified on return to indicate the actual size of the value returned. if no option value is to be supplied or returned, .i optval may be null. .pp .i optname and any specified options are passed uninterpreted to the appropriate protocol module for interpretation. the include file .i contains definitions for socket level options, described below. options at other protocol levels vary in format and name; consult the appropriate entries in section 4 of the manual. .pp most socket-level options utilize an .i int argument for .ir optval . for .br setsockopt (), the argument should be nonzero to enable a boolean option, or zero if the option is to be disabled. .pp for a description of the available socket options see .br socket (7) and the appropriate protocol man pages. .sh return value on success, zero is returned for the standard options. on error, \-1 is returned, and .i errno is set to indicate the error. .pp netfilter allows the programmer to define custom socket options with associated handlers; for such options, the return value on success is the value returned by the handler. .sh errors .tp .b ebadf the argument .i sockfd is not a valid file descriptor. .tp .b efault the address pointed to by .i optval is not in a valid part of the process address space. for .br getsockopt (), this error may also be returned if .i optlen is not in a valid part of the process address space. .tp .b einval .i optlen invalid in .br setsockopt (). in some cases this error can also occur for an invalid value in .ir optval (e.g., for the .b ip_add_membership option described in .br ip (7)). .tp .b enoprotoopt the option is unknown at the level indicated. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd (these system calls first appeared in 4.2bsd). .\" svr4 documents additional enomem and enosr error codes, but does .\" not document the .\" .br so_sndlowat ", " so_rcvlowat ", " so_sndtimeo ", " so_rcvtimeo .\" options .sh notes for background on the .i socklen_t type, see .br accept (2). .sh bugs several of the socket options should be handled at lower levels of the system. .sh see also .br ioctl (2), .br socket (2), .br getprotoent (3), .br protocols (5), .br ip (7), .br packet (7), .br socket (7), .br tcp (7), .br udp (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2003 walter harms, andries brouwer .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th fdim 3 2021-03-22 "" "linux programmer's manual" .sh name fdim, fdimf, fdiml \- positive difference .sh synopsis .nf .b #include .pp .bi "double fdim(double " x ", double " y ); .bi "float fdimf(float " x ", float " y ); .bi "long double fdiml(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fdimf (), .br fdiml (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions return the positive difference, max(\fix\fp-\fiy\fp,0), between their arguments. .sh return value on success, these functions return the positive difference. .pp if .i x or .i y is a nan, a nan is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fdim (), .br fdimf (), .br fdiml () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh bugs before glibc version 2.24 .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6796 on certain architectures (e.g., x86, but not x86_64) these functions did not set .ir errno . .sh see also .br fmax (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2003 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" modified 2003-04-04 walter harms .\" .\" .\" slightly polished, aeb, 2003-04-06 .\" .th rtime 3 2021-03-22 "gnu" "linux programmer's manual" .sh name rtime \- get time from a remote machine .sh synopsis .nf .b "#include " .pp .bi "int rtime(struct sockaddr_in *" addrp ", struct rpc_timeval *" timep , .bi " struct rpc_timeval *" timeout ); .fi .sh description this function uses the time server protocol as described in rfc\ 868 to obtain the time from a remote machine. .pp the time server protocol gives the time in seconds since 00:00:00 utc, 1 jan 1900, and this function subtracts the appropriate constant in order to convert the result to seconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). .pp when .i timeout is non-null, the udp/time socket (port 37) is used. otherwise, the tcp/time socket (port 37) is used. .sh return value on success, 0 is returned, and the obtained 32-bit time value is stored in .ir timep\->tv_sec . in case of error \-1 is returned, and .i errno is set to indicate the error. .sh errors all errors for underlying functions .rb ( sendto (2), .br poll (2), .br recvfrom (2), .br connect (2), .br read (2)) can occur. moreover: .tp .b eio the number of returned bytes is not 4. .tp .b etimedout the waiting time as defined in timeout has expired. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br rtime () t} thread safety mt-safe .te .hy .ad .sp 1 .sh notes only ipv4 is supported. .pp some .i in.timed versions support only tcp. try the example program with .i use_tcp set to 1. .\" .pp .\" libc5 uses the prototype .\" .pp .\" .nf .\" int rtime(struct sockaddr_in *, struct timeval *, struct timeval *); .\" .fi .\" .pp .\" and requires .\" .i .\" instead of .\" .ir . .sh bugs .br rtime () in glibc 2.2.5 and earlier does not work properly on 64-bit machines. .sh examples this example requires that port 37 is up and open. you may check that the time entry within .i /etc/inetd.conf is not commented out. .pp the program connects to a computer called "linux". using "localhost" does not work. the result is the localtime of the computer "linux". .pp .ex #include #include #include #include #include #include #include static int use_tcp = 0; static char *servername = "linux"; int main(void) { struct sockaddr_in name; struct rpc_timeval time1 = {0,0}; struct rpc_timeval timeout = {1,0}; struct hostent *hent; int ret; memset(&name, 0, sizeof(name)); sethostent(1); hent = gethostbyname(servername); memcpy(&name.sin_addr, hent\->h_addr, hent\->h_length); ret = rtime(&name, &time1, use_tcp ? null : &timeout); if (ret < 0) perror("rtime error"); else { time_t t = time1.tv_sec; printf("%s\en", ctime(&t)); } exit(exit_success); } .ee .sh see also .\" .br netdate (1), .br ntpdate (1), .\" .br rdate (1), .br inetd (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th isfdtype 3 2021-03-22 "linux" "linux programmer's manual" .sh name isfdtype \- test file type of a file descriptor .sh synopsis .nf .b #include .b #include .pp .bi "int isfdtype(int " fd ", int " fdtype ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br isfdtype (): .nf since glibc 2.20: _default_source before glibc 2.20: _bsd_source || _svid_source .fi .sh description the .br isfdtype () function tests whether the file descriptor .i fd refers to a file of type .ir fdtype . the .i fdtype argument specifies one of the .b s_if* constants defined in .i and documented in .br stat (2) (e.g., .br s_ifreg ). .sh return value the .br isfdtype () function returns 1 if the file descriptor .i fd is of type .ir fdtype and 0 if it is not. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors the .br isfdtype () function can fail with any of the same errors as .br fstat (2). .sh conforming to the .br isfdtype () function is not specified in any standard, but did appear in the draft posix.1g standard. it is present on openbsd and tru64 unix (where the required header file in both cases is just .ir , as shown in the posix.1g draft), and possibly other systems. .sh notes portable applications should use .br fstat (2) instead. .sh see also .br fstat (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" $id: socket.2,v 1.4 1999/05/13 11:33:42 freitag exp $ .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-10-22 by eric s. raymond .\" modified 1998, 1999 by andi kleen .\" modified 2002-07-17 by michael kerrisk .\" modified 2004-06-17 by michael kerrisk .\" .th socket 2 2021-03-22 "linux" "linux programmer's manual" .sh name socket \- create an endpoint for communication .sh synopsis .nf .b #include .pp .bi "int socket(int " domain ", int " type ", int " protocol ); .fi .sh description .br socket () creates an endpoint for communication and returns a file descriptor that refers to that endpoint. the file descriptor returned by a successful call will be the lowest-numbered file descriptor not currently open for the process. .pp the .i domain argument specifies a communication domain; this selects the protocol family which will be used for communication. these families are defined in .ir . the formats currently understood by the linux kernel include: .ts tab(:); l1 lw40 l. name:purpose:man page t{ .br af_unix t}:t{ local communication t}:t{ .br unix (7) t} t{ .b af_local t}:t{ synonym for .b af_unix t}:t{ t} t{ .b af_inet t}:ipv4 internet protocols:t{ .br ip (7) t} t{ .b af_ax25 t}:t{ amateur radio ax.25 protocol t}:t{ .\" part of ax25-tools .br ax25 (4) t} t{ .b af_ipx t}:ipx \- novell protocols: t{ .b af_appletalk t}:appletalk:t{ .br ddp (7) t} t{ .b af_x25 t}:itu-t x.25 / iso-8208 protocol:t{ .br x25 (7) t} t{ .b af_inet6 t}:ipv6 internet protocols:t{ .br ipv6 (7) t} t{ .b af_decnet t}:t{ decet protocol sockets t} t{ .b af_key t}:t{ key management protocol, originally developed for usage with ipsec t} t{ .b af_netlink t}:t{ kernel user interface device t}:t{ .br netlink (7) t} t{ .b af_packet t}:t{ low-level packet interface t}:t{ .br packet (7) t} t{ .b af_rds t}:t{ .\" commit: 639b321b4d8f4e412bfbb2a4a19bfebc1e68ace4 reliable datagram sockets (rds) protocol t}:t{ .\" rds-tools: https://github.com/oracle/rds-tools/blob/master/rds.7 .\" rds-tools: https://github.com/oracle/rds-tools/blob/master/rds-rdma.7 .br rds (7) .br .br rds\-rdma (7) t} t{ .b af_pppox t}:t{ generic ppp transport layer, for setting up l2 tunnels (l2tp and pppoe) t} t{ .b af_llc t}:t{ .\" linux-history commit: 34beb106cde7da233d4df35dd3d6cf4fee937caa logical link control (ieee 802.2 llc) protocol t} t{ .b af_ib t}:t{ .\" commits: 8d36eb01da5d371f..ce117ffac2e93334 infiniband native addressing t} t{ .b af_mpls t}:t{ .\" commits: 0189197f441602acdca3f97750d392a895b778fd multiprotocol label switching t} t{ .b af_can t}:t{ .\" commits: 8dbde28d9711475a..5423dd67bd0108a1 controller area network automotive bus protocol t} t{ .b af_tipc t}:t{ .\" commits: b97bf3fd8f6a16966d4f18983b2c40993ff937d4 tipc, "cluster domain sockets" protocol t} t{ .b af_bluetooth t}:t{ .\" commits: 8d36eb01da5d371f..ce117ffac2e93334 bluetooth low-level socket protocol t} t{ .b af_alg t}:t{ .\" commit: 03c8efc1ffeb6b82a22c1af8dd908af349563314 interface to kernel crypto api t} t{ .b af_vsock t}:t{ .\" commit: d021c344051af91f42c5ba9fdedc176740cbd238 vsock (originally "vmware vsockets") protocol for hypervisor-guest communication t}:t{ .br vsock (7) t} t{ .b af_kcm t}:t{ .\" commit: 03c8efc1ffeb6b82a22c1af8dd908af349563314 kcm (kernel connection multiplexer) interface t} t{ .b af_xdp t}:t{ .\" commit: c0c77d8fb787cfe0c3fca689c2a30d1dad4eaba7 xdp (express data path) interface t} .te .pp further details of the above address families, as well as information on several other address families, can be found in .br address_families (7). .pp the socket has the indicated .ir type , which specifies the communication semantics. currently defined types are: .tp 16 .b sock_stream provides sequenced, reliable, two-way, connection-based byte streams. an out-of-band data transmission mechanism may be supported. .tp .b sock_dgram supports datagrams (connectionless, unreliable messages of a fixed maximum length). .tp .b sock_seqpacket provides a sequenced, reliable, two-way connection-based data transmission path for datagrams of fixed maximum length; a consumer is required to read an entire packet with each input system call. .tp .b sock_raw provides raw network protocol access. .tp .b sock_rdm provides a reliable datagram layer that does not guarantee ordering. .tp .b sock_packet obsolete and should not be used in new programs; see .br packet (7). .pp some socket types may not be implemented by all protocol families. .pp since linux 2.6.27, the .i type argument serves a second purpose: in addition to specifying a socket type, it may include the bitwise or of any of the following values, to modify the behavior of .br socket (): .tp 16 .b sock_nonblock set the .br o_nonblock file status flag on the open file description (see .br open (2)) referred to by the new file descriptor. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .tp .b sock_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .pp the .i protocol specifies a particular protocol to be used with the socket. normally only a single protocol exists to support a particular socket type within a given protocol family, in which case .i protocol can be specified as 0. however, it is possible that many protocols may exist, in which case a particular protocol must be specified in this manner. the protocol number to use is specific to the \*(lqcommunication domain\*(rq in which communication is to take place; see .br protocols (5). see .br getprotoent (3) on how to map protocol name strings to protocol numbers. .pp sockets of type .b sock_stream are full-duplex byte streams. they do not preserve record boundaries. a stream socket must be in a .i connected state before any data may be sent or received on it. a connection to another socket is created with a .br connect (2) call. once connected, data may be transferred using .br read (2) and .br write (2) calls or some variant of the .br send (2) and .br recv (2) calls. when a session has been completed a .br close (2) may be performed. out-of-band data may also be transmitted as described in .br send (2) and received as described in .br recv (2). .pp the communications protocols which implement a .b sock_stream ensure that data is not lost or duplicated. if a piece of data for which the peer protocol has buffer space cannot be successfully transmitted within a reasonable length of time, then the connection is considered to be dead. when .b so_keepalive is enabled on the socket the protocol checks in a protocol-specific manner if the other end is still alive. a .b sigpipe signal is raised if a process sends or receives on a broken stream; this causes naive processes, which do not handle the signal, to exit. .b sock_seqpacket sockets employ the same system calls as .b sock_stream sockets. the only difference is that .br read (2) calls will return only the amount of data requested, and any data remaining in the arriving packet will be discarded. also all message boundaries in incoming datagrams are preserved. .pp .b sock_dgram and .b sock_raw sockets allow sending of datagrams to correspondents named in .br sendto (2) calls. datagrams are generally received with .br recvfrom (2), which returns the next datagram along with the address of its sender. .pp .b sock_packet is an obsolete socket type to receive raw packets directly from the device driver. use .br packet (7) instead. .pp an .br fcntl (2) .b f_setown operation can be used to specify a process or process group to receive a .b sigurg signal when the out-of-band data arrives or .b sigpipe signal when a .b sock_stream connection breaks unexpectedly. this operation may also be used to set the process or process group that receives the i/o and asynchronous notification of i/o events via .br sigio . using .b f_setown is equivalent to an .br ioctl (2) call with the .b fiosetown or .b siocspgrp argument. .pp when the network signals an error condition to the protocol module (e.g., using an icmp message for ip) the pending error flag is set for the socket. the next operation on this socket will return the error code of the pending error. for some protocols it is possible to enable a per-socket error queue to retrieve detailed information about the error; see .b ip_recverr in .br ip (7). .pp the operation of sockets is controlled by socket level .ir options . these options are defined in .ir . the functions .br setsockopt (2) and .br getsockopt (2) are used to set and get options. .sh return value on success, a file descriptor for the new socket is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces permission to create a socket of the specified type and/or protocol is denied. .tp .b eafnosupport the implementation does not support the specified address family. .tp .b einval unknown protocol, or protocol family not available. .tp .b einval .\" since linux 2.6.27 invalid flags in .ir type . .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .br enobufs " or " enomem insufficient memory is available. the socket cannot be created until sufficient resources are freed. .tp .b eprotonosupport the protocol type or the specified protocol is not supported within this domain. .pp other errors may be generated by the underlying protocol modules. .sh conforming to posix.1-2001, posix.1-2008, 4.4bsd. .pp the .b sock_nonblock and .b sock_cloexec flags are linux-specific. .pp .br socket () appeared in 4.2bsd. it is generally portable to/from non-bsd systems supporting clones of the bsd socket layer (including system\ v variants). .sh notes the manifest constants used under 4.x bsd for protocol families are .br pf_unix , .br pf_inet , and so on, while .br af_unix , .br af_inet , and so on are used for address families. however, already the bsd man page promises: "the protocol family generally is the same as the address family", and subsequent standards use af_* everywhere. .sh examples an example of the use of .br socket () is shown in .br getaddrinfo (3). .sh see also .br accept (2), .br bind (2), .br close (2), .br connect (2), .br fcntl (2), .br getpeername (2), .br getsockname (2), .br getsockopt (2), .br ioctl (2), .br listen (2), .br read (2), .br recv (2), .br select (2), .br send (2), .br shutdown (2), .br socketpair (2), .br write (2), .br getprotoent (3), .br address_families (7), .br ip (7), .br socket (7), .br tcp (7), .br udp (7), .br unix (7) .pp \(lqan introductory 4.3bsd interprocess communication tutorial\(rq and \(lqbsd interprocess communication tutorial\(rq, reprinted in .i unix programmer's supplementary documents volume 1. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995 jim van zandt .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 2001-12-13, martin schulze .\" added ttyname_r, aeb, 2002-07-20 .\" .th ttyname 3 2021-03-22 "linux" "linux programmer's manual" .sh name ttyname, ttyname_r \- return name of a terminal .sh synopsis .nf .b #include .pp .bi "char *ttyname(int " fd ); .bi "int ttyname_r(int " fd ", char *" buf ", size_t " buflen ); .fi .sh description the function .br ttyname () returns a pointer to the null-terminated pathname of the terminal device that is open on the file descriptor \fifd\fp, or null on error (for example, if \fifd\fp is not connected to a terminal). the return value may point to static data, possibly overwritten by the next call. the function .br ttyname_r () stores this pathname in the buffer .i buf of length .ir buflen . .sh return value the function .br ttyname () returns a pointer to a pathname on success. on error, null is returned, and .i errno is set to indicate the error. the function .br ttyname_r () returns 0 on success, and an error number upon error. .sh errors .tp .b ebadf bad file descriptor. .tp .\" glibc commit 15e9a4f378c8607c2ae1aa465436af4321db0e23 .b enodev .i fd refers to a slave pseudoterminal device but the corresponding pathname could not be found (see notes). .tp .b enotty .i fd does not refer to a terminal device. .tp .b erange .rb ( ttyname_r ()) .i buflen was too small to allow storing the pathname. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ttyname () t} thread safety mt-unsafe race:ttyname t{ .br ttyname_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, 4.2bsd. .sh notes a process that keeps a file descriptor that refers to a .br pts (4) device open when switching to another mount namespace that uses a different .i /dev/ptmx instance may still accidentally find that a device path of the same name for that file descriptor exists. however, this device path refers to a different device and thus can't be used to access the device that the file descriptor refers to. calling .br ttyname () or .br ttyname_r () on the file descriptor in the new mount namespace will cause these functions to return null and set .i errno to .br enodev . .sh see also .br tty (1), .br fstat (2), .br ctermid (3), .br isatty (3), .br pts (4) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/capget.2 .\" copyright (c) 2007 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sgetmask 2 2021-03-22 "linux" "linux programmer's manual" .sh name sgetmask, ssetmask \- manipulation of signal mask (obsolete) .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .b "long syscall(sys_sgetmask, void);" .bi "long syscall(sys_ssetmask, long " newmask ); .fi .pp .ir note : glibc provides no wrappers for these functions, necessitating the use of .br syscall (2). .sh description these system calls are obsolete. .ir "do not use them" ; use .br sigprocmask (2) instead. .pp .br sgetmask () returns the signal mask of the calling process. .pp .br ssetmask () sets the signal mask of the calling process to the value given in .ir newmask . the previous signal mask is returned. .pp the signal masks dealt with by these two system calls are plain bit masks (unlike the .i sigset_t used by .br sigprocmask (2)); use .br sigmask (3) to create and inspect these masks. .sh return value .br sgetmask () always successfully returns the signal mask. .br ssetmask () always succeeds, and returns the previous signal mask. .sh errors these system calls always succeed. .sh versions since linux 3.16, .\" f6187769dae48234f3877df3c4d99294cc2254fa support for these system calls is optional, depending on whether the kernel was built with the .b config_sgetmask_syscall option. .sh conforming to these system calls are linux-specific. .sh notes these system calls are unaware of signal numbers greater than 31 (i.e., real-time signals). .pp these system calls do not exist on x86-64. .pp it is not possible to block .b sigstop or .br sigkill . .sh see also .br sigprocmask (2), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" this replaces an earlier man page written by walter harms .\" . .\" .th ttyslot 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ttyslot \- find the slot of the current user's terminal in some file .sh synopsis .nf .br "#include " " /* see notes */" .pp .b "int ttyslot(void);" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br ttyslot (): .nf since glibc 2.24: _default_source from glibc 2.20 to 2.23: _default_source || (_xopen_source && _xopen_source < 500) glibc 2.19 and earlier: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description the legacy function .br ttyslot () returns the index of the current user's entry in some file. .pp now "what file?" you ask. well, let's first look at some history. .ss ancient history there used to be a file .i /etc/ttys in unix\ v6, that was read by the .br init (1) program to find out what to do with each terminal line. each line consisted of three characters. the first character was either \(aq0\(aq or \(aq1\(aq, where \(aq0\(aq meant "ignore". the second character denoted the terminal: \(aq8\(aq stood for "/dev/tty8". the third character was an argument to .br getty (8) indicating the sequence of line speeds to try (\(aq\-\(aq was: start trying 110 baud). thus a typical line was "18\-". a hang on some line was solved by changing the \(aq1\(aq to a \(aq0\(aq, signaling init, changing back again, and signaling init again. .pp in unix\ v7 the format was changed: here the second character was the argument to .br getty (8) indicating the sequence of line speeds to try (\(aq0\(aq was: cycle through 300-1200-150-110 baud; \(aq4\(aq was for the on-line console decwriter) while the rest of the line contained the name of the tty. thus a typical line was "14console". .pp later systems have more elaborate syntax. system v-like systems have .i /etc/inittab instead. .ss ancient history (2) on the other hand, there is the file .i /etc/utmp listing the people currently logged in. it is maintained by .br login (1). it has a fixed size, and the appropriate index in the file was determined by .br login (1) using the .br ttyslot () call to find the number of the line in .i /etc/ttys (counting from 1). .ss the semantics of ttyslot thus, the function .br ttyslot () returns the index of the controlling terminal of the calling process in the file .ir /etc/ttys , and that is (usually) the same as the index of the entry for the current user in the file .ir /etc/utmp . bsd still has the .i /etc/ttys file, but system v-like systems do not, and hence cannot refer to it. thus, on such systems the documentation says that .br ttyslot () returns the current user's index in the user accounting data base. .sh return value if successful, this function returns the slot number. on error (e.g., if none of the file descriptors 0, 1, or 2 is associated with a terminal that occurs in this data base) it returns 0 on unix\ v6 and v7 and bsd-like systems, but \-1 on system v-like systems. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ttyslot () t} thread safety mt-unsafe .te .hy .ad .sp 1 .sh conforming to susv1; marked as legacy in susv2; removed in posix.1-2001. susv2 requires \-1 on error. .sh notes the utmp file is found in various places on various systems, such as .ir /etc/utmp , .ir /var/adm/utmp , .ir /var/run/utmp . .pp the glibc2 implementation of this function reads the file .br _path_ttys , defined in .i as "/etc/ttys". it returns 0 on error. since linux systems do not usually have "/etc/ttys", it will always return 0. .pp on bsd-like systems and linux, the declaration of .br ttyslot () is provided by .ir . on system v-like systems, the declaration is provided by .ir . since glibc 2.24, .i also provides the declaration with the following feature test macro definitions: .pp .in +4n .ex (_xopen_source >= 500 || (_xopen_source && _xopen_source_extended)) && ! (_posix_c_source >= 200112l || _xopen_source >= 600) .ee .in .pp minix also has .ir fttyslot ( fd ). .\" .sh history .\" .br ttyslot () .\" appeared in unix v7. .sh see also .br getttyent (3), .br ttyname (3), .br utmp (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/posix_fadvise.2 .\" this manpage is copyright (c) 2004, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2004-05-40 created by michael kerrisk .\" 2004-10-05 aeb, minor correction .\" .th readahead 2 2021-03-22 "linux" "linux programmer's manual" .sh name readahead \- initiate file readahead into page cache .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "ssize_t readahead(int " fd ", off64_t " offset ", size_t " count ); .fi .sh description .br readahead () initiates readahead on a file so that subsequent reads from that file will be satisfied from the cache, and not block on disk i/o (assuming the readahead was initiated early enough and that other activity on the system did not in the meantime flush pages from the cache). .pp the .i fd argument is a file descriptor identifying the file which is to be read. the .i offset argument specifies the starting point from which data is to be read and .i count specifies the number of bytes to be read. i/o is performed in whole pages, so that .i offset is effectively rounded down to a page boundary and bytes are read up to the next page boundary greater than or equal to .ir "(offset+count)" . .br readahead () does not read beyond the end of the file. the file offset of the open file description referred to by the file descriptor .i fd is left unchanged. .sh return value on success, .br readahead () returns 0; on failure, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor or is not open for reading. .tp .b einval .i fd does not refer to a file type to which .br readahead () can be applied. .sh versions the .br readahead () system call appeared in linux 2.4.13; glibc support has been provided since version 2.3. .sh conforming to the .br readahead () system call is linux-specific, and its use should be avoided in portable applications. .sh notes on some 32-bit architectures, the calling signature for this system call differs, for the reasons described in .br syscall (2). .sh bugs .br readahead () attempts to schedule the reads in the background and return immediately. however, it may block while it reads the filesystem metadata needed to locate the requested blocks. this occurs frequently with ext[234] on large files using indirect blocks instead of extents, giving the appearance that the call blocks until the requested data has been read. .sh see also .br lseek (2), .br madvise (2), .br mmap (2), .br posix_fadvise (2), .br read (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cexp.3 .so man3/strsignal.3 .so man2/fchown.2 .so man2/unimplemented.2 .\" copyright 1993 ulrich drepper (drepper@karlsruhe.gmd.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" references consulted: .\" sunos 4.1.1 man pages .\" modified sat sep 30 21:52:01 1995 by jim van zandt .\" remarks from dhw@gamgee.acad.emich.edu fri jun 19 06:46:31 1998 .\" modified 2001-12-26, 2003-11-28, 2004-05-20, aeb .\" 2008-09-02, mtk: various additions and rewrites .\" 2008-09-03, mtk, restructured somewhat, in part after suggestions from .\" timothy s. nelson .\" .th hsearch 3 2021-03-22 "gnu" "linux programmer's manual" .sh name hcreate, hdestroy, hsearch, hcreate_r, hdestroy_r, hsearch_r \- hash table management .sh synopsis .nf .b #include .pp .bi "int hcreate(size_t " nel ); .b "void hdestroy(void);" .pp .bi "entry *hsearch(entry " item ", action " action ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int hcreate_r(size_t " nel ", struct hsearch_data *" htab ); .bi "void hdestroy_r(struct hsearch_data *" htab ); .pp .bi "int hsearch_r(entry " item ", action " action ", entry **" retval , .bi " struct hsearch_data *" htab ); .fi .sh description the three functions .br hcreate (), .br hsearch (), and .br hdestroy () allow the caller to create and manage a hash search table containing entries consisting of a key (a string) and associated data. using these functions, only one hash table can be used at a time. .pp the three functions .br hcreate_r (), .br hsearch_r (), .br hdestroy_r () are reentrant versions that allow a program to use more than one hash search table at the same time. the last argument, .ir htab , points to a structure that describes the table on which the function is to operate. the programmer should treat this structure as opaque (i.e., do not attempt to directly access or modify the fields in this structure). .pp first a hash table must be created using .br hcreate (). the argument \finel\fp specifies the maximum number of entries in the table. (this maximum cannot be changed later, so choose it wisely.) the implementation may adjust this value upward to improve the performance of the resulting hash table. .\" e.g., in glibc it is raised to the next higher prime number .pp the .br hcreate_r () function performs the same task as .br hcreate (), but for the table described by the structure .ir *htab . the structure pointed to by .i htab must be zeroed before the first call to .br hcreate_r (). .pp the function .br hdestroy () frees the memory occupied by the hash table that was created by .br hcreate (). after calling .br hdestroy (), a new hash table can be created using .br hcreate (). the .br hdestroy_r () function performs the analogous task for a hash table described by .ir *htab , which was previously created using .br hcreate_r (). .pp the .br hsearch () function searches the hash table for an item with the same key as \fiitem\fp (where "the same" is determined using .br strcmp (3)), and if successful returns a pointer to it. .pp the argument \fiitem\fp is of type \fientry\fp, which is defined in \fi\fp as follows: .pp .in +4n .ex typedef struct entry { char *key; void *data; } entry; .ee .in .pp the field \fikey\fp points to a null-terminated string which is the search key. the field \fidata\fp points to data that is associated with that key. .pp the argument \fiaction\fp determines what .br hsearch () does after an unsuccessful search. this argument must either have the value .br enter , meaning insert a copy of .ir item (and return a pointer to the new hash table entry as the function result), or the value .br find , meaning that null should be returned. (if .i action is .br find , then .i data is ignored.) .pp the .br hsearch_r () function is like .br hsearch () but operates on the hash table described by .ir *htab . the .br hsearch_r () function differs from .br hsearch () in that a pointer to the found item is returned in .ir *retval , rather than as the function result. .sh return value .br hcreate () and .br hcreate_r () return nonzero on success. they return 0 on error, with .i errno set to indicate the error. .pp on success, .br hsearch () returns a pointer to an entry in the hash table. .br hsearch () returns null on error, that is, if \fiaction\fp is \fbenter\fp and the hash table is full, or \fiaction\fp is \fbfind\fp and \fiitem\fp cannot be found in the hash table. .br hsearch_r () returns nonzero on success, and 0 on error. in the event of an error, these two functions set .i errno to indicate the error. .sh errors .br hcreate_r () and .br hdestroy_r () can fail for the following reasons: .tp .b einval .i htab is null. .pp .br hsearch () and .br hsearch_r () can fail for the following reasons: .tp .b enomem .i action was .br enter , .i key was not found in the table, and there was no room in the table to add a new entry. .tp .b esrch .i action was .br find , and .i key was not found in the table. .pp posix.1 specifies only the .\" prox.1-2001, posix.1-2008 .b enomem error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br hcreate (), .br hsearch (), .br hdestroy () t} thread safety mt-unsafe race:hsearch t{ .br hcreate_r (), .br hsearch_r (), .br hdestroy_r () t} thread safety mt-safe race:htab .te .hy .ad .sp 1 .sh conforming to the functions .br hcreate (), .br hsearch (), and .br hdestroy () are from svr4, and are described in posix.1-2001 and posix.1-2008. .pp the functions .br hcreate_r (), .br hsearch_r (), and .br hdestroy_r () are gnu extensions. .sh notes hash table implementations are usually more efficient when the table contains enough free space to minimize collisions. typically, this means that .i nel should be at least 25% larger than the maximum number of elements that the caller expects to store in the table. .pp the .br hdestroy () and .br hdestroy_r () functions do not free the buffers pointed to by the .i key and .i data elements of the hash table entries. (it can't do this because it doesn't know whether these buffers were allocated dynamically.) if these buffers need to be freed (perhaps because the program is repeatedly creating and destroying hash tables, rather than creating a single table whose lifetime matches that of the program), then the program must maintain bookkeeping data structures that allow it to free them. .sh bugs svr4 and posix.1-2001 specify that \fiaction\fp is significant only for unsuccessful searches, so that an \fbenter\fp should not do anything for a successful search. in libc and glibc (before version 2.3), the implementation violates the specification, updating the \fidata\fp for the given \fikey\fp in this case. .pp individual hash table entries can be added, but not deleted. .sh examples the following program inserts 24 items into a hash table, then prints some of them. .pp .ex #include #include #include static char *data[] = { "alpha", "bravo", "charlie", "delta", "echo", "foxtrot", "golf", "hotel", "india", "juliet", "kilo", "lima", "mike", "november", "oscar", "papa", "quebec", "romeo", "sierra", "tango", "uniform", "victor", "whisky", "x\-ray", "yankee", "zulu" }; int main(void) { entry e; entry *ep; hcreate(30); for (int i = 0; i < 24; i++) { e.key = data[i]; /* data is just an integer, instead of a pointer to something */ e.data = (void *) i; ep = hsearch(e, enter); /* there should be no failures */ if (ep == null) { fprintf(stderr, "entry failed\en"); exit(exit_failure); } } for (int i = 22; i < 26; i++) { /* print two entries from the table, and show that two are not in the table */ e.key = data[i]; ep = hsearch(e, find); printf("%9.9s \-> %9.9s:%d\en", e.key, ep ? ep\->key : "null", ep ? (int)(ep\->data) : 0); } hdestroy(); exit(exit_success); } .ee .sh see also .br bsearch (3), .br lsearch (3), .br malloc (3), .br tsearch (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/finite.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th log2 3 2021-03-22 "" "linux programmer's manual" .sh name log2, log2f, log2l \- base-2 logarithmic function .sh synopsis .nf .b #include .pp .bi "double log2(double " x ); .bi "float log2f(float " x ); .bi "long double log2l(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br log2 (), .br log2f (), .br log2l (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions return the base 2 logarithm of .ir x . .sh return value on success, these functions return the base 2 logarithm of .ir x . .pp for special cases, including where .i x is 0, 1, negative, infinity, or nan, see .br log (3). .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp for a discussion of the errors that can occur for these functions, see .br log (3). .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br log2 (), .br log2f (), .br log2l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh see also .br cbrt (3), .br clog2 (3), .br log (3), .br log10 (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fenv.3 .so man2/shmop.2 .so man3/tzset.3 .so man3/fenv.3 .so man7/system_data_types.7 .so man7/iso_8859-3.7 .so man3/div.3 .\" copyright 2003 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" polished a bit, added a little, aeb .\" .th setaliasent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name setaliasent, endaliasent, getaliasent, getaliasent_r, getaliasbyname, getaliasbyname_r \- read an alias entry .sh synopsis .nf .b #include .pp .b "void setaliasent(void);" .b "void endaliasent(void);" .pp .b "struct aliasent *getaliasent(void);" .bi "int getaliasent_r(struct aliasent *restrict " result , .bi " char *restrict " buffer ", size_t " buflen , .bi " struct aliasent **restrict " res ); .pp .bi "struct aliasent *getaliasbyname(const char *" name ); .bi "int getaliasbyname_r(const char *restrict " name , .bi " struct aliasent *restrict " result , .bi " char *restrict " buffer ", size_t " buflen , .bi " struct aliasent **restrict " res ); .fi .sh description one of the databases available with the name service switch (nss) is the aliases database, that contains mail aliases. (to find out which databases are supported, try .ir "getent \-\-help" .) six functions are provided to access the aliases database. .pp the .br getaliasent () function returns a pointer to a structure containing the group information from the aliases database. the first time it is called it returns the first entry; thereafter, it returns successive entries. .pp the .br setaliasent () function rewinds the file pointer to the beginning of the aliases database. .pp the .br endaliasent () function closes the aliases database. .pp .br getaliasent_r () is the reentrant version of the previous function. the requested structure is stored via the first argument but the programmer needs to fill the other arguments also. not providing enough space causes the function to fail. .pp the function .br getaliasbyname () takes the name argument and searches the aliases database. the entry is returned as a pointer to a .ir "struct aliasent" . .pp .br getaliasbyname_r () is the reentrant version of the previous function. the requested structure is stored via the second argument but the programmer needs to fill the other arguments also. not providing enough space causes the function to fail. .pp the .i "struct aliasent" is defined in .ir : .pp .in +4n .ex struct aliasent { char *alias_name; /* alias name */ size_t alias_members_len; char **alias_members; /* alias name list */ int alias_local; }; .ee .in .sh return value the functions .br getaliasent_r () and .br getaliasbyname_r () return a nonzero value on error. .sh files the default alias database is the file .ir /etc/aliases . this can be changed in the .i /etc/nsswitch.conf file. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br setaliasent (), .br endaliasent (), .br getaliasent_r (), .br getaliasbyname_r () t} thread safety mt-safe locale t{ .br getaliasent (), .br getaliasbyname () t} thread safety mt-unsafe .te .hy .ad .sp 1 .sh conforming to these routines are glibc-specific. the next system has similar routines: .pp .in +4n .ex #include void alias_setent(void); void alias_endent(void); alias_ent *alias_getent(void); alias_ent *alias_getbyname(char *name); .ee .in .sh examples the following example compiles with .ir "gcc example.c \-o example" . it will dump all names in the alias database. .pp .ex #include #include #include #include int main(void) { struct aliasent *al; setaliasent(); for (;;) { al = getaliasent(); if (al == null) break; printf("name: %s\en", al\->alias_name); } if (errno) { perror("reading alias"); exit(exit_failure); } endaliasent(); exit(exit_success); } .ee .sh see also .br getgrent (3), .br getpwent (3), .br getspent (3), .br aliases (5) .\" .\" /etc/sendmail/aliases .\" yellow pages .\" newaliases, postalias .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/toupper.3 .so man2/tkill.2 .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" a few pieces remain from an earlier version written in .\" 2002 by walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getgrouplist 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getgrouplist \- get list of groups to which a user belongs .sh synopsis .nf .b #include .pp .bi "int getgrouplist(const char *" user ", gid_t " group , .bi " gid_t *" groups ", int *" ngroups ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getgrouplist (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the .br getgrouplist () function scans the group database (see .br group (5)) to obtain the list of groups that .i user belongs to. up to .i *ngroups of these groups are returned in the array .ir groups . .pp if it was not among the groups defined for .i user in the group database, then .i group is included in the list of groups returned by .br getgrouplist (); typically this argument is specified as the group id from the password record for .ir user . .pp the .i ngroups argument is a value-result argument: on return it always contains the number of groups found for .ir user , including .ir group ; this value may be greater than the number of groups stored in .ir groups . .sh return value if the number of groups of which .i user is a member is less than or equal to .ir *ngroups , then the value .i *ngroups is returned. .pp if the user is a member of more than .i *ngroups groups, then .br getgrouplist () returns \-1. in this case, the value returned in .ir *ngroups can be used to resize the buffer passed to a further call .br getgrouplist (). .sh versions this function is present since glibc 2.2.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getgrouplist () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to this function is nonstandard; it appears on most bsds. .sh bugs in glibc versions before 2.3.3, the implementation of this function contains a buffer-overrun bug: it returns the complete list of groups for .ir user in the array .ir groups , even when the number of groups exceeds .ir *ngroups . .sh examples the program below displays the group list for the user named in its first command-line argument. the second command-line argument specifies the .i ngroups value to be supplied to .br getgrouplist (). the following shell session shows examples of the use of this program: .pp .in +4n .ex .rb "$" " ./a.out cecilia 0" getgrouplist() returned \-1; ngroups = 3 .rb "$" " ./a.out cecilia 3" ngroups = 3 16 (dialout) 33 (video) 100 (users) .ee .in .ss program source \& .ex #include #include #include #include int main(int argc, char *argv[]) { int ngroups; struct passwd *pw; struct group *gr; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } ngroups = atoi(argv[2]); gid_t *groups = malloc(sizeof(*groups) * ngroups); if (groups == null) { perror("malloc"); exit(exit_failure); } /* fetch passwd structure (contains first group id for user). */ pw = getpwnam(argv[1]); if (pw == null) { perror("getpwnam"); exit(exit_success); } /* retrieve group list. */ if (getgrouplist(argv[1], pw\->pw_gid, groups, &ngroups) == \-1) { fprintf(stderr, "getgrouplist() returned \-1; ngroups = %d\en", ngroups); exit(exit_failure); } /* display list of retrieved groups, along with group names. */ fprintf(stderr, "ngroups = %d\en", ngroups); for (int j = 0; j < ngroups; j++) { printf("%d", groups[j]); gr = getgrgid(groups[j]); if (gr != null) printf(" (%s)", gr\->gr_name); printf("\en"); } exit(exit_success); } .ee .sh see also .br getgroups (2), .br setgroups (2), .br getgrent (3), .br group_member (3), .br group (5), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/lround.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_tryjoin_np 3 2021-08-27 "linux" "linux programmer's manual" .sh name pthread_tryjoin_np, pthread_timedjoin_np \- try to join with a terminated thread .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_tryjoin_np(pthread_t " thread ", void **" retval ); .bi "int pthread_timedjoin_np(pthread_t " thread ", void **" retval , .bi " const struct timespec *" abstime ); .fi .pp compile and link with \fi\-pthread\fp. .sh description these functions operate in the same way as .br pthread_join (3), except for the differences described on this page. .pp the .br pthread_tryjoin_np () function performs a nonblocking join with the thread .ir thread , returning the exit status of the thread in .ir *retval . if .i thread has not yet terminated, then instead of blocking, as is done by .br pthread_join (3), the call returns an error. .pp the .br pthread_timedjoin_np () function performs a join-with-timeout. if .i thread has not yet terminated, then the call blocks until a maximum time, specified in .ir abstime , measured against the .br clock_realtime clock. if the timeout expires before .i thread terminates, the call returns an error. the .i abstime argument is a structure of the following form, specifying an absolute time measured since the epoch (see .br time (2)): .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .sh return value on success, these functions return 0; on error, they return an error number. .sh errors these functions can fail with the same errors as .br pthread_join (3). .br pthread_tryjoin_np () can in addition fail with the following error: .tp .b ebusy .i thread had not yet terminated at the time of the call. .pp .br pthread_timedjoin_np () can in addition fail with the following errors: .tp .br einval .i abstime value is invalid .ri ( tv_sec is less than 0 or .ir tv_nsec is greater than 1e9). .tp .br etimedout the call timed out before .i thread terminated. .pp .br pthread_timedjoin_np () never returns the error .br eintr . .sh versions these functions first appeared in glibc in version 2.3.3. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_tryjoin_np (), .br pthread_timedjoin_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh bugs the .br pthread_timedjoin_np () function measures time by internally calculating a relative sleep interval that is then measured against the .br clock_monotonic clock instead of the .br clock_realtime clock. consequently, the timeout is unaffected by discontinuous changes to the .br clock_realtime clock. .sh examples the following code waits to join for up to 5 seconds: .pp .in +4n .ex struct timespec ts; int s; \&... if (clock_gettime(clock_realtime, &ts) == \-1) { /* handle error */ } ts.tv_sec += 5; s = pthread_timedjoin_np(thread, null, &ts); if (s != 0) { /* handle error */ } .ee .in .sh see also .br clock_gettime (2), .br pthread_exit (3), .br pthread_join (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .so man3/tanh.3 .so man3/inet.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .th exp10 3 2021-03-22 "gnu" "linux programmer's manual" .sh name exp10, exp10f, exp10l \- base-10 exponential function .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "double exp10(double " x ); .bi "float exp10f(float " x ); .bi "long double exp10l(long double " x ); .fi .pp link with \fi\-lm\fp. .sh description these functions return the value of 10 raised to the power of .ir x . .sh return value on success, these functions return the base-10 exponential value of .ir x . .pp for various special cases, including the handling of infinity and nan, as well as overflows and underflows, see .br exp (3). .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp for a discussion of the errors that can occur for these functions, see .br exp (3). .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br exp10 (), .br exp10f (), .br exp10l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. .sh bugs prior to version 2.19, the glibc implementation of these functions did not set .i errno to .b erange when an underflow error occurred. .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6787 .sh see also .br cbrt (3), .br exp (3), .br exp2 (3), .br log10 (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 17:51:42 1993 by rik faith (faith@cs.unc.edu) .\" modified tue aug 17 11:42:20 1999 by ariel scolnicov (ariels@compugen.co.il) .th sysconf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name sysconf \- get configuration information at run time .sh synopsis .nf .b #include .pp .bi "long sysconf(int " "name" ); .fi .sh description posix allows an application to test at compile or run time whether certain options are supported, or what the value is of certain configurable constants or limits. .pp at compile time this is done by including .i and/or .i and testing the value of certain macros. .pp at run time, one can ask for numerical values using the present function .br sysconf (). one can ask for numerical values that may depend on the filesystem in which a file resides using .br fpathconf (3) and .br pathconf (3). one can ask for string values using .br confstr (3). .pp the values obtained from these functions are system configuration constants. they do not change during the lifetime of a process. .\" except that sysconf(_sc_open_max) may change answer after a call .\" to setrlimit( ) which changes the rlimit_nofile soft limit .pp for options, typically, there is a constant .b _posix_foo that may be defined in .ir . if it is undefined, one should ask at run time. if it is defined to \-1, then the option is not supported. if it is defined to 0, then relevant functions and headers exist, but one has to ask at run time what degree of support is available. if it is defined to a value other than \-1 or 0, then the option is supported. usually the value (such as 200112l) indicates the year and month of the posix revision describing the option. glibc uses the value 1 to indicate support as long as the posix revision has not been published yet. .\" and 999 to indicate support for options no longer present in the latest .\" standard. (?) the .br sysconf () argument will be .br _sc_foo . for a list of options, see .br posixoptions (7). .pp for variables or limits, typically, there is a constant .br _foo , maybe defined in .ir , or .br _posix_foo , maybe defined in .ir . the constant will not be defined if the limit is unspecified. if the constant is defined, it gives a guaranteed value, and a greater value might actually be supported. if an application wants to take advantage of values which may change between systems, a call to .br sysconf () can be made. the .br sysconf () argument will be .br _sc_foo . .ss posix.1 variables we give the name of the variable, the name of the .br sysconf () argument used to inquire about its value, and a short description. .pp first, the posix.1 compatible values. .\" [for the moment: only the things that are unconditionally present] .\" .tp .\" .br aio_listio_max " - " _sc_aio_listio_max .\" (if _posix_asynchronous_io) .\" maximum number of i/o operations in a single list i/o call. .\" must not be less than _posix_aio_listio_max. .\" .tp .\" .br aio_max " - " _sc_aio_max .\" (if _posix_asynchronous_io) .\" maximum number of outstanding asynchronous i/o operations. .\" must not be less than _posix_aio_max. .\" .tp .\" .br aio_prio_delta_max " - " _sc_aio_prio_delta_max .\" (if _posix_asynchronous_io) .\" the maximum amount by which a process can decrease its .\" asynchronous i/o priority level from its own scheduling priority. .\" must be nonnegative. .tp .br arg_max " - " _sc_arg_max the maximum length of the arguments to the .br exec (3) family of functions. must not be less than .b _posix_arg_max (4096). .tp .br child_max " - " _sc_child_max the maximum number of simultaneous processes per user id. must not be less than .b _posix_child_max (25). .tp .br host_name_max " - " _sc_host_name_max maximum length of a hostname, not including the terminating null byte, as returned by .br gethostname (2). must not be less than .b _posix_host_name_max (255). .tp .br login_name_max " - " _sc_login_name_max maximum length of a login name, including the terminating null byte. must not be less than .b _posix_login_name_max (9). .tp .br ngroups_max " - " _sc_ngroups_max maximum number of supplementary group ids. .tp .br "" "clock ticks - " _sc_clk_tck the number of clock ticks per second. the corresponding variable is obsolete. it was of course called .br clk_tck . (note: the macro .b clocks_per_sec does not give information: it must equal 1000000.) .tp .br open_max " - " _sc_open_max the maximum number of files that a process can have open at any time. must not be less than .b _posix_open_max (20). .tp .br pagesize " - " _sc_pagesize size of a page in bytes. must not be less than 1. .tp .br page_size " - " _sc_page_size a synonym for .br pagesize / _sc_pagesize . (both .br pagesize and .br page_size are specified in posix.) .tp .br re_dup_max " - " _sc_re_dup_max the number of repeated occurrences of a bre permitted by .br regexec (3) and .br regcomp (3). must not be less than .b _posix2_re_dup_max (255). .tp .br stream_max " - " _sc_stream_max the maximum number of streams that a process can have open at any time. if defined, it has the same value as the standard c macro .br fopen_max . must not be less than .b _posix_stream_max (8). .tp .br symloop_max " - " _sc_symloop_max the maximum number of symbolic links seen in a pathname before resolution returns .br eloop . must not be less than .b _posix_symloop_max (8). .tp .br tty_name_max " - " _sc_tty_name_max the maximum length of terminal device name, including the terminating null byte. must not be less than .b _posix_tty_name_max (9). .tp .br tzname_max " - " _sc_tzname_max the maximum number of bytes in a timezone name. must not be less than .b _posix_tzname_max (6). .tp .br _posix_version " - " _sc_version indicates the year and month the posix.1 standard was approved in the format .br yyyymml ; the value .b 199009l indicates the sept. 1990 revision. .ss posix.2 variables next, the posix.2 values, giving limits for utilities. .tp .br bc_base_max " - " _sc_bc_base_max indicates the maximum .i obase value accepted by the .br bc (1) utility. .tp .br bc_dim_max " - " _sc_bc_dim_max indicates the maximum value of elements permitted in an array by .br bc (1). .tp .br bc_scale_max " - " _sc_bc_scale_max indicates the maximum .i scale value allowed by .br bc (1). .tp .br bc_string_max " - " _sc_bc_string_max indicates the maximum length of a string accepted by .br bc (1). .tp .br coll_weights_max " - " _sc_coll_weights_max indicates the maximum numbers of weights that can be assigned to an entry of the .b lc_collate order keyword in the locale definition file. .tp .br expr_nest_max " - " _sc_expr_nest_max is the maximum number of expressions which can be nested within parentheses by .br expr (1). .tp .br line_max " - " _sc_line_max the maximum length of a utility's input line, either from standard input or from a file. this includes space for a trailing newline. .tp .br re_dup_max " - " _sc_re_dup_max the maximum number of repeated occurrences of a regular expression when the interval notation .b \e{m,n\e} is used. .tp .br posix2_version " - " _sc_2_version indicates the version of the posix.2 standard in the format of yyyymml. .tp .br posix2_c_dev " - " _sc_2_c_dev indicates whether the posix.2 c language development facilities are supported. .tp .br posix2_fort_dev " - " _sc_2_fort_dev indicates whether the posix.2 fortran development utilities are supported. .tp .br posix2_fort_run " - " _sc_2_fort_run indicates whether the posix.2 fortran run-time utilities are supported. .tp .br _posix2_localedef " - " _sc_2_localedef indicates whether the posix.2 creation of locales via .br localedef (1) is supported. .tp .br posix2_sw_dev " - " _sc_2_sw_dev indicates whether the posix.2 software development utilities option is supported. .pp these values also exist, but may not be standard. .tp .br "" " - " _sc_phys_pages the number of pages of physical memory. note that it is possible for the product of this value and the value of .b _sc_pagesize to overflow. .tp .br "" " - " _sc_avphys_pages the number of currently available pages of physical memory. .tp .br "" " - " _sc_nprocessors_conf the number of processors configured. see also .br get_nprocs_conf (3). .tp .br "" " - " _sc_nprocessors_onln the number of processors currently online (available). see also .br get_nprocs_conf (3). .sh return value the return value of .br sysconf () is one of the following: .ip * 3 on error, \-1 is returned and .i errno is set to indicate the error (for example, .br einval , indicating that .i name is invalid). .ip * if .i name corresponds to a maximum or minimum limit, and that limit is indeterminate, \-1 is returned and .i errno is not changed. (to distinguish an indeterminate limit from an error, set .i errno to zero before the call, and then check whether .i errno is nonzero when \-1 is returned.) .ip * if .i name corresponds to an option, a positive value is returned if the option is supported, and \-1 is returned if the option is not supported. .ip * otherwise, the current value of the option or limit is returned. this value will not be more restrictive than the corresponding value that was described to the application in .i or .i when the application was compiled. .sh errors .tp .b einval .i name is invalid. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sysconf () t} thread safety mt-safe env .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh bugs it is difficult to use .b arg_max because it is not specified how much of the argument space for .br exec (3) is consumed by the user's environment variables. .pp some returned values may be huge; they are not suitable for allocating memory. .sh see also .br bc (1), .br expr (1), .br getconf (1), .br locale (1), .br confstr (3), .br fpathconf (3), .br pathconf (3), .br posixoptions (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mcheck.3 .\" copyright 1993 giorgio ciucci (giorgio@crcc.it) .\" and copyright 2004, 2005 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified tue oct 22 17:53:56 1996 by eric s. raymond .\" modified fri jun 19 10:59:15 1998 by andries brouwer .\" modified sun feb 18 01:59:29 2001 by andries brouwer .\" modified 20 dec 2001, michael kerrisk .\" modified 21 dec 2001, aeb .\" modified 27 may 2004, michael kerrisk .\" added notes on cap_ipc_owner requirement .\" modified 17 jun 2004, michael kerrisk .\" added notes on cap_sys_admin requirement for ipc_set and ipc_rmid .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" rewrote semun text .\" added semid_ds and ipc_perm structure definitions .\" 2005-08-02, mtk: added ipc_info, sem_info, sem_stat descriptions. .\" 2018-03-20, dbueso: added sem_stat_any description. .\" .th semctl 2 2021-03-22 "linux" "linux programmer's manual" .sh name semctl \- system v semaphore control operations .sh synopsis .nf .b #include .pp .bi "int semctl(int " semid ", int " semnum ", int " cmd ", ...);" .fi .sh description .br semctl () performs the control operation specified by .i cmd on the system\ v semaphore set identified by .ir semid , or on the .ir semnum -th semaphore of that set. (the semaphores in a set are numbered starting at 0.) .pp this function has three or four arguments, depending on .ir cmd . when there are four, the fourth has the type .ir "union semun" . the \ficalling program\fp must define this union as follows: .pp .in +4n .ex union semun { int val; /* value for setval */ struct semid_ds *buf; /* buffer for ipc_stat, ipc_set */ unsigned short *array; /* array for getall, setall */ struct seminfo *__buf; /* buffer for ipc_info (linux\-specific) */ }; .ee .in .pp the .i semid_ds data structure is defined in \fi\fp as follows: .pp .in +4n .ex struct semid_ds { struct ipc_perm sem_perm; /* ownership and permissions */ time_t sem_otime; /* last semop time */ time_t sem_ctime; /* creation time/time of last modification via semctl() */ unsigned long sem_nsems; /* no. of semaphores in set */ }; .ee .in .pp the fields of the .i semid_ds structure are as follows: .tp 11 .i sem_perm this is an .i ipc_perm structure (see below) that specifies the access permissions on the semaphore set. .tp .i sem_otime time of last .br semop (2) system call. .tp .i sem_ctime time of creation of semaphore set or time of last .br semctl () .br ipcset , .br setval , or .br setall operation. .tp .i sem_nsems number of semaphores in the set. each semaphore of the set is referenced by a nonnegative integer ranging from .b 0 to .ir sem_nsems\-1 . .pp the .i ipc_perm structure is defined as follows (the highlighted fields are settable using .br ipc_set ): .pp .in +4n .ex struct ipc_perm { key_t __key; /* key supplied to semget(2) */ uid_t \fbuid\fp; /* effective uid of owner */ gid_t \fbgid\fp; /* effective gid of owner */ uid_t cuid; /* effective uid of creator */ gid_t cgid; /* effective gid of creator */ unsigned short \fbmode\fp; /* permissions */ unsigned short __seq; /* sequence number */ }; .ee .in .pp the least significant 9 bits of the .i mode field of the .i ipc_perm structure define the access permissions for the shared memory segment. the permission bits are as follows: .ts l l. 0400 read by user 0200 write by user 0040 read by group 0020 write by group 0004 read by others 0002 write by others .te .pp in effect, "write" means "alter" for a semaphore set. bits 0100, 0010, and 0001 (the execute bits) are unused by the system. .pp valid values for .i cmd are: .tp .b ipc_stat copy information from the kernel data structure associated with .i semid into the .i semid_ds structure pointed to by .ir arg.buf . the argument .i semnum is ignored. the calling process must have read permission on the semaphore set. .tp .b ipc_set write the values of some members of the .i semid_ds structure pointed to by .i arg.buf to the kernel data structure associated with this semaphore set, updating also its .i sem_ctime member. .ip the following members of the structure are updated: .ir sem_perm.uid , .ir sem_perm.gid , and (the least significant 9 bits of) .ir sem_perm.mode . .ip the effective uid of the calling process must match the owner .ri ( sem_perm.uid ) or creator .ri ( sem_perm.cuid ) of the semaphore set, or the caller must be privileged. the argument .i semnum is ignored. .tp .b ipc_rmid immediately remove the semaphore set, awakening all processes blocked in .br semop (2) calls on the set (with an error return and .i errno set to .br eidrm ). the effective user id of the calling process must match the creator or owner of the semaphore set, or the caller must be privileged. the argument .i semnum is ignored. .tp .br ipc_info " (linux\-specific)" return information about system-wide semaphore limits and parameters in the structure pointed to by .ir arg.__buf . this structure is of type .ir seminfo , defined in .i if the .b _gnu_source feature test macro is defined: .ip .in +4n .ex struct seminfo { int semmap; /* number of entries in semaphore map; unused within kernel */ int semmni; /* maximum number of semaphore sets */ int semmns; /* maximum number of semaphores in all semaphore sets */ int semmnu; /* system\-wide maximum number of undo structures; unused within kernel */ int semmsl; /* maximum number of semaphores in a set */ int semopm; /* maximum number of operations for semop(2) */ int semume; /* maximum number of undo entries per process; unused within kernel */ int semusz; /* size of struct sem_undo */ int semvmx; /* maximum semaphore value */ int semaem; /* max. value that can be recorded for semaphore adjustment (sem_undo) */ }; .ee .in .ip the .ir semmsl , .ir semmns , .ir semopm , and .i semmni settings can be changed via .ir /proc/sys/kernel/sem ; see .br proc (5) for details. .tp .br sem_info " (linux-specific)" return a .i seminfo structure containing the same information as for .br ipc_info , except that the following fields are returned with information about system resources consumed by semaphores: the .i semusz field returns the number of semaphore sets that currently exist on the system; and the .i semaem field returns the total number of semaphores in all semaphore sets on the system. .tp .br sem_stat " (linux-specific)" return a .i semid_ds structure as for .br ipc_stat . however, the .i semid argument is not a semaphore identifier, but instead an index into the kernel's internal array that maintains information about all semaphore sets on the system. .tp .br sem_stat_any " (linux-specific, since linux 4.17)" return a .i semid_ds structure as for .br sem_stat . however, .i sem_perm.mode is not checked for read access for .ir semid meaning that any user can employ this operation (just as any user may read .ir /proc/sysvipc/sem to obtain the same information). .tp .b getall return .b semval (i.e., the current value) for all semaphores of the set into .ir arg.array . the argument .i semnum is ignored. the calling process must have read permission on the semaphore set. .tp .b getncnt return the .b semncnt value for the .ir semnum \-th semaphore of the set (i.e., the number of processes waiting for the semaphore's value to increase). the calling process must have read permission on the semaphore set. .tp .b getpid return the .b sempid value for the .ir semnum \-th semaphore of the set. this is the pid of the process that last performed an operation on that semaphore (but see notes). the calling process must have read permission on the semaphore set. .tp .b getval return .b semval (i.e., the semaphore value) for the .ir semnum \-th semaphore of the set. the calling process must have read permission on the semaphore set. .tp .b getzcnt return the .b semzcnt value for the .ir semnum \-th semaphore of the set (i.e., the number of processes waiting for the semaphore value to become 0). the calling process must have read permission on the semaphore set. .tp .b setall set the .b semval values for all semaphores of the set using .ir arg.array , updating also the .i sem_ctime member of the .i semid_ds structure associated with the set. undo entries (see .br semop (2)) are cleared for altered semaphores in all processes. if the changes to semaphore values would permit blocked .br semop (2) calls in other processes to proceed, then those processes are woken up. the argument .i semnum is ignored. the calling process must have alter (write) permission on the semaphore set. .tp .b setval set the semaphore value .rb ( semval ) to .i arg.val for the .ir semnum \-th semaphore of the set, updating also the .i sem_ctime member of the .i semid_ds structure associated with the set. undo entries are cleared for altered semaphores in all processes. if the changes to semaphore values would permit blocked .br semop (2) calls in other processes to proceed, then those processes are woken up. the calling process must have alter permission on the semaphore set. .sh return value on success, .br semctl () returns a nonnegative value depending on .i cmd as follows: .tp .b getncnt the value of .br semncnt . .tp .b getpid the value of .br sempid . .tp .b getval the value of .br semval . .tp .b getzcnt the value of .br semzcnt . .tp .b ipc_info the index of the highest used entry in the kernel's internal array recording information about all semaphore sets. (this information can be used with repeated .b sem_stat or .b sem_stat_any operations to obtain information about all semaphore sets on the system.) .tp .b sem_info as for .br ipc_info . .tp .b sem_stat the identifier of the semaphore set whose index was given in .ir semid . .tp .b sem_stat_any as for .br sem_stat . .pp all other .i cmd values return 0 on success. .pp on failure, .br semctl () returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b eacces the argument .i cmd has one of the values .br getall , .br getpid , .br getval , .br getncnt , .br getzcnt , .br ipc_stat , .br sem_stat , .br sem_stat_any , .br setall , or .b setval and the calling process does not have the required permissions on the semaphore set and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b efault the address pointed to by .i arg.buf or .i arg.array isn't accessible. .tp .b eidrm the semaphore set was removed. .tp .b einval invalid value for .i cmd or .ir semid . or: for a .b sem_stat operation, the index value specified in .i semid referred to an array slot that is currently unused. .tp .b eperm the argument .i cmd has the value .b ipc_set or .b ipc_rmid but the effective user id of the calling process is not the creator (as found in .ir sem_perm.cuid ) or the owner (as found in .ir sem_perm.uid ) of the semaphore set, and the process does not have the .b cap_sys_admin capability. .tp .b erange the argument .i cmd has the value .b setall or .b setval and the value to which .b semval is to be set (for some semaphore of the set) is less than 0 or greater than the implementation limit .br semvmx . .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svr4 documents more error conditions einval and eoverflow. .pp posix.1 specifies the .\" posix.1-2001, posix.1-2008 .i sem_nsems field of the .i semid_ds structure as having the type .ir "unsigned\ short" , and the field is so defined on most other systems. it was also so defined on linux 2.2 and earlier, but, since linux 2.4, the field has the type .ir "unsigned\ long" . .sh notes the .br ipc_info , .br sem_stat , and .b sem_info operations are used by the .br ipcs (1) program to provide information on allocated resources. in the future these may modified or moved to a .i /proc filesystem interface. .pp various fields in a \fistruct semid_ds\fp were typed as .i short under linux 2.2 and have become .i long under linux 2.4. to take advantage of this, a recompilation under glibc-2.1.91 or later should suffice. (the kernel distinguishes old and new calls by an .b ipc_64 flag in .ir cmd .) .pp in some earlier versions of glibc, the .i semun union was defined in \fi\fp, but posix.1 requires .\" posix.1-2001, posix.1-2008 that the caller define this union. on versions of glibc where this union is \finot\fp defined, the macro .b _sem_semun_undefined is defined in \fi\fp. .pp the following system limit on semaphore sets affects a .br semctl () call: .tp .b semvmx maximum value for .br semval : implementation dependent (32767). .pp for greater portability, it is best to always call .br semctl () with four arguments. .\" .ss the sempid value posix.1 defines .i sempid as the "process id of [the] last operation" on a semaphore, and explicitly notes that this value is set by a successful .br semop (2) call, with the implication that no other interface affects the .i sempid value. .pp while some implementations conform to the behavior specified in posix.1, others do not. (the fault here probably lies with posix.1 inasmuch as it likely failed to capture the full range of existing implementation behaviors.) various other implementations .\" at least opensolaris (and, one supposes, older solaris) and darwin also update .i sempid for the other operations that update the value of a semaphore: the .b setval and .b setall operations, as well as the semaphore adjustments performed on process termination as a consequence of the use of the .b sem_undo flag (see .br semop (2)). .pp linux also updates .i sempid for .br setval operations and semaphore adjustments. however, somewhat inconsistently, up to and including linux 4.5, the kernel did not update .i sempid for .br setall operations. this was rectified .\" commit a5f4db877177d2a3d7ae62a7bac3a5a27e083d7f in linux 4.6. .sh examples see .br shmop (2). .sh see also .br ipc (2), .br semget (2), .br semop (2), .br capabilities (7), .br sem_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fenv.3 .so man7/system_data_types.7 .\" copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th bswap 3 2021-06-20 "linux" "linux programmer's manual" .sh name bswap_16, bswap_32, bswap_64 \- reverse order of bytes .sh synopsis .nf .b #include .pp .bi "uint16_t bswap_16(uint16_t " x ); .bi "uint32_t bswap_32(uint32_t " x ); .bi "uint64_t bswap_64(uint64_t " x ); .fi .sh description these functions return a value in which the order of the bytes in their 2-, 4-, or 8-byte arguments is reversed. .sh return value these functions return the value of their argument with the bytes reversed. .sh errors these functions always succeed. .sh conforming to these functions are gnu extensions. .sh examples the program below swaps the bytes of the 8-byte integer supplied as its command-line argument. the following shell session demonstrates the use of the program: .pp .in +4n .ex $ \fb./a.out 0x0123456789abcdef\fp 0x123456789abcdef ==> 0xefcdab8967452301 .ee .in .ss program source \& .ex #include #include #include #include #include int main(int argc, char *argv[]) { uint64_t x; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } x = strtoull(argv[1], null, 0); printf("%#" prix64 " ==> %#" prix64 "\en", x, bswap_64(x)); exit(exit_success); } .ee .sh see also .br byteorder (3), .br endian (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on glibc infopages .\" .\" corrections by aeb .\" .th nan 3 2021-03-22 "gnu" "linux programmer's manual" .sh name nan, nanf, nanl \- return 'not a number' .sh synopsis .nf .b #include .pp .bi "double nan(const char *" tagp ); .bi "float nanf(const char *" tagp ); .bi "long double nanl(const char *" tagp ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nan (), .br nanf (), .br nanl (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions return a representation (determined by .ir tagp ) of a quiet nan. if the implementation does not support quiet nans, these functions return zero. .pp the call .i nan("char\-sequence") is equivalent to: .pp .in +4n .ex strtod("nan(char\-sequence)", null); .ee .in .pp similarly, calls to .br nanf () and .br nanl () are equivalent to analogous calls to .br strtof (3) and .br strtold (3). .pp the argument .i tagp is used in an unspecified manner. on ieee 754 systems, there are many representations of nan, and .i tagp selects one. on other systems it may do nothing. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br nan (), .br nanf (), .br nanl () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. see also iec 559 and the appendix with recommended functions in ieee 754/ieee 854. .sh see also .br isnan (3), .br strtod (3), .br math_error (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2000 lars brinkhoff .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified, thu jan 27 19:16:19 cet 2000, lars@nocrew.org .\" .th dsp56k 4 2021-03-22 "linux" "linux programmer's manual" .sh name dsp56k \- dsp56001 interface device .sh synopsis .nf .b #include .pp .bi "ssize_t read(int " fd ", void *" data ", size_t " length ); .bi "ssize_t write(int " fd ", void *" data ", size_t " length ); .pp .bi "int ioctl(int " fd ", dsp56k_upload, struct dsp56k_upload *" program ); .bi "int ioctl(int " fd ", dsp56k_set_tx_wsize, int " wsize ); .bi "int ioctl(int " fd ", dsp56k_set_rx_wsize, int " wsize ); .bi "int ioctl(int " fd ", dsp56k_host_flags, struct dsp56k_host_flags *" flags ); .bi "int ioctl(int " fd ", dsp56k_host_cmd, int " cmd ); .fi .sh configuration the .b dsp56k device is a character device with major number 55 and minor number 0. .sh description the motorola dsp56001 is a fully programmable 24-bit digital signal processor found in atari falcon030-compatible computers. the \fidsp56k\fp special file is used to control the dsp56001, and to send and receive data using the bidirectional handshaked host port. .pp to send a data stream to the signal processor, use .br write (2) to the device, and .br read (2) to receive processed data. the data can be sent or received in 8, 16, 24, or 32-bit quantities on the host side, but will always be seen as 24-bit quantities in the dsp56001. .pp the following .br ioctl (2) calls are used to control the \fidsp56k\fp device: .ip \fbdsp56k_upload\fp resets the dsp56001 and uploads a program. the third .br ioctl (2) argument must be a pointer to a \fistruct dsp56k_upload\fp with members \fibin\fp pointing to a dsp56001 binary program, and \filen\fp set to the length of the program, counted in 24-bit words. .ip \fbdsp56k_set_tx_wsize\fp sets the transmit word size. allowed values are in the range 1 to 4, and is the number of bytes that will be sent at a time to the dsp56001. these data quantities will either be padded with bytes containing zero, or truncated to fit the native 24-bit data format of the dsp56001. .ip \fbdsp56k_set_rx_wsize\fp sets the receive word size. allowed values are in the range 1 to 4, and is the number of bytes that will be received at a time from the dsp56001. these data quantities will either truncated, or padded with a null byte (\(aq\e0\(aq) to fit the native 24-bit data format of the dsp56001. .ip \fbdsp56k_host_flags\fp read and write the host flags. the host flags are four general-purpose bits that can be read by both the hosting computer and the dsp56001. bits 0 and 1 can be written by the host, and bits 2 and 3 can be written by the dsp56001. .ip to access the host flags, the third .br ioctl (2) argument must be a pointer to a \fistruct dsp56k_host_flags\fp. if bit 0 or 1 is set in the \fidir\fp member, the corresponding bit in \fiout\fp will be written to the host flags. the state of all host flags will be returned in the lower four bits of the \fistatus\fp member. .ip \fbdsp56k_host_cmd\fp sends a host command. allowed values are in the range 0 to 31, and is a user-defined command handled by the program running in the dsp56001. .sh files .i /dev/dsp56k .\" .sh authors .\" fredrik noring , lars brinkhoff , .\" tomas berndtsson . .sh see also .ir linux/include/asm\-m68k/dsp56k.h , .ir linux/drivers/char/dsp56k.c , .ur http://dsp56k.nocrew.org/ .ue , dsp56000/dsp56001 digital signal processor user's manual .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .so man7/system_data_types.7 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_join 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_join \- join with a terminated thread .sh synopsis .nf .b #include .pp .bi "int pthread_join(pthread_t " thread ", void **" retval ); .fi .pp compile and link with \fi\-pthread\fp. .sh description the .br pthread_join () function waits for the thread specified by .ir thread to terminate. if that thread has already terminated, then .br pthread_join () returns immediately. the thread specified by .i thread must be joinable. .pp if .i retval is not null, then .br pthread_join () copies the exit status of the target thread (i.e., the value that the target thread supplied to .br pthread_exit (3)) into the location pointed to by .ir retval . if the target thread was canceled, then .b pthread_canceled is placed in the location pointed to by .ir retval . .pp if multiple threads simultaneously try to join with the same thread, the results are undefined. if the thread calling .br pthread_join () is canceled, then the target thread will remain joinable (i.e., it will not be detached). .sh return value on success, .br pthread_join () returns 0; on error, it returns an error number. .sh errors .tp .b edeadlk a deadlock was detected .\" the following verified by testing on glibc 2.8/nptl: (e.g., two threads tried to join with each other); or .\" the following verified by testing on glibc 2.8/nptl: .i thread specifies the calling thread. .tp .b einval .i thread is not a joinable thread. .tp .b einval another thread is already waiting to join with this thread. .\" posix.1-2001 does not specify this error case. .tp .b esrch no thread with the id .i thread could be found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_join () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes after a successful call to .br pthread_join (), the caller is guaranteed that the target thread has terminated. the caller may then choose to do any clean-up that is required after termination of the thread (e.g., freeing memory or other resources that were allocated to the target thread). .pp joining with a thread that has previously been joined results in undefined behavior. .pp failure to join with a thread that is joinable (i.e., one that is not detached), produces a "zombie thread". avoid doing this, since each zombie thread consumes some system resources, and when enough zombie threads have accumulated, it will no longer be possible to create new threads (or processes). .pp there is no pthreads analog of .ir "waitpid(\-1,\ &status,\ 0)" , that is, "join with any terminated thread". if you believe you need this functionality, you probably need to rethink your application design. .pp all of the threads in a process are peers: any thread can join with any other thread in the process. .sh examples see .br pthread_create (3). .sh see also .br pthread_cancel (3), .br pthread_create (3), .br pthread_detach (3), .br pthread_exit (3), .br pthread_tryjoin_np (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strerror.3 .so man3/err.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcscpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcscpy \- copy a wide-character string .sh synopsis .nf .b #include .pp .bi "wchar_t *wcscpy(wchar_t *restrict " dest \ ", const wchar_t *restrict " src ); .fi .sh description the .br wcscpy () function is the wide-character equivalent of the .br strcpy (3) function. it copies the wide-character string pointed to by .ir src , including the terminating null wide character (l\(aq\e0\(aq), to the array pointed to by .ir dest . .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .ir "wcslen(src)+1" wide characters at .ir dest . .sh return value .br wcscpy () returns .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcscpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strcpy (3), .br wcpcpy (3), .br wcscat (3), .br wcsdup (3), .br wmemcpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th acct 5 2021-03-22 "linux" "linux programmer's manual" .sh name acct \- process accounting file .sh synopsis .nf .b #include .fi .sh description if the kernel is built with the process accounting option enabled .rb ( config_bsd_process_acct ), then calling .br acct (2) starts process accounting, for example: .pp .in +4n acct("/var/log/pacct"); .in .pp when process accounting is enabled, the kernel writes a record to the accounting file as each process on the system terminates. this record contains information about the terminated process, and is defined in .i as follows: .pp .in +4n .ex #define acct_comm 16 typedef u_int16_t comp_t; struct acct { char ac_flag; /* accounting flags */ u_int16_t ac_uid; /* accounting user id */ u_int16_t ac_gid; /* accounting group id */ u_int16_t ac_tty; /* controlling terminal */ u_int32_t ac_btime; /* process creation time (seconds since the epoch) */ comp_t ac_utime; /* user cpu time */ comp_t ac_stime; /* system cpu time */ comp_t ac_etime; /* elapsed time */ comp_t ac_mem; /* average memory usage (kb) */ comp_t ac_io; /* characters transferred (unused) */ comp_t ac_rw; /* blocks read or written (unused) */ comp_t ac_minflt; /* minor page faults */ comp_t ac_majflt; /* major page faults */ comp_t ac_swaps; /* number of swaps (unused) */ u_int32_t ac_exitcode; /* process termination status (see wait(2)) */ char ac_comm[acct_comm+1]; /* command name (basename of last executed command; null\-terminated) */ char ac_pad[\fix\fp]; /* padding bytes */ }; enum { /* bits that may be set in ac_flag field */ afork = 0x01, /* has executed fork, but no exec */ asu = 0x02, /* used superuser privileges */ acore = 0x08, /* dumped core */ axsig = 0x10 /* killed by a signal */ }; .ee .in .pp the .i comp_t data type is a floating-point value consisting of a 3-bit, base-8 exponent, and a 13-bit mantissa. a value, .ir c , of this type can be converted to a (long) integer as follows: .pp .nf v = (c & 0x1fff) << (((c >> 13) & 0x7) * 3); .fi .pp the .ir ac_utime , .ir ac_stime , and .i ac_etime fields measure time in "clock ticks"; divide these values by .i sysconf(_sc_clk_tck) to convert them to seconds. .ss version 3 accounting file format since kernel 2.6.8, an optional alternative version of the accounting file can be produced if the .b config_bsd_process_acct_v3 option is set when building the kernel. with this option is set, the records written to the accounting file contain additional fields, and the width of .i c_uid and .i ac_gid fields is widened from 16 to 32 bits (in line with the increased size of uid and gids in linux 2.4 and later). the records are defined as follows: .pp .in +4n .ex struct acct_v3 { char ac_flag; /* flags */ char ac_version; /* always set to acct_version (3) */ u_int16_t ac_tty; /* controlling terminal */ u_int32_t ac_exitcode; /* process termination status */ u_int32_t ac_uid; /* real user id */ u_int32_t ac_gid; /* real group id */ u_int32_t ac_pid; /* process id */ u_int32_t ac_ppid; /* parent process id */ u_int32_t ac_btime; /* process creation time */ float ac_etime; /* elapsed time */ comp_t ac_utime; /* user cpu time */ comp_t ac_stime; /* system time */ comp_t ac_mem; /* average memory usage (kb) */ comp_t ac_io; /* characters transferred (unused) */ comp_t ac_rw; /* blocks read or written (unused) */ comp_t ac_minflt; /* minor page faults */ comp_t ac_majflt; /* major page faults */ comp_t ac_swaps; /* number of swaps (unused) */ char ac_comm[acct_comm]; /* command name */ }; .ee .in .sh versions the .i acct_v3 structure is defined in glibc since version 2.6. .sh conforming to process accounting originated on bsd. although it is present on most systems, it is not standardized, and the details vary somewhat between systems. .sh notes records in the accounting file are ordered by termination time of the process. .pp in kernels up to and including 2.6.9, a separate accounting record is written for each thread created using the nptl threading library; since linux 2.6.10, a single accounting record is written for the entire process on termination of the last thread in the process. .pp the .i /proc/sys/kernel/acct file, described in .br proc (5), defines settings that control the behavior of process accounting when disk space runs low. .sh see also .br lastcomm (1), .br acct (2), .br accton (8), .br sa (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2015 alexei starovoitov .\" and copyright (c) 2015 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th bpf 2 2021-08-27 "linux" "linux programmer's manual" .sh name bpf \- perform a command on an extended bpf map or program .sh synopsis .nf .b #include .pp .bi "int bpf(int " cmd ", union bpf_attr *" attr ", unsigned int " size ); .fi .sh description the .br bpf () system call performs a range of operations related to extended berkeley packet filters. extended bpf (or ebpf) is similar to the original ("classic") bpf (cbpf) used to filter network packets. for both cbpf and ebpf programs, the kernel statically analyzes the programs before loading them, in order to ensure that they cannot harm the running system. .pp ebpf extends cbpf in multiple ways, including the ability to call a fixed set of in-kernel helper functions .\" see 'enum bpf_func_id' in include/uapi/linux/bpf.h (via the .b bpf_call opcode extension provided by ebpf) and access shared data structures such as ebpf maps. .\" .ss extended bpf design/architecture ebpf maps are a generic data structure for storage of different data types. data types are generally treated as binary blobs, so a user just specifies the size of the key and the size of the value at map-creation time. in other words, a key/value for a given map can have an arbitrary structure. .pp a user process can create multiple maps (with key/value-pairs being opaque bytes of data) and access them via file descriptors. different ebpf programs can access the same maps in parallel. it's up to the user process and ebpf program to decide what they store inside maps. .pp there's one special map type, called a program array. this type of map stores file descriptors referring to other ebpf programs. when a lookup in the map is performed, the program flow is redirected in-place to the beginning of another ebpf program and does not return back to the calling program. the level of nesting has a fixed limit of 32, .\" defined by the kernel constant max_tail_call_cnt in include/linux/bpf.h so that infinite loops cannot be crafted. at run time, the program file descriptors stored in the map can be modified, so program functionality can be altered based on specific requirements. all programs referred to in a program-array map must have been previously loaded into the kernel via .br bpf (). if a map lookup fails, the current program continues its execution. see .b bpf_map_type_prog_array below for further details. .pp generally, ebpf programs are loaded by the user process and automatically unloaded when the process exits. in some cases, for example, .br tc\-bpf (8), the program will continue to stay alive inside the kernel even after the process that loaded the program exits. in that case, the tc subsystem holds a reference to the ebpf program after the file descriptor has been closed by the user-space program. thus, whether a specific program continues to live inside the kernel depends on how it is further attached to a given kernel subsystem after it was loaded via .br bpf (). .pp each ebpf program is a set of instructions that is safe to run until its completion. an in-kernel verifier statically determines that the ebpf program terminates and is safe to execute. during verification, the kernel increments reference counts for each of the maps that the ebpf program uses, so that the attached maps can't be removed until the program is unloaded. .pp ebpf programs can be attached to different events. these events can be the arrival of network packets, tracing events, classification events by network queueing disciplines (for ebpf programs attached to a .br tc (8) classifier), and other types that may be added in the future. a new event triggers execution of the ebpf program, which may store information about the event in ebpf maps. beyond storing data, ebpf programs may call a fixed set of in-kernel helper functions. .pp the same ebpf program can be attached to multiple events and different ebpf programs can access the same map: .pp .in +4n .ex tracing tracing tracing packet packet packet event a event b event c on eth0 on eth1 on eth2 | | | | | \(ha | | | | v | \-\-> tracing <\-\- tracing socket tc ingress tc egress prog_1 prog_2 prog_3 classifier action | | | | prog_4 prog_5 |\-\-\- \-\-\-\-\-| |\-\-\-\-\-\-| map_3 | | map_1 map_2 \-\-| map_4 |\-\- .ee .in .\" .ss arguments the operation to be performed by the .br bpf () system call is determined by the .i cmd argument. each operation takes an accompanying argument, provided via .ir attr , which is a pointer to a union of type .i bpf_attr (see below). the .i size argument is the size of the union pointed to by .ir attr . .pp the value provided in .i cmd is one of the following: .tp .b bpf_map_create create a map and return a file descriptor that refers to the map. the close-on-exec file descriptor flag (see .br fcntl (2)) is automatically enabled for the new file descriptor. .tp .b bpf_map_lookup_elem look up an element by key in a specified map and return its value. .tp .b bpf_map_update_elem create or update an element (key/value pair) in a specified map. .tp .b bpf_map_delete_elem look up and delete an element by key in a specified map. .tp .b bpf_map_get_next_key look up an element by key in a specified map and return the key of the next element. .tp .b bpf_prog_load verify and load an ebpf program, returning a new file descriptor associated with the program. the close-on-exec file descriptor flag (see .br fcntl (2)) is automatically enabled for the new file descriptor. .ip the .i bpf_attr union consists of various anonymous structures that are used by different .br bpf () commands: .pp .in +4n .ex union bpf_attr { struct { /* used by bpf_map_create */ __u32 map_type; __u32 key_size; /* size of key in bytes */ __u32 value_size; /* size of value in bytes */ __u32 max_entries; /* maximum number of entries in a map */ }; struct { /* used by bpf_map_*_elem and bpf_map_get_next_key commands */ __u32 map_fd; __aligned_u64 key; union { __aligned_u64 value; __aligned_u64 next_key; }; __u64 flags; }; struct { /* used by bpf_prog_load */ __u32 prog_type; __u32 insn_cnt; __aligned_u64 insns; /* \(aqconst struct bpf_insn *\(aq */ __aligned_u64 license; /* \(aqconst char *\(aq */ __u32 log_level; /* verbosity level of verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied \(aqchar *\(aq buffer */ __u32 kern_version; /* checked when prog_type=kprobe (since linux 4.1) */ .\" commit 2541517c32be2531e0da59dfd7efc1ce844644f5 }; } __attribute__((aligned(8))); .ee .in .\" .ss ebpf maps maps are a generic data structure for storage of different types of data. they allow sharing of data between ebpf kernel programs, and also between kernel and user-space applications. .pp each map type has the following attributes: .ip * 3 type .ip * maximum number of elements .ip * key size in bytes .ip * value size in bytes .pp the following wrapper functions demonstrate how various .br bpf () commands can be used to access the maps. the functions use the .i cmd argument to invoke different operations. .tp .b bpf_map_create the .b bpf_map_create command creates a new map, returning a new file descriptor that refers to the map. .ip .in +4n .ex int bpf_create_map(enum bpf_map_type map_type, unsigned int key_size, unsigned int value_size, unsigned int max_entries) { union bpf_attr attr = { .map_type = map_type, .key_size = key_size, .value_size = value_size, .max_entries = max_entries }; return bpf(bpf_map_create, &attr, sizeof(attr)); } .ee .in .ip the new map has the type specified by .ir map_type , and attributes as specified in .ir key_size , .ir value_size , and .ir max_entries . on success, this operation returns a file descriptor. on error, \-1 is returned and .i errno is set to .br einval , .br eperm , or .br enomem . .ip the .i key_size and .i value_size attributes will be used by the verifier during program loading to check that the program is calling .br bpf_map_*_elem () helper functions with a correctly initialized .i key and to check that the program doesn't access the map element .i value beyond the specified .ir value_size . for example, when a map is created with a .i key_size of 8 and the ebpf program calls .ip .in +4n .ex bpf_map_lookup_elem(map_fd, fp \- 4) .ee .in .ip the program will be rejected, since the in-kernel helper function .ip .in +4n .ex bpf_map_lookup_elem(map_fd, void *key) .ee .in .ip expects to read 8 bytes from the location pointed to by .ir key , but the .i fp\ \-\ 4 (where .i fp is the top of the stack) starting address will cause out-of-bounds stack access. .ip similarly, when a map is created with a .i value_size of 1 and the ebpf program contains .ip .in +4n .ex value = bpf_map_lookup_elem(...); *(u32 *) value = 1; .ee .in .ip the program will be rejected, since it accesses the .i value pointer beyond the specified 1 byte .i value_size limit. .ip currently, the following values are supported for .ir map_type : .ip .in +4n .ex enum bpf_map_type { bpf_map_type_unspec, /* reserve 0 as invalid map type */ bpf_map_type_hash, bpf_map_type_array, bpf_map_type_prog_array, bpf_map_type_perf_event_array, bpf_map_type_percpu_hash, bpf_map_type_percpu_array, bpf_map_type_stack_trace, bpf_map_type_cgroup_array, bpf_map_type_lru_hash, bpf_map_type_lru_percpu_hash, bpf_map_type_lpm_trie, bpf_map_type_array_of_maps, bpf_map_type_hash_of_maps, bpf_map_type_devmap, bpf_map_type_sockmap, bpf_map_type_cpumap, bpf_map_type_xskmap, bpf_map_type_sockhash, bpf_map_type_cgroup_storage, bpf_map_type_reuseport_sockarray, bpf_map_type_percpu_cgroup_storage, bpf_map_type_queue, bpf_map_type_stack, /* see /usr/include/linux/bpf.h for the full list. */ }; .ee .in .ip .i map_type selects one of the available map implementations in the kernel. .\" fixme we need an explanation of why one might choose each of .\" these map implementations for all map types, ebpf programs access maps with the same .br bpf_map_lookup_elem () and .br bpf_map_update_elem () helper functions. further details of the various map types are given below. .tp .b bpf_map_lookup_elem the .b bpf_map_lookup_elem command looks up an element with a given .i key in the map referred to by the file descriptor .ir fd . .ip .in +4n .ex int bpf_lookup_elem(int fd, const void *key, void *value) { union bpf_attr attr = { .map_fd = fd, .key = ptr_to_u64(key), .value = ptr_to_u64(value), }; return bpf(bpf_map_lookup_elem, &attr, sizeof(attr)); } .ee .in .ip if an element is found, the operation returns zero and stores the element's value into .ir value , which must point to a buffer of .i value_size bytes. .ip if no element is found, the operation returns \-1 and sets .i errno to .br enoent . .tp .b bpf_map_update_elem the .b bpf_map_update_elem command creates or updates an element with a given .i key/value in the map referred to by the file descriptor .ir fd . .ip .in +4n .ex int bpf_update_elem(int fd, const void *key, const void *value, uint64_t flags) { union bpf_attr attr = { .map_fd = fd, .key = ptr_to_u64(key), .value = ptr_to_u64(value), .flags = flags, }; return bpf(bpf_map_update_elem, &attr, sizeof(attr)); } .ee .in .ip the .i flags argument should be specified as one of the following: .rs .tp .b bpf_any create a new element or update an existing element. .tp .b bpf_noexist create a new element only if it did not exist. .tp .b bpf_exist update an existing element. .re .ip on success, the operation returns zero. on error, \-1 is returned and .i errno is set to .br einval , .br eperm , .br enomem , or .br e2big . .b e2big indicates that the number of elements in the map reached the .i max_entries limit specified at map creation time. .b eexist will be returned if .i flags specifies .b bpf_noexist and the element with .i key already exists in the map. .b enoent will be returned if .i flags specifies .b bpf_exist and the element with .i key doesn't exist in the map. .tp .b bpf_map_delete_elem the .b bpf_map_delete_elem command deletes the element whose key is .i key from the map referred to by the file descriptor .ir fd . .ip .in +4n .ex int bpf_delete_elem(int fd, const void *key) { union bpf_attr attr = { .map_fd = fd, .key = ptr_to_u64(key), }; return bpf(bpf_map_delete_elem, &attr, sizeof(attr)); } .ee .in .ip on success, zero is returned. if the element is not found, \-1 is returned and .i errno is set to .br enoent . .tp .b bpf_map_get_next_key the .b bpf_map_get_next_key command looks up an element by .i key in the map referred to by the file descriptor .i fd and sets the .i next_key pointer to the key of the next element. .ip .in +4n .ex int bpf_get_next_key(int fd, const void *key, void *next_key) { union bpf_attr attr = { .map_fd = fd, .key = ptr_to_u64(key), .next_key = ptr_to_u64(next_key), }; return bpf(bpf_map_get_next_key, &attr, sizeof(attr)); } .ee .in .ip if .i key is found, the operation returns zero and sets the .i next_key pointer to the key of the next element. if .i key is not found, the operation returns zero and sets the .i next_key pointer to the key of the first element. if .i key is the last element, \-1 is returned and .i errno is set to .br enoent . other possible .i errno values are .br enomem , .br efault , .br eperm , and .br einval . this method can be used to iterate over all elements in the map. .tp .b close(map_fd) delete the map referred to by the file descriptor .ir map_fd . when the user-space program that created a map exits, all maps will be deleted automatically (but see notes). .\" .ss ebpf map types the following map types are supported: .tp .b bpf_map_type_hash .\" commit 0f8e4bd8a1fc8c4185f1630061d0a1f2d197a475 hash-table maps have the following characteristics: .rs .ip * 3 maps are created and destroyed by user-space programs. both user-space and ebpf programs can perform lookup, update, and delete operations. .ip * the kernel takes care of allocating and freeing key/value pairs. .ip * the .br map_update_elem () helper will fail to insert new element when the .i max_entries limit is reached. (this ensures that ebpf programs cannot exhaust memory.) .ip * .br map_update_elem () replaces existing elements atomically. .re .ip hash-table maps are optimized for speed of lookup. .tp .b bpf_map_type_array .\" commit 28fbcfa08d8ed7c5a50d41a0433aad222835e8e3 array maps have the following characteristics: .rs .ip * 3 optimized for fastest possible lookup. in the future the verifier/jit compiler may recognize lookup() operations that employ a constant key and optimize it into constant pointer. it is possible to optimize a non-constant key into direct pointer arithmetic as well, since pointers and .i value_size are constant for the life of the ebpf program. in other words, .br array_map_lookup_elem () may be 'inlined' by the verifier/jit compiler while preserving concurrent access to this map from user space. .ip * all array elements pre-allocated and zero initialized at init time .ip * the key is an array index, and must be exactly four bytes. .ip * .br map_delete_elem () fails with the error .br einval , since elements cannot be deleted. .ip * .br map_update_elem () replaces elements in a .b nonatomic fashion; for atomic updates, a hash-table map should be used instead. there is however one special case that can also be used with arrays: the atomic built-in .b __sync_fetch_and_add() can be used on 32 and 64 bit atomic counters. for example, it can be applied on the whole value itself if it represents a single counter, or in case of a structure containing multiple counters, it could be used on individual counters. this is quite often useful for aggregation and accounting of events. .re .ip among the uses for array maps are the following: .rs .ip * 3 as "global" ebpf variables: an array of 1 element whose key is (index) 0 and where the value is a collection of 'global' variables which ebpf programs can use to keep state between events. .ip * aggregation of tracing events into a fixed set of buckets. .ip * accounting of networking events, for example, number of packets and packet sizes. .re .tp .br bpf_map_type_prog_array " (since linux 4.2)" a program array map is a special kind of array map whose map values contain only file descriptors referring to other ebpf programs. thus, both the .i key_size and .i value_size must be exactly four bytes. this map is used in conjunction with the .br bpf_tail_call () helper. .ip this means that an ebpf program with a program array map attached to it can call from kernel side into .ip .in +4n .ex void bpf_tail_call(void *context, void *prog_map, unsigned int index); .ee .in .ip and therefore replace its own program flow with the one from the program at the given program array slot, if present. this can be regarded as kind of a jump table to a different ebpf program. the invoked program will then reuse the same stack. when a jump into the new program has been performed, it won't return to the old program anymore. .ip if no ebpf program is found at the given index of the program array (because the map slot doesn't contain a valid program file descriptor, the specified lookup index/key is out of bounds, or the limit of 32 .\" max_tail_call_cnt nested calls has been exceed), execution continues with the current ebpf program. this can be used as a fall-through for default cases. .ip a program array map is useful, for example, in tracing or networking, to handle individual system calls or protocols in their own subprograms and use their identifiers as an individual map index. this approach may result in performance benefits, and also makes it possible to overcome the maximum instruction limit of a single ebpf program. in dynamic environments, a user-space daemon might atomically replace individual subprograms at run-time with newer versions to alter overall program behavior, for instance, if global policies change. .\" .ss ebpf programs the .b bpf_prog_load command is used to load an ebpf program into the kernel. the return value for this command is a new file descriptor associated with this ebpf program. .pp .in +4n .ex char bpf_log_buf[log_buf_size]; int bpf_prog_load(enum bpf_prog_type type, const struct bpf_insn *insns, int insn_cnt, const char *license) { union bpf_attr attr = { .prog_type = type, .insns = ptr_to_u64(insns), .insn_cnt = insn_cnt, .license = ptr_to_u64(license), .log_buf = ptr_to_u64(bpf_log_buf), .log_size = log_buf_size, .log_level = 1, }; return bpf(bpf_prog_load, &attr, sizeof(attr)); } .ee .in .pp .i prog_type is one of the available program types: .ip .in +4n .ex enum bpf_prog_type { bpf_prog_type_unspec, /* reserve 0 as invalid program type */ bpf_prog_type_socket_filter, bpf_prog_type_kprobe, bpf_prog_type_sched_cls, bpf_prog_type_sched_act, bpf_prog_type_tracepoint, bpf_prog_type_xdp, bpf_prog_type_perf_event, bpf_prog_type_cgroup_skb, bpf_prog_type_cgroup_sock, bpf_prog_type_lwt_in, bpf_prog_type_lwt_out, bpf_prog_type_lwt_xmit, bpf_prog_type_sock_ops, bpf_prog_type_sk_skb, bpf_prog_type_cgroup_device, bpf_prog_type_sk_msg, bpf_prog_type_raw_tracepoint, bpf_prog_type_cgroup_sock_addr, bpf_prog_type_lwt_seg6local, bpf_prog_type_lirc_mode2, bpf_prog_type_sk_reuseport, bpf_prog_type_flow_dissector, /* see /usr/include/linux/bpf.h for the full list. */ }; .ee .in .pp for further details of ebpf program types, see below. .pp the remaining fields of .i bpf_attr are set as follows: .ip * 3 .i insns is an array of .i "struct bpf_insn" instructions. .ip * .i insn_cnt is the number of instructions in the program referred to by .ir insns . .ip * .i license is a license string, which must be gpl compatible to call helper functions marked .ir gpl_only . (the licensing rules are the same as for kernel modules, so that also dual licenses, such as "dual bsd/gpl", may be used.) .ip * .i log_buf is a pointer to a caller-allocated buffer in which the in-kernel verifier can store the verification log. this log is a multi-line string that can be checked by the program author in order to understand how the verifier came to the conclusion that the ebpf program is unsafe. the format of the output can change at any time as the verifier evolves. .ip * .i log_size size of the buffer pointed to by .ir log_buf . if the size of the buffer is not large enough to store all verifier messages, \-1 is returned and .i errno is set to .br enospc . .ip * .i log_level verbosity level of the verifier. a value of zero means that the verifier will not provide a log; in this case, .i log_buf must be a null pointer, and .i log_size must be zero. .pp applying .br close (2) to the file descriptor returned by .b bpf_prog_load will unload the ebpf program (but see notes). .pp maps are accessible from ebpf programs and are used to exchange data between ebpf programs and between ebpf programs and user-space programs. for example, ebpf programs can process various events (like kprobe, packets) and store their data into a map, and user-space programs can then fetch data from the map. conversely, user-space programs can use a map as a configuration mechanism, populating the map with values checked by the ebpf program, which then modifies its behavior on the fly according to those values. .\" .\" .ss ebpf program types the ebpf program type .ri ( prog_type ) determines the subset of kernel helper functions that the program may call. the program type also determines the program input (context)\(emthe format of .i "struct bpf_context" (which is the data blob passed into the ebpf program as the first argument). .\" .\" fixme .\" somewhere in this page we need a general introduction to the .\" bpf_context. for example, how does a bpf program access the .\" context? .pp for example, a tracing program does not have the exact same subset of helper functions as a socket filter program (though they may have some helpers in common). similarly, the input (context) for a tracing program is a set of register values, while for a socket filter it is a network packet. .pp the set of functions available to ebpf programs of a given type may increase in the future. .pp the following program types are supported: .tp .br bpf_prog_type_socket_filter " (since linux 3.19)" currently, the set of functions for .b bpf_prog_type_socket_filter is: .ip .in +4n .ex bpf_map_lookup_elem(map_fd, void *key) /* look up key in a map_fd */ bpf_map_update_elem(map_fd, void *key, void *value) /* update key/value */ bpf_map_delete_elem(map_fd, void *key) /* delete key in a map_fd */ .ee .in .ip the .i bpf_context argument is a pointer to a .ir "struct __sk_buff" . .\" fixme: we need some text here to explain how the program .\" accesses __sk_buff. .\" see 'struct __sk_buff' and commit 9bac3d6d548e5 .\" .\" alexei commented: .\" actually now in case of socket_filter, sched_cls, sched_act .\" the program can now access skb fields. .\" .tp .br bpf_prog_type_kprobe " (since linux 4.1)" .\" commit 2541517c32be2531e0da59dfd7efc1ce844644f5 [to be documented] .\" fixme document this program type .\" describe allowed helper functions for this program type .\" describe bpf_context for this program type .\" .\" fixme we need text here to describe 'kern_version' .tp .br bpf_prog_type_sched_cls " (since linux 4.1)" .\" commit 96be4325f443dbbfeb37d2a157675ac0736531a1 .\" commit e2e9b6541dd4b31848079da80fe2253daaafb549 [to be documented] .\" fixme document this program type .\" describe allowed helper functions for this program type .\" describe bpf_context for this program type .tp .br bpf_prog_type_sched_act " (since linux 4.1)" .\" commit 94caee8c312d96522bcdae88791aaa9ebcd5f22c .\" commit a8cb5f556b567974d75ea29c15181c445c541b1f [to be documented] .\" fixme document this program type .\" describe allowed helper functions for this program type .\" describe bpf_context for this program type .ss events once a program is loaded, it can be attached to an event. various kernel subsystems have different ways to do so. .pp since linux 3.19, .\" commit 89aa075832b0da4402acebd698d0411dcc82d03e the following call will attach the program .i prog_fd to the socket .ir sockfd , which was created by an earlier call to .br socket (2): .pp .in +4n .ex setsockopt(sockfd, sol_socket, so_attach_bpf, &prog_fd, sizeof(prog_fd)); .ee .in .pp since linux 4.1, .\" commit 2541517c32be2531e0da59dfd7efc1ce844644f5 the following call may be used to attach the ebpf program referred to by the file descriptor .i prog_fd to a perf event file descriptor, .ir event_fd , that was created by a previous call to .br perf_event_open (2): .pp .in +4n .ex ioctl(event_fd, perf_event_ioc_set_bpf, prog_fd); .ee .in .\" .\" .sh return value for a successful call, the return value depends on the operation: .tp .b bpf_map_create the new file descriptor associated with the ebpf map. .tp .b bpf_prog_load the new file descriptor associated with the ebpf program. .tp all other commands zero. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b e2big the ebpf program is too large or a map reached the .i max_entries limit (maximum number of elements). .tp .b eacces for .br bpf_prog_load , even though all program instructions are valid, the program has been rejected because it was deemed unsafe. this may be because it may have accessed a disallowed memory region or an uninitialized stack/register or because the function constraints don't match the actual types or because there was a misaligned memory access. in this case, it is recommended to call .br bpf () again with .i log_level = 1 and examine .i log_buf for the specific reason provided by the verifier. .tp .b ebadf .i fd is not an open file descriptor. .tp .b efault one of the pointers .ri ( key or .i value or .i log_buf or .ir insns ) is outside the accessible address space. .tp .b einval the value specified in .i cmd is not recognized by this kernel. .tp .b einval for .br bpf_map_create , either .i map_type or attributes are invalid. .tp .b einval for .b bpf_map_*_elem commands, some of the fields of .i "union bpf_attr" that are not used by this command are not set to zero. .tp .b einval for .br bpf_prog_load , indicates an attempt to load an invalid program. ebpf programs can be deemed invalid due to unrecognized instructions, the use of reserved fields, jumps out of range, infinite loops or calls of unknown functions. .tp .b enoent for .b bpf_map_lookup_elem or .br bpf_map_delete_elem , indicates that the element with the given .i key was not found. .tp .b enomem cannot allocate sufficient memory. .tp .b eperm the call was made without sufficient privilege (without the .b cap_sys_admin capability). .sh versions the .br bpf () system call first appeared in linux 3.18. .sh conforming to the .br bpf () system call is linux-specific. .sh notes prior to linux 4.4, all .br bpf () commands require the caller to have the .b cap_sys_admin capability. from linux 4.4 onwards, .\" commit 1be7f75d1668d6296b80bf35dcf6762393530afc an unprivileged user may create limited programs of type .br bpf_prog_type_socket_filter and associated maps. however they may not store kernel pointers within the maps and are presently limited to the following helper functions: .\" [linux 5.6] mtk: the list of available functions is, i think, governed .\" by the check in net/core/filter.c::bpf_base_func_proto(). .ip * 3 get_random .pd 0 .ip * get_smp_processor_id .ip * tail_call .ip * ktime_get_ns .pd 1 .pp unprivileged access may be blocked by writing the value 1 to the file .ir /proc/sys/kernel/unprivileged_bpf_disabled . .pp ebpf objects (maps and programs) can be shared between processes. for example, after .br fork (2), the child inherits file descriptors referring to the same ebpf objects. in addition, file descriptors referring to ebpf objects can be transferred over unix domain sockets. file descriptors referring to ebpf objects can be duplicated in the usual way, using .br dup (2) and similar calls. an ebpf object is deallocated only after all file descriptors referring to the object have been closed. .pp ebpf programs can be written in a restricted c that is compiled (using the .b clang compiler) into ebpf bytecode. various features are omitted from this restricted c, such as loops, global variables, variadic functions, floating-point numbers, and passing structures as function arguments. some examples can be found in the .i samples/bpf/*_kern.c files in the kernel source tree. .\" there are also examples for the tc classifier, in the iproute2 .\" project, in examples/bpf .pp the kernel contains a just-in-time (jit) compiler that translates ebpf bytecode into native machine code for better performance. in kernels before linux 4.15, the jit compiler is disabled by default, but its operation can be controlled by writing one of the following integer strings to the file .ir /proc/sys/net/core/bpf_jit_enable : .ip 0 3 disable jit compilation (default). .ip 1 normal compilation. .ip 2 debugging mode. the generated opcodes are dumped in hexadecimal into the kernel log. these opcodes can then be disassembled using the program .i tools/net/bpf_jit_disasm.c provided in the kernel source tree. .pp since linux 4.15, .\" commit 290af86629b25ffd1ed6232c4e9107da031705cb the kernel may configured with the .b config_bpf_jit_always_on option. in this case, the jit compiler is always enabled, and the .i bpf_jit_enable is initialized to 1 and is immutable. (this kernel configuration option was provided as a mitigation for one of the spectre attacks against the bpf interpreter.) .pp the jit compiler for ebpf is currently .\" last reviewed in linux 4.18-rc by grepping for bpf_alu64 in arch/ .\" and by checking the documentation for bpf_jit_enable in .\" documentation/sysctl/net.txt available for the following architectures: .ip * 3 x86-64 (since linux 3.18; cbpf since linux 3.0); .\" commit 0a14842f5a3c0e88a1e59fac5c3025db39721f74 .pd 0 .ip * arm32 (since linux 3.18; cbpf since linux 3.4); .\" commit ddecdfcea0ae891f782ae853771c867ab51024c2 .ip * sparc 32 (since linux 3.18; cbpf since linux 3.5); .\" commit 2809a2087cc44b55e4377d7b9be3f7f5d2569091 .ip * arm-64 (since linux 3.18); .\" commit e54bcde3d69d40023ae77727213d14f920eb264a .ip * s390 (since linux 4.1; cbpf since linux 3.7); .\" commit c10302efe569bfd646b4c22df29577a4595b4580 .ip * powerpc 64 (since linux 4.8; cbpf since linux 3.1); .\" commit 0ca87f05ba8bdc6791c14878464efc901ad71e99 .\" commit 156d0e290e969caba25f1851c52417c14d141b24 .ip * sparc 64 (since linux 4.12); .\" commit 7a12b5031c6b947cc13918237ae652b536243b76 .ip * x86-32 (since linux 4.18); .\" commit 03f5781be2c7b7e728d724ac70ba10799cc710d7 .ip * mips 64 (since linux 4.18; cbpf since linux 3.16); .\" commit c6610de353da5ca6eee5b8960e838a87a90ead0c .\" commit f381bf6d82f032b7410185b35d000ea370ac706b .ip * riscv (since linux 5.1). .\" commit 2353ecc6f91fd15b893fa01bf85a1c7a823ee4f2 .pd .sh examples .ex /* bpf+sockets example: * 1. create array map of 256 elements * 2. load program that counts number of packets received * r0 = skb\->data[eth_hlen + offsetof(struct iphdr, protocol)] * map[r0]++ * 3. attach prog_fd to raw socket via setsockopt() * 4. print number of received tcp/udp packets every second */ int main(int argc, char *argv[]) { int sock, map_fd, prog_fd, key; long long value = 0, tcp_cnt, udp_cnt; map_fd = bpf_create_map(bpf_map_type_array, sizeof(key), sizeof(value), 256); if (map_fd < 0) { printf("failed to create map \(aq%s\(aq\en", strerror(errno)); /* likely not run as root */ return 1; } struct bpf_insn prog[] = { bpf_mov64_reg(bpf_reg_6, bpf_reg_1), /* r6 = r1 */ bpf_ld_abs(bpf_b, eth_hlen + offsetof(struct iphdr, protocol)), /* r0 = ip\->proto */ bpf_stx_mem(bpf_w, bpf_reg_10, bpf_reg_0, \-4), /* *(u32 *)(fp \- 4) = r0 */ bpf_mov64_reg(bpf_reg_2, bpf_reg_10), /* r2 = fp */ bpf_alu64_imm(bpf_add, bpf_reg_2, \-4), /* r2 = r2 \- 4 */ bpf_ld_map_fd(bpf_reg_1, map_fd), /* r1 = map_fd */ bpf_call_func(bpf_func_map_lookup_elem), /* r0 = map_lookup(r1, r2) */ bpf_jmp_imm(bpf_jeq, bpf_reg_0, 0, 2), /* if (r0 == 0) goto pc+2 */ bpf_mov64_imm(bpf_reg_1, 1), /* r1 = 1 */ bpf_xadd(bpf_dw, bpf_reg_0, bpf_reg_1, 0, 0), /* lock *(u64 *) r0 += r1 */ .\" == atomic64_add bpf_mov64_imm(bpf_reg_0, 0), /* r0 = 0 */ bpf_exit_insn(), /* return r0 */ }; prog_fd = bpf_prog_load(bpf_prog_type_socket_filter, prog, sizeof(prog) / sizeof(prog[0]), "gpl"); sock = open_raw_sock("lo"); assert(setsockopt(sock, sol_socket, so_attach_bpf, &prog_fd, sizeof(prog_fd)) == 0); for (;;) { key = ipproto_tcp; assert(bpf_lookup_elem(map_fd, &key, &tcp_cnt) == 0); key = ipproto_udp; assert(bpf_lookup_elem(map_fd, &key, &udp_cnt) == 0); printf("tcp %lld udp %lld packets\en", tcp_cnt, udp_cnt); sleep(1); } return 0; } .ee .pp some complete working code can be found in the .i samples/bpf directory in the kernel source tree. .sh see also .br seccomp (2), .br bpf\-helpers (7), .br socket (7), .br tc (8), .br tc\-bpf (8) .pp both classic and extended bpf are explained in the kernel source file .ir documentation/networking/filter.txt . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/erfc.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:12:45 1993 by rik faith (faith@cs.unc.edu) .th strcasecmp 3 2021-03-22 "" "linux programmer's manual" .sh name strcasecmp, strncasecmp \- compare two strings ignoring case .sh synopsis .nf .b #include .pp .bi "int strcasecmp(const char *" s1 ", const char *" s2 ); .bi "int strncasecmp(const char *" s1 ", const char *" s2 ", size_t " n ); .fi .sh description the .br strcasecmp () function performs a byte-by-byte comparison of the strings .i s1 and .ir s2 , ignoring the case of the characters. it returns an integer less than, equal to, or greater than zero if .i s1 is found, respectively, to be less than, to match, or be greater than .ir s2 . .pp the .br strncasecmp () function is similar, except that it compares no more than .i n bytes of .ir s1 and .ir s2 . .sh return value the .br strcasecmp () and .br strncasecmp () functions return an integer less than, equal to, or greater than zero if .i s1 is, after ignoring case, found to be less than, to match, or be greater than .ir s2 , respectively. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strcasecmp (), .br strncasecmp () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to 4.4bsd, posix.1-2001, posix.1-2008. .sh notes the .br strcasecmp () and .br strncasecmp () functions first appeared in 4.4bsd, where they were declared in .ir . thus, for reasons of historical compatibility, the glibc .i header file also declares these functions, if the .b _default_source (or, in glibc 2.19 and earlier, .br _bsd_source ) feature test macro is defined. .pp the posix.1-2008 standard says of these functions: .pp .rs when the .b lc_ctype category of the locale being used is from the posix locale, these functions shall behave as if the strings had been converted to lowercase and then a byte comparison performed. otherwise, the results are unspecified. .re .sh see also .br bcmp (3), .br memcmp (3), .br strcmp (3), .br strcoll (3), .br string (3), .br strncmp (3), .br wcscasecmp (3), .br wcsncasecmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pow.3 .\" copyright (c) 1992, 1993, 1994 .\" the regents of the university of california. all rights reserved. .\" and copyright (c) 2008, 2014 michael kerrisk .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)symlink.7 8.3 (berkeley) 3/31/94 .\" $freebsd: src/bin/ln/symlink.7,v 1.30 2005/02/13 22:25:09 ru exp $ .\" .\" 2008-06-11, mtk, taken from freebsd 6.2 and heavily edited for .\" specific linux details, improved readability, and man-pages style. .\" .th symlink 7 2021-03-22 "linux" "linux programmer's manual" .sh name symlink \- symbolic link handling .sh description symbolic links are files that act as pointers to other files. to understand their behavior, you must first understand how hard links work. .pp a hard link to a file is indistinguishable from the original file because it is a reference to the object underlying the original filename. (to be precise: each of the hard links to a file is a reference to the same .ir "inode number" , where an inode number is an index into the inode table, which contains metadata about all files on a filesystem. see .br stat (2).) changes to a file are independent of the name used to reference the file. hard links may not refer to directories (to prevent the possibility of loops within the filesystem tree, which would confuse many programs) and may not refer to files on different filesystems (because inode numbers are not unique across filesystems). .pp a symbolic link is a special type of file whose contents are a string that is the pathname of another file, the file to which the link refers. (the contents of a symbolic link can be read using .br readlink (2).) in other words, a symbolic link is a pointer to another name, and not to an underlying object. for this reason, symbolic links may refer to directories and may cross filesystem boundaries. .pp there is no requirement that the pathname referred to by a symbolic link should exist. a symbolic link that refers to a pathname that does not exist is said to be a .ir "dangling link" . .pp because a symbolic link and its referenced object coexist in the filesystem name space, confusion can arise in distinguishing between the link itself and the referenced object. on historical systems, commands and system calls adopted their own link-following conventions in a somewhat ad-hoc fashion. rules for a more uniform approach, as they are implemented on linux and other systems, are outlined here. it is important that site-local applications also conform to these rules, so that the user interface can be as consistent as possible. .\" .ss magic links there is a special class of symbolic-link-like objects known as "magic links", which can be found in certain pseudofilesystems such as .br proc (5) (examples include .ir /proc/[pid]/exe " and " /proc/[pid]/fd/* ). unlike normal symbolic links, magic links are not resolved through pathname-expansion, but instead act as direct references to the kernel's own representation of a file handle. as such, these magic links allow users to access files which cannot be referenced with normal paths (such as unlinked files still referenced by a running program ). .pp because they can bypass ordinary .br mount_namespaces (7)-based restrictions, magic links have been used as attack vectors in various exploits. .\" .ss symbolic link ownership, permissions, and timestamps the owner and group of an existing symbolic link can be changed using .br lchown (2). the only time that the ownership of a symbolic link matters is when the link is being removed or renamed in a directory that has the sticky bit set (see .br stat (2)). .pp the last access and last modification timestamps of a symbolic link can be changed using .br utimensat (2) or .br lutimes (3). .pp .\" linux does not currently implement an lchmod(2). on linux, the permissions of an ordinary symbolic link are not used in any operations; the permissions are always 0777 (read, write, and execute for all user categories), and can't be changed. .pp however, magic links do not follow this rule. they can have a non-0777 mode, though this mode is not currently used in any permission checks. .\" .pp .\" the .\" 4.4bsd .\" system differs from historical .\" 4bsd .\" systems in that the system call .\" .br chown (2) .\" has been changed to follow symbolic links. .\" the .\" .br lchown (2) .\" system call was added later when the limitations of the new .\" .br chown (2) .\" became apparent. .ss obtaining a file descriptor that refers to a symbolic link using the combination of the .b o_path and .br o_nofollow flags to .br open (2) yields a file descriptor that can be passed as the .ir dirfd argument in system calls such as .br fstatat (2), .br fchownat (2), .br fchmodat (2), .br linkat (2), and .br readlinkat (2), in order to operate on the symbolic link itself (rather than the file to which it refers). .pp by default (i.e., if the .br at_symlink_follow flag is not specified), if .br name_to_handle_at (2) is applied to a symbolic link, it yields a handle for the symbolic link (rather than the file to which it refers). one can then obtain a file descriptor for the symbolic link (rather than the file to which it refers) by specifying the .b o_path flag in a subsequent call to .br open_by_handle_at (2). again, that file descriptor can be used in the aforementioned system calls to operate on the symbolic link itself. .ss handling of symbolic links by system calls and commands symbolic links are handled either by operating on the link itself, or by operating on the object referred to by the link. in the latter case, an application or system call is said to .i follow the link. symbolic links may refer to other symbolic links, in which case the links are dereferenced until an object that is not a symbolic link is found, a symbolic link that refers to a file which does not exist is found, or a loop is detected. (loop detection is done by placing an upper limit on the number of links that may be followed, and an error results if this limit is exceeded.) .pp there are three separate areas that need to be discussed. they are as follows: .ip 1. 3 symbolic links used as filename arguments for system calls. .ip 2. symbolic links specified as command-line arguments to utilities that are not traversing a file tree. .ip 3. symbolic links encountered by utilities that are traversing a file tree (either specified on the command line or encountered as part of the file hierarchy walk). .pp before describing the treatment of symbolic links by system calls and commands, we require some terminology. given a pathname of the form .ir a/b/c , the part preceding the final slash (i.e., .ir a/b ) is called the .i dirname component, and the part following the final slash (i.e., .ir c ) is called the .ir basename component. .\" .ss treatment of symbolic links in system calls the first area is symbolic links used as filename arguments for system calls. .pp the treatment of symbolic links within a pathname passed to a system call is as follows: .ip 1. 3 within the dirname component of a pathname, symbolic links are always followed in nearly every system call. (this is also true for commands.) the one exception is .br openat2 (2), which provides flags that can be used to explicitly prevent following of symbolic links in the dirname component. .ip 2. except as noted below, all system calls follow symbolic links in the basename component of a pathname. for example, if there were a symbolic link .i slink which pointed to a file named .ir afile , the system call .i "open(""slink"" ...\&)" would return a file descriptor referring to the file .ir afile . .pp various system calls do not follow links in the basename component of a pathname, and operate on the symbolic link itself. they are: .br lchown (2), .br lgetxattr (2), .br llistxattr (2), .br lremovexattr (2), .br lsetxattr (2), .br lstat (2), .br readlink (2), .br rename (2), .br rmdir (2), and .br unlink (2). .pp certain other system calls optionally follow symbolic links in the basename component of a pathname. they are: .br faccessat (2), .\" maybe one day: .br fchownat (2) .br fchownat (2), .br fstatat (2), .br linkat (2), .br name_to_handle_at (2), .br open (2), .br openat (2), .br open_by_handle_at (2), and .br utimensat (2); see their manual pages for details. because .br remove (3) is an alias for .br unlink (2), that library function also does not follow symbolic links. when .br rmdir (2) is applied to a symbolic link, it fails with the error .br enotdir . .pp .br link (2) warrants special discussion. posix.1-2001 specifies that .br link (2) should dereference .i oldpath if it is a symbolic link. however, linux does not do this. (by default, solaris is the same, but the posix.1-2001 specified behavior can be obtained with suitable compiler options.) posix.1-2008 changed the specification to allow either behavior in an implementation. .ss commands not traversing a file tree the second area is symbolic links, specified as command-line filename arguments, to commands which are not traversing a file tree. .pp except as noted below, commands follow symbolic links named as command-line arguments. for example, if there were a symbolic link .i slink which pointed to a file named .ir afile , the command .i "cat slink" would display the contents of the file .ir afile . .pp it is important to realize that this rule includes commands which may optionally traverse file trees; for example, the command .i "chown file" is included in this rule, while the command .ir "chown\ \-r file" , which performs a tree traversal, is not. (the latter is described in the third area, below.) .pp if it is explicitly intended that the command operate on the symbolic link instead of following the symbolic link\(emfor example, it is desired that .i "chown slink" change the ownership of the file that .i slink is, whether it is a symbolic link or not\(emthen the .i \-h option should be used. in the above example, .i "chown root slink" would change the ownership of the file referred to by .ir slink , while .i "chown\ \-h root slink" would change the ownership of .i slink itself. .pp there are some exceptions to this rule: .ip * 2 the .br mv (1) and .br rm (1) commands do not follow symbolic links named as arguments, but respectively attempt to rename and delete them. (note, if the symbolic link references a file via a relative path, moving it to another directory may very well cause it to stop working, since the path may no longer be correct.) .ip * the .br ls (1) command is also an exception to this rule. for compatibility with historic systems (when .br ls (1) is not doing a tree walk\(emthat is, .i \-r option is not specified), the .br ls (1) command follows symbolic links named as arguments if the .i \-h or .i \-l option is specified, or if the .ir \-f , .ir \-d , or .i \-l options are not specified. (the .br ls (1) command is the only command where the .i \-h and .i \-l options affect its behavior even though it is not doing a walk of a file tree.) .ip * the .br file (1) command is also an exception to this rule. the .br file (1) command does not follow symbolic links named as argument by default. the .br file (1) command does follow symbolic links named as argument if the .i \-l option is specified. .\" .\"the 4.4bsd system differs from historical 4bsd systems in that the .\".br chown (1) .\"and .\".br chgrp (1) .\"commands follow symbolic links specified on the command line. .ss commands traversing a file tree the following commands either optionally or always traverse file trees: .br chgrp (1), .br chmod (1), .br chown (1), .br cp (1), .br du (1), .br find (1), .br ls (1), .br pax (1), .br rm (1), and .br tar (1). .pp it is important to realize that the following rules apply equally to symbolic links encountered during the file tree traversal and symbolic links listed as command-line arguments. .pp the \fifirst rule\fp applies to symbolic links that reference files other than directories. operations that apply to symbolic links are performed on the links themselves, but otherwise the links are ignored. .pp the command .i "rm\ \-r slink directory" will remove .ir slink , as well as any symbolic links encountered in the tree traversal of .ir directory , because symbolic links may be removed. in no case will .br rm (1) affect the file referred to by .ir slink . .pp the \fisecond rule\fp applies to symbolic links that refer to directories. symbolic links that refer to directories are never followed by default. this is often referred to as a "physical" walk, as opposed to a "logical" walk (where symbolic links that refer to directories are followed). .pp certain conventions are (should be) followed as consistently as possible by commands that perform file tree walks: .ip * 2 a command can be made to follow any symbolic links named on the command line, regardless of the type of file they reference, by specifying the .i \-h (for "half-logical") flag. this flag is intended to make the command-line name space look like the logical name space. (note, for commands that do not always do file tree traversals, the .i \-h flag will be ignored if the .i \-r flag is not also specified.) .ip for example, the command .i "chown\ \-hr user slink" will traverse the file hierarchy rooted in the file pointed to by .ir slink . note, the .i \-h is not the same as the previously discussed .i \-h flag. the .i \-h flag causes symbolic links specified on the command line to be dereferenced for the purposes of both the action to be performed and the tree walk, and it is as if the user had specified the name of the file to which the symbolic link pointed. .ip * a command can be made to follow any symbolic links named on the command line, as well as any symbolic links encountered during the traversal, regardless of the type of file they reference, by specifying the .i \-l (for "logical") flag. this flag is intended to make the entire name space look like the logical name space. (note, for commands that do not always do file tree traversals, the .i \-l flag will be ignored if the .i \-r flag is not also specified.) .ip for example, the command .i "chown\ \-lr user slink" will change the owner of the file referred to by .ir slink . if .i slink refers to a directory, .b chown will traverse the file hierarchy rooted in the directory that it references. in addition, if any symbolic links are encountered in any file tree that .b chown traverses, they will be treated in the same fashion as .ir slink . .ip * a command can be made to provide the default behavior by specifying the .i \-p (for "physical") flag. this flag is intended to make the entire name space look like the physical name space. .pp for commands that do not by default do file tree traversals, the .ir \-h , .ir \-l , and .i \-p flags are ignored if the .i \-r flag is not also specified. in addition, you may specify the .ir \-h , .ir \-l , and .i \-p options more than once; the last one specified determines the command's behavior. this is intended to permit you to alias commands to behave one way or the other, and then override that behavior on the command line. .pp the .br ls (1) and .br rm (1) commands have exceptions to these rules: .ip * 2 the .br rm (1) command operates on the symbolic link, and not the file it references, and therefore never follows a symbolic link. the .br rm (1) command does not support the .ir \-h , .ir \-l , or .i \-p options. .ip * to maintain compatibility with historic systems, the .br ls (1) command acts a little differently. if you do not specify the .ir \-f , .ir \-d , or .i \-l options, .br ls (1) will follow symbolic links specified on the command line. if the .i \-l flag is specified, .br ls (1) follows all symbolic links, regardless of their type, whether specified on the command line or encountered in the tree walk. .sh see also .br chgrp (1), .br chmod (1), .br find (1), .br ln (1), .br ls (1), .br mv (1), .br namei (1), .br rm (1), .br lchown (2), .br link (2), .br lstat (2), .br readlink (2), .br rename (2), .br symlink (2), .br unlink (2), .br utimensat (2), .br lutimes (3), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strsignal.3 .so man3/fenv.3 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 2002-04-15 by roger luethi and aeb .\" .th getdtablesize 3 2021-03-22 "linux" "linux programmer's manual" .sh name getdtablesize \- get file descriptor table size .sh synopsis .nf .b #include .pp .b int getdtablesize(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getdtablesize (): .nf since glibc 2.20: _default_source || ! (_posix_c_source >= 200112l) glibc 2.12 to 2.19: _bsd_source || ! (_posix_c_source >= 200112l) before glibc 2.12: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description .br getdtablesize () returns the maximum number of files a process can have open, one more than the largest possible value for a file descriptor. .sh return value the current limit on the number of open files per process. .sh errors on linux, .br getdtablesize () can return any of the errors described for .br getrlimit (2); see notes below. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getdtablesize () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4, 4.4bsd (the .br getdtablesize () function first appeared in 4.2bsd). it is not specified in posix.1; portable applications should employ .i sysconf(_sc_open_max) instead of this call. .sh notes the glibc version of .br getdtablesize () calls .br getrlimit (2) and returns the current .b rlimit_nofile limit, or .b open_max when that fails. .\" the libc4 and libc5 versions return .\" .b open_max .\" (set to 256 since linux 0.98.4). .sh see also .br close (2), .br dup (2), .br getrlimit (2), .br open (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rcmd.3 .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th cp1251 7 2020-08-13 "linux" "linux programmer's manual" .sh name cp1251 \- cp\ 1251 character set encoded in octal, decimal, and hexadecimal .sh description the windows code pages include several 8-bit extensions to the ascii character set (also known as iso 646-irv). cp\ 1251 encodes the characters used in cyrillic scripts. .ss cp\ 1251 characters the following table displays the characters in cp\ 1251 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 200 128 80 ђ cyrillic capital letter dje 201 129 81 ѓ cyrillic capital letter gje 202 130 82 ‚ single low-9 quotation mark 203 131 83 ѓ cyrillic small letter gje 204 132 84 „ double low-9 quotation mark 205 133 85 … horizontal ellipsis 206 134 86 † dagger 207 135 87 ‡ double dagger 210 136 88 € euro sign 211 137 89 ‰ per mille sign 212 138 8a љ cyrillic capital letter lje 213 139 8b ‹ single left-pointing angle quotation mark 214 140 8c њ cyrillic capital letter nje 215 141 8d ќ cyrillic capital letter kje 216 142 8e ћ cyrillic capital letter tshe 217 143 8f џ cyrillic capital letter dzhe 220 144 90 ђ cyrillic small letter dje 221 145 91 ‘ left single quotation mark 222 146 92 ’ right single quotation mark 223 147 93 “ left double quotation mark 224 148 94 ” right double quotation mark 225 149 95 • bullet 226 150 96 – en dash 227 151 97 — em dash 230 152 98 undefined 231 153 99 ™ trade mark sign 232 154 9a љ cyrillic small letter lje 233 155 9b › single right-pointing angle quotation mark 234 156 9c њ cyrillic small letter nje 235 157 9d ќ cyrillic small letter kje 236 158 9e ћ cyrillic small letter tshe 237 159 9f џ cyrillic small letter dzhe 240 160 a0   no-break space 241 161 a1 ў cyrillic capital letter short u 242 162 a2 ў cyrillic small letter short u 243 163 a3 ј cyrillic capital letter je 244 164 a4 ¤ currency sign 245 165 a5 ґ cyrillic capital letter ghe with upturn 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ё cyrillic capital letter io 251 169 a9 © copyright sign 252 170 aa є cyrillic capital letter ukrainian ie 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ї cyrillic capital letter yi 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 і t{ cyrillic capital letter .br byelorussian-ukrainian i t} 263 179 b3 і cyrillic small letter byelorussian-ukrainian i 264 180 b4 ґ cyrillic small letter ghe with upturn 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ё cyrillic small letter io 271 185 b9 № numero sign 272 186 ba є cyrillic small letter ukrainian ie 273 187 bb » right-pointing double angle quotation mark 274 188 bc ј cyrillic small letter je 275 189 bd ѕ cyrillic capital letter dze 276 190 be ѕ cyrillic small letter dze 277 191 bf ї cyrillic small letter yi 300 192 c0 а cyrillic capital letter a 301 193 c1 б cyrillic capital letter be 302 194 c2 в cyrillic capital letter ve 303 195 c3 г cyrillic capital letter ghe 304 196 c4 д cyrillic capital letter de 305 197 c5 е cyrillic capital letter ie 306 198 c6 ж cyrillic capital letter zhe 307 199 c7 з cyrillic capital letter ze 310 200 c8 и cyrillic capital letter i 311 201 c9 й cyrillic capital letter short i 312 202 ca к cyrillic capital letter ka 313 203 cb л cyrillic capital letter el 314 204 cc м cyrillic capital letter em 315 205 cd н cyrillic capital letter en 316 206 ce о cyrillic capital letter o 317 207 cf п cyrillic capital letter pe 320 208 d0 р cyrillic capital letter er 321 209 d1 с cyrillic capital letter es 322 210 d2 т cyrillic capital letter te 323 211 d3 у cyrillic capital letter u 324 212 d4 ф cyrillic capital letter ef 325 213 d5 х cyrillic capital letter ha 326 214 d6 ц cyrillic capital letter tse 327 215 d7 ч cyrillic capital letter che 330 216 d8 ш cyrillic capital letter sha 331 217 d9 щ cyrillic capital letter shcha 332 218 da ъ cyrillic capital letter hard sign 333 219 db ы cyrillic capital letter yeru 334 220 dc ь cyrillic capital letter soft sign 335 221 dd э cyrillic capital letter e 336 222 de ю cyrillic capital letter yu 337 223 df я cyrillic capital letter ya 340 224 e0 а cyrillic small letter a 341 225 e1 б cyrillic small letter be 342 226 e2 в cyrillic small letter ve 343 227 e3 г cyrillic small letter ghe 344 228 e4 д cyrillic small letter de 345 229 e5 е cyrillic small letter ie 346 230 e6 ж cyrillic small letter zhe 347 231 e7 з cyrillic small letter ze 350 232 e8 и cyrillic small letter i 351 233 e9 й cyrillic small letter short i 352 234 ea к cyrillic small letter ka 353 235 eb л cyrillic small letter el 354 236 ec м cyrillic small letter em 355 237 ed н cyrillic small letter en 356 238 ee о cyrillic small letter o 357 239 ef п cyrillic small letter pe 360 240 f0 р cyrillic small letter er 361 241 f1 с cyrillic small letter es 362 242 f2 т cyrillic small letter te 363 243 f3 у cyrillic small letter u 364 244 f4 ф cyrillic small letter ef 365 245 f5 х cyrillic small letter ha 366 246 f6 ц cyrillic small letter tse 367 247 f7 ч cyrillic small letter che 370 248 f8 ш cyrillic small letter sha 371 249 f9 щ cyrillic small letter shcha 372 250 fa ъ cyrillic small letter hard sign 373 251 fb ы cyrillic small letter yeru 374 252 fc ь cyrillic small letter soft sign 375 253 fd э cyrillic small letter e 376 254 fe ю cyrillic small letter yu 377 255 ff я cyrillic small letter ya .te .sh notes cp\ 1251 is also known as windows cyrillic. .sh see also .br ascii (7), .br charsets (7), .br cp1252 (7), .br iso_8859\-5 (7), .br koi8\-r (7), .br koi8\-u (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1997 martin schulze (joey@infodrom.north.de) .\" much of the text is copied from the manpage of resolv+(8). .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2003-08-23 martin schulze updated according to glibc 2.3.2 .th host.conf 5 2019-03-06 "linux" "linux system administration" .sh name host.conf \- resolver configuration file .sh description the file .i /etc/host.conf contains configuration information specific to the resolver library. it should contain one configuration keyword per line, followed by appropriate configuration information. the following keywords are recognized: .tp .i trim this keyword may be listed more than once. each time it should be followed by a list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or commas (\(aq,\(aq), with the leading dot. when set, the resolver library will automatically trim the given domain name from the end of any hostname resolved via dns. this is intended for use with local hosts and domains. (related note: .i trim will not affect hostnames gathered via nis or the .br hosts (5) file. care should be taken to ensure that the first hostname for each entry in the hosts file is fully qualified or unqualified, as appropriate for the local installation.) .tp .i multi valid values are .ir on " and " off . if set to .ir on , the resolver library will return all valid addresses for a host that appears in the .i /etc/hosts file, instead of only the first. this is .i off by default, as it may cause a substantial performance loss at sites with large hosts files. .tp .i reorder valid values are .ir on " and " off . if set to .ir on , the resolver library will attempt to reorder host addresses so that local addresses (i.e., on the same subnet) are listed first when a .br gethostbyname (3) is performed. reordering is done for all lookup methods. the default value is .ir off . .sh environment the following environment variables can be used to allow users to override the behavior which is configured in .ir /etc/host.conf : .tp .b resolv_host_conf if set, this variable points to a file that should be read instead of .ir /etc/host.conf . .tp .b resolv_multi overrides the .i multi command. .tp .b resolv_reorder overrides the .i reorder command. .tp .b resolv_add_trim_domains a list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq), or commas (\(aq,\(aq), with the leading dot, which will be added to the list of domains that should be trimmed. .tp .b resolv_override_trim_domains a list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq), or commas (\(aq,\(aq), with the leading dot, which will replace the list of domains that should be trimmed. overrides the .i trim command. .sh files .tp .i /etc/host.conf resolver configuration file .tp .i /etc/resolv.conf resolver configuration file .tp .i /etc/hosts local hosts database .sh notes the following differences exist compared to the original implementation. a new command .i spoof and a new environment variable .b resolv_spoof_check can take arguments like .ir off ", " nowarn ", and " warn . line comments can appear anywhere and not only at the beginning of a line. .ss historical the .br nsswitch.conf (5) file is the modern way of controlling the order of host lookups. .pp in glibc 2.4 and earlier, the following keyword is recognized: .tp .i order this keyword specifies how host lookups are to be performed. it should be followed by one or more lookup methods, separated by commas. valid methods are .ir bind ", " hosts ", and " nis . .tp .b resolv_serv_order overrides the .i order command. .pp .\" commit 7d68cdaa4f748e87ee921f587ee2d483db624b3d since glibc 2.0.7, and up through glibc 2.24, the following keywords and environment variable have been recognized but never implemented: .tp .i nospoof valid values are .ir on " and " off . if set to .ir on , the resolver library will attempt to prevent hostname spoofing to enhance the security of .br rlogin " and " rsh . it works as follows: after performing a host address lookup, the resolver library will perform a hostname lookup for that address. if the two hostnames do not match, the query fails. the default value is .ir off . .tp .i spoofalert valid values are .ir on " and " off . if this option is set to .i on and the .i nospoof option is also set, the resolver library will log a warning of the error via the syslog facility. the default value is .ir off . .tp .i spoof valid values are .ir off ", " nowarn ", and " warn . if this option is set to .ir off , spoofed addresses are permitted and no warnings will be emitted via the syslog facility. if this option is set to .ir warn , the resolver library will attempt to prevent hostname spoofing to enhance the security and log a warning of the error via the syslog facility. if this option is set to .ir nowarn , the resolver library will attempt to prevent hostname spoofing to enhance the security but not emit warnings via the syslog facility. setting this option to anything else is equal to setting it to .ir nowarn . .tp .b resolv_spoof_check overrides the .ir nospoof ", " spoofalert ", and " spoof commands in the same way as the .i spoof command is parsed. valid values are .ir off ", " nowarn ", and " warn . .sh see also .br gethostbyname (3), .br hosts (5), .br nsswitch.conf (5), .br resolv.conf (5), .br hostname (7), .br named (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1995 mark d. roth (roth@uiuc.edu) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" solaris manpages .\" .\" modified thu jul 25 14:43:46 met dst 1996 by michael haardt .\" .\" .th getutent 3 2021-03-22 "" "linux programmer's manual" .sh name getutent, getutid, getutline, pututline, setutent, endutent, utmpname \- access utmp file entries .sh synopsis .nf .b #include .pp .b struct utmp *getutent(void); .bi "struct utmp *getutid(const struct utmp *" ut ); .bi "struct utmp *getutline(const struct utmp *" ut ); .pp .bi "struct utmp *pututline(const struct utmp *" ut ); .pp .b void setutent(void); .b void endutent(void); .pp .bi "int utmpname(const char *" file ); .fi .sh description new applications should use the posix.1-specified "utmpx" versions of these functions; see conforming to. .pp .br utmpname () sets the name of the utmp-format file for the other utmp functions to access. if .br utmpname () is not used to set the filename before the other functions are used, they assume \fb_path_utmp\fp, as defined in \fi\fp. .pp .br setutent () rewinds the file pointer to the beginning of the utmp file. it is generally a good idea to call it before any of the other functions. .pp .br endutent () closes the utmp file. it should be called when the user code is done accessing the file with the other functions. .pp .br getutent () reads a line from the current file position in the utmp file. it returns a pointer to a structure containing the fields of the line. the definition of this structure is shown in .br utmp (5). .pp .br getutid () searches forward from the current file position in the utmp file based upon \fiut\fp. if \fiut\->ut_type\fp is one of \fbrun_lvl\fp, \fbboot_time\fp, \fbnew_time\fp, or \fbold_time\fp, .br getutid () will find the first entry whose \fiut_type\fp field matches \fiut\->ut_type\fp. if \fiut\->ut_type\fp is one of \fbinit_process\fp, \fblogin_process\fp, \fbuser_process\fp, or \fbdead_process\fp, .br getutid () will find the first entry whose .i ut_id field matches \fiut\->ut_id\fp. .pp .br getutline () searches forward from the current file position in the utmp file. it scans entries whose .i ut_type is \fbuser_process\fp or \fblogin_process\fp and returns the first one whose .i ut_line field matches \fiut\->ut_line\fp. .pp .br pututline () writes the .i utmp structure \fiut\fp into the utmp file. it uses .br getutid () to search for the proper place in the file to insert the new entry. if it cannot find an appropriate slot for \fiut\fp, .br pututline () will append the new entry to the end of the file. .sh return value .br getutent (), .br getutid (), and .br getutline () return a pointer to a \fistruct utmp\fp on success, and null on failure (which includes the "record not found" case). this \fistruct utmp\fp is allocated in static storage, and may be overwritten by subsequent calls. .pp on success .br pututline () returns .ir ut ; on failure, it returns null. .pp .br utmpname () returns 0 if the new name was successfully stored, or \-1 on failure. .pp on failure, these functions .i errno set to indicate the error. .sh errors .tp .b enomem out of memory. .tp .b esrch record not found. .pp .br setutent (), .br pututline (), and the .br getut* () functions can also fail for the reasons described in .br open (2). .sh files .tp .i /var/run/utmp database of currently logged-in users .tp .i /var/log/wtmp database of past user logins .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getutent () t} thread safety t{ mt-unsafe init race:utent race:utentbuf sig:alrm timer t} t{ .br getutid (), .br getutline () t} thread safety t{ mt-unsafe init race:utent sig:alrm timer t} t{ .br pututline () t} thread safety t{ mt-unsafe race:utent sig:alrm timer t} t{ .br setutent (), .br endutent (), .br utmpname () t} thread safety mt-unsafe race:utent .te .hy .ad .sp 1 in the above table, .i utent in .i race:utent signifies that if any of the functions .br setutent (), .br getutent (), .br getutid (), .br getutline (), .br pututline (), .br utmpname (), or .br endutent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to xpg2, svr4. .pp in xpg2 and svid 2 the function .br pututline () is documented to return void, and that is what it does on many systems (aix, hp-ux). hp-ux introduces a new function .br _pututline () with the prototype given above for .br pututline (). .pp all these functions are obsolete now on non-linux systems. posix.1-2001 and posix.1-2008, following susv1, does not have any of these functions, but instead uses .pp .rs 4 .ex .b #include .pp .b struct utmpx *getutxent(void); .b struct utmpx *getutxid(const struct utmpx *); .b struct utmpx *getutxline(const struct utmpx *); .b struct utmpx *pututxline(const struct utmpx *); .b void setutxent(void); .b void endutxent(void); .ee .re .pp these functions are provided by glibc, and perform the same task as their equivalents without the "x", but use .ir "struct utmpx" , defined on linux to be the same as .ir "struct utmp" . for completeness, glibc also provides .br utmpxname (), although this function is not specified by posix.1. .pp on some other systems, the \fiutmpx\fp structure is a superset of the \fiutmp\fp structure, with additional fields, and larger versions of the existing fields, and parallel files are maintained, often .i /var/*/utmpx and .ir /var/*/wtmpx . .pp linux glibc on the other hand does not use a parallel \fiutmpx\fp file since its \fiutmp\fp structure is already large enough. the "x" functions listed above are just aliases for their counterparts without the "x" (e.g., .br getutxent () is an alias for .br getutent ()). .sh notes .ss glibc notes the above functions are not thread-safe. glibc adds reentrant versions .pp .nf .b #include .pp .bi "int getutent_r(struct utmp *" ubuf ", struct utmp **" ubufp ); .bi "int getutid_r(struct utmp *" ut , .bi " struct utmp *" ubuf ", struct utmp **" ubufp ); .bi "int getutline_r(struct utmp *" ut , .bi " struct utmp *" ubuf ", struct utmp **" ubufp ); .fi .pp feature test macro requirements for glibc (see .br feature_test_macros (7)): .pp .br getutent_r (), .br getutid_r (), .br getutline_r (): .nf _gnu_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .pp these functions are gnu extensions, analogs of the functions of the same name without the _r suffix. the .i ubuf argument gives these functions a place to store their result. on success, they return 0, and a pointer to the result is written in .ir *ubufp . on error, these functions return \-1. there are no utmpx equivalents of the above functions. (posix.1 does not specify such functions.) .sh examples the following example adds and removes a utmp record, assuming it is run from within a pseudo terminal. for usage in a real application, you should check the return values of .br getpwuid (3) and .br ttyname (3). .pp .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { struct utmp entry; system("echo before adding entry:;who"); entry.ut_type = user_process; entry.ut_pid = getpid(); strcpy(entry.ut_line, ttyname(stdin_fileno) + strlen("/dev/")); /* only correct for ptys named /dev/tty[pqr][0\-9a\-z] */ strcpy(entry.ut_id, ttyname(stdin_fileno) + strlen("/dev/tty")); time(&entry.ut_time); strcpy(entry.ut_user, getpwuid(getuid())\->pw_name); memset(entry.ut_host, 0, ut_hostsize); entry.ut_addr = 0; setutent(); pututline(&entry); system("echo after adding entry:;who"); entry.ut_type = dead_process; memset(entry.ut_line, 0, ut_linesize); entry.ut_time = 0; memset(entry.ut_user, 0, ut_namesize); setutent(); pututline(&entry); system("echo after removing entry:;who"); endutent(); exit(exit_success); } .ee .sh see also .br getutmp (3), .br utmp (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page is copyright (c) 1998 heiner eisen. .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: x25.7,v 1.4 1999/05/18 10:35:12 freitag exp $ .\" .th x25 7 2021-03-22 "linux" "linux programmer's manual" .sh name x25 \- itu-t x.25 / iso-8208 protocol interface .sh synopsis .nf .b #include .b #include .pp .b x25_socket = socket(af_x25, sock_seqpacket, 0); .fi .sh description x25 sockets provide an interface to the x.25 packet layer protocol. this allows applications to communicate over a public x.25 data network as standardized by international telecommunication union's recommendation x.25 (x.25 dte-dce mode). x25 sockets can also be used for communication without an intermediate x.25 network (x.25 dte-dte mode) as described in iso-8208. .pp message boundaries are preserved \(em a .br read (2) from a socket will retrieve the same chunk of data as output with the corresponding .br write (2) to the peer socket. when necessary, the kernel takes care of segmenting and reassembling long messages by means of the x.25 m-bit. there is no hard-coded upper limit for the message size. however, reassembling of a long message might fail if there is a temporary lack of system resources or when other constraints (such as socket memory or buffer size limits) become effective. if that occurs, the x.25 connection will be reset. .ss socket addresses the .b af_x25 socket address family uses the .i struct sockaddr_x25 for representing network addresses as defined in itu-t recommendation x.121. .pp .in +4n .ex struct sockaddr_x25 { sa_family_t sx25_family; /* must be af_x25 */ x25_address sx25_addr; /* x.121 address */ }; .ee .in .pp .i sx25_addr contains a char array .i x25_addr[] to be interpreted as a null-terminated string. .i sx25_addr.x25_addr[] consists of up to 15 (not counting the terminating null byte) ascii characters forming the x.121 address. only the decimal digit characters from \(aq0\(aq to \(aq9\(aq are allowed. .ss socket options the following x.25-specific socket options can be set by using .br setsockopt (2) and read with .br getsockopt (2) with the .i level argument set to .br sol_x25 . .tp .b x25_qbitincl controls whether the x.25 q-bit (qualified data bit) is accessible by the user. it expects an integer argument. if set to 0 (default), the q-bit is never set for outgoing packets and the q-bit of incoming packets is ignored. if set to 1, an additional first byte is prepended to each message read from or written to the socket. for data read from the socket, a 0 first byte indicates that the q-bits of the corresponding incoming data packets were not set. a first byte with value 1 indicates that the q-bit of the corresponding incoming data packets was set. if the first byte of the data written to the socket is 1, the q-bit of the corresponding outgoing data packets will be set. if the first byte is 0, the q-bit will not be set. .sh versions the af_x25 protocol family is a new feature of linux 2.2. .sh bugs plenty, as the x.25 plp implementation is .br config_experimental . .pp this man page is incomplete. .pp there is no dedicated application programmer's header file yet; you need to include the kernel header file .ir . .b config_experimental might also imply that future versions of the interface are not binary compatible. .pp x.25 n-reset events are not propagated to the user process yet. thus, if a reset occurred, data might be lost without notice. .sh see also .br socket (2), .br socket (7) .pp jonathan simon naylor: \(lqthe re-analysis and re-implementation of x.25.\(rq the url is .ur ftp://ftp.pspt.fi\:/pub\:/ham\:/linux\:/ax25\:/x25doc.tgz .ue . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2007 silicon graphics, inc. all rights reserved .\" written by dave chinner .\" .\" %%%license_start(gplv2_oneline) .\" may be distributed as per gnu general public license version 2. .\" %%%license_end .\" .\" 2011-09-19: added falloc_fl_punch_hole .\" 2011-09-19: substantial restructuring of the page .\" .th fallocate 2 2019-11-19 "linux" "linux programmer's manual" .sh name fallocate \- manipulate file space .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int fallocate(int " fd ", int " mode ", off_t " offset \ ", off_t " len ");" .fi .sh description this is a nonportable, linux-specific system call. for the portable, posix.1-specified method of ensuring that space is allocated for a file, see .br posix_fallocate (3). .pp .br fallocate () allows the caller to directly manipulate the allocated disk space for the file referred to by .i fd for the byte range starting at .i offset and continuing for .i len bytes. .pp the .i mode argument determines the operation to be performed on the given range. details of the supported operations are given in the subsections below. .ss allocating disk space the default operation (i.e., .i mode is zero) of .br fallocate () allocates the disk space within the range specified by .i offset and .ir len . the file size (as reported by .br stat (2)) will be changed if .ir offset + len is greater than the file size. any subregion within the range specified by .i offset and .ir len that did not contain data before the call will be initialized to zero. this default behavior closely resembles the behavior of the .br posix_fallocate (3) library function, and is intended as a method of optimally implementing that function. .pp after a successful call, subsequent writes into the range specified by .ir offset and .ir len are guaranteed not to fail because of lack of disk space. .pp if the .b falloc_fl_keep_size flag is specified in .ir mode , the behavior of the call is similar, but the file size will not be changed even if .ir offset + len is greater than the file size. preallocating zeroed blocks beyond the end of the file in this manner is useful for optimizing append workloads. .pp if the .b falloc_fl_unshare_range flag is specified in .ir mode , shared file data extents will be made private to the file to guarantee that a subsequent write will not fail due to lack of space. typically, this will be done by performing a copy-on-write operation on all shared data in the file. this flag may not be supported by all filesystems. .pp because allocation is done in block size chunks, .br fallocate () may allocate a larger range of disk space than was specified. .ss deallocating file space specifying the .br falloc_fl_punch_hole flag (available since linux 2.6.38) in .i mode deallocates space (i.e., creates a hole) in the byte range starting at .i offset and continuing for .i len bytes. within the specified range, partial filesystem blocks are zeroed, and whole filesystem blocks are removed from the file. after a successful call, subsequent reads from this range will return zeros. .pp the .br falloc_fl_punch_hole flag must be ored with .br falloc_fl_keep_size in .ir mode ; in other words, even when punching off the end of the file, the file size (as reported by .br stat (2)) does not change. .pp not all filesystems support .br falloc_fl_punch_hole ; if a filesystem doesn't support the operation, an error is returned. the operation is supported on at least the following filesystems: .ip * 3 xfs (since linux 2.6.38) .ip * ext4 (since linux 3.0) .\" commit a4bb6b64e39abc0e41ca077725f2a72c868e7622 .ip * btrfs (since linux 3.7) .ip * .br tmpfs (5) (since linux 3.5) .\" commit 83e4fa9c16e4af7122e31be3eca5d57881d236fe .ip * .br gfs2 (5) (since linux 4.16) .\" commit 4e56a6411fbce6f859566e17298114c2434391a4 .ss collapsing file space .\" commit 00f5e61998dd17f5375d9dfc01331f104b83f841 specifying the .br falloc_fl_collapse_range flag (available since linux 3.15) in .i mode removes a byte range from a file, without leaving a hole. the byte range to be collapsed starts at .i offset and continues for .i len bytes. at the completion of the operation, the contents of the file starting at the location .i offset+len will be appended at the location .ir offset , and the file will be .i len bytes smaller. .pp a filesystem may place limitations on the granularity of the operation, in order to ensure efficient implementation. typically, .i offset and .i len must be a multiple of the filesystem logical block size, which varies according to the filesystem type and configuration. if a filesystem has such a requirement, .br fallocate () fails with the error .br einval if this requirement is violated. .pp if the region specified by .i offset plus .i len reaches or passes the end of file, an error is returned; instead, use .br ftruncate (2) to truncate a file. .pp no other flags may be specified in .ir mode in conjunction with .br falloc_fl_collapse_range . .pp as at linux 3.15, .b falloc_fl_collapse_range is supported by ext4 (only for extent-based files) .\" commit 9eb79482a97152930b113b51dff530aba9e28c8e and xfs. .\" commit e1d8fb88a64c1f8094b9f6c3b6d2d9e6719c970d .ss zeroing file space specifying the .br falloc_fl_zero_range flag (available since linux 3.15) .\" commit 409332b65d3ed8cfa7a8030f1e9d52f372219642 in .i mode zeros space in the byte range starting at .i offset and continuing for .i len bytes. within the specified range, blocks are preallocated for the regions that span the holes in the file. after a successful call, subsequent reads from this range will return zeros. .pp zeroing is done within the filesystem preferably by converting the range into unwritten extents. this approach means that the specified range will not be physically zeroed out on the device (except for partial blocks at the either end of the range), and i/o is (otherwise) required only to update metadata. .pp if the .b falloc_fl_keep_size flag is additionally specified in .ir mode , the behavior of the call is similar, but the file size will not be changed even if .ir offset + len is greater than the file size. this behavior is the same as when preallocating space with .b falloc_fl_keep_size specified. .pp not all filesystems support .br falloc_fl_zero_range ; if a filesystem doesn't support the operation, an error is returned. the operation is supported on at least the following filesystems: .ip * 3 xfs (since linux 3.15) .\" commit 376ba313147b4172f3e8cf620b9fb591f3e8cdfa .ip * ext4, for extent-based files (since linux 3.15) .\" commit b8a8684502a0fc852afa0056c6bb2a9273f6fcc0 .ip * smb3 (since linux 3.17) .\" commit 30175628bf7f521e9ee31ac98fa6d6fe7441a556 .ip * btrfs (since linux 4.16) .\" commit f27451f229966874a8793995b8e6b74326d125df .ss increasing file space specifying the .br falloc_fl_insert_range flag (available since linux 4.1) .\" commit dd46c787788d5bf5b974729d43e4c405814a4c7d in .i mode increases the file space by inserting a hole within the file size without overwriting any existing data. the hole will start at .i offset and continue for .i len bytes. when inserting the hole inside file, the contents of the file starting at .i offset will be shifted upward (i.e., to a higher file offset) by .i len bytes. inserting a hole inside a file increases the file size by .i len bytes. .pp this mode has the same limitations as .br falloc_fl_collapse_range regarding the granularity of the operation. if the granularity requirements are not met, .br fallocate () fails with the error .br einval . if the .i offset is equal to or greater than the end of file, an error is returned. for such operations (i.e., inserting a hole at the end of file), .br ftruncate (2) should be used. .pp no other flags may be specified in .ir mode in conjunction with .br falloc_fl_insert_range . .pp .b falloc_fl_insert_range requires filesystem support. filesystems that support this operation include xfs (since linux 4.1) .\" commit a904b1ca5751faf5ece8600e18cd3b674afcca1b and ext4 (since linux 4.2). .\" commit 331573febb6a224bc50322e3670da326cb7f4cfc .\" f2fs also has support since linux 4.2 .\" commit f62185d0e283e9d311e3ac1020f159d95f0aab39 .sh return value on success, .br fallocate () returns zero. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor, or is not opened for writing. .tp .b efbig .ir offset + len exceeds the maximum file size. .tp .b efbig .i mode is .br falloc_fl_insert_range , and the current file size+\filen\fp exceeds the maximum file size. .tp .b eintr a signal was caught during execution; see .br signal (7). .tp .b einval .i offset was less than 0, or .i len .\" fixme . (raise a kernel bug) probably the len==0 case should be .\" a no-op, rather than an error. that would be consistent with .\" similar apis for the len==0 case. .\" see "re: [patch] fallocate.2: add falloc_fl_punch_hole flag definition" .\" 21 sep 2012 .\" http://thread.gmane.org/gmane.linux.file-systems/48331/focus=1193526 was less than or equal to 0. .tp .b einval .i mode is .br falloc_fl_collapse_range and the range specified by .i offset plus .i len reaches or passes the end of the file. .tp .b einval .i mode is .br falloc_fl_insert_range and the range specified by .i offset reaches or passes the end of the file. .tp .b einval .i mode is .br falloc_fl_collapse_range or .br falloc_fl_insert_range , but either .i offset or .i len is not a multiple of the filesystem block size. .tp .b einval .i mode contains one of .b falloc_fl_collapse_range or .b falloc_fl_insert_range and also other flags; no other flags are permitted with .br falloc_fl_collapse_range or .br falloc_fl_insert_range . .tp .b einval .i mode is .br falloc_fl_collapse_range or .br falloc_fl_zero_range or .br falloc_fl_insert_range , but the file referred to by .i fd is not a regular file. .\" there was an inconsistency in 3.15-rc1, that should be resolved so that all .\" filesystems use this error for this case. (tytso says ex4 will change.) .\" http://thread.gmane.org/gmane.comp.file-systems.xfs.general/60485/focus=5521 .\" from: michael kerrisk (man-pages .\" subject: re: [patch v5 10/10] manpage: update falloc_fl_collapse_range flag in fallocate .\" newsgroups: gmane.linux.man, gmane.linux.file-systems .\" date: 2014-04-17 13:40:05 gmt .tp .b eio an i/o error occurred while reading from or writing to a filesystem. .tp .b enodev .i fd does not refer to a regular file or a directory. (if .i fd is a pipe or fifo, a different error results.) .tp .b enospc there is not enough space left on the device containing the file referred to by .ir fd . .tp .b enosys this kernel does not implement .br fallocate (). .tp .b eopnotsupp the filesystem containing the file referred to by .i fd does not support this operation; or the .i mode is not supported by the filesystem containing the file referred to by .ir fd . .tp .b eperm the file referred to by .i fd is marked immutable (see .br chattr (1)). .tp .b eperm .i mode specifies .br falloc_fl_punch_hole or .br falloc_fl_collapse_range or .br falloc_fl_insert_range and the file referred to by .i fd is marked append-only (see .br chattr (1)). .tp .b eperm the operation was prevented by a file seal; see .br fcntl (2). .tp .b espipe .i fd refers to a pipe or fifo. .tp .b etxtbsy .i mode specifies .br falloc_fl_collapse_range or .br falloc_fl_insert_range , but the file referred to by .ir fd is currently being executed. .sh versions .br fallocate () is available on linux since kernel 2.6.23. support is provided by glibc since version 2.10. the .br falloc_fl_* flags are defined in glibc headers only since version 2.18. .\" see http://sourceware.org/bugzilla/show_bug.cgi?id=14964 .sh conforming to .br fallocate () is linux-specific. .sh see also .br fallocate (1), .br ftruncate (2), .br posix_fadvise (3), .br posix_fallocate (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" this replaces an earlier man page written by walter harms .\" . .\" .th qecvt 3 2021-03-22 "gnu" "linux programmer's manual" .sh name qecvt, qfcvt, qgcvt \- convert a floating-point number to a string .sh synopsis .nf .b #include .pp .bi "char *qecvt(long double " number ", int " ndigits \ ", int *restrict " decpt , .bi " int *restrict " sign ); .bi "char *qfcvt(long double " number ", int " ndigits \ ", int *restrict " decpt , .bi " int *restrict " sign ); .bi "char *qgcvt(long double " number ", int " ndigit ", char *" buf ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br qecvt (), .br qfcvt (), .br qgcvt (): .nf since glibc 2.19: _default_source in glibc up to and including 2.19: _svid_source .fi .\" fixme . the full ftm picture looks to have been something like the .\" following mess: .\" glibc 2.20 onward .\" _default_source .\" glibc 2.18 to glibc 2.19 .\" _bsd_source || _svid_source .\" glibc 2.10 to glibc 2.17 .\" _svid_source || (_xopen_source >= 500 || .\" (_xopen_source && _xopen_source_extended) && .\" ! (_posix_c_source >= 200809l)) .\" before glibc 2.10: .\" _svid_source || _xopen_source >= 500 || .\" (_xopen_source && _xopen_source_extended) .sh description the functions .br qecvt (), .br qfcvt (), and .br qgcvt () are identical to .br ecvt (3), .br fcvt (3), and .br gcvt (3) respectively, except that they use a .i "long double" argument .ir number . see .br ecvt (3) and .br gcvt (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br qecvt () t} thread safety mt-unsafe race:qecvt t{ .br qfcvt () t} thread safety mt-unsafe race:qfcvt t{ .br qgcvt () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4. not seen in most common unix implementations, but occurs in sunos. .\" not supported by libc4 and libc5. supported by glibc. .sh notes these functions are obsolete. instead, .br snprintf (3) is recommended. .sh see also .br ecvt (3), .br ecvt_r (3), .br gcvt (3), .br sprintf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright (c) 2014 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 17:51:15 1993 by rik faith (faith@cs.unc.edu) .\" modified 11 may 1998 by joseph s. myers (jsm28@cam.ac.uk) .\" modified 14 may 2001, 23 sep 2001 by aeb .\" 2004-12-20, mtk .\" .th system 3 2021-03-22 "" "linux programmer's manual" .sh name system \- execute a shell command .sh synopsis .nf .b #include .pp .bi "int system(const char *" "command" ); .fi .sh description the .br system () library function uses .br fork (2) to create a child process that executes the shell command specified in .i command using .br execl (3) as follows: .pp .in +4n .ex execl("/bin/sh", "sh", "\-c", command, (char *) null); .ee .in .pp .br system () returns after the command has been completed. .pp during execution of the command, .b sigchld will be blocked, and .b sigint and .b sigquit will be ignored, in the process that calls .br system (). (these signals will be handled according to their defaults inside the child process that executes .ir command .) .pp if .i command is null, then .br system () returns a status indicating whether a shell is available on the system. .sh return value the return value of .br system () is one of the following: .ip * 3 if .i command is null, then a nonzero value if a shell is available, or 0 if no shell is available. .ip * if a child process could not be created, or its status could not be retrieved, the return value is \-1 and .i errno is set to indicate the error. .ip * if a shell could not be executed in the child process, then the return value is as though the child shell terminated by calling .br _exit (2) with the status 127. .ip * if all system calls succeed, then the return value is the termination status of the child shell used to execute .ir command . (the termination status of a shell is the termination status of the last command it executes.) .pp in the last two cases, the return value is a "wait status" that can be examined using the macros described in .br waitpid (2). (i.e., .br wifexited (), .br wexitstatus (), and so on). .pp .br system () does not affect the wait status of any other children. .sh errors .br system () can fail with any of the same errors as .br fork (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br system () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. .sh notes .br system () provides simplicity and convenience: it handles all of the details of calling .br fork (2), .br execl (3), and .br waitpid (2), as well as the necessary manipulations of signals; in addition, the shell performs the usual substitutions and i/o redirections for .ir command . the main cost of .br system () is inefficiency: additional system calls are required to create the process that runs the shell and to execute the shell. .pp if the .b _xopen_source feature test macro is defined (before including .i any header files), then the macros described in .br waitpid (2) .rb ( wexitstatus (), etc.) are made available when including .ir . .pp as mentioned, .br system () ignores .b sigint and .br sigquit . this may make programs that call it from a loop uninterruptible, unless they take care themselves to check the exit status of the child. for example: .pp .in +4n .ex while (something) { int ret = system("foo"); if (wifsignaled(ret) && (wtermsig(ret) == sigint || wtermsig(ret) == sigquit)) break; } .ee .in .pp according to posix.1, it is unspecified whether handlers registered using .br pthread_atfork (3) are called during the execution of .br system (). in the glibc implementation, such handlers are not called. .pp in versions of glibc before 2.1.3, the check for the availability of .i /bin/sh was not actually performed if .i command was null; instead it was always assumed to be available, and .br system () always returned 1 in this case. since glibc 2.1.3, this check is performed because, even though posix.1-2001 requires a conforming implementation to provide a shell, that shell may not be available or executable if the calling program has previously called .br chroot (2) (which is not specified by posix.1-2001). .pp it is possible for the shell command to terminate with a status of 127, which yields a .br system () return value that is indistinguishable from the case where a shell could not be executed in the child process. .\" .ss caveats do not use .br system () from a privileged program (a set-user-id or set-group-id program, or a program with capabilities) because strange values for some environment variables might be used to subvert system integrity. for example, .br path could be manipulated so that an arbitrary program is executed with privilege. use the .br exec (3) family of functions instead, but not .br execlp (3) or .br execvp (3) (which also use the .b path environment variable to search for an executable). .pp .br system () will not, in fact, work properly from programs with set-user-id or set-group-id privileges on systems on which .i /bin/sh is bash version 2: as a security measure, bash 2 drops privileges on startup. (debian uses a different shell, .br dash (1), which does not do this when invoked as .br sh .) .pp any user input that is employed as part of .i command should be .i carefully sanitized, to ensure that unexpected shell commands or command options are not executed. such risks are especially grave when using .br system () from a privileged program. .sh bugs .\" [bug 211029](https://bugzilla.kernel.org/show_bug.cgi?id=211029) .\" [glibc bug](https://sourceware.org/bugzilla/show_bug.cgi?id=27143) .\" [posix bug](https://www.austingroupbugs.net/view.php?id=1440) if the command name starts with a hyphen, .br sh (1) interprets the command name as an option, and the behavior is undefined. (see the .b \-c option to .br sh (1).) to work around this problem, prepend the command with a space as in the following call: .pp .in +4n .ex system(" \-unfortunate\-command\-name"); .ee .in .sh see also .br sh (1), .br execve (2), .br fork (2), .br sigaction (2), .br sigprocmask (2), .br wait (2), .br exec (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 davide libenzi .\" davide libenzi .\" and copyright 2009, 2014, 2016, 2018, 2019 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th epoll_ctl 2 2021-03-22 "linux" "linux programmer's manual" .sh name epoll_ctl \- control interface for an epoll file descriptor .sh synopsis .nf .b #include .pp .bi "int epoll_ctl(int " epfd ", int " op ", int " fd \ ", struct epoll_event *" event ); .fi .sh description this system call is used to add, modify, or remove entries in the interest list of the .br epoll (7) instance referred to by the file descriptor .ir epfd . it requests that the operation .i op be performed for the target file descriptor, .ir fd . .pp valid values for the .i op argument are: .tp .b epoll_ctl_add add an entry to the interest list of the epoll file descriptor, .ir epfd . the entry includes the file descriptor, .ir fd , a reference to the corresponding open file description (see .br epoll (7) and .br open (2)), and the settings specified in .ir event . .tp .b epoll_ctl_mod change the settings associated with .ir fd in the interest list to the new settings specified in .ir event . .tp .b epoll_ctl_del remove (deregister) the target file descriptor .i fd from the interest list. the .i event argument is ignored and can be null (but see bugs below). .pp the .i event argument describes the object linked to the file descriptor .ir fd . the .i struct epoll_event is defined as: .pp .in +4n .ex typedef union epoll_data { void *ptr; int fd; uint32_t u32; uint64_t u64; } epoll_data_t; struct epoll_event { uint32_t events; /* epoll events */ epoll_data_t data; /* user data variable */ }; .ee .in .pp the .i data member of the .i epoll_event structure specifies data that the kernel should save and then return (via .br epoll_wait (2)) when this file descriptor becomes ready. .pp the .i events member of the .i epoll_event structure is a bit mask composed by oring together zero or more of the following available event types: .tp .b epollin the associated file is available for .br read (2) operations. .tp .b epollout the associated file is available for .br write (2) operations. .tp .br epollrdhup " (since linux 2.6.17)" stream socket peer closed connection, or shut down writing half of connection. (this flag is especially useful for writing simple code to detect peer shutdown when using edge-triggered monitoring.) .tp .b epollpri there is an exceptional condition on the file descriptor. see the discussion of .b pollpri in .br poll (2). .tp .b epollerr error condition happened on the associated file descriptor. this event is also reported for the write end of a pipe when the read end has been closed. .ip .br epoll_wait (2) will always report for this event; it is not necessary to set it in .ir events when calling .br epoll_ctl (). .tp .b epollhup hang up happened on the associated file descriptor. .ip .br epoll_wait (2) will always wait for this event; it is not necessary to set it in .ir events when calling .br epoll_ctl (). .ip note that when reading from a channel such as a pipe or a stream socket, this event merely indicates that the peer closed its end of the channel. subsequent reads from the channel will return 0 (end of file) only after all outstanding data in the channel has been consumed. .tp .b epollet requests edge-triggered notification for the associated file descriptor. the default behavior for .b epoll is level-triggered. see .br epoll (7) for more detailed information about edge-triggered and level-triggered notification. .ip this flag is an input flag for the .i event.events field when calling .br epoll_ctl (); it is never returned by .br epoll_wait (2). .tp .br epolloneshot " (since linux 2.6.2)" requests one-shot notification for the associated file descriptor. this means that after an event notified for the file descriptor by .br epoll_wait (2), the file descriptor is disabled in the interest list and no other events will be reported by the .b epoll interface. the user must call .br epoll_ctl () with .b epoll_ctl_mod to rearm the file descriptor with a new event mask. .ip this flag is an input flag for the .i event.events field when calling .br epoll_ctl (); it is never returned by .br epoll_wait (2). .tp .br epollwakeup " (since linux 3.5)" .\" commit 4d7e30d98939a0340022ccd49325a3d70f7e0238 if .b epolloneshot and .b epollet are clear and the process has the .b cap_block_suspend capability, ensure that the system does not enter "suspend" or "hibernate" while this event is pending or being processed. the event is considered as being "processed" from the time when it is returned by a call to .br epoll_wait (2) until the next call to .br epoll_wait (2) on the same .br epoll (7) file descriptor, the closure of that file descriptor, the removal of the event file descriptor with .br epoll_ctl_del , or the clearing of .b epollwakeup for the event file descriptor with .br epoll_ctl_mod . see also bugs. .ip this flag is an input flag for the .i event.events field when calling .br epoll_ctl (); it is never returned by .br epoll_wait (2). .tp .br epollexclusive " (since linux 4.5)" sets an exclusive wakeup mode for the epoll file descriptor that is being attached to the target file descriptor, .ir fd . when a wakeup event occurs and multiple epoll file descriptors are attached to the same target file using .br epollexclusive , one or more of the epoll file descriptors will receive an event with .br epoll_wait (2). the default in this scenario (when .br epollexclusive is not set) is for all epoll file descriptors to receive an event. .br epollexclusive is thus useful for avoiding thundering herd problems in certain scenarios. .ip if the same file descriptor is in multiple epoll instances, some with the .br epollexclusive flag, and others without, then events will be provided to all epoll instances that did not specify .br epollexclusive , and at least one of the epoll instances that did specify .br epollexclusive . .ip the following values may be specified in conjunction with .br epollexclusive : .br epollin , .br epollout , .br epollwakeup , and .br epollet . .br epollhup and .br epollerr can also be specified, but this is not required: as usual, these events are always reported if they occur, regardless of whether they are specified in .ir events . attempts to specify other values in .i events yield the error .br einval . .ip .b epollexclusive may be used only in an .b epoll_ctl_add operation; attempts to employ it with .b epoll_ctl_mod yield an error. if .b epollexclusive has been set using .br epoll_ctl (), then a subsequent .b epoll_ctl_mod on the same .ir epfd ",\ " fd pair yields an error. a call to .br epoll_ctl () that specifies .b epollexclusive in .i events and specifies the target file descriptor .i fd as an epoll instance will likewise fail. the error in all of these cases is .br einval . .ip the .br epollexclusive flag is an input flag for the .i event.events field when calling .br epoll_ctl (); it is never returned by .br epoll_wait (2). .sh return value when successful, .br epoll_ctl () returns zero. when an error occurs, .br epoll_ctl () returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i epfd or .i fd is not a valid file descriptor. .tp .b eexist .i op was .br epoll_ctl_add , and the supplied file descriptor .i fd is already registered with this epoll instance. .tp .b einval .i epfd is not an .b epoll file descriptor, or .i fd is the same as .ir epfd , or the requested operation .i op is not supported by this interface. .tp .b einval an invalid event type was specified along with .b epollexclusive in .ir events . .tp .b einval .i op was .b epoll_ctl_mod and .ir events included .br epollexclusive . .tp .b einval .i op was .b epoll_ctl_mod and the .br epollexclusive flag has previously been applied to this .ir epfd ",\ " fd pair. .tp .b einval .br epollexclusive was specified in .ir event and .i fd refers to an epoll instance. .tp .b eloop .i fd refers to an epoll instance and this .b epoll_ctl_add operation would result in a circular loop of epoll instances monitoring one another or a nesting depth of epoll instances greater than 5. .tp .b enoent .i op was .b epoll_ctl_mod or .br epoll_ctl_del , and .i fd is not registered with this epoll instance. .tp .b enomem there was insufficient memory to handle the requested .i op control operation. .tp .b enospc the limit imposed by .i /proc/sys/fs/epoll/max_user_watches was encountered while trying to register .rb ( epoll_ctl_add ) a new file descriptor on an epoll instance. see .br epoll (7) for further details. .tp .b eperm the target file .i fd does not support .br epoll . this error can occur if .i fd refers to, for example, a regular file or a directory. .sh versions .br epoll_ctl () was added to the kernel in version 2.6. .\" to be precise: kernel 2.5.44. .\" the interface should be finalized by linux kernel 2.5.66. library support is provided in glibc starting with version 2.3.2. .sh conforming to .br epoll_ctl () is linux-specific. .sh notes the .b epoll interface supports all file descriptors that support .br poll (2). .sh bugs in kernel versions before 2.6.9, the .b epoll_ctl_del operation required a non-null pointer in .ir event , even though this argument is ignored. since linux 2.6.9, .i event can be specified as null when using .br epoll_ctl_del . applications that need to be portable to kernels before 2.6.9 should specify a non-null pointer in .ir event . .pp if .b epollwakeup is specified in .ir flags , but the caller does not have the .br cap_block_suspend capability, then the .b epollwakeup flag is .ir "silently ignored" . this unfortunate behavior is necessary because no validity checks were performed on the .ir flags argument in the original implementation, and the addition of the .b epollwakeup with a check that caused the call to fail if the caller did not have the .b cap_block_suspend capability caused a breakage in at least one existing user-space application that happened to randomly (and uselessly) specify this bit. .\" commit a8159414d7e3af7233e7a5a82d1c5d85379bd75c (behavior change) .\" https://lwn.net/articles/520198/ a robust application should therefore double check that it has the .b cap_block_suspend capability if attempting to use the .b epollwakeup flag. .sh see also .br epoll_create (2), .br epoll_wait (2), .br poll (2), .br epoll (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/csin.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-03-29, david metcalfe .\" modified 1993-07-24, rik faith (faith@cs.unc.edu) .\" modified 2003-10-25, walter harms .\" .th atexit 3 2021-03-22 "linux" "linux programmer's manual" .sh name atexit \- register a function to be called at normal process termination .sh synopsis .nf .b #include .pp .bi "int atexit(void (*" function )(void)); .fi .sh description the .br atexit () function registers the given .i function to be called at normal process termination, either via .br exit (3) or via return from the program's .ir main (). functions so registered are called in the reverse order of their registration; no arguments are passed. .pp the same function may be registered multiple times: it is called once for each registration. .pp posix.1 requires that an implementation allow at least .\" posix.1-2001, posix.1-2008 .b atexit_max (32) such functions to be registered. the actual limit supported by an implementation can be obtained using .br sysconf (3). .pp when a child process is created via .br fork (2), it inherits copies of its parent's registrations. upon a successful call to one of the .br exec (3) functions, all registrations are removed. .sh return value the .br atexit () function returns the value 0 if successful; otherwise it returns a nonzero value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br atexit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes functions registered using .br atexit () (and .br on_exit (3)) are not called if a process terminates abnormally because of the delivery of a signal. .pp if one of the registered functions calls .br _exit (2), then any remaining functions are not invoked, and the other process termination steps performed by .br exit (3) are not performed. .pp posix.1 says that the result of calling .\" posix.1-2001, posix.1-2008 .br exit (3) more than once (i.e., calling .br exit (3) within a function registered using .br atexit ()) is undefined. on some systems (but not linux), this can result in an infinite recursion; .\" this can happen on openbsd 4.2 for example, and is documented .\" as occurring on freebsd as well. .\" glibc does "the right thing" -- invocation of the remaining .\" exit handlers carries on as normal. portable programs should not invoke .br exit (3) inside a function registered using .br atexit (). .pp the .br atexit () and .br on_exit (3) functions register functions on the same list: at normal process termination, the registered functions are invoked in reverse order of their registration by these two functions. .pp according to posix.1, the result is undefined if .br longjmp (3) is used to terminate execution of one of the functions registered using .br atexit (). .\" in glibc, things seem to be handled okay .ss linux notes since glibc 2.2.3, .br atexit () (and .br on_exit (3)) can be used within a shared library to establish functions that are called when the shared library is unloaded. .sh examples .ex #include #include #include void bye(void) { printf("that was all, folks\en"); } int main(void) { long a; int i; a = sysconf(_sc_atexit_max); printf("atexit_max = %ld\en", a); i = atexit(bye); if (i != 0) { fprintf(stderr, "cannot set exit function\en"); exit(exit_failure); } exit(exit_success); } .ee .sh see also .br _exit (2), .br dlopen (3), .br exit (3), .br on_exit (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th tanh 3 2021-03-22 "" "linux programmer's manual" .sh name tanh, tanhf, tanhl \- hyperbolic tangent function .sh synopsis .nf .b #include .pp .bi "double tanh(double " x ); .bi "float tanhf(float " x ); .bi "long double tanhl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br tanhf (), .br tanhl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the hyperbolic tangent of .ir x , which is defined mathematically as: .pp .nf tanh(x) = sinh(x) / cosh(x) .fi .sh return value on success, these functions return the hyperbolic tangent of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is positive infinity (negative infinity), +1 (\-1) is returned. .\" .\" posix.1-2001 documents an optional range error (underflow) .\" for subnormal x; .\" glibc 2.8 does not do this. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tanh (), .br tanhf (), .br tanhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br acosh (3), .br asinh (3), .br atanh (3), .br cosh (3), .br ctanh (3), .br sinh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. #!/bin/sh # # find_dot_no_parens.sh # # look for function names after /^.[bir]/ that aren't # followed by "()". # # this script is designed to help with "by hand" tidy-ups after # the automated changes made by add_parens_for_own_funcs.sh. # # the first argument to this script names a manual page directory where # 'man2' and 'man3' subdirectories can be found. the pages names in # these directories are used to generate a series of regular expressions # that can be used to search the manual page files that are named in # the remaining command-line arguments. # # example usage: # # cd man-pages-x.yy # sh find_dots_no_parens.sh . man?/*.? > matches.log # ###################################################################### # # (c) copyright 2005 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # if test $# -lt 2; then echo "usage: $0 man-page-root-dir file file..." 1>&2 exit 1 fi dir=$1 if ! test -d $dir/man2 || ! test -d $dir/man3; then echo "can't find man2 and man3 under $dir" 1>&2 exit 1 fi shift 1 echo "this will take probably a few moments..." 1>&2 awk_script_file=tmp.$0.awk rm -f $awk_script_file # we grep out a few page names that are likely to generate false # positives... echo '{' >> $awk_script_file echo ' myvar = $2;' >> $awk_script_file echo ' gsub("[^a-z_0-9]*$", "", myvar);' >> $awk_script_file echo ' if ( myvar == "nomatchesforthis" || ' >> $awk_script_file for page in $( find $dir/man2/* $dir/man3/* -type f -name '*.[23]' | egrep -v '/(stderr|stdin|stdout|errno|termios|string)\..$'); do base=$(basename $page | sed -e 's/\.[23]$//') echo " myvar == \"$base\" ||" >> $awk_script_file done echo ' myvar == "nomatchesforthis" )' >> $awk_script_file echo ' print $0' >> $awk_script_file echo '}' >> $awk_script_file grep '^\.[bri][bri]* [a-za-z0-9_][a-za-z0-9_]*[^a-za-z_]*$' $* | awk -f $awk_script_file | grep -v '([0-9]*)' rm -f $awk_script_file exit 0 .so man3/rpc.3 .so man2/rt_sigqueueinfo.2 .\" copyright (c) 1997 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2005, 2010, 2014, 2015, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, 2003-05-26, michael kerrisk, .th setresuid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setresuid, setresgid \- set real, effective, and saved user or group id .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int setresuid(uid_t " ruid ", uid_t " euid ", uid_t " suid ); .bi "int setresgid(gid_t " rgid ", gid_t " egid ", gid_t " sgid ); .fi .sh description .br setresuid () sets the real user id, the effective user id, and the saved set-user-id of the calling process. .pp an unprivileged process may change its real uid, effective uid, and saved set-user-id, each to one of: the current real uid, the current effective uid, or the current saved set-user-id. .pp a privileged process (on linux, one having the \fbcap_setuid\fp capability) may set its real uid, effective uid, and saved set-user-id to arbitrary values. .pp if one of the arguments equals \-1, the corresponding value is not changed. .pp regardless of what changes are made to the real uid, effective uid, and saved set-user-id, the filesystem uid is always set to the same value as the (possibly new) effective uid. .pp completely analogously, .br setresgid () sets the real gid, effective gid, and saved set-group-id of the calling process (and always modifies the filesystem gid to be the same as the effective gid), with the same restrictions for unprivileged processes. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .pp .ir note : there are cases where .br setresuid () can fail even when the caller is uid 0; it is a grave security error to omit checking for a failure return from .br setresuid (). .sh errors .tp .b eagain the call would change the caller's real uid (i.e., .i ruid does not match the caller's real uid), but there was a temporary failure allocating the necessary kernel data structures. .tp .b eagain .i ruid does not match the caller's real uid and this call would bring the number of processes belonging to the real user id .i ruid over the caller's .b rlimit_nproc resource limit. since linux 3.1, this error case no longer occurs (but robust applications should check for this error); see the description of .b eagain in .br execve (2). .tp .b einval one or more of the target user or group ids is not valid in this user namespace. .tp .b eperm the calling process is not privileged (did not have the necessary capability in its user namespace) and tried to change the ids to values that are not permitted. for .br setresuid (), the necessary capability is .br cap_setuid ; for .br setresgid (), it is .br cap_setgid . .sh versions these calls are available under linux since linux 2.1.44. .sh conforming to these calls are nonstandard; they also appear on hp-ux and some of the bsds. .sh notes under hp-ux and freebsd, the prototype is found in .ir . under linux, the prototype is provided by glibc since version 2.3.2. .pp the original linux .br setresuid () and .br setresgid () system calls supported only 16-bit user and group ids. subsequently, linux 2.4 added .br setresuid32 () and .br setresgid32 (), supporting 32-bit ids. the glibc .br setresuid () and .br setresgid () wrapper functions transparently deal with the variations across kernel versions. .\" .ss c library/kernel differences at the kernel level, user ids and group ids are a per-thread attribute. however, posix requires that all threads in a process share the same credentials. the nptl threading implementation handles the posix requirements by providing wrapper functions for the various system calls that change process uids and gids. these wrapper functions (including those for .br setresuid () and .br setresgid ()) employ a signal-based technique to ensure that when one thread changes credentials, all of the other threads in the process also change their credentials. for details, see .br nptl (7). .sh see also .br getresuid (2), .br getuid (2), .br setfsgid (2), .br setfsuid (2), .br setreuid (2), .br setuid (2), .br capabilities (7), .br credentials (7), .br user_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/drand48.3 .so man3/argz_add.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" tue jul 6 12:42:46 mdt 1993 .\" added "calling directly" and supporting paragraphs .\" .\" modified sat jul 24 15:19:12 1993 by rik faith .\" .\" modified 21 aug 1994 by michael chastain : .\" added explanation of arg stacking when 6 or more args. .\" .\" modified 10 june 1995 by andries brouwer .\" .\" 2007-10-23 mtk: created as a new page, by taking the content .\" specific to the _syscall() macros from intro(2). .\" .th _syscall 2 2021-03-22 "linux" "linux programmer's manual" .sh name _syscall \- invoking a system call without library support (obsolete) .sh synopsis .nf .b #include .pp a _syscall macro .pp desired system call .fi .sh description the important thing to know about a system call is its prototype. you need to know how many arguments, their types, and the function return type. there are seven macros that make the actual call into the system easier. they have the form: .pp .in +4n .ex .ri _syscall x ( type , name , type1 , arg1 , type2 , arg2 ,...) .ee .in .pp where .ip .i x is 0\(en6, which are the number of arguments taken by the system call .ip .i type is the return type of the system call .ip .i name is the name of the system call .ip .i typen is the nth argument's type .ip .i argn is the name of the nth argument .pp these macros create a function called .i name with the arguments you specify. once you include the _syscall() in your source file, you call the system call by .ir name . .sh files .i /usr/include/linux/unistd.h .sh conforming to the use of these macros is linux-specific, and deprecated. .sh notes starting around kernel 2.6.18, the _syscall macros were removed from header files supplied to user space. use .br syscall (2) instead. (some architectures, notably ia64, never provided the _syscall macros; on those architectures, .br syscall (2) was always required.) .pp the _syscall() macros .i "do not" produce a prototype. you may have to create one, especially for c++ users. .pp system calls are not required to return only positive or negative error codes. you need to read the source to be sure how it will return errors. usually, it is the negative of a standard error code, for example, .ri \- eperm . the _syscall() macros will return the result .i r of the system call when .i r is nonnegative, but will return \-1 and set the variable .i errno to .ri \- r when .i r is negative. for the error codes, see .br errno (3). .pp when defining a system call, the argument types .i must be passed by-value or by-pointer (for aggregates like structs). .\" the preferred way to invoke system calls that glibc does not know .\" about yet is via .\" .br syscall (2). .\" however, this mechanism can be used only if using a libc .\" (such as glibc) that supports .\" .br syscall (2), .\" and if the .\" .i .\" header file contains the required sys_foo definition. .\" otherwise, the use of a _syscall macro is required. .\" .sh examples .ex #include #include #include #include /* for _syscallx macros/related stuff */ #include /* for struct sysinfo */ _syscall1(int, sysinfo, struct sysinfo *, info); int main(void) { struct sysinfo s_info; int error; error = sysinfo(&s_info); printf("code error = %d\en", error); printf("uptime = %lds\enload: 1 min %lu / 5 min %lu / 15 min %lu\en" "ram: total %lu / free %lu / shared %lu\en" "memory in buffers = %lu\enswap: total %lu / free %lu\en" "number of processes = %d\en", s_info.uptime, s_info.loads[0], s_info.loads[1], s_info.loads[2], s_info.totalram, s_info.freeram, s_info.sharedram, s_info.bufferram, s_info.totalswap, s_info.freeswap, s_info.procs); exit(exit_success); } .ee .ss sample output .ex code error = 0 uptime = 502034s load: 1 min 13376 / 5 min 5504 / 15 min 1152 ram: total 15343616 / free 827392 / shared 8237056 memory in buffers = 5066752 swap: total 27881472 / free 24698880 number of processes = 40 .ee .sh see also .br intro (2), .br syscall (2), .br errno (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcpcpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcpcpy \- copy a wide-character string, returning a pointer to its end .sh synopsis .nf .b #include .pp .bi "wchar_t *wcpcpy(wchar_t *restrict " dest \ ", const wchar_t *restrict " src ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcpcpy (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcpcpy () function is the wide-character equivalent of the .br stpcpy (3) function. it copies the wide-character string pointed to by .ir src , including the terminating null wide character (l\(aq\e0\(aq), to the array pointed to by .ir dest . .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .ir wcslen(src)+1 wide characters at .ir dest . .sh return value .br wcpcpy () returns a pointer to the end of the wide-character string .ir dest , that is, a pointer to the terminating null wide character. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcpcpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. .sh see also .br strcpy (3), .br wcscpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getmntent.3 .so man3/getutmp.3 .so man3/login.3 .\" copyright 1995 michael chastain (mec@shell.portal.com), 15 april 1995. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" updated, aeb, 980612 .\" .th unimplemented 2 2021-03-22 "linux" "linux programmer's manual" .sh name afs_syscall, break, fattach, fdetach, ftime, getmsg, getpmsg, gtty, isastream, lock, madvise1, mpx, prof, profil, putmsg, putpmsg, security, stty, tuxcall, ulimit, vserver \- unimplemented system calls .sh synopsis .nf unimplemented system calls. .fi .sh description these system calls are not implemented in the linux kernel. .sh return value these system calls always return \-1 and set .i errno to .br enosys . .sh notes note that .br ftime (3), .br profil (3), and .br ulimit (3) are implemented as library functions. .pp some system calls, like .br alloc_hugepages (2), .br free_hugepages (2), .br ioperm (2), .br iopl (2), and .br vm86 (2) exist only on certain architectures. .pp some system calls, like .br ipc (2), .br create_module (2), .br init_module (2), and .br delete_module (2) exist only when the linux kernel was built with support for them. .sh see also .br syscalls (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/syslog.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" and copyright (c) 2021 michael kerrisk .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" converted for linux, mon nov 29 14:24:40 1993, faith@cs.unc.edu .\" added remark on ebadf for fileno, aeb, 2001-03-22 .\" .th fileno 3 2021-03-22 "" "linux programmer's manual" .sh name fileno \- obtain file descriptor of a stdio stream .sh synopsis .nf .b #include .pp .bi "int fileno(file *" stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fileno (): .nf _posix_c_source .fi .sh description .pp the function .br fileno () examines the argument .i stream and returns the integer file descriptor used to implement this stream. the file descriptor is still owned by .i stream and will be closed when .br fclose (3) is called. duplicate the file descriptor with .br dup (2) before passing it to code that might close it. .pp for the nonlocking counterpart, see .br unlocked_stdio (3). .sh return value on success, .br fileno () returns the file descriptor associated with .ir stream . on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i stream is not associated with a file. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fileno () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the function .br fileno () conforms to posix.1-2001 and posix.1-2008. .sh see also .br open (2), .br fdopen (3), .br stdio (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/argz_add.3 .so man3/termios.3 .so man3/setaliasent.3 .so man3/getopt.3 .so man3/getspnam.3 .\" copyright (c) 2007, 2008 michael kerrisk .\" and copyright (c) 2006 ulrich drepper .\" a few pieces of an earlier version remain: .\" copyright 2000, sam varshavchik .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references: rfc 2553 .\" .\" 2005-08-09, mtk, added ai_all, ai_addrconfig, ai_v4mapped, .\" and ai_numericserv. .\" 2006-11-25, ulrich drepper .\" add text describing internationalized domain name extensions. .\" 2007-06-08, mtk: added example programs .\" 2008-02-26, mtk; clarify discussion of null 'hints' argument; other .\" minor rewrites. .\" 2008-06-18, mtk: many parts rewritten .\" 2008-12-04, petr baudis .\" describe results ordering and reference /etc/gai.conf. .\" .\" fixme . glibc's 2.9 news file documents dccp and udp-lite support .\" and is sctp support now also there? .\" .th getaddrinfo 3 2021-08-27 "gnu" "linux programmer's manual" .sh name getaddrinfo, freeaddrinfo, gai_strerror \- network address and service translation .sh synopsis .nf .b #include .b #include .b #include .pp .bi "int getaddrinfo(const char *restrict " node , .bi " const char *restrict " service , .bi " const struct addrinfo *restrict " hints , .bi " struct addrinfo **restrict " res ); .pp .bi "void freeaddrinfo(struct addrinfo *" res ); .pp .bi "const char *gai_strerror(int " errcode ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getaddrinfo (), .br freeaddrinfo (), .br gai_strerror (): .nf since glibc 2.22: _posix_c_source >= 200112l glibc 2.21 and earlier: _posix_c_source .fi .sh description given .i node and .ir service , which identify an internet host and a service, .br getaddrinfo () returns one or more .i addrinfo structures, each of which contains an internet address that can be specified in a call to .br bind (2) or .br connect (2). the .br getaddrinfo () function combines the functionality provided by the .\" .br getipnodebyname (3), .\" .br getipnodebyaddr (3), .br gethostbyname (3) and .br getservbyname (3) functions into a single interface, but unlike the latter functions, .br getaddrinfo () is reentrant and allows programs to eliminate ipv4-versus-ipv6 dependencies. .pp the .i addrinfo structure used by .br getaddrinfo () contains the following fields: .pp .in +4n .ex struct addrinfo { int ai_flags; int ai_family; int ai_socktype; int ai_protocol; socklen_t ai_addrlen; struct sockaddr *ai_addr; char *ai_canonname; struct addrinfo *ai_next; }; .ee .in .pp the .i hints argument points to an .i addrinfo structure that specifies criteria for selecting the socket address structures returned in the list pointed to by .ir res . if .i hints is not null it points to an .i addrinfo structure whose .ir ai_family , .ir ai_socktype , and .i ai_protocol specify criteria that limit the set of socket addresses returned by .br getaddrinfo (), as follows: .tp .i ai_family this field specifies the desired address family for the returned addresses. valid values for this field include .br af_inet and .br af_inet6 . the value .b af_unspec indicates that .br getaddrinfo () should return socket addresses for any address family (either ipv4 or ipv6, for example) that can be used with .i node and .ir service . .tp .i ai_socktype this field specifies the preferred socket type, for example .br sock_stream or .br sock_dgram . specifying 0 in this field indicates that socket addresses of any type can be returned by .br getaddrinfo (). .tp .i ai_protocol this field specifies the protocol for the returned socket addresses. specifying 0 in this field indicates that socket addresses with any protocol can be returned by .br getaddrinfo (). .tp .i ai_flags this field specifies additional options, described below. multiple flags are specified by bitwise or-ing them together. .pp all the other fields in the structure pointed to by .i hints must contain either 0 or a null pointer, as appropriate. .pp specifying .i hints as null is equivalent to setting .i ai_socktype and .i ai_protocol to 0; .i ai_family to .br af_unspec ; and .i ai_flags to .br "(ai_v4mapped\ |\ ai_addrconfig)" . (posix specifies different defaults for .ir ai_flags ; see notes.) .i node specifies either a numerical network address (for ipv4, numbers-and-dots notation as supported by .br inet_aton (3); for ipv6, hexadecimal string format as supported by .br inet_pton (3)), or a network hostname, whose network addresses are looked up and resolved. if .i hints.ai_flags contains the .b ai_numerichost flag, then .i node must be a numerical network address. the .b ai_numerichost flag suppresses any potentially lengthy network host address lookups. .pp if the .b ai_passive flag is specified in .ir hints.ai_flags , and .i node is null, then the returned socket addresses will be suitable for .br bind (2)ing a socket that will .br accept (2) connections. the returned socket address will contain the "wildcard address" .rb ( inaddr_any for ipv4 addresses, .br in6addr_any_init for ipv6 address). the wildcard address is used by applications (typically servers) that intend to accept connections on any of the host's network addresses. if .i node is not null, then the .b ai_passive flag is ignored. .pp if the .b ai_passive flag is not set in .ir hints.ai_flags , then the returned socket addresses will be suitable for use with .br connect (2), .br sendto (2), or .br sendmsg (2). if .i node is null, then the network address will be set to the loopback interface address .rb ( inaddr_loopback for ipv4 addresses, .br in6addr_loopback_init for ipv6 address); this is used by applications that intend to communicate with peers running on the same host. .pp .i service sets the port in each returned address structure. if this argument is a service name (see .br services (5)), it is translated to the corresponding port number. this argument can also be specified as a decimal number, which is simply converted to binary. if .i service is null, then the port number of the returned socket addresses will be left uninitialized. if .b ai_numericserv is specified in .i hints.ai_flags and .i service is not null, then .i service must point to a string containing a numeric port number. this flag is used to inhibit the invocation of a name resolution service in cases where it is known not to be required. .pp either .i node or .ir service , but not both, may be null. .pp the .br getaddrinfo () function allocates and initializes a linked list of .i addrinfo structures, one for each network address that matches .i node and .ir service , subject to any restrictions imposed by .ir hints , and returns a pointer to the start of the list in .ir res . the items in the linked list are linked by the .i ai_next field. .pp there are several reasons why the linked list may have more than one .i addrinfo structure, including: the network host is multihomed, accessible over multiple protocols (e.g., both .br af_inet and .br af_inet6 ); or the same service is available from multiple socket types (one .b sock_stream address and another .b sock_dgram address, for example). normally, the application should try using the addresses in the order in which they are returned. the sorting function used within .br getaddrinfo () is defined in rfc\ 3484; the order can be tweaked for a particular system by editing .ir /etc/gai.conf (available since glibc 2.5). .pp if .i hints.ai_flags includes the .b ai_canonname flag, then the .i ai_canonname field of the first of the .i addrinfo structures in the returned list is set to point to the official name of the host. .\" in glibc prior to 2.3.4, the ai_canonname of each addrinfo .\" structure was set pointing to the canonical name; that was .\" more than posix.1-2001 specified, or other implementations provided. .\" mtk, aug 05 .pp the remaining fields of each returned .i addrinfo structure are initialized as follows: .ip * 2 the .ir ai_family , .ir ai_socktype , and .i ai_protocol fields return the socket creation parameters (i.e., these fields have the same meaning as the corresponding arguments of .br socket (2)). for example, .i ai_family might return .b af_inet or .br af_inet6 ; .i ai_socktype might return .b sock_dgram or .br sock_stream ; and .i ai_protocol returns the protocol for the socket. .ip * a pointer to the socket address is placed in the .i ai_addr field, and the length of the socket address, in bytes, is placed in the .i ai_addrlen field. .pp if .i hints.ai_flags includes the .b ai_addrconfig flag, then ipv4 addresses are returned in the list pointed to by .i res only if the local system has at least one ipv4 address configured, and ipv6 addresses are returned only if the local system has at least one ipv6 address configured. the loopback address is not considered for this case as valid as a configured address. this flag is useful on, for example, ipv4-only systems, to ensure that .br getaddrinfo () does not return ipv6 socket addresses that would always fail in .br connect (2) or .br bind (2). .pp if .i hints.ai_flags specifies the .b ai_v4mapped flag, and .i hints.ai_family was specified as .br af_inet6 , and no matching ipv6 addresses could be found, then return ipv4-mapped ipv6 addresses in the list pointed to by .ir res . if both .b ai_v4mapped and .b ai_all are specified in .ir hints.ai_flags , then return both ipv6 and ipv4-mapped ipv6 addresses in the list pointed to by .ir res . .b ai_all is ignored if .b ai_v4mapped is not also specified. .pp the .br freeaddrinfo () function frees the memory that was allocated for the dynamically allocated linked list .ir res . .ss extensions to getaddrinfo() for internationalized domain names starting with glibc 2.3.4, .br getaddrinfo () has been extended to selectively allow the incoming and outgoing hostnames to be transparently converted to and from the internationalized domain name (idn) format (see rfc 3490, .ir "internationalizing domain names in applications (idna)" ). four new flags are defined: .tp .b ai_idn if this flag is specified, then the node name given in .i node is converted to idn format if necessary. the source encoding is that of the current locale. .ip if the input name contains non-ascii characters, then the idn encoding is used. those parts of the node name (delimited by dots) that contain non-ascii characters are encoded using ascii compatible encoding (ace) before being passed to the name resolution functions. .\" implementation detail: .\" to minimize effects on system performance the implementation might .\" want to check whether the input string contains any non-ascii .\" characters. if there are none the idn step can be skipped completely. .\" on systems which allow not-ascii safe encodings for a locale this .\" might be a problem. .tp .b ai_canonidn after a successful name lookup, and if the .b ai_canonname flag was specified, .br getaddrinfo () will return the canonical name of the node corresponding to the .i addrinfo structure value passed back. the return value is an exact copy of the value returned by the name resolution function. .ip if the name is encoded using ace, then it will contain the .i xn\-\- prefix for one or more components of the name. to convert these components into a readable form the .b ai_canonidn flag can be passed in addition to .br ai_canonname . the resulting string is encoded using the current locale's encoding. .\" .\"implementation detail: .\"if no component of the returned name starts with xn\-\- the idn .\"step can be skipped, therefore avoiding unnecessary slowdowns. .tp .br ai_idn_allow_unassigned ", " ai_idn_use_std3_ascii_rules setting these flags will enable the idna_allow_unassigned (allow unassigned unicode code points) and idna_use_std3_ascii_rules (check output to make sure it is a std3 conforming hostname) flags respectively to be used in the idna handling. .sh return value .\" fixme glibc defines the following additional errors, some which .\" can probably be returned by getaddrinfo(); they need to .\" be documented. .\" #ifdef __use_gnu .\" #define eai_inprogress -100 /* processing request in progress. */ .\" #define eai_canceled -101 /* request canceled. */ .\" #define eai_notcanceled -102 /* request not canceled. */ .\" #define eai_alldone -103 /* all requests done. */ .\" #define eai_intr -104 /* interrupted by a signal. */ .\" #define eai_idn_encode -105 /* idn encoding failed. */ .\" #endif .br getaddrinfo () returns 0 if it succeeds, or one of the following nonzero error codes: .tp .b eai_addrfamily .\" not in susv3 the specified network host does not have any network addresses in the requested address family. .tp .b eai_again the name server returned a temporary failure indication. try again later. .tp .b eai_badflags .i hints.ai_flags contains invalid flags; or, .i hints.ai_flags included .b ai_canonname and .i name was null. .tp .b eai_fail the name server returned a permanent failure indication. .tp .b eai_family the requested address family is not supported. .tp .b eai_memory out of memory. .tp .b eai_nodata .\" not in susv3 the specified network host exists, but does not have any network addresses defined. .tp .b eai_noname the .i node or .i service is not known; or both .i node and .i service are null; or .b ai_numericserv was specified in .i hints.ai_flags and .i service was not a numeric port-number string. .tp .b eai_service the requested service is not available for the requested socket type. it may be available through another socket type. for example, this error could occur if .i service was "shell" (a service available only on stream sockets), and either .i hints.ai_protocol was .br ipproto_udp , or .i hints.ai_socktype was .br sock_dgram ; or the error could occur if .i service was not null, and .i hints.ai_socktype was .br sock_raw (a socket type that does not support the concept of services). .tp .b eai_socktype the requested socket type is not supported. this could occur, for example, if .i hints.ai_socktype and .i hints.ai_protocol are inconsistent (e.g., .br sock_dgram and .br ipproto_tcp , respectively). .tp .b eai_system other system error; .i errno is set to indicate the error. .pp the .br gai_strerror () function translates these error codes to a human readable string, suitable for error reporting. .sh files .i /etc/gai.conf .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getaddrinfo () t} thread safety mt-safe env locale t{ .br freeaddrinfo (), .br gai_strerror () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. the .br getaddrinfo () function is documented in rfc\ 2553. .sh notes .br getaddrinfo () supports the .ib address % scope-id notation for specifying the ipv6 scope-id. .pp .br ai_addrconfig , .br ai_all , and .b ai_v4mapped are available since glibc 2.3.3. .b ai_numericserv is available since glibc 2.3.4. .pp according to posix.1, specifying .\" posix.1-2001, posix.1-2008 .i hints as null should cause .i ai_flags to be assumed as 0. the gnu c library instead assumes a value of .br "(ai_v4mapped\ |\ ai_addrconfig)" for this case, since this value is considered an improvement on the specification. .sh examples .\" getnameinfo.3 refers to this example .\" socket.2 refers to this example .\" bind.2 refers to this example .\" connect.2 refers to this example .\" recvfrom.2 refers to this example .\" sendto.2 refers to this example the following programs demonstrate the use of .br getaddrinfo (), .br gai_strerror (), .br freeaddrinfo (), and .br getnameinfo (3). the programs are an echo server and client for udp datagrams. .ss server program \& .ex #include #include #include #include #include #include #include #define buf_size 500 int main(int argc, char *argv[]) { struct addrinfo hints; struct addrinfo *result, *rp; int sfd, s; struct sockaddr_storage peer_addr; socklen_t peer_addr_len; ssize_t nread; char buf[buf_size]; if (argc != 2) { fprintf(stderr, "usage: %s port\en", argv[0]); exit(exit_failure); } memset(&hints, 0, sizeof(hints)); hints.ai_family = af_unspec; /* allow ipv4 or ipv6 */ hints.ai_socktype = sock_dgram; /* datagram socket */ hints.ai_flags = ai_passive; /* for wildcard ip address */ hints.ai_protocol = 0; /* any protocol */ hints.ai_canonname = null; hints.ai_addr = null; hints.ai_next = null; s = getaddrinfo(null, argv[1], &hints, &result); if (s != 0) { fprintf(stderr, "getaddrinfo: %s\en", gai_strerror(s)); exit(exit_failure); } /* getaddrinfo() returns a list of address structures. try each address until we successfully bind(2). if socket(2) (or bind(2)) fails, we (close the socket and) try the next address. */ for (rp = result; rp != null; rp = rp\->ai_next) { sfd = socket(rp\->ai_family, rp\->ai_socktype, rp\->ai_protocol); if (sfd == \-1) continue; if (bind(sfd, rp\->ai_addr, rp\->ai_addrlen) == 0) break; /* success */ close(sfd); } freeaddrinfo(result); /* no longer needed */ if (rp == null) { /* no address succeeded */ fprintf(stderr, "could not bind\en"); exit(exit_failure); } /* read datagrams and echo them back to sender. */ for (;;) { peer_addr_len = sizeof(peer_addr); nread = recvfrom(sfd, buf, buf_size, 0, (struct sockaddr *) &peer_addr, &peer_addr_len); if (nread == \-1) continue; /* ignore failed request */ char host[ni_maxhost], service[ni_maxserv]; s = getnameinfo((struct sockaddr *) &peer_addr, peer_addr_len, host, ni_maxhost, service, ni_maxserv, ni_numericserv); if (s == 0) printf("received %zd bytes from %s:%s\en", nread, host, service); else fprintf(stderr, "getnameinfo: %s\en", gai_strerror(s)); if (sendto(sfd, buf, nread, 0, (struct sockaddr *) &peer_addr, peer_addr_len) != nread) fprintf(stderr, "error sending response\en"); } } .ee .ss client program \& .ex #include #include #include #include #include #include #include #define buf_size 500 int main(int argc, char *argv[]) { struct addrinfo hints; struct addrinfo *result, *rp; int sfd, s; size_t len; ssize_t nread; char buf[buf_size]; if (argc < 3) { fprintf(stderr, "usage: %s host port msg...\en", argv[0]); exit(exit_failure); } /* obtain address(es) matching host/port. */ memset(&hints, 0, sizeof(hints)); hints.ai_family = af_unspec; /* allow ipv4 or ipv6 */ hints.ai_socktype = sock_dgram; /* datagram socket */ hints.ai_flags = 0; hints.ai_protocol = 0; /* any protocol */ s = getaddrinfo(argv[1], argv[2], &hints, &result); if (s != 0) { fprintf(stderr, "getaddrinfo: %s\en", gai_strerror(s)); exit(exit_failure); } /* getaddrinfo() returns a list of address structures. try each address until we successfully connect(2). if socket(2) (or connect(2)) fails, we (close the socket and) try the next address. */ for (rp = result; rp != null; rp = rp\->ai_next) { sfd = socket(rp\->ai_family, rp\->ai_socktype, rp\->ai_protocol); if (sfd == \-1) continue; if (connect(sfd, rp\->ai_addr, rp\->ai_addrlen) != \-1) break; /* success */ close(sfd); } freeaddrinfo(result); /* no longer needed */ if (rp == null) { /* no address succeeded */ fprintf(stderr, "could not connect\en"); exit(exit_failure); } /* send remaining command\-line arguments as separate datagrams, and read responses from server. */ for (int j = 3; j < argc; j++) { len = strlen(argv[j]) + 1; /* +1 for terminating null byte */ if (len > buf_size) { fprintf(stderr, "ignoring long message in argument %d\en", j); continue; } if (write(sfd, argv[j], len) != len) { fprintf(stderr, "partial/failed write\en"); exit(exit_failure); } nread = read(sfd, buf, buf_size); if (nread == \-1) { perror("read"); exit(exit_failure); } printf("received %zd bytes: %s\en", nread, buf); } exit(exit_success); } .ee .sh see also .\" .br getipnodebyaddr (3), .\" .br getipnodebyname (3), .br getaddrinfo_a (3), .br gethostbyname (3), .br getnameinfo (3), .br inet (3), .br gai.conf (5), .br hostname (7), .br ip (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:46:03 1993 by rik faith (faith@cs.unc.edu) .th drand48 3 2021-03-22 "" "linux programmer's manual" .sh name drand48, erand48, lrand48, nrand48, mrand48, jrand48, srand48, seed48, lcong48 \- generate uniformly distributed pseudo-random numbers .sh synopsis .nf .b #include .pp .b double drand48(void); .bi "double erand48(unsigned short " xsubi [3]); .pp .b long lrand48(void); .bi "long nrand48(unsigned short " xsubi [3]); .pp .b long mrand48(void); .bi "long jrand48(unsigned short " xsubi [3]); .pp .bi "void srand48(long " seedval ); .bi "unsigned short *seed48(unsigned short " seed16v [3]); .bi "void lcong48(unsigned short " param [7]); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .\" .br drand48 (), .\" .br erand48 (), .\" .br lrand48 (), .\" .br nrand48 (), .\" .br mrand48 (), .\" .br jrand48 (), .\" .br srand48 (), .\" .br seed48 (), .\" .br lcong48 (): .nf _xopen_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source .fi .sh description these functions generate pseudo-random numbers using the linear congruential algorithm and 48-bit integer arithmetic. .pp the .br drand48 () and .br erand48 () functions return nonnegative double-precision floating-point values uniformly distributed over the interval [0.0,\ 1.0). .pp the .br lrand48 () and .br nrand48 () functions return nonnegative long integers uniformly distributed over the interval [0,\ 2^31). .pp the .br mrand48 () and .br jrand48 () functions return signed long integers uniformly distributed over the interval [\-2^31,\ 2^31). .pp the .br srand48 (), .br seed48 (), and .br lcong48 () functions are initialization functions, one of which should be called before using .br drand48 (), .br lrand48 (), or .br mrand48 (). the functions .br erand48 (), .br nrand48 (), and .br jrand48 () do not require an initialization function to be called first. .pp all the functions work by generating a sequence of 48-bit integers, .ir xi , according to the linear congruential formula: .pp .in +4n .ex .b xn+1 = (axn + c) mod m, where n >= 0 .ee .in .pp the parameter .i m = 2^48, hence 48-bit integer arithmetic is performed. unless .br lcong48 () is called, .ir a and .i c are given by: .pp .in +4n .ex .b a = 0x5deece66d .b c = 0xb .ee .in .pp the value returned by any of the functions .br drand48 (), .br erand48 (), .br lrand48 (), .br nrand48 (), .br mrand48 (), or .br jrand48 () is computed by first generating the next 48-bit .i xi in the sequence. then the appropriate number of bits, according to the type of data item to be returned, is copied from the high-order bits of .i xi and transformed into the returned value. .pp the functions .br drand48 (), .br lrand48 (), and .br mrand48 () store the last 48-bit .i xi generated in an internal buffer. the functions .br erand48 (), .br nrand48 (), and .br jrand48 () require the calling program to provide storage for the successive .i xi values in the array argument .ir xsubi . the functions are initialized by placing the initial value of .i xi into the array before calling the function for the first time. .pp the initializer function .br srand48 () sets the high order 32-bits of .i xi to the argument .ir seedval . the low order 16-bits are set to the arbitrary value 0x330e. .pp the initializer function .br seed48 () sets the value of .i xi to the 48-bit value specified in the array argument .ir seed16v . the previous value of .i xi is copied into an internal buffer and a pointer to this buffer is returned by .br seed48 (). .pp the initialization function .br lcong48 () allows the user to specify initial values for .ir xi , .ir a , and .ir c . array argument elements .i param[0\-2] specify .ir xi , .i param[3\-5] specify .ir a , and .i param[6] specifies .ir c . after .br lcong48 () has been called, a subsequent call to either .br srand48 () or .br seed48 () will restore the standard values of .i a and .ir c . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br drand48 (), .br erand48 (), .br lrand48 (), .br nrand48 (), .br mrand48 (), .br jrand48 (), .br srand48 (), .br seed48 (), .br lcong48 () t} thread safety t{ mt-unsafe race:drand48 t} .te .hy .ad .sp 1 .pp the above functions record global state information for the random number generator, so they are not thread-safe. .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh see also .br rand (3), .br random (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:23:25 1993 by rik faith (faith@cs.unc.edu) .\" modified mon may 27 21:37:47 1996 by martin schulze (joey@linux.de) .\" .th getpw 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getpw \- reconstruct password line entry .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .b #include .pp .bi "int getpw(uid_t " uid ", char *" buf ); .fi .sh description the .br getpw () function reconstructs the password line entry for the given user id \fiuid\fp in the buffer \fibuf\fp. the returned buffer contains a line of format .pp .in +4n .ex .b name:passwd:uid:gid:gecos:dir:shell .ee .in .pp the \fipasswd\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct passwd { char *pw_name; /* username */ char *pw_passwd; /* user password */ uid_t pw_uid; /* user id */ gid_t pw_gid; /* group id */ char *pw_gecos; /* user information */ char *pw_dir; /* home directory */ char *pw_shell; /* shell program */ }; .ee .in .pp for more information about the fields of this structure, see .br passwd (5). .sh return value the .br getpw () function returns 0 on success; on error, it returns \-1, and .i errno is set to indicate the error. .pp if .i uid is not found in the password database, .br getpw () returns \-1, sets .i errno to 0, and leaves .i buf unchanged. .sh errors .tp .br 0 " or " enoent no user corresponding to .ir uid . .tp .b einval .i buf is null. .tp .b enomem insufficient memory to allocate .i passwd structure. .sh files .tp .i /etc/passwd password database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getpw () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to svr2. .sh bugs the .br getpw () function is dangerous as it may overflow the provided buffer .ir buf . it is obsoleted by .br getpwuid (3). .sh see also .br endpwent (3), .br fgetpwent (3), .br getpwent (3), .br getpwnam (3), .br getpwuid (3), .br putpwent (3), .br setpwent (3), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/ioctl_tty.2 .\" link for old name of this page .\" copyright (c) 2013, heinrich schuchardt .\" and copyright (c) 2014, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .th fanotify 7 2021-08-27 "linux" "linux programmer's manual" .sh name fanotify \- monitoring filesystem events .sh description the fanotify api provides notification and interception of filesystem events. use cases include virus scanning and hierarchical storage management. in the original fanotify api, only a limited set of events was supported. in particular, there was no support for create, delete, and move events. the support for those events was added in linux 5.1. (see .br inotify (7) for details of an api that did notify those events pre linux 5.1.) .pp additional capabilities compared to the .br inotify (7) api include the ability to monitor all of the objects in a mounted filesystem, the ability to make access permission decisions, and the possibility to read or modify files before access by other applications. .pp the following system calls are used with this api: .br fanotify_init (2), .br fanotify_mark (2), .br read (2), .br write (2), and .br close (2). .ss fanotify_init(), fanotify_mark(), and notification groups the .br fanotify_init (2) system call creates and initializes an fanotify notification group and returns a file descriptor referring to it. .pp an fanotify notification group is a kernel-internal object that holds a list of files, directories, filesystems, and mounts for which events shall be created. .pp for each entry in an fanotify notification group, two bit masks exist: the .i mark mask and the .i ignore mask. the mark mask defines file activities for which an event shall be created. the ignore mask defines activities for which no event shall be generated. having these two types of masks permits a filesystem, mount, or directory to be marked for receiving events, while at the same time ignoring events for specific objects under a mount or directory. .pp the .br fanotify_mark (2) system call adds a file, directory, filesystem, or mount to a notification group and specifies which events shall be reported (or ignored), or removes or modifies such an entry. .pp a possible usage of the ignore mask is for a file cache. events of interest for a file cache are modification of a file and closing of the same. hence, the cached directory or mount is to be marked to receive these events. after receiving the first event informing that a file has been modified, the corresponding cache entry will be invalidated. no further modification events for this file are of interest until the file is closed. hence, the modify event can be added to the ignore mask. upon receiving the close event, the modify event can be removed from the ignore mask and the file cache entry can be updated. .pp the entries in the fanotify notification groups refer to files and directories via their inode number and to mounts via their mount id. if files or directories are renamed or moved within the same mount, the respective entries survive. if files or directories are deleted or moved to another mount or if filesystems or mounts are unmounted, the corresponding entries are deleted. .ss the event queue as events occur on the filesystem objects monitored by a notification group, the fanotify system generates events that are collected in a queue. these events can then be read (using .br read (2) or similar) from the fanotify file descriptor returned by .br fanotify_init (2). .pp two types of events are generated: .i notification events and .i permission events. notification events are merely informative and require no action to be taken by the receiving application with one exception: if a valid file descriptor is provided within a generic event, the file descriptor must be closed. permission events are requests to the receiving application to decide whether permission for a file access shall be granted. for these events, the recipient must write a response which decides whether access is granted or not. .pp an event is removed from the event queue of the fanotify group when it has been read. permission events that have been read are kept in an internal list of the fanotify group until either a permission decision has been taken by writing to the fanotify file descriptor or the fanotify file descriptor is closed. .ss reading fanotify events calling .br read (2) for the file descriptor returned by .br fanotify_init (2) blocks (if the flag .b fan_nonblock is not specified in the call to .br fanotify_init (2)) until either a file event occurs or the call is interrupted by a signal (see .br signal (7)). .pp the use of one of the flags .br fan_report_fid , .br fan_report_dir_fid in .br fanotify_init (2) influences what data structures are returned to the event listener for each event. events reported to a group initialized with one of these flags will use file handles to identify filesystem objects instead of file descriptors. .pp after a successful .br read (2), the read buffer contains one or more of the following structures: .pp .in +4n .ex struct fanotify_event_metadata { __u32 event_len; __u8 vers; __u8 reserved; __u16 metadata_len; __aligned_u64 mask; __s32 fd; __s32 pid; }; .ee .in .pp in case of an fanotify group that identifies filesystem objects by file handles, you should also expect to receive one or more additional information records of the structure detailed below following the generic .i fanotify_event_metadata structure within the read buffer: .pp .in +4n .ex struct fanotify_event_info_header { __u8 info_type; __u8 pad; __u16 len; }; struct fanotify_event_info_fid { struct fanotify_event_info_header hdr; __kernel_fsid_t fsid; unsigned char file_handle[0]; }; .ee .in .pp for performance reasons, it is recommended to use a large buffer size (for example, 4096 bytes), so that multiple events can be retrieved by a single .br read (2). .pp the return value of .br read (2) is the number of bytes placed in the buffer, or \-1 in case of an error (but see bugs). .pp the fields of the .i fanotify_event_metadata structure are as follows: .tp .i event_len this is the length of the data for the current event and the offset to the next event in the buffer. unless the group identifies filesystem objects by file handles, the value of .i event_len is always .br fan_event_metadata_len . for a group that identifies filesystem objects by file handles, .i event_len also includes the variable length file identifier records. .tp .i vers this field holds a version number for the structure. it must be compared to .b fanotify_metadata_version to verify that the structures returned at run time match the structures defined at compile time. in case of a mismatch, the application should abandon trying to use the fanotify file descriptor. .tp .i reserved this field is not used. .tp .i metadata_len this is the length of the structure. the field was introduced to facilitate the implementation of optional headers per event type. no such optional headers exist in the current implementation. .tp .i mask this is a bit mask describing the event (see below). .tp .i fd this is an open file descriptor for the object being accessed, or .b fan_nofd if a queue overflow occurred. with an fanotify group that identifies filesystem objects by file handles, applications should expect this value to be set to .b fan_nofd for each event that is received. the file descriptor can be used to access the contents of the monitored file or directory. the reading application is responsible for closing this file descriptor. .ip when calling .br fanotify_init (2), the caller may specify (via the .i event_f_flags argument) various file status flags that are to be set on the open file description that corresponds to this file descriptor. in addition, the (kernel-internal) .b fmode_nonotify file status flag is set on the open file description. this flag suppresses fanotify event generation. hence, when the receiver of the fanotify event accesses the notified file or directory using this file descriptor, no additional events will be created. .tp .i pid if flag .b fan_report_tid was set in .br fanotify_init (2), this is the tid of the thread that caused the event. otherwise, this the pid of the process that caused the event. .pp a program listening to fanotify events can compare this pid to the pid returned by .br getpid (2), to determine whether the event is caused by the listener itself, or is due to a file access by another process. .pp the bit mask in .i mask indicates which events have occurred for a single filesystem object. multiple bits may be set in this mask, if more than one event occurred for the monitored filesystem object. in particular, consecutive events for the same filesystem object and originating from the same process may be merged into a single event, with the exception that two permission events are never merged into one queue entry. .pp the bits that may appear in .i mask are as follows: .tp .b fan_access a file or a directory (but see bugs) was accessed (read). .tp .b fan_open a file or a directory was opened. .tp .b fan_open_exec a file was opened with the intent to be executed. see notes in .br fanotify_mark (2) for additional details. .tp .b fan_attrib a file or directory metadata was changed. .tp .b fan_create a child file or directory was created in a watched parent. .tp .b fan_delete a child file or directory was deleted in a watched parent. .tp .b fan_delete_self a watched file or directory was deleted. .tp .b fan_moved_from a file or directory has been moved from a watched parent directory. .tp .b fan_moved_to a file or directory has been moved to a watched parent directory. .tp .b fan_move_self a watched file or directory was moved. .tp .b fan_modify a file was modified. .tp .b fan_close_write a file that was opened for writing .rb ( o_wronly or .br o_rdwr ) was closed. .tp .b fan_close_nowrite a file or directory that was opened read-only .rb ( o_rdonly ) was closed. .tp .b fan_q_overflow the event queue exceeded the limit of 16384 entries. this limit can be overridden by specifying the .br fan_unlimited_queue flag when calling .br fanotify_init (2). .tp .b fan_access_perm an application wants to read a file or directory, for example using .br read (2) or .br readdir (2). the reader must write a response (as described below) that determines whether the permission to access the filesystem object shall be granted. .tp .b fan_open_perm an application wants to open a file or directory. the reader must write a response that determines whether the permission to open the filesystem object shall be granted. .tp .b fan_open_exec_perm an application wants to open a file for execution. the reader must write a response that determines whether the permission to open the filesystem object for execution shall be granted. see notes in .br fanotify_mark (2) for additional details. .pp to check for any close event, the following bit mask may be used: .tp .b fan_close a file was closed. this is a synonym for: .ip fan_close_write | fan_close_nowrite .pp to check for any move event, the following bit mask may be used: .tp .b fan_move a file or directory was moved. this is a synonym for: .ip fan_moved_from | fan_moved_to .pp the following bits may appear in .i mask only in conjunction with other event type bits: .tp .b fan_ondir the events described in the .i mask have occurred on a directory object. reporting events on directories requires setting this flag in the mark mask. see .br fanotify_mark (2) for additional details. the .br fan_ondir flag is reported in an event mask only if the fanotify group identifies filesystem objects by file handles. .pp the fields of the .i fanotify_event_info_fid structure are as follows: .tp .i hdr this is a structure of type .ir fanotify_event_info_header . it is a generic header that contains information used to describe an additional information record attached to the event. for example, when an fanotify file descriptor is created using .br fan_report_fid , a single information record is expected to be attached to the event with .i info_type field value of .br fan_event_info_type_fid . when an fanotify file descriptor is created using the combination of .br fan_report_fid and .br fan_report_dir_fid , there may be two information records attached to the event: one with .i info_type field value of .br fan_event_info_type_dfid , identifying a parent directory object, and one with .i info_type field value of .br fan_event_info_type_fid , identifying a non-directory object. the .i fanotify_event_info_header contains a .i len field. the value of .i len is the size of the additional information record including the .ir fanotify_event_info_header itself. the total size of all additional information records is not expected to be bigger than ( .ir event_len \- .ir metadata_len ). .tp .i fsid this is a unique identifier of the filesystem containing the object associated with the event. it is a structure of type .i __kernel_fsid_t and contains the same value as .i f_fsid when calling .br statfs (2). .tp .i file_handle this is a variable length structure of type struct file_handle. it is an opaque handle that corresponds to a specified object on a filesystem as returned by .br name_to_handle_at (2). it can be used to uniquely identify a file on a filesystem and can be passed as an argument to .br open_by_handle_at (2). note that for the directory entry modification events .br fan_create , .br fan_delete , and .br fan_move , the .ir file_handle identifies the modified directory and not the created/deleted/moved child object. if the value of .i info_type field is .br fan_event_info_type_dfid_name , the file handle is followed by a null terminated string that identifies the created/deleted/moved directory entry name. for other events such as .br fan_open , .br fan_attrib , .br fan_delete_self , and .br fan_move_self , if the value of .i info_type field is .br fan_event_info_type_fid , the .ir file_handle identifies the object correlated to the event. if the value of .i info_type field is .br fan_event_info_type_dfid , the .ir file_handle identifies the directory object correlated to the event or the parent directory of a non-directory object correlated to the event. if the value of .i info_type field is .br fan_event_info_type_dfid_name , the .ir file_handle identifies the same directory object that would be reported with .br fan_event_info_type_dfid and the file handle is followed by a null terminated string that identifies the name of a directory entry in that directory, or '.' to identify the directory object itself. .pp the following macros are provided to iterate over a buffer containing fanotify event metadata returned by a .br read (2) from an fanotify file descriptor: .tp .b fan_event_ok(meta, len) this macro checks the remaining length .i len of the buffer .i meta against the length of the metadata structure and the .i event_len field of the first metadata structure in the buffer. .tp .b fan_event_next(meta, len) this macro uses the length indicated in the .i event_len field of the metadata structure pointed to by .ir meta to calculate the address of the next metadata structure that follows .ir meta . .i len is the number of bytes of metadata that currently remain in the buffer. the macro returns a pointer to the next metadata structure that follows .ir meta , and reduces .i len by the number of bytes in the metadata structure that has been skipped over (i.e., it subtracts .ir meta\->event_len from .ir len ). .pp in addition, there is: .tp .b fan_event_metadata_len this macro returns the size (in bytes) of the structure .ir fanotify_event_metadata . this is the minimum size (and currently the only size) of any event metadata. .\" .ss monitoring an fanotify file descriptor for events when an fanotify event occurs, the fanotify file descriptor indicates as readable when passed to .br epoll (7), .br poll (2), or .br select (2). .ss dealing with permission events for permission events, the application must .br write (2) a structure of the following form to the fanotify file descriptor: .pp .in +4n .ex struct fanotify_response { __s32 fd; __u32 response; }; .ee .in .pp the fields of this structure are as follows: .tp .i fd this is the file descriptor from the structure .ir fanotify_event_metadata . .tp .i response this field indicates whether or not the permission is to be granted. its value must be either .b fan_allow to allow the file operation or .b fan_deny to deny the file operation. .pp if access is denied, the requesting application call will receive an .br eperm error. additionally, if the notification group has been created with the .b fan_enable_audit flag, then the .b fan_audit flag can be set in the .i response field. in that case, the audit subsystem will log information about the access decision to the audit logs. .\" .ss closing the fanotify file descriptor when all file descriptors referring to the fanotify notification group are closed, the fanotify group is released and its resources are freed for reuse by the kernel. upon .br close (2), outstanding permission events will be set to allowed. .ss /proc/[pid]/fdinfo the file .i /proc/[pid]/fdinfo/[fd] contains information about fanotify marks for file descriptor .i fd of process .ir pid . see .br proc (5) for details. .sh errors in addition to the usual errors for .br read (2), the following errors can occur when reading from the fanotify file descriptor: .tp .b einval the buffer is too small to hold the event. .tp .b emfile the per-process limit on the number of open files has been reached. see the description of .b rlimit_nofile in .br getrlimit (2). .tp .b enfile the system-wide limit on the total number of open files has been reached. see .i /proc/sys/fs/file\-max in .br proc (5). .tp .b etxtbsy this error is returned by .br read (2) if .b o_rdwr or .b o_wronly was specified in the .i event_f_flags argument when calling .br fanotify_init (2) and an event occurred for a monitored file that is currently being executed. .pp in addition to the usual errors for .br write (2), the following errors can occur when writing to the fanotify file descriptor: .tp .b einval fanotify access permissions are not enabled in the kernel configuration or the value of .i response in the response structure is not valid. .tp .b enoent the file descriptor .i fd in the response structure is not valid. this may occur when a response for the permission event has already been written. .sh versions the fanotify api was introduced in version 2.6.36 of the linux kernel and enabled in version 2.6.37. fdinfo support was added in version 3.8. .sh conforming to the fanotify api is linux-specific. .sh notes the fanotify api is available only if the kernel was built with the .b config_fanotify configuration option enabled. in addition, fanotify permission handling is available only if the .b config_fanotify_access_permissions configuration option is enabled. .ss limitations and caveats fanotify reports only events that a user-space program triggers through the filesystem api. as a result, it does not catch remote events that occur on network filesystems. .pp the fanotify api does not report file accesses and modifications that may occur because of .br mmap (2), .br msync (2), and .br munmap (2). .pp events for directories are created only if the directory itself is opened, read, and closed. adding, removing, or changing children of a marked directory does not create events for the monitored directory itself. .pp fanotify monitoring of directories is not recursive: to monitor subdirectories under a directory, additional marks must be created. the .b fan_create event can be used for detecting when a subdirectory has been created under a marked directory. an additional mark must then be set on the newly created subdirectory. this approach is racy, because it can lose events that occurred inside the newly created subdirectory, before a mark is added on that subdirectory. monitoring mounts offers the capability to monitor a whole directory tree in a race-free manner. monitoring filesystems offers the capability to monitor changes made from any mount of a filesystem instance in a race-free manner. .pp the event queue can overflow. in this case, events are lost. .sh bugs before linux 3.19, .br fallocate (2) did not generate fanotify events. since linux 3.19, .\" commit 820c12d5d6c0890bc93dd63893924a13041fdc35 calls to .br fallocate (2) generate .b fan_modify events. .pp as of linux 3.17, the following bugs exist: .ip * 3 on linux, a filesystem object may be accessible through multiple paths, for example, a part of a filesystem may be remounted using the .ir \-\-bind option of .br mount (8). a listener that marked a mount will be notified only of events that were triggered for a filesystem object using the same mount. any other event will pass unnoticed. .ip * .\" fixme . a patch was proposed. when an event is generated, no check is made to see whether the user id of the receiving process has authorization to read or write the file before passing a file descriptor for that file. this poses a security risk, when the .b cap_sys_admin capability is set for programs executed by unprivileged users. .ip * if a call to .br read (2) processes multiple events from the fanotify queue and an error occurs, the return value will be the total length of the events successfully copied to the user-space buffer before the error occurred. the return value will not be \-1, and .i errno will not be set. thus, the reading application has no way to detect the error. .sh examples the two example programs below demonstrate the usage of the fanotify api. .ss example program: fanotify_example.c the first program is an example of fanotify being used with its event object information passed in the form of a file descriptor. the program marks the mount passed as a command-line argument and waits for events of type .b fan_open_perm and .br fan_close_write . when a permission event occurs, a .b fan_allow response is given. .pp the following shell session shows an example of running this program. this session involved editing the file .ir /home/user/temp/notes . before the file was opened, a .b fan_open_perm event occurred. after the file was closed, a .b fan_close_write event occurred. execution of the program ends when the user presses the enter key. .pp .in +4n .ex # \fb./fanotify_example /home\fp press enter key to terminate. listening for events. fan_open_perm: file /home/user/temp/notes fan_close_write: file /home/user/temp/notes listening for events stopped. .ee .in .ss program source: fanotify_example.c \& .ex #define _gnu_source /* needed to get o_largefile definition */ #include #include #include #include #include #include #include #include /* read all available fanotify events from the file descriptor \(aqfd\(aq. */ static void handle_events(int fd) { const struct fanotify_event_metadata *metadata; struct fanotify_event_metadata buf[200]; ssize_t len; char path[path_max]; ssize_t path_len; char procfd_path[path_max]; struct fanotify_response response; /* loop while events can be read from fanotify file descriptor. */ for (;;) { /* read some events. */ len = read(fd, buf, sizeof(buf)); if (len == \-1 && errno != eagain) { perror("read"); exit(exit_failure); } /* check if end of available data reached. */ if (len <= 0) break; /* point to the first event in the buffer. */ metadata = buf; /* loop over all events in the buffer. */ while (fan_event_ok(metadata, len)) { /* check that run\-time and compile\-time structures match. */ if (metadata\->vers != fanotify_metadata_version) { fprintf(stderr, "mismatch of fanotify metadata version.\en"); exit(exit_failure); } /* metadata\->fd contains either fan_nofd, indicating a queue overflow, or a file descriptor (a nonnegative integer). here, we simply ignore queue overflow. */ if (metadata\->fd >= 0) { /* handle open permission event. */ if (metadata\->mask & fan_open_perm) { printf("fan_open_perm: "); /* allow file to be opened. */ response.fd = metadata\->fd; response.response = fan_allow; write(fd, &response, sizeof(response)); } /* handle closing of writable file event. */ if (metadata\->mask & fan_close_write) printf("fan_close_write: "); /* retrieve and print pathname of the accessed file. */ snprintf(procfd_path, sizeof(procfd_path), "/proc/self/fd/%d", metadata\->fd); path_len = readlink(procfd_path, path, sizeof(path) \- 1); if (path_len == \-1) { perror("readlink"); exit(exit_failure); } path[path_len] = \(aq\e0\(aq; printf("file %s\en", path); /* close the file descriptor of the event. */ close(metadata\->fd); } /* advance to next event. */ metadata = fan_event_next(metadata, len); } } } int main(int argc, char *argv[]) { char buf; int fd, poll_num; nfds_t nfds; struct pollfd fds[2]; /* check mount point is supplied. */ if (argc != 2) { fprintf(stderr, "usage: %s mount\en", argv[0]); exit(exit_failure); } printf("press enter key to terminate.\en"); /* create the file descriptor for accessing the fanotify api. */ fd = fanotify_init(fan_cloexec | fan_class_content | fan_nonblock, o_rdonly | o_largefile); if (fd == \-1) { perror("fanotify_init"); exit(exit_failure); } /* mark the mount for: \- permission events before opening files \- notification events after closing a write\-enabled file descriptor. */ if (fanotify_mark(fd, fan_mark_add | fan_mark_mount, fan_open_perm | fan_close_write, at_fdcwd, argv[1]) == \-1) { perror("fanotify_mark"); exit(exit_failure); } /* prepare for polling. */ nfds = 2; fds[0].fd = stdin_fileno; /* console input */ fds[0].events = pollin; fds[1].fd = fd; /* fanotify input */ fds[1].events = pollin; /* this is the loop to wait for incoming events. */ printf("listening for events.\en"); while (1) { poll_num = poll(fds, nfds, \-1); if (poll_num == \-1) { if (errno == eintr) /* interrupted by a signal */ continue; /* restart poll() */ perror("poll"); /* unexpected error */ exit(exit_failure); } if (poll_num > 0) { if (fds[0].revents & pollin) { /* console input is available: empty stdin and quit. */ while (read(stdin_fileno, &buf, 1) > 0 && buf != \(aq\en\(aq) continue; break; } if (fds[1].revents & pollin) { /* fanotify events are available. */ handle_events(fd); } } } printf("listening for events stopped.\en"); exit(exit_success); } .ee .\" .ss example program: fanotify_fid.c the second program is an example of fanotify being used with a group that identifies objects by file handles. the program marks the filesystem object that is passed as a command-line argument and waits until an event of type .b fan_create has occurred. the event mask indicates which type of filesystem object\(emeither a file or a directory\(emwas created. once all events have been read from the buffer and processed accordingly, the program simply terminates. .pp the following shell sessions show two different invocations of this program, with different actions performed on a watched object. .pp the first session shows a mark being placed on .ir /home/user . this is followed by the creation of a regular file, .ir /home/user/testfile.txt . this results in a .b fan_create event being generated and reported against the file's parent watched directory object and with the created file name. program execution ends once all events captured within the buffer have been processed. .pp .in +4n .ex # \fb./fanotify_fid /home/user\fp listening for events. fan_create (file created): directory /home/user has been modified. entry \(aqtestfile.txt\(aq is not a subdirectory. all events processed successfully. program exiting. $ \fbtouch /home/user/testfile.txt\fp # in another terminal .ee .in .pp the second session shows a mark being placed on .ir /home/user . this is followed by the creation of a directory, .ir /home/user/testdir . this specific action results in a .b fan_create event being generated and is reported with the .b fan_ondir flag set and with the created directory name. .pp .in +4n .ex # \fb./fanotify_fid /home/user\fp listening for events. fan_create | fan_ondir (subdirectory created): directory /home/user has been modified. entry \(aqtestdir\(aq is a subdirectory. all events processed successfully. program exiting. $ \fbmkdir \-p /home/user/testdir\fp # in another terminal .ee .in .ss program source: fanotify_fid.c \& .ex #define _gnu_source #include #include #include #include #include #include #include #include #include #define buf_size 256 int main(int argc, char *argv[]) { int fd, ret, event_fd, mount_fd; ssize_t len, path_len; char path[path_max]; char procfd_path[path_max]; char events_buf[buf_size]; struct file_handle *file_handle; struct fanotify_event_metadata *metadata; struct fanotify_event_info_fid *fid; const char *file_name; struct stat sb; if (argc != 2) { fprintf(stderr, "invalid number of command line arguments.\en"); exit(exit_failure); } mount_fd = open(argv[1], o_directory | o_rdonly); if (mount_fd == \-1) { perror(argv[1]); exit(exit_failure); } /* create an fanotify file descriptor with fan_report_dfid_name as a flag so that program can receive fid events with directory entry name. */ fd = fanotify_init(fan_class_notif | fan_report_dfid_name, 0); if (fd == \-1) { perror("fanotify_init"); exit(exit_failure); } /* place a mark on the filesystem object supplied in argv[1]. */ ret = fanotify_mark(fd, fan_mark_add | fan_mark_onlydir, fan_create | fan_ondir, at_fdcwd, argv[1]); if (ret == \-1) { perror("fanotify_mark"); exit(exit_failure); } printf("listening for events.\en"); /* read events from the event queue into a buffer. */ len = read(fd, events_buf, sizeof(events_buf)); if (len == \-1 && errno != eagain) { perror("read"); exit(exit_failure); } /* process all events within the buffer. */ for (metadata = (struct fanotify_event_metadata *) events_buf; fan_event_ok(metadata, len); metadata = fan_event_next(metadata, len)) { fid = (struct fanotify_event_info_fid *) (metadata + 1); file_handle = (struct file_handle *) fid\->handle; /* ensure that the event info is of the correct type. */ if (fid\->hdr.info_type == fan_event_info_type_fid || fid\->hdr.info_type == fan_event_info_type_dfid) { file_name = null; } else if (fid\->hdr.info_type == fan_event_info_type_dfid_name) { file_name = file_handle\->f_handle + file_handle\->handle_bytes; } else { fprintf(stderr, "received unexpected event info type.\en"); exit(exit_failure); } if (metadata\->mask == fan_create) printf("fan_create (file created):\en"); if (metadata\->mask == (fan_create | fan_ondir)) printf("fan_create | fan_ondir (subdirectory created):\en"); /* metadata\->fd is set to fan_nofd when the group identifies objects by file handles. to obtain a file descriptor for the file object corresponding to an event you can use the struct file_handle that\(aqs provided within the fanotify_event_info_fid in conjunction with the open_by_handle_at(2) system call. a check for estale is done to accommodate for the situation where the file handle for the object was deleted prior to this system call. */ event_fd = open_by_handle_at(mount_fd, file_handle, o_rdonly); if (event_fd == \-1) { if (errno == estale) { printf("file handle is no longer valid. " "file has been deleted\en"); continue; } else { perror("open_by_handle_at"); exit(exit_failure); } } snprintf(procfd_path, sizeof(procfd_path), "/proc/self/fd/%d", event_fd); /* retrieve and print the path of the modified dentry. */ path_len = readlink(procfd_path, path, sizeof(path) \- 1); if (path_len == \-1) { perror("readlink"); exit(exit_failure); } path[path_len] = \(aq\e0\(aq; printf("\etdirectory \(aq%s\(aq has been modified.\en", path); if (file_name) { ret = fstatat(event_fd, file_name, &sb, 0); if (ret == \-1) { if (errno != enoent) { perror("fstatat"); exit(exit_failure); } printf("\etentry \(aq%s\(aq does not exist.\en", file_name); } else if ((sb.st_mode & s_ifmt) == s_ifdir) { printf("\etentry \(aq%s\(aq is a subdirectory.\en", file_name); } else { printf("\etentry \(aq%s\(aq is not a subdirectory.\en", file_name); } } /* close associated file descriptor for this event. */ close(event_fd); } printf("all events processed successfully. program exiting.\en"); exit(exit_success); } .ee .sh see also .ad l .br fanotify_init (2), .br fanotify_mark (2), .br inotify (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/exec.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcsstr 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsstr \- locate a substring in a wide-character string .sh synopsis .nf .b #include .pp .bi "wchar_t *wcsstr(const wchar_t *" haystack ", const wchar_t *" needle ); .fi .sh description the .br wcsstr () function is the wide-character equivalent of the .br strstr (3) function. it searches for the first occurrence of the wide-character string .i needle (without its terminating null wide character (l\(aq\e0\(aq)) as a substring in the wide-character string .ir haystack . .sh return value the .br wcsstr () function returns a pointer to the first occurrence of .i needle in .ir haystack . it returns null if .i needle does not occur as a substring in .ir haystack . .pp note the special case: if .i needle is the empty wide-character string, the return value is always .i haystack itself. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsstr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strstr (3), .br wcschr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. import os import glob import random import shutil # step 1: navigate to the directory data_dir = '/media/external/man-pages-dataset/man-pages-5.13' os.chdir(data_dir) # step 2: organize the data (in this example, we'll assume the data is already organized) # step 3: preprocess the text def preprocess_text(file_path): with open(file_path, 'r', encoding='utf-8') as file: text = file.read() # simple preprocessing (e.g., lowercase conversion) text = text.lower() return text # step 4: format the data for training all_data = [] for file_path in glob.glob('**/*.txt', recursive=true): preprocessed_text = preprocess_text(file_path) all_data.append(preprocessed_text) # step 5: split the data random.shuffle(all_data) train_size = int(0.8 * len(all_data)) train_data, val_test_data = all_data[:train_size], all_data[train_size:] val_size = int(0.5 * len(val_test_data)) val_data, test_data = val_test_data[:val_size], val_test_data[val_size:] # step 6: save the preprocessed data output_dir = os.path.join(data_dir, 'preprocessed_data') os.makedirs(output_dir, exist_ok=true) with open(os.path.join(output_dir, 'train.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(train_data)) with open(os.path.join(output_dir, 'val.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(val_data)) with open(os.path.join(output_dir, 'test.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(test_data)) print(f'data preprocessing and splitting completed. preprocessed data saved to {output_dir}') .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-05-22, david metcalfe .\" modified 1993-07-25, rik faith (faith@cs.unc.edu) .\" modified 1997-02-16, andries brouwer (aeb@cwi.nl) .\" modified 1998-12-21, andries brouwer (aeb@cwi.nl) .\" modified 2000-08-12, andries brouwer (aeb@cwi.nl) .\" modified 2001-05-19, andries brouwer (aeb@cwi.nl) .\" modified 2002-08-05, michael kerrisk .\" modified 2004-10-31, andries brouwer .\" .th gethostbyname 3 2021-03-22 "" "linux programmer's manual" .sh name gethostbyname, gethostbyaddr, sethostent, gethostent, endhostent, h_errno, herror, hstrerror, gethostbyaddr_r, gethostbyname2, gethostbyname2_r, gethostbyname_r, gethostent_r \- get network host entry .sh synopsis .nf .b #include .pp .b extern int h_errno; .pp .bi "struct hostent *gethostbyname(const char *" name ); .bi "struct hostent *gethostbyaddr(const void *" addr , .bi " socklen_t " len ", int " type ); .pp .bi "void sethostent(int " stayopen ); .b void endhostent(void); .pp .bi "void herror(const char *" s ); .bi "const char *hstrerror(int " err ); .pp /* system v/posix extension */ .b struct hostent *gethostent(void); .pp /* gnu extensions */ .bi "struct hostent *gethostbyname2(const char *" name ", int " af ); .pp .bi "int gethostent_r(struct hostent *restrict " ret , .bi " char *restrict " buf ", size_t " buflen , .bi " struct hostent **restrict " result , .bi " int *restrict " h_errnop ); .pp .bi "int gethostbyaddr_r(const void *restrict " addr ", socklen_t " len \ ", int " type , .bi " struct hostent *restrict " ret , .bi " char *restrict " buf ", size_t " buflen , .bi " struct hostent **restrict " result , .bi " int *restrict " h_errnop ); .bi "int gethostbyname_r(const char *restrict " name , .bi " struct hostent *restrict " ret , .bi " char *restrict " buf ", size_t " buflen , .bi " struct hostent **restrict " result , .bi " int *restrict " h_errnop ); .bi "int gethostbyname2_r(const char *restrict " name ", int " af, .bi " struct hostent *restrict " ret , .bi " char *restrict " buf ", size_t " buflen , .bi " struct hostent **restrict " result , .bi " int *restrict " h_errnop ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br gethostbyname2 (), .br gethostent_r (), .br gethostbyaddr_r (), .br gethostbyname_r (), .br gethostbyname2_r (): .nf since glibc 2.19: _default_source glibc up to and including 2.19: _bsd_source || _svid_source .fi .pp .br herror (), .br hstrerror (): .nf since glibc 2.19: _default_source glibc 2.8 to 2.19: _bsd_source || _svid_source before glibc 2.8: none .fi .pp .br h_errno : .nf since glibc 2.19 _default_source || _posix_c_source < 200809l glibc 2.12 to 2.19: _bsd_source || _svid_source || _posix_c_source < 200809l before glibc 2.12: none .fi .sh description the .br gethostbyname* (), .br gethostbyaddr* (), .br herror (), and .br hstrerror () functions are obsolete. applications should use .br getaddrinfo (3), .br getnameinfo (3), and .br gai_strerror (3) instead. .pp the .br gethostbyname () function returns a structure of type .i hostent for the given host .ir name . here .i name is either a hostname or an ipv4 address in standard dot notation (as for .br inet_addr (3)). if .i name is an ipv4 address, no lookup is performed and .br gethostbyname () simply copies .i name into the .i h_name field and its .i struct in_addr equivalent into the .i h_addr_list[0] field of the returned .i hostent structure. if .i name doesn't end in a dot and the environment variable .b hostaliases is set, the alias file pointed to by .b hostaliases will first be searched for .i name (see .br hostname (7) for the file format). the current domain and its parents are searched unless \finame\fp ends in a dot. .pp the .br gethostbyaddr () function returns a structure of type \fihostent\fp for the given host address \fiaddr\fp of length \filen\fp and address type \fitype\fp. valid address types are .b af_inet and .br af_inet6 (defined in .ir ). the host address argument is a pointer to a struct of a type depending on the address type, for example a \fistruct in_addr *\fp (probably obtained via a call to .br inet_addr (3)) for address type .br af_inet . .pp the .br sethostent () function specifies, if \fistayopen\fp is true (1), that a connected tcp socket should be used for the name server queries and that the connection should remain open during successive queries. otherwise, name server queries will use udp datagrams. .pp the .br endhostent () function ends the use of a tcp connection for name server queries. .pp the (obsolete) .br herror () function prints the error message associated with the current value of \fih_errno\fp on \fistderr\fp. .pp the (obsolete) .br hstrerror () function takes an error number (typically \fih_errno\fp) and returns the corresponding message string. .pp the domain name queries carried out by .br gethostbyname () and .br gethostbyaddr () rely on the name service switch .rb ( nsswitch.conf (5)) configured sources or a local name server .rb ( named (8)). the default action is to query the name service switch .rb ( nsswitch.conf (5)) configured sources, failing that, a local name server .rb ( named (8)). .\" .ss historical the .br nsswitch.conf (5) file is the modern way of controlling the order of host lookups. .pp in glibc 2.4 and earlier, the .i order keyword was used to control the order of host lookups as defined in .ir /etc/host.conf .rb ( host.conf (5)). .pp the \fihostent\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct hostent { char *h_name; /* official name of host */ char **h_aliases; /* alias list */ int h_addrtype; /* host address type */ int h_length; /* length of address */ char **h_addr_list; /* list of addresses */ } #define h_addr h_addr_list[0] /* for backward compatibility */ .ee .in .pp the members of the \fihostent\fp structure are: .tp .i h_name the official name of the host. .tp .i h_aliases an array of alternative names for the host, terminated by a null pointer. .tp .i h_addrtype the type of address; always .b af_inet or .b af_inet6 at present. .tp .i h_length the length of the address in bytes. .tp .i h_addr_list an array of pointers to network addresses for the host (in network byte order), terminated by a null pointer. .tp .i h_addr the first address in \fih_addr_list\fp for backward compatibility. .sh return value the .br gethostbyname () and .br gethostbyaddr () functions return the .i hostent structure or a null pointer if an error occurs. on error, the .i h_errno variable holds an error number. when non-null, the return value may point at static data, see the notes below. .sh errors the variable \fih_errno\fp can have the following values: .tp .b host_not_found the specified host is unknown. .tp .br no_data the requested name is valid but does not have an ip address. another type of request to the name server for this domain may return an answer. the constant .br no_address is a synonym for .br no_data . .tp .b no_recovery a nonrecoverable name server error occurred. .tp .b try_again a temporary error occurred on an authoritative name server. try again later. .sh files .tp .i /etc/host.conf resolver configuration file .tp .i /etc/hosts host database file .tp .i /etc/nsswitch.conf name service switch configuration .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br gethostbyname () t} thread safety t{ mt-unsafe race:hostbyname env locale t} t{ .br gethostbyaddr () t} thread safety t{ mt-unsafe race:hostbyaddr env locale t} t{ .br sethostent (), .br endhostent (), .br gethostent_r () t} thread safety t{ mt-unsafe race:hostent env locale t} t{ .br herror (), .br hstrerror () t} thread safety mt-safe t{ .br gethostent () t} thread safety t{ mt-unsafe race:hostent race:hostentbuf env locale t} t{ .br gethostbyname2 () t} thread safety t{ mt-unsafe race:hostbyname2 env locale t} t{ .br gethostbyaddr_r (), .br gethostbyname_r (), .br gethostbyname2_r () t} thread safety mt-safe env locale .te .hy .ad .sp 1 in the above table, .i hostent in .i race:hostent signifies that if any of the functions .br sethostent (), .br gethostent (), .br gethostent_r (), or .br endhostent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to posix.1-2001 specifies .br gethostbyname (), .br gethostbyaddr (), .br sethostent (), .br endhostent (), .br gethostent (), and .ir h_errno ; .br gethostbyname (), .br gethostbyaddr (), and .ir h_errno are marked obsolescent in that standard. posix.1-2008 removes the specifications of .br gethostbyname (), .br gethostbyaddr (), and .ir h_errno , recommending the use of .br getaddrinfo (3) and .br getnameinfo (3) instead. .sh notes the functions .br gethostbyname () and .br gethostbyaddr () may return pointers to static data, which may be overwritten by later calls. copying the .i struct hostent does not suffice, since it contains pointers; a deep copy is required. .pp in the original bsd implementation the .i len argument of .br gethostbyname () was an .ir int . the susv2 standard is buggy and declares the .i len argument of .br gethostbyaddr () to be of type .ir size_t . (that is wrong, because it has to be .ir int , and .i size_t is not. posix.1-2001 makes it .ir socklen_t , which is ok.) see also .br accept (2). .pp the bsd prototype for .br gethostbyaddr () uses .i "const char\ *" for the first argument. .ss system v/posix extension posix requires the .br gethostent () call, which should return the next entry in the host data base. when using dns/bind this does not make much sense, but it may be reasonable if the host data base is a file that can be read line by line. on many systems, a routine of this name reads from the file .ir /etc/hosts . .\" e.g., linux, freebsd, unixware, hp-ux it may be available only when the library was built without dns support. .\" e.g., freebsd, aix the glibc version will ignore ipv6 entries. this function is not reentrant, and glibc adds a reentrant version .br gethostent_r (). .ss gnu extensions glibc2 also has a .br gethostbyname2 () that works like .br gethostbyname (), but permits to specify the address family to which the address must belong. .pp glibc2 also has reentrant versions .br gethostent_r (), .br gethostbyaddr_r (), .br gethostbyname_r (), and .br gethostbyname2_r (). the caller supplies a .i hostent structure .i ret which will be filled in on success, and a temporary work buffer .i buf of size .ir buflen . after the call, .i result will point to the result on success. in case of an error or if no entry is found .i result will be null. the functions return 0 on success and a nonzero error number on failure. in addition to the errors returned by the nonreentrant versions of these functions, if .i buf is too small, the functions will return .br erange , and the call should be retried with a larger buffer. the global variable .i h_errno is not modified, but the address of a variable in which to store error numbers is passed in .ir h_errnop . .sh bugs .br gethostbyname () does not recognize components of a dotted ipv4 address string that are expressed in hexadecimal. .\" http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=482973 .sh see also .br getaddrinfo (3), .\" .br getipnodebyaddr (3), .\" .br getipnodebyname (3), .br getnameinfo (3), .br inet (3), .br inet_ntop (3), .br inet_pton (3), .br resolver (3), .br hosts (5), .br nsswitch.conf (5), .br hostname (7), .br named (8) .\" .br resolv+ (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:17:50 1993 by rik faith .\" modified thu oct 19 21:25:21 met 1995 by martin schulze .\" modified mon oct 21 17:47:19 edt 1996 by eric s. raymond .\" xk .th ttytype 5 2020-06-09 "linux" "linux programmer's manual" .sh name ttytype \- terminal device to default terminal type mapping .sh description the .i /etc/ttytype file associates .br termcap (5)/ terminfo (5) terminal type names with tty lines. each line consists of a terminal type, followed by whitespace, followed by a tty name (a device name without the .ir /dev/ ") prefix." .pp this association is used by the program .br tset (1) to set the environment variable .b term to the default terminal name for the user's current tty. .pp this facility was designed for a traditional time-sharing environment featuring character-cell terminals hardwired to a unix minicomputer. it is little used on modern workstation and personal unix systems. .sh files .tp .i /etc/ttytype the tty definitions file. .sh examples a typical .i /etc/ttytype is: .pp .in +4n .ex con80x25 tty1 vt320 ttys0 .ee .in .sh see also .br termcap (5), .br terminfo (5), .br agetty (8), .br mingetty (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/mprotect.2 .\" this manpage has been automatically generated by docbook2man .\" from a docbook document. this tool can be found at: .\" .\" please send any bug reports, improvements, comments, patches, .\" etc. to steve cheng . .\" .\" %%%license_start(mit) .\" this page is made available under the mit license. .\" %%%license_end .\" .th futex 7 2017-09-15 "linux" "linux programmer's manual" .sh name futex \- fast user-space locking .sh synopsis .nf .b #include .fi .sh description the linux kernel provides futexes ("fast user-space mutexes") as a building block for fast user-space locking and semaphores. futexes are very basic and lend themselves well for building higher-level locking abstractions such as mutexes, condition variables, read-write locks, barriers, and semaphores. .pp most programmers will in fact not be using futexes directly but will instead rely on system libraries built on them, such as the native posix thread library (nptl) (see .br pthreads (7)). .pp a futex is identified by a piece of memory which can be shared between processes or threads. in these different processes, the futex need not have identical addresses. in its bare form, a futex has semaphore semantics; it is a counter that can be incremented and decremented atomically; processes can wait for the value to become positive. .pp futex operation occurs entirely in user space for the noncontended case. the kernel is involved only to arbitrate the contended case. as any sane design will strive for noncontention, futexes are also optimized for this situation. .pp in its bare form, a futex is an aligned integer which is touched only by atomic assembler instructions. this integer is four bytes long on all platforms. processes can share this integer using .br mmap (2), via shared memory segments, or because they share memory space, in which case the application is commonly called multithreaded. .ss semantics any futex operation starts in user space, but it may be necessary to communicate with the kernel using the .br futex (2) system call. .pp to "up" a futex, execute the proper assembler instructions that will cause the host cpu to atomically increment the integer. afterward, check if it has in fact changed from 0 to 1, in which case there were no waiters and the operation is done. this is the noncontended case which is fast and should be common. .pp in the contended case, the atomic increment changed the counter from \-1 (or some other negative number). if this is detected, there are waiters. user space should now set the counter to 1 and instruct the kernel to wake up any waiters using the .b futex_wake operation. .pp waiting on a futex, to "down" it, is the reverse operation. atomically decrement the counter and check if it changed to 0, in which case the operation is done and the futex was uncontended. in all other circumstances, the process should set the counter to \-1 and request that the kernel wait for another process to up the futex. this is done using the .b futex_wait operation. .pp the .br futex (2) system call can optionally be passed a timeout specifying how long the kernel should wait for the futex to be upped. in this case, semantics are more complex and the programmer is referred to .br futex (2) for more details. the same holds for asynchronous futex waiting. .sh versions initial futex support was merged in linux 2.5.7 but with different semantics from those described above. current semantics are available from linux 2.5.40 onward. .sh notes to reiterate, bare futexes are not intended as an easy-to-use abstraction for end users. implementors are expected to be assembly literate and to have read the sources of the futex user-space library referenced below. .pp this man page illustrates the most common use of the .br futex (2) primitives; it is by no means the only one. .\" .sh authors .\" .pp .\" futexes were designed and worked on by hubertus franke .\" (ibm thomas j. watson research center), .\" matthew kirkwood, ingo molnar (red hat) and .\" rusty russell (ibm linux technology center). .\" this page written by bert hubert. .sh see also .br clone (2), .br futex (2), .br get_robust_list (2), .br set_robust_list (2), .br set_tid_address (2), .br pthreads (7) .pp .ir "fuss, futexes and furwocks: fast userlevel locking in linux" (proceedings of the ottawa linux symposium 2002), futex example library, futex-*.tar.bz2 .ur ftp://ftp.kernel.org\:/pub\:/linux\:/kernel\:/people\:/rusty/ .ue . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2001 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th floor 3 2021-03-22 "" "linux programmer's manual" .sh name floor, floorf, floorl \- largest integral value not greater than argument .sh synopsis .nf .b #include .pp .bi "double floor(double " x ); .bi "float floorf(float " x ); .bi "long double floorl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br floorf (), .br floorl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the largest integral value that is not greater than .ir x . .pp for example, .ir floor(0.5) is 0.0, and .ir floor(\-0.5) is \-1.0. .sh return value these functions return the floor of .ir x . .pp if .i x is integral, +0, \-0, nan, or an infinity, .i x itself is returned. .sh errors no errors occur. posix.1-2001 documents a range error for overflows, but see notes. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br floor (), .br floorf (), .br floorl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh notes susv2 and posix.1-2001 contain text about overflow (which might set .i errno to .br erange , or raise an .b fe_overflow exception). in practice, the result cannot overflow on any current machine, so this error-handling stuff is just nonsense. .\" the posix.1-2001 application usage section discusses this point. (more precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of mantissa bits. for the ieee-754 standard 32-bit and 64-bit floating-point numbers the maximum value of the exponent is 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively, 53).) .sh see also .br ceil (3), .br lrint (3), .br nearbyint (3), .br rint (3), .br round (3), .br trunc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/access.2 .\" copyright (c) 1983, 1991 regents of the university of california. .\" and copyright (c) 2007, michael kerrisk .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)getpgrp.2 6.4 (berkeley) 3/10/91 .\" .\" modified 1993-07-24 by rik faith .\" modified 1995-04-15 by michael chastain : .\" added 'getpgid'. .\" modified 1996-07-21 by andries brouwer .\" modified 1996-11-06 by eric s. raymond .\" modified 1999-09-02 by michael haardt .\" modified 2002-01-18 by michael kerrisk .\" modified 2003-01-20 by andries brouwer .\" 2007-07-25, mtk, fairly substantial rewrites and rearrangements .\" of text. .\" .th setpgid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setpgid, getpgid, setpgrp, getpgrp \- set/get process group .sh synopsis .nf .b #include .pp .bi "int setpgid(pid_t " pid ", pid_t " pgid ); .bi "pid_t getpgid(pid_t " pid ); .pp .br "pid_t getpgrp(void);" " /* posix.1 version */" .bi "pid_t getpgrp(pid_t " pid ");\fr /* bsd version */" .pp .br "int setpgrp(void);" " /* system v version */" .bi "int setpgrp(pid_t " pid ", pid_t " pgid ");\fr /* bsd version */" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getpgid (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l .fi .pp .br setpgrp "() (posix.1):" .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source .fi .pp .br setpgrp "() (bsd)," .br getpgrp "() (bsd):" .nf [these are available only before glibc 2.19] _bsd_source && ! (_posix_source || _posix_c_source || _xopen_source || _gnu_source || _svid_source) .fi .sh description all of these interfaces are available on linux, and are used for getting and setting the process group id (pgid) of a process. the preferred, posix.1-specified ways of doing this are: .br getpgrp (void), for retrieving the calling process's pgid; and .br setpgid (), for setting a process's pgid. .pp .br setpgid () sets the pgid of the process specified by .i pid to .ir pgid . if .i pid is zero, then the process id of the calling process is used. if .i pgid is zero, then the pgid of the process specified by .i pid is made the same as its process id. if .br setpgid () is used to move a process from one process group to another (as is done by some shells when creating pipelines), both process groups must be part of the same session (see .br setsid (2) and .br credentials (7)). in this case, the \fipgid\fp specifies an existing process group to be joined and the session id of that group must match the session id of the joining process. .pp the posix.1 version of .br getpgrp (), which takes no arguments, returns the pgid of the calling process. .pp .br getpgid () returns the pgid of the process specified by .ir pid . if .i pid is zero, the process id of the calling process is used. (retrieving the pgid of a process other than the caller is rarely necessary, and the posix.1 .br getpgrp () is preferred for that task.) .pp the system\ v-style .br setpgrp (), which takes no arguments, is equivalent to .ir "setpgid(0,\ 0)" . .pp the bsd-specific .br setpgrp () call, which takes arguments .i pid and .ir pgid , is a wrapper function that calls .pp setpgid(pid, pgid) .pp .\" the true bsd setpgrp() system call differs in allowing the pgid .\" to be set to arbitrary values, rather than being restricted to .\" pgids in the same session. since glibc 2.19, the bsd-specific .br setpgrp () function is no longer exposed by .ir ; calls should be replaced with the .br setpgid () call shown above. .pp the bsd-specific .br getpgrp () call, which takes a single .i pid argument, is a wrapper function that calls .pp getpgid(pid) .pp since glibc 2.19, the bsd-specific .br getpgrp () function is no longer exposed by .ir ; calls should be replaced with calls to the posix.1 .br getpgrp () which takes no arguments (if the intent is to obtain the caller's pgid), or with the .br getpgid () call shown above. .sh return value on success, .br setpgid () and .br setpgrp () return zero. on error, \-1 is returned, and .i errno is set to indicate the error. .pp the posix.1 .br getpgrp () always returns the pgid of the caller. .pp .br getpgid (), and the bsd-specific .br getpgrp () return a process group on success. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces an attempt was made to change the process group id of one of the children of the calling process and the child had already performed an .br execve (2) .rb ( setpgid (), .br setpgrp ()). .tp .b einval .i pgid is less than 0 .rb ( setpgid (), .br setpgrp ()). .tp .b eperm an attempt was made to move a process into a process group in a different session, or to change the process group id of one of the children of the calling process and the child was in a different session, or to change the process group id of a session leader .rb ( setpgid (), .br setpgrp ()). .tp .b esrch for .br getpgid (): .i pid does not match any process. for .br setpgid (): .i pid is not the calling process and not a child of the calling process. .sh conforming to .br setpgid () and the version of .br getpgrp () with no arguments conform to posix.1-2001. .pp posix.1-2001 also specifies .br getpgid () and the version of .br setpgrp () that takes no arguments. (posix.1-2008 marks this .br setpgrp () specification as obsolete.) .pp the version of .br getpgrp () with one argument and the version of .br setpgrp () that takes two arguments derive from 4.2bsd, and are not specified by posix.1. .sh notes a child created via .br fork (2) inherits its parent's process group id. the pgid is preserved across an .br execve (2). .pp each process group is a member of a session and each process is a member of the session of which its process group is a member. (see .br credentials (7).) .pp a session can have a controlling terminal. at any time, one (and only one) of the process groups in the session can be the foreground process group for the terminal; the remaining process groups are in the background. if a signal is generated from the terminal (e.g., typing the interrupt key to generate .br sigint ), that signal is sent to the foreground process group. (see .br termios (3) for a description of the characters that generate signals.) only the foreground process group may .br read (2) from the terminal; if a background process group tries to .br read (2) from the terminal, then the group is sent a .b sigttin signal, which suspends it. the .br tcgetpgrp (3) and .br tcsetpgrp (3) functions are used to get/set the foreground process group of the controlling terminal. .pp the .br setpgid () and .br getpgrp () calls are used by programs such as .br bash (1) to create process groups in order to implement shell job control. .pp if the termination of a process causes a process group to become orphaned, and if any member of the newly orphaned process group is stopped, then a .b sighup signal followed by a .b sigcont signal will be sent to each process in the newly orphaned process group. .\" exit.3 refers to the following text: an orphaned process group is one in which the parent of every member of process group is either itself also a member of the process group or is a member of a process group in a different session (see also .br credentials (7)). .sh see also .br getuid (2), .br setsid (2), .br tcgetpgrp (3), .br tcsetpgrp (3), .br termios (3), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_getsetattr 2 2021-03-22 "linux" "linux programmer's manual" .sh name mq_getsetattr \- get/set message queue attributes .sh synopsis .nf .br "#include " " /* definition of " "struct mq_attr" " */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_mq_getsetattr, mqd_t " mqdes , .bi " const struct mq_attr *" newattr ", struct mq_attr *" oldattr ); .fi .sh description do not use this system call. .pp this is the low-level system call used to implement .br mq_getattr (3) and .br mq_setattr (3). for an explanation of how this system call operates, see the description of .br mq_setattr (3). .sh conforming to this interface is nonstandard; avoid its use. .sh notes never call it unless you are writing a c library! .sh see also .br mq_getattr (3), .br mq_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/resolver.3 .so man7/system_data_types.7 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setstackaddr 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setstackaddr, pthread_attr_getstackaddr \- set/get stack address attribute in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setstackaddr(pthread_attr_t *" attr \ ", void *" stackaddr ); .bi "int pthread_attr_getstackaddr(const pthread_attr_t *restrict " attr , .bi " void **restrict " stackaddr ); .pp compile and link with \fi\-pthread\fp. .fi .sh description these functions are obsolete: .b do not use them. use .br pthread_attr_setstack (3) and .br pthread_attr_getstack (3) instead. .pp the .br pthread_attr_setstackaddr () function sets the stack address attribute of the thread attributes object referred to by .i attr to the value specified in .ir stackaddr . this attribute specifies the location of the stack that should be used by a thread that is created using the thread attributes object .ir attr . .pp .i stackaddr should point to a buffer of at least .b pthread_stack_min bytes that was allocated by the caller. the pages of the allocated buffer should be both readable and writable. .pp the .br pthread_attr_getstackaddr () function returns the stack address attribute of the thread attributes object referred to by .i attr in the buffer pointed to by .ir stackaddr . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors no errors are defined (but applications should nevertheless handle a possible error return). .sh versions these functions are provided by glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setstackaddr (), .br pthread_attr_getstackaddr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001 specifies these functions but marks them as obsolete. posix.1-2008 removes the specification of these functions. .sh notes .i do not use these functions! they cannot be portably used, since they provide no way of specifying the direction of growth or the range of the stack. for example, on architectures with a stack that grows downward, .i stackaddr specifies the next address past the .i highest address of the allocated stack area. however, on architectures with a stack that grows upward, .i stackaddr specifies the .i lowest address in the allocated stack area. by contrast, the .i stackaddr used by .br pthread_attr_setstack (3) and .br pthread_attr_getstack (3), is always a pointer to the lowest address in the allocated stack area (and the .i stacksize argument specifies the range of the stack). .sh see also .br pthread_attr_init (3), .br pthread_attr_setstack (3), .br pthread_attr_setstacksize (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/clone.2 .so man3/getnetent.3 .\" copyright (c) 2019, microchip technology inc. and its subsidiaries .\" copyright (c) 2016-2018, microsemi corporation .\" copyright (c) 2016, pmc-sierra, inc. .\" written by kevin barnett .\" .\" %%%license_start(gplv2_oneline) .\" licensed under gnu general public license version 2 (gplv2) .\" %%%license_end .th smartpqi 4 2021-03-22 "linux" "linux programmer's manual" .sh name smartpqi \- microsemi smart family scsi driver .sh synopsis .sy "modprobe smartpqi" .rb [ disable_device_id_wildcards= { 0 | 1 }] .rb [ disable_heartbeat= { 0 | 1 }] .rb [ disable_ctrl_shutdown= { 0 | 1 }] .rb [ lockup_action= { none | reboot | panic }] .rb [ expose_ld_first= { 0 | 1 }] .rb [ hide_vsep= { 0 | 1 }] .ys .sh description .b smartpqi is a scsi driver for microsemi smart family controllers. .ss supported \f[bi]ioctl\fp\/() operations for compatibility with applications written for the .br cciss (4) and .br hpsa (4) drivers, many, but not all of the .br ioctl (2) operations supported by the .b hpsa driver are also supported by the .b smartpqi driver. the data structures used by these operations are described in the linux kernel source file .ir include/linux/cciss_ioctl.h . .tp .br cciss_deregdisk ", " cciss_regnewdisk ", " cciss_regnewd these operations all do exactly the same thing, which is to cause the driver to re-scan for new devices. this does exactly the same thing as writing to the .br smartpqi -specific host .i rescan attribute. .tp .b cciss_getpciinfo this operation returns the pci domain, bus, device, and function and "board id" (pci subsystem id). .tp .b cciss_getdrivver this operation returns the driver version in four bytes, encoded as: .ip .in +4n .ex (major_version << 28) | (minor_version << 24) | (release << 16) | revision .ee .in .tp .b cciss_passthru allows bmic and ciss commands to be passed through to the controller. .ss boot options .tp .br disable_device_id_wildcards= { 0 | 1 } disables support for device id wildcards. the default value is 0. .tp .br disable_heartbeat= { 0 | 1 } disables support for the controller's heartbeat check. this parameter is used for debugging purposes. the default value is 0, leaving the controller's heartbeat check active. .tp .br disable_ctrl_shutdown= { 0 | 1 } disables support for shutting down the controller in the event of a controller lockup. the default value is 0. .tp .br lockup_action= { none | reboot | panic } specifies the action the driver takes when a controller lockup is detected. the default action is .br none . .ts l l --- l l. parameter action \fbnone\fp take controller offline only \fbreboot\fp reboot the system \fbpanic\fp panic the system .te .tp .br expose_ld_first= { 0 | 1 } this option enables support for exposing logical devices to the operating system before physical devices. the default value is 0. .tp .br hide_vsep= { 0 | 1 } this option enables disabling exposure of the virtual sep to the host. this is usually associated with direct attached drives. the default value is 0. .sh files .ss device nodes logical drives are accessed via the scsi disk driver .ri ( sd ), tape drives via the scsi tape driver .ri ( st ), and the raid controller via the scsi generic driver .ri ( sg ), with device nodes named .ir /dev/sd *, .ir /dev/st *, and .ir /dev/sg *, respectively. .ss smartpqi-specific host attribute files in \f[bi]/sys\fp .tp .ir /sys/class/scsi_host/host * /rescan the host .i rescan attribute is a write-only attribute. writing to this attribute will cause the driver to scan for new, changed, or removed devices (e.g., hot-plugged tape drives, or newly configured or deleted logical drives) and notify the scsi mid-layer of any changes detected. usually this action is triggered automatically by configuration changes, so the user should not normally have to write to this file. doing so may be useful when hot-plugging devices such as tape drives or entire storage boxes containing pre-configured logical drives. .tp .ir /sys/class/scsi_host/host * /version the host .i version attribute is a read-only attribute. this attribute contains the driver version and the controller firmware version. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_host/host1/version driver: 1.1.2\-126 firmware: 1.29\-112 .ee .in .tp .ir /sys/class/scsi_host/host * /lockup_action the host .i lockup_action attribute is a read/write attribute. this attribute will cause the driver to perform a specific action in the unlikely event that a controller lockup has been detected. see .br options above for an explanation of the .i lockup_action values. .tp .ir /sys/class/scsi_host/host*/driver_version the .i driver_version attribute is read-only. this attribute contains the smartpqi driver version. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_host/host1/driver_version 1.1.2\-126 .ee .in .tp .ir /sys/class/scsi_host/host*/firmware_version the .i firmware_version attribute is read-only. this attribute contains the controller firmware version. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_host/host1/firmware_version 1.29\-112 .ee .in .tp .ir /sys/class/scsi_host/host*/model the .i model attribute is read-only. this attribute contains the product identification string of the controller. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_host/host1/model 1100\-16i .ee .in .tp .ir /sys/class/scsi_host/host*/serial_number the .i serial_number attribute is read-only. this attribute contains the unique identification number of the controller. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_host/host1/serial_number 6a316373777 .ee .in .tp .ir /sys/class/scsi_host/host*/vendor the .i vendor attribute is read-only. this attribute contains the vendor identification string of the controller. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_host/host1/vendor adaptec .ee .in .ss smartpqi-specific disk attribute files in \f[bi]/sys\fp in the file specifications below, .i c stands for the number of the appropriate scsi controller, .i b is the bus number, .i t the target number, and .i l is the logical unit number (lun). .tp .ir /sys/class/scsi_disk/ c : b : t : l /device/raid_level the .i raid_level attribute is read-only. this attribute contains the raid level of each logical drive. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_disk/4:0:0:0/device/raid_level raid 0 .ee .in .tp .ir /sys/class/scsi_disk/c : b : t : l/device/sas_address the .i sas_address attribute is read-only. this attribute contains the unique identifier of the disk. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_disk/1:0:3:0/device/sas_address 0x5001173d028543a2 .ee .in .tp .ir /sys/class/scsi_disk/c : b : t : l/device/ssd_smart_path_enabled the .i ssd_smart_path_enabled attribute is read-only. this attribute is for ioaccel-enabled volumes. (ioaccel is an alternative driver submission path that allows the driver to send i/o requests directly to backend scsi devices, bypassing the controller firmware. this results in an increase in performance. this method is used for hba disks and for logical volumes comprised of ssds.) contains 1 if ioaccel is enabled for the volume and 0 otherwise. .ip for example: .ip .in +4n .ex $ \c .b cat /sys/class/scsi_disk/1:0:3:0/device/ssd_smart_path_enabled 0 .ee .in .sh versions the .b smartpqi driver was added in linux 4.9. .sh notes .ss configuration to configure a microsemi smart family controller, refer to the user guide for the controller, which can be found by searching for the specific controller at .ur https://storage.microsemi.com/ .ue . .sh see also .br cciss (4), .br hpsa (4), .br sd (4), .br st (4) .pp .i documentation/abi/testing/sysfs\-bus\-pci\-devices\-cciss in the linux kernel source tree. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/setpgid.2 .\" copyright (c) 2013, 2016, 2017 by michael kerrisk .\" and copyright (c) 2012 by eric w. biederman .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th namespaces 7 2021-08-27 "linux" "linux programmer's manual" .sh name namespaces \- overview of linux namespaces .sh description a namespace wraps a global system resource in an abstraction that makes it appear to the processes within the namespace that they have their own isolated instance of the global resource. changes to the global resource are visible to other processes that are members of the namespace, but are invisible to other processes. one use of namespaces is to implement containers. .pp this page provides pointers to information on the various namespace types, describes the associated .i /proc files, and summarizes the apis for working with namespaces. .\" .ss namespace types the following table shows the namespace types available on linux. the second column of the table shows the flag value that is used to specify the namespace type in various apis. the third column identifies the manual page that provides details on the namespace type. the last column is a summary of the resources that are isolated by the namespace type. .ad l .nh .ts lb lb lb lb l1 lb1 l1 l. namespace flag page isolates cgroup clone_newcgroup \fbcgroup_namespaces\fp(7) t{ cgroup root directory t} ipc clone_newipc \fbipc_namespaces\fp(7) t{ system v ipc, posix message queues t} network clone_newnet \fbnetwork_namespaces\fp(7) t{ network devices, stacks, ports, etc. t} mount clone_newns \fbmount_namespaces\fp(7) mount points pid clone_newpid \fbpid_namespaces\fp(7) process ids time clone_newtime \fbtime_namespaces\fp(7) t{ boot and monotonic clocks t} user clone_newuser \fbuser_namespaces\fp(7) t{ user and group ids t} uts clone_newuts \fbuts_namespaces\fp(7) t{ hostname and nis domain name t} .te .hy .ad .\" .\" ==================== the namespaces api ==================== .\" .ss the namespaces api as well as various .i /proc files described below, the namespaces api includes the following system calls: .tp .br clone (2) the .br clone (2) system call creates a new process. if the .i flags argument of the call specifies one or more of the .b clone_new* flags listed above, then new namespaces are created for each flag, and the child process is made a member of those namespaces. (this system call also implements a number of features unrelated to namespaces.) .tp .br setns (2) the .br setns (2) system call allows the calling process to join an existing namespace. the namespace to join is specified via a file descriptor that refers to one of the .ir /proc/[pid]/ns files described below. .tp .br unshare (2) the .br unshare (2) system call moves the calling process to a new namespace. if the .i flags argument of the call specifies one or more of the .b clone_new* flags listed above, then new namespaces are created for each flag, and the calling process is made a member of those namespaces. (this system call also implements a number of features unrelated to namespaces.) .tp .br ioctl (2) various .br ioctl (2) operations can be used to discover information about namespaces. these operations are described in .br ioctl_ns (2). .pp creation of new namespaces using .br clone (2) and .br unshare (2) in most cases requires the .br cap_sys_admin capability, since, in the new namespace, the creator will have the power to change global resources that are visible to other processes that are subsequently created in, or join the namespace. user namespaces are the exception: since linux 3.8, no privilege is required to create a user namespace. .\" .\" ==================== the /proc/[pid]/ns/ directory ==================== .\" .ss the /proc/[pid]/ns/ directory each process has a .ir /proc/[pid]/ns/ .\" see commit 6b4e306aa3dc94a0545eb9279475b1ab6209a31f subdirectory containing one entry for each namespace that supports being manipulated by .br setns (2): .pp .in +4n .ex $ \fbls \-l /proc/$$/ns | awk \(aq{print $1, $9, $10, $11}\(aq\fp total 0 lrwxrwxrwx. cgroup \-> cgroup:[4026531835] lrwxrwxrwx. ipc \-> ipc:[4026531839] lrwxrwxrwx. mnt \-> mnt:[4026531840] lrwxrwxrwx. net \-> net:[4026531969] lrwxrwxrwx. pid \-> pid:[4026531836] lrwxrwxrwx. pid_for_children \-> pid:[4026531834] lrwxrwxrwx. time \-> time:[4026531834] lrwxrwxrwx. time_for_children \-> time:[4026531834] lrwxrwxrwx. user \-> user:[4026531837] lrwxrwxrwx. uts \-> uts:[4026531838] .ee .in .pp bind mounting (see .br mount (2)) one of the files in this directory to somewhere else in the filesystem keeps the corresponding namespace of the process specified by .i pid alive even if all processes currently in the namespace terminate. .pp opening one of the files in this directory (or a file that is bind mounted to one of these files) returns a file handle for the corresponding namespace of the process specified by .ir pid . as long as this file descriptor remains open, the namespace will remain alive, even if all processes in the namespace terminate. the file descriptor can be passed to .br setns (2). .pp in linux 3.7 and earlier, these files were visible as hard links. since linux 3.8, .\" commit bf056bfa80596a5d14b26b17276a56a0dcb080e5 they appear as symbolic links. if two processes are in the same namespace, then the device ids and inode numbers of their .ir /proc/[pid]/ns/xxx symbolic links will be the same; an application can check this using the .i stat.st_dev .\" eric biederman: "i reserve the right for st_dev to be significant .\" when comparing namespaces." .\" https://lore.kernel.org/lkml/87poky5ca9.fsf@xmission.com/ .\" re: documenting the ioctl interfaces to discover relationships... .\" date: mon, 12 dec 2016 11:30:38 +1300 and .i stat.st_ino fields returned by .br stat (2). the content of this symbolic link is a string containing the namespace type and inode number as in the following example: .pp .in +4n .ex $ \fbreadlink /proc/$$/ns/uts\fp uts:[4026531838] .ee .in .pp the symbolic links in this subdirectory are as follows: .tp .ir /proc/[pid]/ns/cgroup " (since linux 4.6)" this file is a handle for the cgroup namespace of the process. .tp .ir /proc/[pid]/ns/ipc " (since linux 3.0)" this file is a handle for the ipc namespace of the process. .tp .ir /proc/[pid]/ns/mnt " (since linux 3.8)" .\" commit 8823c079ba7136dc1948d6f6dcb5f8022bde438e this file is a handle for the mount namespace of the process. .tp .ir /proc/[pid]/ns/net " (since linux 3.0)" this file is a handle for the network namespace of the process. .tp .ir /proc/[pid]/ns/pid " (since linux 3.8)" .\" commit 57e8391d327609cbf12d843259c968b9e5c1838f this file is a handle for the pid namespace of the process. this handle is permanent for the lifetime of the process (i.e., a process's pid namespace membership never changes). .tp .ir /proc/[pid]/ns/pid_for_children " (since linux 4.12)" .\" commit eaa0d190bfe1ed891b814a52712dcd852554cb08 this file is a handle for the pid namespace of child processes created by this process. this can change as a consequence of calls to .br unshare (2) and .br setns (2) (see .br pid_namespaces (7)), so the file may differ from .ir /proc/[pid]/ns/pid . the symbolic link gains a value only after the first child process is created in the namespace. (beforehand, .br readlink (2) of the symbolic link will return an empty buffer.) .tp .ir /proc/[pid]/ns/time " (since linux 5.6)" this file is a handle for the time namespace of the process. .tp .ir /proc/[pid]/ns/time_for_children " (since linux 5.6)" this file is a handle for the time namespace of child processes created by this process. this can change as a consequence of calls to .br unshare (2) and .br setns (2) (see .br time_namespaces (7)), so the file may differ from .ir /proc/[pid]/ns/time . .tp .ir /proc/[pid]/ns/user " (since linux 3.8)" .\" commit cde1975bc242f3e1072bde623ef378e547b73f91 this file is a handle for the user namespace of the process. .tp .ir /proc/[pid]/ns/uts " (since linux 3.0)" this file is a handle for the uts namespace of the process. .pp permission to dereference or read .rb ( readlink (2)) these symbolic links is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .\" .\" ==================== the /proc/sys/user directory ==================== .\" .ss the /proc/sys/user directory the files in the .i /proc/sys/user directory (which is present since linux 4.9) expose limits on the number of namespaces of various types that can be created. the files are as follows: .tp .ir max_cgroup_namespaces the value in this file defines a per-user limit on the number of cgroup namespaces that may be created in the user namespace. .tp .ir max_ipc_namespaces the value in this file defines a per-user limit on the number of ipc namespaces that may be created in the user namespace. .tp .ir max_mnt_namespaces the value in this file defines a per-user limit on the number of mount namespaces that may be created in the user namespace. .tp .ir max_net_namespaces the value in this file defines a per-user limit on the number of network namespaces that may be created in the user namespace. .tp .ir max_pid_namespaces the value in this file defines a per-user limit on the number of pid namespaces that may be created in the user namespace. .tp .ir max_time_namespaces " (since linux 5.7)" .\" commit eeec26d5da8248ea4e240b8795bb4364213d3247 the value in this file defines a per-user limit on the number of time namespaces that may be created in the user namespace. .tp .ir max_user_namespaces the value in this file defines a per-user limit on the number of user namespaces that may be created in the user namespace. .tp .ir max_uts_namespaces the value in this file defines a per-user limit on the number of uts namespaces that may be created in the user namespace. .pp note the following details about these files: .ip * 3 the values in these files are modifiable by privileged processes. .ip * the values exposed by these files are the limits for the user namespace in which the opening process resides. .ip * the limits are per-user. each user in the same user namespace can create namespaces up to the defined limit. .ip * the limits apply to all users, including uid 0. .ip * these limits apply in addition to any other per-namespace limits (such as those for pid and user namespaces) that may be enforced. .ip * upon encountering these limits, .br clone (2) and .br unshare (2) fail with the error .br enospc . .ip * for the initial user namespace, the default value in each of these files is half the limit on the number of threads that may be created .ri ( /proc/sys/kernel/threads\-max ). in all descendant user namespaces, the default value in each file is .br maxint . .ip * when a namespace is created, the object is also accounted against ancestor namespaces. more precisely: .rs .ip + 3 each user namespace has a creator uid. .ip + when a namespace is created, it is accounted against the creator uids in each of the ancestor user namespaces, and the kernel ensures that the corresponding namespace limit for the creator uid in the ancestor namespace is not exceeded. .ip + the aforementioned point ensures that creating a new user namespace cannot be used as a means to escape the limits in force in the current user namespace. .re .\" .ss namespace lifetime absent any other factors, a namespace is automatically torn down when the last process in the namespace terminates or leaves the namespace. however, there are a number of other factors that may pin a namespace into existence even though it has no member processes. these factors include the following: .ip * 3 an open file descriptor or a bind mount exists for the corresponding .ir /proc/[pid]/ns/* file. .ip * the namespace is hierarchical (i.e., a pid or user namespace), and has a child namespace. .ip * it is a user namespace that owns one or more nonuser namespaces. .ip * it is a pid namespace, and there is a process that refers to the namespace via a .ir /proc/[pid]/ns/pid_for_children symbolic link. .ip * it is a time namespace, and there is a process that refers to the namespace via a .ir /proc/[pid]/ns/time_for_children symbolic link. .ip * it is an ipc namespace, and a corresponding mount of an .i mqueue filesystem (see .br mq_overview (7)) refers to this namespace. .ip * it is a pid namespace, and a corresponding mount of a .br proc (5) filesystem refers to this namespace. .sh examples see .br clone (2) and .br user_namespaces (7). .sh see also .br nsenter (1), .br readlink (1), .br unshare (1), .br clone (2), .br ioctl_ns (2), .br setns (2), .br unshare (2), .br proc (5), .br capabilities (7), .br cgroup_namespaces (7), .br cgroups (7), .br credentials (7), .br ipc_namespaces (7), .br network_namespaces (7), .br pid_namespaces (7), .br user_namespaces (7), .br uts_namespaces (7), .br lsns (8), .br switch_root (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sigaltstack.2 .\" no new programs should use sigstack(3). .\" sigaltstack(2) briefly discusses sigstack(3), so point the user there. .so man3/finite.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 17:45:39 1993 by rik faith (faith@cs.unc.edu) .\" modified 2000-02-13 by nicolás lichtmaier .th toupper 3 2021-03-22 "gnu" "linux programmer's manual" .sh name toupper, tolower, toupper_l, tolower_l \- convert uppercase or lowercase .sh synopsis .nf .b #include .pp .bi "int toupper(int " "c" ); .bi "int tolower(int " "c" ); .pp .bi "int toupper_l(int " c ", locale_t " locale ); .bi "int tolower_l(int " c ", locale_t " locale ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br toupper_l (), .br tolower_l (): .nf since glibc 2.10: _xopen_source >= 700 before glibc 2.10: _gnu_source .fi .sh description these functions convert lowercase letters to uppercase, and vice versa. .pp if .i c is a lowercase letter, .br toupper () returns its uppercase equivalent, if an uppercase representation exists in the current locale. otherwise, it returns .ir c . the .br toupper_l () function performs the same task, but uses the locale referred to by the locale handle .ir locale . .pp if .i c is an uppercase letter, .br tolower () returns its lowercase equivalent, if a lowercase representation exists in the current locale. otherwise, it returns .ir c . the .br tolower_l () function performs the same task, but uses the locale referred to by the locale handle .ir locale . .pp if .i c is neither an .i "unsigned char" value nor .br eof , the behavior of these functions is undefined. .pp the behavior of .br toupper_l () and .br tolower_l () is undefined if .i locale is the special locale object .b lc_global_locale (see .br duplocale (3)) or is not a valid locale object handle. .sh return value the value returned is that of the converted letter, or .i c if the conversion was not possible. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br toupper (), .br tolower (), .br toupper_l (), .br tolower_l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br toupper (), .br tolower (): c89, c99, 4.3bsd, posix.1-2001, posix.1-2008. .pp .br toupper_l (), .br tolower_l (): posix.1-2008. .sh notes the standards require that the argument .i c for these functions is either .b eof or a value that is representable in the type .ir "unsigned char" . if the argument .i c is of type .ir char , it must be cast to .ir "unsigned char" , as in the following example: .pp .in +4n .ex char c; \&... res = toupper((unsigned char) c); .ee .in .pp this is necessary because .i char may be the equivalent .ir "signed char" , in which case a byte where the top bit is set would be sign extended when converting to .ir int , yielding a value that is outside the range of .ir "unsigned char" . .pp the details of what constitutes an uppercase or lowercase letter depend on the locale. for example, the default .b """c""" locale does not know about umlauts, so no conversion is done for them. .pp in some non-english locales, there are lowercase letters with no corresponding uppercase equivalent; .\" fixme one day the statement about "sharp s" needs to be reworked, .\" since there is nowadays a capital "sharp s" that has a codepoint .\" in unicode 5.0; see https://en.wikipedia.org/wiki/capital_%e1%ba%9e the german sharp s is one example. .sh see also .br isalpha (3), .br newlocale (3), .br setlocale (3), .br towlower (3), .br towupper (3), .br uselocale (3), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ceil.3 .so man3/termios.3 .\" copyright (c) 2016 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th ntp_gettime 3 2021-03-22 "linux" "linux programmer's manual" .sh name ntp_gettime, ntp_gettimex \- get time parameters (ntp daemon interface) .sh synopsis .nf .b #include .pp .bi "int ntp_gettime(struct ntptimeval *" ntv ); .bi "int ntp_gettimex(struct ntptimeval *" ntv ); .fi .sh description both of these apis return information to the caller via the .i ntv argument, a structure of the following type: .pp .in +4n .ex struct ntptimeval { struct timeval time; /* current time */ long maxerror; /* maximum error */ long esterror; /* estimated error */ long tai; /* tai offset */ /* further padding bytes allowing for future expansion */ }; .ee .in .pp the fields of this structure are as follows: .tp .i time the current time, expressed as a .i timeval structure: .ip .in +4n .ex struct timeval { time_t tv_sec; /* seconds since the epoch */ suseconds_t tv_usec; /* microseconds */ }; .ee .in .tp .i maxerror maximum error, in microseconds. this value can be initialized by .br ntp_adjtime (3), and is increased periodically (on linux: each second), but is clamped to an upper limit (the kernel constant .br ntp_phase_max , with a value of 16,000). .tp .i esterror estimated error, in microseconds. this value can be set via .br ntp_adjtime (3) to contain an estimate of the difference between the system clock and the true time. this value is not used inside the kernel. .tp .i tai tai (atomic international time) offset. .pp .br ntp_gettime () returns an .i ntptimeval structure in which the .ir time , .ir maxerror , and .ir esterror fields are filled in. .pp .br ntp_gettimex () performs the same task as .br ntp_gettime (), but also returns information in the .i tai field. .sh return value the return values for .br ntp_gettime () and .br ntp_gettimex () are as for .br adjtimex (2). given a correct pointer argument, these functions always succeed. .\" fixme . the info page incorrectly describes the return values. .sh versions the .br ntp_gettime () function is available since glibc 2.1. the .br ntp_gettimex () function is available since glibc 2.12. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ntp_gettime (), .br ntp_gettimex () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br ntp_gettime () is described in the ntp kernel application program interface. .br ntp_gettimex () is a gnu extension. .sh see also .br adjtimex (2), .br ntp_adjtime (3), .br time (7) .pp .ad l .ur http://www.slac.stanford.edu/comp/unix/\:package/\:rtems/\:src/\:ssrlapps/\:ntpnanoclock/\:api.htm ntp "kernel application program interface" .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdio_ext.3 .so man3/stailq.3 .so man3/sinh.3 .so man7/system_data_types.7 .so man2/getdents.2 .so man3/acosh.3 .so man3/pthread_attr_setdetachstate.3 .so man3/cpu_set.3 .so man3/fread.3 .\" copyright (c) 2005 michael kerrisk .\" based on earlier work by faith@cs.unc.edu and .\" mike battersby .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2005-09-15, mtk, created new page by splitting off from sigaction.2 .\" .th sigprocmask 2 2021-03-22 "linux" "linux programmer's manual" .sh name sigprocmask, rt_sigprocmask \- examine and change blocked signals .sh synopsis .b #include .pp .nf /* prototype for the glibc wrapper function */ .bi "int sigprocmask(int " how ", const sigset_t *restrict " set , .bi " sigset_t *restrict " oldset ); .pp .br "#include " " /* definition of " sig_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp /* prototype for the underlying system call */ .bi "int syscall(sys_rt_sigprocmask, int " how ", const kernel_sigset_t *" set , .bi " kernel_sigset_t *" oldset ", size_t " sigsetsize ); .pp /* prototype for the legacy system call (deprecated) */ .bi "int syscall(sys_sigprocmask, int " how ", const old_kernel_sigset_t *" set , .bi " old_kernel_sigset_t *" oldset ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigprocmask (): .nf _posix_c_source .fi .sh description .br sigprocmask () is used to fetch and/or change the signal mask of the calling thread. the signal mask is the set of signals whose delivery is currently blocked for the caller (see also .br signal (7) for more details). .pp the behavior of the call is dependent on the value of .ir how , as follows. .tp .b sig_block the set of blocked signals is the union of the current set and the .i set argument. .tp .b sig_unblock the signals in .i set are removed from the current set of blocked signals. it is permissible to attempt to unblock a signal which is not blocked. .tp .b sig_setmask the set of blocked signals is set to the argument .ir set . .pp if .i oldset is non-null, the previous value of the signal mask is stored in .ir oldset . .pp if .i set is null, then the signal mask is unchanged (i.e., .i how is ignored), but the current value of the signal mask is nevertheless returned in .i oldset (if it is not null). .pp a set of functions for modifying and inspecting variables of type .i sigset_t ("signal sets") is described in .br sigsetops (3). .pp the use of .br sigprocmask () is unspecified in a multithreaded process; see .br pthread_sigmask (3). .sh return value .br sigprocmask () returns 0 on success. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault the .i set or .i oldset argument points outside the process's allocated address space. .tp .b einval either the value specified in .i how was invalid or the kernel does not support the size passed in .i sigsetsize. .sh conforming to posix.1-2001, posix.1-2008. .sh notes it is not possible to block .br sigkill " or " sigstop . attempts to do so are silently ignored. .pp each of the threads in a process has its own signal mask. .pp a child created via .br fork (2) inherits a copy of its parent's signal mask; the signal mask is preserved across .br execve (2). .pp if .br sigbus , .br sigfpe , .br sigill , or .b sigsegv are generated while they are blocked, the result is undefined, unless the signal was generated by .br kill (2), .br sigqueue (3), or .br raise (3). .pp see .br sigsetops (3) for details on manipulating signal sets. .pp note that it is permissible (although not very useful) to specify both .i set and .i oldset as null. .\" .ss c library/kernel differences the kernel's definition of .ir sigset_t differs in size from that used by the c library. in this manual page, the former is referred to as .i kernel_sigset_t (it is nevertheless named .i sigset_t in the kernel sources). .pp the glibc wrapper function for .br sigprocmask () silently ignores attempts to block the two real-time signals that are used internally by the nptl threading implementation. see .br nptl (7) for details. .pp the original linux system call was named .br sigprocmask (). however, with the addition of real-time signals in linux 2.2, the fixed-size, 32-bit .ir sigset_t (referred to as .ir old_kernel_sigset_t in this manual page) type supported by that system call was no longer fit for purpose. consequently, a new system call, .br rt_sigprocmask (), was added to support an enlarged .ir sigset_t type (referred to as .ir kernel_sigset_t in this manual page). the new system call takes a fourth argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the signal sets in .ir set and .ir oldset . this argument is currently required to have a fixed architecture specific value (equal to .ir sizeof(kernel_sigset_t) ). .\" sizeof(kernel_sigset_t) == _nsig / 8, .\" which equals to 8 on most architectures, but e.g. on mips it's 16. .pp the glibc .br sigprocmask () wrapper function hides these details from us, transparently calling .br rt_sigprocmask () when the kernel provides it. .\" .sh see also .br kill (2), .br pause (2), .br sigaction (2), .br signal (2), .br sigpending (2), .br sigsuspend (2), .br pthread_sigmask (3), .br sigqueue (3), .br sigsetops (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cacos.3 .so man3/qsort.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_testcancel 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_testcancel \- request delivery of any pending cancellation request .sh synopsis .nf .b #include .pp .b void pthread_testcancel(void); .pp compile and link with \fi\-pthread\fp. .fi .sh description calling .br pthread_testcancel () creates a cancellation point within the calling thread, so that a thread that is otherwise executing code that contains no cancellation points will respond to a cancellation request. .pp if cancelability is disabled (using .br pthread_setcancelstate (3)), or no cancellation request is pending, then a call to .br pthread_testcancel () has no effect. .sh return value this function does not return a value. if the calling thread is canceled as a consequence of a call to this function, then the function does not return. .sh errors this function always succeeds. .\" sh versions .\" available since glibc 2.0 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_testcancel () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples see .br pthread_cleanup_push (3). .sh see also .br pthread_cancel (3), .br pthread_cleanup_push (3), .br pthread_setcancelstate (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2011 by andi kleen .\" and copyright (c) 2011 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" syscall added in following commit .\" commit a2e2725541fad72416326798c2d7fa4dafb7d337 .\" author: arnaldo carvalho de melo .\" date: mon oct 12 23:40:10 2009 -0700 .\" .th recvmmsg 2 2020-11-01 "linux" "linux programmer's manual" .sh name recvmmsg \- receive multiple messages on a socket .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .bi "#include " .pp .bi "int recvmmsg(int " sockfd ", struct mmsghdr *" msgvec \ ", unsigned int " vlen "," .bi " int " flags ", struct timespec *" timeout ");" .fi .sh description the .br recvmmsg () system call is an extension of .br recvmsg (2) that allows the caller to receive multiple messages from a socket using a single system call. (this has performance benefits for some applications.) a further extension over .br recvmsg (2) is support for a timeout on the receive operation. .pp the .i sockfd argument is the file descriptor of the socket to receive data from. .pp the .i msgvec argument is a pointer to an array of .i mmsghdr structures. the size of this array is specified in .ir vlen . .pp the .i mmsghdr structure is defined in .i as: .pp .in +4n .ex struct mmsghdr { struct msghdr msg_hdr; /* message header */ unsigned int msg_len; /* number of received bytes for header */ }; .ee .in .pp the .i msg_hdr field is a .i msghdr structure, as described in .br recvmsg (2). the .i msg_len field is the number of bytes returned for the message in the entry. this field has the same value as the return value of a single .br recvmsg (2) on the header. .pp the .i flags argument contains flags ored together. the flags are the same as documented for .br recvmsg (2), with the following addition: .tp .br msg_waitforone " (since linux 2.6.34)" turns on .b msg_dontwait after the first message has been received. .pp the .i timeout argument points to a .i struct timespec (see .br clock_gettime (2)) defining a timeout (seconds plus nanoseconds) for the receive operation .ri ( "but see bugs!" ). (this interval will be rounded up to the system clock granularity, and kernel scheduling delays mean that the blocking interval may overrun by a small amount.) if .i timeout is null, then the operation blocks indefinitely. .pp a blocking .br recvmmsg () call blocks until .i vlen messages have been received or until the timeout expires. a nonblocking call reads as many messages as are available (up to the limit specified by .ir vlen ) and returns immediately. .pp on return from .br recvmmsg (), successive elements of .ir msgvec are updated to contain information about each received message: .i msg_len contains the size of the received message; the subfields of .i msg_hdr are updated as described in .br recvmsg (2). the return value of the call indicates the number of elements of .i msgvec that have been updated. .sh return value on success, .br recvmmsg () returns the number of messages received in .ir msgvec ; on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors errors are as for .br recvmsg (2). in addition, the following error can occur: .tp .b einval .i timeout is invalid. .pp see also bugs. .sh versions the .br recvmmsg () system call was added in linux 2.6.33. support in glibc was added in version 2.12. .sh conforming to .br recvmmsg () is linux-specific. .sh bugs the .i timeout argument does not work as intended. .\" fixme . https://bugzilla.kernel.org/show_bug.cgi?id=75371 .\" http://thread.gmane.org/gmane.linux.man/5677 the timeout is checked only after the receipt of each datagram, so that if up to .i vlen\-1 datagrams are received before the timeout expires, but then no further datagrams are received, the call will block forever. .pp if an error occurs after at least one message has been received, the call succeeds, and returns the number of messages received. the error code is expected to be returned on a subsequent call to .br recvmmsg (). in the current implementation, however, the error code can be overwritten in the meantime by an unrelated network event on a socket, for example an incoming icmp packet. .sh examples the following program uses .br recvmmsg () to receive multiple messages on a socket and stores them in multiple buffers. the call returns if all buffers are filled or if the timeout specified has expired. .pp the following snippet periodically generates udp datagrams containing a random number: .pp .in +4n .ex .rb "$" " while true; do echo $random > /dev/udp/127.0.0.1/1234;" .b " sleep 0.25; done" .ee .in .pp these datagrams are read by the example application, which can give the following output: .pp .in +4n .ex .rb "$" " ./a.out" 5 messages received 1 11782 2 11345 3 304 4 13514 5 28421 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include int main(void) { #define vlen 10 #define bufsize 200 #define timeout 1 int sockfd, retval; struct sockaddr_in addr; struct mmsghdr msgs[vlen]; struct iovec iovecs[vlen]; char bufs[vlen][bufsize+1]; struct timespec timeout; sockfd = socket(af_inet, sock_dgram, 0); if (sockfd == \-1) { perror("socket()"); exit(exit_failure); } addr.sin_family = af_inet; addr.sin_addr.s_addr = htonl(inaddr_loopback); addr.sin_port = htons(1234); if (bind(sockfd, (struct sockaddr *) &addr, sizeof(addr)) == \-1) { perror("bind()"); exit(exit_failure); } memset(msgs, 0, sizeof(msgs)); for (int i = 0; i < vlen; i++) { iovecs[i].iov_base = bufs[i]; iovecs[i].iov_len = bufsize; msgs[i].msg_hdr.msg_iov = &iovecs[i]; msgs[i].msg_hdr.msg_iovlen = 1; } timeout.tv_sec = timeout; timeout.tv_nsec = 0; retval = recvmmsg(sockfd, msgs, vlen, 0, &timeout); if (retval == \-1) { perror("recvmmsg()"); exit(exit_failure); } printf("%d messages received\en", retval); for (int i = 0; i < retval; i++) { bufs[i][msgs[i].msg_len] = 0; printf("%d %s", i+1, bufs[i]); } exit(exit_success); } .ee .sh see also .br clock_gettime (2), .br recvmsg (2), .br sendmmsg (2), .br sendmsg (2), .br socket (2), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" and copyright (c) 2020 by alejandro colomar .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" .th tailq 3 2021-03-22 "gnu" "linux programmer's manual" .sh name tailq_concat, tailq_empty, tailq_entry, tailq_first, tailq_foreach, .\"tailq_foreach_from, .\"tailq_foreach_from_safe, tailq_foreach_reverse, .\"tailq_foreach_reverse_from, .\"tailq_foreach_reverse_from_safe, .\"tailq_foreach_reverse_safe, .\"tailq_foreach_safe, tailq_head, tailq_head_initializer, tailq_init, tailq_insert_after, tailq_insert_before, tailq_insert_head, tailq_insert_tail, tailq_last, tailq_next, tailq_prev, tailq_remove .\"tailq_swap \- implementation of a doubly linked tail queue .sh synopsis .nf .b #include .pp .b tailq_entry(type); .pp .b tailq_head(headname, type); .bi "tailq_head tailq_head_initializer(tailq_head " head ); .bi "void tailq_init(tailq_head *" head ); .pp .bi "int tailq_empty(tailq_head *" head ); .pp .bi "void tailq_insert_head(tailq_head *" head , .bi " struct type *" elm ", tailq_entry " name ); .bi "void tailq_insert_tail(tailq_head *" head , .bi " struct type *" elm ", tailq_entry " name ); .bi "void tailq_insert_before(struct type *" listelm , .bi " struct type *" elm ", tailq_entry " name ); .bi "void tailq_insert_after(tailq_head *" head ", struct type *" listelm , .bi " struct type *" elm ", tailq_entry " name ); .pp .bi "struct type *tailq_first(tailq_head *" head ); .bi "struct type *tailq_last(tailq_head *" head ", headname);" .bi "struct type *tailq_prev(struct type *" elm ", headname, tailq_entry " name ); .bi "struct type *tailq_next(struct type *" elm ", tailq_entry " name ); .pp .bi "tailq_foreach(struct type *" var ", tailq_head *" head , .bi " tailq_entry " name ); .\" .bi "tailq_foreach_from(struct type *" var ", tailq_head *" head , .\" .bi " tailq_entry " name ); .bi "tailq_foreach_reverse(struct type *" var ", tailq_head *" head ", headname," .bi " tailq_entry " name ); .\" .bi "tailq_foreach_reverse_from(struct type *" var ", tailq_head *" head ", headname," .\" .bi " tailq_entry " name ); .\" .pp .\" .bi "tailq_foreach_safe(struct type *" var ", tailq_head *" head , .\" .bi " tailq_entry " name , .\" .bi " struct type *" temp_var ); .\" .bi "tailq_foreach_from_safe(struct type *" var ", tailq_head *" head , .\" .bi " tailq_entry " name , .\" .bi " struct type *" temp_var ); .\" .bi "tailq_foreach_reverse_safe(struct type *" var ", tailq_head *" head , .\" .bi " headname, tailq_entry " name , .\" .bi " struct type *" temp_var ); .\" .bi "tailq_foreach_reverse_from_safe(struct type *" var ", tailq_head *" head , .\" .bi " headname, tailq_entry " name , .\" .bi " struct type *" temp_var ); .pp .bi "void tailq_remove(tailq_head *" head ", struct type *" elm , .bi " tailq_entry " name ); .pp .bi "void tailq_concat(tailq_head *" head1 ", tailq_head *" head2 , .bi " tailq_entry " name ); .\" .bi "void tailq_swap(tailq_head *" head1 ", tailq_head *" head2 ", type," .\" .bi " tailq_entry " name ); .fi .sh description these macros define and operate on doubly linked tail queues. .pp in the macro definitions, .i type is the name of a user defined structure, that must contain a field of type .ir tailq_entry , named .ir name . the argument .i headname is the name of a user defined structure that must be declared using the macro .br tailq_head (). .ss creation a tail queue is headed by a structure defined by the .br tailq_head () macro. this structure contains a pair of pointers, one to the first element in the queue and the other to the last element in the queue. the elements are doubly linked so that an arbitrary element can be removed without traversing the queue. new elements can be added to the queue after an existing element, before an existing element, at the head of the queue, or at the end of the queue. a .i tailq_head structure is declared as follows: .pp .in +4 .ex tailq_head(headname, type) head; .ee .in .pp where .i struct headname is the structure to be defined, and .i struct type is the type of the elements to be linked into the queue. a pointer to the head of the queue can later be declared as: .pp .in +4 .ex struct headname *headp; .ee .in .pp (the names .i head and .i headp are user selectable.) .pp .br tailq_entry () declares a structure that connects the elements in the queue. .pp .br tailq_head_initializer () evaluates to an initializer for the queue .ir head . .pp .br tailq_init () initializes the queue referenced by .pp .br tailq_empty () evaluates to true if there are no items on the queue. .ir head . .ss insertion .br tailq_insert_head () inserts the new element .i elm at the head of the queue. .pp .br tailq_insert_tail () inserts the new element .i elm at the end of the queue. .pp .br tailq_insert_before () inserts the new element .i elm before the element .ir listelm . .pp .br tailq_insert_after () inserts the new element .i elm after the element .ir listelm . .ss traversal .br tailq_first () returns the first item on the queue, or null if the queue is empty. .pp .br tailq_last () returns the last item on the queue. if the queue is empty the return value is null. .pp .br tailq_prev () returns the previous item on the queue, or null if this item is the first. .pp .br tailq_next () returns the next item on the queue, or null if this item is the last. .pp .br tailq_foreach () traverses the queue referenced by .i head in the forward direction, assigning each element in turn to .ir var . .i var is set to null if the loop completes normally, or if there were no elements. .\" .pp .\" .br tailq_foreach_from () .\" behaves identically to .\" .br tailq_foreach () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found tailq element and begins the loop at .\" .i var .\" instead of the first element in the tailq referenced by .\" .ir head . .pp .br tailq_foreach_reverse () traverses the queue referenced by .i head in the reverse direction, assigning each element in turn to .ir var . .\" .pp .\" .br tailq_foreach_reverse_from () .\" behaves identically to .\" .br tailq_foreach_reverse () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found tailq element and begins the reverse loop at .\" .i var .\" instead of the last element in the tailq referenced by .\" .ir head . .\" .pp .\" .br tailq_foreach_safe () .\" and .\" .br tailq_foreach_reverse_safe () .\" traverse the list referenced by .\" .i head .\" in the forward or reverse direction respectively, .\" assigning each element in turn to .\" .ir var . .\" however, unlike their unsafe counterparts, .\" .br tailq_foreach () .\" and .\" .br tailq_foreach_reverse () .\" permit to both remove .\" .i var .\" as well as free it from within the loop safely without interfering with the .\" traversal. .\" .pp .\" .br tailq_foreach_from_safe () .\" behaves identically to .\" .br tailq_foreach_safe () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found tailq element and begins the loop at .\" .i var .\" instead of the first element in the tailq referenced by .\" .ir head . .\" .pp .\" .br tailq_foreach_reverse_from_safe () .\" behaves identically to .\" .br tailq_foreach_reverse_safe () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found tailq element and begins the reverse loop at .\" .i var .\" instead of the last element in the tailq referenced by .\" .ir head . .ss removal .br tailq_remove () removes the element .i elm from the queue. .ss other features .\" .br tailq_swap () .\" swaps the contents of .\" .i head1 .\" and .\" .ir head2 . .\" .pp .br tailq_concat () concatenates the queue headed by .i head2 onto the end of the one headed by .i head1 removing all entries from the former. .sh return value .br tailq_empty () returns nonzero if the queue is empty, and zero if the queue contains at least one entry. .pp .br tailq_first (), .br tailq_last (), .br tailq_prev (), and .br tailq_next () return a pointer to the first, last, previous, or next .i type structure, respectively. .pp .br tailq_head_initializer () returns an initializer that can be assigned to the queue .ir head . .sh conforming to not in posix.1, posix.1-2001, or posix.1-2008. present on the bsds. (tailq functions first appeared in 4.4bsd). .sh bugs .br tailq_foreach () and .br tailq_foreach_reverse () don't allow .i var to be removed or freed within the loop, as it would interfere with the traversal. .br tailq_foreach_safe () and .br tailq_foreach_reverse_safe (), which are present on the bsds but are not present in glibc, fix this limitation by allowing .i var to safely be removed from the list and freed from within the loop without interfering with the traversal. .sh examples .ex #include #include #include #include struct entry { int data; tailq_entry(entry) entries; /* tail queue */ }; tailq_head(tailhead, entry); int main(void) { struct entry *n1, *n2, *n3, *np; struct tailhead head; /* tail queue head */ int i; tailq_init(&head); /* initialize the queue */ n1 = malloc(sizeof(struct entry)); /* insert at the head */ tailq_insert_head(&head, n1, entries); n1 = malloc(sizeof(struct entry)); /* insert at the tail */ tailq_insert_tail(&head, n1, entries); n2 = malloc(sizeof(struct entry)); /* insert after */ tailq_insert_after(&head, n1, n2, entries); n3 = malloc(sizeof(struct entry)); /* insert before */ tailq_insert_before(n2, n3, entries); tailq_remove(&head, n2, entries); /* deletion */ free(n2); /* forward traversal */ i = 0; tailq_foreach(np, &head, entries) np\->data = i++; /* reverse traversal */ tailq_foreach_reverse(np, &head, tailhead, entries) printf("%i\en", np\->data); /* tailq deletion */ n1 = tailq_first(&head); while (n1 != null) { n2 = tailq_next(n1, entries); free(n1); n1 = n2; } tailq_init(&head); exit(exit_success); } .ee .sh see also .br insque (3), .br queue (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/setbuf.3 .so man3/argz_add.3 .so man3/ctime.3 .\" this manpage is copyright (c) 2006 jens axboe .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th vmsplice 2 2021-03-22 "linux" "linux programmer's manual" .sh name vmsplice \- splice user pages to/from a pipe .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "ssize_t vmsplice(int " fd ", const struct iovec *" iov , .bi " size_t " nr_segs ", unsigned int " flags ); .fi .\" return type was long before glibc 2.7 .sh description .\" linus: vmsplice() system call to basically do a "write to .\" the buffer", but using the reference counting and vm traversal .\" to actually fill the buffer. this means that the user needs to .\" be careful not to reuse the user-space buffer it spliced into .\" the kernel-space one (contrast this to "write()", which copies .\" the actual data, and you can thus reuse the buffer immediately .\" after a successful write), but that is often easy to do. if .i fd is opened for writing, the .br vmsplice () system call maps .i nr_segs ranges of user memory described by .i iov into a pipe. if .i fd is opened for reading, .\" since linux 2.6.23 .\" commit 6a14b90bb6bc7cd83e2a444bf457a2ea645cbfe7 the .br vmsplice () system call fills .i nr_segs ranges of user memory described by .i iov from a pipe. the file descriptor .i fd must refer to a pipe. .pp the pointer .i iov points to an array of .i iovec structures as defined in .ir : .pp .in +4n .ex struct iovec { void *iov_base; /* starting address */ size_t iov_len; /* number of bytes */ }; .ee .in .pp the .i flags argument is a bit mask that is composed by oring together zero or more of the following values: .tp .b splice_f_move unused for .br vmsplice (); see .br splice (2). .tp .b splice_f_nonblock .\" not used for vmsplice .\" may be in the future -- therefore eagain do not block on i/o; see .br splice (2) for further details. .tp .b splice_f_more currently has no effect for .br vmsplice (), but may be implemented in the future; see .br splice (2). .tp .b splice_f_gift the user pages are a gift to the kernel. the application may not modify this memory ever, .\" fixme . explain the following line in a little more detail: otherwise the page cache and on-disk data may differ. gifting pages to the kernel means that a subsequent .br splice (2) .b splice_f_move can successfully move the pages; if this flag is not specified, then a subsequent .br splice (2) .b splice_f_move must copy the pages. data must also be properly page aligned, both in memory and length. .\" fixme .\" it looks like the page-alignment requirement went away with .\" commit bd1a68b59c8e3bce45fb76632c64e1e063c3962d .\" .\" .... if we expect to later splice_f_move to the cache. .sh return value upon successful completion, .br vmsplice () returns the number of bytes transferred to the pipe. on error, .br vmsplice () returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b eagain .b splice_f_nonblock was specified in .ir flags , and the operation would block. .tp .b ebadf .i fd either not valid, or doesn't refer to a pipe. .tp .b einval .i nr_segs is greater than .br iov_max ; or memory not aligned if .b splice_f_gift set. .tp .b enomem out of memory. .sh versions the .br vmsplice () system call first appeared in linux 2.6.17; library support was added to glibc in version 2.5. .sh conforming to this system call is linux-specific. .sh notes .br vmsplice () follows the other vectorized read/write type functions when it comes to limitations on the number of segments being passed in. this limit is .b iov_max as defined in .ir . currently, .\" uio_maxiov in kernel source this limit is 1024. .pp .\" commit 6a14b90bb6bc7cd83e2a444bf457a2ea645cbfe7 .br vmsplice () really supports true splicing only from user memory to a pipe. in the opposite direction, it actually just copies the data to user space. but this makes the interface nice and symmetric and enables people to build on .br vmsplice () with room for future improvement in performance. .sh see also .br splice (2), .br tee (2), .br pipe (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/endian.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th hypot 3 2021-03-22 "" "linux programmer's manual" .sh name hypot, hypotf, hypotl \- euclidean distance function .sh synopsis .nf .b #include .pp .bi "double hypot(double " x ", double " y ); .bi "float hypotf(float " x ", float " y ); .bi "long double hypotl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br hypot (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br hypotf (), .br hypotl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return .ri sqrt( x * x + y * y ). this is the length of the hypotenuse of a right-angled triangle with sides of length .i x and .ir y , or the distance of the point .ri ( x , y ) from the origin. .pp the calculation is performed without undue overflow or underflow during the intermediate steps of the calculation. .\" e.g., hypot(dbl_min, dbl_min) does the right thing, as does, say .\" hypot(dbl_max/2.0, dbl_max/2.0). .sh return value on success, these functions return the length of the hypotenuse of a right-angled triangle with sides of length .i x and .ir y . .pp if .i x or .i y is an infinity, positive infinity is returned. .pp if .i x or .i y is a nan, and the other argument is not an infinity, a nan is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively. .pp if both arguments are subnormal, and the result is subnormal, .\" actually, could the result not be subnormal if both arguments .\" are subnormal? i think not -- mtk, jul 2008 a range error occurs, and the correct result is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error: result underflow an underflow floating-point exception .rb ( fe_underflow ) is raised. .ip these functions do not set .ir errno for this case. .\" this is intentional; see .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6795 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br hypot (), .br hypotf (), .br hypotl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh see also .br cabs (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2007 michael kerrisk .\" and copyright (c) 2007 justin pryzby .\" .\" %%%license_start(permissive_misc) .\" permission is hereby granted, free of charge, to any person obtaining .\" a copy of this software and associated documentation files (the .\" "software"), to deal in the software without restriction, including .\" without limitation the rights to use, copy, modify, merge, publish, .\" distribute, sublicense, and/or sell copies of the software, and to .\" permit persons to whom the software is furnished to do so, subject to .\" the following conditions: .\" .\" the above copyright notice and this permission notice shall be .\" included in all copies or substantial portions of the software. .\" .\" the software is provided "as is", without warranty of any kind, .\" express or implied, including but not limited to the warranties of .\" merchantability, fitness for a particular purpose and noninfringement. .\" in no event shall the authors or copyright holders be liable for any .\" claim, damages or other liability, whether in an action of contract, .\" tort or otherwise, arising from, out of or in connection with the .\" software or the use or other dealings in the software. .\" %%%license_end .\" .th getsubopt 3 2021-08-27 "gnu" "linux programmer's manual" .sh name getsubopt \- parse suboption arguments from a string .sh synopsis .nf .b #include .pp .bi "int getsubopt(char **restrict " optionp ", char *const *restrict " tokens , .bi " char **restrict " valuep ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getsubopt (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l .fi .sh description .br getsubopt () parses the list of comma-separated suboptions provided in .ir optionp . (such a suboption list is typically produced when .br getopt (3) is used to parse a command line; see for example the \fi\-o\fp option of .br mount (8).) each suboption may include an associated value, which is separated from the suboption name by an equal sign. the following is an example of the kind of string that might be passed in .ir optionp : .pp .in +4n .ex .b ro,name=xyz .ee .in .pp the .i tokens argument is a pointer to a null-terminated array of pointers to the tokens that .br getsubopt () will look for in .ir optionp . the tokens should be distinct, null-terminated strings containing at least one character, with no embedded equal signs or commas. .pp each call to .br getsubopt () returns information about the next unprocessed suboption in .ir optionp . the first equal sign in a suboption (if any) is interpreted as a separator between the name and the value of that suboption. the value extends to the next comma, or (for the last suboption) to the end of the string. if the name of the suboption matches a known name from .ir tokens , and a value string was found, .br getsubopt () sets .i *valuep to the address of that string. the first comma in .i optionp is overwritten with a null byte, so .i *valuep is precisely the "value string" for that suboption. .pp if the suboption is recognized, but no value string was found, .i *valuep is set to null. .pp when .br getsubopt () returns, .i optionp points to the next suboption, or to the null byte (\(aq\e0\(aq) at the end of the string if the last suboption was just processed. .sh return value if the first suboption in .i optionp is recognized, .br getsubopt () returns the index of the matching suboption element in .ir tokens . otherwise, \-1 is returned and .i *valuep is the entire .ib name [= value ] string. .pp since .i *optionp is changed, the first suboption before the call to .br getsubopt () is not (necessarily) the same as the first suboption after .br getsubopt (). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getsubopt () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes since .br getsubopt () overwrites any commas it finds in the string .ir *optionp , that string must be writable; it cannot be a string constant. .sh examples the following program expects suboptions following a "\-o" option. .pp .ex #define _xopen_source 500 #include #include #include int main(int argc, char *argv[]) { enum { ro_opt = 0, rw_opt, name_opt }; char *const token[] = { [ro_opt] = "ro", [rw_opt] = "rw", [name_opt] = "name", null }; char *subopts; char *value; int opt; int readonly = 0; int readwrite = 0; char *name = null; int errfnd = 0; while ((opt = getopt(argc, argv, "o:")) != \-1) { switch (opt) { case \(aqo\(aq: subopts = optarg; while (*subopts != \(aq\e0\(aq && !errfnd) { switch (getsubopt(&subopts, token, &value)) { case ro_opt: readonly = 1; break; case rw_opt: readwrite = 1; break; case name_opt: if (value == null) { fprintf(stderr, "missing value for " "suboption \(aq%s\(aq\en", token[name_opt]); errfnd = 1; continue; } name = value; break; default: fprintf(stderr, "no match found " "for token: /%s/\en", value); errfnd = 1; break; } } if (readwrite && readonly) { fprintf(stderr, "only one of \(aq%s\(aq and \(aq%s\(aq can be " "specified\en", token[ro_opt], token[rw_opt]); errfnd = 1; } break; default: errfnd = 1; } } if (errfnd || argc == 1) { fprintf(stderr, "\enusage: %s \-o \en", argv[0]); fprintf(stderr, "suboptions are \(aqro\(aq, \(aqrw\(aq, " "and \(aqname=\(aq\en"); exit(exit_failure); } /* remainder of program... */ exit(exit_success); } .ee .sh see also .br getopt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/random_r.3 .\" copyright (c) andreas gruenbacher, february 2001 .\" copyright (c) silicon graphics inc, september 2001 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th removexattr 2 2021-03-22 "linux" "linux programmer's manual" .sh name removexattr, lremovexattr, fremovexattr \- remove an extended attribute .sh synopsis .fam c .nf .b #include .pp .bi "int removexattr(const char\ *" path ", const char\ *" name ); .bi "int lremovexattr(const char\ *" path ", const char\ *" name ); .bi "int fremovexattr(int " fd ", const char\ *" name ); .fi .fam t .sh description extended attributes are .ir name : value pairs associated with inodes (files, directories, symbolic links, etc.). they are extensions to the normal attributes which are associated with all inodes in the system (i.e., the .br stat (2) data). a complete overview of extended attributes concepts can be found in .br xattr (7). .pp .br removexattr () removes the extended attribute identified by .i name and associated with the given .i path in the filesystem. .pp .br lremovexattr () is identical to .br removexattr (), except in the case of a symbolic link, where the extended attribute is removed from the link itself, not the file that it refers to. .pp .br fremovexattr () is identical to .br removexattr (), only the extended attribute is removed from the open file referred to by .i fd (as returned by .br open (2)) in place of .ir path . .pp an extended attribute name is a null-terminated string. the .i name includes a namespace prefix; there may be several, disjoint namespaces associated with an individual inode. .sh return value on success, zero is returned. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b enodata the named attribute does not exist. .\" .rb ( enoattr .\" is defined to be a synonym for .\" .br enodata .\" in .\" .ir .) .tp .b enotsup extended attributes are not supported by the filesystem, or are disabled. .pp in addition, the errors documented in .br stat (2) can also occur. .sh versions these system calls have been available on linux since kernel 2.4; glibc support is provided since version 2.3. .sh conforming to these system calls are linux-specific. .\" .sh authors .\" andreas gruenbacher, .\" .ri < a.gruenbacher@computer.org > .\" and the sgi xfs development team, .\" .ri < linux-xfs@oss.sgi.com >. .\" please send any bug reports or comments to these addresses. .sh see also .br getfattr (1), .br setfattr (1), .br getxattr (2), .br listxattr (2), .br open (2), .br setxattr (2), .br stat (2), .br symlink (7), .br xattr (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/mmap.2 .so man3/rpc.3 .so man3/flockfile.3 .\" copyright (c) 2006, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th standards 7 2020-11-01 "linux" "linux programmer's manual" .sh name standards \- c and unix standards .sh description the conforming to section that appears in many manual pages identifies various standards to which the documented interface conforms. the following list briefly describes these standards. .tp .b v7 version 7 (also known as seventh edition) unix, released by at&t/bell labs in 1979. after this point, unix systems diverged into two main dialects: bsd and system v. .tp .b 4.2bsd this is an implementation standard defined by the 4.2 release of the .ir "berkeley software distribution", released by the university of california at berkeley. this was the first berkeley release that contained a tcp/ip stack and the sockets api. 4.2bsd was released in 1983. .ip earlier major bsd releases included .ir 3bsd (1980), .i 4bsd (1980), and .i 4.1bsd (1981). .tp .b 4.3bsd the successor to 4.2bsd, released in 1986. .tp .b 4.4bsd the successor to 4.3bsd, released in 1993. this was the last major berkeley release. .tp .b system v this is an implementation standard defined by at&t's milestone 1983 release of its commercial system v (five) release. the previous major at&t release was .ir "system iii" , released in 1981. .tp .b system v release 2 (svr2) this was the next system v release, made in 1985. the svr2 was formally described in the .i "system v interface definition version 1" .ri ( "svid 1" ) published in 1985. .tp .b system v release 3 (svr3) this was the successor to svr2, released in 1986. this release was formally described in the .i "system v interface definition version 2" .ri ( "svid 2" ). .tp .b system v release 4 (svr4) this was the successor to svr3, released in 1989. this version of system v is described in the "programmer's reference manual: operating system api (intel processors)" (prentice-hall 1992, isbn 0-13-951294-2) this release was formally described in the .i "system v interface definition version 3" .ri ( "svid 3" ), and is considered the definitive system v release. .tp .b svid 4 system v interface definition version 4, issued in 1995. available online at .ur http://www.sco.com\:/developers\:/devspecs/ .ue . .tp .b c89 this was the first c language standard, ratified by ansi (american national standards institute) in 1989 .ri ( x3.159-1989 ). sometimes this is known as .ir "ansi c" , but since c99 is also an ansi standard, this term is ambiguous. this standard was also ratified by iso (international standards organization) in 1990 .ri ( "iso/iec 9899:1990" ), and is thus occasionally referred to as .ir "iso c90" . .tp .b c99 this revision of the c language standard was ratified by iso in 1999 .ri ( "iso/iec 9899:1999" ). available online at .ur http://www.open\-std.org\:/jtc1\:/sc22\:/wg14\:/www\:/standards .ue . .tp .b c11 this revision of the c language standard was ratified by iso in 2011 .ri ( "iso/iec 9899:2011" ). .ip .b lfs the large file summit specification, completed in 1996. this specification defined mechanisms that allowed 32-bit systems to support the use of large files (i.e., 64-bit file offsets). see .ur https://www.opengroup.org\:/platform\:/lfs.html .ue . .tp .b posix.1-1988 this was the first posix standard, ratified by ieee as ieee std 1003.1-1988, and subsequently adopted (with minor revisions) as an iso standard in 1990. the term "posix" was coined by richard stallman. .tp .b posix.1-1990 "portable operating system interface for computing environments". ieee 1003.1-1990 part 1, ratified by iso in 1990 .ri ( "iso/iec 9945-1:1990" ). .tp .b posix.2 ieee std 1003.2-1992, describing commands and utilities, ratified by iso in 1993 .ri ( "iso/iec 9945-2:1993" ). .tp .br posix.1b " (formerly known as \fiposix.4\fp)" ieee std 1003.1b-1993, describing real-time facilities for portable operating systems, ratified by iso in 1996 .ri ( "iso/iec 9945-1:1996" ). .tp .b posix.1c " (formerly known as \fiposix.4a\fp)" ieee std 1003.1c-1995, which describes the posix threads interfaces. .tp .br posix.1d ieee std 1003.1c-1999, which describes additional real-time extensions. .tp .b posix.1g ieee std 1003.1g-2000, which describes networking apis (including sockets). .tp .b posix.1j ieee std 1003.1j-2000, which describes advanced real-time extensions. .tp .b posix.1-1996 a 1996 revision of posix.1 which incorporated posix.1b and posix.1c. .tp .b xpg3 released in 1989, this was the first release of the x/open portability guide to be based on a posix standard (posix.1-1988). this multivolume guide was developed by the x/open group, a multivendor consortium. .tp .b xpg4 a revision of the x/open portability guide, released in 1992. this revision incorporated posix.2. .tp .b xpg4v2 a 1994 revision of xpg4. this is also referred to as .ir "spec 1170" , where 1170 referred to the number of interfaces defined by this standard. .tp .b "sus (susv1)" single unix specification. this was a repackaging of xpg4v2 and other x/open standards (x/open curses issue 4 version 2, x/open networking service (xns) issue 4). systems conforming to this standard can be branded .ir "unix 95" . .tp .b susv2 single unix specification version 2. sometimes also referred to (incorrectly) as .ir xpg5 . this standard appeared in 1997. systems conforming to this standard can be branded .ir "unix 98" . see also .ur http://www.unix.org\:/version2/ .ue .) .tp .b posix.1-2001, susv3 this was a 2001 revision and consolidation of the posix.1, posix.2, and sus standards into a single document, conducted under the auspices of the austin group .ur http://www.opengroup.org\:/austin/ .ue . the standard is available online at .ur http://www.unix.org\:/version3/ .ue . .ip the standard defines two levels of conformance: .ir "posix conformance" , which is a baseline set of interfaces required of a conforming system; and .ir "xsi conformance", which additionally mandates a set of interfaces (the "xsi extension") which are only optional for posix conformance. xsi-conformant systems can be branded .ir "unix 03" . .ip the posix.1-2001 document is broken into four parts: .ip .br xbd : definitions, terms, and concepts, header file specifications. .ip .br xsh : specifications of functions (i.e., system calls and library functions in actual implementations). .ip .br xcu : specifications of commands and utilities (i.e., the area formerly described by posix.2). .ip .br xrat : informative text on the other parts of the standard. .ip posix.1-2001 is aligned with c99, so that all of the library functions standardized in c99 are also standardized in posix.1-2001. .ip the single unix specification version 3 (susv3) comprises the base specifications containing xbd, xsh, xcu, and xrat as above, plus x/open curses issue 4 version 2 as an extra volume that is not in posix.1-2001. .ip two technical corrigenda (minor fixes and improvements) of the original 2001 standard have occurred: tc1 in 2003 and tc2 in 2004. .tp .b posix.1-2008, susv4 work on the next revision of posix.1/sus was completed and ratified in 2008. the standard is available online at .ur http://www.unix.org\:/version4/ .ue . .ip the changes in this revision are not as large as those that occurred for posix.1-2001/susv3, but a number of new interfaces are added and various details of existing specifications are modified. many of the interfaces that were optional in posix.1-2001 become mandatory in the 2008 revision of the standard. a few interfaces that are present in posix.1-2001 are marked as obsolete in posix.1-2008, or removed from the standard altogether. .ip the revised standard is structured in the same way as its predecessor. the single unix specification version 4 (susv4) comprises the base specifications containing xbd, xsh, xcu, and xrat, plus x/open curses issue 7 as an extra volume that is not in posix.1-2008. .ip again there are two levels of conformance: the baseline .ir "posix conformance" , and .ir "xsi conformance" , which mandates an additional set of interfaces beyond those in the base specification. .ip in general, where the conforming to section of a manual page lists posix.1-2001, it can be assumed that the interface also conforms to posix.1-2008, unless otherwise noted. .ip technical corrigendum 1 (minor fixes and improvements) of this standard was released in 2013. .ip technical corrigendum 2 of this standard was released in 2016. .ip further information can be found on the austin group web site, .ur http://www.opengroup.org\:/austin/ .ue . .tp .b susv4 2016 edition this is equivalent to posix.1-2008, with the addition of technical corrigenda 1 and 2 and the xcurses specification. .tp .b posix.1-2017 this revision of posix is technically identical to posix.1-2008 with technical corrigenda 1 and 2 applied. .tp .b susv4 2018 edition this is equivalent to posix.1-2017, with the addition of the xcurses specification. .pp the interfaces documented in posix.1/sus are available as manual pages under sections 0p (header files), 1p (commands), and 3p (functions); thus one can write "man 3p open". .sh see also .br getconf (1), .br confstr (3), .br pathconf (3), .br sysconf (3), .br attributes (7), .br feature_test_macros (7), .br libc (7), .br posixoptions (7), .br system_data_types (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995 by jim van zandt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" added bugs section, aeb, 950919 .\" .th toascii 3 2021-03-22 "gnu" "linux programmer's manual" .sh name toascii \- convert character to ascii .sh synopsis .nf .b #include .pp .bi "int toascii(int " "c" ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br toascii (): .nf _xopen_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description .br toascii () converts .i c to a 7-bit .i "unsigned char" value that fits into the ascii character set, by clearing the high-order bits. .sh return value the value returned is that of the converted character. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br toascii () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4, bsd, posix.1-2001. posix.1-2008 marks .br toascii () as obsolete, noting that it cannot be used portably in a localized application. .sh bugs many people will be unhappy if you use this function. this function will convert accented letters into random characters. .sh see also .br isascii (3), .br tolower (3), .br toupper (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_attr_setstacksize.3 .so man2/dup.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2007, 2012 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's "posix programmer's guide" (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:30:29 1993 by rik faith (faith@cs.unc.edu) .\" modified fri feb 14 21:47:50 1997 by andries brouwer (aeb@cwi.nl) .\" .th getenv 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getenv, secure_getenv \- get an environment variable .sh synopsis .nf .b #include .pp .bi "char *getenv(const char *" name ); .bi "char *secure_getenv(const char *" name ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br secure_getenv (): .nf _gnu_source .fi .sh description the .br getenv () function searches the environment list to find the environment variable .ir name , and returns a pointer to the corresponding .i value string. .pp the gnu-specific .br secure_getenv () function is just like .br getenv () except that it returns null in cases where "secure execution" is required. secure execution is required if one of the following conditions was true when the program run by the calling process was loaded: .ip * 3 the process's effective user id did not match its real user id or the process's effective group id did not match its real group id (typically this is the result of executing a set-user-id or set-group-id program); .ip * the effective capability bit was set on the executable file; or .ip * the process has a nonempty permitted capability set. .pp secure execution may also be required if triggered by some linux security modules. .pp the .br secure_getenv () function is intended for use in general-purpose libraries to avoid vulnerabilities that could occur if set-user-id or set-group-id programs accidentally trusted the environment. .sh return value the .br getenv () function returns a pointer to the value in the environment, or null if there is no match. .sh versions .br secure_getenv () first appeared in glibc 2.17. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getenv (), .br secure_getenv () t} thread safety mt-safe env .te .hy .ad .sp 1 .sh conforming to .br getenv (): posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .pp .br secure_getenv () is a gnu extension. .sh notes the strings in the environment list are of the form \finame=value\fp. .pp as typically implemented, .br getenv () returns a pointer to a string within the environment list. the caller must take care not to modify this string, since that would change the environment of the process. .pp the implementation of .br getenv () is not required to be reentrant. the string pointed to by the return value of .br getenv () may be statically allocated, and can be modified by a subsequent call to .br getenv (), .br putenv (3), .br setenv (3), or .br unsetenv (3). .pp the "secure execution" mode of .br secure_getenv () is controlled by the .b at_secure flag contained in the auxiliary vector passed from the kernel to user space. .sh see also .br clearenv (3), .br getauxval (3), .br putenv (3), .br setenv (3), .br unsetenv (3), .br capabilities (7), .br environ (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fts.3 .\" copyright (c) 2007 michael kerrisk .\" with some input from stepan kasal .\" .\" some content retained from an earlier version of this page: .\" copyright (c) 1998 andries brouwer (aeb@cwi.nl) .\" modifications for 2.2 and 2.4 copyright (c) 2002 ian redfern .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th syscalls 2 2021-08-27 "linux" "linux programmer's manual" .sh name syscalls \- linux system calls .sh synopsis .nf linux system calls. .fi .sh description the system call is the fundamental interface between an application and the linux kernel. .ss system calls and library wrapper functions system calls are generally not invoked directly, but rather via wrapper functions in glibc (or perhaps some other library). for details of direct invocation of a system call, see .br intro (2). often, but not always, the name of the wrapper function is the same as the name of the system call that it invokes. for example, glibc contains a function .br chdir () which invokes the underlying "chdir" system call. .pp often the glibc wrapper function is quite thin, doing little work other than copying arguments to the right registers before invoking the system call, and then setting .i errno appropriately after the system call has returned. (these are the same steps that are performed by .br syscall (2), which can be used to invoke system calls for which no wrapper function is provided.) note: system calls indicate a failure by returning a negative error number to the caller on architectures without a separate error register/flag, as noted in .br syscall (2); when this happens, the wrapper function negates the returned error number (to make it positive), copies it to .ir errno , and returns \-1 to the caller of the wrapper. .pp sometimes, however, the wrapper function does some extra work before invoking the system call. for example, nowadays there are (for reasons described below) two related system calls, .br truncate (2) and .br truncate64 (2), and the glibc .br truncate () wrapper function checks which of those system calls are provided by the kernel and determines which should be employed. .ss system call list below is a list of the linux system calls. in the list, the .i kernel column indicates the kernel version for those system calls that were new in linux 2.2, or have appeared since that kernel version. note the following points: .ip * 3 where no kernel version is indicated, the system call appeared in kernel 1.0 or earlier. .ip * where a system call is marked "1.2" this means the system call probably appeared in a 1.1.x kernel version, and first appeared in a stable kernel with 1.2. (development of the 1.2 kernel was initiated from a branch of kernel 1.0.6 via the 1.1.x unstable kernel series.) .ip * where a system call is marked "2.0" this means the system call probably appeared in a 1.3.x kernel version, and first appeared in a stable kernel with 2.0. (development of the 2.0 kernel was initiated from a branch of kernel 1.2.x, somewhere around 1.2.10, via the 1.3.x unstable kernel series.) .\" was kernel 2.0 started from a branch of 1.2.10? .\" at least from the timestamps of the tarballs of .\" of 1.2.10 and 1.3.0, that's how it looks, but in .\" fact the diff doesn't seem very clear, the .\" 1.3.0 .tar.bz is much bigger (2.0 mb) than the .\" 1.2.10 .tar.bz2 (1.8 mb), and aeb points out the .\" timestamps of some files in 1.3.0 seem to be older .\" than those in 1.2.10. all of this suggests .\" that there might not have been a clean branch point. .ip * where a system call is marked "2.2" this means the system call probably appeared in a 2.1.x kernel version, and first appeared in a stable kernel with 2.2.0. (development of the 2.2 kernel was initiated from a branch of kernel 2.0.21 via the 2.1.x unstable kernel series.) .ip * where a system call is marked "2.4" this means the system call probably appeared in a 2.3.x kernel version, and first appeared in a stable kernel with 2.4.0. (development of the 2.4 kernel was initiated from a branch of kernel 2.2.8 via the 2.3.x unstable kernel series.) .ip * where a system call is marked "2.6" this means the system call probably appeared in a 2.5.x kernel version, and first appeared in a stable kernel with 2.6.0. (development of kernel 2.6 was initiated from a branch of kernel 2.4.15 via the 2.5.x unstable kernel series.) .ip * starting with kernel 2.6.0, the development model changed, and new system calls may appear in each 2.6.x release. in this case, the exact version number where the system call appeared is shown. this convention continues with the 3.x kernel series, which followed on from kernel 2.6.39; and the 4.x kernel series, which followed on from kernel 3.19; and the 5.x kernel series, which followed on from kernel 4.20. .ip * in some cases, a system call was added to a stable kernel series after it branched from the previous stable kernel series, and then backported into the earlier stable kernel series. for example some system calls that appeared in 2.6.x were also backported into a 2.4.x release after 2.4.15. when this is so, the version where the system call appeared in both of the major kernel series is listed. .pp the list of system calls that are available as at kernel 5.11 (or in a few cases only on older kernels) is as follows: .\" .\" looking at scripts/checksyscalls.sh in the kernel source is .\" instructive about x86 specifics. .\" .nh .ad l .ts l2 le l --- l l l. \fbsystem call\fp \fbkernel\fp \fbnotes\fp \fb_llseek\fp(2) 1.2 \fb_newselect\fp(2) 2.0 \fb_sysctl\fp(2) 2.0 removed in 5.5 \fbaccept\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbaccept4\fp(2) 2.6.28 \fbaccess\fp(2) 1.0 \fbacct\fp(2) 1.0 \fbadd_key\fp(2) 2.6.10 \fbadjtimex\fp(2) 1.0 \fbalarm\fp(2) 1.0 \fballoc_hugepages\fp(2) 2.5.36 removed in 2.5.44 .\" 4adeefe161a74369e44cc8e663f240ece0470dc3 \fbarc_gettls\fp(2) 3.9 arc only \fbarc_settls\fp(2) 3.9 arc only .\" 91e040a79df73d371f70792f30380d4e44805250 \fbarc_usr_cmpxchg\fp(2) 4.9 arc only .\" x86: 79170fda313ed5be2394f87aa2a00d597f8ed4a1 \fbarch_prctl\fp(2) 2.6 t{ x86_64, x86 since 4.12 t} .\" 9674cdc74d63f346870943ef966a034f8c71ee57 \fbatomic_barrier\fp(2) 2.6.34 m68k only \fbatomic_cmpxchg_32\fp(2) 2.6.34 m68k only \fbbdflush\fp(2) 1.2 t{ deprecated (does nothing) since 2.6 t} \fbbind\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbbpf\fp(2) 3.18 \fbbrk\fp(2) 1.0 \fbbreakpoint\fp(2) 2.2 t{ arm oabi only, defined with \fb__arm_nr\fp prefix t} \fbcacheflush\fp(2) 1.2 not on x86 \fbcapget\fp(2) 2.2 \fbcapset\fp(2) 2.2 \fbchdir\fp(2) 1.0 \fbchmod\fp(2) 1.0 \fbchown\fp(2) 2.2 t{ see \fbchown\fp(2) for version details t} \fbchown32\fp(2) 2.4 \fbchroot\fp(2) 1.0 \fbclock_adjtime\fp(2) 2.6.39 \fbclock_getres\fp(2) 2.6 \fbclock_gettime\fp(2) 2.6 \fbclock_nanosleep\fp(2) 2.6 \fbclock_settime\fp(2) 2.6 \fbclone2\fp(2) 2.4 ia-64 only \fbclone\fp(2) 1.0 \fbclone3\fp(2) 5.3 \fbclose\fp(2) 1.0 \fbclose_range\fp(2) 5.9 .\" .\" dcef1f634657dabe7905af3ccda12cf7f0b6fcc1 .\" .\" cc20d42986d5807cbe4f5c7c8e3dab2e59ea0db3 .\" .\" db695c0509d6ec9046ee5e4c520a19fa17d9fce2 .\" \fbcmpxchg\fp(2) 2.6.12 t{ .\" arm, syscall constant never was .\" exposed to user space, in-kernel .\" definition had \fb__arm_nr\fp prefix, .\" removed in 4.4 .\" t} .\" 867e359b97c970a60626d5d76bbe2a8fadbf38fb .\" bb9d812643d8a121df7d614a2b9c60193a92deb0 \fbconnect\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbcopy_file_range\fp(2) 4.5 \fbcreat\fp(2) 1.0 \fbcreate_module\fp(2) 1.0 removed in 2.6 \fbdelete_module\fp(2) 1.0 .\" 1394f03221790a988afc3e4b3cb79f2e477246a9 .\" 4ba66a9760722ccbb691b8f7116cad2f791cca7b \fbdup\fp(2) 1.0 \fbdup2\fp(2) 1.0 \fbdup3\fp(2) 2.6.27 \fbepoll_create\fp(2) 2.6 \fbepoll_create1\fp(2) 2.6.27 \fbepoll_ctl\fp(2) 2.6 \fbepoll_pwait\fp(2) 2.6.19 \fbepoll_pwait2\fp(2) 5.11 \fbepoll_wait\fp(2) 2.6 \fbeventfd\fp(2) 2.6.22 \fbeventfd2\fp(2) 2.6.27 \fbexecv\fp(2) 2.0 t{ sparc/sparc64 only, for compatibility with sunos t} \fbexecve\fp(2) 1.0 \fbexecveat\fp(2) 3.19 \fbexit\fp(2) 1.0 \fbexit_group\fp(2) 2.6 \fbfaccessat\fp(2) 2.6.16 \fbfaccessat2\fp(2) 5.8 \fbfadvise64\fp(2) 2.6 .\" implements \fbposix_fadvise\fp(2) \fbfadvise64_64\fp(2) 2.6 \fbfallocate\fp(2) 2.6.23 \fbfanotify_init\fp(2) 2.6.37 \fbfanotify_mark\fp(2) 2.6.37 .\" the fanotify calls were added in linux 2.6.36, .\" but disabled while the api was finalized. \fbfchdir\fp(2) 1.0 \fbfchmod\fp(2) 1.0 \fbfchmodat\fp(2) 2.6.16 \fbfchown\fp(2) 1.0 \fbfchown32\fp(2) 2.4 \fbfchownat\fp(2) 2.6.16 \fbfcntl\fp(2) 1.0 \fbfcntl64\fp(2) 2.4 \fbfdatasync\fp(2) 2.0 \fbfgetxattr\fp(2) 2.6; 2.4.18 \fbfinit_module\fp(2) 3.8 \fbflistxattr\fp(2) 2.6; 2.4.18 \fbflock\fp(2) 2.0 \fbfork\fp(2) 1.0 \fbfree_hugepages\fp(2) 2.5.36 removed in 2.5.44 \fbfremovexattr\fp(2) 2.6; 2.4.18 \fbfsconfig\fp(2) 5.2 \fbfsetxattr\fp(2) 2.6; 2.4.18 \fbfsmount\fp(2) 5.2 \fbfsopen\fp(2) 5.2 \fbfspick\fp(2) 5.2 \fbfstat\fp(2) 1.0 \fbfstat64\fp(2) 2.4 \fbfstatat64\fp(2) 2.6.16 \fbfstatfs\fp(2) 1.0 \fbfstatfs64\fp(2) 2.6 \fbfsync\fp(2) 1.0 \fbftruncate\fp(2) 1.0 \fbftruncate64\fp(2) 2.4 \fbfutex\fp(2) 2.6 \fbfutimesat\fp(2) 2.6.16 \fbget_kernel_syms\fp(2) 1.0 removed in 2.6 \fbget_mempolicy\fp(2) 2.6.6 \fbget_robust_list\fp(2) 2.6.17 \fbget_thread_area\fp(2) 2.6 .\" 8fcd6c45f5a65621ec809b7866a3623e9a01d4ed \fbget_tls\fp(2) 4.15 t{ arm oabi only, has \fb__arm_nr\fp prefix t} \fbgetcpu\fp(2) 2.6.19 \fbgetcwd\fp(2) 2.2 \fbgetdents\fp(2) 2.0 \fbgetdents64\fp(2) 2.4 .\" parisc: 863722e856e64dae0e252b6bb546737c6c5626ce \fbgetdomainname\fp(2) 2.2 t{ sparc, sparc64; available as \fbosf_getdomainname\fp(2) on alpha since linux 2.0 t} .\" ec98c6b9b47df6df1c1fa6cf3d427414f8c2cf16 \fbgetdtablesize\fp(2) 2.0 t{ sparc (removed in 2.6.26), available on alpha as \fbosf_getdtablesize\fp(2) t} \fbgetegid\fp(2) 1.0 \fbgetegid32\fp(2) 2.4 \fbgeteuid\fp(2) 1.0 \fbgeteuid32\fp(2) 2.4 \fbgetgid\fp(2) 1.0 \fbgetgid32\fp(2) 2.4 \fbgetgroups\fp(2) 1.0 \fbgetgroups32\fp(2) 2.4 .\" sparc removal: ec98c6b9b47df6df1c1fa6cf3d427414f8c2cf16 \fbgethostname\fp(2) 2.0 t{ alpha, was available on sparc up to linux 2.6.26 t} \fbgetitimer\fp(2) 1.0 \fbgetpeername\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbgetpagesize\fp(2) 2.0 not on x86 \fbgetpgid\fp(2) 1.0 \fbgetpgrp\fp(2) 1.0 \fbgetpid\fp(2) 1.0 \fbgetppid\fp(2) 1.0 \fbgetpriority\fp(2) 1.0 \fbgetrandom\fp(2) 3.17 \fbgetresgid\fp(2) 2.2 \fbgetresgid32\fp(2) 2.4 \fbgetresuid\fp(2) 2.2 \fbgetresuid32\fp(2) 2.4 \fbgetrlimit\fp(2) 1.0 \fbgetrusage\fp(2) 1.0 \fbgetsid\fp(2) 2.0 \fbgetsockname\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbgetsockopt\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbgettid\fp(2) 2.4.11 \fbgettimeofday\fp(2) 1.0 \fbgetuid\fp(2) 1.0 \fbgetuid32\fp(2) 2.4 \fbgetunwind\fp(2) 2.4.8 t{ ia-64 only; deprecated t} \fbgetxattr\fp(2) 2.6; 2.4.18 \fbgetxgid\fp(2) 2.0 t{ alpha only; see notes t} \fbgetxpid\fp(2) 2.0 t{ alpha only; see notes t} \fbgetxuid\fp(2) 2.0 t{ alpha only; see notes t} \fbinit_module\fp(2) 1.0 \fbinotify_add_watch\fp(2) 2.6.13 \fbinotify_init\fp(2) 2.6.13 \fbinotify_init1\fp(2) 2.6.27 \fbinotify_rm_watch\fp(2) 2.6.13 \fbio_cancel\fp(2) 2.6 \fbio_destroy\fp(2) 2.6 \fbio_getevents\fp(2) 2.6 \fbio_pgetevents\fp(2) 4.18 \fbio_setup\fp(2) 2.6 \fbio_submit\fp(2) 2.6 \fbio_uring_enter\fp(2) 5.1 \fbio_uring_register\fp(2) 5.1 \fbio_uring_setup\fp(2) 5.1 \fbioctl\fp(2) 1.0 \fbioperm\fp(2) 1.0 \fbiopl\fp(2) 1.0 \fbioprio_get\fp(2) 2.6.13 \fbioprio_set\fp(2) 2.6.13 \fbipc\fp(2) 1.0 .\" implements system v ipc calls \fbkcmp\fp(2) 3.5 \fbkern_features\fp(2) 3.7 sparc64 only .\" fixme . document kern_features(): .\" commit 517ffce4e1a03aea979fe3a18a3dd1761a24fafb \fbkexec_file_load\fp(2) 3.17 \fbkexec_load\fp(2) 2.6.13 .\" the entry in the syscall table was reserved starting in 2.6.7 .\" was named sys_kexec_load() from 2.6.7 to 2.6.16 \fbkeyctl\fp(2) 2.6.10 \fbkill\fp(2) 1.0 \fblandlock_add_rule\fp(2) 5.13 \fblandlock_create_ruleset\fp(2) 5.13 \fblandlock_restrict_self\fp(2) 5.13 \fblandlock_add_rule\fp(2) 5.13 \fblchown\fp(2) 1.0 t{ see \fbchown\fp(2) for version details t} \fblchown32\fp(2) 2.4 \fblgetxattr\fp(2) 2.6; 2.4.18 \fblink\fp(2) 1.0 \fblinkat\fp(2) 2.6.16 \fblisten\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fblistxattr\fp(2) 2.6; 2.4.18 \fbllistxattr\fp(2) 2.6; 2.4.18 \fblookup_dcookie\fp(2) 2.6 \fblremovexattr\fp(2) 2.6; 2.4.18 \fblseek\fp(2) 1.0 \fblsetxattr\fp(2) 2.6; 2.4.18 \fblstat\fp(2) 1.0 \fblstat64\fp(2) 2.4 \fbmadvise\fp(2) 2.4 \fbmbind\fp(2) 2.6.6 \fbmemory_ordering\fp(2) 2.2 sparc64 only .\" 26025bbfbba33a9425be1b89eccb4664ea4c17b6 .\" bb6fb6dfcc17cddac11ac295861f7608194447a7 \fbmembarrier\fp(2) 3.17 \fbmemfd_create\fp(2) 3.17 \fbmigrate_pages\fp(2) 2.6.16 \fbmincore\fp(2) 2.4 \fbmkdir\fp(2) 1.0 \fbmkdirat\fp(2) 2.6.16 \fbmknod\fp(2) 1.0 \fbmknodat\fp(2) 2.6.16 \fbmlock\fp(2) 2.0 \fbmlock2\fp(2) 4.4 \fbmlockall\fp(2) 2.0 \fbmmap\fp(2) 1.0 \fbmmap2\fp(2) 2.4 \fbmodify_ldt\fp(2) 1.0 \fbmount\fp(2) 1.0 \fbmove_mount\fp(2) 5.2 \fbmove_pages\fp(2) 2.6.18 \fbmprotect\fp(2) 1.0 \fbmq_getsetattr\fp(2) 2.6.6 .\" implements \fbmq_getattr\fp(3) and \fbmq_setattr\fp(3) \fbmq_notify\fp(2) 2.6.6 \fbmq_open\fp(2) 2.6.6 \fbmq_timedreceive\fp(2) 2.6.6 \fbmq_timedsend\fp(2) 2.6.6 \fbmq_unlink\fp(2) 2.6.6 \fbmremap\fp(2) 2.0 \fbmsgctl\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbmsgget\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbmsgrcv\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbmsgsnd\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbmsync\fp(2) 2.0 .\" \fbmultiplexer\fp(2) ?? __nr_multiplexer reserved on .\" powerpc, but unimplemented? \fbmunlock\fp(2) 2.0 \fbmunlockall\fp(2) 2.0 \fbmunmap\fp(2) 1.0 \fbname_to_handle_at\fp(2) 2.6.39 \fbnanosleep\fp(2) 2.0 .\" 5590ff0d5528b60153c0b4e7b771472b5a95e297 \fbnewfstatat\fp(2) 2.6.16 see \fbstat\fp(2) \fbnfsservctl\fp(2) 2.2 removed in 3.1 \fbnice\fp(2) 1.0 \fbold_adjtimex\fp(2) 2.0 t{ alpha only; see notes t} \fbold_getrlimit\fp(2) 2.4 t{ old variant of \fbgetrlimit\fp(2) that used a different value for \fbrlim_infinity\fp t} \fboldfstat\fp(2) 1.0 \fboldlstat\fp(2) 1.0 \fboldolduname\fp(2) 1.0 \fboldstat\fp(2) 1.0 \fboldumount\fp(2) 2.4.116 t{ name of the old \fbumount\fp(2) syscall on alpha t} \fbolduname\fp(2) 1.0 \fbopen\fp(2) 1.0 \fbopen_by_handle_at\fp(2) 2.6.39 \fbopen_tree\fp(2) 5.2 \fbopenat\fp(2) 2.6.16 \fbopenat2\fp(2) 5.6 .\" 9d02a4283e9ce4e9ca11ff00615bdacdb0515a1a \fbor1k_atomic\fp(2) 3.1 t{ openrisc 1000 only t} \fbpause\fp(2) 1.0 \fbpciconfig_iobase\fp(2) 2.2.15; 2.4 not on x86 .\" alpha, powerpc, arm; not x86 \fbpciconfig_read\fp(2) 2.0.26; 2.2 not on x86 .\" , powerpc, arm; not x86 \fbpciconfig_write\fp(2) 2.0.26; 2.2 not on x86 .\" , powerpc, arm; not x86 \fbperf_event_open\fp(2) 2.6.31 t{ was perf_counter_open() in 2.6.31; renamed in 2.6.32 t} \fbpersonality\fp(2) 1.2 \fbperfctr\fp(2) 2.2 t{ sparc only; removed in 2.6.34 t} .\" commit c7d5a0050773e98d1094eaa9f2a1a793fafac300 removed perfctr() \fbperfmonctl\fp(2) 2.4 ia-64 only; removed in 5.10 \fbpidfd_getfd\fp(2) 5.6 \fbpidfd_send_signal\fp(2) 5.1 \fbpidfd_open\fp(2) 5.3 \fbpipe\fp(2) 1.0 \fbpipe2\fp(2) 2.6.27 \fbpivot_root\fp(2) 2.4 \fbpkey_alloc\fp(2) 4.8 \fbpkey_free\fp(2) 4.8 \fbpkey_mprotect\fp(2) 4.8 \fbpoll\fp(2) 2.0.36; 2.2 \fbppoll\fp(2) 2.6.16 \fbprctl\fp(2) 2.2 \fbpread64\fp(2) t{ added as "pread" in 2.2; renamed "pread64" in 2.6 t} \fbpreadv\fp(2) 2.6.30 \fbpreadv2\fp(2) 4.6 \fbprlimit64\fp(2) 2.6.36 \fbprocess_madvise\fp(2) 5.10 \fbprocess_vm_readv\fp(2) 3.2 \fbprocess_vm_writev\fp(2) 3.2 \fbpselect6\fp(2) 2.6.16 .\" implements \fbpselect\fp(2) \fbptrace\fp(2) 1.0 \fbpwrite64\fp(2) t{ added as "pwrite" in 2.2; renamed "pwrite64" in 2.6 t} \fbpwritev\fp(2) 2.6.30 \fbpwritev2\fp(2) 4.6 \fbquery_module\fp(2) 2.2 removed in 2.6 \fbquotactl\fp(2) 1.0 \fbquotactl_fd\fp(2) 5.14 \fbread\fp(2) 1.0 \fbreadahead\fp(2) 2.4.13 \fbreaddir\fp(2) 1.0 .\" supersedes \fbgetdents\fp(2) \fbreadlink\fp(2) 1.0 \fbreadlinkat\fp(2) 2.6.16 \fbreadv\fp(2) 2.0 \fbreboot\fp(2) 1.0 \fbrecv\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbrecvfrom\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbrecvmsg\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbrecvmmsg\fp(2) 2.6.33 \fbremap_file_pages\fp(2) 2.6 t{ deprecated since 3.16 t} \fbremovexattr\fp(2) 2.6; 2.4.18 \fbrename\fp(2) 1.0 \fbrenameat\fp(2) 2.6.16 \fbrenameat2\fp(2) 3.15 \fbrequest_key\fp(2) 2.6.10 \fbrestart_syscall\fp(2) 2.6 .\" 921ebd8f2c081b3cf6c3b29ef4103eef3ff26054 \fbriscv_flush_icache\fp(2) 4.15 risc-v only \fbrmdir\fp(2) 1.0 \fbrseq\fp(2) 4.18 \fbrt_sigaction\fp(2) 2.2 \fbrt_sigpending\fp(2) 2.2 \fbrt_sigprocmask\fp(2) 2.2 \fbrt_sigqueueinfo\fp(2) 2.2 \fbrt_sigreturn\fp(2) 2.2 \fbrt_sigsuspend\fp(2) 2.2 \fbrt_sigtimedwait\fp(2) 2.2 \fbrt_tgsigqueueinfo\fp(2) 2.6.31 \fbrtas\fp(2) 2.6.2 t{ powerpc/powerpc64 only t} \fbs390_runtime_instr\fp(2) 3.7 s390 only \fbs390_pci_mmio_read\fp(2) 3.19 s390 only \fbs390_pci_mmio_write\fp(2) 3.19 s390 only \fbs390_sthyi\fp(2) 4.15 s390 only \fbs390_guarded_storage\fp(2) 4.12 s390 only \fbsched_get_affinity\fp(2) 2.6 t{ name of \fbsched_getaffinity\fp(2) on sparc and sparc64 t} \fbsched_get_priority_max\fp(2) 2.0 \fbsched_get_priority_min\fp(2) 2.0 \fbsched_getaffinity\fp(2) 2.6 \fbsched_getattr\fp(2) 3.14 \fbsched_getparam\fp(2) 2.0 \fbsched_getscheduler\fp(2) 2.0 \fbsched_rr_get_interval\fp(2) 2.0 \fbsched_set_affinity\fp(2) 2.6 t{ name of \fbsched_setaffinity\fp(2) on sparc and sparc64 t} \fbsched_setaffinity\fp(2) 2.6 \fbsched_setattr\fp(2) 3.14 \fbsched_setparam\fp(2) 2.0 \fbsched_setscheduler\fp(2) 2.0 \fbsched_yield\fp(2) 2.0 \fbseccomp\fp(2) 3.17 \fbselect\fp(2) 1.0 \fbsemctl\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbsemget\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbsemop\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbsemtimedop\fp(2) 2.6; 2.4.22 \fbsend\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbsendfile\fp(2) 2.2 \fbsendfile64\fp(2) 2.6; 2.4.19 \fbsendmmsg\fp(2) 3.0 \fbsendmsg\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbsendto\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbset_mempolicy\fp(2) 2.6.6 \fbset_robust_list\fp(2) 2.6.17 \fbset_thread_area\fp(2) 2.6 \fbset_tid_address\fp(2) 2.6 \fbset_tls\fp(2) 2.6.11 t{ arm oabi/eabi only (constant has \fb__arm_nr\fp prefix) t} .\" \fbsetaltroot\fp(2) 2.6.10 t{ .\" removed in 2.6.11, exposed one .\" of implementation details of .\" \fbpersonality\fp(2) (creating an .\" alternative root, precursor of .\" mount namespaces) to user space. .\" t} .\" see http://lkml.org/lkml/2005/8/1/83 .\" "[patch] remove sys_set_zone_reclaim()" \fbsetdomainname\fp(2) 1.0 \fbsetfsgid\fp(2) 1.2 \fbsetfsgid32\fp(2) 2.4 \fbsetfsuid\fp(2) 1.2 \fbsetfsuid32\fp(2) 2.4 \fbsetgid\fp(2) 1.0 \fbsetgid32\fp(2) 2.4 \fbsetgroups\fp(2) 1.0 \fbsetgroups32\fp(2) 2.4 .\" arch/alpha/include/asm/core_lca.h \fbsethae\fp(2) 2.0 t{ alpha only; see notes t} \fbsethostname\fp(2) 1.0 \fbsetitimer\fp(2) 1.0 \fbsetns\fp(2) 3.0 \fbsetpgid\fp(2) 1.0 \fbsetpgrp\fp(2) 2.0 t{ alternative name for \fbsetpgid\fp(2) on alpha t} \fbsetpriority\fp(2) 1.0 \fbsetregid\fp(2) 1.0 \fbsetregid32\fp(2) 2.4 \fbsetresgid\fp(2) 2.2 \fbsetresgid32\fp(2) 2.4 \fbsetresuid\fp(2) 2.2 \fbsetresuid32\fp(2) 2.4 \fbsetreuid\fp(2) 1.0 \fbsetreuid32\fp(2) 2.4 \fbsetrlimit\fp(2) 1.0 \fbsetsid\fp(2) 1.0 \fbsetsockopt\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbsettimeofday\fp(2) 1.0 \fbsetuid\fp(2) 1.0 \fbsetuid32\fp(2) 2.4 \fbsetup\fp(2) 1.0 removed in 2.2 \fbsetxattr\fp(2) 2.6; 2.4.18 \fbsgetmask\fp(2) 1.0 \fbshmat\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbshmctl\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbshmdt\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbshmget\fp(2) 2.0 t{ see notes on \fbipc\fp(2) t} \fbshutdown\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbsigaction\fp(2) 1.0 \fbsigaltstack\fp(2) 2.2 \fbsignal\fp(2) 1.0 \fbsignalfd\fp(2) 2.6.22 \fbsignalfd4\fp(2) 2.6.27 \fbsigpending\fp(2) 1.0 \fbsigprocmask\fp(2) 1.0 \fbsigreturn\fp(2) 1.0 \fbsigsuspend\fp(2) 1.0 \fbsocket\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} \fbsocketcall\fp(2) 1.0 .\" implements bsd socket calls \fbsocketpair\fp(2) 2.0 t{ see notes on \fbsocketcall\fp(2) t} .\" 5a0015d62668e64c8b6e02e360fbbea121bfd5e6 \fbspill\fp(2) 2.6.13 xtensa only \fbsplice\fp(2) 2.6.17 \fbspu_create\fp(2) 2.6.16 t{ powerpc/powerpc64 only t} \fbspu_run\fp(2) 2.6.16 t{ powerpc/powerpc64 only t} \fbssetmask\fp(2) 1.0 \fbstat\fp(2) 1.0 \fbstat64\fp(2) 2.4 \fbstatfs\fp(2) 1.0 \fbstatfs64\fp(2) 2.6 \fbstatx\fp(2) 4.11 \fbstime\fp(2) 1.0 \fbsubpage_prot\fp(2) 2.6.25 t{ powerpc/powerpc64 only t} \fbswapcontext\fp(2) 2.6.3 t{ powerpc/powerpc64 only t} .\" 529d235a0e190ded1d21ccc80a73e625ebcad09b \fbswitch_endian\fp(2) 4.1 powerpc64 only \fbswapoff\fp(2) 1.0 \fbswapon\fp(2) 1.0 \fbsymlink\fp(2) 1.0 \fbsymlinkat\fp(2) 2.6.16 \fbsync\fp(2) 1.0 \fbsync_file_range\fp(2) 2.6.17 \fbsync_file_range2\fp(2) 2.6.22 .\" powerpc, arm, tile .\" first appeared on arm, as arm_sync_file_range(), but later renamed .\" \fbsys_debug_setcontext\fp(2) ??? powerpc if config_ppc32 \fbsyncfs\fp(2) 2.6.39 \fbsys_debug_setcontext\fp(2) 2.6.11 powerpc only \fbsyscall\fp(2) 1.0 t{ still available on arm oabi and mips o32 abi t} \fbsysfs\fp(2) 1.2 \fbsysinfo\fp(2) 1.0 \fbsyslog\fp(2) 1.0 .\" glibc interface is \fbklogctl\fp(3) \fbsysmips\fp(2) 2.6.0 mips only \fbtee\fp(2) 2.6.17 \fbtgkill\fp(2) 2.6 \fbtime\fp(2) 1.0 \fbtimer_create\fp(2) 2.6 \fbtimer_delete\fp(2) 2.6 \fbtimer_getoverrun\fp(2) 2.6 \fbtimer_gettime\fp(2) 2.6 \fbtimer_settime\fp(2) 2.6 .\" .\" b215e283992899650c4271e7385c79e26fb9a88e .\" .\" 4d672e7ac79b5ec5cdc90e450823441e20464691 .\" \fbtimerfd\fp(2) 2.6.22 t{ .\" old timerfd interface, .\" removed in 2.6.25 .\" t} \fbtimerfd_create\fp(2) 2.6.25 \fbtimerfd_gettime\fp(2) 2.6.25 \fbtimerfd_settime\fp(2) 2.6.25 \fbtimes\fp(2) 1.0 \fbtkill\fp(2) 2.6; 2.4.22 \fbtruncate\fp(2) 1.0 \fbtruncate64\fp(2) 2.4 \fbugetrlimit\fp(2) 2.4 \fbumask\fp(2) 1.0 \fbumount\fp(2) 1.0 .\" sys_oldumount() -- __nr_umount \fbumount2\fp(2) 2.2 .\" sys_umount() -- __nr_umount2 \fbuname\fp(2) 1.0 \fbunlink\fp(2) 1.0 \fbunlinkat\fp(2) 2.6.16 \fbunshare\fp(2) 2.6.16 \fbuselib\fp(2) 1.0 \fbustat\fp(2) 1.0 \fbuserfaultfd\fp(2) 4.3 \fbusr26\fp(2) 2.4.8.1 arm oabi only \fbusr32\fp(2) 2.4.8.1 arm oabi only \fbutime\fp(2) 1.0 \fbutimensat\fp(2) 2.6.22 \fbutimes\fp(2) 2.2 \fbutrap_install\fp(2) 2.2 sparc64 only .\" fixme . document utrap_install() .\" there's a man page for solaris 5.11 \fbvfork\fp(2) 2.2 \fbvhangup\fp(2) 1.0 \fbvm86old\fp(2) 1.0 t{ was "vm86"; renamed in 2.0.28/2.2 t} \fbvm86\fp(2) 2.0.28; 2.2 \fbvmsplice\fp(2) 2.6.17 \fbwait4\fp(2) 1.0 \fbwaitid\fp(2) 2.6.10 \fbwaitpid\fp(2) 1.0 \fbwrite\fp(2) 1.0 \fbwritev\fp(2) 2.0 .\" 5a0015d62668e64c8b6e02e360fbbea121bfd5e6 \fbxtensa\fp(2) 2.6.13 xtensa only .te .ad .hy .pp on many platforms, including x86-32, socket calls are all multiplexed (via glibc wrapper functions) through .br socketcall (2) and similarly system\ v ipc calls are multiplexed through .br ipc (2). .pp although slots are reserved for them in the system call table, the following system calls are not implemented in the standard kernel: .br afs_syscall (2), \" __nr_afs_syscall is 53 on linux 2.6.22/i386 .br break (2), \" __nr_break is 17 on linux 2.6.22/i386 .br ftime (2), \" __nr_ftime is 35 on linux 2.6.22/i386 .br getpmsg (2), \" __nr_getpmsg is 188 on linux 2.6.22/i386 .br gtty (2), \" __nr_gtty is 32 on linux 2.6.22/i386 .br idle (2), \" __nr_idle is 112 on linux 2.6.22/i386 .br lock (2), \" __nr_lock is 53 on linux 2.6.22/i386 .br madvise1 (2), \" __nr_madvise1 is 219 on linux 2.6.22/i386 .br mpx (2), \" __nr_mpx is 66 on linux 2.6.22/i386 .br phys (2), \" slot has been reused .br prof (2), \" __nr_prof is 44 on linux 2.6.22/i386 .br profil (2), \" __nr_profil is 98 on linux 2.6.22/i386 .br putpmsg (2), \" __nr_putpmsg is 189 on linux 2.6.22/i386 .\" __nr_security is 223 on linux 2.4/i386; absent on 2.6/i386, present .\" on a couple of 2.6 architectures .br security (2), \" __nr_security is 223 on linux 2.4/i386 .\" the security call is for future use. .br stty (2), \" __nr_stty is 31 on linux 2.6.22/i386 .br tuxcall (2), \" __nr_tuxcall is 184 on x86_64, also on ppc and alpha .br ulimit (2), \" __nr_ulimit is 58 on linux 2.6.22/i386 and .br vserver (2) \" __nr_vserver is 273 on linux 2.6.22/i386 (see also .br unimplemented (2)). however, .br ftime (3), .br profil (3), and .br ulimit (3) exist as library routines. the slot for .br phys (2) is in use since kernel 2.1.116 for .br umount (2); .br phys (2) will never be implemented. the .br getpmsg (2) and .br putpmsg (2) calls are for kernels patched to support streams, and may never be in the standard kernel. .pp there was briefly .br set_zone_reclaim (2), added in linux 2.6.13, and removed in 2.6.16; this system call was never available to user space. .\" .ss system calls on removed ports some system calls only ever existed on linux architectures that have since been removed from the kernel: .tp avr32 (port removed in linux 4.12) .rs .pd 0 .ip * 2 .br pread (2) .ip * .br pwrite (2) .pd .re .tp blackfin (port removed in linux 4.17) .rs .pd 0 .ip * 2 .br bfin_spinlock (2) (added in linux 2.6.22) .ip * .br dma_memcpy (2) (added in linux 2.6.22) .ip * .br pread (2) (added in linux 2.6.22) .ip * .br pwrite (2) (added in linux 2.6.22) .ip * .br sram_alloc (2) (added in linux 2.6.22) .ip * .br sram_free (2) (added in linux 2.6.22) .pd .re .tp metag (port removed in linux 4.17) .rs .pd 0 .ip * 2 .br metag_get_tls (2) (add in linux 3.9) .ip * .br metag_set_fpu_flags (2) (add in linux 3.9) .ip * .br metag_set_tls (2) (add in linux 3.9) .ip * .br metag_setglobalbit (2) (add in linux 3.9) .pd .re .tp tile (port removed in linux 4.17) .rs .pd 0 .ip * 2 .br cmpxchg_badaddr (2) (added in linux 2.6.36) .pd .re .sh notes roughly speaking, the code belonging to the system call with number __nr_xxx defined in .i /usr/include/asm/unistd.h can be found in the linux kernel source in the routine .ir sys_xxx (). there are many exceptions, however, mostly because older system calls were superseded by newer ones, and this has been treated somewhat unsystematically. on platforms with proprietary operating-system emulation, such as sparc, sparc64, and alpha, there are many additional system calls; mips64 also contains a full set of 32-bit system calls. .pp over time, changes to the interfaces of some system calls have been necessary. one reason for such changes was the need to increase the size of structures or scalar values passed to the system call. because of these changes, certain architectures (notably, longstanding 32-bit architectures such as i386) now have various groups of related system calls (e.g., .br truncate (2) and .br truncate64 (2)) which perform similar tasks, but which vary in details such as the size of their arguments. (as noted earlier, applications are generally unaware of this: the glibc wrapper functions do some work to ensure that the right system call is invoked, and that abi compatibility is preserved for old binaries.) examples of systems calls that exist in multiple versions are the following: .ip * 3 by now there are three different versions of .br stat (2): .ir sys_stat () (slot .ir __nr_oldstat ), .ir sys_newstat () (slot .ir __nr_stat ), and .ir sys_stat64 () (slot .ir __nr_stat64 ), with the last being the most current. .\" e.g., on 2.6.22/i386: __nr_oldstat 18, __nr_stat 106, __nr_stat64 195 .\" the stat system calls deal with three different data structures, .\" defined in include/asm-i386/stat.h: __old_kernel_stat, stat, stat64 a similar story applies for .br lstat (2) and .br fstat (2). .ip * similarly, the defines .ir __nr_oldolduname , .ir __nr_olduname , and .i __nr_uname refer to the routines .ir sys_olduname (), .ir sys_uname (), and .ir sys_newuname (). .ip * in linux 2.0, a new version of .br vm86 (2) appeared, with the old and the new kernel routines being named .ir sys_vm86old () and .ir sys_vm86 (). .ip * in linux 2.4, a new version of .br getrlimit (2) appeared, with the old and the new kernel routines being named .ir sys_old_getrlimit () (slot .ir __nr_getrlimit ) and .ir sys_getrlimit () (slot .ir __nr_ugetrlimit ). .ip * linux 2.4 increased the size of user and group ids from 16 to 32 bits. .\" 64-bit off_t changes: ftruncate64, *stat64, .\" fcntl64 (because of the flock structure), getdents64, *statfs64 to support this change, a range of system calls were added (e.g., .br chown32 (2), .br getuid32 (2), .br getgroups32 (2), .br setresuid32 (2)), superseding earlier calls of the same name without the "32" suffix. .ip * linux 2.4 added support for applications on 32-bit architectures to access large files (i.e., files for which the sizes and file offsets can't be represented in 32 bits.) to support this change, replacements were required for system calls that deal with file offsets and sizes. thus the following system calls were added: .br fcntl64 (2), .br getdents64 (2), .br stat64 (2), .br statfs64 (2), .br truncate64 (2), and their analogs that work with file descriptors or symbolic links. these system calls supersede the older system calls which, except in the case of the "stat" calls, have the same name without the "64" suffix. .ip on newer platforms that only have 64-bit file access and 32-bit uids/gids (e.g., alpha, ia64, s390x, x86-64), there is just a single version of the uid/gid and file access system calls. on platforms (typically, 32-bit platforms) where the *64 and *32 calls exist, the other versions are obsolete. .ip * the .i rt_sig* calls were added in kernel 2.2 to support the addition of real-time signals (see .br signal (7)). these system calls supersede the older system calls of the same name without the "rt_" prefix. .ip * the .br select (2) and .br mmap (2) system calls use five or more arguments, which caused problems in the way argument passing on the i386 used to be set up. thus, while other architectures have .ir sys_select () and .ir sys_mmap () corresponding to .i __nr_select and .ir __nr_mmap , on i386 one finds .ir old_select () and .ir old_mmap () (routines that use a pointer to an argument block) instead. these days passing five arguments is not a problem any more, and there is a .i __nr__newselect .\" (used by libc 6) that corresponds directly to .ir sys_select () and similarly .ir __nr_mmap2 . s390x is the only 64-bit architecture that has .ir old_mmap (). .\" .pp .\" two system call numbers, .\" .ir __nr__llseek .\" and .\" .ir __nr__sysctl .\" have an additional underscore absent in .\" .ir sys_llseek () .\" and .\" .ir sys_sysctl (). .\" .\" in kernel 2.1.81, .\" .br lchown (2) .\" and .\" .br chown (2) .\" were swapped; that is, .\" .br lchown (2) .\" was added with the semantics that were then current for .\" .br chown (2), .\" and the semantics of the latter call were changed to what .\" they are today. .\" .\" .ss "architecture-specific details: alpha" .ip * 3 .br getxgid (2) returns a pair of gid and effective gid via registers \fbr0\fp and \fbr20\fp; it is provided instead of \fbgetgid\fp(2) and \fbgetegid\fp(2). .ip * .br getxpid (2) returns a pair of pid and parent pid via registers \fbr0\fp and \fbr20\fp; it is provided instead of \fbgetpid\fp(2) and \fbgetppid\fp(2). .ip * .br old_adjtimex (2) is a variant of \fbadjtimex\fp(2) that uses \fistruct timeval32\fp, for compatibility with osf/1. .ip * .br getxuid (2) returns a pair of gid and effective gid via registers \fbr0\fp and \fbr20\fp; it is provided instead of \fbgetuid\fp(2) and \fbgeteuid\fp(2). .ip * .br sethae (2) is used for configuring the host address extension register on low-cost alphas in order to access address space beyond first 27 bits. .sh see also .br ausyscall (1) .br intro (2), .br syscall (2), .br unimplemented (2), .br errno (3), .br libc (7), .br vdso (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: cmsg.3,v 1.8 2000/12/20 18:10:31 ak exp $ .th cmsg 3 2021-03-22 "linux" "linux programmer's manual" .sh name cmsg_align, cmsg_space, cmsg_nxthdr, cmsg_firsthdr \- access ancillary data .sh synopsis .nf .b #include .pp .bi "struct cmsghdr *cmsg_firsthdr(struct msghdr *" msgh ); .bi "struct cmsghdr *cmsg_nxthdr(struct msghdr *" msgh , .br " struct cmsghdr *" cmsg ); .bi "size_t cmsg_align(size_t " length ); .bi "size_t cmsg_space(size_t " length ); .bi "size_t cmsg_len(size_t " length ); .bi "unsigned char *cmsg_data(struct cmsghdr *" cmsg ); .fi .sh description these macros are used to create and access control messages (also called ancillary data) that are not a part of the socket payload. this control information may include the interface the packet was received on, various rarely used header fields, an extended error description, a set of file descriptors, or unix credentials. for instance, control messages can be used to send additional header fields such as ip options. ancillary data is sent by calling .br sendmsg (2) and received by calling .br recvmsg (2). see their manual pages for more information. .pp ancillary data is a sequence of .i cmsghdr structures with appended data. see the specific protocol man pages for the available control message types. the maximum ancillary buffer size allowed per socket can be set using .ir /proc/sys/net/core/optmem_max ; see .br socket (7). .pp the .i cmsghdr structure is defined as follows: .pp .in +4n .ex struct cmsghdr { size_t cmsg_len; /* data byte count, including header (type is socklen_t in posix) */ int cmsg_level; /* originating protocol */ int cmsg_type; /* protocol\-specific type */ /* followed by unsigned char cmsg_data[]; */ }; .ee .in .pp the sequence of .i cmsghdr structures should never be accessed directly. instead, use only the following macros: .ip * 3 .br cmsg_firsthdr () returns a pointer to the first .i cmsghdr in the ancillary data buffer associated with the passed .ir msghdr . it returns null if there isn't enough space for a .i cmsghdr in the buffer. .ip * .br cmsg_nxthdr () returns the next valid .i cmsghdr after the passed .ir cmsghdr . it returns null when there isn't enough space left in the buffer. .ip when initializing a buffer that will contain a series of .i cmsghdr structures (e.g., to be sent with .br sendmsg (2)), that buffer should first be zero-initialized to ensure the correct operation of .br cmsg_nxthdr (). .ip * .br cmsg_align (), given a length, returns it including the required alignment. this is a constant expression. .ip * .br cmsg_space () returns the number of bytes an ancillary element with payload of the passed data length occupies. this is a constant expression. .ip * .br cmsg_data () returns a pointer to the data portion of a .ir cmsghdr . the pointer returned cannot be assumed to be suitably aligned for accessing arbitrary payload data types. applications should not cast it to a pointer type matching the payload, but should instead use .br memcpy (3) to copy data to or from a suitably declared object. .ip * .br cmsg_len () returns the value to store in the .i cmsg_len member of the .i cmsghdr structure, taking into account any necessary alignment. it takes the data length as an argument. this is a constant expression. .pp to create ancillary data, first initialize the .i msg_controllen member of the .i msghdr with the length of the control message buffer. use .br cmsg_firsthdr () on the .i msghdr to get the first control message and .br cmsg_nxthdr () to get all subsequent ones. in each control message, initialize .i cmsg_len (with .br cmsg_len ()), the other .i cmsghdr header fields, and the data portion using .br cmsg_data (). finally, the .i msg_controllen field of the .i msghdr should be set to the sum of the .br cmsg_space () of the length of all control messages in the buffer. for more information on the .ir msghdr , see .br recvmsg (2). .sh conforming to this ancillary data model conforms to the posix.1g draft, 4.4bsd-lite, the ipv6 advanced api described in rfc\ 2292 and susv2. .br cmsg_firsthdr (), .br cmsg_nxthdr (), and .br cmsg_data () are specified in posix.1-2008. .br cmsg_space () and .br cmsg_len () .\" https://www.austingroupbugs.net/view.php?id=978#c3242 will be included in the next posix release (issue 8). .pp .br cmsg_align () is a linux extension. .sh notes for portability, ancillary data should be accessed using only the macros described here. .br cmsg_align () is a linux extension and should not be used in portable programs. .pp in linux, .br cmsg_len (), .br cmsg_data (), and .br cmsg_align () are constant expressions (assuming their argument is constant), meaning that these values can be used to declare the size of global variables. this may not be portable, however. .sh examples this code looks for the .b ip_ttl option in a received ancillary buffer: .pp .in +4n .ex struct msghdr msgh; struct cmsghdr *cmsg; int received_ttl; /* receive auxiliary data in msgh */ for (cmsg = cmsg_firsthdr(&msgh); cmsg != null; cmsg = cmsg_nxthdr(&msgh, cmsg)) { if (cmsg\->cmsg_level == ipproto_ip && cmsg\->cmsg_type == ip_ttl) { memcpy(&receive_ttl, cmsg_data(cmsg), sizeof(received_ttl)); break; } } if (cmsg == null) { /* error: ip_ttl not enabled or small buffer or i/o error */ } .ee .in .pp the code below passes an array of file descriptors over a unix domain socket using .br scm_rights : .pp .in +4n .ex struct msghdr msg = { 0 }; struct cmsghdr *cmsg; int myfds[num_fd]; /* contains the file descriptors to pass */ char iobuf[1]; struct iovec io = { .iov_base = iobuf, .iov_len = sizeof(iobuf) }; union { /* ancillary data buffer, wrapped in a union in order to ensure it is suitably aligned */ char buf[cmsg_space(sizeof(myfds))]; struct cmsghdr align; } u; msg.msg_iov = &io; msg.msg_iovlen = 1; msg.msg_control = u.buf; msg.msg_controllen = sizeof(u.buf); cmsg = cmsg_firsthdr(&msg); cmsg\->cmsg_level = sol_socket; cmsg\->cmsg_type = scm_rights; cmsg\->cmsg_len = cmsg_len(sizeof(myfds)); memcpy(cmsg_data(cmsg), myfds, sizeof(myfds)); .ee .in .pp for a complete code example that shows passing of file descriptors over a unix domain socket, see .br seccomp_unotify (2). .sh see also .br recvmsg (2), .br sendmsg (2) .pp rfc\ 2292 .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getrlimit.2 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_detach 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_detach \- detach a thread .sh synopsis .nf .b #include .pp .bi "int pthread_detach(pthread_t " thread ); .fi .pp compile and link with \fi\-pthread\fp. .sh description the .br pthread_detach () function marks the thread identified by .ir thread as detached. when a detached thread terminates, its resources are automatically released back to the system without the need for another thread to join with the terminated thread. .pp attempting to detach an already detached thread results in unspecified behavior. .sh return value on success, .br pthread_detach () returns 0; on error, it returns an error number. .sh errors .tp .b einval .i thread is not a joinable thread. .tp .b esrch no thread with the id .i thread could be found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_detach () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes once a thread has been detached, it can't be joined with .br pthread_join (3) or be made joinable again. .pp a new thread can be created in a detached state using .br pthread_attr_setdetachstate (3) to set the detached attribute of the .i attr argument of .br pthread_create (3). .pp the detached attribute merely determines the behavior of the system when the thread terminates; it does not prevent the thread from being terminated if the process terminates using .br exit (3) (or equivalently, if the main thread returns). .pp either .br pthread_join (3) or .br pthread_detach () should be called for each thread that an application creates, so that system resources for the thread can be released. (but note that the resources of any threads for which one of these actions has not been done will be freed when the process terminates.) .sh examples the following statement detaches the calling thread: .pp pthread_detach(pthread_self()); .sh see also .br pthread_attr_setdetachstate (3), .br pthread_cancel (3), .br pthread_create (3), .br pthread_exit (3), .br pthread_join (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sync.2 .so man3/rpc.3 .so man3/getprotoent.3 .\" this manpage is copyright (c) 2006, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th futimesat 2 2021-08-27 "linux" "linux programmer's manual" .sh name futimesat \- change timestamps of a file relative to a \ directory file descriptor .sh synopsis .nf .br "#include " " /* definition of " at_* " constants */" .b #include .pp .bi "int futimesat(int " dirfd ", const char *" pathname , .bi " const struct timeval " times [2]); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br futimesat (): .nf _gnu_source .fi .sh description this system call is obsolete. use .br utimensat (2) instead. .pp the .br futimesat () system call operates in exactly the same way as .br utimes (2), except for the differences described in this manual page. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br utimes (2) for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br utimes (2)). .pp if .i pathname is absolute, then .i dirfd is ignored. (see .br openat (2) for an explanation of why the .i dirfd argument is useful.) .sh return value on success, .br futimesat () returns a 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors the same errors that occur for .br utimes (2) can also occur for .br futimesat (). the following additional errors can occur for .br futimesat (): .tp .b ebadf .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b enotdir .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .sh versions .br futimesat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to this system call is nonstandard. it was implemented from a specification that was proposed for posix.1, but that specification was replaced by the one for .br utimensat (2). .pp a similar system call exists on solaris. .sh notes .ss glibc notes if .i pathname is null, then the glibc .br futimesat () wrapper function updates the times for the file referred to by .ir dirfd . .\" the solaris futimesat() also has this strangeness. .sh see also .br stat (2), .br utimensat (2), .br utimes (2), .br futimes (3), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:32:25 1993 by rik faith (faith@cs.unc.edu) .th gcvt 3 2021-03-22 "" "linux programmer's manual" .sh name gcvt \- convert a floating-point number to a string .sh synopsis .nf .b #include .pp .bi "char *gcvt(double " number ", int " ndigit ", char *" buf ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br gcvt (): .nf since glibc 2.17 (_xopen_source >= 500 && ! (_posix_c_source >= 200809l)) || /* glibc >= 2.20 */ _default_source || /* glibc <= 2.19 */ _svid_source glibc versions 2.12 to 2.16: (_xopen_source >= 500 && ! (_posix_c_source >= 200112l)) || _svid_source before glibc 2.12: _svid_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description the .br gcvt () function converts \finumber\fp to a minimal length null-terminated ascii string and stores the result in \fibuf\fp. it produces \findigit\fp significant digits in either .br printf (3) f format or e format. .sh return value the .br gcvt () function returns \fibuf\fp. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br gcvt () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to marked as legacy in posix.1-2001. posix.1-2008 removes the specification of .br gcvt (), recommending the use of .br sprintf (3) instead (though .br snprintf (3) may be preferable). .sh see also .br ecvt (3), .br fcvt (3), .br sprintf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2006, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-23 by rik faith .\" modified 1994-08-21 by michael haardt .\" modified 2004-06-23 by michael kerrisk .\" modified 2005-04-04, as per suggestion by michael hardt for rename.2 .\" .th link 2 2021-08-27 "linux" "linux programmer's manual" .sh name link, linkat \- make a new name for a file .sh synopsis .nf .b #include .pp .bi "int link(const char *" oldpath ", const char *" newpath ); .pp .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "int linkat(int " olddirfd ", const char *" oldpath , .bi " int " newdirfd ", const char *" newpath ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br linkat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br link () creates a new link (also known as a hard link) to an existing file. .pp if .i newpath exists, it will .i not be overwritten. .pp this new name may be used exactly as the old one for any operation; both names refer to the same file (and so have the same permissions and ownership) and it is impossible to tell which name was the "original". .ss linkat() the .br linkat () system call operates in exactly the same way as .br link (), except for the differences described here. .pp if the pathname given in .i oldpath is relative, then it is interpreted relative to the directory referred to by the file descriptor .i olddirfd (rather than relative to the current working directory of the calling process, as is done by .br link () for a relative pathname). .pp if .i oldpath is relative and .i olddirfd is the special value .br at_fdcwd , then .i oldpath is interpreted relative to the current working directory of the calling process (like .br link ()). .pp if .i oldpath is absolute, then .i olddirfd is ignored. .pp the interpretation of .i newpath is as for .ir oldpath , except that a relative pathname is interpreted relative to the directory referred to by the file descriptor .ir newdirfd . .pp the following values can be bitwise ored in .ir flags : .tp .br at_empty_path " (since linux 2.6.39)" .\" commit 11a7b371b64ef39fc5fb1b6f2218eef7c4d035e3 if .i oldpath is an empty string, create a link to the file referenced by .ir olddirfd (which may have been obtained using the .br open (2) .b o_path flag). in this case, .i olddirfd can refer to any type of file except a directory. this will generally not work if the file has a link count of zero (files created with .br o_tmpfile and without .br o_excl are an exception). the caller must have the .br cap_dac_read_search capability in order to use this flag. this flag is linux-specific; define .b _gnu_source .\" before glibc 2.16, defining _atfile_source sufficed to obtain its definition. .tp .br at_symlink_follow " (since linux 2.6.18)" by default, .br linkat (), does not dereference .i oldpath if it is a symbolic link (like .br link ()). the flag .b at_symlink_follow can be specified in .i flags to cause .i oldpath to be dereferenced if it is a symbolic link. if procfs is mounted, this can be used as an alternative to .br at_empty_path , like this: .ip .in +4n .ex linkat(at_fdcwd, "/proc/self/fd/", newdirfd, newname, at_symlink_follow); .ee .in .pp before kernel 2.6.18, the .i flags argument was unused, and had to be specified as 0. .pp see .br openat (2) for an explanation of the need for .br linkat (). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces write access to the directory containing .i newpath is denied, or search permission is denied for one of the directories in the path prefix of .i oldpath or .ir newpath . (see also .br path_resolution (7).) .tp .b edquot the user's quota of disk blocks on the filesystem has been exhausted. .tp .b eexist .i newpath already exists. .tp .b efault .ir oldpath " or " newpath " points outside your accessible address space." .tp .b eio an i/o error occurred. .tp .b eloop too many symbolic links were encountered in resolving .ir oldpath " or " newpath . .tp .b emlink the file referred to by .i oldpath already has the maximum number of links to it. for example, on an .br ext4 (5) filesystem that does not employ the .i dir_index feature, the limit on the number of hard links to a file is 65,000; on .br btrfs (5), the limit is 65,535 links. .tp .b enametoolong .ir oldpath " or " newpath " was too long." .tp .b enoent a directory component in .ir oldpath " or " newpath does not exist or is a dangling symbolic link. .tp .b enomem insufficient kernel memory was available. .tp .b enospc the device containing the file has no room for the new directory entry. .tp .b enotdir a component used as a directory in .ir oldpath " or " newpath is not, in fact, a directory. .tp .b eperm .i oldpath is a directory. .tp .b eperm the filesystem containing .ir oldpath " and " newpath does not support the creation of hard links. .tp .br eperm " (since linux 3.6)" the caller does not have permission to create a hard link to this file (see the description of .ir /proc/sys/fs/protected_hardlinks in .br proc (5)). .tp .b eperm .i oldpath is marked immutable or append-only. (see .br ioctl_iflags (2).) .tp .b erofs the file is on a read-only filesystem. .tp .b exdev .ir oldpath " and " newpath are not on the same mounted filesystem. (linux permits a filesystem to be mounted at multiple points, but .br link () does not work across different mounts, even if the same filesystem is mounted on both.) .pp the following additional errors can occur for .br linkat (): .tp .b ebadf .i oldpath .ri ( newpath ) is relative but .i olddirfd .ri ( newdirfd ) is neither .b at_fdcwd nor a valid file descriptor. .tp .b einval an invalid flag value was specified in .ir flags . .tp .b enoent .b at_empty_path was specified in .ir flags , but the caller did not have the .b cap_dac_read_search capability. .tp .b enoent an attempt was made to link to the .i /proc/self/fd/nn file corresponding to a file descriptor created with .ip .in +4n .ex open(path, o_tmpfile | o_excl, mode); .ee .in .ip see .br open (2). .tp .b enoent an attempt was made to link to a .i /proc/self/fd/nn file corresponding to a file that has been deleted. .tp .b enoent .i oldpath is a relative pathname and .i olddirfd refers to a directory that has been deleted, or .i newpath is a relative pathname and .i newdirfd refers to a directory that has been deleted. .tp .b enotdir .i oldpath is relative and .i olddirfd is a file descriptor referring to a file other than a directory; or similar for .i newpath and .i newdirfd .tp .b eperm .br at_empty_path was specified in .ir flags , .i oldpath is an empty string, and .ir olddirfd refers to a directory. .sh versions .br linkat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br link (): svr4, 4.3bsd, posix.1-2001 (but see notes), posix.1-2008. .\" svr4 documents additional enolink and .\" emultihop error conditions; posix.1 does not document eloop. .\" x/open does not document efault, enomem or eio. .pp .br linkat (): posix.1-2008. .sh notes hard links, as created by .br link (), cannot span filesystems. use .br symlink (2) if this is required. .pp posix.1-2001 says that .br link () should dereference .i oldpath if it is a symbolic link. however, since kernel 2.0, .\" more precisely: since kernel 1.3.56 linux does not do so: if .i oldpath is a symbolic link, then .i newpath is created as a (hard) link to the same symbolic link file (i.e., .i newpath becomes a symbolic link to the same file that .i oldpath refers to). some other implementations behave in the same manner as linux. .\" for example, the default solaris compilation environment .\" behaves like linux, and contributors to a march 2005 .\" thread in the austin mailing list reported that some .\" other (system v) implementations did/do the same -- mtk, apr 05 posix.1-2008 changes the specification of .br link (), making it implementation-dependent whether or not .i oldpath is dereferenced if it is a symbolic link. for precise control over the treatment of symbolic links when creating a link, use .br linkat (). .ss glibc notes on older kernels where .br linkat () is unavailable, the glibc wrapper function falls back to the use of .br link (), unless the .b at_symlink_follow is specified. when .i oldpath and .i newpath are relative pathnames, glibc constructs pathnames based on the symbolic links in .ir /proc/self/fd that correspond to the .i olddirfd and .ir newdirfd arguments. .sh bugs on nfs filesystems, the return code may be wrong in case the nfs server performs the link creation and dies before it can say so. use .br stat (2) to find out if the link got created. .sh see also .br ln (1), .br open (2), .br rename (2), .br stat (2), .br symlink (2), .br unlink (2), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1999 andries brouwer (aeb@cwi.nl), 1 nov 1999 .\" and copyright 2006, 2012, 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 1999-11-10: merged text taken from the page contributed by .\" reed h. petty (rhp@draper.net) .\" .th vfork 2 2021-03-22 "linux" "linux programmer's manual" .sh name vfork \- create a child process and block parent .sh synopsis .nf .b #include .pp .b pid_t vfork(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br vfork (): .nf since glibc 2.12: (_xopen_source >= 500) && ! (_posix_c_source >= 200809l) || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source before glibc 2.12: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description .ss standard description (from posix.1) the .br vfork () function has the same effect as .br fork (2), except that the behavior is undefined if the process created by .br vfork () either modifies any data other than a variable of type .i pid_t used to store the return value from .br vfork (), or returns from the function in which .br vfork () was called, or calls any other function before successfully calling .br _exit (2) or one of the .br exec (3) family of functions. .ss linux description .br vfork (), just like .br fork (2), creates a child process of the calling process. for details and return value and errors, see .br fork (2). .pp .br vfork () is a special case of .br clone (2). it is used to create new processes without copying the page tables of the parent process. it may be useful in performance-sensitive applications where a child is created which then immediately issues an .br execve (2). .pp .br vfork () differs from .br fork (2) in that the calling thread is suspended until the child terminates (either normally, by calling .br _exit (2), or abnormally, after delivery of a fatal signal), or it makes a call to .br execve (2). until that point, the child shares all memory with its parent, including the stack. the child must not return from the current function or call .br exit (3) (which would have the effect of calling exit handlers established by the parent process and flushing the parent's .br stdio (3) buffers), but may call .br _exit (2). .pp as with .br fork (2), the child process created by .br vfork () inherits copies of various of the caller's process attributes (e.g., file descriptors, signal dispositions, and current working directory); the .br vfork () call differs only in the treatment of the virtual address space, as described above. .pp signals sent to the parent arrive after the child releases the parent's memory (i.e., after the child terminates or calls .br execve (2)). .ss historic description under linux, .br fork (2) is implemented using copy-on-write pages, so the only penalty incurred by .br fork (2) is the time and memory required to duplicate the parent's page tables, and to create a unique task structure for the child. however, in the bad old days a .br fork (2) would require making a complete copy of the caller's data space, often needlessly, since usually immediately afterward an .br exec (3) is done. thus, for greater efficiency, bsd introduced the .br vfork () system call, which did not fully copy the address space of the parent process, but borrowed the parent's memory and thread of control until a call to .br execve (2) or an exit occurred. the parent process was suspended while the child was using its resources. the use of .br vfork () was tricky: for example, not modifying data in the parent process depended on knowing which variables were held in a register. .sh conforming to 4.3bsd; posix.1-2001 (but marked obsolete). posix.1-2008 removes the specification of .br vfork (). .pp the requirements put on .br vfork () by the standards are weaker than those put on .br fork (2), so an implementation where the two are synonymous is compliant. in particular, the programmer cannot rely on the parent remaining blocked until the child either terminates or calls .br execve (2), and cannot rely on any specific behavior with respect to shared memory. .\" in aixv3.1 vfork is equivalent to fork. .sh notes some consider the semantics of .br vfork () to be an architectural blemish, and the 4.2bsd man page stated: "this system call will be eliminated when proper system sharing mechanisms are implemented. users should not depend on the memory sharing semantics of .br vfork () as it will, in that case, be made synonymous to .br fork (2).\c " however, even though modern memory management hardware has decreased the performance difference between .br fork (2) and .br vfork (), there are various reasons why linux and other systems have retained .br vfork (): .ip * 3 some performance-critical applications require the small performance advantage conferred by .br vfork (). .ip * .br vfork () can be implemented on systems that lack a memory-management unit (mmu), but .br fork (2) can't be implemented on such systems. (posix.1-2008 removed .br vfork () from the standard; the posix rationale for the .br posix_spawn (3) function notes that that function, which provides functionality equivalent to .br fork (2)+ exec (3), is designed to be implementable on systems that lack an mmu.) .\" http://stackoverflow.com/questions/4259629/what-is-the-difference-between-fork-and-vfork .\" http://developers.sun.com/solaris/articles/subprocess/subprocess.html .\" http://mailman.uclinux.org/pipermail/uclinux-dev/2009-april/000684.html .\" .ip * on systems where memory is constrained, .br vfork () avoids the need to temporarily commit memory (see the description of .ir /proc/sys/vm/overcommit_memory in .br proc (5)) in order to execute a new program. (this can be especially beneficial where a large parent process wishes to execute a small helper program in a child process.) by contrast, using .br fork (2) in this scenario requires either committing an amount of memory equal to the size of the parent process (if strict overcommitting is in force) or overcommitting memory with the risk that a process is terminated by the out-of-memory (oom) killer. .\" .ss caveats the child process should take care not to modify the memory in unintended ways, since such changes will be seen by the parent process once the child terminates or executes another program. in this regard, signal handlers can be especially problematic: if a signal handler that is invoked in the child of .br vfork () changes memory, those changes may result in an inconsistent process state from the perspective of the parent process (e.g., memory changes would be visible in the parent, but changes to the state of open file descriptors would not be visible). .pp when .br vfork () is called in a multithreaded process, only the calling thread is suspended until the child terminates or executes a new program. this means that the child is sharing an address space with other running code. this can be dangerous if another thread in the parent process changes credentials (using .br setuid (2) or similar), since there are now two processes with different privilege levels running in the same address space. as an example of the dangers, suppose that a multithreaded program running as root creates a child using .br vfork (). after the .br vfork (), a thread in the parent process drops the process to an unprivileged user in order to run some untrusted code (e.g., perhaps via plug-in opened with .br dlopen (3)). in this case, attacks are possible where the parent process uses .br mmap (2) to map in code that will be executed by the privileged child process. .\" .ss linux notes fork handlers established using .br pthread_atfork (3) are not called when a multithreaded program employing the nptl threading library calls .br vfork (). fork handlers are called in this case in a program using the linuxthreads threading library. (see .br pthreads (7) for a description of linux threading libraries.) .pp a call to .br vfork () is equivalent to calling .br clone (2) with .i flags specified as: .pp clone_vm | clone_vfork | sigchld .ss history the .br vfork () system call appeared in 3.0bsd. .\" in the release notes for 4.2bsd sam leffler wrote: `vfork: is still .\" present, but definitely on its way out'. in 4.4bsd it was made synonymous to .br fork (2) but netbsd introduced it again; see .ur http://www.netbsd.org\:/documentation\:/kernel\:/vfork.html .ue . in linux, it has been equivalent to .br fork (2) until 2.2.0-pre6 or so. since 2.2.0-pre9 (on i386, somewhat later on other architectures) it is an independent system call. support was added in glibc 2.0.112. .sh bugs details of the signal handling are obscure and differ between systems. the bsd man page states: "to avoid a possible deadlock situation, processes that are children in the middle of a .br vfork () are never sent .b sigttou or .b sigttin signals; rather, output or .ir ioctl s are allowed and input attempts result in an end-of-file indication." .\" .\" as far as i can tell, the following is not true in 2.6.19: .\" currently (linux 2.3.25), .\" .br strace (1) .\" cannot follow .\" .br vfork () .\" and requires a kernel patch. .sh see also .br clone (2), .br execve (2), .br _exit (2), .br fork (2), .br unshare (2), .br wait (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/kexec_load.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wmemmove 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wmemmove \- copy an array of wide-characters .sh synopsis .nf .b #include .pp .bi "wchar_t *wmemmove(wchar_t *" dest ", const wchar_t *" src ", size_t " n ); .fi .sh description the .br wmemmove () function is the wide-character equivalent of the .br memmove (3) function. it copies .i n wide characters from the array starting at .i src to the array starting at .ir dest . the arrays may overlap. .pp the programmer must ensure that there is room for at least .i n wide characters at .ir dest . .sh return value .br wmemmove () returns .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wmemmove () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br memmove (3), .br wmemcpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright (c) 2011 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cacos 3 2021-03-22 "" "linux programmer's manual" .sh name cacos, cacosf, cacosl \- complex arc cosine .sh synopsis .nf .b #include .pp .bi "double complex cacos(double complex " z ); .bi "float complex cacosf(float complex " z ); .bi "long double complex cacosl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex arc cosine of .ir z . if \fiy\ =\ cacos(z)\fp, then \fiz\ =\ ccos(y)\fp. the real part of .i y is chosen in the interval [0,pi]. .pp one has: .pp .nf cacos(z) = \-i * clog(z + i * csqrt(1 \- z * z)) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cacos (), .br cacosf (), .br cacosl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh examples .ex /* link with "\-lm" */ #include #include #include #include int main(int argc, char *argv[]) { double complex z, c, f; double complex i = i; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } z = atof(argv[1]) + atof(argv[2]) * i; c = cacos(z); printf("cacos() = %6.3f %6.3f*i\en", creal(c), cimag(c)); f = \-i * clog(z + i * csqrt(1 \- z * z)); printf("formula = %6.3f %6.3f*i\en", creal(f), cimag(f)); exit(exit_success); } .ee .sh see also .br ccos (3), .br clog (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setnetgrent.3 .so man3/sigvec.3 .so man2/setresuid.2 .so man3/posix_memalign.3 .so man3/pthread_rwlockattr_setkind_np.3 .\" copyright 1996 daniel quinlan (daniel.quinlan@linux.org) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2007-12-14 mtk added reiserfs, xfs, jfs. .\" .th filesystems 5 2020-12-21 "linux" "linux programmer's manual" .nh .sh name filesystems \- linux filesystem types: ext, ext2, ext3, ext4, hpfs, iso9660, jfs, minix, msdos, ncpfs nfs, ntfs, proc, reiserfs, smb, sysv, umsdos, vfat, xfs, xiafs .sh description when, as is customary, the .b proc filesystem is mounted on .ir /proc , you can find in the file .i /proc/filesystems which filesystems your kernel currently supports; see .br proc (5) for more details. there is also a legacy .br sysfs (2) system call (whose availability is controlled by the .\" commit: 6af9f7bf3c399e0ab1eee048e13572c6d4e15fe9 .b config_sysfs_syscall kernel build configuration option since linux 3.15) that enables enumeration of the currently available filesystem types regardless of .i /proc availability and/or sanity. .pp if you need a currently unsupported filesystem, insert the corresponding kernel module or recompile the kernel. .pp in order to use a filesystem, you have to .i mount it; see .br mount (2) and .br mount (8). .pp the following list provides a short description of the available or historically available filesystems in the linux kernel. see the kernel documentation for a comprehensive description of all options and limitations. .tp 10 .b ext is an elaborate extension of the .b minix filesystem. it has been completely superseded by the second version of the extended filesystem .rb ( ext2 ) and has been removed from the kernel (in 2.1.21). .tp .b ext2 is the high performance disk filesystem used by linux for fixed disks as well as removable media. the second extended filesystem was designed as an extension of the extended filesystem .rb ( ext ). see .br ext2 (5). .tp .b ext3 is a journaling version of the .b ext2 filesystem. it is easy to switch back and forth between .b ext2 and .br ext3 . see .br ext3 (5). .tp .b ext4 is a set of upgrades to .b ext3 including substantial performance and reliability enhancements, plus large increases in volume, file, and directory size limits. see .br ext4 (5). .tp .b hpfs is the high performance filesystem, used in os/2. this filesystem is read-only under linux due to the lack of available documentation. .tp .b iso9660 is a cd-rom filesystem type conforming to the iso 9660 standard. .rs .tp .b "high sierra" linux supports high sierra, the precursor to the iso 9660 standard for cd-rom filesystems. it is automatically recognized within the .b iso9660 filesystem support under linux. .tp .b "rock ridge" linux also supports the system use sharing protocol records specified by the rock ridge interchange protocol. they are used to further describe the files in the .b iso9660 filesystem to a unix host, and provide information such as long filenames, uid/gid, posix permissions, and devices. it is automatically recognized within the .b iso9660 filesystem support under linux. .re .tp .b jfs is a journaling filesystem, developed by ibm, that was integrated into linux in kernel 2.4.24. .tp .b minix is the filesystem used in the minix operating system, the first to run under linux. it has a number of shortcomings, including a 64\ mb partition size limit, short filenames, and a single timestamp. it remains useful for floppies and ram disks. .tp .b msdos is the filesystem used by dos, windows, and some os/2 computers. .b msdos filenames can be no longer than 8 characters, followed by an optional period and 3 character extension. .tp .b ncpfs is a network filesystem that supports the ncp protocol, used by novell netware. it was removed from the kernel in 4.17. .ip to use .br ncpfs , you need special programs, which can be found at .ur ftp://ftp.gwdg.de\:/pub\:/linux\:/misc\:/ncpfs .ue . .tp .b nfs is the network filesystem used to access disks located on remote computers. .tp .b ntfs is the filesystem native to microsoft windows nt, supporting features like acls, journaling, encryption, and so on. .tp .b proc is a pseudo filesystem which is used as an interface to kernel data structures rather than reading and interpreting .ir /dev/kmem . in particular, its files do not take disk space. see .br proc (5). .tp .b reiserfs is a journaling filesystem, designed by hans reiser, that was integrated into linux in kernel 2.4.1. .tp .b smb is a network filesystem that supports the smb protocol, used by windows for workgroups, windows nt, and lan manager. see .ur https://www.samba.org\:/samba\:/smbfs/ .ue . .tp .b sysv is an implementation of the system v/coherent filesystem for linux. it implements all of xenix fs, system v/386 fs, and coherent fs. .tp .b umsdos is an extended dos filesystem used by linux. it adds capability for long filenames, uid/gid, posix permissions, and special files (devices, named pipes, etc.) under the dos filesystem, without sacrificing compatibility with dos. .tp .b tmpfs is a filesystem whose contents reside in virtual memory. since the files on such filesystems typically reside in ram, file access is extremely fast. see .br tmpfs (5). .tp .b vfat is an extended fat filesystem used by microsoft windows95 and windows nt. .b vfat adds the capability to use long filenames under the msdos filesystem. .tp .b xfs is a journaling filesystem, developed by sgi, that was integrated into linux in kernel 2.4.20. .tp .b xiafs was designed and implemented to be a stable, safe filesystem by extending the minix filesystem code. it provides the basic most requested features without undue complexity. the .b xiafs filesystem is no longer actively developed or maintained. it was removed from the kernel in 2.1.21. .sh see also .br fuse (4), .br btrfs (5), .br ext2 (5), .br ext3 (5), .br ext4 (5), .br nfs (5), .br proc (5), .br sysfs (5), .br tmpfs (5), .br xfs (5), .br fsck (8), .br mkfs (8), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 2008 michael kerrisk .\" starting from a version by davide libenzi .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2008-10-10, mtk: describe eventfd2(), and efd_nonblock and efd_cloexec .\" .th eventfd 2 2021-03-22 linux "linux programmer's manual" .sh name eventfd \- create a file descriptor for event notification .sh synopsis .nf .b #include .pp .bi "int eventfd(unsigned int " initval ", int " flags ); .fi .sh description .br eventfd () creates an "eventfd object" that can be used as an event wait/notify mechanism by user-space applications, and by the kernel to notify user-space applications of events. the object contains an unsigned 64-bit integer .ri ( uint64_t ) counter that is maintained by the kernel. this counter is initialized with the value specified in the argument .ir initval . .pp as its return value, .br eventfd () returns a new file descriptor that can be used to refer to the eventfd object. .pp the following values may be bitwise ored in .ir flags to change the behavior of .br eventfd (): .tp .br efd_cloexec " (since linux 2.6.27)" set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .tp .br efd_nonblock " (since linux 2.6.27)" set the .br o_nonblock file status flag on the open file description (see .br open (2)) referred to by the new file descriptor. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .tp .br efd_semaphore " (since linux 2.6.30)" provide semaphore-like semantics for reads from the new file descriptor. see below. .pp in linux up to version 2.6.26, the .i flags argument is unused, and must be specified as zero. .pp the following operations can be performed on the file descriptor returned by .br eventfd (): .tp .br read (2) each successful .br read (2) returns an 8-byte integer. a .br read (2) fails with the error .b einval if the size of the supplied buffer is less than 8 bytes. .ip the value returned by .br read (2) is in host byte order\(emthat is, the native byte order for integers on the host machine. .ip the semantics of .br read (2) depend on whether the eventfd counter currently has a nonzero value and whether the .br efd_semaphore flag was specified when creating the eventfd file descriptor: .rs .ip * 3 if .br efd_semaphore was not specified and the eventfd counter has a nonzero value, then a .br read (2) returns 8 bytes containing that value, and the counter's value is reset to zero. .ip * if .br efd_semaphore was specified and the eventfd counter has a nonzero value, then a .br read (2) returns 8 bytes containing the value 1, and the counter's value is decremented by 1. .ip * if the eventfd counter is zero at the time of the call to .br read (2), then the call either blocks until the counter becomes nonzero (at which time, the .br read (2) proceeds as described above) or fails with the error .b eagain if the file descriptor has been made nonblocking. .re .tp .br write (2) a .br write (2) call adds the 8-byte integer value supplied in its buffer to the counter. the maximum value that may be stored in the counter is the largest unsigned 64-bit value minus 1 (i.e., 0xfffffffffffffffe). if the addition would cause the counter's value to exceed the maximum, then the .br write (2) either blocks until a .br read (2) is performed on the file descriptor, or fails with the error .b eagain if the file descriptor has been made nonblocking. .ip a .br write (2) fails with the error .b einval if the size of the supplied buffer is less than 8 bytes, or if an attempt is made to write the value 0xffffffffffffffff. .tp .br poll "(2), " select "(2) (and similar)" the returned file descriptor supports .br poll (2) (and analogously .br epoll (7)) and .br select (2), as follows: .rs .ip * 3 the file descriptor is readable (the .br select (2) .i readfds argument; the .br poll (2) .b pollin flag) if the counter has a value greater than 0. .ip * the file descriptor is writable (the .br select (2) .i writefds argument; the .br poll (2) .b pollout flag) if it is possible to write a value of at least "1" without blocking. .ip * if an overflow of the counter value was detected, then .br select (2) indicates the file descriptor as being both readable and writable, and .br poll (2) returns a .b pollerr event. as noted above, .br write (2) can never overflow the counter. however an overflow can occur if 2^64 eventfd "signal posts" were performed by the kaio subsystem (theoretically possible, but practically unlikely). if an overflow has occurred, then .br read (2) will return that maximum .i uint64_t value (i.e., 0xffffffffffffffff). .re .ip the eventfd file descriptor also supports the other file-descriptor multiplexing apis: .br pselect (2) and .br ppoll (2). .tp .br close (2) when the file descriptor is no longer required it should be closed. when all file descriptors associated with the same eventfd object have been closed, the resources for object are freed by the kernel. .pp a copy of the file descriptor created by .br eventfd () is inherited by the child produced by .br fork (2). the duplicate file descriptor is associated with the same eventfd object. file descriptors created by .br eventfd () are preserved across .br execve (2), unless the close-on-exec flag has been set. .sh return value on success, .br eventfd () returns a new eventfd file descriptor. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b einval an unsupported value was specified in .ir flags . .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enodev .\" note from davide: .\" the enodev error is basically never going to happen if .\" the kernel boots correctly. that error happen only if during .\" the kernel initialization, some error occur in the anonymous .\" inode source initialization. could not mount (internal) anonymous inode device. .tp .b enomem there was insufficient memory to create a new eventfd file descriptor. .sh versions .br eventfd () is available on linux since kernel 2.6.22. working support is provided in glibc since version 2.8. .\" eventfd() is in glibc 2.7, but reportedly does not build the .br eventfd2 () system call (see notes) is available on linux since kernel 2.6.27. since version 2.9, the glibc .br eventfd () wrapper will employ the .br eventfd2 () system call, if it is supported by the kernel. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br eventfd () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br eventfd () and .br eventfd2 () are linux-specific. .sh notes applications can use an eventfd file descriptor instead of a pipe (see .br pipe (2)) in all cases where a pipe is used simply to signal events. the kernel overhead of an eventfd file descriptor is much lower than that of a pipe, and only one file descriptor is required (versus the two required for a pipe). .pp when used in the kernel, an eventfd file descriptor can provide a bridge from kernel to user space, allowing, for example, functionalities like kaio (kernel aio) .\" or eventually syslets/threadlets to signal to a file descriptor that some operation is complete. .pp a key point about an eventfd file descriptor is that it can be monitored just like any other file descriptor using .br select (2), .br poll (2), or .br epoll (7). this means that an application can simultaneously monitor the readiness of "traditional" files and the readiness of other kernel mechanisms that support the eventfd interface. (without the .br eventfd () interface, these mechanisms could not be multiplexed via .br select (2), .br poll (2), or .br epoll (7).) .pp the current value of an eventfd counter can be viewed via the entry for the corresponding file descriptor in the process's .ir /proc/[pid]/fdinfo directory. see .br proc (5) for further details. .\" .ss c library/kernel differences there are two underlying linux system calls: .br eventfd () and the more recent .br eventfd2 (). the former system call does not implement a .i flags argument. the latter system call implements the .i flags values described above. the glibc wrapper function will use .br eventfd2 () where it is available. .ss additional glibc features the gnu c library defines an additional type, and two functions that attempt to abstract some of the details of reading and writing on an eventfd file descriptor: .pp .in +4n .ex typedef uint64_t eventfd_t; int eventfd_read(int fd, eventfd_t *value); int eventfd_write(int fd, eventfd_t value); .ee .in .pp the functions perform the read and write operations on an eventfd file descriptor, returning 0 if the correct number of bytes was transferred, or \-1 otherwise. .sh examples the following program creates an eventfd file descriptor and then forks to create a child process. while the parent briefly sleeps, the child writes each of the integers supplied in the program's command-line arguments to the eventfd file descriptor. when the parent has finished sleeping, it reads from the eventfd file descriptor. .pp the following shell session shows a sample run of the program: .pp .in +4n .ex .rb "$" " ./a.out 1 2 4 7 14" child writing 1 to efd child writing 2 to efd child writing 4 to efd child writing 7 to efd child writing 14 to efd child completed write loop parent about to read parent read 28 (0x1c) from efd .ee .in .ss program source \& .ex #include #include #include /* definition of priu64 & prix64 */ #include #include #include /* definition of uint64_t */ #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) int main(int argc, char *argv[]) { int efd; uint64_t u; ssize_t s; if (argc < 2) { fprintf(stderr, "usage: %s ...\en", argv[0]); exit(exit_failure); } efd = eventfd(0, 0); if (efd == \-1) handle_error("eventfd"); switch (fork()) { case 0: for (int j = 1; j < argc; j++) { printf("child writing %s to efd\en", argv[j]); u = strtoull(argv[j], null, 0); /* strtoull() allows various bases */ s = write(efd, &u, sizeof(uint64_t)); if (s != sizeof(uint64_t)) handle_error("write"); } printf("child completed write loop\en"); exit(exit_success); default: sleep(2); printf("parent about to read\en"); s = read(efd, &u, sizeof(uint64_t)); if (s != sizeof(uint64_t)) handle_error("read"); printf("parent read %"priu64" (%#"prix64") from efd\en", u, u); exit(exit_success); case \-1: handle_error("fork"); } } .ee .sh see also .br futex (2), .br pipe (2), .br poll (2), .br read (2), .br select (2), .br signalfd (2), .br timerfd_create (2), .br write (2), .br epoll (7), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2011, mark r. bannister .\" copyright (c) 2015, robin h. johnson .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th getent 1 2021-03-22 "linux" "user commands" .sh name getent \- get entries from name service switch libraries .sh synopsis .nf .b getent [\fioption\fp]... \fidatabase\fp \fikey\fp... .fi .sh description the .b getent command displays entries from databases supported by the name service switch libraries, which are configured in .ir /etc/nsswitch.conf . if one or more .i key arguments are provided, then only the entries that match the supplied keys will be displayed. otherwise, if no .i key is provided, all entries will be displayed (unless the database does not support enumeration). .pp the .i database may be any of those supported by the gnu c library, listed below: .rs 3 .tp 10 .b ahosts when no .i key is provided, use .br sethostent (3), .br gethostent (3), and .br endhostent (3) to enumerate the hosts database. this is identical to using .br hosts . when one or more .i key arguments are provided, pass each .i key in succession to .br getaddrinfo (3) with the address family .br af_unspec , enumerating each socket address structure returned. .tp .b ahostsv4 same as .br ahosts , but use the address family .br af_inet . .tp .b ahostsv6 same as .br ahosts , but use the address family .br af_inet6 . the call to .br getaddrinfo (3) in this case includes the .b ai_v4mapped flag. .tp .b aliases when no .i key is provided, use .br setaliasent (3), .br getaliasent (3), and .br endaliasent (3) to enumerate the aliases database. when one or more .i key arguments are provided, pass each .i key in succession to .br getaliasbyname (3) and display the result. .tp .b ethers when one or more .i key arguments are provided, pass each .i key in succession to .br ether_aton (3) and .br ether_hostton (3) until a result is obtained, and display the result. enumeration is not supported on .br ethers , so a .i key must be provided. .tp .b group when no .i key is provided, use .br setgrent (3), .br getgrent (3), and .br endgrent (3) to enumerate the group database. when one or more .i key arguments are provided, pass each numeric .i key to .br getgrgid (3) and each nonnumeric .i key to .br getgrnam (3) and display the result. .tp .b gshadow when no .i key is provided, use .br setsgent (3), .br getsgent (3), and .br endsgent (3) to enumerate the gshadow database. when one or more .i key arguments are provided, pass each .i key in succession to .br getsgnam (3) and display the result. .tp .b hosts when no .i key is provided, use .br sethostent (3), .br gethostent (3), and .br endhostent (3) to enumerate the hosts database. when one or more .i key arguments are provided, pass each .i key to .br gethostbyaddr (3) or .br gethostbyname2 (3), depending on whether a call to .br inet_pton (3) indicates that the .i key is an ipv6 or ipv4 address or not, and display the result. .tp .b initgroups when one or more .i key arguments are provided, pass each .i key in succession to .br getgrouplist (3) and display the result. enumeration is not supported on .br initgroups , so a .i key must be provided. .tp .b netgroup when one .i key is provided, pass the .i key to .br setnetgrent (3) and, using .br getnetgrent (3) display the resulting string triple .ri ( hostname ", " username ", " domainname ). alternatively, three .i keys may be provided, which are interpreted as the .ir hostname , .ir username , and .i domainname to match to a netgroup name via .br innetgr (3). enumeration is not supported on .br netgroup , so either one or three .i keys must be provided. .tp .b networks when no .i key is provided, use .br setnetent (3), .br getnetent (3), and .br endnetent (3) to enumerate the networks database. when one or more .i key arguments are provided, pass each numeric .i key to .br getnetbyaddr (3) and each nonnumeric .i key to .br getnetbyname (3) and display the result. .tp .b passwd when no .i key is provided, use .br setpwent (3), .br getpwent (3), and .br endpwent (3) to enumerate the passwd database. when one or more .i key arguments are provided, pass each numeric .i key to .br getpwuid (3) and each nonnumeric .i key to .br getpwnam (3) and display the result. .tp .b protocols when no .i key is provided, use .br setprotoent (3), .br getprotoent (3), and .br endprotoent (3) to enumerate the protocols database. when one or more .i key arguments are provided, pass each numeric .i key to .br getprotobynumber (3) and each nonnumeric .i key to .br getprotobyname (3) and display the result. .tp .b rpc when no .i key is provided, use .br setrpcent (3), .br getrpcent (3), and .br endrpcent (3) to enumerate the rpc database. when one or more .i key arguments are provided, pass each numeric .i key to .br getrpcbynumber (3) and each nonnumeric .i key to .br getrpcbyname (3) and display the result. .tp .b services when no .i key is provided, use .br setservent (3), .br getservent (3), and .br endservent (3) to enumerate the services database. when one or more .i key arguments are provided, pass each numeric .i key to .br getservbynumber (3) and each nonnumeric .i key to .br getservbyname (3) and display the result. .tp .b shadow when no .i key is provided, use .br setspent (3), .br getspent (3), and .br endspent (3) to enumerate the shadow database. when one or more .i key arguments are provided, pass each .i key in succession to .br getspnam (3) and display the result. .re .sh options .tp .br \-s\ \fiservice\fp ", " \-\-service\ \fiservice\fp .\" commit 9d0881aa76b399e6a025c5cf44bebe2ae0efa8af (glibc) override all databases with the specified service. (since glibc 2.2.5.) .tp .br \-s\ \fidatabase\fp:\fiservice\fp ", "\ \-\-service\ \fidatabase\fp:\fiservice\fp .\" commit b4f6f4be85d32b9c03361c38376e36f08100e3e8 (glibc) override only specified databases with the specified service. the option may be used multiple times, but only the last service for each database will be used. (since glibc 2.4.) .tp .br \-i ", " \-\-no\-idn .\" commit a160f8d808cf8020b13bd0ef4a9eaf3c11f964ad (glibc) disables idn encoding in lookups for .br ahosts / getaddrinfo (3) (since glibc-2.13.) .tp .br \-? ", " \-\-help print a usage summary and exit. .tp .b "\-\-usage" print a short usage summary and exit. .tp .br \-v ", " \-\-version print the version number, license, and disclaimer of warranty for .br getent . .sh exit status one of the following exit values can be returned by .br getent : .rs 3 .tp .b 0 command completed successfully. .tp .b 1 missing arguments, or .i database unknown. .tp .b 2 one or more supplied .i key could not be found in the .ir database . .tp .b 3 enumeration not supported on this .ir database . .re .sh see also .br nsswitch.conf (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/asprintf.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-21 by rik faith .\" modified 1994-08-21 by michael chastain .\" modified 1996-06-13 by aeb .\" modified 1996-11-06 by eric s. raymond .\" modified 1997-08-21 by joseph s. myers .\" modified 2004-06-23 by michael kerrisk .\" .th chroot 2 2021-03-22 "linux" "linux programmer's manual" .sh name chroot \- change root directory .sh synopsis .nf .b #include .pp .bi "int chroot(const char *" path ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br chroot (): .nf since glibc 2.2.2: _xopen_source && ! (_posix_c_source >= 200112l) || /* since glibc 2.20: */ _default_source || /* glibc <= 2.19: */ _bsd_source before glibc 2.2.2: none .fi .sh description .br chroot () changes the root directory of the calling process to that specified in .ir path . this directory will be used for pathnames beginning with \fi/\fp. the root directory is inherited by all children of the calling process. .pp only a privileged process (linux: one with the .b cap_sys_chroot capability in its user namespace) may call .br chroot (). .pp this call changes an ingredient in the pathname resolution process and does nothing else. in particular, it is not intended to be used for any kind of security purpose, neither to fully sandbox a process nor to restrict filesystem system calls. in the past, .br chroot () has been used by daemons to restrict themselves prior to passing paths supplied by untrusted users to system calls such as .br open (2). however, if a folder is moved out of the chroot directory, an attacker can exploit that to get out of the chroot directory as well. the easiest way to do that is to .br chdir (2) to the to-be-moved directory, wait for it to be moved out, then open a path like ../../../etc/passwd. .pp .\" this is how the "slightly trickier variation" works: .\" https://github.com/qubesos/qubes-secpack/blob/master/qsbs/qsb-014-2015.txt#l142 a slightly trickier variation also works under some circumstances if .br chdir (2) is not permitted. if a daemon allows a "chroot directory" to be specified, that usually means that if you want to prevent remote users from accessing files outside the chroot directory, you must ensure that folders are never moved out of it. .pp this call does not change the current working directory, so that after the call \(aq\fi.\fp\(aq can be outside the tree rooted at \(aq\fi/\fp\(aq. in particular, the superuser can escape from a "chroot jail" by doing: .pp .in +4n .ex mkdir foo; chroot foo; cd .. .ee .in .pp this call does not close open file descriptors, and such file descriptors may allow access to files outside the chroot tree. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors depending on the filesystem, other errors can be returned. the more general errors are listed below: .tp .b eacces search permission is denied on a component of the path prefix. (see also .br path_resolution (7).) .\" also search permission is required on the final component, .\" maybe just to guarantee that it is a directory? .tp .b efault .i path points outside your accessible address space. .tp .b eio an i/o error occurred. .tp .b eloop too many symbolic links were encountered in resolving .ir path . .tp .b enametoolong .i path is too long. .tp .b enoent the file does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of .i path is not a directory. .tp .b eperm the caller has insufficient privilege. .sh conforming to svr4, 4.4bsd, susv2 (marked legacy). this function is not part of posix.1-2001. .\" svr4 documents additional eintr, enolink and emultihop error conditions. .\" x/open does not document eio, enomem or efault error conditions. .sh notes a child process created via .br fork (2) inherits its parent's root directory. the root directory is left unchanged by .br execve (2). .pp the magic symbolic link, .ir /proc/[pid]/root , can be used to discover a process's root directory; see .br proc (5) for details. .pp freebsd has a stronger .br jail () system call. .sh see also .br chroot (1), .br chdir (2), .br pivot_root (2), .br path_resolution (7), .br switch_root (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isgreater.3 .so man3/getservent.3 .so man3/pthread_spin_lock.3 .so man3/cmsg.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:40:44 1993 by rik faith (faith@cs.unc.edu) .th strcoll 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strcoll \- compare two strings using the current locale .sh synopsis .nf .b #include .pp .bi "int strcoll(const char *" s1 ", const char *" s2 ); .fi .sh description the .br strcoll () function compares the two strings .i s1 and .ir s2 . it returns an integer less than, equal to, or greater than zero if .i s1 is found, respectively, to be less than, to match, or be greater than .ir s2 . the comparison is based on strings interpreted as appropriate for the program's current locale for category .br lc_collate . (see .br setlocale (3).) .sh return value the .br strcoll () function returns an integer less than, equal to, or greater than zero if .i s1 is found, respectively, to be less than, to match, or be greater than .ir s2 , when both are interpreted as appropriate for the current locale. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strcoll () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes in the .i "posix" or .i "c" locales .br strcoll () is equivalent to .br strcmp (3). .sh see also .br bcmp (3), .br memcmp (3), .br setlocale (3), .br strcasecmp (3), .br strcmp (3), .br string (3), .br strxfrm (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified sat jul 24 19:37:37 1993 by rik faith (faith@cs.unc.edu) .\" modified mon may 27 22:40:48 1996 by martin schulze (joey@linux.de) .\" .th fgetpwent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fgetpwent \- get password file entry .sh synopsis .nf .b #include .b #include .b #include .pp .bi "struct passwd *fgetpwent(file *" stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fgetpwent (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description the .br fgetpwent () function returns a pointer to a structure containing the broken out fields of a line in the file \fistream\fp. the first time it is called it returns the first entry; thereafter, it returns successive entries. the file referred to by .i stream must have the same format as .i /etc/passwd (see .br passwd (5)). .pp the \fipasswd\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct passwd { char *pw_name; /* username */ char *pw_passwd; /* user password */ uid_t pw_uid; /* user id */ gid_t pw_gid; /* group id */ char *pw_gecos; /* real name */ char *pw_dir; /* home directory */ char *pw_shell; /* shell program */ }; .ee .in .sh return value the .br fgetpwent () function returns a pointer to a .i passwd structure, or null if there are no more entries or an error occurs. in the event of an error, .i errno is set to indicate the error. .sh errors .tp .b enomem insufficient memory to allocate .i passwd structure. .sh files .tp .i /etc/passwd password database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fgetpwent () t} thread safety mt-unsafe race:fgetpwent .te .hy .ad .sp 1 .\" fixme: the marking is different from that in the glibc manual, .\" which has: .\" .\" fgetpwent: mt-unsafe race:fpwent .\" .\" we think race:fpwent in glibc maybe hard for users to understand, .\" and have sent a patch to the gnu libc community for changing it to .\" race:fgetpwent, however, something about the copyright impeded the .\" progress. .sh conforming to svr4. .sh see also .br endpwent (3), .br fgetpwent_r (3), .br fopen (3), .br getpw (3), .br getpwent (3), .br getpwnam (3), .br getpwuid (3), .br putpwent (3), .br setpwent (3), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mallopt 3 2021-03-22 "linux" "linux programmer's manual" .sh name mallopt \- set memory allocation parameters .sh synopsis .nf .b #include .pp .bi "int mallopt(int " param ", int " value ); .fi .sh description the .br mallopt () function adjusts parameters that control the behavior of the memory-allocation functions (see .br malloc (3)). the .ir param argument specifies the parameter to be modified, and .i value specifies the new value for that parameter. .pp the following values can be specified for .ir param : .tp .br m_arena_max if this parameter has a nonzero value, it defines a hard limit on the maximum number of arenas that can be created. an arena represents a pool of memory that can be used by .br malloc (3) (and similar) calls to service allocation requests. arenas are thread safe and therefore may have multiple concurrent memory requests. the trade-off is between the number of threads and the number of arenas. the more arenas you have, the lower the per-thread contention, but the higher the memory usage. .ip the default value of this parameter is 0, meaning that the limit on the number of arenas is determined according to the setting of .br m_arena_test . .ip this parameter has been available since glibc 2.10 via .br \-\-enable\-experimental\-malloc , and since glibc 2.15 by default. in some versions of the allocator there was no limit on the number of created arenas (e.g., centos 5, rhel 5). .ip when employing newer glibc versions, applications may in some cases exhibit high contention when accessing arenas. in these cases, it may be beneficial to increase .b m_arena_max to match the number of threads. this is similar in behavior to strategies taken by tcmalloc and jemalloc (e.g., per-thread allocation pools). .tp .br m_arena_test this parameter specifies a value, in number of arenas created, at which point the system configuration will be examined to determine a hard limit on the number of created arenas. (see .b m_arena_max for the definition of an arena.) .ip the computation of the arena hard limit is implementation-defined and is usually calculated as a multiple of the number of available cpus. once the hard limit is computed, the result is final and constrains the total number of arenas. .ip the default value for the .b m_arena_test parameter is 2 on systems where .ir sizeof(long) is 4; otherwise the default value is 8. .ip this parameter has been available since glibc 2.10 via .br \-\-enable\-experimental\-malloc , and since glibc 2.15 by default. .ip the value of .b m_arena_test is not used when .b m_arena_max has a nonzero value. .tp .br m_check_action setting this parameter controls how glibc responds when various kinds of programming errors are detected (e.g., freeing the same pointer twice). the 3 least significant bits (2, 1, and 0) of the value assigned to this parameter determine the glibc behavior, as follows: .rs .tp bit 0 if this bit is set, then print a one-line message on .i stderr that provides details about the error. the message starts with the string "***\ glibc detected\ ***", followed by the program name, the name of the memory-allocation function in which the error was detected, a brief description of the error, and the memory address where the error was detected. .tp bit 1 if this bit is set, then, after printing any error message specified by bit 0, the program is terminated by calling .br abort (3). in glibc versions since 2.4, if bit 0 is also set, then, between printing the error message and aborting, the program also prints a stack trace in the manner of .br backtrace (3), and prints the process's memory mapping in the style of .ir /proc/[pid]/maps (see .br proc (5)). .tp bit 2 (since glibc 2.4) this bit has an effect only if bit 0 is also set. if this bit is set, then the one-line message describing the error is simplified to contain just the name of the function where the error was detected and the brief description of the error. .re .ip the remaining bits in .i value are ignored. .ip combining the above details, the following numeric values are meaningful for .br m_check_action : .rs 12 .ip 0 3 ignore error conditions; continue execution (with undefined results). .ip 1 print a detailed error message and continue execution. .ip 2 abort the program. .ip 3 print detailed error message, stack trace, and memory mappings, and abort the program. .ip 5 print a simple error message and continue execution. .ip 7 print simple error message, stack trace, and memory mappings, and abort the program. .re .ip since glibc 2.3.4, the default value for the .br m_check_action parameter is 3. in glibc version 2.3.3 and earlier, the default value is 1. .ip using a nonzero .b m_check_action value can be useful because otherwise a crash may happen much later, and the true cause of the problem is then very hard to track down. .tp .br m_mmap_max .\" the following text adapted from comments in the glibc source: this parameter specifies the maximum number of allocation requests that may be simultaneously serviced using .br mmap (2). this parameter exists because some systems have a limited number of internal tables for use by .br mmap (2), and using more than a few of them may degrade performance. .ip the default value is 65,536, a value which has no special significance and which serves only as a safeguard. setting this parameter to 0 disables the use of .br mmap (2) for servicing large allocation requests. .tp .br m_mmap_threshold for allocations greater than or equal to the limit specified (in bytes) by .br m_mmap_threshold that can't be satisfied from the free list, the memory-allocation functions employ .br mmap (2) instead of increasing the program break using .br sbrk (2). .ip allocating memory using .br mmap (2) has the significant advantage that the allocated memory blocks can always be independently released back to the system. (by contrast, the heap can be trimmed only if memory is freed at the top end.) on the other hand, there are some disadvantages to the use of .br mmap (2): deallocated space is not placed on the free list for reuse by later allocations; memory may be wasted because .br mmap (2) allocations must be page-aligned; and the kernel must perform the expensive task of zeroing out memory allocated via .br mmap (2). balancing these factors leads to a default setting of 128*1024 for the .br m_mmap_threshold parameter. .ip the lower limit for this parameter is 0. the upper limit is .br default_mmap_threshold_max : 512*1024 on 32-bit systems or .ir 4*1024*1024*sizeof(long) on 64-bit systems. .ip .ir note: nowadays, glibc uses a dynamic mmap threshold by default. the initial value of the threshold is 128*1024, but when blocks larger than the current threshold and less than or equal to .br default_mmap_threshold_max are freed, the threshold is adjusted upward to the size of the freed block. when dynamic mmap thresholding is in effect, the threshold for trimming the heap is also dynamically adjusted to be twice the dynamic mmap threshold. dynamic adjustment of the mmap threshold is disabled if any of the .br m_trim_threshold , .br m_top_pad , .br m_mmap_threshold , or .br m_mmap_max parameters is set. .tp .br m_mxfast " (since glibc 2.3)" .\" the following text adapted from comments in the glibc sources: set the upper limit for memory allocation requests that are satisfied using "fastbins". (the measurement unit for this parameter is bytes.) fastbins are storage areas that hold deallocated blocks of memory of the same size without merging adjacent free blocks. subsequent reallocation of blocks of the same size can be handled very quickly by allocating from the fastbin, although memory fragmentation and the overall memory footprint of the program can increase. .ip the default value for this parameter is .ir "64*sizeof(size_t)/4" (i.e., 64 on 32-bit architectures). the range for this parameter is 0 to .ir "80*sizeof(size_t)/4" . setting .b m_mxfast to 0 disables the use of fastbins. .tp .br m_perturb " (since glibc 2.4)" if this parameter is set to a nonzero value, then bytes of allocated memory (other than allocations via .br calloc (3)) are initialized to the complement of the value in the least significant byte of .ir value , and when allocated memory is released using .br free (3), the freed bytes are set to the least significant byte of .ir value . this can be useful for detecting errors where programs incorrectly rely on allocated memory being initialized to zero, or reuse values in memory that has already been freed. .ip the default value for this parameter is 0. .tp .br m_top_pad this parameter defines the amount of padding to employ when calling .br sbrk (2) to modify the program break. (the measurement unit for this parameter is bytes.) this parameter has an effect in the following circumstances: .rs .ip * 3 when the program break is increased, then .br m_top_pad bytes are added to the .br sbrk (2) request. .ip * when the heap is trimmed as a consequence of calling .br free (3) (see the discussion of .br m_trim_threshold ) this much free space is preserved at the top of the heap. .re .ip in either case, the amount of padding is always rounded to a system page boundary. .ip modifying .br m_top_pad is a trade-off between increasing the number of system calls (when the parameter is set low) and wasting unused memory at the top of the heap (when the parameter is set high). .ip the default value for this parameter is 128*1024. .\" default_top_pad in glibc source .tp .br m_trim_threshold when the amount of contiguous free memory at the top of the heap grows sufficiently large, .br free (3) employs .br sbrk (2) to release this memory back to the system. (this can be useful in programs that continue to execute for a long period after freeing a significant amount of memory.) the .br m_trim_threshold parameter specifies the minimum size (in bytes) that this block of memory must reach before .br sbrk (2) is used to trim the heap. .ip the default value for this parameter is 128*1024. setting .br m_trim_threshold to \-1 disables trimming completely. .ip modifying .br m_trim_threshold is a trade-off between increasing the number of system calls (when the parameter is set low) and wasting unused memory at the top of the heap (when the parameter is set high). .\" .ss environment variables a number of environment variables can be defined to modify some of the same parameters as are controlled by .br mallopt (). using these variables has the advantage that the source code of the program need not be changed. to be effective, these variables must be defined before the first call to a memory-allocation function. (if the same parameters are adjusted via .br mallopt (), then the .br mallopt () settings take precedence.) for security reasons, these variables are ignored in set-user-id and set-group-id programs. .pp the environment variables are as follows (note the trailing underscore at the end of the name of some variables): .tp .br malloc_arena_max controls the same parameter as .br mallopt () .br m_arena_max . .tp .br malloc_arena_test controls the same parameter as .br mallopt () .br m_arena_test . .tp .br malloc_check_ this environment variable controls the same parameter as .br mallopt () .br m_check_action . if this variable is set to a nonzero value, then a special implementation of the memory-allocation functions is used. (this is accomplished using the .br malloc_hook (3) feature.) this implementation performs additional error checking, but is slower .\" on glibc 2.12/x86, a simple malloc()+free() loop is about 70% slower .\" when malloc_check_ was set. than the standard set of memory-allocation functions. (this implementation does not detect all possible errors; memory leaks can still occur.) .ip the value assigned to this environment variable should be a single digit, whose meaning is as described for .br m_check_action . any characters beyond the initial digit are ignored. .ip for security reasons, the effect of .br malloc_check_ is disabled by default for set-user-id and set-group-id programs. however, if the file .ir /etc/suid\-debug exists (the content of the file is irrelevant), then .br malloc_check_ also has an effect for set-user-id and set-group-id programs. .tp .br malloc_mmap_max_ controls the same parameter as .br mallopt () .br m_mmap_max . .tp .br malloc_mmap_threshold_ controls the same parameter as .br mallopt () .br m_mmap_threshold . .tp .br malloc_perturb_ controls the same parameter as .br mallopt () .br m_perturb . .tp .br malloc_trim_threshold_ controls the same parameter as .br mallopt () .br m_trim_threshold . .tp .br malloc_top_pad_ controls the same parameter as .br mallopt () .br m_top_pad . .sh return value on success, .br mallopt () returns 1. on error, it returns 0. .sh errors on error, .i errno is .i not set. .\" .sh versions .\" available already in glibc 2.0, possibly earlier .sh conforming to this function is not specified by posix or the c standards. a similar function exists on many system v derivatives, but the range of values for .ir param varies across systems. the svid defined options .br m_mxfast , .br m_nlblks , .br m_grain , and .br m_keep , but only the first of these is implemented in glibc. .\" .sh notes .sh bugs specifying an invalid value for .i param does not generate an error. .pp a calculation error within the glibc implementation means that a call of the form: .\" fixme . this looks buggy: .\" setting the m_mxfast limit rounds up: (s + size_sz) & ~malloc_align_mask) .\" malloc requests are rounded up: .\" (req) + size_sz + malloc_align_mask) & ~malloc_align_mask .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=12129 .pp .in +4n .ex mallopt(m_mxfast, n) .ee .in .pp does not result in fastbins being employed for all allocations of size up to .ir n . to ensure desired results, .i n should be rounded up to the next multiple greater than or equal to .ir (2k+1)*sizeof(size_t) , where .i k is an integer. .\" bins are multiples of 2 * sizeof(size_t) + sizeof(size_t) .pp if .br mallopt () is used to set .br m_perturb , then, as expected, the bytes of allocated memory are initialized to the complement of the byte in .ir value , and when that memory is freed, the bytes of the region are initialized to the byte specified in .ir value . however, there is an .ri off-by- sizeof(size_t) error in the implementation: .\" fixme . http://sources.redhat.com/bugzilla/show_bug.cgi?id=12140 instead of initializing precisely the block of memory being freed by the call .ir free(p) , the block starting at .i p+sizeof(size_t) is initialized. .sh examples the program below demonstrates the use of .br m_check_action . if the program is supplied with an (integer) command-line argument, then that argument is used to set the .br m_check_action parameter. the program then allocates a block of memory, and frees it twice (an error). .pp the following shell session shows what happens when we run this program under glibc, with the default value for .br m_check_action : .pp .in +4n .ex $ \fb./a.out\fp main(): returned from first free() call *** glibc detected *** ./a.out: double free or corruption (top): 0x09d30008 *** ======= backtrace: ========= /lib/libc.so.6(+0x6c501)[0x523501] /lib/libc.so.6(+0x6dd70)[0x524d70] /lib/libc.so.6(cfree+0x6d)[0x527e5d] \&./a.out[0x80485db] /lib/libc.so.6(__libc_start_main+0xe7)[0x4cdce7] \&./a.out[0x8048471] ======= memory map: ======== 001e4000\-001fe000 r\-xp 00000000 08:06 1083555 /lib/libgcc_s.so.1 001fe000\-001ff000 r\-\-p 00019000 08:06 1083555 /lib/libgcc_s.so.1 [some lines omitted] b7814000\-b7817000 rw\-p 00000000 00:00 0 bff53000\-bff74000 rw\-p 00000000 00:00 0 [stack] aborted (core dumped) .ee .in .pp the following runs show the results when employing other values for .br m_check_action : .pp .in +4n .ex $ \fb./a.out 1\fp # diagnose error and continue main(): returned from first free() call *** glibc detected *** ./a.out: double free or corruption (top): 0x09cbe008 *** main(): returned from second free() call $ \fb./a.out 2\fp # abort without error message main(): returned from first free() call aborted (core dumped) $ \fb./a.out 0\fp # ignore error and continue main(): returned from first free() call main(): returned from second free() call .ee .in .pp the next run shows how to set the same parameter using the .b malloc_check_ environment variable: .pp .in +4n .ex $ \fbmalloc_check_=1 ./a.out\fp main(): returned from first free() call *** glibc detected *** ./a.out: free(): invalid pointer: 0x092c2008 *** main(): returned from second free() call .ee .in .ss program source \& .ex #include #include #include int main(int argc, char *argv[]) { char *p; if (argc > 1) { if (mallopt(m_check_action, atoi(argv[1])) != 1) { fprintf(stderr, "mallopt() failed"); exit(exit_failure); } } p = malloc(1000); if (p == null) { fprintf(stderr, "malloc() failed"); exit(exit_failure); } free(p); printf("main(): returned from first free() call\en"); free(p); printf("main(): returned from second free() call\en"); exit(exit_success); } .ee .sh see also .ad l .nh .br mmap (2), .br sbrk (2), .br mallinfo (3), .br malloc (3), .br malloc_hook (3), .br malloc_info (3), .br malloc_stats (3), .br malloc_trim (3), .br mcheck (3), .br mtrace (3), .br posix_memalign (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fenv.3 .\" copyright (c) 2000 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th getpass 3 2021-03-22 "linux" "linux programmer's manual" .sh name getpass \- get a password .sh synopsis .nf .b #include .pp .bi "char *getpass(const char *" prompt ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getpass (): .nf since glibc 2.2.2: _xopen_source && ! (_posix_c_source >= 200112l) || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source before glibc 2.2.2: none .fi .sh description this function is obsolete. do not use it. if you want to read input without terminal echoing enabled, see the description of the .i echo flag in .br termios (3). .pp the .br getpass () function opens .i /dev/tty (the controlling terminal of the process), outputs the string .ir prompt , turns off echoing, reads one line (the "password"), restores the terminal state and closes .i /dev/tty again. .sh return value the function .br getpass () returns a pointer to a static buffer containing (the first .b pass_max bytes of) the password without the trailing newline, terminated by a null byte (\(aq\e0\(aq). this buffer may be overwritten by a following call. on error, the terminal state is restored, .i errno is set to indicate the error, and null is returned. .sh errors .tp .b enxio the process does not have a controlling terminal. .sh files .i /dev/tty .\" .sh history .\" a .\" .br getpass () .\" function appeared in version 7 at&t unix. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getpass () t} thread safety mt-unsafe term .te .hy .ad .sp 1 .sh conforming to present in susv2, but marked legacy. removed in posix.1-2001. .sh notes .\" for libc4 and libc5, the prompt is not written to .\" .i /dev/tty .\" but to .\" .ir stderr . .\" moreover, if .\" .i /dev/tty .\" cannot be opened, the password is read from .\" .ir stdin . .\" the static buffer has length 128 so that only the first 127 .\" bytes of the password are returned. .\" while reading the password, signal generation .\" .rb ( sigint , .\" .br sigquit , .\" .br sigstop , .\" .br sigtstp ) .\" is disabled and the corresponding characters .\" (usually control-c, control-\e, control-z and control-y) .\" are transmitted as part of the password. .\" since libc 5.4.19 also line editing is disabled, so that also .\" backspace and the like will be seen as part of the password. . in the gnu c library implementation, if .i /dev/tty cannot be opened, the prompt is written to .i stderr and the password is read from .ir stdin . there is no limit on the length of the password. line editing is not disabled. .pp according to susv2, the value of .b pass_max must be defined in .i in case it is smaller than 8, and can in any case be obtained using .ir sysconf(_sc_pass_max) . however, posix.2 withdraws the constants .b pass_max and .br _sc_pass_max , and the function .br getpass (). .\" libc4 and libc5 have never supported .\" .b pass_max .\" or .\" .br _sc_pass_max . the glibc version accepts .b _sc_pass_max and returns .b bufsiz (e.g., 8192). .sh bugs the calling process should zero the password as soon as possible to avoid leaving the cleartext password visible in the process's address space. .sh see also .br crypt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/openpty.3 .so man3/rpc.3 .so man3/inet.3 .so man3/argz_add.3 .\" copyright (c) 2020 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pidfd_getfd 2 2021-03-22 "linux" "linux programmer's manual" .sh name pidfd_getfd \- obtain a duplicate of another process's file descriptor .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_pidfd_getfd, int " pidfd ", int " targetfd , .bi " unsigned int " flags ); .fi .pp .ir note : glibc provides no wrapper for .br pidfd_getfd (), necessitating the use of .br syscall (2). .sh description the .br pidfd_getfd () system call allocates a new file descriptor in the calling process. this new file descriptor is a duplicate of an existing file descriptor, .ir targetfd , in the process referred to by the pid file descriptor .ir pidfd . .pp the duplicate file descriptor refers to the same open file description (see .br open (2)) as the original file descriptor in the process referred to by .ir pidfd . the two file descriptors thus share file status flags and file offset. furthermore, operations on the underlying file object (for example, assigning an address to a socket object using .br bind (2)) can equally be performed via the duplicate file descriptor. .pp the close-on-exec flag .rb ( fd_cloexec ; see .br fcntl (2)) is set on the file descriptor returned by .br pidfd_getfd (). .pp the .i flags argument is reserved for future use. currently, it must be specified as 0. .pp permission to duplicate another process's file descriptor is governed by a ptrace access mode .b ptrace_mode_attach_realcreds check (see .br ptrace (2)). .sh return value on success, .br pidfd_getfd () returns a file descriptor (a nonnegative integer). on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i pidfd is not a valid pid file descriptor. .tp .b ebadf .i targetfd is not an open file descriptor in the process referred to by .ir pidfd . .tp .b einval .i flags is not 0. .tp .b emfile the per-process limit on the number of open file descriptors has been reached (see the description of .br rlimit_nofile in .br getrlimit (2)). .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b eperm the calling process did not have .b ptrace_mode_attach_realcreds permissions (see .br ptrace (2)) over the process referred to by .ir pidfd . .tp .b esrch the process referred to by .i pidfd does not exist (i.e., it has terminated and been waited on). .sh versions .br pidfd_getfd () first appeared in linux 5.6. .\" commit 8649c322f75c96e7ced2fec201e123b2b073bf09 .sh conforming to .br pidfd_getfd () is linux specific. .sh notes for a description of pid file descriptors, see .br pidfd_open (2). .pp the effect of .br pidfd_getfd () is similar to the use of .br scm_rights messages described in .br unix (7), but differs in the following respects: .ip \(bu 2 in order to pass a file descriptor using an .br scm_rights message, the two processes must first establish a unix domain socket connection. .ip \(bu the use of .br scm_rights requires cooperation on the part of the process whose file descriptor is being copied. by contrast, no such cooperation is necessary when using .br pidfd_getfd (). .ip \(bu the ability to use .br pidfd_getfd () is restricted by a .br ptrace_mode_attach_realcreds ptrace access mode check. .sh see also .br clone3 (2), .br dup (2), .br kcmp (2), .br pidfd_open (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswxdigit 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswxdigit \- test for hexadecimal digit wide character .sh synopsis .nf .b #include .pp .bi "int iswxdigit(wint_t " wc ); .fi .sh description the .br iswxdigit () function is the wide-character equivalent of the .br isxdigit (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "xdigit". .pp the wide-character class "xdigit" is a subclass of the wide-character class "alnum", and therefore also a subclass of the wide-character class "graph" and of the wide-character class "print". .pp being a subclass of the wide-character class "print", the wide-character class "xdigit" is disjoint from the wide-character class "cntrl". .pp being a subclass of the wide-character class "graph", the wide-character class "xdigit" is disjoint from the wide-character class "space" and its subclass "blank". .pp being a subclass of the wide-character class "alnum", the wide-character class "xdigit" is disjoint from the wide-character class "punct". .pp the wide-character class "xdigit" always contains at least the letters \(aqa\(aq to \(aqf\(aq, \(aqa\(aq to \(aqf\(aq and the digits \(aq0\(aq to \(aq9\(aq. .sh return value the .br iswxdigit () function returns nonzero if .i wc is a wide character belonging to the wide-character class "xdigit". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswxdigit () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswxdigit () depends on the .b lc_ctype category of the current locale. .sh see also .br iswctype (3), .br isxdigit (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/inotify_init.2 .\" copyright (c) 1998 andries brouwer (aeb@cwi.nl), 24 september 1998 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th reboot 2 2021-03-22 "linux" "linux programmer's manual" .sh name reboot \- reboot or enable/disable ctrl-alt-del .sh synopsis .nf .rb "/* since kernel version 2.1.30 there are symbolic names " linux_reboot_* for the constants and a fourth argument to the call: */ .pp .br "#include " \ "/* definition of " linux_reboot_* " constants */" .br "#include " "/* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_reboot, int " magic ", int " magic2 ", int " cmd ", void *" arg ); .pp /* under glibc and most alternative libc's (including uclibc, dietlibc, musl and a few others), some of the constants involved have gotten .rb " symbolic names " rb_* ", and the library call is a 1-argument" wrapper around the system call: */ .pp .br "#include " "/* definition of " rb_* " constants */" .b #include .pp .bi "int reboot(int " cmd ); .fi .sh description the .br reboot () call reboots the system, or enables/disables the reboot keystroke (abbreviated cad, since the default is ctrl-alt-delete; it can be changed using .br loadkeys (1)). .pp this system call fails (with the error .br einval ) unless .i magic equals .b linux_reboot_magic1 (that is, 0xfee1dead) and .i magic2 equals .b linux_reboot_magic2 (that is, 672274793). however, since 2.1.17 also .b linux_reboot_magic2a (that is, 85072278) and since 2.1.97 also .b linux_reboot_magic2b (that is, 369367448) and since 2.5.71 also .b linux_reboot_magic2c (that is, 537993216) are permitted as values for .ir magic2 . (the hexadecimal values of these constants are meaningful.) .pp the .i cmd argument can have the following values: .tp .b linux_reboot_cmd_cad_off .rb ( rb_disable_cad , 0). cad is disabled. this means that the cad keystroke will cause a .b sigint signal to be sent to init (process 1), whereupon this process may decide upon a proper action (maybe: kill all processes, sync, reboot). .tp .b linux_reboot_cmd_cad_on .rb ( rb_enable_cad , 0x89abcdef). cad is enabled. this means that the cad keystroke will immediately cause the action associated with .br linux_reboot_cmd_restart . .tp .b linux_reboot_cmd_halt .rb ( rb_halt_system , 0xcdef0123; since linux 1.1.76). the message "system halted." is printed, and the system is halted. control is given to the rom monitor, if there is one. if not preceded by a .br sync (2), data will be lost. .tp .br linux_reboot_cmd_kexec .rb ( rb_kexec , 0x45584543, since linux 2.6.13). execute a kernel that has been loaded earlier with .br kexec_load (2). this option is available only if the kernel was configured with .br config_kexec . .tp .b linux_reboot_cmd_power_off .rb ( rb_power_off , 0x4321fedc; since linux 2.1.30). the message "power down." is printed, the system is stopped, and all power is removed from the system, if possible. if not preceded by a .br sync (2), data will be lost. .tp .b linux_reboot_cmd_restart .rb ( rb_autoboot , 0x1234567). the message "restarting system." is printed, and a default restart is performed immediately. if not preceded by a .br sync (2), data will be lost. .tp .b linux_reboot_cmd_restart2 (0xa1b2c3d4; since linux 2.1.30). the message "restarting system with command \(aq%s\(aq" is printed, and a restart (using the command string given in .ir arg ) is performed immediately. if not preceded by a .br sync (2), data will be lost. .tp .br linux_reboot_cmd_sw_suspend .rb ( rb_sw_suspend , 0xd000fce1; since linux 2.5.18). the system is suspended (hibernated) to disk. this option is available only if the kernel was configured with .br config_hibernation . .pp only the superuser may call .br reboot (). .pp the precise effect of the above actions depends on the architecture. for the i386 architecture, the additional argument does not do anything at present (2.1.122), but the type of reboot can be determined by kernel command-line arguments ("reboot=...") to be either warm or cold, and either hard or through the bios. .\" .ss behavior inside pid namespaces .\" commit cf3f89214ef6a33fad60856bc5ffd7bb2fc4709b .\" see also commit 923c7538236564c46ee80c253a416705321f13e3 since linux 3.4, if .br reboot () is called from a pid namespace other than the initial pid namespace with one of the .i cmd values listed below, it performs a "reboot" of that namespace: the "init" process of the pid namespace is immediately terminated, with the effects described in .br pid_namespaces (7). .pp the values that can be supplied in .i cmd when calling .br reboot () in this case are as follows: .tp .br linux_reboot_cmd_restart ", " linux_reboot_cmd_restart2 the "init" process is terminated, and .br wait (2) in the parent process reports that the child was killed with a .b sighup signal. .tp .br linux_reboot_cmd_power_off ", " linux_reboot_cmd_halt the "init" process is terminated, and .br wait (2) in the parent process reports that the child was killed with a .b sigint signal. .pp for the other .i cmd values, .br reboot () returns \-1 and .i errno is set to .br einval . .sh return value for the values of .i cmd that stop or restart the system, a successful call to .br reboot () does not return. for the other .i cmd values, zero is returned on success. in all cases, \-1 is returned on failure, and .i errno is set to indicate the error. .sh errors .tp .b efault problem with getting user-space data under .br linux_reboot_cmd_restart2 . .tp .b einval bad magic numbers or \ficmd\fp. .tp .b eperm the calling process has insufficient privilege to call .br reboot (); the caller must have the .b cap_sys_boot inside its user namespace. .sh conforming to .br reboot () is linux-specific, and should not be used in programs intended to be portable. .sh see also .br systemctl (1), .br systemd (1), .br kexec_load (2), .br sync (2), .br bootparam (7), .br capabilities (7), .br ctrlaltdel (8), .br halt (8), .br shutdown (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ccosh.3 .so man3/xdr.3 .so man3/rpc.3 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" portions extracted from linux/kernel/ioport.c (no copyright notice). .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified tue aug 1 16:47 1995 by jochen karrer .\" .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .\" modified fri nov 27 14:50:36 cet 1998 by andries brouwer .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th iopl 2 2021-03-22 "linux" "linux programmer's manual" .sh name iopl \- change i/o privilege level .sh synopsis .nf .b #include .pp .bi "int iopl(int " level ); .fi .sh description .br iopl () changes the i/o privilege level of the calling thread, as specified by the two least significant bits in .ir level . .pp the i/o privilege level for a normal thread is 0. permissions are inherited from parents to children. .pp this call is deprecated, is significantly slower than .br ioperm (2), and is only provided for older x servers which require access to all 65536 i/o ports. it is mostly for the i386 architecture. on many other architectures it does not exist or will always return an error. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i level is greater than 3. .tp .b enosys this call is unimplemented. .tp .b eperm the calling thread has insufficient privilege to call .br iopl (); the .b cap_sys_rawio capability is required to raise the i/o privilege level above its current value. .sh conforming to .br iopl () is linux-specific and should not be used in programs that are intended to be portable. .sh notes .\" libc5 treats it as a system call and has a prototype in .\" .ir . .\" glibc1 does not have a prototype. glibc2 has a prototype both in .i and in .ir . avoid the latter, it is available on i386 only. .pp prior to linux 5.5 .br iopl () allowed the thread to disable interrupts while running at a higher i/o privilege level. this will probably crash the system, and is not recommended. .pp prior to linux 3.7, on some architectures (such as i386), permissions .i were inherited by the child produced by .br fork (2) and were preserved across .br execve (2). this behavior was inadvertently changed in linux 3.7, and won't be reinstated. .sh see also .br ioperm (2), .br outb (2), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2003 abhijit menon-sen .\" and copyright (c) 2010, 2015, 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2005-04-08 mtk, noted kernel version and added bugs .\" 2010-10-09, mtk, document arm_fadvise64_64() .\" .th posix_fadvise 2 2021-03-22 "linux" "linux programmer's manual" .sh name posix_fadvise \- predeclare an access pattern for file data .sh synopsis .nf .b #include .pp .bi "int posix_fadvise(int " fd ", off_t " offset ", off_t " len \ ", int " advice ");" .fi .pp .ad l .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br posix_fadvise (): .nf _posix_c_source >= 200112l .fi .sh description programs can use .br posix_fadvise () to announce an intention to access file data in a specific pattern in the future, thus allowing the kernel to perform appropriate optimizations. .pp the \fiadvice\fp applies to a (not necessarily existent) region starting at \fioffset\fp and extending for \filen\fp bytes (or until the end of the file if \filen\fp is 0) within the file referred to by \fifd\fp. the \fiadvice\fp is not binding; it merely constitutes an expectation on behalf of the application. .pp permissible values for \fiadvice\fp include: .tp .b posix_fadv_normal indicates that the application has no advice to give about its access pattern for the specified data. if no advice is given for an open file, this is the default assumption. .tp .b posix_fadv_sequential the application expects to access the specified data sequentially (with lower offsets read before higher ones). .tp .b posix_fadv_random the specified data will be accessed in random order. .tp .b posix_fadv_noreuse the specified data will be accessed only once. .ip in kernels before 2.6.18, \fbposix_fadv_noreuse\fp had the same semantics as \fbposix_fadv_willneed\fp. this was probably a bug; since kernel 2.6.18, this flag is a no-op. .tp .b posix_fadv_willneed the specified data will be accessed in the near future. .ip \fbposix_fadv_willneed\fp initiates a nonblocking read of the specified region into the page cache. the amount of data read may be decreased by the kernel depending on virtual memory load. (a few megabytes will usually be fully satisfied, and more is rarely useful.) .tp .b posix_fadv_dontneed the specified data will not be accessed in the near future. .ip \fbposix_fadv_dontneed\fp attempts to free cached pages associated with the specified region. this is useful, for example, while streaming large files. a program may periodically request the kernel to free cached data that has already been used, so that more useful cached pages are not discarded instead. .ip requests to discard partial pages are ignored. it is preferable to preserve needed data than discard unneeded data. if the application requires that data be considered for discarding, then .i offset and .i len must be page-aligned. .ip the implementation .i may attempt to write back dirty pages in the specified region, but this is not guaranteed. any unwritten dirty pages will not be freed. if the application wishes to ensure that dirty pages will be released, it should call .br fsync (2) or .br fdatasync (2) first. .sh return value on success, zero is returned. on error, an error number is returned. .sh errors .tp .b ebadf the \fifd\fp argument was not a valid file descriptor. .tp .b einval an invalid value was specified for \fiadvice\fp. .tp .b espipe the specified file descriptor refers to a pipe or fifo. .rb ( espipe is the error specified by posix, but before kernel version 2.6.16, .\" commit 87ba81dba431232548ce29d5d224115d0c2355ac linux returned .b einval in this case.) .sh versions kernel support first appeared in linux 2.5.60; the underlying system call is called .br fadvise64 (). .\" of fadvise64_64() library support has been provided since glibc version 2.2, via the wrapper function .br posix_fadvise (). .pp since linux 3.18, .\" commit d3ac21cacc24790eb45d735769f35753f5b56ceb support for the underlying system call is optional, depending on the setting of the .b config_advise_syscalls configuration option. .sh conforming to posix.1-2001, posix.1-2008. note that the type of the .i len argument was changed from .i size_t to .i off_t in posix.1-2001 tc1. .sh notes under linux, \fbposix_fadv_normal\fp sets the readahead window to the default size for the backing device; \fbposix_fadv_sequential\fp doubles this size, and \fbposix_fadv_random\fp disables file readahead entirely. these changes affect the entire file, not just the specified region (but other open file handles to the same file are unaffected). .pp the contents of the kernel buffer cache can be cleared via the .ir /proc/sys/vm/drop_caches interface described in .br proc (5). .pp one can obtain a snapshot of which pages of a file are resident in the buffer cache by opening a file, mapping it with .br mmap (2), and then applying .br mincore (2) to the mapping. .ss c library/kernel differences the name of the wrapper function in the c library is .br posix_fadvise (). the underlying system call is called .br fadvise64 () (or, on some architectures, .br fadvise64_64 ()); the difference between the two is that the former system call assumes that the type of the \filen\fp argument is \fisize_t\fp, while the latter expects \filoff_t\fp there. .ss architecture-specific variants some architectures require 64-bit arguments to be aligned in a suitable pair of registers (see .br syscall (2) for further detail). on such architectures, the call signature of .br posix_fadvise () shown in the synopsis would force a register to be wasted as padding between the .i fd and .i offset arguments. therefore, these architectures define a version of the system call that orders the arguments suitably, but is otherwise exactly the same as .br posix_fadvise (). .pp for example, since linux 2.6.14, arm has the following system call: .pp .in +4n .ex .bi "long arm_fadvise64_64(int " fd ", int " advice , .bi " loff_t " offset ", loff_t " len ); .ee .in .pp these architecture-specific details are generally hidden from applications by the glibc .br posix_fadvise () wrapper function, which invokes the appropriate architecture-specific system call. .sh bugs in kernels before 2.6.6, if .i len was specified as 0, then this was interpreted literally as "zero bytes", rather than as meaning "all bytes through to the end of the file". .sh see also .br fincore (1), .br mincore (2), .br readahead (2), .br sync_file_range (2), .br posix_fallocate (3), .br posix_madvise (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .\" copyright (c) 2012 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th delete_module 2 2021-03-22 "linux" "linux programmer's manual" .sh name delete_module \- unload a kernel module .sh synopsis .nf .br "#include " " /* definition of " o_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .br "#include .pp .bi "int syscall(sys_delete_module, const char *" name ", unsigned int " flags ); .fi .pp .ir note : glibc provides no wrapper for .br delete_module (), necessitating the use of .br syscall (2). .sh description the .br delete_module () system call attempts to remove the unused loadable module entry identified by .ir name . if the module has an .i exit function, then that function is executed before unloading the module. the .ir flags argument is used to modify the behavior of the system call, as described below. this system call requires privilege. .pp module removal is attempted according to the following rules: .ip 1. 4 if there are other loaded modules that depend on (i.e., refer to symbols defined in) this module, then the call fails. .ip 2. otherwise, if the reference count for the module (i.e., the number of processes currently using the module) is zero, then the module is immediately unloaded. .ip 3. if a module has a nonzero reference count, then the behavior depends on the bits set in .ir flags . in normal usage (see notes), the .br o_nonblock flag is always specified, and the .br o_trunc flag may additionally be specified. .\" o_trunc == kmod_remove_force in kmod library .\" o_nonblock == kmod_remove_nowait in kmod library .ip the various combinations for .i flags have the following effect: .rs 4 .tp .b flags == o_nonblock the call returns immediately, with an error. .tp .b flags == (o_nonblock | o_trunc) the module is unloaded immediately, regardless of whether it has a nonzero reference count. .tp .b (flags & o_nonblock) == 0 if .i flags does not specify .br o_nonblock , the following steps occur: .rs .ip * 3 the module is marked so that no new references are permitted. .ip * if the module's reference count is nonzero, the caller is placed in an uninterruptible sleep state .rb ( task_uninterruptible ) until the reference count is zero, at which point the call unblocks. .ip * the module is unloaded in the usual way. .re .re .pp the .b o_trunc flag has one further effect on the rules described above. by default, if a module has an .i init function but no .i exit function, then an attempt to remove the module fails. however, if .br o_trunc was specified, this requirement is bypassed. .pp using the .b o_trunc flag is dangerous! if the kernel was not built with .br config_module_force_unload , this flag is silently ignored. (normally, .br config_module_force_unload is enabled.) using this flag taints the kernel (taint_forced_rmmod). .sh return value on success, zero is returned. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebusy the module is not "live" (i.e., it is still being initialized or is already marked for removal); or, the module has an .i init function but has no .i exit function, and .b o_trunc was not specified in .ir flags . .tp .b efault .i name refers to a location outside the process's accessible address space. .tp .b enoent no module by that name exists. .tp .b eperm the caller was not privileged (did not have the .b cap_sys_module capability), or module unloading is disabled (see .ir /proc/sys/kernel/modules_disabled in .br proc (5)). .tp .b ewouldblock other modules depend on this module; or, .br o_nonblock was specified in .ir flags , but the reference count of this module is nonzero and .b o_trunc was not specified in .ir flags . .sh conforming to .br delete_module () is linux-specific. .sh notes the .br delete_module () system call is not supported by glibc. no declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an abi for this system call. therefore, in order to employ this system call, it is (before glibc 2.23) sufficient to manually declare the interface in your code; alternatively, you can invoke the system call using .br syscall (2). .pp the uninterruptible sleep that may occur if .br o_nonblock is omitted from .ir flags is considered undesirable, because the sleeping process is left in an unkillable state. as at linux 3.7, specifying .br o_nonblock is optional, but in future kernels it is likely to become mandatory. .ss linux 2.4 and earlier in linux 2.4 and earlier, the system call took only one argument: .pp .bi " int delete_module(const char *" name ); .pp if .i name is null, all unused modules marked auto-clean are removed. .pp some further details of differences in the behavior of .br delete_module () in linux 2.4 and earlier are .i not currently explained in this manual page. .sh see also .br create_module (2), .br init_module (2), .br query_module (2), .br lsmod (8), .br modprobe (8), .br rmmod (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th strtoimax 3 2021-03-22 "" "linux programmer's manual" .sh name strtoimax, strtoumax \- convert string to integer .sh synopsis .nf .b #include .pp .bi "intmax_t strtoimax(const char *restrict " nptr ", char **restrict " endptr , .bi " int " base ); .bi "uintmax_t strtoumax(const char *restrict " nptr ", char **restrict " endptr , .bi " int " base ); .fi .sh description these functions are just like .br strtol (3) and .br strtoul (3), except that they return a value of type .i intmax_t and .ir uintmax_t , respectively. .sh return value on success, the converted value is returned. if nothing was found to convert, zero is returned. on overflow or underflow .b intmax_max or .b intmax_min or .b uintmax_max is returned, and .i errno is set to .br erange . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strtoimax (), .br strtoumax () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br imaxabs (3), .br imaxdiv (3), .br strtol (3), .br strtoul (3), .br wcstoimax (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/ioprio_set.2 .so man3/strerror.3 .so man3/ptsname.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified mon apr 12 12:54:34 1993, david metcalfe .\" modified sat jul 24 19:13:52 1993, rik faith (faith@cs.unc.edu) .th index 3 2021-03-22 "gnu" "linux programmer's manual" .sh name index, rindex \- locate character in string .sh synopsis .nf .b #include .pp .bi "char *index(const char *" s ", int " c ); .bi "char *rindex(const char *" s ", int " c ); .fi .sh description the .br index () function returns a pointer to the first occurrence of the character \fic\fp in the string \fis\fp. .pp the .br rindex () function returns a pointer to the last occurrence of the character \fic\fp in the string \fis\fp. .pp the terminating null byte (\(aq\e0\(aq) is considered to be a part of the strings. .sh return value the .br index () and .br rindex () functions return a pointer to the matched character or null if the character is not found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br index (), .br rindex () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd; marked as legacy in posix.1-2001. posix.1-2008 removes the specifications of .br index () and .br rindex (), recommending .br strchr (3) and .br strrchr (3) instead. .sh see also .br memchr (3), .br strchr (3), .br string (3), .br strpbrk (3), .br strrchr (3), .br strsep (3), .br strspn (3), .br strstr (3), .br strtok (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/makedev.3 .\" copyright (c) 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)dbopen.3 8.5 (berkeley) 1/2/94 .\" .th dbopen 3 2017-09-15 "" "linux programmer's manual" .uc 7 .sh name dbopen \- database access methods .sh synopsis .nf .b #include .b #include .b #include .b #include .pp .bi "db *dbopen(const char *" file ", int " flags ", int " mode \ ", dbtype " type , .bi " const void *" openinfo ); .fi .sh description .ir "note well" : this page documents interfaces provided in glibc up until version 2.1. since version 2.2, glibc no longer provides these interfaces. probably, you are looking for the apis provided by the .i libdb library instead. .pp .br dbopen () is the library interface to database files. the supported file formats are btree, hashed, and unix file oriented. the btree format is a representation of a sorted, balanced tree structure. the hashed format is an extensible, dynamic hashing scheme. the flat-file format is a byte stream file with fixed or variable length records. the formats and file-format-specific information are described in detail in their respective manual pages .br btree (3), .br hash (3), and .br recno (3). .pp .br dbopen () opens .i file for reading and/or writing. files never intended to be preserved on disk may be created by setting the .i file argument to null. .pp the .i flags and .i mode arguments are as specified to the .br open (2) routine, however, only the .br o_creat , .br o_excl , .br o_exlock , .br o_nonblock , .br o_rdonly , .br o_rdwr , .br o_shlock , and .b o_trunc flags are meaningful. (note, opening a database file .b o_wronly is not possible.) .\"three additional options may be specified by oring .\"them into the .\".i flags .\"argument. .\".tp .\"db_lock .\"do the necessary locking in the database to support concurrent access. .\"if concurrent access isn't needed or the database is read-only this .\"flag should not be set, as it tends to have an associated performance .\"penalty. .\".tp .\"db_shmem .\"place the underlying memory pool used by the database in shared .\"memory. .\"necessary for concurrent access. .\".tp .\"db_txn .\"support transactions in the database. .\"the db_lock and db_shmem flags must be set as well. .pp the .i type argument is of type .i dbtype (as defined in the .i include file) and may be set to .br db_btree , .br db_hash , or .br db_recno . .pp the .i openinfo argument is a pointer to an access-method-specific structure described in the access method's manual page. if .i openinfo is null, each access method will use defaults appropriate for the system and the access method. .pp .br dbopen () returns a pointer to a .i db structure on success and null on error. the .i db structure is defined in the .i include file, and contains at least the following fields: .pp .in +4n .ex typedef struct { dbtype type; int (*close)(const db *db); int (*del)(const db *db, const dbt *key, unsigned int flags); int (*fd)(const db *db); int (*get)(const db *db, dbt *key, dbt *data, unsigned int flags); int (*put)(const db *db, dbt *key, const dbt *data, unsigned int flags); int (*sync)(const db *db, unsigned int flags); int (*seq)(const db *db, dbt *key, dbt *data, unsigned int flags); } db; .ee .in .pp these elements describe a database type and a set of functions performing various actions. these functions take a pointer to a structure as returned by .br dbopen (), and sometimes one or more pointers to key/data structures and a flag value. .tp .i type the type of the underlying access method (and file format). .tp .i close a pointer to a routine to flush any cached information to disk, free any allocated resources, and close the underlying file(s). since key/data pairs may be cached in memory, failing to sync the file with a .i close or .i sync function may result in inconsistent or lost information. .i close routines return \-1 on error (setting .ir errno ) and 0 on success. .tp .i del a pointer to a routine to remove key/data pairs from the database. .ip the argument .i flag may be set to the following value: .rs .tp .b r_cursor delete the record referenced by the cursor. the cursor must have previously been initialized. .re .ip .i delete routines return \-1 on error (setting .ir errno ), 0 on success, and 1 if the specified .i key was not in the file. .tp .i fd a pointer to a routine which returns a file descriptor representative of the underlying database. a file descriptor referencing the same file will be returned to all processes which call .br dbopen () with the same .i file name. this file descriptor may be safely used as an argument to the .br fcntl (2) and .br flock (2) locking functions. the file descriptor is not necessarily associated with any of the underlying files used by the access method. no file descriptor is available for in memory databases. .i fd routines return \-1 on error (setting .ir errno ), and the file descriptor on success. .tp .i get a pointer to a routine which is the interface for keyed retrieval from the database. the address and length of the data associated with the specified .i key are returned in the structure referenced by .ir data . .i get routines return \-1 on error (setting .ir errno ), 0 on success, and 1 if the .i key was not in the file. .tp .i put a pointer to a routine to store key/data pairs in the database. .ip the argument .i flag may be set to one of the following values: .rs .tp .b r_cursor replace the key/data pair referenced by the cursor. the cursor must have previously been initialized. .tp .b r_iafter append the data immediately after the data referenced by .ir key , creating a new key/data pair. the record number of the appended key/data pair is returned in the .i key structure. (applicable only to the .b db_recno access method.) .tp .b r_ibefore insert the data immediately before the data referenced by .ir key , creating a new key/data pair. the record number of the inserted key/data pair is returned in the .i key structure. (applicable only to the .b db_recno access method.) .tp .b r_nooverwrite enter the new key/data pair only if the key does not previously exist. .tp .b r_setcursor store the key/data pair, setting or initializing the position of the cursor to reference it. (applicable only to the .b db_btree and .b db_recno access methods.) .re .ip .b r_setcursor is available only for the .b db_btree and .b db_recno access methods because it implies that the keys have an inherent order which does not change. .ip .b r_iafter and .b r_ibefore are available only for the .b db_recno access method because they each imply that the access method is able to create new keys. this is true only if the keys are ordered and independent, record numbers for example. .ip the default behavior of the .i put routines is to enter the new key/data pair, replacing any previously existing key. .ip .i put routines return \-1 on error (setting .ir errno ), 0 on success, and 1 if the .b r_nooverwrite .i flag was set and the key already exists in the file. .tp .i seq a pointer to a routine which is the interface for sequential retrieval from the database. the address and length of the key are returned in the structure referenced by .ir key , and the address and length of the data are returned in the structure referenced by .ir data . .ip sequential key/data pair retrieval may begin at any time, and the position of the "cursor" is not affected by calls to the .ir del , .ir get , .ir put , or .i sync routines. modifications to the database during a sequential scan will be reflected in the scan, that is, records inserted behind the cursor will not be returned while records inserted in front of the cursor will be returned. .ip the flag value .b must be set to one of the following values: .rs .tp .b r_cursor the data associated with the specified key is returned. this differs from the .i get routines in that it sets or initializes the cursor to the location of the key as well. (note, for the .b db_btree access method, the returned key is not necessarily an exact match for the specified key. the returned key is the smallest key greater than or equal to the specified key, permitting partial key matches and range searches.) .tp .b r_first the first key/data pair of the database is returned, and the cursor is set or initialized to reference it. .tp .b r_last the last key/data pair of the database is returned, and the cursor is set or initialized to reference it. (applicable only to the .b db_btree and .b db_recno access methods.) .tp .b r_next retrieve the key/data pair immediately after the cursor. if the cursor is not yet set, this is the same as the .b r_first flag. .tp .b r_prev retrieve the key/data pair immediately before the cursor. if the cursor is not yet set, this is the same as the .b r_last flag. (applicable only to the .b db_btree and .b db_recno access methods.) .re .ip .b r_last and .b r_prev are available only for the .b db_btree and .b db_recno access methods because they each imply that the keys have an inherent order which does not change. .ip .i seq routines return \-1 on error (setting .ir errno ), 0 on success and 1 if there are no key/data pairs less than or greater than the specified or current key. if the .b db_recno access method is being used, and if the database file is a character special file and no complete key/data pairs are currently available, the .i seq routines return 2. .tp .i sync a pointer to a routine to flush any cached information to disk. if the database is in memory only, the .i sync routine has no effect and will always succeed. .ip the flag value may be set to the following value: .rs .tp .b r_recnosync if the .b db_recno access method is being used, this flag causes the sync routine to apply to the btree file which underlies the recno file, not the recno file itself. (see the .i bfname field of the .br recno (3) manual page for more information.) .re .ip .i sync routines return \-1 on error (setting .ir errno ) and 0 on success. .ss key/data pairs access to all file types is based on key/data pairs. both keys and data are represented by the following data structure: .pp .in +4n .ex typedef struct { void *data; size_t size; } dbt; .ee .in .pp the elements of the .i dbt structure are defined as follows: .tp .i data a pointer to a byte string. .tp .i size the length of the byte string. .pp key and data byte strings may reference strings of essentially unlimited length although any two of them must fit into available memory at the same time. it should be noted that the access methods provide no guarantees about byte string alignment. .sh errors the .br dbopen () routine may fail and set .i errno for any of the errors specified for the library routines .br open (2) and .br malloc (3) or the following: .tp .b eftype a file is incorrectly formatted. .tp .b einval a parameter has been specified (hash function, pad byte, etc.) that is incompatible with the current file specification or which is not meaningful for the function (for example, use of the cursor without prior initialization) or there is a mismatch between the version number of file and the software. .pp the .i close routines may fail and set .i errno for any of the errors specified for the library routines .br close (2), .br read (2), .br write (2), .br free (3), or .br fsync (2). .pp the .ir del , .ir get , .ir put , and .i seq routines may fail and set .i errno for any of the errors specified for the library routines .br read (2), .br write (2), .br free (3), or .br malloc (3). .pp the .i fd routines will fail and set .i errno to .b enoent for in memory databases. .pp the .i sync routines may fail and set .i errno for any of the errors specified for the library routine .br fsync (2). .sh bugs the typedef .i dbt is a mnemonic for "data base thang", and was used because no one could think of a reasonable name that wasn't already used. .pp the file descriptor interface is a kludge and will be deleted in a future version of the interface. .pp none of the access methods provide any form of concurrent access, locking, or transactions. .sh see also .br btree (3), .br hash (3), .br mpool (3), .br recno (3) .pp .ir "libtp: portable, modular transactions for unix" , margo seltzer, michael olson, usenix proceedings, winter 1992. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getifaddrs.3 .so man3/gethostid.3 import os import glob import random # navigate to the directory data_dir = '/media/external/man-pages-dataset/man-pages-5.13' os.chdir(data_dir) # function to preprocess the text def preprocess_text(file_path): with open(file_path, 'r', encoding='utf-8') as file: text = file.read() # simple preprocessing (e.g., lowercase conversion) text = text.lower() return text # collect and preprocess the data all_data = [] file_paths = glob.glob('**/*.txt', recursive=true) print(f'found {len(file_paths)} files.') for file_path in file_paths: preprocessed_text = preprocess_text(file_path) all_data.append(preprocessed_text) print(f'processed {len(all_data)} files.') # shuffle and split the data random.shuffle(all_data) train_size = int(0.8 * len(all_data)) train_data, val_test_data = all_data[:train_size], all_data[train_size:] val_size = int(0.5 * len(val_test_data)) val_data, test_data = val_test_data[:val_size], val_test_data[val_size:] # save the preprocessed data output_dir = os.path.join(data_dir, 'preprocessed_data') os.makedirs(output_dir, exist_ok=true) with open(os.path.join(output_dir, 'train.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(train_data)) with open(os.path.join(output_dir, 'val.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(val_data)) with open(os.path.join(output_dir, 'test.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(test_data)) print(f'data preprocessing and splitting completed. preprocessed data saved to {output_dir}') .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th exp 3 2021-03-22 "" "linux programmer's manual" .sh name exp, expf, expl \- base-e exponential function .sh synopsis .nf .b #include .pp .bi "double exp(double " x ); .bi "float expf(float " x ); .bi "long double expl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br expf (), .br expl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the value of e (the base of natural logarithms) raised to the power of .ir x . .sh return value on success, these functions return the exponential value of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity, positive infinity is returned. .pp if .i x is negative infinity, +0 is returned. .pp if the result underflows, a range error occurs, and zero is returned. .pp if the result overflows, a range error occurs, and the functions return .rb + huge_val , .rb + huge_valf , or .rb + huge_vall , respectively. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error, overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error, underflow .i errno is set to .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br exp (), .br expf (), .br expl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br cbrt (3), .br cexp (3), .br exp10 (3), .br exp2 (3), .br expm1 (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strtol.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-21 by rik faith .\" modified 1994-08-21 by michael chastain : .\" modified 1997-01-31 by eric s. raymond .\" modified 1999-11-12 by urs thuermann .\" modified 2004-06-23 by michael kerrisk .\" 2006-09-04 michael kerrisk .\" added list of process attributes that are not preserved on exec(). .\" 2007-09-14 ollie wild , mtk .\" add text describing limits on command-line arguments + environment .\" .th execve 2 2021-08-27 "linux" "linux programmer's manual" .sh name execve \- execute program .sh synopsis .nf .b #include .pp .bi "int execve(const char *" pathname ", char *const " argv [], .bi " char *const " envp []); .fi .sh description .br execve () executes the program referred to by \fipathname\fp. this causes the program that is currently being run by the calling process to be replaced with a new program, with newly initialized stack, heap, and (initialized and uninitialized) data segments. .pp \fipathname\fp must be either a binary executable, or a script starting with a line of the form: .pp .in +4n .ex \fb#!\fp\fiinterpreter \fp[optional-arg] .ee .in .pp for details of the latter case, see "interpreter scripts" below. .pp \fiargv\fp is an array of pointers to strings passed to the new program as its command-line arguments. by convention, the first of these strings (i.e., .ir argv[0] ) should contain the filename associated with the file being executed. the .i argv array must be terminated by a null pointer. (thus, in the new program, .ir argv[argc] will be null.) .pp \fienvp\fp is an array of pointers to strings, conventionally of the form \fbkey=value\fp, which are passed as the environment of the new program. the .i envp array must be terminated by a null pointer. .pp the argument vector and environment can be accessed by the new program's main function, when it is defined as: .pp .in +4n .ex int main(int argc, char *argv[], char *envp[]) .ee .in .pp note, however, that the use of a third argument to the main function is not specified in posix.1; according to posix.1, the environment should be accessed via the external variable .br environ (7). .pp .br execve () does not return on success, and the text, initialized data, uninitialized data (bss), and stack of the calling process are overwritten according to the contents of the newly loaded program. .pp if the current program is being ptraced, a \fbsigtrap\fp signal is sent to it after a successful .br execve (). .pp if the set-user-id bit is set on the program file referred to by \fipathname\fp, then the effective user id of the calling process is changed to that of the owner of the program file. similarly, if the set-group-id bit is set on the program file, then the effective group id of the calling process is set to the group of the program file. .pp the aforementioned transformations of the effective ids are .i not performed (i.e., the set-user-id and set-group-id bits are ignored) if any of the following is true: .ip * 3 the .i no_new_privs attribute is set for the calling thread (see .br prctl (2)); .ip * the underlying filesystem is mounted .i nosuid (the .b ms_nosuid flag for .br mount (2)); or .ip * the calling process is being ptraced. .pp the capabilities of the program file (see .br capabilities (7)) are also ignored if any of the above are true. .pp the effective user id of the process is copied to the saved set-user-id; similarly, the effective group id is copied to the saved set-group-id. this copying takes place after any effective id changes that occur because of the set-user-id and set-group-id mode bits. .pp the process's real uid and real gid, as well as its supplementary group ids, are unchanged by a call to .br execve (). .pp if the executable is an a.out dynamically linked binary executable containing shared-library stubs, the linux dynamic linker .br ld.so (8) is called at the start of execution to bring needed shared objects into memory and link the executable with them. .pp if the executable is a dynamically linked elf executable, the interpreter named in the pt_interp segment is used to load the needed shared objects. this interpreter is typically .i /lib/ld\-linux.so.2 for binaries linked with glibc (see .br ld\-linux.so (8)). .\" .ss effect on process attributes all process attributes are preserved during an .br execve (), except the following: .ip * 3 the dispositions of any signals that are being caught are reset to the default .rb ( signal (7)). .ip * any alternate signal stack is not preserved .rb ( sigaltstack (2)). .ip * memory mappings are not preserved .rb ( mmap (2)). .ip * attached system\ v shared memory segments are detached .rb ( shmat (2)). .ip * posix shared memory regions are unmapped .rb ( shm_open (3)). .ip * open posix message queue descriptors are closed .rb ( mq_overview (7)). .ip * any open posix named semaphores are closed .rb ( sem_overview (7)). .ip * posix timers are not preserved .rb ( timer_create (2)). .ip * any open directory streams are closed .rb ( opendir (3)). .ip * memory locks are not preserved .rb ( mlock (2), .br mlockall (2)). .ip * exit handlers are not preserved .rb ( atexit (3), .br on_exit (3)). .ip * the floating-point environment is reset to the default (see .br fenv (3)). .pp the process attributes in the preceding list are all specified in posix.1. the following linux-specific process attributes are also not preserved during an .br execve (): .ip * 3 the process's "dumpable" attribute is set to the value 1, unless a set-user-id program, a set-group-id program, or a program with capabilities is being executed, in which case the dumpable flag may instead be reset to the value in .ir /proc/sys/fs/suid_dumpable , in the circumstances described under .br pr_set_dumpable in .br prctl (2). note that changes to the "dumpable" attribute may cause ownership of files in the process's .ir /proc/[pid] directory to change to .ir root:root , as described in .br proc (5). .ip * the .br prctl (2) .b pr_set_keepcaps flag is cleared. .ip * (since linux 2.4.36 / 2.6.23) if a set-user-id or set-group-id program is being executed, then the parent death signal set by .br prctl (2) .b pr_set_pdeathsig flag is cleared. .ip * the process name, as set by .br prctl (2) .b pr_set_name (and displayed by .ir "ps\ \-o comm" ), is reset to the name of the new executable file. .ip * the .b secbit_keep_caps .i securebits flag is cleared. see .br capabilities (7). .ip * the termination signal is reset to .b sigchld (see .br clone (2)). .ip * the file descriptor table is unshared, undoing the effect of the .b clone_files flag of .br clone (2). .pp note the following further points: .ip * 3 all threads other than the calling thread are destroyed during an .br execve (). mutexes, condition variables, and other pthreads objects are not preserved. .ip * the equivalent of \fisetlocale(lc_all, "c")\fp is executed at program start-up. .ip * posix.1 specifies that the dispositions of any signals that are ignored or set to the default are left unchanged. posix.1 specifies one exception: if .b sigchld is being ignored, then an implementation may leave the disposition unchanged or reset it to the default; linux does the former. .ip * any outstanding asynchronous i/o operations are canceled .rb ( aio_read (3), .br aio_write (3)). .ip * for the handling of capabilities during .br execve (), see .br capabilities (7). .ip * by default, file descriptors remain open across an .br execve (). file descriptors that are marked close-on-exec are closed; see the description of .b fd_cloexec in .br fcntl (2). (if a file descriptor is closed, this will cause the release of all record locks obtained on the underlying file by this process. see .br fcntl (2) for details.) posix.1 says that if file descriptors 0, 1, and 2 would otherwise be closed after a successful .br execve (), and the process would gain privilege because the set-user-id or set-group-id mode bit was set on the executed file, then the system may open an unspecified file for each of these file descriptors. as a general principle, no portable program, whether privileged or not, can assume that these three file descriptors will remain closed across an .br execve (). .\" on linux it appears that these file descriptors are .\" always open after an execve(), and it looks like .\" solaris 8 and freebsd 6.1 are the same. -- mtk, 30 apr 2007 .ss interpreter scripts an interpreter script is a text file that has execute permission enabled and whose first line is of the form: .pp .in +4n .ex \fb#!\fp\fiinterpreter \fp[optional-arg] .ee .in .pp the .i interpreter must be a valid pathname for an executable file. .pp if the .i pathname argument of .br execve () specifies an interpreter script, then .i interpreter will be invoked with the following arguments: .pp .in +4n .ex \fiinterpreter\fp [optional-arg] \fipathname\fp arg... .ee .in .pp where .i pathname is the pathname of the file specified as the first argument of .br execve (), and .i arg... is the series of words pointed to by the .i argv argument of .br execve (), starting at .ir argv[1] . note that there is no way to get the .ir argv[0] that was passed to the .br execve () call. .\" see the p - preserve-argv[0] option. .\" documentation/admin-guide/binfmt-misc.rst .\" https://www.kernel.org/doc/html/latest/admin-guide/binfmt-misc.html .pp for portable use, .i optional-arg should either be absent, or be specified as a single word (i.e., it should not contain white space); see notes below. .pp since linux 2.6.28, .\" commit bf2a9a39639b8b51377905397a5005f444e9a892 the kernel permits the interpreter of a script to itself be a script. this permission is recursive, up to a limit of four recursions, so that the interpreter may be a script which is interpreted by a script, and so on. .ss limits on size of arguments and environment most unix implementations impose some limit on the total size of the command-line argument .ri ( argv ) and environment .ri ( envp ) strings that may be passed to a new program. posix.1 allows an implementation to advertise this limit using the .b arg_max constant (either defined in .i or available at run time using the call .ir "sysconf(_sc_arg_max)" ). .pp on linux prior to kernel 2.6.23, the memory used to store the environment and argument strings was limited to 32 pages (defined by the kernel constant .br max_arg_pages ). on architectures with a 4-kb page size, this yields a maximum size of 128\ kb. .pp on kernel 2.6.23 and later, most architectures support a size limit derived from the soft .b rlimit_stack resource limit (see .br getrlimit (2)) that is in force at the time of the .br execve () call. (architectures with no memory management unit are excepted: they maintain the limit that was in effect before kernel 2.6.23.) this change allows programs to have a much larger argument and/or environment list. .\" for some background on the changes to arg_max in kernels 2.6.23 and .\" 2.6.25, see: .\" http://sourceware.org/bugzilla/show_bug.cgi?id=5786 .\" http://bugzilla.kernel.org/show_bug.cgi?id=10095 .\" http://thread.gmane.org/gmane.linux.kernel/646709/focus=648101, .\" checked into 2.6.25 as commit a64e715fc74b1a7dcc5944f848acc38b2c4d4ee2. for these architectures, the total size is limited to 1/4 of the allowed stack size. (imposing the 1/4-limit ensures that the new program always has some stack space.) .\" ollie: that doesn't include the lists of pointers, though, .\" so the actual usage is a bit higher (1 pointer per argument). additionally, the total size is limited to 3/4 of the value of the kernel constant .b _stk_lim (8 mib). since linux 2.6.25, the kernel also places a floor of 32 pages on this size limit, so that, even when .br rlimit_stack is set very low, applications are guaranteed to have at least as much argument and environment space as was provided by linux 2.6.22 and earlier. (this guarantee was not provided in linux 2.6.23 and 2.6.24.) additionally, the limit per string is 32 pages (the kernel constant .br max_arg_strlen ), and the maximum number of strings is 0x7fffffff. .sh return value on success, .br execve () does not return, on error \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b e2big the total number of bytes in the environment .ri ( envp ) and argument list .ri ( argv ) is too large. .tp .b eacces search permission is denied on a component of the path prefix of .i pathname or the name of a script interpreter. (see also .br path_resolution (7).) .tp .b eacces the file or a script interpreter is not a regular file. .tp .b eacces execute permission is denied for the file or a script or elf interpreter. .tp .b eacces the filesystem is mounted .ir noexec . .tp .br eagain " (since linux 3.1)" .\" commit 72fa59970f8698023045ab0713d66f3f4f96945c having changed its real uid using one of the .br set*uid () calls, the caller was\(emand is now still\(emabove its .br rlimit_nproc resource limit (see .br setrlimit (2)). for a more detailed explanation of this error, see notes. .tp .b efault .i pathname or one of the pointers in the vectors .i argv or .i envp points outside your accessible address space. .tp .b einval an elf executable had more than one pt_interp segment (i.e., tried to name more than one interpreter). .tp .b eio an i/o error occurred. .tp .b eisdir an elf interpreter was a directory. .tp .b elibbad an elf interpreter was not in a recognized format. .tp .b eloop too many symbolic links were encountered in resolving .i pathname or the name of a script or elf interpreter. .tp .b eloop the maximum recursion limit was reached during recursive script interpretation (see "interpreter scripts", above). before linux 3.8, .\" commit d740269867021faf4ce38a449353d2b986c34a67 the error produced for this case was .br enoexec . .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enametoolong .i pathname is too long. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoent the file .i pathname or a script or elf interpreter does not exist. .tp .b enoexec an executable is not in a recognized format, is for the wrong architecture, or has some other format error that means it cannot be executed. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of the path prefix of .i pathname or a script or elf interpreter is not a directory. .tp .b eperm the filesystem is mounted .ir nosuid , the user is not the superuser, and the file has the set-user-id or set-group-id bit set. .tp .b eperm the process is being traced, the user is not the superuser and the file has the set-user-id or set-group-id bit set. .tp .b eperm a "capability-dumb" applications would not obtain the full set of permitted capabilities granted by the executable file. see .br capabilities (7). .tp .b etxtbsy the specified executable was open for writing by one or more processes. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. posix does not document the #! behavior, but it exists (with some variations) on other unix systems. .\" svr4 documents additional error .\" conditions eagain, eintr, elibacc, enolink, emultihop; posix does not .\" document etxtbsy, eperm, efault, eloop, eio, enfile, emfile, einval, .\" eisdir or elibbad error conditions. .sh notes one sometimes sees .br execve () (and the related functions described in .br exec (3)) described as "executing a .i new process" (or similar). this is a highly misleading description: there is no new process; many attributes of the calling process remain unchanged (in particular, its pid). all that .br execve () does is arrange for an existing process (the calling process) to execute a new program. .pp set-user-id and set-group-id processes can not be .br ptrace (2)d. .pp the result of mounting a filesystem .i nosuid varies across linux kernel versions: some will refuse execution of set-user-id and set-group-id executables when this would give the user powers they did not have already (and return .br eperm ), some will just ignore the set-user-id and set-group-id bits and .br exec () successfully. .pp on linux, .i argv and .i envp can be specified as null. in both cases, this has the same effect as specifying the argument as a pointer to a list containing a single null pointer. .b "do not take advantage of this nonstandard and nonportable misfeature!" on many other unix systems, specifying .i argv as null will result in an error .rb ( efault ). .i some other unix systems treat the .i envp==null case the same as linux. .\" e.g., efault on solaris 8 and freebsd 6.1; but .\" hp-ux 11 is like linux -- mtk, apr 2007 .\" bug filed 30 apr 2007: http://bugzilla.kernel.org/show_bug.cgi?id=8408 .\" bug rejected (because fix would constitute an abi change). .\" .pp posix.1 says that values returned by .br sysconf (3) should be invariant over the lifetime of a process. however, since linux 2.6.23, if the .br rlimit_stack resource limit changes, then the value reported by .b _sc_arg_max will also change, to reflect the fact that the limit on space for holding command-line arguments and environment variables has changed. .pp in most cases where .br execve () fails, control returns to the original executable image, and the caller of .br execve () can then handle the error. however, in (rare) cases (typically caused by resource exhaustion), failure may occur past the point of no return: the original executable image has been torn down, but the new image could not be completely built. in such cases, the kernel kills the process with a .\" commit 19d860a140beac48a1377f179e693abe86a9dac9 .br sigsegv .rb ( sigkill until linux 3.17) signal. .\" .ss interpreter scripts the kernel imposes a maximum length on the text that follows the "#!" characters at the start of a script; characters beyond the limit are ignored. before linux 5.1, the limit is 127 characters. since linux 5.1, .\" commit 6eb3c3d0a52dca337e327ae8868ca1f44a712e02 the limit is 255 characters. .pp the semantics of the .i optional-arg argument of an interpreter script vary across implementations. on linux, the entire string following the .i interpreter name is passed as a single argument to the interpreter, and this string can include white space. however, behavior differs on some other systems. some systems .\" e.g., solaris 8 use the first white space to terminate .ir optional-arg . on some systems, .\" e.g., freebsd before 6.0, but not freebsd 6.0 onward an interpreter script can have multiple arguments, and white spaces in .i optional-arg are used to delimit the arguments. .pp linux (like most other modern unix systems) ignores the set-user-id and set-group-id bits on scripts. .\" .\" .sh bugs .\" some linux versions have failed to check permissions on elf .\" interpreters. this is a security hole, because it allows users to .\" open any file, such as a rewinding tape device, for reading. some .\" linux versions have also had other security holes in .\" .br execve () .\" that could be exploited for denial of service by a suitably crafted .\" elf binary. there are no known problems with 2.0.34 or 2.2.15. .ss execve() and eagain a more detailed explanation of the .br eagain error that can occur (since linux 3.1) when calling .br execve () is as follows. .pp the .br eagain error can occur when a .i preceding call to .br setuid (2), .br setreuid (2), or .br setresuid (2) caused the real user id of the process to change, and that change caused the process to exceed its .br rlimit_nproc resource limit (i.e., the number of processes belonging to the new real uid exceeds the resource limit). from linux 2.6.0 to 3.0, this caused the .br set*uid () call to fail. (prior to 2.6, .\" commit 909cc4ae86f3380152a18e2a3c44523893ee11c4 the resource limit was not imposed on processes that changed their user ids.) .pp since linux 3.1, the scenario just described no longer causes the .br set*uid () call to fail, because it too often led to security holes where buggy applications didn't check the return status and assumed that\(emif the caller had root privileges\(emthe call would always succeed. instead, the .br set*uid () calls now successfully change the real uid, but the kernel sets an internal flag, named .br pf_nproc_exceeded , to note that the .br rlimit_nproc resource limit has been exceeded. if the .br pf_nproc_exceeded flag is set and the resource limit is still exceeded at the time of a subsequent .br execve () call, that call fails with the error .br eagain . this kernel logic ensures that the .br rlimit_nproc resource limit is still enforced for the common privileged daemon workflow\(emnamely, .br fork (2) + .br set*uid () + .br execve (). .pp if the resource limit was not still exceeded at the time of the .br execve () call (because other processes belonging to this real uid terminated between the .br set*uid () call and the .br execve () call), then the .br execve () call succeeds and the kernel clears the .br pf_nproc_exceeded process flag. the flag is also cleared if a subsequent call to .br fork (2) by this process succeeds. .ss historical with unix\ v6, the argument list of an .br exec () call was ended by 0, while the argument list of .i main was ended by \-1. thus, this argument list was not directly usable in a further .br exec () call. since unix\ v7, both are null. .\" .\" .sh bugs .\" some linux versions have failed to check permissions on elf .\" interpreters. this is a security hole, because it allows users to .\" open any file, such as a rewinding tape device, for reading. some .\" linux versions have also had other security holes in .\" .br execve () .\" that could be exploited for denial of service by a suitably crafted .\" elf binary. there are no known problems with 2.0.34 or 2.2.15. .sh examples the following program is designed to be execed by the second program below. it just echoes its command-line arguments, one per line. .pp .in +4n .ex /* myecho.c */ #include #include int main(int argc, char *argv[]) { for (int j = 0; j < argc; j++) printf("argv[%d]: %s\en", j, argv[j]); exit(exit_success); } .ee .in .pp this program can be used to exec the program named in its command-line argument: .pp .in +4n .ex /* execve.c */ #include #include #include int main(int argc, char *argv[]) { char *newargv[] = { null, "hello", "world", null }; char *newenviron[] = { null }; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } newargv[0] = argv[1]; execve(argv[1], newargv, newenviron); perror("execve"); /* execve() returns only on error */ exit(exit_failure); } .ee .in .pp we can use the second program to exec the first as follows: .pp .in +4n .ex .rb "$" " cc myecho.c \-o myecho" .rb "$" " cc execve.c \-o execve" .rb "$" " ./execve ./myecho" argv[0]: ./myecho argv[1]: hello argv[2]: world .ee .in .pp we can also use these programs to demonstrate the use of a script interpreter. to do this we create a script whose "interpreter" is our .i myecho program: .pp .in +4n .ex .rb "$" " cat > script" .b #!./myecho script\-arg .b \(had .rb "$" " chmod +x script" .ee .in .pp we can then use our program to exec the script: .pp .in +4n .ex .rb "$" " ./execve ./script" argv[0]: ./myecho argv[1]: script\-arg argv[2]: ./script argv[3]: hello argv[4]: world .ee .in .sh see also .br chmod (2), .br execveat (2), .br fork (2), .br get_robust_list (2), .br ptrace (2), .br exec (3), .br fexecve (3), .br getauxval (3), .br getopt (3), .br system (3), .br capabilities (7), .br credentials (7), .br environ (7), .br path_resolution (7), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-13 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-13 \- iso 8859-13 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-13 encodes the characters used in baltic rim languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-13 characters the following table displays the characters in iso 8859-13 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ” right double quotation mark 242 162 a2 ¢ cent sign 243 163 a3 £ pound sign 244 164 a4 ¤ currency sign 245 165 a5 „ double low-9 quotation mark 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ø latin capital letter o with stroke 251 169 a9 © copyright sign 252 170 aa ŗ latin capital letter r with cedilla 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af æ latin capital letter ae 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 “ left double quotation mark 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ø latin small letter o with stroke 271 185 b9 ¹ superscript one 272 186 ba ŗ latin small letter r with cedilla 273 187 bb » right-pointing double angle quotation mark 274 188 bc ¼ vulgar fraction one quarter 275 189 bd ½ vulgar fraction one half 276 190 be ¾ vulgar fraction three quarters 277 191 bf æ latin small letter ae 300 192 c0 ą latin capital letter a with ogonek 301 193 c1 į latin capital letter i with ogonek 302 194 c2 ā latin capital letter a with macron 303 195 c3 ć latin capital letter c with acute 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 ę latin capital letter e with ogonek 307 199 c7 ē latin capital letter e with macron 310 200 c8 č latin capital letter c with caron 311 201 c9 é latin capital letter e with acute 312 202 ca ź latin capital letter z with acute 313 203 cb ė latin capital letter e with dot above 314 204 cc ģ latin capital letter g with cedilla 315 205 cd ķ latin capital letter k with cedilla 316 206 ce ī latin capital letter i with macron 317 207 cf ļ latin capital letter l with cedilla 320 208 d0 š latin capital letter s with caron 321 209 d1 ń latin capital letter n with acute 322 210 d2 ņ latin capital letter n with cedilla 323 211 d3 ó latin capital letter o with acute 324 212 d4 ō latin capital letter o with macron 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ų latin capital letter u with ogonek 331 217 d9 ł latin capital letter l with stroke 332 218 da ś latin capital letter s with acute 333 219 db ū latin capital letter u with macron 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ż latin capital letter z with dot above 336 222 de ž latin capital letter z with caron 337 223 df ß latin small letter sharp s 340 224 e0 ą latin small letter a with ogonek 341 225 e1 į latin small letter i with ogonek 342 226 e2 ā latin small letter a with macron 343 227 e3 ć latin small letter c with acute 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 ę latin small letter e with ogonek 347 231 e7 ē latin small letter e with macron 350 232 e8 č latin small letter c with caron 351 233 e9 é latin small letter e with acute 352 234 ea ź latin small letter z with acute 353 235 eb ė latin small letter e with dot above 354 236 ec ģ latin small letter g with cedilla 355 237 ed ķ latin small letter k with cedilla 356 238 ee ī latin small letter i with macron 357 239 ef ļ latin small letter l with cedilla 360 240 f0 š latin small letter s with caron 361 241 f1 ń latin small letter n with acute 362 242 f2 ņ latin small letter n with cedilla 363 243 f3 ó latin small letter o with acute 364 244 f4 ō latin small letter o with macron 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ų latin small letter u with ogonek 371 249 f9 ł latin small letter l with stroke 372 250 fa ś latin small letter s with acute 373 251 fb ū latin small letter u with macron 374 252 fc ü latin small letter u with diaeresis 375 253 fd ż latin small letter z with dot above 376 254 fe ž latin small letter z with caron 377 255 ff ’ right single quotation mark .te .sh notes iso 8859-13 is also known as latin-7. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2013 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" http://thread.gmane.org/gmane.linux.kernel/76552/focus=76803 .\" from: linus torvalds transmeta.com> .\" subject: re: [patch] compatibility syscall layer (lets try again) .\" newsgroups: gmane.linux.kernel .\" date: 2002-12-05 02:51:12 gmt .\" .\" see also section 11.3.3 of understanding the linux kernel, 3rd edition .\" .th restart_syscall 2 2021-03-22 "linux" "linux programmer's manual" .sh name restart_syscall \- restart a system call after interruption by a stop signal .sh synopsis .nf .b long restart_syscall(void); .fi .pp .ir note : there is no glibc wrapper for this system call; see notes. .sh description the .br restart_syscall () system call is used to restart certain system calls after a process that was stopped by a signal (e.g., .br sigstop or .br sigtstp ) is later resumed after receiving a .br sigcont signal. this system call is designed only for internal use by the kernel. .pp .br restart_syscall () is used for restarting only those system calls that, when restarted, should adjust their time-related parameters\(emnamely .br poll (2) (since linux 2.6.24), .br nanosleep (2) (since linux 2.6), .br clock_nanosleep (2) (since linux 2.6), and .br futex (2), when employed with the .br futex_wait (since linux 2.6.22) and .br futex_wait_bitset (since linux 2.6.31) operations. .\" these system calls correspond to the special internal errno value .\" erestart_restartblock. each of the system calls has a "restart" .\" helper function that is invoked by restart_syscall(). .\" notable (as at linux 3.17) is that poll() has such a "restart" .\" function, but ppoll(), select(), and pselect() do not. .\" this means that the latter system calls do not take account of the .\" time spent in the stopped state when restarting. .br restart_syscall () restarts the interrupted system call with a time argument that is suitably adjusted to account for the time that has already elapsed (including the time where the process was stopped by a signal). without the .br restart_syscall () mechanism, restarting these system calls would not correctly deduct the already elapsed time when the process continued execution. .sh return value the return value of .br restart_syscall () is the return value of whatever system call is being restarted. .sh errors .i errno is set as per the errors for whatever system call is being restarted by .br restart_syscall (). .sh versions the .br restart_syscall () system call is present since linux 2.6. .sh conforming to this system call is linux-specific. .sh notes there is no glibc wrapper for this system call, because it is intended for use only by the kernel and should never be called by applications. .pp the kernel uses .br restart_syscall () to ensure that when a system call is restarted after a process has been stopped by a signal and then resumed by .br sigcont , then the time that the process spent in the stopped state is counted against the timeout interval specified in the original system call. in the case of system calls that take a timeout argument and automatically restart after a stop signal plus .br sigcont , but which do not have the .br restart_syscall () mechanism built in, then, after the process resumes execution, the time that the process spent in the stop state is .i not counted against the timeout value. notable examples of system calls that suffer this problem are .br ppoll (2), .br select (2), and .br pselect (2). .pp from user space, the operation of .br restart_syscall () is largely invisible: to the process that made the system call that is restarted, it appears as though that system call executed and returned in the usual fashion. .sh see also .br sigaction (2), .br sigreturn (2), .br signal (7) .\" fixme . ppoll(2), select(2), and pselect(2) .\" should probably get the restart_syscall() treatment: .\" if a select() call is suspended by stop-sig+sigcont, the time .\" spent suspended is *not* deducted when the select() is restarted. .\" fixme . check whether recvmmsg() handles stop-sig+sigcont properly. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcschr 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcschr \- search a wide character in a wide-character string .sh synopsis .nf .b #include .pp .bi "wchar_t *wcschr(const wchar_t *" wcs ", wchar_t " wc ); .fi .sh description the .br wcschr () function is the wide-character equivalent of the .br strchr (3) function. it searches the first occurrence of .i wc in the wide-character string pointed to by .ir wcs . .sh return value the .br wcschr () function returns a pointer to the first occurrence of .i wc in the wide-character string pointed to by .ir wcs , or null if .i wc does not occur in the string. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcschr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strchr (3), .br wcspbrk (3), .br wcsrchr (3), .br wcsstr (3), .br wmemchr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2013, heinrich schuchardt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .th fanotify_mark 2 2021-08-27 "linux" "linux programmer's manual" .sh name fanotify_mark \- add, remove, or modify an fanotify mark on a filesystem object .sh synopsis .nf .b #include .pp .bi "int fanotify_mark(int " fanotify_fd ", unsigned int " flags , .bi " uint64_t " mask ", int " dirfd \ ", const char *" pathname ); .fi .sh description for an overview of the fanotify api, see .br fanotify (7). .pp .br fanotify_mark () adds, removes, or modifies an fanotify mark on a filesystem object. the caller must have read permission on the filesystem object that is to be marked. .pp the .i fanotify_fd argument is a file descriptor returned by .br fanotify_init (2). .pp .i flags is a bit mask describing the modification to perform. it must include exactly one of the following values: .tp .b fan_mark_add the events in .i mask will be added to the mark mask (or to the ignore mask). .i mask must be nonempty or the error .b einval will occur. .tp .b fan_mark_remove the events in argument .i mask will be removed from the mark mask (or from the ignore mask). .i mask must be nonempty or the error .b einval will occur. .tp .b fan_mark_flush remove either all marks for filesystems, all marks for mounts, or all marks for directories and files from the fanotify group. if .i flags contains .br fan_mark_mount , all marks for mounts are removed from the group. if .i flags contains .br fan_mark_filesystem , all marks for filesystems are removed from the group. otherwise, all marks for directories and files are removed. no flag other than, and at most one of, the flags .b fan_mark_mount or .b fan_mark_filesystem can be used in conjunction with .br fan_mark_flush . .i mask is ignored. .pp if none of the values above is specified, or more than one is specified, the call fails with the error .br einval . .pp in addition, zero or more of the following values may be ored into .ir flags : .tp .b fan_mark_dont_follow if .i pathname is a symbolic link, mark the link itself, rather than the file to which it refers. (by default, .br fanotify_mark () dereferences .i pathname if it is a symbolic link.) .tp .b fan_mark_onlydir if the filesystem object to be marked is not a directory, the error .b enotdir shall be raised. .tp .b fan_mark_mount mark the mount specified by .ir pathname . if .i pathname is not itself a mount point, the mount containing .i pathname will be marked. all directories, subdirectories, and the contained files of the mount will be monitored. the events which require that filesystem objects are identified by file handles, such as .br fan_create , .br fan_attrib , .br fan_move , and .br fan_delete_self , cannot be provided as a .ir mask when .i flags contains .br fan_mark_mount . attempting to do so will result in the error .b einval being returned. .tp .br fan_mark_filesystem " (since linux 4.20)" .\" commit d54f4fba889b205e9cd8239182ca5d27d0ac3bc2 mark the filesystem specified by .ir pathname . the filesystem containing .i pathname will be marked. all the contained files and directories of the filesystem from any mount point will be monitored. .tp .b fan_mark_ignored_mask the events in .i mask shall be added to or removed from the ignore mask. .tp .b fan_mark_ignored_surv_modify the ignore mask shall survive modify events. if this flag is not set, the ignore mask is cleared when a modify event occurs for the ignored file or directory. .pp .i mask defines which events shall be listened for (or which shall be ignored). it is a bit mask composed of the following values: .tp .b fan_access create an event when a file or directory (but see bugs) is accessed (read). .tp .b fan_modify create an event when a file is modified (write). .tp .b fan_close_write create an event when a writable file is closed. .tp .b fan_close_nowrite create an event when a read-only file or directory is closed. .tp .b fan_open create an event when a file or directory is opened. .tp .br fan_open_exec " (since linux 5.0)" .\" commit 9b076f1c0f4869b838a1b7aa0edb5664d47ec8aa create an event when a file is opened with the intent to be executed. see notes for additional details. .tp .br fan_attrib " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when the metadata for a file or directory has changed. an fanotify group that identifies filesystem objects by file handles is required. .tp .br fan_create " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when a file or directory has been created in a marked parent directory. an fanotify group that identifies filesystem objects by file handles is required. .tp .br fan_delete " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when a file or directory has been deleted in a marked parent directory. an fanotify group that identifies filesystem objects by file handles is required. .tp .br fan_delete_self " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when a marked file or directory itself is deleted. an fanotify group that identifies filesystem objects by file handles is required. .tp .br fan_moved_from " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when a file or directory has been moved from a marked parent directory. an fanotify group that identifies filesystem objects by file handles is required. .tp .br fan_moved_to " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when a file or directory has been moved to a marked parent directory. an fanotify group that identifies filesystem objects by file handles is required. .tp .br fan_move_self " (since linux 5.1)" .\" commit 235328d1fa4251c6dcb32351219bb553a58838d2 create an event when a marked file or directory itself has been moved. an fanotify group that identifies filesystem objects by file handles is required. .tp .b fan_open_perm create an event when a permission to open a file or directory is requested. an fanotify file descriptor created with .b fan_class_pre_content or .b fan_class_content is required. .tp .br fan_open_exec_perm " (since linux 5.0)" .\" commit 66917a3130f218dcef9eeab4fd11a71cd00cd7c9 create an event when a permission to open a file for execution is requested. an fanotify file descriptor created with .b fan_class_pre_content or .b fan_class_content is required. see notes for additional details. .tp .b fan_access_perm create an event when a permission to read a file or directory is requested. an fanotify file descriptor created with .b fan_class_pre_content or .b fan_class_content is required. .tp .b fan_ondir create events for directories\(emfor example, when .br opendir (3), .br readdir (3) (but see bugs), and .br closedir (3) are called. without this flag, events are created only for files. in the context of directory entry events, such as .br fan_create , .br fan_delete , .br fan_moved_from , and .br fan_moved_to , specifying the flag .br fan_ondir is required in order to create events when subdirectory entries are modified (i.e., .br mkdir (2)/ .br rmdir (2)). .tp .b fan_event_on_child events for the immediate children of marked directories shall be created. the flag has no effect when marking mounts and filesystems. note that events are not generated for children of the subdirectories of marked directories. more specifically, the directory entry modification events .br fan_create , .br fan_delete , .br fan_moved_from , and .br fan_moved_to are not generated for any entry modifications performed inside subdirectories of marked directories. note that the events .br fan_delete_self and .br fan_move_self are not generated for children of marked directories. to monitor complete directory trees it is necessary to mark the relevant mount or filesystem. .pp the following composed values are defined: .tp .b fan_close a file is closed .rb ( fan_close_write | fan_close_nowrite ). .tp .b fan_move a file or directory has been moved .rb ( fan_moved_from | fan_moved_to ). .pp the filesystem object to be marked is determined by the file descriptor .i dirfd and the pathname specified in .ir pathname : .ip * 3 if .i pathname is null, .i dirfd defines the filesystem object to be marked. .ip * if .i pathname is null, and .i dirfd takes the special value .br at_fdcwd , the current working directory is to be marked. .ip * if .i pathname is absolute, it defines the filesystem object to be marked, and .i dirfd is ignored. .ip * if .i pathname is relative, and .i dirfd does not have the value .br at_fdcwd , then the filesystem object to be marked is determined by interpreting .i pathname relative the directory referred to by .ir dirfd . .ip * if .i pathname is relative, and .i dirfd has the value .br at_fdcwd , then the filesystem object to be marked is determined by interpreting .i pathname relative to the current working directory. (see .br openat (2) for an explanation of why the .i dirfd argument is useful.) .sh return value on success, .br fanotify_mark () returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf an invalid file descriptor was passed in .ir fanotify_fd . .tp .b ebadf .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b einval an invalid value was passed in .ir flags or .ir mask , or .i fanotify_fd was not an fanotify file descriptor. .tp .b einval the fanotify file descriptor was opened with .b fan_class_notif or the fanotify group identifies filesystem objects by file handles and mask contains a flag for permission events .rb ( fan_open_perm or .br fan_access_perm ). .tp .b enodev the filesystem object indicated by .i pathname is not associated with a filesystem that supports .i fsid (e.g., .br tmpfs (5)). this error can be returned only with an fanotify group that identifies filesystem objects by file handles. .tp .b enoent the filesystem object indicated by .ir dirfd and .ir pathname does not exist. this error also occurs when trying to remove a mark from an object which is not marked. .tp .b enomem the necessary memory could not be allocated. .tp .b enospc the number of marks exceeds the limit of 8192 and the .b fan_unlimited_marks flag was not specified when the fanotify file descriptor was created with .br fanotify_init (2). .tp .b enosys this kernel does not implement .br fanotify_mark (). the fanotify api is available only if the kernel was configured with .br config_fanotify . .tp .b enotdir .i flags contains .br fan_mark_onlydir , and .i dirfd and .i pathname do not specify a directory. .tp .b eopnotsupp the object indicated by .i pathname is associated with a filesystem that does not support the encoding of file handles. this error can be returned only with an fanotify group that identifies filesystem objects by file handles. .tp .b exdev the filesystem object indicated by .i pathname resides within a filesystem subvolume (e.g., .br btrfs (5)) which uses a different .i fsid than its root superblock. this error can be returned only with an fanotify group that identifies filesystem objects by file handles. .sh versions .br fanotify_mark () was introduced in version 2.6.36 of the linux kernel and enabled in version 2.6.37. .sh conforming to this system call is linux-specific. .sh notes .ss fan_open_exec and fan_open_exec_perm when using either .b fan_open_exec or .b fan_open_exec_perm within the .ir mask , events of these types will be returned only when the direct execution of a program occurs. more specifically, this means that events of these types will be generated for files that are opened using .br execve (2), .br execveat (2), or .br uselib (2). events of these types will not be raised in the situation where an interpreter is passed (or reads) a file for interpretation. .pp additionally, if a mark has also been placed on the linux dynamic linker, a user should also expect to receive an event for it when an elf object has been successfully opened using .br execve (2) or .br execveat (2). .pp for example, if the following elf binary were to be invoked and a .br fan_open_exec mark has been placed on /: .pp .in +4n .ex $ /bin/echo foo .ee .in .pp the listening application in this case would receive .br fan_open_exec events for both the elf binary and interpreter, respectively: .pp .in +4n .ex /bin/echo /lib64/ld\-linux\-x86\-64.so.2 .ee .in .sh bugs the following bugs were present in linux kernels before version 3.16: .ip * 3 .\" fixed by commit 0a8dd2db579f7a0ac7033d6b857c3d5dbaa77563 if .i flags contains .br fan_mark_flush , .ir dirfd , and .i pathname must specify a valid filesystem object, even though this object is not used. .ip * .\" fixed by commit d4c7cf6cffb1bc711a833b5e304ba5bcfe76398b .br readdir (2) does not generate a .b fan_access event. .ip * .\" fixed by commit cc299a98eb13a9853675a9cbb90b30b4011e1406 if .br fanotify_mark () is called with .br fan_mark_flush , .i flags is not checked for invalid values. .sh see also .br fanotify_init (2), .br fanotify (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th malloc_info 3 2021-03-22 "gnu" "linux programmer's manual" .sh name malloc_info \- export malloc state to a stream .sh synopsis .nf .b #include .pp .bi "int malloc_info(int " options ", file *" stream ); .fi .sh description the .br malloc_info () function exports an xml string that describes the current state of the memory-allocation implementation in the caller. the string is printed on the file stream .ir stream . the exported string includes information about all arenas (see .br malloc (3)). .pp as currently implemented, .i options must be zero. .sh return value on success, .br malloc_info () returns 0. on failure, it returns \-1, and .i errno is set to indicate the error. .sh errors .tp .b einval .i options was nonzero. .sh versions .br malloc_info () was added to glibc in version 2.10. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br malloc_info () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a gnu extension. .sh notes the memory-allocation information is provided as an xml string (rather than a c structure) because the information may change over time (according to changes in the underlying implementation). the output xml string includes a version field. .pp the .br open_memstream (3) function can be used to send the output of .br malloc_info () directly into a buffer in memory, rather than to a file. .pp the .br malloc_info () function is designed to address deficiencies in .br malloc_stats (3) and .br mallinfo (3). .sh examples the program below takes up to four command-line arguments, of which the first three are mandatory. the first argument specifies the number of threads that the program should create. all of the threads, including the main thread, allocate the number of blocks of memory specified by the second argument. the third argument controls the size of the blocks to be allocated. the main thread creates blocks of this size, the second thread created by the program allocates blocks of twice this size, the third thread allocates blocks of three times this size, and so on. .pp the program calls .br malloc_info () twice to display the memory-allocation state. the first call takes place before any threads are created or memory allocated. the second call is performed after all threads have allocated memory. .pp in the following example, the command-line arguments specify the creation of one additional thread, and both the main thread and the additional thread allocate 10000 blocks of memory. after the blocks of memory have been allocated, .br malloc_info () shows the state of two allocation arenas. .pp .in +4n .ex .rb "$ " "getconf gnu_libc_version" glibc 2.13 .rb "$ " "./a.out 1 10000 100" ============ before allocating blocks ============ ============ after allocating blocks ============ .ee .in .ss program source .ex #include #include #include #include #include static size_t blocksize; static int numthreads, numblocks; #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static void * thread_func(void *arg) { int tn = (int) arg; /* the multiplier \(aq(2 + tn)\(aq ensures that each thread (including the main thread) allocates a different amount of memory. */ for (int j = 0; j < numblocks; j++) if (malloc(blocksize * (2 + tn)) == null) errexit("malloc\-thread"); sleep(100); /* sleep until main thread terminates. */ return null; } int main(int argc, char *argv[]) { int sleeptime; if (argc < 4) { fprintf(stderr, "%s num\-threads num\-blocks block\-size [sleep\-time]\en", argv[0]); exit(exit_failure); } numthreads = atoi(argv[1]); numblocks = atoi(argv[2]); blocksize = atoi(argv[3]); sleeptime = (argc > 4) ? atoi(argv[4]) : 0; pthread_t *thr = calloc(numthreads, sizeof(*thr)); if (thr == null) errexit("calloc"); printf("============ before allocating blocks ============\en"); malloc_info(0, stdout); /* create threads that allocate different amounts of memory. */ for (int tn = 0; tn < numthreads; tn++) { errno = pthread_create(&thr[tn], null, thread_func, (void *) tn); if (errno != 0) errexit("pthread_create"); /* if we add a sleep interval after the start\-up of each thread, the threads likely won\(aqt contend for malloc mutexes, and therefore additional arenas won\(aqt be allocated (see malloc(3)). */ if (sleeptime > 0) sleep(sleeptime); } /* the main thread also allocates some memory. */ for (int j = 0; j < numblocks; j++) if (malloc(blocksize) == null) errexit("malloc"); sleep(2); /* give all threads a chance to complete allocations. */ printf("\en============ after allocating blocks ============\en"); malloc_info(0, stdout); exit(exit_success); } .ee .sh see also .br mallinfo (3), .br malloc (3), .br malloc_stats (3), .br mallopt (3), .br open_memstream (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th clog10 3 2021-03-22 "" "linux programmer's manual" .sh name clog10, clog10f, clog10l \- base-10 logarithm of a complex number .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "double complex clog10(double complex " z ); .bi "float complex clog10f(float complex " z ); .bi "long double complex clog10l(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description the call .i clog10(z) is equivalent to: .pp clog(z)/log(10) .pp or equally: .pp log10(cabs(c)) + i * carg(c) / log(10) .pp the other functions perform the same task for .i float and .ir "long double" . .pp note that .i z close to zero will cause an overflow. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clog10 (), .br clog10f (), .br clog10l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. the identifiers are reserved for future use in c99 and c11. .sh see also .br cabs (3), .br cexp (3), .br clog (3), .br clog2 (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/resolver.3 .so man3/remainder.3 .so man2/recv.2 .so man3/atoi.3 .\" copyright michael haardt (michael@cantor.informatik.rwth-aachen.de) .\" sat aug 27 20:43:50 met dst 1994 .\" and copyright (c) 2014, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sun sep 11 19:19:05 1994 .\" modified mon mar 25 10:19:00 1996 (merged a few .\" tiny changes from a man page by charles livingston). .\" modified sun jul 21 14:45:46 1996 .\" .th setsid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setsid \- creates a session and sets the process group id .sh synopsis .nf .ad l .b #include .pp .b pid_t setsid(void); .ad b .fi .sh description .br setsid () creates a new session if the calling process is not a process group leader. the calling process is the leader of the new session (i.e., its session id is made the same as its process id). the calling process also becomes the process group leader of a new process group in the session (i.e., its process group id is made the same as its process id). .pp the calling process will be the only process in the new process group and in the new session. .pp initially, the new session has no controlling terminal. for details of how a session acquires a controlling terminal, see .br credentials (7). .sh return value on success, the (new) session id of the calling process is returned. on error, .i "(pid_t)\ \-1" is returned, and .i errno is set to indicate the error. .sh errors .tp .b eperm the process group id of any process equals the pid of the calling process. thus, in particular, .br setsid () fails if the calling process is already a process group leader. .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh notes a child created via .br fork (2) inherits its parent's session id. the session id is preserved across an .br execve (2). .pp a process group leader is a process whose process group id equals its pid. disallowing a process group leader from calling .br setsid () prevents the possibility that a process group leader places itself in a new session while other processes in the process group remain in the original session; such a scenario would break the strict two-level hierarchy of sessions and process groups. in order to be sure that .br setsid () will succeed, call .br fork (2) and have the parent .br _exit (2), while the child (which by definition can't be a process group leader) calls .br setsid (). .pp if a session has a controlling terminal, and the .b clocal flag for that terminal is not set, and a terminal hangup occurs, then the session leader is sent a .br sighup signal. .pp if a process that is a session leader terminates, then a .b sighup signal is sent to each process in the foreground process group of the controlling terminal. .sh see also .br setsid (1), .br getsid (2), .br setpgid (2), .br setpgrp (2), .br tcgetsid (3), .br credentials (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdarg.3 .so man3/unlocked_stdio.3 .\" copyright (c) 2020 by alejandro colomar .\" and copyright (c) 2020 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th system_data_types 7 2021-03-22 "linux" "linux programmer's manual" .sh name system_data_types \- overview of system data types .sh description .\" layout: .\" a list of type names (the struct/union keyword will be omitted). .\" each entry will have the following parts: .\" * include (see notes) .\" .\" * definition (no "definition" header) .\" only struct/union types will have definition; .\" typedefs will remain opaque. .\" .\" * description (no "description" header) .\" a few lines describing the type. .\" .\" * versions (optional) .\" .\" * conforming to (see notes) .\" format: cxy and later; posix.1-xxxx and later. .\" .\" * notes (optional) .\" .\" * bugs (if any) .\" .\" * see also .\"------------------------------------- aiocb ------------------------/ .tp .i aiocb .rs .ir include : .ir . .pp .ex struct aiocb { int aio_fildes; /* file descriptor */ off_t aio_offset; /* file offset */ volatile void *aio_buf; /* location of buffer */ size_t aio_nbytes; /* length of transfer */ int aio_reqprio; /* request priority offset */ struct sigevent aio_sigevent; /* signal number and value */ int aio_lio_opcode;/* operation to be performed */ }; .ee .pp for further information about this structure, see .br aio (7). .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br aio_cancel (3), .br aio_error (3), .br aio_fsync (3), .br aio_read (3), .br aio_return (3), .br aio_suspend (3), .br aio_write (3), .br lio_listio (3) .re .\"------------------------------------- blkcnt_t ---------------------/ .tp .i blkcnt_t .rs .ir include : .ir . alternatively, .ir . .pp used for file block counts. according to posix, it shall be a signed integer type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br stat (2) .re .\"------------------------------------- blksize_t --------------------/ .tp .i blksize_t .rs .ir include : .ir . alternatively, .ir . .pp used for file block sizes. according to posix, it shall be a signed integer type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br stat (2) .re .\"------------------------------------- cc_t -------------------------/ .tp .i cc_t .rs .ir include : .ir . .pp used for terminal special characters. according to posix, it shall be an unsigned integer type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br termios (3) .re .\"------------------------------------- clock_t ----------------------/ .tp .i clock_t .rs .ir include : .i or .ir . alternatively, .ir . .pp used for system time in clock ticks or .b clocks_per_sec (defined in .ir ). according to posix, it shall be an integer type or a real-floating type. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br times (2), .br clock (3) .re .\"------------------------------------- clockid_t --------------------/ .tp .i clockid_t .rs .ir include : .ir . alternatively, .ir . .pp used for clock id type in the clock and timer functions. according to posix, it shall be defined as an arithmetic type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br clock_adjtime (2), .br clock_getres (2), .br clock_nanosleep (2), .br timer_create (2), .br clock_getcpuclockid (3) .re .\"------------------------------------- dev_t ------------------------/ .tp .i dev_t .rs .ir include : .ir . alternatively, .ir . .pp used for device ids. according to posix, it shall be an integer type. for further details of this type, see .br makedev (3). .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br mknod (2), .br stat (2) .re .\"------------------------------------- div_t ------------------------/ .tp .i div_t .rs .ir include : .ir . .pp .ex typedef struct { int quot; /* quotient */ int rem; /* remainder */ } div_t; .ee .pp it is the type of the value returned by the .br div (3) function. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br div (3) .re .\"------------------------------------- double_t ---------------------/ .tp .i double_t .rs .ir include : .ir . .pp the implementation's most efficient floating type at least as wide as .ir double . its type depends on the value of the macro .b flt_eval_method (defined in .ir ): .tp 0 .i double_t is .ir double . .tp 1 .i double_t is .ir double . .tp 2 .i double_t is .ir "long double" . .pp for other values of .br flt_eval_method , the type of .i double_t is implementation-defined. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .i float_t type in this page. .re .\"------------------------------------- fd_set -----------------------/ .tp .i fd_set .rs .ir include : .ir . alternatively, .ir . .pp a structure type that can represent a set of file descriptors. according to posix, the maximum number of file descriptors in an .i fd_set structure is the value of the macro .br fd_setsize . .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br select (2) .re .\"------------------------------------- fenv_t -----------------------/ .tp .i fenv_t .rs .ir include : .ir . .pp this type represents the entire floating-point environment, including control modes and status flags; for further details, see .br fenv (3). .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br fenv (3) .re .\"------------------------------------- fexcept_t --------------------/ .tp .i fexcept_t .rs .ir include : .ir . .pp this type represents the floating-point status flags collectively; for further details see .br fenv (3). .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br fenv (3) .re .\"------------------------------------- file -------------------------/ .tp .i file .rs .ir include : .ir . alternatively, .ir . .pp an object type used for streams. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br fclose (3), .br flockfile (3), .br fopen (3), .br fprintf (3), .br fread (3), .br fscanf (3), .br stdin (3), .br stdio (3) .re .\"------------------------------------- float_t ----------------------/ .tp .i float_t .rs .ir include : .ir . .pp the implementation's most efficient floating type at least as wide as .ir float . its type depends on the value of the macro .b flt_eval_method (defined in .ir ): .tp 0 .i float_t is .ir float . .tp 1 .i float_t is .ir double . .tp 2 .i float_t is .ir "long double" . .pp for other values of .br flt_eval_method , the type of .i float_t is implementation-defined. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .i double_t type in this page. .re .\"------------------------------------- gid_t ------------------------/ .tp .i gid_t .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , .ir , or .ir . .pp a type used to hold group ids. according to posix, this shall be an integer type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br chown (2), .br getgid (2), .br getegid (2), .br getgroups (2), .br getresgid (2), .br getgrnam (3), .br credentials (7) .re .\"------------------------------------- id_t -------------------------/ .tp .i id_t .rs .ir include : .ir . alternatively, .ir . .pp a type used to hold a general identifier. according to posix, this shall be an integer type that can be used to contain a .ir pid_t , .ir uid_t , or .ir gid_t . .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br getpriority (2), .br waitid (2) .re .\"------------------------------------- imaxdiv_t --------------------/ .tp .i imaxdiv_t .rs .ir include : .ir . .pp .ex typedef struct { intmax_t quot; /* quotient */ intmax_t rem; /* remainder */ } imaxdiv_t; .ee .pp it is the type of the value returned by the .br imaxdiv (3) function. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br imaxdiv (3) .re .\"------------------------------------- intmax_t ---------------------/ .tp .i intmax_t .rs .ir include : .ir . alternatively, .ir . .pp a signed integer type capable of representing any value of any signed integer type supported by the implementation. according to the c language standard, it shall be capable of storing values in the range .rb [ intmax_min , .br intmax_max ]. .pp the macro .br intmax_c () .\" todo: document int*_c(3) expands its argument to an integer constant of type .ir intmax_t . .pp the length modifier for .i intmax_t for the .br printf (3) and the .br scanf (3) families of functions is .br j ; resulting commonly in .b %jd or .b %ji for printing .i intmax_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir bugs : .i intmax_t is not large enough to represent values of type .i __int128 in implementations where .i __int128 is defined and .i long long is less than 128 bits wide. .pp .ir "see also" : the .i uintmax_t type in this page. .re .\"------------------------------------- intn_t -----------------------/ .tp .ir int n _t .rs .ir include : .ir . alternatively, .ir . .pp .ir int8_t , .ir int16_t , .ir int32_t , .i int64_t .pp a signed integer type of a fixed width of exactly n bits, n being the value specified in its type name. according to the c language standard, they shall be capable of storing values in the range .rb [ int n _min , .br int n _max ], substituting n by the appropriate number. .pp according to posix, .ir int8_t , .ir int16_t , and .i int32_t are required; .i int64_t is only required in implementations that provide integer types with width 64; and all other types of this form are optional. .pp the length modifiers for the .ir int n _t types for the .br printf (3) family of functions are expanded by macros of the forms .br prid n and .br prii n (defined in .ir ); resulting for example in .b %"prid64" or .b %"prii64" for printing .i int64_t values. the length modifiers for the .ir int n _t types for the .br scanf (3) family of functions are expanded by macros of the forms .br scnd n and .br scni n, (defined in .ir ); resulting for example in .b %"scnd8" or .b %"scni8" for scanning .i int8_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .ir intmax_t , .ir uint n _t , and .i uintmax_t types in this page. .re .\"------------------------------------- intptr_t ---------------------/ .tp .i intptr_t .rs .ir include : .ir . alternatively, .ir . .pp a signed integer type such that any valid .ri ( "void *" ) value can be converted to this type and back. according to the c language standard, it shall be capable of storing values in the range .rb [ intptr_min , .br intptr_max ]. .pp the length modifier for .i intptr_t for the .br printf (3) family of functions is expanded by the macros .b pridptr and .b priiptr (defined in .ir ); resulting commonly in .b %"pridptr" or .b %"priiptr" for printing .i intptr_t values. the length modifier for .i intptr_t for the .br scanf (3) family of functions is expanded by the macros .b scndptr and .b scniptr, (defined in .ir ); resulting commonly in .b %"scndptr" or .b %"scniptr" for scanning .i intptr_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .i uintptr_t and .i void * types in this page. .re .\"------------------------------------- lconv ------------------------/ .tp .i lconv .rs .ir include : .ir . .pp .ex struct lconv { /* values in the "c" locale: */ char *decimal_point; /* "." */ char *thousands_sep; /* "" */ char *grouping; /* "" */ char *mon_decimal_point; /* "" */ char *mon_thousands_sep; /* "" */ char *mon_grouping; /* "" */ char *positive_sign; /* "" */ char *negative_sign; /* "" */ char *currency_symbol; /* "" */ char frac_digits; /* char_max */ char p_cs_precedes; /* char_max */ char n_cs_precedes; /* char_max */ char p_sep_by_space; /* char_max */ char n_sep_by_space; /* char_max */ char p_sign_posn; /* char_max */ char n_sign_posn; /* char_max */ char *int_curr_symbol; /* "" */ char int_frac_digits; /* char_max */ char int_p_cs_precedes; /* char_max */ char int_n_cs_precedes; /* char_max */ char int_p_sep_by_space; /* char_max */ char int_n_sep_by_space; /* char_max */ char int_p_sign_posn; /* char_max */ char int_n_sign_posn; /* char_max */ }; .ee .pp contains members related to the formatting of numeric values. in the "c" locale, its members have the values shown in the comments above. .pp .ir "conforming to" : c11 and later; posix.1-2001 and later. .pp .ir "see also" : .br setlocale (3), .br localeconv (3), .br charsets (7), .br locale (7) .re .\"------------------------------------- ldiv_t -----------------------/ .tp .i ldiv_t .rs .ir include : .ir . .pp .ex typedef struct { long quot; /* quotient */ long rem; /* remainder */ } ldiv_t; .ee .pp it is the type of the value returned by the .br ldiv (3) function. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br ldiv (3) .re .\"------------------------------------- lldiv_t ----------------------/ .tp .i lldiv_t .rs .ir include : .ir . .pp .ex typedef struct { long long quot; /* quotient */ long long rem; /* remainder */ } lldiv_t; .ee .pp it is the type of the value returned by the .br lldiv (3) function. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br lldiv (3) .re .\"------------------------------------- mode_t -----------------------/ .tp .i mode_t .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , or .ir . .pp used for some file attributes (e.g., file mode). according to posix, it shall be an integer type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br chmod (2), .br mkdir (2), .br open (2), .br stat (2), .br umask (2) .re .\"------------------------------------- off64_t ----------------------/ .tp .i off64_t .rs .ir include : .ir . .pp used for file sizes. it is a 64-bit signed integer type. .pp .ir "conforming to" : present in glibc. it is not standardized by the c language standard nor posix. .pp .ir notes : the feature test macro .b _largefile64_source has to be defined for this type to be available. .pp .ir "see also" : .br copy_file_range (2), .br readahead (2), .br sync_file_range (2), .br lseek64 (3), .br feature_test_macros (7) .pp see also the .\" .i loff_t .\" and .i off_t type in this page. .re .\"------------------------------------- off_t ------------------------/ .tp .i off_t .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , or .ir . .pp used for file sizes. according to posix, this shall be a signed integer type. .pp .ir versions : .i and .i define .i off_t since posix.1-2008. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir notes : on some architectures, the width of this type can be controlled with the feature test macro .br _file_offset_bits . .pp .ir "see also" : .\" .br fallocate (2), .br lseek (2), .br mmap (2), .\" .br mmap2 (2), .br posix_fadvise (2), .br pread (2), .\" .br preadv (2), .br truncate (2), .br fseeko (3), .\" .br getdirentries (3), .br lockf (3), .br posix_fallocate (3), .br feature_test_macros (7) .pp see also the .\" .i loff_t .\" and .i off64_t type in this page. .re .\"------------------------------------- pid_t ------------------------/ .tp .i pid_t .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , or .ir . .pp this type is used for storing process ids, process group ids, and session ids. according to posix, it shall be a signed integer type, and the implementation shall support one or more programming environments where the width of .i pid_t is no greater than the width of the type .ir long . .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br fork (2), .br getpid (2), .br getppid (2), .br getsid (2), .br gettid (2), .br getpgid (2), .br kill (2), .br pidfd_open (2), .br sched_setscheduler (2), .br waitpid (2), .br sigqueue (3), .br credentials (7), .re .\"------------------------------------- ptrdiff_t --------------------/ .tp .i ptrdiff_t .rs .ir include : .ir . .pp used for a count of elements, and array indices. it is the result of subtracting two pointers. according to the c language standard, it shall be a signed integer type capable of storing values in the range .rb [ ptrdiff_min , .br ptrdiff_max ]. .pp the length modifier for .i ptrdiff_t for the .br printf (3) and the .br scanf (3) families of functions is .br t ; resulting commonly in .b %td or .b %ti for printing .i ptrdiff_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .i size_t and .i ssize_t types in this page. .re .\"------------------------------------- regex_t ----------------------/ .tp .i regex_t .rs .ir include : .ir . .pp .ex typedef struct { size_t re_nsub; /* number of parenthesized subexpressions */ } regex_t; .ee .pp this is a structure type used in regular expression matching. it holds a compiled regular expression, compiled with .br regcomp (3). .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br regex (3) .re .\"------------------------------------- regmatch_t -------------------/ .tp .i regmatch_t .rs .ir include : .ir . .pp .ex typedef struct { regoff_t rm_so; /* byte offset from start of string to start of substring */ regoff_t rm_eo; /* byte offset from start of string of the first character after the end of substring */ } regmatch_t; .ee .pp this is a structure type used in regular expression matching. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br regexec (3) .re .\"------------------------------------- regoff_t ---------------------/ .tp .i regoff_t .rs .ir include : .ir . .pp according to posix, it shall be a signed integer type capable of storing the largest value that can be stored in either a .i ptrdiff_t type or a .i ssize_t type. .pp .ir versions : prior to posix.1-2008, the type was capable of storing the largest value that can be stored in either an .i off_t type or a .i ssize_t type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : the .i regmatch_t structure and the .i ptrdiff_t and .i ssize_t types in this page. .re .\"------------------------------------- sigevent ---------------------/ .tp .i sigevent .rs .ir include : .ir . alternatively, .ir , .ir , or .ir . .pp .ex struct sigevent { int sigev_notify; /* notification type */ int sigev_signo; /* signal number */ union sigval sigev_value; /* signal value */ void (*sigev_notify_function)(union sigval); /* notification function */ pthread_attr_t *sigev_notify_attributes; /* notification attributes */ }; .ee .pp for further details about this type, see .br sigevent (7). .pp .ir versions : .i and .i define .i sigevent since posix.1-2008. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br timer_create (2), .br getaddrinfo_a (3), .br lio_listio (3), .br mq_notify (3) .pp see also the .i aiocb structure in this page. .re .\"------------------------------------- siginfo_t --------------------/ .tp .i siginfo_t .rs .ir include : .ir . alternatively, .ir . .pp .ex typedef struct { int si_signo; /* signal number */ int si_code; /* signal code */ pid_t si_pid; /* sending process id */ uid_t si_uid; /* real user id of sending process */ void *si_addr; /* address of faulting instruction */ int si_status; /* exit value or signal */ union sigval si_value; /* signal value */ } siginfo_t; .ee .pp information associated with a signal. for further details on this structure (including additional, linux-specific fields), see .br sigaction (2). .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br pidfd_send_signal (2), .br rt_sigqueueinfo (2), .br sigaction (2), .br sigwaitinfo (2), .br psiginfo (3) .re .\"------------------------------------- sigset_t ---------------------/ .tp .i sigset_t .rs .ir include : .ir . alternatively, .ir , or .ir . .pp this is a type that represents a set of signals. according to posix, this shall be an integer or structure type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br epoll_pwait (2), .br ppoll (2), .br pselect (2), .br sigaction (2), .br signalfd (2), .br sigpending (2), .br sigprocmask (2), .br sigsuspend (2), .br sigwaitinfo (2), .br signal (7) .re .\"------------------------------------- sigval -----------------------/ .tp .i sigval .rs .ir include : .ir . .pp .ex union sigval { int sigval_int; /* integer value */ void *sigval_ptr; /* pointer value */ }; .ee .pp data passed with a signal. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br pthread_sigqueue (3), .br sigqueue (3), .br sigevent (7) .pp see also the .i sigevent structure and the .i siginfo_t type in this page. .re .\"------------------------------------- size_t -----------------------/ .tp .i size_t .rs .ir include : .i or .ir . alternatively, .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , .ir , or .ir . .pp used for a count of bytes. it is the result of the .i sizeof operator. according to the c language standard, it shall be an unsigned integer type capable of storing values in the range [0, .br size_max ]. according to posix, the implementation shall support one or more programming environments where the width of .i size_t is no greater than the width of the type .ir long . .pp the length modifier for .i size_t for the .br printf (3) and the .br scanf (3) families of functions is .br z ; resulting commonly in .b %zu or .b %zx for printing .i size_t values. .pp .ir versions : .ir , .ir , .ir , .ir , .ir , .ir , .ir , and .i define .i size_t since posix.1-2008. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br read (2), .br write (2), .br fread (3), .br fwrite (3), .br memcmp (3), .br memcpy (3), .br memset (3), .br offsetof (3) .pp see also the .i ptrdiff_t and .i ssize_t types in this page. .re .\"------------------------------------- sockaddr ---------------------/ .tp .i sockaddr .rs .ir include : .ir . .pp .ex struct sockaddr { sa_family_t sa_family; /* address family */ char sa_data[]; /* socket address */ }; .ee .pp describes a socket address. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br accept (2), .br getpeername (2), .br getsockname (2), .br socket (2) .re .\"------------------------------------- socklen_t --------------------/ .tp .i socklen_t .rs .ir include : .ir . alternatively, .ir . .pp describes the length of a socket address. according to posix, this shall be an integer type of at least 32 bits. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br accept (2), .br bind (2), .br connect (2), .br gethostbyaddr (2), .br getnameinfo (2), .br socket (2) .pp see also the .i sockaddr structure in this page. .re .\"------------------------------------- ssize_t ----------------------/ .tp .i ssize_t .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , .ir , .ir , or .ir . .pp used for a count of bytes or an error indication. according to posix, it shall be a signed integer type capable of storing values at least in the range [-1, .br ssize_max ], and the implementation shall support one or more programming environments where the width of .i ssize_t is no greater than the width of the type .ir long . .pp glibc and most other implementations provide a length modifier for .i ssize_t for the .br printf (3) and the .br scanf (3) families of functions, which is .br z ; resulting commonly in .b %zd or .b %zi for printing .i ssize_t values. although .b z works for .i ssize_t on most implementations, portable posix programs should avoid using it\(emfor example, by converting the value to .i intmax_t and using its length modifier .rb ( j ). .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br read (2), .br readlink (2), .br readv (2), .br recv (2), .br send (2), .br write (2) .pp see also the .i ptrdiff_t and .i size_t types in this page. .re .\"------------------------------------- suseconds_t ------------------/ .tp .i suseconds_t .rs .ir include : .ir . alternatively, .ir , or .ir . .pp used for time in microseconds. according to posix, it shall be a signed integer type capable of storing values at least in the range [-1, 1000000], and the implementation shall support one or more programming environments where the width of .i suseconds_t is no greater than the width of the type .ir long . .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : the .i timeval structure in this page. .re .\"------------------------------------- time_t -----------------------/ .tp .i time_t .rs .ir include : .i or .ir . alternatively, .ir , .ir , .ir , .ir , .ir , .ir , .ir , or .ir . .pp used for time in seconds. according to posix, it shall be an integer type. .\" in posix.1-2001, the type was specified as being either an integer .\" type or a real-floating type. however, existing implementations .\" used an integer type, and posix.1-2008 tightened the specification .\" to reflect this. .pp .ir versions : .i defines .i time_t since posix.1-2008. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br stime (2), .br time (2), .br ctime (3), .br difftime (3) .re .\"------------------------------------- timer_t ----------------------/ .tp .i timer_t .rs .ir include : .ir . alternatively, .ir . .pp used for timer id returned by .br timer_create (2). according to posix, there are no defined comparison or assignment operators for this type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br timer_create (2), .br timer_delete (2), .br timer_getoverrun (2), .br timer_settime (2) .re .\"------------------------------------- timespec ---------------------/ .tp .i timespec .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , or .ir . .pp .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .pp describes times in seconds and nanoseconds. .pp .ir "conforming to" : c11 and later; posix.1-2001 and later. .pp .ir "see also" : .br clock_gettime (2), .br clock_nanosleep (2), .br nanosleep (2), .br timerfd_gettime (2), .br timer_gettime (2) .re .\"------------------------------------- timeval ----------------------/ .tp .i timeval .rs .ir include : .ir . alternatively, .ir , .ir , or .ir . .pp .ex struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ }; .ee .pp describes times in seconds and microseconds. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br gettimeofday (2), .br select (2), .br utimes (2), .br adjtime (3), .br futimes (3), .br timeradd (3) .re .\"------------------------------------- uid_t ----------------------/ .tp .i uid_t .rs .ir include : .ir . alternatively, .ir , .ir , .ir , .ir , .ir , or .ir . .pp a type used to hold user ids. according to posix, this shall be an integer type. .pp .ir "conforming to" : posix.1-2001 and later. .pp .ir "see also" : .br chown (2), .br getuid (2), .br geteuid (2), .br getresuid (2), .br getpwnam (3), .br credentials (7) .re .\"------------------------------------- uintmax_t --------------------/ .tp .i uintmax_t .rs .ir include : .ir . alternatively, .ir . .pp an unsigned integer type capable of representing any value of any unsigned integer type supported by the implementation. according to the c language standard, it shall be capable of storing values in the range [0, .br uintmax_max ]. .pp the macro .br uintmax_c () .\" todo: document uint*_c(3) expands its argument to an integer constant of type .ir uintmax_t . .pp the length modifier for .i uintmax_t for the .br printf (3) and the .br scanf (3) families of functions is .br j ; resulting commonly in .b %ju or .b %jx for printing .i uintmax_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir bugs : .i uintmax_t is not large enough to represent values of type .i unsigned __int128 in implementations where .i unsigned __int128 is defined and .i unsigned long long is less than 128 bits wide. .pp .ir "see also" : the .i intmax_t type in this page. .re .\"------------------------------------- uintn_t ----------------------/ .tp .ir uint n _t .rs .ir include : .ir . alternatively, .ir . .pp .ir uint8_t , .ir uint16_t , .ir uint32_t , .i uint64_t .pp an unsigned integer type of a fixed width of exactly n bits, n being the value specified in its type name. according to the c language standard, they shall be capable of storing values in the range [0, .br uint n _max ], substituting n by the appropriate number. .pp according to posix, .ir uint8_t , .ir uint16_t , and .i uint32_t are required; .i uint64_t is only required in implementations that provide integer types with width 64; and all other types of this form are optional. .pp the length modifiers for the .ir uint n _t types for the .br printf (3) family of functions are expanded by macros of the forms .br priu n, .br prio n, .br prix n, and .br prix n (defined in .ir ); resulting for example in .b %"priu32" or .b %"prix32" for printing .i uint32_t values. the length modifiers for the .ir uint n _t types for the .br scanf (3) family of functions are expanded by macros of the forms .br scnu n, .br scno n, .br scnx n, and .br scnx n (defined in .ir ); resulting for example in .b %"scnu16" or .b %"scnx16" for scanning .i uint16_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .ir intmax_t , .ir int n _t , and .ir uintmax_t types in this page. .re .\"------------------------------------- uintptr_t --------------------/ .tp .i uintptr_t .rs .ir include : .ir . alternatively, .ir . .pp an unsigned integer type such that any valid .ri ( "void *" ) value can be converted to this type and back. according to the c language standard, it shall be capable of storing values in the range [0, .br uintptr_max ]. .pp the length modifier for .i uintptr_t for the .br printf (3) family of functions is expanded by the macros .br priuptr , .br prioptr , .br prixptr , and .b prixptr (defined in .ir ); resulting commonly in .b %"priuptr" or .b %"prixptr" for printing .i uintptr_t values. the length modifier for .i uintptr_t for the .br scanf (3) family of functions is expanded by the macros .br scnuptr, .br scnoptr, .br scnxptr , and .b scnxptr (defined in .ir ); resulting commonly in .b %"scnuptr" or .b %"scnxptr" for scanning .i uintptr_t values. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : the .i intptr_t and .i void * types in this page. .re .\"------------------------------------- va_list ----------------------/ .tp .i va_list .rs .ir include : .ir . alternatively, .ir , or .ir . .pp used by functions with a varying number of arguments of varying types. the function must declare an object of type .i va_list which is used by the macros .br va_start (3), .br va_arg (3), .br va_copy (3), and .br va_end (3) to traverse the list of arguments. .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br va_start (3), .br va_arg (3), .br va_copy (3), .br va_end (3) .re .\"------------------------------------- void * -----------------------/ .tp .i void * .rs according to the c language standard, a pointer to any object type may be converted to a pointer to .i void and back. posix further requires that any pointer, including pointers to functions, may be converted to a pointer to .i void and back. .pp conversions from and to any other pointer type are done implicitly, not requiring casts at all. note that this feature prevents any kind of type checking: the programmer should be careful not to convert a .i void * value to a type incompatible to that of the underlying data, because that would result in undefined behavior. .pp this type is useful in function parameters and return value to allow passing values of any type. the function will typically use some mechanism to know the real type of the data being passed via a pointer to .ir void . .pp a value of this type can't be dereferenced, as it would give a value of type .ir void , which is not possible. likewise, pointer arithmetic is not possible with this type. however, in gnu c, pointer arithmetic is allowed as an extension to the standard; this is done by treating the size of a .i void or of a function as 1. a consequence of this is that .i sizeof is also allowed on .i void and on function types, and returns 1. .pp the conversion specifier for .i void * for the .br printf (3) and the .br scanf (3) families of functions is .br p . .pp .ir versions : the posix requirement about compatibility between .i void * and function pointers was added in posix.1-2008 technical corrigendum 1 (2013). .pp .ir "conforming to" : c99 and later; posix.1-2001 and later. .pp .ir "see also" : .br malloc (3), .br memcmp (3), .br memcpy (3), .br memset (3) .pp see also the .i intptr_t and .i uintptr_t types in this page. .re .\"--------------------------------------------------------------------/ .sh notes the structures described in this manual page shall contain, at least, the members shown in their definition, in no particular order. .pp most of the integer types described in this page don't have a corresponding length modifier for the .br printf (3) and the .br scanf (3) families of functions. to print a value of an integer type that doesn't have a length modifier, it should be converted to .i intmax_t or .i uintmax_t by an explicit cast. to scan into a variable of an integer type that doesn't have a length modifier, an intermediate temporary variable of type .i intmax_t or .i uintmax_t should be used. when copying from the temporary variable to the destination variable, the value could overflow. if the type has upper and lower limits, the user should check that the value is within those limits, before actually copying the value. the example below shows how these conversions should be done. .ss conventions used in this page in "conforming to" we only concern ourselves with c99 and later and posix.1-2001 and later. some types may be specified in earlier versions of one of these standards, but in the interests of simplicity we omit details from earlier standards. .pp in "include", we first note the "primary" header(s) that define the type according to either the c or posix.1 standards. under "alternatively", we note additional headers that the standards specify shall define the type. .sh examples the program shown below scans from a string and prints a value stored in a variable of an integer type that doesn't have a length modifier. the appropriate conversions from and to .ir intmax_t , and the appropriate range checks, are used as explained in the notes section above. .pp .ex #include #include #include #include int main (void) { static const char *const str = "500000 us in half a second"; suseconds_t us; intmax_t tmp; /* scan the number from the string into the temporary variable. */ sscanf(str, "%jd", &tmp); /* check that the value is within the valid range of suseconds_t. */ if (tmp < \-1 || tmp > 1000000) { fprintf(stderr, "scanned value outside valid range!\en"); exit(exit_failure); } /* copy the value to the suseconds_t variable \(aqus\(aq. */ us = tmp; /* even though suseconds_t can hold the value \-1, this isn\(aqt a sensible number of microseconds. */ if (us < 0) { fprintf(stderr, "scanned value shouldn\(aqt be negative!\en"); exit(exit_failure); } /* print the value. */ printf("there are %jd microseconds in half a second.\en", (intmax_t) us); exit(exit_success); } .ee .sh see also .br feature_test_macros (7), .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getnetent_r.3 .\" copyright (c) 2015, 2016 ibm corporation. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th __ppc_set_ppr_med 3 2021-03-22 "gnu c library" "linux\ programmer's manual" .sh name __ppc_set_ppr_med, __ppc_set_ppr_very_low, __ppc_set_ppr_low, __ppc_set_ppr_med_low, __ppc_set_ppr_med_high \- set the program priority register .sh synopsis .nf .b #include .pp .b void __ppc_set_ppr_med(void); .b void __ppc_set_ppr_very_low(void); .b void __ppc_set_ppr_low(void); .b void __ppc_set_ppr_med_low(void); .b void __ppc_set_ppr_med_high(void); .fi .sh description these functions provide access to the .i program priority register (ppr) on the power architecture. .pp the ppr is a 64-bit register that controls the program's priority. by adjusting the ppr value the programmer may improve system throughput by causing system resources to be used more efficiently, especially in contention situations. the available unprivileged states are covered by the following functions: .ip * 3 .br __ppc_set_ppr_med () sets the program priority register value to .ir medium (default). .ip * .br __ppc_set_ppr_very_low () sets the program priority register value to .ir "very low" . .ip * .br __ppc_set_ppr_low () sets the program priority register value to .ir low . .ip * .br __ppc_set_ppr_med_low () sets the program priority register value to .ir "medium low" . .pp the privileged state .ir "medium high" may also be set during certain time intervals by problem-state (unprivileged) programs, with the following function: .ip * 3 .br __ppc_set_ppr_med_high () sets the program priority to .ir "medium high" . .pp if the program priority is medium high when the time interval expires or if an attempt is made to set the priority to medium high when it is not allowed, the priority is set to medium. .sh versions the functions .br __ppc_set_ppr_med (), .br __ppc_set_ppr_low (), and .br __ppc_set_ppr_med_low () are provided by glibc since version 2.18. the functions .br __ppc_set_ppr_very_low () and .br __ppc_set_ppr_med_high () first appeared in glibc in version 2.23. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br __ppc_set_ppr_med (), .br __ppc_set_ppr_very_low (), .br __ppc_set_ppr_low (), .br __ppc_set_ppr_med_low (), .br __ppc_set_ppr_med_high () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions. .sh notes the functions .br __ppc_set_ppr_very_low () and .br __ppc_set_ppr_med_high () will be defined by .i if .b _arch_pwr8 is defined. availability of these functions can be tested using .br "#ifdef _arch_pwr8" . .sh see also .br __ppc_yield (3) .pp .ir "power isa, book\ ii - section\ 3.1 (program priority registers)" .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/setreuid.2 .so man3/isalpha.3 .so man3/j0.3 .so man7/system_data_types.7 .so man2/getuid.2 .so man3/tailq.3 .so man5/proc.5 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .th sqrt 3 2021-03-22 "" "linux programmer's manual" .sh name sqrt, sqrtf, sqrtl \- square root function .sh synopsis .nf .b #include .pp .bi "double sqrt(double " x ); .bi "float sqrtf(float " x ); .bi "long double sqrtl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sqrtf (), .br sqrtl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the nonnegative square root of .ir x . .sh return value on success, these functions return the square root of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is positive infinity, positive infinity is returned. .pp if .i x is less than \-0, a domain error occurs, and a nan is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp less than \-0 .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sqrt (), .br sqrtf (), .br sqrtl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br cbrt (3), .br csqrt (3), .br hypot (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/gettimeofday.2 .so man3/stailq.3 .so man2/setxattr.2 .\" copyright (c) 1995 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" written 11 june 1995 by andries brouwer .\" modified 22 july 1995 by michael chastain : .\" in 1.3.x, returns only one entry each time; return value is different. .\" modified 2004-12-01, mtk, fixed headers listed in synopsis .\" .th readdir 2 2021-03-22 "linux" "linux programmer's manual" .sh name readdir \- read directory entry .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_readdir, unsigned int " fd , .bi " struct old_linux_dirent *" dirp ", unsigned int " count ); .fi .pp .ir note : there is no definition of .br "struct old_linux_dirent" ; see notes. .sh description this is not the function you are interested in. look at .br readdir (3) for the posix conforming c library interface. this page documents the bare kernel system call interface, which is superseded by .br getdents (2). .pp .br readdir () reads one .i old_linux_dirent structure from the directory referred to by the file descriptor .i fd into the buffer pointed to by .ir dirp . the argument .i count is ignored; at most one .i old_linux_dirent structure is read. .pp the .i old_linux_dirent structure is declared (privately in linux kernel file .br fs/readdir.c ) as follows: .pp .in +4n .ex struct old_linux_dirent { unsigned long d_ino; /* inode number */ unsigned long d_offset; /* offset to this \fiold_linux_dirent\fp */ unsigned short d_namlen; /* length of this \fid_name\fp */ char d_name[1]; /* filename (null\-terminated) */ } .ee .in .pp .i d_ino is an inode number. .i d_offset is the distance from the start of the directory to this .ir old_linux_dirent . .i d_reclen is the size of .ir d_name , not counting the terminating null byte (\(aq\e0\(aq). .i d_name is a null-terminated filename. .sh return value on success, 1 is returned. on end of directory, 0 is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf invalid file descriptor .ir fd . .tp .b efault argument points outside the calling process's address space. .tp .b einval result buffer is too small. .tp .b enoent no such directory. .tp .b enotdir file descriptor does not refer to a directory. .sh conforming to this system call is linux-specific. .sh notes you will need to define the .i old_linux_dirent structure yourself. however, probably you should use .br readdir (3) instead. .pp this system call does not exist on x86-64. .sh see also .br getdents (2), .br readdir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xdr.3 .so man3/getpwent_r.3 .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th persistent-keyring 7 2020-08-13 linux "linux programmer's manual" .sh name persistent-keyring \- per-user persistent keyring .sh description the persistent keyring is a keyring used to anchor keys on behalf of a user. each uid the kernel deals with has its own persistent keyring that is shared between all threads owned by that uid. the persistent keyring has a name (description) of the form .i _persistent. where .i is the user id of the corresponding user. .pp the persistent keyring may not be accessed directly, even by processes with the appropriate uid. .\" fixme the meaning of the preceding sentence isn't clear. what is meant? instead, it must first be linked to one of a process's keyrings, before that keyring can access the persistent keyring by virtue of its possessor permits. this linking is done with the .br keyctl_get_persistent (3) function. .pp if a persistent keyring does not exist when it is accessed by the .br keyctl_get_persistent (3) operation, it will be automatically created. .pp each time the .br keyctl_get_persistent (3) operation is performed, the persistent key's expiration timer is reset to the value in: .pp /proc/sys/kernel/keys/persistent_keyring_expiry .pp should the timeout be reached, the persistent keyring will be removed and everything it pins can then be garbage collected. the key will then be re-created on a subsequent call to .br keyctl_get_persistent (3). .pp the persistent keyring is not directly searched by .br request_key (2); it is searched only if it is linked into one of the keyrings that is searched by .br request_key (2). .pp the persistent keyring is independent of .br clone (2), .br fork (2), .br vfork (2), .br execve (2), and .br _exit (2). it persists until its expiration timer triggers, at which point it is garbage collected. this allows the persistent keyring to carry keys beyond the life of the kernel's record of the corresponding uid (the destruction of which results in the destruction of the .br user\-keyring (7) and the .br user\-session\-keyring (7)). the persistent keyring can thus be used to hold authentication tokens for processes that run without user interaction, such as programs started by .br cron (8). .pp the persistent keyring is used to store uid-specific objects that themselves have limited lifetimes (e.g., kerberos tokens). if those tokens cease to be used (i.e., the persistent keyring is not accessed), then the timeout of the persistent keyring ensures that the corresponding objects are automatically discarded. .\" .ss special operations the .i keyutils library provides the .br keyctl_get_persistent (3) function for manipulating persistent keyrings. (this function is an interface to the .br keyctl (2) .b keyctl_get_persistent operation.) this operation allows the calling thread to get the persistent keyring corresponding to its own uid or, if the thread has the .br cap_setuid capability, the persistent keyring corresponding to some other uid in the same user namespace. .sh notes each user namespace owns a keyring called .ir .persistent_register that contains links to all of the persistent keys in that namespace. (the .ir .persistent_register keyring can be seen when reading the contents of the .ir /proc/keys file for the uid 0 in the namespace.) the .br keyctl_get_persistent (3) operation looks for a key with a name of the form .ir _persistent. in that keyring, creates the key if it does not exist, and links it into the keyring. .sh see also .ad l .nh .br keyctl (1), .br keyctl (3), .br keyctl_get_persistent (3), .br keyrings (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setaliasent.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" .th strnlen 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strnlen \- determine the length of a fixed-size string .sh synopsis .nf .b #include .pp .bi "size_t strnlen(const char *" s ", size_t " maxlen ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strnlen (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br strnlen () function returns the number of bytes in the string pointed to by .ir s , excluding the terminating null byte (\(aq\e0\(aq), but at most .ir maxlen . in doing this, .br strnlen () looks only at the first .i maxlen characters in the string pointed to by .i s and never beyond .ir s[maxlen\-1] . .sh return value the .br strnlen () function returns .ir strlen(s) , if that is less than .ir maxlen , or .i maxlen if there is no null terminating (\(aq\e0\(aq) among the first .i maxlen characters pointed to by .ir s . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strnlen () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. .sh see also .br strlen (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2001 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" [should really be seteuid.3] .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th seteuid 2 2021-03-22 "linux" "linux programmer's manual" .sh name seteuid, setegid \- set effective user or group id .sh synopsis .nf .b #include .pp .bi "int seteuid(uid_t " euid ); .bi "int setegid(gid_t " egid ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br seteuid (), .br setegid (): .nf _posix_c_source >= 200112l || /* glibc <= 2.19: */ _bsd_source .fi .sh description .br seteuid () sets the effective user id of the calling process. unprivileged processes may only set the effective user id to the real user id, the effective user id or the saved set-user-id. .pp precisely the same holds for .br setegid () with "group" instead of "user". .\" when .\" .i euid .\" equals \-1, nothing is changed. .\" (this is an artifact of the implementation in glibc of seteuid() .\" using setresuid(2).) .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .pp .ir note : there are cases where .br seteuid () can fail even when the caller is uid 0; it is a grave security error to omit checking for a failure return from .br seteuid (). .sh errors .tp .b einval the target user or group id is not valid in this user namespace. .tp .b eperm in the case of .br seteuid (): the calling process is not privileged (does not have the .br cap_setuid capability in its user namespace) and .i euid does not match the current real user id, current effective user id, or current saved set-user-id. .ip in the case of .br setegid (): the calling process is not privileged (does not have the .br cap_setgid capability in its user namespace) and .i egid does not match the current real group id, current effective group id, or current saved set-group-id. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh notes setting the effective user (group) id to the saved set-user-id (saved set-group-id) is possible since linux 1.1.37 (1.1.38). on an arbitrary system one should check .br _posix_saved_ids . .pp under glibc 2.0, .bi seteuid( euid ) is equivalent to .bi setreuid(\-1, " euid" ) and hence may change the saved set-user-id. under glibc 2.1 and later, it is equivalent to .bi setresuid(\-1, " euid" ", \-1)" and hence does not change the saved set-user-id. analogous remarks hold for .br setegid (), with the difference that the change in implementation from .bi setregid(\-1, " egid" ) to .bi setresgid(\-1, " egid" ", \-1)" occurred in glibc 2.2 or 2.3 (depending on the hardware architecture). .pp according to posix.1, .br seteuid () .rb ( setegid ()) need not permit .i euid .ri ( egid ) to be the same value as the current effective user (group) id, and some implementations do not permit this. .ss c library/kernel differences on linux, .br seteuid () and .br setegid () are implemented as library functions that call, respectively, .br setreuid (2) and .br setregid (2). .sh see also .br geteuid (2), .br setresuid (2), .br setreuid (2), .br setuid (2), .br capabilities (7), .br credentials (7), .br user_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: ip.7,v 1.19 2000/12/20 18:10:31 ak exp $ .\" .\" fixme the following socket options are yet to be documented .\" .\" ip_xfrm_policy (2.5.48) .\" needs cap_net_admin .\" .\" ip_ipsec_policy (2.5.47) .\" needs cap_net_admin .\" .\" ip_minttl (2.6.34) .\" commit d218d11133d888f9745802146a50255a4781d37a .\" author: stephen hemminger .\" .\" mcast_join_group (2.4.22 / 2.6) .\" .\" mcast_block_source (2.4.22 / 2.6) .\" .\" mcast_unblock_source (2.4.22 / 2.6) .\" .\" mcast_leave_group (2.4.22 / 2.6) .\" .\" mcast_join_source_group (2.4.22 / 2.6) .\" .\" mcast_leave_source_group (2.4.22 / 2.6) .\" .\" mcast_msfilter (2.4.22 / 2.6) .\" .\" ip_unicast_if (3.4) .\" commit 76e21053b5bf33a07c76f99d27a74238310e3c71 .\" author: erich e. hoover .\" .th ip 7 2021-03-22 "linux" "linux programmer's manual" .sh name ip \- linux ipv4 protocol implementation .sh synopsis .nf .b #include .\" .b #include -- does not exist anymore .\" .b #include -- never include .b #include .b #include \fr/* superset of previous */ .pp .ib tcp_socket " = socket(af_inet, sock_stream, 0);" .ib udp_socket " = socket(af_inet, sock_dgram, 0);" .ib raw_socket " = socket(af_inet, sock_raw, " protocol ");" .fi .sh description linux implements the internet protocol, version 4, described in rfc\ 791 and rfc\ 1122. .b ip contains a level 2 multicasting implementation conforming to rfc\ 1112. it also contains an ip router including a packet filter. .pp the programming interface is bsd-sockets compatible. for more information on sockets, see .br socket (7). .pp an ip socket is created using .br socket (2): .pp socket(af_inet, socket_type, protocol); .pp valid socket types include .b sock_stream to open a stream socket, .b sock_dgram to open a datagram socket, and .b sock_raw to open a .br raw (7) socket to access the ip protocol directly. .pp .i protocol is the ip protocol in the ip header to be received or sent. valid values for .i protocol include: .ip \(bu 2 0 and .b ipproto_tcp for .br tcp (7) stream sockets; .ip \(bu 0 and .b ipproto_udp for .br udp (7) datagram sockets; .ip \(bu .b ipproto_sctp for .br sctp (7) stream sockets; and .ip \(bu .b ipproto_udplite for .br udplite (7) datagram sockets. .pp for .b sock_raw you may specify a valid iana ip protocol defined in rfc\ 1700 assigned numbers. .pp when a process wants to receive new incoming packets or connections, it should bind a socket to a local interface address using .br bind (2). in this case, only one ip socket may be bound to any given local (address, port) pair. when .b inaddr_any is specified in the bind call, the socket will be bound to .i all local interfaces. when .br listen (2) is called on an unbound socket, the socket is automatically bound to a random free port with the local address set to .br inaddr_any . when .br connect (2) is called on an unbound socket, the socket is automatically bound to a random free port or to a usable shared port with the local address set to .br inaddr_any . .pp a tcp local socket address that has been bound is unavailable for some time after closing, unless the .b so_reuseaddr flag has been set. care should be taken when using this flag as it makes tcp less reliable. .ss address format an ip socket address is defined as a combination of an ip interface address and a 16-bit port number. the basic ip protocol does not supply port numbers, they are implemented by higher level protocols like .br udp (7) and .br tcp (7). on raw sockets .i sin_port is set to the ip protocol. .pp .in +4n .ex struct sockaddr_in { sa_family_t sin_family; /* address family: af_inet */ in_port_t sin_port; /* port in network byte order */ struct in_addr sin_addr; /* internet address */ }; /* internet address */ struct in_addr { uint32_t s_addr; /* address in network byte order */ }; .ee .in .pp .i sin_family is always set to .br af_inet . this is required; in linux 2.2 most networking functions return .b einval when this setting is missing. .i sin_port contains the port in network byte order. the port numbers below 1024 are called .ir "privileged ports" (or sometimes: .ir "reserved ports" ). only a privileged process (on linux: a process that has the .b cap_net_bind_service capability in the user namespace governing its network namespace) may .br bind (2) to these sockets. note that the raw ipv4 protocol as such has no concept of a port, they are implemented only by higher protocols like .br tcp (7) and .br udp (7). .pp .i sin_addr is the ip host address. the .i s_addr member of .i struct in_addr contains the host interface address in network byte order. .i in_addr should be assigned one of the .br inaddr_* values (e.g., .br inaddr_loopback ) using .br htonl (3) or set using the .br inet_aton (3), .br inet_addr (3), .br inet_makeaddr (3) library functions or directly with the name resolver (see .br gethostbyname (3)). .pp ipv4 addresses are divided into unicast, broadcast, and multicast addresses. unicast addresses specify a single interface of a host, broadcast addresses specify all hosts on a network, and multicast addresses address all hosts in a multicast group. datagrams to broadcast addresses can be sent or received only when the .b so_broadcast socket flag is set. in the current implementation, connection-oriented sockets are allowed to use only unicast addresses. .\" leave a loophole for xtp @) .pp note that the address and the port are always stored in network byte order. in particular, this means that you need to call .br htons (3) on the number that is assigned to a port. all address/port manipulation functions in the standard library work in network byte order. .pp there are several special addresses: .b inaddr_loopback (127.0.0.1) always refers to the local host via the loopback device; .b inaddr_any (0.0.0.0) means any address for binding; .b inaddr_broadcast (255.255.255.255) means any host and has the same effect on bind as .b inaddr_any for historical reasons. .ss socket options ip supports some protocol-specific socket options that can be set with .br setsockopt (2) and read with .br getsockopt (2). the socket option level for ip is .br ipproto_ip . .\" or sol_ip on linux a boolean integer flag is zero when it is false, otherwise true. .pp when an invalid socket option is specified, .br getsockopt (2) and .br setsockopt (2) fail with the error .br enoprotoopt . .tp .br ip_add_membership " (since linux 1.2)" join a multicast group. argument is an .i ip_mreqn structure. .pp .in +4n .ex struct ip_mreqn { struct in_addr imr_multiaddr; /* ip multicast group address */ struct in_addr imr_address; /* ip address of local interface */ int imr_ifindex; /* interface index */ }; .ee .in .pp .i imr_multiaddr contains the address of the multicast group the application wants to join or leave. it must be a valid multicast address .\" (i.e., within the 224.0.0.0-239.255.255.255 range) (or .br setsockopt (2) fails with the error .br einval ). .i imr_address is the address of the local interface with which the system should join the multicast group; if it is equal to .br inaddr_any , an appropriate interface is chosen by the system. .i imr_ifindex is the interface index of the interface that should join/leave the .i imr_multiaddr group, or 0 to indicate any interface. .ip the .i ip_mreqn structure is available only since linux 2.2. for compatibility, the old .i ip_mreq structure (present since linux 1.2) is still supported; it differs from .i ip_mreqn only by not including the .i imr_ifindex field. (the kernel determines which structure is being passed based on the size passed in .ir optlen .) .ip .b ip_add_membership is valid only for .br setsockopt (2). .\" .tp .br ip_add_source_membership " (since linux 2.4.22 / 2.5.68)" join a multicast group and allow receiving data only from a specified source. argument is an .i ip_mreq_source structure. .pp .in +4n .ex struct ip_mreq_source { struct in_addr imr_multiaddr; /* ip multicast group address */ struct in_addr imr_interface; /* ip address of local interface */ struct in_addr imr_sourceaddr; /* ip address of multicast source */ }; .ee .in .pp the .i ip_mreq_source structure is similar to .i ip_mreqn described under .br ip_add_membership . the .i imr_multiaddr field contains the address of the multicast group the application wants to join or leave. the .i imr_interface field is the address of the local interface with which the system should join the multicast group. finally, the .i imr_sourceaddr field contains the address of the source the application wants to receive data from. .ip this option can be used multiple times to allow receiving data from more than one source. .tp .br ip_bind_address_no_port " (since linux 4.2)" .\" commit 90c337da1524863838658078ec34241f45d8394d inform the kernel to not reserve an ephemeral port when using .br bind (2) with a port number of 0. the port will later be automatically chosen at .br connect (2) time, in a way that allows sharing a source port as long as the 4-tuple is unique. .tp .br ip_block_source " (since linux 2.4.22 / 2.5.68)" stop receiving multicast data from a specific source in a given group. this is valid only after the application has subscribed to the multicast group using either .br ip_add_membership or .br ip_add_source_membership . .ip argument is an .i ip_mreq_source structure as described under .br ip_add_source_membership . .tp .br ip_drop_membership " (since linux 1.2)" leave a multicast group. argument is an .i ip_mreqn or .i ip_mreq structure similar to .br ip_add_membership . .tp .br ip_drop_source_membership " (since linux 2.4.22 / 2.5.68)" leave a source-specific group\(emthat is, stop receiving data from a given multicast group that come from a given source. if the application has subscribed to multiple sources within the same group, data from the remaining sources will still be delivered. to stop receiving data from all sources at once, use .br ip_drop_membership . .ip argument is an .i ip_mreq_source structure as described under .br ip_add_source_membership . .tp .br ip_freebind " (since linux 2.4)" .\" precisely: 2.4.0-test10 if enabled, this boolean option allows binding to an ip address that is nonlocal or does not (yet) exist. this permits listening on a socket, without requiring the underlying network interface or the specified dynamic ip address to be up at the time that the application is trying to bind to it. this option is the per-socket equivalent of the .ir ip_nonlocal_bind .i /proc interface described below. .tp .br ip_hdrincl " (since linux 2.0)" if enabled, the user supplies an ip header in front of the user data. valid only for .b sock_raw sockets; see .br raw (7) for more information. when this flag is enabled, the values set by .br ip_options , .br ip_ttl , and .b ip_tos are ignored. .tp .br ip_msfilter " (since linux 2.4.22 / 2.5.68)" this option provides access to the advanced full-state filtering api. argument is an .i ip_msfilter structure. .pp .in +4n .ex struct ip_msfilter { struct in_addr imsf_multiaddr; /* ip multicast group address */ struct in_addr imsf_interface; /* ip address of local interface */ uint32_t imsf_fmode; /* filter\-mode */ uint32_t imsf_numsrc; /* number of sources in the following array */ struct in_addr imsf_slist[1]; /* array of source addresses */ }; .ee .in .pp there are two macros, .br mcast_include and .br mcast_exclude , which can be used to specify the filtering mode. additionally, the .br ip_msfilter_size (n) macro exists to determine how much memory is needed to store .i ip_msfilter structure with .i n sources in the source list. .ip for the full description of multicast source filtering refer to rfc 3376. .tp .br ip_mtu " (since linux 2.2)" .\" precisely: 2.1.124 retrieve the current known path mtu of the current socket. returns an integer. .ip .b ip_mtu is valid only for .br getsockopt (2) and can be employed only when the socket has been connected. .tp .br ip_mtu_discover " (since linux 2.2)" .\" precisely: 2.1.124 set or receive the path mtu discovery setting for a socket. when enabled, linux will perform path mtu discovery as defined in rfc\ 1191 on .b sock_stream sockets. for .rb non- sock_stream sockets, .b ip_pmtudisc_do forces the don't-fragment flag to be set on all outgoing packets. it is the user's responsibility to packetize the data in mtu-sized chunks and to do the retransmits if necessary. the kernel will reject (with .br emsgsize ) datagrams that are bigger than the known path mtu. .b ip_pmtudisc_want will fragment a datagram if needed according to the path mtu, or will set the don't-fragment flag otherwise. .ip the system-wide default can be toggled between .b ip_pmtudisc_want and .b ip_pmtudisc_dont by writing (respectively, zero and nonzero values) to the .i /proc/sys/net/ipv4/ip_no_pmtu_disc file. .ts tab(:); c l l l. path mtu discovery value:meaning ip_pmtudisc_want:use per-route settings. ip_pmtudisc_dont:never do path mtu discovery. ip_pmtudisc_do:always do path mtu discovery. ip_pmtudisc_probe:set df but ignore path mtu. .te .sp 1 when pmtu discovery is enabled, the kernel automatically keeps track of the path mtu per destination host. when it is connected to a specific peer with .br connect (2), the currently known path mtu can be retrieved conveniently using the .b ip_mtu socket option (e.g., after an .b emsgsize error occurred). the path mtu may change over time. for connectionless sockets with many destinations, the new mtu for a given destination can also be accessed using the error queue (see .br ip_recverr ). a new error will be queued for every incoming mtu update. .ip while mtu discovery is in progress, initial packets from datagram sockets may be dropped. applications using udp should be aware of this and not take it into account for their packet retransmit strategy. .ip to bootstrap the path mtu discovery process on unconnected sockets, it is possible to start with a big datagram size (headers up to 64 kilobytes long) and let it shrink by updates of the path mtu. .ip to get an initial estimate of the path mtu, connect a datagram socket to the destination address using .br connect (2) and retrieve the mtu by calling .br getsockopt (2) with the .b ip_mtu option. .ip it is possible to implement rfc 4821 mtu probing with .b sock_dgram or .b sock_raw sockets by setting a value of .br ip_pmtudisc_probe (available since linux 2.6.22). this is also particularly useful for diagnostic tools such as .br tracepath (8) that wish to deliberately send probe packets larger than the observed path mtu. .tp .br ip_multicast_all " (since linux 2.6.31)" this option can be used to modify the delivery policy of multicast messages to sockets bound to the wildcard .b inaddr_any address. the argument is a boolean integer (defaults to 1). if set to 1, the socket will receive messages from all the groups that have been joined globally on the whole system. otherwise, it will deliver messages only from the groups that have been explicitly joined (for example via the .b ip_add_membership option) on this particular socket. .tp .br ip_multicast_if " (since linux 1.2)" set the local device for a multicast socket. the argument for .br setsockopt (2) is an .i ip_mreqn or .\" net: ip_multicast_if setsockopt now recognizes struct mreq .\" commit: 3a084ddb4bf299a6e898a9a07c89f3917f0713f7 (since linux 3.5) .i ip_mreq structure similar to .br ip_add_membership , or an .i in_addr structure. (the kernel determines which structure is being passed based on the size passed in .ir optlen .) for .br getsockopt (2), the argument is an .i in_addr structure. .tp .br ip_multicast_loop " (since linux 1.2)" set or read a boolean integer argument that determines whether sent multicast packets should be looped back to the local sockets. .tp .br ip_multicast_ttl " (since linux 1.2)" set or read the time-to-live value of outgoing multicast packets for this socket. it is very important for multicast packets to set the smallest ttl possible. the default is 1 which means that multicast packets don't leave the local network unless the user program explicitly requests it. argument is an integer. .tp .br ip_nodefrag " (since linux 2.6.36)" if enabled (argument is nonzero), the reassembly of outgoing packets is disabled in the netfilter layer. the argument is an integer. .ip this option is valid only for .b sock_raw sockets. .tp .br ip_options " (since linux 2.0)" .\" precisely: 1.3.30 set or get the ip options to be sent with every packet from this socket. the arguments are a pointer to a memory buffer containing the options and the option length. the .br setsockopt (2) call sets the ip options associated with a socket. the maximum option size for ipv4 is 40 bytes. see rfc\ 791 for the allowed options. when the initial connection request packet for a .b sock_stream socket contains ip options, the ip options will be set automatically to the options from the initial packet with routing headers reversed. incoming packets are not allowed to change options after the connection is established. the processing of all incoming source routing options is disabled by default and can be enabled by using the .i accept_source_route .i /proc interface. other options like timestamps are still handled. for datagram sockets, ip options can be set only by the local user. calling .br getsockopt (2) with .b ip_options puts the current ip options used for sending into the supplied buffer. .tp .br ip_passsec " (since linux 2.6.17)" .\" commit 2c7946a7bf45ae86736ab3b43d0085e43947945c if labeled ipsec or netlabel is configured on the sending and receiving hosts, this option enables receiving of the security context of the peer socket in an ancillary message of type .b scm_security retrieved using .br recvmsg (2). this option is supported only for udp sockets; for tcp or sctp sockets, see the description of the .b so_peersec option below. .ip the value given as an argument to .br setsockopt (2) and returned as the result of .br getsockopt (2) is an integer boolean flag. .ip the security context returned in the .b scm_security ancillary message is of the same format as the one described under the .b so_peersec option below. .ip note: the reuse of the .b scm_security message type for the .b ip_passsec socket option was likely a mistake, since other ip control messages use their own numbering scheme in the ip namespace and often use the socket option value as the message type. there is no conflict currently since the ip option with the same value as .b scm_security is .b ip_hdrincl and this is never used for a control message type. .tp .br ip_pktinfo " (since linux 2.2)" .\" precisely: 2.1.68 pass an .b ip_pktinfo ancillary message that contains a .i pktinfo structure that supplies some information about the incoming packet. this works only for datagram oriented sockets. the argument is a flag that tells the socket whether the .b ip_pktinfo message should be passed or not. the message itself can be sent/retrieved only as a control message with a packet using .br recvmsg (2) or .br sendmsg (2). .ip .in +4n .ex struct in_pktinfo { unsigned int ipi_ifindex; /* interface index */ struct in_addr ipi_spec_dst; /* local address */ struct in_addr ipi_addr; /* header destination address */ }; .ee .in .ip .i ipi_ifindex is the unique index of the interface the packet was received on. .i ipi_spec_dst is the local address of the packet and .i ipi_addr is the destination address in the packet header. if .b ip_pktinfo is passed to .br sendmsg (2) and .\" this field is grossly misnamed .i ipi_spec_dst is not zero, then it is used as the local source address for the routing table lookup and for setting up ip source route options. when .i ipi_ifindex is not zero, the primary local address of the interface specified by the index overwrites .i ipi_spec_dst for the routing table lookup. .tp .br ip_recverr " (since linux 2.2)" .\" precisely: 2.1.15 enable extended reliable error message passing. when enabled on a datagram socket, all generated errors will be queued in a per-socket error queue. when the user receives an error from a socket operation, the errors can be received by calling .br recvmsg (2) with the .b msg_errqueue flag set. the .i sock_extended_err structure describing the error will be passed in an ancillary message with the type .b ip_recverr and the level .br ipproto_ip . .\" or sol_ip on linux this is useful for reliable error handling on unconnected sockets. the received data portion of the error queue contains the error packet. .ip the .b ip_recverr control message contains a .i sock_extended_err structure: .ip .in +4n .ex #define so_ee_origin_none 0 #define so_ee_origin_local 1 #define so_ee_origin_icmp 2 #define so_ee_origin_icmp6 3 struct sock_extended_err { uint32_t ee_errno; /* error number */ uint8_t ee_origin; /* where the error originated */ uint8_t ee_type; /* type */ uint8_t ee_code; /* code */ uint8_t ee_pad; uint32_t ee_info; /* additional information */ uint32_t ee_data; /* other data */ /* more data may follow */ }; struct sockaddr *so_ee_offender(struct sock_extended_err *); .ee .in .ip .i ee_errno contains the .i errno number of the queued error. .i ee_origin is the origin code of where the error originated. the other fields are protocol-specific. the macro .b so_ee_offender returns a pointer to the address of the network object where the error originated from given a pointer to the ancillary message. if this address is not known, the .i sa_family member of the .i sockaddr contains .b af_unspec and the other fields of the .i sockaddr are undefined. .ip ip uses the .i sock_extended_err structure as follows: .i ee_origin is set to .b so_ee_origin_icmp for errors received as an icmp packet, or .b so_ee_origin_local for locally generated errors. unknown values should be ignored. .i ee_type and .i ee_code are set from the type and code fields of the icmp header. .i ee_info contains the discovered mtu for .b emsgsize errors. the message also contains the .i sockaddr_in of the node caused the error, which can be accessed with the .b so_ee_offender macro. the .i sin_family field of the .b so_ee_offender address is .b af_unspec when the source was unknown. when the error originated from the network, all ip options .rb ( ip_options ", " ip_ttl , etc.) enabled on the socket and contained in the error packet are passed as control messages. the payload of the packet causing the error is returned as normal payload. .\" fixme . is it a good idea to document that? it is a dubious feature. .\" on .\" .b sock_stream .\" sockets, .\" .b ip_recverr .\" has slightly different semantics. instead of .\" saving the errors for the next timeout, it passes all incoming .\" errors immediately to the user. .\" this might be useful for very short-lived tcp connections which .\" need fast error handling. use this option with care: .\" it makes tcp unreliable .\" by not allowing it to recover properly from routing .\" shifts and other normal .\" conditions and breaks the protocol specification. note that tcp has no error queue; .b msg_errqueue is not permitted on .b sock_stream sockets. .b ip_recverr is valid for tcp, but all errors are returned by socket function return or .b so_error only. .ip for raw sockets, .b ip_recverr enables passing of all received icmp errors to the application, otherwise errors are reported only on connected sockets .ip it sets or retrieves an integer boolean flag. .b ip_recverr defaults to off. .tp .br ip_recvopts " (since linux 2.2)" .\" precisely: 2.1.15 pass all incoming ip options to the user in a .b ip_options control message. the routing header and other options are already filled in for the local host. not supported for .b sock_stream sockets. .tp .br ip_recvorigdstaddr " (since linux 2.6.29)" .\" commit e8b2dfe9b4501ed0047459b2756ba26e5a940a69 this boolean option enables the .b ip_origdstaddr ancillary message in .br recvmsg (2), in which the kernel returns the original destination address of the datagram being received. the ancillary message contains a .ir "struct sockaddr_in" . .tp .br ip_recvtos " (since linux 2.2)" .\" precisely: 2.1.68 if enabled, the .b ip_tos ancillary message is passed with incoming packets. it contains a byte which specifies the type of service/precedence field of the packet header. expects a boolean integer flag. .tp .br ip_recvttl " (since linux 2.2)" .\" precisely: 2.1.68 when this flag is set, pass a .b ip_ttl control message with the time-to-live field of the received packet as a 32 bit integer. not supported for .b sock_stream sockets. .tp .br ip_retopts " (since linux 2.2)" .\" precisely: 2.1.15 identical to .br ip_recvopts , but returns raw unprocessed options with timestamp and route record options not filled in for this hop. .tp .br ip_router_alert " (since linux 2.2)" .\" precisely: 2.1.68 pass all to-be forwarded packets with the ip router alert option set to this socket. valid only for raw sockets. this is useful, for instance, for user-space rsvp daemons. the tapped packets are not forwarded by the kernel; it is the user's responsibility to send them out again. socket binding is ignored, such packets are filtered only by protocol. expects an integer flag. .tp .br ip_tos " (since linux 1.0)" set or receive the type-of-service (tos) field that is sent with every ip packet originating from this socket. it is used to prioritize packets on the network. tos is a byte. there are some standard tos flags defined: .b iptos_lowdelay to minimize delays for interactive traffic, .b iptos_throughput to optimize throughput, .b iptos_reliability to optimize for reliability, .b iptos_mincost should be used for "filler data" where slow transmission doesn't matter. at most one of these tos values can be specified. other bits are invalid and shall be cleared. linux sends .b iptos_lowdelay datagrams first by default, but the exact behavior depends on the configured queueing discipline. .\" fixme elaborate on this some high-priority levels may require superuser privileges (the .b cap_net_admin capability). .\" the priority can also be set in a protocol-independent way by the .\" .rb ( sol_socket ", " so_priority ) .\" socket option (see .\" .br socket (7)). .tp .br ip_transparent " (since linux 2.6.24)" .\" commit f5715aea4564f233767ea1d944b2637a5fd7cd2e .\" this patch introduces the ip_transparent socket option: enabling that .\" will make the ipv4 routing omit the non-local source address check on .\" output. setting ip_transparent requires net_admin capability. .\" http://lwn.net/articles/252545/ setting this boolean option enables transparent proxying on this socket. this socket option allows the calling application to bind to a nonlocal ip address and operate both as a client and a server with the foreign address as the local endpoint. note: this requires that routing be set up in a way that packets going to the foreign address are routed through the tproxy box (i.e., the system hosting the application that employs the .b ip_transparent socket option). enabling this socket option requires superuser privileges (the .br cap_net_admin capability). .ip tproxy redirection with the iptables tproxy target also requires that this option be set on the redirected socket. .tp .br ip_ttl " (since linux 1.0)" set or retrieve the current time-to-live field that is used in every packet sent from this socket. .tp .br ip_unblock_source " (since linux 2.4.22 / 2.5.68)" unblock previously blocked multicast source. returns .br eaddrnotavail when given source is not being blocked. .ip argument is an .i ip_mreq_source structure as described under .br ip_add_source_membership . .tp .br so_peersec " (since linux 2.6.17)" if labeled ipsec or netlabel is configured on both the sending and receiving hosts, this read-only socket option returns the security context of the peer socket connected to this socket. by default, this will be the same as the security context of the process that created the peer socket unless overridden by the policy or by a process with the required permissions. .ip the argument to .br getsockopt (2) is a pointer to a buffer of the specified length in bytes into which the security context string will be copied. if the buffer length is less than the length of the security context string, then .br getsockopt (2) returns \-1, sets .i errno to .br erange , and returns the required length via .ir optlen . the caller should allocate at least .br name_max bytes for the buffer initially, although this is not guaranteed to be sufficient. resizing the buffer to the returned length and retrying may be necessary. .ip the security context string may include a terminating null character in the returned length, but is not guaranteed to do so: a security context "foo" might be represented as either {'f','o','o'} of length 3 or {'f','o','o','\\0'} of length 4, which are considered to be interchangeable. the string is printable, does not contain non-terminating null characters, and is in an unspecified encoding (in particular, it is not guaranteed to be ascii or utf-8). .ip the use of this option for sockets in the .b af_inet address family is supported since linux 2.6.17 .\" commit 2c7946a7bf45ae86736ab3b43d0085e43947945c for tcp sockets, and since linux 4.17 .\" commit d452930fd3b9031e59abfeddb2fa383f1403d61a for sctp sockets. .ip for selinux, netlabel conveys only the mls portion of the security context of the peer across the wire, defaulting the rest of the security context to the values defined in the policy for the netmsg initial security identifier (sid). however, netlabel can be configured to pass full security contexts over loopback. labeled ipsec always passes full security contexts as part of establishing the security association (sa) and looks them up based on the association for each packet. .\" .ss /proc interfaces the ip protocol supports a set of .i /proc interfaces to configure some global parameters. the parameters can be accessed by reading or writing files in the directory .ir /proc/sys/net/ipv4/ . .\" fixme as at 2.6.12, 14 jun 2005, the following are undocumented: .\" ip_queue_maxlen .\" ip_conntrack_max interfaces described as .i boolean take an integer value, with a nonzero value ("true") meaning that the corresponding option is enabled, and a zero value ("false") meaning that the option is disabled. .\" .tp .ir ip_always_defrag " (boolean; since linux 2.2.13)" [new with kernel 2.2.13; in earlier kernel versions this feature was controlled at compile time by the .b config_ip_always_defrag option; this option is not present in 2.4.x and later] .ip when this boolean flag is enabled (not equal 0), incoming fragments (parts of ip packets that arose when some host between origin and destination decided that the packets were too large and cut them into pieces) will be reassembled (defragmented) before being processed, even if they are about to be forwarded. .ip enable only if running either a firewall that is the sole link to your network or a transparent proxy; never ever use it for a normal router or host. otherwise, fragmented communication can be disturbed if the fragments travel over different links. defragmentation also has a large memory and cpu time cost. .ip this is automagically turned on when masquerading or transparent proxying are configured. .\" .tp .ir ip_autoconfig " (since linux 2.2 to 2.6.17)" .\" precisely: since 2.1.68 .\" fixme document ip_autoconfig not documented. .\" .tp .ir ip_default_ttl " (integer; default: 64; since linux 2.2)" .\" precisely: 2.1.15 set the default time-to-live value of outgoing packets. this can be changed per socket with the .b ip_ttl option. .\" .tp .ir ip_dynaddr " (boolean; default: disabled; since linux 2.0.31)" enable dynamic socket address and masquerading entry rewriting on interface address change. this is useful for dialup interface with changing ip addresses. 0 means no rewriting, 1 turns it on and 2 enables verbose mode. .\" .tp .ir ip_forward " (boolean; default: disabled; since linux 1.2)" enable ip forwarding with a boolean flag. ip forwarding can be also set on a per-interface basis. .\" .tp .ir ip_local_port_range " (since linux 2.2)" .\" precisely: since 2.1.68 this file contains two integers that define the default local port range allocated to sockets that are not explicitly bound to a port number\(emthat is, the range used for .ir "ephemeral ports" . an ephemeral port is allocated to a socket in the following circumstances: .rs .ip * 3 the port number in a socket address is specified as 0 when calling .br bind (2); .ip * .br listen (2) is called on a stream socket that was not previously bound; .ip * .br connect (2) was called on a socket that was not previously bound; .ip * .br sendto (2) is called on a datagram socket that was not previously bound. .re .ip allocation of ephemeral ports starts with the first number in .ir ip_local_port_range and ends with the second number. if the range of ephemeral ports is exhausted, then the relevant system call returns an error (but see bugs). .ip note that the port range in .ir ip_local_port_range should not conflict with the ports used by masquerading (although the case is handled). also, arbitrary choices may cause problems with some firewall packet filters that make assumptions about the local ports in use. the first number should be at least greater than 1024, or better, greater than 4096, to avoid clashes with well known ports and to minimize firewall problems. .\" .tp .ir ip_no_pmtu_disc " (boolean; default: disabled; since linux 2.2)" .\" precisely: 2.1.15 if enabled, don't do path mtu discovery for tcp sockets by default. path mtu discovery may fail if misconfigured firewalls (that drop all icmp packets) or misconfigured interfaces (e.g., a point-to-point link where the both ends don't agree on the mtu) are on the path. it is better to fix the broken routers on the path than to turn off path mtu discovery globally, because not doing it incurs a high cost to the network. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir ip_nonlocal_bind " (boolean; default: disabled; since linux 2.4)" .\" precisely: patch-2.4.0-test10 if set, allows processes to .br bind (2) to nonlocal ip addresses, which can be quite useful, but may break some applications. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir ip6frag_time " (integer; default: 30)" time in seconds to keep an ipv6 fragment in memory. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir ip6frag_secret_interval " (integer; default: 600)" regeneration interval (in seconds) of the hash secret (or lifetime for the hash secret) for ipv6 fragments. .tp .ir ipfrag_high_thresh " (integer), " ipfrag_low_thresh " (integer)" if the amount of queued ip fragments reaches .ir ipfrag_high_thresh , the queue is pruned down to .ir ipfrag_low_thresh . contains an integer with the number of bytes. .tp .i neigh/* see .br arp (7). .\" fixme document the conf/*/* interfaces .\" .\" fixme document the route/* interfaces .ss ioctls all ioctls described in .br socket (7) apply to .br ip . .pp ioctls to configure generic device parameters are described in .br netdevice (7). .\" fixme add a discussion of multicasting .sh errors .\" fixme document all errors. .\" we should really fix the kernels to give more uniform .\" error returns (enomem vs enobufs, eperm vs eacces etc.) .tp .b eacces the user tried to execute an operation without the necessary permissions. these include: sending a packet to a broadcast address without having the .b so_broadcast flag set; sending a packet via a .i prohibit route; modifying firewall settings without superuser privileges (the .b cap_net_admin capability); binding to a privileged port without superuser privileges (the .b cap_net_bind_service capability). .tp .b eaddrinuse tried to bind to an address already in use. .tp .b eaddrnotavail a nonexistent interface was requested or the requested source address was not local. .tp .b eagain operation on a nonblocking socket would block. .tp .b ealready a connection operation on a nonblocking socket is already in progress. .tp .b econnaborted a connection was closed during an .br accept (2). .tp .b ehostunreach no valid routing table entry matches the destination address. this error can be caused by an icmp message from a remote router or for the local routing table. .tp .b einval invalid argument passed. for send operations this can be caused by sending to a .i blackhole route. .tp .b eisconn .br connect (2) was called on an already connected socket. .tp .b emsgsize datagram is bigger than an mtu on the path and it cannot be fragmented. .tp .br enobufs ", " enomem not enough free memory. this often means that the memory allocation is limited by the socket buffer limits, not by the system memory, but this is not 100% consistent. .tp .b enoent .b siocgstamp was called on a socket where no packet arrived. .tp .b enopkg a kernel subsystem was not configured. .tp .br enoprotoopt " and " eopnotsupp invalid socket option passed. .tp .b enotconn the operation is defined only on a connected socket, but the socket wasn't connected. .tp .b eperm user doesn't have permission to set high priority, change configuration, or send signals to the requested process or group. .tp .b epipe the connection was unexpectedly closed or shut down by the other end. .tp .b esocktnosupport the socket is not configured or an unknown socket type was requested. .pp other errors may be generated by the overlaying protocols; see .br tcp (7), .br raw (7), .br udp (7), and .br socket (7). .sh notes .br ip_freebind , .br ip_msfilter , .br ip_mtu , .br ip_mtu_discover , .br ip_recvorigdstaddr , .br ip_passsec , .br ip_pktinfo , .br ip_recverr , .br ip_router_alert , and .br ip_transparent are linux-specific. .\" ip_xfrm_policy is linux-specific .\" ip_ipsec_policy is a nonstandard extension, also present on some bsds .pp be very careful with the .b so_broadcast option \- it is not privileged in linux. it is easy to overload the network with careless broadcasts. for new application protocols it is better to use a multicast group instead of broadcasting. broadcasting is discouraged. .pp some other bsd sockets implementations provide .b ip_rcvdstaddr and .b ip_recvif socket options to get the destination address and the interface of received datagrams. linux has the more general .b ip_pktinfo for the same task. .pp some bsd sockets implementations also provide an .b ip_recvttl option, but an ancillary message with type .b ip_recvttl is passed with the incoming packet. this is different from the .b ip_ttl option used in linux. .pp using the .b sol_ip socket options level isn't portable; bsd-based stacks use the .b ipproto_ip level. .pp .b inaddr_any (0.0.0.0) and .b inaddr_broadcast (255.255.255.255) are byte-order-neutral. this means .br htonl (3) has no effect on them. .ss compatibility for compatibility with linux 2.0, the obsolete .bi "socket(af_inet, sock_packet, " protocol ) syntax is still supported to open a .br packet (7) socket. this is deprecated and should be replaced by .bi "socket(af_packet, sock_raw, " protocol ) instead. the main difference is the new .i sockaddr_ll address structure for generic link layer information instead of the old .br sockaddr_pkt . .sh bugs there are too many inconsistent error values. .pp the error used to diagnose exhaustion of the ephemeral port range differs across the various system calls .rb ( connect (2), .br bind (2), .br listen (2), .br sendto (2)) that can assign ephemeral ports. .pp the ioctls to configure ip-specific interface options and arp tables are not described. .\" .pp .\" some versions of glibc forget to declare .\" .ir in_pktinfo . .\" workaround currently is to copy it into your program from this man page. .pp receiving the original destination address with .b msg_errqueue in .i msg_name by .br recvmsg (2) does not work in some 2.2 kernels. .\" .sh authors .\" this man page was written by andi kleen. .sh see also .br recvmsg (2), .br sendmsg (2), .br byteorder (3), .br capabilities (7), .br icmp (7), .br ipv6 (7), .br netdevice (7), .br netlink (7), .br raw (7), .br socket (7), .br tcp (7), .br udp (7), .br ip (8) .pp the kernel source file .ir documentation/networking/ip\-sysctl.txt . .pp rfc\ 791 for the original ip specification. rfc\ 1122 for the ipv4 host requirements. rfc\ 1812 for the ipv4 router requirements. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/lstat.2 .\" copyright (c) 2016 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th tmpfs 5 2021-03-22 "linux" "linux programmer's manual" .sh name tmpfs \- a virtual memory filesystem .sh description the .b tmpfs facility allows the creation of filesystems whose contents reside in virtual memory. since the files on such filesystems typically reside in ram, file access is extremely fast. .pp the filesystem is automatically created when mounting a filesystem with the type .br tmpfs via a command such as the following: .pp .in +4n .ex $ sudo mount \-t tmpfs \-o size=10m tmpfs /mnt/mytmpfs .ee .in .pp a .b tmpfs filesystem has the following properties: .ip * 3 the filesystem can employ swap space when physical memory pressure demands it. .ip * the filesystem consumes only as much physical memory and swap space as is required to store the current contents of the filesystem. .ip * during a remount operation .ri ( "mount\ \-o\ remount" ), the filesystem size can be changed (without losing the existing contents of the filesystem). .pp if a .b tmpfs filesystem is unmounted, its contents are discarded (lost). .\" see mm/shmem.c:shmem_parse_options for options it supports. .ss mount options the .b tmpfs filesystem supports the following mount options: .tp .br size "=\fibytes\fp" specify an upper limit on the size of the filesystem. the size is given in bytes, and rounded up to entire pages. .ip the size may have a .br k , .br m , or .b g suffix for ki, mi, gi (binary kilo (kibi), binary mega (mebi), and binary giga (gibi)). .ip the size may also have a % suffix to limit this instance to a percentage of physical ram. .ip the default, when neither .b size nor .b nr_blocks is specified, is .ir size=50% . .tp .br nr_blocks "=\fiblocks\fp" the same as .br size , but in blocks of .br page_cache_size . .ip blocks may be specified with .br k , .br m , or .b g suffixes like .br size , but not a % suffix. .tp .br nr_inodes "=\fiinodes\fp" the maximum number of inodes for this instance. the default is half of the number of your physical ram pages, or (on a machine with highmem) the number of lowmem ram pages, whichever is smaller. .ip inodes may be specified with .br k , .br m , or .b g suffixes like .br size , but not a % suffix. .tp .br mode "=\fimode\fp" set initial permissions of the root directory. .tp .br gid "=\figid\fp (since linux 2.5.7)" .\" technically this is also in some version of linux 2.4. .\" commit 099445b489625b80b1d6687c9b6072dbeaca4096 set the initial group id of the root directory. .tp .br uid "=\fiuid\fp (since linux 2.5.7)" .\" technically this is also in some version of linux 2.4. .\" commit 099445b489625b80b1d6687c9b6072dbeaca4096 set the initial user id of the root directory. .tp .br huge "=\fihuge_option\fr (since linux 4.7.0)" .\" commit 5a6e75f8110c97e2a5488894d4e922187e6cb343 set the huge table memory allocation policy for all files in this instance (if .b config_transparent_huge_pagecache is enabled). .ip the .i huge_option value is one of the following: .rs .tp .b never do not allocate huge pages. this is the default. .tp .b always attempt to allocate huge pages every time a new page is needed. .tp .b within_size only allocate huge page if it will be fully within .ir i_size . also respect .br fadvise (2)/ madvise (2) hints .tp .b advise only allocate huge pages if requested with .br fadvise (2)/ madvise (2). .tp .b deny for use in emergencies, to force the huge option off from all mounts. .tp .b force force the huge option on for all mounts; useful for testing. .re .tp .br mpol "=\fimpol_option\fr (since linux 2.6.15)" .\" commit 7339ff8302fd70aabf5f1ae26e0c4905fa74a495 set the numa memory allocation policy for all files in this instance (if .b config_numa is enabled). .ip the .i mpol_option value is one of the following: .rs .tp .b default use the process allocation policy (see .br set_mempolicy (2)). .tp .br prefer ":\finode\fp" preferably allocate memory from the given .ir node . .tp .br bind ":\finodelist\fp" allocate memory only from nodes in .ir nodelist . .tp .b interleave allocate from each node in turn. .tp .br interleave ":\finodelist\fp" allocate from each node of .i in turn. .tp .b local preferably allocate memory from the local node. .re .ip in the above, .i nodelist is a comma-separated list of decimal numbers and ranges that specify numa nodes. a range is a pair of hyphen-separated decimal numbers, the smallest and largest node numbers in the range. for example, .ir mpol=bind:0\-3,5,7,9\-15 . .sh versions the .b tmpfs facility was added in linux 2.4, as a successor to the older .b ramfs facility, which did not provide limit checking or allow for the use of swap space. .sh notes in order for user-space tools and applications to create .b tmpfs filesystems, the kernel must be configured with the .b config_tmpfs option. .pp the .br tmpfs filesystem supports extended attributes (see .br xattr (7)), but .i user extended attributes are not permitted. .pp an internal shared memory filesystem is used for system v shared memory .rb ( shmget (2)) and shared anonymous mappings .rb ( mmap (2) with the .b map_shared and .br map_anonymous flags). this filesystem is available regardless of whether the kernel was configured with the .b config_tmpfs option. .pp a .b tmpfs filesystem mounted at .ir /dev/shm is used for the implementation of posix shared memory .rb ( shm_overview (7)) and posix semaphores .rb ( sem_overview (7)). .pp the amount of memory consumed by all .b tmpfs filesystems is shown in the .i shmem field of .ir /proc/meminfo and in the .i shared field displayed by .br free (1). .pp the .b tmpfs facility was formerly called .br shmfs . .sh see also .br df (1), .br du (1), .br memfd_create (2), .br mmap (2), .br set_mempolicy (2), .br shm_open (3), .br mount (8) .pp the kernel source files .ir documentation/filesystems/tmpfs.txt and .ir documentation/admin\-guide/mm/transhuge.rst . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ether_aton.3 .so man2/mlock.2 .\" this man page is copyright (c) 1999 andi kleen . .\" and copyright (c) 1999 matthew wilcox. .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" 2002-10-30, michael kerrisk, .\" added description of so_acceptconn .\" 2004-05-20, aeb, added so_rcvtimeo/so_sndtimeo text. .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" a few small grammar fixes .\" 2010-06-13 jan engelhardt .\" documented so_domain and so_protocol. .\" .\" fixme .\" the following are not yet documented: .\" .\" so_peername (2.4?) .\" get only .\" seems to do something similar to getpeername(), but then .\" why is it necessary / how does it differ? .\" .\" so_timestamping (2.6.30) .\" documentation/networking/timestamping.txt .\" commit cb9eff097831007afb30d64373f29d99825d0068 .\" author: patrick ohly .\" .\" so_wifi_status (3.3) .\" commit 6e3e939f3b1bf8534b32ad09ff199d88800835a0 .\" author: johannes berg .\" also: scm_wifi_status .\" .\" so_nofcs (3.4) .\" commit 3bdc0eba0b8b47797f4a76e377dd8360f317450f .\" author: ben greear .\" .\" so_get_filter (3.8) .\" commit a8fc92778080c845eaadc369a0ecf5699a03bef0 .\" author: pavel emelyanov .\" .\" so_max_pacing_rate (3.13) .\" commit 62748f32d501f5d3712a7c372bbb92abc7c62bc7 .\" author: eric dumazet .\" .\" so_bpf_extensions (3.14) .\" commit ea02f9411d9faa3553ed09ce0ec9f00ceae9885e .\" author: michal sekletar .\" .th socket 7 2021-03-22 linux "linux programmer's manual" .sh name socket \- linux socket interface .sh synopsis .nf .b #include .pp .ib sockfd " = socket(int " socket_family ", int " socket_type ", int " protocol ); .fi .sh description this manual page describes the linux networking socket layer user interface. the bsd compatible sockets are the uniform interface between the user process and the network protocol stacks in the kernel. the protocol modules are grouped into .i protocol families such as .br af_inet ", " af_ipx ", and " af_packet , and .i socket types such as .b sock_stream or .br sock_dgram . see .br socket (2) for more information on families and types. .ss socket-layer functions these functions are used by the user process to send or receive packets and to do other socket operations. for more information see their respective manual pages. .pp .br socket (2) creates a socket, .br connect (2) connects a socket to a remote socket address, the .br bind (2) function binds a socket to a local socket address, .br listen (2) tells the socket that new connections shall be accepted, and .br accept (2) is used to get a new socket with a new incoming connection. .br socketpair (2) returns two connected anonymous sockets (implemented only for a few local families like .br af_unix ) .pp .br send (2), .br sendto (2), and .br sendmsg (2) send data over a socket, and .br recv (2), .br recvfrom (2), .br recvmsg (2) receive data from a socket. .br poll (2) and .br select (2) wait for arriving data or a readiness to send data. in addition, the standard i/o operations like .br write (2), .br writev (2), .br sendfile (2), .br read (2), and .br readv (2) can be used to read and write data. .pp .br getsockname (2) returns the local socket address and .br getpeername (2) returns the remote socket address. .br getsockopt (2) and .br setsockopt (2) are used to set or get socket layer or protocol options. .br ioctl (2) can be used to set or read some other options. .pp .br close (2) is used to close a socket. .br shutdown (2) closes parts of a full-duplex socket connection. .pp seeking, or calling .br pread (2) or .br pwrite (2) with a nonzero position is not supported on sockets. .pp it is possible to do nonblocking i/o on sockets by setting the .b o_nonblock flag on a socket file descriptor using .br fcntl (2). then all operations that would block will (usually) return with .b eagain (operation should be retried later); .br connect (2) will return .b einprogress error. the user can then wait for various events via .br poll (2) or .br select (2). .ts tab(:) allbox; c s s l l lx. i/o events event:poll flag:occurrence read:pollin:t{ new data arrived. t} read:pollin:t{ a connection setup has been completed (for connection-oriented sockets) t} read:pollhup:t{ a disconnection request has been initiated by the other end. t} read:pollhup:t{ a connection is broken (only for connection-oriented protocols). when the socket is written .b sigpipe is also sent. t} write:pollout:t{ socket has enough send buffer space for writing new data. t} read/write:t{ pollin | .br pollout t}:t{ an outgoing .br connect (2) finished. t} read/write:pollerr:t{ an asynchronous error occurred. t} read/write:pollhup:t{ the other end has shut down one direction. t} exception:pollpri:t{ urgent data arrived. .b sigurg is sent then. t} .\" fixme . the following is not true currently: .\" it is no i/o event when the connection .\" is broken from the local end using .\" .br shutdown (2) .\" or .\" .br close (2). .te .pp an alternative to .br poll (2) and .br select (2) is to let the kernel inform the application about events via a .b sigio signal. for that the .b o_async flag must be set on a socket file descriptor via .br fcntl (2) and a valid signal handler for .b sigio must be installed via .br sigaction (2). see the .i signals discussion below. .ss socket address structures each socket domain has its own format for socket addresses, with a domain-specific address structure. each of these structures begins with an integer "family" field (typed as .ir sa_family_t ) that indicates the type of the address structure. this allows the various system calls (e.g., .br connect (2), .br bind (2), .br accept (2), .br getsockname (2), .br getpeername (2)), which are generic to all socket domains, to determine the domain of a particular socket address. .pp to allow any type of socket address to be passed to interfaces in the sockets api, the type .ir "struct sockaddr" is defined. the purpose of this type is purely to allow casting of domain-specific socket address types to a "generic" type, so as to avoid compiler warnings about type mismatches in calls to the sockets api. .pp in addition, the sockets api provides the data type .ir "struct sockaddr_storage". this type is suitable to accommodate all supported domain-specific socket address structures; it is large enough and is aligned properly. (in particular, it is large enough to hold ipv6 socket addresses.) the structure includes the following field, which can be used to identify the type of socket address actually stored in the structure: .pp .in +4n .ex sa_family_t ss_family; .ee .in .pp the .i sockaddr_storage structure is useful in programs that must handle socket addresses in a generic way (e.g., programs that must deal with both ipv4 and ipv6 socket addresses). .ss socket options the socket options listed below can be set by using .br setsockopt (2) and read with .br getsockopt (2) with the socket level set to .b sol_socket for all sockets. unless otherwise noted, .i optval is a pointer to an .ir int . .\" fixme . .\" in the list below, the text used to describe argument types .\" for each socket option should be more consistent .\" .\" so_acceptconn is in posix.1-2001, and its origin is explained in .\" w r stevens, unpv1 .tp .b so_acceptconn returns a value indicating whether or not this socket has been marked to accept connections with .br listen (2). the value 0 indicates that this is not a listening socket, the value 1 indicates that this is a listening socket. this socket option is read-only. .tp .br so_attach_filter " (since linux 2.2), " so_attach_bpf " (since linux 3.19)" attach a classic bpf .rb ( so_attach_filter ) or an extended bpf .rb ( so_attach_bpf ) program to the socket for use as a filter of incoming packets. a packet will be dropped if the filter program returns zero. if the filter program returns a nonzero value which is less than the packet's data length, the packet will be truncated to the length returned. if the value returned by the filter is greater than or equal to the packet's data length, the packet is allowed to proceed unmodified. .ip the argument for .br so_attach_filter is a .i sock_fprog structure, defined in .ir : .ip .in +4n .ex struct sock_fprog { unsigned short len; struct sock_filter *filter; }; .ee .in .ip the argument for .br so_attach_bpf is a file descriptor returned by the .br bpf (2) system call and must refer to a program of type .br bpf_prog_type_socket_filter . .ip these options may be set multiple times for a given socket, each time replacing the previous filter program. the classic and extended versions may be called on the same socket, but the previous filter will always be replaced such that a socket never has more than one filter defined. .ip both classic and extended bpf are explained in the kernel source file .i documentation/networking/filter.txt .tp .br so_attach_reuseport_cbpf ", " so_attach_reuseport_ebpf for use with the .br so_reuseport option, these options allow the user to set a classic bpf .rb ( so_attach_reuseport_cbpf ) or an extended bpf .rb ( so_attach_reuseport_ebpf ) program which defines how packets are assigned to the sockets in the reuseport group (that is, all sockets which have .br so_reuseport set and are using the same local address to receive packets). .ip the bpf program must return an index between 0 and n\-1 representing the socket which should receive the packet (where n is the number of sockets in the group). if the bpf program returns an invalid index, socket selection will fall back to the plain .br so_reuseport mechanism. .ip sockets are numbered in the order in which they are added to the group (that is, the order of .br bind (2) calls for udp sockets or the order of .br listen (2) calls for tcp sockets). new sockets added to a reuseport group will inherit the bpf program. when a socket is removed from a reuseport group (via .br close (2)), the last socket in the group will be moved into the closed socket's position. .ip these options may be set repeatedly at any time on any socket in the group to replace the current bpf program used by all sockets in the group. .ip .br so_attach_reuseport_cbpf takes the same argument type as .br so_attach_filter and .br so_attach_reuseport_ebpf takes the same argument type as .br so_attach_bpf . .ip udp support for this feature is available since linux 4.5; tcp support is available since linux 4.6. .tp .b so_bindtodevice bind this socket to a particular device like \(lqeth0\(rq, as specified in the passed interface name. if the name is an empty string or the option length is zero, the socket device binding is removed. the passed option is a variable-length null-terminated interface name string with the maximum size of .br ifnamsiz . if a socket is bound to an interface, only packets received from that particular interface are processed by the socket. note that this works only for some socket types, particularly .b af_inet sockets. it is not supported for packet sockets (use normal .br bind (2) there). .ip before linux 3.8, this socket option could be set, but could not retrieved with .br getsockopt (2). since linux 3.8, it is readable. the .i optlen argument should contain the buffer size available to receive the device name and is recommended to be .br ifnamsiz bytes. the real device name length is reported back in the .i optlen argument. .tp .b so_broadcast set or get the broadcast flag. when enabled, datagram sockets are allowed to send packets to a broadcast address. this option has no effect on stream-oriented sockets. .tp .b so_bsdcompat enable bsd bug-to-bug compatibility. this is used by the udp protocol module in linux 2.0 and 2.2. if enabled, icmp errors received for a udp socket will not be passed to the user program. in later kernel versions, support for this option has been phased out: linux 2.4 silently ignores it, and linux 2.6 generates a kernel warning (printk()) if a program uses this option. linux 2.0 also enabled bsd bug-to-bug compatibility options (random header changing, skipping of the broadcast flag) for raw sockets with this option, but that was removed in linux 2.2. .tp .b so_debug enable socket debugging. allowed only for processes with the .b cap_net_admin capability or an effective user id of 0. .tp .br so_detach_filter " (since linux 2.2), " so_detach_bpf " (since linux 3.19)" these two options, which are synonyms, may be used to remove the classic or extended bpf program attached to a socket with either .br so_attach_filter or .br so_attach_bpf . the option value is ignored. .tp .br so_domain " (since linux 2.6.32)" retrieves the socket domain as an integer, returning a value such as .br af_inet6 . see .br socket (2) for details. this socket option is read-only. .tp .b so_error get and clear the pending socket error. this socket option is read-only. expects an integer. .tp .b so_dontroute don't send via a gateway, send only to directly connected hosts. the same effect can be achieved by setting the .b msg_dontroute flag on a socket .br send (2) operation. expects an integer boolean flag. .tp .br so_incoming_cpu " (gettable since linux 3.19, settable since linux 4.4)" .\" getsockopt 2c8c56e15df3d4c2af3d656e44feb18789f75837 .\" setsockopt 70da268b569d32a9fddeea85dc18043de9d89f89 sets or gets the cpu affinity of a socket. expects an integer flag. .ip .in +4n .ex int cpu = 1; setsockopt(fd, sol_socket, so_incoming_cpu, &cpu, sizeof(cpu)); .ee .in .ip because all of the packets for a single stream (i.e., all packets for the same 4-tuple) arrive on the single rx queue that is associated with a particular cpu, the typical use case is to employ one listening process per rx queue, with the incoming flow being handled by a listener on the same cpu that is handling the rx queue. this provides optimal numa behavior and keeps cpu caches hot. .\" .\" from an email conversation with eric dumazet: .\" >> note that setting the option is not supported if so_reuseport is used. .\" > .\" > please define "not supported". does this yield an api diagnostic? .\" > if so, what is it? .\" > .\" >> socket will be selected from an array, either by a hash or bpf program .\" >> that has no access to this information. .\" > .\" > sorry -- i'm lost here. how does this comment relate to the proposed .\" > man page text above? .\" .\" simply that : .\" .\" if an application uses both so_incoming_cpu and so_reuseport, then .\" so_reuseport logic, selecting the socket to receive the packet, ignores .\" so_incoming_cpu setting. .tp .br so_incoming_napi_id " (gettable since linux 4.12)" .\" getsockopt 6d4339028b350efbf87c61e6d9e113e5373545c9 returns a system-level unique id called napi id that is associated with a rx queue on which the last packet associated with that socket is received. .ip this can be used by an application to split the incoming flows among worker threads based on the rx queue on which the packets associated with the flows are received. it allows each worker thread to be associated with a nic hw receive queue and service all the connection requests received on that rx queue. this mapping between a app thread and a hw nic queue streamlines the flow of data from the nic to the application. .tp .b so_keepalive enable sending of keep-alive messages on connection-oriented sockets. expects an integer boolean flag. .tp .b so_linger sets or gets the .b so_linger option. the argument is a .i linger structure. .ip .in +4n .ex struct linger { int l_onoff; /* linger active */ int l_linger; /* how many seconds to linger for */ }; .ee .in .ip when enabled, a .br close (2) or .br shutdown (2) will not return until all queued messages for the socket have been successfully sent or the linger timeout has been reached. otherwise, the call returns immediately and the closing is done in the background. when the socket is closed as part of .br exit (2), it always lingers in the background. .tp .b so_lock_filter .\" commit d59577b6ffd313d0ab3be39cb1ab47e29bdc9182 when set, this option will prevent changing the filters associated with the socket. these filters include any set using the socket options .br so_attach_filter , .br so_attach_bpf , .br so_attach_reuseport_cbpf , and .br so_attach_reuseport_ebpf . .ip the typical use case is for a privileged process to set up a raw socket (an operation that requires the .br cap_net_raw capability), apply a restrictive filter, set the .br so_lock_filter option, and then either drop its privileges or pass the socket file descriptor to an unprivileged process via a unix domain socket. .ip once the .br so_lock_filter option has been enabled, attempts to change or remove the filter attached to a socket, or to disable the .br so_lock_filter option will fail with the error .br eperm . .tp .br so_mark " (since linux 2.6.25)" .\" commit 4a19ec5800fc3bb64e2d87c4d9fdd9e636086fe0 .\" and 914a9ab386a288d0f22252fc268ecbc048cdcbd5 set the mark for each packet sent through this socket (similar to the netfilter mark target but socket-based). changing the mark can be used for mark-based routing without netfilter or for packet filtering. setting this option requires the .b cap_net_admin capability. .tp .b so_oobinline if this option is enabled, out-of-band data is directly placed into the receive data stream. otherwise, out-of-band data is passed only when the .b msg_oob flag is set during receiving. .\" don't document it because it can do too much harm. .\".b so_no_check .\" the kernel has support for the so_no_check socket .\" option (boolean: 0 == default, calculate checksum on xmit, .\" 1 == do not calculate checksum on xmit). .\" additional note from andi kleen on so_no_check (2010-08-30) .\" on linux udp checksums are essentially free and there's no reason .\" to turn them off and it would disable another safety line. .\" that is why i didn't document the option. .tp .b so_passcred enable or disable the receiving of the .b scm_credentials control message. for more information see .br unix (7). .tp .b so_passsec enable or disable the receiving of the .b scm_security control message. for more information see .br unix (7). .tp .br so_peek_off " (since linux 3.4)" .\" commit ef64a54f6e558155b4f149bb10666b9e914b6c54 this option, which is currently supported only for .br unix (7) sockets, sets the value of the "peek offset" for the .br recv (2) system call when used with .br msg_peek flag. .ip when this option is set to a negative value (it is set to \-1 for all new sockets), traditional behavior is provided: .br recv (2) with the .br msg_peek flag will peek data from the front of the queue. .ip when the option is set to a value greater than or equal to zero, then the next peek at data queued in the socket will occur at the byte offset specified by the option value. at the same time, the "peek offset" will be incremented by the number of bytes that were peeked from the queue, so that a subsequent peek will return the next data in the queue. .ip if data is removed from the front of the queue via a call to .br recv (2) (or similar) without the .br msg_peek flag, the "peek offset" will be decreased by the number of bytes removed. in other words, receiving data without the .b msg_peek flag will cause the "peek offset" to be adjusted to maintain the correct relative position in the queued data, so that a subsequent peek will retrieve the data that would have been retrieved had the data not been removed. .ip for datagram sockets, if the "peek offset" points to the middle of a packet, the data returned will be marked with the .br msg_trunc flag. .ip the following example serves to illustrate the use of .br so_peek_off . suppose a stream socket has the following queued input data: .ip aabbccddeeff .ip the following sequence of .br recv (2) calls would have the effect noted in the comments: .ip .in +4n .ex int ov = 4; // set peek offset to 4 setsockopt(fd, sol_socket, so_peek_off, &ov, sizeof(ov)); recv(fd, buf, 2, msg_peek); // peeks "cc"; offset set to 6 recv(fd, buf, 2, msg_peek); // peeks "dd"; offset set to 8 recv(fd, buf, 2, 0); // reads "aa"; offset set to 6 recv(fd, buf, 2, msg_peek); // peeks "ee"; offset set to 8 .ee .in .tp .b so_peercred return the credentials of the peer process connected to this socket. for further details, see .br unix (7). .tp .br so_peersec " (since linux 2.6.2)" return the security context of the peer socket connected to this socket. for further details, see .br unix (7) and .br ip (7). .tp .b so_priority set the protocol-defined priority for all packets to be sent on this socket. linux uses this value to order the networking queues: packets with a higher priority may be processed first depending on the selected device queueing discipline. .\" for .\" .br ip (7), .\" this also sets the ip type-of-service (tos) field for outgoing packets. setting a priority outside the range 0 to 6 requires the .b cap_net_admin capability. .tp .br so_protocol " (since linux 2.6.32)" retrieves the socket protocol as an integer, returning a value such as .br ipproto_sctp . see .br socket (2) for details. this socket option is read-only. .tp .b so_rcvbuf sets or gets the maximum socket receive buffer in bytes. the kernel doubles this value (to allow space for bookkeeping overhead) when it is set using .\" most (all?) other implementations do not do this -- mtk, dec 05 .br setsockopt (2), and this doubled value is returned by .br getsockopt (2). .\" the following thread on lmkl is quite informative: .\" getsockopt/setsockopt with so_rcvbuf and so_sndbuf "non-standard" behavior .\" 17 july 2012 .\" http://thread.gmane.org/gmane.linux.kernel/1328935 the default value is set by the .i /proc/sys/net/core/rmem_default file, and the maximum allowed value is set by the .i /proc/sys/net/core/rmem_max file. the minimum (doubled) value for this option is 256. .tp .br so_rcvbufforce " (since linux 2.6.14)" using this socket option, a privileged .rb ( cap_net_admin ) process can perform the same task as .br so_rcvbuf , but the .i rmem_max limit can be overridden. .tp .br so_rcvlowat " and " so_sndlowat specify the minimum number of bytes in the buffer until the socket layer will pass the data to the protocol .rb ( so_sndlowat ) or the user on receiving .rb ( so_rcvlowat ). these two values are initialized to 1. .b so_sndlowat is not changeable on linux .rb ( setsockopt (2) fails with the error .br enoprotoopt ). .b so_rcvlowat is changeable only since linux 2.4. .ip before linux 2.6.28 .\" tested on kernel 2.6.14 -- mtk, 30 nov 05 .br select (2), .br poll (2), and .br epoll (7) did not respect the .b so_rcvlowat setting on linux, and indicated a socket as readable when even a single byte of data was available. a subsequent read from the socket would then block until .b so_rcvlowat bytes are available. since linux 2.6.28, .\" commit c7004482e8dcb7c3c72666395cfa98a216a4fb70 .br select (2), .br poll (2), and .br epoll (7) indicate a socket as readable only if at least .b so_rcvlowat bytes are available. .tp .br so_rcvtimeo " and " so_sndtimeo .\" not implemented in 2.0. .\" implemented in 2.1.11 for getsockopt: always return a zero struct. .\" implemented in 2.3.41 for setsockopt, and actually used. specify the receiving or sending timeouts until reporting an error. the argument is a .ir "struct timeval" . if an input or output function blocks for this period of time, and data has been sent or received, the return value of that function will be the amount of data transferred; if no data has been transferred and the timeout has been reached, then \-1 is returned with .i errno set to .br eagain or .br ewouldblock , .\" in fact to eagain or .b einprogress (for .br connect (2)) just as if the socket was specified to be nonblocking. if the timeout is set to zero (the default), then the operation will never timeout. timeouts only have effect for system calls that perform socket i/o (e.g., .br read (2), .br recvmsg (2), .br send (2), .br sendmsg (2)); timeouts have no effect for .br select (2), .br poll (2), .br epoll_wait (2), and so on. .tp .b so_reuseaddr .\" commit c617f398edd4db2b8567a28e899a88f8f574798d .\" https://lwn.net/articles/542629/ indicates that the rules used in validating addresses supplied in a .br bind (2) call should allow reuse of local addresses. for .b af_inet sockets this means that a socket may bind, except when there is an active listening socket bound to the address. when the listening socket is bound to .b inaddr_any with a specific port then it is not possible to bind to this port for any local address. argument is an integer boolean flag. .tp .br so_reuseport " (since linux 3.9)" permits multiple .b af_inet or .b af_inet6 sockets to be bound to an identical socket address. this option must be set on each socket (including the first socket) prior to calling .br bind (2) on the socket. to prevent port hijacking, all of the processes binding to the same address must have the same effective uid. this option can be employed with both tcp and udp sockets. .ip for tcp sockets, this option allows .br accept (2) load distribution in a multi-threaded server to be improved by using a distinct listener socket for each thread. this provides improved load distribution as compared to traditional techniques such using a single .br accept (2)ing thread that distributes connections, or having multiple threads that compete to .br accept (2) from the same socket. .ip for udp sockets, the use of this option can provide better distribution of incoming datagrams to multiple processes (or threads) as compared to the traditional technique of having multiple processes compete to receive datagrams on the same socket. .tp .br so_rxq_ovfl " (since linux 2.6.33)" .\" commit 3b885787ea4112eaa80945999ea0901bf742707f indicates that an unsigned 32-bit value ancillary message (cmsg) should be attached to received skbs indicating the number of packets dropped by the socket since its creation. .tp .br so_select_err_queue " (since linux 3.10)" .\" commit 7d4c04fc170087119727119074e72445f2bb192b .\" author: keller, jacob e when this option is set on a socket, an error condition on a socket causes notification not only via the .i exceptfds set of .br select (2). similarly, .br poll (2) also returns a .b pollpri whenever an .b pollerr event is returned. .\" it does not affect wake up. .ip background: this option was added when waking up on an error condition occurred only via the .ir readfds and .ir writefds sets of .br select (2). the option was added to allow monitoring for error conditions via the .i exceptfds argument without simultaneously having to receive notifications (via .ir readfds ) for regular data that can be read from the socket. after changes in linux 4.16, .\" commit 6e5d58fdc9bedd0255a8 .\" ("skbuff: fix not waking applications when errors are enqueued") the use of this flag to achieve the desired notifications is no longer necessary. this option is nevertheless retained for backwards compatibility. .tp .b so_sndbuf sets or gets the maximum socket send buffer in bytes. the kernel doubles this value (to allow space for bookkeeping overhead) when it is set using .\" most (all?) other implementations do not do this -- mtk, dec 05 .\" see also the comment to so_rcvbuf (17 jul 2012 lkml mail) .br setsockopt (2), and this doubled value is returned by .br getsockopt (2). the default value is set by the .i /proc/sys/net/core/wmem_default file and the maximum allowed value is set by the .i /proc/sys/net/core/wmem_max file. the minimum (doubled) value for this option is 2048. .tp .br so_sndbufforce " (since linux 2.6.14)" using this socket option, a privileged .rb ( cap_net_admin ) process can perform the same task as .br so_sndbuf , but the .i wmem_max limit can be overridden. .tp .b so_timestamp enable or disable the receiving of the .b so_timestamp control message. the timestamp control message is sent with level .b sol_socket and a .i cmsg_type of .br scm_timestamp . the .i cmsg_data field is a .i "struct timeval" indicating the reception time of the last packet passed to the user in this call. see .br cmsg (3) for details on control messages. .tp .br so_timestampns " (since linux 2.6.22)" .\" commit 92f37fd2ee805aa77925c1e64fd56088b46094fc enable or disable the receiving of the .b so_timestampns control message. the timestamp control message is sent with level .b sol_socket and a .i cmsg_type of .br scm_timestampns . the .i cmsg_data field is a .i "struct timespec" indicating the reception time of the last packet passed to the user in this call. the clock used for the timestamp is .br clock_realtime . see .br cmsg (3) for details on control messages. .ip a socket cannot mix .b so_timestamp and .br so_timestampns : the two modes are mutually exclusive. .tp .b so_type gets the socket type as an integer (e.g., .br sock_stream ). this socket option is read-only. .tp .br so_busy_poll " (since linux 3.11)" sets the approximate time in microseconds to busy poll on a blocking receive when there is no data. increasing this value requires .br cap_net_admin . the default for this option is controlled by the .i /proc/sys/net/core/busy_read file. .ip the value in the .i /proc/sys/net/core/busy_poll file determines how long .br select (2) and .br poll (2) will busy poll when they operate on sockets with .br so_busy_poll set and no events to report are found. .ip in both cases, busy polling will only be done when the socket last received data from a network device that supports this option. .ip while busy polling may improve latency of some applications, care must be taken when using it since this will increase both cpu utilization and power usage. .ss signals when writing onto a connection-oriented socket that has been shut down (by the local or the remote end) .b sigpipe is sent to the writing process and .b epipe is returned. the signal is not sent when the write call specified the .b msg_nosignal flag. .pp when requested with the .b fiosetown .br fcntl (2) or .b siocspgrp .br ioctl (2), .b sigio is sent when an i/o event occurs. it is possible to use .br poll (2) or .br select (2) in the signal handler to find out which socket the event occurred on. an alternative (in linux 2.2) is to set a real-time signal using the .b f_setsig .br fcntl (2); the handler of the real time signal will be called with the file descriptor in the .i si_fd field of its .ir siginfo_t . see .br fcntl (2) for more information. .pp under some circumstances (e.g., multiple processes accessing a single socket), the condition that caused the .b sigio may have already disappeared when the process reacts to the signal. if this happens, the process should wait again because linux will resend the signal later. .\" .ss ancillary messages .ss /proc interfaces the core socket networking parameters can be accessed via files in the directory .ir /proc/sys/net/core/ . .tp .i rmem_default contains the default setting in bytes of the socket receive buffer. .tp .i rmem_max contains the maximum socket receive buffer size in bytes which a user may set by using the .b so_rcvbuf socket option. .tp .i wmem_default contains the default setting in bytes of the socket send buffer. .tp .i wmem_max contains the maximum socket send buffer size in bytes which a user may set by using the .b so_sndbuf socket option. .tp .ir message_cost " and " message_burst configure the token bucket filter used to load limit warning messages caused by external network events. .tp .i netdev_max_backlog maximum number of packets in the global input queue. .tp .i optmem_max maximum length of ancillary data and user control data like the iovecs per socket. .\" netdev_fastroute is not documented because it is experimental .ss ioctls these operations can be accessed using .br ioctl (2): .pp .in +4n .ex .ib error " = ioctl(" ip_socket ", " ioctl_type ", " &value_result ");" .ee .in .tp .b siocgstamp return a .i struct timeval with the receive timestamp of the last packet passed to the user. this is useful for accurate round trip time measurements. see .br setitimer (2) for a description of .ir "struct timeval" . .\" this ioctl should be used only if the socket options .b so_timestamp and .b so_timestampns are not set on the socket. otherwise, it returns the timestamp of the last packet that was received while .b so_timestamp and .b so_timestampns were not set, or it fails if no such packet has been received, (i.e., .br ioctl (2) returns \-1 with .i errno set to .br enoent ). .tp .b siocspgrp set the process or process group that is to receive .b sigio or .b sigurg signals when i/o becomes possible or urgent data is available. the argument is a pointer to a .ir pid_t . for further details, see the description of .br f_setown in .br fcntl (2). .tp .b fioasync change the .b o_async flag to enable or disable asynchronous i/o mode of the socket. asynchronous i/o mode means that the .b sigio signal or the signal set with .b f_setsig is raised when a new i/o event occurs. .ip argument is an integer boolean flag. (this operation is synonymous with the use of .br fcntl (2) to set the .b o_async flag.) .\" .tp .b siocgpgrp get the current process or process group that receives .b sigio or .b sigurg signals, or 0 when none is set. .pp valid .br fcntl (2) operations: .tp .b fiogetown the same as the .b siocgpgrp .br ioctl (2). .tp .b fiosetown the same as the .b siocspgrp .br ioctl (2). .sh versions .b so_bindtodevice was introduced in linux 2.0.30. .b so_passcred is new in linux 2.2. the .i /proc interfaces were introduced in linux 2.2. .b so_rcvtimeo and .b so_sndtimeo are supported since linux 2.3.41. earlier, timeouts were fixed to a protocol-specific setting, and could not be read or written. .sh notes linux assumes that half of the send/receive buffer is used for internal kernel structures; thus the values in the corresponding .i /proc files are twice what can be observed on the wire. .pp linux will allow port reuse only with the .b so_reuseaddr option when this option was set both in the previous program that performed a .br bind (2) to the port and in the program that wants to reuse the port. this differs from some implementations (e.g., freebsd) where only the later program needs to set the .b so_reuseaddr option. typically this difference is invisible, since, for example, a server program is designed to always set this option. .\" .sh authors .\" this man page was written by andi kleen. .sh see also .br wireshark (1), .br bpf (2), .br connect (2), .br getsockopt (2), .br setsockopt (2), .br socket (2), .br pcap (3), .br address_families (7), .br capabilities (7), .br ddp (7), .br ip (7), .br ipv6 (7), .br packet (7), .br tcp (7), .br udp (7), .br unix (7), .br tcpdump (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getrpcent.3 .\" copyright 2001 alexey mahotkin .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th koi8-r 7 2020-08-13 "linux" "linux programmer's manual" .sh name koi8-r \- russian character set encoded in octal, decimal, and hexadecimal .sh description rfc\ 1489 defines an 8-bit character set, koi8-r. koi8-r encodes the characters used in russian. .ss koi8-r characters the following table displays the characters in koi8-r that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 200 128 80 ─ box drawings light horizontal 201 129 81 │ box drawings light vertical 202 130 82 ┌ box drawings light down and right 203 131 83 ┐ box drawings light down and left 204 132 84 └ box drawings light up and right 205 133 85 ┘ box drawings light up and left 206 134 86 ├ box drawings light vertical and right 207 135 87 ┤ box drawings light vertical and left 210 136 88 ┬ box drawings light down and horizontal 211 137 89 ┴ box drawings light up and horizontal 212 138 8a ┼ box drawings light vertical and horizontal 213 139 8b ▀ upper half block 214 140 8c ▄ lower half block 215 141 8d █ full block 216 142 8e ▌ left half block 217 143 8f ▐ right half block 220 144 90 ░ light shade 221 145 91 ▒ medium shade 222 146 92 ▓ dark shade 223 147 93 ⌠ top half integral 224 148 94 ■ black square 225 149 95 ∙ bullet operator 226 150 96 √ square root 227 151 97 ≈ almost equal to 230 152 98 ≤ less-than or equal to 231 153 99 ≥ greater-than or equal to 232 154 9a   no-break space 233 155 9b ⌡ bottom half integral 234 156 9c ° degree sign 235 157 9d ² superscript two 236 158 9e · middle dot 237 159 9f ÷ division sign 240 160 a0 ═ box drawings double horizontal 241 161 a1 ║ box drawings double vertical 242 162 a2 ╒ box drawings down single and right double 243 163 a3 ё cyrillic small letter io 244 164 a4 ╓ box drawings down double and right single 245 165 a5 ╔ box drawings double down and right 246 166 a6 ╕ box drawings down single and left double 247 167 a7 ╖ box drawings down double and left single 250 168 a8 ╗ box drawings double down and left 251 169 a9 ╘ box drawings up single and right double 252 170 aa ╙ box drawings up double and right single 253 171 ab ╚ box drawings double up and right 254 172 ac ╛ box drawings up single and left double 255 173 ad ╜ box drawings up double and left single 256 174 ae ╝ box drawings double up and left 257 175 af ╞ box drawings vertical single and right double 260 176 b0 ╟ box drawings vertical double and right single 261 177 b1 ╠ box drawings double vertical and right 262 178 b2 ╡ box drawings vertical single and left double 263 179 b3 ё cyrillic capital letter io 264 180 b4 ╢ box drawings vertical double and left single 265 181 b5 ╣ box drawings double vertical and left 266 182 b6 ╤ box drawings down single and horizontal double 267 183 b7 ╥ box drawings down double and horizontal single 270 184 b8 ╦ box drawings double down and horizontal 271 185 b9 ╧ box drawings up single and horizontal double 272 186 ba ╨ box drawings up double and horizontal single 273 187 bb ╩ box drawings double up and horizontal 274 188 bc ╪ t{ box drawings vertical single .br and horizontal double t} 275 189 bd ╫ t{ box drawings vertical double .br and horizontal single t} 276 190 be ╬ box drawings double vertical and horizontal 277 191 bf © copyright sign 300 192 c0 ю cyrillic small letter yu 301 193 c1 а cyrillic small letter a 302 194 c2 б cyrillic small letter be 303 195 c3 ц cyrillic small letter tse 304 196 c4 д cyrillic small letter de 305 197 c5 е cyrillic small letter ie 306 198 c6 ф cyrillic small letter ef 307 199 c7 г cyrillic small letter ghe 310 200 c8 х cyrillic small letter ha 311 201 c9 и cyrillic small letter i 312 202 ca й cyrillic small letter short i 313 203 cb к cyrillic small letter ka 314 204 cc л cyrillic small letter el 315 205 cd м cyrillic small letter em 316 206 ce н cyrillic small letter en 317 207 cf о cyrillic small letter o 320 208 d0 п cyrillic small letter pe 321 209 d1 я cyrillic small letter ya 322 210 d2 р cyrillic small letter er 323 211 d3 с cyrillic small letter es 324 212 d4 т cyrillic small letter te 325 213 d5 у cyrillic small letter u 326 214 d6 ж cyrillic small letter zhe 327 215 d7 в cyrillic small letter ve 330 216 d8 ь cyrillic small letter soft sign 331 217 d9 ы cyrillic small letter yeru 332 218 da з cyrillic small letter ze 333 219 db ш cyrillic small letter sha 334 220 dc э cyrillic small letter e 335 221 dd щ cyrillic small letter shcha 336 222 de ч cyrillic small letter che 337 223 df ъ cyrillic small letter hard sign 340 224 e0 ю cyrillic capital letter yu 341 225 e1 а cyrillic capital letter a 342 226 e2 б cyrillic capital letter be 343 227 e3 ц cyrillic capital letter tse 344 228 e4 д cyrillic capital letter de 345 229 e5 е cyrillic capital letter ie 346 230 e6 ф cyrillic capital letter ef 347 231 e7 г cyrillic capital letter ghe 350 232 e8 х cyrillic capital letter ha 351 233 e9 и cyrillic capital letter i 352 234 ea й cyrillic capital letter short i 353 235 eb к cyrillic capital letter ka 354 236 ec л cyrillic capital letter el 355 237 ed м cyrillic capital letter em 356 238 ee н cyrillic capital letter en 357 239 ef о cyrillic capital letter o 360 240 f0 п cyrillic capital letter pe 361 241 f1 я cyrillic capital letter ya 362 242 f2 р cyrillic capital letter er 363 243 f3 с cyrillic capital letter es 364 244 f4 т cyrillic capital letter te 365 245 f5 у cyrillic capital letter u 366 246 f6 ж cyrillic capital letter zhe 367 247 f7 в cyrillic capital letter ve 370 248 f8 ь cyrillic capital letter soft sign 371 249 f9 ы cyrillic capital letter yeru 372 250 fa з cyrillic capital letter ze 373 251 fb ш cyrillic capital letter sha 374 252 fc э cyrillic capital letter e 375 253 fd щ cyrillic capital letter shcha 376 254 fe ч cyrillic capital letter che 377 255 ff ъ cyrillic capital letter hard sign .te .sh notes the differences with koi8-u are in the hex positions a4, a6, a7, ad, b4, b6, b7, and bd. .sh see also .br ascii (7), .br charsets (7), .br cp1251 (7), .br iso_8859\-5 (7), .br koi8\-u (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/endian.3 .\" copyright (c) 2006 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th adjtime 3 2021-03-22 "linux" "linux programmer's manual" .sh name adjtime \- correct the time to synchronize the system clock .sh synopsis .nf .b #include .pp .bi "int adjtime(const struct timeval *" delta ", struct timeval *" olddelta ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br adjtime (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the .br adjtime () function gradually adjusts the system clock (as returned by .br gettimeofday (2)). the amount of time by which the clock is to be adjusted is specified in the structure pointed to by .ir delta . this structure has the following form: .pp .in +4n .ex struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ }; .ee .in .pp if the adjustment in .i delta is positive, then the system clock is speeded up by some small percentage (i.e., by adding a small amount of time to the clock value in each second) until the adjustment has been completed. if the adjustment in .i delta is negative, then the clock is slowed down in a similar fashion. .pp if a clock adjustment from an earlier .br adjtime () call is already in progress at the time of a later .br adjtime () call, and .i delta is not null for the later call, then the earlier adjustment is stopped, but any already completed part of that adjustment is not undone. .pp if .i olddelta is not null, then the buffer that it points to is used to return the amount of time remaining from any previous adjustment that has not yet been completed. .sh return value on success, .br adjtime () returns 0. on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval the adjustment in .i delta is outside the permitted range. .tp .b eperm the caller does not have sufficient privilege to adjust the time. under linux, the .b cap_sys_time capability is required. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br adjtime () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd, system v. .sh notes the adjustment that .br adjtime () makes to the clock is carried out in such a manner that the clock is always monotonically increasing. using .br adjtime () to adjust the time prevents the problems that can be caused for certain applications (e.g., .br make (1)) by abrupt positive or negative jumps in the system time. .pp .br adjtime () is intended to be used to make small adjustments to the system time. most systems impose a limit on the adjustment that can be specified in .ir delta . in the glibc implementation, .i delta must be less than or equal to (int_max / 1000000 \- 2) and greater than or equal to (int_min / 1000000 + 2) (respectively 2145 and \-2145 seconds on i386). .sh bugs a longstanding bug .\" http://sourceware.org/bugzilla/show_bug?id=2449 .\" http://bugzilla.kernel.org/show_bug.cgi?id=6761 meant that if .i delta was specified as null, no valid information about the outstanding clock adjustment was returned in .ir olddelta . (in this circumstance, .br adjtime () should return the outstanding clock adjustment, without changing it.) this bug is fixed .\" thanks to the new adjtimex() adj_offset_ss_read flag on systems with glibc 2.8 or later and linux kernel 2.6.26 or later. .sh see also .br adjtimex (2), .br gettimeofday (2), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ctan.3 .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" .\" %%%license_start(bsd_oneline_cdrom) .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" %%%license_end .\" .\" @(#)getrpcent.3n 2.2 88/08/02 4.0 rpcsrc; from 1.11 88/03/14 smi .th getrpcent 3 2021-03-22 "" "linux programmer's manual" .sh name getrpcent, getrpcbyname, getrpcbynumber, setrpcent, endrpcent \- get rpc entry .sh synopsis .nf .b #include .pp .bi "struct rpcent *getrpcent(void);" .pp .bi "struct rpcent *getrpcbyname(const char *" name ); .bi "struct rpcent *getrpcbynumber(int " number ); .pp .bi "void setrpcent(int " stayopen ); .bi "void endrpcent(void);" .fi .sh description the .br getrpcent (), .br getrpcbyname (), and .br getrpcbynumber () functions each return a pointer to an object with the following structure containing the broken-out fields of an entry in the rpc program number data base. .pp .in +4n .ex struct rpcent { char *r_name; /* name of server for this rpc program */ char **r_aliases; /* alias list */ long r_number; /* rpc program number */ }; .ee .in .pp the members of this structure are: .tp .i r_name the name of the server for this rpc program. .tp .i r_aliases a null-terminated list of alternate names for the rpc program. .tp .i r_number the rpc program number for this service. .pp the .br getrpcent () function reads the next entry from the database. a connection is opened to the database if necessary. .pp the .br setrpcent () function opens a connection to the database, and sets the next entry to the first entry. if .i stayopen is nonzero, then the connection to the database will not be closed between calls to one of the .br getrpc* () functions. .pp the .br endrpcent () function closes the connection to the database. .pp the .br getrpcbyname () and .br getrpcbynumber () functions sequentially search from the beginning of the file until a matching rpc program name or program number is found, or until end-of-file is encountered. .sh return value on success, .br getrpcent (), .br getrpcbyname (), and .br getrpcbynumber () return a pointer to a statically allocated .i rpcent structure. null is returned on eof or error. .sh files .tp .i /etc/rpc rpc program number database. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getrpcent (), .br getrpcbyname (), .br getrpcbynumber () t} thread safety mt-unsafe t{ .br setrpcent (), .br endrpcent () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to not in posix.1. present on the bsds, solaris, and many other systems. .sh bugs all information is contained in a static area so it must be copied if it is to be saved. .sh see also .br getrpcent_r (3), .br rpc (5), .br rpcinfo (8), .br ypserv (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/fsync.2 .\" copyright (c) openbsd group .\" all rights reserved. .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" converted into a manpage again by martin schulze .\" .\" added -lutil remark, 030718 .\" .th openpty 3 2021-03-22 "gnu" "linux programmer's manual" .sh name openpty, login_tty, forkpty \- terminal utility functions .sh synopsis .nf .b #include .pp .bi "int openpty(int *" amaster ", int *" aslave ", char *" name , .bi " const struct termios *" termp , .bi " const struct winsize *" winp ); .bi "pid_t forkpty(int *" amaster ", char *" name , .bi " const struct termios *" termp , .bi " const struct winsize *" winp ); .pp .b #include .pp .bi "int login_tty(int " fd ); .pp link with \fi\-lutil\fp. .fi .sh description the .br openpty () function finds an available pseudoterminal and returns file descriptors for the master and slave in .i amaster and .ir aslave . if .i name is not null, the filename of the slave is returned in .ir name . if .i termp is not null, the terminal parameters of the slave will be set to the values in .ir termp . if .i winp is not null, the window size of the slave will be set to the values in .ir winp . .pp the .br login_tty () function prepares for a login on the terminal referred to by the file descriptor .i fd (which may be a real terminal device, or the slave of a pseudoterminal as returned by .br openpty ()) by creating a new session, making .i fd the controlling terminal for the calling process, setting .i fd to be the standard input, output, and error streams of the current process, and closing .ir fd . .pp the .br forkpty () function combines .br openpty (), .br fork (2), and .br login_tty () to create a new process operating in a pseudoterminal. a file descriptor referring to master side of the pseudoterminal is returned in .ir amaster . if .i name is not null, the buffer it points to is used to return the filename of the slave. the .i termp and .i winp arguments, if not null, will determine the terminal attributes and window size of the slave side of the pseudoterminal. .sh return value if a call to .br openpty (), .br login_tty (), or .br forkpty () is not successful, \-1 is returned and .i errno is set to indicate the error. otherwise, .br openpty (), .br login_tty (), and the child process of .br forkpty () return 0, and the parent process of .br forkpty () returns the process id of the child process. .sh errors .br openpty () fails if: .tp .b enoent there are no available terminals. .pp .br login_tty () fails if .br ioctl (2) fails to set .i fd to the controlling terminal of the calling process. .pp .br forkpty () fails if either .br openpty () or .br fork (2) fails. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br forkpty (), .br openpty () t} thread safety mt-safe locale t{ .br login_tty () t} thread safety mt-unsafe race:ttyname .te .hy .ad .sp 1 .sh conforming to these are bsd functions, present in glibc. they are not standardized in posix. .sh notes the .b const modifiers were added to the structure pointer arguments of .br openpty () and .br forkpty () in glibc 2.8. .pp in versions of glibc before 2.0.92, .br openpty () returns file descriptors for a bsd pseudoterminal pair; since glibc 2.0.92, it first attempts to open a unix 98 pseudoterminal pair, and falls back to opening a bsd pseudoterminal pair if that fails. .sh bugs nobody knows how much space should be reserved for .ir name . so, calling .br openpty () or .br forkpty () with non-null .i name may not be secure. .sh see also .br fork (2), .br ttyname (3), .br pty (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mq_notify.3 .\" because mq_notify(3) is layered on a system call of the same name .so man3/infinity.3 .so man3/rpc.3 .so man3/malloc_get_state.3 .so man3/isalpha.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright 2006-2008, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:27:50 1993 by rik faith (faith@cs.unc.edu) .\" modified mon aug 30 22:02:34 1995 by jim van zandt .\" longindex is a pointer, has_arg can take 3 values, using consistent .\" names for optstring and longindex, "\n" in formats fixed. documenting .\" opterr and getopt_long_only. clarified explanations (borrowing heavily .\" from the source code). .\" modified 8 may 1998 by joseph s. myers (jsm28@cam.ac.uk) .\" modified 990715, aeb: changed `eof' into `-1' since that is what posix .\" says; moreover, eof is not defined in . .\" modified 2002-02-16, joey: added information about nonexistent .\" option character and colon as first option character .\" modified 2004-07-28, michael kerrisk .\" added text to explain how to order both '[-+]' and ':' at .\" the start of optstring .\" modified 2006-12-15, mtk, added getopt() example program. .\" .th getopt 3 2021-08-27 "gnu" "linux programmer's manual" .sh name getopt, getopt_long, getopt_long_only, optarg, optind, opterr, optopt \- parse command-line options .sh synopsis .nf .b #include .pp .bi "int getopt(int " argc ", char *const " argv [], .bi " const char *" optstring ); .pp .bi "extern char *" optarg ; .bi "extern int " optind ", " opterr ", " optopt ; .pp .b #include .pp .bi "int getopt_long(int " argc ", char *const " argv [], .bi " const char *" optstring , .bi " const struct option *" longopts ", int *" longindex ); .bi "int getopt_long_only(int " argc ", char *const " argv [], .bi " const char *" optstring , .bi " const struct option *" longopts ", int *" longindex ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getopt (): .nf _posix_c_source >= 2 || _xopen_source .fi .pp .br getopt_long (), .br getopt_long_only (): .nf _gnu_source .fi .sh description the .br getopt () function parses the command-line arguments. its arguments .i argc and .i argv are the argument count and array as passed to the .ir main () function on program invocation. an element of \fiargv\fp that starts with \(aq\-\(aq (and is not exactly "\-" or "\-\-") is an option element. the characters of this element (aside from the initial \(aq\-\(aq) are option characters. if .br getopt () is called repeatedly, it returns successively each of the option characters from each of the option elements. .pp the variable .i optind is the index of the next element to be processed in .ir argv . the system initializes this value to 1. the caller can reset it to 1 to restart scanning of the same .ir argv , or when scanning a new argument vector. .pp if .br getopt () finds another option character, it returns that character, updating the external variable \fioptind\fp and a static variable \finextchar\fp so that the next call to .br getopt () can resume the scan with the following option character or \fiargv\fp-element. .pp if there are no more option characters, .br getopt () returns \-1. then \fioptind\fp is the index in \fiargv\fp of the first \fiargv\fp-element that is not an option. .pp .i optstring is a string containing the legitimate option characters. a legitimate option character is any visible one byte .br ascii (7) character (for which .br isgraph (3) would return nonzero) that is not \(aq\-\(aq, \(aq:\(aq, or \(aq;\(aq. if such a character is followed by a colon, the option requires an argument, so .br getopt () places a pointer to the following text in the same \fiargv\fp-element, or the text of the following \fiargv\fp-element, in .ir optarg . two colons mean an option takes an optional arg; if there is text in the current \fiargv\fp-element (i.e., in the same word as the option name itself, for example, "\-oarg"), then it is returned in \fioptarg\fp, otherwise \fioptarg\fp is set to zero. this is a gnu extension. if .i optstring contains .b w followed by a semicolon, then .b \-w foo is treated as the long option .br \-\-foo . (the .b \-w option is reserved by posix.2 for implementation extensions.) this behavior is a gnu extension, not available with libraries before glibc 2. .pp by default, .br getopt () permutes the contents of \fiargv\fp as it scans, so that eventually all the nonoptions are at the end. two other scanning modes are also implemented. if the first character of \fioptstring\fp is \(aq+\(aq or the environment variable .b posixly_correct is set, then option processing stops as soon as a nonoption argument is encountered. if \(aq+\(aq is not the first character of .ir optstring , it is treated as a normal option. if .b posixly_correct behaviour is required in this case .i optstring will contain two \(aq+\(aq symbols. if the first character of \fioptstring\fp is \(aq\-\(aq, then each nonoption \fiargv\fp-element is handled as if it were the argument of an option with character code 1. (this is used by programs that were written to expect options and other \fiargv\fp-elements in any order and that care about the ordering of the two.) the special argument "\-\-" forces an end of option-scanning regardless of the scanning mode. .pp while processing the option list, .br getopt () can detect two kinds of errors: (1) an option character that was not specified in .ir optstring and (2) a missing option argument (i.e., an option at the end of the command line without an expected argument). such errors are handled and reported as follows: .ip * 3 by default, .br getopt () prints an error message on standard error, places the erroneous option character in .ir optopt , and returns \(aq?\(aq as the function result. .ip * if the caller has set the global variable .ir opterr to zero, then .br getopt () does not print an error message. the caller can determine that there was an error by testing whether the function return value is \(aq?\(aq. (by default, .ir opterr has a nonzero value.) .ip * if the first character (following any optional \(aq+\(aq or \(aq\-\(aq described above) of \fioptstring\fp is a colon (\(aq:\(aq), then .br getopt () likewise does not print an error message. in addition, it returns \(aq:\(aq instead of \(aq?\(aq to indicate a missing option argument. this allows the caller to distinguish the two different types of errors. .\" .ss getopt_long() and getopt_long_only() the .br getopt_long () function works like .br getopt () except that it also accepts long options, started with two dashes. (if the program accepts only long options, then .i optstring should be specified as an empty string (""), not null.) long option names may be abbreviated if the abbreviation is unique or is an exact match for some defined option. a long option may take a parameter, of the form .b \-\-arg=param or .br "\-\-arg param" . .pp .i longopts is a pointer to the first element of an array of .i struct option declared in .i as .pp .in +4n .ex struct option { const char *name; int has_arg; int *flag; int val; }; .ee .in .pp the meanings of the different fields are: .tp .i name is the name of the long option. .tp .i has_arg is: \fbno_argument\fp (or 0) if the option does not take an argument; \fbrequired_argument\fp (or 1) if the option requires an argument; or \fboptional_argument\fp (or 2) if the option takes an optional argument. .tp .i flag specifies how results are returned for a long option. if \fiflag\fp is null, then .br getopt_long () returns \fival\fp. (for example, the calling program may set \fival\fp to the equivalent short option character.) otherwise, .br getopt_long () returns 0, and \fiflag\fp points to a variable which is set to \fival\fp if the option is found, but left unchanged if the option is not found. .tp \fival\fp is the value to return, or to load into the variable pointed to by \fiflag\fp. .pp the last element of the array has to be filled with zeros. .pp if \filongindex\fp is not null, it points to a variable which is set to the index of the long option relative to .ir longopts . .pp .br getopt_long_only () is like .br getopt_long (), but \(aq\-\(aq as well as "\-\-" can indicate a long option. if an option that starts with \(aq\-\(aq (not "\-\-") doesn't match a long option, but does match a short option, it is parsed as a short option instead. .sh return value if an option was successfully found, then .br getopt () returns the option character. if all command-line options have been parsed, then .br getopt () returns \-1. if .br getopt () encounters an option character that was not in .ir optstring , then \(aq?\(aq is returned. if .br getopt () encounters an option with a missing argument, then the return value depends on the first character in .ir optstring : if it is \(aq:\(aq, then \(aq:\(aq is returned; otherwise \(aq?\(aq is returned. .pp .br getopt_long () and .br getopt_long_only () also return the option character when a short option is recognized. for a long option, they return \fival\fp if \fiflag\fp is null, and 0 otherwise. error and \-1 returns are the same as for .br getopt (), plus \(aq?\(aq for an ambiguous match or an extraneous parameter. .sh environment .tp .b posixly_correct if this is set, then option processing stops as soon as a nonoption argument is encountered. .tp .b __gnu_nonoption_argv_flags_ this variable was used by .br bash (1) 2.0 to communicate to glibc which arguments are the results of wildcard expansion and so should not be considered as options. this behavior was removed in .br bash (1) version 2.01, but the support remains in glibc. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getopt (), .br getopt_long (), .br getopt_long_only () t} thread safety t{ mt-unsafe race:getopt env t} .te .hy .ad .sp 1 .sh conforming to .tp .br getopt (): posix.1-2001, posix.1-2008, and posix.2, provided the environment variable .b posixly_correct is set. otherwise, the elements of \fiargv\fp aren't really .ir const , because these functions permute them. nevertheless, .i const is used in the prototype to be compatible with other systems. .ip the use of \(aq+\(aq and \(aq\-\(aq in .i optstring is a gnu extension. .ip on some older implementations, .br getopt () was declared in .ir . susv1 permitted the declaration to appear in either .i or .ir . posix.1-1996 marked the use of .i for this purpose as legacy. posix.1-2001 does not require the declaration to appear in .ir . .tp .br getopt_long "() and " getopt_long_only (): these functions are gnu extensions. .sh notes a program that scans multiple argument vectors, or rescans the same vector more than once, and wants to make use of gnu extensions such as \(aq+\(aq and \(aq\-\(aq at the start of .ir optstring , or changes the value of .b posixly_correct between scans, must reinitialize .br getopt () by resetting .i optind to 0, rather than the traditional value of 1. (resetting to 0 forces the invocation of an internal initialization routine that rechecks .b posixly_correct and checks for gnu extensions in .ir optstring .) .pp command-line arguments are parsed in strict order meaning that an option requiring an argument will consume the next argument, regardless of whether that argument is the correctly specified option argument or simply the next option (in the scenario the user mis-specifies the command line). for example, if .i optstring is specified as "1n:" and the user specifies the command line arguments incorrectly as .ir "prog\ \-n\ \-1" , the .i \-n option will be given the .b optarg value "\-1", and the .i \-1 option will be considered to have not been specified. .sh examples .ss getopt() the following trivial example program uses .br getopt () to handle two program options: .ir \-n , with no associated value; and .ir "\-t val" , which expects an associated value. .pp .ex #include #include #include int main(int argc, char *argv[]) { int flags, opt; int nsecs, tfnd; nsecs = 0; tfnd = 0; flags = 0; while ((opt = getopt(argc, argv, "nt:")) != \-1) { switch (opt) { case \(aqn\(aq: flags = 1; break; case \(aqt\(aq: nsecs = atoi(optarg); tfnd = 1; break; default: /* \(aq?\(aq */ fprintf(stderr, "usage: %s [\-t nsecs] [\-n] name\en", argv[0]); exit(exit_failure); } } printf("flags=%d; tfnd=%d; nsecs=%d; optind=%d\en", flags, tfnd, nsecs, optind); if (optind >= argc) { fprintf(stderr, "expected argument after options\en"); exit(exit_failure); } printf("name argument = %s\en", argv[optind]); /* other code omitted */ exit(exit_success); } .ee .ss getopt_long() the following example program illustrates the use of .br getopt_long () with most of its features. .pp .ex #include /* for printf */ #include /* for exit */ #include int main(int argc, char *argv[]) { int c; int digit_optind = 0; while (1) { int this_option_optind = optind ? optind : 1; int option_index = 0; static struct option long_options[] = { {"add", required_argument, 0, 0 }, {"append", no_argument, 0, 0 }, {"delete", required_argument, 0, 0 }, {"verbose", no_argument, 0, 0 }, {"create", required_argument, 0, \(aqc\(aq}, {"file", required_argument, 0, 0 }, {0, 0, 0, 0 } }; c = getopt_long(argc, argv, "abc:d:012", long_options, &option_index); if (c == \-1) break; switch (c) { case 0: printf("option %s", long_options[option_index].name); if (optarg) printf(" with arg %s", optarg); printf("\en"); break; case \(aq0\(aq: case \(aq1\(aq: case \(aq2\(aq: if (digit_optind != 0 && digit_optind != this_option_optind) printf("digits occur in two different argv\-elements.\en"); digit_optind = this_option_optind; printf("option %c\en", c); break; case \(aqa\(aq: printf("option a\en"); break; case \(aqb\(aq: printf("option b\en"); break; case \(aqc\(aq: printf("option c with value \(aq%s\(aq\en", optarg); break; case \(aqd\(aq: printf("option d with value \(aq%s\(aq\en", optarg); break; case \(aq?\(aq: break; default: printf("?? getopt returned character code 0%o ??\en", c); } } if (optind < argc) { printf("non\-option argv\-elements: "); while (optind < argc) printf("%s ", argv[optind++]); printf("\en"); } exit(exit_success); } .ee .sh see also .br getopt (1), .br getsubopt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2017 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th network_namespaces 7 2020-06-09 "linux" "linux programmer's manual" .sh name network_namespaces \- overview of linux network namespaces .sh description network namespaces provide isolation of the system resources associated with networking: network devices, ipv4 and ipv6 protocol stacks, ip routing tables, firewall rules, the .i /proc/net directory (which is a symbolic link to .ir /proc/pid/net ), the .i /sys/class/net directory, various files under .ir /proc/sys/net , port numbers (sockets), and so on. in addition, network namespaces isolate the unix domain abstract socket namespace (see .br unix (7)). .pp a physical network device can live in exactly one network namespace. when a network namespace is freed (i.e., when the last process in the namespace terminates), its physical network devices are moved back to the initial network namespace (not to the parent of the process). .pp a virtual network .rb ( veth (4)) device pair provides a pipe-like abstraction that can be used to create tunnels between network namespaces, and can be used to create a bridge to a physical network device in another namespace. when a namespace is freed, the .br veth (4) devices that it contains are destroyed. .pp use of network namespaces requires a kernel that is configured with the .b config_net_ns option. .\" fixme .sh examples .sh see also .br nsenter (1), .br unshare (1), .br clone (2), .br veth (4), .br proc (5), .br sysfs (5), .br namespaces (7), .br user_namespaces (7), .br brctl (8), .br ip (8), .br ip\-address (8), .br ip\-link (8), .br ip\-netns (8), .br iptables (8), .br ovs\-vsctl (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sync_file_range.2 .so man3/fenv.3 .\" copyright (c) 1994 michael haardt (michael@moria.de), 1994-06-04 .\" copyright (c) 1995 michael haardt .\" (michael@cantor.informatik.rwth-aachen.de), 1995-03-16 .\" copyright (c) 1996 andries brouwer (aeb@cwi.nl), 1996-01-13 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-01-13 aeb: merged in some text contributed by melvin smith .\" (msmith@falcon.mercer.peachnet.edu) and various other changes. .\" modified 1996-05-16 by martin schulze (joey@infodrom.north.de) .\" .th perror 3 2021-03-22 "" "linux programmer's manual" .sh name perror \- print a system error message .sh synopsis .nf .b #include .pp .bi "void perror(const char *" s ); .pp .b #include .pp .bi "const char *const " sys_errlist []; .bi "int " sys_nerr ; .bi "int " errno "; \fr/* not really declared this way; see errno(3) */" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .ir sys_errlist , .ir sys_nerr : .nf from glibc 2.19 to 2.31: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the .br perror () function produces a message on standard error describing the last error encountered during a call to a system or library function. .pp first (if .i s is not null and .i *s is not a null byte (\(aq\e0\(aq)), the argument string .i s is printed, followed by a colon and a blank. then an error message corresponding to the current value of .i errno and a new-line. .pp to be of most use, the argument string should include the name of the function that incurred the error. .pp the global error list .ir sys_errlist "[]," which can be indexed by .ir errno , can be used to obtain the error message without the newline. the largest message number provided in the table is .ir sys_nerr "\-1." be careful when directly accessing this list, because new error values may not have been added to .ir sys_errlist "[]." the use of .ir sys_errlist "[]" is nowadays deprecated; use .br strerror (3) instead. .pp when a system call fails, it usually returns \-1 and sets the variable .i errno to a value describing what went wrong. (these values can be found in .ir .) many library functions do likewise. the function .br perror () serves to translate this error code into human-readable form. note that .i errno is undefined after a successful system call or library function call: this call may well change this variable, even though it succeeds, for example because it internally used some other library function that failed. thus, if a failing call is not immediately followed by a call to .br perror (), the value of .i errno should be saved. .sh versions since glibc version 2.32, the declarations of .i sys_errlist and .i sys_nerr are no longer exposed by .ir . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br perror () t} thread safety mt-safe race:stderr .te .hy .ad .sp 1 .sh conforming to .br perror (), .ir errno : posix.1-2001, posix.1-2008, c89, c99, 4.3bsd. .pp the externals .i sys_nerr and .i sys_errlist derive from bsd, but are not specified in posix.1. .sh notes the externals .i sys_nerr and .i sys_errlist are defined by glibc, but in .ir . .\" and only when _bsd_source is defined. .\" when .\" .b _gnu_source .\" is defined, the symbols .\" .i _sys_nerr .\" and .\" .i _sys_errlist .\" are provided. .sh see also .br err (3), .br errno (3), .br error (3), .br strerror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. man1/memusagestat.1 man1/intro.1 man1/pldd.1 man1/time.1 man1/iconv.1 man1/getent.1 man1/localedef.1 man1/memusage.1 man1/locale.1 man1/ldd.1 man1/sprof.1 man1/mtrace.1 man2/vserver.2 man2/rt_sigtimedwait.2 man2/epoll_pwait.2 man2/init_module.2 man2/shmat.2 man2/process_madvise.2 man2/perf_event_open.2 man2/get_robust_list.2 man2/times.2 man2/linkat.2 man2/sched_setattr.2 man2/sigreturn.2 man2/perfmonctl.2 man2/epoll_ctl.2 man2/add_key.2 man2/timerfd_gettime.2 man2/fdetach.2 man2/alloc_hugepages.2 man2/getsid.2 man2/getpagesize.2 man2/isastream.2 man2/semget.2 man2/setfsuid.2 man2/setuid32.2 man2/getpgid.2 man2/mprotect.2 man2/sched_setaffinity.2 man2/chroot.2 man2/rmdir.2 man2/pread64.2 man2/rt_tgsigqueueinfo.2 man2/getcpu.2 man2/ioctl_fideduperange.2 man2/lookup_dcookie.2 man2/getdents.2 man2/fadvise64.2 man2/getgroups32.2 man2/setup.2 man2/io_getevents.2 man2/setfsgid32.2 man2/getpeername.2 man2/truncate64.2 man2/_syscall.2 man2/break.2 man2/sigaltstack.2 man2/fanotify_init.2 man2/ioperm.2 man2/munmap.2 man2/getpmsg.2 man2/unlinkat.2 man2/mq_unlink.2 man2/readlinkat.2 man2/signalfd4.2 man2/readv.2 man2/clock_adjtime.2 man2/sbrk.2 man2/setxattr.2 man2/madvise1.2 man2/getegid32.2 man2/signalfd.2 man2/inl.2 man2/pciconfig_iobase.2 man2/rt_sigsuspend.2 man2/setgid.2 man2/shmop.2 man2/pidfd_send_signal.2 man2/removexattr.2 man2/getdents64.2 man2/setpgrp.2 man2/mount.2 man2/ftruncate.2 man2/pselect.2 man2/mknodat.2 man2/msgctl.2 man2/utimes.2 man2/free_hugepages.2 man2/chown32.2 man2/preadv.2 man2/select.2 man2/pkey_free.2 man2/seteuid.2 man2/pselect6.2 man2/eventfd2.2 man2/sched_getaffinity.2 man2/setresuid.2 man2/exit.2 man2/spu_run.2 man2/inl_p.2 man2/modify_ldt.2 man2/sysctl.2 man2/arm_sync_file_range.2 man2/fchmod.2 man2/msgget.2 man2/poll.2 man2/setreuid.2 man2/getunwind.2 man2/inw.2 man2/mq_timedsend.2 man2/fallocate.2 man2/fchdir.2 man2/ioctl_userfaultfd.2 man2/set_thread_area.2 man2/syscall.2 man2/lchown.2 man2/getgid.2 man2/get_kernel_syms.2 man2/pidfd_open.2 man2/getresgid.2 man2/sync.2 man2/set_tid_address.2 man2/timer_settime.2 man2/pause.2 man2/stty.2 man2/idle.2 man2/outb_p.2 man2/gethostname.2 man2/readlink.2 man2/sched_yield.2 man2/wait3.2 man2/accept4.2 man2/sigpending.2 man2/msgop.2 man2/ioctl_ficlone.2 man2/open_by_handle_at.2 man2/pivot_root.2 man2/recvmsg.2 man2/fadvise64_64.2 man2/query_module.2 man2/uname.2 man2/fork.2 man2/recv.2 man2/unlink.2 man2/oldolduname.2 man2/renameat.2 man2/rt_sigaction.2 man2/clock_nanosleep.2 man2/spu_create.2 man2/outsw.2 man2/timer_getoverrun.2 man2/setregid32.2 man2/ppoll.2 man2/move_pages.2 man2/futimesat.2 man2/symlinkat.2 man2/inb.2 man2/ioctl_ficlonerange.2 man2/timer_create.2 man2/process_vm_writev.2 man2/remap_file_pages.2 man2/recvmmsg.2 man2/setrlimit.2 man2/sgetmask.2 man2/oldfstat.2 man2/mq_notify.2 man2/vm86.2 man2/epoll_create1.2 man2/subpage_prot.2 man2/s390_pci_mmio_read.2 man2/timer_gettime.2 man2/getresuid32.2 man2/faccessat2.2 man2/fsync.2 man2/iopl.2 man2/semop.2 man2/olduname.2 man2/sched_rr_get_interval.2 man2/dup3.2 man2/__clone2.2 man2/flock.2 man2/accept.2 man2/semctl.2 man2/signal.2 man2/sigsuspend.2 man2/setpgid.2 man2/clone3.2 man2/setresgid32.2 man2/set_mempolicy.2 man2/s390_guarded_storage.2 man2/getdomainname.2 man2/pkey_mprotect.2 man2/io_submit.2 man2/s390_pci_mmio_write.2 man2/putmsg.2 man2/preadv2.2 man2/outsb.2 man2/oldlstat.2 man2/msync.2 man2/symlink.2 man2/link.2 man2/set_robust_list.2 man2/kill.2 man2/setsockopt.2 man2/setpriority.2 man2/setfsuid32.2 man2/getitimer.2 man2/kexec_load.2 man2/dup.2 man2/clone2.2 man2/get_mempolicy.2 man2/seccomp_unotify.2 man2/setuid.2 man2/setitimer.2 man2/mpx.2 man2/lgetxattr.2 man2/nfsservctl.2 man2/swapon.2 man2/epoll_wait.2 man2/epoll_create.2 man2/inotify_init.2 man2/tkill.2 man2/setgroups32.2 man2/sendfile64.2 man2/ioctl_ns.2 man2/s390_sthyi.2 man2/getpriority.2 man2/ioctl.2 man2/listen.2 man2/cacheflush.2 man2/lstat64.2 man2/mincore.2 man2/mknod.2 man2/fcntl64.2 man2/insl.2 man2/outw_p.2 man2/execveat.2 man2/recvfrom.2 man2/mlockall.2 man2/pwritev2.2 man2/munlockall.2 man2/ftruncate64.2 man2/wait.2 man2/writev.2 man2/uselib.2 man2/getsockopt.2 man2/delete_module.2 man2/pread.2 man2/security.2 man2/pkey_alloc.2 man2/pipe2.2 man2/clone.2 man2/gtty.2 man2/setresgid.2 man2/get_thread_area.2 man2/arch_prctl.2 man2/socketcall.2 man2/inb_p.2 man2/close.2 man2/mkdirat.2 man2/timer_delete.2 man2/vfork.2 man2/ipc.2 man2/ioctl_console.2 man2/swapoff.2 man2/personality.2 man2/phys.2 man2/flistxattr.2 man2/chmod.2 man2/lremovexattr.2 man2/setfsgid.2 man2/putpmsg.2 man2/fanotify_mark.2 man2/madvise.2 man2/prlimit64.2 man2/statx.2 man2/lstat.2 man2/unshare.2 man2/keyctl.2 man2/s390_runtime_instr.2 man2/newfstatat.2 man2/settimeofday.2 man2/llistxattr.2 man2/pwritev.2 man2/msgsnd.2 man2/getrandom.2 man2/mount_setattr.2 man2/insw.2 man2/pciconfig_write.2 man2/acct.2 man2/open.2 man2/pipe.2 man2/alarm.2 man2/rt_sigreturn.2 man2/unimplemented.2 man2/fchownat.2 man2/mlock2.2 man2/umask.2 man2/fdatasync.2 man2/inotify_rm_watch.2 man2/syscalls.2 man2/fchown.2 man2/membarrier.2 man2/stime.2 man2/sysfs.2 man2/outb.2 man2/sched_getattr.2 man2/sendto.2 man2/sethostname.2 man2/renameat2.2 man2/mlock.2 man2/outw.2 man2/mq_getsetattr.2 man2/gettimeofday.2 man2/setns.2 man2/wait4.2 man2/rt_sigqueueinfo.2 man2/close_range.2 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man2/epoll_pwait2.2 man2/sysinfo.2 man2/vhangup.2 man2/statfs.2 man2/prof.2 man2/fcntl.2 man2/stat64.2 man2/tee.2 man2/syslog.2 man2/tuxcall.2 man2/mq_timedreceive.2 man2/_llseek.2 man2/ioctl_fslabel.2 man2/gettid.2 man2/fstatat64.2 man2/ptrace.2 man2/getxattr.2 man2/quotactl.2 man2/bpf.2 man2/bind.2 man2/chown.2 man2/getsockname.2 man2/sched_getparam.2 man2/lseek.2 man2/getuid32.2 man2/pciconfig_read.2 man2/ssetmask.2 man2/fstatfs64.2 man2/getresgid32.2 man2/getpgrp.2 man2/select_tut.2 man2/sigwaitinfo.2 man2/outl.2 man2/creat.2 man2/exit_group.2 man2/ugetrlimit.2 man2/insb.2 man2/process_vm_readv.2 man2/capget.2 man2/getrusage.2 man2/setgid32.2 man2/mbind.2 man2/ustat.2 man2/stat.2 man2/send.2 man2/splice.2 man2/lock.2 man2/timerfd_settime.2 man2/access.2 man2/ioprio_set.2 man2/openat.2 man2/intro.2 man2/vmsplice.2 man2/outl_p.2 man2/sched_get_priority_min.2 man2/ioctl_fat.2 man2/lchown32.2 man2/io_destroy.2 man2/statfs64.2 man2/prctl.2 man2/socketpair.2 man2/_newselect.2 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man3/file.3 man3/gethostbyname_r.3 man3/log10.3 man3/updwtmpx.3 man3/powf.3 man3/pthread_attr_setguardsize.3 man3/nearbyintf.3 man3/getipnodebyaddr.3 man3/wcsnrtombs.3 man3/xdr_pmaplist.3 man3/atan.3 man3/mcheck_pedantic.3 man3/erfl.3 man3/isatty.3 man3/scandir.3 man3/remainderf.3 man3/endspent.3 man3/size_t.3 man3/fminl.3 man3/mq_timedsend.3 man3/hypotl.3 man3/open_wmemstream.3 man3/__ppc_yield.3 man3/asctime_r.3 man3/ether_hostton.3 man3/cexpl.3 man3/fmodl.3 man3/swab.3 man3/vwarn.3 man3/sem_wait.3 man3/__ppc_set_ppr_very_low.3 man3/remquof.3 man3/muntrace.3 man3/getrpcbynumber_r.3 man3/bindresvport.3 man3/j1l.3 man3/finitef.3 man3/stailq_remove.3 man3/islower_l.3 man3/h_errno.3 man3/tgamma.3 man3/tmpnam.3 man3/ccosh.3 man3/sockatmark.3 man3/nextup.3 man3/setrpcent.3 man3/fputws_unlocked.3 man3/cimagl.3 man3/j1f.3 man3/get_current_dir_name.3 man3/mq_notify.3 man3/getgrent_r.3 man3/cexp2l.3 man3/ether_ntoa_r.3 man3/utmpname.3 man3/pthread_attr_setinheritsched.3 man3/malloc_info.3 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man3/csqrtf.3 man3/getservbyport_r.3 man3/isinfl.3 man3/lseek64.3 man3/clog2l.3 man3/sleep.3 man3/slist_insert_head.3 man3/endpwent.3 man3/twalk.3 man3/jnf.3 man3/cexp2f.3 man3/fgetgrent.3 man3/logbl.3 man3/cproj.3 man3/getnetbyname_r.3 man3/xdr.3 man3/isnormal.3 man3/double_t.3 man3/mempcpy.3 man3/erand48_r.3 man3/stdio_ext.3 man3/profil.3 man3/authunix_create.3 man3/ceill.3 man3/stpcpy.3 man3/etext.3 man3/strfroml.3 man3/pthread_attr_getschedparam.3 man3/xdr_callmsg.3 man3/catopen.3 man3/cargf.3 man3/__fwritable.3 man3/if_nametoindex.3 man3/tailq_next.3 man3/getrpcbynumber.3 man3/atan2l.3 man3/pthread_rwlockattr_setkind_np.3 man3/getttyent.3 man3/pthread_getconcurrency.3 man3/frexpl.3 man3/tailq_insert_before.3 man3/getutent_r.3 man3/isgreaterequal.3 man3/floor.3 man3/svc_getcaller.3 man3/circleq_empty.3 man3/setjmp.3 man3/regfree.3 man3/dprintf.3 man3/mq_unlink.3 man3/getchar_unlocked.3 man3/__ppc_mdoio.3 man3/pow10f.3 man3/pthread_mutexattr_getrobust_np.3 man3/putc_unlocked.3 man3/socklen_t.3 man3/forkpty.3 man3/int64_t.3 man3/mallinfo2.3 man3/getsubopt.3 man3/j0.3 man3/encrypt_r.3 man3/atan2.3 man3/vfwprintf.3 man3/iswalnum.3 man3/list_remove.3 man3/pthread_setschedprio.3 man3/ecb_crypt.3 man3/getpass.3 man3/pthread_sigmask.3 man3/getnetent.3 man3/tdestroy.3 man3/y1f.3 man3/getrpcbyname.3 man3/isblank_l.3 man3/floorl.3 man3/tailq_foreach_reverse.3 man3/pthread_mutex_consistent.3 man3/setvbuf.3 man3/exp10f.3 man3/getgrgid.3 man3/wcpncpy.3 man3/realpath.3 man3/ferror.3 man3/intmax_t.3 man3/rand_r.3 man3/herror.3 man3/aligned_alloc.3 man3/setusershell.3 man3/pthread_self.3 man3/pthread_cleanup_push.3 man3/hypotf.3 man3/creal.3 man3/edata.3 man3/ptsname_r.3 man3/pututxline.3 man3/fpathconf.3 man3/open_memstream.3 man3/intn_t.3 man3/getdate_err.3 man3/matherr.3 man3/infinity.3 man3/gnu_get_libc_version.3 man3/svcudp_bufcreate.3 man3/string.3 man3/va_arg.3 man3/wcsrchr.3 man3/pthread_attr_getstack.3 man3/xdr_long.3 man3/svc_unregister.3 man3/pid_t.3 man3/modf.3 man3/imaxdiv_t.3 man3/authunix_create_default.3 man3/daemon.3 man3/div_t.3 man3/clnt_control.3 man3/killpg.3 man3/mkstemps.3 man3/nanl.3 man3/swapcontext.3 man3/toupper_l.3 man3/ldiv.3 man3/lldiv_t.3 man3/xdr_float.3 man3/putspent.3 man3/nan.3 man3/isalnum.3 man3/srandom_r.3 man3/iscntrl_l.3 man3/cmsg_firsthdr.3 man3/sem_timedwait.3 man3/lcong48_r.3 man3/conj.3 man3/getspnam.3 man3/system.3 man3/wcscpy.3 man3/ulimit.3 man3/posix_memalign.3 man3/tailq_swap.3 man3/clnt_pcreateerror.3 man3/llrintl.3 man3/clogl.3 man3/erff.3 man3/ftw.3 man3/regex.3 man3/mbrtowc.3 man3/utmpxname.3 man3/argz.3 man3/error.3 man3/isblank.3 man3/tanhl.3 man3/freeifaddrs.3 man3/getaliasbyname.3 man3/__malloc_initialize_hook.3 man3/xdr_bytes.3 man3/csinhf.3 man3/ether_ntoa.3 man3/endusershell.3 man3/initstate.3 man3/fsetpos.3 man3/rewind.3 man4/ptmx.4 man4/ttys.4 man4/dsp56k.4 man4/port.4 man4/ram.4 man4/veth.4 man4/st.4 man4/loop.4 man4/wavelan.4 man4/sk98lin.4 man4/loop-control.4 man4/hd.4 man4/rtc.4 man4/random.4 man4/mouse.4 man4/kmem.4 man4/console_codes.4 man4/pts.4 man4/vcs.4 man4/tty_ioctl.4 man4/fuse.4 man4/lp.4 man4/smartpqi.4 man4/cpuid.4 man4/full.4 man4/intro.4 man4/fd.4 man4/initrd.4 man4/sd.4 man4/lirc.4 man4/cciss.4 man4/tty.4 man4/msr.4 man4/zero.4 man4/null.4 man4/urandom.4 man4/hpsa.4 man4/vcsa.4 man4/mem.4 man4/console_ioctl.4 man5/ftpusers.5 man5/dir_colors.5 man5/sysfs.5 man5/securetty.5 man5/nss.5 man5/core.5 man5/locale.5 man5/motd.5 man5/utmp.5 man5/passwd.5 man5/nsswitch.conf.5 man5/gai.conf.5 man5/intro.5 man5/fs.5 man5/hosts.equiv.5 man5/elf.5 man5/resolv.conf.5 man5/utmpx.5 man5/wtmp.5 man5/nscd.conf.5 man5/termcap.5 man5/slabinfo.5 man5/repertoiremap.5 man5/ttytype.5 man5/shells.5 man5/protocols.5 man5/host.conf.5 man5/charmap.5 man5/issue.5 man5/resolver.5 man5/networks.5 man5/filesystems.5 man5/hosts.5 man5/procfs.5 man5/tzfile.5 man5/group.5 man5/rpc.5 man5/acct.5 man5/proc.5 man5/tmpfs.5 man5/nologin.5 man5/services.5 man6/intro.6 man7/uts_namespaces.7 man7/user_namespaces.7 man7/iso_8859_1.7 man7/queue.7 man7/iso_8859-14.7 man7/iso_8859_11.7 man7/glob.7 man7/iso_8859-8.7 man7/iso-8859-10.7 man7/charsets.7 man7/netdevice.7 man7/posixoptions.7 man7/process-keyring.7 man7/suffixes.7 man7/iso_8859_7.7 man7/credentials.7 man7/netlink.7 man7/iso_8859-6.7 man7/pipe.7 man7/cp1252.7 man7/latin10.7 man7/address_families.7 man7/latin3.7 man7/latin5.7 man7/latin2.7 man7/session-keyring.7 man7/latin8.7 man7/socket.7 man7/iso-8859-9.7 man7/namespaces.7 man7/iso-8859-13.7 man7/cgroups.7 man7/udp.7 man7/bpf-helpers.7 man7/tcp.7 man7/ipc_namespaces.7 man7/sem_overview.7 man7/environ.7 man7/termio.7 man7/url.7 man7/iso_8859_6.7 man7/iso_8859_10.7 man7/armscii-8.7 man7/sysvipc.7 man7/aio.7 man7/hier.7 man7/iso_8859-1.7 man7/operator.7 man7/glibc.7 man7/cp1251.7 man7/vdso.7 man7/keyrings.7 man7/iso_8859_3.7 man7/iso-8859-2.7 man7/iso_8859_13.7 man7/packet.7 man7/ipv6.7 man7/regex.7 man7/iso_8859-13.7 man7/symlink.7 man7/latin9.7 man7/unicode.7 man7/iso_8859_16.7 man7/user-session-keyring.7 man7/uri.7 man7/iso-8859-1.7 man7/unix.7 man7/svipc.7 man7/mount_namespaces.7 man7/numa.7 man7/iso-8859-11.7 man7/mq_overview.7 man7/iso-8859-8.7 man7/iso_8859_2.7 man7/iso_8859_4.7 man7/pthreads.7 man7/rtld-audit.7 man7/iso-8859-6.7 man7/mailaddr.7 man7/iso_8859-11.7 man7/pkeys.7 man7/standards.7 man7/complex.7 man7/intro.7 man7/nptl.7 man7/precedence.7 man7/iso-8859-7.7 man7/ddp.7 man7/ascii.7 man7/time_namespaces.7 man7/epoll.7 man7/sched.7 man7/pid_namespaces.7 man7/udplite.7 man7/feature_test_macros.7 man7/libc.7 man7/cgroup_namespaces.7 man7/iso_8859-9.7 man7/iso_8859-4.7 man7/attributes.7 man7/iso_8859_9.7 man7/user-keyring.7 man7/inode.7 man7/thread-keyring.7 man7/x25.7 man7/utf-8.7 man7/rtnetlink.7 man7/math_error.7 man7/iso_8859_14.7 man7/inotify.7 man7/iso_8859-7.7 man7/iso_8859-2.7 man7/urn.7 man7/arp.7 man7/capabilities.7 man7/time.7 man7/iso_8859-15.7 man7/icmp.7 man7/iso-8859-3.7 man7/iso-8859-4.7 man7/units.7 man7/hostname.7 man7/koi8-u.7 man7/sock_diag.7 man7/iso-8859-16.7 man7/iso_8859-10.7 man7/cpuset.7 man7/iso_8859-16.7 man7/raw.7 man7/boot.7 man7/xattr.7 man7/locale.7 man7/signal.7 man7/iso-8859-14.7 man7/man.7 man7/kernel_lockdown.7 man7/iso_8859_8.7 man7/koi8-r.7 man7/spufs.7 man7/utf8.7 man7/random.7 man7/latin1.7 man7/signal-safety.7 man7/path_resolution.7 man7/iso-8859-15.7 man7/vsock.7 man7/shm_overview.7 man7/latin4.7 man7/persistent-keyring.7 man7/system_data_types.7 man7/latin7.7 man7/latin6.7 man7/tis-620.7 man7/bootparam.7 man7/sigevent.7 man7/iso-8859-5.7 man7/ip.7 man7/iso_8859_15.7 man7/fifo.7 man7/pty.7 man7/man-pages.7 man7/network_namespaces.7 man7/iso_8859-3.7 man7/fanotify.7 man7/iso_8859_5.7 man7/iso_8859-5.7 man7/futex.7 man8/ld.so.8 man8/ldconfig.8 man8/zic.8 man8/sln.8 man8/zdump.8 man8/nscd.8 man8/ld-linux.so.8 man8/ld-linux.8 man8/tzselect.8 man8/intro.8 man8/iconvconfig.8 .so man3/encrypt.3 .so man3/isalpha.3 .\" copyright (c) 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" fixme . there are a lot of other process termination actions that .\" could be listed on this page. see, for example, the list in the .\" posix exit(3p) page. .\" .th exit 3 2021-03-22 "linux" "linux programmer's manual" .sh name exit \- cause normal process termination .sh synopsis .nf .b #include .pp .bi "noreturn void exit(int " status ); .fi .sh description the .br exit () function causes normal process termination and the least significant byte of .i status (i.e., \fistatus & 0xff\fp) is returned to the parent (see .br wait (2)). .pp all functions registered with .br atexit (3) and .br on_exit (3) are called, in the reverse order of their registration. (it is possible for one of these functions to use .br atexit (3) or .br on_exit (3) to register an additional function to be executed during exit processing; the new registration is added to the front of the list of functions that remain to be called.) if one of these functions does not return (e.g., it calls .br _exit (2), or kills itself with a signal), then none of the remaining functions is called, and further exit processing (in particular, flushing of .br stdio (3) streams) is abandoned. if a function has been registered multiple times using .br atexit (3) or .br on_exit (3), then it is called as many times as it was registered. .pp all open .br stdio (3) streams are flushed and closed. files created by .br tmpfile (3) are removed. .pp the c standard specifies two constants, \fbexit_success\fp and \fbexit_failure\fp, that may be passed to .br exit () to indicate successful or unsuccessful termination, respectively. .sh return value the .br exit () function does not return. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br exit () t} thread safety mt-unsafe race:exit .te .hy .ad .sp 1 .pp the .br exit () function uses a global variable that is not protected, so it is not thread-safe. .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes the behavior is undefined if one of the functions registered using .br atexit (3) and .br on_exit (3) calls either .br exit () or .br longjmp (3). note that a call to .br execve (2) removes registrations created using .br atexit (3) and .br on_exit (3). .pp the use of .b exit_success and .b exit_failure is slightly more portable (to non-unix environments) than the use of 0 and some nonzero value like 1 or \-1. in particular, vms uses a different convention. .pp bsd has attempted to standardize exit codes (which some c libraries such as the gnu c library have also adopted); see the file .ir . .pp after .br exit (), the exit status must be transmitted to the parent process. there are three cases: .ip \(bu 3 if the parent has set .br sa_nocldwait , or has set the .b sigchld handler to .br sig_ign , the status is discarded and the child dies immediately. .ip \(bu if the parent was waiting on the child, it is notified of the exit status and the child dies immediately. .ip \(bu otherwise, the child becomes a "zombie" process: most of the process resources are recycled, but a slot containing minimal information about the child process (termination status, resource usage statistics) is retained in process table. this allows the parent to subsequently use .br waitpid (2) (or similar) to learn the termination status of the child; at that point the zombie process slot is released. .pp if the implementation supports the .b sigchld signal, this signal is sent to the parent. if the parent has set .br sa_nocldwait , it is undefined whether a .b sigchld signal is sent. .\" .ss signals sent to other processes if the exiting process is a session leader and its controlling terminal is the controlling terminal of the session, then each process in the foreground process group of this controlling terminal is sent a .b sighup signal, and the terminal is disassociated from this session, allowing it to be acquired by a new controlling process. .pp if the exit of the process causes a process group to become orphaned, and if any member of the newly orphaned process group is stopped, then a .b sighup signal followed by a .b sigcont signal will be sent to each process in this process group. see .br setpgid (2) for an explanation of orphaned process groups. .pp except in the above cases, where the signalled processes may be children of the terminating process, termination of a process does .i not in general cause a signal to be sent to children of that process. however, a process can use the .br prctl (2) .b pr_set_pdeathsig operation to arrange that it receives a signal if its parent terminates. .sh see also .br _exit (2), .br get_robust_list (2), .br setpgid (2), .br wait (2), .br atexit (3), .br on_exit (3), .br tmpfile (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fabs.3 .so man3/ccos.3 .so man3/des_crypt.3 .so man3/getdate.3 .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th timer_settime 2 2021-03-22 linux "linux programmer's manual" .sh name timer_settime, timer_gettime \- arm/disarm and fetch state of posix per-process timer .sh synopsis .nf .b #include .pp .bi "int timer_settime(timer_t " timerid ", int " flags , .bi " const struct itimerspec *restrict " new_value , .bi " struct itimerspec *restrict " old_value ); .bi "int timer_gettime(timer_t " timerid ", struct itimerspec *" curr_value ); .fi .pp link with \fi\-lrt\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br timer_settime (), .br timer_gettime (): .nf _posix_c_source >= 199309l .fi .sh description .br timer_settime () arms or disarms the timer identified by .ir timerid . the .i new_value argument is pointer to an .i itimerspec structure that specifies the new initial value and the new interval for the timer. the .i itimerspec structure is defined as follows: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; struct itimerspec { struct timespec it_interval; /* timer interval */ struct timespec it_value; /* initial expiration */ }; .ee .in .pp each of the substructures of the .i itimerspec structure is a .i timespec structure that allows a time value to be specified in seconds and nanoseconds. these time values are measured according to the clock that was specified when the timer was created by .br timer_create (2). .pp if .i new_value\->it_value specifies a nonzero value (i.e., either subfield is nonzero), then .br timer_settime () arms (starts) the timer, setting it to initially expire at the given time. (if the timer was already armed, then the previous settings are overwritten.) if .i new_value\->it_value specifies a zero value (i.e., both subfields are zero), then the timer is disarmed. .pp the .i new_value\->it_interval field specifies the period of the timer, in seconds and nanoseconds. if this field is nonzero, then each time that an armed timer expires, the timer is reloaded from the value specified in .ir new_value\->it_interval . if .i new_value\->it_interval specifies a zero value, then the timer expires just once, at the time specified by .ir it_value . .pp by default, the initial expiration time specified in .i new_value\->it_value is interpreted relative to the current time on the timer's clock at the time of the call. this can be modified by specifying .b timer_abstime in .ir flags , in which case .i new_value\->it_value is interpreted as an absolute value as measured on the timer's clock; that is, the timer will expire when the clock value reaches the value specified by .ir new_value\->it_value . if the specified absolute time has already passed, then the timer expires immediately, and the overrun count (see .br timer_getoverrun (2)) will be set correctly. .\" by experiment: the overrun count is set correctly, for clock_realtime. .pp if the value of the .b clock_realtime clock is adjusted while an absolute timer based on that clock is armed, then the expiration of the timer will be appropriately adjusted. adjustments to the .b clock_realtime clock have no effect on relative timers based on that clock. .\" similar remarks might apply with respect to process and thread cpu time .\" clocks, but these clocks are not currently (2.6.28) settable on linux. .pp if .i old_value is not null, then it points to a buffer that is used to return the previous interval of the timer (in .ir old_value\->it_interval ) and the amount of time until the timer would previously have next expired (in .ir old_value\->it_value ). .pp .br timer_gettime () returns the time until next expiration, and the interval, for the timer specified by .ir timerid , in the buffer pointed to by .ir curr_value . the time remaining until the next timer expiration is returned in .ir curr_value\->it_value ; this is always a relative value, regardless of whether the .br timer_abstime flag was used when arming the timer. if the value returned in .ir curr_value\->it_value is zero, then the timer is currently disarmed. the timer interval is returned in .ir curr_value\->it_interval . if the value returned in .ir curr_value\->it_interval is zero, then this is a "one-shot" timer. .sh return value on success, .br timer_settime () and .br timer_gettime () return 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors these functions may fail with the following errors: .tp .b efault .ir new_value , .ir old_value , or .i curr_value is not a valid pointer. .tp .b einval .i timerid is invalid. .\" fixme . eventually: invalid value in flags .pp .br timer_settime () may fail with the following errors: .tp .b einval .i new_value.it_value is negative; or .i new_value.it_value.tv_nsec is negative or greater than 999,999,999. .sh versions these system calls are available since linux 2.6. .sh conforming to posix.1-2001, posix.1-2008. .sh examples see .br timer_create (2). .sh see also .br timer_create (2), .br timer_getoverrun (2), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fgetc.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th mbrlen 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mbrlen \- determine number of bytes in next multibyte character .sh synopsis .nf .b #include .pp .bi "size_t mbrlen(const char *restrict " s ", size_t " n , .bi " mbstate_t *restrict " ps ); .fi .sh description the .br mbrlen () function inspects at most .i n bytes of the multibyte string starting at .i s and extracts the next complete multibyte character. it updates the shift state .ir *ps . if the multibyte character is not the null wide character, it returns the number of bytes that were consumed from .ir s . if the multibyte character is the null wide character, it resets the shift state .i *ps to the initial state and returns 0. .pp if the .ir n bytes starting at .i s do not contain a complete multibyte character, .br mbrlen () returns .ir "(size_t)\ \-2" . this can happen even if .i n >= .ir mb_cur_max , if the multibyte string contains redundant shift sequences. .pp if the multibyte string starting at .i s contains an invalid multibyte sequence before the next complete character, .br mbrlen () returns .ir "(size_t)\ \-1" and sets .i errno to .br eilseq . in this case, the effects on .i *ps are undefined. .pp if .i ps is null, a static anonymous state known only to the .br mbrlen () function is used instead. .sh return value the .br mbrlen () function returns the number of bytes parsed from the multibyte sequence starting at .ir s , if a non-null wide character was recognized. it returns 0, if a null wide character was recognized. it returns .i "(size_t)\ \-1" and sets .i errno to .br eilseq , if an invalid multibyte sequence was encountered. it returns .ir "(size_t)\ \-2" if it couldn't parse a complete multibyte character, meaning that .i n should be increased. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mbrlen () t} thread safety mt-unsafe race:mbrlen/!ps .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br mbrlen () depends on the .b lc_ctype category of the current locale. .sh see also .br mbrtowc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/ioctl_ficlonerange.2 .so man3/ecvt_r.3 .so man3/puts.3 .so man2/chdir.2 .so man2/pread.2 .so man7/iso_8859-14.7 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th clog 3 2021-03-22 "" "linux programmer's manual" .sh name clog, clogf, clogl \- natural logarithm of a complex number .sh synopsis .nf .b #include .pp .bi "double complex clog(double complex " z ); .bi "float complex clogf(float complex " z ); .bi "long double complex clogl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex natural logarithm of .ir z , with a branch cut along the negative real axis. .pp the logarithm .br clog () is the inverse function of the exponential .br cexp (3). thus, if \fiy\ =\ clog(z)\fp, then \fiz\ =\ cexp(y)\fp. the imaginary part of .i y is chosen in the interval [\-pi,pi]. .pp one has: .pp .nf clog(z) = log(cabs(z)) + i * carg(z) .fi .pp note that .i z close to zero will cause an overflow. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clog (), .br clogf (), .br clogl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br cexp (3), .br clog10 (3), .br clog2 (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th svipc 7 2020-04-11 "linux" "linux programmer's manual" .sh name sysvipc \- system v interprocess communication mechanisms .sh description system v ipc is the name given to three interprocess communication mechanisms that are widely available on unix systems: message queues, semaphore, and shared memory. .\" .ss message queues system v message queues allow data to be exchanged in units called messages. each messages can have an associated priority, posix message queues provide an alternative api for achieving the same result; see .br mq_overview (7). .pp the system v message queue api consists of the following system calls: .tp .br msgget (2) create a new message queue or obtain the id of an existing message queue. this call returns an identifier that is used in the remaining apis. .tp .br msgsnd (2) add a message to a queue. .tp .br msgrcv (2) remove a message from a queue. .tp .br msgctl (2) perform various control operations on a queue, including deletion. .\" .ss semaphore sets system v semaphores allow processes to synchronize their actions. system v semaphores are allocated in groups called sets; each semaphore in a set is a counting semaphore. posix semaphores provide an alternative api for achieving the same result; see .br sem_overview (7). .pp the system v semaphore api consists of the following system calls: .tp .br semget (2) create a new set or obtain the id of an existing set. this call returns an identifier that is used in the remaining apis. .tp .br semop (2) perform operations on the semaphores in a set. .tp .br semctl (2) perform various control operations on a set, including deletion. .\" .ss shared memory segments system v shared memory allows processes to share a region a memory (a "segment"). posix shared memory is an alternative api for achieving the same result; see .br shm_overview (7). .pp the system v shared memory api consists of the following system calls: .tp .br shmget (2) create a new segment or obtain the id of an existing segment. this call returns an identifier that is used in the remaining apis. .tp .br shmat (2) attach an existing shared memory object into the calling process's address space. .tp .br shmdt (2) detach a segment from the calling process's address space. .tp .br shmctl (2) perform various control operations on a segment, including deletion. .\" .ss ipc namespaces for a discussion of the interaction of system v ipc objects and ipc namespaces, see .br ipc_namespaces (7). .sh see also .br ipcmk (1), .br ipcrm (1), .br ipcs (1), .br lsipc (1), .br ipc (2), .br msgctl (2), .br msgget (2), .br msgrcv (2), .br msgsnd (2), .br semctl (2), .br semget (2), .br semop (2), .br shmat (2), .br shmctl (2), .br shmdt (2), .br shmget (2), .br ftok (3), .br ipc_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/unlocked_stdio.3 .so man3/lgamma.3 .so man3/frexp.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 18:16:02 1993 by rik faith (faith@cs.unc.edu) .th sleep 3 2021-03-22 "gnu" "linux programmer's manual" .sh name sleep \- sleep for a specified number of seconds .sh synopsis .nf .b #include .pp .bi "unsigned int sleep(unsigned int " "seconds" ); .fi .sh description .br sleep () causes the calling thread to sleep either until the number of real-time seconds specified in .i seconds have elapsed or until a signal arrives which is not ignored. .sh return value zero if the requested time has elapsed, or the number of seconds left to sleep, if the call was interrupted by a signal handler. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sleep () t} thread safety mt-unsafe sig:sigchld/linux .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on linux, .br sleep () is implemented via .br nanosleep (2). see the .br nanosleep (2) man page for a discussion of the clock used. .ss portability notes on some systems, .br sleep () may be implemented using .br alarm (2) and .br sigalrm (posix.1 permits this); mixing calls to .br alarm (2) and .br sleep () is a bad idea. .pp using .br longjmp (3) from a signal handler or modifying the handling of .b sigalrm while sleeping will cause undefined results. .sh see also .br sleep (1), .br alarm (2), .br nanosleep (2), .br signal (2), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/euidaccess.3 .so man2/removexattr.2 .so man3/exp10.3 .so man3/conj.3 .\" %%%license_start(public_domain) .\" this file is in the public domain, so clarified as of .\" 1996-06-05 by arthur david olson . .\" %%%license_end .\" .th tzfile 5 2020-04-27 "" "linux programmer's manual" .sh name tzfile \- timezone information .sh description .ie '\(lq'' .ds lq \&"\" .el .ds lq \(lq\" .ie '\(rq'' .ds rq \&"\" .el .ds rq \(rq\" .de q \\$3\*(lq\\$1\*(rq\\$2 .. .ie \n(.g .ds - \f(cw-\fp .el ds - \- the timezone information files used by .br tzset (3) are typically found under a directory with a name like .ir /usr/share/zoneinfo . these files use the format described in internet rfc 8536. each file is a sequence of 8-bit bytes. in a file, a binary integer is represented by a sequence of one or more bytes in network order (bigendian, or high-order byte first), with all bits significant, a signed binary integer is represented using two's complement, and a boolean is represented by a one-byte binary integer that is either 0 (false) or 1 (true). the format begins with a 44-byte header containing the following fields: .ip * 2 the magic four-byte ascii sequence .q "tzif" identifies the file as a timezone information file. .ip * a byte identifying the version of the file's format (as of 2017, either an ascii nul, or .q "2", or .q "3" ). .ip * fifteen bytes containing zeros reserved for future use. .ip * six four-byte integer values, in the following order: .rs .tp .i tzh_ttisutcnt the number of ut/local indicators stored in the file. (ut is universal time.) .tp .i tzh_ttisstdcnt the number of standard/wall indicators stored in the file. .tp .i tzh_leapcnt the number of leap seconds for which data entries are stored in the file. .tp .i tzh_timecnt the number of transition times for which data entries are stored in the file. .tp .i tzh_typecnt the number of local time types for which data entries are stored in the file (must not be zero). .tp .i tzh_charcnt the number of bytes of time zone abbreviation strings stored in the file. .re .pp the above header is followed by the following fields, whose lengths depend on the contents of the header: .ip * 2 .i tzh_timecnt four-byte signed integer values sorted in ascending order. these values are written in network byte order. each is used as a transition time (as returned by .br time (2)) at which the rules for computing local time change. .ip * .i tzh_timecnt one-byte unsigned integer values; each one but the last tells which of the different types of local time types described in the file is associated with the time period starting with the same-indexed transition time and continuing up to but not including the next transition time. (the last time type is present only for consistency checking with the posix-style tz string described below.) these values serve as indices into the next field. .ip * .i tzh_typecnt .i ttinfo entries, each defined as follows: .in +.5i .sp .nf .ta .5i +\w'unsigned char\0\0'u struct ttinfo { int32_t tt_utoff; unsigned char tt_isdst; unsigned char tt_desigidx; }; .in -.5i .fi .sp each structure is written as a four-byte signed integer value for .ir tt_utoff , in network byte order, followed by a one-byte boolean for .i tt_isdst and a one-byte value for .ir tt_desigidx . in each structure, .i tt_utoff gives the number of seconds to be added to ut, .i tt_isdst tells whether .i tm_isdst should be set by .br localtime (3) and .i tt_desigidx serves as an index into the array of time zone abbreviation bytes that follow the .i ttinfo structure(s) in the file. the .i tt_utoff value is never equal to \-2**31, to let 32-bit clients negate it without overflow. also, in realistic applications .i tt_utoff is in the range [\-89999, 93599] (i.e., more than \-25 hours and less than 26 hours); this allows easy support by implementations that already support the posix-required range [\-24:59:59, 25:59:59]. .ip * .i tzh_leapcnt pairs of four-byte values, written in network byte order; the first value of each pair gives the nonnegative time (as returned by .br time (2)) at which a leap second occurs; the second is a signed integer specifying the .i total number of leap seconds to be applied during the time period starting at the given time. the pairs of values are sorted in ascending order by time. each transition is for one leap second, either positive or negative; transitions always separated by at least 28 days minus 1 second. .ip * .i tzh_ttisstdcnt standard/wall indicators, each stored as a one-byte boolean; they tell whether the transition times associated with local time types were specified as standard time or local (wall clock) time. .ip * .i tzh_ttisutcnt ut/local indicators, each stored as a one-byte boolean; they tell whether the transition times associated with local time types were specified as ut or local time. if a ut/local indicator is set, the corresponding standard/wall indicator must also be set. .pp the standard/wall and ut/local indicators were designed for transforming a tzif file's transition times into transitions appropriate for another time zone specified via a posix-style tz string that lacks rules. for example, when tz="eet\*-2eest" and there is no tzif file "eet\*-2eest", the idea was to adapt the transition times from a tzif file with the well-known name "posixrules" that is present only for this purpose and is a copy of the file "europe/brussels", a file with a different ut offset. posix does not specify this obsolete transformational behavior, the default rules are installation-dependent, and no implementation is known to support this feature for timestamps past 2037, so users desiring (say) greek time should instead specify tz="europe/athens" for better historical coverage, falling back on tz="eet\*-2eest,m3.5.0/3,m10.5.0/4" if posix conformance is required and older timestamps need not be handled accurately. .pp the .br localtime (3) function normally uses the first .i ttinfo structure in the file if either .i tzh_timecnt is zero or the time argument is less than the first transition time recorded in the file. .ss version 2 format for version-2-format timezone files, the above header and data are followed by a second header and data, identical in format except that eight bytes are used for each transition time or leap second time. (leap second counts remain four bytes.) after the second header and data comes a newline-enclosed, posix-tz-environment-variable-style string for use in handling instants after the last transition time stored in the file or for all instants if the file has no transitions. the posix-style tz string is empty (i.e., nothing between the newlines) if there is no posix representation for such instants. if nonempty, the posix-style tz string must agree with the local time type after the last transition time if present in the eight-byte data; for example, given the string .q "wet0west,m3.5.0,m10.5.0/3" then if a last transition time is in july, the transition's local time type must specify a daylight-saving time abbreviated .q "west" that is one hour east of ut. also, if there is at least one transition, time type 0 is associated with the time period from the indefinite past up to but not including the earliest transition time. .ss version 3 format for version-3-format timezone files, the posix-tz-style string may use two minor extensions to the posix tz format, as described in .br newtzset (3). first, the hours part of its transition times may be signed and range from \-167 through 167 instead of the posix-required unsigned values from 0 through 24. second, dst is in effect all year if it starts january 1 at 00:00 and ends december 31 at 24:00 plus the difference between daylight saving and standard time. .ss interoperability considerations future changes to the format may append more data. .pp version 1 files are considered a legacy format and should be avoided, as they do not support transition times after the year 2038. readers that only understand version 1 must ignore any data that extends beyond the calculated end of the version 1 data block. .pp writers should generate a version 3 file if tz string extensions are necessary to accurately model transition times. otherwise, version 2 files should be generated. .pp the sequence of time changes defined by the version 1 header and data block should be a contiguous subsequence of the time changes defined by the version 2+ header and data block, and by the footer. this guideline helps obsolescent version 1 readers agree with current readers about timestamps within the contiguous subsequence. it also lets writers not supporting obsolescent readers use a .i tzh_timecnt of zero in the version 1 data block to save space. .pp time zone designations should consist of at least three (3) and no more than six (6) ascii characters from the set of alphanumerics, .q "\*-", and .q "+". this is for compatibility with posix requirements for time zone abbreviations. .pp when reading a version 2 or 3 file, readers should ignore the version 1 header and data block except for the purpose of skipping over them. .pp readers should calculate the total lengths of the headers and data blocks and check that they all fit within the actual file size, as part of a validity check for the file. .ss common interoperability issues this section documents common problems in reading or writing tzif files. most of these are problems in generating tzif files for use by older readers. the goals of this section are: .ip * 2 to help tzif writers output files that avoid common pitfalls in older or buggy tzif readers, .ip * to help tzif readers avoid common pitfalls when reading files generated by future tzif writers, and .ip * to help any future specification authors see what sort of problems arise when the tzif format is changed. .pp when new versions of the tzif format have been defined, a design goal has been that a reader can successfully use a tzif file even if the file is of a later tzif version than what the reader was designed for. when complete compatibility was not achieved, an attempt was made to limit glitches to rarely used timestamps, and to allow simple partial workarounds in writers designed to generate new-version data useful even for older-version readers. this section attempts to document these compatibility issues and workarounds, as well as to document other common bugs in readers. .pp interoperability problems with tzif include the following: .ip * 2 some readers examine only version 1 data. as a partial workaround, a writer can output as much version 1 data as possible. however, a reader should ignore version 1 data, and should use version 2+ data even if the reader's native timestamps have only 32 bits. .ip * some readers designed for version 2 might mishandle timestamps after a version 3 file's last transition, because they cannot parse extensions to posix in the tz-like string. as a partial workaround, a writer can output more transitions than necessary, so that only far-future timestamps are mishandled by version 2 readers. .ip * some readers designed for version 2 do not support permanent daylight saving time, e.g., a tz string .q "est5edt,0/0,j365/25" denoting permanent eastern daylight time (\-04). as a partial workaround, a writer can substitute standard time for the next time zone east, e.g., .q "ast4" for permanent atlantic standard time (\-04). .ip * some readers ignore the footer, and instead predict future timestamps from the time type of the last transition. as a partial workaround, a writer can output more transitions than necessary. .ip * some readers do not use time type 0 for timestamps before the first transition, in that they infer a time type using a heuristic that does not always select time type 0. as a partial workaround, a writer can output a dummy (no-op) first transition at an early time. .ip * some readers mishandle timestamps before the first transition that has a timestamp not less than \-2**31. readers that support only 32-bit timestamps are likely to be more prone to this problem, for example, when they process 64-bit transitions only some of which are representable in 32 bits. as a partial workaround, a writer can output a dummy transition at timestamp \-2**31. .ip * some readers mishandle a transition if its timestamp has the minimum possible signed 64-bit value. timestamps less than \-2**59 are not recommended. .ip * some readers mishandle posix-style tz strings that contain .q "<" or .q ">". as a partial workaround, a writer can avoid using .q "<" or .q ">" for time zone abbreviations containing only alphabetic characters. .ip * many readers mishandle time zone abbreviations that contain non-ascii characters. these characters are not recommended. .ip * some readers may mishandle time zone abbreviations that contain fewer than 3 or more than 6 characters, or that contain ascii characters other than alphanumerics, .q "\*-", and .q "+". these abbreviations are not recommended. .ip * some readers mishandle tzif files that specify daylight-saving time ut offsets that are less than the ut offsets for the corresponding standard time. these readers do not support locations like ireland, which uses the equivalent of the posix tz string .q "ist\*-1gmt0,m10.5.0,m3.5.0/1", observing standard time (ist, +01) in summer and daylight saving time (gmt, +00) in winter. as a partial workaround, a writer can output data for the equivalent of the posix tz string .q "gmt0ist,m3.5.0/1,m10.5.0", thus swapping standard and daylight saving time. although this workaround misidentifies which part of the year uses daylight saving time, it records ut offsets and time zone abbreviations correctly. .pp some interoperability problems are reader bugs that are listed here mostly as warnings to developers of readers. .ip * 2 some readers do not support negative timestamps. developers of distributed applications should keep this in mind if they need to deal with pre-1970 data. .ip * some readers mishandle timestamps before the first transition that has a nonnegative timestamp. readers that do not support negative timestamps are likely to be more prone to this problem. .ip * some readers mishandle time zone abbreviations like .q "\*-08" that contain .q "+", .q "\*-", or digits. .ip * some readers mishandle ut offsets that are out of the traditional range of \-12 through +12 hours, and so do not support locations like kiritimati that are outside this range. .ip * some readers mishandle ut offsets in the range [\-3599, \-1] seconds from ut, because they integer-divide the offset by 3600 to get 0 and then display the hour part as .q "+00". .ip * some readers mishandle ut offsets that are not a multiple of one hour, or of 15 minutes, or of 1 minute. .sh see also .br time (2), .br localtime (3), .br tzset (3), .br tzselect (8), .br zdump (8), .br zic (8). .pp olson a, eggert p, murchison k. the time zone information format (tzif). 2019 feb. .ur https://\:www.rfc-editor.org/\:info/\:rfc8536 internet rfc 8536 .ue .ur https://\:doi.org/\:10.17487/\:rfc8536 doi:10.17487/rfc8536 .ue . .\" this file is in the public domain, so clarified as of .\" 1996-06-05 by arthur david olson. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt, .\" copyright (c) 1995 michael shields, .\" copyright (c) 2001 paul sheer, .\" copyright (c) 2006, 2019 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1995-05-18 by jim van zandt .\" sun feb 11 14:07:00 met 1996 martin schulze .\" * layout slightly modified .\" .\" modified mon oct 21 23:05:29 edt 1996 by eric s. raymond .\" modified thu feb 24 01:41:09 cet 2000 by aeb .\" modified thu feb 9 22:32:09 cet 2001 by bert hubert , aeb .\" modified mon nov 11 14:35:00 pst 2002 by ben woodard .\" 2005-03-11, mtk, modified pselect() text (it is now a system .\" call in 2.6.16. .\" .th select 2 2021-03-22 "linux" "linux programmer's manual" .sh name select, pselect, fd_clr, fd_isset, fd_set, fd_zero \- synchronous i/o multiplexing .sh synopsis .nf .b #include .pp .bi "int select(int " nfds ", fd_set *restrict " readfds , .bi " fd_set *restrict " writefds ", fd_set *restrict " exceptfds , .bi " struct timeval *restrict " timeout ); .pp .bi "void fd_clr(int " fd ", fd_set *" set ); .bi "int fd_isset(int " fd ", fd_set *" set ); .bi "void fd_set(int " fd ", fd_set *" set ); .bi "void fd_zero(fd_set *" set ); .pp .bi "int pselect(int " nfds ", fd_set *restrict " readfds , .bi " fd_set *restrict " writefds ", fd_set *restrict " exceptfds , .bi " const struct timespec *restrict " timeout , .bi " const sigset_t *restrict " sigmask ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pselect (): .nf _posix_c_source >= 200112l .fi .sh description .br "warning" : .br select () can monitor only file descriptors numbers that are less than .br fd_setsize (1024)\(eman unreasonably low limit for many modern applications\(emand this limitation will not change. all modern applications should instead use .br poll (2) or .br epoll (7), which do not suffer this limitation. .pp .br select () allows a program to monitor multiple file descriptors, waiting until one or more of the file descriptors become "ready" for some class of i/o operation (e.g., input possible). a file descriptor is considered ready if it is possible to perform a corresponding i/o operation (e.g., .br read (2), or a sufficiently small .br write (2)) without blocking. .\" .ss file descriptor sets the principal arguments of .br select () are three "sets" of file descriptors (declared with the type .ir fd_set ), which allow the caller to wait for three classes of events on the specified set of file descriptors. each of the .i fd_set arguments may be specified as null if no file descriptors are to be watched for the corresponding class of events. .pp .br "note well" : upon return, each of the file descriptor sets is modified in place to indicate which file descriptors are currently "ready". thus, if using .br select () within a loop, the sets \fimust be reinitialized\fp before each call. .pp the contents of a file descriptor set can be manipulated using the following macros: .tp .br fd_zero () this macro clears (removes all file descriptors from) .ir set . it should be employed as the first step in initializing a file descriptor set. .tp .br fd_set () this macro adds the file descriptor .i fd to .ir set . adding a file descriptor that is already present in the set is a no-op, and does not produce an error. .tp .br fd_clr () this macro removes the file descriptor .i fd from .ir set . removing a file descriptor that is not present in the set is a no-op, and does not produce an error. .tp .br fd_isset () .br select () modifies the contents of the sets according to the rules described below. after calling .br select (), the .br fd_isset () macro can be used to test if a file descriptor is still present in a set. .br fd_isset () returns nonzero if the file descriptor .i fd is present in .ir set , and zero if it is not. .\" .ss arguments the arguments of .br select () are as follows: .tp .i readfds the file descriptors in this set are watched to see if they are ready for reading. a file descriptor is ready for reading if a read operation will not block; in particular, a file descriptor is also ready on end-of-file. .ip after .br select () has returned, \fireadfds\fp will be cleared of all file descriptors except for those that are ready for reading. .tp .i writefds the file descriptors in this set are watched to see if they are ready for writing. a file descriptor is ready for writing if a write operation will not block. however, even if a file descriptor indicates as writable, a large write may still block. .ip after .br select () has returned, \fiwritefds\fp will be cleared of all file descriptors except for those that are ready for writing. .tp .i exceptfds the file descriptors in this set are watched for "exceptional conditions". for examples of some exceptional conditions, see the discussion of .b pollpri in .br poll (2). .ip after .br select () has returned, \fiexceptfds\fp will be cleared of all file descriptors except for those for which an exceptional condition has occurred. .tp .i nfds this argument should be set to the highest-numbered file descriptor in any of the three sets, plus 1. the indicated file descriptors in each set are checked, up to this limit (but see bugs). .tp .i timeout the .i timeout argument is a .i timeval structure (shown below) that specifies the interval that .br select () should block waiting for a file descriptor to become ready. the call will block until either: .rs .ip \(bu 2 a file descriptor becomes ready; .ip \(bu the call is interrupted by a signal handler; or .ip \(bu the timeout expires. .re .ip note that the .i timeout interval will be rounded up to the system clock granularity, and kernel scheduling delays mean that the blocking interval may overrun by a small amount. .ip if both fields of the .i timeval structure are zero, then .br select () returns immediately. (this is useful for polling.) .ip if .i timeout is specified as null, .br select () blocks indefinitely waiting for a file descriptor to become ready. .\" .ss pselect() the .br pselect () system call allows an application to safely wait until either a file descriptor becomes ready or until a signal is caught. .pp the operation of .br select () and .br pselect () is identical, other than these three differences: .ip \(bu 2 .br select () uses a timeout that is a .i struct timeval (with seconds and microseconds), while .br pselect () uses a .i struct timespec (with seconds and nanoseconds). .ip \(bu .br select () may update the .i timeout argument to indicate how much time was left. .br pselect () does not change this argument. .ip \(bu .br select () has no .i sigmask argument, and behaves as .br pselect () called with null .ir sigmask . .pp .i sigmask is a pointer to a signal mask (see .br sigprocmask (2)); if it is not null, then .br pselect () first replaces the current signal mask by the one pointed to by .ir sigmask , then does the "select" function, and then restores the original signal mask. (if .i sigmask is null, the signal mask is not modified during the .br pselect () call.) .pp other than the difference in the precision of the .i timeout argument, the following .br pselect () call: .pp .in +4n .ex ready = pselect(nfds, &readfds, &writefds, &exceptfds, timeout, &sigmask); .ee .in .pp is equivalent to .i atomically executing the following calls: .pp .in +4n .ex sigset_t origmask; pthread_sigmask(sig_setmask, &sigmask, &origmask); ready = select(nfds, &readfds, &writefds, &exceptfds, timeout); pthread_sigmask(sig_setmask, &origmask, null); .ee .in .pp the reason that .br pselect () is needed is that if one wants to wait for either a signal or for a file descriptor to become ready, then an atomic test is needed to prevent race conditions. (suppose the signal handler sets a global flag and returns. then a test of this global flag followed by a call of .br select () could hang indefinitely if the signal arrived just after the test but just before the call. by contrast, .br pselect () allows one to first block signals, handle the signals that have come in, then call .br pselect () with the desired .ir sigmask , avoiding the race.) .ss the timeout the .i timeout argument for .br select () is a structure of the following type: .pp .in +4n .ex struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ }; .ee .in .pp the corresponding argument for .br pselect () has the following type: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp on linux, .br select () modifies .i timeout to reflect the amount of time not slept; most other implementations do not do this. (posix.1 permits either behavior.) this causes problems both when linux code which reads .i timeout is ported to other operating systems, and when code is ported to linux that reuses a \fistruct timeval\fp for multiple .br select ()s in a loop without reinitializing it. consider .i timeout to be undefined after .br select () returns. .\" .pp - it is rumored that: .\" on bsd, when a timeout occurs, the file descriptor bits are not changed. .\" - it is certainly true that: .\" linux follows susv2 and sets the bit masks to zero upon a timeout. .sh return value on success, .br select () and .br pselect () return the number of file descriptors contained in the three returned descriptor sets (that is, the total number of bits that are set in .ir readfds , .ir writefds , .ir exceptfds ). the return value may be zero if the timeout expired before any file descriptors became ready. .pp on error, \-1 is returned, and .i errno is set to indicate the error; the file descriptor sets are unmodified, and .i timeout becomes undefined. .sh errors .tp .b ebadf an invalid file descriptor was given in one of the sets. (perhaps a file descriptor that was already closed, or one on which an error has occurred.) however, see bugs. .tp .b eintr a signal was caught; see .br signal (7). .tp .b einval .i nfds is negative or exceeds the .br rlimit_nofile resource limit (see .br getrlimit (2)). .tp .b einval the value contained within .i timeout is invalid. .tp .b enomem unable to allocate memory for internal tables. .sh versions .br pselect () was added to linux in kernel 2.6.16. prior to this, .br pselect () was emulated in glibc (but see bugs). .sh conforming to .br select () conforms to posix.1-2001, posix.1-2008, and 4.4bsd .rb ( select () first appeared in 4.2bsd). generally portable to/from non-bsd systems supporting clones of the bsd socket layer (including system\ v variants). however, note that the system\ v variant typically sets the timeout variable before returning, but the bsd variant does not. .pp .br pselect () is defined in posix.1g, and in posix.1-2001 and posix.1-2008. .sh notes an .i fd_set is a fixed size buffer. executing .br fd_clr () or .br fd_set () with a value of .i fd that is negative or is equal to or larger than .b fd_setsize will result in undefined behavior. moreover, posix requires .i fd to be a valid file descriptor. .pp the operation of .br select () and .br pselect () is not affected by the .br o_nonblock flag. .pp on some other unix systems, .\" darwin, according to a report by jeremy sequoia, relayed by josh triplett .br select () can fail with the error .b eagain if the system fails to allocate kernel-internal resources, rather than .b enomem as linux does. posix specifies this error for .br poll (2), but not for .br select (). portable programs may wish to check for .b eagain and loop, just as with .br eintr . .\" .ss the self-pipe trick on systems that lack .br pselect (), reliable (and more portable) signal trapping can be achieved using the self-pipe trick. in this technique, a signal handler writes a byte to a pipe whose other end is monitored by .br select () in the main program. (to avoid possibly blocking when writing to a pipe that may be full or reading from a pipe that may be empty, nonblocking i/o is used when reading from and writing to the pipe.) .\" .ss emulating usleep(3) before the advent of .br usleep (3), some code employed a call to .br select () with all three sets empty, .i nfds zero, and a non-null .i timeout as a fairly portable way to sleep with subsecond precision. .\" .ss correspondence between select() and poll() notifications within the linux kernel source, .\" fs/select.c we find the following definitions which show the correspondence between the readable, writable, and exceptional condition notifications of .br select () and the event notifications provided by .br poll (2) and .br epoll (7): .pp .in +4n .ex #define pollin_set (epollrdnorm | epollrdband | epollin | epollhup | epollerr) /* ready for reading */ #define pollout_set (epollwrband | epollwrnorm | epollout | epollerr) /* ready for writing */ #define pollex_set (epollpri) /* exceptional condition */ .ee .in .\" .ss multithreaded applications if a file descriptor being monitored by .br select () is closed in another thread, the result is unspecified. on some unix systems, .br select () unblocks and returns, with an indication that the file descriptor is ready (a subsequent i/o operation will likely fail with an error, unless another process reopens file descriptor between the time .br select () returned and the i/o operation is performed). on linux (and some other systems), closing the file descriptor in another thread has no effect on .br select (). in summary, any application that relies on a particular behavior in this scenario must be considered buggy. .\" .ss c library/kernel differences the linux kernel allows file descriptor sets of arbitrary size, determining the length of the sets to be checked from the value of .ir nfds . however, in the glibc implementation, the .ir fd_set type is fixed in size. see also bugs. .pp the .br pselect () interface described in this page is implemented by glibc. the underlying linux system call is named .br pselect6 (). this system call has somewhat different behavior from the glibc wrapper function. .pp the linux .br pselect6 () system call modifies its .i timeout argument. however, the glibc wrapper function hides this behavior by using a local variable for the timeout argument that is passed to the system call. thus, the glibc .br pselect () function does not modify its .i timeout argument; this is the behavior required by posix.1-2001. .pp the final argument of the .br pselect6 () system call is not a .i "sigset_t\ *" pointer, but is instead a structure of the form: .pp .in +4n .ex struct { const kernel_sigset_t *ss; /* pointer to signal set */ size_t ss_len; /* size (in bytes) of object pointed to by \(aqss\(aq */ }; .ee .in .pp this allows the system call to obtain both a pointer to the signal set and its size, while allowing for the fact that most architectures support a maximum of 6 arguments to a system call. see .br sigprocmask (2) for a discussion of the difference between the kernel and libc notion of the signal set. .\" .ss historical glibc details glibc 2.0 provided an incorrect version of .br pselect () that did not take a .i sigmask argument. .pp in glibc versions 2.1 to 2.2.1, one must define .b _gnu_source in order to obtain the declaration of .br pselect () from .ir . .sh bugs posix allows an implementation to define an upper limit, advertised via the constant .br fd_setsize , on the range of file descriptors that can be specified in a file descriptor set. the linux kernel imposes no fixed limit, but the glibc implementation makes .ir fd_set a fixed-size type, with .br fd_setsize defined as 1024, and the .br fd_* () macros operating according to that limit. to monitor file descriptors greater than 1023, use .br poll (2) or .br epoll (7) instead. .pp the implementation of the .i fd_set arguments as value-result arguments is a design error that is avoided in .br poll (2) and .br epoll (7). .pp according to posix, .br select () should check all specified file descriptors in the three file descriptor sets, up to the limit .ir nfds\-1 . however, the current implementation ignores any file descriptor in these sets that is greater than the maximum file descriptor number that the process currently has open. according to posix, any such file descriptor that is specified in one of the sets should result in the error .br ebadf . .pp starting with version 2.1, glibc provided an emulation of .br pselect () that was implemented using .br sigprocmask (2) and .br select (). this implementation remained vulnerable to the very race condition that .br pselect () was designed to prevent. modern versions of glibc use the (race-free) .br pselect () system call on kernels where it is provided. .pp on linux, .br select () may report a socket file descriptor as "ready for reading", while nevertheless a subsequent read blocks. this could for example happen when data has arrived but upon examination has the wrong checksum and is discarded. there may be other circumstances in which a file descriptor is spuriously reported as ready. .\" stevens discusses a case where accept can block after select .\" returns successfully because of an intervening rst from the client. thus it may be safer to use .b o_nonblock on sockets that should not block. .\" maybe the kernel should have returned eio in such a situation? .pp on linux, .br select () also modifies .i timeout if the call is interrupted by a signal handler (i.e., the .b eintr error return). this is not permitted by posix.1. the linux .br pselect () system call has the same behavior, but the glibc wrapper hides this behavior by internally copying the .i timeout to a local variable and passing that variable to the system call. .sh examples .ex #include #include #include int main(void) { fd_set rfds; struct timeval tv; int retval; /* watch stdin (fd 0) to see when it has input. */ fd_zero(&rfds); fd_set(0, &rfds); /* wait up to five seconds. */ tv.tv_sec = 5; tv.tv_usec = 0; retval = select(1, &rfds, null, null, &tv); /* don\(aqt rely on the value of tv now! */ if (retval == \-1) perror("select()"); else if (retval) printf("data is available now.\en"); /* fd_isset(0, &rfds) will be true. */ else printf("no data within five seconds.\en"); exit(exit_success); } .ee .sh see also .br accept (2), .br connect (2), .br poll (2), .br read (2), .br recv (2), .br restart_syscall (2), .br send (2), .br sigprocmask (2), .br write (2), .br epoll (7), .br time (7) .pp for a tutorial with discussion and examples, see .br select_tut (2). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:29:54 1993 by rik faith (faith@cs.unc.edu) .th getgrent 3 2021-03-22 "" "linux programmer's manual" .sh name getgrent, setgrent, endgrent \- get group file entry .sh synopsis .nf .b #include .b #include .pp .b struct group *getgrent(void); .pp .b void setgrent(void); .b void endgrent(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br setgrent (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br getgrent (), .br endgrent (): .nf since glibc 2.22: _xopen_source >= 500 || _default_source .\" || _xopen_source && _xopen_source_extended glibc 2.21 and earlier _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br getgrent () function returns a pointer to a structure containing the broken-out fields of a record in the group database (e.g., the local group file .ir /etc/group , nis, and ldap). the first time .br getgrent () is called, it returns the first entry; thereafter, it returns successive entries. .pp the .br setgrent () function rewinds to the beginning of the group database, to allow repeated scans. .pp the .br endgrent () function is used to close the group database after all processing has been performed. .pp the \figroup\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ gid_t gr_gid; /* group id */ char **gr_mem; /* null\-terminated array of pointers to names of group members */ }; .ee .in .pp for more information about the fields of this structure, see .br group (5). .sh return value the .br getgrent () function returns a pointer to a .i group structure, or null if there are no more entries or an error occurs. .pp upon error, .i errno may be set. if one wants to check .i errno after the call, it should be set to zero before the call. .pp the return value may point to a static area, and may be overwritten by subsequent calls to .br getgrent (), .br getgrgid (3), or .br getgrnam (3). (do not pass the returned pointer to .br free (3).) .sh errors .tp .b eagain the service was temporarily unavailable; try again later. for nss backends in glibc this indicates a temporary error talking to the backend. the error may correct itself, retrying later is suggested. .tp .b eintr a signal was caught; see .br signal (7). .tp .b eio i/o error. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .\" not in posix .b enoent a necessary input file cannot be found. for nss backends in glibc this indicates the backend is not correctly configured. .tp .b enomem .\" not in posix insufficient memory to allocate .i group structure. .tp .b erange insufficient buffer space supplied. .sh files .tp .i /etc/group local group database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getgrent () t} thread safety t{ mt-unsafe race:grent race:grentbuf locale t} t{ .br setgrent (), .br endgrent () t} thread safety t{ mt-unsafe race:grent locale t} .te .hy .ad .sp 1 .pp in the above table, .i grent in .i race:grent signifies that if any of the functions .br setgrent (), .br getgrent (), or .br endgrent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br fgetgrent (3), .br getgrent_r (3), .br getgrgid (3), .br getgrnam (3), .br getgrouplist (3), .br putgrent (3), .br group (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2001 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getcontext 3 2021-03-22 "linux" "linux programmer's manual" .sh name getcontext, setcontext \- get or set the user context .sh synopsis .nf .b #include .pp .bi "int getcontext(ucontext_t *" ucp ); .bi "int setcontext(const ucontext_t *" ucp ); .fi .sh description in a system v-like environment, one has the two types .i mcontext_t and .i ucontext_t defined in .i and the four functions .br getcontext (), .br setcontext (), .br makecontext (3), and .br swapcontext (3) that allow user-level context switching between multiple threads of control within a process. .pp the .i mcontext_t type is machine-dependent and opaque. the .i ucontext_t type is a structure that has at least the following fields: .pp .in +4n .ex typedef struct ucontext_t { struct ucontext_t *uc_link; sigset_t uc_sigmask; stack_t uc_stack; mcontext_t uc_mcontext; ... } ucontext_t; .ee .in .pp with .ir sigset_t and .i stack_t defined in .ir . here .i uc_link points to the context that will be resumed when the current context terminates (in case the current context was created using .br makecontext (3)), .i uc_sigmask is the set of signals blocked in this context (see .br sigprocmask (2)), .i uc_stack is the stack used by this context (see .br sigaltstack (2)), and .i uc_mcontext is the machine-specific representation of the saved context, that includes the calling thread's machine registers. .pp the function .br getcontext () initializes the structure pointed to by .i ucp to the currently active context. .pp the function .br setcontext () restores the user context pointed to by .ir ucp . a successful call does not return. the context should have been obtained by a call of .br getcontext (), or .br makecontext (3), or received as the third argument to a signal handler (see the discussion of the .br sa_siginfo flag in .br sigaction (2)). .pp if the context was obtained by a call of .br getcontext (), program execution continues as if this call just returned. .pp if the context was obtained by a call of .br makecontext (3), program execution continues by a call to the function .i func specified as the second argument of that call to .br makecontext (3). when the function .i func returns, we continue with the .i uc_link member of the structure .i ucp specified as the first argument of that call to .br makecontext (3). when this member is null, the thread exits. .pp if the context was obtained by a call to a signal handler, then old standard text says that "program execution continues with the program instruction following the instruction interrupted by the signal". however, this sentence was removed in susv2, and the present verdict is "the result is unspecified". .sh return value when successful, .br getcontext () returns 0 and .br setcontext () does not return. on error, both return \-1 and set .i errno to indicate the error. .sh errors none defined. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getcontext (), .br setcontext () t} thread safety mt-safe race:ucp .te .hy .ad .sp 1 .sh conforming to susv2, posix.1-2001. posix.1-2008 removes the specification of .br getcontext (), citing portability issues, and recommending that applications be rewritten to use posix threads instead. .sh notes the earliest incarnation of this mechanism was the .br setjmp (3)/ longjmp (3) mechanism. since that does not define the handling of the signal context, the next stage was the .br sigsetjmp (3)/ siglongjmp (3) pair. the present mechanism gives much more control. on the other hand, there is no easy way to detect whether a return from .br getcontext () is from the first call, or via a .br setcontext () call. the user has to invent their own bookkeeping device, and a register variable won't do since registers are restored. .pp when a signal occurs, the current user context is saved and a new context is created by the kernel for the signal handler. do not leave the handler using .br longjmp (3): it is undefined what would happen with contexts. use .br siglongjmp (3) or .br setcontext () instead. .sh see also .br sigaction (2), .br sigaltstack (2), .br sigprocmask (2), .br longjmp (3), .br makecontext (3), .br sigsetjmp (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getmntent.3 .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th malloc_usable_size 3 2021-03-22 "gnu" "linux programmer's manual" .sh name malloc_usable_size \- obtain size of block of memory allocated from heap .sh synopsis .nf .b #include .pp .bi "size_t malloc_usable_size(void *" ptr ); .fi .sh description the .br malloc_usable_size () function returns the number of usable bytes in the block pointed to by .ir ptr , a pointer to a block of memory allocated by .br malloc (3) or a related function. .sh return value .br malloc_usable_size () returns the number of usable bytes in the block of allocated memory pointed to by .ir ptr . if .i ptr is null, 0 is returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br malloc_usable_size () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a gnu extension. .sh notes the value returned by .br malloc_usable_size () may be greater than the requested size of the allocation because of alignment and minimum size constraints. although the excess bytes can be overwritten by the application without ill effects, this is not good programming practice: the number of excess bytes in an allocation depends on the underlying implementation. .pp the main use of this function is for debugging and introspection. .sh see also .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man4/random.4 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and (c) copyright 2015 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-25 by rik faith (faith@cs.unc.edu) .\" modified 2004-10-31 by aeb .\" .th resolver 3 2021-03-22 "gnu" "linux programmer's manual" .sh name res_ninit, res_nclose, res_nquery, res_nsearch, res_nquerydomain, res_nmkquery, res_nsend, res_init, res_query, res_search, res_querydomain, res_mkquery, res_send, dn_comp, dn_expand \- resolver routines .sh synopsis .nf .b #include .b #include .b #include .pp .b struct __res_state; .b typedef struct __res_state *res_state; .pp .bi "int res_ninit(res_state " statep ); .pp .bi "void res_nclose(res_state " statep ); .pp .bi "int res_nquery(res_state " statep , .bi " const char *" dname ", int " class ", int " type , .bi " unsigned char *" answer ", int " anslen ); .pp .bi "int res_nsearch(res_state " statep , .bi " const char *" dname ", int " class ", int " type , .bi " unsigned char *" answer ", int " anslen ); .pp .bi "int res_nquerydomain(res_state " statep , .bi " const char *" name ", const char *" domain , .bi " int " class ", int " type ", unsigned char *" answer , .bi " int " anslen ); .pp .bi "int res_nmkquery(res_state " statep , .bi " int " op ", const char *" dname ", int " class , .bi " int " type ", const unsigned char *" data ", int " datalen , .bi " const unsigned char *" newrr , .bi " unsigned char *" buf ", int " buflen ); .pp .bi "int res_nsend(res_state " statep , .bi " const unsigned char *" msg ", int " msglen , .bi " unsigned char *" answer ", int " anslen ); .pp .bi "int dn_comp(const char *" exp_dn ", unsigned char *" comp_dn , .bi " int " length ", unsigned char **" dnptrs , .bi " unsigned char **" lastdnptr ); .pp .bi "int dn_expand(const unsigned char *" msg , .bi " const unsigned char *" eomorig , .bi " const unsigned char *" comp_dn ", char *" exp_dn , .bi " int " length ); .fi .\" .ss deprecated .nf .b extern struct __res_state _res; .pp .b int res_init(void); .pp .bi "int res_query(const char *" dname ", int " class ", int " type , .bi " unsigned char *" answer ", int " anslen ); .pp .bi "int res_search(const char *" dname ", int " class ", int " type , .bi " unsigned char *" answer ", int " anslen ); .pp .bi "int res_querydomain(const char *" name ", const char *" domain , .bi " int " class ", int " type ", unsigned char *" answer , .bi " int " anslen ); .pp .bi "int res_mkquery(int " op ", const char *" dname ", int " class , .bi " int " type ", const unsigned char *" data ", int " datalen , .bi " const unsigned char *" newrr , .bi " unsigned char *" buf ", int " buflen ); .pp .bi "int res_send(const unsigned char *" msg ", int " msglen , .bi " unsigned char *" answer ", int " anslen ); .fi .pp link with \fi\-lresolv\fp. .sh description .b note: this page is incomplete (various resolver functions provided by glibc are not described) and likely out of date. .pp the functions described below make queries to and interpret the responses from internet domain name servers. .pp the api consists of a set of more modern, reentrant functions and an older set of nonreentrant functions that have been superseded. the traditional resolver interfaces such as .br res_init () and .br res_query () use some static (global) state stored in the .i _res structure, rendering these functions non-thread-safe. bind 8.2 introduced a set of new interfaces .br res_ninit (), .br res_nquery (), and so on, which take a .i res_state as their first argument, so you can use a per-thread resolver state. .pp the .br res_ninit () and .br res_init () functions read the configuration files (see .br resolv.conf (5)) to get the default domain name and name server address(es). if no server is given, the local host is tried. if no domain is given, that associated with the local host is used. it can be overridden with the environment variable .br localdomain . .br res_ninit () or .br res_init () is normally executed by the first call to one of the other functions. every call to .br res_ninit () requires a corresponding call to .br res_nclose () to free memory allocated by .br res_ninit () and subsequent calls to .br res_nquery (). .pp the .br res_nquery () and .br res_query () functions query the name server for the fully qualified domain name \finame\fp of specified \fitype\fp and \ficlass\fp. the reply is left in the buffer \fianswer\fp of length \fianslen\fp supplied by the caller. .pp the .br res_nsearch () and .br res_search () functions make a query and waits for the response like .br res_nquery () and .br res_query (), but in addition they implement the default and search rules controlled by .b res_defnames and .b res_dnsrch (see description of \fi_res\fp options below). .pp the .br res_nquerydomain () and .br res_querydomain () functions make a query using .br res_nquery ()/ res_query () on the concatenation of \finame\fp and \fidomain\fp. .pp the following functions are lower-level routines used by .br res_nquery ()/ res_query (). .pp the .br res_nmkquery () and .br res_mkquery () functions construct a query message in \fibuf\fp of length \fibuflen\fp for the domain name \fidname\fp. the query type \fiop\fp is one of the following (typically .br query ): .tp .b query standard query. .tp .b iquery inverse query. this option was removed in glibc 2.26, .\" commit e4e794841e3140875f2aa86b90e2ada3d61e1244 since it has not been supported by dns servers for a very long time. .tp .b ns_notify_op notify secondary of soa (start of authority) change. .pp \finewrr\fp is currently unused. .pp the .br res_nsend () and .br res_send () function send a preformatted query given in \fimsg\fp of length \fimsglen\fp and returns the answer in \fianswer\fp which is of length \fianslen\fp. they will call .br res_ninit ()/ res_init () if it has not already been called. .pp the .br dn_comp () function compresses the domain name \fiexp_dn\fp and stores it in the buffer \ficomp_dn\fp of length \filength\fp. the compression uses an array of pointers \fidnptrs\fp to previously compressed names in the current message. the first pointer points to the beginning of the message and the list ends with null. the limit of the array is specified by \filastdnptr\fp. if \fidnptr\fp is null, domain names are not compressed. if \filastdnptr\fp is null, the list of labels is not updated. .pp the .br dn_expand () function expands the compressed domain name \ficomp_dn\fp to a full domain name, which is placed in the buffer \fiexp_dn\fp of size \filength\fp. the compressed name is contained in a query or reply message, and \fimsg\fp points to the beginning of the message. .pp the resolver routines use configuration and state information contained in a .ir __res_state structure (either passed as the .ir statep argument, or in the global variable .ir _res , in the case of the older nonreentrant functions). the only field of this structure that is normally manipulated by the user is the .ir options field. this field can contain the bitwise "or" of the following options: .tp .b res_init true if .br res_ninit () or .br res_init () has been called. .tp .b res_debug print debugging messages. this option is available only if glibc was built with debugging enabled, .\" see resolv/readme. .\" support for res_debug was made conditional in glibc 2.2. which is not the default. .tp .br res_aaonly " (unimplemented; deprecated in glibc 2.25)" accept authoritative answers only. .br res_send () continues until it finds an authoritative answer or returns an error. this option was present but unimplemented in glibc until version 2.24; since glibc 2.25, it is deprecated, and its usage produces a warning. .tp .b res_usevc use tcp connections for queries rather than udp datagrams. .tp .br res_primary " (unimplemented; deprecated in glibc 2.25)" query primary domain name server only. this option was present but unimplemented in glibc until version 2.24; since glibc 2.25, it is deprecated, and its usage produces a warning. .tp .b res_igntc ignore truncation errors. don't retry with tcp. .tp .b res_recurse set the recursion desired bit in queries. recursion is carried out by the domain name server, not by .br res_send (). [enabled by default]. .tp .b res_defnames if set, .br res_search () will append the default domain name to single component names\(emthat is, those that do not contain a dot. [enabled by default]. .tp .b res_stayopen used with .b res_usevc to keep the tcp connection open between queries. .tp .b res_dnsrch if set, .br res_search () will search for hostnames in the current domain and in parent domains. this option is used by .br gethostbyname (3). [enabled by default]. .tp .b res_insecure1 accept a response from a wrong server. this can be used to detect potential security hazards, but you need to compile glibc with debugging enabled and use .b res_debug option (for debug purpose only). .tp .b res_insecure2 accept a response which contains a wrong query. this can be used to detect potential security hazards, but you need to compile glibc with debugging enabled and use .b res_debug option (for debug purpose only). .tp .b res_noaliases disable usage of .b hostaliases environment variable. .tp .b res_use_inet6 try an aaaa query before an a query inside the .br gethostbyname (3) function, and map ipv4 responses in ipv6 "tunneled form" if no aaaa records are found but an a record set exists. since glibc 2.25, this option is deprecated, and its usage produces a warning; applications should use .br getaddrinfo (3), rather than .br gethostbyname (3). .tp .b res_rotate causes round-robin selection of name servers from among those listed. this has the effect of spreading the query load among all listed servers, rather than having all clients try the first listed server first every time. .tp .br res_nocheckname " (unimplemented; deprecated in glibc 2.25)" disable the modern bind checking of incoming hostnames and mail names for invalid characters such as underscore (_), non-ascii, or control characters. this option was present in glibc until version 2.24; since glibc 2.25, it is deprecated, and its usage produces a warning. .tp .br res_keeptsig " (unimplemented; deprecated in glibc 2.25)" do not strip tsig records. this option was present but unimplemented in glibc until version 2.24; since glibc 2.25, it is deprecated, and its usage produces a warning. .tp .br res_blast " (unimplemented; deprecated in glibc 2.25)" send each query simultaneously and recursively to all servers. this option was present but unimplemented in glibc until version 2.24; since glibc 2.25, it is deprecated, and its usage produces a warning. .tp .br res_usebstring " (glibc 2.3.4 to 2.24)" make reverse ipv6 lookups using the bit-label format described in rfc 2673; if this option is not set (which is the default), then nibble format is used. this option was removed in glibc 2.25, since it relied on a backward-incompatible dns extension that was never deployed on the internet. .tp .br res_noip6dotint " (glibc 2.24 and earlier)" use .i ip6.arpa zone in ipv6 reverse lookup instead of .ir ip6.int , which is deprecated since glibc 2.3.4. this option is present in glibc up to and including version 2.24, where it is enabled by default. in glibc 2.25, this option was removed. .tp .br res_use_edns0 " (since glibc 2.6)" enables support for the dns extensions (edns0) described in rfc 2671. .tp .br res_snglkup " (since glibc 2.10)" by default, glibc performs ipv4 and ipv6 lookups in parallel since version 2.9. some appliance dns servers cannot handle these queries properly and make the requests time out. this option disables the behavior and makes glibc perform the ipv6 and ipv4 requests sequentially (at the cost of some slowdown of the resolving process). .tp .b res_snglkupreop when .b res_snglkup option is enabled, opens a new socket for the each request. .tp .b res_use_dnssec use dnssec with ok bit in opt record. this option implies .br res_use_edns0 . .tp .b res_notldquery do not look up unqualified name as a top-level domain (tld). .tp .b res_default default option which implies: .br res_recurse , .br res_defnames , .br res_dnsrch , and .br res_noip6dotint . .\" .sh return value the .br res_ninit () and .br res_init () functions return 0 on success, or \-1 if an error occurs. .pp the .br res_nquery (), .br res_query (), .br res_nsearch (), .br res_search (), .br res_nquerydomain (), .br res_querydomain (), .br res_nmkquery (), .br res_mkquery (), .br res_nsend (), and .br res_send () functions return the length of the response, or \-1 if an error occurs. .pp the .br dn_comp () and .br dn_expand () functions return the length of the compressed name, or \-1 if an error occurs. .pp in the case of an error return from .br res_nquery (), .br res_query (), .br res_nsearch (), .br res_search (), .br res_nquerydomain (), or .br res_querydomain (), the global variable .i h_errno (see .br gethostbyname (3)) can be consulted to determine the cause of the error. .sh files .tp .i /etc/resolv.conf resolver configuration file .tp .i /etc/host.conf resolver configuration file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br res_ninit (), .br res_nclose (), .br res_nquery (), .br res_nsearch (), .br res_nquerydomain (), .br res_nsend () t} thread safety mt-safe locale t{ .br res_nmkquery (), .br dn_comp (), .br dn_expand () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd. .sh see also .br gethostbyname (3), .br resolv.conf (5), .br resolver (5), .br hostname (7), .br named (8) .pp the gnu c library source file .ir resolv/readme . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scandir.3 .\" copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getprotoent_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getprotoent_r, getprotobyname_r, getprotobynumber_r \- get protocol entry (reentrant) .sh synopsis .nf .b #include .pp .bi "int getprotoent_r(struct protoent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct protoent **restrict " result ); .bi "int getprotobyname_r(const char *restrict " name , .bi " struct protoent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct protoent **restrict " result ); .bi "int getprotobynumber_r(int " proto , .bi " struct protoent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct protoent **restrict " result ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getprotoent_r (), .br getprotobyname_r (), .br getprotobynumber_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the .br getprotoent_r (), .br getprotobyname_r (), and .br getprotobynumber_r () functions are the reentrant equivalents of, respectively, .br getprotoent (3), .br getprotobyname (3), and .br getprotobynumber (3). they differ in the way that the .i protoent structure is returned, and in the function calling signature and return value. this manual page describes just the differences from the nonreentrant functions. .pp instead of returning a pointer to a statically allocated .i protoent structure as the function result, these functions copy the structure into the location pointed to by .ir result_buf . .pp the .i buf array is used to store the string fields pointed to by the returned .i protoent structure. (the nonreentrant functions allocate these strings in static storage.) the size of this array is specified in .ir buflen . if .i buf is too small, the call fails with the error .br erange , and the caller must try again with a larger buffer. (a buffer of length 1024 bytes should be sufficient for most applications.) .\" i can find no information on the required/recommended buffer size; .\" the nonreentrant functions use a 1024 byte buffer. .\" the 1024 byte value is also what the solaris man page suggests. -- mtk .pp if the function call successfully obtains a protocol record, then .i *result is set pointing to .ir result_buf ; otherwise, .i *result is set to null. .sh return value on success, these functions return 0. on error, they return one of the positive error numbers listed in errors. .pp on error, record not found .rb ( getprotobyname_r (), .br getprotobynumber_r ()), or end of input .rb ( getprotoent_r ()) .i result is set to null. .sh errors .tp .b enoent .rb ( getprotoent_r ()) no more records in database. .tp .b erange .i buf is too small. try again with a larger buffer (and increased .ir buflen ). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getprotoent_r (), .br getprotobyname_r (), .br getprotobynumber_r () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. functions with similar names exist on some other systems, though typically with different calling signatures. .sh examples the program below uses .br getprotobyname_r () to retrieve the protocol record for the protocol named in its first command-line argument. if a second (integer) command-line argument is supplied, it is used as the initial value for .ir buflen ; if .br getprotobyname_r () fails with the error .br erange , the program retries with larger buffer sizes. the following shell session shows a couple of sample runs: .pp .in +4n .ex .rb "$" " ./a.out tcp 1" erange! retrying with larger buffer getprotobyname_r() returned: 0 (success) (buflen=78) p_name=tcp; p_proto=6; aliases=tcp .rb "$" " ./a.out xxx 1" erange! retrying with larger buffer getprotobyname_r() returned: 0 (success) (buflen=100) call failed/record not found .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include #define max_buf 10000 int main(int argc, char *argv[]) { int buflen, erange_cnt, s; struct protoent result_buf; struct protoent *result; char buf[max_buf]; if (argc < 2) { printf("usage: %s proto\-name [buflen]\en", argv[0]); exit(exit_failure); } buflen = 1024; if (argc > 2) buflen = atoi(argv[2]); if (buflen > max_buf) { printf("exceeded buffer limit (%d)\en", max_buf); exit(exit_failure); } erange_cnt = 0; do { s = getprotobyname_r(argv[1], &result_buf, buf, buflen, &result); if (s == erange) { if (erange_cnt == 0) printf("erange! retrying with larger buffer\en"); erange_cnt++; /* increment a byte at a time so we can see exactly what size buffer was required. */ buflen++; if (buflen > max_buf) { printf("exceeded buffer limit (%d)\en", max_buf); exit(exit_failure); } } } while (s == erange); printf("getprotobyname_r() returned: %s (buflen=%d)\en", (s == 0) ? "0 (success)" : (s == enoent) ? "enoent" : strerror(s), buflen); if (s != 0 || result == null) { printf("call failed/record not found\en"); exit(exit_failure); } printf("p_name=%s; p_proto=%d; aliases=", result_buf.p_name, result_buf.p_proto); for (char **p = result_buf.p_aliases; *p != null; p++) printf("%s ", *p); printf("\en"); exit(exit_success); } .ee .sh see also .br getprotoent (3), .br protocols (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/listxattr.2 .so man3/exp2.3 .\" copyright (c) 2015 michael kerrisk .\" .\" %%%license_start(gplv2+) .\" .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th posix_madvise 3 2021-03-22 linux "linux programmer's manual" .sh name posix_madvise \- give advice about patterns of memory usage .sh synopsis .nf .b #include .pp .bi "int posix_madvise(void *" addr ", size_t " len ", int " advice ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br posix_madvise (): .nf _posix_c_source >= 200112l .fi .sh description the .br posix_madvise () function allows an application to advise the system about its expected patterns of usage of memory in the address range starting at .i addr and continuing for .i len bytes. the system is free to use this advice in order to improve the performance of memory accesses (or to ignore the advice altogether), but calling .br posix_madvise () shall not affect the semantics of access to memory in the specified range. .pp the .i advice argument is one of the following: .tp .b posix_madv_normal the application has no special advice regarding its memory usage patterns for the specified address range. this is the default behavior. .tp .b posix_madv_sequential the application expects to access the specified address range sequentially, running from lower addresses to higher addresses. hence, pages in this region can be aggressively read ahead, and may be freed soon after they are accessed. .tp .b posix_madv_random the application expects to access the specified address range randomly. thus, read ahead may be less useful than normally. .tp .b posix_madv_willneed the application expects to access the specified address range in the near future. thus, read ahead may be beneficial. .tp .b posix_madv_dontneed the application expects that it will not access the specified address range in the near future. .sh return value on success, .br posix_madvise () returns 0. on failure, it returns a positive error number. .sh errors .tp .b einval .i addr is not a multiple of the system page size or .i len is negative. .tp .b einval .i advice is invalid. .tp .b enomem addresses in the specified range are partially or completely outside the caller's address space. .sh versions support for .br posix_madvise () first appeared in glibc version 2.2. .sh conforming to posix.1-2001. .sh notes posix.1 permits an implementation to generate an error if .i len is 0. on linux, specifying .i len as 0 is permitted (as a successful no-op). .pp in glibc, this function is implemented using .br madvise (2). however, since glibc 2.6, .br posix_madv_dontneed is treated as a no-op, because the corresponding .br madvise (2) value, .br madv_dontneed , has destructive semantics. .sh see also .br madvise (2), .br posix_fadvise (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)daemon.3 8.1 (berkeley) 6/9/93 .\" added mentioning of glibc weirdness wrt unistd.h. 5/11/98, al viro .th daemon 3 2021-03-22 "gnu" "linux programmer's manual" .sh name daemon \- run in the background .sh synopsis .nf .b #include .pp .bi "int daemon(int " nochdir ", int " noclose ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br daemon (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description the .br daemon () function is for programs wishing to detach themselves from the controlling terminal and run in the background as system daemons. .pp if .i nochdir is zero, .br daemon () changes the process's current working directory to the root directory ("/"); otherwise, the current working directory is left unchanged. .pp if .i noclose is zero, .br daemon () redirects standard input, standard output, and standard error to .ir /dev/null ; otherwise, no changes are made to these file descriptors. .sh return value (this function forks, and if the .br fork (2) succeeds, the parent calls .\" not .ir in order not to underline _ .br _exit (2), so that further errors are seen by the child only.) on success .br daemon () returns zero. if an error occurs, .br daemon () returns \-1 and sets .i errno to any of the errors specified for the .br fork (2) and .br setsid (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br daemon () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to not in posix.1. a similar function appears on the bsds. the .br daemon () function first appeared in 4.4bsd. .sh notes the glibc implementation can also return \-1 when .i /dev/null exists but is not a character device with the expected major and minor numbers. in this case, .i errno need not be set. .sh bugs the gnu c library implementation of this function was taken from bsd, and does not employ the double-fork technique (i.e., .br fork (2), .br setsid (2), .br fork (2)) that is necessary to ensure that the resulting daemon process is not a session leader. instead, the resulting daemon .i is a session leader. .\" fixme . https://sourceware.org/bugzilla/show_bug.cgi?id=19144 .\" tested using a program that uses daemon() and then opens an .\" otherwise unused console device (/dev/ttyn) that does not .\" have an associated getty process. on systems that follow system v semantics (e.g., linux), this means that if the daemon opens a terminal that is not already a controlling terminal for another session, then that terminal will inadvertently become the controlling terminal for the daemon. .sh see also .br fork (2), .br setsid (2), .br daemon (7), .br logrotate (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/malloc_hook.3 .so man3/statvfs.3 .\" copyright (c) 2019 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pidfd_send_signal 2 2021-03-22 "linux" "linux programmer's manual" .sh name pidfd_send_signal \- send a signal to a process specified by a file descriptor .sh synopsis .nf .br "#include " " /* definition of " sig* " constants */" .br "#include " " /* definition of " si_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_pidfd_send_signal, int " pidfd ", int " sig \ ", siginfo_t *" info , .bi " unsigned int " flags ); .fi .pp .ir note : glibc provides no wrapper for .br pidfd_send_signal (), necessitating the use of .br syscall (2). .sh description the .br pidfd_send_signal () system call sends the signal .i sig to the target process referred to by .ir pidfd , a pid file descriptor that refers to a process. .\" see the very detailed commit message for kernel commit .\" 3eb39f47934f9d5a3027fe00d906a45fe3a15fad .pp if the .i info argument points to a .i siginfo_t buffer, that buffer should be populated as described in .br rt_sigqueueinfo (2). .pp if the .i info argument is a null pointer, this is equivalent to specifying a pointer to a .i siginfo_t buffer whose fields match the values that are implicitly supplied when a signal is sent using .br kill (2): .pp .pd 0 .ip * 3 .i si_signo is set to the signal number; .ip * .i si_errno is set to 0; .ip * .i si_code is set to .br si_user ; .ip * .i si_pid is set to the caller's pid; and .ip * .i si_uid is set to the caller's real user id. .pd .pp the calling process must either be in the same pid namespace as the process referred to by .ir pidfd , or be in an ancestor of that namespace. .pp the .i flags argument is reserved for future use; currently, this argument must be specified as 0. .sh return value on success, .br pidfd_send_signal () returns 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i pidfd is not a valid pid file descriptor. .tp .b einval .i sig is not a valid signal. .tp .b einval the calling process is not in a pid namespace from which it can send a signal to the target process. .tp .b einval .i flags is not 0. .tp .b eperm the calling process does not have permission to send the signal to the target process. .tp .b eperm .i pidfd doesn't refer to the calling process, and .ir info.si_code is invalid (see .br rt_sigqueueinfo (2)). .tp .b esrch the target process does not exist (i.e., it has terminated and been waited on). .sh versions .br pidfd_send_signal () first appeared in linux 5.1. .sh conforming to .br pidfd_send_signal () is linux specific. .sh notes .ss pid file descriptors the .i pidfd argument is a pid file descriptor, a file descriptor that refers to process. such a file descriptor can be obtained in any of the following ways: .ip * 3 by opening a .ir /proc/[pid] directory; .ip * using .br pidfd_open (2); or .ip * via the pid file descriptor that is returned by a call to .br clone (2) or .br clone3 (2) that specifies the .br clone_pidfd flag. .pp the .br pidfd_send_signal () system call allows the avoidance of race conditions that occur when using traditional interfaces (such as .br kill (2)) to signal a process. the problem is that the traditional interfaces specify the target process via a process id (pid), with the result that the sender may accidentally send a signal to the wrong process if the originally intended target process has terminated and its pid has been recycled for another process. by contrast, a pid file descriptor is a stable reference to a specific process; if that process terminates, .br pidfd_send_signal () fails with the error .br esrch . .sh examples .ex #define _gnu_source #include #include #include #include #include #include #include #include #ifndef __nr_pidfd_send_signal #define __nr_pidfd_send_signal 424 #endif static int pidfd_send_signal(int pidfd, int sig, siginfo_t *info, unsigned int flags) { return syscall(__nr_pidfd_send_signal, pidfd, sig, info, flags); } int main(int argc, char *argv[]) { siginfo_t info; char path[path_max]; int pidfd, sig; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } sig = atoi(argv[2]); /* obtain a pid file descriptor by opening the /proc/pid directory of the target process. */ snprintf(path, sizeof(path), "/proc/%s", argv[1]); pidfd = open(path, o_rdonly); if (pidfd == \-1) { perror("open"); exit(exit_failure); } /* populate a \(aqsiginfo_t\(aq structure for use with pidfd_send_signal(). */ memset(&info, 0, sizeof(info)); info.si_code = si_queue; info.si_signo = sig; info.si_errno = 0; info.si_uid = getuid(); info.si_pid = getpid(); info.si_value.sival_int = 1234; /* send the signal. */ if (pidfd_send_signal(pidfd, sig, &info, 0) == \-1) { perror("pidfd_send_signal"); exit(exit_failure); } exit(exit_success); } .ee .sh see also .br clone (2), .br kill (2), .br pidfd_open (2), .br rt_sigqueueinfo (2), .br sigaction (2), .br pid_namespaces (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/hypot.3 .so man3/list.3 .so man2/outb.2 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-10-22 by eric s. raymond .\" modified oct 1998 by andi kleen .\" modified oct 2003 by aeb .\" modified 2004-07-01 by mtk .\" .th send 2 2021-03-22 "linux" "linux programmer's manual" .sh name send, sendto, sendmsg \- send a message on a socket .sh synopsis .nf .b #include .pp .bi "ssize_t send(int " sockfd ", const void *" buf ", size_t " len \ ", int " flags ); .bi "ssize_t sendto(int " sockfd ", const void *" buf ", size_t " len \ ", int " flags , .bi " const struct sockaddr *" dest_addr ", socklen_t " addrlen ); .bi "ssize_t sendmsg(int " sockfd ", const struct msghdr *" msg \ ", int " flags ); .fi .sh description the system calls .br send (), .br sendto (), and .br sendmsg () are used to transmit a message to another socket. .pp the .br send () call may be used only when the socket is in a .i connected state (so that the intended recipient is known). the only difference between .br send () and .br write (2) is the presence of .ir flags . with a zero .i flags argument, .br send () is equivalent to .br write (2). also, the following call .pp send(sockfd, buf, len, flags); .pp is equivalent to .pp sendto(sockfd, buf, len, flags, null, 0); .pp the argument .i sockfd is the file descriptor of the sending socket. .pp if .br sendto () is used on a connection-mode .rb ( sock_stream , .br sock_seqpacket ) socket, the arguments .i dest_addr and .i addrlen are ignored (and the error .b eisconn may be returned when they are not null and 0), and the error .b enotconn is returned when the socket was not actually connected. otherwise, the address of the target is given by .i dest_addr with .i addrlen specifying its size. for .br sendmsg (), the address of the target is given by .ir msg.msg_name , with .i msg.msg_namelen specifying its size. .pp for .br send () and .br sendto (), the message is found in .i buf and has length .ir len . for .br sendmsg (), the message is pointed to by the elements of the array .ir msg.msg_iov . the .br sendmsg () call also allows sending ancillary data (also known as control information). .pp if the message is too long to pass atomically through the underlying protocol, the error .b emsgsize is returned, and the message is not transmitted. .pp no indication of failure to deliver is implicit in a .br send (). locally detected errors are indicated by a return value of \-1. .pp when the message does not fit into the send buffer of the socket, .br send () normally blocks, unless the socket has been placed in nonblocking i/o mode. in nonblocking mode it would fail with the error .b eagain or .b ewouldblock in this case. the .br select (2) call may be used to determine when it is possible to send more data. .ss the flags argument the .i flags argument is the bitwise or of zero or more of the following flags. .\" fixme . ? document msg_proxy (which went away in 2.3.15) .tp .br msg_confirm " (since linux 2.3.15)" tell the link layer that forward progress happened: you got a successful reply from the other side. if the link layer doesn't get this it will regularly reprobe the neighbor (e.g., via a unicast arp). valid only on .b sock_dgram and .b sock_raw sockets and currently implemented only for ipv4 and ipv6. see .br arp (7) for details. .tp .b msg_dontroute don't use a gateway to send out the packet, send to hosts only on directly connected networks. this is usually used only by diagnostic or routing programs. this is defined only for protocol families that route; packet sockets don't. .tp .br msg_dontwait " (since linux 2.2)" enables nonblocking operation; if the operation would block, .b eagain or .b ewouldblock is returned. this provides similar behavior to setting the .b o_nonblock flag (via the .br fcntl (2) .b f_setfl operation), but differs in that .b msg_dontwait is a per-call option, whereas .b o_nonblock is a setting on the open file description (see .br open (2)), which will affect all threads in the calling process and as well as other processes that hold file descriptors referring to the same open file description. .tp .br msg_eor " (since linux 2.2)" terminates a record (when this notion is supported, as for sockets of type .br sock_seqpacket ). .tp .br msg_more " (since linux 2.4.4)" the caller has more data to send. this flag is used with tcp sockets to obtain the same effect as the .b tcp_cork socket option (see .br tcp (7)), with the difference that this flag can be set on a per-call basis. .ip since linux 2.6, this flag is also supported for udp sockets, and informs the kernel to package all of the data sent in calls with this flag set into a single datagram which is transmitted only when a call is performed that does not specify this flag. (see also the .b udp_cork socket option described in .br udp (7).) .tp .br msg_nosignal " (since linux 2.2)" don't generate a .b sigpipe signal if the peer on a stream-oriented socket has closed the connection. the .b epipe error is still returned. this provides similar behavior to using .br sigaction (2) to ignore .br sigpipe , but, whereas .b msg_nosignal is a per-call feature, ignoring .b sigpipe sets a process attribute that affects all threads in the process. .tp .b msg_oob sends .i out-of-band data on sockets that support this notion (e.g., of type .br sock_stream ); the underlying protocol must also support .i out-of-band data. .ss sendmsg() the definition of the .i msghdr structure employed by .br sendmsg () is as follows: .pp .in +4n .ex struct msghdr { void *msg_name; /* optional address */ socklen_t msg_namelen; /* size of address */ struct iovec *msg_iov; /* scatter/gather array */ size_t msg_iovlen; /* # elements in msg_iov */ void *msg_control; /* ancillary data, see below */ size_t msg_controllen; /* ancillary data buffer len */ int msg_flags; /* flags (unused) */ }; .ee .in .pp the .i msg_name field is used on an unconnected socket to specify the target address for a datagram. it points to a buffer containing the address; the .i msg_namelen field should be set to the size of the address. for a connected socket, these fields should be specified as null and 0, respectively. .pp the .i msg_iov and .i msg_iovlen fields specify scatter-gather locations, as for .br writev (2). .pp you may send control information (ancillary data) using the .i msg_control and .i msg_controllen members. the maximum control buffer length the kernel can process is limited per socket by the value in .ir /proc/sys/net/core/optmem_max ; see .br socket (7). for further information on the use of ancillary data in various socket domains, see .br unix (7) and .br ip (7). .pp the .i msg_flags field is ignored. .\" still to be documented: .\" send file descriptors and user credentials using the .\" msg_control* fields. .sh return value on success, these calls return the number of bytes sent. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors these are some standard errors generated by the socket layer. additional errors may be generated and returned from the underlying protocol modules; see their respective manual pages. .tp .b eacces (for unix domain sockets, which are identified by pathname) write permission is denied on the destination socket file, or search permission is denied for one of the directories the path prefix. (see .br path_resolution (7).) .ip (for udp sockets) an attempt was made to send to a network/broadcast address as though it was a unicast address. .tp .br eagain " or " ewouldblock .\" actually eagain on linux the socket is marked nonblocking and the requested operation would block. posix.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities. .tp .b eagain (internet domain datagram sockets) the socket referred to by .i sockfd had not previously been bound to an address and, upon attempting to bind it to an ephemeral port, it was determined that all port numbers in the ephemeral port range are currently in use. see the discussion of .i /proc/sys/net/ipv4/ip_local_port_range in .br ip (7). .tp .b ealready another fast open is in progress. .tp .b ebadf .i sockfd is not a valid open file descriptor. .tp .b econnreset connection reset by peer. .tp .b edestaddrreq the socket is not connection-mode, and no peer address is set. .tp .b efault an invalid user space address was specified for an argument. .tp .b eintr a signal occurred before any data was transmitted; see .br signal (7). .tp .b einval invalid argument passed. .tp .b eisconn the connection-mode socket was connected already but a recipient was specified. (now either this error is returned, or the recipient specification is ignored.) .tp .b emsgsize the socket type .\" (e.g., sock_dgram ) requires that message be sent atomically, and the size of the message to be sent made this impossible. .tp .b enobufs the output queue for a network interface was full. this generally indicates that the interface has stopped sending, but may be caused by transient congestion. (normally, this does not occur in linux. packets are just silently dropped when a device queue overflows.) .tp .b enomem no memory available. .tp .b enotconn the socket is not connected, and no target has been given. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .tp .b eopnotsupp some bit in the .i flags argument is inappropriate for the socket type. .tp .b epipe the local end has been shut down on a connection oriented socket. in this case, the process will also receive a .b sigpipe unless .b msg_nosignal is set. .sh conforming to 4.4bsd, svr4, posix.1-2001. these interfaces first appeared in 4.2bsd. .pp posix.1-2001 describes only the .b msg_oob and .b msg_eor flags. posix.1-2008 adds a specification of .br msg_nosignal . the .b msg_confirm flag is a linux extension. .sh notes according to posix.1-2001, the .i msg_controllen field of the .i msghdr structure should be typed as .ir socklen_t , and the .i msg_iovlen field should be typed as .ir int , but glibc currently types both as .ir size_t . .\" glibc bug for msg_controllen raised 12 mar 2006 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=2448 .\" the problem is an underlying kernel issue: the size of the .\" __kernel_size_t type used to type these fields varies .\" across architectures, but socklen_t is always 32 bits, .\" as (at least with gcc) is int. .pp see .br sendmmsg (2) for information about a linux-specific system call that can be used to transmit multiple datagrams in a single call. .sh bugs linux may return .b epipe instead of .br enotconn . .sh examples an example of the use of .br sendto () is shown in .br getaddrinfo (3). .sh see also .br fcntl (2), .br getsockopt (2), .br recv (2), .br select (2), .br sendfile (2), .br sendmmsg (2), .br shutdown (2), .br socket (2), .br write (2), .br cmsg (3), .br ip (7), .br ipv6 (7), .br socket (7), .br tcp (7), .br udp (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdin.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcscspn 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcscspn \- search a wide-character string for any of a set of wide characters .sh synopsis .nf .b #include .pp .bi "size_t wcscspn(const wchar_t *" wcs ", const wchar_t *" reject ); .fi .sh description the .br wcscspn () function is the wide-character equivalent of the .br strcspn (3) function. it determines the length of the longest initial segment of .i wcs which consists entirely of wide-characters not listed in .ir reject . in other words, it searches for the first occurrence in the wide-character string .i wcs of any of the characters in the wide-character string .ir reject . .sh return value the .br wcscspn () function returns the number of wide characters in the longest initial segment of .i wcs which consists entirely of wide-characters not listed in .ir reject . in other words, it returns the position of the first occurrence in the wide-character string .i wcs of any of the characters in the wide-character string .ir reject , or .ir wcslen(wcs) if there is none. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcscspn () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strcspn (3), .br wcspbrk (3), .br wcsspn (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2007 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2007-06-13 creation .\" .th credentials 7 2020-11-01 "linux" "linux programmer's manual" .sh name credentials \- process identifiers .sh description .ss process id (pid) each process has a unique nonnegative integer identifier that is assigned when the process is created using .br fork (2). a process can obtain its pid using .br getpid (2). a pid is represented using the type .i pid_t (defined in .ir ). .pp pids are used in a range of system calls to identify the process affected by the call, for example: .br kill (2), .br ptrace (2), .br setpriority (2) .\" .br sched_rr_get_interval (2), .\" .br sched_getaffinity (2), .\" .br sched_setaffinity (2), .\" .br sched_getparam (2), .\" .br sched_setparam (2), .\" .br sched_setscheduler (2), .\" .br sched_getscheduler (2), .br setpgid (2), .\" .br getsid (2), .br setsid (2), .br sigqueue (3), and .br waitpid (2). .\" .br waitid (2), .\" .br wait4 (2), .pp a process's pid is preserved across an .br execve (2). .ss parent process id (ppid) a process's parent process id identifies the process that created this process using .br fork (2). a process can obtain its ppid using .br getppid (2). a ppid is represented using the type .ir pid_t . .pp a process's ppid is preserved across an .br execve (2). .ss process group id and session id each process has a session id and a process group id, both represented using the type .ir pid_t . a process can obtain its session id using .br getsid (2), and its process group id using .br getpgrp (2). .pp a child created by .br fork (2) inherits its parent's session id and process group id. a process's session id and process group id are preserved across an .br execve (2). .pp sessions and process groups are abstractions devised to support shell job control. a process group (sometimes called a "job") is a collection of processes that share the same process group id; the shell creates a new process group for the process(es) used to execute single command or pipeline (e.g., the two processes created to execute the command "ls\ |\ wc" are placed in the same process group). a process's group membership can be set using .br setpgid (2). the process whose process id is the same as its process group id is the \fiprocess group leader\fp for that group. .pp a session is a collection of processes that share the same session id. all of the members of a process group also have the same session id (i.e., all of the members of a process group always belong to the same session, so that sessions and process groups form a strict two-level hierarchy of processes.) a new session is created when a process calls .br setsid (2), which creates a new session whose session id is the same as the pid of the process that called .br setsid (2). the creator of the session is called the \fisession leader\fp. .pp all of the processes in a session share a .ir "controlling terminal" . the controlling terminal is established when the session leader first opens a terminal (unless the .br o_noctty flag is specified when calling .br open (2)). a terminal may be the controlling terminal of at most one session. .pp at most one of the jobs in a session may be the .ir "foreground job" ; other jobs in the session are .ir "background jobs" . only the foreground job may read from the terminal; when a process in the background attempts to read from the terminal, its process group is sent a .br sigttin signal, which suspends the job. if the .br tostop flag has been set for the terminal (see .br termios (3)), then only the foreground job may write to the terminal; writes from background job cause a .br sigttou signal to be generated, which suspends the job. when terminal keys that generate a signal (such as the .i interrupt key, normally control-c) are pressed, the signal is sent to the processes in the foreground job. .pp various system calls and library functions may operate on all members of a process group, including .br kill (2), .br killpg (3), .br getpriority (2), .br setpriority (2), .br ioprio_get (2), .br ioprio_set (2), .br waitid (2), and .br waitpid (2). see also the discussion of the .br f_getown , .br f_getown_ex , .br f_setown , and .br f_setown_ex operations in .br fcntl (2). .ss user and group identifiers each process has various associated user and group ids. these ids are integers, respectively represented using the types .i uid_t and .i gid_t (defined in .ir ). .pp on linux, each process has the following user and group identifiers: .ip * 3 real user id and real group id. these ids determine who owns the process. a process can obtain its real user (group) id using .br getuid (2) .rb ( getgid (2)). .ip * effective user id and effective group id. these ids are used by the kernel to determine the permissions that the process will have when accessing shared resources such as message queues, shared memory, and semaphores. on most unix systems, these ids also determine the permissions when accessing files. however, linux uses the filesystem ids described below for this task. a process can obtain its effective user (group) id using .br geteuid (2) .rb ( getegid (2)). .ip * saved set-user-id and saved set-group-id. these ids are used in set-user-id and set-group-id programs to save a copy of the corresponding effective ids that were set when the program was executed (see .br execve (2)). a set-user-id program can assume and drop privileges by switching its effective user id back and forth between the values in its real user id and saved set-user-id. this switching is done via calls to .br seteuid (2), .br setreuid (2), or .br setresuid (2). a set-group-id program performs the analogous tasks using .br setegid (2), .br setregid (2), or .br setresgid (2). a process can obtain its saved set-user-id (set-group-id) using .br getresuid (2) .rb ( getresgid (2)). .ip * filesystem user id and filesystem group id (linux-specific). these ids, in conjunction with the supplementary group ids described below, are used to determine permissions for accessing files; see .br path_resolution (7) for details. whenever a process's effective user (group) id is changed, the kernel also automatically changes the filesystem user (group) id to the same value. consequently, the filesystem ids normally have the same values as the corresponding effective id, and the semantics for file-permission checks are thus the same on linux as on other unix systems. the filesystem ids can be made to differ from the effective ids by calling .br setfsuid (2) and .br setfsgid (2). .ip * supplementary group ids. this is a set of additional group ids that are used for permission checks when accessing files and other shared resources. on linux kernels before 2.6.4, a process can be a member of up to 32 supplementary groups; since kernel 2.6.4, a process can be a member of up to 65536 supplementary groups. the call .i sysconf(_sc_ngroups_max) can be used to determine the number of supplementary groups of which a process may be a member. .\" since kernel 2.6.4, the limit is visible via the read-only file .\" /proc/sys/kernel/ngroups_max. .\" as at 2.6.22-rc2, this file is still read-only. a process can obtain its set of supplementary group ids using .br getgroups (2). .pp a child process created by .br fork (2) inherits copies of its parent's user and groups ids. during an .br execve (2), a process's real user and group id and supplementary group ids are preserved; the effective and saved set ids may be changed, as described in .br execve (2). .pp aside from the purposes noted above, a process's user ids are also employed in a number of other contexts: .ip * 3 when determining the permissions for sending signals (see .br kill (2)); .ip * when determining the permissions for setting process-scheduling parameters (nice value, real time scheduling policy and priority, cpu affinity, i/o priority) using .br setpriority (2), .br sched_setaffinity (2), .br sched_setscheduler (2), .br sched_setparam (2), .br sched_setattr (2), and .br ioprio_set (2); .ip * when checking resource limits (see .br getrlimit (2)); .ip * when checking the limit on the number of inotify instances that the process may create (see .br inotify (7)). .\" .ss modifying process user and group ids subject to rules described in the relevant manual pages, a process can use the following apis to modify its user and group ids: .tp .br setuid "(2) (" setgid (2)) modify the process's real (and possibly effective and saved-set) user (group) ids. .tp .br seteuid "(2) (" setegid (2)) modify the process's effective user (group) id. .tp .br setfsuid "(2) (" setfsgid (2)) modify the process's filesystem user (group) id. .tp .br setreuid "(2) (" setregid (2)) modify the process's real and effective (and possibly saved-set) user (group) ids. .tp .br setresuid "(2) (" setresgid (2)) modify the process's real, effective, and saved-set user (group) ids. .tp .br setgroups (2) modify the process's supplementary group list. .pp any changes to a process's effective user (group) id are automatically carried over to the process's filesystem user (group) id. changes to a process's effective user or group id can also affect the process "dumpable" attribute, as described in .br prctl (2). .pp changes to process user and group ids can affect the capabilities of the process, as described in .br capabilities (7). .sh conforming to process ids, parent process ids, process group ids, and session ids are specified in posix.1. the real, effective, and saved set user and groups ids, and the supplementary group ids, are specified in posix.1. the filesystem user and group ids are a linux extension. .sh notes various fields in the .ir /proc/[pid]/status file show the process credentials described above. see .br proc (5) for further information. .pp the posix threads specification requires that credentials are shared by all of the threads in a process. however, at the kernel level, linux maintains separate user and group credentials for each thread. the nptl threading implementation does some work to ensure that any change to user or group credentials (e.g., calls to .br setuid (2), .br setresuid (2)) is carried through to all of the posix threads in a process. see .br nptl (7) for further details. .sh see also .br bash (1), .br csh (1), .br groups (1), .br id (1), .br newgrp (1), .br ps (1), .br runuser (1), .br setpriv (1), .br sg (1), .br su (1), .br access (2), .br execve (2), .br faccessat (2), .br fork (2), .br getgroups (2), .br getpgrp (2), .br getpid (2), .br getppid (2), .br getsid (2), .br kill (2), .br setegid (2), .br seteuid (2), .br setfsgid (2), .br setfsuid (2), .br setgid (2), .br setgroups (2), .br setpgid (2), .br setresgid (2), .br setresuid (2), .br setsid (2), .br setuid (2), .br waitpid (2), .br euidaccess (3), .br initgroups (3), .br killpg (3), .br tcgetpgrp (3), .br tcgetsid (3), .br tcsetpgrp (3), .br group (5), .br passwd (5), .br shadow (5), .br capabilities (7), .br namespaces (7), .br path_resolution (7), .br pid_namespaces (7), .br pthreads (7), .br signal (7), .br system_data_types (7), .br unix (7), .br user_namespaces (7), .br sudo (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:06:49 1993 by rik faith (faith@cs.unc.edu) .\" modified fri aug 25 23:17:51 1995 by andries brouwer (aeb@cwi.nl) .\" modified wed dec 18 00:47:18 1996 by andries brouwer (aeb@cwi.nl) .\" 2007-06-15, marc boyer + mtk .\" improve discussion of strncpy(). .\" .th strcpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strcpy, strncpy \- copy a string .sh synopsis .nf .b #include .pp .bi "char *strcpy(char *restrict " dest ", const char *" src ); .bi "char *strncpy(char *restrict " dest ", const char *restrict " src \ ", size_t " n ); .fi .sh description the .br strcpy () function copies the string pointed to by .ir src , including the terminating null byte (\(aq\e0\(aq), to the buffer pointed to by .ir dest . the strings may not overlap, and the destination string .i dest must be large enough to receive the copy. .ir "beware of buffer overruns!" (see bugs.) .pp the .br strncpy () function is similar, except that at most .i n bytes of .i src are copied. .br warning : if there is no null byte among the first .i n bytes of .ir src , the string placed in .i dest will not be null-terminated. .pp if the length of .i src is less than .ir n , .br strncpy () writes additional null bytes to .i dest to ensure that a total of .i n bytes are written. .pp a simple implementation of .br strncpy () might be: .pp .in +4n .ex char * strncpy(char *dest, const char *src, size_t n) { size_t i; for (i = 0; i < n && src[i] != \(aq\e0\(aq; i++) dest[i] = src[i]; for ( ; i < n; i++) dest[i] = \(aq\e0\(aq; return dest; } .ee .in .sh return value the .br strcpy () and .br strncpy () functions return a pointer to the destination string .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strcpy (), .br strncpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes some programmers consider .br strncpy () to be inefficient and error prone. if the programmer knows (i.e., includes code to test!) that the size of .i dest is greater than the length of .ir src , then .br strcpy () can be used. .pp one valid (and intended) use of .br strncpy () is to copy a c string to a fixed-length buffer while ensuring both that the buffer is not overflowed and that unused bytes in the destination buffer are zeroed out (perhaps to prevent information leaks if the buffer is to be written to media or transmitted to another process via an interprocess communication technique). .pp if there is no terminating null byte in the first .i n bytes of .ir src , .br strncpy () produces an unterminated string in .ir dest . if .i buf has length .ir buflen , you can force termination using something like the following: .pp .in +4n .ex if (buflen > 0) { strncpy(buf, str, buflen \- 1); buf[buflen \- 1]= \(aq\e0\(aq; } .ee .in .pp (of course, the above technique ignores the fact that, if .i src contains more than .i "buflen\ \-\ 1" bytes, information is lost in the copying to .ir dest .) .\" .ss strlcpy() some systems (the bsds, solaris, and others) provide the following function: .pp size_t strlcpy(char *dest, const char *src, size_t size); .pp .\" http://static.usenix.org/event/usenix99/full_papers/millert/millert_html/index.html .\" "strlcpy and strlcat - consistent, safe, string copy and concatenation" .\" 1999 usenix annual technical conference this function is similar to .br strncpy (), but it copies at most .i size\-1 bytes to .ir dest , always adds a terminating null byte, and does not pad the destination with (further) null bytes. this function fixes some of the problems of .br strcpy () and .br strncpy (), but the caller must still handle the possibility of data loss if .i size is too small. the return value of the function is the length of .ir src , which allows truncation to be easily detected: if the return value is greater than or equal to .ir size , truncation occurred. if loss of data matters, the caller .i must either check the arguments before the call, or test the function return value. .br strlcpy () is not present in glibc and is not standardized by posix, .\" https://lwn.net/articles/506530/ but is available on linux via the .ir libbsd library. .sh bugs if the destination string of a .br strcpy () is not large enough, then anything might happen. overflowing fixed-length string buffers is a favorite cracker technique for taking complete control of the machine. any time a program reads or copies data into a buffer, the program first needs to check that there's enough space. this may be unnecessary if you can show that overflow is impossible, but be careful: programs can get changed over time, in ways that may make the impossible possible. .sh see also .br bcopy (3), .br memccpy (3), .br memcpy (3), .br memmove (3), .br stpcpy (3), .br stpncpy (3), .br strdup (3), .br string (3), .br wcscpy (3), .br wcsncpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getutent.3 .so man3/stdio_ext.3 .so man3/getprotoent.3 .\" copyright (c) 2015-2016, alec leamas .\" copyright (c) 2018, sean young .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th lirc 4 2019-03-06 "linux" "linux programmer's manual" .sh name lirc \- lirc devices .sh description the .i /dev/lirc* character devices provide a low-level bidirectional interface to infra-red (ir) remotes. most of these devices can receive, and some can send. when receiving or sending data, the driver works in two different modes depending on the underlying hardware. .pp some hardware (typically tv-cards) decodes the ir signal internally and provides decoded button presses as scancode values. drivers for this kind of hardware work in .br lirc_mode_scancode mode. such hardware usually does not support sending ir signals. furthermore, such hardware can only decode a limited set of ir protocols, usually only the protocol of the specific remote which is bundled with, for example, a tv-card. .pp other hardware provides a stream of pulse/space durations. such drivers work in .br lirc_mode_mode2 mode. sometimes, this kind of hardware also supports sending ir data. such hardware can be used with (almost) any kind of remote. this type of hardware can also be used in .br lirc_mode_scancode mode, in which case the kernel ir decoders will decode the ir. these decoders can be written in extended bpf (see .br bpf (2)) and attached to the .b lirc device. .pp the \fblirc_get_features\fr ioctl (see below) allows probing for whether receiving and sending is supported, and in which modes, amongst other features. .\" .ss reading input with the lirc_mode_mode2 mode in the \fblirc_mode_mode2 mode\fr, the data returned by .br read (2) provides 32-bit values representing a space or a pulse duration. the time of the duration (microseconds) is encoded in the lower 24 bits. the upper 8 bits indicate the type of package: .tp 4 .br lirc_mode2_space value reflects a space duration (microseconds). .tp 4 .br lirc_mode2_pulse value reflects a pulse duration (microseconds). .tp 4 .br lirc_mode2_frequency value reflects a frequency (hz); see the .b lirc_set_measure_carrier_mode ioctl. .tp 4 .br lirc_mode2_timeout value reflects a space duration (microseconds). the package reflects a timeout; see the .b lirc_set_rec_timeout_reports ioctl. .\" .ss reading input with the lirc_mode_scancode mode in the \fblirc_mode_scancode\fr mode, the data returned by .br read (2) reflects decoded button presses, in the struct \filirc_scancode\fr. the scancode is stored in the \fiscancode\fr field, and the ir protocol is stored in \firc_proto\fr. this field has one the values of the \fienum rc_proto\fr. .\" .ss writing output with the lirc_mode_pulse mode the data written to the character device using .br write (2) is a pulse/space sequence of integer values. pulses and spaces are only marked implicitly by their position. the data must start and end with a pulse, thus it must always include an odd number of samples. the .br write (2) function blocks until the data has been transmitted by the hardware. if more data is provided than the hardware can send, the .br write (2) call fails with the error .br einval . .ss writing output with the lirc_mode_scancode mode the data written to the character devices must be a single struct \filirc_scancode\fr. the \fiscancode\fr and \firc_proto\fr fields must filled in, all other fields must be 0. the kernel ir encoders will convert the scancode to pulses and spaces. the protocol or scancode is invalid, or the .b lirc device cannot transmit. .sh ioctl commands the lirc device's ioctl definition is bound by the ioctl function definition of .ir "struct file_operations" , leaving us with an .ir "unsigned int" for the ioctl command and an .ir "unsigned long" for the argument. for the purposes of ioctl portability across 32-bit and 64-bit architectures, these values are capped to their 32-bit sizes. .pp .nf #include /* but see bugs */ int ioctl(int fd, int cmd, ...); .fi .pp the following ioctls can be used to probe or change specific .b lirc hardware settings. many require a third argument, usually an .ir int , referred to below as .ir val . .\" .ss always supported commands \fi/dev/lirc*\fr devices always support the following commands: .tp 4 .br lirc_get_features " (\fivoid\fp)" returns a bit mask of combined features bits; see features. .pp if a device returns an error code for .br lirc_get_features , it is safe to assume it is not a .b lirc device. .\" .ss optional commands some .b lirc devices support the commands listed below. unless otherwise stated, these fail with the error \fbenotty\fr if the operation isn't supported, or with the error \fbeinval\fr if the operation failed, or invalid arguments were provided. if a driver does not announce support of certain features, invoking the corresponding ioctls will fail with the error .br enotty . .tp .br lirc_get_rec_mode " (\fivoid\fp)" if the .b lirc device has no receiver, this operation fails with the error .br enotty . otherwise, it returns the receive mode, which will be one of: .rs .tp .br lirc_mode_mode2 the driver returns a sequence of pulse/space durations. .tp .br lirc_mode_scancode the driver returns struct .i lirc_scancode values, each of which represents a decoded button press. .re .tp .br lirc_set_rec_mode " (\fiint\fp)" set the receive mode. .ir val is either .br lirc_mode_scancode or .br lirc_mode_mode2 . if the .b lirc device has no receiver, this operation fails with the error .b enotty. .tp .br lirc_get_send_mode " (\fivoid\fp)" return the send mode. .br lirc_mode_pulse or .br lirc_mode_scancode is supported. if the .b lirc device cannot send, this operation fails with the error .b enotty. .tp .br lirc_set_send_mode " (\fiint\fp)" set the send mode. .ir val is either .br lirc_mode_scancode or .br lirc_mode_pulse . if the .b lirc device cannot send, this operation fails with the error .br enotty . .tp .br lirc_set_send_carrier " (\fiint\fp)" set the modulation frequency. the argument is the frequency (hz). .tp .br lirc_set_send_duty_cycle " (\fiint\fp)" set the carrier duty cycle. .i val is a number in the range [0,100] which describes the pulse width as a percentage of the total cycle. currently, no special meaning is defined for 0 or 100, but the values are reserved for future use. .ip .tp .br lirc_get_min_timeout " (\fivoid\fp)", " "\ lirc_get_max_timeout " (\fivoid\fp)" some devices have internal timers that can be used to detect when there has been no ir activity for a long time. this can help .br lircd (8) in detecting that an ir signal is finished and can speed up the decoding process. these operations return integer values with the minimum/maximum timeout that can be set (microseconds). some devices have a fixed timeout. for such drivers, .br lirc_get_min_timeout and .br lirc_get_max_timeout will fail with the error .br enotty . .tp .br lirc_set_rec_timeout " (\fiint\fp)" set the integer value for ir inactivity timeout (microseconds). to be accepted, the value must be within the limits defined by .br lirc_get_min_timeout and .br lirc_get_max_timeout . a value of 0 (if supported by the hardware) disables all hardware timeouts and data should be reported as soon as possible. if the exact value cannot be set, then the next possible value .i greater than the given value should be set. .tp .br lirc_get_rec_timeout " (\fivoid\fp)" return the current inactivity timeout (microseconds). available since linux 4.18. .tp .br lirc_set_rec_timeout_reports " (\fiint\fp)" enable .ri ( val is 1) or disable .ri ( val is 0) timeout packages in .br lirc_mode_mode2 . the behavior of this operation has varied across kernel versions: .rs .ip * 3 since linux 4.16: each time the .b lirc device is opened, timeout reports are by default enabled for the resulting file descriptor. the .b lirc_set_rec_timeout operation can be used to disable (and, if desired, to later re-enable) the timeout on the file descriptor. .ip * in linux 4.15 and earlier: timeout reports are disabled by default, and enabling them (via .br lirc_set_rec_timeout ) on any file descriptor associated with the .b lirc device has the effect of enabling timeouts for all file descriptors referring to that device (until timeouts are disabled again). .re .tp .br lirc_set_rec_carrier " (\fiint\fp)" set the upper bound of the receive carrier frequency (hz). see .br lirc_set_rec_carrier_range . .tp .br lirc_set_rec_carrier_range " (\fiint\fp)" sets the lower bound of the receive carrier frequency (hz). for this to take affect, first set the lower bound using the .br lirc_set_rec_carrier_range ioctl, and then the upper bound using the .br lirc_set_rec_carrier ioctl. .tp .br lirc_set_measure_carrier_mode " (\fiint\fp)" enable .ri ( val is 1) or disable .ri ( val is 0) the measure mode. if enabled, from the next key press on, the driver will send .br lirc_mode2_frequency packets. by default, this should be turned off. .tp .br lirc_get_rec_resolution " (\fivoid\fp)" return the driver resolution (microseconds). .tp .br lirc_set_transmitter_mask " (\fiint\fp)" enable the set of transmitters specified in .ir val , which contains a bit mask where each enabled transmitter is a 1. the first transmitter is encoded by the least significant bit, and so on. when an invalid bit mask is given, for example a bit is set even though the device does not have so many transmitters, this operation returns the number of available transmitters and does nothing otherwise. .tp .br lirc_set_wideband_receiver " (\fiint\fp)" some devices are equipped with a special wide band receiver which is intended to be used to learn the output of an existing remote. this ioctl can be used to enable .ri ( val equals 1) or disable .ri ( val equals 0) this functionality. this might be useful for devices that otherwise have narrow band receivers that prevent them to be used with certain remotes. wide band receivers may also be more precise. on the other hand, their disadvantage usually is reduced range of reception. .ip note: wide band receiver may be implicitly enabled if you enable carrier reports. in that case, it will be disabled as soon as you disable carrier reports. trying to disable a wide band receiver while carrier reports are active will do nothing. .\" .sh features the .br lirc_get_features ioctl returns a bit mask describing features of the driver. the following bits may be returned in the mask: .tp .br lirc_can_rec_mode2 the driver is capable of receiving using .br lirc_mode_mode2 . .tp .br lirc_can_rec_scancode the driver is capable of receiving using .br lirc_mode_scancode . .tp .br lirc_can_set_send_carrier the driver supports changing the modulation frequency using .br lirc_set_send_carrier . .tp .br lirc_can_set_send_duty_cycle the driver supports changing the duty cycle using .br lirc_set_send_duty_cycle . .tp .br lirc_can_set_transmitter_mask the driver supports changing the active transmitter(s) using .br lirc_set_transmitter_mask . .tp .br lirc_can_set_rec_carrier the driver supports setting the receive carrier frequency using .br lirc_set_rec_carrier . any .b lirc device since the drivers were merged in kernel release 2.6.36 must have .br lirc_can_set_rec_carrier_range set if .br lirc_can_set_rec_carrier feature is set. .tp .br lirc_can_set_rec_carrier_range the driver supports .br lirc_set_rec_carrier_range . the lower bound of the carrier must first be set using the .br lirc_set_rec_carrier_range ioctl, before using the .br lirc_set_rec_carrier ioctl to set the upper bound. .tp .br lirc_can_get_rec_resolution the driver supports .br lirc_get_rec_resolution . .tp .br lirc_can_set_rec_timeout the driver supports .br lirc_set_rec_timeout . .tp .br lirc_can_measure_carrier the driver supports measuring of the modulation frequency using .br lirc_set_measure_carrier_mode . .tp .br lirc_can_use_wideband_receiver the driver supports learning mode using .br lirc_set_wideband_receiver . .tp .br lirc_can_send_pulse the driver supports sending using .br lirc_mode_pulse or .br lirc_mode_scancode .\" .sh bugs using these devices requires the kernel source header file .ir lirc.h . this file is not available before kernel release 4.6. users of older kernels could use the file bundled in .ur http://www.lirc.org .ue . .\" .sh see also \fbir\-ctl\fp(1), \fblircd\fp(8),\ \fbbpf\fp(2) .pp https://www.kernel.org/doc/html/latest/media/uapi/rc/lirc-dev.html .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_setschedparam 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_setschedparam, pthread_getschedparam \- set/get scheduling policy and parameters of a thread .sh synopsis .nf .b #include .pp .bi "int pthread_setschedparam(pthread_t " thread ", int " policy , .bi " const struct sched_param *" param ); .bi "int pthread_getschedparam(pthread_t " thread ", int *restrict " policy , .bi " struct sched_param *restrict " param ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_setschedparam () function sets the scheduling policy and parameters of the thread .ir thread . .pp .i policy specifies the new scheduling policy for .ir thread . the supported values for .ir policy , and their semantics, are described in .br sched (7). .\" fixme . pthread_setschedparam() places no restriction on the policy, .\" but pthread_attr_setschedpolicy() restricts policy to rr/fifo/other .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7013 .pp the structure pointed to by .i param specifies the new scheduling parameters for .ir thread . scheduling parameters are maintained in the following structure: .pp .in +4n .ex struct sched_param { int sched_priority; /* scheduling priority */ }; .ee .in .pp as can be seen, only one scheduling parameter is supported. for details of the permitted ranges for scheduling priorities in each scheduling policy, see .br sched (7). .pp the .br pthread_getschedparam () function returns the scheduling policy and parameters of the thread .ir thread , in the buffers pointed to by .i policy and .ir param , respectively. the returned priority value is that set by the most recent .br pthread_setschedparam (), .br pthread_setschedprio (3), or .br pthread_create (3) call that affected .ir thread . the returned priority does not reflect any temporary priority adjustments as a result of calls to any priority inheritance or priority ceiling functions (see, for example, .br pthread_mutexattr_setprioceiling (3) and .br pthread_mutexattr_setprotocol (3)). .\" fixme . nptl/pthread_setschedparam.c has the following .\" /* if the thread should have higher priority because of some .\" pthread_prio_protect mutexes it holds, adjust the priority. */ .\" eventually (perhaps after writing the mutexattr pages), we .\" may want to add something on the topic to this page. .sh return value on success, these functions return 0; on error, they return a nonzero error number. if .br pthread_setschedparam () fails, the scheduling policy and parameters of .i thread are not changed. .sh errors both of these functions can fail with the following error: .tp .b esrch no thread with the id .i thread could be found. .pp .br pthread_setschedparam () may additionally fail with the following errors: .tp .b einval .i policy is not a recognized policy, or .i param does not make sense for the .ir policy . .tp .b eperm the caller does not have appropriate privileges to set the specified scheduling policy and parameters. .pp posix.1 also documents an .b enotsup ("attempt was made to set the policy or scheduling parameters to an unsupported value") error for .br pthread_setschedparam (). .\" .sh versions .\" available since glibc 2.0 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_setschedparam (), .br pthread_getschedparam () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes for a description of the permissions required to, and the effect of, changing a thread's scheduling policy and priority, and details of the permitted ranges for priorities in each scheduling policy, see .br sched (7). .sh examples the program below demonstrates the use of .br pthread_setschedparam () and .br pthread_getschedparam (), as well as the use of a number of other scheduling-related pthreads functions. .pp in the following run, the main thread sets its scheduling policy to .br sched_fifo with a priority of 10, and initializes a thread attributes object with a scheduling policy attribute of .br sched_rr and a scheduling priority attribute of 20. the program then sets (using .br pthread_attr_setinheritsched (3)) the inherit scheduler attribute of the thread attributes object to .br pthread_explicit_sched , meaning that threads created using this attributes object should take their scheduling attributes from the thread attributes object. the program then creates a thread using the thread attributes object, and that thread displays its scheduling policy and priority. .pp .in +4n .ex $ \fbsu\fp # need privilege to set real\-time scheduling policies password: # \fb./a.out \-mf10 \-ar20 \-i e\fp scheduler settings of main thread policy=sched_fifo, priority=10 scheduler settings in \(aqattr\(aq policy=sched_rr, priority=20 inheritsched is explicit scheduler attributes of new thread policy=sched_rr, priority=20 .ee .in .pp in the above output, one can see that the scheduling policy and priority were taken from the values specified in the thread attributes object. .pp the next run is the same as the previous, except that the inherit scheduler attribute is set to .br pthread_inherit_sched , meaning that threads created using the thread attributes object should ignore the scheduling attributes specified in the attributes object and instead take their scheduling attributes from the creating thread. .pp .in +4n .ex # \fb./a.out \-mf10 \-ar20 \-i i\fp scheduler settings of main thread policy=sched_fifo, priority=10 scheduler settings in \(aqattr\(aq policy=sched_rr, priority=20 inheritsched is inherit scheduler attributes of new thread policy=sched_fifo, priority=10 .ee .in .pp in the above output, one can see that the scheduling policy and priority were taken from the creating thread, rather than the thread attributes object. .pp note that if we had omitted the .ir "\-i\ i" option, the output would have been the same, since .br pthread_inherit_sched is the default for the inherit scheduler attribute. .ss program source \& .ex /* pthreads_sched_test.c */ #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static void usage(char *prog_name, char *msg) { if (msg != null) fputs(msg, stderr); fprintf(stderr, "usage: %s [options]\en", prog_name); fprintf(stderr, "options are:\en"); #define fpe(msg) fprintf(stderr, "\et%s", msg); /* shorter */ fpe("\-a set scheduling policy and priority in\en"); fpe(" thread attributes object\en"); fpe(" can be\en"); fpe(" f sched_fifo\en"); fpe(" r sched_rr\en"); fpe(" o sched_other\en"); fpe("\-a use default thread attributes object\en"); fpe("\-i {e|i} set inherit scheduler attribute to\en"); fpe(" \(aqexplicit\(aq or \(aqinherit\(aq\en"); fpe("\-m set scheduling policy and priority on\en"); fpe(" main thread before pthread_create() call\en"); exit(exit_failure); } static int get_policy(char p, int *policy) { switch (p) { case \(aqf\(aq: *policy = sched_fifo; return 1; case \(aqr\(aq: *policy = sched_rr; return 1; case \(aqo\(aq: *policy = sched_other; return 1; default: return 0; } } static void display_sched_attr(int policy, struct sched_param *param) { printf(" policy=%s, priority=%d\en", (policy == sched_fifo) ? "sched_fifo" : (policy == sched_rr) ? "sched_rr" : (policy == sched_other) ? "sched_other" : "???", param\->sched_priority); } static void display_thread_sched_attr(char *msg) { int policy, s; struct sched_param param; s = pthread_getschedparam(pthread_self(), &policy, ¶m); if (s != 0) handle_error_en(s, "pthread_getschedparam"); printf("%s\en", msg); display_sched_attr(policy, ¶m); } static void * thread_start(void *arg) { display_thread_sched_attr("scheduler attributes of new thread"); return null; } int main(int argc, char *argv[]) { int s, opt, inheritsched, use_null_attrib, policy; pthread_t thread; pthread_attr_t attr; pthread_attr_t *attrp; char *attr_sched_str, *main_sched_str, *inheritsched_str; struct sched_param param; /* process command\-line options. */ use_null_attrib = 0; attr_sched_str = null; main_sched_str = null; inheritsched_str = null; while ((opt = getopt(argc, argv, "a:ai:m:")) != \-1) { switch (opt) { case \(aqa\(aq: attr_sched_str = optarg; break; case \(aqa\(aq: use_null_attrib = 1; break; case \(aqi\(aq: inheritsched_str = optarg; break; case \(aqm\(aq: main_sched_str = optarg; break; default: usage(argv[0], "unrecognized option\en"); } } if (use_null_attrib && (inheritsched_str != null || attr_sched_str != null)) usage(argv[0], "can\(aqt specify \-a with \-i or \-a\en"); /* optionally set scheduling attributes of main thread, and display the attributes. */ if (main_sched_str != null) { if (!get_policy(main_sched_str[0], &policy)) usage(argv[0], "bad policy for main thread (\-m)\en"); param.sched_priority = strtol(&main_sched_str[1], null, 0); s = pthread_setschedparam(pthread_self(), policy, ¶m); if (s != 0) handle_error_en(s, "pthread_setschedparam"); } display_thread_sched_attr("scheduler settings of main thread"); printf("\en"); /* initialize thread attributes object according to options. */ attrp = null; if (!use_null_attrib) { s = pthread_attr_init(&attr); if (s != 0) handle_error_en(s, "pthread_attr_init"); attrp = &attr; } if (inheritsched_str != null) { if (inheritsched_str[0] == \(aqe\(aq) inheritsched = pthread_explicit_sched; else if (inheritsched_str[0] == \(aqi\(aq) inheritsched = pthread_inherit_sched; else usage(argv[0], "value for \-i must be \(aqe\(aq or \(aqi\(aq\en"); s = pthread_attr_setinheritsched(&attr, inheritsched); if (s != 0) handle_error_en(s, "pthread_attr_setinheritsched"); } if (attr_sched_str != null) { if (!get_policy(attr_sched_str[0], &policy)) usage(argv[0], "bad policy for \(aqattr\(aq (\-a)\en"); param.sched_priority = strtol(&attr_sched_str[1], null, 0); s = pthread_attr_setschedpolicy(&attr, policy); if (s != 0) handle_error_en(s, "pthread_attr_setschedpolicy"); s = pthread_attr_setschedparam(&attr, ¶m); if (s != 0) handle_error_en(s, "pthread_attr_setschedparam"); } /* if we initialized a thread attributes object, display the scheduling attributes that were set in the object. */ if (attrp != null) { s = pthread_attr_getschedparam(&attr, ¶m); if (s != 0) handle_error_en(s, "pthread_attr_getschedparam"); s = pthread_attr_getschedpolicy(&attr, &policy); if (s != 0) handle_error_en(s, "pthread_attr_getschedpolicy"); printf("scheduler settings in \(aqattr\(aq\en"); display_sched_attr(policy, ¶m); s = pthread_attr_getinheritsched(&attr, &inheritsched); printf(" inheritsched is %s\en", (inheritsched == pthread_inherit_sched) ? "inherit" : (inheritsched == pthread_explicit_sched) ? "explicit" : "???"); printf("\en"); } /* create a thread that will display its scheduling attributes. */ s = pthread_create(&thread, attrp, &thread_start, null); if (s != 0) handle_error_en(s, "pthread_create"); /* destroy unneeded thread attributes object. */ if (!use_null_attrib) { s = pthread_attr_destroy(&attr); if (s != 0) handle_error_en(s, "pthread_attr_destroy"); } s = pthread_join(thread, null); if (s != 0) handle_error_en(s, "pthread_join"); exit(exit_success); } .ee .sh see also .ad l .nh .br getrlimit (2), .br sched_get_priority_min (2), .br pthread_attr_init (3), .br pthread_attr_setinheritsched (3), .br pthread_attr_setschedparam (3), .br pthread_attr_setschedpolicy (3), .br pthread_create (3), .br pthread_self (3), .br pthread_setschedprio (3), .br pthreads (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/carg.3 .so man3/tsearch.3 .\" copyright 1995 jim van zandt .\" from jrv@vanzandt.mv.com mon sep 4 21:11:50 1995 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 1996-11-08, meem@sherilyn.wustl.edu, corrections .\" 2004-10-31, aeb, changed maintainer address, updated list .\" 2015-04-20, william@tuffbizz.com, updated list .\" .th undocumented 3 2021-03-22 "linux" "linux programmer's manual" .sh name undocumented \- undocumented library functions .sh synopsis .nf undocumented library functions .fi .sh description this man page mentions those library functions which are implemented in the standard libraries but not yet documented in man pages. .ss solicitation if you have information about these functions, please look in the source code, write a man page (using a style similar to that of the other linux section 3 man pages), and send it to .b mtk.manpages@gmail.com for inclusion in the next man page release. .ss the list .br authdes_create (3), .br authdes_getucred (3), .br authdes_pk_create (3), .\" .br chflags (3), .br clntunix_create (3), .br creat64 (3), .br dn_skipname (3), .\" .br fattach (3), .\" .br fchflags (3), .\" .br fclean (3), .br fcrypt (3), .\" .br fdetach (3), .br fp_nquery (3), .br fp_query (3), .br fp_resstat (3), .br freading (3), .br freopen64 (3), .br fseeko64 (3), .br ftello64 (3), .br ftw64 (3), .br fwscanf (3), .br get_avphys_pages (3), .br getdirentries64 (3), .br getmsg (3), .br getnetname (3), .br get_phys_pages (3), .br getpublickey (3), .br getsecretkey (3), .br h_errlist (3), .br host2netname (3), .br hostalias (3), .br inet_nsap_addr (3), .br inet_nsap_ntoa (3), .br init_des (3), .br libc_nls_init (3), .br mstats (3), .br netname2host (3), .br netname2user (3), .br nlist (3), .br obstack_free (3), .\" .br obstack stuff (3), .br parse_printf_format (3), .br p_cdname (3), .br p_cdnname (3), .br p_class (3), .br p_fqname (3), .br p_option (3), .br p_query (3), .br printf_size (3), .br printf_size_info (3), .br p_rr (3), .br p_time (3), .br p_type (3), .br putlong (3), .br putshort (3), .br re_compile_fastmap (3), .br re_compile_pattern (3), .br register_printf_function (3), .br re_match (3), .br re_match_2 (3), .br re_rx_search (3), .br re_search (3), .br re_search_2 (3), .br re_set_registers (3), .br re_set_syntax (3), .br res_send_setqhook (3), .br res_send_setrhook (3), .br ruserpass (3), .br setfileno (3), .br sethostfile (3), .br svc_exit (3), .br svcudp_enablecache (3), .br tell (3), .br tr_break (3), .br tzsetwall (3), .br ufc_dofinalperm (3), .br ufc_doit (3), .br user2netname (3), .br wcschrnul (3), .br wcsftime (3), .br wscanf (3), .br xdr_authdes_cred (3), .br xdr_authdes_verf (3), .br xdr_cryptkeyarg (3), .br xdr_cryptkeyres (3), .br xdr_datum (3), .br xdr_des_block (3), .br xdr_domainname (3), .br xdr_getcredres (3), .br xdr_keybuf (3), .br xdr_keystatus (3), .br xdr_mapname (3), .br xdr_netnamestr (3), .br xdr_netobj (3), .br xdr_passwd (3), .br xdr_peername (3), .br xdr_rmtcall_args (3), .br xdr_rmtcallres (3), .br xdr_unixcred (3), .br xdr_yp_buf (3), .br xdr_yp_inaddr (3), .br xdr_ypbind_binding (3), .br xdr_ypbind_resp (3), .br xdr_ypbind_resptype (3), .br xdr_ypbind_setdom (3), .br xdr_ypdelete_args (3), .br xdr_ypmaplist (3), .br xdr_ypmaplist_str (3), .br xdr_yppasswd (3), .br xdr_ypreq_key (3), .br xdr_ypreq_nokey (3), .br xdr_ypresp_all (3), .br xdr_ypresp_all_seq (3), .br xdr_ypresp_key_val (3), .br xdr_ypresp_maplist (3), .br xdr_ypresp_master (3), .br xdr_ypresp_order (3), .br xdr_ypresp_val (3), .br xdr_ypstat (3), .br xdr_ypupdate_args (3), .br yp_all (3), .br yp_bind (3), .br yperr_string (3), .br yp_first (3), .br yp_get_default_domain (3), .br yp_maplist (3), .br yp_master (3), .br yp_match (3), .br yp_next (3), .br yp_order (3), .br ypprot_err (3), .br yp_unbind (3), .br yp_update (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" (c) copyright 1999-2000 david a. wheeler (dwheeler@dwheeler.com) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" fragments of this document are directly derived from ietf standards. .\" for those fragments which are directly derived from such standards, .\" the following notice applies, which is the standard copyright and .\" rights announcement of the internet society: .\" .\" copyright (c) the internet society (1998). all rights reserved. .\" this document and translations of it may be copied and furnished to .\" others, and derivative works that comment on or otherwise explain it .\" or assist in its implementation may be prepared, copied, published .\" and distributed, in whole or in part, without restriction of any .\" kind, provided that the above copyright notice and this paragraph are .\" included on all such copies and derivative works. however, this .\" document itself may not be modified in any way, such as by removing .\" the copyright notice or references to the internet society or other .\" internet organizations, except as needed for the purpose of .\" developing internet standards in which case the procedures for .\" copyrights defined in the internet standards process must be .\" followed, or as required to translate it into languages other than english. .\" .\" modified fri jul 25 23:00:00 1999 by david a. wheeler (dwheeler@dwheeler.com) .\" modified fri aug 21 23:00:00 1999 by david a. wheeler (dwheeler@dwheeler.com) .\" modified tue mar 14 2000 by david a. wheeler (dwheeler@dwheeler.com) .\" .th uri 7 2021-03-22 "linux" "linux programmer's manual" .sh name uri, url, urn \- uniform resource identifier (uri), including a url or urn .sh synopsis .nf .hp 0.2i uri = [ absoluteuri | relativeuri ] [ "#" fragment ] .hp absoluteuri = scheme ":" ( hierarchical_part | opaque_part ) .hp relativeuri = ( net_path | absolute_path | relative_path ) [ "?" query ] .hp scheme = "http" | "ftp" | "gopher" | "mailto" | "news" | "telnet" | "file" | "man" | "info" | "whatis" | "ldap" | "wais" | \&... .hp hierarchical_part = ( net_path | absolute_path ) [ "?" query ] .hp net_path = "//" authority [ absolute_path ] .hp absolute_path = "/" path_segments .hp relative_path = relative_segment [ absolute_path ] .fi .sh description a uniform resource identifier (uri) is a short string of characters identifying an abstract or physical resource (for example, a web page). a uniform resource locator (url) is a uri that identifies a resource through its primary access mechanism (e.g., its network "location"), rather than by name or some other attribute of that resource. a uniform resource name (urn) is a uri that must remain globally unique and persistent even when the resource ceases to exist or becomes unavailable. .pp uris are the standard way to name hypertext link destinations for tools such as web browsers. the string "http://www.kernel.org" is a url (and thus it is also a uri). many people use the term url loosely as a synonym for uri (though technically urls are a subset of uris). .pp uris can be absolute or relative. an absolute identifier refers to a resource independent of context, while a relative identifier refers to a resource by describing the difference from the current context. within a relative path reference, the complete path segments "." and ".." have special meanings: "the current hierarchy level" and "the level above this hierarchy level", respectively, just like they do in unix-like systems. a path segment which contains a colon character can't be used as the first segment of a relative uri path (e.g., "this:that"), because it would be mistaken for a scheme name; precede such segments with ./ (e.g., "./this:that"). note that descendants of ms-dos (e.g., microsoft windows) replace devicename colons with the vertical bar ("|") in uris, so "c:" becomes "c|". .pp a fragment identifier, if included, refers to a particular named portion (fragment) of a resource; text after a \(aq#\(aq identifies the fragment. a uri beginning with \(aq#\(aq refers to that fragment in the current resource. .ss usage there are many different uri schemes, each with specific additional rules and meanings, but they are intentionally made to be as similar as possible. for example, many url schemes permit the authority to be the following format, called here an .i ip_server (square brackets show what's optional): .hp .ir "ip_server = " [ user " [ : " password " ] @ ] " host " [ : " port ] .pp this format allows you to optionally insert a username, a user plus password, and/or a port number. the .i host is the name of the host computer, either its name as determined by dns or an ip address (numbers separated by periods). thus the uri logs into a web server on host example.com as fred (using fredpassword) using port 8080. avoid including a password in a uri if possible because of the many security risks of having a password written down. if the url supplies a username but no password, and the remote server requests a password, the program interpreting the url should request one from the user. .pp here are some of the most common schemes in use on unix-like systems that are understood by many tools. note that many tools using uris also have internal schemes or specialized schemes; see those tools' documentation for information on those schemes. .pp .b "http \- web (http) server" .pp .ri http:// ip_server / path .br .ri http:// ip_server / path ? query .pp this is a url accessing a web (http) server. the default port is 80. if the path refers to a directory, the web server will choose what to return; usually if there is a file named "index.html" or "index.htm" its content is returned, otherwise, a list of the files in the current directory (with appropriate links) is generated and returned. an example is . .pp a query can be given in the archaic "isindex" format, consisting of a word or phrase and not including an equal sign (=). a query can also be in the longer "get" format, which has one or more query entries of the form .ir key = value separated by the ampersand character (&). note that .i key can be repeated more than once, though it's up to the web server and its application programs to determine if there's any meaning to that. there is an unfortunate interaction with html/xml/sgml and the get query format; when such uris with more than one key are embedded in sgml/xml documents (including html), the ampersand (&) has to be rewritten as &. note that not all queries use this format; larger forms may be too long to store as a uri, so they use a different interaction mechanism (called post) which does not include the data in the uri. see the common gateway interface specification at .ur http://www.w3.org\:/cgi .ue for more information. .pp .b "ftp \- file transfer protocol (ftp)" .pp .ri ftp:// ip_server / path .pp this is a url accessing a file through the file transfer protocol (ftp). the default port (for control) is 21. if no username is included, the username "anonymous" is supplied, and in that case many clients provide as the password the requestor's internet email address. an example is . .pp .b "gopher \- gopher server" .pp .ri gopher:// ip_server / "gophertype selector" .br .ri gopher:// ip_server / "gophertype selector" %09 search .br .ri gopher:// ip_server / "gophertype selector" %09 search %09 gopher+_string .br .pp the default gopher port is 70. .i gophertype is a single-character field to denote the gopher type of the resource to which the url refers. the entire path may also be empty, in which case the delimiting "/" is also optional and the gophertype defaults to "1". .pp .i selector is the gopher selector string. in the gopher protocol, gopher selector strings are a sequence of octets which may contain any octets except 09 hexadecimal (us-ascii ht or tab), 0a hexadecimal (us-ascii character lf), and 0d (us-ascii character cr). .pp .b "mailto \- email address" .pp .ri mailto: email-address .pp this is an email address, usually of the form .ir name @ hostname . see .br mailaddr (7) for more information on the correct format of an email address. note that any % character must be rewritten as %25. an example is . .pp .b "news \- newsgroup or news message" .pp .ri news: newsgroup-name .br .ri news: message-id .pp a .i newsgroup-name is a period-delimited hierarchical name, such as "comp.infosystems.www.misc". if is "*" (as in ), it is used to refer to "all available news groups". an example is . .pp a .i message-id corresponds to the message-id of .ur http://www.ietf.org\:/rfc\:/rfc1036.txt ietf rfc\ 1036, .ue without the enclosing "<" and ">"; it takes the form .ir unique @ full_domain_name . a message identifier may be distinguished from a news group name by the presence of the "@" character. .pp .b "telnet \- telnet login" .pp .ri telnet:// ip_server / .pp the telnet url scheme is used to designate interactive text services that may be accessed by the telnet protocol. the final "/" character may be omitted. the default port is 23. an example is . .pp .b "file \- normal file" .pp .ri file:// ip_server / path_segments .br .ri file: path_segments .pp this represents a file or directory accessible locally. as a special case, .i ip_server can be the string "localhost" or the empty string; this is interpreted as "the machine from which the url is being interpreted". if the path is to a directory, the viewer should display the directory's contents with links to each containee; not all viewers currently do this. kde supports generated files through the url . if the given file isn't found, browser writers may want to try to expand the filename via filename globbing (see .br glob (7) and .br glob (3)). .pp the second format (e.g., ) is a correct format for referring to a local file. however, older standards did not permit this format, and some programs don't recognize this as a uri. a more portable syntax is to use an empty string as the server name, for example, ; this form does the same thing and is easily recognized by pattern matchers and older programs as a uri. note that if you really mean to say "start from the current location", don't specify the scheme at all; use a relative address like <../test.txt>, which has the side-effect of being scheme-independent. an example of this scheme is . .pp .b "man \- man page documentation" .pp .ri man: command-name .br .ri man: command-name ( section ) .pp this refers to local online manual (man) reference pages. the command name can optionally be followed by a parenthesis and section number; see .br man (7) for more information on the meaning of the section numbers. this uri scheme is unique to unix-like systems (such as linux) and is not currently registered by the ietf. an example is . .pp .b "info \- info page documentation" .pp .ri info: virtual-filename .br .ri info: virtual-filename # nodename .br .ri info:( virtual-filename ) .br .ri info:( virtual-filename ) nodename .pp this scheme refers to online info reference pages (generated from texinfo files), a documentation format used by programs such as the gnu tools. this uri scheme is unique to unix-like systems (such as linux) and is not currently registered by the ietf. as of this writing, gnome and kde differ in their uri syntax and do not accept the other's syntax. the first two formats are the gnome format; in nodenames all spaces are written as underscores. the second two formats are the kde format; spaces in nodenames must be written as spaces, even though this is forbidden by the uri standards. it's hoped that in the future most tools will understand all of these formats and will always accept underscores for spaces in nodenames. in both gnome and kde, if the form without the nodename is used the nodename is assumed to be "top". examples of the gnome format are and . examples of the kde format are and . .pp .b "whatis \- documentation search" .pp .ri whatis: string .pp this scheme searches the database of short (one-line) descriptions of commands and returns a list of descriptions containing that string. only complete word matches are returned. see .br whatis (1). this uri scheme is unique to unix-like systems (such as linux) and is not currently registered by the ietf. .pp .b "ghelp \- gnome help documentation" .pp .ri ghelp: name-of-application .pp this loads gnome help for the given application. note that not much documentation currently exists in this format. .pp .b "ldap \- lightweight directory access protocol" .pp .ri ldap:// hostport .br .ri ldap:// hostport / .br .ri ldap:// hostport / dn .br .ri ldap:// hostport / dn ? attributes .br .ri ldap:// hostport / dn ? attributes ? scope .br .ri ldap:// hostport / dn ? attributes ? scope ? filter .br .ri ldap:// hostport / dn ? attributes ? scope ? filter ? extensions .pp this scheme supports queries to the lightweight directory access protocol (ldap), a protocol for querying a set of servers for hierarchically organized information (such as people and computing resources). see .ur http://www.ietf.org\:/rfc\:/rfc2255.txt rfc\ 2255 .ue for more information on the ldap url scheme. the components of this url are: .ip hostport 12 the ldap server to query, written as a hostname optionally followed by a colon and the port number. the default ldap port is tcp port 389. if empty, the client determines which the ldap server to use. .ip dn the ldap distinguished name, which identifies the base object of the ldap search (see .ur http://www.ietf.org\:/rfc\:/rfc2253.txt rfc\ 2253 .ue section 3). .ip attributes a comma-separated list of attributes to be returned; see rfc\ 2251 section 4.1.5. if omitted, all attributes should be returned. .ip scope specifies the scope of the search, which can be one of "base" (for a base object search), "one" (for a one-level search), or "sub" (for a subtree search). if scope is omitted, "base" is assumed. .ip filter specifies the search filter (subset of entries to return). if omitted, all entries should be returned. see .ur http://www.ietf.org\:/rfc\:/rfc2254.txt rfc\ 2254 .ue section 4. .ip extensions a comma-separated list of type=value pairs, where the =value portion may be omitted for options not requiring it. an extension prefixed with a \(aq!\(aq is critical (must be supported to be valid), otherwise it is noncritical (optional). .pp ldap queries are easiest to explain by example. here's a query that asks ldap.itd.umich.edu for information about the university of michigan in the u.s.: .pp .nf ldap://ldap.itd.umich.edu/o=university%20of%20michigan,c=us .fi .pp to just get its postal address attribute, request: .pp .nf ldap://ldap.itd.umich.edu/o=university%20of%20michigan,c=us?postaladdress .fi .pp to ask a host.com at port 6666 for information about the person with common name (cn) "babs jensen" at university of michigan, request: .pp .nf ldap://host.com:6666/o=university%20of%20michigan,c=us??sub?(cn=babs%20jensen) .fi .pp .b "wais \- wide area information servers" .pp .ri wais:// hostport / database .br .ri wais:// hostport / database ? search .br .ri wais:// hostport / database / wtype / wpath .pp this scheme designates a wais database, search, or document (see .ur http://www.ietf.org\:/rfc\:/rfc1625.txt ietf rfc\ 1625 .ue for more information on wais). hostport is the hostname, optionally followed by a colon and port number (the default port number is 210). .pp the first form designates a wais database for searching. the second form designates a particular search of the wais database .ir database . the third form designates a particular document within a wais database to be retrieved. .i wtype is the wais designation of the type of the object and .i wpath is the wais document-id. .pp .b "other schemes" .pp there are many other uri schemes. most tools that accept uris support a set of internal uris (e.g., mozilla has the about: scheme for internal information, and the gnome help browser has the toc: scheme for various starting locations). there are many schemes that have been defined but are not as widely used at the current time (e.g., prospero). the nntp: scheme is deprecated in favor of the news: scheme. urns are to be supported by the urn: scheme, with a hierarchical name space (e.g., urn:ietf:... would identify ietf documents); at this time urns are not widely implemented. not all tools support all schemes. .ss character encoding uris use a limited number of characters so that they can be typed in and used in a variety of situations. .pp the following characters are reserved, that is, they may appear in a uri but their use is limited to their reserved purpose (conflicting data must be escaped before forming the uri): .ip ; / ? : @ & = + $ , .pp unreserved characters may be included in a uri. unreserved characters include uppercase and lowercase latin letters, decimal digits, and the following limited set of punctuation marks and symbols: .ip \- _ . ! \(ti * ' ( ) .pp all other characters must be escaped. an escaped octet is encoded as a character triplet, consisting of the percent character "%" followed by the two hexadecimal digits representing the octet code (you can use uppercase or lowercase letters for the hexadecimal digits). for example, a blank space must be escaped as "%20", a tab character as "%09", and the "&" as "%26". because the percent "%" character always has the reserved purpose of being the escape indicator, it must be escaped as "%25". it is common practice to escape space characters as the plus symbol (+) in query text; this practice isn't uniformly defined in the relevant rfcs (which recommend %20 instead) but any tool accepting uris with query text should be prepared for them. a uri is always shown in its "escaped" form. .pp unreserved characters can be escaped without changing the semantics of the uri, but this should not be done unless the uri is being used in a context that does not allow the unescaped character to appear. for example, "%7e" is sometimes used instead of "\(ti" in an http url path, but the two are equivalent for an http url. .pp for uris which must handle characters outside the us ascii character set, the html 4.01 specification (section b.2) and ietf rfc\ 2718 (section 2.2.5) recommend the following approach: .ip 1. 4 translate the character sequences into utf-8 (ietf rfc\ 2279)\(emsee .br utf\-8 (7)\(emand then .ip 2. use the uri escaping mechanism, that is, use the %hh encoding for unsafe octets. .ss writing a uri when written, uris should be placed inside double quotes (e.g., "http://www.kernel.org"), enclosed in angle brackets (e.g., ), or placed on a line by themselves. a warning for those who use double-quotes: .b never move extraneous punctuation (such as the period ending a sentence or the comma in a list) inside a uri, since this will change the value of the uri. instead, use angle brackets instead, or switch to a quoting system that never includes extraneous characters inside quotation marks. this latter system, called the 'new' or 'logical' quoting system by "hart's rules" and the "oxford dictionary for writers and editors", is preferred practice in great britain and in various european languages. older documents suggested inserting the prefix "url:" just before the uri, but this form has never caught on. .pp the uri syntax was designed to be unambiguous. however, as uris have become commonplace, traditional media (television, radio, newspapers, billboards, etc.) have increasingly used abbreviated uri references consisting of only the authority and path portions of the identified resource (e.g., ). such references are primarily intended for human interpretation rather than machine, with the assumption that context-based heuristics are sufficient to complete the uri (e.g., hostnames beginning with "www" are likely to have a uri prefix of "http://" and hostnames beginning with "ftp" likely to have a prefix of "ftp://"). many client implementations heuristically resolve these references. such heuristics may change over time, particularly when new schemes are introduced. since an abbreviated uri has the same syntax as a relative url path, abbreviated uri references cannot be used where relative uris are permitted, and can be used only when there is no defined base (such as in dialog boxes). don't use abbreviated uris as hypertext links inside a document; use the standard format as described here. .sh conforming to .ur http://www.ietf.org\:/rfc\:/rfc2396.txt (ietf rfc\ 2396) .ue , .ur http://www.w3.org\:/tr\:/rec\-html40 (html 4.0) .ue . .sh notes any tool accepting uris (e.g., a web browser) on a linux system should be able to handle (directly or indirectly) all of the schemes described here, including the man: and info: schemes. handling them by invoking some other program is fine and in fact encouraged. .pp technically the fragment isn't part of the uri. .pp for information on how to embed uris (including urls) in a data format, see documentation on that format. html uses the format .i text . texinfo files use the format @uref{\fiuri\fp}. man and mdoc have the recently added ur macro, or just include the uri in the text (viewers should be able to detect :// as part of a uri). .pp the gnome and kde desktop environments currently vary in the uris they accept, in particular in their respective help browsers. to list man pages, gnome uses while kde uses , and to list info pages, gnome uses while kde uses (the author of this man page prefers the kde approach here, though a more regular format would be even better). in general, kde uses as a prefix to a set of generated files. kde prefers documentation in html, accessed via the . gnome prefers the ghelp scheme to store and find documentation. neither browser handles file: references to directories at the time of this writing, making it difficult to refer to an entire directory with a browsable uri. as noted above, these environments differ in how they handle the info: scheme, probably the most important variation. it is expected that gnome and kde will converge to common uri formats, and a future version of this man page will describe the converged result. efforts to aid this convergence are encouraged. .ss security a uri does not in itself pose a security threat. there is no general guarantee that a url, which at one time located a given resource, will continue to do so. nor is there any guarantee that a url will not locate a different resource at some later point in time; such a guarantee can be obtained only from the person(s) controlling that namespace and the resource in question. .pp it is sometimes possible to construct a url such that an attempt to perform a seemingly harmless operation, such as the retrieval of an entity associated with the resource, will in fact cause a possibly damaging remote operation to occur. the unsafe url is typically constructed by specifying a port number other than that reserved for the network protocol in question. the client unwittingly contacts a site that is in fact running a different protocol. the content of the url contains instructions that, when interpreted according to this other protocol, cause an unexpected operation. an example has been the use of a gopher url to cause an unintended or impersonating message to be sent via a smtp server. .pp caution should be used when using any url that specifies a port number other than the default for the protocol, especially when it is a number within the reserved space. .pp care should be taken when a uri contains escaped delimiters for a given protocol (for example, cr and lf characters for telnet protocols) that these are not unescaped before transmission. this might violate the protocol, but avoids the potential for such characters to be used to simulate an extra operation or parameter in that protocol, which might lead to an unexpected and possibly harmful remote operation to be performed. .pp it is clearly unwise to use a uri that contains a password which is intended to be secret. in particular, the use of a password within the "userinfo" component of a uri is strongly recommended against except in those rare cases where the "password" parameter is intended to be public. .sh bugs documentation may be placed in a variety of locations, so there currently isn't a good uri scheme for general online documentation in arbitrary formats. references of the form don't work because different distributions and local installation requirements may place the files in different directories (it may be in /usr/doc, or /usr/local/doc, or /usr/share, or somewhere else). also, the directory zzz usually changes when a version changes (though filename globbing could partially overcome this). finally, using the file: scheme doesn't easily support people who dynamically load documentation from the internet (instead of loading the files onto a local filesystem). a future uri scheme may be added (e.g., "userdoc:") to permit programs to include cross-references to more detailed documentation without having to know the exact location of that documentation. alternatively, a future version of the filesystem specification may specify file locations sufficiently so that the file: scheme will be able to locate documentation. .pp many programs and file formats don't include a way to incorporate or implement links using uris. .pp many programs can't handle all of these different uri formats; there should be a standard mechanism to load an arbitrary uri that automatically detects the users' environment (e.g., text or graphics, desktop environment, local user preferences, and currently executing tools) and invokes the right tool for any uri. .\" .sh author .\" david a. wheeler (dwheeler@dwheeler.com) wrote this man page. .sh see also .br lynx (1), .br man2html (1), .br mailaddr (7), .br utf\-8 (7) .pp .ur http://www.ietf.org\:/rfc\:/rfc2255.txt ietf rfc\ 2255 .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified mon mar 29 22:31:13 1993, david metcalfe .\" modified sun jun 6 23:27:50 1993, david metcalfe .\" modified sat jul 24 21:45:37 1993, rik faith (faith@cs.unc.edu) .\" modified sat dec 16 15:02:59 2000, joseph s. myers .\" .th abs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name abs, labs, llabs, imaxabs \- compute the absolute value of an integer .sh synopsis .nf .b #include .pp .bi "int abs(int " j ); .bi "long labs(long " j ); .bi "long long llabs(long long " j ); .pp .b #include .pp .bi "intmax_t imaxabs(intmax_t " j ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br llabs (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description the .br abs () function computes the absolute value of the integer argument \fij\fp. the .br labs (), .br llabs (), and .br imaxabs () functions compute the absolute value of the argument \fij\fp of the appropriate integer type for the function. .sh return value returns the absolute value of the integer argument, of the appropriate integer type for the function. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br abs (), .br labs (), .br llabs (), .br imaxabs () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99, svr4, 4.3bsd. .\" posix.1 (1996 edition) requires only the .\" .br abs () .\" function. c89 only includes the .br abs () and .br labs () functions; the functions .br llabs () and .br imaxabs () were added in c99. .sh notes trying to take the absolute value of the most negative integer is not defined. .pp the .br llabs () function is included in glibc since version 2.0. the .br imaxabs () function is included in glibc since version 2.1.1. .pp for .br llabs () to be declared, it may be necessary to define \fb_isoc99_source\fp or \fb_isoc9x_source\fp (depending on the version of glibc) before including any standard headers. .pp by default, gcc handles .br abs (), .br labs (), and (since gcc 3.0) .br llabs () and .br imaxabs () as built-in functions. .sh see also .br cabs (3), .br ceil (3), .br fabs (3), .br floor (3), .br rint (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setnetgrent.3 .so man3/acos.3 .so man3/j0.3 .so man3/pthread_setaffinity_np.3 .so man3/bswap.3 .so man2/getrusage.2 .\" no new programs should use vtimes(3). .\" getrusage(2) briefly discusses vtimes(3), so point the user there. .so man3/tsearch.3 .so man2/outb.2 .so man3/sin.3 .\" copyright (c) 2002 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 6 aug 2002 - initial creation .\" modified 2003-05-23, michael kerrisk, .\" modified 2004-05-27, michael kerrisk, .\" 2004-12-08, mtk added o_noatime for cap_fowner .\" 2005-08-16, mtk, added cap_audit_control and cap_audit_write .\" 2008-07-15, serge hallyn .\" document file capabilities, per-process capability .\" bounding set, changed semantics for cap_setpcap, .\" and other changes in 2.6.2[45]. .\" add cap_mac_admin, cap_mac_override, cap_setfcap. .\" 2008-07-15, mtk .\" add text describing circumstances in which cap_setpcap .\" (theoretically) permits a thread to change the .\" capability sets of another thread. .\" add section describing rules for programmatically .\" adjusting thread capability sets. .\" describe rationale for capability bounding set. .\" document "securebits" flags. .\" add text noting that if we set the effective flag for one file .\" capability, then we must also set the effective flag for all .\" other capabilities where the permitted or inheritable bit is set. .\" 2011-09-07, mtk/serge hallyn: add cap_syslog .\" .th capabilities 7 2021-08-27 "linux" "linux programmer's manual" .sh name capabilities \- overview of linux capabilities .sh description for the purpose of performing permission checks, traditional unix implementations distinguish two categories of processes: .i privileged processes (whose effective user id is 0, referred to as superuser or root), and .i unprivileged processes (whose effective uid is nonzero). privileged processes bypass all kernel permission checks, while unprivileged processes are subject to full permission checking based on the process's credentials (usually: effective uid, effective gid, and supplementary group list). .pp starting with kernel 2.2, linux divides the privileges traditionally associated with superuser into distinct units, known as .ir capabilities , which can be independently enabled and disabled. capabilities are a per-thread attribute. .\" .ss capabilities list the following list shows the capabilities implemented on linux, and the operations or behaviors that each capability permits: .tp .br cap_audit_control " (since linux 2.6.11)" enable and disable kernel auditing; change auditing filter rules; retrieve auditing status and filtering rules. .tp .br cap_audit_read " (since linux 3.16)" .\" commit a29b694aa1739f9d76538e34ae25524f9c549d59 .\" commit 3a101b8de0d39403b2c7e5c23fd0b005668acf48 allow reading the audit log via a multicast netlink socket. .tp .br cap_audit_write " (since linux 2.6.11)" write records to kernel auditing log. .\" fixme add fan_enable_audit .tp .br cap_block_suspend " (since linux 3.5)" employ features that can block system suspend .rb ( epoll (7) .br epollwakeup , .ir /proc/sys/wake_lock ). .tp .br cap_bpf " (since linux 5.8)" employ privileged bpf operations; see .br bpf (2) and .br bpf\-helpers (7). .ip this capability was added in linux 5.8 to separate out bpf functionality from the overloaded .br cap_sys_admin capability. .tp .br cap_checkpoint_restore " (since linux 5.9)" .\" commit 124ea650d3072b005457faed69909221c2905a1f .pd 0 .rs .ip * 2 update .i /proc/sys/kernel/ns_last_pid (see .br pid_namespaces (7)); .ip * employ the .i set_tid feature of .br clone3 (2); .\" fixme there is also some use case relating to .\" prctl_set_mm_exe_file(); in the 5.9 sources, see .\" prctl_set_mm_map(). .ip * read the contents of the symbolic links in .ir /proc/[pid]/map_files for other processes. .re .pd .ip this capability was added in linux 5.9 to separate out checkpoint/restore functionality from the overloaded .br cap_sys_admin capability. .tp .b cap_chown make arbitrary changes to file uids and gids (see .br chown (2)). .tp .b cap_dac_override bypass file read, write, and execute permission checks. (dac is an abbreviation of "discretionary access control".) .tp .b cap_dac_read_search .pd 0 .rs .ip * 2 bypass file read permission checks and directory read and execute permission checks; .ip * invoke .br open_by_handle_at (2); .ip * use the .br linkat (2) .b at_empty_path flag to create a link to a file referred to by a file descriptor. .re .pd .tp .b cap_fowner .pd 0 .rs .ip * 2 bypass permission checks on operations that normally require the filesystem uid of the process to match the uid of the file (e.g., .br chmod (2), .br utime (2)), excluding those operations covered by .b cap_dac_override and .br cap_dac_read_search ; .ip * set inode flags (see .br ioctl_iflags (2)) on arbitrary files; .ip * set access control lists (acls) on arbitrary files; .ip * ignore directory sticky bit on file deletion; .ip * modify .i user extended attributes on sticky directory owned by any user; .ip * specify .b o_noatime for arbitrary files in .br open (2) and .br fcntl (2). .re .pd .tp .b cap_fsetid .pd 0 .rs .ip * 2 don't clear set-user-id and set-group-id mode bits when a file is modified; .ip * set the set-group-id bit for a file whose gid does not match the filesystem or any of the supplementary gids of the calling process. .re .pd .tp .b cap_ipc_lock .\" fixme . as at linux 3.2, there are some strange uses of this capability .\" in other places; they probably should be replaced with something else. .pd 0 .rs .ip * 2 lock memory .rb ( mlock (2), .br mlockall (2), .br mmap (2), .br shmctl (2)); .ip * allocate memory using huge pages .rb ( memfd_create (2), .br mmap (2), .br shmctl (2)). .pd 0 .re .tp .b cap_ipc_owner bypass permission checks for operations on system v ipc objects. .tp .b cap_kill bypass permission checks for sending signals (see .br kill (2)). this includes use of the .br ioctl (2) .b kdsigaccept operation. .\" fixme . cap_kill also has an effect for threads + setting child .\" termination signal to other than sigchld: without this .\" capability, the termination signal reverts to sigchld .\" if the child does an exec(). what is the rationale .\" for this? .tp .br cap_lease " (since linux 2.4)" establish leases on arbitrary files (see .br fcntl (2)). .tp .b cap_linux_immutable set the .b fs_append_fl and .b fs_immutable_fl inode flags (see .br ioctl_iflags (2)). .tp .br cap_mac_admin " (since linux 2.6.25)" allow mac configuration or state changes. implemented for the smack linux security module (lsm). .tp .br cap_mac_override " (since linux 2.6.25)" override mandatory access control (mac). implemented for the smack lsm. .tp .br cap_mknod " (since linux 2.4)" create special files using .br mknod (2). .tp .b cap_net_admin perform various network-related operations: .pd 0 .rs .ip * 2 interface configuration; .ip * administration of ip firewall, masquerading, and accounting; .ip * modify routing tables; .ip * bind to any address for transparent proxying; .ip * set type-of-service (tos); .ip * clear driver statistics; .ip * set promiscuous mode; .ip * enabling multicasting; .ip * use .br setsockopt (2) to set the following socket options: .br so_debug , .br so_mark , .br so_priority (for a priority outside the range 0 to 6), .br so_rcvbufforce , and .br so_sndbufforce . .re .pd .tp .b cap_net_bind_service bind a socket to internet domain privileged ports (port numbers less than 1024). .tp .b cap_net_broadcast (unused) make socket broadcasts, and listen to multicasts. .\" fixme since linux 4.2, there are use cases for netlink sockets .\" commit 59324cf35aba5336b611074028777838a963d03b .tp .b cap_net_raw .pd 0 .rs .ip * 2 use raw and packet sockets; .ip * bind to any address for transparent proxying. .re .pd .\" also various ip options and setsockopt(so_bindtodevice) .tp .br cap_perfmon " (since linux 5.8)" employ various performance-monitoring mechanisms, including: .rs .ip * 2 .pd 0 call .br perf_event_open (2); .ip * employ various bpf operations that have performance implications. .re .pd .ip this capability was added in linux 5.8 to separate out performance monitoring functionality from the overloaded .br cap_sys_admin capability. see also the kernel source file .ir documentation/admin\-guide/perf\-security.rst . .tp .b cap_setgid .rs .pd 0 .ip * 2 make arbitrary manipulations of process gids and supplementary gid list; .ip * forge gid when passing socket credentials via unix domain sockets; .ip * write a group id mapping in a user namespace (see .br user_namespaces (7)). .pd .re .tp .br cap_setfcap " (since linux 2.6.24)" set arbitrary capabilities on a file. .ip .\" commit db2e718a47984b9d71ed890eb2ea36ecf150de18 since linux 5.12, this capability is also needed to map user id 0 in a new user namespace; see .br user_namespaces (7) for details. .tp .b cap_setpcap if file capabilities are supported (i.e., since linux 2.6.24): add any capability from the calling thread's bounding set to its inheritable set; drop capabilities from the bounding set (via .br prctl (2) .br pr_capbset_drop ); make changes to the .i securebits flags. .ip if file capabilities are not supported (i.e., kernels before linux 2.6.24): grant or remove any capability in the caller's permitted capability set to or from any other process. (this property of .b cap_setpcap is not available when the kernel is configured to support file capabilities, since .b cap_setpcap has entirely different semantics for such kernels.) .tp .b cap_setuid .rs .pd 0 .ip * 2 make arbitrary manipulations of process uids .rb ( setuid (2), .br setreuid (2), .br setresuid (2), .br setfsuid (2)); .ip * forge uid when passing socket credentials via unix domain sockets; .ip * write a user id mapping in a user namespace (see .br user_namespaces (7)). .pd .re .\" fixme cap_setuid also an effect in exec(); document this. .tp .b cap_sys_admin .ir note : this capability is overloaded; see .ir "notes to kernel developers" , below. .ip .pd 0 .rs .ip * 2 perform a range of system administration operations including: .br quotactl (2), .br mount (2), .br umount (2), .br pivot_root (2), .br swapon (2), .br swapoff (2), .br sethostname (2), and .br setdomainname (2); .ip * perform privileged .br syslog (2) operations (since linux 2.6.37, .br cap_syslog should be used to permit such operations); .ip * perform .b vm86_request_irq .br vm86 (2) command; .ip * access the same checkpoint/restore functionality that is governed by .br cap_checkpoint_restore (but the latter, weaker capability is preferred for accessing that functionality). .ip * perform the same bpf operations as are governed by .br cap_bpf (but the latter, weaker capability is preferred for accessing that functionality). .ip * employ the same performance monitoring mechanisms as are governed by .br cap_perfmon (but the latter, weaker capability is preferred for accessing that functionality). .ip * perform .b ipc_set and .b ipc_rmid operations on arbitrary system v ipc objects; .ip * override .b rlimit_nproc resource limit; .ip * perform operations on .i trusted and .i security extended attributes (see .br xattr (7)); .ip * use .br lookup_dcookie (2); .ip * use .br ioprio_set (2) to assign .b ioprio_class_rt and (before linux 2.6.25) .b ioprio_class_idle i/o scheduling classes; .ip * forge pid when passing socket credentials via unix domain sockets; .ip * exceed .ir /proc/sys/fs/file\-max , the system-wide limit on the number of open files, in system calls that open files (e.g., .br accept (2), .br execve (2), .br open (2), .br pipe (2)); .ip * employ .b clone_* flags that create new namespaces with .br clone (2) and .br unshare (2) (but, since linux 3.8, creating user namespaces does not require any capability); .ip * access privileged .i perf event information; .ip * call .br setns (2) (requires .b cap_sys_admin in the .i target namespace); .ip * call .br fanotify_init (2); .ip * perform privileged .b keyctl_chown and .b keyctl_setperm .br keyctl (2) operations; .ip * perform .br madvise (2) .b madv_hwpoison operation; .ip * employ the .b tiocsti .br ioctl (2) to insert characters into the input queue of a terminal other than the caller's controlling terminal; .ip * employ the obsolete .br nfsservctl (2) system call; .ip * employ the obsolete .br bdflush (2) system call; .ip * perform various privileged block-device .br ioctl (2) operations; .ip * perform various privileged filesystem .br ioctl (2) operations; .ip * perform privileged .br ioctl (2) operations on the .ir /dev/random device (see .br random (4)); .ip * install a .br seccomp (2) filter without first having to set the .i no_new_privs thread attribute; .ip * modify allow/deny rules for device control groups; .ip * employ the .br ptrace (2) .b ptrace_seccomp_get_filter operation to dump tracee's seccomp filters; .ip * employ the .br ptrace (2) .b ptrace_setoptions operation to suspend the tracee's seccomp protections (i.e., the .b ptrace_o_suspend_seccomp flag); .ip * perform administrative operations on many device drivers; .ip * modify autogroup nice values by writing to .ir /proc/[pid]/autogroup (see .br sched (7)). .re .pd .tp .b cap_sys_boot use .br reboot (2) and .br kexec_load (2). .tp .b cap_sys_chroot .rs .pd 0 .ip * 2 use .br chroot (2); .ip * change mount namespaces using .br setns (2). .pd .re .tp .b cap_sys_module .rs .pd 0 .ip * 2 load and unload kernel modules (see .br init_module (2) and .br delete_module (2)); .ip * in kernels before 2.6.25: drop capabilities from the system-wide capability bounding set. .pd .re .tp .b cap_sys_nice .pd 0 .rs .ip * 2 lower the process nice value .rb ( nice (2), .br setpriority (2)) and change the nice value for arbitrary processes; .ip * set real-time scheduling policies for calling process, and set scheduling policies and priorities for arbitrary processes .rb ( sched_setscheduler (2), .br sched_setparam (2), .br sched_setattr (2)); .ip * set cpu affinity for arbitrary processes .rb ( sched_setaffinity (2)); .ip * set i/o scheduling class and priority for arbitrary processes .rb ( ioprio_set (2)); .ip * apply .br migrate_pages (2) to arbitrary processes and allow processes to be migrated to arbitrary nodes; .\" fixme cap_sys_nice also has the following effect for .\" migrate_pages(2): .\" do_migrate_pages(mm, &old, &new, .\" capable(cap_sys_nice) ? mpol_mf_move_all : mpol_mf_move); .\" .\" document this. .ip * apply .br move_pages (2) to arbitrary processes; .ip * use the .b mpol_mf_move_all flag with .br mbind (2) and .br move_pages (2). .re .pd .tp .b cap_sys_pacct use .br acct (2). .tp .b cap_sys_ptrace .pd 0 .rs .ip * 2 trace arbitrary processes using .br ptrace (2); .ip * apply .br get_robust_list (2) to arbitrary processes; .ip * transfer data to or from the memory of arbitrary processes using .br process_vm_readv (2) and .br process_vm_writev (2); .ip * inspect processes using .br kcmp (2). .re .pd .tp .b cap_sys_rawio .pd 0 .rs .ip * 2 perform i/o port operations .rb ( iopl (2) and .br ioperm (2)); .ip * access .ir /proc/kcore ; .ip * employ the .b fibmap .br ioctl (2) operation; .ip * open devices for accessing x86 model-specific registers (msrs, see .br msr (4)); .ip * update .ir /proc/sys/vm/mmap_min_addr ; .ip * create memory mappings at addresses below the value specified by .ir /proc/sys/vm/mmap_min_addr ; .ip * map files in .ir /proc/bus/pci ; .ip * open .ir /dev/mem and .ir /dev/kmem ; .ip * perform various scsi device commands; .ip * perform certain operations on .br hpsa (4) and .br cciss (4) devices; .ip * perform a range of device-specific operations on other devices. .re .pd .tp .b cap_sys_resource .pd 0 .rs .ip * 2 use reserved space on ext2 filesystems; .ip * make .br ioctl (2) calls controlling ext3 journaling; .ip * override disk quota limits; .ip * increase resource limits (see .br setrlimit (2)); .ip * override .b rlimit_nproc resource limit; .ip * override maximum number of consoles on console allocation; .ip * override maximum number of keymaps; .ip * allow more than 64hz interrupts from the real-time clock; .ip * raise .i msg_qbytes limit for a system v message queue above the limit in .i /proc/sys/kernel/msgmnb (see .br msgop (2) and .br msgctl (2)); .ip * allow the .b rlimit_nofile resource limit on the number of "in-flight" file descriptors to be bypassed when passing file descriptors to another process via a unix domain socket (see .br unix (7)); .ip * override the .i /proc/sys/fs/pipe\-size\-max limit when setting the capacity of a pipe using the .b f_setpipe_sz .br fcntl (2) command; .ip * use .br f_setpipe_sz to increase the capacity of a pipe above the limit specified by .ir /proc/sys/fs/pipe\-max\-size ; .ip * override .ir /proc/sys/fs/mqueue/queues_max , .ir /proc/sys/fs/mqueue/msg_max , and .i /proc/sys/fs/mqueue/msgsize_max limits when creating posix message queues (see .br mq_overview (7)); .ip * employ the .br prctl (2) .b pr_set_mm operation; .ip * set .ir /proc/[pid]/oom_score_adj to a value lower than the value last set by a process with .br cap_sys_resource . .re .pd .tp .b cap_sys_time set system clock .rb ( settimeofday (2), .br stime (2), .br adjtimex (2)); set real-time (hardware) clock. .tp .b cap_sys_tty_config use .br vhangup (2); employ various privileged .br ioctl (2) operations on virtual terminals. .tp .br cap_syslog " (since linux 2.6.37)" .rs .pd 0 .ip * 2 perform privileged .br syslog (2) operations. see .br syslog (2) for information on which operations require privilege. .ip * view kernel addresses exposed via .i /proc and other interfaces when .ir /proc/sys/kernel/kptr_restrict has the value 1. (see the discussion of the .i kptr_restrict in .br proc (5).) .pd .re .tp .br cap_wake_alarm " (since linux 3.0)" trigger something that will wake up the system (set .b clock_realtime_alarm and .b clock_boottime_alarm timers). .\" .ss past and current implementation a full implementation of capabilities requires that: .ip 1. 3 for all privileged operations, the kernel must check whether the thread has the required capability in its effective set. .ip 2. the kernel must provide system calls allowing a thread's capability sets to be changed and retrieved. .ip 3. the filesystem must support attaching capabilities to an executable file, so that a process gains those capabilities when the file is executed. .pp before kernel 2.6.24, only the first two of these requirements are met; since kernel 2.6.24, all three requirements are met. .\" .ss notes to kernel developers when adding a new kernel feature that should be governed by a capability, consider the following points. .ip * 3 the goal of capabilities is divide the power of superuser into pieces, such that if a program that has one or more capabilities is compromised, its power to do damage to the system would be less than the same program running with root privilege. .ip * you have the choice of either creating a new capability for your new feature, or associating the feature with one of the existing capabilities. in order to keep the set of capabilities to a manageable size, the latter option is preferable, unless there are compelling reasons to take the former option. (there is also a technical limit: the size of capability sets is currently limited to 64 bits.) .ip * to determine which existing capability might best be associated with your new feature, review the list of capabilities above in order to find a "silo" into which your new feature best fits. one approach to take is to determine if there are other features requiring capabilities that will always be used along with the new feature. if the new feature is useless without these other features, you should use the same capability as the other features. .ip * .ir don't choose .b cap_sys_admin if you can possibly avoid it! a vast proportion of existing capability checks are associated with this capability (see the partial list above). it can plausibly be called "the new root", since on the one hand, it confers a wide range of powers, and on the other hand, its broad scope means that this is the capability that is required by many privileged programs. don't make the problem worse. the only new features that should be associated with .b cap_sys_admin are ones that .i closely match existing uses in that silo. .ip * if you have determined that it really is necessary to create a new capability for your feature, don't make or name it as a "single-use" capability. thus, for example, the addition of the highly specific .br cap_sys_pacct was probably a mistake. instead, try to identify and name your new capability as a broader silo into which other related future use cases might fit. .\" .ss thread capability sets each thread has the following capability sets containing zero or more of the above capabilities: .tp .ir permitted this is a limiting superset for the effective capabilities that the thread may assume. it is also a limiting superset for the capabilities that may be added to the inheritable set by a thread that does not have the .b cap_setpcap capability in its effective set. .ip if a thread drops a capability from its permitted set, it can never reacquire that capability (unless it .br execve (2)s either a set-user-id-root program, or a program whose associated file capabilities grant that capability). .tp .ir inheritable this is a set of capabilities preserved across an .br execve (2). inheritable capabilities remain inheritable when executing any program, and inheritable capabilities are added to the permitted set when executing a program that has the corresponding bits set in the file inheritable set. .ip because inheritable capabilities are not generally preserved across .br execve (2) when running as a non-root user, applications that wish to run helper programs with elevated capabilities should consider using ambient capabilities, described below. .tp .ir effective this is the set of capabilities used by the kernel to perform permission checks for the thread. .tp .ir bounding " (per-thread since linux 2.6.25)" the capability bounding set is a mechanism that can be used to limit the capabilities that are gained during .br execve (2). .ip since linux 2.6.25, this is a per-thread capability set. in older kernels, the capability bounding set was a system wide attribute shared by all threads on the system. .ip for more details on the capability bounding set, see below. .tp .ir ambient " (since linux 4.3)" .\" commit 58319057b7847667f0c9585b9de0e8932b0fdb08 this is a set of capabilities that are preserved across an .br execve (2) of a program that is not privileged. the ambient capability set obeys the invariant that no capability can ever be ambient if it is not both permitted and inheritable. .ip the ambient capability set can be directly modified using .br prctl (2). ambient capabilities are automatically lowered if either of the corresponding permitted or inheritable capabilities is lowered. .ip executing a program that changes uid or gid due to the set-user-id or set-group-id bits or executing a program that has any file capabilities set will clear the ambient set. ambient capabilities are added to the permitted set and assigned to the effective set when .br execve (2) is called. if ambient capabilities cause a process's permitted and effective capabilities to increase during an .br execve (2), this does not trigger the secure-execution mode described in .br ld.so (8). .pp a child created via .br fork (2) inherits copies of its parent's capability sets. see below for a discussion of the treatment of capabilities during .br execve (2). .pp using .br capset (2), a thread may manipulate its own capability sets (see below). .pp since linux 3.2, the file .i /proc/sys/kernel/cap_last_cap .\" commit 73efc0394e148d0e15583e13712637831f926720 exposes the numerical value of the highest capability supported by the running kernel; this can be used to determine the highest bit that may be set in a capability set. .\" .ss file capabilities since kernel 2.6.24, the kernel supports associating capability sets with an executable file using .br setcap (8). the file capability sets are stored in an extended attribute (see .br setxattr (2) and .br xattr (7)) named .ir "security.capability" . writing to this extended attribute requires the .br cap_setfcap capability. the file capability sets, in conjunction with the capability sets of the thread, determine the capabilities of a thread after an .br execve (2). .pp the three file capability sets are: .tp .ir permitted " (formerly known as " forced ): these capabilities are automatically permitted to the thread, regardless of the thread's inheritable capabilities. .tp .ir inheritable " (formerly known as " allowed ): this set is anded with the thread's inheritable set to determine which inheritable capabilities are enabled in the permitted set of the thread after the .br execve (2). .tp .ir effective : this is not a set, but rather just a single bit. if this bit is set, then during an .br execve (2) all of the new permitted capabilities for the thread are also raised in the effective set. if this bit is not set, then after an .br execve (2), none of the new permitted capabilities is in the new effective set. .ip enabling the file effective capability bit implies that any file permitted or inheritable capability that causes a thread to acquire the corresponding permitted capability during an .br execve (2) (see the transformation rules described below) will also acquire that capability in its effective set. therefore, when assigning capabilities to a file .rb ( setcap (8), .br cap_set_file (3), .br cap_set_fd (3)), if we specify the effective flag as being enabled for any capability, then the effective flag must also be specified as enabled for all other capabilities for which the corresponding permitted or inheritable flags is enabled. .\" .ss file capability extended attribute versioning to allow extensibility, the kernel supports a scheme to encode a version number inside the .i security.capability extended attribute that is used to implement file capabilities. these version numbers are internal to the implementation, and not directly visible to user-space applications. to date, the following versions are supported: .tp .br vfs_cap_revision_1 this was the original file capability implementation, which supported 32-bit masks for file capabilities. .tp .br vfs_cap_revision_2 " (since linux 2.6.25)" .\" commit e338d263a76af78fe8f38a72131188b58fceb591 this version allows for file capability masks that are 64 bits in size, and was necessary as the number of supported capabilities grew beyond 32. the kernel transparently continues to support the execution of files that have 32-bit version 1 capability masks, but when adding capabilities to files that did not previously have capabilities, or modifying the capabilities of existing files, it automatically uses the version 2 scheme (or possibly the version 3 scheme, as described below). .tp .br vfs_cap_revision_3 " (since linux 4.14)" .\" commit 8db6c34f1dbc8e06aa016a9b829b06902c3e1340 version 3 file capabilities are provided to support namespaced file capabilities (described below). .ip as with version 2 file capabilities, version 3 capability masks are 64 bits in size. but in addition, the root user id of namespace is encoded in the .i security.capability extended attribute. (a namespace's root user id is the value that user id 0 inside that namespace maps to in the initial user namespace.) .ip version 3 file capabilities are designed to coexist with version 2 capabilities; that is, on a modern linux system, there may be some files with version 2 capabilities while others have version 3 capabilities. .pp before linux 4.14, the only kind of file capability extended attribute that could be attached to a file was a .b vfs_cap_revision_2 attribute. since linux 4.14, the version of the .i security.capability extended attribute that is attached to a file depends on the circumstances in which the attribute was created. .pp starting with linux 4.14, a .i security.capability extended attribute is automatically created as (or converted to) a version 3 .rb ( vfs_cap_revision_3 ) attribute if both of the following are true: .ip (1) 4 the thread writing the attribute resides in a noninitial user namespace. (more precisely: the thread resides in a user namespace other than the one from which the underlying filesystem was mounted.) .ip (2) the thread has the .br cap_setfcap capability over the file inode, meaning that (a) the thread has the .b cap_setfcap capability in its own user namespace; and (b) the uid and gid of the file inode have mappings in the writer's user namespace. .pp when a .br vfs_cap_revision_3 .i security.capability extended attribute is created, the root user id of the creating thread's user namespace is saved in the extended attribute. .pp by contrast, creating or modifying a .i security.capability extended attribute from a privileged .rb ( cap_setfcap ) thread that resides in the namespace where the underlying filesystem was mounted (this normally means the initial user namespace) automatically results in the creation of a version 2 .rb ( vfs_cap_revision_2 ) attribute. .pp note that the creation of a version 3 .i security.capability extended attribute is automatic. that is to say, when a user-space application writes .rb ( setxattr (2)) a .i security.capability attribute in the version 2 format, the kernel will automatically create a version 3 attribute if the attribute is created in the circumstances described above. correspondingly, when a version 3 .i security.capability attribute is retrieved .rb ( getxattr (2)) by a process that resides inside a user namespace that was created by the root user id (or a descendant of that user namespace), the returned attribute is (automatically) simplified to appear as a version 2 attribute (i.e., the returned value is the size of a version 2 attribute and does not include the root user id). these automatic translations mean that no changes are required to user-space tools (e.g., .br setcap (1) and .br getcap (1)) in order for those tools to be used to create and retrieve version 3 .i security.capability attributes. .pp note that a file can have either a version 2 or a version 3 .i security.capability extended attribute associated with it, but not both: creation or modification of the .i security.capability extended attribute will automatically modify the version according to the circumstances in which the extended attribute is created or modified. .\" .ss transformation of capabilities during execve() during an .br execve (2), the kernel calculates the new capabilities of the process using the following algorithm: .pp .in +4n .ex p'(ambient) = (file is privileged) ? 0 : p(ambient) p'(permitted) = (p(inheritable) & f(inheritable)) | (f(permitted) & p(bounding)) | p'(ambient) p'(effective) = f(effective) ? p'(permitted) : p'(ambient) p'(inheritable) = p(inheritable) [i.e., unchanged] p'(bounding) = p(bounding) [i.e., unchanged] .ee .in .pp where: .rs 4 .ip p() 6 denotes the value of a thread capability set before the .br execve (2) .ip p'() denotes the value of a thread capability set after the .br execve (2) .ip f() denotes a file capability set .re .pp note the following details relating to the above capability transformation rules: .ip * 3 the ambient capability set is present only since linux 4.3. when determining the transformation of the ambient set during .br execve (2), a privileged file is one that has capabilities or has the set-user-id or set-group-id bit set. .ip * prior to linux 2.6.25, the bounding set was a system-wide attribute shared by all threads. that system-wide value was employed to calculate the new permitted set during .br execve (2) in the same manner as shown above for .ir p(bounding) . .pp .ir note : during the capability transitions described above, file capabilities may be ignored (treated as empty) for the same reasons that the set-user-id and set-group-id bits are ignored; see .br execve (2). file capabilities are similarly ignored if the kernel was booted with the .i no_file_caps option. .pp .ir note : according to the rules above, if a process with nonzero user ids performs an .br execve (2) then any capabilities that are present in its permitted and effective sets will be cleared. for the treatment of capabilities when a process with a user id of zero performs an .br execve (2), see below under .ir "capabilities and execution of programs by root" . .\" .ss safety checking for capability-dumb binaries a capability-dumb binary is an application that has been marked to have file capabilities, but has not been converted to use the .br libcap (3) api to manipulate its capabilities. (in other words, this is a traditional set-user-id-root program that has been switched to use file capabilities, but whose code has not been modified to understand capabilities.) for such applications, the effective capability bit is set on the file, so that the file permitted capabilities are automatically enabled in the process effective set when executing the file. the kernel recognizes a file which has the effective capability bit set as capability-dumb for the purpose of the check described here. .pp when executing a capability-dumb binary, the kernel checks if the process obtained all permitted capabilities that were specified in the file permitted set, after the capability transformations described above have been performed. (the typical reason why this might .i not occur is that the capability bounding set masked out some of the capabilities in the file permitted set.) if the process did not obtain the full set of file permitted capabilities, then .br execve (2) fails with the error .br eperm . this prevents possible security risks that could arise when a capability-dumb application is executed with less privilege that it needs. note that, by definition, the application could not itself recognize this problem, since it does not employ the .br libcap (3) api. .\" .ss capabilities and execution of programs by root .\" see cap_bprm_set_creds(), bprm_caps_from_vfs_cap() and .\" handle_privileged_root() in security/commoncap.c (linux 5.0 source) in order to mirror traditional unix semantics, the kernel performs special treatment of file capabilities when a process with uid 0 (root) executes a program and when a set-user-id-root program is executed. .pp after having performed any changes to the process effective id that were triggered by the set-user-id mode bit of the binary\(eme.g., switching the effective user id to 0 (root) because a set-user-id-root program was executed\(emthe kernel calculates the file capability sets as follows: .ip 1. 3 if the real or effective user id of the process is 0 (root), then the file inheritable and permitted sets are ignored; instead they are notionally considered to be all ones (i.e., all capabilities enabled). (there is one exception to this behavior, described below in .ir "set-user-id-root programs that have file capabilities" .) .ip 2. if the effective user id of the process is 0 (root) or the file effective bit is in fact enabled, then the file effective bit is notionally defined to be one (enabled). .pp these notional values for the file's capability sets are then used as described above to calculate the transformation of the process's capabilities during .br execve (2). .pp thus, when a process with nonzero uids .br execve (2)s a set-user-id-root program that does not have capabilities attached, or when a process whose real and effective uids are zero .br execve (2)s a program, the calculation of the process's new permitted capabilities simplifies to: .pp .in +4n .ex p'(permitted) = p(inheritable) | p(bounding) p'(effective) = p'(permitted) .ee .in .pp consequently, the process gains all capabilities in its permitted and effective capability sets, except those masked out by the capability bounding set. (in the calculation of p'(permitted), the p'(ambient) term can be simplified away because it is by definition a proper subset of p(inheritable).) .pp the special treatments of user id 0 (root) described in this subsection can be disabled using the securebits mechanism described below. .\" .\" .ss set-user-id-root programs that have file capabilities there is one exception to the behavior described under .ir "capabilities and execution of programs by root" . if (a) the binary that is being executed has capabilities attached and (b) the real user id of the process is .i not 0 (root) and (c) the effective user id of the process .i is 0 (root), then the file capability bits are honored (i.e., they are not notionally considered to be all ones). the usual way in which this situation can arise is when executing a set-uid-root program that also has file capabilities. when such a program is executed, the process gains just the capabilities granted by the program (i.e., not all capabilities, as would occur when executing a set-user-id-root program that does not have any associated file capabilities). .pp note that one can assign empty capability sets to a program file, and thus it is possible to create a set-user-id-root program that changes the effective and saved set-user-id of the process that executes the program to 0, but confers no capabilities to that process. .\" .ss capability bounding set the capability bounding set is a security mechanism that can be used to limit the capabilities that can be gained during an .br execve (2). the bounding set is used in the following ways: .ip * 2 during an .br execve (2), the capability bounding set is anded with the file permitted capability set, and the result of this operation is assigned to the thread's permitted capability set. the capability bounding set thus places a limit on the permitted capabilities that may be granted by an executable file. .ip * (since linux 2.6.25) the capability bounding set acts as a limiting superset for the capabilities that a thread can add to its inheritable set using .br capset (2). this means that if a capability is not in the bounding set, then a thread can't add this capability to its inheritable set, even if it was in its permitted capabilities, and thereby cannot have this capability preserved in its permitted set when it .br execve (2)s a file that has the capability in its inheritable set. .pp note that the bounding set masks the file permitted capabilities, but not the inheritable capabilities. if a thread maintains a capability in its inheritable set that is not in its bounding set, then it can still gain that capability in its permitted set by executing a file that has the capability in its inheritable set. .pp depending on the kernel version, the capability bounding set is either a system-wide attribute, or a per-process attribute. .pp .b "capability bounding set from linux 2.6.25 onward" .pp from linux 2.6.25, the .i "capability bounding set" is a per-thread attribute. (the system-wide capability bounding set described below no longer exists.) .pp the bounding set is inherited at .br fork (2) from the thread's parent, and is preserved across an .br execve (2). .pp a thread may remove capabilities from its capability bounding set using the .br prctl (2) .b pr_capbset_drop operation, provided it has the .b cap_setpcap capability. once a capability has been dropped from the bounding set, it cannot be restored to that set. a thread can determine if a capability is in its bounding set using the .br prctl (2) .b pr_capbset_read operation. .pp removing capabilities from the bounding set is supported only if file capabilities are compiled into the kernel. in kernels before linux 2.6.33, file capabilities were an optional feature configurable via the .b config_security_file_capabilities option. since linux 2.6.33, .\" commit b3a222e52e4d4be77cc4520a57af1a4a0d8222d1 the configuration option has been removed and file capabilities are always part of the kernel. when file capabilities are compiled into the kernel, the .b init process (the ancestor of all processes) begins with a full bounding set. if file capabilities are not compiled into the kernel, then .b init begins with a full bounding set minus .br cap_setpcap , because this capability has a different meaning when there are no file capabilities. .pp removing a capability from the bounding set does not remove it from the thread's inheritable set. however it does prevent the capability from being added back into the thread's inheritable set in the future. .pp .b "capability bounding set prior to linux 2.6.25" .pp in kernels before 2.6.25, the capability bounding set is a system-wide attribute that affects all threads on the system. the bounding set is accessible via the file .ir /proc/sys/kernel/cap\-bound . (confusingly, this bit mask parameter is expressed as a signed decimal number in .ir /proc/sys/kernel/cap\-bound .) .pp only the .b init process may set capabilities in the capability bounding set; other than that, the superuser (more precisely: a process with the .b cap_sys_module capability) may only clear capabilities from this set. .pp on a standard system the capability bounding set always masks out the .b cap_setpcap capability. to remove this restriction (dangerous!), modify the definition of .b cap_init_eff_set in .i include/linux/capability.h and rebuild the kernel. .pp the system-wide capability bounding set feature was added to linux starting with kernel version 2.2.11. .\" .\" .\" .ss effect of user id changes on capabilities to preserve the traditional semantics for transitions between 0 and nonzero user ids, the kernel makes the following changes to a thread's capability sets on changes to the thread's real, effective, saved set, and filesystem user ids (using .br setuid (2), .br setresuid (2), or similar): .ip 1. 3 if one or more of the real, effective, or saved set user ids was previously 0, and as a result of the uid changes all of these ids have a nonzero value, then all capabilities are cleared from the permitted, effective, and ambient capability sets. .ip 2. if the effective user id is changed from 0 to nonzero, then all capabilities are cleared from the effective set. .ip 3. if the effective user id is changed from nonzero to 0, then the permitted set is copied to the effective set. .ip 4. if the filesystem user id is changed from 0 to nonzero (see .br setfsuid (2)), then the following capabilities are cleared from the effective set: .br cap_chown , .br cap_dac_override , .br cap_dac_read_search , .br cap_fowner , .br cap_fsetid , .b cap_linux_immutable (since linux 2.6.30), .br cap_mac_override , and .b cap_mknod (since linux 2.6.30). if the filesystem uid is changed from nonzero to 0, then any of these capabilities that are enabled in the permitted set are enabled in the effective set. .pp if a thread that has a 0 value for one or more of its user ids wants to prevent its permitted capability set being cleared when it resets all of its user ids to nonzero values, it can do so using the .b secbit_keep_caps securebits flag described below. .\" .ss programmatically adjusting capability sets a thread can retrieve and change its permitted, effective, and inheritable capability sets using the .br capget (2) and .br capset (2) system calls. however, the use of .br cap_get_proc (3) and .br cap_set_proc (3), both provided in the .i libcap package, is preferred for this purpose. the following rules govern changes to the thread capability sets: .ip 1. 3 if the caller does not have the .b cap_setpcap capability, the new inheritable set must be a subset of the combination of the existing inheritable and permitted sets. .ip 2. (since linux 2.6.25) the new inheritable set must be a subset of the combination of the existing inheritable set and the capability bounding set. .ip 3. the new permitted set must be a subset of the existing permitted set (i.e., it is not possible to acquire permitted capabilities that the thread does not currently have). .ip 4. the new effective set must be a subset of the new permitted set. .ss the securebits flags: establishing a capabilities-only environment .\" for some background: .\" see http://lwn.net/articles/280279/ and .\" http://article.gmane.org/gmane.linux.kernel.lsm/5476/ starting with kernel 2.6.26, and with a kernel in which file capabilities are enabled, linux implements a set of per-thread .i securebits flags that can be used to disable special handling of capabilities for uid 0 .ri ( root ). these flags are as follows: .tp .b secbit_keep_caps setting this flag allows a thread that has one or more 0 uids to retain capabilities in its permitted set when it switches all of its uids to nonzero values. if this flag is not set, then such a uid switch causes the thread to lose all permitted capabilities. this flag is always cleared on an .br execve (2). .ip note that even with the .b secbit_keep_caps flag set, the effective capabilities of a thread are cleared when it switches its effective uid to a nonzero value. however, if the thread has set this flag and its effective uid is already nonzero, and the thread subsequently switches all other uids to nonzero values, then the effective capabilities will not be cleared. .ip the setting of the .b secbit_keep_caps flag is ignored if the .b secbit_no_setuid_fixup flag is set. (the latter flag provides a superset of the effect of the former flag.) .ip this flag provides the same functionality as the older .br prctl (2) .b pr_set_keepcaps operation. .tp .b secbit_no_setuid_fixup setting this flag stops the kernel from adjusting the process's permitted, effective, and ambient capability sets when the thread's effective and filesystem uids are switched between zero and nonzero values. (see the subsection .ir "effect of user id changes on capabilities" .) .tp .b secbit_noroot if this bit is set, then the kernel does not grant capabilities when a set-user-id-root program is executed, or when a process with an effective or real uid of 0 calls .br execve (2). (see the subsection .ir "capabilities and execution of programs by root" .) .tp .b secbit_no_cap_ambient_raise setting this flag disallows raising ambient capabilities via the .br prctl (2) .br pr_cap_ambient_raise operation. .pp each of the above "base" flags has a companion "locked" flag. setting any of the "locked" flags is irreversible, and has the effect of preventing further changes to the corresponding "base" flag. the locked flags are: .br secbit_keep_caps_locked , .br secbit_no_setuid_fixup_locked , .br secbit_noroot_locked , and .br secbit_no_cap_ambient_raise_locked . .pp the .i securebits flags can be modified and retrieved using the .br prctl (2) .b pr_set_securebits and .b pr_get_securebits operations. the .b cap_setpcap capability is required to modify the flags. note that the .br secbit_* constants are available only after including the .i header file. .pp the .i securebits flags are inherited by child processes. during an .br execve (2), all of the flags are preserved, except .b secbit_keep_caps which is always cleared. .pp an application can use the following call to lock itself, and all of its descendants, into an environment where the only way of gaining capabilities is by executing a program with associated file capabilities: .pp .in +4n .ex prctl(pr_set_securebits, /* secbit_keep_caps off */ secbit_keep_caps_locked | secbit_no_setuid_fixup | secbit_no_setuid_fixup_locked | secbit_noroot | secbit_noroot_locked); /* setting/locking secbit_no_cap_ambient_raise is not required */ .ee .in .\" .\" .ss per-user-namespace """set-user-id-root""" programs a set-user-id program whose uid matches the uid that created a user namespace will confer capabilities in the process's permitted and effective sets when executed by any process inside that namespace or any descendant user namespace. .pp the rules about the transformation of the process's capabilities during the .br execve (2) are exactly as described in the subsections .ir "transformation of capabilities during execve()" and .ir "capabilities and execution of programs by root" , with the difference that, in the latter subsection, "root" is the uid of the creator of the user namespace. .\" .\" .ss namespaced file capabilities .\" commit 8db6c34f1dbc8e06aa016a9b829b06902c3e1340 traditional (i.e., version 2) file capabilities associate only a set of capability masks with a binary executable file. when a process executes a binary with such capabilities, it gains the associated capabilities (within its user namespace) as per the rules described above in "transformation of capabilities during execve()". .pp because version 2 file capabilities confer capabilities to the executing process regardless of which user namespace it resides in, only privileged processes are permitted to associate capabilities with a file. here, "privileged" means a process that has the .br cap_setfcap capability in the user namespace where the filesystem was mounted (normally the initial user namespace). this limitation renders file capabilities useless for certain use cases. for example, in user-namespaced containers, it can be desirable to be able to create a binary that confers capabilities only to processes executed inside that container, but not to processes that are executed outside the container. .pp linux 4.14 added so-called namespaced file capabilities to support such use cases. namespaced file capabilities are recorded as version 3 (i.e., .br vfs_cap_revision_3 ) .i security.capability extended attributes. such an attribute is automatically created in the circumstances described above under "file capability extended attribute versioning". when a version 3 .i security.capability extended attribute is created, the kernel records not just the capability masks in the extended attribute, but also the namespace root user id. .pp as with a binary that has .br vfs_cap_revision_2 file capabilities, a binary with .br vfs_cap_revision_3 file capabilities confers capabilities to a process during .br execve (). however, capabilities are conferred only if the binary is executed by a process that resides in a user namespace whose uid 0 maps to the root user id that is saved in the extended attribute, or when executed by a process that resides in a descendant of such a namespace. .\" .\" .ss interaction with user namespaces for further information on the interaction of capabilities and user namespaces, see .br user_namespaces (7). .sh conforming to no standards govern capabilities, but the linux capability implementation is based on the withdrawn posix.1e draft standard; see .ur https://archive.org\:/details\:/posix_1003.1e-990310 .ue . .sh notes when attempting to .br strace (1) binaries that have capabilities (or set-user-id-root binaries), you may find the .i \-u option useful. something like: .pp .in +4n .ex $ \fbsudo strace \-o trace.log \-u ceci ./myprivprog\fp .ee .in .pp from kernel 2.5.27 to kernel 2.6.26, .\" commit 5915eb53861c5776cfec33ca4fcc1fd20d66dd27 removed .\" config_security_capabilities capabilities were an optional kernel component, and could be enabled/disabled via the .b config_security_capabilities kernel configuration option. .pp the .i /proc/[pid]/task/tid/status file can be used to view the capability sets of a thread. the .i /proc/[pid]/status file shows the capability sets of a process's main thread. before linux 3.8, nonexistent capabilities were shown as being enabled (1) in these sets. since linux 3.8, .\" 7b9a7ec565505699f503b4fcf61500dceb36e744 all nonexistent capabilities (above .br cap_last_cap ) are shown as disabled (0). .pp the .i libcap package provides a suite of routines for setting and getting capabilities that is more comfortable and less likely to change than the interface provided by .br capset (2) and .br capget (2). this package also provides the .br setcap (8) and .br getcap (8) programs. it can be found at .br .ur https://git.kernel.org\:/pub\:/scm\:/libs\:/libcap\:/libcap.git\:/refs/ .ue . .pp before kernel 2.6.24, and from kernel 2.6.24 to kernel 2.6.32 if file capabilities are not enabled, a thread with the .b cap_setpcap capability can manipulate the capabilities of threads other than itself. however, this is only theoretically possible, since no thread ever has .br cap_setpcap in either of these cases: .ip * 2 in the pre-2.6.25 implementation the system-wide capability bounding set, .ir /proc/sys/kernel/cap\-bound , always masks out the .b cap_setpcap capability, and this can not be changed without modifying the kernel source and rebuilding the kernel. .ip * if file capabilities are disabled (i.e., the kernel .b config_security_file_capabilities option is disabled), then .b init starts out with the .b cap_setpcap capability removed from its per-process bounding set, and that bounding set is inherited by all other processes created on the system. .sh see also .br capsh (1), .br setpriv (1), .br prctl (2), .br setfsuid (2), .br cap_clear (3), .br cap_copy_ext (3), .br cap_from_text (3), .br cap_get_file (3), .br cap_get_proc (3), .br cap_init (3), .br capgetp (3), .br capsetp (3), .br libcap (3), .br proc (5), .br credentials (7), .br pthreads (7), .br user_namespaces (7), .br captest (8), \" from libcap-ng .br filecap (8), \" from libcap-ng .br getcap (8), .br getpcaps (8), .br netcap (8), \" from libcap-ng .br pscap (8), \" from libcap-ng .br setcap (8) .pp .i include/linux/capability.h in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .so man2/getpid.2 .so man3/tan.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" modified 2004-11-15, added further text on flt_rounds .\" as suggested by aeb and fabian kreutz .\" .th fma 3 2021-03-22 "" "linux programmer's manual" .sh name fma, fmaf, fmal \- floating-point multiply and add .sh synopsis .nf .b #include .pp .bi "double fma(double " x ", double " y ", double " z ); .bi "float fmaf(float " x ", float " y ", float " z ); .bi "long double fmal(long double " x ", long double " y ", long double " z ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fma (), .br fmaf (), .br fmal (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions compute .ir x " * " y " + " z . the result is rounded as one ternary operation according to the current rounding mode (see .br fenv (3)). .sh return value these functions return the value of .ir x " * " y " + " z , rounded as one ternary operation. .pp if .i x or .i y is a nan, a nan is returned. .pp if .i x times .i y is an exact infinity, and .i z is an infinity with the opposite sign, a domain error occurs, and a nan is returned. .pp .\" posix.1-2008 allows some possible differences for the following two .\" domain error cases, but on linux they are treated the same (afaics). .\" nevertheless, we'll mirror posix.1 and describe the two cases .\" separately. if one of .i x or .i y is an infinity, the other is 0, and .i z is not a nan, a domain error occurs, and a nan is returned. .\" posix.1 says that a nan or an implementation-defined value shall .\" be returned for this case. .pp if one of .i x or .i y is an infinity, and the other is 0, and .i z is a nan, .\" posix.1 makes the domain error optional for this case. a domain error occurs, and a nan is returned. .pp if .i x times .i y is not an infinity times zero (or vice versa), and .i z is a nan, a nan is returned. .pp if the result overflows, a range error occurs, and an infinity with the correct sign is returned. .pp if the result underflows, a range error occurs, and a signed 0 is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp * \fiy\fp + \fiz\fp, \ or \fix\fp * \fiy\fp is invalid and \fiz\fp is not a nan .\" .i errno .\" is set to .\" .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp range error: result overflow .\" .i errno .\" is set to .\" .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error: result underflow .\" .i errno .\" is set to .\" .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .pp these functions do not set .ir errno . .\" fixme . is it intentional that these functions do not set errno? .\" bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6801 .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fma (), .br fmaf (), .br fmal () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br remainder (3), .br remquo (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt; .\" and copyright (c) 1993,1995 ian jackson .\" and copyright (c) 2006, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 00:35:52 1993 by rik faith .\" modified thu jun 4 12:21:13 1998 by andries brouwer .\" modified thu mar 3 09:49:35 2005 by michael haardt .\" 2007-03-25, mtk, added various text to description. .\" .th rename 2 2021-08-27 "linux" "linux programmer's manual" .sh name rename, renameat, renameat2 \- change the name or location of a file .sh synopsis .nf .b #include .pp .bi "int rename(const char *" oldpath ", const char *" newpath ); .pp .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "int renameat(int " olddirfd ", const char *" oldpath , .bi " int " newdirfd ", const char *" newpath ); .bi "int renameat2(int " olddirfd ", const char *" oldpath , .bi " int " newdirfd ", const char *" newpath \ ", unsigned int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .nf .br renameat (): since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .pp .br renameat2 (): _gnu_source .fi .sh description .br rename () renames a file, moving it between directories if required. any other hard links to the file (as created using .br link (2)) are unaffected. open file descriptors for .i oldpath are also unaffected. .pp various restrictions determine whether or not the rename operation succeeds: see errors below. .pp if .i newpath already exists, it will be atomically replaced, so that there is no point at which another process attempting to access .i newpath will find it missing. however, there will probably be a window in which both .i oldpath and .i newpath refer to the file being renamed. .pp if .i oldpath and .i newpath are existing hard links referring to the same file, then .br rename () does nothing, and returns a success status. .pp if .i newpath exists but the operation fails for some reason, .br rename () guarantees to leave an instance of .i newpath in place. .pp .i oldpath can specify a directory. in this case, .i newpath must either not exist, or it must specify an empty directory. .pp if .i oldpath refers to a symbolic link, the link is renamed; if .i newpath refers to a symbolic link, the link will be overwritten. .ss renameat() the .br renameat () system call operates in exactly the same way as .br rename (), except for the differences described here. .pp if the pathname given in .i oldpath is relative, then it is interpreted relative to the directory referred to by the file descriptor .i olddirfd (rather than relative to the current working directory of the calling process, as is done by .br rename () for a relative pathname). .pp if .i oldpath is relative and .i olddirfd is the special value .br at_fdcwd , then .i oldpath is interpreted relative to the current working directory of the calling process (like .br rename ()). .pp if .i oldpath is absolute, then .i olddirfd is ignored. .pp the interpretation of .i newpath is as for .ir oldpath , except that a relative pathname is interpreted relative to the directory referred to by the file descriptor .ir newdirfd . .pp see .br openat (2) for an explanation of the need for .br renameat (). .ss renameat2() .br renameat2 () has an additional .i flags argument. a .br renameat2 () call with a zero .i flags argument is equivalent to .br renameat (). .pp the .i flags argument is a bit mask consisting of zero or more of the following flags: .tp .b rename_exchange atomically exchange .ir oldpath and .ir newpath . both pathnames must exist but may be of different types (e.g., one could be a non-empty directory and the other a symbolic link). .tp .b rename_noreplace don't overwrite .ir newpath of the rename. return an error if .ir newpath already exists. .ip .b rename_noreplace can't be employed together with .br rename_exchange . .ip .b rename_noreplace requires support from the underlying filesystem. support for various filesystems was added as follows: .rs .ip * 3 ext4 (linux 3.15); .\" ext4: commit 0a7c3937a1f23f8cb5fc77ae01661e9968a51d0c .ip * btrfs, tmpfs, and cifs (linux 3.17); .ip * xfs (linux 4.0); .\" btrfs: commit 80ace85c915d0f41016f82917218997b72431258 .\" tmpfs: commit 3b69ff51d087d265aa4af3a532fc4f20bf33e718 .\" cifs: commit 7c33d5972ce382bcc506d16235f1e9b7d22cbef8 .\" .\" gfs2 in 4.2? .ip * support for many other filesystems was added in linux 4.9, including ext2, minix, reiserfs, jfs, vfat, and bpf. .\" also affs, bfs, exofs, hfs, hfsplus, jffs2, logfs, msdos, .\" nilfs2, omfs, sysvfs, ubifs, udf, ufs .\" hugetlbfs, ramfs .\" local filesystems: commit f03b8ad8d38634d13e802165cc15917481b47835 .\" libfs: commit e0e0be8a835520e2f7c89f214dfda570922a1b90 .re .tp .br rename_whiteout " (since linux 3.18)" .\" commit 0d7a855526dd672e114aff2ac22b60fc6f155b08 .\" commit 787fb6bc9682ec7c05fb5d9561b57100fbc1cc41 this operation makes sense only for overlay/union filesystem implementations. .ip specifying .b rename_whiteout creates a "whiteout" object at the source of the rename at the same time as performing the rename. the whole operation is atomic, so that if the rename succeeds then the whiteout will also have been created. .ip a "whiteout" is an object that has special meaning in union/overlay filesystem constructs. in these constructs, multiple layers exist and only the top one is ever modified. a whiteout on an upper layer will effectively hide a matching file in the lower layer, making it appear as if the file didn't exist. .ip when a file that exists on the lower layer is renamed, the file is first copied up (if not already on the upper layer) and then renamed on the upper, read-write layer. at the same time, the source file needs to be "whiteouted" (so that the version of the source file in the lower layer is rendered invisible). the whole operation needs to be done atomically. .ip when not part of a union/overlay, the whiteout appears as a character device with a {0,0} device number. .\" https://www.freebsd.org/cgi/man.cgi?query=mount_unionfs&manpath=freebsd+11.0-release (note that other union/overlay implementations may employ different methods for storing whiteout entries; specifically, bsd union mount employs a separate inode type, .br dt_wht , which, while supported by some filesystems available in linux, such as coda and xfs, is ignored by the kernel's whiteout support code, as of linux 4.19, at least.) .ip .b rename_whiteout requires the same privileges as creating a device node (i.e., the .br cap_mknod capability). .ip .b rename_whiteout can't be employed together with .br rename_exchange . .ip .b rename_whiteout requires support from the underlying filesystem. among the filesystems that support it are tmpfs (since linux 3.18), .\" tmpfs: commit 46fdb794e3f52ef18b859ebc92f0a9d7db21c5df ext4 (since linux 3.18), .\" ext4: commit cd808deced431b66b5fa4e5c193cb7ec0059eaff xfs (since linux 4.1), .\" xfs: commit 7dcf5c3e4527cfa2807567b00387cf2ed5e07f00 f2fs (since linux 4.2), .\" f2fs: commit 7e01e7ad746bc8198a8b46163ddc73a1c7d22339 btrfs (since linux 4.7), .\" btrfs: commit cdd1fedf8261cd7a73c0596298902ff4f0f04492 and ubifs (since linux 4.9). .\" ubifs: commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces write permission is denied for the directory containing .i oldpath or .ir newpath , or, search permission is denied for one of the directories in the path prefix of .i oldpath or .ir newpath , or .i oldpath is a directory and does not allow write permission (needed to update the .i .. entry). (see also .br path_resolution (7).) .tp .b ebusy the rename fails because .ir oldpath " or " newpath is a directory that is in use by some process (perhaps as current working directory, or as root directory, or because it was open for reading) or is in use by the system (for example as a mount point), while the system considers this an error. (note that there is no requirement to return .b ebusy in such cases\(emthere is nothing wrong with doing the rename anyway\(embut it is allowed to return .b ebusy if the system cannot otherwise handle such situations.) .tp .b edquot the user's quota of disk blocks on the filesystem has been exhausted. .tp .b efault .ir oldpath " or " newpath " points outside your accessible address space." .tp .b einval the new pathname contained a path prefix of the old, or, more generally, an attempt was made to make a directory a subdirectory of itself. .tp .b eisdir .i newpath is an existing directory, but .i oldpath is not a directory. .tp .b eloop too many symbolic links were encountered in resolving .ir oldpath " or " newpath . .tp .b emlink .i oldpath already has the maximum number of links to it, or it was a directory and the directory containing .i newpath has the maximum number of links. .tp .b enametoolong .ir oldpath " or " newpath " was too long." .tp .b enoent the link named by .i oldpath does not exist; or, a directory component in .i newpath does not exist; or, .i oldpath or .i newpath is an empty string. .tp .b enomem insufficient kernel memory was available. .tp .b enospc the device containing the file has no room for the new directory entry. .tp .b enotdir a component used as a directory in .ir oldpath " or " newpath is not, in fact, a directory. or, .i oldpath is a directory, and .i newpath exists but is not a directory. .tp .br enotempty " or " eexist .i newpath is a nonempty directory, that is, contains entries other than "." and "..". .tp .br eperm " or " eacces the directory containing .i oldpath has the sticky bit .rb ( s_isvtx ) set and the process's effective user id is neither the user id of the file to be deleted nor that of the directory containing it, and the process is not privileged (linux: does not have the .b cap_fowner capability); or .i newpath is an existing file and the directory containing it has the sticky bit set and the process's effective user id is neither the user id of the file to be replaced nor that of the directory containing it, and the process is not privileged (linux: does not have the .b cap_fowner capability); or the filesystem containing .i oldpath does not support renaming of the type requested. .tp .b erofs the file is on a read-only filesystem. .tp .b exdev .ir oldpath " and " newpath are not on the same mounted filesystem. (linux permits a filesystem to be mounted at multiple points, but .br rename () does not work across different mount points, even if the same filesystem is mounted on both.) .pp the following additional errors can occur for .br renameat () and .br renameat2 (): .tp .b ebadf .i oldpath .ri ( newpath ) is relative but .i olddirfd .ri ( newdirfd ) is not a valid file descriptor. .tp .b enotdir .i oldpath is relative and .i olddirfd is a file descriptor referring to a file other than a directory; or similar for .i newpath and .i newdirfd .pp the following additional errors can occur for .br renameat2 (): .tp .b eexist .i flags contains .b rename_noreplace and .i newpath already exists. .tp .b einval an invalid flag was specified in .ir flags . .tp .b einval both .b rename_noreplace and .b rename_exchange were specified in .ir flags . .tp .b einval both .b rename_whiteout and .b rename_exchange were specified in .ir flags . .tp .b einval the filesystem does not support one of the flags in .ir flags . .tp .b enoent .i flags contains .b rename_exchange and .ir newpath does not exist. .tp .b eperm .b rename_whiteout was specified in .ir flags , but the caller does not have the .b cap_mknod capability. .sh versions .br renameat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .pp .br renameat2 () was added to linux in kernel 3.15; library support was added in glibc 2.28. .sh conforming to .br rename (): 4.3bsd, c89, c99, posix.1-2001, posix.1-2008. .pp .br renameat (): posix.1-2008. .pp .br renameat2 () is linux-specific. .sh notes .\" .ss glibc notes on older kernels where .br renameat () is unavailable, the glibc wrapper function falls back to the use of .br rename (). when .i oldpath and .i newpath are relative pathnames, glibc constructs pathnames based on the symbolic links in .ir /proc/self/fd that correspond to the .i olddirfd and .ir newdirfd arguments. .sh bugs on nfs filesystems, you can not assume that if the operation failed, the file was not renamed. if the server does the rename operation and then crashes, the retransmitted rpc which will be processed when the server is up again causes a failure. the application is expected to deal with this. see .br link (2) for a similar problem. .sh see also .br mv (1), .br rename (1), .br chmod (2), .br link (2), .br symlink (2), .br unlink (2), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:40:39 1993 by rik faith (faith@cs.unc.edu) .\" modified fri jun 25 12:10:47 1999 by andries brouwer (aeb@cwi.nl) .\" .th ecvt 3 2021-03-22 "" "linux programmer's manual" .sh name ecvt, fcvt \- convert a floating-point number to a string .sh synopsis .nf .b #include .pp .bi "char *ecvt(double " number ", int " ndigits ", int *restrict " decpt , .bi " int *restrict " sign ); .bi "char *fcvt(double " number ", int " ndigits ", int *restrict " decpt , .bi " int *restrict " sign ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br ecvt (), .br fcvt (): .nf since glibc 2.17 (_xopen_source >= 500 && ! (_posix_c_source >= 200809l)) || /* glibc >= 2.20 */ _default_source || /* glibc <= 2.19 */ _svid_source glibc versions 2.12 to 2.16: (_xopen_source >= 500 && ! (_posix_c_source >= 200112l)) || _svid_source before glibc 2.12: _svid_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description the .br ecvt () function converts \finumber\fp to a null-terminated string of \findigits\fp digits (where \findigits\fp is reduced to a system-specific limit determined by the precision of a .ir double ), and returns a pointer to the string. the high-order digit is nonzero, unless .i number is zero. the low order digit is rounded. the string itself does not contain a decimal point; however, the position of the decimal point relative to the start of the string is stored in \fi*decpt\fp. a negative value for \fi*decpt\fp means that the decimal point is to the left of the start of the string. if the sign of \finumber\fp is negative, \fi*sign\fp is set to a nonzero value, otherwise it is set to 0. if .i number is zero, it is unspecified whether \fi*decpt\fp is 0 or 1. .pp the .br fcvt () function is identical to .br ecvt (), except that \findigits\fp specifies the number of digits after the decimal point. .sh return value both the .br ecvt () and .br fcvt () functions return a pointer to a static string containing the ascii representation of \finumber\fp. the static string is overwritten by each call to .br ecvt () or .br fcvt (). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ecvt () t} thread safety mt-unsafe race:ecvt t{ .br fcvt () t} thread safety mt-unsafe race:fcvt .te .hy .ad .sp 1 .sh conforming to svr2; marked as legacy in posix.1-2001. posix.1-2008 removes the specifications of .br ecvt () and .br fcvt (), recommending the use of .br sprintf (3) instead (though .br snprintf (3) may be preferable). .sh notes .\" linux libc4 and libc5 specified the type of .\" .i ndigits .\" as .\" .ir size_t . not all locales use a point as the radix character ("decimal point"). .sh see also .br ecvt_r (3), .br gcvt (3), .br qecvt (3), .br setlocale (3), .br sprintf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getaddrinfo_a.3 .so man3/catopen.3 .so man3/opendir.3 .so man3/timeradd.3 .\" copyright (c) 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)recno.3 8.5 (berkeley) 8/18/94 .\" .th recno 3 2017-09-15 "" "linux programmer's manual" .uc 7 .sh name recno \- record number database access method .sh synopsis .nf .ft b #include #include .ft r .fi .sh description .ir "note well" : this page documents interfaces provided in glibc up until version 2.1. since version 2.2, glibc no longer provides these interfaces. probably, you are looking for the apis provided by the .i libdb library instead. .pp the routine .br dbopen (3) is the library interface to database files. one of the supported file formats is record number files. the general description of the database access methods is in .br dbopen (3), this manual page describes only the recno-specific information. .pp the record number data structure is either variable or fixed-length records stored in a flat-file format, accessed by the logical record number. the existence of record number five implies the existence of records one through four, and the deletion of record number one causes record number five to be renumbered to record number four, as well as the cursor, if positioned after record number one, to shift down one record. .pp the recno access-method-specific data structure provided to .br dbopen (3) is defined in the .i include file as follows: .pp .in +4n .ex typedef struct { unsigned long flags; unsigned int cachesize; unsigned int psize; int lorder; size_t reclen; unsigned char bval; char *bfname; } recnoinfo; .ee .in .pp the elements of this structure are defined as follows: .tp .i flags the flag value is specified by oring any of the following values: .rs .tp .b r_fixedlen the records are fixed-length, not byte delimited. the structure element .i reclen specifies the length of the record, and the structure element .i bval is used as the pad character. any records, inserted into the database, that are less than .i reclen bytes long are automatically padded. .tp .b r_nokey in the interface specified by .br dbopen (3), the sequential record retrieval fills in both the caller's key and data structures. if the .b r_nokey flag is specified, the .i cursor routines are not required to fill in the key structure. this permits applications to retrieve records at the end of files without reading all of the intervening records. .tp .b r_snapshot this flag requires that a snapshot of the file be taken when .br dbopen (3) is called, instead of permitting any unmodified records to be read from the original file. .re .tp .i cachesize a suggested maximum size, in bytes, of the memory cache. this value is .b only advisory, and the access method will allocate more memory rather than fail. if .i cachesize is 0 (no size is specified), a default cache is used. .tp .i psize the recno access method stores the in-memory copies of its records in a btree. this value is the size (in bytes) of the pages used for nodes in that tree. if .i psize is 0 (no page size is specified), a page size is chosen based on the underlying filesystem i/o block size. see .br btree (3) for more information. .tp .i lorder the byte order for integers in the stored database metadata. the number should represent the order as an integer; for example, big endian order would be the number 4,321. if .i lorder is 0 (no order is specified), the current host order is used. .tp .i reclen the length of a fixed-length record. .tp .i bval the delimiting byte to be used to mark the end of a record for variable-length records, and the pad character for fixed-length records. if no value is specified, newlines ("\en") are used to mark the end of variable-length records and fixed-length records are padded with spaces. .tp .i bfname the recno access method stores the in-memory copies of its records in a btree. if .i bfname is non-null, it specifies the name of the btree file, as if specified as the filename for a .br dbopen (3) of a btree file. .pp the data part of the key/data pair used by the .i recno access method is the same as other access methods. the key is different. the .i data field of the key should be a pointer to a memory location of type .ir recno_t , as defined in the .i include file. this type is normally the largest unsigned integral type available to the implementation. the .i size field of the key should be the size of that type. .pp because there can be no metadata associated with the underlying recno access method files, any changes made to the default values (e.g., fixed record length or byte separator value) must be explicitly specified each time the file is opened. .pp in the interface specified by .br dbopen (3), using the .i put interface to create a new record will cause the creation of multiple, empty records if the record number is more than one greater than the largest record currently in the database. .sh errors the .i recno access method routines may fail and set .i errno for any of the errors specified for the library routine .br dbopen (3) or the following: .tp .b einval an attempt was made to add a record to a fixed-length database that was too large to fit. .sh bugs only big and little endian byte order is supported. .sh see also .br btree (3), .br dbopen (3), .br hash (3), .br mpool (3) .pp .ir "document processing in a relational database system" , michael stonebraker, heidi stettner, joseph kalash, antonin guttman, nadene lynn, memorandum no. ucb/erl m82/32, may 1982. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xcrypt.3 .so man7/system_data_types.7 .so man2/select.2 .so man3/syslog.3 .\" copyright (c) 2010, jan kara .\" a few pieces copyright (c) 1996 andries brouwer (aeb@cwi.nl) .\" and copyright 2010 (c) michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th quotactl 2 2021-03-22 "linux" "linux programmer's manual" .sh name quotactl \- manipulate disk quotas .sh synopsis .nf .b #include .br "#include " " /* definition of " q_x* " and " xfs_quota_* \ " constants" .rb " (or " "; see notes) */" .pp .bi "int quotactl(int " cmd ", const char *" special ", int " id \ ", caddr_t " addr ); .fi .sh description the quota system can be used to set per-user, per-group, and per-project limits on the amount of disk space used on a filesystem. for each user and/or group, a soft limit and a hard limit can be set for each filesystem. the hard limit can't be exceeded. the soft limit can be exceeded, but warnings will ensue. moreover, the user can't exceed the soft limit for more than grace period duration (one week by default) at a time; after this, the soft limit counts as a hard limit. .pp the .br quotactl () call manipulates disk quotas. the .i cmd argument indicates a command to be applied to the user or group id specified in .ir id . to initialize the .ir cmd argument, use the .ir "qcmd(subcmd, type)" macro. the .i type value is either .br usrquota , for user quotas, .br grpquota , for group quotas, or (since linux 4.1) .\" 847aac644e92e5624f2c153bab409bf713d5ff9a .br prjquota , for project quotas. the .i subcmd value is described below. .pp the .i special argument is a pointer to a null-terminated string containing the pathname of the (mounted) block special device for the filesystem being manipulated. .pp the .i addr argument is the address of an optional, command-specific, data structure that is copied in or out of the system. the interpretation of .i addr is given with each operation below. .pp the .i subcmd value is one of the following operations: .tp .b q_quotaon turn on quotas for a filesystem. the .i id argument is the identification number of the quota format to be used. currently, there are three supported quota formats: .rs .tp 13 .br qfmt_vfs_old the original quota format. .tp .br qfmt_vfs_v0 the standard vfs v0 quota format, which can handle 32-bit uids and gids and quota limits up to 2^42 bytes and 2^32 inodes. .tp .br qfmt_vfs_v1 a quota format that can handle 32-bit uids and gids and quota limits of 2^64 bytes and 2^64 inodes. .re .ip the .ir addr argument points to the pathname of a file containing the quotas for the filesystem. the quota file must exist; it is normally created with the .br quotacheck (8) program .ip quota information can be also stored in hidden system inodes for ext4, xfs, and other filesystems if the filesystem is configured so. in this case, there are no visible quota files and there is no need to use .br quotacheck (8). quota information is always kept consistent by the filesystem and the .b q_quotaon operation serves only to enable enforcement of quota limits. the presence of hidden system inodes with quota information is indicated by the .b dqf_sys_file flag in the .i dqi_flags field returned by the .b q_getinfo operation. .ip this operation requires privilege .rb ( cap_sys_admin ). .tp .b q_quotaoff turn off quotas for a filesystem. the .i addr and .i id arguments are ignored. this operation requires privilege .rb ( cap_sys_admin ). .tp .b q_getquota get disk quota limits and current usage for user or group .ir id . the .i addr argument is a pointer to a .i dqblk structure defined in .ir as follows: .ip .in +4n .ex /* uint64_t is an unsigned 64\-bit integer; uint32_t is an unsigned 32\-bit integer */ struct dqblk { /* definition since linux 2.4.22 */ uint64_t dqb_bhardlimit; /* absolute limit on disk quota blocks alloc */ uint64_t dqb_bsoftlimit; /* preferred limit on disk quota blocks */ uint64_t dqb_curspace; /* current occupied space (in bytes) */ uint64_t dqb_ihardlimit; /* maximum number of allocated inodes */ uint64_t dqb_isoftlimit; /* preferred inode limit */ uint64_t dqb_curinodes; /* current number of allocated inodes */ uint64_t dqb_btime; /* time limit for excessive disk use */ uint64_t dqb_itime; /* time limit for excessive files */ uint32_t dqb_valid; /* bit mask of qif_* constants */ }; /* flags in dqb_valid that indicate which fields in dqblk structure are valid. */ #define qif_blimits 1 #define qif_space 2 #define qif_ilimits 4 #define qif_inodes 8 #define qif_btime 16 #define qif_itime 32 #define qif_limits (qif_blimits | qif_ilimits) #define qif_usage (qif_space | qif_inodes) #define qif_times (qif_btime | qif_itime) #define qif_all (qif_limits | qif_usage | qif_times) .ee .in .ip the .i dqb_valid field is a bit mask that is set to indicate the entries in the .i dqblk structure that are valid. currently, the kernel fills in all entries of the .i dqblk structure and marks them as valid in the .i dqb_valid field. unprivileged users may retrieve only their own quotas; a privileged user .rb ( cap_sys_admin ) can retrieve the quotas of any user. .tp .br q_getnextquota " (since linux 4.6)" .\" commit 926132c0257a5a8d149a6a395cc3405e55420566 this operation is the same as .br q_getquota , but it returns quota information for the next id greater than or equal to .ir id that has a quota set. .ip the .i addr argument is a pointer to a .i nextdqblk structure whose fields are as for the .ir dqblk , except for the addition of a .i dqb_id field that is used to return the id for which quota information is being returned: .ip .in +4n .ex struct nextdqblk { uint64_t dqb_bhardlimit; uint64_t dqb_bsoftlimit; uint64_t dqb_curspace; uint64_t dqb_ihardlimit; uint64_t dqb_isoftlimit; uint64_t dqb_curinodes; uint64_t dqb_btime; uint64_t dqb_itime; uint32_t dqb_valid; uint32_t dqb_id; }; .ee .in .tp .b q_setquota set quota information for user or group .ir id , using the information supplied in the .i dqblk structure pointed to by .ir addr . the .i dqb_valid field of the .i dqblk structure indicates which entries in the structure have been set by the caller. this operation supersedes the .b q_setqlim and .b q_setuse operations in the previous quota interfaces. this operation requires privilege .rb ( cap_sys_admin ). .tp .br q_getinfo " (since linux 2.4.22)" get information (like grace times) about quotafile. the .i addr argument should be a pointer to a .i dqinfo structure. this structure is defined in .ir as follows: .ip .in +4n .ex /* uint64_t is an unsigned 64\-bit integer; uint32_t is an unsigned 32\-bit integer */ struct dqinfo { /* defined since kernel 2.4.22 */ uint64_t dqi_bgrace; /* time before block soft limit becomes hard limit */ uint64_t dqi_igrace; /* time before inode soft limit becomes hard limit */ uint32_t dqi_flags; /* flags for quotafile (dqf_*) */ uint32_t dqi_valid; }; /* bits for dqi_flags */ /* quota format qfmt_vfs_old */ #define dqf_root_squash (1 << 0) /* root squash enabled */ /* before linux v4.0, this had been defined privately as v1_dqf_rsquash */ /* quota format qfmt_vfs_v0 / qfmt_vfs_v1 */ #define dqf_sys_file (1 << 16) /* quota stored in a system file */ /* flags in dqi_valid that indicate which fields in dqinfo structure are valid. */ #define iif_bgrace 1 #define iif_igrace 2 #define iif_flags 4 #define iif_all (iif_bgrace | iif_igrace | iif_flags) .ee .in .ip the .i dqi_valid field in the .i dqinfo structure indicates the entries in the structure that are valid. currently, the kernel fills in all entries of the .i dqinfo structure and marks them all as valid in the .i dqi_valid field. the .i id argument is ignored. .tp .br q_setinfo " (since linux 2.4.22)" set information about quotafile. the .i addr argument should be a pointer to a .i dqinfo structure. the .i dqi_valid field of the .i dqinfo structure indicates the entries in the structure that have been set by the caller. this operation supersedes the .b q_setgrace and .b q_setflags operations in the previous quota interfaces. the .i id argument is ignored. this operation requires privilege .rb ( cap_sys_admin ). .tp .br q_getfmt " (since linux 2.4.22)" get quota format used on the specified filesystem. the .i addr argument should be a pointer to a 4-byte buffer where the format number will be stored. .tp .b q_sync update the on-disk copy of quota usages for a filesystem. if .i special is null, then all filesystems with active quotas are sync'ed. the .i addr and .i id arguments are ignored. .tp .br q_getstats " (supported up to linux 2.4.21)" get statistics and other generic information about the quota subsystem. the .i addr argument should be a pointer to a .i dqstats structure in which data should be stored. this structure is defined in .ir . the .i special and .i id arguments are ignored. .ip this operation is obsolete and was removed in linux 2.4.22. files in .i /proc/sys/fs/quota/ carry the information instead. .pp for xfs filesystems making use of the xfs quota manager (xqm), the above operations are bypassed and the following operations are used: .tp .b q_xquotaon turn on quotas for an xfs filesystem. xfs provides the ability to turn on/off quota limit enforcement with quota accounting. therefore, xfs expects .i addr to be a pointer to an .i "unsigned int" that contains a bitwise combination of the following flags (defined in .ir ): .ip .in +4n .ex xfs_quota_udq_acct /* user quota accounting */ xfs_quota_udq_enfd /* user quota limits enforcement */ xfs_quota_gdq_acct /* group quota accounting */ xfs_quota_gdq_enfd /* group quota limits enforcement */ xfs_quota_pdq_acct /* project quota accounting */ xfs_quota_pdq_enfd /* project quota limits enforcement */ .ee .in .ip this operation requires privilege .rb ( cap_sys_admin ). the .i id argument is ignored. .tp .b q_xquotaoff turn off quotas for an xfs filesystem. as with .br q_quotaon , xfs filesystems expect a pointer to an .i "unsigned int" that specifies whether quota accounting and/or limit enforcement need to be turned off (using the same flags as for .b q_xquotaon operation). this operation requires privilege .rb ( cap_sys_admin ). the .i id argument is ignored. .tp .b q_xgetquota get disk quota limits and current usage for user .ir id . the .i addr argument is a pointer to an .i fs_disk_quota structure, which is defined in .i as follows: .ip .in +4n .ex /* all the blk units are in bbs (basic blocks) of 512 bytes. */ #define fs_dquot_version 1 /* fs_disk_quota.d_version */ #define xfs_user_quota (1<<0) /* user quota type */ #define xfs_proj_quota (1<<1) /* project quota type */ #define xfs_group_quota (1<<2) /* group quota type */ struct fs_disk_quota { int8_t d_version; /* version of this structure */ int8_t d_flags; /* xfs_{user,proj,group}_quota */ uint16_t d_fieldmask; /* field specifier */ uint32_t d_id; /* user, project, or group id */ uint64_t d_blk_hardlimit; /* absolute limit on disk blocks */ uint64_t d_blk_softlimit; /* preferred limit on disk blocks */ uint64_t d_ino_hardlimit; /* maximum # allocated inodes */ uint64_t d_ino_softlimit; /* preferred inode limit */ uint64_t d_bcount; /* # disk blocks owned by the user */ uint64_t d_icount; /* # inodes owned by the user */ int32_t d_itimer; /* zero if within inode limits */ /* if not, we refuse service */ int32_t d_btimer; /* similar to above; for disk blocks */ uint16_t d_iwarns; /* # warnings issued with respect to # of inodes */ uint16_t d_bwarns; /* # warnings issued with respect to disk blocks */ int32_t d_padding2; /* padding \- for future use */ uint64_t d_rtb_hardlimit; /* absolute limit on realtime (rt) disk blocks */ uint64_t d_rtb_softlimit; /* preferred limit on rt disk blocks */ uint64_t d_rtbcount; /* # realtime blocks owned */ int32_t d_rtbtimer; /* similar to above; for rt disk blocks */ uint16_t d_rtbwarns; /* # warnings issued with respect to rt disk blocks */ int16_t d_padding3; /* padding \- for future use */ char d_padding4[8]; /* yet more padding */ }; .ee .in .ip unprivileged users may retrieve only their own quotas; a privileged user .rb ( cap_sys_admin ) may retrieve the quotas of any user. .tp .br q_xgetnextquota " (since linux 4.6)" .\" commit 8b37524962b9c54423374717786198f5c0820a28 this operation is the same as .br q_xgetquota , but it returns (in the .i fs_disk_quota structure pointed by .ir addr ) quota information for the next id greater than or equal to .ir id that has a quota set. note that since .i fs_disk_quota already has .i q_id field, no separate structure type is needed (in contrast with .b q_getquota and .b q_getnextquota operations) .tp .b q_xsetqlim set disk quota limits for user .ir id . the .i addr argument is a pointer to an .i fs_disk_quota structure. this operation requires privilege .rb ( cap_sys_admin ). .tp .b q_xgetqstat returns xfs filesystem-specific quota information in the .i fs_quota_stat structure pointed by .ir addr . this is useful for finding out how much space is used to store quota information, and also to get the quota on/off status of a given local xfs filesystem. the .i fs_quota_stat structure itself is defined as follows: .ip .in +4n .ex #define fs_qstat_version 1 /* fs_quota_stat.qs_version */ struct fs_qfilestat { uint64_t qfs_ino; /* inode number */ uint64_t qfs_nblks; /* number of bbs 512\-byte\-blocks */ uint32_t qfs_nextents; /* number of extents */ }; struct fs_quota_stat { int8_t qs_version; /* version number for future changes */ uint16_t qs_flags; /* xfs_quota_{u,p,g}dq_{acct,enfd} */ int8_t qs_pad; /* unused */ struct fs_qfilestat qs_uquota; /* user quota storage information */ struct fs_qfilestat qs_gquota; /* group quota storage information */ uint32_t qs_incoredqs; /* number of dquots in core */ int32_t qs_btimelimit; /* limit for blocks timer */ int32_t qs_itimelimit; /* limit for inodes timer */ int32_t qs_rtbtimelimit;/* limit for rt blocks timer */ uint16_t qs_bwarnlimit; /* limit for # of warnings */ uint16_t qs_iwarnlimit; /* limit for # of warnings */ }; .ee .in .ip the .i id argument is ignored. .tp .b q_xgetqstatv returns xfs filesystem-specific quota information in the .i fs_quota_statv pointed to by .ir addr . this version of the operation uses a structure with proper versioning support, along with appropriate layout (all fields are naturally aligned) and padding to avoiding special compat handling; it also provides the ability to get statistics regarding the project quota file. the .i fs_quota_statv structure itself is defined as follows: .ip .in +4n .ex #define fs_qstatv_version1 1 /* fs_quota_statv.qs_version */ struct fs_qfilestatv { uint64_t qfs_ino; /* inode number */ uint64_t qfs_nblks; /* number of bbs 512\-byte\-blocks */ uint32_t qfs_nextents; /* number of extents */ uint32_t qfs_pad; /* pad for 8\-byte alignment */ }; struct fs_quota_statv { int8_t qs_version; /* version for future changes */ uint8_t qs_pad1; /* pad for 16\-bit alignment */ uint16_t qs_flags; /* xfs_quota_.* flags */ uint32_t qs_incoredqs; /* number of dquots incore */ struct fs_qfilestatv qs_uquota; /* user quota information */ struct fs_qfilestatv qs_gquota; /* group quota information */ struct fs_qfilestatv qs_pquota; /* project quota information */ int32_t qs_btimelimit; /* limit for blocks timer */ int32_t qs_itimelimit; /* limit for inodes timer */ int32_t qs_rtbtimelimit; /* limit for rt blocks timer */ uint16_t qs_bwarnlimit; /* limit for # of warnings */ uint16_t qs_iwarnlimit; /* limit for # of warnings */ uint64_t qs_pad2[8]; /* for future proofing */ }; .ee .in .ip the .i qs_version field of the structure should be filled with the version of the structure supported by the callee (for now, only .i fs_qstat_version1 is supported). the kernel will fill the structure in accordance with version provided. the .i id argument is ignored. .tp .b q_xquotarm " (since linux 3.16)" .\" 9da93f9b7cdf8ab28da6b364cdc1fafc8670b4dc free the disk space taken by disk quotas. the .i addr argument should be a pointer to an .i "unsigned int" value containing flags (the same as in .i d_flags field of .i fs_disk_quota structure) which identify what types of quota should be removed. (note that the quota type passed in the .i cmd argument is ignored, but should remain valid in order to pass preliminary quotactl syscall handler checks.) .ip quotas must have already been turned off. the .i id argument is ignored. .tp .br q_xquotasync " (since linux 2.6.15; no-op since linux 3.4)" .\" added in commit ee34807a65aa0c5911dc27682863afca780a003e this operation was an xfs quota equivalent to .br q_sync , but it is no-op since linux 3.4, .\" 4b217ed9e30f94b6e8e5e262020ef0ceab6113af as .br sync (1) writes quota information to disk now (in addition to the other filesystem metadata that it writes out). the .ir special ", " id " and " addr arguments are ignored. .sh return value on success, .br quotactl () returns 0; on error \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces .i cmd is .br q_quotaon , and the quota file pointed to by .i addr exists, but is not a regular file or is not on the filesystem pointed to by .ir special . .tp .b ebusy .i cmd is .br q_quotaon , but another .b q_quotaon had already been performed. .tp .b efault .i addr or .i special is invalid. .tp .b einval .i cmd or .i type is invalid. .tp .b einval .i cmd is .br q_quotaon , but the specified quota file is corrupted. .tp .br einval " (since linux 5.5)" .\" 3dd4d40b420846dd35869ccc8f8627feef2cff32 .i cmd is .br q_xquotarm , but .i addr does not point to valid quota types. .tp .b enoent the file specified by .i special or .i addr does not exist. .tp .b enosys the kernel has not been compiled with the .b config_quota option. .tp .b enotblk .i special is not a block device. .tp .b eperm the caller lacked the required privilege .rb ( cap_sys_admin ) for the specified operation. .tp .b erange .i cmd is .br q_setquota , but the specified limits are out of the range allowed by the quota format. .tp .b esrch no disk quota is found for the indicated user. quotas have not been turned on for this filesystem. .tp .b esrch .i cmd is .br q_quotaon , but the specified quota format was not found. .tp .b esrch .i cmd is .b q_getnextquota or .br q_xgetnextquota , but there is no id greater than or equal to .ir id that has an active quota. .sh notes instead of .i one can use .ir , taking into account that there are several naming discrepancies: .ip \(bu 3 quota enabling flags (of format .br xfs_quota_[ugp]dq_{acct,enfd} ) are defined without a leading "x", as .br fs_quota_[ugp]dq_{acct,enfd} . .ip \(bu the same is true for .b xfs_{user,group,proj}_quota quota type flags, which are defined as .br fs_{user,group,proj}_quota . .ip \(bu the .i dqblk_xfs.h header file defines its own .br xqm_usrquota , .br xqm_grpquota , and .b xqm_prjquota constants for the available quota types, but their values are the same as for constants without the .b xqm_ prefix. .sh see also .br quota (1), .br getrlimit (2), .br quotacheck (8), .br quotaon (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getutent.3 .so man3/cpu_set.3 .\" copyright (c) 2006, 2008, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th futimes 3 2021-03-22 "linux" "linux programmer's manual" .sh name futimes, lutimes \- change file timestamps .sh synopsis .nf .b #include .pp .bi "int futimes(int " fd ", const struct timeval " tv [2]); .bi "int lutimes(const char *" filename ", const struct timeval " tv [2]); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br futimes (), .br lutimes (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description .br futimes () changes the access and modification times of a file in the same way as .br utimes (2), with the difference that the file whose timestamps are to be changed is specified via a file descriptor, .ir fd , rather than via a pathname. .pp .br lutimes () changes the access and modification times of a file in the same way as .br utimes (2), with the difference that if .i filename refers to a symbolic link, then the link is not dereferenced: instead, the timestamps of the symbolic link are changed. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors errors are as for .br utimes (2), with the following additions for .br futimes (): .tp .b ebadf .i fd is not a valid file descriptor. .tp .b enosys the .i /proc filesystem could not be accessed. .pp the following additional error may occur for .br lutimes (): .tp .b enosys the kernel does not support this call; linux 2.6.22 or later is required. .sh versions .br futimes () is available since glibc 2.3. .br lutimes () is available since glibc 2.6, and is implemented using the .br utimensat (2) system call, which is supported since kernel 2.6.22. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br futimes (), .br lutimes () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are not specified in any standard. other than linux, they are available only on the bsds. .sh see also .br utime (2), .br utimensat (2), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2004-10-31 by aeb .\" .th ldexp 3 2021-03-22 "" "linux programmer's manual" .sh name ldexp, ldexpf, ldexpl \- multiply floating-point number by integral power of 2 .sh synopsis .nf .b #include .pp .bi "double ldexp(double " x ", int " exp ); .bi "float ldexpf(float " x ", int " exp ); .bi "long double ldexpl(long double " x ", int " exp ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br ldexpf (), .br ldexpl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the result of multiplying the floating-point number .i x by 2 raised to the power .ir exp . .sh return value on success, these functions return .ir "x * (2^exp)" . .pp if .i exp is zero, then .i x is returned. .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity (negative infinity), positive infinity (negative infinity) is returned. .pp if the result underflows, a range error occurs, and zero is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with a sign the same as .ir x . .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error, overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error, underflow .i errno is set to .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ldexp (), .br ldexpf (), .br ldexpl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br frexp (3), .br modf (3), .br scalbln (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fdim.3 .so man3/ceil.3 .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2008, 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 16:09:49 1993 by rik faith (faith@cs.unc.edu) .\" modified 11 june 1995 by andries brouwer (aeb@cwi.nl) .\" modified 22 july 1996 by andries brouwer (aeb@cwi.nl) .\" 2007-07-30 ulrich drepper , mtk: .\" rework discussion of nonstandard structure fields. .\" .th readdir 3 2021-03-22 "" "linux programmer's manual" .sh name readdir \- read a directory .sh synopsis .nf .b #include .pp .bi "struct dirent *readdir(dir *" dirp ); .fi .sh description the .br readdir () function returns a pointer to a \fidirent\fp structure representing the next directory entry in the directory stream pointed to by \fidirp\fp. it returns null on reaching the end of the directory stream or if an error occurred. .pp in the glibc implementation, the .i dirent structure is defined as follows: .pp .in +4n .ex struct dirent { ino_t d_ino; /* inode number */ off_t d_off; /* not an offset; see below */ unsigned short d_reclen; /* length of this record */ unsigned char d_type; /* type of file; not supported by all filesystem types */ char d_name[256]; /* null\-terminated filename */ }; .ee .in .pp the only fields in the .i dirent structure that are mandated by posix.1 are .ir d_name and .ir d_ino . the other fields are unstandardized, and not present on all systems; see notes below for some further details. .pp the fields of the .i dirent structure are as follows: .tp .i d_ino this is the inode number of the file. .tp .i d_off the value returned in .i d_off is the same as would be returned by calling .br telldir (3) at the current position in the directory stream. be aware that despite its type and name, the .i d_off field is seldom any kind of directory offset on modern filesystems. .\" https://lwn.net/articles/544298/ applications should treat this field as an opaque value, making no assumptions about its contents; see also .br telldir (3). .tp .i d_reclen this is the size (in bytes) of the returned record. this may not match the size of the structure definition shown above; see notes. .tp .i d_type this field contains a value indicating the file type, making it possible to avoid the expense of calling .br lstat (2) if further actions depend on the type of the file. .ip when a suitable feature test macro is defined .rb ( _default_source on glibc versions since 2.19, or .br _bsd_source on glibc versions 2.19 and earlier), glibc defines the following macro constants for the value returned in .ir d_type : .rs .tp 12 .b dt_blk this is a block device. .tp .b dt_chr this is a character device. .tp .b dt_dir this is a directory. .tp .b dt_fifo this is a named pipe (fifo). .tp .b dt_lnk this is a symbolic link. .tp .b dt_reg this is a regular file. .tp .b dt_sock this is a unix domain socket. .tp .b dt_unknown the file type could not be determined. .re .ip currently, .\" kernel 2.6.27 .\" the same sentence is in getdents.2 only some filesystems (among them: btrfs, ext2, ext3, and ext4) have full support for returning the file type in .ir d_type . all applications must properly handle a return of .br dt_unknown . .tp .i d_name this field contains the null terminated filename. .ir "see notes" . .pp the data returned by .br readdir () may be overwritten by subsequent calls to .br readdir () for the same directory stream. .sh return value on success, .br readdir () returns a pointer to a .i dirent structure. (this structure may be statically allocated; do not attempt to .br free (3) it.) .pp if the end of the directory stream is reached, null is returned and .i errno is not changed. if an error occurs, null is returned and .i errno is set to indicate the error. to distinguish end of stream from an error, set .i errno to zero before calling .br readdir () and then check the value of .i errno if null is returned. .sh errors .tp .b ebadf invalid directory stream descriptor \fidirp\fp. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br readdir () t} thread safety mt-unsafe race:dirstream .te .hy .ad .sp 1 .pp in the current posix.1 specification (posix.1-2008), .br readdir () is not required to be thread-safe. however, in modern implementations (including the glibc implementation), concurrent calls to .br readdir () that specify different directory streams are thread-safe. in cases where multiple threads must read from the same directory stream, using .br readdir () with external synchronization is still preferable to the use of the deprecated .br readdir_r (3) function. it is expected that a future version of posix.1 .\" fixme . .\" http://www.austingroupbugs.net/view.php?id=696 will require that .br readdir () be thread-safe when concurrently employed on different directory streams. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes a directory stream is opened using .br opendir (3). .pp the order in which filenames are read by successive calls to .br readdir () depends on the filesystem implementation; it is unlikely that the names will be sorted in any fashion. .pp only the fields .i d_name and (as an xsi extension) .i d_ino are specified in posix.1. .\" posix.1-2001, posix.1-2008 other than linux, the .i d_type field is available mainly only on bsd systems. the remaining fields are available on many, but not all systems. under glibc, programs can check for the availability of the fields not defined in posix.1 by testing whether the macros .br _dirent_have_d_namlen , .br _dirent_have_d_reclen , .br _dirent_have_d_off , or .b _dirent_have_d_type are defined. .\" .ss the d_name field the .i dirent structure definition shown above is taken from the glibc headers, and shows the .i d_name field with a fixed size. .pp .ir warning : applications should avoid any dependence on the size of the .i d_name field. posix defines it as .ir "char\ d_name[]", a character array of unspecified size, with at most .b name_max characters preceding the terminating null byte (\(aq\e0\(aq). .pp posix.1 explicitly notes that this field should not be used as an lvalue. the standard also notes that the use of .i sizeof(d_name) is incorrect; use .ir strlen(d_name) instead. (on some systems, this field is defined as .ir char\ d_name[1] !) by implication, the use .ir "sizeof(struct dirent)" to capture the size of the record including the size of .ir d_name is also incorrect. .pp note that while the call .pp fpathconf(fd, _pc_name_max) .pp returns the value 255 for most filesystems, on some filesystems (e.g., cifs, windows smb servers), the null-terminated filename that is (correctly) returned in .i d_name can actually exceed this size. in such cases, the .i d_reclen field will contain a value that exceeds the size of the glibc .i dirent structure shown above. .sh see also .br getdents (2), .br read (2), .br closedir (3), .br dirfd (3), .br ftw (3), .br offsetof (3), .br opendir (3), .br readdir_r (3), .br rewinddir (3), .br scandir (3), .br seekdir (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/malloc_hook.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:19:11 1993 by rik faith (faith@cs.unc.edu) .\" modified wed oct 18 20:23:54 1995 by martin schulze .\" modified mon apr 22 01:50:54 1996 by martin schulze .\" 2001-07-25 added a clause about null proto (martin michlmayr or david n. welton) .\" .th getservent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getservent, getservbyname, getservbyport, setservent, endservent \- get service entry .sh synopsis .nf .b #include .pp .b struct servent *getservent(void); .pp .bi "struct servent *getservbyname(const char *" name ", const char *" proto ); .bi "struct servent *getservbyport(int " port ", const char *" proto ); .pp .bi "void setservent(int " stayopen ); .b void endservent(void); .fi .sh description the .br getservent () function reads the next entry from the services database (see .br services (5)) and returns a .i servent structure containing the broken-out fields from the entry. a connection is opened to the database if necessary. .pp the .br getservbyname () function returns a .i servent structure for the entry from the database that matches the service .i name using protocol .ir proto . if .i proto is null, any protocol will be matched. a connection is opened to the database if necessary. .pp the .br getservbyport () function returns a .i servent structure for the entry from the database that matches the port .i port (given in network byte order) using protocol .ir proto . if .i proto is null, any protocol will be matched. a connection is opened to the database if necessary. .pp the .br setservent () function opens a connection to the database, and sets the next entry to the first entry. if .i stayopen is nonzero, then the connection to the database will not be closed between calls to one of the .br getserv* () functions. .pp the .br endservent () function closes the connection to the database. .pp the .i servent structure is defined in .i as follows: .pp .in +4n .ex struct servent { char *s_name; /* official service name */ char **s_aliases; /* alias list */ int s_port; /* port number */ char *s_proto; /* protocol to use */ } .ee .in .pp the members of the .i servent structure are: .tp .i s_name the official name of the service. .tp .i s_aliases a null-terminated list of alternative names for the service. .tp .i s_port the port number for the service given in network byte order. .tp .i s_proto the name of the protocol to use with this service. .sh return value the .br getservent (), .br getservbyname (), and .br getservbyport () functions return a pointer to a statically allocated .i servent structure, or null if an error occurs or the end of the file is reached. .sh files .tp .i /etc/services services database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getservent () t} thread safety t{ mt-unsafe race:servent race:serventbuf locale t} t{ .br getservbyname () t} thread safety t{ mt-unsafe race:servbyname locale t} t{ .br getservbyport () t} thread safety t{ mt-unsafe race:servbyport locale t} t{ .br setservent (), .br endservent () t} thread safety t{ mt-unsafe race:servent locale t} .te .hy .ad .sp 1 in the above table, .i servent in .i race:servent signifies that if any of the functions .br setservent (), .br getservent (), or .br endservent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh see also .br getnetent (3), .br getprotoent (3), .br getservent_r (3), .br services (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1997 nicolás lichtmaier .\" created thu aug 7 00:44:00 art 1997 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" added section stuff, aeb, 2002-04-22. .\" corrected include file, drepper, 2003-06-15. .\" .th lockf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name lockf \- apply, test or remove a posix lock on an open file .sh synopsis .nf .b #include .pp .bi "int lockf(int " fd ", int " cmd ", off_t " len ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br lockf (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description apply, test, or remove a posix lock on a section of an open file. the file is specified by .ir fd , a file descriptor open for writing, the action by .ir cmd , and the section consists of byte positions .ir pos .. pos + len \-1 if .i len is positive, and .ir pos \- len .. pos \-1 if .i len is negative, where .i pos is the current file position, and if .i len is zero, the section extends from the current file position to infinity, encompassing the present and future end-of-file positions. in all cases, the section may extend past current end-of-file. .pp on linux, .br lockf () is just an interface on top of .br fcntl (2) locking. many other systems implement .br lockf () in this way, but note that posix.1 leaves the relationship between .br lockf () and .br fcntl (2) locks unspecified. a portable application should probably avoid mixing calls to these interfaces. .pp valid operations are given below: .tp .b f_lock set an exclusive lock on the specified section of the file. if (part of) this section is already locked, the call blocks until the previous lock is released. if this section overlaps an earlier locked section, both are merged. file locks are released as soon as the process holding the locks closes some file descriptor for the file. a child process does not inherit these locks. .tp .b f_tlock same as .b f_lock but the call never blocks and returns an error instead if the file is already locked. .tp .b f_ulock unlock the indicated section of the file. this may cause a locked section to be split into two locked sections. .tp .b f_test test the lock: return 0 if the specified section is unlocked or locked by this process; return \-1, set .i errno to .b eagain .rb ( eacces on some other systems), if another process holds a lock. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .br eacces " or " eagain the file is locked and .b f_tlock or .b f_test was specified, or the operation is prohibited because the file has been memory-mapped by another process. .tp .b ebadf .i fd is not an open file descriptor; or .i cmd is .b f_lock or .br f_tlock and .i fd is not a writable file descriptor. .tp .b edeadlk the command was .b f_lock and this lock operation would cause a deadlock. .tp .b eintr while waiting to acquire a lock, the call was interrupted by delivery of a signal caught by a handler; see .br signal (7). .tp .b einval an invalid operation was specified in .ir cmd . .tp .b enolck too many segment locks open, lock table is full. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br lockf () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh see also .br fcntl (2), .br flock (2) .pp .i locks.txt and .i mandatory\-locking.txt in the linux kernel source directory .ir documentation/filesystems (on older kernels, these files are directly under the .i documentation directory, and .i mandatory\-locking.txt is called .ir mandatory.txt ) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .so man7/iso_8859-15.7 .so man3/stailq.3 .\" copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getservent_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getservent_r, getservbyname_r, getservbyport_r \- get service entry (reentrant) .sh synopsis .nf .b #include .pp .bi "int getservent_r(struct servent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct servent **restrict " result ); .bi "int getservbyname_r(const char *restrict " name , .bi " const char *restrict " proto , .bi " struct servent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct servent **restrict " result ); .bi "int getservbyport_r(int " port , .bi " const char *restrict " proto , .bi " struct servent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct servent **restrict " result ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getservent_r (), .br getservbyname_r (), .br getservbyport_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the .br getservent_r (), .br getservbyname_r (), and .br getservbyport_r () functions are the reentrant equivalents of, respectively, .br getservent (3), .br getservbyname (3), and .br getservbyport (3). they differ in the way that the .i servent structure is returned, and in the function calling signature and return value. this manual page describes just the differences from the nonreentrant functions. .pp instead of returning a pointer to a statically allocated .i servent structure as the function result, these functions copy the structure into the location pointed to by .ir result_buf . .pp the .i buf array is used to store the string fields pointed to by the returned .i servent structure. (the nonreentrant functions allocate these strings in static storage.) the size of this array is specified in .ir buflen . if .i buf is too small, the call fails with the error .br erange , and the caller must try again with a larger buffer. (a buffer of length 1024 bytes should be sufficient for most applications.) .\" i can find no information on the required/recommended buffer size; .\" the nonreentrant functions use a 1024 byte buffer -- mtk. .pp if the function call successfully obtains a service record, then .i *result is set pointing to .ir result_buf ; otherwise, .i *result is set to null. .sh return value on success, these functions return 0. on error, they return one of the positive error numbers listed in errors. .pp on error, record not found .rb ( getservbyname_r (), .br getservbyport_r ()), or end of input .rb ( getservent_r ()) .i result is set to null. .sh errors .tp .b enoent .rb ( getservent_r ()) no more records in database. .tp .b erange .i buf is too small. try again with a larger buffer (and increased .ir buflen ). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getservent_r (), .br getservbyname_r (), .br getservbyport_r () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. functions with similar names exist on some other systems, though typically with different calling signatures. .sh examples the program below uses .br getservbyport_r () to retrieve the service record for the port and protocol named in its first command-line argument. if a third (integer) command-line argument is supplied, it is used as the initial value for .ir buflen ; if .br getservbyport_r () fails with the error .br erange , the program retries with larger buffer sizes. the following shell session shows a couple of sample runs: .pp .in +4n .ex .rb "$" " ./a.out 7 tcp 1" erange! retrying with larger buffer getservbyport_r() returned: 0 (success) (buflen=87) s_name=echo; s_proto=tcp; s_port=7; aliases= .rb "$" " ./a.out 77777 tcp" getservbyport_r() returned: 0 (success) (buflen=1024) call failed/record not found .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include #define max_buf 10000 int main(int argc, char *argv[]) { int buflen, erange_cnt, port, s; struct servent result_buf; struct servent *result; char buf[max_buf]; char *protop; if (argc < 3) { printf("usage: %s port\-num proto\-name [buflen]\en", argv[0]); exit(exit_failure); } port = htons(atoi(argv[1])); protop = (strcmp(argv[2], "null") == 0 || strcmp(argv[2], "null") == 0) ? null : argv[2]; buflen = 1024; if (argc > 3) buflen = atoi(argv[3]); if (buflen > max_buf) { printf("exceeded buffer limit (%d)\en", max_buf); exit(exit_failure); } erange_cnt = 0; do { s = getservbyport_r(port, protop, &result_buf, buf, buflen, &result); if (s == erange) { if (erange_cnt == 0) printf("erange! retrying with larger buffer\en"); erange_cnt++; /* increment a byte at a time so we can see exactly what size buffer was required. */ buflen++; if (buflen > max_buf) { printf("exceeded buffer limit (%d)\en", max_buf); exit(exit_failure); } } } while (s == erange); printf("getservbyport_r() returned: %s (buflen=%d)\en", (s == 0) ? "0 (success)" : (s == enoent) ? "enoent" : strerror(s), buflen); if (s != 0 || result == null) { printf("call failed/record not found\en"); exit(exit_failure); } printf("s_name=%s; s_proto=%s; s_port=%d; aliases=", result_buf.s_name, result_buf.s_proto, ntohs(result_buf.s_port)); for (char **p = result_buf.s_aliases; *p != null; p++) printf("%s ", *p); printf("\en"); exit(exit_success); } .ee .sh see also .br getservent (3), .br services (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcstok 3 2021-08-27 "gnu" "linux programmer's manual" .sh name wcstok \- split wide-character string into tokens .sh synopsis .nf .b #include .pp .bi "wchar_t *wcstok(wchar_t *restrict " wcs \ ", const wchar_t *restrict " delim , .bi " wchar_t **restrict " ptr ); .fi .sh description the .br wcstok () function is the wide-character equivalent of the .br strtok (3) function, with an added argument to make it multithread-safe. it can be used to split a wide-character string .i wcs into tokens, where a token is defined as a substring not containing any wide-characters from .ir delim . .pp the search starts at .ir wcs , if .i wcs is not null, or at .ir *ptr , if .i wcs is null. first, any delimiter wide-characters are skipped, that is, the pointer is advanced beyond any wide-characters which occur in .ir delim . if the end of the wide-character string is now reached, .br wcstok () returns null, to indicate that no tokens were found, and stores an appropriate value in .ir *ptr , so that subsequent calls to .br wcstok () will continue to return null. otherwise, the .br wcstok () function recognizes the beginning of a token and returns a pointer to it, but before doing that, it zero-terminates the token by replacing the next wide-character which occurs in .i delim with a null wide character (l\(aq\e0\(aq), and it updates .i *ptr so that subsequent calls will continue searching after the end of recognized token. .sh return value the .br wcstok () function returns a pointer to the next token, or null if no further token was found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcstok () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the original .i wcs wide-character string is destructively modified during the operation. .sh examples the following code loops over the tokens contained in a wide-character string. .pp .ex wchar_t *wcs = ...; wchar_t *token; wchar_t *state; for (token = wcstok(wcs, l" \et\en", &state); token != null; token = wcstok(null, l" \et\en", &state)) { ... } .ee .sh see also .br strtok (3), .br wcschr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sigsetops.3 .so man3/mq_getattr.3 .so man3/pthread_attr_setstack.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2004, 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:20:58 1993 by rik faith (faith@cs.unc.edu) .\" modified fri feb 14 21:47:50 1997 by andries brouwer (aeb@cwi.nl) .\" modified 9 jun 2004, michael kerrisk .\" changed unsetenv() prototype; added einval error .\" noted nonstandard behavior of setenv() if name contains '=' .\" 2005-08-12, mtk, glibc 2.3.4 fixed the "name contains '='" bug .\" .th setenv 3 2021-03-22 "gnu" "linux programmer's manual" .sh name setenv \- change or add an environment variable .sh synopsis .nf .b #include .pp .bi "int setenv(const char *" name ", const char *" value ", int " overwrite ); .bi "int unsetenv(const char *" name ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br setenv (), .br unsetenv (): .nf _posix_c_source >= 200112l || /* glibc <= 2.19: */ _bsd_source .fi .sh description the .br setenv () function adds the variable .i name to the environment with the value .ir value , if .i name does not already exist. if .i name does exist in the environment, then its value is changed to .ir value if .i overwrite is nonzero; if .ir overwrite is zero, then the value of .i name is not changed (and .br setenv () returns a success status). this function makes copies of the strings pointed to by .i name and .i value (by contrast with .br putenv (3)). .pp the .br unsetenv () function deletes the variable .i name from the environment. if .i name does not exist in the environment, then the function succeeds, and the environment is unchanged. .sh return value .br setenv () and .br unsetenv () functions return zero on success, or \-1 on error, with .i errno set to indicate the error. .sh errors .tp .b einval .i name is null, points to a string of length 0, or contains an \(aq=\(aq character. .tp .b enomem insufficient memory to add a new variable to the environment. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br setenv (), .br unsetenv () t} thread safety mt-unsafe const:env .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh notes posix.1 does not require .br setenv () or .br unsetenv () to be reentrant. .pp prior to glibc 2.2.2, .br unsetenv () was prototyped as returning .ir void ; more recent glibc versions follow the posix.1-compliant prototype shown in the synopsis. .sh bugs posix.1 specifies that if .i name contains an \(aq=\(aq character, then .br setenv () should fail with the error .br einval ; however, versions of glibc before 2.3.4 allowed an \(aq=\(aq sign in .ir name . .sh see also .br clearenv (3), .br getenv (3), .br putenv (3), .br environ (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1997-01-31 by eric s. raymond .\" modified 2004-06-23 by michael kerrisk .\" .th rmdir 2 2021-03-22 "linux" "linux programmer's manual" .sh name rmdir \- delete a directory .sh synopsis .nf .b #include .pp .bi "int rmdir(const char *" pathname ); .fi .sh description .br rmdir () deletes a directory, which must be empty. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces write access to the directory containing .i pathname was not allowed, or one of the directories in the path prefix of .i pathname did not allow search permission. (see also .br path_resolution (7).) .tp .b ebusy .i pathname is currently in use by the system or some process that prevents its removal. on linux, this means .i pathname is currently used as a mount point or is the root directory of the calling process. .tp .b efault .ir pathname " points outside your accessible address space." .tp .b einval .i pathname has .i . as last component. .tp .b eloop too many symbolic links were encountered in resolving .ir pathname . .tp .b enametoolong .ir pathname " was too long." .tp .b enoent a directory component in .i pathname does not exist or is a dangling symbolic link. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir .ir pathname , or a component used as a directory in .ir pathname , is not, in fact, a directory. .tp .b enotempty .i pathname contains entries other than .ir . " and " .. " ;" or, .i pathname has .i .. as its final component. posix.1 also allows .\" posix.1-2001, posix.1-2008 .b eexist for this condition. .tp .b eperm the directory containing .i pathname has the sticky bit .rb ( s_isvtx ) set and the process's effective user id is neither the user id of the file to be deleted nor that of the directory containing it, and the process is not privileged (linux: does not have the .b cap_fowner capability). .tp .b eperm the filesystem containing .i pathname does not support the removal of directories. .tp .b erofs .i pathname refers to a directory on a read-only filesystem. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh bugs infelicities in the protocol underlying nfs can cause the unexpected disappearance of directories which are still being used. .sh see also .br rm (1), .br rmdir (1), .br chdir (2), .br chmod (2), .br mkdir (2), .br rename (2), .br unlink (2), .br unlinkat (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rand.3 .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: raw.7,v 1.6 1999/06/05 10:32:08 freitag exp $ .\" .th raw 7 2021-03-22 "linux" "linux programmer's manual" .sh name raw \- linux ipv4 raw sockets .sh synopsis .nf .b #include .b #include .bi "raw_socket = socket(af_inet, sock_raw, int " protocol ); .fi .sh description raw sockets allow new ipv4 protocols to be implemented in user space. a raw socket receives or sends the raw datagram not including link level headers. .pp the ipv4 layer generates an ip header when sending a packet unless the .b ip_hdrincl socket option is enabled on the socket. when it is enabled, the packet must contain an ip header. for receiving, the ip header is always included in the packet. .pp in order to create a raw socket, a process must have the .b cap_net_raw capability in the user namespace that governs its network namespace. .pp all packets or errors matching the .i protocol number specified for the raw socket are passed to this socket. for a list of the allowed protocols, see the iana list of assigned protocol numbers at .ur http://www.iana.org/assignments/protocol\-numbers/ .ue and .br getprotobyname (3). .pp a protocol of .b ipproto_raw implies enabled .b ip_hdrincl and is able to send any ip protocol that is specified in the passed header. receiving of all ip protocols via .b ipproto_raw is not possible using raw sockets. .rs .ts tab(:) allbox; c s l l. ip header fields modified on sending by \fbip_hdrincl\fp ip checksum:always filled in source address:filled in when zero packet id:filled in when zero total length:always filled in .te .re .pp .pp if .b ip_hdrincl is specified and the ip header has a nonzero destination address, then the destination address of the socket is used to route the packet. when .b msg_dontroute is specified, the destination address should refer to a local interface, otherwise a routing table lookup is done anyway but gatewayed routes are ignored. .pp if .b ip_hdrincl isn't set, then ip header options can be set on raw sockets with .br setsockopt (2); see .br ip (7) for more information. .pp starting with linux 2.2, all ip header fields and options can be set using ip socket options. this means raw sockets are usually needed only for new protocols or protocols with no user interface (like icmp). .pp when a packet is received, it is passed to any raw sockets which have been bound to its protocol before it is passed to other protocol handlers (e.g., kernel protocol modules). .ss address format for sending and receiving datagrams .rb ( sendto (2), .br recvfrom (2), and similar), raw sockets use the standard .i sockaddr_in address structure defined in .br ip (7). the .i sin_port field could be used to specify the ip protocol number, but it is ignored for sending in linux 2.2 and later, and should be always set to 0 (see bugs). for incoming packets, .i sin_port .\" commit f59fc7f30b710d45aadf715460b3e60dbe9d3418 is set to zero. .ss socket options raw socket options can be set with .br setsockopt (2) and read with .br getsockopt (2) by passing the .b ipproto_raw .\" or sol_raw on linux family flag. .tp .b icmp_filter enable a special filter for raw sockets bound to the .b ipproto_icmp protocol. the value has a bit set for each icmp message type which should be filtered out. the default is to filter no icmp messages. .pp in addition, all .br ip (7) .b ipproto_ip socket options valid for datagram sockets are supported. .ss error handling errors originating from the network are passed to the user only when the socket is connected or the .b ip_recverr flag is enabled. for connected sockets, only .b emsgsize and .b eproto are passed for compatibility. with .br ip_recverr , all network errors are saved in the error queue. .sh errors .tp .b eacces user tried to send to a broadcast address without having the broadcast flag set on the socket. .tp .b efault an invalid memory address was supplied. .tp .b einval invalid argument. .tp .b emsgsize packet too big. either path mtu discovery is enabled (the .b ip_mtu_discover socket flag) or the packet size exceeds the maximum allowed ipv4 packet size of 64\ kb. .tp .b eopnotsupp invalid flag has been passed to a socket call (like .br msg_oob ). .tp .b eperm the user doesn't have permission to open raw sockets. only processes with an effective user id of 0 or the .b cap_net_raw attribute may do that. .tp .b eproto an icmp error has arrived reporting a parameter problem. .sh versions .b ip_recverr and .b icmp_filter are new in linux 2.2. they are linux extensions and should not be used in portable programs. .pp linux 2.0 enabled some bug-to-bug compatibility with bsd in the raw socket code when the .b so_bsdcompat socket option was set; since linux 2.2, this option no longer has that effect. .sh notes by default, raw sockets do path mtu (maximum transmission unit) discovery. this means the kernel will keep track of the mtu to a specific target ip address and return .b emsgsize when a raw packet write exceeds it. when this happens, the application should decrease the packet size. path mtu discovery can be also turned off using the .b ip_mtu_discover socket option or the .i /proc/sys/net/ipv4/ip_no_pmtu_disc file, see .br ip (7) for details. when turned off, raw sockets will fragment outgoing packets that exceed the interface mtu. however, disabling it is not recommended for performance and reliability reasons. .pp a raw socket can be bound to a specific local address using the .br bind (2) call. if it isn't bound, all packets with the specified ip protocol are received. in addition, a raw socket can be bound to a specific network device using .br so_bindtodevice ; see .br socket (7). .pp an .b ipproto_raw socket is send only. if you really want to receive all ip packets, use a .br packet (7) socket with the .b eth_p_ip protocol. note that packet sockets don't reassemble ip fragments, unlike raw sockets. .pp if you want to receive all icmp packets for a datagram socket, it is often better to use .b ip_recverr on that particular socket; see .br ip (7). .pp raw sockets may tap all ip protocols in linux, even protocols like icmp or tcp which have a protocol module in the kernel. in this case, the packets are passed to both the kernel module and the raw socket(s). this should not be relied upon in portable programs, many other bsd socket implementation have limitations here. .pp linux never changes headers passed from the user (except for filling in some zeroed fields as described for .br ip_hdrincl ). this differs from many other implementations of raw sockets. .pp raw sockets are generally rather unportable and should be avoided in programs intended to be portable. .pp sending on raw sockets should take the ip protocol from .ir sin_port ; this ability was lost in linux 2.2. the workaround is to use .br ip_hdrincl . .sh bugs transparent proxy extensions are not described. .pp when the .b ip_hdrincl option is set, datagrams will not be fragmented and are limited to the interface mtu. .pp setting the ip protocol for sending in .i sin_port got lost in linux 2.2. the protocol that the socket was bound to or that was specified in the initial .br socket (2) call is always used. .\" .sh authors .\" this man page was written by andi kleen. .sh see also .br recvmsg (2), .br sendmsg (2), .br capabilities (7), .br ip (7), .br socket (7) .pp .b rfc\ 1191 for path mtu discovery. .b rfc\ 791 and the .i header file for the ip protocol. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wmemcmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wmemcmp \- compare two arrays of wide-characters .sh synopsis .nf .b #include .pp .bi "int wmemcmp(const wchar_t *" s1 ", const wchar_t *" s2 ", size_t " n ); .fi .sh description the .br wmemcmp () function is the wide-character equivalent of the .br memcmp (3) function. it compares the .ir n wide-characters starting at .i s1 and the .i n wide-characters starting at .ir s2 . .sh return value the .br wmemcmp () function returns zero if the wide-character arrays of size .i n at .ir s1 and .i s2 are equal. it returns an integer greater than zero if at the first differing position .i i .ri ( i " <" .ir n ), the corresponding wide-character .i s1[i] is greater than .ir s2[i] . it returns an integer less than zero if at the first differing position .i i .ri ( i < .ir n ), the corresponding wide-character .i s1[i] is less than .ir s2[i] . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wmemcmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br memcmp (3), .br wcscmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man3/fmod.3 .so man3/printf.3 .\" copyright (c) 1993 luigi p. bai (lpb@softint.com) july 28, 1993 .\" and copyright 1993 giorgio ciucci .\" and copyright 2004, 2005 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-28, rik faith .\" modified 1993-11-28, giorgio ciucci .\" modified 1997-01-31, eric s. raymond .\" modified 2001-02-18, andries brouwer .\" modified 2002-01-05, 2004-05-27, 2004-06-17, .\" michael kerrisk .\" modified 2004-10-11, aeb .\" modified, nov 2004, michael kerrisk .\" language and formatting clean-ups .\" updated shmid_ds structure definitions .\" added information on shm_dest and shm_locked flags .\" noted that cap_ipc_lock is not required for shm_unlock .\" since kernel 2.6.9 .\" modified, 2004-11-25, mtk, notes on 2.6.9 rlimit_memlock changes .\" 2005-04-25, mtk -- noted aberrant linux behavior w.r.t. new .\" attaches to a segment that has already been marked for deletion. .\" 2005-08-02, mtk: added ipc_info, shm_info, shm_stat descriptions. .\" 2018-03-20, dbueso: added shm_stat_any description. .\" .th shmctl 2 2021-03-22 "linux" "linux programmer's manual" .sh name shmctl \- system v shared memory control .sh synopsis .nf .ad l .b #include .pp .bi "int shmctl(int " shmid ", int " cmd ", struct shmid_ds *" buf ); .ad b .fi .sh description .br shmctl () performs the control operation specified by .i cmd on the system\ v shared memory segment whose identifier is given in .ir shmid . .pp the .i buf argument is a pointer to a \fishmid_ds\fp structure, defined in \fi\fp as follows: .pp .in +4n .ex struct shmid_ds { struct ipc_perm shm_perm; /* ownership and permissions */ size_t shm_segsz; /* size of segment (bytes) */ time_t shm_atime; /* last attach time */ time_t shm_dtime; /* last detach time */ time_t shm_ctime; /* creation time/time of last modification via shmctl() */ pid_t shm_cpid; /* pid of creator */ pid_t shm_lpid; /* pid of last shmat(2)/shmdt(2) */ shmatt_t shm_nattch; /* no. of current attaches */ ... }; .ee .in .pp the fields of the .i shmid_ds structure are as follows: .tp 12 .i shm_perm this is an .i ipc_perm structure (see below) that specifies the access permissions on the shared memory segment. .tp .i shm_segsz size in bytes of the shared memory segment. .tp .i shm_atime time of the last .br shmat (2) system call that attached this segment. .tp .i shm_dtime time of the last .br shmdt (2) system call that detached tgis segment. .tp .i shm_ctime time of creation of segment or time of the last .br shmctl () .br ipc_set operation. .tp .i shm_cpid id of the process that created the shared memory segment. .tp .i shm_lpid id of the last process that executed a .br shmat (2) or .br shmdt (2) system call on this segment. .tp .i shm_nattch number of processes that have this segment attached. .pp the .i ipc_perm structure is defined as follows (the highlighted fields are settable using .br ipc_set ): .pp .in +4n .ex struct ipc_perm { key_t __key; /* key supplied to shmget(2) */ uid_t \fbuid\fp; /* effective uid of owner */ gid_t \fbgid\fp; /* effective gid of owner */ uid_t cuid; /* effective uid of creator */ gid_t cgid; /* effective gid of creator */ unsigned short \fbmode\fp; /* \fbpermissions\fp + shm_dest and shm_locked flags */ unsigned short __seq; /* sequence number */ }; .ee .in .pp the least significant 9 bits of the .i mode field of the .i ipc_perm structure define the access permissions for the shared memory segment. the permission bits are as follows: .ts l l. 0400 read by user 0200 write by user 0040 read by group 0020 write by group 0004 read by others 0002 write by others .te .pp bits 0100, 0010, and 0001 (the execute bits) are unused by the system. (it is not necessary to have execute permission on a segment in order to perform a .br shmat (2) call with the .b shm_exec flag.) .pp valid values for .i cmd are: .tp .b ipc_stat copy information from the kernel data structure associated with .i shmid into the .i shmid_ds structure pointed to by \fibuf\fp. the caller must have read permission on the shared memory segment. .tp .b ipc_set write the values of some members of the .i shmid_ds structure pointed to by .i buf to the kernel data structure associated with this shared memory segment, updating also its .i shm_ctime member. .ip the following fields are updated: \fishm_perm.uid\fp, \fishm_perm.gid\fp, and (the least significant 9 bits of) \fishm_perm.mode\fp. .ip the effective uid of the calling process must match the owner .ri ( shm_perm.uid ) or creator .ri ( shm_perm.cuid ) of the shared memory segment, or the caller must be privileged. .tp .b ipc_rmid mark the segment to be destroyed. the segment will actually be destroyed only after the last process detaches it (i.e., when the .i shm_nattch member of the associated structure .i shmid_ds is zero). the caller must be the owner or creator of the segment, or be privileged. the .i buf argument is ignored. .ip if a segment has been marked for destruction, then the (nonstandard) .b shm_dest flag of the .i shm_perm.mode field in the associated data structure retrieved by .b ipc_stat will be set. .ip the caller \fimust\fp ensure that a segment is eventually destroyed; otherwise its pages that were faulted in will remain in memory or swap. .ip see also the description of .i /proc/sys/kernel/shm_rmid_forced in .br proc (5). .tp .br ipc_info " (linux-specific)" return information about system-wide shared memory limits and parameters in the structure pointed to by .ir buf . this structure is of type .i shminfo (thus, a cast is required), defined in .i if the .b _gnu_source feature test macro is defined: .ip .in +4n .ex struct shminfo { unsigned long shmmax; /* maximum segment size */ unsigned long shmmin; /* minimum segment size; always 1 */ unsigned long shmmni; /* maximum number of segments */ unsigned long shmseg; /* maximum number of segments that a process can attach; unused within kernel */ unsigned long shmall; /* maximum number of pages of shared memory, system\-wide */ }; .ee .in .ip the .ir shmmni , .ir shmmax , and .i shmall settings can be changed via .i /proc files of the same name; see .br proc (5) for details. .tp .br shm_info " (linux-specific)" return a .i shm_info structure whose fields contain information about system resources consumed by shared memory. this structure is defined in .i if the .b _gnu_source feature test macro is defined: .ip .in +4n .ex struct shm_info { int used_ids; /* # of currently existing segments */ unsigned long shm_tot; /* total number of shared memory pages */ unsigned long shm_rss; /* # of resident shared memory pages */ unsigned long shm_swp; /* # of swapped shared memory pages */ unsigned long swap_attempts; /* unused since linux 2.4 */ unsigned long swap_successes; /* unused since linux 2.4 */ }; .ee .in .tp .br shm_stat " (linux-specific)" return a .i shmid_ds structure as for .br ipc_stat . however, the .i shmid argument is not a segment identifier, but instead an index into the kernel's internal array that maintains information about all shared memory segments on the system. .tp .br shm_stat_any " (linux-specific, since linux 4.17)" return a .i shmid_ds structure as for .br shm_stat . however, .i shm_perm.mode is not checked for read access for .ir shmid , meaning that any user can employ this operation (just as any user may read .ir /proc/sysvipc/shm to obtain the same information). .pp the caller can prevent or allow swapping of a shared memory segment with the following \ficmd\fp values: .tp .br shm_lock " (linux-specific)" prevent swapping of the shared memory segment. the caller must fault in any pages that are required to be present after locking is enabled. if a segment has been locked, then the (nonstandard) .b shm_locked flag of the .i shm_perm.mode field in the associated data structure retrieved by .b ipc_stat will be set. .tp .br shm_unlock " (linux-specific)" unlock the segment, allowing it to be swapped out. .pp in kernels before 2.6.10, only a privileged process could employ .b shm_lock and .br shm_unlock . since kernel 2.6.10, an unprivileged process can employ these operations if its effective uid matches the owner or creator uid of the segment, and (for .br shm_lock ) the amount of memory to be locked falls within the .b rlimit_memlock resource limit (see .br setrlimit (2)). .\" there was some weirdness in 2.6.9: shm_lock and shm_unlock could .\" be applied to a segment, regardless of ownership of the segment. .\" this was a botch-up in the move to rlimit_memlock, and was fixed .\" in 2.6.10. mtk, may 2005 .sh return value a successful .b ipc_info or .b shm_info operation returns the index of the highest used entry in the kernel's internal array recording information about all shared memory segments. (this information can be used with repeated .b shm_stat or .b shm_stat_any operations to obtain information about all shared memory segments on the system.) a successful .b shm_stat operation returns the identifier of the shared memory segment whose index was given in .ir shmid . other operations return 0 on success. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces \fbipc_stat\fp or \fbshm_stat\fp is requested and \fishm_perm.mode\fp does not allow read access for .ir shmid , and the calling process does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b efault the argument .i cmd has value .b ipc_set or .b ipc_stat but the address pointed to by .i buf isn't accessible. .tp .b eidrm \fishmid\fp points to a removed identifier. .tp .b einval \fishmid\fp is not a valid identifier, or \ficmd\fp is not a valid command. or: for a .b shm_stat or .b shm_stat_any operation, the index value specified in .i shmid referred to an array slot that is currently unused. .tp .b enomem (in kernels since 2.6.9), .b shm_lock was specified and the size of the to-be-locked segment would mean that the total bytes in locked shared memory segments would exceed the limit for the real user id of the calling process. this limit is defined by the .b rlimit_memlock soft resource limit (see .br setrlimit (2)). .tp .b eoverflow \fbipc_stat\fp is attempted, and the gid or uid value is too large to be stored in the structure pointed to by .ir buf . .tp .b eperm \fbipc_set\fp or \fbipc_rmid\fp is attempted, and the effective user id of the calling process is not that of the creator (found in .ir shm_perm.cuid ), or the owner (found in .ir shm_perm.uid ), and the process was not privileged (linux: did not have the .b cap_sys_admin capability). .ip or (in kernels before 2.6.9), .b shm_lock or .b shm_unlock was specified, but the process was not privileged (linux: did not have the .b cap_ipc_lock capability). (since linux 2.6.9, this error can also occur if the .b rlimit_memlock is 0 and the caller is not privileged.) .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svr4 documents additional error conditions einval, .\" enoent, enospc, enomem, eexist. neither svr4 nor svid documents .\" an eidrm error condition. .sh notes the .br ipc_info , .br shm_stat , and .b shm_info operations are used by the .br ipcs (1) program to provide information on allocated resources. in the future, these may modified or moved to a .i /proc filesystem interface. .pp linux permits a process to attach .rb ( shmat (2)) a shared memory segment that has already been marked for deletion using .ir shmctl(ipc_rmid) . this feature is not available on other unix implementations; portable applications should avoid relying on it. .pp various fields in a \fistruct shmid_ds\fp were typed as .i short under linux 2.2 and have become .i long under linux 2.4. to take advantage of this, a recompilation under glibc-2.1.91 or later should suffice. (the kernel distinguishes old and new calls by an .b ipc_64 flag in .ir cmd .) .sh see also .br mlock (2), .br setrlimit (2), .br shmget (2), .br shmop (2), .br capabilities (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th timer_create 2 2021-03-22 linux "linux programmer's manual" .sh name timer_create \- create a posix per-process timer .sh synopsis .nf .br "#include " " /* definition of " sigev_* " constants */" .b #include .pp .bi "int timer_create(clockid_t " clockid ", struct sigevent *restrict " sevp , .bi " timer_t *restrict " timerid ); .fi .pp link with \fi\-lrt\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br timer_create (): .nf _posix_c_source >= 199309l .fi .sh description .br timer_create () creates a new per-process interval timer. the id of the new timer is returned in the buffer pointed to by .ir timerid , which must be a non-null pointer. this id is unique within the process, until the timer is deleted. the new timer is initially disarmed. .pp the .i clockid argument specifies the clock that the new timer uses to measure time. it can be specified as one of the following values: .tp .b clock_realtime a settable system-wide real-time clock. .tp .b clock_monotonic a nonsettable monotonically increasing clock that measures time from some unspecified point in the past that does not change after system startup. .\" note: the clock_monotonic_raw clock added for clock_gettime() .\" in 2.6.28 is not supported for posix timers -- mtk, feb 2009 .tp .br clock_process_cputime_id " (since linux 2.6.12)" a clock that measures (user and system) cpu time consumed by (all of the threads in) the calling process. .tp .br clock_thread_cputime_id " (since linux 2.6.12)" a clock that measures (user and system) cpu time consumed by the calling thread. .\" the clock_monotonic_raw that was added in 2.6.28 can't be used .\" to create a timer -- mtk, feb 2009 .tp .br clock_boottime " (since linux 2.6.39)" .\" commit 70a08cca1227dc31c784ec930099a4417a06e7d0 like .br clock_monotonic , this is a monotonically increasing clock. however, whereas the .br clock_monotonic clock does not measure the time while a system is suspended, the .br clock_boottime clock does include the time during which the system is suspended. this is useful for applications that need to be suspend-aware. .br clock_realtime is not suitable for such applications, since that clock is affected by discontinuous changes to the system clock. .tp .br clock_realtime_alarm " (since linux 3.0)" .\" commit 9a7adcf5c6dea63d2e47e6f6d2f7a6c9f48b9337 this clock is like .br clock_realtime , but will wake the system if it is suspended. the caller must have the .b cap_wake_alarm capability in order to set a timer against this clock. .tp .br clock_boottime_alarm " (since linux 3.0)" .\" commit 9a7adcf5c6dea63d2e47e6f6d2f7a6c9f48b9337 this clock is like .br clock_boottime , but will wake the system if it is suspended. the caller must have the .b cap_wake_alarm capability in order to set a timer against this clock. .tp .br clock_tai " (since linux 3.10)" a system-wide clock derived from wall-clock time but ignoring leap seconds. .pp see .br clock_getres (2) for some further details on the above clocks. .pp as well as the above values, .i clockid can be specified as the .i clockid returned by a call to .br clock_getcpuclockid (3) or .br pthread_getcpuclockid (3). .pp the .i sevp argument points to a .i sigevent structure that specifies how the caller should be notified when the timer expires. for the definition and general details of this structure, see .br sigevent (7). .pp the .i sevp.sigev_notify field can have the following values: .tp .br sigev_none don't asynchronously notify when the timer expires. progress of the timer can be monitored using .br timer_gettime (2). .tp .br sigev_signal upon timer expiration, generate the signal .i sigev_signo for the process. see .br sigevent (7) for general details. the .i si_code field of the .i siginfo_t structure will be set to .br si_timer . at any point in time, at most one signal is queued to the process for a given timer; see .br timer_getoverrun (2) for more details. .tp .br sigev_thread upon timer expiration, invoke .i sigev_notify_function as if it were the start function of a new thread. see .br sigevent (7) for details. .tp .br sigev_thread_id " (linux-specific)" as for .br sigev_signal , but the signal is targeted at the thread whose id is given in .ir sigev_notify_thread_id , which must be a thread in the same process as the caller. the .ir sigev_notify_thread_id field specifies a kernel thread id, that is, the value returned by .br clone (2) or .br gettid (2). this flag is intended only for use by threading libraries. .pp specifying .i sevp as null is equivalent to specifying a pointer to a .i sigevent structure in which .i sigev_notify is .br sigev_signal , .i sigev_signo is .br sigalrm , and .i sigev_value.sival_int is the timer id. .sh return value on success, .br timer_create () returns 0, and the id of the new timer is placed in .ir *timerid . on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eagain temporary error during kernel allocation of timer structures. .tp .b einval clock id, .ir sigev_notify , .ir sigev_signo , or .ir sigev_notify_thread_id is invalid. .tp .b enomem .\" glibc layer: malloc() could not allocate memory. .tp .b enotsup the kernel does not support creating a timer against this .ir clockid . .tp .b eperm .i clockid was .br clock_realtime_alarm or .br clock_boottime_alarm but the caller did not have the .br cap_wake_alarm capability. .sh versions this system call is available since linux 2.6. .sh conforming to posix.1-2001, posix.1-2008. .sh notes a program may create multiple interval timers using .br timer_create (). .pp timers are not inherited by the child of a .br fork (2), and are disarmed and deleted during an .br execve (2). .pp the kernel preallocates a "queued real-time signal" for each timer created using .br timer_create (). consequently, the number of timers is limited by the .br rlimit_sigpending resource limit (see .br setrlimit (2)). .pp the timers created by .br timer_create () are commonly known as "posix (interval) timers". the posix timers api consists of the following interfaces: .ip * 3 .br timer_create (): create a timer. .ip * .br timer_settime (2): arm (start) or disarm (stop) a timer. .ip * .br timer_gettime (2): fetch the time remaining until the next expiration of a timer, along with the interval setting of the timer. .ip * .br timer_getoverrun (2): return the overrun count for the last timer expiration. .ip * .br timer_delete (2): disarm and delete a timer. .pp since linux 3.10, the .ir /proc/[pid]/timers file can be used to list the posix timers for the process with pid .ir pid . see .br proc (5) for further information. .pp since linux 4.10, .\" baa73d9e478ff32d62f3f9422822b59dd9a95a21 support for posix timers is a configurable option that is enabled by default. kernel support can be disabled via the .br config_posix_timers option. .\" .ss c library/kernel differences part of the implementation of the posix timers api is provided by glibc. .\" see nptl/sysdeps/unix/sysv/linux/timer_create.c in particular: .ip * 3 much of the functionality for .br sigev_thread is implemented within glibc, rather than the kernel. (this is necessarily so, since the thread involved in handling the notification is one that must be managed by the c library posix threads implementation.) although the notification delivered to the process is via a thread, internally the nptl implementation uses a .i sigev_notify value of .br sigev_thread_id along with a real-time signal that is reserved by the implementation (see .br nptl (7)). .ip * the implementation of the default case where .i evp is null is handled inside glibc, which invokes the underlying system call with a suitably populated .i sigevent structure. .ip * the timer ids presented at user level are maintained by glibc, which maps these ids to the timer ids employed by the kernel. .\" see the glibc source file kernel-posix-timers.h for the structure .\" that glibc uses to map user-space timer ids to kernel timer ids .\" the kernel-level timer id is exposed via siginfo.si_tid. .pp the posix timers system calls first appeared in linux 2.6. prior to this, glibc provided an incomplete user-space implementation .rb ( clock_realtime timers only) using posix threads, and in glibc versions before 2.17, .\" glibc commit 93a78ac437ba44f493333d7e2a4b0249839ce460 the implementation falls back to this technique on systems running pre-2.6 linux kernels. .sh examples the program below takes two arguments: a sleep period in seconds, and a timer frequency in nanoseconds. the program establishes a handler for the signal it uses for the timer, blocks that signal, creates and arms a timer that expires with the given frequency, sleeps for the specified number of seconds, and then unblocks the timer signal. assuming that the timer expired at least once while the program slept, the signal handler will be invoked, and the handler displays some information about the timer notification. the program terminates after one invocation of the signal handler. .pp in the following example run, the program sleeps for 1 second, after creating a timer that has a frequency of 100 nanoseconds. by the time the signal is unblocked and delivered, there have been around ten million overruns. .pp .in +4n .ex $ \fb./a.out 1 100\fp establishing handler for signal 34 blocking signal 34 timer id is 0x804c008 sleeping for 1 seconds unblocking signal 34 caught signal 34 sival_ptr = 0xbfb174f4; *sival_ptr = 0x804c008 overrun count = 10004886 .ee .in .ss program source \& .ex #include #include #include #include #include #include #define clockid clock_realtime #define sig sigrtmin #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static void print_siginfo(siginfo_t *si) { timer_t *tidp; int or; tidp = si\->si_value.sival_ptr; printf(" sival_ptr = %p; ", si\->si_value.sival_ptr); printf(" *sival_ptr = %#jx\en", (uintmax_t) *tidp); or = timer_getoverrun(*tidp); if (or == \-1) errexit("timer_getoverrun"); else printf(" overrun count = %d\en", or); } static void handler(int sig, siginfo_t *si, void *uc) { /* note: calling printf() from a signal handler is not safe (and should not be done in production programs), since printf() is not async\-signal\-safe; see signal\-safety(7). nevertheless, we use printf() here as a simple way of showing that the handler was called. */ printf("caught signal %d\en", sig); print_siginfo(si); signal(sig, sig_ign); } int main(int argc, char *argv[]) { timer_t timerid; struct sigevent sev; struct itimerspec its; long long freq_nanosecs; sigset_t mask; struct sigaction sa; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } /* establish handler for timer signal. */ printf("establishing handler for signal %d\en", sig); sa.sa_flags = sa_siginfo; sa.sa_sigaction = handler; sigemptyset(&sa.sa_mask); if (sigaction(sig, &sa, null) == \-1) errexit("sigaction"); /* block timer signal temporarily. */ printf("blocking signal %d\en", sig); sigemptyset(&mask); sigaddset(&mask, sig); if (sigprocmask(sig_setmask, &mask, null) == \-1) errexit("sigprocmask"); /* create the timer. */ sev.sigev_notify = sigev_signal; sev.sigev_signo = sig; sev.sigev_value.sival_ptr = &timerid; if (timer_create(clockid, &sev, &timerid) == \-1) errexit("timer_create"); printf("timer id is %#jx\en", (uintmax_t) timerid); /* start the timer. */ freq_nanosecs = atoll(argv[2]); its.it_value.tv_sec = freq_nanosecs / 1000000000; its.it_value.tv_nsec = freq_nanosecs % 1000000000; its.it_interval.tv_sec = its.it_value.tv_sec; its.it_interval.tv_nsec = its.it_value.tv_nsec; if (timer_settime(timerid, 0, &its, null) == \-1) errexit("timer_settime"); /* sleep for a while; meanwhile, the timer may expire multiple times. */ printf("sleeping for %d seconds\en", atoi(argv[1])); sleep(atoi(argv[1])); /* unlock the timer signal, so that timer notification can be delivered. */ printf("unblocking signal %d\en", sig); if (sigprocmask(sig_unblock, &mask, null) == \-1) errexit("sigprocmask"); exit(exit_success); } .ee .sh see also .ad l .nh .br clock_gettime (2), .br setitimer (2), .br timer_delete (2), .br timer_getoverrun (2), .br timer_settime (2), .br timerfd_create (2), .br clock_getcpuclockid (3), .br pthread_getcpuclockid (3), .br pthreads (7), .br sigevent (7), .br signal (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/err.3 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" and copyright (c) 2011 guillem jover .\" and copyright (c) 2006, 2014 michael kerrisk .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)readlink.2 6.8 (berkeley) 3/10/91 .\" .\" modified sat jul 24 00:10:21 1993 by rik faith (faith@cs.unc.edu) .\" modified tue jul 9 23:55:17 1996 by aeb .\" modified fri jan 24 00:26:00 1997 by aeb .\" 2011-09-20, guillem jover : .\" added text on dynamically allocating buffer + example program .\" .th readlink 2 2021-08-27 "linux" "linux programmer's manual" .sh name readlink, readlinkat \- read value of a symbolic link .sh synopsis .nf .b #include .pp .bi "ssize_t readlink(const char *restrict " pathname ", char *restrict " buf , .bi " size_t " bufsiz ); .pp .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "ssize_t readlinkat(int " dirfd ", const char *restrict " pathname , .bi " char *restrict " buf ", size_t " bufsiz ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br readlink (): .nf _xopen_source >= 500 || _posix_c_source >= 200112l .\" || _xopen_source && _xopen_source_extended || /* glibc <= 2.19: */ _bsd_source .fi .pp .br readlinkat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br readlink () places the contents of the symbolic link .i pathname in the buffer .ir buf , which has size .ir bufsiz . .br readlink () does not append a terminating null byte to .ir buf . it will (silently) truncate the contents (to a length of .i bufsiz characters), in case the buffer is too small to hold all of the contents. .ss readlinkat() the .br readlinkat () system call operates in exactly the same way as .br readlink (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br readlink () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br readlink ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp since linux 2.6.39, .\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d .i pathname can be an empty string, in which case the call operates on the symbolic link referred to by .ir dirfd (which should have been obtained using .br open (2) with the .b o_path and .b o_nofollow flags). .pp see .br openat (2) for an explanation of the need for .br readlinkat (). .sh return value on success, these calls return the number of bytes placed in .ir buf . (if the returned value equals .ir bufsiz , then truncation may have occurred.) on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces search permission is denied for a component of the path prefix. (see also .br path_resolution (7).) .tp .b ebadf .rb ( readlinkat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b efault .i buf extends outside the process's allocated address space. .tp .b einval .i bufsiz is not positive. .\" at the glibc level, bufsiz is unsigned, so this error can only occur .\" if bufsiz==0. however, the in the kernel syscall, bufsiz is signed, .\" and this error can also occur if bufsiz < 0. .\" see: http://thread.gmane.org/gmane.linux.man/380 .\" subject: [patch 0/3] [rfc] kernel/glibc mismatch of "readlink" syscall? .tp .b einval the named file (i.e., the final filename component of .ir pathname ) is not a symbolic link. .tp .b eio an i/o error occurred while reading from the filesystem. .tp .b eloop too many symbolic links were encountered in translating the pathname. .tp .b enametoolong a pathname, or a component of a pathname, was too long. .tp .b enoent the named file does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of the path prefix is not a directory. .tp .b enotdir .rb ( readlinkat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .sh versions .br readlinkat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br readlink (): 4.4bsd .rb ( readlink () first appeared in 4.2bsd), posix.1-2001, posix.1-2008. .pp .br readlinkat (): posix.1-2008. .sh notes in versions of glibc up to and including glibc 2.4, the return type of .br readlink () was declared as .ir int . nowadays, the return type is declared as .ir ssize_t , as (newly) required in posix.1-2001. .pp using a statically sized buffer might not provide enough room for the symbolic link contents. the required size for the buffer can be obtained from the .i stat.st_size value returned by a call to .br lstat (2) on the link. however, the number of bytes written by .br readlink () and .br readlinkat () should be checked to make sure that the size of the symbolic link did not increase between the calls. dynamically allocating the buffer for .br readlink () and .br readlinkat () also addresses a common portability problem when using .b path_max for the buffer size, as this constant is not guaranteed to be defined per posix if the system does not have such limit. .ss glibc notes on older kernels where .br readlinkat () is unavailable, the glibc wrapper function falls back to the use of .br readlink (). when .i pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir dirfd argument. .sh examples the following program allocates the buffer needed by .br readlink () dynamically from the information provided by .br lstat (2), falling back to a buffer of size .br path_max in cases where .br lstat (2) reports a size of zero. .pp .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { struct stat sb; char *buf; ssize_t nbytes, bufsiz; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } if (lstat(argv[1], &sb) == \-1) { perror("lstat"); exit(exit_failure); } /* add one to the link size, so that we can determine whether the buffer returned by readlink() was truncated. */ bufsiz = sb.st_size + 1; /* some magic symlinks under (for example) /proc and /sys report \(aqst_size\(aq as zero. in that case, take path_max as a "good enough" estimate. */ if (sb.st_size == 0) bufsiz = path_max; buf = malloc(bufsiz); if (buf == null) { perror("malloc"); exit(exit_failure); } nbytes = readlink(argv[1], buf, bufsiz); if (nbytes == \-1) { perror("readlink"); exit(exit_failure); } /* print only \(aqnbytes\(aq of \(aqbuf\(aq, as it doesn't contain a terminating null byte (\(aq\e0\(aq). */ printf("\(aq%s\(aq points to \(aq%.*s\(aq\en", argv[1], (int) nbytes, buf); /* if the return value was equal to the buffer size, then the the link target was larger than expected (perhaps because the target was changed between the call to lstat() and the call to readlink()). warn the user that the returned target may have been truncated. */ if (nbytes == bufsiz) printf("(returned buffer may have been truncated)\en"); free(buf); exit(exit_success); } .ee .sh see also .br readlink (1), .br lstat (2), .br stat (2), .br symlink (2), .br realpath (3), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) tom bjorkholm & markus kuhn, 1996 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-04-01 tom bjorkholm .\" first version written .\" 1996-04-10 markus kuhn .\" revision .\" .th sched_yield 2 2021-03-22 "linux" "linux programmer's manual" .sh name sched_yield \- yield the processor .sh synopsis .nf .b #include .pp .b int sched_yield(void); .fi .sh description .br sched_yield () causes the calling thread to relinquish the cpu. the thread is moved to the end of the queue for its static priority and a new thread gets to run. .sh return value on success, .br sched_yield () returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors in the linux implementation, .br sched_yield () always succeeds. .sh conforming to posix.1-2001, posix.1-2008. .sh notes if the calling thread is the only thread in the highest priority list at that time, it will continue to run after a call to .br sched_yield (). .pp posix systems on which .br sched_yield () is available define .b _posix_priority_scheduling in .ir . .pp strategic calls to .br sched_yield () can improve performance by giving other threads or processes a chance to run when (heavily) contended resources (e.g., mutexes) have been released by the caller. avoid calling .br sched_yield () unnecessarily or inappropriately (e.g., when resources needed by other schedulable threads are still held by the caller), since doing so will result in unnecessary context switches, which will degrade system performance. .pp .br sched_yield () is intended for use with real-time scheduling policies (i.e., .br sched_fifo or .br sched_rr ). use of .br sched_yield () with nondeterministic scheduling policies such as .br sched_other is unspecified and very likely means your application design is broken. .sh see also .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cos.3 .so man3/j0.3 .so man3/drand48.3 .so man7/system_data_types.7 .so man2/getrlimit.2 .\" no new programs should use vlimit(3). .\" getrlimit(2) briefly discusses vlimit(3), so point the user there. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wctrans 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wctrans \- wide-character translation mapping .sh synopsis .nf .b #include .pp .bi "wctrans_t wctrans(const char *" name ); .fi .sh description the .i wctrans_t type represents a mapping which can map a wide character to another wide character. its nature is implementation-dependent, but the special value .ir "(wctrans_t)\ 0" denotes an invalid mapping. nonzero .i wctrans_t values can be passed to the .br towctrans (3) function to actually perform the wide-character mapping. .pp the .br wctrans () function returns a mapping, given by its name. the set of valid names depends on the .b lc_ctype category of the current locale, but the following names are valid in all locales. .pp .nf "tolower" \- realizes the \fbtolower\fp(3) mapping "toupper" \- realizes the \fbtoupper\fp(3) mapping .fi .sh return value the .br wctrans () function returns a mapping descriptor if the .i name is valid. otherwise, it returns .ir "(wctrans_t)\ 0" . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wctrans () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wctrans () depends on the .b lc_ctype category of the current locale. .sh see also .br towctrans (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2000 christoph j. thompson .\" .\" %%%license_start(gplv2+_doc_misc) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th ftpusers 5 2000-08-27 "linux" "linux programmer's manual" .sh name ftpusers \- list of users that may not log in via the ftp daemon .sh description the text file .b ftpusers contains a list of users that may not log in using the file transfer protocol (ftp) server daemon. this file is used not merely for system administration purposes but also for improving security within a tcp/ip networked environment. .pp the .b ftpusers file will typically contain a list of the users that either have no business using ftp or have too many privileges to be allowed to log in through the ftp server daemon. such users usually include root, daemon, bin, uucp, and news. .pp if your ftp server daemon doesn't use .br ftpusers , then it is suggested that you read its documentation to find out how to block access for certain users. washington university ftp server daemon (wuftpd) and professional ftp daemon (proftpd) are known to make use of .br ftpusers . .ss format the format of .b ftpusers is very simple. there is one account name (or username) per line. lines starting with a # are ignored. .sh files .i /etc/ftpusers .sh see also .br passwd (5), .br proftpd (8), .br wuftpd (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getpriority.2 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" and copyright (c) 2007, michael kerrisk .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" $id: listen.2,v 1.6 1999/05/18 14:10:32 freitag exp $ .\" .\" modified fri jul 23 22:07:54 1993 by rik faith .\" modified 950727 by aeb, following a suggestion by urs thuermann .\" .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .\" modified 1998 by andi kleen .\" modified 11 may 2001 by sam varshavchik .\" .\" .th listen 2 2021-03-22 "linux" "linux programmer's manual" .sh name listen \- listen for connections on a socket .sh synopsis .nf .b #include .pp .bi "int listen(int " sockfd ", int " backlog ); .fi .sh description .br listen () marks the socket referred to by .i sockfd as a passive socket, that is, as a socket that will be used to accept incoming connection requests using .br accept (2). .pp the .i sockfd argument is a file descriptor that refers to a socket of type .b sock_stream or .br sock_seqpacket . .pp the .i backlog argument defines the maximum length to which the queue of pending connections for .i sockfd may grow. if a connection request arrives when the queue is full, the client may receive an error with an indication of .b econnrefused or, if the underlying protocol supports retransmission, the request may be ignored so that a later reattempt at connection succeeds. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eaddrinuse another socket is already listening on the same port. .tp .b eaddrinuse (internet domain sockets) the socket referred to by .i sockfd had not previously been bound to an address and, upon attempting to bind it to an ephemeral port, it was determined that all port numbers in the ephemeral port range are currently in use. see the discussion of .i /proc/sys/net/ipv4/ip_local_port_range in .br ip (7). .tp .b ebadf the argument .i sockfd is not a valid file descriptor. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .tp .b eopnotsupp the socket is not of a type that supports the .br listen () operation. .sh conforming to posix.1-2001, posix.1-2008, 4.4bsd .rb ( listen () first appeared in 4.2bsd). .sh notes to accept connections, the following steps are performed: .rs 4 .ip 1. 4 a socket is created with .br socket (2). .ip 2. the socket is bound to a local address using .br bind (2), so that other sockets may be .br connect (2)ed to it. .ip 3. a willingness to accept incoming connections and a queue limit for incoming connections are specified with .br listen (). .ip 4. connections are accepted with .br accept (2). .re .pp the behavior of the .i backlog argument on tcp sockets changed with linux 2.2. now it specifies the queue length for .i completely established sockets waiting to be accepted, instead of the number of incomplete connection requests. the maximum length of the queue for incomplete sockets can be set using .ir /proc/sys/net/ipv4/tcp_max_syn_backlog . when syncookies are enabled there is no logical maximum length and this setting is ignored. see .br tcp (7) for more information. .pp if the .i backlog argument is greater than the value in .ir /proc/sys/net/core/somaxconn , then it is silently capped to that value. since linux 5.4, the default in this file is 4096; in earlier kernels, the default value is 128. in kernels before 2.4.25, this limit was a hard coded value, .br somaxconn , with the value 128. .\" the following is now rather historic information (mtk, jun 05) .\" don't rely on this value in portable applications since bsd .\" (and some bsd-derived systems) limit the backlog to 5. .sh examples see .br bind (2). .sh see also .br accept (2), .br bind (2), .br connect (2), .br socket (2), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:35:54 1993 by rik faith (faith@cs.unc.edu) .\" modified mon oct 16 00:16:29 2000 following joseph s. myers .\" .th fnmatch 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fnmatch \- match filename or pathname .sh synopsis .nf .b #include .pp .bi "int fnmatch(const char *" "pattern" ", const char *" string ", int " flags ); .fi .sh description the .br fnmatch () function checks whether the .i string argument matches the .i pattern argument, which is a shell wildcard pattern (see .br glob (7)). .pp the .i flags argument modifies the behavior; it is the bitwise or of zero or more of the following flags: .tp .b fnm_noescape if this flag is set, treat backslash as an ordinary character, instead of an escape character. .tp .b fnm_pathname if this flag is set, match a slash in .i string only with a slash in .i pattern and not by an asterisk (*) or a question mark (?) metacharacter, nor by a bracket expression ([]) containing a slash. .tp .b fnm_period if this flag is set, a leading period in .i string has to be matched exactly by a period in .ir pattern . a period is considered to be leading if it is the first character in .ir string , or if both .b fnm_pathname is set and the period immediately follows a slash. .tp .b fnm_file_name this is a gnu synonym for .br fnm_pathname . .tp .b fnm_leading_dir if this flag (a gnu extension) is set, the pattern is considered to be matched if it matches an initial segment of .i string which is followed by a slash. this flag is mainly for the internal use of glibc and is implemented only in certain cases. .tp .b fnm_casefold if this flag (a gnu extension) is set, the pattern is matched case-insensitively. .tp .b fnm_extmatch if this flag (a gnu extension) is set, extended patterns are supported, as introduced by \&'ksh' and now supported by other shells. the extended format is as follows, with \fipattern\-list\fr being a \&'|' separated list of patterns. .tp \&'?(\fipattern\-list\fr)' the pattern matches if zero or one occurrences of any of the patterns in the \fipattern\-list\fr match the input \fistring\fr. .tp \&'*(\fipattern\-list\fr)' the pattern matches if zero or more occurrences of any of the patterns in the \fipattern\-list\fr match the input \fistring\fr. .tp \&'+(\fipattern\-list\fr)' the pattern matches if one or more occurrences of any of the patterns in the \fipattern\-list\fr match the input \fistring\fr. .tp \&'@(\fipattern\-list\fr)' the pattern matches if exactly one occurrence of any of the patterns in the \fipattern\-list\fr match the input \fistring\fr. .tp \&'!(\fipattern\-list\fr)' the pattern matches if the input \fistring\fr cannot be matched with any of the patterns in the \fipattern\-list\fr. .sh return value zero if .i string matches .ir pattern , .b fnm_nomatch if there is no match or another nonzero value if there is an error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fnmatch () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, posix.2. the .br fnm_file_name ", " fnm_leading_dir ", and " fnm_casefold flags are gnu extensions. .sh see also .br sh (1), .br glob (3), .br scandir (3), .br wordexp (3), .br glob (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/a64l.3 .so man3/xdr.3 .so man3/ferror.3 .\" copyright (c) 2008 silicon graphics, inc. .\" .\" author: paul jackson (http://oss.sgi.com/projects/cpusets) .\" .\" %%%license_start(gplv2_misc) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" version 2 as published by the free software foundation. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th cpuset 7 2020-11-01 "linux" "linux programmer's manual" .sh name cpuset \- confine processes to processor and memory node subsets .sh description the cpuset filesystem is a pseudo-filesystem interface to the kernel cpuset mechanism, which is used to control the processor placement and memory placement of processes. it is commonly mounted at .ir /dev/cpuset . .pp on systems with kernels compiled with built in support for cpusets, all processes are attached to a cpuset, and cpusets are always present. if a system supports cpusets, then it will have the entry .b nodev cpuset in the file .ir /proc/filesystems . by mounting the cpuset filesystem (see the .b examples section below), the administrator can configure the cpusets on a system to control the processor and memory placement of processes on that system. by default, if the cpuset configuration on a system is not modified or if the cpuset filesystem is not even mounted, then the cpuset mechanism, though present, has no effect on the system's behavior. .pp a cpuset defines a list of cpus and memory nodes. .pp the cpus of a system include all the logical processing units on which a process can execute, including, if present, multiple processor cores within a package and hyper-threads within a processor core. memory nodes include all distinct banks of main memory; small and smp systems typically have just one memory node that contains all the system's main memory, while numa (non-uniform memory access) systems have multiple memory nodes. .pp cpusets are represented as directories in a hierarchical pseudo-filesystem, where the top directory in the hierarchy .ri ( /dev/cpuset ) represents the entire system (all online cpus and memory nodes) and any cpuset that is the child (descendant) of another parent cpuset contains a subset of that parent's cpus and memory nodes. the directories and files representing cpusets have normal filesystem permissions. .pp every process in the system belongs to exactly one cpuset. a process is confined to run only on the cpus in the cpuset it belongs to, and to allocate memory only on the memory nodes in that cpuset. when a process .br fork (2)s, the child process is placed in the same cpuset as its parent. with sufficient privilege, a process may be moved from one cpuset to another and the allowed cpus and memory nodes of an existing cpuset may be changed. .pp when the system begins booting, a single cpuset is defined that includes all cpus and memory nodes on the system, and all processes are in that cpuset. during the boot process, or later during normal system operation, other cpusets may be created, as subdirectories of this top cpuset, under the control of the system administrator, and processes may be placed in these other cpusets. .pp cpusets are integrated with the .br sched_setaffinity (2) scheduling affinity mechanism and the .br mbind (2) and .br set_mempolicy (2) memory-placement mechanisms in the kernel. neither of these mechanisms let a process make use of a cpu or memory node that is not allowed by that process's cpuset. if changes to a process's cpuset placement conflict with these other mechanisms, then cpuset placement is enforced even if it means overriding these other mechanisms. the kernel accomplishes this overriding by silently restricting the cpus and memory nodes requested by these other mechanisms to those allowed by the invoking process's cpuset. this can result in these other calls returning an error, if for example, such a call ends up requesting an empty set of cpus or memory nodes, after that request is restricted to the invoking process's cpuset. .pp typically, a cpuset is used to manage the cpu and memory-node confinement for a set of cooperating processes such as a batch scheduler job, and these other mechanisms are used to manage the placement of individual processes or memory regions within that set or job. .sh files each directory below .i /dev/cpuset represents a cpuset and contains a fixed set of pseudo-files describing the state of that cpuset. .pp new cpusets are created using the .br mkdir (2) system call or the .br mkdir (1) command. the properties of a cpuset, such as its flags, allowed cpus and memory nodes, and attached processes, are queried and modified by reading or writing to the appropriate file in that cpuset's directory, as listed below. .pp the pseudo-files in each cpuset directory are automatically created when the cpuset is created, as a result of the .br mkdir (2) invocation. it is not possible to directly add or remove these pseudo-files. .pp a cpuset directory that contains no child cpuset directories, and has no attached processes, can be removed using .br rmdir (2) or .br rmdir (1). it is not necessary, or possible, to remove the pseudo-files inside the directory before removing it. .pp the pseudo-files in each cpuset directory are small text files that may be read and written using traditional shell utilities such as .br cat (1), and .br echo (1), or from a program by using file i/o library functions or system calls, such as .br open (2), .br read (2), .br write (2), and .br close (2). .pp the pseudo-files in a cpuset directory represent internal kernel state and do not have any persistent image on disk. each of these per-cpuset files is listed and described below. .\" ====================== tasks ====================== .tp .i tasks list of the process ids (pids) of the processes in that cpuset. the list is formatted as a series of ascii decimal numbers, each followed by a newline. a process may be added to a cpuset (automatically removing it from the cpuset that previously contained it) by writing its pid to that cpuset's .i tasks file (with or without a trailing newline). .ip .b warning: only one pid may be written to the .i tasks file at a time. if a string is written that contains more than one pid, only the first one will be used. .\" =================== notify_on_release =================== .tp .i notify_on_release flag (0 or 1). if set (1), that cpuset will receive special handling after it is released, that is, after all processes cease using it (i.e., terminate or are moved to a different cpuset) and all child cpuset directories have been removed. see the \fbnotify on release\fr section, below. .\" ====================== cpus ====================== .tp .i cpuset.cpus list of the physical numbers of the cpus on which processes in that cpuset are allowed to execute. see \fblist format\fr below for a description of the format of .ir cpus . .ip the cpus allowed to a cpuset may be changed by writing a new list to its .i cpus file. .\" ==================== cpu_exclusive ==================== .tp .i cpuset.cpu_exclusive flag (0 or 1). if set (1), the cpuset has exclusive use of its cpus (no sibling or cousin cpuset may overlap cpus). by default, this is off (0). newly created cpusets also initially default this to off (0). .ip two cpusets are .i sibling cpusets if they share the same parent cpuset in the .i /dev/cpuset hierarchy. two cpusets are .i cousin cpusets if neither is the ancestor of the other. regardless of the .i cpu_exclusive setting, if one cpuset is the ancestor of another, and if both of these cpusets have nonempty .ir cpus , then their .i cpus must overlap, because the .i cpus of any cpuset are always a subset of the .i cpus of its parent cpuset. .\" ====================== mems ====================== .tp .i cpuset.mems list of memory nodes on which processes in this cpuset are allowed to allocate memory. see \fblist format\fr below for a description of the format of .ir mems . .\" ==================== mem_exclusive ==================== .tp .i cpuset.mem_exclusive flag (0 or 1). if set (1), the cpuset has exclusive use of its memory nodes (no sibling or cousin may overlap). also if set (1), the cpuset is a \fbhardwall\fr cpuset (see below). by default, this is off (0). newly created cpusets also initially default this to off (0). .ip regardless of the .i mem_exclusive setting, if one cpuset is the ancestor of another, then their memory nodes must overlap, because the memory nodes of any cpuset are always a subset of the memory nodes of that cpuset's parent cpuset. .\" ==================== mem_hardwall ==================== .tp .ir cpuset.mem_hardwall " (since linux 2.6.26)" flag (0 or 1). if set (1), the cpuset is a \fbhardwall\fr cpuset (see below). unlike \fbmem_exclusive\fr, there is no constraint on whether cpusets marked \fbmem_hardwall\fr may have overlapping memory nodes with sibling or cousin cpusets. by default, this is off (0). newly created cpusets also initially default this to off (0). .\" ==================== memory_migrate ==================== .tp .ir cpuset.memory_migrate " (since linux 2.6.16)" flag (0 or 1). if set (1), then memory migration is enabled. by default, this is off (0). see the \fbmemory migration\fr section, below. .\" ==================== memory_pressure ==================== .tp .ir cpuset.memory_pressure " (since linux 2.6.16)" a measure of how much memory pressure the processes in this cpuset are causing. see the \fbmemory pressure\fr section, below. unless .i memory_pressure_enabled is enabled, always has value zero (0). this file is read-only. see the .b warnings section, below. .\" ================= memory_pressure_enabled ================= .tp .ir cpuset.memory_pressure_enabled " (since linux 2.6.16)" flag (0 or 1). this file is present only in the root cpuset, normally .ir /dev/cpuset . if set (1), the .i memory_pressure calculations are enabled for all cpusets in the system. by default, this is off (0). see the \fbmemory pressure\fr section, below. .\" ================== memory_spread_page ================== .tp .ir cpuset.memory_spread_page " (since linux 2.6.17)" flag (0 or 1). if set (1), pages in the kernel page cache (filesystem buffers) are uniformly spread across the cpuset. by default, this is off (0) in the top cpuset, and inherited from the parent cpuset in newly created cpusets. see the \fbmemory spread\fr section, below. .\" ================== memory_spread_slab ================== .tp .ir cpuset.memory_spread_slab " (since linux 2.6.17)" flag (0 or 1). if set (1), the kernel slab caches for file i/o (directory and inode structures) are uniformly spread across the cpuset. by default, is off (0) in the top cpuset, and inherited from the parent cpuset in newly created cpusets. see the \fbmemory spread\fr section, below. .\" ================== sched_load_balance ================== .tp .ir cpuset.sched_load_balance " (since linux 2.6.24)" flag (0 or 1). if set (1, the default) the kernel will automatically load balance processes in that cpuset over the allowed cpus in that cpuset. if cleared (0) the kernel will avoid load balancing processes in this cpuset, .i unless some other cpuset with overlapping cpus has its .i sched_load_balance flag set. see \fbscheduler load balancing\fr, below, for further details. .\" ================== sched_relax_domain_level ================== .tp .ir cpuset.sched_relax_domain_level " (since linux 2.6.26)" integer, between \-1 and a small positive value. the .i sched_relax_domain_level controls the width of the range of cpus over which the kernel scheduler performs immediate rebalancing of runnable tasks across cpus. if .i sched_load_balance is disabled, then the setting of .i sched_relax_domain_level does not matter, as no such load balancing is done. if .i sched_load_balance is enabled, then the higher the value of the .ir sched_relax_domain_level , the wider the range of cpus over which immediate load balancing is attempted. see \fbscheduler relax domain level\fr, below, for further details. .\" ================== proc cpuset ================== .pp in addition to the above pseudo-files in each directory below .ir /dev/cpuset , each process has a pseudo-file, .ir /proc//cpuset , that displays the path of the process's cpuset directory relative to the root of the cpuset filesystem. .\" ================== proc status ================== .pp also the .i /proc//status file for each process has four added lines, displaying the process's .i cpus_allowed (on which cpus it may be scheduled) and .i mems_allowed (on which memory nodes it may obtain memory), in the two formats \fbmask format\fr and \fblist format\fr (see below) as shown in the following example: .pp .in +4n .ex cpus_allowed: ffffffff,ffffffff,ffffffff,ffffffff cpus_allowed_list: 0\-127 mems_allowed: ffffffff,ffffffff mems_allowed_list: 0\-63 .ee .in .pp the "allowed" fields were added in linux 2.6.24; the "allowed_list" fields were added in linux 2.6.26. .\" ================== extended capabilities ================== .sh extended capabilities in addition to controlling which .i cpus and .i mems a process is allowed to use, cpusets provide the following extended capabilities. .\" ================== exclusive cpusets ================== .ss exclusive cpusets if a cpuset is marked .i cpu_exclusive or .ir mem_exclusive , no other cpuset, other than a direct ancestor or descendant, may share any of the same cpus or memory nodes. .pp a cpuset that is .i mem_exclusive restricts kernel allocations for buffer cache pages and other internal kernel data pages commonly shared by the kernel across multiple users. all cpusets, whether .i mem_exclusive or not, restrict allocations of memory for user space. this enables configuring a system so that several independent jobs can share common kernel data, while isolating each job's user allocation in its own cpuset. to do this, construct a large .i mem_exclusive cpuset to hold all the jobs, and construct child, .ri non- mem_exclusive cpusets for each individual job. only a small amount of kernel memory, such as requests from interrupt handlers, is allowed to be placed on memory nodes outside even a .i mem_exclusive cpuset. .\" ================== hardwall ================== .ss hardwall a cpuset that has .i mem_exclusive or .i mem_hardwall set is a .i hardwall cpuset. a .i hardwall cpuset restricts kernel allocations for page, buffer, and other data commonly shared by the kernel across multiple users. all cpusets, whether .i hardwall or not, restrict allocations of memory for user space. .pp this enables configuring a system so that several independent jobs can share common kernel data, such as filesystem pages, while isolating each job's user allocation in its own cpuset. to do this, construct a large .i hardwall cpuset to hold all the jobs, and construct child cpusets for each individual job which are not .i hardwall cpusets. .pp only a small amount of kernel memory, such as requests from interrupt handlers, is allowed to be taken outside even a .i hardwall cpuset. .\" ================== notify on release ================== .ss notify on release if the .i notify_on_release flag is enabled (1) in a cpuset, then whenever the last process in the cpuset leaves (exits or attaches to some other cpuset) and the last child cpuset of that cpuset is removed, the kernel will run the command .ir /sbin/cpuset_release_agent , supplying the pathname (relative to the mount point of the cpuset filesystem) of the abandoned cpuset. this enables automatic removal of abandoned cpusets. .pp the default value of .i notify_on_release in the root cpuset at system boot is disabled (0). the default value of other cpusets at creation is the current value of their parent's .i notify_on_release setting. .pp the command .i /sbin/cpuset_release_agent is invoked, with the name .ri ( /dev/cpuset relative path) of the to-be-released cpuset in .ir argv[1] . .pp the usual contents of the command .i /sbin/cpuset_release_agent is simply the shell script: .pp .in +4n .ex #!/bin/sh rmdir /dev/cpuset/$1 .ee .in .pp as with other flag values below, this flag can be changed by writing an ascii number 0 or 1 (with optional trailing newline) into the file, to clear or set the flag, respectively. .\" ================== memory pressure ================== .ss memory pressure the .i memory_pressure of a cpuset provides a simple per-cpuset running average of the rate that the processes in a cpuset are attempting to free up in-use memory on the nodes of the cpuset to satisfy additional memory requests. .pp this enables batch managers that are monitoring jobs running in dedicated cpusets to efficiently detect what level of memory pressure that job is causing. .pp this is useful both on tightly managed systems running a wide mix of submitted jobs, which may choose to terminate or reprioritize jobs that are trying to use more memory than allowed on the nodes assigned them, and with tightly coupled, long-running, massively parallel scientific computing jobs that will dramatically fail to meet required performance goals if they start to use more memory than allowed to them. .pp this mechanism provides a very economical way for the batch manager to monitor a cpuset for signs of memory pressure. it's up to the batch manager or other user code to decide what action to take if it detects signs of memory pressure. .pp unless memory pressure calculation is enabled by setting the pseudo-file .ir /dev/cpuset/cpuset.memory_pressure_enabled , it is not computed for any cpuset, and reads from any .i memory_pressure always return zero, as represented by the ascii string "0\en". see the \fbwarnings\fr section, below. .pp a per-cpuset, running average is employed for the following reasons: .ip * 3 because this meter is per-cpuset rather than per-process or per virtual memory region, the system load imposed by a batch scheduler monitoring this metric is sharply reduced on large systems, because a scan of the tasklist can be avoided on each set of queries. .ip * because this meter is a running average rather than an accumulating counter, a batch scheduler can detect memory pressure with a single read, instead of having to read and accumulate results for a period of time. .ip * because this meter is per-cpuset rather than per-process, the batch scheduler can obtain the key information\(emmemory pressure in a cpuset\(emwith a single read, rather than having to query and accumulate results over all the (dynamically changing) set of processes in the cpuset. .pp the .i memory_pressure of a cpuset is calculated using a per-cpuset simple digital filter that is kept within the kernel. for each cpuset, this filter tracks the recent rate at which processes attached to that cpuset enter the kernel direct reclaim code. .pp the kernel direct reclaim code is entered whenever a process has to satisfy a memory page request by first finding some other page to repurpose, due to lack of any readily available already free pages. dirty filesystem pages are repurposed by first writing them to disk. unmodified filesystem buffer pages are repurposed by simply dropping them, though if that page is needed again, it will have to be reread from disk. .pp the .i cpuset.memory_pressure file provides an integer number representing the recent (half-life of 10 seconds) rate of entries to the direct reclaim code caused by any process in the cpuset, in units of reclaims attempted per second, times 1000. .\" ================== memory spread ================== .ss memory spread there are two boolean flag files per cpuset that control where the kernel allocates pages for the filesystem buffers and related in-kernel data structures. they are called .i cpuset.memory_spread_page and .ir cpuset.memory_spread_slab . .pp if the per-cpuset boolean flag file .i cpuset.memory_spread_page is set, then the kernel will spread the filesystem buffers (page cache) evenly over all the nodes that the faulting process is allowed to use, instead of preferring to put those pages on the node where the process is running. .pp if the per-cpuset boolean flag file .i cpuset.memory_spread_slab is set, then the kernel will spread some filesystem-related slab caches, such as those for inodes and directory entries, evenly over all the nodes that the faulting process is allowed to use, instead of preferring to put those pages on the node where the process is running. .pp the setting of these flags does not affect the data segment (see .br brk (2)) or stack segment pages of a process. .pp by default, both kinds of memory spreading are off and the kernel prefers to allocate memory pages on the node local to where the requesting process is running. if that node is not allowed by the process's numa memory policy or cpuset configuration or if there are insufficient free memory pages on that node, then the kernel looks for the nearest node that is allowed and has sufficient free memory. .pp when new cpusets are created, they inherit the memory spread settings of their parent. .pp setting memory spreading causes allocations for the affected page or slab caches to ignore the process's numa memory policy and be spread instead. however, the effect of these changes in memory placement caused by cpuset-specified memory spreading is hidden from the .br mbind (2) or .br set_mempolicy (2) calls. these two numa memory policy calls always appear to behave as if no cpuset-specified memory spreading is in effect, even if it is. if cpuset memory spreading is subsequently turned off, the numa memory policy most recently specified by these calls is automatically reapplied. .pp both .i cpuset.memory_spread_page and .i cpuset.memory_spread_slab are boolean flag files. by default, they contain "0", meaning that the feature is off for that cpuset. if a "1" is written to that file, that turns the named feature on. .pp cpuset-specified memory spreading behaves similarly to what is known (in other contexts) as round-robin or interleave memory placement. .pp cpuset-specified memory spreading can provide substantial performance improvements for jobs that: .ip a) 3 need to place thread-local data on memory nodes close to the cpus which are running the threads that most frequently access that data; but also .ip b) need to access large filesystem data sets that must to be spread across the several nodes in the job's cpuset in order to fit. .pp without this policy, the memory allocation across the nodes in the job's cpuset can become very uneven, especially for jobs that might have just a single thread initializing or reading in the data set. .\" ================== memory migration ================== .ss memory migration normally, under the default setting (disabled) of .ir cpuset.memory_migrate , once a page is allocated (given a physical page of main memory), then that page stays on whatever node it was allocated, so long as it remains allocated, even if the cpuset's memory-placement policy .i mems subsequently changes. .pp when memory migration is enabled in a cpuset, if the .i mems setting of the cpuset is changed, then any memory page in use by any process in the cpuset that is on a memory node that is no longer allowed will be migrated to a memory node that is allowed. .pp furthermore, if a process is moved into a cpuset with .i memory_migrate enabled, any memory pages it uses that were on memory nodes allowed in its previous cpuset, but which are not allowed in its new cpuset, will be migrated to a memory node allowed in the new cpuset. .pp the relative placement of a migrated page within the cpuset is preserved during these migration operations if possible. for example, if the page was on the second valid node of the prior cpuset, then the page will be placed on the second valid node of the new cpuset, if possible. .\" ================== scheduler load balancing ================== .ss scheduler load balancing the kernel scheduler automatically load balances processes. if one cpu is underutilized, the kernel will look for processes on other more overloaded cpus and move those processes to the underutilized cpu, within the constraints of such placement mechanisms as cpusets and .br sched_setaffinity (2). .pp the algorithmic cost of load balancing and its impact on key shared kernel data structures such as the process list increases more than linearly with the number of cpus being balanced. for example, it costs more to load balance across one large set of cpus than it does to balance across two smaller sets of cpus, each of half the size of the larger set. (the precise relationship between the number of cpus being balanced and the cost of load balancing depends on implementation details of the kernel process scheduler, which is subject to change over time, as improved kernel scheduler algorithms are implemented.) .pp the per-cpuset flag .i sched_load_balance provides a mechanism to suppress this automatic scheduler load balancing in cases where it is not needed and suppressing it would have worthwhile performance benefits. .pp by default, load balancing is done across all cpus, except those marked isolated using the kernel boot time "isolcpus=" argument. (see \fbscheduler relax domain level\fr, below, to change this default.) .pp this default load balancing across all cpus is not well suited to the following two situations: .ip * 3 on large systems, load balancing across many cpus is expensive. if the system is managed using cpusets to place independent jobs on separate sets of cpus, full load balancing is unnecessary. .ip * systems supporting real-time on some cpus need to minimize system overhead on those cpus, including avoiding process load balancing if that is not needed. .pp when the per-cpuset flag .i sched_load_balance is enabled (the default setting), it requests load balancing across all the cpus in that cpuset's allowed cpus, ensuring that load balancing can move a process (not otherwise pinned, as by .br sched_setaffinity (2)) from any cpu in that cpuset to any other. .pp when the per-cpuset flag .i sched_load_balance is disabled, then the scheduler will avoid load balancing across the cpus in that cpuset, \fiexcept\fr in so far as is necessary because some overlapping cpuset has .i sched_load_balance enabled. .pp so, for example, if the top cpuset has the flag .i sched_load_balance enabled, then the scheduler will load balance across all cpus, and the setting of the .i sched_load_balance flag in other cpusets has no effect, as we're already fully load balancing. .pp therefore in the above two situations, the flag .i sched_load_balance should be disabled in the top cpuset, and only some of the smaller, child cpusets would have this flag enabled. .pp when doing this, you don't usually want to leave any unpinned processes in the top cpuset that might use nontrivial amounts of cpu, as such processes may be artificially constrained to some subset of cpus, depending on the particulars of this flag setting in descendant cpusets. even if such a process could use spare cpu cycles in some other cpus, the kernel scheduler might not consider the possibility of load balancing that process to the underused cpu. .pp of course, processes pinned to a particular cpu can be left in a cpuset that disables .i sched_load_balance as those processes aren't going anywhere else anyway. .\" ================== scheduler relax domain level ================== .ss scheduler relax domain level the kernel scheduler performs immediate load balancing whenever a cpu becomes free or another task becomes runnable. this load balancing works to ensure that as many cpus as possible are usefully employed running tasks. the kernel also performs periodic load balancing off the software clock described in .br time (7). the setting of .i sched_relax_domain_level applies only to immediate load balancing. regardless of the .i sched_relax_domain_level setting, periodic load balancing is attempted over all cpus (unless disabled by turning off .ir sched_load_balance .) in any case, of course, tasks will be scheduled to run only on cpus allowed by their cpuset, as modified by .br sched_setaffinity (2) system calls. .pp on small systems, such as those with just a few cpus, immediate load balancing is useful to improve system interactivity and to minimize wasteful idle cpu cycles. but on large systems, attempting immediate load balancing across a large number of cpus can be more costly than it is worth, depending on the particular performance characteristics of the job mix and the hardware. .pp the exact meaning of the small integer values of .i sched_relax_domain_level will depend on internal implementation details of the kernel scheduler code and on the non-uniform architecture of the hardware. both of these will evolve over time and vary by system architecture and kernel version. .pp as of this writing, when this capability was introduced in linux 2.6.26, on certain popular architectures, the positive values of .i sched_relax_domain_level have the following meanings. .pp .pd 0 .ip \fb(1)\fr 4 perform immediate load balancing across hyper-thread siblings on the same core. .ip \fb(2)\fr perform immediate load balancing across other cores in the same package. .ip \fb(3)\fr perform immediate load balancing across other cpus on the same node or blade. .ip \fb(4)\fr perform immediate load balancing across over several (implementation detail) nodes [on numa systems]. .ip \fb(5)\fr perform immediate load balancing across over all cpus in system [on numa systems]. .pd .pp the .i sched_relax_domain_level value of zero (0) always means don't perform immediate load balancing, hence that load balancing is done only periodically, not immediately when a cpu becomes available or another task becomes runnable. .pp the .i sched_relax_domain_level value of minus one (\-1) always means use the system default value. the system default value can vary by architecture and kernel version. this system default value can be changed by kernel boot-time "relax_domain_level=" argument. .pp in the case of multiple overlapping cpusets which have conflicting .i sched_relax_domain_level values, then the highest such value applies to all cpus in any of the overlapping cpusets. in such cases, the value \fbminus one (\-1)\fr is the lowest value, overridden by any other value, and the value \fbzero (0)\fr is the next lowest value. .sh formats the following formats are used to represent sets of cpus and memory nodes. .\" ================== mask format ================== .ss mask format the \fbmask format\fr is used to represent cpu and memory-node bit masks in the .i /proc//status file. .pp this format displays each 32-bit word in hexadecimal (using ascii characters "0" - "9" and "a" - "f"); words are filled with leading zeros, if required. for masks longer than one word, a comma separator is used between words. words are displayed in big-endian order, which has the most significant bit first. the hex digits within a word are also in big-endian order. .pp the number of 32-bit words displayed is the minimum number needed to display all bits of the bit mask, based on the size of the bit mask. .pp examples of the \fbmask format\fr: .pp .in +4n .ex 00000001 # just bit 0 set 40000000,00000000,00000000 # just bit 94 set 00000001,00000000,00000000 # just bit 64 set 000000ff,00000000 # bits 32\-39 set 00000000,000e3862 # 1,5,6,11\-13,17\-19 set .ee .in .pp a mask with bits 0, 1, 2, 4, 8, 16, 32, and 64 set displays as: .pp .in +4n .ex 00000001,00000001,00010117 .ee .in .pp the first "1" is for bit 64, the second for bit 32, the third for bit 16, the fourth for bit 8, the fifth for bit 4, and the "7" is for bits 2, 1, and 0. .\" ================== list format ================== .ss list format the \fblist format\fr for .i cpus and .i mems is a comma-separated list of cpu or memory-node numbers and ranges of numbers, in ascii decimal. .pp examples of the \fblist format\fr: .pp .in +4n .ex 0\-4,9 # bits 0, 1, 2, 3, 4, and 9 set 0\-2,7,12\-14 # bits 0, 1, 2, 7, 12, 13, and 14 set .ee .in .\" ================== rules ================== .sh rules the following rules apply to each cpuset: .ip * 3 its cpus and memory nodes must be a (possibly equal) subset of its parent's. .ip * it can be marked .ir cpu_exclusive only if its parent is. .ip * it can be marked .ir mem_exclusive only if its parent is. .ip * if it is .ir cpu_exclusive , its cpus may not overlap any sibling. .ip * if it is .ir memory_exclusive , its memory nodes may not overlap any sibling. .\" ================== permissions ================== .sh permissions the permissions of a cpuset are determined by the permissions of the directories and pseudo-files in the cpuset filesystem, normally mounted at .ir /dev/cpuset . .pp for instance, a process can put itself in some other cpuset (than its current one) if it can write the .i tasks file for that cpuset. this requires execute permission on the encompassing directories and write permission on the .i tasks file. .pp an additional constraint is applied to requests to place some other process in a cpuset. one process may not attach another to a cpuset unless it would have permission to send that process a signal (see .br kill (2)). .pp a process may create a child cpuset if it can access and write the parent cpuset directory. it can modify the cpus or memory nodes in a cpuset if it can access that cpuset's directory (execute permissions on the each of the parent directories) and write the corresponding .i cpus or .i mems file. .pp there is one minor difference between the manner in which these permissions are evaluated and the manner in which normal filesystem operation permissions are evaluated. the kernel interprets relative pathnames starting at a process's current working directory. even if one is operating on a cpuset file, relative pathnames are interpreted relative to the process's current working directory, not relative to the process's current cpuset. the only ways that cpuset paths relative to a process's current cpuset can be used are if either the process's current working directory is its cpuset (it first did a .b cd or .br chdir (2) to its cpuset directory beneath .ir /dev/cpuset , which is a bit unusual) or if some user code converts the relative cpuset path to a full filesystem path. .pp in theory, this means that user code should specify cpusets using absolute pathnames, which requires knowing the mount point of the cpuset filesystem (usually, but not necessarily, .ir /dev/cpuset ). in practice, all user level code that this author is aware of simply assumes that if the cpuset filesystem is mounted, then it is mounted at .ir /dev/cpuset . furthermore, it is common practice for carefully written user code to verify the presence of the pseudo-file .i /dev/cpuset/tasks in order to verify that the cpuset pseudo-filesystem is currently mounted. .\" ================== warnings ================== .sh warnings .ss enabling memory_pressure by default, the per-cpuset file .i cpuset.memory_pressure always contains zero (0). unless this feature is enabled by writing "1" to the pseudo-file .ir /dev/cpuset/cpuset.memory_pressure_enabled , the kernel does not compute per-cpuset .ir memory_pressure . .ss using the echo command when using the .b echo command at the shell prompt to change the values of cpuset files, beware that the built-in .b echo command in some shells does not display an error message if the .br write (2) system call fails. .\" gack! csh(1)'s echo does this for example, if the command: .pp .in +4n .ex echo 19 > cpuset.mems .ee .in .pp failed because memory node 19 was not allowed (perhaps the current system does not have a memory node 19), then the .b echo command might not display any error. it is better to use the .b /bin/echo external command to change cpuset file settings, as this command will display .br write (2) errors, as in the example: .pp .in +4n .ex /bin/echo 19 > cpuset.mems /bin/echo: write error: invalid argument .ee .in .\" ================== exceptions ================== .sh exceptions .ss memory placement not all allocations of system memory are constrained by cpusets, for the following reasons. .pp if hot-plug functionality is used to remove all the cpus that are currently assigned to a cpuset, then the kernel will automatically update the .i cpus_allowed of all processes attached to cpus in that cpuset to allow all cpus. when memory hot-plug functionality for removing memory nodes is available, a similar exception is expected to apply there as well. in general, the kernel prefers to violate cpuset placement, rather than starving a process that has had all its allowed cpus or memory nodes taken offline. user code should reconfigure cpusets to refer only to online cpus and memory nodes when using hot-plug to add or remove such resources. .pp a few kernel-critical, internal memory-allocation requests, marked gfp_atomic, must be satisfied immediately. the kernel may drop some request or malfunction if one of these allocations fail. if such a request cannot be satisfied within the current process's cpuset, then we relax the cpuset, and look for memory anywhere we can find it. it's better to violate the cpuset than stress the kernel. .pp allocations of memory requested by kernel drivers while processing an interrupt lack any relevant process context, and are not confined by cpusets. .ss renaming cpusets you can use the .br rename (2) system call to rename cpusets. only simple renaming is supported; that is, changing the name of a cpuset directory is permitted, but moving a directory into a different directory is not permitted. .\" ================== errors ================== .sh errors the linux kernel implementation of cpusets sets .i errno to specify the reason for a failed system call affecting cpusets. .pp the possible .i errno settings and their meaning when set on a failed cpuset call are as listed below. .tp .b e2big attempted a .br write (2) on a special cpuset file with a length larger than some kernel-determined upper limit on the length of such writes. .tp .b eacces attempted to .br write (2) the process id (pid) of a process to a cpuset .i tasks file when one lacks permission to move that process. .tp .b eacces attempted to add, using .br write (2), a cpu or memory node to a cpuset, when that cpu or memory node was not already in its parent. .tp .b eacces attempted to set, using .br write (2), .i cpuset.cpu_exclusive or .i cpuset.mem_exclusive on a cpuset whose parent lacks the same setting. .tp .b eacces attempted to .br write (2) a .i cpuset.memory_pressure file. .tp .b eacces attempted to create a file in a cpuset directory. .tp .b ebusy attempted to remove, using .br rmdir (2), a cpuset with attached processes. .tp .b ebusy attempted to remove, using .br rmdir (2), a cpuset with child cpusets. .tp .b ebusy attempted to remove a cpu or memory node from a cpuset that is also in a child of that cpuset. .tp .b eexist attempted to create, using .br mkdir (2), a cpuset that already exists. .tp .b eexist attempted to .br rename (2) a cpuset to a name that already exists. .tp .b efault attempted to .br read (2) or .br write (2) a cpuset file using a buffer that is outside the writing processes accessible address space. .tp .b einval attempted to change a cpuset, using .br write (2), in a way that would violate a .i cpu_exclusive or .i mem_exclusive attribute of that cpuset or any of its siblings. .tp .b einval attempted to .br write (2) an empty .i cpuset.cpus or .i cpuset.mems list to a cpuset which has attached processes or child cpusets. .tp .b einval attempted to .br write (2) a .i cpuset.cpus or .i cpuset.mems list which included a range with the second number smaller than the first number. .tp .b einval attempted to .br write (2) a .i cpuset.cpus or .i cpuset.mems list which included an invalid character in the string. .tp .b einval attempted to .br write (2) a list to a .i cpuset.cpus file that did not include any online cpus. .tp .b einval attempted to .br write (2) a list to a .i cpuset.mems file that did not include any online memory nodes. .tp .b einval attempted to .br write (2) a list to a .i cpuset.mems file that included a node that held no memory. .tp .b eio attempted to .br write (2) a string to a cpuset .i tasks file that does not begin with an ascii decimal integer. .tp .b eio attempted to .br rename (2) a cpuset into a different directory. .tp .b enametoolong attempted to .br read (2) a .i /proc//cpuset file for a cpuset path that is longer than the kernel page size. .tp .b enametoolong attempted to create, using .br mkdir (2), a cpuset whose base directory name is longer than 255 characters. .tp .b enametoolong attempted to create, using .br mkdir (2), a cpuset whose full pathname, including the mount point (typically "/dev/cpuset/") prefix, is longer than 4095 characters. .tp .b enodev the cpuset was removed by another process at the same time as a .br write (2) was attempted on one of the pseudo-files in the cpuset directory. .tp .b enoent attempted to create, using .br mkdir (2), a cpuset in a parent cpuset that doesn't exist. .tp .b enoent attempted to .br access (2) or .br open (2) a nonexistent file in a cpuset directory. .tp .b enomem insufficient memory is available within the kernel; can occur on a variety of system calls affecting cpusets, but only if the system is extremely short of memory. .tp .b enospc attempted to .br write (2) the process id (pid) of a process to a cpuset .i tasks file when the cpuset had an empty .i cpuset.cpus or empty .i cpuset.mems setting. .tp .b enospc attempted to .br write (2) an empty .i cpuset.cpus or .i cpuset.mems setting to a cpuset that has tasks attached. .tp .b enotdir attempted to .br rename (2) a nonexistent cpuset. .tp .b eperm attempted to remove a file from a cpuset directory. .tp .b erange specified a .i cpuset.cpus or .i cpuset.mems list to the kernel which included a number too large for the kernel to set in its bit masks. .tp .b esrch attempted to .br write (2) the process id (pid) of a nonexistent process to a cpuset .i tasks file. .\" ================== versions ================== .sh versions cpusets appeared in version 2.6.12 of the linux kernel. .\" ================== notes ================== .sh notes despite its name, the .i pid parameter is actually a thread id, and each thread in a threaded group can be attached to a different cpuset. the value returned from a call to .br gettid (2) can be passed in the argument .ir pid . .\" ================== bugs ================== .sh bugs .i cpuset.memory_pressure cpuset files can be opened for writing, creation, or truncation, but then the .br write (2) fails with .i errno set to .br eacces , and the creation and truncation options on .br open (2) have no effect. .\" ================== examples ================== .sh examples the following examples demonstrate querying and setting cpuset options using shell commands. .ss creating and attaching to a cpuset. to create a new cpuset and attach the current command shell to it, the steps are: .pp .pd 0 .ip 1) 4 mkdir /dev/cpuset (if not already done) .ip 2) mount \-t cpuset none /dev/cpuset (if not already done) .ip 3) create the new cpuset using .br mkdir (1). .ip 4) assign cpus and memory nodes to the new cpuset. .ip 5) attach the shell to the new cpuset. .pd .pp for example, the following sequence of commands will set up a cpuset named "charlie", containing just cpus 2 and 3, and memory node 1, and then attach the current shell to that cpuset. .pp .in +4n .ex .rb "$" " mkdir /dev/cpuset" .rb "$" " mount \-t cpuset cpuset /dev/cpuset" .rb "$" " cd /dev/cpuset" .rb "$" " mkdir charlie" .rb "$" " cd charlie" .rb "$" " /bin/echo 2\-3 > cpuset.cpus" .rb "$" " /bin/echo 1 > cpuset.mems" .rb "$" " /bin/echo $$ > tasks" # the current shell is now running in cpuset charlie # the next line should display \(aq/charlie\(aq .rb "$" " cat /proc/self/cpuset" .ee .in .\" .ss migrating a job to different memory nodes. to migrate a job (the set of processes attached to a cpuset) to different cpus and memory nodes in the system, including moving the memory pages currently allocated to that job, perform the following steps. .pp .pd 0 .ip 1) 4 let's say we want to move the job in cpuset .i alpha (cpus 4\(en7 and memory nodes 2\(en3) to a new cpuset .i beta (cpus 16\(en19 and memory nodes 8\(en9). .ip 2) first create the new cpuset .ir beta . .ip 3) then allow cpus 16\(en19 and memory nodes 8\(en9 in .ir beta . .ip 4) then enable .i memory_migration in .ir beta . .ip 5) then move each process from .i alpha to .ir beta . .pd .pp the following sequence of commands accomplishes this. .pp .in +4n .ex .rb "$" " cd /dev/cpuset" .rb "$" " mkdir beta" .rb "$" " cd beta" .rb "$" " /bin/echo 16\-19 > cpuset.cpus" .rb "$" " /bin/echo 8\-9 > cpuset.mems" .rb "$" " /bin/echo 1 > cpuset.memory_migrate" .rb "$" " while read i; do /bin/echo $i; done < ../alpha/tasks > tasks" .ee .in .pp the above should move any processes in .i alpha to .ir beta , and any memory held by these processes on memory nodes 2\(en3 to memory nodes 8\(en9, respectively. .pp notice that the last step of the above sequence did not do: .pp .in +4n .ex .rb "$" " cp ../alpha/tasks tasks" .ee .in .pp the .i while loop, rather than the seemingly easier use of the .br cp (1) command, was necessary because only one process pid at a time may be written to the .i tasks file. .pp the same effect (writing one pid at a time) as the .i while loop can be accomplished more efficiently, in fewer keystrokes and in syntax that works on any shell, but alas more obscurely, by using the .b \-u (unbuffered) option of .br sed (1): .pp .in +4n .ex .rb "$" " sed \-un p < ../alpha/tasks > tasks" .ee .in .\" ================== see also ================== .sh see also .br taskset (1), .br get_mempolicy (2), .br getcpu (2), .br mbind (2), .br sched_getaffinity (2), .br sched_setaffinity (2), .br sched_setscheduler (2), .br set_mempolicy (2), .br cpu_set (3), .br proc (5), .br cgroups (7), .br numa (7), .br sched (7), .br migratepages (8), .br numactl (8) .pp .ir documentation/admin\-guide/cgroup\-v1/cpusets.rst in the linux kernel source tree .\" commit 45ce80fb6b6f9594d1396d44dd7e7c02d596fef8 (or .ir documentation/cgroup\-v1/cpusets.txt before linux 4.18, and .ir documentation/cpusets.txt before linux 2.6.29) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/send.2 begin3 title: section 2, 3, 4, 5 and 7 man pages for linux version: 5.13 entered-date: 2021-08-27 description: linux manual pages keywords: man pages author: several maintained-by: michael kerrisk primary-site: http://www.kernel.org/pub/linux/docs/man-pages 2825k man-pages-5.13.tar.gz copying-policy: several; the pages are all freely distributable as long as nroff source is provided end .so man3/getspnam.3 .so man3/copysign.3 .so man2/adjtimex.2 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_setaffinity_np 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_setaffinity_np, pthread_getaffinity_np \- set/get cpu affinity of a thread .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_setaffinity_np(pthread_t " thread ", size_t " cpusetsize , .bi " const cpu_set_t *" cpuset ); .bi "int pthread_getaffinity_np(pthread_t " thread ", size_t " cpusetsize , .bi " cpu_set_t *" cpuset ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_setaffinity_np () function sets the cpu affinity mask of the thread .i thread to the cpu set pointed to by .ir cpuset . if the call is successful, and the thread is not currently running on one of the cpus in .ir cpuset , then it is migrated to one of those cpus. .pp the .br pthread_getaffinity_np () function returns the cpu affinity mask of the thread .i thread in the buffer pointed to by .ir cpuset . .pp for more details on cpu affinity masks, see .br sched_setaffinity (2). for a description of a set of macros that can be used to manipulate and inspect cpu sets, see .br cpu_set (3). .pp the argument .i cpusetsize is the length (in bytes) of the buffer pointed to by .ir cpuset . typically, this argument would be specified as .ir sizeof(cpu_set_t) . (it may be some other value, if using the macros described in .br cpu_set (3) for dynamically allocating a cpu set.) .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .tp .b efault a supplied memory address was invalid. .tp .b einval .rb ( pthread_setaffinity_np ()) the affinity bit mask .i mask contains no processors that are currently physically on the system and permitted to the thread according to any restrictions that may be imposed by the "cpuset" mechanism described in .br cpuset (7). .tp .br einval .rb ( pthread_setaffinity_np ()) .i cpuset specified a cpu that was outside the set supported by the kernel. (the kernel configuration option .br config_nr_cpus defines the range of the set supported by the kernel data type .\" cpumask_t used to represent cpu sets.) .\" the raw sched_getaffinity() system call returns the size (in bytes) .\" of the cpumask_t type. .tp .b einval .rb ( pthread_getaffinity_np ()) .i cpusetsize is smaller than the size of the affinity mask used by the kernel. .tp .b esrch no thread with the id .i thread could be found. .sh versions these functions are provided by glibc since version 2.3.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_setaffinity_np (), .br pthread_getaffinity_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh notes after a call to .br pthread_setaffinity_np (), the set of cpus on which the thread will actually run is the intersection of the set specified in the .i cpuset argument and the set of cpus actually present on the system. the system may further restrict the set of cpus on which the thread runs if the "cpuset" mechanism described in .br cpuset (7) is being used. these restrictions on the actual set of cpus on which the thread will run are silently imposed by the kernel. .pp these functions are implemented on top of the .br sched_setaffinity (2) and .br sched_getaffinity (2) system calls. .pp in glibc 2.3.3 only, versions of these functions were provided that did not have a .i cpusetsize argument. instead the cpu set size given to the underlying system calls was always .ir sizeof(cpu_set_t) . .pp a new thread created by .br pthread_create (3) inherits a copy of its creator's cpu affinity mask. .sh examples in the following program, the main thread uses .br pthread_setaffinity_np () to set its cpu affinity mask to include cpus 0 to 7 (which may not all be available on the system), and then calls .br pthread_getaffinity_np () to check the resulting cpu affinity mask of the thread. .pp .ex #define _gnu_source #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) int main(int argc, char *argv[]) { int s; cpu_set_t cpuset; pthread_t thread; thread = pthread_self(); /* set affinity mask to include cpus 0 to 7. */ cpu_zero(&cpuset); for (int j = 0; j < 8; j++) cpu_set(j, &cpuset); s = pthread_setaffinity_np(thread, sizeof(cpuset), &cpuset); if (s != 0) handle_error_en(s, "pthread_setaffinity_np"); /* check the actual affinity mask assigned to the thread. */ s = pthread_getaffinity_np(thread, sizeof(cpuset), &cpuset); if (s != 0) handle_error_en(s, "pthread_getaffinity_np"); printf("set returned by pthread_getaffinity_np() contained:\en"); for (int j = 0; j < cpu_setsize; j++) if (cpu_isset(j, &cpuset)) printf(" cpu %d\en", j); exit(exit_success); } .ee .sh see also .br sched_setaffinity (2), .br cpu_set (3), .br pthread_attr_setaffinity_np (3), .br pthread_self (3), .br sched_getcpu (3), .br cpuset (7), .br pthreads (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/wait.2 .so man3/xdr.3 .so man3/inet.3 .so man3/rpc.3 .\" copyright (c) 2001 john levon .\" based in part on gnu libc documentation .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getline 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getline, getdelim \- delimited string input .sh synopsis .nf .b #include .pp .bi "ssize_t getline(char **restrict " lineptr ", size_t *restrict " n , .bi " file *restrict " stream ); .bi "ssize_t getdelim(char **restrict " lineptr ", size_t *restrict " n , .bi " int " delim ", file *restrict " stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getline (), .br getdelim (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description .br getline () reads an entire line from \fistream\fp, storing the address of the buffer containing the text into .ir "*lineptr" . the buffer is null-terminated and includes the newline character, if one was found. .pp if .i "*lineptr" is set to null before the call, then .br getline () will allocate a buffer for storing the line. this buffer should be freed by the user program even if .br getline () failed. .pp alternatively, before calling .br getline (), .i "*lineptr" can contain a pointer to a .br malloc (3)\-allocated buffer .i "*n" bytes in size. if the buffer is not large enough to hold the line, .br getline () resizes it with .br realloc (3), updating .i "*lineptr" and .i "*n" as necessary. .pp in either case, on a successful call, .i "*lineptr" and .i "*n" will be updated to reflect the buffer address and allocated size respectively. .pp .br getdelim () works like .br getline (), except that a line delimiter other than newline can be specified as the .i delimiter argument. as with .br getline (), a delimiter character is not added if one was not present in the input before end of file was reached. .sh return value on success, .br getline () and .br getdelim () return the number of characters read, including the delimiter character, but not including the terminating null byte (\(aq\e0\(aq). this value can be used to handle embedded null bytes in the line read. .pp both functions return \-1 on failure to read a line (including end-of-file condition). in the event of a failure, .i errno is set to indicate the error. .sh errors .tp .b einval bad arguments .ri ( n or .i lineptr is null, or .i stream is not valid). .tp .b enomem allocation or reallocation of the line buffer failed. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getline (), .br getdelim () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to both .br getline () and .br getdelim () were originally gnu extensions. they were standardized in posix.1-2008. .sh examples .ex #define _gnu_source #include #include int main(int argc, char *argv[]) { file *stream; char *line = null; size_t len = 0; ssize_t nread; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } stream = fopen(argv[1], "r"); if (stream == null) { perror("fopen"); exit(exit_failure); } while ((nread = getline(&line, &len, stream)) != \-1) { printf("retrieved line of length %zd:\en", nread); fwrite(line, nread, 1, stdout); } free(line); fclose(stream); exit(exit_success); } .ee .sh see also .br read (2), .br fgets (3), .br fopen (3), .br fread (3), .br scanf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/basename.3 .\" copyright (c) 1994,1995 mike battersby .\" and copyright 2004, 2005 michael kerrisk .\" based on work by faith@cs.unc.edu .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, aeb, 960424 .\" modified fri jan 31 17:31:20 1997 by eric s. raymond .\" modified thu nov 26 02:12:45 1998 by aeb - add sigchld stuff. .\" modified sat may 8 17:40:19 1999 by matthew wilcox .\" add posix.1b signals .\" modified sat dec 29 01:44:52 2001 by evan jones .\" sa_onstack .\" modified 2004-11-11 by michael kerrisk .\" added mention of sigcont under sa_nocldstop .\" added sa_nocldwait .\" modified 2004-11-17 by michael kerrisk .\" updated discussion for posix.1-2001 and sigchld and sa_flags. .\" formatting fixes .\" 2004-12-09, mtk, added si_tkill + other minor changes .\" 2005-09-15, mtk, split sigpending(), sigprocmask(), sigsuspend() .\" out of this page into separate pages. .\" 2010-06-11 andi kleen, add hwpoison signal extensions .\" 2010-06-11 mtk, improvements to discussion of various siginfo_t fields. .\" 2015-01-17, kees cook .\" added notes on ptrace sigtrap and sys_seccomp. .\" .th sigaction 2 2021-08-27 "linux" "linux programmer's manual" .sh name sigaction, rt_sigaction \- examine and change a signal action .sh synopsis .nf .b #include .pp .bi "int sigaction(int " signum ", const struct sigaction *restrict " act , .bi " struct sigaction *restrict " oldact ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigaction (): .nf _posix_c_source .fi .pp .ir siginfo_t : .nf _posix_c_source >= 199309l .fi .sh description the .br sigaction () system call is used to change the action taken by a process on receipt of a specific signal. (see .br signal (7) for an overview of signals.) .pp .i signum specifies the signal and can be any valid signal except .b sigkill and .br sigstop . .pp if .i act is non-null, the new action for signal .i signum is installed from .ir act . if .i oldact is non-null, the previous action is saved in .ir oldact . .pp the .i sigaction structure is defined as something like: .pp .in +4n .ex struct sigaction { void (*sa_handler)(int); void (*sa_sigaction)(int, siginfo_t *, void *); sigset_t sa_mask; int sa_flags; void (*sa_restorer)(void); }; .ee .in .pp on some architectures a union is involved: do not assign to both .i sa_handler and .ir sa_sigaction . .pp the .i sa_restorer field is not intended for application use. (posix does not specify a .i sa_restorer field.) some further details of the purpose of this field can be found in .br sigreturn (2). .pp .i sa_handler specifies the action to be associated with .i signum and is be one of the following: .ip * 2 .b sig_dfl for the default action. .ip * .b sig_ign to ignore this signal. .ip * a pointer to a signal handling function. this function receives the signal number as its only argument. .pp if .b sa_siginfo is specified in .ir sa_flags , then .i sa_sigaction (instead of .ir sa_handler ) specifies the signal-handling function for .ir signum . this function receives three arguments, as described below. .pp .i sa_mask specifies a mask of signals which should be blocked (i.e., added to the signal mask of the thread in which the signal handler is invoked) during execution of the signal handler. in addition, the signal which triggered the handler will be blocked, unless the .b sa_nodefer flag is used. .pp .i sa_flags specifies a set of flags which modify the behavior of the signal. it is formed by the bitwise or of zero or more of the following: .tp .b sa_nocldstop if .i signum is .br sigchld , do not receive notification when child processes stop (i.e., when they receive one of .br sigstop ", " sigtstp ", " sigttin , or .br sigttou ) or resume (i.e., they receive .br sigcont ) (see .br wait (2)). this flag is meaningful only when establishing a handler for .br sigchld . .tp .br sa_nocldwait " (since linux 2.6)" .\" to be precise: linux 2.5.60 -- mtk if .i signum is .br sigchld , do not transform children into zombies when they terminate. see also .br waitpid (2). this flag is meaningful only when establishing a handler for .br sigchld , or when setting that signal's disposition to .br sig_dfl . .ip if the .b sa_nocldwait flag is set when establishing a handler for .br sigchld , posix.1 leaves it unspecified whether a .b sigchld signal is generated when a child process terminates. on linux, a .b sigchld signal is generated in this case; on some other implementations, it is not. .tp .b sa_nodefer do not add the signal to the thread's signal mask while the handler is executing, unless the signal is specified in .ir act.sa_mask . consequently, a further instance of the signal may be delivered to the thread while it is executing the handler. this flag is meaningful only when establishing a signal handler. .ip .b sa_nomask is an obsolete, nonstandard synonym for this flag. .tp .b sa_onstack call the signal handler on an alternate signal stack provided by .br sigaltstack (2). if an alternate stack is not available, the default stack will be used. this flag is meaningful only when establishing a signal handler. .tp .br sa_resethand restore the signal action to the default upon entry to the signal handler. this flag is meaningful only when establishing a signal handler. .ip .b sa_oneshot is an obsolete, nonstandard synonym for this flag. .tp .b sa_restart provide behavior compatible with bsd signal semantics by making certain system calls restartable across signals. this flag is meaningful only when establishing a signal handler. see .br signal (7) for a discussion of system call restarting. .tp .br sa_restorer .ir "not intended for application use" . this flag is used by c libraries to indicate that the .ir sa_restorer field contains the address of a "signal trampoline". see .br sigreturn (2) for more details. .tp .br sa_siginfo " (since linux 2.2)" the signal handler takes three arguments, not one. in this case, .i sa_sigaction should be set instead of .ir sa_handler . this flag is meaningful only when establishing a signal handler. .\" (the .\" .i sa_sigaction .\" field was added in linux 2.1.86.) .\" .tp .br sa_unsupported " (since linux 5.11)" used to dynamically probe for flag bit support. .ip if an attempt to register a handler succeeds with this flag set in .i act\->sa_flags alongside other flags that are potentially unsupported by the kernel, and an immediately subsequent .br sigaction () call specifying the same signal number and with a non-null .i oldact argument yields .b sa_unsupported .i clear in .ir oldact->sa_flags , then .i oldact->sa_flags may be used as a bitmask describing which of the potentially unsupported flags are, in fact, supported. see the section "dynamically probing for flag bit support" below for more details. .tp .br sa_expose_tagbits " (since linux 5.11)" normally, when delivering a signal, an architecture-specific set of tag bits are cleared from the .i si_addr field of .ir siginfo_t . if this flag is set, an architecture-specific subset of the tag bits will be preserved in .ir si_addr . .ip programs that need to be compatible with linux versions older than 5.11 must use .b sa_unsupported to probe for support. .ss the siginfo_t argument to a sa_siginfo handler when the .b sa_siginfo flag is specified in .ir act.sa_flags , the signal handler address is passed via the .ir act.sa_sigaction field. this handler takes three arguments, as follows: .pp .in +4n .ex void handler(int sig, siginfo_t *info, void *ucontext) { ... } .ee .in .pp these three arguments are as follows .tp .i sig the number of the signal that caused invocation of the handler. .tp .i info a pointer to a .ir siginfo_t , which is a structure containing further information about the signal, as described below. .tp .i ucontext this is a pointer to a .i ucontext_t structure, cast to \fivoid\ *\fp. the structure pointed to by this field contains signal context information that was saved on the user-space stack by the kernel; for details, see .br sigreturn (2). further information about the .ir ucontext_t structure can be found in .br getcontext (3) and .br signal (7). commonly, the handler function doesn't make any use of the third argument. .pp the .i siginfo_t data type is a structure with the following fields: .pp .in +4n .ex siginfo_t { int si_signo; /* signal number */ int si_errno; /* an errno value */ int si_code; /* signal code */ int si_trapno; /* trap number that caused hardware\-generated signal (unused on most architectures) */ .\" fixme .\" the siginfo_t 'si_trapno' field seems to be used .\" only on sparc and alpha; this page could use .\" a little more detail on its purpose there. pid_t si_pid; /* sending process id */ uid_t si_uid; /* real user id of sending process */ int si_status; /* exit value or signal */ clock_t si_utime; /* user time consumed */ clock_t si_stime; /* system time consumed */ union sigval si_value; /* signal value */ int si_int; /* posix.1b signal */ void *si_ptr; /* posix.1b signal */ int si_overrun; /* timer overrun count; posix.1b timers */ int si_timerid; /* timer id; posix.1b timers */ .\" in the kernel: si_tid void *si_addr; /* memory location which caused fault */ long si_band; /* band event (was \fiint\fp in glibc 2.3.2 and earlier) */ int si_fd; /* file descriptor */ short si_addr_lsb; /* least significant bit of address (since linux 2.6.32) */ void *si_lower; /* lower bound when address violation occurred (since linux 3.19) */ void *si_upper; /* upper bound when address violation occurred (since linux 3.19) */ int si_pkey; /* protection key on pte that caused fault (since linux 4.6) */ void *si_call_addr; /* address of system call instruction (since linux 3.5) */ int si_syscall; /* number of attempted system call (since linux 3.5) */ unsigned int si_arch; /* architecture of attempted system call (since linux 3.5) */ } .ee .in .pp .ir si_signo ", " si_errno " and " si_code are defined for all signals. .ri ( si_errno is generally unused on linux.) the rest of the struct may be a union, so that one should read only the fields that are meaningful for the given signal: .ip * 2 signals sent with .br kill (2) and .br sigqueue (3) fill in .ir si_pid " and " si_uid . in addition, signals sent with .br sigqueue (3) fill in .ir si_int " and " si_ptr with the values specified by the sender of the signal; see .br sigqueue (3) for more details. .ip * signals sent by posix.1b timers (since linux 2.6) fill in .i si_overrun and .ir si_timerid . the .i si_timerid field is an internal id used by the kernel to identify the timer; it is not the same as the timer id returned by .br timer_create (2). the .i si_overrun field is the timer overrun count; this is the same information as is obtained by a call to .br timer_getoverrun (2). these fields are nonstandard linux extensions. .ip * signals sent for message queue notification (see the description of .b sigev_signal in .br mq_notify (3)) fill in .ir si_int / si_ptr , with the .i sigev_value supplied to .br mq_notify (3); .ir si_pid , with the process id of the message sender; and .ir si_uid , with the real user id of the message sender. .ip * .b sigchld fills in .ir si_pid ", " si_uid ", " si_status ", " si_utime ", and " si_stime , providing information about the child. the .i si_pid field is the process id of the child; .i si_uid is the child's real user id. the .i si_status field contains the exit status of the child (if .i si_code is .br cld_exited ), or the signal number that caused the process to change state. the .i si_utime and .i si_stime contain the user and system cpu time used by the child process; these fields do not include the times used by waited-for children (unlike .br getrusage (2) and .br times (2)). in kernels up to 2.6, and since 2.6.27, these fields report cpu time in units of .ir sysconf(_sc_clk_tck) . in 2.6 kernels before 2.6.27, a bug meant that these fields reported time in units of the (configurable) system jiffy (see .br time (7)). .\" fixme . .\" when si_utime and si_stime where originally implemented, the .\" measurement unit was hz, which was the same as clock ticks .\" (sysconf(_sc_clk_tck)). in 2.6, hz became configurable, and .\" was *still* used as the unit to return the info these fields, .\" with the result that the field values depended on the .\" configured hz. of course, the should have been measured in .\" user_hz instead, so that sysconf(_sc_clk_tck) could be used to .\" convert to seconds. i have a queued patch to fix this: .\" http://thread.gmane.org/gmane.linux.kernel/698061/ . .\" this patch made it into 2.6.27. .\" but note that these fields still don't return the times of .\" waited-for children (as is done by getrusage() and times() .\" and wait4()). solaris 8 does include child times. .ip * .br sigill , .br sigfpe , .br sigsegv , .br sigbus , and .br sigtrap fill in .i si_addr with the address of the fault. on some architectures, these signals also fill in the .i si_trapno field. .ip some suberrors of .br sigbus , in particular .b bus_mceerr_ao and .br bus_mceerr_ar , also fill in .ir si_addr_lsb . this field indicates the least significant bit of the reported address and therefore the extent of the corruption. for example, if a full page was corrupted, .i si_addr_lsb contains .ir log2(sysconf(_sc_pagesize)) . when .br sigtrap is delivered in response to a .br ptrace (2) event (ptrace_event_foo), .i si_addr is not populated, but .i si_pid and .i si_uid are populated with the respective process id and user id responsible for delivering the trap. in the case of .br seccomp (2), the tracee will be shown as delivering the event. .b bus_mceerr_* and .i si_addr_lsb are linux-specific extensions. .ip the .br segv_bnderr suberror of .b sigsegv populates .ir si_lower and .ir si_upper . .ip the .br segv_pkuerr suberror of .b sigsegv populates .ir si_pkey . .ip * .br sigio / sigpoll (the two names are synonyms on linux) fills in .ir si_band " and " si_fd . the .i si_band event is a bit mask containing the same values as are filled in the .i revents field by .br poll (2). the .i si_fd field indicates the file descriptor for which the i/o event occurred; for further details, see the description of .br f_setsig in .br fcntl (2). .ip * .br sigsys , generated (since linux 3.5) .\" commit a0727e8ce513fe6890416da960181ceb10fbfae6 when a seccomp filter returns .br seccomp_ret_trap , fills in .ir si_call_addr , .ir si_syscall , .ir si_arch , .ir si_errno , and other fields as described in .br seccomp (2). .\" .ss the si_code field the .i si_code field inside the .i siginfo_t argument that is passed to a .b sa_siginfo signal handler is a value (not a bit mask) indicating why this signal was sent. for a .br ptrace (2) event, .i si_code will contain .br sigtrap and have the ptrace event in the high byte: .pp .in +4n .ex (sigtrap | ptrace_event_foo << 8). .ee .in .pp for a .rb non- ptrace (2) event, the values that can appear in .i si_code are described in the remainder of this section. since glibc 2.20, the definitions of most of these symbols are obtained from .i by defining feature test macros (before including .i any header file) as follows: .ip * 3 .b _xopen_source with the value 500 or greater; .ip * .b _xopen_source and .br _xopen_source_extended ; or .ip * .b _posix_c_source with the value 200809l or greater. .pp for the .b trap_* constants, the symbol definitions are provided only in the first two cases. before glibc 2.20, no feature test macros were required to obtain these symbols. .pp for a regular signal, the following list shows the values which can be placed in .i si_code for any signal, along with the reason that the signal was generated. .rs 4 .tp .b si_user .br kill (2). .tp .b si_kernel sent by the kernel. .tp .b si_queue .br sigqueue (3). .tp .b si_timer posix timer expired. .tp .br si_mesgq " (since linux 2.6.6)" posix message queue state changed; see .br mq_notify (3). .tp .b si_asyncio aio completed. .tp .b si_sigio queued .b sigio (only in kernels up to linux 2.2; from linux 2.4 onward .br sigio / sigpoll fills in .i si_code as described below). .tp .br si_tkill " (since linux 2.4.19)" .br tkill (2) or .br tgkill (2). .\" si_dethread is defined in 2.6.9 sources, but isn't implemented .\" it appears to have been an idea that was tried during 2.5.6 .\" through to 2.5.24 and then was backed out. .re .pp the following values can be placed in .i si_code for a .b sigill signal: .rs 4 .tp .b ill_illopc illegal opcode. .tp .b ill_illopn illegal operand. .tp .b ill_illadr illegal addressing mode. .tp .b ill_illtrp illegal trap. .tp .b ill_prvopc privileged opcode. .tp .b ill_prvreg privileged register. .tp .b ill_coproc coprocessor error. .tp .b ill_badstk internal stack error. .re .pp the following values can be placed in .i si_code for a .b sigfpe signal: .rs 4 .tp .b fpe_intdiv integer divide by zero. .tp .b fpe_intovf integer overflow. .tp .b fpe_fltdiv floating-point divide by zero. .tp .b fpe_fltovf floating-point overflow. .tp .b fpe_fltund floating-point underflow. .tp .b fpe_fltres floating-point inexact result. .tp .b fpe_fltinv floating-point invalid operation. .tp .b fpe_fltsub subscript out of range. .re .pp the following values can be placed in .i si_code for a .b sigsegv signal: .rs 4 .tp .b segv_maperr address not mapped to object. .tp .b segv_accerr invalid permissions for mapped object. .tp .br segv_bnderr " (since linux 3.19)" .\" commit ee1b58d36aa1b5a79eaba11f5c3633c88231da83 failed address bound checks. .tp .br segv_pkuerr " (since linux 4.6)" .\" commit cd0ea35ff5511cde299a61c21a95889b4a71464e access was denied by memory protection keys. see .br pkeys (7). the protection key which applied to this access is available via .ir si_pkey . .re .pp the following values can be placed in .i si_code for a .b sigbus signal: .rs 4 .tp .b bus_adraln invalid address alignment. .tp .b bus_adrerr nonexistent physical address. .tp .b bus_objerr object-specific hardware error. .tp .br bus_mceerr_ar " (since linux 2.6.32)" hardware memory error consumed on a machine check; action required. .tp .br bus_mceerr_ao " (since linux 2.6.32)" hardware memory error detected in process but not consumed; action optional. .re .pp the following values can be placed in .i si_code for a .b sigtrap signal: .rs 4 .tp .b trap_brkpt process breakpoint. .tp .b trap_trace process trace trap. .tp .br trap_branch " (since linux 2.4, ia64 only)" process taken branch trap. .tp .br trap_hwbkpt " (since linux 2.4, ia64 only)" hardware breakpoint/watchpoint. .re .pp the following values can be placed in .i si_code for a .b sigchld signal: .rs 4 .tp .b cld_exited child has exited. .tp .b cld_killed child was killed. .tp .b cld_dumped child terminated abnormally. .tp .b cld_trapped traced child has trapped. .tp .b cld_stopped child has stopped. .tp .br cld_continued " (since linux 2.6.9)" stopped child has continued. .re .pp the following values can be placed in .i si_code for a .br sigio / sigpoll signal: .rs 4 .tp .b poll_in data input available. .tp .b poll_out output buffers available. .tp .b poll_msg input message available. .tp .b poll_err i/o error. .tp .b poll_pri high priority input available. .tp .b poll_hup device disconnected. .re .pp the following value can be placed in .i si_code for a .br sigsys signal: .rs 4 .tp .br sys_seccomp " (since linux 3.5)" triggered by a .br seccomp (2) filter rule. .re .ss dynamically probing for flag bit support the .br sigaction () call on linux accepts unknown bits set in .i act\->sa_flags without error. the behavior of the kernel starting with linux 5.11 is that a second .br sigaction () will clear unknown bits from .ir oldact\->sa_flags . however, historically, a second .br sigaction () call would typically leave those bits set in .ir oldact\->sa_flags . .pp this means that support for new flags cannot be detected simply by testing for a flag in .ir sa_flags , and a program must test that .b sa_unsupported has been cleared before relying on the contents of .ir sa_flags . .pp since the behavior of the signal handler cannot be guaranteed unless the check passes, it is wise to either block the affected signal while registering the handler and performing the check in this case, or where this is not possible, for example if the signal is synchronous, to issue the second .br sigaction () in the signal handler itself. .pp in kernels that do not support a specific flag, the kernel's behavior is as if the flag was not set, even if the flag was set in .ir act\->sa_flags . .pp the flags .br sa_nocldstop , .br sa_nocldwait , .br sa_siginfo , .br sa_onstack , .br sa_restart , .br sa_nodefer , .br sa_resethand , and, if defined by the architecture, .b sa_restorer may not be reliably probed for using this mechanism, because they were introduced before linux 5.11. however, in general, programs may assume that these flags are supported, since they have all been supported since linux 2.6, which was released in the year 2003. .pp see examples below for a demonstration of the use of .br sa_unsupported . .sh return value .br sigaction () returns 0 on success; on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .ir act " or " oldact points to memory which is not a valid part of the process address space. .tp .b einval an invalid signal was specified. this will also be generated if an attempt is made to change the action for .br sigkill " or " sigstop , which cannot be caught or ignored. .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svr4 does not document the eintr condition. .sh notes a child created via .br fork (2) inherits a copy of its parent's signal dispositions. during an .br execve (2), the dispositions of handled signals are reset to the default; the dispositions of ignored signals are left unchanged. .pp according to posix, the behavior of a process is undefined after it ignores a .br sigfpe , .br sigill , or .b sigsegv signal that was not generated by .br kill (2) or .br raise (3). integer division by zero has undefined result. on some architectures it will generate a .b sigfpe signal. (also dividing the most negative integer by \-1 may generate .br sigfpe .) ignoring this signal might lead to an endless loop. .pp posix.1-1990 disallowed setting the action for .b sigchld to .br sig_ign . posix.1-2001 and later allow this possibility, so that ignoring .b sigchld can be used to prevent the creation of zombies (see .br wait (2)). nevertheless, the historical bsd and system\ v behaviors for ignoring .b sigchld differ, so that the only completely portable method of ensuring that terminated children do not become zombies is to catch the .b sigchld signal and perform a .br wait (2) or similar. .pp posix.1-1990 specified only .br sa_nocldstop . posix.1-2001 added .br sa_nocldstop , .br sa_nocldwait , .br sa_nodefer , .br sa_onstack , .br sa_resethand , .br sa_restart , and .br sa_siginfo . use of these latter values in .i sa_flags may be less portable in applications intended for older unix implementations. .pp the .b sa_resethand flag is compatible with the svr4 flag of the same name. .pp the .b sa_nodefer flag is compatible with the svr4 flag of the same name under kernels 1.3.9 and later. on older kernels the linux implementation allowed the receipt of any signal, not just the one we are installing (effectively overriding any .i sa_mask settings). .pp .br sigaction () can be called with a null second argument to query the current signal handler. it can also be used to check whether a given signal is valid for the current machine by calling it with null second and third arguments. .pp it is not possible to block .br sigkill " or " sigstop (by specifying them in .ir sa_mask ). attempts to do so are silently ignored. .pp see .br sigsetops (3) for details on manipulating signal sets. .pp see .br signal\-safety (7) for a list of the async-signal-safe functions that can be safely called inside from inside a signal handler. .\" .ss c library/kernel differences the glibc wrapper function for .br sigaction () gives an error .rb ( einval ) on attempts to change the disposition of the two real-time signals used internally by the nptl threading implementation. see .br nptl (7) for details. .pp on architectures where the signal trampoline resides in the c library, the glibc wrapper function for .br sigaction () places the address of the trampoline code in the .i act.sa_restorer field and sets the .b sa_restorer flag in the .ir act.sa_flags field. see .br sigreturn (2). .pp the original linux system call was named .br sigaction (). however, with the addition of real-time signals in linux 2.2, the fixed-size, 32-bit .ir sigset_t type supported by that system call was no longer fit for purpose. consequently, a new system call, .br rt_sigaction (), was added to support an enlarged .ir sigset_t type. the new system call takes a fourth argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the signal sets in .ir act.sa_mask and .ir oldact.sa_mask . this argument is currently required to have the value .ir sizeof(sigset_t) (or the error .b einval results). the glibc .br sigaction () wrapper function hides these details from us, transparently calling .br rt_sigaction () when the kernel provides it. .\" .ss undocumented before the introduction of .br sa_siginfo , it was also possible to get some additional information about the signal. this was done by providing an .i sa_handler signal handler with a second argument of type .ir "struct sigcontext" , which is the same structure as the one that is passed in the .i uc_mcontext field of the .i ucontext structure that is passed (via a pointer) in the third argument of the .i sa_sigaction handler. see the relevant linux kernel sources for details. this use is obsolete now. .sh bugs when delivering a signal with a .b sa_siginfo handler, the kernel does not always provide meaningful values for all of the fields of the .i siginfo_t that are relevant for that signal. .pp in kernels up to and including 2.6.13, specifying .b sa_nodefer in .i sa_flags prevents not only the delivered signal from being masked during execution of the handler, but also the signals specified in .ir sa_mask . this bug was fixed in kernel 2.6.14. .\" commit 69be8f189653cd81aae5a74e26615b12871bb72e .sh examples see .br mprotect (2). .ss probing for flag support the following example program exits with status .b exit_success if .b sa_expose_tagbits is determined to be supported, and .b exit_failure otherwise. .pp .ex #include #include #include #include void handler(int signo, siginfo_t *info, void *context) { struct sigaction oldact; if (sigaction(sigsegv, null, &oldact) == \-1 || (oldact.sa_flags & sa_unsupported) || !(oldact.sa_flags & sa_expose_tagbits)) { _exit(exit_failure); } _exit(exit_success); } int main(void) { struct sigaction act = { 0 }; act.sa_flags = sa_siginfo | sa_unsupported | sa_expose_tagbits; act.sa_sigaction = &handler; if (sigaction(sigsegv, &act, null) == \-1) { perror("sigaction"); exit(exit_failure); } raise(sigsegv); } .ee .sh see also .br kill (1), .br kill (2), .br pause (2), .br pidfd_send_signal (2), .br restart_syscall (2), .br seccomp (2), .br sigaltstack (2), .br signal (2), .br signalfd (2), .br sigpending (2), .br sigprocmask (2), .br sigreturn (2), .br sigsuspend (2), .br wait (2), .br killpg (3), .br raise (3), .br siginterrupt (3), .br sigqueue (3), .br sigsetops (3), .br sigvec (3), .br core (5), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2004 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" inspired by a page by walter harms created 2002-08-10 .\" .th ilogb 3 2021-03-22 "" "linux programmer's manual" .sh name ilogb, ilogbf, ilogbl \- get integer exponent of a floating-point value .sh synopsis .nf .b #include .pp .bi "int ilogb(double " x ); .bi "int ilogbf(float " x ); .bi "int ilogbl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br ilogb (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br ilogbf (), .br ilogbl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the exponent part of their argument as a signed integer. when no error occurs, these functions are equivalent to the corresponding .br logb (3) functions, cast to .ir int . .sh return value on success, these functions return the exponent of .ir x , as a signed integer. .pp if .i x is zero, then a domain error occurs, and the functions return .\" the posix.1 spec for logb() says logb() gives pole error for this .\" case, but for ilogb() it says domain error. .br fp_ilogb0 . .\" glibc: the numeric value is either `int_min' or `-int_max'. .pp if .i x is a nan, then a domain error occurs, and the functions return .br fp_ilogbnan . .\" glibc: the numeric value is either `int_min' or `int_max'. .\" on i386, fp_ilogb0 and fp_ilogbnan have the same value. .pp if .i x is negative infinity or positive infinity, then a domain error occurs, and the functions return .br int_max . .\" .\" posix.1-2001 also says: .\" if the correct value is greater than {int_max}, {int_max} .\" shall be returned and a domain error shall occur. .\" .\" if the correct value is less than {int_min}, {int_min} .\" shall be returned and a domain error shall occur. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is 0 or a nan an invalid floating-point exception .rb ( fe_invalid ) is raised, and .i errno is set to .br edom (but see bugs). .tp domain error: \fix\fp is an infinity an invalid floating-point exception .rb ( fe_invalid ) is raised, and .i errno is set to .br edom (but see bugs). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ilogb (), .br ilogbf (), .br ilogbl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh bugs .\" bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794 before version 2.16, the following bugs existed in the glibc implementation of these functions: .ip * 3 the domain error case where .i x is 0 or a nan did not cause .i errno to be set or (on some architectures) raise a floating-point exception. .ip * 3 the domain error case where .i x is an infinity did not cause .i errno to be set or raise a floating-point exception. .sh see also .br log (3), .br logb (3), .br significand (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/glob.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswdigit 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswdigit \- test for decimal digit wide character .sh synopsis .nf .b #include .pp .bi "int iswdigit(wint_t " wc ); .fi .sh description the .br iswdigit () function is the wide-character equivalent of the .br isdigit (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "digit". .pp the wide-character class "digit" is a subclass of the wide-character class "xdigit", and therefore also a subclass of the wide-character class "alnum", of the wide-character class "graph" and of the wide-character class "print". .pp being a subclass of the wide character class "print", the wide-character class "digit" is disjoint from the wide-character class "cntrl". .pp being a subclass of the wide-character class "graph", the wide-character class "digit" is disjoint from the wide-character class "space" and its subclass "blank". .pp being a subclass of the wide-character class "alnum", the wide-character class "digit" is disjoint from the wide-character class "punct". .pp the wide-character class "digit" is disjoint from the wide-character class "alpha" and therefore also disjoint from its subclasses "lower", "upper". .pp the wide-character class "digit" always contains exactly the digits \(aq0\(aq to \(aq9\(aq. .sh return value the .br iswdigit () function returns nonzero if .i wc is a wide character belonging to the wide-character class "digit". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswdigit () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswdigit () depends on the .b lc_ctype category of the current locale. .sh see also .br isdigit (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" the pathconf note is from walter harms .\" this is not a system call on linux .\" .\" modified 2004-06-23 by michael kerrisk .\" .th statvfs 3 2021-03-22 "linux" "linux programmer's manual" .sh name statvfs, fstatvfs \- get filesystem statistics .sh synopsis .nf .b #include .pp .bi "int statvfs(const char *restrict " path \ ", struct statvfs *restrict " buf ); .bi "int fstatvfs(int " fd ", struct statvfs *" buf ); .fi .sh description the function .br statvfs () returns information about a mounted filesystem. .i path is the pathname of any file within the mounted filesystem. .i buf is a pointer to a .i statvfs structure defined approximately as follows: .pp .in +4n .ex struct statvfs { unsigned long f_bsize; /* filesystem block size */ unsigned long f_frsize; /* fragment size */ fsblkcnt_t f_blocks; /* size of fs in f_frsize units */ fsblkcnt_t f_bfree; /* number of free blocks */ fsblkcnt_t f_bavail; /* number of free blocks for unprivileged users */ fsfilcnt_t f_files; /* number of inodes */ fsfilcnt_t f_ffree; /* number of free inodes */ fsfilcnt_t f_favail; /* number of free inodes for unprivileged users */ unsigned long f_fsid; /* filesystem id */ unsigned long f_flag; /* mount flags */ unsigned long f_namemax; /* maximum filename length */ }; .ee .in .pp here the types .i fsblkcnt_t and .i fsfilcnt_t are defined in .ir . both used to be .ir "unsigned long" . .pp the field .i f_flag is a bit mask indicating various options that were employed when mounting this filesystem. it contains zero or more of the following flags: .\" xxx keep this list in sync with statfs(2) .tp .b st_mandlock mandatory locking is permitted on the filesystem (see .br fcntl (2)). .tp .b st_noatime do not update access times; see .br mount (2). .tp .b st_nodev disallow access to device special files on this filesystem. .tp .b st_nodiratime do not update directory access times; see .br mount (2). .tp .b st_noexec execution of programs is disallowed on this filesystem. .tp .b st_nosuid the set-user-id and set-group-id bits are ignored by .br exec (3) for executable files on this filesystem .tp .b st_rdonly this filesystem is mounted read-only. .tp .b st_relatime update atime relative to mtime/ctime; see .br mount (2). .tp .b st_synchronous writes are synched to the filesystem immediately (see the description of .b o_sync in .br open (2)). .pp it is unspecified whether all members of the returned struct have meaningful values on all filesystems. .pp .br fstatvfs () returns the same information about an open file referenced by descriptor .ir fd . .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces .rb ( statvfs ()) search permission is denied for a component of the path prefix of .ir path . (see also .br path_resolution (7).) .tp .b ebadf .rb ( fstatvfs ()) .i fd is not a valid open file descriptor. .tp .b efault .i buf or .i path points to an invalid address. .tp .b eintr this call was interrupted by a signal; see .br signal (7). .tp .b eio an i/o error occurred while reading from the filesystem. .tp .b eloop .rb ( statvfs ()) too many symbolic links were encountered in translating .ir path . .tp .b enametoolong .rb ( statvfs ()) .i path is too long. .tp .b enoent .rb ( statvfs ()) the file referred to by .i path does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enosys the filesystem does not support this call. .tp .b enotdir .rb ( statvfs ()) a component of the path prefix of .i path is not a directory. .tp .b eoverflow some values were too large to be represented in the returned struct. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br statvfs (), .br fstatvfs () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp only the .b st_nosuid and .b st_rdonly flags of the .i f_flag field are specified in posix.1. to obtain definitions of the remaining flags, one must define .br _gnu_source . .sh notes the linux kernel has system calls .br statfs (2) and .br fstatfs (2) to support this library call. .pp in glibc versions before 2.13, .\" glibc commit 3cdaa6adb113a088fdfb87aa6d7747557eccc58d .br statvfs () populated the bits of the .ir f_flag field by scanning the mount options shown in .ir /proc/mounts . however, starting with linux 2.6.36, the underlying .br statfs (2) system call provides the necessary information via the .ir f_flags field, and since glibc version 2.13, the .br statvfs () function will use information from that field rather than scanning .ir /proc/mounts . .pp the glibc implementations of .pp .in +4n .ex pathconf(path, _pc_rec_xfer_align); pathconf(path, _pc_alloc_size_min); pathconf(path, _pc_rec_min_xfer_size); .ee .in .pp respectively use the .ir f_frsize , .ir f_frsize , and .i f_bsize fields returned by a call to .br statvfs () with the argument .ir path . .sh see also .br statfs (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .so man2/ftruncate.2 .so man3/scanf.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" the american national standards committee x3, on information .\" processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)strtod.3 5.3 (berkeley) 6/29/91 .\" .\" modified sun aug 21 17:16:22 1994 by rik faith (faith@cs.unc.edu) .\" modified sat may 04 19:34:31 met dst 1996 by michael haardt .\" (michael@cantor.informatik.rwth-aachen.de) .\" added strof, strtold, aeb, 2001-06-07 .\" .th strtod 3 2021-03-22 "linux" "linux programmer's manual" .sh name strtod, strtof, strtold \- convert ascii string to floating-point number .sh synopsis .nf .b #include .pp .bi "double strtod(const char *restrict " nptr ", char **restrict " endptr ); .bi "float strtof(const char *restrict " nptr ", char **restrict " endptr ); .bi "long double strtold(const char *restrict " nptr \ ", char **restrict " endptr ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strtof (), .br strtold (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description the .br strtod (), .br strtof (), and .br strtold () functions convert the initial portion of the string pointed to by .i nptr to .ir double , .ir float , and .i long double representation, respectively. .pp the expected form of the (initial portion of the) string is optional leading white space as recognized by .br isspace (3), an optional plus (\(aq+\(aq) or minus sign (\(aq\-\(aq) and then either (i) a decimal number, or (ii) a hexadecimal number, or (iii) an infinity, or (iv) a nan (not-a-number). .pp a .i "decimal number" consists of a nonempty sequence of decimal digits possibly containing a radix character (decimal point, locale-dependent, usually \(aq.\(aq), optionally followed by a decimal exponent. a decimal exponent consists of an \(aqe\(aq or \(aqe\(aq, followed by an optional plus or minus sign, followed by a nonempty sequence of decimal digits, and indicates multiplication by a power of 10. .pp a .i "hexadecimal number" consists of a "0x" or "0x" followed by a nonempty sequence of hexadecimal digits possibly containing a radix character, optionally followed by a binary exponent. a binary exponent consists of a \(aqp\(aq or \(aqp\(aq, followed by an optional plus or minus sign, followed by a nonempty sequence of decimal digits, and indicates multiplication by a power of 2. at least one of radix character and binary exponent must be present. .pp an .i infinity is either "inf" or "infinity", disregarding case. .pp a .i nan is "nan" (disregarding case) optionally followed by a string, .ir (n-char-sequence) , where .ir n-char-sequence specifies in an implementation-dependent way the type of nan (see notes). .sh return value these functions return the converted value, if any. .pp if .i endptr is not null, a pointer to the character after the last character used in the conversion is stored in the location referenced by .ir endptr . .pp if no conversion is performed, zero is returned and (unless .i endptr is null) the value of .i nptr is stored in the location referenced by .ir endptr . .pp if the correct value would cause overflow, plus or minus .br huge_val , .br huge_valf , or .b huge_vall is returned (according to the return type and sign of the value), and .b erange is stored in .ir errno . .pp if the correct value would cause underflow, a value with magnitude no larger than .br dbl_min , .br flt_min , or .b ldbl_min is returned and .b erange is stored in .ir errno . .sh errors .tp .b erange overflow or underflow occurred. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strtod (), .br strtof (), .br strtold () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .pp .br strtod () was also described in c89. .sh notes since 0 can legitimately be returned on both success and failure, the calling program should set .i errno to 0 before the call, and then determine if an error occurred by checking whether .i errno has a nonzero value after the call. .pp in the glibc implementation, the .ir n-char-sequence that optionally follows "nan" is interpreted as an integer number (with an optional '0' or '0x' prefix to select base 8 or 16) that is to be placed in the mantissa component of the returned value. .\" from glibc 2.8's stdlib/strtod_l.c: .\" we expect it to be a number which is put in the .\" mantissa of the number. .\" it looks as though at least freebsd (according to the manual) does .\" something similar. .\" c11 says: "an implementation may use the n-char sequence to determine .\" extra information to be represented in the nan's significant." .sh examples see the example on the .br strtol (3) manual page; the use of the functions described in this manual page is similar. .sh see also .br atof (3), .br atoi (3), .br atol (3), .br nan (3), .br nanf (3), .br nanl (3), .br strfromd (3), .br strtol (3), .br strtoul (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2010 michael kerrisk, .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_sigqueue 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_sigqueue \- queue a signal and data to a thread .sh synopsis .nf .b #include .b #include .pp .bi "int pthread_sigqueue(pthread_t " thread ", int " sig , .bi " const union sigval " value ); .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_sigqueue (): .nf _gnu_source .fi .sh description the .br pthread_sigqueue () function performs a similar task to .br sigqueue (3), but, rather than sending a signal to a process, it sends a signal to a thread in the same process as the calling thread. .pp the .i thread argument is the id of a thread in the same process as the caller. the .i sig argument specifies the signal to be sent. the .i value argument specifies data to accompany the signal; see .br sigqueue (3) for details. .sh return value on success, .br pthread_sigqueue () returns 0; on error, it returns an error number. .sh errors .tp .b eagain the limit of signals which may be queued has been reached. (see .br signal (7) for further information.) .tp .b einval .i sig was invalid. .tp .b enosys .br pthread_sigqueue () is not supported on this system. .tp .b esrch .i thread is not valid. .sh versions the .br pthread_sigqueue () function first appeared in glibc 2.11. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_sigqueue () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a gnu extension. .sh notes the glibc implementation of .br pthread_sigqueue () gives an error .rb ( einval ) on attempts to send either of the real-time signals used internally by the nptl threading implementation. see .br nptl (7) for details. .sh see also .br rt_tgsigqueueinfo (2), .br sigaction (2), .br pthread_sigmask (3), .br sigqueue (3), .br sigwait (3), .br pthreads (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/psignal.3 .so man3/xdr.3 .so man3/circleq.3 .\" this man page is copyright (c) 2006 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" 2008, mtk, various edits .\" .th getcpu 2 2021-03-22 "linux" "linux programmer's manual" .sh name getcpu \- determine cpu and numa node on which the calling thread is running .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int getcpu(unsigned int *" cpu ", unsigned int *" node ); .fi .sh description the .br getcpu () system call identifies the processor and node on which the calling thread or process is currently running and writes them into the integers pointed to by the .i cpu and .i node arguments. the processor is a unique small integer identifying a cpu. the node is a unique small identifier identifying a numa node. when either .i cpu or .i node is null nothing is written to the respective pointer. .pp the information placed in .i cpu is guaranteed to be current only at the time of the call: unless the cpu affinity has been fixed using .br sched_setaffinity (2), the kernel might change the cpu at any time. (normally this does not happen because the scheduler tries to minimize movements between cpus to keep caches hot, but it is possible.) the caller must allow for the possibility that the information returned in .i cpu and .i node is no longer current by the time the call returns. .sh return value on success, 0 is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault arguments point outside the calling process's address space. .sh versions .br getcpu () was added in kernel 2.6.19 for x86-64 and i386. library support was added in glibc 2.29 (earlier glibc versions did not provide a wrapper for this system call, necessitating the use of .br syscall (2).) .sh conforming to .br getcpu () is linux-specific. .sh notes linux makes a best effort to make this call as fast as possible. (on some architectures, this is done via an implementation in the .br vdso (7).) the intention of .br getcpu () is to allow programs to make optimizations with per-cpu data or for numa optimization. .\" .ss c library/kernel differences the kernel system call has a third argument: .pp .in +4n .nf .bi "int getcpu(unsigned int *" cpu ", unsigned int *" node , .bi " struct getcpu_cache *" tcache ); .fi .in .pp the .i tcache argument is unused since linux 2.6.24, and (when invoking the system call directly) should be specified as null, unless portability to linux 2.6.23 or earlier is required. .pp .\" commit 4307d1e5ada595c87f9a4d16db16ba5edb70dcb1 .\" author: ingo molnar .\" date: wed nov 7 18:37:48 2007 +0100 .\" x86: ignore the sys_getcpu() tcache parameter in linux 2.6.23 and earlier, if the .i tcache argument was non-null, then it specified a pointer to a caller-allocated buffer in thread-local storage that was used to provide a caching mechanism for .br getcpu (). use of the cache could speed .br getcpu () calls, at the cost that there was a very small chance that the returned information would be out of date. the caching mechanism was considered to cause problems when migrating threads between cpus, and so the argument is now ignored. .\" .\" ===== before kernel 2.6.24: ===== .\" .i tcache .\" is a pointer to a .\" .ir "struct getcpu_cache" .\" that is used as a cache by .\" .br getcpu (). .\" the caller should put the cache into a thread-local variable .\" if the process is multithreaded, .\" because the cache cannot be shared between different threads. .\" .i tcache .\" can be null. .\" if it is not null .\" .br getcpu () .\" will use it to speed up operation. .\" the information inside the cache is private to the system call .\" and should not be accessed by the user program. .\" the information placed in the cache can change between kernel releases. .\" .\" when no cache is specified .\" .br getcpu () .\" will be slower, .\" but always retrieve the current cpu and node information. .\" with a cache .\" .br getcpu () .\" is faster. .\" however, the cached information is updated only once per jiffy (see .\" .br time (7)). .\" this means that the information could theoretically be out of date, .\" although in practice the scheduler's attempt to maintain .\" soft cpu affinity means that the information is unlikely to change .\" over the course of the caching interval. .sh see also .br mbind (2), .br sched_setaffinity (2), .br set_mempolicy (2), .br sched_getcpu (3), .br cpuset (7), .br vdso (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/regex.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 28 11:12:07 1993 by rik faith (faith@cs.unc.edu) .\" modified fri sep 8 15:48:13 1995 by andries brouwer (aeb@cwi.nl) .\" modified 2013-12-31, david malcolm .\" split gets(3) into its own page; fgetc() et al. move to fgetc(3) .th gets 3 2021-03-22 "gnu" "linux programmer's manual" .sh name gets \- get a string from standard input (deprecated) .sh synopsis .nf .b #include .pp .bi "char *gets(char *" "s" ); .fi .sh description .ir "never use this function" . .pp .br gets () reads a line from .i stdin into the buffer pointed to by .i s until either a terminating newline or .br eof , which it replaces with a null byte (\(aq\e0\(aq). no check for buffer overrun is performed (see bugs below). .sh return value .br gets () returns .i s on success, and null on error or when end of file occurs while no characters have been read. however, given the lack of buffer overrun checking, there can be no guarantees that the function will even return. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br gets () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c89, c99, posix.1-2001. .pp lsb deprecates .br gets (). posix.1-2008 marks .br gets () obsolescent. iso c11 removes the specification of .br gets () from the c language, and since version 2.16, glibc header files don't expose the function declaration if the .b _isoc11_source feature test macro is defined. .sh bugs never use .br gets (). because it is impossible to tell without knowing the data in advance how many characters .br gets () will read, and because .br gets () will continue to store characters past the end of the buffer, it is extremely dangerous to use. it has been used to break computer security. use .br fgets () instead. .pp for more information, see cwe-242 (aka "use of inherently dangerous function") at http://cwe.mitre.org/data/definitions/242.html .sh see also .br read (2), .br write (2), .br ferror (3), .br fgetc (3), .br fgets (3), .br fgetwc (3), .br fgetws (3), .br fopen (3), .br fread (3), .br fseek (3), .br getline (3), .br getwchar (3), .br puts (3), .br scanf (3), .br ungetwc (3), .br unlocked_stdio (3), .br feature_test_macros (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pldd 1 2020-11-01 "gnu" "linux user manual" .sh name pldd \- display dynamic shared objects linked into a process .sh synopsis .nf .bi "pldd " "pid" .bi pldd " option" .fi .sh description the .b pldd command displays a list of the dynamic shared objects (dsos) that are linked into the process with the specified process id (pid). the list includes the libraries that have been dynamically loaded using .br dlopen (3). .sh options .tp .br \-? ", " \-\-help display a help message and exit. .tp .b \-\-usage display a short usage message and exit. .tp .br \-v ", " \-\-version display program version information and exit. .sh exit status on success, .b pldd exits with the status 0. if the specified process does not exist, the user does not have permission to access its dynamic shared object list, or no command-line arguments are supplied, .b pldd exists with a status of 1. if given an invalid option, it exits with the status 64. .sh versions .b pldd is available since glibc 2.15. .sh conforming to the .b pldd command is not specified by posix.1. some other systems .\" there are man pages on solaris and hp-ux. have a similar command. .sh notes the command .pp .in +4n .ex lsof \-p pid .ee .in .pp also shows output that includes the dynamic shared objects that are linked into a process. .pp the .br gdb (1) .i "info shared" command also shows the shared libraries being used by a process, so that one can obtain similar output to .b pldd using a command such as the following (to monitor the process with the specified .ir pid ): .pp .in +4n .ex $ \fbgdb \-ex "set confirm off" \-ex "set height 0" \-ex "info shared" \e\fp \fb\-ex "quit" \-p $pid | grep \(aq\(ha0x.*0x\(aq\fp .ee .in .sh bugs from glibc 2.19 to 2.29, .b pldd was broken: it just hung when executed. .\" glibc commit 1a4c27355e146b6d8cc6487b998462c7fdd1048f this problem was fixed in glibc 2.30, and the fix has been backported to earlier glibc versions in some distributions. .sh examples .ex $ \fbecho $$\fp # display pid of shell 1143 $ \fbpldd $$\fp # display dsos linked into the shell 1143: /usr/bin/bash linux\-vdso.so.1 /lib64/libtinfo.so.5 /lib64/libdl.so.2 /lib64/libc.so.6 /lib64/ld\-linux\-x86\-64.so.2 /lib64/libnss_files.so.2 .ee .sh see also .br ldd (1), .br lsof (1), .br dlopen (3), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 2008, george spelvin , .\" and copyright (c) 2008, matt mackall .\" and copyright (c) 2016, laurent georget .\" and copyright (c) 2016, nikos mavrogiannopoulos .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" the following web page is quite informative: .\" http://www.2uo.de/myths-about-urandom/ .\" .th random 7 2017-03-13 "linux" "linux programmer's manual" .sh name random \- overview of interfaces for obtaining randomness .sh description the kernel random-number generator relies on entropy gathered from device drivers and other sources of environmental noise to seed a cryptographically secure pseudorandom number generator (csprng). it is designed for security, rather than speed. .pp the following interfaces provide access to output from the kernel csprng: .ip * 3 the .i /dev/urandom and .i /dev/random devices, both described in .br random (4). these devices have been present on linux since early times, and are also available on many other systems. .ip * the linux-specific .br getrandom (2) system call, available since linux 3.17. this system call provides access either to the same source as .i /dev/urandom (called the .i urandom source in this page) or to the same source as .i /dev/random (called the .i random source in this page). the default is the .i urandom source; the .i random source is selected by specifying the .br grnd_random flag to the system call. (the .br getentropy (3) function provides a slightly more portable interface on top of .br getrandom (2).) .\" .ss initialization of the entropy pool the kernel collects bits of entropy from the environment. when a sufficient number of random bits has been collected, the entropy pool is considered to be initialized. .ss choice of random source unless you are doing long-term key generation (and most likely not even then), you probably shouldn't be reading from the .ir /dev/random device or employing .br getrandom (2) with the .br grnd_random flag. instead, either read from the .ir /dev/urandom device or employ .br getrandom (2) without the .b grnd_random flag. the cryptographic algorithms used for the .ir urandom source are quite conservative, and so should be sufficient for all purposes. .pp the disadvantage of .b grnd_random and reads from .i /dev/random is that the operation can block for an indefinite period of time. furthermore, dealing with the partially fulfilled requests that can occur when using .b grnd_random or when reading from .i /dev/random increases code complexity. .\" .ss monte carlo and other probabilistic sampling applications using these interfaces to provide large quantities of data for monte carlo simulations or other programs/algorithms which are doing probabilistic sampling will be slow. furthermore, it is unnecessary, because such applications do not need cryptographically secure random numbers. instead, use the interfaces described in this page to obtain a small amount of data to seed a user-space pseudorandom number generator for use by such applications. .\" .ss comparison between getrandom, /dev/urandom, and /dev/random the following table summarizes the behavior of the various interfaces that can be used to obtain randomness. .b grnd_nonblock is a flag that can be used to control the blocking behavior of .br getrandom (2). the final column of the table considers the case that can occur in early boot time when the entropy pool is not yet initialized. .ad l .ts allbox; lbw13 lbw12 lbw14 lbw18 l l l l. interface pool t{ blocking \%behavior t} t{ behavior when pool is not yet ready t} t{ .i /dev/random t} t{ blocking pool t} t{ if entropy too low, blocks until there is enough entropy again t} t{ blocks until enough entropy gathered t} t{ .i /dev/urandom t} t{ csprng output t} t{ never blocks t} t{ returns output from uninitialized csprng (may be low entropy and unsuitable for cryptography) t} t{ .br getrandom () t} t{ same as .i /dev/urandom t} t{ does not block once is pool ready t} t{ blocks until pool ready t} t{ .br getrandom () .b grnd_random t} t{ same as .i /dev/random t} t{ if entropy too low, blocks until there is enough entropy again t} t{ blocks until pool ready t} t{ .br getrandom () .b grnd_nonblock t} t{ same as .i /dev/urandom t} t{ does not block once is pool ready t} t{ .b eagain t} t{ .br getrandom () .b grnd_random + .b grnd_nonblock t} t{ same as .i /dev/random t} t{ .b eagain if not enough entropy available t} t{ .b eagain t} .te .ad .\" .ss generating cryptographic keys the amount of seed material required to generate a cryptographic key equals the effective key size of the key. for example, a 3072-bit rsa or diffie-hellman private key has an effective key size of 128 bits (it requires about 2^128 operations to break) so a key generator needs only 128 bits (16 bytes) of seed material from .ir /dev/random . .pp while some safety margin above that minimum is reasonable, as a guard against flaws in the csprng algorithm, no cryptographic primitive available today can hope to promise more than 256 bits of security, so if any program reads more than 256 bits (32 bytes) from the kernel random pool per invocation, or per reasonable reseed interval (not less than one minute), that should be taken as a sign that its cryptography is .i not skillfully implemented. .\" .sh see also .br getrandom (2), .br getauxval (3), .br getentropy (3), .br random (4), .br urandom (4), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ldexp.3 .so man3/fabs.3 .so man3/xdr.3 .so man3/fpclassify.3 .\" copyright (c) international business machines corp., 2006 .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see .\" the gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" history: .\" 2005-09-28, created by arnd bergmann .\" 2006-06-16, revised by eduardo m. fleury .\" 2007-07-10, some polishing by mtk .\" 2007-09-28, updates for newer kernels, added example .\" by jeremy kerr .\" .th spu_run 2 2021-03-22 linux "linux programmer's manual" .sh name spu_run \- execute an spu context .sh synopsis .nf .br "#include " " /* definition of " spu_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int spu_run(int " fd ", uint32_t *" npc ", uint32_t *" event ); .fi .pp .ir note : glibc provides no wrapper for .br spu_run (), necessitating the use of .br syscall (2). .sh description the .br spu_run () system call is used on powerpc machines that implement the cell broadband engine architecture in order to access synergistic processor units (spus). the .i fd argument is a file descriptor returned by .br spu_create (2) that refers to a specific spu context. when the context gets scheduled to a physical spu, it starts execution at the instruction pointer passed in .ir npc . .pp execution of spu code happens synchronously, meaning that .br spu_run () blocks while the spu is still running. if there is a need to execute spu code in parallel with other code on either the main cpu or other spus, a new thread of execution must be created first (e.g., using .br pthread_create (3)). .pp when .br spu_run () returns, the current value of the spu program counter is written to .ir npc , so successive calls to .br spu_run () can use the same .i npc pointer. .pp the .i event argument provides a buffer for an extended status code. if the spu context was created with the .b spu_create_events_enabled flag, then this buffer is populated by the linux kernel before .br spu_run () returns. .pp the status code may be one (or more) of the following constants: .tp .b spe_event_dma_alignment a dma alignment error occurred. .tp .b spe_event_invalid_dma an invalid mfc dma command was attempted. .\" spe_event_spe_data_segment is defined, but does not seem to be generated .\" at any point (in linux 5.9 sources). .tp .b spe_event_spe_data_storage a dma storage error occurred. .tp .b spe_event_spe_error an illegal instruction was executed. .pp null is a valid value for the .i event argument. in this case, the events will not be reported to the calling process. .sh return value on success, .br spu_run () returns the value of the .i spu_status register. on failure, it returns \-1 and sets .i errno is set to indicate the error. .pp the .i spu_status register value is a bit mask of status codes and optionally a 14-bit code returned from the .br stop-and-signal instruction on the spu. the bit masks for the status codes are: .tp .b 0x02 spu was stopped by a .br stop-and-signal instruction. .tp .b 0x04 spu was stopped by a .br halt instruction. .tp .b 0x08 spu is waiting for a channel. .tp .b 0x10 spu is in single-step mode. .tp .b 0x20 spu has tried to execute an invalid instruction. .tp .b 0x40 spu has tried to access an invalid channel. .tp .b 0x3fff0000 the bits masked with this value contain the code returned from a .br stop-and-signal instruction. these bits are valid only if the 0x02 bit is set. .pp if .br spu_run () has not returned an error, one or more bits among the lower eight ones are always set. .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b efault .i npc is not a valid pointer, or .i event is non-null and an invalid pointer. .tp .b eintr a signal occurred while .br spu_run () was in progress; see .br signal (7). the .i npc value has been updated to the new program counter value if necessary. .tp .b einval .i fd is not a valid file descriptor returned from .br spu_create (2). .tp .b enomem there was not enough memory available to handle a page fault resulting from a memory flow controller (mfc) direct memory access. .tp .b enosys the functionality is not provided by the current system, because either the hardware does not provide spus or the spufs module is not loaded. .sh versions the .br spu_run () system call was added to linux in kernel 2.6.16. .sh conforming to this call is linux-specific and implemented only by the powerpc architecture. programs using this system call are not portable. .sh notes .br spu_run () is meant to be used from libraries that implement a more abstract interface to spus, not to be used from regular applications. see .ur http://www.bsc.es\:/projects\:/deepcomputing\:/linuxoncell/ .ue for the recommended libraries. .sh examples the following is an example of running a simple, one-instruction spu program with the .br spu_run () system call. .pp .ex #include #include #include #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) int main(void) { int context, fd, spu_status; uint32_t instruction, npc; context = spu_create("/spu/example\-context", 0, 0755); if (context == \-1) handle_error("spu_create"); /* * write a \(aqstop 0x1234\(aq instruction to the spu\(aqs * local store memory. */ instruction = 0x00001234; fd = open("/spu/example\-context/mem", o_rdwr); if (fd == \-1) handle_error("open"); write(fd, &instruction, sizeof(instruction)); /* * set npc to the starting instruction address of the * spu program. since we wrote the instruction at the * start of the mem file, the entry point will be 0x0. */ npc = 0; spu_status = spu_run(context, &npc, null); if (spu_status == \-1) handle_error("open"); /* * we should see a status code of 0x1234002: * 0x00000002 (spu was stopped due to stop\-and\-signal) * | 0x12340000 (the stop\-and\-signal code) */ printf("spu status: %#08x\en", spu_status); exit(exit_success); } .ee .\" .sh authors .\" arnd bergmann , jeremy kerr .sh see also .br close (2), .br spu_create (2), .br capabilities (7), .br spufs (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th exp2 3 2021-03-22 "" "linux programmer's manual" .sh name exp2, exp2f, exp2l \- base-2 exponential function .sh synopsis .nf .b #include .pp .bi "double exp2(double " x ); .bi "float exp2f(float " x ); .bi "long double exp2l(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br exp2 (), .br exp2f (), .br exp2l (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions return the value of 2 raised to the power of .ir x . .sh return value on success, these functions return the base-2 exponential value of .ir x . .pp for various special cases, including the handling of infinity and nan, as well as overflows and underflows, see .br exp (3). .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp for a discussion of the errors that can occur for these functions, see .br exp (3). .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br exp2 (), .br exp2f (), .br exp2l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh see also .br cbrt (3), .br cexp2 (3), .br exp (3), .br exp10 (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-11.7 .so man2/s390_pci_mmio_write.2 .so man3/exp.3 .so man3/rint.3 .so man2/outb.2 .so man3/termios.3 .so man3/xdr.3 .so man3/getipnodebyname.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th carg 3 2021-03-22 "" "linux programmer's manual" .sh name carg, cargf, cargl \- calculate the complex argument .sh synopsis .nf .b #include .pp .bi "double carg(double complex " z ");" .bi "float cargf(float complex " z ");" .bi "long double cargl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex argument (also called phase angle) of .ir z , with a branch cut along the negative real axis. .pp a complex number can be described by two real coordinates. one may use rectangular coordinates and gets .pp .nf z = x + i * y .fi .pp where .ir "x\ =\ creal(z)" and .ir "y\ =\ cimag(z)" . .pp or one may use polar coordinates and gets .pp .nf z = r * cexp(i * a) .fi .pp where .ir "r\ =\ cabs(z)" is the "radius", the "modulus", the absolute value of .ir z , and .ir "a\ =\ carg(z)" is the "phase angle", the argument of .ir z . .pp one has: .pp .nf tan(carg(z)) = cimag(z) / creal(z) .fi .sh return value the return value is in the range of [\-pi,pi]. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br carg (), .br cargf (), .br cargl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified mon mar 29 22:39:41 1993, david metcalfe .\" modified sat jul 24 21:38:42 1993, rik faith (faith@cs.unc.edu) .\" modified sun dec 17 18:35:06 2000, joseph s. myers .\" .th atoi 3 2021-03-22 "gnu" "linux programmer's manual" .sh name atoi, atol, atoll \- convert a string to an integer .sh synopsis .nf .b #include .pp .bi "int atoi(const char *" nptr ); .bi "long atol(const char *" nptr ); .bi "long long atoll(const char *" nptr ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br atoll (): .nf _isoc99_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br atoi () function converts the initial portion of the string pointed to by \finptr\fp to .ir int . the behavior is the same as .pp .in +4n .ex strtol(nptr, null, 10); .ee .in .pp except that .br atoi () does not detect errors. .pp the .br atol () and .br atoll () functions behave the same as .br atoi (), except that they convert the initial portion of the string to their return type of \filong\fp or \filong long\fp. .sh return value the converted value or 0 on error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br atoi (), .br atol (), .br atoll () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99, svr4, 4.3bsd. c89 and posix.1-1996 include the functions .br atoi () and .br atol () only. .\" .sh notes .\" linux libc provided .\" .br atoq () .\" as an obsolete name for .\" .br atoll (); .\" .br atoq () .\" is not provided by glibc. .\" the .\" .br atoll () .\" function is present in glibc 2 since version 2.0.2, but .\" not in libc4 or libc5. .sh notes posix.1 leaves the return value of .br atoi () on error unspecified. on glibc, musl libc, and uclibc, 0 is returned on error. .sh bugs .i errno is not set on error so there is no way to distinguish between 0 as an error and as the converted value. no checks for overflow or underflow are done. only base-10 input can be converted. it is recommended to instead use the .br strtol () and .br strtoul () family of functions in new programs. .sh see also .br atof (3), .br strtod (3), .br strtol (3), .br strtoul (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_write 3 2021-03-22 "" "linux programmer's manual" .sh name aio_write \- asynchronous write .sh synopsis .nf .b "#include " .pp .bi "int aio_write(struct aiocb *" aiocbp ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_write () function queues the i/o request described by the buffer pointed to by .ir aiocbp . this function is the asynchronous analog of .br write (2). the arguments of the call .pp write(fd, buf, count) .pp correspond (in order) to the fields .ir aio_fildes , .ir aio_buf , and .ir aio_nbytes of the structure pointed to by .ir aiocbp . (see .br aio (7) for a description of the .i aiocb structure.) .pp if .b o_append is not set, the data is written starting at the absolute position .ir aiocbp\->aio_offset , regardless of the file offset. if .b o_append is set, data is written at the end of the file in the same order as .br aio_write () calls are made. after the call, the value of the file offset is unspecified. .pp the "asynchronous" means that this call returns as soon as the request has been enqueued; the write may or may not have completed when the call returns. one tests for completion using .br aio_error (3). the return status of a completed i/o operation can be obtained .br aio_return (3). asynchronous notification of i/o completion can be obtained by setting .ir aiocbp\->aio_sigevent appropriately; see .br sigevent (7) for details. .pp if .b _posix_prioritized_io is defined, and this file supports it, then the asynchronous operation is submitted at a priority equal to that of the calling process minus .ir aiocbp\->aio_reqprio . .pp the field .i aiocbp\->aio_lio_opcode is ignored. .pp no data is written to a regular file beyond its maximum offset. .sh return value on success, 0 is returned. on error, the request is not enqueued, \-1 is returned, and .i errno is set to indicate the error. if an error is detected only later, it will be reported via .br aio_return (3) (returns status \-1) and .br aio_error (3) (error status\(emwhatever one would have gotten in .ir errno , such as .br ebadf ). .sh errors .tp .b eagain out of resources. .tp .b ebadf .i aio_fildes is not a valid file descriptor open for writing. .tp .b efbig the file is a regular file, we want to write at least one byte, but the starting position is at or beyond the maximum offset for this file. .tp .b einval one or more of .ir aio_offset , .ir aio_reqprio , .i aio_nbytes are invalid. .tp .b enosys .br aio_write () is not implemented. .sh versions the .br aio_write () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_write () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes it is a good idea to zero out the control block before use. the control block must not be changed while the write operation is in progress. the buffer area being written out .\" or the control block of the operation must not be accessed during the operation or undefined results may occur. the memory areas involved must remain valid. .pp simultaneous i/o operations specifying the same .i aiocb structure produce undefined results. .sh see also .br aio_cancel (3), .br aio_error (3), .br aio_fsync (3), .br aio_read (3), .br aio_return (3), .br aio_suspend (3), .br lio_listio (3), .br aio (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/hsearch.3 .so man2/epoll_create.2 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on glibc infopages, copyright free software foundation .\" .th signbit 3 2021-03-22 "gnu" "linux programmer's manual" .sh name signbit \- test sign of a real floating-point number .sh synopsis .nf .b "#include " .pp .bi "int signbit(" x ");" .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br signbit (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description .br signbit () is a generic macro which can work on all real floating-point types. it returns a nonzero value if the value of .i x has its sign bit set. .pp this is not the same as .ir "x < 0.0" , because ieee 754 floating point allows zero to be signed. the comparison .ir "\-0.0 < 0.0" is false, but .ir "signbit(\-0.0)" will return a nonzero value. .pp nans and infinities have a sign bit. .sh return value the .br signbit () macro returns nonzero if the sign of .i x is negative; otherwise it returns zero. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br signbit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. this function is defined in iec 559 (and the appendix with recommended functions in ieee 754/ieee 854). .sh see also .br copysign (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1996 tom bjorkholm .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-04-11 tom bjorkholm .\" first version written (1.3.86) .\" 1996-04-12 tom bjorkholm .\" update for linux 1.3.87 and later .\" 2005-10-11 mtk: added notes for mremap_fixed; revised einval text. .\" .th mremap 2 2021-03-22 "linux" "linux programmer's manual" .sh name mremap \- remap a virtual memory address .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void *mremap(void *" old_address ", size_t " old_size , .bi " size_t " new_size ", int " flags ", ... /* void *" new_address " */);" .fi .sh description .br mremap () expands (or shrinks) an existing memory mapping, potentially moving it at the same time (controlled by the \fiflags\fp argument and the available virtual address space). .pp \fiold_address\fp is the old address of the virtual memory block that you want to expand (or shrink). note that \fiold_address\fp has to be page aligned. \fiold_size\fp is the old size of the virtual memory block. \finew_size\fp is the requested size of the virtual memory block after the resize. an optional fifth argument, .ir new_address , may be provided; see the description of .b mremap_fixed below. .pp if the value of \fiold_size\fp is zero, and \fiold_address\fp refers to a shareable mapping (see .br mmap (2) .br map_shared ), then .br mremap () will create a new mapping of the same pages. \finew_size\fp will be the size of the new mapping and the location of the new mapping may be specified with \finew_address\fp; see the description of .b mremap_fixed below. if a new mapping is requested via this method, then the .b mremap_maymove flag must also be specified. .pp the \fiflags\fp bit-mask argument may be 0, or include the following flags: .tp .b mremap_maymove by default, if there is not sufficient space to expand a mapping at its current location, then .br mremap () fails. if this flag is specified, then the kernel is permitted to relocate the mapping to a new virtual address, if necessary. if the mapping is relocated, then absolute pointers into the old mapping location become invalid (offsets relative to the starting address of the mapping should be employed). .tp .br mremap_fixed " (since linux 2.3.31)" this flag serves a similar purpose to the .b map_fixed flag of .br mmap (2). if this flag is specified, then .br mremap () accepts a fifth argument, .ir "void\ *new_address" , which specifies a page-aligned address to which the mapping must be moved. any previous mapping at the address range specified by .i new_address and .i new_size is unmapped. .ip if .b mremap_fixed is specified, then .b mremap_maymove must also be specified. .tp .br mremap_dontunmap " (since linux 5.7)" .\" commit e346b3813067d4b17383f975f197a9aa28a3b077 this flag, which must be used in conjunction with .br mremap_maymove , remaps a mapping to a new address but does not unmap the mapping at .ir old_address . .ip the .b mremap_dontunmap flag can be used only with private anonymous mappings (see the description of .br map_private and .br map_anonymous in .br mmap (2)). .ip after completion, any access to the range specified by .ir old_address and .i old_size will result in a page fault. the page fault will be handled by a .br userfaultfd (2) handler if the address is in a range previously registered with .br userfaultfd (2). otherwise, the kernel allocates a zero-filled page to handle the fault. .ip the .br mremap_dontunmap flag may be used to atomically move a mapping while leaving the source mapped. see notes for some possible applications of .br mremap_dontunmap . .pp if the memory segment specified by .i old_address and .i old_size is locked (using .br mlock (2) or similar), then this lock is maintained when the segment is resized and/or relocated. as a consequence, the amount of memory locked by the process may change. .sh return value on success .br mremap () returns a pointer to the new virtual memory area. on error, the value .b map_failed (that is, \fi(void\ *)\ \-1\fp) is returned, and \fierrno\fp is set to indicate the error. .sh errors .tp .b eagain the caller tried to expand a memory segment that is locked, but this was not possible without exceeding the .b rlimit_memlock resource limit. .tp .b efault some address in the range \fiold_address\fp to \fiold_address\fp+\fiold_size\fp is an invalid virtual memory address for this process. you can also get .b efault even if there exist mappings that cover the whole address space requested, but those mappings are of different types. .tp .b einval an invalid argument was given. possible causes are: .rs .ip * 3 \fiold_address\fp was not page aligned; .ip * a value other than .b mremap_maymove or .b mremap_fixed or .b mremap_dontunmap was specified in .ir flags ; .ip * .i new_size was zero; .ip * .i new_size or .i new_address was invalid; .ip * the new address range specified by .i new_address and .i new_size overlapped the old address range specified by .i old_address and .ir old_size ; .ip * .b mremap_fixed or .b mremap_dontunmap was specified without also specifying .br mremap_maymove ; .ip * .b mremap_dontunmap was specified, but one or more pages in the range specified by .ir old_address and .ir old_size were not private anonymous; .ip * .b mremap_dontunmap was specified and .ir old_size was not equal to .ir new_size ; .ip * \fiold_size\fp was zero and \fiold_address\fp does not refer to a shareable mapping (but see bugs); .ip * \fiold_size\fp was zero and the .br mremap_maymove flag was not specified. .re .tp .b enomem not enough memory was available to complete the operation. possible causes are: .rs .ip * 3 the memory area cannot be expanded at the current virtual address, and the .b mremap_maymove flag is not set in \fiflags\fp. or, there is not enough (virtual) memory available. .ip * .b mremap_dontunmap was used causing a new mapping to be created that would exceed the (virtual) memory available. or, it would exceed the maximum number of allowed mappings. .re .sh conforming to this call is linux-specific, and should not be used in programs intended to be portable. .\" 4.2bsd had a (never actually implemented) .\" .br mremap (2) .\" call with completely different semantics. .sh notes .br mremap () changes the mapping between virtual addresses and memory pages. this can be used to implement a very efficient .br realloc (3). .pp in linux, memory is divided into pages. a process has (one or) several linear virtual memory segments. each virtual memory segment has one or more mappings to real memory pages (in the page table). each virtual memory segment has its own protection (access rights), which may cause a segmentation violation .rb ( sigsegv ) if the memory is accessed incorrectly (e.g., writing to a read-only segment). accessing virtual memory outside of the segments will also cause a segmentation violation. .pp if .br mremap () is used to move or expand an area locked with .br mlock (2) or equivalent, the .br mremap () call will make a best effort to populate the new area but will not fail with .b enomem if the area cannot be populated. .pp prior to version 2.4, glibc did not expose the definition of .br mremap_fixed , and the prototype for .br mremap () did not allow for the .i new_address argument. .\" .ss mremap_dontunmap use cases possible applications for .br mremap_dontunmap include: .ip * 3 non-cooperative .br userfaultfd (2): an application can yank out a virtual address range using .br mremap_dontunmap and then employ a .br userfaultfd (2) handler to handle the page faults that subsequently occur as other threads in the process touch pages in the yanked range. .ip * garbage collection: .br mremap_dontunmap can be used in conjunction with .br userfaultfd (2) to implement garbage collection algorithms (e.g., in a java virtual machine). such an implementation can be cheaper (and simpler) than conventional garbage collection techniques that involve marking pages with protection .br prot_none in conjunction with the of a .br sigsegv handler to catch accesses to those pages. .sh bugs before linux 4.14, if .i old_size was zero and the mapping referred to by .i old_address was a private mapping .rb ( mmap "(2) " map_private ), .br mremap () created a new private mapping unrelated to the original mapping. this behavior was unintended and probably unexpected in user-space applications (since the intention of .br mremap () is to create a new mapping based on the original mapping). since linux 4.14, .\" commit dba58d3b8c5045ad89c1c95d33d01451e3964db7 .br mremap () fails with the error .b einval in this scenario. .sh see also .br brk (2), .br getpagesize (2), .br getrlimit (2), .br mlock (2), .br mmap (2), .br sbrk (2), .br malloc (3), .br realloc (3) .pp your favorite text book on operating systems for more information on paged memory (e.g., \fimodern operating systems\fp by andrew s.\& tanenbaum, \fiinside linux\fp by randolph bentson, \fithe design of the unix operating system\fp by maurice j.\& bach) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .so man3/argz_add.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setaffinity_np 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setaffinity_np, pthread_attr_getaffinity_np \- set/get cpu affinity attribute in thread attributes object .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_attr_setaffinity_np(pthread_attr_t *" attr , .bi " size_t " cpusetsize ", const cpu_set_t *" cpuset ); .bi "int pthread_attr_getaffinity_np(const pthread_attr_t *" attr , .bi " size_t " cpusetsize ", cpu_set_t *" cpuset ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setaffinity_np () function sets the cpu affinity mask attribute of the thread attributes object referred to by .i attr to the value specified in .ir cpuset . this attribute determines the cpu affinity mask of a thread created using the thread attributes object .ir attr . .pp the .br pthread_attr_getaffinity_np () function returns the cpu affinity mask attribute of the thread attributes object referred to by .ir attr in the buffer pointed to by .ir cpuset . .pp the argument .i cpusetsize is the length (in bytes) of the buffer pointed to by .ir cpuset . typically, this argument would be specified as .ir sizeof(cpu_set_t) . .pp for more details on cpu affinity masks, see .br sched_setaffinity (2). for a description of a set of macros that can be used to manipulate and inspect cpu sets, see .br cpu_set (3). .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .tp .br einval .rb ( pthread_attr_setaffinity_np ()) .i cpuset specified a cpu that was outside the set supported by the kernel. (the kernel configuration option .br config_nr_cpus defines the range of the set supported by the kernel data type .\" cpumask_t used to represent cpu sets.) .\" the raw sched_getaffinity() system call returns the size (in bytes) .\" of the cpumask_t type. .tp .b einval .rb ( pthread_attr_getaffinity_np ()) a cpu in the affinity mask of the thread attributes object referred to by .i attr lies outside the range specified by .ir cpusetsize (i.e., .ir cpuset / cpusetsize is too small). .tp .b enomem .rb ( pthread_attr_setaffinity_np ()) could not allocate memory. .sh versions these functions are provided by glibc since version 2.3.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setaffinity_np (), .br pthread_attr_getaffinity_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh notes in glibc 2.3.3 only, versions of these functions were provided that did not have a .i cpusetsize argument. instead the cpu set size given to the underlying system calls was always .ir sizeof(cpu_set_t) . .sh see also .br sched_setaffinity (2), .br pthread_attr_init (3), .br pthread_setaffinity_np (3), .br cpuset (7), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .so man3/__ppc_get_timebase.3 .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-6 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-6 \- iso 8859-6 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-6 encodes the characters used in the arabic language. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-6 characters the following table displays the characters in iso 8859-6 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 244 164 a4 ¤ currency sign 254 172 ac ، arabic comma 255 173 ad ­ soft hyphen 273 187 bb ؛ arabic semicolon 277 191 bf ؟ arabic question mark 301 193 c1 ء arabic letter hamza 302 194 c2 آ arabic letter alef with madda above 303 195 c3 أ arabic letter alef with hamza above 304 196 c4 ؤ arabic letter waw with hamza above 305 197 c5 إ arabic letter alef with hamza below 306 198 c6 ئ arabic letter yeh with hamza above 307 199 c7 ا arabic letter alef 310 200 c8 ب arabic letter beh 311 201 c9 ة arabic letter teh marbuta 312 202 ca ت arabic letter teh 313 203 cb ث arabic letter theh 314 204 cc ج arabic letter jeem 315 205 cd ح arabic letter hah 316 206 ce خ arabic letter khah 317 207 cf د arabic letter dal 320 208 d0 ذ arabic letter thal 321 209 d1 ر arabic letter reh 322 210 d2 ز arabic letter zain 323 211 d3 س arabic letter seen 324 212 d4 ش arabic letter sheen 325 213 d5 ص arabic letter sad 326 214 d6 ض arabic letter dad 327 215 d7 ط arabic letter tah 330 216 d8 ظ arabic letter zah 331 217 d9 ع arabic letter ain 332 218 da غ arabic letter ghain 340 224 e0 ـ arabic tatweel 341 225 e1 ف arabic letter feh 342 226 e2 ق arabic letter qaf 343 227 e3 ك arabic letter kaf 344 228 e4 ل arabic letter lam 345 229 e5 م arabic letter meem 346 230 e6 ن arabic letter noon 347 231 e7 ه arabic letter heh 350 232 e8 و arabic letter waw 351 233 e9 ى arabic letter alef maksura 352 234 ea ي arabic letter yeh 353 235 eb ً arabic fathatan 354 236 ec ٌ arabic dammatan 355 237 ed ٍ arabic kasratan 356 238 ee َ arabic fatha 357 239 ef ُ arabic damma 360 240 f0 ِ arabic kasra 361 241 f1 ّ arabic shadda 362 242 f2 ْ arabic sukun .te .sh notes iso 8859-6 lacks the glyphs required for many related languages, such as urdu and persian (farsi). .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .\" copyright (c) 2013 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sln 8 2021-03-22 "gnu" "linux programmer's manual" .sh name sln \- create symbolic links .sh synopsis .nf .bi sln " source dest" .bi sln " filelist" .fi .sh description the .b sln program creates symbolic links. unlike the .br ln (1) program, it is statically linked. this means that if for some reason the dynamic linker is not working, .br sln can be used to make symbolic links to dynamic libraries. .pp the command line has two forms. in the first form, it creates .i dest as a new symbolic link to .ir source . .pp in the second form, .i filelist is a list of space-separated pathname pairs, and the effect is as if .br sln was executed once for each line of the file, with the two pathnames as the arguments. .pp the .b sln program supports no command-line options. .sh see also .br ln (1), .br ld.so (8), .br ldconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/get_phys_pages.3 .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_sigmask 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_sigmask \- examine and change mask of blocked signals .sh synopsis .nf .b #include .pp .bi "int pthread_sigmask(int " how ", const sigset_t *" set \ ", sigset_t *" oldset ); .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_sigmask (): .nf _posix_c_source >= 199506l || _xopen_source >= 500 .fi .sh description the .br pthread_sigmask () function is just like .br sigprocmask (2), with the difference that its use in multithreaded programs is explicitly specified by posix.1. other differences are noted in this page. .pp for a description of the arguments and operation of this function, see .br sigprocmask (2). .sh return value on success, .br pthread_sigmask () returns 0; on error, it returns an error number. .sh errors see .br sigprocmask (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_sigmask () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes a new thread inherits a copy of its creator's signal mask. .pp the glibc .br pthread_sigmask () function silently ignores attempts to block the two real-time signals that are used internally by the nptl threading implementation. see .br nptl (7) for details. .sh examples the program below blocks some signals in the main thread, and then creates a dedicated thread to fetch those signals via .br sigwait (3). the following shell session demonstrates its use: .pp .in +4n .ex .rb "$" " ./a.out &" [1] 5423 .rb "$" " kill \-quit %1" signal handling thread got signal 3 .rb "$" " kill \-usr1 %1" signal handling thread got signal 10 .rb "$" " kill \-term %1" [1]+ terminated ./a.out .ee .in .ss program source \& .ex #include #include #include #include #include #include /* simple error handling functions */ #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static void * sig_thread(void *arg) { sigset_t *set = arg; int s, sig; for (;;) { s = sigwait(set, &sig); if (s != 0) handle_error_en(s, "sigwait"); printf("signal handling thread got signal %d\en", sig); } } int main(int argc, char *argv[]) { pthread_t thread; sigset_t set; int s; /* block sigquit and sigusr1; other threads created by main() will inherit a copy of the signal mask. */ sigemptyset(&set); sigaddset(&set, sigquit); sigaddset(&set, sigusr1); s = pthread_sigmask(sig_block, &set, null); if (s != 0) handle_error_en(s, "pthread_sigmask"); s = pthread_create(&thread, null, &sig_thread, &set); if (s != 0) handle_error_en(s, "pthread_create"); /* main thread carries on to create other threads and/or do other work. */ pause(); /* dummy pause so we can test program */ } .ee .sh see also .br sigaction (2), .br sigpending (2), .br sigprocmask (2), .br pthread_attr_setsigmask_np (3), .br pthread_create (3), .br pthread_kill (3), .br sigsetops (3), .br pthreads (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sem_wait.3 .so man3/atoi.3 .so man3/towupper.3 .so man5/utmp.5 .\" copyright (c) 2007 michael kerrisk .\" drawing on material by justin pryzby .\" .\" %%%license_start(permissive_misc) .\" permission is hereby granted, free of charge, to any person obtaining .\" a copy of this software and associated documentation files (the .\" "software"), to deal in the software without restriction, including .\" without limitation the rights to use, copy, modify, merge, publish, .\" distribute, sublicense, and/or sell copies of the software, and to .\" permit persons to whom the software is furnished to do so, subject to .\" the following conditions: .\" .\" the above copyright notice and this permission notice shall be .\" included in all copies or substantial portions of the software. .\" .\" the software is provided "as is", without warranty of any kind, .\" express or implied, including but not limited to the warranties of .\" merchantability, fitness for a particular purpose and noninfringement. .\" in no event shall the authors or copyright holders be liable for any .\" claim, damages or other liability, whether in an action of contract, .\" tort or otherwise, arising from, out of or in connection with the .\" software or the use or other dealings in the software. .\" %%%license_end .\" .\" references: .\" glibc manual and source .th backtrace 3 2021-03-22 gnu "linux programmer's manual" .sh name backtrace, backtrace_symbols, backtrace_symbols_fd \- support for application self-debugging .sh synopsis .nf .b #include .pp .bi "int backtrace(void **" buffer ", int " size ); .pp .bi "char **backtrace_symbols(void *const *" buffer ", int " size ); .bi "void backtrace_symbols_fd(void *const *" buffer ", int " size ", int " fd ); .fi .sh description .br backtrace () returns a backtrace for the calling program, in the array pointed to by .ir buffer . a backtrace is the series of currently active function calls for the program. each item in the array pointed to by .i buffer is of type .ir "void\ *" , and is the return address from the corresponding stack frame. the .i size argument specifies the maximum number of addresses that can be stored in .ir buffer . if the backtrace is larger than .ir size , then the addresses corresponding to the .i size most recent function calls are returned; to obtain the complete backtrace, make sure that .i buffer and .i size are large enough. .pp given the set of addresses returned by .br backtrace () in .ir buffer , .br backtrace_symbols () translates the addresses into an array of strings that describe the addresses symbolically. the .i size argument specifies the number of addresses in .ir buffer . the symbolic representation of each address consists of the function name (if this can be determined), a hexadecimal offset into the function, and the actual return address (in hexadecimal). the address of the array of string pointers is returned as the function result of .br backtrace_symbols (). this array is .br malloc (3)ed by .br backtrace_symbols (), and must be freed by the caller. (the strings pointed to by the array of pointers need not and should not be freed.) .pp .br backtrace_symbols_fd () takes the same .i buffer and .i size arguments as .br backtrace_symbols (), but instead of returning an array of strings to the caller, it writes the strings, one per line, to the file descriptor .ir fd . .br backtrace_symbols_fd () does not call .br malloc (3), and so can be employed in situations where the latter function might fail, but see notes. .sh return value .br backtrace () returns the number of addresses returned in .ir buffer , which is not greater than .ir size . if the return value is less than .ir size , then the full backtrace was stored; if it is equal to .ir size , then it may have been truncated, in which case the addresses of the oldest stack frames are not returned. .pp on success, .br backtrace_symbols () returns a pointer to the array .br malloc (3)ed by the call; on error, null is returned. .sh versions .br backtrace (), .br backtrace_symbols (), and .br backtrace_symbols_fd () are provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br backtrace (), .br backtrace_symbols (), .br backtrace_symbols_fd () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. .sh notes these functions make some assumptions about how a function's return address is stored on the stack. note the following: .ip * 3 omission of the frame pointers (as implied by any of .br gcc (1)'s nonzero optimization levels) may cause these assumptions to be violated. .ip * inlined functions do not have stack frames. .ip * tail-call optimization causes one stack frame to replace another. .ip * .br backtrace () and .br backtrace_symbols_fd () don't call .br malloc () explicitly, but they are part of .ir libgcc , which gets loaded dynamically when first used. dynamic loading usually triggers a call to .br malloc (3). if you need certain calls to these two functions to not allocate memory (in signal handlers, for example), you need to make sure .i libgcc is loaded beforehand. .pp the symbol names may be unavailable without the use of special linker options. for systems using the gnu linker, it is necessary to use the .i \-rdynamic linker option. note that names of "static" functions are not exposed, and won't be available in the backtrace. .sh examples the program below demonstrates the use of .br backtrace () and .br backtrace_symbols (). the following shell session shows what we might see when running the program: .pp .in +4n .ex .rb "$" " cc \-rdynamic prog.c \-o prog" .rb "$" " ./prog 3" backtrace() returned 8 addresses \&./prog(myfunc3+0x5c) [0x80487f0] \&./prog [0x8048871] \&./prog(myfunc+0x21) [0x8048894] \&./prog(myfunc+0x1a) [0x804888d] \&./prog(myfunc+0x1a) [0x804888d] \&./prog(main+0x65) [0x80488fb] \&/lib/libc.so.6(__libc_start_main+0xdc) [0xb7e38f9c] \&./prog [0x8048711] .ee .in .ss program source \& .ex #include #include #include #include #define bt_buf_size 100 void myfunc3(void) { int nptrs; void *buffer[bt_buf_size]; char **strings; nptrs = backtrace(buffer, bt_buf_size); printf("backtrace() returned %d addresses\en", nptrs); /* the call backtrace_symbols_fd(buffer, nptrs, stdout_fileno) would produce similar output to the following: */ strings = backtrace_symbols(buffer, nptrs); if (strings == null) { perror("backtrace_symbols"); exit(exit_failure); } for (int j = 0; j < nptrs; j++) printf("%s\en", strings[j]); free(strings); } static void /* "static" means don\(aqt export the symbol... */ myfunc2(void) { myfunc3(); } void myfunc(int ncalls) { if (ncalls > 1) myfunc(ncalls \- 1); else myfunc2(); } int main(int argc, char *argv[]) { if (argc != 2) { fprintf(stderr, "%s num\-calls\en", argv[0]); exit(exit_failure); } myfunc(atoi(argv[1])); exit(exit_success); } .ee .sh see also .br addr2line (1), .br gcc (1), .br gdb (1), .br ld (1), .br dlopen (3), .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fgetc.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" opengroup's single unix specification .\" http://www.unix-systems.org/online.html .\" .\" 2007-03-31 bruno haible, describe the glibc/libiconv //translit .\" and //ignore extensions for 'tocode'. .\" .th iconv_open 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iconv_open \- allocate descriptor for character set conversion .sh synopsis .nf .b #include .pp .bi "iconv_t iconv_open(const char *" tocode ", const char *" fromcode ); .fi .sh description the .br iconv_open () function allocates a conversion descriptor suitable for converting byte sequences from character encoding .i fromcode to character encoding .ir tocode . .pp the values permitted for .ir fromcode and .i tocode and the supported combinations are system-dependent. for the gnu c library, the permitted values are listed by the .i "iconv \-\-list" command, and all combinations of the listed values are supported. furthermore the gnu c library and the gnu libiconv library support the following two suffixes: .tp //translit when the string "//translit" is appended to .ir tocode , transliteration is activated. this means that when a character cannot be represented in the target character set, it can be approximated through one or several similarly looking characters. .tp //ignore when the string "//ignore" is appended to .ir tocode , characters that cannot be represented in the target character set will be silently discarded. .pp the resulting conversion descriptor can be used with .br iconv (3) any number of times. it remains valid until deallocated using .br iconv_close (3). .pp a conversion descriptor contains a conversion state. after creation using .br iconv_open (), the state is in the initial state. using .br iconv (3) modifies the descriptor's conversion state. to bring the state back to the initial state, use .br iconv (3) with null as .i inbuf argument. .sh return value on success, .br iconv_open () returns a freshly allocated conversion descriptor. on failure, it returns .ir (iconv_t)\ \-1 and sets .i errno to indicate the error. .sh errors the following error can occur, among others: .tp .b einval the conversion from .ir fromcode to .i tocode is not supported by the implementation. .sh versions this function is available in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iconv_open () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2. .sh see also .br iconv (1), .br iconv (3), .br iconv_close (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/readlink.2 .so man3/getusershell.3 .so man3/drand48.3 .so man3/unlocked_stdio.3 .so man3/rpc.3 .so man3/gethostbyname.3 .so man3/acosh.3 .so man3/err.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2008, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:48:48 1993 by rik faith (faith@cs.unc.edu) .\" modified 980310, aeb .\" modified 990328, aeb .\" 2008-06-19, mtk, added mkostemp(); various other changes .\" .th mkstemp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mkstemp, mkostemp, mkstemps, mkostemps \- create a unique temporary file .sh synopsis .nf .b #include .pp .bi "int mkstemp(char *" template ); .bi "int mkostemp(char *" template ", int " flags ); .bi "int mkstemps(char *" template ", int " suffixlen ); .bi "int mkostemps(char *" template ", int " suffixlen ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mkstemp (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .pp .br mkostemp (): .nf _gnu_source .fi .pp .br mkstemps (): .nf /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .pp .br mkostemps (): .nf _gnu_source .fi .sh description the .br mkstemp () function generates a unique temporary filename from .ir template , creates and opens the file, and returns an open file descriptor for the file. .pp the last six characters of .i template must be "xxxxxx" and these are replaced with a string that makes the filename unique. since it will be modified, .i template must not be a string constant, but should be declared as a character array. .pp the file is created with permissions 0600, that is, read plus write for owner only. the returned file descriptor provides both read and write access to the file. the file is opened with the .br open (2) .b o_excl flag, guaranteeing that the caller is the process that creates the file. .pp the .br mkostemp () function is like .br mkstemp (), with the difference that the following bits\(emwith the same meaning as for .br open (2)\(emmay be specified in .ir flags : .br o_append , .br o_cloexec , and .br o_sync . note that when creating the file, .br mkostemp () includes the values .br o_rdwr , .br o_creat , and .br o_excl in the .i flags argument given to .br open (2); including these values in the .i flags argument given to .br mkostemp () is unnecessary, and produces errors on some .\" reportedly, freebsd systems. .pp the .br mkstemps () function is like .br mkstemp (), except that the string in .i template contains a suffix of .i suffixlen characters. thus, .i template is of the form .ir "prefixxxxxxxsuffix" , and the string xxxxxx is modified as for .br mkstemp (). .pp the .br mkostemps () function is to .br mkstemps () as .br mkostemp () is to .br mkstemp (). .sh return value on success, these functions return the file descriptor of the temporary file. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eexist could not create a unique temporary filename. now the contents of \fitemplate\fp are undefined. .tp .b einval for .br mkstemp () and .br mkostemp (): the last six characters of \fitemplate\fp were not xxxxxx; now \fitemplate\fp is unchanged. .ip for .br mkstemps () and .br mkostemps (): .i template is less than .i "(6 + suffixlen)" characters long, or the last 6 characters before the suffix in .i template were not xxxxxx. .pp these functions may also fail with any of the errors described for .br open (2). .sh versions .br mkostemp () is available since glibc 2.7. .br mkstemps () and .br mkostemps () are available since glibc 2.11. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mkstemp (), .br mkostemp (), .br mkstemps (), .br mkostemps () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br mkstemp (): 4.3bsd, posix.1-2001. .pp .br mkstemps (): unstandardized, but appears on several other systems. .\" mkstemps() appears to be at least on the bsds, mac os x, solaris, .\" and tru64. .pp .br mkostemp () and .br mkostemps (): are glibc extensions. .sh notes in glibc versions 2.06 and earlier, the file is created with permissions 0666, that is, read and write for all users. this old behavior may be a security risk, especially since other unix flavors use 0600, and somebody might overlook this detail when porting programs. posix.1-2008 adds a requirement that the file be created with mode 0600. .pp more generally, the posix specification of .br mkstemp () does not say anything about file modes, so the application should make sure its file mode creation mask (see .br umask (2)) is set appropriately before calling .br mkstemp () (and .br mkostemp ()). .\" .\" the prototype for .\" .br mkstemp () .\" is in .\" .i .\" for libc4, libc5, glibc1; glibc2 follows posix.1 and has the prototype in .\" .ir . .sh see also .br mkdtemp (3), .br mktemp (3), .br tempnam (3), .br tmpfile (3), .br tmpnam (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getresuid.2 .so man3/toupper.3 .so man3/fenv.3 .\" copyright 2004 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" inspired by a page by walter harms created 2002-08-10 .\" .th logb 3 2021-03-22 "" "linux programmer's manual" .sh name logb, logbf, logbl \- get exponent of a floating-point value .sh synopsis .nf .b #include .pp .bi "double logb(double " x ); .bi "float logbf(float " x ); .bi "long double logbl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br logb (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br logbf (), .br logbl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions extract the exponent from the internal floating-point representation of .i x and return it as a floating-point value. the integer constant .br flt_radix , defined in .ir , indicates the radix used for the system's floating-point representation. if .b flt_radix is 2, .bi logb( x ) is equal to .bi floor(log2( x ))\fr, except that it is probably faster. .pp if .i x is subnormal, .br logb () returns the exponent .i x would have if it were normalized. .sh return value on success, these functions return the exponent of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is zero, then a pole error occurs, and the functions return .rb \- huge_val , .rb \- huge_valf , or .rb \- huge_vall , respectively. .pp if .i x is negative infinity or positive infinity, then positive infinity is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp pole error: \fix\fp is 0 .\" .i errno .\" is set to .\" .br erange . a divide-by-zero floating-point exception .rb ( fe_divbyzero ) is raised. .pp these functions do not set .ir errno . .\" fixme . is it intentional that these functions do not set errno? .\" log(), log2(), log10() do set errno .\" bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6793 .\" .\" .sh history .\" the .\" .br logb () .\" function occurs in 4.3bsd. .\" see ieee.3 in the 4.3bsd manual .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br logb (), .br logbf (), .br logbl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br ilogb (3), .br log (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getaddrinfo_a.3 .\" copyright (c) andreas gruenbacher, february 2001 .\" copyright (c) silicon graphics inc, september 2001 .\" copyright (c) 2015 heinrich schuchardt .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th listxattr 2 2021-03-22 "linux" "linux programmer's manual" .sh name listxattr, llistxattr, flistxattr \- list extended attribute names .sh synopsis .fam c .nf .b #include .pp .bi "ssize_t listxattr(const char *" path ", char *" list \ ", size_t " size ); .bi "ssize_t llistxattr(const char *" path ", char *" list \ ", size_t " size ); .bi "ssize_t flistxattr(int " fd ", char *" list ", size_t " size ); .fi .fam t .sh description extended attributes are .ir name : value pairs associated with inodes (files, directories, symbolic links, etc.). they are extensions to the normal attributes which are associated with all inodes in the system (i.e., the .br stat (2) data). a complete overview of extended attributes concepts can be found in .br xattr (7). .pp .br listxattr () retrieves the list of extended attribute names associated with the given .i path in the filesystem. the retrieved list is placed in .ir list , a caller-allocated buffer whose size (in bytes) is specified in the argument .ir size . the list is the set of (null-terminated) names, one after the other. names of extended attributes to which the calling process does not have access may be omitted from the list. the length of the attribute name .i list is returned. .pp .br llistxattr () is identical to .br listxattr (), except in the case of a symbolic link, where the list of names of extended attributes associated with the link itself is retrieved, not the file that it refers to. .pp .br flistxattr () is identical to .br listxattr (), only the open file referred to by .i fd (as returned by .br open (2)) is interrogated in place of .ir path . .pp a single extended attribute .i name is a null-terminated string. the name includes a namespace prefix; there may be several, disjoint namespaces associated with an individual inode. .pp if .i size is specified as zero, these calls return the current size of the list of extended attribute names (and leave .i list unchanged). this can be used to determine the size of the buffer that should be supplied in a subsequent call. (but, bear in mind that there is a possibility that the set of extended attributes may change between the two calls, so that it is still necessary to check the return status from the second call.) .ss example the .i list of names is returned as an unordered array of null-terminated character strings (attribute names are separated by null bytes (\(aq\e0\(aq)), like this: .pp .in +4n .ex user.name1\e0system.name1\e0user.name2\e0 .ee .in .pp filesystems that implement posix acls using extended attributes might return a .i list like this: .pp .in +4n .ex system.posix_acl_access\e0system.posix_acl_default\e0 .ee .in .sh return value on success, a nonnegative number is returned indicating the size of the extended attribute name list. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b e2big the size of the list of extended attribute names is larger than the maximum size allowed; the list cannot be retrieved. this can happen on filesystems that support an unlimited number of extended attributes per file such as xfs, for example. see bugs. .tp .b enotsup extended attributes are not supported by the filesystem, or are disabled. .tp .b erange the .i size of the .i list buffer is too small to hold the result. .pp in addition, the errors documented in .br stat (2) can also occur. .sh versions these system calls have been available on linux since kernel 2.4; glibc support is provided since version 2.3. .sh conforming to these system calls are linux-specific. .\" .sh authors .\" andreas gruenbacher, .\" .ri < a.gruenbacher@computer.org > .\" and the sgi xfs development team, .\" .ri < linux-xfs@oss.sgi.com >. .\" please send any bug reports or comments to these addresses. .sh bugs .\" the xattr(7) page refers to this text: as noted in .br xattr (7), the vfs imposes a limit of 64\ kb on the size of the extended attribute name list returned by .br listxattr (7). if the total size of attribute names attached to a file exceeds this limit, it is no longer possible to retrieve the list of attribute names. .sh examples the following program demonstrates the usage of .br listxattr () and .br getxattr (2). for the file whose pathname is provided as a command-line argument, it lists all extended file attributes and their values. .pp to keep the code simple, the program assumes that attribute keys and values are constant during the execution of the program. a production program should expect and handle changes during execution of the program. for example, the number of bytes required for attribute keys might increase between the two calls to .br listxattr (). an application could handle this possibility using a loop that retries the call (perhaps up to a predetermined maximum number of attempts) with a larger buffer each time it fails with the error .br erange . calls to .br getxattr (2) could be handled similarly. .pp the following output was recorded by first creating a file, setting some extended file attributes, and then listing the attributes with the example program. .ss example output .in +4n .ex $ \fbtouch /tmp/foo\fp $ \fbsetfattr \-n user.fred \-v chocolate /tmp/foo\fp $ \fbsetfattr \-n user.frieda \-v bar /tmp/foo\fp $ \fbsetfattr \-n user.empty /tmp/foo\fp $ \fb./listxattr /tmp/foo\fp user.fred: chocolate user.frieda: bar user.empty: .ee .in .ss program source (listxattr.c) .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { ssize_t buflen, keylen, vallen; char *buf, *key, *val; if (argc != 2) { fprintf(stderr, "usage: %s path\en", argv[0]); exit(exit_failure); } /* * determine the length of the buffer needed. */ buflen = listxattr(argv[1], null, 0); if (buflen == \-1) { perror("listxattr"); exit(exit_failure); } if (buflen == 0) { printf("%s has no attributes.\en", argv[1]); exit(exit_success); } /* * allocate the buffer. */ buf = malloc(buflen); if (buf == null) { perror("malloc"); exit(exit_failure); } /* * copy the list of attribute keys to the buffer. */ buflen = listxattr(argv[1], buf, buflen); if (buflen == \-1) { perror("listxattr"); exit(exit_failure); } /* * loop over the list of zero terminated strings with the * attribute keys. use the remaining buffer length to determine * the end of the list. */ key = buf; while (buflen > 0) { /* * output attribute key. */ printf("%s: ", key); /* * determine length of the value. */ vallen = getxattr(argv[1], key, null, 0); if (vallen == \-1) perror("getxattr"); if (vallen > 0) { /* * allocate value buffer. * one extra byte is needed to append 0x00. */ val = malloc(vallen + 1); if (val == null) { perror("malloc"); exit(exit_failure); } /* * copy value to buffer. */ vallen = getxattr(argv[1], key, val, vallen); if (vallen == \-1) perror("getxattr"); else { /* * output attribute value. */ val[vallen] = 0; printf("%s", val); } free(val); } else if (vallen == 0) printf(""); printf("\en"); /* * forward to next attribute key. */ keylen = strlen(key) + 1; buflen \-= keylen; key += keylen; } free(buf); exit(exit_success); } .ee .sh see also .br getfattr (1), .br setfattr (1), .br getxattr (2), .br open (2), .br removexattr (2), .br setxattr (2), .br stat (2), .br symlink (7), .br xattr (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man3/getfsent.3 .\" copyright (c) 1993 michael haardt .\" (michael@moria.de), fri apr 2 11:32:09 met dst .\" 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified by thomas koenig (ig25@rz.uni-karlsruhe.de) 24 apr 1993 .\" modified sat jul 24 17:28:08 1993 by rik faith (faith@cs.unc.edu) .th intro 7 2007-10-23 "linux" "linux programmer's manual" .sh name intro \- introduction to overview and miscellany section .sh description section 7 of the manual provides overviews on various topics, and describes conventions and protocols, character set standards, the standard filesystem layout, and miscellaneous other things. .sh notes .ss authors and copyright conditions look at the header of the manual page source for the author(s) and copyright conditions. note that these can be different from page to page! .sh see also .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2009 petr baudis .\" and clean-ups and additions (c) copyright 2010 michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references: http://people.redhat.com/drepper/asynchnl.pdf, .\" http://www.imperialviolet.org/2005/06/01/asynchronous-dns-lookups-with-glibc.html .\" .th getaddrinfo_a 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getaddrinfo_a, gai_suspend, gai_error, gai_cancel \- asynchronous network address and service translation .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int getaddrinfo_a(int " mode ", struct gaicb *" list [restrict], .bi " int " nitems ", struct sigevent *restrict " sevp ); .bi "int gai_suspend(const struct gaicb *const " list "[], int " nitems , .bi " const struct timespec *" timeout ); .pp .bi "int gai_error(struct gaicb *" req ); .bi "int gai_cancel(struct gaicb *" req ); .pp link with \fi\-lanl\fp. .fi .sh description the .br getaddrinfo_a () function performs the same task as .br getaddrinfo (3), but allows multiple name look-ups to be performed asynchronously, with optional notification on completion of look-up operations. .pp the .i mode argument has one of the following values: .tp .b gai_wait perform the look-ups synchronously. the call blocks until the look-ups have completed. .tp .b gai_nowait perform the look-ups asynchronously. the call returns immediately, and the requests are resolved in the background. see the discussion of the .i sevp argument below. .pp the array .i list specifies the look-up requests to process. the .i nitems argument specifies the number of elements in .ir list . the requested look-up operations are started in parallel. null elements in .i list are ignored. each request is described by a .i gaicb structure, defined as follows: .pp .in +4n .ex struct gaicb { const char *ar_name; const char *ar_service; const struct addrinfo *ar_request; struct addrinfo *ar_result; }; .ee .in .pp the elements of this structure correspond to the arguments of .br getaddrinfo (3). thus, .i ar_name corresponds to the .i node argument and .i ar_service to the .i service argument, identifying an internet host and a service. the .i ar_request element corresponds to the .i hints argument, specifying the criteria for selecting the returned socket address structures. finally, .i ar_result corresponds to the .i res argument; you do not need to initialize this element, it will be automatically set when the request is resolved. the .i addrinfo structure referenced by the last two elements is described in .br getaddrinfo (3). .pp when .i mode is specified as .br gai_nowait , notifications about resolved requests can be obtained by employing the .i sigevent structure pointed to by the .i sevp argument. for the definition and general details of this structure, see .br sigevent (7). the .i sevp\->sigev_notify field can have the following values: .tp .br sigev_none don't provide any notification. .tp .br sigev_signal when a look-up completes, generate the signal .i sigev_signo for the process. see .br sigevent (7) for general details. the .i si_code field of the .i siginfo_t structure will be set to .br si_asyncnl . .\" si_pid and si_uid are also set, to the values of the calling process, .\" which doesn't provide useful information, so we'll skip mentioning it. .tp .br sigev_thread when a look-up completes, invoke .i sigev_notify_function as if it were the start function of a new thread. see .br sigevent (7) for details. .pp for .br sigev_signal and .br sigev_thread , it may be useful to point .ir sevp\->sigev_value.sival_ptr to .ir list . .pp the .br gai_suspend () function suspends execution of the calling thread, waiting for the completion of one or more requests in the array .ir list . the .i nitems argument specifies the size of the array .ir list . the call blocks until one of the following occurs: .ip * 3 one or more of the operations in .i list completes. .ip * the call is interrupted by a signal that is caught. .ip * the time interval specified in .i timeout elapses. this argument specifies a timeout in seconds plus nanoseconds (see .br nanosleep (2) for details of the .i timespec structure). if .i timeout is null, then the call blocks indefinitely (until one of the events above occurs). .pp no explicit indication of which request was completed is given; you must determine which request(s) have completed by iterating with .br gai_error () over the list of requests. .pp the .br gai_error () function returns the status of the request .ir req : either .b eai_inprogress if the request was not completed yet, 0 if it was handled successfully, or an error code if the request could not be resolved. .pp the .br gai_cancel () function cancels the request .ir req . if the request has been canceled successfully, the error status of the request will be set to .b eai_canceled and normal asynchronous notification will be performed. the request cannot be canceled if it is currently being processed; in that case, it will be handled as if .br gai_cancel () has never been called. if .i req is null, an attempt is made to cancel all outstanding requests that the process has made. .sh return value the .br getaddrinfo_a () function returns 0 if all of the requests have been enqueued successfully, or one of the following nonzero error codes: .tp .b eai_again the resources necessary to enqueue the look-up requests were not available. the application may check the error status of each request to determine which ones failed. .tp .b eai_memory out of memory. .tp .b eai_system .i mode is invalid. .pp the .br gai_suspend () function returns 0 if at least one of the listed requests has been completed. otherwise, it returns one of the following nonzero error codes: .tp .b eai_again the given timeout expired before any of the requests could be completed. .tp .b eai_alldone there were no actual requests given to the function. .tp .b eai_intr a signal has interrupted the function. note that this interruption might have been caused by signal notification of some completed look-up request. .pp the .br gai_error () function can return .b eai_inprogress for an unfinished look-up request, 0 for a successfully completed look-up (as described above), one of the error codes that could be returned by .br getaddrinfo (3), or the error code .b eai_canceled if the request has been canceled explicitly before it could be finished. .pp the .br gai_cancel () function can return one of these values: .tp .b eai_canceled the request has been canceled successfully. .tp .b eai_notcanceled the request has not been canceled. .tp .b eai_alldone the request has already completed. .pp the .br gai_strerror (3) function translates these error codes to a human readable string, suitable for error reporting. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getaddrinfo_a (), .br gai_suspend (), .br gai_error (), .br gai_cancel () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions; they first appeared in glibc in version 2.2.3. .sh notes the interface of .br getaddrinfo_a () was modeled after the .br lio_listio (3) interface. .sh examples two examples are provided: a simple example that resolves several requests in parallel synchronously, and a complex example showing some of the asynchronous capabilities. .ss synchronous example the program below simply resolves several hostnames in parallel, giving a speed-up compared to resolving the hostnames sequentially using .br getaddrinfo (3). the program might be used like this: .pp .in +4n .ex $ \fb./a.out ftp.us.kernel.org enoent.linuxfoundation.org gnu.cz\fp ftp.us.kernel.org: 128.30.2.36 enoent.linuxfoundation.org: name or service not known gnu.cz: 87.236.197.13 .ee .in .pp here is the program source code .pp .ex #define _gnu_source #include #include #include #include int main(int argc, char *argv[]) { int ret; struct gaicb *reqs[argc \- 1]; char host[ni_maxhost]; struct addrinfo *res; if (argc < 2) { fprintf(stderr, "usage: %s host...\en", argv[0]); exit(exit_failure); } for (int i = 0; i < argc \- 1; i++) { reqs[i] = malloc(sizeof(*reqs[0])); if (reqs[i] == null) { perror("malloc"); exit(exit_failure); } memset(reqs[i], 0, sizeof(*reqs[0])); reqs[i]\->ar_name = argv[i + 1]; } ret = getaddrinfo_a(gai_wait, reqs, argc \- 1, null); if (ret != 0) { fprintf(stderr, "getaddrinfo_a() failed: %s\en", gai_strerror(ret)); exit(exit_failure); } for (int i = 0; i < argc \- 1; i++) { printf("%s: ", reqs[i]\->ar_name); ret = gai_error(reqs[i]); if (ret == 0) { res = reqs[i]\->ar_result; ret = getnameinfo(res\->ai_addr, res\->ai_addrlen, host, sizeof(host), null, 0, ni_numerichost); if (ret != 0) { fprintf(stderr, "getnameinfo() failed: %s\en", gai_strerror(ret)); exit(exit_failure); } puts(host); } else { puts(gai_strerror(ret)); } } exit(exit_success); } .ee .ss asynchronous example this example shows a simple interactive .br getaddrinfo_a () front-end. the notification facility is not demonstrated. .pp an example session might look like this: .pp .in +4n .ex $ \fb./a.out\fp > a ftp.us.kernel.org enoent.linuxfoundation.org gnu.cz > c 2 [2] gnu.cz: request not canceled > w 0 1 [00] ftp.us.kernel.org: finished > l [00] ftp.us.kernel.org: 216.165.129.139 [01] enoent.linuxfoundation.org: processing request in progress [02] gnu.cz: 87.236.197.13 > l [00] ftp.us.kernel.org: 216.165.129.139 [01] enoent.linuxfoundation.org: name or service not known [02] gnu.cz: 87.236.197.13 .ee .in .pp the program source is as follows: .pp .ex #define _gnu_source #include #include #include #include static struct gaicb **reqs = null; static int nreqs = 0; static char * getcmd(void) { static char buf[256]; fputs("> ", stdout); fflush(stdout); if (fgets(buf, sizeof(buf), stdin) == null) return null; if (buf[strlen(buf) \- 1] == \(aq\en\(aq) buf[strlen(buf) \- 1] = 0; return buf; } /* add requests for specified hostnames. */ static void add_requests(void) { int nreqs_base = nreqs; char *host; int ret; while ((host = strtok(null, " "))) { nreqs++; reqs = realloc(reqs, sizeof(reqs[0]) * nreqs); reqs[nreqs \- 1] = calloc(1, sizeof(*reqs[0])); reqs[nreqs \- 1]\->ar_name = strdup(host); } /* queue nreqs_base..nreqs requests. */ ret = getaddrinfo_a(gai_nowait, &reqs[nreqs_base], nreqs \- nreqs_base, null); if (ret) { fprintf(stderr, "getaddrinfo_a() failed: %s\en", gai_strerror(ret)); exit(exit_failure); } } /* wait until at least one of specified requests completes. */ static void wait_requests(void) { char *id; int ret, n; struct gaicb const **wait_reqs = calloc(nreqs, sizeof(*wait_reqs)); /* null elements are ignored by gai_suspend(). */ while ((id = strtok(null, " ")) != null) { n = atoi(id); if (n >= nreqs) { printf("bad request number: %s\en", id); return; } wait_reqs[n] = reqs[n]; } ret = gai_suspend(wait_reqs, nreqs, null); if (ret) { printf("gai_suspend(): %s\en", gai_strerror(ret)); return; } for (int i = 0; i < nreqs; i++) { if (wait_reqs[i] == null) continue; ret = gai_error(reqs[i]); if (ret == eai_inprogress) continue; printf("[%02d] %s: %s\en", i, reqs[i]\->ar_name, ret == 0 ? "finished" : gai_strerror(ret)); } } /* cancel specified requests. */ static void cancel_requests(void) { char *id; int ret, n; while ((id = strtok(null, " ")) != null) { n = atoi(id); if (n >= nreqs) { printf("bad request number: %s\en", id); return; } ret = gai_cancel(reqs[n]); printf("[%s] %s: %s\en", id, reqs[atoi(id)]\->ar_name, gai_strerror(ret)); } } /* list all requests. */ static void list_requests(void) { int ret; char host[ni_maxhost]; struct addrinfo *res; for (int i = 0; i < nreqs; i++) { printf("[%02d] %s: ", i, reqs[i]\->ar_name); ret = gai_error(reqs[i]); if (!ret) { res = reqs[i]\->ar_result; ret = getnameinfo(res\->ai_addr, res\->ai_addrlen, host, sizeof(host), null, 0, ni_numerichost); if (ret) { fprintf(stderr, "getnameinfo() failed: %s\en", gai_strerror(ret)); exit(exit_failure); } puts(host); } else { puts(gai_strerror(ret)); } } } int main(int argc, char *argv[]) { char *cmdline; char *cmd; while ((cmdline = getcmd()) != null) { cmd = strtok(cmdline, " "); if (cmd == null) { list_requests(); } else { switch (cmd[0]) { case \(aqa\(aq: add_requests(); break; case \(aqw\(aq: wait_requests(); break; case \(aqc\(aq: cancel_requests(); break; case \(aql\(aq: list_requests(); break; default: fprintf(stderr, "bad command: %c\en", cmd[0]); break; } } } exit(exit_success); } .ee .sh see also .br getaddrinfo (3), .br inet (3), .br lio_listio (3), .br hostname (7), .br ip (7), .br sigevent (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .\" modified, aeb, 990824 .\" .th mb_cur_max 3 2015-08-08 "linux" "linux programmer's manual" .sh name mb_cur_max \- maximum length of a multibyte character in the current locale .sh synopsis .nf .b #include .fi .sh description the .b mb_cur_max macro defines an integer expression giving the maximum number of bytes needed to represent a single wide character in the current locale. this value is locale dependent and therefore not a compile-time constant. .sh return value an integer in the range [1, .br mb_len_max ]. the value 1 denotes traditional 8-bit encoded characters. .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br mb_len_max (3), .br mblen (3), .br mbstowcs (3), .br mbtowc (3), .br wcstombs (3), .br wctomb (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getopt.3 .so man3/sigvec.3 .so man3/scalbln.3 .so man3/exp10.3 .so man3/getpwnam.3 .so man3/dlopen.3 .\" copyright 2007 (c) michael kerrisk .\" some parts copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 21:46:21 1993 by rik faith (faith@cs.unc.edu) .\" modified fri aug 4 10:51:53 2000 - patch from joseph s. myers .\" 2007-12-15, mtk, mostly rewritten .\" .th abort 3 2021-03-22 "gnu" "linux programmer's manual" .sh name abort \- cause abnormal process termination .sh synopsis .nf .b #include .pp .b noreturn void abort(void); .fi .sh description the .br abort () function first unblocks the .b sigabrt signal, and then raises that signal for the calling process (as though .br raise (3) was called). this results in the abnormal termination of the process unless the .b sigabrt signal is caught and the signal handler does not return (see .br longjmp (3)). .pp if the .b sigabrt signal is ignored, or caught by a handler that returns, the .br abort () function will still terminate the process. it does this by restoring the default disposition for .b sigabrt and then raising the signal for a second time. .sh return value the .br abort () function never returns. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br abort () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4, posix.1-2001, posix.1-2008, 4.3bsd, c89, c99. .sh notes up until glibc 2.26, if the .br abort () function caused process termination, all open streams were closed and flushed (as with .br fclose (3)). however, in some cases this could result in deadlocks and data corruption. therefore, starting with glibc 2.27, .\" glibc commit 91e7cf982d0104f0e71770f5ae8e3faf352dea9f .br abort () terminates the process without flushing streams. posix.1 permits either possible behavior, saying that .br abort () "may include an attempt to effect fclose() on all open streams". .sh see also .br gdb (1), .br sigaction (2), .br assert (3), .br exit (3), .br longjmp (3), .br raise (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_destroy 3 2021-03-22 "linux" "linux programmer's manual" .sh name sem_destroy \- destroy an unnamed semaphore .sh synopsis .nf .b #include .pp .bi "int sem_destroy(sem_t *" sem ); .fi .pp link with \fi\-pthread\fp. .sh description .br sem_destroy () destroys the unnamed semaphore at the address pointed to by .ir sem . .pp only a semaphore that has been initialized by .br sem_init (3) should be destroyed using .br sem_destroy (). .pp destroying a semaphore that other processes or threads are currently blocked on (in .br sem_wait (3)) produces undefined behavior. .pp using a semaphore that has been destroyed produces undefined results, until the semaphore has been reinitialized using .br sem_init (3). .sh return value .br sem_destroy () returns 0 on success; on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i sem is not a valid semaphore. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_destroy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes an unnamed semaphore should be destroyed with .br sem_destroy () before the memory in which it is located is deallocated. failure to do this can result in resource leaks on some implementations. .\" but not on nptl, where sem_destroy () is a no-op.. .sh see also .br sem_init (3), .br sem_post (3), .br sem_wait (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/__ppc_yield.3 .\" copyright 2000 sam varshavchik .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references: rfc 2553 .th inet_ntop 3 2021-03-22 "linux" "linux programmer's manual" .sh name inet_ntop \- convert ipv4 and ipv6 addresses from binary to text form .sh synopsis .nf .b #include .pp .bi "const char *inet_ntop(int " af ", const void *restrict " src , .bi " char *restrict " dst ", socklen_t " size ); .fi .sh description this function converts the network address structure .i src in the .i af address family into a character string. the resulting string is copied to the buffer pointed to by .ir dst , which must be a non-null pointer. the caller specifies the number of bytes available in this buffer in the argument .ir size . .pp .br inet_ntop () extends the .br inet_ntoa (3) function to support multiple address families, .br inet_ntoa (3) is now considered to be deprecated in favor of .br inet_ntop (). the following address families are currently supported: .tp .b af_inet .i src points to a .i struct in_addr (in network byte order) which is converted to an ipv4 network address in the dotted-decimal format, "\fiddd.ddd.ddd.ddd\fp". the buffer .i dst must be at least .b inet_addrstrlen bytes long. .tp .b af_inet6 .i src points to a .i struct in6_addr (in network byte order) which is converted to a representation of this address in the most appropriate ipv6 network address format for this address. the buffer .i dst must be at least .b inet6_addrstrlen bytes long. .sh return value on success, .br inet_ntop () returns a non-null pointer to .ir dst . null is returned if there was an error, with .i errno set to indicate the error. .sh errors .tp .b eafnosupport .i af was not a valid address family. .tp .b enospc the converted address string would exceed the size given by .ir size . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br inet_ntop () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. note that rfc\ 2553 defines a prototype where the last argument .i size is of type .ir size_t . many systems follow rfc\ 2553. glibc 2.0 and 2.1 have .ir size_t , but 2.2 and later have .ir socklen_t . .\" 2.1.3: size_t, 2.1.91: socklen_t .sh bugs .b af_inet6 converts ipv4-mapped ipv6 addresses into an ipv6 format. .sh examples see .br inet_pton (3). .sh see also .br getnameinfo (3), .br inet (3), .br inet_pton (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th fmin 3 2021-03-22 "" "linux programmer's manual" .sh name fmin, fminf, fminl \- determine minimum of two floating-point numbers .sh synopsis .nf .b #include .pp .bi "double fmin(double " x ", double " y ); .bi "float fminf(float " x ", float " y ); .bi "long double fminl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fmin (), .br fminf (), .br fminl (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions return the lesser value of .i x and .ir y . .sh return value these functions return the minimum of .i x and .ir y . .pp if one argument is a nan, the other argument is returned. .pp if both arguments are nan, a nan is returned. .sh errors no errors occur. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fmin (), .br fminf (), .br fminl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br fdim (3), .br fmax (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-04-02, david metcalfe .\" modified 1993-07-25, rik faith (faith@cs.unc.edu) .th on_exit 3 2021-03-22 "gnu" "linux programmer's manual" .sh name on_exit \- register a function to be called at normal process termination .sh synopsis .nf .b #include .pp .bi "int on_exit(void (*" function ")(int, void *), void *" arg ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br on_exit (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the .br on_exit () function registers the given .i function to be called at normal process termination, whether via .br exit (3) or via return from the program's .ir main (). the .i function is passed the status argument given to the last call to .br exit (3) and the .i arg argument from .br on_exit (). .pp the same function may be registered multiple times: it is called once for each registration. .pp when a child process is created via .br fork (2), it inherits copies of its parent's registrations. upon a successful call to one of the .br exec (3) functions, all registrations are removed. .sh return value the .br on_exit () function returns the value 0 if successful; otherwise it returns a nonzero value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br on_exit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function comes from sunos 4, but is also present in glibc. it no longer occurs in solaris (sunos 5). portable application should avoid this function, and use the standard .br atexit (3) instead. .sh notes by the time .i function is executed, stack .ri ( auto ) variables may already have gone out of scope. therefore, .i arg should not be a pointer to a stack variable; it may however be a pointer to a heap variable or a global variable. .sh see also .br _exit (2), .br atexit (3), .br exit (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/select.2 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cexp 3 2021-03-22 "" "linux programmer's manual" .sh name cexp, cexpf, cexpl \- complex exponential function .sh synopsis .nf .b #include .pp .bi "double complex cexp(double complex " z ");" .bi "float complex cexpf(float complex " z ");" .bi "long double complex cexpl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate e (2.71828..., the base of natural logarithms) raised to the power of .ir z . .pp one has: .pp .nf cexp(i * z) = ccos(z) + i * csin(z) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cexp (), .br cexpf (), .br cexpl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br cexp2 (3), .br clog (3), .br cpow (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .so man3/tailq.3 .so man2/clock_getres.2 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 21:27:01 1993 by rik faith (faith@cs.unc.edu) .\" modified 14 jun 2002, michael kerrisk .\" added notes on differences from other unix systems with respect to .\" waited-for children. .th clock 3 2021-03-22 "gnu" "linux programmer's manual" .sh name clock \- determine processor time .sh synopsis .nf .b #include .pp .b clock_t clock(void); .fi .sh description the .br clock () function returns an approximation of processor time used by the program. .sh return value the value returned is the cpu time used so far as a .ir clock_t ; to get the number of seconds used, divide by .br clocks_per_sec . if the processor time used is not available or its value cannot be represented, the function returns the value .ir (clock_t)\ \-1 . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clock () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. xsi requires that .b clocks_per_sec equals 1000000 independent of the actual resolution. .sh notes the c standard allows for arbitrary values at the start of the program; subtract the value returned from a call to .br clock () at the start of the program to get maximum portability. .pp note that the time can wrap around. on a 32-bit system where .b clocks_per_sec equals 1000000 this function will return the same value approximately every 72 minutes. .pp on several other implementations, the value returned by .br clock () also includes the times of any children whose status has been collected via .br wait (2) (or another wait-type call). linux does not include the times of waited-for children in the value returned by .br clock (). .\" i have seen this behavior on irix 6.3, and the osf/1, hp/ux, and .\" solaris manual pages say that clock() also does this on those systems. .\" posix.1-2001 doesn't explicitly allow this, nor is there an .\" explicit prohibition. -- mtk the .br times (2) function, which explicitly returns (separate) information about the caller and its children, may be preferable. .pp in glibc 2.17 and earlier, .br clock () was implemented on top of .br times (2). for improved accuracy, since glibc 2.18, it is implemented on top of .br clock_gettime (2) (using the .br clock_process_cputime_id clock). .sh see also .br clock_gettime (2), .br getrusage (2), .br times (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified sun feb 26 14:52:00 1995 by rik faith .\" modified tue oct 22 23:48:10 1996 by eric s. raymond .\" " .th bcopy 3 2021-03-22 "linux" "linux programmer's manual" .sh name bcopy \- copy byte sequence .sh synopsis .nf .b #include .pp .bi "void bcopy(const void *" src ", void *" dest ", size_t " n ); .fi .sh description the .br bcopy () function copies .i n bytes from .i src to .ir dest . the result is correct, even when both areas overlap. .sh return value none. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br bcopy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd. this function is deprecated (marked as legacy in posix.1-2001): use .br memcpy (3) or .br memmove (3) in new programs. note that the first two arguments are interchanged for .br memcpy (3) and .br memmove (3). posix.1-2008 removes the specification of .br bcopy (). .sh see also .br bstring (3), .br memccpy (3), .br memcpy (3), .br memmove (3), .br strcpy (3), .br strncpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/pread.2 .so man2/seteuid.2 .so man3/timeradd.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on glibc infopages .\" polished, aeb .\" .th remquo 3 2021-03-22 "gnu" "linux programmer's manual" .sh name remquo, remquof, remquol \- remainder and part of quotient .sh synopsis .nf .b #include .pp .bi "double remquo(double " x ", double " y ", int *" quo ); .bi "float remquof(float " x ", float " y ", int *" quo ); .bi "long double remquol(long double " x ", long double " y ", int *" quo ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br remquo (), .br remquof (), .br remquol (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions compute the remainder and part of the quotient upon division of .i x by .ir y . a few bits of the quotient are stored via the .i quo pointer. the remainder is returned as the function result. .pp the value of the remainder is the same as that computed by the .br remainder (3) function. .pp the value stored via the .i quo pointer has the sign of .ir "x\ /\ y" and agrees with the quotient in at least the low order 3 bits. .pp for example, \firemquo(29.0,\ 3.0)\fp returns \-1.0 and might store 2. note that the actual quotient might not fit in an integer. .\" a possible application of this function might be the computation .\" of sin(x). compute remquo(x, pi/2, &quo) or so. .\" .\" glibc, unixware: return 3 bits .\" macos 10: return 7 bits .sh return value on success, these functions return the same value as the analogous functions described in .br remainder (3). .pp if .i x or .i y is a nan, a nan is returned. .pp if .i x is an infinity, and .i y is not a nan, a domain error occurs, and a nan is returned. .pp if .i y is zero, and .i x is not a nan, a domain error occurs, and a nan is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is an infinity or \fiy\fp is 0, \ and the other argument is not a nan .\" .i errno .\" is set to .\" .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .pp these functions do not set .ir errno . .\" fixme . is it intentional that these functions do not set errno? .\" bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6802 .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br remquo (), .br remquof (), .br remquol () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br fmod (3), .br logb (3), .br remainder (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/posix_memalign.3 .\" copyright (c) 2001 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getpagesize 2 2021-03-22 "linux" "linux programmer's manual" .sh name getpagesize \- get memory page size .sh synopsis .nf .b #include .pp .b int getpagesize(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getpagesize (): .nf since glibc 2.20: _default_source || ! (_posix_c_source >= 200112l) glibc 2.12 to 2.19: _bsd_source || ! (_posix_c_source >= 200112l) before glibc 2.12: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description the function .br getpagesize () returns the number of bytes in a memory page, where "page" is a fixed-length block, the unit for memory allocation and file mapping performed by .br mmap (2). .\" .sh history .\" this call first appeared in 4.2bsd. .sh conforming to svr4, 4.4bsd, susv2. in susv2 the .br getpagesize () call is labeled legacy, and in posix.1-2001 it has been dropped; hp-ux does not have this call. .sh notes portable applications should employ .i sysconf(_sc_pagesize) instead of .br getpagesize (): .pp .in +4n .ex #include long sz = sysconf(_sc_pagesize); .ee .in .pp (most systems allow the synonym .b _sc_page_size for .br _sc_pagesize .) .pp whether .br getpagesize () is present as a linux system call depends on the architecture. if it is, it returns the kernel symbol .br page_size , whose value depends on the architecture and machine model. generally, one uses binaries that are dependent on the architecture but not on the machine model, in order to have a single binary distribution per architecture. this means that a user program should not find .b page_size at compile time from a header file, but use an actual system call, at least for those architectures (like sun4) where this dependency exists. here glibc 2.0 fails because its .br getpagesize () returns a statically derived value, and does not use a system call. things are ok in glibc 2.1. .sh see also .br mmap (2), .br sysconf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .\" copyright 2014 (c) marko myllynen .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th cp1252 7 2020-08-13 "linux" "linux programmer's manual" .sh name cp1252 \- cp\ 1252 character set encoded in octal, decimal, and hexadecimal .sh description the windows code pages include several 8-bit extensions to the ascii character set (also known as iso 646-irv). cp\ 1252 encodes the characters used in many west european languages. .ss cp\ 1252 characters the following table displays the characters in cp\ 1252 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 200 128 80 € euro sign 202 130 82 ‚ single low-9 quotation mark 203 131 83 ƒ latin small letter f with hook 204 132 84 „ double low-9 quotation mark 205 133 85 … horizontal ellipsis 206 134 86 † dagger 207 135 87 ‡ double dagger 210 136 88 ˆ modifier letter circumflex accent 211 137 89 ‰ per mille sign 212 138 8a š latin capital letter s with caron 213 139 8b ‹ single left-pointing angle quotation mark 214 140 8c œ latin capital ligature oe 216 142 8e ž latin capital letter z with caron 221 145 91 ‘ left single quotation mark 222 146 92 ’ right single quotation mark 223 147 93 “ left double quotation mark 224 148 94 ” right double quotation mark 225 149 95 • bullet 226 150 96 – en dash 227 151 97 — em dash 230 152 98 ˜ small tilde 231 153 99 ™ trade mark sign 232 154 9a š latin small letter s with caron 233 155 9b › single right-pointing angle quotation mark 234 156 9c œ latin small ligature oe 236 158 9e ž latin small letter z with caron 237 159 9f ÿ latin capital letter y with diaeresis 240 160 a0   no-break space 241 161 a1 ¡ inverted exclamation mark 242 162 a2 ¢ cent sign 243 163 a3 £ pound sign 244 164 a4 ¤ currency sign 245 165 a5 ¥ yen sign 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 © copyright sign 252 170 aa ª feminine ordinal indicator 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ¯ macron 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ´ acute accent 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ¸ cedilla 271 185 b9 ¹ superscript one 272 186 ba º masculine ordinal indicator 273 187 bb » right-pointing double angle quotation mark 274 188 bc ¼ vulgar fraction one quarter 275 189 bd ½ vulgar fraction one half 276 190 be ¾ vulgar fraction three quarters 277 191 bf ¿ inverted question mark 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 ð latin capital letter eth 321 209 d1 ñ latin capital letter n with tilde 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ý latin capital letter y with acute 336 222 de þ latin capital letter thorn 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 ð latin small letter eth 361 241 f1 ñ latin small letter n with tilde 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ø latin small letter o with stroke 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ý latin small letter y with acute 376 254 fe þ latin small letter thorn 377 255 ff ÿ latin small letter y with diaeresis .te .sh notes cp\ 1252 is also known as windows-1252. .sh see also .br ascii (7), .br charsets (7), .br cp1251 (7), .br iso_8859\-1 (7), .br iso_8859\-15 (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getaddrinfo.3 .so man3/unlocked_stdio.3 .so man3/isalpha.3 .so man3/circleq.3 .so man3/nextup.3 .\" and copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th towupper 3 2021-03-22 "gnu" "linux programmer's manual" .sh name towupper, towupper_l \- convert a wide character to uppercase .sh synopsis .nf .b #include .pp .bi "wint_t towupper(wint_t " wc ); .bi "wint_t towupper_l(wint_t " wc ", locale_t " locale ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br towupper_l (): .nf since glibc 2.10: _xopen_source >= 700 before glibc 2.10: _gnu_source .fi .sh description the .br towupper () function is the wide-character equivalent of the .br toupper (3) function. if .i wc is a lowercase wide character, and there exists an uppercase equivalent in the current locale, it returns the uppercase equivalent of .ir wc . in all other cases, .i wc is returned unchanged. .pp the .br towupper_l () function performs the same task, but performs the conversion based on the character type information in the locale specified by .ir locale . the behavior of .br towupper_l () is undefined if .i locale is the special locale object .b lc_global_locale (see .br duplocale (3)) or is not a valid locale object handle. .pp the argument .i wc must be representable as a .i wchar_t and be a valid character in the locale or be the value .br weof . .sh return value if .i wc was convertible to uppercase, .br towupper () returns its uppercase equivalent; otherwise it returns .ir wc . .sh versions the .br towupper_l () function first appeared in glibc 2.3. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br towupper () t} thread safety mt-safe locale t{ .br towupper_l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br towupper (): c99, posix.1-2001 (xsi); present as an xsi extension in posix.1-2008, but marked obsolete. .pp .br towupper_l (): posix.1-2008. .sh notes the behavior of these functions depends on the .b lc_ctype category of the locale. .pp these functions are not very appropriate for dealing with unicode characters, because unicode knows about three cases: upper, lower, and title case. .sh see also .br iswupper (3), .br towctrans (3), .br towlower (3), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strdup.3 .so man3/rpc.3 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified fri jun 23 01:35:19 1995 andries brouwer .\" (prompted by bas v. de bakker ) .\" corrected (and moved to man3), 980612, aeb .th profil 3 2021-03-22 "linux" "linux programmer's manual" .sh name profil \- execution time profile .sh synopsis .nf .b #include .pp .bi "int profil(unsigned short *" buf ", size_t " bufsiz , .bi " size_t " offset ", unsigned int " scale ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br profil (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description this routine provides a means to find out in what areas your program spends most of its time. the argument .i buf points to .i bufsiz bytes of core. every virtual 10 milliseconds, the user's program counter (pc) is examined: .i offset is subtracted and the result is multiplied by .i scale and divided by 65536. if the resulting value is less than .ir bufsiz , then the corresponding entry in .i buf is incremented. if .i buf is null, profiling is disabled. .sh return value zero is always returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br profil () t} thread safety mt-unsafe .te .hy .ad .sp 1 .sh conforming to similar to a call in svr4 (but not posix.1). .sh bugs .br profil () cannot be used on a program that also uses .b itimer_prof interval timers (see .br setitimer (2)). .pp true kernel profiling provides more accurate results. .\" libc 4.4 contained a kernel patch providing a system call profil. .sh see also .br gprof (1), .br sprof (1), .br setitimer (2), .br sigaction (2), .br signal (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getsockopt.2 .so man3/cosh.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:06:03 1993 by rik faith (faith@cs.unc.edu) .th group 5 2020-04-11 "linux" "linux programmer's manual" .sh name group \- user group file .sh description the .i /etc/group file is a text file that defines the groups on the system. there is one entry per line, with the following format: .pp .in +4n .ex group_name:password:gid:user_list .ee .in .pp the fields are as follows: .tp .i group_name the name of the group. .tp .i password the (encrypted) group password. if this field is empty, no password is needed. .tp .i gid the numeric group id. .tp .i user_list a list of the usernames that are members of this group, separated by commas. .sh files .i /etc/group .sh bugs as the 4.2bsd .br initgroups (3) man page says: no one seems to keep .i /etc/group up-to-date. .sh see also .br chgrp (1), .br gpasswd (1), .br groups (1), .br login (1), .br newgrp (1), .br sg (1), .br getgrent (3), .br getgrnam (3), .br gshadow (5), .br passwd (5), .br vigr (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2009 lefteris dimitroulakis .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\"thanomsub noppaburana made valuable suggestions. .\" .th iso_8859-11 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-11 \- iso 8859-11 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-11 encodes the characters used in the thai language. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-11 characters the following table displays the characters in iso 8859-11 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ก thai character ko kai 242 162 a2 ข thai character kho khai 243 163 a3 ฃ thai character kho khuat 244 164 a4 ค thai character kho khwai 245 165 a5 ฅ thai character kho khon 246 166 a6 ฆ thai character kho rakhang 247 167 a7 ง thai character ngo ngu 250 168 a8 จ thai character cho chan 251 169 a9 ฉ thai character cho ching 252 170 aa ช thai character cho chang 253 171 ab ซ thai character so so 254 172 ac ฌ thai character cho choe 255 173 ad ญ thai character yo ying 256 174 ae ฎ thai character do chada 257 175 af ฏ thai character to patak 260 176 b0 ฐ thai character tho than 261 177 b1 ฑ thai character tho nangmontho 262 178 b2 ฒ thai character tho phuthao 263 179 b3 ณ thai character no nen 264 180 b4 ด thai character do dek 265 181 b5 ต thai character to tao 266 182 b6 ถ thai character tho thung 267 183 b7 ท thai character tho thahan 270 184 b8 ธ thai character tho thong 271 185 b9 น thai character no nu 272 186 ba บ thai character bo baimai 273 187 bb ป thai character po pla 274 188 bc ผ thai character pho phung 275 189 bd ฝ thai character fo fa 276 190 be พ thai character pho phan 277 191 bf ฟ thai character fo fan 300 192 c0 ภ thai character pho samphao 301 193 c1 ม thai character mo ma 302 194 c2 ย thai character yo yak 303 195 c3 ร thai character ro rua 304 196 c4 ฤ thai character ru 305 197 c5 ล thai character lo ling 306 198 c6 ฦ thai character lu 307 199 c7 ว thai character wo waen 310 200 c8 ศ thai character so sala 311 201 c9 ษ thai character so rusi 312 202 ca ส thai character so sua 313 203 cb ห thai character ho hip 314 204 cc ฬ thai character lo chula 315 205 cd อ thai character o ang 316 206 ce ฮ thai character ho nokhuk 317 207 cf ฯ thai character paiyannoi 320 208 d0 ะ thai character sara a 321 209 d1 ั thai character mai han-akat 322 210 d2 า thai character sara aa 323 211 d3 ำ thai character sara am 324 212 d4 ิ thai character sara i 325 213 d5 ี thai character sara ii 326 214 d6 ึ thai character sara ue 327 215 d7 ื thai character sara uee 330 216 d8 ุ thai character sara u 331 217 d9 ู thai character sara uu 332 218 da ฺ thai character phinthu 337 223 df ฿ thai currency symbol baht 340 224 e0 เ thai character sara e 341 225 e1 แ thai character sara ae 342 226 e2 โ thai character sara o 343 227 e3 ใ thai character sara ai maimuan 344 228 e4 ไ thai character sara ai maimalai 345 229 e5 ๅ thai character lakkhangyao 346 230 e6 ๆ thai character maiyamok 347 231 e7 ็ thai character maitaikhu 350 232 e8 ่ thai character mai ek 351 233 e9 ้ thai character mai tho 352 234 ea ๊ thai character mai tri 353 235 eb ๋ thai character mai chattawa 354 236 ec ์ thai character thanthakhat 355 237 ed ํ thai character nikhahit 356 238 ee ๎ thai character yamakkan 357 239 ef ๏ thai character fongman 360 240 f0 ๐ thai digit zero 361 241 f1 ๑ thai digit one 362 242 f2 ๒ thai digit two 363 243 f3 ๓ thai digit three 364 244 f4 ๔ thai digit four 365 245 f5 ๕ thai digit five 366 246 f6 ๖ thai digit six 367 247 f7 ๗ thai digit seven 370 248 f8 ๘ thai digit eight 371 249 f9 ๙ thai digit nine 372 250 fa ๚ thai character angkhankhu 373 251 fb ๛ thai character khomut .te .sh notes iso 8859-11 is the same as tis (thai industrial standard) 620-2253, commonly known as tis-620, except for the character in position a0: iso 8859-11 defines this as no-break space, while tis-620 leaves it undefined. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/open_by_handle_at.2 .so man3/getrpcent.3 ######################################################################## # copyright (c) 2021 alejandro colomar # spdx-license-identifier: gpl-2.0 or lgpl-2.0 ######################################################################## # conventions: # # - follow "makefile conventions" from the "gnu coding standards" closely. # however, when something could be improved, don't follow those. # - uppercase variables, when referring files, refer to files in this repo. # - lowercase variables, when referring files, refer to system files. # - variables starting with '_' refer to absolute paths, including $(destdir). # - variables ending with '_' refer to a subdir of their parent dir, which # is in a variable of the same name but without the '_'. the subdir is # named after this project: <*/man>. # - variables ending in '_rm' refer to files that can be removed (exist). # - variables ending in '_rmdir' refer to dirs that can be removed (exist). # - targets of the form '%-rm' remove their corresponding file '%'. # - targets of the form '%/.-rmdir' remove their corresponding dir '%/'. # - targets of the form '%/.' create their corresponding directory '%/'. # - every file or directory to be created depends on its parent directory. # this avoids race conditions caused by `mkdir -p`. only the root # directories are created with parents. # - the 'force' target is used to make phony some variables that can't be # .phony to avoid some optimizations. # ######################################################################## makeflags += --no-print-directory makeflags += --silent makeflags += --warn-undefined-variables htmlbuilddir := $(curdir)/.html htopts := destdir := prefix := /usr/local datarootdir := $(prefix)/share docdir := $(datarootdir)/doc mandir := $(curdir) mandir := $(datarootdir)/man man1dir := $(mandir)/man1 man2dir := $(mandir)/man2 man3dir := $(mandir)/man3 man4dir := $(mandir)/man4 man5dir := $(mandir)/man5 man6dir := $(mandir)/man6 man7dir := $(mandir)/man7 man8dir := $(mandir)/man8 man1dir := $(mandir)/man1 man2dir := $(mandir)/man2 man3dir := $(mandir)/man3 man4dir := $(mandir)/man4 man5dir := $(mandir)/man5 man6dir := $(mandir)/man6 man7dir := $(mandir)/man7 man8dir := $(mandir)/man8 manext := \.[0-9] man1ext := .1 man2ext := .2 man3ext := .3 man4ext := .4 man5ext := .5 man6ext := .6 man7ext := .7 man8ext := .8 htmldir := $(docdir) htmldir_ := $(htmldir)/man htmlext := .html install := install install_data := $(install) -m 644 install_dir := $(install) -m 755 -d rm := rm rmdir := rmdir --ignore-fail-on-non-empty man_sections := 1 2 3 4 5 6 7 8 .phony: all all: $(make) uninstall $(make) install %/.: $(info - install $(@d)) $(install_dir) $(@d) %-rm: $(info - rm $*) $(rm) $* %-rmdir: $(info - rmdir $(@d)) $(rmdir) $(@d) .phony: install install: install-man | installdirs @: .phony: installdirs installdirs: | installdirs-man @: .phony: uninstall remove uninstall remove: uninstall-man @: .phony: clean clean: find man?/ -type f \ |while read f; do \ rm -f "$(htmlbuilddir)/$$f".*; \ done; ######################################################################## # man manpages := $(sort $(shell find $(mandir)/man?/ -type f | grep '$(manext)$$')) _manpages := $(patsubst $(mandir)/%,$(destdir)$(mandir)/%,$(manpages)) _man1pages := $(filter %$(man1ext),$(_manpages)) _man2pages := $(filter %$(man2ext),$(_manpages)) _man3pages := $(filter %$(man3ext),$(_manpages)) _man4pages := $(filter %$(man4ext),$(_manpages)) _man5pages := $(filter %$(man5ext),$(_manpages)) _man6pages := $(filter %$(man6ext),$(_manpages)) _man7pages := $(filter %$(man7ext),$(_manpages)) _man8pages := $(filter %$(man8ext),$(_manpages)) mandirs := $(sort $(shell find $(mandir)/man? -type d)) _mandirs := $(patsubst $(mandir)/%,$(destdir)$(mandir)/%/.,$(mandirs)) _man1dir := $(filter %man1/.,$(_mandirs)) _man2dir := $(filter %man2/.,$(_mandirs)) _man3dir := $(filter %man3/.,$(_mandirs)) _man4dir := $(filter %man4/.,$(_mandirs)) _man5dir := $(filter %man5/.,$(_mandirs)) _man6dir := $(filter %man6/.,$(_mandirs)) _man7dir := $(filter %man7/.,$(_mandirs)) _man8dir := $(filter %man8/.,$(_mandirs)) _mandir := $(destdir)$(mandir)/. _manpages_rm := $(addsuffix -rm,$(wildcard $(_manpages))) _man1pages_rm := $(filter %$(man1ext)-rm,$(_manpages_rm)) _man2pages_rm := $(filter %$(man2ext)-rm,$(_manpages_rm)) _man3pages_rm := $(filter %$(man3ext)-rm,$(_manpages_rm)) _man4pages_rm := $(filter %$(man4ext)-rm,$(_manpages_rm)) _man5pages_rm := $(filter %$(man5ext)-rm,$(_manpages_rm)) _man6pages_rm := $(filter %$(man6ext)-rm,$(_manpages_rm)) _man7pages_rm := $(filter %$(man7ext)-rm,$(_manpages_rm)) _man8pages_rm := $(filter %$(man8ext)-rm,$(_manpages_rm)) _mandirs_rmdir := $(addsuffix -rmdir,$(wildcard $(_mandirs))) _man1dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man1dir))) _man2dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man2dir))) _man3dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man3dir))) _man4dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man4dir))) _man5dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man5dir))) _man6dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man6dir))) _man7dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man7dir))) _man8dir_rmdir := $(addsuffix -rmdir,$(wildcard $(_man8dir))) _mandir_rmdir := $(addsuffix -rmdir,$(wildcard $(_mandir))) install_manx := $(foreach x,$(man_sections),install-man$(x)) installdirs_manx := $(foreach x,$(man_sections),installdirs-man$(x)) uninstall_manx := $(foreach x,$(man_sections),uninstall-man$(x)) .secondexpansion: $(_manpages): $(destdir)$(mandir)/man%: $(mandir)/man% | $$(@d)/. $(info - install $@) $(install_data) -t $< $@ $(_mandirs): %/.: | $$(dir %). $(_mandir) $(_mandirs_rmdir): $(destdir)$(mandir)/man%/.-rmdir: $$(_man%pages_rm) force $(_mandir_rmdir): $(uninstall_manx) force .phony: $(install_manx) $(install_manx): install-man%: $$(_man%pages) | installdirs-man% @: .phony: install-man install-man: $(install_manx) @: .phony: $(installdirs_manx) $(installdirs_manx): installdirs-man%: $$(_man%dir) $(_mandir) @: .phony: installdirs-man installdirs-man: $(installdirs_manx) @: .phony: $(uninstall_manx) $(uninstall_manx): uninstall-man%: $$(_man%pages_rm) $$(_man%dir_rmdir) @: .phony: uninstall-man uninstall-man: $(_mandir_rmdir) $(uninstall_manx) @: ######################################################################## # html # use with # make htopts=whatever html # the sed removes the lines "content-type: text/html\n\n" .phony: html html: | builddirs-html find man?/ -type f \ |while read f; do \ man2html $(htopts) "$$f" \ |sed -e '1,2d' \ >"$(htmlbuilddir)/$${f}$(htmlext)" \ || exit $$?; \ done; .phony: builddirs-html builddirs-html: find man?/ -type d \ |while read d; do \ $(install_dir) "$(htmlbuilddir)/$$d" || exit $$?; \ done; .phony: install-html install-html: | installdirs-html cd $(htmlbuilddir) && \ find man?/ -type f \ |while read f; do \ $(install_data) -t "$$f" "$(destdir)$(htmldir_)/$$f" || exit $$?; \ done; .phony: installdirs-html installdirs-html: find man?/ -type d \ |while read d; do \ $(install_dir) "$(destdir)$(htmldir_)/$$d" || exit $$?; \ done; .phony: uninstall-html uninstall-html: find man?/ -type f \ |while read f; do \ rm -f "$(destdir)$(htmldir_)/$$f".* || exit $$?; \ done; ######################################################################## # tests # check if groff reports warnings (may be words of sentences not displayed) # from https://lintian.debian.org/tags/groff-message.html .phony: check-groff-warnings check-groff-warnings: groff_log="$$(mktemp --tmpdir manpages-checksxxxx)" || exit $$?; \ for i in man?/*.[1-9]; \ do \ if grep -q 'sh.*name' "$$i"; then \ lc_all=en_us.utf-8 manwidth=80 man --warnings -e utf-8 -l "$$i" > /dev/null 2>| "$$groff_log"; \ [ -s "$$groff_log" ] && { echo "$$i: "; cat "$$groff_log"; echo; }; \ fi; \ done; \ rm -f "$$groff_log" # someone might also want to look at /var/catman/cat2 or so ... # a problem is that the location of cat pages varies a lot ######################################################################## force: .so man3/tan.3 .so man3/inet_net_pton.3 .\" copyright (c) 1980, 1991 regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)alloca.3 5.1 (berkeley) 5/2/91 .\" .\" converted mon nov 29 11:05:55 1993 by rik faith .\" modified tue oct 22 23:41:56 1996 by eric s. raymond .\" modified 2002-07-17, aeb .\" 2008-01-24, mtk: .\" various rewrites and additions (notes on longjmp() and sigsegv). .\" weaken warning against use of alloca() (as per debian bug 461100). .\" .th alloca 3 2021-03-22 "gnu" "linux programmer's manual" .sh name alloca \- allocate memory that is automatically freed .sh synopsis .nf .b #include .pp .bi "void *alloca(size_t " size ); .fi .sh description the .br alloca () function allocates .i size bytes of space in the stack frame of the caller. this temporary space is automatically freed when the function that called .br alloca () returns to its caller. .sh return value the .br alloca () function returns a pointer to the beginning of the allocated space. if the allocation causes stack overflow, program behavior is undefined. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br alloca () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is not in posix.1. .pp there is evidence that the .br alloca () function appeared in 32v, pwb, pwb.2, 3bsd, and 4bsd. there is a man page for it in 4.3bsd. linux uses the gnu version. .sh notes the .br alloca () function is machine- and compiler-dependent. for certain applications, its use can improve efficiency compared to the use of .br malloc (3) plus .br free (3). in certain cases, it can also simplify memory deallocation in applications that use .br longjmp (3) or .br siglongjmp (3). otherwise, its use is discouraged. .pp because the space allocated by .br alloca () is allocated within the stack frame, that space is automatically freed if the function return is jumped over by a call to .br longjmp (3) or .br siglongjmp (3). .pp the space allocated by .br alloca () is .i not automatically deallocated if the pointer that refers to it simply goes out of scope. .pp do not attempt to .br free (3) space allocated by .br alloca ()! .ss notes on the gnu version normally, .br gcc (1) translates calls to .br alloca () with inlined code. this is not done when either the .ir "\-ansi" , .ir "\-std=c89" , .ir "\-std=c99" , or the .ir "\-std=c11" option is given .br and the header .i is not included. otherwise, (without an \-ansi or \-std=c* option) the glibc version of .i includes .i and that contains the lines: .pp .in +4n .ex #ifdef __gnuc__ #define alloca(size) __builtin_alloca (size) #endif .ee .in .pp with messy consequences if one has a private version of this function. .pp the fact that the code is inlined means that it is impossible to take the address of this function, or to change its behavior by linking with a different library. .pp the inlined code often consists of a single instruction adjusting the stack pointer, and does not check for stack overflow. thus, there is no null error return. .sh bugs there is no error indication if the stack frame cannot be extended. (however, after a failed allocation, the program is likely to receive a .b sigsegv signal if it attempts to access the unallocated space.) .pp on many systems .br alloca () cannot be used inside the list of arguments of a function call, because the stack space reserved by .br alloca () would appear on the stack in the middle of the space for the function arguments. .sh see also .br brk (2), .br longjmp (3), .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" (c) copyright 1992-1999 rickard e. faith and david a. wheeler .\" (faith@cs.unc.edu and dwheeler@ida.org) .\" and (c) copyright 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2007-05-30 created by mtk, using text from old man.7 plus .\" rewrites and additional text. .\" .th man-pages 7 2021-03-22 "linux" "linux programmer's manual" .sh name man-pages \- conventions for writing linux man pages .sh synopsis .b man .ri [ section ] .i title .sh description this page describes the conventions that should be employed when writing man pages for the linux \fiman-pages\fp project, which documents the user-space api provided by the linux kernel and the gnu c library. the project thus provides most of the pages in section 2, many of the pages that appear in sections 3, 4, and 7, and a few of the pages that appear in sections 1, 5, and 8 of the man pages on a linux system. the conventions described on this page may also be useful for authors writing man pages for other projects. .ss sections of the manual pages the manual sections are traditionally defined as follows: .tp .b 1 user commands (programs) commands that can be executed by the user from within a shell. .tp .b 2 system calls functions which wrap operations performed by the kernel. .tp .b 3 library calls all library functions excluding the system call wrappers (most of the .i libc functions). .tp .b 4 special files (devices) files found in .i /dev which allow to access to devices through the kernel. .tp .b 5 file formats and configuration files describes various human-readable file formats and configuration files. .tp .b 6 games games and funny little programs available on the system. .tp .b 7 overview, conventions, and miscellaneous overviews or descriptions of various topics, conventions, and protocols, character set standards, the standard filesystem layout, and miscellaneous other things. .tp .b 8 system management commands commands like .br mount (8), many of which only root can execute. .\" .tp .\" .b 9 kernel routines .\" this is an obsolete manual section. .\" once it was thought a good idea to document the linux kernel here, .\" but in fact very little has been documented, and the documentation .\" that exists is outdated already. .\" there are better sources of .\" information for kernel developers. .ss macro package new manual pages should be marked up using the .b groff an.tmac package described in .br man (7). this choice is mainly for consistency: the vast majority of existing linux manual pages are marked up using these macros. .ss conventions for source file layout please limit source code line length to no more than about 75 characters wherever possible. this helps avoid line-wrapping in some mail clients when patches are submitted inline. .ss title line the first command in a man page should be a .b th command: .pp .rs .b \&.th .i "title section date source manual" .re .pp the arguments of the command are as follows: .tp .i title the title of the man page, written in all caps (e.g., .ir man-pages ). .tp .i section the section number in which the man page should be placed (e.g., .ir 7 ). .tp .i date the date of the last nontrivial change that was made to the man page. (within the .i man-pages project, the necessary updates to these timestamps are handled automatically by scripts, so there is no need to manually update them as part of a patch.) dates should be written in the form yyyy-mm-dd. .tp .i source the source of the command, function, or system call. .ip for those few \fiman-pages\fp pages in sections 1 and 8, probably you just want to write .ir gnu . .ip for system calls, just write .ir "linux" . (an earlier practice was to write the version number of the kernel from which the manual page was being written/checked. however, this was never done consistently, and so was probably worse than including no version number. henceforth, avoid including a version number.) .ip for library calls that are part of glibc or one of the other common gnu libraries, just use .ir "gnu c library" ", " gnu , or an empty string. .ip for section 4 pages, use .ir "linux" . .ip in cases of doubt, just write .ir linux ", or " gnu . .tp .i manual the title of the manual (e.g., for section 2 and 3 pages in the \fiman-pages\fp package, use .ir "linux programmer's manual" ). .\" .ss sections within a manual page the list below shows conventional or suggested sections. most manual pages should include at least the .b highlighted sections. arrange a new manual page so that sections are placed in the order shown in the list. .pp .rs .ts l l. \fbname\fp \fbsynopsis\fp configuration [normally only in section 4] \fbdescription\fp options [normally only in sections 1, 8] exit status [normally only in sections 1, 8] return value [normally only in sections 2, 3] .\" may 07: few current man pages have an error handling section,,, .\" error handling, errors [typically only in sections 2, 3] .\" may 07: almost no current man pages have a usage section,,, .\" usage, .\" diagnostics, .\" may 07: almost no current man pages have a security section,,, .\" security, environment files versions [normally only in sections 2, 3] attributes [normally only in sections 2, 3] conforming to notes bugs examples .\" authors sections are discouraged authors [discouraged] reporting bugs [not used in man-pages] copyright [not used in man-pages] \fbsee also\fp .te .re .pp .ir "where a traditional heading would apply" ", " "please use it" ; this kind of consistency can make the information easier to understand. if you must, you can create your own headings if they make things easier to understand (this can be especially useful for pages in sections 4 and 5). however, before doing this, consider whether you could use the traditional headings, with some subsections (\fi.ss\fp) within those sections. .pp the following list elaborates on the contents of each of the above sections. .tp .b name the name of this manual page. .ip see .br man (7) for important details of the line(s) that should follow the \fb.sh name\fp command. all words in this line (including the word immediately following the "\e\-") should be in lowercase, except where english or technical terminological convention dictates otherwise. .tp .b synopsis a brief summary of the command or function's interface. .ip for commands, this shows the syntax of the command and its arguments (including options); boldface is used for as-is text and italics are used to indicate replaceable arguments. brackets ([]) surround optional arguments, vertical bars (|) separate choices, and ellipses (\&...) can be repeated. for functions, it shows any required data declarations or .b #include directives, followed by the function declaration. .ip where a feature test macro must be defined in order to obtain the declaration of a function (or a variable) from a header file, then the synopsis should indicate this, as described in .br feature_test_macros (7). .\" fixme . say something here about compiler options .tp .b configuration configuration details for a device. .ip this section normally appears only in section 4 pages. .tp .b description an explanation of what the program, function, or format does. .ip discuss how it interacts with files and standard input, and what it produces on standard output or standard error. omit internals and implementation details unless they're critical for understanding the interface. describe the usual case; for information on command-line options of a program use the .b options section. .\" if there is some kind of input grammar or complex set of subcommands, .\" consider describing them in a separate .\" .b usage .\" section (and just place an overview in the .\" .b description .\" section). .ip when describing new behavior or new flags for a system call or library function, be careful to note the kernel or c library version that introduced the change. the preferred method of noting this information for flags is as part of a .b .tp list, in the following form (here, for a new system call flag): .rs 16 .tp .br xyz_flag " (since linux 3.7)" description of flag... .re .ip including version information is especially useful to users who are constrained to using older kernel or c library versions (which is typical in embedded systems, for example). .tp .b options a description of the command-line options accepted by a program and how they change its behavior. .ip this section should appear only for section 1 and 8 manual pages. .\" .tp .\" .b usage .\" describes the grammar of any sublanguage this implements. .tp .b exit status a list of the possible exit status values of a program and the conditions that cause these values to be returned. .ip this section should appear only for section 1 and 8 manual pages. .tp .b return value for section 2 and 3 pages, this section gives a list of the values the library routine will return to the caller and the conditions that cause these values to be returned. .tp .b errors for section 2 and 3 manual pages, this is a list of the values that may be placed in .i errno in the event of an error, along with information about the cause of the errors. .ip where several different conditions produce the same error, the preferred approach is to create separate list entries (with duplicate error names) for each of the conditions. this makes the separate conditions clear, may make the list easier to read, and allows metainformation (e.g., kernel version number where the condition first became applicable) to be more easily marked for each condition. .ip .ir "the error list should be in alphabetical order" . .tp .b environment a list of all environment variables that affect the program or function and how they affect it. .tp .b files a list of the files the program or function uses, such as configuration files, startup files, and files the program directly operates on. .ip give the full pathname of these files, and use the installation process to modify the directory part to match user preferences. for many programs, the default installation location is in .ir /usr/local , so your base manual page should use .i /usr/local as the base. .\" may 07: almost no current man pages have a diagnostics section; .\" "return value" or "exit status" is preferred. .\" .tp .\" .b diagnostics .\" gives an overview of the most common error messages and how to .\" cope with them. .\" you don't need to explain system error messages .\" or fatal signals that can appear during execution of any program .\" unless they're special in some way to the program. .\" .\" may 07: almost no current man pages have a security section. .\".tp .\".b security .\"discusses security issues and implications. .\"warn about configurations or environments that should be avoided, .\"commands that may have security implications, and so on, especially .\"if they aren't obvious. .\"discussing security in a separate section isn't necessary; .\"if it's easier to understand, place security information in the .\"other sections (such as the .\" .b description .\" or .\" .b usage .\" section). .\" however, please include security information somewhere! .tp .b attributes a summary of various attributes of the function(s) documented on this page. see .br attributes (7) for further details. .tp .b versions a brief summary of the linux kernel or glibc versions where a system call or library function appeared, or changed significantly in its operation. .ip as a general rule, every new interface should include a versions section in its manual page. unfortunately, many existing manual pages don't include this information (since there was no policy to do so when they were written). patches to remedy this are welcome, but, from the perspective of programmers writing new code, this information probably matters only in the case of kernel interfaces that have been added in linux 2.4 or later (i.e., changes since kernel 2.2), and library functions that have been added to glibc since version 2.1 (i.e., changes since glibc 2.0). .ip the .br syscalls (2) manual page also provides information about kernel versions in which various system calls first appeared. .tp .b conforming to a description of any standards or conventions that relate to the function or command described by the manual page. .ip the preferred terms to use for the various standards are listed as headings in .br standards (7). .ip for a page in section 2 or 3, this section should note the posix.1 version(s) that the call conforms to, and also whether the call is specified in c99. (don't worry too much about other standards like sus, susv2, and xpg, or the svr4 and 4.xbsd implementation standards, unless the call was specified in those standards, but isn't in the current version of posix.1.) .ip if the call is not governed by any standards but commonly exists on other systems, note them. if the call is linux-specific, note this. .ip if this section consists of just a list of standards (which it commonly does), terminate the list with a period (\(aq.\(aq). .tp .b notes miscellaneous notes. .ip for section 2 and 3 man pages you may find it useful to include subsections (\fbss\fp) named \filinux notes\fp and \figlibc notes\fp. .ip in section 2, use the heading .i "c library/kernel differences" to mark off notes that describe the differences (if any) between the c library wrapper function for a system call and the raw system call interface provided by the kernel. .tp .b bugs a list of limitations, known defects or inconveniences, and other questionable activities. .tp .b examples one or more examples demonstrating how this function, file, or command is used. .ip for details on writing example programs, see \fiexample programs\fp below. .tp .b authors a list of authors of the documentation or program. .ip \fbuse of an authors section is strongly discouraged\fp. generally, it is better not to clutter every page with a list of (over time potentially numerous) authors; if you write or significantly amend a page, add a copyright notice as a comment in the source file. if you are the author of a device driver and want to include an address for reporting bugs, place this under the bugs section. .tp .b reporting bugs the .ir man-pages project doesn't use a reporting bugs section in manual pages. information on reporting bugs is instead supplied in the script-generated colophon section. however, various projects do use a reporting bugs section. it is recommended to place it near the foot of the page. .tp .b copyright the .ir man-pages project doesn't use a copyright section in manual pages. copyright information is instead maintained in the page source. in pages where this section is present, it is recommended to place it near the foot of the page, just above see also. .tp .b see also a comma-separated list of related man pages, possibly followed by other related pages or documents. .ip the list should be ordered by section number and then alphabetically by name. do not terminate this list with a period. .ip where the see also list contains many long manual page names, to improve the visual result of the output, it may be useful to employ the .i .ad l (don't right justify) and .i .nh (don't hyphenate) directives. hyphenation of individual page names can be prevented by preceding words with the string "\e%". .ip given the distributed, autonomous nature of foss projects and their documentation, it is sometimes necessary\(emand in many cases desirable\(emthat the see also section includes references to manual pages provided by other projects. .sh formatting and wording conventions the following subsections note some details for preferred formatting and wording conventions in various sections of the pages in the .ir man-pages project. .ss synopsis wrap the function prototype(s) in a .ir .nf / .fi pair to prevent filling. .pp in general, where more than one function prototype is shown in the synopsis, the prototypes should .i not be separated by blank lines. however, blank lines (achieved using .ir .pp ) may be added in the following cases: .ip * 3 to separate long lists of function prototypes into related groups (see for example .br list (3)); .ip * in other cases that may improve readability. .pp in the synopsis, a long function prototype may need to be continued over to the next line. the continuation line is indented according to the following rules: .ip 1. 3 if there is a single such prototype that needs to be continued, then align the continuation line so that when the page is rendered on a fixed-width font device (e.g., on an xterm) the continuation line starts just below the start of the argument list in the line above. (exception: the indentation may be adjusted if necessary to prevent a very long continuation line or a further continuation line where the function prototype is very long.) as an example: .pp .rs .nf .bi "int tcsetattr(int " fd ", int " optional_actions , .bi " const struct termios *" termios_p ); .fi .re .ip 2. 3 but, where multiple functions in the synopsis require continuation lines, and the function names have different lengths, then align all continuation lines to start in the same column. this provides a nicer rendering in pdf output (because the synopsis uses a variable width font where spaces render narrower than most characters). as an example: .pp .rs .nf .bi "int getopt(int " argc ", char * const " argv[] , .bi " const char *" optstring ); .bi "int getopt_long(int " argc ", char * const " argv[] , .bi " const char *" optstring , .bi " const struct option *" longopts ", int *" longindex ); .fi .re .ss return value the preferred wording to describe how .i errno is set is .ri \(dq errno is set to indicate the error" or similar. .\" before man-pages 5.11, many different wordings were used, which .\" was confusing, and potentially made scripted edits more difficult. this wording is consistent with the wording used in both posix.1 and freebsd. .ss attributes .\" see man-pages commit c466875ecd64ed3d3cd3e578406851b7dfb397bf note the following: .ip * 3 wrap the table in this section in a .ir ".ad\ l" / .ad pair to disable text filling and a .ir .nh / .hy pair to disable hyphenation. .ip * ensure that the table occupies the full page width through the use of an .i lbx description for one of the columns (usually the first column, though in some cases the last column if it contains a lot of text). .ip * make free use of .ir t{ / t} macro pairs to allow table cells to be broken over multiple lines (also bearing in mind that pages may sometimes be rendered to a width of less than 80 columns). .pp for examples of all of the above, see the source code of various pages. .sh style guide the following subsections describe the preferred style for the .ir man-pages project. for details not covered below, the chicago manual of style is usually a good source; try also grepping for preexisting usage in the project source tree. .ss use of gender-neutral language as far as possible, use gender-neutral language in the text of man pages. use of "they" ("them", "themself", "their") as a gender-neutral singular pronoun is acceptable. .\" .ss formatting conventions for manual pages describing commands for manual pages that describe a command (typically in sections 1 and 8), the arguments are always specified using italics, .ir "even in the synopsis section" . .pp the name of the command, and its options, should always be formatted in bold. .\" .ss formatting conventions for manual pages describing functions for manual pages that describe functions (typically in sections 2 and 3), the arguments are always specified using italics, .ir "even in the synopsis section" , where the rest of the function is specified in bold: .pp .bi " int myfunction(int " argc ", char **" argv ); .pp variable names should, like argument names, be specified in italics. .pp any reference to the subject of the current manual page should be written with the name in bold followed by a pair of parentheses in roman (normal) font. for example, in the .br fcntl (2) man page, references to the subject of the page would be written as: .br fcntl (). the preferred way to write this in the source file is: .pp .ex .br fcntl () .ee .pp (using this format, rather than the use of "\efb...\efp()" makes it easier to write tools that parse man page source files.) .\" .ss use semantic newlines in the source of a manual page, new sentences should be started on new lines, and long sentences should be split into lines at clause breaks (commas, semicolons, colons, and so on). this convention, sometimes known as "semantic newlines", makes it easier to see the effect of patches, which often operate at the level of individual sentences or sentence clauses. .\" .ss formatting conventions (general) paragraphs should be separated by suitable markers (usually either .i .pp or .ir .ip ). do .i not separate paragraphs using blank lines, as this results in poor rendering in some output formats (such as postscript and pdf). .pp filenames (whether pathnames, or references to header files) are always in italics (e.g., .ir ), except in the synopsis section, where included files are in bold (e.g., .br "#include " ). when referring to a standard header file include, specify the header file surrounded by angle brackets, in the usual c way (e.g., .ir ). .pp special macros, which are usually in uppercase, are in bold (e.g., .br maxint ). exception: don't boldface null. .pp when enumerating a list of error codes, the codes are in bold (this list usually uses the .b \&.tp macro). .pp complete commands should, if long, be written as an indented line on their own, with a blank line before and after the command, for example .pp .in +4n .ex man 7 man\-pages .ee .in .pp if the command is short, then it can be included inline in the text, in italic format, for example, .ir "man 7 man-pages" . in this case, it may be worth using nonbreaking spaces ("\e\ ") at suitable places in the command. command options should be written in italics (e.g., .ir \-l ). .pp expressions, if not written on a separate indented line, should be specified in italics. again, the use of nonbreaking spaces may be appropriate if the expression is inlined with normal text. .pp when showing example shell sessions, user input should be formatted in bold, for example .pp .in +4n .ex $ \fbdate\fp thu jul 7 13:01:27 cest 2016 .ee .in .pp any reference to another man page should be written with the name in bold, .i always followed by the section number, formatted in roman (normal) font, without any separating spaces (e.g., .br intro (2)). the preferred way to write this in the source file is: .pp .ex .br intro (2) .ee .pp (including the section number in cross references lets tools like .br man2html (1) create properly hyperlinked pages.) .pp control characters should be written in bold face, with no quotes; for example, .br \(hax . .ss spelling starting with release 2.59, .i man-pages follows american spelling conventions (previously, there was a random mix of british and american spellings); please write all new pages and patches according to these conventions. .pp aside from the well-known spelling differences, there are a few other subtleties to watch for: .ip * 3 american english tends to use the forms "backward", "upward", "toward", and so on rather than the british forms "backwards", "upwards", "towards", and so on. .ip * opinions are divided on "acknowledgement" vs "acknowledgment". the latter is predominant, but not universal usage in american english. posix and the bsd license use the former spelling. in the linux man-pages project, we use "acknowledgement". .ss bsd version numbers the classical scheme for writing bsd version numbers is .ir x.ybsd , where .i x.y is the version number (e.g., 4.2bsd). avoid forms such as .ir "bsd 4.3" . .ss capitalization in subsection ("ss") headings, capitalize the first word in the heading, but otherwise use lowercase, except where english usage (e.g., proper nouns) or programming language requirements (e.g., identifier names) dictate otherwise. for example: .pp .ex .ss unicode under linux .ee .\" .ss indentation of structure definitions, shell session logs, and so on when structure definitions, shell session logs, and so on are included in running text, indent them by 4 spaces (i.e., a block enclosed by .i ".in\ +4n" and .ir ".in" ), format them using the .i .ex and .i ee macros, and surround them with suitable paragraph markers (either .i .pp or .ir .ip ). for example: .pp .in +4n .ex .pp .in +4n .ex int main(int argc, char *argv[]) { return 0; } .ee .in .pp .ee .in .ss preferred terms the following table lists some preferred terms to use in man pages, mainly to ensure consistency across pages. .ad l .ts l l l --- l l ll. term avoid using notes bit mask bitmask built-in builtin epoch epoch t{ for the unix epoch (00:00:00, 1 jan 1970 utc) t} filename file name filesystem file system hostname host name inode i-node lowercase lower case, lower-case nonzero non-zero pathname path name pseudoterminal pseudo-terminal privileged port t{ reserved port, system port t} real-time t{ realtime, real time t} run time runtime saved set-group-id t{ saved group id, saved set-gid t} saved set-user-id t{ saved user id, saved set-uid t} set-group-id set-gid, setgid set-user-id set-uid, setuid superuser t{ super user, super-user t} superblock t{ super block, super-block t} timestamp time stamp timezone time zone uppercase upper case, upper-case usable useable user space userspace username user name x86-64 x86_64 t{ except if referring to result of "uname\ \-m" or similar t} zeros zeroes .te .pp see also the discussion .ir "hyphenation of attributive compounds" below. .ss terms to avoid the following table lists some terms to avoid using in man pages, along with some suggested alternatives, mainly to ensure consistency across pages. .ad l .ts l l l --- l l l. avoid use instead notes 32bit 32-bit t{ same for 8-bit, 16-bit, etc. t} current process calling process t{ a common mistake made by kernel programmers when writing man pages t} manpage t{ man page, manual page t} minus infinity negative infinity non-root unprivileged user non-superuser unprivileged user nonprivileged unprivileged os operating system plus infinity positive infinity pty pseudoterminal tty terminal unices unix systems unixes unix systems .te .ad .\" .ss trademarks use the correct spelling and case for trademarks. the following is a list of the correct spellings of various relevant trademarks that are sometimes misspelled: .pp dg/ux hp-ux unix unixware .ss null, nul, null pointer, and null byte a .ir "null pointer" is a pointer that points to nothing, and is normally indicated by the constant .ir null . on the other hand, .i nul is the .ir "null byte", a byte with the value 0, represented in c via the character constant .ir \(aq\e0\(aq . .pp the preferred term for the pointer is "null pointer" or simply "null"; avoid writing "null pointer". .pp the preferred term for the byte is "null byte". avoid writing "nul", since it is too easily confused with "null". avoid also the terms "zero byte" and "null character". the byte that terminates a c string should be described as "the terminating null byte"; strings may be described as "null-terminated", but avoid the use of "nul-terminated". .ss hyperlinks for hyperlinks, use the .ir .ur / .ue macro pair (see .br groff_man (7)). this produces proper hyperlinks that can be used in a web browser, when rendering a page with, say: .pp browser=firefox man -h pagename .ss use of e.g., i.e., etc., a.k.a., and similar in general, the use of abbreviations such as "e.g.", "i.e.", "etc.", "cf.", and "a.k.a." should be avoided, in favor of suitable full wordings ("for example", "that is", "and so on", "compare to", "also known as"). .pp the only place where such abbreviations may be acceptable is in .i short parenthetical asides (e.g., like this one). .pp always include periods in such abbreviations, as shown here. in addition, "e.g." and "i.e." should always be followed by a comma. .ss em-dashes the way to write an em-dash\(emthe glyph that appears at either end of this subphrase\(emin *roff is with the macro "\e(em". (on an ascii terminal, an em-dash typically renders as two hyphens, but in other typographical contexts it renders as a long dash.) em-dashes should be written .i without surrounding spaces. .ss hyphenation of attributive compounds compound terms should be hyphenated when used attributively (i.e., to qualify a following noun). some examples: .pp 32-bit value command-line argument floating-point number run-time check user-space function wide-character string .ss hyphenation with multi, non, pre, re, sub, and so on the general tendency in modern english is not to hyphenate after prefixes such as "multi", "non", "pre", "re", "sub", and so on. manual pages should generally follow this rule when these prefixes are used in natural english constructions with simple suffixes. the following list gives some examples of the preferred forms: .pp interprocess multithreaded multiprocess nonblocking nondefault nonempty noninteractive nonnegative nonportable nonzero preallocated precreate prerecorded reestablished reinitialize rearm reread subcomponent subdirectory subsystem .pp hyphens should be retained when the prefixes are used in nonstandard english words, with trademarks, proper nouns, acronyms, or compound terms. some examples: .pp non-ascii non-english non-null non-real-time .pp finally, note that "re-create" and "recreate" are two different verbs, and the former is probably what you want. .\" .ss generating optimal glyphs where a real minus character is required (e.g., for numbers such as \-1, for man page cross references such as .br utf\-8 (7), or when writing options that have a leading dash, such as in .ir "ls\ \-l"), use the following form in the man page source: .pp \e\- .pp this guideline applies also to code examples. .pp the use of real minus signs serves the following purposes: .\" https://lore.kernel.org/linux-man/20210121061158.5ul7226fgbrmodbt@localhost.localdomain/ .ip * 3 to provide better renderings on various targets other than ascii terminals, notably in pdf and on unicode/utf\-8-capable terminals. .ip * to generate glyphs that when copied from rendered pages will produce real minus signs when pasted into a terminal. .pp to produce unslanted single quotes that render well in ascii, utf-8, and pdf, use "\e(aq" ("apostrophe quote"); for example .pp \e(aqc\e(aq .pp where .i c is the quoted character. this guideline applies also to character constants used in code examples. .pp where a proper caret (\(ha) that renders well in both a terminal and pdf is required, use "\\(ha". this is especially necessary in code samples, to get a nicely rendered caret when rendering to pdf. .pp using a naked "\(ti" character results in a poor rendering in pdf. instead use "\\(ti". this is especially necessary in code samples, to get a nicely rendered tilde when rendering to pdf. .\" .ss example programs and shell sessions manual pages may include example programs demonstrating how to use a system call or library function. however, note the following: .ip * 3 example programs should be written in c. .ip * an example program is necessary and useful only if it demonstrates something beyond what can easily be provided in a textual description of the interface. an example program that does nothing other than call an interface usually serves little purpose. .ip * example programs should ideally be short (e.g., a good example can often be provided in less than 100 lines of code), though in some cases longer programs may be necessary to properly illustrate the use of an api. .ip * expressive code is appreciated. .ip * comments should included where helpful. complete sentences in free-standing comments should be terminated by a period. periods should generally be omitted in "tag" comments (i.e., comments that are placed on the same line of code); such comments are in any case typically brief phrases rather than complete sentences. .ip * example programs should do error checking after system calls and library function calls. .ip * example programs should be complete, and compile without warnings when compiled with \ficc\ \-wall\fp. .ip * where possible and appropriate, example programs should allow experimentation, by varying their behavior based on inputs (ideally from command-line arguments, or alternatively, via input read by the program). .ip * example programs should be laid out according to kernighan and ritchie style, with 4-space indents. (avoid the use of tab characters in source code!) the following command can be used to format your source code to something close to the preferred style: .ip indent \-npro \-kr \-i4 \-ts4 \-sob \-l72 \-ss \-nut \-psl prog.c .ip * for consistency, all example programs should terminate using either of: .ip exit(exit_success); exit(exit_failure); .ip avoid using the following forms to terminate a program: .ip exit(0); exit(1); return n; .ip * if there is extensive explanatory text before the program source code, mark off the source code with a subsection heading .ir "program source" , as in: .ip .ss program source .ip always do this if the explanatory text includes a shell session log. .pp if you include a shell session log demonstrating the use of a program or other system feature: .ip * 3 place the session log above the source code listing .ip * indent the session log by four spaces. .ip * boldface the user input text, to distinguish it from output produced by the system. .pp for some examples of what example programs should look like, see .br wait (2) and .br pipe (2). .sh examples for canonical examples of how man pages in the .i man-pages package should look, see .br pipe (2) and .br fcntl (2). .sh see also .br man (1), .br man2html (1), .br attributes (7), .br groff (7), .br groff_man (7), .br man (7), .br mdoc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mallinfo 3 2021-03-22 "linux" "linux programmer's manual" .sh name mallinfo, mallinfo2 \- obtain memory allocation information .sh synopsis .nf .b #include .pp .b struct mallinfo mallinfo(void); .b struct mallinfo2 mallinfo2(void); .fi .sh description these functions return a copy of a structure containing information about memory allocations performed by .br malloc (3) and related functions. the structure returned by each function contains the same fields. however, the older function, .br mallinfo (), is deprecated since the type used for the fields is too small (see bugs). .pp note that not all allocations are visible to these functions; see bugs and consider using .br malloc_info (3) instead. .pp the .i mallinfo2 structure returned by .br mallinfo2 () is defined as follows: .pp .in +4n .ex struct mallinfo2 { size_t arena; /* non\-mmapped space allocated (bytes) */ size_t ordblks; /* number of free chunks */ size_t smblks; /* number of free fastbin blocks */ size_t hblks; /* number of mmapped regions */ size_t hblkhd; /* space allocated in mmapped regions (bytes) */ size_t usmblks; /* see below */ size_t fsmblks; /* space in freed fastbin blocks (bytes) */ size_t uordblks; /* total allocated space (bytes) */ size_t fordblks; /* total free space (bytes) */ size_t keepcost; /* top\-most, releasable space (bytes) */ }; .ee .in .pp the .i mallinfo structure returned by the deprecated .br mallinfo () function is exactly the same, except that the fields are typed as .ir int . .pp the structure fields contain the following information: .tp 10 .i arena the total amount of memory allocated by means other than .br mmap (2) (i.e., memory allocated on the heap). this figure includes both in-use blocks and blocks on the free list. .tp .i ordblks the number of ordinary (i.e., non-fastbin) free blocks. .tp .i smblks .\" the glibc info page wrongly says this field is unused .\" https://sourceware.org/bugzilla/show_bug.cgi?id=26746 the number of fastbin free blocks (see .br mallopt (3)). .tp .i hblks the number of blocks currently allocated using .br mmap (2). (see the discussion of .b m_mmap_threshold in .br mallopt (3).) .tp .i hblkhd the number of bytes in blocks currently allocated using .br mmap (2). .tp .i usmblks this field is unused, and is always 0. .\" it seems to have been zero since at least as far back as glibc 2.15 historically, it was the "highwater mark" for allocated space\(emthat is, the maximum amount of space that was ever allocated (in bytes); this field was maintained only in nonthreading environments. .tp .i fsmblks .\" the glibc info page wrongly says this field is unused .\" https://sourceware.org/bugzilla/show_bug.cgi?id=26746 the total number of bytes in fastbin free blocks. .tp .i uordblks the total number of bytes used by in-use allocations. .tp .i fordblks the total number of bytes in free blocks. .tp .i keepcost the total amount of releasable free space at the top of the heap. this is the maximum number of bytes that could ideally (i.e., ignoring page alignment restrictions, and so on) be released by .br malloc_trim (3). .sh versions .\" mallinfo(): available already in glibc 2.0, possibly earlier the .br mallinfo2 () function was added .\" commit e3960d1c57e57f33e0e846d615788f4ede73b945 in glibc 2.33. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br mallinfo (), .br mallinfo2 () t} thread safety t{ mt-unsafe init const:mallopt t} .te .hy .ad .sp 1 .br mallinfo ()/ .br mallinfo2 () would access some global internal objects. if modify them with non-atomically, may get inconsistent results. the identifier .i mallopt in .i const:mallopt mean that .br mallopt () would modify the global internal objects with atomics, that make sure .br mallinfo ()/ .br mallinfo2 () is safe enough, others modify with non-atomically maybe not. .sh conforming to these functions are not specified by posix or the c standards. a .br mallinfo () function exists on many system v derivatives, and was specified in the svid. .sh bugs .\" fixme . http://sourceware.org/bugzilla/show_bug.cgi?id=208 .\" see the 24 aug 2011 mail by paul pluzhnikov: .\" "[patch] fix mallinfo() to accumulate results for all arenas" .\" on libc-alpha@sourceware.org .b information is returned for only the main memory allocation area. allocations in other arenas are excluded. see .br malloc_stats (3) and .br malloc_info (3) for alternatives that include information about other arenas. .pp the fields of the .i mallinfo structure that is returned by the older .br mallinfo () function are typed as .ir int . however, because some internal bookkeeping values may be of type .ir long , the reported values may wrap around zero and thus be inaccurate. .sh examples the program below employs .br mallinfo2 () to retrieve memory allocation statistics before and after allocating and freeing some blocks of memory. the statistics are displayed on standard output. .pp the first two command-line arguments specify the number and size of blocks to be allocated with .br malloc (3). .pp the remaining three arguments specify which of the allocated blocks should be freed with .br free (3). these three arguments are optional, and specify (in order): the step size to be used in the loop that frees blocks (the default is 1, meaning free all blocks in the range); the ordinal position of the first block to be freed (default 0, meaning the first allocated block); and a number one greater than the ordinal position of the last block to be freed (default is one greater than the maximum block number). if these three arguments are omitted, then the defaults cause all allocated blocks to be freed. .pp in the following example run of the program, 1000 allocations of 100 bytes are performed, and then every second allocated block is freed: .pp .in +4n .ex $ \fb./a.out 1000 100 2\fp ============== before allocating blocks ============== total non\-mmapped bytes (arena): 0 # of free chunks (ordblks): 1 # of free fastbin blocks (smblks): 0 # of mapped regions (hblks): 0 bytes in mapped regions (hblkhd): 0 max. total allocated space (usmblks): 0 free bytes held in fastbins (fsmblks): 0 total allocated space (uordblks): 0 total free space (fordblks): 0 topmost releasable block (keepcost): 0 ============== after allocating blocks ============== total non\-mmapped bytes (arena): 135168 # of free chunks (ordblks): 1 # of free fastbin blocks (smblks): 0 # of mapped regions (hblks): 0 bytes in mapped regions (hblkhd): 0 max. total allocated space (usmblks): 0 free bytes held in fastbins (fsmblks): 0 total allocated space (uordblks): 104000 total free space (fordblks): 31168 topmost releasable block (keepcost): 31168 ============== after freeing blocks ============== total non\-mmapped bytes (arena): 135168 # of free chunks (ordblks): 501 # of free fastbin blocks (smblks): 0 # of mapped regions (hblks): 0 bytes in mapped regions (hblkhd): 0 max. total allocated space (usmblks): 0 free bytes held in fastbins (fsmblks): 0 total allocated space (uordblks): 52000 total free space (fordblks): 83168 topmost releasable block (keepcost): 31168 .ee .in .ss program source \& .ex #include #include #include static void display_mallinfo2(void) { struct mallinfo2 mi; mi = mallinfo2(); printf("total non\-mmapped bytes (arena): %zu\en", mi.arena); printf("# of free chunks (ordblks): %zu\en", mi.ordblks); printf("# of free fastbin blocks (smblks): %zu\en", mi.smblks); printf("# of mapped regions (hblks): %zu\en", mi.hblks); printf("bytes in mapped regions (hblkhd): %zu\en", mi.hblkhd); printf("max. total allocated space (usmblks): %zu\en", mi.usmblks); printf("free bytes held in fastbins (fsmblks): %zu\en", mi.fsmblks); printf("total allocated space (uordblks): %zu\en", mi.uordblks); printf("total free space (fordblks): %zu\en", mi.fordblks); printf("topmost releasable block (keepcost): %zu\en", mi.keepcost); } int main(int argc, char *argv[]) { #define max_allocs 2000000 char *alloc[max_allocs]; int numblocks, freebegin, freeend, freestep; size_t blocksize; if (argc < 3 || strcmp(argv[1], "\-\-help") == 0) { fprintf(stderr, "%s num\-blocks block\-size [free\-step " "[start\-free [end\-free]]]\en", argv[0]); exit(exit_failure); } numblocks = atoi(argv[1]); blocksize = atoi(argv[2]); freestep = (argc > 3) ? atoi(argv[3]) : 1; freebegin = (argc > 4) ? atoi(argv[4]) : 0; freeend = (argc > 5) ? atoi(argv[5]) : numblocks; printf("============== before allocating blocks ==============\en"); display_mallinfo2(); for (int j = 0; j < numblocks; j++) { if (numblocks >= max_allocs) { fprintf(stderr, "too many allocations\en"); exit(exit_failure); } alloc[j] = malloc(blocksize); if (alloc[j] == null) { perror("malloc"); exit(exit_failure); } } printf("\en============== after allocating blocks ==============\en"); display_mallinfo2(); for (int j = freebegin; j < freeend; j += freestep) free(alloc[j]); printf("\en============== after freeing blocks ==============\en"); display_mallinfo2(); exit(exit_success); } .ee .sh see also .ad l .nh .br mmap (2), .br malloc (3), .br malloc_info (3), .br malloc_stats (3), .br malloc_trim (3), .br mallopt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/adjtimex.2 .\" from dholland@burgundy.eecs.harvard.edu tue mar 24 18:08:15 1998 .\" .\" this man page was written in 1998 by david a. holland .\" polished a bit by aeb. .\" .\" %%%license_start(public_domain) .\" placed in the public domain. .\" %%%license_end .\" .\" 2005-06-16 mtk, mentioned freopen() .\" 2007-12-08, mtk, converted from mdoc to man macros .\" .th stdin 3 2017-09-15 "linux" "linux programmer's manual" .sh name stdin, stdout, stderr \- standard i/o streams .sh synopsis .nf .b #include .pp .bi "extern file *" stdin ; .bi "extern file *" stdout ; .bi "extern file *" stderr ; .fi .sh description under normal circumstances every unix program has three streams opened for it when it starts up, one for input, one for output, and one for printing diagnostic or error messages. these are typically attached to the user's terminal (see .br tty (4)) but might instead refer to files or other devices, depending on what the parent process chose to set up. (see also the "redirection" section of .br sh (1).) .pp the input stream is referred to as "standard input"; the output stream is referred to as "standard output"; and the error stream is referred to as "standard error". these terms are abbreviated to form the symbols used to refer to these files, namely .ir stdin , .ir stdout , and .ir stderr . .pp each of these symbols is a .br stdio (3) macro of type pointer to .ir file , and can be used with functions like .br fprintf (3) or .br fread (3). .pp since .ir file s are a buffering wrapper around unix file descriptors, the same underlying files may also be accessed using the raw unix file interface, that is, the functions like .br read (2) and .br lseek (2). .pp on program startup, the integer file descriptors associated with the streams .ir stdin , .ir stdout , and .i stderr are 0, 1, and 2, respectively. the preprocessor symbols .br stdin_fileno , .br stdout_fileno , and .b stderr_fileno are defined with these values in .ir . (applying .br freopen (3) to one of these streams can change the file descriptor number associated with the stream.) .pp note that mixing use of .ir file s and raw file descriptors can produce unexpected results and should generally be avoided. (for the masochistic among you: posix.1, section 8.2.3, describes in detail how this interaction is supposed to work.) a general rule is that file descriptors are handled in the kernel, while stdio is just a library. this means for example, that after an .br exec (3), the child inherits all open file descriptors, but all old streams have become inaccessible. .pp since the symbols .ir stdin , .ir stdout , and .i stderr are specified to be macros, assigning to them is nonportable. the standard streams can be made to refer to different files with help of the library function .br freopen (3), specially introduced to make it possible to reassign .ir stdin , .ir stdout , and .ir stderr . the standard streams are closed by a call to .br exit (3) and by normal program termination. .sh conforming to the .ir stdin , .ir stdout , and .i stderr macros conform to c89 and this standard also stipulates that these three streams shall be open at program startup. .sh notes the stream .i stderr is unbuffered. the stream .i stdout is line-buffered when it points to a terminal. partial lines will not appear until .br fflush (3) or .br exit (3) is called, or a newline is printed. this can produce unexpected results, especially with debugging output. the buffering mode of the standard streams (or any other stream) can be changed using the .br setbuf (3) or .br setvbuf (3) call. note that in case .i stdin is associated with a terminal, there may also be input buffering in the terminal driver, entirely unrelated to stdio buffering. (indeed, normally terminal input is line buffered in the kernel.) this kernel input handling can be modified using calls like .br tcsetattr (3); see also .br stty (1), and .br termios (3). .sh see also .br csh (1), .br sh (1), .br open (2), .br fopen (3), .br stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcsnlen 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsnlen \- determine the length of a fixed-size wide-character string .sh synopsis .nf .b #include .pp .bi "size_t wcsnlen(const wchar_t *" s ", size_t " maxlen ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcsnlen (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcsnlen () function is the wide-character equivalent of the .br strnlen (3) function. it returns the number of wide-characters in the string pointed to by .ir s , not including the terminating null wide character (l\(aq\e0\(aq), but at most .i maxlen wide characters (note: this parameter is not a byte count). in doing this, .br wcsnlen () looks at only the first .i maxlen wide characters at .i s and never beyond .ir s+maxlen . .sh return value the .br wcsnlen () function returns .ir wcslen(s) , if that is less than .ir maxlen , or .i maxlen if there is no null wide character among the first .i maxlen wide characters pointed to by .ir s . .sh versions the .br wcsnlen () function is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsnlen () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. .sh see also .br strnlen (3), .br wcslen (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/random_r.3 .so man7/iso_8859-10.7 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 21:36:50 1993 by rik faith .\" modified tue oct 22 23:47:36 1996 by eric s. raymond .th bcmp 3 2021-03-22 "linux" "linux programmer's manual" .sh name bcmp \- compare byte sequences .sh synopsis .nf .b #include .pp .bi "int bcmp(const void *" s1 ", const void *" s2 ", size_t " n ); .fi .sh description the .br bcmp () function compares the two byte sequences .i s1 and .i s2 of length .i n each. if they are equal, and in particular if .i n is zero, .br bcmp () returns 0. otherwise, it returns a nonzero result. .sh return value the .br bcmp () function returns 0 if the byte sequences are equal, otherwise a nonzero result is returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br bcmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd. this function is deprecated (marked as legacy in posix.1-2001): use .br memcmp (3) in new programs. posix.1-2008 removes the specification of .br bcmp (). .sh see also .br bstring (3), .br memcmp (3), .br strcasecmp (3), .br strcmp (3), .br strcoll (3), .br strncasecmp (3), .br strncmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 16:56:20 1993 by rik faith .\" modified mon oct 21 21:38:51 1996 by eric s. raymond .\" (and some more by aeb) .\" .th hd 4 2017-09-15 "linux" "linux programmer's manual" .sh name hd \- mfm/ide hard disk devices .sh description the .b hd* devices are block devices to access mfm/ide hard disk drives in raw mode. the master drive on the primary ide controller (major device number 3) is .br hda ; the slave drive is .br hdb . the master drive of the second controller (major device number 22) is .b hdc and the slave is .br hdd . .pp general ide block device names have the form .bi hd x\c , or .bi hd xp\c , where .i x is a letter denoting the physical drive, and .i p is a number denoting the partition on that physical drive. the first form, .bi hd x\c , is used to address the whole drive. partition numbers are assigned in the order the partitions are discovered, and only nonempty, nonextended partitions get a number. however, partition numbers 1\(en4 are given to the four partitions described in the mbr (the "primary" partitions), regardless of whether they are unused or extended. thus, the first logical partition will be .bi hd x 5\c \&. both dos-type partitioning and bsd-disklabel partitioning are supported. you can have at most 63 partitions on an ide disk. .pp for example, .i /dev/hda refers to all of the first ide drive in the system; and .i /dev/hdb3 refers to the third dos "primary" partition on the second one. .pp they are typically created by: .pp .in +4n .ex mknod \-m 660 /dev/hda b 3 0 mknod \-m 660 /dev/hda1 b 3 1 mknod \-m 660 /dev/hda2 b 3 2 \&... mknod \-m 660 /dev/hda8 b 3 8 mknod \-m 660 /dev/hdb b 3 64 mknod \-m 660 /dev/hdb1 b 3 65 mknod \-m 660 /dev/hdb2 b 3 66 \&... mknod \-m 660 /dev/hdb8 b 3 72 chown root:disk /dev/hd* .ee .in .sh files .i /dev/hd* .sh see also .br chown (1), .br mknod (1), .br sd (4), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getlogin.3 .so man7/iso_8859-14.7 .so man3/end.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" and copyright (c) 2011 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified sat jul 24 12:02:47 1993 by rik faith .\" modified 15 apr 1995 by michael chastain : .\" added reference to `bdflush(2)'. .\" modified 960414 by andries brouwer : .\" added the fact that since 1.3.20 sync actually waits. .\" modified tue oct 22 22:27:07 1996 by eric s. raymond .\" modified 2001-10-10 by aeb, following michael kerrisk. .\" 2011-09-07, mtk, added syncfs() documentation, .\" .th sync 2 2021-03-22 "linux" "linux programmer's manual" .sh name sync, syncfs \- commit filesystem caches to disk .sh synopsis .nf .b #include .pp .b void sync(void); .pp .bi "int syncfs(int " fd ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sync (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source .fi .pp .br syncfs (): .nf _gnu_source .fi .sh description .br sync () causes all pending modifications to filesystem metadata and cached file data to be written to the underlying filesystems. .pp .br syncfs () is like .br sync (), but synchronizes just the filesystem containing file referred to by the open file descriptor .ir fd . .sh return value .br syncfs () returns 0 on success; on error, it returns \-1 and sets .i errno to indicate the error. .sh errors .br sync () is always successful. .pp .br syncfs () can fail for at least the following reasons: .tp .b ebadf .i fd is not a valid file descriptor. .tp .b eio an error occurred during synchronization. this error may relate to data written to any file on the filesystem, or on metadata related to the filesystem itself. .tp .b enospc disk space was exhausted while synchronizing. .tp .br enospc ", " edquot data was written to a file on nfs or another filesystem which does not allocate space at the time of a .br write (2) system call, and some previous write failed due to insufficient storage space. .sh versions .br syncfs () first appeared in linux 2.6.39; library support was added to glibc in version 2.14. .sh conforming to .br sync (): posix.1-2001, posix.1-2008, svr4, 4.3bsd. .pp .br syncfs () is linux-specific. .sh notes since glibc 2.2.2, the linux prototype for .br sync () is as listed above, following the various standards. in glibc 2.2.1 and earlier, it was "int sync(void)", and .br sync () always returned 0. .pp according to the standard specification (e.g., posix.1-2001), .br sync () schedules the writes, but may return before the actual writing is done. however linux waits for i/o completions, and thus .br sync () or .br syncfs () provide the same guarantees as .br fsync () called on every file in the system or filesystem respectively. .pp in mainline kernel versions prior to 5.8, .br syncfs () will fail only when passed a bad file descriptor .rb ( ebadf ). since linux 5.8, .\" commit 735e4ae5ba28c886d249ad04d3c8cc097dad6336 .br syncfs () will also report an error if one or more inodes failed to be written back since the last .br syncfs () call. .sh bugs before version 1.3.20 linux did not wait for i/o to complete before returning. .sh see also .br sync (1), .br fdatasync (2), .br fsync (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/y0.3 .so man3/fdim.3 .\" this man page is copyright (c) 1999 andi kleen . .\" and copyright (c) 2008 michael kerrisk .\" note also that many pieces are drawn from the kernel source file .\" documentation/networking/ip-sysctl.txt. .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" 2.4 updates by nivedita singhvi 4/20/02 . .\" modified, 2004-11-11, michael kerrisk and andries brouwer .\" updated details of interaction of tcp_cork and tcp_nodelay. .\" .\" 2008-11-21, mtk, many, many updates. .\" the descriptions of /proc files and socket options should now .\" be more or less up to date and complete as at linux 2.6.27 .\" (other than the remaining fixmes in the page source below). .\" .\" fixme the following need to be documented .\" tcp_md5sig (2.6.20) .\" commit cfb6eeb4c860592edd123fdea908d23c6ad1c7dc .\" author was yoshfuji@linux-ipv6.org .\" needs config_tcp_md5sig .\" from net/inet/kconfig: .\" bool "tcp: md5 signature option support (rfc2385) (experimental)" .\" rfc2385 specifies a method of giving md5 protection to tcp sessions. .\" its main (only?) use is to protect bgp sessions between core routers .\" on the internet. .\" .\" there is a tcp_md5sig option documented in freebsd's tcp(4), .\" but probably many details are different on linux .\" http://thread.gmane.org/gmane.linux.network/47490 .\" http://www.daemon-systems.org/man/tcp.4.html .\" http://article.gmane.org/gmane.os.netbsd.devel.network/3767/match=tcp_md5sig+freebsd .\" .\" tcp_cookie_transactions (2.6.33) .\" commit 519855c508b9a17878c0977a3cdefc09b59b30df .\" author: william allen simpson .\" commit e56fb50f2b7958b931c8a2fc0966061b3f3c8f3a .\" author: william allen simpson .\" .\" removed in linux 3.10 .\" commit 1a2c6181c4a1922021b4d7df373bba612c3e5f04 .\" author: christoph paasch .\" .\" tcp_thin_linear_timeouts (2.6.34) .\" commit 36e31b0af58728071e8023cf8e20c5166b700717 .\" author: andreas petlund .\" .\" tcp_thin_dupack (2.6.34) .\" commit 7e38017557bc0b87434d184f8804cadb102bb903 .\" author: andreas petlund .\" .\" tcp_repair (3.5) .\" commit ee9952831cfd0bbe834f4a26489d7dce74582e37 .\" author: pavel emelyanov .\" see also .\" http://criu.org/tcp_connection .\" https://lwn.net/articles/495304/ .\" .\" tcp_repair_queue (3.5) .\" commit ee9952831cfd0bbe834f4a26489d7dce74582e37 .\" author: pavel emelyanov .\" .\" tcp_queue_seq (3.5) .\" commit ee9952831cfd0bbe834f4a26489d7dce74582e37 .\" author: pavel emelyanov .\" .\" tcp_repair_options (3.5) .\" commit b139ba4e90dccbf4cd4efb112af96a5c9e0b098c .\" author: pavel emelyanov .\" .\" tcp_fastopen (3.6) .\" (fast open server side implementation completed in 3.7) .\" http://lwn.net/articles/508865/ .\" .\" tcp_timestamp (3.9) .\" commit 93be6ce0e91b6a94783e012b1857a347a5e6e9f2 .\" author: andrey vagin .\" .\" tcp_notsent_lowat (3.12) .\" commit c9bee3b7fdecb0c1d070c7b54113b3bdfb9a3d36 .\" author: eric dumazet .\" .\" tcp_cc_info (4.1) .\" commit 6e9250f59ef9efb932c84850cd221f22c2a03c4a .\" author: eric dumazet .\" .\" tcp_save_syn, tcp_saved_syn (4.2) .\" commit cd8ae85299d54155702a56811b2e035e63064d3d .\" author: eric dumazet .\" .th tcp 7 2021-03-22 "linux" "linux programmer's manual" .sh name tcp \- tcp protocol .sh synopsis .nf .b #include .b #include .b #include .pp .b tcp_socket = socket(af_inet, sock_stream, 0); .fi .sh description this is an implementation of the tcp protocol defined in rfc\ 793, rfc\ 1122 and rfc\ 2001 with the newreno and sack extensions. it provides a reliable, stream-oriented, full-duplex connection between two sockets on top of .br ip (7), for both v4 and v6 versions. tcp guarantees that the data arrives in order and retransmits lost packets. it generates and checks a per-packet checksum to catch transmission errors. tcp does not preserve record boundaries. .pp a newly created tcp socket has no remote or local address and is not fully specified. to create an outgoing tcp connection use .br connect (2) to establish a connection to another tcp socket. to receive new incoming connections, first .br bind (2) the socket to a local address and port and then call .br listen (2) to put the socket into the listening state. after that a new socket for each incoming connection can be accepted using .br accept (2). a socket which has had .br accept (2) or .br connect (2) successfully called on it is fully specified and may transmit data. data cannot be transmitted on listening or not yet connected sockets. .pp linux supports rfc\ 1323 tcp high performance extensions. these include protection against wrapped sequence numbers (paws), window scaling and timestamps. window scaling allows the use of large (> 64\ kb) tcp windows in order to support links with high latency or bandwidth. to make use of them, the send and receive buffer sizes must be increased. they can be set globally with the .i /proc/sys/net/ipv4/tcp_wmem and .i /proc/sys/net/ipv4/tcp_rmem files, or on individual sockets by using the .b so_sndbuf and .b so_rcvbuf socket options with the .br setsockopt (2) call. .pp the maximum sizes for socket buffers declared via the .b so_sndbuf and .b so_rcvbuf mechanisms are limited by the values in the .i /proc/sys/net/core/rmem_max and .i /proc/sys/net/core/wmem_max files. note that tcp actually allocates twice the size of the buffer requested in the .br setsockopt (2) call, and so a succeeding .br getsockopt (2) call will not return the same size of buffer as requested in the .br setsockopt (2) call. tcp uses the extra space for administrative purposes and internal kernel structures, and the .i /proc file values reflect the larger sizes compared to the actual tcp windows. on individual connections, the socket buffer size must be set prior to the .br listen (2) or .br connect (2) calls in order to have it take effect. see .br socket (7) for more information. .pp tcp supports urgent data. urgent data is used to signal the receiver that some important message is part of the data stream and that it should be processed as soon as possible. to send urgent data specify the .b msg_oob option to .br send (2). when urgent data is received, the kernel sends a .b sigurg signal to the process or process group that has been set as the socket "owner" using the .b siocspgrp or .b fiosetown ioctls (or the posix.1-specified .br fcntl (2) .b f_setown operation). when the .b so_oobinline socket option is enabled, urgent data is put into the normal data stream (a program can test for its location using the .b siocatmark ioctl described below), otherwise it can be received only when the .b msg_oob flag is set for .br recv (2) or .br recvmsg (2). .pp when out-of-band data is present, .br select (2) indicates the file descriptor as having an exceptional condition and .i poll (2) indicates a .b pollpri event. .pp linux 2.4 introduced a number of changes for improved throughput and scaling, as well as enhanced functionality. some of these features include support for zero-copy .br sendfile (2), explicit congestion notification, new management of time_wait sockets, keep-alive socket options and support for duplicate sack extensions. .ss address formats tcp is built on top of ip (see .br ip (7)). the address formats defined by .br ip (7) apply to tcp. tcp supports point-to-point communication only; broadcasting and multicasting are not supported. .ss /proc interfaces system-wide tcp parameter settings can be accessed by files in the directory .ir /proc/sys/net/ipv4/ . in addition, most ip .i /proc interfaces also apply to tcp; see .br ip (7). variables described as .i boolean take an integer value, with a nonzero value ("true") meaning that the corresponding option is enabled, and a zero value ("false") meaning that the option is disabled. .tp .ir tcp_abc " (integer; default: 0; linux 2.6.15 to linux 3.8)" .\" since 2.6.15; removed in 3.9 .\" commit ca2eb5679f8ddffff60156af42595df44a315ef0 .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt control the appropriate byte count (abc), defined in rfc 3465. abc is a way of increasing the congestion window .ri ( cwnd ) more slowly in response to partial acknowledgements. possible values are: .rs .ip 0 3 increase .i cwnd once per acknowledgement (no abc) .ip 1 increase .i cwnd once per acknowledgement of full sized segment .ip 2 allow increase .i cwnd by two if acknowledgement is of two segments to compensate for delayed acknowledgements. .re .tp .ir tcp_abort_on_overflow " (boolean; default: disabled; since linux 2.4)" .\" since 2.3.41 enable resetting connections if the listening service is too slow and unable to keep up and accept them. it means that if overflow occurred due to a burst, the connection will recover. enable this option .i only if you are really sure that the listening daemon cannot be tuned to accept connections faster. enabling this option can harm the clients of your server. .tp .ir tcp_adv_win_scale " (integer; default: 2; since linux 2.4)" .\" since 2.4.0-test7 count buffering overhead as .ir "bytes/2^tcp_adv_win_scale" , if .i tcp_adv_win_scale is greater than 0; or .ir "bytes\-bytes/2^(\-tcp_adv_win_scale)" , if .i tcp_adv_win_scale is less than or equal to zero. .ip the socket receive buffer space is shared between the application and kernel. tcp maintains part of the buffer as the tcp window, this is the size of the receive window advertised to the other end. the rest of the space is used as the "application" buffer, used to isolate the network from scheduling and application latencies. the .i tcp_adv_win_scale default value of 2 implies that the space used for the application buffer is one fourth that of the total. .tp .ir tcp_allowed_congestion_control " (string; default: see text; since linux 2.4.20)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt show/set the congestion control algorithm choices available to unprivileged processes (see the description of the .b tcp_congestion socket option). the items in the list are separated by white space and terminated by a newline character. the list is a subset of those listed in .ir tcp_available_congestion_control . the default value for this list is "reno" plus the default setting of .ir tcp_congestion_control . .tp .ir tcp_autocorking " (boolean; default: enabled; since linux 3.14)" .\" commit f54b311142a92ea2e42598e347b84e1655caf8e3 .\" text heavily based on documentation/networking/ip-sysctl.txt if this option is enabled, the kernel tries to coalesce small writes (from consecutive .br write (2) and .br sendmsg (2) calls) as much as possible, in order to decrease the total number of sent packets. coalescing is done if at least one prior packet for the flow is waiting in qdisc queues or device transmit queue. applications can still use the .b tcp_cork socket option to obtain optimal behavior when they know how/when to uncork their sockets. .tp .ir tcp_available_congestion_control " (string; read-only; since linux 2.4.20)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt show a list of the congestion-control algorithms that are registered. the items in the list are separated by white space and terminated by a newline character. this list is a limiting set for the list in .ir tcp_allowed_congestion_control . more congestion-control algorithms may be available as modules, but not loaded. .tp .ir tcp_app_win " (integer; default: 31; since linux 2.4)" .\" since 2.4.0-test7 this variable defines how many bytes of the tcp window are reserved for buffering overhead. .ip a maximum of (\fiwindow/2^tcp_app_win\fp, mss) bytes in the window are reserved for the application buffer. a value of 0 implies that no amount is reserved. .\" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt .tp .ir tcp_base_mss " (integer; default: 512; since linux 2.6.17)" the initial value of .i search_low to be used by the packetization layer path mtu discovery (mtu probing). if mtu probing is enabled, this is the initial mss used by the connection. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_bic " (boolean; default: disabled; linux 2.4.27/2.6.6 to 2.6.13)" enable bic tcp congestion control algorithm. bic-tcp is a sender-side-only change that ensures a linear rtt fairness under large windows while offering both scalability and bounded tcp-friendliness. the protocol combines two schemes called additive increase and binary search increase. when the congestion window is large, additive increase with a large increment ensures linear rtt fairness as well as good scalability. under small congestion windows, binary search increase provides tcp friendliness. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_bic_low_window " (integer; default: 14; linux 2.4.27/2.6.6 to 2.6.13)" set the threshold window (in packets) where bic tcp starts to adjust the congestion window. below this threshold bic tcp behaves the same as the default tcp reno. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_bic_fast_convergence " (boolean; default: enabled; linux 2.4.27/2.6.6 to 2.6.13)" force bic tcp to more quickly respond to changes in congestion window. allows two flows sharing the same connection to converge more rapidly. .tp .ir tcp_congestion_control " (string; default: see text; since linux 2.4.13)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt set the default congestion-control algorithm to be used for new connections. the algorithm "reno" is always available, but additional choices may be available depending on kernel configuration. the default value for this file is set as part of kernel configuration. .tp .ir tcp_dma_copybreak " (integer; default: 4096; since linux 2.6.24)" lower limit, in bytes, of the size of socket reads that will be offloaded to a dma copy engine, if one is present in the system and the kernel was configured with the .b config_net_dma option. .tp .ir tcp_dsack " (boolean; default: enabled; since linux 2.4)" .\" since 2.4.0-test7 enable rfc\ 2883 tcp duplicate sack support. .tp .ir tcp_ecn " (integer; default: see below; since linux 2.4)" .\" since 2.4.0-test7 enable rfc\ 3168 explicit congestion notification. .ip this file can have one of the following values: .rs .ip 0 disable ecn. neither initiate nor accept ecn. this was the default up to and including linux 2.6.30. .ip 1 enable ecn when requested by incoming connections and also request ecn on outgoing connection attempts. .ip 2 .\" commit 255cac91c3c9ce7dca7713b93ab03c75b7902e0e enable ecn when requested by incoming connections, but do not request ecn on outgoing connections. this value is supported, and is the default, since linux 2.6.31. .re .ip when enabled, connectivity to some destinations could be affected due to older, misbehaving middle boxes along the path, causing connections to be dropped. however, to facilitate and encourage deployment with option 1, and to work around such buggy equipment, the .b tcp_ecn_fallback option has been introduced. .tp .ir tcp_ecn_fallback " (boolean; default: enabled; since linux 4.1)" .\" commit 492135557dc090a1abb2cfbe1a412757e3ed68ab enable rfc\ 3168, section 6.1.1.1. fallback. when enabled, outgoing ecn-setup syns that time out within the normal syn retransmission timeout will be resent with cwr and ece cleared. .tp .ir tcp_fack " (boolean; default: enabled; since linux 2.2)" .\" since 2.1.92 enable tcp forward acknowledgement support. .tp .ir tcp_fin_timeout " (integer; default: 60; since linux 2.2)" .\" since 2.1.53 this specifies how many seconds to wait for a final fin packet before the socket is forcibly closed. this is strictly a violation of the tcp specification, but required to prevent denial-of-service attacks. in linux 2.2, the default value was 180. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_frto " (integer; default: see below; since linux 2.4.21/2.6)" .\" since 2.4.21/2.5.43 enable f-rto, an enhanced recovery algorithm for tcp retransmission timeouts (rtos). it is particularly beneficial in wireless environments where packet loss is typically due to random radio interference rather than intermediate router congestion. see rfc 4138 for more details. .ip this file can have one of the following values: .rs .ip 0 3 disabled. this was the default up to and including linux 2.6.23. .ip 1 the basic version f-rto algorithm is enabled. .ip 2 .\" commit c96fd3d461fa495400df24be3b3b66f0e0b152f9 enable sack-enhanced f-rto if flow uses sack. the basic version can be used also when sack is in use though in that case scenario(s) exists where f-rto interacts badly with the packet counting of the sack-enabled tcp flow. this value is the default since linux 2.6.24. .re .ip before linux 2.6.22, this parameter was a boolean value, supporting just values 0 and 1 above. .tp .ir tcp_frto_response " (integer; default: 0; since linux 2.6.22)" when f-rto has detected that a tcp retransmission timeout was spurious (i.e., the timeout would have been avoided had tcp set a longer retransmission timeout), tcp has several options concerning what to do next. possible values are: .rs .ip 0 3 rate halving based; a smooth and conservative response, results in halved congestion window .ri ( cwnd ) and slow-start threshold .ri ( ssthresh ) after one rtt. .ip 1 very conservative response; not recommended because even though being valid, it interacts poorly with the rest of linux tcp; halves .i cwnd and .i ssthresh immediately. .ip 2 aggressive response; undoes congestion-control measures that are now known to be unnecessary (ignoring the possibility of a lost retransmission that would require tcp to be more cautious); .i cwnd and .i ssthresh are restored to the values prior to timeout. .re .tp .ir tcp_keepalive_intvl " (integer; default: 75; since linux 2.4)" .\" since 2.3.18 the number of seconds between tcp keep-alive probes. .tp .ir tcp_keepalive_probes " (integer; default: 9; since linux 2.2)" .\" since 2.1.43 the maximum number of tcp keep-alive probes to send before giving up and killing the connection if no response is obtained from the other end. .tp .ir tcp_keepalive_time " (integer; default: 7200; since linux 2.2)" .\" since 2.1.43 the number of seconds a connection needs to be idle before tcp begins sending out keep-alive probes. keep-alives are sent only when the .b so_keepalive socket option is enabled. the default value is 7200 seconds (2 hours). an idle connection is terminated after approximately an additional 11 minutes (9 probes an interval of 75 seconds apart) when keep-alive is enabled. .ip note that underlying connection tracking mechanisms and application timeouts may be much shorter. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_low_latency " (boolean; default: disabled; since linux 2.4.21/2.6; \ obsolete since linux 4.14)" .\" since 2.4.21/2.5.60 if enabled, the tcp stack makes decisions that prefer lower latency as opposed to higher throughput. it this option is disabled, then higher throughput is preferred. an example of an application where this default should be changed would be a beowulf compute cluster. since linux 4.14, .\" commit b6690b14386698ce2c19309abad3f17656bdfaea this file still exists, but its value is ignored. .tp .ir tcp_max_orphans " (integer; default: see below; since linux 2.4)" .\" since 2.3.41 the maximum number of orphaned (not attached to any user file handle) tcp sockets allowed in the system. when this number is exceeded, the orphaned connection is reset and a warning is printed. this limit exists only to prevent simple denial-of-service attacks. lowering this limit is not recommended. network conditions might require you to increase the number of orphans allowed, but note that each orphan can eat up to \(ti64\ kb of unswappable memory. the default initial value is set equal to the kernel parameter nr_file. this initial default is adjusted depending on the memory in the system. .tp .ir tcp_max_syn_backlog " (integer; default: see below; since linux 2.2)" .\" since 2.1.53 the maximum number of queued connection requests which have still not received an acknowledgement from the connecting client. if this number is exceeded, the kernel will begin dropping requests. the default value of 256 is increased to 1024 when the memory present in the system is adequate or greater (>= 128\ mb), and reduced to 128 for those systems with very low memory (<= 32\ mb). .ip prior to linux 2.6.20, .\" commit 72a3effaf633bcae9034b7e176bdbd78d64a71db it was recommended that if this needed to be increased above 1024, the size of the synack hash table .rb ( tcp_synq_hsize ) in .i include/net/tcp.h should be modified to keep .ip tcp_synq_hsize * 16 <= tcp_max_syn_backlog .ip and the kernel should be recompiled. in linux 2.6.20, the fixed sized .b tcp_synq_hsize was removed in favor of dynamic sizing. .tp .ir tcp_max_tw_buckets " (integer; default: see below; since linux 2.4)" .\" since 2.3.41 the maximum number of sockets in time_wait state allowed in the system. this limit exists only to prevent simple denial-of-service attacks. the default value of nr_file*2 is adjusted depending on the memory in the system. if this number is exceeded, the socket is closed and a warning is printed. .tp .ir tcp_moderate_rcvbuf " (boolean; default: enabled; since linux 2.4.17/2.6.7)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt if enabled, tcp performs receive buffer auto-tuning, attempting to automatically size the buffer (no greater than .ir tcp_rmem[2] ) to match the size required by the path for full throughput. .tp .ir tcp_mem " (since linux 2.4)" .\" since 2.4.0-test7 this is a vector of 3 integers: [low, pressure, high]. these bounds, measured in units of the system page size, are used by tcp to track its memory usage. the defaults are calculated at boot time from the amount of available memory. (tcp can only use .i "low memory" for this, which is limited to around 900 megabytes on 32-bit systems. 64-bit systems do not suffer this limitation.) .rs .tp .i low tcp doesn't regulate its memory allocation when the number of pages it has allocated globally is below this number. .tp .i pressure when the amount of memory allocated by tcp exceeds this number of pages, tcp moderates its memory consumption. this memory pressure state is exited once the number of pages allocated falls below the .i low mark. .tp .i high the maximum number of pages, globally, that tcp will allocate. this value overrides any other limits imposed by the kernel. .re .tp .ir tcp_mtu_probing " (integer; default: 0; since linux 2.6.17)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt this parameter controls tcp packetization-layer path mtu discovery. the following values may be assigned to the file: .rs .ip 0 3 disabled .ip 1 disabled by default, enabled when an icmp black hole detected .ip 2 always enabled, use initial mss of .ir tcp_base_mss . .re .tp .ir tcp_no_metrics_save " (boolean; default: disabled; since linux 2.6.6)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt by default, tcp saves various connection metrics in the route cache when the connection closes, so that connections established in the near future can use these to set initial conditions. usually, this increases overall performance, but it may sometimes cause performance degradation. if .i tcp_no_metrics_save is enabled, tcp will not cache metrics on closing connections. .tp .ir tcp_orphan_retries " (integer; default: 8; since linux 2.4)" .\" since 2.3.41 the maximum number of attempts made to probe the other end of a connection which has been closed by our end. .tp .ir tcp_reordering " (integer; default: 3; since linux 2.4)" .\" since 2.4.0-test7 the maximum a packet can be reordered in a tcp packet stream without tcp assuming packet loss and going into slow start. it is not advisable to change this number. this is a packet reordering detection metric designed to minimize unnecessary back off and retransmits provoked by reordering of packets on a connection. .tp .ir tcp_retrans_collapse " (boolean; default: enabled; since linux 2.2)" .\" since 2.1.96 try to send full-sized packets during retransmit. .tp .ir tcp_retries1 " (integer; default: 3; since linux 2.2)" .\" since 2.1.43 the number of times tcp will attempt to retransmit a packet on an established connection normally, without the extra effort of getting the network layers involved. once we exceed this number of retransmits, we first have the network layer update the route if possible before each new retransmit. the default is the rfc specified minimum of 3. .tp .ir tcp_retries2 " (integer; default: 15; since linux 2.2)" .\" since 2.1.43 the maximum number of times a tcp packet is retransmitted in established state before giving up. the default value is 15, which corresponds to a duration of approximately between 13 to 30 minutes, depending on the retransmission timeout. the rfc\ 1122 specified minimum limit of 100 seconds is typically deemed too short. .tp .ir tcp_rfc1337 " (boolean; default: disabled; since linux 2.2)" .\" since 2.1.90 enable tcp behavior conformant with rfc\ 1337. when disabled, if a rst is received in time_wait state, we close the socket immediately without waiting for the end of the time_wait period. .tp .ir tcp_rmem " (since linux 2.4)" .\" since 2.4.0-test7 this is a vector of 3 integers: [min, default, max]. these parameters are used by tcp to regulate receive buffer sizes. tcp dynamically adjusts the size of the receive buffer from the defaults listed below, in the range of these values, depending on memory available in the system. .rs .tp .i min minimum size of the receive buffer used by each tcp socket. the default value is the system page size. (on linux 2.4, the default value is 4\ kb, lowered to .b page_size bytes in low-memory systems.) this value is used to ensure that in memory pressure mode, allocations below this size will still succeed. this is not used to bound the size of the receive buffer declared using .b so_rcvbuf on a socket. .tp .i default the default size of the receive buffer for a tcp socket. this value overwrites the initial default buffer size from the generic global .i net.core.rmem_default defined for all protocols. the default value is 87380 bytes. (on linux 2.4, this will be lowered to 43689 in low-memory systems.) if larger receive buffer sizes are desired, this value should be increased (to affect all sockets). to employ large tcp windows, the .i net.ipv4.tcp_window_scaling must be enabled (default). .tp .i max the maximum size of the receive buffer used by each tcp socket. this value does not override the global .ir net.core.rmem_max . this is not used to limit the size of the receive buffer declared using .b so_rcvbuf on a socket. the default value is calculated using the formula .ip max(87380, min(4\ mb, \fitcp_mem\fp[1]*page_size/128)) .ip (on linux 2.4, the default is 87380*2 bytes, lowered to 87380 in low-memory systems). .re .tp .ir tcp_sack " (boolean; default: enabled; since linux 2.2)" .\" since 2.1.36 enable rfc\ 2018 tcp selective acknowledgements. .tp .ir tcp_slow_start_after_idle " (boolean; default: enabled; since linux 2.6.18)" .\" the following is from 2.6.28-rc4: documentation/networking/ip-sysctl.txt if enabled, provide rfc 2861 behavior and time out the congestion window after an idle period. an idle period is defined as the current rto (retransmission timeout). if disabled, the congestion window will not be timed out after an idle period. .tp .ir tcp_stdurg " (boolean; default: disabled; since linux 2.2)" .\" since 2.1.44 if this option is enabled, then use the rfc\ 1122 interpretation of the tcp urgent-pointer field. .\" rfc 793 was ambiguous in its specification of the meaning of the .\" urgent pointer. rfc 1122 (and rfc 961) fixed on a particular .\" resolution of this ambiguity (unfortunately the "wrong" one). according to this interpretation, the urgent pointer points to the last byte of urgent data. if this option is disabled, then use the bsd-compatible interpretation of the urgent pointer: the urgent pointer points to the first byte after the urgent data. enabling this option may lead to interoperability problems. .tp .ir tcp_syn_retries " (integer; default: 6; since linux 2.2)" .\" since 2.1.38 the maximum number of times initial syns for an active tcp connection attempt will be retransmitted. this value should not be higher than 255. the default value is 6, which corresponds to retrying for up to approximately 127 seconds. before linux 3.7, .\" commit 6c9ff979d1921e9fd05d89e1383121c2503759b9 the default value was 5, which (in conjunction with calculation based on other kernel parameters) corresponded to approximately 180 seconds. .tp .ir tcp_synack_retries " (integer; default: 5; since linux 2.2)" .\" since 2.1.38 the maximum number of times a syn/ack segment for a passive tcp connection will be retransmitted. this number should not be higher than 255. .tp .ir tcp_syncookies " (integer; default: 1; since linux 2.2)" .\" since 2.1.43 enable tcp syncookies. the kernel must be compiled with .br config_syn_cookies . the syncookies feature attempts to protect a socket from a syn flood attack. this should be used as a last resort, if at all. this is a violation of the tcp protocol, and conflicts with other areas of tcp such as tcp extensions. it can cause problems for clients and relays. it is not recommended as a tuning mechanism for heavily loaded servers to help with overloaded or misconfigured conditions. for recommended alternatives see .ir tcp_max_syn_backlog , .ir tcp_synack_retries , and .ir tcp_abort_on_overflow . set to one of the following values: .rs .ip 0 3 disable tcp syncookies. .ip 1 send out syncookies when the syn backlog queue of a socket overflows. .ip 2 (since linux 3.12) .\" commit 5ad37d5deee1ff7150a2d0602370101de158ad86 send out syncookies unconditionally. this can be useful for network testing. .re .tp .ir tcp_timestamps " (integer; default: 1; since linux 2.2)" .\" since 2.1.36 set to one of the following values to enable or disable rfc\ 1323 tcp timestamps: .rs .ip 0 3 disable timestamps. .ip 1 enable timestamps as defined in rfc1323 and use random offset for each connection rather than only using the current time. .ip 2 as for the value 1, but without random offsets. .\" commit 25429d7b7dca01dc4f17205de023a30ca09390d0 setting .i tcp_timestamps to this value is meaningful since linux 4.10. .re .tp .ir tcp_tso_win_divisor " (integer; default: 3; since linux 2.6.9)" this parameter controls what percentage of the congestion window can be consumed by a single tcp segmentation offload (tso) frame. the setting of this parameter is a tradeoff between burstiness and building larger tso frames. .tp .ir tcp_tw_recycle " (boolean; default: disabled; linux 2.4 to 4.11)" .\" since 2.3.15 .\" removed in 4.12; commit 4396e46187ca5070219b81773c4e65088dac50cc enable fast recycling of time_wait sockets. enabling this option is not recommended as the remote ip may not use monotonically increasing timestamps (devices behind nat, devices with per-connection timestamp offsets). see rfc 1323 (paws) and rfc 6191. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_tw_reuse " (boolean; default: disabled; since linux 2.4.19/2.6)" .\" since 2.4.19/2.5.43 allow to reuse time_wait sockets for new connections when it is safe from protocol viewpoint. it should not be changed without advice/request of technical experts. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_vegas_cong_avoid " (boolean; default: disabled; linux 2.2 to 2.6.13)" .\" since 2.1.8; removed in 2.6.13 enable tcp vegas congestion avoidance algorithm. tcp vegas is a sender-side-only change to tcp that anticipates the onset of congestion by estimating the bandwidth. tcp vegas adjusts the sending rate by modifying the congestion window. tcp vegas should provide less packet loss, but it is not as aggressive as tcp reno. .\" .\" the following is from 2.6.12: documentation/networking/ip-sysctl.txt .tp .ir tcp_westwood " (boolean; default: disabled; linux 2.4.26/2.6.3 to 2.6.13)" enable tcp westwood+ congestion control algorithm. tcp westwood+ is a sender-side-only modification of the tcp reno protocol stack that optimizes the performance of tcp congestion control. it is based on end-to-end bandwidth estimation to set congestion window and slow start threshold after a congestion episode. using this estimation, tcp westwood+ adaptively sets a slow start threshold and a congestion window which takes into account the bandwidth used at the time congestion is experienced. tcp westwood+ significantly increases fairness with respect to tcp reno in wired networks and throughput over wireless links. .tp .ir tcp_window_scaling " (boolean; default: enabled; since linux 2.2)" .\" since 2.1.36 enable rfc\ 1323 tcp window scaling. this feature allows the use of a large window (> 64\ kb) on a tcp connection, should the other end support it. normally, the 16 bit window length field in the tcp header limits the window size to less than 64\ kb. if larger windows are desired, applications can increase the size of their socket buffers and the window scaling option will be employed. if .i tcp_window_scaling is disabled, tcp will not negotiate the use of window scaling with the other end during connection setup. .tp .ir tcp_wmem " (since linux 2.4)" .\" since 2.4.0-test7 this is a vector of 3 integers: [min, default, max]. these parameters are used by tcp to regulate send buffer sizes. tcp dynamically adjusts the size of the send buffer from the default values listed below, in the range of these values, depending on memory available. .rs .tp .i min minimum size of the send buffer used by each tcp socket. the default value is the system page size. (on linux 2.4, the default value is 4\ kb.) this value is used to ensure that in memory pressure mode, allocations below this size will still succeed. this is not used to bound the size of the send buffer declared using .b so_sndbuf on a socket. .tp .i default the default size of the send buffer for a tcp socket. this value overwrites the initial default buffer size from the generic global .i /proc/sys/net/core/wmem_default defined for all protocols. the default value is 16\ kb. .\" true in linux 2.4 and 2.6 if larger send buffer sizes are desired, this value should be increased (to affect all sockets). to employ large tcp windows, the .i /proc/sys/net/ipv4/tcp_window_scaling must be set to a nonzero value (default). .tp .i max the maximum size of the send buffer used by each tcp socket. this value does not override the value in .ir /proc/sys/net/core/wmem_max . this is not used to limit the size of the send buffer declared using .b so_sndbuf on a socket. the default value is calculated using the formula .ip max(65536, min(4\ mb, \fitcp_mem\fp[1]*page_size/128)) .ip (on linux 2.4, the default value is 128\ kb, lowered 64\ kb depending on low-memory systems.) .re .tp .ir tcp_workaround_signed_windows " (boolean; default: disabled; since linux 2.6.26)" if enabled, assume that no receipt of a window-scaling option means that the remote tcp is broken and treats the window as a signed quantity. if disabled, assume that the remote tcp is not broken even if we do not receive a window scaling option from it. .ss socket options to set or get a tcp socket option, call .br getsockopt (2) to read or .br setsockopt (2) to write the option with the option level argument set to .br ipproto_tcp . unless otherwise noted, .i optval is a pointer to an .ir int . .\" or sol_tcp on linux in addition, most .b ipproto_ip socket options are valid on tcp sockets. for more information see .br ip (7). .pp following is a list of tcp-specific socket options. for details of some other socket options that are also applicable for tcp sockets, see .br socket (7). .tp .br tcp_congestion " (since linux 2.6.13)" .\" commit 5f8ef48d240963093451bcf83df89f1a1364f51d .\" author: stephen hemminger the argument for this option is a string. this option allows the caller to set the tcp congestion control algorithm to be used, on a per-socket basis. unprivileged processes are restricted to choosing one of the algorithms in .ir tcp_allowed_congestion_control (described above). privileged processes .rb ( cap_net_admin ) can choose from any of the available congestion-control algorithms (see the description of .ir tcp_available_congestion_control above). .tp .br tcp_cork " (since linux 2.2)" .\" precisely: since 2.1.127 if set, don't send out partial frames. all queued partial frames are sent when the option is cleared again. this is useful for prepending headers before calling .br sendfile (2), or for throughput optimization. as currently implemented, there is a 200 millisecond ceiling on the time for which output is corked by .br tcp_cork . if this ceiling is reached, then queued data is automatically transmitted. this option can be combined with .b tcp_nodelay only since linux 2.5.71. this option should not be used in code intended to be portable. .tp .br tcp_defer_accept " (since linux 2.4)" .\" precisely: since 2.3.38 .\" useful references: .\" http://www.techrepublic.com/article/take-advantage-of-tcp-ip-options-to-optimize-data-transmission/ .\" http://unix.stackexchange.com/questions/94104/real-world-use-of-tcp-defer-accept allow a listener to be awakened only when data arrives on the socket. takes an integer value (seconds), this can bound the maximum number of attempts tcp will make to complete the connection. this option should not be used in code intended to be portable. .tp .br tcp_info " (since linux 2.4)" used to collect information about this socket. the kernel returns a \fistruct tcp_info\fp as defined in the file .ir /usr/include/linux/tcp.h . this option should not be used in code intended to be portable. .tp .br tcp_keepcnt " (since linux 2.4)" .\" precisely: since 2.3.18 the maximum number of keepalive probes tcp should send before dropping the connection. this option should not be used in code intended to be portable. .tp .br tcp_keepidle " (since linux 2.4)" .\" precisely: since 2.3.18 the time (in seconds) the connection needs to remain idle before tcp starts sending keepalive probes, if the socket option .b so_keepalive has been set on this socket. this option should not be used in code intended to be portable. .tp .br tcp_keepintvl " (since linux 2.4)" .\" precisely: since 2.3.18 the time (in seconds) between individual keepalive probes. this option should not be used in code intended to be portable. .tp .br tcp_linger2 " (since linux 2.4)" .\" precisely: since 2.3.41 the lifetime of orphaned fin_wait2 state sockets. this option can be used to override the system-wide setting in the file .i /proc/sys/net/ipv4/tcp_fin_timeout for this socket. this is not to be confused with the .br socket (7) level option .br so_linger . this option should not be used in code intended to be portable. .tp .b tcp_maxseg .\" present in linux 1.0 the maximum segment size for outgoing tcp packets. in linux 2.2 and earlier, and in linux 2.6.28 and later, if this option is set before connection establishment, it also changes the mss value announced to the other end in the initial packet. values greater than the (eventual) interface mtu have no effect. tcp will also impose its minimum and maximum bounds over the value provided. .tp .b tcp_nodelay .\" present in linux 1.0 if set, disable the nagle algorithm. this means that segments are always sent as soon as possible, even if there is only a small amount of data. when not set, data is buffered until there is a sufficient amount to send out, thereby avoiding the frequent sending of small packets, which results in poor utilization of the network. this option is overridden by .br tcp_cork ; however, setting this option forces an explicit flush of pending output, even if .b tcp_cork is currently set. .tp .br tcp_quickack " (since linux 2.4.4)" enable quickack mode if set or disable quickack mode if cleared. in quickack mode, acks are sent immediately, rather than delayed if needed in accordance to normal tcp operation. this flag is not permanent, it only enables a switch to or from quickack mode. subsequent operation of the tcp protocol will once again enter/leave quickack mode depending on internal protocol processing and factors such as delayed ack timeouts occurring and data transfer. this option should not be used in code intended to be portable. .tp .br tcp_syncnt " (since linux 2.4)" .\" precisely: since 2.3.18 set the number of syn retransmits that tcp should send before aborting the attempt to connect. it cannot exceed 255. this option should not be used in code intended to be portable. .tp .br tcp_user_timeout " (since linux 2.6.37)" .\" commit dca43c75e7e545694a9dd6288553f55c53e2a3a3 .\" author: jerry chu .\" the following text taken nearly verbatim from jerry chu's (excellent) .\" commit message. .\" this option takes an .ir "unsigned int" as an argument. when the value is greater than 0, it specifies the maximum amount of time in milliseconds that transmitted data may remain unacknowledged, or bufferred data may remain untransmitted (due to zero window size) before tcp will forcibly close the corresponding connection and return .b etimedout to the application. if the option value is specified as 0, tcp will use the system default. .ip increasing user timeouts allows a tcp connection to survive extended periods without end-to-end connectivity. decreasing user timeouts allows applications to "fail fast", if so desired. otherwise, failure may take up to 20 minutes with the current system defaults in a normal wan environment. .ip this option can be set during any state of a tcp connection, but is effective only during the synchronized states of a connection (established, fin-wait-1, fin-wait-2, close-wait, closing, and last-ack). moreover, when used with the tcp keepalive .rb ( so_keepalive ) option, .b tcp_user_timeout will override keepalive to determine when to close a connection due to keepalive failure. .ip the option has no effect on when tcp retransmits a packet, nor when a keepalive probe is sent. .ip this option, like many others, will be inherited by the socket returned by .br accept (2), if it was set on the listening socket. .ip further details on the user timeout feature can be found in rfc\ 793 and rfc\ 5482 ("tcp user timeout option"). .tp .br tcp_window_clamp " (since linux 2.4)" .\" precisely: since 2.3.41 bound the size of the advertised window to this value. the kernel imposes a minimum size of sock_min_rcvbuf/2. this option should not be used in code intended to be portable. .ss sockets api tcp provides limited support for out-of-band data, in the form of (a single byte of) urgent data. in linux this means if the other end sends newer out-of-band data the older urgent data is inserted as normal data into the stream (even when .b so_oobinline is not set). this differs from bsd-based stacks. .pp linux uses the bsd compatible interpretation of the urgent pointer field by default. this violates rfc\ 1122, but is required for interoperability with other stacks. it can be changed via .ir /proc/sys/net/ipv4/tcp_stdurg . .pp it is possible to peek at out-of-band data using the .br recv (2) .b msg_peek flag. .pp since version 2.4, linux supports the use of .b msg_trunc in the .i flags argument of .br recv (2) (and .br recvmsg (2)). this flag causes the received bytes of data to be discarded, rather than passed back in a caller-supplied buffer. since linux 2.4.4, .br msg_trunc also has this effect when used in conjunction with .br msg_oob to receive out-of-band data. .ss ioctls the following .br ioctl (2) calls return information in .ir value . the correct syntax is: .pp .rs .nf .bi int " value"; .ib error " = ioctl(" tcp_socket ", " ioctl_type ", &" value ");" .fi .re .pp .i ioctl_type is one of the following: .tp .b siocinq returns the amount of queued unread data in the receive buffer. the socket must not be in listen state, otherwise an error .rb ( einval ) is returned. .b siocinq is defined in .ir . .\" fixme http://sources.redhat.com/bugzilla/show_bug.cgi?id=12002, .\" filed 2010-09-10, may cause siocinq to be defined in glibc headers alternatively, you can use the synonymous .br fionread , defined in .ir . .tp .b siocatmark returns true (i.e., .i value is nonzero) if the inbound data stream is at the urgent mark. .ip if the .b so_oobinline socket option is set, and .b siocatmark returns true, then the next read from the socket will return the urgent data. if the .b so_oobinline socket option is not set, and .b siocatmark returns true, then the next read from the socket will return the bytes following the urgent data (to actually read the urgent data requires the .b recv(msg_oob) flag). .ip note that a read never reads across the urgent mark. if an application is informed of the presence of urgent data via .br select (2) (using the .i exceptfds argument) or through delivery of a .b sigurg signal, then it can advance up to the mark using a loop which repeatedly tests .b siocatmark and performs a read (requesting any number of bytes) as long as .b siocatmark returns false. .tp .b siocoutq returns the amount of unsent data in the socket send queue. the socket must not be in listen state, otherwise an error .rb ( einval ) is returned. .b siocoutq is defined in .ir . .\" fixme . http://sources.redhat.com/bugzilla/show_bug.cgi?id=12002, .\" filed 2010-09-10, may cause siocoutq to be defined in glibc headers alternatively, you can use the synonymous .br tiocoutq , defined in .ir . .ss error handling when a network error occurs, tcp tries to resend the packet. if it doesn't succeed after some time, either .b etimedout or the last received error on this connection is reported. .pp some applications require a quicker error notification. this can be enabled with the .b ipproto_ip level .b ip_recverr socket option. when this option is enabled, all incoming errors are immediately passed to the user program. use this option with care \(em it makes tcp less tolerant to routing changes and other normal network conditions. .sh errors .tp .b eafnotsupport passed socket address type in .i sin_family was not .br af_inet . .tp .b epipe the other end closed the socket unexpectedly or a read is executed on a shut down socket. .tp .b etimedout the other end didn't acknowledge retransmitted data after some time. .pp any errors defined for .br ip (7) or the generic socket layer may also be returned for tcp. .sh versions support for explicit congestion notification, zero-copy .br sendfile (2), reordering support and some sack extensions (dsack) were introduced in 2.4. support for forward acknowledgement (fack), time_wait recycling, and per-connection keepalive socket options were introduced in 2.3. .sh bugs not all errors are documented. .pp ipv6 is not described. .\" only a single linux kernel version is described .\" info for 2.2 was lost. should be added again, .\" or put into a separate page. .\" .sh authors .\" this man page was originally written by andi kleen. .\" it was updated for 2.4 by nivedita singhvi with input from .\" alexey kuznetsov's documentation/networking/ip-sysctl.txt .\" document. .sh see also .br accept (2), .br bind (2), .br connect (2), .br getsockopt (2), .br listen (2), .br recvmsg (2), .br sendfile (2), .br sendmsg (2), .br socket (2), .br ip (7), .br socket (7) .pp the kernel source file .ir documentation/networking/ip\-sysctl.txt . .pp rfc\ 793 for the tcp specification. .br rfc\ 1122 for the tcp requirements and a description of the nagle algorithm. .br rfc\ 1323 for tcp timestamp and window scaling options. .br rfc\ 1337 for a description of time_wait assassination hazards. .br rfc\ 3168 for a description of explicit congestion notification. .br rfc\ 2581 for tcp congestion control algorithms. .br rfc\ 2018 and rfc\ 2883 for sack and extensions to sack. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1996 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified thu oct 31 14:18:40 1996 by eric s. raymond .\" modified 2001-12-17, aeb .th getsid 2 2021-03-22 "linux" "linux programmer's manual" .sh name getsid \- get session id .sh synopsis .nf .b #include .pp .bi "pid_t getsid(pid_t" " pid" ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getsid (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l .fi .sh description .i getsid(0) returns the session id of the calling process. .br getsid () returns the session id of the process with process id .ir pid . if .i pid is 0, .br getsid () returns the session id of the calling process. .sh return value on success, a session id is returned. on error, \fi(pid_t)\ \-1\fp is returned, and .i errno is set to indicate the error. .sh errors .tp .b eperm a process with process id .i pid exists, but it is not in the same session as the calling process, and the implementation considers this an error. .tp .b esrch no process with process id .i pid was found. .sh versions this system call is available on linux since version 2.0. .\" linux has this system call since linux 1.3.44. .\" there is libc support since libc 5.2.19. .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh notes linux does not return .br eperm . .pp see .br credentials (7) for a description of sessions and session ids. .sh see also .br getpgid (2), .br setsid (2), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/select.2 .so man5/resolv.conf.5 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 21 22:35:42 1993 by rik faith (faith@cs.unc.edu) .\" modified 18 mar 1996 by martin schulze (joey@infodrom.north.de): .\" corrected description of getwd(). .\" modified sat aug 21 12:32:12 met 1999 by aeb - applied fix by aj .\" modified mon dec 11 13:32:51 met 2000 by aeb .\" modified thu apr 22 03:49:15 cest 2002 by roger luethi .\" .th getcwd 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getcwd, getwd, get_current_dir_name \- get current working directory .sh synopsis .nf .b #include .pp .bi "char *getcwd(char *" buf ", size_t " size ); .bi "char *getwd(char *" buf ); .b "char *get_current_dir_name(void);" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br get_current_dir_name (): .nf _gnu_source .fi .pp .br getwd (): .nf since glibc 2.12: (_xopen_source >= 500) && ! (_posix_c_source >= 200809l) || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source before glibc 2.12: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description these functions return a null-terminated string containing an absolute pathname that is the current working directory of the calling process. the pathname is returned as the function result and via the argument .ir buf , if present. .pp the .br getcwd () function copies an absolute pathname of the current working directory to the array pointed to by .ir buf , which is of length .ir size . .pp if the length of the absolute pathname of the current working directory, including the terminating null byte, exceeds .i size bytes, null is returned, and .i errno is set to .br erange ; an application should check for this error, and allocate a larger buffer if necessary. .pp as an extension to the posix.1-2001 standard, glibc's .br getcwd () allocates the buffer dynamically using .br malloc (3) if .i buf is null. in this case, the allocated buffer has the length .i size unless .i size is zero, when .i buf is allocated as big as necessary. the caller should .br free (3) the returned buffer. .pp .br get_current_dir_name () will .br malloc (3) an array big enough to hold the absolute pathname of the current working directory. if the environment variable .b pwd is set, and its value is correct, then that value will be returned. the caller should .br free (3) the returned buffer. .pp .br getwd () does not .br malloc (3) any memory. the .i buf argument should be a pointer to an array at least .b path_max bytes long. if the length of the absolute pathname of the current working directory, including the terminating null byte, exceeds .b path_max bytes, null is returned, and .i errno is set to .br enametoolong . (note that on some systems, .b path_max may not be a compile-time constant; furthermore, its value may depend on the filesystem, see .br pathconf (3).) for portability and security reasons, use of .br getwd () is deprecated. .sh return value on success, these functions return a pointer to a string containing the pathname of the current working directory. in the case of .br getcwd () and .br getwd () this is the same value as .ir buf . .pp on failure, these functions return null, and .i errno is set to indicate the error. the contents of the array pointed to by .i buf are undefined on error. .sh errors .tp .b eacces permission to read or search a component of the filename was denied. .tp .b efault .i buf points to a bad address. .tp .b einval the .i size argument is zero and .i buf is not a null pointer. .tp .b einval .br getwd (): .i buf is null. .tp .b enametoolong .br getwd (): the size of the null-terminated absolute pathname string exceeds .b path_max bytes. .tp .b enoent the current working directory has been unlinked. .tp .b enomem out of memory. .tp .b erange the .i size argument is less than the length of the absolute pathname of the working directory, including the terminating null byte. you need to allocate a bigger array and try again. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getcwd (), .br getwd () t} thread safety mt-safe t{ .br get_current_dir_name () t} thread safety mt-safe env .te .hy .ad .sp 1 .sh conforming to .br getcwd () conforms to posix.1-2001. note however that posix.1-2001 leaves the behavior of .br getcwd () unspecified if .i buf is null. .pp .br getwd () is present in posix.1-2001, but marked legacy. posix.1-2008 removes the specification of .br getwd (). use .br getcwd () instead. posix.1-2001 does not define any errors for .br getwd (). .pp .br get_current_dir_name () is a gnu extension. .sh notes under linux, these functions make use of the .br getcwd () system call (available since linux 2.1.92). on older systems they would query .ir /proc/self/cwd . if both system call and proc filesystem are missing, a generic implementation is called. only in that case can these calls fail under linux with .br eacces . .pp these functions are often used to save the location of the current working directory for the purpose of returning to it later. opening the current directory (".") and calling .br fchdir (2) to return is usually a faster and more reliable alternative when sufficiently many file descriptors are available, especially on platforms other than linux. .\" .ss c library/kernel differences on linux, the kernel provides a .br getcwd () system call, which the functions described in this page will use if possible. the system call takes the same arguments as the library function of the same name, but is limited to returning at most .br path_max bytes. (before linux 3.12, .\" commit 3272c544da48f8915a0e34189182aed029bd0f2b the limit on the size of the returned pathname was the system page size. on many architectures, .br path_max and the system page size are both 4096 bytes, but a few architectures have a larger page size.) if the length of the pathname of the current working directory exceeds this limit, then the system call fails with the error .br enametoolong . in this case, the library functions fall back to a (slower) alternative implementation that returns the full pathname. .pp following a change in linux 2.6.36, .\" commit 8df9d1a4142311c084ffeeacb67cd34d190eff74 the pathname returned by the .br getcwd () system call will be prefixed with the string "(unreachable)" if the current directory is not below the root directory of the current process (e.g., because the process set a new filesystem root using .br chroot (2) without changing its current directory into the new root). such behavior can also be caused by an unprivileged user by changing the current directory into another mount namespace. when dealing with pathname from untrusted sources, callers of the functions described in this page should consider checking whether the returned pathname starts with '/' or '(' to avoid misinterpreting an unreachable path as a relative pathname. .sh bugs since the linux 2.6.36 change that added "(unreachable)" in the circumstances described above, the glibc implementation of .br getcwd () has failed to conform to posix and returned a relative pathname when the api contract requires an absolute pathname. with glibc 2.27 onwards this is corrected; calling .br getcwd () from such a pathname will now result in failure with .br enoent . .sh see also .br pwd (1), .br chdir (2), .br fchdir (2), .br open (2), .br unlink (2), .br free (3), .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-9.7 .\" copyright (c) 2016, 2019, 2021 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th mount_namespaces 7 2021-08-27 "linux" "linux programmer's manual" .sh name mount_namespaces \- overview of linux mount namespaces .sh description for an overview of namespaces, see .br namespaces (7). .pp mount namespaces provide isolation of the list of mounts seen by the processes in each namespace instance. thus, the processes in each of the mount namespace instances will see distinct single-directory hierarchies. .pp the views provided by the .ir /proc/[pid]/mounts , .ir /proc/[pid]/mountinfo , and .ir /proc/[pid]/mountstats files (all described in .br proc (5)) correspond to the mount namespace in which the process with the pid .ir [pid] resides. (all of the processes that reside in the same mount namespace will see the same view in these files.) .pp a new mount namespace is created using either .br clone (2) or .br unshare (2) with the .br clone_newns flag. when a new mount namespace is created, its mount list is initialized as follows: .ip * 3 if the namespace is created using .br clone (2), the mount list of the child's namespace is a copy of the mount list in the parent process's mount namespace. .ip * if the namespace is created using .br unshare (2), the mount list of the new namespace is a copy of the mount list in the caller's previous mount namespace. .pp subsequent modifications to the mount list .rb ( mount (2) and .br umount (2)) in either mount namespace will not (by default) affect the mount list seen in the other namespace (but see the following discussion of shared subtrees). .\" .sh shared subtrees after the implementation of mount namespaces was completed, experience showed that the isolation that they provided was, in some cases, too great. for example, in order to make a newly loaded optical disk available in all mount namespaces, a mount operation was required in each namespace. for this use case, and others, the shared subtree feature was introduced in linux 2.6.15. this feature allows for automatic, controlled propagation of mount and unmount .i events between namespaces (or, more precisely, between the mounts that are members of a .ir "peer group" that are propagating events to one another). .pp each mount is marked (via .br mount (2)) as having one of the following .ir "propagation types" : .tp .br ms_shared this mount shares events with members of a peer group. mount and unmount events immediately under this mount will propagate to the other mounts that are members of the peer group. .i propagation here means that the same mount or unmount will automatically occur under all of the other mounts in the peer group. conversely, mount and unmount events that take place under peer mounts will propagate to this mount. .tp .br ms_private this mount is private; it does not have a peer group. mount and unmount events do not propagate into or out of this mount. .tp .br ms_slave mount and unmount events propagate into this mount from a (master) shared peer group. mount and unmount events under this mount do not propagate to any peer. .ip note that a mount can be the slave of another peer group while at the same time sharing mount and unmount events with a peer group of which it is a member. (more precisely, one peer group can be the slave of another peer group.) .tp .br ms_unbindable this is like a private mount, and in addition this mount can't be bind mounted. attempts to bind mount this mount .rb ( mount (2) with the .br ms_bind flag) will fail. .ip when a recursive bind mount .rb ( mount (2) with the .br ms_bind and .br ms_rec flags) is performed on a directory subtree, any bind mounts within the subtree are automatically pruned (i.e., not replicated) when replicating that subtree to produce the target subtree. .pp for a discussion of the propagation type assigned to a new mount, see notes. .pp the propagation type is a per-mount-point setting; some mounts may be marked as shared (with each shared mount being a member of a distinct peer group), while others are private (or slaved or unbindable). .pp note that a mount's propagation type determines whether mounts and unmounts of mounts .i "immediately under" the mount are propagated. thus, the propagation type does not affect propagation of events for grandchildren and further removed descendant mounts. what happens if the mount itself is unmounted is determined by the propagation type that is in effect for the .i parent of the mount. .pp members are added to a .ir "peer group" when a mount is marked as shared and either: .ip * 3 the mount is replicated during the creation of a new mount namespace; or .ip * a new bind mount is created from the mount. .pp in both of these cases, the new mount joins the peer group of which the existing mount is a member. .pp a new peer group is also created when a child mount is created under an existing mount that is marked as shared. in this case, the new child mount is also marked as shared and the resulting peer group consists of all the mounts that are replicated under the peers of parent mounts. .pp a mount ceases to be a member of a peer group when either the mount is explicitly unmounted, or when the mount is implicitly unmounted because a mount namespace is removed (because it has no more member processes). .pp the propagation type of the mounts in a mount namespace can be discovered via the "optional fields" exposed in .ir /proc/[pid]/mountinfo . (see .br proc (5) for details of this file.) the following tags can appear in the optional fields for a record in that file: .tp .i shared:x this mount is shared in peer group .ir x . each peer group has a unique id that is automatically generated by the kernel, and all mounts in the same peer group will show the same id. (these ids are assigned starting from the value 1, and may be recycled when a peer group ceases to have any members.) .tp .i master:x this mount is a slave to shared peer group .ir x . .tp .ir propagate_from:x " (since linux 2.6.26)" .\" commit 97e7e0f71d6d948c25f11f0a33878d9356d9579e this mount is a slave and receives propagation from shared peer group .ir x . this tag will always appear in conjunction with a .ir master:x tag. here, .ir x is the closest dominant peer group under the process's root directory. if .ir x is the immediate master of the mount, or if there is no dominant peer group under the same root, then only the .ir master:x field is present and not the .ir propagate_from:x field. for further details, see below. .tp .ir unbindable this is an unbindable mount. .pp if none of the above tags is present, then this is a private mount. .ss ms_shared and ms_private example suppose that on a terminal in the initial mount namespace, we mark one mount as shared and another as private, and then view the mounts in .ir /proc/self/mountinfo : .pp .in +4n .ex sh1# \fbmount \-\-make\-shared /mnts\fp sh1# \fbmount \-\-make\-private /mntp\fp sh1# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 77 61 8:17 / /mnts rw,relatime shared:1 83 61 8:15 / /mntp rw,relatime .ee .in .pp from the .ir /proc/self/mountinfo output, we see that .ir /mnts is a shared mount in peer group 1, and that .ir /mntp has no optional tags, indicating that it is a private mount. the first two fields in each record in this file are the unique id for this mount, and the mount id of the parent mount. we can further inspect this file to see that the parent mount of .ir /mnts and .ir /mntp is the root directory, .ir / , which is mounted as private: .pp .in +4n .ex sh1# \fbcat /proc/self/mountinfo | awk \(aq$1 == 61\(aq | sed \(aqs/ \- .*//\(aq\fp 61 0 8:2 / / rw,relatime .ee .in .pp on a second terminal, we create a new mount namespace where we run a second shell and inspect the mounts: .pp .in +4n .ex $ \fbps1=\(aqsh2# \(aq sudo unshare \-m \-\-propagation unchanged sh\fp sh2# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 222 145 8:17 / /mnts rw,relatime shared:1 225 145 8:15 / /mntp rw,relatime .ee .in .pp the new mount namespace received a copy of the initial mount namespace's mounts. these new mounts maintain the same propagation types, but have unique mount ids. (the .ir \-\-propagation\ unchanged option prevents .br unshare (1) from marking all mounts as private when creating a new mount namespace, .\" since util-linux 2.27 which it does by default.) .pp in the second terminal, we then create submounts under each of .ir /mnts and .ir /mntp and inspect the set-up: .pp .in +4n .ex sh2# \fbmkdir /mnts/a\fp sh2# \fbmount /dev/sdb6 /mnts/a\fp sh2# \fbmkdir /mntp/b\fp sh2# \fbmount /dev/sdb7 /mntp/b\fp sh2# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 222 145 8:17 / /mnts rw,relatime shared:1 225 145 8:15 / /mntp rw,relatime 178 222 8:22 / /mnts/a rw,relatime shared:2 230 225 8:23 / /mntp/b rw,relatime .ee .in .pp from the above, it can be seen that .ir /mnts/a was created as shared (inheriting this setting from its parent mount) and .ir /mntp/b was created as a private mount. .pp returning to the first terminal and inspecting the set-up, we see that the new mount created under the shared mount .ir /mnts propagated to its peer mount (in the initial mount namespace), but the new mount created under the private mount .ir /mntp did not propagate: .pp .in +4n .ex sh1# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 77 61 8:17 / /mnts rw,relatime shared:1 83 61 8:15 / /mntp rw,relatime 179 77 8:22 / /mnts/a rw,relatime shared:2 .ee .in .\" .ss ms_slave example making a mount a slave allows it to receive propagated mount and unmount events from a master shared peer group, while preventing it from propagating events to that master. this is useful if we want to (say) receive a mount event when an optical disk is mounted in the master shared peer group (in another mount namespace), but want to prevent mount and unmount events under the slave mount from having side effects in other namespaces. .pp we can demonstrate the effect of slaving by first marking two mounts as shared in the initial mount namespace: .pp .in +4n .ex sh1# \fbmount \-\-make\-shared /mntx\fp sh1# \fbmount \-\-make\-shared /mnty\fp sh1# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 132 83 8:23 / /mntx rw,relatime shared:1 133 83 8:22 / /mnty rw,relatime shared:2 .ee .in .pp on a second terminal, we create a new mount namespace and inspect the mounts: .pp .in +4n .ex sh2# \fbunshare \-m \-\-propagation unchanged sh\fp sh2# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 168 167 8:23 / /mntx rw,relatime shared:1 169 167 8:22 / /mnty rw,relatime shared:2 .ee .in .pp in the new mount namespace, we then mark one of the mounts as a slave: .pp .in +4n .ex sh2# \fbmount \-\-make\-slave /mnty\fp sh2# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 168 167 8:23 / /mntx rw,relatime shared:1 169 167 8:22 / /mnty rw,relatime master:2 .ee .in .pp from the above output, we see that .ir /mnty is now a slave mount that is receiving propagation events from the shared peer group with the id 2. .pp continuing in the new namespace, we create submounts under each of .ir /mntx and .ir /mnty : .pp .in +4n .ex sh2# \fbmkdir /mntx/a\fp sh2# \fbmount /dev/sda3 /mntx/a\fp sh2# \fbmkdir /mnty/b\fp sh2# \fbmount /dev/sda5 /mnty/b\fp .ee .in .pp when we inspect the state of the mounts in the new mount namespace, we see that .ir /mntx/a was created as a new shared mount (inheriting the "shared" setting from its parent mount) and .ir /mnty/b was created as a private mount: .pp .in +4n .ex sh2# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 168 167 8:23 / /mntx rw,relatime shared:1 169 167 8:22 / /mnty rw,relatime master:2 173 168 8:3 / /mntx/a rw,relatime shared:3 175 169 8:5 / /mnty/b rw,relatime .ee .in .pp returning to the first terminal (in the initial mount namespace), we see that the mount .ir /mntx/a propagated to the peer (the shared .ir /mntx ), but the mount .ir /mnty/b was not propagated: .pp .in +4n .ex sh1# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 132 83 8:23 / /mntx rw,relatime shared:1 133 83 8:22 / /mnty rw,relatime shared:2 174 132 8:3 / /mntx/a rw,relatime shared:3 .ee .in .pp now we create a new mount under .ir /mnty in the first shell: .pp .in +4n .ex sh1# \fbmkdir /mnty/c\fp sh1# \fbmount /dev/sda1 /mnty/c\fp sh1# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 132 83 8:23 / /mntx rw,relatime shared:1 133 83 8:22 / /mnty rw,relatime shared:2 174 132 8:3 / /mntx/a rw,relatime shared:3 178 133 8:1 / /mnty/c rw,relatime shared:4 .ee .in .pp when we examine the mounts in the second mount namespace, we see that in this case the new mount has been propagated to the slave mount, and that the new mount is itself a slave mount (to peer group 4): .pp .in +4n .ex sh2# \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 168 167 8:23 / /mntx rw,relatime shared:1 169 167 8:22 / /mnty rw,relatime master:2 173 168 8:3 / /mntx/a rw,relatime shared:3 175 169 8:5 / /mnty/b rw,relatime 179 169 8:1 / /mnty/c rw,relatime master:4 .ee .in .\" .ss ms_unbindable example one of the primary purposes of unbindable mounts is to avoid the "mount explosion" problem when repeatedly performing bind mounts of a higher-level subtree at a lower-level mount. the problem is illustrated by the following shell session. .pp suppose we have a system with the following mounts: .pp .in +4n .ex # \fbmount | awk \(aq{print $1, $2, $3}\(aq\fp /dev/sda1 on / /dev/sdb6 on /mntx /dev/sdb7 on /mnty .ee .in .pp suppose furthermore that we wish to recursively bind mount the root directory under several users' home directories. we do this for the first user, and inspect the mounts: .pp .in +4n .ex # \fbmount \-\-rbind / /home/cecilia/\fp # \fbmount | awk \(aq{print $1, $2, $3}\(aq\fp /dev/sda1 on / /dev/sdb6 on /mntx /dev/sdb7 on /mnty /dev/sda1 on /home/cecilia /dev/sdb6 on /home/cecilia/mntx /dev/sdb7 on /home/cecilia/mnty .ee .in .pp when we repeat this operation for the second user, we start to see the explosion problem: .pp .in +4n .ex # \fbmount \-\-rbind / /home/henry\fp # \fbmount | awk \(aq{print $1, $2, $3}\(aq\fp /dev/sda1 on / /dev/sdb6 on /mntx /dev/sdb7 on /mnty /dev/sda1 on /home/cecilia /dev/sdb6 on /home/cecilia/mntx /dev/sdb7 on /home/cecilia/mnty /dev/sda1 on /home/henry /dev/sdb6 on /home/henry/mntx /dev/sdb7 on /home/henry/mnty /dev/sda1 on /home/henry/home/cecilia /dev/sdb6 on /home/henry/home/cecilia/mntx /dev/sdb7 on /home/henry/home/cecilia/mnty .ee .in .pp under .ir /home/henry , we have not only recursively added the .ir /mntx and .ir /mnty mounts, but also the recursive mounts of those directories under .ir /home/cecilia that were created in the previous step. upon repeating the step for a third user, it becomes obvious that the explosion is exponential in nature: .pp .in +4n .ex # \fbmount \-\-rbind / /home/otto\fp # \fbmount | awk \(aq{print $1, $2, $3}\(aq\fp /dev/sda1 on / /dev/sdb6 on /mntx /dev/sdb7 on /mnty /dev/sda1 on /home/cecilia /dev/sdb6 on /home/cecilia/mntx /dev/sdb7 on /home/cecilia/mnty /dev/sda1 on /home/henry /dev/sdb6 on /home/henry/mntx /dev/sdb7 on /home/henry/mnty /dev/sda1 on /home/henry/home/cecilia /dev/sdb6 on /home/henry/home/cecilia/mntx /dev/sdb7 on /home/henry/home/cecilia/mnty /dev/sda1 on /home/otto /dev/sdb6 on /home/otto/mntx /dev/sdb7 on /home/otto/mnty /dev/sda1 on /home/otto/home/cecilia /dev/sdb6 on /home/otto/home/cecilia/mntx /dev/sdb7 on /home/otto/home/cecilia/mnty /dev/sda1 on /home/otto/home/henry /dev/sdb6 on /home/otto/home/henry/mntx /dev/sdb7 on /home/otto/home/henry/mnty /dev/sda1 on /home/otto/home/henry/home/cecilia /dev/sdb6 on /home/otto/home/henry/home/cecilia/mntx /dev/sdb7 on /home/otto/home/henry/home/cecilia/mnty .ee .in .pp the mount explosion problem in the above scenario can be avoided by making each of the new mounts unbindable. the effect of doing this is that recursive mounts of the root directory will not replicate the unbindable mounts. we make such a mount for the first user: .pp .in +4n .ex # \fbmount \-\-rbind \-\-make\-unbindable / /home/cecilia\fp .ee .in .pp before going further, we show that unbindable mounts are indeed unbindable: .pp .in +4n .ex # \fbmkdir /mntz\fp # \fbmount \-\-bind /home/cecilia /mntz\fp mount: wrong fs type, bad option, bad superblock on /home/cecilia, missing codepage or helper program, or other error in some cases useful info is found in syslog \- try dmesg | tail or so. .ee .in .pp now we create unbindable recursive bind mounts for the other two users: .pp .in +4n .ex # \fbmount \-\-rbind \-\-make\-unbindable / /home/henry\fp # \fbmount \-\-rbind \-\-make\-unbindable / /home/otto\fp .ee .in .pp upon examining the list of mounts, we see there has been no explosion of mounts, because the unbindable mounts were not replicated under each user's directory: .pp .in +4n .ex # \fbmount | awk \(aq{print $1, $2, $3}\(aq\fp /dev/sda1 on / /dev/sdb6 on /mntx /dev/sdb7 on /mnty /dev/sda1 on /home/cecilia /dev/sdb6 on /home/cecilia/mntx /dev/sdb7 on /home/cecilia/mnty /dev/sda1 on /home/henry /dev/sdb6 on /home/henry/mntx /dev/sdb7 on /home/henry/mnty /dev/sda1 on /home/otto /dev/sdb6 on /home/otto/mntx /dev/sdb7 on /home/otto/mnty .ee .in .\" .ss propagation type transitions the following table shows the effect that applying a new propagation type (i.e., .ir "mount \-\-make\-xxxx") has on the existing propagation type of a mount. the rows correspond to existing propagation types, and the columns are the new propagation settings. for reasons of space, "private" is abbreviated as "priv" and "unbindable" as "unbind". .ts lb2 lb2 lb2 lb2 lb1 lb | l l l l l. make-shared make-slave make-priv make-unbind _ shared shared slave/priv [1] priv unbind slave slave+shared slave [2] priv unbind slave+shared slave+shared slave priv unbind private shared priv [2] priv unbind unbindable shared unbind [2] priv unbind .te .sp 1 note the following details to the table: .ip [1] 4 if a shared mount is the only mount in its peer group, making it a slave automatically makes it private. .ip [2] slaving a nonshared mount has no effect on the mount. .\" .ss bind (ms_bind) semantics suppose that the following command is performed: .pp .in +4n .ex mount \-\-bind a/a b/b .ee .in .pp here, .i a is the source mount, .i b is the destination mount, .i a is a subdirectory path under the mount point .ir a , and .i b is a subdirectory path under the mount point .ir b . the propagation type of the resulting mount, .ir b/b , depends on the propagation types of the mounts .ir a and .ir b , and is summarized in the following table. .pp .ts lb2 lb1 lb2 lb2 lb2 lb0 lb2 lb1 lb2 lb2 lb2 lb0 lb lb | l l l l l. source(a) shared private slave unbind _ dest(b) shared shared shared slave+shared invalid nonshared shared private slave invalid .te .sp 1 note that a recursive bind of a subtree follows the same semantics as for a bind operation on each mount in the subtree. (unbindable mounts are automatically pruned at the target mount point.) .pp for further details, see .i documentation/filesystems/sharedsubtree.txt in the kernel source tree. .\" .ss move (ms_move) semantics suppose that the following command is performed: .pp .in +4n .ex mount \-\-move a b/b .ee .in .pp here, .i a is the source mount, .i b is the destination mount, and .i b is a subdirectory path under the mount point .ir b . the propagation type of the resulting mount, .ir b/b , depends on the propagation types of the mounts .ir a and .ir b , and is summarized in the following table. .pp .ts lb2 lb1 lb2 lb2 lb2 lb0 lb2 lb1 lb2 lb2 lb2 lb0 lb lb | l l l l l. source(a) shared private slave unbind _ dest(b) shared shared shared slave+shared invalid nonshared shared private slave unbindable .te .sp 1 note: moving a mount that resides under a shared mount is invalid. .pp for further details, see .i documentation/filesystems/sharedsubtree.txt in the kernel source tree. .\" .ss mount semantics suppose that we use the following command to create a mount: .pp .in +4n .ex mount device b/b .ee .in .pp here, .i b is the destination mount, and .i b is a subdirectory path under the mount point .ir b . the propagation type of the resulting mount, .ir b/b , follows the same rules as for a bind mount, where the propagation type of the source mount is considered always to be private. .\" .ss unmount semantics suppose that we use the following command to tear down a mount: .pp .in +4n .ex unmount a .ee .in .pp here, .i a is a mount on .ir b/b , where .i b is the parent mount and .i b is a subdirectory path under the mount point .ir b . if .b b is shared, then all most-recently-mounted mounts at .i b on mounts that receive propagation from mount .i b and do not have submounts under them are unmounted. .\" .ss the /proc/[pid]/mountinfo "propagate_from" tag the .i propagate_from:x tag is shown in the optional fields of a .ir /proc/[pid]/mountinfo record in cases where a process can't see a slave's immediate master (i.e., the pathname of the master is not reachable from the filesystem root directory) and so cannot determine the chain of propagation between the mounts it can see. .pp in the following example, we first create a two-link master-slave chain between the mounts .ir /mnt , .ir /tmp/etc , and .ir /mnt/tmp/etc . then the .br chroot (1) command is used to make the .ir /tmp/etc mount point unreachable from the root directory, creating a situation where the master of .ir /mnt/tmp/etc is not reachable from the (new) root directory of the process. .pp first, we bind mount the root directory onto .ir /mnt and then bind mount .ir /proc at .ir /mnt/proc so that after the later .br chroot (1) the .br proc (5) filesystem remains visible at the correct location in the chroot-ed environment. .pp .in +4n .ex # \fbmkdir \-p /mnt/proc\fp # \fbmount \-\-bind / /mnt\fp # \fbmount \-\-bind /proc /mnt/proc\fp .ee .in .pp next, we ensure that the .ir /mnt mount is a shared mount in a new peer group (with no peers): .pp .in +4n .ex # \fbmount \-\-make\-private /mnt\fp # isolate from any previous peer group # \fbmount \-\-make\-shared /mnt\fp # \fbcat /proc/self/mountinfo | grep \(aq/mnt\(aq | sed \(aqs/ \- .*//\(aq\fp 239 61 8:2 / /mnt ... shared:102 248 239 0:4 / /mnt/proc ... shared:5 .ee .in .pp next, we bind mount .ir /mnt/etc onto .ir /tmp/etc : .pp .in +4n .ex # \fbmkdir \-p /tmp/etc\fp # \fbmount \-\-bind /mnt/etc /tmp/etc\fp # \fbcat /proc/self/mountinfo | egrep \(aq/mnt|/tmp/\(aq | sed \(aqs/ \- .*//\(aq\fp 239 61 8:2 / /mnt ... shared:102 248 239 0:4 / /mnt/proc ... shared:5 267 40 8:2 /etc /tmp/etc ... shared:102 .ee .in .pp initially, these two mounts are in the same peer group, but we then make the .ir /tmp/etc a slave of .ir /mnt/etc , and then make .ir /tmp/etc shared as well, so that it can propagate events to the next slave in the chain: .pp .in +4n .ex # \fbmount \-\-make\-slave /tmp/etc\fp # \fbmount \-\-make\-shared /tmp/etc\fp # \fbcat /proc/self/mountinfo | egrep \(aq/mnt|/tmp/\(aq | sed \(aqs/ \- .*//\(aq\fp 239 61 8:2 / /mnt ... shared:102 248 239 0:4 / /mnt/proc ... shared:5 267 40 8:2 /etc /tmp/etc ... shared:105 master:102 .ee .in .pp then we bind mount .ir /tmp/etc onto .ir /mnt/tmp/etc . again, the two mounts are initially in the same peer group, but we then make .ir /mnt/tmp/etc a slave of .ir /tmp/etc : .pp .in +4n .ex # \fbmkdir \-p /mnt/tmp/etc\fp # \fbmount \-\-bind /tmp/etc /mnt/tmp/etc\fp # \fbmount \-\-make\-slave /mnt/tmp/etc\fp # \fbcat /proc/self/mountinfo | egrep \(aq/mnt|/tmp/\(aq | sed \(aqs/ \- .*//\(aq\fp 239 61 8:2 / /mnt ... shared:102 248 239 0:4 / /mnt/proc ... shared:5 267 40 8:2 /etc /tmp/etc ... shared:105 master:102 273 239 8:2 /etc /mnt/tmp/etc ... master:105 .ee .in .pp from the above, we see that .ir /mnt is the master of the slave .ir /tmp/etc , which in turn is the master of the slave .ir /mnt/tmp/etc . .pp we then .br chroot (1) to the .ir /mnt directory, which renders the mount with id 267 unreachable from the (new) root directory: .pp .in +4n .ex # \fbchroot /mnt\fp .ee .in .pp when we examine the state of the mounts inside the chroot-ed environment, we see the following: .pp .in +4n .ex # \fbcat /proc/self/mountinfo | sed \(aqs/ \- .*//\(aq\fp 239 61 8:2 / / ... shared:102 248 239 0:4 / /proc ... shared:5 273 239 8:2 /etc /tmp/etc ... master:105 propagate_from:102 .ee .in .pp above, we see that the mount with id 273 is a slave whose master is the peer group 105. the mount point for that master is unreachable, and so a .ir propagate_from tag is displayed, indicating that the closest dominant peer group (i.e., the nearest reachable mount in the slave chain) is the peer group with the id 102 (corresponding to the .ir /mnt mount point before the .br chroot (1) was performed. .\" .sh versions mount namespaces first appeared in linux 2.4.19. .sh conforming to namespaces are a linux-specific feature. .\" .sh notes the propagation type assigned to a new mount depends on the propagation type of the parent mount. if the mount has a parent (i.e., it is a non-root mount point) and the propagation type of the parent is .br ms_shared , then the propagation type of the new mount is also .br ms_shared . otherwise, the propagation type of the new mount is .br ms_private . .pp notwithstanding the fact that the default propagation type for new mount is in many cases .br ms_private , .br ms_shared is typically more useful. for this reason, .br systemd (1) automatically remounts all mounts as .br ms_shared on system startup. thus, on most modern systems, the default propagation type is in practice .br ms_shared . .pp since, when one uses .br unshare (1) to create a mount namespace, the goal is commonly to provide full isolation of the mounts in the new namespace, .br unshare (1) (since .ir util\-linux version 2.27) in turn reverses the step performed by .br systemd (1), by making all mounts private in the new namespace. that is, .br unshare (1) performs the equivalent of the following in the new mount namespace: .pp .in +4n .ex mount \-\-make\-rprivate / .ee .in .pp to prevent this, one can use the .ir "\-\-propagation\ unchanged" option to .br unshare (1). .pp an application that creates a new mount namespace directly using .br clone (2) or .br unshare (2) may desire to prevent propagation of mount events to other mount namespaces (as is done by .br unshare (1)). this can be done by changing the propagation type of mounts in the new namespace to either .b ms_slave or .br ms_private , using a call such as the following: .pp .in +4n .ex mount(null, "/", ms_slave | ms_rec, null); .ee .in .pp for a discussion of propagation types when moving mounts .rb ( ms_move ) and creating bind mounts .rb ( ms_bind ), see .ir documentation/filesystems/sharedsubtree.txt . .\" .\" ============================================================ .\" .ss restrictions on mount namespaces note the following points with respect to mount namespaces: .ip [1] 4 each mount namespace has an owner user namespace. as explained above, when a new mount namespace is created, its mount list is initialized as a copy of the mount list of another mount namespace. if the new namespace and the namespace from which the mount list was copied are owned by different user namespaces, then the new mount namespace is considered .ir "less privileged" . .ip [2] when creating a less privileged mount namespace, shared mounts are reduced to slave mounts. this ensures that mappings performed in less privileged mount namespaces will not propagate to more privileged mount namespaces. .ip [3] mounts that come as a single unit from a more privileged mount namespace are locked together and may not be separated in a less privileged mount namespace. (the .br unshare (2) .b clone_newns operation brings across all of the mounts from the original mount namespace as a single unit, and recursive mounts that propagate between mount namespaces propagate as a single unit.) .ip in this context, "may not be separated" means that the mounts are locked so that they may not be individually unmounted. consider the following example: .ip .rs .in +4n .ex $ \fbsudo sh\fp # \fbmount \-\-bind /dev/null /etc/shadow\fp # \fbcat /etc/shadow\fp # produces no output .ee .in .re .ip the above steps, performed in a more privileged mount namespace, have created a bind mount that obscures the contents of the shadow password file, .ir /etc/shadow . for security reasons, it should not be possible to unmount that mount in a less privileged mount namespace, since that would reveal the contents of .ir /etc/shadow . .ip suppose we now create a new mount namespace owned by a new user namespace. the new mount namespace will inherit copies of all of the mounts from the previous mount namespace. however, those mounts will be locked because the new mount namespace is less privileged. consequently, an attempt to unmount the mount fails as show in the following step: .ip .rs .in +4n .ex # \fbunshare \-\-user \-\-map\-root\-user \-\-mount \e\fp \fbstrace \-o /tmp/log \e\fp \fbumount /mnt/dir\fp umount: /etc/shadow: not mounted. # \fbgrep \(aq^umount\(aq /tmp/log\fp umount2("/etc/shadow", 0) = \-1 einval (invalid argument) .ee .in .re .ip the error message from .br mount (8) is a little confusing, but the .br strace (1) output reveals that the underlying .br umount2 (2) system call failed with the error .br einval , which is the error that the kernel returns to indicate that the mount is locked. .ip note, however, that it is possible to stack (and unstack) a mount on top of one of the inherited locked mounts in a less privileged mount namespace: .ip .in +4n .ex # \fbecho \(aqaaaaa\(aq > /tmp/a\fp # file to mount onto /etc/shadow # \fbunshare \-\-user \-\-map\-root\-user \-\-mount \e\fp \fbsh \-c \(aqmount \-\-bind /tmp/a /etc/shadow; cat /etc/shadow\(aq\fp aaaaa # \fbumount /etc/shadow\fp .ee .in .ip the final .br umount (8) command above, which is performed in the initial mount namespace, makes the original .i /etc/shadow file once more visible in that namespace. .ip [4] following on from point [3], note that it is possible to unmount an entire subtree of mounts that propagated as a unit into a less privileged mount namespace, as illustrated in the following example. .ip first, we create new user and mount namespaces using .br unshare (1). in the new mount namespace, the propagation type of all mounts is set to private. we then create a shared bind mount at .ir /mnt , and a small hierarchy of mounts underneath that mount. .ip .in +4n .ex $ \fbps1=\(aqns1# \(aq sudo unshare \-\-user \-\-map\-root\-user \e\fp \fb\-\-mount \-\-propagation private bash\fp ns1# \fbecho $$\fp # we need the pid of this shell later 778501 ns1# \fbmount \-\-make\-shared \-\-bind /mnt /mnt\fp ns1# \fbmkdir /mnt/x\fp ns1# \fbmount \-\-make\-private \-t tmpfs none /mnt/x\fp ns1# \fbmkdir /mnt/x/y\fp ns1# \fbmount \-\-make\-private \-t tmpfs none /mnt/x/y\fp ns1# \fbgrep /mnt /proc/self/mountinfo | sed \(aqs/ \- .*//\(aq\fp 986 83 8:5 /mnt /mnt rw,relatime shared:344 989 986 0:56 / /mnt/x rw,relatime 990 989 0:57 / /mnt/x/y rw,relatime .ee .in .ip continuing in the same shell session, we then create a second shell in a new user namespace and a new (less privileged) mount namespace and check the state of the propagated mounts rooted at .ir /mnt . .ip .in +4n .ex ns1# \fbps1=\(aqns2# \(aq unshare \-\-user \-\-map\-root\-user \e\fp \fb\-\-mount \-\-propagation unchanged bash\fp ns2# \fbgrep /mnt /proc/self/mountinfo | sed \(aqs/ \- .*//\(aq\fp 1239 1204 8:5 /mnt /mnt rw,relatime master:344 1240 1239 0:56 / /mnt/x rw,relatime 1241 1240 0:57 / /mnt/x/y rw,relatime .ee .in .ip of note in the above output is that the propagation type of the mount .i /mnt has been reduced to slave, as explained in point [2]. this means that submount events will propagate from the master .i /mnt in "ns1", but propagation will not occur in the opposite direction. .ip from a separate terminal window, we then use .br nsenter (1) to enter the mount and user namespaces corresponding to "ns1". in that terminal window, we then recursively bind mount .ir /mnt/x at the location .ir /mnt/ppp . .ip .in +4n .ex $ \fbps1=\(aqns3# \(aq sudo nsenter \-t 778501 \-\-user \-\-mount\fp ns3# \fbmount \-\-rbind \-\-make\-private /mnt/x /mnt/ppp\fp ns3# \fbgrep /mnt /proc/self/mountinfo | sed \(aqs/ \- .*//\(aq\fp 986 83 8:5 /mnt /mnt rw,relatime shared:344 989 986 0:56 / /mnt/x rw,relatime 990 989 0:57 / /mnt/x/y rw,relatime 1242 986 0:56 / /mnt/ppp rw,relatime 1243 1242 0:57 / /mnt/ppp/y rw,relatime shared:518 .ee .in .ip because the propagation type of the parent mount, .ir /mnt , was shared, the recursive bind mount propagated a small subtree of mounts under the slave mount .i /mnt into "ns2", as can be verified by executing the following command in that shell session: .ip .in +4n .ex ns2# \fbgrep /mnt /proc/self/mountinfo | sed \(aqs/ \- .*//\(aq\fp 1239 1204 8:5 /mnt /mnt rw,relatime master:344 1240 1239 0:56 / /mnt/x rw,relatime 1241 1240 0:57 / /mnt/x/y rw,relatime 1244 1239 0:56 / /mnt/ppp rw,relatime 1245 1244 0:57 / /mnt/ppp/y rw,relatime master:518 .ee .in .ip while it is not possible to unmount a part of the propagated subtree .ri ( /mnt/ppp/y ) in "ns2", it is possible to unmount the entire subtree, as shown by the following commands: .ip .in +4n .ex ns2# \fbumount /mnt/ppp/y\fp umount: /mnt/ppp/y: not mounted. ns2# \fbumount \-l /mnt/ppp | sed \(aqs/ \- .*//\(aq\fp # succeeds... ns2# \fbgrep /mnt /proc/self/mountinfo\fp 1239 1204 8:5 /mnt /mnt rw,relatime master:344 1240 1239 0:56 / /mnt/x rw,relatime 1241 1240 0:57 / /mnt/x/y rw,relatime .ee .in .ip [5] the .br mount (2) flags .br ms_rdonly , .br ms_nosuid , .br ms_noexec , and the "atime" flags .rb ( ms_noatime , .br ms_nodiratime , .br ms_relatime ) settings become locked .\" commit 9566d6742852c527bf5af38af5cbb878dad75705 .\" author: eric w. biederman .\" date: mon jul 28 17:26:07 2014 -0700 .\" .\" mnt: correct permission checks in do_remount .\" when propagated from a more privileged to a less privileged mount namespace, and may not be changed in the less privileged mount namespace. .ip this point is illustrated in the following example where, in a more privileged mount namespace, we create a bind mount that is marked as read-only. for security reasons, it should not be possible to make the mount writable in a less privileged mount namespace, and indeed the kernel prevents this: .ip .rs .in +4n .ex $ \fbsudo mkdir /mnt/dir\fp $ \fbsudo mount \-\-bind \-o ro /some/path /mnt/dir\fp $ \fbsudo unshare \-\-user \-\-map\-root\-user \-\-mount \e\fp \fbmount \-o remount,rw /mnt/dir\fp mount: /mnt/dir: permission denied. .ee .in .re .ip [6] .\" (as of 3.18-rc1 (in al viro's 2014-08-30 vfs.git#for-next tree)) a file or directory that is a mount point in one namespace that is not a mount point in another namespace, may be renamed, unlinked, or removed .rb ( rmdir (2)) in the mount namespace in which it is not a mount point (subject to the usual permission checks). consequently, the mount point is removed in the mount namespace where it was a mount point. .ip previously (before linux 3.18), .\" mtk: the change was in linux 3.18, i think, with this commit: .\" commit 8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe .\" author: eric w. biederman .\" date: tue oct 1 18:33:48 2013 -0700 .\" .\" vfs: lazily remove mounts on unlinked files and directories. attempting to unlink, rename, or remove a file or directory that was a mount point in another mount namespace would result in the error .br ebusy . that behavior had technical problems of enforcement (e.g., for nfs) and permitted denial-of-service attacks against more privileged users (i.e., preventing individual files from being updated by bind mounting on top of them). .sh examples see .br pivot_root (2). .sh see also .br unshare (1), .br clone (2), .br mount (2), .br mount_setattr (2), .br pivot_root (2), .br setns (2), .br umount (2), .br unshare (2), .br proc (5), .br namespaces (7), .br user_namespaces (7), .br findmnt (8), .br mount (8), .br pam_namespace (8), .br pivot_root (8), .br umount (8) .pp .ir documentation/filesystems/sharedsubtree.txt in the kernel source tree. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .so man3/strsignal.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 16:59:10 1993 by rik faith (faith@cs.unc.edu) .th mem 4 2015-01-02 "linux" "linux programmer's manual" .sh name mem, kmem, port \- system memory, kernel memory and system ports .sh description .ir /dev/mem is a character device file that is an image of the main memory of the computer. it may be used, for example, to examine (and even patch) the system. .pp byte addresses in .ir /dev/mem are interpreted as physical memory addresses. references to nonexistent locations cause errors to be returned. .pp examining and patching is likely to lead to unexpected results when read-only or write-only bits are present. .pp since linux 2.6.26, and depending on the architecture, the .b config_strict_devmem kernel configuration option limits the areas which can be accessed through this file. for example: on x86, ram access is not allowed but accessing memory-mapped pci regions is. .pp it is typically created by: .pp .in +4n .ex mknod \-m 660 /dev/mem c 1 1 chown root:kmem /dev/mem .ee .in .pp the file .ir /dev/kmem is the same as .ir /dev/mem , except that the kernel virtual memory rather than physical memory is accessed. since linux 2.6.26, this file is available only if the .b config_devkmem kernel configuration option is enabled. .pp it is typically created by: .pp .in +4n .ex mknod \-m 640 /dev/kmem c 1 2 chown root:kmem /dev/kmem .ee .in .pp .ir /dev/port is similar to .ir /dev/mem , but the i/o ports are accessed. .pp it is typically created by: .pp .in +4n .ex mknod \-m 660 /dev/port c 1 4 chown root:kmem /dev/port .ee .in .sh files .i /dev/mem .br .i /dev/kmem .br .i /dev/port .sh see also .br chown (1), .br mknod (1), .br ioperm (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. #!/bin/sh # # add_parens_for_own_funcs.sh # # this script is designed to fix inconsistencies in the use of # parentheses after function names in the manual pages. # it changes manual pages to add these parentheses. # the problem is how to determine what is a "function name". # the approach this script takes is the following: # # for each manual page named in the command line that contains # more than one line (i.e., skip man-page link files) # create a set of names taken from the .sh section of the # page and from grepping all pages for names that # have .so links to this page # for each name obtained above # if we can find something that looks like a prototype on # the page, then # try to substitute instances of that name on the page. # (instances are considered to be words formatted # using ^.[bi] or \f[bi]...\f[pr] -- this script # ignores unformatted instances of function names.) # fi # done # done # # the rationale of the above is that the most likely function names # that appear on a page are those that the manual page is describing. # it doesn't fix everything, but it catches many instances. # the rest will have to be done manually. # # this script is rather verbose because it provides a computer-assisted # solution, rather than one that is fully automated. when running it, # pipe the output through # # ... 2>&1 | less # # and take a good look at the output. in particular, you can scan # the output for *possible* problems by looking for the pattern: /^%%%/ # the script's output should be enough to help you determine if the # problem is real or not. # # suggested usage (in this case to fix pages in section 2): # # cd man2 # sh add_parens_for_own_funcs.sh *.2 2>&1 | tee changes.log | less # # use the "-n" option for a dry run, in order to see what would be # done, without actually doing it. # # (and, yes, there are many ways that this script could probably be # made to work faster...) # ###################################################################### # # (c) copyright 2005 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # # # file_base="tmp.$(basename $0)" work_dst_file="$file_base.dst" work_src_file="$file_base.src" matches_for_all_names="$file_base.all_match" matches_for_this_name="$file_base.this_match" all_files="$work_dst_file $work_src_file $matches_for_all_names \ $matches_for_this_name" rm -f $all_files # command-line option processing really_do_it=1 while getopts "n" optname; do case "$optname" in n) really_do_it=0; ;; *) echo "unknown option: $optarg" exit 1 ;; esac done shift $(( $optind - 1 )) # only process files with > 1 line -- single-line files are link files for page in $(wc "$@" 2> /dev/null | awk '$1 > 1 {print $4}'| \ grep -v '^total'); do echo ">>>>>>>>>>>>>>>>>>>>>>>>>" $page "<<<<<<<<<<<<<<<<<<<<<<<<<" echo ">>>>>>>>>>>>>>>>>>>>>>>>>" $page "<<<<<<<<<<<<<<<<<<<<<<<<<" 1>&2 # extract names that follow the ".sh name" directive -- these will # be our guesses about function names to look for sh_nlist=$(cat $page | \ awk 'begin { p = 0 } /^\.sh name/ { p = nr } /^.sh/ && nr > p { p = 0 } # stop at the next .sh directive p > 0 && nr > p { print $0 } # these are the lines between # the two .sh directives ') sh_nlist=$(echo $sh_nlist | sed -e 's/ *\\-.*//' -e 's/, */ /g') echo "### .sh name list:" $sh_nlist # some pages like msgop.2 don't actually list the function names in # the .sh section -- but we can try using link pages to give us # another guess at the right function names to look for so_nlist=$(grep -l "^\\.so.*/$(echo $page| \ sed -e 's/\.[1-8]$//')\\." $* | \ sed -e 's/\.[1-8]$//g') echo "### .so name list:" $so_nlist # combine the two lists, eliminate duplicates nlist=$(echo $sh_nlist $so_nlist | tr ' ' '\012' | sort -u) maybechanged=0 cp $page $work_dst_file rm -f $matches_for_all_names; # touch $matches_for_all_names for rname in $nlist; do # try each name from out list for this page # a very few names in .sh sections contain regexp characters! name=$(echo $rname | sed -e 's/\*/\\*/g' -e 's/\./\\./g' \ -e 's/\[/\\[/g' -e 's/\+/\\+/g') echo "########## trying $rname ##########" rm -f $matches_for_this_name grep "^.br* $name *$" $page | \ >> $matches_for_this_name grep "^.br $name [^(\"]$" $page | \ >> $matches_for_this_name grep '\\fb'"$name"'\\f[pr][ .,;:]' $page | \ >> $matches_for_this_name grep '\\fb'"$name"'\\f[pr]$' $page | \ >> $matches_for_this_name cat $matches_for_this_name | sed -e 's/^/### match: /' cat $matches_for_this_name >> $matches_for_all_names # only process a page if we can see something that looks # like a function prototype for this name in the page if grep -q "$name *(" $page || \ grep -q "$name\\\\f.[\\ ]*(" $page; then # '.b name$' # '.br name [^("]*$ # (the use of [^"] in the above eliminates lines # like: .br func " and " func # those lines better be done manually.) cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e "s/^.br* $name *\$/.br $name ()/" \ -e "/^.br *$name [^(\"]*\$/s/^.br *$name /.br $name ()/" \ > $work_dst_file # '\fbname\fp[ .,;:]' # '\fbname\fp$' cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e 's/\\fb'$name'\\fp /\\fb'$name'\\fp() /g' \ -e 's/\\fb'$name'\\fp\./\\fb'$name'\\fp()./g' \ -e 's/\\fb'$name'\\fp,/\\fb'$name'\\fp(),/g' \ -e 's/\\fb'$name'\\fp;/\\fb'$name'\\fp();/g' \ -e 's/\\fb'$name'\\fp:/\\fb'$name'\\fp():/g' \ -e 's/\\fb'$name'\\fp$/\\fb'$name'\\fp()/g' \ > $work_dst_file # '\fbname\fr[ .,;:]' # '\fbname\fr$' cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e 's/\\fb'$name'\\fr /\\fb'$name'\\fr() /g' \ -e 's/\\fb'$name'\\fr\./\\fb'$name'\\fr()./g' \ -e 's/\\fb'$name'\\fr,/\\fb'$name'\\fr(),/g' \ -e 's/\\fb'$name'\\fr;/\\fb'$name'\\fr();/g' \ -e 's/\\fb'$name'\\fr:/\\fb'$name'\\fr():/g' \ -e 's/\\fb'$name'\\fr$/\\fb'$name'\\fr()/g' \ > $work_dst_file maybechanged=1 else echo "%%%%%%%%%% warning: no prototype matches for: $name" fi done # if the file was changed, then: # show "diff -u" output to user; # and count number of changed lines and compare it with what # we expected, displaying a warning if it wasn't what was expected if test $maybechanged -ne 0 && ! cmp -s $page $work_dst_file; then diff -u $page $work_dst_file made_matches=$(diff -u 0 $page $work_dst_file | grep '^\+[^+]' | \ wc -l | awk '{print $1}') # the following line makes the changes -- comment it out if you # just want to do a dry run to see what changes would be made. if test $really_do_it -ne 0; then cat $work_dst_file > $page fi else echo "### nothing changed" made_matches=0 fi min_match=$(cat $matches_for_all_names | \ sort -u | wc -l | awk '{print $1}') echo "### expected matches >= $min_match" echo "### made matches $made_matches" if test $made_matches -lt $min_match; then echo "%%%%%%%%%% warning: not enough matches: " \ "$made_matches < $min_match" fi done # clean up rm -f $all_files exit 0 .so man3/pow10.3 .so man2/open.2 .so man2/select.2 .so man3/scalbln.3 .\" copyright (c) 1995 michael chastain (mec@shell.portal.com), 15 april 1995. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified tue oct 22 22:11:53 1996 by eric s. raymond .th socketcall 2 2021-03-22 "linux" "linux programmer's manual" .sh name socketcall \- socket system calls .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .br "#include " " /* definition of " sys_socketcall " */" .b #include .pp .bi "int syscall(sys_socketcall, int " call ", unsigned long *" args ); .fi .pp .ir note : glibc provides no wrapper for .br socketcall (), necessitating the use of .br syscall (2). .sh description .br socketcall () is a common kernel entry point for the socket system calls. .i call determines which socket function to invoke. .i args points to a block containing the actual arguments, which are passed through to the appropriate call. .pp user programs should call the appropriate functions by their usual names. only standard library implementors and kernel hackers need to know about .br socketcall (). .pp .ts tab(:); l l. \ficall\fr:man page t{ .b sys_socket t}:t{ .br socket (2) t} t{ .b sys_bind t}:t{ .br bind (2) t} t{ .b sys_connect t}:t{ .br connect (2) t} t{ .b sys_listen t}:t{ .br listen (2) t} t{ .b sys_accept t}:t{ .br accept (2) t} t{ .b sys_getsockname t}:t{ .br getsockname (2) t} t{ .b sys_getpeername t}:t{ .br getpeername (2) t} t{ .b sys_socketpair t}:t{ .br socketpair (2) t} t{ .b sys_send t}:t{ .br send (2) t} t{ .b sys_recv t}:t{ .br recv (2) t} t{ .b sys_sendto t}:t{ .br sendto (2) t} t{ .b sys_recvfrom t}:t{ .br recvfrom (2) t} t{ .b sys_shutdown t}:t{ .br shutdown (2) t} t{ .b sys_setsockopt t}:t{ .br setsockopt (2) t} t{ .b sys_getsockopt t}:t{ .br getsockopt (2) t} t{ .b sys_sendmsg t}:t{ .br sendmsg (2) t} t{ .b sys_recvmsg t}:t{ .br recvmsg (2) t} t{ .b sys_accept4 t}:t{ .br accept4 (2) t} t{ .b sys_recvmmsg t}:t{ .br recvmmsg (2) t} t{ .b sys_sendmmsg t}:t{ .br sendmmsg (2) t} .te .sh conforming to this call is specific to linux, and should not be used in programs intended to be portable. .sh notes on some architectures\(emfor example, x86-64 and arm\(emthere is no .br socketcall () system call; instead .br socket (2), .br accept (2), .br bind (2), and so on really are implemented as separate system calls. .pp on x86-32, .br socketcall () was historically the only entry point for the sockets api. however, starting in linux 4.3, .\" commit 9dea5dc921b5f4045a18c63eb92e84dc274d17eb direct system calls are provided on x86-32 for the sockets api. this facilitates the creation of .br seccomp (2) filters that filter sockets system calls (for new user-space binaries that are compiled to use the new entry points) and also provides a (very) small performance improvement. .sh see also .br accept (2), .br bind (2), .br connect (2), .br getpeername (2), .br getsockname (2), .br getsockopt (2), .br listen (2), .br recv (2), .br recvfrom (2), .br recvmsg (2), .br send (2), .br sendmsg (2), .br sendto (2), .br setsockopt (2), .br shutdown (2), .br socket (2), .br socketpair (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getutmp 3 2021-03-22 "linux" "linux programmer's manual" .sh name getutmp, getutmpx \- copy utmp structure to utmpx, and vice versa .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void getutmp(const struct utmpx *" ux ", struct utmp *" u ); .bi "void getutmpx(const struct utmp *" u ", struct utmpx *" ux ); .fi .sh description the .br getutmp () function copies the fields of the .i utmpx structure pointed to by .i ux to the corresponding fields of the .i utmp structure pointed to by .ir u . the .br getutmpx () function performs the converse operation. .sh return value these functions do not return a value. .sh versions these functions first appeared in glibc in version 2.1.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getutmp (), .br getutmpx () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard, but appear on a few other systems, such as solaris and netbsd. .sh notes these functions exist primarily for compatibility with other systems where the .i utmp and .i utmpx structures contain different fields, or the size of corresponding fields differs. .\" e.g., on solaris, the utmpx structure is rather larger than utmp. on linux, the two structures contain the same fields, and the fields have the same sizes. .sh see also .br utmpdump (1), .br getutent (3), .br utmp (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getopt.3 .so man3/gnu_get_libc_version.3 .so man7/system_data_types.7 .so man3/isalpha.3 .so man3/__ppc_set_ppr_med.3 .so man3/pthread_mutexattr_setrobust.3 .so man3/rexec.3 .so man3/printf.3 .so man3/perror.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th erf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name erf, erff, erfl \- error function .sh synopsis .nf .b #include .pp .bi "double erf(double " x ); .bi "float erff(float " x ); .bi "long double erfl(long double " x ); .pp .fi link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br erf (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br erff (), .br erfl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the error function of .ir x , defined as .tp erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(\-t*t) dt .sh return value on success, these functions return the value of the error function of .ir x , a value in the range [\-1,\ 1]. .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is positive infinity (negative infinity), +1 (\-1) is returned. .pp if .i x is subnormal, a range error occurs, and the return value is 2*x/sqrt(pi). .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result underflow (\fix\fp is subnormal) .\" .i errno .\" is set to .\" .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .pp these functions do not set .ir errno . .\" it is intentional that these functions do not set errno for this case .\" see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br erf (), .br erff (), .br erfl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh see also .br cerf (3), .br erfc (3), .br exp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-04-12, david metcalfe .\" modified 1993-07-24, rik faith (faith@cs.unc.edu) .\" modified 2002-01-20, walter harms .th bstring 3 2021-03-22 "" "linux programmer's manual" .sh name bcmp, bcopy, bzero, memccpy, memchr, memcmp, memcpy, memfrob, memmem, memmove, memset \- byte string operations .sh synopsis .nf .b #include .pp .bi "int bcmp(const void *" s1 ", const void *" s2 ", size_t " n ); .pp .bi "void bcopy(const void *" src ", void *" dest ", size_t " n ); .pp .bi "void bzero(void *" s ", size_t " n ); .pp .bi "void *memccpy(void *" dest ", const void *" src ", int " c ", size_t " n ); .pp .bi "void *memchr(const void *" s ", int " c ", size_t " n ); .pp .bi "int memcmp(const void *" s1 ", const void *" s2 ", size_t " n ); .pp .bi "void *memcpy(void *" dest ", const void *" src ", size_t " n ); .pp .bi "void *memfrob(void *" s ", size_t " n ); .pp .bi "void *memmem(const void *" haystack ", size_t " haystacklen , .bi " const void *" needle ", size_t " needlelen ); .pp .bi "void *memmove(void *" dest ", const void *" src ", size_t " n ); .pp .bi "void *memset(void *" s ", int " c ", size_t " n ); .fi .sh description the byte string functions perform operations on strings (byte arrays) that are not necessarily null-terminated. see the individual man pages for descriptions of each function. .sh notes the functions .br bcmp (), .br bcopy (), and .br bzero () are obsolete. use .br memcmp (), .br memcpy (), and .br memset () instead. .\" the old functions are not even available on some non-gnu/linux systems. .sh see also .br bcmp (3), .br bcopy (3), .br bzero (3), .br memccpy (3), .br memchr (3), .br memcmp (3), .br memcpy (3), .br memfrob (3), .br memmem (3), .br memmove (3), .br memset (3), .br string (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/nextafter.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cimag 3 2021-03-22 "" "linux programmer's manual" .sh name cimag, cimagf, cimagl \- get imaginary part of a complex number .sh synopsis .nf .b #include .pp .bi "double cimag(double complex " z ");" .bi "float cimagf(float complex " z ");" .bi "long double cimagl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions return the imaginary part of the complex number .ir z . .pp one has: .pp .nf z = creal(z) + i * cimag(z) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cimag (), .br cimagf (), .br cimagl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes gcc also supports __imag__. that is a gnu extension. .sh see also .br cabs (3), .br creal (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdio_ext.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_overview 7 2020-06-09 "linux" "linux programmer's manual" .sh name mq_overview \- overview of posix message queues .sh description posix message queues allow processes to exchange data in the form of messages. this api is distinct from that provided by system v message queues .rb ( msgget (2), .br msgsnd (2), .br msgrcv (2), etc.), but provides similar functionality. .pp message queues are created and opened using .br mq_open (3); this function returns a .i message queue descriptor .ri ( mqd_t ), which is used to refer to the open message queue in later calls. each message queue is identified by a name of the form .ir /somename ; that is, a null-terminated string of up to .bi name_max (i.e., 255) characters consisting of an initial slash, followed by one or more characters, none of which are slashes. two processes can operate on the same queue by passing the same name to .br mq_open (3). .pp messages are transferred to and from a queue using .br mq_send (3) and .br mq_receive (3). when a process has finished using the queue, it closes it using .br mq_close (3), and when the queue is no longer required, it can be deleted using .br mq_unlink (3). queue attributes can be retrieved and (in some cases) modified using .br mq_getattr (3) and .br mq_setattr (3). a process can request asynchronous notification of the arrival of a message on a previously empty queue using .br mq_notify (3). .pp a message queue descriptor is a reference to an .i "open message queue description" (see .br open (2)). after a .br fork (2), a child inherits copies of its parent's message queue descriptors, and these descriptors refer to the same open message queue descriptions as the corresponding message queue descriptors in the parent. corresponding message queue descriptors in the two processes share the flags .ri ( mq_flags ) that are associated with the open message queue description. .pp each message has an associated .ir priority , and messages are always delivered to the receiving process highest priority first. message priorities range from 0 (low) to .i sysconf(_sc_mq_prio_max)\ \-\ 1 (high). on linux, .i sysconf(_sc_mq_prio_max) returns 32768, but posix.1 requires only that an implementation support at least priorities in the range 0 to 31; some implementations provide only this range. .pp the remainder of this section describes some specific details of the linux implementation of posix message queues. .ss library interfaces and system calls in most cases the .br mq_* () library interfaces listed above are implemented on top of underlying system calls of the same name. deviations from this scheme are indicated in the following table: .rs .ts lb lb l l. library interface system call mq_close(3) close(2) mq_getattr(3) mq_getsetattr(2) mq_notify(3) mq_notify(2) mq_open(3) mq_open(2) mq_receive(3) mq_timedreceive(2) mq_send(3) mq_timedsend(2) mq_setattr(3) mq_getsetattr(2) mq_timedreceive(3) mq_timedreceive(2) mq_timedsend(3) mq_timedsend(2) mq_unlink(3) mq_unlink(2) .te .re .ss versions posix message queues have been supported on linux since kernel 2.6.6. glibc support has been provided since version 2.3.4. .ss kernel configuration support for posix message queues is configurable via the .b config_posix_mqueue kernel configuration option. this option is enabled by default. .ss persistence posix message queues have kernel persistence: if not removed by .br mq_unlink (3), a message queue will exist until the system is shut down. .ss linking programs using the posix message queue api must be compiled with .i cc \-lrt to link against the real-time library, .ir librt . .ss /proc interfaces the following interfaces can be used to limit the amount of kernel memory consumed by posix message queues and to set the default attributes for new message queues: .tp .ir /proc/sys/fs/mqueue/msg_default " (since linux 3.5)" this file defines the value used for a new queue's .i mq_maxmsg setting when the queue is created with a call to .br mq_open (3) where .i attr is specified as null. the default value for this file is 10. the minimum and maximum are as for .ir /proc/sys/fs/mqueue/msg_max . a new queue's default .i mq_maxmsg value will be the smaller of .ir msg_default and .ir msg_max . up until linux 2.6.28, the default .i mq_maxmsg was 10; from linux 2.6.28 to linux 3.4, the default was the value defined for the .i msg_max limit. .tp .i /proc/sys/fs/mqueue/msg_max this file can be used to view and change the ceiling value for the maximum number of messages in a queue. this value acts as a ceiling on the .i attr\->mq_maxmsg argument given to .br mq_open (3). the default value for .i msg_max is 10. the minimum value is 1 (10 in kernels before 2.6.28). the upper limit is .br hard_msgmax . the .i msg_max limit is ignored for privileged processes .rb ( cap_sys_resource ), but the .br hard_msgmax ceiling is nevertheless imposed. .ip the definition of .br hard_msgmax has changed across kernel versions: .rs .ip * 3 up to linux 2.6.32: .ir "131072\ /\ sizeof(void\ *)" .ip * linux 2.6.33 to 3.4: .ir "(32768\ *\ sizeof(void\ *) / 4)" .ip * since linux 3.5: .\" commit 5b5c4d1a1440e94994c73dddbad7be0676cd8b9a 65,536 .re .tp .ir /proc/sys/fs/mqueue/msgsize_default " (since linux 3.5)" this file defines the value used for a new queue's .i mq_msgsize setting when the queue is created with a call to .br mq_open (3) where .i attr is specified as null. the default value for this file is 8192 (bytes). the minimum and maximum are as for .ir /proc/sys/fs/mqueue/msgsize_max . if .ir msgsize_default exceeds .ir msgsize_max , a new queue's default .i mq_msgsize value is capped to the .i msgsize_max limit. up until linux 2.6.28, the default .i mq_msgsize was 8192; from linux 2.6.28 to linux 3.4, the default was the value defined for the .i msgsize_max limit. .tp .i /proc/sys/fs/mqueue/msgsize_max this file can be used to view and change the ceiling on the maximum message size. this value acts as a ceiling on the .i attr\->mq_msgsize argument given to .br mq_open (3). the default value for .i msgsize_max is 8192 bytes. the minimum value is 128 (8192 in kernels before 2.6.28). the upper limit for .i msgsize_max has varied across kernel versions: .rs .ip * 3 before linux 2.6.28, the upper limit is .br int_max . .ip * from linux 2.6.28 to 3.4, the limit is 1,048,576. .ip * since linux 3.5, the limit is 16,777,216 .rb ( hard_msgsizemax ). .re .ip the .i msgsize_max limit is ignored for privileged process .rb ( cap_sys_resource ), but, since linux 3.5, the .br hard_msgsizemax ceiling is enforced for privileged processes. .tp .i /proc/sys/fs/mqueue/queues_max this file can be used to view and change the system-wide limit on the number of message queues that can be created. the default value for .i queues_max is 256. no ceiling is imposed on the .i queues_max limit; privileged processes .rb ( cap_sys_resource ) can exceed the limit (but see bugs). .ss resource limit the .b rlimit_msgqueue resource limit, which places a limit on the amount of space that can be consumed by all of the message queues belonging to a process's real user id, is described in .br getrlimit (2). .ss mounting the message queue filesystem on linux, message queues are created in a virtual filesystem. (other implementations may also provide such a feature, but the details are likely to differ.) this filesystem can be mounted (by the superuser) using the following commands: .pp .in +4n .ex .rb "#" " mkdir /dev/mqueue" .rb "#" " mount \-t mqueue none /dev/mqueue" .ee .in .pp the sticky bit is automatically enabled on the mount directory. .pp after the filesystem has been mounted, the message queues on the system can be viewed and manipulated using the commands usually used for files (e.g., .br ls (1) and .br rm (1)). .pp the contents of each file in the directory consist of a single line containing information about the queue: .pp .in +4n .ex .rb "$" " cat /dev/mqueue/mymq" qsize:129 notify:2 signo:0 notify_pid:8260 .ee .in .pp these fields are as follows: .tp .b qsize number of bytes of data in all messages in the queue (but see bugs). .tp .b notify_pid if this is nonzero, then the process with this pid has used .br mq_notify (3) to register for asynchronous message notification, and the remaining fields describe how notification occurs. .tp .b notify notification method: 0 is .br sigev_signal ; 1 is .br sigev_none ; and 2 is .br sigev_thread . .tp .b signo signal number to be used for .br sigev_signal . .ss linux implementation of message queue descriptors on linux, a message queue descriptor is actually a file descriptor. (posix does not require such an implementation.) this means that a message queue descriptor can be monitored using .br select (2), .br poll (2), or .br epoll (7). this is not portable. .pp the close-on-exec flag (see .br open (2)) is automatically set on the file descriptor returned by .br mq_open (2). .ss ipc namespaces for a discussion of the interaction of posix message queue objects and ipc namespaces, see .br ipc_namespaces (7). .sh notes system v message queues .rb ( msgget (2), .br msgsnd (2), .br msgrcv (2), etc.) are an older api for exchanging messages between processes. posix message queues provide a better designed interface than system v message queues; on the other hand posix message queues are less widely available (especially on older systems) than system v message queues. .pp linux does not currently (2.6.26) support the use of access control lists (acls) for posix message queues. .sh bugs in linux versions 3.5 to 3.14, the kernel imposed a ceiling of 1024 .rb ( hard_queuesmax ) on the value to which the .i queues_max limit could be raised, and the ceiling was enforced even for privileged processes. this ceiling value was removed in linux 3.14, and patches to stable kernels 3.5.x to 3.13.x also removed the ceiling. .pp as originally implemented (and documented), the qsize field displayed the total number of (user-supplied) bytes in all messages in the message queue. some changes in linux 3.5 .\" commit d6629859b36d inadvertently changed the behavior, so that this field also included a count of kernel overhead bytes used to store the messages in the queue. this behavioral regression was rectified in linux 4.2 .\" commit de54b9ac253787c366bbfb28d901a31954eb3511 (and earlier stable kernel series), so that the count once more included just the bytes of user data in messages in the queue. .sh examples an example of the use of various message queue functions is shown in .br mq_notify (3). .sh see also .br getrlimit (2), .br mq_getsetattr (2), .br poll (2), .br select (2), .br mq_close (3), .br mq_getattr (3), .br mq_notify (3), .br mq_open (3), .br mq_receive (3), .br mq_send (3), .br mq_unlink (3), .br epoll (7), .br namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fopen.3 .so man3/makecontext.3 .\" copyright (c) 2017 david howells .\" .\" derived from the stat.2 manual page: .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" parts copyright (c) 1995 nicolai langfeldt (janl@ifi.uio.no), 1/1/95 .\" and copyright (c) 2006, 2007, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th statx 2 2021-08-27 "linux" "linux programmer's manual" .sh name statx \- get file status (extended) .sh synopsis .nf .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "int statx(int " dirfd ", const char *restrict " pathname ", int " flags , .bi " unsigned int " mask ", struct statx *restrict " statxbuf ); .fi .sh description this function returns information about a file, storing it in the buffer pointed to by .ir statxbuf . the returned buffer is a structure of the following type: .pp .in +4n .ex struct statx { __u32 stx_mask; /* mask of bits indicating filled fields */ __u32 stx_blksize; /* block size for filesystem i/o */ __u64 stx_attributes; /* extra file attribute indicators */ __u32 stx_nlink; /* number of hard links */ __u32 stx_uid; /* user id of owner */ __u32 stx_gid; /* group id of owner */ __u16 stx_mode; /* file type and mode */ __u64 stx_ino; /* inode number */ __u64 stx_size; /* total size in bytes */ __u64 stx_blocks; /* number of 512b blocks allocated */ __u64 stx_attributes_mask; /* mask to show what\(aqs supported in stx_attributes */ /* the following fields are file timestamps */ struct statx_timestamp stx_atime; /* last access */ struct statx_timestamp stx_btime; /* creation */ struct statx_timestamp stx_ctime; /* last status change */ struct statx_timestamp stx_mtime; /* last modification */ /* if this file represents a device, then the next two fields contain the id of the device */ __u32 stx_rdev_major; /* major id */ __u32 stx_rdev_minor; /* minor id */ /* the next two fields contain the id of the device containing the filesystem where the file resides */ __u32 stx_dev_major; /* major id */ __u32 stx_dev_minor; /* minor id */ __u64 stx_mnt_id; /* mount id */ }; .ee .in .pp the file timestamps are structures of the following type: .pp .in +4n .ex struct statx_timestamp { __s64 tv_sec; /* seconds since the epoch (unix time) */ __u32 tv_nsec; /* nanoseconds since tv_sec */ }; .ee .in .pp (note that reserved space and padding is omitted.) .ss invoking \fbstatx\fr(): to access a file's status, no permissions are required on the file itself, but in the case of .br statx () with a pathname, execute (search) permission is required on all of the directories in .i pathname that lead to the file. .pp .br statx () uses .ir pathname , .ir dirfd , and .ir flags to identify the target file in one of the following ways: .tp an absolute pathname if .i pathname begins with a slash, then it is an absolute pathname that identifies the target file. in this case, .i dirfd is ignored. .tp a relative pathname if .i pathname is a string that begins with a character other than a slash and .ir dirfd is .br at_fdcwd , then .i pathname is a relative pathname that is interpreted relative to the process's current working directory. .tp a directory-relative pathname if .i pathname is a string that begins with a character other than a slash and .i dirfd is a file descriptor that refers to a directory, then .i pathname is a relative pathname that is interpreted relative to the directory referred to by .ir dirfd . (see .br openat (2) for an explanation of why this is useful.) .tp by file descriptor if .ir pathname is an empty string and the .b at_empty_path flag is specified in .ir flags (see below), then the target file is the one referred to by the file descriptor .ir dirfd . .pp .i flags can be used to influence a pathname-based lookup. a value for .i flags is constructed by oring together zero or more of the following constants: .tp .br at_empty_path .\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d if .i pathname is an empty string, operate on the file referred to by .ir dirfd (which may have been obtained using the .br open (2) .b o_path flag). in this case, .i dirfd can refer to any type of file, not just a directory. .ip if .i dirfd is .br at_fdcwd , the call operates on the current working directory. .ip this flag is linux-specific; define .b _gnu_source .\" before glibc 2.16, defining _atfile_source sufficed to obtain its definition. .tp .br at_no_automount don't automount the terminal ("basename") component of .i pathname if it is a directory that is an automount point. this allows the caller to gather attributes of an automount point (rather than the location it would mount). this flag can be used in tools that scan directories to prevent mass-automounting of a directory of automount points. the .b at_no_automount flag has no effect if the mount point has already been mounted over. this flag is linux-specific; define .b _gnu_source .\" before glibc 2.16, defining _atfile_source sufficed to obtain its definition. .tp .b at_symlink_nofollow if .i pathname is a symbolic link, do not dereference it: instead return information about the link itself, like .br lstat (2). .pp .i flags can also be used to control what sort of synchronization the kernel will do when querying a file on a remote filesystem. this is done by oring in one of the following values: .tp .b at_statx_sync_as_stat do whatever .br stat (2) does. this is the default and is very much filesystem-specific. .tp .b at_statx_force_sync force the attributes to be synchronized with the server. this may require that a network filesystem perform a data writeback to get the timestamps correct. .tp .b at_statx_dont_sync don't synchronize anything, but rather just take whatever the system has cached if possible. this may mean that the information returned is approximate, but, on a network filesystem, it may not involve a round trip to the server - even if no lease is held. .pp the .i mask argument to .br statx () is used to tell the kernel which fields the caller is interested in. .i mask is an ored combination of the following constants: .pp .in +4n .ts lb l. statx_type want stx_mode & s_ifmt statx_mode want stx_mode & \(tis_ifmt statx_nlink want stx_nlink statx_uid want stx_uid statx_gid want stx_gid statx_atime want stx_atime statx_mtime want stx_mtime statx_ctime want stx_ctime statx_ino want stx_ino statx_size want stx_size statx_blocks want stx_blocks statx_basic_stats [all of the above] statx_btime want stx_btime statx_mnt_id want stx_mnt_id (since linux 5.8) statx_all [all currently available fields] .te .in .pp note that, in general, the kernel does .i not reject values in .i mask other than the above. (for an exception, see .b einval in errors.) instead, it simply informs the caller which values are supported by this kernel and filesystem via the .i statx.stx_mask field. therefore, .i "do not" simply set .i mask to .b uint_max (all bits set), as one or more bits may, in the future, be used to specify an extension to the buffer. .ss the returned information the status information for the target file is returned in the .i statx structure pointed to by .ir statxbuf . included in this is .i stx_mask which indicates what other information has been returned. .i stx_mask has the same format as the .i mask argument and bits are set in it to indicate which fields have been filled in. .pp it should be noted that the kernel may return fields that weren't requested and may fail to return fields that were requested, depending on what the backing filesystem supports. (fields that are given values despite being unrequested can just be ignored.) in either case, .i stx_mask will not be equal .ir mask . .pp if a filesystem does not support a field or if it has an unrepresentable value (for instance, a file with an exotic type), then the mask bit corresponding to that field will be cleared in .i stx_mask even if the user asked for it and a dummy value will be filled in for compatibility purposes if one is available (e.g., a dummy uid and gid may be specified to mount under some circumstances). .pp a filesystem may also fill in fields that the caller didn't ask for if it has values for them available and the information is available at no extra cost. if this happens, the corresponding bits will be set in .ir stx_mask . .pp .\" background: inode attributes are modified with i_mutex held, but .\" read by stat() without taking the mutex. .ir note : for performance and simplicity reasons, different fields in the .i statx structure may contain state information from different moments during the execution of the system call. for example, if .ir stx_mode or .ir stx_uid is changed by another process by calling .br chmod (2) or .br chown (2), .br stat () might return the old .i stx_mode together with the new .ir stx_uid , or the old .i stx_uid together with the new .ir stx_mode . .pp apart from .i stx_mask (which is described above), the fields in the .i statx structure are: .tp .i stx_blksize the "preferred" block size for efficient filesystem i/o. (writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.) .tp .i stx_attributes further status information about the file (see below for more information). .tp .i stx_nlink the number of hard links on a file. .tp .i stx_uid this field contains the user id of the owner of the file. .tp .i stx_gid this field contains the id of the group owner of the file. .tp .i stx_mode the file type and mode. see .br inode (7) for details. .tp .i stx_ino the inode number of the file. .tp .i stx_size the size of the file (if it is a regular file or a symbolic link) in bytes. the size of a symbolic link is the length of the pathname it contains, without a terminating null byte. .tp .i stx_blocks the number of blocks allocated to the file on the medium, in 512-byte units. (this may be smaller than .ir stx_size /512 when the file has holes.) .tp .i stx_attributes_mask a mask indicating which bits in .ir stx_attributes are supported by the vfs and the filesystem. .tp .i stx_atime the file's last access timestamp. .tp .i stx_btime the file's creation timestamp. .tp .i stx_ctime the file's last status change timestamp. .tp .i stx_mtime the file's last modification timestamp. .tp .ir stx_dev_major " and " stx_dev_minor the device on which this file (inode) resides. .tp .ir stx_rdev_major " and " stx_rdev_minor the device that this file (inode) represents if the file is of block or character device type. .tp .i stx_mnt_id .\" commit fa2fcf4f1df1559a0a4ee0f46915b496cc2ebf60 the mount id of the mount containing the file. this is the same number reported by .br name_to_handle_at (2) and corresponds to the number in the first field in one of the records in .ir /proc/self/mountinfo . .pp for further information on the above fields, see .br inode (7). .\" .ss file attributes the .i stx_attributes field contains a set of ored flags that indicate additional attributes of the file. note that any attribute that is not indicated as supported by .i stx_attributes_mask has no usable value here. the bits in .i stx_attributes_mask correspond bit-by-bit to .ir stx_attributes . .pp the flags are as follows: .tp .b statx_attr_compressed the file is compressed by the filesystem and may take extra resources to access. .tp .b statx_attr_immutable the file cannot be modified: it cannot be deleted or renamed, no hard links can be created to this file and no data can be written to it. see .br chattr (1). .tp .b statx_attr_append the file can only be opened in append mode for writing. random access writing is not permitted. see .br chattr (1). .tp .b statx_attr_nodump file is not a candidate for backup when a backup program such as .br dump (8) is run. see .br chattr (1). .tp .b statx_attr_encrypted a key is required for the file to be encrypted by the filesystem. .tp .br statx_attr_verity " (since linux 5.5)" .\" commit 3ad2522c64cff1f5aebb987b00683268f0cc7c29 the file has fs-verity enabled. it cannot be written to, and all reads from it will be verified against a cryptographic hash that covers the entire file (e.g., via a merkle tree). .tp .br statx_attr_dax " (since linux 5.8)" the file is in the dax (cpu direct access) state. dax state attempts to minimize software cache effects for both i/o and memory mappings of this file. it requires a file system which has been configured to support dax. .ip dax generally assumes all accesses are via cpu load / store instructions which can minimize overhead for small accesses, but may adversely affect cpu utilization for large transfers. .ip file i/o is done directly to/from user-space buffers and memory mapped i/o may be performed with direct memory mappings that bypass the kernel page cache. .ip while the dax property tends to result in data being transferred synchronously, it does not give the same guarantees as the .b o_sync flag (see .br open (2)), where data and the necessary metadata are transferred together. .ip a dax file may support being mapped with the .b map_sync flag, which enables a program to use cpu cache flush instructions to persist cpu store operations without an explicit .br fsync (2). see .br mmap (2) for more information. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces search permission is denied for one of the directories in the path prefix of .ir pathname . (see also .br path_resolution (7).) .tp .b ebadf .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b efault .i pathname or .i statxbuf is null or points to a location outside the process's accessible address space. .tp .b einval invalid flag specified in .ir flags . .tp .b einval reserved flag specified in .ir mask . (currently, there is one such flag, designated by the constant .br statx__reserved , with the value 0x80000000u.) .tp .b eloop too many symbolic links encountered while traversing the pathname. .tp .b enametoolong .i pathname is too long. .tp .b enoent a component of .i pathname does not exist, or .i pathname is an empty string and .b at_empty_path was not specified in .ir flags . .tp .b enomem out of memory (i.e., kernel memory). .tp .b enotdir a component of the path prefix of .i pathname is not a directory or .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .sh versions .br statx () was added to linux in kernel 4.11; library support was added in glibc 2.28. .sh conforming to .br statx () is linux-specific. .sh see also .br ls (1), .br stat (1), .br access (2), .br chmod (2), .br chown (2), .br name_to_handle_at (2), .br readlink (2), .br stat (2), .br utime (2), .br proc (5), .br capabilities (7), .br inode (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getrpcent.3 .so man3/cpu_set.3 .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: icmp.7,v 1.6 2000/08/14 08:03:45 ak exp $ .\" .th icmp 7 2017-11-26 "linux" "linux programmer's manual" .sh name icmp \- linux ipv4 icmp kernel module. .sh description this kernel protocol module implements the internet control message protocol defined in rfc\ 792. it is used to signal error conditions and for diagnosis. the user doesn't interact directly with this module; instead it communicates with the other protocols in the kernel and these pass the icmp errors to the application layers. the kernel icmp module also answers icmp requests. .pp a user protocol may receive icmp packets for all local sockets by opening a raw socket with the protocol .br ipproto_icmp . see .br raw (7) for more information. the types of icmp packets passed to the socket can be filtered using the .b icmp_filter socket option. icmp packets are always processed by the kernel too, even when passed to a user socket. .pp linux limits the rate of icmp error packets to each destination. .b icmp_redirect and .b icmp_dest_unreach are also limited by the destination route of the incoming packets. .ss /proc interfaces icmp supports a set of .i /proc interfaces to configure some global ip parameters. the parameters can be accessed by reading or writing files in the directory .ir /proc/sys/net/ipv4/ . most of these parameters are rate limitations for specific icmp types. linux 2.2 uses a token bucket filter to limit icmps. .\" fixme . better description needed the value is the timeout in jiffies until the token bucket filter is cleared after a burst. a jiffy is a system dependent unit, usually 10ms on i386 and about 1ms on alpha and ia64. .tp .ir icmp_destunreach_rate " (linux 2.2 to 2.4.9)" .\" precisely: from 2.1.102 maximum rate to send icmp destination unreachable packets. this limits the rate at which packets are sent to any individual route or destination. the limit does not affect sending of .b icmp_frag_needed packets needed for path mtu discovery. .tp .ir icmp_echo_ignore_all " (since linux 2.2)" .\" precisely: 2.1.68 if this value is nonzero, linux will ignore all .b icmp_echo requests. .tp .ir icmp_echo_ignore_broadcasts " (since linux 2.2)" .\" precisely: from 2.1.68 if this value is nonzero, linux will ignore all .b icmp_echo packets sent to broadcast addresses. .tp .ir icmp_echoreply_rate " (linux 2.2 to 2.4.9)" .\" precisely: from 2.1.102 maximum rate for sending .b icmp_echoreply packets in response to .b icmp_echorequest packets. .tp .ir icmp_errors_use_inbound_ifaddr " (boolean; default: disabled; since linux 2.6.12)" .\" the following taken from 2.6.28-rc4 documentation/networking/ip-sysctl.txt if disabled, icmp error messages are sent with the primary address of the exiting interface. .ip if enabled, the message will be sent with the primary address of the interface that received the packet that caused the icmp error. this is the behavior that many network administrators will expect from a router. and it can make debugging complicated network layouts much easier. .ip note that if no primary address exists for the interface selected, then the primary address of the first non-loopback interface that has one will be used regardless of this setting. .tp .ir icmp_ignore_bogus_error_responses " (boolean; default: disabled; since linux 2.2)" .\" precisely: since 2.1.32 .\" the following taken from 2.6.28-rc4 documentation/networking/ip-sysctl.txt some routers violate rfc1122 by sending bogus responses to broadcast frames. such violations are normally logged via a kernel warning. if this parameter is enabled, the kernel will not give such warnings, which will avoid log file clutter. .tp .ir icmp_paramprob_rate " (linux 2.2 to 2.4.9)" .\" precisely: from 2.1.102 maximum rate for sending .b icmp_parameterprob packets. these packets are sent when a packet arrives with an invalid ip header. .tp .ir icmp_ratelimit " (integer; default: 1000; since linux 2.4.10)" .\" the following taken from 2.6.28-rc4 documentation/networking/ip-sysctl.txt limit the maximum rates for sending icmp packets whose type matches .ir icmp_ratemask (see below) to specific targets. 0 to disable any limiting, otherwise the minimum space between responses in milliseconds. .tp .ir icmp_ratemask " (integer; default: see below; since linux 2.4.10)" .\" the following taken from 2.6.28-rc4 documentation/networking/ip-sysctl.txt mask made of icmp types for which rates are being limited. .ip significant bits: ihgfedcba9876543210 .br default mask: 0000001100000011000 (0x1818) .ip bit definitions (see the linux kernel source file .ir include/linux/icmp.h ): .rs 12 .ts l l. 0 echo reply 3 destination unreachable * 4 source quench * 5 redirect 8 echo request b time exceeded * c parameter problem * d timestamp request e timestamp reply f info request g info reply h address mask request i address mask reply .te .re .pp the bits marked with an asterisk are rate limited by default (see the default mask above). .tp .ir icmp_timeexceed_rate " (linux 2.2 to 2.4.9)" maximum rate for sending .b icmp_time_exceeded packets. these packets are sent to prevent loops when a packet has crossed too many hops. .tp .ir ping_group_range " (two integers; default: see below; since linux 2.6.39)" range of the group ids (minimum and maximum group ids, inclusive) that are allowed to create icmp echo sockets. the default is "1 0", which means no group is allowed to create icmp echo sockets. .sh versions support for the .b icmp_address request was removed in 2.2. .pp support for .b icmp_source_quench was removed in linux 2.2. .sh notes as many other implementations don't support .b ipproto_icmp raw sockets, this feature should not be relied on in portable programs. .\" not really true atm .\" .pp .\" linux icmp should be compliant to rfc 1122. .pp .b icmp_redirect packets are not sent when linux is not acting as a router. they are also accepted only from the old gateway defined in the routing table and the redirect routes are expired after some time. .pp the 64-bit timestamp returned by .b icmp_timestamp is in milliseconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). .pp linux icmp internally uses a raw socket to send icmps. this raw socket may appear in .br netstat (8) output with a zero inode. .sh see also .br ip (7), .br rdisc (8) .pp rfc\ 792 for a description of the icmp protocol. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/epoll_wait.2 .\" copyright (c) 2006, 2014 michael kerrisk .\" copyright (c) 2014 heinrich schuchardt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th inotify 7 2021-03-22 "linux" "linux programmer's manual" .sh name inotify \- monitoring filesystem events .sh description the .i inotify api provides a mechanism for monitoring filesystem events. inotify can be used to monitor individual files, or to monitor directories. when a directory is monitored, inotify will return events for the directory itself, and for files inside the directory. .pp the following system calls are used with this api: .ip * 3 .br inotify_init (2) creates an inotify instance and returns a file descriptor referring to the inotify instance. the more recent .br inotify_init1 (2) is like .br inotify_init (2), but has a .ir flags argument that provides access to some extra functionality. .ip * .br inotify_add_watch (2) manipulates the "watch list" associated with an inotify instance. each item ("watch") in the watch list specifies the pathname of a file or directory, along with some set of events that the kernel should monitor for the file referred to by that pathname. .br inotify_add_watch (2) either creates a new watch item, or modifies an existing watch. each watch has a unique "watch descriptor", an integer returned by .br inotify_add_watch (2) when the watch is created. .ip * when events occur for monitored files and directories, those events are made available to the application as structured data that can be read from the inotify file descriptor using .br read (2) (see below). .ip * .br inotify_rm_watch (2) removes an item from an inotify watch list. .ip * when all file descriptors referring to an inotify instance have been closed (using .br close (2)), the underlying object and its resources are freed for reuse by the kernel; all associated watches are automatically freed. .pp with careful programming, an application can use inotify to efficiently monitor and cache the state of a set of filesystem objects. however, robust applications should allow for the fact that bugs in the monitoring logic or races of the kind described below may leave the cache inconsistent with the filesystem state. it is probably wise to do some consistency checking, and rebuild the cache when inconsistencies are detected. .ss reading events from an inotify file descriptor to determine what events have occurred, an application .br read (2)s from the inotify file descriptor. if no events have so far occurred, then, assuming a blocking file descriptor, .br read (2) will block until at least one event occurs (unless interrupted by a signal, in which case the call fails with the error .br eintr ; see .br signal (7)). .pp each successful .br read (2) returns a buffer containing one or more of the following structures: .pp .in +4n .ex struct inotify_event { int wd; /* watch descriptor */ .\" fixme . the type of the 'wd' field should probably be "int32_t". .\" i submitted a patch to fix this. see the lkml thread .\" "[patch] fix type errors in inotify interfaces", 18 nov 2008 .\" glibc bug filed: http://sources.redhat.com/bugzilla/show_bug.cgi?id=7040 uint32_t mask; /* mask describing event */ uint32_t cookie; /* unique cookie associating related events (for rename(2)) */ uint32_t len; /* size of \finame\fp field */ char name[]; /* optional null\-terminated name */ }; .ee .in .pp .i wd identifies the watch for which this event occurs. it is one of the watch descriptors returned by a previous call to .br inotify_add_watch (2). .pp .i mask contains bits that describe the event that occurred (see below). .pp .i cookie is a unique integer that connects related events. currently, this is used only for rename events, and allows the resulting pair of .b in_moved_from and .b in_moved_to events to be connected by the application. for all other event types, .i cookie is set to 0. .pp the .i name field is present only when an event is returned for a file inside a watched directory; it identifies the filename within the watched directory. this filename is null-terminated, and may include further null bytes (\(aq\e0\(aq) to align subsequent reads to a suitable address boundary. .pp the .i len field counts all of the bytes in .ir name , including the null bytes; the length of each .i inotify_event structure is thus .ir "sizeof(struct inotify_event)+len" . .pp the behavior when the buffer given to .br read (2) is too small to return information about the next event depends on the kernel version: in kernels before 2.6.21, .br read (2) returns 0; since kernel 2.6.21, .br read (2) fails with the error .br einval . specifying a buffer of size .pp sizeof(struct inotify_event) + name_max + 1 .pp will be sufficient to read at least one event. .ss inotify events the .br inotify_add_watch (2) .i mask argument and the .i mask field of the .i inotify_event structure returned when .br read (2)ing an inotify file descriptor are both bit masks identifying inotify events. the following bits can be specified in .i mask when calling .br inotify_add_watch (2) and may be returned in the .i mask field returned by .br read (2): .rs 4 .tp .br in_access " (+)" file was accessed (e.g., .br read (2), .br execve (2)). .tp .br in_attrib " (*)" metadata changed\(emfor example, permissions (e.g., .br chmod (2)), timestamps (e.g., .br utimensat (2)), extended attributes .rb ( setxattr (2)), link count (since linux 2.6.25; e.g., .\" fixme . .\" events do not occur for link count changes on a file inside a monitored .\" directory. this differs from other metadata changes for files inside .\" a monitored directory. for the target of .br link (2) and for .br unlink (2)), and user/group id (e.g., .br chown (2)). .tp .br in_close_write " (+)" file opened for writing was closed. .tp .br in_close_nowrite " (*)" file or directory not opened for writing was closed. .tp .br in_create " (+)" file/directory created in watched directory (e.g., .br open (2) .br o_creat , .br mkdir (2), .br link (2), .br symlink (2), .br bind (2) on a unix domain socket). .tp .br in_delete " (+)" file/directory deleted from watched directory. .tp .b in_delete_self watched file/directory was itself deleted. (this event also occurs if an object is moved to another filesystem, since .br mv (1) in effect copies the file to the other filesystem and then deletes it from the original filesystem.) in addition, an .b in_ignored event will subsequently be generated for the watch descriptor. .tp .br in_modify " (+)" file was modified (e.g., .br write (2), .br truncate (2)). .tp .b in_move_self watched file/directory was itself moved. .tp .br in_moved_from " (+)" generated for the directory containing the old filename when a file is renamed. .tp .br in_moved_to " (+)" generated for the directory containing the new filename when a file is renamed. .tp .br in_open " (*)" file or directory was opened. .re .pp inotify monitoring is inode-based: when monitoring a file (but not when monitoring the directory containing a file), an event can be generated for activity on any link to the file (in the same or a different directory). .pp when monitoring a directory: .ip * 3 the events marked above with an asterisk (*) can occur both for the directory itself and for objects inside the directory; and .ip * the events marked with a plus sign (+) occur only for objects inside the directory (not for the directory itself). .pp .ir note : when monitoring a directory, events are not generated for the files inside the directory when the events are performed via a pathname (i.e., a link) that lies outside the monitored directory. .pp when events are generated for objects inside a watched directory, the .i name field in the returned .i inotify_event structure identifies the name of the file within the directory. .pp the .b in_all_events macro is defined as a bit mask of all of the above events. this macro can be used as the .i mask argument when calling .br inotify_add_watch (2). .pp two additional convenience macros are defined: .rs 4 .tp .br in_move equates to .br "in_moved_from | in_moved_to" . .tp .br in_close equates to .br "in_close_write | in_close_nowrite" . .re .pp the following further bits can be specified in .i mask when calling .br inotify_add_watch (2): .rs 4 .tp .br in_dont_follow " (since linux 2.6.15)" don't dereference .i pathname if it is a symbolic link. .tp .br in_excl_unlink " (since linux 2.6.36)" .\" commit 8c1934c8d70b22ca8333b216aec6c7d09fdbd6a6 by default, when watching events on the children of a directory, events are generated for children even after they have been unlinked from the directory. this can result in large numbers of uninteresting events for some applications (e.g., if watching .ir /tmp , in which many applications create temporary files whose names are immediately unlinked). specifying .b in_excl_unlink changes the default behavior, so that events are not generated for children after they have been unlinked from the watched directory. .tp .b in_mask_add if a watch instance already exists for the filesystem object corresponding to .ir pathname , add (or) the events in .i mask to the watch mask (instead of replacing the mask); the error .b einval results if .b in_mask_create is also specified. .tp .b in_oneshot monitor the filesystem object corresponding to .i pathname for one event, then remove from watch list. .tp .br in_onlydir " (since linux 2.6.15)" watch .i pathname only if it is a directory; the error .b enotdir results if .i pathname is not a directory. using this flag provides an application with a race-free way of ensuring that the monitored object is a directory. .tp .br in_mask_create " (since linux 4.18)" watch .i pathname only if it does not already have a watch associated with it; the error .b eexist results if .i pathname is already being watched. .ip using this flag provides an application with a way of ensuring that new watches do not modify existing ones. this is useful because multiple paths may refer to the same inode, and multiple calls to .br inotify_add_watch (2) without this flag may clobber existing watch masks. .re .pp the following bits may be set in the .i mask field returned by .br read (2): .rs 4 .tp .b in_ignored watch was removed explicitly .rb ( inotify_rm_watch (2)) or automatically (file was deleted, or filesystem was unmounted). see also bugs. .tp .b in_isdir subject of this event is a directory. .tp .b in_q_overflow event queue overflowed .ri ( wd is \-1 for this event). .tp .b in_unmount filesystem containing watched object was unmounted. in addition, an .b in_ignored event will subsequently be generated for the watch descriptor. .re .ss examples suppose an application is watching the directory .i dir and the file .ir dir/myfile for all events. the examples below show some events that will be generated for these two objects. .rs 4 .tp fd = open("dir/myfile", o_rdwr); generates .b in_open events for both .i dir and .ir dir/myfile . .tp read(fd, buf, count); generates .b in_access events for both .i dir and .ir dir/myfile . .tp write(fd, buf, count); generates .b in_modify events for both .i dir and .ir dir/myfile . .tp fchmod(fd, mode); generates .b in_attrib events for both .i dir and .ir dir/myfile . .tp close(fd); generates .b in_close_write events for both .i dir and .ir dir/myfile . .re .pp suppose an application is watching the directories .i dir1 and .ir dir2 , and the file .ir dir1/myfile . the following examples show some events that may be generated. .rs 4 .tp link("dir1/myfile", "dir2/new"); generates an .b in_attrib event for .ir myfile and an .b in_create event for .ir dir2 . .tp rename("dir1/myfile", "dir2/myfile"); generates an .b in_moved_from event for .ir dir1 , an .b in_moved_to event for .ir dir2 , and an .b in_move_self event for .ir myfile . the .b in_moved_from and .b in_moved_to events will have the same .i cookie value. .re .pp suppose that .ir dir1/xx and .ir dir2/yy are (the only) links to the same file, and an application is watching .ir dir1 , .ir dir2 , .ir dir1/xx , and .ir dir2/yy . executing the following calls in the order given below will generate the following events: .rs 4 .tp unlink("dir2/yy"); generates an .br in_attrib event for .ir xx (because its link count changes) and an .b in_delete event for .ir dir2 . .tp unlink("dir1/xx"); generates .br in_attrib , .br in_delete_self , and .br in_ignored events for .ir xx , and an .br in_delete event for .ir dir1 . .re .pp suppose an application is watching the directory .ir dir and (the empty) directory .ir dir/subdir . the following examples show some events that may be generated. .rs 4 .tp mkdir("dir/new", mode); generates an .b "in_create | in_isdir" event for .ir dir . .tp rmdir("dir/subdir"); generates .b in_delete_self and .b in_ignored events for .ir subdir , and an .b "in_delete | in_isdir" event for .ir dir . .re .ss /proc interfaces the following interfaces can be used to limit the amount of kernel memory consumed by inotify: .tp .i /proc/sys/fs/inotify/max_queued_events the value in this file is used when an application calls .br inotify_init (2) to set an upper limit on the number of events that can be queued to the corresponding inotify instance. events in excess of this limit are dropped, but an .b in_q_overflow event is always generated. .tp .i /proc/sys/fs/inotify/max_user_instances this specifies an upper limit on the number of inotify instances that can be created per real user id. .tp .i /proc/sys/fs/inotify/max_user_watches this specifies an upper limit on the number of watches that can be created per real user id. .sh versions inotify was merged into the 2.6.13 linux kernel. the required library interfaces were added to glibc in version 2.4. .rb ( in_dont_follow , .br in_mask_add , and .b in_onlydir were added in glibc version 2.5.) .sh conforming to the inotify api is linux-specific. .sh notes inotify file descriptors can be monitored using .br select (2), .br poll (2), and .br epoll (7). when an event is available, the file descriptor indicates as readable. .pp since linux 2.6.25, signal-driven i/o notification is available for inotify file descriptors; see the discussion of .b f_setfl (for setting the .b o_async flag), .br f_setown , and .b f_setsig in .br fcntl (2). the .i siginfo_t structure (described in .br sigaction (2)) that is passed to the signal handler has the following fields set: .ir si_fd is set to the inotify file descriptor number; .ir si_signo is set to the signal number; .ir si_code is set to .br poll_in ; and .b pollin is set in .ir si_band . .pp if successive output inotify events produced on the inotify file descriptor are identical (same .ir wd , .ir mask , .ir cookie , and .ir name ), then they are coalesced into a single event if the older event has not yet been read (but see bugs). this reduces the amount of kernel memory required for the event queue, but also means that an application can't use inotify to reliably count file events. .pp the events returned by reading from an inotify file descriptor form an ordered queue. thus, for example, it is guaranteed that when renaming from one directory to another, events will be produced in the correct order on the inotify file descriptor. .pp the set of watch descriptors that is being monitored via an inotify file descriptor can be viewed via the entry for the inotify file descriptor in the process's .ir /proc/[pid]/fdinfo directory. see .br proc (5) for further details. the .b fionread .br ioctl (2) returns the number of bytes available to read from an inotify file descriptor. .ss limitations and caveats the inotify api provides no information about the user or process that triggered the inotify event. in particular, there is no easy way for a process that is monitoring events via inotify to distinguish events that it triggers itself from those that are triggered by other processes. .pp inotify reports only events that a user-space program triggers through the filesystem api. as a result, it does not catch remote events that occur on network filesystems. (applications must fall back to polling the filesystem to catch such events.) furthermore, various pseudo-filesystems such as .ir /proc , .ir /sys , and .ir /dev/pts are not monitorable with inotify. .pp the inotify api does not report file accesses and modifications that may occur because of .br mmap (2), .br msync (2), and .br munmap (2). .pp the inotify api identifies affected files by filename. however, by the time an application processes an inotify event, the filename may already have been deleted or renamed. .pp the inotify api identifies events via watch descriptors. it is the application's responsibility to cache a mapping (if one is needed) between watch descriptors and pathnames. be aware that directory renamings may affect multiple cached pathnames. .pp inotify monitoring of directories is not recursive: to monitor subdirectories under a directory, additional watches must be created. this can take a significant amount time for large directory trees. .pp if monitoring an entire directory subtree, and a new subdirectory is created in that tree or an existing directory is renamed into that tree, be aware that by the time you create a watch for the new subdirectory, new files (and subdirectories) may already exist inside the subdirectory. therefore, you may want to scan the contents of the subdirectory immediately after adding the watch (and, if desired, recursively add watches for any subdirectories that it contains). .pp note that the event queue can overflow. in this case, events are lost. robust applications should handle the possibility of lost events gracefully. for example, it may be necessary to rebuild part or all of the application cache. (one simple, but possibly expensive, approach is to close the inotify file descriptor, empty the cache, create a new inotify file descriptor, and then re-create watches and cache entries for the objects to be monitored.) .pp if a filesystem is mounted on top of a monitored directory, no event is generated, and no events are generated for objects immediately under the new mount point. if the filesystem is subsequently unmounted, events will subsequently be generated for the directory and the objects it contains. .\" .ss dealing with rename() events as noted above, the .b in_moved_from and .b in_moved_to event pair that is generated by .br rename (2) can be matched up via their shared cookie value. however, the task of matching has some challenges. .pp these two events are usually consecutive in the event stream available when reading from the inotify file descriptor. however, this is not guaranteed. if multiple processes are triggering events for monitored objects, then (on rare occasions) an arbitrary number of other events may appear between the .b in_moved_from and .b in_moved_to events. furthermore, it is not guaranteed that the event pair is atomically inserted into the queue: there may be a brief interval where the .b in_moved_from has appeared, but the .b in_moved_to has not. .pp matching up the .b in_moved_from and .b in_moved_to event pair generated by .br rename (2) is thus inherently racy. (don't forget that if an object is renamed outside of a monitored directory, there may not even be an .br in_moved_to event.) heuristic approaches (e.g., assume the events are always consecutive) can be used to ensure a match in most cases, but will inevitably miss some cases, causing the application to perceive the .b in_moved_from and .b in_moved_to events as being unrelated. if watch descriptors are destroyed and re-created as a result, then those watch descriptors will be inconsistent with the watch descriptors in any pending events. (re-creating the inotify file descriptor and rebuilding the cache may be useful to deal with this scenario.) .pp applications should also allow for the possibility that the .b in_moved_from event was the last event that could fit in the buffer returned by the current call to .br read (2), and the accompanying .b in_moved_to event might be fetched only on the next .br read (2), which should be done with a (small) timeout to allow for the fact that insertion of the .br in_moved_from + in_moved_to event pair is not atomic, and also the possibility that there may not be any .b in_moved_to event. .sh bugs before linux 3.19, .br fallocate (2) did not create any inotify events. since linux 3.19, .\" commit 820c12d5d6c0890bc93dd63893924a13041fdc35 calls to .br fallocate (2) generate .b in_modify events. .pp .\" fixme . kernel commit 611da04f7a31b2208e838be55a42c7a1310ae321 .\" implies that unmount events were buggy 2.6.11 to 2.6.36 .\" in kernels before 2.6.16, the .b in_oneshot .i mask flag does not work. .pp as originally designed and implemented, the .b in_oneshot flag did not cause an .b in_ignored event to be generated when the watch was dropped after one event. however, as an unintended effect of other changes, since linux 2.6.36, an .b in_ignored event is generated in this case. .pp before kernel 2.6.25, .\" commit 1c17d18e3775485bf1e0ce79575eb637a94494a2 the kernel code that was intended to coalesce successive identical events (i.e., the two most recent events could potentially be coalesced if the older had not yet been read) instead checked if the most recent event could be coalesced with the .i oldest unread event. .pp when a watch descriptor is removed by calling .br inotify_rm_watch (2) (or because a watch file is deleted or the filesystem that contains it is unmounted), any pending unread events for that watch descriptor remain available to read. as watch descriptors are subsequently allocated with .br inotify_add_watch (2), the kernel cycles through the range of possible watch descriptors (0 to .br int_max ) incrementally. when allocating a free watch descriptor, no check is made to see whether that watch descriptor number has any pending unread events in the inotify queue. thus, it can happen that a watch descriptor is reallocated even when pending unread events exist for a previous incarnation of that watch descriptor number, with the result that the application might then read those events and interpret them as belonging to the file associated with the newly recycled watch descriptor. in practice, the likelihood of hitting this bug may be extremely low, since it requires that an application cycle through .b int_max watch descriptors, release a watch descriptor while leaving unread events for that watch descriptor in the queue, and then recycle that watch descriptor. for this reason, and because there have been no reports of the bug occurring in real-world applications, as of linux 3.15, .\" fixme . https://bugzilla.kernel.org/show_bug.cgi?id=77111 no kernel changes have yet been made to eliminate this possible bug. .sh examples the following program demonstrates the usage of the inotify api. it marks the directories passed as a command-line arguments and waits for events of type .br in_open , .br in_close_nowrite , and .br in_close_write . .pp the following output was recorded while editing the file .i /home/user/temp/foo and listing directory .ir /tmp . before the file and the directory were opened, .b in_open events occurred. after the file was closed, an .b in_close_write event occurred. after the directory was closed, an .b in_close_nowrite event occurred. execution of the program ended when the user pressed the enter key. .ss example output .in +4n .ex $ \fb./a.out /tmp /home/user/temp\fp press enter key to terminate. listening for events. in_open: /home/user/temp/foo [file] in_close_write: /home/user/temp/foo [file] in_open: /tmp/ [directory] in_close_nowrite: /tmp/ [directory] listening for events stopped. .ee .in .ss program source \& .ex #include #include #include #include #include #include #include /* read all available inotify events from the file descriptor \(aqfd\(aq. wd is the table of watch descriptors for the directories in argv. argc is the length of wd and argv. argv is the list of watched directories. entry 0 of wd and argv is unused. */ static void handle_events(int fd, int *wd, int argc, char* argv[]) { /* some systems cannot read integer variables if they are not properly aligned. on other systems, incorrect alignment may decrease performance. hence, the buffer used for reading from the inotify file descriptor should have the same alignment as struct inotify_event. */ char buf[4096] __attribute__ ((aligned(__alignof__(struct inotify_event)))); const struct inotify_event *event; ssize_t len; /* loop while events can be read from inotify file descriptor. */ for (;;) { /* read some events. */ len = read(fd, buf, sizeof(buf)); if (len == \-1 && errno != eagain) { perror("read"); exit(exit_failure); } /* if the nonblocking read() found no events to read, then it returns \-1 with errno set to eagain. in that case, we exit the loop. */ if (len <= 0) break; /* loop over all events in the buffer. */ for (char *ptr = buf; ptr < buf + len; ptr += sizeof(struct inotify_event) + event\->len) { event = (const struct inotify_event *) ptr; /* print event type. */ if (event\->mask & in_open) printf("in_open: "); if (event\->mask & in_close_nowrite) printf("in_close_nowrite: "); if (event\->mask & in_close_write) printf("in_close_write: "); /* print the name of the watched directory. */ for (int i = 1; i < argc; ++i) { if (wd[i] == event\->wd) { printf("%s/", argv[i]); break; } } /* print the name of the file. */ if (event\->len) printf("%s", event\->name); /* print type of filesystem object. */ if (event\->mask & in_isdir) printf(" [directory]\en"); else printf(" [file]\en"); } } } int main(int argc, char* argv[]) { char buf; int fd, i, poll_num; int *wd; nfds_t nfds; struct pollfd fds[2]; if (argc < 2) { printf("usage: %s path [path ...]\en", argv[0]); exit(exit_failure); } printf("press enter key to terminate.\en"); /* create the file descriptor for accessing the inotify api. */ fd = inotify_init1(in_nonblock); if (fd == \-1) { perror("inotify_init1"); exit(exit_failure); } /* allocate memory for watch descriptors. */ wd = calloc(argc, sizeof(int)); if (wd == null) { perror("calloc"); exit(exit_failure); } /* mark directories for events \- file was opened \- file was closed */ for (i = 1; i < argc; i++) { wd[i] = inotify_add_watch(fd, argv[i], in_open | in_close); if (wd[i] == \-1) { fprintf(stderr, "cannot watch \(aq%s\(aq: %s\en", argv[i], strerror(errno)); exit(exit_failure); } } /* prepare for polling. */ nfds = 2; fds[0].fd = stdin_fileno; /* console input */ fds[0].events = pollin; fds[1].fd = fd; /* inotify input */ fds[1].events = pollin; /* wait for events and/or terminal input. */ printf("listening for events.\en"); while (1) { poll_num = poll(fds, nfds, \-1); if (poll_num == \-1) { if (errno == eintr) continue; perror("poll"); exit(exit_failure); } if (poll_num > 0) { if (fds[0].revents & pollin) { /* console input is available. empty stdin and quit. */ while (read(stdin_fileno, &buf, 1) > 0 && buf != \(aq\en\(aq) continue; break; } if (fds[1].revents & pollin) { /* inotify events are available. */ handle_events(fd, wd, argc, argv); } } } printf("listening for events stopped.\en"); /* close inotify file descriptor. */ close(fd); free(wd); exit(exit_success); } .ee .sh see also .br inotifywait (1), .br inotifywatch (1), .br inotify_add_watch (2), .br inotify_init (2), .br inotify_init1 (2), .br inotify_rm_watch (2), .br read (2), .br stat (2), .br fanotify (7) .pp .ir documentation/filesystems/inotify.txt in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th log10 3 2021-03-22 "" "linux programmer's manual" .sh name log10, log10f, log10l \- base-10 logarithmic function .sh synopsis .nf .b #include .pp .bi "double log10(double " x ); .bi "float log10f(float " x ); .bi "long double log10l(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br log10f (), .br log10l (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the base 10 logarithm of .ir x . .sh return value on success, these functions return the base 10 logarithm of .ir x . .pp for special cases, including where .i x is 0, 1, negative, infinity, or nan, see .br log (3). .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp for a discussion of the errors that can occur for these functions, see .br log (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br log10 (), .br log10f (), .br log10l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br cbrt (3), .br clog10 (3), .br exp10 (3), .br log (3), .br log2 (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/j0.3 .so man3/stailq.3 .so man7/iso_8859-16.7 .\" copyright 1997 nicolás lichtmaier .\" created wed jul 2 23:27:34 art 1997 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" added info on availability, aeb, 971207 .\" added -lutil remark, 030718 .\" 2008-07-02, mtk, document updwtmpx() .\" .th updwtmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name updwtmp, logwtmp \- append an entry to the wtmp file .sh synopsis .nf .b #include .pp .bi "void updwtmp(const char *" wtmp_file ", const struct utmp *" ut ); .bi "void logwtmp(const char *" line ", const char *" name \ ", const char *" host ); .fi .pp for .br logwtmp (), link with \fi\-lutil\fp. .sh description .br updwtmp () appends the utmp structure .i ut to the wtmp file. .pp .br logwtmp () constructs a utmp structure using .ir line ", " name ", " host , current time, and current process id. then it calls .br updwtmp () to append the structure to the wtmp file. .sh files .tp .i /var/log/wtmp database of past user logins .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br updwtmp (), .br logwtmp () t} thread safety mt-unsafe sig:alrm timer .te .hy .ad .sp 1 .sh conforming to not in posix.1. present on solaris, netbsd, and perhaps other systems. .sh notes for consistency with the other "utmpx" functions (see .br getutxent (3)), glibc provides (since version 2.1): .pp .in +4n .ex .b #include .bi "void updwtmpx (const char *" wtmpx_file ", const struct utmpx *" utx ); .ee .in .pp this function performs the same task as .br updwtmp (), but differs in that it takes a .i utmpx structure as its last argument. .sh see also .br getutxent (3), .br wtmp (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th isatty 3 2021-03-22 "linux" "linux programmer's manual" .sh name isatty \- test whether a file descriptor refers to a terminal .sh synopsis .nf .b #include .pp .bi "int isatty(int " fd ); .fi .sh description the .br isatty () function tests whether .i fd is an open file descriptor referring to a terminal. .sh return value .br isatty () returns 1 if .i fd is an open file descriptor referring to a terminal; otherwise 0 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b enotty .i fd refers to a file other than a terminal. on some older kernels, some types of files .\" e.g., fifos and pipes on 2.6.32 resulted in the error .b einval in this case (which is a violation of posix, which specifies the error .br enotty ). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br isatty () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br fstat (2), .br ttyname (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .so man3/cmsg.3 .so man3/envz_add.3 .so man3/sigsetops.3 .\" copyright (c) 2011, eric biederman .\" and copyright (c) 2011, 2012, michael kerrisk .\" .\" %%%license_start(gplv2_oneline) .\" licensed under the gplv2 .\" %%%license_end .\" .th setns 2 2020-08-13 "linux" "linux programmer's manual" .sh name setns \- reassociate thread with a namespace .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int setns(int " fd ", int " nstype ); .fi .sh description the .br setns () system call allows the calling thread to move into different namespaces. the .i fd argument is one of the following: .ip \(bu 2 a file descriptor referring to one of the magic links in a .i /proc/[pid]/ns/ directory (or a bind mount to such a link); .ip \(bu a pid file descriptor (see .br pidfd_open (2)). .pp the .i nstype argument is interpreted differently in each case. .\" .ss fd refers to a /proc/[pid]/ns/ link if .i fd refers to a .i /proc/[pid]/ns/ link, then .br setns () reassociates the calling thread with the namespace associated with that link, subject to any constraints imposed by the .i nstype argument. in this usage, each call to .br setns () changes just one of the caller's namespace memberships. .pp the .i nstype argument specifies which type of namespace the calling thread may be reassociated with. this argument can have .i one of the following values: .tp .br 0 allow any type of namespace to be joined. .tp .br clone_newcgroup " (since linux 4.6)" .i fd must refer to a cgroup namespace. .tp .br clone_newipc " (since linux 3.0)" .i fd must refer to an ipc namespace. .tp .br clone_newnet " (since linux 3.0)" .i fd must refer to a network namespace. .tp .br clone_newns " (since linux 3.8)" .i fd must refer to a mount namespace. .tp .br clone_newpid " (since linux 3.8)" .i fd must refer to a descendant pid namespace. .tp .br clone_newtime " (since linux 5.8)" .\" commit 76c12881a38aaa83e1eb4ce2fada36c3a732bad4 .i fd must refer to a time namespace. .tp .br clone_newuser " (since linux 3.8)" .i fd must refer to a user namespace. .tp .br clone_newuts " (since linux 3.0)" .i fd must refer to a uts namespace. .pp specifying .i nstype as 0 suffices if the caller knows (or does not care) what type of namespace is referred to by .ir fd . specifying a nonzero value for .i nstype is useful if the caller does not know what type of namespace is referred to by .ir fd and wants to ensure that the namespace is of a particular type. (the caller might not know the type of the namespace referred to by .ir fd if the file descriptor was opened by another process and, for example, passed to the caller via a unix domain socket.) .\" .ss fd is a pid file descriptor since linux 5.8, .i fd may refer to a pid file descriptor obtained from .br pidfd_open (2) or .br clone (2). in this usage, .br setns () atomically moves the calling thread into one or more of the same namespaces as the thread referred to by .ir fd . .pp the .ir nstype argument is a bit mask specified by oring together .i "one or more" of the .br clone_new* namespace constants listed above. the caller is moved into each of the target thread's namespaces that is specified in .ir nstype ; the caller's memberships in the remaining namespaces are left unchanged. .pp for example, the following code would move the caller into the same user, network, and uts namespaces as pid 1234, but would leave the caller's other namespace memberships unchanged: .pp .in +4n .ex int fd = pidfd_open(1234, 0); setns(fd, clone_newuser | clone_newnet | clone_newuts); .ee .in .\" .ss details for specific namespace types note the following details and restrictions when reassociating with specific namespace types: .tp user namespaces a process reassociating itself with a user namespace must have the .b cap_sys_admin .\" see kernel/user_namespace.c:userns_install() [3.8 source] capability in the target user namespace. (this necessarily implies that it is only possible to join a descendant user namespace.) upon successfully joining a user namespace, a process is granted all capabilities in that namespace, regardless of its user and group ids. .ip a multithreaded process may not change user namespace with .br setns (). .ip it is not permitted to use .br setns () to reenter the caller's current user namespace. this prevents a caller that has dropped capabilities from regaining those capabilities via a call to .br setns (). .ip for security reasons, .\" commit e66eded8309ebf679d3d3c1f5820d1f2ca332c71 .\" https://lwn.net/articles/543273/ a process can't join a new user namespace if it is sharing filesystem-related attributes (the attributes whose sharing is controlled by the .br clone (2) .b clone_fs flag) with another process. .ip for further details on user namespaces, see .br user_namespaces (7). .tp mount namespaces changing the mount namespace requires that the caller possess both .b cap_sys_chroot and .br cap_sys_admin capabilities in its own user namespace and .br cap_sys_admin in the user namespace that owns the target mount namespace. .ip a process can't join a new mount namespace if it is sharing filesystem-related attributes (the attributes whose sharing is controlled by the .br clone (2) .b clone_fs flag) with another process. .\" above check is in fs/namespace.c:mntns_install() [3.8 source] .ip see .br user_namespaces (7) for details on the interaction of user namespaces and mount namespaces. .tp pid namespaces in order to reassociate itself with a new pid namespace, the caller must have the .b cap_sys_admin capability both in its own user namespace and in the user namespace that owns the target pid namespace. .ip reassociating the pid namespace has somewhat different from other namespace types. reassociating the calling thread with a pid namespace changes only the pid namespace that subsequently created child processes of the caller will be placed in; it does not change the pid namespace of the caller itself. .ip reassociating with a pid namespace is allowed only if the target pid namespace is a descendant (child, grandchild, etc.) of, or is the same as, the current pid namespace of the caller. .ip for further details on pid namespaces, see .br pid_namespaces (7). .tp cgroup namespaces in order to reassociate itself with a new cgroup namespace, the caller must have the .b cap_sys_admin capability both in its own user namespace and in the user namespace that owns the target cgroup namespace. .ip using .br setns () to change the caller's cgroup namespace does not change the caller's cgroup memberships. .tp network, ipc, time, and uts namespaces in order to reassociate itself with a new network, ipc, time, or uts namespace, the caller must have the .b cap_sys_admin capability both in its own user namespace and in the user namespace that owns the target namespace. .sh return value on success, .br setns () returns 0. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b einval .i fd refers to a namespace whose type does not match that specified in .ir nstype . .tp .b einval there is problem with reassociating the thread with the specified namespace. .tp .\" see kernel/pid_namespace.c::pidns_install() [kernel 3.18 sources] .b einval the caller tried to join an ancestor (parent, grandparent, and so on) pid namespace. .tp .b einval the caller attempted to join the user namespace in which it is already a member. .tp .b einval .\" commit e66eded8309ebf679d3d3c1f5820d1f2ca332c71 the caller shares filesystem .rb ( clone_fs ) state (in particular, the root directory) with other processes and tried to join a new user namespace. .tp .b einval .\" see kernel/user_namespace.c::userns_install() [kernel 3.15 sources] the caller is multithreaded and tried to join a new user namespace. .tp .b einval .i fd is a pid file descriptor and .i nstype is invalid (e.g., it is 0). .tp .b enomem cannot allocate sufficient memory to change the specified namespace. .tp .b eperm the calling thread did not have the required capability for this operation. .tp .b esrch .i fd is a pid file descriptor but the process it refers to no longer exists (i.e., it has terminated and been waited on). .sh versions the .br setns () system call first appeared in linux in kernel 3.0; library support was added to glibc in version 2.14. .sh conforming to the .br setns () system call is linux-specific. .sh notes for further information on the .ir /proc/[pid]/ns/ magic links, see .br namespaces (7). .pp not all of the attributes that can be shared when a new thread is created using .br clone (2) can be changed using .br setns (). .sh examples the program below takes two or more arguments. the first argument specifies the pathname of a namespace file in an existing .i /proc/[pid]/ns/ directory. the remaining arguments specify a command and its arguments. the program opens the namespace file, joins that namespace using .br setns (), and executes the specified command inside that namespace. .pp the following shell session demonstrates the use of this program (compiled as a binary named .ir ns_exec ) in conjunction with the .br clone_newuts example program in the .br clone (2) man page (complied as a binary named .ir newuts ). .pp we begin by executing the example program in .br clone (2) in the background. that program creates a child in a separate uts namespace. the child changes the hostname in its namespace, and then both processes display the hostnames in their uts namespaces, so that we can see that they are different. .pp .in +4n .ex $ \fbsu\fp # need privilege for namespace operations password: # \fb./newuts bizarro &\fp [1] 3549 clone() returned 3550 uts.nodename in child: bizarro uts.nodename in parent: antero # \fbuname \-n\fp # verify hostname in the shell antero .ee .in .pp we then run the program shown below, using it to execute a shell. inside that shell, we verify that the hostname is the one set by the child created by the first program: .pp .in +4n .ex # \fb./ns_exec /proc/3550/ns/uts /bin/bash\fp # \fbuname \-n\fp # executed in shell started by ns_exec bizarro .ee .in .ss program source .ex #define _gnu_source #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { int fd; if (argc < 3) { fprintf(stderr, "%s /proc/pid/ns/file cmd args...\en", argv[0]); exit(exit_failure); } /* get file descriptor for namespace; the file descriptor is opened with o_cloexec so as to ensure that it is not inherited by the program that is later executed. */ fd = open(argv[1], o_rdonly | o_cloexec); if (fd == \-1) errexit("open"); if (setns(fd, 0) == \-1) /* join that namespace */ errexit("setns"); execvp(argv[2], &argv[2]); /* execute a command in namespace */ errexit("execvp"); } .ee .sh see also .br nsenter (1), .br clone (2), .br fork (2), .br unshare (2), .br vfork (2), .br namespaces (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" and copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th cpu_set 3 2021-03-22 "linux" "linux programmer's manual" .sh name cpu_set, cpu_clr, cpu_isset, cpu_zero, cpu_count, cpu_and, cpu_or, cpu_xor, cpu_equal, cpu_alloc, cpu_alloc_size, cpu_free, cpu_set_s, cpu_clr_s, cpu_isset_s, cpu_zero_s, cpu_count_s, cpu_and_s, cpu_or_s, cpu_xor_s, cpu_equal_s \- macros for manipulating cpu sets .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void cpu_zero(cpu_set_t *" set ); .pp .bi "void cpu_set(int " cpu ", cpu_set_t *" set ); .bi "void cpu_clr(int " cpu ", cpu_set_t *" set ); .bi "int cpu_isset(int " cpu ", cpu_set_t *" set ); .pp .bi "int cpu_count(cpu_set_t *" set ); .pp .bi "void cpu_and(cpu_set_t *" destset , .bi " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); .bi "void cpu_or(cpu_set_t *" destset , .bi " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); .bi "void cpu_xor(cpu_set_t *" destset , .bi " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); .pp .bi "int cpu_equal(cpu_set_t *" set1 ", cpu_set_t *" set2 ); .pp .bi "cpu_set_t *cpu_alloc(int " num_cpus ); .bi "void cpu_free(cpu_set_t *" set ); .bi "size_t cpu_alloc_size(int " num_cpus ); .pp .bi "void cpu_zero_s(size_t " setsize ", cpu_set_t *" set ); .pp .bi "void cpu_set_s(int " cpu ", size_t " setsize ", cpu_set_t *" set ); .bi "void cpu_clr_s(int " cpu ", size_t " setsize ", cpu_set_t *" set ); .bi "int cpu_isset_s(int " cpu ", size_t " setsize ", cpu_set_t *" set ); .pp .bi "int cpu_count_s(size_t " setsize ", cpu_set_t *" set ); .pp .bi "void cpu_and_s(size_t " setsize ", cpu_set_t *" destset , .bi " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); .bi "void cpu_or_s(size_t " setsize ", cpu_set_t *" destset , .bi " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); .bi "void cpu_xor_s(size_t " setsize ", cpu_set_t *" destset , .bi " cpu_set_t *" srcset1 ", cpu_set_t *" srcset2 ); .pp .bi "int cpu_equal_s(size_t " setsize ", cpu_set_t *" set1 \ ", cpu_set_t *" set2 ); .fi .sh description the .i cpu_set_t data structure represents a set of cpus. cpu sets are used by .br sched_setaffinity (2) and similar interfaces. .pp the .i cpu_set_t data type is implemented as a bit mask. however, the data structure should be treated as opaque: all manipulation of cpu sets should be done via the macros described in this page. .pp the following macros are provided to operate on the cpu set .ir set : .tp .br cpu_zero () clears .ir set , so that it contains no cpus. .tp .br cpu_set () add cpu .i cpu to .ir set . .tp .br cpu_clr () remove cpu .i cpu from .ir set . .tp .br cpu_isset () test to see if cpu .i cpu is a member of .ir set . .tp .br cpu_count () return the number of cpus in .ir set . .pp where a .i cpu argument is specified, it should not produce side effects, since the above macros may evaluate the argument more than once. .pp the first cpu on the system corresponds to a .i cpu value of 0, the next cpu corresponds to a .i cpu value of 1, and so on. no assumptions should be made about particular cpus being available, or the set of cpus being contiguous, since cpus can be taken offline dynamically or be otherwise absent. the constant .b cpu_setsize (currently 1024) specifies a value one greater than the maximum cpu number that can be stored in .ir cpu_set_t . .pp the following macros perform logical operations on cpu sets: .tp .br cpu_and () store the intersection of the sets .i srcset1 and .i srcset2 in .i destset (which may be one of the source sets). .tp .br cpu_or () store the union of the sets .i srcset1 and .i srcset2 in .i destset (which may be one of the source sets). .tp .br cpu_xor () store the xor of the sets .i srcset1 and .i srcset2 in .i destset (which may be one of the source sets). the xor means the set of cpus that are in either .i srcset1 or .ir srcset2 , but not both. .tp .br cpu_equal () test whether two cpu set contain exactly the same cpus. .ss dynamically sized cpu sets because some applications may require the ability to dynamically size cpu sets (e.g., to allocate sets larger than that defined by the standard .i cpu_set_t data type), glibc nowadays provides a set of macros to support this. .pp the following macros are used to allocate and deallocate cpu sets: .tp .br cpu_alloc () allocate a cpu set large enough to hold cpus in the range 0 to .ir num_cpus\-1 . .tp .br cpu_alloc_size () return the size in bytes of the cpu set that would be needed to hold cpus in the range 0 to .ir num_cpus\-1 . this macro provides the value that can be used for the .i setsize argument in the .br cpu_*_s () macros described below. .tp .br cpu_free () free a cpu set previously allocated by .br cpu_alloc (). .pp the macros whose names end with "_s" are the analogs of the similarly named macros without the suffix. these macros perform the same tasks as their analogs, but operate on the dynamically allocated cpu set(s) whose size is .i setsize bytes. .sh return value .br cpu_isset () and .br cpu_isset_s () return nonzero if .i cpu is in .ir set ; otherwise, it returns 0. .pp .br cpu_count () and .br cpu_count_s () return the number of cpus in .ir set . .pp .br cpu_equal () and .br cpu_equal_s () return nonzero if the two cpu sets are equal; otherwise they return 0. .pp .br cpu_alloc () returns a pointer on success, or null on failure. (errors are as for .br malloc (3).) .pp .br cpu_alloc_size () returns the number of bytes required to store a cpu set of the specified cardinality. .pp the other functions do not return a value. .sh versions the .br cpu_zero (), .br cpu_set (), .br cpu_clr (), and .br cpu_isset () macros were added in glibc 2.3.3. .pp .br cpu_count () first appeared in glibc 2.6. .pp .br cpu_and (), .br cpu_or (), .br cpu_xor (), .br cpu_equal (), .br cpu_alloc (), .br cpu_alloc_size (), .br cpu_free (), .br cpu_zero_s (), .br cpu_set_s (), .br cpu_clr_s (), .br cpu_isset_s (), .br cpu_and_s (), .br cpu_or_s (), .br cpu_xor_s (), and .br cpu_equal_s () first appeared in glibc 2.7. .sh conforming to these interfaces are linux-specific. .sh notes to duplicate a cpu set, use .br memcpy (3). .pp since cpu sets are bit masks allocated in units of long words, the actual number of cpus in a dynamically allocated cpu set will be rounded up to the next multiple of .ir "sizeof(unsigned long)" . an application should consider the contents of these extra bits to be undefined. .pp notwithstanding the similarity in the names, note that the constant .b cpu_setsize indicates the number of cpus in the .i cpu_set_t data type (thus, it is effectively a count of the bits in the bit mask), while the .i setsize argument of the .br cpu_*_s () macros is a size in bytes. .pp the data types for arguments and return values shown in the synopsis are hints what about is expected in each case. however, since these interfaces are implemented as macros, the compiler won't necessarily catch all type errors if you violate the suggestions. .sh bugs on 32-bit platforms with glibc 2.8 and earlier, .br cpu_alloc () allocates twice as much space as is required, and .br cpu_alloc_size () returns a value twice as large as it should. this bug should not affect the semantics of a program, but does result in wasted memory and less efficient operation of the macros that operate on dynamically allocated cpu sets. these bugs are fixed in glibc 2.9. .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7029 .sh examples the following program demonstrates the use of some of the macros used for dynamically allocated cpu sets. .pp .ex #define _gnu_source #include #include #include #include #include int main(int argc, char *argv[]) { cpu_set_t *cpusetp; size_t size; int num_cpus; if (argc < 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } num_cpus = atoi(argv[1]); cpusetp = cpu_alloc(num_cpus); if (cpusetp == null) { perror("cpu_alloc"); exit(exit_failure); } size = cpu_alloc_size(num_cpus); cpu_zero_s(size, cpusetp); for (int cpu = 0; cpu < num_cpus; cpu += 2) cpu_set_s(cpu, size, cpusetp); printf("cpu_count() of set: %d\en", cpu_count_s(size, cpusetp)); cpu_free(cpusetp); exit(exit_success); } .ee .sh see also .br sched_setaffinity (2), .br pthread_attr_setaffinity_np (3), .br pthread_setaffinity_np (3), .br cpuset (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/pthread_attr_setguardsize.3 .so man3/pthread_setname_np.3 .\" copyright 1993-1995 daniel quinlan (quinlan@yggdrasil.com) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" slightly rearranged, aeb, 950713 .\" updated, dpo, 990531 .th iso_8859-1 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-1 \- iso 8859-1 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-1 encodes the characters used in many west european languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-1 characters the following table displays the characters in iso 8859-1 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ¡ inverted exclamation mark 242 162 a2 ¢ cent sign 243 163 a3 £ pound sign 244 164 a4 ¤ currency sign 245 165 a5 ¥ yen sign 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 © copyright sign 252 170 aa ª feminine ordinal indicator 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ¯ macron 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ´ acute accent 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ¸ cedilla 271 185 b9 ¹ superscript one 272 186 ba º masculine ordinal indicator 273 187 bb » right-pointing double angle quotation mark 274 188 bc ¼ vulgar fraction one quarter 275 189 bd ½ vulgar fraction one half 276 190 be ¾ vulgar fraction three quarters 277 191 bf ¿ inverted question mark 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 ð latin capital letter eth 321 209 d1 ñ latin capital letter n with tilde 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ý latin capital letter y with acute 336 222 de þ latin capital letter thorn 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 ð latin small letter eth 361 241 f1 ñ latin small letter n with tilde 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ø latin small letter o with stroke 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ý latin small letter y with acute 376 254 fe þ latin small letter thorn 377 255 ff ÿ latin small letter y with diaeresis .te .sh notes iso 8859-1 is also known as latin-1. .sh see also .br ascii (7), .br charsets (7), .br cp1252 (7), .br iso_8859\-15 (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/perror.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified mon mar 29 22:39:24 1993, david metcalfe .\" modified sat jul 24 21:39:22 1993, rik faith (faith@cs.unc.edu) .th atof 3 2021-03-22 "gnu" "linux programmer's manual" .sh name atof \- convert a string to a double .sh synopsis .nf .b #include .pp .bi "double atof(const char *" nptr ); .fi .sh description the .br atof () function converts the initial portion of the string pointed to by \finptr\fp to .ir double . the behavior is the same as .pp .in +4n .ex strtod(nptr, null); .ee .in .pp except that .br atof () does not detect errors. .sh return value the converted value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br atof () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh see also .br atoi (3), .br atol (3), .br strfromd (3), .br strtod (3), .br strtol (3), .br strtoul (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdio_ext.3 .so man7/system_data_types.7 .so man3/nan.3 .\" copyright (c) 1995,1997 paul gortmaker and andries brouwer .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" this man page written 950814 by aeb, based on paul gortmaker's howto .\" (dated v1.0.1, 15/08/95). .\" major update, aeb, 970114. .\" .th bootparam 7 2021-03-22 "linux" "linux programmer's manual" .sh name bootparam \- introduction to boot time parameters of the linux kernel .sh description the linux kernel accepts certain 'command-line options' or 'boot time parameters' at the moment it is started. in general, this is used to supply the kernel with information about hardware parameters that the kernel would not be able to determine on its own, or to avoid/override the values that the kernel would otherwise detect. .pp when the kernel is booted directly by the bios, you have no opportunity to specify any parameters. so, in order to take advantage of this possibility you have to use a boot loader that is able to pass parameters, such as grub. .ss the argument list the kernel command line is parsed into a list of strings (boot arguments) separated by spaces. most of the boot arguments have the form: .pp .in +4n .ex name[=value_1][,value_2]...[,value_10] .ee .in .pp where 'name' is a unique keyword that is used to identify what part of the kernel the associated values (if any) are to be given to. note the limit of 10 is real, as the present code handles only 10 comma separated parameters per keyword. (however, you can reuse the same keyword with up to an additional 10 parameters in unusually complicated situations, assuming the setup function supports it.) .pp most of the sorting is coded in the kernel source file .ir init/main.c . first, the kernel checks to see if the argument is any of the special arguments 'root=', \&'nfsroot=', 'nfsaddrs=', 'ro', 'rw', 'debug', or 'init'. the meaning of these special arguments is described below. .pp then it walks a list of setup functions to see if the specified argument string (such as 'foo') has been associated with a setup function ('foo_setup()') for a particular device or part of the kernel. if you passed the kernel the line foo=3,4,5,6 then the kernel would search the bootsetups array to see if 'foo' was registered. if it was, then it would call the setup function associated with 'foo' (foo_setup()) and hand it the arguments 3, 4, 5, and 6 as given on the kernel command line. .pp anything of the form 'foo=bar' that is not accepted as a setup function as described above is then interpreted as an environment variable to be set. a (useless?) example would be to use 'term=vt100' as a boot argument. .pp any remaining arguments that were not picked up by the kernel and were not interpreted as environment variables are then passed onto pid 1, which is usually the .br init (1) program. the most common argument that is passed to the .i init process is the word 'single' which instructs it to boot the computer in single user mode, and not launch all the usual daemons. check the manual page for the version of .br init (1) installed on your system to see what arguments it accepts. .ss general non-device-specific boot arguments .tp .b "'init=...'" this sets the initial command to be executed by the kernel. if this is not set, or cannot be found, the kernel will try .ir /sbin/init , then .ir /etc/init , then .ir /bin/init , then .i /bin/sh and panic if all of this fails. .tp .b "'nfsaddrs=...'" this sets the nfs boot address to the given string. this boot address is used in case of a net boot. .tp .b "'nfsroot=...'" this sets the nfs root name to the given string. if this string does not begin with '/' or ',' or a digit, then it is prefixed by \&'/tftpboot/'. this root name is used in case of a net boot. .tp .b "'root=...'" this argument tells the kernel what device is to be used as the root filesystem while booting. the default of this setting is determined at compile time, and usually is the value of the root device of the system that the kernel was built on. to override this value, and select the second floppy drive as the root device, one would use 'root=/dev/fd1'. .ip the root device can be specified symbolically or numerically. a symbolic specification has the form .ir /dev/xxyn , where xx designates the device type (e.g., 'hd' for st-506 compatible hard disk, with y in \&'a'\(en'd'; 'sd' for scsi compatible disk, with y in 'a'\(en'e'), y the driver letter or number, and n the number (in decimal) of the partition on this device. .ip note that this has nothing to do with the designation of these devices on your filesystem. the '/dev/' part is purely conventional. .ip the more awkward and less portable numeric specification of the above possible root devices in major/minor format is also accepted. (for example, .i /dev/sda3 is major 8, minor 3, so you could use 'root=0x803' as an alternative.) .tp .br "'rootdelay='" this parameter sets the delay (in seconds) to pause before attempting to mount the root filesystem. .tp .br "'rootflags=...'" this parameter sets the mount option string for the root filesystem (see also .br fstab (5)). .tp .br "'rootfstype=...'" the 'rootfstype' option tells the kernel to mount the root filesystem as if it where of the type specified. this can be useful (for example) to mount an ext3 filesystem as ext2 and then remove the journal in the root filesystem, in fact reverting its format from ext3 to ext2 without the need to boot the box from alternate media. .tp .br 'ro' " and " 'rw' the 'ro' option tells the kernel to mount the root filesystem as 'read-only' so that filesystem consistency check programs (fsck) can do their work on a quiescent filesystem. no processes can write to files on the filesystem in question until it is 'remounted' as read/write capable, for example, by 'mount \-w \-n \-o remount /'. (see also .br mount (8).) .ip the 'rw' option tells the kernel to mount the root filesystem read/write. this is the default. .tp .b "'resume=...'" this tells the kernel the location of the suspend-to-disk data that you want the machine to resume from after hibernation. usually, it is the same as your swap partition or file. example: .ip .in +4n .ex resume=/dev/hda2 .ee .in .tp .b "'reserve=...'" this is used to protect i/o port regions from probes. the form of the command is: .ip .in +4n .ex .bi reserve= iobase,extent[,iobase,extent]... .ee .in .ip in some machines it may be necessary to prevent device drivers from checking for devices (auto-probing) in a specific region. this may be because of hardware that reacts badly to the probing, or hardware that would be mistakenly identified, or merely hardware you don't want the kernel to initialize. .ip the reserve boot-time argument specifies an i/o port region that shouldn't be probed. a device driver will not probe a reserved region, unless another boot argument explicitly specifies that it do so. .ip for example, the boot line .ip .in +4n .ex reserve=0x300,32 blah=0x300 .ee .in .ip keeps all device drivers except the driver for 'blah' from probing 0x300\-0x31f. .tp .b "'panic=n'" by default, the kernel will not reboot after a panic, but this option will cause a kernel reboot after n seconds (if n is greater than zero). this panic timeout can also be set by .ip .in +4n .ex echo n > /proc/sys/kernel/panic .ee .in .tp .b "'reboot=[warm|cold][,[bios|hard]]'" since linux 2.0.22, a reboot is by default a cold reboot. one asks for the old default with 'reboot=warm'. (a cold reboot may be required to reset certain hardware, but might destroy not yet written data in a disk cache. a warm reboot may be faster.) by default, a reboot is hard, by asking the keyboard controller to pulse the reset line low, but there is at least one type of motherboard where that doesn't work. the option 'reboot=bios' will instead jump through the bios. .tp .br 'nosmp' " and " 'maxcpus=n' (only when __smp__ is defined.) a command-line option of 'nosmp' or 'maxcpus=0' will disable smp activation entirely; an option 'maxcpus=n' limits the maximum number of cpus activated in smp mode to n. .ss boot arguments for use by kernel developers .tp .b "'debug'" kernel messages are handed off to a daemon (e.g., .br klogd (8) or similar) so that they may be logged to disk. messages with a priority above .i console_loglevel are also printed on the console. (for a discussion of log levels, see .br syslog (2).) by default, .i console_loglevel is set to log messages at levels higher than .br kern_debug . this boot argument will cause the kernel to also print messages logged at level .br kern_debug . the console loglevel can also be set on a booted system via the .ir /proc/sys/kernel/printk file (described in .br syslog (2)), the .br syslog (2) .b syslog_action_console_level operation, or .br dmesg (8). .tp .b "'profile=n'" it is possible to enable a kernel profiling function, if one wishes to find out where the kernel is spending its cpu cycles. profiling is enabled by setting the variable .i prof_shift to a nonzero value. this is done either by specifying .b config_profile at compile time, or by giving the 'profile=' option. now the value that .i prof_shift gets will be n, when given, or .br config_profile_shift , when that is given, or 2, the default. the significance of this variable is that it gives the granularity of the profiling: each clock tick, if the system was executing kernel code, a counter is incremented: .ip .in +4n .ex profile[address >> prof_shift]++; .ee .in .ip the raw profiling information can be read from .ir /proc/profile . probably you'll want to use a tool such as readprofile.c to digest it. writing to .i /proc/profile will clear the counters. .ss boot arguments for ramdisk use (only if the kernel was compiled with .br config_blk_dev_ram .) in general it is a bad idea to use a ramdisk under linux\(emthe system will use available memory more efficiently itself. but while booting, it is often useful to load the floppy contents into a ramdisk. one might also have a system in which first some modules (for filesystem or hardware) must be loaded before the main disk can be accessed. .ip in linux 1.3.48, ramdisk handling was changed drastically. earlier, the memory was allocated statically, and there was a 'ramdisk=n' parameter to tell its size. (this could also be set in the kernel image at compile time.) these days ram disks use the buffer cache, and grow dynamically. for a lot of information on the current ramdisk setup, see the kernel source file .ir documentation/blockdev/ramdisk.txt .ri ( documentation/ramdisk.txt in older kernels). .ip there are four parameters, two boolean and two integral. .tp .b "'load_ramdisk=n'" if n=1, do load a ramdisk. if n=0, do not load a ramdisk. (this is the default.) .tp .b "'prompt_ramdisk=n'" if n=1, do prompt for insertion of the floppy. (this is the default.) if n=0, do not prompt. (thus, this parameter is never needed.) .tp .br 'ramdisk_size=n' " or (obsolete) " 'ramdisk=n' set the maximal size of the ramdisk(s) to n kb. the default is 4096 (4\ mb). .tp .b "'ramdisk_start=n'" sets the starting block number (the offset on the floppy where the ramdisk starts) to n. this is needed in case the ramdisk follows a kernel image. .tp .b "'noinitrd'" (only if the kernel was compiled with .b config_blk_dev_ram and .br config_blk_dev_initrd .) these days it is possible to compile the kernel to use initrd. when this feature is enabled, the boot process will load the kernel and an initial ramdisk; then the kernel converts initrd into a "normal" ramdisk, which is mounted read-write as root device; then .i /linuxrc is executed; afterward the "real" root filesystem is mounted, and the initrd filesystem is moved over to .ir /initrd ; finally the usual boot sequence (e.g., invocation of .ir /sbin/init ) is performed. .ip for a detailed description of the initrd feature, see the kernel source file .i documentation/admin\-guide/initrd.rst .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/initrd.txt before linux 4.10). .ip the 'noinitrd' option tells the kernel that although it was compiled for operation with initrd, it should not go through the above steps, but leave the initrd data under .ir /dev/initrd . (this device can be used only once: the data is freed as soon as the last process that used it has closed .ir /dev/initrd .) .ss boot arguments for scsi devices general notation for this section: .pp .i iobase -- the first i/o port that the scsi host occupies. these are specified in hexadecimal notation, and usually lie in the range from 0x200 to 0x3ff. .pp .i irq -- the hardware interrupt that the card is configured to use. valid values will be dependent on the card in question, but will usually be 5, 7, 9, 10, 11, 12, and 15. the other values are usually used for common peripherals like ide hard disks, floppies, serial ports, and so on. .pp .i scsi\-id -- the id that the host adapter uses to identify itself on the scsi bus. only some host adapters allow you to change this value, as most have it permanently specified internally. the usual default value is 7, but the seagate and future domain tmc-950 boards use 6. .pp .i parity -- whether the scsi host adapter expects the attached devices to supply a parity value with all information exchanges. specifying a one indicates parity checking is enabled, and a zero disables parity checking. again, not all adapters will support selection of parity behavior as a boot argument. .tp .b "'max_scsi_luns=...'" a scsi device can have a number of 'subdevices' contained within itself. the most common example is one of the new scsi cd-roms that handle more than one disk at a time. each cd is addressed as a \&'logical unit number' (lun) of that particular device. but most devices, such as hard disks, tape drives, and such are only one device, and will be assigned to lun zero. .ip some poorly designed scsi devices cannot handle being probed for luns not equal to zero. therefore, if the compile-time flag .b config_scsi_multi_lun is not set, newer kernels will by default probe only lun zero. .ip to specify the number of probed luns at boot, one enters \&'max_scsi_luns=n' as a boot arg, where n is a number between one and eight. to avoid problems as described above, one would use n=1 to avoid upsetting such broken devices. .tp .b "scsi tape configuration" some boot time configuration of the scsi tape driver can be achieved by using the following: .ip .in +4n .ex .bi st= buf_size[,write_threshold[,max_bufs]] .ee .in .ip the first two numbers are specified in units of kb. the default .i buf_size is 32k\ b, and the maximum size that can be specified is a ridiculous 16384\ kb. the .i write_threshold is the value at which the buffer is committed to tape, with a default value of 30\ kb. the maximum number of buffers varies with the number of drives detected, and has a default of two. an example usage would be: .ip .in +4n .ex st=32,30,2 .ee .in .ip full details can be found in the file .i documentation/scsi/st.txt (or .i drivers/scsi/readme.st for older kernels) in the linux kernel source. .ss hard disks .tp .b "ide disk/cd-rom driver parameters" the ide driver accepts a number of parameters, which range from disk geometry specifications, to support for broken controller chips. drive-specific options are specified by using 'hdx=' with x in 'a'\(en'h'. .ip non-drive-specific options are specified with the prefix 'hd='. note that using a drive-specific prefix for a non-drive-specific option will still work, and the option will just be applied as expected. .ip also note that 'hd=' can be used to refer to the next unspecified drive in the (a, ..., h) sequence. for the following discussions, the 'hd=' option will be cited for brevity. see the file .i documentation/ide/ide.txt (or .i documentation/ide.txt .\" linux 2.0, 2.2, 2.4 in older kernels, or .i drivers/block/readme.ide in ancient kernels) in the linux kernel source for more details. .tp .b "the 'hd=cyls,heads,sects[,wpcom[,irq]]' options" these options are used to specify the physical geometry of the disk. only the first three values are required. the cylinder/head/sectors values will be those used by fdisk. the write precompensation value is ignored for ide disks. the irq value specified will be the irq used for the interface that the drive resides on, and is not really a drive-specific parameter. .tp .b "the 'hd=serialize' option" the dual ide interface cmd-640 chip is broken as designed such that when drives on the secondary interface are used at the same time as drives on the primary interface, it will corrupt your data. using this option tells the driver to make sure that both interfaces are never used at the same time. .tp .b "the 'hd=noprobe' option" do not probe for this drive. for example, .ip .in +4n .ex hdb=noprobe hdb=1166,7,17 .ee .in .ip would disable the probe, but still specify the drive geometry so that it would be registered as a valid block device, and hence usable. .tp .b "the 'hd=nowerr' option" some drives apparently have the .b wrerr_stat bit stuck on permanently. this enables a work-around for these broken devices. .tp .b "the 'hd=cdrom' option" this tells the ide driver that there is an atapi compatible cd-rom attached in place of a normal ide hard disk. in most cases the cd-rom is identified automatically, but if it isn't then this may help. .tp .b "standard st-506 disk driver options ('hd=')" the standard disk driver can accept geometry arguments for the disks similar to the ide driver. note however that it expects only three values (c/h/s); any more or any less and it will silently ignore you. also, it accepts only 'hd=' as an argument, that is, 'hda=' and so on are not valid here. the format is as follows: .ip .in +4n .ex hd=cyls,heads,sects .ee .in .ip if there are two disks installed, the above is repeated with the geometry parameters of the second disk. .ss ethernet devices different drivers make use of different parameters, but they all at least share having an irq, an i/o port base value, and a name. in its most generic form, it looks something like this: .pp .in +4n .ex ether=irq,iobase[,param_1[,...param_8]],name .ee .in .pp the first nonnumeric argument is taken as the name. the param_n values (if applicable) usually have different meanings for each different card/driver. typical param_n values are used to specify things like shared memory address, interface selection, dma channel and the like. .pp the most common use of this parameter is to force probing for a second ethercard, as the default is to probe only for one. this can be accomplished with a simple: .pp .in +4n .ex ether=0,0,eth1 .ee .in .pp note that the values of zero for the irq and i/o base in the above example tell the driver(s) to autoprobe. .pp the ethernet-howto has extensive documentation on using multiple cards and on the card/driver-specific implementation of the param_n values where used. interested readers should refer to the section in that document on their particular card. .ss the floppy disk driver there are many floppy driver options, and they are all listed in .i documentation/blockdev/floppy.txt (or .i documentation/floppy.txt in older kernels, or .i drivers/block/readme.fd for ancient kernels) in the linux kernel source. see that file for the details. .ss the sound driver the sound driver can also accept boot arguments to override the compiled-in values. this is not recommended, as it is rather complex. it is described in the linux kernel source file .ir documentation/sound/oss/readme.oss .ri ( drivers/sound/readme.linux in older kernel versions). it accepts a boot argument of the form: .pp .in +4n .ex sound=device1[,device2[,device3...[,device10]]] .ee .in .pp where each devicen value is of the following format 0xtaaaid and the bytes are used as follows: .pp t \- device type: 1=fm, 2=sb, 3=pas, 4=gus, 5=mpu401, 6=sb16, 7=sb16-mpu401 .pp aaa \- i/o address in hex. .pp i \- interrupt line in hex (i.e., 10=a, 11=b, ...) .pp d \- dma channel. .pp as you can see, it gets pretty messy, and you are better off to compile in your own personal values as recommended. using a boot argument of \&'sound=0' will disable the sound driver entirely. .ss the line printer driver .tp .b "'lp='" .br syntax: .ip .in +4n .ex lp=0 lp=auto lp=reset lp=port[,port...] .ee .in .ip you can tell the printer driver what ports to use and what ports not to use. the latter comes in handy if you don't want the printer driver to claim all available parallel ports, so that other drivers (e.g., plip, ppa) can use them instead. .ip the format of the argument is multiple port names. for example, lp=none,parport0 would use the first parallel port for lp1, and disable lp0. to disable the printer driver entirely, one can use lp=0. .\" .sh authors .\" linus torvalds (and many others) .sh see also .br klogd (8), .br mount (8) .pp for up-to-date information, see the kernel source file .ir documentation/admin\-guide/kernel\-parameters.txt . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wmemcpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wmemcpy \- copy an array of wide-characters .sh synopsis .nf .b #include .pp .bi "wchar_t *wmemcpy(wchar_t *restrict " dest \ ", const wchar_t *restrict " src , .bi " size_t " n ); .fi .sh description the .br wmemcpy () function is the wide-character equivalent of the .br memcpy (3) function. it copies .i n wide characters from the array starting at .i src to the array starting at .ir dest . .pp the arrays may not overlap; use .br wmemmove (3) to copy between overlapping arrays. .pp the programmer must ensure that there is room for at least .i n wide characters at .ir dest . .sh return value .br wmemcpy () returns .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wmemcpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br memcpy (3), .br wcscpy (3), .br wmemmove (3), .br wmempcpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getutent.3 .so man3/tailq.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified sun jul 25 10:14:13 1993 by rik faith .\" modified 15 april 1995 by michael chastain .\" update calling parameters to linux 1.2.4 values. .\" modified 10 june 1995 by andries brouwer .\" modified 3 may 1996 by martin schulze .\" modified wed nov 6 04:05:28 1996 by eric s. raymond .\" modified sat jan 29 01:08:23 2000 by aeb .\" .th setup 2 2021-03-22 "linux" "linux programmer's manual" .sh name setup \- setup devices and filesystems, mount root filesystem .sh synopsis .nf .b #include .pp .b int setup(void); .fi .sh description .br setup () is called once from within .ir linux/init/main.c . it calls initialization functions for devices and filesystems configured into the kernel and then mounts the root filesystem. .pp no user process may call .br setup (). any user process, even a process with superuser permission, will receive .br eperm . .sh return value .br setup () always returns \-1 for a user process. .sh errors .tp .b eperm always, for a user process. .sh versions since linux 2.1.121, no such function exists anymore. .sh conforming to this function is linux-specific, and should not be used in programs intended to be portable, or indeed in any programs at all. .sh notes the calling sequence varied: at some times .br setup () has had a single argument .i "void\ *bios" and at other times a single argument .ir "int magic" . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. release the linux man page maintainer proudly announces. . . man-pages-5.13.tar.gz - man pages for linux differences from the previous manual pages release are listed in the file "changes". for further information, visit http://www.kernel.org/doc/man-pages/ posix pages this package used to contains a copy of the posix 1003.1-2003 man pages. the posix pages are now distributed in the separate man-pages-posix package. the pages these pages are most of the section 2, 3, 4, 5, 7 man pages for linux. a few pages are provided in sections 1 and 8 for commands that are not documented in other packages, and there are a few pages in sections 5 and 8 for the timezone utilities. [the timezone pages were taken from ftp://elsie.nci.nih.gov/pub/tzcode2001a.tar.gz.] [the section 3 man pages for the db routines have been taken from ftp://ftp.terra.net/pub/sleepycat/db.1.86.tar.gz.] [the rpc man pages were taken from the 4.4bsd-lite cdrom.] here is a breakdown of what this distribution contains: section 1 = user commands (intro, plus a few other pages) section 2 = system calls section 3 = libc calls section 4 = devices (e.g., hd, sd) section 5 = file formats and configuration files (e.g., wtmp, /etc/passwd) section 6 = games (intro only) section 7 = overviews, conventions, macro packages, etc. section 8 = system administration (intro, plus a few other pages) this package contains no, or very few, section 1, 6, and 8 man pages because these should be distributed with the binaries they are written for. sometimes section 9 is used for man pages describing parts of the kernel. note that only section 2 is rather complete, but section 3 contains several hundred man pages. if you want to write some man pages, or suggest improvements to existing pages, please visit http://www.kernel.org/doc/man-pages/ . copyright information: these man pages are distributed under a variety of copyright licenses. although these licenses permit free distribution of the nroff sources contained in this package, commercial distribution may impose other requirements (e.g., acknowledgement of copyright or inclusion of the raw nroff sources with the commercial distribution). if you distribute these man pages commercially, it is your responsibility to figure out your obligations. (for many man pages, these obligations require you to distribute nroff sources with any pre-formatted man pages that you provide.) each file that contains nroff source for a man page also contains the author(s) name, email address, and copyright notice. .so man3/pthread_cleanup_push.3 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt .\" and copyright (c) 1993,1994 ian jackson .\" and copyright (c) 2006, 2014 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" you may distribute it under the terms of the gnu general .\" public license. it comes with no warranty. .\" %%%license_end .\" .th mkdir 2 2021-08-27 "linux" "linux programmer's manual" .sh name mkdir, mkdirat \- create a directory .sh synopsis .nf .b #include .\" .b #include .pp .bi "int mkdir(const char *" pathname ", mode_t " mode ); .pp .br "#include " "/* definition of at_* constants */" .b #include .pp .bi "int mkdirat(int " dirfd ", const char *" pathname ", mode_t " mode ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mkdirat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br mkdir () attempts to create a directory named .ir pathname . .pp the argument .i mode specifies the mode for the new directory (see .br inode (7)). it is modified by the process's .i umask in the usual way: in the absence of a default acl, the mode of the created directory is .ri ( mode " & \(ti" umask " & 0777)." whether other .i mode bits are honored for the created directory depends on the operating system. for linux, see notes below. .pp the newly created directory will be owned by the effective user id of the process. if the directory containing the file has the set-group-id bit set, or if the filesystem is mounted with bsd group semantics .ri ( "mount \-o bsdgroups" or, synonymously .ir "mount \-o grpid" ), the new directory will inherit the group ownership from its parent; otherwise it will be owned by the effective group id of the process. .pp if the parent directory has the set-group-id bit set, then so will the newly created directory. .\" .\" .ss mkdirat() the .br mkdirat () system call operates in exactly the same way as .br mkdir (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br mkdir () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br mkdir ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp see .br openat (2) for an explanation of the need for .br mkdirat (). .sh return value .br mkdir () and .br mkdirat () return zero on success. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces the parent directory does not allow write permission to the process, or one of the directories in .i pathname did not allow search permission. (see also .br path_resolution (7).) .tp .b ebadf .rb ( mkdirat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b edquot the user's quota of disk blocks or inodes on the filesystem has been exhausted. .tp .b eexist .i pathname already exists (not necessarily as a directory). this includes the case where .i pathname is a symbolic link, dangling or not. .tp .b efault .ir pathname " points outside your accessible address space." .tp .b einval the final component ("basename") of the new directory's .i pathname is invalid (e.g., it contains characters not permitted by the underlying filesystem). .tp .b eloop too many symbolic links were encountered in resolving .ir pathname . .tp .b emlink the number of links to the parent directory would exceed .br link_max . .tp .b enametoolong .ir pathname " was too long." .tp .b enoent a directory component in .i pathname does not exist or is a dangling symbolic link. .tp .b enomem insufficient kernel memory was available. .tp .b enospc the device containing .i pathname has no room for the new directory. .tp .b enospc the new directory cannot be created because the user's disk quota is exhausted. .tp .b enotdir a component used as a directory in .i pathname is not, in fact, a directory. .tp .b enotdir .rb ( mkdirat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b eperm the filesystem containing .i pathname does not support the creation of directories. .tp .b erofs .i pathname refers to a file on a read-only filesystem. .sh versions .br mkdirat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br mkdir (): svr4, bsd, posix.1-2001, posix.1-2008. .\" svr4 documents additional eio, emultihop .pp .br mkdirat (): posix.1-2008. .sh notes under linux, apart from the permission bits, the .b s_isvtx .i mode bit is also honored. .pp there are many infelicities in the protocol underlying nfs. some of these affect .br mkdir (). .ss glibc notes on older kernels where .br mkdirat () is unavailable, the glibc wrapper function falls back to the use of .br mkdir (). when .i pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir dirfd argument. .sh see also .br mkdir (1), .br chmod (2), .br chown (2), .br mknod (2), .br mount (2), .br rmdir (2), .br stat (2), .br umask (2), .br unlink (2), .br acl (5), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" updated with additions from mitchum dsouza .\" portions copyright 1993 mitchum dsouza .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified tue oct 22 00:22:35 edt 1996 by eric s. raymond .th gethostid 3 2021-03-22 "linux" "linux programmer's manual" .sh name gethostid, sethostid \- get or set the unique identifier of the current host .sh synopsis .nf .b #include .pp .b long gethostid(void); .bi "int sethostid(long " hostid ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br gethostid (): .nf since glibc 2.20: _default_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended up to and including glibc 2.19: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .pp .br sethostid (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description .br gethostid () and .br sethostid () respectively get or set a unique 32-bit identifier for the current machine. the 32-bit identifier was intended to be unique among all unix systems in existence. this normally resembles the internet address for the local machine, as returned by .br gethostbyname (3), and thus usually never needs to be set. .pp the .br sethostid () call is restricted to the superuser. .sh return value .br gethostid () returns the 32-bit identifier for the current host as set by .br sethostid (). .pp on success, .br sethostid () returns 0; on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .br sethostid () can fail with the following errors: .tp .b eacces the caller did not have permission to write to the file used to store the host id. .tp .b eperm the calling process's effective user or group id is not the same as its corresponding real id. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br gethostid () t} thread safety t{ mt-safe hostid env locale t} t{ .br sethostid () t} thread safety t{ mt-unsafe const:hostid t} .te .hy .ad .sp 1 .sh conforming to 4.2bsd; these functions were dropped in 4.4bsd. svr4 includes .br gethostid () but not .br sethostid (). .pp posix.1-2001 and posix.1-2008 specify .br gethostid () but not .br sethostid (). .sh notes in the glibc implementation, the .i hostid is stored in the file .ir /etc/hostid . (in glibc versions before 2.2, the file .i /var/adm/hostid was used.) .\" libc5 used /etc/hostid; libc4 didn't have these functions .pp in the glibc implementation, if .br gethostid () cannot open the file containing the host id, then it obtains the hostname using .br gethostname (2), passes that hostname to .br gethostbyname_r (3) in order to obtain the host's ipv4 address, and returns a value obtained by bit-twiddling the ipv4 address. (this value may not be unique.) .sh bugs it is impossible to ensure that the identifier is globally unique. .sh see also .br hostid (1), .br gethostbyname (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man3/cmsg.3 .so man3/rcmd.3 .so man3/inet.3 .\" copyright (c) 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th flockfile 3 2021-03-22 "" "linux programmer's manual" .sh name flockfile, ftrylockfile, funlockfile \- lock file for stdio .sh synopsis .nf .b #include .pp .bi "void flockfile(file *" filehandle ); .bi "int ftrylockfile(file *" filehandle ); .bi "void funlockfile(file *" filehandle ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .nf /* since glibc 2.24: */ _posix_c_source >= 199309l || /* glibc <= 2.23: */ _posix_c_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the stdio functions are thread-safe. this is achieved by assigning to each .i file object a lockcount and (if the lockcount is nonzero) an owning thread. for each library call, these functions wait until the .i file object is no longer locked by a different thread, then lock it, do the requested i/o, and unlock the object again. .pp (note: this locking has nothing to do with the file locking done by functions like .br flock (2) and .br lockf (3).) .pp all this is invisible to the c-programmer, but there may be two reasons to wish for more detailed control. on the one hand, maybe a series of i/o actions by one thread belongs together, and should not be interrupted by the i/o of some other thread. on the other hand, maybe the locking overhead should be avoided for greater efficiency. .pp to this end, a thread can explicitly lock the .i file object, then do its series of i/o actions, then unlock. this prevents other threads from coming in between. if the reason for doing this was to achieve greater efficiency, one does the i/o with the nonlocking versions of the stdio functions: with .br getc_unlocked (3) and .br putc_unlocked (3) instead of .br getc (3) and .br putc (3). .pp the .br flockfile () function waits for .i *filehandle to be no longer locked by a different thread, then makes the current thread owner of .ir *filehandle , and increments the lockcount. .pp the .br funlockfile () function decrements the lock count. .pp the .br ftrylockfile () function is a nonblocking version of .br flockfile (). it does nothing in case some other thread owns .ir *filehandle , and it obtains ownership and increments the lockcount otherwise. .sh return value the .br ftrylockfile () function returns zero for success (the lock was obtained), and nonzero for failure. .sh errors none. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br flockfile (), .br ftrylockfile (), .br funlockfile () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp these functions are available when .b _posix_thread_safe_functions is defined. .sh see also .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/y0.3 .so man2/unimplemented.2 .\" copyright (c) 1995 andries brouwer (aeb@cwi.nl) .\" and copyright 2008, 2015 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" written 11 june 1995 by andries brouwer .\" modified 22 july 1995 by michael chastain : .\" derived from 'readdir.2'. .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .\" .th getdents 2 2021-03-22 "linux" "linux programmer's manual" .sh name getdents, getdents64 \- get directory entries .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(sys_getdents, unsigned int " fd \ ", struct linux_dirent *" dirp , .bi " unsigned int " count ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .br "#include " .pp .bi "ssize_t getdents64(int " fd ", void *" dirp ", size_t " count ); .fi .pp .ir note : glibc provides no wrapper for .br getdents (), necessitating the use of .br syscall (2). .pp .ir note : there is no definition of .i struct linux_dirent in glibc; see notes. .sh description these are not the interfaces you are interested in. look at .br readdir (3) for the posix-conforming c library interface. this page documents the bare kernel system call interfaces. .ss getdents() the system call .br getdents () reads several .i linux_dirent structures from the directory referred to by the open file descriptor .i fd into the buffer pointed to by .ir dirp . the argument .i count specifies the size of that buffer. .pp the .i linux_dirent structure is declared as follows: .pp .in +4n .ex struct linux_dirent { unsigned long d_ino; /* inode number */ unsigned long d_off; /* offset to next \filinux_dirent\fp */ unsigned short d_reclen; /* length of this \filinux_dirent\fp */ char d_name[]; /* filename (null\-terminated) */ /* length is actually (d_reclen \- 2 \- offsetof(struct linux_dirent, d_name)) */ /* char pad; // zero padding byte char d_type; // file type (only since linux // 2.6.4); offset is (d_reclen \- 1) */ } .ee .in .pp .i d_ino is an inode number. .i d_off is the distance from the start of the directory to the start of the next .ir linux_dirent . .i d_reclen is the size of this entire .ir linux_dirent . .i d_name is a null-terminated filename. .pp .i d_type is a byte at the end of the structure that indicates the file type. it contains one of the following values (defined in .ir ): .tp 12 .b dt_blk this is a block device. .tp .b dt_chr this is a character device. .tp .b dt_dir this is a directory. .tp .b dt_fifo this is a named pipe (fifo). .tp .b dt_lnk this is a symbolic link. .tp .b dt_reg this is a regular file. .tp .b dt_sock this is a unix domain socket. .tp .b dt_unknown the file type is unknown. .pp the .i d_type field is implemented since linux 2.6.4. it occupies a space that was previously a zero-filled padding byte in the .ir linux_dirent structure. thus, on kernels up to and including 2.6.3, attempting to access this field always provides the value 0 .rb ( dt_unknown ). .pp currently, .\" kernel 2.6.27 .\" the same sentence is in readdir.2 only some filesystems (among them: btrfs, ext2, ext3, and ext4) have full support for returning the file type in .ir d_type . all applications must properly handle a return of .br dt_unknown . .ss getdents64() the original linux .br getdents () system call did not handle large filesystems and large file offsets. consequently, linux 2.4 added .br getdents64 (), with wider types for the .i d_ino and .i d_off fields. in addition, .br getdents64 () supports an explicit .i d_type field. .pp the .br getdents64 () system call is like .br getdents (), except that its second argument is a pointer to a buffer containing structures of the following type: .pp .in +4n .ex struct linux_dirent64 { ino64_t d_ino; /* 64\-bit inode number */ off64_t d_off; /* 64\-bit offset to next structure */ unsigned short d_reclen; /* size of this dirent */ unsigned char d_type; /* file type */ char d_name[]; /* filename (null\-terminated) */ }; .ee .in .sh return value on success, the number of bytes read is returned. on end of directory, 0 is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf invalid file descriptor .ir fd . .tp .b efault argument points outside the calling process's address space. .tp .b einval result buffer is too small. .tp .b enoent no such directory. .tp .b enotdir file descriptor does not refer to a directory. .sh conforming to svr4. .\" svr4 documents additional enolink, eio error conditions. .sh notes library support for .br getdents64 () was added in glibc 2.30; glibc does not provide a wrapper for .br getdents (); call .br getdents () (or .br getdents64 () on earlier glibc versions) using .br syscall (2). in that case you will need to define the .i linux_dirent or .i linux_dirent64 structure yourself. .pp probably, you want to use .br readdir (3) instead of these system calls. .pp these calls supersede .br readdir (2). .sh examples .\" fixme the example program needs to be revised, since it uses the older .\" getdents() system call and the structure with smaller field widths. the program below demonstrates the use of .br getdents (). the following output shows an example of what we see when running this program on an ext2 directory: .pp .in +4n .ex .rb "$" " ./a.out /testfs/" -\-\-\-\-\-\-\-\-\-\-\-\-\-\- nread=120 \-\-\-\-\-\-\-\-\-\-\-\-\-\-\- inode# file type d_reclen d_off d_name 2 directory 16 12 . 2 directory 16 24 .. 11 directory 24 44 lost+found 12 regular 16 56 a 228929 directory 16 68 sub 16353 directory 16 80 sub2 130817 directory 16 4096 sub3 .ee .in .ss program source \& .ex #define _gnu_source #include /* defines dt_* constants */ #include #include #include #include #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) struct linux_dirent { unsigned long d_ino; off_t d_off; unsigned short d_reclen; char d_name[]; }; #define buf_size 1024 int main(int argc, char *argv[]) { int fd; long nread; char buf[buf_size]; struct linux_dirent *d; char d_type; fd = open(argc > 1 ? argv[1] : ".", o_rdonly | o_directory); if (fd == \-1) handle_error("open"); for (;;) { nread = syscall(sys_getdents, fd, buf, buf_size); if (nread == \-1) handle_error("getdents"); if (nread == 0) break; printf("\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- nread=%d \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\en", nread); printf("inode# file type d_reclen d_off d_name\en"); for (long bpos = 0; bpos < nread;) { d = (struct linux_dirent *) (buf + bpos); printf("%8ld ", d\->d_ino); d_type = *(buf + bpos + d\->d_reclen \- 1); printf("%\-10s ", (d_type == dt_reg) ? "regular" : (d_type == dt_dir) ? "directory" : (d_type == dt_fifo) ? "fifo" : (d_type == dt_sock) ? "socket" : (d_type == dt_lnk) ? "symlink" : (d_type == dt_blk) ? "block dev" : (d_type == dt_chr) ? "char dev" : "???"); printf("%4d %10jd %s\en", d\->d_reclen, (intmax_t) d\->d_off, d\->d_name); bpos += d\->d_reclen; } } exit(exit_success); } .ee .sh see also .br readdir (2), .br readdir (3), .br inode (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/log2.3 .so man3/xdr.3 .so man3/mq_unlink.3 .\" because mq_unlink(3) is layered on a system call of the same name .so man3/acos.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th atanh 3 2021-03-22 "" "linux programmer's manual" .sh name atanh, atanhf, atanhl \- inverse hyperbolic tangent function .sh synopsis .nf .b #include .pp .bi "double atanh(double " x ); .bi "float atanhf(float " x ); .bi "long double atanhl(long double " x ); .pp .fi link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br atanh (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br atanhf (), .br atanhl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions calculate the inverse hyperbolic tangent of .ir x ; that is the value whose hyperbolic tangent is .ir x . .sh return value on success, these functions return the inverse hyperbolic tangent of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is +1 or \-1, a pole error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with the mathematically correct sign. .pp if the absolute value of .i x is greater than 1, a domain error occurs, and a nan is returned. .\" .\" posix.1-2001 documents an optional range error for subnormal x; .\" glibc 2.8 does not do this. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp less than \-1 or greater than +1 .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp pole error: \fix\fp is +1 or \-1 .i errno is set to .br erange (but see bugs). a divide-by-zero floating-point exception .rb ( fe_divbyzero ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br atanh (), .br atanhf (), .br atanhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh bugs in glibc 2.9 and earlier, .\" bug: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759 .\" this can be seen in sysdeps/ieee754/k_standard.c when a pole error occurs, .i errno is set to .br edom instead of the posix-mandated .br erange . since version 2.10, glibc does the right thing. .sh see also .br acosh (3), .br asinh (3), .br catanh (3), .br cosh (3), .br sinh (3), .br tanh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/log10.3 .\" copyright 1993 giorgio ciucci (giorgio@crcc.it) .\" and copyright (c) 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified tue oct 22 17:54:56 1996 by eric s. raymond .\" modified 1 jan 2002, martin schulze .\" modified 4 jan 2002, michael kerrisk .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" added notes on /proc files .\" rewrote bugs note about semget()'s failure to initialize .\" semaphore values .\" .th semget 2 2021-03-22 "linux" "linux programmer's manual" .sh name semget \- get a system v semaphore set identifier .sh synopsis .nf .b #include .fi .pp .bi "int semget(key_t " key , .bi "int " nsems , .bi "int " semflg ); .sh description the .br semget () system call returns the system\ v semaphore set identifier associated with the argument .ir key . it may be used either to obtain the identifier of a previously created semaphore set (when .i semflg is zero and .i key does not have the value .br ipc_private ), or to create a new set. .pp a new set of .i nsems semaphores is created if .i key has the value .b ipc_private or if no existing semaphore set is associated with .i key and .b ipc_creat is specified in .ir semflg . .pp if .i semflg specifies both .b ipc_creat and .b ipc_excl and a semaphore set already exists for .ir key , then .br semget () fails with .i errno set to .br eexist . (this is analogous to the effect of the combination .b o_creat | o_excl for .br open (2).) .pp upon creation, the least significant 9 bits of the argument .i semflg define the permissions (for owner, group, and others) for the semaphore set. these bits have the same format, and the same meaning, as the .i mode argument of .br open (2) (though the execute permissions are not meaningful for semaphores, and write permissions mean permission to alter semaphore values). .pp when creating a new semaphore set, .br semget () initializes the set's associated data structure, .i semid_ds (see .br semctl (2)), as follows: .ip \(bu 2 .i sem_perm.cuid and .i sem_perm.uid are set to the effective user id of the calling process. .ip \(bu .i sem_perm.cgid and .i sem_perm.gid are set to the effective group id of the calling process. .ip \(bu the least significant 9 bits of .i sem_perm.mode are set to the least significant 9 bits of .ir semflg . .ip \(bu .i sem_nsems is set to the value of .ir nsems . .ip \(bu .i sem_otime is set to 0. .ip \(bu .i sem_ctime is set to the current time. .pp the argument .i nsems can be 0 (a don't care) when a semaphore set is not being created. otherwise, .i nsems must be greater than 0 and less than or equal to the maximum number of semaphores per semaphore set .rb ( semmsl ). .pp if the semaphore set already exists, the permissions are verified. .\" and a check is made to see if it is marked for destruction. .sh return value on success, .br semget () returns the semaphore set identifier (a nonnegative integer). on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces a semaphore set exists for .ir key , but the calling process does not have permission to access the set, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b eexist .b ipc_creat and .br ipc_excl were specified in .ir semflg , but a semaphore set already exists for .ir key . .\" .tp .\" .b eidrm .\" the semaphore set is marked to be deleted. .tp .b einval .i nsems is less than 0 or greater than the limit on the number of semaphores per semaphore set .rb ( semmsl ). .tp .b einval a semaphore set corresponding to .i key already exists, but .i nsems is larger than the number of semaphores in that set. .tp .b enoent no semaphore set exists for .i key and .i semflg did not specify .br ipc_creat . .tp .b enomem a semaphore set has to be created but the system does not have enough memory for the new data structure. .tp .b enospc a semaphore set has to be created but the system limit for the maximum number of semaphore sets .rb ( semmni ), or the system wide maximum number of semaphores .rb ( semmns ), would be exceeded. .sh conforming to svr4, posix.1-2001. .\" svr4 documents additional error conditions efbig, e2big, eagain, .\" erange, efault. .sh notes .b ipc_private isn't a flag field but a .i key_t type. if this special value is used for .ir key , the system call ignores all but the least significant 9 bits of .i semflg and creates a new semaphore set (on success). .\" .ss semaphore initialization the values of the semaphores in a newly created set are indeterminate. (posix.1-2001 and posix.1-2008 are explicit on this point, although posix.1-2008 notes that a future version of the standard may require an implementation to initialize the semaphores to 0.) although linux, like many other implementations, initializes the semaphore values to 0, a portable application cannot rely on this: it should explicitly initialize the semaphores to the desired values. .\" in truth, every one of the many implementations that i've tested sets .\" the values to zero, but i suppose there is/was some obscure .\" implementation out there that does not. .pp initialization can be done using .br semctl (2) .b setval or .b setall operation. where multiple peers do not know who will be the first to initialize the set, checking for a nonzero .i sem_otime in the associated data structure retrieved by a .br semctl (2) .b ipc_stat operation can be used to avoid races. .\" .ss semaphore limits the following limits on semaphore set resources affect the .br semget () call: .tp .b semmni system-wide limit on the number of semaphore sets. on linux systems before version 3.19, the default value for this limit was 128. since linux 3.19, .\" commit e843e7d2c88b7db107a86bd2c7145dc715c058f4 the default value is 32,000. on linux, this limit can be read and modified via the fourth field of .ir /proc/sys/kernel/sem . .\" this /proc file is not available in linux 2.2 and earlier -- mtk .tp .b semmsl maximum number of semaphores per semaphore id. on linux systems before version 3.19, the default value for this limit was 250. since linux 3.19, .\" commit e843e7d2c88b7db107a86bd2c7145dc715c058f4 the default value is 32,000. on linux, this limit can be read and modified via the first field of .ir /proc/sys/kernel/sem . .tp .b semmns system-wide limit on the number of semaphores: policy dependent (on linux, this limit can be read and modified via the second field of .ir /proc/sys/kernel/sem ). note that the number of semaphores system-wide is also limited by the product of .b semmsl and .br semmni . .sh bugs the name choice .b ipc_private was perhaps unfortunate, .b ipc_new would more clearly show its function. .sh examples the program shown below uses .br semget () to create a new semaphore set or retrieve the id of an existing set. it generates the .i key for .br semget () using .br ftok (3). the first two command-line arguments are used as the .i pathname and .i proj_id arguments for .br ftok (3). the third command-line argument is an integer that specifies the .i nsems argument for .br semget (). command-line options can be used to specify the .br ipc_creat .ri ( \-c ) and .br ipc_excl .ri ( \-x ) flags for the call to .br semget (). the usage of this program is demonstrated below. .pp we first create two files that will be used to generate keys using .br ftok (3), create two semaphore sets using those files, and then list the sets using .br ipcs (1): .pp .in +4n .ex $ \fbtouch mykey mykey2\fp $ \fb./t_semget \-c mykey p 1\fp id = 9 $ \fb./t_semget \-c mykey2 p 2\fp id = 10 $ \fbipcs \-s\fp \-\-\-\-\-\- semaphore arrays \-\-\-\-\-\-\-\- key semid owner perms nsems 0x7004136d 9 mtk 600 1 0x70041368 10 mtk 600 2 .ee .in .pp next, we demonstrate that when .br semctl (2) is given the same .i key (as generated by the same arguments to .br ftok (3)), it returns the id of the already existing semaphore set: .pp .in +4n .ex $ \fb./t_semget \-c mykey p 1\fp id = 9 .ee .in .pp finally, we demonstrate the kind of collision that can occur when .br ftok (3) is given different .i pathname arguments that have the same inode number: .pp .in +4n .ex $ \fbln mykey link\fp $ \fbls \-i1 link mykey\fp 2233197 link 2233197 mykey $ \fb./t_semget link p 1\fp # generates same key as \(aqmykey\(aq id = 9 .ee .in .ss program source \& .ex /* t_semget.c licensed under gnu general public license v2 or later. */ #include #include #include #include #include #include #include static void usage(const char *pname) { fprintf(stderr, "usage: %s [\-cx] pathname proj\-id num\-sems\en", pname); fprintf(stderr, " \-c use ipc_creat flag\en"); fprintf(stderr, " \-x use ipc_excl flag\en"); exit(exit_failure); } int main(int argc, char *argv[]) { int semid, nsems, flags, opt; key_t key; flags = 0; while ((opt = getopt(argc, argv, "cx")) != \-1) { switch (opt) { case \(aqc\(aq: flags |= ipc_creat; break; case \(aqx\(aq: flags |= ipc_excl; break; default: usage(argv[0]); } } if (argc != optind + 3) usage(argv[0]); key = ftok(argv[optind], argv[optind + 1][0]); if (key == \-1) { perror("ftok"); exit(exit_failure); } nsems = atoi(argv[optind + 2]); semid = semget(key, nsems, flags | 0600); if (semid == \-1) { perror("semget"); exit(exit_failure); } printf("id = %d\en", semid); exit(exit_success); } .ee .sh see also .br semctl (2), .br semop (2), .br ftok (3), .br capabilities (7), .br sem_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getnetent.3 .so man3/stailq.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on glibc infopages .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" modified 2004-11-15, fixed error noted by fabian kreutz .\" .\" .th tgamma 3 2021-03-22 "gnu" "linux programmer's manual" .sh name tgamma, tgammaf, tgammal \- true gamma function .sh synopsis .nf .b #include .pp .bi "double tgamma(double " x ); .bi "float tgammaf(float " x ); .bi "long double tgammal(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br tgamma (), .br tgammaf (), .br tgammal (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions calculate the gamma function of .ir x . .pp the gamma function is defined by .pp .rs gamma(x) = integral from 0 to infinity of t^(x\-1) e^\-t dt .re .pp it is defined for every real number except for nonpositive integers. for nonnegative integral .i m one has .pp .rs gamma(m+1) = m! .re .pp and, more generally, for all .ir x : .pp .rs gamma(x+1) = x * gamma(x) .re .pp furthermore, the following is valid for all values of .i x outside the poles: .pp .rs gamma(x) * gamma(1 \- x) = pi / sin(pi * x) .re .sh return value on success, these functions return gamma(x). .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity, positive infinity is returned. .pp if .i x is a negative integer, or is negative infinity, a domain error occurs, and a nan is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with the correct mathematical sign. .pp if the result underflows, a range error occurs, and the functions return 0, with the correct mathematical sign. .pp if .i x is \-0 or +0, a pole error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with the same sign as the 0. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is a negative integer, or negative infinity .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised (but see bugs). .tp pole error: \fix\fp is +0 or \-0 .i errno is set to .br erange . a divide-by-zero floating-point exception .rb ( fe_divbyzero ) is raised. .tp range error: result overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .pp glibc also gives the following error which is not specified in c99 or posix.1-2001. .tp range error: result underflow .\" e.g., tgamma(-172.5) on glibc 2.8/x86-32 .\" .i errno .\" is set to .\" .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised, and .i errno is set to .br erange . .\" glibc (as at 2.8) also supports an inexact .\" exception for various cases. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tgamma (), .br tgammaf (), .br tgammal () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes this function had to be called "true gamma function" since there is already a function .br gamma (3) that returns something else (see .br gamma (3) for details). .sh bugs before version 2.18, the glibc implementation of these functions did not set .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6809 .i errno to .b edom when .i x is negative infinity. .pp before glibc 2.19, .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6810 the glibc implementation of these functions did not set .i errno to .b erange on an underflow range error. .pp .\" in glibc versions 2.3.3 and earlier, an argument of +0 or \-0 incorrectly produced a domain error .ri ( errno set to .b edom and an .b fe_invalid exception raised), rather than a pole error. .sh see also .br gamma (3), .br lgamma (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .so man3/csinh.3 .\" copyright 2003 abhijit menon-sen .\" and copyright (c) 2008 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th gettid 2 2021-03-22 "linux" "linux programmer's manual" .sh name gettid \- get thread identification .sh synopsis .nf .b #define _gnu_source .b #include .pp .b pid_t gettid(void); .fi .sh description .br gettid () returns the caller's thread id (tid). in a single-threaded process, the thread id is equal to the process id (pid, as returned by .br getpid (2)). in a multithreaded process, all threads have the same pid, but each one has a unique tid. for further details, see the discussion of .br clone_thread in .br clone (2). .sh return value on success, returns the thread id of the calling thread. .sh errors this call is always successful. .sh versions the .br gettid () system call first appeared on linux in kernel 2.4.11. library support was added in glibc 2.30. (earlier glibc versions did not provide a wrapper for this system call, necessitating the use of .br syscall (2).) .sh conforming to .br gettid () is linux-specific and should not be used in programs that are intended to be portable. .sh notes the thread id returned by this call is not the same thing as a posix thread id (i.e., the opaque value returned by .br pthread_self (3)). .pp in a new thread group created by a .br clone (2) call that does not specify the .br clone_thread flag (or, equivalently, a new process created by .br fork (2)), the new process is a thread group leader, and its thread group id (the value returned by .br getpid (2)) is the same as its thread id (the value returned by .br gettid ()). .sh see also .br capget (2), .br clone (2), .br fcntl (2), .br fork (2), .br get_robust_list (2), .br getpid (2), .\" .br kcmp (2), .br ioprio_set (2), .\" .br move_pages (2), .\" .br migrate_pages (2), .br perf_event_open (2), .\" .br process_vm_readv (2), .\" .br ptrace (2), .br sched_setaffinity (2), .br sched_setparam (2), .br sched_setscheduler (2), .br tgkill (2), .br timer_create (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt .\" (michael@moria.de) .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 14:23:14 1993 by rik faith (faith@cs.unc.edu) .\" modified sun oct 18 17:31:43 1998 by andries brouwer (aeb@cwi.nl) .\" 2008-06-23, mtk, minor rewrites, added some details .\" .th ftime 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ftime \- return date and time .sh synopsis .nf .b "#include " .pp .bi "int ftime(struct timeb *" tp ); .fi .sh description .br note : this function is no longer provided by the gnu c library. use .br clock_gettime (2) instead. .pp this function returns the current time as seconds and milliseconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). the time is returned in .ir tp , which is declared as follows: .pp .in +4n .ex struct timeb { time_t time; unsigned short millitm; short timezone; short dstflag; }; .ee .in .pp here \fitime\fp is the number of seconds since the epoch, and \fimillitm\fp is the number of milliseconds since \fitime\fp seconds since the epoch. the \fitimezone\fp field is the local timezone measured in minutes of time west of greenwich (with a negative value indicating minutes east of greenwich). the \fidstflag\fp field is a flag that, if nonzero, indicates that daylight saving time applies locally during the appropriate part of the year. .pp posix.1-2001 says that the contents of the \fitimezone\fp and \fidstflag\fp fields are unspecified; avoid relying on them. .sh return value this function always returns 0. (posix.1-2001 specifies, and some systems document, a \-1 error return.) .sh versions starting with glibc 2.33, the .br ftime () function and the .i header have been removed. to support old binaries, glibc continues to provide a compatibility symbol for applications linked against glibc 2.32 and earlier. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ftime () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.2bsd, posix.1-2001. posix.1-2008 removes the specification of .br ftime (). .pp this function is obsolete. don't use it. if the time in seconds suffices, .br time (2) can be used; .br gettimeofday (2) gives microseconds; .br clock_gettime (2) gives nanoseconds but is not as widely available. .sh bugs early glibc2 is buggy and returns 0 in the .i millitm field; glibc 2.1.1 is correct again. .\" .sh history .\" the .\" .br ftime () .\" function appeared in 4.2bsd. .sh see also .br gettimeofday (2), .br time (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1999 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" rewritten old page, 990824, aeb@cwi.nl .\" 2004-12-14, mtk, added discussion of resolved_path == null .\" .th realpath 3 2021-03-22 "" "linux programmer's manual" .sh name realpath \- return the canonicalized absolute pathname .sh synopsis .nf .b #include .b #include .pp .bi "char *realpath(const char *restrict " path , .bi " char *restrict " resolved_path ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br realpath (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source .fi .sh description .br realpath () expands all symbolic links and resolves references to .ir "/./" ", " "/../" and extra \(aq/\(aq characters in the null-terminated string named by .i path to produce a canonicalized absolute pathname. the resulting pathname is stored as a null-terminated string, up to a maximum of .b path_max bytes, in the buffer pointed to by .ir resolved_path . the resulting path will have no symbolic link, .i "/./" or .i "/../" components. .pp if .i resolved_path is specified as null, then .br realpath () uses .br malloc (3) to allocate a buffer of up to .b path_max bytes to hold the resolved pathname, and returns a pointer to this buffer. the caller should deallocate this buffer using .br free (3). .\" even if we use resolved_path == null, then realpath() will still .\" return enametoolong if the resolved pathname would exceed path_max .\" bytes -- mtk, dec 04 .\" .sh history .\" the .\" .br realpath () .\" function first appeared in 4.4bsd, contributed by jan-simon pendry. .sh return value if there is no error, .br realpath () returns a pointer to the .ir resolved_path . .pp otherwise, it returns null, the contents of the array .i resolved_path are undefined, and .i errno is set to indicate the error. .sh errors .tp .b eacces read or search permission was denied for a component of the path prefix. .tp .b einval .i path is null. .\" (in libc5 this would just cause a segfault.) (in glibc versions before 2.3, this error is also returned if .ir resolved_path is null.) .tp .b eio an i/o error occurred while reading from the filesystem. .tp .b eloop too many symbolic links were encountered in translating the pathname. .tp .b enametoolong a component of a pathname exceeded .b name_max characters, or an entire pathname exceeded .b path_max characters. .tp .b enoent the named file does not exist. .tp .b enomem out of memory. .tp .b enotdir a component of the path prefix is not a directory. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br realpath () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.4bsd, posix.1-2001. .pp posix.1-2001 says that the behavior if .i resolved_path is null is implementation-defined. posix.1-2008 specifies the behavior described in this page. .sh notes in 4.4bsd and solaris, the limit on the pathname length is .b maxpathlen (found in \fi\fp). susv2 prescribes .b path_max and .br name_max , as found in \fi\fp or provided by the .br pathconf (3) function. a typical source fragment would be .pp .in +4n .ex #ifdef path_max path_max = path_max; #else path_max = pathconf(path, _pc_path_max); if (path_max <= 0) path_max = 4096; #endif .ee .in .pp (but see the bugs section.) .\".pp .\" 2012-05-05, according to casper dik, the statement about .\" solaris was not true at least as far back as 1997, and .\" may never have been true. .\" .\" the 4.4bsd, linux and susv2 versions always return an absolute .\" pathname. .\" solaris may return a relative pathname when the .\" .i path .\" argument is relative. .\" the prototype of .\" .br realpath () .\" is given in \fi\fp in libc4 and libc5, .\" but in \fi\fp everywhere else. .ss gnu extensions if the call fails with either .br eacces or .br enoent and .i resolved_path is not null, then the prefix of .i path that is not readable or does not exist is returned in .ir resolved_path . .sh bugs the posix.1-2001 standard version of this function is broken by design, since it is impossible to determine a suitable size for the output buffer, .ir resolved_path . according to posix.1-2001 a buffer of size .b path_max suffices, but .b path_max need not be a defined constant, and may have to be obtained using .br pathconf (3). and asking .br pathconf (3) does not really help, since, on the one hand posix warns that the result of .br pathconf (3) may be huge and unsuitable for mallocing memory, and on the other hand .br pathconf (3) may return \-1 to signify that .b path_max is not bounded. the .i "resolved_path\ ==\ null" feature, not standardized in posix.1-2001, but standardized in posix.1-2008, allows this design problem to be avoided. .\" .lp .\" the libc4 and libc5 implementation contained a buffer overflow .\" (fixed in libc-5.4.13). .\" thus, set-user-id programs like .\" .br mount (8) .\" needed a private version. .sh see also .br realpath (1), .br readlink (2), .br canonicalize_file_name (3), .br getcwd (3), .br pathconf (3), .br sysconf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/printf.3 .so man7/iso_8859-13.7 .so man3/getgrnam.3 .\" copyright 1993 giorgio ciucci .\" and copyright 2015 bill pemberton .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified tue oct 22 16:40:11 1996 by eric s. raymond .\" modified mon jul 10 21:09:59 2000 by aeb .\" modified 1 jun 2002, michael kerrisk .\" language clean-ups. .\" enhanced and corrected information on msg_qbytes, msgmnb and msgmax .\" added note on restart behavior of msgsnd() and msgrcv() .\" formatting clean-ups (argument and field names marked as .i .\" instead of .b) .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" added notes on /proc files .\" .th msgop 2 2021-03-22 "linux" "linux programmer's manual" .sh name msgrcv, msgsnd \- system v message queue operations .sh synopsis .nf .b #include .pp .bi "int msgsnd(int " msqid ", const void *" msgp ", size_t " msgsz \ ", int " msgflg ); .pp .bi "ssize_t msgrcv(int " msqid ", void *" msgp ", size_t " msgsz \ ", long " msgtyp , .bi " int " msgflg ); .fi .sh description the .br msgsnd () and .br msgrcv () system calls are used to send messages to, and receive messages from, a system\ v message queue. the calling process must have write permission on the message queue in order to send a message, and read permission to receive a message. .pp the .i msgp argument is a pointer to a caller-defined structure of the following general form: .pp .in +4n .ex struct msgbuf { long mtype; /* message type, must be > 0 */ char mtext[1]; /* message data */ }; .ee .in .pp the .i mtext field is an array (or other structure) whose size is specified by .ir msgsz , a nonnegative integer value. messages of zero length (i.e., no .i mtext field) are permitted. the .i mtype field must have a strictly positive integer value. this value can be used by the receiving process for message selection (see the description of .br msgrcv () below). .ss msgsnd() the .br msgsnd () system call appends a copy of the message pointed to by .i msgp to the message queue whose identifier is specified by .ir msqid . .pp if sufficient space is available in the queue, .br msgsnd () succeeds immediately. the queue capacity is governed by the .i msg_qbytes field in the associated data structure for the message queue. during queue creation this field is initialized to .b msgmnb bytes, but this limit can be modified using .br msgctl (2). a message queue is considered to be full if either of the following conditions is true: .ip \(bu 2 adding a new message to the queue would cause the total number of bytes in the queue to exceed the queue's maximum size (the .i msg_qbytes field). .ip \(bu adding another message to the queue would cause the total number of messages in the queue to exceed the queue's maximum size (the .i msg_qbytes field). this check is necessary to prevent an unlimited number of zero-length messages being placed on the queue. although such messages contain no data, they nevertheless consume (locked) kernel memory. .pp if insufficient space is available in the queue, then the default behavior of .br msgsnd () is to block until space becomes available. if .b ipc_nowait is specified in .ir msgflg , then the call instead fails with the error .br eagain . .pp a blocked .br msgsnd () call may also fail if: .ip \(bu 2 the queue is removed, in which case the system call fails with .i errno set to .br eidrm ; or .ip \(bu a signal is caught, in which case the system call fails with .i errno set to .br eintr ; see .br signal (7). .rb ( msgsnd () is never automatically restarted after being interrupted by a signal handler, regardless of the setting of the .b sa_restart flag when establishing a signal handler.) .pp upon successful completion the message queue data structure is updated as follows: .ip \(bu 2 .i msg_lspid is set to the process id of the calling process. .ip \(bu .i msg_qnum is incremented by 1. .ip \(bu .i msg_stime is set to the current time. .ss msgrcv() the .br msgrcv () system call removes a message from the queue specified by .i msqid and places it in the buffer pointed to by .ir msgp . .pp the argument .i msgsz specifies the maximum size in bytes for the member .i mtext of the structure pointed to by the .i msgp argument. if the message text has length greater than .ir msgsz , then the behavior depends on whether .b msg_noerror is specified in .ir msgflg . if .b msg_noerror is specified, then the message text will be truncated (and the truncated part will be lost); if .b msg_noerror is not specified, then the message isn't removed from the queue and the system call fails returning \-1 with .i errno set to .br e2big . .pp unless .b msg_copy is specified in .ir msgflg (see below), the .i msgtyp argument specifies the type of message requested, as follows: .ip \(bu 2 if .i msgtyp is 0, then the first message in the queue is read. .ip \(bu if .i msgtyp is greater than 0, then the first message in the queue of type .i msgtyp is read, unless .b msg_except was specified in .ir msgflg , in which case the first message in the queue of type not equal to .i msgtyp will be read. .ip \(bu if .i msgtyp is less than 0, then the first message in the queue with the lowest type less than or equal to the absolute value of .i msgtyp will be read. .pp the .i msgflg argument is a bit mask constructed by oring together zero or more of the following flags: .tp .b ipc_nowait return immediately if no message of the requested type is in the queue. the system call fails with .i errno set to .br enomsg . .tp .br msg_copy " (since linux 3.8)" .\" commit 4a674f34ba04a002244edaf891b5da7fc1473ae8 nondestructively fetch a copy of the message at the ordinal position in the queue specified by .i msgtyp (messages are considered to be numbered starting at 0). .ip this flag must be specified in conjunction with .br ipc_nowait , with the result that, if there is no message available at the given position, the call fails immediately with the error .br enomsg . because they alter the meaning of .i msgtyp in orthogonal ways, .br msg_copy and .br msg_except may not both be specified in .ir msgflg . .ip the .br msg_copy flag was added for the implementation of the kernel checkpoint-restore facility and is available only if the kernel was built with the .b config_checkpoint_restore option. .tp .b msg_except used with .i msgtyp greater than 0 to read the first message in the queue with message type that differs from .ir msgtyp . .tp .b msg_noerror to truncate the message text if longer than .i msgsz bytes. .pp if no message of the requested type is available and .b ipc_nowait isn't specified in .ir msgflg , the calling process is blocked until one of the following conditions occurs: .ip \(bu 2 a message of the desired type is placed in the queue. .ip \(bu the message queue is removed from the system. in this case, the system call fails with .i errno set to .br eidrm . .ip \(bu the calling process catches a signal. in this case, the system call fails with .i errno set to .br eintr . .rb ( msgrcv () is never automatically restarted after being interrupted by a signal handler, regardless of the setting of the .b sa_restart flag when establishing a signal handler.) .pp upon successful completion the message queue data structure is updated as follows: .ip .i msg_lrpid is set to the process id of the calling process. .ip .i msg_qnum is decremented by 1. .ip .i msg_rtime is set to the current time. .sh return value on success, .br msgsnd () returns 0 and .br msgrcv () returns the number of bytes actually copied into the .i mtext array. on failure, both functions return \-1, and set .i errno to indicate the error. .sh errors .br msgsnd () can fail with the following errors: .tp .b eacces the calling process does not have write permission on the message queue, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b eagain the message can't be sent due to the .i msg_qbytes limit for the queue and .b ipc_nowait was specified in .ir msgflg . .tp .b efault the address pointed to by .i msgp isn't accessible. .tp .b eidrm the message queue was removed. .tp .b eintr sleeping on a full message queue condition, the process caught a signal. .tp .b einval invalid .i msqid value, or nonpositive .i mtype value, or invalid .i msgsz value (less than 0 or greater than the system value .br msgmax ). .tp .b enomem the system does not have enough memory to make a copy of the message pointed to by .ir msgp . .pp .br msgrcv () can fail with the following errors: .tp .b e2big the message text length is greater than .i msgsz and .b msg_noerror isn't specified in .ir msgflg . .tp .b eacces the calling process does not have read permission on the message queue, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b efault the address pointed to by .i msgp isn't accessible. .tp .b eidrm while the process was sleeping to receive a message, the message queue was removed. .tp .b eintr while the process was sleeping to receive a message, the process caught a signal; see .br signal (7). .tp .b einval .i msqid was invalid, or .i msgsz was less than 0. .tp .br einval " (since linux 3.14)" .i msgflg specified .br msg_copy , but not .br ipc_nowait . .tp .br einval " (since linux 3.14)" .i msgflg specified both .br msg_copy and .br msg_except . .tp .b enomsg .b ipc_nowait was specified in .i msgflg and no message of the requested type existed on the message queue. .tp .b enomsg .b ipc_nowait and .b msg_copy were specified in .i msgflg and the queue contains less than .i msgtyp messages. .tp .br enosys " (since linux 3.8)" both .b msg_copy and .b ipc_nowait were specified in .ir msgflg , and this kernel was configured without .br config_checkpoint_restore . .sh conforming to posix.1-2001, posix.1-2008, svr4. .pp the .b msg_except and .b msg_copy flags are linux-specific; their definitions can be obtained by defining the .b _gnu_source .\" msg_copy since glibc 2.18 feature test macro. .sh notes the .i msgp argument is declared as \fistruct msgbuf\ *\fp in glibc 2.0 and 2.1. it is declared as \fivoid\ *\fp in glibc 2.2 and later, as required by susv2 and susv3. .pp the following limits on message queue resources affect the .br msgsnd () call: .tp .b msgmax maximum size of a message text, in bytes (default value: 8192 bytes). on linux, this limit can be read and modified via .ir /proc/sys/kernel/msgmax . .tp .b msgmnb maximum number of bytes that can be held in a message queue (default value: 16384 bytes). on linux, this limit can be read and modified via .ir /proc/sys/kernel/msgmnb . a privileged process (linux: a process with the .b cap_sys_resource capability) can increase the size of a message queue beyond .b msgmnb using the .br msgctl (2) .b ipc_set operation. .pp the implementation has no intrinsic system-wide limits on the number of message headers .rb ( msgtql ) and the number of bytes in the message pool .rb ( msgpool ). .sh bugs in linux 3.13 and earlier, if .br msgrcv () was called with the .br msg_copy flag, but without .br ipc_nowait , and the message queue contained less than .i msgtyp messages, then the call would block until the next message is written to the queue. .\" http://marc.info/?l=linux-kernel&m=139048542803605&w=2 at that point, the call would return a copy of the message, .i regardless of whether that message was at the ordinal position .ir msgtyp . this bug is fixed .\" commit 4f87dac386cc43d5525da7a939d4b4e7edbea22c in linux 3.14. .pp specifying both .b msg_copy and .b msc_except in .i msgflg is a logical error (since these flags impose different interpretations on .ir msgtyp ). in linux 3.13 and earlier, .\" http://marc.info/?l=linux-kernel&m=139048542803605&w=2 this error was not diagnosed by .br msgrcv (). this bug is fixed .\" commit 4f87dac386cc43d5525da7a939d4b4e7edbea22c in linux 3.14. .sh examples the program below demonstrates the use of .br msgsnd () and .br msgrcv (). .pp the example program is first run with the \fb\-s\fp option to send a message and then run again with the \fb\-r\fp option to receive a message. .pp the following shell session shows a sample run of the program: .pp .in +4n .ex .rb "$" " ./a.out \-s" sent: a message at wed mar 4 16:25:45 2015 .rb "$" " ./a.out \-r" message received: a message at wed mar 4 16:25:45 2015 .ee .in .ss program source \& .ex #include #include #include #include #include #include #include #include #include struct msgbuf { long mtype; char mtext[80]; }; static void usage(char *prog_name, char *msg) { if (msg != null) fputs(msg, stderr); fprintf(stderr, "usage: %s [options]\en", prog_name); fprintf(stderr, "options are:\en"); fprintf(stderr, "\-s send message using msgsnd()\en"); fprintf(stderr, "\-r read message using msgrcv()\en"); fprintf(stderr, "\-t message type (default is 1)\en"); fprintf(stderr, "\-k message queue key (default is 1234)\en"); exit(exit_failure); } static void send_msg(int qid, int msgtype) { struct msgbuf msg; time_t t; msg.mtype = msgtype; time(&t); snprintf(msg.mtext, sizeof(msg.mtext), "a message at %s", ctime(&t)); if (msgsnd(qid, &msg, sizeof(msg.mtext), ipc_nowait) == \-1) { perror("msgsnd error"); exit(exit_failure); } printf("sent: %s\en", msg.mtext); } static void get_msg(int qid, int msgtype) { struct msgbuf msg; if (msgrcv(qid, &msg, sizeof(msg.mtext), msgtype, msg_noerror | ipc_nowait) == \-1) { if (errno != enomsg) { perror("msgrcv"); exit(exit_failure); } printf("no message available for msgrcv()\en"); } else printf("message received: %s\en", msg.mtext); } int main(int argc, char *argv[]) { int qid, opt; int mode = 0; /* 1 = send, 2 = receive */ int msgtype = 1; int msgkey = 1234; while ((opt = getopt(argc, argv, "srt:k:")) != \-1) { switch (opt) { case \(aqs\(aq: mode = 1; break; case \(aqr\(aq: mode = 2; break; case \(aqt\(aq: msgtype = atoi(optarg); if (msgtype <= 0) usage(argv[0], "\-t option must be greater than 0\en"); break; case \(aqk\(aq: msgkey = atoi(optarg); break; default: usage(argv[0], "unrecognized option\en"); } } if (mode == 0) usage(argv[0], "must use either \-s or \-r option\en"); qid = msgget(msgkey, ipc_creat | 0666); if (qid == \-1) { perror("msgget"); exit(exit_failure); } if (mode == 2) get_msg(qid, msgtype); else send_msg(qid, msgtype); exit(exit_success); } .ee .sh see also .br msgctl (2), .br msgget (2), .br capabilities (7), .br mq_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sigvec.3 .so man7/iso_8859-6.7 .so man2/unimplemented.2 .\" copyright (c) 2018, red hat, inc. all rights reserved. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th ioctl_fslabel 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_fslabel \- get or set a filesystem label .sh synopsis .nf .br "#include " " /* definition of " *fslabel* " constants */" .b #include .pp .bi "int ioctl(int " fd ", fs_ioc_getfslabel, char " label [fslabel_max]); .bi "int ioctl(int " fd ", fs_ioc_setfslabel, char " label [fslabel_max]); .fi .sh description if a filesystem supports online label manipulation, these .br ioctl (2) operations can be used to get or set the filesystem label for the filesystem on which .i fd resides. the .b fs_ioc_setfslabel operation requires privilege .rb ( cap_sys_admin ). .sh return value on success zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors possible errors include (but are not limited to) the following: .tp .b efault .i label references an inaccessible memory area. .tp .b einval the specified label exceeds the maximum label length for the filesystem. .tp .b enotty this can appear if the filesystem does not support online label manipulation. .tp .b eperm the calling process does not have sufficient permissions to set the label. .sh versions these .br ioctl (2) operations first appeared in linux 4.18. they were previously known as .b btrfs_ioc_get_fslabel and .b btrfs_ioc_set_fslabel and were private to btrfs. .sh conforming to this api is linux-specific. .sh notes the maximum string length for this interface is .br fslabel_max , including the terminating null byte (\(aq\\0\(aq). filesystems have differing maximum label lengths, which may or may not include the terminating null. the string provided to .b fs_ioc_setfslabel must always be null-terminated, and the string returned by .b fs_ioc_getfslabel will always be null-terminated. .sh see also .br ioctl (2), .br blkid (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995, thomas k. dyas .\" and copyright (c) 2016, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created sat aug 21 1995 thomas k. dyas .\" .\" typo corrected, aeb, 950825 .\" added layout change from joey, 960722 .\" changed prototype, documented 0xffffffff, aeb, 030101 .\" modified 2004-11-03 patch from martin schulze .\" .th personality 2 2021-03-22 "linux" "linux programmer's manual" .sh name personality \- set the process execution domain .sh synopsis .nf .b #include .pp .bi "int personality(unsigned long " persona ); .fi .sh description linux supports different execution domains, or personalities, for each process. among other things, execution domains tell linux how to map signal numbers into signal actions. the execution domain system allows linux to provide limited support for binaries compiled under other unix-like operating systems. .pp if .i persona is not 0xffffffff, then .br personality () sets the caller's execution domain to the value specified by .ir persona . specifying .ir persona as 0xffffffff provides a way of retrieving the current persona without changing it. .pp a list of the available execution domains can be found in .ir . the execution domain is a 32-bit value in which the top three bytes are set aside for flags that cause the kernel to modify the behavior of certain system calls so as to emulate historical or architectural quirks. the least significant byte is a value defining the personality the kernel should assume. the flag values are as follows: .tp .br addr_compat_layout " (since linux 2.6.9)" with this flag set, provide legacy virtual address space layout. .tp .br addr_no_randomize " (since linux 2.6.12)" with this flag set, disable address-space-layout randomization. .tp .br addr_limit_32bit " (since linux 2.2)" limit the address space to 32 bits. .tp .br addr_limit_3gb " (since linux 2.4.0)" with this flag set, use 0xc0000000 as the offset at which to search a virtual memory chunk on .br mmap (2); otherwise use 0xffffe000. .tp .br fdpic_funcptrs " (since linux 2.6.11)" user-space function pointers to signal handlers point (on certain architectures) to descriptors. .tp .br mmap_page_zero " (since linux 2.4.0)" map page 0 as read-only (to support binaries that depend on this svr4 behavior). .tp .br read_implies_exec " (since linux 2.6.8)" with this flag set, .br prot_read implies .br prot_exec for .br mmap (2). .tp .br short_inode " (since linux 2.4.0)" no effects(?). .tp .br sticky_timeouts " (since linux 1.2.0)" with this flag set, .br select (2), .br pselect (2), and .br ppoll (2) do not modify the returned timeout argument when interrupted by a signal handler. .tp .br uname26 " (since linux 3.1)" have .br uname (2) report a 2.6.40+ version number rather than a 3.x version number. added as a stopgap measure to support broken applications that could not handle the kernel version-numbering switch from 2.6.x to 3.x. .tp .br whole_seconds " (since linux 1.2.0)" no effects(?). .pp the available execution domains are: .tp .br per_bsd " (since linux 1.2.0)" bsd. (no effects.) .tp .br per_hpux " (since linux 2.4)" support for 32-bit hp/ux. this support was never complete, and was dropped so that since linux 4.0, this value has no effect. .tp .br per_irix32 " (since linux 2.2)" irix 5 32-bit. never fully functional; support dropped in linux 2.6.27. implies .br sticky_timeouts . .tp .br per_irix64 " (since linux 2.2)" irix 6 64-bit. implies .br sticky_timeouts ; otherwise no effects. .tp .br per_irixn32 " (since linux 2.2)" irix 6 new 32-bit. implies .br sticky_timeouts ; otherwise no effects. .tp .br per_iscr4 " (since linux 1.2.0)" implies .br sticky_timeouts ; otherwise no effects. .tp .br per_linux " (since linux 1.2.0)" linux. .tp .br per_linux32 " (since linux 2.2)" [to be documented.] .tp .br per_linux32_3gb " (since linux 2.4)" implies .br addr_limit_3gb . .tp .br per_linux_32bit " (since linux 2.0)" implies .br addr_limit_32bit . .tp .br per_linux_fdpic " (since linux 2.6.11)" implies .br fdpic_funcptrs . .tp .br per_osf4 " (since linux 2.4)" osf/1 v4. on alpha, .\" following is from a comment in arch/alpha/kernel/osf_sys.c clear top 32 bits of iov_len in the user's buffer for compatibility with old versions of osf/1 where iov_len was defined as. .ir int . .tp .br per_osr5 " (since linux 2.4)" implies .br sticky_timeouts and .br whole_seconds ; otherwise no effects. .tp .br per_riscos " (since linux 2.2)" [to be documented.] .tp .br per_scosvr3 " (since linux 1.2.0)" implies .br sticky_timeouts , .br whole_seconds , and .br short_inode ; otherwise no effects. .tp .br per_solaris " (since linux 2.4)" implies .br sticky_timeouts ; otherwise no effects. .tp .br per_sunos " (since linux 2.4.0)" implies .br sticky_timeouts . divert library and dynamic linker searches to .ir /usr/gnemul . buggy, largely unmaintained, and almost entirely unused; support was removed in linux 2.6.26. .tp .br per_svr3 " (since linux 1.2.0)" implies .br sticky_timeouts and .br short_inode ; otherwise no effects. .tp .br per_svr4 " (since linux 1.2.0)" implies .br sticky_timeouts and .br mmap_page_zero ; otherwise no effects. .tp .br per_uw7 " (since linux 2.4)" implies .br sticky_timeouts and .br mmap_page_zero ; otherwise no effects. .tp .br per_wysev386 " (since linux 1.2.0)" implies .br sticky_timeouts and .br short_inode ; otherwise no effects. .tp .br per_xenix " (since linux 1.2.0)" implies .br sticky_timeouts and .br short_inode ; otherwise no effects. .sh return value on success, the previous .i persona is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval the kernel was unable to change the personality. .sh versions this system call first appeared in linux 1.1.20 (and thus first in a stable kernel release with linux 1.2.0); library support was added in glibc 2.3. .\" personality wrapper first appeared in glibc 1.90, .\" was added later in 2.2.91. .sh conforming to .br personality () is linux-specific and should not be used in programs intended to be portable. .sh see also .br setarch (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt, march 28, 1992 .\" and copyright (c) 2002, 2004, 2005, 2008, 2010 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-23 by rik faith .\" modified 1996-01-13 by arnt gulbrandsen .\" modified 1996-01-22 by aeb, following a remark by .\" tigran aivazian .\" modified 1996-04-14 by aeb, following a remark by .\" robert bihlmeyer .\" modified 1996-10-22 by eric s. raymond .\" modified 2001-05-04 by aeb, following a remark by .\" håvard lygre .\" modified 2001-04-17 by michael kerrisk .\" modified 2002-06-13 by michael kerrisk .\" added note on nonstandard behavior when sigchld is ignored. .\" modified 2002-07-09 by michael kerrisk .\" enhanced descriptions of 'resource' values .\" modified 2003-11-28 by aeb, added rlimit_core .\" modified 2004-03-26 by aeb, added rlimit_as .\" modified 2004-06-16 by michael kerrisk .\" added notes on cap_sys_resource .\" .\" 2004-11-16 -- mtk: the getrlimit.2 page, which formally included .\" coverage of getrusage(2), has been split, so that the latter .\" is now covered in its own getrusage.2. .\" .\" modified 2004-11-16, mtk: a few other minor changes .\" modified 2004-11-23, mtk .\" added notes on rlimit_memlock, rlimit_nproc, and rlimit_rss .\" to "conforming to" .\" modified 2004-11-25, mtk .\" rewrote discussion on rlimit_memlock to incorporate kernel .\" 2.6.9 changes. .\" added note on rlimit_cpu error in older kernels .\" 2004-11-03, mtk, added rlimit_sigpending .\" 2005-07-13, mtk, documented rlimit_msgqueue limit. .\" 2005-07-28, mtk, added descriptions of rlimit_nice and rlimit_rtprio .\" 2008-05-07, mtk / peter zijlstra, added description of rlimit_rttime .\" 2010-11-06, mtk: added documentation of prlimit() .\" .th getrlimit 2 2021-03-22 "linux" "linux programmer's manual" .sh name getrlimit, setrlimit, prlimit \- get/set resource limits .sh synopsis .nf .b #include .pp .bi "int getrlimit(int " resource ", struct rlimit *" rlim ); .bi "int setrlimit(int " resource ", const struct rlimit *" rlim ); .pp .bi "int prlimit(pid_t " pid ", int " resource ", const struct rlimit *" new_limit , .bi " struct rlimit *" old_limit ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br prlimit (): .nf _gnu_source .fi .sh description the .br getrlimit () and .br setrlimit () system calls get and set resource limits. each resource has an associated soft and hard limit, as defined by the .i rlimit structure: .pp .in +4n .ex struct rlimit { rlim_t rlim_cur; /* soft limit */ rlim_t rlim_max; /* hard limit (ceiling for rlim_cur) */ }; .ee .in .pp the soft limit is the value that the kernel enforces for the corresponding resource. the hard limit acts as a ceiling for the soft limit: an unprivileged process may set only its soft limit to a value in the range from 0 up to the hard limit, and (irreversibly) lower its hard limit. a privileged process (under linux: one with the .b cap_sys_resource capability in the initial user namespace) may make arbitrary changes to either limit value. .pp the value .b rlim_infinity denotes no limit on a resource (both in the structure returned by .br getrlimit () and in the structure passed to .br setrlimit ()). .pp the .i resource argument must be one of: .tp .b rlimit_as this is the maximum size of the process's virtual memory (address space). the limit is specified in bytes, and is rounded down to the system page size. .\" since 2.0.27 / 2.1.12 this limit affects calls to .br brk (2), .br mmap (2), and .br mremap (2), which fail with the error .b enomem upon exceeding this limit. in addition, automatic stack expansion fails (and generates a .b sigsegv that kills the process if no alternate stack has been made available via .br sigaltstack (2)). since the value is a \filong\fp, on machines with a 32-bit \filong\fp either this limit is at most 2\ gib, or this resource is unlimited. .tp .b rlimit_core this is the maximum size of a .i core file (see .br core (5)) in bytes that the process may dump. when 0 no core dump files are created. when nonzero, larger dumps are truncated to this size. .tp .b rlimit_cpu this is a limit, in seconds, on the amount of cpu time that the process can consume. when the process reaches the soft limit, it is sent a .b sigxcpu signal. the default action for this signal is to terminate the process. however, the signal can be caught, and the handler can return control to the main program. if the process continues to consume cpu time, it will be sent .b sigxcpu once per second until the hard limit is reached, at which time it is sent .br sigkill . (this latter point describes linux behavior. implementations vary in how they treat processes which continue to consume cpu time after reaching the soft limit. portable applications that need to catch this signal should perform an orderly termination upon first receipt of .br sigxcpu .) .tp .b rlimit_data this is the maximum size of the process's data segment (initialized data, uninitialized data, and heap). the limit is specified in bytes, and is rounded down to the system page size. this limit affects calls to .br brk (2), .br sbrk (2), and (since linux 4.7) .br mmap (2), .\" commits 84638335900f1995495838fe1bd4870c43ec1f67 .\" ("mm: rework virtual memory accounting"), .\" f4fcd55841fc9e46daac553b39361572453c2b88 .\" (mm: enable rlimit_data by default with workaround for valgrind). which fail with the error .b enomem upon encountering the soft limit of this resource. .tp .b rlimit_fsize this is the maximum size in bytes of files that the process may create. attempts to extend a file beyond this limit result in delivery of a .b sigxfsz signal. by default, this signal terminates a process, but a process can catch this signal instead, in which case the relevant system call (e.g., .br write (2), .br truncate (2)) fails with the error .br efbig . .tp .br rlimit_locks " (linux 2.4.0 to 2.4.24)" .\" to be precise: linux 2.4.0-test9; no longer in 2.4.25 / 2.5.65 this is a limit on the combined number of .br flock (2) locks and .br fcntl (2) leases that this process may establish. .tp .b rlimit_memlock this is the maximum number of bytes of memory that may be locked into ram. this limit is in effect rounded down to the nearest multiple of the system page size. this limit affects .br mlock (2), .br mlockall (2), and the .br mmap (2) .b map_locked operation. since linux 2.6.9, it also affects the .br shmctl (2) .b shm_lock operation, where it sets a maximum on the total bytes in shared memory segments (see .br shmget (2)) that may be locked by the real user id of the calling process. the .br shmctl (2) .b shm_lock locks are accounted for separately from the per-process memory locks established by .br mlock (2), .br mlockall (2), and .br mmap (2) .br map_locked ; a process can lock bytes up to this limit in each of these two categories. .ip in linux kernels before 2.6.9, this limit controlled the amount of memory that could be locked by a privileged process. since linux 2.6.9, no limits are placed on the amount of memory that a privileged process may lock, and this limit instead governs the amount of memory that an unprivileged process may lock. .tp .br rlimit_msgqueue " (since linux 2.6.8)" this is a limit on the number of bytes that can be allocated for posix message queues for the real user id of the calling process. this limit is enforced for .br mq_open (3). each message queue that the user creates counts (until it is removed) against this limit according to the formula: .ip since linux 3.5: .ip .ex bytes = attr.mq_maxmsg * sizeof(struct msg_msg) + min(attr.mq_maxmsg, mq_prio_max) * sizeof(struct posix_msg_tree_node)+ /* for overhead */ attr.mq_maxmsg * attr.mq_msgsize; /* for message data */ .ee .ip linux 3.4 and earlier: .ip .ex bytes = attr.mq_maxmsg * sizeof(struct msg_msg *) + /* for overhead */ attr.mq_maxmsg * attr.mq_msgsize; /* for message data */ .ee .ip where .i attr is the .i mq_attr structure specified as the fourth argument to .br mq_open (3), and the .i msg_msg and .i posix_msg_tree_node structures are kernel-internal structures. .ip the "overhead" addend in the formula accounts for overhead bytes required by the implementation and ensures that the user cannot create an unlimited number of zero-length messages (such messages nevertheless each consume some system memory for bookkeeping overhead). .tp .br rlimit_nice " (since linux 2.6.12, but see bugs below)" this specifies a ceiling to which the process's nice value can be raised using .br setpriority (2) or .br nice (2). the actual ceiling for the nice value is calculated as .ir "20\ \-\ rlim_cur" . the useful range for this limit is thus from 1 (corresponding to a nice value of 19) to 40 (corresponding to a nice value of \-20). this unusual choice of range was necessary because negative numbers cannot be specified as resource limit values, since they typically have special meanings. for example, .b rlim_infinity typically is the same as \-1. for more detail on the nice value, see .br sched (7). .tp .b rlimit_nofile this specifies a value one greater than the maximum file descriptor number that can be opened by this process. attempts .rb ( open (2), .br pipe (2), .br dup (2), etc.) to exceed this limit yield the error .br emfile . (historically, this limit was named .b rlimit_ofile on bsd.) .ip since linux 4.5, this limit also defines the maximum number of file descriptors that an unprivileged process (one without the .br cap_sys_resource capability) may have "in flight" to other processes, by being passed across unix domain sockets. this limit applies to the .br sendmsg (2) system call. for further details, see .br unix (7). .tp .b rlimit_nproc this is a limit on the number of extant process (or, more precisely on linux, threads) for the real user id of the calling process. so long as the current number of processes belonging to this process's real user id is greater than or equal to this limit, .br fork (2) fails with the error .br eagain . .ip the .b rlimit_nproc limit is not enforced for processes that have either the .b cap_sys_admin or the .b cap_sys_resource capability. .tp .b rlimit_rss this is a limit (in bytes) on the process's resident set (the number of virtual pages resident in ram). this limit has effect only in linux 2.4.x, x < 30, and there affects only calls to .br madvise (2) specifying .br madv_willneed . .\" as at kernel 2.6.12, this limit still does nothing in 2.6 though .\" talk of making it do something has surfaced from time to time in lkml .\" -- mtk, jul 05 .tp .br rlimit_rtprio " (since linux 2.6.12, but see bugs)" this specifies a ceiling on the real-time priority that may be set for this process using .br sched_setscheduler (2) and .br sched_setparam (2). .ip for further details on real-time scheduling policies, see .br sched (7) .tp .br rlimit_rttime " (since linux 2.6.25)" this is a limit (in microseconds) on the amount of cpu time that a process scheduled under a real-time scheduling policy may consume without making a blocking system call. for the purpose of this limit, each time a process makes a blocking system call, the count of its consumed cpu time is reset to zero. the cpu time count is not reset if the process continues trying to use the cpu but is preempted, its time slice expires, or it calls .br sched_yield (2). .ip upon reaching the soft limit, the process is sent a .b sigxcpu signal. if the process catches or ignores this signal and continues consuming cpu time, then .b sigxcpu will be generated once each second until the hard limit is reached, at which point the process is sent a .b sigkill signal. .ip the intended use of this limit is to stop a runaway real-time process from locking up the system. .ip for further details on real-time scheduling policies, see .br sched (7) .tp .br rlimit_sigpending " (since linux 2.6.8)" this is a limit on the number of signals that may be queued for the real user id of the calling process. both standard and real-time signals are counted for the purpose of checking this limit. however, the limit is enforced only for .br sigqueue (3); it is always possible to use .br kill (2) to queue one instance of any of the signals that are not already queued to the process. .\" this replaces the /proc/sys/kernel/rtsig-max system-wide limit .\" that was present in kernels <= 2.6.7. mtk dec 04 .tp .b rlimit_stack this is the maximum size of the process stack, in bytes. upon reaching this limit, a .b sigsegv signal is generated. to handle this signal, a process must employ an alternate signal stack .rb ( sigaltstack (2)). .ip since linux 2.6.23, this limit also determines the amount of space used for the process's command-line arguments and environment variables; for details, see .br execve (2). .ss prlimit() .\" commit c022a0acad534fd5f5d5f17280f6d4d135e74e81 .\" author: jiri slaby .\" date: tue may 4 18:03:50 2010 +0200 .\" .\" rlimits: implement prlimit64 syscall .\" .\" commit 6a1d5e2c85d06da35cdfd93f1a27675bfdc3ad8c .\" author: jiri slaby .\" date: wed mar 24 17:06:58 2010 +0100 .\" .\" rlimits: add rlimit64 structure .\" the linux-specific .br prlimit () system call combines and extends the functionality of .br setrlimit () and .br getrlimit (). it can be used to both set and get the resource limits of an arbitrary process. .pp the .i resource argument has the same meaning as for .br setrlimit () and .br getrlimit (). .pp if the .ir new_limit argument is a not null, then the .i rlimit structure to which it points is used to set new values for the soft and hard limits for .ir resource . if the .ir old_limit argument is a not null, then a successful call to .br prlimit () places the previous soft and hard limits for .i resource in the .i rlimit structure pointed to by .ir old_limit . .pp the .i pid argument specifies the id of the process on which the call is to operate. if .i pid is 0, then the call applies to the calling process. to set or get the resources of a process other than itself, the caller must have the .b cap_sys_resource capability in the user namespace of the process whose resource limits are being changed, or the real, effective, and saved set user ids of the target process must match the real user id of the caller .i and the real, effective, and saved set group ids of the target process must match the real group id of the caller. .\" fixme . this permission check is strange .\" asked about this on lkml, 7 nov 2010 .\" "inconsistent credential checking in prlimit() syscall" .sh return value on success, these system calls return 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault a pointer argument points to a location outside the accessible address space. .tp .b einval the value specified in .i resource is not valid; or, for .br setrlimit () or .br prlimit (): .i rlim\->rlim_cur was greater than .ir rlim\->rlim_max . .tp .b eperm an unprivileged process tried to raise the hard limit; the .b cap_sys_resource capability is required to do this. .tp .b eperm the caller tried to increase the hard .b rlimit_nofile limit above the maximum defined by .ir /proc/sys/fs/nr_open (see .br proc (5)) .tp .b eperm .rb ( prlimit ()) the calling process did not have permission to set limits for the process specified by .ir pid . .tp .b esrch could not find a process with the id specified in .ir pid . .sh versions the .br prlimit () system call is available since linux 2.6.36. library support is available since glibc 2.13. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getrlimit (), .br setrlimit (), .br prlimit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br getrlimit (), .br setrlimit (): posix.1-2001, posix.1-2008, svr4, 4.3bsd. .pp .br prlimit (): linux-specific. .pp .b rlimit_memlock and .b rlimit_nproc derive from bsd and are not specified in posix.1; they are present on the bsds and linux, but on few other implementations. .b rlimit_rss derives from bsd and is not specified in posix.1; it is nevertheless present on most implementations. .br rlimit_msgqueue , .br rlimit_nice , .br rlimit_rtprio , .br rlimit_rttime , and .b rlimit_sigpending are linux-specific. .sh notes a child process created via .br fork (2) inherits its parent's resource limits. resource limits are preserved across .br execve (2). .pp resource limits are per-process attributes that are shared by all of the threads in a process. .pp lowering the soft limit for a resource below the process's current consumption of that resource will succeed (but will prevent the process from further increasing its consumption of the resource). .pp one can set the resource limits of the shell using the built-in .ir ulimit command .ri ( limit in .br csh (1)). the shell's resource limits are inherited by the processes that it creates to execute commands. .pp since linux 2.6.24, the resource limits of any process can be inspected via .ir /proc/[pid]/limits ; see .br proc (5). .pp ancient systems provided a .br vlimit () function with a similar purpose to .br setrlimit (). for backward compatibility, glibc also provides .br vlimit (). all new applications should be written using .br setrlimit (). .ss c library/kernel abi differences since version 2.13, the glibc .br getrlimit () and .br setrlimit () wrapper functions no longer invoke the corresponding system calls, but instead employ .br prlimit (), for the reasons described in bugs. .pp the name of the glibc wrapper function is .br prlimit (); the underlying system call is .br prlimit64 (). .sh bugs in older linux kernels, the .b sigxcpu and .b sigkill signals delivered when a process encountered the soft and hard .b rlimit_cpu limits were delivered one (cpu) second later than they should have been. this was fixed in kernel 2.6.8. .pp in 2.6.x kernels before 2.6.17, a .b rlimit_cpu limit of 0 is wrongly treated as "no limit" (like .br rlim_infinity ). since linux 2.6.17, setting a limit of 0 does have an effect, but is actually treated as a limit of 1 second. .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=114008066530167&w=2 .pp a kernel bug means that .\" see https://lwn.net/articles/145008/ .b rlimit_rtprio does not work in kernel 2.6.12; the problem is fixed in kernel 2.6.13. .pp in kernel 2.6.12, there was an off-by-one mismatch between the priority ranges returned by .br getpriority (2) and .br rlimit_nice . this had the effect that the actual ceiling for the nice value was calculated as .ir "19\ \-\ rlim_cur" . this was fixed in kernel 2.6.13. .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=112256338703880&w=2 .pp since linux 2.6.12, .\" the relevant patch, sent to lkml, seems to be .\" http://thread.gmane.org/gmane.linux.kernel/273462 .\" from: roland mcgrath redhat.com> .\" subject: [patch 7/7] make rlimit_cpu/sigxcpu per-process .\" date: 2005-01-23 23:27:46 gmt if a process reaches its soft .br rlimit_cpu limit and has a handler installed for .br sigxcpu , then, in addition to invoking the signal handler, the kernel increases the soft limit by one second. this behavior repeats if the process continues to consume cpu time, until the hard limit is reached, at which point the process is killed. other implementations .\" tested solaris 10, freebsd 9, openbsd 5.0 do not change the .br rlimit_cpu soft limit in this manner, and the linux behavior is probably not standards conformant; portable applications should avoid relying on this linux-specific behavior. .\" fixme . https://bugzilla.kernel.org/show_bug.cgi?id=50951 the linux-specific .br rlimit_rttime limit exhibits the same behavior when the soft limit is encountered. .pp kernels before 2.4.22 did not diagnose the error .b einval for .br setrlimit () when .i rlim\->rlim_cur was greater than .ir rlim\->rlim_max . .\" d3561f78fd379a7110e46c87964ba7aa4120235c .pp linux doesn't return an error when an attempt to set .b rlimit_cpu has failed, for compatibility reasons. .\" .ss representation of """large""" resource limit values on 32-bit platforms the glibc .br getrlimit () and .br setrlimit () wrapper functions use a 64-bit .ir rlim_t data type, even on 32-bit platforms. however, the .i rlim_t data type used in the .br getrlimit () and .br setrlimit () system calls is a (32-bit) .ir "unsigned long" . .\" linux still uses long for limits internally: .\" c022a0acad534fd5f5d5f17280f6d4d135e74e81 .\" kernel/sys.c:do_prlimit() still uses struct rlimit which .\" uses kernel_ulong_t for its members, i.e. 32-bit on 32-bit kernel. furthermore, in linux, the kernel represents resource limits on 32-bit platforms as .ir "unsigned long" . however, a 32-bit data type is not wide enough. .\" https://bugzilla.kernel.org/show_bug.cgi?id=5042 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=12201 the most pertinent limit here is .br rlimit_fsize , which specifies the maximum size to which a file can grow: to be useful, this limit must be represented using a type that is as wide as the type used to represent file offsets\(emthat is, as wide as a 64-bit .br off_t (assuming a program compiled with .ir _file_offset_bits=64 ). .pp to work around this kernel limitation, if a program tried to set a resource limit to a value larger than can be represented in a 32-bit .ir "unsigned long" , then the glibc .br setrlimit () wrapper function silently converted the limit value to .br rlim_infinity . in other words, the requested resource limit setting was silently ignored. .pp since version 2.13, .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=12201 glibc works around the limitations of the .br getrlimit () and .br setrlimit () system calls by implementing .br setrlimit () and .br getrlimit () as wrapper functions that call .br prlimit (). .sh examples the program below demonstrates the use of .br prlimit (). .pp .ex #define _gnu_source #define _file_offset_bits 64 #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { struct rlimit old, new; struct rlimit *newp; pid_t pid; if (!(argc == 2 || argc == 4)) { fprintf(stderr, "usage: %s [ " "]\en", argv[0]); exit(exit_failure); } pid = atoi(argv[1]); /* pid of target process */ newp = null; if (argc == 4) { new.rlim_cur = atoi(argv[2]); new.rlim_max = atoi(argv[3]); newp = &new; } /* set cpu time limit of target process; retrieve and display previous limit */ if (prlimit(pid, rlimit_cpu, newp, &old) == \-1) errexit("prlimit\-1"); printf("previous limits: soft=%jd; hard=%jd\en", (intmax_t) old.rlim_cur, (intmax_t) old.rlim_max); /* retrieve and display new cpu time limit */ if (prlimit(pid, rlimit_cpu, null, &old) == \-1) errexit("prlimit\-2"); printf("new limits: soft=%jd; hard=%jd\en", (intmax_t) old.rlim_cur, (intmax_t) old.rlim_max); exit(exit_success); } .ee .sh see also .br prlimit (1), .br dup (2), .br fcntl (2), .br fork (2), .br getrusage (2), .br mlock (2), .br mmap (2), .br open (2), .br quotactl (2), .br sbrk (2), .br shmctl (2), .br malloc (3), .br sigqueue (3), .br ulimit (3), .br core (5), .br capabilities (7), .br cgroups (7), .br credentials (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2009 intel corporation, author andi kleen .\" description based on comments in arch/x86/kernel/cpuid.c .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th cpuid 4 2019-08-02 "linux" "linux programmer's manual" .sh name cpuid \- x86 cpuid access device .sh description cpuid provides an interface for querying information about the x86 cpu. .pp this device is accessed by .br lseek (2) or .br pread (2) to the appropriate cpuid level and reading in chunks of 16 bytes. a larger read size means multiple reads of consecutive levels. .pp the lower 32 bits of the file position is used as the incoming .ir %eax , and the upper 32 bits of the file position as the incoming .ir %ecx , the latter is intended for "counting" .i eax levels like .ir eax=4 . .pp this driver uses .ir /dev/cpu/cpunum/cpuid , where .i cpunum is the minor number, and on an smp box will direct the access to cpu .i cpunum as listed in .ir /proc/cpuinfo . .pp this file is protected so that it can be read only by the user .ir root , or members of the group .ir root . .sh notes the cpuid instruction can be directly executed by a program using inline assembler. however this device allows convenient access to all cpus without changing process affinity. .pp most of the information in .i cpuid is reported by the kernel in cooked form either in .i /proc/cpuinfo or through subdirectories in .ir /sys/devices/system/cpu . direct cpuid access through this device should only be used in exceptional cases. .pp the .i cpuid driver is not auto-loaded. on modular kernels you might need to use the following command to load it explicitly before use: .pp .in +4n .ex $ modprobe cpuid .ee .in .pp there is no support for cpuid functions that require additional input registers. .pp very old x86 cpus don't support cpuid. .sh see also .br cpuid (1) .pp intel corporation, intel 64 and ia-32 architectures software developer's manual volume 2a: instruction set reference, a-m, 3-180 cpuid reference. .pp intel corporation, intel processor identification and the cpuid instruction, application note 485. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man3/pthread_attr_setinheritsched.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified 1993-03-29, david metcalfe .\" modified 1993-07-24, rik faith (faith@cs.unc.edu) .\" modified 2002-08-10, 2003-11-01 walter harms, aeb .\" .th div 3 2021-03-22 "" "linux programmer's manual" .sh name div, ldiv, lldiv, imaxdiv \- compute quotient and remainder of an integer division .sh synopsis .nf .b #include .pp .bi "div_t div(int " numerator ", int " denominator ); .bi "ldiv_t ldiv(long " numerator ", long " denominator ); .bi "lldiv_t lldiv(long long " numerator ", long long " denominator ); .pp .b #include .pp .bi "imaxdiv_t imaxdiv(intmax_t " numerator ", intmax_t " denominator ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br lldiv (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description the .br div () function computes the value \finumerator\fp/\fidenominator\fp and returns the quotient and remainder in a structure named \fidiv_t\fp that contains two integer members (in unspecified order) named \fiquot\fp and \firem\fp. the quotient is rounded toward zero. the result satisfies \fiquot\fp*\fidenominator\fp+\firem\fp = \finumerator\fp. .pp the .br ldiv (), .br lldiv (), and .br imaxdiv () functions do the same, dividing numbers of the indicated type and returning the result in a structure of the indicated name, in all cases with fields \fiquot\fp and \firem\fp of the same type as the function arguments. .sh return value the \fidiv_t\fp (etc.) structure. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br div (), .br ldiv (), .br lldiv (), .br imaxdiv () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. the functions .br lldiv () and .br imaxdiv () were added in c99. .sh examples after .pp .in +4n .ex div_t q = div(\-5, 3); .ee .in .pp the values \fiq.quot\fp and \fiq.rem\fp are \-1 and \-2, respectively. .sh see also .br abs (3), .br remainder (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1997 john s. kallal (kallal@voicenet.com) .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" some changes by tytso and aeb. .\" .\" 2004-12-16, john v. belmonte/mtk, updated init and quit scripts .\" 2004-04-08, aeb, improved description of read from /dev/urandom .\" 2008-06-20, george spelvin , .\" matt mackall .\" .th random 4 2021-03-22 "linux" "linux programmer's manual" .sh name random, urandom \- kernel random number source devices .sh synopsis .nf #include .pp .bi "int ioctl(" fd ", rnd" request ", " param ");" .fi .sh description the character special files \fi/dev/random\fp and \fi/dev/urandom\fp (present since linux 1.3.30) provide an interface to the kernel's random number generator. the file .i /dev/random has major device number 1 and minor device number 8. the file .i /dev/urandom has major device number 1 and minor device number 9. .pp the random number generator gathers environmental noise from device drivers and other sources into an entropy pool. the generator also keeps an estimate of the number of bits of noise in the entropy pool. from this entropy pool, random numbers are created. .pp linux 3.17 and later provides the simpler and safer .br getrandom (2) interface which requires no special files; see the .br getrandom (2) manual page for details. .pp when read, the .i /dev/urandom device returns random bytes using a pseudorandom number generator seeded from the entropy pool. reads from this device do not block (i.e., the cpu is not yielded), but can incur an appreciable delay when requesting large amounts of data. .pp when read during early boot time, .ir /dev/urandom may return data prior to the entropy pool being initialized. .\" this is a real problem; see .\" commit 9b4d008787f864f17d008c9c15bbe8a0f7e2fc24 if this is of concern in your application, use .br getrandom (2) or \fi/dev/random\fp instead. .pp the \fi/dev/random\fp device is a legacy interface which dates back to a time where the cryptographic primitives used in the implementation of \fi/dev/urandom\fp were not widely trusted. it will return random bytes only within the estimated number of bits of fresh noise in the entropy pool, blocking if necessary. \fi/dev/random\fp is suitable for applications that need high quality randomness, and can afford indeterminate delays. .pp when the entropy pool is empty, reads from \fi/dev/random\fp will block until additional environmental noise is gathered. if .br open (2) is called for .i /dev/random with the .br o_nonblock flag, a subsequent .br read (2) will not block if the requested number of bytes is not available. instead, the available bytes are returned. if no byte is available, .br read (2) will return \-1 and .i errno will be set to .br eagain . .pp the .b o_nonblock flag has no effect when opening .ir /dev/urandom . when calling .br read (2) for the device .ir /dev/urandom , reads of up to 256 bytes will return as many bytes as are requested and will not be interrupted by a signal handler. reads with a buffer over this limit may return less than the requested number of bytes or fail with the error .br eintr , if interrupted by a signal handler. .pp since linux 3.16, .\" commit 79a8468747c5f95ed3d5ce8376a3e82e0c5857fc a .br read (2) from .ir /dev/urandom will return at most 32\ mb. a .br read (2) from .ir /dev/random will return at most 512 bytes .\" sec_xfer_size in drivers/char/random.c (340 bytes on linux kernels before version 2.6.12). .pp writing to \fi/dev/random\fp or \fi/dev/urandom\fp will update the entropy pool with the data written, but this will not result in a higher entropy count. this means that it will impact the contents read from both files, but it will not make reads from \fi/dev/random\fp faster. .ss usage the .ir /dev/random interface is considered a legacy interface, and .ir /dev/urandom is preferred and sufficient in all use cases, with the exception of applications which require randomness during early boot time; for these applications, .br getrandom (2) must be used instead, because it will block until the entropy pool is initialized. .pp if a seed file is saved across reboots as recommended below, the output is cryptographically secure against attackers without local root access as soon as it is reloaded in the boot sequence, and perfectly adequate for network encryption session keys. (all major linux distributions have saved the seed file across reboots since 2000 at least.) since reads from .i /dev/random may block, users will usually want to open it in nonblocking mode (or perform a read with timeout), and provide some sort of user notification if the desired entropy is not immediately available. .\" .ss configuration if your system does not have \fi/dev/random\fp and \fi/dev/urandom\fp created already, they can be created with the following commands: .pp .in +4n .ex mknod \-m 666 /dev/random c 1 8 mknod \-m 666 /dev/urandom c 1 9 chown root:root /dev/random /dev/urandom .ee .in .pp when a linux system starts up without much operator interaction, the entropy pool may be in a fairly predictable state. this reduces the actual amount of noise in the entropy pool below the estimate. in order to counteract this effect, it helps to carry entropy pool information across shut-downs and start-ups. to do this, add the lines to an appropriate script which is run during the linux system start-up sequence: .pp .in +4n .ex echo "initializing random number generator..." random_seed=/var/run/random\-seed # carry a random seed from start\-up to start\-up # load and then save the whole entropy pool if [ \-f $random_seed ]; then cat $random_seed >/dev/urandom else touch $random_seed fi chmod 600 $random_seed poolfile=/proc/sys/kernel/random/poolsize [ \-r $poolfile ] && bits=$(cat $poolfile) || bits=4096 bytes=$(expr $bits / 8) dd if=/dev/urandom of=$random_seed count=1 bs=$bytes .ee .in .pp also, add the following lines in an appropriate script which is run during the linux system shutdown: .pp .in +4n .ex # carry a random seed from shut\-down to start\-up # save the whole entropy pool echo "saving random seed..." random_seed=/var/run/random\-seed touch $random_seed chmod 600 $random_seed poolfile=/proc/sys/kernel/random/poolsize [ \-r $poolfile ] && bits=$(cat $poolfile) || bits=4096 bytes=$(expr $bits / 8) dd if=/dev/urandom of=$random_seed count=1 bs=$bytes .ee .in .pp in the above examples, we assume linux 2.6.0 or later, where .ir /proc/sys/kernel/random/poolsize returns the size of the entropy pool in bits (see below). .\" .ss /proc interfaces the files in the directory .i /proc/sys/kernel/random (present since 2.3.16) provide additional information about the .i /dev/random device: .tp .i entropy_avail this read-only file gives the available entropy, in bits. this will be a number in the range 0 to 4096. .tp .i poolsize this file gives the size of the entropy pool. the semantics of this file vary across kernel versions: .rs .tp linux 2.4: this file gives the size of the entropy pool in .ir bytes . normally, this file will have the value 512, but it is writable, and can be changed to any value for which an algorithm is available. the choices are 32, 64, 128, 256, 512, 1024, or 2048. .tp linux 2.6 and later: this file is read-only, and gives the size of the entropy pool in .ir bits . it contains the value 4096. .re .tp .i read_wakeup_threshold this file contains the number of bits of entropy required for waking up processes that sleep waiting for entropy from .ir /dev/random . the default is 64. .tp .i write_wakeup_threshold this file contains the number of bits of entropy below which we wake up processes that do a .br select (2) or .br poll (2) for write access to .ir /dev/random . these values can be changed by writing to the files. .tp .ir uuid " and " boot_id these read-only files contain random strings like 6fd5a44b-35f4-4ad4-a9b9-6b9be13e1fe9. the former is generated afresh for each read, the latter was generated once. .\" .ss ioctl(2) interface the following .br ioctl (2) requests are defined on file descriptors connected to either \fi/dev/random\fp or \fi/dev/urandom\fp. all requests performed will interact with the input entropy pool impacting both \fi/dev/random\fp and \fi/dev/urandom\fp. the .b cap_sys_admin capability is required for all requests except .br rndgetentcnt . .tp .br rndgetentcnt retrieve the entropy count of the input pool, the contents will be the same as the .i entropy_avail file under proc. the result will be stored in the int pointed to by the argument. .tp .br rndaddtoentcnt increment or decrement the entropy count of the input pool by the value pointed to by the argument. .tp .br rndgetpool removed in linux 2.6.9. .tp .br rndaddentropy add some additional entropy to the input pool, incrementing the entropy count. this differs from writing to \fi/dev/random\fp or \fi/dev/urandom\fp, which only adds some data but does not increment the entropy count. the following structure is used: .ip .in +4n .ex struct rand_pool_info { int entropy_count; int buf_size; __u32 buf[0]; }; .ee .in .ip here .i entropy_count is the value added to (or subtracted from) the entropy count, and .i buf is the buffer of size .i buf_size which gets added to the entropy pool. .tp .br rndzapentcnt ", " rndclearpool zero the entropy count of all pools and add some system data (such as wall clock) to the pools. .sh files .i /dev/random .br .i /dev/urandom .sh notes for an overview and comparison of the various interfaces that can be used to obtain randomness, see .br random (7). .sh bugs during early boot time, reads from .i /dev/urandom may return data prior to the entropy pool being initialized. .\" .sh author .\" the kernel's random number generator was written by .\" theodore ts'o (tytso@athena.mit.edu). .sh see also .br mknod (1), .br getrandom (2), .br random (7) .pp rfc\ 1750, "randomness recommendations for security" .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pty 7 2020-08-13 "linux" "linux programmer's manual" .sh name pty \- pseudoterminal interfaces .sh description a pseudoterminal (sometimes abbreviated "pty") is a pair of virtual character devices that provide a bidirectional communication channel. one end of the channel is called the .ir master ; the other end is called the .ir slave . .pp the slave end of the pseudoterminal provides an interface that behaves exactly like a classical terminal. a process that expects to be connected to a terminal, can open the slave end of a pseudoterminal and then be driven by a program that has opened the master end. anything that is written on the master end is provided to the process on the slave end as though it was input typed on a terminal. for example, writing the interrupt character (usually control-c) to the master device would cause an interrupt signal .rb ( sigint ) to be generated for the foreground process group that is connected to the slave. conversely, anything that is written to the slave end of the pseudoterminal can be read by the process that is connected to the master end. .pp data flow between master and slave is handled asynchronously, much like data flow with a physical terminal. data written to the slave will be available at the master promptly, but may not be available immediately. similarly, there may be a small processing delay between a write to the master, and the effect being visible at the slave. .pp historically, two pseudoterminal apis have evolved: bsd and system v. susv1 standardized a pseudoterminal api based on the system v api, and this api should be employed in all new programs that use pseudoterminals. .pp linux provides both bsd-style and (standardized) system v-style pseudoterminals. system v-style terminals are commonly called unix 98 pseudoterminals on linux systems. .pp since kernel 2.6.4, bsd-style pseudoterminals are considered deprecated: support can be disabled when building the kernel by disabling the .b config_legacy_ptys option. (starting with linux 2.6.30, that option is disabled by default in the mainline kernel.) unix 98 pseudoterminals should be used in new applications. .ss unix 98 pseudoterminals an unused unix 98 pseudoterminal master is opened by calling .br posix_openpt (3). (this function opens the master clone device, .ir /dev/ptmx ; see .br pts (4).) after performing any program-specific initializations, changing the ownership and permissions of the slave device using .br grantpt (3), and unlocking the slave using .br unlockpt (3)), the corresponding slave device can be opened by passing the name returned by .br ptsname (3) in a call to .br open (2). .pp the linux kernel imposes a limit on the number of available unix 98 pseudoterminals. in kernels up to and including 2.6.3, this limit is configured at kernel compilation time .rb ( config_unix98_ptys ), and the permitted number of pseudoterminals can be up to 2048, with a default setting of 256. since kernel 2.6.4, the limit is dynamically adjustable via .ir /proc/sys/kernel/pty/max , and a corresponding file, .ir /proc/sys/kernel/pty/nr , indicates how many pseudoterminals are currently in use. for further details on these two files, see .br proc (5). .ss bsd pseudoterminals bsd-style pseudoterminals are provided as precreated pairs, with names of the form .i /dev/ptyxy (master) and .i /dev/ttyxy (slave), where x is a letter from the 16-character set [p\-za\-e], and y is a letter from the 16-character set [0\-9a\-f]. (the precise range of letters in these two sets varies across unix implementations.) for example, .i /dev/ptyp1 and .i /dev/ttyp1 constitute a bsd pseudoterminal pair. a process finds an unused pseudoterminal pair by trying to .br open (2) each pseudoterminal master until an open succeeds. the corresponding pseudoterminal slave (substitute "tty" for "pty" in the name of the master) can then be opened. .sh files .tp .i /dev/ptmx unix 98 master clone device .tp .i /dev/pts/* unix 98 slave devices .tp .i /dev/pty[p\-za\-e][0\-9a\-f] bsd master devices .tp .i /dev/tty[p\-za\-e][0\-9a\-f] bsd slave devices .sh notes pseudoterminals are used by applications such as network login services .rb ( ssh "(1), " rlogin "(1), " telnet (1)), terminal emulators such as .br xterm (1), .br script (1), .br screen (1), .br tmux (1), .br unbuffer (1), and .br expect (1). .pp a description of the .b tiocpkt .br ioctl (2), which controls packet mode operation, can be found in .br ioctl_tty (2). .pp the bsd .br ioctl (2) operations .br tiocstop , .br tiocstart , .br tiocucntl , and .br tiocremote have not been implemented under linux. .sh see also .br ioctl_tty (2), .br select (2), .br setsid (2), .br forkpty (3), .br openpty (3), .br termios (3), .br pts (4), .br tty (4) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2013 michael kerrisk .\" (replaces an earlier page by walter harms and michael kerrisk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th canonicalize_file_name 3 2021-03-22 "gnu" "linux programmer's manual" .sh name canonicalize_file_name \- return the canonicalized absolute pathname .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "char *canonicalize_file_name(const char *" path ");" .fi .sh description the .br canonicalize_file_name () function returns a null-terminated string containing the canonicalized absolute pathname corresponding to .ir path . in the returned string, symbolic links are resolved, as are .i . and .i .. pathname components. consecutive slash .ri ( / ) characters are replaced by a single slash. .pp the returned string is dynamically allocated by .br canonicalize_file_name () and the caller should deallocate it with .br free (3) when it is no longer required. .pp the call .i canonicalize_file_name(path) is equivalent to the call: .pp realpath(path, null); .sh return value on success, .br canonicalize_file_name () returns a null-terminated string. on error (e.g., a pathname component is unreadable or does not exist), .br canonicalize_file_name () returns null and sets .i errno to indicate the error. .sh errors see .br realpath (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br canonicalize_file_name () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a gnu extension. .sh see also .br readlink (2), .br realpath (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" thu may 20 20:45:48 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:11:07 1993 by rik faith (faith@cs.unc.edu) .\" modified sun nov 21 10:49:38 1993 by michael haardt .\" modified sun feb 26 15:09:15 1995 by rik faith (faith@cs.unc.edu) .th shells 5 2020-06-09 "" "linux programmer's manual" .sh name shells \- pathnames of valid login shells .sh description .i /etc/shells is a text file which contains the full pathnames of valid login shells. this file is consulted by .br chsh (1) and available to be queried by other programs. .pp be aware that there are programs which consult this file to find out if a user is a normal user; for example, ftp daemons traditionally disallow access to users with shells not included in this file. .sh files .i /etc/shells .sh examples .i /etc/shells may contain the following paths: .pp .in +4n .ex .i /bin/sh .i /bin/bash .i /bin/csh .ee .in .sh see also .br chsh (1), .br getusershell (3), .br pam_shells (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" @(#)des_crypt.3 2.1 88/08/11 4.0 rpcsrc; from 1.16 88/03/02 smi; .\" .\" taken from libc4 sources, which say: .\" copyright (c) 1993 eric young - can be distributed under gpl. .\" .\" however, the above header line suggests that this file in fact is .\" copyright sun microsystems, inc (and is provided for unrestricted use, .\" see other sun rpc sources). .\" .\" %%%license_start(gpl_noversion_oneline) .\" can be distributed under gpl. .\" %%%license_end .\" .th des_crypt 3 2021-03-22 "" "linux programmer's manual" .sh name des_crypt, ecb_crypt, cbc_crypt, des_setparity, des_failed \- fast des encryption .sh synopsis .nf .\" sun version .\" .b #include .b #include .pp .bi "int ecb_crypt(char *" key ", char *" data ", unsigned int " datalen , .bi " unsigned int " mode ); .bi "int cbc_crypt(char *" key ", char *" data ", unsigned int " datalen , .bi " unsigned int " mode ", char *" ivec ); .pp .bi "void des_setparity(char *" key ); .pp .bi "int des_failed(int " status ); .fi .sh description .br ecb_crypt () and .br cbc_crypt () implement the nbs des (data encryption standard). these routines are faster and more general purpose than .br crypt (3). they also are able to utilize des hardware if it is available. .br ecb_crypt () encrypts in ecb (electronic code book) mode, which encrypts blocks of data independently. .br cbc_crypt () encrypts in cbc (cipher block chaining) mode, which chains together successive blocks. cbc mode protects against insertions, deletions, and substitutions of blocks. also, regularities in the clear text will not appear in the cipher text. .pp here is how to use these routines. the first argument, .ir key , is the 8-byte encryption key with parity. to set the key's parity, which for des is in the low bit of each byte, use .br des_setparity (). the second argument, .ir data , contains the data to be encrypted or decrypted. the third argument, .ir datalen , is the length in bytes of .ir data , which must be a multiple of 8. the fourth argument, .ir mode , is formed by oring together some things. for the encryption direction or in either .br des_encrypt or .br des_decrypt . for software versus hardware encryption, or in either .br des_hw or .br des_sw . if .br des_hw is specified, and there is no hardware, then the encryption is performed in software and the routine returns .br deserr_nohwdevice . for .br cbc_crypt (), the argument .i ivec is the 8-byte initialization vector for the chaining. it is updated to the next initialization vector upon return. .sh return value .tp .br deserr_none no error. .tp .br deserr_nohwdevice encryption succeeded, but done in software instead of the requested hardware. .tp .br deserr_hwerror an error occurred in the hardware or driver. .tp .br deserr_badparam bad argument to routine. .pp given a result status .ir stat , the macro .\" .br des_failed\c .\" .br ( stat ) .bi des_failed( stat ) is false only for the first two statuses. .\" so far the sun page .\" some additions - aeb .sh versions these functions were added to glibc in version 2.1. .pp because they employ the des block cipher, which is no longer considered secure, .br ecb_crypt (), .br ecb_crypt (), .br crypt_r (), and .br des_setparity () were removed in glibc 2.28. applications should switch to a modern cryptography library, such as .br libgcrypt . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ecb_crypt (), .br cbc_crypt (), .br des_setparity () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd. not in posix.1. .sh see also .br des (1), .br crypt (3), .br xcrypt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-1.7 .so man3/pthread_spin_init.3 .so man3/ether_aton.3 .so man3/stailq.3 .so man3/xdr.3 .so man3/cpu_set.3 .so man3/termios.3 .\" copyright (c) 2001 bert hubert .\" and copyright (c) 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created sun jun 3 17:23:32 2001 by bert hubert .\" slightly adapted, following comments by hugh dickins, aeb, 2001-06-04. .\" modified, 20 may 2003, michael kerrisk .\" modified, 30 apr 2004, michael kerrisk .\" 2005-04-05 mtk, fixed error descriptions .\" after message from .\" 2007-01-08 mtk, rewrote various parts .\" .th mincore 2 2021-03-22 "linux" "linux programmer's manual" .sh name mincore \- determine whether pages are resident in memory .sh synopsis .nf .b #include .pp .bi "int mincore(void *" addr ", size_t " length ", unsigned char *" vec ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mincore (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description .br mincore () returns a vector that indicates whether pages of the calling process's virtual memory are resident in core (ram), and so will not cause a disk access (page fault) if referenced. the kernel returns residency information about the pages starting at the address .ir addr , and continuing for .i length bytes. .pp the .i addr argument must be a multiple of the system page size. the .i length argument need not be a multiple of the page size, but since residency information is returned for whole pages, .i length is effectively rounded up to the next multiple of the page size. one may obtain the page size .rb ( page_size ) using .ir sysconf(_sc_pagesize) . .pp the .i vec argument must point to an array containing at least .i "(length+page_size\-1) / page_size" bytes. on return, the least significant bit of each byte will be set if the corresponding page is currently resident in memory, and be clear otherwise. (the settings of the other bits in each byte are undefined; these bits are reserved for possible later use.) of course the information returned in .i vec is only a snapshot: pages that are not locked in memory can come and go at any moment, and the contents of .i vec may already be stale by the time this call returns. .sh return value on success, .br mincore () returns zero. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .b eagain kernel is temporarily out of resources. .tp .b efault .i vec points to an invalid address. .tp .b einval .i addr is not a multiple of the page size. .tp .b enomem .i length is greater than .ri ( task_size " \- " addr ). (this could occur if a negative value is specified for .ir length , since that value will be interpreted as a large unsigned integer.) in linux 2.6.11 and earlier, the error .b einval was returned for this condition. .tp .b enomem .i addr to .i addr + .i length contained unmapped memory. .sh versions available since linux 2.3.99pre1 and glibc 2.2. .sh conforming to .br mincore () is not specified in posix.1, and it is not available on all unix implementations. .\" it is on at least netbsd, freebsd, openbsd, solaris 8, .\" aix 5.1, sunos 4.1 .\" .sh history .\" the .\" .br mincore () .\" function first appeared in 4.4bsd. .sh bugs before kernel 2.6.21, .br mincore () did not return correct information for .b map_private mappings, or for nonlinear mappings (established using .br remap_file_pages (2)). .\" linux (up to now, 2.6.5), .\" .b mincore .\" does not return correct information for map_private mappings: .\" for a map_private file mapping, .\" .b mincore .\" returns the residency of the file pages, rather than any .\" modified process-private pages that have been copied on write; .\" for a map_private mapping of .\" .ir /dev/zero , .\" .b mincore .\" always reports pages as nonresident; .\" and for a map_private, map_anonymous mapping, .\" .b mincore .\" always fails with the error .\" .br enomem . .sh see also .br fincore (1), .br madvise (2), .br mlock (2), .br mmap (2), .br posix_fadvise (2), .br posix_madvise (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sigwait 3 2021-03-22 "linux" "linux programmer's manual" .sh name sigwait \- wait for a signal .sh synopsis .nf .b #include .pp .bi "int sigwait(const sigset_t *restrict " set ", int *restrict " sig ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigwait (): .nf since glibc 2.26: _posix_c_source >= 199506l glibc 2.25 and earlier: _posix_c_source .fi .sh description the .br sigwait () function suspends execution of the calling thread until one of the signals specified in the signal set .ir set becomes pending. the function accepts the signal (removes it from the pending list of signals), and returns the signal number in .ir sig . .pp the operation of .br sigwait () is the same as .br sigwaitinfo (2), except that: .ip * 2 .br sigwait () returns only the signal number, rather than a .i siginfo_t structure describing the signal. .ip * the return values of the two functions are different. .sh return value on success, .br sigwait () returns 0. on error, it returns a positive error number (listed in errors). .sh errors .tp .b einval .\" does not occur for glibc. .i set contains an invalid signal number. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigwait () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes .br sigwait () is implemented using .br sigtimedwait (2). .pp the glibc implementation of .br sigwait () silently ignores attempts to wait for the two real-time signals that are used internally by the nptl threading implementation. see .br nptl (7) for details. .sh examples see .br pthread_sigmask (3). .sh see also .br sigaction (2), .br signalfd (2), .br sigpending (2), .br sigsuspend (2), .br sigwaitinfo (2), .br sigsetops (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th wordexp 3 2021-08-27 "" "linux programmer's manual" .sh name wordexp, wordfree \- perform word expansion like a posix-shell .sh synopsis .nf .b "#include " .pp .bi "int wordexp(const char *restrict " s ", wordexp_t *restrict " p \ ", int " flags ); .bi "void wordfree(wordexp_t *" p ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wordexp (), .br wordfree (): .nf _xopen_source .fi .sh description the function .br wordexp () performs a shell-like expansion of the string .i s and returns the result in the structure pointed to by .ir p . the data type .i wordexp_t is a structure that at least has the fields .ir we_wordc , .ir we_wordv , and .ir we_offs . the field .i we_wordc is a .i size_t that gives the number of words in the expansion of .ir s . the field .i we_wordv is a .i "char\ **" that points to the array of words found. the field .i we_offs of type .i size_t is sometimes (depending on .ir flags , see below) used to indicate the number of initial elements in the .i we_wordv array that should be filled with nulls. .pp the function .br wordfree () frees the allocated memory again. more precisely, it does not free its argument, but it frees the array .i we_wordv and the strings that points to. .ss the string argument since the expansion is the same as the expansion by the shell (see .br sh (1)) of the parameters to a command, the string .i s must not contain characters that would be illegal in shell command parameters. in particular, there must not be any unescaped newline or |, &, ;, <, >, (, ), {, } characters outside a command substitution or parameter substitution context. .pp if the argument .i s contains a word that starts with an unquoted comment character #, then it is unspecified whether that word and all following words are ignored, or the # is treated as a non-comment character. .ss the expansion the expansion done consists of the following stages: tilde expansion (replacing \(tiuser by user's home directory), variable substitution (replacing $foo by the value of the environment variable foo), command substitution (replacing $(command) or \`command\` by the output of command), arithmetic expansion, field splitting, wildcard expansion, quote removal. .pp the result of expansion of special parameters ($@, $*, $#, $?, $\-, $$, $!, $0) is unspecified. .pp field splitting is done using the environment variable $ifs. if it is not set, the field separators are space, tab, and newline. .ss the output array the array .i we_wordv contains the words found, followed by a null. .ss the flags argument the .i flag argument is a bitwise inclusive or of the following values: .tp .b wrde_append append the words found to the array resulting from a previous call. .tp .b wrde_dooffs insert .i we_offs initial nulls in the array .ir we_wordv . (these are not counted in the returned .ir we_wordc .) .tp .b wrde_nocmd don't do command substitution. .tp .b wrde_reuse the argument .i p resulted from a previous call to .br wordexp (), and .br wordfree () was not called. reuse the allocated storage. .tp .b wrde_showerr normally during command substitution .i stderr is redirected to .ir /dev/null . this flag specifies that .i stderr is not to be redirected. .tp .b wrde_undef consider it an error if an undefined shell variable is expanded. .sh return value on success, .br wordexp () returns 0. on failure, .br wordexp () returns one of the following nonzero values: .tp .b wrde_badchar illegal occurrence of newline or one of |, &, ;, <, >, (, ), {, }. .tp .b wrde_badval an undefined shell variable was referenced, and the .b wrde_undef flag told us to consider this an error. .tp .b wrde_cmdsub command substitution requested, but the .b wrde_nocmd flag told us to consider this an error. .tp .b wrde_nospace out of memory. .tp .b wrde_syntax shell syntax error, such as unbalanced parentheses or unmatched quotes. .sh versions .br wordexp () and .br wordfree () are provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br wordexp () t} thread safety t{ mt-unsafe race:utent const:env env sig:alrm timer locale t} t{ .br wordfree () t} thread safety mt-safe .te .hy .ad .sp 1 in the above table, .i utent in .i race:utent signifies that if any of the functions .br setutent (3), .br getutent (3), or .br endutent (3) are used in parallel in different threads of a program, then data races could occur. .br wordexp () calls those functions, so we use race:utent to remind users. .sh conforming to posix.1-2001, posix.1-2008. .sh examples the output of the following example program is approximately that of "ls [a-c]*.c". .pp .ex #include #include #include int main(int argc, char *argv[]) { wordexp_t p; char **w; wordexp("[a\-c]*.c", &p, 0); w = p.we_wordv; for (int i = 0; i < p.we_wordc; i++) printf("%s\en", w[i]); wordfree(&p); exit(exit_success); } .ee .sh see also .br fnmatch (3), .br glob (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wctomb 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wctomb \- convert a wide character to a multibyte sequence .sh synopsis .nf .b #include .pp .bi "int wctomb(char *" s ", wchar_t " wc ); .fi .sh description if .i s is not null, the .br wctomb () function converts the wide character .i wc to its multibyte representation and stores it at the beginning of the character array pointed to by .ir s . it updates the shift state, which is stored in a static anonymous variable known only to the .br wctomb () function, and returns the length of said multibyte representation, that is, the number of bytes written at .ir s . .pp the programmer must ensure that there is room for at least .b mb_cur_max bytes at .ir s . .pp if .i s is null, the .br wctomb () function .\" the dinkumware doc and the single unix specification say this, but .\" glibc doesn't implement this. resets the shift state, known only to this function, to the initial state, and returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless. .sh return value if .i s is not null, the .br wctomb () function returns the number of bytes that have been written to the byte array at .ir s . if .i wc can not be represented as a multibyte sequence (according to the current locale), \-1 is returned. .pp if .i s is null, the .br wctomb () function returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wctomb () t} thread safety mt-unsafe race .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wctomb () depends on the .b lc_ctype category of the current locale. .pp the function .br wcrtomb (3) provides a better interface to the same functionality. .sh see also .br mb_cur_max (3), .br mblen (3), .br mbstowcs (3), .br mbtowc (3), .br wcrtomb (3), .br wcstombs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995 jim van zandt and aeb .\" sun feb 26 11:46:23 met 1995 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified, sun feb 26 15:04:20 1995, faith@cs.unc.edu .\" modified, thu apr 20 22:08:17 1995, jrv@vanzandt.mv.com .\" modified, mon sep 18 22:32:47 1995, hpa@storm.net (h. peter anvin) .\" fixme the following are not documented: .\" kdfontop (since 2.1.111) .\" kdgkbdiacruc (since 2.6.24) .\" kdskbdiacr .\" kdskbdiacruc (since 2.6.24) .\" kdkbdrep (since 2.1.113) .\" kdmapdisp (not implemented as at 2.6.27) .\" kdunmapdisp (not implemented as at 2.6.27) .\" vt_lockswitch (since 1.3.47, needs cap_sys_tty_config) .\" vt_unlockswitch (since 1.3.47, needs cap_sys_tty_config) .\" vt_gethifontmask (since 2.6.18) .\" .th ioctl_console 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_console \- ioctls for console terminal and virtual consoles .sh description the following linux-specific .br ioctl (2) requests are supported for console terminals and virtual consoles. each requires a third argument, assumed here to be .ir argp . .tp .b kdgetled get state of leds. .i argp points to a .ir char . the lower three bits of .i *argp are set to the state of the leds, as follows: .ts l l l. led_cap 0x04 caps lock led led_num 0x02 num lock led led_scr 0x01 scroll lock led .te .tp .b kdsetled set the leds. the leds are set to correspond to the lower three bits of the unsigned long integer in .ir argp . however, if a higher order bit is set, the leds revert to normal: displaying the state of the keyboard functions of caps lock, num lock, and scroll lock. .pp before linux 1.1.54, the leds just reflected the state of the corresponding keyboard flags, and kdgetled/kdsetled would also change the keyboard flags. since linux 1.1.54 the leds can be made to display arbitrary information, but by default they display the keyboard flags. the following two ioctls are used to access the keyboard flags. .tp .b kdgkbled get keyboard flags capslock, numlock, scrolllock (not lights). .i argp points to a char which is set to the flag state. the low order three bits (mask 0x7) get the current flag state, and the low order bits of the next nibble (mask 0x70) get the default flag state. (since linux 1.1.54.) .tp .b kdskbled set keyboard flags capslock, numlock, scrolllock (not lights). .i argp is an unsigned long integer that has the desired flag state. the low order three bits (mask 0x7) have the flag state, and the low order bits of the next nibble (mask 0x70) have the default flag state. (since linux 1.1.54.) .tp .b kdgkbtype get keyboard type. this returns the value kb_101, defined as 0x02. .tp .b kdaddio add i/o port as valid. equivalent to .ir ioperm(arg,1,1) . .tp .b kddelio delete i/o port as valid. equivalent to .ir ioperm(arg,1,0) . .tp .b kdenabio enable i/o to video board. equivalent to .ir "ioperm(0x3b4, 0x3df\-0x3b4+1, 1)" . .tp .b kddisabio disable i/o to video board. equivalent to .ir "ioperm(0x3b4, 0x3df\-0x3b4+1, 0)" . .tp .b kdsetmode set text/graphics mode. .i argp is an unsigned integer containing one of: .ts l l. kd_text 0x00 kd_graphics 0x01 .te .tp .b kdgetmode get text/graphics mode. .i argp points to an .i int which is set to one of the values shown above for .br kdsetmode . .tp .b kdmktone generate tone of specified length. the lower 16 bits of the unsigned long integer in .i argp specify the period in clock cycles, and the upper 16 bits give the duration in msec. if the duration is zero, the sound is turned off. control returns immediately. for example, .i argp = (125<<16) + 0x637 would specify the beep normally associated with a ctrl-g. (thus since linux 0.99pl1; broken in linux 2.1.49-50.) .tp .b kiocsound start or stop sound generation. the lower 16 bits of .i argp specify the period in clock cycles (that is, .i argp = 1193180/frequency). .i argp = 0 turns sound off. in either case, control returns immediately. .tp .b gio_cmap get the current default color map from kernel. .i argp points to a 48-byte array. (since linux 1.3.3.) .tp .b pio_cmap change the default text-mode color map. .i argp points to a 48-byte array which contains, in order, the red, green, and blue values for the 16 available screen colors: 0 is off, and 255 is full intensity. the default colors are, in order: black, dark red, dark green, brown, dark blue, dark purple, dark cyan, light grey, dark grey, bright red, bright green, yellow, bright blue, bright purple, bright cyan, and white. (since linux 1.3.3.) .tp .b gio_font gets 256-character screen font in expanded form. .i argp points to an 8192-byte array. fails with error code .b einval if the currently loaded font is a 512-character font, or if the console is not in text mode. .tp .b gio_fontx gets screen font and associated information. .i argp points to a .i "struct consolefontdesc" (see .br pio_fontx ). on call, the .i charcount field should be set to the maximum number of characters that would fit in the buffer pointed to by .ir chardata . on return, the .i charcount and .i charheight are filled with the respective data for the currently loaded font, and the .i chardata array contains the font data if the initial value of .i charcount indicated enough space was available; otherwise the buffer is untouched and .i errno is set to .br enomem . (since linux 1.3.1.) .tp .b pio_font sets 256-character screen font. load font into the ega/vga character generator. .i argp points to an 8192-byte map, with 32 bytes per character. only the first .i n of them are used for an 8x\fin\fp font (0 < .i n <= 32). this call also invalidates the unicode mapping. .tp .b pio_fontx sets screen font and associated rendering information. .i argp points to a .ip .in +4n .ex struct consolefontdesc { unsigned short charcount; /* characters in font (256 or 512) */ unsigned short charheight; /* scan lines per character (1\-32) */ char *chardata; /* font data in expanded form */ }; .ee .in .ip if necessary, the screen will be appropriately resized, and .b sigwinch sent to the appropriate processes. this call also invalidates the unicode mapping. (since linux 1.3.1.) .tp .b pio_fontreset resets the screen font, size, and unicode mapping to the bootup defaults. .i argp is unused, but should be set to null to ensure compatibility with future versions of linux. (since linux 1.3.28.) .tp .b gio_scrnmap get screen mapping from kernel. .i argp points to an area of size e_tabsz, which is loaded with the font positions used to display each character. this call is likely to return useless information if the currently loaded font is more than 256 characters. .tp .b gio_uniscrnmap get full unicode screen mapping from kernel. .i argp points to an area of size .ir "e_tabsz*sizeof(unsigned short)" , which is loaded with the unicodes each character represent. a special set of unicodes, starting at u+f000, are used to represent "direct to font" mappings. (since linux 1.3.1.) .tp .b pio_scrnmap loads the "user definable" (fourth) table in the kernel which maps bytes into console screen symbols. .i argp points to an area of size e_tabsz. .tp .b pio_uniscrnmap loads the "user definable" (fourth) table in the kernel which maps bytes into unicodes, which are then translated into screen symbols according to the currently loaded unicode-to-font map. special unicodes starting at u+f000 can be used to map directly to the font symbols. (since linux 1.3.1.) .tp .b gio_unimap get unicode-to-font mapping from kernel. .i argp points to a .ip .in +4n .ex struct unimapdesc { unsigned short entry_ct; struct unipair *entries; }; .ee .in .ip where .i entries points to an array of .ip .in +4n .ex struct unipair { unsigned short unicode; unsigned short fontpos; }; .ee .in .ip (since linux 1.1.92.) .tp .b pio_unimap put unicode-to-font mapping in kernel. .i argp points to a .ir "struct unimapdesc" . (since linux 1.1.92) .tp .b pio_unimapclr clear table, possibly advise hash algorithm. .i argp points to a .ip .in +4n .ex struct unimapinit { unsigned short advised_hashsize; /* 0 if no opinion */ unsigned short advised_hashstep; /* 0 if no opinion */ unsigned short advised_hashlevel; /* 0 if no opinion */ }; .ee .in .ip (since linux 1.1.92.) .tp .b kdgkbmode gets current keyboard mode. .i argp points to a .i long which is set to one of these: .ts l l. k_raw 0x00 /* raw (scancode) mode */ k_xlate 0x01 /* translate keycodes using keymap */ k_mediumraw 0x02 /* medium raw (scancode) mode */ k_unicode 0x03 /* unicode mode */ k_off 0x04 /* disabled mode; since linux 2.6.39 */ .\" k_off: commit 9fc3de9c83565fcaa23df74c2fc414bb6e7efb0a .te .tp .b kdskbmode sets current keyboard mode. .i argp is a .i long equal to one of the values shown for .br kdgkbmode . .tp .b kdgkbmeta gets meta key handling mode. .i argp points to a .i long which is set to one of these: .ts l l l. k_metabit 0x03 set high order bit k_escprefix 0x04 escape prefix .te .tp .b kdskbmeta sets meta key handling mode. .i argp is a .i long equal to one of the values shown above for .br kdgkbmeta . .tp .b kdgkbent gets one entry in key translation table (keycode to action code). .i argp points to a .ip .in +4n .ex struct kbentry { unsigned char kb_table; unsigned char kb_index; unsigned short kb_value; }; .ee .in .ip with the first two members filled in: .i kb_table selects the key table (0 <= .i kb_table < max_nr_keymaps), and .ir kb_index is the keycode (0 <= .i kb_index < nr_keys). .i kb_value is set to the corresponding action code, or k_hole if there is no such key, or k_nosuchmap if .i kb_table is invalid. .tp .b kdskbent sets one entry in translation table. .i argp points to a .ir "struct kbentry" . .tp .b kdgkbsent gets one function key string. .i argp points to a .ip .in +4n .ex struct kbsentry { unsigned char kb_func; unsigned char kb_string[512]; }; .ee .in .ip .i kb_string is set to the (null-terminated) string corresponding to the .ir kb_func th function key action code. .tp .b kdskbsent sets one function key string entry. .i argp points to a .ir "struct kbsentry" . .tp .b kdgkbdiacr read kernel accent table. .i argp points to a .ip .in +4n .ex struct kbdiacrs { unsigned int kb_cnt; struct kbdiacr kbdiacr[256]; }; .ee .in .ip where .i kb_cnt is the number of entries in the array, each of which is a .ip .in +4n .ex struct kbdiacr { unsigned char diacr; unsigned char base; unsigned char result; }; .ee .in .tp .b kdgetkeycode read kernel keycode table entry (scan code to keycode). .i argp points to a .ip .in +4n .ex struct kbkeycode { unsigned int scancode; unsigned int keycode; }; .ee .in .ip .i keycode is set to correspond to the given .ir scancode . (89 <= .i scancode <= 255 only. for 1 <= .i scancode <= 88, .ir keycode == scancode .) (since linux 1.1.63.) .tp .b kdsetkeycode write kernel keycode table entry. .i argp points to a .ir "struct kbkeycode" . (since linux 1.1.63.) .tp .b kdsigaccept the calling process indicates its willingness to accept the signal .i argp when it is generated by pressing an appropriate key combination. (1 <= .i argp <= nsig). (see .ir spawn_console () in .ir linux/drivers/char/keyboard.c .) .tp .b vt_openqry returns the first available (non-opened) console. .i argp points to an .i int which is set to the number of the vt (1 <= .i *argp <= max_nr_consoles). .tp .b vt_getmode get mode of active vt. .i argp points to a .ip .in +4n .ex struct vt_mode { char mode; /* vt mode */ char waitv; /* if set, hang on writes if not active */ short relsig; /* signal to raise on release req */ short acqsig; /* signal to raise on acquisition */ short frsig; /* unused (set to 0) */ }; .ee .in .ip which is set to the mode of the active vt. .i mode is set to one of these values: .ts l l. vt_auto auto vt switching vt_process process controls switching vt_ackacq acknowledge switch .te .tp .b vt_setmode set mode of active vt. .i argp points to a .ir "struct vt_mode" . .tp .b vt_getstate get global vt state info. .i argp points to a .ip .in +4n .ex struct vt_stat { unsigned short v_active; /* active vt */ unsigned short v_signal; /* signal to send */ unsigned short v_state; /* vt bit mask */ }; .ee .in .ip for each vt in use, the corresponding bit in the .i v_state member is set. (kernels 1.0 through 1.1.92.) .tp .b vt_reldisp release a display. .tp .b vt_activate switch to vt .ir argp (1 <= .i argp <= max_nr_consoles). .tp .b vt_waitactive wait until vt .i argp has been activated. .tp .b vt_disallocate deallocate the memory associated with vt .ir argp . (since linux 1.1.54.) .tp .b vt_resize set the kernel's idea of screensize. .i argp points to a .ip .in +4n .ex struct vt_sizes { unsigned short v_rows; /* # rows */ unsigned short v_cols; /* # columns */ unsigned short v_scrollsize; /* no longer used */ }; .ee .in .ip note that this does not change the videomode. see .br resizecons (8). (since linux 1.1.54.) .tp .b vt_resizex set the kernel's idea of various screen parameters. .i argp points to a .ip .in +4n .ex struct vt_consize { unsigned short v_rows; /* number of rows */ unsigned short v_cols; /* number of columns */ unsigned short v_vlin; /* number of pixel rows on screen */ unsigned short v_clin; /* number of pixel rows per character */ unsigned short v_vcol; /* number of pixel columns on screen */ unsigned short v_ccol; /* number of pixel columns per character */ }; .ee .in .ip any parameter may be set to zero, indicating "no change", but if multiple parameters are set, they must be self-consistent. note that this does not change the videomode. see .br resizecons (8). (since linux 1.3.3.) .pp the action of the following ioctls depends on the first byte in the struct pointed to by .ir argp , referred to here as the .ir subcode . these are legal only for the superuser or the owner of the current terminal. .tp .b "tioclinux, subcode=0" dump the screen. disappeared in linux 1.1.92. (with kernel 1.1.92 or later, read from .i /dev/vcsn or .i /dev/vcsan instead.) .tp .b "tioclinux, subcode=1" get task information. disappeared in linux 1.1.92. .tp .b "tioclinux, subcode=2" set selection. .i argp points to a .ip .in +4n .ex struct { char subcode; short xs, ys, xe, ye; short sel_mode; }; .ee .in .ip .i xs and .i ys are the starting column and row. .i xe and .i ye are the ending column and row. (upper left corner is row=column=1.) .i sel_mode is 0 for character-by-character selection, 1 for word-by-word selection, or 2 for line-by-line selection. the indicated screen characters are highlighted and saved in the static array sel_buffer in .ir devices/char/console.c . .tp .b "tioclinux, subcode=3" paste selection. the characters in the selection buffer are written to .ir fd . .tp .b "tioclinux, subcode=4" unblank the screen. .tp .b "tioclinux, subcode=5" sets contents of a 256-bit look up table defining characters in a "word", for word-by-word selection. (since linux 1.1.32.) .tp .b "tioclinux, subcode=6" .i argp points to a char which is set to the value of the kernel variable .ir shift_state . (since linux 1.1.32.) .tp .b "tioclinux, subcode=7" .i argp points to a char which is set to the value of the kernel variable .ir report_mouse . (since linux 1.1.33.) .tp .b "tioclinux, subcode=8" dump screen width and height, cursor position, and all the character-attribute pairs. (kernels 1.1.67 through 1.1.91 only. with kernel 1.1.92 or later, read from .i /dev/vcsa* instead.) .tp .b "tioclinux, subcode=9" restore screen width and height, cursor position, and all the character-attribute pairs. (kernels 1.1.67 through 1.1.91 only. with kernel 1.1.92 or later, write to .i /dev/vcsa* instead.) .tp .b "tioclinux, subcode=10" handles the power saving feature of the new generation of monitors. vesa screen blanking mode is set to .ir argp[1] , which governs what screen blanking does: .rs .ip 0: 3 screen blanking is disabled. .ip 1: the current video adapter register settings are saved, then the controller is programmed to turn off the vertical synchronization pulses. this puts the monitor into "standby" mode. if your monitor has an off_mode timer, then it will eventually power down by itself. .ip 2: the current settings are saved, then both the vertical and horizontal synchronization pulses are turned off. this puts the monitor into "off" mode. if your monitor has no off_mode timer, or if you want your monitor to power down immediately when the blank_timer times out, then you choose this option. .ri ( caution: powering down frequently will damage the monitor.) (since linux 1.1.76.) .re .sh return value on success, 0 is returned. on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf the file descriptor is invalid. .tp .b einval the file descriptor or .i argp is invalid. .tp .b enotty the file descriptor is not associated with a character special device, or the specified request does not apply to it. .tp .b eperm insufficient permission. .sh notes .br warning : do not regard this man page as documentation of the linux console ioctls. this is provided for the curious only, as an alternative to reading the source. ioctl's are undocumented linux internals, liable to be changed without warning. (and indeed, this page more or less describes the situation as of kernel version 1.1.94; there are many minor and not-so-minor differences with earlier versions.) .pp very often, ioctls are introduced for communication between the kernel and one particular well-known program (fdisk, hdparm, setserial, tunelp, loadkeys, selection, setfont, etc.), and their behavior will be changed when required by this particular program. .pp programs using these ioctls will not be portable to other versions of unix, will not work on older versions of linux, and will not work on future versions of linux. .pp use posix functions. .sh see also .br dumpkeys (1), .br kbd_mode (1), .br loadkeys (1), .br mknod (1), .br setleds (1), .br setmetamode (1), .br execve (2), .br fcntl (2), .br ioctl_tty (2), .br ioperm (2), .br termios (3), .br console_codes (4), .br mt (4), .br sd (4), .br tty (4), .br ttys (4), .br vcs (4), .br vcsa (4), .br charsets (7), .br mapscrn (8), .br resizecons (8), .br setfont (8) .pp .ir /usr/include/linux/kd.h , .i /usr/include/linux/vt.h .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:39:35 1993 by rik faith (faith@cs.unc.edu) .\" .\" modified 2003 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .th ffs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ffs, ffsl, ffsll \- find first bit set in a word .sh synopsis .nf .b #include .pp .bi "int ffs(int " i ); .pp .b #include .pp .bi "int ffsl(long " i ); .bi "int ffsll(long long " i ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br ffs (): .nf since glibc 2.12: _xopen_source >= 700 || ! (_posix_c_source >= 200809l) || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source before glibc 2.12: none .fi .pp .br ffsl (), .br ffsll (): .nf since glibc 2.27: .\" glibc commit 68fe16dd327c895c08b9ee443b234c49c13b36e9 _default_source before glibc 2.27: _gnu_source .fi .sh description the .br ffs () function returns the position of the first (least significant) bit set in the word \fii\fp. the least significant bit is position 1 and the most significant position is, for example, 32 or 64. the functions .br ffsll () and .br ffsl () do the same but take arguments of possibly different size. .sh return value these functions return the position of the first bit set, or 0 if no bits are set in .ir i . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ffs (), .br ffsl (), .br ffsll () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br ffs (): posix.1-2001, posix.1-2008, 4.3bsd. .pp the .br ffsl () and .br ffsll () functions are glibc extensions. .sh notes bsd systems have a prototype in .ir . .sh see also .br memchr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2004 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th finite 3 2021-03-22 "" "linux programmer's manual" .sh name finite, finitef, finitel, isinf, isinff, isinfl, isnan, isnanf, isnanl \- bsd floating-point classification functions .sh synopsis .nf .b #include .pp .bi "int finite(double " x ); .bi "int finitef(float " x ); .bi "int finitel(long double " x ); .pp .bi "int isinf(double " x ); .bi "int isinff(float " x ); .bi "int isinfl(long double " x ); .pp .bi "int isnan(double " x ); .bi "int isnanf(float " x ); .bi "int isnanl(long double " x ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br finite (), .br finitef (), .br finitel (): .nf /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .pp .br isinf (): _xopen_source >= 600 || _isoc99_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br isinff (), .br isinfl (): .nf /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br isnan (): .nf _xopen_source || _isoc99_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br isnanf (), .br isnanl (): .nf _xopen_source >= 600 || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br finite (), .br finitef (), and .br finitel () functions return a nonzero value if .i x is neither infinite nor a "not-a-number" (nan) value, and 0 otherwise. .pp the .br isnan (), .br isnanf (), and .br isnanl () functions return a nonzero value if .i x is a nan value, and 0 otherwise. .pp the .br isinf (), .br isinff (), and .br isinfl () functions return 1 if .i x is positive infinity, \-1 if .i x is negative infinity, and 0 otherwise. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br finite (), .br finitef (), .br finitel (), .br isinf (), .br isinff (), .br isinfl (), .br isnan (), .br isnanf (), .br isnanl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh notes note that these functions are obsolete. c99 defines macros .br isfinite (), .br isinf (), and .br isnan () (for all types) replacing them. further note that the c99 .br isinf () has weaker guarantees on the return value. see .br fpclassify (3). .\" .\" finite* not on hp-ux; they exist on tru64. .\" .sh history .\" the .\" .br finite () .\" function occurs in 4.3bsd. .\" see ieee.3 in the 4.3bsd manual .sh see also .br fpclassify (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/atanh.3 .so man3/regex.3 .so man3/get_nprocs_conf.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:02:26 1993 by rik faith (faith@cs.unc.edu) .th strlen 3 2021-08-27 "gnu" "linux programmer's manual" .sh name strlen \- calculate the length of a string .sh synopsis .nf .b #include .pp .bi "size_t strlen(const char *" s ); .fi .sh description the .br strlen () function calculates the length of the string pointed to by .ir s , excluding the terminating null byte (\(aq\e0\(aq). .sh return value the .br strlen () function returns the number of bytes in the string pointed to by .ir s . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strlen () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, c11, svr4, 4.3bsd. .sh notes in cases where the input buffer may not contain a terminating null byte, .br strnlen (3) should be used instead. .sh see also .br string (3), .br strnlen (3), .br wcslen (3), .br wcsnlen (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2005, 2014, 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:05:30 1993 by rik faith .\" modified fri feb 16 14:25:17 1996 by andries brouwer .\" modified sun jul 21 20:55:44 1996 by andries brouwer .\" modified mon oct 15 21:16:25 2001 by john levon .\" modified tue oct 16 00:04:43 2001 by andries brouwer .\" modified fri jun 20 03:04:30 2003 by andries brouwer .\" 2005-12-13, mtk, substantial rewrite of strerror_r() description .\" addition of extra material on portability and standards. .\" .th strerror 3 2021-03-22 "" "linux programmer's manual" .sh name strerror, strerrorname_np, strerrordesc_np, strerror_r, strerror_l \- return string describing error number .sh synopsis .nf .b #include .pp .bi "char *strerror(int " errnum ); .bi "const char *strerrorname_np(int " errnum ); .bi "const char *strerrordesc_np(int " errnum ); .pp .bi "int strerror_r(int " errnum ", char *" buf ", size_t " buflen ); /* xsi-compliant */ .pp .bi "char *strerror_r(int " errnum ", char *" buf ", size_t " buflen ); /* gnu-specific */ .pp .bi "char *strerror_l(int " errnum ", locale_t " locale ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strerrorname_np (), .br strerrordesc_np (): .nf _gnu_source .fi .pp .br strerror_r (): .nf the xsi-compliant version is provided if: (_posix_c_source >= 200112l) && ! _gnu_source otherwise, the gnu-specific version is provided. .fi .sh description the .br strerror () function returns a pointer to a string that describes the error code passed in the argument .ir errnum , possibly using the .b lc_messages part of the current locale to select the appropriate language. (for example, if .i errnum is .br einval , the returned description will be "invalid argument".) this string must not be modified by the application, but may be modified by a subsequent call to .br strerror () or .br strerror_l (). no other library function, including .br perror (3), will modify this string. .pp like .br strerror (), the .br strerrordesc_np () function returns a pointer to a string that describes the error code passed in the argument .ir errnum , with the difference that the returned string is not translated according to the current locale. .pp the .br strerrorname_np () function returns a pointer to a string containing the name of the error code passed in the argument .ir errnum . for example, given .br eperm as an argument, this function returns a pointer to the string "eperm". .\" .ss strerror_r() the .br strerror_r () function is similar to .br strerror (), but is thread safe. this function is available in two versions: an xsi-compliant version specified in posix.1-2001 (available since glibc 2.3.4, but not posix-compliant until glibc 2.13), and a gnu-specific version (available since glibc 2.0). the xsi-compliant version is provided with the feature test macros settings shown in the synopsis; otherwise the gnu-specific version is provided. if no feature test macros are explicitly defined, then (since glibc 2.4) .b _posix_c_source is defined by default with the value 200112l, so that the xsi-compliant version of .br strerror_r () is provided by default. .pp the xsi-compliant .br strerror_r () is preferred for portable applications. it returns the error string in the user-supplied buffer .i buf of length .ir buflen . .pp the gnu-specific .br strerror_r () returns a pointer to a string containing the error message. this may be either a pointer to a string that the function stores in .ir buf , or a pointer to some (immutable) static string (in which case .i buf is unused). if the function stores a string in .ir buf , then at most .i buflen bytes are stored (the string may be truncated if .i buflen is too small and .i errnum is unknown). the string always includes a terminating null byte (\(aq\e0\(aq). .\" .ss strerror_l() .br strerror_l () is like .br strerror (), but maps .i errnum to a locale-dependent error message in the locale specified by .ir locale . the behavior of .br strerror_l () is undefined if .i locale is the special locale object .br lc_global_locale or is not a valid locale object handle. .sh return value the .br strerror (), .br strerror_l (), and the gnu-specific .br strerror_r () functions return the appropriate error description string, or an "unknown error nnn" message if the error number is unknown. .pp on success, .br strerrorname_np () and .br strerrordesc_np () return the appropriate error description string. if .i errnum is an invalid error number, these functions return null. .pp the xsi-compliant .br strerror_r () function returns 0 on success. on error, a (positive) error number is returned (since glibc 2.13), or \-1 is returned and .i errno is set to indicate the error (glibc versions before 2.13). .pp posix.1-2001 and posix.1-2008 require that a successful call to .br strerror () or .br strerror_l () shall leave .i errno unchanged, and note that, since no function return value is reserved to indicate an error, an application that wishes to check for errors should initialize .i errno to zero before the call, and then check .i errno after the call. .sh errors .tp .b einval the value of .i errnum is not a valid error number. .tp .b erange insufficient storage was supplied to contain the error description string. .sh versions the .br strerror_l () function first appeared in glibc 2.6. .pp the .br strerrorname_np () and .br strerrordesc_np () functions first appeared in glibc 2.32. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br strerror () t} thread safety t{ mt-unsafe race:strerror t} t{ .br strerrorname_np (), .br strerrordesc_np () t} thread safety mt-safe t{ .br strerror_r (), .br strerror_l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br strerror () is specified by posix.1-2001, posix.1-2008, c89, and c99. .br strerror_r () is specified by posix.1-2001 and posix.1-2008. .\" fixme . for later review when issue 8 is one day released... .\" a future posix.1 may remove strerror_r() .\" http://austingroupbugs.net/tag_view_page.php?tag_id=8 .\" http://austingroupbugs.net/view.php?id=508 .pp .br strerror_l () is specified in posix.1-2008. .pp the gnu-specific functions .br strerror_r (), .br strerrorname_np (), and .br strerrordesc_np () are nonstandard extensions. .pp posix.1-2001 permits .br strerror () to set .i errno if the call encounters an error, but does not specify what value should be returned as the function result in the event of an error. on some systems, .\" e.g., solaris 8, hp-ux 11 .br strerror () returns null if the error number is unknown. on other systems, .\" e.g., freebsd 5.4, tru64 5.1b .br strerror () returns a string something like "error nnn occurred" and sets .i errno to .b einval if the error number is unknown. c99 and posix.1-2008 require the return value to be non-null. .sh notes the gnu c library uses a buffer of 1024 characters for .br strerror (). this buffer size therefore should be sufficient to avoid an .b erange error when calling .br strerror_r (). .pp .br strerrorname_np () and .br strerrordesc_np () are thread-safe and async-signal-safe. .sh see also .br err (3), .br errno (3), .br error (3), .br perror (3), .br strsignal (3), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/finite.3 .\"copyright (c) 2010 novell inc., written by robert schweikert .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_rwlockattr_setkind_np 3 2021-03-22 "linux programmer's manual" .sh name pthread_rwlockattr_setkind_np, pthread_rwlockattr_getkind_np \- set/get the read-write lock kind of the thread read-write lock attribute object .sh synopsis .nf .b #include .pp .bi "int pthread_rwlockattr_setkind_np(pthread_rwlockattr_t *" attr , .bi " int " pref ); .bi "int pthread_rwlockattr_getkind_np(" .bi " const pthread_rwlockattr_t *restrict " attr , .bi " int *restrict " pref ); .pp compile and link with \fi\-pthread\fp. .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_rwlockattr_setkind_np (), .br pthread_rwlockattr_getkind_np (): .nf _xopen_source >= 500 || _posix_c_source >= 200809l .fi .sh description the .br pthread_rwlockattr_setkind_np () function sets the "lock kind" attribute of the read-write lock attribute object referred to by .i attr to the value specified in .ir pref . the argument .i pref may be set to one of the following: .tp .b pthread_rwlock_prefer_reader_np this is the default. a thread may hold multiple read locks; that is, read locks are recursive. according to the single unix specification, the behavior is unspecified when a reader tries to place a lock, and there is no write lock but writers are waiting. giving preference to the reader, as is set by .br pthread_rwlock_prefer_reader_np , implies that the reader will receive the requested lock, even if a writer is waiting. as long as there are readers, the writer will be starved. .tp .b pthread_rwlock_prefer_writer_np this is intended as the write lock analog of .br pthread_rwlock_prefer_reader_np . this is ignored by glibc because the posix requirement to support recursive read locks would cause this option to create trivial deadlocks; instead use .b pthread_rwlock_prefer_writer_nonrecursive_np which ensures the application developer will not take recursive read locks thus avoiding deadlocks. .\" --- .\" here is the relevant wording: .\" .\" a thread may hold multiple concurrent read locks on rwlock (that is, .\" successfully call the pthread_rwlock_rdlock() function n times). if .\" so, the thread must perform matching unlocks (that is, it must call .\" the pthread_rwlock_unlock() function n times). .\" .\" by making write-priority work correctly, i broke the above requirement, .\" because i had no clue that recursive read locks are permissible. .\" .\" if a thread which holds a read lock tries to acquire another read lock, .\" and now one or more writers is waiting for a write lock, then the algorithm .\" will lead to an obvious deadlock. the reader will be suspended, waiting for .\" the writers to acquire and release the lock, and the writers will be .\" suspended waiting for every existing read lock to be released. .\" --- .\" https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_rdlock.html .\" https://sourceware.org/legacy-ml/libc-alpha/2000-01/msg00055.html .\" https://sourceware.org/bugzilla/show_bug.cgi?id=7057 .tp .b pthread_rwlock_prefer_writer_nonrecursive_np setting the lock kind to this avoids writer starvation as long as any read locking is not done in a recursive fashion. .pp the .br pthread_rwlockattr_getkind_np () function returns the value of the lock kind attribute of the read-write lock attribute object referred to by .ir attr in the pointer .ir pref . .sh return value on success, these functions return 0. given valid pointer arguments, .br pthread_rwlockattr_getkind_np () always succeeds. on error, .br pthread_rwlockattr_setkind_np () returns a nonzero error number. .sh errors .tp .br einval .i pref specifies an unsupported value. .sh versions the .br pthread_rwlockattr_getkind_np () and .br pthread_rwlockattr_setkind_np () functions first appeared in glibc 2.1. .sh conforming to these functions are non-standard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh see also .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .\" copyright (c) 2002 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th tcgetpgrp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name tcgetpgrp, tcsetpgrp \- get and set terminal foreground process group .sh synopsis .nf .b "#include " .pp .bi "pid_t tcgetpgrp(int " fd ); .bi "int tcsetpgrp(int " fd ", pid_t " pgrp ); .fi .sh description the function .br tcgetpgrp () returns the process group id of the foreground process group on the terminal associated to .ir fd , which must be the controlling terminal of the calling process. .\" the process itself may be a background process. .pp the function .br tcsetpgrp () makes the process group with process group id .i pgrp the foreground process group on the terminal associated to .ir fd , which must be the controlling terminal of the calling process, and still be associated with its session. moreover, .i pgrp must be a (nonempty) process group belonging to the same session as the calling process. .pp if .br tcsetpgrp () is called by a member of a background process group in its session, and the calling process is not blocking or ignoring .br sigttou , a .b sigttou signal is sent to all members of this background process group. .sh return value when .i fd refers to the controlling terminal of the calling process, the function .br tcgetpgrp () will return the foreground process group id of that terminal if there is one, and some value larger than 1 that is not presently a process group id otherwise. when .i fd does not refer to the controlling terminal of the calling process, \-1 is returned, and .i errno is set to indicate the error. .pp when successful, .br tcsetpgrp () returns 0. otherwise, it returns \-1, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b einval .i pgrp has an unsupported value. .tp .b enotty the calling process does not have a controlling terminal, or it has one but it is not described by .ir fd , or, for .br tcsetpgrp (), this controlling terminal is no longer associated with the session of the calling process. .tp .b eperm .i pgrp has a supported value, but is not the process group id of a process in the same session as the calling process. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tcgetpgrp (), .br tcsetpgrp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes these functions are implemented via the .b tiocgpgrp and .b tiocspgrp ioctls. .ss history the ioctls appeared in 4.2bsd. the functions are posix inventions. .sh see also .br setpgid (2), .br setsid (2), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mcheck.3 .so man3/circleq.3 .\" copyright 2002 ionel mugurel ciobîcă (imciobica@netscape.net) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-16 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-16 \- iso 8859-16 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-16 encodes the latin characters used in southeast european languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-16 characters the following table displays the characters in iso 8859-16 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ą latin capital letter a with ogonek 242 162 a2 ą latin small letter a with ogonek 243 163 a3 ł latin capital letter l with stroke 244 164 a4 € euro sign 245 165 a5 „ double low-9 quotation mark 246 166 a6 š latin capital letter s with caron 247 167 a7 § section sign 250 168 a8 š latin small letter s with caron 251 169 a9 © copyright sign 252 170 aa ș latin capital letter s with comma below 253 171 ab « left-pointing double angle quotation mark 254 172 ac ź latin capital letter z with acute 255 173 ad ­ soft hyphen 256 174 ae ź latin small letter z with acute 257 175 af ż latin capital letter z with dot above 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 č latin capital letter c with caron 263 179 b3 ł latin small letter l with stroke 264 180 b4 ž latin capital letter z with caron 265 181 b5 ” left double quotation mark 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ž latin small letter z with caron 271 185 b9 č latin small letter c with caron 272 186 ba ș latin small letter s with comma below 273 187 bb » right-pointing double angle quotation mark 274 188 bc œ latin capital ligature oe 275 189 bd œ latin small ligature oe 276 190 be ÿ latin capital letter y with diaeresis 277 191 bf ż latin small letter z with dot above 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ă latin capital letter a with breve 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 ć latin capital letter c with acute 306 198 c6 æ latin capital letter ae 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 đ latin capital letter d with stroke 321 209 d1 ń latin capital letter n with acute 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 ő latin capital letter o with double acute 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 ś latin capital letter s with acute 330 216 d8 ű latin capital letter u with double acute 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ę latin capital letter e with ogonek 336 222 de ț latin capital letter t with comma below 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ă latin small letter a with breve 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 ć latin small letter c with acute 346 230 e6 æ latin small letter ae 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 đ latin small letter d with stroke 361 241 f1 ń latin small letter n with acute 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 ő latin small letter o with double acute 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ś latin small letter s with acute 370 248 f8 ű latin small letter u with double acute 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ę latin small letter e with ogonek 376 254 fe ț latin small letter t with comma below 377 255 ff ÿ latin small letter y with diaeresis .te .sh notes iso 8859-16 is also known as latin-10. .sh see also .br ascii (7), .br charsets (7), .br iso_8859\-3 (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. externally generated pages ========================== a few pages come from external sources. fixes to the pages should really go to the upstream source. tzfile(5), zdump(8), and zic(8) come from the tz project (https://www.iana.org/time-zones). bpf-helpers(7) is autogenerated from the kernel sources using scripts. see man-pages commit 53666f6c30451cde022f65d35a8d448f5a7132ba for details. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_receive 3 2021-03-22 "linux" "linux programmer's manual" .sh name mq_receive, mq_timedreceive \- receive a message from a message queue .sh synopsis .nf .b #include .pp .bi "ssize_t mq_receive(mqd_t " mqdes ", char *" msg_ptr , .bi " size_t " msg_len ", unsigned int *" msg_prio ); .pp .b #include .b #include .pp .bi "ssize_t mq_timedreceive(mqd_t " mqdes ", char *restrict " msg_ptr , .bi " size_t " msg_len ", unsigned int *restrict " msg_prio , .bi " const struct timespec *restrict " abs_timeout ); .fi .pp link with \fi\-lrt\fp. .pp .ad l .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mq_timedreceive (): .nf _posix_c_source >= 200112l .fi .sh description .br mq_receive () removes the oldest message with the highest priority from the message queue referred to by the message queue descriptor .ir mqdes , and places it in the buffer pointed to by .ir msg_ptr . the .i msg_len argument specifies the size of the buffer pointed to by .ir msg_ptr ; this must be greater than or equal to the .i mq_msgsize attribute of the queue (see .br mq_getattr (3)). if .i msg_prio is not null, then the buffer to which it points is used to return the priority associated with the received message. .pp if the queue is empty, then, by default, .br mq_receive () blocks until a message becomes available, or the call is interrupted by a signal handler. if the .b o_nonblock flag is enabled for the message queue description, then the call instead fails immediately with the error .br eagain . .pp .br mq_timedreceive () behaves just like .br mq_receive (), except that if the queue is empty and the .b o_nonblock flag is not enabled for the message queue description, then .i abs_timeout points to a structure which specifies how long the call will block. this value is an absolute timeout in seconds and nanoseconds since the epoch, 1970-01-01 00:00:00 +0000 (utc), specified in the following structure: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp if no message is available, and the timeout has already expired by the time of the call, .br mq_timedreceive () returns immediately. .sh return value on success, .br mq_receive () and .br mq_timedreceive () return the number of bytes in the received message; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b eagain the queue was empty, and the .b o_nonblock flag was set for the message queue description referred to by .ir mqdes . .tp .b ebadf the descriptor specified in .i mqdes was invalid or not opened for reading. .tp .b eintr the call was interrupted by a signal handler; see .br signal (7). .tp .b einval the call would have blocked, and .i abs_timeout was invalid, either because .i tv_sec was less than zero, or because .i tv_nsec was less than zero or greater than 1000 million. .tp .b emsgsize .i msg_len was less than the .i mq_msgsize attribute of the message queue. .tp .b etimedout the call timed out before a message could be transferred. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mq_receive (), .br mq_timedreceive () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on linux, .br mq_timedreceive () is a system call, and .br mq_receive () is a library function layered on top of that system call. .sh see also .br mq_close (3), .br mq_getattr (3), .br mq_notify (3), .br mq_open (3), .br mq_send (3), .br mq_unlink (3), .br mq_overview (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .so man3/re_comp.3 .\" copyright (c) 1983, 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" $id: recv.2,v 1.3 1999/05/13 11:33:38 freitag exp $ .\" .\" modified sat jul 24 00:22:20 1993 by rik faith .\" modified tue oct 22 17:45:19 1996 by eric s. raymond .\" modified 1998,1999 by andi kleen .\" 2001-06-19 corrected so_ee_offender, bug report by james hawtin .\" .th recv 2 2021-03-22 "linux" "linux programmer's manual" .sh name recv, recvfrom, recvmsg \- receive a message from a socket .sh synopsis .nf .b #include .pp .bi "ssize_t recv(int " sockfd ", void *" buf ", size_t " len ", int " flags ); .bi "ssize_t recvfrom(int " sockfd ", void *restrict " buf ", size_t " len \ ", int " flags , .bi " struct sockaddr *restrict " src_addr , .bi " socklen_t *restrict " addrlen ); .bi "ssize_t recvmsg(int " sockfd ", struct msghdr *" msg ", int " flags ); .fi .sh description the .br recv (), .br recvfrom (), and .br recvmsg () calls are used to receive messages from a socket. they may be used to receive data on both connectionless and connection-oriented sockets. this page first describes common features of all three system calls, and then describes the differences between the calls. .pp the only difference between .br recv () and .br read (2) is the presence of .ir flags . with a zero .i flags argument, .br recv () is generally equivalent to .br read (2) (but see notes). also, the following call .pp recv(sockfd, buf, len, flags); .pp is equivalent to .pp recvfrom(sockfd, buf, len, flags, null, null); .pp all three calls return the length of the message on successful completion. if a message is too long to fit in the supplied buffer, excess bytes may be discarded depending on the type of socket the message is received from. .pp if no messages are available at the socket, the receive calls wait for a message to arrive, unless the socket is nonblocking (see .br fcntl (2)), in which case the value \-1 is returned and .i errno is set to .br eagain " or " ewouldblock . the receive calls normally return any data available, up to the requested amount, rather than waiting for receipt of the full amount requested. .pp an application can use .br select (2), .br poll (2), or .br epoll (7) to determine when more data arrives on a socket. .ss the flags argument the .i flags argument is formed by oring one or more of the following values: .tp .br msg_cmsg_cloexec " (" recvmsg "() only; since linux 2.6.23)" set the close-on-exec flag for the file descriptor received via a unix domain file descriptor using the .b scm_rights operation (described in .br unix (7)). this flag is useful for the same reasons as the .b o_cloexec flag of .br open (2). .tp .br msg_dontwait " (since linux 2.2)" enables nonblocking operation; if the operation would block, the call fails with the error .br eagain " or " ewouldblock . this provides similar behavior to setting the .b o_nonblock flag (via the .br fcntl (2) .b f_setfl operation), but differs in that .b msg_dontwait is a per-call option, whereas .b o_nonblock is a setting on the open file description (see .br open (2)), which will affect all threads in the calling process and as well as other processes that hold file descriptors referring to the same open file description. .tp .br msg_errqueue " (since linux 2.2)" this flag specifies that queued errors should be received from the socket error queue. the error is passed in an ancillary message with a type dependent on the protocol (for ipv4 .br ip_recverr ). the user should supply a buffer of sufficient size. see .br cmsg (3) and .br ip (7) for more information. the payload of the original packet that caused the error is passed as normal data via .ir msg_iovec . the original destination address of the datagram that caused the error is supplied via .ir msg_name . .ip the error is supplied in a .i sock_extended_err structure: .ip .in +4n .ex #define so_ee_origin_none 0 #define so_ee_origin_local 1 #define so_ee_origin_icmp 2 #define so_ee_origin_icmp6 3 struct sock_extended_err { uint32_t ee_errno; /* error number */ uint8_t ee_origin; /* where the error originated */ uint8_t ee_type; /* type */ uint8_t ee_code; /* code */ uint8_t ee_pad; /* padding */ uint32_t ee_info; /* additional information */ uint32_t ee_data; /* other data */ /* more data may follow */ }; struct sockaddr *so_ee_offender(struct sock_extended_err *); .ee .in .ip .i ee_errno contains the .i errno number of the queued error. .i ee_origin is the origin code of where the error originated. the other fields are protocol-specific. the macro .b so_ee_offender returns a pointer to the address of the network object where the error originated from given a pointer to the ancillary message. if this address is not known, the .i sa_family member of the .i sockaddr contains .b af_unspec and the other fields of the .i sockaddr are undefined. the payload of the packet that caused the error is passed as normal data. .ip for local errors, no address is passed (this can be checked with the .i cmsg_len member of the .ir cmsghdr ). for error receives, the .b msg_errqueue flag is set in the .ir msghdr . after an error has been passed, the pending socket error is regenerated based on the next queued error and will be passed on the next socket operation. .tp .b msg_oob this flag requests receipt of out-of-band data that would not be received in the normal data stream. some protocols place expedited data at the head of the normal data queue, and thus this flag cannot be used with such protocols. .tp .b msg_peek this flag causes the receive operation to return data from the beginning of the receive queue without removing that data from the queue. thus, a subsequent receive call will return the same data. .tp .br msg_trunc " (since linux 2.2)" for raw .rb ( af_packet ), internet datagram (since linux 2.4.27/2.6.8), netlink (since linux 2.6.22), and unix datagram .\" commit 9f6f9af7694ede6314bed281eec74d588ba9474f (since linux 3.4) sockets: return the real length of the packet or datagram, even when it was longer than the passed buffer. .ip for use with internet stream sockets, see .br tcp (7). .tp .br msg_waitall " (since linux 2.2)" this flag requests that the operation block until the full request is satisfied. however, the call may still return less data than requested if a signal is caught, an error or disconnect occurs, or the next data to be received is of a different type than that returned. this flag has no effect for datagram sockets. .\" .ss recvfrom() .br recvfrom () places the received message into the buffer .ir buf . the caller must specify the size of the buffer in .ir len . .pp if .i src_addr is not null, and the underlying protocol provides the source address of the message, that source address is placed in the buffer pointed to by .ir src_addr . .\" (note: for datagram sockets in both the unix and internet domains, .\" .i src_addr .\" is filled in. .\" .i src_addr .\" is also filled in for stream sockets in the unix domain, but is not .\" filled in for stream sockets in the internet domain.) .\" [the above notes on af_unix and af_inet sockets apply as at .\" kernel 2.4.18. (mtk, 22 jul 02)] in this case, .i addrlen is a value-result argument. before the call, it should be initialized to the size of the buffer associated with .ir src_addr . upon return, .i addrlen is updated to contain the actual size of the source address. the returned address is truncated if the buffer provided is too small; in this case, .i addrlen will return a value greater than was supplied to the call. .pp if the caller is not interested in the source address, .i src_addr and .i addrlen should be specified as null. .\" .ss recv() the .br recv () call is normally used only on a .i connected socket (see .br connect (2)). it is equivalent to the call: .pp recvfrom(fd, buf, len, flags, null, 0); .\" .ss recvmsg() the .br recvmsg () call uses a .i msghdr structure to minimize the number of directly supplied arguments. this structure is defined as follows in .ir : .pp .in +4n .ex struct iovec { /* scatter/gather array items */ void *iov_base; /* starting address */ size_t iov_len; /* number of bytes to transfer */ }; struct msghdr { void *msg_name; /* optional address */ socklen_t msg_namelen; /* size of address */ struct iovec *msg_iov; /* scatter/gather array */ size_t msg_iovlen; /* # elements in msg_iov */ void *msg_control; /* ancillary data, see below */ size_t msg_controllen; /* ancillary data buffer len */ int msg_flags; /* flags on received message */ }; .ee .in .pp the .i msg_name field points to a caller-allocated buffer that is used to return the source address if the socket is unconnected. the caller should set .i msg_namelen to the size of this buffer before this call; upon return from a successful call, .i msg_namelen will contain the length of the returned address. if the application does not need to know the source address, .i msg_name can be specified as null. .pp the fields .i msg_iov and .i msg_iovlen describe scatter-gather locations, as discussed in .br readv (2). .pp the field .ir msg_control , which has length .ir msg_controllen , points to a buffer for other protocol control-related messages or miscellaneous ancillary data. when .br recvmsg () is called, .i msg_controllen should contain the length of the available buffer in .ir msg_control ; upon return from a successful call it will contain the length of the control message sequence. .pp the messages are of the form: .pp .in +4n .ex struct cmsghdr { size_t cmsg_len; /* data byte count, including header (type is socklen_t in posix) */ int cmsg_level; /* originating protocol */ int cmsg_type; /* protocol\-specific type */ /* followed by unsigned char cmsg_data[]; */ }; .ee .in .pp ancillary data should be accessed only by the macros defined in .br cmsg (3). .pp as an example, linux uses this ancillary data mechanism to pass extended errors, ip options, or file descriptors over unix domain sockets. for further information on the use of ancillary data in various socket domains, see .br unix (7) and .br ip (7). .pp the .i msg_flags field in the .i msghdr is set on return of .br recvmsg (). it can contain several flags: .tp .b msg_eor indicates end-of-record; the data returned completed a record (generally used with sockets of type .br sock_seqpacket ). .tp .b msg_trunc indicates that the trailing portion of a datagram was discarded because the datagram was larger than the buffer supplied. .tp .b msg_ctrunc indicates that some control data was discarded due to lack of space in the buffer for ancillary data. .tp .b msg_oob is returned to indicate that expedited or out-of-band data was received. .tp .b msg_errqueue indicates that no data was received but an extended error from the socket error queue. .sh return value these calls return the number of bytes received, or \-1 if an error occurred. in the event of an error, .i errno is set to indicate the error. .pp when a stream socket peer has performed an orderly shutdown, the return value will be 0 (the traditional "end-of-file" return). .pp datagram sockets in various domains (e.g., the unix and internet domains) permit zero-length datagrams. when such a datagram is received, the return value is 0. .pp the value 0 may also be returned if the requested number of bytes to receive from a stream socket was 0. .sh errors these are some standard errors generated by the socket layer. additional errors may be generated and returned from the underlying protocol modules; see their manual pages. .tp .br eagain " or " ewouldblock .\" actually eagain on linux the socket is marked nonblocking and the receive operation would block, or a receive timeout had been set and the timeout expired before data was received. posix.1 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities. .tp .b ebadf the argument .i sockfd is an invalid file descriptor. .tp .b econnrefused a remote host refused to allow the network connection (typically because it is not running the requested service). .tp .b efault the receive buffer pointer(s) point outside the process's address space. .tp .b eintr the receive was interrupted by delivery of a signal before any data was available; see .br signal (7). .tp .b einval invalid argument passed. .\" e.g., msg_namelen < 0 for recvmsg() or addrlen < 0 for recvfrom() .tp .b enomem could not allocate memory for .br recvmsg (). .tp .b enotconn the socket is associated with a connection-oriented protocol and has not been connected (see .br connect (2) and .br accept (2)). .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .sh conforming to posix.1-2001, posix.1-2008, 4.4bsd (these interfaces first appeared in 4.2bsd). .pp posix.1 describes only the .br msg_oob , .br msg_peek , and .b msg_waitall flags. .sh notes if a zero-length datagram is pending, .br read (2) and .br recv () with a .i flags argument of zero provide different behavior. in this circumstance, .br read (2) has no effect (the datagram remains pending), while .br recv () consumes the pending datagram. .pp the .i socklen_t type was invented by posix. see also .br accept (2). .pp according to posix.1, .\" posix.1-2001, posix.1-2008 the .i msg_controllen field of the .i msghdr structure should be typed as .ir socklen_t , and the .i msg_iovlen field should be typed as .ir int , but glibc currently types both as .ir size_t . .\" glibc bug for msg_controllen raised 12 mar 2006 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=2448 .\" the problem is an underlying kernel issue: the size of the .\" __kernel_size_t type used to type these fields varies .\" across architectures, but socklen_t is always 32 bits, .\" as (at least with gcc) is int. .pp see .br recvmmsg (2) for information about a linux-specific system call that can be used to receive multiple datagrams in a single call. .sh examples an example of the use of .br recvfrom () is shown in .br getaddrinfo (3). .sh see also .br fcntl (2), .br getsockopt (2), .br read (2), .br recvmmsg (2), .br select (2), .br shutdown (2), .br socket (2), .br cmsg (3), .br sockatmark (3), .br ip (7), .br ipv6 (7), .br socket (7), .br tcp (7), .br udp (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:06:52 1993 by rik faith (faith@cs.unc.edu) .\" modified sun jan 14 00:34:09 1996 by andries brouwer (aeb@cwi.nl) .th intro 5 2017-03-13 "linux" "linux programmer's manual" .sh name intro \- introduction to file formats and filesystems .sh description section 5 of the manual describes various file formats, as well as the corresponding c structures, if any. .pp in addition, this section contains a number of pages that document various filesystems. .sh notes .ss authors and copyright conditions look at the header of the manual page source for the author(s) and copyright conditions. note that these can be different from page to page! .sh see also .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/byteorder.3 .so man7/system_data_types.7 .\" copyright (c) 2001 david gómez .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" based on comments from mm/filemap.c. last modified on 10-06-2001 .\" modified, 25 feb 2002, michael kerrisk, .\" added notes on madv_dontneed .\" 2010-06-19, mtk, added documentation of madv_mergeable and .\" madv_unmergeable .\" 2010-06-15, andi kleen, add documentation of madv_hwpoison. .\" 2010-06-19, andi kleen, add documentation of madv_soft_offline. .\" 2011-09-18, doug goldstein .\" document madv_hugepage and madv_nohugepage .\" .th madvise 2 2021-03-22 "linux" "linux programmer's manual" .sh name madvise \- give advice about use of memory .sh synopsis .nf .b #include .pp .bi "int madvise(void *" addr ", size_t " length ", int " advice ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br madvise (): .nf since glibc 2.19: _default_source up to and including glibc 2.19: _bsd_source .fi .sh description the .br madvise () system call is used to give advice or directions to the kernel about the address range beginning at address .i addr and with size .i length bytes in most cases, the goal of such advice is to improve system or application performance. .pp initially, the system call supported a set of "conventional" .i advice values, which are also available on several other implementations. (note, though, that .br madvise () is not specified in posix.) subsequently, a number of linux-specific .ir advice values have been added. .\" .\" ====================================================================== .\" .ss conventional advice values the .i advice values listed below allow an application to tell the kernel how it expects to use some mapped or shared memory areas, so that the kernel can choose appropriate read-ahead and caching techniques. these .i advice values do not influence the semantics of the application (except in the case of .br madv_dontneed ), but may influence its performance. all of the .i advice values listed here have analogs in the posix-specified .br posix_madvise (3) function, and the values have the same meanings, with the exception of .br madv_dontneed . .pp the advice is indicated in the .i advice argument, which is one of the following: .tp .b madv_normal no special treatment. this is the default. .tp .b madv_random expect page references in random order. (hence, read ahead may be less useful than normally.) .tp .b madv_sequential expect page references in sequential order. (hence, pages in the given range can be aggressively read ahead, and may be freed soon after they are accessed.) .tp .b madv_willneed expect access in the near future. (hence, it might be a good idea to read some pages ahead.) .tp .b madv_dontneed do not expect access in the near future. (for the time being, the application is finished with the given range, so the kernel can free resources associated with it.) .ip after a successful .b madv_dontneed operation, the semantics of memory access in the specified region are changed: subsequent accesses of pages in the range will succeed, but will result in either repopulating the memory contents from the up-to-date contents of the underlying mapped file (for shared file mappings, shared anonymous mappings, and shmem-based techniques such as system v shared memory segments) or zero-fill-on-demand pages for anonymous private mappings. .ip note that, when applied to shared mappings, .br madv_dontneed might not lead to immediate freeing of the pages in the range. the kernel is free to delay freeing the pages until an appropriate moment. the resident set size (rss) of the calling process will be immediately reduced however. .ip .b madv_dontneed cannot be applied to locked pages, huge tlb pages, or .br vm_pfnmap pages. (pages marked with the kernel-internal .b vm_pfnmap .\" http://lwn.net/articles/162860/ flag are special memory areas that are not managed by the virtual memory subsystem. such pages are typically created by device drivers that map the pages into user space.) .\" .\" ====================================================================== .\" .ss linux-specific advice values the following linux-specific .i advice values have no counterparts in the posix-specified .br posix_madvise (3), and may or may not have counterparts in the .br madvise () interface available on other implementations. note that some of these operations change the semantics of memory accesses. .tp .br madv_remove " (since linux 2.6.16)" .\" commit f6b3ec238d12c8cc6cc71490c6e3127988460349 free up a given range of pages and its associated backing store. this is equivalent to punching a hole in the corresponding byte range of the backing store (see .br fallocate (2)). subsequent accesses in the specified address range will see bytes containing zero. .\" databases want to use this feature to drop a section of their .\" bufferpool (shared memory segments) - without writing back to .\" disk/swap space. this feature is also useful for supporting .\" hot-plug memory on uml. .ip the specified address range must be mapped shared and writable. this flag cannot be applied to locked pages, huge tlb pages, or .br vm_pfnmap pages. .ip in the initial implementation, only .br tmpfs (5) was supported .br madv_remove ; but since linux 3.5, .\" commit 3f31d07571eeea18a7d34db9af21d2285b807a17 any filesystem which supports the .br fallocate (2) .br falloc_fl_punch_hole mode also supports .br madv_remove . hugetlbfs fails with the error .br einval and other filesystems fail with the error .br eopnotsupp . .tp .br madv_dontfork " (since linux 2.6.16)" .\" commit f822566165dd46ff5de9bf895cfa6c51f53bb0c4 .\" see http://lwn.net/articles/171941/ do not make the pages in this range available to the child after a .br fork (2). this is useful to prevent copy-on-write semantics from changing the physical location of a page if the parent writes to it after a .br fork (2). (such page relocations cause problems for hardware that dmas into the page.) .\" [patch] madvise madv_dontfork/madv_dofork .\" currently, copy-on-write may change the physical address of .\" a page even if the user requested that the page is pinned in .\" memory (either by mlock or by get_user_pages). this happens .\" if the process forks meanwhile, and the parent writes to that .\" page. as a result, the page is orphaned: in case of .\" get_user_pages, the application will never see any data hardware .\" dma's into this page after the cow. in case of mlock'd memory, .\" the parent is not getting the realtime/security benefits of mlock. .\" .\" in particular, this affects the infiniband modules which do dma from .\" and into user pages all the time. .\" .\" this patch adds madvise options to control whether memory range is .\" inherited across fork. useful e.g. for when hardware is doing dma .\" from/into these pages. could also be useful to an application .\" wanting to speed up its forks by cutting large areas out of .\" consideration. .\" .\" see also: http://lwn.net/articles/171941/ .\" "tweaks to madvise() and posix_fadvise()", 14 feb 2006 .tp .br madv_dofork " (since linux 2.6.16)" undo the effect of .br madv_dontfork , restoring the default behavior, whereby a mapping is inherited across .br fork (2). .tp .br madv_hwpoison " (since linux 2.6.32)" .\" commit 9893e49d64a4874ea67849ee2cfbf3f3d6817573 poison the pages in the range specified by .i addr and .ir length and handle subsequent references to those pages like a hardware memory corruption. this operation is available only for privileged .rb ( cap_sys_admin ) processes. this operation may result in the calling process receiving a .b sigbus and the page being unmapped. .ip this feature is intended for testing of memory error-handling code; it is available only if the kernel was configured with .br config_memory_failure . .tp .br madv_mergeable " (since linux 2.6.32)" .\" commit f8af4da3b4c14e7267c4ffb952079af3912c51c5 enable kernel samepage merging (ksm) for the pages in the range specified by .i addr and .ir length . the kernel regularly scans those areas of user memory that have been marked as mergeable, looking for pages with identical content. these are replaced by a single write-protected page (which is automatically copied if a process later wants to update the content of the page). ksm merges only private anonymous pages (see .br mmap (2)). .ip the ksm feature is intended for applications that generate many instances of the same data (e.g., virtualization systems such as kvm). it can consume a lot of processing power; use with care. see the linux kernel source file .i documentation/admin\-guide/mm/ksm.rst for more details. .ip the .br madv_mergeable and .br madv_unmergeable operations are available only if the kernel was configured with .br config_ksm . .tp .br madv_unmergeable " (since linux 2.6.32)" undo the effect of an earlier .br madv_mergeable operation on the specified address range; ksm unmerges whatever pages it had merged in the address range specified by .ir addr and .ir length . .tp .br madv_soft_offline " (since linux 2.6.33)" .\" commit afcf938ee0aac4ef95b1a23bac704c6fbeb26de6 soft offline the pages in the range specified by .i addr and .ir length . the memory of each page in the specified range is preserved (i.e., when next accessed, the same content will be visible, but in a new physical page frame), and the original page is offlined (i.e., no longer used, and taken out of normal memory management). the effect of the .b madv_soft_offline operation is invisible to (i.e., does not change the semantics of) the calling process. .ip this feature is intended for testing of memory error-handling code; it is available only if the kernel was configured with .br config_memory_failure . .tp .br madv_hugepage " (since linux 2.6.38)" .\" commit 0af4e98b6b095c74588af04872f83d333c958c32 .\" http://lwn.net/articles/358904/ .\" https://lwn.net/articles/423584/ enable transparent huge pages (thp) for pages in the range specified by .i addr and .ir length . currently, transparent huge pages work only with private anonymous pages (see .br mmap (2)). the kernel will regularly scan the areas marked as huge page candidates to replace them with huge pages. the kernel will also allocate huge pages directly when the region is naturally aligned to the huge page size (see .br posix_memalign (2)). .ip this feature is primarily aimed at applications that use large mappings of data and access large regions of that memory at a time (e.g., virtualization systems such as qemu). it can very easily waste memory (e.g., a 2\ mb mapping that only ever accesses 1 byte will result in 2\ mb of wired memory instead of one 4\ kb page). see the linux kernel source file .i documentation/admin\-guide/mm/transhuge.rst for more details. .ip most common kernels configurations provide .br madv_hugepage -style behavior by default, and thus .br madv_hugepage is normally not necessary. it is mostly intended for embedded systems, where .br madv_hugepage -style behavior may not be enabled by default in the kernel. on such systems, this flag can be used in order to selectively enable thp. whenever .br madv_hugepage is used, it should always be in regions of memory with an access pattern that the developer knows in advance won't risk to increase the memory footprint of the application when transparent hugepages are enabled. .ip the .br madv_hugepage and .br madv_nohugepage operations are available only if the kernel was configured with .br config_transparent_hugepage . .tp .br madv_nohugepage " (since linux 2.6.38)" ensures that memory in the address range specified by .ir addr and .ir length will not be backed by transparent hugepages. .tp .br madv_dontdump " (since linux 3.4)" .\" commit 909af768e88867016f427264ae39d27a57b6a8ed .\" commit accb61fe7bb0f5c2a4102239e4981650f9048519 exclude from a core dump those pages in the range specified by .i addr and .ir length . this is useful in applications that have large areas of memory that are known not to be useful in a core dump. the effect of .br madv_dontdump takes precedence over the bit mask that is set via the .i /proc/[pid]/coredump_filter file (see .br core (5)). .tp .br madv_dodump " (since linux 3.4)" undo the effect of an earlier .br madv_dontdump . .tp .br madv_free " (since linux 4.5)" the application no longer requires the pages in the range specified by .ir addr and .ir len . the kernel can thus free these pages, but the freeing could be delayed until memory pressure occurs. for each of the pages that has been marked to be freed but has not yet been freed, the free operation will be canceled if the caller writes into the page. after a successful .b madv_free operation, any stale data (i.e., dirty, unwritten pages) will be lost when the kernel frees the pages. however, subsequent writes to pages in the range will succeed and then kernel cannot free those dirtied pages, so that the caller can always see just written data. if there is no subsequent write, the kernel can free the pages at any time. once pages in the range have been freed, the caller will see zero-fill-on-demand pages upon subsequent page references. .ip the .b madv_free operation can be applied only to private anonymous pages (see .br mmap (2)). in linux before version 4.12, .\" commit 93e06c7a645343d222c9a838834a51042eebbbf7 when freeing pages on a swapless system, the pages in the given range are freed instantly, regardless of memory pressure. .tp .br madv_wipeonfork " (since linux 4.14)" .\" commit d2cd9ede6e193dd7d88b6d27399e96229a551b19 present the child process with zero-filled memory in this range after a .br fork (2). this is useful in forking servers in order to ensure that sensitive per-process data (for example, prng seeds, cryptographic secrets, and so on) is not handed to child processes. .ip the .b madv_wipeonfork operation can be applied only to private anonymous pages (see .br mmap (2)). .ip within the child created by .br fork (2), the .b madv_wipeonfork setting remains in place on the specified address range. this setting is cleared during .br execve (2). .tp .br madv_keeponfork " (since linux 4.14)" .\" commit d2cd9ede6e193dd7d88b6d27399e96229a551b19 undo the effect of an earlier .br madv_wipeonfork . .tp .br madv_cold " (since linux 5.4)" .\" commit 9c276cc65a58faf98be8e56962745ec99ab87636 deactivate a given range of pages. this will make the pages a more probable reclaim target should there be a memory pressure. this is a nondestructive operation. the advice might be ignored for some pages in the range when it is not applicable. .tp .br madv_pageout " (since linux 5.4)" .\" commit 1a4e58cce84ee88129d5d49c064bd2852b481357 reclaim a given range of pages. this is done to free up memory occupied by these pages. if a page is anonymous, it will be swapped out. if a page is file-backed and dirty, it will be written back to the backing storage. the advice might be ignored for some pages in the range when it is not applicable. .sh return value on success, .br madvise () returns zero. on error, it returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b eacces .i advice is .br madv_remove , but the specified address range is not a shared writable mapping. .tp .b eagain a kernel resource was temporarily unavailable. .tp .b ebadf the map exists, but the area maps something that isn't a file. .tp .b einval .i addr is not page-aligned or .i length is negative. .\" .i length .\" is zero, .tp .b einval .i advice is not a valid. .tp .b einval .i advice is .b madv_dontneed or .br madv_remove and the specified address range includes locked, huge tlb pages, or .b vm_pfnmap pages. .tp .b einval .i advice is .br madv_mergeable or .br madv_unmergeable , but the kernel was not configured with .br config_ksm . .tp .b einval .i advice is .br madv_free or .br madv_wipeonfork but the specified address range includes file, huge tlb, .br map_shared , or .br vm_pfnmap ranges. .tp .b eio (for .br madv_willneed ) paging in this area would exceed the process's maximum resident set size. .tp .b enomem (for .br madv_willneed ) not enough memory: paging in failed. .tp .b enomem addresses in the specified range are not currently mapped, or are outside the address space of the process. .tp .b eperm .i advice is .br madv_hwpoison , but the caller does not have the .b cap_sys_admin capability. .sh versions since linux 3.18, .\" commit d3ac21cacc24790eb45d735769f35753f5b56ceb support for this system call is optional, depending on the setting of the .b config_advise_syscalls configuration option. .sh conforming to .br madvise () is not specified by any standards. versions of this system call, implementing a wide variety of .i advice values, exist on many other implementations. other implementations typically implement at least the flags listed above under .ir "conventional advice flags" , albeit with some variation in semantics. .pp posix.1-2001 describes .br posix_madvise (3) with constants .br posix_madv_normal , .br posix_madv_random , .br posix_madv_sequential , .br posix_madv_willneed , and .br posix_madv_dontneed , and so on, with behavior close to the similarly named flags listed above. .sh notes .ss linux notes the linux implementation requires that the address .i addr be page-aligned, and allows .i length to be zero. if there are some parts of the specified address range that are not mapped, the linux version of .br madvise () ignores them and applies the call to the rest (but returns .b enomem from the system call, as it should). .\" .sh history .\" the .\" .br madvise () .\" function first appeared in 4.4bsd. .sh see also .br getrlimit (2), .br mincore (2), .br mmap (2), .br mprotect (2), .br msync (2), .br munmap (2), .br prctl (2), .br process_madvise (2), .br posix_madvise (3), .br core (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .\" copyright (c) 2020 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th time_namespaces 7 2021-03-22 "linux" "linux programmer's manual" .sh name time_namespaces \- overview of linux time namespaces .sh description time namespaces virtualize the values of two system clocks: .ip \(bu 2 .br clock_monotonic (and likewise .br clock_monotonic_coarse and .br clock_monotonic_raw ), a nonsettable clock that represents monotonic time since\(emas described by posix\(em"some unspecified point in the past". .ip \(bu .br clock_boottime (and likewise .br clock_boottime_alarm ), a nonsettable clock that is identical to .br clock_monotonic , except that it also includes any time that the system is suspended. .pp thus, the processes in a time namespace share per-namespace values for these clocks. this affects various apis that measure against these clocks, including: .br clock_gettime (2), .br clock_nanosleep (2), .br nanosleep (2), .br timer_settime (2), .br timerfd_settime (2), and .ir /proc/uptime . .pp currently, the only way to create a time namespace is by calling .br unshare (2) with the .br clone_newtime flag. this call creates a new time namespace but does .i not place the calling process in the new namespace. instead, the calling process's subsequently created children are placed in the new namespace. this allows clock offsets (see below) for the new namespace to be set before the first process is placed in the namespace. the .ir /proc/[pid]/ns/time_for_children symbolic link shows the time namespace in which the children of a process will be created. (a process can use a file descriptor opened on this symbolic link in a call to .br setns (2) in order to move into the namespace.) .\" .ss /proc/pid/timens_offsets associated with each time namespace are offsets, expressed with respect to the initial time namespace, that define the values of the monotonic and boot-time clocks in that namespace. these offsets are exposed via the file .ir /proc/pid/timens_offsets . within this file, the offsets are expressed as lines consisting of three space-delimited fields: .pp .in +4n .ex .ee .in .pp the .i clock-id is a string that identifies the clock whose offsets are being shown. this field is either .ir monotonic , for .br clock_monotonic , or .ir boottime , for .br clock_boottime . the remaining fields express the offset (seconds plus nanoseconds) for the clock in this time namespace. these offsets are expressed relative to the clock values in the initial time namespace. the .i offset-secs value can be negative, subject to restrictions noted below; .i offset-nanosecs is an unsigned value. .pp in the initial time namespace, the contents of the .i timens_offsets file are as follows: .pp .in +4n .ex $ \fbcat /proc/self/timens_offsets\fp monotonic 0 0 boottime 0 0 .ee .in .pp in a new time namespace that has had no member processes, the clock offsets can be modified by writing newline-terminated records of the same form to the .i timens_offsets file. the file can be written to multiple times, but after the first process has been created in or has entered the namespace, .br write (2)s on this file fail with the error .br eacces . in order to write to the .ir timens_offsets file, a process must have the .br cap_sys_time capability in the user namespace that owns the time namespace. .pp writes to the .i timens_offsets file can fail with the following errors: .tp .b einval an .i offset-nanosecs value is greater than 999,999,999. .tp .b einval a .i clock-id value is not valid. .tp .b eperm the caller does not have the .br cap_sys_time capability. .tp .b erange an .i offset-secs value is out of range. in particular; .rs .ip \(bu 2 .i offset-secs can't be set to a value which would make the current time on the corresponding clock inside the namespace a negative value; and .ip \(bu .i offset-secs can't be set to a value such that the time on the corresponding clock inside the namespace would exceed half of the value of the kernel constant .br ktime_sec_max (this limits the clock value to a maximum of approximately 146 years). .re .pp in a new time namespace created by .br unshare (2), the contents of the .i timens_offsets file are inherited from the time namespace of the creating process. .sh notes use of time namespaces requires a kernel that is configured with the .b config_time_ns option. .pp note that time namespaces do not virtualize the .br clock_realtime clock. virtualization of this clock was avoided for reasons of complexity and overhead within the kernel. .pp for compatibility with the initial implementation, when writing a .i clock-id to the .ir /proc/[pid]/timens_offsets file, the numerical values of the ids can be written instead of the symbolic names show above; i.e., 1 instead of .ir monotonic , and 7 instead of .ir boottime . for readability, the use of the symbolic names over the numbers is preferred. .pp the motivation for adding time namespaces was to allow the monotonic and boot-time clocks to maintain consistent values during container migration and checkpoint/restore. .sh examples the following shell session demonstrates the operation of time namespaces. we begin by displaying the inode number of the time namespace of a shell in the initial time namespace: .pp .in +4n .ex $ \fbreadlink /proc/$$/ns/time\fp time:[4026531834] .ee .in .pp continuing in the initial time namespace, we display the system uptime using .br uptime (1) and use the .i clock_times example program shown in .br clock_getres (2) to display the values of various clocks: .pp .in +4n .ex $ \fbuptime \-\-pretty\fp up 21 hours, 17 minutes $ \fb./clock_times\fp clock_realtime : 1585989401.971 (18356 days + 8h 36m 41s) clock_tai : 1585989438.972 (18356 days + 8h 37m 18s) clock_monotonic: 56338.247 (15h 38m 58s) clock_boottime : 76633.544 (21h 17m 13s) .ee .in .pp we then use .br unshare (1) to create a time namespace and execute a .br bash (1) shell. from the new shell, we use the built-in .b echo command to write records to the .i timens_offsets file adjusting the offset for the .b clock_monotonic clock forward 2 days and the offset for the .b clock_boottime clock forward 7 days: .pp .in +4n .ex $ \fbps1="ns2# " sudo unshare \-t \-\- bash \-\-norc\fp ns2# \fbecho "monotonic $((2*24*60*60)) 0" > /proc/$$/timens_offsets\fp ns2# \fbecho "boottime $((7*24*60*60)) 0" > /proc/$$/timens_offsets\fp .ee .in .pp above, we started the .br bash (1) shell with the .b \-\-norc options so that no start-up scripts were executed. this ensures that no child processes are created from the shell before we have a chance to update the .i timens_offsets file. .pp we then use .br cat (1) to display the contents of the .i timens_offsets file. the execution of .br cat (1) creates the first process in the new time namespace, after which further attempts to update the .i timens_offsets file produce an error. .pp .in +4n .ex ns2# \fbcat /proc/$$/timens_offsets\fp monotonic 172800 0 boottime 604800 0 ns2# \fbecho "boottime $((9*24*60*60)) 0" > /proc/$$/timens_offsets\fp bash: echo: write error: permission denied .ee .in .pp continuing in the new namespace, we execute .br uptime (1) and the .i clock_times example program: .pp .in +4n .ex ns2# \fbuptime \-\-pretty\fp up 1 week, 21 hours, 18 minutes ns2# \fb./clock_times\fp clock_realtime : 1585989457.056 (18356 days + 8h 37m 37s) clock_tai : 1585989494.057 (18356 days + 8h 38m 14s) clock_monotonic: 229193.332 (2 days + 15h 39m 53s) clock_boottime : 681488.629 (7 days + 21h 18m 8s) .ee .in .pp from the above output, we can see that the monotonic and boot-time clocks have different values in the new time namespace. .pp examining the .i /proc/[pid]/ns/time and .i /proc/[pid]/ns/time_for_children symbolic links, we see that the shell is a member of the initial time namespace, but its children are created in the new namespace. .pp .in +4n .ex ns2# \fbreadlink /proc/$$/ns/time\fp time:[4026531834] ns2# \fbreadlink /proc/$$/ns/time_for_children\fp time:[4026532900] ns2# \fbreadlink /proc/self/ns/time\fp # creates a child process time:[4026532900] .ee .in .pp returning to the shell in the initial time namespace, we see that the monotonic and boot-time clocks are unaffected by the .i timens_offsets changes that were made in the other time namespace: .pp .in +4n .ex $ \fbuptime \-\-pretty\fp up 21 hours, 19 minutes $ \fb./clock_times\fp clock_realtime : 1585989401.971 (18356 days + 8h 38m 51s) clock_tai : 1585989438.972 (18356 days + 8h 39m 28s) clock_monotonic: 56338.247 (15h 41m 8s) clock_boottime : 76633.544 (21h 19m 23s) .ee .in .sh see also .br nsenter (1), .br unshare (1), .br clock_settime (2), .\" clone3() support for time namespaces is a work in progress .\" .br clone3 (2), .br setns (2), .br unshare (2), .br namespaces (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sun jul 25 11:06:27 1993 by rik faith (faith@cs.unc.edu) .th securetty 5 2020-06-09 "linux" "linux programmer's manual" .sh name securetty \- list of terminals on which root is allowed to login .sh description the file .i /etc/securetty contains the names of terminals (one per line, without leading .ir /dev/ ) which are considered secure for the transmission of certain authentication tokens. .pp it is used by (some versions of) .br login (1) to restrict the terminals on which root is allowed to login. see .br login.defs (5) if you use the shadow suite. .pp on pam enabled systems, it is used for the same purpose by .br pam_securetty (8) to restrict the terminals on which empty passwords are accepted. .sh files .i /etc/securetty .sh see also .br login (1), .br login.defs (5), .br pam_securetty (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sun jul 25 10:46:28 1993 by rik faith (faith@cs.unc.edu) .\" modified sun aug 21 18:12:27 1994 by rik faith (faith@cs.unc.edu) .\" modified sun jun 18 01:53:57 1995 by andries brouwer (aeb@cwi.nl) .\" modified mon jan 5 20:24:40 met 1998 by michael haardt .\" (michael@cantor.informatik.rwth-aachen.de) .th passwd 5 2018-04-30 "linux" "linux programmer's manual" .sh name passwd \- password file .sh description the .ir /etc/passwd file is a text file that describes user login accounts for the system. it should have read permission allowed for all users (many utilities, like .br ls (1) use it to map user ids to usernames), but write access only for the superuser. .pp in the good old days there was no great problem with this general read permission. everybody could read the encrypted passwords, but the hardware was too slow to crack a well-chosen password, and moreover the basic assumption used to be that of a friendly user-community. these days many people run some version of the shadow password suite, where .i /etc/passwd has an \(aqx\(aq character in the password field, and the encrypted passwords are in .ir /etc/shadow , which is readable by the superuser only. .pp if the encrypted password, whether in .i /etc/passwd or in .ir /etc/shadow , is an empty string, login is allowed without even asking for a password. note that this functionality may be intentionally disabled in applications, or configurable (for example using the "nullok" or "nonull" arguments to pam_unix.so). .pp if the encrypted password in .i /etc/passwd is "\fi*np*\fp" (without the quotes), the shadow record should be obtained from an nis+ server. .pp regardless of whether shadow passwords are used, many system administrators use an asterisk (*) in the encrypted password field to make sure that this user can not authenticate themself using a password. (but see notes below.) .pp if you create a new login, first put an asterisk (*) in the password field, then use .br passwd (1) to set it. .pp each line of the file describes a single user, and contains seven colon-separated fields: .pp .in +4n .ex name:password:uid:gid:gecos:directory:shell .ee .in .pp the field are as follows: .tp 12 .i name this is the user's login name. it should not contain capital letters. .tp .i password this is either the encrypted user password, an asterisk (*), or the letter \(aqx\(aq. (see .br pwconv (8) for an explanation of \(aqx\(aq.) .tp .i uid the privileged .i root login account (superuser) has the user id 0. .tp .i gid this is the numeric primary group id for this user. (additional groups for the user are defined in the system group file; see .br group (5)). .tp .i gecos this field (sometimes called the "comment field") is optional and used only for informational purposes. usually, it contains the full username. some programs (for example, .br finger (1)) display information from this field. .ip gecos stands for "general electric comprehensive operating system", which was renamed to gcos when ge's large systems division was sold to honeywell. dennis ritchie has reported: "sometimes we sent printer output or batch jobs to the gcos machine. the gcos field in the password file was a place to stash the information for the $identcard. not elegant." .tp .i directory this is the user's home directory: the initial directory where the user is placed after logging in. the value in this field is used to set the .b home environment variable. .tp .i shell this is the program to run at login (if empty, use .ir /bin/sh ). if set to a nonexistent executable, the user will be unable to login through .br login (1). the value in this field is used to set the .b shell environment variable. .sh files .i /etc/passwd .sh notes if you want to create user groups, there must be an entry in .ir /etc/group , or no group will exist. .pp if the encrypted password is set to an asterisk (*), the user will be unable to login using .br login (1), but may still login using .br rlogin (1), run existing processes and initiate new ones through .br rsh (1), .br cron (8), .br at (1), or mail filters, etc. trying to lock an account by simply changing the shell field yields the same result and additionally allows the use of .br su (1). .sh see also .br chfn (1), .br chsh (1), .br login (1), .br passwd (1), .br su (1), .br crypt (3), .br getpwent (3), .br getpwnam (3), .br group (5), .br shadow (5), .br vipw (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .\" copyright (c) 1995 michael chastain (mec@shell.portal.com), 15 april 1995. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1997-01-31 by eric s. raymond .\" modified 2004-06-17 by michael kerrisk .\" .th bdflush 2 2021-03-22 "linux" "linux programmer's manual" .sh name bdflush \- start, flush, or tune buffer-dirty-flush daemon .sh synopsis .nf .b #include .pp .bi "int bdflush(int " func ", long *" address ); .bi "int bdflush(int " func ", long " data ); .fi .pp .ir note : there is no glibc wrapper for this system call; see versions. .sh description .ir note : since linux 2.6, .\" as noted in changes in the 2.5.12 source this system call is deprecated and does nothing. it is likely to disappear altogether in a future kernel release. nowadays, the task performed by .br bdflush () is handled by the kernel .i pdflush thread. .pp .br bdflush () starts, flushes, or tunes the buffer-dirty-flush daemon. only a privileged process (one with the .b cap_sys_admin capability) may call .br bdflush (). .pp if .i func is negative or 0, and no daemon has been started, then .br bdflush () enters the daemon code and never returns. .pp if .i func is 1, some dirty buffers are written to disk. .pp if .i func is 2 or more and is even (low bit is 0), then .i address is the address of a long word, and the tuning parameter numbered .ri "(" "func" "\-2)/2" is returned to the caller in that address. .pp if .i func is 3 or more and is odd (low bit is 1), then .i data is a long word, and the kernel sets tuning parameter numbered .ri "(" "func" "\-3)/2" to that value. .pp the set of parameters, their values, and their valid ranges are defined in the linux kernel source file .ir fs/buffer.c . .sh return value if .i func is negative or 0 and the daemon successfully starts, .br bdflush () never returns. otherwise, the return value is 0 on success and \-1 on failure, with .i errno set to indicate the error. .sh errors .tp .b ebusy an attempt was made to enter the daemon code after another process has already entered. .tp .b efault .i address points outside your accessible address space. .tp .b einval an attempt was made to read or write an invalid parameter number, or to write an invalid value to a parameter. .tp .b eperm caller does not have the .b cap_sys_admin capability. .sh versions since version 2.23, glibc no longer supports this obsolete system call. .sh conforming to .br bdflush () is linux-specific and should not be used in programs intended to be portable. .sh see also .br sync (1), .br fsync (2), .br sync (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1995 jim van zandt .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .th log1p 3 2021-03-22 "" "linux programmer's manual" .sh name log1p, log1pf, log1pl \- logarithm of 1 plus argument .sh synopsis .nf .b #include .pp .bi "double log1p(double " x ); .bi "float log1pf(float " x ); .bi "long double log1pl(long double " x ); .pp .fi link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .nf .br log1p (): _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br log1pf (), .br log1pl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return a value equivalent to .pp .nf log (1 + \fix\fp) .fi .pp the result is computed in a way that is accurate even if the value of .i x is near zero. .sh return value on success, these functions return the natural logarithm of .ir "(1\ +\ x)" . .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity, positive infinity is returned. .pp if .i x is \-1, a pole error occurs, and the functions return .rb \- huge_val , .rb \- huge_valf , or .rb \- huge_vall , respectively. .pp if .i x is less than \-1 (including negative infinity), a domain error occurs, and a nan (not a number) is returned. .\" posix.1 specifies a possible range error if x is subnormal .\" glibc 2.8 doesn't do this .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is less than \-1 .i errno is set to .br edom (but see bugs). an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp pole error: \fix\fp is \-1 .i errno is set to .br erange (but see bugs). a divide-by-zero floating-point exception .rb ( fe_divbyzero ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br log1p (), .br log1pf (), .br log1pl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .\" bsd .sh bugs before version 2.22, the glibc implementation did not set .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6792 .i errno to .b edom when a domain error occurred. .pp before version 2.22, the glibc implementation did not set .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6792 .i errno to .b erange when a range error occurred. .sh see also .br exp (3), .br expm1 (3), .br log (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-15.7 .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" author: ulrich drepper .\" .\" %%%license_start(gplv2_misc) .\" this copyrighted material is made available to anyone wishing to use, .\" modify, copy, or redistribute it subject to the terms and conditions of the .\" gnu general public license v.2. .\" .\" this program is distributed in the hope that it will be useful, but without .\" any warranty; without even the implied warranty of merchantability or .\" fitness for a particular purpose. see the gnu general public license for .\" more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th gai.conf 5 2020-06-09 "linux" "linux programmer's manual" .sh name gai.conf \- getaddrinfo(3) configuration file .sh description a call to .br getaddrinfo (3) might return multiple answers. according to rfc\ 3484 these answers must be sorted so that the answer with the highest success rate is first in the list. the rfc provides an algorithm for the sorting. the static rules are not always adequate, though. for this reason, the rfc also requires that system administrators should have the possibility to dynamically change the sorting. for the glibc implementation, this can be achieved with the .i /etc/gai.conf file. .pp each line in the configuration file consists of a keyword and its parameters. white spaces in any place are ignored. lines starting with \(aq#\(aq are comments and are ignored. .pp the keywords currently recognized are: .tp \fblabel\fr \finetmask\fr \fiprecedence\fr the value is added to the label table used in the rfc\ 3484 sorting. if any \fblabel\fr definition is present in the configuration file, the default table is not used. all the label definitions of the default table which are to be maintained have to be duplicated. following the keyword, the line has to contain a network mask and a precedence value. .tp \fbprecedence\fr \finetmask\fr \fiprecedence\fr this keyword is similar to \fblabel\fr, but instead the value is added to the precedence table as specified in rfc\ 3484. once again, the presence of a single \fbprecedence\fr line in the configuration file causes the default table to not be used. .tp \fbreload\fr <\fbyes\fr|\fbno\fr> this keyword controls whether a process checks whether the configuration file has been changed since the last time it was read. if the value is "\fbyes\fr", the file is reread. this might cause problems in multithreaded applications and is generally a bad idea. the default is "\fbno\fr". .tp \fbscopev4\fr \fimask\fr \fivalue\fr add another rule to the rfc\ 3484 scope table for ipv4 address. by default, the scope ids described in section 3.2 in rfc\ 3438 are used. changing these defaults should hardly ever be necessary. .sh files \fi/etc/gai.conf\fr .sh versions the .i gai.conf .\" added in 2006 file is supported by glibc since version 2.5. .sh examples the default table according to rfc\ 3484 would be specified with the following configuration file: .pp .in +4n .ex label ::1/128 0 label ::/0 1 label 2002::/16 2 label ::/96 3 label ::ffff:0:0/96 4 precedence ::1/128 50 precedence ::/0 40 precedence 2002::/16 30 precedence ::/96 20 precedence ::ffff:0:0/96 10 .ee .in .\" .sh author .\" ulrich drepper .\" .sh see also .br getaddrinfo (3), rfc\ 3484 .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms .\" and andries brouwer . .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th ioctl_tty 2 2021-08-27 "linux" "linux programmer's manual" .sh name ioctl_tty \- ioctls for terminals and serial lines .sh synopsis .nf .b #include .br "#include " " /* definition of " clocal ", and" .br " tc*" { flush , on , off "} constants */" .pp .bi "int ioctl(int " fd ", int " cmd ", ...);" .fi .sh description the .br ioctl (2) call for terminals and serial ports accepts many possible command arguments. most require a third argument, of varying type, here called .i argp or .ir arg . .pp use of .br ioctl () makes for nonportable programs. use the posix interface described in .br termios (3) whenever possible. .ss get and set terminal attributes .tp .b tcgets argument: .bi "struct termios *" argp .ip equivalent to .ir "tcgetattr(fd, argp)" . .ip get the current serial port settings. .tp .b tcsets argument: .bi "const struct termios *" argp .ip equivalent to .ir "tcsetattr(fd, tcsanow, argp)" . .ip set the current serial port settings. .tp .b tcsetsw argument: .bi "const struct termios *" argp .ip equivalent to .ir "tcsetattr(fd, tcsadrain, argp)" . .ip allow the output buffer to drain, and set the current serial port settings. .tp .b tcsetsf argument: .bi "const struct termios *" argp .ip equivalent to .ir "tcsetattr(fd, tcsaflush, argp)" . .ip allow the output buffer to drain, discard pending input, and set the current serial port settings. .pp the following four ioctls, added in linux 2.6.20, .\" commit 64bb6c5e1ddcd47c951740485026ef08975ee2e6 .\" commit 592ee3a5e5e2a981ef2829a0380093006d045661 are just like .br tcgets , .br tcsets , .br tcsetsw , .br tcsetsf , except that they take a .i "struct termios2\ *" instead of a .ir "struct termios\ *" . if the structure member .b c_cflag contains the flag .br bother , then the baud rate is stored in the structure members .b c_ispeed and .b c_ospeed as integer values. these ioctls are not supported on all architectures. .rs .ts lb l. tcgets2 \fbstruct termios2 *\fpargp tcsets2 \fbconst struct termios2 *\fpargp tcsetsw2 \fbconst struct termios2 *\fpargp tcsetsf2 \fbconst struct termios2 *\fpargp .te .re .pp the following four ioctls are just like .br tcgets , .br tcsets , .br tcsetsw , .br tcsetsf , except that they take a .i "struct termio\ *" instead of a .ir "struct termios\ *" . .rs .ts lb l. tcgeta \fbstruct termio *\fpargp tcseta \fbconst struct termio *\fpargp tcsetaw \fbconst struct termio *\fpargp tcsetaf \fbconst struct termio *\fpargp .te .re .ss locking the termios structure the .i termios structure of a terminal can be locked. the lock is itself a .i termios structure, with nonzero bits or fields indicating a locked value. .tp .b tiocglcktrmios argument: .bi "struct termios *" argp .ip gets the locking status of the .i termios structure of the terminal. .tp .b tiocslcktrmios argument: .bi "const struct termios *" argp .ip sets the locking status of the .i termios structure of the terminal. only a process with the .br cap_sys_admin capability can do this. .ss get and set window size window sizes are kept in the kernel, but not used by the kernel (except in the case of virtual consoles, where the kernel will update the window size when the size of the virtual console changes, for example, by loading a new font). .tp .b tiocgwinsz argument: .bi "struct winsize *" argp .ip get window size. .tp .b tiocswinsz argument: .bi "const struct winsize *" argp .ip set window size. .pp the struct used by these ioctls is defined as .pp .in +4n .ex struct winsize { unsigned short ws_row; unsigned short ws_col; unsigned short ws_xpixel; /* unused */ unsigned short ws_ypixel; /* unused */ }; .ee .in .pp when the window size changes, a .b sigwinch signal is sent to the foreground process group. .ss sending a break .tp .b tcsbrk argument: .bi "int " arg .ip equivalent to .ir "tcsendbreak(fd, arg)" . .ip if the terminal is using asynchronous serial data transmission, and .i arg is zero, then send a break (a stream of zero bits) for between 0.25 and 0.5 seconds. if the terminal is not using asynchronous serial data transmission, then either a break is sent, or the function returns without doing anything. when .i arg is nonzero, nobody knows what will happen. .ip (svr4, unixware, solaris, and linux treat .i "tcsendbreak(fd,arg)" with nonzero .i arg like .ir "tcdrain(fd)" . sunos treats .i arg as a multiplier, and sends a stream of bits .i arg times as long as done for zero .ir arg . dg/ux and aix treat .i arg (when nonzero) as a time interval measured in milliseconds. hp-ux ignores .ir arg .) .tp .b tcsbrkp argument: .bi "int " arg .ip so-called "posix version" of .br tcsbrk . it treats nonzero .i arg as a time interval measured in deciseconds, and does nothing when the driver does not support breaks. .tp .b tiocsbrk argument: .bi "void" .ip turn break on, that is, start sending zero bits. .tp .b tioccbrk argument: .bi "void" .ip turn break off, that is, stop sending zero bits. .ss software flow control .tp .b tcxonc argument: .bi "int " arg .ip equivalent to .ir "tcflow(fd, arg)" . .ip see .br tcflow (3) for the argument values .br tcooff , .br tcoon , .br tcioff , .br tcion . .ss buffer count and flushing .tp .bi fionread argument: .bi "int *" argp .ip get the number of bytes in the input buffer. .tp .b tiocinq argument: .bi "int *" argp .ip same as .br fionread . .tp .b tiocoutq argument: .bi "int *" argp .ip get the number of bytes in the output buffer. .tp .b tcflsh argument: .bi "int " arg .ip equivalent to .ir "tcflush(fd, arg)" . .ip see .br tcflush (3) for the argument values .br tciflush , .br tcoflush , .br tcioflush . .ss faking input .tp .b tiocsti argument: .bi "const char *" argp .ip insert the given byte in the input queue. .ss redirecting console output .tp .b tioccons argument: .bi "void" .ip redirect output that would have gone to .i /dev/console or .i /dev/tty0 to the given terminal. if that was a pseudoterminal master, send it to the slave. in linux before version 2.6.10, anybody can do this as long as the output was not redirected yet; since version 2.6.10, only a process with the .br cap_sys_admin capability may do this. if output was redirected already, then .b ebusy is returned, but redirection can be stopped by using this ioctl with .i fd pointing at .i /dev/console or .ir /dev/tty0 . .ss controlling terminal .tp .b tiocsctty argument: .bi "int " arg .ip make the given terminal the controlling terminal of the calling process. the calling process must be a session leader and not have a controlling terminal already. for this case, .i arg should be specified as zero. .ip if this terminal is already the controlling terminal of a different session group, then the ioctl fails with .br eperm , unless the caller has the .br cap_sys_admin capability and .i arg equals 1, in which case the terminal is stolen, and all processes that had it as controlling terminal lose it. .tp .b tiocnotty argument: .bi "void" .ip if the given terminal was the controlling terminal of the calling process, give up this controlling terminal. if the process was session leader, then send .b sighup and .b sigcont to the foreground process group and all processes in the current session lose their controlling terminal. .ss process group and session id .tp .b tiocgpgrp argument: .bi "pid_t *" argp .ip when successful, equivalent to .ir "*argp = tcgetpgrp(fd)" . .ip get the process group id of the foreground process group on this terminal. .tp .b tiocspgrp argument: .bi "const pid_t *" argp .ip equivalent to .ir "tcsetpgrp(fd, *argp)" . .ip set the foreground process group id of this terminal. .tp .b tiocgsid argument: .bi "pid_t *" argp .ip get the session id of the given terminal. this fails with the error .b enotty if the terminal is not a master pseudoterminal and not our controlling terminal. strange. .ss exclusive mode .tp .b tiocexcl argument: .bi "void" .ip put the terminal into exclusive mode. no further .br open (2) operations on the terminal are permitted. (they fail with .br ebusy , except for a process with the .br cap_sys_admin capability.) .tp .b tiocgexcl argument: .bi "int *" argp .ip (since linux 3.8) if the terminal is currently in exclusive mode, place a nonzero value in the location pointed to by .ir argp ; otherwise, place zero in .ir *argp . .tp .b tiocnxcl argument: .bi "void" .ip disable exclusive mode. .ss line discipline .tp .b tiocgetd argument: .bi "int *" argp .ip get the line discipline of the terminal. .tp .b tiocsetd argument: .bi "const int *" argp .ip set the line discipline of the terminal. .ss pseudoterminal ioctls .tp .b tiocpkt argument: .bi "const int *" argp .ip enable (when .ri * argp is nonzero) or disable packet mode. can be applied to the master side of a pseudoterminal only (and will return .b enotty otherwise). in packet mode, each subsequent .br read (2) will return a packet that either contains a single nonzero control byte, or has a single byte containing zero (\(aq\e0\(aq) followed by data written on the slave side of the pseudoterminal. if the first byte is not .b tiocpkt_data (0), it is an or of one or more of the following bits: .ip .ad l .ts lb l. tiocpkt_flushread t{ the read queue for the terminal is flushed. t} tiocpkt_flushwrite t{ the write queue for the terminal is flushed. t} tiocpkt_stop t{ output to the terminal is stopped. t} tiocpkt_start t{ output to the terminal is restarted. t} tiocpkt_dostop t{ the start and stop characters are \fb\(has\fp/\fb\(haq\fp. t} tiocpkt_nostop t{ the start and stop characters are not \fb\(has\fp/\fb\(haq\fp. t} .te .ad .ip while packet mode is in use, the presence of control status information to be read from the master side may be detected by a .br select (2) for exceptional conditions or a .br poll (2) for the .b pollpri event. .ip this mode is used by .br rlogin (1) and .br rlogind (8) to implement a remote-echoed, locally \fb\(has\fp/\fb\(haq\fp flow-controlled remote login. .tp .b tiocgpkt argument: .bi "const int *" argp .ip (since linux 3.8) return the current packet mode setting in the integer pointed to by .ir argp . .tp .b tiocsptlck argument: .bi "int *" argp .ip set (if .ir *argp is nonzero) or remove (if .ir *argp is zero) the lock on the pseudoterminal slave device. (see also .br unlockpt (3).) .tp .b tiocgptlck argument: .bi "int *" argp .ip (since linux 3.8) place the current lock state of the pseudoterminal slave device in the location pointed to by .ir argp . .tp .b tiocgptpeer argument: .bi "int " flags .ip .\" commit 54ebbfb1603415d9953c150535850d30609ef077 (since linux 4.13) given a file descriptor in .i fd that refers to a pseudoterminal master, open (with the given .br open (2)-style .ir flags ) and return a new file descriptor that refers to the peer pseudoterminal slave device. this operation can be performed regardless of whether the pathname of the slave device is accessible through the calling process's mount namespace. .ip security-conscious programs interacting with namespaces may wish to use this operation rather than .br open (2) with the pathname returned by .br ptsname (3), and similar library functions that have insecure apis. (for example, confusion can occur in some cases using .br ptsname (3) with a pathname where a devpts filesystem has been mounted in a different mount namespace.) .pp the bsd ioctls .br tiocstop , .br tiocstart , .br tiocucntl , and .b tiocremote have not been implemented under linux. .ss modem control .tp .b tiocmget argument: .bi "int *" argp .ip get the status of modem bits. .tp .b tiocmset argument: .bi "const int *" argp .ip set the status of modem bits. .tp .b tiocmbic argument: .bi "const int *" argp .ip clear the indicated modem bits. .tp .b tiocmbis argument: .bi "const int *" argp .ip set the indicated modem bits. .pp the following bits are used by the above ioctls: .pp .ts lb l. tiocm_le dsr (data set ready/line enable) tiocm_dtr dtr (data terminal ready) tiocm_rts rts (request to send) tiocm_st secondary txd (transmit) tiocm_sr secondary rxd (receive) tiocm_cts cts (clear to send) tiocm_car dcd (data carrier detect) tiocm_cd see tiocm_car tiocm_rng rng (ring) tiocm_ri see tiocm_rng tiocm_dsr dsr (data set ready) .te .tp .b tiocmiwait argument: .bi "int " arg .ip wait for any of the 4 modem bits (dcd, ri, dsr, cts) to change. the bits of interest are specified as a bit mask in .ir arg , by oring together any of the bit values, .br tiocm_rng , .br tiocm_dsr , .br tiocm_cd , and .br tiocm_cts . the caller should use .b tiocgicount to see which bit has changed. .tp .b tiocgicount argument: .bi "struct serial_icounter_struct *" argp .ip get counts of input serial line interrupts (dcd, ri, dsr, cts). the counts are written to the .i serial_icounter_struct structure pointed to by .ir argp . .ip note: both 1->0 and 0->1 transitions are counted, except for ri, where only 0->1 transitions are counted. .ss marking a line as local .tp .b tiocgsoftcar argument: .bi "int *" argp .ip ("get software carrier flag") get the status of the clocal flag in the c_cflag field of the .i termios structure. .tp .b tiocssoftcar argument: .bi "const int *" argp .ip ("set software carrier flag") set the clocal flag in the .i termios structure when .ri * argp is nonzero, and clear it otherwise. .pp if the .b clocal flag for a line is off, the hardware carrier detect (dcd) signal is significant, and an .br open (2) of the corresponding terminal will block until dcd is asserted, unless the .b o_nonblock flag is given. if .b clocal is set, the line behaves as if dcd is always asserted. the software carrier flag is usually turned on for local devices, and is off for lines with modems. .ss linux-specific for the .b tioclinux ioctl, see .br ioctl_console (2). .ss kernel debugging .b "#include " .tp .b tiocttygstruct argument: .bi "struct tty_struct *" argp .ip get the .i tty_struct corresponding to .ir fd . this command was removed in linux 2.5.67. .\" commit b3506a09d15dc5aee6d4bb88d759b157016e1864 .\" author: andries e. brouwer .\" date: tue apr 1 04:42:46 2003 -0800 .\" .\" [patch] kill tiocttygstruct .\" .\" only used for (dubious) debugging purposes, and exposes .\" internal kernel state. .\" .\" .ss serial info .\" .br "#include " .\" .pp .\" .tp .\" .bi "tiocgserial struct serial_struct *" argp .\" get serial info. .\" .tp .\" .bi "tiocsserial const struct serial_struct *" argp .\" set serial info. .sh return value the .br ioctl (2) system call returns 0 on success. on error, it returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b einval invalid command parameter. .tp .b enoioctlcmd unknown command. .tp .b enotty inappropriate .ir fd . .tp .b eperm insufficient permission. .sh examples check the condition of dtr on the serial port. .pp .ex #include #include #include #include int main(void) { int fd, serial; fd = open("/dev/ttys0", o_rdonly); ioctl(fd, tiocmget, &serial); if (serial & tiocm_dtr) puts("tiocm_dtr is set"); else puts("tiocm_dtr is not set"); close(fd); } .ee .sh see also .br ldattach (1), .br ioctl (2), .br ioctl_console (2), .br termios (3), .br pty (7) .\" .\" fionbio const int * .\" fionclex void .\" fioclex void .\" fioasync const int * .\" from serial.c: .\" tiocserconfig void .\" tiocsergwild int * .\" tiocserswild const int * .\" tiocsergstruct struct async_struct * .\" tiocsergetlsr int * .\" tiocsergetmulti struct serial_multiport_struct * .\" tiocsersetmulti const struct serial_multiport_struct * .\" tiocgserial, tiocsserial (see above) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fpclassify.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:01:20 1993 by rik faith (faith@cs.unc.edu) .th localeconv 3 2021-03-22 "gnu" "linux programmer's manual" .sh name localeconv \- get numeric formatting information .sh synopsis .nf .b #include .pp .b struct lconv *localeconv(void); .fi .sh description the .br localeconv () function returns a pointer to a .i struct lconv for the current locale. this structure is shown in .br locale (7), and contains all values associated with the locale categories .b lc_numeric and .br lc_monetary . programs may also use the functions .br printf (3) and .br strfmon (3), which behave according to the actual locale in use. .sh return value the .br localeconv () function returns a pointer to a filled in .ir "struct lconv" . this structure may be (in glibc, .ir is ) statically allocated, and may be overwritten by subsequent calls. according to posix, the caller should not modify the contents of this structure. the .br localeconv () function always succeeds. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br localeconv () t} thread safety t{ mt-unsafe race:localeconv locale t} .te .hy .ad .sp 1 .sh conforming to c89, c99. .sh bugs the .br printf (3) family of functions may or may not honor the current locale. .sh see also .br locale (1), .br localedef (1), .br isalpha (3), .br nl_langinfo (3), .br setlocale (3), .br strcoll (3), .br strftime (3), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/lrint.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:43:46 1993 by rik faith (faith@cs.unc.edu) .th putpwent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name putpwent \- write a password file entry .sh synopsis .nf .b #include .b #include .b #include .pp .bi "int putpwent(const struct passwd *restrict " p \ ", file *restrict " stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br putpwent (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description the .br putpwent () function writes a password entry from the structure \fip\fp in the file associated with \fistream\fp. .pp the \fipasswd\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct passwd { char *pw_name; /* username */ char *pw_passwd; /* user password */ uid_t pw_uid; /* user id */ gid_t pw_gid; /* group id */ char *pw_gecos; /* real name */ char *pw_dir; /* home directory */ char *pw_shell; /* shell program */ }; .ee .in .sh return value the .br putpwent () function returns 0 on success. on failure, it returns \-1, and .i errno is set to indicate the error. .sh errors .tp .b einval invalid (null) argument given. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br putpwent () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to svr4. .sh see also .br endpwent (3), .br fgetpwent (3), .br getpw (3), .br getpwent (3), .br getpwnam (3), .br getpwuid (3), .br setpwent (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" and copyright (c) 2020 by alejandro colomar .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" .th list 3 2021-03-22 "gnu" "linux programmer's manual" .sh name list_empty, list_entry, list_first, list_foreach, .\"list_foreach_from, .\"list_foreach_safe, .\"list_foreach_from_safe, list_head, list_head_initializer, list_init, list_insert_after, list_insert_before, list_insert_head, list_next, .\"list_prev, list_remove .\"list_swap \- implementation of a doubly linked list .sh synopsis .nf .b #include .pp .b list_entry(type); .pp .b list_head(headname, type); .bi "list_head list_head_initializer(list_head " head ); .bi "void list_init(list_head *" head ); .pp .bi "int list_empty(list_head *" head ); .pp .bi "void list_insert_head(list_head *" head , .bi " struct type *" elm ", list_entry " name ); .bi "void list_insert_before(struct type *" listelm , .bi " struct type *" elm ", list_entry " name ); .bi "void list_insert_after(struct type *" listelm , .bi " struct type *" elm ", list_entry " name ); .pp .bi "struct type *list_first(list_head *" head ); .\" .bi "struct type *list_prev(struct type *" elm ", list_head *" head , .\" .bi " struct type, list_entry " name ); .bi "struct type *list_next(struct type *" elm ", list_entry " name ); .pp .bi "list_foreach(struct type *" var ", list_head *" head ", list_entry " name ); .\" .bi "list_foreach_from(struct type *" var ", list_head *" head ", list_entry " name ); .\" .pp .\" .bi "list_foreach_safe(struct type *" var ", list_head *" head , .\" .bi " list_entry " name ", struct type *" temp_var ); .\" .bi "list_foreach_from_safe(struct type *" var ", list_head *" head , .\" .bi " list_entry " name ", struct type *" temp_var ); .pp .bi "void list_remove(struct type *" elm ", list_entry " name ); .\" .pp .\" .bi "void list_swap(list_head *" head1 ", list_head *" head2 , .\" .bi " struct type, list_entry " name ); .fi .sh description these macros define and operate on doubly linked lists. .pp in the macro definitions, .i type is the name of a user-defined structure, that must contain a field of type .ir list_entry , named .ir name . the argument .ir headname is the name of a user-defined structure that must be declared using the macro .br list_head (). .ss creation a list is headed by a structure defined by the .br list_head () macro. this structure contains a single pointer to the first element on the list. the elements are doubly linked so that an arbitrary element can be removed without traversing the list. new elements can be added to the list after an existing element, before an existing element, or at the head of the list. a .i list_head structure is declared as follows: .pp .in +4 .ex list_head(headname, type) head; .ee .in .pp where .i struct headname is the structure to be defined, and .i struct type is the type of the elements to be linked into the list. a pointer to the head of the list can later be declared as: .pp .in +4 .ex struct headname *headp; .ee .in .pp (the names .i head and .i headp are user selectable.) .pp .br list_entry () declares a structure that connects the elements in the list. .pp .br list_head_initializer () evaluates to an initializer for the list .ir head . .pp .br list_init () initializes the list referenced by .ir head . .pp .br list_empty () evaluates to true if there are no elements in the list. .ss insertion .br list_insert_head () inserts the new element .i elm at the head of the list. .pp .br list_insert_before () inserts the new element .i elm before the element .ir listelm . .pp .br list_insert_after () inserts the new element .i elm after the element .ir listelm . .ss traversal .br list_first () returns the first element in the list, or null if the list is empty. .\" .pp .\" .br list_prev () .\" returns the previous element in the list, or null if this is the first. .\" list .\" .i head .\" must contain element .\" .ir elm . .pp .br list_next () returns the next element in the list, or null if this is the last. .pp .br list_foreach () traverses the list referenced by .i head in the forward direction, assigning each element in turn to .ir var . .\" .pp .\" .br list_foreach_from () .\" behaves identically to .\" .br list_foreach () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found list element and begins the loop at .\" .i var .\" instead of the first element in the list referenced by .\" .ir head . .\" .pp .\" .br list_foreach_safe () .\" traverses the list referenced by .\" .i head .\" in the forward direction, assigning each element in turn to .\" .ir var . .\" however, unlike .\" .br list_foreach () .\" here it is permitted to both remove .\" .i var .\" as well as free it from within the loop safely without interfering with the .\" traversal. .\" .pp .\" .br list_foreach_from_safe () .\" behaves identically to .\" .br list_foreach_safe () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found list element and begins the loop at .\" .i var .\" instead of the first element in the list referenced by .\" .ir head . .ss removal .br list_remove () removes the element .i elm from the list. .\" .ss other features .\" .br list_swap () .\" swaps the contents of .\" .i head1 .\" and .\" .ir head2 . .sh return value .br list_empty () returns nonzero if the list is empty, and zero if the list contains at least one entry. .pp .br list_first (), and .br list_next () return a pointer to the first or next .i type structure, respectively. .pp .br list_head_initializer () returns an initializer that can be assigned to the list .ir head . .sh conforming to not in posix.1, posix.1-2001, or posix.1-2008. present on the bsds (list macros first appeared in 4.4bsd). .sh bugs .br list_foreach () doesn't allow .i var to be removed or freed within the loop, as it would interfere with the traversal. .br list_foreach_safe (), which is present on the bsds but is not present in glibc, fixes this limitation by allowing .i var to safely be removed from the list and freed from within the loop without interfering with the traversal. .sh examples .ex #include #include #include #include struct entry { int data; list_entry(entry) entries; /* list */ }; list_head(listhead, entry); int main(void) { struct entry *n1, *n2, *n3, *np; struct listhead head; /* list head */ int i; list_init(&head); /* initialize the list */ n1 = malloc(sizeof(struct entry)); /* insert at the head */ list_insert_head(&head, n1, entries); n2 = malloc(sizeof(struct entry)); /* insert after */ list_insert_after(n1, n2, entries); n3 = malloc(sizeof(struct entry)); /* insert before */ list_insert_before(n2, n3, entries); i = 0; /* forward traversal */ list_foreach(np, &head, entries) np\->data = i++; list_remove(n2, entries); /* deletion */ free(n2); /* forward traversal */ list_foreach(np, &head, entries) printf("%i\en", np\->data); /* list deletion */ n1 = list_first(&head); while (n1 != null) { n2 = list_next(n1, entries); free(n1); n1 = n2; } list_init(&head); exit(exit_success); } .ee .sh see also .br insque (3), .br queue (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-14 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-14 \- iso 8859-14 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-14 encodes the characters used in celtic languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-14 characters the following table displays the characters in iso 8859-14 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ḃ latin capital letter b with dot above 242 162 a2 ḃ latin small letter b with dot above 243 163 a3 £ pound sign 244 164 a4 ċ latin capital letter c with dot above 245 165 a5 ċ latin small letter c with dot above 246 166 a6 ḋ latin capital letter d with dot above 247 167 a7 § section sign 250 168 a8 ẁ latin capital letter w with grave 251 169 a9 © copyright sign 252 170 aa ẃ latin capital letter w with acute 253 171 ab ḋ latin small letter d with dot above 254 172 ac ỳ latin capital letter y with grave 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ÿ latin capital letter y with diaeresis 260 176 b0 ḟ latin capital letter f with dot above 261 177 b1 ḟ latin small letter f with dot above 262 178 b2 ġ latin capital letter g with dot above 263 179 b3 ġ latin small letter g with dot above 264 180 b4 ṁ latin capital letter m with dot above 265 181 b5 ṁ latin small letter m with dot above 266 182 b6 ¶ pilcrow sign 267 183 b7 ṗ latin capital letter p with dot above 270 184 b8 ẁ latin small letter w with grave 271 185 b9 ṗ latin small letter p with dot above 272 186 ba ẃ latin small letter w with acute 273 187 bb ṡ latin capital letter s with dot above 274 188 bc ỳ latin small letter y with grave 275 189 bd ẅ latin capital letter w with diaeresis 276 190 be ẅ latin small letter w with diaeresis 277 191 bf ṡ latin small letter s with dot above 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 ŵ latin capital letter w with circumflex 321 209 d1 ñ latin capital letter n with tilde 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 ṫ latin capital letter t with dot above 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ý latin capital letter y with acute 336 222 de ŷ latin capital letter y with circumflex 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 ŵ latin small letter w with circumflex 361 241 f1 ñ latin small letter n with tilde 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ṫ latin small letter t with dot above 370 248 f8 ø latin small letter o with stroke 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ý latin small letter y with acute 376 254 fe ŷ latin small letter y with circumflex 377 255 ff ÿ latin small letter y with diaeresis .te .sh notes iso 8859-14 is also known as latin-8. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" written by ralf baechle (ralf@waldorf-gmbh.de), .\" copyright (c) 1994, 1995 waldorf gmbh .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th cacheflush 2 2021-03-22 "linux" "linux programmer's manual" .sh name cacheflush \- flush contents of instruction and/or data cache .sh synopsis .nf .b #include .pp .bi "int cacheflush(void *" addr ", int "nbytes ", int "cache ); .fi .pp .ir note : on some architectures, there is no glibc wrapper for this system call; see notes. .sh description .br cacheflush () flushes the contents of the indicated cache(s) for the user addresses in the range .i addr to .ir (addr+nbytes\-1) . .i cache may be one of: .tp .b icache flush the instruction cache. .tp .b dcache write back to memory and invalidate the affected valid cache lines. .tp .b bcache same as .br (icache|dcache) . .sh return value .br cacheflush () returns 0 on success. on error, it returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b efault some or all of the address range .i addr to .i (addr+nbytes\-1) is not accessible. .tp .b einval .i cache is not one of .br icache , .br dcache , or .br bcache (but see bugs). .sh conforming to historically, this system call was available on all mips unix variants including risc/os, irix, ultrix, netbsd, openbsd, and freebsd (and also on some non-unix mips operating systems), so that the existence of this call in mips operating systems is a de-facto standard. .ss caveat .br cacheflush () should not be used in programs intended to be portable. on linux, this call first appeared on the mips architecture, but nowadays, linux provides a .br cacheflush () system call on some other architectures, but with different arguments. .sh notes .ss architecture-specific variants glibc provides a wrapper for this system call, with the prototype shown in synopsis, for the following architectures: arc, csky, mips, and nios2. .pp on some other architectures, linux provides this system call, with different arguments: .tp m68k: .nf .bi "int cacheflush(unsigned long " addr ", int " scope ", int " cache , .bi " unsigned long " len ); .fi .tp sh: .nf .bi "int cacheflush(unsigned long " addr ", unsigned long " len ", int " op ); .fi .tp nds32: .nf .bi "int cacheflush(unsigned int " start ", unsigned int " end ", int " cache ); .fi .pp on the above architectures, glibc does not provide a wrapper for this system call; call it using .br syscall (2). .ss gcc alternative unless you need the finer grained control that this system call provides, you probably want to use the gcc built-in function .br __builtin___clear_cache (), which provides a portable interface across platforms supported by gcc and compatible compilers: .pp .in +4n .ex .bi "void __builtin___clear_cache(void *" begin ", void *" end ); .ee .in .pp on platforms that don't require instruction cache flushes, .br __builtin___clear_cache () has no effect. .pp .ir note : on some gcc-compatible compilers, the prototype for this built-in function uses .i char * instead of .i void * for the parameters. .sh bugs linux kernels older than version 2.6.11 ignore the .i addr and .i nbytes arguments, making this function fairly expensive. therefore, the whole cache is always flushed. .pp this function always behaves as if .br bcache has been passed for the .i cache argument and does not do any error checking on the .i cache argument. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_init 3 2021-03-22 "linux" "linux programmer's manual" .sh name sem_init \- initialize an unnamed semaphore .sh synopsis .nf .b #include .pp .bi "int sem_init(sem_t *" sem ", int " pshared ", unsigned int " value ); .fi .pp link with \fi\-pthread\fp. .sh description .br sem_init () initializes the unnamed semaphore at the address pointed to by .ir sem . the .i value argument specifies the initial value for the semaphore. .pp the .i pshared argument indicates whether this semaphore is to be shared between the threads of a process, or between processes. .pp if .i pshared has the value 0, then the semaphore is shared between the threads of a process, and should be located at some address that is visible to all threads (e.g., a global variable, or a variable allocated dynamically on the heap). .pp if .i pshared is nonzero, then the semaphore is shared between processes, and should be located in a region of shared memory (see .br shm_open (3), .br mmap (2), and .br shmget (2)). (since a child created by .br fork (2) inherits its parent's memory mappings, it can also access the semaphore.) any process that can access the shared memory region can operate on the semaphore using .br sem_post (3), .br sem_wait (3), and so on. .pp initializing a semaphore that has already been initialized results in undefined behavior. .sh return value .br sem_init () returns 0 on success; on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i value exceeds .br sem_value_max . .tp .b enosys .i pshared is nonzero, but the system does not support process-shared semaphores (see .br sem_overview (7)). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_init () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001. .sh notes bizarrely, posix.1-2001 does not specify the value that should be returned by a successful call to .br sem_init (). posix.1-2008 rectifies this, specifying the zero return on success. .sh examples see .br shm_open (3) and .br sem_wait (3). .sh see also .br sem_destroy (3), .br sem_post (3), .br sem_wait (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th dirfd 3 2021-03-22 "linux" "linux programmer's manual" .sh name dirfd \- get directory stream file descriptor .sh synopsis .nf .b #include .b #include .pp .bi "int dirfd(dir *" dirp ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br dirfd (): .nf /* since glibc 2.10: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the function .br dirfd () returns the file descriptor associated with the directory stream .ir dirp . .pp this file descriptor is the one used internally by the directory stream. as a result, it is useful only for functions which do not depend on or alter the file position, such as .br fstat (2) and .br fchdir (2). it will be automatically closed when .br closedir (3) is called. .sh return value on success, .br dirfd () returns a file descriptor (a nonnegative integer). on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors posix.1-2008 specifies two errors, neither of which is returned by the current .\" glibc 2.8 implementation. .tp .b einval .i dirp does not refer to a valid directory stream. .tp .b enotsup the implementation does not support the association of a file descriptor with a directory. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dirfd () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function was a bsd extension, present in 4.3bsd-reno, not in 4.2bsd. .\" it is present in libc5 (since 5.1.2) and in glibc2. .sh see also .br open (2), .br openat (2), .br closedir (3), .br opendir (3), .br readdir (3), .br rewinddir (3), .br scandir (3), .br seekdir (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th duplocale 3 2021-03-22 "linux" "linux programmer's manual" .sh name duplocale \- duplicate a locale object .sh synopsis .nf .b #include .pp .bi "locale_t duplocale(locale_t " locobj ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br duplocale (): .nf since glibc 2.10: _xopen_source >= 700 before glibc 2.10: _gnu_source .fi .sh description the .br duplocale () function creates a duplicate of the locale object referred to by .ir locobj . .pp if .i locobj is .br lc_global_locale , .br duplocale () creates a locale object containing a copy of the global locale determined by .br setlocale (3). .sh return value on success, .br duplocale () returns a handle for the new locale object. on error, it returns .ir "(locale_t)\ 0", and sets .i errno to indicate the error. .sh errors .tp .b enomem insufficient memory to create the duplicate locale object. .sh versions the .br duplocale () function first appeared in version 2.3 of the gnu c library. .sh conforming to posix.1-2008. .sh notes duplicating a locale can serve the following purposes: .ip * 3 to create a copy of a locale object in which one of more categories are to be modified (using .br newlocale (3)). .ip * to obtain a handle for the current locale which can used in other functions that employ a locale handle, such as .br toupper_l (3). this is done by applying .br duplocale () to the value returned by the following call: .ip loc = uselocale((locale_t) 0); .ip this technique is necessary, because the above .br uselocale (3) call may return the value .br lc_global_locale , which results in undefined behavior if passed to functions such as .br toupper_l (3). calling .br duplocale () can be used to ensure that the .br lc_global_locale value is converted into a usable locale object. see examples, below. .pp each locale object created by .br duplocale () should be deallocated using .br freelocale (3). .sh examples the program below uses .br uselocale (3) and .br duplocale () to obtain a handle for the current locale which is then passed to .br toupper_l (3). the program takes one command-line argument, a string of characters that is converted to uppercase and displayed on standard output. an example of its use is the following: .pp .in +4n .ex $ \fb./a.out abc\fp abc .ee .in .ss program source \& .ex #define _xopen_source 700 #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { locale_t loc, nloc; if (argc != 2) { fprintf(stderr, "usage: %s string\en", argv[0]); exit(exit_failure); } /* this sequence is necessary, because uselocale() might return the value lc_global_locale, which can\(aqt be passed as an argument to toupper_l(). */ loc = uselocale((locale_t) 0); if (loc == (locale_t) 0) errexit("uselocale"); nloc = duplocale(loc); if (nloc == (locale_t) 0) errexit("duplocale"); for (char *p = argv[1]; *p; p++) putchar(toupper_l(*p, nloc)); printf("\en"); freelocale(nloc); exit(exit_success); } .ee .sh see also .br freelocale (3), .br newlocale (3), .br setlocale (3), .br uselocale (3), .br locale (5), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getrlimit.2 .so man3/isalpha.3 .\" copyright 1993-1995 daniel quinlan (quinlan@yggdrasil.com) .\" copyright 1999 dimitri papadopoulos (dpo@club-internet.fr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-15 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-15 \- iso 8859-15 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-15 encodes the characters used in many west european languages and adds the euro sign. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-15 characters the following table displays the characters in iso 8859-15 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ¡ inverted exclamation mark 242 162 a2 ¢ cent sign 243 163 a3 £ pound sign 244 164 a4 € euro sign 245 165 a5 ¥ yen sign 246 166 a6 š latin capital letter s with caron 247 167 a7 § section sign 250 168 a8 š latin small letter s with caron 251 169 a9 © copyright sign 252 170 aa ª feminine ordinal indicator 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ¯ macron 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ž latin capital letter z with caron 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ž latin small letter z with caron 271 185 b9 ¹ superscript one 272 186 ba º masculine ordinal indicator 273 187 bb » right-pointing double angle quotation mark 274 188 bc œ latin capital ligature oe 275 189 bd œ latin small ligature oe 276 190 be ÿ latin capital letter y with diaeresis 277 191 bf ¿ inverted question mark 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 ð latin capital letter eth 321 209 d1 ñ latin capital letter n with tilde 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ý latin capital letter y with acute 336 222 de þ latin capital letter thorn 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 ð latin small letter eth 361 241 f1 ñ latin small letter n with tilde 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ø latin small letter o with stroke 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ý latin small letter y with acute 376 254 fe þ latin small letter thorn 377 255 ff ÿ latin small letter y with diaeresis .te .sh notes iso 8859-15 is also known as latin-9 (or sometimes as latin-0). .sh see also .br ascii (7), .br charsets (7), .br cp1252 (7), .br iso_8859\-1 (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" %%%license_start(public_domain) .\" this page is in the public domain. .\" %%%license_end .\" .\" almost all details are from rfc 2553. .\" .\" 2004-12-14, mtk, added eai_overflow error .\" 2004-12-14 fixed description of error return .\" .th getnameinfo 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getnameinfo \- address-to-name translation in protocol-independent manner .sh synopsis .nf .b #include .b #include .pp .bi "int getnameinfo(const struct sockaddr *restrict " addr \ ", socklen_t " addrlen , .bi " char *restrict " host ", socklen_t " hostlen , .bi " char *restrict " serv ", socklen_t " servlen \ ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getnameinfo (): .nf since glibc 2.22: _posix_c_source >= 200112l glibc 2.21 and earlier: _posix_c_source .fi .sh description the .br getnameinfo () function is the inverse of .br getaddrinfo (3): it converts a socket address to a corresponding host and service, in a protocol-independent manner. it combines the functionality of .br gethostbyaddr (3) and .br getservbyport (3), but unlike those functions, .br getnameinfo () is reentrant and allows programs to eliminate ipv4-versus-ipv6 dependencies. .pp the .i addr argument is a pointer to a generic socket address structure (of type .i sockaddr_in or .ir sockaddr_in6 ) of size .i addrlen that holds the input ip address and port number. the arguments .i host and .i serv are pointers to caller-allocated buffers (of size .i hostlen and .i servlen respectively) into which .br getnameinfo () places null-terminated strings containing the host and service names respectively. .pp the caller can specify that no hostname (or no service name) is required by providing a null .i host (or .ir serv ) argument or a zero .i hostlen (or .ir servlen ) argument. however, at least one of hostname or service name must be requested. .pp the .i flags argument modifies the behavior of .br getnameinfo () as follows: .tp .b ni_namereqd if set, then an error is returned if the hostname cannot be determined. .tp .b ni_dgram if set, then the service is datagram (udp) based rather than stream (tcp) based. this is required for the few ports (512\(en514) that have different services for udp and tcp. .tp .b ni_nofqdn if set, return only the hostname part of the fully qualified domain name for local hosts. .tp .b ni_numerichost if set, then the numeric form of the hostname is returned. .\" for example, by calling .\" .br inet_ntop () .\" instead of .\" .br gethostbyaddr (). (when not set, this will still happen in case the node's name cannot be determined.) .\" posix.1-2001 tc1 has ni_numericscope, but glibc doesn't have it. .tp .b ni_numericserv if set, then the numeric form of the service address is returned. (when not set, this will still happen in case the service's name cannot be determined.) .ss extensions to getnameinfo() for internationalized domain names starting with glibc 2.3.4, .br getnameinfo () has been extended to selectively allow hostnames to be transparently converted to and from the internationalized domain name (idn) format (see rfc 3490, .ir "internationalizing domain names in applications (idna)" ). three new flags are defined: .tp .b ni_idn if this flag is used, then the name found in the lookup process is converted from idn format to the locale's encoding if necessary. ascii-only names are not affected by the conversion, which makes this flag usable in existing programs and environments. .tp .br ni_idn_allow_unassigned ", " ni_idn_use_std3_ascii_rules setting these flags will enable the idna_allow_unassigned (allow unassigned unicode code points) and idna_use_std3_ascii_rules (check output to make sure it is a std3 conforming hostname) flags respectively to be used in the idna handling. .sh return value .\" fixme glibc defines the following additional errors, some which .\" can probably be returned by getnameinfo(); they need to .\" be documented. .\" .\" #ifdef __use_gnu .\" #define eai_inprogress -100 /* processing request in progress. */ .\" #define eai_canceled -101 /* request canceled. */ .\" #define eai_notcanceled -102 /* request not canceled. */ .\" #define eai_alldone -103 /* all requests done. */ .\" #define eai_intr -104 /* interrupted by a signal. */ .\" #define eai_idn_encode -105 /* idn encoding failed. */ .\" #endif on success, 0 is returned, and node and service names, if requested, are filled with null-terminated strings, possibly truncated to fit the specified buffer lengths. on error, one of the following nonzero error codes is returned: .tp .b eai_again the name could not be resolved at this time. try again later. .tp .b eai_badflags the .i flags argument has an invalid value. .tp .b eai_fail a nonrecoverable error occurred. .tp .b eai_family the address family was not recognized, or the address length was invalid for the specified family. .tp .b eai_memory out of memory. .tp .b eai_noname the name does not resolve for the supplied arguments. .b ni_namereqd is set and the host's name cannot be located, or neither hostname nor service name were requested. .tp .b eai_overflow the buffer pointed to by .i host or .i serv was too small. .tp .b eai_system a system error occurred. the error code can be found in .ir errno . .pp the .br gai_strerror (3) function translates these error codes to a human readable string, suitable for error reporting. .sh files .i /etc/hosts .br .i /etc/nsswitch.conf .br .i /etc/resolv.conf .sh versions .br getnameinfo () is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getnameinfo () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, rfc\ 2553. .sh notes in order to assist the programmer in choosing reasonable sizes for the supplied buffers, .i defines the constants .pp .in +4n .ex #define ni_maxhost 1025 #define ni_maxserv 32 .ee .in .pp since glibc 2.8, these definitions are exposed only if suitable feature test macros are defined, namely: .br _gnu_source , .br _default_source (since glibc 2.19), or (in glibc versions up to and including 2.19) .br _bsd_source or .br _svid_source . .pp the former is the constant .b maxdname in recent versions of bind's .i header file. the latter is a guess based on the services listed in the current assigned numbers rfc. .pp before glibc version 2.2, the .i hostlen and .i servlen arguments were typed as .ir size_t . .sh examples the following code tries to get the numeric hostname and service name, for a given socket address. note that there is no hardcoded reference to a particular address family. .pp .in +4n .ex struct sockaddr *addr; /* input */ socklen_t addrlen; /* input */ char hbuf[ni_maxhost], sbuf[ni_maxserv]; if (getnameinfo(addr, addrlen, hbuf, sizeof(hbuf), sbuf, sizeof(sbuf), ni_numerichost | ni_numericserv) == 0) printf("host=%s, serv=%s\en", hbuf, sbuf); .ee .in .pp the following version checks if the socket address has a reverse address mapping. .pp .in +4n .ex struct sockaddr *addr; /* input */ socklen_t addrlen; /* input */ char hbuf[ni_maxhost]; if (getnameinfo(addr, addrlen, hbuf, sizeof(hbuf), null, 0, ni_namereqd)) printf("could not resolve hostname"); else printf("host=%s\en", hbuf); .ee .in .pp an example program using .br getnameinfo () can be found in .br getaddrinfo (3). .sh see also .br accept (2), .br getpeername (2), .br getsockname (2), .br recvfrom (2), .br socket (2), .br getaddrinfo (3), .br gethostbyaddr (3), .br getservbyname (3), .br getservbyport (3), .br inet_ntop (3), .br hosts (5), .br services (5), .br hostname (7), .br named (8) .pp r.\& gilligan, s.\& thomson, j.\& bound and w.\& stevens, .ir "basic socket interface extensions for ipv6" , rfc\ 2553, march 1999. .pp tatsuya jinmei and atsushi onoe, .ir "an extension of format for ipv6 scoped addresses" , internet draft, work in progress .ur ftp://ftp.ietf.org\:/internet\-drafts\:/draft\-ietf\-ipngwg\-scopedaddr\-format\-02.txt .ue . .pp craig metz, .ir "protocol independence using the sockets api" , proceedings of the freenix track: 2000 usenix annual technical conference, june 2000 .ad l .ur http://www.usenix.org\:/publications\:/library\:/proceedings\:/usenix2000\:/freenix\:/metzprotocol.html .ue . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fpclassify.3 .so man2/truncate.2 .so man3/isgreater.3 .so man3/scandir.3 .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th shm_overview 7 2021-03-22 "linux" "linux programmer's manual" .sh name shm_overview \- overview of posix shared memory .sh description the posix shared memory api allows processes to communicate information by sharing a region of memory. .pp the interfaces employed in the api are: .tp 15 .br shm_open (3) create and open a new object, or open an existing object. this is analogous to .br open (2). the call returns a file descriptor for use by the other interfaces listed below. .tp .br ftruncate (2) set the size of the shared memory object. (a newly created shared memory object has a length of zero.) .tp .br mmap (2) map the shared memory object into the virtual address space of the calling process. .tp .br munmap (2) unmap the shared memory object from the virtual address space of the calling process. .tp .br shm_unlink (3) remove a shared memory object name. .tp .br close (2) close the file descriptor allocated by .br shm_open (3) when it is no longer needed. .tp .br fstat (2) obtain a .i stat structure that describes the shared memory object. among the information returned by this call are the object's size .ri ( st_size ), permissions .ri ( st_mode ), owner .ri ( st_uid ), and group .ri ( st_gid ). .tp .br fchown (2) to change the ownership of a shared memory object. .tp .br fchmod (2) to change the permissions of a shared memory object. .ss versions posix shared memory is supported since linux 2.4 and glibc 2.2. .ss persistence posix shared memory objects have kernel persistence: a shared memory object will exist until the system is shut down, or until all processes have unmapped the object and it has been deleted with .br shm_unlink (3) .ss linking programs using the posix shared memory api must be compiled with .i cc \-lrt to link against the real-time library, .ir librt . .ss accessing shared memory objects via the filesystem on linux, shared memory objects are created in a .rb ( tmpfs (5)) virtual filesystem, normally mounted under .ir /dev/shm . since kernel 2.6.19, linux supports the use of access control lists (acls) to control the permissions of objects in the virtual filesystem. .sh notes typically, processes must synchronize their access to a shared memory object, using, for example, posix semaphores. .pp system v shared memory .rb ( shmget (2), .br shmop (2), etc.) is an older shared memory api. posix shared memory provides a simpler, and better designed interface; on the other hand posix shared memory is somewhat less widely available (especially on older systems) than system v shared memory. .sh see also .br fchmod (2), .br fchown (2), .br fstat (2), .br ftruncate (2), .br memfd_create (2), .br mmap (2), .br mprotect (2), .br munmap (2), .br shmget (2), .br shmop (2), .br shm_open (3), .br shm_unlink (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1989, 1991, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)getloadavg.3 8.1 (berkeley) 6/4/93 .\" .\" 2007-12-08, mtk, converted from mdoc to man macros .\" .th getloadavg 3 2021-03-22 "linux" "linux programmer's manual" .sh name getloadavg \- get system load averages .sh synopsis .nf .b #include .pp .bi "int getloadavg(double " loadavg[] ", int " nelem ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getloadavg (): .nf since glibc 2.19: _default_source in glibc up to and including 2.19: _bsd_source .fi .sh description the .br getloadavg () function returns the number of processes in the system run queue averaged over various periods of time. up to .i nelem samples are retrieved and assigned to successive elements of .ir loadavg[] . the system imposes a maximum of 3 samples, representing averages over the last 1, 5, and 15 minutes, respectively. .sh return value if the load average was unobtainable, \-1 is returned; otherwise, the number of samples actually retrieved is returned. .\" .sh history .\" the .\" br getloadavg () .\" function appeared in .\" 4.3bsd reno . .sh versions this function is available in glibc since version 2.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getloadavg () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to not in posix.1. present on the bsds and solaris. .\" mdoc seems to have a bug - there must be no newline here .sh see also .br uptime (1), .br proc (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man3/termios.3 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2006, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-04-26 by nick duffek .\" modified 1996-11-06 by eric s. raymond .\" modified 1997-01-31 by eric s. raymond .\" modified 2004-06-23 by michael kerrisk .\" .th symlink 2 2021-08-27 "linux" "linux programmer's manual" .sh name symlink, symlinkat \- make a new name for a file .sh synopsis .nf .b #include .pp .bi "int symlink(const char *" target ", const char *" linkpath ); .pp .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "int symlinkat(const char *" target ", int " newdirfd \ ", const char *" linkpath ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br symlink (): .nf _xopen_source >= 500 || _posix_c_source >= 200112l .\" || _xopen_source && _xopen_source_extended || /* glibc <= 2.19: */ _bsd_source .fi .pp .br symlinkat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br symlink () creates a symbolic link named .i linkpath which contains the string .ir target . .pp symbolic links are interpreted at run time as if the contents of the link had been substituted into the path being followed to find a file or directory. .pp symbolic links may contain .i .. path components, which (if used at the start of the link) refer to the parent directories of that in which the link resides. .pp a symbolic link (also known as a soft link) may point to an existing file or to a nonexistent one; the latter case is known as a dangling link. .pp the permissions of a symbolic link are irrelevant; the ownership is ignored when following the link, but is checked when removal or renaming of the link is requested and the link is in a directory with the sticky bit .rb ( s_isvtx ) set. .pp if .i linkpath exists, it will .i not be overwritten. .ss symlinkat() the .br symlinkat () system call operates in exactly the same way as .br symlink (), except for the differences described here. .pp if the pathname given in .i linkpath is relative, then it is interpreted relative to the directory referred to by the file descriptor .i newdirfd (rather than relative to the current working directory of the calling process, as is done by .br symlink () for a relative pathname). .pp if .i linkpath is relative and .i newdirfd is the special value .br at_fdcwd , then .i linkpath is interpreted relative to the current working directory of the calling process (like .br symlink ()). .pp if .i linkpath is absolute, then .i newdirfd is ignored. .pp see .br openat (2) for an explanation of the need for .br symlinkat (). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces write access to the directory containing .i linkpath is denied, or one of the directories in the path prefix of .i linkpath did not allow search permission. (see also .br path_resolution (7).) .tp .b ebadf .rb ( symlinkat ()) .i linkpath is relative but .i newdirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b edquot the user's quota of resources on the filesystem has been exhausted. the resources could be inodes or disk blocks, depending on the filesystem implementation. .tp .b eexist .i linkpath already exists. .tp .b efault .ir target " or " linkpath " points outside your accessible address space." .tp .b eio an i/o error occurred. .tp .b eloop too many symbolic links were encountered in resolving .ir linkpath . .tp .b enametoolong .ir target " or " linkpath " was too long." .tp .b enoent a directory component in .i linkpath does not exist or is a dangling symbolic link, or .i target or .i linkpath is an empty string. .tp .b enoent .rb ( symlinkat ()) .i linkpath is a relative pathname and .ir newdirfd refers to a directory that has been deleted. .tp .b enomem insufficient kernel memory was available. .tp .b enospc the device containing the file has no room for the new directory entry. .tp .b enotdir a component used as a directory in .i linkpath is not, in fact, a directory. .tp .b enotdir .rb ( symlinkat ()) .i linkpath is relative and .i newdirfd is a file descriptor referring to a file other than a directory. .tp .b eperm the filesystem containing .i linkpath does not support the creation of symbolic links. .tp .b erofs .i linkpath is on a read-only filesystem. .sh versions .br symlinkat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br symlink (): svr4, 4.3bsd, posix.1-2001, posix.1-2008. .\" svr4 documents additional error codes edquot and enosys. .\" see .\" .br open (2) .\" re multiple files with the same name, and nfs. .pp .br symlinkat (): posix.1-2008. .sh notes no checking of .i target is done. .pp deleting the name referred to by a symbolic link will actually delete the file (unless it also has other hard links). if this behavior is not desired, use .br link (2). .ss glibc notes on older kernels where .br symlinkat () is unavailable, the glibc wrapper function falls back to the use of .br symlink (). when .i linkpath is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir newdirfd argument. .sh see also .br ln (1), .br namei (1), .br lchown (2), .br link (2), .br lstat (2), .br open (2), .br readlink (2), .br rename (2), .br unlink (2), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1999 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th tempnam 3 2021-03-22 "" "linux programmer's manual" .sh name tempnam \- create a name for a temporary file .sh synopsis .nf .b #include .pp .bi "char *tempnam(const char *" dir ", const char *" pfx ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br tempnam (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description .i "never use this function." use .br mkstemp (3) or .br tmpfile (3) instead. .pp the .br tempnam () function returns a pointer to a string that is a valid filename, and such that a file with this name did not exist when .br tempnam () checked. the filename suffix of the pathname generated will start with .i pfx in case .i pfx is a non-null string of at most five bytes. the directory prefix part of the pathname generated is required to be "appropriate" (often that at least implies writable). .pp attempts to find an appropriate directory go through the following steps: .tp 3 a) in case the environment variable .b tmpdir exists and contains the name of an appropriate directory, that is used. .tp b) otherwise, if the .i dir argument is non-null and appropriate, it is used. .tp c) otherwise, .i p_tmpdir (as defined in .ir ) is used when appropriate. .tp d) finally an implementation-defined directory may be used. .pp the string returned by .br tempnam () is allocated using .br malloc (3) and hence should be freed by .br free (3). .sh return value on success, the .br tempnam () function returns a pointer to a unique temporary filename. it returns null if a unique name cannot be generated, with .i errno set to indicate the error. .sh errors .tp .b enomem allocation of storage failed. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tempnam () t} thread safety mt-safe env .te .hy .ad .sp 1 .sh conforming to svr4, 4.3bsd, posix.1-2001. posix.1-2008 marks .br tempnam () as obsolete. .sh notes although .br tempnam () generates names that are difficult to guess, it is nevertheless possible that between the time that .br tempnam () returns a pathname, and the time that the program opens it, another program might create that pathname using .br open (2), or create it as a symbolic link. this can lead to security holes. to avoid such possibilities, use the .br open (2) .b o_excl flag to open the pathname. or better yet, use .br mkstemp (3) or .br tmpfile (3). .pp susv2 does not mention the use of .br tmpdir ; glibc will use it only when the program is not set-user-id. on svr4, the directory used under \fbd)\fp is .i /tmp (and this is what glibc does). .pp because it dynamically allocates memory used to return the pathname, .br tempnam () is reentrant, and thus thread safe, unlike .br tmpnam (3). .pp the .br tempnam () function generates a different string each time it is called, up to .b tmp_max (defined in .ir ) times. if it is called more than .b tmp_max times, the behavior is implementation defined. .pp .br tempnam () uses at most the first five bytes from .ir pfx . .pp the glibc implementation of .br tempnam () fails with the error .b eexist upon failure to find a unique name. .sh bugs the precise meaning of "appropriate" is undefined; it is unspecified how accessibility of a directory is determined. .sh see also .br mkstemp (3), .br mktemp (3), .br tmpfile (3), .br tmpnam (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/__ppc_set_ppr_med.3 .so man3/syslog.3 .so man2/pipe.2 .so man3/rpc.3 .so man3/cpow.3 #!/bin/sh # # print_encoding.sh # # print man pages with encoding other than us-ascii, together with # their encoding by file utility and by the first line in the man page. # # example usage: # # cd man-pages-x.yy # sh print_encoding.sh man?/* # ###################################################################### # # (c) copyright 2013, peter schiffer # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # if [[ $# -lt 1 ]]; then echo "usage: ${0} man?/*" 1>&2 exit 1 fi printf "\n %-23s%-19s%s\n\n" "man page" "encoding by file" "encoding by first line" for f in "$@"; do if [[ ! -f "$f" ]]; then continue fi enc=$(file -bi "$f" | cut -d = -f 2) if [[ $enc != "us-ascii" ]]; then lenc=$(head -n 1 "$f" | sed -n "s/.*coding: \([^ ]*\).*/\1/p") printf " * %-23s%-19s%s\n" "$f" "$enc" "$lenc" fi done exit 0 .so man3/fseek.3 .\" copyright (c) 2005 michael kerrisk .\" based on earlier work by faith@cs.unc.edu and .\" mike battersby .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2005-09-15, mtk, created new page by splitting off from sigaction.2 .\" .th sigpending 2 2021-03-22 "linux" "linux programmer's manual" .sh name sigpending, rt_sigpending \- examine pending signals .sh synopsis .nf .b #include .pp .bi "int sigpending(sigset_t *" set ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigpending (): .nf _posix_c_source .fi .sh description .br sigpending () returns the set of signals that are pending for delivery to the calling thread (i.e., the signals which have been raised while blocked). the mask of pending signals is returned in .ir set . .sh return value .br sigpending () returns 0 on success. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault .i set points to memory which is not a valid part of the process address space. .sh conforming to posix.1-2001, posix.1-2008. .sh notes see .br sigsetops (3) for details on manipulating signal sets. .pp if a signal is both blocked and has a disposition of "ignored", it is .i not added to the mask of pending signals when generated. .pp the set of signals that is pending for a thread is the union of the set of signals that is pending for that thread and the set of signals that is pending for the process as a whole; see .br signal (7). .pp a child created via .br fork (2) initially has an empty pending signal set; the pending signal set is preserved across an .br execve (2). .\" .ss c library/kernel differences the original linux system call was named .br sigpending (). however, with the addition of real-time signals in linux 2.2, the fixed-size, 32-bit .ir sigset_t argument supported by that system call was no longer fit for purpose. consequently, a new system call, .br rt_sigpending (), was added to support an enlarged .ir sigset_t type. the new system call takes a second argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the signal set in .ir set . .\" this argument is currently required to be less than or equal to .\" .ir sizeof(sigset_t) .\" (or the error .\" .b einval .\" results). the glibc .br sigpending () wrapper function hides these details from us, transparently calling .br rt_sigpending () when the kernel provides it. .\" .sh bugs in versions of glibc up to and including 2.2.1, there is a bug in the wrapper function for .br sigpending () which means that information about pending real-time signals is not correctly returned. .sh see also .br kill (2), .br sigaction (2), .br signal (2), .br sigprocmask (2), .br sigsuspend (2), .br sigsetops (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/slist.3 .so man3/getutent.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_open 3 2021-03-22 "linux" "linux programmer's manual" .sh name mq_open \- open a message queue .sh synopsis .nf .br "#include " " /* for o_* constants */" .br "#include " " /* for mode constants */" .b #include .pp .bi "mqd_t mq_open(const char *" name ", int " oflag ); .bi "mqd_t mq_open(const char *" name ", int " oflag ", mode_t " mode , .bi " struct mq_attr *" attr ); .fi .pp link with \fi\-lrt\fp. .sh description .br mq_open () creates a new posix message queue or opens an existing queue. the queue is identified by .ir name . for details of the construction of .ir name , see .br mq_overview (7). .pp the .i oflag argument specifies flags that control the operation of the call. (definitions of the flags values can be obtained by including .ir .) exactly one of the following must be specified in .ir oflag : .tp .b o_rdonly open the queue to receive messages only. .tp .b o_wronly open the queue to send messages only. .tp .b o_rdwr open the queue to both send and receive messages. .pp zero or more of the following flags can additionally be .ir or ed in .ir oflag : .tp .br o_cloexec " (since linux 2.6.26)" .\" commit 269f21344b23e552c21c9e2d7ca258479dcd7a0a set the close-on-exec flag for the message queue descriptor. see .br open (2) for a discussion of why this flag is useful. .tp .b o_creat create the message queue if it does not exist. the owner (user id) of the message queue is set to the effective user id of the calling process. the group ownership (group id) is set to the effective group id of the calling process. .\" in reality the filesystem ids are used on linux. .tp .b o_excl if .b o_creat was specified in .ir oflag , and a queue with the given .i name already exists, then fail with the error .br eexist . .tp .b o_nonblock open the queue in nonblocking mode. in circumstances where .br mq_receive (3) and .br mq_send (3) would normally block, these functions instead fail with the error .br eagain . .pp if .b o_creat is specified in .ir oflag , then two additional arguments must be supplied. the .i mode argument specifies the permissions to be placed on the new queue, as for .br open (2). (symbolic definitions for the permissions bits can be obtained by including .ir .) the permissions settings are masked against the process umask. .pp the fields of the .ir "struct mq_attr" pointed to .i attr specify the maximum number of messages and the maximum size of messages that the queue will allow. this structure is defined as follows: .pp .in +4n .ex struct mq_attr { long mq_flags; /* flags (ignored for mq_open()) */ long mq_maxmsg; /* max. # of messages on queue */ long mq_msgsize; /* max. message size (bytes) */ long mq_curmsgs; /* # of messages currently in queue (ignored for mq_open()) */ }; .ee .in .pp only the .i mq_maxmsg and .i mq_msgsize fields are employed when calling .br mq_open (); the values in the remaining fields are ignored. .pp if .i attr is null, then the queue is created with implementation-defined default attributes. since linux 3.5, two .i /proc files can be used to control these defaults; see .br mq_overview (7) for details. .sh return value on success, .br mq_open () returns a message queue descriptor for use by other message queue functions. on error, .br mq_open () returns .ir "(mqd_t)\ \-1", with .i errno set to indicate the error. .sh errors .tp .b eacces the queue exists, but the caller does not have permission to open it in the specified mode. .tp .b eacces .i name contained more than one slash. .\" note that this isn't consistent with the same case for sem_open() .tp .b eexist both .b o_creat and .b o_excl were specified in .ir oflag , but a queue with this .i name already exists. .tp .b einval .\" glibc checks whether the name starts with a "/" and if not, .\" gives this error .i name doesn't follow the format in .br mq_overview (7). .tp .b einval .b o_creat was specified in .ir oflag , and .i attr was not null, but .i attr\->mq_maxmsg or .i attr\->mq_msqsize was invalid. both of these fields must be greater than zero. in a process that is unprivileged (does not have the .b cap_sys_resource capability), .i attr\->mq_maxmsg must be less than or equal to the .i msg_max limit, and .i attr\->mq_msgsize must be less than or equal to the .i msgsize_max limit. in addition, even in a privileged process, .i attr\->mq_maxmsg cannot exceed the .b hard_max limit. (see .br mq_overview (7) for details of these limits.) .tp .b emfile the per-process limit on the number of open file and message queue descriptors has been reached (see the description of .br rlimit_nofile in .br getrlimit (2)). .tp .b enametoolong .i name was too long. .tp .b enfile the system-wide limit on the total number of open files and message queues has been reached. .tp .b enoent the .b o_creat flag was not specified in .ir oflag , and no queue with this .i name exists. .tp .b enoent .i name was just "/" followed by no other characters. .\" note that this isn't consistent with the same case for sem_open() .tp .b enomem insufficient memory. .tp .b enospc insufficient space for the creation of a new message queue. this probably occurred because the .i queues_max limit was encountered; see .br mq_overview (7). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mq_open () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes .ss c library/kernel differences the .br mq_open () library function is implemented on top of a system call of the same name. the library function performs the check that the .i name starts with a slash (/), giving the .b einval error if it does not. the kernel system call expects .i name to contain no preceding slash, so the c library function passes .i name without the preceding slash (i.e., .ir name+1 ) to the system call. .sh bugs in kernels before 2.6.14, the process umask was not applied to the permissions specified in .ir mode . .sh see also .br mq_close (3), .br mq_getattr (3), .br mq_notify (3), .br mq_receive (3), .br mq_send (3), .br mq_unlink (3), .br mq_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1980, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)getpriority.2 6.9 (berkeley) 3/10/91 .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-07-01 by andries brouwer .\" modified 1996-11-06 by eric s. raymond .\" modified 2001-10-21 by michael kerrisk .\" corrected statement under eperm to clarify privileges required .\" modified 2002-06-21 by michael kerrisk .\" clarified meaning of 0 value for 'who' argument .\" modified 2004-05-27 by michael kerrisk .\" .th getpriority 2 2021-08-27 "linux" "linux programmer's manual" .sh name getpriority, setpriority \- get/set program scheduling priority .sh synopsis .nf .b #include .pp .bi "int getpriority(int " which ", id_t " who ); .bi "int setpriority(int " which ", id_t " who ", int " prio ); .fi .sh description the scheduling priority of the process, process group, or user, as indicated by .i which and .i who is obtained with the .br getpriority () call and set with the .br setpriority () call. the process attribute dealt with by these system calls is the same attribute (also known as the "nice" value) that is dealt with by .br nice (2). .pp the value .i which is one of .br prio_process , .br prio_pgrp , or .br prio_user , and .i who is interpreted relative to .i which (a process identifier for .br prio_process , process group identifier for .br prio_pgrp , and a user id for .br prio_user ). a zero value for .i who denotes (respectively) the calling process, the process group of the calling process, or the real user id of the calling process. .pp the .i prio argument is a value in the range \-20 to 19 (but see notes below), with \-20 being the highest priority and 19 being the lowest priority. attempts to set a priority outside this range are silently clamped to the range. the default priority is 0; lower values give a process a higher scheduling priority. .pp the .br getpriority () call returns the highest priority (lowest numerical value) enjoyed by any of the specified processes. the .br setpriority () call sets the priorities of all of the specified processes to the specified value. .pp traditionally, only a privileged process could lower the nice value (i.e., set a higher priority). however, since linux 2.6.12, an unprivileged process can decrease the nice value of a target process that has a suitable .br rlimit_nice soft limit; see .br getrlimit (2) for details. .sh return value on success, .br getpriority () returns the calling thread's nice value, which may be a negative number. on error, it returns \-1 and sets .i errno to indicate the error. .pp since a successful call to .br getpriority () can legitimately return the value \-1, it is necessary to clear .i errno prior to the call, then check .i errno afterward to determine if \-1 is an error or a legitimate value. .pp .br setpriority () returns 0 on success. on failure, it returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b eacces the caller attempted to set a lower nice value (i.e., a higher process priority), but did not have the required privilege (on linux: did not have the .b cap_sys_nice capability). .tp .b einval .i which was not one of .br prio_process , .br prio_pgrp , or .br prio_user . .tp .b eperm a process was located, but its effective user id did not match either the effective or the real user id of the caller, and was not privileged (on linux: did not have the .b cap_sys_nice capability). but see notes below. .tp .b esrch no process was located using the .i which and .i who values specified. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd (these interfaces first appeared in 4.2bsd). .sh notes for further details on the nice value, see .br sched (7). .pp .ir note : the addition of the "autogroup" feature in linux 2.6.38 means that the nice value no longer has its traditional effect in many circumstances. for details, see .br sched (7). .pp a child created by .br fork (2) inherits its parent's nice value. the nice value is preserved across .br execve (2). .pp the details on the condition for .b eperm depend on the system. the above description is what posix.1-2001 says, and seems to be followed on all system\ v-like systems. linux kernels before 2.6.12 required the real or effective user id of the caller to match the real user of the process \fiwho\fp (instead of its effective user id). linux 2.6.12 and later require the effective user id of the caller to match the real or effective user id of the process \fiwho\fp. all bsd-like systems (sunos 4.1.3, ultrix 4.2, 4.3bsd, freebsd 4.3, openbsd-2.5, ...) behave in the same manner as linux 2.6.12 and later. .\" .ss c library/kernel differences within the kernel, nice values are actually represented using the range 40..1 (since negative numbers are error codes) and these are the values employed by the .br setpriority () and .br getpriority () system calls. the glibc wrapper functions for these system calls handle the translations between the user-land and kernel representations of the nice value according to the formula .ir "unice\ =\ 20\ \-\ knice" . (thus, the kernel's 40..1 range corresponds to the range \-20..19 as seen by user space.) .sh bugs according to posix, the nice value is a per-process setting. however, under the current linux/nptl implementation of posix threads, the nice value is a per-thread attribute: different threads in the same process can have different nice values. portable applications should avoid relying on the linux behavior, which may be made standards conformant in the future. .sh see also .br nice (1), .br renice (1), .br fork (2), .br capabilities (7), .br sched (7) .pp .i documentation/scheduler/sched\-nice\-design.txt in the linux kernel source tree (since linux 2.6.23) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 17:59:03 1993 by rik faith (faith@cs.unc.edu) .th strsignal 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strsignal, sigabbrev_np, sigdescr_np, sys_siglist \- return string describing signal .sh synopsis .nf .b #include .pp .bi "char *strsignal(int " sig ); .bi "const char *sigdescr_np(int " sig ); .bi "const char *sigabbrev_np(int " sig ); .pp .bi "extern const char *const " sys_siglist []; .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigabbrev_np (), .br sigdescr_np (): .nf _gnu_source .fi .pp .br strsignal (): .nf from glibc 2.10 to 2.31: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .pp .ir sys_siglist : .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the .br strsignal () function returns a string describing the signal number passed in the argument .ir sig . the string can be used only until the next call to .br strsignal (). the string returned by .br strsignal () is localized according to the .b lc_messages category in the current locale. .pp the .br sigdescr_np () function returns a string describing the signal number passed in the argument .ir sig . unlike .br strsignal () this string is not influenced by the current locale. .pp the .br sigabbrev_np () function returns the abbreviated name of the signal, .ir sig . for example, given the value .br sigint , it returns the string "int". .pp the (deprecated) array .i sys_siglist holds the signal description strings indexed by signal number. the .br strsignal () or the .br sigdescr_np () function should be used instead of this array; see also versions. .sh return value the .br strsignal () function returns the appropriate description string, or an unknown signal message if the signal number is invalid. on some systems (but not on linux), null may instead be returned for an invalid signal number. .pp the .br sigdescr_np () and .br sigabbrev_np () functions return the appropriate description string. the returned string is statically allocated and valid for the lifetime of the program. these functions return null for an invalid signal number. .sh versions .br sigdescr_np () and .br sigabbrev_np () first appeared in glibc 2.32. .pp starting with version 2.32, .\" glibc commit b1ccfc061feee9ce616444ded8e1cd5acf9fa97f the .i sys_siglist symbol is no longer exported by glibc. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br strsignal () t} thread safety t{ mt-unsafe race:strsignal locale t} t{ .br sigdescr_np (), .br sigabbrev_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br strsignal (): posix.1-2008. present on solaris and the bsds. .pp .br sigdescr_np () and .br sigdabbrev_np () are gnu extensions. .pp .i sys_siglist is nonstandard, but present on many other systems. .sh notes .br sigdescr_np () and .br sigdabbrev_np () are thread-safe and async-signal-safe. .sh see also .br psignal (3), .br strerror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/puts.3 .so man2/chown.2 .so man3/termios.3 .so man2/timerfd_create.2 .\" copyright (c) 1996 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" moved to man3, aeb, 980612 .\" .th ulimit 3 2021-03-22 "linux" "linux programmer's manual" .sh name ulimit \- get and set user limits .sh synopsis .nf .b #include .pp .bi "long ulimit(int " cmd ", long " newlimit ); .fi .sh description warning: this routine is obsolete. use .br getrlimit (2), .br setrlimit (2), and .br sysconf (3) instead. for the shell command .br ulimit , see .br bash (1). .pp the .br ulimit () call will get or set some limit for the calling process. the .i cmd argument can have one of the following values. .tp .b ul_getfsize return the limit on the size of a file, in units of 512 bytes. .tp .b ul_setfsize set the limit on the size of a file. .tp .b 3 (not implemented for linux.) return the maximum possible address of the data segment. .tp .b 4 (implemented but no symbolic constant provided.) return the maximum number of files that the calling process can open. .sh return value on success, .br ulimit () returns a nonnegative value. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eperm an unprivileged process tried to increase a limit. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ulimit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4, posix.1-2001. posix.1-2008 marks .br ulimit () as obsolete. .sh see also .br bash (1), .br getrlimit (2), .br setrlimit (2), .br sysconf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:25:21 1993 by rik faith (faith@cs.unc.edu) .\" .th seekdir 3 2021-03-22 "" "linux programmer's manual" .sh name seekdir \- set the position of the next readdir() call in the directory stream. .sh synopsis .nf .b #include .pp .bi "void seekdir(dir *" dirp ", long " loc ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br seekdir (): .nf _xopen_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br seekdir () function sets the location in the directory stream from which the next .br readdir (2) call will start. the .i loc argument should be a value returned by a previous call to .br telldir (3). .sh return value the .br seekdir () function returns no value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br seekdir () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh notes in glibc up to version 2.1.1, the type of the .i loc argument was .ir off_t . posix.1-2001 specifies .ir long , and this is the type used since glibc 2.1.2. see .br telldir (3) for information on why you should be careful in making any assumptions about the value in this argument. .sh see also .br lseek (2), .br closedir (3), .br opendir (3), .br readdir (3), .br rewinddir (3), .br scandir (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)btree.3 8.4 (berkeley) 8/18/94 .\" .th btree 3 2020-12-21 "" "linux programmer's manual" .\".uc 7 .sh name btree \- btree database access method .sh synopsis .nf .ft b #include #include .ft r .fi .sh description .ir "note well" : this page documents interfaces provided in glibc up until version 2.1. since version 2.2, glibc no longer provides these interfaces. probably, you are looking for the apis provided by the .i libdb library instead. .pp the routine .br dbopen (3) is the library interface to database files. one of the supported file formats is btree files. the general description of the database access methods is in .br dbopen (3), this manual page describes only the btree-specific information. .pp the btree data structure is a sorted, balanced tree structure storing associated key/data pairs. .pp the btree access-method-specific data structure provided to .br dbopen (3) is defined in the .i include file as follows: .pp .in +4n .ex typedef struct { unsigned long flags; unsigned int cachesize; int maxkeypage; int minkeypage; unsigned int psize; int (*compare)(const dbt *key1, const dbt *key2); size_t (*prefix)(const dbt *key1, const dbt *key2); int lorder; } btreeinfo; .ee .in .pp the elements of this structure are as follows: .tp .i flags the flag value is specified by oring any of the following values: .rs .tp .b r_dup permit duplicate keys in the tree, that is, permit insertion if the key to be inserted already exists in the tree. the default behavior, as described in .br dbopen (3), is to overwrite a matching key when inserting a new key or to fail if the .b r_nooverwrite flag is specified. the .b r_dup flag is overridden by the .b r_nooverwrite flag, and if the .b r_nooverwrite flag is specified, attempts to insert duplicate keys into the tree will fail. .ip if the database contains duplicate keys, the order of retrieval of key/data pairs is undefined if the .i get routine is used, however, .i seq routine calls with the .b r_cursor flag set will always return the logical "first" of any group of duplicate keys. .re .tp .i cachesize a suggested maximum size (in bytes) of the memory cache. this value is .i only advisory, and the access method will allocate more memory rather than fail. since every search examines the root page of the tree, caching the most recently used pages substantially improves access time. in addition, physical writes are delayed as long as possible, so a moderate cache can reduce the number of i/o operations significantly. obviously, using a cache increases (but only increases) the likelihood of corruption or lost data if the system crashes while a tree is being modified. if .i cachesize is 0 (no size is specified), a default cache is used. .tp .i maxkeypage the maximum number of keys which will be stored on any single page. not currently implemented. .\" the maximum number of keys which will be stored on any single page. .\" because of the way the btree data structure works, .\" .i maxkeypage .\" must always be greater than or equal to 2. .\" if .\" .i maxkeypage .\" is 0 (no maximum number of keys is specified), the page fill factor is .\" made as large as possible (which is almost invariably what is wanted). .tp .i minkeypage the minimum number of keys which will be stored on any single page. this value is used to determine which keys will be stored on overflow pages, that is, if a key or data item is longer than the pagesize divided by the minkeypage value, it will be stored on overflow pages instead of in the page itself. if .i minkeypage is 0 (no minimum number of keys is specified), a value of 2 is used. .tp .i psize page size is the size (in bytes) of the pages used for nodes in the tree. the minimum page size is 512 bytes and the maximum page size is 64\ kib. if .i psize is 0 (no page size is specified), a page size is chosen based on the underlying filesystem i/o block size. .tp .i compare compare is the key comparison function. it must return an integer less than, equal to, or greater than zero if the first key argument is considered to be respectively less than, equal to, or greater than the second key argument. the same comparison function must be used on a given tree every time it is opened. if .i compare is null (no comparison function is specified), the keys are compared lexically, with shorter keys considered less than longer keys. .tp .i prefix prefix is the prefix comparison function. if specified, this routine must return the number of bytes of the second key argument which are necessary to determine that it is greater than the first key argument. if the keys are equal, the key length should be returned. note, the usefulness of this routine is very data-dependent, but, in some data sets can produce significantly reduced tree sizes and search times. if .i prefix is null (no prefix function is specified), .i and no comparison function is specified, a default lexical comparison routine is used. if .i prefix is null and a comparison routine is specified, no prefix comparison is done. .tp .i lorder the byte order for integers in the stored database metadata. the number should represent the order as an integer; for example, big endian order would be the number 4,321. if .i lorder is 0 (no order is specified), the current host order is used. .pp if the file already exists (and the .b o_trunc flag is not specified), the values specified for the arguments .ir flags , .ir lorder , and .i psize are ignored in favor of the values used when the tree was created. .pp forward sequential scans of a tree are from the least key to the greatest. .pp space freed up by deleting key/data pairs from the tree is never reclaimed, although it is normally made available for reuse. this means that the btree storage structure is grow-only. the only solutions are to avoid excessive deletions, or to create a fresh tree periodically from a scan of an existing one. .pp searches, insertions, and deletions in a btree will all complete in o lg base n where base is the average fill factor. often, inserting ordered data into btrees results in a low fill factor. this implementation has been modified to make ordered insertion the best case, resulting in a much better than normal page fill factor. .sh errors the .i btree access method routines may fail and set .i errno for any of the errors specified for the library routine .br dbopen (3). .sh bugs only big and little endian byte order is supported. .sh see also .br dbopen (3), .br hash (3), .br mpool (3), .br recno (3) .pp .ir "the ubiquitous b-tree" , douglas comer, acm comput. surv. 11, 2 (june 1979), 121-138. .pp .ir "prefix b-trees" , bayer and unterauer, acm transactions on database systems, vol. 2, 1 (march 1977), 11-26. .pp .ir "the art of computer programming vol. 3: sorting and searching" , d.e. knuth, 1968, pp 471-480. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1996 michael haardt. .\" updates nov 1998, andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .th mouse 4 2020-08-13 "linux" "linux programmer's manual" .sh name mouse \- serial mouse interface .sh configuration serial mice are connected to a serial rs232/v24 dialout line, see .br ttys (4) for a description. .sh description .ss introduction the pinout of the usual 9 pin plug as used for serial mice is: .pp .ts center; r c l. pin name used for 2 rx data 3 tx \-12 v, imax = 10 ma 4 dtr +12 v, imax = 10 ma 7 rts +12 v, imax = 10 ma 5 gnd ground .te .pp this is the specification, in fact 9 v suffices with most mice. .pp the mouse driver can recognize a mouse by dropping rts to low and raising it again. about 14 ms later the mouse will send 0x4d (\(aqm\(aq) on the data line. after a further 63 ms, a microsoft-compatible 3-button mouse will send 0x33 (\(aq3\(aq). .pp the relative mouse movement is sent as .i dx (positive means right) and .i dy (positive means down). various mice can operate at different speeds. to select speeds, cycle through the speeds 9600, 4800, 2400, and 1200 bit/s, each time writing the two characters from the table below and waiting 0.1 seconds. the following table shows available speeds and the strings that select them: .pp .ts center; l l. bit/s string 9600 *q 4800 *p 2400 *o 1200 *n .te .pp the first byte of a data packet can be used for synchronization purposes. .ss microsoft protocol the .b microsoft protocol uses 1 start bit, 7 data bits, no parity and one stop bit at the speed of 1200 bits/sec. data is sent to rxd in 3-byte packets. the .ir dx and .i dy movements are sent as two's-complement, .i lb .ri ( rb ) are set when the left (right) button is pressed: .pp .ts center; r c c c c c c c. byte d6 d5 d4 d3 d2 d1 d0 1 1 lb rb dy7 dy6 dx7 dx6 2 0 dx5 dx4 dx3 dx2 dx1 dx0 3 0 dy5 dy4 dy3 dy2 dy1 dy0 .te .ss 3-button microsoft protocol original microsoft mice only have two buttons. however, there are some three button mice which also use the microsoft protocol. pressing or releasing the middle button is reported by sending a packet with zero movement and no buttons pressed. (thus, unlike for the other two buttons, the status of the middle button is not reported in each packet.) .ss logitech protocol logitech serial 3-button mice use a different extension of the microsoft protocol: when the middle button is up, the above 3-byte packet is sent. when the middle button is down a 4-byte packet is sent, where the 4th byte has value 0x20 (or at least has the 0x20 bit set). in particular, a press of the middle button is reported as 0,0,0,0x20 when no other buttons are down. .ss mousesystems protocol the .b mousesystems protocol uses 1 start bit, 8 data bits, no parity, and two stop bits at the speed of 1200 bits/sec. data is sent to rxd in 5-byte packets. .i dx is sent as the sum of the two two's-complement values, .i dy is send as negated sum of the two two's-complement values. .i lb .ri ( mb , .ir rb ) are cleared when the left (middle, right) button is pressed: .pp .ts center; r c c c c c c c c. byte d7 d6 d5 d4 d3 d2 d1 d0 1 1 0 0 0 0 lb mb rb 2 0 dxa6 dxa5 dxa4 dxa3 dxa2 dxa1 dxa0 3 0 dya6 dya5 dya4 dya3 dya2 dya1 dya0 4 0 dxb6 dxb5 dxb4 dxb3 dxb2 dxb1 dxb0 5 0 dyb6 dyb5 dyb4 dyb3 dyb2 dyb1 dyb0 .te .pp bytes 4 and 5 describe the change that occurred since bytes 2 and 3 were transmitted. .ss sun protocol the .b sun protocol is the 3-byte version of the above 5-byte mousesystems protocol: the last two bytes are not sent. .ss mm protocol the .b mm protocol uses 1 start bit, 8 data bits, odd parity, and one stop bit at the speed of 1200 bits/sec. data is sent to rxd in 3-byte packets. .i dx and .i dy are sent as single signed values, the sign bit indicating a negative value. .i lb .ri ( mb , .ir rb ) are set when the left (middle, right) button is pressed: .pp .ts center; r c c c c c c c c. byte d7 d6 d5 d4 d3 d2 d1 d0 1 1 0 0 dxs dys lb mb rb 2 0 dx6 dx5 dx4 dx3 dx2 dx1 dx0 3 0 dy6 dy5 dy4 dy3 dy2 dy1 dy0 .te .sh files .tp .i /dev/mouse a commonly used symbolic link pointing to a mouse device. .sh see also .br ttys (4), .br gpm (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@cantor.informatik.rwth-aachen.de) .\" and 1994,1995 alain knaff (alain.knaff@imag.fr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified, sun feb 26 15:00:02 1995, faith@cs.unc.edu .\" .th fd 4 2020-08-13 "linux" "linux programmer's manual" .sh name fd \- floppy disk device .sh configuration floppy drives are block devices with major number 2. typically they are owned by root:floppy (i.e., user root, group floppy) and have either mode 0660 (access checking via group membership) or mode 0666 (everybody has access). the minor numbers encode the device type, drive number, and controller number. for each device type (that is, combination of density and track count) there is a base minor number. to this base number, add the drive's number on its controller and 128 if the drive is on the secondary controller. in the following device tables, \fin\fp represents the drive number. .pp \fbwarning: if you use formats with more tracks than supported by your drive, you may cause it mechanical damage.\fp trying once if more tracks than the usual 40/80 are supported should not damage it, but no warranty is given for that. if you are not sure, don't create device entries for those formats, so as to prevent their usage. .pp drive-independent device files which automatically detect the media format and capacity: .ts l c l c. name base minor # _ \fbfd\fp\fin\fp 0 .te .pp 5.25 inch double-density device files: .ts lw(1i) l l l l c lw(1i) c c c c c. name capacity cyl. sect. heads base kib minor # _ \fbfd\fp\fin\fp\fbd360\fp 360 40 9 2 4 .te .pp 5.25 inch high-density device files: .ts lw(1i) l l l l c lw(1i) c c c c c. name capacity cyl. sect. heads base kib minor # _ \fbfd\fp\fin\fp\fbh360\fp 360 40 9 2 20 \fbfd\fp\fin\fp\fbh410\fp 410 41 10 2 48 \fbfd\fp\fin\fp\fbh420\fp 420 42 10 2 64 \fbfd\fp\fin\fp\fbh720\fp 720 80 9 2 24 \fbfd\fp\fin\fp\fbh880\fp 880 80 11 2 80 \fbfd\fp\fin\fp\fbh1200\fp 1200 80 15 2 8 \fbfd\fp\fin\fp\fbh1440\fp 1440 80 18 2 40 \fbfd\fp\fin\fp\fbh1476\fp 1476 82 18 2 56 \fbfd\fp\fin\fp\fbh1494\fp 1494 83 18 2 72 \fbfd\fp\fin\fp\fbh1600\fp 1600 80 20 2 92 .te .pp 3.5 inch double-density device files: .ts lw(1i) l l l l c lw(1i) c c c c c. name capacity cyl. sect. heads base kib minor # _ \fbfd\fp\fin\fp\fbu360\fp 360 80 9 1 12 \fbfd\fp\fin\fp\fbu720\fp 720 80 9 2 16 \fbfd\fp\fin\fp\fbu800\fp 800 80 10 2 120 \fbfd\fp\fin\fp\fbu1040\fp 1040 80 13 2 84 \fbfd\fp\fin\fp\fbu1120\fp 1120 80 14 2 88 .te .pp 3.5 inch high-density device files: .ts lw(1i) l l l l c lw(1i) c c c c c. name capacity cyl. sect. heads base kib minor # _ \fbfd\fp\fin\fp\fbu360\fp 360 40 9 2 12 \fbfd\fp\fin\fp\fbu720\fp 720 80 9 2 16 \fbfd\fp\fin\fp\fbu820\fp 820 82 10 2 52 \fbfd\fp\fin\fp\fbu830\fp 830 83 10 2 68 \fbfd\fp\fin\fp\fbu1440\fp 1440 80 18 2 28 \fbfd\fp\fin\fp\fbu1600\fp 1600 80 20 2 124 \fbfd\fp\fin\fp\fbu1680\fp 1680 80 21 2 44 \fbfd\fp\fin\fp\fbu1722\fp 1722 82 21 2 60 \fbfd\fp\fin\fp\fbu1743\fp 1743 83 21 2 76 \fbfd\fp\fin\fp\fbu1760\fp 1760 80 22 2 96 \fbfd\fp\fin\fp\fbu1840\fp 1840 80 23 2 116 \fbfd\fp\fin\fp\fbu1920\fp 1920 80 24 2 100 .te .pp 3.5 inch extra-density device files: .ts lw(1i) l l l l c lw(1i) c c c c c. name capacity cyl. sect. heads base kib minor # _ \fbfd\fp\fin\fp\fbu2880\fp 2880 80 36 2 32 \fbfd\fp\fin\fp\fbcompaq\fp 2880 80 36 2 36 \fbfd\fp\fin\fp\fbu3200\fp 3200 80 40 2 104 \fbfd\fp\fin\fp\fbu3520\fp 3520 80 44 2 108 \fbfd\fp\fin\fp\fbu3840\fp 3840 80 48 2 112 .te .sh description \fbfd\fp special files access the floppy disk drives in raw mode. the following .br ioctl (2) calls are supported by \fbfd\fp devices: .ip \fbfdclrprm\fp clears the media information of a drive (geometry of disk in drive). .ip \fbfdsetprm\fp sets the media information of a drive. the media information will be lost when the media is changed. .ip \fbfddefprm\fp sets the media information of a drive (geometry of disk in drive). the media information will not be lost when the media is changed. this will disable autodetection. in order to reenable autodetection, you have to issue an \fbfdclrprm\fp. .ip \fbfdgetdrvtyp\fp returns the type of a drive (name parameter). for formats which work in several drive types, \fbfdgetdrvtyp\fp returns a name which is appropriate for the oldest drive type which supports this format. .ip \fbfdflush\fp invalidates the buffer cache for the given drive. .ip \fbfdsetmaxerrs\fp sets the error thresholds for reporting errors, aborting the operation, recalibrating, resetting, and reading sector by sector. .ip \fbfdsetmaxerrs\fp gets the current error thresholds. .ip \fbfdgetdrvtyp\fp gets the internal name of the drive. .ip \fbfdwerrorclr\fp clears the write error statistics. .ip \fbfdwerrorget\fp reads the write error statistics. these include the total number of write errors, the location and disk of the first write error, and the location and disk of the last write error. disks are identified by a generation number which is incremented at (almost) each disk change. .ip \fbfdtwaddle\fp switch the drive motor off for a few microseconds. this might be needed in order to access a disk whose sectors are too close together. .ip \fbfdsetdrvprm\fp sets various drive parameters. .ip \fbfdgetdrvprm\fp reads these parameters back. .ip \fbfdgetdrvstat\fp gets the cached drive state (disk changed, write protected et al.) .ip \fbfdpolldrvstat\fp polls the drive and return its state. .ip \fbfdgetfdcstat\fp gets the floppy controller state. .ip \fbfdreset\fp resets the floppy controller under certain conditions. .ip \fbfdrawcmd\fp sends a raw command to the floppy controller. .pp for more precise information, consult also the \fi\fp and \fi\fp include files, as well as the .br floppycontrol (1) manual page. .sh files .i /dev/fd* .sh notes the various formats permit reading and writing many types of disks. however, if a floppy is formatted with an inter-sector gap that is too small, performance may drop, to the point of needing a few seconds to access an entire track. to prevent this, use interleaved formats. .pp it is not possible to read floppies which are formatted using gcr (group code recording), which is used by apple ii and macintosh computers (800k disks). .pp reading floppies which are hard sectored (one hole per sector, with the index hole being a little skewed) is not supported. this used to be common with older 8-inch floppies. .\" .sh authors .\" alain knaff (alain.knaff@imag.fr), david niemi .\" (niemidc@clark.net), bill broadhurst (bbroad@netcom.com). .sh see also .br chown (1), .br floppycontrol (1), .br getfdprm (1), .br mknod (1), .br superformat (1), .br mount (8), .br setfdprm (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th clock_nanosleep 2 2021-03-22 "linux" "linux programmer's manual" .sh name clock_nanosleep \- high-resolution sleep with specifiable clock .sh synopsis .b #include .nf .pp .bi "int clock_nanosleep(clockid_t " clockid ", int " flags , .bi " const struct timespec *" request , .bi " struct timespec *" remain ); .fi .pp link with \fi\-lrt\fp (only for glibc versions before 2.17). .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br clock_nanosleep (): .nf _posix_c_source >= 200112l .fi .sh description like .br nanosleep (2), .br clock_nanosleep () allows the calling thread to sleep for an interval specified with nanosecond precision. it differs in allowing the caller to select the clock against which the sleep interval is to be measured, and in allowing the sleep interval to be specified as either an absolute or a relative value. .pp the time values passed to and returned by this call are specified using .i timespec structures, defined as follows: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds [0 .. 999999999] */ }; .ee .in .pp the .i clockid argument specifies the clock against which the sleep interval is to be measured. this argument can have one of the following values: .\" look in time/posix-timers.c (kernel 5.6 sources) for the .\" 'struct k_clock' structures that have an 'nsleep' method .tp .br clock_realtime a settable system-wide real-time clock. .tp .br clock_tai " (since linux 3.10)" a system-wide clock derived from wall-clock time but ignoring leap seconds. .tp .br clock_monotonic a nonsettable, monotonically increasing clock that measures time since some unspecified point in the past that does not change after system startup. .\" on linux this clock measures time since boot. .tp .br clock_bootime " (since linux 2.6.39)" identical to .br clock_monotonic , except that it also includes any time that the system is suspended. .tp .br clock_process_cputime_id a settable per-process clock that measures cpu time consumed by all threads in the process. .\" there is some trickery between glibc and the kernel .\" to deal with the clock_process_cputime_id case. .pp see .br clock_getres (2) for further details on these clocks. in addition, the cpu clock ids returned by .br clock_getcpuclockid (3) and .br pthread_getcpuclockid (3) can also be passed in .ir clockid . .\" sleeping against clock_realtime_alarm and clock_boottime_alarm .\" is also possible (tested), with cap_wake_alarm, but i'm not .\" sure if this is useful or needs to be documented. .pp if .i flags is 0, then the value specified in .i request is interpreted as an interval relative to the current value of the clock specified by .ir clockid . .pp if .i flags is .br timer_abstime , then .i request is interpreted as an absolute time as measured by the clock, .ir clockid . if .i request is less than or equal to the current value of the clock, then .br clock_nanosleep () returns immediately without suspending the calling thread. .pp .br clock_nanosleep () suspends the execution of the calling thread until either at least the time specified by .ir request has elapsed, or a signal is delivered that causes a signal handler to be called or that terminates the process. .pp if the call is interrupted by a signal handler, .br clock_nanosleep () fails with the error .br eintr . in addition, if .i remain is not null, and .i flags was not .br timer_abstime , it returns the remaining unslept time in .ir remain . this value can then be used to call .br clock_nanosleep () again and complete a (relative) sleep. .sh return value on successfully sleeping for the requested interval, .br clock_nanosleep () returns 0. if the call is interrupted by a signal handler or encounters an error, then it returns one of the positive error number listed in errors. .sh errors .tp .b efault .i request or .i remain specified an invalid address. .tp .b eintr the sleep was interrupted by a signal handler; see .br signal (7). .tp .b einval the value in the .i tv_nsec field was not in the range 0 to 999999999 or .i tv_sec was negative. .tp .b einval .i clockid was invalid. .rb ( clock_thread_cputime_id is not a permitted value for .ir clockid .) .tp .b enotsup the kernel does not support sleeping against this .ir clockid . .sh versions the .br clock_nanosleep () system call first appeared in linux 2.6. support is available in glibc since version 2.1. .sh conforming to posix.1-2001, posix.1-2008. .sh notes if the interval specified in .i request is not an exact multiple of the granularity underlying clock (see .br time (7)), then the interval will be rounded up to the next multiple. furthermore, after the sleep completes, there may still be a delay before the cpu becomes free to once again execute the calling thread. .pp using an absolute timer is useful for preventing timer drift problems of the type described in .br nanosleep (2). (such problems are exacerbated in programs that try to restart a relative sleep that is repeatedly interrupted by signals.) to perform a relative sleep that avoids these problems, call .br clock_gettime (2) for the desired clock, add the desired interval to the returned time value, and then call .br clock_nanosleep () with the .b timer_abstime flag. .pp .br clock_nanosleep () is never restarted after being interrupted by a signal handler, regardless of the use of the .br sigaction (2) .b sa_restart flag. .pp the .i remain argument is unused, and unnecessary, when .i flags is .br timer_abstime . (an absolute sleep can be restarted using the same .i request argument.) .pp posix.1 specifies that .br clock_nanosleep () has no effect on signals dispositions or the signal mask. .pp posix.1 specifies that after changing the value of the .b clock_realtime clock via .br clock_settime (2), the new clock value shall be used to determine the time at which a thread blocked on an absolute .br clock_nanosleep () will wake up; if the new clock value falls past the end of the sleep interval, then the .br clock_nanosleep () call will return immediately. .pp posix.1 specifies that changing the value of the .b clock_realtime clock via .br clock_settime (2) shall have no effect on a thread that is blocked on a relative .br clock_nanosleep (). .sh see also .br clock_getres (2), .br nanosleep (2), .br restart_syscall (2), .br timer_create (2), .br sleep (3), .br usleep (3), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .so man3/getservent.3 .\" copyright (c) 2000 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2000-08-14 added gnu additions from andreas jaeger .\" 2000-12-05 some changes inspired by acahalan's remarks .\" .th fenv 3 2021-03-22 "linux" "linux programmer's manual" .sh name feclearexcept, fegetexceptflag, feraiseexcept, fesetexceptflag, fetestexcept, fegetenv, fegetround, feholdexcept, fesetround, fesetenv, feupdateenv, feenableexcept, fedisableexcept, fegetexcept \- floating-point rounding and exception handling .sh synopsis .nf .b #include .pp .bi "int feclearexcept(int " excepts ); .bi "int fegetexceptflag(fexcept_t *" flagp ", int " excepts ); .bi "int feraiseexcept(int " excepts ); .bi "int fesetexceptflag(const fexcept_t *" flagp ", int " excepts ); .bi "int fetestexcept(int " excepts ); .pp .b "int fegetround(void);" .bi "int fesetround(int " rounding_mode ); .pp .bi "int fegetenv(fenv_t *" envp ); .bi "int feholdexcept(fenv_t *" envp ); .bi "int fesetenv(const fenv_t *" envp ); .bi "int feupdateenv(const fenv_t *" envp ); .fi .pp link with \fi\-lm\fp. .sh description these eleven functions were defined in c99, and describe the handling of floating-point rounding and exceptions (overflow, zero-divide, etc.). .ss exceptions the .i divide-by-zero exception occurs when an operation on finite numbers produces infinity as exact answer. .pp the .i overflow exception occurs when a result has to be represented as a floating-point number, but has (much) larger absolute value than the largest (finite) floating-point number that is representable. .pp the .i underflow exception occurs when a result has to be represented as a floating-point number, but has smaller absolute value than the smallest positive normalized floating-point number (and would lose much accuracy when represented as a denormalized number). .pp the .i inexact exception occurs when the rounded result of an operation is not equal to the infinite precision result. it may occur whenever .i overflow or .i underflow occurs. .pp the .i invalid exception occurs when there is no well-defined result for an operation, as for 0/0 or infinity \- infinity or sqrt(\-1). .ss exception handling exceptions are represented in two ways: as a single bit (exception present/absent), and these bits correspond in some implementation-defined way with bit positions in an integer, and also as an opaque structure that may contain more information about the exception (perhaps the code address where it occurred). .pp each of the macros .br fe_divbyzero , .br fe_inexact , .br fe_invalid , .br fe_overflow , .b fe_underflow is defined when the implementation supports handling of the corresponding exception, and if so then defines the corresponding bit(s), so that one can call exception handling functions, for example, using the integer argument .br fe_overflow | fe_underflow . other exceptions may be supported. the macro .b fe_all_except is the bitwise or of all bits corresponding to supported exceptions. .pp the .br feclearexcept () function clears the supported exceptions represented by the bits in its argument. .pp the .br fegetexceptflag () function stores a representation of the state of the exception flags represented by the argument .i excepts in the opaque object .ir *flagp . .pp the .br feraiseexcept () function raises the supported exceptions represented by the bits in .ir excepts . .pp the .br fesetexceptflag () function sets the complete status for the exceptions represented by .i excepts to the value .ir *flagp . this value must have been obtained by an earlier call of .br fegetexceptflag () with a last argument that contained all bits in .ir excepts . .pp the .br fetestexcept () function returns a word in which the bits are set that were set in the argument .i excepts and for which the corresponding exception is currently set. .ss rounding mode the rounding mode determines how the result of floating-point operations is treated when the result cannot be exactly represented in the significand. various rounding modes may be provided: round to nearest (the default), round up (toward positive infinity), round down (toward negative infinity), and round toward zero. .pp each of the macros .br fe_tonearest , .br fe_upward , .br fe_downward , and .br fe_towardzero is defined when the implementation supports getting and setting the corresponding rounding direction. .pp the .br fegetround () function returns the macro corresponding to the current rounding mode. .pp the .br fesetround () function sets the rounding mode as specified by its argument and returns zero when it was successful. .pp c99 and posix.1-2008 specify an identifier, .br flt_rounds , defined in .ir , which indicates the implementation-defined rounding behavior for floating-point addition. this identifier has one of the following values: .ip \-1 the rounding mode is not determinable. .ip 0 rounding is toward 0. .ip 1 rounding is toward nearest number. .ip 2 rounding is toward positive infinity. .ip 3 rounding is toward negative infinity. .pp other values represent machine-dependent, nonstandard rounding modes. .pp the value of .br flt_rounds should reflect the current rounding mode as set by .br fesetround () (but see bugs). .ss floating-point environment the entire floating-point environment, including control modes and status flags, can be handled as one opaque object, of type .ir fenv_t . the default environment is denoted by .b fe_dfl_env (of type .ir "const fenv_t\ *" ). this is the environment setup at program start and it is defined by iso c to have round to nearest, all exceptions cleared and a nonstop (continue on exceptions) mode. .pp the .br fegetenv () function saves the current floating-point environment in the object .ir *envp . .pp the .br feholdexcept () function does the same, then clears all exception flags, and sets a nonstop (continue on exceptions) mode, if available. it returns zero when successful. .pp the .br fesetenv () function restores the floating-point environment from the object .ir *envp . this object must be known to be valid, for example, the result of a call to .br fegetenv () or .br feholdexcept () or equal to .br fe_dfl_env . this call does not raise exceptions. .pp the .br feupdateenv () function installs the floating-point environment represented by the object .ir *envp , except that currently raised exceptions are not cleared. after calling this function, the raised exceptions will be a bitwise or of those previously set with those in .ir *envp . as before, the object .i *envp must be known to be valid. .sh return value these functions return zero on success and nonzero if an error occurred. .\" earlier seven of these functions were listed as returning void. .\" this was corrected in corrigendum 1 (iso/iec 9899:1999/cor.1:2001(e)) .\" of the c99 standard. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .nh .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br feclearexcept (), .br fegetexceptflag (), .br feraiseexcept (), .br fesetexceptflag (), .br fetestexcept (), .br fegetround (), .br fesetround (), .br fegetenv (), .br feholdexcept (), .br fesetenv (), .br feupdateenv (), .br feenableexcept (), .br fedisableexcept (), .br fegetexcept () t} thread safety t{ mt-safe t} .te .hy .ad .sp 1 .hy .sh conforming to iec 60559 (iec 559:1989), ansi/ieee 854, c99, posix.1-2001. .sh notes .ss glibc notes if possible, the gnu c library defines a macro .b fe_nomask_env which represents an environment where every exception raised causes a trap to occur. you can test for this macro using .br #ifdef . it is defined only if .b _gnu_source is defined. the c99 standard does not define a way to set individual bits in the floating-point mask, for example, to trap on specific flags. since version 2.2, glibc supports the functions .br feenableexcept () and .br fedisableexcept () to set individual floating-point traps, and .br fegetexcept () to query the state. .pp .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b "#include " .pp .bi "int feenableexcept(int " excepts ); .bi "int fedisableexcept(int " excepts ); .b "int fegetexcept(void);" .fi .pp the .br feenableexcept () and .br fedisableexcept () functions enable (disable) traps for each of the exceptions represented by .i excepts and return the previous set of enabled exceptions when successful, and \-1 otherwise. the .br fegetexcept () function returns the set of all currently enabled exceptions. .sh bugs c99 specifies that the value of .b flt_rounds should reflect changes to the current rounding mode, as set by .br fesetround (). currently, .\" aug 08, glibc 2.8 this does not occur: .b flt_rounds always has the value 1. .\" see http://gcc.gnu.org/ml/gcc/2002-02/msg01535.html .sh see also .br math_error (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/slist.3 .\" copyright (c) 2014 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th open_by_handle_at 2 2021-08-27 "linux" "linux programmer's manual" .sh name name_to_handle_at, open_by_handle_at \- obtain handle for a pathname and open file via a handle .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int name_to_handle_at(int " dirfd ", const char *" pathname , .bi " struct file_handle *" handle , .bi " int *" mount_id ", int " flags ); .bi "int open_by_handle_at(int " mount_fd ", struct file_handle *" handle , .bi " int " flags ); .fi .sh description the .br name_to_handle_at () and .br open_by_handle_at () system calls split the functionality of .br openat (2) into two parts: .br name_to_handle_at () returns an opaque handle that corresponds to a specified file; .br open_by_handle_at () opens the file corresponding to a handle returned by a previous call to .br name_to_handle_at () and returns an open file descriptor. .\" .\" .ss name_to_handle_at() the .br name_to_handle_at () system call returns a file handle and a mount id corresponding to the file specified by the .ir dirfd and .ir pathname arguments. the file handle is returned via the argument .ir handle , which is a pointer to a structure of the following form: .pp .in +4n .ex struct file_handle { unsigned int handle_bytes; /* size of f_handle [in, out] */ int handle_type; /* handle type [out] */ unsigned char f_handle[0]; /* file identifier (sized by caller) [out] */ }; .ee .in .pp it is the caller's responsibility to allocate the structure with a size large enough to hold the handle returned in .ir f_handle . before the call, the .ir handle_bytes field should be initialized to contain the allocated size for .ir f_handle . (the constant .br max_handle_sz , defined in .ir , specifies the maximum expected size for a file handle. it is not a guaranteed upper limit as future filesystems may require more space.) upon successful return, the .ir handle_bytes field is updated to contain the number of bytes actually written to .ir f_handle . .pp the caller can discover the required size for the .i file_handle structure by making a call in which .ir handle\->handle_bytes is zero; in this case, the call fails with the error .br eoverflow and .ir handle\->handle_bytes is set to indicate the required size; the caller can then use this information to allocate a structure of the correct size (see examples below). some care is needed here as .br eoverflow can also indicate that no file handle is available for this particular name in a filesystem which does normally support file-handle lookup. this case can be detected when the .b eoverflow error is returned without .i handle_bytes being increased. .pp other than the use of the .ir handle_bytes field, the caller should treat the .ir file_handle structure as an opaque data type: the .ir handle_type and .ir f_handle fields are needed only by a subsequent call to .br open_by_handle_at (). .pp the .i flags argument is a bit mask constructed by oring together zero or more of .br at_empty_path and .br at_symlink_follow , described below. .pp together, the .i pathname and .i dirfd arguments identify the file for which a handle is to be obtained. there are four distinct cases: .ip * 3 if .i pathname is a nonempty string containing an absolute pathname, then a handle is returned for the file referred to by that pathname. in this case, .ir dirfd is ignored. .ip * if .i pathname is a nonempty string containing a relative pathname and .ir dirfd has the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the caller, and a handle is returned for the file to which it refers. .ip * if .i pathname is a nonempty string containing a relative pathname and .ir dirfd is a file descriptor referring to a directory, then .i pathname is interpreted relative to the directory referred to by .ir dirfd , and a handle is returned for the file to which it refers. (see .br openat (2) for an explanation of why "directory file descriptors" are useful.) .ip * if .i pathname is an empty string and .i flags specifies the value .br at_empty_path , then .ir dirfd can be an open file descriptor referring to any type of file, or .br at_fdcwd , meaning the current working directory, and a handle is returned for the file to which it refers. .pp the .i mount_id argument returns an identifier for the filesystem mount that corresponds to .ir pathname . this corresponds to the first field in one of the records in .ir /proc/self/mountinfo . opening the pathname in the fifth field of that record yields a file descriptor for the mount point; that file descriptor can be used in a subsequent call to .br open_by_handle_at (). .i mount_id is returned both for a successful call and for a call that results in the error .br eoverflow . .pp by default, .br name_to_handle_at () does not dereference .i pathname if it is a symbolic link, and thus returns a handle for the link itself. if .b at_symlink_follow is specified in .ir flags , .i pathname is dereferenced if it is a symbolic link (so that the call returns a handle for the file referred to by the link). .pp .br name_to_handle_at () does not trigger a mount when the final component of the pathname is an automount point. when a filesystem supports both file handles and automount points, a .br name_to_handle_at () call on an automount point will return with error .br eoverflow without having increased .ir handle_bytes . this can happen since linux 4.13 .\" commit 20fa19027286983ab2734b5910c4a687436e0c31 with nfs when accessing a directory which is on a separate filesystem on the server. in this case, the automount can be triggered by adding a "/" to the end of the pathname. .ss open_by_handle_at() the .br open_by_handle_at () system call opens the file referred to by .ir handle , a file handle returned by a previous call to .br name_to_handle_at (). .pp the .ir mount_fd argument is a file descriptor for any object (file, directory, etc.) in the mounted filesystem with respect to which .ir handle should be interpreted. the special value .b at_fdcwd can be specified, meaning the current working directory of the caller. .pp the .i flags argument is as for .br open (2). if .i handle refers to a symbolic link, the caller must specify the .b o_path flag, and the symbolic link is not dereferenced; the .b o_nofollow flag, if specified, is ignored. .pp the caller must have the .b cap_dac_read_search capability to invoke .br open_by_handle_at (). .sh return value on success, .br name_to_handle_at () returns 0, and .br open_by_handle_at () returns a file descriptor (a nonnegative integer). .pp in the event of an error, both system calls return \-1 and set .i errno to indicate the error. .sh errors .br name_to_handle_at () and .br open_by_handle_at () can fail for the same errors as .br openat (2). in addition, they can fail with the errors noted below. .pp .br name_to_handle_at () can fail with the following errors: .tp .b efault .ir pathname , .ir mount_id , or .ir handle points outside your accessible address space. .tp .b einval .i flags includes an invalid bit value. .tp .b einval .ir handle\->handle_bytes is greater than .br max_handle_sz . .tp .b enoent .i pathname is an empty string, but .br at_empty_path was not specified in .ir flags . .tp .b enotdir the file descriptor supplied in .i dirfd does not refer to a directory, and it is not the case that both .i flags includes .br at_empty_path and .i pathname is an empty string. .tp .b eopnotsupp the filesystem does not support decoding of a pathname to a file handle. .tp .b eoverflow the .i handle\->handle_bytes value passed into the call was too small. when this error occurs, .i handle\->handle_bytes is updated to indicate the required size for the handle. .\" .\" .pp .br open_by_handle_at () can fail with the following errors: .tp .b ebadf .ir mount_fd is not an open file descriptor. .tp .b ebadf .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b efault .ir handle points outside your accessible address space. .tp .b einval .i handle\->handle_bytes is greater than .br max_handle_sz or is equal to zero. .tp .b eloop .i handle refers to a symbolic link, but .b o_path was not specified in .ir flags . .tp .b eperm the caller does not have the .br cap_dac_read_search capability. .tp .b estale the specified .i handle is not valid. this error will occur if, for example, the file has been deleted. .sh versions these system calls first appeared in linux 2.6.39. library support is provided in glibc since version 2.14. .sh conforming to these system calls are nonstandard linux extensions. .pp freebsd has a broadly similar pair of system calls in the form of .br getfh () and .br openfh (). .sh notes a file handle can be generated in one process using .br name_to_handle_at () and later used in a different process that calls .br open_by_handle_at (). .pp some filesystem don't support the translation of pathnames to file handles, for example, .ir /proc , .ir /sys , and various network filesystems. .pp a file handle may become invalid ("stale") if a file is deleted, or for other filesystem-specific reasons. invalid handles are notified by an .b estale error from .br open_by_handle_at (). .pp these system calls are designed for use by user-space file servers. for example, a user-space nfs server might generate a file handle and pass it to an nfs client. later, when the client wants to open the file, it could pass the handle back to the server. .\" https://lwn.net/articles/375888/ .\" "open by handle" - jonathan corbet, 2010-02-23 this sort of functionality allows a user-space file server to operate in a stateless fashion with respect to the files it serves. .pp if .i pathname refers to a symbolic link and .ir flags does not specify .br at_symlink_follow , then .br name_to_handle_at () returns a handle for the link (rather than the file to which it refers). .\" commit bcda76524cd1fa32af748536f27f674a13e56700 the process receiving the handle can later perform operations on the symbolic link by converting the handle to a file descriptor using .br open_by_handle_at () with the .br o_path flag, and then passing the file descriptor as the .ir dirfd argument in system calls such as .br readlinkat (2) and .br fchownat (2). .ss obtaining a persistent filesystem id the mount ids in .ir /proc/self/mountinfo can be reused as filesystems are unmounted and mounted. therefore, the mount id returned by .br name_to_handle_at () (in .ir *mount_id ) should not be treated as a persistent identifier for the corresponding mounted filesystem. however, an application can use the information in the .i mountinfo record that corresponds to the mount id to derive a persistent identifier. .pp for example, one can use the device name in the fifth field of the .i mountinfo record to search for the corresponding device uuid via the symbolic links in .ir /dev/disks/by\-uuid . (a more comfortable way of obtaining the uuid is to use the .\" e.g., http://stackoverflow.com/questions/6748429/using-libblkid-to-find-uuid-of-a-partition .br libblkid (3) library.) that process can then be reversed, using the uuid to look up the device name, and then obtaining the corresponding mount point, in order to produce the .ir mount_fd argument used by .br open_by_handle_at (). .sh examples the two programs below demonstrate the use of .br name_to_handle_at () and .br open_by_handle_at (). the first program .ri ( t_name_to_handle_at.c ) uses .br name_to_handle_at () to obtain the file handle and mount id for the file specified in its command-line argument; the handle and mount id are written to standard output. .pp the second program .ri ( t_open_by_handle_at.c ) reads a mount id and file handle from standard input. the program then employs .br open_by_handle_at () to open the file using that handle. if an optional command-line argument is supplied, then the .ir mount_fd argument for .br open_by_handle_at () is obtained by opening the directory named in that argument. otherwise, .ir mount_fd is obtained by scanning .ir /proc/self/mountinfo to find a record whose mount id matches the mount id read from standard input, and the mount directory specified in that record is opened. (these programs do not deal with the fact that mount ids are not persistent.) .pp the following shell session demonstrates the use of these two programs: .pp .in +4n .ex $ \fbecho \(aqcan you please think about it?\(aq > cecilia.txt\fp $ \fb./t_name_to_handle_at cecilia.txt > fh\fp $ \fb./t_open_by_handle_at < fh\fp open_by_handle_at: operation not permitted $ \fbsudo ./t_open_by_handle_at < fh\fp # need cap_sys_admin read 31 bytes $ \fbrm cecilia.txt\fp .ee .in .pp now we delete and (quickly) re-create the file so that it has the same content and (by chance) the same inode. nevertheless, .br open_by_handle_at () .\" christoph hellwig: that's why the file handles contain a generation .\" counter that gets incremented in this case. recognizes that the original file referred to by the file handle no longer exists. .pp .in +4n .ex $ \fbstat \-\-printf="%i\en" cecilia.txt\fp # display inode number 4072121 $ \fbrm cecilia.txt\fp $ \fbecho \(aqcan you please think about it?\(aq > cecilia.txt\fp $ \fbstat \-\-printf="%i\en" cecilia.txt\fp # check inode number 4072121 $ \fbsudo ./t_open_by_handle_at < fh\fp open_by_handle_at: stale nfs file handle .ee .in .ss program source: t_name_to_handle_at.c \& .ex #define _gnu_source #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { struct file_handle *fhp; int mount_id, fhsize, flags, dirfd; char *pathname; if (argc != 2) { fprintf(stderr, "usage: %s pathname\en", argv[0]); exit(exit_failure); } pathname = argv[1]; /* allocate file_handle structure. */ fhsize = sizeof(*fhp); fhp = malloc(fhsize); if (fhp == null) errexit("malloc"); /* make an initial call to name_to_handle_at() to discover the size required for file handle. */ dirfd = at_fdcwd; /* for name_to_handle_at() calls */ flags = 0; /* for name_to_handle_at() calls */ fhp\->handle_bytes = 0; if (name_to_handle_at(dirfd, pathname, fhp, &mount_id, flags) != \-1 || errno != eoverflow) { fprintf(stderr, "unexpected result from name_to_handle_at()\en"); exit(exit_failure); } /* reallocate file_handle structure with correct size. */ fhsize = sizeof(*fhp) + fhp\->handle_bytes; fhp = realloc(fhp, fhsize); /* copies fhp\->handle_bytes */ if (fhp == null) errexit("realloc"); /* get file handle from pathname supplied on command line. */ if (name_to_handle_at(dirfd, pathname, fhp, &mount_id, flags) == \-1) errexit("name_to_handle_at"); /* write mount id, file handle size, and file handle to stdout, for later reuse by t_open_by_handle_at.c. */ printf("%d\en", mount_id); printf("%u %d ", fhp\->handle_bytes, fhp\->handle_type); for (int j = 0; j < fhp\->handle_bytes; j++) printf(" %02x", fhp\->f_handle[j]); printf("\en"); exit(exit_success); } .ee .ss program source: t_open_by_handle_at.c \& .ex #define _gnu_source #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) /* scan /proc/self/mountinfo to find the line whose mount id matches \(aqmount_id\(aq. (an easier way to do this is to install and use the \(aqlibmount\(aq library provided by the \(aqutil\-linux\(aq project.) open the corresponding mount path and return the resulting file descriptor. */ static int open_mount_path_by_id(int mount_id) { char *linep; size_t lsize; char mount_path[path_max]; int mi_mount_id, found; ssize_t nread; file *fp; fp = fopen("/proc/self/mountinfo", "r"); if (fp == null) errexit("fopen"); found = 0; linep = null; while (!found) { nread = getline(&linep, &lsize, fp); if (nread == \-1) break; nread = sscanf(linep, "%d %*d %*s %*s %s", &mi_mount_id, mount_path); if (nread != 2) { fprintf(stderr, "bad sscanf()\en"); exit(exit_failure); } if (mi_mount_id == mount_id) found = 1; } free(linep); fclose(fp); if (!found) { fprintf(stderr, "could not find mount point\en"); exit(exit_failure); } return open(mount_path, o_rdonly); } int main(int argc, char *argv[]) { struct file_handle *fhp; int mount_id, fd, mount_fd, handle_bytes; ssize_t nread; char buf[1000]; #define line_size 100 char line1[line_size], line2[line_size]; char *nextp; if ((argc > 1 && strcmp(argv[1], "\-\-help") == 0) || argc > 2) { fprintf(stderr, "usage: %s [mount\-path]\en", argv[0]); exit(exit_failure); } /* standard input contains mount id and file handle information: line 1: line 2: */ if ((fgets(line1, sizeof(line1), stdin) == null) || (fgets(line2, sizeof(line2), stdin) == null)) { fprintf(stderr, "missing mount_id / file handle\en"); exit(exit_failure); } mount_id = atoi(line1); handle_bytes = strtoul(line2, &nextp, 0); /* given handle_bytes, we can now allocate file_handle structure. */ fhp = malloc(sizeof(*fhp) + handle_bytes); if (fhp == null) errexit("malloc"); fhp\->handle_bytes = handle_bytes; fhp\->handle_type = strtoul(nextp, &nextp, 0); for (int j = 0; j < fhp\->handle_bytes; j++) fhp\->f_handle[j] = strtoul(nextp, &nextp, 16); /* obtain file descriptor for mount point, either by opening the pathname specified on the command line, or by scanning /proc/self/mounts to find a mount that matches the \(aqmount_id\(aq that we received from stdin. */ if (argc > 1) mount_fd = open(argv[1], o_rdonly); else mount_fd = open_mount_path_by_id(mount_id); if (mount_fd == \-1) errexit("opening mount fd"); /* open file using handle and mount point. */ fd = open_by_handle_at(mount_fd, fhp, o_rdonly); if (fd == \-1) errexit("open_by_handle_at"); /* try reading a few bytes from the file. */ nread = read(fd, buf, sizeof(buf)); if (nread == \-1) errexit("read"); printf("read %zd bytes\en", nread); exit(exit_success); } .ee .sh see also .br open (2), .br libblkid (3), .br blkid (8), .br findfs (8), .br mount (8) .pp the .i libblkid and .i libmount documentation in the latest .i util\-linux release at .ur https://www.kernel.org/pub/linux/utils/util\-linux/ .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mq_send.3 .so man3/tailq.3 .so man3/stailq.3 .so man2/unimplemented.2 .\" copyright (c) 2003, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2003-12-10 initial creation, michael kerrisk .\" 2004-10-28 aeb, corrected prototype, prot must be 0 .\" .th remap_file_pages 2 2021-03-22 "linux" "linux programmer's manual" .sh name remap_file_pages \- create a nonlinear file mapping .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int remap_file_pages(void *" addr ", size_t " size ", int " prot , .bi " size_t " pgoff ", int " flags ); .fi .sh description .br note : .\" commit 33041a0d76d3c3e0aff28ac95a2ffdedf1282dbc .\" http://lwn.net/articles/597632/ this system call was marked as deprecated starting with linux 3.16. in linux 4.0, the implementation was replaced .\" commit c8d78c1823f46519473949d33f0d1d33fe21ea16 by a slower in-kernel emulation. those few applications that use this system call should consider migrating to alternatives. this change was made because the kernel code for this system call was complex, and it is believed to be little used or perhaps even completely unused. while it had some use cases in database applications on 32-bit systems, those use cases don't exist on 64-bit systems. .pp the .br remap_file_pages () system call is used to create a nonlinear mapping, that is, a mapping in which the pages of the file are mapped into a nonsequential order in memory. the advantage of using .br remap_file_pages () over using repeated calls to .br mmap (2) is that the former approach does not require the kernel to create additional vma (virtual memory area) data structures. .pp to create a nonlinear mapping we perform the following steps: .tp 3 1. use .br mmap (2) to create a mapping (which is initially linear). this mapping must be created with the .b map_shared flag. .tp 2. use one or more calls to .br remap_file_pages () to rearrange the correspondence between the pages of the mapping and the pages of the file. it is possible to map the same page of a file into multiple locations within the mapped region. .pp the .i pgoff and .i size arguments specify the region of the file that is to be relocated within the mapping: .i pgoff is a file offset in units of the system page size; .i size is the length of the region in bytes. .pp the .i addr argument serves two purposes. first, it identifies the mapping whose pages we want to rearrange. thus, .i addr must be an address that falls within a region previously mapped by a call to .br mmap (2). second, .i addr specifies the address at which the file pages identified by .i pgoff and .i size will be placed. .pp the values specified in .i addr and .i size should be multiples of the system page size. if they are not, then the kernel rounds .i both values .i down to the nearest multiple of the page size. .\" this rounding is weird, and not consistent with the treatment of .\" the analogous arguments for munmap()/mprotect() and for mlock(). .\" mtk, 14 sep 2005 .pp the .i prot argument must be specified as 0. .pp the .i flags argument has the same meaning as for .br mmap (2), but all flags other than .b map_nonblock are ignored. .sh return value on success, .br remap_file_pages () returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i addr does not refer to a valid mapping created with the .b map_shared flag. .tp .b einval .ir addr , .ir size , .ir prot , or .i pgoff is invalid. .\" and possibly others from vma->vm_ops->populate() .sh versions the .br remap_file_pages () system call appeared in linux 2.5.46; glibc support was added in version 2.3.3. .sh conforming to the .br remap_file_pages () system call is linux-specific. .sh notes since linux 2.6.23, .\" commit 3ee6dafc677a68e461a7ddafc94a580ebab80735 .br remap_file_pages () creates non-linear mappings only on in-memory filesystems such as .br tmpfs (5), hugetlbfs or ramfs. on filesystems with a backing store, .br remap_file_pages () is not much more efficient than using .br mmap (2) to adjust which parts of the file are mapped to which addresses. .sh see also .br getpagesize (2), .br mmap (2), .br mmap2 (2), .br mprotect (2), .br mremap (2), .br msync (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. #!/bin/bash # # check_unbalanced_macros.sh # # dec 2007, michael kerrisk # # look for unbalanced pairs of macros in man page source files, with # $1 and $2 specifying the macro pair. these arguments should # _not_ include the leading dot (.) in the macro. # as output, the program prints the line numbers containing each macro, # and if an unbalanced macro is detected, the string "unbalanced!" # is printed. # # example usage: # # sh check_unbalanced_macros.sh nf fi */*.[1-8] # sh check_unbalanced_macros.sh rs re */*.[1-8] # sh check_unbalanced_macros.sh ex ee */*.[1-8] # ###################################################################### # # (c) copyright 2020, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # if test $# -lt 4; then echo "usage: $0 opener closer pages..." exit 1 fi opener="$1" closer="$2" shift 2 for f in $@; do if egrep "^\.($opener|$closer)" $f > /dev/null; then echo "================== $f" nl -ba $f | awk 'begin { level = 0 } $2 == "'".$opener"'" { level++ } $2 == "'".$opener"'" || $2 == "'".$closer"'" { printf "%s %s %d", $1, $2, level if (level == 0) print " unbalanced!" else print "" } $2 == "'".$closer"'" { level-- } end { if (level != 0) print "unbalanced!" }' fi done .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setschedparam 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setschedparam, pthread_attr_getschedparam \- set/get scheduling parameter attributes in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setschedparam(pthread_attr_t *restrict " attr , .bi " const struct sched_param *restrict " param ); .bi "int pthread_attr_getschedparam(const pthread_attr_t *restrict " attr , .bi " struct sched_param *restrict " param ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setschedparam () function sets the scheduling parameter attributes of the thread attributes object referred to by .ir attr to the values specified in the buffer pointed to by .ir param . these attributes determine the scheduling parameters of a thread created using the thread attributes object .ir attr . .pp the .br pthread_attr_getschedparam () returns the scheduling parameter attributes of the thread attributes object .ir attr in the buffer pointed to by .ir param . .pp scheduling parameters are maintained in the following structure: .pp .in +4n .ex struct sched_param { int sched_priority; /* scheduling priority */ }; .ee .in .pp as can be seen, only one scheduling parameter is supported. for details of the permitted ranges for scheduling priorities in each scheduling policy, see .br sched (7). .pp in order for the parameter setting made by .br pthread_attr_setschedparam () to have effect when calling .br pthread_create (3), the caller must use .br pthread_attr_setinheritsched (3) to set the inherit-scheduler attribute of the attributes object .i attr to .br pthread_explicit_sched . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .br pthread_attr_setschedparam () can fail with the following error: .tp .b einval the priority specified in .i param does not make sense for the current scheduling policy of .ir attr . .pp posix.1 also documents an .b enotsup error for .br pthread_attr_setschedparam (). this value is never returned on linux (but portable and future-proof applications should nevertheless handle this error return value). .\" .sh versions .\" available since glibc 2.0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setschedparam (), .br pthread_attr_getschedparam () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes see .br pthread_attr_setschedpolicy (3) for a list of the thread scheduling policies supported on linux. .sh examples see .br pthread_setschedparam (3). .sh see also .ad l .nh .br sched_get_priority_min (2), .br pthread_attr_init (3), .br pthread_attr_setinheritsched (3), .br pthread_attr_setschedpolicy (3), .br pthread_create (3), .br pthread_setschedparam (3), .br pthread_setschedprio (3), .br pthreads (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wmemset 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wmemset \- fill an array of wide-characters with a constant wide character .sh synopsis .nf .b #include .pp .bi "wchar_t *wmemset(wchar_t *" wcs ", wchar_t " wc ", size_t " n ); .fi .sh description the .br wmemset () function is the wide-character equivalent of the .br memset (3) function. it fills the array of .i n wide-characters starting at .i wcs with .i n copies of the wide character .ir wc . .sh return value .br wmemset () returns .ir wcs . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wmemset () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br memset (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page was written by jeremy phelps . .\" notes added - aeb .\" .\" %%%license_start(freely_redistributable) .\" redistribute and revise at will. .\" %%%license_end .\" .th pts 4 2020-08-13 "linux" "linux programmer's manual" .sh name ptmx, pts \- pseudoterminal master and slave .sh description the file .i /dev/ptmx (the pseudoterminal multiplexor device) is a character file with major number 5 and minor number 2, usually with mode 0666 and ownership root:root. it is used to create a pseudoterminal master and slave pair. .pp when a process opens .ir /dev/ptmx , it gets a file descriptor for a pseudoterminal master and a pseudoterminal slave device is created in the .i /dev/pts directory. each file descriptor obtained by opening .ir /dev/ptmx is an independent pseudoterminal master with its own associated slave, whose path can be found by passing the file descriptor to .br ptsname (3). .pp before opening the pseudoterminal slave, you must pass the master's file descriptor to .br grantpt (3) and .br unlockpt (3). .pp once both the pseudoterminal master and slave are open, the slave provides processes with an interface that is identical to that of a real terminal. .pp data written to the slave is presented on the master file descriptor as input. data written to the master is presented to the slave as input. .pp in practice, pseudoterminals are used for implementing terminal emulators such as .br xterm (1), in which data read from the pseudoterminal master is interpreted by the application in the same way a real terminal would interpret the data, and for implementing remote-login programs such as .br sshd (8), in which data read from the pseudoterminal master is sent across the network to a client program that is connected to a terminal or terminal emulator. .pp pseudoterminals can also be used to send input to programs that normally refuse to read input from pipes (such as .br su (1), and .br passwd (1)). .sh files .ir /dev/ptmx , .i /dev/pts/* .sh notes the linux support for the above (known as unix 98 pseudoterminal naming) is done using the .i devpts filesystem, which should be mounted on .ir /dev/pts . .sh see also .br getpt (3), .br grantpt (3), .br ptsname (3), .br unlockpt (3), .br pty (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man7/iso_8859-5.7 .so man3/xdr.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:38:44 1993 by rik faith (faith@cs.unc.edu) .th fgetgrent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fgetgrent \- get group file entry .sh synopsis .nf .b #include .b #include .b #include .pp .bi "struct group *fgetgrent(file *" stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fgetgrent (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description the .br fgetgrent () function returns a pointer to a structure containing the group information from the file referred to by .ir stream . the first time it is called it returns the first entry; thereafter, it returns successive entries. the file referred to by .i stream must have the same format as .i /etc/group (see .br group (5)). .pp the \figroup\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ gid_t gr_gid; /* group id */ char **gr_mem; /* null\-terminated array of pointers to names of group members */ }; .ee .in .sh return value the .br fgetgrent () function returns a pointer to a .i group structure, or null if there are no more entries or an error occurs. in the event of an error, .i errno is set to indicate the error. .sh errors .tp .b enomem insufficient memory to allocate .i group structure. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fgetgrent () t} thread safety mt-unsafe race:fgetgrent .te .hy .ad .sp 1 .\" fixme the marking is different from that in the glibc manual, .\" which has: .\" .\" fgetgrent: mt-unsafe race:fgrent .\" .\" we think race:fgrent in glibc may be hard for users to understand, .\" and have sent a patch to the gnu libc community for changing it to .\" race:fgetgrent, however, something about the copyright impeded the .\" progress. .sh conforming to svr4. .sh see also .br endgrent (3), .br fgetgrent_r (3), .br fopen (3), .br getgrent (3), .br getgrgid (3), .br getgrnam (3), .br putgrent (3), .br setgrent (3), .br group (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_getattr 3 2021-03-22 "linux" "linux programmer's manual" .sh name mq_getattr, mq_setattr \- get/set message queue attributes .sh synopsis .nf .b #include .pp .bi "int mq_getattr(mqd_t " mqdes ", struct mq_attr *" attr ); .bi "int mq_setattr(mqd_t " mqdes ", const struct mq_attr *restrict " newattr , .bi " struct mq_attr *restrict " oldattr ); .fi .pp link with \fi\-lrt\fp. .sh description .br mq_getattr () and .br mq_setattr () respectively retrieve and modify attributes of the message queue referred to by the message queue descriptor .ir mqdes . .pp .br mq_getattr () returns an .i mq_attr structure in the buffer pointed by .ir attr . this structure is defined as: .pp .in +4n .ex struct mq_attr { long mq_flags; /* flags: 0 or o_nonblock */ long mq_maxmsg; /* max. # of messages on queue */ long mq_msgsize; /* max. message size (bytes) */ long mq_curmsgs; /* # of messages currently in queue */ }; .ee .in .pp the .i mq_flags field contains flags associated with the open message queue description. this field is initialized when the queue is created by .br mq_open (3). the only flag that can appear in this field is .br o_nonblock . .pp the .i mq_maxmsg and .i mq_msgsize fields are set when the message queue is created by .br mq_open (3). the .i mq_maxmsg field is an upper limit on the number of messages that may be placed on the queue using .br mq_send (3). the .i mq_msgsize field is an upper limit on the size of messages that may be placed on the queue. both of these fields must have a value greater than zero. two .i /proc files that place ceilings on the values for these fields are described in .br mq_overview (7). .pp the .i mq_curmsgs field returns the number of messages currently held in the queue. .pp .br mq_setattr () sets message queue attributes using information supplied in the .i mq_attr structure pointed to by .ir newattr . the only attribute that can be modified is the setting of the .b o_nonblock flag in .ir mq_flags . the other fields in .i newattr are ignored. if the .i oldattr field is not null, then the buffer that it points to is used to return an .i mq_attr structure that contains the same information that is returned by .br mq_getattr (). .sh return value on success .br mq_getattr () and .br mq_setattr () return 0; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b ebadf the message queue descriptor specified in .i mqdes is invalid. .tp .b einval .i newattr\->mq_flags contained set bits other than .br o_nonblock . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mq_getattr (), .br mq_setattr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on linux, .br mq_getattr () and .br mq_setattr () are library functions layered on top of the .br mq_getsetattr (2) system call. .sh examples the program below can be used to show the default .i mq_maxmsg and .i mq_msgsize values that are assigned to a message queue that is created with a call to .br mq_open (3) in which the .i attr argument is null. here is an example run of the program: .pp .in +4n .ex $ \fb./a.out /testq\fp maximum # of messages on queue: 10 maximum message size: 8192 .ee .in .pp since linux 3.5, the following .i /proc files (described in .br mq_overview (7)) can be used to control the defaults: .pp .in +4n .ex $ \fbuname \-sr\fp linux 3.8.0 $ \fbcat /proc/sys/fs/mqueue/msg_default\fp 10 $ \fbcat /proc/sys/fs/mqueue/msgsize_default\fp 8192 .ee .in .ss program source \& .ex #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { mqd_t mqd; struct mq_attr attr; if (argc != 2) { fprintf(stderr, "usage: %s mq\-name\en", argv[0]); exit(exit_failure); } mqd = mq_open(argv[1], o_creat | o_excl, s_irusr | s_iwusr, null); if (mqd == (mqd_t) \-1) errexit("mq_open"); if (mq_getattr(mqd, &attr) == \-1) errexit("mq_getattr"); printf("maximum # of messages on queue: %ld\en", attr.mq_maxmsg); printf("maximum message size: %ld\en", attr.mq_msgsize); if (mq_unlink(argv[1]) == \-1) errexit("mq_unlink"); exit(exit_success); } .ee .sh see also .br mq_close (3), .br mq_notify (3), .br mq_open (3), .br mq_receive (3), .br mq_send (3), .br mq_unlink (3), .br mq_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/slist.3 .so man2/readv.2 .so man3/getspnam.3 .so man3/getusershell.3 .\" copyright (c) 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sysv_signal 3 2021-03-22 "" "linux programmer's manual" .sh name sysv_signal \- signal handling with system v semantics .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .b typedef void (*sighandler_t)(int); .pp .bi "sighandler_t sysv_signal(int " signum ", sighandler_t " handler ); .fi .sh description the .br sysv_signal () function takes the same arguments, and performs the same task, as .br signal (2). .pp however .br sysv_signal () provides the system v unreliable signal semantics, that is: a) the disposition of the signal is reset to the default when the handler is invoked; b) delivery of further instances of the signal is not blocked while the signal handler is executing; and c) if the handler interrupts (certain) blocking system calls, then the system call is not automatically restarted. .sh return value the .br sysv_signal () function returns the previous value of the signal handler, or .b sig_err on error. .sh errors as for .br signal (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sysv_signal () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is nonstandard. .sh notes use of .br sysv_signal () should be avoided; use .br sigaction (2) instead. .pp on older linux systems, .br sysv_signal () and .br signal (2) were equivalent. but on newer systems, .br signal (2) provides reliable signal semantics; see .br signal (2) for details. .pp the use of .i sighandler_t is a gnu extension; this type is defined only if the .b _gnu_source feature test macro is defined. .sh see also .br sigaction (2), .br signal (2), .br bsd_signal (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/wordexp.3 .so man3/drand48.3 .\" copyright (c) 2012 yoshifuji hideaki .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th if_nametoindex 3 2021-03-22 "gnu" "linux programmer's manual" .sh name if_nametoindex, if_indextoname \- mappings between network interface names and indexes .sh synopsis .nf .b #include .pp .bi "unsigned int if_nametoindex(const char *" "ifname" ); .bi "char *if_indextoname(unsigned int ifindex, char *" ifname ); .fi .sh description the .br if_nametoindex () function returns the index of the network interface corresponding to the name .ir ifname . .pp the .br if_indextoname () function returns the name of the network interface corresponding to the interface index .ir ifindex . the name is placed in the buffer pointed to by .ir ifname . the buffer must allow for the storage of at least .b if_namesize bytes. .sh return value on success, .br if_nametoindex () returns the index number of the network interface; on error, 0 is returned and .i errno is set to indicate the error. .pp on success, .br if_indextoname () returns .ir ifname ; on error, null is returned and .i errno is set to indicate the error. .sh errors .br if_nametoindex () may fail and set .i errno if: .tp .b enodev no interface found with given name. .pp .br if_indextoname () may fail and set .i errno if: .tp .b enxio no interface found for the index. .pp .br if_nametoindex () and .br if_indextoname () may also fail for any of the errors specified for .br socket (2) or .br ioctl (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br if_nametoindex (), .br if_indextoname () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, rfc\ 3493. .pp this function first appeared in bsdi. .sh see also .br getifaddrs (3), .br if_nameindex (3), .br ifconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2004 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pow10 3 2021-03-22 "" "linux programmer's manual" .sh name pow10, pow10f, pow10l \- base-10 power functions .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "double pow10(double " x ); .bi "float pow10f(float " x ); .bi "long double pow10l(long double " x ); .fi .pp link with \fi\-lm\fp. .sh description these functions return the value of 10 raised to the power .ir x . .pp .br "note well" : these functions perform exactly the same task as the functions described in .br exp10 (3), with the difference that the latter functions are now standardized in ts\ 18661-4:2015. those latter functions should be used in preference to the functions described in this page. .sh versions these functions first appeared in glibc in version 2.1. since glibc 2.27, .\" glibc commit 5a80d39d0d2587e9bd8e72f19e92eeb2a66fbe9e the use of these functions in new programs is no longer supported. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pow10 (), .br pow10f (), .br pow10l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this functions are nonstandard gnu extensions. .sh see also .br exp10 (3), .br pow (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getnetent_r.3 .\" copyright: written by andrew morgan .\" and copyright 2006, 2008, michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" may be distributed as per gpl .\" %%%license_end .\" .\" modified by david a. wheeler .\" modified 2004-05-27, mtk .\" modified 2004-06-21, aeb .\" modified 2008-04-28, morgan of kernel.org .\" update in line with addition of file capabilities and .\" 64-bit capability sets in kernel 2.6.2[45]. .\" modified 2009-01-26, andi kleen .\" .th capget 2 2021-03-22 "linux" "linux programmer's manual" .sh name capget, capset \- set/get capabilities of thread(s) .sh synopsis .nf .br "#include " " /* definition of " cap_* " and" .br " _linux_capability_*" " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_capget, cap_user_header_t " hdrp , .bi " cap_user_data_t " datap ); .bi "int syscall(sys_capset, cap_user_header_t " hdrp , .bi " const cap_user_data_t " datap ); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description these two system calls are the raw kernel interface for getting and setting thread capabilities. not only are these system calls specific to linux, but the kernel api is likely to change and use of these system calls (in particular the format of the .i cap_user_*_t types) is subject to extension with each kernel revision, but old programs will keep working. .pp the portable interfaces are .br cap_set_proc (3) and .br cap_get_proc (3); if possible, you should use those interfaces in applications; see notes. .\" .ss current details now that you have been warned, some current kernel details. the structures are defined as follows. .pp .in +4n .ex #define _linux_capability_version_1 0x19980330 #define _linux_capability_u32s_1 1 /* v2 added in linux 2.6.25; deprecated */ #define _linux_capability_version_2 0x20071026 .\" commit e338d263a76af78fe8f38a72131188b58fceb591 .\" added 64 bit capability support #define _linux_capability_u32s_2 2 /* v3 added in linux 2.6.26 */ #define _linux_capability_version_3 0x20080522 .\" commit ca05a99a54db1db5bca72eccb5866d2a86f8517f #define _linux_capability_u32s_3 2 typedef struct __user_cap_header_struct { __u32 version; int pid; } *cap_user_header_t; typedef struct __user_cap_data_struct { __u32 effective; __u32 permitted; __u32 inheritable; } *cap_user_data_t; .ee .in .pp the .ir effective , .ir permitted , and .i inheritable fields are bit masks of the capabilities defined in .br capabilities (7). note that the .b cap_* values are bit indexes and need to be bit-shifted before oring into the bit fields. to define the structures for passing to the system call, you have to use the .i struct __user_cap_header_struct and .i struct __user_cap_data_struct names because the typedefs are only pointers. .pp kernels prior to 2.6.25 prefer 32-bit capabilities with version .br _linux_capability_version_1 . linux 2.6.25 added 64-bit capability sets, with version .br _linux_capability_version_2 . there was, however, an api glitch, and linux 2.6.26 added .br _linux_capability_version_3 to fix the problem. .pp note that 64-bit capabilities use .i datap[0] and .ir datap[1] , whereas 32-bit capabilities use only .ir datap[0] . .pp on kernels that support file capabilities (vfs capabilities support), these system calls behave slightly differently. this support was added as an option in linux 2.6.24, and became fixed (nonoptional) in linux 2.6.33. .pp for .br capget () calls, one can probe the capabilities of any process by specifying its process id with the .i hdrp\->pid field value. .pp for details on the data, see .br capabilities (7). .\" .ss with vfs capabilities support vfs capabilities employ a file extended attribute (see .br xattr (7)) to allow capabilities to be attached to executables. this privilege model obsoletes kernel support for one process asynchronously setting the capabilities of another. that is, on kernels that have vfs capabilities support, when calling .br capset (), the only permitted values for .i hdrp\->pid are 0 or, equivalently, the value returned by .br gettid (2). .\" .ss without vfs capabilities support on older kernels that do not provide vfs capabilities support .br capset () can, if the caller has the .br cap_setpcap capability, be used to change not only the caller's own capabilities, but also the capabilities of other threads. the call operates on the capabilities of the thread specified by the .i pid field of .i hdrp when that is nonzero, or on the capabilities of the calling thread if .i pid is 0. if .i pid refers to a single-threaded process, then .i pid can be specified as a traditional process id; operating on a thread of a multithreaded process requires a thread id of the type returned by .br gettid (2). for .br capset (), .i pid can also be: \-1, meaning perform the change on all threads except the caller and .br init (1); or a value less than \-1, in which case the change is applied to all members of the process group whose id is \-\fipid\fp. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .pp the calls fail with the error .br einval , and set the .i version field of .i hdrp to the kernel preferred value of .b _linux_capability_version_? when an unsupported .i version value is specified. in this way, one can probe what the current preferred capability revision is. .sh errors .tp .b efault bad memory address. .i hdrp must not be null. .i datap may be null only when the user is trying to determine the preferred capability version format supported by the kernel. .tp .b einval one of the arguments was invalid. .tp .b eperm an attempt was made to add a capability to the permitted set, or to set a capability in the effective set that is not in the permitted set. .tp .b eperm an attempt was made to add a capability to the inheritable set, and either: .rs .ip * 3 that capability was not in the caller's bounding set; or .ip * the capability was not in the caller's permitted set and the caller lacked the .b cap_setpcap capability in its effective set. .re .tp .b eperm the caller attempted to use .br capset () to modify the capabilities of a thread other than itself, but lacked sufficient privilege. for kernels supporting vfs capabilities, this is never permitted. for kernels lacking vfs support, the .b cap_setpcap capability is required. (a bug in kernels before 2.6.11 meant that this error could also occur if a thread without this capability tried to change its own capabilities by specifying the .i pid field as a nonzero value (i.e., the value returned by .br getpid (2)) instead of 0.) .tp .b esrch no such thread. .sh conforming to these system calls are linux-specific. .sh notes the portable interface to the capability querying and setting functions is provided by the .i libcap library and is available here: .br .ur http://git.kernel.org/cgit\:/linux\:/kernel\:/git\:/morgan\:\:/libcap.git .ue .sh see also .br clone (2), .br gettid (2), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006, 2019 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" additions from richard gooch and aeb, 971207 .\" 2006-03-13, mtk, added ppoll() + various other rewordings .\" 2006-07-01, mtk, added pollrdhup + various other wording and .\" formatting changes. .\" .th poll 2 2021-03-22 "linux" "linux programmer's manual" .sh name poll, ppoll \- wait for some event on a file descriptor .sh synopsis .nf .b #include .pp .bi "int poll(struct pollfd *" fds ", nfds_t " nfds ", int " timeout ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int ppoll(struct pollfd *" fds ", nfds_t " nfds , .bi " const struct timespec *" tmo_p ", const sigset_t *" sigmask ); .fi .sh description .br poll () performs a similar task to .br select (2): it waits for one of a set of file descriptors to become ready to perform i/o. the linux-specific .br epoll (7) api performs a similar task, but offers features beyond those found in .br poll (). .pp the set of file descriptors to be monitored is specified in the .i fds argument, which is an array of structures of the following form: .pp .in +4n .ex struct pollfd { int fd; /* file descriptor */ short events; /* requested events */ short revents; /* returned events */ }; .ee .in .pp the caller should specify the number of items in the .i fds array in .ir nfds . .pp the field .i fd contains a file descriptor for an open file. if this field is negative, then the corresponding .i events field is ignored and the .i revents field returns zero. (this provides an easy way of ignoring a file descriptor for a single .br poll () call: simply negate the .i fd field. note, however, that this technique can't be used to ignore file descriptor 0.) .pp the field .i events is an input parameter, a bit mask specifying the events the application is interested in for the file descriptor .ir fd . this field may be specified as zero, in which case the only events that can be returned in .i revents are .br pollhup , .br pollerr , and .b pollnval (see below). .pp the field .i revents is an output parameter, filled by the kernel with the events that actually occurred. the bits returned in .i revents can include any of those specified in .ir events , or one of the values .br pollerr , .br pollhup , or .br pollnval . (these three bits are meaningless in the .i events field, and will be set in the .i revents field whenever the corresponding condition is true.) .pp if none of the events requested (and no error) has occurred for any of the file descriptors, then .br poll () blocks until one of the events occurs. .pp the .i timeout argument specifies the number of milliseconds that .br poll () should block waiting for a file descriptor to become ready. the call will block until either: .ip \(bu 2 a file descriptor becomes ready; .ip \(bu the call is interrupted by a signal handler; or .ip \(bu the timeout expires. .pp note that the .i timeout interval will be rounded up to the system clock granularity, and kernel scheduling delays mean that the blocking interval may overrun by a small amount. specifying a negative value in .i timeout means an infinite timeout. specifying a .i timeout of zero causes .br poll () to return immediately, even if no file descriptors are ready. .pp the bits that may be set/returned in .i events and .i revents are defined in \fi\fp: .tp .b pollin there is data to read. .tp .b pollpri there is some exceptional condition on the file descriptor. possibilities include: .rs .ip \(bu 2 there is out-of-band data on a tcp socket (see .br tcp (7)). .ip \(bu a pseudoterminal master in packet mode has seen a state change on the slave (see .br ioctl_tty (2)). .ip \(bu a .i cgroup.events file has been modified (see .br cgroups (7)). .re .tp .b pollout writing is now possible, though a write larger than the available space in a socket or pipe will still block (unless .b o_nonblock is set). .tp .br pollrdhup " (since linux 2.6.17)" stream socket peer closed connection, or shut down writing half of connection. the .b _gnu_source feature test macro must be defined (before including .i any header files) in order to obtain this definition. .tp .b pollerr error condition (only returned in .ir revents ; ignored in .ir events ). this bit is also set for a file descriptor referring to the write end of a pipe when the read end has been closed. .tp .b pollhup hang up (only returned in .ir revents ; ignored in .ir events ). note that when reading from a channel such as a pipe or a stream socket, this event merely indicates that the peer closed its end of the channel. subsequent reads from the channel will return 0 (end of file) only after all outstanding data in the channel has been consumed. .tp .b pollnval invalid request: .i fd not open (only returned in .ir revents ; ignored in .ir events ). .pp when compiling with .b _xopen_source defined, one also has the following, which convey no further information beyond the bits listed above: .tp .b pollrdnorm equivalent to .br pollin . .tp .b pollrdband priority band data can be read (generally unused on linux). .\" pollrdband is used in the decnet protocol. .tp .b pollwrnorm equivalent to .br pollout . .tp .b pollwrband priority data may be written. .pp linux also knows about, but does not use .br pollmsg . .ss ppoll() the relationship between .br poll () and .br ppoll () is analogous to the relationship between .br select (2) and .br pselect (2): like .br pselect (2), .br ppoll () allows an application to safely wait until either a file descriptor becomes ready or until a signal is caught. .pp other than the difference in the precision of the .i timeout argument, the following .br ppoll () call: .pp .in +4n .ex ready = ppoll(&fds, nfds, tmo_p, &sigmask); .ee .in .pp is nearly equivalent to .i atomically executing the following calls: .pp .in +4n .ex sigset_t origmask; int timeout; timeout = (tmo_p == null) ? \-1 : (tmo_p\->tv_sec * 1000 + tmo_p\->tv_nsec / 1000000); pthread_sigmask(sig_setmask, &sigmask, &origmask); ready = poll(&fds, nfds, timeout); pthread_sigmask(sig_setmask, &origmask, null); .ee .in .pp the above code segment is described as .i nearly equivalent because whereas a negative .i timeout value for .br poll () is interpreted as an infinite timeout, a negative value expressed in .ir *tmo_p results in an error from .br ppoll (). .pp see the description of .br pselect (2) for an explanation of why .br ppoll () is necessary. .pp if the .i sigmask argument is specified as null, then no signal mask manipulation is performed (and thus .br ppoll () differs from .br poll () only in the precision of the .i timeout argument). .pp the .i tmo_p argument specifies an upper limit on the amount of time that .br ppoll () will block. this argument is a pointer to a structure of the following form: .pp .in +4n .ex struct timespec { long tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp if .i tmo_p is specified as null, then .br ppoll () can block indefinitely. .sh return value on success, .br poll () returns a nonnegative value which is the number of elements in the .i pollfds whose .i revents fields have been set to a nonzero value (indicating an event or an error). a return value of zero indicates that the system call timed out before any file descriptors became read. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i fds points outside the process's accessible address space. the array given as argument was not contained in the calling program's address space. .tp .b eintr a signal occurred before any requested event; see .br signal (7). .tp .b einval the .i nfds value exceeds the .b rlimit_nofile value. .tp .b einval .rb ( ppoll ()) the timeout value expressed in .ir *ip is invalid (negative). .tp .b enomem unable to allocate memory for kernel data structures. .sh versions the .br poll () system call was introduced in linux 2.1.23. on older kernels that lack this system call, the glibc .br poll () wrapper function provides emulation using .br select (2). .pp the .br ppoll () system call was added to linux in kernel 2.6.16. the .br ppoll () library call was added in glibc 2.4. .sh conforming to .br poll () conforms to posix.1-2001 and posix.1-2008. .br ppoll () is linux-specific. .\" fixme . .\" ppoll() is proposed for inclusion in posix: .\" https://www.austingroupbugs.net/view.php?id=1263 .\" netbsd 3.0 has a pollts() which is like linux ppoll(). .sh notes the operation of .br poll () and .br ppoll () is not affected by the .br o_nonblock flag. .pp on some other unix systems, .\" darwin, according to a report by jeremy sequoia, relayed by josh triplett .br poll () can fail with the error .b eagain if the system fails to allocate kernel-internal resources, rather than .b enomem as linux does. posix permits this behavior. portable programs may wish to check for .b eagain and loop, just as with .br eintr . .pp some implementations define the nonstandard constant .b inftim with the value \-1 for use as a .ir timeout for .br poll (). this constant is not provided in glibc. .pp for a discussion of what may happen if a file descriptor being monitored by .br poll () is closed in another thread, see .br select (2). .ss c library/kernel differences the linux .br ppoll () system call modifies its .i tmo_p argument. however, the glibc wrapper function hides this behavior by using a local variable for the timeout argument that is passed to the system call. thus, the glibc .br ppoll () function does not modify its .i tmo_p argument. .pp the raw .br ppoll () system call has a fifth argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the .ir sigmask argument. the glibc .br ppoll () wrapper function specifies this argument as a fixed value (equal to .ir sizeof(kernel_sigset_t) ). see .br sigprocmask (2) for a discussion on the differences between the kernel and the libc notion of the sigset. .sh bugs see the discussion of spurious readiness notifications under the bugs section of .br select (2). .sh examples the program below opens each of the files named in its command-line arguments and monitors the resulting file descriptors for readiness to read .rb ( pollin ). the program loops, repeatedly using .br poll () to monitor the file descriptors, printing the number of ready file descriptors on return. for each ready file descriptor, the program: .ip \(bu 2 displays the returned .i revents field in a human-readable form; .ip \(bu if the file descriptor is readable, reads some data from it, and displays that data on standard output; and .ip \(bu if the file descriptors was not readable, but some other event occurred (presumably .br pollhup ), closes the file descriptor. .pp suppose we run the program in one terminal, asking it to open a fifo: .pp .in +4n .ex $ \fbmkfifo myfifo\fp $ \fb./poll_input myfifo\fp .ee .in .pp in a second terminal window, we then open the fifo for writing, write some data to it, and close the fifo: .pp .in +4n .ex $ \fbecho aaaaabbbbbccccc > myfifo\fp .ee .in .pp in the terminal where we are running the program, we would then see: .pp .in +4n .ex opened "myfifo" on fd 3 about to poll() ready: 1 fd=3; events: pollin pollhup read 10 bytes: aaaaabbbbb about to poll() ready: 1 fd=3; events: pollin pollhup read 6 bytes: ccccc about to poll() ready: 1 fd=3; events: pollhup closing fd 3 all file descriptors closed; bye .ee .in .pp in the above output, we see that .br poll () returned three times: .ip \(bu 2 on the first return, the bits returned in the .i revents field were .br pollin , indicating that the file descriptor is readable, and .br pollhup , indicating that the other end of the fifo has been closed. the program then consumed some of the available input. .ip \(bu the second return from .br poll () also indicated .br pollin and .br pollhup ; the program then consumed the last of the available input. .ip \(bu on the final return, .br poll () indicated only .br pollhup on the fifo, at which point the file descriptor was closed and the program terminated. .\" .ss program source \& .ex /* poll_input.c licensed under gnu general public license v2 or later. */ #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { int nfds, num_open_fds; struct pollfd *pfds; if (argc < 2) { fprintf(stderr, "usage: %s file...\en", argv[0]); exit(exit_failure); } num_open_fds = nfds = argc \- 1; pfds = calloc(nfds, sizeof(struct pollfd)); if (pfds == null) errexit("malloc"); /* open each file on command line, and add it \(aqpfds\(aq array. */ for (int j = 0; j < nfds; j++) { pfds[j].fd = open(argv[j + 1], o_rdonly); if (pfds[j].fd == \-1) errexit("open"); printf("opened \e"%s\e" on fd %d\en", argv[j + 1], pfds[j].fd); pfds[j].events = pollin; } /* keep calling poll() as long as at least one file descriptor is open. */ while (num_open_fds > 0) { int ready; printf("about to poll()\en"); ready = poll(pfds, nfds, \-1); if (ready == \-1) errexit("poll"); printf("ready: %d\en", ready); /* deal with array returned by poll(). */ for (int j = 0; j < nfds; j++) { char buf[10]; if (pfds[j].revents != 0) { printf(" fd=%d; events: %s%s%s\en", pfds[j].fd, (pfds[j].revents & pollin) ? "pollin " : "", (pfds[j].revents & pollhup) ? "pollhup " : "", (pfds[j].revents & pollerr) ? "pollerr " : ""); if (pfds[j].revents & pollin) { ssize_t s = read(pfds[j].fd, buf, sizeof(buf)); if (s == \-1) errexit("read"); printf(" read %zd bytes: %.*s\en", s, (int) s, buf); } else { /* pollerr | pollhup */ printf(" closing fd %d\en", pfds[j].fd); if (close(pfds[j].fd) == \-1) errexit("close"); num_open_fds\-\-; } } } } printf("all file descriptors closed; bye\en"); exit(exit_success); } .ee .sh see also .br restart_syscall (2), .br select (2), .br select_tut (2), .br epoll (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/_exit.2 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright (c) 2011 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th catanh 3 2021-03-22 "" "linux programmer's manual" .sh name catanh, catanhf, catanhl \- complex arc tangents hyperbolic .sh synopsis .nf .b #include .pp .bi "double complex catanh(double complex " z ); .bi "float complex catanhf(float complex " z ); .bi "long double complex catanhl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex arc hyperbolic tangent of .ir z . if \fiy\ =\ catanh(z)\fp, then \fiz\ =\ ctanh(y)\fp. the imaginary part of .i y is chosen in the interval [\-pi/2,pi/2]. .pp one has: .pp .nf catanh(z) = 0.5 * (clog(1 + z) \- clog(1 \- z)) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br catanh (), .br catanhf (), .br catanhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh examples .ex /* link with "\-lm" */ #include #include #include #include int main(int argc, char *argv[]) { double complex z, c, f; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } z = atof(argv[1]) + atof(argv[2]) * i; c = catanh(z); printf("catanh() = %6.3f %6.3f*i\en", creal(c), cimag(c)); f = 0.5 * (clog(1 + z) \- clog(1 \- z)); printf("formula = %6.3f %6.3f*i\en", creal(f2), cimag(f2)); exit(exit_success); } .ee .sh see also .br atanh (3), .br cabs (3), .br cimag (3), .br ctanh (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002, 2011 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th rt_sigqueueinfo 2 2021-03-22 "linux" "linux programmer's manual" .sh name rt_sigqueueinfo, rt_tgsigqueueinfo \- queue a signal and data .sh synopsis .nf .br "#include " " /* definition of " si_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_rt_sigqueueinfo, pid_t " tgid , .bi " int " sig ", siginfo_t *" info ); .bi "int syscall(sys_rt_tgsigqueueinfo, pid_t " tgid ", pid_t " tid , .bi " int " sig ", siginfo_t *" info ); .fi .pp .ir note : there are no glibc wrappers for these system calls; see notes. .sh description the .br rt_sigqueueinfo () and .br rt_tgsigqueueinfo () system calls are the low-level interfaces used to send a signal plus data to a process or thread. the receiver of the signal can obtain the accompanying data by establishing a signal handler with the .br sigaction (2) .b sa_siginfo flag. .pp these system calls are not intended for direct application use; they are provided to allow the implementation of .br sigqueue (3) and .br pthread_sigqueue (3). .pp the .br rt_sigqueueinfo () system call sends the signal .i sig to the thread group with the id .ir tgid . (the term "thread group" is synonymous with "process", and .i tid corresponds to the traditional unix process id.) the signal will be delivered to an arbitrary member of the thread group (i.e., one of the threads that is not currently blocking the signal). .pp the .i info argument specifies the data to accompany the signal. this argument is a pointer to a structure of type .ir siginfo_t , described in .br sigaction (2) (and defined by including .ir ). the caller should set the following fields in this structure: .tp .i si_code this should be one of the .b si_* codes in the linux kernel source file .ir include/asm\-generic/siginfo.h . if the signal is being sent to any process other than the caller itself, the following restrictions apply: .rs .ip * 3 the code can't be a value greater than or equal to zero. in particular, it can't be .br si_user , which is used by the kernel to indicate a signal sent by .br kill (2), and nor can it be .br si_kernel , which is used to indicate a signal generated by the kernel. .ip * the code can't (since linux 2.6.39) be .br si_tkill , which is used by the kernel to indicate a signal sent using .\" tkill(2) or .br tgkill (2). .re .tp .i si_pid this should be set to a process id, typically the process id of the sender. .tp .i si_uid this should be set to a user id, typically the real user id of the sender. .tp .i si_value this field contains the user data to accompany the signal. for more information, see the description of the last .ri ( "union sigval" ) argument of .br sigqueue (3). .pp internally, the kernel sets the .i si_signo field to the value specified in .ir sig , so that the receiver of the signal can also obtain the signal number via that field. .pp the .br rt_tgsigqueueinfo () system call is like .br rt_sigqueueinfo (), but sends the signal and data to the single thread specified by the combination of .ir tgid , a thread group id, and .ir tid , a thread in that thread group. .sh return value on success, these system calls return 0. on error, they return \-1 and .i errno is set to indicate the error. .sh errors .tp .b eagain the limit of signals which may be queued has been reached. (see .br signal (7) for further information.) .tp .b einval .ir sig , .ir tgid , or .ir tid was invalid. .tp .b eperm the caller does not have permission to send the signal to the target. for the required permissions, see .br kill (2). .tp .b eperm .i tgid specifies a process other than the caller and .i info\->si_code is invalid. .tp .b esrch .br rt_sigqueueinfo (): no thread group matching .i tgid was found. .pp .br rt_tgsigqueinfo (): no thread matching .i tgid and .i tid was found. .sh versions the .br rt_sigqueueinfo () system call was added to linux in version 2.2. the .br rt_tgsigqueueinfo () system call was added to linux in version 2.6.31. .sh conforming to these system calls are linux-specific. .sh notes since these system calls are not intended for application use, there are no glibc wrapper functions; use .br syscall (2) in the unlikely case that you want to call them directly. .pp as with .br kill (2), the null signal (0) can be used to check if the specified process or thread exists. .sh see also .br kill (2), .br pidfd_send_signal (2), .br sigaction (2), .br sigprocmask (2), .br tgkill (2), .br pthread_sigqueue (3), .br sigqueue (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man7/system_data_types.7 .so man3/cpu_set.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" and copyright (c) 2007 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:35:48 1993 by rik faith (faith@cs.unc.edu) .\" 2007-10-23 mtk: minor rewrites, and added paragraph on exit status .\" .th intro 8 2007-10-23 "linux" "linux programmer's manual" .sh name intro \- introduction to administration and privileged commands .sh description section 8 of the manual describes commands which either can be or are used only by the superuser, like system-administration commands, daemons, and hardware-related commands. .pp as with the commands described in section 1, the commands described in this section terminate with an exit status that indicates whether the command succeeded or failed. see .br intro (1) for more information. .sh notes .ss authors and copyright conditions look at the header of the manual page source for the author(s) and copyright conditions. note that these can be different from page to page! .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fenv.3 .so man3/openpty.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th sincos 3 2021-03-22 "gnu" "linux programmer's manual" .sh name sincos, sincosf, sincosl \- calculate sin and cos simultaneously .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void sincos(double " x ", double *" sin ", double *" cos ); .bi "void sincosf(float " x ", float *" sin ", float *" cos ); .bi "void sincosl(long double " x ", long double *" sin ", long double *" cos ); .fi .pp link with \fi\-lm\fp. .sh description several applications need sine and cosine of the same angle .ir x . these functions compute both at the same time, and store the results in .i *sin and .ir *cos . using this function can be more efficient than two separate calls to .br sin (3) and .br cos (3). .pp if .i x is a nan, a nan is returned in .i *sin and .ir *cos . .pp if .i x is positive infinity or negative infinity, a domain error occurs, and a nan is returned in .i *sin and .ir *cos . .sh return value these functions return .ir void . .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is an infinity .i errno is set to .br edom (but see bugs). an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sincos (), .br sincosf (), .br sincosl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. .sh notes to see the performance advantage of .br sincos (), it may be necessary to disable .br gcc (1) built-in optimizations, using flags such as: .pp .in +4n .ex cc \-o \-lm \-fno\-builtin prog.c .ee .in .sh bugs before version 2.22, the glibc implementation did not set .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=15467 .i errno to .b edom when a domain error occurred. .sh see also .br cos (3), .br sin (3), .br tan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 21:42:42 1993 by rik faith .\" modified tue oct 22 23:44:11 1996 by eric s. raymond .\" modified thu jun 2 23:44:11 2016 by nikos mavrogiannopoulos .th assert 3 2021-03-22 "gnu" "linux programmer's manual" .sh name assert \- abort the program if assertion is false .sh synopsis .nf .b #include .pp .bi "void assert(scalar " expression ); .fi .sh description this macro can help programmers find bugs in their programs, or handle exceptional cases via a crash that will produce limited debugging output. .pp if .i expression is false (i.e., compares equal to zero), .br assert () prints an error message to standard error and terminates the program by calling .br abort (3). the error message includes the name of the file and function containing the .br assert () call, the source code line number of the call, and the text of the argument; something like: .pp .in +4n .ex prog: some_file.c:16: some_func: assertion \`val == 0\(aq failed. .ee .in .pp if the macro .b ndebug is defined at the moment .i was last included, the macro .br assert () generates no code, and hence does nothing at all. it is not recommended to define .b ndebug if using .br assert () to detect error conditions since the software may behave non-deterministically. .sh return value no value is returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br assert () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. in c89, .i expression is required to be of type .i int and undefined behavior results if it is not, but in c99 it may have any scalar type. .\" see defect report 107 for more details. .sh bugs .br assert () is implemented as a macro; if the expression tested has side-effects, program behavior will be different depending on whether .b ndebug is defined. this may create heisenbugs which go away when debugging is turned on. .sh see also .br abort (3), .br assert_perror (3), .br exit (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995, thomas k. dyas .\" and copyright (c) 2019, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created 1995-08-06 thomas k. dyas .\" modified 2000-07-01 aeb .\" modified 2002-07-23 aeb .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th setfsgid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setfsgid \- set group identity used for filesystem checks .sh synopsis .nf .b #include .pp .bi "int setfsgid(gid_t " fsgid ); .fi .sh description on linux, a process has both a filesystem group id and an effective group id. the (linux-specific) filesystem group id is used for permissions checking when accessing filesystem objects, while the effective group id is used for some other kinds of permissions checks (see .br credentials (7)). .pp normally, the value of the process's filesystem group id is the same as the value of its effective group id. this is so, because whenever a process's effective group id is changed, the kernel also changes the filesystem group id to be the same as the new value of the effective group id. a process can cause the value of its filesystem group id to diverge from its effective group id by using .br setfsgid () to change its filesystem group id to the value given in .ir fsgid . .pp .br setfsgid () will succeed only if the caller is the superuser or if .i fsgid matches either the caller's real group id, effective group id, saved set-group-id, or current the filesystem user id. .sh return value on both success and failure, this call returns the previous filesystem group id of the caller. .sh versions this system call is present in linux since version 1.2. .\" this system call is present since linux 1.1.44 .\" and in libc since libc 4.7.6. .sh conforming to .br setfsgid () is linux-specific and should not be used in programs intended to be portable. .sh notes the filesystem group id concept and the .br setfsgid () system call were invented for historical reasons that are no longer applicable on modern linux kernels. see .br setfsuid (2) for a discussion of why the use of both .br setfsuid (2) and .br setfsgid () is nowadays unneeded. .pp the original linux .br setfsgid () system call supported only 16-bit group ids. subsequently, linux 2.4 added .br setfsgid32 () supporting 32-bit ids. the glibc .br setfsgid () wrapper function transparently deals with the variation across kernel versions. .ss c library/kernel differences in glibc 2.15 and earlier, when the wrapper for this system call determines that the argument can't be passed to the kernel without integer truncation (because the kernel is old and does not support 32-bit group ids), it will return \-1 and set \fierrno\fp to .b einval without attempting the system call. .sh bugs no error indications of any kind are returned to the caller, and the fact that both successful and unsuccessful calls return the same value makes it impossible to directly determine whether the call succeeded or failed. instead, the caller must resort to looking at the return value from a further call such as .ir setfsgid(\-1) (which will always fail), in order to determine if a preceding call to .br setfsgid () changed the filesystem group id. at the very least, .b eperm should be returned when the call fails (because the caller lacks the .b cap_setgid capability). .sh see also .br kill (2), .br setfsuid (2), .br capabilities (7), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/backtrace.3 .so man3/hsearch.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-08-10 walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" modified 2003-11-18, 2004-10-05 aeb .\" .th remainder 3 2021-03-22 "" "linux programmer's manual" .sh name drem, dremf, dreml, remainder, remainderf, remainderl \- \ floating-point remainder function .sh synopsis .nf .b #include .pp /* the c99 versions */ .bi "double remainder(double " x ", double " y ); .bi "float remainderf(float " x ", float " y ); .bi "long double remainderl(long double " x ", long double " y ); .pp /* obsolete synonyms */ .bi "double drem(double " x ", double " y ); .bi "float dremf(float " x ", float " y ); .bi "long double dreml(long double " x ", long double " y ); .pp .fi link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br remainder (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br remainderf (), .br remainderl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br drem (), .br dremf (), .br dreml (): .nf /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions compute the remainder of dividing .i x by .ir y . the return value is \fix\fp\-\fin\fp*\fiy\fp, where .i n is the value .ir "x\ /\ y" , rounded to the nearest integer. if the absolute value of \fix\fp\-\fin\fp*\fiy\fp is 0.5, .i n is chosen to be even. .pp these functions are unaffected by the current rounding mode (see .br fenv (3)). .pp the .br drem () function does precisely the same thing. .sh return value on success, these functions return the floating-point remainder, \fix\fp\-\fin\fp*\fiy\fp. if the return value is 0, it has the sign of .ir x . .pp if .i x or .i y is a nan, a nan is returned. .pp if .i x is an infinity, and .i y is not a nan, a domain error occurs, and a nan is returned. .pp if .i y is zero, .\" fixme . instead, glibc gives a domain error even if x is a nan and .i x is not a nan, .\" interestingly, remquo(3) does not have the same problem. a domain error occurs, and a nan is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is an infinity and \fiy\fp is not a nan .i errno is set to .br edom (but see bugs). an invalid floating-point exception .rb ( fe_invalid ) is raised. .ip these functions do not set .ir errno for this case. .tp domain error: \fiy\fp is zero\" [xxx see bug above] and \fix\fp is not a nan .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br drem (), .br dremf (), .br dreml (), .br remainder (), .br remainderf (), .br remainderl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .\" iec 60559. the functions .br remainder (), .br remainderf (), and .br remainderl () are specified in c99, posix.1-2001, and posix.1-2008. .pp the function .br drem () is from 4.3bsd. the .i float and .i "long double" variants .br dremf () and .br dreml () exist on some systems, such as tru64 and glibc2. avoid the use of these functions in favor of .br remainder () etc. .sh bugs before glibc 2.15, .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6779 the call .pp remainder(nan(""), 0); .pp returned a nan, as expected, but wrongly caused a domain error. since glibc 2.15, a silent nan (i.e., no domain error) is returned. .pp before glibc 2.15, .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783 .i errno was not set to .br edom for the domain error that occurs when .i x is an infinity and .i y is not a nan. .sh examples the call "remainder(29.0, 3.0)" returns \-1. .sh see also .br div (3), .br fmod (3), .br remquo (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/slist.3 .so man3/rpc.3 .\" copyright 2000 sam varshavchik .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references: rfc 2553 .th getipnodebyname 3 2021-03-22 "linux" "linux programmer's manual" .sh name getipnodebyname, getipnodebyaddr, freehostent \- get network hostnames and addresses .sh synopsis .nf .b #include .b #include .b #include .pp .bi "struct hostent *getipnodebyname(const char *" name ", int " af , .bi " int " flags ", int *" error_num ); .bi "struct hostent *getipnodebyaddr(const void *" addr ", size_t " len , .bi " int " af ", int *" "error_num" ); .bi "void freehostent(struct hostent *" "ip" ); .fi .sh description these functions are deprecated (and unavailable in glibc). use .br getaddrinfo (3) and .br getnameinfo (3) instead. .pp the .br getipnodebyname () and .br getipnodebyaddr () functions return the names and addresses of a network host. these functions return a pointer to the following structure: .pp .in +4n .ex struct hostent { char *h_name; char **h_aliases; int h_addrtype; int h_length; char **h_addr_list; }; .ee .in .pp these functions replace the .br gethostbyname (3) and .br gethostbyaddr (3) functions, which could access only the ipv4 network address family. the .br getipnodebyname () and .br getipnodebyaddr () functions can access multiple network address families. .pp unlike the .b gethostby functions, these functions return pointers to dynamically allocated memory. the .br freehostent () function is used to release the dynamically allocated memory after the caller no longer needs the .i hostent structure. .ss getipnodebyname() arguments the .br getipnodebyname () function looks up network addresses for the host specified by the .i name argument. the .i af argument specifies one of the following values: .tp .b af_inet the .i name argument points to a dotted-quad ipv4 address or a name of an ipv4 network host. .tp .b af_inet6 the .i name argument points to a hexadecimal ipv6 address or a name of an ipv6 network host. .pp the .i flags argument specifies additional options. more than one option can be specified by bitwise or-ing them together. .i flags should be set to 0 if no options are desired. .tp .b ai_v4mapped this flag is used with .b af_inet6 to request a query for ipv4 addresses instead of ipv6 addresses; the ipv4 addresses will be mapped to ipv6 addresses. .tp .b ai_all this flag is used with .b ai_v4mapped to request a query for both ipv4 and ipv6 addresses. any ipv4 address found will be mapped to an ipv6 address. .tp .b ai_addrconfig this flag is used with .b af_inet6 to further request that queries for ipv6 addresses should not be made unless the system has at least one ipv6 address assigned to a network interface, and that queries for ipv4 addresses should not be made unless the system has at least one ipv4 address assigned to a network interface. this flag may be used by itself or with the .b ai_v4mapped flag. .tp .b ai_default this flag is equivalent to .br "(ai_addrconfig | ai_v4mapped)" . .ss getipnodebyaddr() arguments the .br getipnodebyaddr () function looks up the name of the host whose network address is specified by the .i addr argument. the .i af argument specifies one of the following values: .tp .b af_inet the .i addr argument points to a .i struct in_addr and .i len must be set to .ir "sizeof(struct in_addr)" . .tp .b af_inet6 the .i addr argument points to a .i struct in6_addr and .i len must be set to .ir "sizeof(struct in6_addr)" . .sh return value null is returned if an error occurred, and .i error_num will contain an error code from the following list: .tp .b host_not_found the hostname or network address was not found. .tp .b no_address the domain name server recognized the network address or name, but no answer was returned. this can happen if the network host has only ipv4 addresses and a request has been made for ipv6 information only, or vice versa. .tp .b no_recovery the domain name server returned a permanent failure response. .tp .b try_again the domain name server returned a temporary failure response. you might have better luck next time. .pp a successful query returns a pointer to a .i hostent structure that contains the following fields: .tp .i h_name this is the official name of this network host. .tp .i h_aliases this is an array of pointers to unofficial aliases for the same host. the array is terminated by a null pointer. .tp .i h_addrtype this is a copy of the .i af argument to .br getipnodebyname () or .br getipnodebyaddr (). .i h_addrtype will always be .b af_inet if the .i af argument was .br af_inet . .i h_addrtype will always be .b af_inet6 if the .i af argument was .br af_inet6 . .tp .i h_length this field will be set to .i sizeof(struct in_addr) if .i h_addrtype is .br af_inet , and to .i sizeof(struct in6_addr) if .i h_addrtype is .br af_inet6 . .tp .i h_addr_list this is an array of one or more pointers to network address structures for the network host. the array is terminated by a null pointer. .sh conforming to rfc\ 2553. .\" not in posix.1-2001. .sh notes these functions were present in glibc 2.1.91-95, but were removed again. several unix-like systems support them, but all call them deprecated. .sh see also .br getaddrinfo (3), .br getnameinfo (3), .br inet_ntop (3), .br inet_pton (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cexp2.3 .so man3/abs.3 .so man3/rpc.3 .\" copyright (c) ibm corp. 2012 .\" author: jan glauber .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th s390_runtime_instr 2 2021-03-22 "linux programmer's manual" .sh name s390_runtime_instr \- enable/disable s390 cpu run-time instrumentation .sh synopsis .nf .br "#include " " /* definition of " s390_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_s390_runtime_instr, int " command ", int " signum ); .fi .pp .ir note : glibc provides no wrapper for .br s390_runtime_instr (), necessitating the use of .br syscall (2). .sh description the .br s390_runtime_instr () system call starts or stops cpu run-time instrumentation for the calling thread. .pp the .ir command argument controls whether run-time instrumentation is started .rb ( s390_runtime_instr_start , 1) or stopped .rb ( s390_runtime_instr_stop , 2) for the calling thread. .pp the .ir signum argument specifies the number of a real-time signal. this argument was used to specify a signal number that should be delivered to the thread if the run-time instrumentation buffer was full or if the run-time-instrumentation-halted interrupt had occurred. this feature was never used, and in linux 4.4 support for this feature was removed; .\" commit b38feccd663b55ab07116208b68e1ffc7c3c7e78 thus, in current kernels, this argument is ignored. .sh return value on success, .br s390_runtime_instr () returns 0 and enables the thread for run-time instrumentation by assigning the thread a default run-time instrumentation control block. the caller can then read and modify the control block and start the run-time instrumentation. on error, \-1 is returned and .ir errno is set to indicate the error. .sh errors .tp .b einval the value specified in .ir command is not a valid command. .tp .b einval the value specified in .ir signum is not a real-time signal number. from linux 4.4 onwards, the .ir signum argument has no effect, so that an invalid signal number will not result in an error. .tp .b enomem allocating memory for the run-time instrumentation control block failed. .tp .b eopnotsupp the run-time instrumentation facility is not available. .sh versions this system call is available since linux 3.7. .sh conforming to this linux-specific system call is available only on the s390 architecture. the run-time instrumentation facility is available beginning with system z ec12. .sh notes the .i asm/runtime_instr.h header file is available .\" commit df2f815a7df7edb5335a3bdeee6a8f9f6f9c35c4 since linux 4.16. .pp starting with linux 4.4, support for signalling was removed, as was the check whether .ir signum is a valid real-time signal. for backwards compatibility with older kernels, it is recommended to pass a valid real-time signal number in .i signum and install a handler for that signal. .sh see also .br syscall (2), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getfsent.3 .so man4/loop.4 .so man3/xdr.3 .so man3/malloc.3 .so man3/rpc.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th fmod 3 2021-03-22 "" "linux programmer's manual" .sh name fmod, fmodf, fmodl \- floating-point remainder function .sh synopsis .nf .b #include .pp .bi "double fmod(double " x ", double " y ); .bi "float fmodf(float " x ", float " y ); .bi "long double fmodl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fmodf (), .br fmodl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions compute the floating-point remainder of dividing .i x by .ir y . the return value is .ir x \- .i n * .ir y , where .i n is the quotient of .i x / .ir y , rounded toward zero to an integer. .sh return value on success, these functions return the value \fix\fp\ \-\ \fin\fp*\fiy\fp, for some integer .ir n , such that the returned value has the same sign as .i x and a magnitude less than the magnitude of .ir y . .pp if .i x or .i y is a nan, a nan is returned. .pp if .i x is an infinity, a domain error occurs, and a nan is returned. .pp if .i y is zero, a domain error occurs, and a nan is returned. .pp if .i x is +0 (\-0), and .i y is not zero, +0 (\-0) is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is an infinity .i errno is set to .br edom (but see bugs). an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp domain error: \fiy\fp is zero .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .\" posix.1 documents an optional underflow error, but afaict it doesn't .\" (can't?) occur -- mtk, jul 2008 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fmod (), .br fmodf (), .br fmodl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh bugs before version 2.10, the glibc implementation did not set .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6784 .i errno to .b edom when a domain error occurred for an infinite .ir x . .sh see also .br remainder (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/carg.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cpow 3 2021-03-22 "" "linux programmer's manual" .sh name cpow, cpowf, cpowl \- complex power function .sh synopsis .nf .b #include .pp .bi "double complex cpow(double complex " x ", double complex " z ); .bi "float complex cpowf(float complex " x ", float complex " z ); .bi "long double complex cpowl(long double complex " x , .bi " long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate .i x raised to the power .ir z (with a branch cut for .i x along the negative real axis.) .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cpow (), .br cpowf (), .br cpowl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br pow (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .\" copyright (c) 2002, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 31 jan 2002, michael kerrisk .\" added description of mmap2 .\" modified, 2004-11-25, mtk -- removed stray #endif in prototype .\" .th mmap2 2 2021-03-22 "linux" "linux programmer's manual" .sh name mmap2 \- map files or devices into memory .sh synopsis .nf .br "#include " " /* definition of " map_* " and " prot_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .br "#include .pp .bi "void *syscall(sys_mmap2, unsigned long " addr ", unsigned long " length , .bi " unsigned long " prot ", unsigned long " flags , .bi " unsigned long " fd ", unsigned long " pgoffset ); .fi .sh description this is probably not the system call that you are interested in; instead, see .br mmap (2), which describes the glibc wrapper function that invokes this system call. .pp the .br mmap2 () system call provides the same interface as .br mmap (2), except that the final argument specifies the offset into the file in 4096-byte units (instead of bytes, as is done by .br mmap (2)). this enables applications that use a 32-bit .i off_t to map large files (up to 2^44 bytes). .sh return value on success, .br mmap2 () returns a pointer to the mapped area. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault problem with getting the data from user space. .tp .b einval (various platforms where the page size is not 4096 bytes.) .i "offset\ *\ 4096" is not a multiple of the system page size. .pp .br mmap2 () can also return any of the errors described in .br mmap (2). .sh versions .br mmap2 () is available since linux 2.3.31. .sh conforming to this system call is linux-specific. .sh notes on architectures where this system call is present, the glibc .br mmap () wrapper function invokes this system call rather than the .br mmap (2) system call. .pp this system call does not exist on x86-64. .pp on ia64, the unit for .i offset is actually the system page size, rather than 4096 bytes. .\" ia64 can have page sizes ranging from 4 kb to 64 kb. .\" on cris, it looks like the unit might also be the page size, .\" which is 8192 bytes. -- mtk, june 2007 .sh see also .br getpagesize (2), .br mmap (2), .br mremap (2), .br msync (2), .br shm_open (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xdr.3 .so man3/tailq.3 .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" .\" %%%license_start(bsd_oneline_cdrom) .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" %%%license_end .\" .\" @(#)getrpcport.3r 2.2 88/08/02 4.0 rpcsrc; from 1.12 88/02/26 smi .th getrpcport 3 2021-03-22 "" "linux programmer's manual" .sh name getrpcport \- get rpc port number .sh synopsis .nf .b "#include " .pp .bi "int getrpcport(const char *" host ", unsigned long " prognum , .bi " unsigned long " versnum ", unsigned int " proto ); .fi .sh description .br getrpcport () returns the port number for version .i versnum of the rpc program .i prognum running on .i host and using protocol .ir proto . it returns 0 if it cannot contact the portmapper, or if .i prognum is not registered. if .i prognum is registered but not with version .ir versnum , it will still return a port number (for some version of the program) indicating that the program is indeed registered. the version mismatch will be detected upon the first call to the service. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getrpcport () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to not in posix.1. present on the bsds, solaris, and many other systems. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rcmd.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th asinh 3 2021-03-22 "gnu" "linux programmer's manual" .sh name asinh, asinhf, asinhl \- inverse hyperbolic sine function .sh synopsis .nf .b #include .pp .bi "double asinh(double " x ); .bi "float asinhf(float " x ); .bi "long double asinhl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br asinh (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br asinhf (), .br asinhl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions calculate the inverse hyperbolic sine of .ir x ; that is the value whose hyperbolic sine is .ir x . .sh return value on success, these functions return the inverse hyperbolic sine of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is positive infinity (negative infinity), positive infinity (negative infinity) is returned. .\" .\" posix.1-2001 documents an optional range error for subnormal x; .\" glibc 2.8 does not do this. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br asinh (), .br asinhf (), .br asinhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh see also .br acosh (3), .br atanh (3), .br casinh (3), .br cosh (3), .br sinh (3), .br tanh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .\" this man page is copyright (c) 1998 by andi kleen. .\" .\" %%%license_start(gpl_noversion_oneline) .\" subject to the gpl. .\" %%%license_end .\" .\" based on the original comments from alexey kuznetsov .\" modified 2005-12-27 by hasso tepper .\" $id: netlink.7,v 1.8 2000/06/22 13:23:00 ak exp $ .th netlink 7 2021-03-22 "linux" "linux programmer's manual" .sh name netlink \- communication between kernel and user space (af_netlink) .sh synopsis .nf .b #include .b #include .b #include .pp .bi "netlink_socket = socket(af_netlink, " socket_type ", " netlink_family ); .fi .sh description netlink is used to transfer information between the kernel and user-space processes. it consists of a standard sockets-based interface for user space processes and an internal kernel api for kernel modules. the internal kernel interface is not documented in this manual page. there is also an obsolete netlink interface via netlink character devices; this interface is not documented here and is provided only for backward compatibility. .pp netlink is a datagram-oriented service. both .b sock_raw and .b sock_dgram are valid values for .ir socket_type . however, the netlink protocol does not distinguish between datagram and raw sockets. .pp .i netlink_family selects the kernel module or netlink group to communicate with. the currently assigned netlink families are: .tp .br netlink_route receives routing and link updates and may be used to modify the routing tables (both ipv4 and ipv6), ip addresses, link parameters, neighbor setups, queueing disciplines, traffic classes, and packet classifiers (see .br rtnetlink (7)). .tp .br netlink_w1 " (linux 2.6.13 to 2.16.17)" messages from 1-wire subsystem. .tp .br netlink_usersock reserved for user-mode socket protocols. .tp .br netlink_firewall " (up to and including linux 3.4)" .\" removed by commit d16cf20e2f2f13411eece7f7fb72c17d141c4a84 transport ipv4 packets from netfilter to user space. used by .i ip_queue kernel module. after a long period of being declared obsolete (in favor of the more advanced .i nfnetlink_queue feature), .br netlink_firewall was removed in linux 3.5. .tp .br netlink_sock_diag " (since linux 3.3)" .\" commit 7f1fb60c4fc9fb29fbb406ac8c4cfb4e59e168d6 query information about sockets of various protocol families from the kernel (see .br sock_diag (7)). .tp .br netlink_inet_diag " (since linux 2.6.14)" an obsolete synonym for .br netlink_sock_diag . .tp .br netlink_nflog " (up to and including linux 3.16)" netfilter/iptables ulog. .tp .br netlink_xfrm .\" fixme more details on netlink_xfrm needed. ipsec. .tp .br netlink_selinux " (since linux 2.6.4)" selinux event notifications. .tp .br netlink_iscsi " (since linux 2.6.15)" .\" fixme more details on netlink_iscsi needed. open-iscsi. .tp .br netlink_audit " (since linux 2.6.6)" .\" fixme more details on netlink_audit needed. auditing. .tp .br netlink_fib_lookup " (since linux 2.6.13)" .\" fixme more details on netlink_fib_lookup needed. access to fib lookup from user space. .tp .br netlink_connector " (since linux 2.6.14)" kernel connector. see .i documentation/driver\-api/connector.rst (or .ir /documentation/connector/connector.* .\" commit baa293e9544bea71361950d071579f0e4d5713ed in kernel 5.2 and earlier) in the linux kernel source tree for further information. .tp .br netlink_netfilter " (since linux 2.6.14)" .\" fixme more details on netlink_netfilter needed. netfilter subsystem. .tp .br netlink_scsitransport " (since linux 2.6.19)" .\" commit 84314fd4740ad73550c76dee4a9578979d84af48 .\" fixme more details on netlink_scsitransport needed. scsi transports. .tp .br netlink_rdma " (since linux 3.0)" .\" commit b2cbae2c248776d81cc265ff7d48405b6a4cc463 .\" fixme more details on netlink_rdma needed. infiniband rdma. .tp .br netlink_ip6_fw " (up to and including linux 3.4)" transport ipv6 packets from netfilter to user space. used by .i ip6_queue kernel module. .tp .b netlink_dnrtmsg decnet routing messages. .tp .br netlink_kobject_uevent " (since linux 2.6.10)" .\" fixme more details on netlink_kobject_uevent needed. kernel messages to user space. .tp .br netlink_generic " (since linux 2.6.15)" generic netlink family for simplified netlink usage. .tp .br netlink_crypto " (since linux 3.2)" .\" commit a38f7907b926e4c6c7d389ad96cc38cec2e5a9e9 .\" author: steffen klassert netlink interface to request information about ciphers registered with the kernel crypto api as well as allow configuration of the kernel crypto api. .pp netlink messages consist of a byte stream with one or multiple .i nlmsghdr headers and associated payload. the byte stream should be accessed only with the standard .b nlmsg_* macros. see .br netlink (3) for further information. .pp in multipart messages (multiple .i nlmsghdr headers with associated payload in one byte stream) the first and all following headers have the .b nlm_f_multi flag set, except for the last header which has the type .br nlmsg_done . .pp after each .i nlmsghdr the payload follows. .pp .in +4n .ex struct nlmsghdr { __u32 nlmsg_len; /* length of message including header */ __u16 nlmsg_type; /* type of message content */ __u16 nlmsg_flags; /* additional flags */ __u32 nlmsg_seq; /* sequence number */ __u32 nlmsg_pid; /* sender port id */ }; .ee .in .pp .i nlmsg_type can be one of the standard message types: .b nlmsg_noop message is to be ignored, .b nlmsg_error message signals an error and the payload contains an .i nlmsgerr structure, .b nlmsg_done message terminates a multipart message. error messages get the original request appened, unless the user requests to cap the error message, and get extra error data if requested. .pp .in +4n .ex struct nlmsgerr { int error; /* negative errno or 0 for acknowledgements */ struct nlmsghdr msg; /* message header that caused the error */ /* * followed by the message contents unless netlink_cap_ack was set * or the ack indicates success (error == 0). * for example generic netlink message with attributes. * message length is aligned with nlmsg_align() */ /* * followed by tlvs defined in enum nlmsgerr_attrs * if netlink_ext_ack was set */ }; .ee .in .pp a netlink family usually specifies more message types, see the appropriate manual pages for that, for example, .br rtnetlink (7) for .br netlink_route . .nh .ad l .ts tab(:); l s lb lx. standard flag bits in \finlmsg_flags\fp _ nlm_f_request:t{ must be set on all request messages. t} nlm_f_multi:t{ the message is part of a multipart message terminated by .br nlmsg_done . t} nlm_f_ack:t{ request for an acknowledgement on success. t} nlm_f_echo:t{ echo this request. t} .te .ad .hy .\" no right adjustment for text blocks in tables .nh .ad l .ts tab(:); l s lb lx. additional flag bits for get requests _ nlm_f_root:t{ return the complete table instead of a single entry. t} nlm_f_match:t{ return all entries matching criteria passed in message content. not implemented yet. t} nlm_f_atomic:t{ return an atomic snapshot of the table. t} nlm_f_dump:t{ convenience macro; equivalent to (nlm_f_root|nlm_f_match). t} .te .ad .hy .\" fixme nlm_f_atomic is not used anymore? .pp note that .b nlm_f_atomic requires the .b cap_net_admin capability or an effective uid of 0. .nh .ad l .ts tab(:); l s lb lx. additional flag bits for new requests _ nlm_f_replace:t{ replace existing matching object. t} nlm_f_excl:t{ don't replace if the object already exists. t} nlm_f_create:t{ create object if it doesn't already exist. t} nlm_f_append:t{ add to the end of the object list. t} .te .ad .hy .pp .i nlmsg_seq and .i nlmsg_pid are used to track messages. .i nlmsg_pid shows the origin of the message. note that there isn't a 1:1 relationship between .i nlmsg_pid and the pid of the process if the message originated from a netlink socket. see the .b address formats section for further information. .pp both .i nlmsg_seq and .i nlmsg_pid .\" fixme explain more about nlmsg_seq and nlmsg_pid. are opaque to netlink core. .pp netlink is not a reliable protocol. it tries its best to deliver a message to its destination(s), but may drop messages when an out-of-memory condition or other error occurs. for reliable transfer the sender can request an acknowledgement from the receiver by setting the .b nlm_f_ack flag. an acknowledgement is an .b nlmsg_error packet with the error field set to 0. the application must generate acknowledgements for received messages itself. the kernel tries to send an .b nlmsg_error message for every failed packet. a user process should follow this convention too. .pp however, reliable transmissions from kernel to user are impossible in any case. the kernel can't send a netlink message if the socket buffer is full: the message will be dropped and the kernel and the user-space process will no longer have the same view of kernel state. it is up to the application to detect when this happens (via the .b enobufs error returned by .br recvmsg (2)) and resynchronize. .ss address formats the .i sockaddr_nl structure describes a netlink client in user space or in the kernel. a .i sockaddr_nl can be either unicast (only sent to one peer) or sent to netlink multicast groups .ri ( nl_groups not equal 0). .pp .in +4n .ex struct sockaddr_nl { sa_family_t nl_family; /* af_netlink */ unsigned short nl_pad; /* zero */ pid_t nl_pid; /* port id */ __u32 nl_groups; /* multicast groups mask */ }; .ee .in .pp .i nl_pid is the unicast address of netlink socket. it's always 0 if the destination is in the kernel. for a user-space process, .i nl_pid is usually the pid of the process owning the destination socket. however, .i nl_pid identifies a netlink socket, not a process. if a process owns several netlink sockets, then .i nl_pid can be equal to the process id only for at most one socket. there are two ways to assign .i nl_pid to a netlink socket. if the application sets .i nl_pid before calling .br bind (2), then it is up to the application to make sure that .i nl_pid is unique. if the application sets it to 0, the kernel takes care of assigning it. the kernel assigns the process id to the first netlink socket the process opens and assigns a unique .i nl_pid to every netlink socket that the process subsequently creates. .pp .i nl_groups is a bit mask with every bit representing a netlink group number. each netlink family has a set of 32 multicast groups. when .br bind (2) is called on the socket, the .i nl_groups field in the .i sockaddr_nl should be set to a bit mask of the groups which it wishes to listen to. the default value for this field is zero which means that no multicasts will be received. a socket may multicast messages to any of the multicast groups by setting .i nl_groups to a bit mask of the groups it wishes to send to when it calls .br sendmsg (2) or does a .br connect (2). only processes with an effective uid of 0 or the .b cap_net_admin capability may send or listen to a netlink multicast group. since linux 2.6.13, .\" commit d629b836d151d43332492651dd841d32e57ebe3b messages can't be broadcast to multiple groups. any replies to a message received for a multicast group should be sent back to the sending pid and the multicast group. some linux kernel subsystems may additionally allow other users to send and/or receive messages. as at linux 3.0, the .br netlink_kobject_uevent , .br netlink_generic , .br netlink_route , and .br netlink_selinux groups allow other users to receive messages. no groups allow other users to send messages. .ss socket options to set or get a netlink socket option, call .br getsockopt (2) to read or .br setsockopt (2) to write the option with the option level argument set to .br sol_netlink . unless otherwise noted, .i optval is a pointer to an .ir int . .tp .br netlink_pktinfo " (since linux 2.6.14)" .\" commit 9a4595bc7e67962f13232ee55a64e063062c3a99 .\" author: patrick mchardy enable .b nl_pktinfo control messages for received packets to get the extended destination group number. .tp .br netlink_add_membership ,\ netlink_drop_membership " (since linux 2.6.14)" .\" commit 9a4595bc7e67962f13232ee55a64e063062c3a99 .\" author: patrick mchardy join/leave a group specified by .ir optval . .tp .br netlink_list_memberships " (since linux 4.2)" .\" commit b42be38b2778eda2237fc759e55e3b698b05b315 .\" author: david herrmann retrieve all groups a socket is a member of. .i optval is a pointer to .b __u32 and .i optlen is the size of the array. the array is filled with the full membership set of the socket, and the required array size is returned in .ir optlen . .tp .br netlink_broadcast_error " (since linux 2.6.30)" .\" commit be0c22a46cfb79ab2342bb28fde99afa94ef868e .\" author: pablo neira ayuso when not set, .b netlink_broadcast() only reports .b esrch errors and silently ignore .b enobufs errors. .tp .br netlink_no_enobufs " (since linux 2.6.30)" .\" commit 38938bfe3489394e2eed5e40c9bb8f66a2ce1405 .\" author: pablo neira ayuso this flag can be used by unicast and broadcast listeners to avoid receiving .b enobufs errors. .tp .br netlink_listen_all_nsid " (since linux 4.2)" .\" commit 59324cf35aba5336b611074028777838a963d03b .\" author: nicolas dichtel when set, this socket will receive netlink notifications from all network namespaces that have an .i nsid assigned into the network namespace where the socket has been opened. the .i nsid is sent to user space via an ancillary data. .tp .br netlink_cap_ack " (since linux 4.3)" .\" commit 0a6a3a23ea6efde079a5b77688541a98bf202721 .\" author: christophe ricard the kernel may fail to allocate the necessary room for the acknowledgement message back to user space. this option trims off the payload of the original netlink message. the netlink message header is still included, so the user can guess from the sequence number which message triggered the acknowledgement. .sh versions the socket interface to netlink first appeared linux 2.2. .pp linux 2.0 supported a more primitive device-based netlink interface (which is still available as a compatibility option). this obsolete interface is not described here. .sh notes it is often better to use netlink via .i libnetlink or .i libnl than via the low-level kernel interface. .sh bugs this manual page is not complete. .sh examples the following example creates a .b netlink_route netlink socket which will listen to the .b rtmgrp_link (network interface create/delete/up/down events) and .b rtmgrp_ipv4_ifaddr (ipv4 addresses add/delete events) multicast groups. .pp .in +4n .ex struct sockaddr_nl sa; memset(&sa, 0, sizeof(sa)); sa.nl_family = af_netlink; sa.nl_groups = rtmgrp_link | rtmgrp_ipv4_ifaddr; fd = socket(af_netlink, sock_raw, netlink_route); bind(fd, (struct sockaddr *) &sa, sizeof(sa)); .ee .in .pp the next example demonstrates how to send a netlink message to the kernel (pid 0). note that the application must take care of message sequence numbers in order to reliably track acknowledgements. .pp .in +4n .ex struct nlmsghdr *nh; /* the nlmsghdr with payload to send */ struct sockaddr_nl sa; struct iovec iov = { nh, nh\->nlmsg_len }; struct msghdr msg; msg = { &sa, sizeof(sa), &iov, 1, null, 0, 0 }; memset(&sa, 0, sizeof(sa)); sa.nl_family = af_netlink; nh\->nlmsg_pid = 0; nh\->nlmsg_seq = ++sequence_number; /* request an ack from kernel by setting nlm_f_ack */ nh\->nlmsg_flags |= nlm_f_ack; sendmsg(fd, &msg, 0); .ee .in .pp and the last example is about reading netlink message. .pp .in +4n .ex int len; /* 8192 to avoid message truncation on platforms with page size > 4096 */ struct nlmsghdr buf[8192/sizeof(struct nlmsghdr)]; struct iovec iov = { buf, sizeof(buf) }; struct sockaddr_nl sa; struct msghdr msg; struct nlmsghdr *nh; msg = { &sa, sizeof(sa), &iov, 1, null, 0, 0 }; len = recvmsg(fd, &msg, 0); for (nh = (struct nlmsghdr *) buf; nlmsg_ok (nh, len); nh = nlmsg_next (nh, len)) { /* the end of multipart message */ if (nh\->nlmsg_type == nlmsg_done) return; if (nh\->nlmsg_type == nlmsg_error) /* do some error handling */ ... /* continue with parsing payload */ ... } .ee .in .sh see also .br cmsg (3), .br netlink (3), .br capabilities (7), .br rtnetlink (7), .br sock_diag (7) .pp .ur ftp://ftp.inr.ac.ru\:/ip\-routing\:/iproute2* information about libnetlink .ue .pp .ur http://www.infradead.org\:/\(titgr\:/libnl/ information about libnl .ue .pp rfc 3549 "linux netlink as an ip services protocol" .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sigset 3 2021-03-22 "linux" "linux programmer's manual" .sh name sigset, sighold, sigrelse, sigignore \- system v signal api .sh synopsis .nf .b #include .pp .b typedef void (*sighandler_t)(int); .pp .bi "sighandler_t sigset(int " sig ", sighandler_t " disp ); .pp .bi "int sighold(int " sig ); .bi "int sigrelse(int " sig ); .bi "int sigignore(int " sig ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigset (), .br sighold (), .br sigrelse (), .br sigignore (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description these functions are provided in glibc as a compatibility interface for programs that make use of the historical system v signal api. this api is obsolete: new applications should use the posix signal api .rb ( sigaction (2), .br sigprocmask (2), etc.) .pp the .br sigset () function modifies the disposition of the signal .ir sig . the .i disp argument can be the address of a signal handler function, or one of the following constants: .tp .b sig_dfl reset the disposition of .i sig to the default. .tp .b sig_ign ignore .ir sig . .tp .b sig_hold add .i sig to the process's signal mask, but leave the disposition of .i sig unchanged. .pp if .i disp specifies the address of a signal handler, then .i sig is added to the process's signal mask during execution of the handler. .pp if .i disp was specified as a value other than .br sig_hold , then .i sig is removed from the process's signal mask. .pp the dispositions for .b sigkill and .b sigstop cannot be changed. .pp the .br sighold () function adds .i sig to the calling process's signal mask. .pp the .br sigrelse () function removes .i sig from the calling process's signal mask. .pp the .br sigignore () function sets the disposition of .i sig to .br sig_ign . .sh return value on success, .br sigset () returns .b sig_hold if .i sig was blocked before the call, or the signal's previous disposition if it was not blocked before the call. on error, .br sigset () returns \-1, with .i errno set to indicate the error. (but see bugs below.) .pp the .br sighold (), .br sigrelse (), and .br sigignore () functions return 0 on success; on error, these functions return \-1 and set .i errno to indicate the error. .sh errors for .br sigset () see the errors under .br sigaction (2) and .br sigprocmask (2). .pp for .br sighold () and .br sigrelse () see the errors under .br sigprocmask (2). .pp for .br sigignore (), see the errors under .br sigaction (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigset (), .br sighold (), .br sigrelse (), .br sigignore () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4, posix.1-2001, posix.1-2008. these functions are obsolete: do not use them in new programs. posix.1-2008 marks .br sighold (), .br sigignore (), .br sigpause (3), .br sigrelse (), and .br sigset () as obsolete, recommending the use of .br sigaction (2), .br sigprocmask (2), .br pthread_sigmask (3), and .br sigsuspend (2) instead. .sh notes these functions appeared in glibc version 2.1. .pp the .i sighandler_t type is a gnu extension; it is used on this page only to make the .br sigset () prototype more easily readable. .pp the .br sigset () function provides reliable signal handling semantics (as when calling .br sigaction (2) with .i sa_mask equal to 0). .pp on system v, the .br signal () function provides unreliable semantics (as when calling .br sigaction (2) with .i sa_mask equal to .ir "sa_resethand | sa_nodefer" ). on bsd, .br signal () provides reliable semantics. posix.1-2001 leaves these aspects of .br signal () unspecified. see .br signal (2) for further details. .pp in order to wait for a signal, bsd and system v both provided a function named .br sigpause (3), but this function has a different argument on the two systems. see .br sigpause (3) for details. .sh bugs in versions of glibc before 2.2, .br sigset () did not unblock .i sig if .i disp was specified as a value other than .br sig_hold . .pp in versions of glibc before 2.5, .br sigset () does not correctly return the previous disposition of the signal in two cases. first, if .i disp is specified as .br sig_hold , then a successful .br sigset () always returns .br sig_hold . instead, it should return the previous disposition of the signal (unless the signal was blocked, in which case .b sig_hold should be returned). second, if the signal is currently blocked, then the return value of a successful .br sigset () should be .br sig_hold . instead, the previous disposition of the signal is returned. these problems have been fixed since glibc 2.5. .\" see http://sourceware.org/bugzilla/show_bug.cgi?id=1951 .sh see also .br kill (2), .br pause (2), .br sigaction (2), .br signal (2), .br sigprocmask (2), .br raise (3), .br sigpause (3), .br sigvec (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th conj 3 2021-03-22 "" "linux programmer's manual" .sh name conj, conjf, conjl \- calculate the complex conjugate .sh synopsis .nf .b #include .pp .bi "double complex conj(double complex " z ); .bi "float complex conjf(float complex " z ); .bi "long double complex conjl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions return the complex conjugate value of .ir z . that is the value obtained by changing the sign of the imaginary part. .pp one has: .pp .nf cabs(z) = csqrt(z * conj(z)) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br conj (), .br conjf (), .br conjl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br csqrt (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/qecvt.3 .so man3/resolver.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th iconv_close 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iconv_close \- deallocate descriptor for character set conversion .sh synopsis .nf .b #include .pp .bi "int iconv_close(iconv_t " cd ); .fi .sh description the .br iconv_close () function deallocates a conversion descriptor .i cd previously allocated using .br iconv_open (3). .sh return value on success, .br iconv_close () returns 0; otherwise, it returns \-1 and sets .i errno to indicate the error. .sh versions this function is available in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iconv_close () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2. .sh see also .br iconv (3), .br iconv_open (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/error.3 .so man3/pthread_attr_setaffinity_np.3 .\" copyright (c) 2012 by michael kerrisk .\" with some material from a draft by .\" stephan mueller .\" in turn based on andi kleen's recvmmsg.2 page. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sendmmsg 2 2020-06-09 "linux" "linux programmer's manual" .sh name sendmmsg \- send multiple messages on a socket .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .bi "#include " .pp .bi "int sendmmsg(int " sockfd ", struct mmsghdr *" msgvec \ ", unsigned int " vlen "," .bi " int " flags ");" .fi .sh description the .br sendmmsg () system call is an extension of .br sendmsg (2) that allows the caller to transmit multiple messages on a socket using a single system call. (this has performance benefits for some applications.) .\" see commit 228e548e602061b08ee8e8966f567c12aa079682 .pp the .i sockfd argument is the file descriptor of the socket on which data is to be transmitted. .pp the .i msgvec argument is a pointer to an array of .i mmsghdr structures. the size of this array is specified in .ir vlen . .pp the .i mmsghdr structure is defined in .i as: .pp .in +4n .ex struct mmsghdr { struct msghdr msg_hdr; /* message header */ unsigned int msg_len; /* number of bytes transmitted */ }; .ee .in .pp the .i msg_hdr field is a .i msghdr structure, as described in .br sendmsg (2). the .i msg_len field is used to return the number of bytes sent from the message in .ir msg_hdr (i.e., the same as the return value from a single .br sendmsg (2) call). .pp the .i flags argument contains flags ored together. the flags are the same as for .br sendmsg (2). .pp a blocking .br sendmmsg () call blocks until .i vlen messages have been sent. a nonblocking call sends as many messages as possible (up to the limit specified by .ir vlen ) and returns immediately. .pp on return from .br sendmmsg (), the .i msg_len fields of successive elements of .ir msgvec are updated to contain the number of bytes transmitted from the corresponding .ir msg_hdr . the return value of the call indicates the number of elements of .i msgvec that have been updated. .sh return value on success, .br sendmmsg () returns the number of messages sent from .ir msgvec ; if this is less than .ir vlen , the caller can retry with a further .br sendmmsg () call to send the remaining messages. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors errors are as for .br sendmsg (2). an error is returned only if no datagrams could be sent. see also bugs. .\" commit 728ffb86f10873aaf4abd26dde691ee40ae731fe .\" ... only return an error if no datagrams could be sent. .\" if less than the requested number of messages were sent, the application .\" must retry starting at the first failed one and if the problem is .\" persistent the error will be returned. .\" .\" this matches the behavior of other syscalls like read/write - it .\" is not an error if less than the requested number of elements are sent. .sh versions the .br sendmmsg () system call was added in linux 3.0. support in glibc was added in version 2.14. .sh conforming to .br sendmmsg () is linux-specific. .sh notes the value specified in .i vlen is capped to .b uio_maxiov (1024). .\" commit 98382f419f32d2c12d021943b87dea555677144b .\" net: cap number of elements for sendmmsg .\" .\" to limit the amount of time we can spend in sendmmsg, cap the .\" number of elements to uio_maxiov (currently 1024). .\" .\" for error handling an application using sendmmsg needs to retry at .\" the first unsent message, so capping is simpler and requires less .\" application logic than returning einval. .sh bugs if an error occurs after at least one message has been sent, the call succeeds, and returns the number of messages sent. the error code is lost. the caller can retry the transmission, starting at the first failed message, but there is no guarantee that, if an error is returned, it will be the same as the one that was lost on the previous call. .sh examples the example below uses .br sendmmsg () to send .i onetwo and .i three in two distinct udp datagrams using one system call. the contents of the first datagram originates from a pair of buffers. .pp .ex #define _gnu_source #include #include #include #include #include #include int main(void) { int sockfd; struct sockaddr_in addr; struct mmsghdr msg[2]; struct iovec msg1[2], msg2; int retval; sockfd = socket(af_inet, sock_dgram, 0); if (sockfd == \-1) { perror("socket()"); exit(exit_failure); } addr.sin_family = af_inet; addr.sin_addr.s_addr = htonl(inaddr_loopback); addr.sin_port = htons(1234); if (connect(sockfd, (struct sockaddr *) &addr, sizeof(addr)) == \-1) { perror("connect()"); exit(exit_failure); } memset(msg1, 0, sizeof(msg1)); msg1[0].iov_base = "one"; msg1[0].iov_len = 3; msg1[1].iov_base = "two"; msg1[1].iov_len = 3; memset(&msg2, 0, sizeof(msg2)); msg2.iov_base = "three"; msg2.iov_len = 5; memset(msg, 0, sizeof(msg)); msg[0].msg_hdr.msg_iov = msg1; msg[0].msg_hdr.msg_iovlen = 2; msg[1].msg_hdr.msg_iov = &msg2; msg[1].msg_hdr.msg_iovlen = 1; retval = sendmmsg(sockfd, msg, 2, 0); if (retval == \-1) perror("sendmmsg()"); else printf("%d messages sent\en", retval); exit(0); } .ee .sh see also .br recvmmsg (2), .br sendmsg (2), .br socket (2), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1987, 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)hostname.7 8.2 (berkeley) 12/30/93 .\" $freebsd: src/share/man/man7/hostname.7,v 1.7 2004/07/03 18:29:23 ru exp $ .\" .\" 2008-06-11, mtk, taken from freebsd 6.2 and modified for linux. .\" .th hostname 7 2019-05-09 "linux" "linux programmer's manual" .sh name hostname \- hostname resolution description .sh description hostnames are domains, where a domain is a hierarchical, dot-separated list of subdomains; for example, the machine "monet", in the "example" subdomain of the "com" domain would be represented as "monet.example.com". .pp each element of the hostname must be from 1 to 63 characters long and the entire hostname, including the dots, can be at most 253 characters long. valid characters for hostnames are .br ascii (7) letters from .i a to .ir z , the digits from .i 0 to .ir 9 , and the hyphen (\-). a hostname may not start with a hyphen. .pp hostnames are often used with network client and server programs, which must generally translate the name to an address for use. (this task is generally performed by either .br getaddrinfo (3) or the obsolete .br gethostbyname (3).) .pp hostnames are resolved by the nss framework in glibc according to the .b hosts configuration in .br nsswitch.conf . the dns-based name resolver (in the .b dns nss service module) resolves them in the following fashion. .pp if the name consists of a single component, that is, contains no dot, and if the environment variable .b hostaliases is set to the name of a file, that file is searched for any string matching the input hostname. the file should consist of lines made up of two white-space separated strings, the first of which is the hostname alias, and the second of which is the complete hostname to be substituted for that alias. if a case-insensitive match is found between the hostname to be resolved and the first field of a line in the file, the substituted name is looked up with no further processing. .pp if the input name ends with a trailing dot, the trailing dot is removed, and the remaining name is looked up with no further processing. .pp if the input name does not end with a trailing dot, it is looked up by searching through a list of domains until a match is found. the default search list includes first the local domain, then its parent domains with at least 2 name components (longest first). for example, in the domain cs.example.com, the name lithium.cchem will be checked first as lithium.cchem.cs.example and then as lithium.cchem.example.com. lithium.cchem.com will not be tried, as there is only one component remaining from the local domain. the search path can be changed from the default by a system-wide configuration file (see .br resolver (5)). .sh see also .br getaddrinfo (3), .br gethostbyname (3), .br nsswitch.conf (5), .br resolver (5), .br mailaddr (7), .br named (8) .pp .ur http://www.ietf.org\:/rfc\:/rfc1123.txt ietf rfc\ 1123 .ue .pp .ur http://www.ietf.org\:/rfc\:/rfc1178.txt ietf rfc\ 1178 .ue .\" .sh history .\" hostname appeared in .\" 4.2bsd. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .so man3/setaliasent.3 .\" copyright 2002 urs thuermann (urs@isnogud.escape.de) .\" and copyright 2015 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, write to the free .\" software foundation, inc., 59 temple place, suite 330, boston, ma 02111, .\" usa. .\" %%%license_end .\" .th loop 4 2021-03-22 "linux" "linux programmer's manual" .sh name loop, loop-control \- loop devices .sh synopsis .nf #include .fi .sh description the loop device is a block device that maps its data blocks not to a physical device such as a hard disk or optical disk drive, but to the blocks of a regular file in a filesystem or to another block device. this can be useful for example to provide a block device for a filesystem image stored in a file, so that it can be mounted with the .br mount (8) command. you could do .pp .in +4n .ex $ \fbdd if=/dev/zero of=file.img bs=1mib count=10\fp $ \fbsudo losetup /dev/loop4 file.img\fp $ \fbsudo mkfs \-t ext4 /dev/loop4\fp $ \fbsudo mkdir /myloopdev\fp $ \fbsudo mount /dev/loop4 /myloopdev\fp .ee .in .pp see .br losetup (8) for another example. .pp a transfer function can be specified for each loop device for encryption and decryption purposes. .pp the following .br ioctl (2) operations are provided by the loop block device: .tp .b loop_set_fd associate the loop device with the open file whose file descriptor is passed as the (third) .br ioctl (2) argument. .tp .b loop_clr_fd disassociate the loop device from any file descriptor. .tp .b loop_set_status set the status of the loop device using the (third) .br ioctl (2) argument. this argument is a pointer to a .i loop_info structure, defined in .i as: .ip .in +4n .ex struct loop_info { int lo_number; /* ioctl r/o */ dev_t lo_device; /* ioctl r/o */ unsigned long lo_inode; /* ioctl r/o */ dev_t lo_rdevice; /* ioctl r/o */ int lo_offset; int lo_encrypt_type; int lo_encrypt_key_size; /* ioctl w/o */ int lo_flags; /* ioctl r/w (r/o before linux 2.6.25) */ char lo_name[lo_name_size]; unsigned char lo_encrypt_key[lo_key_size]; /* ioctl w/o */ unsigned long lo_init[2]; char reserved[4]; }; .ee .in .ip the encryption type .ri ( lo_encrypt_type ) should be one of .br lo_crypt_none , .br lo_crypt_xor , .br lo_crypt_des , .br lo_crypt_fish2 , .br lo_crypt_blow , .br lo_crypt_cast128 , .br lo_crypt_idea , .br lo_crypt_dummy , .br lo_crypt_skipjack , or (since linux 2.6.0) .br lo_crypt_cryptoapi . .ip the .i lo_flags field is a bit mask that can include zero or more of the following: .rs .tp .br lo_flags_read_only the loopback device is read-only. .tp .br lo_flags_autoclear " (since linux 2.6.25)" .\" commit 96c5865559cee0f9cbc5173f3c949f6ce3525581 the loopback device will autodestruct on last close. .tp .br lo_flags_partscan " (since linux 3.2)" .\" commit e03c8dd14915fabc101aa495828d58598dc5af98 allow automatic partition scanning. .tp .br lo_flags_direct_io " (since linux 4.10)" .\" commit 2e5ab5f379f96a6207c45be40c357ebb1beb8ef3 use direct i/o mode to access the backing file. .re .ip the only .i lo_flags that can be modified by .br loop_set_status are .br lo_flags_autoclear and .br lo_flags_partscan . .tp .b loop_get_status get the status of the loop device. the (third) .br ioctl (2) argument must be a pointer to a .ir "struct loop_info" . .tp .br loop_change_fd " (since linux 2.6.5)" switch the backing store of the loop device to the new file identified file descriptor specified in the (third) .br ioctl (2) argument, which is an integer. this operation is possible only if the loop device is read-only and the new backing store is the same size and type as the old backing store. .tp .br loop_set_capacity " (since linux 2.6.30)" .\" commit 53d6660836f233df66490707365ab177e5fb2bb4 resize a live loop device. one can change the size of the underlying backing store and then use this operation so that the loop driver learns about the new size. this operation takes no argument. .tp .br loop_set_direct_io " (since linux 4.10)" .\" commit ab1cb278bc7027663adbfb0b81404f8398437e11 set direct i/o mode on the loop device, so that it can be used to open backing file. the (third) .br ioctl (2) argument is an unsigned long value. a nonzero represents direct i/o mode. .tp .br loop_set_block_size " (since linux 4.14)" .\" commit 89e4fdecb51cf5535867026274bc97de9480ade5 set the block size of the loop device. the (third) .br ioctl (2) argument is an unsigned long value. this value must be a power of two in the range [512,pagesize]; otherwise, an .b einval error results. .tp .br loop_configure " (since linux 5.8)" .\" commit 3448914e8cc550ba792d4ccc74471d1ca4293aae setup and configure all loop device parameters in a single step using the (third) .br ioctl (2) argument. this argument is a pointer to a .i loop_config structure, defined in .i as: .ip .in +4n .ex struct loop_config { __u32 fd; __u32 block_size; struct loop_info64 info; __u64 __reserved[8]; }; .ee .in .ip in addition to doing what .br loop_set_status can do, .br loop_configure can also be used to do the following: .rs .ip * 2 set the correct block size immediately by setting .ir loop_config.block_size ; .ip * explicitly request direct i/o mode by setting .br lo_flags_direct_io in .ir loop_config.info.lo_flags ; and .ip * explicitly request read-only mode by setting .br lo_flags_read_only in .ir loop_config.info.lo_flags . .re .pp since linux 2.6, there are two new .br ioctl (2) operations: .tp .br loop_set_status64 ", " loop_get_status64 these are similar to .br loop_set_status " and " loop_get_status described above but use the .i loop_info64 structure, which has some additional fields and a larger range for some other fields: .ip .in +4n .ex struct loop_info64 { uint64_t lo_device; /* ioctl r/o */ uint64_t lo_inode; /* ioctl r/o */ uint64_t lo_rdevice; /* ioctl r/o */ uint64_t lo_offset; uint64_t lo_sizelimit; /* bytes, 0 == max available */ uint32_t lo_number; /* ioctl r/o */ uint32_t lo_encrypt_type; uint32_t lo_encrypt_key_size; /* ioctl w/o */ uint32_t lo_flags; i /* ioctl r/w (r/o before linux 2.6.25) */ uint8_t lo_file_name[lo_name_size]; uint8_t lo_crypt_name[lo_name_size]; uint8_t lo_encrypt_key[lo_key_size]; /* ioctl w/o */ uint64_t lo_init[2]; }; .ee .in .ss /dev/loop-control since linux 3.1, .\" commit 770fe30a46a12b6fb6b63fbe1737654d28e84844 the kernel provides the .i /dev/loop\-control device, which permits an application to dynamically find a free device, and to add and remove loop devices from the system. to perform these operations, one first opens .ir /dev/loop\-control and then employs one of the following .br ioctl (2) operations: .tp .b loop_ctl_get_free allocate or find a free loop device for use. on success, the device number is returned as the result of the call. this operation takes no argument. .tp .b loop_ctl_add add the new loop device whose device number is specified as a long integer in the third .br ioctl (2) argument. on success, the device index is returned as the result of the call. if the device is already allocated, the call fails with the error .br eexist . .tp .b loop_ctl_remove remove the loop device whose device number is specified as a long integer in the third .br ioctl (2) argument. on success, the device number is returned as the result of the call. if the device is in use, the call fails with the error .br ebusy . .sh files .tp .ir /dev/loop* the loop block special device files. .sh examples the program below uses the .i /dev/loop\-control device to find a free loop device, opens the loop device, opens a file to be used as the underlying storage for the device, and then associates the loop device with the backing store. the following shell session demonstrates the use of the program: .pp .in +4n .ex $ \fbdd if=/dev/zero of=file.img bs=1mib count=10\fp 10+0 records in 10+0 records out 10485760 bytes (10 mb) copied, 0.00609385 s, 1.7 gb/s $ \fbsudo ./mnt_loop file.img\fp loopname = /dev/loop5 .ee .in .ss program source \& .ex #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { int loopctlfd, loopfd, backingfile; long devnr; char loopname[4096]; if (argc != 2) { fprintf(stderr, "usage: %s backing\-file\en", argv[0]); exit(exit_failure); } loopctlfd = open("/dev/loop\-control", o_rdwr); if (loopctlfd == \-1) errexit("open: /dev/loop\-control"); devnr = ioctl(loopctlfd, loop_ctl_get_free); if (devnr == \-1) errexit("ioctl\-loop_ctl_get_free"); sprintf(loopname, "/dev/loop%ld", devnr); printf("loopname = %s\en", loopname); loopfd = open(loopname, o_rdwr); if (loopfd == \-1) errexit("open: loopname"); backingfile = open(argv[1], o_rdwr); if (backingfile == \-1) errexit("open: backing\-file"); if (ioctl(loopfd, loop_set_fd, backingfile) == \-1) errexit("ioctl\-loop_set_fd"); exit(exit_success); } .ee .sh see also .br losetup (8), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ntp_gettime.3 .\" copyright (c), 1995, graeme w. wilford. (wilf.) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" wed jun 14 16:10:28 bst 1995 wilf. (g.wilford@@ee.surrey.ac.uk) .\" .th re_comp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name re_comp, re_exec \- bsd regex functions .sh synopsis .nf .b #define _regex_re_comp .b #include .b #include .pp .bi "char *re_comp(const char *" regex ); .bi "int re_exec(const char *" string ); .fi .sh description .br re_comp () is used to compile the null-terminated regular expression pointed to by .ir regex . the compiled pattern occupies a static area, the pattern buffer, which is overwritten by subsequent use of .br re_comp (). if .i regex is null, no operation is performed and the pattern buffer's contents are not altered. .pp .br re_exec () is used to assess whether the null-terminated string pointed to by .i string matches the previously compiled .ir regex . .sh return value .br re_comp () returns null on successful compilation of .i regex otherwise it returns a pointer to an appropriate error message. .pp .br re_exec () returns 1 for a successful match, zero for failure. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br re_comp (), .br re_exec () t} thread safety mt-unsafe .te .hy .ad .sp 1 .sh conforming to 4.3bsd. .sh notes these functions are obsolete; the functions documented in .br regcomp (3) should be used instead. .sh see also .br regcomp (3), .br regex (7), gnu regex manual .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/timeradd.3 .so man3/getopt.3 .so man3/argz_add.3 .so man7/system_data_types.7 .so man3/isalpha.3 .so man3/rpc.3 .\" copyright 1999 roman maurer (roman.maurer@hermes.si) .\" copyright 1993-1995 daniel quinlan (quinlan@yggdrasil.com) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" slightly rearranged, aeb, 950713 .\" updated, dpo, 990531 .th iso_8859-2 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-2 \- iso 8859-2 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-2 encodes the latin characters used in many central and east european languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-2 characters the following table displays the characters in iso 8859-2 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ą latin capital letter a with ogonek 242 162 a2 ˘ breve 243 163 a3 ł latin capital letter l with stroke 244 164 a4 ¤ currency sign 245 165 a5 ľ latin capital letter l with caron 246 166 a6 ś latin capital letter s with acute 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 š latin capital letter s with caron 252 170 aa ş latin capital letter s with cedilla 253 171 ab ť latin capital letter t with caron 254 172 ac ź latin capital letter z with acute 255 173 ad ­ soft hyphen 256 174 ae ž latin capital letter z with caron 257 175 af ż latin capital letter z with dot above 260 176 b0 ° degree sign 261 177 b1 ą latin small letter a with ogonek 262 178 b2 ˛ ogonek 263 179 b3 ł latin small letter l with stroke 264 180 b4 ´ acute accent 265 181 b5 ľ latin small letter l with caron 266 182 b6 ś latin small letter s with acute 267 183 b7 ˇ caron 270 184 b8 ¸ cedilla 271 185 b9 š latin small letter s with caron 272 186 ba ş latin small letter s with cedilla 273 187 bb ť latin small letter t with caron 274 188 bc ź latin small letter z with acute 275 189 bd ˝ double acute accent 276 190 be ž latin small letter z with caron 277 191 bf ż latin small letter z with dot above 300 192 c0 ŕ latin capital letter r with acute 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ă latin capital letter a with breve 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 ĺ latin capital letter l with acute 306 198 c6 ć latin capital letter c with acute 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 č latin capital letter c with caron 311 201 c9 é latin capital letter e with acute 312 202 ca ę latin capital letter e with ogonek 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ě latin capital letter e with caron 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ď latin capital letter d with caron 320 208 d0 đ latin capital letter d with stroke 321 209 d1 ń latin capital letter n with acute 322 210 d2 ň latin capital letter n with caron 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 ő latin capital letter o with double acute 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ř latin capital letter r with caron 331 217 d9 ů latin capital letter u with ring above 332 218 da ú latin capital letter u with acute 333 219 db ű latin capital letter u with double acute 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ý latin capital letter y with acute 336 222 de ţ latin capital letter t with cedilla 337 223 df ß latin small letter sharp s 340 224 e0 ŕ latin small letter r with acute 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ă latin small letter a with breve 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 ĺ latin small letter l with acute 346 230 e6 ć latin small letter c with acute 347 231 e7 ç latin small letter c with cedilla 350 232 e8 č latin small letter c with caron 351 233 e9 é latin small letter e with acute 352 234 ea ę latin small letter e with ogonek 353 235 eb ë latin small letter e with diaeresis 354 236 ec ě latin small letter e with caron 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ď latin small letter d with caron 360 240 f0 đ latin small letter d with stroke 361 241 f1 ń latin small letter n with acute 362 242 f2 ň latin small letter n with caron 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 ő latin small letter o with double acute 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ř latin small letter r with caron 371 249 f9 ů latin small letter u with ring above 372 250 fa ú latin small letter u with acute 373 251 fb ű latin small letter u with double acute 374 252 fc ü latin small letter u with diaeresis 375 253 fd ý latin small letter y with acute 376 254 fe ţ latin small letter t with cedilla 377 255 ff ˙ dot above .te .sh notes iso 8859-2 is also known as latin-2. .sh see also .br ascii (7), .br charsets (7), .br iso_8859\-1 (7), .br iso_8859\-16 (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gamma.3 .so man2/outb.2 .so man3/significand.3 .so man3/remainder.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcsncasecmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsncasecmp \- compare two fixed-size wide-character strings, ignoring case .sh synopsis .nf .b #include .pp .bi "int wcsncasecmp(const wchar_t *" s1 ", const wchar_t *" s2 ", size_t " n ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcsncasecmp (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcsncasecmp () function is the wide-character equivalent of the .br strncasecmp (3) function. it compares the wide-character string pointed to by .i s1 and the wide-character string pointed to by .ir s2 , but at most .i n wide characters from each string, ignoring case differences .rb ( towupper (3), .br towlower (3)). .sh return value the .br wcsncasecmp () function returns zero if the wide-character strings at .i s1 and .ir s2 , truncated to at most length .ir n , are equal except for case distinctions. it returns a positive integer if truncated .i s1 is greater than truncated .ir s2 , ignoring case. it returns a negative integer if truncated .i s1 is smaller than truncated .ir s2 , ignoring case. .sh versions the .br wcsncasecmp () function is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsncasecmp () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function is not specified in posix.1-2001, and is not widely available on other systems. .sh notes the behavior of .br wcsncasecmp () depends on the .b lc_ctype category of the current locale. .sh see also .br strncasecmp (3), .br wcsncmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .\" .\" copyright (c) 2017 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th kernel_lockdown 7 2021-06-20 linux "linux programmer's manual" .sh name kernel_lockdown \- kernel image access prevention feature .sh description the kernel lockdown feature is designed to prevent both direct and indirect access to a running kernel image, attempting to protect against unauthorized modification of the kernel image and to prevent access to security and cryptographic data located in kernel memory, whilst still permitting driver modules to be loaded. .pp if a prohibited or restricted feature is accessed or used, the kernel will emit a message that looks like: .pp .rs lockdown: x: y is restricted, see man kernel_lockdown.7 .re .pp where x indicates the process name and y indicates what is restricted. .pp on an efi-enabled x86 or arm64 machine, lockdown will be automatically enabled if the system boots in efi secure boot mode. .\" .ss coverage when lockdown is in effect, a number of features are disabled or have their use restricted. this includes special device files and kernel services that allow direct access of the kernel image: .pp .rs /dev/mem .br /dev/kmem .br /dev/kcore .br /dev/ioports .br bpf .br kprobes .re .pp and the ability to directly configure and control devices, so as to prevent the use of a device to access or modify a kernel image: .ip \(bu 2 the use of module parameters that directly specify hardware parameters to drivers through the kernel command line or when loading a module. .ip \(bu the use of direct pci bar access. .ip \(bu the use of the ioperm and iopl instructions on x86. .ip \(bu the use of the kd*io console ioctls. .ip \(bu the use of the tiocsserial serial ioctl. .ip \(bu the alteration of msr registers on x86. .ip \(bu the replacement of the pcmcia cis. .ip \(bu the overriding of acpi tables. .ip \(bu the use of acpi error injection. .ip \(bu the specification of the acpi rdsp address. .ip \(bu the use of acpi custom methods. .pp certain facilities are restricted: .ip \(bu 2 only validly signed modules may be loaded (waived if the module file being loaded is vouched for by ima appraisal). .ip \(bu only validly signed binaries may be kexec'd (waived if the binary image file to be executed is vouched for by ima appraisal). .ip \(bu unencrypted hibernation/suspend to swap are disallowed as the kernel image is saved to a medium that can then be accessed. .ip \(bu use of debugfs is not permitted as this allows a whole range of actions including direct configuration of, access to and driving of hardware. .ip \(bu ima requires the addition of the "secure_boot" rules to the policy, whether or not they are specified on the command line, for both the built-in and custom policies in secure boot lockdown mode. .sh versions the kernel lockdown feature was added in linux 5.4. .sh notes the kernel lockdown feature is enabled by config_security_lockdown_lsm. the .i lsm=lsm1,...,lsmn command line parameter controls the sequence of the initialization of linux security modules. it must contain the string .i lockdown to enable the kernel lockdown feature. if the command line parameter is not specified, the initialization falls back to the value of the deprecated .i security= command line parameter and further to the value of config_lsm. .\" commit 000d388ed3bbed745f366ce71b2bb7c2ee70f449 .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1998 andries brouwer .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2003-08-24 fix for / by john kristoff + joey .\" .th glob 7 2020-08-13 "linux" "linux programmer's manual" .sh name glob \- globbing pathnames .sh description long ago, in unix\ v6, there was a program .i /etc/glob that would expand wildcard patterns. soon afterward this became a shell built-in. .pp these days there is also a library routine .br glob (3) that will perform this function for a user program. .pp the rules are as follows (posix.2, 3.13). .ss wildcard matching a string is a wildcard pattern if it contains one of the characters \(aq?\(aq, \(aq*\(aq, or \(aq[\(aq. globbing is the operation that expands a wildcard pattern into the list of pathnames matching the pattern. matching is defined by: .pp a \(aq?\(aq (not between brackets) matches any single character. .pp a \(aq*\(aq (not between brackets) matches any string, including the empty string. .pp .b "character classes" .pp an expression "\fi[...]\fp" where the first character after the leading \(aq[\(aq is not an \(aq!\(aq matches a single character, namely any of the characters enclosed by the brackets. the string enclosed by the brackets cannot be empty; therefore \(aq]\(aq can be allowed between the brackets, provided that it is the first character. (thus, "\fi[][!]\fp" matches the three characters \(aq[\(aq, \(aq]\(aq, and \(aq!\(aq.) .pp .b ranges .pp there is one special convention: two characters separated by \(aq\-\(aq denote a range. (thus, "\fi[a\-fa\-f0\-9]\fp" is equivalent to "\fi[abcdefabcdef0123456789]\fp".) one may include \(aq\-\(aq in its literal meaning by making it the first or last character between the brackets. (thus, "\fi[]\-]\fp" matches just the two characters \(aq]\(aq and \(aq\-\(aq, and "\fi[\-\-0]\fp" matches the three characters \(aq\-\(aq, \(aq.\(aq, \(aq0\(aq, since \(aq/\(aq cannot be matched.) .pp .b complementation .pp an expression "\fi[!...]\fp" matches a single character, namely any character that is not matched by the expression obtained by removing the first \(aq!\(aq from it. (thus, "\fi[!]a\-]\fp" matches any single character except \(aq]\(aq, \(aqa\(aq, and \(aq\-\(aq.) .pp one can remove the special meaning of \(aq?\(aq, \(aq*\(aq, and \(aq[\(aq by preceding them by a backslash, or, in case this is part of a shell command line, enclosing them in quotes. between brackets these characters stand for themselves. thus, "\fi[[?*\e]\fp" matches the four characters \(aq[\(aq, \(aq?\(aq, \(aq*\(aq, and \(aq\e\(aq. .ss pathnames globbing is applied on each of the components of a pathname separately. a \(aq/\(aq in a pathname cannot be matched by a \(aq?\(aq or \(aq*\(aq wildcard, or by a range like "\fi[.\-0]\fp". a range containing an explicit \(aq/\(aq character is syntactically incorrect. (posix requires that syntactically incorrect patterns are left unchanged.) .pp if a filename starts with a \(aq.\(aq, this character must be matched explicitly. (thus, \firm\ *\fp will not remove .profile, and \fitar\ c\ *\fp will not archive all your files; \fitar\ c\ .\fp is better.) .ss empty lists the nice and simple rule given above: "expand a wildcard pattern into the list of matching pathnames" was the original unix definition. it allowed one to have patterns that expand into an empty list, as in .pp .nf xv \-wait 0 *.gif *.jpg .fi .pp where perhaps no *.gif files are present (and this is not an error). however, posix requires that a wildcard pattern is left unchanged when it is syntactically incorrect, or the list of matching pathnames is empty. with .i bash one can force the classical behavior using this command: .pp shopt \-s nullglob .\" in bash v1, by setting allow_null_glob_expansion=true .pp (similar problems occur elsewhere. for example, where old scripts have .pp .nf rm \`find . \-name "*\(ti"\` .fi .pp new scripts require .pp .nf rm \-f nosuchfile \`find . \-name "*\(ti"\` .fi .pp to avoid error messages from .i rm called with an empty argument list.) .sh notes .ss regular expressions note that wildcard patterns are not regular expressions, although they are a bit similar. first of all, they match filenames, rather than text, and secondly, the conventions are not the same: for example, in a regular expression \(aq*\(aq means zero or more copies of the preceding thing. .pp now that regular expressions have bracket expressions where the negation is indicated by a \(aq\(ha\(aq, posix has declared the effect of a wildcard pattern "\fi[\(ha...]\fp" to be undefined. .ss character classes and internationalization of course ranges were originally meant to be ascii ranges, so that "\fi[\ \-%]\fp" stands for "\fi[\ !"#$%]\fp" and "\fi[a\-z]\fp" stands for "any lowercase letter". some unix implementations generalized this so that a range x\-y stands for the set of characters with code between the codes for x and for y. however, this requires the user to know the character coding in use on the local system, and moreover, is not convenient if the collating sequence for the local alphabet differs from the ordering of the character codes. therefore, posix extended the bracket notation greatly, both for wildcard patterns and for regular expressions. in the above we saw three types of items that can occur in a bracket expression: namely (i) the negation, (ii) explicit single characters, and (iii) ranges. posix specifies ranges in an internationally more useful way and adds three more types: .pp (iii) ranges x\-y comprise all characters that fall between x and y (inclusive) in the current collating sequence as defined by the .b lc_collate category in the current locale. .pp (iv) named character classes, like .pp .nf [:alnum:] [:alpha:] [:blank:] [:cntrl:] [:digit:] [:graph:] [:lower:] [:print:] [:punct:] [:space:] [:upper:] [:xdigit:] .fi .pp so that one can say "\fi[[:lower:]]\fp" instead of "\fi[a\-z]\fp", and have things work in denmark, too, where there are three letters past \(aqz\(aq in the alphabet. these character classes are defined by the .b lc_ctype category in the current locale. .pp (v) collating symbols, like "\fi[.ch.]\fp" or "\fi[.a-acute.]\fp", where the string between "\fi[.\fp" and "\fi.]\fp" is a collating element defined for the current locale. note that this may be a multicharacter element. .pp (vi) equivalence class expressions, like "\fi[=a=]\fp", where the string between "\fi[=\fp" and "\fi=]\fp" is any collating element from its equivalence class, as defined for the current locale. for example, "\fi[[=a=]]\fp" might be equivalent to "\fi[a\('a\(\`a\(:a\(^a]\fp", that is, to "\fi[a[.a-acute.][.a-grave.][.a-umlaut.][.a-circumflex.]]\fp". .sh see also .br sh (1), .br fnmatch (3), .br glob (3), .br locale (7), .br regex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:26:16 1993 by rik faith (faith@cs.unc.edu) .\" modified thu apr 11 17:11:33 1996 by andries brouwer (aeb@cwi.nl): .\" corrected type of compar routines, as suggested by .\" miguel barreiro (enano@avalon.yaix.es). added example. .\" modified sun sep 24 20:15:46 2000 by aeb, following petter reinholdtsen. .\" modified 2001-12-26 by aeb, following joey. added versionsort. .\" .\" the pieces on scandirat(3) were copyright and licensed as follows. .\" .\" copyright (c) 2012, mark r. bannister .\" based on text in mkfifoat.3 copyright (c) 2006, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th scandir 3 2021-08-27 "gnu" "linux programmer's manual" .sh name scandir, scandirat, alphasort, versionsort \- scan a directory for matching entries .sh synopsis .nf .b #include .pp .bi "int scandir(const char *restrict " dirp , .bi " struct dirent ***restrict " namelist , .bi " int (*" filter ")(const struct dirent *)," .bi " int (*" compar ")(const struct dirent **," .br " const struct dirent **));" .pp .bi "int alphasort(const struct dirent **" a ", const struct dirent **" b ); .bi "int versionsort(const struct dirent **" a ", const struct dirent **" b ); .pp .br "#include " " /* definition of at_* constants */" .b #include .pp .bi "int scandirat(int " dirfd ", const char *restrict " dirp , .bi " struct dirent ***restrict " namelist , .bi " int (*" filter ")(const struct dirent *)," .bi " int (*" compar ")(const struct dirent **," .bi " const struct dirent **));" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br scandir (), .br alphasort (): .nf /* since glibc 2.10: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br versionsort (): .nf _gnu_source .fi .pp .br scandirat (): .nf _gnu_source .fi .sh description the .br scandir () function scans the directory \fidirp\fp, calling \fifilter\fp() on each directory entry. entries for which \fifilter\fp() returns nonzero are stored in strings allocated via .br malloc (3), sorted using .br qsort (3) with the comparison function \ficompar\fp(), and collected in array \finamelist\fp which is allocated via .br malloc (3). if \fifilter\fp is null, all entries are selected. .pp the .br alphasort () and .br versionsort () functions can be used as the comparison function .ir compar (). the former sorts directory entries using .br strcoll (3), the latter using .br strverscmp (3) on the strings \fi(*a)\->d_name\fp and \fi(*b)\->d_name\fp. .ss scandirat() the .br scandirat () function operates in exactly the same way as .br scandir (), except for the differences described here. .pp if the pathname given in .i dirp is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br scandir () for a relative pathname). .pp if .i dirp is relative and .i dirfd is the special value .br at_fdcwd , then .i dirp is interpreted relative to the current working directory of the calling process (like .br scandir ()). .pp if .i dirp is absolute, then .i dirfd is ignored. .pp see .br openat (2) for an explanation of the need for .br scandirat (). .sh return value the .br scandir () function returns the number of directory entries selected. on error, \-1 is returned, with .i errno set to indicate the error. .pp the .br alphasort () and .br versionsort () functions return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. .sh errors .tp .b ebadf .rb ( scandirat ()) .i dirp is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b enoent the path in \fidirp\fr does not exist. .tp .b enomem insufficient memory to complete the operation. .tp .b enotdir the path in \fidirp\fr is not a directory. .tp .b enotdir .rb ( scandirat ()) .i dirp is a relative pathname and .i dirfd is a file descriptor referring to a file other than a directory. .sh versions .br versionsort () was added to glibc in version 2.1. .pp .br scandirat () was added to glibc in version 2.15. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br scandir (), .br scandirat () t} thread safety mt-safe t{ .br alphasort (), .br versionsort () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to .br alphasort (), .br scandir (): 4.3bsd, posix.1-2008. .pp .br versionsort () and .br scandirat () are gnu extensions. .\" .lp .\" the functions .\" .br scandir () .\" and .\" .br alphasort () .\" are from 4.3bsd, and have been available under linux since libc4. .\" libc4 and libc5 use the more precise prototype .\" .sp .\" .nf .\" int alphasort(const struct dirent ** a, .\" const struct dirent **b); .\" .fi .\" .sp .\" but glibc 2.0 returns to the imprecise bsd prototype. .sh notes since glibc 2.1, .br alphasort () calls .br strcoll (3); earlier it used .br strcmp (3). .pp before glibc 2.10, the two arguments of .br alphasort () and .br versionsort () were typed as .ir "const void\ *" . when .br alphasort () was standardized in posix.1-2008, the argument type was specified as the type-safe .ir "const struct dirent\ **", and glibc 2.10 changed the definition of .br alphasort () (and the nonstandard .br versionsort ()) to match the standard. .sh examples the program below prints a list of the files in the current directory in reverse order. .\" .ss program source \& .ex #define _default_source #include #include #include int main(void) { struct dirent **namelist; int n; n = scandir(".", &namelist, null, alphasort); if (n == \-1) { perror("scandir"); exit(exit_failure); } while (n\-\-) { printf("%s\en", namelist[n]\->d_name); free(namelist[n]); } free(namelist); exit(exit_success); } .ee .sh see also .br closedir (3), .br fnmatch (3), .br opendir (3), .br readdir (3), .br rewinddir (3), .br seekdir (3), .br strcmp (3), .br strcoll (3), .br strverscmp (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th trunc 3 2021-03-22 "" "linux programmer's manual" .sh name trunc, truncf, truncl \- round to integer, toward zero .sh synopsis .nf .b #include .pp .bi "double trunc(double " x ); .bi "float truncf(float " x ); .bi "long double truncl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br trunc (), .br truncf (), .br truncl (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions round .i x to the nearest integer value that is not larger in magnitude than .ir x . .sh return value these functions return the rounded integer value, in floating format. .pp if .i x is integral, infinite, or nan, .i x itself is returned. .sh errors no errors occur. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br trunc (), .br truncf (), .br truncl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes the integral value returned by these functions may be too large to store in an integer type .ri ( int , .ir long , etc.). to avoid an overflow, which will produce undefined results, an application should perform a range check on the returned value before assigning it to an integer type. .sh see also .br ceil (3), .br floor (3), .br lrint (3), .br nearbyint (3), .br rint (3), .br round (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" heavily based on glibc infopages, copyright free software foundation .\" .\" aeb, 2003, polished a little .th mempcpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mempcpy, wmempcpy \- copy memory area .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void *mempcpy(void *restrict " dest ", const void *restrict " src \ ", size_t " n ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "wchar_t *wmempcpy(wchar_t *restrict " dest \ ", const wchar_t *restrict " src , .bi " size_t " n ); .fi .sh description the .br mempcpy () function is nearly identical to the .br memcpy (3) function. it copies .i n bytes from the object beginning at .i src into the object pointed to by .ir dest . but instead of returning the value of .i dest it returns a pointer to the byte following the last written byte. .pp this function is useful in situations where a number of objects shall be copied to consecutive memory positions. .pp the .br wmempcpy () function is identical but takes .i wchar_t type arguments and copies .i n wide characters. .sh return value .i dest + .ir n . .sh versions .br mempcpy () first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mempcpy (), .br wmempcpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a gnu extension. .sh examples .ex void * combine(void *o1, size_t s1, void *o2, size_t s2) { void *result = malloc(s1 + s2); if (result != null) mempcpy(mempcpy(result, o1, s1), o2, s2); return result; } .ee .sh see also .br memccpy (3), .br memcpy (3), .br memmove (3), .br wmemcpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/termios.3 .so man3/backtrace.3 .so man2/fstatat.2 .\" copyright (c) tom bjorkholm & markus kuhn, 1996 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-04-01 tom bjorkholm .\" first version written .\" 1996-04-10 markus kuhn .\" revision .\" .th sched_get_priority_max 2 2021-03-22 "linux" "linux programmer's manual" .sh name sched_get_priority_max, sched_get_priority_min \- get static priority range .sh synopsis .nf .b #include .pp .bi "int sched_get_priority_max(int " policy ); .bi "int sched_get_priority_min(int " policy ); .fi .sh description .br sched_get_priority_max () returns the maximum priority value that can be used with the scheduling algorithm identified by .ir policy . .br sched_get_priority_min () returns the minimum priority value that can be used with the scheduling algorithm identified by .ir policy . supported .i policy values are .br sched_fifo , .br sched_rr , .br sched_other , .br sched_batch , .br sched_idle , and .br sched_deadline . further details about these policies can be found in .br sched (7). .pp processes with numerically higher priority values are scheduled before processes with numerically lower priority values. thus, the value returned by .br sched_get_priority_max () will be greater than the value returned by .br sched_get_priority_min (). .pp linux allows the static priority range 1 to 99 for the .b sched_fifo and .b sched_rr policies, and the priority 0 for the remaining policies. scheduling priority ranges for the various policies are not alterable. .pp the range of scheduling priorities may vary on other posix systems, thus it is a good idea for portable applications to use a virtual priority range and map it to the interval given by .br sched_get_priority_max () and .br sched_get_priority_min () posix.1 requires .\" posix.1-2001, posix.1-2008 (xbd 2.8.4) a spread of at least 32 between the maximum and the minimum values for .b sched_fifo and .br sched_rr . .pp posix systems on which .br sched_get_priority_max () and .br sched_get_priority_min () are available define .b _posix_priority_scheduling in .ir . .sh return value on success, .br sched_get_priority_max () and .br sched_get_priority_min () return the maximum/minimum priority value for the named scheduling policy. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval the argument .i policy does not identify a defined scheduling policy. .sh conforming to posix.1-2001, posix.1-2008. .sh see also .ad l .nh .br sched_getaffinity (2), .br sched_getparam (2), .br sched_getscheduler (2), .br sched_setaffinity (2), .br sched_setparam (2), .br sched_setscheduler (2), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" heavily based on glibc documentation .\" polished, added docs, removed glibc doc bug, 2002-07-20, aeb .\" .th malloc_hook 3 2021-03-22 "gnu" "linux programmer's manual" .sh name __malloc_hook, __malloc_initialize_hook, __memalign_hook, __free_hook, __realloc_hook, __after_morecore_hook \- malloc debugging variables .sh synopsis .nf .b "#include " .pp .bi "void *(*volatile __malloc_hook)(size_t " size ", const void *" caller ); .pp .bi "void *(*volatile __realloc_hook)(void *" ptr ", size_t " size \ ", const void *" caller ); .pp .bi "void *(*volatile __memalign_hook)(size_t " alignment ", size_t " size , .bi " const void *" caller ); .pp .bi "void (*volatile __free_hook)(void *" ptr ", const void *" caller ); .pp .b "void (*__malloc_initialize_hook)(void);" .pp .b "void (*volatile __after_morecore_hook)(void);" .fi .sh description the gnu c library lets you modify the behavior of .br malloc (3), .br realloc (3), and .br free (3) by specifying appropriate hook functions. you can use these hooks to help you debug programs that use dynamic memory allocation, for example. .pp the variable .b __malloc_initialize_hook points at a function that is called once when the malloc implementation is initialized. this is a weak variable, so it can be overridden in the application with a definition like the following: .pp .in +4n .ex void (*__malloc_initialize_hook)(void) = my_init_hook; .ee .in .pp now the function .ir my_init_hook () can do the initialization of all hooks. .pp the four functions pointed to by .br __malloc_hook , .br __realloc_hook , .br __memalign_hook , .b __free_hook have a prototype like the functions .br malloc (3), .br realloc (3), .br memalign (3), .br free (3), respectively, except that they have a final argument .i caller that gives the address of the caller of .br malloc (3), etc. .pp the variable .b __after_morecore_hook points at a function that is called each time after .br sbrk (2) was asked for more memory. .sh conforming to these functions are gnu extensions. .sh notes the use of these hook functions is not safe in multithreaded programs, and they are now deprecated. from glibc 2.24 onwards, the .b __malloc_initialize_hook variable has been removed from the api. .\" https://bugzilla.redhat.com/show_bug.cgi?id=450187 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=9957 programmers should instead preempt calls to the relevant functions by defining and exporting functions such as "malloc" and "free". .sh examples here is a short example of how to use these variables. .pp .ex #include #include /* prototypes for our hooks */ static void my_init_hook(void); static void *my_malloc_hook(size_t, const void *); /* variables to save original hooks */ static void *(*old_malloc_hook)(size_t, const void *); /* override initializing hook from the c library */ void (*__malloc_initialize_hook)(void) = my_init_hook; static void my_init_hook(void) { old_malloc_hook = __malloc_hook; __malloc_hook = my_malloc_hook; } static void * my_malloc_hook(size_t size, const void *caller) { void *result; /* restore all old hooks */ __malloc_hook = old_malloc_hook; /* call recursively */ result = malloc(size); /* save underlying hooks */ old_malloc_hook = __malloc_hook; /* printf() might call malloc(), so protect it too */ printf("malloc(%zu) called from %p returns %p\en", size, caller, result); /* restore our own hooks */ __malloc_hook = my_malloc_hook; return result; } .ee .sh see also .br mallinfo (3), .br malloc (3), .br mcheck (3), .br mtrace (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man3/error.3 .so man3/list.3 .so man2/statfs.2 .so man3/round.3 .\" man page generated from restructuredtext. . .th bpf-helpers 7 "" "" "" .sh name bpf-helpers \- list of ebpf helper functions . .nr rst2man-indent-level 0 . .de1 rstreportmargin \\$1 \\n[an-margin] level \\n[rst2man-indent-level] level margin: \\n[rst2man-indent\\n[rst2man-indent-level]] - \\n[rst2man-indent0] \\n[rst2man-indent1] \\n[rst2man-indent2] .. .de1 indent .\" .rstreportmargin pre: . rs \\$1 . nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin] . nr rst2man-indent-level +1 .\" .rstreportmargin post: .. .de unindent . re .\" indent \\n[an-margin] .\" old: \\n[rst2man-indent\\n[rst2man-indent-level]] .nr rst2man-indent-level -1 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]] .in \\n[rst2man-indent\\n[rst2man-indent-level]]u .. .\" copyright (c) all bpf authors and contributors from 2014 to present. . .\" see git log include/uapi/linux/bpf.h in kernel tree for details. . .\" . .\" %%%license_start(verbatim) . .\" permission is granted to make and distribute verbatim copies of this . .\" manual provided the copyright notice and this permission notice are . .\" preserved on all copies. . .\" . .\" permission is granted to copy and distribute modified versions of this . .\" manual under the conditions for verbatim copying, provided that the . .\" entire resulting derived work is distributed under the terms of a . .\" permission notice identical to this one. . .\" . .\" since the linux kernel and libraries are constantly changing, this . .\" manual page may be incorrect or out-of-date. the author(s) assume no . .\" responsibility for errors or omissions, or for damages resulting from . .\" the use of the information contained herein. the author(s) may not . .\" have taken the same level of care in the production of this manual, . .\" which is licensed free of charge, as they might when working . .\" professionally. . .\" . .\" formatted or processed versions of this manual, if unaccompanied by . .\" the source, must acknowledge the copyright and authors of this work. . .\" %%%license_end . .\" . .\" please do not edit this file. it was generated from the documentation . .\" located in file include/uapi/linux/bpf.h of the linux kernel sources . .\" (helpers description), and from scripts/bpf_helpers_doc.py in the same . .\" repository (header and footer). . .sh description .sp the extended berkeley packet filter (ebpf) subsystem consists in programs written in a pseudo\-assembly language, then attached to one of the several kernel hooks and run in reaction of specific events. this framework differs from the older, "classic" bpf (or "cbpf") in several aspects, one of them being the ability to call special functions (or "helpers") from within a program. these functions are restricted to a white\-list of helpers defined in the kernel. .sp these helpers are used by ebpf programs to interact with the system, or with the context in which they work. for instance, they can be used to print debugging messages, to get the time since the system was booted, to interact with ebpf maps, or to manipulate network packets. since there are several ebpf program types, and that they do not run in the same context, each program type can only call a subset of those helpers. .sp due to ebpf conventions, a helper can not have more than five arguments. .sp internally, ebpf programs call directly into the compiled helper functions without requiring any foreign\-function interface. as a result, calling helpers introduces no overhead, thus offering excellent performance. .sp this document is an attempt to list and document the helpers available to ebpf developers. they are sorted by chronological order (the oldest helpers in the kernel at the top). .sh helpers .indent 0.0 .tp .b \fbvoid *bpf_map_lookup_elem(struct bpf_map *\fp\fimap\fp\fb, const void *\fp\fikey\fp\fb)\fp .indent 7.0 .tp .b description perform a lookup in \fimap\fp for an entry associated to \fikey\fp\&. .tp .b return map value associated to \fikey\fp, or \fbnull\fp if no entry was found. .unindent .tp .b \fblong bpf_map_update_elem(struct bpf_map *\fp\fimap\fp\fb, const void *\fp\fikey\fp\fb, const void *\fp\fivalue\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description add or update the value of the entry associated to \fikey\fp in \fimap\fp with \fivalue\fp\&. \fiflags\fp is one of: .indent 7.0 .tp .b \fbbpf_noexist\fp the entry for \fikey\fp must not exist in the map. .tp .b \fbbpf_exist\fp the entry for \fikey\fp must already exist in the map. .tp .b \fbbpf_any\fp no condition on the existence of the entry for \fikey\fp\&. .unindent .sp flag value \fbbpf_noexist\fp cannot be used for maps of types \fbbpf_map_type_array\fp or \fbbpf_map_type_percpu_array\fp (all elements always exist), the helper would return an error. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_map_delete_elem(struct bpf_map *\fp\fimap\fp\fb, const void *\fp\fikey\fp\fb)\fp .indent 7.0 .tp .b description delete entry with \fikey\fp from \fimap\fp\&. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_probe_read(void *\fp\fidst\fp\fb, u32\fp \fisize\fp\fb, const void *\fp\fiunsafe_ptr\fp\fb)\fp .indent 7.0 .tp .b description for tracing programs, safely attempt to read \fisize\fp bytes from kernel space address \fiunsafe_ptr\fp and store the data in \fidst\fp\&. .sp generally, use \fbbpf_probe_read_user\fp() or \fbbpf_probe_read_kernel\fp() instead. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbu64 bpf_ktime_get_ns(void)\fp .indent 7.0 .tp .b description return the time elapsed since system boot, in nanoseconds. does not include time the system was suspended. see: \fbclock_gettime\fp(\fbclock_monotonic\fp) .tp .b return current \fiktime\fp\&. .unindent .tp .b \fblong bpf_trace_printk(const char *\fp\fifmt\fp\fb, u32\fp \fifmt_size\fp\fb, ...)\fp .indent 7.0 .tp .b description this helper is a "printk()\-like" facility for debugging. it prints a message defined by format \fifmt\fp (of size \fifmt_size\fp) to file \fi/sys/kernel/debug/tracing/trace\fp from debugfs, if available. it can take up to three additional \fbu64\fp arguments (as an ebpf helpers, the total number of arguments is limited to five). .sp each time the helper is called, it appends a line to the trace. lines are discarded while \fi/sys/kernel/debug/tracing/trace\fp is open, use \fi/sys/kernel/debug/tracing/trace_pipe\fp to avoid this. the format of the trace is customizable, and the exact output one will get depends on the options set in \fi/sys/kernel/debug/tracing/trace_options\fp (see also the \fireadme\fp file under the same directory). however, it usually defaults to something like: .indent 7.0 .indent 3.5 .sp .nf .ft c telnet\-470 [001] .n.. 419421.045894: 0x00000001: .ft p .fi .unindent .unindent .sp in the above: .indent 7.0 .indent 3.5 .indent 0.0 .ip \(bu 2 \fbtelnet\fp is the name of the current task. .ip \(bu 2 \fb470\fp is the pid of the current task. .ip \(bu 2 \fb001\fp is the cpu number on which the task is running. .ip \(bu 2 in \fb\&.n..\fp, each character refers to a set of options (whether irqs are enabled, scheduling options, whether hard/softirqs are running, level of preempt_disabled respectively). \fbn\fp means that \fbtif_need_resched\fp and \fbpreempt_need_resched\fp are set. .ip \(bu 2 \fb419421.045894\fp is a timestamp. .ip \(bu 2 \fb0x00000001\fp is a fake value used by bpf for the instruction pointer register. .ip \(bu 2 \fb\fp is the message formatted with \fifmt\fp\&. .unindent .unindent .unindent .sp the conversion specifiers supported by \fifmt\fp are similar, but more limited than for printk(). they are \fb%d\fp, \fb%i\fp, \fb%u\fp, \fb%x\fp, \fb%ld\fp, \fb%li\fp, \fb%lu\fp, \fb%lx\fp, \fb%lld\fp, \fb%lli\fp, \fb%llu\fp, \fb%llx\fp, \fb%p\fp, \fb%s\fp\&. no modifier (size of field, padding with zeroes, etc.) is available, and the helper will return \fb\-einval\fp (but print nothing) if it encounters an unknown specifier. .sp also, note that \fbbpf_trace_printk\fp() is slow, and should only be used for debugging purposes. for this reason, a notice block (spanning several lines) is printed to kernel logs and states that the helper should not be used "for production use" the first time this helper is used (or more precisely, when \fbtrace_printk\fp() buffers are allocated). for passing values to user space, perf events should be preferred. .tp .b return the number of bytes written to the buffer, or a negative error in case of failure. .unindent .tp .b \fbu32 bpf_get_prandom_u32(void)\fp .indent 7.0 .tp .b description get a pseudo\-random number. .sp from a security point of view, this helper uses its own pseudo\-random internal state, and cannot be used to infer the seed of other random functions in the kernel. however, it is essential to note that the generator used by the helper is not cryptographically secure. .tp .b return a random 32\-bit unsigned value. .unindent .tp .b \fbu32 bpf_get_smp_processor_id(void)\fp .indent 7.0 .tp .b description get the smp (symmetric multiprocessing) processor id. note that all programs run with preemption disabled, which means that the smp processor id is stable during all the execution of the program. .tp .b return the smp id of the processor running the program. .unindent .tp .b \fblong bpf_skb_store_bytes(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, const void *\fp\fifrom\fp\fb, u32\fp \filen\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description store \filen\fp bytes from address \fifrom\fp into the packet associated to \fiskb\fp, at \fioffset\fp\&. \fiflags\fp are a combination of \fbbpf_f_recompute_csum\fp (automatically recompute the checksum for the packet after storing the bytes) and \fbbpf_f_invalidate_hash\fp (set \fiskb\fp\fb\->hash\fp, \fiskb\fp\fb\->swhash\fp and \fiskb\fp\fb\->l4hash\fp to 0). .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_l3_csum_replace(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, u64\fp \fifrom\fp\fb, u64\fp \fito\fp\fb, u64\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description recompute the layer 3 (e.g. ip) checksum for the packet associated to \fiskb\fp\&. computation is incremental, so the helper must know the former value of the header field that was modified (\fifrom\fp), the new value of this field (\fito\fp), and the number of bytes (2 or 4) for this field, stored in \fisize\fp\&. alternatively, it is possible to store the difference between the previous and the new values of the header field in \fito\fp, by setting \fifrom\fp and \fisize\fp to 0. for both methods, \fioffset\fp indicates the location of the ip checksum within the packet. .sp this helper works in combination with \fbbpf_csum_diff\fp(), which does not update the checksum in\-place, but offers more flexibility and can handle sizes larger than 2 or 4 for the checksum to update. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_l4_csum_replace(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, u64\fp \fifrom\fp\fb, u64\fp \fito\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description recompute the layer 4 (e.g. tcp, udp, or icmp) checksum for the packet associated to \fiskb\fp\&. computation is incremental, so the helper must know the former value of the header field that was modified (\fifrom\fp), the new value of this field (\fito\fp), and the number of bytes (2 or 4) for this field, stored on the lowest four bits of \fiflags\fp\&. alternatively, it is possible to store the difference between the previous and the new values of the header field in \fito\fp, by setting \fifrom\fp and the four lowest bits of \fiflags\fp to 0. for both methods, \fioffset\fp indicates the location of the ip checksum within the packet. in addition to the size of the field, \fiflags\fp can be added (bitwise or) actual flags. with \fbbpf_f_mark_mangled_0\fp, a null checksum is left untouched (unless \fbbpf_f_mark_enforce\fp is added as well), and for updates resulting in a null checksum the value is set to \fbcsum_mangled_0\fp instead. flag \fbbpf_f_pseudo_hdr\fp indicates the checksum is to be computed against a pseudo\-header. .sp this helper works in combination with \fbbpf_csum_diff\fp(), which does not update the checksum in\-place, but offers more flexibility and can handle sizes larger than 2 or 4 for the checksum to update. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_tail_call(void *\fp\fictx\fp\fb, struct bpf_map *\fp\fiprog_array_map\fp\fb, u32\fp \fiindex\fp\fb)\fp .indent 7.0 .tp .b description this special helper is used to trigger a "tail call", or in other words, to jump into another ebpf program. the same stack frame is used (but values on stack and in registers for the caller are not accessible to the callee). this mechanism allows for program chaining, either for raising the maximum number of available ebpf instructions, or to execute given programs in conditional blocks. for security reasons, there is an upper limit to the number of successive tail calls that can be performed. .sp upon call of this helper, the program attempts to jump into a program referenced at index \fiindex\fp in \fiprog_array_map\fp, a special map of type \fbbpf_map_type_prog_array\fp, and passes \fictx\fp, a pointer to the context. .sp if the call succeeds, the kernel immediately runs the first instruction of the new program. this is not a function call, and it never returns to the previous program. if the call fails, then the helper has no effect, and the caller continues to run its subsequent instructions. a call can fail if the destination program for the jump does not exist (i.e. \fiindex\fp is superior to the number of entries in \fiprog_array_map\fp), or if the maximum number of tail calls has been reached for this chain of programs. this limit is defined in the kernel by the macro \fbmax_tail_call_cnt\fp (not accessible to user space), which is currently set to 32. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_clone_redirect(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fiifindex\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description clone and redirect the packet associated to \fiskb\fp to another net device of index \fiifindex\fp\&. both ingress and egress interfaces can be used for redirection. the \fbbpf_f_ingress\fp value in \fiflags\fp is used to make the distinction (ingress path is selected if the flag is present, egress path otherwise). this is the only flag supported for now. .sp in comparison with \fbbpf_redirect\fp() helper, \fbbpf_clone_redirect\fp() has the associated cost of duplicating the packet buffer, but this can be executed out of the ebpf program. conversely, \fbbpf_redirect\fp() is more efficient, but it is handled through an action code where the redirection happens only after the ebpf program has returned. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbu64 bpf_get_current_pid_tgid(void)\fp .indent 7.0 .tp .b return a 64\-bit integer containing the current tgid and pid, and created as such: \ficurrent_task\fp\fb\->tgid << 32 |\fp \ficurrent_task\fp\fb\->pid\fp\&. .unindent .tp .b \fbu64 bpf_get_current_uid_gid(void)\fp .indent 7.0 .tp .b return a 64\-bit integer containing the current gid and uid, and created as such: \ficurrent_gid\fp \fb<< 32 |\fp \ficurrent_uid\fp\&. .unindent .tp .b \fblong bpf_get_current_comm(void *\fp\fibuf\fp\fb, u32\fp \fisize_of_buf\fp\fb)\fp .indent 7.0 .tp .b description copy the \fbcomm\fp attribute of the current task into \fibuf\fp of \fisize_of_buf\fp\&. the \fbcomm\fp attribute contains the name of the executable (excluding the path) for the current task. the \fisize_of_buf\fp must be strictly positive. on success, the helper makes sure that the \fibuf\fp is nul\-terminated. on failure, it is filled with zeroes. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbu32 bpf_get_cgroup_classid(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description retrieve the classid for the current task, i.e. for the net_cls cgroup to which \fiskb\fp belongs. .sp this helper can be used on tc egress path, but not on ingress. .sp the net_cls cgroup provides an interface to tag network packets based on a user\-provided identifier for all traffic coming from the tasks belonging to the related cgroup. see also the related kernel documentation, available from the linux sources in file \fidocumentation/admin\-guide/cgroup\-v1/net_cls.rst\fp\&. .sp the linux kernel has two versions for cgroups: there are cgroups v1 and cgroups v2. both are available to users, who can use a mixture of them, but note that the net_cls cgroup is for cgroup v1 only. this makes it incompatible with bpf programs run on cgroups, which is a cgroup\-v2\-only feature (a socket can only hold data for one version of cgroups at a time). .sp this helper is only available is the kernel was compiled with the \fbconfig_cgroup_net_classid\fp configuration option set to "\fby\fp" or to "\fbm\fp". .tp .b return the classid, or 0 for the default unconfigured classid. .unindent .tp .b \fblong bpf_skb_vlan_push(struct sk_buff *\fp\fiskb\fp\fb, __be16\fp \fivlan_proto\fp\fb, u16\fp \fivlan_tci\fp\fb)\fp .indent 7.0 .tp .b description push a \fivlan_tci\fp (vlan tag control information) of protocol \fivlan_proto\fp to the packet associated to \fiskb\fp, then update the checksum. note that if \fivlan_proto\fp is different from \fbeth_p_8021q\fp and \fbeth_p_8021ad\fp, it is considered to be \fbeth_p_8021q\fp\&. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_vlan_pop(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description pop a vlan header from the packet associated to \fiskb\fp\&. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_get_tunnel_key(struct sk_buff *\fp\fiskb\fp\fb, struct bpf_tunnel_key *\fp\fikey\fp\fb, u32\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description get tunnel metadata. this helper takes a pointer \fikey\fp to an empty \fbstruct bpf_tunnel_key\fp of \fbsize\fp, that will be filled with tunnel metadata for the packet associated to \fiskb\fp\&. the \fiflags\fp can be set to \fbbpf_f_tuninfo_ipv6\fp, which indicates that the tunnel is based on ipv6 protocol instead of ipv4. .sp the \fbstruct bpf_tunnel_key\fp is an object that generalizes the principal parameters used by various tunneling protocols into a single struct. this way, it can be used to easily make a decision based on the contents of the encapsulation header, "summarized" in this struct. in particular, it holds the ip address of the remote end (ipv4 or ipv6, depending on the case) in \fikey\fp\fb\->remote_ipv4\fp or \fikey\fp\fb\->remote_ipv6\fp\&. also, this struct exposes the \fikey\fp\fb\->tunnel_id\fp, which is generally mapped to a vni (virtual network identifier), making it programmable together with the \fbbpf_skb_set_tunnel_key\fp() helper. .sp let\(aqs imagine that the following code is part of a program attached to the tc ingress interface, on one end of a gre tunnel, and is supposed to filter out all messages coming from remote ends with ipv4 address other than 10.0.0.1: .indent 7.0 .indent 3.5 .sp .nf .ft c int ret; struct bpf_tunnel_key key = {}; ret = bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0); if (ret < 0) return tc_act_shot; // drop packet if (key.remote_ipv4 != 0x0a000001) return tc_act_shot; // drop packet return tc_act_ok; // accept packet .ft p .fi .unindent .unindent .sp this interface can also be used with all encapsulation devices that can operate in "collect metadata" mode: instead of having one network device per specific configuration, the "collect metadata" mode only requires a single device where the configuration can be extracted from this helper. .sp this can be used together with various tunnels such as vxlan, geneve, gre, or ip in ip (ipip). .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_set_tunnel_key(struct sk_buff *\fp\fiskb\fp\fb, struct bpf_tunnel_key *\fp\fikey\fp\fb, u32\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description populate tunnel metadata for packet associated to \fiskb.\fp the tunnel metadata is set to the contents of \fikey\fp, of \fisize\fp\&. the \fiflags\fp can be set to a combination of the following values: .indent 7.0 .tp .b \fbbpf_f_tuninfo_ipv6\fp indicate that the tunnel is based on ipv6 protocol instead of ipv4. .tp .b \fbbpf_f_zero_csum_tx\fp for ipv4 packets, add a flag to tunnel metadata indicating that checksum computation should be skipped and checksum set to zeroes. .tp .b \fbbpf_f_dont_fragment\fp add a flag to tunnel metadata indicating that the packet should not be fragmented. .tp .b \fbbpf_f_seq_number\fp add a flag to tunnel metadata indicating that a sequence number should be added to tunnel header before sending the packet. this flag was added for gre encapsulation, but might be used with other protocols as well in the future. .unindent .sp here is a typical usage on the transmit path: .indent 7.0 .indent 3.5 .sp .nf .ft c struct bpf_tunnel_key key; populate key ... bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0); bpf_clone_redirect(skb, vxlan_dev_ifindex, 0); .ft p .fi .unindent .unindent .sp see also the description of the \fbbpf_skb_get_tunnel_key\fp() helper for additional information. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbu64 bpf_perf_event_read(struct bpf_map *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description read the value of a perf event counter. this helper relies on a \fimap\fp of type \fbbpf_map_type_perf_event_array\fp\&. the nature of the perf event counter is selected when \fimap\fp is updated with perf event file descriptors. the \fimap\fp is an array whose size is the number of available cpus, and each cell contains a value relative to one cpu. the value to retrieve is indicated by \fiflags\fp, that contains the index of the cpu to look up, masked with \fbbpf_f_index_mask\fp\&. alternatively, \fiflags\fp can be set to \fbbpf_f_current_cpu\fp to indicate that the value for the current cpu should be retrieved. .sp note that before linux 4.13, only hardware perf event can be retrieved. .sp also, be aware that the newer helper \fbbpf_perf_event_read_value\fp() is recommended over \fbbpf_perf_event_read\fp() in general. the latter has some abi quirks where error and counter value are used as a return code (which is wrong to do since ranges may overlap). this issue is fixed with \fbbpf_perf_event_read_value\fp(), which at the same time provides more features over the \fbbpf_perf_event_read\fp() interface. please refer to the description of \fbbpf_perf_event_read_value\fp() for details. .tp .b return the value of the perf event counter read from the map, or a negative error code in case of failure. .unindent .tp .b \fblong bpf_redirect(u32\fp \fiifindex\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description redirect the packet to another net device of index \fiifindex\fp\&. this helper is somewhat similar to \fbbpf_clone_redirect\fp(), except that the packet is not cloned, which provides increased performance. .sp except for xdp, both ingress and egress interfaces can be used for redirection. the \fbbpf_f_ingress\fp value in \fiflags\fp is used to make the distinction (ingress path is selected if the flag is present, egress path otherwise). currently, xdp only supports redirection to the egress interface, and accepts no flag at all. .sp the same effect can also be attained with the more generic \fbbpf_redirect_map\fp(), which uses a bpf map to store the redirect target instead of providing it directly to the helper. .tp .b return for xdp, the helper returns \fbxdp_redirect\fp on success or \fbxdp_aborted\fp on error. for other program types, the values are \fbtc_act_redirect\fp on success or \fbtc_act_shot\fp on error. .unindent .tp .b \fbu32 bpf_get_route_realm(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description retrieve the realm or the route, that is to say the \fbtclassid\fp field of the destination for the \fiskb\fp\&. the identifier retrieved is a user\-provided tag, similar to the one used with the net_cls cgroup (see description for \fbbpf_get_cgroup_classid\fp() helper), but here this tag is held by a route (a destination entry), not by a task. .sp retrieving this identifier works with the clsact tc egress hook (see also \fbtc\-bpf(8)\fp), or alternatively on conventional classful egress qdiscs, but not on tc ingress path. in case of clsact tc egress hook, this has the advantage that, internally, the destination entry has not been dropped yet in the transmit path. therefore, the destination entry does not need to be artificially held via \fbnetif_keep_dst\fp() for a classful qdisc until the \fiskb\fp is freed. .sp this helper is available only if the kernel was compiled with \fbconfig_ip_route_classid\fp configuration option. .tp .b return the realm of the route for the packet associated to \fiskb\fp, or 0 if none was found. .unindent .tp .b \fblong bpf_perf_event_output(void *\fp\fictx\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb, void *\fp\fidata\fp\fb, u64\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description write raw \fidata\fp blob into a special bpf perf event held by \fimap\fp of type \fbbpf_map_type_perf_event_array\fp\&. this perf event must have the following attributes: \fbperf_sample_raw\fp as \fbsample_type\fp, \fbperf_type_software\fp as \fbtype\fp, and \fbperf_count_sw_bpf_output\fp as \fbconfig\fp\&. .sp the \fiflags\fp are used to indicate the index in \fimap\fp for which the value must be put, masked with \fbbpf_f_index_mask\fp\&. alternatively, \fiflags\fp can be set to \fbbpf_f_current_cpu\fp to indicate that the index of the current cpu core should be used. .sp the value to write, of \fisize\fp, is passed through ebpf stack and pointed by \fidata\fp\&. .sp the context of the program \fictx\fp needs also be passed to the helper. .sp on user space, a program willing to read the values needs to call \fbperf_event_open\fp() on the perf event (either for one or for all cpus) and to store the file descriptor into the \fimap\fp\&. this must be done before the ebpf program can send data into it. an example is available in file \fisamples/bpf/trace_output_user.c\fp in the linux kernel source tree (the ebpf program counterpart is in \fisamples/bpf/trace_output_kern.c\fp). .sp \fbbpf_perf_event_output\fp() achieves better performance than \fbbpf_trace_printk\fp() for sharing data with user space, and is much better suitable for streaming data from ebpf programs. .sp note that this helper is not restricted to tracing use cases and can be used with programs attached to tc or xdp as well, where it allows for passing data to user space listeners. data can be: .indent 7.0 .ip \(bu 2 only custom structs, .ip \(bu 2 only the packet payload, or .ip \(bu 2 a combination of both. .unindent .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_load_bytes(const void *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, void *\fp\fito\fp\fb, u32\fp \filen\fp\fb)\fp .indent 7.0 .tp .b description this helper was provided as an easy way to load data from a packet. it can be used to load \filen\fp bytes from \fioffset\fp from the packet associated to \fiskb\fp, into the buffer pointed by \fito\fp\&. .sp since linux 4.7, usage of this helper has mostly been replaced by "direct packet access", enabling packet data to be manipulated with \fiskb\fp\fb\->data\fp and \fiskb\fp\fb\->data_end\fp pointing respectively to the first byte of packet data and to the byte after the last byte of packet data. however, it remains useful if one wishes to read large quantities of data at once from a packet into the ebpf stack. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_get_stackid(void *\fp\fictx\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description walk a user or a kernel stack and return its id. to achieve this, the helper needs \fictx\fp, which is a pointer to the context on which the tracing program is executed, and a pointer to a \fimap\fp of type \fbbpf_map_type_stack_trace\fp\&. .sp the last argument, \fiflags\fp, holds the number of stack frames to skip (from 0 to 255), masked with \fbbpf_f_skip_field_mask\fp\&. the next bits can be used to set a combination of the following flags: .indent 7.0 .tp .b \fbbpf_f_user_stack\fp collect a user space stack instead of a kernel stack. .tp .b \fbbpf_f_fast_stack_cmp\fp compare stacks by hash only. .tp .b \fbbpf_f_reuse_stackid\fp if two different stacks hash into the same \fistackid\fp, discard the old one. .unindent .sp the stack id retrieved is a 32 bit long integer handle which can be further combined with other data (including other stack ids) and used as a key into maps. this can be useful for generating a variety of graphs (such as flame graphs or off\-cpu graphs). .sp for walking a stack, this helper is an improvement over \fbbpf_probe_read\fp(), which can be used with unrolled loops but is not efficient and consumes a lot of ebpf instructions. instead, \fbbpf_get_stackid\fp() can collect up to \fbperf_max_stack_depth\fp both kernel and user frames. note that this limit can be controlled with the \fbsysctl\fp program, and that it should be manually increased in order to profile long user stacks (such as stacks for java programs). to do so, use: .indent 7.0 .indent 3.5 .sp .nf .ft c # sysctl kernel.perf_event_max_stack= .ft p .fi .unindent .unindent .tp .b return the positive or null stack id on success, or a negative error in case of failure. .unindent .tp .b \fbs64 bpf_csum_diff(__be32 *\fp\fifrom\fp\fb, u32\fp \fifrom_size\fp\fb, __be32 *\fp\fito\fp\fb, u32\fp \fito_size\fp\fb, __wsum\fp \fiseed\fp\fb)\fp .indent 7.0 .tp .b description compute a checksum difference, from the raw buffer pointed by \fifrom\fp, of length \fifrom_size\fp (that must be a multiple of 4), towards the raw buffer pointed by \fito\fp, of size \fito_size\fp (same remark). an optional \fiseed\fp can be added to the value (this can be cascaded, the seed may come from a previous call to the helper). .sp this is flexible enough to be used in several ways: .indent 7.0 .ip \(bu 2 with \fifrom_size\fp == 0, \fito_size\fp > 0 and \fiseed\fp set to checksum, it can be used when pushing new data. .ip \(bu 2 with \fifrom_size\fp > 0, \fito_size\fp == 0 and \fiseed\fp set to checksum, it can be used when removing data from a packet. .ip \(bu 2 with \fifrom_size\fp > 0, \fito_size\fp > 0 and \fiseed\fp set to 0, it can be used to compute a diff. note that \fifrom_size\fp and \fito_size\fp do not need to be equal. .unindent .sp this helper can be used in combination with \fbbpf_l3_csum_replace\fp() and \fbbpf_l4_csum_replace\fp(), to which one can feed in the difference computed with \fbbpf_csum_diff\fp(). .tp .b return the checksum result, or a negative error code in case of failure. .unindent .tp .b \fblong bpf_skb_get_tunnel_opt(struct sk_buff *\fp\fiskb\fp\fb, void *\fp\fiopt\fp\fb, u32\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description retrieve tunnel options metadata for the packet associated to \fiskb\fp, and store the raw tunnel option data to the buffer \fiopt\fp of \fisize\fp\&. .sp this helper can be used with encapsulation devices that can operate in "collect metadata" mode (please refer to the related note in the description of \fbbpf_skb_get_tunnel_key\fp() for more details). a particular example where this can be used is in combination with the geneve encapsulation protocol, where it allows for pushing (with \fbbpf_skb_get_tunnel_opt\fp() helper) and retrieving arbitrary tlvs (type\-length\-value headers) from the ebpf program. this allows for full customization of these headers. .tp .b return the size of the option data retrieved. .unindent .tp .b \fblong bpf_skb_set_tunnel_opt(struct sk_buff *\fp\fiskb\fp\fb, void *\fp\fiopt\fp\fb, u32\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description set tunnel options metadata for the packet associated to \fiskb\fp to the option data contained in the raw buffer \fiopt\fp of \fisize\fp\&. .sp see also the description of the \fbbpf_skb_get_tunnel_opt\fp() helper for additional information. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_change_proto(struct sk_buff *\fp\fiskb\fp\fb, __be16\fp \fiproto\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description change the protocol of the \fiskb\fp to \fiproto\fp\&. currently supported are transition from ipv4 to ipv6, and from ipv6 to ipv4. the helper takes care of the groundwork for the transition, including resizing the socket buffer. the ebpf program is expected to fill the new headers, if any, via \fbskb_store_bytes\fp() and to recompute the checksums with \fbbpf_l3_csum_replace\fp() and \fbbpf_l4_csum_replace\fp(). the main case for this helper is to perform nat64 operations out of an ebpf program. .sp internally, the gso type is marked as dodgy so that headers are checked and segments are recalculated by the gso/gro engine. the size for gso target is adapted as well. .sp all values for \fiflags\fp are reserved for future usage, and must be left at zero. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_change_type(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fitype\fp\fb)\fp .indent 7.0 .tp .b description change the packet type for the packet associated to \fiskb\fp\&. this comes down to setting \fiskb\fp\fb\->pkt_type\fp to \fitype\fp, except the ebpf program does not have a write access to \fiskb\fp\fb\->pkt_type\fp beside this helper. using a helper here allows for graceful handling of errors. .sp the major use case is to change incoming \fiskb*s to **packet_host*\fp in a programmatic way instead of having to recirculate via \fbredirect\fp(..., \fbbpf_f_ingress\fp), for example. .sp note that \fitype\fp only allows certain values. at this time, they are: .indent 7.0 .tp .b \fbpacket_host\fp packet is for us. .tp .b \fbpacket_broadcast\fp send packet to all. .tp .b \fbpacket_multicast\fp send packet to group. .tp .b \fbpacket_otherhost\fp send packet to someone else. .unindent .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_under_cgroup(struct sk_buff *\fp\fiskb\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u32\fp \fiindex\fp\fb)\fp .indent 7.0 .tp .b description check whether \fiskb\fp is a descendant of the cgroup2 held by \fimap\fp of type \fbbpf_map_type_cgroup_array\fp, at \fiindex\fp\&. .tp .b return the return value depends on the result of the test, and can be: .indent 7.0 .ip \(bu 2 0, if the \fiskb\fp failed the cgroup2 descendant test. .ip \(bu 2 1, if the \fiskb\fp succeeded the cgroup2 descendant test. .ip \(bu 2 a negative error code, if an error occurred. .unindent .unindent .tp .b \fbu32 bpf_get_hash_recalc(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description retrieve the hash of the packet, \fiskb\fp\fb\->hash\fp\&. if it is not set, in particular if the hash was cleared due to mangling, recompute this hash. later accesses to the hash can be done directly with \fiskb\fp\fb\->hash\fp\&. .sp calling \fbbpf_set_hash_invalid\fp(), changing a packet prototype with \fbbpf_skb_change_proto\fp(), or calling \fbbpf_skb_store_bytes\fp() with the \fbbpf_f_invalidate_hash\fp are actions susceptible to clear the hash and to trigger a new computation for the next call to \fbbpf_get_hash_recalc\fp(). .tp .b return the 32\-bit hash. .unindent .tp .b \fbu64 bpf_get_current_task(void)\fp .indent 7.0 .tp .b return a pointer to the current task struct. .unindent .tp .b \fblong bpf_probe_write_user(void *\fp\fidst\fp\fb, const void *\fp\fisrc\fp\fb, u32\fp \filen\fp\fb)\fp .indent 7.0 .tp .b description attempt in a safe way to write \filen\fp bytes from the buffer \fisrc\fp to \fidst\fp in memory. it only works for threads that are in user context, and \fidst\fp must be a valid user space address. .sp this helper should not be used to implement any kind of security mechanism because of toc\-tou attacks, but rather to debug, divert, and manipulate execution of semi\-cooperative processes. .sp keep in mind that this feature is meant for experiments, and it has a risk of crashing the system and running programs. therefore, when an ebpf program using this helper is attached, a warning including pid and process name is printed to kernel logs. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_current_task_under_cgroup(struct bpf_map *\fp\fimap\fp\fb, u32\fp \fiindex\fp\fb)\fp .indent 7.0 .tp .b description check whether the probe is being run is the context of a given subset of the cgroup2 hierarchy. the cgroup2 to test is held by \fimap\fp of type \fbbpf_map_type_cgroup_array\fp, at \fiindex\fp\&. .tp .b return the return value depends on the result of the test, and can be: .indent 7.0 .ip \(bu 2 0, if the \fiskb\fp task belongs to the cgroup2. .ip \(bu 2 1, if the \fiskb\fp task does not belong to the cgroup2. .ip \(bu 2 a negative error code, if an error occurred. .unindent .unindent .tp .b \fblong bpf_skb_change_tail(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \filen\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description resize (trim or grow) the packet associated to \fiskb\fp to the new \filen\fp\&. the \fiflags\fp are reserved for future usage, and must be left at zero. .sp the basic idea is that the helper performs the needed work to change the size of the packet, then the ebpf program rewrites the rest via helpers like \fbbpf_skb_store_bytes\fp(), \fbbpf_l3_csum_replace\fp(), \fbbpf_l3_csum_replace\fp() and others. this helper is a slow path utility intended for replies with control messages. and because it is targeted for slow path, the helper itself can afford to be slow: it implicitly linearizes, unclones and drops offloads from the \fiskb\fp\&. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_pull_data(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \filen\fp\fb)\fp .indent 7.0 .tp .b description pull in non\-linear data in case the \fiskb\fp is non\-linear and not all of \filen\fp are part of the linear section. make \filen\fp bytes from \fiskb\fp readable and writable. if a zero value is passed for \filen\fp, then the whole length of the \fiskb\fp is pulled. .sp this helper is only needed for reading and writing with direct packet access. .sp for direct packet access, testing that offsets to access are within packet boundaries (test on \fiskb\fp\fb\->data_end\fp) is susceptible to fail if offsets are invalid, or if the requested data is in non\-linear parts of the \fiskb\fp\&. on failure the program can just bail out, or in the case of a non\-linear buffer, use a helper to make the data available. the \fbbpf_skb_load_bytes\fp() helper is a first solution to access the data. another one consists in using \fbbpf_skb_pull_data\fp to pull in once the non\-linear parts, then retesting and eventually access the data. .sp at the same time, this also makes sure the \fiskb\fp is uncloned, which is a necessary condition for direct write. as this needs to be an invariant for the write part only, the verifier detects writes and adds a prologue that is calling \fbbpf_skb_pull_data()\fp to effectively unclone the \fiskb\fp from the very beginning in case it is indeed cloned. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbs64 bpf_csum_update(struct sk_buff *\fp\fiskb\fp\fb, __wsum\fp \ficsum\fp\fb)\fp .indent 7.0 .tp .b description add the checksum \ficsum\fp into \fiskb\fp\fb\->csum\fp in case the driver has supplied a checksum for the entire packet into that field. return an error otherwise. this helper is intended to be used in combination with \fbbpf_csum_diff\fp(), in particular when the checksum needs to be updated after data has been written into the packet through direct packet access. .tp .b return the checksum on success, or a negative error code in case of failure. .unindent .tp .b \fbvoid bpf_set_hash_invalid(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description invalidate the current \fiskb\fp\fb\->hash\fp\&. it can be used after mangling on headers through direct packet access, in order to indicate that the hash is outdated and to trigger a recalculation the next time the kernel tries to access this hash or when the \fbbpf_get_hash_recalc\fp() helper is called. .unindent .tp .b \fblong bpf_get_numa_node_id(void)\fp .indent 7.0 .tp .b description return the id of the current numa node. the primary use case for this helper is the selection of sockets for the local numa node, when the program is attached to sockets using the \fbso_attach_reuseport_ebpf\fp option (see also \fbsocket(7)\fp), but the helper is also available to other ebpf program types, similarly to \fbbpf_get_smp_processor_id\fp(). .tp .b return the id of current numa node. .unindent .tp .b \fblong bpf_skb_change_head(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \filen\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description grows headroom of packet associated to \fiskb\fp and adjusts the offset of the mac header accordingly, adding \filen\fp bytes of space. it automatically extends and reallocates memory as required. .sp this helper can be used on a layer 3 \fiskb\fp to push a mac header for redirection into a layer 2 device. .sp all values for \fiflags\fp are reserved for future usage, and must be left at zero. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_xdp_adjust_head(struct xdp_buff *\fp\fixdp_md\fp\fb, int\fp \fidelta\fp\fb)\fp .indent 7.0 .tp .b description adjust (move) \fixdp_md\fp\fb\->data\fp by \fidelta\fp bytes. note that it is possible to use a negative value for \fidelta\fp\&. this helper can be used to prepare the packet for pushing or popping headers. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_probe_read_str(void *\fp\fidst\fp\fb, u32\fp \fisize\fp\fb, const void *\fp\fiunsafe_ptr\fp\fb)\fp .indent 7.0 .tp .b description copy a nul terminated string from an unsafe kernel address \fiunsafe_ptr\fp to \fidst\fp\&. see \fbbpf_probe_read_kernel_str\fp() for more details. .sp generally, use \fbbpf_probe_read_user_str\fp() or \fbbpf_probe_read_kernel_str\fp() instead. .tp .b return on success, the strictly positive length of the string, including the trailing nul character. on error, a negative value. .unindent .tp .b \fbu64 bpf_get_socket_cookie(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description if the \fbstruct sk_buff\fp pointed by \fiskb\fp has a known socket, retrieve the cookie (generated by the kernel) of this socket. if no cookie has been set yet, generate a new cookie. once generated, the socket cookie remains stable for the life of the socket. this helper can be useful for monitoring per socket networking traffic statistics as it provides a global socket identifier that can be assumed unique. .tp .b return a 8\-byte long non\-decreasing number on success, or 0 if the socket field is missing inside \fiskb\fp\&. .unindent .tp .b \fbu64 bpf_get_socket_cookie(struct bpf_sock_addr *\fp\fictx\fp\fb)\fp .indent 7.0 .tp .b description equivalent to bpf_get_socket_cookie() helper that accepts \fiskb\fp, but gets socket from \fbstruct bpf_sock_addr\fp context. .tp .b return a 8\-byte long non\-decreasing number. .unindent .tp .b \fbu64 bpf_get_socket_cookie(struct bpf_sock_ops *\fp\fictx\fp\fb)\fp .indent 7.0 .tp .b description equivalent to \fbbpf_get_socket_cookie\fp() helper that accepts \fiskb\fp, but gets socket from \fbstruct bpf_sock_ops\fp context. .tp .b return a 8\-byte long non\-decreasing number. .unindent .tp .b \fbu32 bpf_get_socket_uid(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b return the owner uid of the socket associated to \fiskb\fp\&. if the socket is \fbnull\fp, or if it is not a full socket (i.e. if it is a time\-wait or a request socket instead), \fboverflowuid\fp value is returned (note that \fboverflowuid\fp might also be the actual uid value for the socket). .unindent .tp .b \fblong bpf_set_hash(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fihash\fp\fb)\fp .indent 7.0 .tp .b description set the full hash for \fiskb\fp (set the field \fiskb\fp\fb\->hash\fp) to value \fihash\fp\&. .tp .b return 0 .unindent .tp .b \fblong bpf_setsockopt(void *\fp\fibpf_socket\fp\fb, int\fp \filevel\fp\fb, int\fp \fioptname\fp\fb, void *\fp\fioptval\fp\fb, int\fp \fioptlen\fp\fb)\fp .indent 7.0 .tp .b description emulate a call to \fbsetsockopt()\fp on the socket associated to \fibpf_socket\fp, which must be a full socket. the \filevel\fp at which the option resides and the name \fioptname\fp of the option must be specified, see \fbsetsockopt(2)\fp for more information. the option value of length \fioptlen\fp is pointed by \fioptval\fp\&. .sp \fibpf_socket\fp should be one of the following: .indent 7.0 .ip \(bu 2 \fbstruct bpf_sock_ops\fp for \fbbpf_prog_type_sock_ops\fp\&. .ip \(bu 2 \fbstruct bpf_sock_addr\fp for \fbbpf_cgroup_inet4_connect\fp and \fbbpf_cgroup_inet6_connect\fp\&. .unindent .sp this helper actually implements a subset of \fbsetsockopt()\fp\&. it supports the following \filevel\fps: .indent 7.0 .ip \(bu 2 \fbsol_socket\fp, which supports the following \fioptname\fps: \fbso_rcvbuf\fp, \fbso_sndbuf\fp, \fbso_max_pacing_rate\fp, \fbso_priority\fp, \fbso_rcvlowat\fp, \fbso_mark\fp, \fbso_bindtodevice\fp, \fbso_keepalive\fp\&. .ip \(bu 2 \fbipproto_tcp\fp, which supports the following \fioptname\fps: \fbtcp_congestion\fp, \fbtcp_bpf_iw\fp, \fbtcp_bpf_sndcwnd_clamp\fp, \fbtcp_save_syn\fp, \fbtcp_keepidle\fp, \fbtcp_keepintvl\fp, \fbtcp_keepcnt\fp, \fbtcp_syncnt\fp, \fbtcp_user_timeout\fp\&. .ip \(bu 2 \fbipproto_ip\fp, which supports \fioptname\fp \fbip_tos\fp\&. .ip \(bu 2 \fbipproto_ipv6\fp, which supports \fioptname\fp \fbipv6_tclass\fp\&. .unindent .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_adjust_room(struct sk_buff *\fp\fiskb\fp\fb, s32\fp \filen_diff\fp\fb, u32\fp \fimode\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description grow or shrink the room for data in the packet associated to \fiskb\fp by \filen_diff\fp, and according to the selected \fimode\fp\&. .sp by default, the helper will reset any offloaded checksum indicator of the skb to checksum_none. this can be avoided by the following flag: .indent 7.0 .ip \(bu 2 \fbbpf_f_adj_room_no_csum_reset\fp: do not reset offloaded checksum data of the skb to checksum_none. .unindent .sp there are two supported modes at this time: .indent 7.0 .ip \(bu 2 \fbbpf_adj_room_mac\fp: adjust room at the mac layer (room space is added or removed below the layer 2 header). .ip \(bu 2 \fbbpf_adj_room_net\fp: adjust room at the network layer (room space is added or removed below the layer 3 header). .unindent .sp the following flags are supported at this time: .indent 7.0 .ip \(bu 2 \fbbpf_f_adj_room_fixed_gso\fp: do not adjust gso_size. adjusting mss in this way is not allowed for datagrams. .ip \(bu 2 \fbbpf_f_adj_room_encap_l3_ipv4\fp, \fbbpf_f_adj_room_encap_l3_ipv6\fp: any new space is reserved to hold a tunnel header. configure skb offsets and other fields accordingly. .ip \(bu 2 \fbbpf_f_adj_room_encap_l4_gre\fp, \fbbpf_f_adj_room_encap_l4_udp\fp: use with encap_l3 flags to further specify the tunnel type. .ip \(bu 2 \fbbpf_f_adj_room_encap_l2\fp(\filen\fp): use with encap_l3/l4 flags to further specify the tunnel type; \filen\fp is the length of the inner mac header. .unindent .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_redirect_map(struct bpf_map *\fp\fimap\fp\fb, u32\fp \fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description redirect the packet to the endpoint referenced by \fimap\fp at index \fikey\fp\&. depending on its type, this \fimap\fp can contain references to net devices (for forwarding packets through other ports), or to cpus (for redirecting xdp frames to another cpu; but this is only implemented for native xdp (with driver support) as of this writing). .sp the lower two bits of \fiflags\fp are used as the return code if the map lookup fails. this is so that the return value can be one of the xdp program return codes up to \fbxdp_tx\fp, as chosen by the caller. any higher bits in the \fiflags\fp argument must be unset. .sp see also \fbbpf_redirect\fp(), which only supports redirecting to an ifindex, but doesn\(aqt require a map to do so. .tp .b return \fbxdp_redirect\fp on success, or the value of the two lower bits of the \fiflags\fp argument on error. .unindent .tp .b \fblong bpf_sk_redirect_map(struct sk_buff *\fp\fiskb\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u32\fp \fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description redirect the packet to the socket referenced by \fimap\fp (of type \fbbpf_map_type_sockmap\fp) at index \fikey\fp\&. both ingress and egress interfaces can be used for redirection. the \fbbpf_f_ingress\fp value in \fiflags\fp is used to make the distinction (ingress path is selected if the flag is present, egress path otherwise). this is the only flag supported for now. .tp .b return \fbsk_pass\fp on success, or \fbsk_drop\fp on error. .unindent .tp .b \fblong bpf_sock_map_update(struct bpf_sock_ops *\fp\fiskops\fp\fb, struct bpf_map *\fp\fimap\fp\fb, void *\fp\fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description add an entry to, or update a \fimap\fp referencing sockets. the \fiskops\fp is used as a new value for the entry associated to \fikey\fp\&. \fiflags\fp is one of: .indent 7.0 .tp .b \fbbpf_noexist\fp the entry for \fikey\fp must not exist in the map. .tp .b \fbbpf_exist\fp the entry for \fikey\fp must already exist in the map. .tp .b \fbbpf_any\fp no condition on the existence of the entry for \fikey\fp\&. .unindent .sp if the \fimap\fp has ebpf programs (parser and verdict), those will be inherited by the socket being added. if the socket is already attached to ebpf programs, this results in an error. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_xdp_adjust_meta(struct xdp_buff *\fp\fixdp_md\fp\fb, int\fp \fidelta\fp\fb)\fp .indent 7.0 .tp .b description adjust the address pointed by \fixdp_md\fp\fb\->data_meta\fp by \fidelta\fp (which can be positive or negative). note that this operation modifies the address stored in \fixdp_md\fp\fb\->data\fp, so the latter must be loaded only after the helper has been called. .sp the use of \fixdp_md\fp\fb\->data_meta\fp is optional and programs are not required to use it. the rationale is that when the packet is processed with xdp (e.g. as dos filter), it is possible to push further meta data along with it before passing to the stack, and to give the guarantee that an ingress ebpf program attached as a tc classifier on the same device can pick this up for further post\-processing. since tc works with socket buffers, it remains possible to set from xdp the \fbmark\fp or \fbpriority\fp pointers, or other pointers for the socket buffer. having this scratch space generic and programmable allows for more flexibility as the user is free to store whatever meta data they need. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_perf_event_read_value(struct bpf_map *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb, struct bpf_perf_event_value *\fp\fibuf\fp\fb, u32\fp \fibuf_size\fp\fb)\fp .indent 7.0 .tp .b description read the value of a perf event counter, and store it into \fibuf\fp of size \fibuf_size\fp\&. this helper relies on a \fimap\fp of type \fbbpf_map_type_perf_event_array\fp\&. the nature of the perf event counter is selected when \fimap\fp is updated with perf event file descriptors. the \fimap\fp is an array whose size is the number of available cpus, and each cell contains a value relative to one cpu. the value to retrieve is indicated by \fiflags\fp, that contains the index of the cpu to look up, masked with \fbbpf_f_index_mask\fp\&. alternatively, \fiflags\fp can be set to \fbbpf_f_current_cpu\fp to indicate that the value for the current cpu should be retrieved. .sp this helper behaves in a way close to \fbbpf_perf_event_read\fp() helper, save that instead of just returning the value observed, it fills the \fibuf\fp structure. this allows for additional data to be retrieved: in particular, the enabled and running times (in \fibuf\fp\fb\->enabled\fp and \fibuf\fp\fb\->running\fp, respectively) are copied. in general, \fbbpf_perf_event_read_value\fp() is recommended over \fbbpf_perf_event_read\fp(), which has some abi issues and provides fewer functionalities. .sp these values are interesting, because hardware pmu (performance monitoring unit) counters are limited resources. when there are more pmu based perf events opened than available counters, kernel will multiplex these events so each event gets certain percentage (but not all) of the pmu time. in case that multiplexing happens, the number of samples or counter value will not reflect the case compared to when no multiplexing occurs. this makes comparison between different runs difficult. typically, the counter value should be normalized before comparing to other experiments. the usual normalization is done as follows. .indent 7.0 .indent 3.5 .sp .nf .ft c normalized_counter = counter * t_enabled / t_running .ft p .fi .unindent .unindent .sp where t_enabled is the time enabled for event and t_running is the time running for event since last normalization. the enabled and running times are accumulated since the perf event open. to achieve scaling factor between two invocations of an ebpf program, users can use cpu id as the key (which is typical for perf array usage model) to remember the previous value and do the calculation inside the ebpf program. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_perf_prog_read_value(struct bpf_perf_event_data *\fp\fictx\fp\fb, struct bpf_perf_event_value *\fp\fibuf\fp\fb, u32\fp \fibuf_size\fp\fb)\fp .indent 7.0 .tp .b description for en ebpf program attached to a perf event, retrieve the value of the event counter associated to \fictx\fp and store it in the structure pointed by \fibuf\fp and of size \fibuf_size\fp\&. enabled and running times are also stored in the structure (see description of helper \fbbpf_perf_event_read_value\fp() for more details). .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_getsockopt(void *\fp\fibpf_socket\fp\fb, int\fp \filevel\fp\fb, int\fp \fioptname\fp\fb, void *\fp\fioptval\fp\fb, int\fp \fioptlen\fp\fb)\fp .indent 7.0 .tp .b description emulate a call to \fbgetsockopt()\fp on the socket associated to \fibpf_socket\fp, which must be a full socket. the \filevel\fp at which the option resides and the name \fioptname\fp of the option must be specified, see \fbgetsockopt(2)\fp for more information. the retrieved value is stored in the structure pointed by \fiopval\fp and of length \fioptlen\fp\&. .sp \fibpf_socket\fp should be one of the following: .indent 7.0 .ip \(bu 2 \fbstruct bpf_sock_ops\fp for \fbbpf_prog_type_sock_ops\fp\&. .ip \(bu 2 \fbstruct bpf_sock_addr\fp for \fbbpf_cgroup_inet4_connect\fp and \fbbpf_cgroup_inet6_connect\fp\&. .unindent .sp this helper actually implements a subset of \fbgetsockopt()\fp\&. it supports the following \filevel\fps: .indent 7.0 .ip \(bu 2 \fbipproto_tcp\fp, which supports \fioptname\fp \fbtcp_congestion\fp\&. .ip \(bu 2 \fbipproto_ip\fp, which supports \fioptname\fp \fbip_tos\fp\&. .ip \(bu 2 \fbipproto_ipv6\fp, which supports \fioptname\fp \fbipv6_tclass\fp\&. .unindent .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_override_return(struct pt_regs *\fp\firegs\fp\fb, u64\fp \firc\fp\fb)\fp .indent 7.0 .tp .b description used for error injection, this helper uses kprobes to override the return value of the probed function, and to set it to \firc\fp\&. the first argument is the context \firegs\fp on which the kprobe works. .sp this helper works by setting the pc (program counter) to an override function which is run in place of the original probed function. this means the probed function is not run at all. the replacement function just returns with the required value. .sp this helper has security implications, and thus is subject to restrictions. it is only available if the kernel was compiled with the \fbconfig_bpf_kprobe_override\fp configuration option, and in this case it only works on functions tagged with \fballow_error_injection\fp in the kernel code. .sp also, the helper is only available for the architectures having the config_function_error_injection option. as of this writing, x86 architecture is the only one to support this feature. .tp .b return 0 .unindent .tp .b \fblong bpf_sock_ops_cb_flags_set(struct bpf_sock_ops *\fp\fibpf_sock\fp\fb, int\fp \fiargval\fp\fb)\fp .indent 7.0 .tp .b description attempt to set the value of the \fbbpf_sock_ops_cb_flags\fp field for the full tcp socket associated to \fibpf_sock_ops\fp to \fiargval\fp\&. .sp the primary use of this field is to determine if there should be calls to ebpf programs of type \fbbpf_prog_type_sock_ops\fp at various points in the tcp code. a program of the same type can change its value, per connection and as necessary, when the connection is established. this field is directly accessible for reading, but this helper must be used for updates in order to return an error if an ebpf program tries to set a callback that is not supported in the current kernel. .sp \fiargval\fp is a flag array which can combine these flags: .indent 7.0 .ip \(bu 2 \fbbpf_sock_ops_rto_cb_flag\fp (retransmission time out) .ip \(bu 2 \fbbpf_sock_ops_retrans_cb_flag\fp (retransmission) .ip \(bu 2 \fbbpf_sock_ops_state_cb_flag\fp (tcp state change) .ip \(bu 2 \fbbpf_sock_ops_rtt_cb_flag\fp (every rtt) .unindent .sp therefore, this function can be used to clear a callback flag by setting the appropriate bit to zero. e.g. to disable the rto callback: .indent 7.0 .tp .b \fbbpf_sock_ops_cb_flags_set(bpf_sock,\fp \fbbpf_sock\->bpf_sock_ops_cb_flags & ~bpf_sock_ops_rto_cb_flag)\fp .unindent .sp here are some examples of where one could call such ebpf program: .indent 7.0 .ip \(bu 2 when rto fires. .ip \(bu 2 when a packet is retransmitted. .ip \(bu 2 when the connection terminates. .ip \(bu 2 when a packet is sent. .ip \(bu 2 when a packet is received. .unindent .tp .b return code \fb\-einval\fp if the socket is not a full tcp socket; otherwise, a positive number containing the bits that could not be set is returned (which comes down to 0 if all bits were set as required). .unindent .tp .b \fblong bpf_msg_redirect_map(struct sk_msg_buff *\fp\fimsg\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u32\fp \fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description this helper is used in programs implementing policies at the socket level. if the message \fimsg\fp is allowed to pass (i.e. if the verdict ebpf program returns \fbsk_pass\fp), redirect it to the socket referenced by \fimap\fp (of type \fbbpf_map_type_sockmap\fp) at index \fikey\fp\&. both ingress and egress interfaces can be used for redirection. the \fbbpf_f_ingress\fp value in \fiflags\fp is used to make the distinction (ingress path is selected if the flag is present, egress path otherwise). this is the only flag supported for now. .tp .b return \fbsk_pass\fp on success, or \fbsk_drop\fp on error. .unindent .tp .b \fblong bpf_msg_apply_bytes(struct sk_msg_buff *\fp\fimsg\fp\fb, u32\fp \fibytes\fp\fb)\fp .indent 7.0 .tp .b description for socket policies, apply the verdict of the ebpf program to the next \fibytes\fp (number of bytes) of message \fimsg\fp\&. .sp for example, this helper can be used in the following cases: .indent 7.0 .ip \(bu 2 a single \fbsendmsg\fp() or \fbsendfile\fp() system call contains multiple logical messages that the ebpf program is supposed to read and for which it should apply a verdict. .ip \(bu 2 an ebpf program only cares to read the first \fibytes\fp of a \fimsg\fp\&. if the message has a large payload, then setting up and calling the ebpf program repeatedly for all bytes, even though the verdict is already known, would create unnecessary overhead. .unindent .sp when called from within an ebpf program, the helper sets a counter internal to the bpf infrastructure, that is used to apply the last verdict to the next \fibytes\fp\&. if \fibytes\fp is smaller than the current data being processed from a \fbsendmsg\fp() or \fbsendfile\fp() system call, the first \fibytes\fp will be sent and the ebpf program will be re\-run with the pointer for start of data pointing to byte number \fibytes\fp \fb+ 1\fp\&. if \fibytes\fp is larger than the current data being processed, then the ebpf verdict will be applied to multiple \fbsendmsg\fp() or \fbsendfile\fp() calls until \fibytes\fp are consumed. .sp note that if a socket closes with the internal counter holding a non\-zero value, this is not a problem because data is not being buffered for \fibytes\fp and is sent as it is received. .tp .b return 0 .unindent .tp .b \fblong bpf_msg_cork_bytes(struct sk_msg_buff *\fp\fimsg\fp\fb, u32\fp \fibytes\fp\fb)\fp .indent 7.0 .tp .b description for socket policies, prevent the execution of the verdict ebpf program for message \fimsg\fp until \fibytes\fp (byte number) have been accumulated. .sp this can be used when one needs a specific number of bytes before a verdict can be assigned, even if the data spans multiple \fbsendmsg\fp() or \fbsendfile\fp() calls. the extreme case would be a user calling \fbsendmsg\fp() repeatedly with 1\-byte long message segments. obviously, this is bad for performance, but it is still valid. if the ebpf program needs \fibytes\fp bytes to validate a header, this helper can be used to prevent the ebpf program to be called again until \fibytes\fp have been accumulated. .tp .b return 0 .unindent .tp .b \fblong bpf_msg_pull_data(struct sk_msg_buff *\fp\fimsg\fp\fb, u32\fp \fistart\fp\fb, u32\fp \fiend\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description for socket policies, pull in non\-linear data from user space for \fimsg\fp and set pointers \fimsg\fp\fb\->data\fp and \fimsg\fp\fb\->data_end\fp to \fistart\fp and \fiend\fp bytes offsets into \fimsg\fp, respectively. .sp if a program of type \fbbpf_prog_type_sk_msg\fp is run on a \fimsg\fp it can only parse data that the (\fbdata\fp, \fbdata_end\fp) pointers have already consumed. for \fbsendmsg\fp() hooks this is likely the first scatterlist element. but for calls relying on the \fbsendpage\fp handler (e.g. \fbsendfile\fp()) this will be the range (\fb0\fp, \fb0\fp) because the data is shared with user space and by default the objective is to avoid allowing user space to modify data while (or after) ebpf verdict is being decided. this helper can be used to pull in data and to set the start and end pointer to given values. data will be copied if necessary (i.e. if data was not linear and if start and end pointers do not point to the same chunk). .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .sp all values for \fiflags\fp are reserved for future usage, and must be left at zero. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_bind(struct bpf_sock_addr *\fp\fictx\fp\fb, struct sockaddr *\fp\fiaddr\fp\fb, int\fp \fiaddr_len\fp\fb)\fp .indent 7.0 .tp .b description bind the socket associated to \fictx\fp to the address pointed by \fiaddr\fp, of length \fiaddr_len\fp\&. this allows for making outgoing connection from the desired ip address, which can be useful for example when all processes inside a cgroup should use one single ip address on a host that has multiple ip configured. .sp this helper works for ipv4 and ipv6, tcp and udp sockets. the domain (\fiaddr\fp\fb\->sa_family\fp) must be \fbaf_inet\fp (or \fbaf_inet6\fp). it\(aqs advised to pass zero port (\fbsin_port\fp or \fbsin6_port\fp) which triggers ip_bind_address_no_port\-like behavior and lets the kernel efficiently pick up an unused port as long as 4\-tuple is unique. passing non\-zero port might lead to degraded performance. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_xdp_adjust_tail(struct xdp_buff *\fp\fixdp_md\fp\fb, int\fp \fidelta\fp\fb)\fp .indent 7.0 .tp .b description adjust (move) \fixdp_md\fp\fb\->data_end\fp by \fidelta\fp bytes. it is possible to both shrink and grow the packet tail. shrink done via \fidelta\fp being a negative integer. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_get_xfrm_state(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fiindex\fp\fb, struct bpf_xfrm_state *\fp\fixfrm_state\fp\fb, u32\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description retrieve the xfrm state (ip transform framework, see also \fbip\-xfrm(8)\fp) at \fiindex\fp in xfrm "security path" for \fiskb\fp\&. .sp the retrieved value is stored in the \fbstruct bpf_xfrm_state\fp pointed by \fixfrm_state\fp and of length \fisize\fp\&. .sp all values for \fiflags\fp are reserved for future usage, and must be left at zero. .sp this helper is available only if the kernel was compiled with \fbconfig_xfrm\fp configuration option. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_get_stack(void *\fp\fictx\fp\fb, void *\fp\fibuf\fp\fb, u32\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description return a user or a kernel stack in bpf program provided buffer. to achieve this, the helper needs \fictx\fp, which is a pointer to the context on which the tracing program is executed. to store the stacktrace, the bpf program provides \fibuf\fp with a nonnegative \fisize\fp\&. .sp the last argument, \fiflags\fp, holds the number of stack frames to skip (from 0 to 255), masked with \fbbpf_f_skip_field_mask\fp\&. the next bits can be used to set the following flags: .indent 7.0 .tp .b \fbbpf_f_user_stack\fp collect a user space stack instead of a kernel stack. .tp .b \fbbpf_f_user_build_id\fp collect buildid+offset instead of ips for user stack, only valid if \fbbpf_f_user_stack\fp is also specified. .unindent .sp \fbbpf_get_stack\fp() can collect up to \fbperf_max_stack_depth\fp both kernel and user frames, subject to sufficient large buffer size. note that this limit can be controlled with the \fbsysctl\fp program, and that it should be manually increased in order to profile long user stacks (such as stacks for java programs). to do so, use: .indent 7.0 .indent 3.5 .sp .nf .ft c # sysctl kernel.perf_event_max_stack= .ft p .fi .unindent .unindent .tp .b return a non\-negative value equal to or less than \fisize\fp on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_skb_load_bytes_relative(const void *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, void *\fp\fito\fp\fb, u32\fp \filen\fp\fb, u32\fp \fistart_header\fp\fb)\fp .indent 7.0 .tp .b description this helper is similar to \fbbpf_skb_load_bytes\fp() in that it provides an easy way to load \filen\fp bytes from \fioffset\fp from the packet associated to \fiskb\fp, into the buffer pointed by \fito\fp\&. the difference to \fbbpf_skb_load_bytes\fp() is that a fifth argument \fistart_header\fp exists in order to select a base offset to start from. \fistart_header\fp can be one of: .indent 7.0 .tp .b \fbbpf_hdr_start_mac\fp base offset to load data from is \fiskb\fp\(aqs mac header. .tp .b \fbbpf_hdr_start_net\fp base offset to load data from is \fiskb\fp\(aqs network header. .unindent .sp in general, "direct packet access" is the preferred method to access packet data, however, this helper is in particular useful in socket filters where \fiskb\fp\fb\->data\fp does not always point to the start of the mac header and where "direct packet access" is not available. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_fib_lookup(void *\fp\fictx\fp\fb, struct bpf_fib_lookup *\fp\fiparams\fp\fb, int\fp \fiplen\fp\fb, u32\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description do fib lookup in kernel tables using parameters in \fiparams\fp\&. if lookup is successful and result shows packet is to be forwarded, the neighbor tables are searched for the nexthop. if successful (ie., fib lookup shows forwarding and nexthop is resolved), the nexthop address is returned in ipv4_dst or ipv6_dst based on family, smac is set to mac address of egress device, dmac is set to nexthop mac address, rt_metric is set to metric from route (ipv4/ipv6 only), and ifindex is set to the device index of the nexthop from the fib lookup. .sp \fiplen\fp argument is the size of the passed in struct. \fiflags\fp argument can be a combination of one or more of the following values: .indent 7.0 .tp .b \fbbpf_fib_lookup_direct\fp do a direct table lookup vs full lookup using fib rules. .tp .b \fbbpf_fib_lookup_output\fp perform lookup from an egress perspective (default is ingress). .unindent .sp \fictx\fp is either \fbstruct xdp_md\fp for xdp programs or \fbstruct sk_buff\fp tc cls_act programs. .tp .b return .indent 7.0 .ip \(bu 2 < 0 if any input argument is invalid .ip \(bu 2 0 on success (packet is forwarded, nexthop neighbor exists) .ip \(bu 2 > 0 one of \fbbpf_fib_lkup_ret_\fp codes explaining why the packet is not forwarded or needs assist from full stack .unindent .unindent .tp .b \fblong bpf_sock_hash_update(struct bpf_sock_ops *\fp\fiskops\fp\fb, struct bpf_map *\fp\fimap\fp\fb, void *\fp\fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description add an entry to, or update a sockhash \fimap\fp referencing sockets. the \fiskops\fp is used as a new value for the entry associated to \fikey\fp\&. \fiflags\fp is one of: .indent 7.0 .tp .b \fbbpf_noexist\fp the entry for \fikey\fp must not exist in the map. .tp .b \fbbpf_exist\fp the entry for \fikey\fp must already exist in the map. .tp .b \fbbpf_any\fp no condition on the existence of the entry for \fikey\fp\&. .unindent .sp if the \fimap\fp has ebpf programs (parser and verdict), those will be inherited by the socket being added. if the socket is already attached to ebpf programs, this results in an error. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_msg_redirect_hash(struct sk_msg_buff *\fp\fimsg\fp\fb, struct bpf_map *\fp\fimap\fp\fb, void *\fp\fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description this helper is used in programs implementing policies at the socket level. if the message \fimsg\fp is allowed to pass (i.e. if the verdict ebpf program returns \fbsk_pass\fp), redirect it to the socket referenced by \fimap\fp (of type \fbbpf_map_type_sockhash\fp) using hash \fikey\fp\&. both ingress and egress interfaces can be used for redirection. the \fbbpf_f_ingress\fp value in \fiflags\fp is used to make the distinction (ingress path is selected if the flag is present, egress path otherwise). this is the only flag supported for now. .tp .b return \fbsk_pass\fp on success, or \fbsk_drop\fp on error. .unindent .tp .b \fblong bpf_sk_redirect_hash(struct sk_buff *\fp\fiskb\fp\fb, struct bpf_map *\fp\fimap\fp\fb, void *\fp\fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description this helper is used in programs implementing policies at the skb socket level. if the sk_buff \fiskb\fp is allowed to pass (i.e. if the verdict ebpf program returns \fbsk_pass\fp), redirect it to the socket referenced by \fimap\fp (of type \fbbpf_map_type_sockhash\fp) using hash \fikey\fp\&. both ingress and egress interfaces can be used for redirection. the \fbbpf_f_ingress\fp value in \fiflags\fp is used to make the distinction (ingress path is selected if the flag is present, egress otherwise). this is the only flag supported for now. .tp .b return \fbsk_pass\fp on success, or \fbsk_drop\fp on error. .unindent .tp .b \fblong bpf_lwt_push_encap(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fitype\fp\fb, void *\fp\fihdr\fp\fb, u32\fp \filen\fp\fb)\fp .indent 7.0 .tp .b description encapsulate the packet associated to \fiskb\fp within a layer 3 protocol header. this header is provided in the buffer at address \fihdr\fp, with \filen\fp its size in bytes. \fitype\fp indicates the protocol of the header and can be one of: .indent 7.0 .tp .b \fbbpf_lwt_encap_seg6\fp ipv6 encapsulation with segment routing header (\fbstruct ipv6_sr_hdr\fp). \fihdr\fp only contains the srh, the ipv6 header is computed by the kernel. .tp .b \fbbpf_lwt_encap_seg6_inline\fp only works if \fiskb\fp contains an ipv6 packet. insert a segment routing header (\fbstruct ipv6_sr_hdr\fp) inside the ipv6 header. .tp .b \fbbpf_lwt_encap_ip\fp ip encapsulation (gre/gue/ipip/etc). the outer header must be ipv4 or ipv6, followed by zero or more additional headers, up to \fblwt_bpf_max_headroom\fp total bytes in all prepended headers. please note that if \fbskb_is_gso\fp(\fiskb\fp) is true, no more than two headers can be prepended, and the inner header, if present, should be either gre or udp/gue. .unindent .sp \fbbpf_lwt_encap_seg6\fp* types can be called by bpf programs of type \fbbpf_prog_type_lwt_in\fp; \fbbpf_lwt_encap_ip\fp type can be called by bpf programs of types \fbbpf_prog_type_lwt_in\fp and \fbbpf_prog_type_lwt_xmit\fp\&. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_lwt_seg6_store_bytes(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, const void *\fp\fifrom\fp\fb, u32\fp \filen\fp\fb)\fp .indent 7.0 .tp .b description store \filen\fp bytes from address \fifrom\fp into the packet associated to \fiskb\fp, at \fioffset\fp\&. only the flags, tag and tlvs inside the outermost ipv6 segment routing header can be modified through this helper. .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_lwt_seg6_adjust_srh(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fioffset\fp\fb, s32\fp \fidelta\fp\fb)\fp .indent 7.0 .tp .b description adjust the size allocated to tlvs in the outermost ipv6 segment routing header contained in the packet associated to \fiskb\fp, at position \fioffset\fp by \fidelta\fp bytes. only offsets after the segments are accepted. \fidelta\fp can be as well positive (growing) as negative (shrinking). .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_lwt_seg6_action(struct sk_buff *\fp\fiskb\fp\fb, u32\fp \fiaction\fp\fb, void *\fp\fiparam\fp\fb, u32\fp \fiparam_len\fp\fb)\fp .indent 7.0 .tp .b description apply an ipv6 segment routing action of type \fiaction\fp to the packet associated to \fiskb\fp\&. each action takes a parameter contained at address \fiparam\fp, and of length \fiparam_len\fp bytes. \fiaction\fp can be one of: .indent 7.0 .tp .b \fbseg6_local_action_end_x\fp end.x action: endpoint with layer\-3 cross\-connect. type of \fiparam\fp: \fbstruct in6_addr\fp\&. .tp .b \fbseg6_local_action_end_t\fp end.t action: endpoint with specific ipv6 table lookup. type of \fiparam\fp: \fbint\fp\&. .tp .b \fbseg6_local_action_end_b6\fp end.b6 action: endpoint bound to an srv6 policy. type of \fiparam\fp: \fbstruct ipv6_sr_hdr\fp\&. .tp .b \fbseg6_local_action_end_b6_encap\fp end.b6.encap action: endpoint bound to an srv6 encapsulation policy. type of \fiparam\fp: \fbstruct ipv6_sr_hdr\fp\&. .unindent .sp a call to this helper is susceptible to change the underlying packet buffer. therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_rc_repeat(void *\fp\fictx\fp\fb)\fp .indent 7.0 .tp .b description this helper is used in programs implementing ir decoding, to report a successfully decoded repeat key message. this delays the generation of a key up event for previously generated key down event. .sp some ir protocols like nec have a special ir message for repeating last button, for when a button is held down. .sp the \fictx\fp should point to the lirc sample as passed into the program. .sp this helper is only available is the kernel was compiled with the \fbconfig_bpf_lirc_mode2\fp configuration option set to "\fby\fp". .tp .b return 0 .unindent .tp .b \fblong bpf_rc_keydown(void *\fp\fictx\fp\fb, u32\fp \fiprotocol\fp\fb, u64\fp \fiscancode\fp\fb, u32\fp \fitoggle\fp\fb)\fp .indent 7.0 .tp .b description this helper is used in programs implementing ir decoding, to report a successfully decoded key press with \fiscancode\fp, \fitoggle\fp value in the given \fiprotocol\fp\&. the scancode will be translated to a keycode using the rc keymap, and reported as an input key down event. after a period a key up event is generated. this period can be extended by calling either \fbbpf_rc_keydown\fp() again with the same values, or calling \fbbpf_rc_repeat\fp(). .sp some protocols include a toggle bit, in case the button was released and pressed again between consecutive scancodes. .sp the \fictx\fp should point to the lirc sample as passed into the program. .sp the \fiprotocol\fp is the decoded protocol number (see \fbenum rc_proto\fp for some predefined values). .sp this helper is only available is the kernel was compiled with the \fbconfig_bpf_lirc_mode2\fp configuration option set to "\fby\fp". .tp .b return 0 .unindent .tp .b \fbu64 bpf_skb_cgroup_id(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description return the cgroup v2 id of the socket associated with the \fiskb\fp\&. this is roughly similar to the \fbbpf_get_cgroup_classid\fp() helper for cgroup v1 by providing a tag resp. identifier that can be matched on or used for map lookups e.g. to implement policy. the cgroup v2 id of a given path in the hierarchy is exposed in user space through the f_handle api in order to get to the same 64\-bit id. .sp this helper can be used on tc egress path, but not on ingress, and is available only if the kernel was compiled with the \fbconfig_sock_cgroup_data\fp configuration option. .tp .b return the id is returned or 0 in case the id could not be retrieved. .unindent .tp .b \fbu64 bpf_get_current_cgroup_id(void)\fp .indent 7.0 .tp .b return a 64\-bit integer containing the current cgroup id based on the cgroup within which the current task is running. .unindent .tp .b \fbvoid *bpf_get_local_storage(void *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description get the pointer to the local storage area. the type and the size of the local storage is defined by the \fimap\fp argument. the \fiflags\fp meaning is specific for each map type, and has to be 0 for cgroup local storage. .sp depending on the bpf program type, a local storage area can be shared between multiple instances of the bpf program, running simultaneously. .sp a user should care about the synchronization by himself. for example, by using the \fbbpf_stx_xadd\fp instruction to alter the shared data. .tp .b return a pointer to the local storage area. .unindent .tp .b \fblong bpf_sk_select_reuseport(struct sk_reuseport_md *\fp\fireuse\fp\fb, struct bpf_map *\fp\fimap\fp\fb, void *\fp\fikey\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description select a \fbso_reuseport\fp socket from a \fbbpf_map_type_reuseport_array\fp \fimap\fp\&. it checks the selected socket is matching the incoming request in the socket buffer. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbu64 bpf_skb_ancestor_cgroup_id(struct sk_buff *\fp\fiskb\fp\fb, int\fp \fiancestor_level\fp\fb)\fp .indent 7.0 .tp .b description return id of cgroup v2 that is ancestor of cgroup associated with the \fiskb\fp at the \fiancestor_level\fp\&. the root cgroup is at \fiancestor_level\fp zero and each step down the hierarchy increments the level. if \fiancestor_level\fp == level of cgroup associated with \fiskb\fp, then return value will be same as that of \fbbpf_skb_cgroup_id\fp(). .sp the helper is useful to implement policies based on cgroups that are upper in hierarchy than immediate cgroup associated with \fiskb\fp\&. .sp the format of returned id and helper limitations are same as in \fbbpf_skb_cgroup_id\fp(). .tp .b return the id is returned or 0 in case the id could not be retrieved. .unindent .tp .b \fbstruct bpf_sock *bpf_sk_lookup_tcp(void *\fp\fictx\fp\fb, struct bpf_sock_tuple *\fp\fituple\fp\fb, u32\fp \fituple_size\fp\fb, u64\fp \finetns\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description look for tcp socket matching \fituple\fp, optionally in a child network namespace \finetns\fp\&. the return value must be checked, and if non\-\fbnull\fp, released via \fbbpf_sk_release\fp(). .sp the \fictx\fp should point to the context of the program, such as the skb or socket (depending on the hook in use). this is used to determine the base network namespace for the lookup. .sp \fituple_size\fp must be one of: .indent 7.0 .tp .b \fbsizeof\fp(\fituple\fp\fb\->ipv4\fp) look for an ipv4 socket. .tp .b \fbsizeof\fp(\fituple\fp\fb\->ipv6\fp) look for an ipv6 socket. .unindent .sp if the \finetns\fp is a negative signed 32\-bit integer, then the socket lookup table in the netns associated with the \fictx\fp will be used. for the tc hooks, this is the netns of the device in the skb. for socket hooks, this is the netns of the socket. if \finetns\fp is any other signed 32\-bit value greater than or equal to zero then it specifies the id of the netns relative to the netns associated with the \fictx\fp\&. \finetns\fp values beyond the range of 32\-bit integers are reserved for future use. .sp all values for \fiflags\fp are reserved for future usage, and must be left at zero. .sp this helper is available only if the kernel was compiled with \fbconfig_net\fp configuration option. .tp .b return pointer to \fbstruct bpf_sock\fp, or \fbnull\fp in case of failure. for sockets with reuseport option, the \fbstruct bpf_sock\fp result is from \fireuse\fp\fb\->socks\fp[] using the hash of the tuple. .unindent .tp .b \fbstruct bpf_sock *bpf_sk_lookup_udp(void *\fp\fictx\fp\fb, struct bpf_sock_tuple *\fp\fituple\fp\fb, u32\fp \fituple_size\fp\fb, u64\fp \finetns\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description look for udp socket matching \fituple\fp, optionally in a child network namespace \finetns\fp\&. the return value must be checked, and if non\-\fbnull\fp, released via \fbbpf_sk_release\fp(). .sp the \fictx\fp should point to the context of the program, such as the skb or socket (depending on the hook in use). this is used to determine the base network namespace for the lookup. .sp \fituple_size\fp must be one of: .indent 7.0 .tp .b \fbsizeof\fp(\fituple\fp\fb\->ipv4\fp) look for an ipv4 socket. .tp .b \fbsizeof\fp(\fituple\fp\fb\->ipv6\fp) look for an ipv6 socket. .unindent .sp if the \finetns\fp is a negative signed 32\-bit integer, then the socket lookup table in the netns associated with the \fictx\fp will be used. for the tc hooks, this is the netns of the device in the skb. for socket hooks, this is the netns of the socket. if \finetns\fp is any other signed 32\-bit value greater than or equal to zero then it specifies the id of the netns relative to the netns associated with the \fictx\fp\&. \finetns\fp values beyond the range of 32\-bit integers are reserved for future use. .sp all values for \fiflags\fp are reserved for future usage, and must be left at zero. .sp this helper is available only if the kernel was compiled with \fbconfig_net\fp configuration option. .tp .b return pointer to \fbstruct bpf_sock\fp, or \fbnull\fp in case of failure. for sockets with reuseport option, the \fbstruct bpf_sock\fp result is from \fireuse\fp\fb\->socks\fp[] using the hash of the tuple. .unindent .tp .b \fblong bpf_sk_release(struct bpf_sock *\fp\fisock\fp\fb)\fp .indent 7.0 .tp .b description release the reference held by \fisock\fp\&. \fisock\fp must be a non\-\fbnull\fp pointer that was returned from \fbbpf_sk_lookup_xxx\fp(). .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_map_push_elem(struct bpf_map *\fp\fimap\fp\fb, const void *\fp\fivalue\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description push an element \fivalue\fp in \fimap\fp\&. \fiflags\fp is one of: .indent 7.0 .tp .b \fbbpf_exist\fp if the queue/stack is full, the oldest element is removed to make room for this. .unindent .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_map_pop_elem(struct bpf_map *\fp\fimap\fp\fb, void *\fp\fivalue\fp\fb)\fp .indent 7.0 .tp .b description pop an element from \fimap\fp\&. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_map_peek_elem(struct bpf_map *\fp\fimap\fp\fb, void *\fp\fivalue\fp\fb)\fp .indent 7.0 .tp .b description get an element from \fimap\fp without removing it. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_msg_push_data(struct sk_msg_buff *\fp\fimsg\fp\fb, u32\fp \fistart\fp\fb, u32\fp \filen\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description for socket policies, insert \filen\fp bytes into \fimsg\fp at offset \fistart\fp\&. .sp if a program of type \fbbpf_prog_type_sk_msg\fp is run on a \fimsg\fp it may want to insert metadata or options into the \fimsg\fp\&. this can later be read and used by any of the lower layer bpf hooks. .sp this helper may fail if under memory pressure (a malloc fails) in these cases bpf programs will get an appropriate error and bpf programs will need to handle them. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_msg_pop_data(struct sk_msg_buff *\fp\fimsg\fp\fb, u32\fp \fistart\fp\fb, u32\fp \filen\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description will remove \filen\fp bytes from a \fimsg\fp starting at byte \fistart\fp\&. this may result in \fbenomem\fp errors under certain situations if an allocation and copy are required due to a full ring buffer. however, the helper will try to avoid doing the allocation if possible. other errors can occur if input parameters are invalid either due to \fistart\fp byte not being valid part of \fimsg\fp payload and/or \fipop\fp value being to large. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_rc_pointer_rel(void *\fp\fictx\fp\fb, s32\fp \firel_x\fp\fb, s32\fp \firel_y\fp\fb)\fp .indent 7.0 .tp .b description this helper is used in programs implementing ir decoding, to report a successfully decoded pointer movement. .sp the \fictx\fp should point to the lirc sample as passed into the program. .sp this helper is only available is the kernel was compiled with the \fbconfig_bpf_lirc_mode2\fp configuration option set to "\fby\fp". .tp .b return 0 .unindent .tp .b \fblong bpf_spin_lock(struct bpf_spin_lock *\fp\filock\fp\fb)\fp .indent 7.0 .tp .b description acquire a spinlock represented by the pointer \filock\fp, which is stored as part of a value of a map. taking the lock allows to safely update the rest of the fields in that value. the spinlock can (and must) later be released with a call to \fbbpf_spin_unlock\fp(\filock\fp). .sp spinlocks in bpf programs come with a number of restrictions and constraints: .indent 7.0 .ip \(bu 2 \fbbpf_spin_lock\fp objects are only allowed inside maps of types \fbbpf_map_type_hash\fp and \fbbpf_map_type_array\fp (this list could be extended in the future). .ip \(bu 2 btf description of the map is mandatory. .ip \(bu 2 the bpf program can take one lock at a time, since taking two or more could cause dead locks. .ip \(bu 2 only one \fbstruct bpf_spin_lock\fp is allowed per map element. .ip \(bu 2 when the lock is taken, calls (either bpf to bpf or helpers) are not allowed. .ip \(bu 2 the \fbbpf_ld_abs\fp and \fbbpf_ld_ind\fp instructions are not allowed inside a spinlock\-ed region. .ip \(bu 2 the bpf program must call \fbbpf_spin_unlock\fp() to release the lock, on all execution paths, before it returns. .ip \(bu 2 the bpf program can access \fbstruct bpf_spin_lock\fp only via the \fbbpf_spin_lock\fp() and \fbbpf_spin_unlock\fp() helpers. loading or storing data into the \fbstruct bpf_spin_lock\fp \filock\fp\fb;\fp field of a map is not allowed. .ip \(bu 2 to use the \fbbpf_spin_lock\fp() helper, the btf description of the map value must be a struct and have \fbstruct bpf_spin_lock\fp \fianyname\fp\fb;\fp field at the top level. nested lock inside another struct is not allowed. .ip \(bu 2 the \fbstruct bpf_spin_lock\fp \filock\fp field in a map value must be aligned on a multiple of 4 bytes in that value. .ip \(bu 2 syscall with command \fbbpf_map_lookup_elem\fp does not copy the \fbbpf_spin_lock\fp field to user space. .ip \(bu 2 syscall with command \fbbpf_map_update_elem\fp, or update from a bpf program, do not update the \fbbpf_spin_lock\fp field. .ip \(bu 2 \fbbpf_spin_lock\fp cannot be on the stack or inside a networking packet (it can only be inside of a map values). .ip \(bu 2 \fbbpf_spin_lock\fp is available to root only. .ip \(bu 2 tracing programs and socket filter programs cannot use \fbbpf_spin_lock\fp() due to insufficient preemption checks (but this may change in the future). .ip \(bu 2 \fbbpf_spin_lock\fp is not allowed in inner maps of map\-in\-map. .unindent .tp .b return 0 .unindent .tp .b \fblong bpf_spin_unlock(struct bpf_spin_lock *\fp\filock\fp\fb)\fp .indent 7.0 .tp .b description release the \filock\fp previously locked by a call to \fbbpf_spin_lock\fp(\filock\fp). .tp .b return 0 .unindent .tp .b \fbstruct bpf_sock *bpf_sk_fullsock(struct bpf_sock *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description this helper gets a \fbstruct bpf_sock\fp pointer such that all the fields in this \fbbpf_sock\fp can be accessed. .tp .b return a \fbstruct bpf_sock\fp pointer on success, or \fbnull\fp in case of failure. .unindent .tp .b \fbstruct bpf_tcp_sock *bpf_tcp_sock(struct bpf_sock *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description this helper gets a \fbstruct bpf_tcp_sock\fp pointer from a \fbstruct bpf_sock\fp pointer. .tp .b return a \fbstruct bpf_tcp_sock\fp pointer on success, or \fbnull\fp in case of failure. .unindent .tp .b \fblong bpf_skb_ecn_set_ce(struct sk_buff *\fp\fiskb\fp\fb)\fp .indent 7.0 .tp .b description set ecn (explicit congestion notification) field of ip header to \fbce\fp (congestion encountered) if current value is \fbect\fp (ecn capable transport). otherwise, do nothing. works with ipv6 and ipv4. .tp .b return 1 if the \fbce\fp flag is set (either by the current helper call or because it was already present), 0 if it is not set. .unindent .tp .b \fbstruct bpf_sock *bpf_get_listener_sock(struct bpf_sock *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description return a \fbstruct bpf_sock\fp pointer in \fbtcp_listen\fp state. \fbbpf_sk_release\fp() is unnecessary and not allowed. .tp .b return a \fbstruct bpf_sock\fp pointer on success, or \fbnull\fp in case of failure. .unindent .tp .b \fbstruct bpf_sock *bpf_skc_lookup_tcp(void *\fp\fictx\fp\fb, struct bpf_sock_tuple *\fp\fituple\fp\fb, u32\fp \fituple_size\fp\fb, u64\fp \finetns\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description look for tcp socket matching \fituple\fp, optionally in a child network namespace \finetns\fp\&. the return value must be checked, and if non\-\fbnull\fp, released via \fbbpf_sk_release\fp(). .sp this function is identical to \fbbpf_sk_lookup_tcp\fp(), except that it also returns timewait or request sockets. use \fbbpf_sk_fullsock\fp() or \fbbpf_tcp_sock\fp() to access the full structure. .sp this helper is available only if the kernel was compiled with \fbconfig_net\fp configuration option. .tp .b return pointer to \fbstruct bpf_sock\fp, or \fbnull\fp in case of failure. for sockets with reuseport option, the \fbstruct bpf_sock\fp result is from \fireuse\fp\fb\->socks\fp[] using the hash of the tuple. .unindent .tp .b \fblong bpf_tcp_check_syncookie(struct bpf_sock *\fp\fisk\fp\fb, void *\fp\fiiph\fp\fb, u32\fp \fiiph_len\fp\fb, struct tcphdr *\fp\fith\fp\fb, u32\fp \fith_len\fp\fb)\fp .indent 7.0 .tp .b description check whether \fiiph\fp and \fith\fp contain a valid syn cookie ack for the listening socket in \fisk\fp\&. .sp \fiiph\fp points to the start of the ipv4 or ipv6 header, while \fiiph_len\fp contains \fbsizeof\fp(\fbstruct iphdr\fp) or \fbsizeof\fp(\fbstruct ip6hdr\fp). .sp \fith\fp points to the start of the tcp header, while \fith_len\fp contains \fbsizeof\fp(\fbstruct tcphdr\fp). .tp .b return 0 if \fiiph\fp and \fith\fp are a valid syn cookie ack, or a negative error otherwise. .unindent .tp .b \fblong bpf_sysctl_get_name(struct bpf_sysctl *\fp\fictx\fp\fb, char *\fp\fibuf\fp\fb, size_t\fp \fibuf_len\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description get name of sysctl in /proc/sys/ and copy it into provided by program buffer \fibuf\fp of size \fibuf_len\fp\&. .sp the buffer is always nul terminated, unless it\(aqs zero\-sized. .sp if \fiflags\fp is zero, full name (e.g. "net/ipv4/tcp_mem") is copied. use \fbbpf_f_sysctl_base_name\fp flag to copy base name only (e.g. "tcp_mem"). .tp .b return number of character copied (not including the trailing nul). .sp \fb\-e2big\fp if the buffer wasn\(aqt big enough (\fibuf\fp will contain truncated name in this case). .unindent .tp .b \fblong bpf_sysctl_get_current_value(struct bpf_sysctl *\fp\fictx\fp\fb, char *\fp\fibuf\fp\fb, size_t\fp \fibuf_len\fp\fb)\fp .indent 7.0 .tp .b description get current value of sysctl as it is presented in /proc/sys (incl. newline, etc), and copy it as a string into provided by program buffer \fibuf\fp of size \fibuf_len\fp\&. .sp the whole value is copied, no matter what file position user space issued e.g. sys_read at. .sp the buffer is always nul terminated, unless it\(aqs zero\-sized. .tp .b return number of character copied (not including the trailing nul). .sp \fb\-e2big\fp if the buffer wasn\(aqt big enough (\fibuf\fp will contain truncated name in this case). .sp \fb\-einval\fp if current value was unavailable, e.g. because sysctl is uninitialized and read returns \-eio for it. .unindent .tp .b \fblong bpf_sysctl_get_new_value(struct bpf_sysctl *\fp\fictx\fp\fb, char *\fp\fibuf\fp\fb, size_t\fp \fibuf_len\fp\fb)\fp .indent 7.0 .tp .b description get new value being written by user space to sysctl (before the actual write happens) and copy it as a string into provided by program buffer \fibuf\fp of size \fibuf_len\fp\&. .sp user space may write new value at file position > 0. .sp the buffer is always nul terminated, unless it\(aqs zero\-sized. .tp .b return number of character copied (not including the trailing nul). .sp \fb\-e2big\fp if the buffer wasn\(aqt big enough (\fibuf\fp will contain truncated name in this case). .sp \fb\-einval\fp if sysctl is being read. .unindent .tp .b \fblong bpf_sysctl_set_new_value(struct bpf_sysctl *\fp\fictx\fp\fb, const char *\fp\fibuf\fp\fb, size_t\fp \fibuf_len\fp\fb)\fp .indent 7.0 .tp .b description override new value being written by user space to sysctl with value provided by program in buffer \fibuf\fp of size \fibuf_len\fp\&. .sp \fibuf\fp should contain a string in same form as provided by user space on sysctl write. .sp user space may write new value at file position > 0. to override the whole sysctl value file position should be set to zero. .tp .b return 0 on success. .sp \fb\-e2big\fp if the \fibuf_len\fp is too big. .sp \fb\-einval\fp if sysctl is being read. .unindent .tp .b \fblong bpf_strtol(const char *\fp\fibuf\fp\fb, size_t\fp \fibuf_len\fp\fb, u64\fp \fiflags\fp\fb, long *\fp\fires\fp\fb)\fp .indent 7.0 .tp .b description convert the initial part of the string from buffer \fibuf\fp of size \fibuf_len\fp to a long integer according to the given base and save the result in \fires\fp\&. .sp the string may begin with an arbitrary amount of white space (as determined by \fbisspace\fp(3)) followed by a single optional \(aq\fb\-\fp\(aq sign. .sp five least significant bits of \fiflags\fp encode base, other bits are currently unused. .sp base must be either 8, 10, 16, or 0 to detect it automatically similar to user space \fbstrtol\fp(3). .tp .b return number of characters consumed on success. must be positive but no more than \fibuf_len\fp\&. .sp \fb\-einval\fp if no valid digits were found or unsupported base was provided. .sp \fb\-erange\fp if resulting value was out of range. .unindent .tp .b \fblong bpf_strtoul(const char *\fp\fibuf\fp\fb, size_t\fp \fibuf_len\fp\fb, u64\fp \fiflags\fp\fb, unsigned long *\fp\fires\fp\fb)\fp .indent 7.0 .tp .b description convert the initial part of the string from buffer \fibuf\fp of size \fibuf_len\fp to an unsigned long integer according to the given base and save the result in \fires\fp\&. .sp the string may begin with an arbitrary amount of white space (as determined by \fbisspace\fp(3)). .sp five least significant bits of \fiflags\fp encode base, other bits are currently unused. .sp base must be either 8, 10, 16, or 0 to detect it automatically similar to user space \fbstrtoul\fp(3). .tp .b return number of characters consumed on success. must be positive but no more than \fibuf_len\fp\&. .sp \fb\-einval\fp if no valid digits were found or unsupported base was provided. .sp \fb\-erange\fp if resulting value was out of range. .unindent .tp .b \fbvoid *bpf_sk_storage_get(struct bpf_map *\fp\fimap\fp\fb, struct bpf_sock *\fp\fisk\fp\fb, void *\fp\fivalue\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description get a bpf\-local\-storage from a \fisk\fp\&. .sp logically, it could be thought of getting the value from a \fimap\fp with \fisk\fp as the \fbkey\fp\&. from this perspective, the usage is not much different from \fbbpf_map_lookup_elem\fp(\fimap\fp, \fb&\fp\fisk\fp) except this helper enforces the key must be a full socket and the map must be a \fbbpf_map_type_sk_storage\fp also. .sp underneath, the value is stored locally at \fisk\fp instead of the \fimap\fp\&. the \fimap\fp is used as the bpf\-local\-storage "type". the bpf\-local\-storage "type" (i.e. the \fimap\fp) is searched against all bpf\-local\-storages residing at \fisk\fp\&. .sp an optional \fiflags\fp (\fbbpf_sk_storage_get_f_create\fp) can be used such that a new bpf\-local\-storage will be created if one does not exist. \fivalue\fp can be used together with \fbbpf_sk_storage_get_f_create\fp to specify the initial value of a bpf\-local\-storage. if \fivalue\fp is \fbnull\fp, the new bpf\-local\-storage will be zero initialized. .tp .b return a bpf\-local\-storage pointer is returned on success. .sp \fbnull\fp if not found or there was an error in adding a new bpf\-local\-storage. .unindent .tp .b \fblong bpf_sk_storage_delete(struct bpf_map *\fp\fimap\fp\fb, struct bpf_sock *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description delete a bpf\-local\-storage from a \fisk\fp\&. .tp .b return 0 on success. .sp \fb\-enoent\fp if the bpf\-local\-storage cannot be found. .unindent .tp .b \fblong bpf_send_signal(u32\fp \fisig\fp\fb)\fp .indent 7.0 .tp .b description send signal \fisig\fp to the process of the current task. the signal may be delivered to any of this process\(aqs threads. .tp .b return 0 on success or successfully queued. .sp \fb\-ebusy\fp if work queue under nmi is full. .sp \fb\-einval\fp if \fisig\fp is invalid. .sp \fb\-eperm\fp if no permission to send the \fisig\fp\&. .sp \fb\-eagain\fp if bpf program can try again. .unindent .tp .b \fbs64 bpf_tcp_gen_syncookie(struct bpf_sock *\fp\fisk\fp\fb, void *\fp\fiiph\fp\fb, u32\fp \fiiph_len\fp\fb, struct tcphdr *\fp\fith\fp\fb, u32\fp \fith_len\fp\fb)\fp .indent 7.0 .tp .b description try to issue a syn cookie for the packet with corresponding ip/tcp headers, \fiiph\fp and \fith\fp, on the listening socket in \fisk\fp\&. .sp \fiiph\fp points to the start of the ipv4 or ipv6 header, while \fiiph_len\fp contains \fbsizeof\fp(\fbstruct iphdr\fp) or \fbsizeof\fp(\fbstruct ip6hdr\fp). .sp \fith\fp points to the start of the tcp header, while \fith_len\fp contains the length of the tcp header. .tp .b return on success, lower 32 bits hold the generated syn cookie in followed by 16 bits which hold the mss value for that cookie, and the top 16 bits are unused. .sp on failure, the returned value is one of the following: .sp \fb\-einval\fp syn cookie cannot be issued due to error .sp \fb\-enoent\fp syn cookie should not be issued (no syn flood) .sp \fb\-eopnotsupp\fp kernel configuration does not enable syn cookies .sp \fb\-eprotonosupport\fp ip packet version is not 4 or 6 .unindent .tp .b \fblong bpf_skb_output(void *\fp\fictx\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb, void *\fp\fidata\fp\fb, u64\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description write raw \fidata\fp blob into a special bpf perf event held by \fimap\fp of type \fbbpf_map_type_perf_event_array\fp\&. this perf event must have the following attributes: \fbperf_sample_raw\fp as \fbsample_type\fp, \fbperf_type_software\fp as \fbtype\fp, and \fbperf_count_sw_bpf_output\fp as \fbconfig\fp\&. .sp the \fiflags\fp are used to indicate the index in \fimap\fp for which the value must be put, masked with \fbbpf_f_index_mask\fp\&. alternatively, \fiflags\fp can be set to \fbbpf_f_current_cpu\fp to indicate that the index of the current cpu core should be used. .sp the value to write, of \fisize\fp, is passed through ebpf stack and pointed by \fidata\fp\&. .sp \fictx\fp is a pointer to in\-kernel struct sk_buff. .sp this helper is similar to \fbbpf_perf_event_output\fp() but restricted to raw_tracepoint bpf programs. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_probe_read_user(void *\fp\fidst\fp\fb, u32\fp \fisize\fp\fb, const void *\fp\fiunsafe_ptr\fp\fb)\fp .indent 7.0 .tp .b description safely attempt to read \fisize\fp bytes from user space address \fiunsafe_ptr\fp and store the data in \fidst\fp\&. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_probe_read_kernel(void *\fp\fidst\fp\fb, u32\fp \fisize\fp\fb, const void *\fp\fiunsafe_ptr\fp\fb)\fp .indent 7.0 .tp .b description safely attempt to read \fisize\fp bytes from kernel space address \fiunsafe_ptr\fp and store the data in \fidst\fp\&. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_probe_read_user_str(void *\fp\fidst\fp\fb, u32\fp \fisize\fp\fb, const void *\fp\fiunsafe_ptr\fp\fb)\fp .indent 7.0 .tp .b description copy a nul terminated string from an unsafe user address \fiunsafe_ptr\fp to \fidst\fp\&. the \fisize\fp should include the terminating nul byte. in case the string length is smaller than \fisize\fp, the target is not padded with further nul bytes. if the string length is larger than \fisize\fp, just \fisize\fp\-1 bytes are copied and the last byte is set to nul. .sp on success, the length of the copied string is returned. this makes this helper useful in tracing programs for reading strings, and more importantly to get its length at runtime. see the following snippet: .indent 7.0 .indent 3.5 .sp .nf .ft c sec("kprobe/sys_open") void bpf_sys_open(struct pt_regs *ctx) { char buf[pathlen]; // pathlen is defined to 256 int res = bpf_probe_read_user_str(buf, sizeof(buf), ctx\->di); // consume buf, for example push it to // user space via bpf_perf_event_output(); we // can use res (the string length) as event // size, after checking its boundaries. } .ft p .fi .unindent .unindent .sp in comparison, using \fbbpf_probe_read_user\fp() helper here instead to read the string would require to estimate the length at compile time, and would often result in copying more memory than necessary. .sp another useful use case is when parsing individual process arguments or individual environment variables navigating \ficurrent\fp\fb\->mm\->arg_start\fp and \ficurrent\fp\fb\->mm\->env_start\fp: using this helper and the return value, one can quickly iterate at the right offset of the memory area. .tp .b return on success, the strictly positive length of the string, including the trailing nul character. on error, a negative value. .unindent .tp .b \fblong bpf_probe_read_kernel_str(void *\fp\fidst\fp\fb, u32\fp \fisize\fp\fb, const void *\fp\fiunsafe_ptr\fp\fb)\fp .indent 7.0 .tp .b description copy a nul terminated string from an unsafe kernel address \fiunsafe_ptr\fp to \fidst\fp\&. same semantics as with \fbbpf_probe_read_user_str\fp() apply. .tp .b return on success, the strictly positive length of the string, including the trailing nul character. on error, a negative value. .unindent .tp .b \fblong bpf_tcp_send_ack(void *\fp\fitp\fp\fb, u32\fp \fircv_nxt\fp\fb)\fp .indent 7.0 .tp .b description send out a tcp\-ack. \fitp\fp is the in\-kernel struct \fbtcp_sock\fp\&. \fircv_nxt\fp is the ack_seq to be sent out. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fblong bpf_send_signal_thread(u32\fp \fisig\fp\fb)\fp .indent 7.0 .tp .b description send signal \fisig\fp to the thread corresponding to the current task. .tp .b return 0 on success or successfully queued. .sp \fb\-ebusy\fp if work queue under nmi is full. .sp \fb\-einval\fp if \fisig\fp is invalid. .sp \fb\-eperm\fp if no permission to send the \fisig\fp\&. .sp \fb\-eagain\fp if bpf program can try again. .unindent .tp .b \fbu64 bpf_jiffies64(void)\fp .indent 7.0 .tp .b description obtain the 64bit jiffies .tp .b return the 64 bit jiffies .unindent .tp .b \fblong bpf_read_branch_records(struct bpf_perf_event_data *\fp\fictx\fp\fb, void *\fp\fibuf\fp\fb, u32\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description for an ebpf program attached to a perf event, retrieve the branch records (\fbstruct perf_branch_entry\fp) associated to \fictx\fp and store it in the buffer pointed by \fibuf\fp up to size \fisize\fp bytes. .tp .b return on success, number of bytes written to \fibuf\fp\&. on error, a negative value. .sp the \fiflags\fp can be set to \fbbpf_f_get_branch_records_size\fp to instead return the number of bytes required to store all the branch entries. if this flag is set, \fibuf\fp may be null. .sp \fb\-einval\fp if arguments invalid or \fbsize\fp not a multiple of \fbsizeof\fp(\fbstruct perf_branch_entry\fp). .sp \fb\-enoent\fp if architecture does not support branch records. .unindent .tp .b \fblong bpf_get_ns_current_pid_tgid(u64\fp \fidev\fp\fb, u64\fp \fiino\fp\fb, struct bpf_pidns_info *\fp\finsdata\fp\fb, u32\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description returns 0 on success, values for \fipid\fp and \fitgid\fp as seen from the current \finamespace\fp will be returned in \finsdata\fp\&. .tp .b return 0 on success, or one of the following in case of failure: .sp \fb\-einval\fp if dev and inum supplied don\(aqt match dev_t and inode number with nsfs of current task, or if dev conversion to dev_t lost high bits. .sp \fb\-enoent\fp if pidns does not exists for the current task. .unindent .tp .b \fblong bpf_xdp_output(void *\fp\fictx\fp\fb, struct bpf_map *\fp\fimap\fp\fb, u64\fp \fiflags\fp\fb, void *\fp\fidata\fp\fb, u64\fp \fisize\fp\fb)\fp .indent 7.0 .tp .b description write raw \fidata\fp blob into a special bpf perf event held by \fimap\fp of type \fbbpf_map_type_perf_event_array\fp\&. this perf event must have the following attributes: \fbperf_sample_raw\fp as \fbsample_type\fp, \fbperf_type_software\fp as \fbtype\fp, and \fbperf_count_sw_bpf_output\fp as \fbconfig\fp\&. .sp the \fiflags\fp are used to indicate the index in \fimap\fp for which the value must be put, masked with \fbbpf_f_index_mask\fp\&. alternatively, \fiflags\fp can be set to \fbbpf_f_current_cpu\fp to indicate that the index of the current cpu core should be used. .sp the value to write, of \fisize\fp, is passed through ebpf stack and pointed by \fidata\fp\&. .sp \fictx\fp is a pointer to in\-kernel struct xdp_buff. .sp this helper is similar to \fbbpf_perf_eventoutput\fp() but restricted to raw_tracepoint bpf programs. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbu64 bpf_get_netns_cookie(void *\fp\fictx\fp\fb)\fp .indent 7.0 .tp .b description retrieve the cookie (generated by the kernel) of the network namespace the input \fictx\fp is associated with. the network namespace cookie remains stable for its lifetime and provides a global identifier that can be assumed unique. if \fictx\fp is null, then the helper returns the cookie for the initial network namespace. the cookie itself is very similar to that of \fbbpf_get_socket_cookie\fp() helper, but for network namespaces instead of sockets. .tp .b return a 8\-byte long opaque number. .unindent .tp .b \fbu64 bpf_get_current_ancestor_cgroup_id(int\fp \fiancestor_level\fp\fb)\fp .indent 7.0 .tp .b description return id of cgroup v2 that is ancestor of the cgroup associated with the current task at the \fiancestor_level\fp\&. the root cgroup is at \fiancestor_level\fp zero and each step down the hierarchy increments the level. if \fiancestor_level\fp == level of cgroup associated with the current task, then return value will be the same as that of \fbbpf_get_current_cgroup_id\fp(). .sp the helper is useful to implement policies based on cgroups that are upper in hierarchy than immediate cgroup associated with the current task. .sp the format of returned id and helper limitations are same as in \fbbpf_get_current_cgroup_id\fp(). .tp .b return the id is returned or 0 in case the id could not be retrieved. .unindent .tp .b \fblong bpf_sk_assign(struct sk_buff *\fp\fiskb\fp\fb, struct bpf_sock *\fp\fisk\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description helper is overloaded depending on bpf program type. this description applies to \fbbpf_prog_type_sched_cls\fp and \fbbpf_prog_type_sched_act\fp programs. .sp assign the \fisk\fp to the \fiskb\fp\&. when combined with appropriate routing configuration to receive the packet towards the socket, will cause \fiskb\fp to be delivered to the specified socket. subsequent redirection of \fiskb\fp via \fbbpf_redirect\fp(), \fbbpf_clone_redirect\fp() or other methods outside of bpf may interfere with successful delivery to the socket. .sp this operation is only valid from tc ingress path. .sp the \fiflags\fp argument must be zero. .tp .b return 0 on success, or a negative error in case of failure: .sp \fb\-einval\fp if specified \fiflags\fp are not supported. .sp \fb\-enoent\fp if the socket is unavailable for assignment. .sp \fb\-enetunreach\fp if the socket is unreachable (wrong netns). .sp \fb\-eopnotsupp\fp if the operation is not supported, for example a call from outside of tc ingress. .sp \fb\-esocktnosupport\fp if the socket type is not supported (reuseport). .unindent .tp .b \fblong bpf_sk_assign(struct bpf_sk_lookup *\fp\fictx\fp\fb, struct bpf_sock *\fp\fisk\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description helper is overloaded depending on bpf program type. this description applies to \fbbpf_prog_type_sk_lookup\fp programs. .sp select the \fisk\fp as a result of a socket lookup. .sp for the operation to succeed passed socket must be compatible with the packet description provided by the \fictx\fp object. .sp l4 protocol (\fbipproto_tcp\fp or \fbipproto_udp\fp) must be an exact match. while ip family (\fbaf_inet\fp or \fbaf_inet6\fp) must be compatible, that is ipv6 sockets that are not v6\-only can be selected for ipv4 packets. .sp only tcp listeners and udp unconnected sockets can be selected. \fisk\fp can also be null to reset any previous selection. .sp \fiflags\fp argument can combination of following values: .indent 7.0 .ip \(bu 2 \fbbpf_sk_lookup_f_replace\fp to override the previous socket selection, potentially done by a bpf program that ran before us. .ip \(bu 2 \fbbpf_sk_lookup_f_no_reuseport\fp to skip load\-balancing within reuseport group for the socket being selected. .unindent .sp on success \fictx\->sk\fp will point to the selected socket. .tp .b return 0 on success, or a negative errno in case of failure. .indent 7.0 .ip \(bu 2 \fb\-eafnosupport\fp if socket family (\fisk\->family\fp) is not compatible with packet family (\fictx\->family\fp). .ip \(bu 2 \fb\-eexist\fp if socket has been already selected, potentially by another program, and \fbbpf_sk_lookup_f_replace\fp flag was not specified. .ip \(bu 2 \fb\-einval\fp if unsupported flags were specified. .ip \(bu 2 \fb\-eprototype\fp if socket l4 protocol (\fisk\->protocol\fp) doesn\(aqt match packet protocol (\fictx\->protocol\fp). .ip \(bu 2 \fb\-esocktnosupport\fp if socket is not in allowed state (tcp listening or udp unconnected). .unindent .unindent .tp .b \fbu64 bpf_ktime_get_boot_ns(void)\fp .indent 7.0 .tp .b description return the time elapsed since system boot, in nanoseconds. does include the time the system was suspended. see: \fbclock_gettime\fp(\fbclock_boottime\fp) .tp .b return current \fiktime\fp\&. .unindent .tp .b \fblong bpf_seq_printf(struct seq_file *\fp\fim\fp\fb, const char *\fp\fifmt\fp\fb, u32\fp \fifmt_size\fp\fb, const void *\fp\fidata\fp\fb, u32\fp \fidata_len\fp\fb)\fp .indent 7.0 .tp .b description \fbbpf_seq_printf\fp() uses seq_file \fbseq_printf\fp() to print out the format string. the \fim\fp represents the seq_file. the \fifmt\fp and \fifmt_size\fp are for the format string itself. the \fidata\fp and \fidata_len\fp are format string arguments. the \fidata\fp are a \fbu64\fp array and corresponding format string values are stored in the array. for strings and pointers where pointees are accessed, only the pointer values are stored in the \fidata\fp array. the \fidata_len\fp is the size of \fidata\fp in bytes. .sp formats \fb%s\fp, \fb%p{i,i}{4,6}\fp requires to read kernel memory. reading kernel memory may fail due to either invalid address or valid address but requiring a major memory fault. if reading kernel memory fails, the string for \fb%s\fp will be an empty string, and the ip address for \fb%p{i,i}{4,6}\fp will be 0. not returning error to bpf program is consistent with what \fbbpf_trace_printk\fp() does for now. .tp .b return 0 on success, or a negative error in case of failure: .sp \fb\-ebusy\fp if per\-cpu memory copy buffer is busy, can try again by returning 1 from bpf program. .sp \fb\-einval\fp if arguments are invalid, or if \fifmt\fp is invalid/unsupported. .sp \fb\-e2big\fp if \fifmt\fp contains too many format specifiers. .sp \fb\-eoverflow\fp if an overflow happened: the same object will be tried again. .unindent .tp .b \fblong bpf_seq_write(struct seq_file *\fp\fim\fp\fb, const void *\fp\fidata\fp\fb, u32\fp \filen\fp\fb)\fp .indent 7.0 .tp .b description \fbbpf_seq_write\fp() uses seq_file \fbseq_write\fp() to write the data. the \fim\fp represents the seq_file. the \fidata\fp and \filen\fp represent the data to write in bytes. .tp .b return 0 on success, or a negative error in case of failure: .sp \fb\-eoverflow\fp if an overflow happened: the same object will be tried again. .unindent .tp .b \fbu64 bpf_sk_cgroup_id(struct bpf_sock *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description return the cgroup v2 id of the socket \fisk\fp\&. .sp \fisk\fp must be a non\-\fbnull\fp pointer to a full socket, e.g. one returned from \fbbpf_sk_lookup_xxx\fp(), \fbbpf_sk_fullsock\fp(), etc. the format of returned id is same as in \fbbpf_skb_cgroup_id\fp(). .sp this helper is available only if the kernel was compiled with the \fbconfig_sock_cgroup_data\fp configuration option. .tp .b return the id is returned or 0 in case the id could not be retrieved. .unindent .tp .b \fbu64 bpf_sk_ancestor_cgroup_id(struct bpf_sock *\fp\fisk\fp\fb, int\fp \fiancestor_level\fp\fb)\fp .indent 7.0 .tp .b description return id of cgroup v2 that is ancestor of cgroup associated with the \fisk\fp at the \fiancestor_level\fp\&. the root cgroup is at \fiancestor_level\fp zero and each step down the hierarchy increments the level. if \fiancestor_level\fp == level of cgroup associated with \fisk\fp, then return value will be same as that of \fbbpf_sk_cgroup_id\fp(). .sp the helper is useful to implement policies based on cgroups that are upper in hierarchy than immediate cgroup associated with \fisk\fp\&. .sp the format of returned id and helper limitations are same as in \fbbpf_sk_cgroup_id\fp(). .tp .b return the id is returned or 0 in case the id could not be retrieved. .unindent .tp .b \fblong bpf_ringbuf_output(void *\fp\firingbuf\fp\fb, void *\fp\fidata\fp\fb, u64\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description copy \fisize\fp bytes from \fidata\fp into a ring buffer \firingbuf\fp\&. if \fbbpf_rb_no_wakeup\fp is specified in \fiflags\fp, no notification of new data availability is sent. if \fbbpf_rb_force_wakeup\fp is specified in \fiflags\fp, notification of new data availability is sent unconditionally. .tp .b return 0 on success, or a negative error in case of failure. .unindent .tp .b \fbvoid *bpf_ringbuf_reserve(void *\fp\firingbuf\fp\fb, u64\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description reserve \fisize\fp bytes of payload in a ring buffer \firingbuf\fp\&. .tp .b return valid pointer with \fisize\fp bytes of memory available; null, otherwise. .unindent .tp .b \fbvoid bpf_ringbuf_submit(void *\fp\fidata\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description submit reserved ring buffer sample, pointed to by \fidata\fp\&. if \fbbpf_rb_no_wakeup\fp is specified in \fiflags\fp, no notification of new data availability is sent. if \fbbpf_rb_force_wakeup\fp is specified in \fiflags\fp, notification of new data availability is sent unconditionally. .tp .b return nothing. always succeeds. .unindent .tp .b \fbvoid bpf_ringbuf_discard(void *\fp\fidata\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description discard reserved ring buffer sample, pointed to by \fidata\fp\&. if \fbbpf_rb_no_wakeup\fp is specified in \fiflags\fp, no notification of new data availability is sent. if \fbbpf_rb_force_wakeup\fp is specified in \fiflags\fp, notification of new data availability is sent unconditionally. .tp .b return nothing. always succeeds. .unindent .tp .b \fbu64 bpf_ringbuf_query(void *\fp\firingbuf\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description query various characteristics of provided ring buffer. what exactly is queries is determined by \fiflags\fp: .indent 7.0 .ip \(bu 2 \fbbpf_rb_avail_data\fp: amount of data not yet consumed. .ip \(bu 2 \fbbpf_rb_ring_size\fp: the size of ring buffer. .ip \(bu 2 \fbbpf_rb_cons_pos\fp: consumer position (can wrap around). .ip \(bu 2 \fbbpf_rb_prod_pos\fp: producer(s) position (can wrap around). .unindent .sp data returned is just a momentary snapshot of actual values and could be inaccurate, so this facility should be used to power heuristics and for reporting, not to make 100% correct calculation. .tp .b return requested value, or 0, if \fiflags\fp are not recognized. .unindent .tp .b \fblong bpf_csum_level(struct sk_buff *\fp\fiskb\fp\fb, u64\fp \filevel\fp\fb)\fp .indent 7.0 .tp .b description change the skbs checksum level by one layer up or down, or reset it entirely to none in order to have the stack perform checksum validation. the level is applicable to the following protocols: tcp, udp, gre, sctp, fcoe. for example, a decap of | eth | ip | udp | gue | ip | tcp | into | eth | ip | tcp | through \fbbpf_skb_adjust_room\fp() helper with passing in \fbbpf_f_adj_room_no_csum_reset\fp flag would require one call to \fbbpf_csum_level\fp() with \fbbpf_csum_level_dec\fp since the udp header is removed. similarly, an encap of the latter into the former could be accompanied by a helper call to \fbbpf_csum_level\fp() with \fbbpf_csum_level_inc\fp if the skb is still intended to be processed in higher layers of the stack instead of just egressing at tc. .sp there are three supported level settings at this time: .indent 7.0 .ip \(bu 2 \fbbpf_csum_level_inc\fp: increases skb\->csum_level for skbs with checksum_unnecessary. .ip \(bu 2 \fbbpf_csum_level_dec\fp: decreases skb\->csum_level for skbs with checksum_unnecessary. .ip \(bu 2 \fbbpf_csum_level_reset\fp: resets skb\->csum_level to 0 and sets checksum_none to force checksum validation by the stack. .ip \(bu 2 \fbbpf_csum_level_query\fp: no\-op, returns the current skb\->csum_level. .unindent .tp .b return 0 on success, or a negative error in case of failure. in the case of \fbbpf_csum_level_query\fp, the current skb\->csum_level is returned or the error code \-eacces in case the skb is not subject to checksum_unnecessary. .unindent .tp .b \fbstruct tcp6_sock *bpf_skc_to_tcp6_sock(void *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description dynamically cast a \fisk\fp pointer to a \fitcp6_sock\fp pointer. .tp .b return \fisk\fp if casting is valid, or null otherwise. .unindent .tp .b \fbstruct tcp_sock *bpf_skc_to_tcp_sock(void *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description dynamically cast a \fisk\fp pointer to a \fitcp_sock\fp pointer. .tp .b return \fisk\fp if casting is valid, or null otherwise. .unindent .tp .b \fbstruct tcp_timewait_sock *bpf_skc_to_tcp_timewait_sock(void *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description dynamically cast a \fisk\fp pointer to a \fitcp_timewait_sock\fp pointer. .tp .b return \fisk\fp if casting is valid, or null otherwise. .unindent .tp .b \fbstruct tcp_request_sock *bpf_skc_to_tcp_request_sock(void *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description dynamically cast a \fisk\fp pointer to a \fitcp_request_sock\fp pointer. .tp .b return \fisk\fp if casting is valid, or null otherwise. .unindent .tp .b \fbstruct udp6_sock *bpf_skc_to_udp6_sock(void *\fp\fisk\fp\fb)\fp .indent 7.0 .tp .b description dynamically cast a \fisk\fp pointer to a \fiudp6_sock\fp pointer. .tp .b return \fisk\fp if casting is valid, or null otherwise. .unindent .tp .b \fblong bpf_get_task_stack(struct task_struct *\fp\fitask\fp\fb, void *\fp\fibuf\fp\fb, u32\fp \fisize\fp\fb, u64\fp \fiflags\fp\fb)\fp .indent 7.0 .tp .b description return a user or a kernel stack in bpf program provided buffer. to achieve this, the helper needs \fitask\fp, which is a valid pointer to struct task_struct. to store the stacktrace, the bpf program provides \fibuf\fp with a nonnegative \fisize\fp\&. .sp the last argument, \fiflags\fp, holds the number of stack frames to skip (from 0 to 255), masked with \fbbpf_f_skip_field_mask\fp\&. the next bits can be used to set the following flags: .indent 7.0 .tp .b \fbbpf_f_user_stack\fp collect a user space stack instead of a kernel stack. .tp .b \fbbpf_f_user_build_id\fp collect buildid+offset instead of ips for user stack, only valid if \fbbpf_f_user_stack\fp is also specified. .unindent .sp \fbbpf_get_task_stack\fp() can collect up to \fbperf_max_stack_depth\fp both kernel and user frames, subject to sufficient large buffer size. note that this limit can be controlled with the \fbsysctl\fp program, and that it should be manually increased in order to profile long user stacks (such as stacks for java programs). to do so, use: .indent 7.0 .indent 3.5 .sp .nf .ft c # sysctl kernel.perf_event_max_stack= .ft p .fi .unindent .unindent .tp .b return a non\-negative value equal to or less than \fisize\fp on success, or a negative error in case of failure. .unindent .unindent .sh examples .sp example usage for most of the ebpf helpers listed in this manual page are available within the linux kernel sources, at the following locations: .indent 0.0 .ip \(bu 2 \fisamples/bpf/\fp .ip \(bu 2 \fitools/testing/selftests/bpf/\fp .unindent .sh license .sp ebpf programs can have an associated license, passed along with the bytecode instructions to the kernel when the programs are loaded. the format for that string is identical to the one in use for kernel modules (dual licenses, such as "dual bsd/gpl", may be used). some helper functions are only accessible to programs that are compatible with the gnu privacy license (gpl). .sp in order to use such helpers, the ebpf program must be loaded with the correct license string passed (via \fbattr\fp) to the \fbbpf\fp() system call, and this generally translates into the c source code of the program containing a line similar to the following: .indent 0.0 .indent 3.5 .sp .nf .ft c char ____license[] __attribute__((section("license"), used)) = "gpl"; .ft p .fi .unindent .unindent .sh implementation .sp this manual page is an effort to document the existing ebpf helper functions. but as of this writing, the bpf sub\-system is under heavy development. new ebpf program or map types are added, along with new helper functions. some helpers are occasionally made available for additional program types. so in spite of the efforts of the community, this page might not be up\-to\-date. if you want to check by yourself what helper functions exist in your kernel, or what types of programs they can support, here are some files among the kernel tree that you may be interested in: .indent 0.0 .ip \(bu 2 \fiinclude/uapi/linux/bpf.h\fp is the main bpf header. it contains the full list of all helper functions, as well as many other bpf definitions including most of the flags, structs or constants used by the helpers. .ip \(bu 2 \finet/core/filter.c\fp contains the definition of most network\-related helper functions, and the list of program types from which they can be used. .ip \(bu 2 \fikernel/trace/bpf_trace.c\fp is the equivalent for most tracing program\-related helpers. .ip \(bu 2 \fikernel/bpf/verifier.c\fp contains the functions used to check that valid types of ebpf maps are used with a given helper function. .ip \(bu 2 \fikernel/bpf/\fp directory contains other files in which additional helpers are defined (for cgroups, sockmaps, etc.). .ip \(bu 2 the bpftool utility can be used to probe the availability of helper functions on the system (as well as supported program and map types, and a number of other parameters). to do so, run \fbbpftool feature probe\fp (see \fbbpftool\-feature\fp(8) for details). add the \fbunprivileged\fp keyword to list features available to unprivileged users. .unindent .sp compatibility between helper functions and program types can generally be found in the files where helper functions are defined. look for the \fbstruct bpf_func_proto\fp objects and for functions returning them: these functions contain a list of helpers that a given program type can call. note that the \fbdefault:\fp label of the \fbswitch ... case\fp used to filter helpers can call other functions, themselves allowing access to additional helpers. the requirement for gpl license is also in those \fbstruct bpf_func_proto\fp\&. .sp compatibility between helper functions and map types can be found in the \fbcheck_map_func_compatibility\fp() function in file \fikernel/bpf/verifier.c\fp\&. .sp helper functions that invalidate the checks on \fbdata\fp and \fbdata_end\fp pointers for network processing are listed in function \fbbpf_helper_changes_pkt_data\fp() in file \finet/core/filter.c\fp\&. .sh see also .sp \fbbpf\fp(2), \fbbpftool\fp(8), \fbcgroups\fp(7), \fbip\fp(8), \fbperf_event_open\fp(2), \fbsendmsg\fp(2), \fbsocket\fp(7), \fbtc\-bpf\fp(8) .\" generated by docutils manpage writer. . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt .\" fri apr 2 11:32:09 met dst 1993 .\" .\" and changes copyright (c) 1999 mike coleman (mkc@acm.org) .\" -- major revision to fully document ptrace semantics per recent linux .\" kernel (2.2.10) and glibc (2.1.2) .\" sun nov 7 03:18:35 cst 1999 .\" .\" and copyright (c) 2011, denys vlasenko .\" and copyright (c) 2015, 2016, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified fri jul 23 23:47:18 1993 by rik faith .\" modified fri jan 31 16:46:30 1997 by eric s. raymond .\" modified thu oct 7 17:28:49 1999 by andries brouwer .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .\" 2006-03-24, chuck ebbert <76306.1226@compuserve.com> .\" added ptrace_setoptions, ptrace_geteventmsg, ptrace_getsiginfo, .\" ptrace_setsiginfo, ptrace_sysemu, ptrace_sysemu_singlestep .\" (thanks to blaisorblade, daniel jacobowitz and others who helped.) .\" 2011-09, major update by denys vlasenko .\" 2015-01, kees cook .\" added ptrace_o_traceseccomp, ptrace_event_seccomp .\" .\" fixme the following are undocumented: .\" .\" ptrace_getwmmxregs .\" ptrace_setwmmxregs .\" arm .\" linux 2.6.12 .\" .\" ptrace_set_syscall .\" arm and arm64 .\" linux 2.6.16 .\" commit 3f471126ee53feb5e9b210ea2f525ed3bb9b7a7f .\" author: nicolas pitre .\" date: sat jan 14 19:30:04 2006 +0000 .\" .\" ptrace_getcrunchregs .\" ptrace_setcrunchregs .\" arm .\" linux 2.6.18 .\" commit 3bec6ded282b331552587267d67a06ed7fd95ddd .\" author: lennert buytenhek .\" date: tue jun 27 22:56:18 2006 +0100 .\" .\" ptrace_getvfpregs .\" ptrace_setvfpregs .\" arm and arm64 .\" linux 2.6.30 .\" commit 3d1228ead618b88e8606015cbabc49019981805d .\" author: catalin marinas .\" date: wed feb 11 13:12:56 2009 +0100 .\" .\" ptrace_gethbpregs .\" ptrace_sethbpregs .\" arm and arm64 .\" linux 2.6.37 .\" commit 864232fa1a2f8dfe003438ef0851a56722740f3e .\" author: will deacon .\" date: fri sep 3 10:42:55 2010 +0100 .\" .\" ptrace_singleblock .\" since at least linux 2.4.0 on various architectures .\" since linux 2.6.25 on x86 (and others?) .\" commit 5b88abbf770a0e1975c668743100f42934f385e8 .\" author: roland mcgrath .\" date: wed jan 30 13:30:53 2008 +0100 .\" ptrace: generic ptrace_singleblock .\" .\" ptrace_getfpxregs .\" ptrace_setfpxregs .\" since at least linux 2.4.0 on various architectures .\" .\" ptrace_getfdpic .\" ptrace_getfdpic_exec .\" ptrace_getfdpic_interp .\" blackfin, c6x, frv, sh .\" first appearance in linux 2.6.11 on frv .\" .\" and others that can be found in the arch/*/include/uapi/asm/ptrace files .\" .th ptrace 2 2021-03-22 "linux" "linux programmer's manual" .sh name ptrace \- process trace .sh synopsis .nf .b #include .pp .bi "long ptrace(enum __ptrace_request " request ", pid_t " pid , .bi " void *" addr ", void *" data ); .fi .sh description the .br ptrace () system call provides a means by which one process (the "tracer") may observe and control the execution of another process (the "tracee"), and examine and change the tracee's memory and registers. it is primarily used to implement breakpoint debugging and system call tracing. .pp a tracee first needs to be attached to the tracer. attachment and subsequent commands are per thread: in a multithreaded process, every thread can be individually attached to a (potentially different) tracer, or left not attached and thus not debugged. therefore, "tracee" always means "(one) thread", never "a (possibly multithreaded) process". ptrace commands are always sent to a specific tracee using a call of the form .pp ptrace(ptrace_foo, pid, ...) .pp where .i pid is the thread id of the corresponding linux thread. .pp (note that in this page, a "multithreaded process" means a thread group consisting of threads created using the .br clone (2) .b clone_thread flag.) .pp a process can initiate a trace by calling .br fork (2) and having the resulting child do a .br ptrace_traceme , followed (typically) by an .br execve (2). alternatively, one process may commence tracing another process using .b ptrace_attach or .br ptrace_seize . .pp while being traced, the tracee will stop each time a signal is delivered, even if the signal is being ignored. (an exception is .br sigkill , which has its usual effect.) the tracer will be notified at its next call to .br waitpid (2) (or one of the related "wait" system calls); that call will return a .i status value containing information that indicates the cause of the stop in the tracee. while the tracee is stopped, the tracer can use various ptrace requests to inspect and modify the tracee. the tracer then causes the tracee to continue, optionally ignoring the delivered signal (or even delivering a different signal instead). .pp if the .b ptrace_o_traceexec option is not in effect, all successful calls to .br execve (2) by the traced process will cause it to be sent a .b sigtrap signal, giving the parent a chance to gain control before the new program begins execution. .pp when the tracer is finished tracing, it can cause the tracee to continue executing in a normal, untraced mode via .br ptrace_detach . .pp the value of .i request determines the action to be performed: .tp .b ptrace_traceme indicate that this process is to be traced by its parent. a process probably shouldn't make this request if its parent isn't expecting to trace it. .ri ( pid , .ir addr , and .ir data are ignored.) .ip the .b ptrace_traceme request is used only by the tracee; the remaining requests are used only by the tracer. in the following requests, .i pid specifies the thread id of the tracee to be acted on. for requests other than .br ptrace_attach , .br ptrace_seize , .br ptrace_interrupt , and .br ptrace_kill , the tracee must be stopped. .tp .br ptrace_peektext ", " ptrace_peekdata read a word at the address .i addr in the tracee's memory, returning the word as the result of the .br ptrace () call. linux does not have separate text and data address spaces, so these two requests are currently equivalent. .ri ( data is ignored; but see notes.) .tp .b ptrace_peekuser .\" ptrace_peekusr in kernel source, but glibc uses ptrace_peekuser, .\" and that is the name that seems common on other systems. read a word at offset .i addr in the tracee's user area, which holds the registers and other information about the process (see .ir ). the word is returned as the result of the .br ptrace () call. typically, the offset must be word-aligned, though this might vary by architecture. see notes. .ri ( data is ignored; but see notes.) .tp .br ptrace_poketext ", " ptrace_pokedata copy the word .i data to the address .i addr in the tracee's memory. as for .br ptrace_peektext and .br ptrace_peekdata , these two requests are currently equivalent. .tp .b ptrace_pokeuser .\" ptrace_pokeusr in kernel source, but glibc uses ptrace_pokeuser, .\" and that is the name that seems common on other systems. copy the word .i data to offset .i addr in the tracee's user area. as for .br ptrace_peekuser , the offset must typically be word-aligned. in order to maintain the integrity of the kernel, some modifications to the user area are disallowed. .\" fixme in the preceding sentence, which modifications are disallowed, .\" and when they are disallowed, how does user space discover that fact? .tp .br ptrace_getregs ", " ptrace_getfpregs copy the tracee's general-purpose or floating-point registers, respectively, to the address .i data in the tracer. see .i for information on the format of this data. .ri ( addr is ignored.) note that sparc systems have the meaning of .i data and .i addr reversed; that is, .i data is ignored and the registers are copied to the address .ir addr . .b ptrace_getregs and .b ptrace_getfpregs are not present on all architectures. .tp .br ptrace_getregset " (since linux 2.6.34)" read the tracee's registers. .i addr specifies, in an architecture-dependent way, the type of registers to be read. .b nt_prstatus (with numerical value 1) usually results in reading of general-purpose registers. if the cpu has, for example, floating-point and/or vector registers, they can be retrieved by setting .i addr to the corresponding .b nt_foo constant. .i data points to a .br "struct iovec" , which describes the destination buffer's location and length. on return, the kernel modifies .b iov.len to indicate the actual number of bytes returned. .tp .br ptrace_setregs ", " ptrace_setfpregs modify the tracee's general-purpose or floating-point registers, respectively, from the address .i data in the tracer. as for .br ptrace_pokeuser , some general-purpose register modifications may be disallowed. .\" fixme . in the preceding sentence, which modifications are disallowed, .\" and when they are disallowed, how does user space discover that fact? .ri ( addr is ignored.) note that sparc systems have the meaning of .i data and .i addr reversed; that is, .i data is ignored and the registers are copied from the address .ir addr . .b ptrace_setregs and .b ptrace_setfpregs are not present on all architectures. .tp .br ptrace_setregset " (since linux 2.6.34)" modify the tracee's registers. the meaning of .i addr and .i data is analogous to .br ptrace_getregset . .tp .br ptrace_getsiginfo " (since linux 2.3.99-pre6)" retrieve information about the signal that caused the stop. copy a .i siginfo_t structure (see .br sigaction (2)) from the tracee to the address .i data in the tracer. .ri ( addr is ignored.) .tp .br ptrace_setsiginfo " (since linux 2.3.99-pre6)" set signal information: copy a .i siginfo_t structure from the address .i data in the tracer to the tracee. this will affect only signals that would normally be delivered to the tracee and were caught by the tracer. it may be difficult to tell these normal signals from synthetic signals generated by .br ptrace () itself. .ri ( addr is ignored.) .tp .br ptrace_peeksiginfo " (since linux 3.10)" .\" commit 84c751bd4aebbaae995fe32279d3dba48327bad4 retrieve .i siginfo_t structures without removing signals from a queue. .i addr points to a .i ptrace_peeksiginfo_args structure that specifies the ordinal position from which copying of signals should start, and the number of signals to copy. .i siginfo_t structures are copied into the buffer pointed to by .ir data . the return value contains the number of copied signals (zero indicates that there is no signal corresponding to the specified ordinal position). within the returned .i siginfo structures, the .ir si_code field includes information .rb ( __si_chld , .br __si_fault , etc.) that are not otherwise exposed to user space. .pp .in +4n .ex struct ptrace_peeksiginfo_args { u64 off; /* ordinal position in queue at which to start copying signals */ u32 flags; /* ptrace_peeksiginfo_shared or 0 */ s32 nr; /* number of signals to copy */ }; .ee .in .ip currently, there is only one flag, .br ptrace_peeksiginfo_shared , for dumping signals from the process-wide signal queue. if this flag is not set, signals are read from the per-thread queue of the specified thread. .in .tp .br ptrace_getsigmask " (since linux 3.11)" .\" commit 29000caecbe87b6b66f144f72111f0d02fbbf0c1 place a copy of the mask of blocked signals (see .br sigprocmask (2)) in the buffer pointed to by .ir data , which should be a pointer to a buffer of type .ir sigset_t . the .i addr argument contains the size of the buffer pointed to by .ir data (i.e., .ir sizeof(sigset_t) ). .tp .br ptrace_setsigmask " (since linux 3.11)" change the mask of blocked signals (see .br sigprocmask (2)) to the value specified in the buffer pointed to by .ir data , which should be a pointer to a buffer of type .ir sigset_t . the .i addr argument contains the size of the buffer pointed to by .ir data (i.e., .ir sizeof(sigset_t) ). .tp .br ptrace_setoptions " (since linux 2.4.6; see bugs for caveats)" set ptrace options from .ir data . .ri ( addr is ignored.) .ir data is interpreted as a bit mask of options, which are specified by the following flags: .rs .tp .br ptrace_o_exitkill " (since linux 3.8)" .\" commit 992fb6e170639b0849bace8e49bf31bd37c4123 send a .b sigkill signal to the tracee if the tracer exits. this option is useful for ptrace jailers that want to ensure that tracees can never escape the tracer's control. .tp .br ptrace_o_traceclone " (since linux 2.5.46)" stop the tracee at the next .br clone (2) and automatically start tracing the newly cloned process, which will start with a .br sigstop , or .b ptrace_event_stop if .b ptrace_seize was used. a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_clone<<8)) .fi .ip the pid of the new process can be retrieved with .br ptrace_geteventmsg . .ip this option may not catch .br clone (2) calls in all cases. if the tracee calls .br clone (2) with the .b clone_vfork flag, .b ptrace_event_vfork will be delivered instead if .b ptrace_o_tracevfork is set; otherwise if the tracee calls .br clone (2) with the exit signal set to .br sigchld , .b ptrace_event_fork will be delivered if .b ptrace_o_tracefork is set. .tp .br ptrace_o_traceexec " (since linux 2.5.46)" stop the tracee at the next .br execve (2). a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_exec<<8)) .fi .ip if the execing thread is not a thread group leader, the thread id is reset to thread group leader's id before this stop. since linux 3.0, the former thread id can be retrieved with .br ptrace_geteventmsg . .tp .br ptrace_o_traceexit " (since linux 2.5.60)" stop the tracee at exit. a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_exit<<8)) .fi .ip the tracee's exit status can be retrieved with .br ptrace_geteventmsg . .ip the tracee is stopped early during process exit, when registers are still available, allowing the tracer to see where the exit occurred, whereas the normal exit notification is done after the process is finished exiting. even though context is available, the tracer cannot prevent the exit from happening at this point. .tp .br ptrace_o_tracefork " (since linux 2.5.46)" stop the tracee at the next .br fork (2) and automatically start tracing the newly forked process, which will start with a .br sigstop , or .b ptrace_event_stop if .b ptrace_seize was used. a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_fork<<8)) .fi .ip the pid of the new process can be retrieved with .br ptrace_geteventmsg . .tp .br ptrace_o_tracesysgood " (since linux 2.4.6)" when delivering system call traps, set bit 7 in the signal number (i.e., deliver .ir "sigtrap|0x80" ). this makes it easy for the tracer to distinguish normal traps from those caused by a system call. .tp .br ptrace_o_tracevfork " (since linux 2.5.46)" stop the tracee at the next .br vfork (2) and automatically start tracing the newly vforked process, which will start with a .br sigstop , or .b ptrace_event_stop if .b ptrace_seize was used. a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_vfork<<8)) .fi .ip the pid of the new process can be retrieved with .br ptrace_geteventmsg . .tp .br ptrace_o_tracevforkdone " (since linux 2.5.60)" stop the tracee at the completion of the next .br vfork (2). a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_vfork_done<<8)) .fi .ip the pid of the new process can (since linux 2.6.18) be retrieved with .br ptrace_geteventmsg . .tp .br ptrace_o_traceseccomp " (since linux 3.5)" stop the tracee when a .br seccomp (2) .br seccomp_ret_trace rule is triggered. a .br waitpid (2) by the tracer will return a .i status value such that .ip .nf status>>8 == (sigtrap | (ptrace_event_seccomp<<8)) .fi .ip while this triggers a .br ptrace_event stop, it is similar to a syscall-enter-stop. for details, see the note on .b ptrace_event_seccomp below. the seccomp event message data (from the .br seccomp_ret_data portion of the seccomp filter rule) can be retrieved with .br ptrace_geteventmsg . .tp .br ptrace_o_suspend_seccomp " (since linux 4.3)" .\" commit 13c4a90119d28cfcb6b5bdd820c233b86c2b0237 suspend the tracee's seccomp protections. this applies regardless of mode, and can be used when the tracee has not yet installed seccomp filters. that is, a valid use case is to suspend a tracee's seccomp protections before they are installed by the tracee, let the tracee install the filters, and then clear this flag when the filters should be resumed. setting this option requires that the tracer have the .br cap_sys_admin capability, not have any seccomp protections installed, and not have .br ptrace_o_suspend_seccomp set on itself. .re .tp .br ptrace_geteventmsg " (since linux 2.5.46)" retrieve a message (as an .ir "unsigned long" ) about the ptrace event that just happened, placing it at the address .i data in the tracer. for .br ptrace_event_exit , this is the tracee's exit status. for .br ptrace_event_fork , .br ptrace_event_vfork , .br ptrace_event_vfork_done , and .br ptrace_event_clone , this is the pid of the new process. for .br ptrace_event_seccomp , this is the .br seccomp (2) filter's .br seccomp_ret_data associated with the triggered rule. .ri ( addr is ignored.) .tp .b ptrace_cont restart the stopped tracee process. if .i data is nonzero, it is interpreted as the number of a signal to be delivered to the tracee; otherwise, no signal is delivered. thus, for example, the tracer can control whether a signal sent to the tracee is delivered or not. .ri ( addr is ignored.) .tp .br ptrace_syscall ", " ptrace_singlestep restart the stopped tracee as for .br ptrace_cont , but arrange for the tracee to be stopped at the next entry to or exit from a system call, or after execution of a single instruction, respectively. (the tracee will also, as usual, be stopped upon receipt of a signal.) from the tracer's perspective, the tracee will appear to have been stopped by receipt of a .br sigtrap . so, for .br ptrace_syscall , for example, the idea is to inspect the arguments to the system call at the first stop, then do another .b ptrace_syscall and inspect the return value of the system call at the second stop. the .i data argument is treated as for .br ptrace_cont . .ri ( addr is ignored.) .tp .br ptrace_set_syscall " (since linux 2.6.16)" .\" commit 3f471126ee53feb5e9b210ea2f525ed3bb9b7a7f when in syscall-enter-stop, change the number of the system call that is about to be executed to the number specified in the .i data argument. the .i addr argument is ignored. this request is currently .\" as of 4.19-rc2 supported only on arm (and arm64, though only for backwards compatibility), .\" commit 27aa55c5e5123fa8b8ad0156559d34d7edff58ca but most other architectures have other means of accomplishing this (usually by changing the register that the userland code passed the system call number in). .\" see change_syscall in tools/testing/selftests/seccomp/seccomp_bpf.c .\" and also strace's linux/*/set_scno.c files. .tp .br ptrace_sysemu ", " ptrace_sysemu_singlestep " (since linux 2.6.14)" for .br ptrace_sysemu , continue and stop on entry to the next system call, which will not be executed. see the documentation on syscall-stops below. for .br ptrace_sysemu_singlestep , do the same but also singlestep if not a system call. this call is used by programs like user mode linux that want to emulate all the tracee's system calls. the .i data argument is treated as for .br ptrace_cont . the .i addr argument is ignored. these requests are currently .\" as at 3.7 supported only on x86. .tp .br ptrace_listen " (since linux 3.4)" restart the stopped tracee, but prevent it from executing. the resulting state of the tracee is similar to a process which has been stopped by a .b sigstop (or other stopping signal). see the "group-stop" subsection for additional information. .b ptrace_listen works only on tracees attached by .br ptrace_seize . .tp .b ptrace_kill send the tracee a .b sigkill to terminate it. .ri ( addr and .i data are ignored.) .ip .i this operation is deprecated; do not use it! instead, send a .br sigkill directly using .br kill (2) or .br tgkill (2). the problem with .b ptrace_kill is that it requires the tracee to be in signal-delivery-stop, otherwise it may not work (i.e., may complete successfully but won't kill the tracee). by contrast, sending a .b sigkill directly has no such limitation. .\" [note from denys vlasenko: .\" deprecation suggested by oleg nesterov. he prefers to deprecate it .\" instead of describing (and needing to support) ptrace_kill's quirks.] .tp .br ptrace_interrupt " (since linux 3.4)" stop a tracee. if the tracee is running or sleeping in kernel space and .b ptrace_syscall is in effect, the system call is interrupted and syscall-exit-stop is reported. (the interrupted system call is restarted when the tracee is restarted.) if the tracee was already stopped by a signal and .b ptrace_listen was sent to it, the tracee stops with .b ptrace_event_stop and .i wstopsig(status) returns the stop signal. if any other ptrace-stop is generated at the same time (for example, if a signal is sent to the tracee), this ptrace-stop happens. if none of the above applies (for example, if the tracee is running in user space), it stops with .b ptrace_event_stop with .i wstopsig(status) == .br sigtrap . .b ptrace_interrupt only works on tracees attached by .br ptrace_seize . .tp .b ptrace_attach attach to the process specified in .ir pid , making it a tracee of the calling process. .\" no longer true (removed by denys vlasenko, 2011, who remarks: .\" "i think it isn't true in non-ancient 2.4 and in 2.6/3.x. .\" basically, it's not true for any linux in practical use. .\" ; the behavior of the tracee is as if it had done a .\" .br ptrace_traceme . .\" the calling process actually becomes the parent of the tracee .\" process for most purposes (e.g., it will receive .\" notification of tracee events and appears in .\" .br ps (1) .\" output as the tracee's parent), but a .\" .br getppid (2) .\" by the tracee will still return the pid of the original parent. the tracee is sent a .br sigstop , but will not necessarily have stopped by the completion of this call; use .br waitpid (2) to wait for the tracee to stop. see the "attaching and detaching" subsection for additional information. .ri ( addr and .i data are ignored.) .ip permission to perform a .br ptrace_attach is governed by a ptrace access mode .b ptrace_mode_attach_realcreds check; see below. .tp .br ptrace_seize " (since linux 3.4)" .\" .\" noted by dmitry levin: .\" .\" ptrace_seize was introduced by commit v3.1-rc1~308^2~28, but .\" it had to be used along with a temporary flag ptrace_seize_devel, .\" which was removed later by commit v3.4-rc1~109^2~20. .\" .\" that is, [before] v3.4 we had a test mode of ptrace_seize api, .\" which was not compatible with the current ptrace_seize api introduced .\" in linux 3.4. .\" attach to the process specified in .ir pid , making it a tracee of the calling process. unlike .br ptrace_attach , .b ptrace_seize does not stop the process. group-stops are reported as .b ptrace_event_stop and .i wstopsig(status) returns the stop signal. automatically attached children stop with .b ptrace_event_stop and .i wstopsig(status) returns .b sigtrap instead of having .b sigstop signal delivered to them. .br execve (2) does not deliver an extra .br sigtrap . only a .br ptrace_seize d process can accept .b ptrace_interrupt and .b ptrace_listen commands. the "seized" behavior just described is inherited by children that are automatically attached using .br ptrace_o_tracefork , .br ptrace_o_tracevfork , and .br ptrace_o_traceclone . .i addr must be zero. .i data contains a bit mask of ptrace options to activate immediately. .ip permission to perform a .br ptrace_seize is governed by a ptrace access mode .b ptrace_mode_attach_realcreds check; see below. .\" .tp .br ptrace_seccomp_get_filter " (since linux 4.4)" .\" commit f8e529ed941ba2bbcbf310b575d968159ce7e895 this operation allows the tracer to dump the tracee's classic bpf filters. .ip .i addr is an integer specifying the index of the filter to be dumped. the most recently installed filter has the index 0. if .i addr is greater than the number of installed filters, the operation fails with the error .br enoent . .ip .i data is either a pointer to a .ir "struct sock_filter" array that is large enough to store the bpf program, or null if the program is not to be stored. .ip upon success, the return value is the number of instructions in the bpf program. if .i data was null, then this return value can be used to correctly size the .ir "struct sock_filter" array passed in a subsequent call. .ip this operation fails with the error .b eacces if the caller does not have the .b cap_sys_admin capability or if the caller is in strict or filter seccomp mode. if the filter referred to by .i addr is not a classic bpf filter, the operation fails with the error .br emediumtype . .ip this operation is available if the kernel was configured with both the .b config_seccomp_filter and the .b config_checkpoint_restore options. .tp .b ptrace_detach restart the stopped tracee as for .br ptrace_cont , but first detach from it. under linux, a tracee can be detached in this way regardless of which method was used to initiate tracing. .ri ( addr is ignored.) .\" .tp .br ptrace_get_thread_area " (since linux 2.6.0)" this operation performs a similar task to .br get_thread_area (2). it reads the tls entry in the gdt whose index is given in .ir addr , placing a copy of the entry into the .ir "struct user_desc" pointed to by .ir data . (by contrast with .br get_thread_area (2), the .i entry_number of the .ir "struct user_desc" is ignored.) .tp .br ptrace_set_thread_area " (since linux 2.6.0)" this operation performs a similar task to .br set_thread_area (2). it sets the tls entry in the gdt whose index is given in .ir addr , assigning it the data supplied in the .ir "struct user_desc" pointed to by .ir data . (by contrast with .br set_thread_area (2), the .i entry_number of the .ir "struct user_desc" is ignored; in other words, this ptrace operation can't be used to allocate a free tls entry.) .tp .br ptrace_get_syscall_info " (since linux 5.3)" .\" commit 201766a20e30f982ccfe36bebfad9602c3ff574a retrieve information about the system call that caused the stop. the information is placed into the buffer pointed by the .i data argument, which should be a pointer to a buffer of type .ir "struct ptrace_syscall_info" . the .i addr argument contains the size of the buffer pointed to by the .i data argument (i.e., .ir "sizeof(struct ptrace_syscall_info)" ). the return value contains the number of bytes available to be written by the kernel. if the size of the data to be written by the kernel exceeds the size specified by the .i addr argument, the output data is truncated. .ip the .i ptrace_syscall_info structure contains the following fields: .ip .in +4n .ex struct ptrace_syscall_info { __u8 op; /* type of system call stop */ __u32 arch; /* audit_arch_* value; see seccomp(2) */ __u64 instruction_pointer; /* cpu instruction pointer */ __u64 stack_pointer; /* cpu stack pointer */ union { struct { /* op == ptrace_syscall_info_entry */ __u64 nr; /* system call number */ __u64 args[6]; /* system call arguments */ } entry; struct { /* op == ptrace_syscall_info_exit */ __s64 rval; /* system call return value */ __u8 is_error; /* system call error flag; boolean: does rval contain an error value (\-errcode) or a nonerror return value? */ } exit; struct { /* op == ptrace_syscall_info_seccomp */ __u64 nr; /* system call number */ __u64 args[6]; /* system call arguments */ __u32 ret_data; /* seccomp_ret_data portion of seccomp_ret_trace return value */ } seccomp; }; }; .ee .in .ip the .ir op , .ir arch , .ir instruction_pointer , and .i stack_pointer fields are defined for all kinds of ptrace system call stops. the rest of the structure is a union; one should read only those fields that are meaningful for the kind of system call stop specified by the .ir op field. .ip the .i op field has one of the following values (defined in .ir ) indicating what type of stop occurred and which part of the union is filled: .rs .tp .br ptrace_syscall_info_entry the .i entry component of the union contains information relating to a system call entry stop. .tp .br ptrace_syscall_info_exit the .i exit component of the union contains information relating to a system call exit stop. .tp .br ptrace_syscall_info_seccomp the .i seccomp component of the union contains information relating to a .b ptrace_event_seccomp stop. .tp .br ptrace_syscall_info_none no component of the union contains relevant information. .re .\" .ss death under ptrace when a (possibly multithreaded) process receives a killing signal (one whose disposition is set to .b sig_dfl and whose default action is to kill the process), all threads exit. tracees report their death to their tracer(s). notification of this event is delivered via .br waitpid (2). .pp note that the killing signal will first cause signal-delivery-stop (on one tracee only), and only after it is injected by the tracer (or after it was dispatched to a thread which isn't traced), will death from the signal happen on .i all tracees within a multithreaded process. (the term "signal-delivery-stop" is explained below.) .pp .b sigkill does not generate signal-delivery-stop and therefore the tracer can't suppress it. .b sigkill kills even within system calls (syscall-exit-stop is not generated prior to death by .br sigkill ). the net effect is that .b sigkill always kills the process (all its threads), even if some threads of the process are ptraced. .pp when the tracee calls .br _exit (2), it reports its death to its tracer. other threads are not affected. .pp when any thread executes .br exit_group (2), every tracee in its thread group reports its death to its tracer. .pp if the .b ptrace_o_traceexit option is on, .b ptrace_event_exit will happen before actual death. this applies to exits via .br exit (2), .br exit_group (2), and signal deaths (except .br sigkill , depending on the kernel version; see bugs below), and when threads are torn down on .br execve (2) in a multithreaded process. .pp the tracer cannot assume that the ptrace-stopped tracee exists. there are many scenarios when the tracee may die while stopped (such as .br sigkill ). therefore, the tracer must be prepared to handle an .b esrch error on any ptrace operation. unfortunately, the same error is returned if the tracee exists but is not ptrace-stopped (for commands which require a stopped tracee), or if it is not traced by the process which issued the ptrace call. the tracer needs to keep track of the stopped/running state of the tracee, and interpret .b esrch as "tracee died unexpectedly" only if it knows that the tracee has been observed to enter ptrace-stop. note that there is no guarantee that .i waitpid(wnohang) will reliably report the tracee's death status if a ptrace operation returned .br esrch . .i waitpid(wnohang) may return 0 instead. in other words, the tracee may be "not yet fully dead", but already refusing ptrace requests. .pp the tracer can't assume that the tracee .i always ends its life by reporting .i wifexited(status) or .ir wifsignaled(status) ; there are cases where this does not occur. for example, if a thread other than thread group leader does an .br execve (2), it disappears; its pid will never be seen again, and any subsequent ptrace stops will be reported under the thread group leader's pid. .ss stopped states a tracee can be in two states: running or stopped. for the purposes of ptrace, a tracee which is blocked in a system call (such as .br read (2), .br pause (2), etc.) is nevertheless considered to be running, even if the tracee is blocked for a long time. the state of the tracee after .br ptrace_listen is somewhat of a gray area: it is not in any ptrace-stop (ptrace commands won't work on it, and it will deliver .br waitpid (2) notifications), but it also may be considered "stopped" because it is not executing instructions (is not scheduled), and if it was in group-stop before .br ptrace_listen , it will not respond to signals until .b sigcont is received. .pp there are many kinds of states when the tracee is stopped, and in ptrace discussions they are often conflated. therefore, it is important to use precise terms. .pp in this manual page, any stopped state in which the tracee is ready to accept ptrace commands from the tracer is called .ir ptrace-stop . ptrace-stops can be further subdivided into .ir signal-delivery-stop , .ir group-stop , .ir syscall-stop , .ir "ptrace_event stops" , and so on. these stopped states are described in detail below. .pp when the running tracee enters ptrace-stop, it notifies its tracer using .br waitpid (2) (or one of the other "wait" system calls). most of this manual page assumes that the tracer waits with: .pp pid = waitpid(pid_or_minus_1, &status, __wall); .pp ptrace-stopped tracees are reported as returns with .i pid greater than 0 and .i wifstopped(status) true. .\" denys vlasenko: .\" do we require __wall usage, or will just using 0 be ok? (with 0, .\" i am not 100% sure there aren't ugly corner cases.) are the .\" rules different if user wants to use waitid? will waitid require .\" wexited? .\" .pp the .b __wall flag does not include the .b wstopped and .b wexited flags, but implies their functionality. .pp setting the .b wcontinued flag when calling .br waitpid (2) is not recommended: the "continued" state is per-process and consuming it can confuse the real parent of the tracee. .pp use of the .b wnohang flag may cause .br waitpid (2) to return 0 ("no wait results available yet") even if the tracer knows there should be a notification. example: .pp .in +4n .ex errno = 0; ptrace(ptrace_cont, pid, 0l, 0l); if (errno == esrch) { /* tracee is dead */ r = waitpid(tracee, &status, __wall | wnohang); /* r can still be 0 here! */ } .ee .in .\" fixme . .\" waitid usage? wnowait? .\" describe how wait notifications queue (or not queue) .pp the following kinds of ptrace-stops exist: signal-delivery-stops, group-stops, .b ptrace_event stops, syscall-stops. they all are reported by .br waitpid (2) with .i wifstopped(status) true. they may be differentiated by examining the value .ir status>>8 , and if there is ambiguity in that value, by querying .br ptrace_getsiginfo . (note: the .i wstopsig(status) macro can't be used to perform this examination, because it returns the value .ir "(status>>8)\ &\ 0xff" .) .ss signal-delivery-stop when a (possibly multithreaded) process receives any signal except .br sigkill , the kernel selects an arbitrary thread which handles the signal. (if the signal is generated with .br tgkill (2), the target thread can be explicitly selected by the caller.) if the selected thread is traced, it enters signal-delivery-stop. at this point, the signal is not yet delivered to the process, and can be suppressed by the tracer. if the tracer doesn't suppress the signal, it passes the signal to the tracee in the next ptrace restart request. this second step of signal delivery is called .i "signal injection" in this manual page. note that if the signal is blocked, signal-delivery-stop doesn't happen until the signal is unblocked, with the usual exception that .b sigstop can't be blocked. .pp signal-delivery-stop is observed by the tracer as .br waitpid (2) returning with .i wifstopped(status) true, with the signal returned by .ir wstopsig(status) . if the signal is .br sigtrap , this may be a different kind of ptrace-stop; see the "syscall-stops" and "execve" sections below for details. if .i wstopsig(status) returns a stopping signal, this may be a group-stop; see below. .ss signal injection and suppression after signal-delivery-stop is observed by the tracer, the tracer should restart the tracee with the call .pp ptrace(ptrace_restart, pid, 0, sig) .pp where .b ptrace_restart is one of the restarting ptrace requests. if .i sig is 0, then a signal is not delivered. otherwise, the signal .i sig is delivered. this operation is called .i "signal injection" in this manual page, to distinguish it from signal-delivery-stop. .pp the .i sig value may be different from the .i wstopsig(status) value: the tracer can cause a different signal to be injected. .pp note that a suppressed signal still causes system calls to return prematurely. in this case, system calls will be restarted: the tracer will observe the tracee to reexecute the interrupted system call (or .br restart_syscall (2) system call for a few system calls which use a different mechanism for restarting) if the tracer uses .br ptrace_syscall . even system calls (such as .br poll (2)) which are not restartable after signal are restarted after signal is suppressed; however, kernel bugs exist which cause some system calls to fail with .b eintr even though no observable signal is injected to the tracee. .pp restarting ptrace commands issued in ptrace-stops other than signal-delivery-stop are not guaranteed to inject a signal, even if .i sig is nonzero. no error is reported; a nonzero .i sig may simply be ignored. ptrace users should not try to "create a new signal" this way: use .br tgkill (2) instead. .pp the fact that signal injection requests may be ignored when restarting the tracee after ptrace stops that are not signal-delivery-stops is a cause of confusion among ptrace users. one typical scenario is that the tracer observes group-stop, mistakes it for signal-delivery-stop, restarts the tracee with .pp ptrace(ptrace_restart, pid, 0, stopsig) .pp with the intention of injecting .ir stopsig , but .i stopsig gets ignored and the tracee continues to run. .pp the .b sigcont signal has a side effect of waking up (all threads of) a group-stopped process. this side effect happens before signal-delivery-stop. the tracer can't suppress this side effect (it can only suppress signal injection, which only causes the .br sigcont handler to not be executed in the tracee, if such a handler is installed). in fact, waking up from group-stop may be followed by signal-delivery-stop for signal(s) .i other than .br sigcont , if they were pending when .b sigcont was delivered. in other words, .b sigcont may be not the first signal observed by the tracee after it was sent. .pp stopping signals cause (all threads of) a process to enter group-stop. this side effect happens after signal injection, and therefore can be suppressed by the tracer. .pp in linux 2.4 and earlier, the .b sigstop signal can't be injected. .\" in the linux 2.4 sources, in arch/i386/kernel/signal.c::do_signal(), .\" there is: .\" .\" /* the debugger continued. ignore sigstop. */ .\" if (signr == sigstop) .\" continue; .pp .b ptrace_getsiginfo can be used to retrieve a .i siginfo_t structure which corresponds to the delivered signal. .b ptrace_setsiginfo may be used to modify it. if .b ptrace_setsiginfo has been used to alter .ir siginfo_t , the .i si_signo field and the .i sig parameter in the restarting command must match, otherwise the result is undefined. .ss group-stop when a (possibly multithreaded) process receives a stopping signal, all threads stop. if some threads are traced, they enter a group-stop. note that the stopping signal will first cause signal-delivery-stop (on one tracee only), and only after it is injected by the tracer (or after it was dispatched to a thread which isn't traced), will group-stop be initiated on .i all tracees within the multithreaded process. as usual, every tracee reports its group-stop separately to the corresponding tracer. .pp group-stop is observed by the tracer as .br waitpid (2) returning with .i wifstopped(status) true, with the stopping signal available via .ir wstopsig(status) . the same result is returned by some other classes of ptrace-stops, therefore the recommended practice is to perform the call .pp ptrace(ptrace_getsiginfo, pid, 0, &siginfo) .pp the call can be avoided if the signal is not .br sigstop , .br sigtstp , .br sigttin , or .br sigttou ; only these four signals are stopping signals. if the tracer sees something else, it can't be a group-stop. otherwise, the tracer needs to call .br ptrace_getsiginfo . if .b ptrace_getsiginfo fails with .br einval , then it is definitely a group-stop. (other failure codes are possible, such as .b esrch ("no such process") if a .b sigkill killed the tracee.) .pp if tracee was attached using .br ptrace_seize , group-stop is indicated by .br ptrace_event_stop : .ir "status>>16 == ptrace_event_stop" . this allows detection of group-stops without requiring an extra .b ptrace_getsiginfo call. .pp as of linux 2.6.38, after the tracer sees the tracee ptrace-stop and until it restarts or kills it, the tracee will not run, and will not send notifications (except .b sigkill death) to the tracer, even if the tracer enters into another .br waitpid (2) call. .pp the kernel behavior described in the previous paragraph causes a problem with transparent handling of stopping signals. if the tracer restarts the tracee after group-stop, the stopping signal is effectively ignored\(emthe tracee doesn't remain stopped, it runs. if the tracer doesn't restart the tracee before entering into the next .br waitpid (2), future .b sigcont signals will not be reported to the tracer; this would cause the .b sigcont signals to have no effect on the tracee. .pp since linux 3.4, there is a method to overcome this problem: instead of .br ptrace_cont , a .b ptrace_listen command can be used to restart a tracee in a way where it does not execute, but waits for a new event which it can report via .br waitpid (2) (such as when it is restarted by a .br sigcont ). .ss ptrace_event stops if the tracer sets .b ptrace_o_trace_* options, the tracee will enter ptrace-stops called .b ptrace_event stops. .pp .b ptrace_event stops are observed by the tracer as .br waitpid (2) returning with .ir wifstopped(status) , and .i wstopsig(status) returns .br sigtrap (or for .br ptrace_event_stop , returns the stopping signal if tracee is in a group-stop). an additional bit is set in the higher byte of the status word: the value .i status>>8 will be .pp ((ptrace_event_foo<<8) | sigtrap). .pp the following events exist: .tp .b ptrace_event_vfork stop before return from .br vfork (2) or .br clone (2) with the .b clone_vfork flag. when the tracee is continued after this stop, it will wait for child to exit/exec before continuing its execution (in other words, the usual behavior on .br vfork (2)). .tp .b ptrace_event_fork stop before return from .br fork (2) or .br clone (2) with the exit signal set to .br sigchld . .tp .b ptrace_event_clone stop before return from .br clone (2). .tp .b ptrace_event_vfork_done stop before return from .br vfork (2) or .br clone (2) with the .b clone_vfork flag, but after the child unblocked this tracee by exiting or execing. .pp for all four stops described above, the stop occurs in the parent (i.e., the tracee), not in the newly created thread. .br ptrace_geteventmsg can be used to retrieve the new thread's id. .tp .b ptrace_event_exec stop before return from .br execve (2). since linux 3.0, .br ptrace_geteventmsg returns the former thread id. .tp .b ptrace_event_exit stop before exit (including death from .br exit_group (2)), signal death, or exit caused by .br execve (2) in a multithreaded process. .b ptrace_geteventmsg returns the exit status. registers can be examined (unlike when "real" exit happens). the tracee is still alive; it needs to be .br ptrace_cont ed or .br ptrace_detach ed to finish exiting. .tp .b ptrace_event_stop stop induced by .b ptrace_interrupt command, or group-stop, or initial ptrace-stop when a new child is attached (only if attached using .br ptrace_seize ). .tp .b ptrace_event_seccomp stop triggered by a .br seccomp (2) rule on tracee syscall entry when .br ptrace_o_traceseccomp has been set by the tracer. the seccomp event message data (from the .br seccomp_ret_data portion of the seccomp filter rule) can be retrieved with .br ptrace_geteventmsg . the semantics of this stop are described in detail in a separate section below. .pp .b ptrace_getsiginfo on .b ptrace_event stops returns .b sigtrap in .ir si_signo , with .i si_code set to .ir "(event<<8)\ |\ sigtrap" . .ss syscall-stops if the tracee was restarted by .br ptrace_syscall or .br ptrace_sysemu , the tracee enters syscall-enter-stop just prior to entering any system call (which will not be executed if the restart was using .br ptrace_sysemu , regardless of any change made to registers at this point or how the tracee is restarted after this stop). no matter which method caused the syscall-entry-stop, if the tracer restarts the tracee with .br ptrace_syscall , the tracee enters syscall-exit-stop when the system call is finished, or if it is interrupted by a signal. (that is, signal-delivery-stop never happens between syscall-enter-stop and syscall-exit-stop; it happens .i after syscall-exit-stop.). if the tracee is continued using any other method (including .br ptrace_sysemu ), no syscall-exit-stop occurs. note that all mentions .br ptrace_sysemu apply equally to .br ptrace_sysemu_singlestep . .pp however, even if the tracee was continued using .br ptrace_syscall , it is not guaranteed that the next stop will be a syscall-exit-stop. other possibilities are that the tracee may stop in a .b ptrace_event stop (including seccomp stops), exit (if it entered .br _exit (2) or .br exit_group (2)), be killed by .br sigkill , or die silently (if it is a thread group leader, the .br execve (2) happened in another thread, and that thread is not traced by the same tracer; this situation is discussed later). .pp syscall-enter-stop and syscall-exit-stop are observed by the tracer as .br waitpid (2) returning with .i wifstopped(status) true, and .i wstopsig(status) giving .br sigtrap . if the .b ptrace_o_tracesysgood option was set by the tracer, then .i wstopsig(status) will give the value .ir "(sigtrap\ |\ 0x80)" . .pp syscall-stops can be distinguished from signal-delivery-stop with .b sigtrap by querying .br ptrace_getsiginfo for the following cases: .tp .ir si_code " <= 0" .b sigtrap was delivered as a result of a user-space action, for example, a system call .rb ( tgkill (2), .br kill (2), .br sigqueue (3), etc.), expiration of a posix timer, change of state on a posix message queue, or completion of an asynchronous i/o request. .tp .ir si_code " == si_kernel (0x80)" .b sigtrap was sent by the kernel. .tp .ir si_code " == sigtrap or " si_code " == (sigtrap|0x80)" this is a syscall-stop. .pp however, syscall-stops happen very often (twice per system call), and performing .b ptrace_getsiginfo for every syscall-stop may be somewhat expensive. .pp some architectures allow the cases to be distinguished by examining registers. for example, on x86, .i rax == .rb \- enosys in syscall-enter-stop. since .b sigtrap (like any other signal) always happens .i after syscall-exit-stop, and at this point .i rax almost never contains .rb \- enosys , the .b sigtrap looks like "syscall-stop which is not syscall-enter-stop"; in other words, it looks like a "stray syscall-exit-stop" and can be detected this way. but such detection is fragile and is best avoided. .pp using the .b ptrace_o_tracesysgood option is the recommended method to distinguish syscall-stops from other kinds of ptrace-stops, since it is reliable and does not incur a performance penalty. .pp syscall-enter-stop and syscall-exit-stop are indistinguishable from each other by the tracer. the tracer needs to keep track of the sequence of ptrace-stops in order to not misinterpret syscall-enter-stop as syscall-exit-stop or vice versa. in general, a syscall-enter-stop is always followed by syscall-exit-stop, .b ptrace_event stop, or the tracee's death; no other kinds of ptrace-stop can occur in between. however, note that seccomp stops (see below) can cause syscall-exit-stops, without preceding syscall-entry-stops. if seccomp is in use, care needs to be taken not to misinterpret such stops as syscall-entry-stops. .pp if after syscall-enter-stop, the tracer uses a restarting command other than .br ptrace_syscall , syscall-exit-stop is not generated. .pp .b ptrace_getsiginfo on syscall-stops returns .b sigtrap in .ir si_signo , with .i si_code set to .b sigtrap or .ir (sigtrap|0x80) . .\" .ss ptrace_event_seccomp stops (linux 3.5 to 4.7) the behavior of .br ptrace_event_seccomp stops and their interaction with other kinds of ptrace stops has changed between kernel versions. this documents the behavior from their introduction until linux 4.7 (inclusive). the behavior in later kernel versions is documented in the next section. .pp a .br ptrace_event_seccomp stop occurs whenever a .br seccomp_ret_trace rule is triggered. this is independent of which methods was used to restart the system call. notably, seccomp still runs even if the tracee was restarted using .br ptrace_sysemu and this system call is unconditionally skipped. .pp restarts from this stop will behave as if the stop had occurred right before the system call in question. in particular, both .br ptrace_syscall and .br ptrace_sysemu will normally cause a subsequent syscall-entry-stop. however, if after the .br ptrace_event_seccomp the system call number is negative, both the syscall-entry-stop and the system call itself will be skipped. this means that if the system call number is negative after a .br ptrace_event_seccomp and the tracee is restarted using .br ptrace_syscall , the next observed stop will be a syscall-exit-stop, rather than the syscall-entry-stop that might have been expected. .\" .ss ptrace_event_seccomp stops (since linux 4.8) starting with linux 4.8, .\" commit 93e35efb8de45393cf61ed07f7b407629bf698ea the .br ptrace_event_seccomp stop was reordered to occur between syscall-entry-stop and syscall-exit-stop. note that seccomp no longer runs (and no .b ptrace_event_seccomp will be reported) if the system call is skipped due to .br ptrace_sysemu . .pp functionally, a .b ptrace_event_seccomp stop functions comparably to a syscall-entry-stop (i.e., continuations using .br ptrace_syscall will cause syscall-exit-stops, the system call number may be changed and any other modified registers are visible to the to-be-executed system call as well). note that there may be, but need not have been a preceding syscall-entry-stop. .pp after a .br ptrace_event_seccomp stop, seccomp will be rerun, with a .br seccomp_ret_trace rule now functioning the same as a .br seccomp_ret_allow . specifically, this means that if registers are not modified during the .br ptrace_event_seccomp stop, the system call will then be allowed. .\" .ss ptrace_singlestep stops [details of these kinds of stops are yet to be documented.] .\" .\" fixme . .\" document stops occurring with ptrace_singlestep .\" .ss informational and restarting ptrace commands most ptrace commands (all except .br ptrace_attach , .br ptrace_seize , .br ptrace_traceme , .br ptrace_interrupt , and .br ptrace_kill ) require the tracee to be in a ptrace-stop, otherwise they fail with .br esrch . .pp when the tracee is in ptrace-stop, the tracer can read and write data to the tracee using informational commands. these commands leave the tracee in ptrace-stopped state: .pp .in +4n .ex ptrace(ptrace_peektext/peekdata/peekuser, pid, addr, 0); ptrace(ptrace_poketext/pokedata/pokeuser, pid, addr, long_val); ptrace(ptrace_getregs/getfpregs, pid, 0, &struct); ptrace(ptrace_setregs/setfpregs, pid, 0, &struct); ptrace(ptrace_getregset, pid, nt_foo, &iov); ptrace(ptrace_setregset, pid, nt_foo, &iov); ptrace(ptrace_getsiginfo, pid, 0, &siginfo); ptrace(ptrace_setsiginfo, pid, 0, &siginfo); ptrace(ptrace_geteventmsg, pid, 0, &long_var); ptrace(ptrace_setoptions, pid, 0, ptrace_o_flags); .ee .in .pp note that some errors are not reported. for example, setting signal information .ri ( siginfo ) may have no effect in some ptrace-stops, yet the call may succeed (return 0 and not set .ir errno ); querying .b ptrace_geteventmsg may succeed and return some random value if current ptrace-stop is not documented as returning a meaningful event message. .pp the call .pp ptrace(ptrace_setoptions, pid, 0, ptrace_o_flags); .pp affects one tracee. the tracee's current flags are replaced. flags are inherited by new tracees created and "auto-attached" via active .br ptrace_o_tracefork , .br ptrace_o_tracevfork , or .br ptrace_o_traceclone options. .pp another group of commands makes the ptrace-stopped tracee run. they have the form: .pp ptrace(cmd, pid, 0, sig); .pp where .i cmd is .br ptrace_cont , .br ptrace_listen , .br ptrace_detach , .br ptrace_syscall , .br ptrace_singlestep , .br ptrace_sysemu , or .br ptrace_sysemu_singlestep . if the tracee is in signal-delivery-stop, .i sig is the signal to be injected (if it is nonzero). otherwise, .i sig may be ignored. (when restarting a tracee from a ptrace-stop other than signal-delivery-stop, recommended practice is to always pass 0 in .ir sig .) .ss attaching and detaching a thread can be attached to the tracer using the call .pp ptrace(ptrace_attach, pid, 0, 0); .pp or .pp ptrace(ptrace_seize, pid, 0, ptrace_o_flags); .pp .b ptrace_attach sends .b sigstop to this thread. if the tracer wants this .b sigstop to have no effect, it needs to suppress it. note that if other signals are concurrently sent to this thread during attach, the tracer may see the tracee enter signal-delivery-stop with other signal(s) first! the usual practice is to reinject these signals until .b sigstop is seen, then suppress .b sigstop injection. the design bug here is that a ptrace attach and a concurrently delivered .b sigstop may race and the concurrent .b sigstop may be lost. .\" .\" fixme describe how to attach to a thread which is already group-stopped. .pp since attaching sends .b sigstop and the tracer usually suppresses it, this may cause a stray .b eintr return from the currently executing system call in the tracee, as described in the "signal injection and suppression" section. .pp since linux 3.4, .b ptrace_seize can be used instead of .br ptrace_attach . .b ptrace_seize does not stop the attached process. if you need to stop it after attach (or at any other time) without sending it any signals, use .b ptrace_interrupt command. .pp the request .pp ptrace(ptrace_traceme, 0, 0, 0); .pp turns the calling thread into a tracee. the thread continues to run (doesn't enter ptrace-stop). a common practice is to follow the .b ptrace_traceme with .pp raise(sigstop); .pp and allow the parent (which is our tracer now) to observe our signal-delivery-stop. .pp if the .br ptrace_o_tracefork , .br ptrace_o_tracevfork , or .br ptrace_o_traceclone options are in effect, then children created by, respectively, .br vfork (2) or .br clone (2) with the .b clone_vfork flag, .br fork (2) or .br clone (2) with the exit signal set to .br sigchld , and other kinds of .br clone (2), are automatically attached to the same tracer which traced their parent. .b sigstop is delivered to the children, causing them to enter signal-delivery-stop after they exit the system call which created them. .pp detaching of the tracee is performed by: .pp ptrace(ptrace_detach, pid, 0, sig); .pp .b ptrace_detach is a restarting operation; therefore it requires the tracee to be in ptrace-stop. if the tracee is in signal-delivery-stop, a signal can be injected. otherwise, the .i sig parameter may be silently ignored. .pp if the tracee is running when the tracer wants to detach it, the usual solution is to send .b sigstop (using .br tgkill (2), to make sure it goes to the correct thread), wait for the tracee to stop in signal-delivery-stop for .b sigstop and then detach it (suppressing .b sigstop injection). a design bug is that this can race with concurrent .br sigstop s. another complication is that the tracee may enter other ptrace-stops and needs to be restarted and waited for again, until .b sigstop is seen. yet another complication is to be sure that the tracee is not already ptrace-stopped, because no signal delivery happens while it is\(emnot even .br sigstop . .\" fixme describe how to detach from a group-stopped tracee so that it .\" doesn't run, but continues to wait for sigcont. .pp if the tracer dies, all tracees are automatically detached and restarted, unless they were in group-stop. handling of restart from group-stop is currently buggy, but the "as planned" behavior is to leave tracee stopped and waiting for .br sigcont . if the tracee is restarted from signal-delivery-stop, the pending signal is injected. .ss execve(2) under ptrace .\" clone(2) clone_thread says: .\" if any of the threads in a thread group performs an execve(2), .\" then all threads other than the thread group leader are terminated, .\" and the new program is executed in the thread group leader. .\" when one thread in a multithreaded process calls .br execve (2), the kernel destroys all other threads in the process, .\" in kernel 3.1 sources, see fs/exec.c::de_thread() and resets the thread id of the execing thread to the thread group id (process id). (or, to put things another way, when a multithreaded process does an .br execve (2), at completion of the call, it appears as though the .br execve (2) occurred in the thread group leader, regardless of which thread did the .br execve (2).) this resetting of the thread id looks very confusing to tracers: .ip * 3 all other threads stop in .b ptrace_event_exit stop, if the .br ptrace_o_traceexit option was turned on. then all other threads except the thread group leader report death as if they exited via .br _exit (2) with exit code 0. .ip * the execing tracee changes its thread id while it is in the .br execve (2). (remember, under ptrace, the "pid" returned from .br waitpid (2), or fed into ptrace calls, is the tracee's thread id.) that is, the tracee's thread id is reset to be the same as its process id, which is the same as the thread group leader's thread id. .ip * then a .b ptrace_event_exec stop happens, if the .br ptrace_o_traceexec option was turned on. .ip * if the thread group leader has reported its .b ptrace_event_exit stop by this time, it appears to the tracer that the dead thread leader "reappears from nowhere". (note: the thread group leader does not report death via .i wifexited(status) until there is at least one other live thread. this eliminates the possibility that the tracer will see it dying and then reappearing.) if the thread group leader was still alive, for the tracer this may look as if thread group leader returns from a different system call than it entered, or even "returned from a system call even though it was not in any system call". if the thread group leader was not traced (or was traced by a different tracer), then during .br execve (2) it will appear as if it has become a tracee of the tracer of the execing tracee. .pp all of the above effects are the artifacts of the thread id change in the tracee. .pp the .b ptrace_o_traceexec option is the recommended tool for dealing with this situation. first, it enables .br ptrace_event_exec stop, which occurs before .br execve (2) returns. in this stop, the tracer can use .b ptrace_geteventmsg to retrieve the tracee's former thread id. (this feature was introduced in linux 3.0.) second, the .b ptrace_o_traceexec option disables legacy .b sigtrap generation on .br execve (2). .pp when the tracer receives .b ptrace_event_exec stop notification, it is guaranteed that except this tracee and the thread group leader, no other threads from the process are alive. .pp on receiving the .b ptrace_event_exec stop notification, the tracer should clean up all its internal data structures describing the threads of this process, and retain only one data structure\(emone which describes the single still running tracee, with .pp thread id == thread group id == process id. .pp example: two threads call .br execve (2) at the same time: .pp .nf *** we get syscall-enter-stop in thread 1: ** pid1 execve("/bin/foo", "foo" *** we issue ptrace_syscall for thread 1 ** *** we get syscall-enter-stop in thread 2: ** pid2 execve("/bin/bar", "bar" *** we issue ptrace_syscall for thread 2 ** *** we get ptrace_event_exec for pid0, we issue ptrace_syscall ** *** we get syscall-exit-stop for pid0: ** pid0 <... execve resumed> ) = 0 .fi .pp if the .b ptrace_o_traceexec option is .i not in effect for the execing tracee, and if the tracee was .br ptrace_attach ed rather that .br ptrace_seize d, the kernel delivers an extra .b sigtrap to the tracee after .br execve (2) returns. this is an ordinary signal (similar to one which can be generated by .ir "kill \-trap" ), not a special kind of ptrace-stop. employing .b ptrace_getsiginfo for this signal returns .i si_code set to 0 .ri ( si_user ). this signal may be blocked by signal mask, and thus may be delivered (much) later. .pp usually, the tracer (for example, .br strace (1)) would not want to show this extra post-execve .b sigtrap signal to the user, and would suppress its delivery to the tracee (if .b sigtrap is set to .br sig_dfl , it is a killing signal). however, determining .i which .b sigtrap to suppress is not easy. setting the .b ptrace_o_traceexec option or using .b ptrace_seize and thus suppressing this extra .b sigtrap is the recommended approach. .ss real parent the ptrace api (ab)uses the standard unix parent/child signaling over .br waitpid (2). this used to cause the real parent of the process to stop receiving several kinds of .br waitpid (2) notifications when the child process is traced by some other process. .pp many of these bugs have been fixed, but as of linux 2.6.38 several still exist; see bugs below. .pp as of linux 2.6.38, the following is believed to work correctly: .ip * 3 exit/death by signal is reported first to the tracer, then, when the tracer consumes the .br waitpid (2) result, to the real parent (to the real parent only when the whole multithreaded process exits). if the tracer and the real parent are the same process, the report is sent only once. .sh return value on success, the .b ptrace_peek* requests return the requested data (but see notes), the .b ptrace_seccomp_get_filter request returns the number of instructions in the bpf program, the .b ptrace_get_syscall_info request returns the number of bytes available to be written by the kernel, and other requests return zero. .pp on error, all requests return \-1, and .i errno is set to indicate the error. since the value returned by a successful .b ptrace_peek* request may be \-1, the caller must clear .i errno before the call, and then check it afterward to determine whether or not an error occurred. .sh errors .tp .b ebusy (i386 only) there was an error with allocating or freeing a debug register. .tp .b efault there was an attempt to read from or write to an invalid area in the tracer's or the tracee's memory, probably because the area wasn't mapped or accessible. unfortunately, under linux, different variations of this fault will return .b eio or .b efault more or less arbitrarily. .tp .b einval an attempt was made to set an invalid option. .tp .b eio .i request is invalid, or an attempt was made to read from or write to an invalid area in the tracer's or the tracee's memory, or there was a word-alignment violation, or an invalid signal was specified during a restart request. .tp .b eperm the specified process cannot be traced. this could be because the tracer has insufficient privileges (the required capability is .br cap_sys_ptrace ); unprivileged processes cannot trace processes that they cannot send signals to or those running set-user-id/set-group-id programs, for obvious reasons. alternatively, the process may already be being traced, or (on kernels before 2.6.26) be .br init (1) (pid 1). .tp .b esrch the specified process does not exist, or is not currently being traced by the caller, or is not stopped (for requests that require a stopped tracee). .sh conforming to svr4, 4.3bsd. .sh notes although arguments to .br ptrace () are interpreted according to the prototype given, glibc currently declares .br ptrace () as a variadic function with only the .i request argument fixed. it is recommended to always supply four arguments, even if the requested operation does not use them, setting unused/ignored arguments to .i 0l or .ir "(void\ *)\ 0". .pp in linux kernels before 2.6.26, .\" see commit 00cd5c37afd5f431ac186dd131705048c0a11fdb .br init (1), the process with pid 1, may not be traced. .pp a tracees parent continues to be the tracer even if that tracer calls .br execve (2). .pp the layout of the contents of memory and the user area are quite operating-system- and architecture-specific. the offset supplied, and the data returned, might not entirely match with the definition of .ir "struct user" . .\" see http://lkml.org/lkml/2008/5/8/375 .pp the size of a "word" is determined by the operating-system variant (e.g., for 32-bit linux it is 32 bits). .pp this page documents the way the .br ptrace () call works currently in linux. its behavior differs significantly on other flavors of unix. in any case, use of .br ptrace () is highly specific to the operating system and architecture. .\" .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .ss ptrace access mode checking various parts of the kernel-user-space api (not just .br ptrace () operations), require so-called "ptrace access mode" checks, whose outcome determines whether an operation is permitted (or, in a few cases, causes a "read" operation to return sanitized data). these checks are performed in cases where one process can inspect sensitive information about, or in some cases modify the state of, another process. the checks are based on factors such as the credentials and capabilities of the two processes, whether or not the "target" process is dumpable, and the results of checks performed by any enabled linux security module (lsm)\(emfor example, selinux, yama, or smack\(emand by the commoncap lsm (which is always invoked). .pp prior to linux 2.6.27, all access checks were of a single type. since linux 2.6.27, .\" commit 006ebb40d3d65338bd74abb03b945f8d60e362bd two access mode levels are distinguished: .tp .br ptrace_mode_read for "read" operations or other operations that are less dangerous, such as: .br get_robust_list (2); .br kcmp (2); reading .ir /proc/[pid]/auxv , .ir /proc/[pid]/environ , or .ir /proc/[pid]/stat ; or .br readlink (2) of a .ir /proc/[pid]/ns/* file. .tp .br ptrace_mode_attach for "write" operations, or other operations that are more dangerous, such as: ptrace attaching .rb ( ptrace_attach ) to another process or calling .br process_vm_writev (2). .rb ( ptrace_mode_attach was effectively the default before linux 2.6.27.) .\" .\" regarding the above description of the distinction between .\" ptrace_mode_read and ptrace_mode_attach, stephen smalley notes: .\" .\" that was the intent when the distinction was introduced, but it doesn't .\" appear to have been properly maintained, e.g. there is now a common .\" helper lock_trace() that is used for .\" /proc/pid/{stack,syscall,personality} but checks ptrace_mode_attach, and .\" ptrace_mode_attach is also used in timerslack_ns_write/show(). likely .\" should review and make them consistent. there was also some debate .\" about proper handling of /proc/pid/fd. arguably that one might belong .\" back in the _attach camp. .\" .pp since linux 4.5, .\" commit caaee6234d05a58c5b4d05e7bf766131b810a657 the above access mode checks are combined (ored) with one of the following modifiers: .tp .b ptrace_mode_fscreds use the caller's filesystem uid and gid (see .br credentials (7)) or effective capabilities for lsm checks. .tp .b ptrace_mode_realcreds use the caller's real uid and gid or permitted capabilities for lsm checks. this was effectively the default before linux 4.5. .pp because combining one of the credential modifiers with one of the aforementioned access modes is typical, some macros are defined in the kernel sources for the combinations: .tp .b ptrace_mode_read_fscreds defined as .br "ptrace_mode_read | ptrace_mode_fscreds" . .tp .b ptrace_mode_read_realcreds defined as .br "ptrace_mode_read | ptrace_mode_realcreds" . .tp .b ptrace_mode_attach_fscreds defined as .br "ptrace_mode_attach | ptrace_mode_fscreds" . .tp .b ptrace_mode_attach_realcreds defined as .br "ptrace_mode_attach | ptrace_mode_realcreds" . .pp one further modifier can be ored with the access mode: .tp .br ptrace_mode_noaudit " (since linux 3.3)" .\" commit 69f594a38967f4540ce7a29b3fd214e68a8330bd .\" just for /proc/pid/stat don't audit this access mode check. this modifier is employed for ptrace access mode checks (such as checks when reading .ir /proc/[pid]/stat ) that merely cause the output to be filtered or sanitized, rather than causing an error to be returned to the caller. in these cases, accessing the file is not a security violation and there is no reason to generate a security audit record. this modifier suppresses the generation of such an audit record for the particular access check. .pp note that all of the .br ptrace_mode_* constants described in this subsection are kernel-internal, and not visible to user space. the constant names are mentioned here in order to label the various kinds of ptrace access mode checks that are performed for various system calls and accesses to various pseudofiles (e.g., under .ir /proc ). these names are used in other manual pages to provide a simple shorthand for labeling the different kernel checks. .pp the algorithm employed for ptrace access mode checking determines whether the calling process is allowed to perform the corresponding action on the target process. (in the case of opening .ir /proc/[pid] files, the "calling process" is the one opening the file, and the process with the corresponding pid is the "target process".) the algorithm is as follows: .ip 1. 3 if the calling thread and the target thread are in the same thread group, access is always allowed. .ip 2. if the access mode specifies .br ptrace_mode_fscreds , then, for the check in the next step, employ the caller's filesystem uid and gid. (as noted in .br credentials (7), the filesystem uid and gid almost always have the same values as the corresponding effective ids.) .ip otherwise, the access mode specifies .br ptrace_mode_realcreds , so use the caller's real uid and gid for the checks in the next step. (most apis that check the caller's uid and gid use the effective ids. for historical reasons, the .br ptrace_mode_realcreds check uses the real ids instead.) .ip 3. deny access if .i neither of the following is true: .rs .ip \(bu 2 the real, effective, and saved-set user ids of the target match the caller's user id, .ir and the real, effective, and saved-set group ids of the target match the caller's group id. .ip \(bu the caller has the .b cap_sys_ptrace capability in the user namespace of the target. .re .ip 4. deny access if the target process "dumpable" attribute has a value other than 1 .rb ( suid_dump_user ; see the discussion of .br pr_set_dumpable in .br prctl (2)), and the caller does not have the .br cap_sys_ptrace capability in the user namespace of the target process. .ip 5. the kernel lsm .ir security_ptrace_access_check () interface is invoked to see if ptrace access is permitted. the results depend on the lsm(s). the implementation of this interface in the commoncap lsm performs the following steps: .\" (in cap_ptrace_access_check()): .rs .ip a) 3 if the access mode includes .br ptrace_mode_fscreds , then use the caller's .i effective capability set in the following check; otherwise (the access mode specifies .br ptrace_mode_realcreds , so) use the caller's .i permitted capability set. .ip b) deny access if .i neither of the following is true: .rs .ip \(bu 2 the caller and the target process are in the same user namespace, and the caller's capabilities are a superset of the target process's .i permitted capabilities. .ip \(bu the caller has the .b cap_sys_ptrace capability in the target process's user namespace. .re .ip note that the commoncap lsm does not distinguish between .b ptrace_mode_read and .br ptrace_mode_attach . .re .ip 6. if access has not been denied by any of the preceding steps, then access is allowed. .\" .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .ss /proc/sys/kernel/yama/ptrace_scope on systems with the yama linux security module (lsm) installed (i.e., the kernel was configured with .br config_security_yama ), the .i /proc/sys/kernel/yama/ptrace_scope file (available since linux 3.4) .\" commit 2d514487faf188938a4ee4fb3464eeecfbdcf8eb can be used to restrict the ability to trace a process with .br ptrace () (and thus also the ability to use tools such as .br strace (1) and .br gdb (1)). the goal of such restrictions is to prevent attack escalation whereby a compromised process can ptrace-attach to other sensitive processes (e.g., a gpg agent or an ssh session) owned by the user in order to gain additional credentials that may exist in memory and thus expand the scope of the attack. .pp more precisely, the yama lsm limits two types of operations: .ip * 3 any operation that performs a ptrace access mode .br ptrace_mode_attach check\(emfor example, .br ptrace () .br ptrace_attach . (see the "ptrace access mode checking" discussion above.) .ip * .br ptrace () .br ptrace_traceme . .pp a process that has the .b cap_sys_ptrace capability can update the .ir /proc/sys/kernel/yama/ptrace_scope file with one of the following values: .tp 0 ("classic ptrace permissions") no additional restrictions on operations that perform .br ptrace_mode_attach checks (beyond those imposed by the commoncap and other lsms). .ip the use of .br ptrace_traceme is unchanged. .tp 1 ("restricted ptrace") [default value] when performing an operation that requires a .br ptrace_mode_attach check, the calling process must either have the .b cap_sys_ptrace capability in the user namespace of the target process or it must have a predefined relationship with the target process. by default, the predefined relationship is that the target process must be a descendant of the caller. .ip a target process can employ the .br prctl (2) .b pr_set_ptracer operation to declare an additional pid that is allowed to perform .br ptrace_mode_attach operations on the target. see the kernel source file .ir documentation/admin\-guide/lsm/yama.rst .\" commit 90bb766440f2147486a2acc3e793d7b8348b0c22 (or .ir documentation/security/yama.txt before linux 4.13) for further details. .ip the use of .br ptrace_traceme is unchanged. .tp 2 ("admin-only attach") only processes with the .b cap_sys_ptrace capability in the user namespace of the target process may perform .br ptrace_mode_attach operations or trace children that employ .br ptrace_traceme . .tp 3 ("no attach") no process may perform .br ptrace_mode_attach operations or trace children that employ .br ptrace_traceme . .ip once this value has been written to the file, it cannot be changed. .pp with respect to values 1 and 2, note that creating a new user namespace effectively removes the protection offered by yama. this is because a process in the parent user namespace whose effective uid matches the uid of the creator of a child namespace has all capabilities (including .br cap_sys_ptrace ) when performing operations within the child user namespace (and further-removed descendants of that namespace). consequently, when a process tries to use user namespaces to sandbox itself, it inadvertently weakens the protections offered by the yama lsm. .\" .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .ss c library/kernel differences at the system call level, the .br ptrace_peektext , .br ptrace_peekdata , and .br ptrace_peekuser requests have a different api: they store the result at the address specified by the .i data parameter, and the return value is the error flag. the glibc wrapper function provides the api given in description above, with the result being returned via the function return value. .sh bugs on hosts with 2.6 kernel headers, .b ptrace_setoptions is declared with a different value than the one for 2.4. this leads to applications compiled with 2.6 kernel headers failing when run on 2.4 kernels. this can be worked around by redefining .b ptrace_setoptions to .br ptrace_oldsetoptions , if that is defined. .pp group-stop notifications are sent to the tracer, but not to real parent. last confirmed on 2.6.38.6. .pp if a thread group leader is traced and exits by calling .br _exit (2), .\" note from denys vlasenko: .\" here "exits" means any kind of death - _exit, exit_group, .\" signal death. signal death and exit_group cases are trivial, .\" though: since signal death and exit_group kill all other threads .\" too, "until all other threads exit" thing happens rather soon .\" in these cases. therefore, only _exit presents observably .\" puzzling behavior to ptrace users: thread leader _exit's, .\" but wifexited isn't reported! we are trying to explain here .\" why it is so. a .b ptrace_event_exit stop will happen for it (if requested), but the subsequent .b wifexited notification will not be delivered until all other threads exit. as explained above, if one of other threads calls .br execve (2), the death of the thread group leader will .i never be reported. if the execed thread is not traced by this tracer, the tracer will never know that .br execve (2) happened. one possible workaround is to .b ptrace_detach the thread group leader instead of restarting it in this case. last confirmed on 2.6.38.6. .\" fixme . need to test/verify this scenario .pp a .b sigkill signal may still cause a .b ptrace_event_exit stop before actual signal death. this may be changed in the future; .b sigkill is meant to always immediately kill tasks even under ptrace. last confirmed on linux 3.13. .pp some system calls return with .b eintr if a signal was sent to a tracee, but delivery was suppressed by the tracer. (this is very typical operation: it is usually done by debuggers on every attach, in order to not introduce a bogus .br sigstop ). as of linux 3.2.9, the following system calls are affected (this list is likely incomplete): .br epoll_wait (2), and .br read (2) from an .br inotify (7) file descriptor. the usual symptom of this bug is that when you attach to a quiescent process with the command .pp .in +4n .ex strace \-p .ee .in .pp then, instead of the usual and expected one-line output such as .pp .in +4n .ex restart_syscall(<... resuming interrupted call ...>_ .ee .in .pp or .pp .in +4n .ex select(6, [5], null, [5], null_ .ee .in .pp ('_' denotes the cursor position), you observe more than one line. for example: .pp .in +4n .ex clock_gettime(clock_monotonic, {15370, 690928118}) = 0 epoll_wait(4,_ .ee .in .pp what is not visible here is that the process was blocked in .br epoll_wait (2) before .br strace (1) has attached to it. attaching caused .br epoll_wait (2) to return to user space with the error .br eintr . in this particular case, the program reacted to .b eintr by checking the current time, and then executing .br epoll_wait (2) again. (programs which do not expect such "stray" .br eintr errors may behave in an unintended way upon an .br strace (1) attach.) .pp contrary to the normal rules, the glibc wrapper for .br ptrace () can set .i errno to zero. .sh see also .br gdb (1), .br ltrace (1), .br strace (1), .br clone (2), .br execve (2), .br fork (2), .br gettid (2), .br prctl (2), .br seccomp (2), .br sigaction (2), .br tgkill (2), .br vfork (2), .br waitpid (2), .br exec (3), .br capabilities (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" this replaces an earlier man page written by walter harms .\" . .\" .th assert_perror 3 2021-03-22 "gnu" "linux programmer's manual" .sh name assert_perror \- test errnum and abort .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void assert_perror(int " errnum ); .fi .sh description if the macro .b ndebug was defined at the moment .i was last included, the macro .br assert_perror () generates no code, and hence does nothing at all. otherwise, the macro .br assert_perror () prints an error message to standard error and terminates the program by calling .br abort (3) if .i errnum is nonzero. the message contains the filename, function name and line number of the macro call, and the output of .ir strerror(errnum) . .sh return value no value is returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br assert_perror () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this is a gnu extension. .sh bugs the purpose of the assert macros is to help programmers find bugs in their programs, things that cannot happen unless there was a coding mistake. however, with system or library calls the situation is rather different, and error returns can happen, and will happen, and should be tested for. not by an assert, where the test goes away when .b ndebug is defined, but by proper error handling code. never use this macro. .sh see also .br abort (3), .br assert (3), .br exit (3), .br strerror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-16.7 .so man2/fcntl.2 .\" copyright (c) 2008 petr baudis .\" and copyright (c) 2009, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 2008-12-08 petr baudis .\" rewrite the bsd manpage in the linux man pages style and account .\" for glibc specificities, provide an example. .\" 2009-01-14 mtk, many edits and changes, rewrote example program. .\" .th getifaddrs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getifaddrs, freeifaddrs \- get interface addresses .sh synopsis .nf .b #include .b #include .pp .bi "int getifaddrs(struct ifaddrs **" "ifap" ); .bi "void freeifaddrs(struct ifaddrs *" "ifa" ); .fi .sh description the .br getifaddrs () function creates a linked list of structures describing the network interfaces of the local system, and stores the address of the first item of the list in .ir *ifap . the list consists of .i ifaddrs structures, defined as follows: .pp .in +4n .ex struct ifaddrs { struct ifaddrs *ifa_next; /* next item in list */ char *ifa_name; /* name of interface */ unsigned int ifa_flags; /* flags from siocgifflags */ struct sockaddr *ifa_addr; /* address of interface */ struct sockaddr *ifa_netmask; /* netmask of interface */ union { struct sockaddr *ifu_broadaddr; /* broadcast address of interface */ struct sockaddr *ifu_dstaddr; /* point\-to\-point destination address */ } ifa_ifu; #define ifa_broadaddr ifa_ifu.ifu_broadaddr #define ifa_dstaddr ifa_ifu.ifu_dstaddr void *ifa_data; /* address\-specific data */ }; .ee .in .pp the .i ifa_next field contains a pointer to the next structure on the list, or null if this is the last item of the list. .pp the .i ifa_name points to the null-terminated interface name. .\" the constant .\" .b if namesize .\" indicates the maximum length of this field. .pp the .i ifa_flags field contains the interface flags, as returned by the .b siocgifflags .br ioctl (2) operation (see .br netdevice (7) for a list of these flags). .pp the .i ifa_addr field points to a structure containing the interface address. (the .i sa_family subfield should be consulted to determine the format of the address structure.) this field may contain a null pointer. .pp the .i ifa_netmask field points to a structure containing the netmask associated with .ir ifa_addr , if applicable for the address family. this field may contain a null pointer. .pp depending on whether the bit .b iff_broadcast or .b iff_pointopoint is set in .i ifa_flags (only one can be set at a time), either .i ifa_broadaddr will contain the broadcast address associated with .i ifa_addr (if applicable for the address family) or .i ifa_dstaddr will contain the destination address of the point-to-point interface. .pp the .i ifa_data field points to a buffer containing address-family-specific data; this field may be null if there is no such data for this interface. .pp the data returned by .br getifaddrs () is dynamically allocated and should be freed using .br freeifaddrs () when no longer needed. .sh return value on success, .br getifaddrs () returns zero; on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .br getifaddrs () may fail and set .i errno for any of the errors specified for .br socket (2), .br bind (2), .br getsockname (2), .br recvmsg (2), .br sendto (2), .br malloc (3), or .br realloc (3). .sh versions the .br getifaddrs () function first appeared in glibc 2.3, but before glibc 2.3.3, the implementation supported only ipv4 addresses; ipv6 support was added in glibc 2.3.3. support of address families other than ipv4 is available only on kernels that support netlink. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getifaddrs (), .br freeifaddrs () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to not in posix.1. this function first appeared in bsdi and is present on the bsd systems, but with slightly different semantics documented\(emreturning one entry per interface, not per address. this means .i ifa_addr and other fields can actually be null if the interface has no address, and no link-level address is returned if the interface has an ip address assigned. also, the way of choosing either .i ifa_broadaddr or .i ifa_dstaddr differs on various systems. .\" , but the bsd-derived documentation generally .\" appears to be confused and obsolete on this point. .\" i.e., commonly it still says one of them will be null, even if .\" the ifa_ifu union is already present .sh notes the addresses returned on linux will usually be the ipv4 and ipv6 addresses assigned to the interface, but also one .b af_packet address per interface containing lower-level details about the interface and its physical layer. in this case, the .i ifa_data field may contain a pointer to a .ir "struct rtnl_link_stats" , defined in .ir (in linux 2.4 and earlier, .ir "struct net_device_stats" , defined in .ir ), which contains various interface attributes and statistics. .sh examples the program below demonstrates the use of .br getifaddrs (), .br freeifaddrs (), and .br getnameinfo (3). here is what we see when running this program on one system: .pp .in +4n .ex $ \fb./a.out\fp lo af_packet (17) tx_packets = 524; rx_packets = 524 tx_bytes = 38788; rx_bytes = 38788 wlp3s0 af_packet (17) tx_packets = 108391; rx_packets = 130245 tx_bytes = 30420659; rx_bytes = 94230014 em1 af_packet (17) tx_packets = 0; rx_packets = 0 tx_bytes = 0; rx_bytes = 0 lo af_inet (2) address: <127.0.0.1> wlp3s0 af_inet (2) address: <192.168.235.137> lo af_inet6 (10) address: <::1> wlp3s0 af_inet6 (10) address: .ee .in .ss program source \& .ex #define _gnu_source /* to get defns of ni_maxserv and ni_maxhost */ #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { struct ifaddrs *ifaddr; int family, s; char host[ni_maxhost]; if (getifaddrs(&ifaddr) == \-1) { perror("getifaddrs"); exit(exit_failure); } /* walk through linked list, maintaining head pointer so we can free list later. */ for (struct ifaddrs *ifa = ifaddr; ifa != null; ifa = ifa\->ifa_next) { if (ifa\->ifa_addr == null) continue; family = ifa\->ifa_addr\->sa_family; /* display interface name and family (including symbolic form of the latter for the common families). */ printf("%\-8s %s (%d)\en", ifa\->ifa_name, (family == af_packet) ? "af_packet" : (family == af_inet) ? "af_inet" : (family == af_inet6) ? "af_inet6" : "???", family); /* for an af_inet* interface address, display the address. */ if (family == af_inet || family == af_inet6) { s = getnameinfo(ifa\->ifa_addr, (family == af_inet) ? sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6), host, ni_maxhost, null, 0, ni_numerichost); if (s != 0) { printf("getnameinfo() failed: %s\en", gai_strerror(s)); exit(exit_failure); } printf("\et\etaddress: <%s>\en", host); } else if (family == af_packet && ifa\->ifa_data != null) { struct rtnl_link_stats *stats = ifa\->ifa_data; printf("\et\ettx_packets = %10u; rx_packets = %10u\en" "\et\ettx_bytes = %10u; rx_bytes = %10u\en", stats\->tx_packets, stats\->rx_packets, stats\->tx_bytes, stats\->rx_bytes); } } freeifaddrs(ifaddr); exit(exit_success); } .ee .sh see also .br bind (2), .br getsockname (2), .br socket (2), .br packet (7), .br ifconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on the description in glibc source and infopages .\" .\" corrections and additions, aeb .th argz_add 3 2021-03-22 "" "linux programmer's manual" .sh name argz_add, argz_add_sep, argz_append, argz_count, argz_create, argz_create_sep, argz_delete, argz_extract, argz_insert, argz_next, argz_replace, argz_stringify \- functions to handle an argz list .sh synopsis .nf .b "#include " .pp .bi "error_t argz_add(char **restrict " argz ", size_t *restrict " argz_len ", .bi " const char *restrict " str ); .pp .bi "error_t argz_add_sep(char **restrict " argz \ ", size_t *restrict " argz_len , .bi " const char *restrict " str ", int " delim ); .pp .bi "error_t argz_append(char **restrict " argz ", size_t *restrict " argz_len , .bi " const char *restrict " buf ", size_t " buf_len ); .pp .bi "size_t argz_count(const char *" argz ", size_t " argz_len ); .pp .bi "error_t argz_create(char *const " argv "[], char **restrict " argz , .bi " size_t *restrict " argz_len ); .pp .bi "error_t argz_create_sep(const char *restrict " str ", int " sep , .bi " char **restrict " argz ", size_t *restrict " argz_len ); .pp .bi "void argz_delete(char **restrict " argz ", size_t *restrict " argz_len , .bi " char *restrict " entry ); .pp .bi "void argz_extract(const char *restrict " argz ", size_t " argz_len , .bi " char **restrict " argv ); .pp .bi "error_t argz_insert(char **restrict " argz ", size_t *restrict " argz_len , .bi " char *restrict " before ", const char *restrict " entry ); .pp .bi "char *argz_next(const char *restrict " argz ", size_t " argz_len , .bi " const char *restrict " entry ); .pp .bi "error_t argz_replace(char **restrict " argz \ ", size_t *restrict " argz_len , .bi " const char *restrict " str ", const char *restrict " with , .bi " unsigned int *restrict " replace_count ); .pp .bi "void argz_stringify(char *" argz ", size_t " len ", int " sep ); .fi .sh description these functions are glibc-specific. .pp an argz vector is a pointer to a character buffer together with a length. the intended interpretation of the character buffer is an array of strings, where the strings are separated by null bytes (\(aq\e0\(aq). if the length is nonzero, the last byte of the buffer must be a null byte. .pp these functions are for handling argz vectors. the pair (null,0) is an argz vector, and, conversely, argz vectors of length 0 must have null pointer. allocation of nonempty argz vectors is done using .br malloc (3), so that .br free (3) can be used to dispose of them again. .pp .br argz_add () adds the string .i str at the end of the array .ir *argz , and updates .i *argz and .ir *argz_len . .pp .br argz_add_sep () is similar, but splits the string .i str into substrings separated by the delimiter .ir delim . for example, one might use this on a unix search path with delimiter \(aq:\(aq. .pp .br argz_append () appends the argz vector .ri ( buf ,\ buf_len ) after .ri ( *argz ,\ *argz_len ) and updates .ir *argz and .ir *argz_len . (thus, .i *argz_len will be increased by .ir buf_len .) .pp .br argz_count () counts the number of strings, that is, the number of null bytes (\(aq\e0\(aq), in .ri ( argz ,\ argz_len ). .pp .br argz_create () converts a unix-style argument vector .ir argv , terminated by .ir "(char\ *)\ 0" , into an argz vector .ri ( *argz ,\ *argz_len ). .pp .br argz_create_sep () converts the null-terminated string .i str into an argz vector .ri ( *argz ,\ *argz_len ) by breaking it up at every occurrence of the separator .ir sep . .pp .br argz_delete () removes the substring pointed to by .i entry from the argz vector .ri ( *argz ,\ *argz_len ) and updates .i *argz and .ir *argz_len . .pp .br argz_extract () is the opposite of .br argz_create (). it takes the argz vector .ri ( argz ,\ argz_len ) and fills the array starting at .i argv with pointers to the substrings, and a final null, making a unix-style argv vector. the array .i argv must have room for .ir argz_count ( argz ", " argz_len ") + 1" pointers. .pp .br argz_insert () is the opposite of .br argz_delete (). it inserts the argument .i entry at position .i before into the argz vector .ri ( *argz ,\ *argz_len ) and updates .i *argz and .ir *argz_len . if .i before is null, then .i entry will inserted at the end. .pp .br argz_next () is a function to step through the argz vector. if .i entry is null, the first entry is returned. otherwise, the entry following is returned. it returns null if there is no following entry. .pp .br argz_replace () replaces each occurrence of .i str with .ir with , reallocating argz as necessary. if .i replace_count is non-null, .i *replace_count will be incremented by the number of replacements. .pp .br argz_stringify () is the opposite of .br argz_create_sep (). it transforms the argz vector into a normal string by replacing all null bytes (\(aq\e0\(aq) except the last by .ir sep . .sh return value all argz functions that do memory allocation have a return type of .ir error_t (an integer type), and return 0 for success, and .b enomem if an allocation error occurs. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br argz_add (), .br argz_add_sep (), .br argz_append (), .br argz_count (), .br argz_create (), .br argz_create_sep (), .br argz_delete (), .br argz_extract (), .br argz_insert (), .br argz_next (), .br argz_replace (), .br argz_stringify () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are a gnu extension. .sh bugs argz vectors without a terminating null byte may lead to segmentation faults. .sh see also .br envz_add (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" opengroup's single unix specification .\" http://www.unix-systems.org/online.html .\" .\" 2000-06-30 correction by yuichi sato .\" 2000-11-15 aeb, fixed prototype .\" .th iconv 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iconv \- perform character set conversion .sh synopsis .nf .b #include .pp .bi "size_t iconv(iconv_t " cd , .bi " char **restrict " inbuf ", size_t *restrict " inbytesleft , .bi " char **restrict " outbuf ", size_t *restrict " outbytesleft ); .fi .sh description the .br iconv () function converts a sequence of characters in one character encoding to a sequence of characters in another character encoding. the .i cd argument is a conversion descriptor, previously created by a call to .br iconv_open (3); the conversion descriptor defines the character encodings that .br iconv () uses for the conversion. the .i inbuf argument is the address of a variable that points to the first character of the input sequence; .i inbytesleft indicates the number of bytes in that buffer. the .i outbuf argument is the address of a variable that points to the first byte available in the output buffer; .i outbytesleft indicates the number of bytes available in the output buffer. .pp the main case is when \fiinbuf\fp is not null and \fi*inbuf\fp is not null. in this case, the .br iconv () function converts the multibyte sequence starting at \fi*inbuf\fp to a multibyte sequence starting at \fi*outbuf\fp. at most \fi*inbytesleft\fp bytes, starting at \fi*inbuf\fp, will be read. at most \fi*outbytesleft\fp bytes, starting at \fi*outbuf\fp, will be written. .pp the .br iconv () function converts one multibyte character at a time, and for each character conversion it increments \fi*inbuf\fp and decrements \fi*inbytesleft\fp by the number of converted input bytes, it increments \fi*outbuf\fp and decrements \fi*outbytesleft\fp by the number of converted output bytes, and it updates the conversion state contained in \ficd\fp. if the character encoding of the input is stateful, the .br iconv () function can also convert a sequence of input bytes to an update to the conversion state without producing any output bytes; such input is called a \fishift sequence\fp. the conversion can stop for four reasons: .ip 1. 3 an invalid multibyte sequence is encountered in the input. in this case, it sets \fierrno\fp to \fbeilseq\fp and returns .ir (size_t)\ \-1 . \fi*inbuf\fp is left pointing to the beginning of the invalid multibyte sequence. .ip 2. the input byte sequence has been entirely converted, that is, \fi*inbytesleft\fp has gone down to 0. in this case, .br iconv () returns the number of nonreversible conversions performed during this call. .ip 3. an incomplete multibyte sequence is encountered in the input, and the input byte sequence terminates after it. in this case, it sets \fierrno\fp to \fbeinval\fp and returns .ir (size_t)\ \-1 . \fi*inbuf\fp is left pointing to the beginning of the incomplete multibyte sequence. .ip 4. the output buffer has no more room for the next converted character. in this case, it sets \fierrno\fp to \fbe2big\fp and returns .ir (size_t)\ \-1 . .pp a different case is when \fiinbuf\fp is null or \fi*inbuf\fp is null, but \fioutbuf\fp is not null and \fi*outbuf\fp is not null. in this case, the .br iconv () function attempts to set \ficd\fp's conversion state to the initial state and store a corresponding shift sequence at \fi*outbuf\fp. at most \fi*outbytesleft\fp bytes, starting at \fi*outbuf\fp, will be written. if the output buffer has no more room for this reset sequence, it sets \fierrno\fp to \fbe2big\fp and returns .ir (size_t)\ \-1 . otherwise, it increments \fi*outbuf\fp and decrements \fi*outbytesleft\fp by the number of bytes written. .pp a third case is when \fiinbuf\fp is null or \fi*inbuf\fp is null, and \fioutbuf\fp is null or \fi*outbuf\fp is null. in this case, the .br iconv () function sets \ficd\fp's conversion state to the initial state. .sh return value the .br iconv () function returns the number of characters converted in a nonreversible way during this call; reversible conversions are not counted. in case of error, .br iconv () returns .ir (size_t)\ \-1 and sets .i errno to indicate the error. .sh errors the following errors can occur, among others: .tp .b e2big there is not sufficient room at \fi*outbuf\fp. .tp .b eilseq an invalid multibyte sequence has been encountered in the input. .tp .b einval an incomplete multibyte sequence has been encountered in the input. .sh versions this function is available in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iconv () t} thread safety mt-safe race:cd .te .hy .ad .sp 1 .pp the .br iconv () function is mt-safe, as long as callers arrange for mutual exclusion on the .i cd argument. .sh conforming to posix.1-2001, posix.1-2008. .sh notes in each series of calls to .br iconv (), the last should be one with \fiinbuf\fp or \fi*inbuf\fp equal to null, in order to flush out any partially converted input. .pp although .i inbuf and .i outbuf are typed as .ir "char\ **" , this does not mean that the objects they point can be interpreted as c strings or as arrays of characters: the interpretation of character byte sequences is handled internally by the conversion functions. in some encodings, a zero byte may be a valid part of a multibyte character. .pp the caller of .br iconv () must ensure that the pointers passed to the function are suitable for accessing characters in the appropriate character set. this includes ensuring correct alignment on platforms that have tight restrictions on alignment. .sh see also .br iconv_close (3), .br iconv_open (3), .br iconvconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/readv.2 .so man2/posix_fadvise.2 .so man3/rpc.3 .\" copyright (c) 2006, 2014, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th fexecve 3 2021-03-22 "linux" "linux programmer's manual" .sh name fexecve \- execute program specified via file descriptor .sh synopsis .nf .b #include .pp .bi "int fexecve(int " fd ", char *const " argv "[], char *const " envp []); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fexecve (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description .br fexecve () performs the same task as .br execve (2), with the difference that the file to be executed is specified via a file descriptor, .ir fd , rather than via a pathname. the file descriptor .i fd must be opened read-only .rb ( o_rdonly ) or with the .b o_path flag and the caller must have permission to execute the file that it refers to. .sh return value a successful call to .br fexecve () never returns. on error, the function does return, with a result value of \-1, and .i errno is set to indicate the error. .sh errors errors are as for .br execve (2), with the following additions: .tp .b einval .i fd is not a valid file descriptor, or .i argv is null, or .i envp is null. .tp .b enoent the close-on-exec flag is set on .ir fd , and .i fd refers to a script. see bugs. .tp .b enosys the kernel does not provide the .br execveat (2) system call, and the .i /proc filesystem could not be accessed. .sh versions .br fexecve () is implemented since glibc 2.3.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fexecve () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function is not specified in posix.1-2001, and is not widely available on other systems. it is specified in posix.1-2008. .sh notes on linux with glibc versions 2.26 and earlier, .br fexecve () is implemented using the .br proc (5) filesystem, so .i /proc needs to be mounted and available at the time of the call. since glibc 2.27, .\" glibc commit 43ffc53a352a67672210c9dd4959f6c6b7407e60 if the underlying kernel supports the .br execveat (2) system call, then .br fexecve () is implemented using that system call, with the benefit that .ir /proc does not need to be mounted. .pp the idea behind .br fexecve () is to allow the caller to verify (checksum) the contents of an executable before executing it. simply opening the file, checksumming the contents, and then doing an .br execve (2) would not suffice, since, between the two steps, the filename, or a directory prefix of the pathname, could have been exchanged (by, for example, modifying the target of a symbolic link). .br fexecve () does not mitigate the problem that the .i contents of a file could be changed between the checksumming and the call to .br fexecve (); for that, the solution is to ensure that the permissions on the file prevent it from being modified by malicious users. .pp the natural idiom when using .br fexecve () is to set the close-on-exec flag on .ir fd , so that the file descriptor does not leak through to the program that is executed. this approach is natural for two reasons. first, it prevents file descriptors being consumed unnecessarily. (the executed program normally has no need of a file descriptor that refers to the program itself.) second, if .br fexecve () is used recursively, employing the close-on-exec flag prevents the file descriptor exhaustion that would result from the fact that each step in the recursion would cause one more file descriptor to be passed to the new program. (but see bugs.) .sh bugs if .i fd refers to a script (i.e., it is an executable text file that names a script interpreter with a first line that begins with the characters .ir #! ) and the close-on-exec flag has been set for .ir fd , then .br fexecve () fails with the error .br enoent . this error occurs because, by the time the script interpreter is executed, .i fd has already been closed because of the close-on-exec flag. thus, the close-on-exec flag can't be set on .i fd if it refers to a script, leading to the problems described in notes. .sh see also .br execve (2), .br execveat (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cexp.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:49:59 1993 by rik faith (faith@cs.unc.edu) .th memmove 3 2021-03-22 "gnu" "linux programmer's manual" .sh name memmove \- copy memory area .sh synopsis .nf .b #include .pp .bi "void *memmove(void *" dest ", const void *" src ", size_t " n ); .fi .sh description the .br memmove () function copies .i n bytes from memory area .i src to memory area .ir dest . the memory areas may overlap: copying takes place as though the bytes in .i src are first copied into a temporary array that does not overlap .i src or .ir dest , and the bytes are then copied from the temporary array to .ir dest . .sh return value the .br memmove () function returns a pointer to .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memmove () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh see also .br bcopy (3), .br bstring (3), .br memccpy (3), .br memcpy (3), .br strcpy (3), .br strncpy (3), .br wmemmove (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1997 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2007, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, 2003-05-26, michael kerrisk, .\" .th getresuid 2 2021-03-22 "linux" "linux programmer's manual" .sh name getresuid, getresgid \- get real, effective, and saved user/group ids .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int getresuid(uid_t *" ruid ", uid_t *" euid ", uid_t *" suid ); .bi "int getresgid(gid_t *" rgid ", gid_t *" egid ", gid_t *" sgid ); .fi .sh description .br getresuid () returns the real uid, the effective uid, and the saved set-user-id of the calling process, in the arguments .ir ruid , .ir euid , and .ir suid , respectively. .br getresgid () performs the analogous task for the process's group ids. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault one of the arguments specified an address outside the calling program's address space. .sh versions these system calls appeared on linux starting with kernel 2.1.44. .pp the prototypes are given by glibc since version 2.3.2, provided .b _gnu_source is defined. .sh conforming to these calls are nonstandard; they also appear on hp-ux and some of the bsds. .sh notes the original linux .br getresuid () and .br getresgid () system calls supported only 16-bit user and group ids. subsequently, linux 2.4 added .br getresuid32 () and .br getresgid32 (), supporting 32-bit ids. the glibc .br getresuid () and .br getresgid () wrapper functions transparently deal with the variations across kernel versions. .sh see also .br getuid (2), .br setresuid (2), .br setreuid (2), .br setuid (2), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th math_error 7 2021-03-22 "linux" "linux programmer's manual" .sh name math_error \- detecting errors from mathematical functions .sh synopsis .nf .b #include .b #include .b #include .fi .sh description when an error occurs, most library functions indicate this fact by returning a special value (e.g., \-1 or null). because they typically return a floating-point number, the mathematical functions declared in .ir indicate an error using other mechanisms. there are two error-reporting mechanisms: the older one sets .ir errno ; the newer one uses the floating-point exception mechanism (the use of .br feclearexcept (3) and .br fetestexcept (3), as outlined below) described in .br fenv (3). .pp a portable program that needs to check for an error from a mathematical function should set .i errno to zero, and make the following call .pp .in +4n .ex feclearexcept(fe_all_except); .ee .in .pp before calling a mathematical function. .pp upon return from the mathematical function, if .i errno is nonzero, or the following call (see .br fenv (3)) returns nonzero .pp .in +4n .ex fetestexcept(fe_invalid | fe_divbyzero | fe_overflow | fe_underflow); .ee .in .pp .\" enum .\" { .\" fe_invalid = 0x01, .\" __fe_denorm = 0x02, .\" fe_divbyzero = 0x04, .\" fe_overflow = 0x08, .\" fe_underflow = 0x10, .\" fe_inexact = 0x20 .\" }; then an error occurred in the mathematical function. .pp the error conditions that can occur for mathematical functions are described below. .ss domain error a .i domain error occurs when a mathematical function is supplied with an argument whose value falls outside the domain for which the function is defined (e.g., giving a negative argument to .br log (3)). when a domain error occurs, math functions commonly return a nan (though some functions return a different value in this case); .i errno is set to .br edom , and an "invalid" .rb ( fe_invalid ) floating-point exception is raised. .ss pole error a .i pole error occurs when the mathematical result of a function is an exact infinity (e.g., the logarithm of 0 is negative infinity). when a pole error occurs, the function returns the (signed) value .br huge_val , .br huge_valf , or .br huge_vall , depending on whether the function result type is .ir double , .ir float , or .ir "long double" . the sign of the result is that which is mathematically correct for the function. .i errno is set to .br erange , and a "divide-by-zero" .rb ( fe_divbyzero ) floating-point exception is raised. .ss range error a .i range error occurs when the magnitude of the function result means that it cannot be represented in the result type of the function. the return value of the function depends on whether the range error was an overflow or an underflow. .pp a floating result .i overflows if the result is finite, but is too large to represented in the result type. when an overflow occurs, the function returns the value .br huge_val , .br huge_valf , or .br huge_vall , depending on whether the function result type is .ir double , .ir float , or .ir "long double" . .i errno is set to .br erange , and an "overflow" .rb ( fe_overflow ) floating-point exception is raised. .pp a floating result .i underflows if the result is too small to be represented in the result type. if an underflow occurs, a mathematical function typically returns 0.0 (c99 says a function shall return "an implementation-defined value whose magnitude is no greater than the smallest normalized positive number in the specified type"). .i errno may be set to .br erange , and an "underflow" .rb ( fe_underflow ) floating-point exception may be raised. .pp some functions deliver a range error if the supplied argument value, or the correct function result, would be .ir subnormal . a subnormal value is one that is nonzero, but with a magnitude that is so small that it can't be presented in normalized form (i.e., with a 1 in the most significant bit of the significand). the representation of a subnormal number will contain one or more leading zeros in the significand. .sh notes the .i math_errhandling identifier specified by c99 and posix.1 is not supported by glibc. .\" see conformance in the glibc 2.8 (and earlier) source. this identifier is supposed to indicate which of the two error-notification mechanisms .ri ( errno , exceptions retrievable via .br fetestexcept (3)) is in use. the standards require that at least one be in use, but permit both to be available. the current (version 2.8) situation under glibc is messy. most (but not all) functions raise exceptions on errors. some also set .ir errno . a few functions set .ir errno , but don't raise an exception. a very few functions do neither. see the individual manual pages for details. .pp to avoid the complexities of using .i errno and .br fetestexcept (3) for error checking, it is often advised that one should instead check for bad argument values before each call. .\" http://www.securecoding.cert.org/confluence/display/seccode/flp32-c.+prevent+or+detect+domain+and+range+errors+in+math+functions for example, the following code ensures that .br log (3)'s argument is not a nan and is not zero (a pole error) or less than zero (a domain error): .pp .in +4n .ex double x, r; if (isnan(x) || islessequal(x, 0)) { /* deal with nan / pole error / domain error */ } r = log(x); .ee .in .pp the discussion on this page does not apply to the complex mathematical functions (i.e., those declared by .ir ), which in general are not required to return errors by c99 and posix.1. .pp the .br gcc (1) .i "\-fno\-math\-errno" option causes the executable to employ implementations of some mathematical functions that are faster than the standard implementations, but do not set .i errno on error. (the .br gcc (1) .i "\-ffast\-math" option also enables .ir "\-fno\-math\-errno" .) an error can still be tested for using .br fetestexcept (3). .sh see also .br gcc (1), .br errno (3), .br fenv (3), .br fpclassify (3), .br infinity (3), .br isgreater (3), .br matherr (3), .br nan (3) .pp .i "info libc" .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" portions extracted from linux/mm/swap.c: .\" copyright (c) 1991, 1992 linus torvalds .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 21 aug 1994 by michael chastain : .\" added text about calling restriction (new in kernel 1.1.20 i believe). .\" n.b. calling "idle" from user process used to hang process! .\" modified thu oct 31 14:41:15 1996 by eric s. raymond .\" " .th idle 2 2021-03-22 "linux" "linux programmer's manual" .sh name idle \- make process 0 idle .sh synopsis .nf .b #include .pp .b int idle(void); .fi .sh description .br idle () is an internal system call used during bootstrap. it marks the process's pages as swappable, lowers its priority, and enters the main scheduling loop. .br idle () never returns. .pp only process 0 may call .br idle (). any user process, even a process with superuser permission, will receive .br eperm . .sh return value .br idle () never returns for process 0, and always returns \-1 for a user process. .sh errors .tp .b eperm always, for a user process. .sh versions since linux 2.3.13, this system call does not exist anymore. .sh conforming to this function is linux-specific, and should not be used in programs intended to be portable. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2017, yubin ruan .\" and copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_mutexattr_setrobust 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_mutexattr_getrobust, pthread_mutexattr_setrobust \- get and set the robustness attribute of a mutex attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_mutexattr_getrobust(const pthread_mutexattr_t *" attr , .bi " int *" robustness ");" .bi "int pthread_mutexattr_setrobust(pthread_mutexattr_t *" attr , .bi " int " robustness ");" .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_mutexattr_getrobust (), .br pthread_mutexattr_setrobust (): .nf _posix_c_source >= 200809l .\" fixme . .\" but see https://sourceware.org/bugzilla/show_bug.cgi?id=22125 .fi .sh description the .br pthread_mutexattr_getrobust () function places the value of the robustness attribute of the mutex attributes object referred to by .i attr in .ir *robustness . the .br pthread_mutexattr_setrobust () function sets the value of the robustness attribute of the mutex attributes object referred to by .i attr to the value specified in .ir *robustness . .pp the robustness attribute specifies the behavior of the mutex when the owning thread dies without unlocking the mutex. the following values are valid for .ir robustness : .tp .br pthread_mutex_stalled this is the default value for a mutex attributes object. if a mutex is initialized with the .br pthread_mutex_stalled attribute and its owner dies without unlocking it, the mutex remains locked afterwards and any future attempts to call .br pthread_mutex_lock (3) on the mutex will block indefinitely. .tp .b pthread_mutex_robust if a mutex is initialized with the .br pthread_mutex_robust attribute and its owner dies without unlocking it, any future attempts to call .br pthread_mutex_lock (3) on this mutex will succeed and return .b eownerdead to indicate that the original owner no longer exists and the mutex is in an inconsistent state. usually after .b eownerdead is returned, the next owner should call .br pthread_mutex_consistent (3) on the acquired mutex to make it consistent again before using it any further. .ip if the next owner unlocks the mutex using .br pthread_mutex_unlock (3) before making it consistent, the mutex will be permanently unusable and any subsequent attempts to lock it using .br pthread_mutex_lock (3) will fail with the error .br enotrecoverable . the only permitted operation on such a mutex is .br pthread_mutex_destroy (3). .ip if the next owner terminates before calling .br pthread_mutex_consistent (3), further .br pthread_mutex_lock (3) operations on this mutex will still return .br eownerdead . .pp note that the .ir attr argument of .br pthread_mutexattr_getrobust () and .br pthread_mutexattr_setrobust () should refer to a mutex attributes object that was initialized by .br pthread_mutexattr_init (3), otherwise the behavior is undefined. .sh return value on success, these functions return 0. on error, they return a positive error number. .pp in the glibc implementation, .br pthread_mutexattr_getrobust () always return zero. .sh errors .tp .b einval a value other than .b pthread_mutex_stalled or .b pthread_mutex_robust was passed to .br pthread_mutexattr_setrobust (). .sh versions .br pthread_mutexattr_getrobust () and .br pthread_mutexattr_setrobust () were added to glibc in version 2.12. .sh conforming to posix.1-2008. .sh notes in the linux implementation, when using process-shared robust mutexes, a waiting thread also receives the .b eownerdead notification if the owner of a robust mutex performs an .br execve (2) without first unlocking the mutex. posix.1 does not specify this detail, but the same behavior also occurs in at least some .\" e.g., solaris, according to its manual page other implementations. .pp before the addition of .br pthread_mutexattr_getrobust () and .br pthread_mutexattr_setrobust () to posix, glibc defined the following equivalent nonstandard functions if .br _gnu_source was defined: .pp .nf .bi "int pthread_mutexattr_getrobust_np(const pthread_mutexattr_t *" attr , .bi " int *" robustness ");" .bi "int pthread_mutexattr_setrobust_np(const pthread_mutexattr_t *" attr , .bi " int " robustness ");" .fi .pp correspondingly, the constants .b pthread_mutex_stalled_np and .b pthread_mutex_robust_np were also defined. .pp these gnu-specific apis, which first appeared in glibc 2.4, are nowadays obsolete and should not be used in new programs; since glibc 2.34 these apis are marked as deprecated. .sh examples the program below demonstrates the use of the robustness attribute of a mutex attributes object. in this program, a thread holding the mutex dies prematurely without unlocking the mutex. the main thread subsequently acquires the mutex successfully and gets the error .br eownerdead , after which it makes the mutex consistent. .pp the following shell session shows what we see when running this program: .pp .in +4n .ex $ \fb./a.out\fp [original owner] setting lock... [original owner] locked. now exiting without unlocking. [main] attempting to lock the robust mutex. [main] pthread_mutex_lock() returned eownerdead [main] now make the mutex consistent [main] mutex is now consistent; unlocking .ee .in .ss program source .ex #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static pthread_mutex_t mtx; static void * original_owner_thread(void *ptr) { printf("[original owner] setting lock...\en"); pthread_mutex_lock(&mtx); printf("[original owner] locked. now exiting without unlocking.\en"); pthread_exit(null); } int main(int argc, char *argv[]) { pthread_t thr; pthread_mutexattr_t attr; int s; pthread_mutexattr_init(&attr); pthread_mutexattr_setrobust(&attr, pthread_mutex_robust); pthread_mutex_init(&mtx, &attr); pthread_create(&thr, null, original_owner_thread, null); sleep(2); /* "original_owner_thread" should have exited by now. */ printf("[main] attempting to lock the robust mutex.\en"); s = pthread_mutex_lock(&mtx); if (s == eownerdead) { printf("[main] pthread_mutex_lock() returned eownerdead\en"); printf("[main] now make the mutex consistent\en"); s = pthread_mutex_consistent(&mtx); if (s != 0) handle_error_en(s, "pthread_mutex_consistent"); printf("[main] mutex is now consistent; unlocking\en"); s = pthread_mutex_unlock(&mtx); if (s != 0) handle_error_en(s, "pthread_mutex_unlock"); exit(exit_success); } else if (s == 0) { printf("[main] pthread_mutex_lock() unexpectedly succeeded\en"); exit(exit_failure); } else { printf("[main] pthread_mutex_lock() unexpectedly failed\en"); handle_error_en(s, "pthread_mutex_lock"); } } .ee .sh see also .ad l .nh .br get_robust_list (2), .br set_robust_list (2), .br pthread_mutex_consistent (3), .br pthread_mutex_init (3), .br pthread_mutex_lock (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th towctrans 3 2021-03-22 "gnu" "linux programmer's manual" .sh name towctrans \- wide-character transliteration .sh synopsis .nf .b #include .pp .bi "wint_t towctrans(wint_t " wc ", wctrans_t " desc ); .fi .sh description if .i wc is a wide character, the .br towctrans () function translates it according to the transliteration descriptor .ir desc . if .i wc is .br weof , .b weof is returned. .pp .i desc must be a transliteration descriptor returned by the .br wctrans (3) function. .sh return value the .br towctrans () function returns the translated wide character, or .b weof if .i wc is .br weof . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br towctrans () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br towctrans () depends on the .b lc_ctype category of the current locale. .sh see also .br towlower (3), .br towupper (3), .br wctrans (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" and copyright (c) 2020 by alejandro colomar .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" .th queue 7 2021-03-22 "gnu" "linux programmer's manual" .sh name queue \- implementations of linked lists and queues .sh description the .i header file provides a set of macros that define and operate on the following data structures: .ip * 3 singly linked lists (slist) .ip * doubly linked lists (list) .ip * singly linked tail queues (stailq) .ip * doubly linked tail queues (tailq) .ip * doubly linked circular queues (circleq) .pp all structures support the following functionality: .ip * 3 insertion of a new entry at the head of the list. .ip * insertion of a new entry after any element in the list. .ip * o(1) removal of an entry from the head of the list. .ip * forward traversal through the list. .\".ip * .\" swapping the contents of two lists. .pp code size and execution time depend on the complexity of the data structure being used, so programmers should take care to choose the appropriate one. .ss singly linked lists (slist) singly linked lists are the simplest and support only the above functionality. singly linked lists are ideal for applications with large datasets and few or no removals, or for implementing a lifo queue. singly linked lists add the following functionality: .ip * 3 o(n) removal of any entry in the list. .ss singly linked tail queues (stailq) singly linked tail queues add the following functionality: .ip * 3 entries can be added at the end of a list. .ip * o(n) removal of any entry in the list. .ip * they may be concatenated. .pp however: .ip * 3 all list insertions must specify the head of the list. .ip * each head entry requires two pointers rather than one. .pp singly linked tail queues are ideal for applications with large datasets and few or no removals, or for implementing a fifo queue. .ss doubly linked data structures all doubly linked types of data structures (lists and tail queues) additionally allow: .ip * 3 insertion of a new entry before any element in the list. .ip * o(1) removal of any entry in the list. .pp however: .ip * 3 each element requires two pointers rather than one. .ss doubly linked lists (list) linked lists are the simplest of the doubly linked data structures. they add the following functionality over the above: .ip * 3 they may be traversed backwards. .pp however: .ip * 3 to traverse backwards, an entry to begin the traversal and the list in which it is contained must be specified. .ss doubly linked tail queues (tailq) tail queues add the following functionality: .ip * 3 entries can be added at the end of a list. .ip * they may be traversed backwards, from tail to head. .ip * they may be concatenated. .pp however: .ip * 3 all list insertions and removals must specify the head of the list. .ip * each head entry requires two pointers rather than one. .ss doubly linked circular queues (circleq) circular queues add the following functionality over the above: .ip * 3 the first and last entries are connected. .pp however: .ip * 3 the termination condition for traversal is more complex. .sh conforming to not in posix.1, posix.1-2001, or posix.1-2008. present on the bsds. .i macros first appeared in 4.4bsd. .sh notes some bsds provide simpleq instead of stailq. they are identical, but for historical reasons they were named differently on different bsds. stailq originated on freebsd, and simpleq originated on netbsd. for compatibility reasons, some systems provide both sets of macros. glibc provides both stailq and simpleq, which are identical except for a missing simpleq equivalent to .br stailq_concat (). .sh see also .br circleq (3), .br insque (3), .br list (3), .br slist (3), .br stailq (3), .br tailq (3) .\" .br tree (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getutent.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_setcancelstate 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_setcancelstate, pthread_setcanceltype \- set cancelability state and type .sh synopsis .nf .b #include .pp .bi "int pthread_setcancelstate(int " state ", int *" oldstate ); .bi "int pthread_setcanceltype(int " type ", int *" oldtype ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_setcancelstate () sets the cancelability state of the calling thread to the value given in .ir state . the previous cancelability state of the thread is returned in the buffer pointed to by .ir oldstate . the .i state argument must have one of the following values: .tp .b pthread_cancel_enable the thread is cancelable. this is the default cancelability state in all new threads, including the initial thread. the thread's cancelability type determines when a cancelable thread will respond to a cancellation request. .tp .b pthread_cancel_disable the thread is not cancelable. if a cancellation request is received, it is blocked until cancelability is enabled. .pp the .br pthread_setcanceltype () sets the cancelability type of the calling thread to the value given in .ir type . the previous cancelability type of the thread is returned in the buffer pointed to by .ir oldtype . the .i type argument must have one of the following values: .tp .b pthread_cancel_deferred a cancellation request is deferred until the thread next calls a function that is a cancellation point (see .br pthreads (7)). this is the default cancelability type in all new threads, including the initial thread. .ip even with deferred cancellation, a cancellation point in an asynchronous signal handler may still be acted upon and the effect is as if it was an asynchronous cancellation. .tp .b pthread_cancel_asynchronous the thread can be canceled at any time. (typically, it will be canceled immediately upon receiving a cancellation request, but the system doesn't guarantee this.) .pp the set-and-get operation performed by each of these functions is atomic with respect to other threads in the process calling the same function. .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors the .br pthread_setcancelstate () can fail with the following error: .tp .b einval invalid value for .ir state . .pp the .br pthread_setcanceltype () can fail with the following error: .tp .b einval invalid value for .ir type . .\" .sh versions .\" available since glibc 2.0 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_setcancelstate (), .br pthread_setcanceltype () t} thread safety t{ mt-safe t} t{ .br pthread_setcancelstate (), .br pthread_setcanceltype () t} async-cancel safety t{ ac-safe t} .te .hy .ad .sp 1 .hy .sh conforming to posix.1-2001, posix.1-2008. .sh notes for details of what happens when a thread is canceled, see .br pthread_cancel (3). .pp briefly disabling cancelability is useful if a thread performs some critical action that must not be interrupted by a cancellation request. beware of disabling cancelability for long periods, or around operations that may block for long periods, since that will render the thread unresponsive to cancellation requests. .ss asynchronous cancelability setting the cancelability type to .b pthread_cancel_asynchronous is rarely useful. since the thread could be canceled at .i any time, it cannot safely reserve resources (e.g., allocating memory with .br malloc (3)), acquire mutexes, semaphores, or locks, and so on. reserving resources is unsafe because the application has no way of knowing what the state of these resources is when the thread is canceled; that is, did cancellation occur before the resources were reserved, while they were reserved, or after they were released? furthermore, some internal data structures (e.g., the linked list of free blocks managed by the .br malloc (3) family of functions) may be left in an inconsistent state if cancellation occurs in the middle of the function call. consequently, clean-up handlers cease to be useful. .pp functions that can be safely asynchronously canceled are called .ir "async-cancel-safe functions" . posix.1-2001 and posix.1-2008 require only that .br pthread_cancel (3), .br pthread_setcancelstate (), and .br pthread_setcanceltype () be async-cancel-safe. in general, other library functions can't be safely called from an asynchronously cancelable thread. .pp one of the few circumstances in which asynchronous cancelability is useful is for cancellation of a thread that is in a pure compute-bound loop. .ss portability notes the linux threading implementations permit the .i oldstate argument of .br pthread_setcancelstate () to be null, in which case the information about the previous cancelability state is not returned to the caller. many other implementations also permit a null .i oldstat argument, .\" it looks like at least solaris, freebsd and tru64 support this. but posix.1 does not specify this point, so portable applications should always specify a non-null value in .ir oldstate . a precisely analogous set of statements applies for the .i oldtype argument of .br pthread_setcanceltype (). .sh examples see .br pthread_cancel (3). .sh see also .br pthread_cancel (3), .br pthread_cleanup_push (3), .br pthread_testcancel (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)socketpair.2 6.4 (berkeley) 3/10/91 .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-10-22 by eric s. raymond .\" modified 2002-07-22 by michael kerrisk .\" modified 2004-06-17 by michael kerrisk .\" 2008-10-11, mtk: add description of sock_nonblock and sock_cloexec .\" .th socketpair 2 2021-03-22 "linux" "linux programmer's manual" .sh name socketpair \- create a pair of connected sockets .sh synopsis .nf .b #include .pp .bi "int socketpair(int " domain ", int " type ", int " protocol \ ", int " sv [2]); .fi .sh description the .br socketpair () call creates an unnamed pair of connected sockets in the specified .ir domain , of the specified .ir type , and using the optionally specified .ir protocol . for further details of these arguments, see .br socket (2). .pp the file descriptors used in referencing the new sockets are returned in .i sv[0] and .ir sv[1] . the two sockets are indistinguishable. .sh return value on success, zero is returned. on error, \-1 is returned, .i errno is set to indicate the error, and .i sv is left unchanged .pp on linux (and other systems), .br socketpair () does not modify .i sv on failure. a requirement standardizing this behavior was added in posix.1-2008 tc2. .\" http://austingroupbugs.net/view.php?id=483 .sh errors .tp .b eafnosupport the specified address family is not supported on this machine. .tp .b efault the address .i sv does not specify a valid part of the process address space. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b eopnotsupp the specified protocol does not support creation of socket pairs. .tp .b eprotonosupport the specified protocol is not supported on this machine. .sh conforming to posix.1-2001, posix.1-2008, 4.4bsd. .br socketpair () first appeared in 4.2bsd. it is generally portable to/from non-bsd systems supporting clones of the bsd socket layer (including system\ v variants). .sh notes on linux, the only supported domains for this call are .b af_unix (or synonymously, .br af_local ) and .b af_tipc .\" commit: 70b03759e9ecfae400605fa34f3d7154cccbbba3 (since linux 4.12). .pp since linux 2.6.27, .br socketpair () supports the .br sock_nonblock and .br sock_cloexec flags in the .i type argument, as described in .br socket (2). .sh see also .br pipe (2), .br read (2), .br socket (2), .br write (2), .br socket (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 2011, hewlett-packard development company, l.p. .\" written by stephen m. cameron .\" .\" %%%license_start(gplv2_oneline) .\" licensed under gnu general public license version 2 (gplv2) .\" %%%license_end .\" .\" shorthand for double quote that works everywhere. .ds q \n'34' .th hpsa 4 2021-03-22 "linux" "linux programmer's manual" .sh name hpsa \- hp smart array scsi driver .sh synopsis .nf modprobe hpsa [ hpsa_allow_any=1 ] .fi .sh description .b hpsa is a scsi driver for hp smart array raid controllers. .ss options .ir "hpsa_allow_any=1" : this option allows the driver to attempt to operate on any hp smart array hardware raid controller, even if it is not explicitly known to the driver. this allows newer hardware to work with older drivers. typically this is used to allow installation of operating systems from media that predates the raid controller, though it may also be used to enable .b hpsa to drive older controllers that would normally be handled by the .br cciss (4) driver. these older boards have not been tested and are not supported with .br hpsa , and .br cciss (4) should still be used for these. .ss supported hardware the .b hpsa driver supports the following smart array boards: .pp .nf smart array p700m smart array p212 smart array p410 smart array p410i smart array p411 smart array p812 smart array p712m smart array p711m storageworks p1210m .fi .pp .\" commit 135ae6edeb51979d0998daf1357f149a7d6ebb08 since linux 4.14, the following smart array boards are also supported: .pp .nf smart array 5300 smart array 5312 smart array 532 smart array 5i smart array 6400 smart array 6400 em smart array 641 smart array 642 smart array 6i smart array e200 smart array e200i smart array e200i smart array e200i smart array e200i smart array e500 smart array p400 smart array p400i smart array p600 smart array p700m smart array p800 .fi .ss configuration details to configure hp smart array controllers, use the hp array configuration utility (either .br hpacuxe (8) or .br hpacucli (8)) or the offline rom-based configuration utility (orca) run from the smart array's option rom at boot time. .sh files .ss device nodes logical drives are accessed via the scsi disk driver .rb ( sd (4)), tape drives via the scsi tape driver .rb ( st (4)), and the raid controller via the scsi generic driver .rb ( sg (4)), with device nodes named .ir /dev/sd* , .ir /dev/st* , and .ir /dev/sg* , respectively. .ss hpsa-specific host attribute files in /sys .tp .i /sys/class/scsi_host/host*/rescan this is a write-only attribute. writing to this attribute will cause the driver to scan for new, changed, or removed devices (e.g., hot-plugged tape drives, or newly configured or deleted logical drives, etc.) and notify the scsi midlayer of any changes detected. normally a rescan is triggered automatically by hp's array configuration utility (either the gui or the command-line variety); thus, for logical drive changes, the user should not normally have to use this attribute. this attribute may be useful when hot plugging devices like tape drives, or entire storage boxes containing preconfigured logical drives. .tp .i /sys/class/scsi_host/host*/firmware_revision this attribute contains the firmware version of the smart array. .ip for example: .ip .in +4n .ex # \fbcd /sys/class/scsi_host/host4\fp # \fbcat firmware_revision\fp 7.14 .ee .in .\" .ss hpsa-specific disk attribute files in /sys .tp .i /sys/class/scsi_disk/c:b:t:l/device/unique_id this attribute contains a 32 hex-digit unique id for each logical drive. .ip for example: .ip .in +4n .ex # \fbcd /sys/class/scsi_disk/4:0:0:0/device\fp # \fbcat unique_id\fp 600508b1001044395355323037570f77 .ee .in .tp .i /sys/class/scsi_disk/c:b:t:l/device/raid_level this attribute contains the raid level of each logical drive. .ip for example: .ip .in +4n .ex # \fbcd /sys/class/scsi_disk/4:0:0:0/device\fp # \fbcat raid_level\fp raid 0 .ee .in .tp .i /sys/class/scsi_disk/c:b:t:l/device/lunid this attribute contains the 16 hex-digit (8 byte) lun id by which a logical drive or physical device can be addressed. .ir c : b : t : l are the controller, bus, target, and lun of the device. .pp for example: .ip .in +4n .ex # \fbcd /sys/class/scsi_disk/4:0:0:0/device\fp # \fbcat lunid\fp 0x0000004000000000 .ee .in .\" .ss supported ioctl() operations for compatibility with applications written for the .br cciss (4) driver, many, but not all of the ioctls supported by the .br cciss (4) driver are also supported by the .b hpsa driver. the data structures used by these ioctls are described in the linux kernel source file .ir include/linux/cciss_ioctl.h . .tp .br cciss_deregdisk ", " cciss_regnewdisk ", " cciss_regnewd these three ioctls all do exactly the same thing, which is to cause the driver to rescan for new devices. this does exactly the same thing as writing to the hpsa-specific host "rescan" attribute. .tp .b cciss_getpciinfo returns pci domain, bus, device, and function and "board id" (pci subsystem id). .tp .b cciss_getdrivver returns driver version in three bytes encoded as: .ip .in +4n .ex (major_version << 16) | (minor_version << 8) | (subminor_version) .ee .in .tp .br cciss_passthru ", " cciss_big_passthru allows "bmic" and "ciss" commands to be passed through to the smart array. these are used extensively by the hp array configuration utility, snmp storage agents, and so on. see .i cciss_vol_status at .ur http://cciss.sf.net .ue for some examples. .sh see also .br cciss (4), .br sd (4), .br st (4), .br cciss_vol_status (8), .br hpacucli (8), .br hpacuxe (8), .pp .ur http://cciss.sf.net .ue , and .i documentation/scsi/hpsa.txt and .i documentation/abi/testing/sysfs\-bus\-pci\-devices\-cciss in the linux kernel source tree .\" .sh authors .\" don brace, steve cameron, tom lawler, mike miller, scott teel .\" and probably some other people. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/wprintf.3 .\" copyright 2002 ian redfern (redferni@logica.com) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" freebsd 4.4 man pages .\" .\" minor additions, aeb, 2013-06-21 .\" .th ether_aton 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ether_aton, ether_ntoa, ether_ntohost, ether_hostton, ether_line, ether_ntoa_r, ether_aton_r \- ethernet address manipulation routines .sh synopsis .nf .b #include .pp .bi "char *ether_ntoa(const struct ether_addr *" addr ); .bi "struct ether_addr *ether_aton(const char *" asc ); .pp .bi "int ether_ntohost(char *" hostname ", const struct ether_addr *" addr ); .bi "int ether_hostton(const char *" hostname ", struct ether_addr *" addr ); .pp .bi "int ether_line(const char *" line ", struct ether_addr *" addr , .bi " char *" hostname ); .pp /* gnu extensions */ .bi "char *ether_ntoa_r(const struct ether_addr *" addr ", char *" buf ); .pp .bi "struct ether_addr *ether_aton_r(const char *" asc , .bi " struct ether_addr *" addr ); .fi .sh description .br ether_aton () converts the 48-bit ethernet host address .i asc from the standard hex-digits-and-colons notation into binary data in network byte order and returns a pointer to it in a statically allocated buffer, which subsequent calls will overwrite. .br ether_aton () returns null if the address is invalid. .pp the .br ether_ntoa () function converts the ethernet host address .i addr given in network byte order to a string in standard hex-digits-and-colons notation, omitting leading zeros. the string is returned in a statically allocated buffer, which subsequent calls will overwrite. .pp the .br ether_ntohost () function maps an ethernet address to the corresponding hostname in .i /etc/ethers and returns nonzero if it cannot be found. .pp the .br ether_hostton () function maps a hostname to the corresponding ethernet address in .i /etc/ethers and returns nonzero if it cannot be found. .pp the .br ether_line () function parses a line in .i /etc/ethers format (ethernet address followed by whitespace followed by hostname; \(aq#\(aq introduces a comment) and returns an address and hostname pair, or nonzero if it cannot be parsed. the buffer pointed to by .i hostname must be sufficiently long, for example, have the same length as .ir line . .pp the functions .br ether_ntoa_r () and .br ether_aton_r () are reentrant thread-safe versions of .br ether_ntoa () and .br ether_aton () respectively, and do not use static buffers. .pp the structure .i ether_addr is defined in .i as: .pp .in +4n .ex struct ether_addr { uint8_t ether_addr_octet[6]; } .ee .in .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ether_aton (), .br ether_ntoa () t} thread safety mt-unsafe t{ .br ether_ntohost (), .br ether_hostton (), .br ether_line (), .br ether_ntoa_r (), .br ether_aton_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd, sunos. .sh bugs in glibc 2.2.5 and earlier, the implementation of .br ether_line () .\" the fix was presumably commit c0a0f9a32c8baa6ab93d00eb42d92c02e9e146d7 .\" which was in glibc 2.3 is broken. .sh see also .br ethers (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-1.7 .so man2/clock_getres.2 .\" copyright (c) 2006 justin pryzby .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(permissive_misc) .\" permission is hereby granted, free of charge, to any person obtaining .\" a copy of this software and associated documentation files (the .\" "software"), to deal in the software without restriction, including .\" without limitation the rights to use, copy, modify, merge, publish, .\" distribute, sublicense, and/or sell copies of the software, and to .\" permit persons to whom the software is furnished to do so, subject to .\" the following conditions: .\" .\" the above copyright notice and this permission notice shall be .\" included in all copies or substantial portions of the software. .\" .\" the software is provided "as is", without warranty of any kind, .\" express or implied, including but not limited to the warranties of .\" merchantability, fitness for a particular purpose and noninfringement. .\" in no event shall the authors or copyright holders be liable for any .\" claim, damages or other liability, whether in an action of contract, .\" tort or otherwise, arising from, out of or in connection with the .\" software or the use or other dealings in the software. .\" %%%license_end .\" .\" references: .\" /usr/lib/gcc/i486-linux-gnu/4.1.1/include/stddef.h .\" glibc-doc .th offsetof 3 2020-11-01 "gnu" "linux programmer's manual" .sh name offsetof \- offset of a structure member .sh synopsis .nf .b #include .pp .bi "size_t offsetof(" type ", " member ); .fi .sh description the macro .br offsetof () returns the offset of the field .i member from the start of the structure .ir type . .pp this macro is useful because the sizes of the fields that compose a structure can vary across implementations, and compilers may insert different numbers of padding bytes between fields. consequently, an element's offset is not necessarily given by the sum of the sizes of the previous elements. .pp a compiler error will result if .i member is not aligned to a byte boundary (i.e., it is a bit field). .sh return value .br offsetof () returns the offset of the given .i member within the given .ir type , in units of bytes. .sh conforming to posix.1-2001, posix.1-2008, c89, c99. .sh examples on a linux/i386 system, when compiled using the default .br gcc (1) options, the program below produces the following output: .pp .in +4n .ex .rb "$" " ./a.out" offsets: i=0; c=4; d=8 a=16 sizeof(struct s)=16 .ee .in .ss program source \& .ex #include #include #include int main(void) { struct s { int i; char c; double d; char a[]; }; /* output is compiler dependent */ printf("offsets: i=%zu; c=%zu; d=%zu a=%zu\en", offsetof(struct s, i), offsetof(struct s, c), offsetof(struct s, d), offsetof(struct s, a)); printf("sizeof(struct s)=%zu\en", sizeof(struct s)); exit(exit_success); } .ee .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016, oracle. all rights reserved. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th ioctl_ficlonerange 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_ficlonerange, ioctl_ficlone \- share some the data of one file with another file .sh synopsis .nf .br "#include " " /* definition of " ficlone* " constants */" .b #include .pp .bi "int ioctl(int " dest_fd ", ficlonerange, struct file_clone_range *" arg ); .bi "int ioctl(int " dest_fd ", ficlone, int " src_fd ); .fi .sh description if a filesystem supports files sharing physical storage between multiple files ("reflink"), this .br ioctl (2) operation can be used to make some of the data in the .i src_fd file appear in the .i dest_fd file by sharing the underlying storage, which is faster than making a separate physical copy of the data. both files must reside within the same filesystem. if a file write should occur to a shared region, the filesystem must ensure that the changes remain private to the file being written. this behavior is commonly referred to as "copy on write". .pp this ioctl reflinks up to .ir src_length bytes from file descriptor .ir src_fd at offset .ir src_offset into the file .ir dest_fd at offset .ir dest_offset , provided that both are files. if .ir src_length is zero, the ioctl reflinks to the end of the source file. this information is conveyed in a structure of the following form: .pp .in +4n .ex struct file_clone_range { __s64 src_fd; __u64 src_offset; __u64 src_length; __u64 dest_offset; }; .ee .in .pp clones are atomic with regards to concurrent writes, so no locks need to be taken to obtain a consistent cloned copy. .pp the .b ficlone ioctl clones entire files. .sh return value on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors error codes can be one of, but are not limited to, the following: .tp .b ebadf .ir src_fd is not open for reading; .ir dest_fd is not open for writing or is open for append-only writes; or the filesystem which .ir src_fd resides on does not support reflink. .tp .b einval the filesystem does not support reflinking the ranges of the given files. this error can also appear if either file descriptor represents a device, fifo, or socket. disk filesystems generally require the offset and length arguments to be aligned to the fundamental block size. xfs and btrfs do not support overlapping reflink ranges in the same file. .tp .b eisdir one of the files is a directory and the filesystem does not support shared regions in directories. .tp .b eopnotsupp this can appear if the filesystem does not support reflinking either file descriptor, or if either file descriptor refers to special inodes. .tp .b eperm .ir dest_fd is immutable. .tp .b etxtbsy one of the files is a swap file. swap files cannot share storage. .tp .b exdev .ir dest_fd " and " src_fd are not on the same mounted filesystem. .sh versions these ioctl operations first appeared in linux 4.5. they were previously known as .b btrfs_ioc_clone and .br btrfs_ioc_clone_range , and were private to btrfs. .sh conforming to this api is linux-specific. .sh notes because a copy-on-write operation requires the allocation of new storage, the .br fallocate (2) operation may unshare shared blocks to guarantee that subsequent writes will not fail because of lack of disk space. .sh see also .br ioctl (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/clog.3 .\" copyright (c) 2001 andries brouwer .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th strverscmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strverscmp \- compare two version strings .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int strverscmp(const char *" s1 ", const char *" s2 ); .fi .sh description often one has files .ir jan1 ", " jan2 ", ..., " jan9 ", " jan10 ", ..." and it feels wrong when .br ls (1) orders them .ir jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 . .\" classical solution: "rename jan jan0 jan?" in order to rectify this, gnu introduced the .i \-v option to .br ls (1), which is implemented using .br versionsort (3), which again uses .br strverscmp (). .pp thus, the task of .br strverscmp () is to compare two strings and find the "right" order, while .br strcmp (3) finds only the lexicographic order. this function does not use the locale category .br lc_collate , so is meant mostly for situations where the strings are expected to be in ascii. .pp what this function does is the following. if both strings are equal, return 0. otherwise, find the position between two bytes with the property that before it both strings are equal, while directly after it there is a difference. find the largest consecutive digit strings containing (or starting at, or ending at) this position. if one or both of these is empty, then return what .br strcmp (3) would have returned (numerical ordering of byte values). otherwise, compare both digit strings numerically, where digit strings with one or more leading zeros are interpreted as if they have a decimal point in front (so that in particular digit strings with more leading zeros come before digit strings with fewer leading zeros). thus, the ordering is .ir 000 ", " 00 ", " 01 ", " 010 ", " 09 ", " 0 ", " 1 ", " 9 ", " 10 . .sh return value the .br strverscmp () function returns an integer less than, equal to, or greater than zero if .i s1 is found, respectively, to be earlier than, equal to, or later than .ir s2 . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strverscmp () t} thread safety mt-safe .te .hy .ad .sp 1 .\" fixme: the marking is different from that in the glibc manual, .\" which has: .\" .\" strverscmp: mt-safe locale .\" .\" glibc manual says strverscmp should have marking locale because it calls .\" isdigit() multiple times and isdigit() uses locale variable. .\" but isdigit() has two implementations. with different compiling conditions, .\" we may call isdigit() in macro, then strverscmp() should not have locale .\" problem. .sh conforming to this function is a gnu extension. .sh examples the program below can be used to demonstrate the behavior of .br strverscmp (). it uses .br strverscmp () to compare the two strings given as its command-line arguments. an example of its use is the following: .pp .in +4n .ex $ \fb./a.out jan1 jan10\fp jan1 < jan10 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include int main(int argc, char *argv[]) { int res; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } res = strverscmp(argv[1], argv[2]); printf("%s %s %s\en", argv[1], (res < 0) ? "<" : (res == 0) ? "==" : ">", argv[2]); exit(exit_success); } .ee .sh see also .br rename (1), .br strcasecmp (3), .br strcmp (3), .br strcoll (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/posix_fadvise.2 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setstacksize 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setstacksize, pthread_attr_getstacksize \- set/get stack size attribute in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setstacksize(pthread_attr_t *" attr \ ", size_t " stacksize ); .bi "int pthread_attr_getstacksize(const pthread_attr_t *restrict " attr , .bi " size_t *restrict " stacksize ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setstacksize () function sets the stack size attribute of the thread attributes object referred to by .i attr to the value specified in .ir stacksize . .pp the stack size attribute determines the minimum size (in bytes) that will be allocated for threads created using the thread attributes object .ir attr . .pp the .br pthread_attr_getstacksize () function returns the stack size attribute of the thread attributes object referred to by .i attr in the buffer pointed to by .ir stacksize . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .br pthread_attr_setstacksize () can fail with the following error: .tp .b einval the stack size is less than .br pthread_stack_min (16384) bytes. .pp on some systems, .\" e.g., macos .br pthread_attr_setstacksize () can fail with the error .b einval if .i stacksize is not a multiple of the system page size. .sh versions these functions are provided by glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setstacksize (), .br pthread_attr_getstacksize () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes for details on the default stack size of new threads, see .br pthread_create (3). .pp a thread's stack size is fixed at the time of thread creation. only the main thread can dynamically grow its stack. .pp the .br pthread_attr_setstack (3) function allows an application to set both the size and location of a caller-allocated stack that is to be used by a thread. .sh bugs as at glibc 2.8, if the specified .i stacksize is not a multiple of .br stack_align (16 bytes on most architectures), it may be rounded .ir downward , in violation of posix.1, which says that the allocated stack will be at least .i stacksize bytes. .sh examples see .br pthread_create (3). .sh see also .br getrlimit (2), .br pthread_attr_init (3), .br pthread_attr_setguardsize (3), .br pthread_attr_setstack (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th fseeko 3 2021-03-22 "" "linux programmer's manual" .sh name fseeko, ftello \- seek to or report file position .sh synopsis .nf .b #include .pp .bi "int fseeko(file *" stream ", off_t " offset ", int " whence ); .bi "off_t ftello(file *" stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fseeko (), .br ftello (): .nf _file_offset_bits == 64 || _posix_c_source >= 200112l .fi .sh description the .br fseeko () and .br ftello () functions are identical to .br fseek (3) and .br ftell (3) (see .br fseek (3)), respectively, except that the .i offset argument of .br fseeko () and the return value of .br ftello () is of type .i off_t instead of .ir long . .pp on some architectures, both .ir off_t and .i long are 32-bit types, but defining .br _file_offset_bits with the value 64 (before including .i any header files) will turn .i off_t into a 64-bit type. .sh return value on successful completion, .br fseeko () returns 0, while .br ftello () returns the current offset. otherwise, \-1 is returned and .i errno is set to indicate the error. .sh errors see the errors in .br fseek (3). .sh versions these functions are available under glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fseeko (), .br ftello () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2. .sh notes the declarations of these functions can also be obtained by defining the obsolete .b _largefile_source feature test macro. .sh see also .br fseek (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getmntent.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcsncmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsncmp \- compare two fixed-size wide-character strings .sh synopsis .nf .b #include .pp .bi "int wcsncmp(const wchar_t *" s1 ", const wchar_t *" s2 ", size_t " n ); .fi .sh description the .br wcsncmp () function is the wide-character equivalent of the .br strncmp (3) function. it compares the wide-character string pointed to by .i s1 and the wide-character string pointed to by .ir s2 , but at most .i n wide characters from each string. in each string, the comparison extends only up to the first occurrence of a null wide character (l\(aq\e0\(aq), if any. .sh return value the .br wcsncmp () function returns zero if the wide-character strings at .i s1 and .ir s2 , truncated to at most length .ir n , are equal. it returns an integer greater than zero if at the first differing position .i i .ri ( i < .ir n ), the corresponding wide-character .i s1[i] is greater than .ir s2[i] . it returns an integer less than zero if at the first differing position .i i .ri ( i < .ir n ), the corresponding wide-character .i s1[i] is less than .ir s2[i] . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsncmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strncmp (3), .br wcsncasecmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sigtimedwait.2 #!/bin/sh # # unformat_parens.sh # # the manual pages before 2.10 format parentheses # inconsistently. in some cases they are like: # # .b name() # # while in others they are like: # # .br name () # # this script changes instances to the latter format. # it does not fix all such instances: some will have to be # done manually. # # use the "-n" option for a dry run, in order to see what would be # done, without actually doing it. # ###################################################################### # # (c) copyright 2005 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # # file_base="tmp.$(basename $0)" work_dst_file="$file_base.dst" work_src_file="$file_base.src" all_files="$work_dst_file $work_src_file" # command-line option processing really_do_it=1 while getopts "n" optname; do case "$optname" in n) really_do_it=0; ;; *) echo "unknown option: $optarg" exit 1 ;; esac done shift $(( $optind - 1 )) # only process files with > 1 line -- single-line files are link files for page in $(wc "$@" 2> /dev/null | awk '$1 > 1 {print $4}'| \ grep -v '^total'); do cp $page $work_dst_file echo ">>>>>>>>>>>>>>>>>>>>>>>>>" $page "<<<<<<<<<<<<<<<<<<<<<<<<<" if false; then grep '^\.i *[a-z0-9_][a-z0-9_]*()$' $page grep '^\.b *[a-z0-9_][a-z0-9_]*()$' $page echo '###' grep '^\.[bir][bir] *[a-z0-9_][a-z0-9_]*()$' $page echo '###' grep '^\.[bir][bir] *[a-z0-9_][a-z0-9_]*() [^"]*$' $page echo '###' grep '()\\f[pr]' $page echo '###' fi cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e '/^\.b *[a-z0-9_][a-z0-9_]*() *$/s/^\.b/.br/' \ -e '/^\.i *[a-z0-9_][a-z0-9_]*() *$/s/^\.i/.ir/' \ > $work_dst_file cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e '/^\.[bir][bir] *[a-z0-9_][a-z0-9_]*()$/s/()/ ()/' \ > $work_dst_file cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e '/^\.[bir][bir] *[a-z0-9_][a-z0-9_]*() [^"]*$/s/() / ()/' \ > $work_dst_file cp $work_dst_file $work_src_file cat $work_src_file | \ sed \ -e '/()\\fp/s/()\\fp/\\fp()/g' \ -e '/()\\fr/s/()\\fr/\\fr()/g' \ > $work_dst_file if ! cmp -s $page $work_dst_file; then diff -u $page $work_dst_file if test $really_do_it -ne 0; then cat $work_dst_file > $page fi else echo "### nothing changed" fi done # clean up rm -f $all_files exit 0 .so man3/erf.3 .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" .\" %%%license_start(bsd_oneline_cdrom) .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" %%%license_end .\" .\" @(#)rpc.5 2.2 88/08/03 4.0 rpcsrc; from 1.4 87/11/27 smi; .th rpc 5 2021-03-22 "" "linux programmer's manual" .sh name rpc \- rpc program number data base .sh synopsis .nf .b /etc/rpc .fi .sh description the .i rpc file contains user readable names that can be used in place of rpc program numbers. each line has the following information: .pp .pd 0 .ip \(bu 3 name of server for the rpc program .ip \(bu rpc program number .ip \(bu aliases .pd .pp items are separated by any number of blanks and/or tab characters. a \(aq#\(aq indicates the beginning of a comment; characters from the \(aq#\(aq to the end of the line are not interpreted by routines which search the file. .pp here is an example of the .i /etc/rpc file from the sun rpc source distribution. .pp .in +4n .ex # # rpc 88/08/01 4.0 rpcsrc; from 1.12 88/02/07 smi # portmapper 100000 portmap sunrpc rstatd 100001 rstat rstat_svc rup perfmeter rusersd 100002 rusers nfs 100003 nfsprog ypserv 100004 ypprog mountd 100005 mount showmount ypbind 100007 walld 100008 rwall shutdown yppasswdd 100009 yppasswd etherstatd 100010 etherstat rquotad 100011 rquotaprog quota rquota sprayd 100012 spray 3270_mapper 100013 rje_mapper 100014 selection_svc 100015 selnsvc database_svc 100016 rexd 100017 rex alis 100018 sched 100019 llockmgr 100020 nlockmgr 100021 x25.inr 100022 statmon 100023 status 100024 bootparam 100026 ypupdated 100028 ypupdate keyserv 100029 keyserver tfsd 100037 nsed 100038 nsemntd 100039 .ee .in .sh files .tp .i /etc/rpc rpc program number data base .sh see also .br getrpcent (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/chmod.2 .\" %%%license_start(public_domain) .\" this page is in the public domain. - aeb .\" %%%license_end .\" .th grantpt 3 2021-03-22 "gnu" "linux programmer's manual" .sh name grantpt \- grant access to the slave pseudoterminal .sh synopsis .nf .b #include .pp .bi "int grantpt(int " fd ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br grantpt (): .nf since glibc 2.24: _xopen_source >= 500 .\" || (_xopen_source && _xopen_source_extended) glibc 2.23 and earlier: _xopen_source .fi .sh description the .br grantpt () function changes the mode and owner of the slave pseudoterminal device corresponding to the master pseudoterminal referred to by the file descriptor .ir fd . the user id of the slave is set to the real uid of the calling process. the group id is set to an unspecified value (e.g., .ir tty ). the mode of the slave is set to 0620 (crw\-\-w\-\-\-\-). .pp the behavior of .br grantpt () is unspecified if a signal handler is installed to catch .b sigchld signals. .sh return value when successful, .br grantpt () returns 0. otherwise, it returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b eacces the corresponding slave pseudoterminal could not be accessed. .tp .b ebadf the .i fd argument is not a valid open file descriptor. .tp .b einval the .i fd argument is valid but not associated with a master pseudoterminal. .sh versions .br grantpt () is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br grantpt () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes this is part of the unix 98 pseudoterminal support, see .br pts (4). .pp many systems implement this function via a set-user-id helper binary called "pt_chown". on linux systems with a devpts filesystem (present since linux 2.2), the kernel normally sets the correct ownership and permissions for the pseudoterminal slave when the master is opened .rb ( posix_openpt (3)), so that nothing must be done by .br grantpt (). thus, no such helper binary is required (and indeed it is configured to be absent during the glibc build that is typical on many systems). .sh see also .br open (2), .br posix_openpt (3), .br ptsname (3), .br unlockpt (3), .br pts (4), .br pty (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/atan.3 this package contains linux man pages for sections 1 through 8. some more information is given in the 'man-pages-x.y.announce' file. homepage ======== for information about the linux man-pages project, see http://www.kernel.org/doc/man-pages/index.html. bug reports and contributing ============================ if you have corrections and additions to suggest, see http://www.kernel.org/doc/man-pages/contributing.html (although there is a mirror of this repository on github, please don't report issues via the github issue tracker!) for further information on contributing, see the contributing file. installing and uninstalling =========================== "make install" will copy these man pages to /usr/local/share/man/man[1-8]. to install to a path different from /usr/local, use "make install prefix=/install/path". "make remove" or "make uninstall" will remove any man page in this distribution from its destination. use with caution, and remember to use "prefix" if desired, as with the "install" target. to install only a specific man section (mandir) such as man3, use "make install-man3". similar syntax can be used to uninstall a specific man section, such as man7: "make uninstall-man7". "make" or "make all" will perform "make uninstall" followed by "make install". consider using multiple threads (at least 2) when installing these man pages, as the makefile is optimized for multiple threads: "make -j install". copyrights ========== see the 'man-pages-x.y.announce' file. .so man2/clone.2 .so man4/pts.4 .so man3/log1p.3 .\" copyright (c) 2007, 2010 michael kerrisk .\" and copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 18:34:44 1993 by rik faith (faith@cs.unc.edu) .\" merged readv.[23], 2002-10-17, aeb .\" 2007-04-30 mtk, a fairly major rewrite to fix errors and .\" add more details. .\" 2010-11-16, mtk, added documentation of preadv() and pwritev() .\" .th readv 2 2021-08-27 "linux" "linux programmer's manual" .sh name readv, writev, preadv, pwritev, preadv2, pwritev2 \- read or write data into multiple buffers .sh synopsis .nf .b #include .pp .bi "ssize_t readv(int " fd ", const struct iovec *" iov ", int " iovcnt ); .bi "ssize_t writev(int " fd ", const struct iovec *" iov ", int " iovcnt ); .pp .bi "ssize_t preadv(int " fd ", const struct iovec *" iov ", int " iovcnt , .bi " off_t " offset ); .bi "ssize_t pwritev(int " fd ", const struct iovec *" iov ", int " iovcnt , .bi " off_t " offset ); .pp .bi "ssize_t preadv2(int " fd ", const struct iovec *" iov ", int " iovcnt , .bi " off_t " offset ", int " flags ); .bi "ssize_t pwritev2(int " fd ", const struct iovec *" iov ", int " iovcnt , .bi " off_t " offset ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br preadv (), .br pwritev (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the .br readv () system call reads .i iovcnt buffers from the file associated with the file descriptor .i fd into the buffers described by .i iov ("scatter input"). .pp the .br writev () system call writes .i iovcnt buffers of data described by .i iov to the file associated with the file descriptor .i fd ("gather output"). .pp the pointer .i iov points to an array of .i iovec structures, defined in .i as: .pp .in +4n .ex struct iovec { void *iov_base; /* starting address */ size_t iov_len; /* number of bytes to transfer */ }; .ee .in .pp the .br readv () system call works just like .br read (2) except that multiple buffers are filled. .pp the .br writev () system call works just like .br write (2) except that multiple buffers are written out. .pp buffers are processed in array order. this means that .br readv () completely fills .i iov[0] before proceeding to .ir iov[1] , and so on. (if there is insufficient data, then not all buffers pointed to by .i iov may be filled.) similarly, .br writev () writes out the entire contents of .i iov[0] before proceeding to .ir iov[1] , and so on. .pp the data transfers performed by .br readv () and .br writev () are atomic: the data written by .\" regarding atomicity, see https://bugzilla.kernel.org/show_bug.cgi?id=10596 .br writev () is written as a single block that is not intermingled with output from writes in other processes; analogously, .br readv () is guaranteed to read a contiguous block of data from the file, regardless of read operations performed in other threads or processes that have file descriptors referring to the same open file description (see .br open (2)). .ss preadv() and pwritev() the .br preadv () system call combines the functionality of .br readv () and .br pread (2). it performs the same task as .br readv (), but adds a fourth argument, .ir offset , which specifies the file offset at which the input operation is to be performed. .pp the .br pwritev () system call combines the functionality of .br writev () and .br pwrite (2). it performs the same task as .br writev (), but adds a fourth argument, .ir offset , which specifies the file offset at which the output operation is to be performed. .pp the file offset is not changed by these system calls. the file referred to by .i fd must be capable of seeking. .ss preadv2() and pwritev2() these system calls are similar to .br preadv () and .br pwritev () calls, but add a fifth argument, .ir flags , which modifies the behavior on a per-call basis. .pp unlike .br preadv () and .br pwritev (), if the .i offset argument is \-1, then the current file offset is used and updated. .pp the .i flags argument contains a bitwise or of zero or more of the following flags: .tp .br rwf_dsync " (since linux 4.7)" .\" commit e864f39569f4092c2b2bc72c773b6e486c7e3bd9 provide a per-write equivalent of the .b o_dsync .br open (2) flag. this flag is meaningful only for .br pwritev2 (), and its effect applies only to the data range written by the system call. .tp .br rwf_hipri " (since linux 4.6)" high priority read/write. allows block-based filesystems to use polling of the device, which provides lower latency, but may use additional resources. (currently, this feature is usable only on a file descriptor opened using the .br o_direct flag.) .tp .br rwf_sync " (since linux 4.7)" .\" commit e864f39569f4092c2b2bc72c773b6e486c7e3bd9 provide a per-write equivalent of the .b o_sync .br open (2) flag. this flag is meaningful only for .br pwritev2 (), and its effect applies only to the data range written by the system call. .tp .br rwf_nowait " (since linux 4.14)" .\" commit 3239d834847627b6634a4139cf1dc58f6f137a46 .\" commit 91f9943e1c7b6638f27312d03fe71fcc67b23571 do not wait for data which is not immediately available. if this flag is specified, the .br preadv2 () system call will return instantly if it would have to read data from the backing storage or wait for a lock. if some data was successfully read, it will return the number of bytes read. if no bytes were read, it will return \-1 and set .ir errno to .br eagain (but see .br bugs ). currently, this flag is meaningful only for .br preadv2 (). .tp .br rwf_append " (since linux 4.16)" .\" commit e1fc742e14e01d84d9693c4aca4ab23da65811fb provide a per-write equivalent of the .b o_append .br open (2) flag. this flag is meaningful only for .br pwritev2 (), and its effect applies only to the data range written by the system call. the .i offset argument does not affect the write operation; the data is always appended to the end of the file. however, if the .i offset argument is \-1, the current file offset is updated. .sh return value on success, .br readv (), .br preadv (), and .br preadv2 () return the number of bytes read; .br writev (), .br pwritev (), and .br pwritev2 () return the number of bytes written. .pp note that it is not an error for a successful call to transfer fewer bytes than requested (see .br read (2) and .br write (2)). .pp on error, \-1 is returned, and \fierrno\fp is set to indicate the error. .sh errors the errors are as given for .br read (2) and .br write (2). furthermore, .br preadv (), .br preadv2 (), .br pwritev (), and .br pwritev2 () can also fail for the same reasons as .br lseek (2). additionally, the following errors are defined: .tp .b einval the sum of the .i iov_len values overflows an .i ssize_t value. .tp .b einval the vector count, .ir iovcnt , is less than zero or greater than the permitted maximum. .tp .b eopnotsupp an unknown flag is specified in \fiflags\fp. .sh versions .br preadv () and .br pwritev () first appeared in linux 2.6.30; library support was added in glibc 2.10. .pp .br preadv2 () and .br pwritev2 () first appeared in linux 4.6. library support was added in glibc 2.26. .sh conforming to .br readv (), .br writev (): posix.1-2001, posix.1-2008, 4.4bsd (these system calls first appeared in 4.2bsd). .\" linux libc5 used \fisize_t\fp as the type of the \fiiovcnt\fp argument, .\" and \fiint\fp as the return type. .\" the readv/writev system calls were buggy before linux 1.3.40. .\" (says release.libc.) .pp .br preadv (), .br pwritev (): nonstandard, but present also on the modern bsds. .pp .br preadv2 (), .br pwritev2 (): nonstandard linux extension. .sh notes posix.1 allows an implementation to place a limit on the number of items that can be passed in .ir iov . an implementation can advertise its limit by defining .b iov_max in .i or at run time via the return value from .ir sysconf(_sc_iov_max) . on modern linux systems, the limit is 1024. back in linux 2.0 days, this limit was 16. .\" .\" .ss c library/kernel differences the raw .br preadv () and .br pwritev () system calls have call signatures that differ slightly from that of the corresponding gnu c library wrapper functions shown in the synopsis. the final argument, .ir offset , is unpacked by the wrapper functions into two arguments in the system calls: .pp .bi " unsigned long " pos_l ", unsigned long " pos .pp these arguments contain, respectively, the low order and high order 32 bits of .ir offset . .ss historical c library/kernel differences to deal with the fact that .b iov_max was so low on early versions of linux, the glibc wrapper functions for .br readv () and .br writev () did some extra work if they detected that the underlying kernel system call failed because this limit was exceeded. in the case of .br readv (), the wrapper function allocated a temporary buffer large enough for all of the items specified by .ir iov , passed that buffer in a call to .br read (2), copied data from the buffer to the locations specified by the .i iov_base fields of the elements of .ir iov , and then freed the buffer. the wrapper function for .br writev () performed the analogous task using a temporary buffer and a call to .br write (2). .pp the need for this extra effort in the glibc wrapper functions went away with linux 2.2 and later. however, glibc continued to provide this behavior until version 2.10. starting with glibc version 2.9, the wrapper functions provide this behavior only if the library detects that the system is running a linux kernel older than version 2.6.18 (an arbitrarily selected kernel version). and since glibc 2.20 (which requires a minimum linux kernel version of 2.6.32), the glibc wrapper functions always just directly invoke the system calls. .sh bugs linux 5.9 and 5.10 have a bug where .br preadv2() with the .br rwf_nowait flag may return 0 even when not at end of file. .\" see .\" .\" the bug was introduced in .\" efa8480a831 fs: rwf_nowait should imply iocb_noio .\"and fixed in .\" 06c0444290 mm/filemap.c: generic_file_buffered_read() now uses find_get_pages_contig .sh examples the following code sample demonstrates the use of .br writev (): .pp .in +4n .ex char *str0 = "hello "; char *str1 = "world\en"; struct iovec iov[2]; ssize_t nwritten; iov[0].iov_base = str0; iov[0].iov_len = strlen(str0); iov[1].iov_base = str1; iov[1].iov_len = strlen(str1); nwritten = writev(stdout_fileno, iov, 2); .ee .in .sh see also .br pread (2), .br read (2), .br write (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/sqrt.3 .so man3/rpc.3 .\" this man-page is copyright (c) 1997 john s. kallal .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and author(s) of this work. .\" %%%license_end .\" .\" if the you wish to distribute versions of this work under other .\" conditions than the above, please contact the author(s) at the following .\" for permission: .\" .\" john s. kallal - .\" email: .\" mail: 518 kerfoot farm rd, wilmington, de 19803-2444, usa .\" phone: (302)654-5478 .\" .\" $id: initrd.4,v 0.9 1997/11/07 05:05:32 kallal exp kallal $ .th initrd 4 2021-03-22 "linux" "linux programmer's manual" .sh name initrd \- boot loader initialized ram disk .sh configuration .i /dev/initrd is a read-only block device assigned major number 1 and minor number 250. typically .i /dev/initrd is owned by root:disk with mode 0400 (read access by root only). if the linux system does not have .i /dev/initrd already created, it can be created with the following commands: .pp .in +4n .ex mknod \-m 400 /dev/initrd b 1 250 chown root:disk /dev/initrd .ee .in .pp also, support for both "ram disk" and "initial ram disk" (e.g., .br config_blk_dev_ram=y and .br config_blk_dev_initrd=y ) must be compiled directly into the linux kernel to use .ir /dev/initrd . when using .ir /dev/initrd , the ram disk driver cannot be loaded as a module. .\" .\" .\" .sh description the special file .i /dev/initrd is a read-only block device. this device is a ram disk that is initialized (e.g., loaded) by the boot loader before the kernel is started. the kernel then can use .ir /dev/initrd "'s" contents for a two-phase system boot-up. .pp in the first boot-up phase, the kernel starts up and mounts an initial root filesystem from the contents of .i /dev/initrd (e.g., ram disk initialized by the boot loader). in the second phase, additional drivers or other modules are loaded from the initial root device's contents. after loading the additional modules, a new root filesystem (i.e., the normal root filesystem) is mounted from a different device. .\" .\" .\" .ss boot-up operation when booting up with .br initrd , the system boots as follows: .ip 1. 3 the boot loader loads the kernel program and .ir /dev/initrd 's contents into memory. .ip 2. on kernel startup, the kernel uncompresses and copies the contents of the device .i /dev/initrd onto device .i /dev/ram0 and then frees the memory used by .ir /dev/initrd . .ip 3. the kernel then read-write mounts the device .i /dev/ram0 as the initial root filesystem. .ip 4. if the indicated normal root filesystem is also the initial root filesystem (e.g., .ir /dev/ram0 ) then the kernel skips to the last step for the usual boot sequence. .ip 5. if the executable file .ir /linuxrc is present in the initial root filesystem, .i /linuxrc is executed with uid 0. (the file .i /linuxrc must have executable permission. the file .i /linuxrc can be any valid executable, including a shell script.) .ip 6. if .i /linuxrc is not executed or when .i /linuxrc terminates, the normal root filesystem is mounted. (if .i /linuxrc exits with any filesystems mounted on the initial root filesystem, then the behavior of the kernel is .br unspecified . see the notes section for the current kernel behavior.) .ip 7. if the normal root filesystem has a directory .ir /initrd , the device .i /dev/ram0 is moved from .ir / to .ir /initrd . otherwise, if the directory .ir /initrd does not exist, the device .i /dev/ram0 is unmounted. (when moved from .ir / to .ir /initrd , .i /dev/ram0 is not unmounted and therefore processes can remain running from .ir /dev/ram0 . if directory .i /initrd does not exist on the normal root filesystem and any processes remain running from .ir /dev/ram0 when .i /linuxrc exits, the behavior of the kernel is .br unspecified . see the notes section for the current kernel behavior.) .ip 8. the usual boot sequence (e.g., invocation of .ir /sbin/init ) is performed on the normal root filesystem. .\" .\" .\" .ss options the following boot loader options, when used with .br initrd , affect the kernel's boot-up operation: .tp .bi initrd= "filename" specifies the file to load as the contents of .ir /dev/initrd . for .b loadlin this is a command-line option. for .b lilo you have to use this command in the .b lilo configuration file .ir /etc/lilo.config . the filename specified with this option will typically be a gzipped filesystem image. .tp .b noinitrd this boot option disables the two-phase boot-up operation. the kernel performs the usual boot sequence as if .i /dev/initrd was not initialized. with this option, any contents of .i /dev/initrd loaded into memory by the boot loader contents are preserved. this option permits the contents of .i /dev/initrd to be any data and need not be limited to a filesystem image. however, device .i /dev/initrd is read-only and can be read only one time after system startup. .tp .bi root= "device-name" specifies the device to be used as the normal root filesystem. for .b loadlin this is a command-line option. for .b lilo this is a boot time option or can be used as an option line in the .b lilo configuration file .ir /etc/lilo.config . the device specified by this option must be a mountable device having a suitable root filesystem. .\" .\" .\" .ss changing the normal root filesystem by default, the kernel's settings (e.g., set in the kernel file with .br rdev (8) or compiled into the kernel file), or the boot loader option setting is used for the normal root filesystems. for an nfs-mounted normal root filesystem, one has to use the .b nfs_root_name and .b nfs_root_addrs boot options to give the nfs settings. for more information on nfs-mounted root see the kernel documentation file .i documentation/filesystems/nfs/nfsroot.txt .\" commit dc7a08166f3a5f23e79e839a8a88849bd3397c32 (or .i documentation/filesystems/nfsroot.txt before linux 2.6.33). for more information on setting the root filesystem see also the .br lilo and .br loadlin documentation. .pp it is also possible for the .i /linuxrc executable to change the normal root device. for .i /linuxrc to change the normal root device, .ir /proc must be mounted. after mounting .ir /proc , .i /linuxrc changes the normal root device by writing into the proc files .ir /proc/sys/kernel/real\-root\-dev , .ir /proc/sys/kernel/nfs\-root\-name , and .ir /proc/sys/kernel/nfs\-root\-addrs . for a physical root device, the root device is changed by having .i /linuxrc write the new root filesystem device number into .ir /proc/sys/kernel/real\-root\-dev . for an nfs root filesystem, the root device is changed by having .i /linuxrc write the nfs setting into files .ir /proc/sys/kernel/nfs\-root\-name and .i /proc/sys/kernel/nfs\-root\-addrs and then writing 0xff (e.g., the pseudo-nfs-device number) into file .ir /proc/sys/kernel/real\-root\-dev . for example, the following shell command line would change the normal root device to .ir /dev/hdb1 : .pp .in +4n .ex echo 0x365 >/proc/sys/kernel/real\-root\-dev .ee .in .pp for an nfs example, the following shell command lines would change the normal root device to the nfs directory .i /var/nfsroot on a local networked nfs server with ip number 193.8.232.7 for a system with ip number 193.8.232.2 and named "idefix": .pp .in +4n .ex echo /var/nfsroot >/proc/sys/kernel/nfs\-root\-name echo 193.8.232.2:193.8.232.7::255.255.255.0:idefix \e >/proc/sys/kernel/nfs\-root\-addrs echo 255 >/proc/sys/kernel/real\-root\-dev .ee .in .pp .br note : the use of .i /proc/sys/kernel/real\-root\-dev to change the root filesystem is obsolete. see the linux kernel source file .i documentation/admin\-guide/initrd.rst .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/initrd.txt before linux 4.10) as well as .br pivot_root (2) and .br pivot_root (8) for information on the modern method of changing the root filesystem. .\" fixme . should this manual page describe the pivot_root mechanism? .\" .\" .\" .ss usage the main motivation for implementing .b initrd was to allow for modular kernel configuration at system installation. .pp a possible system installation scenario is as follows: .ip 1. 3 the loader program boots from floppy or other media with a minimal kernel (e.g., support for .ir /dev/ram , .ir /dev/initrd , and the ext2 filesystem) and loads .ir /dev/initrd with a gzipped version of the initial filesystem. .ip 2. the executable .i /linuxrc determines what is needed to (1) mount the normal root filesystem (i.e., device type, device drivers, filesystem) and (2) the distribution media (e.g., cd-rom, network, tape, ...). this can be done by asking the user, by auto-probing, or by using a hybrid approach. .ip 3. the executable .i /linuxrc loads the necessary modules from the initial root filesystem. .ip 4. the executable .i /linuxrc creates and populates the root filesystem. (at this stage the normal root filesystem does not have to be a completed system yet.) .ip 5. the executable .ir /linuxrc sets .ir /proc/sys/kernel/real\-root\-dev , unmounts .ir /proc , the normal root filesystem and any other filesystems it has mounted, and then terminates. .ip 6. the kernel then mounts the normal root filesystem. .ip 7. now that the filesystem is accessible and intact, the boot loader can be installed. .ip 8. the boot loader is configured to load into .i /dev/initrd a filesystem with the set of modules that was used to bring up the system. (e.g., device .i /dev/ram0 can be modified, then unmounted, and finally, the image is written from .i /dev/ram0 to a file.) .ip 9. the system is now bootable and additional installation tasks can be performed. .pp the key role of .i /dev/initrd in the above is to reuse the configuration data during normal system operation without requiring initial kernel selection, a large generic kernel or, recompiling the kernel. .pp a second scenario is for installations where linux runs on systems with different hardware configurations in a single administrative network. in such cases, it may be desirable to use only a small set of kernels (ideally only one) and to keep the system-specific part of configuration information as small as possible. in this case, create a common file with all needed modules. then, only the .i /linuxrc file or a file executed by .i /linuxrc would be different. .pp a third scenario is more convenient recovery disks. because information like the location of the root filesystem partition is not needed at boot time, the system loaded from .i /dev/initrd can use a dialog and/or auto-detection followed by a possible sanity check. .pp last but not least, linux distributions on cd-rom may use .b initrd for easy installation from the cd-rom. the distribution can use .b loadlin to directly load .i /dev/initrd from cd-rom without the need of any floppies. the distribution could also use a .b lilo boot floppy and then bootstrap a bigger ram disk via .ir /dev/initrd from the cd-rom. .\" .\" .\" .sh files .i /dev/initrd .br .i /dev/ram0 .br .i /linuxrc .br .i /initrd .\" .\" .\" .sh notes .ip 1. 3 with the current kernel, any filesystems that remain mounted when .i /dev/ram0 is moved from .i / to .i /initrd continue to be accessible. however, the .i /proc/mounts entries are not updated. .ip 2. with the current kernel, if directory .i /initrd does not exist, then .i /dev/ram0 will .b not be fully unmounted if .i /dev/ram0 is used by any process or has any filesystem mounted on it. if .ir /dev/ram0 is .b not fully unmounted, then .i /dev/ram0 will remain in memory. .ip 3. users of .i /dev/initrd should not depend on the behavior given in the above notes. the behavior may change in future versions of the linux kernel. .\" .\" .\" .\" .sh authors .\" the kernel code for device .\" .br initrd .\" was written by werner almesberger and .\" hans lermen . .\" the code for .\" .br initrd .\" was added to the baseline linux kernel in development version 1.3.73. .sh see also .br chown (1), .br mknod (1), .br ram (4), .br freeramdisk (8), .br rdev (8) .pp .i documentation/admin\-guide/initrd.rst .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/initrd.txt before linux 4.10) in the linux kernel source tree, the lilo documentation, the loadlin documentation, the syslinux documentation .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th setjmp 3 2021-03-22 "" "linux programmer's manual" .sh name setjmp, sigsetjmp, longjmp, siglongjmp \- performing a nonlocal goto .sh synopsis .nf .b #include .pp .bi "int setjmp(jmp_buf " env ); .bi "int sigsetjmp(sigjmp_buf " env ", int " savesigs ); .pp .bi "noreturn void longjmp(jmp_buf " env ", int " val ); .bi "noreturn void siglongjmp(sigjmp_buf " env ", int " val ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br setjmp (): see notes. .pp .br sigsetjmp (): .nf _posix_c_source .fi .sh description the functions described on this page are used for performing "nonlocal gotos": transferring execution from one function to a predetermined location in another function. the .br setjmp () function dynamically establishes the target to which control will later be transferred, and .br longjmp () performs the transfer of execution. .pp the .br setjmp () function saves various information about the calling environment (typically, the stack pointer, the instruction pointer, possibly the values of other registers and the signal mask) in the buffer .ir env for later use by .br longjmp (). in this case, .br setjmp () returns 0. .pp the .br longjmp () function uses the information saved in .ir env to transfer control back to the point where .br setjmp () was called and to restore ("rewind") the stack to its state at the time of the .br setjmp () call. in addition, and depending on the implementation (see notes), the values of some other registers and the process signal mask may be restored to their state at the time of the .br setjmp () call. .pp following a successful .br longjmp (), execution continues as if .br setjmp () had returned for a second time. this "fake" return can be distinguished from a true .br setjmp () call because the "fake" return returns the value provided in .ir val . if the programmer mistakenly passes the value 0 in .ir val , the "fake" return will instead return 1. .ss sigsetjmp() and siglongjmp() .br sigsetjmp () and .br siglongjmp () also perform nonlocal gotos, but provide predictable handling of the process signal mask. .pp if, and only if, the .i savesigs argument provided to .br sigsetjmp () is nonzero, the process's current signal mask is saved in .i env and will be restored if a .br siglongjmp () is later performed with this .ir env . .sh return value .br setjmp () and .br sigsetjmp () return 0 when called directly; on the "fake" return that occurs after .br longjmp () or .br siglongjmp (), the nonzero value specified in .i val is returned. .pp the .br longjmp () or .br siglongjmp () functions do not return. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br setjmp (), .br sigsetjmp () t} thread safety mt-safe t{ .br longjmp (), .br siglongjmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br setjmp (), .br longjmp (): posix.1-2001, posix.1-2008, c89, c99. .pp .br sigsetjmp (), .br siglongjmp (): posix.1-2001, posix.1-2008. .sh notes posix does not specify whether .br setjmp () will save the signal mask (to be later restored during .br longjmp ()). in system v it will not. in 4.3bsd it will, and there is a function .br _setjmp () that will not. the behavior under linux depends on the glibc version and the setting of feature test macros. on linux with glibc versions before 2.19, .br setjmp () follows the system v behavior by default, but the bsd behavior is provided if the .br _bsd_source feature test macro is explicitly defined .\" so that _favor_bsd is triggered and none of .br _posix_source , .br _posix_c_source , .br _xopen_source , .\" .br _xopen_source_extended , .br _gnu_source , or .b _svid_source is defined. since glibc 2.19, .ir exposes only the system v version of .br setjmp (). programs that need the bsd semantics should replace calls to .br setjmp () with calls to .br sigsetjmp () with a nonzero .i savesigs argument. .pp .br setjmp () and .br longjmp () can be useful for dealing with errors inside deeply nested function calls or to allow a signal handler to pass control to a specific point in the program, rather than returning to the point where the handler interrupted the main program. in the latter case, if you want to portably save and restore signal masks, use .br sigsetjmp () and .br siglongjmp (). see also the discussion of program readability below. .pp the compiler may optimize variables into registers, and .br longjmp () may restore the values of other registers in addition to the stack pointer and program counter. consequently, the values of automatic variables are unspecified after a call to .br longjmp () if they meet all the following criteria: .ip \(bu 3 they are local to the function that made the corresponding .br setjmp () call; .ip \(bu their values are changed between the calls to .br setjmp () and .br longjmp (); and .ip \(bu they are not declared as .ir volatile . .pp analogous remarks apply for .br siglongjmp (). .\" .ss nonlocal gotos and program readability while it can be abused, the traditional c "goto" statement at least has the benefit that lexical cues (the goto statement and the target label) allow the programmer to easily perceive the flow of control. nonlocal gotos provide no such cues: multiple .br setjmp () calls might employ the same .ir jmp_buf variable so that the content of the variable may change over the lifetime of the application. consequently, the programmer may be forced to perform detailed reading of the code to determine the dynamic target of a particular .br longjmp () call. (to make the programmer's life easier, each .br setjmp () call should employ a unique .ir jmp_buf variable.) .pp adding further difficulty, the .br setjmp () and .br longjmp () calls may not even be in the same source code module. .pp in summary, nonlocal gotos can make programs harder to understand and maintain, and an alternative should be used if possible. .\" .ss caveats if the function which called .br setjmp () returns before .br longjmp () is called, the behavior is undefined. some kind of subtle or unsubtle chaos is sure to result. .pp if, in a multithreaded program, a .br longjmp () call employs an .i env buffer that was initialized by a call to .br setjmp () in a different thread, the behavior is undefined. .\" .\" the following statement appeared in versions up to posix.1-2008 tc1, .\" but is set to be removed in posix.1-2008 tc2: .\" .\" according to posix.1, if a .\" .br longjmp () .\" call is performed from a nested signal handler .\" (i.e., from a handler that was invoked in response to a signal that was .\" generated while another signal was already in the process of being .\" handled), the behavior is undefined. .pp posix.1-2008 technical corrigendum 2 adds .\" http://austingroupbugs.net/view.php?id=516#c1195 .br longjmp () and .br siglongjmp () to the list of async-signal-safe functions. however, the standard recommends avoiding the use of these functions from signal handlers and goes on to point out that if these functions are called from a signal handler that interrupted a call to a non-async-signal-safe function (or some equivalent, such as the steps equivalent to .br exit (3) that occur upon a return from the initial call to .ir main ()), the behavior is undefined if the program subsequently makes a call to a non-async-signal-safe function. the only way of avoiding undefined behavior is to ensure one of the following: .ip * 3 after long jumping from the signal handler, the program does not call any non-async-signal-safe functions and does not return from the initial call to .ir main (). .ip * any signal whose handler performs a long jump must be blocked during .i every call to a non-async-signal-safe function and no non-async-signal-safe functions are called after returning from the initial call to .ir main (). .sh see also .br signal (7), .br signal\-safety (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wmemchr 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wmemchr \- search a wide character in a wide-character array .sh synopsis .nf .b #include .pp .bi "wchar_t *wmemchr(const wchar_t *" s ", wchar_t " c ", size_t " n ); .fi .sh description the .br wmemchr () function is the wide-character equivalent of the .br memchr (3) function. it searches the .ir n wide characters starting at .i s for the first occurrence of the wide character .ir c . .sh return value the .br wmemchr () function returns a pointer to the first occurrence of .i c among the .ir n wide characters starting at .ir s , or null if .i c does not occur among these. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wmemchr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br memchr (3), .br wcschr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) international business machines corp., 2006 .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see .\" the gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" history: .\" 2005-09-28, created by arnd bergmann .\" 2006-06-16, revised by eduardo m. fleury .\" 2007-07-10, some polishing by mtk .\" 2007-09-28, updates for newer kernels by jeremy kerr .\" .th spu_create 2 2021-03-22 linux "linux programmer's manual" .sh name spu_create \- create a new spu context .sh synopsis .nf .br "#include " " /* definition of " spu_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_spu_create, const char *" pathname \ ", unsigned int " flags , .bi " mode_t " mode ", int " neighbor_fd ); .fi .pp .ir note : glibc provides no wrapper for .br spu_create (), necessitating the use of .br syscall (2). .sh description the .br spu_create () system call is used on powerpc machines that implement the cell broadband engine architecture in order to access synergistic processor units (spus). it creates a new logical context for an spu in .i pathname and returns a file descriptor associated with it. .i pathname must refer to a nonexistent directory in the mount point of the spu filesystem .rb ( spufs ). if .br spu_create () is successful, a directory is created at .i pathname and it is populated with the files described in .br spufs (7). .pp when a context is created, the returned file descriptor can only be passed to .br spu_run (2), used as the .i dirfd argument to the .b *at family of system calls (e.g., .br openat (2)), or closed; other operations are not defined. a logical spu context is destroyed (along with all files created within the context's .i pathname directory) once the last reference to the context has gone; this usually occurs when the file descriptor returned by .br spu_create () is closed. .pp the .i mode argument (minus any bits set in the process's .br umask (2)) specifies the permissions used for creating the new directory in .br spufs . see .br stat (2) for a full list of the possible .i mode values. .pp the .i neighbor_fd is used only when the .b spu_create_affinity_spu flag is specified; see below. .pp the .i flags argument can be zero or any bitwise or-ed combination of the following constants: .tp .b spu_create_events_enabled rather than using signals for reporting dma errors, use the .i event argument to .br spu_run (2). .tp .b spu_create_gang create an spu gang instead of a context. (a gang is a group of spu contexts that are functionally related to each other and which share common scheduling parameters\(empriority and policy. in the future, gang scheduling may be implemented causing the group to be switched in and out as a single unit.) .ip a new directory will be created at the location specified by the .i pathname argument. this gang may be used to hold other spu contexts, by providing a pathname that is within the gang directory to further calls to .br spu_create (). .tp .b spu_create_nosched create a context that is not affected by the spu scheduler. once the context is run, it will not be scheduled out until it is destroyed by the creating process. .ip because the context cannot be removed from the spu, some functionality is disabled for .br spu_create_nosched contexts. only a subset of the files will be available in this context directory in .br spufs . additionally, .br spu_create_nosched contexts cannot dump a core file when crashing. .ip creating .br spu_create_nosched contexts requires the .b cap_sys_nice capability. .tp .b spu_create_isolate create an isolated spu context. isolated contexts are protected from some ppe (powerpc processing element) operations, such as access to the spu local store and the npc register. .ip creating .b spu_create_isolate contexts also requires the .b spu_create_nosched flag. .tp .br spu_create_affinity_spu " (since linux 2.6.23)" .\" commit 8e68e2f248332a9c3fd4f08258f488c209bd3e0c create a context with affinity to another spu context. this affinity information is used within the spu scheduling algorithm. using this flag requires that a file descriptor referring to the other spu context be passed in the .i neighbor_fd argument. .tp .br spu_create_affinity_mem " (since linux 2.6.23)" .\" commit 8e68e2f248332a9c3fd4f08258f488c209bd3e0c create a context with affinity to system memory. this affinity information is used within the spu scheduling algorithm. .sh return value on success, .br spu_create () returns a new file descriptor. on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces the current user does not have write access to the .br spufs (7) mount point. .tp .b eexist an spu context already exists at the given pathname. .tp .b efault .i pathname is not a valid string pointer in the calling process's address space. .tp .b einval .i pathname is not a directory in the .br spufs (7) mount point, or invalid flags have been provided. .tp .b eloop too many symbolic links were found while resolving .ir pathname . .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enametoolong .i pathname is too long. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enodev an isolated context was requested, but the hardware does not support spu isolation. .tp .b enoent part of .i pathname could not be resolved. .tp .b enomem the kernel could not allocate all resources required. .tp .b enospc there are not enough spu resources available to create a new context or the user-specific limit for the number of spu contexts has been reached. .tp .b enosys the functionality is not provided by the current system, because either the hardware does not provide spus or the spufs module is not loaded. .tp .b enotdir a part of .i pathname is not a directory. .tp .b eperm the .b spu_create_nosched flag has been given, but the user does not have the .b cap_sys_nice capability. .sh files .i pathname must point to a location beneath the mount point of .br spufs . by convention, it gets mounted in .ir /spu . .sh versions the .br spu_create () system call was added to linux in kernel 2.6.16. .sh conforming to this call is linux-specific and implemented only on the powerpc architecture. programs using this system call are not portable. .sh notes .br spu_create () is meant to be used from libraries that implement a more abstract interface to spus, not to be used from regular applications. see .ur http://www.bsc.es\:/projects\:/deepcomputing\:/linuxoncell/ .ue for the recommended libraries. .pp prior to the addition of the .b spu_create_affinity_spu flag in linux 2.6.23, the .br spu_create () system call took only three arguments (i.e., there was no .i neighbor_fd argument). .sh examples see .br spu_run (2) for an example of the use of .br spu_create () .sh see also .br close (2), .br spu_run (2), .br capabilities (7), .br spufs (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2011 christopher yeoh .\" and copyright (c) 2012 mike frysinger .\" and copyright (c) 2012 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" commit fcf634098c00dd9cd247447368495f0b79be12d1 .\" .th process_vm_readv 2 2021-03-22 "linux" "linux programmer's manual" .sh name process_vm_readv, process_vm_writev \- transfer data between process address spaces .sh synopsis .nf .b #include .pp .bi "ssize_t process_vm_readv(pid_t " pid , .bi " const struct iovec *" local_iov , .bi " unsigned long " liovcnt , .bi " const struct iovec *" remote_iov , .bi " unsigned long " riovcnt , .bi " unsigned long " flags ");" .bi "ssize_t process_vm_writev(pid_t " pid , .bi " const struct iovec *" local_iov , .bi " unsigned long " liovcnt , .bi " const struct iovec *" remote_iov , .bi " unsigned long " riovcnt , .bi " unsigned long " flags ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br process_vm_readv (), .br process_vm_writev (): .nf _gnu_source .fi .sh description these system calls transfer data between the address space of the calling process ("the local process") and the process identified by .ir pid ("the remote process"). the data moves directly between the address spaces of the two processes, without passing through kernel space. .pp the .br process_vm_readv () system call transfers data from the remote process to the local process. the data to be transferred is identified by .ir remote_iov and .ir riovcnt : .ir remote_iov is a pointer to an array describing address ranges in the process .ir pid , and .ir riovcnt specifies the number of elements in .ir remote_iov . the data is transferred to the locations specified by .ir local_iov and .ir liovcnt : .ir local_iov is a pointer to an array describing address ranges in the calling process, and .ir liovcnt specifies the number of elements in .ir local_iov . .pp the .br process_vm_writev () system call is the converse of .br process_vm_readv ()\(emit transfers data from the local process to the remote process. other than the direction of the transfer, the arguments .ir liovcnt , .ir local_iov , .ir riovcnt , and .ir remote_iov have the same meaning as for .br process_vm_readv (). .pp the .i local_iov and .i remote_iov arguments point to an array of .i iovec structures, defined in .ir as: .pp .in +4n .ex struct iovec { void *iov_base; /* starting address */ size_t iov_len; /* number of bytes to transfer */ }; .ee .in .pp buffers are processed in array order. this means that .br process_vm_readv () completely fills .i local_iov[0] before proceeding to .ir local_iov[1] , and so on. likewise, .i remote_iov[0] is completely read before proceeding to .ir remote_iov[1] , and so on. .pp similarly, .br process_vm_writev () writes out the entire contents of .i local_iov[0] before proceeding to .ir local_iov[1] , and it completely fills .i remote_iov[0] before proceeding to .ir remote_iov[1] . .pp the lengths of .i remote_iov[i].iov_len and .i local_iov[i].iov_len do not have to be the same. thus, it is possible to split a single local buffer into multiple remote buffers, or vice versa. .pp the .i flags argument is currently unused and must be set to 0. .pp the values specified in the .i liovcnt and .i riovcnt arguments must be less than or equal to .br iov_max (defined in .i or accessible via the call .ir sysconf(_sc_iov_max) ). .\" in time, glibc might provide a wrapper that works around this limit, .\" as is done for readv()/writev() .pp the count arguments and .ir local_iov are checked before doing any transfers. if the counts are too big, or .i local_iov is invalid, or the addresses refer to regions that are inaccessible to the local process, none of the vectors will be processed and an error will be returned immediately. .pp note, however, that these system calls do not check the memory regions in the remote process until just before doing the read/write. consequently, a partial read/write (see return value) may result if one of the .i remote_iov elements points to an invalid memory region in the remote process. no further reads/writes will be attempted beyond that point. keep this in mind when attempting to read data of unknown length (such as c strings that are null-terminated) from a remote process, by avoiding spanning memory pages (typically 4\ kib) in a single remote .i iovec element. (instead, split the remote read into two .i remote_iov elements and have them merge back into a single write .i local_iov entry. the first read entry goes up to the page boundary, while the second starts on the next page boundary.) .pp permission to read from or write to another process is governed by a ptrace access mode .b ptrace_mode_attach_realcreds check; see .br ptrace (2). .sh return value on success, .br process_vm_readv () returns the number of bytes read and .br process_vm_writev () returns the number of bytes written. this return value may be less than the total number of requested bytes, if a partial read/write occurred. (partial transfers apply at the granularity of .i iovec elements. these system calls won't perform a partial transfer that splits a single .i iovec element.) the caller should check the return value to determine whether a partial read/write occurred. .pp on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault the memory described by .i local_iov is outside the caller's accessible address space. .tp .b efault the memory described by .i remote_iov is outside the accessible address space of the process .ir pid . .tp .b einval the sum of the .i iov_len values of either .i local_iov or .i remote_iov overflows a .i ssize_t value. .tp .b einval .i flags is not 0. .tp .b einval .i liovcnt or .i riovcnt is too large. .tp .b enomem could not allocate memory for internal copies of the .i iovec structures. .tp .b eperm the caller does not have permission to access the address space of the process .ir pid . .tp .b esrch no process with id .i pid exists. .sh versions these system calls were added in linux 3.2. support is provided in glibc since version 2.15. .sh conforming to these system calls are nonstandard linux extensions. .sh notes the data transfers performed by .br process_vm_readv () and .br process_vm_writev () are not guaranteed to be atomic in any way. .pp these system calls were designed to permit fast message passing by allowing messages to be exchanged with a single copy operation (rather than the double copy that would be required when using, for example, shared memory or pipes). .\" original user is mpi, http://www.mcs.anl.gov/research/projects/mpi/ .\" see also some benchmarks at http://lwn.net/articles/405284/ .\" and http://marc.info/?l=linux-mm&m=130105930902915&w=2 .sh examples the following code sample demonstrates the use of .br process_vm_readv (). it reads 20 bytes at the address 0x10000 from the process with pid 10 and writes the first 10 bytes into .i buf1 and the second 10 bytes into .ir buf2 . .pp .ex #include int main(void) { struct iovec local[2]; struct iovec remote[1]; char buf1[10]; char buf2[10]; ssize_t nread; pid_t pid = 10; /* pid of remote process */ local[0].iov_base = buf1; local[0].iov_len = 10; local[1].iov_base = buf2; local[1].iov_len = 10; remote[0].iov_base = (void *) 0x10000; remote[0].iov_len = 20; nread = process_vm_readv(pid, local, 2, remote, 1, 0); if (nread != 20) return 1; else return 0; } .ee .sh see also .br readv (2), .br writev (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tgamma.3 .so man3/endian.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" i had no way the check the functions out .\" be careful .th key_setsecret 3 2021-03-22 "" "linux programmer's manual" .sh name key_decryptsession, key_encryptsession, key_setsecret, key_gendes, key_secretkey_is_set \- interfaces to rpc keyserver daemon .sh synopsis .nf .b "#include " .pp .bi "int key_decryptsession(char *" remotename ", des_block *" deskey ); .bi "int key_encryptsession(char *" remotename ", des_block *" deskey ); .pp .bi "int key_gendes(des_block *" deskey ); .pp .bi "int key_setsecret(char *" key ); .b "int key_secretkey_is_set(void);" .fi .sh description the functions here are used within the rpc's secure authentication mechanism (auth_des). there should be no need for user programs to use this functions. .pp the function .br key_decryptsession () uses the (remote) server netname and takes the des key for decrypting. it uses the public key of the server and the secret key associated with the effective uid of the calling process. .pp the function .br key_encryptsession () is the inverse of .br key_decryptsession (). it encrypts the des keys with the public key of the server and the secret key associated with the effective uid of the calling process. .pp the function .br key_gendes () is used to ask the keyserver for a secure conversation key. .pp the function .br key_setsecret () is used to set the key for the effective uid of the calling process. .pp the function .br key_secretkey_is_set () can be used to determine whether a key has been set for the effective uid of the calling process. .sh return value these functions return 1 on success and 0 on failure. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br key_decryptsession (), .br key_encryptsession (), .br key_gendes (), .br key_setsecret (), .br key_secretkey_is_set () t} thread safety mt-safe .te .hy .ad .sp 1 .sh notes note that we talk about two types of encryption here. one is asymmetric using a public and secret key. the other is symmetric, the 64-bit des. .pp these routines were part of the linux/doors-project, abandoned by now. .sh see also .br crypt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strerror.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)fflush.3 5.4 (berkeley) 6/29/91 .\" .\" converted for linux, mon nov 29 15:22:01 1993, faith@cs.unc.edu .\" .\" modified 2000-07-22 by nicolás lichtmaier .\" modified 2001-10-16 by john levon .\" .th fflush 3 2021-08-27 "gnu" "linux programmer's manual" .sh name fflush \- flush a stream .sh synopsis .nf .b #include .pp .bi "int fflush(file *" stream ); .fi .sh description for output streams, .br fflush () forces a write of all user-space buffered data for the given output or update .i stream via the stream's underlying write function. .pp for input streams associated with seekable files (e.g., disk files, but not pipes or terminals), .br fflush () discards any buffered data that has been fetched from the underlying file, but has not been consumed by the application. .pp the open status of the stream is unaffected. .pp if the .i stream argument is null, .br fflush () flushes .i all open output streams. .\" mtk: posix specifies that only output streams are flushed for this case. .\" also verified for glibc by experiment. .pp for a nonlocking counterpart, see .br unlocked_stdio (3). .sh return value upon successful completion 0 is returned. otherwise, .b eof is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i stream is not an open stream, or is not open for writing. .pp the function .br fflush () may also fail and set .i errno for any of the errors specified for .br write (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fflush () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c89, c99, posix.1-2001, posix.1-2008. .pp posix.1-2001 did not specify the behavior for flushing of input streams, but the behavior is specified in posix.1-2008. .sh notes note that .br fflush () flushes only the user-space buffers provided by the c library. to ensure that the data is physically stored on disk the kernel buffers must be flushed too, for example, with .br sync (2) or .br fsync (2). .sh see also .br fsync (2), .br sync (2), .br write (2), .br fclose (3), .br fileno (3), .br fopen (3), .br fpurge (3), .br setbuf (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tzset.3 .so man3/xdr.3 .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" written by marcela maslanova .\" and copyright 2013, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getunwind 2 2021-03-22 linux "linux programmer's manual" .sh name getunwind \- copy the unwind data to caller's buffer .sh synopsis .nf .b #include .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(sys_getunwind, void " *buf ", size_t " buf_size ); .fi .pp .ir note : glibc provides no wrapper for .br getunwind (), necessitating the use of .br syscall (2). .sh description .i note: this system call is obsolete. .pp the ia-64-specific .br getunwind () system call copies the kernel's call frame unwind data into the buffer pointed to by .i buf and returns the size of the unwind data; this data describes the gate page (kernel code that is mapped into user space). .pp the size of the buffer .i buf is specified in .ir buf_size . the data is copied only if .i buf_size is greater than or equal to the size of the unwind data and .i buf is not null; otherwise, no data is copied, and the call succeeds, returning the size that would be needed to store the unwind data. .pp the first part of the unwind data contains an unwind table. the rest contains the associated unwind information, in no particular order. the unwind table contains entries of the following form: .pp .in +4n .ex u64 start; (64\-bit address of start of function) u64 end; (64\-bit address of end of function) u64 info; (buf\-relative offset to unwind info) .ee .in .pp an entry whose .i start value is zero indicates the end of the table. for more information about the format, see the .i ia-64 software conventions and runtime architecture manual. .sh return value on success, .br getunwind () returns the size of the unwind data. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .br getunwind () fails with the error .b efault if the unwind info can't be stored in the space specified by .ir buf . .sh versions this system call is available since linux 2.4. .sh conforming to this system call is linux-specific, and is available only on the ia-64 architecture. .sh notes this system call has been deprecated. the modern way to obtain the kernel's unwind data is via the .br vdso (7). .sh see also .br getauxval (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1990, 1991 regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)stdio.3 6.5 (berkeley) 5/6/91 .\" .\" converted for linux, mon nov 29 16:07:22 1993, faith@cs.unc.edu .\" modified, 2001-12-26, aeb .\" .th stdio 3 2021-03-22 "" "linux programmer's manual" .sh name stdio \- standard input/output library functions .sh synopsis .nf .b #include .pp .bi "file *" stdin ; .bi "file *" stdout ; .bi "file *" stderr ; .fi .sh description the standard i/o library provides a simple and efficient buffered stream i/o interface. input and output is mapped into logical data streams and the physical i/o characteristics are concealed. the functions and macros are listed below; more information is available from the individual man pages. .pp a stream is associated with an external file (which may be a physical device) by .i opening a file, which may involve creating a new file. creating an existing file causes its former contents to be discarded. if a file can support positioning requests (such as a disk file, as opposed to a terminal), then a .i file position indicator associated with the stream is positioned at the start of the file (byte zero), unless the file is opened with append mode. if append mode is used, it is unspecified whether the position indicator will be placed at the start or the end of the file. the position indicator is maintained by subsequent reads, writes, and positioning requests. all input occurs as if the characters were read by successive calls to the .br fgetc (3) function; all output takes place as if all characters were written by successive calls to the .br fputc (3) function. .pp a file is disassociated from a stream by .i closing the file. output streams are flushed (any unwritten buffer contents are transferred to the host environment) before the stream is disassociated from the file. the value of a pointer to a .i file object is indeterminate after a file is closed (garbage). .pp a file may be subsequently reopened, by the same or another program execution, and its contents reclaimed or modified (if it can be repositioned at the start). if the main function returns to its original caller, or the .br exit (3) function is called, all open files are closed (hence all output streams are flushed) before program termination. other methods of program termination, such as .br abort (3) do not bother about closing files properly. .pp at program startup, three text streams are predefined and need not be opened explicitly: .i standard input (for reading conventional input), .i standard output (for writing conventional output), and .i standard error (for writing diagnostic output). these streams are abbreviated .ir stdin , .ir stdout , and .ir stderr . when opened, the standard error stream is not fully buffered; the standard input and output streams are fully buffered if and only if the streams do not refer to an interactive device. .pp output streams that refer to terminal devices are always line buffered by default; pending output to such streams is written automatically whenever an input stream that refers to a terminal device is read. in cases where a large amount of computation is done after printing part of a line on an output terminal, it is necessary to .br fflush (3) the standard output before going off and computing so that the output will appear. .pp the .i stdio library is a part of the library .b libc and routines are automatically loaded as needed by .br cc (1). the synopsis sections of the following manual pages indicate which include files are to be used, what the compiler declaration for the function looks like and which external variables are of interest. .pp the following are defined as macros; these names may not be reused without first removing their current definitions with .br #undef : .br bufsiz , .br eof , .br filename_max , .br fopen_max , .br l_cuserid , .br l_ctermid , .br l_tmpnam , .br null , .br seek_end , .br seek_set , .br seek_cur , .br tmp_max , .br clearerr , .br feof , .br ferror , .br fileno , .\" not on linux: .br fropen , .\" not on linux: .br fwopen , .br getc , .br getchar , .br putc , .br putchar , .br stderr , .br stdin , .br stdout . function versions of the macro functions .br feof , .br ferror , .br clearerr , .br fileno , .br getc , .br getchar , .br putc , and .b putchar exist and will be used if the macros definitions are explicitly removed. .ss list of functions .nh .ad l .ts ; lb lbx l l. function description _ \fbclearerr\fp(3) t{ check and reset stream status t} \fbfclose\fp(3) t{ close a stream t} \fbfdopen\fp(3) t{ stream open functions t} \fbfeof\fp(3) t{ check and reset stream status t} \fbferror\fp(3) t{ check and reset stream status t} \fbfflush\fp(3) t{ flush a stream t} \fbfgetc\fp(3) t{ get next character or word from input stream t} \fbfgetpos\fp(3) t{ reposition a stream t} \fbfgets\fp(3) t{ get a line from a stream t} \fbfileno\fp(3) t{ return the integer descriptor of the argument stream t} \fbfopen\fp(3) t{ stream open functions t} \fbfprintf\fp(3) t{ formatted output conversion t} \fbfpurge\fp(3) t{ flush a stream t} \fbfputc\fp(3) t{ output a character or word to a stream t} \fbfputs\fp(3) t{ output a line to a stream t} \fbfread\fp(3) t{ binary stream input/output t} \fbfreopen\fp(3) t{ stream open functions t} \fbfscanf\fp(3) t{ input format conversion t} \fbfseek\fp(3) t{ reposition a stream t} \fbfsetpos\fp(3) t{ reposition a stream t} \fbftell\fp(3) t{ reposition a stream t} \fbfwrite\fp(3) t{ binary stream input/output t} \fbgetc\fp(3) t{ get next character or word from input stream t} \fbgetchar\fp(3) t{ get next character or word from input stream t} \fbgets\fp(3) t{ get a line from a stream t} \fbgetw\fp(3) t{ get next character or word from input stream t} \fbmktemp\fp(3) t{ make temporary filename (unique) t} \fbperror\fp(3) t{ system error messages t} \fbprintf\fp(3) t{ formatted output conversion t} \fbputc\fp(3) t{ output a character or word to a stream t} \fbputchar\fp(3) t{ output a character or word to a stream t} \fbputs\fp(3) t{ output a line to a stream t} \fbputw\fp(3) t{ output a character or word to a stream t} \fbremove\fp(3) t{ remove directory entry t} \fbrewind\fp(3) t{ reposition a stream t} \fbscanf\fp(3) t{ input format conversion t} \fbsetbuf\fp(3) t{ stream buffering operations t} \fbsetbuffer\fp(3) t{ stream buffering operations t} \fbsetlinebuf\fp(3) t{ stream buffering operations t} \fbsetvbuf\fp(3) t{ stream buffering operations t} \fbsprintf\fp(3) t{ formatted output conversion t} \fbsscanf\fp(3) t{ input format conversion t} \fbstrerror\fp(3) t{ system error messages t} \fbsys_errlist\fp(3) t{ system error messages t} \fbsys_nerr\fp(3) t{ system error messages t} \fbtempnam\fp(3) t{ temporary file routines t} \fbtmpfile\fp(3) t{ temporary file routines t} \fbtmpnam\fp(3) t{ temporary file routines t} \fbungetc\fp(3) t{ un-get character from input stream t} \fbvfprintf\fp(3) t{ formatted output conversion t} \fbvfscanf\fp(3) t{ input format conversion t} \fbvprintf\fp(3) t{ formatted output conversion t} \fbvscanf\fp(3) t{ input format conversion t} \fbvsprintf\fp(3) t{ formatted output conversion t} \fbvsscanf\fp(3) t{ input format conversion t} .te .ad .hy .sh conforming to the .i stdio library conforms to c89. .sh see also .br close (2), .br open (2), .br read (2), .br write (2), .br stdout (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005, 2008, michael kerrisk .\" (a few fragments remain from an earlier (1992) version by .\" drew eckhardt .) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-23 by rik faith .\" modified 1996-10-22 by eric s. raymond .\" modified 2004-06-17 by michael kerrisk .\" modified 2005, mtk: added an example program .\" modified 2008-01-09, mtk: rewrote description; minor additions .\" to example text. .\" 2008-10-10, mtk: add description of pipe2() .\" .th pipe 2 2021-03-22 "linux" "linux programmer's manual" .sh name pipe, pipe2 \- create pipe .sh synopsis .nf .b #include .pp .bi "int pipe(int " pipefd [2]); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .br "#include " " /* definition of " o_* " constants */" .b #include .pp .bi "int pipe2(int " pipefd "[2], int " flags ); .pp /* on alpha, ia-64, mips, superh, and sparc/sparc64, pipe() has the following prototype; see notes */ .pp .b #include .pp .b struct fd_pair { .b " long fd[2];" .b "};" .b struct fd_pair pipe(void); .fi .sh description .br pipe () creates a pipe, a unidirectional data channel that can be used for interprocess communication. the array .ir pipefd is used to return two file descriptors referring to the ends of the pipe. .ir pipefd[0] refers to the read end of the pipe. .ir pipefd[1] refers to the write end of the pipe. data written to the write end of the pipe is buffered by the kernel until it is read from the read end of the pipe. for further details, see .br pipe (7). .pp if .ir flags is 0, then .br pipe2 () is the same as .br pipe (). the following values can be bitwise ored in .ir flags to obtain different behavior: .tp .b o_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the two new file descriptors. see the description of the same flag in .br open (2) for reasons why this may be useful. .tp .br o_direct " (since linux 3.4)" .\" commit 9883035ae7edef3ec62ad215611cb8e17d6a1a5d create a pipe that performs i/o in "packet" mode. each .br write (2) to the pipe is dealt with as a separate packet, and .br read (2)s from the pipe will read one packet at a time. note the following points: .rs .ip * 3 writes of greater than .br pipe_buf bytes (see .br pipe (7)) will be split into multiple packets. the constant .br pipe_buf is defined in .ir . .ip * if a .br read (2) specifies a buffer size that is smaller than the next packet, then the requested number of bytes are read, and the excess bytes in the packet are discarded. specifying a buffer size of .br pipe_buf will be sufficient to read the largest possible packets (see the previous point). .ip * zero-length packets are not supported. (a .br read (2) that specifies a buffer size of zero is a no-op, and returns 0.) .re .ip older kernels that do not support this flag will indicate this via an .b einval error. .ip since linux 4.5, .\" commit 0dbf5f20652108106cb822ad7662c786baaa03ff .\" fixme . but, it is not possible to specify o_direct when opening a fifo it is possible to change the .b o_direct setting of a pipe file descriptor using .br fcntl (2). .tp .b o_nonblock set the .br o_nonblock file status flag on the open file descriptions referred to by the new file descriptors. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .sh return value on success, zero is returned. on error, \-1 is returned, .i errno is set to indicate the error, and .i pipefd is left unchanged. .pp on linux (and other systems), .br pipe () does not modify .i pipefd on failure. a requirement standardizing this behavior was added in posix.1-2008 tc2. .\" http://austingroupbugs.net/view.php?id=467 the linux-specific .br pipe2 () system call likewise does not modify .i pipefd on failure. .sh errors .tp .b efault .i pipefd is not valid. .tp .b einval .rb ( pipe2 ()) invalid value in .ir flags . .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enfile the user hard limit on memory that can be allocated for pipes has been reached and the caller is not privileged; see .br pipe (7). .sh versions .br pipe2 () was added to linux in version 2.6.27; glibc support is available starting with version 2.9. .sh conforming to .br pipe (): posix.1-2001, posix.1-2008. .pp .br pipe2 () is linux-specific. .sh notes .\" see http://math-atlas.sourceforge.net/devel/assembly/64.psabi.1.33.ps.z .\" for example, section 3.2.1 "registers and the stack frame". the system v abi on some architectures allows the use of more than one register for returning multiple values; several architectures (namely, alpha, ia-64, mips, superh, and sparc/sparc64) (ab)use this feature in order to implement the .br pipe () system call in a functional manner: the call doesn't take any arguments and returns a pair of file descriptors as the return value on success. the glibc .br pipe () wrapper function transparently deals with this. see .br syscall (2) for information regarding registers used for storing second file descriptor. .sh examples .\" fork.2 refers to this example program. the following program creates a pipe, and then .br fork (2)s to create a child process; the child inherits a duplicate set of file descriptors that refer to the same pipe. after the .br fork (2), each process closes the file descriptors that it doesn't need for the pipe (see .br pipe (7)). the parent then writes the string contained in the program's command-line argument to the pipe, and the child reads this string a byte at a time from the pipe and echoes it on standard output. .ss program source .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { int pipefd[2]; pid_t cpid; char buf; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } if (pipe(pipefd) == \-1) { perror("pipe"); exit(exit_failure); } cpid = fork(); if (cpid == \-1) { perror("fork"); exit(exit_failure); } if (cpid == 0) { /* child reads from pipe */ close(pipefd[1]); /* close unused write end */ while (read(pipefd[0], &buf, 1) > 0) write(stdout_fileno, &buf, 1); write(stdout_fileno, "\en", 1); close(pipefd[0]); _exit(exit_success); } else { /* parent writes argv[1] to pipe */ close(pipefd[0]); /* close unused read end */ write(pipefd[1], argv[1], strlen(argv[1])); close(pipefd[1]); /* reader will see eof */ wait(null); /* wait for child */ exit(exit_success); } } .ee .sh see also .br fork (2), .br read (2), .br socketpair (2), .br splice (2), .br tee (2), .br vmsplice (2), .br write (2), .br popen (3), .br pipe (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xdr.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 11:01:58 1993 by rik faith (faith@cs.unc.edu) .\" modified 2001-11-13, aeb .\" modified 2004-12-01 mtk and martin schulze .\" .th tzset 3 2021-03-22 "" "linux programmer's manual" .sh name tzset, tzname, timezone, daylight \- initialize time conversion information .sh synopsis .nf .b #include .pp .b void tzset(void); .pp .bi "extern char *" tzname [2]; .bi "extern long " timezone ; .bi "extern int " daylight ; .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br tzset (): .nf _posix_c_source .fi .pp .ir tzname : .nf _posix_c_source .fi .pp .ir timezone , .ir daylight : .nf _xopen_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source .fi .sh description the .br tzset () function initializes the \fitzname\fp variable from the .b tz environment variable. this function is automatically called by the other time conversion functions that depend on the timezone. in a system-v-like environment, it will also set the variables \fitimezone\fp (seconds west of utc) and \fidaylight\fp (to 0 if this timezone does not have any daylight saving time rules, or to nonzero if there is a time, past, present, or future when daylight saving time applies). .pp if the .b tz variable does not appear in the environment, the system timezone is used. the system timezone is configured by copying, or linking, a file in the .br tzfile (5) format to .ir /etc/localtime . a timezone database of these files may be located in the system timezone directory (see the \fbfiles\fp section below). .pp if the .b tz variable does appear in the environment, but its value is empty, or its value cannot be interpreted using any of the formats specified below, then coordinated universal time (utc) is used. .pp the value of .b tz can be one of two formats. the first format is a string of characters that directly represent the timezone to be used: .pp .in +4n .ex .ir "std offset" [ dst [ offset ][, start [ /time ], end [ /time ]]] .ee .in .pp there are no spaces in the specification. the \fistd\fp string specifies an abbreviation for the timezone and must be three or more alphabetic characters. when enclosed between the less-than (<) and greater-than (>) signs, the characters set is expanded to include the plus (+) sign, the minus (-) sign, and digits. the \fioffset\fp string immediately follows \fistd\fp and specifies the time value to be added to the local time to get coordinated universal time (utc). the \fioffset\fp is positive if the local timezone is west of the prime meridian and negative if it is east. the hour must be between 0 and 24, and the minutes and seconds 00 and 59: .pp .in +4n .ex .ri [ + | \- ] hh [ :mm [ :ss ]] .ee .in .pp the \fidst\fp string and \fioffset\fp specify the name and offset for the corresponding daylight saving timezone. if the offset is omitted, it defaults to one hour ahead of standard time. .pp the \fistart\fp field specifies when daylight saving time goes into effect and the \fiend\fp field specifies when the change is made back to standard time. these fields may have the following formats: .tp j\fin\fp this specifies the julian day with \fin\fp between 1 and 365. leap days are not counted. in this format, february 29 can't be represented; february 28 is day 59, and march 1 is always day 60. .tp .i n this specifies the zero-based julian day with \fin\fp between 0 and 365. february 29 is counted in leap years. .tp m\fim\fp.\fiw\fp.\fid\fp this specifies day \fid\fp (0 <= \fid\fp <= 6) of week \fiw\fp (1 <= \fiw\fp <= 5) of month \fim\fp (1 <= \fim\fp <= 12). week 1 is the first week in which day \fid\fp occurs and week 5 is the last week in which day \fid\fp occurs. day 0 is a sunday. .pp the \fitime\fp fields specify when, in the local time currently in effect, the change to the other time occurs. if omitted, the default is 02:00:00. .pp here is an example for new zealand, where the standard time (nzst) is 12 hours ahead of utc, and daylight saving time (nzdt), 13 hours ahead of utc, runs from the first sunday in october to the third sunday in march, and the changeovers happen at the default time of 02:00:00: .pp .in +4n .ex tz="nzst\-12:00:00nzdt\-13:00:00,m10.1.0,m3.3.0" .ee .in .pp the second format specifies that the timezone information should be read from a file: .pp .in +4n .ex :[filespec] .ee .in .pp if the file specification \fifilespec\fp is omitted, or its value cannot be interpreted, then coordinated universal time (utc) is used. if \fifilespec\fp is given, it specifies another .br tzfile (5)-format file to read the timezone information from. if \fifilespec\fp does not begin with a \(aq/\(aq, the file specification is relative to the system timezone directory. if the colon is omitted each of the above \fbtz\fp formats will be tried. .pp here's an example, once more for new zealand: .pp .in +4n .ex tz=":pacific/auckland" .ee .in .sh environment .tp .b tz if this variable is set its value takes precedence over the system configured timezone. .tp .b tzdir if this variable is set its value takes precedence over the system configured timezone database directory path. .sh files .tp .i /etc/localtime the system timezone file. .tp .i /usr/share/zoneinfo/ the system timezone database directory. .tp .i /usr/share/zoneinfo/posixrules when a tz string includes a dst timezone without anything following it, then this file is used for the start/end rules. it is in the .br tzfile (5) format. by default, the zoneinfo makefile hard links it to the .ir america/new_york " tzfile." .pp above are the current standard file locations, but they are configurable when glibc is compiled. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tzset () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes 4.3bsd had a function .bi "char *timezone(" zone ", " dst ) that returned the name of the timezone corresponding to its first argument (minutes west of utc). if the second argument was 0, the standard name was used, otherwise the daylight saving time version. .sh see also .br date (1), .br gettimeofday (2), .br time (2), .br ctime (3), .br getenv (3), .br tzfile (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006, 2008 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th core 5 2021-03-22 "linux" "linux programmer's manual" .sh name core \- core dump file .sh description the default action of certain signals is to cause a process to terminate and produce a .ir "core dump file" , a file containing an image of the process's memory at the time of termination. this image can be used in a debugger (e.g., .br gdb (1)) to inspect the state of the program at the time that it terminated. a list of the signals which cause a process to dump core can be found in .br signal (7). .pp a process can set its soft .b rlimit_core resource limit to place an upper limit on the size of the core dump file that will be produced if it receives a "core dump" signal; see .br getrlimit (2) for details. .pp there are various circumstances in which a core dump file is not produced: .ip * 3 the process does not have permission to write the core file. (by default, the core file is called .ir core or .ir core.pid , where .i pid is the id of the process that dumped core, and is created in the current working directory. see below for details on naming.) writing the core file fails if the directory in which it is to be created is not writable, or if a file with the same name exists and is not writable or is not a regular file (e.g., it is a directory or a symbolic link). .ip * a (writable, regular) file with the same name as would be used for the core dump already exists, but there is more than one hard link to that file. .ip * the filesystem where the core dump file would be created is full; or has run out of inodes; or is mounted read-only; or the user has reached their quota for the filesystem. .ip * the directory in which the core dump file is to be created does not exist. .ip * the .b rlimit_core (core file size) or .b rlimit_fsize (file size) resource limits for the process are set to zero; see .br getrlimit (2) and the documentation of the shell's .i ulimit command .ri ( limit in .br csh (1)). .ip * the binary being executed by the process does not have read permission enabled. (this is a security measure to ensure that an executable whose contents are not readable does not produce a\(empossibly readable\(emcore dump containing an image of the executable.) .ip * the process is executing a set-user-id (set-group-id) program that is owned by a user (group) other than the real user (group) id of the process, or the process is executing a program that has file capabilities (see .br capabilities (7)). (however, see the description of the .br prctl (2) .b pr_set_dumpable operation, and the description of the .i /proc/sys/fs/suid_dumpable .\" fixme . perhaps relocate discussion of /proc/sys/fs/suid_dumpable .\" and pr_set_dumpable to this page? file in .br proc (5).) .ip * .i /proc/sys/kernel/core_pattern is empty and .i /proc/sys/kernel/core_uses_pid contains the value 0. (these files are described below.) note that if .i /proc/sys/kernel/core_pattern is empty and .i /proc/sys/kernel/core_uses_pid contains the value 1, core dump files will have names of the form .ir .pid , and such files are hidden unless one uses the .br ls (1) .i \-a option. .ip * (since linux 3.7) .\" commit 046d662f481830e652ac34cd112249adde16452a the kernel was configured without the .br config_coredump option. .pp in addition, a core dump may exclude part of the address space of the process if the .br madvise (2) .b madv_dontdump flag was employed. .pp on systems that employ .br systemd (1) as the .i init framework, core dumps may instead be placed in a location determined by .br systemd (1). see below for further details. .\" .ss naming of core dump files by default, a core dump file is named .ir core , but the .i /proc/sys/kernel/core_pattern file (since linux 2.6 and 2.4.21) can be set to define a template that is used to name core dump files. the template can contain % specifiers which are substituted by the following values when a core file is created: .pp .rs 4 .pd 0 .tp 4 %% a single % character. .tp %c core file size soft resource limit of crashing process (since linux 2.6.24). .tp %d .\" added in git commit 12a2b4b2241e318b4f6df31228e4272d2c2968a1 dump mode\(emsame as value returned by .br prctl (2) .b pr_get_dumpable (since linux 3.7). .tp %e the process or thread's .i comm value, which typically is the same as the executable filename (without path prefix, and truncated to a maximum of 15 characters), but may have been modified to be something different; see the discussion of .i /proc/[pid]/comm and .i /proc/[pid]/task/[tid]/comm in .br proc (5). .tp %e pathname of executable, with slashes (\(aq/\(aq) replaced by exclamation marks (\(aq!\(aq) (since linux 3.0). .tp %g numeric real gid of dumped process. .tp %h hostname (same as \finodename\fp returned by \fbuname\fp(2)). .tp %i tid of thread that triggered core dump, as seen in the pid namespace in which the thread resides .\" commit b03023ecbdb76c1dec86b41ed80b123c22783220 (since linux 3.18). .tp %i tid of thread that triggered core dump, as seen in the initial pid namespace .\" commit b03023ecbdb76c1dec86b41ed80b123c22783220 (since linux 3.18). .tp %p pid of dumped process, as seen in the pid namespace in which the process resides. .tp %p .\" added in git commit 65aafb1e7484b7434a0c1d4c593191ebe5776a2f pid of dumped process, as seen in the initial pid namespace (since linux 3.12). .tp %s number of signal causing dump. .tp %t time of dump, expressed as seconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). .tp %u numeric real uid of dumped process. .pd .re .pp a single % at the end of the template is dropped from the core filename, as is the combination of a % followed by any character other than those listed above. all other characters in the template become a literal part of the core filename. the template may include \(aq/\(aq characters, which are interpreted as delimiters for directory names. the maximum size of the resulting core filename is 128 bytes (64 bytes in kernels before 2.6.19). the default value in this file is "core". for backward compatibility, if .i /proc/sys/kernel/core_pattern does not include .i %p and .i /proc/sys/kernel/core_uses_pid (see below) is nonzero, then .pid will be appended to the core filename. .pp paths are interpreted according to the settings that are active for the crashing process. that means the crashing process's mount namespace (see .br mount_namespaces (7)), its current working directory (found via .br getcwd (2)), and its root directory (see .br chroot (2)). .pp since version 2.4, linux has also provided a more primitive method of controlling the name of the core dump file. if the .i /proc/sys/kernel/core_uses_pid file contains the value 0, then a core dump file is simply named .ir core . if this file contains a nonzero value, then the core dump file includes the process id in a name of the form .ir core.pid . .pp since linux 3.6, .\" 9520628e8ceb69fa9a4aee6b57f22675d9e1b709 if .i /proc/sys/fs/suid_dumpable is set to 2 ("suidsafe"), the pattern must be either an absolute pathname (starting with a leading \(aq/\(aq character) or a pipe, as defined below. .ss piping core dumps to a program since kernel 2.6.19, linux supports an alternate syntax for the .i /proc/sys/kernel/core_pattern file. if the first character of this file is a pipe symbol (\fb|\fp), then the remainder of the line is interpreted as the command-line for a user-space program (or script) that is to be executed. .pp since kernel 5.3.0, .\" commit 315c69261dd3fa12dbc830d4fa00d1fad98d3b03 the pipe template is split on spaces into an argument list .i before the template parameters are expanded. in earlier kernels, the template parameters are expanded first and the resulting string is split on spaces into an argument list. this means that in earlier kernels executable names added by the .i %e and .i %e template parameters could get split into multiple arguments. so the core dump handler needs to put the executable names as the last argument and ensure it joins all parts of the executable name using spaces. executable names with multiple spaces in them are not correctly represented in earlier kernels, meaning that the core dump handler needs to use mechanisms to find the executable name. .pp instead of being written to a file, the core dump is given as standard input to the program. note the following points: .ip * 3 the program must be specified using an absolute pathname (or a pathname relative to the root directory, \fi/\fp), and must immediately follow the '|' character. .ip * the command-line arguments can include any of the % specifiers listed above. for example, to pass the pid of the process that is being dumped, specify .i %p in an argument. .ip * the process created to run the program runs as user and group .ir root . .ip * running as .i root does not confer any exceptional security bypasses. namely, lsms (e.g., selinux) are still active and may prevent the handler from accessing details about the crashed process via .ir /proc/[pid] . .ip * the program pathname is interpreted with respect to the initial mount namespace as it is always executed there. it is not affected by the settings (e.g., root directory, mount namespace, current working directory) of the crashing process. .ip * the process runs in the initial namespaces (pid, mount, user, and so on) and not in the namespaces of the crashing process. one can utilize specifiers such as .i %p to find the right .i /proc/[pid] directory and probe/enter the crashing process's namespaces if needed. .ip * the process starts with its current working directory as the root directory. if desired, it is possible change to the working directory of the dumping process by employing the value provided by the .i %p specifier to change to the location of the dumping process via .ir /proc/[pid]/cwd . .ip * command-line arguments can be supplied to the program (since linux 2.6.24), delimited by white space (up to a total line length of 128 bytes). .ip * the .b rlimit_core limit is not enforced for core dumps that are piped to a program via this mechanism. .\" .ss /proc/sys/kernel/core_pipe_limit when collecting core dumps via a pipe to a user-space program, it can be useful for the collecting program to gather data about the crashing process from that process's .ir /proc/[pid] directory. in order to do this safely, the kernel must wait for the program collecting the core dump to exit, so as not to remove the crashing process's .ir /proc/[pid] files prematurely. this in turn creates the possibility that a misbehaving collecting program can block the reaping of a crashed process by simply never exiting. .pp since linux 2.6.32, .\" commit a293980c2e261bd5b0d2a77340dd04f684caff58 the .i /proc/sys/kernel/core_pipe_limit can be used to defend against this possibility. the value in this file defines how many concurrent crashing processes may be piped to user-space programs in parallel. if this value is exceeded, then those crashing processes above this value are noted in the kernel log and their core dumps are skipped. .pp a value of 0 in this file is special. it indicates that unlimited processes may be captured in parallel, but that no waiting will take place (i.e., the collecting program is not guaranteed access to .ir /proc/ ). the default value for this file is 0. .\" .ss controlling which mappings are written to the core dump since kernel 2.6.23, the linux-specific .ir /proc/[pid]/coredump_filter file can be used to control which memory segments are written to the core dump file in the event that a core dump is performed for the process with the corresponding process id. .pp the value in the file is a bit mask of memory mapping types (see .br mmap (2)). if a bit is set in the mask, then memory mappings of the corresponding type are dumped; otherwise they are not dumped. the bits in this file have the following meanings: .pp .pd 0 .rs 4 .tp bit 0 dump anonymous private mappings. .tp bit 1 dump anonymous shared mappings. .tp bit 2 dump file-backed private mappings. .tp bit 3 dump file-backed shared mappings. .\" file-backed shared mappings of course also update the underlying .\" mapped file. .tp bit 4 (since linux 2.6.24) dump elf headers. .tp bit 5 (since linux 2.6.28) dump private huge pages. .tp bit 6 (since linux 2.6.28) dump shared huge pages. .tp bit 7 (since linux 4.4) .\" commit ab27a8d04b32b6ee8c30c14c4afd1058e8addc82 dump private dax pages. .tp bit 8 (since linux 4.4) .\" commit ab27a8d04b32b6ee8c30c14c4afd1058e8addc82 dump shared dax pages. .re .pd .pp by default, the following bits are set: 0, 1, 4 (if the .b config_core_dump_default_elf_headers kernel configuration option is enabled), and 5. this default can be modified at boot time using the .i coredump_filter boot option. .pp the value of this file is displayed in hexadecimal. (the default value is thus displayed as 33.) .pp memory-mapped i/o pages such as frame buffer are never dumped, and virtual dso .rb ( vdso (7)) pages are always dumped, regardless of the .i coredump_filter value. .pp a child process created via .br fork (2) inherits its parent's .i coredump_filter value; the .i coredump_filter value is preserved across an .br execve (2). .pp it can be useful to set .i coredump_filter in the parent shell before running a program, for example: .pp .in +4n .ex .rb "$" " echo 0x7 > /proc/self/coredump_filter" .rb "$" " ./some_program" .ee .in .pp this file is provided only if the kernel was built with the .b config_elf_core configuration option. .\" .ss core dumps and systemd on systems using the .br systemd (1) .i init framework, core dumps may be placed in a location determined by .br systemd (1). to do this, .br systemd (1) employs the .i core_pattern feature that allows piping core dumps to a program. one can verify this by checking whether core dumps are being piped to the .br systemd\-coredump (8) program: .pp .in +4n .ex $ \fbcat /proc/sys/kernel/core_pattern\fp |/usr/lib/systemd/systemd\-coredump %p %u %g %s %t %c %e .ee .in .pp in this case, core dumps will be placed in the location configured for .br systemd\-coredump (8), typically as .br lz4 (1) compressed files in the directory .ir /var/lib/systemd/coredump/ . one can list the core dumps that have been recorded by .br systemd\-coredump (8) using .br coredumpctl (1): .pp .ex $ \fbcoredumpctl list | tail \-5\fp wed 2017\-10\-11 22:25:30 cest 2748 1000 1000 3 present /usr/bin/sleep thu 2017\-10\-12 06:29:10 cest 2716 1000 1000 3 present /usr/bin/sleep thu 2017\-10\-12 06:30:50 cest 2767 1000 1000 3 present /usr/bin/sleep thu 2017\-10\-12 06:37:40 cest 2918 1000 1000 3 present /usr/bin/cat thu 2017\-10\-12 08:13:07 cest 2955 1000 1000 3 present /usr/bin/cat .ee .pp the information shown for each core dump includes the date and time of the dump, the pid, uid, and gid of the dumping process, the signal number that caused the core dump, and the pathname of the executable that was being run by the dumped process. various options to .br coredumpctl (1) allow a specified coredump file to be pulled from the .br systemd (1) location into a specified file. for example, to extract the core dump for pid 2955 shown above to a file named .ir core in the current directory, one could use: .pp .in +4n .ex $ \fbcoredumpctl dump 2955 \-o core\fp .ee .in .pp for more extensive details, see the .br coredumpctl (1) manual page. .pp to (persistently) disable the .br systemd (1) mechanism that archives core dumps, restoring to something more like traditional linux behavior, one can set an override for the .br systemd (1) mechanism, using something like: .pp .in +4n .ex # \fbecho "kernel.core_pattern=core.%p" > \e\fp \fb /etc/sysctl.d/50\-coredump.conf\fp # \fb/lib/systemd/systemd\-sysctl\fp .ee .in .pp it is also possible to temporarily (i.e., until the next reboot) change the .i core_pattern setting using a command such as the following (which causes the names of core dump files to include the executable name as well as the number of the signal which triggered the core dump): .pp .in +4n .ex # \fbsysctl \-w kernel.core_pattern="%e\-%s.core"\fp .ee .in .\" .sh notes the .br gdb (1) .i gcore command can be used to obtain a core dump of a running process. .pp in linux versions up to and including 2.6.27, .\" changed with commit 6409324b385f3f63a03645b4422e3be67348d922 if a multithreaded process (or, more precisely, a process that shares its memory with another process by being created with the .b clone_vm flag of .br clone (2)) dumps core, then the process id is always appended to the core filename, unless the process id was already included elsewhere in the filename via a .i %p specification in .ir /proc/sys/kernel/core_pattern . (this is primarily useful when employing the obsolete linuxthreads implementation, where each thread of a process has a different pid.) .\" always including the pid in the name of the core file made .\" sense for linuxthreads, where each thread had a unique pid, .\" but doesn't seem to serve any purpose with nptl, where all the .\" threads in a process share the same pid (as posix.1 requires). .\" probably the behavior is maintained so that applications using .\" linuxthreads continue appending the pid (the kernel has no easy .\" way of telling which threading implementation the user-space .\" application is using). -- mtk, april 2006 .sh examples the program below can be used to demonstrate the use of the pipe syntax in the .i /proc/sys/kernel/core_pattern file. the following shell session demonstrates the use of this program (compiled to create an executable named .ir core_pattern_pipe_test ): .pp .in +4n .ex .rb "$" " cc \-o core_pattern_pipe_test core_pattern_pipe_test.c" .rb "$" " su" password: .rb "#" " echo \(dq|$pwd/core_pattern_pipe_test %p \ uid=%u gid=%g sig=%s\(dq > \e" .b " /proc/sys/kernel/core_pattern" .rb "#" " exit" .rb "$" " sleep 100" .br "\(ha\e" " # type control\-backslash" quit (core dumped) .rb "$" " cat core.info" argc=5 argc[0]= argc[1]=<20575> argc[2]= argc[3]= argc[4]= total bytes in core dump: 282624 .ee .in .ss program source \& .ex /* core_pattern_pipe_test.c */ #define _gnu_source #include #include #include #include #include #include #define buf_size 1024 int main(int argc, char *argv[]) { ssize_t nread, tot; char buf[buf_size]; file *fp; char cwd[path_max]; /* change our current working directory to that of the crashing process. */ snprintf(cwd, path_max, "/proc/%s/cwd", argv[1]); chdir(cwd); /* write output to file "core.info" in that directory. */ fp = fopen("core.info", "w+"); if (fp == null) exit(exit_failure); /* display command\-line arguments given to core_pattern pipe program. */ fprintf(fp, "argc=%d\en", argc); for (int j = 0; j < argc; j++) fprintf(fp, "argc[%d]=<%s>\en", j, argv[j]); /* count bytes in standard input (the core dump). */ tot = 0; while ((nread = read(stdin_fileno, buf, buf_size)) > 0) tot += nread; fprintf(fp, "total bytes in core dump: %zd\en", tot); fclose(fp); exit(exit_success); } .ee .sh see also .br bash (1), .br coredumpctl (1), .br gdb (1), .br getrlimit (2), .br mmap (2), .br prctl (2), .br sigaction (2), .br elf (5), .br proc (5), .br pthreads (7), .br signal (7), .br systemd\-coredump (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/puts.3 .so man3/trunc.3 .\" copyright (c) 1995 james r. van zandt .\" sat feb 18 09:11:07 est 1995 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified, sun feb 26 15:08:05 1995, faith@cs.unc.edu .\" 2007-12-17, samuel thibault : .\" document the vt_gethifontmask ioctl .\" " .th vcs 4 2020-11-01 "linux" "linux programmer's manual" .sh name vcs, vcsa \- virtual console memory .sh description .i /dev/vcs0 is a character device with major number 7 and minor number 0, usually with mode 0644 and ownership root:tty. it refers to the memory of the currently displayed virtual console terminal. .pp .i /dev/vcs[1\-63] are character devices for virtual console terminals, they have major number 7 and minor number 1 to 63, usually mode 0644 and ownership root:tty. .ir /dev/vcsa[0\-63] are the same, but using .ir "unsigned short" s (in host byte order) that include attributes, and prefixed with four bytes giving the screen dimensions and cursor position: .ir lines , .ir columns , .ir x , .ir y . .ri ( x = .i y = 0 at the top left corner of the screen.) .pp when a 512-character font is loaded, the 9th bit position can be fetched by applying the .br ioctl (2) .b vt_gethifontmask operation (available in linux kernels 2.6.18 and above) on .ir /dev/tty[1\-63] ; the value is returned in the .i "unsigned short" pointed to by the third .br ioctl (2) argument. .pp these devices replace the screendump .br ioctl (2) operations of .br ioctl_console (2), so the system administrator can control access using filesystem permissions. .pp the devices for the first eight virtual consoles may be created by: .pp .in +4n .ex for x in 0 1 2 3 4 5 6 7 8; do mknod \-m 644 /dev/vcs$x c 7 $x; mknod \-m 644 /dev/vcsa$x c 7 $[$x+128]; done chown root:tty /dev/vcs* .ee .in .pp no .br ioctl (2) requests are supported. .sh files .i /dev/vcs[0\-63] .br .i /dev/vcsa[0\-63] .\" .sh author .\" andries brouwer .sh versions introduced with version 1.1.92 of the linux kernel. .sh examples you may do a screendump on vt3 by switching to vt1 and typing .pp .in +4n .ex cat /dev/vcs3 >foo .ee .in .pp note that the output does not contain newline characters, so some processing may be required, like in .pp .in +4n .ex fold \-w 81 /dev/vcs3 | lpr .ee .in .pp or (horrors) .pp .in +4n .ex setterm \-dump 3 \-file /proc/self/fd/1 .ee .in .pp the .i /dev/vcsa0 device is used for braille support. .pp this program displays the character and screen attributes under the cursor of the second virtual console, then changes the background color there: .pp .ex #include #include #include #include #include #include int main(void) { int fd; char *device = "/dev/vcsa2"; char *console = "/dev/tty2"; struct {unsigned char lines, cols, x, y;} scrn; unsigned short s; unsigned short mask; unsigned char attrib; int ch; fd = open(console, o_rdwr); if (fd < 0) { perror(console); exit(exit_failure); } if (ioctl(fd, vt_gethifontmask, &mask) < 0) { perror("vt_gethifontmask"); exit(exit_failure); } (void) close(fd); fd = open(device, o_rdwr); if (fd < 0) { perror(device); exit(exit_failure); } (void) read(fd, &scrn, 4); (void) lseek(fd, 4 + 2*(scrn.y*scrn.cols + scrn.x), seek_set); (void) read(fd, &s, 2); ch = s & 0xff; if (s & mask) ch |= 0x100; attrib = ((s & \(timask) >> 8); printf("ch=%#03x attrib=%#02x\en", ch, attrib); s \(ha= 0x1000; (void) lseek(fd, \-2, seek_cur); (void) write(fd, &s, 2); exit(exit_success); } .ee .sh see also .br ioctl_console (2), .br tty (4), .br ttys (4), .br gpm (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getlogin.3 .\" copyright 2004 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th scalb 3 2021-03-22 "" "linux programmer's manual" .sh name scalb, scalbf, scalbl \- multiply floating-point number by integral power of radix (obsolete) .sh synopsis .nf .b #include .pp .bi "double scalb(double " x ", double " exp ); .bi "float scalbf(float " x ", float " exp ); .bi "long double scalbl(long double " x ", long double " exp ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br scalb (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br scalbf (), .br scalbl (): .nf _xopen_source >= 600 || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions multiply their first argument .i x by .b flt_radix (probably 2) to the power of .ir exp , that is: .pp .nf x * flt_radix ** exp .fi .pp the definition of .b flt_radix can be obtained by including .ir . .\" not in /usr/include but in a gcc lib .sh return value on success, these functions return .ir x * .b flt_radix ** .ir exp . .pp if .i x or .i exp is a nan, a nan is returned. .pp if .i x is positive infinity (negative infinity), and .i exp is not negative infinity, positive infinity (negative infinity) is returned. .pp if .i x is +0 (\-0), and .i exp is not positive infinity, +0 (\-0) is returned. .pp if .i x is zero, and .i exp is positive infinity, a domain error occurs, and a nan is returned. .pp if .i x is an infinity, and .i exp is negative infinity, a domain error occurs, and a nan is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with a sign the same as .ir x . .pp if the result underflows, a range error occurs, and the functions return zero, with a sign the same as .ir x . .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is 0, and \fiexp\fp is positive infinity, \ or \fix\fp is positive infinity and \fiexp\fp is negative infinity \ and the other argument is not a nan .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp range error, overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error, underflow .i errno is set to .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br scalb (), .br scalbf (), .br scalbl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br scalb () is specified in posix.1-2001, but marked obsolescent. posix.1-2008 removes the specification of .br scalb (), recommending the use of .br scalbln (3), .br scalblnf (3), or .br scalblnl (3) instead. the .br scalb () function is from 4.3bsd. .pp .br scalbf () and .br scalbl () are unstandardized; .br scalbf () is nevertheless present on several other systems .\" looking at header files: scalbf() is present on the .\" bsds, tru64, hp-ux 11, irix 6.5; scalbl() is on hp-ux 11 and tru64. .sh bugs before glibc 2.20, .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6804 these functions did not set .i errno for domain and range errors. .sh see also .br ldexp (3), .br scalbln (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/printf.3 .\" copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_getattr_default_np 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_getattr_default_np, pthread_setattr_default_np, \- get or set default thread-creation attributes .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_getattr_default_np(pthread_attr_t *" attr ); .bi "int pthread_setattr_default_np(const pthread_attr_t *" attr ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_setattr_default_np () function sets the default attributes used for creation of a new thread\(emthat is, the attributes that are used when .br pthread_create (3) is called with a second argument that is null. the default attributes are set using the attributes supplied in .ir *attr , a previously initialized thread attributes object. note the following details about the supplied attributes object: .ip * 3 the attribute settings in the object must be valid. .ip * the .ir "stack address" attribute must not be set in the object. .ip * setting the .ir "stack size" attribute to zero means leave the default stack size unchanged. .pp the .br pthread_getattr_default_np () function initializes the thread attributes object referred to by .i attr so that it contains the default attributes used for thread creation. .sh errors .tp .b einval .rb ( pthread_setattr_default_np ()) one of the attribute settings in .ir attr is invalid, or the stack address attribute is set in .ir attr . .tp .b enomem .\" can happen (but unlikely) while trying to allocate memory for cpuset .rb ( pthread_setattr_default_np ()) insufficient memory. .sh versions these functions are available in glibc since version 2.18. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_getattr_default_np (), .br pthread_setattr_default_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in their names. .sh examples the program below uses .br pthread_getattr_default_np () to fetch the default thread-creation attributes and then displays various settings from the returned thread attributes object. when running the program, we see the following output: .pp .in +4n .ex $ \fb./a.out\fp stack size: 8388608 guard size: 4096 scheduling policy: sched_other scheduling priority: 0 detach state: joinable inherit scheduler: inherit .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #define errexiten(en, msg) \e do { errno = en; perror(msg); \e exit(exit_failure); } while (0) static void display_pthread_attr(pthread_attr_t *attr) { int s; size_t stacksize; size_t guardsize; int policy; struct sched_param schedparam; int detachstate; int inheritsched; s = pthread_attr_getstacksize(attr, &stacksize); if (s != 0) errexiten(s, "pthread_attr_getstacksize"); printf("stack size: %zd\en", stacksize); s = pthread_attr_getguardsize(attr, &guardsize); if (s != 0) errexiten(s, "pthread_attr_getguardsize"); printf("guard size: %zd\en", guardsize); s = pthread_attr_getschedpolicy(attr, &policy); if (s != 0) errexiten(s, "pthread_attr_getschedpolicy"); printf("scheduling policy: %s\en", (policy == sched_fifo) ? "sched_fifo" : (policy == sched_rr) ? "sched_rr" : (policy == sched_other) ? "sched_other" : "[unknown]"); s = pthread_attr_getschedparam(attr, &schedparam); if (s != 0) errexiten(s, "pthread_attr_getschedparam"); printf("scheduling priority: %d\en", schedparam.sched_priority); s = pthread_attr_getdetachstate(attr, &detachstate); if (s != 0) errexiten(s, "pthread_attr_getdetachstate"); printf("detach state: %s\en", (detachstate == pthread_create_detached) ? "detached" : (detachstate == pthread_create_joinable) ? "joinable" : "???"); s = pthread_attr_getinheritsched(attr, &inheritsched); if (s != 0) errexiten(s, "pthread_attr_getinheritsched"); printf("inherit scheduler: %s\en", (inheritsched == pthread_inherit_sched) ? "inherit" : (inheritsched == pthread_explicit_sched) ? "explicit" : "???"); } int main(int argc, char *argv[]) { int s; pthread_attr_t attr; s = pthread_getattr_default_np(&attr); if (s != 0) errexiten(s, "pthread_getattr_default_np"); display_pthread_attr(&attr); exit(exit_success); } .ee .sh see also .ad l .nh .br pthread_attr_getaffinity_np (3), .br pthread_attr_getdetachstate (3), .br pthread_attr_getguardsize (3), .br pthread_attr_getinheritsched (3), .br pthread_attr_getschedparam (3), .br pthread_attr_getschedpolicy (3), .br pthread_attr_getscope (3), .br pthread_attr_getstack (3), .br pthread_attr_getstackaddr (3), .br pthread_attr_getstacksize (3), .br pthread_attr_init (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdin.3 .so man3/stdio_ext.3 .\" copyright 2009 lefteris dimitroulakis .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th armscii-8 7 2020-08-13 "linux" "linux programmer's manual" .sh name armscii-8 \- armenian character set encoded in octal, decimal, and hexadecimal .sh description the armenian standard code for information interchange, 8-bit coded character set. .ss armscii-8 characters the following table displays the characters in armscii-8 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 242 162 a2 և armenian small ligature ech yiwn 243 163 a3 ։ armenian full stop 244 164 a4 ) right parenthesis 245 165 a5 ( left parenthesis 246 166 a6 » right-pointing double angle quotation mark 247 167 a7 « left-pointing double angle quotation mark 250 168 a8 — em dash 251 169 a9 . full stop 252 170 aa ՝ armenian comma 253 171 ab , comma 254 172 ac - hyphen-minus 255 173 ad ֊ armenian hyphen 256 174 ae … horizontal ellipsis 257 175 af ՜ armenian exclamation mark 260 176 b0 ՛ armenian emphasis mark 261 177 b1 ՞ armenian question mark 262 178 b2 ա armenian capital letter ayb 263 179 b3 ա armenian small letter ayb 264 180 b4 բ armenian capital letter ben 265 181 b5 բ armenian small letter ben 266 182 b6 գ armenian capital letter gim 267 183 b7 գ armenian small letter gim 270 184 b8 դ armenian capital letter da 271 185 b9 դ armenian small letter da 272 186 ba ե armenian capital letter ech 273 187 bb ե armenian small letter ech 274 188 bc զ armenian capital letter za 275 189 bd զ armenian small letter za 276 190 be է armenian capital letter eh 277 191 bf է armenian small letter eh 300 192 c0 ը armenian capital letter et 301 193 c1 ը armenian small letter et 302 194 c2 թ armenian capital letter to 303 195 c3 թ armenian small letter to 304 196 c4 ժ armenian capital letter zhe 305 197 c5 ժ armenian small letter zhe 306 198 c6 ի armenian capital letter ini 307 199 c7 ի armenian small letter ini 310 200 c8 լ armenian capital letter liwn 311 201 c9 լ armenian small letter liwn 312 202 ca խ armenian capital letter xeh 313 203 cb խ armenian small letter xeh 314 204 cc ծ armenian capital letter ca 315 205 cd ծ armenian small letter ca 316 206 ce կ armenian capital letter ken 317 207 cf կ armenian small letter ken 320 208 d0 հ armenian capital letter ho 321 209 d1 հ armenian small letter ho 322 210 d2 ձ armenian capital letter ja 323 211 d3 ձ armenian small letter ja 324 212 d4 ղ armenian capital letter ghad 325 213 d5 ղ armenian small letter ghad 326 214 d6 ճ armenian capital letter cheh 327 215 d7 ճ armenian small letter cheh 330 216 d8 մ armenian capital letter men 331 217 d9 մ armenian small letter men 332 218 da յ armenian capital letter yi 333 219 db յ armenian small letter yi 334 220 dc ն armenian capital letter now 335 221 dd ն armenian small letter now 336 222 de շ armenian capital letter sha 337 223 df շ armenian small letter sha 340 224 e0 ո armenian capital letter vo 341 225 e1 ո armenian small letter vo 342 226 e2 չ armenian capital letter cha 343 227 e3 չ armenian small letter cha 344 228 e4 պ armenian capital letter peh 345 229 e5 պ armenian small letter peh 346 230 e6 ջ armenian capital letter jheh 347 231 e7 ջ armenian small letter jheh 350 232 e8 ռ armenian capital letter ra 351 233 e9 ռ armenian small letter ra 352 234 ea ս armenian capital letter seh 353 235 eb ս armenian small letter seh 354 236 ec վ armenian capital letter vew 355 237 ed վ armenian small letter vew 356 238 ee տ armenian capital letter tiwn 357 239 ef տ armenian small letter tiwn 360 240 f0 ր armenian capital letter reh 361 241 f1 ր armenian small letter reh 362 242 f2 ց armenian capital letter co 363 243 f3 ց armenian small letter co 364 244 f4 ւ armenian capital letter yiwn 365 245 f5 ւ armenian small letter yiwn 366 246 f6 փ armenian capital letter piwr 367 247 f7 փ armenian small letter piwr 370 248 f8 ք armenian capital letter keh 371 249 f9 ք armenian small letter keh 372 250 fa օ armenian capital letter oh 373 251 fb օ armenian small letter oh 374 252 fc ֆ armenian capital letter feh 375 253 fd ֆ armenian small letter feh 376 254 fe ՚ armenian apostrophe .te .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2001 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th rint 3 2021-03-22 "" "linux programmer's manual" .sh name nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl \- round to nearest integer .sh synopsis .nf .b #include .pp .bi "double nearbyint(double " x ); .bi "float nearbyintf(float " x ); .bi "long double nearbyintl(long double " x ); .pp .bi "double rint(double " x ); .bi "float rintf(float " x ); .bi "long double rintl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nearbyint (), .br nearbyintf (), .br nearbyintl (): .nf _posix_c_source >= 200112l || _isoc99_source .fi .pp .br rint (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br rintf (), .br rintl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br nearbyint (), .br nearbyintf (), and .br nearbyintl () functions round their argument to an integer value in floating-point format, using the current rounding direction (see .br fesetround (3)) and without raising the .i inexact exception. when the current rounding direction is to nearest, these functions round halfway cases to the even integer in accordance with ieee-754. .pp the .br rint (), .br rintf (), and .br rintl () functions do the same, but will raise the .i inexact exception .rb ( fe_inexact , checkable via .br fetestexcept (3)) when the result differs in value from the argument. .sh return value these functions return the rounded integer value. .pp if .i x is integral, +0, \-0, nan, or infinite, .i x itself is returned. .sh errors no errors occur. posix.1-2001 documents a range error for overflows, but see notes. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br nearbyint (), .br nearbyintf (), .br nearbyintl (), .br rint (), .br rintf (), .br rintl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes susv2 and posix.1-2001 contain text about overflow (which might set .i errno to .br erange , or raise an .b fe_overflow exception). in practice, the result cannot overflow on any current machine, so this error-handling stuff is just nonsense. (more precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of mantissa bits. for the ieee-754 standard 32-bit and 64-bit floating-point numbers the maximum value of the exponent is 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively, 53).) .pp if you want to store the rounded value in an integer type, you probably want to use one of the functions described in .br lrint (3) instead. .sh see also .br ceil (3), .br floor (3), .br lrint (3), .br round (3), .br trunc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt .\" (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1993-07-22 by rik faith .\" modified 1993-08-10 by alan cox .\" modified 1998-11-04 by tigran aivazian .\" modified 2004-05-27, 2004-06-17, 2004-06-23 by michael kerrisk .\" .th acct 2 2021-03-22 "linux" "linux programmer's manual" .sh name acct \- switch process accounting on or off .sh synopsis .ad l .nf .b #include .pp .bi "int acct(const char *" filename ); .fi .ad b .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br acct (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description the .br acct () system call enables or disables process accounting. if called with the name of an existing file as its argument, accounting is turned on, and records for each terminating process are appended to .i filename as it terminates. an argument of null causes accounting to be turned off. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces write permission is denied for the specified file, or search permission is denied for one of the directories in the path prefix of .i filename (see also .br path_resolution (7)), or .i filename is not a regular file. .tp .b efault .i filename points outside your accessible address space. .tp .b eio error writing to the file .ir filename . .tp .b eisdir .i filename is a directory. .tp .b eloop too many symbolic links were encountered in resolving .ir filename . .tp .b enametoolong .i filename was too long. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoent the specified file does not exist. .tp .b enomem out of memory. .tp .b enosys bsd process accounting has not been enabled when the operating system kernel was compiled. the kernel configuration parameter controlling this feature is .br config_bsd_process_acct . .tp .b enotdir a component used as a directory in .i filename is not in fact a directory. .tp .b eperm the calling process has insufficient privilege to enable process accounting. on linux, the .b cap_sys_pacct capability is required. .tp .b erofs .i filename refers to a file on a read-only filesystem. .tp .b eusers there are no more free file structures or we ran out of memory. .sh conforming to svr4, 4.3bsd (but not posix). .\" svr4 documents an ebusy error condition, but no eisdir or enosys. .\" also aix and hp-ux document ebusy (attempt is made .\" to enable accounting when it is already enabled), as does solaris .\" (attempt is made to enable accounting using the same file that is .\" currently being used). .sh notes no accounting is produced for programs running when a system crash occurs. in particular, nonterminating processes are never accounted for. .pp the structure of the records written to the accounting file is described in .br acct (5). .sh see also .br acct (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man7/system_data_types.7 .so man3/rpc.3 .so man5/utmp.5 .\" copyright (c) 2009 michael kerrisk, .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_yield 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_yield \- yield the processor .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .b int pthread_yield(void); .fi .pp compile and link with \fi\-pthread\fp. .sh description .br note : this function is deprecated; see below. .pp .br pthread_yield () causes the calling thread to relinquish the cpu. the thread is placed at the end of the run queue for its static priority and another thread is scheduled to run. for further details, see .br sched_yield (2) .sh return value on success, .br pthread_yield () returns 0; on error, it returns an error number. .sh errors on linux, this call always succeeds (but portable and future-proof applications should nevertheless handle a possible error return). .sh versions since glibc 2.34, this function is marked as deprecated. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_yield () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this call is nonstandard, but present on several other systems. use the standardized .br sched_yield (2) instead. .\" e.g., the bsds, tru64, aix, and irix. .sh notes on linux, this function is implemented as a call to .br sched_yield (2). .pp .br pthread_yield () is intended for use with real-time scheduling policies (i.e., .br sched_fifo or .br sched_rr ). use of .br pthread_yield () with nondeterministic scheduling policies such as .br sched_other is unspecified and very likely means your application design is broken. .sh see also .br sched_yield (2), .\" fixme . .br pthread_cond_wait (3), .br pthreads (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/asinh.3 .so man2/eventfd.2 .\" copyright (c) 2013, peter schiffer .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th memusagestat 1 2021-03-22 "gnu" "linux programmer's manual" .sh name memusagestat \- generate graphic from memory profiling data .sh synopsis .nf .br memusagestat " [\fioption\fr]... \fidatafile\fr [\fioutfile\fr]" .fi .sh description .b memusagestat creates a png file containing a graphical representation of the memory profiling data in the file .ir datafile ; that file is generated via the .i \-d (or .ir \-\-data ) option of .br memusage (1). .pp the red line in the graph shows the heap usage (allocated memory) and the green line shows the stack usage. the x-scale is either the number of memory-handling function calls or (if the .i \-t option is specified) time. .sh options .tp .bi \-o\ file \fr,\ \fb\-\-output= file name of the output file. .tp .bi \-s\ string \fr,\ \fb\-\-string= string use .i string as the title inside the output graph. .tp .b \-t\fr,\ \fb\-\-time use time (rather than number of function calls) as the scale for the x axis. .tp .b \-t\fr,\ \fb\-\-total also draw a graph of total memory consumption. .tp .bi \-x\ size \fr,\ \fb\-\-x\-size= size make the output graph .i size pixels wide. .tp .bi \-y\ size \fr,\ \fb\-\-y\-size= size make the output graph .i size pixels high. .tp .b \-?\fr,\ \fb\-\-help print a help message and exit. .tp .b \-\-usage print a short usage message and exit. .tp .b \-v\fr,\ \fb\-\-version print version information and exit. .sh bugs to report bugs, see .ur http://www.gnu.org/software/libc/bugs.html .ue .sh examples see .br memusage (1). .sh see also .br memusage (1), .br mtrace (1) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .so man3/envz_add.3 .so man3/rint.3 .so man3/ether_aton.3 .so man2/pwrite.2 .\" copyright (c) 2001 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th units 7 2020-08-13 "linux" "linux programmer's manual" .sh name units \- decimal and binary prefixes .sh description .ss decimal prefixes the si system of units uses prefixes that indicate powers of ten. a kilometer is 1000 meter, and a megawatt is 1000000 watt. below the standard prefixes. .rs .ts l l l. prefix name value y yocto 10^\-24 = 0.000000000000000000000001 z zepto 10^\-21 = 0.000000000000000000001 a atto 10^\-18 = 0.000000000000000001 f femto 10^\-15 = 0.000000000000001 p pico 10^\-12 = 0.000000000001 n nano 10^\-9 = 0.000000001 \(mc micro 10^\-6 = 0.000001 m milli 10^\-3 = 0.001 c centi 10^\-2 = 0.01 d deci 10^\-1 = 0.1 da deka 10^ 1 = 10 h hecto 10^ 2 = 100 k kilo 10^ 3 = 1000 m mega 10^ 6 = 1000000 g giga 10^ 9 = 1000000000 t tera 10^12 = 1000000000000 p peta 10^15 = 1000000000000000 e exa 10^18 = 1000000000000000000 z zetta 10^21 = 1000000000000000000000 y yotta 10^24 = 1000000000000000000000000 .te .re .pp the symbol for micro is the greek letter mu, often written u in an ascii context where this greek letter is not available. see also .pp .rs .ur http://physics.nist.gov\:/cuu\:/units\:/prefixes.html .ue .re .ss binary prefixes the binary prefixes resemble the decimal ones, but have an additional \(aqi\(aq (and "ki" starts with a capital \(aqk\(aq). the names are formed by taking the first syllable of the names of the decimal prefix with roughly the same size, followed by "bi" for "binary". .rs .ts l l l. prefix name value ki kibi 2^10 = 1024 mi mebi 2^20 = 1048576 gi gibi 2^30 = 1073741824 ti tebi 2^40 = 1099511627776 pi pebi 2^50 = 1125899906842624 ei exbi 2^60 = 1152921504606846976 .te .re .pp see also .pp .ur http://physics.nist.gov\:/cuu\:/units\:/binary.html .ue .ss discussion before these binary prefixes were introduced, it was fairly common to use k=1000 and k=1024, just like b=bit, b=byte. unfortunately, the m is capital already, and cannot be capitalized to indicate binary-ness. .pp at first that didn't matter too much, since memory modules and disks came in sizes that were powers of two, so everyone knew that in such contexts "kilobyte" and "megabyte" meant 1024 and 1048576 bytes, respectively. what originally was a sloppy use of the prefixes "kilo" and "mega" started to become regarded as the "real true meaning" when computers were involved. but then disk technology changed, and disk sizes became arbitrary numbers. after a period of uncertainty all disk manufacturers settled on the standard, namely k=1000, m=1000\ k, g=1000\ m. .pp the situation was messy: in the 14k4 modems, k=1000; in the 1.44\ mb .\" also common: 14.4k modem diskettes, m=1024000; and so on. in 1998 the iec approved the standard that defines the binary prefixes given above, enabling people to be precise and unambiguous. .pp thus, today, mb = 1000000\ b and mib = 1048576\ b. .pp in the free software world programs are slowly being changed to conform. when the linux kernel boots and says .pp .in +4n .ex hda: 120064896 sectors (61473 mb) w/2048kib cache .ee .in .pp the mb are megabytes and the kib are kibibytes. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th process-keyring 7 2020-08-13 linux "linux programmer's manual" .sh name process-keyring \- per-process shared keyring .sh description the process keyring is a keyring used to anchor keys on behalf of a process. it is created only when a process requests it. the process keyring has the name (description) .ir _pid . .pp a special serial number value, .br key_spec_process_keyring , is defined that can be used in lieu of the actual serial number of the calling process's process keyring. .pp from the .br keyctl (1) utility, '\fb@p\fp' can be used instead of a numeric key id in much the same way, but since .br keyctl (1) is a program run after forking, this is of no utility. .pp a thread created using the .br clone (2) .b clone_thread flag has the same process keyring as the caller of .br clone (2). when a new process is created using .br fork () it initially has no process keyring. a process's process keyring is cleared on .br execve (2). the process keyring is destroyed when the last thread that refers to it terminates. .pp if a process doesn't have a process keyring when it is accessed, then the process keyring will be created if the keyring is to be modified; otherwise, the error .b enokey results. .sh see also .ad l .nh .br keyctl (1), .br keyctl (3), .br keyrings (7), .br persistent\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ffs.3 .so man3/ctime.3 .so man3/getutent.3 .so man3/sigsetops.3 .\" this manpage is copyright (c) 1996 austin donnelly , .\" with additional material copyright (c) 1995 martin schulze .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" this manpage was made by merging two independently written manpages, .\" one written by martin schulze (18 oct 95), the other written by .\" austin donnelly, (9 jan 96). .\" .\" thu jan 11 12:14:41 1996 austin donnelly .\" * merged two services(5) manpages .\" .th services 5 2020-04-11 "linux" "linux programmer's manual" .sh name services \- internet network services list .sh description .b services is a plain ascii file providing a mapping between human-friendly textual names for internet services, and their underlying assigned port numbers and protocol types. every networking program should look into this file to get the port number (and protocol) for its service. the c library routines .br getservent (3), .br getservbyname (3), .br getservbyport (3), .br setservent (3), and .br endservent (3) support querying this file from programs. .pp port numbers are assigned by the iana (internet assigned numbers authority), and their current policy is to assign both tcp and udp protocols when assigning a port number. therefore, most entries will have two entries, even for tcp-only services. .pp port numbers below 1024 (so-called "low numbered" ports) can be bound to only by root (see .br bind (2), .br tcp (7), and .br udp (7)). this is so clients connecting to low numbered ports can trust that the service running on the port is the standard implementation, and not a rogue service run by a user of the machine. well-known port numbers specified by the iana are normally located in this root-only space. .pp the presence of an entry for a service in the .b services file does not necessarily mean that the service is currently running on the machine. see .br inetd.conf (5) for the configuration of internet services offered. note that not all networking services are started by .br inetd (8), and so won't appear in .br inetd.conf (5). in particular, news (nntp) and mail (smtp) servers are often initialized from the system boot scripts. .pp the location of the .b services file is defined by .b _path_services in .ir "." this is usually set to .ir /etc/services "." .pp each line describes one service, and is of the form: .ip \f2service-name\ \ \ port\f3/\f2protocol\ \ \ \f1[\f2aliases ...\f1] .tp where: .tp .i service-name is the friendly name the service is known by and looked up under. it is case sensitive. often, the client program is named after the .ir service-name "." .tp .i port is the port number (in decimal) to use for this service. .tp .i protocol is the type of protocol to be used. this field should match an entry in the .br protocols (5) file. typical values include .b tcp and .br udp . .tp .i aliases is an optional space or tab separated list of other names for this service. again, the names are case sensitive. .pp either spaces or tabs may be used to separate the fields. .pp comments are started by the hash sign (#) and continue until the end of the line. blank lines are skipped. .pp the .i service-name should begin in the first column of the file, since leading spaces are not stripped. .i service-names can be any printable characters excluding space and tab. however, a conservative choice of characters should be used to minimize compatibility problems. for example, a\-z, 0\-9, and hyphen (\-) would seem a sensible choice. .pp lines not matching this format should not be present in the file. (currently, they are silently skipped by .br getservent (3), .br getservbyname (3), and .br getservbyport (3). however, this behavior should not be relied on.) .pp .\" the following is not true as at glibc 2.8 (a line with a comma is .\" ignored by getservent()); it's not clear if/when it was ever true. .\" as a backward compatibility feature, the slash (/) between the .\" .i port .\" number and .\" .i protocol .\" name can in fact be either a slash or a comma (,). .\" use of the comma in .\" modern installations is deprecated. .\" this file might be distributed over a network using a network-wide naming service like yellow pages/nis or bind/hesiod. .pp a sample .b services file might look like this: .pp .in +4n .ex netstat 15/tcp qotd 17/tcp quote msp 18/tcp # message send protocol msp 18/udp # message send protocol chargen 19/tcp ttytst source chargen 19/udp ttytst source ftp 21/tcp # 22 \- unassigned telnet 23/tcp .ee .in .sh files .tp .i /etc/services the internet network services list .tp .i definition of .b _path_services .\" .sh bugs .\" it's not clear when/if the following was ever true; .\" it isn't true for glibc 2.8: .\" there is a maximum of 35 aliases, due to the way the .\" .br getservent (3) .\" code is written. .\" .\" it's not clear when/if the following was ever true; .\" it isn't true for glibc 2.8: .\" lines longer than .\" .b bufsiz .\" (currently 1024) characters will be ignored by .\" .br getservent (3), .\" .br getservbyname (3), .\" and .\" .br getservbyport (3). .\" however, this will also cause the next line to be mis-parsed. .sh see also .br listen (2), .br endservent (3), .br getservbyname (3), .br getservbyport (3), .br getservent (3), .br setservent (3), .br inetd.conf (5), .br protocols (5), .br inetd (8) .pp assigned numbers rfc, most recently rfc\ 1700, (aka std0002). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man4/vcs.4 .\" this file is derived from unlink.2, which has the following copyright: .\" .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 ian jackson. .\" .\" edited into remove.3 shape by: .\" graeme w. wilford (g.wilford@ee.surrey.ac.uk) on 13th july 1994 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th remove 3 2021-03-22 "gnu" "linux programmer's manual" .sh name remove \- remove a file or directory .sh synopsis .nf .b #include .pp .bi "int remove(const char *" pathname ); .fi .sh description .br remove () deletes a name from the filesystem. it calls .br unlink (2) for files, and .br rmdir (2) for directories. .pp if the removed name was the last link to a file and no processes have the file open, the file is deleted and the space it was using is made available for reuse. .pp if the name was the last link to a file, but any processes still have the file open, the file will remain in existence until the last file descriptor referring to it is closed. .pp if the name referred to a symbolic link, the link is removed. .pp if the name referred to a socket, fifo, or device, the name is removed, but processes which have the object open may continue to use it. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors the errors that occur are those for .br unlink (2) and .br rmdir (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br remove () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, 4.3bsd. .\" .sh notes .\" under libc4 and libc5, .\" .br remove () .\" was an alias for .\" .br unlink (2) .\" (and hence would not remove directories). .sh bugs infelicities in the protocol underlying nfs can cause the unexpected disappearance of files which are still being used. .sh see also .br rm (1), .br unlink (1), .br link (2), .br mknod (2), .br open (2), .br rename (2), .br rmdir (2), .br unlink (2), .br mkfifo (3), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/j0.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcpncpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcpncpy \- copy a fixed-size string of wide characters, returning a pointer to its end .sh synopsis .nf .b #include .pp .bi "wchar_t *wcpncpy(wchar_t *restrict " dest \ ", const wchar_t *restrict " src , .bi " size_t " n ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcpncpy (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcpncpy () function is the wide-character equivalent of the .br stpncpy (3) function. it copies at most .i n wide characters from the wide-character string pointed to by .ir src , including the terminating null wide (l\(aq\e0\(aq), to the array pointed to by .ir dest . exactly .i n wide characters are written at .ir dest . if the length .ir wcslen(src) is smaller than .ir n , the remaining wide characters in the array pointed to by .i dest are filled with l\(aq\e0\(aq characters. if the length .ir wcslen(src) is greater than or equal to .ir n , the string pointed to by .i dest will not be l\(aq\e0\(aq terminated. .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .i n wide characters at .ir dest . .sh return value .br wcpncpy () returns a pointer to the last wide character written, that is, .ir dest + n \-1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcpncpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. .sh see also .br stpncpy (3), .br wcsncpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\"this manpage is copyright (c) 2015 anna schumaker .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th copy_file_range 2 2021-08-27 "linux" "linux programmer's manual" .sh name copy_file_range \- copy a range of data from one file to another .sh synopsis .nf .b #define _gnu_source .b #include .pp .bi "ssize_t copy_file_range(int " fd_in ", off64_t *" off_in , .bi " int " fd_out ", off64_t *" off_out , .bi " size_t " len ", unsigned int " flags ); .fi .sh description the .br copy_file_range () system call performs an in-kernel copy between two file descriptors without the additional cost of transferring data from the kernel to user space and then back into the kernel. it copies up to .i len bytes of data from the source file descriptor .i fd_in to the target file descriptor .ir fd_out , overwriting any data that exists within the requested range of the target file. .pp the following semantics apply for .ir off_in , and similar statements apply to .ir off_out : .ip * 3 if .i off_in is null, then bytes are read from .i fd_in starting from the file offset, and the file offset is adjusted by the number of bytes copied. .ip * if .i off_in is not null, then .i off_in must point to a buffer that specifies the starting offset where bytes from .i fd_in will be read. the file offset of .i fd_in is not changed, but .i off_in is adjusted appropriately. .pp .i fd_in and .i fd_out can refer to the same file. if they refer to the same file, then the source and target ranges are not allowed to overlap. .pp the .i flags argument is provided to allow for future extensions and currently must be set to 0. .sh return value upon successful completion, .br copy_file_range () will return the number of bytes copied between files. this could be less than the length originally requested. if the file offset of .i fd_in is at or past the end of file, no bytes are copied, and .br copy_file_range () returns zero. .pp on error, .br copy_file_range () returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b ebadf one or more file descriptors are not valid. .tp .b ebadf .i fd_in is not open for reading; or .i fd_out is not open for writing. .tp .b ebadf the .b o_append flag is set for the open file description (see .br open (2)) referred to by the file descriptor .ir fd_out . .tp .b efbig an attempt was made to write at a position past the maximum file offset the kernel supports. .tp .b efbig an attempt was made to write a range that exceeds the allowed maximum file size. the maximum file size differs between filesystem implementations and can be different from the maximum allowed file offset. .tp .b efbig an attempt was made to write beyond the process's file size resource limit. this may also result in the process receiving a .b sigxfsz signal. .tp .b einval the .i flags argument is not 0. .tp .b einval .i fd_in and .i fd_out refer to the same file and the source and target ranges overlap. .tp .b einval either .i fd_in or .i fd_out is not a regular file. .tp .b eio a low-level i/o error occurred while copying. .tp .b eisdir either .i fd_in or .i fd_out refers to a directory. .tp .b enomem out of memory. .tp .b enospc there is not enough space on the target filesystem to complete the copy. .tp .b eoverflow the requested source or destination range is too large to represent in the specified data types. .tp .b eperm .i fd_out refers to an immutable file. .tp .b etxtbsy either .i fd_in or .i fd_out refers to an active swap file. .tp .b exdev the files referred to by .ir fd_in " and " fd_out are not on the same mounted filesystem (pre linux 5.3). .sh versions the .br copy_file_range () system call first appeared in linux 4.5, but glibc 2.27 provides a user-space emulation when it is not available. .\" https://sourceware.org/git/?p=glibc.git;a=commit;f=posix/unistd.h;h=bad7a0c81f501fbbcc79af9eaa4b8254441c4a1f .pp a major rework of the kernel implementation occurred in 5.3. areas of the api that weren't clearly defined were clarified and the api bounds are much more strictly checked than on earlier kernels. applications should target the behaviour and requirements of 5.3 kernels. .pp first support for cross-filesystem copies was introduced in linux 5.3. older kernels will return -exdev when cross-filesystem copies are attempted. .sh conforming to the .br copy_file_range () system call is a nonstandard linux and gnu extension. .sh notes if .i fd_in is a sparse file, then .br copy_file_range () may expand any holes existing in the requested range. users may benefit from calling .br copy_file_range () in a loop, and using the .br lseek (2) .br seek_data and .br seek_hole operations to find the locations of data segments. .pp .br copy_file_range () gives filesystems an opportunity to implement "copy acceleration" techniques, such as the use of reflinks (i.e., two or more inodes that share pointers to the same copy-on-write disk blocks) or server-side-copy (in the case of nfs). .sh examples .ex #define _gnu_source #include #include #include #include #include int main(int argc, char *argv[]) { int fd_in, fd_out; struct stat stat; off64_t len, ret; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } fd_in = open(argv[1], o_rdonly); if (fd_in == \-1) { perror("open (argv[1])"); exit(exit_failure); } if (fstat(fd_in, &stat) == \-1) { perror("fstat"); exit(exit_failure); } len = stat.st_size; fd_out = open(argv[2], o_creat | o_wronly | o_trunc, 0644); if (fd_out == \-1) { perror("open (argv[2])"); exit(exit_failure); } do { ret = copy_file_range(fd_in, null, fd_out, null, len, 0); if (ret == \-1) { perror("copy_file_range"); exit(exit_failure); } len \-= ret; } while (len > 0 && ret > 0); close(fd_in); close(fd_out); exit(exit_success); } .ee .sh see also .br lseek (2), .br sendfile (2), .br splice (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/msgop.2 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 2003-08-17 by walter harms .\" modified 2004-06-23 by michael kerrisk .\" .th statfs 2 2021-03-22 "linux" "linux programmer's manual" .sh name statfs, fstatfs \- get filesystem statistics .sh synopsis .nf .br "#include " "/* or */" .pp .bi "int statfs(const char *" path ", struct statfs *" buf ); .bi "int fstatfs(int " fd ", struct statfs *" buf ); .fi .sh description the .br statfs () system call returns information about a mounted filesystem. .i path is the pathname of any file within the mounted filesystem. .i buf is a pointer to a .i statfs structure defined approximately as follows: .pp .in +4n .ex struct statfs { __fsword_t f_type; /* type of filesystem (see below) */ __fsword_t f_bsize; /* optimal transfer block size */ fsblkcnt_t f_blocks; /* total data blocks in filesystem */ fsblkcnt_t f_bfree; /* free blocks in filesystem */ fsblkcnt_t f_bavail; /* free blocks available to unprivileged user */ fsfilcnt_t f_files; /* total inodes in filesystem */ fsfilcnt_t f_ffree; /* free inodes in filesystem */ fsid_t f_fsid; /* filesystem id */ __fsword_t f_namelen; /* maximum length of filenames */ __fsword_t f_frsize; /* fragment size (since linux 2.6) */ __fsword_t f_flags; /* mount flags of filesystem (since linux 2.6.36) */ __fsword_t f_spare[xxx]; /* padding bytes reserved for future use */ }; .ee .in .pp the following filesystem types may appear in .ir f_type : .pp .in +4n .ex adfs_super_magic 0xadf5 affs_super_magic 0xadff afs_super_magic 0x5346414f anon_inode_fs_magic 0x09041934 /* anonymous inode fs (for pseudofiles that have no name; e.g., epoll, signalfd, bpf) */ autofs_super_magic 0x0187 bdevfs_magic 0x62646576 befs_super_magic 0x42465331 bfs_magic 0x1badface binfmtfs_magic 0x42494e4d bpf_fs_magic 0xcafe4a11 btrfs_super_magic 0x9123683e btrfs_test_magic 0x73727279 cgroup_super_magic 0x27e0eb /* cgroup pseudo fs */ cgroup2_super_magic 0x63677270 /* cgroup v2 pseudo fs */ cifs_magic_number 0xff534d42 coda_super_magic 0x73757245 coh_super_magic 0x012ff7b7 cramfs_magic 0x28cd3d45 debugfs_magic 0x64626720 devfs_super_magic 0x1373 /* linux 2.6.17 and earlier */ devpts_super_magic 0x1cd1 ecryptfs_super_magic 0xf15f efivarfs_magic 0xde5e81e4 efs_super_magic 0x00414a53 ext_super_magic 0x137d /* linux 2.0 and earlier */ ext2_old_super_magic 0xef51 ext2_super_magic 0xef53 ext3_super_magic 0xef53 ext4_super_magic 0xef53 f2fs_super_magic 0xf2f52010 fuse_super_magic 0x65735546 futexfs_super_magic 0xbad1dea /* unused */ hfs_super_magic 0x4244 hostfs_super_magic 0x00c0ffee hpfs_super_magic 0xf995e849 hugetlbfs_magic 0x958458f6 isofs_super_magic 0x9660 jffs2_super_magic 0x72b6 jfs_super_magic 0x3153464a minix_super_magic 0x137f /* original minix fs */ minix_super_magic2 0x138f /* 30 char minix fs */ minix2_super_magic 0x2468 /* minix v2 fs */ minix2_super_magic2 0x2478 /* minix v2 fs, 30 char names */ minix3_super_magic 0x4d5a /* minix v3 fs, 60 char names */ mqueue_magic 0x19800202 /* posix message queue fs */ msdos_super_magic 0x4d44 mtd_inode_fs_magic 0x11307854 ncp_super_magic 0x564c nfs_super_magic 0x6969 nilfs_super_magic 0x3434 nsfs_magic 0x6e736673 ntfs_sb_magic 0x5346544e ocfs2_super_magic 0x7461636f openprom_super_magic 0x9fa1 overlayfs_super_magic 0x794c7630 pipefs_magic 0x50495045 proc_super_magic 0x9fa0 /* /proc fs */ pstorefs_magic 0x6165676c qnx4_super_magic 0x002f qnx6_super_magic 0x68191122 ramfs_magic 0x858458f6 reiserfs_super_magic 0x52654973 romfs_magic 0x7275 securityfs_magic 0x73636673 selinux_magic 0xf97cff8c smack_magic 0x43415d53 smb_super_magic 0x517b smb2_magic_number 0xfe534d42 sockfs_magic 0x534f434b squashfs_magic 0x73717368 sysfs_magic 0x62656572 sysv2_super_magic 0x012ff7b6 sysv4_super_magic 0x012ff7b5 tmpfs_magic 0x01021994 tracefs_magic 0x74726163 udf_super_magic 0x15013346 ufs_magic 0x00011954 usbdevice_super_magic 0x9fa2 v9fs_magic 0x01021997 vxfs_super_magic 0xa501fcf5 xenfs_super_magic 0xabba1974 xenix_super_magic 0x012ff7b4 xfs_super_magic 0x58465342 _xiafs_super_magic 0x012fd16d /* linux 2.0 and earlier */ .ee .in .pp most of these magic constants are defined in .ir /usr/include/linux/magic.h , and some are hardcoded in kernel sources. .pp the .ir f_flags field is a bit mask indicating mount options for the filesystem. it contains zero or more of the following bits: .\" xxx keep this list in sync with statvfs(3) .tp .b st_mandlock mandatory locking is permitted on the filesystem (see .br fcntl (2)). .tp .b st_noatime do not update access times; see .br mount (2). .tp .b st_nodev disallow access to device special files on this filesystem. .tp .b st_nodiratime do not update directory access times; see .br mount (2). .tp .b st_noexec execution of programs is disallowed on this filesystem. .tp .b st_nosuid the set-user-id and set-group-id bits are ignored by .br exec (3) for executable files on this filesystem .tp .b st_rdonly this filesystem is mounted read-only. .tp .b st_relatime update atime relative to mtime/ctime; see .br mount (2). .tp .b st_synchronous writes are synched to the filesystem immediately (see the description of .b o_sync in .br open (2)). .tp .br st_nosymfollow " (since linux 5.10)" .\" dab741e0e02bd3c4f5e2e97be74b39df2523fc6e symbolic links are not followed when resolving paths; see .br mount (2). .pp nobody knows what .i f_fsid is supposed to contain (but see below). .pp fields that are undefined for a particular filesystem are set to 0. .pp .br fstatfs () returns the same information about an open file referenced by descriptor .ir fd . .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces .rb ( statfs ()) search permission is denied for a component of the path prefix of .ir path . (see also .br path_resolution (7).) .tp .b ebadf .rb ( fstatfs ()) .i fd is not a valid open file descriptor. .tp .b efault .i buf or .i path points to an invalid address. .tp .b eintr the call was interrupted by a signal; see .br signal (7). .tp .b eio an i/o error occurred while reading from the filesystem. .tp .b eloop .rb ( statfs ()) too many symbolic links were encountered in translating .ir path . .tp .b enametoolong .rb ( statfs ()) .i path is too long. .tp .b enoent .rb ( statfs ()) the file referred to by .i path does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enosys the filesystem does not support this call. .tp .b enotdir .rb ( statfs ()) a component of the path prefix of .i path is not a directory. .tp .b eoverflow some values were too large to be represented in the returned struct. .sh conforming to linux-specific. the linux .br statfs () was inspired by the 4.4bsd one (but they do not use the same structure). .sh notes the .i __fsword_t type used for various fields in the .i statfs structure definition is a glibc internal type, not intended for public use. this leaves the programmer in a bit of a conundrum when trying to copy or compare these fields to local variables in a program. using .i "unsigned\ int" for such variables suffices on most systems. .pp the original linux .br statfs () and .br fstatfs () system calls were not designed with extremely large file sizes in mind. subsequently, linux 2.6 added new .br statfs64 () and .br fstatfs64 () system calls that employ a new structure, .ir statfs64 . the new structure contains the same fields as the original .i statfs structure, but the sizes of various fields are increased, to accommodate large file sizes. the glibc .br statfs () and .br fstatfs () wrapper functions transparently deal with the kernel differences. .pp some systems have only \fi\fp, other systems also have \fi\fp, where the former includes the latter. so it seems including the former is the best choice. .pp lsb has deprecated the library calls .br statfs () and .br fstatfs () and tells us to use .br statvfs (3) and .br fstatvfs (3) instead. .ss the f_fsid field solaris, irix, and posix have a system call .br statvfs (2) that returns a .i "struct statvfs" (defined in .ir ) containing an .i "unsigned long" .ir f_fsid . linux, sunos, hp-ux, 4.4bsd have a system call .br statfs () that returns a .i "struct statfs" (defined in .ir ) containing a .i fsid_t .ir f_fsid , where .i fsid_t is defined as .ir "struct { int val[2]; }" . the same holds for freebsd, except that it uses the include file .ir . .pp the general idea is that .i f_fsid contains some random stuff such that the pair .ri ( f_fsid , ino ) uniquely determines a file. some operating systems use (a variation on) the device number, or the device number combined with the filesystem type. several operating systems restrict giving out the .i f_fsid field to the superuser only (and zero it for unprivileged users), because this field is used in the filehandle of the filesystem when nfs-exported, and giving it out is a security concern. .pp under some operating systems, the .i fsid can be used as the second argument to the .br sysfs (2) system call. .sh bugs from linux 2.6.38 up to and including linux 3.1, .\" broken in commit ff0c7d15f9787b7e8c601533c015295cc68329f8 .\" fixed in commit d70ef97baf048412c395bb5d65791d8fe133a52b .br fstatfs () failed with the error .b enosys for file descriptors created by .br pipe (2). .sh see also .br stat (2), .br statvfs (3), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .\" copyright (c) 2003, 2017 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th dl_iterate_phdr 3 2021-03-22 "gnu" "linux programmer's manual" .sh name dl_iterate_phdr \- walk through list of shared objects .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int dl_iterate_phdr(" .bi " int (*" callback ")(struct dl_phdr_info *" info , .bi " size_t " size ", void *" data ")," .bi " void *" data ");" .fi .sh description the .br dl_iterate_phdr () function allows an application to inquire at run time to find out which shared objects it has loaded, and the order in which they were loaded. .pp the .br dl_iterate_phdr () function walks through the list of an application's shared objects and calls the function .i callback once for each object, until either all shared objects have been processed or .i callback returns a nonzero value. .pp each call to .i callback receives three arguments: .ir info , which is a pointer to a structure containing information about the shared object; .ir size , which is the size of the structure pointed to by .ir info ; and .ir data , which is a copy of whatever value was passed by the calling program as the second argument (also named .ir data ) in the call to .br dl_iterate_phdr (). .pp the .i info argument is a structure of the following type: .pp .in +4n .ex struct dl_phdr_info { elfw(addr) dlpi_addr; /* base address of object */ const char *dlpi_name; /* (null\-terminated) name of object */ const elfw(phdr) *dlpi_phdr; /* pointer to array of elf program headers for this object */ elfw(half) dlpi_phnum; /* # of items in \fidlpi_phdr\fp */ /* the following fields were added in glibc 2.4, after the first version of this structure was available. check the \fisize\fp argument passed to the dl_iterate_phdr callback to determine whether or not each later member is available. */ unsigned long long dlpi_adds; /* incremented when a new object may have been added */ unsigned long long dlpi_subs; /* incremented when an object may have been removed */ size_t dlpi_tls_modid; /* if there is a pt_tls segment, its module id as used in tls relocations, else zero */ void *dlpi_tls_data; /* the address of the calling thread\(aqs instance of this module\(aqs pt_tls segment, if it has one and it has been allocated in the calling thread, otherwise a null pointer */ }; .ee .in .pp (the .ir elfw () macro definition turns its argument into the name of an elf data type suitable for the hardware architecture. for example, on a 32-bit platform, .i elfw(addr) yields the data type name .ir elf32_addr . further information on these types can be found in the .ir " and " header files.) .pp the .i dlpi_addr field indicates the base address of the shared object (i.e., the difference between the virtual memory address of the shared object and the offset of that object in the file from which it was loaded). the .i dlpi_name field is a null-terminated string giving the pathname from which the shared object was loaded. .pp to understand the meaning of the .i dlpi_phdr and .i dlpi_phnum fields, we need to be aware that an elf shared object consists of a number of segments, each of which has a corresponding program header describing the segment. the .i dlpi_phdr field is a pointer to an array of the program headers for this shared object. the .i dlpi_phnum field indicates the size of this array. .pp these program headers are structures of the following form: .pp .in +4n .ex typedef struct { elf32_word p_type; /* segment type */ elf32_off p_offset; /* segment file offset */ elf32_addr p_vaddr; /* segment virtual address */ elf32_addr p_paddr; /* segment physical address */ elf32_word p_filesz; /* segment size in file */ elf32_word p_memsz; /* segment size in memory */ elf32_word p_flags; /* segment flags */ elf32_word p_align; /* segment alignment */ } elf32_phdr; .ee .in .pp note that we can calculate the location of a particular program header, .ir x , in virtual memory using the formula: .pp .in +4n .ex addr == info\->dlpi_addr + info\->dlpi_phdr[x].p_vaddr; .ee .in .pp possible values for .i p_type include the following (see .ir for further details): .pp .in +4n .ex #define pt_load 1 /* loadable program segment */ #define pt_dynamic 2 /* dynamic linking information */ #define pt_interp 3 /* program interpreter */ #define pt_note 4 /* auxiliary information */ #define pt_shlib 5 /* reserved */ #define pt_phdr 6 /* entry for header table itself */ #define pt_tls 7 /* thread\-local storage segment */ #define pt_gnu_eh_frame 0x6474e550 /* gcc .eh_frame_hdr segment */ #define pt_gnu_stack 0x6474e551 /* indicates stack executability */ .\" for pt_gnu_stack, see http://www.airs.com/blog/archives/518 #define pt_gnu_relro 0x6474e552 /* read\-only after relocation */ .ee .in .sh return value the .br dl_iterate_phdr () function returns whatever value was returned by the last call to .ir callback . .sh versions .br dl_iterate_phdr () has been supported in glibc since version 2.2.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dl_iterate_phdr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the .br dl_iterate_phdr () function is not specified in any standard. various other systems provide a version of this function, although details of the returned .i dl_phdr_info structure differ. on the bsds and solaris, the structure includes the fields .ir dlpi_addr , .ir dlpi_name , .ir dlpi_phdr , and .ir dlpi_phnum in addition to other implementation-specific fields. .sh notes future versions of the c library may add further fields to the .ir dl_phdr_info structure; in that event, the .i size argument provides a mechanism for the callback function to discover whether it is running on a system with added fields. .pp the first object visited by .ir callback is the main program. for the main program, the .i dlpi_name field will be an empty string. .sh examples the following program displays a list of pathnames of the shared objects it has loaded. for each shared object, the program lists some information (virtual address, size, flags, and type) for each of the objects elf segments. .pp the following shell session demonstrates the output produced by the program on an x86-64 system. the first shared object for which output is displayed (where the name is an empty string) is the main program. .pp .in +4n .ex $ \fb./a.out\fp name: "" (9 segments) 0: [ 0x400040; memsz: 1f8] flags: 0x5; pt_phdr 1: [ 0x400238; memsz: 1c] flags: 0x4; pt_interp 2: [ 0x400000; memsz: ac4] flags: 0x5; pt_load 3: [ 0x600e10; memsz: 240] flags: 0x6; pt_load 4: [ 0x600e28; memsz: 1d0] flags: 0x6; pt_dynamic 5: [ 0x400254; memsz: 44] flags: 0x4; pt_note 6: [ 0x400970; memsz: 3c] flags: 0x4; pt_gnu_eh_frame 7: [ (nil); memsz: 0] flags: 0x6; pt_gnu_stack 8: [ 0x600e10; memsz: 1f0] flags: 0x4; pt_gnu_relro name: "linux\-vdso.so.1" (4 segments) 0: [0x7ffc6edd1000; memsz: e89] flags: 0x5; pt_load 1: [0x7ffc6edd1360; memsz: 110] flags: 0x4; pt_dynamic 2: [0x7ffc6edd17b0; memsz: 3c] flags: 0x4; pt_note 3: [0x7ffc6edd17ec; memsz: 3c] flags: 0x4; pt_gnu_eh_frame name: "/lib64/libc.so.6" (10 segments) 0: [0x7f55712ce040; memsz: 230] flags: 0x5; pt_phdr 1: [0x7f557145b980; memsz: 1c] flags: 0x4; pt_interp 2: [0x7f55712ce000; memsz: 1b6a5c] flags: 0x5; pt_load 3: [0x7f55716857a0; memsz: 9240] flags: 0x6; pt_load 4: [0x7f5571688b80; memsz: 1f0] flags: 0x6; pt_dynamic 5: [0x7f55712ce270; memsz: 44] flags: 0x4; pt_note 6: [0x7f55716857a0; memsz: 78] flags: 0x4; pt_tls 7: [0x7f557145b99c; memsz: 544c] flags: 0x4; pt_gnu_eh_frame 8: [0x7f55712ce000; memsz: 0] flags: 0x6; pt_gnu_stack 9: [0x7f55716857a0; memsz: 3860] flags: 0x4; pt_gnu_relro name: "/lib64/ld\-linux\-x86\-64.so.2" (7 segments) 0: [0x7f557168f000; memsz: 20828] flags: 0x5; pt_load 1: [0x7f55718afba0; memsz: 15a8] flags: 0x6; pt_load 2: [0x7f55718afe10; memsz: 190] flags: 0x6; pt_dynamic 3: [0x7f557168f1c8; memsz: 24] flags: 0x4; pt_note 4: [0x7f55716acec4; memsz: 604] flags: 0x4; pt_gnu_eh_frame 5: [0x7f557168f000; memsz: 0] flags: 0x6; pt_gnu_stack 6: [0x7f55718afba0; memsz: 460] flags: 0x4; pt_gnu_relro .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include static int callback(struct dl_phdr_info *info, size_t size, void *data) { char *type; int p_type; printf("name: \e"%s\e" (%d segments)\en", info\->dlpi_name, info\->dlpi_phnum); for (int j = 0; j < info\->dlpi_phnum; j++) { p_type = info\->dlpi_phdr[j].p_type; type = (p_type == pt_load) ? "pt_load" : (p_type == pt_dynamic) ? "pt_dynamic" : (p_type == pt_interp) ? "pt_interp" : (p_type == pt_note) ? "pt_note" : (p_type == pt_interp) ? "pt_interp" : (p_type == pt_phdr) ? "pt_phdr" : (p_type == pt_tls) ? "pt_tls" : (p_type == pt_gnu_eh_frame) ? "pt_gnu_eh_frame" : (p_type == pt_gnu_stack) ? "pt_gnu_stack" : (p_type == pt_gnu_relro) ? "pt_gnu_relro" : null; printf(" %2d: [%14p; memsz:%7jx] flags: %#jx; ", j, (void *) (info\->dlpi_addr + info\->dlpi_phdr[j].p_vaddr), (uintmax_t) info\->dlpi_phdr[j].p_memsz, (uintmax_t) info\->dlpi_phdr[j].p_flags); if (type != null) printf("%s\en", type); else printf("[other (%#x)]\en", p_type); } return 0; } int main(int argc, char *argv[]) { dl_iterate_phdr(callback, null); exit(exit_success); } .ee .sh see also .br ldd (1), .br objdump (1), .br readelf (1), .br dladdr (3), .br dlopen (3), .br elf (5), .br ld.so (8) .pp .ir "executable and linking format specification" , available at various locations online. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt .\" (michael@moria.de) .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 15:12:05 1993 by rik faith .\" modified tue aug 1 16:27 1995 by jochen karrer .\" .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .\" modified mon feb 15 17:28:41 cet 1999 by andries e. brouwer .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th ioperm 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioperm \- set port input/output permissions .sh synopsis .nf .b #include .pp .bi "int ioperm(unsigned long " from ", unsigned long " num ", int " turn_on ); .fi .sh description .br ioperm () sets the port access permission bits for the calling thread for .i num bits starting from port address .ir from . if .i turn_on is nonzero, then permission for the specified bits is enabled; otherwise it is disabled. if .i turn_on is nonzero, the calling thread must be privileged .rb ( cap_sys_rawio ). .pp before linux 2.6.8, only the first 0x3ff i/o ports could be specified in this manner. for more ports, the .br iopl (2) system call had to be used (with a .i level argument of 3). since linux 2.6.8, 65,536 i/o ports can be specified. .pp permissions are inherited by the child created by .br fork (2) (but see notes). permissions are preserved across .br execve (2); this is useful for giving port access permissions to unprivileged programs. .pp this call is mostly for the i386 architecture. on many other architectures it does not exist or will always return an error. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval invalid values for .i from or .ir num . .tp .b eio (on powerpc) this call is not supported. .tp .b enomem .\" could not allocate i/o bitmap. out of memory. .tp .b eperm the calling thread has insufficient privilege. .sh conforming to .br ioperm () is linux-specific and should not be used in programs intended to be portable. .sh notes the .i /proc/ioports file shows the i/o ports that are currently allocated on the system. .pp before linux 2.4, permissions were not inherited by a child created by .br fork (2). .pp glibc has an .br ioperm () prototype both in .i and in .ir . avoid the latter, it is available on i386 only. .sh see also .br iopl (2), .br outb (2), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getrpcent_r.3 .so man3/dlsym.3 .so man3/creal.3 .so man2/readv.2 .so man3/resolver.3 .so man3/fenv.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" and andries brouwer (aeb@cwi.nl), fri feb 14 21:47:50 1997. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sun jul 25 10:45:30 1993 by rik faith (faith@cs.unc.edu) .\" modified sun jul 21 21:25:26 1996 by andries brouwer (aeb@cwi.nl) .\" modified mon oct 21 17:47:19 1996 by eric s. raymond (esr@thyrsus.com) .\" modified wed aug 27 20:28:58 1997 by nicolás lichtmaier (nick@debian.org) .\" modified mon sep 21 00:00:26 1998 by andries brouwer (aeb@cwi.nl) .\" modified wed jan 24 06:37:24 2001 by eric s. raymond (esr@thyrsus.com) .\" modified thu dec 13 23:53:27 2001 by martin schulze .\" .th environ 7 2021-03-22 "linux" "linux programmer's manual" .sh name environ \- user environment .sh synopsis .nf .bi "extern char **" environ ; .fi .sh description the variable .i environ points to an array of pointers to strings called the "environment". the last pointer in this array has the value null. this array of strings is made available to the process by the .br execve (2) call when a new program is started. when a child process is created via .br fork (2), it inherits a .i copy of its parent's environment. .pp by convention, the strings in .i environ have the form "\finame\fp\fb=\fp\fivalue\fp". the name is case-sensitive and may not contain the character "\fb=\fp". the value can be anything that can be represented as a string. the name and the value may not contain an embedded null byte (\(aq\e0\(aq), since this is assumed to terminate the string. .pp environment variables may be placed in the shell's environment by the .i export command in .br sh (1), or by the .i setenv command if you use .br csh (1). .pp the initial environment of the shell is populated in various ways, such as definitions from .ir /etc/environment that are processed by .br pam_env (8) for all users at login time (on systems that employ .br pam (8)). in addition, various shell initialization scripts, such as the system-wide .ir /etc/profile script and per-user initializations script may include commands that add variables to the shell's environment; see the manual page of your preferred shell for details. .pp bourne-style shells support the syntax .pp name=value command .pp to create an environment variable definition only in the scope of the process that executes .ir command . multiple variable definitions, separated by white space, may precede .ir command . .pp arguments may also be placed in the environment at the point of an .br exec (3). a c program can manipulate its environment using the functions .br getenv (3), .br putenv (3), .br setenv (3), and .br unsetenv (3). .pp what follows is a list of environment variables typically seen on a system. this list is incomplete and includes only common variables seen by average users in their day-to-day routine. environment variables specific to a particular program or library function are documented in the environment section of the appropriate manual page. .tp .b user the name of the logged-in user (used by some bsd-derived programs). set at login time, see section notes below. .tp .b logname the name of the logged-in user (used by some system-v derived programs). set at login time, see section notes below. .tp .b home a user's login directory. set at login time, see section notes below. .tp .b lang the name of a locale to use for locale categories when not overridden by .b lc_all or more specific environment variables such as .br lc_collate , .br lc_ctype , .br lc_messages , .br lc_monetary , .br lc_numeric , and .br lc_time (see .br locale (7) for further details of the .br lc_* environment variables). .tp .b path the sequence of directory prefixes that .br sh (1) and many other programs employ when searching for an executable file that is specified as a simple filename (i.a., a pathname that contains no slashes). the prefixes are separated by colons (\fb:\fp). the list of prefixes is searched from beginning to end, by checking the pathname formed by concatenating a prefix, a slash, and the filename, until a file with execute permission is found. .ip as a legacy feature, a zero-length prefix (specified as two adjacent colons, or an initial or terminating colon) is interpreted to mean the current working directory. however, use of this feature is deprecated, and posix notes that a conforming application shall use an explicit pathname (e.g., .ir . ) to specify the current working directory. .ip analogously to .br path , one has .b cdpath used by some shells to find the target of a change directory command, .b manpath used by .br man (1) to find manual pages, and so on. .tp .b pwd the current working directory. set by some shells. .tp .b shell the absolute pathname of the user's login shell. set at login time, see section notes below. .tp .b term the terminal type for which output is to be prepared. .tp .b pager the user's preferred utility to display text files. any string acceptable as a command-string operand to the .i sh\ \-c command shall be valid. if .b pager is null or is not set, then applications that launch a pager will default to a program such as .br less (1) or .br more (1). .tp .br editor / visual the user's preferred utility to edit text files. any string acceptable as a command_string operand to the .i sh\ \-c command shall be valid. .\" .tp .\" .b browser .\" the user's preferred utility to browse urls. sequence of colon-separated .\" browser commands. see http://www.catb.org/\(tiesr/browser/ . .pp note that the behavior of many programs and library routines is influenced by the presence or value of certain environment variables. examples include the following: .ip * 3 the variables .br lang ", " language ", " nlspath ", " locpath , .br lc_all ", " lc_messages , and so on influence locale handling; see .br catopen (3), .br gettext (3), and .br locale (7). .ip * .b tmpdir influences the path prefix of names created by .br tempnam (3) and other routines, and the temporary directory used by .br sort (1) and other programs. .ip * .br ld_library_path ", " ld_preload , and other .br ld_* variables influence the behavior of the dynamic loader/linker. see also .br ld.so (8). .ip * .b posixly_correct makes certain programs and library routines follow the prescriptions of posix. .ip * the behavior of .br malloc (3) is influenced by .b malloc_* variables. .ip * the variable .b hostaliases gives the name of a file containing aliases to be used with .br gethostbyname (3). .ip * .br tz " and " tzdir give timezone information used by .br tzset (3) and through that by functions like .br ctime (3), .br localtime (3), .br mktime (3), .br strftime (3). see also .br tzselect (8). .ip * .b termcap gives information on how to address a given terminal (or gives the name of a file containing such information). .ip * .br columns " and " lines tell applications about the window size, possibly overriding the actual size. .ip * .br printer " or " lpdest may specify the desired printer to use. see .br lpr (1). .sh notes historically and by standard, .i environ must be declared in the user program. however, as a (nonstandard) programmer convenience, .i environ is declared in the header file .i if the .b _gnu_source feature test macro is defined (see .br feature_test_macros (7)). .pp the .br prctl (2) .b pr_set_mm_env_start and .b pr_set_mm_env_end operations can be used to control the location of the process's environment. .pp the .br home , .br logname , .br shell , and .b user variables are set when the user is changed via a session management interface, typically by a program such as .br login (1) from a user database (such as .br passwd (5)). (switching to the root user using .br su (1) may result in a mixed environment where .b logname and .b user are retained from old user; see the .br su (1) manual page.) .sh bugs clearly there is a security risk here. many a system command has been tricked into mischief by a user who specified unusual values for .br ifs " or " ld_library_path . .pp there is also the risk of name space pollution. programs like .i make and .i autoconf allow overriding of default utility names from the environment with similarly named variables in all caps. thus one uses .b cc to select the desired c compiler (and similarly .br make , .br ar , .br as , .br fc , .br ld , .br lex , .br rm , .br yacc , etc.). however, in some traditional uses such an environment variable gives options for the program instead of a pathname. thus, one has .b more and .br less . such usage is considered mistaken, and to be avoided in new programs. .sh see also .br bash (1), .br csh (1), .br env (1), .br login (1), .br printenv (1), .br sh (1), .br su (1), .br tcsh (1), .br execve (2), .br clearenv (3), .br exec (3), .br getenv (3), .br putenv (3), .br setenv (3), .br unsetenv (3), .br locale (7), .br ld.so (8), .br pam_env (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rcmd.3 .so man7/iso_8859-8.7 .so man3/xdr.3 .so man3/unlocked_stdio.3 .\" copyright (c) 1996 eric s. raymond .\" and copyright (c) andries brouwer .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" this is combined from many sources, including notes by aeb and .\" research by esr. portions derive from a writeup by roman czyborra. .\" .\" changes also by david starner . .\" .th charsets 7 2020-08-13 "linux" "linux programmer's manual" .sh name charsets \- character set standards and internationalization .sh description this manual page gives an overview on different character set standards and how they were used on linux before unicode became ubiquitous. some of this information is still helpful for people working with legacy systems and documents. .pp standards discussed include such as ascii, gb 2312, iso 8859, jis, koi8-r, ks, and unicode. .pp the primary emphasis is on character sets that were actually used by locale character sets, not the myriad others that could be found in data from other systems. .ss ascii ascii (american standard code for information interchange) is the original 7-bit character set, originally designed for american english. also known as us-ascii. it is currently described by the iso 646:1991 irv (international reference version) standard. .pp various ascii variants replacing the dollar sign with other currency symbols and replacing punctuation with non-english alphabetic characters to cover german, french, spanish, and others in 7 bits emerged. all are deprecated; glibc does not support locales whose character sets are not true supersets of ascii. .pp as unicode, when using utf-8, is ascii-compatible, plain ascii text still renders properly on modern utf-8 using systems. .ss iso 8859 iso 8859 is a series of 15 8-bit character sets, all of which have ascii in their low (7-bit) half, invisible control characters in positions 128 to 159, and 96 fixed-width graphics in positions 160\(en255. .pp of these, the most important is iso 8859-1 ("latin alphabet no .1" / latin-1). it was widely adopted and supported by different systems, and is gradually being replaced with unicode. the iso 8859-1 characters are also the first 256 characters of unicode. .pp console support for the other 8859 character sets is available under linux through user-mode utilities (such as .br setfont (8)) that modify keyboard bindings and the ega graphics table and employ the "user mapping" font table in the console driver. .pp here are brief descriptions of each set: .tp 8859-1 (latin-1) latin-1 covers many west european languages such as albanian, basque, danish, english, faroese, galician, icelandic, irish, italian, norwegian, portuguese, spanish, and swedish. the lack of the ligatures dutch ij/ij, french œ, and old-style „german“ quotation marks was considered tolerable. .tp 8859-2 (latin-2) latin-2 supports many latin-written central and east european languages such as bosnian, croatian, czech, german, hungarian, polish, slovak, and slovene. replacing romanian ș/ț with ş/ţ was considered tolerable. .tp 8859-3 (latin-3) latin-3 was designed to cover of esperanto, maltese, and turkish, but 8859-9 later superseded it for turkish. .tp 8859-4 (latin-4) latin-4 introduced letters for north european languages such as estonian, latvian, and lithuanian, but was superseded by 8859-10 and 8859-13. .tp 8859-5 cyrillic letters supporting bulgarian, byelorussian, macedonian, russian, serbian, and (almost completely) ukrainian. it was never widely used, see the discussion of koi8-r/koi8-u below. .tp 8859-6 was created for arabic. the 8859-6 glyph table is a fixed font of separate letter forms, but a proper display engine should combine these using the proper initial, medial, and final forms. .tp 8859-7 was created for modern greek in 1987, updated in 2003. .tp 8859-8 supports modern hebrew without niqud (punctuation signs). niqud and full-fledged biblical hebrew were outside the scope of this character set. .tp 8859-9 (latin-5) this is a variant of latin-1 that replaces icelandic letters with turkish ones. .tp 8859-10 (latin-6) latin-6 added the inuit (greenlandic) and sami (lappish) letters that were missing in latin-4 to cover the entire nordic area. .tp 8859-11 supports the thai alphabet and is nearly identical to the tis-620 standard. .tp 8859-12 this set does not exist. .tp 8859-13 (latin-7) supports the baltic rim languages; in particular, it includes latvian characters not found in latin-4. .tp 8859-14 (latin-8) this is the celtic character set, covering old irish, manx, gaelic, welsh, cornish, and breton. .tp 8859-15 (latin-9) latin-9 is similar to the widely used latin-1 but replaces some less common symbols with the euro sign and french and finnish letters that were missing in latin-1. .tp 8859-16 (latin-10) this set covers many southeast european languages, and most importantly supports romanian more completely than latin-2. .ss koi8-r / koi8-u koi8-r is a non-iso character set popular in russia before unicode. the lower half is ascii; the upper is a cyrillic character set somewhat better designed than iso 8859-5. koi8-u, based on koi8-r, has better support for ukrainian. neither of these sets are iso-2022 compatible, unlike the iso 8859 series. .pp console support for koi8-r is available under linux through user-mode utilities that modify keyboard bindings and the ega graphics table, and employ the "user mapping" font table in the console driver. .ss gb 2312 gb 2312 is a mainland chinese national standard character set used to express simplified chinese. just like jis x 0208, characters are mapped into a 94x94 two-byte matrix used to construct euc-cn. euc-cn is the most important encoding for linux and includes ascii and gb 2312. note that euc-cn is often called as gb, gb 2312, or cn-gb. .ss big5 big5 was a popular character set in taiwan to express traditional chinese. (big5 is both a character set and an encoding.) it is a superset of ascii. non-ascii characters are expressed in two bytes. bytes 0xa1\(en0xfe are used as leading bytes for two-byte characters. big5 and its extension were widely used in taiwan and hong kong. it is not iso 2022 compliant. .\" thanks to tomohiro kubota for the following sections about .\" national standards. .ss jis x 0208 jis x 0208 is a japanese national standard character set. though there are some more japanese national standard character sets (like jis x 0201, jis x 0212, and jis x 0213), this is the most important one. characters are mapped into a 94x94 two-byte matrix, whose each byte is in the range 0x21\(en0x7e. note that jis x 0208 is a character set, not an encoding. this means that jis x 0208 itself is not used for expressing text data. jis x 0208 is used as a component to construct encodings such as euc-jp, shift_jis, and iso-2022-jp. euc-jp is the most important encoding for linux and includes ascii and jis x 0208. in euc-jp, jis x 0208 characters are expressed in two bytes, each of which is the jis x 0208 code plus 0x80. .ss ks x 1001 ks x 1001 is a korean national standard character set. just as jis x 0208, characters are mapped into a 94x94 two-byte matrix. ks x 1001 is used like jis x 0208, as a component to construct encodings such as euc-kr, johab, and iso-2022-kr. euc-kr is the most important encoding for linux and includes ascii and ks x 1001. ks c 5601 is an older name for ks x 1001. .ss iso 2022 and iso 4873 the iso 2022 and 4873 standards describe a font-control model based on vt100 practice. this model is (partially) supported by the linux kernel and by .br xterm (1). several iso 2022-based character encodings have been defined, especially for japanese. .pp there are 4 graphic character sets, called g0, g1, g2, and g3, and one of them is the current character set for codes with high bit zero (initially g0), and one of them is the current character set for codes with high bit one (initially g1). each graphic character set has 94 or 96 characters, and is essentially a 7-bit character set. it uses codes either 040\(en0177 (041\(en0176) or 0240\(en0377 (0241\(en0376). g0 always has size 94 and uses codes 041\(en0176. .pp switching between character sets is done using the shift functions \fb\(han\fp (so or ls1), \fb\(hao\fp (si or ls0), esc n (ls2), esc o (ls3), esc n (ss2), esc o (ss3), esc \(ti (ls1r), esc } (ls2r), esc | (ls3r). the function ls\fin\fp makes character set g\fin\fp the current one for codes with high bit zero. the function ls\fin\fpr makes character set g\fin\fp the current one for codes with high bit one. the function ss\fin\fp makes character set g\fin\fp (\fin\fp=2 or 3) the current one for the next character only (regardless of the value of its high order bit). .pp a 94-character set is designated as g\fin\fp character set by an escape sequence esc ( xx (for g0), esc ) xx (for g1), esc * xx (for g2), esc + xx (for g3), where xx is a symbol or a pair of symbols found in the iso 2375 international register of coded character sets. for example, esc ( @ selects the iso 646 character set as g0, esc ( a selects the uk standard character set (with pound instead of number sign), esc ( b selects ascii (with dollar instead of currency sign), esc ( m selects a character set for african languages, esc ( ! a selects the cuban character set, and so on. .pp a 96-character set is designated as g\fin\fp character set by an escape sequence esc \- xx (for g1), esc . xx (for g2) or esc / xx (for g3). for example, esc \- g selects the hebrew alphabet as g1. .pp a multibyte character set is designated as g\fin\fp character set by an escape sequence esc $ xx or esc $ ( xx (for g0), esc $ ) xx (for g1), esc $ * xx (for g2), esc $ + xx (for g3). for example, esc $ ( c selects the korean character set for g0. the japanese character set selected by esc $ b has a more recent version selected by esc & @ esc $ b. .pp iso 4873 stipulates a narrower use of character sets, where g0 is fixed (always ascii), so that g1, g2, and g3 can be invoked only for codes with the high order bit set. in particular, \fb\(han\fp and \fb\(hao\fp are not used anymore, esc ( xx can be used only with xx=b, and esc ) xx, esc * xx, esc + xx are equivalent to esc \- xx, esc . xx, esc / xx, respectively. .ss tis-620 tis-620 is a thai national standard character set and a superset of ascii. in the same fashion as the iso 8859 series, thai characters are mapped into 0xa1\(en0xfe. .ss unicode unicode (iso 10646) is a standard which aims to unambiguously represent every character in every human language. unicode's structure permits 20.1 bits to encode every character. since most computers don't include 20.1-bit integers, unicode is usually encoded as 32-bit integers internally and either a series of 16-bit integers (utf-16) (needing two 16-bit integers only when encoding certain rare characters) or a series of 8-bit bytes (utf-8). .pp linux represents unicode using the 8-bit unicode transformation format (utf-8). utf-8 is a variable length encoding of unicode. it uses 1 byte to code 7 bits, 2 bytes for 11 bits, 3 bytes for 16 bits, 4 bytes for 21 bits, 5 bytes for 26 bits, 6 bytes for 31 bits. .pp let 0,1,x stand for a zero, one, or arbitrary bit. a byte 0xxxxxxx stands for the unicode 00000000 0xxxxxxx which codes the same symbol as the ascii 0xxxxxxx. thus, ascii goes unchanged into utf-8, and people using only ascii do not notice any change: not in code, and not in file size. .pp a byte 110xxxxx is the start of a 2-byte code, and 110xxxxx 10yyyyyy is assembled into 00000xxx xxyyyyyy. a byte 1110xxxx is the start of a 3-byte code, and 1110xxxx 10yyyyyy 10zzzzzz is assembled into xxxxyyyy yyzzzzzz. (when utf-8 is used to code the 31-bit iso 10646 then this progression continues up to 6-byte codes.) .pp for most texts in iso 8859 character sets, this means that the characters outside of ascii are now coded with two bytes. this tends to expand ordinary text files by only one or two percent. for russian or greek texts, this expands ordinary text files by 100%, since text in those languages is mostly outside of ascii. for japanese users this means that the 16-bit codes now in common use will take three bytes. while there are algorithmic conversions from some character sets (especially iso 8859-1) to unicode, general conversion requires carrying around conversion tables, which can be quite large for 16-bit codes. .pp note that utf-8 is self-synchronizing: 10xxxxxx is a tail, any other byte is the head of a code. note that the only way ascii bytes occur in a utf-8 stream, is as themselves. in particular, there are no embedded nuls (\(aq\e0\(aq) or \(aq/\(aqs that form part of some larger code. .pp since ascii, and, in particular, nul and \(aq/\(aq, are unchanged, the kernel does not notice that utf-8 is being used. it does not care at all what the bytes it is handling stand for. .pp rendering of unicode data streams is typically handled through "subfont" tables which map a subset of unicode to glyphs. internally the kernel uses unicode to describe the subfont loaded in video ram. this means that in the linux console in utf-8 mode, one can use a character set with 512 different symbols. this is not enough for japanese, chinese, and korean, but it is enough for most other purposes. .sh see also .br iconv (1), .br ascii (7), .br iso_8859\-1 (7), .br unicode (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/open.2 .so man2/outb.2 .so man3/drand48_r.3 .so man3/ecvt_r.3 .so man7/system_data_types.7 .so man3/y0.3 .\" copyright 2001 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, 2001-12-26, aeb .\" 2008-09-07, mtk, various rewrites; added an example program. .\" .th getdate 3 2021-03-22 "" "linux programmer's manual" .sh name getdate, getdate_r \- convert a date-plus-time string to broken-down time .sh synopsis .nf .b "#include " .pp .bi "struct tm *getdate(const char *" string ); .pp .b "extern int getdate_err;" .pp .b "#include " .pp .bi "int getdate_r(const char *restrict " string ", struct tm *restrict " res ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getdate (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .pp .br getdate_r (): .nf _gnu_source .fi .sh description the function .br getdate () converts a string representation of a date and time, contained in the buffer pointed to by .ir string , into a broken-down time. the broken-down time is stored in a .i tm structure, and a pointer to this structure is returned as the function result. this .i tm structure is allocated in static storage, and consequently it will be overwritten by further calls to .br getdate (). .pp in contrast to .br strptime (3), (which has a .i format argument), .br getdate () uses the formats found in the file whose full pathname is given in the environment variable .br datemsk . the first line in the file that matches the given input string is used for the conversion. .pp the matching is done case insensitively. superfluous whitespace, either in the pattern or in the string to be converted, is ignored. .pp the conversion specifications that a pattern can contain are those given for .br strptime (3). one more conversion specification is specified in posix.1-2001: .tp .b %z timezone name. .\" fixme is it (still) true that %z is not supported in glibc? .\" looking at the glibc 2.21 source code, where the implementation uses .\" strptime(), suggests that it might be supported. this is not implemented in glibc. .pp when .b %z is given, the structure containing the broken-down time is initialized with values corresponding to the current time in the given timezone. otherwise, the structure is initialized to the broken-down time corresponding to the current local time (as by a call to .br localtime (3)). .pp when only the day of the week is given, the day is taken to be the first such day on or after today. .pp when only the month is given (and no year), the month is taken to be the first such month equal to or after the current month. if no day is given, it is the first day of the month. .pp when no hour, minute, and second are given, the current hour, minute, and second are taken. .pp if no date is given, but we know the hour, then that hour is taken to be the first such hour equal to or after the current hour. .pp .br getdate_r () is a gnu extension that provides a reentrant version of .br getdate (). rather than using a global variable to report errors and a static buffer to return the broken down time, it returns errors via the function result value, and returns the resulting broken-down time in the caller-allocated buffer pointed to by the argument .ir res . .sh return value when successful, .br getdate () returns a pointer to a .ir "struct tm" . otherwise, it returns null and sets the global variable .ir getdate_err to one of the error numbers shown below. changes to .i errno are unspecified. .pp on success .br getdate_r () returns 0; on error it returns one of the error numbers shown below. .sh errors the following errors are returned via .ir getdate_err (for .br getdate ()) or as the function result (for .br getdate_r ()): .tp 4n .b 1 the .b datemsk environment variable is not defined, or its value is an empty string. .tp .b 2 the template file specified by .b datemsk cannot be opened for reading. .tp .b 3 failed to get file status information. .\" stat() .tp .b 4 the template file is not a regular file. .tp .b 5 an error was encountered while reading the template file. .tp .b 6 memory allocation failed (not enough memory available). .\" error 6 doesn't seem to occur in glibc .tp .b 7 there is no line in the file that matches the input. .tp .b 8 invalid input specification. .sh environment .tp .b datemsk file containing format patterns. .tp .br tz ", " lc_time variables used by .br strptime (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getdate () t} thread safety t{ mt-unsafe race:getdate env locale t} t{ .br getdate_r () t} thread safety t{ mt-safe env locale t} .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the posix.1 specification for .br strptime (3) contains conversion specifications using the .b %e or .b %o modifier, while such specifications are not given for .br getdate (). in glibc, .br getdate () is implemented using .br strptime (3), so that precisely the same conversions are supported by both. .sh examples the program below calls .br getdate () for each of its command-line arguments, and for each call displays the values in the fields of the returned .i tm structure. the following shell session demonstrates the operation of the program: .pp .in +4n .ex .rb "$" " tfile=$pwd/tfile" .rb "$" " echo \(aq%a\(aq > $tfile " " # full name of the day of the week" .rb "$" " echo \(aq%t\(aq >> $tfile" " # iso date (yyyy\-mm\-dd)" .rb "$" " echo \(aq%f\(aq >> $tfile" " # time (hh:mm:ss)" .rb "$" " date" .rb "$" " export datemsk=$tfile" .rb "$" " ./a.out tuesday \(aq2009\-12\-28\(aq \(aq12:22:33\(aq" sun sep 7 06:03:36 cest 2008 call 1 ("tuesday") succeeded: tm_sec = 36 tm_min = 3 tm_hour = 6 tm_mday = 9 tm_mon = 8 tm_year = 108 tm_wday = 2 tm_yday = 252 tm_isdst = 1 call 2 ("2009\-12\-28") succeeded: tm_sec = 36 tm_min = 3 tm_hour = 6 tm_mday = 28 tm_mon = 11 tm_year = 109 tm_wday = 1 tm_yday = 361 tm_isdst = 0 call 3 ("12:22:33") succeeded: tm_sec = 33 tm_min = 22 tm_hour = 12 tm_mday = 7 tm_mon = 8 tm_year = 108 tm_wday = 0 tm_yday = 250 tm_isdst = 1 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include int main(int argc, char *argv[]) { struct tm *tmp; for (int j = 1; j < argc; j++) { tmp = getdate(argv[j]); if (tmp == null) { printf("call %d failed; getdate_err = %d\en", j, getdate_err); continue; } printf("call %d (\e"%s\e") succeeded:\en", j, argv[j]); printf(" tm_sec = %d\en", tmp\->tm_sec); printf(" tm_min = %d\en", tmp\->tm_min); printf(" tm_hour = %d\en", tmp\->tm_hour); printf(" tm_mday = %d\en", tmp\->tm_mday); printf(" tm_mon = %d\en", tmp\->tm_mon); printf(" tm_year = %d\en", tmp\->tm_year); printf(" tm_wday = %d\en", tmp\->tm_wday); printf(" tm_yday = %d\en", tmp\->tm_yday); printf(" tm_isdst = %d\en", tmp\->tm_isdst); } exit(exit_success); } .ee .sh see also .br time (2), .br localtime (3), .br setlocale (3), .br strftime (3), .br strptime (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tsearch.3 .so man3/stailq.3 .so man7/system_data_types.7 .so man2/link.2 .so man3/sigsetops.3 .so man3/finite.3 .so man3/stdio_ext.3 .so man3/getttyent.3 .so man3/cos.3 .\" copyright 1993 mitchum dsouza .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified thu dec 13 22:51:19 2001 by martin schulze .\" modified 2001-12-14 aeb .\" .th catopen 3 2021-03-22 "gnu" "linux programmer's manual" .sh name catopen, catclose \- open/close a message catalog .sh synopsis .nf .b #include .pp .bi "nl_catd catopen(const char *" name ", int " flag ); .bi "int catclose(nl_catd " catalog ); .fi .sh description the function .br catopen () opens a message catalog and returns a catalog descriptor. the descriptor remains valid until .br catclose () or .br execve (2). if a file descriptor is used to implement catalog descriptors, then the .b fd_cloexec flag will be set. .pp the argument .i name specifies the name of the message catalog to be opened. if .i name specifies an absolute path (i.e., contains a \(aq/\(aq), then .i name specifies a pathname for the message catalog. otherwise, the environment variable .b nlspath is used with .i name substituted for .b %n (see .br locale (7)). it is unspecified whether .b nlspath will be used when the process has root privileges. if .b nlspath does not exist in the environment, or if a message catalog cannot be opened in any of the paths specified by it, then an implementation defined path is used. this latter default path may depend on the .b lc_messages locale setting when the .i flag argument is .b nl_cat_locale and on the .b lang environment variable when the .i flag argument is 0. changing the .b lc_messages part of the locale may invalidate open catalog descriptors. .pp the .i flag argument to .br catopen () is used to indicate the source for the language to use. if it is set to .br nl_cat_locale , then it will use the current locale setting for .br lc_messages . otherwise, it will use the .b lang environment variable. .pp the function .br catclose () closes the message catalog identified by .ir catalog . it invalidates any subsequent references to the message catalog defined by .ir catalog . .sh return value the function .br catopen () returns a message catalog descriptor of type .i nl_catd on success. on failure, it returns .ir "(nl_catd)\ \-1" and sets .i errno to indicate the error. the possible error values include all possible values for the .br open (2) call. .pp the function .br catclose () returns 0 on success, or \-1 on failure. .sh environment .tp .b lc_messages may be the source of the .b lc_messages locale setting, and thus determine the language to use if .i flag is set to .br nl_cat_locale . .tp .b lang the language to use if .i flag is 0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br catopen () t} thread safety mt-safe env t{ .br catclose () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .\" in xpg 1987, vol. 3 it says: .\" .i "the flag argument of catopen is reserved for future use" .\" .ir "and should be set to 0" . .\" .\" it is unclear what the source was for the constants .\" .b mcloadbyset .\" and .\" .b mcloadall .\" (see below). .sh notes the above is the posix.1 description. the glibc value for .b nl_cat_locale is 1. .\" (compare .\" .b mcloadall .\" below.) the default path varies, but usually looks at a number of places below .ir /usr/share/locale . .\" .ss linux notes .\" these functions are available for linux since libc 4.4.4c. .\" in the case of linux libc4 and libc5, the catalog descriptor .\" .i nl_catd .\" is a .\" .br mmap (2)'ed .\" area of memory and not a file descriptor. .\" the .\" .i flag .\" argument to .\" .br catopen () .\" should be either .\" .b mcloadbyset .\" (=0) or .\" .b mcloadall .\" (=1). .\" the former value indicates that a set from the catalog is to be .\" loaded when needed, whereas the latter causes the initial call to .\" .br catopen () .\" to load the entire catalog into memory. .\" the default search path varies, but usually looks at a number of places below .\" .i /etc/locale .\" and .\" .ir /usr/lib/locale . .sh see also .br catgets (3), .br setlocale (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/chown.2 .so man3/byteorder.3 .so man3/circleq.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setscope 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setscope, pthread_attr_getscope \- set/get contention scope attribute in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setscope(pthread_attr_t *" attr ", int " scope ); .bi "int pthread_attr_getscope(const pthread_attr_t *restrict " attr , .bi " int *restrict " scope ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setscope () function sets the contention scope attribute of the thread attributes object referred to by .i attr to the value specified in .ir scope . the contention scope attribute defines the set of threads against which a thread competes for resources such as the cpu. posix.1 specifies two possible values for .ir scope : .tp .b pthread_scope_system the thread competes for resources with all other threads in all processes on the system that are in the same scheduling allocation domain (a group of one or more processors). .b pthread_scope_system threads are scheduled relative to one another according to their scheduling policy and priority. .tp .b pthread_scope_process the thread competes for resources with all other threads in the same process that were also created with the .br pthread_scope_process contention scope. .br pthread_scope_process threads are scheduled relative to other threads in the process according to their scheduling policy and priority. posix.1 leaves it unspecified how these threads contend with other threads in other process on the system or with other threads in the same process that were created with the .b pthread_scope_system contention scope. .pp posix.1 requires that an implementation support at least one of these contention scopes. linux supports .br pthread_scope_system , but not .br pthread_scope_process . .pp on systems that support multiple contention scopes, then, in order for the parameter setting made by .br pthread_attr_setscope () to have effect when calling .br pthread_create (3), the caller must use .br pthread_attr_setinheritsched (3) to set the inherit-scheduler attribute of the attributes object .i attr to .br pthread_explicit_sched . .pp the .br pthread_attr_getscope () function returns the contention scope attribute of the thread attributes object referred to by .i attr in the buffer pointed to by .ir scope . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .br pthread_attr_setscope () can fail with the following errors: .tp .b einval an invalid value was specified in .ir scope . .tp .b enotsup .ir scope specified the value .br pthread_scope_process , which is not supported on linux. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setscope (), .br pthread_attr_getscope () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the .b pthread_scope_system contention scope typically indicates that a user-space thread is bound directly to a single kernel-scheduling entity. this is the case on linux for the obsolete linuxthreads implementation and the modern nptl implementation, which are both 1:1 threading implementations. .pp posix.1 specifies that the default contention scope is implementation-defined. .sh see also .ad l .nh .br pthread_attr_init (3), .br pthread_attr_setaffinity_np (3), .br pthread_attr_setinheritsched (3), .br pthread_attr_setschedparam (3), .br pthread_attr_setschedpolicy (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006, janak desai .\" and copyright (c) 2006, 2012 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" licensed under the gpl .\" %%%license_end .\" .\" patch justification: .\" unshare system call is needed to implement, using pam, .\" per-security_context and/or per-user namespace to provide .\" polyinstantiated directories. using unshare and bind mounts, a .\" pam module can create private namespace with appropriate .\" directories(based on user's security context) bind mounted on .\" public directories such as /tmp, thus providing an instance of .\" /tmp that is based on user's security context. without the .\" unshare system call, namespace separation can only be achieved .\" by clone, which would require porting and maintaining all commands .\" such as login, and su, that establish a user session. .\" .th unshare 2 2021-03-22 "linux" "linux programmer's manual" .sh name unshare \- disassociate parts of the process execution context .sh synopsis .nf .b #define _gnu_source .b #include .pp .bi "int unshare(int " flags ); .fi .sh description .br unshare () allows a process (or thread) to disassociate parts of its execution context that are currently being shared with other processes (or threads). part of the execution context, such as the mount namespace, is shared implicitly when a new process is created using .br fork (2) or .br vfork (2), while other parts, such as virtual memory, may be shared by explicit request when creating a process or thread using .br clone (2). .pp the main use of .br unshare () is to allow a process to control its shared execution context without creating a new process. .pp the .i flags argument is a bit mask that specifies which parts of the execution context should be unshared. this argument is specified by oring together zero or more of the following constants: .tp .b clone_files reverse the effect of the .br clone (2) .b clone_files flag. unshare the file descriptor table, so that the calling process no longer shares its file descriptors with any other process. .tp .b clone_fs reverse the effect of the .br clone (2) .b clone_fs flag. unshare filesystem attributes, so that the calling process no longer shares its root directory .rb ( chroot (2)), current directory .rb ( chdir (2)), or umask .rb ( umask (2)) attributes with any other process. .tp .br clone_newcgroup " (since linux 4.6)" this flag has the same effect as the .br clone (2) .b clone_newcgroup flag. unshare the cgroup namespace. use of .br clone_newcgroup requires the .br cap_sys_admin capability. .tp .br clone_newipc " (since linux 2.6.19)" this flag has the same effect as the .br clone (2) .b clone_newipc flag. unshare the ipc namespace, so that the calling process has a private copy of the ipc namespace which is not shared with any other process. specifying this flag automatically implies .br clone_sysvsem as well. use of .br clone_newipc requires the .br cap_sys_admin capability. .tp .br clone_newnet " (since linux 2.6.24)" this flag has the same effect as the .br clone (2) .b clone_newnet flag. unshare the network namespace, so that the calling process is moved into a new network namespace which is not shared with any previously existing process. use of .br clone_newnet requires the .br cap_sys_admin capability. .tp .b clone_newns .\" these flag name are inconsistent: .\" clone_newns does the same thing in clone(), but clone_vm, .\" clone_fs, and clone_files reverse the action of the clone() .\" flags of the same name. this flag has the same effect as the .br clone (2) .b clone_newns flag. unshare the mount namespace, so that the calling process has a private copy of its namespace which is not shared with any other process. specifying this flag automatically implies .b clone_fs as well. use of .br clone_newns requires the .br cap_sys_admin capability. for further information, see .br mount_namespaces (7). .tp .br clone_newpid " (since linux 3.8)" this flag has the same effect as the .br clone (2) .b clone_newpid flag. unshare the pid namespace, so that the calling process has a new pid namespace for its children which is not shared with any previously existing process. the calling process is .i not moved into the new namespace. the first child created by the calling process will have the process id 1 and will assume the role of .br init (1) in the new namespace. .br clone_newpid automatically implies .br clone_thread as well. use of .br clone_newpid requires the .br cap_sys_admin capability. for further information, see .br pid_namespaces (7). .tp .br clone_newtime " (since linux 5.6)" unshare the time namespace, so that the calling process has a new time namespace for its children which is not shared with any previously existing process. the calling process is .i not moved into the new namespace. use of .br clone_newtime requires the .br cap_sys_admin capability. for further information, see .br time_namespaces (7). .tp .br clone_newuser " (since linux 3.8)" this flag has the same effect as the .br clone (2) .b clone_newuser flag. unshare the user namespace, so that the calling process is moved into a new user namespace which is not shared with any previously existing process. as with the child process created by .br clone (2) with the .b clone_newuser flag, the caller obtains a full set of capabilities in the new namespace. .ip .br clone_newuser requires that the calling process is not threaded; specifying .br clone_newuser automatically implies .br clone_thread . since linux 3.9, .\" commit e66eded8309ebf679d3d3c1f5820d1f2ca332c71 .\" https://lwn.net/articles/543273/ .br clone_newuser also automatically implies .br clone_fs . .br clone_newuser requires that the user id and group id of the calling process are mapped to user ids and group ids in the user namespace of the calling process at the time of the call. .ip for further information on user namespaces, see .br user_namespaces (7). .tp .br clone_newuts " (since linux 2.6.19)" this flag has the same effect as the .br clone (2) .b clone_newuts flag. unshare the uts ipc namespace, so that the calling process has a private copy of the uts namespace which is not shared with any other process. use of .br clone_newuts requires the .br cap_sys_admin capability. .tp .br clone_sysvsem " (since linux 2.6.26)" .\" commit 9edff4ab1f8d82675277a04e359d0ed8bf14a7b7 this flag reverses the effect of the .br clone (2) .b clone_sysvsem flag. unshare system\ v semaphore adjustment .ri ( semadj ) values, so that the calling process has a new empty .i semadj list that is not shared with any other process. if this is the last process that has a reference to the process's current .i semadj list, then the adjustments in that list are applied to the corresponding semaphores, as described in .br semop (2). .\" clone_newns if clone_sighand is set and signals are also being shared .\" (i.e., current->signal->count > 1), force clone_thread. .pp in addition, .br clone_thread , .br clone_sighand , and .br clone_vm can be specified in .i flags if the caller is single threaded (i.e., it is not sharing its address space with another process or thread). in this case, these flags have no effect. (note also that specifying .br clone_thread automatically implies .br clone_vm , and specifying .br clone_vm automatically implies .br clone_sighand .) .\" as at 3.9, the following forced implications also apply, .\" although the relevant flags are not yet implemented. .\" if clone_thread is set force clone_vm. .\" if clone_vm is set, force clone_sighand. .\" if the process is multithreaded, then the use of these flags results in an error. .\" see kernel/fork.c::check_unshare_flags() .pp if .i flags is specified as zero, then .br unshare () is a no-op; no changes are made to the calling process's execution context. .sh return value on success, zero returned. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b einval an invalid bit was specified in .ir flags . .tp .b einval .br clone_thread , .br clone_sighand , or .br clone_vm was specified in .ir flags , and the caller is multithreaded. .tp .b einval .br clone_newipc was specified in .ir flags , but the kernel was not configured with the .b config_sysvipc and .br config_ipc_ns options. .tp .b einval .br clone_newnet was specified in .ir flags , but the kernel was not configured with the .b config_net_ns option. .tp .b einval .br clone_newpid was specified in .ir flags , but the kernel was not configured with the .b config_pid_ns option. .tp .b einval .br clone_newuser was specified in .ir flags , but the kernel was not configured with the .b config_user_ns option. .tp .b einval .br clone_newuts was specified in .ir flags , but the kernel was not configured with the .b config_uts_ns option. .tp .b einval .br clone_newpid was specified in .ir flags , but the process has previously called .br unshare () with the .br clone_newpid flag. .tp .b enomem cannot allocate sufficient memory to copy parts of caller's context that need to be unshared. .tp .br enospc " (since linux 3.7)" .\" commit f2302505775fd13ba93f034206f1e2a587017929 .b clone_newpid was specified in flags, but the limit on the nesting depth of pid namespaces would have been exceeded; see .br pid_namespaces (7). .tp .br enospc " (since linux 4.9; beforehand " eusers ) .b clone_newuser was specified in .ir flags , and the call would cause the limit on the number of nested user namespaces to be exceeded. see .br user_namespaces (7). .ip from linux 3.11 to linux 4.8, the error diagnosed in this case was .br eusers . .tp .br enospc " (since linux 4.9)" one of the values in .i flags specified the creation of a new user namespace, but doing so would have caused the limit defined by the corresponding file in .ir /proc/sys/user to be exceeded. for further details, see .br namespaces (7). .tp .b eperm the calling process did not have the required privileges for this operation. .tp .b eperm .br clone_newuser was specified in .ir flags , but either the effective user id or the effective group id of the caller does not have a mapping in the parent namespace (see .br user_namespaces (7)). .tp .br eperm " (since linux 3.9)" .\" commit 3151527ee007b73a0ebd296010f1c0454a919c7d .b clone_newuser was specified in .i flags and the caller is in a chroot environment .\" fixme what is the rationale for this restriction? (i.e., the caller's root directory does not match the root directory of the mount namespace in which it resides). .tp .br eusers " (from linux 3.11 to linux 4.8)" .b clone_newuser was specified in .ir flags , and the limit on the number of nested user namespaces would be exceeded. see the discussion of the .br enospc error above. .sh versions the .br unshare () system call was added to linux in kernel 2.6.16. .sh conforming to the .br unshare () system call is linux-specific. .sh notes not all of the process attributes that can be shared when a new process is created using .br clone (2) can be unshared using .br unshare (). in particular, as at kernel 3.8, .\" fixme all of the following needs to be reviewed for the current kernel .br unshare () does not implement flags that reverse the effects of .br clone_sighand , .\" however, we can do unshare(clone_sighand) if clone_sighand .\" was not specified when doing clone(); i.e., unsharing .\" signal handlers is permitted if we are not actually .\" sharing signal handlers. mtk .br clone_thread , or .br clone_vm . .\" however, we can do unshare(clone_vm) if clone_vm .\" was not specified when doing clone(); i.e., unsharing .\" virtual memory is permitted if we are not actually .\" sharing virtual memory. mtk such functionality may be added in the future, if required. .\" .\"9) future work .\"-------------- .\"the current implementation of unshare does not allow unsharing of .\"signals and signal handlers. signals are complex to begin with and .\"to unshare signals and/or signal handlers of a currently running .\"process is even more complex. if in the future there is a specific .\"need to allow unsharing of signals and/or signal handlers, it can .\"be incrementally added to unshare without affecting legacy .\"applications using unshare. .\" .sh examples the program below provides a simple implementation of the .br unshare (1) command, which unshares one or more namespaces and executes the command supplied in its command-line arguments. here's an example of the use of this program, running a shell in a new mount namespace, and verifying that the original shell and the new shell are in separate mount namespaces: .pp .in +4n .ex $ \fbreadlink /proc/$$/ns/mnt\fp mnt:[4026531840] $ \fbsudo ./unshare \-m /bin/bash\fp # \fbreadlink /proc/$$/ns/mnt\fp mnt:[4026532325] .ee .in .pp the differing output of the two .br readlink (1) commands shows that the two shells are in different mount namespaces. .ss program source \& .ex /* unshare.c a simple implementation of the unshare(1) command: unshare namespaces and execute a command. */ #define _gnu_source #include #include #include #include /* a simple error\-handling function: print an error message based on the value in \(aqerrno\(aq and terminate the calling process. */ #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static void usage(char *pname) { fprintf(stderr, "usage: %s [options] program [arg...]\en", pname); fprintf(stderr, "options can be:\en"); fprintf(stderr, " \-c unshare cgroup namespace\en"); fprintf(stderr, " \-i unshare ipc namespace\en"); fprintf(stderr, " \-m unshare mount namespace\en"); fprintf(stderr, " \-n unshare network namespace\en"); fprintf(stderr, " \-p unshare pid namespace\en"); fprintf(stderr, " \-t unshare time namespace\en"); fprintf(stderr, " \-u unshare uts namespace\en"); fprintf(stderr, " \-u unshare user namespace\en"); exit(exit_failure); } int main(int argc, char *argv[]) { int flags, opt; flags = 0; while ((opt = getopt(argc, argv, "cimnptuu")) != \-1) { switch (opt) { case \(aqc\(aq: flags |= clone_newcgroup; break; case \(aqi\(aq: flags |= clone_newipc; break; case \(aqm\(aq: flags |= clone_newns; break; case \(aqn\(aq: flags |= clone_newnet; break; case \(aqp\(aq: flags |= clone_newpid; break; case \(aqt\(aq: flags |= clone_newtime; break; case \(aqu\(aq: flags |= clone_newuts; break; case \(aqu\(aq: flags |= clone_newuser; break; default: usage(argv[0]); } } if (optind >= argc) usage(argv[0]); if (unshare(flags) == \-1) errexit("unshare"); execvp(argv[optind], &argv[optind]); errexit("execvp"); } .ee .sh see also .br unshare (1), .br clone (2), .br fork (2), .br kcmp (2), .br setns (2), .br vfork (2), .br namespaces (7) .pp .i documentation/userspace\-api/unshare.rst in the linux kernel source tree .\" commit f504d47be5e8fa7ecf2bf660b18b42e6960c0eb2 (or .i documentation/unshare.txt before linux 4.12) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cproj.3 .\" %%%license_start(public_domain) .\" this page is in the public domain .\" %%%license_end .\" .th zic 8 2020-08-13 "" "linux system administration" .sh name zic \- timezone compiler .sh synopsis .b zic [ .i option \&... ] [ .i filename \&... ] .sh description .ie '\(lq'' .ds lq \&"\" .el .ds lq \(lq\" .ie '\(rq'' .ds rq \&"\" .el .ds rq \(rq\" .de q \\$3\*(lq\\$1\*(rq\\$2 .. .ie '\(la'' .ds < < .el .ds < \(la .ie '\(ra'' .ds > > .el .ds > \(ra .ie \n(.g \{\ . ds : \: . ds - \f(cw-\fp .\} .el \{\ . ds : . ds - \- .\} the .b zic program reads text from the file(s) named on the command line and creates the time conversion information files specified in this input. if a .i filename is .q "\*-" , standard input is read. .sh options .tp .b "\*-\*-version" output version information and exit. .tp .b \*-\*-help output short usage message and exit. .tp .bi "\*-b " bloat output backward-compatibility data as specified by .ir bloat . if .i bloat is .br fat , generate additional data entries that work around potential bugs or incompatibilities in older software, such as software that mishandles the 64-bit generated data. if .i bloat is .br slim , keep the output files small; this can help check for the bugs and incompatibilities. although the default is currently .br fat , this is intended to change in future .b zic versions, as software that mishandles the 64-bit data typically mishandles timestamps after the year 2038 anyway. also see the .b \*-r option for another way to shrink output size. .tp .bi "\*-d " directory create time conversion information files in the named directory rather than in the standard directory named below. .tp .bi "\*-l " timezone use .i timezone as local time. .b zic will act as if the input contained a link line of the form .sp .ti +.5i .ta \w'link\0\0'u +\w'\fitimezone\fp\0\0'u link \fitimezone\fp localtime .tp .bi "\*-l " leapsecondfilename read leap second information from the file with the given name. if this option is not used, no leap second information appears in output files. .tp .bi "\*-p " timezone use .ir timezone 's rules when handling nonstandard tz strings like "eet\*-2eest" that lack transition rules. .b zic will act as if the input contained a link line of the form .sp .ti +.5i link \fitimezone\fp posixrules .sp this feature is obsolete and poorly supported. among other things it should not be used for timestamps after the year 2037, and it should not be combined with .b "\*-b slim" if .ir timezone 's transitions are at standard time or universal time (ut) instead of local time. .tp .br "\*-r " "[\fb@\fp\filo\fp][\fb/@\fp\fihi\fp]" reduce the size of output files by limiting their applicability to timestamps in the range from .i lo (inclusive) to .i hi (exclusive), where .i lo and .i hi are possibly-signed decimal counts of seconds since the epoch (1970-01-01 00:00:00 utc). omitted counts default to extreme values. for example, .q "zic \*-r @0" omits data intended for negative timestamps (i.e., before the epoch), and .q "zic \*-r @0/@2147483648" outputs data intended only for nonnegative timestamps that fit into 31-bit signed integers. on platforms with gnu .br date , .q "zic \-r @$(date +%s)" omits data intended for past timestamps. also see the .b "\*-b slim" option for another way to shrink output size. .tp .bi "\*-t " file when creating local time information, put the configuration link in the named file rather than in the standard location. .tp .b \*-v be more verbose, and complain about the following situations: .rs .pp the input specifies a link to a link. .pp a year that appears in a data file is outside the range of representable years. .pp a time of 24:00 or more appears in the input. pre-1998 versions of .b zic prohibit 24:00, and pre-2007 versions prohibit times greater than 24:00. .pp a rule goes past the start or end of the month. pre-2004 versions of .b zic prohibit this. .pp a time zone abbreviation uses a .b %z format. pre-2015 versions of .b zic do not support this. .pp a timestamp contains fractional seconds. pre-2018 versions of .b zic do not support this. .pp the input contains abbreviations that are mishandled by pre-2018 versions of .b zic due to a longstanding coding bug. these abbreviations include .q l for .q link , .q mi for .q min , .q sa for .q sat , and .q su for .q sun . .pp the output file does not contain all the information about the long-term future of a timezone, because the future cannot be summarized as an extended posix tz string. for example, as of 2019 this problem occurs for iran's daylight-saving rules for the predicted future, as these rules are based on the iranian calendar, which cannot be represented. .pp the output contains data that may not be handled properly by client code designed for older .b zic output formats. these compatibility issues affect only timestamps before 1970 or after the start of 2038. .pp the output file contains more than 1200 transitions, which may be mishandled by some clients. the current reference client supports at most 2000 transitions; pre-2014 versions of the reference client support at most 1200 transitions. .pp a time zone abbreviation has fewer than 3 or more than 6 characters. posix requires at least 3, and requires implementations to support at least 6. .pp an output file name contains a byte that is not an ascii letter, .q "\*-" , .q "/" , or .q "_" ; or it contains a file name component that contains more than 14 bytes or that starts with .q "\*-" . .re .sh files input files use the format described in this section; output files use .br tzfile (5) format. .pp input files should be text files, that is, they should be a series of zero or more lines, each ending in a newline byte and containing at most 511 bytes, and without any nul bytes. the input text's encoding is typically utf-8 or ascii; it should have a unibyte representation for the posix portable character set (ppcs) \* and the encoding's non-unibyte characters should consist entirely of non-ppcs bytes. non-ppcs characters typically occur only in comments: although output file names and time zone abbreviations can contain nearly any character, other software will work better if these are limited to the restricted syntax described under the .b \*-v option. .pp input lines are made up of fields. fields are separated from one another by one or more white space characters. the white space characters are space, form feed, carriage return, newline, tab, and vertical tab. leading and trailing white space on input lines is ignored. an unquoted sharp character (#) in the input introduces a comment which extends to the end of the line the sharp character appears on. white space characters and sharp characters may be enclosed in double quotes (") if they're to be used as part of a field. any line that is blank (after comment stripping) is ignored. nonblank lines are expected to be of one of three types: rule lines, zone lines, and link lines. .pp names must be in english and are case insensitive. they appear in several contexts, and include month and weekday names and keywords such as .br "maximum" , .br "only" , .br "rolling" , and .br "zone" . a name can be abbreviated by omitting all but an initial prefix; any abbreviation must be unambiguous in context. .pp a rule line has the form .nf .ti +.5i .ta \w'rule\0\0'u +\w'name\0\0'u +\w'from\0\0'u +\w'1973\0\0'u +\w'type\0\0'u +\w'apr\0\0'u +\w'lastsun\0\0'u +\w'2:00w\0\0'u +\w'1:00d\0\0'u .sp rule name from to type in on at save letter/s .sp for example: .ti +.5i .sp rule us 1967 1973 \*- apr lastsun 2:00w 1:00d d .sp .fi the fields that make up a rule line are: .tp "\w'letter/s'u" .b name gives the name of the rule set that contains this line. the name must start with a character that is neither an ascii digit nor .q \*- nor .q + . to allow for future extensions, an unquoted name should not contain characters from the set .q !$%&'()*,/:;<=>?@[\e]\(ha\`{|}\(ti . .tp .b from gives the first year in which the rule applies. any signed integer year can be supplied; the proleptic gregorian calendar is assumed, with year 0 preceding year 1. the word .b minimum (or an abbreviation) means the indefinite past. the word .b maximum (or an abbreviation) means the indefinite future. rules can describe times that are not representable as time values, with the unrepresentable times ignored; this allows rules to be portable among hosts with differing time value types. .tp .b to gives the final year in which the rule applies. in addition to .b minimum and .b maximum (as above), the word .b only (or an abbreviation) may be used to repeat the value of the .b from field. .tp .b type should be .q \*- and is present for compatibility with older versions of .b zic in which it could contain year types. .tp .b in names the month in which the rule takes effect. month names may be abbreviated. .tp .b on gives the day on which the rule takes effect. recognized forms include: .nf .in +.5i .sp .ta \w'sun<=25\0\0'u 5 the fifth of the month lastsun the last sunday in the month lastmon the last monday in the month sun>=8 first sunday on or after the eighth sun<=25 last sunday on or before the 25th .fi .in -.5i .sp a weekday name (e.g., .br "sunday" ) or a weekday name preceded by .q "last" (e.g., .br "lastsunday" ) may be abbreviated or spelled out in full. there must be no white space characters within the .b on field. the .q <= and .q >= constructs can result in a day in the neighboring month; for example, the in-on combination .q "oct sun>=31" stands for the first sunday on or after october 31, even if that sunday occurs in november. .tp .b at gives the time of day at which the rule takes effect, relative to 00:00, the start of a calendar day. recognized forms include: .nf .in +.5i .sp .ta \w'00:19:32.13\0\0'u 2 time in hours 2:00 time in hours and minutes 01:28:14 time in hours, minutes, and seconds 00:19:32.13 time with fractional seconds 12:00 midday, 12 hours after 00:00 15:00 3 pm, 15 hours after 00:00 24:00 end of day, 24 hours after 00:00 260:00 260 hours after 00:00 \*-2:30 2.5 hours before 00:00 \*- equivalent to 0 .fi .in -.5i .sp although .b zic rounds times to the nearest integer second (breaking ties to the even integer), the fractions may be useful to other applications requiring greater precision. the source format does not specify any maximum precision. any of these forms may be followed by the letter .b w if the given time is local or .q "wall clock" time, .b s if the given time is standard time without any adjustment for daylight saving, or .b u (or .b g or .br z ) if the given time is universal time; in the absence of an indicator, local (wall clock) time is assumed. these forms ignore leap seconds; for example, if a leap second occurs at 00:59:60 local time, .q "1:00" stands for 3601 seconds after local midnight instead of the usual 3600 seconds. the intent is that a rule line describes the instants when a clock/calendar set to the type of time specified in the .b at field would show the specified date and time of day. .tp .b save gives the amount of time to be added to local standard time when the rule is in effect, and whether the resulting time is standard or daylight saving. this field has the same format as the .b at field except with a different set of suffix letters: .b s for standard time and .b d for daylight saving time. the suffix letter is typically omitted, and defaults to .b s if the offset is zero and to .b d otherwise. negative offsets are allowed; in ireland, for example, daylight saving time is observed in winter and has a negative offset relative to irish standard time. the offset is merely added to standard time; for example, .b zic does not distinguish a 10:30 standard time plus an 0:30 .b save from a 10:00 standard time plus a 1:00 .br save . .tp .b letter/s gives the .q "variable part" (for example, the .q "s" or .q "d" in .q "est" or .q "edt" ) of time zone abbreviations to be used when this rule is in effect. if this field is .q \*- , the variable part is null. .pp a zone line has the form .sp .nf .ti +.5i .ta \w'zone\0\0'u +\w'asia/amman\0\0'u +\w'stdoff\0\0'u +\w'jordan\0\0'u +\w'format\0\0'u zone name stdoff rules format [until] .sp for example: .sp .ti +.5i zone asia/amman 2:00 jordan ee%st 2017 oct 27 01:00 .sp .fi the fields that make up a zone line are: .tp "\w'stdoff'u" .b name the name of the timezone. this is the name used in creating the time conversion information file for the timezone. it should not contain a file name component .q ".\&" or .q ".." ; a file name component is a maximal substring that does not contain .q "/" . .tp .b stdoff the amount of time to add to ut to get standard time, without any adjustment for daylight saving. this field has the same format as the .b at and .b save fields of rule lines; begin the field with a minus sign if time must be subtracted from ut. .tp .b rules the name of the rules that apply in the timezone or, alternatively, a field in the same format as a rule-line save column, giving of the amount of time to be added to local standard time effect, and whether the resulting time is standard or daylight saving. if this field is .b \*- then standard time always applies. when an amount of time is given, only the sum of standard time and this amount matters. .tp .b format the format for time zone abbreviations. the pair of characters .b %s is used to show where the .q "variable part" of the time zone abbreviation goes. alternatively, a format can use the pair of characters .b %z to stand for the ut offset in the form .ri \(+- hh , .ri \(+- hhmm , or .ri \(+- hhmmss , using the shortest form that does not lose information, where .ir hh , .ir mm , and .i ss are the hours, minutes, and seconds east (+) or west (\(mi) of ut. alternatively, a slash (/) separates standard and daylight abbreviations. to conform to posix, a time zone abbreviation should contain only alphanumeric ascii characters, .q "+" and .q "\*-". .tp .b until the time at which the ut offset or the rule(s) change for a location. it takes the form of one to four fields year [month [day [time]]]. if this is specified, the time zone information is generated from the given ut offset and rule change until the time specified, which is interpreted using the rules in effect just before the transition. the month, day, and time of day have the same format as the in, on, and at fields of a rule; trailing fields can be omitted, and default to the earliest possible value for the missing fields. .ip the next line must be a .q "continuation" line; this has the same form as a zone line except that the string .q "zone" and the name are omitted, as the continuation line will place information starting at the time specified as the .q "until" information in the previous line in the file used by the previous line. continuation lines may contain .q "until" information, just as zone lines do, indicating that the next line is a further continuation. .pp if a zone changes at the same instant that a rule would otherwise take effect in the earlier zone or continuation line, the rule is ignored. a zone or continuation line .i l with a named rule set starts with standard time by default: that is, any of .ir l 's timestamps preceding .ir l 's earliest rule use the rule in effect after .ir l 's first transition into standard time. in a single zone it is an error if two rules take effect at the same instant, or if two zone changes take effect at the same instant. .pp a link line has the form .sp .nf .ti +.5i .ta \w'link\0\0'u +\w'europe/istanbul\0\0'u link target link-name .sp for example: .sp .ti +.5i link europe/istanbul asia/istanbul .sp .fi the .b target field should appear as the .b name field in some zone line. the .b link-name field is used as an alternative name for that zone; it has the same syntax as a zone line's .b name field. .pp except for continuation lines, lines may appear in any order in the input. however, the behavior is unspecified if multiple zone or link lines define the same name, or if the source of one link line is the target of another. .pp the file that describes leap seconds can have leap lines and an expiration line. leap lines have the following form: .nf .ti +.5i .ta \w'leap\0\0'u +\w'year\0\0'u +\w'month\0\0'u +\w'day\0\0'u +\w'hh:mm:ss\0\0'u +\w'corr\0\0'u .sp leap year month day hh:mm:ss corr r/s .sp for example: .ti +.5i .sp leap 2016 dec 31 23:59:60 + s .sp .fi the .br year , .br month , .br day , and .b hh:mm:ss fields tell when the leap second happened. the .b corr field should be .q "+" if a second was added or .q "\*-" if a second was skipped. the .b r/s field should be (an abbreviation of) .q "stationary" if the leap second time given by the other fields should be interpreted as utc or (an abbreviation of) .q "rolling" if the leap second time given by the other fields should be interpreted as local (wall clock) time. .pp the expiration line, if present, has the form: .nf .ti +.5i .ta \w'expires\0\0'u +\w'year\0\0'u +\w'month\0\0'u +\w'day\0\0'u .sp expires year month day hh:mm:ss .sp for example: .ti +.5i .sp expires 2020 dec 28 00:00:00 .sp .fi the .br year , .br month , .br day , and .b hh:mm:ss fields give the expiration timestamp in utc for the leap second table; .b zic outputs this expiration timestamp by truncating the end of the output file to the timestamp. if there is no expiration line, .b zic also accepts a comment .q "#expires \fie\fp ...\&" where .i e is the expiration timestamp as a decimal integer count of seconds since the epoch, not counting leap seconds. however, the .q "#expires" comment is an obsolescent feature, and the leap second file should use an expiration line instead of relying on a comment. .sh "extended example" here is an extended example of .b zic input, intended to illustrate many of its features. in this example, the eu rules are for the european union and for its predecessor organization, the european communities. .br .ne 22 .nf .in +2m .ta \w'# rule\0\0'u +\w'name\0\0'u +\w'from\0\0'u +\w'1973\0\0'u +\w'type\0\0'u +\w'apr\0\0'u +\w'lastsun\0\0'u +\w'2:00\0\0'u +\w'save\0\0'u .sp # rule name from to type in on at save letter/s rule swiss 1941 1942 \*- may mon>=1 1:00 1:00 s rule swiss 1941 1942 \*- oct mon>=1 2:00 0 \*- .sp .5 rule eu 1977 1980 \*- apr sun>=1 1:00u 1:00 s rule eu 1977 only \*- sep lastsun 1:00u 0 \*- rule eu 1978 only \*- oct 1 1:00u 0 \*- rule eu 1979 1995 \*- sep lastsun 1:00u 0 \*- rule eu 1981 max \*- mar lastsun 1:00u 1:00 s rule eu 1996 max \*- oct lastsun 1:00u 0 \*- .sp .ta \w'# zone\0\0'u +\w'europe/zurich\0\0'u +\w'0:29:45.50\0\0'u +\w'rules\0\0'u +\w'format\0\0'u # zone name stdoff rules format [until] zone europe/zurich 0:34:08 \*- lmt 1853 jul 16 0:29:45.50 \*- bmt 1894 jun 1:00 swiss ce%st 1981 1:00 eu ce%st .sp link europe/zurich europe/vaduz .sp .in .fi in this example, the timezone is named europe/zurich but it has an alias as europe/vaduz. this example says that zurich was 34 minutes and 8 seconds east of ut until 1853-07-16 at 00:00, when the legal offset was changed to .ds o 7 degrees 26 minutes 22.50 seconds .if \n(.g .if c \(de .if c \(fm .if c \(sd .ds o 7\(de\|26\(fm\|22.50\(sd \*o, which works out to 0:29:45.50; .b zic treats this by rounding it to 0:29:46. after 1894-06-01 at 00:00 the ut offset became one hour and swiss daylight saving rules (defined with lines beginning with .q "rule swiss") apply. from 1981 to the present, eu daylight saving rules have applied, and the utc offset has remained at one hour. .pp in 1941 and 1942, daylight saving time applied from the first monday in may at 01:00 to the first monday in october at 02:00. the pre-1981 eu daylight-saving rules have no effect here, but are included for completeness. since 1981, daylight saving has begun on the last sunday in march at 01:00 utc. until 1995 it ended the last sunday in september at 01:00 utc, but this changed to the last sunday in october starting in 1996. .pp for purposes of display, .q "lmt" and .q "bmt" were initially used, respectively. since swiss rules and later eu rules were applied, the time zone abbreviation has been cet for standard time and cest for daylight saving time. .sh files .tp .i /etc/localtime default local timezone file. .tp .i /usr/share/zoneinfo default timezone information directory. .sh notes for areas with more than two types of local time, you may need to use local standard time in the .b at field of the earliest transition time's rule to ensure that the earliest transition time recorded in the compiled file is correct. .pp if, for a particular timezone, a clock advance caused by the start of daylight saving coincides with and is equal to a clock retreat caused by a change in ut offset, .b zic produces a single transition to daylight saving at the new ut offset without any change in local (wall clock) time. to get separate transitions use multiple zone continuation lines specifying transition instants using universal time. .sh see also .br tzfile (5), .br zdump (8) .\" this file is in the public domain, so clarified as of .\" 2009-05-17 by arthur david olson. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-21 by rik faith .\" modified 1995-04-15 by michael chastain : .\" added 'fchdir'. fixed bugs in error section. .\" modified 1996-10-21 by eric s. raymond .\" modified 1997-08-21 by joseph s. myers .\" modified 2004-06-23 by michael kerrisk .\" .th chdir 2 2021-03-22 "linux" "linux programmer's manual" .sh name chdir, fchdir \- change working directory .sh synopsis .nf .b #include .pp .bi "int chdir(const char *" path ); .bi "int fchdir(int " fd ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fchdir (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc up to and including 2.19: */ _bsd_source .fi .sh description .br chdir () changes the current working directory of the calling process to the directory specified in .ir path . .pp .br fchdir () is identical to .br chdir (); the only difference is that the directory is given as an open file descriptor. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors depending on the filesystem, other errors can be returned. the more general errors for .br chdir () are listed below: .tp .b eacces search permission is denied for one of the components of .ir path . (see also .br path_resolution (7).) .tp .b efault .i path points outside your accessible address space. .tp .b eio an i/o error occurred. .tp .b eloop too many symbolic links were encountered in resolving .ir path . .tp .b enametoolong .i path is too long. .tp .b enoent the directory specified in .i path does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of .i path is not a directory. .pp the general errors for .br fchdir () are listed below: .tp .b eacces search permission was denied on the directory open on .ir fd . .tp .b ebadf .i fd is not a valid file descriptor. .tp .b enotdir .i fd does not refer to a directory. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd. .sh notes the current working directory is the starting point for interpreting relative pathnames (those not starting with \(aq/\(aq). .pp a child process created via .br fork (2) inherits its parent's current working directory. the current working directory is left unchanged by .br execve (2). .sh see also .br chroot (2), .br getcwd (3), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .so man8/ld.so.8 .so man3/endian.3 .so man3/lsearch.3 .so man2/unimplemented.2 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:00:12 1993 by rik faith (faith@cs.unc.edu) .th null 4 2015-07-23 "linux" "linux programmer's manual" .sh name null, zero \- data sink .sh description data written to the .ir /dev/null and .ir /dev/zero special files is discarded. .pp reads from .ir /dev/null always return end of file (i.e., .br read (2) returns 0), whereas reads from .ir /dev/zero always return bytes containing zero (\(aq\e0\(aq characters). .pp these devices are typically created by: .pp .in +4n .ex mknod \-m 666 /dev/null c 1 3 mknod \-m 666 /dev/zero c 1 5 chown root:root /dev/null /dev/zero .ee .in .sh files .i /dev/null .br .i /dev/zero .sh notes if these devices are not writable and readable for all users, many programs will act strangely. .pp since linux 2.6.31, .\" commit 2b83868723d090078ac0e2120e06a1cc94dbaef0 reads from .ir /dev/zero are interruptible by signals. (this change was made to help with bad latencies for large reads from .ir /dev/zero .) .sh see also .br chown (1), .br mknod (1), .br full (4) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getcontext.3 .so man7/system_data_types.7 .so man3/circleq.3 .so man2/unimplemented.2 .\" copyright (c) 2021 alejandro colomar .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th max 3 2020-11-01 "linux" "linux programmer's manual" .sh name max, min \- maximum or minimum of two values .sh synopsis .nf .b #include .pp .bi max( a ", " b ); .bi min( a ", " b ); .fi .sh description these macros return the maximum or minimum of .i a and .ir b . .sh return value these macros return the value of one of their arguments, possibly converted to a different type (see bugs). .sh errors these macros may raise the "invalid" floating-point exception when any of the arguments is nan. .sh conforming to these nonstandard macros are present in glibc and the bsds. .sh notes if either of the arguments is of a floating-point type, you might prefer to use .br fmax (3) or .br fmin (3), which can handle nan. .pp the arguments may be evaluated more than once, or not at all. .pp some unix systems might provide these macros in a different header, or not at all. .sh bugs due to the usual arithmetic conversions, the result of these macros may be very different from either of the arguments. to avoid this, ensure that both arguments have the same type. .sh examples .ex #include #include #include int main(int argc, char *argv[]) { int a, b, x; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } a = atoi(argv[1]); b = atoi(argv[2]); x = max(a, b); printf("max(%d, %d) is %d\en", a, b, x); exit(exit_success); } .ee .sh see also .br fmax (3), .br fmin (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 2008 michael kerrisk .\" and copyright 2003 abhijit menon-sen .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2004-05-31, added tgkill, ahu, aeb .\" 2008-01-15 mtk -- rewrote description .\" .th tkill 2 2021-03-22 "linux" "linux programmer's manual" .sh name tkill, tgkill \- send a signal to a thread .sh synopsis .nf .br "#include " " /* definition of " sig* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_tkill, pid_t " tid ", int " sig ); .pp .b #include .pp .bi "int tgkill(pid_t " tgid ", pid_t " tid ", int " sig ); .fi .pp .ir note : glibc provides no wrapper for .br tkill (), necessitating the use of .br syscall (2). .sh description .br tgkill () sends the signal .i sig to the thread with the thread id .i tid in the thread group .ir tgid . (by contrast, .br kill (2) can be used to send a signal only to a process (i.e., thread group) as a whole, and the signal will be delivered to an arbitrary thread within that process.) .pp .br tkill () is an obsolete predecessor to .br tgkill (). it allows only the target thread id to be specified, which may result in the wrong thread being signaled if a thread terminates and its thread id is recycled. avoid using this system call. .\" fixme maybe say something about the following: .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12889 .\" .\" quoting rich felker : .\" .\" there is a race condition in pthread_kill: it is possible that, .\" between the time pthread_kill reads the pid/tid from the target .\" thread descriptor and the time it makes the tgkill syscall, .\" the target thread terminates and the same tid gets assigned .\" to a new thread in the same process. .\" .\" (the tgkill syscall was designed to eliminate a similar race .\" condition in tkill, but it only succeeded in eliminating races .\" where the tid gets reused in a different process, and does not .\" help if the same tid gets assigned to a new thread in the .\" same process.) .\" .\" the only solution i can see is to introduce a mutex that ensures .\" that a thread cannot exit while pthread_kill is being called on it. .\" .\" note that in most real-world situations, like almost all race .\" conditions, this one will be extremely rare. to make it .\" measurable, one could exhaust all but 1-2 available pid values, .\" possibly by lowering the max pid parameter in /proc, forcing .\" the same tid to be reused rapidly. .pp these are the raw system call interfaces, meant for internal thread library use. .sh return value on success, zero is returned. on error, \-1 is returned, and \fierrno\fp is set to indicate the error. .sh errors .tp .b eagain the .b rlimit_sigpending resource limit was reached and .i sig is a real-time signal. .tp .b eagain insufficient kernel memory was available and .i sig is a real-time signal. .tp .b einval an invalid thread id, thread group id, or signal was specified. .tp .b eperm permission denied. for the required permissions, see .br kill (2). .tp .b esrch no process with the specified thread id (and thread group id) exists. .sh versions .br tkill () is supported since linux 2.4.19 / 2.5.4. .br tgkill () was added in linux 2.5.75. .pp library support for .br tgkill () was added to glibc in version 2.30. .sh conforming to .br tkill () and .br tgkill () are linux-specific and should not be used in programs that are intended to be portable. .sh notes see the description of .b clone_thread in .br clone (2) for an explanation of thread groups. .pp before glibc 2.30, there was also no wrapper function for .br tgkill (). .sh see also .br clone (2), .br gettid (2), .br kill (2), .br rt_sigqueueinfo (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/dprintf.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th clog2 3 2021-03-22 "" "linux programmer's manual" .sh name clog2, clog2f, clog2l \- base-2 logarithm of a complex number .sh synopsis .nf .b #include .pp .bi "double complex clog2(double complex " z ); .bi "float complex clog2f(float complex " z ); .bi "long double complex clog2l(long double complex " z ); .\" .pp .\" link with \fi\-lm\fp. .fi .sh description the call .i clog2(z) is equivalent to .ir clog(z)/log(2) . .pp the other functions perform the same task for .i float and .ir "long double" . .pp note that .i z close to zero will cause an overflow. .sh conforming to these function names are reserved for future use in c99. .pp not yet in glibc, as at version 2.19. .\" but reserved in namespace. .sh see also .br cabs (3), .br cexp (3), .br clog (3), .br clog10 (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2017 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th ioctl_ns 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_ns \- ioctl() operations for linux namespaces .sh description .\" ============================================================ .\" .ss discovering namespace relationships the following .br ioctl (2) operations are provided to allow discovery of namespace relationships (see .br user_namespaces (7) and .br pid_namespaces (7)). the form of the calls is: .pp .in +4n .ex new_fd = ioctl(fd, request); .ee .in .pp in each case, .i fd refers to a .ir /proc/[pid]/ns/* file. both operations return a new file descriptor on success. .tp .br ns_get_userns " (since linux 4.9)" .\" commit bcac25a58bfc6bd79191ac5d7afb49bea96da8c9 .\" commit 6786741dbf99e44fb0c0ed85a37582b8a26f1c3b returns a file descriptor that refers to the owning user namespace for the namespace referred to by .ir fd . .tp .br ns_get_parent " (since linux 4.9)" .\" commit a7306ed8d94af729ecef8b6e37506a1c6fc14788 returns a file descriptor that refers to the parent namespace of the namespace referred to by .ir fd . this operation is valid only for hierarchical namespaces (i.e., pid and user namespaces). for user namespaces, .br ns_get_parent is synonymous with .br ns_get_userns . .pp the new file descriptor returned by these operations is opened with the .br o_rdonly and .br o_cloexec (close-on-exec; see .br fcntl (2)) flags. .pp by applying .br fstat (2) to the returned file descriptor, one obtains a .i stat structure whose .i st_dev (resident device) and .i st_ino (inode number) fields together identify the owning/parent namespace. this inode number can be matched with the inode number of another .ir /proc/[pid]/ns/{pid,user} file to determine whether that is the owning/parent namespace. .pp either of these .br ioctl (2) operations can fail with the following errors: .tp .b eperm the requested namespace is outside of the caller's namespace scope. this error can occur if, for example, the owning user namespace is an ancestor of the caller's current user namespace. it can also occur on attempts to obtain the parent of the initial user or pid namespace. .tp .b enotty the operation is not supported by this kernel version. .pp additionally, the .b ns_get_parent operation can fail with the following error: .tp .b einval .i fd refers to a nonhierarchical namespace. .pp see the examples section for an example of the use of these operations. .\" ============================================================ .\" .ss discovering the namespace type the .b ns_get_nstype .\" commit e5ff5ce6e20ee22511398bb31fb912466cf82a36 operation (available since linux 4.11) can be used to discover the type of namespace referred to by the file descriptor .ir fd : .pp .in +4n .ex nstype = ioctl(fd, ns_get_nstype); .ee .in .pp .i fd refers to a .ir /proc/[pid]/ns/* file. .pp the return value is one of the .br clone_new* values that can be specified to .br clone (2) or .br unshare (2) in order to create a namespace. .\" ============================================================ .\" .ss discovering the owner of a user namespace the .b ns_get_owner_uid .\" commit 015bb305b8ebe8d601a238ab70ebdc394c7a19ba operation (available since linux 4.11) can be used to discover the owner user id of a user namespace (i.e., the effective user id of the process that created the user namespace). the form of the call is: .pp .in +4n .ex uid_t uid; ioctl(fd, ns_get_owner_uid, &uid); .ee .in .pp .i fd refers to a .ir /proc/[pid]/ns/user file. .pp the owner user id is returned in the .i uid_t pointed to by the third argument. .pp this operation can fail with the following error: .tp .b einval .i fd does not refer to a user namespace. .sh errors any of the above .br ioctl () operations can return the following errors: .tp .b enotty .i fd does not refer to a .i /proc/[pid]/ns/* file. .sh conforming to namespaces and the operations described on this page are a linux-specific. .sh examples the example shown below uses the .br ioctl (2) operations described above to perform simple discovery of namespace relationships. the following shell sessions show various examples of the use of this program. .pp trying to get the parent of the initial user namespace fails, since it has no parent: .pp .in +4n .ex $ \fb./ns_show /proc/self/ns/user p\fp the parent namespace is outside your namespace scope .ee .in .pp create a process running .br sleep (1) that resides in new user and uts namespaces, and show that the new uts namespace is associated with the new user namespace: .pp .in +4n .ex $ \fbunshare \-uu sleep 1000 &\fp [1] 23235 $ \fb./ns_show /proc/23235/ns/uts u\fp device/inode of owning user namespace is: [0,3] / 4026532448 $ \fbreadlink /proc/23235/ns/user\fp user:[4026532448] .ee .in .pp then show that the parent of the new user namespace in the preceding example is the initial user namespace: .pp .in +4n .ex $ \fbreadlink /proc/self/ns/user\fp user:[4026531837] $ \fb./ns_show /proc/23235/ns/user p\fp device/inode of parent namespace is: [0,3] / 4026531837 .ee .in .pp start a shell in a new user namespace, and show that from within this shell, the parent user namespace can't be discovered. similarly, the uts namespace (which is associated with the initial user namespace) can't be discovered. .pp .in +4n .ex $ \fbps1="sh2$ " unshare \-u bash\fp sh2$ \fb./ns_show /proc/self/ns/user p\fp the parent namespace is outside your namespace scope sh2$ \fb./ns_show /proc/self/ns/uts u\fp the owning user namespace is outside your namespace scope .ee .in .ss program source \& .ex /* ns_show.c licensed under the gnu general public license v2 or later. */ #include #include #include #include #include #include #include #include #include #include #ifndef ns_get_userns #define nsio 0xb7 #define ns_get_userns _io(nsio, 0x1) #define ns_get_parent _io(nsio, 0x2) #endif int main(int argc, char *argv[]) { int fd, userns_fd, parent_fd; struct stat sb; if (argc < 2) { fprintf(stderr, "usage: %s /proc/[pid]/ns/[file] [p|u]\en", argv[0]); fprintf(stderr, "\endisplay the result of one or both " "of ns_get_userns (u) or ns_get_parent (p)\en" "for the specified /proc/[pid]/ns/[file]. if neither " "\(aqp\(aq nor \(aqu\(aq is specified,\en" "ns_get_userns is the default.\en"); exit(exit_failure); } /* obtain a file descriptor for the \(aqns\(aq file specified in argv[1]. */ fd = open(argv[1], o_rdonly); if (fd == \-1) { perror("open"); exit(exit_failure); } /* obtain a file descriptor for the owning user namespace and then obtain and display the inode number of that namespace. */ if (argc < 3 || strchr(argv[2], \(aqu\(aq)) { userns_fd = ioctl(fd, ns_get_userns); if (userns_fd == \-1) { if (errno == eperm) printf("the owning user namespace is outside " "your namespace scope\en"); else perror("ioctl\-ns_get_userns"); exit(exit_failure); } if (fstat(userns_fd, &sb) == \-1) { perror("fstat\-userns"); exit(exit_failure); } printf("device/inode of owning user namespace is: " "[%jx,%jx] / %ju\en", (uintmax_t) major(sb.st_dev), (uintmax_t) minor(sb.st_dev), (uintmax_t) sb.st_ino); close(userns_fd); } /* obtain a file descriptor for the parent namespace and then obtain and display the inode number of that namespace. */ if (argc > 2 && strchr(argv[2], \(aqp\(aq)) { parent_fd = ioctl(fd, ns_get_parent); if (parent_fd == \-1) { if (errno == einval) printf("can\(aq get parent namespace of a " "nonhierarchical namespace\en"); else if (errno == eperm) printf("the parent namespace is outside " "your namespace scope\en"); else perror("ioctl\-ns_get_parent"); exit(exit_failure); } if (fstat(parent_fd, &sb) == \-1) { perror("fstat\-parentns"); exit(exit_failure); } printf("device/inode of parent namespace is: [%jx,%jx] / %ju\en", (uintmax_t) major(sb.st_dev), (uintmax_t) minor(sb.st_dev), (uintmax_t) sb.st_ino); close(parent_fd); } exit(exit_success); } .ee .sh see also .br fstat (2), .br ioctl (2), .br proc (5), .br namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scalbln.3 .so man3/sincos.3 .\" copyright 1993 giorgio ciucci (giorgio@crcc.it) .\" and copyright 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sun nov 28 17:06:19 1993, rik faith (faith@cs.unc.edu) .\" with material from luigi p. bai (lpb@softint.com) .\" portions copyright 1993 luigi p. bai .\" modified tue oct 22 22:04:23 1996 by eric s. raymond .\" modified, 5 jan 2002, michael kerrisk .\" modified, 19 sep 2002, michael kerrisk .\" added shm_remap flag description .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" changed wording and placement of sentence regarding attachment .\" of segments marked for destruction .\" .th shmop 2 2021-03-22 "linux" "linux programmer's manual" .sh name shmat, shmdt \- system v shared memory operations .sh synopsis .nf .b #include .pp .bi "void *shmat(int " shmid ", const void *" shmaddr ", int " shmflg ); .bi "int shmdt(const void *" shmaddr ); .fi .sh description .ss shmat() .br shmat () attaches the system\ v shared memory segment identified by .i shmid to the address space of the calling process. the attaching address is specified by .i shmaddr with one of the following criteria: .ip \(bu 2 if .i shmaddr is null, the system chooses a suitable (unused) page-aligned address to attach the segment. .ip \(bu if .i shmaddr isn't null and .b shm_rnd is specified in .ir shmflg , the attach occurs at the address equal to .i shmaddr rounded down to the nearest multiple of .br shmlba . .ip \(bu otherwise, .i shmaddr must be a page-aligned address at which the attach occurs. .pp in addition to .br shm_rnd , the following flags may be specified in the .i shmflg bit-mask argument: .tp .br shm_exec " (linux-specific; since linux 2.6.9)" allow the contents of the segment to be executed. the caller must have execute permission on the segment. .tp .br shm_rdonly attach the segment for read-only access. the process must have read permission for the segment. if this flag is not specified, the segment is attached for read and write access, and the process must have read and write permission for the segment. there is no notion of a write-only shared memory segment. .tp .br shm_remap " (linux-specific)" this flag specifies that the mapping of the segment should replace any existing mapping in the range starting at .i shmaddr and continuing for the size of the segment. (normally, an .b einval error would result if a mapping already exists in this address range.) in this case, .i shmaddr must not be null. .pp the .br brk (2) value of the calling process is not altered by the attach. the segment will automatically be detached at process exit. the same segment may be attached as a read and as a read-write one, and more than once, in the process's address space. .pp a successful .br shmat () call updates the members of the .i shmid_ds structure (see .br shmctl (2)) associated with the shared memory segment as follows: .ip \(bu 2 .i shm_atime is set to the current time. .ip \(bu .i shm_lpid is set to the process-id of the calling process. .ip \(bu .i shm_nattch is incremented by one. .\" .ss shmdt() .br shmdt () detaches the shared memory segment located at the address specified by .i shmaddr from the address space of the calling process. the to-be-detached segment must be currently attached with .i shmaddr equal to the value returned by the attaching .br shmat () call. .pp on a successful .br shmdt () call, the system updates the members of the .i shmid_ds structure associated with the shared memory segment as follows: .ip \(bu 2 .i shm_dtime is set to the current time. .ip \(bu .i shm_lpid is set to the process-id of the calling process. .ip \(bu .i shm_nattch is decremented by one. if it becomes 0 and the segment is marked for deletion, the segment is deleted. .sh return value on success, .br shmat () returns the address of the attached shared memory segment; on error, .i (void\ *)\ \-1 is returned, and .i errno is set to indicate the error. .pp on success, .br shmdt () returns 0; on error \-1 is returned, and .i errno is set to indicate the error. .sh errors .br shmat () can fail with one of the following errors: .tp .b eacces the calling process does not have the required permissions for the requested attach type, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b eidrm \fishmid\fp points to a removed identifier. .tp .b einval invalid .i shmid value, unaligned (i.e., not page-aligned and \fbshm_rnd\fp was not specified) or invalid .i shmaddr value, or can't attach segment at .ir shmaddr , or .b shm_remap was specified and .i shmaddr was null. .tp .b enomem could not allocate memory for the descriptor or for the page tables. .pp .br shmdt () can fail with one of the following errors: .tp .b einval there is no shared memory segment attached at .ir shmaddr ; or, .\" the following since 2.6.17-rc1: .i shmaddr is not aligned on a page boundary. .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svr4 documents an additional error condition emfile. .pp in svid 3 (or perhaps earlier), the type of the \fishmaddr\fp argument was changed from .i "char\ *" into .ir "const void\ *" , and the returned type of .br shmat () from .i "char\ *" into .ir "void\ *" . .sh notes after a .br fork (2), the child inherits the attached shared memory segments. .pp after an .br execve (2), all attached shared memory segments are detached from the process. .pp upon .br _exit (2), all attached shared memory segments are detached from the process. .pp using .br shmat () with .i shmaddr equal to null is the preferred, portable way of attaching a shared memory segment. be aware that the shared memory segment attached in this way may be attached at different addresses in different processes. therefore, any pointers maintained within the shared memory must be made relative (typically to the starting address of the segment), rather than absolute. .pp on linux, it is possible to attach a shared memory segment even if it is already marked to be deleted. however, posix.1 does not specify this behavior and many other implementations do not support it. .pp the following system parameter affects .br shmat (): .tp .b shmlba segment low boundary address multiple. when explicitly specifying an attach address in a call to .br shmat (), the caller should ensure that the address is a multiple of this value. this is necessary on some architectures, in order either to ensure good cpu cache performance or to ensure that different attaches of the same segment have consistent views within the cpu cache. .b shmlba is normally some multiple of the system page size. (on many linux architectures, .b shmlba is the same as the system page size.) .pp the implementation places no intrinsic per-process limit on the number of shared memory segments .rb ( shmseg ). .sh examples the two programs shown below exchange a string using a shared memory segment. further details about the programs are given below. first, we show a shell session demonstrating their use. .pp in one terminal window, we run the "reader" program, which creates a system v shared memory segment and a system v semaphore set. the program prints out the ids of the created objects, and then waits for the semaphore to change value. .pp .in +4n .ex $ \fb./svshm_string_read\fp shmid = 1114194; semid = 15 .ee .in .pp in another terminal window, we run the "writer" program. the "writer" program takes three command-line arguments: the ids of the shared memory segment and semaphore set created by the "reader", and a string. it attaches the existing shared memory segment, copies the string to the shared memory, and modifies the semaphore value. .pp .in +4n .ex $ \fb./svshm_string_write 1114194 15 \(aqhello, world\(aq\fp .ee .in .pp returning to the terminal where the "reader" is running, we see that the program has ceased waiting on the semaphore and has printed the string that was copied into the shared memory segment by the writer: .pp .in +4n .ex hello, world .ee .in .\" .ss program source: svshm_string.h the following header file is included by the "reader" and "writer" programs: .pp .in +4n .ex /* svshm_string.h licensed under gnu general public license v2 or later. */ #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) union semun { /* used in calls to semctl() */ int val; struct semid_ds * buf; unsigned short * array; #if defined(__linux__) struct seminfo * __buf; #endif }; #define mem_size 4096 .ee .in .\" .ss program source: svshm_string_read.c the "reader" program creates a shared memory segment and a semaphore set containing one semaphore. it then attaches the shared memory object into its address space and initializes the semaphore value to 1. finally, the program waits for the semaphore value to become 0, and afterwards prints the string that has been copied into the shared memory segment by the "writer". .pp .in +4n .ex /* svshm_string_read.c licensed under gnu general public license v2 or later. */ #include "svshm_string.h" int main(int argc, char *argv[]) { int semid, shmid; union semun arg, dummy; struct sembuf sop; char *addr; /* create shared memory and semaphore set containing one semaphore. */ shmid = shmget(ipc_private, mem_size, ipc_creat | 0600); if (shmid == \-1) errexit("shmget"); semid = semget(ipc_private, 1, ipc_creat | 0600); if (semid == \-1) errexit("semget"); /* attach shared memory into our address space. */ addr = shmat(shmid, null, shm_rdonly); if (addr == (void *) \-1) errexit("shmat"); /* initialize semaphore 0 in set with value 1. */ arg.val = 1; if (semctl(semid, 0, setval, arg) == \-1) errexit("semctl"); printf("shmid = %d; semid = %d\en", shmid, semid); /* wait for semaphore value to become 0. */ sop.sem_num = 0; sop.sem_op = 0; sop.sem_flg = 0; if (semop(semid, &sop, 1) == \-1) errexit("semop"); /* print the string from shared memory. */ printf("%s\en", addr); /* remove shared memory and semaphore set. */ if (shmctl(shmid, ipc_rmid, null) == \-1) errexit("shmctl"); if (semctl(semid, 0, ipc_rmid, dummy) == \-1) errexit("semctl"); exit(exit_success); } .ee .in .\" .ss program source: svshm_string_write.c the writer program takes three command-line arguments: the ids of the shared memory segment and semaphore set that have already been created by the "reader", and a string. it attaches the shared memory segment into its address space, and then decrements the semaphore value to 0 in order to inform the "reader" that it can now examine the contents of the shared memory. .pp .in +4n .ex /* svshm_string_write.c licensed under gnu general public license v2 or later. */ #include "svshm_string.h" int main(int argc, char *argv[]) { int semid, shmid; struct sembuf sop; char *addr; size_t len; if (argc != 4) { fprintf(stderr, "usage: %s shmid semid string\en", argv[0]); exit(exit_failure); } len = strlen(argv[3]) + 1; /* +1 to include trailing \(aq\e0\(aq */ if (len > mem_size) { fprintf(stderr, "string is too big!\en"); exit(exit_failure); } /* get object ids from command\-line. */ shmid = atoi(argv[1]); semid = atoi(argv[2]); /* attach shared memory into our address space and copy string (including trailing null byte) into memory. */ addr = shmat(shmid, null, 0); if (addr == (void *) \-1) errexit("shmat"); memcpy(addr, argv[3], len); /* decrement semaphore to 0. */ sop.sem_num = 0; sop.sem_op = \-1; sop.sem_flg = 0; if (semop(semid, &sop, 1) == \-1) errexit("semop"); exit(exit_success); } .ee .in .sh see also .br brk (2), .br mmap (2), .br shmctl (2), .br shmget (2), .br capabilities (7), .br shm_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 2006, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th feature_test_macros 7 2021-03-22 "linux" "linux programmer's manual" .sh name feature_test_macros \- feature test macros .sh description feature test macros allow the programmer to control the definitions that are exposed by system header files when a program is compiled. .pp .b note: in order to be effective, a feature test macro .ir "must be defined before including any header files" . this can be done either in the compilation command .ri ( "cc \-dmacro=value" ) or by defining the macro within the source code before including any headers. the requirement that the macro must be defined before including any header file exists because header files may freely include one another. thus, for example, in the following lines, defining the .b _gnu_source macro may have no effect because the header .i itself includes .i (posix explicitly allows this): .pp .in +4n .ex #include #define _gnu_source #include .ee .in .pp some feature test macros are useful for creating portable applications, by preventing nonstandard definitions from being exposed. other macros can be used to expose nonstandard definitions that are not exposed by default. .pp the precise effects of each of the feature test macros described below can be ascertained by inspecting the .i header file. .br note : applications do .i not need to directly include .ir ; indeed, doing so is actively discouraged. see notes. .ss specification of feature test macro requirements in manual pages when a function requires that a feature test macro is defined, the manual page synopsis typically includes a note of the following form (this example from the .br acct (2) manual page): .pp .rs .b #include .pp .bi "int acct(const char *" filename ); .pp .rs -4 .ex feature test macro requirements for glibc (see .br feature_test_macros (7)): .ee .re .pp .br acct (): _bsd_source || (_xopen_source && _xopen_source < 500) .re .pp the .b || means that in order to obtain the declaration of .br acct (2) from .ir , .i either of the following macro definitions must be made before including any header files: .pp .in +4n .ex #define _bsd_source #define _xopen_source /* or any value < 500 */ .ee .in .pp alternatively, equivalent definitions can be included in the compilation command: .pp .in +4n .ex cc \-d_bsd_source cc \-d_xopen_source # or any value < 500 .ee .in .pp note that, as described below, .br "some feature test macros are defined by default" , so that it may not always be necessary to explicitly specify the feature test macro(s) shown in the synopsis. .pp in a few cases, manual pages use a shorthand for expressing the feature test macro requirements (this example from .br readahead (2)): .pp .rs +4 .ex .b #define _gnu_source .b #include .pp .bi "ssize_t readahead(int " fd ", off64_t *" offset ", size_t " count ); .ee .re .pp this format is employed in cases where only a single feature test macro can be used to expose the function declaration, and that macro is not defined by default. .ss feature test macros understood by glibc the paragraphs below explain how feature test macros are handled in glibc 2.\fix\fp, .i x > 0. .pp first, though, a summary of a few details for the impatient: .ip * 3 the macros that you most likely need to use in modern source code are .br _posix_c_source (for definitions from various versions of posix.1), .br _xopen_source (for definitions from various versions of sus), .br _gnu_source (for gnu and/or linux specific stuff), and .br _default_source (to get definitions that would normally be provided by default). .ip * certain macros are defined with default values. thus, although one or more macros may be indicated as being required in the synopsis of a man page, it may not be necessary to define them explicitly. full details of the defaults are given later in this man page. .ip * defining .br _xopen_source with a value of 600 or greater produces the same effects as defining .br _posix_c_source with a value of 200112l or greater. where one sees .ip .in +4n .ex _posix_c_source >= 200112l .ee .in .ip in the feature test macro requirements in the synopsis of a man page, it is implicit that the following has the same effect: .ip .in +4n .ex _xopen_source >= 600 .ee .in .ip * defining .br _xopen_source with a value of 700 or greater produces the same effects as defining .br _posix_c_source with a value of 200809l or greater. where one sees .ip .in +4n .ex _posix_c_source >= 200809l .ee .in .ip in the feature test macro requirements in the synopsis of a man page, it is implicit that the following has the same effect: .ip .in +4n .ex _xopen_source >= 700 .ee .in .\" the details in glibc 2.0 are simpler, but combining a .\" a description of them with the details in later glibc versions .\" would make for a complicated description. .pp glibc understands the following feature test macros: .tp .b __strict_ansi__ iso standard c. this macro is implicitly defined by .br gcc (1) when invoked with, for example, the .i \-std=c99 or .i \-ansi flag. .tp .b _posix_c_source defining this macro causes header files to expose definitions as follows: .rs .ip \(bu 3 the value 1 exposes definitions conforming to posix.1-1990 and iso c (1990). .ip \(bu the value 2 or greater additionally exposes definitions for posix.2-1992. .ip \(bu the value 199309l or greater additionally exposes definitions for posix.1b (real-time extensions). .\" 199506l functionality is available only since glibc 2.1 .ip \(bu the value 199506l or greater additionally exposes definitions for posix.1c (threads). .ip \(bu (since glibc 2.3.3) the value 200112l or greater additionally exposes definitions corresponding to the posix.1-2001 base specification (excluding the xsi extension). this value also causes c95 (since glibc 2.12) and c99 (since glibc 2.10) features to be exposed (in other words, the equivalent of defining .br _isoc99_source ). .ip \(bu (since glibc 2.10) the value 200809l or greater additionally exposes definitions corresponding to the posix.1-2008 base specification (excluding the xsi extension). .re .tp .b _posix_source defining this obsolete macro with any value is equivalent to defining .b _posix_c_source with the value 1. .ip since this macro is obsolete, its usage is generally not documented when discussing feature test macro requirements in the man pages. .tp .b _xopen_source defining this macro causes header files to expose definitions as follows: .rs .ip \(bu 3 defining with any value exposes definitions conforming to posix.1, posix.2, and xpg4. .ip \(bu the value 500 or greater additionally exposes definitions for susv2 (unix 98). .ip \(bu (since glibc 2.2) the value 600 or greater additionally exposes definitions for susv3 (unix 03; i.e., the posix.1-2001 base specification plus the xsi extension) and c99 definitions. .ip \(bu (since glibc 2.10) the value 700 or greater additionally exposes definitions for susv4 (i.e., the posix.1-2008 base specification plus the xsi extension). .re .ip if .b __strict_ansi__ is not defined, or .br _xopen_source is defined with a value greater than or equal to 500 .i and neither .b _posix_source nor .b _posix_c_source is explicitly defined, then the following macros are implicitly defined: .rs .ip \(bu 3 .b _posix_source is defined with the value 1. .ip \(bu .b _posix_c_source is defined, according to the value of .br _xopen_source : .rs .tp .br _xopen_source " < 500" .b _posix_c_source is defined with the value 2. .tp .rb "500 <= " _xopen_source " < 600" .b _posix_c_source is defined with the value 199506l. .tp .rb "600 <= " _xopen_source " < 700" .b _posix_c_source is defined with the value 200112l. .tp .rb "700 <= " _xopen_source " (since glibc 2.10)" .b _posix_c_source is defined with the value 200809l. .re .re .ip in addition, defining .br _xopen_source with a value of 500 or greater produces the same effects as defining .br _xopen_source_extended . .tp .b _xopen_source_extended if this macro is defined, .i and .b _xopen_source is defined, then expose definitions corresponding to the xpg4v2 (susv1) unix extensions (unix 95). defining .b _xopen_source with a value of 500 or more also produces the same effect as defining .br _xopen_source_extended . use of .br _xopen_source_extended in new source code should be avoided. .ip since defining .b _xopen_source with a value of 500 or more has the same effect as defining .br _xopen_source_extended , the latter (obsolete) feature test macro is generally not described in the synopsis in man pages. .tp .br _isoc99_source " (since glibc 2.1.3)" exposes declarations consistent with the iso c99 standard. .ip earlier glibc 2.1.x versions recognized an equivalent macro named .b _isoc9x_source (because the c99 standard had not then been finalized). although the use of this macro is obsolete, glibc continues to recognize it for backward compatibility. .ip defining .b _isoc99_source also exposes iso c (1990) amendment 1 ("c95") definitions. (the primary change in c95 was support for international character sets.) .ip invoking the c compiler with the option .ir \-std=c99 produces the same effects as defining this macro. .tp .br _isoc11_source " (since glibc 2.16)" exposes declarations consistent with the iso c11 standard. defining this macro also enables c99 and c95 features (like .br _isoc99_source ). .ip invoking the c compiler with the option .ir \-std=c11 produces the same effects as defining this macro. .tp .b _largefile64_source expose definitions for the alternative api specified by the lfs (large file summit) as a "transitional extension" to the single unix specification. (see .ur http:\:/\:/opengroup.org\:/platform\:/lfs.html .ue .) the alternative api consists of a set of new objects (i.e., functions and types) whose names are suffixed with "64" (e.g., .i off64_t versus .ir off_t , .br lseek64 () versus .br lseek (), etc.). new programs should not employ this macro; instead .i _file_offset_bits=64 should be employed. .tp .br _largefile_source this macro was historically used to expose certain functions (specifically .br fseeko (3) and .br ftello (3)) that address limitations of earlier apis .rb ( fseek (3) and .br ftell (3)) that use .ir "long" for file offsets. this macro is implicitly defined if .br _xopen_source is defined with a value greater than or equal to 500. new programs should not employ this macro; defining .br _xopen_source as just described or defining .b _file_offset_bits with the value 64 is the preferred mechanism to achieve the same result. .tp .b _file_offset_bits defining this macro with the value 64 automatically converts references to 32-bit functions and data types related to file i/o and filesystem operations into references to their 64-bit counterparts. this is useful for performing i/o on large files (> 2 gigabytes) on 32-bit systems. (defining this macro permits correctly written programs to use large files with only a recompilation being required.) .ip 64-bit systems naturally permit file sizes greater than 2 gigabytes, and on those systems this macro has no effect. .tp .br _bsd_source " (deprecated since glibc 2.20)" defining this macro with any value causes header files to expose bsd-derived definitions. .ip in glibc versions up to and including 2.18, defining this macro also causes bsd definitions to be preferred in some situations where standards conflict, unless one or more of .br _svid_source , .br _posix_source , .br _posix_c_source , .br _xopen_source , .br _xopen_source_extended , or .b _gnu_source is defined, in which case bsd definitions are disfavored. since glibc 2.19, .b _bsd_source no longer causes bsd definitions to be preferred in case of conflicts. .ip since glibc 2.20, this macro is deprecated. .\" commit c941736c92fa3a319221f65f6755659b2a5e0a20 .\" commit 498afc54dfee41d33ba519f496e96480badace8e .\" commit acd7f096d79c181866d56d4aaf3b043e741f1e2c it now has the same effect as defining .br _default_source , but generates a compile-time warning (unless .br _default_source .\" commit ade40b10ff5fa59a318cf55b9d8414b758e8df78 is also defined). use .b _default_source instead. to allow code that requires .br _bsd_source in glibc 2.19 and earlier and .br _default_source in glibc 2.20 and later to compile without warnings, define .i both .b _bsd_source and .br _default_source . .tp .br _svid_source " (deprecated since glibc 2.20)" defining this macro with any value causes header files to expose system v-derived definitions. (svid == system v interface definition; see .br standards (7).) .ip since glibc 2.20, this macro is deprecated in the same fashion as .br _bsd_source . .tp .br _default_source " (since glibc 2.19)" this macro can be defined to ensure that the "default" definitions are provided even when the defaults would otherwise be disabled, as happens when individual macros are explicitly defined, or the compiler is invoked in one of its "standard" modes (e.g., .ir "cc\ \-std=c99" ). defining .b _default_source without defining other individual macros or invoking the compiler in one of its "standard" modes has no effect. .ip the "default" definitions comprise those required by posix.1-2008 and iso c99, as well as various definitions originally derived from bsd and system v. on glibc 2.19 and earlier, these defaults were approximately equivalent to explicitly defining the following: .ip cc \-d_bsd_source \-d_svid_source \-d_posix_c_source=200809 .tp .br _atfile_source " (since glibc 2.4)" defining this macro with any value causes header files to expose declarations of a range of functions with the suffix "at"; see .br openat (2). since glibc 2.10, this macro is also implicitly defined if .br _posix_c_source is defined with a value greater than or equal to 200809l. .tp .b _gnu_source defining this macro (with any value) implicitly defines .br _atfile_source , .br _largefile64_source , .br _isoc99_source , .br _xopen_source_extended , .br _posix_source , .b _posix_c_source with the value 200809l (200112l in glibc versions before 2.10; 199506l in glibc versions before 2.5; 199309l in glibc versions before 2.1) and .b _xopen_source with the value 700 (600 in glibc versions before 2.10; 500 in glibc versions before 2.2). in addition, various gnu-specific extensions are also exposed. .ip since glibc 2.19, defining .br _gnu_source also has the effect of implicitly defining .br _default_source . in glibc versions before 2.20, defining .br _gnu_source also had the effect of implicitly defining .br _bsd_source and .br _svid_source . .tp .b _reentrant historically, on various c libraries it was necessary to define this macro in all multithreaded code. .\" zack weinberg .\" there did once exist c libraries where it was necessary. the ones .\" i remember were proprietary unix vendor libcs from the mid-1990s .\" you would get completely unlocked stdio without _reentrant. (some c libraries may still require this.) in glibc, this macro also exposed definitions of certain reentrant functions. .ip however, glibc has been thread-safe by default for many years; since glibc 2.3, the only effect of defining .br _reentrant has been to enable one or two of the same declarations that are also enabled by defining .br _posix_c_source with a value of 199606l or greater. .ip .b _reentrant is now obsolete. in glibc 2.25 and later, defining .b _reentrant is equivalent to defining .b _posix_c_source with the value 199606l. if a higher posix conformance level is selected by any other means (such as .b _posix_c_source itself, .br _xopen_source , .br _default_source , or .br _gnu_source ), then defining .b _reentrant has no effect. .ip this macro is automatically defined if one compiles with .ir "cc\ \-pthread" . .tp .b _thread_safe synonym for the (deprecated) .br _reentrant , provided for compatibility with some other implementations. .tp .br _fortify_source " (since glibc 2.3.4)" .\" for more detail, see: .\" http://gcc.gnu.org/ml/gcc-patches/2004-09/msg02055.html .\" [patch] object size checking to prevent (some) buffer overflows .\" * from: jakub jelinek .\" * to: gcc-patches at gcc dot gnu dot org .\" * date: tue, 21 sep 2004 04:16:40 -0400 defining this macro causes some lightweight checks to be performed to detect some buffer overflow errors when employing various string and memory manipulation functions (for example, .br memcpy (3), .br memset (3), .br stpcpy (3), .br strcpy (3), .br strncpy (3), .br strcat (3), .br strncat (3), .br sprintf (3), .br snprintf (3), .br vsprintf (3), .br vsnprintf (3), .br gets (3), and wide character variants thereof). for some functions, argument consistency is checked; for example, a check is made that .br open (2) has been supplied with a .i mode argument when the specified flags include .br o_creat . not all problems are detected, just some common cases. .\" look for __use_fortify_level in the header files .ip if .b _fortify_source is set to 1, with compiler optimization level 1 .ri ( "gcc\ \-o1" ) and above, checks that shouldn't change the behavior of conforming programs are performed. with .b _fortify_source set to 2, some more checking is added, but some conforming programs might fail. .\" for example, given the following code .\" int d; .\" char buf[1000], buf[1000]; .\" strcpy(fmt, "hello world\n%n"); .\" snprintf(buf, sizeof(buf), fmt, &d); .\" .\" compiling with "gcc -d_fortify_source=2 -o1" and then running will .\" cause the following diagnostic at run time at the snprintf() call .\" .\" *** %n in writable segment detected *** .\" aborted (core dumped) .\" .ip some of the checks can be performed at compile time (via macros logic implemented in header files), and result in compiler warnings; other checks take place at run time, and result in a run-time error if the check fails. .ip use of this macro requires compiler support, available with .br gcc (1) since version 4.0. .ss default definitions, implicit definitions, and combining definitions if no feature test macros are explicitly defined, then the following feature test macros are defined by default: .br _bsd_source (in glibc 2.19 and earlier), .br _svid_source (in glibc 2.19 and earlier), .br _default_source (since glibc 2.19), .br _posix_source , and .br _posix_c_source =200809l (200112l in glibc versions before 2.10; 199506l in glibc versions before 2.4; 199309l in glibc versions before 2.1). .pp if any of .br __strict_ansi__ , .br _isoc99_source , .br _isoc11_source (since glibc 2.18), .br _posix_source , .br _posix_c_source , .br _xopen_source , .br _xopen_source_extended (in glibc 2.11 and earlier), .br _bsd_source (in glibc 2.19 and earlier), or .b _svid_source (in glibc 2.19 and earlier) is explicitly defined, then .br _bsd_source , .br _svid_source , and .br _default_source are not defined by default. .pp if .b _posix_source and .b _posix_c_source are not explicitly defined, and either .b __strict_ansi__ is not defined or .b _xopen_source is defined with a value of 500 or more, then .ip * 3 .b _posix_source is defined with the value 1; and .ip * .b _posix_c_source is defined with one of the following values: .rs 3 .ip \(bu 3 2, if .b _xopen_source is defined with a value less than 500; .ip \(bu 199506l, if .b _xopen_source is defined with a value greater than or equal to 500 and less than 600; or .ip \(bu (since glibc 2.4) 200112l, if .b _xopen_source is defined with a value greater than or equal to 600 and less than 700. .ip \(bu (since glibc 2.10) 200809l, if .b _xopen_source is defined with a value greater than or equal to 700. .ip \(bu older versions of glibc do not know about the values 200112l and 200809l for .br _posix_c_source , and the setting of this macro will depend on the glibc version. .ip \(bu if .b _xopen_source is undefined, then the setting of .b _posix_c_source depends on the glibc version: 199506l, in glibc versions before 2.4; 200112l, in glibc 2.4 to 2.9; and 200809l, since glibc 2.10. .re .pp multiple macros can be defined; the results are additive. .sh conforming to posix.1 specifies .br _posix_c_source , .br _posix_source , and .br _xopen_source . .pp .b _xopen_source_extended was specified by xpg4v2 (aka susv1), but is not present in susv2 and later. .b _file_offset_bits is not specified by any standard, but is employed on some other implementations. .pp .br _bsd_source , .br _svid_source , .br _default_source , .br _atfile_source , .br _gnu_source , .br _fortify_source , .br _reentrant , and .b _thread_safe are specific to linux (glibc). .sh notes .i is a linux/glibc-specific header file. other systems have an analogous file, but typically with a different name. this header file is automatically included by other header files as required: it is not necessary to explicitly include it in order to employ feature test macros. .pp according to which of the above feature test macros are defined, .i internally defines various other macros that are checked by other glibc header files. these macros have names prefixed by two underscores (e.g., .br __use_misc ). programs should .i never define these macros directly: instead, the appropriate feature test macro(s) from the list above should be employed. .sh examples the program below can be used to explore how the various feature test macros are set depending on the glibc version and what feature test macros are explicitly set. the following shell session, on a system with glibc 2.10, shows some examples of what we would see: .pp .in +4n .ex $ \fbcc ftm.c\fp $ \fb./a.out\fp _posix_source defined _posix_c_source defined: 200809l _bsd_source defined _svid_source defined _atfile_source defined $ \fbcc \-d_xopen_source=500 ftm.c\fp $ \fb./a.out\fp _posix_source defined _posix_c_source defined: 199506l _xopen_source defined: 500 $ \fbcc \-d_gnu_source ftm.c\fp $ \fb./a.out\fp _posix_source defined _posix_c_source defined: 200809l _isoc99_source defined _xopen_source defined: 700 _xopen_source_extended defined _largefile64_source defined _bsd_source defined _svid_source defined _atfile_source defined _gnu_source defined .ee .in .ss program source \& .ex /* ftm.c */ #include #include #include #include int main(int argc, char *argv[]) { #ifdef _posix_source printf("_posix_source defined\en"); #endif #ifdef _posix_c_source printf("_posix_c_source defined: %jdl\en", (intmax_t) _posix_c_source); #endif #ifdef _isoc99_source printf("_isoc99_source defined\en"); #endif #ifdef _isoc11_source printf("_isoc11_source defined\en"); #endif #ifdef _xopen_source printf("_xopen_source defined: %d\en", _xopen_source); #endif #ifdef _xopen_source_extended printf("_xopen_source_extended defined\en"); #endif #ifdef _largefile64_source printf("_largefile64_source defined\en"); #endif #ifdef _file_offset_bits printf("_file_offset_bits defined: %d\en", _file_offset_bits); #endif #ifdef _bsd_source printf("_bsd_source defined\en"); #endif #ifdef _svid_source printf("_svid_source defined\en"); #endif #ifdef _default_source printf("_default_source defined\en"); #endif #ifdef _atfile_source printf("_atfile_source defined\en"); #endif #ifdef _gnu_source printf("_gnu_source defined\en"); #endif #ifdef _reentrant printf("_reentrant defined\en"); #endif #ifdef _thread_safe printf("_thread_safe defined\en"); #endif #ifdef _fortify_source printf("_fortify_source defined\en"); #endif exit(exit_success); } .ee .sh see also .br libc (7), .br standards (7), .br system_data_types (7) .pp the section "feature test macros" under .ir "info libc" . .\" but beware: the info libc document is out of date (jul 07, mtk) .pp .i /usr/include/features.h .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .so man3/isgreater.3 .\" copyright (c) 2008 by gerrit renker .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" $id: udplite.7,v 1.12 2008/07/23 15:22:22 gerrit exp gerrit $ .\" .th udplite 7 2021-03-22 "linux" "linux programmer's manual" .sh name udplite \- lightweight user datagram protocol .sh synopsis .nf .b #include .\" fixme . see #defines under `bugs', .\" when glibc supports this, add .\" #include .pp .b sockfd = socket(af_inet, sock_dgram, ipproto_udplite); .fi .sh description this is an implementation of the lightweight user datagram protocol (udp-lite), as described in rfc\ 3828. .pp udp-lite is an extension of udp (rfc\ 768) to support variable-length checksums. this has advantages for some types of multimedia transport that may be able to make use of slightly damaged datagrams, rather than having them discarded by lower-layer protocols. .pp the variable-length checksum coverage is set via a .br setsockopt (2) option. if this option is not set, the only difference from udp is in using a different ip protocol identifier (iana number 136). .pp the udp-lite implementation is a full extension of .br udp (7)\(emthat is, it shares the same api and api behavior, and in addition offers two socket options to control the checksum coverage. .ss address format udp-litev4 uses the .i sockaddr_in address format described in .br ip (7). udp-litev6 uses the .i sockaddr_in6 address format described in .br ipv6 (7). .ss socket options to set or get a udp-lite socket option, call .br getsockopt (2) to read or .br setsockopt (2) to write the option with the option level argument set to .br ipproto_udplite . in addition, all .b ipproto_udp socket options are valid on a udp-lite socket. see .br udp (7) for more information. .pp the following two options are specific to udp-lite. .tp .br udplite_send_cscov this option sets the sender checksum coverage and takes an .i int as argument, with a checksum coverage value in the range 0..2^16-1. .ip a value of 0 means that the entire datagram is always covered. values from 1\-7 are illegal (rfc\ 3828, 3.1) and are rounded up to the minimum coverage of 8. .ip with regard to ipv6 jumbograms (rfc\ 2675), the udp-litev6 checksum coverage is limited to the first 2^16-1 octets, as per rfc\ 3828, 3.5. higher values are therefore silently truncated to 2^16-1. if in doubt, the current coverage value can always be queried using .br getsockopt (2). .tp .br udplite_recv_cscov this is the receiver-side analogue and uses the same argument format and value range as .br udplite_send_cscov . this option is not required to enable traffic with partial checksum coverage. its function is that of a traffic filter: when enabled, it instructs the kernel to drop all packets which have a coverage .i less than the specified coverage value. .ip when the value of .b udplite_recv_cscov exceeds the actual packet coverage, incoming packets are silently dropped, but may generate a warning message in the system log. .\" so_no_check exists and is supported by udpv4, but is .\" commented out in socket(7), hence also commented out here .\".pp .\"since udp-lite mandates checksums, checksumming can not be disabled .\"via the .\".b so_no_check .\"option from .\".br socket (7). .sh errors all errors documented for .br udp (7) may be returned. udp-lite does not add further errors. .sh files .tp .i /proc/net/snmp basic udp-litev4 statistics counters. .tp .i /proc/net/snmp6 basic udp-litev6 statistics counters. .sh versions udp-litev4/v6 first appeared in linux 2.6.20. .sh bugs .\" fixme . remove this section once glibc supports udp-lite where glibc support is missing, the following definitions are needed: .pp .in +4n .ex #define ipproto_udplite 136 .\" the following two are defined in the kernel in linux/net/udplite.h #define udplite_send_cscov 10 #define udplite_recv_cscov 11 .ee .in .sh see also .br ip (7), .br ipv6 (7), .br socket (7), .br udp (7) .pp rfc\ 3828 for the lightweight user datagram protocol (udp-lite). .pp .i documentation/networking/udplite.txt in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/malloc_hook.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-24 by rik faith .\" modified 2001-03-16 by andries brouwer .\" modified 2004-05-27 by michael kerrisk .\" .th stime 2 2021-03-22 "linux" "linux programmer's manual" .sh name stime \- set time .sh synopsis .nf .b #include .pp .bi "int stime(const time_t *" t ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br stime (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description .br note : this function is deprecated; use .br clock_settime (2) instead. .pp .br stime () sets the system's idea of the time and date. the time, pointed to by \fit\fp, is measured in seconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). .br stime () may be executed only by the superuser. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault error in getting information from user space. .tp .b eperm the calling process has insufficient privilege. under linux, the .b cap_sys_time privilege is required. .sh conforming to svr4. .sh notes starting with glibc 2.31, this function is no longer available to newly linked applications and is no longer declared in .ir . .sh see also .br date (1), .br settimeofday (2), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sigsetops.3 .so man3/csqrt.3 .so man2/init_module.2 .\" copyright (c) 2006 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 28 dec 2006 - initial creation .\" .th termio 7 2017-05-03 "linux" "linux programmer's manual" .sh name termio \- system v terminal driver interface .sh description .b termio is the name of the old system v terminal driver interface. this interface defined a .i termio structure used to store terminal settings, and a range of .br ioctl (2) operations to get and set terminal attributes. .pp the .b termio interface is now obsolete: posix.1-1990 standardized a modified version of this interface, under the name .br termios . the posix.1 data structure differs slightly from the system v version, and posix.1 defined a suite of functions to replace the various .br ioctl (2) operations that existed in system v. (this was done because .br ioctl (2) was unstandardized, and its variadic third argument does not allow argument type checking.) .pp if you're looking for a page called "termio", then you can probably find most of the information that you seek in either .br termios (3) or .br ioctl_tty (2). .sh see also .br reset (1), .br setterm (1), .br stty (1), .br ioctl_tty (2), .br termios (3), .br tty (4) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_attr_setschedpolicy.3 .so man2/select.2 .so man3/sigset.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_close 3 2021-03-22 "linux" "linux programmer's manual" .sh name sem_close \- close a named semaphore .sh synopsis .nf .b #include .pp .bi "int sem_close(sem_t *" sem ); .fi .pp link with \fi\-pthread\fp. .sh description .br sem_close () closes the named semaphore referred to by .ir sem , allowing any resources that the system has allocated to the calling process for this semaphore to be freed. .sh return value on success .br sem_close () returns 0; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b einval .i sem is not a valid semaphore. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_close () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes all open named semaphores are automatically closed on process termination, or upon .br execve (2). .sh see also .br sem_getvalue (3), .br sem_open (3), .br sem_post (3), .br sem_unlink (3), .br sem_wait (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified formatting sat jul 24 17:13:38 1993, rik faith (faith@cs.unc.edu) .\" modified (extensions and corrections) .\" sun may 1 14:21:25 met dst 1994 michael haardt .\" if mistakes in the capabilities are found, please send a bug report to: .\" michael@moria.de .\" modified mon oct 21 17:47:19 edt 1996 by eric s. raymond (esr@thyrsus.com) .th termcap 5 2020-08-13 "linux" "linux programmer's manual" .sh name termcap \- terminal capability database .sh description the termcap database is an obsolete facility for describing the capabilities of character-cell terminals and printers. it is retained only for compatibility with old programs; new programs should use the .br terminfo (5) database and associated libraries. .pp .i /etc/termcap is an ascii file (the database master) that lists the capabilities of many different types of terminals. programs can read termcap to find the particular escape codes needed to control the visual attributes of the terminal actually in use. (other aspects of the terminal are handled by .br stty (1).) the termcap database is indexed on the .b term environment variable. .pp termcap entries must be defined on a single logical line, with \(aq\e\(aq used to suppress the newline. fields are separated by \(aq:\(aq. the first field of each entry starts at the left-hand margin, and contains a list of names for the terminal, separated by \(aq|\(aq. .pp the first subfield may (in bsd termcap entries from versions 4.3 and earlier) contain a short name consisting of two characters. this short name may consist of capital or small letters. in 4.4bsd, termcap entries this field is omitted. .pp the second subfield (first, in the newer 4.4bsd format) contains the name used by the environment variable .br term . it should be spelled in lowercase letters. selectable hardware capabilities should be marked by appending a hyphen and a suffix to this name. see below for an example. usual suffixes are w (more than 80 characters wide), am (automatic margins), nam (no automatic margins), and rv (reverse video display). the third subfield contains a long and descriptive name for this termcap entry. .pp subsequent fields contain the terminal capabilities; any continued capability lines must be indented one tab from the left margin. .pp although there is no defined order, it is suggested to write first boolean, then numeric, and then string capabilities, each sorted alphabetically without looking at lower or upper spelling. capabilities of similar functions can be written in one line. .pp example for: .nf .pp head line: vt|vt101|dec vt 101 terminal in 80 character mode:\e head line: vt|vt101-w|dec vt 101 terminal in (wide) 132 character mode:\e boolean: :bs:\e numeric: :co#80:\e string: :sr=\ee[h:\e .fi .ss boolean capabilities .nf 5i printer will not echo on screen am automatic margins which means automatic line wrap bs control-h (8 dec.) performs a backspace bw backspace on left margin wraps to previous line and right margin da display retained above screen db display retained below screen eo a space erases all characters at cursor position es escape sequences and special characters work in status line gn generic device hc this is a hardcopy terminal hc the cursor is hard to see when not on bottom line hs has a status line hz hazeltine bug, the terminal can not print tilde characters in terminal inserts null bytes, not spaces, to fill whitespace km terminal has a meta key mi cursor movement works in insert mode ms cursor movement works in standout/underline mode np no pad character nr ti does not reverse te nx no padding, must use xon/xoff os terminal can overstrike ul terminal underlines although it can not overstrike xb beehive glitch, f1 sends escape, f2 sends \fb\(hac\fp xn newline/wraparound glitch xo terminal uses xon/xoff protocol xs text typed over standout text will be displayed in standout xt teleray glitch, destructive tabs and odd standout mode .fi .ss numeric capabilities .nf co number of columns db delay in milliseconds for backspace on hardcopy terminals dc delay in milliseconds for carriage return on hardcopy terminals df delay in milliseconds for form feed on hardcopy terminals dn delay in milliseconds for new line on hardcopy terminals dt delay in milliseconds for tabulator stop on hardcopy terminals dv delay in milliseconds for vertical tabulator stop on hardcopy terminals it difference between tab positions lh height of soft labels lm lines of memory lw width of soft labels li number of lines nl number of soft labels pb lowest baud rate which needs padding sg standout glitch ug underline glitch vt virtual terminal number ws width of status line if different from screen width .fi .ss string capabilities .nf !1 shifted save key !2 shifted suspend key !3 shifted undo key #1 shifted help key #2 shifted home key #3 shifted input key #4 shifted cursor left key %0 redo key %1 help key %2 mark key %3 message key %4 move key %5 next-object key %6 open key %7 options key %8 previous-object key %9 print key %a shifted message key %b shifted move key %c shifted next key %d shifted options key %e shifted previous key %f shifted print key %g shifted redo key %h shifted replace key %i shifted cursor right key %j shifted resume key &0 shifted cancel key &1 reference key &2 refresh key &3 replace key &4 restart key &5 resume key &6 save key &7 suspend key &8 undo key &9 shifted begin key *0 shifted find key *1 shifted command key *2 shifted copy key *3 shifted create key *4 shifted delete character *5 shifted delete line *6 select key *7 shifted end key *8 shifted clear line key *9 shifted exit key @0 find key @1 begin key @2 cancel key @3 close key @4 command key @5 copy key @6 create key @7 end key @8 enter/send key @9 exit key al insert one line al insert %1 lines ac pairs of block graphic characters to map alternate character set ae end alternative character set as start alternative character set for block graphic characters bc backspace, if not \fb\(hah\fp bl audio bell bt move to previous tab stop cb clear from beginning of line to cursor cc dummy command character cd clear to end of screen ce clear to end of line ch move cursor horizontally only to column %1 cl clear screen and cursor home cm cursor move to row %1 and column %2 (on screen) cm move cursor to row %1 and column %2 (in memory) cr carriage return cs scroll region from line %1 to %2 ct clear tabs cv move cursor vertically only to line %1 dc delete one character dc delete %1 characters dl delete one line dl delete %1 lines dm begin delete mode do cursor down one line do cursor down #1 lines ds disable status line ea enable alternate character set ec erase %1 characters starting at cursor ed end delete mode ei end insert mode ff formfeed character on hardcopy terminals fs return character to its position before going to status line f1 the string sent by function key f11 f2 the string sent by function key f12 f3 the string sent by function key f13 \&... \&... f9 the string sent by function key f19 fa the string sent by function key f20 fb the string sent by function key f21 \&... \&... fz the string sent by function key f45 fa the string sent by function key f46 fb the string sent by function key f47 \&... \&... fr the string sent by function key f63 hd move cursor a half line down ho cursor home hu move cursor a half line up i1 initialization string 1 at login i3 initialization string 3 at login is initialization string 2 at login ic insert one character ic insert %1 characters if initialization file im begin insert mode ip insert pad time and needed special characters after insert ip initialization program k1 upper left key on keypad k2 center key on keypad k3 upper right key on keypad k4 bottom left key on keypad k5 bottom right key on keypad k0 function key 0 k1 function key 1 k2 function key 2 k3 function key 3 k4 function key 4 k5 function key 5 k6 function key 6 k7 function key 7 k8 function key 8 k9 function key 9 k; function key 10 ka clear all tabs key ka insert line key kb backspace key kb back tab stop kc clear screen key kd cursor down key kd key for delete character under cursor ke turn keypad off ke key for clear to end of line kf key for scrolling forward/down kh cursor home key kh cursor hown down key ki insert character/insert mode key kl cursor left key kl key for delete line km key for exit insert mode kn key for next page kp key for previous page kr cursor right key kr key for scrolling backward/up ks turn keypad on ks clear to end of screen key kt clear this tab key kt set tab here key ku cursor up key l0 label of zeroth function key, if not f0 l1 label of first function key, if not f1 l2 label of first function key, if not f2 \&... \&... la label of tenth function key, if not f10 le cursor left one character ll move cursor to lower left corner le cursor left %1 characters lf turn soft labels off lo turn soft labels on mb start blinking mc clear soft margins md start bold mode me end all mode like so, us, mb, md, and mr mh start half bright mode mk dark mode (characters invisible) ml set left soft margin mm put terminal in meta mode mo put terminal out of meta mode mp turn on protected attribute mr start reverse mode mr set right soft margin nd cursor right one character nw carriage return command pc padding character pf turn printer off pk program key %1 to send string %2 as if typed by user pl program key %1 to execute string %2 in local mode pn program soft label %1 to show string %2 po turn the printer on po turn the printer on for %1 (<256) bytes ps print screen contents on printer px program key %1 to send string %2 to computer r1 reset string 1 to set terminal to sane modes r2 reset string 2 to set terminal to sane modes r3 reset string 3 to set terminal to sane modes ra disable automatic margins rc restore saved cursor position rf reset string filename rf request for input from terminal ri cursor right %1 characters rp repeat character %1 for %2 times rp padding after character sent in replace mode rs reset string rx turn off xon/xoff flow control sa set %1 %2 %3 %4 %5 %6 %7 %8 %9 attributes sa enable automatic margins sc save cursor position se end standout mode sf normal scroll one line sf normal scroll %1 lines so start standout mode sr reverse scroll sr scroll back %1 lines st set tabulator stop in all rows at current column sx turn on xon/xoff flow control ta move to next hardware tab tc read in terminal description from another entry te end program that uses cursor motion ti begin program that uses cursor motion ts move cursor to column %1 of status line uc underline character under cursor and move cursor right ue end underlining up cursor up one line up cursor up %1 lines us start underlining vb visible bell ve normal cursor visible vi cursor invisible vs standout cursor wi set window from line %1 to %2 and column %3 to %4 xf xoff character if not \fb\(has\fp .fi .pp there are several ways of defining the control codes for string capabilities: .pp every normal character represents itself, except \(aq\(ha\(aq, \(aq\e\(aq, and \(aq%\(aq. .pp a \fb\(hax\fp means control-x. control-a equals 1 decimal. .pp \ex means a special code. x can be one of the following characters: .rs e escape (27) .br n linefeed (10) .br r carriage return (13) .br t tabulation (9) .br b backspace (8) .br f form feed (12) .br 0 null character. a \exxx specifies the octal character xxx. .re .ip i increments parameters by one. .ip r single parameter capability .ip + add value of next character to this parameter and do binary output .ip 2 do ascii output of this parameter with a field with of 2 .ip d do ascii output of this parameter with a field with of 3 .ip % print a \(aq%\(aq .pp if you use binary output, then you should avoid the null character (\(aq\e0\(aq) because it terminates the string. you should reset tabulator expansion if a tabulator can be the binary output of a parameter. .ip warning: the above metacharacters for parameters may be wrong: they document minix termcap which may not be compatible with linux termcap. .pp the block graphic characters can be specified by three string capabilities: .ip as start the alternative charset .ip ae end the alternative charset .ip ac pairs of characters. the first character is the name of the block graphic symbol and the second characters is its definition. .pp the following names are available: .pp .nf + right arrow (>) , left arrow (<) \&. down arrow (v) 0 full square (#) i lantern (#) - upper arrow (\(ha) \&' rhombus (+) a chess board (:) f degree (') g plus-minus (#) h square (#) j right bottom corner (+) k right upper corner (+) l left upper corner (+) m left bottom corner (+) n cross (+) o upper horizontal line (-) q middle horizontal line (-) s bottom horizontal line (_) t left tee (+) u right tee (+) v bottom tee (+) w normal tee (+) x vertical line (|) \(ti paragraph (???) .fi .pp the values in parentheses are suggested defaults which are used by the .ir curses library, if the capabilities are missing. .sh see also .br ncurses (3), .br termcap (3), .br terminfo (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scalb.3 .so man3/getspnam.3 .so man3/mcheck.3 .\" copyright (c) 2012 chandan apsangi .\" and copyright (c) 2013 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_setname_np 3 2021-08-27 "linux" "linux programmer's manual" .sh name pthread_setname_np, pthread_getname_np \- set/get the name of a thread .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_setname_np(pthread_t " thread ", const char *" name ); .bi "int pthread_getname_np(pthread_t " thread ", char *" name ", size_t " len ); .fi .pp compile and link with \fi\-pthread\fp. .sh description by default, all the threads created using .br pthread_create () inherit the program name. the .br pthread_setname_np () function can be used to set a unique name for a thread, which can be useful for debugging multithreaded applications. the thread name is a meaningful c language string, whose length is restricted to 16 characters, including the terminating null byte (\(aq\e0\(aq). the .i thread argument specifies the thread whose name is to be changed; .i name specifies the new name. .pp the .br pthread_getname_np () function can be used to retrieve the name of the thread. the .i thread argument specifies the thread whose name is to be retrieved. the buffer .i name is used to return the thread name; .i len specifies the number of bytes available in .ir name . the buffer specified by .i name should be at least 16 characters in length. the returned thread name in the output buffer will be null terminated. .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors the .br pthread_setname_np () function can fail with the following error: .tp .b erange the length of the string specified pointed to by .i name exceeds the allowed limit. .pp the .br pthread_getname_np () function can fail with the following error: .tp .b erange the buffer specified by .i name and .i len is too small to hold the thread name. .pp if either of these functions fails to open .ir /proc/self/task/[tid]/comm , then the call may fail with one of the errors described in .br open (2). .sh versions these functions first appeared in glibc in version 2.12. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_setname_np (), .br pthread_getname_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh notes .br pthread_setname_np () internally writes to the thread-specific .i comm file under the .ir /proc filesystem: .ir /proc/self/task/[tid]/comm . .br pthread_getname_np () retrieves it from the same location. .sh examples the program below demonstrates the use of .br pthread_setname_np () and .br pthread_getname_np (). .pp the following shell session shows a sample run of the program: .pp .in +4n .ex .rb "$" " ./a.out" created a thread. default name is: a.out the thread name after setting it is threadfoo. \fb\(haz\fp # suspend the program [1]+ stopped ./a.out .rb "$ " "ps h \-c a.out \-o \(aqpid tid cmd comm\(aq" pid tid cmd command 5990 5990 ./a.out a.out 5990 5991 ./a.out threadfoo .rb "$ " "cat /proc/5990/task/5990/comm" a.out .rb "$ " "cat /proc/5990/task/5991/comm" threadfoo .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include #define namelen 16 #define errexiten(en, msg) \e do { errno = en; perror(msg); \e exit(exit_failure); } while (0) static void * threadfunc(void *parm) { sleep(5); // allow main program to set the thread name return null; } int main(int argc, char *argv[]) { pthread_t thread; int rc; char thread_name[namelen]; rc = pthread_create(&thread, null, threadfunc, null); if (rc != 0) errexiten(rc, "pthread_create"); rc = pthread_getname_np(thread, thread_name, namelen); if (rc != 0) errexiten(rc, "pthread_getname_np"); printf("created a thread. default name is: %s\en", thread_name); rc = pthread_setname_np(thread, (argc > 1) ? argv[1] : "threadfoo"); if (rc != 0) errexiten(rc, "pthread_setname_np"); sleep(2); rc = pthread_getname_np(thread, thread_name, namelen); if (rc != 0) errexiten(rc, "pthread_getname_np"); printf("the thread name after setting it is %s.\en", thread_name); rc = pthread_join(thread, null); if (rc != 0) errexiten(rc, "pthread_join"); printf("done\en"); exit(exit_success); } .ee .sh see also .ad l .nh .br prctl (2), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strtoul.3 .\" copyright (c) 2001, 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" aeb, various minor fixes .th sigaltstack 2 2021-03-22 "linux" "linux programmer's manual" .sh name sigaltstack \- set and/or get signal stack context .sh synopsis .nf .b #include .pp .bi "int sigaltstack(const stack_t *restrict " ss \ ", stack_t *restrict " old_ss ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigaltstack (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source .fi .sh description .br sigaltstack () allows a thread to define a new alternate signal stack and/or retrieve the state of an existing alternate signal stack. an alternate signal stack is used during the execution of a signal handler if the establishment of that handler (see .br sigaction (2)) requested it. .pp the normal sequence of events for using an alternate signal stack is the following: .tp 3 1. allocate an area of memory to be used for the alternate signal stack. .tp 2. use .br sigaltstack () to inform the system of the existence and location of the alternate signal stack. .tp 3. when establishing a signal handler using .br sigaction (2), inform the system that the signal handler should be executed on the alternate signal stack by specifying the \fbsa_onstack\fp flag. .pp the \fiss\fp argument is used to specify a new alternate signal stack, while the \fiold_ss\fp argument is used to retrieve information about the currently established signal stack. if we are interested in performing just one of these tasks, then the other argument can be specified as null. .pp the .i stack_t type used to type the arguments of this function is defined as follows: .pp .in +4n .ex typedef struct { void *ss_sp; /* base address of stack */ int ss_flags; /* flags */ size_t ss_size; /* number of bytes in stack */ } stack_t; .ee .in .pp to establish a new alternate signal stack, the fields of this structure are set as follows: .tp .i ss.ss_flags this field contains either 0, or the following flag: .rs .tp .br ss_autodisarm " (since linux 4.7)" .\" commit 2a74213838104a41588d86fd5e8d344972891ace .\" see tools/testing/selftests/sigaltstack/sas.c in kernel sources clear the alternate signal stack settings on entry to the signal handler. when the signal handler returns, the previous alternate signal stack settings are restored. .ip this flag was added in order to make it safe to switch away from the signal handler with .br swapcontext (3). without this flag, a subsequently handled signal will corrupt the state of the switched-away signal handler. on kernels where this flag is not supported, .br sigaltstack () fails with the error .br einval when this flag is supplied. .re .tp .i ss.ss_sp this field specifies the starting address of the stack. when a signal handler is invoked on the alternate stack, the kernel automatically aligns the address given in \fiss.ss_sp\fp to a suitable address boundary for the underlying hardware architecture. .tp .i ss.ss_size this field specifies the size of the stack. the constant \fbsigstksz\fp is defined to be large enough to cover the usual size requirements for an alternate signal stack, and the constant \fbminsigstksz\fp defines the minimum size required to execute a signal handler. .pp to disable an existing stack, specify \fiss.ss_flags\fp as \fbss_disable\fp. in this case, the kernel ignores any other flags in .ir ss.ss_flags and the remaining fields in \fiss\fp. .pp if \fiold_ss\fp is not null, then it is used to return information about the alternate signal stack which was in effect prior to the call to .br sigaltstack (). the \fiold_ss.ss_sp\fp and \fiold_ss.ss_size\fp fields return the starting address and size of that stack. the \fiold_ss.ss_flags\fp may return either of the following values: .tp .b ss_onstack the thread is currently executing on the alternate signal stack. (note that it is not possible to change the alternate signal stack if the thread is currently executing on it.) .tp .b ss_disable the alternate signal stack is currently disabled. .ip alternatively, this value is returned if the thread is currently executing on an alternate signal stack that was established using the .b ss_autodisarm flag. in this case, it is safe to switch away from the signal handler with .br swapcontext (3). it is also possible to set up a different alternative signal stack using a further call to .br sigaltstack (). .\" fixme was it intended that one can set up a different alternative .\" signal stack in this scenario? (in passing, if one does this, the .\" sigaltstack(null, &old_ss) now returns old_ss.ss_flags==ss_autodisarm .\" rather than old_ss.ss_flags==ss_disable. the api design here seems .\" confusing... .tp .b ss_autodisarm the alternate signal stack has been marked to be autodisarmed as described above. .pp by specifying .i ss as null, and .i old_ss as a non-null value, one can obtain the current settings for the alternate signal stack without changing them. .sh return value .br sigaltstack () returns 0 on success, or \-1 on failure with \fierrno\fp set to indicate the error. .sh errors .tp .b efault either \fiss\fp or \fiold_ss\fp is not null and points to an area outside of the process's address space. .tp .b einval \fiss\fp is not null and the \fiss_flags\fp field contains an invalid flag. .tp .b enomem the specified size of the new alternate signal stack .i ss.ss_size was less than .br minsigstksz . .tp .b eperm an attempt was made to change the alternate signal stack while it was active (i.e., the thread was already executing on the current alternate signal stack). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigaltstack () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2, svr4. .pp the .b ss_autodisarm flag is a linux extension. .sh notes the most common usage of an alternate signal stack is to handle the .b sigsegv signal that is generated if the space available for the standard stack is exhausted: in this case, a signal handler for .b sigsegv cannot be invoked on the standard stack; if we wish to handle it, we must use an alternate signal stack. .pp establishing an alternate signal stack is useful if a thread expects that it may exhaust its standard stack. this may occur, for example, because the stack grows so large that it encounters the upwardly growing heap, or it reaches a limit established by a call to \fbsetrlimit(rlimit_stack, &rlim)\fp. if the standard stack is exhausted, the kernel sends the thread a \fbsigsegv\fp signal. in these circumstances the only way to catch this signal is on an alternate signal stack. .pp on most hardware architectures supported by linux, stacks grow downward. .br sigaltstack () automatically takes account of the direction of stack growth. .pp functions called from a signal handler executing on an alternate signal stack will also use the alternate signal stack. (this also applies to any handlers invoked for other signals while the thread is executing on the alternate signal stack.) unlike the standard stack, the system does not automatically extend the alternate signal stack. exceeding the allocated size of the alternate signal stack will lead to unpredictable results. .pp a successful call to .br execve (2) removes any existing alternate signal stack. a child process created via .br fork (2) inherits a copy of its parent's alternate signal stack settings. the same is also true for a child process created using .br clone (2), unless the clone flags include .br clone_vm and do not include .br clone_vfork , in which case any alternate signal stack that was established in the parent is disabled in the child process. .pp .br sigaltstack () supersedes the older .br sigstack () call. for backward compatibility, glibc also provides .br sigstack (). all new applications should be written using .br sigaltstack (). .ss history 4.2bsd had a .br sigstack () system call. it used a slightly different struct, and had the major disadvantage that the caller had to know the direction of stack growth. .sh bugs in linux 2.2 and earlier, the only flag that could be specified in .i ss.sa_flags was .br ss_disable . in the lead up to the release of the linux 2.4 kernel, .\" linux 2.3.40 .\" after quite a bit of web and mail archive searching, .\" i could not find the patch on any mailing list, and i .\" could find no place where the rationale for this change .\" explained -- mtk a change was made to allow .br sigaltstack () to allow .i ss.ss_flags==ss_onstack with the same meaning as .ir "ss.ss_flags==0" (i.e., the inclusion of .b ss_onstack in .i ss.ss_flags is a no-op). on other implementations, and according to posix.1, .b ss_onstack appears only as a reported flag in .ir old_ss.ss_flags . on linux, there is no need ever to specify .b ss_onstack in .ir ss.ss_flags , and indeed doing so should be avoided on portability grounds: various other systems .\" see the source code of illumos and freebsd, for example. give an error if .b ss_onstack is specified in .ir ss.ss_flags . .sh examples the following code segment demonstrates the use of .br sigaltstack () (and .br sigaction (2)) to install an alternate signal stack that is employed by a handler for the .br sigsegv signal: .pp .in +4n .ex stack_t ss; ss.ss_sp = malloc(sigstksz); if (ss.ss_sp == null) { perror("malloc"); exit(exit_failure); } ss.ss_size = sigstksz; ss.ss_flags = 0; if (sigaltstack(&ss, null) == \-1) { perror("sigaltstack"); exit(exit_failure); } sa.sa_flags = sa_onstack; sa.sa_handler = handler(); /* address of a signal handler */ sigemptyset(&sa.sa_mask); if (sigaction(sigsegv, &sa, null) == \-1) { perror("sigaction"); exit(exit_failure); } .ee .in .sh see also .br execve (2), .br setrlimit (2), .br sigaction (2), .br siglongjmp (3), .br sigsetjmp (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/stat.2 .so man7/system_data_types.7 .\" copyright (c) 2019 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th uts_namespaces 7 2019-11-19 "linux" "linux programmer's manual" .sh name uts_namespaces \- overview of linux uts namespaces .sh description uts namespaces provide isolation of two system identifiers: the hostname and the nis domain name. these identifiers are set using .br sethostname (2) and .br setdomainname (2), and can be retrieved using .br uname (2), .br gethostname (2), and .br getdomainname (2). changes made to these identifiers are visible to all other processes in the same uts namespace, but are not visible to processes in other uts namespaces. .pp .pp when a process creates a new uts namespace using .br clone (2) or .br unshare (2) with the .br clone_newuts flag, the hostname and domain of the new uts namespace are copied from the corresponding values in the caller's uts namespace. .pp use of uts namespaces requires a kernel that is configured with the .b config_uts_ns option. .sh see also .br nsenter (1), .br unshare (1), .br clone (2), .br getdomainname (2), .br gethostname (2), .br setns (2), .br uname (2), .br unshare (2), .br namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/dlopen.3 .\" copyright (c) 1983, 1991, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)rexec.3 8.1 (berkeley) 6/4/93 .\" $freebsd: src/lib/libcompat/4.3/rexec.3,v 1.12 2004/07/02 23:52:14 ru exp $ .\" .\" taken from freebsd 5.4; not checked against linux reality (mtk) .\" .\" 2013-06-21, mtk, converted from mdoc to man macros .\" .th rexec 3 2021-03-22 "linux" "linux programmer's manual" .sh name rexec, rexec_af \- return stream to a remote command .sh synopsis .nf .b #include .pp .bi "int rexec(char **restrict " ahost ", int " inport , .bi " const char *restrict " user ", const char *restrict " passwd , .bi " const char *restrict " cmd ", int *restrict " fd2p ); .bi "int rexec_af(char **restrict " ahost ", int " inport , .bi " const char *restrict " user ", const char *restrict " passwd , .bi " const char *restrict " cmd ", int *restrict " fd2p , .bi " sa_family_t " af ); .fi .pp .br rexec (), .br rexec_af (): .nf since glibc 2.19: _default_source in glibc up to and including 2.19: _bsd_source .fi .sh description this interface is obsoleted by .br rcmd (3). .pp the .br rexec () function looks up the host .ir *ahost using .br gethostbyname (3), returning \-1 if the host does not exist. otherwise, .ir *ahost is set to the standard name of the host. if a username and password are both specified, then these are used to authenticate to the foreign host; otherwise the environment and then the .i .netrc file in user's home directory are searched for appropriate information. if all this fails, the user is prompted for the information. .pp the port .i inport specifies which well-known darpa internet port to use for the connection; the call .i "getservbyname(""exec"", ""tcp"")" (see .br getservent (3)) will return a pointer to a structure that contains the necessary port. the protocol for connection is described in detail in .br rexecd (8). .pp if the connection succeeds, a socket in the internet domain of type .br sock_stream is returned to the caller, and given to the remote command as .ir stdin and .ir stdout . if .i fd2p is nonzero, then an auxiliary channel to a control process will be setup, and a file descriptor for it will be placed in .ir *fd2p . the control process will return diagnostic output from the command (unit 2) on this channel, and will also accept bytes on this channel as being unix signal numbers, to be forwarded to the process group of the command. the diagnostic information returned does not include remote authorization failure, as the secondary connection is set up after authorization has been verified. if .i fd2p is 0, then the .ir stderr (unit 2 of the remote command) will be made the same as the .ir stdout and no provision is made for sending arbitrary signals to the remote process, although you may be able to get its attention by using out-of-band data. .ss rexec_af() the .br rexec () function works over ipv4 .rb ( af_inet ). by contrast, the .br rexec_af () function provides an extra argument, .ir af , that allows the caller to select the protocol. this argument can be specified as .br af_inet , .br af_inet6 , or .br af_unspec (to allow the implementation to select the protocol). .sh versions the .br rexec_af () function was added to glibc in version 2.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br rexec (), .br rexec_af () t} thread safety mt-unsafe .te .hy .ad .sp 1 .sh conforming to these functions are not in posix.1. the .br rexec () function first appeared in 4.2bsd, and is present on the bsds, solaris, and many other systems. the .br rexec_af () function is more recent, and less widespread. .sh bugs the .br rexec () function sends the unencrypted password across the network. .pp the underlying service is considered a big security hole and therefore not enabled on many sites; see .br rexecd (8) for explanations. .sh see also .br rcmd (3), .br rexecd (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/y0.3 .\" derived from text written by martin schulze (or taken from glibc.info) .\" and text written by paul thompson - both copyright 2002. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th login 3 2021-03-22 "gnu" "linux programmer's manual" .sh name login, logout \- write utmp and wtmp entries .sh synopsis .nf .b #include .pp .bi "void login(const struct utmp *" ut ); .bi "int logout(const char *" ut_line ); .fi .pp link with \fi\-lutil\fp. .sh description the utmp file records who is currently using the system. the wtmp file records all logins and logouts. see .br utmp (5). .pp the function .br login () takes the supplied .ir "struct utmp" , .ir ut , and writes it to both the utmp and the wtmp file. .pp the function .br logout () clears the entry in the utmp file again. .ss gnu details more precisely, .br login () takes the argument .i ut struct, fills the field .i ut\->ut_type (if there is such a field) with the value .br user_process , and fills the field .i ut\->ut_pid (if there is such a field) with the process id of the calling process. then it tries to fill the field .ir ut\->ut_line . it takes the first of .ir stdin , .ir stdout , .i stderr that is a terminal, and stores the corresponding pathname minus a possible leading .i /dev/ into this field, and then writes the struct to the utmp file. on the other hand, if no terminal name was found, this field is filled with "???" and the struct is not written to the utmp file. after this, the struct is written to the wtmp file. .pp the .br logout () function searches the utmp file for an entry matching the .i ut_line argument. if a record is found, it is updated by zeroing out the .i ut_name and .i ut_host fields, updating the .i ut_tv timestamp field and setting .i ut_type (if there is such a field) to .br dead_process . .sh return value the .br logout () function returns 1 if the entry was successfully written to the database, or 0 if an error occurred. .sh files .tp .i /var/run/utmp user accounting database, configured through .b _path_utmp in .i .tp .i /var/log/wtmp user accounting log file, configured through .b _path_wtmp in .i .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br login (), .br logout () t} thread safety t{ mt-unsafe race:utent sig:alrm timer t} .te .hy .ad .sp 1 in the above table, .i utent in .i race:utent signifies that if any of the functions .br setutent (3), .br getutent (3), or .br endutent (3) are used in parallel in different threads of a program, then data races could occur. .br login () and .br logout () calls those functions, so we use race:utent to remind users. .sh conforming to not in posix.1. present on the bsds. .sh notes note that the member .i ut_user of .i struct utmp is called .i ut_name in bsd. therefore, .i ut_name is defined as an alias for .i ut_user in .ir . .sh see also .br getutent (3), .br utmp (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .\" this manpage is copyright (c) 2006 jens axboe .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th splice 2 2021-03-22 "linux" "linux programmer's manual" .sh name splice \- splice data to/from a pipe .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "ssize_t splice(int " fd_in ", off64_t *" off_in ", int " fd_out , .bi " off64_t *" off_out ", size_t " len \ ", unsigned int " flags ); .\" return type was long before glibc 2.7 .fi .sh description .br splice () moves data between two file descriptors without copying between kernel address space and user address space. it transfers up to .i len bytes of data from the file descriptor .i fd_in to the file descriptor .ir fd_out , where one of the file descriptors must refer to a pipe. .pp the following semantics apply for .i fd_in and .ir off_in : .ip * 3 if .i fd_in refers to a pipe, then .i off_in must be null. .ip * if .i fd_in does not refer to a pipe and .i off_in is null, then bytes are read from .i fd_in starting from the file offset, and the file offset is adjusted appropriately. .ip * if .i fd_in does not refer to a pipe and .i off_in is not null, then .i off_in must point to a buffer which specifies the starting offset from which bytes will be read from .ir fd_in ; in this case, the file offset of .i fd_in is not changed. .pp analogous statements apply for .i fd_out and .ir off_out . .pp the .i flags argument is a bit mask that is composed by oring together zero or more of the following values: .tp .b splice_f_move attempt to move pages instead of copying. this is only a hint to the kernel: pages may still be copied if the kernel cannot move the pages from the pipe, or if the pipe buffers don't refer to full pages. the initial implementation of this flag was buggy: therefore starting in linux 2.6.21 it is a no-op (but is still permitted in a .br splice () call); in the future, a correct implementation may be restored. .tp .b splice_f_nonblock do not block on i/o. this makes the splice pipe operations nonblocking, but .br splice () may nevertheless block because the file descriptors that are spliced to/from may block (unless they have the .b o_nonblock flag set). .tp .b splice_f_more more data will be coming in a subsequent splice. this is a helpful hint when the .i fd_out refers to a socket (see also the description of .b msg_more in .br send (2), and the description of .b tcp_cork in .br tcp (7)). .tp .b splice_f_gift unused for .br splice (); see .br vmsplice (2). .sh return value upon successful completion, .br splice () returns the number of bytes spliced to or from the pipe. .pp a return value of 0 means end of input. if .i fd_in refers to a pipe, then this means that there was no data to transfer, and it would not make sense to block because there are no writers connected to the write end of the pipe. .pp on error, .br splice () returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b eagain .b splice_f_nonblock was specified in .ir flags or one of the file descriptors had been marked as nonblocking .rb ( o_nonblock ) , and the operation would block. .tp .b ebadf one or both file descriptors are not valid, or do not have proper read-write mode. .tp .b einval the target filesystem doesn't support splicing. .tp .b einval the target file is opened in append mode. .\" the append-mode error is given since 2.6.27; in earlier kernels, .\" splice() in append mode was broken .tp .b einval neither of the file descriptors refers to a pipe. .tp .b einval an offset was given for nonseekable device (e.g., a pipe). .tp .b einval .i fd_in and .i fd_out refer to the same pipe. .tp .b enomem out of memory. .tp .b espipe either .i off_in or .i off_out was not null, but the corresponding file descriptor refers to a pipe. .sh versions the .br splice () system call first appeared in linux 2.6.17; library support was added to glibc in version 2.5. .sh conforming to this system call is linux-specific. .sh notes the three system calls .br splice (), .br vmsplice (2), and .br tee (2), provide user-space programs with full control over an arbitrary kernel buffer, implemented within the kernel using the same type of buffer that is used for a pipe. in overview, these system calls perform the following tasks: .ip \(bu 2 .br splice () moves data from the buffer to an arbitrary file descriptor, or vice versa, or from one buffer to another. .ip \(bu .br tee (2) "copies" the data from one buffer to another. .ip \(bu .br vmsplice (2) "copies" data from user space into the buffer. .pp though we talk of copying, actual copies are generally avoided. the kernel does this by implementing a pipe buffer as a set of reference-counted pointers to pages of kernel memory. the kernel creates "copies" of pages in a buffer by creating new pointers (for the output buffer) referring to the pages, and increasing the reference counts for the pages: only pointers are copied, not the pages of the buffer. .\" .\" linus: now, imagine using the above in a media server, for example. .\" let's say that a year or two has passed, so that the video drivers .\" have been updated to be able to do the splice thing, and what can .\" you do? you can: .\" .\" - splice from the (mpeg or whatever - let's just assume that the video .\" input is either digital or does the encoding on its own - like they .\" pretty much all do) video input into a pipe (remember: no copies - the .\" video input will just dma directly into memory, and splice will just .\" set up the pages in the pipe buffer) .\" - tee that pipe to split it up .\" - splice one end to a file (ie "save the compressed stream to disk") .\" - splice the other end to a real-time video decoder window for your .\" real-time viewing pleasure. .\" .\" linus: now, the advantage of splice()/tee() is that you can .\" do zero-copy movement of data, and unlike sendfile() you can .\" do it on _arbitrary_ data (and, as shown by "tee()", it's more .\" than just sending the data to somebody else: you can duplicate .\" the data and choose to forward it to two or more different .\" users - for things like logging etc.). .\" .pp in linux 2.6.30 and earlier, exactly one of .i fd_in and .i fd_out was required to be a pipe. since linux 2.6.31, .\" commit 7c77f0b3f9208c339a4b40737bb2cb0f0319bb8d both arguments may refer to pipes. .sh examples see .br tee (2). .sh see also .br copy_file_range (2), .br sendfile (2), .br tee (2), .br vmsplice (2), .br pipe (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2019 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th ipc_namespaces 7 2019-08-02 "linux" "linux programmer's manual" .sh name ipc_namespaces \- overview of linux ipc namespaces .sh description ipc namespaces isolate certain ipc resources, namely, system v ipc objects (see .br sysvipc (7)) and (since linux 2.6.30) .\" commit 7eafd7c74c3f2e67c27621b987b28397110d643f .\" https://lwn.net/articles/312232/ posix message queues (see .br mq_overview (7)). the common characteristic of these ipc mechanisms is that ipc objects are identified by mechanisms other than filesystem pathnames. .pp each ipc namespace has its own set of system v ipc identifiers and its own posix message queue filesystem. objects created in an ipc namespace are visible to all other processes that are members of that namespace, but are not visible to processes in other ipc namespaces. .pp the following .i /proc interfaces are distinct in each ipc namespace: .ip * 3 the posix message queue interfaces in .ir /proc/sys/fs/mqueue . .ip * the system v ipc interfaces in .ir /proc/sys/kernel , namely: .ir msgmax , .ir msgmnb , .ir msgmni , .ir sem , .ir shmall , .ir shmmax , .ir shmmni , and .ir shm_rmid_forced . .ip * the system v ipc interfaces in .ir /proc/sysvipc . .pp when an ipc namespace is destroyed (i.e., when the last process that is a member of the namespace terminates), all ipc objects in the namespace are automatically destroyed. .pp use of ipc namespaces requires a kernel that is configured with the .b config_ipc_ns option. .sh see also .br nsenter (1), .br unshare (1), .br clone (2), .br setns (2), .br unshare (2), .br mq_overview (7), .br namespaces (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man7/iso_8859-3.7 .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th end 3 2020-06-09 "gnu" "linux programmer's manual" .sh name etext, edata, end \- end of program segments .sh synopsis .nf .bi extern " etext" ; .bi extern " edata" ; .bi extern " end" ; .fi .sh description the addresses of these symbols indicate the end of various program segments: .tp .i etext this is the first address past the end of the text segment (the program code). .tp .i edata this is the first address past the end of the initialized data segment. .tp .i end this is the first address past the end of the uninitialized data segment (also known as the bss segment). .sh conforming to although these symbols have long been provided on most unix systems, they are not standardized; use with caution. .sh notes the program must explicitly declare these symbols; they are not defined in any header file. .pp on some systems the names of these symbols are preceded by underscores, thus: .ir _etext , .ir _edata , and .ir _end . these symbols are also defined for programs compiled on linux. .pp at the start of program execution, the program break will be somewhere near .ir &end (perhaps at the start of the following page). however, the break will change as memory is allocated via .br brk (2) or .br malloc (3). use .br sbrk (2) with an argument of zero to find the current value of the program break. .sh examples when run, the program below produces output such as the following: .pp .in +4n .ex .rb "$" " ./a.out" first address past: program text (etext) 0x8048568 initialized data (edata) 0x804a01c uninitialized data (end) 0x804a024 .ee .in .ss program source \& .ex #include #include extern char etext, edata, end; /* the symbols must have some type, or "gcc \-wall" complains */ int main(int argc, char *argv[]) { printf("first address past:\en"); printf(" program text (etext) %10p\en", &etext); printf(" initialized data (edata) %10p\en", &edata); printf(" uninitialized data (end) %10p\en", &end); exit(exit_success); } .ee .sh see also .br objdump (1), .br readelf (1), .br sbrk (2), .br elf (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995, thomas k. dyas .\" and copyright (c) 2013, 2019, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created 1995-08-06 thomas k. dyas .\" modified 2000-07-01 aeb .\" modified 2002-07-23 aeb .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th setfsuid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setfsuid \- set user identity used for filesystem checks .sh synopsis .nf .b #include .pp .bi "int setfsuid(uid_t " fsuid ); .fi .sh description on linux, a process has both a filesystem user id and an effective user id. the (linux-specific) filesystem user id is used for permissions checking when accessing filesystem objects, while the effective user id is used for various other kinds of permissions checks (see .br credentials (7)). .pp normally, the value of the process's filesystem user id is the same as the value of its effective user id. this is so, because whenever a process's effective user id is changed, the kernel also changes the filesystem user id to be the same as the new value of the effective user id. a process can cause the value of its filesystem user id to diverge from its effective user id by using .br setfsuid () to change its filesystem user id to the value given in .ir fsuid . .pp explicit calls to .br setfsuid () and .br setfsgid (2) are (were) usually used only by programs such as the linux nfs server that need to change what user and group id is used for file access without a corresponding change in the real and effective user and group ids. a change in the normal user ids for a program such as the nfs server is (was) a security hole that can expose it to unwanted signals. (however, this issue is historical; see below.) .pp .br setfsuid () will succeed only if the caller is the superuser or if .i fsuid matches either the caller's real user id, effective user id, saved set-user-id, or current filesystem user id. .sh return value on both success and failure, this call returns the previous filesystem user id of the caller. .sh versions this system call is present in linux since version 1.2. .\" this system call is present since linux 1.1.44 .\" and in libc since libc 4.7.6. .sh conforming to .br setfsuid () is linux-specific and should not be used in programs intended to be portable. .sh notes at the time when this system call was introduced, one process could send a signal to another process with the same effective user id. this meant that if a privileged process changed its effective user id for the purpose of file permission checking, then it could become vulnerable to receiving signals sent by another (unprivileged) process with the same user id. the filesystem user id attribute was thus added to allow a process to change its user id for the purposes of file permission checking without at the same time becoming vulnerable to receiving unwanted signals. since linux 2.0, signal permission handling is different (see .br kill (2)), with the result that a process can change its effective user id without being vulnerable to receiving signals from unwanted processes. thus, .br setfsuid () is nowadays unneeded and should be avoided in new applications (likewise for .br setfsgid (2)). .pp the original linux .br setfsuid () system call supported only 16-bit user ids. subsequently, linux 2.4 added .br setfsuid32 () supporting 32-bit ids. the glibc .br setfsuid () wrapper function transparently deals with the variation across kernel versions. .ss c library/kernel differences in glibc 2.15 and earlier, when the wrapper for this system call determines that the argument can't be passed to the kernel without integer truncation (because the kernel is old and does not support 32-bit user ids), it will return \-1 and set \fierrno\fp to .b einval without attempting the system call. .sh bugs no error indications of any kind are returned to the caller, and the fact that both successful and unsuccessful calls return the same value makes it impossible to directly determine whether the call succeeded or failed. instead, the caller must resort to looking at the return value from a further call such as .ir setfsuid(\-1) (which will always fail), in order to determine if a preceding call to .br setfsuid () changed the filesystem user id. at the very least, .b eperm should be returned when the call fails (because the caller lacks the .b cap_setuid capability). .sh see also .br kill (2), .br setfsgid (2), .br capabilities (7), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setaliasent.3 .so man3/getrpcent_r.3 .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-4 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-4 \- iso 8859-4 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-4 encodes the characters used in scandinavian and baltic languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-4 characters the following table displays the characters in iso 8859-4 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ą latin capital letter a with ogonek 242 162 a2 ĸ latin small letter kra (greenlandic) 243 163 a3 ŗ latin capital letter r with cedilla 244 164 a4 ¤ currency sign 245 165 a5 ĩ latin capital letter i with tilde 246 166 a6 ļ latin capital letter l with cedilla 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 š latin capital letter s with caron 252 170 aa ē latin capital letter e with macron 253 171 ab ģ latin capital letter g with cedilla 254 172 ac ŧ latin capital letter t with stroke 255 173 ad ­ soft hyphen 256 174 ae ž latin capital letter z with caron 257 175 af ¯ macron 260 176 b0 ° degree sign 261 177 b1 ą latin small letter a with ogonek 262 178 b2 ˛ ogonek 263 179 b3 ŗ latin small letter r with cedilla 264 180 b4 ´ acute accent 265 181 b5 ĩ latin small letter i with tilde 266 182 b6 ļ latin small letter l with cedilla 267 183 b7 ˇ caron 270 184 b8 ¸ cedilla 271 185 b9 š latin small letter s with caron 272 186 ba ē latin small letter e with macron 273 187 bb ģ latin small letter g with cedilla 274 188 bc ŧ latin small letter t with stroke 275 189 bd ŋ latin capital letter eng 276 190 be ž latin small letter z with caron 277 191 bf ŋ latin small letter eng 300 192 c0 ā latin capital letter a with macron 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 į latin capital letter i with ogonek 310 200 c8 č latin capital letter c with caron 311 201 c9 é latin capital letter e with acute 312 202 ca ę latin capital letter e with ogonek 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ė latin capital letter e with dot above 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ī latin capital letter i with macron 320 208 d0 đ latin capital letter d with stroke 321 209 d1 ņ latin capital letter n with cedilla 322 210 d2 ō latin capital letter o with macron 323 211 d3 ķ latin capital letter k with cedilla 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ų latin capital letter u with ogonek 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ũ latin capital letter u with tilde 336 222 de ū latin capital letter u with macron 337 223 df ß latin small letter sharp s 340 224 e0 ā latin small letter a with macron 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 į latin small letter i with ogonek 350 232 e8 č latin small letter c with caron 351 233 e9 é latin small letter e with acute 352 234 ea ę latin small letter e with ogonek 353 235 eb ë latin small letter e with diaeresis 354 236 ec ė latin small letter e with dot above 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ī latin small letter i with macron 360 240 f0 đ latin small letter d with stroke 361 241 f1 ņ latin small letter n with cedilla 362 242 f2 ō latin small letter o with macron 363 243 f3 ķ latin small letter k with cedilla 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ø latin small letter o with stroke 371 249 f9 ų latin small letter u with ogonek 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ũ latin small letter u with tilde 376 254 fe ū latin small letter u with macron 377 255 ff ˙ dot above .te .sh notes iso 8859-4 is also known as latin-4. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2019 michael kerrisk .\" a very few fragments remain from an earlier page written by .\" werner almesberger in 2000 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pivot_root 2 2021-03-22 "linux" "linux programmer's manual" .sh name pivot_root \- change the root mount .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_pivot_root, const char *" new_root \ ", const char *" put_old ); .fi .pp .ir note : glibc provides no wrapper for .br pivot_root (), necessitating the use of .br syscall (2). .sh description .br pivot_root () changes the root mount in the mount namespace of the calling process. more precisely, it moves the root mount to the directory \fiput_old\fp and makes \finew_root\fp the new root mount. the calling process must have the .b cap_sys_admin capability in the user namespace that owns the caller's mount namespace. .pp .br pivot_root () changes the root directory and the current working directory of each process or thread in the same mount namespace to .i new_root if they point to the old root directory. (see also notes.) on the other hand, .br pivot_root () does not change the caller's current working directory (unless it is on the old root directory), and thus it should be followed by a \fbchdir("/")\fp call. .pp the following restrictions apply: .ip \- 3 .ir new_root and .ir put_old must be directories. .ip \- .i new_root and .i put_old must not be on the same mount as the current root. .ip \- \fiput_old\fp must be at or underneath \finew_root\fp; that is, adding some nonnegative number of "\fi/..\fp" prefixes to the pathname pointed to by .i put_old must yield the same directory as \finew_root\fp. .ip \- .i new_root must be a path to a mount point, but can't be .ir """/""" . a path that is not already a mount point can be converted into one by bind mounting the path onto itself. .ip \- the propagation type of the parent mount of .ir new_root and the parent mount of the current root directory must not be .br ms_shared ; similarly, if .i put_old is an existing mount point, its propagation type must not be .br ms_shared . these restrictions ensure that .br pivot_root () never propagates any changes to another mount namespace. .ip \- the current root directory must be a mount point. .sh return value on success, zero is returned. on error, \-1 is returned, and \fierrno\fp is set to indicate the error. .sh errors .br pivot_root () may fail with any of the same errors as .br stat (2). additionally, it may fail with the following errors: .tp .b ebusy .\" reconfirmed that the following error occurs on linux 5.0 by .\" specifying 'new_root' as "/rootfs" and 'put_old' as .\" "/rootfs/oldrootfs", and *not* bind mounting "/rootfs" on top of .\" itself. of course, this is an odd situation, since a later check .\" in the kernel code will in any case yield einval if 'new_root' is .\" not a mount point. however, when the system call was first added, .\" 'new_root' was not required to be a mount point. so, this .\" error is nowadays probably just the result of crufty accumulation. .\" this error can also occur if we bind mount "/" on top of itself .\" and try to specify "/" as the 'new' (again, an odd situation). so, .\" the ebusy check in the kernel does still seem necessary to prevent .\" that case. furthermore, the "or put_old" piece is probably .\" redundant text (although the check is in the kernel), since, .\" in another check, 'put_old' is required to be under 'new_root'. .i new_root or .i put_old is on the current root mount. (this error covers the pathological case where .i new_root is .ir """/""" .) .tp .b einval .i new_root is not a mount point. .tp .b einval \fiput_old\fp is not at or underneath \finew_root\fp. .tp .b einval the current root directory is not a mount point (because of an earlier .br chroot (2)). .tp .b einval the current root is on the rootfs (initial ramfs) mount; see notes. .tp .b einval either the mount point at .ir new_root , or the parent mount of that mount point, has propagation type .br ms_shared . .tp .b einval .i put_old is a mount point and has the propagation type .br ms_shared . .tp .b enotdir \finew_root\fp or \fiput_old\fp is not a directory. .tp .b eperm the calling process does not have the .b cap_sys_admin capability. .sh versions .br pivot_root () was introduced in linux 2.3.41. .sh conforming to .br pivot_root () is linux-specific and hence is not portable. .sh notes a command-line interface for this system call is provided by .br pivot_root (8). .pp .br pivot_root () allows the caller to switch to a new root filesystem while at the same time placing the old root mount at a location under .i new_root from where it can subsequently be unmounted. (the fact that it moves all processes that have a root directory or current working directory on the old root directory to the new root frees the old root directory of users, allowing the old root mount to be unmounted more easily.) .pp one use of .br pivot_root () is during system startup, when the system mounts a temporary root filesystem (e.g., an .br initrd (4)), then mounts the real root filesystem, and eventually turns the latter into the root directory of all relevant processes and threads. a modern use is to set up a root filesystem during the creation of a container. .pp the fact that .br pivot_root () modifies process root and current working directories in the manner noted in description is necessary in order to prevent kernel threads from keeping the old root mount busy with their root and current working directories, even if they never access the filesystem in any way. .pp the rootfs (initial ramfs) cannot be .br pivot_root ()ed. the recommended method of changing the root filesystem in this case is to delete everything in rootfs, overmount rootfs with the new root, attach .ir stdin / stdout / stderr to the new .ir /dev/console , and exec the new .br init (1). helper programs for this process exist; see .br switch_root (8). .\" .ss pivot_root(\(dq.\(dq, \(dq.\(dq) .i new_root and .i put_old may be the same directory. in particular, the following sequence allows a pivot-root operation without needing to create and remove a temporary directory: .pp .in +4n .ex chdir(new_root); pivot_root(".", "."); umount2(".", mnt_detach); .ee .in .pp this sequence succeeds because the .br pivot_root () call stacks the old root mount point on top of the new root mount point at .ir / . at that point, the calling process's root directory and current working directory refer to the new root mount point .ri ( new_root ). during the subsequent .br umount () call, resolution of .ir """.""" starts with .i new_root and then moves up the list of mounts stacked at .ir / , with the result that old root mount point is unmounted. .\" .ss historical notes for many years, this manual page carried the following text: .rs .pp .br pivot_root () may or may not change the current root and the current working directory of any processes or threads which use the old root directory. the caller of .br pivot_root () must ensure that processes with root or current working directory at the old root operate correctly in either case. an easy way to ensure this is to change their root and current working directory to \finew_root\fp before invoking .br pivot_root (). .re .pp this text, written before the system call implementation was even finalized in the kernel, was probably intended to warn users at that time that the implementation might change before final release. however, the behavior stated in description has remained consistent since this system call was first implemented and will not change now. .sh examples .\" fixme .\" would it be better, because simpler, to use unshare(2) .\" rather than clone(2) in the example below? the program below demonstrates the use of .br pivot_root () inside a mount namespace that is created using .br clone (2). after pivoting to the root directory named in the program's first command-line argument, the child created by .br clone (2) then executes the program named in the remaining command-line arguments. .pp we demonstrate the program by creating a directory that will serve as the new root filesystem and placing a copy of the (statically linked) .br busybox (1) executable in that directory. .pp .in +4n .ex $ \fbmkdir /tmp/rootfs\fp $ \fbls \-id /tmp/rootfs\fp # show inode number of new root directory 319459 /tmp/rootfs $ \fbcp $(which busybox) /tmp/rootfs\fp $ \fbps1=\(aqbbsh$ \(aq sudo ./pivot_root_demo /tmp/rootfs /busybox sh\fp bbsh$ \fbpath=/\fp bbsh$ \fbbusybox ln busybox ln\fp bbsh$ \fbln busybox echo\fp bbsh$ \fbln busybox ls\fp bbsh$ \fbls\fp busybox echo ln ls bbsh$ \fbls \-id /\fp # compare with inode number above 319459 / bbsh$ \fbecho \(aqhello world\(aq\fp hello world .ee .in .ss program source \& .pp .ex /* pivot_root_demo.c */ #define _gnu_source #include #include #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static int pivot_root(const char *new_root, const char *put_old) { return syscall(sys_pivot_root, new_root, put_old); } #define stack_size (1024 * 1024) static int /* startup function for cloned child */ child(void *arg) { char **args = arg; char *new_root = args[0]; const char *put_old = "/oldrootfs"; char path[path_max]; /* ensure that \(aqnew_root\(aq and its parent mount don\(aqt have shared propagation (which would cause pivot_root() to return an error), and prevent propagation of mount events to the initial mount namespace. */ if (mount(null, "/", null, ms_rec | ms_private, null) == \-1) errexit("mount\-ms_private"); /* ensure that \(aqnew_root\(aq is a mount point. */ if (mount(new_root, new_root, null, ms_bind, null) == \-1) errexit("mount\-ms_bind"); /* create directory to which old root will be pivoted. */ snprintf(path, sizeof(path), "%s/%s", new_root, put_old); if (mkdir(path, 0777) == \-1) errexit("mkdir"); /* and pivot the root filesystem. */ if (pivot_root(new_root, path) == \-1) errexit("pivot_root"); /* switch the current working directory to "/". */ if (chdir("/") == \-1) errexit("chdir"); /* unmount old root and remove mount point. */ if (umount2(put_old, mnt_detach) == \-1) perror("umount2"); if (rmdir(put_old) == \-1) perror("rmdir"); /* execute the command specified in argv[1]... */ execv(args[1], &args[1]); errexit("execv"); } int main(int argc, char *argv[]) { /* create a child process in a new mount namespace. */ char *stack = mmap(null, stack_size, prot_read | prot_write, map_private | map_anonymous | map_stack, \-1, 0); if (stack == map_failed) errexit("mmap"); if (clone(child, stack + stack_size, clone_newns | sigchld, &argv[1]) == \-1) errexit("clone"); /* parent falls through to here; wait for child. */ if (wait(null) == \-1) errexit("wait"); exit(exit_success); } .ee .sh see also .br chdir (2), .br chroot (2), .br mount (2), .br stat (2), .br initrd (4), .br mount_namespaces (7), .br pivot_root (8), .br switch_root (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1999 suse gmbh nuernberg, germany .\" author: thorsten kukuk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of the .\" license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the gnu .\" general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2008-12-05 petr baudis .\" rewrite the notes section to reflect modern reality .\" .th nscd 8 2015-05-07 "gnu" "linux programmer's manual" .sh name nscd \- name service cache daemon .sh description .b nscd is a daemon that provides a cache for the most common name service requests. the default configuration file, .ir /etc/nscd.conf , determines the behavior of the cache daemon. see .br nscd.conf (5). .pp .b nscd provides caching for accesses of the .br passwd (5), .br group (5), .br hosts (5) .br services (5) and .i netgroup databases through standard libc interfaces, such as .br getpwnam (3), .br getpwuid (3), .br getgrnam (3), .br getgrgid (3), .br gethostbyname (3), and others. .pp there are two caches for each database: a positive one for items found, and a negative one for items not found. each cache has a separate ttl (time-to-live) period for its data. note that the shadow file is specifically not cached. .br getspnam (3) calls remain uncached as a result. .sh options .tp .b "\-\-help" will give you a list with all options and what they do. .sh notes the daemon will try to watch for changes in configuration files appropriate for each database (e.g., .i /etc/passwd for the .i passwd database or .i /etc/hosts and .i /etc/resolv.conf for the .i hosts database), and flush the cache when these are changed. however, this will happen only after a short delay (unless the .br inotify (7) mechanism is available and glibc 2.9 or later is available), and this auto-detection does not cover configuration files required by nonstandard nss modules, if any are specified in .ir /etc/nsswitch.conf . in that case, you need to run the following command after changing the configuration file of the database so that .b nscd invalidates its cache: .pp .in +4n .ex $ \fbnscd \-i\fp \fi\fp .ee .in .sh see also .br nscd.conf (5), .br nsswitch.conf (5) .\" .sh author .\" .b nscd .\" was written by thorsten kukuk and ulrich drepper. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 luigi p. bai (lpb@softint.com) july 28, 1993 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 28 10:57:35 1993, rik faith .\" modified sun nov 28 16:43:30 1993, rik faith .\" with material from giorgio ciucci .\" portions copyright 1993 giorgio ciucci .\" modified tue oct 22 22:03:17 1996 by eric s. raymond .\" modified, 8 jan 2003, michael kerrisk, .\" removed eidrm from errors - that can't happen... .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" added notes on /proc files .\" .th shmget 2 2021-03-22 "linux" "linux programmer's manual" .sh name shmget \- allocates a system v shared memory segment .sh synopsis .nf .ad l .b #include .pp .bi "int shmget(key_t " key ", size_t " size ", int " shmflg ); .ad b .fi .sh description .br shmget () returns the identifier of the system\ v shared memory segment associated with the value of the argument .ir key . it may be used either to obtain the identifier of a previously created shared memory segment (when .i shmflg is zero and .i key does not have the value .br ipc_private ), or to create a new set. .pp a new shared memory segment, with size equal to the value of .i size rounded up to a multiple of .br page_size , is created if .i key has the value .b ipc_private or .i key isn't .br ipc_private , no shared memory segment corresponding to .i key exists, and .b ipc_creat is specified in .ir shmflg . .pp if .i shmflg specifies both .b ipc_creat and .b ipc_excl and a shared memory segment already exists for .ir key , then .br shmget () fails with .i errno set to .br eexist . (this is analogous to the effect of the combination .b o_creat | o_excl for .br open (2).) .pp the value .i shmflg is composed of: .tp .b ipc_creat create a new segment. if this flag is not used, then .br shmget () will find the segment associated with \fikey\fp and check to see if the user has permission to access the segment. .tp .b ipc_excl this flag is used with .b ipc_creat to ensure that this call creates the segment. if the segment already exists, the call fails. .tp .br shm_hugetlb " (since linux 2.6)" allocate the segment using "huge" pages. see the linux kernel source file .i documentation/admin\-guide/mm/hugetlbpage.rst for further information. .tp .br shm_huge_2mb ", " shm_huge_1gb " (since linux 3.8)" .\" see https://lwn.net/articles/533499/ used in conjunction with .b shm_hugetlb to select alternative hugetlb page sizes (respectively, 2\ mb and 1\ gb) on systems that support multiple hugetlb page sizes. .ip more generally, the desired huge page size can be configured by encoding the base-2 logarithm of the desired page size in the six bits at the offset .br shm_huge_shift . thus, the above two constants are defined as: .ip .in +4n .ex #define shm_huge_2mb (21 << shm_huge_shift) #define shm_huge_1gb (30 << shm_huge_shift) .ee .in .ip for some additional details, see the discussion of the similarly named constants in .br mmap (2). .tp .br shm_noreserve " (since linux 2.6.15)" this flag serves the same purpose as the .br mmap (2) .b map_noreserve flag. do not reserve swap space for this segment. when swap space is reserved, one has the guarantee that it is possible to modify the segment. when swap space is not reserved one might get .b sigsegv upon a write if no physical memory is available. see also the discussion of the file .i /proc/sys/vm/overcommit_memory in .br proc (5). .\" as at 2.6.17-rc2, this flag has no effect if shm_hugetlb was also .\" specified. .pp in addition to the above flags, the least significant 9 bits of .i shmflg specify the permissions granted to the owner, group, and others. these bits have the same format, and the same meaning, as the .i mode argument of .br open (2). presently, execute permissions are not used by the system. .pp when a new shared memory segment is created, its contents are initialized to zero values, and its associated data structure, .i shmid_ds (see .br shmctl (2)), is initialized as follows: .ip \(bu 2 .i shm_perm.cuid and .i shm_perm.uid are set to the effective user id of the calling process. .ip \(bu .i shm_perm.cgid and .i shm_perm.gid are set to the effective group id of the calling process. .ip \(bu the least significant 9 bits of .i shm_perm.mode are set to the least significant 9 bit of .ir shmflg . .ip \(bu .i shm_segsz is set to the value of .ir size . .ip \(bu .ir shm_lpid , .ir shm_nattch , .ir shm_atime , and .i shm_dtime are set to 0. .ip \(bu .i shm_ctime is set to the current time. .pp if the shared memory segment already exists, the permissions are verified, and a check is made to see if it is marked for destruction. .sh return value on success, a valid shared memory identifier is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces the user does not have permission to access the shared memory segment, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b eexist .br ipc_creat and .br ipc_excl were specified in .ir shmflg , but a shared memory segment already exists for .ir key . .tp .b einval a new segment was to be created and .i size is less than .b shmmin or greater than .br shmmax . .tp .b einval a segment for the given .i key exists, but \fisize\fp is greater than the size of that segment. .tp .b enfile .\" [2.6.7] shmem_zero_setup()-->shmem_file_setup()-->get_empty_filp() the system-wide limit on the total number of open files has been reached. .tp .b enoent no segment exists for the given \fikey\fp, and .b ipc_creat was not specified. .tp .b enomem no memory could be allocated for segment overhead. .tp .b enospc all possible shared memory ids have been taken .rb ( shmmni ), or allocating a segment of the requested .i size would cause the system to exceed the system-wide limit on shared memory .rb ( shmall ). .tp .b eperm the .b shm_hugetlb flag was specified, but the caller was not privileged (did not have the .b cap_ipc_lock capability) and is not a member of the .i sysctl_hugetlb_shm_group group; see the description of .i /proc/sys/vm/sysctl_hugetlb_shm_group in .br proc (5). .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svr4 documents an additional error condition eexist. .pp .b shm_hugetlb and .b shm_noreserve are linux extensions. .sh notes .b ipc_private isn't a flag field but a .i key_t type. if this special value is used for .ir key , the system call ignores all but the least significant 9 bits of .i shmflg and creates a new shared memory segment. .\" .ss shared memory limits the following limits on shared memory segment resources affect the .br shmget () call: .tp .b shmall system-wide limit on the total amount of shared memory, measured in units of the system page size. .ip on linux, this limit can be read and modified via .ir /proc/sys/kernel/shmall . since linux 3.16, .\" commit 060028bac94bf60a65415d1d55a359c3a17d5c31 the default value for this limit is: .ip ulong_max - 2^24 .ip the effect of this value (which is suitable for both 32-bit and 64-bit systems) is to impose no limitation on allocations. this value, rather than .br ulong_max , was chosen as the default to prevent some cases where historical applications simply raised the existing limit without first checking its current value. such applications would cause the value to overflow if the limit was set at .br ulong_max . .ip from linux 2.4 up to linux 3.15, the default value for this limit was: .ip shmmax / page_size * (shmmni / 16) .ip if .b shmmax and .b shmmni were not modified, then multiplying the result of this formula by the page size (to get a value in bytes) yielded a value of 8\ gb as the limit on the total memory used by all shared memory segments. .tp .b shmmax maximum size in bytes for a shared memory segment. .ip on linux, this limit can be read and modified via .ir /proc/sys/kernel/shmmax . since linux 3.16, .\" commit 060028bac94bf60a65415d1d55a359c3a17d5c31 the default value for this limit is: .ip ulong_max - 2^24 .ip the effect of this value (which is suitable for both 32-bit and 64-bit systems) is to impose no limitation on allocations. see the description of .br shmall for a discussion of why this default value (rather than .br ulong_max ) is used. .ip from linux 2.2 up to linux 3.15, the default value of this limit was 0x2000000 (32\ mb). .ip because it is not possible to map just part of a shared memory segment, the amount of virtual memory places another limit on the maximum size of a usable segment: for example, on i386 the largest segments that can be mapped have a size of around 2.8\ gb, and on x86-64 the limit is around 127 tb. .tp .b shmmin minimum size in bytes for a shared memory segment: implementation dependent (currently 1 byte, though .b page_size is the effective minimum size). .tp .b shmmni system-wide limit on the number of shared memory segments. in linux 2.2, the default value for this limit was 128; since linux 2.4, the default value is 4096. .ip on linux, this limit can be read and modified via .ir /proc/sys/kernel/shmmni . .\" kernels between 2.4.x and 2.6.8 had an off-by-one error that meant .\" that we could create one more segment than shmmni -- mtk .\" this /proc file is not available in linux 2.2 and earlier -- mtk .pp the implementation has no specific limits for the per-process maximum number of shared memory segments .rb ( shmseg ). .ss linux notes until version 2.3.30, linux would return .b eidrm for a .br shmget () on a shared memory segment scheduled for deletion. .sh bugs the name choice .b ipc_private was perhaps unfortunate, .b ipc_new would more clearly show its function. .sh examples see .br shmop (2). .sh see also .br memfd_create (2), .br shmat (2), .br shmctl (2), .br shmdt (2), .br ftok (3), .br capabilities (7), .br shm_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 robert love .\" and copyright (c) 2006, 2015 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2002-11-19 robert love - initial version .\" 2004-04-20 mtk - fixed description of return value .\" 2004-04-22 aeb - added glibc prototype history .\" 2005-05-03 mtk - noted that sched_setaffinity may cause thread .\" migration and that cpu affinity is a per-thread attribute. .\" 2006-02-03 mtk -- major rewrite .\" 2008-11-12, mtk, removed cpu_*() macro descriptions to a .\" separate cpu_set(3) page. .\" .th sched_setaffinity 2 2021-03-22 "linux" "linux programmer's manual" .sh name sched_setaffinity, sched_getaffinity \- \ set and get a thread's cpu affinity mask .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int sched_setaffinity(pid_t " pid ", size_t " cpusetsize , .bi " const cpu_set_t *" mask ); .bi "int sched_getaffinity(pid_t " pid ", size_t " cpusetsize , .bi " cpu_set_t *" mask ); .fi .sh description a thread's cpu affinity mask determines the set of cpus on which it is eligible to run. on a multiprocessor system, setting the cpu affinity mask can be used to obtain performance benefits. for example, by dedicating one cpu to a particular thread (i.e., setting the affinity mask of that thread to specify a single cpu, and setting the affinity mask of all other threads to exclude that cpu), it is possible to ensure maximum execution speed for that thread. restricting a thread to run on a single cpu also avoids the performance cost caused by the cache invalidation that occurs when a thread ceases to execute on one cpu and then recommences execution on a different cpu. .pp a cpu affinity mask is represented by the .i cpu_set_t structure, a "cpu set", pointed to by .ir mask . a set of macros for manipulating cpu sets is described in .br cpu_set (3). .pp .br sched_setaffinity () sets the cpu affinity mask of the thread whose id is .i pid to the value specified by .ir mask . if .i pid is zero, then the calling thread is used. the argument .i cpusetsize is the length (in bytes) of the data pointed to by .ir mask . normally this argument would be specified as .ir "sizeof(cpu_set_t)" . .pp if the thread specified by .i pid is not currently running on one of the cpus specified in .ir mask , then that thread is migrated to one of the cpus specified in .ir mask . .pp .br sched_getaffinity () writes the affinity mask of the thread whose id is .i pid into the .i cpu_set_t structure pointed to by .ir mask . the .i cpusetsize argument specifies the size (in bytes) of .ir mask . if .i pid is zero, then the mask of the calling thread is returned. .sh return value on success, .br sched_setaffinity () and .br sched_getaffinity () return 0 (but see "c library/kernel differences" below, which notes that the underlying .br sched_getaffinity () differs in its return value). on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault a supplied memory address was invalid. .tp .b einval the affinity bit mask .i mask contains no processors that are currently physically on the system and permitted to the thread according to any restrictions that may be imposed by .i cpuset cgroups or the "cpuset" mechanism described in .br cpuset (7). .tp .b einval .rb ( sched_getaffinity () and, in kernels before 2.6.9, .br sched_setaffinity ()) .i cpusetsize is smaller than the size of the affinity mask used by the kernel. .tp .b eperm .rb ( sched_setaffinity ()) the calling thread does not have appropriate privileges. the caller needs an effective user id equal to the real user id or effective user id of the thread identified by .ir pid , or it must possess the .b cap_sys_nice capability in the user namespace of the thread .ir pid . .tp .b esrch the thread whose id is \fipid\fp could not be found. .sh versions the cpu affinity system calls were introduced in linux kernel 2.5.8. the system call wrappers were introduced in glibc 2.3. initially, the glibc interfaces included a .i cpusetsize argument, typed as .ir "unsigned int" . in glibc 2.3.3, the .i cpusetsize argument was removed, but was then restored in glibc 2.3.4, with type .ir size_t . .sh conforming to these system calls are linux-specific. .sh notes after a call to .br sched_setaffinity (), the set of cpus on which the thread will actually run is the intersection of the set specified in the .i mask argument and the set of cpus actually present on the system. the system may further restrict the set of cpus on which the thread runs if the "cpuset" mechanism described in .br cpuset (7) is being used. these restrictions on the actual set of cpus on which the thread will run are silently imposed by the kernel. .pp there are various ways of determining the number of cpus available on the system, including: inspecting the contents of .ir /proc/cpuinfo ; using .br sysconf (3) to obtain the values of the .br _sc_nprocessors_conf and .br _sc_nprocessors_onln parameters; and inspecting the list of cpu directories under .ir /sys/devices/system/cpu/ . .pp .br sched (7) has a description of the linux scheduling scheme. .pp the affinity mask is a per-thread attribute that can be adjusted independently for each of the threads in a thread group. the value returned from a call to .br gettid (2) can be passed in the argument .ir pid . specifying .i pid as 0 will set the attribute for the calling thread, and passing the value returned from a call to .br getpid (2) will set the attribute for the main thread of the thread group. (if you are using the posix threads api, then use .br pthread_setaffinity_np (3) instead of .br sched_setaffinity ().) .pp the .i isolcpus boot option can be used to isolate one or more cpus at boot time, so that no processes are scheduled onto those cpus. following the use of this boot option, the only way to schedule processes onto the isolated cpus is via .br sched_setaffinity () or the .br cpuset (7) mechanism. for further information, see the kernel source file .ir documentation/admin\-guide/kernel\-parameters.txt . as noted in that file, .i isolcpus is the preferred mechanism of isolating cpus (versus the alternative of manually setting the cpu affinity of all processes on the system). .pp a child created via .br fork (2) inherits its parent's cpu affinity mask. the affinity mask is preserved across an .br execve (2). .ss c library/kernel differences this manual page describes the glibc interface for the cpu affinity calls. the actual system call interface is slightly different, with the .i mask being typed as .ir "unsigned long\ *" , reflecting the fact that the underlying implementation of cpu sets is a simple bit mask. .pp on success, the raw .br sched_getaffinity () system call returns the number of bytes placed copied into the .i mask buffer; this will be the minimum of .i cpusetsize and the size (in bytes) of the .i cpumask_t data type that is used internally by the kernel to represent the cpu set bit mask. .ss handling systems with large cpu affinity masks the underlying system calls (which represent cpu masks as bit masks of type .ir "unsigned long\ *" ) impose no restriction on the size of the cpu mask. however, the .i cpu_set_t data type used by glibc has a fixed size of 128 bytes, meaning that the maximum cpu number that can be represented is 1023. .\" fixme . see https://sourceware.org/bugzilla/show_bug.cgi?id=15630 .\" and https://sourceware.org/ml/libc-alpha/2013-07/msg00288.html if the kernel cpu affinity mask is larger than 1024, then calls of the form: .pp sched_getaffinity(pid, sizeof(cpu_set_t), &mask); .pp fail with the error .br einval , the error produced by the underlying system call for the case where the .i mask size specified in .i cpusetsize is smaller than the size of the affinity mask used by the kernel. (depending on the system cpu topology, the kernel affinity mask can be substantially larger than the number of active cpus in the system.) .pp when working on systems with large kernel cpu affinity masks, one must dynamically allocate the .i mask argument (see .br cpu_alloc (3)). currently, the only way to do this is by probing for the size of the required mask using .br sched_getaffinity () calls with increasing mask sizes (until the call does not fail with the error .br einval ). .pp be aware that .br cpu_alloc (3) may allocate a slightly larger cpu set than requested (because cpu sets are implemented as bit masks allocated in units of .ir sizeof(long) ). consequently, .br sched_getaffinity () can set bits beyond the requested allocation size, because the kernel sees a few additional bits. therefore, the caller should iterate over the bits in the returned set, counting those which are set, and stop upon reaching the value returned by .br cpu_count (3) (rather than iterating over the number of bits requested to be allocated). .sh examples the program below creates a child process. the parent and child then each assign themselves to a specified cpu and execute identical loops that consume some cpu time. before terminating, the parent waits for the child to complete. the program takes three command-line arguments: the cpu number for the parent, the cpu number for the child, and the number of loop iterations that both processes should perform. .pp as the sample runs below demonstrate, the amount of real and cpu time consumed when running the program will depend on intra-core caching effects and whether the processes are using the same cpu. .pp we first employ .br lscpu (1) to determine that this (x86) system has two cores, each with two cpus: .pp .in +4n .ex $ \fblscpu | egrep \-i \(aqcore.*:|socket\(aq\fp thread(s) per core: 2 core(s) per socket: 2 socket(s): 1 .ee .in .pp we then time the operation of the example program for three cases: both processes running on the same cpu; both processes running on different cpus on the same core; and both processes running on different cpus on different cores. .pp .in +4n .ex $ \fbtime \-p ./a.out 0 0 100000000\fp real 14.75 user 3.02 sys 11.73 $ \fbtime \-p ./a.out 0 1 100000000\fp real 11.52 user 3.98 sys 19.06 $ \fbtime \-p ./a.out 0 3 100000000\fp real 7.89 user 3.29 sys 12.07 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { cpu_set_t set; int parentcpu, childcpu; int nloops; if (argc != 4) { fprintf(stderr, "usage: %s parent\-cpu child\-cpu num\-loops\en", argv[0]); exit(exit_failure); } parentcpu = atoi(argv[1]); childcpu = atoi(argv[2]); nloops = atoi(argv[3]); cpu_zero(&set); switch (fork()) { case \-1: /* error */ errexit("fork"); case 0: /* child */ cpu_set(childcpu, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == \-1) errexit("sched_setaffinity"); for (int j = 0; j < nloops; j++) getppid(); exit(exit_success); default: /* parent */ cpu_set(parentcpu, &set); if (sched_setaffinity(getpid(), sizeof(set), &set) == \-1) errexit("sched_setaffinity"); for (int j = 0; j < nloops; j++) getppid(); wait(null); /* wait for child to terminate */ exit(exit_success); } } .ee .sh see also .ad l .nh .br lscpu (1), .br nproc (1), .br taskset (1), .br clone (2), .br getcpu (2), .br getpriority (2), .br gettid (2), .br nice (2), .br sched_get_priority_max (2), .br sched_get_priority_min (2), .br sched_getscheduler (2), .br sched_setscheduler (2), .br setpriority (2), .br cpu_set (3), .br get_nprocs (3), .br pthread_setaffinity_np (3), .br sched_getcpu (3), .br capabilities (7), .br cpuset (7), .br sched (7), .br numactl (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/unlocked_stdio.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th getgrent_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getgrent_r, fgetgrent_r \- get group file entry reentrantly .sh synopsis .nf .b #include .pp .bi "int getgrent_r(struct group *restrict " gbuf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct group **restrict " gbufp ); .bi "int fgetgrent_r(file *restrict " stream ", struct group *restrict " gbuf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct group **restrict " gbufp ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getgrent_r (): .nf _gnu_source .fi .\" fixme . the ftm requirements seem inconsistent here. file a glibc bug? .pp .br fgetgrent_r (): since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .sh description the functions .br getgrent_r () and .br fgetgrent_r () are the reentrant versions of .br getgrent (3) and .br fgetgrent (3). the former reads the next group entry from the stream initialized by .br setgrent (3). the latter reads the next group entry from .ir stream . .pp the \figroup\fp structure is defined in .i as follows: .pp .in +4n .ex struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ gid_t gr_gid; /* group id */ char **gr_mem; /* null\-terminated array of pointers to names of group members */ }; .ee .in .pp for more information about the fields of this structure, see .br group (5). .pp the nonreentrant functions return a pointer to static storage, where this static storage contains further pointers to group name, password, and members. the reentrant functions described here return all of that in caller-provided buffers. first of all there is the buffer .i gbuf that can hold a \fistruct group\fp. and next the buffer .i buf of size .i buflen that can hold additional strings. the result of these functions, the \fistruct group\fp read from the stream, is stored in the provided buffer .ir *gbuf , and a pointer to this \fistruct group\fp is returned in .ir *gbufp . .sh return value on success, these functions return 0 and .i *gbufp is a pointer to the \fistruct group\fp. on error, these functions return an error value and .i *gbufp is null. .sh errors .tp .b enoent no more entries. .tp .b erange insufficient buffer space supplied. try again with larger buffer. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getgrent_r () t} thread safety t{ mt-unsafe race:grent locale t} t{ .br fgetgrent_r () t} thread safety t{ mt-safe t} .te .hy .ad .sp 1 in the above table, .i grent in .i race:grent signifies that if any of the functions .br setgrent (3), .br getgrent (3), .br endgrent (3), or .br getgrent_r () are used in parallel in different threads of a program, then data races could occur. .sh conforming to these functions are gnu extensions, done in a style resembling the posix version of functions like .br getpwnam_r (3). other systems use the prototype .pp .in +4n .ex struct group *getgrent_r(struct group *grp, char *buf, int buflen); .ee .in .pp or, better, .pp .in +4n .ex int getgrent_r(struct group *grp, char *buf, int buflen, file **gr_fp); .ee .in .sh notes the function .br getgrent_r () is not really reentrant since it shares the reading position in the stream with all other threads. .sh examples .ex #define _gnu_source #include #include #include #include #define buflen 4096 int main(void) { struct group grp; struct group *grpp; char buf[buflen]; int i; setgrent(); while (1) { i = getgrent_r(&grp, buf, sizeof(buf), &grpp); if (i) break; printf("%s (%jd):", grpp\->gr_name, (intmax_t) grpp\->gr_gid); for (int j = 0; ; j++) { if (grpp\->gr_mem[j] == null) break; printf(" %s", grpp\->gr_mem[j]); } printf("\en"); } endgrent(); exit(exit_success); } .ee .\" perhaps add error checking - should use strerror_r .\" #include .\" #include .\" if (i) { .\" if (i == enoent) .\" break; .\" printf("getgrent_r: %s", strerror(i)); .\" exit(exit_failure); .\" } .sh see also .br fgetgrent (3), .br getgrent (3), .br getgrgid (3), .br getgrnam (3), .br putgrent (3), .br group (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man2/signalfd.2 .so man2/wait.2 .so man3/ctan.3 .so man3/argz_add.3 .so man2/set_thread_area.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1996-06-08 by aeb .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th cosh 3 2021-03-22 "" "linux programmer's manual" .sh name cosh, coshf, coshl \- hyperbolic cosine function .sh synopsis .nf .b #include .pp .bi "double cosh(double " x ); .bi "float coshf(float " x ); .bi "long double coshl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br coshf (), .br coshl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the hyperbolic cosine of .ir x , which is defined mathematically as: .pp .nf cosh(x) = (exp(x) + exp(\-x)) / 2 .fi .sh return value on success, these functions return the hyperbolic cosine of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 or \-0, 1 is returned. .pp if .i x is positive infinity or negative infinity, positive infinity is returned. .pp if the result overflows, a range error occurs, and the functions return .rb + huge_val , .rb + huge_valf , or .rb + huge_vall , respectively. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cosh (), .br coshf (), .br coshl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh bugs in glibc version 2.3.4 and earlier, an overflow floating-point .rb ( fe_overflow ) exception is not raised when an overflow occurs. .sh see also .br acosh (3), .br asinh (3), .br atanh (3), .br ccos (3), .br sinh (3), .br tanh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th mbtowc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mbtowc \- convert a multibyte sequence to a wide character .sh synopsis .nf .b #include .pp .bi "int mbtowc(wchar_t *restrict " pwc ", const char *restrict " s \ ", size_t " n ); .fi .sh description the main case for this function is when .ir s is not null and .i pwc is not null. in this case, the .br mbtowc () function inspects at most .i n bytes of the multibyte string starting at .ir s , extracts the next complete multibyte character, converts it to a wide character and stores it at .ir *pwc . it updates an internal shift state known only to the .br mbtowc () function. if .i s does not point to a null byte (\(aq\e0\(aq), it returns the number of bytes that were consumed from .ir s , otherwise it returns 0. .pp if the .ir n bytes starting at .i s do not contain a complete multibyte character, or if they contain an invalid multibyte sequence, .br mbtowc () returns \-1. this can happen even if .i n >= .ir mb_cur_max , if the multibyte string contains redundant shift sequences. .pp a different case is when .ir s is not null but .i pwc is null. in this case, the .br mbtowc () function behaves as above, except that it does not store the converted wide character in memory. .pp a third case is when .i s is null. in this case, .ir pwc and .i n are ignored. the .br mbtowc () function .\" the dinkumware doc and the single unix specification say this, but .\" glibc doesn't implement this. resets the shift state, only known to this function, to the initial state, and returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless. .sh return value if .i s is not null, the .br mbtowc () function returns the number of consumed bytes starting at .ir s , or 0 if .i s points to a null byte, or \-1 upon failure. .pp if .i s is null, the .br mbtowc () function returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mbtowc () t} thread safety mt-unsafe race .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br mbtowc () depends on the .b lc_ctype category of the current locale. .pp this function is not multithread safe. the function .br mbrtowc (3) provides a better interface to the same functionality. .sh see also .br mb_cur_max (3), .br mblen (3), .br mbrtowc (3), .br mbstowcs (3), .br wcstombs (3), .br wctomb (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/symlink.2 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)truncate.2 6.9 (berkeley) 3/10/91 .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-10-22 by eric s. raymond .\" modified 1998-12-21 by andries brouwer .\" modified 2002-01-07 by michael kerrisk .\" modified 2002-04-06 by andries brouwer .\" modified 2004-06-23 by michael kerrisk .\" .th truncate 2 2021-03-22 "linux" "linux programmer's manual" .sh name truncate, ftruncate \- truncate a file to a specified length .sh synopsis .nf .b #include .pp .bi "int truncate(const char *" path ", off_t " length ); .bi "int ftruncate(int " fd ", off_t " length ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br truncate (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source .fi .pp .br ftruncate (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.3.5: */ _posix_c_source >= 200112l || /* glibc <= 2.19: */ _bsd_source .fi .sh description the .br truncate () and .br ftruncate () functions cause the regular file named by .i path or referenced by .i fd to be truncated to a size of precisely .i length bytes. .pp if the file previously was larger than this size, the extra data is lost. if the file previously was shorter, it is extended, and the extended part reads as null bytes (\(aq\e0\(aq). .pp the file offset is not changed. .pp if the size changed, then the st_ctime and st_mtime fields (respectively, time of last status change and time of last modification; see .br inode (7)) for the file are updated, and the set-user-id and set-group-id mode bits may be cleared. .pp with .br ftruncate (), the file must be open for writing; with .br truncate (), the file must be writable. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors for .br truncate (): .tp .b eacces search permission is denied for a component of the path prefix, or the named file is not writable by the user. (see also .br path_resolution (7).) .tp .b efault the argument .i path points outside the process's allocated address space. .tp .b efbig the argument .i length is larger than the maximum file size. (xsi) .tp .b eintr while blocked waiting to complete, the call was interrupted by a signal handler; see .br fcntl (2) and .br signal (7). .tp .b einval the argument .i length is negative or larger than the maximum file size. .tp .b eio an i/o error occurred updating the inode. .tp .b eisdir the named file is a directory. .tp .b eloop too many symbolic links were encountered in translating the pathname. .tp .b enametoolong a component of a pathname exceeded 255 characters, or an entire pathname exceeded 1023 characters. .tp .b enoent the named file does not exist. .tp .b enotdir a component of the path prefix is not a directory. .tp .b eperm .\" this happens for at least msdos and vfat filesystems .\" on kernel 2.6.13 the underlying filesystem does not support extending a file beyond its current size. .tp .b eperm the operation was prevented by a file seal; see .br fcntl (2). .tp .b erofs the named file resides on a read-only filesystem. .tp .b etxtbsy the file is an executable file that is being executed. .pp for .br ftruncate () the same errors apply, but instead of things that can be wrong with .ir path , we now have things that can be wrong with the file descriptor, .ir fd : .tp .b ebadf .i fd is not a valid file descriptor. .tp .br ebadf " or " einval .i fd is not open for writing. .tp .b einval .i fd does not reference a regular file or a posix shared memory object. .tp .br einval " or " ebadf the file descriptor .i fd is not open for writing. posix permits, and portable applications should handle, either error for this case. (linux produces .br einval .) .sh conforming to posix.1-2001, posix.1-2008, 4.4bsd, svr4 (these calls first appeared in 4.2bsd). .\" posix.1-1996 has .\" .br ftruncate (). .\" posix.1-2001 also has .\" .br truncate (), .\" as an xsi extension. .\" .lp .\" svr4 documents additional .\" .br truncate () .\" error conditions emfile, emultihp, enfile, enolink. svr4 documents for .\" .br ftruncate () .\" an additional eagain error condition. .sh notes .br ftruncate () can also be used to set the size of a posix shared memory object; see .br shm_open (3). .pp the details in description are for xsi-compliant systems. for non-xsi-compliant systems, the posix standard allows two behaviors for .br ftruncate () when .i length exceeds the file length (note that .br truncate () is not specified at all in such an environment): either returning an error, or extending the file. like most unix implementations, linux follows the xsi requirement when dealing with native filesystems. however, some nonnative filesystems do not permit .br truncate () and .br ftruncate () to be used to extend a file beyond its current length: a notable example on linux is vfat. .\" at the very least: osf/1, solaris 7, and freebsd conform, mtk, jan 2002 .pp the original linux .br truncate () and .br ftruncate () system calls were not designed to handle large file offsets. consequently, linux 2.4 added .br truncate64 () and .br ftruncate64 () system calls that handle large files. however, these details can be ignored by applications using glibc, whose wrapper functions transparently employ the more recent system calls where they are available. .pp on some 32-bit architectures, the calling signature for these system calls differ, for the reasons described in .br syscall (2). .sh bugs a header file bug in glibc 2.12 meant that the minimum value of .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12037 .br _posix_c_source required to expose the declaration of .br ftruncate () was 200809l instead of 200112l. this has been fixed in later glibc versions. .sh see also .br truncate (1), .br open (2), .br stat (2), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strdup.3 .so man3/creal.3 .so man3/program_invocation_name.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:11:47 1993 by rik faith (faith@cs.unc.edu) .\" 2007-06-15, marc boyer + mtk .\" improve discussion of strncat(). .th strcat 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strcat, strncat \- concatenate two strings .sh synopsis .nf .b #include .pp .bi "char *strcat(char *restrict " dest ", const char *restrict " src ); .bi "char *strncat(char *restrict " dest ", const char *restrict " src \ ", size_t " n ); .fi .sh description the .br strcat () function appends the .i src string to the .i dest string, overwriting the terminating null byte (\(aq\e0\(aq) at the end of .ir dest , and then adds a terminating null byte. the strings may not overlap, and the .i dest string must have enough space for the result. if .i dest is not large enough, program behavior is unpredictable; .ir "buffer overruns are a favorite avenue for attacking secure programs" . .pp the .br strncat () function is similar, except that .ip * 3 it will use at most .i n bytes from .ir src ; and .ip * .i src does not need to be null-terminated if it contains .i n or more bytes. .pp as with .br strcat (), the resulting string in .i dest is always null-terminated. .pp if .ir src contains .i n or more bytes, .br strncat () writes .i n+1 bytes to .i dest .ri ( n from .i src plus the terminating null byte). therefore, the size of .i dest must be at least .ir "strlen(dest)+n+1" . .pp a simple implementation of .br strncat () might be: .pp .in +4n .ex char * strncat(char *dest, const char *src, size_t n) { size_t dest_len = strlen(dest); size_t i; for (i = 0 ; i < n && src[i] != \(aq\e0\(aq ; i++) dest[dest_len + i] = src[i]; dest[dest_len + i] = \(aq\e0\(aq; return dest; } .ee .in .sh return value the .br strcat () and .br strncat () functions return a pointer to the resulting string .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strcat (), .br strncat () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes some systems (the bsds, solaris, and others) provide the following function: .pp size_t strlcat(char *dest, const char *src, size_t size); .pp this function appends the null-terminated string .i src to the string .ir dest , copying at most .ir "size\-strlen(dest)\-1" from .ir src , and adds a terminating null byte to the result, .i unless .ir size is less than .ir strlen(dest) . this function fixes the buffer overrun problem of .br strcat (), but the caller must still handle the possibility of data loss if .i size is too small. the function returns the length of the string .br strlcat () tried to create; if the return value is greater than or equal to .ir size , data loss occurred. if data loss matters, the caller .i must either check the arguments before the call, or test the function return value. .br strlcat () is not present in glibc and is not standardized by posix, .\" https://lwn.net/articles/506530/ but is available on linux via the .ir libbsd library. .\" .sh examples because .br strcat () and .br strncat () must find the null byte that terminates the string .i dest using a search that starts at the beginning of the string, the execution time of these functions scales according to the length of the string .ir dest . this can be demonstrated by running the program below. (if the goal is to concatenate many strings to one target, then manually copying the bytes from each source string while maintaining a pointer to the end of the target string will provide better performance.) .\" .ss program source \& .ex #include #include #include #include int main(int argc, char *argv[]) { #define lim 4000000 char p[lim + 1]; /* +1 for terminating null byte */ time_t base; base = time(null); p[0] = \(aq\e0\(aq; for (int j = 0; j < lim; j++) { if ((j % 10000) == 0) printf("%d %jd\en", j, (intmax_t) (time(null) \- base)); strcat(p, "a"); } } .ee .\" .sh see also .br bcopy (3), .br memccpy (3), .br memcpy (3), .br strcpy (3), .br string (3), .br strncpy (3), .br wcscat (3), .br wcsncat (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th ccosh 3 2021-03-22 "" "linux programmer's manual" .sh name ccosh, ccoshf, ccoshl \- complex hyperbolic cosine .sh synopsis .nf .b #include .pp .bi "double complex ccosh(double complex " z ");" .bi "float complex ccoshf(float complex " z ");" .bi "long double complex ccoshl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex hyperbolic cosine of .ir z . .pp the complex hyperbolic cosine function is defined as: .pp .nf ccosh(z) = (exp(z)+exp(\-z))/2 .fi .sh versions these functions first appeared in glibc in version 2.1. .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br cacosh (3), .br csinh (3), .br ctanh (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" %%%license_start(public_domain) .\" this text is in the public domain. .\" %%%license_end .\" .th nfsservctl 2 2021-03-22 "linux" "linux programmer's manual" .sh name nfsservctl \- syscall interface to kernel nfs daemon .sh synopsis .nf .b #include .pp .bi "long nfsservctl(int " cmd ", struct nfsctl_arg *" argp , .bi " union nfsctl_res *" resp ); .fi .sh description .ir note : since linux 3.1, this system call no longer exists. it has been replaced by a set of files in the .i nfsd filesystem; see .br nfsd (7). .pp .in +4n .ex /* * these are the commands understood by nfsctl(). */ #define nfsctl_svc 0 /* this is a server process. */ #define nfsctl_addclient 1 /* add an nfs client. */ #define nfsctl_delclient 2 /* remove an nfs client. */ #define nfsctl_export 3 /* export a filesystem. */ #define nfsctl_unexport 4 /* unexport a filesystem. */ #define nfsctl_ugidupdate 5 /* update a client\(aqs uid/gid map (only in linux 2.4.x and earlier). */ #define nfsctl_getfh 6 /* get a file handle (used by mountd) (only in linux 2.4.x and earlier). */ struct nfsctl_arg { int ca_version; /* safeguard */ union { struct nfsctl_svc u_svc; struct nfsctl_client u_client; struct nfsctl_export u_export; struct nfsctl_uidmap u_umap; struct nfsctl_fhparm u_getfh; unsigned int u_debug; } u; } union nfsctl_res { struct knfs_fh cr_getfh; unsigned int cr_debug; }; .ee .in .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh versions this system call was removed from the linux kernel in version 3.1. library support was removed from glibc in version 2.28. .sh conforming to this call is linux-specific. .sh see also .br nfsd (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2015 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th nptl 7 2015-08-08 "linux" "linux programmer's manual" .sh name nptl \- native posix threads library .sh description nptl (native posix threads library) is the gnu c library posix threads implementation that is used on modern linux systems. .\" .ss nptl and signals nptl makes internal use of the first two real-time signals (signal numbers 32 and 33). one of these signals is used to support thread cancellation and posix timers (see .br timer_create (2)); the other is used as part of a mechanism that ensures all threads in a process always have the same uids and gids, as required by posix. these signals cannot be used in applications. .pp to prevent accidental use of these signals in applications, which might interfere with the operation of the nptl implementation, various glibc library functions and system call wrapper functions attempt to hide these signals from applications, as follows: .ip * 3 .b sigrtmin is defined with the value 34 (rather than 32). .ip * the .br sigwaitinfo (2), .br sigtimedwait (2), and .br sigwait (3) interfaces silently ignore requests to wait for these two signals if they are specified in the signal set argument of these calls. .ip * the .br sigprocmask (2) and .br pthread_sigmask (3) interfaces silently ignore attempts to block these two signals. .ip * the .br sigaction (2), .br pthread_kill (3), and .br pthread_sigqueue (3) interfaces fail with the error .b einval (indicating an invalid signal number) if these signals are specified. .ip * .br sigfillset (3) does not include these two signals when it creates a full signal set. .\" .ss nptl and process credential changes at the linux kernel level, credentials (user and group ids) are a per-thread attribute. however, posix requires that all of the posix threads in a process have the same credentials. to accommodate this requirement, the nptl implementation wraps all of the system calls that change process credentials with functions that, in addition to invoking the underlying system call, arrange for all other threads in the process to also change their credentials. .pp the implementation of each of these system calls involves the use of a real-time signal that is sent (using .br tgkill (2)) to each of the other threads that must change its credentials. before sending these signals, the thread that is changing credentials saves the new credential(s) and records the system call being employed in a global buffer. a signal handler in the receiving thread(s) fetches this information and then uses the same system call to change its credentials. .pp wrapper functions employing this technique are provided for .br setgid (2), .br setuid (2), .br setegid (2), .br seteuid (2), .br setregid (2), .br setreuid (2), .br setresgid (2), .br setresuid (2), and .br setgroups (2). .\" fixme . .\" maybe say something about vfork() not being serialized wrt set*id() apis? .\" https://sourceware.org/bugzilla/show_bug.cgi?id=14749 .sh conforming to for details of the conformance of nptl to the posix standard, see .br pthreads (7). .sh notes posix says .\" see posix.1-2008 specification of pthread_mutexattr_init() that any thread in any process with access to the memory containing a process-shared .rb ( pthread_process_shared ) mutex can operate on that mutex. however, on 64-bit x86 systems, the mutex definition for x86-64 is incompatible with the mutex definition for i386, .\" see sysdeps/x86/bits/pthreadtypes.h meaning that 32-bit and 64-bit binaries can't share mutexes on x86-64 systems. .sh see also .br credentials (7), .br pthreads (7), .br signal (7), .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-24 by rik faith .\" modified 1995-07-22 by michael chastain .\" modified 1995-07-23 by aeb .\" modified 1996-10-22 by eric s. raymond .\" modified 1998-09-08 by aeb .\" modified 2004-06-17 by michael kerrisk .\" modified 2004-10-10 by aeb .\" 2004-12-14 mtk, anand kumria: added new errors .\" 2007-06-22 ivana varekova , mtk .\" update text describing limit on number of swap files. .\" .\" fixme linux 3.11 added swap_flag_discard_once and swap_flag_discard_pages .\" commit dcf6b7ddd7df8965727746f89c59229b23180e5a .\" author: rafael aquini .\" date: wed jul 3 15:02:46 2013 -0700 .\" .th swapon 2 2021-03-22 "linux" "linux programmer's manual" .sh name swapon, swapoff \- start/stop swapping to file/device .sh synopsis .nf .b #include .pp .bi "int swapon(const char *" path ", int " swapflags ); .bi "int swapoff(const char *" path ); .fi .sh description .br swapon () sets the swap area to the file or block device specified by .ir path . .br swapoff () stops swapping to the file or block device specified by .ir path . .pp if the .b swap_flag_prefer flag is specified in the .br swapon () .i swapflags argument, the new swap area will have a higher priority than default. the priority is encoded within .i swapflags as: .pp .in +4n .ex .i "(prio << swap_flag_prio_shift) & swap_flag_prio_mask" .ee .in .pp if the .b swap_flag_discard flag is specified in the .br swapon () .i swapflags argument, freed swap pages will be discarded before they are reused, if the swap device supports the discard or trim operation. (this may improve performance on some solid state devices, but often it does not.) see also notes. .pp these functions may be used only by a privileged process (one having the .b cap_sys_admin capability). .ss priority each swap area has a priority, either high or low. the default priority is low. within the low-priority areas, newer areas are even lower priority than older areas. .pp all priorities set with .i swapflags are high-priority, higher than default. they may have any nonnegative value chosen by the caller. higher numbers mean higher priority. .pp swap pages are allocated from areas in priority order, highest priority first. for areas with different priorities, a higher-priority area is exhausted before using a lower-priority area. if two or more areas have the same priority, and it is the highest priority available, pages are allocated on a round-robin basis between them. .pp as of linux 1.3.6, the kernel usually follows these rules, but there are exceptions. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebusy (for .br swapon ()) the specified .i path is already being used as a swap area. .tp .b einval the file .i path exists, but refers neither to a regular file nor to a block device; .tp .b einval .rb ( swapon ()) the indicated path does not contain a valid swap signature or resides on an in-memory filesystem such as .br tmpfs (5). .tp .br einval " (since linux 3.4)" .rb ( swapon ()) an invalid flag value was specified in .ir swapflags . .tp .b einval .rb ( swapoff ()) .i path is not currently a swap area. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoent the file .i path does not exist. .tp .b enomem the system has insufficient memory to start swapping. .tp .b eperm the caller does not have the .b cap_sys_admin capability. alternatively, the maximum number of swap files are already in use; see notes below. .sh conforming to these functions are linux-specific and should not be used in programs intended to be portable. the second .i swapflags argument was introduced in linux 1.3.2. .sh notes the partition or path must be prepared with .br mkswap (8). .pp there is an upper limit on the number of swap files that may be used, defined by the kernel constant .br max_swapfiles . before kernel 2.4.10, .b max_swapfiles has the value 8; since kernel 2.4.10, it has the value 32. since kernel 2.6.18, the limit is decreased by 2 (thus: 30) if the kernel is built with the .b config_migration option (which reserves two swap table entries for the page migration features of .br mbind (2) and .br migrate_pages (2)). since kernel 2.6.32, the limit is further decreased by 1 if the kernel is built with the .b config_memory_failure option. .pp discard of swap pages was introduced in kernel 2.6.29, then made conditional on the .b swap_flag_discard flag in kernel 2.6.36, .\" to be precise: 2.6.35.5 which still discards the entire swap area when .br swapon () is called, even if that flag bit is not set. .sh see also .br mkswap (8), .br swapoff (8), .br swapon (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .so man3/lgamma.3 .so man3/resolver.3 .so man3/significand.3 .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th libc 7 2016-12-12 "linux" "linux programmer's manual" .sh name libc \- overview of standard c libraries on linux .sh description the term "libc" is commonly used as a shorthand for the "standard c library", a library of standard functions that can be used by all c programs (and sometimes by programs in other languages). because of some history (see below), use of the term "libc" to refer to the standard c library is somewhat ambiguous on linux. .ss glibc by far the most widely used c library on linux is the gnu c library .ur http://www.gnu.org\:/software\:/libc/ .ue , often referred to as .ir glibc . this is the c library that is nowadays used in all major linux distributions. it is also the c library whose details are documented in the relevant pages of the .i man-pages project (primarily in section 3 of the manual). documentation of glibc is also available in the glibc manual, available via the command .ir "info libc" . release 1.0 of glibc was made in september 1992. (there were earlier 0.x releases.) the next major release of glibc was 2.0, at the beginning of 1997. .pp the pathname .i /lib/libc.so.6 (or something similar) is normally a symbolic link that points to the location of the glibc library, and executing this pathname will cause glibc to display various information about the version installed on your system. .ss linux libc in the early to mid 1990s, there was for a while .ir "linux libc" , a fork of glibc 1.x created by linux developers who felt that glibc development at the time was not sufficing for the needs of linux. often, this library was referred to (ambiguously) as just "libc". linux libc released major versions 2, 3, 4, and 5, as well as many minor versions of those releases. linux libc4 was the last version to use the a.out binary format, and the first version to provide (primitive) shared library support. linux libc 5 was the first version to support the elf binary format; this version used the shared library soname .ir libc.so.5 . for a while, linux libc was the standard c library in many linux distributions. .pp however, notwithstanding the original motivations of the linux libc effort, by the time glibc 2.0 was released (in 1997), it was clearly superior to linux libc, and all major linux distributions that had been using linux libc soon switched back to glibc. to avoid any confusion with linux libc versions, glibc 2.0 and later used the shared library soname .ir libc.so.6 . .pp since the switch from linux libc to glibc 2.0 occurred long ago, .i man-pages no longer takes care to document linux libc details. nevertheless, the history is visible in vestiges of information about linux libc that remain in a few manual pages, in particular, references to .ir libc4 and .ir libc5 . .ss other c libraries there are various other less widely used c libraries for linux. these libraries are generally smaller than glibc, both in terms of features and memory footprint, and often intended for building small binaries, perhaps targeted at development for embedded linux systems. among such libraries are .ur http://www.uclibc.org/ .i uclibc .ue , .ur http://www.fefe.de/dietlibc/ .i dietlibc .ue , and .ur http://www.musl\-libc.org/ .i "musl libc" .ue . details of these libraries are covered by the .i man-pages project, where they are known. .sh see also .br syscalls (2), .br getauxval (3), .br proc (5), .br feature_test_macros (7), .br man\-pages (7), .br standards (7), .br vdso (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scanf.3 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)getpeername.2 6.5 (berkeley) 3/10/91 .\" .\" modified sat jul 24 16:37:50 1993 by rik faith .\" modified thu jul 30 14:37:50 1993 by martin schulze .\" modified sun mar 28 21:26:46 1999 by andries brouwer .\" modified 17 jul 2002, michael kerrisk .\" added 'socket' to name, so that "man -k socket" will show this page. .\" .th getpeername 2 2021-03-22 "linux" "linux programmer's manual" .sh name getpeername \- get name of connected peer socket .sh synopsis .nf .b #include .pp .bi "int getpeername(int " sockfd ", struct sockaddr *restrict " addr , .bi " socklen_t *restrict " addrlen ); .fi .sh description .br getpeername () returns the address of the peer connected to the socket .ir sockfd , in the buffer pointed to by .ir addr . the .i addrlen argument should be initialized to indicate the amount of space pointed to by .ir addr . on return it contains the actual size of the name returned (in bytes). the name is truncated if the buffer provided is too small. .pp the returned address is truncated if the buffer provided is too small; in this case, .i addrlen will return a value greater than was supplied to the call. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf the argument .i sockfd is not a valid file descriptor. .tp .b efault the .i addr argument points to memory not in a valid part of the process address space. .tp .b einval .i addrlen is invalid (e.g., is negative). .tp .b enobufs insufficient resources were available in the system to perform the operation. .tp .b enotconn the socket is not connected. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd .rb ( getpeername () first appeared in 4.2bsd). .sh notes for background on the .i socklen_t type, see .br accept (2). .pp for stream sockets, once a .br connect (2) has been performed, either socket can call .br getpeername () to obtain the address of the peer socket. on the other hand, datagram sockets are connectionless. calling .br connect (2) on a datagram socket merely sets the peer address for outgoing datagrams sent with .br write (2) or .br recv (2). the caller of .br connect (2) can use .br getpeername () to obtain the peer address that it earlier set for the socket. however, the peer socket is unaware of this information, and calling .br getpeername () on the peer socket will return no useful information (unless a .br connect (2) call was also executed on the peer). note also that the receiver of a datagram can obtain the address of the sender when using .br recvfrom (2). .sh see also .br accept (2), .br bind (2), .br getsockname (2), .br ip (7), .br socket (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/frexp.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th creal 3 2021-03-22 "" "linux programmer's manual" .sh name creal, crealf, creall \- get real part of a complex number .sh synopsis .nf .b #include .pp .bi "double creal(double complex " z ); .bi "float crealf(float complex " z ); .bi "long double creall(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions return the real part of the complex number .ir z . .pp one has: .pp .nf z = creal(z) + i * cimag(z) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br creal (), .br crealf (), .br creall () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes the gcc supports also __real__. that is a gnu extension. .sh see also .br cabs (3), .br cimag (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:54:31 1993, rik faith (faith@cs.unc.edu) .th string 3 2021-03-22 "" "linux programmer's manual" .sh name stpcpy, strcasecmp, strcat, strchr, strcmp, strcoll, strcpy, strcspn, strdup, strfry, strlen, strncat, strncmp, strncpy, strncasecmp, strpbrk, strrchr, strsep, strspn, strstr, strtok, strxfrm, index, rindex \- string operations .sh synopsis .b #include .tp .bi "int strcasecmp(const char *" s1 ", const char *" s2 ); compare the strings .i s1 and .i s2 ignoring case. .tp .bi "int strncasecmp(const char *" s1 ", const char *" s2 ", size_t " n ); compare the first .i n bytes of the strings .i s1 and .i s2 ignoring case. .tp .bi "char *index(const char *" s ", int " c ); return a pointer to the first occurrence of the character .i c in the string .ir s . .tp .bi "char *rindex(const char *" s ", int " c ); return a pointer to the last occurrence of the character .i c in the string .ir s . .tp .b #include .tp .bi "char *stpcpy(char *restrict " dest ", const char *restrict " src ); copy a string from .i src to .ir dest , returning a pointer to the end of the resulting string at .ir dest . .tp .bi "char *strcat(char *restrict " dest ", const char *restrict " src ); append the string .i src to the string .ir dest , returning a pointer .ir dest . .tp .bi "char *strchr(const char *" s ", int " c ); return a pointer to the first occurrence of the character .i c in the string .ir s . .tp .bi "int strcmp(const char *" s1 ", const char *" s2 ); compare the strings .i s1 with .ir s2 . .tp .bi "int strcoll(const char *" s1 ", const char *" s2 ); compare the strings .i s1 with .i s2 using the current locale. .tp .bi "char *strcpy(char *restrict " dest ", const char *restrict " src ); copy the string .i src to .ir dest , returning a pointer to the start of .ir dest . .tp .bi "size_t strcspn(const char *" s ", const char *" reject ); calculate the length of the initial segment of the string .i s which does not contain any of bytes in the string .ir reject , .tp .bi "char *strdup(const char *" s ); return a duplicate of the string .i s in memory allocated using .br malloc (3). .tp .bi "char *strfry(char *" string ); randomly swap the characters in .ir string . .tp .bi "size_t strlen(const char *" s ); return the length of the string .ir s . .tp .bi "char *strncat(char *restrict " dest ", const char *restrict " src \ ", size_t " n ); append at most .i n bytes from the string .i src to the string .ir dest , returning a pointer to .ir dest . .tp .bi "int strncmp(const char *" s1 ", const char *" s2 ", size_t " n ); compare at most .i n bytes of the strings .i s1 and .ir s2 . .tp .bi "char *strncpy(char *restrict " dest ", const char *restrict " src \ ", size_t " n ); copy at most .i n bytes from string .i src to .ir dest , returning a pointer to the start of .ir dest . .tp .bi "char *strpbrk(const char *" s ", const char *" accept ); return a pointer to the first occurrence in the string .i s of one of the bytes in the string .ir accept . .tp .bi "char *strrchr(const char *" s ", int " c ); return a pointer to the last occurrence of the character .i c in the string .ir s . .tp .bi "char *strsep(char **restrict " stringp ", const char *restrict " delim ); extract the initial token in .i stringp that is delimited by one of the bytes in .ir delim . .tp .bi "size_t strspn(const char *" s ", const char *" accept ); calculate the length of the starting segment in the string .i s that consists entirely of bytes in .ir accept . .tp .bi "char *strstr(const char *" haystack ", const char *" needle ); find the first occurrence of the substring .i needle in the string .ir haystack , returning a pointer to the found substring. .tp .bi "char *strtok(char *restrict " s ", const char *restrict " delim ); extract tokens from the string .i s that are delimited by one of the bytes in .ir delim . .tp .bi "size_t strxfrm(char *restrict " dst ", const char *restrict " src \ ", size_t " n ); transforms .i src to the current locale and copies the first .i n bytes to .ir dst . .sh description the string functions perform operations on null-terminated strings. see the individual man pages for descriptions of each function. .sh see also .br bstring (3), .br index (3), .br rindex (3), .br stpcpy (3), .br strcasecmp (3), .br strcat (3), .br strchr (3), .br strcmp (3), .br strcoll (3), .br strcpy (3), .br strcspn (3), .br strdup (3), .br strfry (3), .br strlen (3), .br strncasecmp (3), .br strncat (3), .br strncmp (3), .br strncpy (3), .br strpbrk (3), .br strrchr (3), .br strsep (3), .br strspn (3), .br strstr (3), .br strtok (3), .br strxfrm (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th newlocale 3 2021-03-22 "linux" "linux programmer's manual" .sh name newlocale, freelocale \- create, modify, and free a locale object .sh synopsis .nf .b #include .pp .bi "locale_t newlocale(int " category_mask ", const char *" locale , .bi " locale_t " base ); .bi "void freelocale(locale_t " locobj ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br newlocale (), .br freelocale (): .nf since glibc 2.10: _xopen_source >= 700 before glibc 2.10: _gnu_source .fi .sh description the .br newlocale () function creates a new locale object, or modifies an existing object, returning a reference to the new or modified object as the function result. whether the call creates a new object or modifies an existing object is determined by the value of .ir base : .ip * 3 if .i base is .ir "(locale_t)\ 0" , a new object is created. .ip * if .i base refers to valid existing locale object (i.e., an object returned by a previous call to .br newlocale () or .br duplocale (3)), then that object is modified by the call. if the call is successful, the contents of .i base are unspecified (in particular, the object referred to by .i base may be freed, and a new object created). therefore, the caller should ensure that it stops using .i base before the call to .br newlocale (), and should subsequently refer to the modified object via the reference returned as the function result. if the call fails, the contents of .i base remain valid and unchanged. .pp if .i base is the special locale object .br lc_global_locale (see .br duplocale (3)), or is not .ir "(locale_t)\ 0" and is not a valid locale object handle, the behavior is undefined. .pp the .i category_mask argument is a bit mask that specifies the locale categories that are to be set in a newly created locale object or modified in an existing object. the mask is constructed by a bitwise or of the constants .br lc_address_mask , .br lc_ctype_mask , .br lc_collate_mask , .br lc_identification_mask , .br lc_measurement_mask , .br lc_messages_mask , .br lc_monetary_mask , .br lc_numeric_mask , .br lc_name_mask , .br lc_paper_mask , .br lc_telephone_mask , and .br lc_time_mask . alternatively, the mask can be specified as .br lc_all_mask , which is equivalent to oring all of the preceding constants. .pp for each category specified in .ir category_mask , the locale data from .i locale will be used in the object returned by .br newlocale (). if a new locale object is being created, data for all categories not specified in .ir category_mask is taken from the default ("posix") locale. .pp the following preset values of .i locale are defined for all categories that can be specified in .ir category_mask : .tp "posix" a minimal locale environment for c language programs. .tp "c" equivalent to "posix". .tp "" an implementation-defined native environment corresponding to the values of the .br lc_* and .b lang environment variables (see .br locale (7)). .ss freelocale() the .br freelocale () function deallocates the resources associated with .ir locobj , a locale object previously returned by a call to .br newlocale () or .br duplocale (3). if .i locobj is .br lc_global_locale or is not valid locale object handle, the results are undefined. .pp once a locale object has been freed, the program should make no further use of it. .sh return value on success, .br newlocale () returns a handle that can be used in calls to .br duplocale (3), .br freelocale (), and other functions that take a .i locale_t argument. on error, .br newlocale () returns .ir "(locale_t)\ 0", and sets .i errno to indicate the error. .sh errors .tp .b einval one or more bits in .i category_mask do not correspond to a valid locale category. .tp .b einval .i locale is null. .tp .b enoent .i locale is not a string pointer referring to a valid locale. .tp .b enomem insufficient memory to create a locale object. .sh versions the .br newlocale () and .br freelocale () functions first appeared in version 2.3 of the gnu c library. .sh conforming to posix.1-2008. .sh notes each locale object created by .br newlocale () should be deallocated using .br freelocale (). .sh examples the program below takes up to two command-line arguments, which each identify locales. the first argument is required, and is used to set the .b lc_numeric category in a locale object created using .br newlocale (). the second command-line argument is optional; if it is present, it is used to set the .b lc_time category of the locale object. .pp having created and initialized the locale object, the program then applies it using .br uselocale (3), and then tests the effect of the locale changes by: .ip 1. 3 displaying a floating-point number with a fractional part. this output will be affected by the .b lc_numeric setting. in many european-language locales, the fractional part of the number is separated from the integer part using a comma, rather than a period. .ip 2. displaying the date. the format and language of the output will be affected by the .b lc_time setting. .pp the following shell sessions show some example runs of this program. .pp set the .b lc_numeric category to .ir fr_fr (french): .pp .in +4n .ex $ \fb./a.out fr_fr\fp 123456,789 fri mar 7 00:25:08 2014 .ee .in .pp set the .b lc_numeric category to .ir fr_fr (french), and the .b lc_time category to .ir it_it (italian): .pp .in +4n .ex $ \fb./a.out fr_fr it_it\fp 123456,789 ven 07 mar 2014 00:26:01 cet .ee .in .pp specify the .b lc_time setting as an empty string, which causes the value to be taken from environment variable settings (which, here, specify .ir mi_nz , new zealand māori): .pp .in +4n .ex $ lc_all=mi_nz ./a.out fr_fr "" 123456,789 te paraire, te 07 o poutū\-te\-rangi, 2014 00:38:44 cet .ee .in .ss program source .ex #define _xopen_source 700 #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(int argc, char *argv[]) { char buf[100]; time_t t; size_t s; struct tm *tm; locale_t loc, nloc; if (argc < 2) { fprintf(stderr, "usage: %s locale1 [locale2]\en", argv[0]); exit(exit_failure); } /* create a new locale object, taking the lc_numeric settings from the locale specified in argv[1]. */ loc = newlocale(lc_numeric_mask, argv[1], (locale_t) 0); if (loc == (locale_t) 0) errexit("newlocale"); /* if a second command\-line argument was specified, modify the locale object to take the lc_time settings from the locale specified in argv[2]. we assign the result of this newlocale() call to \(aqnloc\(aq rather than \(aqloc\(aq, since in some cases, we might want to preserve \(aqloc\(aq if this call fails. */ if (argc > 2) { nloc = newlocale(lc_time_mask, argv[2], loc); if (nloc == (locale_t) 0) errexit("newlocale"); loc = nloc; } /* apply the newly created locale to this thread. */ uselocale(loc); /* test effect of lc_numeric. */ printf("%8.3f\en", 123456.789); /* test effect of lc_time. */ t = time(null); tm = localtime(&t); if (tm == null) errexit("time"); s = strftime(buf, sizeof(buf), "%c", tm); if (s == 0) errexit("strftime"); printf("%s\en", buf); /* free the locale object. */ uselocale(lc_global_handle); /* so \(aqloc\(aq is no longer in use */ freelocale(loc); exit(exit_success); } .ee .sh see also .br locale (1), .br duplocale (3), .br setlocale (3), .br uselocale (3), .br locale (5), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th gnu_get_libc_version 3 2021-03-22 "linux" "linux programmer's manual" .sh name gnu_get_libc_version, gnu_get_libc_release \- get glibc version and release .sh synopsis .nf .b #include .pp .b const char *gnu_get_libc_version(void); .b const char *gnu_get_libc_release(void); .fi .sh description the function .br gnu_get_libc_version () returns a string that identifies the glibc version available on the system. .pp the function .br gnu_get_libc_release () returns a string indicates the release status of the glibc version available on the system. this will be a string such as .ir "stable" . .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br gnu_get_libc_version (), .br gnu_get_libc_release () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are glibc-specific. .sh examples when run, the program below will produce output such as the following: .pp .in +4n .ex .rb "$" " ./a.out" gnu libc version: 2.8 gnu libc release: stable .ee .in .ss program source \& .ex #include #include #include int main(int argc, char *argv[]) { printf("gnu libc version: %s\en", gnu_get_libc_version()); printf("gnu libc release: %s\en", gnu_get_libc_release()); exit(exit_success); } .ee .sh see also .br confstr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) markus kuhn, 1996, 2001 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1995-11-26 markus kuhn .\" first version written .\" 2001-05-11 markus kuhn .\" update .\" .th utf-8 7 2019-03-06 "gnu" "linux programmer's manual" .sh name utf-8 \- an ascii compatible multibyte unicode encoding .sh description the unicode 3.0 character set occupies a 16-bit code space. the most obvious unicode encoding (known as ucs-2) consists of a sequence of 16-bit words. such strings can contain\(emas part of many 16-bit characters\(embytes such as \(aq\e0\(aq or \(aq/\(aq, which have a special meaning in filenames and other c library function arguments. in addition, the majority of unix tools expect ascii files and can't read 16-bit words as characters without major modifications. for these reasons, ucs-2 is not a suitable external encoding of unicode in filenames, text files, environment variables, and so on. the iso 10646 universal character set (ucs), a superset of unicode, occupies an even larger code space\(em31\ bits\(emand the obvious ucs-4 encoding for it (a sequence of 32-bit words) has the same problems. .pp the utf-8 encoding of unicode and ucs does not have these problems and is the common way in which unicode is used on unix-style operating systems. .ss properties the utf-8 encoding has the following nice properties: .tp 0.2i * ucs characters 0x00000000 to 0x0000007f (the classic us-ascii characters) are encoded simply as bytes 0x00 to 0x7f (ascii compatibility). this means that files and strings which contain only 7-bit ascii characters have the same encoding under both ascii and utf-8 . .tp * all ucs characters greater than 0x7f are encoded as a multibyte sequence consisting only of bytes in the range 0x80 to 0xfd, so no ascii byte can appear as part of another character and there are no problems with, for example, \(aq\e0\(aq or \(aq/\(aq. .tp * the lexicographic sorting order of ucs-4 strings is preserved. .tp * all possible 2^31 ucs codes can be encoded using utf-8. .tp * the bytes 0xc0, 0xc1, 0xfe, and 0xff are never used in the utf-8 encoding. .tp * the first byte of a multibyte sequence which represents a single non-ascii ucs character is always in the range 0xc2 to 0xfd and indicates how long this multibyte sequence is. all further bytes in a multibyte sequence are in the range 0x80 to 0xbf. this allows easy resynchronization and makes the encoding stateless and robust against missing bytes. .tp * utf-8 encoded ucs characters may be up to six bytes long, however the unicode standard specifies no characters above 0x10ffff, so unicode characters can be only up to four bytes long in utf-8. .ss encoding the following byte sequences are used to represent a character. the sequence to be used depends on the ucs code number of the character: .tp 0.4i 0x00000000 \- 0x0000007f: .ri 0 xxxxxxx .tp 0x00000080 \- 0x000007ff: .ri 110 xxxxx .ri 10 xxxxxx .tp 0x00000800 \- 0x0000ffff: .ri 1110 xxxx .ri 10 xxxxxx .ri 10 xxxxxx .tp 0x00010000 \- 0x001fffff: .ri 11110 xxx .ri 10 xxxxxx .ri 10 xxxxxx .ri 10 xxxxxx .tp 0x00200000 \- 0x03ffffff: .ri 111110 xx .ri 10 xxxxxx .ri 10 xxxxxx .ri 10 xxxxxx .ri 10 xxxxxx .tp 0x04000000 \- 0x7fffffff: .ri 1111110 x .ri 10 xxxxxx .ri 10 xxxxxx .ri 10 xxxxxx .ri 10 xxxxxx .ri 10 xxxxxx .pp the .i xxx bit positions are filled with the bits of the character code number in binary representation, most significant bit first (big-endian). only the shortest possible multibyte sequence which can represent the code number of the character can be used. .pp the ucs code values 0xd800\(en0xdfff (utf-16 surrogates) as well as 0xfffe and 0xffff (ucs noncharacters) should not appear in conforming utf-8 streams. according to rfc 3629 no point above u+10ffff should be used, which limits characters to four bytes. .ss example the unicode character 0xa9 = 1010 1001 (the copyright sign) is encoded in utf-8 as .pp .rs 11000010 10101001 = 0xc2 0xa9 .re .pp and character 0x2260 = 0010 0010 0110 0000 (the "not equal" symbol) is encoded as: .pp .rs 11100010 10001001 10100000 = 0xe2 0x89 0xa0 .re .ss application notes users have to select a utf-8 locale, for example with .pp .rs export lang=en_gb.utf-8 .re .pp in order to activate the utf-8 support in applications. .pp application software that has to be aware of the used character encoding should always set the locale with for example .pp .rs setlocale(lc_ctype, "") .re .pp and programmers can then test the expression .pp .rs strcmp(nl_langinfo(codeset), "utf-8") == 0 .re .pp to determine whether a utf-8 locale has been selected and whether therefore all plaintext standard input and output, terminal communication, plaintext file content, filenames, and environment variables are encoded in utf-8. .pp programmers accustomed to single-byte encodings such as us-ascii or iso 8859 have to be aware that two assumptions made so far are no longer valid in utf-8 locales. firstly, a single byte does not necessarily correspond any more to a single character. secondly, since modern terminal emulators in utf-8 mode also support chinese, japanese, and korean double-width characters as well as nonspacing combining characters, outputting a single character does not necessarily advance the cursor by one position as it did in ascii. library functions such as .br mbsrtowcs (3) and .br wcswidth (3) should be used today to count characters and cursor positions. .pp the official esc sequence to switch from an iso 2022 encoding scheme (as used for instance by vt100 terminals) to utf-8 is esc % g ("\ex1b%g"). the corresponding return sequence from utf-8 to iso 2022 is esc % @ ("\ex1b%@"). other iso 2022 sequences (such as for switching the g0 and g1 sets) are not applicable in utf-8 mode. .ss security the unicode and ucs standards require that producers of utf-8 shall use the shortest form possible, for example, producing a two-byte sequence with first byte 0xc0 is nonconforming. unicode 3.1 has added the requirement that conforming programs must not accept non-shortest forms in their input. this is for security reasons: if user input is checked for possible security violations, a program might check only for the ascii version of "/../" or ";" or nul and overlook that there are many non-ascii ways to represent these things in a non-shortest utf-8 encoding. .ss standards iso/iec 10646-1:2000, unicode 3.1, rfc\ 3629, plan 9. .\" .sh author .\" markus kuhn .sh see also .br locale (1), .br nl_langinfo (3), .br setlocale (3), .br charsets (7), .br unicode (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2001 andreas dilger (adilger@turbolinux.com) .\" and copyright (c) 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th slabinfo 5 2021-03-22 "" "linux programmer's manual" .sh name slabinfo \- kernel slab allocator statistics .sh synopsis .nf .b cat /proc/slabinfo .fi .sh description frequently used objects in the linux kernel (buffer heads, inodes, dentries, etc.) have their own cache. the file .i /proc/slabinfo gives statistics on these caches. the following (edited) output shows an example of the contents of this file: .pp .ex $ \fbsudo cat /proc/slabinfo\fp slabinfo \- version: 2.1 # name ... sigqueue 100 100 160 25 1 : tunables 0 0 0 : slabdata 4 4 0 sighand_cache 355 405 2112 15 8 : tunables 0 0 0 : slabdata 27 27 0 kmalloc\-8192 96 96 8192 4 8 : tunables 0 0 0 : slabdata 24 24 0 \&... .ee .pp the first line of output includes a version number, which allows an application that is reading the file to handle changes in the file format. (see versions, below.) the next line lists the names of the columns in the remaining lines. .pp each of the remaining lines displays information about a specified cache. following the cache name, the output shown in each line shows three components for each cache: .ip * 3 statistics .ip * tunables .ip * slabdata .pp the statistics are as follows: .tp .i active_objs the number of objects that are currently active (i.e., in use). .tp .i num_objs the total number of allocated objects (i.e., objects that are both in use and not in use). .tp .i objsize the size of objects in this slab, in bytes. .tp .i objperslab the number of objects stored in each slab. .tp .i pagesperslab the number of pages allocated for each slab. .pp the .i tunables entries in each line show tunable parameters for the corresponding cache. when using the default slub allocator, there are no tunables, the .i /proc/slabinfo file is not writable, and the value 0 is shown in these fields. when using the older slab allocator, the tunables for a particular cache can be set by writing lines of the following form to .ir /proc/slabinfo : .pp .in +4n .ex # \fbecho \(aqname limit batchcount sharedfactor\(aq > /proc/slabinfo\fp .ee .in .pp here, .i name is the cache name, and .ir limit , .ir batchcount , and .ir sharedfactor are integers defining new values for the corresponding tunables. the .i limit value should be a positive value, .i batchcount should be a positive value that is less than or equal to .ir limit , and .i sharedfactor should be nonnegative. if any of the specified values is invalid, the cache settings are left unchanged. .pp the .i tunables entries in each line contain the following fields: .tp .i limit the maximum number of objects that will be cached. .\" https://lwn.net/articles/56360/ .\" this is the limit on the number of free objects that can be stored .\" in the per-cpu free list for this slab cache. .tp .i batchcount on smp systems, this specifies the number of objects to transfer at one time when refilling the available object list. .\" https://lwn.net/articles/56360/ .\" on smp systems, when we refill the available object list, instead .\" of doing one object at a time, we do batch-count objects at a time. .tp .i sharedfactor [to be documented] .\" .pp the .i slabdata entries in each line contain the following fields: .tp .i active_slabs the number of active slabs. .tp .i nums_slabs the total number of slabs. .tp .i sharedavail [to be documented] .pp note that because of object alignment and slab cache overhead, objects are not normally packed tightly into pages. pages with even one in-use object are considered in-use and cannot be freed. .pp kernels configured with .b config_debug_slab will also have additional statistics fields in each line, and the first line of the file will contain the string "(statistics)". the statistics field include : the high water mark of active objects; the number of times objects have been allocated; the number of times the cache has grown (new pages added to this cache); the number of times the cache has been reaped (unused pages removed from this cache); and the number of times there was an error allocating new pages to this cache. .\" .\" smp systems will also have "(smp)" in the first line of .\" output, and will have two additional columns for each slab, .\" reporting the slab allocation policy for the cpu-local .\" cache (to reduce the need for inter-cpu synchronization .\" when allocating objects from the cache). .\" the first column is the per-cpu limit: the maximum number of objects that .\" will be cached for each cpu. .\" the second column is the .\" batchcount: the maximum number of free objects in the .\" global cache that will be transferred to the per-cpu cache .\" if it is empty, or the number of objects to be returned .\" to the global cache if the per-cpu cache is full. .\" .\" if both slab cache statistics and smp are defined, there .\" will be four additional columns, reporting the per-cpu .\" cache statistics. .\" the first two are the per-cpu cache .\" allocation hit and miss counts: the number of times an .\" object was or was not available in the per-cpu cache .\" for allocation. .\" the next two are the per-cpu cache free .\" hit and miss counts: the number of times a freed object .\" could or could not fit within the per-cpu cache limit, .\" before flushing objects to the global cache. .sh versions the .i /proc/slabinfo file first appeared in linux 2.1.23. the file is versioned, and over time there have been a number of versions with different layouts: .tp 1.0 present throughout the linux 2.2.x kernel series. .tp 1.1 present in the linux 2.4.x kernel series. .\" first appeared in 2.4.0-test3 .tp 1.2 a format that was briefly present in the linux 2.5 development series. .\" from 2.5.45 to 2.5.70 .tp 2.0 present in linux 2.6.x kernels up to and including linux 2.6.9. .\" first appeared in 2.5.71 .tp 2.1 the current format, which first appeared in linux 2.6.10. .sh notes only root can read and (if the kernel was configured with .br config_slab ) write the .ir /proc/slabinfo file. .pp the total amount of memory allocated to the slab/slub cache is shown in the .i slab field of .ir /proc/meminfo . .sh see also .br slabtop (1) .pp the kernel source file .ir documentation/vm/slub.txt and .ir tools/vm/slabinfo.c . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/unlocked_stdio.3 .so man3/rcmd.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcslen 3 2021-08-27 "gnu" "linux programmer's manual" .sh name wcslen \- determine the length of a wide-character string .sh synopsis .nf .b #include .pp .bi "size_t wcslen(const wchar_t *" s ); .fi .sh description the .br wcslen () function is the wide-character equivalent of the .br strlen (3) function. it determines the length of the wide-character string pointed to by .ir s , excluding the terminating null wide character (l\(aq\e0\(aq). .sh return value the .br wcslen () function returns the number of wide characters in .ir s . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcslen () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes in cases where the input buffer may not contain a terminating null wide character, .br wcsnlen (3) should be used instead. .sh see also .br strlen (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/semop.2 .so man3/xdr.3 .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" .\" %%%license_start(bsd_oneline_cdrom) .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" %%%license_end .\" .\" @(#)xdr.3n 2.2 88/08/03 4.0 rpcsrc; from 1.16 88/03/14 smi .\" .\" 2007-12-30, mtk, convert function prototypes to modern c syntax .\" .th xdr 3 2021-03-22 "" "linux programmer's manual" .sh name xdr \- library routines for external data representation .sh synopsis and description these routines allow c programmers to describe arbitrary data structures in a machine-independent fashion. data for remote procedure calls are transmitted using these routines. .pp the prototypes below are declared in .i and make use of the following types: .pp .rs 4 .ex .bi "typedef int " bool_t ; .pp .bi "typedef bool_t (*" xdrproc_t ")(xdr *, void *,...);" .ee .re .pp for the declaration of the .i xdr type, see .ir . .pp .nf .bi "bool_t xdr_array(xdr *" xdrs ", char **" arrp ", unsigned int *" sizep , .bi " unsigned int " maxsize ", unsigned int " elsize , .bi " xdrproc_t " elproc ); .fi .ip a filter primitive that translates between variable-length arrays and their corresponding external representations. the argument .i arrp is the address of the pointer to the array, while .i sizep is the address of the element count of the array; this element count cannot exceed .ir maxsize . the argument .i elsize is the .i sizeof each of the array's elements, and .i elproc is an xdr filter that translates between the array elements' c form, and their external representation. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_bool(xdr *" xdrs ", bool_t *" bp ); .fi .ip a filter primitive that translates between booleans (c integers) and their external representations. when encoding data, this filter produces values of either one or zero. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_bytes(xdr *" xdrs ", char **" sp ", unsigned int *" sizep , .bi " unsigned int " maxsize ); .fi .ip a filter primitive that translates between counted byte strings and their external representations. the argument .i sp is the address of the string pointer. the length of the string is located at address .ir sizep ; strings cannot be longer than .ir maxsize . this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_char(xdr *" xdrs ", char *" cp ); .fi .ip a filter primitive that translates between c characters and their external representations. this routine returns one if it succeeds, zero otherwise. note: encoded characters are not packed, and occupy 4 bytes each. for arrays of characters, it is worthwhile to consider .br xdr_bytes (), .br xdr_opaque (), or .br xdr_string (). .pp .nf .bi "void xdr_destroy(xdr *" xdrs ); .fi .ip a macro that invokes the destroy routine associated with the xdr stream, .ir xdrs . destruction usually involves freeing private data structures associated with the stream. using .i xdrs after invoking .br xdr_destroy () is undefined. .pp .nf .bi "bool_t xdr_double(xdr *" xdrs ", double *" dp ); .fi .ip a filter primitive that translates between c .i double precision numbers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_enum(xdr *" xdrs ", enum_t *" ep ); .fi .ip a filter primitive that translates between c .ir enum s (actually integers) and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_float(xdr *" xdrs ", float *" fp ); .fi .ip a filter primitive that translates between c .ir float s and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "void xdr_free(xdrproc_t " proc ", char *" objp ); .fi .ip generic freeing routine. the first argument is the xdr routine for the object being freed. the second argument is a pointer to the object itself. note: the pointer passed to this routine is .i not freed, but what it points to .i is freed (recursively). .pp .nf .bi "unsigned int xdr_getpos(xdr *" xdrs ); .fi .ip a macro that invokes the get-position routine associated with the xdr stream, .ir xdrs . the routine returns an unsigned integer, which indicates the position of the xdr byte stream. a desirable feature of xdr streams is that simple arithmetic works with this number, although the xdr stream instances need not guarantee this. .pp .nf .bi "long *xdr_inline(xdr *" xdrs ", int " len ); .fi .ip a macro that invokes the inline routine associated with the xdr stream, .ir xdrs . the routine returns a pointer to a contiguous piece of the stream's buffer; .i len is the byte length of the desired buffer. note: pointer is cast to .ir "long\ *" . .ip warning: .br xdr_inline () may return null (0) if it cannot allocate a contiguous piece of a buffer. therefore the behavior may vary among stream instances; it exists for the sake of efficiency. .pp .nf .bi "bool_t xdr_int(xdr *" xdrs ", int *" ip ); .fi .ip a filter primitive that translates between c integers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_long(xdr *" xdrs ", long *" lp ); .fi .ip a filter primitive that translates between c .i long integers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "void xdrmem_create(xdr *" xdrs ", char *" addr ", unsigned int " size , .bi " enum xdr_op " op ); .fi .ip this routine initializes the xdr stream object pointed to by .ir xdrs . the stream's data is written to, or read from, a chunk of memory at location .i addr whose length is no more than .i size bytes long. the .i op determines the direction of the xdr stream (either .br xdr_encode , .br xdr_decode , or .br xdr_free ). .pp .nf .bi "bool_t xdr_opaque(xdr *" xdrs ", char *" cp ", unsigned int " cnt ); .fi .ip a filter primitive that translates between fixed size opaque data and its external representation. the argument .i cp is the address of the opaque object, and .i cnt is its size in bytes. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_pointer(xdr *" xdrs ", char **" objpp , .bi " unsigned int " objsize ", xdrproc_t " xdrobj ); .fi .ip like .br xdr_reference () except that it serializes null pointers, whereas .br xdr_reference () does not. thus, .br xdr_pointer () can represent recursive data structures, such as binary trees or linked lists. .pp .nf .bi "void xdrrec_create(xdr *" xdrs ", unsigned int " sendsize , .bi " unsigned int " recvsize ", char *" handle , .bi " int (*" readit ")(char *, char *, int)," .bi " int (*" writeit ")(char *, char *, int));" .fi .ip this routine initializes the xdr stream object pointed to by .ir xdrs . the stream's data is written to a buffer of size .ir sendsize ; a value of zero indicates the system should use a suitable default. the stream's data is read from a buffer of size .ir recvsize ; it too can be set to a suitable default by passing a zero value. when a stream's output buffer is full, .i writeit is called. similarly, when a stream's input buffer is empty, .i readit is called. the behavior of these two routines is similar to the system calls .br read (2) and .br write (2), except that .i handle is passed to the former routines as the first argument. note: the xdr stream's .i op field must be set by the caller. .ip warning: to read from an xdr stream created by this api, you'll need to call .br xdrrec_skiprecord () first before calling any other xdr apis. this inserts additional bytes in the stream to provide record boundary information. also, xdr streams created with different .br xdr*_create apis are not compatible for the same reason. .pp .nf .bi "bool_t xdrrec_endofrecord(xdr *" xdrs ", int " sendnow ); .fi .ip this routine can be invoked only on streams created by .br xdrrec_create (). the data in the output buffer is marked as a completed record, and the output buffer is optionally written out if .i sendnow is nonzero. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdrrec_eof(xdr *" xdrs ); .fi .ip this routine can be invoked only on streams created by .br xdrrec_create (). after consuming the rest of the current record in the stream, this routine returns one if the stream has no more input, zero otherwise. .pp .nf .bi "bool_t xdrrec_skiprecord(xdr *" xdrs ); .fi .ip this routine can be invoked only on streams created by .br xdrrec_create (). it tells the xdr implementation that the rest of the current record in the stream's input buffer should be discarded. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_reference(xdr *" xdrs ", char **" pp ", unsigned int " size , .bi " xdrproc_t " proc ); .fi .ip a primitive that provides pointer chasing within structures. the argument .i pp is the address of the pointer; .i size is the .i sizeof the structure that .i *pp points to; and .i proc is an xdr procedure that filters the structure between its c form and its external representation. this routine returns one if it succeeds, zero otherwise. .ip warning: this routine does not understand null pointers. use .br xdr_pointer () instead. .pp .nf .bi "xdr_setpos(xdr *" xdrs ", unsigned int " pos ); .fi .ip a macro that invokes the set position routine associated with the xdr stream .ir xdrs . the argument .i pos is a position value obtained from .br xdr_getpos (). this routine returns one if the xdr stream could be repositioned, and zero otherwise. .ip warning: it is difficult to reposition some types of xdr streams, so this routine may fail with one type of stream and succeed with another. .pp .nf .bi "bool_t xdr_short(xdr *" xdrs ", short *" sp ); .fi .ip a filter primitive that translates between c .i short integers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "void xdrstdio_create(xdr *" xdrs ", file *" file ", enum xdr_op " op ); .fi .ip this routine initializes the xdr stream object pointed to by .ir xdrs . the xdr stream data is written to, or read from, the .i stdio stream .ir file . the argument .i op determines the direction of the xdr stream (either .br xdr_encode , .br xdr_decode , or .br xdr_free ). .ip warning: the destroy routine associated with such xdr streams calls .br fflush (3) on the .i file stream, but never .br fclose (3). .pp .nf .bi "bool_t xdr_string(xdr *" xdrs ", char **" sp ", unsigned int " maxsize ); .fi .ip a filter primitive that translates between c strings and their corresponding external representations. strings cannot be longer than .ir maxsize . note: .i sp is the address of the string's pointer. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_u_char(xdr *" xdrs ", unsigned char *" ucp ); .fi .ip a filter primitive that translates between .i unsigned c characters and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_u_int(xdr *" xdrs ", unsigned int *" up ); .fi .ip a filter primitive that translates between c .i unsigned integers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_u_long(xdr *" xdrs ", unsigned long *" ulp ); .fi .ip a filter primitive that translates between c .i "unsigned long" integers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_u_short(xdr *" xdrs ", unsigned short *" usp ); .fi .ip a filter primitive that translates between c .i "unsigned short" integers and their external representations. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_union(xdr *" xdrs ", enum_t *" dscmp ", char *" unp , .bi " const struct xdr_discrim *" choices , .bi " xdrproc_t " defaultarm "); /* may equal null */" .fi .ip a filter primitive that translates between a discriminated c .i union and its corresponding external representation. it first translates the discriminant of the union located at .ir dscmp . this discriminant is always an .ir enum_t . next the union located at .i unp is translated. the argument .i choices is a pointer to an array of .br xdr_discrim () structures. each structure contains an ordered pair of .ri [ value , proc ]. if the union's discriminant is equal to the associated .ir value , then the .i proc is called to translate the union. the end of the .br xdr_discrim () structure array is denoted by a routine of value null. if the discriminant is not found in the .i choices array, then the .i defaultarm procedure is called (if it is not null). returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_vector(xdr *" xdrs ", char *" arrp ", unsigned int " size , .bi " unsigned int " elsize ", xdrproc_t " elproc ); .fi .ip a filter primitive that translates between fixed-length arrays and their corresponding external representations. the argument .i arrp is the address of the pointer to the array, while .i size is the element count of the array. the argument .i elsize is the .i sizeof each of the array's elements, and .i elproc is an xdr filter that translates between the array elements' c form, and their external representation. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "bool_t xdr_void(void);" .fi .ip this routine always returns one. it may be passed to rpc routines that require a function argument, where nothing is to be done. .pp .nf .bi "bool_t xdr_wrapstring(xdr *" xdrs ", char **" sp ); .fi .ip a primitive that calls .b "xdr_string(xdrs, sp,maxun.unsigned );" where .b maxun.unsigned is the maximum value of an unsigned integer. .br xdr_wrapstring () is handy because the rpc package passes a maximum of two xdr routines as arguments, and .br xdr_string (), one of the most frequently used primitives, requires three. returns one if it succeeds, zero otherwise. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br xdr_array (), .br xdr_bool (), .br xdr_bytes (), .br xdr_char (), .br xdr_destroy (), .br xdr_double (), .br xdr_enum (), .br xdr_float (), .br xdr_free (), .br xdr_getpos (), .br xdr_inline (), .br xdr_int (), .br xdr_long (), .br xdrmem_create (), .br xdr_opaque (), .br xdr_pointer (), .br xdrrec_create (), .br xdrrec_eof (), .br xdrrec_endofrecord (), .br xdrrec_skiprecord (), .br xdr_reference (), .br xdr_setpos (), .br xdr_short (), .br xdrstdio_create (), .br xdr_string (), .br xdr_u_char (), .br xdr_u_int (), .br xdr_u_long (), .br xdr_u_short (), .br xdr_union (), .br xdr_vector (), .br xdr_void (), .br xdr_wrapstring () t} thread safety mt-safe .te .hy .ad .sp 1 .sh see also .br rpc (3) .pp the following manuals: .rs external data representation standard: protocol specification .br external data representation: sun technical notes .br .ir "xdr: external data representation standard" , rfc\ 1014, sun microsystems, inc., usc-isi. .re .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016 intel corporation .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and author of this work. .\" %%%license_end .\" .th pkey_alloc 2 2021-03-22 "linux" "linux programmer's manual" .sh name pkey_alloc, pkey_free \- allocate or free a protection key .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pkey_alloc(unsigned int " flags ", unsigned int " access_rights ");" .bi "int pkey_free(int " pkey ");" .fi .sh description .br pkey_alloc () allocates a protection key (pkey) and allows it to be passed to .br pkey_mprotect (2). .pp the .br pkey_alloc () .i flags is reserved for future use and currently must always be specified as 0. .pp the .br pkey_alloc () .i access_rights argument may contain zero or more disable operations: .tp .b pkey_disable_access disable all data access to memory covered by the returned protection key. .tp .b pkey_disable_write disable write access to memory covered by the returned protection key. .pp .br pkey_free () frees a protection key and makes it available for later allocations. after a protection key has been freed, it may no longer be used in any protection-key-related operations. .pp an application should not call .br pkey_free () on any protection key which has been assigned to an address range by .br pkey_mprotect (2) and which is still in use. the behavior in this case is undefined and may result in an error. .sh return value on success, .br pkey_alloc () returns a positive protection key value. on success, .br pkey_free () returns zero. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .ir pkey , .ir flags , or .i access_rights is invalid. .tp .b enospc .rb ( pkey_alloc ()) all protection keys available for the current process have been allocated. the number of keys available is architecture-specific and implementation-specific and may be reduced by kernel-internal use of certain keys. there are currently 15 keys available to user programs on x86. .ip this error will also be returned if the processor or operating system does not support protection keys. applications should always be prepared to handle this error, since factors outside of the application's control can reduce the number of available pkeys. .sh versions .br pkey_alloc () and .br pkey_free () were added to linux in kernel 4.9; library support was added in glibc 2.27. .sh conforming to the .br pkey_alloc () and .br pkey_free () system calls are linux-specific. .sh notes .br pkey_alloc () is always safe to call regardless of whether or not the operating system supports protection keys. it can be used in lieu of any other mechanism for detecting pkey support and will simply fail with the error .b enospc if the operating system has no pkey support. .pp the kernel guarantees that the contents of the hardware rights register (pkru) will be preserved only for allocated protection keys. any time a key is unallocated (either before the first call returning that key from .br pkey_alloc () or after it is freed via .br pkey_free ()), the kernel may make arbitrary changes to the parts of the rights register affecting access to that key. .sh examples see .br pkeys (7). .sh see also .br pkey_mprotect (2), .br pkeys (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1997-08-25 by nicolás lichtmaier .\" modified 2004-06-17 by michael kerrisk .\" modified 2008-11-27 by mtk .\" .th getdomainname 2 2021-03-22 "linux" "linux programmer's manual" .sh name getdomainname, setdomainname \- get/set nis domain name .sh synopsis .nf .b #include .pp .bi "int getdomainname(char *" name ", size_t " len ); .bi "int setdomainname(const char *" name ", size_t " len ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getdomainname (), .br setdomainname (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description these functions are used to access or to change the nis domain name of the host system. more precisely, they operate on the nis domain name associated with the calling process's uts namespace. .pp .br setdomainname () sets the domain name to the value given in the character array .ir name . the .i len argument specifies the number of bytes in .ir name . (thus, .i name does not require a terminating null byte.) .pp .br getdomainname () returns the null-terminated domain name in the character array .ir name , which has a length of .i len bytes. if the null-terminated domain name requires more than \filen\fp bytes, .br getdomainname () returns the first \filen\fp bytes (glibc) or gives an error (libc). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .br setdomainname () can fail with the following errors: .tp .b efault .i name pointed outside of user address space. .tp .b einval .i len was negative or too large. .tp .b eperm the caller did not have the .b cap_sys_admin capability in the user namespace associated with its uts namespace (see .br namespaces (7)). .pp .br getdomainname () can fail with the following errors: .tp .b einval for .br getdomainname () under libc: .i name is null or .i name is longer than .i len bytes. .sh conforming to posix does not specify these calls. .\" but they appear on most systems... .sh notes since linux 1.0, the limit on the length of a domain name, including the terminating null byte, is 64 bytes. in older kernels, it was 8 bytes. .pp on most linux architectures (including x86), there is no .br getdomainname () system call; instead, glibc implements .br getdomainname () as a library function that returns a copy of the .i domainname field returned from a call to .br uname (2). .sh see also .br gethostname (2), .br sethostname (2), .br uname (2), .br uts_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:00:10 1993 by rik faith (faith@cs.unc.edu) .\" modified mon jan 20 12:04:18 1997 by andries brouwer (aeb@cwi.nl) .\" modified tue jan 23 20:23:07 2001 by andries brouwer (aeb@cwi.nl) .\" .th strsep 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strsep \- extract token from string .sh synopsis .nf .b #include .pp .bi "char *strsep(char **restrict " stringp ", const char *restrict " delim ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strsep (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description if .i *stringp is null, the .br strsep () function returns null and does nothing else. otherwise, this function finds the first token in the string .ir *stringp , that is delimited by one of the bytes in the string .ir delim . this token is terminated by overwriting the delimiter with a null byte (\(aq\e0\(aq), and .i *stringp is updated to point past the token. in case no delimiter was found, the token is taken to be the entire string .ir *stringp , and .i *stringp is made null. .sh return value the .br strsep () function returns a pointer to the token, that is, it returns the original value of .ir *stringp . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strsep () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.4bsd. .sh notes the .br strsep () function was introduced as a replacement for .br strtok (3), since the latter cannot handle empty fields. however, .br strtok (3) conforms to c89/c99 and hence is more portable. .sh bugs be cautious when using this function. if you do use it, note that: .ip * 2 this function modifies its first argument. .ip * this function cannot be used on constant strings. .ip * the identity of the delimiting character is lost. .sh see also .br index (3), .br memchr (3), .br rindex (3), .br strchr (3), .br string (3), .br strpbrk (3), .br strspn (3), .br strstr (3), .br strtok (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/stat.2 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" and copyright 2005-2007, michael kerrisk .\" portions extracted from /usr/include/sys/socket.h, which does not have .\" any authorship information in it. it is probably available under the gpl. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .\" other portions are from the 6.9 (berkeley) 3/10/91 man page: .\" .\" copyright (c) 1983 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" modified mon oct 21 23:05:29 edt 1996 by eric s. raymond .\" modified 1998 by andi kleen .\" $id: bind.2,v 1.3 1999/04/23 19:56:07 freitag exp $ .\" modified 2004-06-23 by michael kerrisk .\" .th bind 2 2021-03-22 "linux" "linux programmer's manual" .sh name bind \- bind a name to a socket .sh synopsis .nf .b #include .pp .bi "int bind(int " sockfd ", const struct sockaddr *" addr , .bi " socklen_t " addrlen ); .fi .sh description when a socket is created with .br socket (2), it exists in a name space (address family) but has no address assigned to it. .br bind () assigns the address specified by .i addr to the socket referred to by the file descriptor .ir sockfd . .i addrlen specifies the size, in bytes, of the address structure pointed to by .ir addr . traditionally, this operation is called \(lqassigning a name to a socket\(rq. .pp it is normally necessary to assign a local address using .br bind () before a .b sock_stream socket may receive connections (see .br accept (2)). .pp the rules used in name binding vary between address families. consult the manual entries in section 7 for detailed information. for .br af_inet , see .br ip (7); for .br af_inet6 , see .br ipv6 (7); for .br af_unix , see .br unix (7); for .br af_appletalk , see .br ddp (7); for .br af_packet , see .br packet (7); for .br af_x25 , see .br x25 (7); and for .br af_netlink , see .br netlink (7). .pp the actual structure passed for the .i addr argument will depend on the address family. the .i sockaddr structure is defined as something like: .pp .in +4n .ex struct sockaddr { sa_family_t sa_family; char sa_data[14]; } .ee .in .pp the only purpose of this structure is to cast the structure pointer passed in .i addr in order to avoid compiler warnings. see examples below. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces .\" e.g., privileged port in af_inet domain the address is protected, and the user is not the superuser. .tp .b eaddrinuse the given address is already in use. .tp .b eaddrinuse (internet domain sockets) the port number was specified as zero in the socket address structure, but, upon attempting to bind to an ephemeral port, it was determined that all port numbers in the ephemeral port range are currently in use. see the discussion of .i /proc/sys/net/ipv4/ip_local_port_range .br ip (7). .tp .b ebadf .i sockfd is not a valid file descriptor. .tp .b einval the socket is already bound to an address. .\" this may change in the future: see .\" .i linux/unix/sock.c for details. .tp .b einval .i addrlen is wrong, or .i addr is not a valid address for this socket's domain. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .pp the following errors are specific to unix domain .rb ( af_unix ) sockets: .tp .b eacces search permission is denied on a component of the path prefix. (see also .br path_resolution (7).) .tp .b eaddrnotavail a nonexistent interface was requested or the requested address was not local. .tp .b efault .i addr points outside the user's accessible address space. .tp .b eloop too many symbolic links were encountered in resolving .ir addr . .tp .b enametoolong .i addr is too long. .tp .b enoent a component in the directory prefix of the socket pathname does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of the path prefix is not a directory. .tp .b erofs the socket inode would reside on a read-only filesystem. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd .rb ( bind () first appeared in 4.2bsd). .\" svr4 documents an additional .\" .b enosr .\" general error condition, and .\" additional .\" .b eio .\" and .\" .b eisdir .\" unix-domain error conditions. .sh notes for background on the .i socklen_t type, see .br accept (2). .sh bugs the transparent proxy options are not described. .\" fixme document transparent proxy options .sh examples an example of the use of .br bind () with internet domain sockets can be found in .br getaddrinfo (3). .pp the following example shows how to bind a stream socket in the unix .rb ( af_unix ) domain, and accept connections: .\" listen.7 refers to this example. .\" accept.7 refers to this example. .\" unix.7 refers to this example. .pp .ex #include #include #include #include #include #define my_sock_path "/somepath" #define listen_backlog 50 #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) int main(int argc, char *argv[]) { int sfd, cfd; struct sockaddr_un my_addr, peer_addr; socklen_t peer_addr_size; sfd = socket(af_unix, sock_stream, 0); if (sfd == \-1) handle_error("socket"); memset(&my_addr, 0, sizeof(my_addr)); my_addr.sun_family = af_unix; strncpy(my_addr.sun_path, my_sock_path, sizeof(my_addr.sun_path) \- 1); if (bind(sfd, (struct sockaddr *) &my_addr, sizeof(my_addr)) == \-1) handle_error("bind"); if (listen(sfd, listen_backlog) == \-1) handle_error("listen"); /* now we can accept incoming connections one at a time using accept(2). */ peer_addr_size = sizeof(peer_addr); cfd = accept(sfd, (struct sockaddr *) &peer_addr, &peer_addr_size); if (cfd == \-1) handle_error("accept"); /* code to deal with incoming connection(s)... */ /* when no longer required, the socket pathname, my_sock_path should be deleted using unlink(2) or remove(3). */ } .ee .sh see also .br accept (2), .br connect (2), .br getsockname (2), .br listen (2), .br socket (2), .br getaddrinfo (3), .br getifaddrs (3), .br ip (7), .br ipv6 (7), .br path_resolution (7), .br socket (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 free software foundation, inc. .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .th io_destroy 2 2021-03-22 "linux" "linux programmer's manual" .sh name io_destroy \- destroy an asynchronous i/o context .sh synopsis .nf .br "#include " " /* definition of " aio_context_t " */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_io_destroy, aio_context_t " ctx_id ); .fi .pp .ir note : glibc provides no wrapper for .br io_destroy (), necessitating the use of .br syscall (2). .sh description .ir note : this page describes the raw linux system call interface. the wrapper function provided by .i libaio uses a different type for the .i ctx_id argument. see notes. .pp the .br io_destroy () system call will attempt to cancel all outstanding asynchronous i/o operations against .ir ctx_id , will block on the completion of all operations that could not be canceled, and will destroy the .ir ctx_id . .sh return value on success, .br io_destroy () returns 0. for the failure return, see notes. .sh errors .tp .b efault the context pointed to is invalid. .tp .b einval the aio context specified by \fictx_id\fp is invalid. .tp .b enosys .br io_destroy () is not implemented on this architecture. .sh versions the asynchronous i/o system calls first appeared in linux 2.5. .sh conforming to .br io_destroy () is linux-specific and should not be used in programs that are intended to be portable. .sh notes you probably want to use the .br io_destroy () wrapper function provided by .\" http://git.fedorahosted.org/git/?p=libaio.git .ir libaio . .pp note that the .i libaio wrapper function uses a different type .ri ( io_context_t ) .\" but glibc is confused, since uses 'io_context_t' to declare .\" the system call. for the .i ctx_id argument. note also that the .i libaio wrapper does not follow the usual c library conventions for indicating errors: on error it returns a negated error number (the negative of one of the values listed in errors). if the system call is invoked via .br syscall (2), then the return value follows the usual conventions for indicating an error: \-1, with .i errno set to a (positive) value that indicates the error. .sh see also .br io_cancel (2), .br io_getevents (2), .br io_setup (2), .br io_submit (2), .br aio (7) .\" .sh author .\" kent yoder. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/removexattr.2 .so man3/nextafter.3 .\" from henry spencer's regex package (as found in the apache .\" distribution). the package carries the following copyright: .\" .\" copyright 1992, 1993, 1994 henry spencer. all rights reserved. .\" %%%license_start(misc) .\" this software is not subject to any license of the american telephone .\" and telegraph company or of the regents of the university of california. .\" .\" permission is granted to anyone to use this software for any purpose .\" on any computer system, and to alter it and redistribute it, subject .\" to the following restrictions: .\" .\" 1. the author is not responsible for the consequences of use of this .\" software, no matter how awful, even if they arise from flaws in it. .\" .\" 2. the origin of this software must not be misrepresented, either by .\" explicit claim or by omission. since few users ever read sources, .\" credits must appear in the documentation. .\" .\" 3. altered versions must be plainly marked as such, and must not be .\" misrepresented as being the original software. since few users .\" ever read sources, credits must appear in the documentation. .\" .\" 4. this notice may not be removed or altered. .\" %%%license_end .\" .\" in order to comply with `credits must appear in the documentation' .\" i added an author paragraph below - aeb. .\" .\" in the default nroff environment there is no dagger \(dg. .\" .\" 2005-05-11 removed discussion of `[[:<:]]' and `[[:>:]]', which .\" appear not to be in the glibc implementation of regcomp .\" .ie t .ds dg \(dg .el .ds dg (!) .th regex 7 2020-08-13 "" "linux programmer's manual" .sh name regex \- posix.2 regular expressions .sh description regular expressions ("re"s), as defined in posix.2, come in two forms: modern res (roughly those of .ir egrep ; posix.2 calls these "extended" res) and obsolete res (roughly those of .br ed (1); posix.2 "basic" res). obsolete res mostly exist for backward compatibility in some old programs; they will be discussed at the end. posix.2 leaves some aspects of re syntax and semantics open; "\*(dg" marks decisions on these aspects that may not be fully portable to other posix.2 implementations. .pp a (modern) re is one\*(dg or more nonempty\*(dg \fibranches\fr, separated by \(aq|\(aq. it matches anything that matches one of the branches. .pp a branch is one\*(dg or more \fipieces\fr, concatenated. it matches a match for the first, followed by a match for the second, and so on. .pp a piece is an \fiatom\fr possibly followed by a single\*(dg \(aq*\(aq, \(aq+\(aq, \(aq?\(aq, or \fibound\fr. an atom followed by \(aq*\(aq matches a sequence of 0 or more matches of the atom. an atom followed by \(aq+\(aq matches a sequence of 1 or more matches of the atom. an atom followed by \(aq?\(aq matches a sequence of 0 or 1 matches of the atom. .pp a \fibound\fr is \(aq{\(aq followed by an unsigned decimal integer, possibly followed by \(aq,\(aq possibly followed by another unsigned decimal integer, always followed by \(aq}\(aq. the integers must lie between 0 and .b re_dup_max (255\*(dg) inclusive, and if there are two of them, the first may not exceed the second. an atom followed by a bound containing one integer \fii\fr and no comma matches a sequence of exactly \fii\fr matches of the atom. an atom followed by a bound containing one integer \fii\fr and a comma matches a sequence of \fii\fr or more matches of the atom. an atom followed by a bound containing two integers \fii\fr and \fij\fr matches a sequence of \fii\fr through \fij\fr (inclusive) matches of the atom. .pp an atom is a regular expression enclosed in "\fi()\fp" (matching a match for the regular expression), an empty set of "\fi()\fp" (matching the null string)\*(dg, a \fibracket expression\fr (see below), \(aq.\(aq (matching any single character), \(aq\(ha\(aq (matching the null string at the beginning of a line), \(aq$\(aq (matching the null string at the end of a line), a \(aq\e\(aq followed by one of the characters "\fi\(ha.[$()|*+?{\e\fp" (matching that character taken as an ordinary character), a \(aq\e\(aq followed by any other character\*(dg (matching that character taken as an ordinary character, as if the \(aq\e\(aq had not been present\*(dg), or a single character with no other significance (matching that character). a \(aq{\(aq followed by a character other than a digit is an ordinary character, not the beginning of a bound\*(dg. it is illegal to end an re with \(aq\e\(aq. .pp a \fibracket expression\fr is a list of characters enclosed in "\fi[]\fp". it normally matches any single character from the list (but see below). if the list begins with \(aq\(ha\(aq, it matches any single character (but see below) \finot\fr from the rest of the list. if two characters in the list are separated by \(aq\-\(aq, this is shorthand for the full \firange\fr of characters between those two (inclusive) in the collating sequence, for example, "\fi[0\-9]\fp" in ascii matches any decimal digit. it is illegal\*(dg for two ranges to share an endpoint, for example, "\fia\-c\-e\fp". ranges are very collating-sequence-dependent, and portable programs should avoid relying on them. .pp to include a literal \(aq]\(aq in the list, make it the first character (following a possible \(aq\(ha\(aq). to include a literal \(aq\-\(aq, make it the first or last character, or the second endpoint of a range. to use a literal \(aq\-\(aq as the first endpoint of a range, enclose it in "\fi[.\fp" and "\fi.]\fp" to make it a collating element (see below). with the exception of these and some combinations using \(aq[\(aq (see next paragraphs), all other special characters, including \(aq\e\(aq, lose their special significance within a bracket expression. .pp within a bracket expression, a collating element (a character, a multicharacter sequence that collates as if it were a single character, or a collating-sequence name for either) enclosed in "\fi[.\fp" and "\fi.]\fp" stands for the sequence of characters of that collating element. the sequence is a single element of the bracket expression's list. a bracket expression containing a multicharacter collating element can thus match more than one character, for example, if the collating sequence includes a "ch" collating element, then the re "\fi[[.ch.]]*c\fp" matches the first five characters of "chchcc". .pp within a bracket expression, a collating element enclosed in "\fi[=\fp" and "\fi=]\fp" is an equivalence class, standing for the sequences of characters of all collating elements equivalent to that one, including itself. (if there are no other equivalent collating elements, the treatment is as if the enclosing delimiters were "\fi[.\fp" and "\fi.]\fp".) for example, if o and \o'o\(ha' are the members of an equivalence class, then "\fi[[=o=]]\fp", "\fi[[=\o'o\(ha'=]]\fp", and "\fi[o\o'o\(ha']\fp" are all synonymous. an equivalence class may not\*(dg be an endpoint of a range. .pp within a bracket expression, the name of a \ficharacter class\fr enclosed in "\fi[:\fp" and "\fi:]\fp" stands for the list of all characters belonging to that class. standard character class names are: .pp .rs .ts l l l. alnum digit punct alpha graph space blank lower upper cntrl print xdigit .te .re .pp these stand for the character classes defined in .br wctype (3). a locale may provide others. a character class may not be used as an endpoint of a range. .\" as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=295666 .\" the following does not seem to apply in the glibc implementation .\" .pp .\" there are two special cases\*(dg of bracket expressions: .\" the bracket expressions "\fi[[:<:]]\fp" and "\fi[[:>:]]\fp" match .\" the null string at the beginning and end of a word respectively. .\" a word is defined as a sequence of .\" word characters .\" which is neither preceded nor followed by .\" word characters. .\" a word character is an .\" .i alnum .\" character (as defined by .\" .br wctype (3)) .\" or an underscore. .\" this is an extension, .\" compatible with but not specified by posix.2, .\" and should be used with .\" caution in software intended to be portable to other systems. .pp in the event that an re could match more than one substring of a given string, the re matches the one starting earliest in the string. if the re could match more than one substring starting at that point, it matches the longest. subexpressions also match the longest possible substrings, subject to the constraint that the whole match be as long as possible, with subexpressions starting earlier in the re taking priority over ones starting later. note that higher-level subexpressions thus take priority over their lower-level component subexpressions. .pp match lengths are measured in characters, not collating elements. a null string is considered longer than no match at all. for example, "\fibb*\fp" matches the three middle characters of "abbbc", "\fi(wee|week)(knights|nights)\fp" matches all ten characters of "weeknights", when "\fi(.*).*\fp" is matched against "abc" the parenthesized subexpression matches all three characters, and when "\fi(a*)*\fp" is matched against "bc" both the whole re and the parenthesized subexpression match the null string. .pp if case-independent matching is specified, the effect is much as if all case distinctions had vanished from the alphabet. when an alphabetic that exists in multiple cases appears as an ordinary character outside a bracket expression, it is effectively transformed into a bracket expression containing both cases, for example, \(aqx\(aq becomes "\fi[xx]\fp". when it appears inside a bracket expression, all case counterparts of it are added to the bracket expression, so that, for example, "\fi[x]\fp" becomes "\fi[xx]\fp" and "\fi[\(hax]\fp" becomes "\fi[\(haxx]\fp". .pp no particular limit is imposed on the length of res\*(dg. programs intended to be portable should not employ res longer than 256 bytes, as an implementation can refuse to accept such res and remain posix-compliant. .pp obsolete ("basic") regular expressions differ in several respects. \(aq|\(aq, \(aq+\(aq, and \(aq?\(aq are ordinary characters and there is no equivalent for their functionality. the delimiters for bounds are "\fi\e{\fp" and "\fi\e}\fp", with \(aq{\(aq and \(aq}\(aq by themselves ordinary characters. the parentheses for nested subexpressions are "\fi\e(\fp" and "\fi\e)\fp", with \(aq(\(aq and \(aq)\(aq by themselves ordinary characters. \(aq\(ha\(aq is an ordinary character except at the beginning of the re or\*(dg the beginning of a parenthesized subexpression, \(aq$\(aq is an ordinary character except at the end of the re or\*(dg the end of a parenthesized subexpression, and \(aq*\(aq is an ordinary character if it appears at the beginning of the re or the beginning of a parenthesized subexpression (after a possible leading \(aq\(ha\(aq). .pp finally, there is one new type of atom, a \fiback reference\fr: \(aq\e\(aq followed by a nonzero decimal digit \fid\fr matches the same sequence of characters matched by the \fid\frth parenthesized subexpression (numbering subexpressions by the positions of their opening parentheses, left to right), so that, for example, "\fi\e([bc]\e)\e1\fp" matches "bb" or "cc" but not "bc". .sh bugs having two kinds of res is a botch. .pp the current posix.2 spec says that \(aq)\(aq is an ordinary character in the absence of an unmatched \(aq(\(aq; this was an unintentional result of a wording error, and change is likely. avoid relying on it. .pp back references are a dreadful botch, posing major problems for efficient implementations. they are also somewhat vaguely defined (does "\fia\e(\e(b\e)*\e2\e)*d\fp" match "abbbd"?). avoid using them. .pp posix.2's specification of case-independent matching is vague. the "one case implies all cases" definition given above is current consensus among implementors as to the right interpretation. .\" as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=295666 .\" the following does not seem to apply in the glibc implementation .\" .pp .\" the syntax for word boundaries is incredibly ugly. .sh author .\" sigh... the page license means we must have the author's name .\" in the formatted output. this page was taken from henry spencer's regex package. .sh see also .br grep (1), .br regex (3) .pp posix.2, section 2.8 (regular expression notation). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_create 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_create \- create a new thread .sh synopsis .nf .b #include .pp .bi "int pthread_create(pthread_t *restrict " thread , .bi " const pthread_attr_t *restrict " attr , .bi " void *(*" start_routine ")(void *)," .bi " void *restrict " arg ); .fi .pp compile and link with \fi\-pthread\fp. .sh description the .br pthread_create () function starts a new thread in the calling process. the new thread starts execution by invoking .ir start_routine (); .ir arg is passed as the sole argument of .ir start_routine (). .pp the new thread terminates in one of the following ways: .ip * 2 it calls .br pthread_exit (3), specifying an exit status value that is available to another thread in the same process that calls .br pthread_join (3). .ip * it returns from .ir start_routine (). this is equivalent to calling .br pthread_exit (3) with the value supplied in the .i return statement. .ip * it is canceled (see .br pthread_cancel (3)). .ip * any of the threads in the process calls .br exit (3), or the main thread performs a return from .ir main (). this causes the termination of all threads in the process. .pp the .i attr argument points to a .i pthread_attr_t structure whose contents are used at thread creation time to determine attributes for the new thread; this structure is initialized using .br pthread_attr_init (3) and related functions. if .i attr is null, then the thread is created with default attributes. .pp before returning, a successful call to .br pthread_create () stores the id of the new thread in the buffer pointed to by .ir thread ; this identifier is used to refer to the thread in subsequent calls to other pthreads functions. .pp the new thread inherits a copy of the creating thread's signal mask .rb ( pthread_sigmask (3)). the set of pending signals for the new thread is empty .rb ( sigpending (2)). the new thread does not inherit the creating thread's alternate signal stack .rb ( sigaltstack (2)). .pp the new thread inherits the calling thread's floating-point environment .rb ( fenv (3)). .pp the initial value of the new thread's cpu-time clock is 0 (see .br pthread_getcpuclockid (3)). .\" clock_thread_cputime_id in clock_gettime(2) .ss linux-specific details the new thread inherits copies of the calling thread's capability sets (see .br capabilities (7)) and cpu affinity mask (see .br sched_setaffinity (2)). .sh return value on success, .br pthread_create () returns 0; on error, it returns an error number, and the contents of .ir *thread are undefined. .sh errors .tp .b eagain insufficient resources to create another thread. .tp .b eagain .\" note! the following should match the description in fork(2) a system-imposed limit on the number of threads was encountered. there are a number of limits that may trigger this error: the .br rlimit_nproc soft resource limit (set via .br setrlimit (2)), which limits the number of processes and threads for a real user id, was reached; the kernel's system-wide limit on the number of processes and threads, .ir /proc/sys/kernel/threads\-max , was reached (see .br proc (5)); or the maximum number of pids, .ir /proc/sys/kernel/pid_max , was reached (see .br proc (5)). .tp .b einval invalid settings in .ir attr . .tp .\" fixme . test the following .b eperm no permission to set the scheduling policy and parameters specified in .ir attr . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_create () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes see .br pthread_self (3) for further information on the thread id returned in .ir *thread by .br pthread_create (). unless real-time scheduling policies are being employed, after a call to .br pthread_create (), it is indeterminate which thread\(emthe caller or the new thread\(emwill next execute. .pp a thread may either be .i joinable or .ir detached . if a thread is joinable, then another thread can call .br pthread_join (3) to wait for the thread to terminate and fetch its exit status. only when a terminated joinable thread has been joined are the last of its resources released back to the system. when a detached thread terminates, its resources are automatically released back to the system: it is not possible to join with the thread in order to obtain its exit status. making a thread detached is useful for some types of daemon threads whose exit status the application does not need to care about. by default, a new thread is created in a joinable state, unless .i attr was set to create the thread in a detached state (using .br pthread_attr_setdetachstate (3)). .pp under the nptl threading implementation, if the .br rlimit_stack soft resource limit .ir "at the time the program started" has any value other than "unlimited", then it determines the default stack size of new threads. using .br pthread_attr_setstacksize (3), the stack size attribute can be explicitly set in the .i attr argument used to create a thread, in order to obtain a stack size other than the default. if the .br rlimit_stack resource limit is set to "unlimited", a per-architecture value is used for the stack size. here is the value for a few architectures: .rs .ts allbox; lb lb l r. architecture default stack size i386 2 mb ia-64 32 mb powerpc 4 mb s/390 2 mb sparc-32 2 mb sparc-64 4 mb x86_64 2 mb .te .re .sh bugs in the obsolete linuxthreads implementation, each of the threads in a process has a different process id. this is in violation of the posix threads specification, and is the source of many other nonconformances to the standard; see .br pthreads (7). .sh examples the program below demonstrates the use of .br pthread_create (), as well as a number of other functions in the pthreads api. .pp in the following run, on a system providing the nptl threading implementation, the stack size defaults to the value given by the "stack size" resource limit: .pp .in +4n .ex .rb "$" " ulimit \-s" 8192 # the stack size limit is 8 mb (0x800000 bytes) .rb "$" " ./a.out hola salut servus" thread 1: top of stack near 0xb7dd03b8; argv_string=hola thread 2: top of stack near 0xb75cf3b8; argv_string=salut thread 3: top of stack near 0xb6dce3b8; argv_string=servus joined with thread 1; returned value was hola joined with thread 2; returned value was salut joined with thread 3; returned value was servus .ee .in .pp in the next run, the program explicitly sets a stack size of 1\ mb (using .br pthread_attr_setstacksize (3)) for the created threads: .pp .in +4n .ex .rb "$" " ./a.out \-s 0x100000 hola salut servus" thread 1: top of stack near 0xb7d723b8; argv_string=hola thread 2: top of stack near 0xb7c713b8; argv_string=salut thread 3: top of stack near 0xb7b703b8; argv_string=servus joined with thread 1; returned value was hola joined with thread 2; returned value was salut joined with thread 3; returned value was servus .ee .in .ss program source \& .ex #include #include #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) struct thread_info { /* used as argument to thread_start() */ pthread_t thread_id; /* id returned by pthread_create() */ int thread_num; /* application\-defined thread # */ char *argv_string; /* from command\-line argument */ }; /* thread start function: display address near top of our stack, and return upper\-cased copy of argv_string. */ static void * thread_start(void *arg) { struct thread_info *tinfo = arg; char *uargv; printf("thread %d: top of stack near %p; argv_string=%s\en", tinfo\->thread_num, (void *) &tinfo, tinfo\->argv_string); uargv = strdup(tinfo\->argv_string); if (uargv == null) handle_error("strdup"); for (char *p = uargv; *p != \(aq\e0\(aq; p++) *p = toupper(*p); return uargv; } int main(int argc, char *argv[]) { int s, opt, num_threads; pthread_attr_t attr; ssize_t stack_size; void *res; /* the "\-s" option specifies a stack size for our threads. */ stack_size = \-1; while ((opt = getopt(argc, argv, "s:")) != \-1) { switch (opt) { case \(aqs\(aq: stack_size = strtoul(optarg, null, 0); break; default: fprintf(stderr, "usage: %s [\-s stack\-size] arg...\en", argv[0]); exit(exit_failure); } } num_threads = argc \- optind; /* initialize thread creation attributes. */ s = pthread_attr_init(&attr); if (s != 0) handle_error_en(s, "pthread_attr_init"); if (stack_size > 0) { s = pthread_attr_setstacksize(&attr, stack_size); if (s != 0) handle_error_en(s, "pthread_attr_setstacksize"); } /* allocate memory for pthread_create() arguments. */ struct thread_info *tinfo = calloc(num_threads, sizeof(*tinfo)); if (tinfo == null) handle_error("calloc"); /* create one thread for each command\-line argument. */ for (int tnum = 0; tnum < num_threads; tnum++) { tinfo[tnum].thread_num = tnum + 1; tinfo[tnum].argv_string = argv[optind + tnum]; /* the pthread_create() call stores the thread id into corresponding element of tinfo[]. */ s = pthread_create(&tinfo[tnum].thread_id, &attr, &thread_start, &tinfo[tnum]); if (s != 0) handle_error_en(s, "pthread_create"); } /* destroy the thread attributes object, since it is no longer needed. */ s = pthread_attr_destroy(&attr); if (s != 0) handle_error_en(s, "pthread_attr_destroy"); /* now join with each thread, and display its returned value. */ for (int tnum = 0; tnum < num_threads; tnum++) { s = pthread_join(tinfo[tnum].thread_id, &res); if (s != 0) handle_error_en(s, "pthread_join"); printf("joined with thread %d; returned value was %s\en", tinfo[tnum].thread_num, (char *) res); free(res); /* free memory allocated by thread */ } free(tinfo); exit(exit_success); } .ee .sh see also .ad l .nh .br getrlimit (2), .br pthread_attr_init (3), .br pthread_cancel (3), .br pthread_detach (3), .br pthread_equal (3), .br pthread_exit (3), .br pthread_getattr_np (3), .br pthread_join (3), .br pthread_self (3), .br pthread_setattr_default_np (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" .\" corrected, aeb, 990824 .th stpncpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name stpncpy \- copy a fixed-size string, returning a pointer to its end .sh synopsis .nf .b #include .pp .bi "char *stpncpy(char *restrict " dest ", const char *restrict " src \ ", size_t " n ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br stpncpy (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br stpncpy () function copies at most .i n characters from the string pointed to by .ir src , including the terminating null byte (\(aq\e0\(aq), to the array pointed to by .ir dest . exactly .i n characters are written at .ir dest . if the length .i strlen(src) is smaller than .ir n , the remaining characters in the array pointed to by .i dest are filled with null bytes (\(aq\e0\(aq), if the length .i strlen(src) is greater than or equal to .ir n , the string pointed to by .i dest will not be null-terminated. .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .i n characters at .ir dest . .sh return value .br stpncpy () returns a pointer to the terminating null byte in .ir dest , or, if .i dest is not null-terminated, .ir dest + n . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br stpncpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function was added to posix.1-2008. before that, it was a gnu extension. it first appeared in version 1.07 of the gnu c library in 1993. .sh see also .br strncpy (3), .br wcpncpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/setregid.2 .so man3/clog.3 .\" copyright 2001 john levon .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" additions, aeb, 2001-10-17. .th clearenv 3 2021-03-22 "linux" "linux programmer's manual" .sh name clearenv \- clear the environment .sh synopsis .nf .b #include .pp .b "int clearenv(void);" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br clearenv (): .nf /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description the .br clearenv () function clears the environment of all name-value pairs and sets the value of the external variable .i environ to null. after this call, new variables can be added to the environment using .br putenv (3) and .br setenv (3). .sh return value the .br clearenv () function returns zero on success, and a nonzero value on failure. .\" most versions of unix return -1 on error, or do not even have errors. .\" glibc info and the watcom c library document "a nonzero value". .sh versions available since glibc 2.0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clearenv () t} thread safety mt-unsafe const:env .te .hy .ad .sp 1 .sh conforming to various unix variants (dg/ux, hp-ux, qnx, ...). posix.9 (bindings for fortran77). posix.1-1996 did not accept .br clearenv () and .br putenv (3), but changed its mind and scheduled these functions for some later issue of this standard (see \[sc]b.4.6.1). however, posix.1-2001 adds only .br putenv (3), and rejected .br clearenv (). .sh notes on systems where .br clearenv () is unavailable, the assignment .pp .in +4n .ex environ = null; .ee .in .pp will probably do. .pp the .br clearenv () function may be useful in security-conscious applications that want to precisely control the environment that is passed to programs executed using .br exec (3). the application would do this by first clearing the environment and then adding select environment variables. .pp note that the main effect of .br clearenv () is to adjust the value of the pointer .br environ (7); this function does not erase the contents of the buffers containing the environment definitions. .pp the dg/ux and tru64 man pages write: if .i environ has been modified by anything other than the .br putenv (3), .br getenv (3), or .br clearenv () functions, then .br clearenv () will return an error and the process environment will remain unchanged. .\" .lp .\" hp-ux has a enomem error return. .sh see also .br getenv (3), .br putenv (3), .br setenv (3), .br unsetenv (3), .br environ (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1980, 1991 regents of the university of california. .\" and copyright (c) 2011, michael kerrisk .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)lseek.2 6.5 (berkeley) 3/10/91 .\" .\" modified 1993-07-23 by rik faith .\" modified 1995-06-10 by andries brouwer .\" modified 1996-10-31 by eric s. raymond .\" modified 1998-01-17 by michael haardt .\" .\" modified 2001-09-24 by michael haardt .\" modified 2003-08-21 by andries brouwer .\" 2011-09-18, mtk, added seek_data + seek_hole .\" .th lseek 2 2021-03-22 "linux" "linux programmer's manual" .sh name lseek \- reposition read/write file offset .sh synopsis .nf .b #include .pp .bi "off_t lseek(int " fd ", off_t " offset ", int " whence ); .fi .sh description .br lseek () repositions the file offset of the open file description associated with the file descriptor .i fd to the argument .i offset according to the directive .i whence as follows: .tp .b seek_set the file offset is set to .i offset bytes. .tp .b seek_cur the file offset is set to its current location plus .i offset bytes. .tp .b seek_end the file offset is set to the size of the file plus .i offset bytes. .pp .br lseek () allows the file offset to be set beyond the end of the file (but this does not change the size of the file). if data is later written at this point, subsequent reads of the data in the gap (a "hole") return null bytes (\(aq\e0\(aq) until data is actually written into the gap. .ss seeking file data and holes since version 3.1, linux supports the following additional values for .ir whence : .tp .b seek_data adjust the file offset to the next location in the file greater than or equal to .i offset containing data. if .i offset points to data, then the file offset is set to .ir offset . .tp .b seek_hole adjust the file offset to the next hole in the file greater than or equal to .ir offset . if .i offset points into the middle of a hole, then the file offset is set to .ir offset . if there is no hole past .ir offset , then the file offset is adjusted to the end of the file (i.e., there is an implicit hole at the end of any file). .pp in both of the above cases, .br lseek () fails if .i offset points past the end of the file. .pp these operations allow applications to map holes in a sparsely allocated file. this can be useful for applications such as file backup tools, which can save space when creating backups and preserve holes, if they have a mechanism for discovering holes. .pp for the purposes of these operations, a hole is a sequence of zeros that (normally) has not been allocated in the underlying file storage. however, a filesystem is not obliged to report holes, so these operations are not a guaranteed mechanism for mapping the storage space actually allocated to a file. (furthermore, a sequence of zeros that actually has been written to the underlying storage may not be reported as a hole.) in the simplest implementation, a filesystem can support the operations by making .br seek_hole always return the offset of the end of the file, and making .br seek_data always return .ir offset (i.e., even if the location referred to by .i offset is a hole, it can be considered to consist of data that is a sequence of zeros). .\" https://lkml.org/lkml/2011/4/22/79 .\" http://lwn.net/articles/440255/ .\" http://blogs.oracle.com/bonwick/entry/seek_hole_and_seek_data .pp the .br _gnu_source feature test macro must be defined in order to obtain the definitions of .br seek_data and .br seek_hole from .ir . .pp the .br seek_hole and .br seek_data operations are supported for the following filesystems: .ip * 3 btrfs (since linux 3.1) .ip * 3 ocfs (since linux 3.2) .\" commit 93862d5e1ab875664c6cc95254fc365028a48bb1 .ip * xfs (since linux 3.5) .ip * ext4 (since linux 3.8) .ip * .br tmpfs (5) (since linux 3.8) .ip * nfs (since linux 3.18) .\" commit 1c6dcbe5ceff81c2cf8d929646af675cd59fe7c0 .\" commit 24bab491220faa446d945624086d838af41d616c .ip * fuse (since linux 4.5) .\" commit 0b5da8db145bfd44266ac964a2636a0cf8d7c286 .ip * gfs2 (since linux 4.15) .\" commit 3a27411cb4bc3ce31db228e3569ad01b462a4310 .sh return value upon successful completion, .br lseek () returns the resulting offset location as measured in bytes from the beginning of the file. on error, the value \fi(off_t)\ \-1\fp is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not an open file descriptor. .tp .b einval .i whence is not valid. or: the resulting file offset would be negative, or beyond the end of a seekable device. .\" some systems may allow negative offsets for character devices .\" and/or for remote filesystems. .tp .b enxio .i whence is .b seek_data or .br seek_hole , and .i offset is beyond the end of the file, or .i whence is .b seek_data and .i offset is within a hole at the end of the file. .tp .b eoverflow .\" hp-ux 11 says einval for this case (but posix.1 says eoverflow) the resulting file offset cannot be represented in an .ir off_t . .tp .b espipe .i fd is associated with a pipe, socket, or fifo. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .pp .br seek_data and .br seek_hole are nonstandard extensions also present in solaris, freebsd, and dragonfly bsd; they are proposed for inclusion in the next posix revision (issue 8). .\" fixme . review http://austingroupbugs.net/view.php?id=415 in the future .sh notes see .br open (2) for a discussion of the relationship between file descriptors, open file descriptions, and files. .pp if the .b o_append file status flag is set on the open file description, then a .br write (2) .i always moves the file offset to the end of the file, regardless of the use of .br lseek (). .pp the .i off_t data type is a signed integer data type specified by posix.1. .pp some devices are incapable of seeking and posix does not specify which devices must support .br lseek (). .pp on linux, using .br lseek () on a terminal device fails with the error \fbespipe\fp. .\" other systems return the number of written characters, .\" using seek_set to set the counter. (of written characters.) .sh see also .br dup (2), .br fallocate (2), .br fork (2), .br open (2), .br fseek (3), .br lseek64 (3), .br posix_fallocate (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getgid.2 .so man3/resolver.3 .so man2/eventfd.2 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_error 3 2021-03-22 "" "linux programmer's manual" .sh name aio_error \- get error status of asynchronous i/o operation .sh synopsis .nf .b "#include " .pp .bi "int aio_error(const struct aiocb *" aiocbp ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_error () function returns the error status for the asynchronous i/o request with control block pointed to by .ir aiocbp . (see .br aio (7) for a description of the .i aiocb structure.) .sh return value this function returns one of the following: .ip * 3 .br einprogress , if the request has not been completed yet. .ip * .br ecanceled , if the request was canceled. .ip * 0, if the request completed successfully. .ip * a positive error number, if the asynchronous i/o operation failed. this is the same value that would have been stored in the .i errno variable in the case of a synchronous .br read (2), .br write (2), .br fsync (2), or .br fdatasync (2) call. .sh errors .tp .b einval .i aiocbp does not point at a control block for an asynchronous i/o request of which the return status (see .br aio_return (3)) has not been retrieved yet. .tp .b enosys .br aio_error () is not implemented. .sh versions the .br aio_error () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_error () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples see .br aio (7). .sh see also .br aio_cancel (3), .br aio_fsync (3), .br aio_read (3), .br aio_return (3), .br aio_suspend (3), .br aio_write (3), .br lio_listio (3), .br aio (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" and copyright (c) 2006, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-21 by rik faith .\" modified 1997-01-12 by michael haardt .\" : nfs details .\" modified 2004-06-23 by michael kerrisk .\" .th chmod 2 2021-08-27 "linux" "linux programmer's manual" .sh name chmod, fchmod, fchmodat \- change permissions of a file .sh synopsis .nf .b #include .pp .bi "int chmod(const char *" pathname ", mode_t " mode ); .bi "int fchmod(int " fd ", mode_t " mode ); .pp .br "#include " " /* definition of at_* constants */" .b #include .pp .bi "int fchmodat(int " dirfd ", const char *" pathname ", mode_t " \ mode ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .nf .br fchmod (): since glibc 2.24: _posix_c_source >= 199309l .\" || (_xopen_source && _xopen_source_extended) glibc 2.19 to 2.23 _posix_c_source glibc 2.16 to 2.19: _bsd_source || _posix_c_source glibc 2.12 to 2.16: _bsd_source || _xopen_source >= 500 || _posix_c_source >= 200809l glibc 2.11 and earlier: _bsd_source || _xopen_source >= 500 .\" || (_xopen_source && _xopen_source_extended) .fi .pp .br fchmodat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description the .br chmod () and .br fchmod () system calls change a file's mode bits. (the file mode consists of the file permission bits plus the set-user-id, set-group-id, and sticky bits.) these system calls differ only in how the file is specified: .ip * 2 .br chmod () changes the mode of the file specified whose pathname is given in .ir pathname , which is dereferenced if it is a symbolic link. .ip * .br fchmod () changes the mode of the file referred to by the open file descriptor .ir fd . .pp the new file mode is specified in .ir mode , which is a bit mask created by oring together zero or more of the following: .tp 18 .br s_isuid " (04000)" set-user-id (set process effective user id on .br execve (2)) .tp .br s_isgid " (02000)" set-group-id (set process effective group id on .br execve (2); mandatory locking, as described in .br fcntl (2); take a new file's group from parent directory, as described in .br chown (2) and .br mkdir (2)) .tp .br s_isvtx " (01000)" sticky bit (restricted deletion flag, as described in .br unlink (2)) .tp .br s_irusr " (00400)" read by owner .tp .br s_iwusr " (00200)" write by owner .tp .br s_ixusr " (00100)" execute/search by owner ("search" applies for directories, and means that entries within the directory can be accessed) .tp .br s_irgrp " (00040)" read by group .tp .br s_iwgrp " (00020)" write by group .tp .br s_ixgrp " (00010)" execute/search by group .tp .br s_iroth " (00004)" read by others .tp .br s_iwoth " (00002)" write by others .tp .br s_ixoth " (00001)" execute/search by others .pp the effective uid of the calling process must match the owner of the file, or the process must be privileged (linux: it must have the .b cap_fowner capability). .pp if the calling process is not privileged (linux: does not have the .b cap_fsetid capability), and the group of the file does not match the effective group id of the process or one of its supplementary group ids, the .b s_isgid bit will be turned off, but this will not cause an error to be returned. .pp as a security measure, depending on the filesystem, the set-user-id and set-group-id execution bits may be turned off if a file is written. (on linux, this occurs if the writing process does not have the .b cap_fsetid capability.) on some filesystems, only the superuser can set the sticky bit, which may have a special meaning. for the sticky bit, and for set-user-id and set-group-id bits on directories, see .br inode (7). .pp on nfs filesystems, restricting the permissions will immediately influence already open files, because the access control is done on the server, but open files are maintained by the client. widening the permissions may be delayed for other clients if attribute caching is enabled on them. .\" .\" .ss fchmodat() the .br fchmodat () system call operates in exactly the same way as .br chmod (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br chmod () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br chmod ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp .i flags can either be 0, or include the following flag: .tp .b at_symlink_nofollow if .i pathname is a symbolic link, do not dereference it: instead operate on the link itself. this flag is not currently implemented. .pp see .br openat (2) for an explanation of the need for .br fchmodat (). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors depending on the filesystem, errors other than those listed below can be returned. .pp the more general errors for .br chmod () are listed below: .tp .b eacces search permission is denied on a component of the path prefix. (see also .br path_resolution (7).) .tp .b ebadf .rb ( fchmod ()) the file descriptor .i fd is not valid. .tp .b ebadf .rb ( fchmodat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b efault .i pathname points outside your accessible address space. .tp .b einval .rb ( fchmodat ()) invalid flag specified in .ir flags . .tp .b eio an i/o error occurred. .tp .b eloop too many symbolic links were encountered in resolving .ir pathname . .tp .b enametoolong .i pathname is too long. .tp .b enoent the file does not exist. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component of the path prefix is not a directory. .tp .b enotdir .rb ( fchmodat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b enotsup .rb ( fchmodat ()) .i flags specified .br at_symlink_nofollow , which is not supported. .tp .b eperm the effective uid does not match the owner of the file, and the process is not privileged (linux: it does not have the .b cap_fowner capability). .tp .b eperm the file is marked immutable or append-only. (see .br ioctl_iflags (2).) .tp .b erofs the named file resides on a read-only filesystem. .sh versions .br fchmodat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br chmod (), .br fchmod (): 4.4bsd, svr4, posix.1-2001i, posix.1-2008. .pp .br fchmodat (): posix.1-2008. .sh notes .ss c library/kernel differences the gnu c library .br fchmodat () wrapper function implements the posix-specified interface described in this page. this interface differs from the underlying linux system call, which does .i not have a .i flags argument. .ss glibc notes on older kernels where .br fchmodat () is unavailable, the glibc wrapper function falls back to the use of .br chmod (). when .i pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir dirfd argument. .sh see also .br chmod (1), .br chown (2), .br execve (2), .br open (2), .br stat (2), .br inode (7), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016, ibm corporation. .\" written by mike rapoport .\" and copyright (c) 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th userfaultfd 2 2021-03-22 "linux" "linux programmer's manual" .sh name userfaultfd \- create a file descriptor for handling page faults in user space .sh synopsis .nf .br "#include " " /* definition of " o_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_userfaultfd, int " flags ); .fi .pp .ir note : glibc provides no wrapper for .br userfaultfd (), necessitating the use of .br syscall (2). .sh description .br userfaultfd () creates a new userfaultfd object that can be used for delegation of page-fault handling to a user-space application, and returns a file descriptor that refers to the new object. the new userfaultfd object is configured using .br ioctl (2). .pp once the userfaultfd object is configured, the application can use .br read (2) to receive userfaultfd notifications. the reads from userfaultfd may be blocking or non-blocking, depending on the value of .i flags used for the creation of the userfaultfd or subsequent calls to .br fcntl (2). .pp the following values may be bitwise ored in .ir flags to change the behavior of .br userfaultfd (): .tp .br o_cloexec enable the close-on-exec flag for the new userfaultfd file descriptor. see the description of the .b o_cloexec flag in .br open (2). .tp .br o_nonblock enables non-blocking operation for the userfaultfd object. see the description of the .br o_nonblock flag in .br open (2). .pp when the last file descriptor referring to a userfaultfd object is closed, all memory ranges that were registered with the object are unregistered and unread events are flushed. .\" .pp userfaultfd supports two modes of registration: .tp .br uffdio_register_mode_missing " (since 4.10)" when registered with .b uffdio_register_mode_missing mode, user-space will receive a page-fault notification when a missing page is accessed. the faulted thread will be stopped from execution until the page fault is resolved from user-space by either an .b uffdio_copy or an .b uffdio_zeropage ioctl. .tp .br uffdio_register_mode_wp " (since 5.7)" when registered with .b uffdio_register_mode_wp mode, user-space will receive a page-fault notification when a write-protected page is written. the faulted thread will be stopped from execution until user-space write-unprotects the page using an .b uffdio_writeprotect ioctl. .pp multiple modes can be enabled at the same time for the same memory range. .pp since linux 4.14, a userfaultfd page-fault notification can selectively embed faulting thread id information into the notification. one needs to enable this feature explicitly using the .b uffd_feature_thread_id feature bit when initializing the userfaultfd context. by default, thread id reporting is disabled. .ss usage the userfaultfd mechanism is designed to allow a thread in a multithreaded program to perform user-space paging for the other threads in the process. when a page fault occurs for one of the regions registered to the userfaultfd object, the faulting thread is put to sleep and an event is generated that can be read via the userfaultfd file descriptor. the fault-handling thread reads events from this file descriptor and services them using the operations described in .br ioctl_userfaultfd (2). when servicing the page fault events, the fault-handling thread can trigger a wake-up for the sleeping thread. .pp it is possible for the faulting threads and the fault-handling threads to run in the context of different processes. in this case, these threads may belong to different programs, and the program that executes the faulting threads will not necessarily cooperate with the program that handles the page faults. in such non-cooperative mode, the process that monitors userfaultfd and handles page faults needs to be aware of the changes in the virtual memory layout of the faulting process to avoid memory corruption. .pp since linux 4.11, userfaultfd can also notify the fault-handling threads about changes in the virtual memory layout of the faulting process. in addition, if the faulting process invokes .br fork (2), the userfaultfd objects associated with the parent may be duplicated into the child process and the userfaultfd monitor will be notified (via the .b uffd_event_fork described below) about the file descriptor associated with the userfault objects created for the child process, which allows the userfaultfd monitor to perform user-space paging for the child process. unlike page faults which have to be synchronous and require an explicit or implicit wakeup, all other events are delivered asynchronously and the non-cooperative process resumes execution as soon as the userfaultfd manager executes .br read (2). the userfaultfd manager should carefully synchronize calls to .b uffdio_copy with the processing of events. .pp the current asynchronous model of the event delivery is optimal for single threaded non-cooperative userfaultfd manager implementations. .\" regarding the preceding sentence, mike rapoport says: .\" the major point here is that current events delivery model could be .\" problematic for multi-threaded monitor. i even suspect that it would be .\" impossible to ensure synchronization between page faults and non-page .\" fault events in multi-threaded monitor. .\" .pp .\" fixme elaborate about non-cooperating mode, describe its limitations .\" for kernels before 4.11, features added in 4.11 .\" and limitations remaining in 4.11 .\" maybe it's worth adding a dedicated sub-section... .\" .pp since linux 5.7, userfaultfd is able to do synchronous page dirty tracking using the new write-protect register mode. one should check against the feature bit .b uffd_feature_pagefault_flag_wp before using this feature. similar to the original userfaultfd missing mode, the write-protect mode will generate a userfaultfd notification when the protected page is written. the user needs to resolve the page fault by unprotecting the faulted page and kicking the faulted thread to continue. for more information, please refer to the "userfaultfd write-protect mode" section. .\" .ss userfaultfd operation after the userfaultfd object is created with .br userfaultfd (), the application must enable it using the .b uffdio_api .br ioctl (2) operation. this operation allows a handshake between the kernel and user space to determine the api version and supported features. this operation must be performed before any of the other .br ioctl (2) operations described below (or those operations fail with the .br einval error). .pp after a successful .b uffdio_api operation, the application then registers memory address ranges using the .b uffdio_register .br ioctl (2) operation. after successful completion of a .b uffdio_register operation, a page fault occurring in the requested memory range, and satisfying the mode defined at the registration time, will be forwarded by the kernel to the user-space application. the application can then use the .b uffdio_copy or .b uffdio_zeropage .br ioctl (2) operations to resolve the page fault. .pp since linux 4.14, if the application sets the .b uffd_feature_sigbus feature bit using the .b uffdio_api .br ioctl (2), no page-fault notification will be forwarded to user space. instead a .b sigbus signal is delivered to the faulting process. with this feature, userfaultfd can be used for robustness purposes to simply catch any access to areas within the registered address range that do not have pages allocated, without having to listen to userfaultfd events. no userfaultfd monitor will be required for dealing with such memory accesses. for example, this feature can be useful for applications that want to prevent the kernel from automatically allocating pages and filling holes in sparse files when the hole is accessed through a memory mapping. .pp the .b uffd_feature_sigbus feature is implicitly inherited through .br fork (2) if used in combination with .br uffd_feature_fork . .pp details of the various .br ioctl (2) operations can be found in .br ioctl_userfaultfd (2). .pp since linux 4.11, events other than page-fault may enabled during .b uffdio_api operation. .pp up to linux 4.11, userfaultfd can be used only with anonymous private memory mappings. since linux 4.11, userfaultfd can be also used with hugetlbfs and shared memory mappings. .\" .ss userfaultfd write-protect mode (since 5.7) since linux 5.7, userfaultfd supports write-protect mode. the user needs to first check availability of this feature using .b uffdio_api ioctl against the feature bit .b uffd_feature_pagefault_flag_wp before using this feature. .pp to register with userfaultfd write-protect mode, the user needs to initiate the .b uffdio_register ioctl with mode .b uffdio_register_mode_wp set. note that it is legal to monitor the same memory range with multiple modes. for example, the user can do .b uffdio_register with the mode set to .br "uffdio_register_mode_missing | uffdio_register_mode_wp" . when there is only .b uffdio_register_mode_wp registered, user-space will .i not receive any notification when a missing page is written. instead, user-space will receive a write-protect page-fault notification only when an existing but write-protected page got written. .pp after the .b uffdio_register ioctl completed with .b uffdio_register_mode_wp mode set, the user can write-protect any existing memory within the range using the ioctl .b uffdio_writeprotect where .i uffdio_writeprotect.mode should be set to .br uffdio_writeprotect_mode_wp . .pp when a write-protect event happens, user-space will receive a page-fault notification whose .i uffd_msg.pagefault.flags will be with .b uffd_pagefault_flag_wp flag set. note: since only writes can trigger this kind of fault, write-protect notifications will always have the .b uffd_pagefault_flag_write bit set along with the .br uffd_pagefault_flag_wp bit. .pp to resolve a write-protection page fault, the user should initiate another .b uffdio_writeprotect ioctl, whose .i uffd_msg.pagefault.flags should have the flag .b uffdio_writeprotect_mode_wp cleared upon the faulted page or range. .pp write-protect mode supports only private anonymous memory. .ss reading from the userfaultfd structure each .br read (2) from the userfaultfd file descriptor returns one or more .i uffd_msg structures, each of which describes a page-fault event or an event required for the non-cooperative userfaultfd usage: .pp .in +4n .ex struct uffd_msg { __u8 event; /* type of event */ ... union { struct { __u64 flags; /* flags describing fault */ __u64 address; /* faulting address */ union { __u32 ptid; /* thread id of the fault */ } feat; } pagefault; struct { /* since linux 4.11 */ __u32 ufd; /* userfault file descriptor of the child process */ } fork; struct { /* since linux 4.11 */ __u64 from; /* old address of remapped area */ __u64 to; /* new address of remapped area */ __u64 len; /* original mapping length */ } remap; struct { /* since linux 4.11 */ __u64 start; /* start address of removed area */ __u64 end; /* end address of removed area */ } remove; ... } arg; /* padding fields omitted */ } __packed; .ee .in .pp if multiple events are available and the supplied buffer is large enough, .br read (2) returns as many events as will fit in the supplied buffer. if the buffer supplied to .br read (2) is smaller than the size of the .i uffd_msg structure, the .br read (2) fails with the error .br einval . .pp the fields set in the .i uffd_msg structure are as follows: .tp .i event the type of event. depending of the event type, different fields of the .i arg union represent details required for the event processing. the non-page-fault events are generated only when appropriate feature is enabled during api handshake with .b uffdio_api .br ioctl (2). .ip the following values can appear in the .i event field: .rs .tp .br uffd_event_pagefault " (since linux 4.3)" a page-fault event. the page-fault details are available in the .i pagefault field. .tp .br uffd_event_fork " (since linux 4.11)" generated when the faulting process invokes .br fork (2) (or .br clone (2) without the .br clone_vm flag). the event details are available in the .i fork field. .\" fixme describe duplication of userfault file descriptor during fork .tp .br uffd_event_remap " (since linux 4.11)" generated when the faulting process invokes .br mremap (2). the event details are available in the .i remap field. .tp .br uffd_event_remove " (since linux 4.11)" generated when the faulting process invokes .br madvise (2) with .br madv_dontneed or .br madv_remove advice. the event details are available in the .i remove field. .tp .br uffd_event_unmap " (since linux 4.11)" generated when the faulting process unmaps a memory range, either explicitly using .br munmap (2) or implicitly during .br mmap (2) or .br mremap (2). the event details are available in the .i remove field. .re .tp .i pagefault.address the address that triggered the page fault. .tp .i pagefault.flags a bit mask of flags that describe the event. for .br uffd_event_pagefault , the following flag may appear: .rs .tp .b uffd_pagefault_flag_write if the address is in a range that was registered with the .b uffdio_register_mode_missing flag (see .br ioctl_userfaultfd (2)) and this flag is set, this a write fault; otherwise it is a read fault. .tp .b uffd_pagefault_flag_wp if the address is in a range that was registered with the .b uffdio_register_mode_wp flag, when this bit is set, it means it is a write-protect fault. otherwise it is a page-missing fault. .re .tp .i pagefault.feat.pid the thread id that triggered the page fault. .tp .i fork.ufd the file descriptor associated with the userfault object created for the child created by .br fork (2). .tp .i remap.from the original address of the memory range that was remapped using .br mremap (2). .tp .i remap.to the new address of the memory range that was remapped using .br mremap (2). .tp .i remap.len the original length of the memory range that was remapped using .br mremap (2). .tp .i remove.start the start address of the memory range that was freed using .br madvise (2) or unmapped .tp .i remove.end the end address of the memory range that was freed using .br madvise (2) or unmapped .pp a .br read (2) on a userfaultfd file descriptor can fail with the following errors: .tp .b einval the userfaultfd object has not yet been enabled using the .br uffdio_api .br ioctl (2) operation .pp if the .b o_nonblock flag is enabled in the associated open file description, the userfaultfd file descriptor can be monitored with .br poll (2), .br select (2), and .br epoll (7). when events are available, the file descriptor indicates as readable. if the .b o_nonblock flag is not enabled, then .br poll (2) (always) indicates the file as having a .br pollerr condition, and .br select (2) indicates the file descriptor as both readable and writable. .\" fixme what is the reason for this seemingly odd behavior with respect .\" to the o_nonblock flag? (see userfaultfd_poll() in fs/userfaultfd.c). .\" something needs to be said about this. .sh return value on success, .br userfaultfd () returns a new file descriptor that refers to the userfaultfd object. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval an unsupported value was specified in .ir flags . .tp .br emfile the per-process limit on the number of open file descriptors has been reached .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enomem insufficient kernel memory was available. .tp .br eperm " (since linux 5.2)" .\" cefdca0a86be517bc390fc4541e3674b8e7803b0 the caller is not privileged (does not have the .b cap_sys_ptrace capability in the initial user namespace), and .i /proc/sys/vm/unprivileged_userfaultfd has the value 0. .sh versions the .br userfaultfd () system call first appeared in linux 4.3. .pp the support for hugetlbfs and shared memory areas and non-page-fault events was added in linux 4.11 .sh conforming to .br userfaultfd () is linux-specific and should not be used in programs intended to be portable. .sh notes the userfaultfd mechanism can be used as an alternative to traditional user-space paging techniques based on the use of the .br sigsegv signal and .br mmap (2). it can also be used to implement lazy restore for checkpoint/restore mechanisms, as well as post-copy migration to allow (nearly) uninterrupted execution when transferring virtual machines and linux containers from one host to another. .sh bugs if the .b uffd_feature_event_fork is enabled and a system call from the .br fork (2) family is interrupted by a signal or failed, a stale userfaultfd descriptor might be created. in this case, a spurious .b uffd_event_fork will be delivered to the userfaultfd monitor. .sh examples the program below demonstrates the use of the userfaultfd mechanism. the program creates two threads, one of which acts as the page-fault handler for the process, for the pages in a demand-page zero region created using .br mmap (2). .pp the program takes one command-line argument, which is the number of pages that will be created in a mapping whose page faults will be handled via userfaultfd. after creating a userfaultfd object, the program then creates an anonymous private mapping of the specified size and registers the address range of that mapping using the .b uffdio_register .br ioctl (2) operation. the program then creates a second thread that will perform the task of handling page faults. .pp the main thread then walks through the pages of the mapping fetching bytes from successive pages. because the pages have not yet been accessed, the first access of a byte in each page will trigger a page-fault event on the userfaultfd file descriptor. .pp each of the page-fault events is handled by the second thread, which sits in a loop processing input from the userfaultfd file descriptor. in each loop iteration, the second thread first calls .br poll (2) to check the state of the file descriptor, and then reads an event from the file descriptor. all such events should be .b uffd_event_pagefault events, which the thread handles by copying a page of data into the faulting region using the .b uffdio_copy .br ioctl (2) operation. .pp the following is an example of what we see when running the program: .pp .in +4n .ex $ \fb./userfaultfd_demo 3\fp address returned by mmap() = 0x7fd30106c000 fault_handler_thread(): poll() returns: nready = 1; pollin = 1; pollerr = 0 uffd_event_pagefault event: flags = 0; address = 7fd30106c00f (uffdio_copy.copy returned 4096) read address 0x7fd30106c00f in main(): a read address 0x7fd30106c40f in main(): a read address 0x7fd30106c80f in main(): a read address 0x7fd30106cc0f in main(): a fault_handler_thread(): poll() returns: nready = 1; pollin = 1; pollerr = 0 uffd_event_pagefault event: flags = 0; address = 7fd30106d00f (uffdio_copy.copy returned 4096) read address 0x7fd30106d00f in main(): b read address 0x7fd30106d40f in main(): b read address 0x7fd30106d80f in main(): b read address 0x7fd30106dc0f in main(): b fault_handler_thread(): poll() returns: nready = 1; pollin = 1; pollerr = 0 uffd_event_pagefault event: flags = 0; address = 7fd30106e00f (uffdio_copy.copy returned 4096) read address 0x7fd30106e00f in main(): c read address 0x7fd30106e40f in main(): c read address 0x7fd30106e80f in main(): c read address 0x7fd30106ec0f in main(): c .ee .in .ss program source \& .ex /* userfaultfd_demo.c licensed under the gnu general public license version 2 or later. */ #define _gnu_source #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static int page_size; static void * fault_handler_thread(void *arg) { static struct uffd_msg msg; /* data read from userfaultfd */ static int fault_cnt = 0; /* number of faults so far handled */ long uffd; /* userfaultfd file descriptor */ static char *page = null; struct uffdio_copy uffdio_copy; ssize_t nread; uffd = (long) arg; /* create a page that will be copied into the faulting region. */ if (page == null) { page = mmap(null, page_size, prot_read | prot_write, map_private | map_anonymous, \-1, 0); if (page == map_failed) errexit("mmap"); } /* loop, handling incoming events on the userfaultfd file descriptor. */ for (;;) { /* see what poll() tells us about the userfaultfd. */ struct pollfd pollfd; int nready; pollfd.fd = uffd; pollfd.events = pollin; nready = poll(&pollfd, 1, \-1); if (nready == \-1) errexit("poll"); printf("\enfault_handler_thread():\en"); printf(" poll() returns: nready = %d; " "pollin = %d; pollerr = %d\en", nready, (pollfd.revents & pollin) != 0, (pollfd.revents & pollerr) != 0); /* read an event from the userfaultfd. */ nread = read(uffd, &msg, sizeof(msg)); if (nread == 0) { printf("eof on userfaultfd!\en"); exit(exit_failure); } if (nread == \-1) errexit("read"); /* we expect only one kind of event; verify that assumption. */ if (msg.event != uffd_event_pagefault) { fprintf(stderr, "unexpected event on userfaultfd\en"); exit(exit_failure); } /* display info about the page\-fault event. */ printf(" uffd_event_pagefault event: "); printf("flags = %"prix64"; ", msg.arg.pagefault.flags); printf("address = %"prix64"\en", msg.arg.pagefault.address); /* copy the page pointed to by \(aqpage\(aq into the faulting region. vary the contents that are copied in, so that it is more obvious that each fault is handled separately. */ memset(page, \(aqa\(aq + fault_cnt % 20, page_size); fault_cnt++; uffdio_copy.src = (unsigned long) page; /* we need to handle page faults in units of pages(!). so, round faulting address down to page boundary. */ uffdio_copy.dst = (unsigned long) msg.arg.pagefault.address & \(ti(page_size \- 1); uffdio_copy.len = page_size; uffdio_copy.mode = 0; uffdio_copy.copy = 0; if (ioctl(uffd, uffdio_copy, &uffdio_copy) == \-1) errexit("ioctl\-uffdio_copy"); printf(" (uffdio_copy.copy returned %"prid64")\en", uffdio_copy.copy); } } int main(int argc, char *argv[]) { long uffd; /* userfaultfd file descriptor */ char *addr; /* start of region handled by userfaultfd */ uint64_t len; /* length of region handled by userfaultfd */ pthread_t thr; /* id of thread that handles page faults */ struct uffdio_api uffdio_api; struct uffdio_register uffdio_register; int s; if (argc != 2) { fprintf(stderr, "usage: %s num\-pages\en", argv[0]); exit(exit_failure); } page_size = sysconf(_sc_page_size); len = strtoull(argv[1], null, 0) * page_size; /* create and enable userfaultfd object. */ uffd = syscall(__nr_userfaultfd, o_cloexec | o_nonblock); if (uffd == \-1) errexit("userfaultfd"); uffdio_api.api = uffd_api; uffdio_api.features = 0; if (ioctl(uffd, uffdio_api, &uffdio_api) == \-1) errexit("ioctl\-uffdio_api"); /* create a private anonymous mapping. the memory will be demand\-zero paged\-\-that is, not yet allocated. when we actually touch the memory, it will be allocated via the userfaultfd. */ addr = mmap(null, len, prot_read | prot_write, map_private | map_anonymous, \-1, 0); if (addr == map_failed) errexit("mmap"); printf("address returned by mmap() = %p\en", addr); /* register the memory range of the mapping we just created for handling by the userfaultfd object. in mode, we request to track missing pages (i.e., pages that have not yet been faulted in). */ uffdio_register.range.start = (unsigned long) addr; uffdio_register.range.len = len; uffdio_register.mode = uffdio_register_mode_missing; if (ioctl(uffd, uffdio_register, &uffdio_register) == \-1) errexit("ioctl\-uffdio_register"); /* create a thread that will process the userfaultfd events. */ s = pthread_create(&thr, null, fault_handler_thread, (void *) uffd); if (s != 0) { errno = s; errexit("pthread_create"); } /* main thread now touches memory in the mapping, touching locations 1024 bytes apart. this will trigger userfaultfd events for all pages in the region. */ int l; l = 0xf; /* ensure that faulting address is not on a page boundary, in order to test that we correctly handle that case in fault_handling_thread(). */ while (l < len) { char c = addr[l]; printf("read address %p in main(): ", addr + l); printf("%c\en", c); l += 1024; usleep(100000); /* slow things down a little */ } exit(exit_success); } .ee .sh see also .br fcntl (2), .br ioctl (2), .br ioctl_userfaultfd (2), .br madvise (2), .br mmap (2) .pp .ir documentation/admin\-guide/mm/userfaultfd.rst in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/argz_add.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:48:17 1993 by rik faith (faith@cs.unc.edu) .th difftime 3 2021-03-22 "gnu" "linux programmer's manual" .sh name difftime \- calculate time difference .sh synopsis .nf .b #include .pp .bi "double difftime(time_t " time1 ", time_t " time0 ); .fi .sh description the .br difftime () function returns the number of seconds elapsed between time \fitime1\fp and time \fitime0\fp, represented as a .ir double . each of the times is specified in calendar time, which means its value is a measurement (in seconds) relative to the epoch, 1970-01-01 00:00:00 +0000 (utc). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br difftime () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes on a posix system, .i time_t is an arithmetic type, and one could just define .pp .in +4n .ex #define difftime(t1,t0) (double)(t1 \- t0) .ee .in .pp when the possible overflow in the subtraction is not a concern. .sh see also .br date (1), .br gettimeofday (2), .br time (2), .br ctime (3), .br gmtime (3), .br localtime (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fmax.3 .so man3/cabs.3 .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: udp.7,v 1.7 2000/01/22 01:55:05 freitag exp $ .\" .th udp 7 2021-03-22 "linux" "linux programmer's manual" .sh name udp \- user datagram protocol for ipv4 .sh synopsis .nf .b #include .b #include .b #include .pp .b udp_socket = socket(af_inet, sock_dgram, 0); .fi .sh description this is an implementation of the user datagram protocol described in rfc\ 768. it implements a connectionless, unreliable datagram packet service. packets may be reordered or duplicated before they arrive. udp generates and checks checksums to catch transmission errors. .pp when a udp socket is created, its local and remote addresses are unspecified. datagrams can be sent immediately using .br sendto (2) or .br sendmsg (2) with a valid destination address as an argument. when .br connect (2) is called on the socket, the default destination address is set and datagrams can now be sent using .br send (2) or .br write (2) without specifying a destination address. it is still possible to send to other destinations by passing an address to .br sendto (2) or .br sendmsg (2). in order to receive packets, the socket can be bound to a local address first by using .br bind (2). otherwise, the socket layer will automatically assign a free local port out of the range defined by .i /proc/sys/net/ipv4/ip_local_port_range and bind the socket to .br inaddr_any . .pp all receive operations return only one packet. when the packet is smaller than the passed buffer, only that much data is returned; when it is bigger, the packet is truncated and the .b msg_trunc flag is set. .b msg_waitall is not supported. .pp ip options may be sent or received using the socket options described in .br ip (7). they are processed by the kernel only when the appropriate .i /proc parameter is enabled (but still passed to the user even when it is turned off). see .br ip (7). .pp when the .b msg_dontroute flag is set on sending, the destination address must refer to a local interface address and the packet is sent only to that interface. .pp by default, linux udp does path mtu (maximum transmission unit) discovery. this means the kernel will keep track of the mtu to a specific target ip address and return .b emsgsize when a udp packet write exceeds it. when this happens, the application should decrease the packet size. path mtu discovery can be also turned off using the .b ip_mtu_discover socket option or the .i /proc/sys/net/ipv4/ip_no_pmtu_disc file; see .br ip (7) for details. when turned off, udp will fragment outgoing udp packets that exceed the interface mtu. however, disabling it is not recommended for performance and reliability reasons. .ss address format udp uses the ipv4 .i sockaddr_in address format described in .br ip (7). .ss error handling all fatal errors will be passed to the user as an error return even when the socket is not connected. this includes asynchronous errors received from the network. you may get an error for an earlier packet that was sent on the same socket. this behavior differs from many other bsd socket implementations which don't pass any errors unless the socket is connected. linux's behavior is mandated by .br rfc\ 1122 . .pp for compatibility with legacy code, in linux 2.0 and 2.2 it was possible to set the .b so_bsdcompat .b sol_socket option to receive remote errors only when the socket has been connected (except for .b eproto and .br emsgsize ). locally generated errors are always passed. support for this socket option was removed in later kernels; see .br socket (7) for further information. .pp when the .b ip_recverr option is enabled, all errors are stored in the socket error queue, and can be received by .br recvmsg (2) with the .b msg_errqueue flag set. .ss /proc interfaces system-wide udp parameter settings can be accessed by files in the directory .ir /proc/sys/net/ipv4/ . .tp .ir udp_mem " (since linux 2.6.25)" this is a vector of three integers governing the number of pages allowed for queueing by all udp sockets. .rs .tp .i min below this number of pages, udp is not bothered about its memory appetite. when the amount of memory allocated by udp exceeds this number, udp starts to moderate memory usage. .tp .i pressure this value was introduced to follow the format of .ir tcp_mem (see .br tcp (7)). .tp .i max number of pages allowed for queueing by all udp sockets. .re .ip defaults values for these three items are calculated at boot time from the amount of available memory. .tp .ir udp_rmem_min " (integer; default value: page_size; since linux 2.6.25)" minimal size, in bytes, of receive buffers used by udp sockets in moderation. each udp socket is able to use the size for receiving data, even if total pages of udp sockets exceed .i udp_mem pressure. .tp .ir udp_wmem_min " (integer; default value: page_size; since linux 2.6.25)" minimal size, in bytes, of send buffer used by udp sockets in moderation. each udp socket is able to use the size for sending data, even if total pages of udp sockets exceed .i udp_mem pressure. .ss socket options to set or get a udp socket option, call .br getsockopt (2) to read or .br setsockopt (2) to write the option with the option level argument set to .br ipproto_udp . unless otherwise noted, .i optval is a pointer to an .ir int . .pp following is a list of udp-specific socket options. for details of some other socket options that are also applicable for udp sockets, see .br socket (7). .tp .br udp_cork " (since linux 2.5.44)" if this option is enabled, then all data output on this socket is accumulated into a single datagram that is transmitted when the option is disabled. this option should not be used in code intended to be portable. .\" fixme document udp_encap (new in kernel 2.5.67) .\" from include/linux/udp.h: .\" udp_encap_espinudp_non_ike draft-ietf-ipsec-nat-t-ike-00/01 .\" udp_encap_espinudp draft-ietf-ipsec-udp-encaps-06 .\" udp_encap_l2tpinudp rfc2661 .\" fixme document udp_no_check6_tx and udp_no_check6_rx, added in linux 3.16 .ss ioctls these ioctls can be accessed using .br ioctl (2). the correct syntax is: .pp .rs .nf .bi int " value"; .ib error " = ioctl(" udp_socket ", " ioctl_type ", &" value ");" .fi .re .tp .br fionread " (" siocinq ) gets a pointer to an integer as argument. returns the size of the next pending datagram in the integer in bytes, or 0 when no datagram is pending. .b warning: using .br fionread , it is impossible to distinguish the case where no datagram is pending from the case where the next pending datagram contains zero bytes of data. it is safer to use .br select (2), .br poll (2), or .br epoll (7) to distinguish these cases. .\" see http://www.securiteam.com/unixfocus/5kp0i15iko.html .\" "gnunet dos (udp socket unreachable)", 14 may 2006 .tp .br tiocoutq " (" siocoutq ) returns the number of data bytes in the local send queue. supported only with linux 2.4 and above. .pp in addition, all ioctls documented in .br ip (7) and .br socket (7) are supported. .sh errors all errors documented for .br socket (7) or .br ip (7) may be returned by a send or receive on a udp socket. .tp .b econnrefused no receiver was associated with the destination address. this might be caused by a previous packet sent over the socket. .sh versions .b ip_recverr is a new feature in linux 2.2. .\" .sh credits .\" this man page was written by andi kleen. .sh see also .br ip (7), .br raw (7), .br socket (7), .br udplite (7) .pp the kernel source file .ir documentation/networking/ip\-sysctl.txt . .pp rfc\ 768 for the user datagram protocol. .br rfc\ 1122 for the host requirements. .br rfc\ 1191 for a description of path mtu discovery. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/hsearch.3 .so man3/rpc.3 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1995-07-22 by michael chastain : .\" 'gethostname' is real system call on linux/alpha. .\" modified 1997-01-31 by eric s. raymond .\" modified 2000-06-04, 2001-12-15 by aeb .\" modified 2004-06-17 by mtk .\" modified 2008-11-27 by mtk .\" .th gethostname 2 2021-03-22 "linux" "linux programmer's manual" .sh name gethostname, sethostname \- get/set hostname .sh synopsis .nf .b #include .pp .bi "int gethostname(char *" name ", size_t " len ); .bi "int sethostname(const char *" name ", size_t " len ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br gethostname (): .nf _xopen_source >= 500 || _posix_c_source >= 200112l || /* glibc 2.19 and earlier */ _bsd_source .\" the above is something of a simplification .\" also in glibc before 2.3 there was a bit churn .fi .pp .br sethostname (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description these system calls are used to access or to change the system hostname. more precisely, they operate on the hostname associated with the calling process's uts namespace. .pp .br sethostname () sets the hostname to the value given in the character array .ir name . the .i len argument specifies the number of bytes in .ir name . (thus, .i name does not require a terminating null byte.) .pp .br gethostname () returns the null-terminated hostname in the character array .ir name , which has a length of .i len bytes. if the null-terminated hostname is too large to fit, then the name is truncated, and no error is returned (but see notes below). posix.1 says that if such truncation occurs, then it is unspecified whether the returned buffer includes a terminating null byte. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i name is an invalid address. .tp .b einval .i len is negative .\" can't occur for gethostbyname() wrapper, since 'len' has an .\" unsigned type; can occur for the underlying system call. or, for .br sethostname (), .i len is larger than the maximum allowed size. .tp .b enametoolong .rb "(glibc " gethostname ()) .i len is smaller than the actual size. (before version 2.1, glibc uses .br einval for this case.) .tp .b eperm for .br sethostname (), the caller did not have the .b cap_sys_admin capability in the user namespace associated with its uts namespace (see .br namespaces (7)). .sh conforming to svr4, 4.4bsd (these interfaces first appeared in 4.2bsd). posix.1-2001 and posix.1-2008 specify .br gethostname () but not .br sethostname (). .sh notes susv2 guarantees that "host names are limited to 255 bytes". posix.1 guarantees that "host names (not including the terminating null byte) are limited to .b host_name_max bytes". on linux, .b host_name_max is defined with the value 64, which has been the limit since linux 1.0 (earlier kernels imposed a limit of 8 bytes). .ss c library/kernel differences the gnu c library does not employ the .br gethostname () system call; instead, it implements .br gethostname () as a library function that calls .br uname (2) and copies up to .i len bytes from the returned .i nodename field into .ir name . having performed the copy, the function then checks if the length of the .i nodename was greater than or equal to .ir len , and if it is, then the function returns \-1 with .i errno set to .br enametoolong ; in this case, a terminating null byte is not included in the returned .ir name . .pp versions of glibc before 2.2 .\" at least glibc 2.0 and 2.1, older versions not checked handle the case where the length of the .i nodename was greater than or equal to .i len differently: nothing is copied into .i name and the function returns \-1 with .i errno set to .br enametoolong . .sh see also .br hostname (1), .br getdomainname (2), .br setdomainname (2), .br uname (2), .br uts_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th atan2 3 2021-03-22 "" "linux programmer's manual" .sh name atan2, atan2f, atan2l \- arc tangent function of two variables .sh synopsis .nf .b #include .pp .bi "double atan2(double " y ", double " x ); .bi "float atan2f(float " y ", float " x ); .bi "long double atan2l(long double " y ", long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br atan2f (), .br atan2l (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions calculate the principal value of the arc tangent of .ir y/x , using the signs of the two arguments to determine the quadrant of the result. .sh return value on success, these functions return the principal value of the arc tangent of .ir y/x in radians; the return value is in the range [\-pi,\ pi]. .pp if .i y is +0 (\-0) and .i x is less than 0, +pi (\-pi) is returned. .pp if .i y is +0 (\-0) and .i x is greater than 0, +0 (\-0) is returned. .pp if .i y is less than 0 and .i x is +0 or \-0, \-pi/2 is returned. .pp if .i y is greater than 0 and .i x is +0 or \-0, pi/2 is returned. .pp .\" posix.1 says: .\" if .\" .i x .\" is 0, a pole error shall not occur. .\" if either .i x or .i y is nan, a nan is returned. .pp .\" posix.1 says: .\" if the result underflows, a range error may occur and .\" .i y/x .\" should be returned. .\" if .i y is +0 (\-0) and .i x is \-0, +pi (\-pi) is returned. .pp if .i y is +0 (\-0) and .i x is +0, +0 (\-0) is returned. .pp if .i y is a finite value greater (less) than 0, and .i x is negative infinity, +pi (\-pi) is returned. .pp if .i y is a finite value greater (less) than 0, and .i x is positive infinity, +0 (\-0) is returned. .pp if .i y is positive infinity (negative infinity), and .i x is finite, pi/2 (\-pi/2) is returned. .pp if .i y is positive infinity (negative infinity) and .i x is negative infinity, +3*pi/4 (\-3*pi/4) is returned. .pp if .i y is positive infinity (negative infinity) and .i x is positive infinity, +pi/4 (\-pi/4) is returned. .\" .\" posix.1 says: .\" if both arguments are 0, a domain error shall not occur. .sh errors no errors occur. .\" posix.1 documents an optional underflow error .\" glibc 2.8 does not do this. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br atan2 (), .br atan2f (), .br atan2l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br acos (3), .br asin (3), .br atan (3), .br carg (3), .br cos (3), .br sin (3), .br tan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1980, 1991, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)syscall.2 8.1 (berkeley) 6/16/93 .\" .\" .\" 2002-03-20 christoph hellwig .\" - adopted for linux .\" 2015-01-17, kees cook .\" added mips and arm64. .\" .th syscall 2 2021-03-22 "linux" "linux programmer's manual" .sh name syscall \- indirect system call .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(long " number ", ...);" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br syscall (): .nf since glibc 2.19: _default_source before glibc 2.19: _bsd_source || _svid_source .fi .sh description .br syscall () is a small library function that invokes the system call whose assembly language interface has the specified .i number with the specified arguments. employing .br syscall () is useful, for example, when invoking a system call that has no wrapper function in the c library. .pp .br syscall () saves cpu registers before making the system call, restores the registers upon return from the system call, and stores any error returned by the system call in .br errno (3). .pp symbolic constants for system call numbers can be found in the header file .ir . .sh return value the return value is defined by the system call being invoked. in general, a 0 return value indicates success. a \-1 return value indicates an error, and an error number is stored in .ir errno . .sh notes .br syscall () first appeared in 4bsd. .ss architecture-specific requirements each architecture abi has its own requirements on how system call arguments are passed to the kernel. for system calls that have a glibc wrapper (e.g., most system calls), glibc handles the details of copying arguments to the right registers in a manner suitable for the architecture. however, when using .br syscall () to make a system call, the caller might need to handle architecture-dependent details; this requirement is most commonly encountered on certain 32-bit architectures. .pp for example, on the arm architecture embedded abi (eabi), a 64-bit value (e.g., .ir "long long" ) must be aligned to an even register pair. thus, using .br syscall () instead of the wrapper provided by glibc, the .br readahead (2) system call would be invoked as follows on the arm architecture with the eabi in little endian mode: .pp .in +4n .ex syscall(sys_readahead, fd, 0, (unsigned int) (offset & 0xffffffff), (unsigned int) (offset >> 32), count); .ee .in .pp since the offset argument is 64 bits, and the first argument .ri ( fd ) is passed in .ir r0 , the caller must manually split and align the 64-bit value so that it is passed in the .ir r2 / r3 register pair. that means inserting a dummy value into .i r1 (the second argument of 0). care also must be taken so that the split follows endian conventions (according to the c abi for the platform). .pp similar issues can occur on mips with the o32 abi, on powerpc and parisc with the 32-bit abi, and on xtensa. .\" mike frysinger: this issue ends up forcing mips .\" o32 to take 7 arguments to syscall() .pp .\" see arch/parisc/kernel/sys_parisc.c. note that while the parisc c abi also uses aligned register pairs, it uses a shim layer to hide the issue from user space. .pp the affected system calls are .br fadvise64_64 (2), .br ftruncate64 (2), .br posix_fadvise (2), .br pread64 (2), .br pwrite64 (2), .br readahead (2), .br sync_file_range (2), and .br truncate64 (2). .pp .\" you need to look up the syscalls directly in the kernel source to see if .\" they should be in this list. for example, look at fs/read_write.c and .\" the function signatures that do: .\" ..., unsigned long, pos_l, unsigned long, pos_h, ... .\" if they use off_t, then they most likely do not belong in this list. this does not affect syscalls that manually split and assemble 64-bit values such as .br _llseek (2), .br preadv (2), .br preadv2 (2), .br pwritev (2), and .br pwritev2 (2). welcome to the wonderful world of historical baggage. .ss architecture calling conventions every architecture has its own way of invoking and passing arguments to the kernel. the details for various architectures are listed in the two tables below. .pp the first table lists the instruction used to transition to kernel mode (which might not be the fastest or best way to transition to the kernel, so you might have to refer to .br vdso (7)), the register used to indicate the system call number, the register(s) used to return the system call result, and the register used to signal an error. .if t \{\ .ft cw \} .ts l2 l2 l2 l2 l1 l2 l. arch/abi instruction system ret ret error notes call # val val2 _ alpha callsys v0 v0 a4 a3 1, 6 arc trap0 r8 r0 - - arm/oabi swi nr - r0 - - 2 arm/eabi swi 0x0 r7 r0 r1 - arm64 svc #0 w8 x0 x1 - blackfin excpt 0x0 p0 r0 - - i386 int $0x80 eax eax edx - ia64 break 0x100000 r15 r8 r9 r10 1, 6 m68k trap #0 d0 d0 - - microblaze brki r14,8 r12 r3 - - mips syscall v0 v0 v1 a3 1, 6 nios2 trap r2 r2 - r7 parisc ble 0x100(%sr2, %r0) r20 r28 - - powerpc sc r0 r3 - r0 1 powerpc64 sc r0 r3 - cr0.so 1 riscv ecall a7 a0 a1 - s390 svc 0 r1 r2 r3 - 3 s390x svc 0 r1 r2 r3 - 3 superh trapa #31 r3 r0 r1 - 4, 6 sparc/32 t 0x10 g1 o0 o1 psr/csr 1, 6 sparc/64 t 0x6d g1 o0 o1 psr/csr 1, 6 tile swint1 r10 r00 - r01 1 x86-64 syscall rax rax rdx - 5 x32 syscall rax rax rdx - 5 xtensa syscall a2 a2 - - .te .pp notes: .ip [1] 4 on a few architectures, a register is used as a boolean (0 indicating no error, and \-1 indicating an error) to signal that the system call failed. the actual error value is still contained in the return register. on sparc, the carry bit .ri ( csr ) in the processor status register .ri ( psr ) is used instead of a full register. on powerpc64, the summary overflow bit .ri ( so ) in field 0 of the condition register .ri ( cr0 ) is used. .ip [2] .i nr is the system call number. .ip [3] for s390 and s390x, .i nr (the system call number) may be passed directly with .i "svc\ nr" if it is less than 256. .ip [4] on superh additional trap numbers are supported for historic reasons, but .br trapa #31 is the recommended "unified" abi. .ip [5] the x32 abi shares syscall table with x86-64 abi, but there are some nuances: .rs .ip \(bu 3 in order to indicate that a system call is called under the x32 abi, an additional bit, .br __x32_syscall_bit , is bitwise-ored with the system call number. the abi used by a process affects some process behaviors, including signal handling or system call restarting. .ip \(bu since x32 has different sizes for .i long and pointer types, layouts of some (but not all; .i struct timeval or .i struct rlimit are 64-bit, for example) structures are different. in order to handle this, additional system calls are added to the system call table, starting from number 512 (without the .br __x32_syscall_bit ). for example, .b __nr_readv is defined as 19 for the x86-64 abi and as .ir __x32_syscall_bit " | " \fb515\fp for the x32 abi. most of these additional system calls are actually identical to the system calls used for providing i386 compat. there are some notable exceptions, however, such as .br preadv2 (2), which uses .i struct iovec entities with 4-byte pointers and sizes ("compat_iovec" in kernel terms), but passes an 8-byte .i pos argument in a single register and not two, as is done in every other abi. .re .ip [6] some architectures (namely, alpha, ia-64, mips, superh, sparc/32, and sparc/64) use an additional register ("retval2" in the above table) to pass back a second return value from the .br pipe (2) system call; alpha uses this technique in the architecture-specific .br getxpid (2), .br getxuid (2), and .br getxgid (2) system calls as well. other architectures do not use the second return value register in the system call interface, even if it is defined in the system v abi. .if t \{\ .in .ft p \} .pp the second table shows the registers used to pass the system call arguments. .if t \{\ .ft cw \} .ts l l2 l2 l2 l2 l2 l2 l2 l. arch/abi arg1 arg2 arg3 arg4 arg5 arg6 arg7 notes _ alpha a0 a1 a2 a3 a4 a5 - arc r0 r1 r2 r3 r4 r5 - arm/oabi r0 r1 r2 r3 r4 r5 r6 arm/eabi r0 r1 r2 r3 r4 r5 r6 arm64 x0 x1 x2 x3 x4 x5 - blackfin r0 r1 r2 r3 r4 r5 - i386 ebx ecx edx esi edi ebp - ia64 out0 out1 out2 out3 out4 out5 - m68k d1 d2 d3 d4 d5 a0 - microblaze r5 r6 r7 r8 r9 r10 - mips/o32 a0 a1 a2 a3 - - - 1 mips/n32,64 a0 a1 a2 a3 a4 a5 - nios2 r4 r5 r6 r7 r8 r9 - parisc r26 r25 r24 r23 r22 r21 - powerpc r3 r4 r5 r6 r7 r8 r9 powerpc64 r3 r4 r5 r6 r7 r8 - riscv a0 a1 a2 a3 a4 a5 - s390 r2 r3 r4 r5 r6 r7 - s390x r2 r3 r4 r5 r6 r7 - superh r4 r5 r6 r7 r0 r1 r2 sparc/32 o0 o1 o2 o3 o4 o5 - sparc/64 o0 o1 o2 o3 o4 o5 - tile r00 r01 r02 r03 r04 r05 - x86-64 rdi rsi rdx r10 r8 r9 - x32 rdi rsi rdx r10 r8 r9 - xtensa a6 a3 a4 a5 a8 a9 - .te .pp notes: .ip [1] 4 the mips/o32 system call convention passes arguments 5 through 8 on the user stack. .if t \{\ .in .ft p \} .pp note that these tables don't cover the entire calling convention\(emsome architectures may indiscriminately clobber other registers not listed here. .sh examples .ex #define _gnu_source #include #include #include #include int main(int argc, char *argv[]) { pid_t tid; tid = syscall(sys_gettid); syscall(sys_tgkill, getpid(), tid, sighup); } .ee .sh see also .br _syscall (2), .br intro (2), .br syscalls (2), .br errno (3), .br vdso (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man8/ld.so.8 .so man3/ttyname.3 .\" copyright (c) 2016, ibm corporation. .\" written by wainer dos santos moschetta .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" glibc 2.25 source code and manual. .\" c99 standard document. .\" iso/iec ts 18661-1 technical specification. .\" snprintf and other man.3 pages. .\" .th strfromd 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strfromd, strfromf, strfroml \- convert a floating-point value into a string .sh synopsis .nf .b #include .pp .bi "int strfromd(char *restrict " str ", size_t " n , .bi " const char *restrict " format ", double " fp ");" .bi "int strfromf(char *restrict " str ", size_t " n , .bi " const char *restrict " format ", float "fp ");" .bi "int strfroml(char *restrict " str ", size_t " n , .bi " const char *restrict " format ", long double " fp ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strfromd (), .br strfromf (), .br strfroml (): .nf __stdc_want_iec_60559_bfp_ext__ .fi .sh description these functions convert a floating-point value, .ir fp , into a string of characters, .ir str , with a configurable .ir format string. at most .i n characters are stored into .ir str . .pp the terminating null byte ('\e0') is written if and only if .i n is sufficiently large, otherwise the written string is truncated at .i n characters. .pp the .br strfromd (), .br strfromf (), and .br strfroml () functions are equivalent to .pp .in +4n .ex snprintf(str, n, format, fp); .ee .in .pp except for the .i format string. .ss format of the format string the .i format string must start with the character \(aq%\(aq. this is followed by an optional precision which starts with the period character (.), followed by an optional decimal integer. if no integer is specified after the period character, a precision of zero is used. finally, the format string should have one of the conversion specifiers .br a , .br a , .br e , .br e , .br f , .br f , .br g , or .br g . .pp the conversion specifier is applied based on the floating-point type indicated by the function suffix. therefore, unlike .br snprintf (), the format string does not have a length modifier character. see .br snprintf (3) for a detailed description of these conversion specifiers. .pp the implementation conforms to the c99 standard on conversion of nan and infinity values: .pp .rs if .i fp is a nan, +nan, or \-nan, and .br f (or .br a , .br e , .br g ) is the conversion specifier, the conversion is to "nan", "nan", or "\-nan", respectively. if .b f (or .br a , .br e , .br g ) is the conversion specifier, the conversion is to "nan" or "\-nan". .pp likewise if .i fp is infinity, it is converted to [\-]inf or [\-]inf. .re .pp a malformed .i format string results in undefined behavior. .sh return value the .br strfromd (), .br strfromf (), and .br strfroml () functions return the number of characters that would have been written in .i str if .i n had enough space, not counting the terminating null byte. thus, a return value of .i n or greater means that the output was truncated. .sh versions the .br strfromd (), .br strfromf (), and .br strfroml () functions are available in glibc since version 2.25. .sh attributes for an explanation of the terms used in this section, see .br attributes (7) and the .b posix safety concepts section in gnu c library manual. .pp .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strfromd (), .br strfromf (), .br strfroml () t} thread safety mt-safe locale \^ async-signal safety as-unsafe heap \^ async-cancel safety ac-unsafe mem .te .hy .ad .sp 1 note: these attributes are preliminary. .sh conforming to c99, iso/iec ts 18661-1. .sh notes the .br strfromd (), .br strfromf (), and .br strfroml () functions take account of the .b lc_numeric category of the current locale. .sh examples to convert the value 12.1 as a float type to a string using decimal notation, resulting in "12.100000": .pp .in +4n .ex #define __stdc_want_iec_60559_bfp_ext__ #include int ssize = 10; char s[ssize]; strfromf(s, ssize, "%f", 12.1); .ee .in .pp to convert the value 12.3456 as a float type to a string using decimal notation with two digits of precision, resulting in "12.35": .pp .in +4n .ex #define __stdc_want_iec_60559_bfp_ext__ #include int ssize = 10; char s[ssize]; strfromf(s, ssize, "%.2f", 12.3456); .ee .in .pp to convert the value 12.345e19 as a double type to a string using scientific notation with zero digits of precision, resulting in "1e+20": .pp .in +4n .ex #define __stdc_want_iec_60559_bfp_ext__ #include int ssize = 10; char s[ssize]; strfromd(s, ssize, "%.e", 12.345e19); .ee .in .sh see also .br atof (3), .br snprintf (3), .br strtod (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/shmop.2 .so man3/isalpha.3 .\" copyright 2009 lefteris dimitroulakis .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2009-01-15, mtk, some edits .\" .th koi8-u 7 2020-08-13 "linux" "linux programmer's manual" .sh name koi8-u \- ukrainian character set encoded in octal, decimal, and hexadecimal .sh description rfc\ 2310 defines an 8-bit character set, koi8-u. koi8-u encodes the characters used in ukrainian and byelorussian. .ss koi8-u characters the following table displays the characters in koi8-u that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 200 128 80 ─ box drawings light horizontal 201 129 81 │ box drawings light vertical 202 130 82 ┌ box drawings light down and right 203 131 83 ┐ box drawings light down and left 204 132 84 └ box drawings light up and right 205 133 85 ┘ box drawings light up and left 206 134 86 ├ box drawings light vertical and right 207 135 87 ┤ box drawings light vertical and left 210 136 88 ┬ box drawings light down and horizontal 211 137 89 ┴ box drawings light up and horizontal 212 138 8a ┼ box drawings light vertical and horizontal 213 139 8b ▀ upper half block 214 140 8c ▄ lower half block 215 141 8d █ full block 216 142 8e ▌ left half block 217 143 8f ▐ right half block 220 144 90 ░ light shade 221 145 91 ▒ medium shade 222 146 92 ▓ dark shade 223 147 93 ⌠ top half integral 224 148 94 ■ black square 225 149 95 ∙ bullet operator 226 150 96 √ square root 227 151 97 ≈ almost equal to 230 152 98 ≤ less-than or equal to 231 153 99 ≥ greater-than or equal to 232 154 9a   no-break space 233 155 9b ⌡ bottom half integral 234 156 9c ° degree sign 235 157 9d ² superscript two 236 158 9e · middle dot 237 159 9f ÷ division sign 240 160 a0 ═ box drawings double horizontal 241 161 a1 ║ box drawings double vertical 242 162 a2 ╒ box drawings down single and right double 243 163 a3 ё cyrillic small letter io 244 164 a4 є cyrillic small letter ukrainian ie 245 165 a5 ╔ box drawings double down and right 246 166 a6 і t{ cyrillic small letter .br byelorussian-ukrainian i t} 247 167 a7 ї cyrillic small letter yi (ukrainian) 250 168 a8 ╗ box drawings double down and left 251 169 a9 ╘ box drawings up single and right double 252 170 aa ╙ box drawings up double and right single 253 171 ab ╚ box drawings double up and right 254 172 ac ╛ box drawings up single and left double 255 173 ad ґ cyrillic small letter ghe with upturn 256 174 ae ╝ box drawings double up and left 257 175 af ╞ box drawings vertical single and right double 260 176 b0 ╟ box drawings vertical double and right single 261 177 b1 ╠ box drawings double vertical and right 262 178 b2 ╡ box drawings vertical single and left double 263 179 b3 ё cyrillic capital letter io 264 180 b4 є cyrillic capital letter ukrainian ie 265 181 b5 ╣ box drawings double vertical and left 266 182 b6 і t{ cyrillic capital letter .br byelorussian-ukrainian i t} 267 183 b7 ї cyrillic capital letter yi (ukrainian) 270 184 b8 ╦ box drawings double down and horizontal 271 185 b9 ╧ box drawings up single and horizontal double 272 186 ba ╨ box drawings up double and horizontal single 273 187 bb ╩ box drawings double up and horizontal 274 188 bc ╪ t{ box drawings vertical single .br and horizontal double t} 275 189 bd ґ cyrillic capital letter ghe with upturn 276 190 be ╬ box drawings double vertical and horizontal 277 191 bf © copyright sign 300 192 c0 ю cyrillic small letter yu 301 193 c1 а cyrillic small letter a 302 194 c2 б cyrillic small letter be 303 195 c3 ц cyrillic small letter tse 304 196 c4 д cyrillic small letter de 305 197 c5 е cyrillic small letter ie 306 198 c6 ф cyrillic small letter ef 307 199 c7 г cyrillic small letter ghe 310 200 c8 х cyrillic small letter ha 311 201 c9 и cyrillic small letter i 312 202 ca й cyrillic small letter short i 313 203 cb к cyrillic small letter ka 314 204 cc л cyrillic small letter el 315 205 cd м cyrillic small letter em 316 206 ce н cyrillic small letter en 317 207 cf о cyrillic small letter o 320 208 d0 п cyrillic small letter pe 321 209 d1 я cyrillic small letter ya 322 210 d2 р cyrillic small letter er 323 211 d3 с cyrillic small letter es 324 212 d4 т cyrillic small letter te 325 213 d5 у cyrillic small letter u 326 214 d6 ж cyrillic small letter zhe 327 215 d7 в cyrillic small letter ve 330 216 d8 ь cyrillic small letter soft sign 331 217 d9 ы cyrillic small letter yeru 332 218 da з cyrillic small letter ze 333 219 db ш cyrillic small letter sha 334 220 dc э cyrillic small letter e 335 221 dd щ cyrillic small letter shcha 336 222 de ч cyrillic small letter che 337 223 df ъ cyrillic small letter hard sign 340 224 e0 ю cyrillic capital letter yu 341 225 e1 а cyrillic capital letter a 342 226 e2 б cyrillic capital letter be 343 227 e3 ц cyrillic capital letter tse 344 228 e4 д cyrillic capital letter de 345 229 e5 е cyrillic capital letter ie 346 230 e6 ф cyrillic capital letter ef 347 231 e7 г cyrillic capital letter ghe 350 232 e8 х cyrillic capital letter ha 351 233 e9 и cyrillic capital letter i 352 234 ea й cyrillic capital letter short i 353 235 eb к cyrillic capital letter ka 354 236 ec л cyrillic capital letter el 355 237 ed м cyrillic capital letter em 356 238 ee н cyrillic capital letter en 357 239 ef о cyrillic capital letter o 360 240 f0 п cyrillic capital letter pe 361 241 f1 я cyrillic capital letter ya 362 242 f2 р cyrillic capital letter er 363 243 f3 с cyrillic capital letter es 364 244 f4 т cyrillic capital letter te 365 245 f5 у cyrillic capital letter u 366 246 f6 ж cyrillic capital letter zhe 367 247 f7 в cyrillic capital letter ve 370 248 f8 ь cyrillic capital letter soft sign 371 249 f9 ы cyrillic capital letter yeru 372 250 fa з cyrillic capital letter ze 373 251 fb ш cyrillic capital letter sha 374 252 fc э cyrillic capital letter e 375 253 fd щ cyrillic capital letter shcha 376 254 fe ч cyrillic capital letter che 377 255 ff ъ cyrillic capital letter hard sign .te .sh notes the differences from koi8-r are in the hex positions a4, a6, a7, ad, b4, b6, b7, and bd. .sh see also .br ascii (7), .br charsets (7), .br cp1251 (7), .br iso_8859\-5 (7), .br koi8\-r (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:45:17 1993 by rik faith (faith@cs.unc.edu) .th psignal 3 2021-03-22 "gnu" "linux programmer's manual" .sh name psignal, psiginfo \- print signal description .sh synopsis .nf .b #include .pp .bi "void psignal(int " sig ", const char *" s ); .bi "void psiginfo(const siginfo_t *" pinfo ", const char *" s ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br psignal (): since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .pp .br psiginfo (): .nf _posix_c_source >= 200809l .fi .sh description the .br psignal () function displays a message on \fistderr\fp consisting of the string \fis\fp, a colon, a space, a string describing the signal number \fisig\fp, and a trailing newline. if the string \fis\fp is null or empty, the colon and space are omitted. if \fisig\fp is invalid, the message displayed will indicate an unknown signal. .pp the .br psiginfo () function is like .br psignal (), except that it displays information about the signal described by .ir pinfo , which should point to a valid .i siginfo_t structure. as well as the signal description, .br psiginfo () displays information about the origin of the signal, and other information relevant to the signal (e.g., the relevant memory address for hardware-generated signals, the child process id for .br sigchld , and the user id and process id of the sender, for signals set using .br kill (2) or .br sigqueue (3)). .sh return value the .br psignal () and .br psiginfo () functions return no value. .sh versions the .br psiginfo () function was added to glibc in version 2.10. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br psignal (), .br psiginfo () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2008, 4.3bsd. .sh bugs in glibc versions up to 2.12, .br psiginfo () had the following bugs: .ip * 3 in some circumstances, a trailing newline is not printed. .\" fixme . http://sourceware.org/bugzilla/show_bug.cgi?id=12107 .\" reportedly now fixed; check glibc 2.13 .ip * additional details are not displayed for real-time signals. .\" fixme . http://sourceware.org/bugzilla/show_bug.cgi?id=12108 .\" reportedly now fixed; check glibc 2.13 .sh see also .br sigaction (2), .br perror (3), .br strsignal (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .so man3/cproj.3 .so man3/list.3 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" copyright 1997 andries e. brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th vm86 2 2021-03-22 "linux" "linux programmer's manual" .sh name vm86old, vm86 \- enter virtual 8086 mode .sh synopsis .nf .b #include .pp .bi "int vm86old(struct vm86_struct *" info ); .bi "int vm86(unsigned long " fn ", struct vm86plus_struct *" v86 ); .fi .sh description the system call .br vm86 () was introduced in linux 0.97p2. in linux 2.1.15 and 2.0.28, it was renamed to .br vm86old (), and a new .br vm86 () was introduced. the definition of .ir "struct vm86_struct" was changed in 1.1.8 and 1.1.9. .pp these calls cause the process to enter vm86 mode (virtual-8086 in intel literature), and are used by .br dosemu . .pp vm86 mode is an emulation of real mode within a protected mode task. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault this return value is specific to i386 and indicates a problem with getting user-space data. .tp .b enosys this return value indicates the call is not implemented on the present architecture. .tp .b eperm saved kernel stack exists. (this is a kernel sanity check; the saved stack should exist only within vm86 mode itself.) .sh conforming to this call is specific to linux on 32-bit intel processors, and should not be used in programs intended to be portable. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/malloc_hook.3 .so man3/xdr.3 .so man7/system_data_types.7 .so man2/setpgid.2 .so man3/isgreater.3 .so man3/nextup.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_setschedprio 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_setschedprio \- set scheduling priority of a thread .sh synopsis .nf .b #include .pp .bi "int pthread_setschedprio(pthread_t " thread ", int " prio ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_setschedprio () function sets the scheduling priority of the thread .i thread to the value specified in .ir prio . (by contrast .br pthread_setschedparam (3) changes both the scheduling policy and priority of a thread.) .\" fixme . nptl/pthread_setschedprio.c has the following .\" /* if the thread should have higher priority because of some .\" pthread_prio_protect mutexes it holds, adjust the priority. */ .\" eventually (perhaps after writing the mutexattr pages), we .\" may want to add something on the topic to this page. .\" nptl/pthread_setschedparam.c has a similar case. .sh return value on success, this function returns 0; on error, it returns a nonzero error number. if .br pthread_setschedprio () fails, the scheduling priority of .i thread is not changed. .sh errors .tp .b einval .i prio is not valid for the scheduling policy of the specified thread. .tp .b eperm the caller does not have appropriate privileges to set the specified priority. .tp .b esrch no thread with the id .i thread could be found. .pp posix.1 also documents an .b enotsup ("attempt was made to set the priority to an unsupported value") error for .br pthread_setschedparam (3). .sh versions this function is available in glibc since version 2.3.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_setschedprio () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes for a description of the permissions required to, and the effect of, changing a thread's scheduling priority, and details of the permitted ranges for priorities in each scheduling policy, see .br sched (7). .sh see also .ad l .nh .br getrlimit (2), .br sched_get_priority_min (2), .br pthread_attr_init (3), .br pthread_attr_setinheritsched (3), .br pthread_attr_setschedparam (3), .br pthread_attr_setschedpolicy (3), .br pthread_create (3), .br pthread_self (3), .br pthread_setschedparam (3), .br pthreads (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sysctl.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wprintf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf \- formatted wide-character output conversion .sh synopsis .nf .b #include .b #include .pp .bi "int wprintf(const wchar_t *restrict " format ", ...);" .bi "int fwprintf(file *restrict " stream , .bi " const wchar_t *restrict " format ", ...);" .bi "int swprintf(wchar_t *restrict " wcs ", size_t " maxlen , .bi " const wchar_t *restrict " format ", ...);" .pp .bi "int vwprintf(const wchar_t *restrict " format ", va_list " args ); .bi "int vfwprintf(file *restrict " stream , .bi " const wchar_t *restrict " format ", va_list " args ); .bi "int vswprintf(wchar_t *restrict " wcs ", size_t " maxlen , .bi " const wchar_t *restrict " format ", va_list " args ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .\" .br wprintf (), .\" .br fwprintf (), .\" .br swprintf (), .\" .br vwprintf (), .\" .br vfwprintf (), .\" .br vswprintf (): .nf _xopen_source >= 500 || _isoc99_source || _posix_c_source >= 200112l .fi .sh description the .br wprintf () family of functions is the wide-character equivalent of the .br printf (3) family of functions. it performs formatted output of wide characters. .pp the .br wprintf () and .br vwprintf () functions perform wide-character output to .ir stdout . .i stdout must not be byte oriented; see .br fwide (3) for more information. .pp the .br fwprintf () and .br vfwprintf () functions perform wide-character output to .ir stream . .i stream must not be byte oriented; see .br fwide (3) for more information. .pp the .br swprintf () and .br vswprintf () functions perform wide-character output to an array of wide characters. the programmer must ensure that there is room for at least .i maxlen wide characters at .ir wcs . .pp these functions are like the .br printf (3), .br vprintf (3), .br fprintf (3), .br vfprintf (3), .br sprintf (3), .br vsprintf (3) functions except for the following differences: .tp .b \(bu the .i format string is a wide-character string. .tp .b \(bu the output consists of wide characters, not bytes. .tp .b \(bu .br swprintf () and .br vswprintf () take a .i maxlen argument, .br sprintf (3) and .br vsprintf (3) do not. .rb ( snprintf (3) and .br vsnprintf (3) take a .i maxlen argument, but these functions do not return \-1 upon buffer overflow on linux.) .pp the treatment of the conversion characters .br c and .b s is different: .tp .b c if no .b l modifier is present, the .i int argument is converted to a wide character by a call to the .br btowc (3) function, and the resulting wide character is written. if an .b l modifier is present, the .i wint_t (wide character) argument is written. .tp .b s if no .b l modifier is present: the .i "const\ char\ *" argument is expected to be a pointer to an array of character type (pointer to a string) containing a multibyte character sequence beginning in the initial shift state. characters from the array are converted to wide characters (each by a call to the .br mbrtowc (3) function with a conversion state starting in the initial state before the first byte). the resulting wide characters are written up to (but not including) the terminating null wide character (l\(aq\e0\(aq). if a precision is specified, no more wide characters than the number specified are written. note that the precision determines the number of .i wide characters written, not the number of .i bytes or .ir "screen positions" . the array must contain a terminating null byte (\(aq\e0\(aq), unless a precision is given and it is so small that the number of converted wide characters reaches it before the end of the array is reached. if an .b l modifier is present: the .i "const\ wchar_t\ *" argument is expected to be a pointer to an array of wide characters. wide characters from the array are written up to (but not including) a terminating null wide character. if a precision is specified, no more than the number specified are written. the array must contain a terminating null wide character, unless a precision is given and it is smaller than or equal to the number of wide characters in the array. .sh return value the functions return the number of wide characters written, excluding the terminating null wide character in case of the functions .br swprintf () and .br vswprintf (). they return \-1 when an error occurs. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wprintf (), .br fwprintf (), .br swprintf (), .br vwprintf (), .br vfwprintf (), .br vswprintf () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wprintf () et al. depends on the .b lc_ctype category of the current locale. .pp if the .i format string contains non-ascii wide characters, the program will work correctly only if the .b lc_ctype category of the current locale at run time is the same as the .b lc_ctype category of the current locale at compile time. this is because the .i wchar_t representation is platform- and locale-dependent. (the glibc represents wide characters using their unicode (iso-10646) code point, but other platforms don't do this. also, the use of c99 universal character names of the form \eunnnn does not solve this problem.) therefore, in internationalized programs, the .i format string should consist of ascii wide characters only, or should be constructed at run time in an internationalized way (e.g., using .br gettext (3) or .br iconv (3), followed by .br mbstowcs (3)). .sh see also .br fprintf (3), .br fputwc (3), .br fwide (3), .br printf (3), .br snprintf (3) .\" .br wscanf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" adapted glibc info page .\" .\" this should run as 'guru meditation' (amiga joke :) .\" the function is quite complex and deserves an example .\" .\" polished, aeb, 2003-11-01 .th fmtmsg 3 2021-03-22 "" "linux programmer's manual" .sh name fmtmsg \- print formatted error messages .sh synopsis .nf .b #include .pp .bi "int fmtmsg(long " classification ", const char *" label , .bi " int " severity ", const char *" text , .bi " const char *" action ", const char *" tag ); .fi .sh description this function displays a message described by its arguments on the device(s) specified in the .i classification argument. for messages written to .ir stderr , the format depends on the .b msgverb environment variable. .pp the .i label argument identifies the source of the message. the string must consist of two colon separated parts where the first part has not more than 10 and the second part not more than 14 characters. .pp the .i text argument describes the condition of the error. .pp the .i action argument describes possible steps to recover from the error. if it is printed, it is prefixed by "to fix: ". .pp the .i tag argument is a reference to the online documentation where more information can be found. it should contain the .i label value and a unique identification number. .ss dummy arguments each of the arguments can have a dummy value. the dummy classification value .b mm_nullmc (0l) does not specify any output, so nothing is printed. the dummy severity value .b no_sev (0) says that no severity is supplied. the values .br mm_nulllbl , .br mm_nulltxt , .br mm_nullact , .b mm_nulltag are synonyms for .ir "((char\ *)\ 0)" , the empty string, and .b mm_nullsev is a synonym for .br no_sev . .ss the classification argument the .i classification argument is the sum of values describing 4 types of information. .pp the first value defines the output channel. .tp 12n .b mm_print output to .ir stderr . .tp .b mm_console output to the system console. .tp .b "mm_print | mm_console" output to both. .pp the second value is the source of the error: .tp 12n .b mm_hard a hardware error occurred. .tp .b mm_firm a firmware error occurred. .tp .b mm_soft a software error occurred. .pp the third value encodes the detector of the problem: .tp 12n .b mm_appl it is detected by an application. .tp .b mm_util it is detected by a utility. .tp .b mm_opsys it is detected by the operating system. .pp the fourth value shows the severity of the incident: .tp 12n .b mm_recover it is a recoverable error. .tp .b mm_nrecov it is a nonrecoverable error. .ss the severity argument the .i severity argument can take one of the following values: .tp 12n .b mm_nosev no severity is printed. .tp .b mm_halt this value is printed as halt. .tp .b mm_error this value is printed as error. .tp .b mm_warning this value is printed as warning. .tp .b mm_info this value is printed as info. .pp the numeric values are between 0 and 4. using .br addseverity (3) or the environment variable .b sev_level you can add more levels and strings to print. .sh return value the function can return 4 values: .tp 12n .b mm_ok everything went smooth. .tp .b mm_notok complete failure. .tp .b mm_nomsg error writing to .ir stderr . .tp .b mm_nocon error writing to the console. .sh environment the environment variable .b msgverb ("message verbosity") can be used to suppress parts of the output to .ir stderr . (it does not influence output to the console.) when this variable is defined, is non-null, and is a colon-separated list of valid keywords, then only the parts of the message corresponding to these keywords is printed. valid keywords are "label", "severity", "text", "action", and "tag". .pp the environment variable .b sev_level can be used to introduce new severity levels. by default, only the five severity levels described above are available. any other numeric value would make .br fmtmsg () print nothing. if the user puts .b sev_level with a format like .pp .rs sev_level=[description[:description[:...]]] .re .pp in the environment of the process before the first call to .br fmtmsg (), where each description is of the form .pp .rs severity-keyword,level,printstring .re .pp then .br fmtmsg () will also accept the indicated values for the level (in addition to the standard levels 0\(en4), and use the indicated printstring when such a level occurs. .pp the severity-keyword part is not used by .br fmtmsg () but it has to be present. the level part is a string representation of a number. the numeric value must be a number greater than 4. this value must be used in the severity argument of .br fmtmsg () to select this class. it is not possible to overwrite any of the predefined classes. the printstring is the string printed when a message of this class is processed by .br fmtmsg (). .sh versions .br fmtmsg () is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br fmtmsg () t} thread safety t{ glibc\ >=\ 2.16: mt-safe; glibc\ <\ 2.16: mt-unsafe t} .te .hy .ad .sp 1 .pp before glibc 2.16, the .br fmtmsg () function uses a static variable that is not protected, so it is not thread-safe. .pp since glibc 2.16, .\" modified in commit 7724defcf8873116fe4efab256596861eef21a94 the .br fmtmsg () function uses a lock to protect the static variable, so it is thread-safe. .sh conforming to the functions .br fmtmsg () and .br addseverity (3), and environment variables .b msgverb and .b sev_level come from system v. .pp the function .br fmtmsg () and the environment variable .b msgverb are described in posix.1-2001 and posix.1-2008. .sh notes system v and unixware man pages tell us that these functions have been replaced by "pfmt() and addsev()" or by "pfmt(), vpfmt(), lfmt(), and vlfmt()", and will be removed later. .sh examples .ex #include #include #include int main(void) { long class = mm_print | mm_soft | mm_opsys | mm_recover; int err; err = fmtmsg(class, "util\-linux:mount", mm_error, "unknown mount option", "see mount(8).", "util\-linux:mount:017"); switch (err) { case mm_ok: break; case mm_notok: printf("nothing printed\en"); break; case mm_nomsg: printf("nothing printed to stderr\en"); break; case mm_nocon: printf("no console output\en"); break; default: printf("unknown error from fmtmsg()\en"); } exit(exit_success); } .ee .pp the output should be: .pp .in +4n .ex util\-linux:mount: error: unknown mount option to fix: see mount(8). util\-linux:mount:017 .ee .in .pp and after .pp .in +4n .ex msgverb=text:action; export msgverb .ee .in .pp the output becomes: .pp .in +4n .ex unknown mount option to fix: see mount(8). .ee .in .sh see also .br addseverity (3), .br perror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strdup.3 .so man3/getspnam.3 .so man3/getgrent.3 .so man3/scalb.3 .\" copyright (c) 2005, 2013 michael kerrisk .\" a few fragments from an earlier (1996) version by .\" andries brouwer (aeb@cwi.nl) remain. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" rewritten old page, 960210, aeb@cwi.nl .\" updated, added strtok_r. 2000-02-13 nicolás lichtmaier .\" 2005-11-17, mtk: substantial parts rewritten .\" 2013-05-19, mtk: added much further detail on the operation of strtok() .\" .th strtok 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strtok, strtok_r \- extract tokens from strings .sh synopsis .nf .b #include .pp .bi "char *strtok(char *restrict " str ", const char *restrict " delim ); .bi "char *strtok_r(char *restrict " str ", const char *restrict " delim , .bi " char **restrict " saveptr ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strtok_r (): .nf _posix_c_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br strtok () function breaks a string into a sequence of zero or more nonempty tokens. on the first call to .br strtok (), the string to be parsed should be specified in .ir str . in each subsequent call that should parse the same string, .i str must be null. .pp the .i delim argument specifies a set of bytes that delimit the tokens in the parsed string. the caller may specify different strings in .i delim in successive calls that parse the same string. .pp each call to .br strtok () returns a pointer to a null-terminated string containing the next token. this string does not include the delimiting byte. if no more tokens are found, .br strtok () returns null. .pp a sequence of calls to .br strtok () that operate on the same string maintains a pointer that determines the point from which to start searching for the next token. the first call to .br strtok () sets this pointer to point to the first byte of the string. the start of the next token is determined by scanning forward for the next nondelimiter byte in .ir str . if such a byte is found, it is taken as the start of the next token. if no such byte is found, then there are no more tokens, and .br strtok () returns null. (a string that is empty or that contains only delimiters will thus cause .br strtok () to return null on the first call.) .pp the end of each token is found by scanning forward until either the next delimiter byte is found or until the terminating null byte (\(aq\e0\(aq) is encountered. if a delimiter byte is found, it is overwritten with a null byte to terminate the current token, and .br strtok () saves a pointer to the following byte; that pointer will be used as the starting point when searching for the next token. in this case, .br strtok () returns a pointer to the start of the found token. .pp from the above description, it follows that a sequence of two or more contiguous delimiter bytes in the parsed string is considered to be a single delimiter, and that delimiter bytes at the start or end of the string are ignored. put another way: the tokens returned by .br strtok () are always nonempty strings. thus, for example, given the string "\fiaaa;;bbb,\fp", successive calls to .br strtok () that specify the delimiter string "\fi;,\fp" would return the strings "\fiaaa\fp" and "\fibbb\fp", and then a null pointer. .pp the .br strtok_r () function is a reentrant version of .br strtok (). the .i saveptr argument is a pointer to a .ir "char\ *" variable that is used internally by .br strtok_r () in order to maintain context between successive calls that parse the same string. .pp on the first call to .br strtok_r (), .i str should point to the string to be parsed, and the value of .i *saveptr is ignored (but see notes). in subsequent calls, .i str should be null, and .i saveptr (and the buffer that it points to) should be unchanged since the previous call. .pp different strings may be parsed concurrently using sequences of calls to .br strtok_r () that specify different .i saveptr arguments. .sh return value the .br strtok () and .br strtok_r () functions return a pointer to the next token, or null if there are no more tokens. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strtok () t} thread safety mt-unsafe race:strtok t{ .br strtok_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .tp .br strtok () posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .tp .br strtok_r () posix.1-2001, posix.1-2008. .sh notes on some implementations, .\" tru64, according to its manual page .i *saveptr is required to be null on the first call to .br strtok_r () that is being used to parse .ir str . .sh bugs be cautious when using these functions. if you do use them, note that: .ip * 2 these functions modify their first argument. .ip * these functions cannot be used on constant strings. .ip * the identity of the delimiting byte is lost. .ip * the .br strtok () function uses a static buffer while parsing, so it's not thread safe. use .br strtok_r () if this matters to you. .sh examples the program below uses nested loops that employ .br strtok_r () to break a string into a two-level hierarchy of tokens. the first command-line argument specifies the string to be parsed. the second argument specifies the delimiter byte(s) to be used to separate that string into "major" tokens. the third argument specifies the delimiter byte(s) to be used to separate the "major" tokens into subtokens. .pp an example of the output produced by this program is the following: .pp .in +4n .ex .rb "$" " ./a.out \(aqa/bbb///cc;xxx:yyy:\(aq \(aq:;\(aq \(aq/\(aq" 1: a/bbb///cc \-\-> a \-\-> bbb \-\-> cc 2: xxx \-\-> xxx 3: yyy \-\-> yyy .ee .in .ss program source \& .ex #include #include #include int main(int argc, char *argv[]) { char *str1, *str2, *token, *subtoken; char *saveptr1, *saveptr2; if (argc != 4) { fprintf(stderr, "usage: %s string delim subdelim\en", argv[0]); exit(exit_failure); } for (int j = 1, str1 = argv[1]; ; j++, str1 = null) { token = strtok_r(str1, argv[2], &saveptr1); if (token == null) break; printf("%d: %s\en", j, token); for (str2 = token; ; str2 = null) { subtoken = strtok_r(str2, argv[3], &saveptr2); if (subtoken == null) break; printf("\t \-\-> %s\en", subtoken); } } exit(exit_success); } .ee .pp another example program using .br strtok () can be found in .br getaddrinfo_a (3). .sh see also .br index (3), .br memchr (3), .br rindex (3), .br strchr (3), .br string (3), .br strpbrk (3), .br strsep (3), .br strspn (3), .br strstr (3), .br wcstok (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/clog10.3 .so man3/resolver.3 .so man3/mallinfo.3 .\" copyright 2003,2004 andi kleen, suse labs. .\" and copyright 2007 lee schermerhorn, hewlett packard .\" .\" %%%license_start(verbatim_prof) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2006-02-03, mtk, substantial wording changes and other improvements .\" 2007-08-27, lee schermerhorn .\" more precise specification of behavior. .\" .\" fixme .\" linux 3.8 added mpol_mf_lazy, which needs to be documented. .\" does it also apply for move_pages()? .\" .\" commit b24f53a0bea38b266d219ee651b22dba727c44ae .\" author: lee schermerhorn .\" date: thu oct 25 14:16:32 2012 +0200 .\" .th mbind 2 2021-03-22 linux "linux programmer's manual" .sh name mbind \- set memory policy for a memory range .sh synopsis .nf .b "#include " .pp .bi "long mbind(void *" addr ", unsigned long " len ", int " mode , .bi " const unsigned long *" nodemask ", unsigned long " maxnode , .bi " unsigned int " flags ); .pp link with \fi\-lnuma\fp. .fi .pp .ir note : there is no glibc wrapper for this system call; see notes. .sh description .br mbind () sets the numa memory policy, which consists of a policy mode and zero or more nodes, for the memory range starting with .i addr and continuing for .i len bytes. the memory policy defines from which node memory is allocated. .pp if the memory range specified by the .ir addr " and " len arguments includes an "anonymous" region of memory\(emthat is a region of memory created using the .br mmap (2) system call with the .br map_anonymous \(emor a memory-mapped file, mapped using the .br mmap (2) system call with the .b map_private flag, pages will be allocated only according to the specified policy when the application writes (stores) to the page. for anonymous regions, an initial read access will use a shared page in the kernel containing all zeros. for a file mapped with .br map_private , an initial read access will allocate pages according to the memory policy of the thread that causes the page to be allocated. this may not be the thread that called .br mbind (). .pp the specified policy will be ignored for any .b map_shared mappings in the specified memory range. rather the pages will be allocated according to the memory policy of the thread that caused the page to be allocated. again, this may not be the thread that called .br mbind (). .pp if the specified memory range includes a shared memory region created using the .br shmget (2) system call and attached using the .br shmat (2) system call, pages allocated for the anonymous or shared memory region will be allocated according to the policy specified, regardless of which process attached to the shared memory segment causes the allocation. if, however, the shared memory region was created with the .b shm_hugetlb flag, the huge pages will be allocated according to the policy specified only if the page allocation is caused by the process that calls .br mbind () for that region. .pp by default, .br mbind () has an effect only for new allocations; if the pages inside the range have been already touched before setting the policy, then the policy has no effect. this default behavior may be overridden by the .b mpol_mf_move and .b mpol_mf_move_all flags described below. .pp the .i mode argument must specify one of .br mpol_default , .br mpol_bind , .br mpol_interleave , .br mpol_preferred , or .br mpol_local (which are described in detail below). all policy modes except .b mpol_default require the caller to specify the node or nodes to which the mode applies, via the .i nodemask argument. .pp the .i mode argument may also include an optional .ir "mode flag" . the supported .i "mode flags" are: .tp .br mpol_f_static_nodes " (since linux-2.6.26)" a nonempty .i nodemask specifies physical node ids. linux does not remap the .i nodemask when the thread moves to a different cpuset context, nor when the set of nodes allowed by the thread's current cpuset context changes. .tp .br mpol_f_relative_nodes " (since linux-2.6.26)" a nonempty .i nodemask specifies node ids that are relative to the set of node ids allowed by the thread's current cpuset. .pp .i nodemask points to a bit mask of nodes containing up to .i maxnode bits. the bit mask size is rounded to the next multiple of .ir "sizeof(unsigned long)" , but the kernel will use bits only up to .ir maxnode . a null value of .i nodemask or a .i maxnode value of zero specifies the empty set of nodes. if the value of .i maxnode is zero, the .i nodemask argument is ignored. where a .i nodemask is required, it must contain at least one node that is on-line, allowed by the thread's current cpuset context (unless the .b mpol_f_static_nodes mode flag is specified), and contains memory. .pp the .i mode argument must include one of the following values: .tp .b mpol_default this mode requests that any nondefault policy be removed, restoring default behavior. when applied to a range of memory via .br mbind (), this means to use the thread memory policy, which may have been set with .br set_mempolicy (2). if the mode of the thread memory policy is also .br mpol_default , the system-wide default policy will be used. the system-wide default policy allocates pages on the node of the cpu that triggers the allocation. for .br mpol_default , the .i nodemask and .i maxnode arguments must be specify the empty set of nodes. .tp .b mpol_bind this mode specifies a strict policy that restricts memory allocation to the nodes specified in .ir nodemask . if .i nodemask specifies more than one node, page allocations will come from the node with sufficient free memory that is closest to the node where the allocation takes place. pages will not be allocated from any node not specified in the ir nodemask . (before linux 2.6.26, .\" commit 19770b32609b6bf97a3dece2529089494cbfc549 page allocations came from the node with the lowest numeric node id first, until that node contained no free memory. allocations then came from the node with the next highest node id specified in .i nodemask and so forth, until none of the specified nodes contained free memory.) .tp .b mpol_interleave this mode specifies that page allocations be interleaved across the set of nodes specified in .ir nodemask . this optimizes for bandwidth instead of latency by spreading out pages and memory accesses to those pages across multiple nodes. to be effective the memory area should be fairly large, at least 1\ mb or bigger with a fairly uniform access pattern. accesses to a single page of the area will still be limited to the memory bandwidth of a single node. .tp .b mpol_preferred this mode sets the preferred node for allocation. the kernel will try to allocate pages from this node first and fall back to other nodes if the preferred nodes is low on free memory. if .i nodemask specifies more than one node id, the first node in the mask will be selected as the preferred node. if the .i nodemask and .i maxnode arguments specify the empty set, then the memory is allocated on the node of the cpu that triggered the allocation. .tp .br mpol_local " (since linux 3.8)" .\" commit 479e2802d09f1e18a97262c4c6f8f17ae5884bd8 .\" commit f2a07f40dbc603c15f8b06e6ec7f768af67b424f this mode specifies "local allocation"; the memory is allocated on the node of the cpu that triggered the allocation (the "local node"). the .i nodemask and .i maxnode arguments must specify the empty set. if the "local node" is low on free memory, the kernel will try to allocate memory from other nodes. the kernel will allocate memory from the "local node" whenever memory for this node is available. if the "local node" is not allowed by the thread's current cpuset context, the kernel will try to allocate memory from other nodes. the kernel will allocate memory from the "local node" whenever it becomes allowed by the thread's current cpuset context. by contrast, .b mpol_default reverts to the memory policy of the thread (which may be set via .br set_mempolicy (2)); that policy may be something other than "local allocation". .pp if .b mpol_mf_strict is passed in .i flags and .i mode is not .br mpol_default , then the call fails with the error .b eio if the existing pages in the memory range don't follow the policy. .\" according to the kernel code, the following is not true .\" --lee schermerhorn .\" in 2.6.16 or later the kernel will also try to move pages .\" to the requested node with this flag. .pp if .b mpol_mf_move is specified in .ir flags , then the kernel will attempt to move all the existing pages in the memory range so that they follow the policy. pages that are shared with other processes will not be moved. if .b mpol_mf_strict is also specified, then the call fails with the error .b eio if some pages could not be moved. .pp if .b mpol_mf_move_all is passed in .ir flags , then the kernel will attempt to move all existing pages in the memory range regardless of whether other processes use the pages. the calling thread must be privileged .rb ( cap_sys_nice ) to use this flag. if .b mpol_mf_strict is also specified, then the call fails with the error .b eio if some pages could not be moved. .\" --------------------------------------------------------------- .sh return value on success, .br mbind () returns 0; on error, \-1 is returned and .i errno is set to indicate the error. .\" --------------------------------------------------------------- .sh errors .\" i think i got all of the error returns. --lee schermerhorn .tp .b efault part or all of the memory range specified by .i nodemask and .i maxnode points outside your accessible address space. or, there was an unmapped hole in the specified memory range specified by .ir addr and .ir len . .tp .b einval an invalid value was specified for .i flags or .ir mode ; or .i addr + len was less than .ir addr ; or .i addr is not a multiple of the system page size. or, .i mode is .b mpol_default and .i nodemask specified a nonempty set; or .i mode is .b mpol_bind or .b mpol_interleave and .i nodemask is empty. or, .i maxnode exceeds a kernel-imposed limit. .\" as at 2.6.23, this limit is "a page worth of bits", e.g., .\" 8 * 4096 bits, assuming a 4kb page size. or, .i nodemask specifies one or more node ids that are greater than the maximum supported node id. or, none of the node ids specified by .i nodemask are on-line and allowed by the thread's current cpuset context, or none of the specified nodes contain memory. or, the .i mode argument specified both .b mpol_f_static_nodes and .br mpol_f_relative_nodes . .tp .b eio .b mpol_mf_strict was specified and an existing page was already on a node that does not follow the policy; or .b mpol_mf_move or .b mpol_mf_move_all was specified and the kernel was unable to move all existing pages in the range. .tp .b enomem insufficient kernel memory was available. .tp .b eperm the .i flags argument included the .b mpol_mf_move_all flag and the caller does not have the .b cap_sys_nice privilege. .\" --------------------------------------------------------------- .sh versions the .br mbind () system call was added to the linux kernel in version 2.6.7. .sh conforming to this system call is linux-specific. .sh notes glibc does not provide a wrapper for this system call. for information on library support, see .br numa (7). .pp numa policy is not supported on a memory-mapped file range that was mapped with the .b map_shared flag. .pp the .b mpol_default mode can have different effects for .br mbind () and .br set_mempolicy (2). when .b mpol_default is specified for .br set_mempolicy (2), the thread's memory policy reverts to the system default policy or local allocation. when .b mpol_default is specified for a range of memory using .br mbind (), any pages subsequently allocated for that range will use the thread's memory policy, as set by .br set_mempolicy (2). this effectively removes the explicit policy from the specified range, "falling back" to a possibly nondefault policy. to select explicit "local allocation" for a memory range, specify a .i mode of .b mpol_local or .b mpol_preferred with an empty set of nodes. this method will work for .br set_mempolicy (2), as well. .pp support for huge page policy was added with 2.6.16. for interleave policy to be effective on huge page mappings the policied memory needs to be tens of megabytes or larger. .pp before linux 5.7. .\" commit dcf1763546d76c372f3136c8d6b2b6e77f140cf0 .b mpol_mf_strict was ignored on huge page mappings. .pp .b mpol_mf_move and .b mpol_mf_move_all are available only on linux 2.6.16 and later. .sh see also .br get_mempolicy (2), .br getcpu (2), .br mmap (2), .br set_mempolicy (2), .br shmat (2), .br shmget (2), .br numa (3), .br cpuset (7), .br numa (7), .br numactl (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/encrypt.3 .so man3/fts.3 .so man3/atan2.3 .so man3/stailq.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:01:11 1993 by rik faith (faith@cs.unc.edu) .th ram 4 1992-11-21 "linux" "linux programmer's manual" .sh name ram \- ram disk device .sh description the .i ram device is a block device to access the ram disk in raw mode. .pp it is typically created by: .pp .in +4n .ex mknod \-m 660 /dev/ram b 1 1 chown root:disk /dev/ram .ee .in .sh files .i /dev/ram .sh see also .br chown (1), .br mknod (1), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strtoul.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" heavily based on glibc infopages, copyright free software foundation .\" .th significand 3 2021-03-22 "gnu" "linux programmer's manual" .sh name significand, significandf, significandl \- get mantissa of floating-point number .sh synopsis .nf .b #include .pp .bi "double significand(double " x ); .bi "float significandf(float " x ); .bi "long double significandl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br significand (), .br significandf (), .br significandl (): .nf /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the mantissa of .i x scaled to the range [1,2). they are equivalent to .pp .in +4n .ex scalb(x, (double) \-ilogb(x)) .ee .in .pp this function exists mainly for use in certain standardized tests for ieee 754 conformance. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br significand (), .br significandf (), .br significandl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard; the .i double version is available on a number of other systems. .\" .sh history .\" this function came from bsd. .sh see also .br ilogb (3), .br scalb (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/fstat.2 .so man3/getutent.3 .so man3/setnetgrent.3 .\" copyright 2004 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th infinity 3 2020-12-21 "" "linux programmer's manual" .sh name infinity, nan, huge_val, huge_valf, huge_vall \- floating-point constants .sh synopsis .nf .br "#define _isoc99_source" " /* see feature_test_macros(7) */" .b #include .pp .b infinity .pp .b nan .pp .b huge_val .b huge_valf .b huge_vall .fi .sh description the macro .b infinity expands to a .i float constant representing positive infinity. .pp the macro .b nan expands to a .i float constant representing a quiet nan (when supported). a .i quiet nan is a nan ("not-a-number") that does not raise exceptions when it is used in arithmetic. the opposite is a .i signaling nan. see iec 60559:1989. .pp the macros .br huge_val , .br huge_valf , .b huge_vall expand to constants of types .ir double , .ir float , and .ir "long double" , respectively, that represent a large positive value, possibly positive infinity. .sh conforming to c99. .pp on a glibc system, the macro .b huge_val is always available. availability of the .b nan macro can be tested using .br "#ifdef nan" , and similarly for .br infinity , .br huge_valf , .br huge_vall . they will be defined by .i if .b _isoc99_source or .b _gnu_source is defined, or .b __stdc_version__ is defined and has a value not less than 199901l. .sh see also .br fpclassify (3), .br math_error (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/wprintf.3 .so man3/isalpha.3 .so man3/pthread_cleanup_push_defer_np.3 .\" copyright (c) 2014, heinrich schuchardt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .th ioctl_fat 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_fat \- manipulating the fat filesystem .sh synopsis .nf .br "#include " " /* definition of [" v ] fat_* " and" .br " attr_* " constants */" .b #include .pp .bi "int ioctl(int " fd ", fat_ioctl_get_attributes, uint32_t *" attr ); .bi "int ioctl(int " fd ", fat_ioctl_set_attributes, uint32_t *" attr ); .bi "int ioctl(int " fd ", fat_ioctl_get_volume_id, uint32_t *" id ); .bi "int ioctl(int " fd ", vfat_ioctl_readdir_both," .bi " struct __fat_dirent " entry [2]); .bi "int ioctl(int " fd ", vfat_ioctl_readdir_short," .bi " struct __fat_dirent " entry [2]); .fi .sh description the .br ioctl (2) system call can be used to read and write metadata of fat filesystems that are not accessible using other system calls. .ss reading and setting file attributes files and directories in the fat filesystem possess an attribute bit mask that can be read with .b fat_ioctl_get_attributes and written with .br fat_ioctl_set_attributes . .pp the .i fd argument contains a file descriptor for a file or directory. it is sufficient to create the file descriptor by calling .br open (2) with the .b o_rdonly flag. .pp the .i attr argument contains a pointer to a bit mask. the bits of the bit mask are: .tp .b attr_ro this bit specifies that the file or directory is read-only. .tp .b attr_hidden this bit specifies that the file or directory is hidden. .tp .b attr_sys this bit specifies that the file is a system file. .tp .b attr_volume this bit specifies that the file is a volume label. this attribute is read-only. .tp .b attr_dir this bit specifies that this is a directory. this attribute is read-only. .tp .b attr_arch this bit indicates that this file or directory should be archived. it is set when a file is created or modified. it is reset by an archiving system. .pp the zero value .b attr_none can be used to indicate that no attribute bit is set. .ss reading the volume id fat filesystems are identified by a volume id. the volume id can be read with .br fat_ioctl_get_volume_id . .pp the .i fd argument can be a file descriptor for any file or directory of the filesystem. it is sufficient to create the file descriptor by calling .br open (2) with the .b o_rdonly flag. .pp the .i id argument is a pointer to the field that will be filled with the volume id. typically the volume id is displayed to the user as a group of two 16-bit fields: .pp .in +4n .ex printf("volume id %04x\-%04x\en", id >> 16, id & 0xffff); .ee .in .ss reading short filenames of a directory a file or directory on a fat filesystem always has a short filename consisting of up to 8 capital letters, optionally followed by a period and up to 3 capital letters for the file extension. if the actual filename does not fit into this scheme, it is stored as a long filename of up to 255 utf-16 characters. .pp the short filenames in a directory can be read with .br vfat_ioctl_readdir_short . .b vfat_ioctl_readdir_both reads both the short and the long filenames. .pp the .i fd argument must be a file descriptor for a directory. it is sufficient to create the file descriptor by calling .br open (2) with the .b o_rdonly flag. the file descriptor can be used only once to iterate over the directory entries by calling .br ioctl (2) repeatedly. .pp the .i entry argument is a two-element array of the following structures: .pp .in +4n .ex struct __fat_dirent { long d_ino; __kernel_off_t d_off; uint32_t short d_reclen; char d_name[256]; }; .ee .in .pp the first entry in the array is for the short filename. the second entry is for the long filename. .pp the .i d_ino and .i d_off fields are filled only for long filenames. the .i d_ino field holds the inode number of the directory. the .i d_off field holds the offset of the file entry in the directory. as these values are not available for short filenames, the user code should simply ignore them. .pp the field .i d_reclen contains the length of the filename in the field .ir d_name . to keep backward compatibility, a length of 0 for the short filename signals that the end of the directory has been reached. however, the preferred method for detecting the end of the directory is to test the .br ioctl (2) return value. if no long filename exists, field .i d_reclen is set to 0 and .i d_name is a character string of length 0 for the long filename. .sh return value on error, \-1 is returned, and .i errno is set to indicate the error. .pp for .b vfat_ioctl_readdir_both and .b vfat_ioctl_readdir_short a return value of 1 signals that a new directory entry has been read and a return value of 0 signals that the end of the directory has been reached. .sh errors .tp .b enoent this error is returned by .b vfat_ioctl_readdir_both and .b vfat_ioctl_readdir_short if the file descriptor .i fd refers to a removed, but still open directory. .tp .b enotdir this error is returned by .b vfat_ioctl_readdir_both and .b vfat_ioctl_readdir_short if the file descriptor .i fd does not refer to a directory. .tp .b enotty the file descriptor .i fd does not refer to an object in a fat filesystem. .pp for further error values, see .br ioctl (2). .sh versions .br vfat_ioctl_readdir_both and .b vfat_ioctl_readdir_short first appeared in linux 2.0. .pp .br fat_ioctl_get_attributes and .br fat_ioctl_set_attributes first appeared .\" just before we got git history in linux 2.6.12. .pp .b fat_ioctl_get_volume_id was introduced in version 3.11 .\" commit 6e5b93ee55d401f1619092fb675b57c28c9ed7ec of the linux kernel. .sh conforming to this api is linux-specific. .sh examples .ss toggling the archive flag the following program demonstrates the usage of .br ioctl (2) to manipulate file attributes. the program reads and displays the archive attribute of a file. after inverting the value of the attribute, the program reads and displays the attribute again. .pp the following was recorded when applying the program for the file .ir /mnt/user/foo : .pp .in +4n .ex # ./toggle_fat_archive_flag /mnt/user/foo archive flag is set toggling archive flag archive flag is not set .ee .in .ss program source (toggle_fat_archive_flag.c) \& .ex #include #include #include #include #include #include #include /* * read file attributes of a file on a fat filesystem. * output the state of the archive flag. */ static uint32_t readattr(int fd) { uint32_t attr; int ret; ret = ioctl(fd, fat_ioctl_get_attributes, &attr); if (ret == \-1) { perror("ioctl"); exit(exit_failure); } if (attr & attr_arch) printf("archive flag is set\en"); else printf("archive flag is not set\en"); return attr; } int main(int argc, char *argv[]) { uint32_t attr; int fd; int ret; if (argc != 2) { printf("usage: %s filename\en", argv[0]); exit(exit_failure); } fd = open(argv[1], o_rdonly); if (fd == \-1) { perror("open"); exit(exit_failure); } /* * read and display the fat file attributes. */ attr = readattr(fd); /* * invert archive attribute. */ printf("toggling archive flag\en"); attr \(ha= attr_arch; /* * write the changed fat file attributes. */ ret = ioctl(fd, fat_ioctl_set_attributes, &attr); if (ret == \-1) { perror("ioctl"); exit(exit_failure); } /* * read and display the fat file attributes. */ readattr(fd); close(fd); exit(exit_success); } .ee .\" .ss reading the volume id the following program demonstrates the use of .br ioctl (2) to display the volume id of a fat filesystem. .pp the following output was recorded when applying the program for directory .ir /mnt/user : .pp .in +4n .ex $ ./display_fat_volume_id /mnt/user volume id 6443\-6241 .ee .in .ss program source (display_fat_volume_id.c) \& .ex #include #include #include #include #include #include #include int main(int argc, char *argv[]) { uint32_t id; int fd; int ret; if (argc != 2) { printf("usage: %s filename\en", argv[0]); exit(exit_failure); } fd = open(argv[1], o_rdonly); if (fd == \-1) { perror("open"); exit(exit_failure); } /* * read volume id. */ ret = ioctl(fd, fat_ioctl_get_volume_id, &id); if (ret == \-1) { perror("ioctl"); exit(exit_failure); } /* * format the output as two groups of 16 bits each. */ printf("volume id %04x\-%04x\en", id >> 16, id & 0xffff); close(fd); exit(exit_success); } .ee .\" .ss listing a directory the following program demonstrates the use of .br ioctl (2) to list a directory. .pp the following was recorded when applying the program to the directory .ir /mnt/user : .pp .in +4n .ex $ \fb./fat_dir /mnt/user\fp \[char46] \-> \(aq\(aq \[char46]. \-> \(aq\(aq alongf\(ti1.txt \-> \(aqa long filename.txt\(aq upper.txt \-> \(aq\(aq lower.txt \-> \(aqlower.txt\(aq .ee .in .\" .ss program source .in +4n .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { struct __fat_dirent entry[2]; int fd; int ret; if (argc != 2) { printf("usage: %s directory\en", argv[0]); exit(exit_failure); } /* * open file descriptor for the directory. */ fd = open(argv[1], o_rdonly | o_directory); if (fd == \-1) { perror("open"); exit(exit_failure); } for (;;) { /* * read next directory entry. */ ret = ioctl( fd, vfat_ioctl_readdir_both, entry); /* * if an error occurs, the return value is \-1. * if the end of the directory list has been reached, * the return value is 0. * for backward compatibility the end of the directory * list is also signaled by d_reclen == 0. */ if (ret < 1) break; /* * write both the short name and the long name. */ printf("%s \-> \(aq%s\(aq\en", entry[0].d_name, entry[1].d_name); } if (ret == \-1) { perror("vfat_ioctl_readdir_both"); exit(exit_failure); } /* * close the file descriptor. */ close(fd); exit(exit_success); } .ee .in .sh see also .br ioctl (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1996 andries brouwer .\" and copyright (c) 2006, 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1997-01-31 by eric s. raymond .\" modified 2000-03-25 by jim van zandt .\" modified 2001-10-04 by john levon .\" modified 2003-02-02 by andi kleen .\" modified 2003-05-21 by michael kerrisk .\" map_locked works from 2.5.37 .\" modified 2004-06-17 by michael kerrisk .\" modified 2004-09-11 by aeb .\" modified 2004-12-08, from eric estievenart .\" modified 2004-12-08, mtk, formatting tidy-ups .\" modified 2006-12-04, mtk, various parts rewritten .\" 2007-07-10, mtk, added an example program. .\" 2008-11-18, mtk, document map_stack .\" .th mmap 2 2021-03-22 "linux" "linux programmer's manual" .sh name mmap, munmap \- map or unmap files or devices into memory .sh synopsis .nf .b #include .pp .bi "void *mmap(void *" addr ", size_t " length \ ", int " prot ", int " flags , .bi " int " fd ", off_t " offset ); .bi "int munmap(void *" addr ", size_t " length ); .fi .pp see notes for information on feature test macro requirements. .sh description .br mmap () creates a new mapping in the virtual address space of the calling process. the starting address for the new mapping is specified in .ir addr . the .i length argument specifies the length of the mapping (which must be greater than 0). .pp if .i addr is null, then the kernel chooses the (page-aligned) address at which to create the mapping; this is the most portable method of creating a new mapping. if .i addr is not null, then the kernel takes it as a hint about where to place the mapping; on linux, the kernel will pick a nearby page boundary (but always above or equal to the value specified by .ir /proc/sys/vm/mmap_min_addr ) and attempt to create the mapping there. if another mapping already exists there, the kernel picks a new address that may or may not depend on the hint. .\" before linux 2.6.24, the address was rounded up to the next page .\" boundary; since 2.6.24, it is rounded down! the address of the new mapping is returned as the result of the call. .pp the contents of a file mapping (as opposed to an anonymous mapping; see .b map_anonymous below), are initialized using .i length bytes starting at offset .i offset in the file (or other object) referred to by the file descriptor .ir fd . .i offset must be a multiple of the page size as returned by .ir sysconf(_sc_page_size) . .pp after the .br mmap () call has returned, the file descriptor, .ir fd , can be closed immediately without invalidating the mapping. .pp the .i prot argument describes the desired memory protection of the mapping (and must not conflict with the open mode of the file). it is either .b prot_none or the bitwise or of one or more of the following flags: .tp 1.1i .b prot_exec pages may be executed. .tp .b prot_read pages may be read. .tp .b prot_write pages may be written. .tp .b prot_none pages may not be accessed. .\" .ss the flags argument the .i flags argument determines whether updates to the mapping are visible to other processes mapping the same region, and whether updates are carried through to the underlying file. this behavior is determined by including exactly one of the following values in .ir flags : .tp .b map_shared share this mapping. updates to the mapping are visible to other processes mapping the same region, and (in the case of file-backed mappings) are carried through to the underlying file. (to precisely control when updates are carried through to the underlying file requires the use of .br msync (2).) .tp .br map_shared_validate " (since linux 4.15)" this flag provides the same behavior as .b map_shared except that .b map_shared mappings ignore unknown flags in .ir flags . by contrast, when creating a mapping using .br map_shared_validate , the kernel verifies all passed flags are known and fails the mapping with the error .br eopnotsupp for unknown flags. this mapping type is also required to be able to use some mapping flags (e.g., .br map_sync ). .tp .b map_private create a private copy-on-write mapping. updates to the mapping are not visible to other processes mapping the same file, and are not carried through to the underlying file. it is unspecified whether changes made to the file after the .br mmap () call are visible in the mapped region. .pp both .b map_shared and .b map_private are described in posix.1-2001 and posix.1-2008. .b map_shared_validate is a linux extension. .pp in addition, zero or more of the following values can be ored in .ir flags : .tp .br map_32bit " (since linux 2.4.20, 2.6)" put the mapping into the first 2 gigabytes of the process address space. this flag is supported only on x86-64, for 64-bit programs. it was added to allow thread stacks to be allocated somewhere in the first 2\ gb of memory, so as to improve context-switch performance on some early 64-bit processors. .\" see http://lwn.net/articles/294642 "tangled up in threads", 19 aug 08 modern x86-64 processors no longer have this performance problem, so use of this flag is not required on those systems. the .b map_32bit flag is ignored when .b map_fixed is set. .tp .b map_anon synonym for .br map_anonymous ; provided for compatibility with other implementations. .tp .b map_anonymous the mapping is not backed by any file; its contents are initialized to zero. the .i fd argument is ignored; however, some implementations require .i fd to be \-1 if .b map_anonymous (or .br map_anon ) is specified, and portable applications should ensure this. the .i offset argument should be zero. .\" see the pgoff overflow check in do_mmap(). .\" see the offset check in sys_mmap in arch/x86/kernel/sys_x86_64.c. the use of .b map_anonymous in conjunction with .b map_shared is supported on linux only since kernel 2.4. .tp .b map_denywrite this flag is ignored. .\" introduced in 1.1.36, removed in 1.3.24. (long ago\(emlinux 2.0 and earlier\(emit signaled that attempts to write to the underlying file should fail with .br etxtbsy . but this was a source of denial-of-service attacks.) .tp .b map_executable this flag is ignored. .\" introduced in 1.1.38, removed in 1.3.24. flag tested in proc_follow_link. .\" (long ago, it signaled that the underlying file is an executable. .\" however, that information was not really used anywhere.) .\" linus talked about dos related to map_executable, but he was thinking of .\" map_denywrite? .tp .b map_file compatibility flag. ignored. .\" on some systems, this was required as the opposite of .\" map_anonymous -- mtk, 1 may 2007 .tp .b map_fixed don't interpret .i addr as a hint: place the mapping at exactly that address. .i addr must be suitably aligned: for most architectures a multiple of the page size is sufficient; however, some architectures may impose additional restrictions. if the memory region specified by .i addr and .i length overlaps pages of any existing mapping(s), then the overlapped part of the existing mapping(s) will be discarded. if the specified address cannot be used, .br mmap () will fail. .ip software that aspires to be portable should use the .br map_fixed flag with care, keeping in mind that the exact layout of a process's memory mappings is allowed to change significantly between kernel versions, c library versions, and operating system releases. .ir "carefully read the discussion of this flag in notes!" .tp .br map_fixed_noreplace " (since linux 4.17)" .\" commit a4ff8e8620d3f4f50ac4b41e8067b7d395056843 this flag provides behavior that is similar to .b map_fixed with respect to the .i addr enforcement, but differs in that .b map_fixed_noreplace never clobbers a preexisting mapped range. if the requested range would collide with an existing mapping, then this call fails with the error .b eexist. this flag can therefore be used as a way to atomically (with respect to other threads) attempt to map an address range: one thread will succeed; all others will report failure. .ip note that older kernels which do not recognize the .br map_fixed_noreplace flag will typically (upon detecting a collision with a preexisting mapping) fall back to a "non-\c .b map_fixed\c " type of behavior: they will return an address that is different from the requested address. therefore, backward-compatible software should check the returned address against the requested address. .tp .b map_growsdown this flag is used for stacks. it indicates to the kernel virtual memory system that the mapping should extend downward in memory. the return address is one page lower than the memory area that is actually created in the process's virtual address space. touching an address in the "guard" page below the mapping will cause the mapping to grow by a page. this growth can be repeated until the mapping grows to within a page of the high end of the next lower mapping, at which point touching the "guard" page will result in a .b sigsegv signal. .tp .br map_hugetlb " (since linux 2.6.32)" allocate the mapping using "huge" pages. see the linux kernel source file .i documentation/admin\-guide/mm/hugetlbpage.rst for further information, as well as notes, below. .tp .br map_huge_2mb ", " map_huge_1gb " (since linux 3.8)" .\" see https://lwn.net/articles/533499/ used in conjunction with .b map_hugetlb to select alternative hugetlb page sizes (respectively, 2\ mb and 1\ gb) on systems that support multiple hugetlb page sizes. .ip more generally, the desired huge page size can be configured by encoding the base-2 logarithm of the desired page size in the six bits at the offset .br map_huge_shift . (a value of zero in this bit field provides the default huge page size; the default huge page size can be discovered via the .i hugepagesize field exposed by .ir /proc/meminfo .) thus, the above two constants are defined as: .ip .in +4n .ex #define map_huge_2mb (21 << map_huge_shift) #define map_huge_1gb (30 << map_huge_shift) .ee .in .ip the range of huge page sizes that are supported by the system can be discovered by listing the subdirectories in .ir /sys/kernel/mm/hugepages . .tp .br map_locked " (since linux 2.5.37)" mark the mapped region to be locked in the same way as .br mlock (2). this implementation will try to populate (prefault) the whole range but the .br mmap () call doesn't fail with .b enomem if this fails. therefore major faults might happen later on. so the semantic is not as strong as .br mlock (2). one should use .br mmap () plus .br mlock (2) when major faults are not acceptable after the initialization of the mapping. the .br map_locked flag is ignored in older kernels. .\" if set, the mapped pages will not be swapped out. .tp .br map_nonblock " (since linux 2.5.46)" this flag is meaningful only in conjunction with .br map_populate . don't perform read-ahead: create page tables entries only for pages that are already present in ram. since linux 2.6.23, .\" commit 54cb8821de07f2ffcd28c380ce9b93d5784b40d7 this flag causes .br map_populate to do nothing. one day, the combination of .br map_populate and .br map_nonblock may be reimplemented. .tp .b map_noreserve do not reserve swap space for this mapping. when swap space is reserved, one has the guarantee that it is possible to modify the mapping. when swap space is not reserved one might get .b sigsegv upon a write if no physical memory is available. see also the discussion of the file .i /proc/sys/vm/overcommit_memory in .br proc (5). in kernels before 2.6, this flag had effect only for private writable mappings. .tp .br map_populate " (since linux 2.5.46)" populate (prefault) page tables for a mapping. for a file mapping, this causes read-ahead on the file. this will help to reduce blocking on page faults later. the .br mmap () call doesn't fail if the mapping cannot be populated (for example, due to limitations on the number of mapped huge pages when using .br map_hugetlb ). .br map_populate is supported for private mappings only since linux 2.6.23. .tp .br map_stack " (since linux 2.6.27)" allocate the mapping at an address suitable for a process or thread stack. .ip this flag is currently a no-op on linux. however, by employing this flag, applications can ensure that they transparently obtain support if the flag is implemented in the future. thus, it is used in the glibc threading implementation to allow for the fact that some architectures may (later) require special treatment for stack allocations. .\" see http://lwn.net/articles/294642 "tangled up in threads", 19 aug 08 .\" commit cd98a04a59e2f94fa64d5bf1e26498d27427d5e7 .\" http://thread.gmane.org/gmane.linux.kernel/720412 .\" "pthread_create() slow for many threads; also time to revisit 64b .\" context switch optimization?" a further reason to employ this flag is portability: .br map_stack exists (and has an effect) on some other systems (e.g., some of the bsds). .tp .br map_sync " (since linux 4.15)" this flag is available only with the .b map_shared_validate mapping type; mappings of type .b map_shared will silently ignore this flag. this flag is supported only for files supporting dax (direct mapping of persistent memory). for other files, creating a mapping with this flag results in an .b eopnotsupp error. .ip shared file mappings with this flag provide the guarantee that while some memory is mapped writable in the address space of the process, it will be visible in the same file at the same offset even after the system crashes or is rebooted. in conjunction with the use of appropriate cpu instructions, this provides users of such mappings with a more efficient way of making data modifications persistent. .tp .br map_uninitialized " (since linux 2.6.33)" don't clear anonymous pages. this flag is intended to improve performance on embedded devices. this flag is honored only if the kernel was configured with the .b config_mmap_allow_uninitialized option. because of the security implications, that option is normally enabled only on embedded devices (i.e., devices where one has complete control of the contents of user memory). .pp of the above flags, only .b map_fixed is specified in posix.1-2001 and posix.1-2008. however, most systems also support .b map_anonymous (or its synonym .br map_anon ). .\" fixme . for later review when issue 8 is one day released... .\" posix may add map_anon in the future .\" http://austingroupbugs.net/tag_view_page.php?tag_id=8 .\" http://austingroupbugs.net/view.php?id=850 .ss munmap() the .br munmap () system call deletes the mappings for the specified address range, and causes further references to addresses within the range to generate invalid memory references. the region is also automatically unmapped when the process is terminated. on the other hand, closing the file descriptor does not unmap the region. .pp the address .i addr must be a multiple of the page size (but .i length need not be). all pages containing a part of the indicated range are unmapped, and subsequent references to these pages will generate .br sigsegv . it is not an error if the indicated range does not contain any mapped pages. .sh return value on success, .br mmap () returns a pointer to the mapped area. on error, the value .b map_failed (that is, .ir "(void\ *)\ \-1" ) is returned, and .i errno is set to indicate the error. .pp on success, .br munmap () returns 0. on failure, it returns \-1, and .i errno is set to indicate the error (probably to .br einval ). .sh errors .tp .b eacces a file descriptor refers to a non-regular file. or a file mapping was requested, but .i fd is not open for reading. or .b map_shared was requested and .b prot_write is set, but .i fd is not open in read/write .rb ( o_rdwr ) mode. or .b prot_write is set, but the file is append-only. .tp .b eagain the file has been locked, or too much memory has been locked (see .br setrlimit (2)). .tp .b ebadf .i fd is not a valid file descriptor (and .b map_anonymous was not set). .tp .b eexist .br map_fixed_noreplace was specified in .ir flags , and the range covered by .ir addr and .ir length clashes with an existing mapping. .tp .b einval we don't like .ir addr , .ir length , or .i offset (e.g., they are too large, or not aligned on a page boundary). .tp .b einval (since linux 2.6.12) .i length was 0. .tp .b einval .i flags contained none of .br map_private , .br map_shared , or .br map_shared_validate . .tp .b enfile .\" this is for shared anonymous segments .\" [2.6.7] shmem_zero_setup()-->shmem_file_setup()-->get_empty_filp() the system-wide limit on the total number of open files has been reached. .\" .tp .\" .b enoexec .\" a file could not be mapped for reading. .tp .b enodev the underlying filesystem of the specified file does not support memory mapping. .tp .b enomem no memory is available. .tp .b enomem the process's maximum number of mappings would have been exceeded. this error can also occur for .br munmap (), when unmapping a region in the middle of an existing mapping, since this results in two smaller mappings on either side of the region being unmapped. .tp .b enomem (since linux 4.7) the process's .b rlimit_data limit, described in .br getrlimit (2), would have been exceeded. .tp .b eoverflow on 32-bit architecture together with the large file extension (i.e., using 64-bit .ir off_t ): the number of pages used for .i length plus number of pages used for .i offset would overflow .i "unsigned long" (32 bits). .tp .b eperm the .i prot argument asks for .b prot_exec but the mapped area belongs to a file on a filesystem that was mounted no-exec. .\" (since 2.4.25 / 2.6.0.) .tp .b eperm the operation was prevented by a file seal; see .br fcntl (2). .tp .b eperm the .b map_hugetlb flag was specified, but the caller was not privileged (did not have the .b cap_ipc_lock capability) and is not a member of the .i sysctl_hugetlb_shm_group group; see the description of .i /proc/sys/vm/sysctl_hugetlb_shm_group in .tp .b etxtbsy .b map_denywrite was set but the object specified by .i fd is open for writing. .pp use of a mapped region can result in these signals: .tp .b sigsegv attempted write into a region mapped as read-only. .tp .b sigbus attempted access to a page of the buffer that lies beyond the end of the mapped file. for an explanation of the treatment of the bytes in the page that corresponds to the end of a mapped file that is not a multiple of the page size, see notes. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mmap (), .br munmap () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd. .\" svr4 documents additional error codes enxio and enodev. .\" susv2 documents additional error codes emfile and eoverflow. .pp on posix systems on which .br mmap (), .br msync (2), and .br munmap () are available, .b _posix_mapped_files is defined in \fi\fp to a value greater than 0. (see also .br sysconf (3).) .\" posix.1-2001: it shall be defined to -1 or 0 or 200112l. .\" -1: unavailable, 0: ask using sysconf(). .\" glibc defines it to 1. .sh notes memory mapped by .br mmap () is preserved across .br fork (2), with the same attributes. .pp a file is mapped in multiples of the page size. for a file that is not a multiple of the page size, the remaining bytes in the partial page at the end of the mapping are zeroed when mapped, and modifications to that region are not written out to the file. the effect of changing the size of the underlying file of a mapping on the pages that correspond to added or removed regions of the file is unspecified. .pp on some hardware architectures (e.g., i386), .b prot_write implies .br prot_read . it is architecture dependent whether .b prot_read implies .b prot_exec or not. portable programs should always set .b prot_exec if they intend to execute code in the new mapping. .pp the portable way to create a mapping is to specify .i addr as 0 (null), and omit .b map_fixed from .ir flags . in this case, the system chooses the address for the mapping; the address is chosen so as not to conflict with any existing mapping, and will not be 0. if the .b map_fixed flag is specified, and .i addr is 0 (null), then the mapped address will be 0 (null). .pp certain .i flags constants are defined only if suitable feature test macros are defined (possibly by default): .br _default_source with glibc 2.19 or later; or .br _bsd_source or .br _svid_source in glibc 2.19 and earlier. (employing .br _gnu_source also suffices, and requiring that macro specifically would have been more logical, since these flags are all linux-specific.) the relevant flags are: .br map_32bit , .br map_anonymous (and the synonym .br map_anon ), .br map_denywrite , .br map_executable , .br map_file , .br map_growsdown , .br map_hugetlb , .br map_locked , .br map_nonblock , .br map_noreserve , .br map_populate , and .br map_stack . .pp an application can determine which pages of a mapping are currently resident in the buffer/page cache using .br mincore (2). .\" .ss using map_fixed safely the only safe use for .br map_fixed is where the address range specified by .ir addr and .i length was previously reserved using another mapping; otherwise, the use of .br map_fixed is hazardous because it forcibly removes preexisting mappings, making it easy for a multithreaded process to corrupt its own address space. .pp for example, suppose that thread a looks through .i /proc//maps in order to locate an unused address range that it can map using .br map_fixed , while thread b simultaneously acquires part or all of that same address range. when thread a subsequently employs .br mmap(map_fixed) , it will effectively clobber the mapping that thread b created. in this scenario, thread b need not create a mapping directly; simply making a library call that, internally, uses .br dlopen (3) to load some other shared library, will suffice. the .br dlopen (3) call will map the library into the process's address space. furthermore, almost any library call may be implemented in a way that adds memory mappings to the address space, either with this technique, or by simply allocating memory. examples include .br brk (2), .br malloc (3), .br pthread_create (3), and the pam libraries .ur http://www.linux-pam.org .ue . .pp since linux 4.17, a multithreaded program can use the .br map_fixed_noreplace flag to avoid the hazard described above when attempting to create a mapping at a fixed address that has not been reserved by a preexisting mapping. .\" .ss timestamps changes for file-backed mappings for file-backed mappings, the .i st_atime field for the mapped file may be updated at any time between the .br mmap () and the corresponding unmapping; the first reference to a mapped page will update the field if it has not been already. .pp the .i st_ctime and .i st_mtime field for a file mapped with .b prot_write and .b map_shared will be updated after a write to the mapped region, and before a subsequent .br msync (2) with the .b ms_sync or .b ms_async flag, if one occurs. .\" .ss huge page (huge tlb) mappings for mappings that employ huge pages, the requirements for the arguments of .br mmap () and .br munmap () differ somewhat from the requirements for mappings that use the native system page size. .pp for .br mmap (), .i offset must be a multiple of the underlying huge page size. the system automatically aligns .i length to be a multiple of the underlying huge page size. .pp for .br munmap (), .ir addr , and .i length must both be a multiple of the underlying huge page size. .\" .ss c library/kernel differences this page describes the interface provided by the glibc .br mmap () wrapper function. originally, this function invoked a system call of the same name. since kernel 2.4, that system call has been superseded by .br mmap2 (2), and nowadays .\" since around glibc 2.1/2.2, depending on the platform. the glibc .br mmap () wrapper function invokes .br mmap2 (2) with a suitably adjusted value for .ir offset . .sh bugs on linux, there are no guarantees like those suggested above under .br map_noreserve . by default, any process can be killed at any moment when the system runs out of memory. .pp in kernels before 2.6.7, the .b map_populate flag has effect only if .i prot is specified as .br prot_none . .pp susv3 specifies that .br mmap () should fail if .i length is 0. however, in kernels before 2.6.12, .br mmap () succeeded in this case: no mapping was created and the call returned .ir addr . since kernel 2.6.12, .br mmap () fails with the error .b einval for this case. .pp posix specifies that the system shall always zero fill any partial page at the end of the object and that system will never write any modification of the object beyond its end. on linux, when you write data to such partial page after the end of the object, the data stays in the page cache even after the file is closed and unmapped and even though the data is never written to the file itself, subsequent mappings may see the modified content. in some cases, this could be fixed by calling .br msync (2) before the unmap takes place; however, this doesn't work on .br tmpfs (5) (for example, when using the posix shared memory interface documented in .br shm_overview (7)). .sh examples .\" fixme . add an example here that uses an anonymous shared region for .\" ipc between parent and child. the following program prints part of the file specified in its first command-line argument to standard output. the range of bytes to be printed is specified via offset and length values in the second and third command-line arguments. the program creates a memory mapping of the required pages of the file and then uses .br write (2) to output the desired bytes. .ss program source .ex #include #include #include #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) int main(int argc, char *argv[]) { char *addr; int fd; struct stat sb; off_t offset, pa_offset; size_t length; ssize_t s; if (argc < 3 || argc > 4) { fprintf(stderr, "%s file offset [length]\en", argv[0]); exit(exit_failure); } fd = open(argv[1], o_rdonly); if (fd == \-1) handle_error("open"); if (fstat(fd, &sb) == \-1) /* to obtain file size */ handle_error("fstat"); offset = atoi(argv[2]); pa_offset = offset & \(ti(sysconf(_sc_page_size) \- 1); /* offset for mmap() must be page aligned */ if (offset >= sb.st_size) { fprintf(stderr, "offset is past end of file\en"); exit(exit_failure); } if (argc == 4) { length = atoi(argv[3]); if (offset + length > sb.st_size) length = sb.st_size \- offset; /* can\(aqt display bytes past end of file */ } else { /* no length arg ==> display to end of file */ length = sb.st_size \- offset; } addr = mmap(null, length + offset \- pa_offset, prot_read, map_private, fd, pa_offset); if (addr == map_failed) handle_error("mmap"); s = write(stdout_fileno, addr + offset \- pa_offset, length); if (s != length) { if (s == \-1) handle_error("write"); fprintf(stderr, "partial write"); exit(exit_failure); } munmap(addr, length + offset \- pa_offset); close(fd); exit(exit_success); } .ee .sh see also .br ftruncate (2), .br getpagesize (2), .br memfd_create (2), .br mincore (2), .br mlock (2), .br mmap2 (2), .br mprotect (2), .br mremap (2), .br msync (2), .br remap_file_pages (2), .br setrlimit (2), .br shmat (2), .br userfaultfd (2), .br shm_open (3), .br shm_overview (7) .pp the descriptions of the following files in .br proc (5): .ir /proc/[pid]/maps , .ir /proc/[pid]/map_files , and .ir /proc/[pid]/smaps . .pp b.o. gallmeister, posix.4, o'reilly, pp. 128\(en129 and 389\(en391. .\" .\" repeat after me: private read-only mappings are 100% equivalent to .\" shared read-only mappings. no ifs, buts, or maybes. -- linus .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" contributed by niki a. rahimi, ltc security development .\" narahimi@us.ibm.com .\" .\" %%%license_start(freely_redistributable) .\" may be freely distributed and modified. .\" %%%license_end .\" .th pciconfig_read 2 2021-03-22 "linux" "linux programmer's manual" .sh name pciconfig_read, pciconfig_write, pciconfig_iobase \- pci device information handling .sh synopsis .nf .b #include .pp .bi "int pciconfig_read(unsigned long " bus ", unsigned long " dfn , .bi " unsigned long " off ", unsigned long " len , .bi " unsigned char *" buf ); .bi "int pciconfig_write(unsigned long " bus ", unsigned long " dfn , .bi " unsigned long " off ", unsigned long " len , .bi " unsigned char *" buf ); .bi "int pciconfig_iobase(int " which ", unsigned long " bus , .bi " unsigned long " devfn ); .fi .sh description most of the interaction with pci devices is already handled by the kernel pci layer, and thus these calls should not normally need to be accessed from user space. .tp .br pciconfig_read () reads to .i buf from device .i dev at offset .i off value. .tp .br pciconfig_write () writes from .i buf to device .i dev at offset .i off value. .tp .br pciconfig_iobase () you pass it a bus/devfn pair and get a physical address for either the memory offset (for things like prep, this is 0xc0000000), the io base for pio cycles, or the isa holes if any. .sh return value .tp .br pciconfig_read () on success, zero is returned. on error, \-1 is returned and .i errno is set to indicate the error. .tp .br pciconfig_write () on success, zero is returned. on error, \-1 is returned and .i errno is set to indicate the error. .tp .br pciconfig_iobase () returns information on locations of various i/o regions in physical memory according to the .i which value. values for .i which are: .br iobase_bridge_number , .br iobase_memory , .br iobase_io , .br iobase_isa_io , .br iobase_isa_mem . .sh errors .tp .b einval .i len value is invalid. this does not apply to .br pciconfig_iobase (). .tp .b eio i/o error. .tp .b enodev for .br pciconfig_iobase (), "hose" value is null. for the other calls, could not find a slot. .tp .b enosys the system has not implemented these calls .rb ( config_pci not defined). .tp .b eopnotsupp this return value is valid only for .br pciconfig_iobase (). it is returned if the value for .i which is invalid. .tp .b eperm user does not have the .b cap_sys_admin capability. this does not apply to .br pciconfig_iobase (). .sh conforming to these calls are linux-specific, available since linux 2.0.26/2.1.11. .sh see also .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 free software foundation, inc. .\" copyright (c) 2015 andrew lutomirski .\" author: kent yoder .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .th set_thread_area 2 2021-03-22 "linux" "linux programmer's manual" .sh name get_thread_area, set_thread_area \- manipulate thread-local storage information .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .b #if defined __i386__ || defined __x86_64__ .br "# include " " /* definition of " "struct user_desc" " */" .pp .bi "int syscall(sys_get_thread_area, struct user_desc *" u_info ); .bi "int syscall(sys_set_thread_area, struct user_desc *" u_info ); .pp .b #elif defined __m68k__ .pp .b "int syscall(sys_get_thread_area);" .bi "int syscall(sys_set_thread_area, unsigned long " tp ); .pp .b #elif defined __mips__ .pp .bi "int syscall(sys_set_thread_area, unsigned long " addr ); .pp .b #endif .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description these calls provide architecture-specific support for a thread-local storage implementation. at the moment, .br set_thread_area () is available on m68k, mips, and x86 (both 32-bit and 64-bit variants); .br get_thread_area () is available on m68k and x86. .pp on m68k and mips, .br set_thread_area () allows storing an arbitrary pointer (provided in the .b tp argument on m68k and in the .b addr argument on mips) in the kernel data structure associated with the calling thread; this pointer can later be retrieved using .br get_thread_area () (see also notes for information regarding obtaining the thread pointer on mips). .pp on x86, linux dedicates three global descriptor table (gdt) entries for thread-local storage. for more information about the gdt, see the intel software developer's manual or the amd architecture programming manual. .pp both of these system calls take an argument that is a pointer to a structure of the following type: .pp .in +4n .ex struct user_desc { unsigned int entry_number; unsigned int base_addr; unsigned int limit; unsigned int seg_32bit:1; unsigned int contents:2; unsigned int read_exec_only:1; unsigned int limit_in_pages:1; unsigned int seg_not_present:1; unsigned int useable:1; #ifdef __x86_64__ unsigned int lm:1; #endif }; .ee .in .pp .br get_thread_area () reads the gdt entry indicated by .i u_info\->entry_number and fills in the rest of the fields in .ir u_info . .pp .br set_thread_area () sets a tls entry in the gdt. .pp the tls array entry set by .br set_thread_area () corresponds to the value of .i u_info\->entry_number passed in by the user. if this value is in bounds, .br set_thread_area () writes the tls descriptor pointed to by .i u_info into the thread's tls array. .pp when .br set_thread_area () is passed an .i entry_number of \-1, it searches for a free tls entry. if .br set_thread_area () finds a free tls entry, the value of .i u_info\->entry_number is set upon return to show which entry was changed. .pp a .i user_desc is considered "empty" if .i read_exec_only and .i seg_not_present are set to 1 and all of the other fields are 0. if an "empty" descriptor is passed to .br set_thread_area (), the corresponding tls entry will be cleared. see bugs for additional details. .pp since linux 3.19, .br set_thread_area () cannot be used to write non-present segments, 16-bit segments, or code segments, although clearing a segment is still acceptable. .sh return value on x86, these system calls return 0 on success, and \-1 on failure, with .i errno set to indicate the error. .pp on mips and m68k, .br set_thread_area () always returns 0. on m68k, .br get_thread_area () returns the thread area pointer value (previously set via .br set_thread_area ()). .sh errors .tp .b efault \fiu_info\fp is an invalid pointer. .tp .b einval \fiu_info\->entry_number\fp is out of bounds. .tp .b enosys .br get_thread_area () or .br set_thread_area () was invoked as a 64-bit system call. .tp .b esrch .rb ( set_thread_area ()) a free tls entry could not be located. .sh versions .br set_thread_area () first appeared in linux 2.5.29. .br get_thread_area () first appeared in linux 2.5.32. .sh conforming to .br set_thread_area () and .br get_thread_area () are linux-specific and should not be used in programs that are intended to be portable. .sh notes these system calls are generally intended for use only by threading libraries. .pp .br arch_prctl (2) can interfere with .br set_thread_area () on x86. see .br arch_prctl (2) for more details. this is not normally a problem, as .br arch_prctl (2) is normally used only by 64-bit programs. .pp on mips, the current value of the thread area pointer can be obtained using the instruction: .pp .in +4n .ex rdhwr dest, $29 .ee .in .pp this instruction traps and is handled by kernel. .sh bugs on 64-bit kernels before linux 3.19, .\" commit e30ab185c490e9a9381385529e0fd32f0a399495 one of the padding bits in .ir user_desc , if set, would prevent the descriptor from being considered empty (see .br modify_ldt (2)). as a result, the only reliable way to clear a tls entry is to use .br memset (3) to zero the entire .i user_desc structure, including padding bits, and then to set the .i read_exec_only and .i seg_not_present bits. on linux 3.19, a .i user_desc consisting entirely of zeros except for .i entry_number will also be interpreted as a request to clear a tls entry, but this behaved differently on older kernels. .pp prior to linux 3.19, the ds and es segment registers must not reference tls entries. .sh see also .br arch_prctl (2), .br modify_ldt (2), .br ptrace (2) .rb ( ptrace_get_thread_area " and " ptrace_set_thread_area ) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man2/sigsuspend.2 .\" copyright (c) markus kuhn, 1995, 2001 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1995-11-26 markus kuhn .\" first version written .\" 2001-05-11 markus kuhn .\" update .\" .th unicode 7 2021-03-22 "gnu" "linux programmer's manual" .sh name unicode \- universal character set .sh description the international standard iso 10646 defines the universal character set (ucs). ucs contains all characters of all other character set standards. it also guarantees "round-trip compatibility"; in other words, conversion tables can be built such that no information is lost when a string is converted from any other encoding to ucs and back. .pp ucs contains the characters required to represent practically all known languages. this includes not only the latin, greek, cyrillic, hebrew, arabic, armenian, and georgian scripts, but also chinese, japanese and korean han ideographs as well as scripts such as hiragana, katakana, hangul, devanagari, bengali, gurmukhi, gujarati, oriya, tamil, telugu, kannada, malayalam, thai, lao, khmer, bopomofo, tibetan, runic, ethiopic, canadian syllabics, cherokee, mongolian, ogham, myanmar, sinhala, thaana, yi, and others. for scripts not yet covered, research on how to best encode them for computer usage is still going on and they will be added eventually. this might eventually include not only hieroglyphs and various historic indo-european languages, but even some selected artistic scripts such as tengwar, cirth, and klingon. ucs also covers a large number of graphical, typographical, mathematical, and scientific symbols, including those provided by tex, postscript, apl, ms-dos, ms-windows, macintosh, ocr fonts, as well as many word processing and publishing systems, and more are being added. .pp the ucs standard (iso 10646) describes a 31-bit character set architecture consisting of 128 24-bit .ir groups , each divided into 256 16-bit .i planes made up of 256 8-bit .i rows with 256 .i column positions, one for each character. part 1 of the standard (iso 10646-1) defines the first 65534 code positions (0x0000 to 0xfffd), which form the .ir "basic multilingual plane" (bmp), that is plane 0 in group 0. part 2 of the standard (iso 10646-2) adds characters to group 0 outside the bmp in several .i "supplementary planes" in the range 0x10000 to 0x10ffff. there are no plans to add characters beyond 0x10ffff to the standard, therefore of the entire code space, only a small fraction of group 0 will ever be actually used in the foreseeable future. the bmp contains all characters found in the commonly used other character sets. the supplemental planes added by iso 10646-2 cover only more exotic characters for special scientific, dictionary printing, publishing industry, higher-level protocol and enthusiast needs. .pp the representation of each ucs character as a 2-byte word is referred to as the ucs-2 form (only for bmp characters), whereas ucs-4 is the representation of each character by a 4-byte word. in addition, there exist two encoding forms utf-8 for backward compatibility with ascii processing software and utf-16 for the backward-compatible handling of non-bmp characters up to 0x10ffff by ucs-2 software. .pp the ucs characters 0x0000 to 0x007f are identical to those of the classic us-ascii character set and the characters in the range 0x0000 to 0x00ff are identical to those in iso 8859-1 (latin-1). .ss combining characters some code points in ucs have been assigned to .ir "combining characters" . these are similar to the nonspacing accent keys on a typewriter. a combining character just adds an accent to the previous character. the most important accented characters have codes of their own in ucs, however, the combining character mechanism allows us to add accents and other diacritical marks to any character. the combining characters always follow the character which they modify. for example, the german character umlaut-a ("latin capital letter a with diaeresis") can either be represented by the precomposed ucs code 0x00c4, or alternatively as the combination of a normal "latin capital letter a" followed by a "combining diaeresis": 0x0041 0x0308. .pp combining characters are essential for instance for encoding the thai script or for mathematical typesetting and users of the international phonetic alphabet. .ss implementation levels as not all systems are expected to support advanced mechanisms like combining characters, iso 10646-1 specifies the following three .i implementation levels of ucs: .tp 0.9i level 1 combining characters and hangul jamo (a variant encoding of the korean script, where a hangul syllable glyph is coded as a triplet or pair of vowel/consonant codes) are not supported. .tp level 2 in addition to level 1, combining characters are now allowed for some languages where they are essential (e.g., thai, lao, hebrew, arabic, devanagari, malayalam). .tp level 3 all ucs characters are supported. .pp the unicode 3.0 standard published by the unicode consortium contains exactly the ucs basic multilingual plane at implementation level 3, as described in iso 10646-1:2000. unicode 3.1 added the supplemental planes of iso 10646-2. the unicode standard and technical reports published by the unicode consortium provide much additional information on the semantics and recommended usages of various characters. they provide guidelines and algorithms for editing, sorting, comparing, normalizing, converting, and displaying unicode strings. .ss unicode under linux under gnu/linux, the c type .i wchar_t is a signed 32-bit integer type. its values are always interpreted by the c library as ucs code values (in all locales), a convention that is signaled by the gnu c library to applications by defining the constant .b __stdc_iso_10646__ as specified in the iso c99 standard. .pp ucs/unicode can be used just like ascii in input/output streams, terminal communication, plaintext files, filenames, and environment variables in the ascii compatible utf-8 multibyte encoding. to signal the use of utf-8 as the character encoding to all applications, a suitable .i locale has to be selected via environment variables (e.g., "lang=en_gb.utf-8"). .pp the .b nl_langinfo(codeset) function returns the name of the selected encoding. library functions such as .br wctomb (3) and .br mbsrtowcs (3) can be used to transform the internal .i wchar_t characters and strings into the system character encoding and back and .br wcwidth (3) tells how many positions (0\(en2) the cursor is advanced by the output of a character. .ss private use areas (pua) in the basic multilingual plane, the range 0xe000 to 0xf8ff will never be assigned to any characters by the standard and is reserved for private usage. for the linux community, this private area has been subdivided further into the range 0xe000 to 0xefff which can be used individually by any end-user and the linux zone in the range 0xf000 to 0xf8ff where extensions are coordinated among all linux users. the registry of the characters assigned to the linux zone is maintained by lanana and the registry itself is .i documentation/admin\-guide/unicode.rst in the linux kernel sources .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/unicode.txt before linux 4.10). .pp two other planes are reserved for private usage, plane 15 (supplementary private use area-a, range 0xf0000 to 0xffffd) and plane 16 (supplementary private use area-b, range 0x100000 to 0x10fffd). .ss literature .ip * 3 information technology \(em universal multiple-octet coded character set (ucs) \(em part 1: architecture and basic multilingual plane. international standard iso/iec 10646-1, international organization for standardization, geneva, 2000. .ip this is the official specification of ucs. available from .ur http://www.iso.ch/ .ue . .ip * the unicode standard, version 3.0. the unicode consortium, addison-wesley, reading, ma, 2000, isbn 0-201-61633-5. .ip * s.\& harbison, g.\& steele. c: a reference manual. fourth edition, prentice hall, englewood cliffs, 1995, isbn 0-13-326224-3. .ip a good reference book about the c programming language. the fourth edition covers the 1994 amendment 1 to the iso c90 standard, which adds a large number of new c library functions for handling wide and multibyte character encodings, but it does not yet cover iso c99, which improved wide and multibyte character support even further. .ip * unicode technical reports. .rs .ur http://www.unicode.org\:/reports/ .ue .re .ip * markus kuhn: utf-8 and unicode faq for unix/linux. .rs .ur http://www.cl.cam.ac.uk\:/\(timgk25\:/unicode.html .ue .re .ip * bruno haible: unicode howto. .rs .ur http://www.tldp.org\:/howto\:/unicode\-howto.html .ue .re .\" .sh author .\" markus kuhn .sh see also .br locale (1), .br setlocale (3), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2015 william woodruff (william@tuffbizz.com) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th get_phys_pages 3 2021-03-22 "gnu" "linux programmer's manual" .sh name get_phys_pages, get_avphys_pages \- get total and available physical page counts .sh synopsis .nf .b "#include " .pp .b long get_phys_pages(void); .b long get_avphys_pages(void); .fi .sh description the function .br get_phys_pages () returns the total number of physical pages of memory available on the system. .pp the function .br get_avphys_pages () returns the number of currently available physical pages of memory on the system. .sh return value on success, these functions return a nonnegative value as given in description. on failure, they return \-1 and set .i errno to indicate the error. .sh errors .tp .b enosys the system could not provide the required information (possibly because the .i /proc filesystem was not mounted). .sh conforming to these functions are gnu extensions. .sh notes before glibc 2.23, these functions obtained the required information by scanning the .i memtotal and .i memfree fields of .ir /proc/meminfo . since glibc 2.23, these functions obtain the required information by calling .br sysinfo (2). .pp the following .br sysconf (3) calls provide a portable means of obtaining the same information as the functions described on this page. .pp .in +4n .ex total_pages = sysconf(_sc_phys_pages); /* total pages */ avl_pages = sysconf(_sc_avphys_pages); /* available pages */ .ee .in .sh examples the following example shows how .br get_phys_pages () and .br get_avphys_pages () can be used. .pp .ex #include #include #include int main(int argc, char *argv[]) { printf("this system has %ld pages of physical memory and " "%ld pages of physical memory available.\en", get_phys_pages(), get_avphys_pages()); exit(exit_success); } .ee .sh see also .br sysconf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ether_aton.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_read 3 2021-03-22 "" "linux programmer's manual" .sh name aio_read \- asynchronous read .sh synopsis .nf .b "#include " .pp .bi "int aio_read(struct aiocb *" aiocbp ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_read () function queues the i/o request described by the buffer pointed to by .ir aiocbp . this function is the asynchronous analog of .br read (2). the arguments of the call .pp read(fd, buf, count) .pp correspond (in order) to the fields .ir aio_fildes , .ir aio_buf , and .ir aio_nbytes of the structure pointed to by .ir aiocbp . (see .br aio (7) for a description of the .i aiocb structure.) .pp the data is read starting at the absolute position .ir aiocbp\->aio_offset , regardless of the file offset. after the call, the value of the file offset is unspecified. .pp the "asynchronous" means that this call returns as soon as the request has been enqueued; the read may or may not have completed when the call returns. one tests for completion using .br aio_error (3). the return status of a completed i/o operation can be obtained by .br aio_return (3). asynchronous notification of i/o completion can be obtained by setting .ir aiocbp\->aio_sigevent appropriately; see .br sigevent (7) for details. .pp if .b _posix_prioritized_io is defined, and this file supports it, then the asynchronous operation is submitted at a priority equal to that of the calling process minus .ir aiocbp\->aio_reqprio . .pp the field .i aiocbp\->aio_lio_opcode is ignored. .pp no data is read from a regular file beyond its maximum offset. .sh return value on success, 0 is returned. on error, the request is not enqueued, \-1 is returned, and .i errno is set to indicate the error. if an error is detected only later, it will be reported via .br aio_return (3) (returns status \-1) and .br aio_error (3) (error status\(emwhatever one would have gotten in .ir errno , such as .br ebadf ). .sh errors .tp .b eagain out of resources. .tp .b ebadf .i aio_fildes is not a valid file descriptor open for reading. .tp .b einval one or more of .ir aio_offset , .ir aio_reqprio , or .i aio_nbytes are invalid. .tp .b enosys .br aio_read () is not implemented. .tp .b eoverflow the file is a regular file, we start reading before end-of-file and want at least one byte, but the starting position is past the maximum offset for this file. .sh versions the .br aio_read () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_read () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes it is a good idea to zero out the control block before use. the control block must not be changed while the read operation is in progress. the buffer area being read into .\" or the control block of the operation must not be accessed during the operation or undefined results may occur. the memory areas involved must remain valid. .pp simultaneous i/o operations specifying the same .i aiocb structure produce undefined results. .sh examples see .br aio (7). .sh see also .br aio_cancel (3), .br aio_error (3), .br aio_fsync (3), .br aio_return (3), .br aio_suspend (3), .br aio_write (3), .br lio_listio (3), .br aio (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getpid 2 2021-03-22 "linux" "linux programmer's manual" .sh name getpid, getppid \- get process identification .sh synopsis .nf .b #include .pp .b pid_t getpid(void); .b pid_t getppid(void); .fi .sh description .br getpid () returns the process id (pid) of the calling process. (this is often used by routines that generate unique temporary filenames.) .pp .br getppid () returns the process id of the parent of the calling process. this will be either the id of the process that created this process using .br fork (), or, if that process has already terminated, the id of the process to which this process has been reparented (either .br init (1) or a "subreaper" process defined via the .br prctl (2) .br pr_set_child_subreaper operation). .sh errors these functions are always successful. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd, svr4. .sh notes if the caller's parent is in a different pid namespace (see .br pid_namespaces (7)), .br getppid () returns 0. .pp from a kernel perspective, the pid (which is shared by all of the threads in a multithreaded process) is sometimes also known as the thread group id (tgid). this contrasts with the kernel thread id (tid), which is unique for each thread. for further details, see .br gettid (2) and the discussion of the .br clone_thread flag in .br clone (2). .\" .ss c library/kernel differences from glibc version 2.3.4 up to and including version 2.24, the glibc wrapper function for .br getpid () cached pids, with the goal of avoiding additional system calls when a process calls .br getpid () repeatedly. normally this caching was invisible, but its correct operation relied on support in the wrapper functions for .br fork (2), .br vfork (2), and .br clone (2): if an application bypassed the glibc wrappers for these system calls by using .br syscall (2), then a call to .br getpid () in the child would return the wrong value (to be precise: it would return the pid of the parent process). .\" the following program demonstrates this "feature": .\" .\" #define _gnu_source .\" #include .\" #include .\" #include .\" #include .\" #include .\" #include .\" .\" int .\" main(int argc, char *argv[]) .\" { .\" /* the following statement fills the getpid() cache */ .\" .\" printf("parent pid = %ld\n", (intmax_t) getpid()); .\" .\" if (syscall(sys_fork) == 0) { .\" if (getpid() != syscall(sys_getpid)) .\" printf("child getpid() mismatch: getpid()=%jd; " .\" "syscall(sys_getpid)=%ld\n", .\" (intmax_t) getpid(), (long) syscall(sys_getpid)); .\" exit(exit_success); .\" } .\" wait(null); .\"} in addition, there were cases where .br getpid () could return the wrong value even when invoking .br clone (2) via the glibc wrapper function. (for a discussion of one such case, see bugs in .br clone (2).) furthermore, the complexity of the caching code had been the source of a few bugs within glibc over the years. .pp because of the aforementioned problems, since glibc version 2.25, the pid cache is removed: .\" commit c579f48edba88380635ab98cb612030e3ed8691e .\" https://sourceware.org/glibc/wiki/release/2.25#pid_cache_removal calls to .br getpid () always invoke the actual system call, rather than returning a cached value. .\" fixme . .\" review progress of https://bugzilla.redhat.com/show_bug.cgi?id=1469757 .pp on alpha, instead of a pair of .br getpid () and .br getppid () system calls, a single .br getxpid () system call is provided, which returns a pair of pid and parent pid. the glibc .br getpid () and .br getppid () wrapper functions transparently deal with this. see .br syscall (2) for details regarding register mapping. .sh see also .br clone (2), .br fork (2), .br gettid (2), .br kill (2), .br exec (3), .br mkstemp (3), .br tempnam (3), .br tmpfile (3), .br tmpnam (3), .br credentials (7), .br pid_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/access.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 17:52:15 1993 by rik faith (faith@cs.unc.edu) .\" modified 2001-12-15, aeb .th swab 3 2021-03-22 "" "linux programmer's manual" .sh name swab \- swap adjacent bytes .sh synopsis .nf .br "#define _xopen_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void swab(const void *restrict " from ", void *restrict " to \ ", ssize_t " n ); .fi .sh description the .br swab () function copies .i n bytes from the array pointed to by .i from to the array pointed to by .ir to , exchanging adjacent even and odd bytes. this function is used to exchange data between machines that have different low/high byte ordering. .pp this function does nothing when .i n is negative. when .i n is positive and odd, it handles .i n\-1 bytes as above, and does something unspecified with the last byte. (in other words, .i n should be even.) .sh return value the .br swab () function returns no value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br swab () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br bstring (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sched_getcpu 3 2021-03-22 "linux" "linux programmer's manual" .sh name sched_getcpu \- determine cpu on which the calling thread is running .sh synopsis .nf .b #include .pp .b int sched_getcpu(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sched_getcpu (): .nf since glibc 2.14: _gnu_source before glibc 2.14: _bsd_source || _svid_source /* _gnu_source also suffices */ .fi .sh description .br sched_getcpu () returns the number of the cpu on which the calling thread is currently executing. .sh return value on success, .br sched_getcpu () returns a nonnegative cpu number. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b enosys this kernel does not implement .br getcpu (2). .sh versions this function is available since glibc 2.6. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sched_getcpu () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br sched_getcpu () is glibc-specific. .sh notes the call .pp .in +4n .ex cpu = sched_getcpu(); .ee .in .pp is equivalent to the following .br getcpu (2) call: .pp .in +4n .ex int c, s; s = getcpu(&c, null, null); cpu = (s == \-1) ? s : c; .ee .in .sh see also .br getcpu (2), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getitimer.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wctype 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wctype \- wide-character classification .sh synopsis .nf .b #include .pp .bi "wctype_t wctype(const char *" name ); .fi .sh description the .i wctype_t type represents a property which a wide character may or may not have. in other words, it represents a class of wide characters. this type's nature is implementation-dependent, but the special value .i "(wctype_t) 0" denotes an invalid property. nonzero .i wctype_t values can be passed to the .br iswctype (3) function to actually test whether a given wide character has the property. .pp the .br wctype () function returns a property, given by its name. the set of valid names depends on the .b lc_ctype category of the current locale, but the following names are valid in all locales. .pp .nf "alnum" \- realizes the \fbisalnum\fp(3) classification function "alpha" \- realizes the \fbisalpha\fp(3) classification function "blank" \- realizes the \fbisblank\fp(3) classification function "cntrl" \- realizes the \fbiscntrl\fp(3) classification function "digit" \- realizes the \fbisdigit\fp(3) classification function "graph" \- realizes the \fbisgraph\fp(3) classification function "lower" \- realizes the \fbislower\fp(3) classification function "print" \- realizes the \fbisprint\fp(3) classification function "punct" \- realizes the \fbispunct\fp(3) classification function "space" \- realizes the \fbisspace\fp(3) classification function "upper" \- realizes the \fbisupper\fp(3) classification function "xdigit" \- realizes the \fbisxdigit\fp(3) classification function .fi .sh return value the .br wctype () function returns a property descriptor if the .i name is valid. otherwise, it returns .ir "(wctype_t) 0" . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wctype () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wctype () depends on the .b lc_ctype category of the current locale. .sh see also .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/libc.7 .so man3/fseeko.3 .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th matherr 3 2021-03-22 "linux" "linux programmer's manual" .sh name matherr \- svid math library exception handling .sh synopsis .nf .b #include .pp .bi "int matherr(struct exception *" exc ); .pp .b extern _lib_version_type _lib_version; .fi .pp link with \fi\-lm\fp. .sh description .ir note : the mechanism described in this page is no longer supported by glibc. before glibc 2.27, it had been marked as obsolete. since glibc 2.27, .\" glibc commit 813378e9fe17e029caf627cab76fe23eb46815fa the mechanism has been removed altogether. new applications should use the techniques described in .br math_error (7) and .br fenv (3). this page documents the .br matherr () mechanism as an aid for maintaining and porting older applications. .pp the system v interface definition (svid) specifies that various math functions should invoke a function called .br matherr () if a math exception is detected. this function is called before the math function returns; after .br matherr () returns, the system then returns to the math function, which in turn returns to the caller. .pp to employ .br matherr (), the programmer must define the .b _svid_source feature test macro (before including .i any header files), and assign the value .b _svid_ to the external variable .br _lib_version . .pp the system provides a default version of .br matherr (). this version does nothing, and returns zero (see below for the significance of this). the default .br matherr () can be overridden by a programmer-defined version, which will be invoked when an exception occurs. the function is invoked with one argument, a pointer to an .i exception structure, defined as follows: .pp .in +4n .ex struct exception { int type; /* exception type */ char *name; /* name of function causing exception */ double arg1; /* 1st argument to function */ double arg2; /* 2nd argument to function */ double retval; /* function return value */ } .ee .in .pp the .i type field has one of the following values: .tp 12 .b domain a domain error occurred (the function argument was outside the range for which the function is defined). the return value depends on the function; .i errno is set to .br edom . .tp .b sing a pole error occurred (the function result is an infinity). the return value in most cases is .b huge (the largest single precision floating-point number), appropriately signed. in most cases, .i errno is set to .br edom . .tp .b overflow an overflow occurred. in most cases, the value .b huge is returned, and .i errno is set to .br erange . .tp .b underflow an underflow occurred. 0.0 is returned, and .i errno is set to .br erange . .tp .b tloss total loss of significance. 0.0 is returned, and .i errno is set to .br erange . .tp .b ploss partial loss of significance. this value is unused on glibc (and many other systems). .pp the .i arg1 and .i arg2 fields are the arguments supplied to the function .ri ( arg2 is undefined for functions that take only one argument). .pp the .i retval field specifies the return value that the math function will return to its caller. the programmer-defined .br matherr () can modify this field to change the return value of the math function. .pp if the .br matherr () function returns zero, then the system sets .i errno as described above, and may print an error message on standard error (see below). .pp if the .br matherr () function returns a nonzero value, then the system does not set .ir errno , and doesn't print an error message. .ss math functions that employ matherr() the table below lists the functions and circumstances in which .br matherr () is called. the "type" column indicates the value assigned to .i exc\->type when calling .br matherr (). the "result" column is the default return value assigned to .ir exc\->retval . .pp the "msg?" and "errno" columns describe the default behavior if .br matherr () returns zero. if the "msg?" columns contains "y", then the system prints an error message on standard error. .pp the table uses the following notations and abbreviations: .pp .rs .ts l l. x first argument to function y second argument to function fin finite value for argument neg negative value for argument int integral value for argument o/f result overflowed u/f result underflowed |x| absolute value of x x_tloss is a constant defined in \fi\fp .te .re .\" details below from glibc 2.8's sysdeps/ieee754/k_standard.c .\" a subset of cases were test by experimental programs. .ts lb lb lb cb lb l l l c l. function type result msg? errno acos(|x|>1) domain huge y edom asin(|x|>1) domain huge y edom atan2(0,0) domain huge y edom acosh(x<1) domain nan y edom \" retval is 0.0/0.0 atanh(|x|>1) domain nan y edom \" retval is 0.0/0.0 atanh(|x|==1) sing (x>0.0)? y edom \" retval is x/0.0 \ \ huge_val : \ \ \-huge_val cosh(fin) o/f overflow huge n erange sinh(fin) o/f overflow (x>0.0) ? n erange \ \ huge : \-huge sqrt(x<0) domain 0.0 y edom hypot(fin,fin) o/f overflow huge n erange exp(fin) o/f overflow huge n erange exp(fin) u/f underflow 0.0 n erange exp2(fin) o/f overflow huge n erange exp2(fin) u/f underflow 0.0 n erange exp10(fin) o/f overflow huge n erange exp10(fin) u/f underflow 0.0 n erange j0(|x|>x_tloss) tloss 0.0 y erange j1(|x|>x_tloss) tloss 0.0 y erange jn(|x|>x_tloss) tloss 0.0 y erange y0(x>x_tloss) tloss 0.0 y erange y1(x>x_tloss) tloss 0.0 y erange yn(x>x_tloss) tloss 0.0 y erange y0(0) domain \-huge y edom y0(x<0) domain \-huge y edom y1(0) domain \-huge y edom y1(x<0) domain \-huge y edom yn(n,0) domain \-huge y edom yn(x<0) domain \-huge y edom lgamma(fin) o/f overflow huge n erange lgamma(\-int) or sing huge y edom \ \ lgamma(0) tgamma(fin) o/f overflow huge_val n erange tgamma(\-int) sing nan y edom tgamma(0) sing copysign( y erange \ \ huge_val,x) log(0) sing \-huge y edom log(x<0) domain \-huge y edom log2(0) sing \-huge n edom \" different from log() log2(x<0) domain \-huge n edom \" different from log() log10(0) sing \-huge y edom log10(x<0) domain \-huge y edom pow(0.0,0.0) domain 0.0 y edom pow(x,y) o/f overflow huge n erange pow(x,y) u/f underflow 0.0 n erange pow(nan,0.0) domain x n edom 0**neg domain 0.0 y edom \" +0 and -0 neg**non-int domain 0.0 y edom scalb() o/f overflow (x>0.0) ? n erange \ \ huge_val : \ \ \-huge_val scalb() u/f underflow copysign( n erange \ \ \ \ 0.0,x) fmod(x,0) domain x y edom remainder(x,0) domain nan y edom \" retval is 0.0/0.0 .te .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br matherr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh examples the example program demonstrates the use of .br matherr () when calling .br log (3). the program takes up to three command-line arguments. the first argument is the floating-point number to be given to .br log (3). if the optional second argument is provided, then .b _lib_version is set to .b _svid_ so that .br matherr () is called, and the integer supplied in the command-line argument is used as the return value from .br matherr (). if the optional third command-line argument is supplied, then it specifies an alternative return value that .br matherr () should assign as the return value of the math function. .pp the following example run, where .br log (3) is given an argument of 0.0, does not use .br matherr (): .pp .in +4n .ex .rb "$" " ./a.out 0.0" errno: numerical result out of range x=\-inf .ee .in .pp in the following run, .br matherr () is called, and returns 0: .pp .in +4n .ex .rb "$" " ./a.out 0.0 0" matherr sing exception in log() function args: 0.000000, 0.000000 retval: \-340282346638528859811704183484516925440.000000 log: sing error errno: numerical argument out of domain x=\-340282346638528859811704183484516925440.000000 .ee .in .pp the message "log: sing error" was printed by the c library. .pp in the following run, .br matherr () is called, and returns a nonzero value: .pp .in +4n .ex .rb "$" " ./a.out 0.0 1" matherr sing exception in log() function args: 0.000000, 0.000000 retval: \-340282346638528859811704183484516925440.000000 x=\-340282346638528859811704183484516925440.000000 .ee .in .pp in this case, the c library did not print a message, and .i errno was not set. .pp in the following run, .br matherr () is called, changes the return value of the math function, and returns a nonzero value: .pp .in +4n .ex .rb "$" " ./a.out 0.0 1 12345.0" matherr sing exception in log() function args: 0.000000, 0.000000 retval: \-340282346638528859811704183484516925440.000000 x=12345.000000 .ee .in .ss program source \& .ex #define _svid_source #include #include #include #include static int matherr_ret = 0; /* value that matherr() should return */ static int change_retval = 0; /* should matherr() change function\(aqs return value? */ static double new_retval; /* new function return value */ int matherr(struct exception *exc) { fprintf(stderr, "matherr %s exception in %s() function\en", (exc\->type == domain) ? "domain" : (exc\->type == overflow) ? "overflow" : (exc\->type == underflow) ? "underflow" : (exc\->type == sing) ? "sing" : (exc\->type == tloss) ? "tloss" : (exc\->type == ploss) ? "ploss" : "???", exc\->name); fprintf(stderr, " args: %f, %f\en", exc\->arg1, exc\->arg2); fprintf(stderr, " retval: %f\en", exc\->retval); if (change_retval) exc\->retval = new_retval; return matherr_ret; } int main(int argc, char *argv[]) { double x; if (argc < 2) { fprintf(stderr, "usage: %s " " [ []]\en", argv[0]); exit(exit_failure); } if (argc > 2) { _lib_version = _svid_; matherr_ret = atoi(argv[2]); } if (argc > 3) { change_retval = 1; new_retval = atof(argv[3]); } x = log(atof(argv[1])); if (errno != 0) perror("errno"); printf("x=%f\en", x); exit(exit_success); } .ee .sh see also .br fenv (3), .br math_error (7), .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th fputws 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fputws \- write a wide-character string to a file stream .sh synopsis .nf .b #include .pp .bi "int fputws(const wchar_t *restrict " ws ", file *restrict " stream ); .fi .sh description the .br fputws () function is the wide-character equivalent of the .br fputs (3) function. it writes the wide-character string starting at \fiws\fp, up to but not including the terminating null wide character (l\(aq\e0\(aq), to \fistream\fp. .pp for a nonlocking counterpart, see .br unlocked_stdio (3). .sh return value the .br fputws () function returns a nonnegative integer if the operation was successful, or \-1 to indicate an error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fputws () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br fputws () depends on the .b lc_ctype category of the current locale. .pp in the absence of additional information passed to the .br fopen (3) call, it is reasonable to expect that .br fputws () will actually write the multibyte string corresponding to the wide-character string \fiws\fp. .sh see also .br fputwc (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/get_robust_list.2 .so man3/atanh.3 .so man3/if_nametoindex.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .th cos 3 2021-03-22 "" "linux programmer's manual" .sh name cos, cosf, cosl \- cosine function .sh synopsis .nf .b #include .pp .bi "double cos(double " x ); .bi "float cosf(float " x ); .bi "long double cosl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br cosf (), .br cosl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the cosine of .ir x , where .i x is given in radians. .sh return value on success, these functions return the cosine of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity or negative infinity, a domain error occurs, and a nan is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is an infinity .i errno is set to .br edom (but see bugs). an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cos (), .br cosf (), .br cosl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh bugs before version 2.10, the glibc implementation did not set .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6780 .i errno to .b edom when a domain error occurred. .sh see also .br acos (3), .br asin (3), .br atan (3), .br atan2 (3), .br ccos (3), .br sin (3), .br sincos (3), .br tan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/abs.3 .so man3/xdr.3 .so man3/rpc.3 .so man3/cbrt.3 .\" copyright (c) 2014 marko myllynen .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iconvconfig 8 2021-08-27 "gnu" "linux system administration" .sh name iconvconfig \- create iconv module configuration cache .sh synopsis .b iconvconfig .ri [ options ] .ri [ directory ]... .sh description the .br iconv (3) function internally uses .i gconv modules to convert to and from a character set. a configuration file is used to determine the needed modules for a conversion. loading and parsing such a configuration file would slow down programs that use .br iconv (3), so a caching mechanism is employed. .pp the .b iconvconfig program reads iconv module configuration files and writes a fast-loading gconv module configuration cache file. .pp in addition to the system provided gconv modules, the user can specify custom gconv module directories with the environment variable .br gconv_path . however, iconv module configuration caching is used only when the environment variable .br gconv_path is not set. .sh options .tp .b "\-\-nostdlib" do not search the system default gconv directory, only the directories provided on the command line. .tp .bi \-o " outputfile" ", \-\-output=" outputfile use .i outputfile for output instead of the system default cache location. .tp .bi \-\-prefix= pathname set the prefix to be prepended to the system pathnames. see files, below. by default, the prefix is empty. setting the prefix to .ir foo , the gconv module configuration would be read from .ir foo/usr/lib/gconv/gconv\-modules and the cache would be written to .ir foo/usr/lib/gconv/gconv\-modules.cache . .tp .br \-? ", " \-\-help print a usage summary and exit. .tp .b "\-\-usage" print a short usage summary and exit. .tp .br \-v ", " \-\-version print the version number, license, and disclaimer of warranty for .br iconv . .sh exit status zero on success, nonzero on errors. .sh files .tp .i /usr/lib/gconv usual default gconv module path. .tp .i /usr/lib/gconv/gconv\-modules usual system default gconv module configuration file. .tp .i /usr/lib/gconv/gconv\-modules.cache usual system gconv module configuration cache. .pp depending on the architecture, the above files may instead be located at directories with the path prefix .ir /usr/lib64 . .sh see also .br iconv (1), .br iconv (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/stat.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified sat jul 24 19:22:14 1993 by rik faith (faith@cs.unc.edu) .\" modified mon may 27 21:37:47 1996 by martin schulze (joey@linux.de) .\" .th getpwent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getpwent, setpwent, endpwent \- get password file entry .sh synopsis .nf .b #include .b #include .pp .b struct passwd *getpwent(void); .b void setpwent(void); .b void endpwent(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getpwent (), .br setpwent (), .br endpwent (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br getpwent () function returns a pointer to a structure containing the broken-out fields of a record from the password database (e.g., the local password file .ir /etc/passwd , nis, and ldap). the first time .br getpwent () is called, it returns the first entry; thereafter, it returns successive entries. .pp the .br setpwent () function rewinds to the beginning of the password database. .pp the .br endpwent () function is used to close the password database after all processing has been performed. .pp the \fipasswd\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct passwd { char *pw_name; /* username */ char *pw_passwd; /* user password */ uid_t pw_uid; /* user id */ gid_t pw_gid; /* group id */ char *pw_gecos; /* user information */ char *pw_dir; /* home directory */ char *pw_shell; /* shell program */ }; .ee .in .pp for more information about the fields of this structure, see .br passwd (5). .sh return value the .br getpwent () function returns a pointer to a .i passwd structure, or null if there are no more entries or an error occurred. if an error occurs, .i errno is set to indicate the error. if one wants to check .i errno after the call, it should be set to zero before the call. .pp the return value may point to a static area, and may be overwritten by subsequent calls to .br getpwent (), .br getpwnam (3), or .br getpwuid (3). (do not pass the returned pointer to .br free (3).) .sh errors .tp .b eintr a signal was caught; see .br signal (7). .tp .b eio i/o error. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enomem .\" not in posix insufficient memory to allocate .i passwd structure. .\" to allocate the passwd structure, or to allocate buffers .tp .b erange insufficient buffer space supplied. .sh files .tp .i /etc/passwd local password database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getpwent () t} thread safety t{ mt-unsafe race:pwent race:pwentbuf locale t} t{ .br setpwent (), .br endpwent () t} thread safety t{ mt-unsafe race:pwent locale t} .te .hy .ad .sp 1 in the above table, .i pwent in .i race:pwent signifies that if any of the functions .br setpwent (), .br getpwent (), or .br endpwent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. the .i pw_gecos field is not specified in posix, but is present on most implementations. .sh see also .br fgetpwent (3), .br getpw (3), .br getpwent_r (3), .br getpwnam (3), .br getpwuid (3), .br putpwent (3), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 1995 michael chastain (mec@shell.portal.com), 15 april 1995. .\" and copyright (c) 2014, 2016 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1997-01-31 by eric s. raymond .\" modified 1997-07-30 by paul slootman .\" modified 2004-05-27 by michael kerrisk .\" .th adjtimex 2 2021-03-22 "linux" "linux programmer's manual" .sh name adjtimex, clock_adjtime, ntp_adjtime \- tune kernel clock .sh synopsis .nf .b #include .pp .bi "int adjtimex(struct timex *" "buf" ); .pp .bi "int clock_adjtime(clockid_t " clk_id, " struct timex *" "buf" ); .pp .bi "int ntp_adjtime(struct timex *" buf ); .fi .sh description linux uses david l.\& mills' clock adjustment algorithm (see rfc\ 5905). the system call .br adjtimex () reads and optionally sets adjustment parameters for this algorithm. it takes a pointer to a .i timex structure, updates kernel parameters from (selected) field values, and returns the same structure updated with the current kernel values. this structure is declared as follows: .pp .in +4n .ex struct timex { int modes; /* mode selector */ long offset; /* time offset; nanoseconds, if sta_nano status flag is set, otherwise microseconds */ long freq; /* frequency offset; see notes for units */ long maxerror; /* maximum error (microseconds) */ long esterror; /* estimated error (microseconds) */ int status; /* clock command/status */ long constant; /* pll (phase\-locked loop) time constant */ long precision; /* clock precision (microseconds, read\-only) */ long tolerance; /* clock frequency tolerance (read\-only); see notes for units */ struct timeval time; /* current time (read\-only, except for adj_setoffset); upon return, time.tv_usec contains nanoseconds, if sta_nano status flag is set, otherwise microseconds */ long tick; /* microseconds between clock ticks */ long ppsfreq; /* pps (pulse per second) frequency (read\-only); see notes for units */ long jitter; /* pps jitter (read\-only); nanoseconds, if sta_nano status flag is set, otherwise microseconds */ int shift; /* pps interval duration (seconds, read\-only) */ long stabil; /* pps stability (read\-only); see notes for units */ long jitcnt; /* pps count of jitter limit exceeded events (read\-only) */ long calcnt; /* pps count of calibration intervals (read\-only) */ long errcnt; /* pps count of calibration errors (read\-only) */ long stbcnt; /* pps count of stability limit exceeded events (read\-only) */ int tai; /* tai offset, as set by previous adj_tai operation (seconds, read\-only, since linux 2.6.26) */ /* further padding bytes to allow for future expansion */ }; .ee .in .pp the .i modes field determines which parameters, if any, to set. (as described later in this page, the constants used for .br ntp_adjtime () are equivalent but differently named.) it is a bit mask containing a .ri bitwise- or combination of zero or more of the following bits: .tp .br adj_offset set time offset from .ir buf.offset . since linux 2.6.26, .\" commit 074b3b87941c99bc0ce35385b5817924b1ed0c23 the supplied value is clamped to the range (\-0.5s, +0.5s). in older kernels, an .b einval error occurs if the supplied value is out of range. .tp .br adj_frequency set frequency offset from .ir buf.freq . since linux 2.6.26, .\" commit 074b3b87941c99bc0ce35385b5817924b1ed0c23 the supplied value is clamped to the range (\-32768000, +32768000). in older kernels, an .b einval error occurs if the supplied value is out of range. .tp .br adj_maxerror set maximum time error from .ir buf.maxerror . .tp .br adj_esterror set estimated time error from .ir buf.esterror . .tp .br adj_status set clock status bits from .ir buf.status . a description of these bits is provided below. .tp .br adj_timeconst set pll time constant from .ir buf.constant . if the .b sta_nano status flag (see below) is clear, the kernel adds 4 to this value. .tp .br adj_setoffset " (since linux 2.6.39)" .\" commit 094aa1881fdc1b8889b442eb3511b31f3ec2b762 .\" author: richard cochran add .i buf.time to the current time. if .i buf.status includes the .b adj_nano flag, then .i buf.time.tv_usec is interpreted as a nanosecond value; otherwise it is interpreted as microseconds. .ip the value of .i buf.time is the sum of its two fields, but the field .i buf.time.tv_usec must always be nonnegative. the following example shows how to normalize a .i timeval with nanosecond resolution. .ip .in +4n .ex while (buf.time.tv_usec < 0) { buf.time.tv_sec \-= 1; buf.time.tv_usec += 1000000000; } .ee .in .tp .br adj_micro " (since linux 2.6.26)" .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" author: roman zippel select microsecond resolution. .tp .br adj_nano " (since linux 2.6.26)" .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" author: roman zippel select nanosecond resolution. only one of .br adj_micro and .br adj_nano should be specified. .tp .br adj_tai " (since linux 2.6.26)" .\" commit 153b5d054ac2d98ea0d86504884326b6777f683d set tai (atomic international time) offset from .ir buf.constant . .ip .br adj_tai should not be used in conjunction with .br adj_timeconst , since the latter mode also employs the .ir buf.constant field. .ip for a complete explanation of tai and the difference between tai and utc, see .ur http://www.bipm.org/en/bipm/tai/tai.html .i bipm .ue .tp .br adj_tick set tick value from .ir buf.tick . .pp alternatively, .i modes can be specified as either of the following (multibit mask) values, in which case other bits should not be specified in .ir modes : .\" in general, the other bits are ignored, but adj_offset_singleshot 0x8001 .\" ored with adj_nano (0x2000) gives 0xa0001 == adj_offset_ss_read!! .tp .br adj_offset_singleshot .\" in user space, adj_offset_singleshot is 0x8001 .\" in kernel space it is 0x0001, and must be anded with adj_adjtime (0x8000) old-fashioned .br adjtime (3): (gradually) adjust time by value specified in .ir buf.offset , which specifies an adjustment in microseconds. .tp .br adj_offset_ss_read " (functional since linux 2.6.28)" .\" in user space, adj_offset_ss_read is 0xa001 .\" in kernel space there is adj_offset_readonly (0x2000) anded with .\" adj_adjtime (0x8000) and adj_offset_singleshot (0x0001) to give 0xa001) return (in .ir buf.offset ) the remaining amount of time to be adjusted after an earlier .br adj_offset_singleshot operation. this feature was added in linux 2.6.24, .\" commit 52bfb36050c8529d9031d2c2513b281a360922ec but did not work correctly .\" commit 916c7a855174e3b53d182b97a26b2e27a29726a1 until linux 2.6.28. .pp ordinary users are restricted to a value of either 0 or .b adj_offset_ss_read for .ir modes . only the superuser may set any parameters. .pp the .i buf.status field is a bit mask that is used to set and/or retrieve status bits associated with the ntp implementation. some bits in the mask are both readable and settable, while others are read-only. .tp .br sta_pll " (read-write)" enable phase-locked loop (pll) updates via .br adj_offset . .tp .br sta_ppsfreq " (read-write)" enable pps (pulse-per-second) frequency discipline. .tp .br sta_ppstime " (read-write)" enable pps time discipline. .tp .br sta_fll " (read-write)" select frequency-locked loop (fll) mode. .tp .br sta_ins " (read-write)" insert a leap second after the last second of the utc day, thus extending the last minute of the day by one second. leap-second insertion will occur each day, so long as this flag remains set. .\" john stultz; .\" usually this is written as extending the day by one second, .\" which is represented as: .\" 23:59:59 .\" 23:59:60 .\" 00:00:00 .\" .\" but since posix cannot represent 23:59:60, we repeat the last second: .\" 23:59:59 + time_ins .\" 23:59:59 + time_oop .\" 00:00:00 + time_wait .\" .tp .br sta_del " (read-write)" delete a leap second at the last second of the utc day. .\" john stultz: .\" similarly the progression here is: .\" 23:59:57 + time_del .\" 23:59:58 + time_del .\" 00:00:00 + time_wait leap second deletion will occur each day, so long as this flag remains set. .\" fixme does there need to be a statement that it is nonsensical to set .\" to set both sta_ins and sta_del? .tp .br sta_unsync " (read-write)" clock unsynchronized. .tp .br sta_freqhold " (read-write)" hold frequency. .\" following text from john stultz: normally adjustments made via .b adj_offset result in dampened frequency adjustments also being made. so a single call corrects the current offset, but as offsets in the same direction are made repeatedly, the small frequency adjustments will accumulate to fix the long-term skew. .ip this flag prevents the small frequency adjustment from being made when correcting for an .b adj_offset value. .\" according to the kernel application program interface document, .\" sta_freqhold is not used by the ntp version 4 daemon .tp .br sta_ppssignal " (read-only)" a valid pps (pulse-per-second) signal is present. .tp .br sta_ppsjitter " (read-only)" pps signal jitter exceeded. .tp .br sta_ppswander " (read-only)" pps signal wander exceeded. .tp .br sta_ppserror " (read-only)" pps signal calibration error. .tp .br sta_clockerr " (read-only)" clock hardware fault. .\" not set in current kernel (4.5), but checked in a few places .tp .br sta_nano " (read-only; since linux 2.6.26)" .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" author: roman zippel resolution (0 = microsecond, 1 = nanoseconds). set via .br adj_nano , cleared via .br adj_micro . .tp .br sta_mode " (since linux 2.6.26)" .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" author: roman zippel mode (0 = phase locked loop, 1 = frequency locked loop). .tp .br sta_clk " (read-only; since linux 2.6.26)" .\" commit eea83d896e318bda54be2d2770d2c5d6668d11db .\" author: roman zippel clock source (0 = a, 1 = b); currently unused. .pp attempts to set read-only .i status bits are silently ignored. .\" .ss clock_adjtime () the .br clock_adjtime () system call (added in linux 2.6.39) behaves like .br adjtimex () but takes an additional .ir clk_id argument to specify the particular clock on which to act. .ss ntp_adjtime () the .br ntp_adjtime () library function (described in the ntp "kernel application program api", kapi) is a more portable interface for performing the same task as .br adjtimex (). other than the following points, it is identical to .br adjtimex (): .ip * 3 the constants used in .i modes are prefixed with "mod_" rather than "adj_", and have the same suffixes (thus, .br mod_offset , .br mod_frequency , and so on), other than the exceptions noted in the following points. .ip * .br mod_clka is the synonym for .br adj_offset_singleshot . .ip * .br mod_clkb is the synonym for .br adj_tick . .ip * the is no synonym for .br adj_offset_ss_read , which is not described in the kapi. .sh return value on success, .br adjtimex () and .br ntp_adjtime () return the clock state; that is, one of the following values: .tp 12 .br time_ok clock synchronized, no leap second adjustment pending. .tp .br time_ins indicates that a leap second will be added at the end of the utc day. .tp .br time_del indicates that a leap second will be deleted at the end of the utc day. .tp .br time_oop insertion of a leap second is in progress. .tp .br time_wait a leap-second insertion or deletion has been completed. this value will be returned until the next .br adj_status operation clears the .b sta_ins and .b sta_del flags. .tp .br time_error the system clock is not synchronized to a reliable server. this value is returned when any of the following holds true: .rs .ip * 3 either .b sta_unsync or .b sta_clockerr is set. .ip * .b sta_ppssignal is clear and either .b sta_ppsfreq or .b sta_ppstime is set. .ip * .b sta_ppstime and .b sta_ppsjitter are both set. .ip * .b sta_ppsfreq is set and either .b sta_ppswander or .b sta_ppsjitter is set. .re .ip the symbolic name .b time_bad is a synonym for .br time_error , provided for backward compatibility. .pp note that starting with linux 3.4, .\" commit 6b43ae8a619d17c4935c3320d2ef9e92bdeed05d changed to asynchronous .\" operation, so we can no longer rely on the return code. the call operates asynchronously and the return value usually will not reflect a state change caused by the call itself. .pp on failure, these calls return \-1 and set .ir errno to indicate the error. .sh errors .tp .b efault .i buf does not point to writable memory. .tp .br einval " (kernels before linux 2.6.26)" an attempt was made to set .i buf.freq to a value outside the range (\-33554432, +33554432). .\" from a quick glance, it appears there was no clamping or range check .\" for buf.freq in kernels before 2.0 .tp .br einval " (kernels before linux 2.6.26)" an attempt was made to set .i buf.offset to a value outside the permitted range. in kernels before linux 2.0, the permitted range was (\-131072, +131072). from linux 2.0 onwards, the permitted range was (\-512000, +512000). .tp .b einval an attempt was made to set .i buf.status to a value other than those listed above. .tp .b einval the .i clk_id given to .br clock_adjtime () is invalid for one of two reasons. either the system-v style hard-coded positive clock id value is out of range, or the dynamic .i clk_id does not refer to a valid instance of a clock object. see .br clock_gettime (2) for a discussion of dynamic clocks. .tp .b einval an attempt was made to set .i buf.tick to a value outside the range .rb 900000/ hz to .rb 1100000/ hz , where .b hz is the system timer interrupt frequency. .tp .b enodev the hot-pluggable device (like usb for example) represented by a dynamic .i clk_id has disappeared after its character device was opened. see .br clock_gettime (2) for a discussion of dynamic clocks. .tp .b eopnotsupp the given .i clk_id does not support adjustment. .tp .b eperm .i buf.modes is neither 0 nor .br adj_offset_ss_read , and the caller does not have sufficient privilege. under linux, the .b cap_sys_time capability is required. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ntp_adjtime () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to none of these interfaces is described in posix.1 .pp .br adjtimex () and .br clock_adjtime () are linux-specific and should not be used in programs intended to be portable. .pp the preferred api for the ntp daemon is .br ntp_adjtime (). .sh notes in struct .ir timex , .ir freq , .ir ppsfreq , and .i stabil are ppm (parts per million) with a 16-bit fractional part, which means that a value of 1 in one of those fields actually means 2^-16 ppm, and 2^16=65536 is 1 ppm. this is the case for both input values (in the case of .ir freq ) and output values. .pp the leap-second processing triggered by .b sta_ins and .b sta_del is done by the kernel in timer context. thus, it will take one tick into the second for the leap second to be inserted or deleted. .sh see also .br clock_gettime (2), .br clock_settime (2), .br settimeofday (2), .br adjtime (3), .br ntp_gettime (3), .br capabilities (7), .br time (7), .br adjtimex (8), .br hwclock (8) .pp .ad l .ur http://www.slac.stanford.edu/comp/unix/\:package/\:rtems/\:src/\:ssrlapps/\:ntpnanoclock/\:api.htm ntp "kernel application program interface" .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rcmd.3 .so man2/fstatat.2 .so man3/slist.3 .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th malloc_get_state 3 2021-03-22 "gnu" "linux programmer's manual" .sh name malloc_get_state, malloc_set_state \- record and restore state of malloc implementation .sh synopsis .nf .b #include .pp .bi "void *malloc_get_state(void);" .bi "int malloc_set_state(void *" state ); .fi .sh description .ir note : these function are removed in glibc version 2.25. .pp the .br malloc_get_state () function records the current state of all .br malloc (3) internal bookkeeping variables (but not the actual contents of the heap or the state of .br malloc_hook (3) functions pointers). the state is recorded in a system-dependent opaque data structure dynamically allocated via .br malloc (3), and a pointer to that data structure is returned as the function result. (it is the caller's responsibility to .br free (3) this memory.) .pp the .br malloc_set_state () function restores the state of all .br malloc (3) internal bookkeeping variables to the values recorded in the opaque data structure pointed to by .ir state . .sh return value on success, .br malloc_get_state () returns a pointer to a newly allocated opaque data structure. on error (for example, memory could not be allocated for the data structure), .br malloc_get_state () returns null. .pp on success, .br malloc_set_state () returns 0. if the implementation detects that .i state does not point to a correctly formed data structure, .\" if(ms->magic != malloc_state_magic) return -1; .br malloc_set_state () returns \-1. if the implementation detects that the version of the data structure referred to by .i state is a more recent version than this implementation knows about, .\" /* must fail if the major version is too high. */ .\" if((ms->version & ~0xffl) > (malloc_state_version & ~0xffl)) return -2; .br malloc_set_state () returns \-2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br malloc_get_state (), .br malloc_set_state () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. .sh notes these functions are useful when using this .br malloc (3) implementation as part of a shared library, and the heap contents are saved/restored via some other method. this technique is used by gnu emacs to implement its "dumping" function. .pp hook function pointers are never saved or restored by these functions, with two exceptions: if malloc checking (see .br mallopt (3)) was in use when .br malloc_get_state () was called, then .br malloc_set_state () resets malloc checking hooks .\" i.e., calls __malloc_check_init() if possible; .\" i.e., malloc checking is not already in use .\" and the caller requested malloc checking if malloc checking was not in use in the recorded state, but the caller has requested malloc checking, then the hooks are reset to 0. .sh see also .br malloc (3), .br mallopt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswlower 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswlower \- test for lowercase wide character .sh synopsis .nf .b #include .pp .bi "int iswlower(wint_t " wc ); .fi .sh description the .br iswlower () function is the wide-character equivalent of the .br islower (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "lower". .pp the wide-character class "lower" is a subclass of the wide-character class "alpha", and therefore also a subclass of the wide-character class "alnum", of the wide-character class "graph" and of the wide-character class "print". .pp being a subclass of the wide-character class "print", the wide-character class "lower" is disjoint from the wide-character class "cntrl". .pp being a subclass of the wide-character class "graph", the wide-character class "lower" is disjoint from the wide-character class "space" and its subclass "blank". .pp being a subclass of the wide-character class "alnum", the wide-character class "lower" is disjoint from the wide-character class "punct". .pp being a subclass of the wide-character class "alpha", the wide-character class "lower" is disjoint from the wide-character class "digit". .pp the wide-character class "lower" contains at least those characters .i wc which are equal to .i towlower(wc) and different from .ir towupper(wc) . .pp the wide-character class "lower" always contains at least the letters \(aqa\(aq to \(aqz\(aq. .sh return value the .br iswlower () function returns nonzero if .i wc is a wide character belonging to the wide-character class "lower". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswlower () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswlower () depends on the .b lc_ctype category of the current locale. .pp this function is not very appropriate for dealing with unicode characters, because unicode knows about three cases: upper, lower, and title case. .sh see also .br islower (3), .br iswctype (3), .br towlower (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2004, 2006, 2007, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-21 rik faith (faith@cs.unc.edu) .\" modified 1994-08-21 by michael chastain (mec@shell.portal.com): .\" removed note about old kernel (pre-1.1.44) using wrong id on path. .\" modified 1996-03-18 by martin schulze (joey@infodrom.north.de): .\" stated more clearly how it behaves with symbolic links. .\" added correction due to nick duffek (nsd@bbc.com), aeb, 960426 .\" modified 1996-09-07 by michael haardt: .\" restrictions for nfs .\" modified 1997-09-09 by joseph s. myers .\" modified 1998-01-13 by michael haardt: .\" using access is often insecure .\" modified 2001-10-16 by aeb .\" modified 2002-04-23 by roger luethi .\" modified 2004-06-23 by michael kerrisk .\" 2007-06-10, mtk, various parts rewritten, and added bugs section. .\" .th access 2 2021-08-27 "linux" "linux programmer's manual" .sh name access, faccessat, faccessat2 \- check user's permissions for a file .sh synopsis .nf .b #include .pp .bi "int access(const char *" pathname ", int " mode ); .pp .br "#include " " /* definition of " at_* " constants */" .b #include .pp .bi "int faccessat(int " dirfd ", const char *" pathname ", int " \ mode ", int " flags ); /* but see c library/kernel differences, below */ .pp .br "#include " " /* definition of " at_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_faccessat2," .bi " int " dirfd ", const char *" pathname ", int " mode \ ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br faccessat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br access () checks whether the calling process can access the file .ir pathname . if .i pathname is a symbolic link, it is dereferenced. .pp the .i mode specifies the accessibility check(s) to be performed, and is either the value .br f_ok , .\" f_ok is defined as 0 on every system that i know of. or a mask consisting of the bitwise or of one or more of .br r_ok ", " w_ok ", and " x_ok . .b f_ok tests for the existence of the file. .br r_ok ", " w_ok ", and " x_ok test whether the file exists and grants read, write, and execute permissions, respectively. .pp the check is done using the calling process's .i real uid and gid, rather than the effective ids as is done when actually attempting an operation (e.g., .br open (2)) on the file. similarly, for the root user, the check uses the set of permitted capabilities rather than the set of effective capabilities; and for non-root users, the check uses an empty set of capabilities. .pp this allows set-user-id programs and capability-endowed programs to easily determine the invoking user's authority. in other words, .br access () does not answer the "can i read/write/execute this file?" question. it answers a slightly different question: "(assuming i'm a setuid binary) can .i the user who invoked me read/write/execute this file?", which gives set-user-id programs the possibility to prevent malicious users from causing them to read files which users shouldn't be able to read. .pp if the calling process is privileged (i.e., its real uid is zero), then an .b x_ok check is successful for a regular file if execute permission is enabled for any of the file owner, group, or other. .ss faccessat() .br faccessat () operates in exactly the same way as .br access (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br access () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br access ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp .i flags is constructed by oring together zero or more of the following values: .tp .b at_eaccess perform access checks using the effective user and group ids. by default, .br faccessat () uses the real ids (like .br access ()). .tp .b at_symlink_nofollow if .i pathname is a symbolic link, do not dereference it: instead return information about the link itself. .pp see .br openat (2) for an explanation of the need for .br faccessat (). .\" .ss faccessat2() the description of .br faccessat () given above corresponds to posix.1 and to the implementation provided by glibc. however, the glibc implementation was an imperfect emulation (see bugs) that papered over the fact that the raw linux .br faccessat () system call does not have a .i flags argument. to allow for a proper implementation, linux 5.8 added the .br faccessat2 () system call, which supports the .i flags argument and allows a correct implementation of the .br faccessat () wrapper function. .sh return value on success (all requested permissions granted, or .i mode is .b f_ok and the file exists), zero is returned. on error (at least one bit in .i mode asked for a permission that is denied, or .i mode is .b f_ok and the file does not exist, or some other error occurred), \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces the requested access would be denied to the file, or search permission is denied for one of the directories in the path prefix of .ir pathname . (see also .br path_resolution (7).) .tp .b ebadf .rb ( faccessat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd .rb ( faccessat ()) nor a valid file descriptor. .tp .b efault .i pathname points outside your accessible address space. .tp .b einval .i mode was incorrectly specified. .tp .b einval .rb ( faccessat ()) invalid flag specified in .ir flags . .tp .b eio an i/o error occurred. .tp .b eloop too many symbolic links were encountered in resolving .ir pathname . .tp .b enametoolong .i pathname is too long. .tp .b enoent a component of .i pathname does not exist or is a dangling symbolic link. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component used as a directory in .i pathname is not, in fact, a directory. .tp .b enotdir .rb ( faccessat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b erofs write permission was requested for a file on a read-only filesystem. .tp .b etxtbsy write access was requested to an executable which is being executed. .sh versions .br faccessat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .pp .br faccessat2 () was added to linux in version 5.8. .sh conforming to .br access (): svr4, 4.3bsd, posix.1-2001, posix.1-2008. .pp .br faccessat (): posix.1-2008. .pp .br faccessat2 (): linux-specific. .sh notes .br warning : using these calls to check if a user is authorized to, for example, open a file before actually doing so using .br open (2) creates a security hole, because the user might exploit the short time interval between checking and opening the file to manipulate it. .br "for this reason, the use of this system call should be avoided" . (in the example just described, a safer alternative would be to temporarily switch the process's effective user id to the real id and then call .br open (2).) .pp .br access () always dereferences symbolic links. if you need to check the permissions on a symbolic link, use .br faccessat () with the flag .br at_symlink_nofollow . .pp these calls return an error if any of the access types in .i mode is denied, even if some of the other access types in .i mode are permitted. .pp if the calling process has appropriate privileges (i.e., is superuser), posix.1-2001 permits an implementation to indicate success for an .b x_ok check even if none of the execute file permission bits are set. .\" hpu-ux 11 and tru64 5.1 do this. linux does not do this. .pp a file is accessible only if the permissions on each of the directories in the path prefix of .i pathname grant search (i.e., execute) access. if any directory is inaccessible, then the .br access () call fails, regardless of the permissions on the file itself. .pp only access bits are checked, not the file type or contents. therefore, if a directory is found to be writable, it probably means that files can be created in the directory, and not that the directory can be written as a file. similarly, a dos file may be reported as executable, but the .br execve (2) call will still fail. .pp these calls may not work correctly on nfsv2 filesystems with uid mapping enabled, because uid mapping is done on the server and hidden from the client, which checks permissions. (nfs versions 3 and higher perform the check on the server.) similar problems can occur to fuse mounts. .\" .\" .ss c library/kernel differences the raw .br faccessat () system call takes only the first three arguments. the .b at_eaccess and .b at_symlink_nofollow flags are actually implemented within the glibc wrapper function for .br faccessat (). if either of these flags is specified, then the wrapper function employs .br fstatat (2) to determine access permissions, but see bugs. .\" .ss glibc notes on older kernels where .br faccessat () is unavailable (and when the .b at_eaccess and .b at_symlink_nofollow flags are not specified), the glibc wrapper function falls back to the use of .br access (). when .i pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir dirfd argument. .sh bugs because the linux kernel's .br faccessat () system call does not support a .i flags argument, the glibc .br faccessat () wrapper function provided in glibc 2.32 and earlier emulates the required functionality using a combination of the .br faccessat () system call and .br fstatat (2). however, this emulation does not take acls into account. starting with glibc 2.33, the wrapper function avoids this bug by making use of the .br faccessat2 () system call where it is provided by the underlying kernel. .pp in kernel 2.4 (and earlier) there is some strangeness in the handling of .b x_ok tests for superuser. if all categories of execute permission are disabled for a nondirectory file, then the only .br access () test that returns \-1 is when .i mode is specified as just .br x_ok ; if .b r_ok or .b w_ok is also specified in .ir mode , then .br access () returns 0 for such files. .\" this behavior appears to have been an implementation accident. early 2.6 kernels (up to and including 2.6.3) also behaved in the same way as kernel 2.4. .pp in kernels before 2.6.20, these calls ignored the effect of the .b ms_noexec flag if it was used to .br mount (2) the underlying filesystem. since kernel 2.6.20, the .b ms_noexec flag is honored. .sh see also .br chmod (2), .br chown (2), .br open (2), .br setgid (2), .br setuid (2), .br stat (2), .br euidaccess (3), .br credentials (7), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" written by ivana varekova .\" and copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" fixme something could be added to this page (or exit(2)) .\" about exit_robust_list processing .\" .th get_robust_list 2 2021-03-22 linux "linux system calls" .sh name get_robust_list, set_robust_list \- get/set list of robust futexes .sh synopsis .nf .br "#include " \ " /* definition of " "struct robust_list_head" " */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(sys_get_robust_list, int " pid , .bi " struct robust_list_head **" head_ptr ", size_t *" len_ptr ); .bi "long syscall(sys_set_robust_list," .bi " struct robust_list_head *" head ", size_t " len ); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description these system calls deal with per-thread robust futex lists. these lists are managed in user space: the kernel knows only about the location of the head of the list. a thread can inform the kernel of the location of its robust futex list using .br set_robust_list (). the address of a thread's robust futex list can be obtained using .br get_robust_list (). .pp the purpose of the robust futex list is to ensure that if a thread accidentally fails to unlock a futex before terminating or calling .br execve (2), another thread that is waiting on that futex is notified that the former owner of the futex has died. this notification consists of two pieces: the .br futex_owner_died bit is set in the futex word, and the kernel performs a .br futex (2) .br futex_wake operation on one of the threads waiting on the futex. .pp the .br get_robust_list () system call returns the head of the robust futex list of the thread whose thread id is specified in .ir pid . if .i pid is 0, the head of the list for the calling thread is returned. the list head is stored in the location pointed to by .ir head_ptr . the size of the object pointed to by .i **head_ptr is stored in .ir len_ptr . .pp permission to employ .br get_robust_list () is governed by a ptrace access mode .b ptrace_mode_read_realcreds check; see .br ptrace (2). .pp the .br set_robust_list () system call requests the kernel to record the head of the list of robust futexes owned by the calling thread. the .i head argument is the list head to record. the .i len argument should be .ir sizeof(*head) . .sh return value the .br set_robust_list () and .br get_robust_list () system calls return zero when the operation is successful, an error code otherwise. .sh errors the .br set_robust_list () system call can fail with the following error: .tp .b einval .i len does not equal .ir "sizeof(struct\ robust_list_head)" . .pp the .br get_robust_list () system call can fail with the following errors: .tp .b efault the head of the robust futex list can't be stored at the location .ir head . .tp .b eperm the calling process does not have permission to see the robust futex list of the thread with the thread id .ir pid , and does not have the .br cap_sys_ptrace capability. .tp .b esrch no thread with the thread id .i pid could be found. .sh versions these system calls were added in linux 2.6.17. .sh notes these system calls are not needed by normal applications. .pp a thread can have only one robust futex list; therefore applications that wish to use this functionality should use the robust mutexes provided by glibc. .pp in the initial implementation, a thread waiting on a futex was notified that the owner had died only if the owner terminated. starting with linux 2.6.28, .\" commit 8141c7f3e7aee618312fa1c15109e1219de784a7 notification was extended to include the case where the owner performs an .br execve (2). .pp the thread ids mentioned in the main text are .i kernel thread ids of the kind returned by .br clone (2) and .br gettid (2). .sh see also .br futex (2), .br pthread_mutexattr_setrobust (3) .pp .ir documentation/robust\-futexes.txt and .ir documentation/robust\-futex\-abi.txt in the linux kernel source tree .\" http://lwn.net/articles/172149/ .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setdetachstate 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setdetachstate, pthread_attr_getdetachstate \- set/get detach state attribute in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setdetachstate(pthread_attr_t *" attr \ ", int " detachstate ); .bi "int pthread_attr_getdetachstate(const pthread_attr_t *" attr , .bi " int *" detachstate ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setdetachstate () function sets the detach state attribute of the thread attributes object referred to by .ir attr to the value specified in .ir detachstate . the detach state attribute determines whether a thread created using the thread attributes object .i attr will be created in a joinable or a detached state. .pp the following values may be specified in .ir detachstate : .tp .b pthread_create_detached threads that are created using .i attr will be created in a detached state. .tp .b pthread_create_joinable threads that are created using .i attr will be created in a joinable state. .pp the default setting of the detach state attribute in a newly initialized thread attributes object is .br pthread_create_joinable . .pp the .br pthread_attr_getdetachstate () returns the detach state attribute of the thread attributes object .ir attr in the buffer pointed to by .ir detachstate . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .br pthread_attr_setdetachstate () can fail with the following error: .tp .b einval an invalid value was specified in .ir detachstate . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setdetachstate (), .br pthread_attr_getdetachstate () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes see .br pthread_create (3) for more details on detached and joinable threads. .pp a thread that is created in a joinable state should eventually either be joined using .br pthread_join (3) or detached using .br pthread_detach (3); see .br pthread_create (3). .pp it is an error to specify the thread id of a thread that was created in a detached state in a later call to .br pthread_detach (3) or .br pthread_join (3). .sh examples see .br pthread_attr_init (3). .sh see also .br pthread_attr_init (3), .br pthread_create (3), .br pthread_detach (3), .br pthread_join (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 justin pryzby .\" .\" %%%license_start(permissive_misc) .\" permission is hereby granted, free of charge, to any person obtaining .\" a copy of this software and associated documentation files (the .\" "software"), to deal in the software without restriction, including .\" without limitation the rights to use, copy, modify, merge, publish, .\" distribute, sublicense, and/or sell copies of the software, and to .\" permit persons to whom the software is furnished to do so, subject to .\" the following conditions: .\" .\" the above copyright notice and this permission notice shall be .\" included in all copies or substantial portions of the software. .\" .\" the software is provided "as is", without warranty of any kind, .\" express or implied, including but not limited to the warranties of .\" merchantability, fitness for a particular purpose and noninfringement. .\" in no event shall the authors or copyright holders be liable for any .\" claim, damages or other liability, whether in an action of contract, .\" tort or otherwise, arising from, out of or in connection with the .\" software or the use or other dealings in the software. .\" %%%license_end .\" .\" references: .\" glibc manual and source .\" .\" 2006-05-19, mtk, various edits and example program .\" .th rpmatch 3 2021-03-22 "gnu" "linux programmer's manual" .sh name rpmatch \- determine if the answer to a question is affirmative or negative .sh synopsis .nf .b #include .pp .bi "int rpmatch(const char *" response ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br rpmatch (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description .br rpmatch () handles a user response to yes or no questions, with support for internationalization. .pp .i response should be a null-terminated string containing a user-supplied response, perhaps obtained with .br fgets (3) or .br getline (3). .pp the user's language preference is taken into account per the environment variables .br lang , .br lc_messages , and .br lc_all , if the program has called .br setlocale (3) to effect their changes. .pp regardless of the locale, responses matching .b \(ha[yy] are always accepted as affirmative, and those matching .b \(ha[nn] are always accepted as negative. .sh return value after examining .ir response , .br rpmatch () returns 0 for a recognized negative response ("no"), 1 for a recognized positive response ("yes"), and \-1 when the value of .i response is unrecognized. .sh errors a return value of \-1 may indicate either an invalid input, or some other error. it is incorrect to only test if the return value is nonzero. .pp .br rpmatch () can fail for any of the reasons that .br regcomp (3) or .br regexec (3) can fail; the cause of the error is not available from .i errno or anywhere else, but indicates a failure of the regex engine (but this case is indistinguishable from that of an unrecognized value of .ir response ). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br rpmatch () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to .br rpmatch () is not required by any standard, but is available on a few other systems. .\" it is available on at least aix 5.1 and freebsd 6.0. .sh bugs the .br rpmatch () implementation looks at only the first character of .ir response . as a consequence, "nyes" returns 0, and "ynever; not in a million years" returns 1. it would be preferable to accept input strings much more strictly, for example (using the extended regular expression notation described in .br regex (7)): .b \(ha([yy]|yes|yes)$ and .br \(ha([nn]|no|no)$ . .sh examples the following program displays the results when .br rpmatch () is applied to the string given in the program's command-line argument. .pp .ex #define _svid_source #include #include #include #include int main(int argc, char *argv[]) { if (argc != 2 || strcmp(argv[1], "\-\-help") == 0) { fprintf(stderr, "%s response\en", argv[0]); exit(exit_failure); } setlocale(lc_all, ""); printf("rpmatch() returns: %d\en", rpmatch(argv[1])); exit(exit_success); } .ee .sh see also .br fgets (3), .br getline (3), .br nl_langinfo (3), .br regcomp (3), .br setlocale (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:29:11 1993 by rik faith (faith@cs.unc.edu) .\" modified 11 june 1995 by andries brouwer (aeb@cwi.nl) .th rewinddir 3 2021-03-22 "" "linux programmer's manual" .sh name rewinddir \- reset directory stream .sh synopsis .nf .b #include .b #include .pp .bi "void rewinddir(dir *" dirp ); .fi .sh description the .br rewinddir () function resets the position of the directory stream .i dirp to the beginning of the directory. .sh return value the .br rewinddir () function returns no value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br rewinddir () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br closedir (3), .br opendir (3), .br readdir (3), .br scandir (3), .br seekdir (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xdr.3 .so man2/getuid.2 .so man3/envz_add.3 .\" copyright (c) 2001 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th timegm 3 2021-03-22 "gnu" "linux programmer's manual" .sh name timegm, timelocal \- inverses of gmtime and localtime .sh synopsis .nf .b #include .pp .bi "time_t timelocal(struct tm *" tm ); .bi "time_t timegm(struct tm *" tm ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br timelocal (), .br timegm (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the functions .br timelocal () and .br timegm () are the inverses of .br localtime (3) and .br gmtime (3). both functions take a broken-down time and convert it to calendar time (seconds since the epoch, 1970-01-01 00:00:00 +0000, utc). the difference between the two functions is that .br timelocal () takes the local timezone into account when doing the conversion, while .br timegm () takes the input value to be coordinated universal time (utc). .sh return value on success, these functions return the calendar time (seconds since the epoch), expressed as a value of type .ir time_t . on error, they return the value .i (time_t)\ \-1 and set .i errno to indicate the error. .sh errors .tp .b eoverflow the result cannot be represented. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br timelocal (), .br timegm () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions that are also present on the bsds. avoid their use. .sh notes the .br timelocal () function is equivalent to the posix standard function .br mktime (3). there is no reason to ever use it. .sh see also .br gmtime (3), .br localtime (3), .br mktime (3), .br tzset (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/updwtmp.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_wait 3 2021-08-27 "linux" "linux programmer's manual" .sh name sem_wait, sem_timedwait, sem_trywait \- lock a semaphore .sh synopsis .nf .b #include .pp .bi "int sem_wait(sem_t *" sem ); .bi "int sem_trywait(sem_t *" sem ); .bi "int sem_timedwait(sem_t *restrict " sem , .bi " const struct timespec *restrict " abs_timeout ); .fi .pp link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sem_timedwait (): .nf _posix_c_source >= 200112l .fi .sh description .br sem_wait () decrements (locks) the semaphore pointed to by .ir sem . if the semaphore's value is greater than zero, then the decrement proceeds, and the function returns, immediately. if the semaphore currently has the value zero, then the call blocks until either it becomes possible to perform the decrement (i.e., the semaphore value rises above zero), or a signal handler interrupts the call. .pp .br sem_trywait () is the same as .br sem_wait (), except that if the decrement cannot be immediately performed, then call returns an error .ri ( errno set to .br eagain ) instead of blocking. .pp .br sem_timedwait () is the same as .br sem_wait (), except that .i abs_timeout specifies a limit on the amount of time that the call should block if the decrement cannot be immediately performed. the .i abs_timeout argument points to a structure that specifies an absolute timeout in seconds and nanoseconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). this structure is defined as follows: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds [0 .. 999999999] */ }; .ee .in .pp if the timeout has already expired by the time of the call, and the semaphore could not be locked immediately, then .br sem_timedwait () fails with a timeout error .ri ( errno set to .br etimedout ). .pp if the operation can be performed immediately, then .br sem_timedwait () never fails with a timeout error, regardless of the value of .ir abs_timeout . furthermore, the validity of .i abs_timeout is not checked in this case. .sh return value all of these functions return 0 on success; on error, the value of the semaphore is left unchanged, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eagain .rb ( sem_trywait ()) the operation could not be performed without blocking (i.e., the semaphore currently has the value zero). .tp .b eintr the call was interrupted by a signal handler; see .br signal (7). .tp .b einval .i sem is not a valid semaphore. .tp .b einval .rb ( sem_timedwait ()) the value of .i abs_timeout.tv_nsecs is less than 0, or greater than or equal to 1000 million. .tp .b etimedout .rb ( sem_timedwait ()) the call timed out before the semaphore could be locked. .\" posix.1-2001 also allows edeadlk -- "a deadlock condition .\" was detected", but this does not occur on linux(?). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_wait (), .br sem_trywait (), .br sem_timedwait () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples the (somewhat trivial) program shown below operates on an unnamed semaphore. the program expects two command-line arguments. the first argument specifies a seconds value that is used to set an alarm timer to generate a .b sigalrm signal. this handler performs a .br sem_post (3) to increment the semaphore that is being waited on in .i main() using .br sem_timedwait (). the second command-line argument specifies the length of the timeout, in seconds, for .br sem_timedwait (). the following shows what happens on two different runs of the program: .pp .in +4n .ex .rb "$" " ./a.out 2 3" about to call sem_timedwait() sem_post() from handler sem_timedwait() succeeded .rb "$" " ./a.out 2 1" about to call sem_timedwait() sem_timedwait() timed out .ee .in .ss program source \& .ex #include #include #include #include #include #include #include #include sem_t sem; #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) static void handler(int sig) { write(stdout_fileno, "sem_post() from handler\en", 24); if (sem_post(&sem) == \-1) { write(stderr_fileno, "sem_post() failed\en", 18); _exit(exit_failure); } } int main(int argc, char *argv[]) { struct sigaction sa; struct timespec ts; int s; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } if (sem_init(&sem, 0, 0) == \-1) handle_error("sem_init"); /* establish sigalrm handler; set alarm timer using argv[1]. */ sa.sa_handler = handler; sigemptyset(&sa.sa_mask); sa.sa_flags = 0; if (sigaction(sigalrm, &sa, null) == \-1) handle_error("sigaction"); alarm(atoi(argv[1])); /* calculate relative interval as current time plus number of seconds given argv[2]. */ if (clock_gettime(clock_realtime, &ts) == \-1) handle_error("clock_gettime"); ts.tv_sec += atoi(argv[2]); printf("main() about to call sem_timedwait()\en"); while ((s = sem_timedwait(&sem, &ts)) == \-1 && errno == eintr) continue; /* restart if interrupted by handler. */ /* check what happened. */ if (s == \-1) { if (errno == etimedout) printf("sem_timedwait() timed out\en"); else perror("sem_timedwait"); } else printf("sem_timedwait() succeeded\en"); exit((s == 0) ? exit_success : exit_failure); } .ee .sh see also .br clock_gettime (2), .br sem_getvalue (3), .br sem_post (3), .br sem_overview (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 giorgio ciucci (giorgio@crcc.it) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 2001-11-28, by michael kerrisk, .\" changed data type of proj_id; minor fixes .\" aeb: further fixes; added notes. .\" .th ftok 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ftok \- convert a pathname and a project identifier to a system v ipc key .sh synopsis .nf .b #include .fi .pp .bi "key_t ftok(const char *" pathname ", int " proj_id ); .sh description the .br ftok () function uses the identity of the file named by the given .i pathname (which must refer to an existing, accessible file) and the least significant 8 bits of .i proj_id (which must be nonzero) to generate a .i key_t type system v ipc key, suitable for use with .br msgget (2), .br semget (2), or .br shmget (2). .pp the resulting value is the same for all pathnames that name the same file, when the same value of .i proj_id is used. the value returned should be different when the (simultaneously existing) files or the project ids differ. .sh return value on success, the generated .i key_t value is returned. on failure \-1 is returned, with .i errno indicating the error as for the .br stat (2) system call. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ftok () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on some ancient systems, the prototype was: .pp .in +4n .ex .bi "key_t ftok(char *" pathname ", char " proj_id ); .ee .in .pp today, .i proj_id is an .ir int , but still only 8 bits are used. typical usage has an ascii character .ir proj_id , that is why the behavior is said to be undefined when .i proj_id is zero. .pp of course, no guarantee can be given that the resulting .i key_t is unique. typically, a best-effort attempt combines the given .i proj_id byte, the lower 16 bits of the inode number, and the lower 8 bits of the device number into a 32-bit result. collisions may easily happen, for example between files on .i /dev/hda1 and files on .ir /dev/sda1 . .sh examples see .br semget (2). .sh see also .br msgget (2), .br semget (2), .br shmget (2), .br stat (2), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/j0.3 .so man2/sigreturn.2 .so man2/mknod.2 .so man3/stailq.3 .\" copyright (c) 2010 michael kerrisk .\" based on a proposal from stephan mueller .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" various pieces of text taken from the kernel source and the commentary .\" in kernel commit fa28237cfcc5827553044cbd6ee52e33692b0faa .\" both written by paul mackerras .\" .th subpage_prot 2 2021-03-22 "linux" "linux programmer's manual" .sh name subpage_prot \- define a subpage protection for an address range .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_subpage_prot, unsigned long " addr ", unsigned long " len , .bi " uint32_t *" map ); .fi .pp .ir note : glibc provides no wrapper for .br subpage_prot (), necessitating the use of .br syscall (2). .sh description the powerpc-specific .br subpage_prot () system call provides the facility to control the access permissions on individual 4\ kb subpages on systems configured with a page size of 64\ kb. .pp the protection map is applied to the memory pages in the region starting at .i addr and continuing for .i len bytes. both of these arguments must be aligned to a 64-kb boundary. .pp the protection map is specified in the buffer pointed to by .ir map . the map has 2 bits per 4\ kb subpage; thus each 32-bit word specifies the protections of 16 4\ kb subpages inside a 64\ kb page (so, the number of 32-bit words pointed to by .i map should equate to the number of 64-kb pages specified by .ir len ). each 2-bit field in the protection map is either 0 to allow any access, 1 to prevent writes, or 2 or 3 to prevent all accesses. .sh return value on success, .br subpage_prot () returns 0. otherwise, one of the error codes specified below is returned. .sh errors .tp .b efault the buffer referred to by .i map is not accessible. .tp .b einval the .i addr or .i len arguments are incorrect. both of these arguments must be aligned to a multiple of the system page size, and they must not refer to a region outside of the address space of the process or to a region that consists of huge pages. .tp .b enomem out of memory. .sh versions this system call is provided on the powerpc architecture since linux 2.6.25. the system call is provided only if the kernel is configured with .br config_ppc_64k_pages . no library support is provided. .sh conforming to this system call is linux-specific. .sh notes normal page protections (at the 64-kb page level) also apply; the subpage protection mechanism is an additional constraint, so putting 0 in a 2-bit field won't allow writes to a page that is otherwise write-protected. .ss rationale this system call is provided to assist writing emulators that operate using 64-kb pages on powerpc systems. when emulating systems such as x86, which uses a smaller page size, the emulator can no longer use the memory-management unit (mmu) and normal system calls for controlling page protections. (the emulator could emulate the mmu by checking and possibly remapping the address for each memory access in software, but that is slow.) the idea is that the emulator supplies an array of protection masks to apply to a specified range of virtual addresses. these masks are applied at the level where hardware page-table entries (ptes) are inserted into the hardware page table based on the linux ptes, so the linux ptes are not affected. implicit in this is that the regions of the address space that are protected are switched to use 4-kb hardware pages rather than 64-kb hardware pages (on machines with hardware 64-kb page support). .\" in the initial implementation, it was the case that: .\" in fact the whole process is switched to use 4 kb hardware pages when the .\" subpage_prot system call is used, but this could be improved in future .\" to switch only the affected segments. .\" but paul mackerass says (oct 2010): i'm pretty sure we now only switch .\" the affected segment, not the whole process. .sh see also .br mprotect (2), .br syscall (2) .pp .ir documentation/admin\-guide/mm/hugetlbpage.rst in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/error.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:08:16 1993 by rik faith .\" modified mon oct 21 17:47:19 edt 1996 by eric s. raymond .th motd 5 1992-12-29 "linux" "linux programmer's manual" .sh name motd \- message of the day .sh description the contents of .i /etc/motd are displayed by .br login (1) after a successful login but just before it executes the login shell. .pp the abbreviation "motd" stands for "message of the day", and this file has been traditionally used for exactly that (it requires much less disk space than mail to all users). .sh files .i /etc/motd .sh see also .br login (1), .br issue (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/unlocked_stdio.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1996-06-08 by aeb .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th sinh 3 2021-03-22 "" "linux programmer's manual" .sh name sinh, sinhf, sinhl \- hyperbolic sine function .sh synopsis .nf .b #include .pp .bi "double sinh(double " x ); .bi "float sinhf(float " x ); .bi "long double sinhl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sinhf (), .br sinhl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the hyperbolic sine of .ir x , which is defined mathematically as: .pp .nf sinh(x) = (exp(x) \- exp(\-x)) / 2 .fi .sh return value on success, these functions return the hyperbolic sine of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is positive infinity (negative infinity), positive infinity (negative infinity) is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with the same sign as .ir x . .\" .\" posix.1-2001 documents an optional range error (underflow) .\" for subnormal x; .\" glibc 2.8 does not do this. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result overflow .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sinh (), .br sinhf (), .br sinhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br acosh (3), .br asinh (3), .br atanh (3), .br cosh (3), .br csinh (3), .br tanh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/flockfile.3 .so man3/strcasecmp.3 .so man3/getspnam.3 .so man3/cpu_set.3 .so man7/system_data_types.7 .\" copyright (c) 1995 michael chastain (mec@duracef.shout.net), 22 july 1995. .\" copyright (c) 2015 andrew lutomirski .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th modify_ldt 2 2021-03-22 "linux" "linux programmer's manual" .sh name modify_ldt \- get or set a per-process ldt entry .sh synopsis .nf .br "#include " " /* definition of " "struct user_desc" " */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_modify_ldt, int " func ", void *" ptr , .bi " unsigned long " bytecount ); .fi .pp .ir note : glibc provides no wrapper for .br modify_ldt (), necessitating the use of .br syscall (2). .sh description .br modify_ldt () reads or writes the local descriptor table (ldt) for a process. the ldt is an array of segment descriptors that can be referenced by user code. linux allows processes to configure a per-process (actually per-mm) ldt. for more information about the ldt, see the intel software developer's manual or the amd architecture programming manual. .pp when .i func is 0, .br modify_ldt () reads the ldt into the memory pointed to by .ir ptr . the number of bytes read is the smaller of .i bytecount and the actual size of the ldt, although the kernel may act as though the ldt is padded with additional trailing zero bytes. on success, .br modify_ldt () will return the number of bytes read. .pp when .i func is 1 or 0x11, .br modify_ldt () modifies the ldt entry indicated by .ir ptr\->entry_number . .i ptr points to a .i user_desc structure and .i bytecount must equal the size of this structure. .pp the .i user_desc structure is defined in \fi\fp as: .pp .in +4n .ex struct user_desc { unsigned int entry_number; unsigned int base_addr; unsigned int limit; unsigned int seg_32bit:1; unsigned int contents:2; unsigned int read_exec_only:1; unsigned int limit_in_pages:1; unsigned int seg_not_present:1; unsigned int useable:1; }; .ee .in .pp in linux 2.4 and earlier, this structure was named .ir modify_ldt_ldt_s . .pp the .i contents field is the segment type (data, expand-down data, non-conforming code, or conforming code). the other fields match their descriptions in the cpu manual, although .br modify_ldt () cannot set the hardware-defined "accessed" bit described in the cpu manual. .pp a .i user_desc is considered "empty" if .i read_exec_only and .i seg_not_present are set to 1 and all of the other fields are 0. an ldt entry can be cleared by setting it to an "empty" .i user_desc or, if .i func is 1, by setting both .i base and .i limit to 0. .pp a conforming code segment (i.e., one with .ir contents==3 ) will be rejected if .i func is 1 or if .i seg_not_present is 0. .pp when .i func is 2, .br modify_ldt () will read zeros. this appears to be a leftover from linux 2.4. .sh return value on success, .br modify_ldt () returns either the actual number of bytes read (for reading) or 0 (for writing). on failure, .br modify_ldt () returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b efault .i ptr points outside the address space. .tp .b einval .i ptr is 0, or .i func is 1 and .i bytecount is not equal to the size of the structure .ir user_desc , or .i func is 1 or 0x11 and the new ldt entry has invalid values. .tp .b enosys .i func is neither 0, 1, 2, nor 0x11. .sh conforming to this call is linux-specific and should not be used in programs intended to be portable. .sh notes .br modify_ldt () should not be used for thread-local storage, as it slows down context switches and only supports a limited number of threads. threading libraries should use .br set_thread_area (2) or .br arch_prctl (2) instead, except on extremely old kernels that do not support those system calls. .pp the normal use for .br modify_ldt () is to run legacy 16-bit or segmented 32-bit code. not all kernels allow 16-bit segments to be installed, however. .pp even on 64-bit kernels, .br modify_ldt () cannot be used to create a long mode (i.e., 64-bit) code segment. the undocumented field "lm" in .ir user_desc is not useful, and, despite its name, does not result in a long mode segment. .sh bugs on 64-bit kernels before linux 3.19, .\" commit e30ab185c490e9a9381385529e0fd32f0a399495 setting the "lm" bit in .ir user_desc prevents the descriptor from being considered empty. keep in mind that the "lm" bit does not exist in the 32-bit headers, but these buggy kernels will still notice the bit even when set in a 32-bit process. .sh see also .br arch_prctl (2), .br set_thread_area (2), .br vm86 (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/queue.7 .\" copyright 2001 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th round 3 2021-03-22 "" "linux programmer's manual" .sh name round, roundf, roundl \- round to nearest integer, away from zero .sh synopsis .nf .b #include .pp .bi "double round(double " x ); .bi "float roundf(float " x ); .bi "long double roundl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br round (), .br roundf (), .br roundl (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions round .i x to the nearest integer, but round halfway cases away from zero (regardless of the current rounding direction, see .br fenv (3)), instead of to the nearest even integer like .br rint (3). .pp for example, .ir round(0.5) is 1.0, and .ir round(\-0.5) is \-1.0. .sh return value these functions return the rounded integer value. .pp if .i x is integral, +0, \-0, nan, or infinite, .i x itself is returned. .sh errors no errors occur. posix.1-2001 documents a range error for overflows, but see notes. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br round (), .br roundf (), .br roundl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes posix.1-2001 contains text about overflow (which might set .i errno to .br erange , or raise an .b fe_overflow exception). in practice, the result cannot overflow on any current machine, so this error-handling stuff is just nonsense. .\" the posix.1-2001 application usage section discusses this point. (more precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of mantissa bits. for the ieee-754 standard 32-bit and 64-bit floating-point numbers the maximum value of the exponent is 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively, 53).) .pp if you want to store the rounded value in an integer type, you probably want to use one of the functions described in .br lround (3) instead. .sh see also .br ceil (3), .br floor (3), .br lround (3), .br nearbyint (3), .br rint (3), .br trunc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th clock_getcpuclockid 3 2021-03-22 "linux" "linux programmer's manual" .sh name clock_getcpuclockid \- obtain id of a process cpu-time clock .sh synopsis .b #include .nf .pp .bi "int clock_getcpuclockid(pid_t " pid ", clockid_t *" clockid ); .fi .pp link with \fi\-lrt\fp (only for glibc versions before 2.17). .pp .ad l .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br clock_getcpuclockid (): .nf _posix_c_source >= 200112l .fi .sh description the .br clock_getcpuclockid () function obtains the id of the cpu-time clock of the process whose id is .ir pid , and returns it in the location pointed to by .ir clockid . if .i pid is zero, then the clock id of the cpu-time clock of the calling process is returned. .sh return value on success, .br clock_getcpuclockid () returns 0; on error, it returns one of the positive error numbers listed in errors. .sh errors .tp .b enosys the kernel does not support obtaining the per-process cpu-time clock of another process, and .i pid does not specify the calling process. .tp .b eperm the caller does not have permission to access the cpu-time clock of the process specified by .ir pid . (specified in posix.1-2001; does not occur on linux unless the kernel does not support obtaining the per-process cpu-time clock of another process.) .tp .b esrch there is no process with the id .ir pid . .sh versions the .br clock_getcpuclockid () function is available in glibc since version 2.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clock_getcpuclockid () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes calling .br clock_gettime (2) with the clock id obtained by a call to .br clock_getcpuclockid () with a .i pid of 0, is the same as using the clock id .br clock_process_cputime_id . .sh examples the example program below obtains the cpu-time clock id of the process whose id is given on the command line, and then uses .br clock_gettime (2) to obtain the time on that clock. an example run is the following: .pp .in +4n .ex .rb "$" " ./a.out 1" " # show cpu clock of init process" cpu\-time clock for pid 1 is 2.213466748 seconds .ee .in .ss program source \& .ex #define _xopen_source 600 #include #include #include #include #include int main(int argc, char *argv[]) { clockid_t clockid; struct timespec ts; if (argc != 2) { fprintf(stderr, "%s \en", argv[0]); exit(exit_failure); } if (clock_getcpuclockid(atoi(argv[1]), &clockid) != 0) { perror("clock_getcpuclockid"); exit(exit_failure); } if (clock_gettime(clockid, &ts) == \-1) { perror("clock_gettime"); exit(exit_failure); } printf("cpu\-time clock for pid %s is %jd.%09ld seconds\en", argv[1], (intmax_t) ts.tv_sec, ts.tv_nsec); exit(exit_success); } .ee .sh see also .br clock_getres (2), .br timer_create (2), .br pthread_getcpuclockid (3), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_mutexattr_getpshared.3 .so man3/rpc.3 .\" copyright (c) 2005 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sigvec 3 2021-03-22 "linux" "linux programmer's manual" .sh name sigvec, sigblock, sigsetmask, siggetmask, sigmask \- bsd signal api .sh synopsis .nf .b #include .pp .bi "int sigvec(int " sig ", const struct sigvec *" vec ", struct sigvec *" ovec ); .pp .bi "int sigmask(int " signum ); .pp .bi "int sigblock(int " mask ); .bi "int sigsetmask(int " mask ); .b int siggetmask(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description these functions are provided in glibc as a compatibility interface for programs that make use of the historical bsd signal api. this api is obsolete: new applications should use the posix signal api .rb ( sigaction (2), .br sigprocmask (2), etc.). .pp the .br sigvec () function sets and/or gets the disposition of the signal .i sig (like the posix .br sigaction (2)). if .i vec is not null, it points to a .i sigvec structure that defines the new disposition for .ir sig . if .i ovec is not null, it points to a .i sigvec structure that is used to return the previous disposition of .ir sig . to obtain the current disposition of .i sig without changing it, specify null for .ir vec , and a non-null pointer for .ir ovec . .pp the dispositions for .b sigkill and .b sigstop cannot be changed. .pp the .i sigvec structure has the following form: .pp .in +4n .ex struct sigvec { void (*sv_handler)(int); /* signal disposition */ int sv_mask; /* signals to be blocked in handler */ int sv_flags; /* flags */ }; .ee .in .pp the .i sv_handler field specifies the disposition of the signal, and is either: the address of a signal handler function; .br sig_dfl , meaning the default disposition applies for the signal; or .br sig_ign , meaning that the signal is ignored. .pp if .i sv_handler specifies the address of a signal handler, then .i sv_mask specifies a mask of signals that are to be blocked while the handler is executing. in addition, the signal for which the handler is invoked is also blocked. attempts to block .b sigkill or .b sigstop are silently ignored. .pp if .i sv_handler specifies the address of a signal handler, then the .i sv_flags field specifies flags controlling what happens when the handler is called. this field may contain zero or more of the following flags: .tp .b sv_interrupt if the signal handler interrupts a blocking system call, then upon return from the handler the system call is not restarted: instead it fails with the error .br eintr . if this flag is not specified, then system calls are restarted by default. .tp .b sv_resethand reset the disposition of the signal to the default before calling the signal handler. if this flag is not specified, then the handler remains established until explicitly removed by a later call to .br sigvec () or until the process performs an .br execve (2). .tp .b sv_onstack handle the signal on the alternate signal stack (historically established under bsd using the obsolete .br sigstack () function; the posix replacement is .br sigaltstack (2)). .pp the .br sigmask () macro constructs and returns a "signal mask" for .ir signum . for example, we can initialize the .i vec.sv_mask field given to .br sigvec () using code such as the following: .pp .in +4n .ex vec.sv_mask = sigmask(sigquit) | sigmask(sigabrt); /* block sigquit and sigabrt during handler execution */ .ee .in .pp the .br sigblock () function adds the signals in .i mask to the process's signal mask (like posix .ir sigprocmask(sig_block) ), and returns the process's previous signal mask. attempts to block .b sigkill or .b sigstop are silently ignored. .pp the .br sigsetmask () function sets the process's signal mask to the value given in .i mask (like posix .ir sigprocmask(sig_setmask) ), and returns the process's previous signal mask. .pp the .br siggetmask () function returns the process's current signal mask. this call is equivalent to .ir sigblock(0) . .sh return value the .br sigvec () function returns 0 on success; on error, it returns \-1 and sets .i errno to indicate the error. .pp the .br sigblock () and .br sigsetmask () functions return the previous signal mask. .pp the .br sigmask () macro returns the signal mask for .ir signum . .sh errors see the errors under .br sigaction (2) and .br sigprocmask (2). .sh versions starting with version 2.21, the gnu c library no longer exports the .br sigvec () function as part of the abi. (to ensure backward compatibility, the glibc symbol versioning scheme continues to export the interface to binaries linked against older versions of the library.) .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigvec (), .br sigmask (), .br sigblock (), .br sigsetmask (), .br siggetmask () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to all of these functions were in 4.3bsd, except .br siggetmask (), whose origin is unclear. these functions are obsolete: do not use them in new programs. .sh notes on 4.3bsd, the .br signal () function provided reliable semantics (as when calling .br sigvec () with .i vec.sv_mask equal to 0). on system v, .br signal () provides unreliable semantics. posix.1 leaves these aspects of .br signal () unspecified. see .br signal (2) for further details. .pp in order to wait for a signal, bsd and system v both provided a function named .br sigpause (3), but this function has a different argument on the two systems. see .br sigpause (3) for details. .sh see also .br kill (2), .br pause (2), .br sigaction (2), .br signal (2), .br sigprocmask (2), .br raise (3), .br sigpause (3), .br sigset (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcscasecmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcscasecmp \- compare two wide-character strings, ignoring case .sh synopsis .nf .b #include .pp .bi "int wcscasecmp(const wchar_t *" s1 ", const wchar_t *" s2 ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcscasecmp (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcscasecmp () function is the wide-character equivalent of the .br strcasecmp (3) function. it compares the wide-character string pointed to by .i s1 and the wide-character string pointed to by .ir s2 , ignoring case differences .rb ( towupper (3), .br towlower (3)). .sh return value the .br wcscasecmp () function returns zero if the wide-character strings at .i s1 and .i s2 are equal except for case distinctions. it returns a positive integer if .i s1 is greater than .ir s2 , ignoring case. it returns a negative integer if .i s1 is smaller than .ir s2 , ignoring case. .sh versions the .br wcscasecmp () function is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcscasecmp () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function is not specified in posix.1-2001, and is not widely available on other systems. .sh notes the behavior of .br wcscasecmp () depends on the .b lc_ctype category of the current locale. .sh see also .br strcasecmp (3), .br wcscmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/scandir.3 .so man3/sigsetops.3 .so man3/getfsent.3 .so man3/getenv.3 .so man7/iso_8859-5.7 .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" author: ulrich drepper .\" .\" %%%license_start(gplv2_misc) .\" this copyrighted material is made available to anyone wishing to use, .\" modify, copy, or redistribute it subject to the terms and conditions of the .\" gnu general public license v.2. .\" .\" this program is distributed in the hope that it will be useful, but without .\" any warranty; without even the implied warranty of merchantability or .\" fitness for a particular purpose. see the gnu general public license for .\" more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th nss 5 2020-06-09 "linux" "linux programmer's manual" .sh name nss \- name service switch configuration file .sh description each call to a function which retrieves data from a system database like the password or group database is handled by the name service switch implementation in the gnu c library. the various services provided are implemented by independent modules, each of which naturally varies widely from the other. .pp the default implementations coming with the gnu c library are by default conservative and do not use unsafe data. this might be very costly in some situations, especially when the databases are large. some modules allow the system administrator to request taking shortcuts if these are known to be safe. it is then the system administrator's responsibility to ensure the assumption is correct. .pp there are other modules where the implementation changed over time. if an implementation used to sacrifice speed for memory consumption, it might create problems if the preference is switched. .pp the .i /etc/default/nss file contains a number of variable assignments. each variable controls the behavior of one or more nss modules. white spaces are ignored. lines beginning with \(aq#\(aq are treated as comments. .pp the variables currently recognized are: .tp \fbnetid_authoritative =\fr \fitrue\fr|\fifalse\fr if set to true, the nis backend for the .br initgroups (3) function will accept the information from the .i netid.byname nis map as authoritative. this can speed up the function significantly if the .i group.byname map is large. the content of the .i netid.byname map is used \fbas is\fr. the system administrator has to make sure it is correctly generated. .tp \fbservices_authoritative =\fr \fitrue\fr|\fifalse\fr if set to true, the nis backend for the .br getservbyname (3) and .br getservbyname_r (3) functions will assume that the .i services.byservicename nis map exists and is authoritative, particularly that it contains both keys with /proto and without /proto for both primary service names and service aliases. the system administrator has to make sure it is correctly generated. .tp \fbsetent_batch_read =\fr \fitrue\fr|\fifalse\fr if set to true, the nis backend for the .br setpwent (3) and .br setgrent (3) functions will read the entire database at once and then hand out the requests one by one from memory with every corresponding .br getpwent (3) or .br getgrent (3) call respectively. otherwise, each .br getpwent (3) or .br getgrent (3) call might result in a network communication with the server to get the next entry. .sh files \fi/etc/default/nss\fr .sh examples the default configuration corresponds to the following configuration file: .pp .in +4n .ex netid_authoritative=false services_authoritative=false setent_batch_read=false .ee .in .\" .sh author .\" ulrich drepper .\" .sh see also \finsswitch.conf\fr .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" 2002-07-27 walter harms .\" this was done with the help of the glibc manual .\" .th isgreater 3 2021-03-22 "" "linux programmer's manual" .sh name isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered \- floating-point relational tests without exception for nan .sh synopsis .nf .b #include .pp .bi "int isgreater(" x ", " y ); .bi "int isgreaterequal(" x ", " y ); .bi "int isless(" x ", " y ); .bi "int islessequal(" x ", " y ); .bi "int islessgreater(" x ", " y ); .bi "int isunordered(" x ", " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .nf all functions described here: _isoc99_source || _posix_c_source >= 200112l .fi .sh description the normal relational operations (like .br < , "less than") fail if one of the operands is nan. this will cause an exception. to avoid this, c99 defines the macros listed below. .pp these macros are guaranteed to evaluate their arguments only once. the arguments must be of real floating-point type (note: do not pass integer values as arguments to these macros, since the arguments will .i not be promoted to real-floating types). .tp .br isgreater () determines \fi(x)\ >\ (y)\fp without an exception if .ir x or .i y is nan. .tp .br isgreaterequal () determines \fi(x)\ >=\ (y)\fp without an exception if .ir x or .i y is nan. .tp .br isless () determines \fi(x)\ <\ (y)\fp without an exception if .ir x or .i y is nan. .tp .br islessequal () determines \fi(x)\ <=\ (y)\fp without an exception if .ir x or .i y is nan. .tp .br islessgreater () determines \fi(x)\ < (y) || (x) >\ (y)\fp without an exception if .ir x or .i y is nan. this macro is not equivalent to \fix\ !=\ y\fp because that expression is true if .ir x or .i y is nan. .tp .br isunordered () determines whether its arguments are unordered, that is, whether at least one of the arguments is a nan. .sh return value the macros other than .br isunordered () return the result of the relational comparison; these macros return 0 if either argument is a nan. .pp .br isunordered () returns 1 if .ir x or .i y is nan and 0 otherwise. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br isgreater (), .br isgreaterequal (), .br isless (), .br islessequal (), .br islessgreater (), .br isunordered () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes not all hardware supports these functions, and where hardware support isn't provided, they will be emulated by macros. this will result in a performance penalty. don't use these functions if nan is of no concern for you. .sh see also .br fpclassify (3), .br isnan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/lrint.3 .\" %%%license_start(public_domain) .\" this is in the public domain .\" %%%license_end .\" various parts: .\" copyright (c) 2007-9, 2013, 2016 michael kerrisk .\" .th ld.so 8 2021-08-27 "gnu" "linux programmer's manual" .sh name ld.so, ld\-linux.so \- dynamic linker/loader .sh synopsis the dynamic linker can be run either indirectly by running some dynamically linked program or shared object (in which case no command-line options to the dynamic linker can be passed and, in the elf case, the dynamic linker which is stored in the .b .interp section of the program is executed) or directly by running: .pp .i /lib/ld\-linux.so.* [options] [program [arguments]] .sh description the programs .b ld.so and .b ld\-linux.so* find and load the shared objects (shared libraries) needed by a program, prepare the program to run, and then run it. .pp linux binaries require dynamic linking (linking at run time) unless the .b \-static option was given to .br ld (1) during compilation. .pp the program .b ld.so handles a.out binaries, a binary format used long ago. the program .b ld\-linux.so* (\fi/lib/ld\-linux.so.1\fp for libc5, \fi/lib/ld\-linux.so.2\fp for glibc2) handles binaries that are in the more modern elf format. both programs have the same behavior, and use the same support files and programs .rb ( ldd (1), .br ldconfig (8), and .ir /etc/ld.so.conf ). .pp when resolving shared object dependencies, the dynamic linker first inspects each dependency string to see if it contains a slash (this can occur if a shared object pathname containing slashes was specified at link time). if a slash is found, then the dependency string is interpreted as a (relative or absolute) pathname, and the shared object is loaded using that pathname. .pp if a shared object dependency does not contain a slash, then it is searched for in the following order: .ip o 3 using the directories specified in the dt_rpath dynamic section attribute of the binary if present and dt_runpath attribute does not exist. use of dt_rpath is deprecated. .ip o using the environment variable .br ld_library_path , unless the executable is being run in secure-execution mode (see below), in which case this variable is ignored. .ip o using the directories specified in the dt_runpath dynamic section attribute of the binary if present. such directories are searched only to find those objects required by dt_needed (direct dependencies) entries and do not apply to those objects' children, which must themselves have their own dt_runpath entries. this is unlike dt_rpath, which is applied to searches for all children in the dependency tree. .ip o from the cache file .ir /etc/ld.so.cache , which contains a compiled list of candidate shared objects previously found in the augmented library path. if, however, the binary was linked with the .b \-z nodeflib linker option, shared objects in the default paths are skipped. shared objects installed in hardware capability directories (see below) are preferred to other shared objects. .ip o in the default path .ir /lib , and then .ir /usr/lib . (on some 64-bit architectures, the default paths for 64-bit shared objects are .ir /lib64 , and then .ir /usr/lib64 .) if the binary was linked with the .b \-z nodeflib linker option, this step is skipped. .\" .ss dynamic string tokens in several places, the dynamic linker expands dynamic string tokens: .ip o 3 in the environment variables .br ld_library_path , .br ld_preload , and .br ld_audit , .ip o 3 inside the values of the dynamic section tags .br dt_needed , .br dt_rpath , .br dt_runpath , .br dt_audit , and .br dt_depaudit of elf binaries, .ip o 3 in the arguments to the .b ld.so command line options .br \-\-audit , .br \-\-library\-path , and .b \-\-preload (see below), and .ip o 3 in the filename arguments to the .br dlopen (3) and .br dlmopen (3) functions. .pp the substituted tokens are as follows: .tp .ir $origin " (or equivalently " ${origin} ) this expands to the directory containing the program or shared object. thus, an application located in .i somedir/app could be compiled with .ip .in +4n .ex gcc \-wl,\-rpath,\(aq$origin/../lib\(aq .ee .in .ip so that it finds an associated shared object in .i somedir/lib no matter where .i somedir is located in the directory hierarchy. this facilitates the creation of "turn-key" applications that do not need to be installed into special directories, but can instead be unpacked into any directory and still find their own shared objects. .tp .ir $lib " (or equivalently " ${lib} ) this expands to .i lib or .i lib64 depending on the architecture (e.g., on x86-64, it expands to .ir lib64 and on x86-32, it expands to .ir lib ). .tp .ir $platform " (or equivalently " ${platform} ) this expands to a string corresponding to the processor type of the host system (e.g., "x86_64"). on some architectures, the linux kernel doesn't provide a platform string to the dynamic linker. the value of this string is taken from the .br at_platform value in the auxiliary vector (see .br getauxval (3)). .\" to get an idea of the places that $platform would match, .\" look at the output of the following: .\" .\" mkdir /tmp/d .\" ld_library_path=/tmp/d strace -e open /bin/date 2>&1 | grep /tmp/d .\" .\" ld.so lets names be abbreviated, so $o will work for $origin; .\" don't do this!! .pp note that the dynamic string tokens have to be quoted properly when set from a shell, to prevent their expansion as shell or environment variables. .sh options .tp .br \-\-argv0 " \fistring\fp (since glibc 2.33)" set .i argv[0] to the value .i string before running the program. .tp .bi \-\-audit " list" use objects named in .i list as auditors. the objects in .i list are delimited by colons. .tp .b \-\-inhibit\-cache do not use .ir /etc/ld.so.cache . .tp .bi \-\-library\-path " path" use .i path instead of .b ld_library_path environment variable setting (see below). the names .ir origin , .ir lib , and .ir platform are interpreted as for the .br ld_library_path environment variable. .tp .bi \-\-inhibit\-rpath " list" ignore rpath and runpath information in object names in .ir list . this option is ignored when running in secure-execution mode (see below). the objects in .i list are delimited by colons or spaces. .tp .b \-\-list list all dependencies and how they are resolved. .tp .br \-\-list\-tunables " (since 2.33)" print the names and values of all tunables, along with the minimum and maximum allowed values. .tp .br \-\-preload " \filist\fp (since glibc 2.30)" preload the objects specified in .ir list . the objects in .i list are delimited by colons or spaces. the objects are preloaded as explained in the description of the .br ld_preload environment variable below. .ip by contrast with .br ld_preload , the .br \-\-preload option provides a way to perform preloading for a single executable without affecting preloading performed in any child process that executes a new program. .tp .b \-\-verify verify that program is dynamically linked and this dynamic linker can handle it. .sh environment various environment variables influence the operation of the dynamic linker. .\" .ss secure-execution mode for security reasons, if the dynamic linker determines that a binary should be run in secure-execution mode, the effects of some environment variables are voided or modified, and furthermore those environment variables are stripped from the environment, so that the program does not even see the definitions. some of these environment variables affect the operation of the dynamic linker itself, and are described below. other environment variables treated in this way include: .br gconv_path , .br getconf_dir , .br hostaliases , .br localdomain , .br locpath , .br malloc_trace , .br nis_path , .br nlspath , .br resolv_host_conf , .br res_options , .br tmpdir , and .br tzdir . .pp a binary is executed in secure-execution mode if the .b at_secure entry in the auxiliary vector (see .br getauxval (3)) has a nonzero value. this entry may have a nonzero value for various reasons, including: .ip * 3 the process's real and effective user ids differ, or the real and effective group ids differ. this typically occurs as a result of executing a set-user-id or set-group-id program. .ip * a process with a non-root user id executed a binary that conferred capabilities to the process. .ip * a nonzero value may have been set by a linux security module. .\" .ss environment variables among the more important environment variables are the following: .tp .br ld_assume_kernel " (since glibc 2.2.3)" each shared object can inform the dynamic linker of the minimum kernel abi version that it requires. (this requirement is encoded in an elf note section that is viewable via .ir "readelf\ \-n" as a section labeled .br nt_gnu_abi_tag .) at run time, the dynamic linker determines the abi version of the running kernel and will reject loading shared objects that specify minimum abi versions that exceed that abi version. .ip .br ld_assume_kernel can be used to cause the dynamic linker to assume that it is running on a system with a different kernel abi version. for example, the following command line causes the dynamic linker to assume it is running on linux 2.2.5 when loading the shared objects required by .ir myprog : .ip .in +4n .ex $ \fbld_assume_kernel=2.2.5 ./myprog\fp .ee .in .ip on systems that provide multiple versions of a shared object (in different directories in the search path) that have different minimum kernel abi version requirements, .br ld_assume_kernel can be used to select the version of the object that is used (dependent on the directory search order). .ip historically, the most common use of the .br ld_assume_kernel feature was to manually select the older linuxthreads posix threads implementation on systems that provided both linuxthreads and nptl (which latter was typically the default on such systems); see .br pthreads (7). .tp .br ld_bind_now " (since glibc 2.1.1)" if set to a nonempty string, causes the dynamic linker to resolve all symbols at program startup instead of deferring function call resolution to the point when they are first referenced. this is useful when using a debugger. .tp .b ld_library_path a list of directories in which to search for elf libraries at execution time. the items in the list are separated by either colons or semicolons, and there is no support for escaping either separator. a zero-length directory name indicates the current working directory. .ip this variable is ignored in secure-execution mode. .ip within the pathnames specified in .br ld_library_path , the dynamic linker expands the tokens .ir $origin , .ir $lib , and .ir $platform (or the versions using curly braces around the names) as described above in .ir "dynamic string tokens" . thus, for example, the following would cause a library to be searched for in either the .i lib or .i lib64 subdirectory below the directory containing the program to be executed: .ip .in +4n .ex $ \fbld_library_path=\(aq$origin/$lib\(aq prog\fp .ee .in .ip (note the use of single quotes, which prevent expansion of .i $origin and .i $lib as shell variables!) .tp .b ld_preload a list of additional, user-specified, elf shared objects to be loaded before all others. this feature can be used to selectively override functions in other shared objects. .ip the items of the list can be separated by spaces or colons, and there is no support for escaping either separator. the objects are searched for using the rules given under description. objects are searched for and added to the link map in the left-to-right order specified in the list. .ip in secure-execution mode, preload pathnames containing slashes are ignored. furthermore, shared objects are preloaded only from the standard search directories and only if they have set-user-id mode bit enabled (which is not typical). .ip within the names specified in the .br ld_preload list, the dynamic linker understands the tokens .ir $origin , .ir $lib , and .ir $platform (or the versions using curly braces around the names) as described above in .ir "dynamic string tokens" . (see also the discussion of quoting under the description of .br ld_library_path .) .\" tested with the following: .\" .\" ld_preload='$lib/libmod.so' ld_library_path=. ./prog .\" .\" which will preload the libmod.so in 'lib' or 'lib64', using it .\" in preference to the version in '.'. .ip there are various methods of specifying libraries to be preloaded, and these are handled in the following order: .rs .ip (1) 4 the .br ld_preload environment variable. .ip (2) the .b \-\-preload command-line option when invoking the dynamic linker directly. .ip (3) the .i /etc/ld.so.preload file (described below). .re .tp .br ld_trace_loaded_objects if set (to any value), causes the program to list its dynamic dependencies, as if run by .br ldd (1), instead of running normally. .pp then there are lots of more or less obscure variables, many obsolete or only for internal use. .tp .br ld_audit " (since glibc 2.4)" a list of user-specified, elf shared objects to be loaded before all others in a separate linker namespace (i.e., one that does not intrude upon the normal symbol bindings that would occur in the process) these objects can be used to audit the operation of the dynamic linker. the items in the list are colon-separated, and there is no support for escaping the separator. .ip .b ld_audit is ignored in secure-execution mode. .ip the dynamic linker will notify the audit shared objects at so-called auditing checkpoints\(emfor example, loading a new shared object, resolving a symbol, or calling a symbol from another shared object\(emby calling an appropriate function within the audit shared object. for details, see .br rtld\-audit (7). the auditing interface is largely compatible with that provided on solaris, as described in its .ir "linker and libraries guide" , in the chapter .ir "runtime linker auditing interface" . .ip within the names specified in the .br ld_audit list, the dynamic linker understands the tokens .ir $origin , .ir $lib , and .ir $platform (or the versions using curly braces around the names) as described above in .ir "dynamic string tokens" . (see also the discussion of quoting under the description of .br ld_library_path .) .ip since glibc 2.13, .\" commit 8e9f92e9d5d7737afdacf79b76d98c4c42980508 in secure-execution mode, names in the audit list that contain slashes are ignored, and only shared objects in the standard search directories that have the set-user-id mode bit enabled are loaded. .tp .br ld_bind_not " (since glibc 2.1.95)" if this environment variable is set to a nonempty string, do not update the got (global offset table) and plt (procedure linkage table) after resolving a function symbol. by combining the use of this variable with .br ld_debug (with the categories .ir bindings and .ir symbols ), one can observe all run-time function bindings. .tp .br ld_debug " (since glibc 2.1)" output verbose debugging information about operation of the dynamic linker. the content of this variable is one of more of the following categories, separated by colons, commas, or (if the value is quoted) spaces: .rs .tp 12 .i help specifying .ir help in the value of this variable does not run the specified program, and displays a help message about which categories can be specified in this environment variable. .tp .i all print all debugging information (except .ir statistics and .ir unused ; see below). .tp .i bindings display information about which definition each symbol is bound to. .tp .i files display progress for input file. .tp .i libs display library search paths. .tp .i reloc display relocation processing. .tp .i scopes display scope information. .tp .i statistics display relocation statistics. .tp .i symbols display search paths for each symbol look-up. .tp .i unused determine unused dsos. .tp .i versions display version dependencies. .re .ip since glibc 2.3.4, .b ld_debug is ignored in secure-execution mode, unless the file .ir /etc/suid\-debug exists (the content of the file is irrelevant). .tp .br ld_debug_output " (since glibc 2.1)" by default, .b ld_debug output is written to standard error. if .b ld_debug_output is defined, then output is written to the pathname specified by its value, with the suffix "." (dot) followed by the process id appended to the pathname. .ip .b ld_debug_output is ignored in secure-execution mode. .tp .br ld_dynamic_weak " (since glibc 2.1.91)" by default, when searching shared libraries to resolve a symbol reference, the dynamic linker will resolve to the first definition it finds. .ip old glibc versions (before 2.2), provided a different behavior: if the linker found a symbol that was weak, it would remember that symbol and keep searching in the remaining shared libraries. if it subsequently found a strong definition of the same symbol, then it would instead use that definition. (if no further symbol was found, then the dynamic linker would use the weak symbol that it initially found.) .ip the old glibc behavior was nonstandard. (standard practice is that the distinction between weak and strong symbols should have effect only at static link time.) in glibc 2.2, .\" more precisely 2.1.92 .\" see weak handling .\" https://www.sourceware.org/ml/libc-hacker/2000-06/msg00029.html .\" to: gnu libc hacker .\" subject: weak handling .\" from: ulrich drepper .\" date: 07 jun 2000 20:08:12 -0700 .\" reply-to: drepper at cygnus dot com (ulrich drepper) the dynamic linker was modified to provide the current behavior (which was the behavior that was provided by most other implementations at that time). .ip defining the .b ld_dynamic_weak environment variable (with any value) provides the old (nonstandard) glibc behavior, whereby a weak symbol in one shared library may be overridden by a strong symbol subsequently discovered in another shared library. (note that even when this variable is set, a strong symbol in a shared library will not override a weak definition of the same symbol in the main program.) .ip since glibc 2.3.4, .b ld_dynamic_weak is ignored in secure-execution mode. .tp .br ld_hwcap_mask " (since glibc 2.1)" mask for hardware capabilities. .tp .br ld_origin_path " (since glibc 2.1)" path where the binary is found. .\" used only if $origin can't be determined by normal means .\" (from the origin path saved at load time, or from /proc/self/exe)? .ip since glibc 2.4, .b ld_origin_path is ignored in secure-execution mode. .tp .br ld_pointer_guard " (glibc from 2.4 to 2.22)" set to 0 to disable pointer guarding. any other value enables pointer guarding, which is also the default. pointer guarding is a security mechanism whereby some pointers to code stored in writable program memory (return addresses saved by .br setjmp (3) or function pointers used by various glibc internals) are mangled semi-randomly to make it more difficult for an attacker to hijack the pointers for use in the event of a buffer overrun or stack-smashing attack. since glibc 2.23, .\" commit a014cecd82b71b70a6a843e250e06b541ad524f7 .b ld_pointer_guard can no longer be used to disable pointer guarding, which is now always enabled. .tp .br ld_profile " (since glibc 2.1)" the name of a (single) shared object to be profiled, specified either as a pathname or a soname. profiling output is appended to the file whose name is: "\fi$ld_profile_output\fp/\fi$ld_profile\fp.profile". .ip since glibc 2.2.5, .br ld_profile is ignored in secure-execution mode. .tp .br ld_profile_output " (since glibc 2.1)" directory where .b ld_profile output should be written. if this variable is not defined, or is defined as an empty string, then the default is .ir /var/tmp . .ip .b ld_profile_output is ignored in secure-execution mode; instead .ir /var/profile is always used. (this detail is relevant only before glibc 2.2.5, since in later glibc versions, .b ld_profile is also ignored in secure-execution mode.) .tp .br ld_show_auxv " (since glibc 2.1)" if this environment variable is defined (with any value), show the auxiliary array passed up from the kernel (see also .br getauxval (3)). .ip since glibc 2.3.4, .b ld_show_auxv is ignored in secure-execution mode. .tp .br ld_trace_prelinking " (since glibc 2.4)" if this environment variable is defined, trace prelinking of the object whose name is assigned to this environment variable. (use .br ldd (1) to get a list of the objects that might be traced.) if the object name is not recognized, .\" (this is what seems to happen, from experimenting) then all prelinking activity is traced. .tp .br ld_use_load_bias " (since glibc 2.3.3)" .\" http://sources.redhat.com/ml/libc-hacker/2003-11/msg00127.html .\" subject: [patch] support ld_use_load_bias .\" jakub jelinek by default (i.e., if this variable is not defined), executables and prelinked shared objects will honor base addresses of their dependent shared objects and (nonprelinked) position-independent executables (pies) and other shared objects will not honor them. if .b ld_use_load_bias is defined with the value 1, both executables and pies will honor the base addresses. if .b ld_use_load_bias is defined with the value 0, neither executables nor pies will honor the base addresses. .ip since glibc 2.3.3, this variable is ignored in secure-execution mode. .tp .br ld_verbose " (since glibc 2.1)" if set to a nonempty string, output symbol versioning information about the program if the .b ld_trace_loaded_objects environment variable has been set. .tp .br ld_warn " (since glibc 2.1.3)" if set to a nonempty string, warn about unresolved symbols. .tp .br ld_prefer_map_32bit_exec " (x86-64 only; since glibc 2.23)" according to the intel silvermont software optimization guide, for 64-bit applications, branch prediction performance can be negatively impacted when the target of a branch is more than 4\ gb away from the branch. if this environment variable is set (to any value), the dynamic linker will first try to map executable pages using the .br mmap (2) .br map_32bit flag, and fall back to mapping without that flag if that attempt fails. nb: map_32bit will map to the low 2\ gb (not 4\ gb) of the address space. .ip because .b map_32bit reduces the address range available for address space layout randomization (aslr), .b ld_prefer_map_32bit_exec is always disabled in secure-execution mode. .sh files .tp .i /lib/ld.so a.out dynamic linker/loader .tp .ir /lib/ld\-linux.so. { 1 , 2 } elf dynamic linker/loader .tp .i /etc/ld.so.cache file containing a compiled list of directories in which to search for shared objects and an ordered list of candidate shared objects. see .br ldconfig (8). .tp .i /etc/ld.so.preload file containing a whitespace-separated list of elf shared objects to be loaded before the program. see the discussion of .br ld_preload above. if both .br ld_preload and .i /etc/ld.so.preload are employed, the libraries specified by .br ld_preload are preloaded first. .i /etc/ld.so.preload has a system-wide effect, causing the specified libraries to be preloaded for all programs that are executed on the system. (this is usually undesirable, and is typically employed only as an emergency remedy, for example, as a temporary workaround to a library misconfiguration issue.) .tp .i lib*.so* shared objects .sh notes .ss hardware capabilities some shared objects are compiled using hardware-specific instructions which do not exist on every cpu. such objects should be installed in directories whose names define the required hardware capabilities, such as .ir /usr/lib/sse2/ . the dynamic linker checks these directories against the hardware of the machine and selects the most suitable version of a given shared object. hardware capability directories can be cascaded to combine cpu features. the list of supported hardware capability names depends on the cpu. the following names are currently recognized: .\" presumably, this info comes from sysdeps/i386/dl-procinfo.c and .\" similar files .tp .b alpha ev4, ev5, ev56, ev6, ev67 .tp .b mips loongson2e, loongson2f, octeon, octeon2 .tp .b powerpc 4xxmac, altivec, arch_2_05, arch_2_06, booke, cellbe, dfp, efpdouble, efpsingle, fpu, ic_snoop, mmu, notb, pa6t, power4, power5, power5+, power6x, ppc32, ppc601, ppc64, smt, spe, ucache, vsx .tp .b sparc flush, muldiv, stbar, swap, ultra3, v9, v9v, v9v2 .tp .b s390 dfp, eimm, esan3, etf3enh, g5, highgprs, hpage, ldisp, msa, stfle, z900, z990, z9-109, z10, zarch .tp .b x86 (32-bit only) acpi, apic, clflush, cmov, cx8, dts, fxsr, ht, i386, i486, i586, i686, mca, mmx, mtrr, pat, pbe, pge, pn, pse36, sep, ss, sse, sse2, tm .sh see also .br ld (1), .br ldd (1), .br pldd (1), .br sprof (1), .br dlopen (3), .br getauxval (3), .br elf (5), .br capabilities (7), .br rtld\-audit (7), .br ldconfig (8), .br sln (8) .\" .sh authors .\" ld.so: david engel, eric youngdale, peter macdonald, hongjiu lu, linus .\" torvalds, lars wirzenius and mitch d'souza .\" ld\-linux.so: roland mcgrath, ulrich drepper and others. .\" .\" in the above, (libc5) stands for david engel's ld.so/ld\-linux.so. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/syslog.2 .so man3/crypt.3 .so man3/exp2.3 .so man3/termios.3 .so man3/ilogb.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification .\" http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .\" modified tue oct 16 23:18:40 bst 2001 by john levon .th fgetwc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fgetwc, getwc \- read a wide character from a file stream .sh synopsis .nf .b #include .b #include .pp .bi "wint_t fgetwc(file *" stream ); .bi "wint_t getwc(file *" stream ); .fi .sh description the .br fgetwc () function is the wide-character equivalent of the .br fgetc (3) function. it reads a wide character from \fistream\fp and returns it. if the end of stream is reached, or if \fiferror(stream)\fp becomes true, it returns .br weof . if a wide-character conversion error occurs, it sets \fierrno\fp to \fbeilseq\fp and returns .br weof . .pp the .br getwc () function or macro functions identically to .br fgetwc (). it may be implemented as a macro, and may evaluate its argument more than once. there is no reason ever to use it. .pp for nonlocking counterparts, see .br unlocked_stdio (3). .sh return value on success, .br fgetwc () returns the next wide-character from the stream. otherwise, .b weof is returned, and .i errno is set to indicate the error. .sh errors apart from the usual ones, there is .tp .b eilseq the data obtained from the input stream does not form a valid character. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fgetwc (), .br getwc () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br fgetwc () depends on the .b lc_ctype category of the current locale. .pp in the absence of additional information passed to the .br fopen (3) call, it is reasonable to expect that .br fgetwc () will actually read a multibyte sequence from the stream and then convert it to a wide character. .sh see also .br fgetws (3), .br fputwc (3), .br ungetwc (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th seccomp_unotify 2 2021-06-20 "linux" "linux programmer's manual" .sh name seccomp_unotify \- seccomp user-space notification mechanism .sh synopsis .nf .b #include .b #include .b #include .pp .bi "int seccomp(unsigned int " operation ", unsigned int " flags \ ", void *" args ); .pp .b #include .pp .bi "int ioctl(int " fd ", seccomp_ioctl_notif_recv," .bi " struct seccomp_notif *" req ); .bi "int ioctl(int " fd ", seccomp_ioctl_notif_send," .bi " struct seccomp_notif_resp *" resp ); .bi "int ioctl(int " fd ", seccomp_ioctl_notif_id_valid, __u64 *" id ); .bi "int ioctl(int " fd ", seccomp_ioctl_notif_addfd," .bi " struct seccomp_notif_addfd *" addfd ); .fi .sh description this page describes the user-space notification mechanism provided by the secure computing (seccomp) facility. as well as the use of the .b seccomp_filter_flag_new_listener flag, the .br seccomp_ret_user_notif action value, and the .b seccomp_get_notif_sizes operation described in .br seccomp (2), this mechanism involves the use of a number of related .br ioctl (2) operations (described below). .\" .ss overview in conventional usage of a seccomp filter, the decision about how to treat a system call is made by the filter itself. by contrast, the user-space notification mechanism allows the seccomp filter to delegate the handling of the system call to another user-space process. note that this mechanism is explicitly .b not intended as a method implementing security policy; see notes. .pp in the discussion that follows, the thread(s) on which the seccomp filter is installed is (are) referred to as the .ir target , and the process that is notified by the user-space notification mechanism is referred to as the .ir supervisor . .pp a suitably privileged supervisor can use the user-space notification mechanism to perform actions on behalf of the target. the advantage of the user-space notification mechanism is that the supervisor will usually be able to retrieve information about the target and the performed system call that the seccomp filter itself cannot. (a seccomp filter is limited in the information it can obtain and the actions that it can perform because it is running on a virtual machine inside the kernel.) .pp an overview of the steps performed by the target and the supervisor is as follows: .\"------------------------------------- .ip 1. 3 the target establishes a seccomp filter in the usual manner, but with two differences: .rs .ip \(bu 2 the .br seccomp (2) .i flags argument includes the flag .br seccomp_filter_flag_new_listener . consequently, the return value of the (successful) .br seccomp (2) call is a new "listening" file descriptor that can be used to receive notifications. only one "listening" seccomp filter can be installed for a thread. .\" fixme .\" is the last sentence above correct? .\" .\" kees cook (25 oct 2020) notes: .\" .\" i like this limitation, but i expect that it'll need to change in the .\" future. even with lsms, we see the need for arbitrary stacking, and the .\" idea of there being only 1 supervisor will eventually break down. right .\" now there is only 1 because only container managers are using this .\" feature. but if some daemon starts using it to isolate some thread, .\" suddenly it might break if a container manager is trying to listen to it .\" too, etc. i expect it won't be needed soon, but i do think it'll change. .\" .ip \(bu in cases where it is appropriate, the seccomp filter returns the action value .br seccomp_ret_user_notif . this return value will trigger a notification event. .re .\"------------------------------------- .ip 2. in order that the supervisor can obtain notifications using the listening file descriptor, (a duplicate of) that file descriptor must be passed from the target to the supervisor. one way in which this could be done is by passing the file descriptor over a unix domain socket connection between the target and the supervisor (using the .br scm_rights ancillary message type described in .br unix (7)). another way to do this is through the use of .br pidfd_getfd (2). .\" jann horn: .\" instead of using unix domain sockets to send the fd to the .\" parent, i think you could also use clone3() with .\" flags==clone_files|sigchld, dup2() the seccomp fd to an fd .\" that was reserved in the parent, call unshare(clone_files) .\" in the child after setting up the seccomp fd, and wake .\" up the parent with something like pthread_cond_signal()? .\" i'm not sure whether that'd look better or worse in the .\" end though, so maybe just ignore this comment. .\"------------------------------------- .ip 3. the supervisor will receive notification events on the listening file descriptor. these events are returned as structures of type .ir seccomp_notif . because this structure and its size may evolve over kernel versions, the supervisor must first determine the size of this structure using the .br seccomp (2) .b seccomp_get_notif_sizes operation, which returns a structure of type .ir seccomp_notif_sizes . the supervisor allocates a buffer of size .i seccomp_notif_sizes.seccomp_notif bytes to receive notification events. in addition,the supervisor allocates another buffer of size .i seccomp_notif_sizes.seccomp_notif_resp bytes for the response (a .i struct seccomp_notif_resp structure) that it will provide to the kernel (and thus the target). .\"------------------------------------- .ip 4. the target then performs its workload, which includes system calls that will be controlled by the seccomp filter. whenever one of these system calls causes the filter to return the .b seccomp_ret_user_notif action value, the kernel does .i not (yet) execute the system call; instead, execution of the target is temporarily blocked inside the kernel (in a sleep state that is interruptible by signals) and a notification event is generated on the listening file descriptor. .\"------------------------------------- .ip 5. the supervisor can now repeatedly monitor the listening file descriptor for .br seccomp_ret_user_notif -triggered events. to do this, the supervisor uses the .b seccomp_ioctl_notif_recv .br ioctl (2) operation to read information about a notification event; this operation blocks until an event is available. the operation returns a .i seccomp_notif structure containing information about the system call that is being attempted by the target. (as described in notes, the file descriptor can also be monitored with .br select (2), .br poll (2), or .br epoll (7).) .\" fixme .\" christian brauner: .\" .\" do we support o_nonblock with seccomp_ioctl_notif_recv and if .\" not should we? .\" .\" michael kerrisk: .\" .\" a quick test suggests that o_nonblock has no effect on the blocking .\" behavior of seccomp_ioctl_notif_recv. . .\"------------------------------------- .ip 6. the .i seccomp_notif structure returned by the .b seccomp_ioctl_notif_recv operation includes the same information (a .i seccomp_data structure) that was passed to the seccomp filter. this information allows the supervisor to discover the system call number and the arguments for the target's system call. in addition, the notification event contains the id of the thread that triggered the notification and a unique cookie value that is used in subsequent .b seccomp_ioctl_notif_id_valid and .b seccomp_ioctl_notif_send operations. .ip the information in the notification can be used to discover the values of pointer arguments for the target's system call. (this is something that can't be done from within a seccomp filter.) one way in which the supervisor can do this is to open the corresponding .i /proc/[tid]/mem file (see .br proc (5)) and read bytes from the location that corresponds to one of the pointer arguments whose value is supplied in the notification event. .\" tycho andersen mentioned that there are alternatives to /proc/pid/mem, .\" such as ptrace() and /proc/pid/map_files (the supervisor must be careful to avoid a race condition that can occur when doing this; see the description of the .br seccomp_ioctl_notif_id_valid .br ioctl (2) operation below.) in addition, the supervisor can access other system information that is visible in user space but which is not accessible from a seccomp filter. .\"------------------------------------- .ip 7. having obtained information as per the previous step, the supervisor may then choose to perform an action in response to the target's system call (which, as noted above, is not executed when the seccomp filter returns the .b seccomp_ret_user_notif action value). .ip one example use case here relates to containers. the target may be located inside a container where it does not have sufficient capabilities to mount a filesystem in the container's mount namespace. however, the supervisor may be a more privileged process that does have sufficient capabilities to perform the mount operation. .\"------------------------------------- .ip 8. the supervisor then sends a response to the notification. the information in this response is used by the kernel to construct a return value for the target's system call and provide a value that will be assigned to the .i errno variable of the target. .ip the response is sent using the .b seccomp_ioctl_notif_send .br ioctl (2) operation, which is used to transmit a .i seccomp_notif_resp structure to the kernel. this structure includes a cookie value that the supervisor obtained in the .i seccomp_notif structure returned by the .b seccomp_ioctl_notif_recv operation. this cookie value allows the kernel to associate the response with the target. this structure must include the cookie value that the supervisor obtained in the .i seccomp_notif structure returned by the .b seccomp_ioctl_notif_recv operation; the cookie allows the kernel to associate the response with the target. .\"------------------------------------- .ip 9. once the notification has been sent, the system call in the target thread unblocks, returning the information that was provided by the supervisor in the notification response. .\"------------------------------------- .pp as a variation on the last two steps, the supervisor can send a response that tells the kernel that it should execute the target thread's system call; see the discussion of .br seccomp_user_notif_flag_continue , below. .\" .sh ioctl operations the following .br ioctl (2) operations are supported by the seccomp user-space notification file descriptor. for each of these operations, the first (file descriptor) argument of .br ioctl (2) is the listening file descriptor returned by a call to .br seccomp (2) with the .br seccomp_filter_flag_new_listener flag. .\" .ss seccomp_ioctl_notif_recv the .b seccomp_ioctl_notif_recv operation (available since linux 5.0) is used to obtain a user-space notification event. if no such event is currently pending, the operation blocks until an event occurs. the third .br ioctl (2) argument is a pointer to a structure of the following form which contains information about the event. this structure must be zeroed out before the call. .pp .in +4n .ex struct seccomp_notif { __u64 id; /* cookie */ __u32 pid; /* tid of target thread */ __u32 flags; /* currently unused (0) */ struct seccomp_data data; /* see seccomp(2) */ }; .ee .in .pp the fields in this structure are as follows: .tp .i id this is a cookie for the notification. each such cookie is guaranteed to be unique for the corresponding seccomp filter. .rs .ip \(bu 2 the cookie can be used with the .b seccomp_ioctl_notif_id_valid .br ioctl (2) operation described below. .ip \(bu when returning a notification response to the kernel, the supervisor must include the cookie value in the .ir seccomp_notif_resp structure that is specified as the argument of the .br seccomp_ioctl_notif_send operation. .re .tp .i pid this is the thread id of the target thread that triggered the notification event. .tp .i flags this is a bit mask of flags providing further information on the event. in the current implementation, this field is always zero. .tp .i data this is a .i seccomp_data structure containing information about the system call that triggered the notification. this is the same structure that is passed to the seccomp filter. see .br seccomp (2) for details of this structure. .pp on success, this operation returns 0; on failure, \-1 is returned, and .i errno is set to indicate the cause of the error. this operation can fail with the following errors: .tp .br einval " (since linux 5.5)" .\" commit 2882d53c9c6f3b8311d225062522f03772cf0179 the .i seccomp_notif structure that was passed to the call contained nonzero fields. .tp .b enoent the target thread was killed by a signal as the notification information was being generated, or the target's (blocked) system call was interrupted by a signal handler. .\" fixme .\" from my experiments, .\" it appears that if a seccomp_ioctl_notif_recv is done after .\" the target thread terminates, then the ioctl() simply .\" blocks (rather than returning an error to indicate that the .\" target no longer exists). .\" .\" i found that surprising, and it required some contortions in .\" the example program. it was not possible to code my sigchld .\" handler (which reaps the zombie when the worker/target .\" terminates) to simply set a flag checked in the main .\" handlenotifications() loop, since this created an .\" unavoidable race where the child might terminate just after .\" i had checked the flag, but before i blocked (forever!) in the .\" seccomp_ioctl_notif_recv operation. instead, i had to code .\" the signal handler to simply call _exit(2) in order to .\" terminate the parent process (the supervisor). .\" .\" is this expected behavior? it seems to me rather .\" desirable that seccomp_ioctl_notif_recv should give an error .\" if the target has terminated. .\" .\" jann posted a patch to rectify this, but there was no response .\" (lore link: https://bit.ly/3jvubxk) to his question about fixing .\" this issue. (i've tried building with the patch, but encountered .\" an issue with the target process entering d state after a signal.) .\" .\" for now, this behavior is documented in bugs. .\" .\" kees cook commented: let's change [this] asap! .\" .ss seccomp_ioctl_notif_id_valid the .b seccomp_ioctl_notif_id_valid operation (available since linux 5.0) is used to check that a notification id returned by an earlier .b seccomp_ioctl_notif_recv operation is still valid (i.e., that the target still exists and its system call is still blocked waiting for a response). .pp the third .br ioctl (2) argument is a pointer to the cookie .ri ( id ) returned by the .b seccomp_ioctl_notif_recv operation. .pp this operation is necessary to avoid race conditions that can occur when the .i pid returned by the .b seccomp_ioctl_notif_recv operation terminates, and that process id is reused by another process. an example of this kind of race is the following .ip 1. 3 a notification is generated on the listening file descriptor. the returned .i seccomp_notif contains the tid of the target thread (in the .i pid field of the structure). .ip 2. the target terminates. .ip 3. another thread or process is created on the system that by chance reuses the tid that was freed when the target terminated. .ip 4. the supervisor .br open (2)s the .ir /proc/[tid]/mem file for the tid obtained in step 1, with the intention of (say) inspecting the memory location(s) that containing the argument(s) of the system call that triggered the notification in step 1. .pp in the above scenario, the risk is that the supervisor may try to access the memory of a process other than the target. this race can be avoided by following the call to .br open (2) with a .b seccomp_ioctl_notif_id_valid operation to verify that the process that generated the notification is still alive. (note that if the target terminates after the latter step, a subsequent .br read (2) from the file descriptor may return 0, indicating end of file.) .\" jann horn: .\" the pid can be reused, but the /proc/$pid directory is .\" internally not associated with the numeric pid, but, .\" conceptually speaking, with a specific incarnation of the .\" pid, or something like that. (actually, it is associated .\" with the "struct pid", which is not reused, instead of the .\" numeric pid. .pp see notes for a discussion of other cases where .b seccomp_ioctl_notif_id_valid checks must be performed. .pp on success (i.e., the notification id is still valid), this operation returns 0. on failure (i.e., the notification id is no longer valid), \-1 is returned, and .i errno is set to .br enoent . .\" .ss seccomp_ioctl_notif_send the .b seccomp_ioctl_notif_send operation (available since linux 5.0) is used to send a notification response back to the kernel. the third .br ioctl (2) argument of this structure is a pointer to a structure of the following form: .pp .in +4n .ex struct seccomp_notif_resp { __u64 id; /* cookie value */ __s64 val; /* success return value */ __s32 error; /* 0 (success) or negative error number */ __u32 flags; /* see below */ }; .ee .in .pp the fields of this structure are as follows: .tp .i id this is the cookie value that was obtained using the .b seccomp_ioctl_notif_recv operation. this cookie value allows the kernel to correctly associate this response with the system call that triggered the user-space notification. .tp .i val this is the value that will be used for a spoofed success return for the target's system call; see below. .tp .i error this is the value that will be used as the error number .ri ( errno ) for a spoofed error return for the target's system call; see below. .tp .i flags this is a bit mask that includes zero or more of the following flags: .rs .tp .br seccomp_user_notif_flag_continue " (since linux 5.5)" tell the kernel to execute the target's system call. .\" commit fb3c5386b382d4097476ce9647260fc89b34afdb .re .pp two kinds of response are possible: .ip \(bu 2 a response to the kernel telling it to execute the target's system call. in this case, the .i flags field includes .b seccomp_user_notif_flag_continue and the .i error and .i val fields must be zero. .ip this kind of response can be useful in cases where the supervisor needs to do deeper analysis of the target's system call than is possible from a seccomp filter (e.g., examining the values of pointer arguments), and, having decided that the system call does not require emulation by the supervisor, the supervisor wants the system call to be executed normally in the target. .ip the .b seccomp_user_notif_flag_continue flag should be used with caution; see notes. .ip \(bu a spoofed return value for the target's system call. in this case, the kernel does not execute the target's system call, instead causing the system call to return a spoofed value as specified by fields of the .i seccomp_notif_resp structure. the supervisor should set the fields of this structure as follows: .rs .ip + 3 .i flags does not contain .br seccomp_user_notif_flag_continue . .ip + .i error is set either to 0 for a spoofed "success" return or to a negative error number for a spoofed "failure" return. in the former case, the kernel causes the target's system call to return the value specified in the .i val field. in the latter case, the kernel causes the target's system call to return \-1, and .i errno is assigned the negated .i error value. .ip + .i val is set to a value that will be used as the return value for a spoofed "success" return for the target's system call. the value in this field is ignored if the .i error field contains a nonzero value. .\" fixme .\" kees cook suggested: .\" .\" strictly speaking, this is architecture specific, but .\" all architectures do it this way. should seccomp enforce .\" val == 0 when err != 0 ? .\" .\" christian brauner .\" .\" feels like it should, at least for the send ioctl where we already .\" verify that val and err are both 0 when continue is specified (as you .\" pointed out correctly above). .re .pp on success, this operation returns 0; on failure, \-1 is returned, and .i errno is set to indicate the cause of the error. this operation can fail with the following errors: .tp .b einprogress a response to this notification has already been sent. .tp .b einval an invalid value was specified in the .i flags field. .tp .b .b einval the .i flags field contained .br seccomp_user_notif_flag_continue , and the .i error or .i val field was not zero. .tp .b enoent the blocked system call in the target has been interrupted by a signal handler or the target has terminated. .\" jann horn notes: .\" you could also get this [enoent] if a response has already .\" been sent, instead of einprogress - the only difference is .\" whether the target thread has picked up the response yet .\" .ss seccomp_ioctl_notif_addfd the .b seccomp_ioctl_notif_addfd operation (available since linux 5.9) allows the supervisor to install a file descriptor into the target's file descriptor table. much like the use of .br scm_rights messages described in .br unix (7), this operation is semantically equivalent to duplicating a file descriptor from the supervisor's file descriptor table into the target's file descriptor table. .pp the .br seccomp_ioctl_notif_addfd operation permits the supervisor to emulate a target system call (such as .br socket (2) or .br openat (2)) that generates a file descriptor. the supervisor can perform the system call that generates the file descriptor (and associated open file description) and then use this operation to allocate a file descriptor that refers to the same open file description in the target. (for an explanation of open file descriptions, see .br open (2).) .pp once this operation has been performed, the supervisor can close its copy of the file descriptor. .pp in the target, the received file descriptor is subject to the same linux security module (lsm) checks as are applied to a file descriptor that is received in an .br scm_rights ancillary message. if the file descriptor refers to a socket, it inherits the cgroup version 1 network controller settings .ri ( classid and .ir netprioidx ) of the target. .pp the third .br ioctl (2) argument is a pointer to a structure of the following form: .pp .in +4n .ex struct seccomp_notif_addfd { __u64 id; /* cookie value */ __u32 flags; /* flags */ __u32 srcfd; /* local file descriptor number */ __u32 newfd; /* 0 or desired file descriptor number in target */ __u32 newfd_flags; /* flags to set on target file descriptor */ }; .ee .in .pp the fields in this structure are as follows: .tp .i id this field should be set to the notification id (cookie value) that was obtained via .br seccomp_ioctl_notif_recv . .tp .i flags this field is a bit mask of flags that modify the behavior of the operation. currently, only one flag is supported: .rs .tp .br seccomp_addfd_flag_setfd when allocating the file descriptor in the target, use the file descriptor number specified in the .i newfd field. .tp .br seccomp_addfd_flag_send " (since linux 5.14)" .\" commit 0ae71c7720e3ae3aabd2e8a072d27f7bd173d25c perform the equivalent of .b seccomp_ioctl_notif_addfd plus .b seccomp_ioctl_notif_send as an atomic operation. on successful invocation, the target process's .i errno will be 0 and the return value will be the file descriptor number that was allocated in the target. if allocating the file descriptor in the target fails, the target's system call continues to be blocked until a successful response is sent. .re .tp .i srcfd this field should be set to the number of the file descriptor in the supervisor that is to be duplicated. .tp .i newfd this field determines which file descriptor number is allocated in the target. if the .br seccomp_addfd_flag_setfd flag is set, then this field specifies which file descriptor number should be allocated. if this file descriptor number is already open in the target, it is atomically closed and reused. if the descriptor duplication fails due to an lsm check, or if .i srcfd is not a valid file descriptor, the file descriptor .i newfd will not be closed in the target process. .ip if the .br seccomp_addfd_flag_setfd flag it not set, then this field must be 0, and the kernel allocates the lowest unused file descriptor number in the target. .tp .i newfd_flags this field is a bit mask specifying flags that should be set on the file descriptor that is received in the target process. currently, only the following flag is implemented: .rs .tp .b o_cloexec set the close-on-exec flag on the received file descriptor. .re .pp on success, this .br ioctl (2) call returns the number of the file descriptor that was allocated in the target. assuming that the emulated system call is one that returns a file descriptor as its function result (e.g., .br socket (2)), this value can be used as the return value .ri ( resp.val ) that is supplied in the response that is subsequently sent with the .br seccomp_ioctl_notif_send operation. .pp on error, \-1 is returned and .i errno is set to indicate the cause of the error. .pp this operation can fail with the following errors: .tp .b ebadf allocating the file descriptor in the target would cause the target's .br rlimit_nofile limit to be exceeded (see .br getrlimit (2)). .tp .b ebusy if the flag .b seccomp_ioctl_notif_send is used, this means the operation can't proceed until other .b seccomp_ioctl_notif_addfd requests are processed. .tp .b einprogress the user-space notification specified in the .i id field exists but has not yet been fetched (by a .br seccomp_ioctl_notif_recv ) or has already been responded to (by a .br seccomp_ioctl_notif_send ). .tp .b einval an invalid flag was specified in the .i flags or .i newfd_flags field, or the .i newfd field is nonzero and the .b seccomp_addfd_flag_setfd flag was not specified in the .i flags field. .tp .b emfile the file descriptor number specified in .i newfd exceeds the limit specified in .ir /proc/sys/fs/nr_open . .tp .b enoent the blocked system call in the target has been interrupted by a signal handler or the target has terminated. .pp here is some sample code (with error handling omitted) that uses the .b seccomp_addfd_flag_setfd operation (here, to emulate a call to .br openat (2)): .pp .ex .in +4n int fd, removefd; fd = openat(req->data.args[0], path, req->data.args[2], req->data.args[3]); struct seccomp_notif_addfd addfd; addfd.id = req->id; /* cookie from seccomp_ioctl_notif_recv */ addfd.srcfd = fd; addfd.newfd = 0; addfd.flags = 0; addfd.newfd_flags = o_cloexec; targetfd = ioctl(notifyfd, seccomp_ioctl_notif_addfd, &addfd); close(fd); /* no longer needed in supervisor */ struct seccomp_notif_resp *resp; /* code to allocate 'resp' omitted */ resp->id = req->id; resp->error = 0; /* "success" */ resp->val = targetfd; resp->flags = 0; ioctl(notifyfd, seccomp_ioctl_notif_send, resp); .in .ee .sh notes one example use case for the user-space notification mechanism is to allow a container manager (a process which is typically running with more privilege than the processes inside the container) to mount block devices or create device nodes for the container. the mount use case provides an example of where the .br seccomp_user_notif_flag_continue .br ioctl (2) operation is useful. upon receiving a notification for the .br mount (2) system call, the container manager (the "supervisor") can distinguish a request to mount a block filesystem (which would not be possible for a "target" process inside the container) and mount that file system. if, on the other hand, the container manager detects that the operation could be performed by the process inside the container (e.g., a mount of a .br tmpfs (5) filesystem), it can notify the kernel that the target process's .br mount (2) system call can continue. .\" .ss select()/poll()/epoll semantics the file descriptor returned when .br seccomp (2) is employed with the .b seccomp_filter_flag_new_listener flag can be monitored using .br poll (2), .br epoll (7), and .br select (2). these interfaces indicate that the file descriptor is ready as follows: .ip \(bu 2 when a notification is pending, these interfaces indicate that the file descriptor is readable. following such an indication, a subsequent .b seccomp_ioctl_notif_recv .br ioctl (2) will not block, returning either information about a notification or else failing with the error .b eintr if the target has been killed by a signal or its system call has been interrupted by a signal handler. .ip \(bu after the notification has been received (i.e., by the .b seccomp_ioctl_notif_recv .br ioctl (2) operation), these interfaces indicate that the file descriptor is writable, meaning that a notification response can be sent using the .b seccomp_ioctl_notif_send .br ioctl (2) operation. .ip \(bu after the last thread using the filter has terminated and been reaped using .br waitpid (2) (or similar), the file descriptor indicates an end-of-file condition (readable in .br select (2); .br pollhup / epollhup in .br poll (2)/ .br epoll_wait (2)). .ss design goals; use of seccomp_user_notif_flag_continue the intent of the user-space notification feature is to allow system calls to be performed on behalf of the target. the target's system call should either be handled by the supervisor or allowed to continue normally in the kernel (where standard security policies will be applied). .pp .br "note well" : this mechanism must not be used to make security policy decisions about the system call, which would be inherently race-prone for reasons described next. .pp the .b seccomp_user_notif_flag_continue flag must be used with caution. if set by the supervisor, the target's system call will continue. however, there is a time-of-check, time-of-use race here, since an attacker could exploit the interval of time where the target is blocked waiting on the "continue" response to do things such as rewriting the system call arguments. .pp note furthermore that a user-space notifier can be bypassed if the existing filters allow the use of .br seccomp (2) or .br prctl (2) to install a filter that returns an action value with a higher precedence than .b seccomp_ret_user_notif (see .br seccomp (2)). .pp it should thus be absolutely clear that the seccomp user-space notification mechanism .b can not be used to implement a security policy! it should only ever be used in scenarios where a more privileged process supervises the system calls of a lesser privileged target to get around kernel-enforced security restrictions when the supervisor deems this safe. in other words, in order to continue a system call, the supervisor should be sure that another security mechanism or the kernel itself will sufficiently block the system call if its arguments are rewritten to something unsafe. .\" .ss caveats regarding the use of /proc/[tid]/mem the discussion above noted the need to use the .br seccomp_ioctl_notif_id_valid .br ioctl (2) when opening the .ir /proc/[tid]/mem file of the target to avoid the possibility of accessing the memory of the wrong process in the event that the target terminates and its id is recycled by another (unrelated) thread. however, the use of this .br ioctl (2) operation is also necessary in other situations, as explained in the following paragraphs. .pp consider the following scenario, where the supervisor tries to read the pathname argument of a target's blocked .br mount (2) system call: .ip \(bu 2 from one of its functions .ri ( func() ), the target calls .br mount (2), which triggers a user-space notification and causes the target to block. .ip \(bu the supervisor receives the notification, opens .ir /proc/[tid]/mem , and (successfully) performs the .br seccomp_ioctl_notif_id_valid check. .ip \(bu the target receives a signal, which causes the .br mount (2) to abort. .ip \(bu the signal handler executes in the target, and returns. .ip \(bu upon return from the handler, the execution of .i func() resumes, and it returns (and perhaps other functions are called, overwriting the memory that had been used for the stack frame of .ir func() ). .ip \(bu using the address provided in the notification information, the supervisor reads from the target's memory location that used to contain the pathname. .ip \(bu the supervisor now calls .br mount (2) with some arbitrary bytes obtained in the previous step. .pp the conclusion from the above scenario is this: since the target's blocked system call may be interrupted by a signal handler, the supervisor must be written to expect that the target may abandon its system call at .b any time; in such an event, any information that the supervisor obtained from the target's memory must be considered invalid. .pp to prevent such scenarios, every read from the target's memory must be separated from use of the bytes so obtained by a .br seccomp_ioctl_notif_id_valid check. in the above example, the check would be placed between the two final steps. an example of such a check is shown in examples. .pp following on from the above, it should be clear that a write by the supervisor into the target's memory can .b never be considered safe. .\" .ss caveats regarding blocking system calls suppose that the target performs a blocking system call (e.g., .br accept (2)) that the supervisor should handle. the supervisor might then in turn execute the same blocking system call. .pp in this scenario, it is important to note that if the target's system call is now interrupted by a signal, the supervisor is .i not informed of this. if the supervisor does not take suitable steps to actively discover that the target's system call has been canceled, various difficulties can occur. taking the example of .br accept (2), the supervisor might remain blocked in its .br accept (2) holding a port number that the target (which, after the interruption by the signal handler, perhaps closed its listening socket) might expect to be able to reuse in a .br bind (2) call. .pp therefore, when the supervisor wishes to emulate a blocking system call, it must do so in such a way that it gets informed if the target's system call is interrupted by a signal handler. for example, if the supervisor itself executes the same blocking system call, then it could employ a separate thread that uses the .b seccomp_ioctl_notif_id_valid operation to check if the target is still blocked in its system call. alternatively, in the .br accept (2) example, the supervisor might use .br poll (2) to monitor both the notification file descriptor (so as to discover when the target's .br accept (2) call has been interrupted) and the listening file descriptor (so as to know when a connection is available). .pp if the target's system call is interrupted, the supervisor must take care to release resources (e.g., file descriptors) that it acquired on behalf of the target. .\" .ss interaction with sa_restart signal handlers consider the following scenario: .ip \(bu 2 the target process has used .br sigaction (2) to install a signal handler with the .b sa_restart flag. .ip \(bu the target has made a system call that triggered a seccomp user-space notification and the target is currently blocked until the supervisor sends a notification response. .ip \(bu a signal is delivered to the target and the signal handler is executed. .ip \(bu when (if) the supervisor attempts to send a notification response, the .b seccomp_ioctl_notif_send .br ioctl (2)) operation will fail with the .br enoent error. .pp in this scenario, the kernel will restart the target's system call. consequently, the supervisor will receive another user-space notification. thus, depending on how many times the blocked system call is interrupted by a signal handler, the supervisor may receive multiple notifications for the same instance of a system call in the target. .pp one oddity is that system call restarting as described in this scenario will occur even for the blocking system calls listed in .br signal (7) that would .b never normally be restarted by the .br sa_restart flag. .\" fixme .\" about the above, kees cook commented: .\" .\" does this need fixing? i imagine the correct behavior for this case .\" would be a response to _send of einprogress and the target would see .\" eintr normally? .\" .\" i mean, it's not like seccomp doesn't already expose weirdness with .\" syscall restarts. not even arm64 compat agrees[3] with arm32 in this .\" regard. :( . .\" fixme .\" michael kerrisk: .\" i wonder about the effect of this oddity for system calls that .\" are normally nonrestartable because they have timeouts. my .\" understanding is that the kernel doesn't restart those system .\" calls because it's impossible for the kernel to restart the call .\" with the right timeout value. i wonder what happens when those .\" system calls are restarted in the scenario we're discussing.) .pp furthermore, if the supervisor response is a file descriptor added with .br seccomp_ioctl_notif_addfd , then the flag .b seccomp_addfd_flag_send can be used to atomically add the file descriptor and return that value, making sure no file descriptors are inadvertently leaked into the target. .sh bugs if a .br seccomp_ioctl_notif_recv .br ioctl (2) operation .\" or a poll/epoll/select is performed after the target terminates, then the .br ioctl (2) call simply blocks (rather than returning an error to indicate that the target no longer exists). .\" fixme .\" comment from kees cook: .\" .\" i want this fixed. it caused me no end of pain when building the .\" selftests, and ended up spawning my implementing a global test timeout .\" in kselftest. :p before the usage counter refactor, there was no sane .\" way to deal with this, but now i think we're close. .\" .sh examples the (somewhat contrived) program shown below demonstrates the use of the interfaces described in this page. the program creates a child process that serves as the "target" process. the child process installs a seccomp filter that returns the .b seccomp_ret_user_notif action value if a call is made to .br mkdir (2). the child process then calls .br mkdir (2) once for each of the supplied command-line arguments, and reports the result returned by the call. after processing all arguments, the child process terminates. .pp the parent process acts as the supervisor, listening for the notifications that are generated when the target process calls .br mkdir (2). when such a notification occurs, the supervisor examines the memory of the target process (using .ir /proc/[pid]/mem ) to discover the pathname argument that was supplied to the .br mkdir (2) call, and performs one of the following actions: .ip \(bu 2 if the pathname begins with the prefix "/tmp/", then the supervisor attempts to create the specified directory, and then spoofs a return for the target process based on the return value of the supervisor's .br mkdir (2) call. in the event that that call succeeds, the spoofed success return value is the length of the pathname. .ip \(bu if the pathname begins with "./" (i.e., it is a relative pathname), the supervisor sends a .b seccomp_user_notif_flag_continue response to the kernel to say that the kernel should execute the target process's .br mkdir (2) call. .ip \(bu if the pathname begins with some other prefix, the supervisor spoofs an error return for the target process, so that the target process's .br mkdir (2) call appears to fail with the error .br eopnotsupp ("operation not supported"). additionally, if the specified pathname is exactly "/bye", then the supervisor terminates. .pp this program can be used to demonstrate various aspects of the behavior of the seccomp user-space notification mechanism. to help aid such demonstrations, the program logs various messages to show the operation of the target process (lines prefixed "t:") and the supervisor (indented lines prefixed "s:"). .pp in the following example, the target attempts to create the directory .ir /tmp/x . upon receiving the notification, the supervisor creates the directory on the target's behalf, and spoofs a success return to be received by the target process's .br mkdir (2) call. .pp .in +4n .ex $ \fb./seccomp_unotify /tmp/x\fp t: pid = 23168 t: about to mkdir("/tmp/x") s: got notification (id 0x17445c4a0f4e0e3c) for pid 23168 s: executing: mkdir("/tmp/x", 0700) s: success! spoofed return = 6 s: sending response (flags = 0; val = 6; error = 0) t: success: mkdir(2) returned 6 t: terminating s: target has terminated; bye .ee .in .pp in the above output, note that the spoofed return value seen by the target process is 6 (the length of the pathname .ir /tmp/x ), whereas a normal .br mkdir (2) call returns 0 on success. .pp in the next example, the target attempts to create a directory using the relative pathname .ir ./sub . since this pathname starts with "./", the supervisor sends a .b seccomp_user_notif_flag_continue response to the kernel, and the kernel then (successfully) executes the target process's .br mkdir (2) call. .pp .in +4n .ex $ \fb./seccomp_unotify ./sub\fp t: pid = 23204 t: about to mkdir("./sub") s: got notification (id 0xddb16abe25b4c12) for pid 23204 s: target can execute system call s: sending response (flags = 0x1; val = 0; error = 0) t: success: mkdir(2) returned 0 t: terminating s: target has terminated; bye .ee .in .pp if the target process attempts to create a directory with a pathname that doesn't start with "." and doesn't begin with the prefix "/tmp/", then the supervisor spoofs an error return .rb ( eopnotsupp , "operation not supported") for the target's .br mkdir (2) call (which is not executed): .pp .in +4n .ex $ \fb./seccomp_unotify /xxx\fp t: pid = 23178 t: about to mkdir("/xxx") s: got notification (id 0xe7dc095d1c524e80) for pid 23178 s: spoofing error response (operation not supported) s: sending response (flags = 0; val = 0; error = \-95) t: error: mkdir(2): operation not supported t: terminating s: target has terminated; bye .ee .in .pp in the next example, the target process attempts to create a directory with the pathname .br /tmp/nosuchdir/b . upon receiving the notification, the supervisor attempts to create that directory, but the .br mkdir (2) call fails because the directory .br /tmp/nosuchdir does not exist. consequently, the supervisor spoofs an error return that passes the error that it received back to the target process's .br mkdir (2) call. .pp .in +4n .ex $ \fb./seccomp_unotify /tmp/nosuchdir/b\fp t: pid = 23199 t: about to mkdir("/tmp/nosuchdir/b") s: got notification (id 0x8744454293506046) for pid 23199 s: executing: mkdir("/tmp/nosuchdir/b", 0700) s: failure! (errno = 2; no such file or directory) s: sending response (flags = 0; val = 0; error = \-2) t: error: mkdir(2): no such file or directory t: terminating s: target has terminated; bye .ee .in .pp if the supervisor receives a notification and sees that the argument of the target's .br mkdir (2) is the string "/bye", then (as well as spoofing an .b eopnotsupp error), the supervisor terminates. if the target process subsequently executes another .br mkdir (2) that triggers its seccomp filter to return the .b seccomp_ret_user_notif action value, then the kernel causes the target process's system call to fail with the error .b enosys ("function not implemented"). this is demonstrated by the following example: .pp .in +4n .ex $ \fb./seccomp_unotify /bye /tmp/y\fp t: pid = 23185 t: about to mkdir("/bye") s: got notification (id 0xa81236b1d2f7b0f4) for pid 23185 s: spoofing error response (operation not supported) s: sending response (flags = 0; val = 0; error = \-95) s: terminating ********** t: error: mkdir(2): operation not supported t: about to mkdir("/tmp/y") t: error: mkdir(2): function not implemented t: terminating .ee .in .\" .ss program source .ex #define _gnu_source #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) /* send the file descriptor \(aqfd\(aq over the connected unix domain socket \(aqsockfd\(aq. returns 0 on success, or \-1 on error. */ static int sendfd(int sockfd, int fd) { struct msghdr msgh; struct iovec iov; int data; struct cmsghdr *cmsgp; /* allocate a char array of suitable size to hold the ancillary data. however, since this buffer is in reality a \(aqstruct cmsghdr\(aq, use a union to ensure that it is suitably aligned. */ union { char buf[cmsg_space(sizeof(int))]; /* space large enough to hold an \(aqint\(aq */ struct cmsghdr align; } controlmsg; /* the \(aqmsg_name\(aq field can be used to specify the address of the destination socket when sending a datagram. however, we do not need to use this field because \(aqsockfd\(aq is a connected socket. */ msgh.msg_name = null; msgh.msg_namelen = 0; /* on linux, we must transmit at least one byte of real data in order to send ancillary data. we transmit an arbitrary integer whose value is ignored by recvfd(). */ msgh.msg_iov = &iov; msgh.msg_iovlen = 1; iov.iov_base = &data; iov.iov_len = sizeof(int); data = 12345; /* set \(aqmsghdr\(aq fields that describe ancillary data */ msgh.msg_control = controlmsg.buf; msgh.msg_controllen = sizeof(controlmsg.buf); /* set up ancillary data describing file descriptor to send */ cmsgp = cmsg_firsthdr(&msgh); cmsgp\->cmsg_level = sol_socket; cmsgp\->cmsg_type = scm_rights; cmsgp\->cmsg_len = cmsg_len(sizeof(int)); memcpy(cmsg_data(cmsgp), &fd, sizeof(int)); /* send real plus ancillary data */ if (sendmsg(sockfd, &msgh, 0) == \-1) return \-1; return 0; } /* receive a file descriptor on a connected unix domain socket. returns the received file descriptor on success, or \-1 on error. */ static int recvfd(int sockfd) { struct msghdr msgh; struct iovec iov; int data, fd; ssize_t nr; /* allocate a char buffer for the ancillary data. see the comments in sendfd() */ union { char buf[cmsg_space(sizeof(int))]; struct cmsghdr align; } controlmsg; struct cmsghdr *cmsgp; /* the \(aqmsg_name\(aq field can be used to obtain the address of the sending socket. however, we do not need this information. */ msgh.msg_name = null; msgh.msg_namelen = 0; /* specify buffer for receiving real data */ msgh.msg_iov = &iov; msgh.msg_iovlen = 1; iov.iov_base = &data; /* real data is an \(aqint\(aq */ iov.iov_len = sizeof(int); /* set \(aqmsghdr\(aq fields that describe ancillary data */ msgh.msg_control = controlmsg.buf; msgh.msg_controllen = sizeof(controlmsg.buf); /* receive real plus ancillary data; real data is ignored */ nr = recvmsg(sockfd, &msgh, 0); if (nr == \-1) return \-1; cmsgp = cmsg_firsthdr(&msgh); /* check the validity of the \(aqcmsghdr\(aq */ if (cmsgp == null || cmsgp\->cmsg_len != cmsg_len(sizeof(int)) || cmsgp\->cmsg_level != sol_socket || cmsgp\->cmsg_type != scm_rights) { errno = einval; return \-1; } /* return the received file descriptor to our caller */ memcpy(&fd, cmsg_data(cmsgp), sizeof(int)); return fd; } static void sigchldhandler(int sig) { char msg[] = "\ets: target has terminated; bye\en"; write(stdout_fileno, msg, sizeof(msg) - 1); _exit(exit_success); } static int seccomp(unsigned int operation, unsigned int flags, void *args) { return syscall(__nr_seccomp, operation, flags, args); } /* the following is the x86\-64\-specific bpf boilerplate code for checking that the bpf program is running on the right architecture + abi. at completion of these instructions, the accumulator contains the system call number. */ /* for the x32 abi, all system call numbers have bit 30 set */ #define x32_syscall_bit 0x40000000 #define x86_64_check_arch_and_load_syscall_nr \e bpf_stmt(bpf_ld | bpf_w | bpf_abs, \e (offsetof(struct seccomp_data, arch))), \e bpf_jump(bpf_jmp | bpf_jeq | bpf_k, audit_arch_x86_64, 0, 2), \e bpf_stmt(bpf_ld | bpf_w | bpf_abs, \e (offsetof(struct seccomp_data, nr))), \e bpf_jump(bpf_jmp | bpf_jge | bpf_k, x32_syscall_bit, 0, 1), \e bpf_stmt(bpf_ret | bpf_k, seccomp_ret_kill_process) /* installnotifyfilter() installs a seccomp filter that generates user\-space notifications (seccomp_ret_user_notif) when the process calls mkdir(2); the filter allows all other system calls. the function return value is a file descriptor from which the user\-space notifications can be fetched. */ static int installnotifyfilter(void) { struct sock_filter filter[] = { x86_64_check_arch_and_load_syscall_nr, /* mkdir() triggers notification to user\-space supervisor */ bpf_jump(bpf_jmp | bpf_jeq | bpf_k, __nr_mkdir, 0, 1), bpf_stmt(bpf_ret + bpf_k, seccomp_ret_user_notif), /* every other system call is allowed */ bpf_stmt(bpf_ret | bpf_k, seccomp_ret_allow), }; struct sock_fprog prog = { .len = sizeof(filter) / sizeof(filter[0]), .filter = filter, }; /* install the filter with the seccomp_filter_flag_new_listener flag; as a result, seccomp() returns a notification file descriptor. */ int notifyfd = seccomp(seccomp_set_mode_filter, seccomp_filter_flag_new_listener, &prog); if (notifyfd == \-1) errexit("seccomp\-install\-notify\-filter"); return notifyfd; } /* close a pair of sockets created by socketpair() */ static void closesocketpair(int sockpair[2]) { if (close(sockpair[0]) == \-1) errexit("closesocketpair\-close\-0"); if (close(sockpair[1]) == \-1) errexit("closesocketpair\-close\-1"); } /* implementation of the target process; create a child process that: (1) installs a seccomp filter with the seccomp_filter_flag_new_listener flag; (2) writes the seccomp notification file descriptor returned from the previous step onto the unix domain socket, \(aqsockpair[0]\(aq; (3) calls mkdir(2) for each element of \(aqargv\(aq. the function return value in the parent is the pid of the child process; the child does not return from this function. */ static pid_t targetprocess(int sockpair[2], char *argv[]) { pid_t targetpid = fork(); if (targetpid == \-1) errexit("fork"); if (targetpid > 0) /* in parent, return pid of child */ return targetpid; /* child falls through to here */ printf("t: pid = %ld\en", (long) getpid()); /* install seccomp filter(s) */ if (prctl(pr_set_no_new_privs, 1, 0, 0, 0)) errexit("prctl"); int notifyfd = installnotifyfilter(); /* pass the notification file descriptor to the tracing process over a unix domain socket */ if (sendfd(sockpair[0], notifyfd) == \-1) errexit("sendfd"); /* notification and socket fds are no longer needed in target */ if (close(notifyfd) == \-1) errexit("close\-target\-notify\-fd"); closesocketpair(sockpair); /* perform a mkdir() call for each of the command\-line arguments */ for (char **ap = argv; *ap != null; ap++) { printf("\ent: about to mkdir(\e"%s\e")\en", *ap); int s = mkdir(*ap, 0700); if (s == \-1) perror("t: error: mkdir(2)"); else printf("t: success: mkdir(2) returned %d\en", s); } printf("\ent: terminating\en"); exit(exit_success); } /* check that the notification id provided by a seccomp_ioctl_notif_recv operation is still valid. it will no longer be valid if the target process has terminated or is no longer blocked in the system call that generated the notification (because it was interrupted by a signal). this operation can be used when doing such things as accessing /proc/pid files in the target process in order to avoid toctou race conditions where the pid that is returned by seccomp_ioctl_notif_recv terminates and is reused by another process. */ static bool cookieisvalid(int notifyfd, uint64_t id) { return ioctl(notifyfd, seccomp_ioctl_notif_id_valid, &id) == 0; } /* access the memory of the target process in order to fetch the pathname referred to by the system call argument \(aqargnum\(aq in \(aqreq\->data.args[]\(aq. the pathname is returned in \(aqpath\(aq, a buffer of \(aqlen\(aq bytes allocated by the caller. returns true if the pathname is successfully fetched, and false otherwise. for possible causes of failure, see the comments below. */ static bool gettargetpathname(struct seccomp_notif *req, int notifyfd, int argnum, char *path, size_t len) { char procmempath[path_max]; snprintf(procmempath, sizeof(procmempath), "/proc/%d/mem", req\->pid); int procmemfd = open(procmempath, o_rdonly | o_cloexec); if (procmemfd == \-1) return false; /* check that the process whose info we are accessing is still alive and blocked in the system call that caused the notification. if the seccomp_ioctl_notif_id_valid operation (performed in cookieisvalid()) succeeded, we know that the /proc/pid/mem file descriptor that we opened corresponded to the process for which we received a notification. if that process subsequently terminates, then read() on that file descriptor will return 0 (eof). */ if (!cookieisvalid(notifyfd, req\->id)) { close(procmemfd); return false; } /* read bytes at the location containing the pathname argument */ ssize_t nread = pread(procmemfd, path, len, req\->data.args[argnum]); close(procmemfd); if (nread <= 0) return false; /* once again check that the notification id is still valid. the case we are particularly concerned about here is that just before we fetched the pathname, the target\(aqs blocked system call was interrupted by a signal handler, and after the handler returned, the target carried on execution (past the interrupted system call). in that case, we have no guarantees about what we are reading, since the target\(aqs memory may have been arbitrarily changed by subsequent operations. */ if (!cookieisvalid(notifyfd, req\->id)) { perror("\ets: notification id check failed!!!"); return false; } /* even if the target\(aqs system call was not interrupted by a signal, we have no guarantees about what was in the memory of the target process. (the memory may have been modified by another thread, or even by an external attacking process.) we therefore treat the buffer returned by pread() as untrusted input. the buffer should contain a terminating null byte; if not, then we will trigger an error for the target process. */ if (strnlen(path, nread) < nread) return true; return false; } /* allocate buffers for the seccomp user\-space notification request and response structures. it is the caller\(aqs responsibility to free the buffers returned via \(aqreq\(aq and \(aqresp\(aq. */ static void allocseccompnotifbuffers(struct seccomp_notif **req, struct seccomp_notif_resp **resp, struct seccomp_notif_sizes *sizes) { /* discover the sizes of the structures that are used to receive notifications and send notification responses, and allocate buffers of those sizes. */ if (seccomp(seccomp_get_notif_sizes, 0, sizes) == \-1) errexit("seccomp\-seccomp_get_notif_sizes"); *req = malloc(sizes\->seccomp_notif); if (*req == null) errexit("malloc\-seccomp_notif"); /* when allocating the response buffer, we must allow for the fact that the user\-space binary may have been built with user\-space headers where \(aqstruct seccomp_notif_resp\(aq is bigger than the response buffer expected by the (older) kernel. therefore, we allocate a buffer that is the maximum of the two sizes. this ensures that if the supervisor places bytes into the response structure that are past the response size that the kernel expects, then the supervisor is not touching an invalid memory location. */ size_t resp_size = sizes\->seccomp_notif_resp; if (sizeof(struct seccomp_notif_resp) > resp_size) resp_size = sizeof(struct seccomp_notif_resp); *resp = malloc(resp_size); if (resp == null) errexit("malloc\-seccomp_notif_resp"); } /* handle notifications that arrive via the seccomp_ret_user_notif file descriptor, \(aqnotifyfd\(aq. */ static void handlenotifications(int notifyfd) { struct seccomp_notif_sizes sizes; struct seccomp_notif *req; struct seccomp_notif_resp *resp; char path[path_max]; allocseccompnotifbuffers(&req, &resp, &sizes); /* loop handling notifications */ for (;;) { /* wait for next notification, returning info in \(aq*req\(aq */ memset(req, 0, sizes.seccomp_notif); if (ioctl(notifyfd, seccomp_ioctl_notif_recv, req) == \-1) { if (errno == eintr) continue; errexit("\ets: ioctl\-seccomp_ioctl_notif_recv"); } printf("\ets: got notification (id %#llx) for pid %d\en", req\->id, req\->pid); /* the only system call that can generate a notification event is mkdir(2). nevertheless, we check that the notified system call is indeed mkdir() as kind of future\-proofing of this code in case the seccomp filter is later modified to generate notifications for other system calls. */ if (req\->data.nr != __nr_mkdir) { printf("\ets: notification contained unexpected " "system call number; bye!!!\en"); exit(exit_failure); } bool pathok = gettargetpathname(req, notifyfd, 0, path, sizeof(path)); /* prepopulate some fields of the response */ resp\->id = req\->id; /* response includes notification id */ resp\->flags = 0; resp\->val = 0; /* if gettargetpathname() failed, trigger an einval error response (sending this response may yield an error if the failure occurred because the notification id was no longer valid); if the directory is in /tmp, then create it on behalf of the supervisor; if the pathname starts with \(aq.\(aq, tell the kernel to let the target process execute the mkdir(); otherwise, give an error for a directory pathname in any other location. */ if (!pathok) { resp->error = -einval; printf("\ets: spoofing error for invalid pathname (%s)\en", strerror(-resp->error)); } else if (strncmp(path, "/tmp/", strlen("/tmp/")) == 0) { printf("\ets: executing: mkdir(\e"%s\e", %#llo)\en", path, req\->data.args[1]); if (mkdir(path, req\->data.args[1]) == 0) { resp\->error = 0; /* "success" */ resp\->val = strlen(path); /* used as return value of mkdir() in target */ printf("\ets: success! spoofed return = %lld\en", resp\->val); } else { /* if mkdir() failed in the supervisor, pass the error back to the target */ resp\->error = \-errno; printf("\ets: failure! (errno = %d; %s)\en", errno, strerror(errno)); } } else if (strncmp(path, "./", strlen("./")) == 0) { resp\->error = resp\->val = 0; resp\->flags = seccomp_user_notif_flag_continue; printf("\ets: target can execute system call\en"); } else { resp\->error = \-eopnotsupp; printf("\ets: spoofing error response (%s)\en", strerror(\-resp\->error)); } /* send a response to the notification */ printf("\ets: sending response " "(flags = %#x; val = %lld; error = %d)\en", resp\->flags, resp\->val, resp\->error); if (ioctl(notifyfd, seccomp_ioctl_notif_send, resp) == \-1) { if (errno == enoent) printf("\ets: response failed with enoent; " "perhaps target process\(aqs syscall was " "interrupted by a signal?\en"); else perror("ioctl\-seccomp_ioctl_notif_send"); } /* if the pathname is just "/bye", then the supervisor breaks out of the loop and terminates. this allows us to see what happens if the target process makes further calls to mkdir(2). */ if (strcmp(path, "/bye") == 0) break; } free(req); free(resp); printf("\ets: terminating **********\en"); exit(exit_failure); } /* implementation of the supervisor process: (1) obtains the notification file descriptor from \(aqsockpair[1]\(aq (2) handles notifications that arrive on that file descriptor. */ static void supervisor(int sockpair[2]) { int notifyfd = recvfd(sockpair[1]); if (notifyfd == \-1) errexit("recvfd"); closesocketpair(sockpair); /* we no longer need the socket pair */ handlenotifications(notifyfd); } int main(int argc, char *argv[]) { int sockpair[2]; setbuf(stdout, null); if (argc < 2) { fprintf(stderr, "at least one pathname argument is required\en"); exit(exit_failure); } /* create a unix domain socket that is used to pass the seccomp notification file descriptor from the target process to the supervisor process. */ if (socketpair(af_unix, sock_stream, 0, sockpair) == \-1) errexit("socketpair"); /* create a child process\-\-the "target"\-\-that installs seccomp filtering. the target process writes the seccomp notification file descriptor onto \(aqsockpair[0]\(aq and then calls mkdir(2) for each directory in the command\-line arguments. */ (void) targetprocess(sockpair, &argv[optind]); /* catch sigchld when the target terminates, so that the supervisor can also terminate. */ struct sigaction sa; sa.sa_handler = sigchldhandler; sa.sa_flags = 0; sigemptyset(&sa.sa_mask); if (sigaction(sigchld, &sa, null) == \-1) errexit("sigaction"); supervisor(sockpair); exit(exit_success); } .ee .sh see also .br ioctl (2), .br pidfd_getfd (2), .br pidfd_open (2), .br seccomp (2) .pp a further example program can be found in the kernel source file .ir samples/seccomp/user-trap.c . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th getpwent_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getpwent_r, fgetpwent_r \- get passwd file entry reentrantly .sh synopsis .nf .b #include .pp .bi "int getpwent_r(struct passwd *restrict " pwbuf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct passwd **restrict " pwbufp ); .bi "int fgetpwent_r(file *restrict " stream \ ", struct passwd *restrict " pwbuf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct passwd **restrict " pwbufp ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getpwent_r (), .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .pp .br fgetpwent_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description the functions .br getpwent_r () and .br fgetpwent_r () are the reentrant versions of .br getpwent (3) and .br fgetpwent (3). the former reads the next passwd entry from the stream initialized by .br setpwent (3). the latter reads the next passwd entry from .ir stream . .pp the \fipasswd\fp structure is defined in .i as follows: .pp .in +4n .ex struct passwd { char *pw_name; /* username */ char *pw_passwd; /* user password */ uid_t pw_uid; /* user id */ gid_t pw_gid; /* group id */ char *pw_gecos; /* user information */ char *pw_dir; /* home directory */ char *pw_shell; /* shell program */ }; .ee .in .pp for more information about the fields of this structure, see .br passwd (5). .pp the nonreentrant functions return a pointer to static storage, where this static storage contains further pointers to user name, password, gecos field, home directory and shell. the reentrant functions described here return all of that in caller-provided buffers. first of all there is the buffer .i pwbuf that can hold a \fistruct passwd\fp. and next the buffer .i buf of size .i buflen that can hold additional strings. the result of these functions, the \fistruct passwd\fp read from the stream, is stored in the provided buffer .ir *pwbuf , and a pointer to this \fistruct passwd\fp is returned in .ir *pwbufp . .sh return value on success, these functions return 0 and .i *pwbufp is a pointer to the \fistruct passwd\fp. on error, these functions return an error value and .i *pwbufp is null. .sh errors .tp .b enoent no more entries. .tp .b erange insufficient buffer space supplied. try again with larger buffer. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getpwent_r () t} thread safety t{ mt-unsafe race:pwent locale t} t{ .br fgetpwent_r () t} thread safety mt-safe .te .hy .ad .sp 1 in the above table, .i pwent in .i race:pwent signifies that if any of the functions .br setpwent (), .br getpwent (), .br endpwent (), or .br getpwent_r () are used in parallel in different threads of a program, then data races could occur. .sh conforming to these functions are gnu extensions, done in a style resembling the posix version of functions like .br getpwnam_r (3). other systems use the prototype .pp .in +4n .ex struct passwd * getpwent_r(struct passwd *pwd, char *buf, int buflen); .ee .in .pp or, better, .pp .in +4n .ex int getpwent_r(struct passwd *pwd, char *buf, int buflen, file **pw_fp); .ee .in .sh notes the function .br getpwent_r () is not really reentrant since it shares the reading position in the stream with all other threads. .sh examples .ex #define _gnu_source #include #include #include #define buflen 4096 int main(void) { struct passwd pw; struct passwd *pwp; char buf[buflen]; int i; setpwent(); while (1) { i = getpwent_r(&pw, buf, sizeof(buf), &pwp); if (i) break; printf("%s (%jd)\ethome %s\etshell %s\en", pwp\->pw_name, (intmax_t) pwp\->pw_uid, pwp\->pw_dir, pwp\->pw_shell); } endpwent(); exit(exit_success); } .ee .\" perhaps add error checking - should use strerror_r .\" #include .\" #include .\" if (i) { .\" if (i == enoent) .\" break; .\" printf("getpwent_r: %s", strerror(i)); .\" exit(exit_success); .\" } .sh see also .br fgetpwent (3), .br getpw (3), .br getpwent (3), .br getpwnam (3), .br getpwuid (3), .br putpwent (3), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/resolver.3 .\" copyright (c) 2017 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sysfs 5 2021-03-22 "linux" "linux programmer's manual" .sh name sysfs \- a filesystem for exporting kernel objects .sh description the .b sysfs filesystem is a pseudo-filesystem which provides an interface to kernel data structures. (more precisely, the files and directories in .b sysfs provide a view of the .ir kobject structures defined internally within the kernel.) the files under .b sysfs provide information about devices, kernel modules, filesystems, and other kernel components. .pp the .b sysfs filesystem is commonly mounted at .ir /sys . typically, it is mounted automatically by the system, but it can also be mounted manually using a command such as: .pp .in +4n .ex mount \-t sysfs sysfs /sys .ee .in .pp many of the files in the .b sysfs filesystem are read-only, but some files are writable, allowing kernel variables to be changed. to avoid redundancy, symbolic links are heavily used to connect entries across the filesystem tree. .\" .ss files and directories the following list describes some of the files and directories under the .i /sys hierarchy. .tp .ir /sys/block this subdirectory contains one symbolic link for each block device that has been discovered on the system. the symbolic links point to corresponding directories under .ir /sys/devices . .tp .ir /sys/bus this directory contains one subdirectory for each of the bus types in the kernel. inside each of these directories are two subdirectories: .rs .tp .ir devices this subdirectory contains symbolic links to entries in .ir /sys/devices that correspond to the devices discovered on this bus. .tp .ir drivers this subdirectory contains one subdirectory for each device driver that is loaded on this bus. .re .tp .ir /sys/class this subdirectory contains a single layer of further subdirectories for each of the device classes that have been registered on the system (e.g., terminals, network devices, block devices, graphics devices, sound devices, and so on). inside each of these subdirectories are symbolic links for each of the devices in this class. these symbolic links refer to entries in the .ir /sys/devices directory. .tp .ir /sys/class/net each of the entries in this directory is a symbolic link representing one of the real or virtual networking devices that are visible in the network namespace of the process that is accessing the directory. each of these symbolic links refers to entries in the .ir /sys/devices directory. .tp .ir /sys/dev this directory contains two subdirectories .ir block / and .ir char/ , corresponding, respectively, to the block and character devices on the system. inside each of these subdirectories are symbolic links with names of the form .ir major-id : minor-id , where the id values correspond to the major and minor id of a specific device. each symbolic link points to the .b sysfs directory for a device. the symbolic links inside .ir /sys/dev thus provide an easy way to look up the .b sysfs interface using the device ids returned by a call to .br stat (2) (or similar). .ip the following shell session shows an example from .ir /sys/dev : .ip .in +4n .ex $ \fbstat \-c "%t %t" /dev/null\fp 1 3 $ \fbreadlink /sys/dev/char/1\e:3\fp \&../../devices/virtual/mem/null $ \fbls \-fd /sys/devices/virtual/mem/null\fp /sys/devices/virtual/mem/null/ $ \fbls \-d1 /sys/devices/virtual/mem/null/*\fp /sys/devices/virtual/mem/null/dev /sys/devices/virtual/mem/null/power/ /sys/devices/virtual/mem/null/subsystem@ /sys/devices/virtual/mem/null/uevent .ee .in .tp .ir /sys/devices this is a directory that contains a filesystem representation of the kernel device tree, which is a hierarchy of .i device structures within the kernel. .tp .ir /sys/firmware this subdirectory contains interfaces for viewing and manipulating firmware-specific objects and attributes. .tp .ir /sys/fs this directory contains subdirectories for some filesystems. a filesystem will have a subdirectory here only if it chose to explicitly create the subdirectory. .tp .ir /sys/fs/cgroup this directory conventionally is used as a mount point for a .br tmpfs (5) filesystem containing mount points for .br cgroups (7) filesystems. .tp .ir /sys/fs/smackfs the directory contains configuration files for the smack lsm. see the kernel source file .ir documentation/admin\-guide/lsm/smack.rst . .tp .ir /sys/hypervisor [to be documented] .tp .ir /sys/kernel this subdirectory contains various files and subdirectories that provide information about the running kernel. .tp .ir /sys/kernel/cgroup/ for information about the files in this directory, see .br cgroups (7). .tp .ir /sys/kernel/debug/tracing mount point for the .i tracefs filesystem used by the kernel's .i ftrace facility. (for information on .ir ftrace , see the kernel source file .ir documentation/trace/ftrace.txt .) .tp .ir /sys/kernel/mm this subdirectory contains various files and subdirectories that provide information about the kernel's memory management subsystem. .tp .ir /sys/kernel/mm/hugepages this subdirectory contains one subdirectory for each of the huge page sizes that the system supports. the subdirectory name indicates the huge page size (e.g., .ir hugepages\-2048kb ). within each of these subdirectories is a set of files that can be used to view and (in some cases) change settings associated with that huge page size. for further information, see the kernel source file .ir documentation/admin\-guide/mm/hugetlbpage.rst . .tp .ir /sys/module this subdirectory contains one subdirectory for each module that is loaded into the kernel. the name of each directory is the name of the module. in each of the subdirectories, there may be following files: .rs .tp .i coresize [to be documented] .tp .i initsize [to be documented] .tp .i initstate [to be documented] .tp .i refcnt [to be documented] .tp .i srcversion [to be documented] .tp .i taint [to be documented] .tp .i uevent [to be documented] .tp .i version [to be documented] .re .ip in each of the subdirectories, there may be following subdirectories: .rs .tp .i drivers [to be documented] .tp .i holders [to be documented] .tp .i notes [to be documented] .tp .i parameters this directory contains one file for each module parameter, with each file containing the value of the corresponding parameter. some of these files are writable, allowing the .tp .i sections this subdirectories contains files with information about module sections. this information is mainly used for debugging. .tp .i [to be documented] .re .tp .ir /sys/power [to be documented] .sh versions the .b sysfs filesystem first appeared in linux 2.6.0. .sh conforming to the .b sysfs filesystem is linux-specific. .sh notes this manual page is incomplete, possibly inaccurate, and is the kind of thing that needs to be updated very often. .sh see also .br proc (5), .br udev (7) .pp p.\& mochel. (2005). .ir "the sysfs filesystem" . proceedings of the 2005 ottawa linux symposium. .\" https://www.kernel.org/pub/linux/kernel/people/mochel/doc/papers/ols-2005/mochel.pdf .pp the kernel source file .i documentation/filesystems/sysfs.txt and various other files in .ir documentation/abi and .ir documentation/*/sysfs.txt .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/lround.3 .so man3/endian.3 .so man3/xdr.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_exit 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_exit \- terminate calling thread .sh synopsis .nf .b #include .pp .bi "noreturn void pthread_exit(void *" retval ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_exit () function terminates the calling thread and returns a value via .i retval that (if the thread is joinable) is available to another thread in the same process that calls .br pthread_join (3). .pp any clean-up handlers established by .br pthread_cleanup_push (3) that have not yet been popped, are popped (in the reverse of the order in which they were pushed) and executed. if the thread has any thread-specific data, then, after the clean-up handlers have been executed, the corresponding destructor functions are called, in an unspecified order. .pp when a thread terminates, process-shared resources (e.g., mutexes, condition variables, semaphores, and file descriptors) are not released, and functions registered using .br atexit (3) are not called. .pp after the last thread in a process terminates, the process terminates as by calling .br exit (3) with an exit status of zero; thus, process-shared resources are released and functions registered using .br atexit (3) are called. .sh return value this function does not return to the caller. .sh errors this function always succeeds. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_exit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes performing a return from the start function of any thread other than the main thread results in an implicit call to .br pthread_exit (), using the function's return value as the thread's exit status. .pp to allow other threads to continue execution, the main thread should terminate by calling .br pthread_exit () rather than .br exit (3). .pp the value pointed to by .ir retval should not be located on the calling thread's stack, since the contents of that stack are undefined after the thread terminates. .sh bugs currently, .\" linux 2.6.27 there are limitations in the kernel implementation logic for .br wait (2)ing on a stopped thread group with a dead thread group leader. this can manifest in problems such as a locked terminal if a stop signal is sent to a foreground process whose thread group leader has already called .br pthread_exit (). .\" fixme . review a later kernel to see if this gets fixed .\" http://thread.gmane.org/gmane.linux.kernel/611611 .\" http://marc.info/?l=linux-kernel&m=122525468300823&w=2 .sh see also .br pthread_create (3), .br pthread_join (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995 paul gortmaker .\" (gpg109@rsphy1.anu.edu.au) .\" wed nov 29 10:58:54 est 1995 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th outb 2 2020-11-01 "linux" "linux programmer's manual" .sh name outb, outw, outl, outsb, outsw, outsl, inb, inw, inl, insb, insw, insl, outb_p, outw_p, outl_p, inb_p, inw_p, inl_p \- port i/o .sh synopsis .nf .b #include .pp .bi "unsigned char inb(unsigned short " port ); .bi "unsigned char inb_p(unsigned short " port ); .bi "unsigned short inw(unsigned short " port ); .bi "unsigned short inw_p(unsigned short " port ); .bi "unsigned int inl(unsigned short " port ); .bi "unsigned int inl_p(unsigned short " port ); .pp .bi "void outb(unsigned char " value ", unsigned short " port ); .bi "void outb_p(unsigned char " value ", unsigned short " port ); .bi "void outw(unsigned short " value ", unsigned short " port ); .bi "void outw_p(unsigned short " value ", unsigned short " port ); .bi "void outl(unsigned int " value ", unsigned short " port ); .bi "void outl_p(unsigned int " value ", unsigned short " port ); .pp .bi "void insb(unsigned short " port ", void *" addr , .bi " unsigned long " count ); .bi "void insw(unsigned short " port ", void *" addr , .bi " unsigned long " count ); .bi "void insl(unsigned short " port ", void *" addr , .bi " unsigned long " count ); .bi "void outsb(unsigned short " port ", const void *" addr , .bi " unsigned long " count ); .bi "void outsw(unsigned short " port ", const void *" addr , .bi " unsigned long " count ); .bi "void outsl(unsigned short " port ", const void *" addr , .bi " unsigned long " count ); .fi .sh description this family of functions is used to do low-level port input and output. the out* functions do port output, the in* functions do port input; the b-suffix functions are byte-width and the w-suffix functions word-width; the _p-suffix functions pause until the i/o completes. .pp they are primarily designed for internal kernel use, but can be used from user space. .\" , given the following information .\" in addition to that given in .\" .br outb (9). .pp you must compile with \fb\-o\fp or \fb\-o2\fp or similar. the functions are defined as inline macros, and will not be substituted in without optimization enabled, causing unresolved references at link time. .pp you use .br ioperm (2) or alternatively .br iopl (2) to tell the kernel to allow the user space application to access the i/o ports in question. failure to do this will cause the application to receive a segmentation fault. .sh conforming to .br outb () and friends are hardware-specific. the .i value argument is passed first and the .i port argument is passed second, which is the opposite order from most dos implementations. .sh see also .br ioperm (2), .br iopl (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1995 james r. van zandt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" changed tue sep 19 01:49:29 1995, aeb: moved from man2 to man3 .\" added ref to /etc/utmp, added bugs section, etc. .\" modified 2003 walter harms, aeb - added getlogin_r, note on stdin use .th getlogin 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getlogin, getlogin_r, cuserid \- get username .sh synopsis .nf .b #include .pp .b "char *getlogin(void);" .bi "int getlogin_r(char *" buf ", size_t " bufsize ); .pp .b #include .pp .bi "char *cuserid(char *" string ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getlogin_r (): .nf .\" deprecated: _reentrant || _posix_c_source >= 199506l .fi .pp .br cuserid (): .nf since glibc 2.24: (_xopen_source && ! (_posix_c_source >= 200112l) || _gnu_source up to and including glibc 2.23: _xopen_source .fi .sh description .br getlogin () returns a pointer to a string containing the name of the user logged in on the controlling terminal of the process, or a null pointer if this information cannot be determined. the string is statically allocated and might be overwritten on subsequent calls to this function or to .br cuserid (). .pp .br getlogin_r () returns this same username in the array .i buf of size .ir bufsize . .pp .br cuserid () returns a pointer to a string containing a username associated with the effective user id of the process. if \fistring\fp is not a null pointer, it should be an array that can hold at least \fbl_cuserid\fp characters; the string is returned in this array. otherwise, a pointer to a string in a static area is returned. this string is statically allocated and might be overwritten on subsequent calls to this function or to .br getlogin (). .pp the macro \fbl_cuserid\fp is an integer constant that indicates how long an array you might need to store a username. \fbl_cuserid\fp is declared in \fi\fp. .pp these functions let your program identify positively the user who is running .rb ( cuserid ()) or the user who logged in this session .rb ( getlogin ()). (these can differ when set-user-id programs are involved.) .pp for most purposes, it is more useful to use the environment variable \fblogname\fp to find out who the user is. this is more flexible precisely because the user can set \fblogname\fp arbitrarily. .sh return value .br getlogin () returns a pointer to the username when successful, and null on failure, with .i errno set to indicate the error. .br getlogin_r () returns 0 when successful, and nonzero on failure. .sh errors posix specifies: .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enxio the calling process has no controlling terminal. .tp .b erange (getlogin_r) the length of the username, including the terminating null byte (\(aq\e0\(aq), is larger than .ir bufsize . .pp linux/glibc also has: .tp .b enoent there was no corresponding entry in the utmp-file. .tp .b enomem insufficient memory to allocate passwd structure. .tp .b enotty standard input didn't refer to a terminal. (see bugs.) .sh files .tp \fi/etc/passwd\fp password database file .tp \fi/var/run/utmp\fp (traditionally \fi/etc/utmp\fp; some libc versions used \fi/var/adm/utmp\fp) .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getlogin () t} thread safety t{ mt-unsafe race:getlogin race:utent sig:alrm timer locale t} t{ .br getlogin_r () t} thread safety t{ mt-unsafe race:utent sig:alrm timer locale t} t{ .br cuserid () t} thread safety t{ mt-unsafe race:cuserid/!string locale t} .te .hy .ad .sp 1 in the above table, .i utent in .i race:utent signifies that if any of the functions .br setutent (3), .br getutent (3), or .br endutent (3) are used in parallel in different threads of a program, then data races could occur. .br getlogin () and .br getlogin_r () call those functions, so we use race:utent to remind users. .sh conforming to .br getlogin () and .br getlogin_r (): posix.1-2001, posix.1-2008. .pp system v has a .br cuserid () function which uses the real user id rather than the effective user id. the .br cuserid () function was included in the 1988 version of posix, but removed from the 1990 version. it was present in susv2, but removed in posix.1-2001. .pp openbsd has .br getlogin () and .br setlogin (), and a username associated with a session, even if it has no controlling terminal. .sh bugs unfortunately, it is often rather easy to fool .br getlogin (). sometimes it does not work at all, because some program messed up the utmp file. often, it gives only the first 8 characters of the login name. the user currently logged in on the controlling terminal of our program need not be the user who started it. avoid .br getlogin () for security-related purposes. .pp note that glibc does not follow the posix specification and uses .i stdin instead of .ir /dev/tty . a bug. (other recent systems, like sunos 5.8 and hp-ux 11.11 and freebsd 4.8 all return the login name also when .i stdin is redirected.) .pp nobody knows precisely what .br cuserid () does; avoid it in portable programs. or avoid it altogether: use .i getpwuid(geteuid()) instead, if that is what you meant. .b do not use .br cuserid (). .sh see also .br logname (1), .br geteuid (2), .br getuid (2), .br utmp (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/bzero.3 .so man2/recv.2 .so man3/xdr.3 .so man3/rpc.3 .so man3/drand48_r.3 .\" copyright (c) 2001 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2006-08-02, mtk, added example program .\" .th makecontext 3 2021-03-22 "gnu" "linux programmer's manual" .sh name makecontext, swapcontext \- manipulate user context .sh synopsis .nf .b #include .pp .bi "void makecontext(ucontext_t *" ucp ", void (*" func ")(), int " argc \ ", ...);" .bi "int swapcontext(ucontext_t *restrict " oucp , .bi " const ucontext_t *restrict " ucp ); .fi .sh description in a system v-like environment, one has the type .i ucontext_t (defined in .i and described in .br getcontext (3)) and the four functions .br getcontext (3), .br setcontext (3), .br makecontext (), and .br swapcontext () that allow user-level context switching between multiple threads of control within a process. .pp the .br makecontext () function modifies the context pointed to by \fiucp\fp (which was obtained from a call to .br getcontext (3)). before invoking .br makecontext (), the caller must allocate a new stack for this context and assign its address to \fiucp\->uc_stack\fp, and define a successor context and assign its address to \fiucp\->uc_link\fp. .pp when this context is later activated (using .br setcontext (3) or .br swapcontext ()) the function \fifunc\fp is called, and passed the series of integer .ri ( int ) arguments that follow .ir argc ; the caller must specify the number of these arguments in .ir argc . when this function returns, the successor context is activated. if the successor context pointer is null, the thread exits. .pp the .br swapcontext () function saves the current context in the structure pointed to by \fioucp\fp, and then activates the context pointed to by \fiucp\fp. .sh return value when successful, .br swapcontext () does not return. (but we may return later, in case \fioucp\fp is activated, in which case it looks like .br swapcontext () returns 0.) on error, .br swapcontext () returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b enomem insufficient stack space left. .sh versions .br makecontext () and .br swapcontext () are provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br makecontext () t} thread safety t{ mt-safe race:ucp t} t{ .br swapcontext () t} thread safety t{ mt-safe race:oucp race:ucp t} .te .hy .ad .sp 1 .sh conforming to susv2, posix.1-2001. posix.1-2008 removes the specifications of .br makecontext () and .br swapcontext (), citing portability issues, and recommending that applications be rewritten to use posix threads instead. .sh notes the interpretation of \fiucp\->uc_stack\fp is just as in .br sigaltstack (2), namely, this struct contains the start and length of a memory area to be used as the stack, regardless of the direction of growth of the stack. thus, it is not necessary for the user program to worry about this direction. .pp on architectures where .i int and pointer types are the same size (e.g., x86-32, where both types are 32 bits), you may be able to get away with passing pointers as arguments to .br makecontext () following .ir argc . however, doing this is not guaranteed to be portable, is undefined according to the standards, and won't work on architectures where pointers are larger than .ir int s. nevertheless, starting with version 2.8, glibc makes some changes to .br makecontext (), to permit this on some 64-bit architectures (e.g., x86-64). .sh examples the example program below demonstrates the use of .br getcontext (3), .br makecontext (), and .br swapcontext (). running the program produces the following output: .pp .in +4n .ex .rb "$" " ./a.out" main: swapcontext(&uctx_main, &uctx_func2) func2: started func2: swapcontext(&uctx_func2, &uctx_func1) func1: started func1: swapcontext(&uctx_func1, &uctx_func2) func2: returning func1: returning main: exiting .ee .in .ss program source \& .ex #include #include #include static ucontext_t uctx_main, uctx_func1, uctx_func2; #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) static void func1(void) { printf("func1: started\en"); printf("func1: swapcontext(&uctx_func1, &uctx_func2)\en"); if (swapcontext(&uctx_func1, &uctx_func2) == \-1) handle_error("swapcontext"); printf("func1: returning\en"); } static void func2(void) { printf("func2: started\en"); printf("func2: swapcontext(&uctx_func2, &uctx_func1)\en"); if (swapcontext(&uctx_func2, &uctx_func1) == \-1) handle_error("swapcontext"); printf("func2: returning\en"); } int main(int argc, char *argv[]) { char func1_stack[16384]; char func2_stack[16384]; if (getcontext(&uctx_func1) == \-1) handle_error("getcontext"); uctx_func1.uc_stack.ss_sp = func1_stack; uctx_func1.uc_stack.ss_size = sizeof(func1_stack); uctx_func1.uc_link = &uctx_main; makecontext(&uctx_func1, func1, 0); if (getcontext(&uctx_func2) == \-1) handle_error("getcontext"); uctx_func2.uc_stack.ss_sp = func2_stack; uctx_func2.uc_stack.ss_size = sizeof(func2_stack); /* successor context is f1(), unless argc > 1 */ uctx_func2.uc_link = (argc > 1) ? null : &uctx_func1; makecontext(&uctx_func2, func2, 0); printf("main: swapcontext(&uctx_main, &uctx_func2)\en"); if (swapcontext(&uctx_main, &uctx_func2) == \-1) handle_error("swapcontext"); printf("main: exiting\en"); exit(exit_success); } .ee .sh see also .br sigaction (2), .br sigaltstack (2), .br sigprocmask (2), .br getcontext (3), .br sigsetjmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/unlocked_stdio.3 .so man3/getrpcent.3 .so man3/rpc.3 .so man3/mkfifo.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2010 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_suspend 3 2021-03-22 "" "linux programmer's manual" .sh name aio_suspend \- wait for asynchronous i/o operation or timeout .sh synopsis .nf .pp .b "#include " .pp .bi "int aio_suspend(const struct aiocb *const " aiocb_list "[], int " nitems , .bi " const struct timespec *restrict " timeout ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_suspend () function suspends the calling thread until one of the following occurs: .ip * 3 one or more of the asynchronous i/o requests in the list .i aiocb_list has completed. .ip * a signal is delivered. .ip * .i timeout is not null and the specified time interval has passed. (for details of the .i timespec structure, see .br nanosleep (2).) .pp the .i nitems argument specifies the number of items in .ir aiocb_list . each item in the list pointed to by .i aiocb_list must be either null (and then is ignored), or a pointer to a control block on which i/o was initiated using .br aio_read (3), .br aio_write (3), or .br lio_listio (3). (see .br aio (7) for a description of the .i aiocb structure.) .pp if .b clock_monotonic is supported, this clock is used to measure the timeout interval (see .br clock_gettime (2)). .sh return value if this function returns after completion of one of the i/o requests specified in .ir aiocb_list , 0 is returned. otherwise, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eagain the call timed out before any of the indicated operations had completed. .tp .b eintr the call was ended by signal (possibly the completion signal of one of the operations we were waiting for); see .br signal (7). .tp .b enosys .br aio_suspend () is not implemented. .sh versions the .br aio_suspend () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_suspend () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp posix doesn't specify the parameters to be .ir restrict ; that is specific to glibc. .sh notes one can achieve polling by using a non-null .i timeout that specifies a zero time interval. .pp if one or more of the asynchronous i/o operations specified in .ir aiocb_list has already completed at the time of the call to .br aio_suspend (), then the call returns immediately. .pp to determine which i/o operations have completed after a successful return from .br aio_suspend (), use .br aio_error (3) to scan the list of .i aiocb structures pointed to by .ir aiocb_list . .sh bugs the glibc implementation of .br aio_suspend () is not async-signal-safe, .\" fixme . https://sourceware.org/bugzilla/show_bug.cgi?id=13172 in violation of the requirements of posix.1. .sh see also .br aio_cancel (3), .br aio_error (3), .br aio_fsync (3), .br aio_read (3), .br aio_return (3), .br aio_write (3), .br lio_listio (3), .br aio (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setenv.3 .so man2/unimplemented.2 .\" copyright (c) 2015 serge hallyn .\" and copyright (c) 2016, 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th cgroups 7 2021-08-27 "linux" "linux programmer's manual" .sh name cgroups \- linux control groups .sh description control groups, usually referred to as cgroups, are a linux kernel feature which allow processes to be organized into hierarchical groups whose usage of various types of resources can then be limited and monitored. the kernel's cgroup interface is provided through a pseudo-filesystem called cgroupfs. grouping is implemented in the core cgroup kernel code, while resource tracking and limits are implemented in a set of per-resource-type subsystems (memory, cpu, and so on). .\" .ss terminology a .i cgroup is a collection of processes that are bound to a set of limits or parameters defined via the cgroup filesystem. .pp a .i subsystem is a kernel component that modifies the behavior of the processes in a cgroup. various subsystems have been implemented, making it possible to do things such as limiting the amount of cpu time and memory available to a cgroup, accounting for the cpu time used by a cgroup, and freezing and resuming execution of the processes in a cgroup. subsystems are sometimes also known as .ir "resource controllers" (or simply, controllers). .pp the cgroups for a controller are arranged in a .ir hierarchy . this hierarchy is defined by creating, removing, and renaming subdirectories within the cgroup filesystem. at each level of the hierarchy, attributes (e.g., limits) can be defined. the limits, control, and accounting provided by cgroups generally have effect throughout the subhierarchy underneath the cgroup where the attributes are defined. thus, for example, the limits placed on a cgroup at a higher level in the hierarchy cannot be exceeded by descendant cgroups. .\" .ss cgroups version 1 and version 2 the initial release of the cgroups implementation was in linux 2.6.24. over time, various cgroup controllers have been added to allow the management of various types of resources. however, the development of these controllers was largely uncoordinated, with the result that many inconsistencies arose between controllers and management of the cgroup hierarchies became rather complex. a longer description of these problems can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v2.rst (or .ir documentation/cgroup\-v2.txt in linux 4.17 and earlier). .pp because of the problems with the initial cgroups implementation (cgroups version 1), starting in linux 3.10, work began on a new, orthogonal implementation to remedy these problems. initially marked experimental, and hidden behind the .i "\-o\ __devel__sane_behavior" mount option, the new version (cgroups version 2) was eventually made official with the release of linux 4.5. differences between the two versions are described in the text below. the file .ir cgroup.sane_behavior , present in cgroups v1, is a relic of this mount option. the file always reports "0" and is only retained for backward compatibility. .pp although cgroups v2 is intended as a replacement for cgroups v1, the older system continues to exist (and for compatibility reasons is unlikely to be removed). currently, cgroups v2 implements only a subset of the controllers available in cgroups v1. the two systems are implemented so that both v1 controllers and v2 controllers can be mounted on the same system. thus, for example, it is possible to use those controllers that are supported under version 2, while also using version 1 controllers where version 2 does not yet support those controllers. the only restriction here is that a controller can't be simultaneously employed in both a cgroups v1 hierarchy and in the cgroups v2 hierarchy. .\" .sh cgroups version 1 under cgroups v1, each controller may be mounted against a separate cgroup filesystem that provides its own hierarchical organization of the processes on the system. it is also possible to comount multiple (or even all) cgroups v1 controllers against the same cgroup filesystem, meaning that the comounted controllers manage the same hierarchical organization of processes. .pp for each mounted hierarchy, the directory tree mirrors the control group hierarchy. each control group is represented by a directory, with each of its child control cgroups represented as a child directory. for instance, .ir /user/joe/1.session represents control group .ir 1.session , which is a child of cgroup .ir joe , which is a child of .ir /user . under each cgroup directory is a set of files which can be read or written to, reflecting resource limits and a few general cgroup properties. .\" .ss tasks (threads) versus processes in cgroups v1, a distinction is drawn between .i processes and .ir tasks . in this view, a process can consist of multiple tasks (more commonly called threads, from a user-space perspective, and called such in the remainder of this man page). in cgroups v1, it is possible to independently manipulate the cgroup memberships of the threads in a process. .pp the cgroups v1 ability to split threads across different cgroups caused problems in some cases. for example, it made no sense for the .i memory controller, since all of the threads of a process share a single address space. because of these problems, the ability to independently manipulate the cgroup memberships of the threads in a process was removed in the initial cgroups v2 implementation, and subsequently restored in a more limited form (see the discussion of "thread mode" below). .\" .ss mounting v1 controllers the use of cgroups requires a kernel built with the .br config_cgroup option. in addition, each of the v1 controllers has an associated configuration option that must be set in order to employ that controller. .pp in order to use a v1 controller, it must be mounted against a cgroup filesystem. the usual place for such mounts is under a .br tmpfs (5) filesystem mounted at .ir /sys/fs/cgroup . thus, one might mount the .i cpu controller as follows: .pp .in +4n .ex mount \-t cgroup \-o cpu none /sys/fs/cgroup/cpu .ee .in .pp it is possible to comount multiple controllers against the same hierarchy. for example, here the .ir cpu and .ir cpuacct controllers are comounted against a single hierarchy: .pp .in +4n .ex mount \-t cgroup \-o cpu,cpuacct none /sys/fs/cgroup/cpu,cpuacct .ee .in .pp comounting controllers has the effect that a process is in the same cgroup for all of the comounted controllers. separately mounting controllers allows a process to be in cgroup .i /foo1 for one controller while being in .i /foo2/foo3 for another. .pp it is possible to comount all v1 controllers against the same hierarchy: .pp .in +4n .ex mount \-t cgroup \-o all cgroup /sys/fs/cgroup .ee .in .pp (one can achieve the same result by omitting .ir "\-o all" , since it is the default if no controllers are explicitly specified.) .pp it is not possible to mount the same controller against multiple cgroup hierarchies. for example, it is not possible to mount both the .i cpu and .i cpuacct controllers against one hierarchy, and to mount the .i cpu controller alone against another hierarchy. it is possible to create multiple mount with exactly the same set of comounted controllers. however, in this case all that results is multiple mount points providing a view of the same hierarchy. .pp note that on many systems, the v1 controllers are automatically mounted under .ir /sys/fs/cgroup ; in particular, .br systemd (1) automatically creates such mounts. .\" .ss unmounting v1 controllers a mounted cgroup filesystem can be unmounted using the .br umount (8) command, as in the following example: .pp .in +4n .ex umount /sys/fs/cgroup/pids .ee .in .pp .ir "but note well" : a cgroup filesystem is unmounted only if it is not busy, that is, it has no child cgroups. if this is not the case, then the only effect of the .br umount (8) is to make the mount invisible. thus, to ensure that the mount is really removed, one must first remove all child cgroups, which in turn can be done only after all member processes have been moved from those cgroups to the root cgroup. .\" .ss cgroups version 1 controllers each of the cgroups version 1 controllers is governed by a kernel configuration option (listed below). additionally, the availability of the cgroups feature is governed by the .br config_cgroups kernel configuration option. .tp .ir cpu " (since linux 2.6.24; " \fbconfig_cgroup_sched\fp ) cgroups can be guaranteed a minimum number of "cpu shares" when a system is busy. this does not limit a cgroup's cpu usage if the cpus are not busy. for further information, see .ir documentation/scheduler/sched\-design\-cfs.rst (or .ir documentation/scheduler/sched\-design\-cfs.txt in linux 5.2 and earlier). .ip in linux 3.2, this controller was extended to provide cpu "bandwidth" control. if the kernel is configured with .br config_cfs_bandwidth , then within each scheduling period (defined via a file in the cgroup directory), it is possible to define an upper limit on the cpu time allocated to the processes in a cgroup. this upper limit applies even if there is no other competition for the cpu. further information can be found in the kernel source file .ir documentation/scheduler/sched\-bwc.rst (or .ir documentation/scheduler/sched\-bwc.txt in linux 5.2 and earlier). .tp .ir cpuacct " (since linux 2.6.24; " \fbconfig_cgroup_cpuacct\fp ) this provides accounting for cpu usage by groups of processes. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/cpuacct.rst (or .ir documentation/cgroup\-v1/cpuacct.txt in linux 5.2 and earlier). .tp .ir cpuset " (since linux 2.6.24; " \fbconfig_cpusets\fp ) this cgroup can be used to bind the processes in a cgroup to a specified set of cpus and numa nodes. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/cpusets.rst (or .ir documentation/cgroup\-v1/cpusets.txt in linux 5.2 and earlier). . .tp .ir memory " (since linux 2.6.25; " \fbconfig_memcg\fp ) the memory controller supports reporting and limiting of process memory, kernel memory, and swap used by cgroups. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/memory.rst (or .ir documentation/cgroup\-v1/memory.txt in linux 5.2 and earlier). .tp .ir devices " (since linux 2.6.26; " \fbconfig_cgroup_device\fp ) this supports controlling which processes may create (mknod) devices as well as open them for reading or writing. the policies may be specified as allow-lists and deny-lists. hierarchy is enforced, so new rules must not violate existing rules for the target or ancestor cgroups. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/devices.rst (or .ir documentation/cgroup\-v1/devices.txt in linux 5.2 and earlier). .tp .ir freezer " (since linux 2.6.28; " \fbconfig_cgroup_freezer\fp ) the .ir freezer cgroup can suspend and restore (resume) all processes in a cgroup. freezing a cgroup .i /a also causes its children, for example, processes in .ir /a/b , to be frozen. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/freezer\-subsystem.rst (or .ir documentation/cgroup\-v1/freezer\-subsystem.txt in linux 5.2 and earlier). .tp .ir net_cls " (since linux 2.6.29; " \fbconfig_cgroup_net_classid\fp ) this places a classid, specified for the cgroup, on network packets created by a cgroup. these classids can then be used in firewall rules, as well as used to shape traffic using .br tc (8). this applies only to packets leaving the cgroup, not to traffic arriving at the cgroup. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/net_cls.rst (or .ir documentation/cgroup\-v1/net_cls.txt in linux 5.2 and earlier). .tp .ir blkio " (since linux 2.6.33; " \fbconfig_blk_cgroup\fp ) the .i blkio cgroup controls and limits access to specified block devices by applying io control in the form of throttling and upper limits against leaf nodes and intermediate nodes in the storage hierarchy. .ip two policies are available. the first is a proportional-weight time-based division of disk implemented with cfq. this is in effect for leaf nodes using cfq. the second is a throttling policy which specifies upper i/o rate limits on a device. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/blkio\-controller.rst (or .ir documentation/cgroup\-v1/blkio\-controller.txt in linux 5.2 and earlier). .tp .ir perf_event " (since linux 2.6.39; " \fbconfig_cgroup_perf\fp ) this controller allows .i perf monitoring of the set of processes grouped in a cgroup. .ip further information can be found in the kernel source files .tp .ir net_prio " (since linux 3.3; " \fbconfig_cgroup_net_prio\fp ) this allows priorities to be specified, per network interface, for cgroups. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/net_prio.rst (or .ir documentation/cgroup\-v1/net_prio.txt in linux 5.2 and earlier). .tp .ir hugetlb " (since linux 3.5; " \fbconfig_cgroup_hugetlb\fp ) this supports limiting the use of huge pages by cgroups. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/hugetlb.rst (or .ir documentation/cgroup\-v1/hugetlb.txt in linux 5.2 and earlier). .tp .ir pids " (since linux 4.3; " \fbconfig_cgroup_pids\fp ) this controller permits limiting the number of process that may be created in a cgroup (and its descendants). .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/pids.rst (or .ir documentation/cgroup\-v1/pids.txt in linux 5.2 and earlier). .tp .ir rdma " (since linux 4.11; " \fbconfig_cgroup_rdma\fp ) the rdma controller permits limiting the use of rdma/ib-specific resources per cgroup. .ip further information can be found in the kernel source file .ir documentation/admin\-guide/cgroup\-v1/rdma.rst (or .ir documentation/cgroup\-v1/rdma.txt in linux 5.2 and earlier). .\" .ss creating cgroups and moving processes a cgroup filesystem initially contains a single root cgroup, '/', which all processes belong to. a new cgroup is created by creating a directory in the cgroup filesystem: .pp .in +4n .ex mkdir /sys/fs/cgroup/cpu/cg1 .ee .in .pp this creates a new empty cgroup. .pp a process may be moved to this cgroup by writing its pid into the cgroup's .i cgroup.procs file: .pp .in +4n .ex echo $$ > /sys/fs/cgroup/cpu/cg1/cgroup.procs .ee .in .pp only one pid at a time should be written to this file. .pp writing the value 0 to a .ir cgroup.procs file causes the writing process to be moved to the corresponding cgroup. .pp when writing a pid into the .ir cgroup.procs , all threads in the process are moved into the new cgroup at once. .pp within a hierarchy, a process can be a member of exactly one cgroup. writing a process's pid to a .ir cgroup.procs file automatically removes it from the cgroup of which it was previously a member. .pp the .i cgroup.procs file can be read to obtain a list of the processes that are members of a cgroup. the returned list of pids is not guaranteed to be in order. nor is it guaranteed to be free of duplicates. (for example, a pid may be recycled while reading from the list.) .pp in cgroups v1, an individual thread can be moved to another cgroup by writing its thread id (i.e., the kernel thread id returned by .br clone (2) and .br gettid (2)) to the .ir tasks file in a cgroup directory. this file can be read to discover the set of threads that are members of the cgroup. .\" .ss removing cgroups to remove a cgroup, it must first have no child cgroups and contain no (nonzombie) processes. so long as that is the case, one can simply remove the corresponding directory pathname. note that files in a cgroup directory cannot and need not be removed. .\" .ss cgroups v1 release notification two files can be used to determine whether the kernel provides notifications when a cgroup becomes empty. a cgroup is considered to be empty when it contains no child cgroups and no member processes. .pp a special file in the root directory of each cgroup hierarchy, .ir release_agent , can be used to register the pathname of a program that may be invoked when a cgroup in the hierarchy becomes empty. the pathname of the newly empty cgroup (relative to the cgroup mount point) is provided as the sole command-line argument when the .ir release_agent program is invoked. the .ir release_agent program might remove the cgroup directory, or perhaps repopulate it with a process. .pp the default value of the .ir release_agent file is empty, meaning that no release agent is invoked. .pp the content of the .i release_agent file can also be specified via a mount option when the cgroup filesystem is mounted: .pp .in +4n .ex mount \-o release_agent=pathname ... .ee .in .pp whether or not the .ir release_agent program is invoked when a particular cgroup becomes empty is determined by the value in the .ir notify_on_release file in the corresponding cgroup directory. if this file contains the value 0, then the .ir release_agent program is not invoked. if it contains the value 1, the .ir release_agent program is invoked. the default value for this file in the root cgroup is 0. at the time when a new cgroup is created, the value in this file is inherited from the corresponding file in the parent cgroup. .\" .ss cgroup v1 named hierarchies in cgroups v1, it is possible to mount a cgroup hierarchy that has no attached controllers: .pp .in +4n .ex mount \-t cgroup \-o none,name=somename none /some/mount/point .ee .in .pp multiple instances of such hierarchies can be mounted; each hierarchy must have a unique name. the only purpose of such hierarchies is to track processes. (see the discussion of release notification below.) an example of this is the .i name=systemd cgroup hierarchy that is used by .br systemd (1) to track services and user sessions. .pp since linux 5.0, the .i cgroup_no_v1 kernel boot option (described below) can be used to disable cgroup v1 named hierarchies, by specifying .ir cgroup_no_v1=named . .\" .sh cgroups version 2 in cgroups v2, all mounted controllers reside in a single unified hierarchy. while (different) controllers may be simultaneously mounted under the v1 and v2 hierarchies, it is not possible to mount the same controller simultaneously under both the v1 and the v2 hierarchies. .pp the new behaviors in cgroups v2 are summarized here, and in some cases elaborated in the following subsections. .ip 1. 3 cgroups v2 provides a unified hierarchy against which all controllers are mounted. .ip 2. "internal" processes are not permitted. with the exception of the root cgroup, processes may reside only in leaf nodes (cgroups that do not themselves contain child cgroups). the details are somewhat more subtle than this, and are described below. .ip 3. active cgroups must be specified via the files .ir cgroup.controllers and .ir cgroup.subtree_control . .ip 4. the .i tasks file has been removed. in addition, the .i cgroup.clone_children file that is employed by the .i cpuset controller has been removed. .ip 5. an improved mechanism for notification of empty cgroups is provided by the .ir cgroup.events file. .pp for more changes, see the .ir documentation/admin\-guide/cgroup\-v2.rst file in the kernel source (or .ir documentation/cgroup\-v2.txt in linux 4.17 and earlier). . .pp some of the new behaviors listed above saw subsequent modification with the addition in linux 4.14 of "thread mode" (described below). .\" .ss cgroups v2 unified hierarchy in cgroups v1, the ability to mount different controllers against different hierarchies was intended to allow great flexibility for application design. in practice, though, the flexibility turned out to be less useful than expected, and in many cases added complexity. therefore, in cgroups v2, all available controllers are mounted against a single hierarchy. the available controllers are automatically mounted, meaning that it is not necessary (or possible) to specify the controllers when mounting the cgroup v2 filesystem using a command such as the following: .pp .in +4n .ex mount \-t cgroup2 none /mnt/cgroup2 .ee .in .pp a cgroup v2 controller is available only if it is not currently in use via a mount against a cgroup v1 hierarchy. or, to put things another way, it is not possible to employ the same controller against both a v1 hierarchy and the unified v2 hierarchy. this means that it may be necessary first to unmount a v1 controller (as described above) before that controller is available in v2. since .br systemd (1) makes heavy use of some v1 controllers by default, it can in some cases be simpler to boot the system with selected v1 controllers disabled. to do this, specify the .ir cgroup_no_v1=list option on the kernel boot command line; .i list is a comma-separated list of the names of the controllers to disable, or the word .i all to disable all v1 controllers. (this situation is correctly handled by .br systemd (1), which falls back to operating without the specified controllers.) .pp note that on many modern systems, .br systemd (1) automatically mounts the .i cgroup2 filesystem at .i /sys/fs/cgroup/unified during the boot process. .\" .ss cgroups v2 mount options the following options .ri ( "mount \-o" ) can be specified when mounting the group v2 filesystem: .tp .ir nsdelegate " (since linux 4.15)" treat cgroup namespaces as delegation boundaries. for details, see below. .tp .ir memory_localevents " (since linux 5.2)" .\" commit 9852ae3fe5293264f01c49f2571ef7688f7823ce the .i memory.events should show statistics only for the cgroup itself, and not for any descendant cgroups. this was the behavior before linux 5.2. starting in linux 5.2, the default behavior is to include statistics for descendant cgroups in .ir memory.events , and this mount option can be used to revert to the legacy behavior. this option is system wide and can be set on mount or modified through remount only from the initial mount namespace; it is silently ignored in noninitial namespaces. .\" .ss cgroups v2 controllers the following controllers, documented in the kernel source file .ir documentation/admin\-guide/cgroup\-v2.rst (or .ir documentation/cgroup\-v2.txt in linux 4.17 and earlier), are supported in cgroups version 2: .tp .ir cpu " (since linux 4.15)" this is the successor to the version 1 .i cpu and .i cpuacct controllers. .tp .ir cpuset " (since linux 5.0)" this is the successor of the version 1 .i cpuset controller. .tp .ir freezer " (since linux 5.2)" .\" commit 76f969e8948d82e78e1bc4beb6b9465908e74873 this is the successor of the version 1 .i freezer controller. .tp .ir hugetlb " (since linux 5.6)" this is the successor of the version 1 .i hugetlb controller. .tp .ir io " (since linux 4.5)" this is the successor of the version 1 .i blkio controller. .tp .ir memory " (since linux 4.5)" this is the successor of the version 1 .i memory controller. .tp .ir perf_event " (since linux 4.11)" this is the same as the version 1 .i perf_event controller. .tp .ir pids " (since linux 4.5)" this is the same as the version 1 .i pids controller. .tp .ir rdma " (since linux 4.11)" this is the same as the version 1 .i rdma controller. .pp there is no direct equivalent of the .i net_cls and .i net_prio controllers from cgroups version 1. instead, support has been added to .br iptables (8) to allow ebpf filters that hook on cgroup v2 pathnames to make decisions about network traffic on a per-cgroup basis. .pp the v2 .i devices controller provides no interface files; instead, device control is gated by attaching an ebpf .rb ( bpf_cgroup_device ) program to a v2 cgroup. .\" .ss cgroups v2 subtree control each cgroup in the v2 hierarchy contains the following two files: .tp .ir cgroup.controllers this read-only file exposes a list of the controllers that are .i available in this cgroup. the contents of this file match the contents of the .i cgroup.subtree_control file in the parent cgroup. .tp .i cgroup.subtree_control this is a list of controllers that are .ir active .ri ( enabled ) in the cgroup. the set of controllers in this file is a subset of the set in the .ir cgroup.controllers of this cgroup. the set of active controllers is modified by writing strings to this file containing space-delimited controller names, each preceded by '+' (to enable a controller) or '\-' (to disable a controller), as in the following example: .ip .in +4n .ex echo \(aq+pids \-memory\(aq > x/y/cgroup.subtree_control .ee .in .ip an attempt to enable a controller that is not present in .i cgroup.controllers leads to an .b enoent error when writing to the .i cgroup.subtree_control file. .pp because the list of controllers in .i cgroup.subtree_control is a subset of those .ir cgroup.controllers , a controller that has been disabled in one cgroup in the hierarchy can never be re-enabled in the subtree below that cgroup. .pp a cgroup's .i cgroup.subtree_control file determines the set of controllers that are exercised in the .i child cgroups. when a controller (e.g., .ir pids ) is present in the .i cgroup.subtree_control file of a parent cgroup, then the corresponding controller-interface files (e.g., .ir pids.max ) are automatically created in the children of that cgroup and can be used to exert resource control in the child cgroups. .\" .ss cgroups v2 """no internal processes""" rule cgroups v2 enforces a so-called "no internal processes" rule. roughly speaking, this rule means that, with the exception of the root cgroup, processes may reside only in leaf nodes (cgroups that do not themselves contain child cgroups). this avoids the need to decide how to partition resources between processes which are members of cgroup a and processes in child cgroups of a. .pp for instance, if cgroup .i /cg1/cg2 exists, then a process may reside in .ir /cg1/cg2 , but not in .ir /cg1 . this is to avoid an ambiguity in cgroups v1 with respect to the delegation of resources between processes in .i /cg1 and its child cgroups. the recommended approach in cgroups v2 is to create a subdirectory called .i leaf for any nonleaf cgroup which should contain processes, but no child cgroups. thus, processes which previously would have gone into .i /cg1 would now go into .ir /cg1/leaf . this has the advantage of making explicit the relationship between processes in .i /cg1/leaf and .ir /cg1 's other children. .pp the "no internal processes" rule is in fact more subtle than stated above. more precisely, the rule is that a (nonroot) cgroup can't both (1) have member processes, and (2) distribute resources into child cgroups\(emthat is, have a nonempty .i cgroup.subtree_control file. thus, it .i is possible for a cgroup to have both member processes and child cgroups, but before controllers can be enabled for that cgroup, the member processes must be moved out of the cgroup (e.g., perhaps into the child cgroups). .pp with the linux 4.14 addition of "thread mode" (described below), the "no internal processes" rule has been relaxed in some cases. .\" .ss cgroups v2 cgroup.events file each nonroot cgroup in the v2 hierarchy contains a read-only file, .ir cgroup.events , whose contents are key-value pairs (delimited by newline characters, with the key and value separated by spaces) providing state information about the cgroup: .pp .in +4n .ex $ \fbcat mygrp/cgroup.events\fp populated 1 frozen 0 .ee .in .pp the following keys may appear in this file: .tp .ir populated the value of this key is either 1, if this cgroup or any of its descendants has member processes, or otherwise 0. .tp .ir frozen " (since linux 5.2)" .\" commit 76f969e8948d82e78e1bc4beb6b9465908e7487 the value of this key is 1 if this cgroup is currently frozen, or 0 if it is not. .pp the .ir cgroup.events file can be monitored, in order to receive notification when the value of one of its keys changes. such monitoring can be done using .br inotify (7), which notifies changes as .br in_modify events, or .br poll (2), which notifies changes by returning the .b pollpri and .b pollerr bits in the .ir revents field. .\" .ss cgroup v2 release notification cgroups v2 provides a new mechanism for obtaining notification when a cgroup becomes empty. the cgroups v1 .ir release_agent and .ir notify_on_release files are removed, and replaced by the .i populated key in the .ir cgroup.events file. this key either has the value 0, meaning that the cgroup (and its descendants) contain no (nonzombie) member processes, or 1, meaning that the cgroup (or one of its descendants) contains member processes. .pp the cgroups v2 release-notification mechanism offers the following advantages over the cgroups v1 .ir release_agent mechanism: .ip * 3 it allows for cheaper notification, since a single process can monitor multiple .ir cgroup.events files (using the techniques described earlier). by contrast, the cgroups v1 mechanism requires the expense of creating a process for each notification. .ip * notification for different cgroup subhierarchies can be delegated to different processes. by contrast, the cgroups v1 mechanism allows only one release agent for an entire hierarchy. .\" .ss cgroups v2 cgroup.stat file .\" commit ec39225cca42c05ac36853d11d28f877fde5c42e each cgroup in the v2 hierarchy contains a read-only .ir cgroup.stat file (first introduced in linux 4.14) that consists of lines containing key-value pairs. the following keys currently appear in this file: .tp .i nr_descendants this is the total number of visible (i.e., living) descendant cgroups underneath this cgroup. .tp .i nr_dying_descendants this is the total number of dying descendant cgroups underneath this cgroup. a cgroup enters the dying state after being deleted. it remains in that state for an undefined period (which will depend on system load) while resources are freed before the cgroup is destroyed. note that the presence of some cgroups in the dying state is normal, and is not indicative of any problem. .ip a process can't be made a member of a dying cgroup, and a dying cgroup can't be brought back to life. .\" .ss limiting the number of descendant cgroups each cgroup in the v2 hierarchy contains the following files, which can be used to view and set limits on the number of descendant cgroups under that cgroup: .tp .ir cgroup.max.depth " (since linux 4.14)" .\" commit 1a926e0bbab83bae8207d05a533173425e0496d1 this file defines a limit on the depth of nesting of descendant cgroups. a value of 0 in this file means that no descendant cgroups can be created. an attempt to create a descendant whose nesting level exceeds the limit fails .ri ( mkdir (2) fails with the error .br eagain ). .ip writing the string .ir """max""" to this file means that no limit is imposed. the default value in this file is .ir """max""" . .tp .ir cgroup.max.descendants " (since linux 4.14)" .\" commit 1a926e0bbab83bae8207d05a533173425e0496d1 this file defines a limit on the number of live descendant cgroups that this cgroup may have. an attempt to create more descendants than allowed by the limit fails .ri ( mkdir (2) fails with the error .br eagain ). .ip writing the string .ir """max""" to this file means that no limit is imposed. the default value in this file is .ir """max""" . .\" .sh cgroups delegation: delegating a hierarchy to a less privileged user in the context of cgroups, delegation means passing management of some subtree of the cgroup hierarchy to a nonprivileged user. cgroups v1 provides support for delegation based on file permissions in the cgroup hierarchy but with less strict containment rules than v2 (as noted below). cgroups v2 supports delegation with containment by explicit design. the focus of the discussion in this section is on delegation in cgroups v2, with some differences for cgroups v1 noted along the way. .pp some terminology is required in order to describe delegation. a .i delegater is a privileged user (i.e., root) who owns a parent cgroup. a .i delegatee is a nonprivileged user who will be granted the permissions needed to manage some subhierarchy under that parent cgroup, known as the .ir "delegated subtree" . .pp to perform delegation, the delegater makes certain directories and files writable by the delegatee, typically by changing the ownership of the objects to be the user id of the delegatee. assuming that we want to delegate the hierarchy rooted at (say) .i /dlgt_grp and that there are not yet any child cgroups under that cgroup, the ownership of the following is changed to the user id of the delegatee: .tp .ir /dlgt_grp changing the ownership of the root of the subtree means that any new cgroups created under the subtree (and the files they contain) will also be owned by the delegatee. .tp .ir /dlgt_grp/cgroup.procs changing the ownership of this file means that the delegatee can move processes into the root of the delegated subtree. .tp .ir /dlgt_grp/cgroup.subtree_control " (cgroups v2 only)" changing the ownership of this file means that the delegatee can enable controllers (that are present in .ir /dlgt_grp/cgroup.controllers ) in order to further redistribute resources at lower levels in the subtree. (as an alternative to changing the ownership of this file, the delegater might instead add selected controllers to this file.) .tp .ir /dlgt_grp/cgroup.threads " (cgroups v2 only)" changing the ownership of this file is necessary if a threaded subtree is being delegated (see the description of "thread mode", below). this permits the delegatee to write thread ids to the file. (the ownership of this file can also be changed when delegating a domain subtree, but currently this serves no purpose, since, as described below, it is not possible to move a thread between domain cgroups by writing its thread id to the .ir cgroup.threads file.) .ip in cgroups v1, the corresponding file that should instead be delegated is the .i tasks file. .pp the delegater should .i not change the ownership of any of the controller interfaces files (e.g., .ir pids.max , .ir memory.high ) in .ir dlgt_grp . those files are used from the next level above the delegated subtree in order to distribute resources into the subtree, and the delegatee should not have permission to change the resources that are distributed into the delegated subtree. .pp see also the discussion of the .ir /sys/kernel/cgroup/delegate file in notes for information about further delegatable files in cgroups v2. .pp after the aforementioned steps have been performed, the delegatee can create child cgroups within the delegated subtree (the cgroup subdirectories and the files they contain will be owned by the delegatee) and move processes between cgroups in the subtree. if some controllers are present in .ir dlgt_grp/cgroup.subtree_control , or the ownership of that file was passed to the delegatee, the delegatee can also control the further redistribution of the corresponding resources into the delegated subtree. .\" .ss cgroups v2 delegation: nsdelegate and cgroup namespaces starting with linux 4.13, .\" commit 5136f6365ce3eace5a926e10f16ed2a233db5ba9 there is a second way to perform cgroup delegation in the cgroups v2 hierarchy. this is done by mounting or remounting the cgroup v2 filesystem with the .i nsdelegate mount option. for example, if the cgroup v2 filesystem has already been mounted, we can remount it with the .i nsdelegate option as follows: .pp .in +4n .ex mount \-t cgroup2 \-o remount,nsdelegate \e none /sys/fs/cgroup/unified .ee .in .\" .\" alternatively, we could boot the kernel with the options: .\" .\" cgroup_no_v1=all systemd.legacy_systemd_cgroup_controller .\" .\" the effect of the latter option is to prevent systemd from employing .\" its "hybrid" cgroup mode, where it tries to make use of cgroups v2. .pp the effect of this mount option is to cause cgroup namespaces to automatically become delegation boundaries. more specifically, the following restrictions apply for processes inside the cgroup namespace: .ip * 3 writes to controller interface files in the root directory of the namespace will fail with the error .br eperm . processes inside the cgroup namespace can still write to delegatable files in the root directory of the cgroup namespace such as .ir cgroup.procs and .ir cgroup.subtree_control , and can create subhierarchy underneath the root directory. .ip * attempts to migrate processes across the namespace boundary are denied (with the error .br enoent ). processes inside the cgroup namespace can still (subject to the containment rules described below) move processes between cgroups .i within the subhierarchy under the namespace root. .pp the ability to define cgroup namespaces as delegation boundaries makes cgroup namespaces more useful. to understand why, suppose that we already have one cgroup hierarchy that has been delegated to a nonprivileged user, .ir cecilia , using the older delegation technique described above. suppose further that .i cecilia wanted to further delegate a subhierarchy under the existing delegated hierarchy. (for example, the delegated hierarchy might be associated with an unprivileged container run by .ir cecilia .) even if a cgroup namespace was employed, because both hierarchies are owned by the unprivileged user .ir cecilia , the following illegitimate actions could be performed: .ip * 3 a process in the inferior hierarchy could change the resource controller settings in the root directory of that hierarchy. (these resource controller settings are intended to allow control to be exercised from the .i parent cgroup; a process inside the child cgroup should not be allowed to modify them.) .ip * a process inside the inferior hierarchy could move processes into and out of the inferior hierarchy if the cgroups in the superior hierarchy were somehow visible. .pp employing the .i nsdelegate mount option prevents both of these possibilities. .pp the .i nsdelegate mount option only has an effect when performed in the initial mount namespace; in other mount namespaces, the option is silently ignored. .pp .ir note : on some systems, .br systemd (1) automatically mounts the cgroup v2 filesystem. in order to experiment with the .i nsdelegate operation, it may be useful to boot the kernel with the following command-line options: .pp .in +4n .ex cgroup_no_v1=all systemd.legacy_systemd_cgroup_controller .ee .in .pp these options cause the kernel to boot with the cgroups v1 controllers disabled (meaning that the controllers are available in the v2 hierarchy), and tells .br systemd (1) not to mount and use the cgroup v2 hierarchy, so that the v2 hierarchy can be manually mounted with the desired options after boot-up. .\" .ss cgroup delegation containment rules some delegation .ir "containment rules" ensure that the delegatee can move processes between cgroups within the delegated subtree, but can't move processes from outside the delegated subtree into the subtree or vice versa. a nonprivileged process (i.e., the delegatee) can write the pid of a "target" process into a .ir cgroup.procs file only if all of the following are true: .ip * 3 the writer has write permission on the .i cgroup.procs file in the destination cgroup. .ip * the writer has write permission on the .i cgroup.procs file in the nearest common ancestor of the source and destination cgroups. note that in some cases, the nearest common ancestor may be the source or destination cgroup itself. this requirement is not enforced for cgroups v1 hierarchies, with the consequence that containment in v1 is less strict than in v2. (for example, in cgroups v1 the user that owns two distinct delegated subhierarchies can move a process between the hierarchies.) .ip * if the cgroup v2 filesystem was mounted with the .i nsdelegate option, the writer must be able to see the source and destination cgroups from its cgroup namespace. .ip * in cgroups v1: the effective uid of the writer (i.e., the delegatee) matches the real user id or the saved set-user-id of the target process. before linux 4.11, .\" commit 576dd464505fc53d501bb94569db76f220104d28 this requirement also applied in cgroups v2 (this was a historical requirement inherited from cgroups v1 that was later deemed unnecessary, since the other rules suffice for containment in cgroups v2.) .pp .ir note : one consequence of these delegation containment rules is that the unprivileged delegatee can't place the first process into the delegated subtree; instead, the delegater must place the first process (a process owned by the delegatee) into the delegated subtree. .\" .sh cgroups version 2 thread mode among the restrictions imposed by cgroups v2 that were not present in cgroups v1 are the following: .ip * 3 .ir "no thread-granularity control" : all of the threads of a process must be in the same cgroup. .ip * .ir "no internal processes" : a cgroup can't both have member processes and exercise controllers on child cgroups. .pp both of these restrictions were added because the lack of these restrictions had caused problems in cgroups v1. in particular, the cgroups v1 ability to allow thread-level granularity for cgroup membership made no sense for some controllers. (a notable example was the .i memory controller: since threads share an address space, it made no sense to split threads across different .i memory cgroups.) .pp notwithstanding the initial design decision in cgroups v2, there were use cases for certain controllers, notably the .ir cpu controller, for which thread-level granularity of control was meaningful and useful. to accommodate such use cases, linux 4.14 added .i "thread mode" for cgroups v2. .pp thread mode allows the following: .ip * 3 the creation of .ir "threaded subtrees" in which the threads of a process may be spread across cgroups inside the tree. (a threaded subtree may contain multiple multithreaded processes.) .ip * the concept of .ir "threaded controllers", which can distribute resources across the cgroups in a threaded subtree. .ip * a relaxation of the "no internal processes rule", so that, within a threaded subtree, a cgroup can both contain member threads and exercise resource control over child cgroups. .pp with the addition of thread mode, each nonroot cgroup now contains a new file, .ir cgroup.type , that exposes, and in some circumstances can be used to change, the "type" of a cgroup. this file contains one of the following type values: .tp .i "domain" this is a normal v2 cgroup that provides process-granularity control. if a process is a member of this cgroup, then all threads of the process are (by definition) in the same cgroup. this is the default cgroup type, and provides the same behavior that was provided for cgroups in the initial cgroups v2 implementation. .tp .i "threaded" this cgroup is a member of a threaded subtree. threads can be added to this cgroup, and controllers can be enabled for the cgroup. .tp .i "domain threaded" this is a domain cgroup that serves as the root of a threaded subtree. this cgroup type is also known as "threaded root". .tp .i "domain invalid" this is a cgroup inside a threaded subtree that is in an "invalid" state. processes can't be added to the cgroup, and controllers can't be enabled for the cgroup. the only thing that can be done with this cgroup (other than deleting it) is to convert it to a .ir threaded cgroup by writing the string .ir """threaded""" to the .i cgroup.type file. .ip the rationale for the existence of this "interim" type during the creation of a threaded subtree (rather than the kernel simply immediately converting all cgroups under the threaded root to the type .ir threaded ) is to allow for possible future extensions to the thread mode model .\" .ss threaded versus domain controllers with the addition of threads mode, cgroups v2 now distinguishes two types of resource controllers: .ip * 3 .i threaded .\" in the kernel source, look for ".threaded[ \t]*= true" in .\" initializations of struct cgroup_subsys controllers: these controllers support thread-granularity for resource control and can be enabled inside threaded subtrees, with the result that the corresponding controller-interface files appear inside the cgroups in the threaded subtree. as at linux 4.19, the following controllers are threaded: .ir cpu , .ir perf_event , and .ir pids . .ip * .i domain controllers: these controllers support only process granularity for resource control. from the perspective of a domain controller, all threads of a process are always in the same cgroup. domain controllers can't be enabled inside a threaded subtree. .\" .ss creating a threaded subtree there are two pathways that lead to the creation of a threaded subtree. the first pathway proceeds as follows: .ip 1. 3 we write the string .ir """threaded""" to the .i cgroup.type file of a cgroup .ir y/z that currently has the type .ir domain . this has the following effects: .rs .ip * 3 the type of the cgroup .ir y/z becomes .ir threaded . .ip * the type of the parent cgroup, .ir y , becomes .ir "domain threaded" . the parent cgroup is the root of a threaded subtree (also known as the "threaded root"). .ip * all other cgroups under .ir y that were not already of type .ir threaded (because they were inside already existing threaded subtrees under the new threaded root) are converted to type .ir "domain invalid" . any subsequently created cgroups under .i y will also have the type .ir "domain invalid" . .re .ip 2. we write the string .ir """threaded""" to each of the .ir "domain invalid" cgroups under .ir y , in order to convert them to the type .ir threaded . as a consequence of this step, all threads under the threaded root now have the type .ir threaded and the threaded subtree is now fully usable. the requirement to write .ir """threaded""" to each of these cgroups is somewhat cumbersome, but allows for possible future extensions to the thread-mode model. .pp the second way of creating a threaded subtree is as follows: .ip 1. 3 in an existing cgroup, .ir z , that currently has the type .ir domain , we (1) enable one or more threaded controllers and (2) make a process a member of .ir z . (these two steps can be done in either order.) this has the following consequences: .rs .ip * 3 the type of .i z becomes .ir "domain threaded" . .ip * all of the descendant cgroups of .i x that were not already of type .ir threaded are converted to type .ir "domain invalid" . .re .ip 2. as before, we make the threaded subtree usable by writing the string .ir """threaded""" to each of the .ir "domain invalid" cgroups under .ir y , in order to convert them to the type .ir threaded . .pp one of the consequences of the above pathways to creating a threaded subtree is that the threaded root cgroup can be a parent only to .i threaded (and .ir "domain invalid" ) cgroups. the threaded root cgroup can't be a parent of a .i domain cgroups, and a .i threaded cgroup can't have a sibling that is a .i domain cgroup. .\" .ss using a threaded subtree within a threaded subtree, threaded controllers can be enabled in each subgroup whose type has been changed to .ir threaded ; upon doing so, the corresponding controller interface files appear in the children of that cgroup. .pp a process can be moved into a threaded subtree by writing its pid to the .i cgroup.procs file in one of the cgroups inside the tree. this has the effect of making all of the threads in the process members of the corresponding cgroup and makes the process a member of the threaded subtree. the threads of the process can then be spread across the threaded subtree by writing their thread ids (see .br gettid (2)) to the .i cgroup.threads files in different cgroups inside the subtree. the threads of a process must all reside in the same threaded subtree. .pp as with writing to .ir cgroup.procs , some containment rules apply when writing to the .i cgroup.threads file: .ip * 3 the writer must have write permission on the cgroup.threads file in the destination cgroup. .ip * the writer must have write permission on the .i cgroup.procs file in the common ancestor of the source and destination cgroups. (in some cases, the common ancestor may be the source or destination cgroup itself.) .ip * the source and destination cgroups must be in the same threaded subtree. (outside a threaded subtree, an attempt to move a thread by writing its thread id to the .i cgroup.threads file in a different .i domain cgroup fails with the error .br eopnotsupp .) .pp the .i cgroup.threads file is present in each cgroup (including .i domain cgroups) and can be read in order to discover the set of threads that is present in the cgroup. the set of thread ids obtained when reading this file is not guaranteed to be ordered or free of duplicates. .pp the .i cgroup.procs file in the threaded root shows the pids of all processes that are members of the threaded subtree. the .i cgroup.procs files in the other cgroups in the subtree are not readable. .pp domain controllers can't be enabled in a threaded subtree; no controller-interface files appear inside the cgroups underneath the threaded root. from the point of view of a domain controller, threaded subtrees are invisible: a multithreaded process inside a threaded subtree appears to a domain controller as a process that resides in the threaded root cgroup. .pp within a threaded subtree, the "no internal processes" rule does not apply: a cgroup can both contain member processes (or thread) and exercise controllers on child cgroups. .\" .ss rules for writing to cgroup.type and creating threaded subtrees a number of rules apply when writing to the .i cgroup.type file: .ip * 3 only the string .ir """threaded""" may be written. in other words, the only explicit transition that is possible is to convert a .i domain cgroup to type .ir threaded . .ip * the effect of writing .ir """threaded""" depends on the current value in .ir cgroup.type , as follows: .rs .ip \(bu 3 .ir domain or .ir "domain threaded" : start the creation of a threaded subtree (whose root is the parent of this cgroup) via the first of the pathways described above; .ip \(bu .ir "domain\ invalid" : convert this cgroup (which is inside a threaded subtree) to a usable (i.e., .ir threaded ) state; .ip \(bu .ir threaded : no effect (a "no-op"). .re .ip * we can't write to a .i cgroup.type file if the parent's type is .ir "domain invalid" . in other words, the cgroups of a threaded subtree must be converted to the .i threaded state in a top-down manner. .pp there are also some constraints that must be satisfied in order to create a threaded subtree rooted at the cgroup .ir x : .ip * 3 there can be no member processes in the descendant cgroups of .ir x . (the cgroup .i x can itself have member processes.) .ip * no domain controllers may be enabled in .ir x 's .ir cgroup.subtree_control file. .pp if any of the above constraints is violated, then an attempt to write .ir """threaded""" to a .ir cgroup.type file fails with the error .br enotsup . .\" .ss the """domain threaded""" cgroup type according to the pathways described above, the type of a cgroup can change to .ir "domain threaded" in either of the following cases: .ip * 3 the string .ir """threaded""" is written to a child cgroup. .ip * a threaded controller is enabled inside the cgroup and a process is made a member of the cgroup. .pp a .ir "domain threaded" cgroup, .ir x , can revert to the type .ir domain if the above conditions no longer hold true\(emthat is, if all .i threaded child cgroups of .i x are removed and either .i x no longer has threaded controllers enabled or no longer has member processes. .pp when a .ir "domain threaded" cgroup .ir x reverts to the type .ir domain : .ip * 3 all .ir "domain invalid" descendants of .i x that are not in lower-level threaded subtrees revert to the type .ir domain . .ip * the root cgroups in any lower-level threaded subtrees revert to the type .ir "domain threaded" . .\" .ss exceptions for the root cgroup the root cgroup of the v2 hierarchy is treated exceptionally: it can be the parent of both .i domain and .i threaded cgroups. if the string .i """threaded""" is written to the .i cgroup.type file of one of the children of the root cgroup, then .ip * 3 the type of that cgroup becomes .ir threaded . .ip * the type of any descendants of that cgroup that are not part of lower-level threaded subtrees changes to .ir "domain invalid" . .pp note that in this case, there is no cgroup whose type becomes .ir "domain threaded" . (notionally, the root cgroup can be considered as the threaded root for the cgroup whose type was changed to .ir threaded .) .pp the aim of this exceptional treatment for the root cgroup is to allow a threaded cgroup that employs the .i cpu controller to be placed as high as possible in the hierarchy, so as to minimize the (small) cost of traversing the cgroup hierarchy. .\" .ss the cgroups v2 """cpu""" controller and realtime threads as at linux 4.19, the cgroups v2 .i cpu controller does not support control of realtime threads (specifically threads scheduled under any of the policies .br sched_fifo , .br sched_rr , described .br sched_deadline ; see .br sched (7)). therefore, the .i cpu controller can be enabled in the root cgroup only if all realtime threads are in the root cgroup. (if there are realtime threads in nonroot cgroups, then a .br write (2) of the string .ir """+cpu""" to the .i cgroup.subtree_control file fails with the error .br einval .) .pp on some systems, .br systemd (1) places certain realtime threads in nonroot cgroups in the v2 hierarchy. on such systems, these threads must first be moved to the root cgroup before the .i cpu controller can be enabled. .\" .sh errors the following errors can occur for .br mount (2): .tp .b ebusy an attempt to mount a cgroup version 1 filesystem specified neither the .i name= option (to mount a named hierarchy) nor a controller name (or .ir all ). .sh notes a child process created via .br fork (2) inherits its parent's cgroup memberships. a process's cgroup memberships are preserved across .br execve (2). .pp the .br clone3 (2) .b clone_into_cgroup flag can be used to create a child process that begins its life in a different version 2 cgroup from the parent process. .\" .ss /proc files .tp .ir /proc/cgroups " (since linux 2.6.24)" this file contains information about the controllers that are compiled into the kernel. an example of the contents of this file (reformatted for readability) is the following: .ip .in +4n .ex #subsys_name hierarchy num_cgroups enabled cpuset 4 1 1 cpu 8 1 1 cpuacct 8 1 1 blkio 6 1 1 memory 3 1 1 devices 10 84 1 freezer 7 1 1 net_cls 9 1 1 perf_event 5 1 1 net_prio 9 1 1 hugetlb 0 1 0 pids 2 1 1 .ee .in .ip the fields in this file are, from left to right: .rs .ip 1. 3 the name of the controller. .ip 2. the unique id of the cgroup hierarchy on which this controller is mounted. if multiple cgroups v1 controllers are bound to the same hierarchy, then each will show the same hierarchy id in this field. the value in this field will be 0 if: .rs 5 .ip a) 3 the controller is not mounted on a cgroups v1 hierarchy; .ip b) the controller is bound to the cgroups v2 single unified hierarchy; or .ip c) the controller is disabled (see below). .re .ip 3. the number of control groups in this hierarchy using this controller. .ip 4. this field contains the value 1 if this controller is enabled, or 0 if it has been disabled (via the .ir cgroup_disable kernel command-line boot parameter). .re .tp .ir /proc/[pid]/cgroup " (since linux 2.6.24)" this file describes control groups to which the process with the corresponding pid belongs. the displayed information differs for cgroups version 1 and version 2 hierarchies. .ip for each cgroup hierarchy of which the process is a member, there is one entry containing three colon-separated fields: .ip .in +4n .ex hierarchy\-id:controller\-list:cgroup\-path .ee .in .ip for example: .ip .in +4n .ex 5:cpuacct,cpu,cpuset:/daemons .ee .in .ip the colon-separated fields are, from left to right: .rs .ip 1. 3 for cgroups version 1 hierarchies, this field contains a unique hierarchy id number that can be matched to a hierarchy id in .ir /proc/cgroups . for the cgroups version 2 hierarchy, this field contains the value 0. .ip 2. for cgroups version 1 hierarchies, this field contains a comma-separated list of the controllers bound to the hierarchy. for the cgroups version 2 hierarchy, this field is empty. .ip 3. this field contains the pathname of the control group in the hierarchy to which the process belongs. this pathname is relative to the mount point of the hierarchy. .re .\" .ss /sys/kernel/cgroup files .tp .ir /sys/kernel/cgroup/delegate " (since linux 4.15)" .\" commit 01ee6cfb1483fe57c9cbd8e73817dfbf9bacffd3 this file exports a list of the cgroups v2 files (one per line) that are delegatable (i.e., whose ownership should be changed to the user id of the delegatee). in the future, the set of delegatable files may change or grow, and this file provides a way for the kernel to inform user-space applications of which files must be delegated. as at linux 4.15, one sees the following when inspecting this file: .ip .in +4n .ex $ \fbcat /sys/kernel/cgroup/delegate\fp cgroup.procs cgroup.subtree_control cgroup.threads .ee .in .tp .ir /sys/kernel/cgroup/features " (since linux 4.15)" .\" commit 5f2e673405b742be64e7c3604ed4ed3ac14f35ce over time, the set of cgroups v2 features that are provided by the kernel may change or grow, or some features may not be enabled by default. this file provides a way for user-space applications to discover what features the running kernel supports and has enabled. features are listed one per line: .ip .in +4n .ex $ \fbcat /sys/kernel/cgroup/features\fp nsdelegate memory_localevents .ee .in .ip the entries that can appear in this file are: .rs .tp .ir memory_localevents " (since linux 5.2)" the kernel supports the .i memory_localevents mount option. .tp .ir nsdelegate " (since linux 4.15)" the kernel supports the .i nsdelegate mount option. .re .sh see also .br prlimit (1), .br systemd (1), .br systemd\-cgls (1), .br systemd\-cgtop (1), .br clone (2), .br ioprio_set (2), .br perf_event_open (2), .br setrlimit (2), .br cgroup_namespaces (7), .br cpuset (7), .br namespaces (7), .br sched (7), .br user_namespaces (7) .pp the kernel source file .ir documentation/admin\-guide/cgroup\-v2.rst . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page is copyright (c) 1998 alan cox. .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: ddp.7,v 1.3 1999/05/13 11:33:22 freitag exp $ .\" .th ddp 7 2021-03-22 "linux" "linux programmer's manual" .sh name ddp \- linux appletalk protocol implementation .sh synopsis .nf .b #include .b #include .pp .ib ddp_socket " = socket(af_appletalk, sock_dgram, 0);" .ib raw_socket " = socket(af_appletalk, sock_raw, " protocol ");" .fi .sh description linux implements the appletalk protocols described in .ir "inside appletalk" . only the ddp layer and aarp are present in the kernel. they are designed to be used via the .b netatalk protocol libraries. this page documents the interface for those who wish or need to use the ddp layer directly. .pp the communication between appletalk and the user program works using a bsd-compatible socket interface. for more information on sockets, see .br socket (7). .pp an appletalk socket is created by calling the .br socket (2) function with a .b af_appletalk socket family argument. valid socket types are .b sock_dgram to open a .b ddp socket or .b sock_raw to open a .b raw socket. .i protocol is the appletalk protocol to be received or sent. for .b sock_raw you must specify .br atproto_ddp . .pp raw sockets may be opened only by a process with effective user id 0 or when the process has the .b cap_net_raw capability. .ss address format an appletalk socket address is defined as a combination of a network number, a node number, and a port number. .pp .in +4n .ex struct at_addr { unsigned short s_net; unsigned char s_node; }; struct sockaddr_atalk { sa_family_t sat_family; /* address family */ unsigned char sat_port; /* port */ struct at_addr sat_addr; /* net/node */ }; .ee .in .pp .i sat_family is always set to .br af_appletalk . .i sat_port contains the port. the port numbers below 129 are known as .ir "reserved ports" . only processes with the effective user id 0 or the .b cap_net_bind_service capability may .br bind (2) to these sockets. .i sat_addr is the host address. the .i net member of .i struct at_addr contains the host network in network byte order. the value of .b at_anynet is a wildcard and also implies \(lqthis network.\(rq the .i node member of .i struct at_addr contains the host node number. the value of .b at_anynode is a wildcard and also implies \(lqthis node.\(rq the value of .b ataddr_bcast is a link local broadcast address. .\" fixme . this doesn't make sense [johnl] .ss socket options no protocol-specific socket options are supported. .ss /proc interfaces ip supports a set of .i /proc interfaces to configure some global appletalk parameters. the parameters can be accessed by reading or writing files in the directory .ir /proc/sys/net/atalk/ . .tp .i aarp\-expiry\-time the time interval (in seconds) before an aarp cache entry expires. .tp .i aarp\-resolve\-time the time interval (in seconds) before an aarp cache entry is resolved. .tp .i aarp\-retransmit\-limit the number of retransmissions of an aarp query before the node is declared dead. .tp .i aarp\-tick\-time the timer rate (in seconds) for the timer driving aarp. .pp the default values match the specification and should never need to be changed. .ss ioctls all ioctls described in .br socket (7) apply to ddp. .\" fixme . add a section about multicasting .sh errors .tp .b eacces the user tried to execute an operation without the necessary permissions. these include sending to a broadcast address without having the broadcast flag set, and trying to bind to a reserved port without effective user id 0 or .br cap_net_bind_service . .tp .b eaddrinuse tried to bind to an address already in use. .tp .b eaddrnotavail a nonexistent interface was requested or the requested source address was not local. .tp .b eagain operation on a nonblocking socket would block. .tp .b ealready a connection operation on a nonblocking socket is already in progress. .tp .b econnaborted a connection was closed during an .br accept (2). .tp .b ehostunreach no routing table entry matches the destination address. .tp .b einval invalid argument passed. .tp .b eisconn .br connect (2) was called on an already connected socket. .tp .b emsgsize datagram is bigger than the ddp mtu. .tp .b enodev network device not available or not capable of sending ip. .tp .b enoent .b siocgstamp was called on a socket where no packet arrived. .tp .br enomem " and " enobufs not enough memory available. .tp .b enopkg a kernel subsystem was not configured. .tp .br enoprotoopt " and " eopnotsupp invalid socket option passed. .tp .b enotconn the operation is defined only on a connected socket, but the socket wasn't connected. .tp .b eperm user doesn't have permission to set high priority, make a configuration change, or send signals to the requested process or group. .tp .b epipe the connection was unexpectedly closed or shut down by the other end. .tp .b esocktnosupport the socket was unconfigured, or an unknown socket type was requested. .sh versions appletalk is supported by linux 2.0 or higher. the .i /proc interfaces exist since linux 2.2. .sh notes be very careful with the .b so_broadcast option; it is not privileged in linux. it is easy to overload the network with careless sending to broadcast addresses. .ss compatibility the basic appletalk socket interface is compatible with .b netatalk on bsd-derived systems. many bsd systems fail to check .b so_broadcast when sending broadcast frames; this can lead to compatibility problems. .pp the raw socket mode is unique to linux and exists to support the alternative cap package and appletalk monitoring tools more easily. .sh bugs there are too many inconsistent error values. .pp the ioctls used to configure routing tables, devices, aarp tables, and other devices are not yet described. .sh see also .br recvmsg (2), .br sendmsg (2), .br capabilities (7), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/drand48.3 .so man3/getprotoent.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 21:48:06 1993 by rik faith (faith@cs.unc.edu) .th getnetent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent \- get network entry .sh synopsis .nf .b #include .pp .b struct netent *getnetent(void); .pp .bi "struct netent *getnetbyname(const char *" name ); .bi "struct netent *getnetbyaddr(uint32_t " net ", int " type ); .pp .bi "void setnetent(int " stayopen ); .b void endnetent(void); .fi .sh description the .br getnetent () function reads the next entry from the networks database and returns a .i netent structure containing the broken-out fields from the entry. a connection is opened to the database if necessary. .pp the .br getnetbyname () function returns a .i netent structure for the entry from the database that matches the network .ir name . .pp the .br getnetbyaddr () function returns a .i netent structure for the entry from the database that matches the network number .i net of type .ir type . the .i net argument must be in host byte order. .pp the .br setnetent () function opens a connection to the database, and sets the next entry to the first entry. if .i stayopen is nonzero, then the connection to the database will not be closed between calls to one of the .br getnet* () functions. .pp the .br endnetent () function closes the connection to the database. .pp the .i netent structure is defined in .i as follows: .pp .in +4n .ex struct netent { char *n_name; /* official network name */ char **n_aliases; /* alias list */ int n_addrtype; /* net address type */ uint32_t n_net; /* network number */ } .ee .in .pp the members of the .i netent structure are: .tp .i n_name the official name of the network. .tp .i n_aliases a null-terminated list of alternative names for the network. .tp .i n_addrtype the type of the network number; always .br af_inet . .tp .i n_net the network number in host byte order. .sh return value the .br getnetent (), .br getnetbyname (), and .br getnetbyaddr () functions return a pointer to a statically allocated .i netent structure, or a null pointer if an error occurs or the end of the file is reached. .sh files .tp .i /etc/networks networks database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getnetent () t} thread safety t{ mt-unsafe race:netent race:netentbuf env locale t} t{ .br getnetbyname () t} thread safety t{ mt-unsafe race:netbyname env locale t} t{ .br getnetbyaddr () t} thread safety t{ mt-unsafe race:netbyaddr locale t} t{ .br setnetent (), .br endnetent () t} thread safety t{ mt-unsafe race:netent env locale t} .te .hy .ad .sp 1 in the above table, .i netent in .i race:netent signifies that if any of the functions .br setnetent (), .br getnetent (), or .br endnetent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh notes in glibc versions before 2.2, the .i net argument of .br getnetbyaddr () was of type .ir long . .sh see also .br getnetent_r (3), .br getprotoent (3), .br getservent (3) .\" .br networks (5) .br rfc\ 1101 .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tsearch.3 .\" copyright 1995 yggdrasil computing, incorporated. .\" and copyright 2015 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th dlerror 3 2021-03-22 "linux" "linux programmer's manual" .sh name dlerror \- obtain error diagnostic for functions in the dlopen api .sh synopsis .nf .b #include .pp .b "char *dlerror(void);" .pp link with \fi\-ldl\fp. .fi .sh description the .br dlerror () function returns a human-readable, null-terminated string describing the most recent error that occurred from a call to one of the functions in the dlopen api since the last call to .br dlerror (). the returned string does .i not include a trailing newline. .pp .br dlerror () returns null if no errors have occurred since initialization or since it was last called. .sh versions .br dlerror () is present in glibc 2.0 and later. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dlerror () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001. .sh notes the message returned by .br dlerror () may reside in a statically allocated buffer that is overwritten by subsequent .br dlerror () calls. .\" .lp .\" the string returned by .\" .br dlerror () .\" should not be modified. .\" some systems give the prototype as .\" .sp .\" .in +5 .\" .b "const char *dlerror(void);" .\" .in .ss history this function is part of the dlopen api, derived from sunos. .sh examples see .br dlopen (3). .sh see also .br dladdr (3), .br dlinfo (3), .br dlopen (3), .br dlsym (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 17:57:50 1993 by rik faith (faith@cs.unc.edu) .th strspn 3 2021-03-22 "" "linux programmer's manual" .sh name strspn, strcspn \- get length of a prefix substring .sh synopsis .nf .b #include .pp .bi "size_t strspn(const char *" s ", const char *" accept ); .bi "size_t strcspn(const char *" s ", const char *" reject ); .fi .sh description the .br strspn () function calculates the length (in bytes) of the initial segment of .i s which consists entirely of bytes in .ir accept . .pp the .br strcspn () function calculates the length of the initial segment of .i s which consists entirely of bytes not in .ir reject . .sh return value the .br strspn () function returns the number of bytes in the initial segment of .i s which consist only of bytes from .ir accept . .pp the .br strcspn () function returns the number of bytes in the initial segment of .i s which are not in the string .ir reject . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strspn (), .br strcspn () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh see also .br index (3), .br memchr (3), .br rindex (3), .br strchr (3), .br string (3), .br strpbrk (3), .br strsep (3), .br strstr (3), .br strtok (3), .br wcscspn (3), .br wcsspn (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/ioctl_console.2 .\" link for old name of this page .so man3/posix_memalign.3 .so man3/futimes.3 .so man2/epoll_wait.2 .so man3/getmntent.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th ccos 3 2021-03-22 "" "linux programmer's manual" .sh name ccos, ccosf, ccosl \- complex cosine function .sh synopsis .nf .b #include .pp .bi "double complex ccos(double complex " z ");" .bi "float complex ccosf(float complex " z ");" .bi "long double complex ccosl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex cosine of .ir z . .pp the complex cosine function is defined as: .pp .nf ccos(z) = (exp(i * z) + exp(\-i * z)) / 2 .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ccos (), .br ccosf (), .br ccosl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br cacos (3), .br csin (3), .br ctan (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. #!/bin/sh # # find_repeated_words.sh # # a simple script for finding instances of repeated consecutive words # in manual pages -- human inspection can then determine if these # are real errors in the text. # # usage: sh find_repeated_words.sh [file...] # ###################################################################### # # (c) copyright 2007 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # # for file in "$@" ; do # do not process files that are redirects. grep -qe "^\.so man.*" "$file" if test $? -ne 0; then words=$(manwidth=2000 man -l "$file" 2> /dev/null | col -b | \ tr ' \008' '\012' | sed -e '/^$/d' | \ sed 's/ *$//' | awk 'begin {p=""} {if (p==$0) print p; p=$0}' | \ grep '[a-za-z]' | tr '\012' ' ') if test -n "$words"; then echo "$file: $words" fi fi done .so man2/stat.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th fputwc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fputwc, putwc \- write a wide character to a file stream .sh synopsis .nf .b #include .b #include .pp .bi "wint_t fputwc(wchar_t " wc ", file *" stream ); .bi "wint_t putwc(wchar_t " wc ", file *" stream ); .fi .sh description the .br fputwc () function is the wide-character equivalent of the .br fputc (3) function. it writes the wide character \fiwc\fp to \fistream\fp. if \fiferror(stream)\fp becomes true, it returns .br weof . if a wide-character conversion error occurs, it sets \fierrno\fp to \fbeilseq\fp and returns .br weof . otherwise, it returns \fiwc\fp. .pp the .br putwc () function or macro functions identically to .br fputwc (). it may be implemented as a macro, and may evaluate its argument more than once. there is no reason ever to use it. .pp for nonlocking counterparts, see .br unlocked_stdio (3). .sh return value on success, .br fputwc () function returns .ir wc . otherwise, .b weof is returned, and .i errno is set to indicate the error. .sh errors apart from the usual ones, there is .tp .b eilseq conversion of \fiwc\fp to the stream's encoding fails. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fputwc (), .br putwc () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br fputwc () depends on the .b lc_ctype category of the current locale. .pp in the absence of additional information passed to the .br fopen (3) call, it is reasonable to expect that .br fputwc () will actually write the multibyte sequence corresponding to the wide character \fiwc\fp. .sh see also .br fgetwc (3), .br fputws (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 rickard e. faith .\" and copyright (c) 1994 andries e. brouwer .\" and copyright (c) 2002, 2005, 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1996-11-04 by eric s. raymond .\" modified 2001-10-13 by michael kerrisk .\" added note on historical behavior of ms_nosuid .\" modified 2002-05-16 by michael kerrisk .\" extensive changes and additions .\" modified 2002-05-27 by aeb .\" modified 2002-06-11 by michael kerrisk .\" enhanced descriptions of ms_move, ms_bind, and ms_remount .\" modified 2004-06-17 by michael kerrisk .\" 2005-05-18, mtk, added mnt_expire, plus a few other tidy-ups. .\" 2008-10-06, mtk: move umount*() material into separate umount.2 page. .\" 2008-10-06, mtk: add discussion of namespaces. .\" .th mount 2 2021-08-27 "linux" "linux programmer's manual" .sh name mount \- mount filesystem .sh synopsis .nf .b "#include " .pp .bi "int mount(const char *" source ", const char *" target , .bi " const char *" filesystemtype ", unsigned long " mountflags , .bi " const void *" data ); .fi .sh description .br mount () attaches the filesystem specified by .i source (which is often a pathname referring to a device, but can also be the pathname of a directory or file, or a dummy string) to the location (a directory or file) specified by the pathname in .ir target . .pp appropriate privilege (linux: the .b cap_sys_admin capability) is required to mount filesystems. .pp values for the .i filesystemtype argument supported by the kernel are listed in .i /proc/filesystems (e.g., "btrfs", "ext4", "jfs", "xfs", "vfat", "fuse", "tmpfs", "cgroup", "proc", "mqueue", "nfs", "cifs", "iso9660"). further types may become available when the appropriate modules are loaded. .pp the .i data argument is interpreted by the different filesystems. typically it is a string of comma-separated options understood by this filesystem. see .br mount (8) for details of the options available for each filesystem type. this argument may be specified as null, if there are no options. .pp a call to .br mount () performs one of a number of general types of operation, depending on the bits specified in .ir mountflags . the choice of which operation to perform is determined by testing the bits set in .ir mountflags , with the tests being conducted in the order listed here: .ip * 3 remount an existing mount: .ir mountflags includes .br ms_remount . .ip * create a bind mount: .ir mountflags includes .br ms_bind . .ip * change the propagation type of an existing mount: .ir mountflags includes one of .br ms_shared , .br ms_private , .br ms_slave , or .br ms_unbindable . .ip * move an existing mount to a new location: .ir mountflags includes .br ms_move . .ip * create a new mount: .ir mountflags includes none of the above flags. .pp each of these operations is detailed later in this page. further flags may be specified in .ir mountflags to modify the behavior of .br mount (), as described below. .\" .ss additional mount flags the list below describes the additional flags that can be specified in .ir mountflags . note that some operation types ignore some or all of these flags, as described later in this page. .\" .\" fixme 2.6.25 added ms_i_version, which needs to be documented. .\" commit 7a224228ed79d587ece2304869000aad1b8e97dd .\" (this is a per-superblock flag) .\" .tp .br ms_dirsync " (since linux 2.5.19)" make directory changes on this filesystem synchronous. (this property can be obtained for individual directories or subtrees using .br chattr (1).) .tp .br ms_lazytime " (since linux 4.0)" .\" commit 0ae45f63d4ef8d8eeec49c7d8b44a1775fff13e8 .\" commit fe032c422c5ba562ba9c2d316f55e258e03259c6 .\" commit a26f49926da938f47561f386be56a83dd37a496d reduce on-disk updates of inode timestamps (atime, mtime, ctime) by maintaining these changes only in memory. the on-disk timestamps are updated only when: .rs .ip (a) 4 the inode needs to be updated for some change unrelated to file timestamps; .ip (b) the application employs .br fsync (2), .br syncfs (2), or .br sync (2); .ip (c) an undeleted inode is evicted from memory; or .ip (d) more than 24 hours have passed since the inode was written to disk. .re .ip this mount option significantly reduces writes needed to update the inode's timestamps, especially mtime and atime. however, in the event of a system crash, the atime and mtime fields on disk might be out of date by up to 24 hours. .ip examples of workloads where this option could be of significant benefit include frequent random writes to preallocated files, as well as cases where the .b ms_strictatime mount option is also enabled. (the advantage of combining .br ms_strictatime and .br ms_lazytime is that .br stat (2) will return the correctly updated atime, but the atime updates will be flushed to disk only in the cases listed above.) .tp .b ms_mandlock permit mandatory locking on files in this filesystem. (mandatory locking must still be enabled on a per-file basis, as described in .br fcntl (2).) since linux 4.5, .\" commit 95ace75414f312f9a7b93d873f386987b92a5301 this mount option requires the .b cap_sys_admin capability and a kernel configured with the .b config_mandatory_file_locking option. .tp .b ms_noatime do not update access times for (all types of) files on this filesystem. .tp .b ms_nodev do not allow access to devices (special files) on this filesystem. .tp .b ms_nodiratime do not update access times for directories on this filesystem. this flag provides a subset of the functionality provided by .br ms_noatime ; that is, .br ms_noatime implies .br ms_nodiratime . .tp .b ms_noexec do not allow programs to be executed from this filesystem. .\" (possibly useful for a filesystem that contains non-linux executables. .\" often used as a security feature, e.g., to make sure that restricted .\" users cannot execute files uploaded using ftp or so.) .tp .b ms_nosuid do not honor set-user-id and set-group-id bits or file capabilities when executing programs from this filesystem. in addition, selinux domain transitions require the permission .ir nosuid_transition , which in turn needs also the policy capability .ir nnp_nosuid_transition . .\" (this is a security feature to prevent users executing set-user-id and .\" set-group-id programs from removable disk devices.) .tp .b ms_rdonly mount filesystem read-only. .tp .br ms_rec " (since linux 2.4.11)" used in conjunction with .br ms_bind to create a recursive bind mount, and in conjunction with the propagation type flags to recursively change the propagation type of all of the mounts in a subtree. see below for further details. .tp .br ms_relatime " (since linux 2.6.20)" when a file on this filesystem is accessed, update the file's last access time (atime) only if the current value of atime is less than or equal to the file's last modification time (mtime) or last status change time (ctime). this option is useful for programs, such as .br mutt (1), that need to know when a file has been read since it was last modified. since linux 2.6.30, the kernel defaults to the behavior provided by this flag (unless .br ms_noatime was specified), and the .b ms_strictatime flag is required to obtain traditional semantics. in addition, since linux 2.6.30, the file's last access time is always updated if it is more than 1 day old. .\" matthew garrett notes in the patch that added this behavior .\" that this lets utilities such as tmpreaper (which deletes .\" files based on last access time) work correctly. .tp .br ms_silent " (since linux 2.6.17)" suppress the display of certain .ri ( printk ()) warning messages in the kernel log. this flag supersedes the misnamed and obsolete .br ms_verbose flag (available since linux 2.4.12), which has the same meaning. .tp .br ms_strictatime " (since linux 2.6.30)" always update the last access time (atime) when files on this filesystem are accessed. (this was the default behavior before linux 2.6.30.) specifying this flag overrides the effect of setting the .br ms_noatime and .br ms_relatime flags. .tp .b ms_synchronous make writes on this filesystem synchronous (as though the .b o_sync flag to .br open (2) was specified for all file opens to this filesystem). .tp .br ms_nosymfollow " (since linux 5.10)" .\" dab741e0e02bd3c4f5e2e97be74b39df2523fc6e do not follow symbolic links when resolving paths. symbolic links can still be created, and .br readlink (1), .br readlink (2), .br realpath (1), and .br realpath (3) all still work properly. .pp from linux 2.4 onward, some of the above flags are settable on a per-mount basis, while others apply to the superblock of the mounted filesystem, meaning that all mounts of the same filesystem share those flags. (previously, all of the flags were per-superblock.) .pp the per-mount-point flags are as follows: .ip * 3 since linux 2.4: .br ms_nodev ", " ms_noexec ", and " ms_nosuid flags are settable on a per-mount-point basis. .ip * additionally, since linux 2.6.16: .b ms_noatime and .br ms_nodiratime . .ip * additionally, since linux 2.6.20: .br ms_relatime . .pp the following flags are per-superblock: .br ms_dirsync , .br ms_lazytime , .br ms_mandlock , .br ms_silent , and .br ms_synchronous . .\" and ms_i_version? the initial settings of these flags are determined on the first mount of the filesystem, and will be shared by all subsequent mounts of the same filesystem. subsequently, the settings of the flags can be changed via a remount operation (see below). such changes will be visible via all mounts associated with the filesystem. .pp since linux 2.6.16, .b ms_rdonly can be set or cleared on a per-mount-point basis as well as on the underlying filesystem superblock. the mounted filesystem will be writable only if neither the filesystem nor the mountpoint are flagged as read-only. .\" .ss remounting an existing mount an existing mount may be remounted by specifying .b ms_remount in .ir mountflags . this allows you to change the .i mountflags and .i data of an existing mount without having to unmount and remount the filesystem. .i target should be the same value specified in the initial .br mount () call. .pp the .i source and .i filesystemtype arguments are ignored. .pp the .i mountflags and .i data arguments should match the values used in the original .br mount () call, except for those parameters that are being deliberately changed. .pp the following .i mountflags can be changed: .br ms_lazytime , .\" fixme .\" ms_lazytime seems to be available only on a few filesystems, .\" and on ext4, it seems (from experiment that this flag .\" can only be enabled (but not disabled) on a remount. .\" the following code in ext4_remount() (kernel 4.17) seems to .\" confirm this: .\" .\" if (*flags & sb_lazytime) .\" sb->s_flags |= sb_lazytime; .br ms_mandlock , .br ms_noatime , .br ms_nodev , .br ms_nodiratime , .br ms_noexec , .br ms_nosuid , .br ms_relatime , .br ms_rdonly , .br ms_strictatime (whose effect is to clear the .br ms_noatime and .br ms_relatime flags), and .br ms_synchronous . attempts to change the setting of the .\" see the definition of ms_rmt_mask in include/uapi/linux/fs.h, .\" which excludes ms_dirsync and ms_silent, although sb_dirsync .\" and sb_silent are split out as per-superblock flags in do_mount() .\" (linux 4.17 source code) .br ms_dirsync and .br ms_silent flags during a remount are silently ignored. note that changes to per-superblock flags are visible via all mounts of the associated filesystem (because the per-superblock flags are shared by all mounts). .pp since linux 3.17, .\" commit ffbc6f0ead47fa5a1dc9642b0331cb75c20a640e if none of .br ms_noatime , .br ms_nodiratime , .br ms_relatime , or .br ms_strictatime is specified in .ir mountflags , then the remount operation preserves the existing values of these flags (rather than defaulting to .br ms_relatime ). .pp since linux 2.6.26, the .b ms_remount flag can be used with .b ms_bind to modify only the per-mount-point flags. .\" see https://lwn.net/articles/281157/ this is particularly useful for setting or clearing the "read-only" flag on a mount without changing the underlying filesystem. specifying .ir mountflags as: .pp .in +4n .ex ms_remount | ms_bind | ms_rdonly .ee .in .pp will make access through this mountpoint read-only, without affecting other mounts. .\" .ss creating a bind mount if .i mountflags includes .br ms_bind (available since linux 2.4), .\" since 2.4.0-test9 then perform a bind mount. a bind mount makes a file or a directory subtree visible at another point within the single directory hierarchy. bind mounts may cross filesystem boundaries and span .br chroot (2) jails. .pp the .ir filesystemtype and .ir data arguments are ignored. .pp the remaining bits (other than .br ms_rec , described below) in the .i mountflags argument are also ignored. (the bind mount has the same mount options as the underlying mount.) however, see the discussion of remounting above, for a method of making an existing bind mount read-only. .pp by default, when a directory is bind mounted, only that directory is mounted; if there are any submounts under the directory tree, they are not bind mounted. if the .br ms_rec flag is also specified, then a recursive bind mount operation is performed: all submounts under the .i source subtree (other than unbindable mounts) are also bind mounted at the corresponding location in the .i target subtree. .\" .ss changing the propagation type of an existing mount if .ir mountflags includes one of .br ms_shared , .br ms_private , .br ms_slave , or .br ms_unbindable (all available since linux 2.6.15), then the propagation type of an existing mount is changed. if more than one of these flags is specified, an error results. .pp the only other flags that can be specified while changing the propagation type are .br ms_rec (described below) and .br ms_silent (which is ignored). .pp the .ir source , .ir filesystemtype , and .ir data arguments are ignored. .pp the meanings of the propagation type flags are as follows: .tp .br ms_shared make this mount shared. mount and unmount events immediately under this mount will propagate to the other mounts that are members of this mount's peer group. propagation here means that the same mount or unmount will automatically occur under all of the other mounts in the peer group. conversely, mount and unmount events that take place under peer mounts will propagate to this mount. .tp .br ms_private make this mount private. mount and unmount events do not propagate into or out of this mount. .tp .br ms_slave if this is a shared mount that is a member of a peer group that contains other members, convert it to a slave mount. if this is a shared mount that is a member of a peer group that contains no other members, convert it to a private mount. otherwise, the propagation type of the mount is left unchanged. .ip when a mount is a slave, mount and unmount events propagate into this mount from the (master) shared peer group of which it was formerly a member. mount and unmount events under this mount do not propagate to any peer. .ip a mount can be the slave of another peer group while at the same time sharing mount and unmount events with a peer group of which it is a member. .tp .br ms_unbindable make this mount unbindable. this is like a private mount, and in addition this mount can't be bind mounted. when a recursive bind mount .rb ( mount () with the .br ms_bind and .br ms_rec flags) is performed on a directory subtree, any unbindable mounts within the subtree are automatically pruned (i.e., not replicated) when replicating that subtree to produce the target subtree. .pp by default, changing the propagation type affects only the .i target mount. if the .b ms_rec flag is also specified in .ir mountflags , then the propagation type of all mounts under .ir target is also changed. .pp for further details regarding mount propagation types (including the default propagation type assigned to new mounts), see .br mount_namespaces (7). .\" .ss moving a mount if .i mountflags contains the flag .br ms_move (available since linux 2.4.18), then move a subtree: .i source specifies an existing mount and .i target specifies the new location to which that mount is to be relocated. the move is atomic: at no point is the subtree unmounted. .pp the remaining bits in the .ir mountflags argument are ignored, as are the .ir filesystemtype and .ir data arguments. .\" .ss creating a new mount if none of .br ms_remount , .br ms_bind , .br ms_move , .br ms_shared , .br ms_private , .br ms_slave , or .br ms_unbindable is specified in .ir mountflags , then .br mount () performs its default action: creating a new mount. .ir source specifies the source for the new mount, and .ir target specifies the directory at which to create the mount point. .pp the .i filesystemtype and .i data arguments are employed, and further bits may be specified in .ir mountflags to modify the behavior of the call. .\" .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors the error values given below result from filesystem type independent errors. each filesystem type may have its own special errors and its own special behavior. see the linux kernel source code for details. .tp .b eacces a component of a path was not searchable. (see also .br path_resolution (7).) .tp .b eacces mounting a read-only filesystem was attempted without giving the .b ms_rdonly flag. .ip the filesystem may be read-only for various reasons, including: it resides on a read-only optical disk; it is resides on a device with a physical switch that has been set to mark the device read-only; the filesystem implementation was compiled with read-only support; or errors were detected when initially mounting the filesystem, so that it was marked read-only and can't be remounted as read-write (until the errors are fixed). .ip some filesystems instead return the error .br erofs on an attempt to mount a read-only filesystem. .tp .b eacces the block device .i source is located on a filesystem mounted with the .b ms_nodev option. .\" mtk: probably: write permission is required for ms_bind, with .\" the error eperm if not present; cap_dac_override is required. .tp .b ebusy an attempt was made to stack a new mount directly on top of an existing mount point that was created in this mount namespace with the same .i source and .ir target . .tp .b ebusy .i source cannot be remounted read-only, because it still holds files open for writing. .tp .b efault one of the pointer arguments points outside the user address space. .tp .b einval .i source had an invalid superblock. .tp .b einval a remount operation .rb ( ms_remount ) was attempted, but .i source was not already mounted on .ir target . .tp .b einval a move operation .rb ( ms_move ) was attempted, but the mount tree under .i source includes unbindable mounts and .i target is a mount that has propagation type .br ms_shared . .tp .b einval a move operation .rb ( ms_move ) was attempted, but the parent mount of .i source mount has propagation type .br ms_shared . .tp .b einval a move operation .rb ( ms_move ) was attempted, but .i source was not a mount, or was \(aq/\(aq. .tp .b einval a bind operation .rb ( ms_bind ) was requested where .i source referred a mount namespace magic link (i.e., a .i /proc/[pid]/ns/mnt magic link or a bind mount to such a link) and the propagation type of the parent mount of .i target was .br ms_shared , .\" see commit 8823c079ba7136dc1948d6f6dcb5f8022bde438e but propagation of the requested bind mount could lead to a circular dependency that might prevent the mount namespace from ever being freed. .tp .b einval .i mountflags includes more than one of .br ms_shared , .br ms_private , .br ms_slave , or .br ms_unbindable . .tp .b einval .i mountflags includes .br ms_shared , .br ms_private , .br ms_slave , or .br ms_unbindable and also includes a flag other than .br ms_rec or .br ms_silent . .tp .br einval an attempt was made to bind mount an unbindable mount. .tp .br einval in an unprivileged mount namespace (i.e., a mount namespace owned by a user namespace that was created by an unprivileged user), a bind mount operation .rb ( ms_bind ) was attempted without specifying .rb ( ms_rec ), which would have revealed the filesystem tree underneath one of the submounts of the directory being bound. .tp .b eloop too many links encountered during pathname resolution. .tp .b eloop a move operation was attempted, and .i target is a descendant of .ir source . .tp .b emfile (in case no block device is required:) table of dummy devices is full. .tp .b enametoolong a pathname was longer than .br maxpathlen . .tp .b enodev .i filesystemtype not configured in the kernel. .tp .b enoent a pathname was empty or had a nonexistent component. .tp .b enomem the kernel could not allocate a free page to copy filenames or data into. .tp .b enotblk .i source is not a block device (and a device was required). .tp .b enotdir .ir target , or a prefix of .ir source , is not a directory. .tp .b enxio the major number of the block device .i source is out of range. .tp .b eperm the caller does not have the required privileges. .tp .b eperm an attempt was made to modify .rb ( ms_remount ) the .br ms_rdonly , .br ms_nosuid , or .br ms_noexec flag, or one of the "atime" flags .rb ( ms_noatime , .br ms_nodiratime , .br ms_relatime ) of an existing mount, but the mount is locked; see .br mount_namespaces (7). .tp .b erofs mounting a read-only filesystem was attempted without giving the .b ms_rdonly flag. see .br eacces , above. .sh versions the definitions of .br ms_dirsync , .br ms_move , .br ms_private , .br ms_rec , .br ms_relatime , .br ms_shared , .br ms_slave , .br ms_strictatime , and .br ms_unbindable were added to glibc headers in version 2.12. .\" .sh conforming to this function is linux-specific and should not be used in programs intended to be portable. .sh notes since linux 2.4 a single filesystem can be mounted at multiple mount points, and multiple mounts can be stacked on the same mount point. .\" multiple mounts on same mount point: since 2.3.99pre7. .pp the .i mountflags argument may have the magic number 0xc0ed (\fbms_mgc_val\fp) in the top 16 bits. (all of the other flags discussed in description occupy the low order 16 bits of .ir mountflags .) specifying .br ms_mgc_val was required in kernel versions prior to 2.4, but since linux 2.4 is no longer required and is ignored if specified. .pp the original .b ms_sync flag was renamed .b ms_synchronous in 1.1.69 when a different .b ms_sync was added to \fi\fp. .pp before linux 2.4 an attempt to execute a set-user-id or set-group-id program on a filesystem mounted with .b ms_nosuid would fail with .br eperm . since linux 2.4 the set-user-id and set-group-id bits are just silently ignored in this case. .\" the change is in patch-2.4.0-prerelease. .\" .ss mount namespaces starting with kernel 2.4.19, linux provides mount namespaces. a mount namespace is the set of filesystem mounts that are visible to a process. mount namespaces can be (and usually are) shared between multiple processes, and changes to the namespace (i.e., mounts and unmounts) by one process are visible to all other processes sharing the same namespace. (the pre-2.4.19 linux situation can be considered as one in which a single namespace was shared by every process on the system.) .pp a child process created by .br fork (2) shares its parent's mount namespace; the mount namespace is preserved across an .br execve (2). .pp a process can obtain a private mount namespace if: it was created using the .br clone (2) .br clone_newns flag, in which case its new namespace is initialized to be a .i copy of the namespace of the process that called .br clone (2); or it calls .br unshare (2) with the .br clone_newns flag, which causes the caller's mount namespace to obtain a private copy of the namespace that it was previously sharing with other processes, so that future mounts and unmounts by the caller are invisible to other processes (except child processes that the caller subsequently creates) and vice versa. .pp for further details on mount namespaces, see .br mount_namespaces (7). .\" .ss parental relationship between mounts each mount has a parent mount. the overall parental relationship of all mounts defines the single directory hierarchy seen by the processes within a mount namespace. .pp the parent of a new mount is defined when the mount is created. in the usual case, the parent of a new mount is the mount of the filesystem containing the directory or file at which the new mount is attached. in the case where a new mount is stacked on top of an existing mount, the parent of the new mount is the previous mount that was stacked at that location. .pp the parental relationship between mounts can be discovered via the .i /proc/[pid]/mountinfo file (see below). .\" .ss /proc/[pid]/mounts and /proc/[pid]/mountinfo the linux-specific .i /proc/[pid]/mounts file exposes the list of mounts in the mount namespace of the process with the specified id. the .i /proc/[pid]/mountinfo file exposes even more information about mounts, including the propagation type and mount id information that makes it possible to discover the parental relationship between mounts. see .br proc (5) and .br mount_namespaces (7) for details of this file. .sh see also .br mountpoint (1), .br chroot (2), .br ioctl_iflags (2), .br mount_settatr (2), .br pivot_root (2), .br umount (2), .br mount_namespaces (7), .br path_resolution (7), .br findmnt (8), .br lsblk (8), .br mount (8), .br umount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. for general information about how to contribute, see: https://www.kernel.org/doc/man-pages/contributing.html for information on how to send patches, see: https://www.kernel.org/doc/man-pages/patches.html for a description of the preferred layout of manual pages, as well as some style guide notes, see: $ man 7 man-pages for information about reporting bugs, see: https://www.kernel.org/doc/man-pages/reporting_bugs.html .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mcheck 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mcheck, mcheck_check_all, mcheck_pedantic, mprobe \- heap consistency checking .sh synopsis .nf .b #include .pp .bi "int mcheck(void (*" abortfunc ")(enum mcheck_status " mstatus )); .bi "int mcheck_pedantic(void (*" abortfunc ")(enum mcheck_status " mstatus )); .b void mcheck_check_all(void); .pp .bi "enum mcheck_status mprobe(void *" ptr ); .fi .sh description the .br mcheck () function installs a set of debugging hooks for the .br malloc (3) family of memory-allocation functions. these hooks cause certain consistency checks to be performed on the state of the heap. the checks can detect application errors such as freeing a block of memory more than once or corrupting the bookkeeping data structures that immediately precede a block of allocated memory. .pp to be effective, the .br mcheck () function must be called before the first call to .br malloc (3) or a related function. in cases where this is difficult to ensure, linking the program with .ir \-lmcheck inserts an implicit call to .br mcheck () (with a null argument) before the first call to a memory-allocation function. .pp the .br mcheck_pedantic () function is similar to .br mcheck (), but performs checks on all allocated blocks whenever one of the memory-allocation functions is called. this can be very slow! .pp the .br mcheck_check_all () function causes an immediate check on all allocated blocks. this call is effective only if .br mcheck () is called beforehand. .pp if the system detects an inconsistency in the heap, the caller-supplied function pointed to by .i abortfunc is invoked with a single argument, .ir mstatus , that indicates what type of inconsistency was detected. if .i abortfunc is null, a default function prints an error message on .ir stderr and calls .br abort (3). .pp the .br mprobe () function performs a consistency check on the block of allocated memory pointed to by .ir ptr . the .br mcheck () function should be called beforehand (otherwise .br mprobe () returns .br mcheck_disabled ). .pp the following list describes the values returned by .br mprobe () or passed as the .i mstatus argument when .i abortfunc is invoked: .tp .br mcheck_disabled " (" mprobe "() only)" .br mcheck () was not called before the first memory allocation function was called. consistency checking is not possible. .tp .br mcheck_ok " (" mprobe "() only)" no inconsistency detected. .tp .b mcheck_head memory preceding an allocated block was clobbered. .tp .b mcheck_tail memory following an allocated block was clobbered. .tp .b mcheck_free a block of memory was freed twice. .sh return value .br mcheck () and .br mcheck_pedantic () return 0 on success, or \-1 on error. .sh versions the .br mcheck_pedantic () and .br mcheck_check_all () functions are available since glibc 2.2. the .br mcheck () and .br mprobe () functions are present since at least glibc 2.0 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mcheck (), .br mcheck_pedantic (), .br mcheck_check_all (), .br mprobe () t} thread safety t{ mt-unsafe race:mcheck const:malloc_hooks t} .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. .sh notes linking a program with .i \-lmcheck and using the .b malloc_check_ environment variable (described in .br mallopt (3)) cause the same kinds of errors to be detected. but, using .b malloc_check_ does not require the application to be relinked. .\" but is malloc_check_ slower? .sh examples the program below calls .br mcheck () with a null argument and then frees the same block of memory twice. the following shell session demonstrates what happens when running the program: .pp .in +4n .ex .rb "$" " ./a.out" about to free about to free a second time block freed twice aborted (core dumped) .ee .in .ss program source \& .ex #include #include #include int main(int argc, char *argv[]) { char *p; if (mcheck(null) != 0) { fprintf(stderr, "mcheck() failed\en"); exit(exit_failure); } p = malloc(1000); fprintf(stderr, "about to free\en"); free(p); fprintf(stderr, "\enabout to free a second time\en"); free(p); exit(exit_success); } .ee .sh see also .br malloc (3), .br mallopt (3), .br mtrace (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ctime.3 .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sprof 1 2020-11-01 "linux" "linux user manual" .sh name sprof \- read and display shared object profiling data .sh synopsis .nf .br sprof " [\fioption\fp]... \fishared-object-path\fp \ [\fiprofile-data-path\fp]" .fi .sh description the .b sprof command displays a profiling summary for the shared object (shared library) specified as its first command-line argument. the profiling summary is created using previously generated profiling data in the (optional) second command-line argument. if the profiling data pathname is omitted, then .b sprof will attempt to deduce it using the soname of the shared object, looking for a file with the name .i .profile in the current directory. .sh options the following command-line options specify the profile output to be produced: .tp .br \-c ", " \-\-call\-pairs print a list of pairs of call paths for the interfaces exported by the shared object, along with the number of times each path is used. .tp .br \-p ", " \-\-flat\-profile generate a flat profile of all of the functions in the monitored object, with counts and ticks. .tp .br \-q ", " \-\-graph generate a call graph. .pp if none of the above options is specified, then the default behavior is to display a flat profile and a call graph. .pp the following additional command-line options are available: .tp .br \-? ", " \-\-help display a summary of command-line options and arguments and exit. .tp .b \-\-usage display a short usage message and exit. .tp .br \-v ", " \-\-version display the program version and exit. .sh conforming to the .b sprof command is a gnu extension, not present in posix.1. .sh examples the following example demonstrates the use of .br sprof . the example consists of a main program that calls two functions in a shared object. first, the code of the main program: .pp .in +4n .ex $ \fbcat prog.c\fp #include void x1(void); void x2(void); int main(int argc, char *argv[]) { x1(); x2(); exit(exit_success); } .ee .in .pp the functions .ir x1 () and .ir x2 () are defined in the following source file that is used to construct the shared object: .pp .in +4n .ex $ \fbcat libdemo.c\fp #include void consumecpu1(int lim) { for (int j = 0; j < lim; j++) getppid(); } void x1(void) { for (int j = 0; j < 100; j++) consumecpu1(200000); } void consumecpu2(int lim) { for (int j = 0; j < lim; j++) getppid(); } void x2(void) { for (int j = 0; j < 1000; j++) consumecpu2(10000); } .ee .in .pp now we construct the shared object with the real name .ir libdemo.so.1.0.1 , and the soname .ir libdemo.so.1 : .pp .in +4n .ex $ \fbcc \-g \-fpic \-shared \-wl,\-soname,libdemo.so.1 \e\fp \fb\-o libdemo.so.1.0.1 libdemo.c\fp .ee .in .pp then we construct symbolic links for the library soname and the library linker name: .pp .in +4n .ex $ \fbln \-sf libdemo.so.1.0.1 libdemo.so.1\fp $ \fbln \-sf libdemo.so.1 libdemo.so\fp .ee .in .pp next, we compile the main program, linking it against the shared object, and then list the dynamic dependencies of the program: .pp .in +4n .ex $ \fbcc \-g \-o prog prog.c \-l. \-ldemo\fp $ \fbldd prog\fp linux\-vdso.so.1 => (0x00007fff86d66000) libdemo.so.1 => not found libc.so.6 => /lib64/libc.so.6 (0x00007fd4dc138000) /lib64/ld\-linux\-x86\-64.so.2 (0x00007fd4dc51f000) .ee .in .pp in order to get profiling information for the shared object, we define the environment variable .b ld_profile with the soname of the library: .pp .in +4n .ex $ \fbexport ld_profile=libdemo.so.1\fp .ee .in .pp we then define the environment variable .b ld_profile_output with the pathname of the directory where profile output should be written, and create that directory if it does not exist already: .pp .in +4n .ex $ \fbexport ld_profile_output=$(pwd)/prof_data\fp $ \fbmkdir \-p $ld_profile_output\fp .ee .in .pp .b ld_profile causes profiling output to be .i appended to the output file if it already exists, so we ensure that there is no preexisting profiling data: .pp .in +4n .ex $ \fbrm \-f $ld_profile_output/$ld_profile.profile\fp .ee .in .pp we then run the program to produce the profiling output, which is written to a file in the directory specified in .br ld_profile_output : .pp .in +4n .ex $ \fbld_library_path=. ./prog\fp $ \fbls prof_data\fp libdemo.so.1.profile .ee .in .pp we then use the .b sprof \-p option to generate a flat profile with counts and ticks: .pp .in +4n .ex $ \fbsprof \-p libdemo.so.1 $ld_profile_output/libdemo.so.1.profile\fp flat profile: each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls us/call us/call name 60.00 0.06 0.06 100 600.00 consumecpu1 40.00 0.10 0.04 1000 40.00 consumecpu2 0.00 0.10 0.00 1 0.00 x1 0.00 0.10 0.00 1 0.00 x2 .ee .in .pp the .b sprof \-q option generates a call graph: .pp .in +4n .ex $ \fbsprof \-q libdemo.so.1 $ld_profile_output/libdemo.so.1.profile\fp index % time self children called name 0.00 0.00 100/100 x1 [1] [0] 100.0 0.00 0.00 100 consumecpu1 [0] \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- 0.00 0.00 1/1 [1] 0.0 0.00 0.00 1 x1 [1] 0.00 0.00 100/100 consumecpu1 [0] \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- 0.00 0.00 1000/1000 x2 [3] [2] 0.0 0.00 0.00 1000 consumecpu2 [2] \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- 0.00 0.00 1/1 [3] 0.0 0.00 0.00 1 x2 [3] 0.00 0.00 1000/1000 consumecpu2 [2] \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- .ee .in .pp above and below, the "" strings represent identifiers that are outside of the profiled object (in this example, these are instances of .ir main() ). .pp the .b sprof \-c option generates a list of call pairs and the number of their occurrences: .pp .in +4n .ex $ \fbsprof \-c libdemo.so.1 $ld_profile_output/libdemo.so.1.profile\fp x1 1 x1 consumecpu1 100 x2 1 x2 consumecpu2 1000 .ee .in .sh see also .br gprof (1), .br ldd (1), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) andreas gruenbacher, february 2001 .\" copyright (c) silicon graphics inc, september 2001 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th setxattr 2 2021-03-22 "linux" "linux programmer's manual" .sh name setxattr, lsetxattr, fsetxattr \- set an extended attribute value .sh synopsis .fam c .nf .b #include .pp .bi "int setxattr(const char\ *" path ", const char\ *" name , .bi " const void\ *" value ", size_t " size ", int " flags ); .bi "int lsetxattr(const char\ *" path ", const char\ *" name , .bi " const void\ *" value ", size_t " size ", int " flags ); .bi "int fsetxattr(int " fd ", const char\ *" name , .bi " const void\ *" value ", size_t " size ", int " flags ); .fi .fam t .sh description extended attributes are .ir name :\c .i value pairs associated with inodes (files, directories, symbolic links, etc.). they are extensions to the normal attributes which are associated with all inodes in the system (i.e., the .br stat (2) data). a complete overview of extended attributes concepts can be found in .br xattr (7). .pp .br setxattr () sets the .i value of the extended attribute identified by .i name and associated with the given .i path in the filesystem. the .i size argument specifies the size (in bytes) of .ir value ; a zero-length value is permitted. .pp .br lsetxattr () is identical to .br setxattr (), except in the case of a symbolic link, where the extended attribute is set on the link itself, not the file that it refers to. .pp .br fsetxattr () is identical to .br setxattr (), only the extended attribute is set on the open file referred to by .i fd (as returned by .br open (2)) in place of .ir path . .pp an extended attribute name is a null-terminated string. the .i name includes a namespace prefix; there may be several, disjoint namespaces associated with an individual inode. the .i value of an extended attribute is a chunk of arbitrary textual or binary data of specified length. .pp by default (i.e., .ir flags is zero), the extended attribute will be created if it does not exist, or the value will be replaced if the attribute already exists. to modify these semantics, one of the following values can be specified in .ir flags : .tp .b xattr_create perform a pure create, which fails if the named attribute exists already. .tp .b xattr_replace perform a pure replace operation, which fails if the named attribute does not already exist. .sh return value on success, zero is returned. on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b edquot disk quota limits meant that there is insufficient space remaining to store the extended attribute. .tp .b eexist .b xattr_create was specified, and the attribute exists already. .tp .b enodata .b xattr_replace was specified, and the attribute does not exist. .\" .rb ( enoattr .\" is defined to be a synonym for .\" .br enodata .\" in .\" .ir .) .tp .b enospc there is insufficient space remaining to store the extended attribute. .tp .b enotsup the namespace prefix of .i name is not valid. .tp .b enotsup extended attributes are not supported by the filesystem, or are disabled, .tp .b eperm the file is marked immutable or append-only. (see .br ioctl_iflags (2).) .pp in addition, the errors documented in .br stat (2) can also occur. .tp .b erange the size of .i name or .i value exceeds a filesystem-specific limit. .sh versions these system calls have been available on linux since kernel 2.4; glibc support is provided since version 2.3. .sh conforming to these system calls are linux-specific. .\" .sh authors .\" andreas gruenbacher, .\" .ri < a.gruenbacher@computer.org > .\" and the sgi xfs development team, .\" .ri < linux-xfs@oss.sgi.com >. .\" please send any bug reports or comments to these addresses. .sh see also .br getfattr (1), .br setfattr (1), .br getxattr (2), .br listxattr (2), .br open (2), .br removexattr (2), .br stat (2), .br symlink (7), .br xattr (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/makedev.3 .so man7/iso_8859-14.7 .so man2/poll.2 .\" copyright 2004 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th scalbln 3 2021-03-22 "" "linux programmer's manual" .sh name scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl \- multiply floating-point number by integral power of radix .sh synopsis .nf .b #include .pp .bi "double scalbln(double " x ", long " exp ); .bi "float scalblnf(float " x ", long " exp ); .bi "long double scalblnl(long double " x ", long " exp ); .pp .bi "double scalbn(double " x ", int " exp ); .bi "float scalbnf(float " x ", int " exp ); .bi "long double scalbnl(long double " x ", int " exp ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br scalbln (), .br scalblnf (), .br scalblnl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source .fi .pp .br scalbn (), .br scalbnf (), .br scalbnl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions multiply their first argument .i x by .b flt_radix (probably 2) to the power of .ir exp , that is: .pp .nf x * flt_radix ** exp .fi .pp the definition of .b flt_radix can be obtained by including .ir . .\" not in /usr/include but in a gcc lib .sh return value on success, these functions return .ir x * .b flt_radix ** .ir exp . .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity (negative infinity), positive infinity (negative infinity) is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if the result overflows, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with a sign the same as .ir x . .pp if the result underflows, a range error occurs, and the functions return zero, with a sign the same as .ir x . .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error, overflow .\" .i errno .\" is set to .\" .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error, underflow .i errno is set to .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br scalbn (), .br scalbnf (), .br scalbnl (), .br scalbln (), .br scalblnf (), .br scalblnl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes these functions differ from the obsolete functions described in .br scalb (3) in the type of their second argument. the functions described on this page have a second argument of an integral type, while those in .br scalb (3) have a second argument of type .ir double . .pp if .b flt_radix equals 2 (which is usual), then .br scalbn () is equivalent to .br ldexp (3). .sh bugs before glibc 2.20, .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803 these functions did not set .i errno for range errors. .sh see also .br ldexp (3), .br scalb (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" written by oron peled . .\" .\" %%%license_start(gpl_noversion_oneline) .\" may be distributed subject to the gpl. .\" %%%license_end .\" .\" i tried to be as much generic in the description as possible: .\" - general boot sequence is applicable to almost any .\" os/machine (dos/pc, linux/pc, solaris/sparc, cms/s390) .\" - kernel and init(1) is applicable to almost any unix/linux .\" - boot scripts are applicable to sysv-r4 based unix/linux .\" .\" modified 2004-11-03 patch from martin schulze .\" .th boot 7 2015-03-11 "linux" "linux programmer's manual" .sh name boot \- system bootup process based on unix system v release 4 .sh description the \fbbootup process\fr (or "\fbboot sequence\fr") varies in details among systems, but can be roughly divided into phases controlled by the following components: .ip 1. 4 hardware .ip 2. 4 operating system (os) loader .ip 3. 4 kernel .ip 4. 4 root user-space process (\fiinit\fr and \fiinittab\fr) .ip 5. 4 boot scripts .pp each of these is described below in more detail. .ss hardware after power-on or hard reset, control is given to a program stored in read-only memory (normally prom); for historical reasons involving the personal computer, this program is often called "the \fbbios\fr". .pp this program normally performs a basic self-test of the machine and accesses nonvolatile memory to read further parameters. this memory in the pc is battery-backed cmos memory, so most people refer to it as "the \fbcmos\fr"; outside of the pc world, it is usually called "the \fbnvram\fr" (nonvolatile ram). .pp the parameters stored in the nvram vary among systems, but as a minimum, they should specify which device can supply an os loader, or at least which devices may be probed for one; such a device is known as "the \fbboot device\fr". the hardware boot stage loads the os loader from a fixed position on the boot device, and then transfers control to it. .tp note: the device from which the os loader is read may be attached via a network, in which case the details of booting are further specified by protocols such as dhcp, tftp, pxe, etherboot, etc. .ss os loader the main job of the os loader is to locate the kernel on some device, load it, and run it. most os loaders allow interactive use, in order to enable specification of an alternative kernel (maybe a backup in case the one last compiled isn't functioning) and to pass optional parameters to the kernel. .pp in a traditional pc, the os loader is located in the initial 512-byte block of the boot device; this block is known as "the \fbmbr\fr" (master boot record). .pp in most systems, the os loader is very limited due to various constraints. even on non-pc systems, there are some limitations on the size and complexity of this loader, but the size limitation of the pc mbr (512 bytes, including the partition table) makes it almost impossible to squeeze much functionality into it. .pp therefore, most systems split the role of loading the os between a primary os loader and a secondary os loader; this secondary os loader may be located within a larger portion of persistent storage, such as a disk partition. .pp in linux, the os loader is often either .br lilo (8) or .br grub (8). .ss kernel when the kernel is loaded, it initializes various components of the computer and operating system; each portion of software responsible for such a task is usually consider "a \fbdriver\fr" for the applicable component. the kernel starts the virtual memory swapper (it is a kernel process, called "kswapd" in a modern linux kernel), and mounts some filesystem at the root path, .ir / . .pp some of the parameters that may be passed to the kernel relate to these activities (for example, the default root filesystem can be overridden); for further information on linux kernel parameters, read .br bootparam (7). .pp only then does the kernel create the initial userland process, which is given the number 1 as its .b pid (process id). traditionally, this process executes the program .ir /sbin/init , to which are passed the parameters that haven't already been handled by the kernel. .ss root user-space process .tp note: the following description applies to an os based on unix system v release 4. however, a number of widely used systems have adopted a related but fundamentally different approach known as .br systemd (1), for which the bootup process is detailed in its associated .br bootup (7). .pp when .i /sbin/init starts, it reads .i /etc/inittab for further instructions. this file defines what should be run when the .i /sbin/init program is instructed to enter a particular \firun-level\fr, giving the administrator an easy way to establish an environment for some usage; each run-level is associated with a set of services (for example, run-level \fbs\fr is \fisingle-user\fr mode, and run-level \fb2\fr entails running most network services). .pp the administrator may change the current run-level via .br init (1), and query the current run-level via .br runlevel (8). .pp however, since it is not convenient to manage individual services by editing this file, .i /etc/inittab only bootstraps a set of scripts that actually start/stop the individual services. .ss boot scripts .tp note: the following description applies to an os based on unix system v release 4. however, a number of widely used systems (slackware linux, freebsd, openbsd) have a somewhat different scheme for boot scripts. .pp for each managed service (mail, nfs server, cron, etc.), there is a single startup script located in a specific directory .ri ( /etc/init.d in most versions of linux). each of these scripts accepts as a single argument the word "start" (causing it to start the service) or the word \&"stop" (causing it to stop the service). the script may optionally accept other "convenience" parameters (e.g., "restart" to stop and then start, "status" to display the service status, etc.). running the script without parameters displays the possible arguments. .ss sequencing directories to make specific scripts start/stop at specific run-levels and in a specific order, there are \fisequencing directories\fr, normally of the form \fi/etc/rc[0\-6s].d\fr. in each of these directories, there are links (usually symbolic) to the scripts in the \fi/etc/init.d\fr directory. .pp a primary script (usually \fi/etc/rc\fr) is called from .br inittab (5); this primary script calls each service's script via a link in the relevant sequencing directory. each link whose name begins with \(aqs\(aq is called with the argument "start" (thereby starting the service). each link whose name begins with \(aqk\(aq is called with the argument "stop" (thereby stopping the service). .pp to define the starting or stopping order within the same run-level, the name of a link contains an \fborder-number\fr. also, for clarity, the name of a link usually ends with the name of the service to which it refers. for example, the link \fi/etc/rc2.d/s80sendmail\fr starts the sendmail service on runlevel 2. this happens after \fi/etc/rc2.d/s12syslog\fr is run but before \fi/etc/rc2.d/s90xfs\fr is run. .pp to manage these links is to manage the boot order and run-levels; under many systems, there are tools to help with this task (e.g., .br chkconfig (8)). .ss boot configuration a program that provides a service is often called a "\fbdaemon\fr". usually, a daemon may receive various command-line options and parameters. to allow a system administrator to change these inputs without editing an entire boot script, some separate configuration file is used, and is located in a specific directory where an associated boot script may find it (\fi/etc/sysconfig\fr on older red hat systems). .pp in older unix systems, such a file contained the actual command line options for a daemon, but in modern linux systems (and also in hp-ux), it just contains shell variables. a boot script in \fi/etc/init.d\fr reads and includes its configuration file (that is, it "\fbsources\fr" its configuration file) and then uses the variable values. .sh files .ir /etc/init.d/ , .ir /etc/rc[s0\-6].d/ , .i /etc/sysconfig/ .sh see also .br init (1), .br systemd (1), .br inittab (5), .br bootparam (7), .br bootup (7), .br runlevel (8), .br shutdown (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_attr_init.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on glibc infopages .\" .th nextafter 3 2021-03-22 "gnu" "linux programmer's manual" .sh name nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl \- floating-point number manipulation .sh synopsis .nf .b #include .pp .bi "double nextafter(double " x ", double " y ); .bi "float nextafterf(float " x ", float " y ); .bi "long double nextafterl(long double " x ", long double " y ); .pp .bi "double nexttoward(double " x ", long double " y ); .bi "float nexttowardf(float " x ", long double " y ); .bi "long double nexttowardl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nextafter (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br nextafterf (), .br nextafterl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br nexttoward (), .br nexttowardf (), .br nexttowardl (): .nf _xopen_source >= 600 || _isoc99_source || _posix_c_source >= 200112l .fi .sh description the .br nextafter (), .br nextafterf (), and .br nextafterl () functions return the next representable floating-point value following .i x in the direction of .ir y . if .i y is less than .ir x , these functions will return the largest representable number less than .ir x . .pp if .i x equals .ir y , the functions return .ir y . .pp the .br nexttoward (), .br nexttowardf (), and .br nexttowardl () functions do the same as the corresponding .br nextafter () functions, except that they have a .i "long double" second argument. .sh return value on success, these functions return the next representable floating-point value after .i x in the direction of .ir y . .pp if .i x equals .ir y , then .i y (cast to the same type as .ir x ) is returned. .pp if .i x or .i y is a nan, a nan is returned. .pp if .i x is finite, .\" e.g., dbl_max and the result would overflow, a range error occurs, and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with the correct mathematical sign. .pp if .i x is not equal to .ir y , and the correct function result would be subnormal, zero, or underflow, a range error occurs, and either the correct value (if it can be represented), or 0.0, is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result overflow .\" e.g., nextafter(dbl_max, huge_val); .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error: result is subnormal or underflows .\" e.g., nextafter(dbl_min, 0.0); .i errno is set to .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br nextafter (), .br nextafterf (), .br nextafterl (), .br nexttoward (), .br nexttowardf (), .br nexttowardl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. this function is defined in iec 559 (and the appendix with recommended functions in ieee 754/ieee 854). .sh bugs in glibc version 2.5 and earlier, these functions do not raise an underflow floating-point .rb ( fe_underflow ) exception when an underflow occurs. .pp before glibc version 2.23 .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6799 these functions did not set .ir errno . .sh see also .br nearbyint (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .\" copyright (c) 1983, 1987 the regents of the university of california. .\" all rights reserved. .\" .\" @(#)mailaddr.7 6.5 (berkeley) 2/14/89 .\" .\" extensively rewritten by arnt gulbrandsen . my .\" changes are placed under the same copyright as the original bsd page. .\" .\" adjusted by arnt gulbrandsen in 2004 to .\" account for changes since 1995. route-addrs are now even less .\" common, etc. some minor wording improvements. same copyright. .\" .\" %%%license_start(permissive_misc) .\" redistribution and use in source and binary forms are permitted .\" provided that the above copyright notice and this paragraph are .\" duplicated in all such forms and that any documentation, .\" advertising materials, and other materials related to such .\" distribution and use acknowledge that the software was developed .\" by the university of california, berkeley. the name of the .\" university may not be used to endorse or promote products derived .\" from this software without specific prior written permission. .\" this software is provided ``as is'' and without any express or .\" implied warranties, including, without limitation, the implied .\" warranties of merchantability and fitness for a particular purpose. .\" %%%license_end .\" .th mailaddr 7 2020-08-13 "linux" "linux user's manual" .uc 5 .sh name mailaddr \- mail addressing description .sh description .nh this manual page gives a brief introduction to smtp mail addresses, as used on the internet. these addresses are in the general format .pp user@domain .pp where a domain is a hierarchical dot-separated list of subdomains. these examples are valid forms of the same address: .pp john.doe@monet.example.com .br john doe .br john.doe@monet.example.com (john doe) .pp the domain part ("monet.example.com") is a mail-accepting domain. it can be a host and in the past it usually was, but it doesn't have to be. the domain part is not case sensitive. .pp the local part ("john.doe") is often a username, but its meaning is defined by the local software. sometimes it is case sensitive, although that is unusual. if you see a local-part that looks like garbage, it is usually because of a gateway between an internal e-mail system and the net, here are some examples: .pp "surname/admd=telemail/c=us/o=hp/prmd=hp"@some.where .br user%something@some.where .br machine!machine!name@some.where .br i2461572@some.where .pp (these are, respectively, an x.400 gateway, a gateway to an arbitrary internal mail system that lacks proper internet support, an uucp gateway, and the last one is just boring username policy.) .pp the real-name part ("john doe") can either be placed before <>, or in () at the end. (strictly speaking the two aren't the same, but the difference is beyond the scope of this page.) the name may have to be quoted using "", for example, if it contains ".": .pp "john q. doe" .ss abbreviation some mail systems let users abbreviate the domain name. for instance, users at example.com may get away with "john.doe@monet" to send mail to john doe. .i "this behavior is deprecated." sometimes it works, but you should not depend on it. .ss route-addrs in the past, sometimes one had to route a message through several hosts to get it to its final destination. addresses which show these relays are termed "route-addrs". these use the syntax: .pp <@hosta,@hostb:user@hostc> .pp this specifies that the message should be sent to hosta, from there to hostb, and finally to hostc. many hosts disregard route-addrs and send directly to hostc. .pp route-addrs are very unusual now. they occur sometimes in old mail archives. it is generally possible to ignore all but the "user@hostc" part of the address to determine the actual address. .ss postmaster every site is required to have a user or user alias designated "postmaster" to which problems with the mail system may be addressed. the "postmaster" address is not case sensitive. .sh files .i /etc/aliases .br .i \(ti/.forward .sh see also .br mail (1), .br aliases (5), .br forward (5), .br sendmail (8) .pp .ur http://www.ietf.org\:/rfc\:/rfc5322.txt ietf rfc\ 5322 .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .so man2/dup.2 .so man3/tailq.3 .\" copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_spin_init 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_spin_init, pthread_spin_destroy \- initialize or destroy a spin lock .sh synopsis .nf .b #include .pp .bi "int pthread_spin_init(pthread_spinlock_t *" lock ", int " pshared ");" .bi "int pthread_spin_destroy(pthread_spinlock_t *" lock ");" .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_spin_init (), .br pthread_spin_destroy (): .nf _posix_c_source >= 200112l .fi .sh description .ir "general note" : most programs should use mutexes instead of spin locks. spin locks are primarily useful in conjunction with real-time scheduling policies. see notes. .pp the .br pthread_spin_init () function allocates any resources required for the use of the spin lock referred to by .i lock and initializes the lock to be in the unlocked state. the .i pshared argument must have one of the following values: .tp .b pthread_process_private the spin lock is to be operated on only by threads in the same process as the thread that calls .br pthread_spin_init (). (attempting to share the spin lock between processes results in undefined behavior.) .tp .b pthread_process_shared the spin lock may be operated on by any thread in any process that has access to the memory containing the lock (i.e., the lock may be in a shared memory object that is shared among multiple processes). .pp calling .br pthread_spin_init () on a spin lock that has already been initialized results in undefined behavior. .pp the .br pthread_spin_destroy () function destroys a previously initialized spin lock, freeing any resources that were allocated for that lock. destroying a spin lock that has not been previously been initialized or destroying a spin lock while another thread holds the lock results in undefined behavior. .pp once a spin lock has been destroyed, performing any operation on the lock other than once more initializing it with .br pthread_spin_init () results in undefined behavior. .pp the result of performing operations such as .br pthread_spin_lock (3), .br pthread_spin_unlock (3), and .br pthread_spin_destroy () on .i copies of the object referred to by .i lock is undefined. .sh return value on success, there functions return zero. on failure, they return an error number. in the event that .br pthread_spin_init () fails, the lock is not initialized. .sh errors .br pthread_spin_init () may fail with the following errors: .\" these errors don't occur on the glibc implementation .tp .b eagain the system has insufficient resources to initialize a new spin lock. .tp .b enomem insufficient memory to initialize the spin lock. .sh versions these functions first appeared in glibc in version 2.2. .sh conforming to posix.1-2001. .pp support for process-shared spin locks is a posix option. the option is supported in the glibc implementation. .sh notes spin locks should be employed in conjunction with real-time scheduling policies .rb ( sched_fifo , or possibly .br sched_rr ). use of spin locks with nondeterministic scheduling policies such as .br sched_other probably indicates a design mistake. the problem is that if a thread operating under such a policy is scheduled off the cpu while it holds a spin lock, then other threads will waste time spinning on the lock until the lock holder is once more rescheduled and releases the lock. .pp if threads create a deadlock situation while employing spin locks, those threads will spin forever consuming cpu time. .pp user-space spin locks are .i not applicable as a general locking solution. they are, by definition, prone to priority inversion and unbounded spin times. a programmer using spin locks must be exceptionally careful not only in the code, but also in terms of system configuration, thread placement, and priority assignment. .\" fixme . when pthread_mutex_adaptive_np is one day document .\" make reference to it here .sh see also .ad l .nh .br pthread_mutex_init (3), .br pthread_mutex_lock (3), .br pthread_spin_lock (3), .br pthread_spin_unlock (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/umount.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th mbsinit 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mbsinit \- test for initial shift state .sh synopsis .nf .b #include .pp .bi "int mbsinit(const mbstate_t *" ps ); .fi .sh description character conversion between the multibyte representation and the wide character representation uses conversion state, of type .ir mbstate_t . conversion of a string uses a finite-state machine; when it is interrupted after the complete conversion of a number of characters, it may need to save a state for processing the remaining characters. such a conversion state is needed for the sake of encodings such as iso-2022 and utf-7. .pp the initial state is the state at the beginning of conversion of a string. there are two kinds of state: the one used by multibyte to wide character conversion functions, such as .br mbsrtowcs (3), and the one used by wide character to multibyte conversion functions, such as .br wcsrtombs (3), but they both fit in a .ir mbstate_t , and they both have the same representation for an initial state. .pp for 8-bit encodings, all states are equivalent to the initial state. for multibyte encodings like utf-8, euc-*, big5, or sjis, the wide character to multibyte conversion functions never produce non-initial states, but the multibyte to wide-character conversion functions like .br mbrtowc (3) do produce non-initial states when interrupted in the middle of a character. .pp one possible way to create an .i mbstate_t in initial state is to set it to zero: .pp .in +4n .ex mbstate_t state; memset(&state, 0, sizeof(state)); .ee .in .pp on linux, the following works as well, but might generate compiler warnings: .pp .in +4n .ex mbstate_t state = { 0 }; .ee .in .pp the function .br mbsinit () tests whether .i *ps corresponds to an initial state. .sh return value .br mbsinit () returns nonzero if .i *ps is an initial state, or if .i ps is null. otherwise, it returns 0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mbsinit () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br mbsinit () depends on the .b lc_ctype category of the current locale. .sh see also .br mbrlen (3), .br mbrtowc (3), .br mbsrtowcs (3), .br wcrtomb (3), .br wcsrtombs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/modf.3 .\" copyright (c) 2007 michael kerrisk .\" and copyright (c) 1995 michael shields . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and author of this work. .\" %%%license_end .\" .\" modified 1996-10-22 by eric s. raymond .\" modified 1997-05-31 by andries brouwer .\" modified 2003-08-24 by andries brouwer .\" modified 2004-08-16 by andi kleen .\" 2007-06-02, mtk: fairly substantial rewrites and additions, and .\" a much improved example program. .\" .th mprotect 2 2021-03-22 "linux" "linux programmer's manual" .sh name mprotect, pkey_mprotect \- set protection on a region of memory .sh synopsis .nf .b #include .pp .bi "int mprotect(void *" addr ", size_t " len ", int " prot ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pkey_mprotect(void *" addr ", size_t " len ", int " prot ", int " pkey ");" .fi .sh description .br mprotect () changes the access protections for the calling process's memory pages containing any part of the address range in the interval [\fiaddr\fp,\ \fiaddr\fp+\filen\fp\-1]. .i addr must be aligned to a page boundary. .pp if the calling process tries to access memory in a manner that violates the protections, then the kernel generates a .b sigsegv signal for the process. .pp .i prot is a combination of the following access flags: .b prot_none or a bitwise-or of the other values in the following list: .tp .b prot_none the memory cannot be accessed at all. .tp .b prot_read the memory can be read. .tp .b prot_write the memory can be modified. .tp .b prot_exec the memory can be executed. .tp .br prot_sem " (since linux 2.5.7)" the memory can be used for atomic operations. this flag was introduced as part of the .br futex (2) implementation (in order to guarantee the ability to perform atomic operations required by commands such as .br futex_wait ), but is not currently used in on any architecture. .tp .br prot_sao " (since linux 2.6.26)" .\" commit aba46c5027cb59d98052231b36efcbbde9c77a1d .\" commit ef3d3246a0d06be622867d21af25f997aeeb105f the memory should have strong access ordering. this feature is specific to the powerpc architecture (version 2.06 of the architecture specification adds the sao cpu feature, and it is available on power 7 or powerpc a2, for example). .pp additionally (since linux 2.6.0), .i prot can have one of the following flags set: .tp .\" mm/mmap.c: .\" vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) | .\" mm->def_flags | vm_mayread | vm_maywrite | vm_mayexec; .\" and calc_vm_flag_bits converts only growsdown/denywrite/locked. .b prot_growsup apply the protection mode up to the end of a mapping that grows upwards. (such mappings are created for the stack area on architectures\(emfor example, hp-parisc\(emthat have an upwardly growing stack.) .\" the vma is one that was marked with vm_growsup by the kernel .\" when the stack was created. note that (unlike vm_growsdown), .\" there is no mmap() flag (analogous to map_growsdown) for .\" creating a vma that is marked vm_growsup. .tp .b prot_growsdown apply the protection mode down to the beginning of a mapping that grows downward (which should be a stack segment or a segment mapped with the .b map_growsdown flag set). .pp like .br mprotect (), .br pkey_mprotect () changes the protection on the pages specified by .ir addr and .ir len . the .i pkey argument specifies the protection key (see .br pkeys (7)) to assign to the memory. the protection key must be allocated with .br pkey_alloc (2) before it is passed to .br pkey_mprotect (). for an example of the use of this system call, see .br pkeys (7). .sh return value on success, .br mprotect () and .br pkey_mprotect () return zero. on error, these system calls return \-1, and .i errno is set to indicate the error. .sh errors .tp .b eacces the memory cannot be given the specified access. this can happen, for example, if you .br mmap (2) a file to which you have read-only access, then ask .br mprotect () to mark it .br prot_write . .tp .b einval \fiaddr\fp is not a valid pointer, or not a multiple of the system page size. .tp .br einval .rb ( pkey_mprotect ()) \fipkey\fp has not been allocated with .br pkey_alloc (2) .tp .br einval both .br prot_growsup and .br prot_growsdown were specified in .ir prot . .tp .br einval invalid flags specified in .ir prot . .tp .br einval (powerpc architecture) .b prot_sao was specified in .ir prot , but sao hardware feature is not available. .tp .b enomem internal kernel structures could not be allocated. .tp .b enomem addresses in the range .ri [ addr , .ir addr + len \-1] are invalid for the address space of the process, or specify one or more pages that are not mapped. (before kernel 2.4.19, the error .br efault was incorrectly produced for these cases.) .tp .b enomem changing the protection of a memory region would result in the total number of mappings with distinct attributes (e.g., read versus read/write protection) exceeding the allowed maximum. .\" i.e., the number of vmas would exceed the 64 kb maximum (for example, making the protection of a range .br prot_read in the middle of a region currently protected as .br prot_read|prot_write would result in three mappings: two read/write mappings at each end and a read-only mapping in the middle.) .sh versions .br pkey_mprotect () first appeared in linux 4.9; library support was added in glibc 2.27. .sh conforming to .br mprotect (): posix.1-2001, posix.1-2008, svr4. .\" svr4 defines an additional error .\" code eagain. the svr4 error conditions don't map neatly onto linux's. posix says that the behavior of .br mprotect () is unspecified if it is applied to a region of memory that was not obtained via .br mmap (2). .pp .br pkey_mprotect () is a nonportable linux extension. .sh notes on linux, it is always permissible to call .br mprotect () on any address in a process's address space (except for the kernel vsyscall area). in particular, it can be used to change existing code mappings to be writable. .pp whether .b prot_exec has any effect different from .b prot_read depends on processor architecture, kernel version, and process state. if .b read_implies_exec is set in the process's personality flags (see .br personality (2)), specifying .b prot_read will implicitly add .br prot_exec . .pp on some hardware architectures (e.g., i386), .b prot_write implies .br prot_read . .pp posix.1 says that an implementation may permit access other than that specified in .ir prot , but at a minimum can allow write access only if .b prot_write has been set, and must not allow any access if .b prot_none has been set. .pp applications should be careful when mixing use of .br mprotect () and .br pkey_mprotect (). on x86, when .br mprotect () is used with .ir prot set to .b prot_exec a pkey may be allocated and set on the memory implicitly by the kernel, but only when the pkey was 0 previously. .pp on systems that do not support protection keys in hardware, .br pkey_mprotect () may still be used, but .ir pkey must be set to \-1. when called this way, the operation of .br pkey_mprotect () is equivalent to .br mprotect (). .sh examples .\" sigaction.2 refers to this example the program below demonstrates the use of .br mprotect (). the program allocates four pages of memory, makes the third of these pages read-only, and then executes a loop that walks upward through the allocated region modifying bytes. .pp an example of what we might see when running the program is the following: .pp .in +4n .ex .rb "$" " ./a.out" start of region: 0x804c000 got sigsegv at address: 0x804e000 .ee .in .ss program source \& .ex #include #include #include #include #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) static char *buffer; static void handler(int sig, siginfo_t *si, void *unused) { /* note: calling printf() from a signal handler is not safe (and should not be done in production programs), since printf() is not async\-signal\-safe; see signal\-safety(7). nevertheless, we use printf() here as a simple way of showing that the handler was called. */ printf("got sigsegv at address: %p\en", si\->si_addr); exit(exit_failure); } int main(int argc, char *argv[]) { int pagesize; struct sigaction sa; sa.sa_flags = sa_siginfo; sigemptyset(&sa.sa_mask); sa.sa_sigaction = handler; if (sigaction(sigsegv, &sa, null) == \-1) handle_error("sigaction"); pagesize = sysconf(_sc_page_size); if (pagesize == \-1) handle_error("sysconf"); /* allocate a buffer aligned on a page boundary; initial protection is prot_read | prot_write. */ buffer = memalign(pagesize, 4 * pagesize); if (buffer == null) handle_error("memalign"); printf("start of region: %p\en", buffer); if (mprotect(buffer + pagesize * 2, pagesize, prot_read) == \-1) handle_error("mprotect"); for (char *p = buffer ; ; ) *(p++) = \(aqa\(aq; printf("loop completed\en"); /* should never happen */ exit(exit_success); } .ee .sh see also .br mmap (2), .br sysconf (3), .br pkeys (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright (c) 2004 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 13:32:44 1993 by rik faith (faith@cs.unc.edu) .\" modified mon jun 23 14:09:52 1997 by aeb - add eintr. .\" modified tue jul 7 12:26:42 1998 by aeb - changed return value wait3 .\" modified 2004-11-11, michael kerrisk .\" rewrote much of this page, and removed much duplicated text, .\" replacing with pointers to wait.2 .\" .th wait4 2 2021-03-22 "linux" "linux programmer's manual" .sh name wait3, wait4 \- wait for process to change state, bsd style .sh synopsis .nf .b #include .pp .bi "pid_t wait3(int *" "wstatus" ", int " options ", struct rusage *" rusage ); .bi "pid_t wait4(pid_t " pid ", int *" wstatus ", int " options , .bi " struct rusage *" rusage ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wait3 (): .nf since glibc 2.26: _default_source || (_xopen_source >= 500 && ! (_posix_c_source >= 200112l || _xopen_source >= 600)) from glibc 2.19 to 2.25: _default_source || _xopen_source >= 500 glibc 2.19 and earlier: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .pp .br wait4 (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description these functions are nonstandard; in new programs, the use of .br waitpid (2) or .br waitid (2) is preferable. .pp the .br wait3 () and .br wait4 () system calls are similar to .br waitpid (2), but additionally return resource usage information about the child in the structure pointed to by .ir rusage . .pp other than the use of the .i rusage argument, the following .br wait3 () call: .pp .in +4n .ex wait3(wstatus, options, rusage); .ee .in .pp is equivalent to: .pp .in +4n .ex waitpid(\-1, wstatus, options); .ee .in .pp similarly, the following .br wait4 () call: .pp .in +4n .ex wait4(pid, wstatus, options, rusage); .ee .in .pp is equivalent to: .pp .in +4n .ex waitpid(pid, wstatus, options); .ee .in .pp in other words, .br wait3 () waits of any child, while .br wait4 () can be used to select a specific child, or children, on which to wait. see .br wait (2) for further details. .pp if .i rusage is not null, the .i struct rusage to which it points will be filled with accounting information about the child. see .br getrusage (2) for details. .sh return value as for .br waitpid (2). .sh errors as for .br waitpid (2). .sh conforming to 4.3bsd. .pp susv1 included a specification of .br wait3 (); susv2 included .br wait3 (), but marked it legacy; susv3 removed it. .sh notes including .i is not required these days, but increases portability. (indeed, .i defines the .i rusage structure with fields of type .i struct timeval defined in .ir .) .ss c library/kernel differences on linux, .br wait3 () is a library function implemented on top of the .br wait4 () system call. .sh see also .br fork (2), .br getrusage (2), .br sigaction (2), .br signal (2), .br wait (2), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 17:35:15 1993 by rik faith .\" modified sun feb 19 22:02:32 1995 by rik faith .\" modified tue oct 22 23:28:12 1996 by eric s. raymond .\" modified sun jan 26 21:56:56 1997 by ralph schleicher .\" .\" modified mon jun 16 20:24:58 1997 by nicolás lichtmaier .\" modified sun oct 18 22:11:28 1998 by joseph s. myers .\" modified mon nov 16 17:24:47 1998 by andries brouwer .\" modified thu nov 16 23:28:25 2000 by david a. wheeler .\" .\" .\" "nroff" ("man") (or "tbl") needs a long page to avoid warnings .\" from "grotty" (at imagined page breaks). bug in grotty? .if n .pl 1000v .th suffixes 7 2020-08-13 "linux" "linux programmer's manual" .sh name suffixes \- list of file suffixes .sh description it is customary to indicate the contents of a file with the file suffix, which (typically) consists of a period, followed by one or more letters. many standard utilities, such as compilers, use this to recognize the type of file they are dealing with. the .br make (1) utility is driven by rules based on file suffix. .pp following is a list of suffixes which are likely to be found on a linux system. .pp .ts l | l _ | _ li | l . suffix file type ,v files for rcs (revision control system) - backup file .c c++ source code, equivalent to \fi.cc\fp .f fortran source with \fbcpp\fp(1) directives or file compressed using freeze .s assembler source with \fbcpp\fp(1) directives .y file compressed using yabba .z file compressed using \fbcompress\fp(1) .[0\-9]+gf tex generic font files .[0\-9]+pk tex packed font files .[1\-9] manual page for the corresponding section .[1\-9][a-z] manual page for section plus subsection .a static object code library .ad x application default resource file .ada ada source (may be body, spec, or combination) .adb ada body source .ads ada spec source .afm postscript font metrics .al perl autoload file .am \fbautomake\fp(1) input file .arc \fbarc\fp(1) archive .arj \fbarj\fp(1) archive .asc pgp ascii-armored data .asm (gnu) assembler source file .au audio sound file .aux latex auxiliary file .avi (msvideo) movie .awk awk language program .b lilo boot loader image .bak backup file .bash \fbbash\fp(1) shell script .bb basic block list data produced by gcc \-ftest\-coverage .bbg basic block graph data produced by gcc \-ftest\-coverage .bbl bibtex output .bdf x font file .bib tex bibliographic database, bibtex input .bm bitmap source .bmp bitmap .bz2 file compressed using \fbbzip2\fp(1) .c c source .cat message catalog files .cc c++ source .cf configuration file .cfg configuration file .cgi www content generating script or program .cls latex class definition .class java compiled byte-code .conf configuration file .config configuration file .cpp equivalent to \fi.cc\fr .csh \fbcsh\fp(1) shell script .cxx equivalent to \fi.cc\fr .dat data file .deb debian software package .def modula-2 source for definition modules .def other definition files .desc initial part of mail message unpacked with \fbmunpack\fp(1) .diff file differences (\fbdiff\fp(1) command output) .dir dbm data base directory file .doc documentation file .dsc debian source control (source package) .dtx latex package source file .dvi tex's device independent output .el emacs-lisp source .elc compiled emacs-lisp source .eps encapsulated postscript .exp expect source code .f fortran source .f77 fortran 77 source .f90 fortran 90 source .fas precompiled common-lisp .fi fortran include files .fig fig image file (used by \fbxfig\fp(1)) .fmt tex format file .gif compuserve graphics image file format .gmo gnu format message catalog .gsf ghostscript fonts .gz file compressed using \fbgzip\fp(1) .h c or c++ header files .help help file .hf equivalent to \fi.help\fp .hlp equivalent to \fi.help\fp .htm poor man's \fi.html\fp .html html document used with the world wide web .hqx 7-bit encoded macintosh file .i c source after preprocessing .icon bitmap source .idx reference or datum-index file for hypertext or database system .image bitmap source .in configuration template, especially for gnu autoconf .info files for the emacs info browser .info-[0\-9]+ split info files .ins latex package install file for docstrip .itcl itcl source code; itcl ([incr tcl]) is an oo extension of tcl .java a java source file .jpeg joint photographic experts group format .jpg poor man's \fi.jpeg\fp .kmap \fblyx\fp(1) keymap .l equivalent to \fi.lex\fp or \fi.lisp\fp .lex \fblex\fp(1) or \fbflex\fp(1) files .lha lharc archive .lib common-lisp library .lisp lisp source .ln files for use with \fblint\fp(1) .log log file, in particular produced by tex .lsm linux software map entry .lsp common-lisp source .lzh lharc archive .m objective-c source code .m4 \fbm4\fp(1) source .mac macro files for various programs .man manual page (usually source rather than formatted) .map map files for various programs .me nroff source using the me macro package .mf metafont (font generator for tex) source .mgp magicpoint file .mm sources for \fbgroff\fp(1) in mm - format .mo message catalog binary file .mod modula-2 source for implementation modules .mov (quicktime) movie .mp metapost source .mp2 mpeg layer 2 (audio) file .mp3 mpeg layer 3 (audio) file .mpeg movie file .o object file .old old or backup file .orig backup (original) version of a file, from \fbpatch\fp(1) .out output file, often executable program (a.out) .p pascal source .pag dbm data base data file .patch file differences for \fbpatch\fp(1) .pbm portable bitmap format .pcf x11 font files .pdf adobe portable data format (use acrobat/\fbacroread\fp or \fbxpdf\fp) .perl perl source (see .ph, .pl, and .pm) .pfa postscript font definition files, ascii format .pfb postscript font definition files, binary format .pgm portable greymap format .pgp pgp binary data .ph perl header file .php php program file .php3 php3 program file .pid file to store daemon pid (e.g., crond.pid) .pl tex property list file or perl library file .pm perl module .png portable network graphics file .po message catalog source .pod \fbperldoc\fp(1) file .ppm portable pixmap format .pr bitmap source .ps postscript file .py python source .pyc compiled python .qt quicktime movie .r ratfor source (obsolete) .rej patches that \fbpatch\fp(1) couldn't apply .rpm rpm software package .rtf rich text format file .rules rules for something .s assembler source .sa stub libraries for a.out shared libraries .sc \fbsc\fp(1) spreadsheet commands .scm scheme source code .sed sed source file .sgml sgml source file .sh \fbsh\fp(1) scripts .shar archive created by the \fbshar\fp(1) utility .so shared library or dynamically loadable object .sql sql source .sqml sqml schema or query program .sty latex style files .sym modula-2 compiled definition modules .tar archive created by the \fbtar\fp(1) utility .tar.z tar(1) archive compressed with \fbcompress\fp(1) .tar.bz2 tar(1) archive compressed with \fbbzip2\fp(1) .tar.gz tar(1) archive compressed with \fbgzip\fp(1) .taz tar(1) archive compressed with \fbcompress\fp(1) .tcl tcl source code .tex tex or latex source .texi equivalent to \fi.texinfo\fp .texinfo texinfo documentation source .text text file .tfm tex font metric file .tgz tar archive compressed with \fbgzip\fp(1) .tif poor man's \fi.tiff\fp .tiff tagged image file format .tk tcl/tk script .tmp temporary file .tmpl template files .txt equivalent to \fi.text\fp .uu equivalent to \fi.uue\fp .uue binary file encoded with \fbuuencode\fp(1) .vf tex virtual font file .vpl tex virtual property list file .w silvio levi's cweb .wav wave sound file .web donald knuth's web .wml source file for web meta language .xbm x11 bitmap source .xcf gimp graphic .xml extended markup language file .xpm x11 pixmap source .xs perl xsub file produced by h2xs .xsl xsl stylesheet .y \fbyacc\fp(1) or \fbbison\fp(1) (parser generator) files .z file compressed using \fbpack\fp(1) (or an old \fbgzip\fp(1)) .zip \fbzip\fp(1) archive .zoo \fbzoo\fp(1) archive \(ti emacs or \fbpatch\fp(1) backup file rc startup (`run control') file, e.g., \fi.newsrc\fp .te .sh conforming to general unix conventions. .sh bugs this list is not exhaustive. .sh see also .br file (1), .br make (1) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .\" copyright (c) 1993 michael haardt, (michael@moria.de) .\" and copyright 2006, 2008, michael kerrisk .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified wed jul 21 19:52:58 1993 by rik faith .\" modified sun aug 21 17:40:38 1994 by rik faith .\" .th brk 2 2021-03-22 "linux" "linux programmer's manual" .sh name brk, sbrk \- change data segment size .sh synopsis .nf .b #include .pp .bi "int brk(void *" addr ); .bi "void *sbrk(intptr_t " increment ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br brk (), .br sbrk (): .nf since glibc 2.19: _default_source || ((_xopen_source >= 500) && ! (_posix_c_source >= 200112l)) .\" (_xopen_source >= 500 || .\" _xopen_source && _xopen_source_extended) && from glibc 2.12 to 2.19: _bsd_source || _svid_source || ((_xopen_source >= 500) && ! (_posix_c_source >= 200112l)) .\" (_xopen_source >= 500 || .\" _xopen_source && _xopen_source_extended) && before glibc 2.12: _bsd_source || _svid_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description .br brk () and .br sbrk () change the location of the .ir "program break" , which defines the end of the process's data segment (i.e., the program break is the first location after the end of the uninitialized data segment). increasing the program break has the effect of allocating memory to the process; decreasing the break deallocates memory. .pp .br brk () sets the end of the data segment to the value specified by .ir addr , when that value is reasonable, the system has enough memory, and the process does not exceed its maximum data size (see .br setrlimit (2)). .pp .br sbrk () increments the program's data space by .i increment bytes. calling .br sbrk () with an .i increment of 0 can be used to find the current location of the program break. .sh return value on success, .br brk () returns zero. on error, \-1 is returned, and .i errno is set to .br enomem . .pp on success, .br sbrk () returns the previous program break. (if the break was increased, then this value is a pointer to the start of the newly allocated memory). on error, .i "(void\ *)\ \-1" is returned, and .i errno is set to .br enomem . .sh conforming to 4.3bsd; susv1, marked legacy in susv2, removed in posix.1-2001. .\" .\" .br brk () .\" and .\" .br sbrk () .\" are not defined in the c standard and are deliberately excluded from the .\" posix.1-1990 standard (see paragraphs b.1.1.1.3 and b.8.3.3). .sh notes avoid using .br brk () and .br sbrk (): the .br malloc (3) memory allocation package is the portable and comfortable way of allocating memory. .pp various systems use various types for the argument of .br sbrk (). common are \fiint\fp, \fissize_t\fp, \fiptrdiff_t\fp, \fiintptr_t\fp. .\" one sees .\" \fiint\fp (e.g., xpgv4, du 4.0, hp-ux 11, freebsd 4.0, openbsd 3.2), .\" \fissize_t\fp (osf1 2.0, irix 5.3, 6.5), .\" \fiptrdiff_t\fp (libc4, libc5, ulibc, glibc 2.0, 2.1), .\" \fiintptr_t\fp (e.g., xpgv5, aix, sunos 5.8, 5.9, freebsd 4.7, netbsd 1.6, .\" tru64 5.1, glibc2.2). .ss c library/kernel differences the return value described above for .br brk () is the behavior provided by the glibc wrapper function for the linux .br brk () system call. (on most other implementations, the return value from .br brk () is the same; this return value was also specified in susv2.) however, the actual linux system call returns the new program break on success. on failure, the system call returns the current break. the glibc wrapper function does some work (i.e., checks whether the new break is less than .ir addr ) to provide the 0 and \-1 return values described above. .pp on linux, .br sbrk () is implemented as a library function that uses the .br brk () system call, and does some internal bookkeeping so that it can return the old break value. .sh see also .br execve (2), .br getrlimit (2), .br end (3), .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 tomáš pospíšek (tpo_deb@sourcepole.ch), .\" fri, 03 nov 2012 22:35:33 +0100 .\" and copyright (c) 2012 eric w. biederman .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, write to the free .\" software foundation, inc., 59 temple place, suite 330, boston, ma 02111, .\" usa. .\" %%%license_end .\" .\" .th veth 4 2021-03-22 "linux" "linux programmer's manual" .sh name veth \- virtual ethernet device .sh description the .b veth devices are virtual ethernet devices. they can act as tunnels between network namespaces to create a bridge to a physical network device in another namespace, but can also be used as standalone network devices. .pp .b veth devices are always created in interconnected pairs. a pair can be created using the command: .pp .in +4n .ex # ip link add type veth peer name .ee .in .pp in the above, .i p1-name and .i p2-name are the names assigned to the two connected end points. .pp packets transmitted on one device in the pair are immediately received on the other device. when either devices is down the link state of the pair is down. .pp .b veth device pairs are useful for combining the network facilities of the kernel together in interesting ways. a particularly interesting use case is to place one end of a .b veth pair in one network namespace and the other end in another network namespace, thus allowing communication between network namespaces. to do this, one can provide the .b netns parameter when creating the interfaces: .pp .in +4n .ex # ip link add netns type veth peer netns .ee .in .pp or, for an existing .b veth pair, move one side to the other namespace: .pp .in +4n .ex # ip link set netns .ee .in .pp .br ethtool (8) can be used to find the peer of a .b veth network interface, using commands something like: .pp .in +4n .ex # \fbip link add ve_a type veth peer name ve_b\fp # create veth pair # \fbethtool \-s ve_a\fp # discover interface index of peer nic statistics: peer_ifindex: 16 # \fbip link | grep \(aq\(ha16:\(aq\fp # look up interface 16: ve_b@ve_a: mtu 1500 qdisc ... .ee .in .sh "see also" .br clone (2), .br network_namespaces (7), .br ip (8), .br ip\-link (8), .br ip\-netns (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2009-01-12, mtk, created .\" .th rtld-audit 7 2020-11-01 "linux" "linux programmer's manual" .sh name rtld-audit \- auditing api for the dynamic linker .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .fi .sh description the gnu dynamic linker (run-time linker) provides an auditing api that allows an application to be notified when various dynamic linking events occur. this api is very similar to the auditing interface provided by the solaris run-time linker. the necessary constants and prototypes are defined by including .ir . .pp to use this interface, the programmer creates a shared library that implements a standard set of function names. not all of the functions need to be implemented: in most cases, if the programmer is not interested in a particular class of auditing event, then no implementation needs to be provided for the corresponding auditing function. .pp to employ the auditing interface, the environment variable .br ld_audit must be defined to contain a colon-separated list of shared libraries, each of which can implement (parts of) the auditing api. when an auditable event occurs, the corresponding function is invoked in each library, in the order that the libraries are listed. .ss la_version() \& .nf .bi "unsigned int la_version(unsigned int " version ); .fi .pp this is the only function that .i must be defined by an auditing library: it performs the initial handshake between the dynamic linker and the auditing library. when invoking this function, the dynamic linker passes, in .ir version , the highest version of the auditing interface that the linker supports. .pp a typical implementation of this function simply returns the constant .br lav_current , which indicates the version of .i that was used to build the audit module. if the dynamic linker does not support this version of the audit interface, it will refuse to activate this audit module. if the function returns zero, the dynamic linker also does not activate this audit module. .pp in order to enable backwards compatibility with older dynamic linkers, an audit module can examine the .i version argument and return an earlier version than .br lav_current , assuming the module can adjust its implementation to match the requirements of the previous version of the audit interface. the .b la_version function should not return the value of .i version without further checks because it could correspond to an interface that does not match the .i definitions used to build the audit module. .ss la_objsearch() \& .nf .bi "char *la_objsearch(const char *" name ", uintptr_t *" cookie , .bi " unsigned int " flag ); .fi .pp the dynamic linker invokes this function to inform the auditing library that it is about to search for a shared object. the .i name argument is the filename or pathname that is to be searched for. .i cookie identifies the shared object that initiated the search. .i flag is set to one of the following values: .tp 17 .b la_ser_orig this is the original name that is being searched for. typically, this name comes from an elf .b dt_needed entry, or is the .i filename argument given to .br dlopen (3). .tp .b la_ser_libpath .i name was created using a directory specified in .br ld_library_path . .tp .b la_ser_runpath .i name was created using a directory specified in an elf .b dt_rpath or .b dt_runpath list. .tp .b la_ser_config .i name was found via the .br ldconfig (8) cache .ri ( /etc/ld.so.cache ). .tp .b la_ser_default .i name was found via a search of one of the default directories. .tp .b la_ser_secure .i name is specific to a secure object (unused on linux). .pp as its function result, .br la_objsearch () returns the pathname that the dynamic linker should use for further processing. if null is returned, then this pathname is ignored for further processing. if this audit library simply intends to monitor search paths, then .i name should be returned. .ss la_activity() \& .nf .bi "void la_activity( uintptr_t *" cookie ", unsigned int "flag ); .fi .pp the dynamic linker calls this function to inform the auditing library that link-map activity is occurring. .i cookie identifies the object at the head of the link map. when the dynamic linker invokes this function, .i flag is set to one of the following values: .tp 19 .b la_act_add new objects are being added to the link map. .tp .b la_act_delete objects are being removed from the link map. .tp .b la_act_consistent link-map activity has been completed: the map is once again consistent. .ss la_objopen() \& .nf .bi "unsigned int la_objopen(struct link_map *" map ", lmid_t " lmid , .bi " uintptr_t *" cookie ); .fi .pp the dynamic linker calls this function when a new shared object is loaded. the .i map argument is a pointer to a link-map structure that describes the object. the .i lmid field has one of the following values .tp 17 .b lm_id_base link map is part of the initial namespace. .tp .b lm_id_newlm link map is part of a new namespace requested via .br dlmopen (3). .pp .i cookie is a pointer to an identifier for this object. the identifier is provided to later calls to functions in the auditing library in order to identify this object. this identifier is initialized to point to object's link map, but the audit library can change the identifier to some other value that it may prefer to use to identify the object. .pp as its return value, .br la_objopen () returns a bit mask created by oring zero or more of the following constants, which allow the auditing library to select the objects to be monitored by .br la_symbind* (): .tp 17 .b la_flg_bindto audit symbol bindings to this object. .tp .b la_flg_bindfrom audit symbol bindings from this object. .pp a return value of 0 from .br la_objopen () indicates that no symbol bindings should be audited for this object. .ss la_objclose() \& .nf .bi "unsigned int la_objclose(uintptr_t *" cookie ); .fi .pp the dynamic linker invokes this function after any finalization code for the object has been executed, before the object is unloaded. the .i cookie argument is the identifier obtained from a previous invocation of .br la_objopen (). .pp in the current implementation, the value returned by .br la_objclose () is ignored. .ss la_preinit() \& .nf .bi "void la_preinit(uintptr_t *" cookie ); .fi .pp the dynamic linker invokes this function after all shared objects have been loaded, before control is passed to the application (i.e., before calling .ir main ()). note that .ir main () may still later dynamically load objects using .br dlopen (3). .ss la_symbind*() \& .nf .bi "uintptr_t la_symbind32(elf32_sym *" sym ", unsigned int " ndx , .bi " uintptr_t *" refcook ", uintptr_t *" defcook , .bi " unsigned int *" flags ", const char *" symname ); .bi "uintptr_t la_symbind64(elf64_sym *" sym ", unsigned int " ndx , .bi " uintptr_t *" refcook ", uintptr_t *" defcook , .bi " unsigned int *" flags ", const char *" symname ); .fi .pp the dynamic linker invokes one of these functions when a symbol binding occurs between two shared objects that have been marked for auditing notification by .br la_objopen (). the .br la_symbind32 () function is employed on 32-bit platforms; the .br la_symbind64 () function is employed on 64-bit platforms. .pp the .i sym argument is a pointer to a structure that provides information about the symbol being bound. the structure definition is shown in .ir . among the fields of this structure, .i st_value indicates the address to which the symbol is bound. .pp the .i ndx argument gives the index of the symbol in the symbol table of the bound shared object. .pp the .i refcook argument identifies the shared object that is making the symbol reference; this is the same identifier that is provided to the .br la_objopen () function that returned .br la_flg_bindfrom . the .i defcook argument identifies the shared object that defines the referenced symbol; this is the same identifier that is provided to the .br la_objopen () function that returned .br la_flg_bindto . .pp the .i symname argument points a string containing the name of the symbol. .pp the .i flags argument is a bit mask that both provides information about the symbol and can be used to modify further auditing of this plt (procedure linkage table) entry. the dynamic linker may supply the following bit values in this argument: .\" la_symb_structcall appears to be unused .tp 22 .b la_symb_dlsym the binding resulted from a call to .br dlsym (3). .tp .b la_symb_altvalue a previous .br la_symbind* () call returned an alternate value for this symbol. .pp by default, if the auditing library implements .br la_pltenter () and .br la_pltexit () functions (see below), then these functions are invoked, after .br la_symbind (), for plt entries, each time the symbol is referenced. .\" pltenter/pltexit are called for non-dynamically loaded libraries, .\" but don't seem to be called for dynamically loaded libs? .\" is this the same on solaris? the following flags can be ored into .ir *flags to change this default behavior: .tp 22 .b la_symb_nopltenter don't call .br la_pltenter () for this symbol. .tp 22 .b la_symb_nopltexit don't call .br la_pltexit () for this symbol. .pp the return value of .br la_symbind32 () and .br la_symbind64 () is the address to which control should be passed after the function returns. if the auditing library is simply monitoring symbol bindings, then it should return .ir sym\->st_value . a different value may be returned if the library wishes to direct control to an alternate location. .ss la_pltenter() the precise name and argument types for this function depend on the hardware platform. (the appropriate definition is supplied by .ir .) here is the definition for x86-32: .pp .nf .bi "elf32_addr la_i86_gnu_pltenter(elf32_sym *" sym ", unsigned int " ndx , .bi " uintptr_t *" refcook ", uintptr_t *" defcook , .bi " la_i86_regs *" regs ", unsigned int *" flags , .bi " const char *" symname ", long *" framesizep ); .fi .pp this function is invoked just before a plt entry is called, between two shared objects that have been marked for binding notification. .pp the .ir sym , .ir ndx , .ir refcook , .ir defcook , and .ir symname are as for .br la_symbind* (). .pp the .i regs argument points to a structure (defined in .ir ) containing the values of registers to be used for the call to this plt entry. .pp the .i flags argument points to a bit mask that conveys information about, and can be used to modify subsequent auditing of, this plt entry, as for .br la_symbind* (). .pp .\" fixme . is the following correct? the .ir framesizep argument points to a .ir "long\ int" buffer that can be used to explicitly set the frame size used for the call to this plt entry. if different .br la_pltenter () invocations for this symbol return different values, then the maximum returned value is used. the .br la_pltexit () function is called only if this buffer is explicitly set to a suitable value. .pp the return value of .br la_pltenter () is as for .br la_symbind* (). .ss la_pltexit() the precise name and argument types for this function depend on the hardware platform. (the appropriate definition is supplied by .ir .) here is the definition for x86-32: .pp .nf .bi "unsigned int la_i86_gnu_pltexit(elf32_sym *" sym ", unsigned int " ndx , .bi " uintptr_t *" refcook ", uintptr_t *" defcook , .bi " const la_i86_regs *" inregs ", la_i86_retval *" outregs , .bi " const char *" symname ); .fi .pp this function is called when a plt entry, made between two shared objects that have been marked for binding notification, returns. the function is called just before control returns to the caller of the plt entry. .pp the .ir sym , .ir ndx , .ir refcook , .ir defcook , and .ir symname are as for .br la_symbind* (). .pp the .i inregs argument points to a structure (defined in .ir ) containing the values of registers used for the call to this plt entry. the .i outregs argument points to a structure (defined in .ir ) containing return values for the call to this plt entry. these values can be modified by the caller, and the changes will be visible to the caller of the plt entry. .pp in the current gnu implementation, the return value of .br la_pltexit () is ignored. .\" this differs from solaris, where an audit library that monitors .\" symbol binding should return the value of the 'retval' argument .\" (not provided by gnu, but equivalent to returning outregs->lrv_eax .\" on (say) x86-32). .sh conforming to this api is nonstandard, but very similar to the solaris api, described in the solaris .ir "linker and libraries guide" , in the chapter .ir "runtime linker auditing interface" . .sh notes note the following differences from the solaris dynamic linker auditing api: .ip * 3 the solaris .br la_objfilter () interface is not supported by the gnu implementation. .ip * the solaris .br la_symbind32 () and .br la_pltexit () functions do not provide a .i symname argument. .ip * the solaris .br la_pltexit () function does not provide .i inregs and .i outregs arguments (but does provide a .ir retval argument with the function return value). .sh bugs in glibc versions up to and include 2.9, specifying more than one audit library in .b ld_audit results in a run-time crash. this is reportedly fixed in glibc 2.10. .\" fixme . specifying multiple audit libraries doesn't work on gnu. .\" my simple tests on solaris work okay, but not on linux -- mtk, jan 2009 .\" glibc bug filed: http://sourceware.org/bugzilla/show_bug.cgi?id=9733 .\" reportedly, this is fixed on 16 mar 2009 (i.e., for glibc 2.10) .sh examples .ex #include #include unsigned int la_version(unsigned int version) { printf("la_version(): version = %u; lav_current = %u\en", version, lav_current); return lav_current; } char * la_objsearch(const char *name, uintptr_t *cookie, unsigned int flag) { printf("la_objsearch(): name = %s; cookie = %p", name, cookie); printf("; flag = %s\en", (flag == la_ser_orig) ? "la_ser_orig" : (flag == la_ser_libpath) ? "la_ser_libpath" : (flag == la_ser_runpath) ? "la_ser_runpath" : (flag == la_ser_default) ? "la_ser_default" : (flag == la_ser_config) ? "la_ser_config" : (flag == la_ser_secure) ? "la_ser_secure" : "???"); return name; } void la_activity (uintptr_t *cookie, unsigned int flag) { printf("la_activity(): cookie = %p; flag = %s\en", cookie, (flag == la_act_consistent) ? "la_act_consistent" : (flag == la_act_add) ? "la_act_add" : (flag == la_act_delete) ? "la_act_delete" : "???"); } unsigned int la_objopen(struct link_map *map, lmid_t lmid, uintptr_t *cookie) { printf("la_objopen(): loading \e"%s\e"; lmid = %s; cookie=%p\en", map\->l_name, (lmid == lm_id_base) ? "lm_id_base" : (lmid == lm_id_newlm) ? "lm_id_newlm" : "???", cookie); return la_flg_bindto | la_flg_bindfrom; } unsigned int la_objclose (uintptr_t *cookie) { printf("la_objclose(): %p\en", cookie); return 0; } void la_preinit(uintptr_t *cookie) { printf("la_preinit(): %p\en", cookie); } uintptr_t la_symbind32(elf32_sym *sym, unsigned int ndx, uintptr_t *refcook, uintptr_t *defcook, unsigned int *flags, const char *symname) { printf("la_symbind32(): symname = %s; sym\->st_value = %p\en", symname, sym\->st_value); printf(" ndx = %u; flags = %#x", ndx, *flags); printf("; refcook = %p; defcook = %p\en", refcook, defcook); return sym\->st_value; } uintptr_t la_symbind64(elf64_sym *sym, unsigned int ndx, uintptr_t *refcook, uintptr_t *defcook, unsigned int *flags, const char *symname) { printf("la_symbind64(): symname = %s; sym\->st_value = %p\en", symname, sym\->st_value); printf(" ndx = %u; flags = %#x", ndx, *flags); printf("; refcook = %p; defcook = %p\en", refcook, defcook); return sym\->st_value; } elf32_addr la_i86_gnu_pltenter(elf32_sym *sym, unsigned int ndx, uintptr_t *refcook, uintptr_t *defcook, la_i86_regs *regs, unsigned int *flags, const char *symname, long *framesizep) { printf("la_i86_gnu_pltenter(): %s (%p)\en", symname, sym\->st_value); return sym\->st_value; } .ee .sh see also .br ldd (1), .br dlopen (3), .br ld.so (8), .br ldconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995 peter tobias .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file may be distributed under the gnu general public license. .\" %%%license_end .th hosts.equiv 5 2020-06-09 "linux" "linux programmer's manual" .sh name hosts.equiv \- list of hosts and users that are granted "trusted" .b r command access to your system .sh description the file .i /etc/hosts.equiv allows or denies hosts and users to use the \fbr\fp-commands (e.g., .br rlogin , .br rsh , or .br rcp ) without supplying a password. .pp the file uses the following format: .tp \fi+|[\-]hostname|+@netgroup|\-@netgroup\fp \fi[+|[\-]username|+@netgroup|\-@netgroup]\fp .pp the .i hostname is the name of a host which is logically equivalent to the local host. users logged into that host are allowed to access like-named user accounts on the local host without supplying a password. the .i hostname may be (optionally) preceded by a plus (+) sign. if the plus sign is used alone, it allows any host to access your system. you can explicitly deny access to a host by preceding the .i hostname by a minus (\-) sign. users from that host must always supply additional credentials, including possibly a password. for security reasons you should always use the fqdn of the hostname and not the short hostname. .pp the .i username entry grants a specific user access to all user accounts (except root) without supplying a password. that means the user is not restricted to like-named accounts. the .i username may be (optionally) preceded by a plus (+) sign. you can also explicitly deny access to a specific user by preceding the .i username with a minus (\-) sign. this says that the user is not trusted no matter what other entries for that host exist. .pp netgroups can be specified by preceding the netgroup by an @ sign. .pp be extremely careful when using the plus (+) sign. a simple typographical error could result in a standalone plus sign. a standalone plus sign is a wildcard character that means "any host"! .sh files .i /etc/hosts.equiv .sh notes some systems will honor the contents of this file only when it has owner root and no write permission for anybody else. some exceptionally paranoid systems even require that there be no other hard links to the file. .pp modern systems use the pluggable authentication modules library (pam). with pam a standalone plus sign is considered a wildcard character which means "any host" only when the word .i promiscuous is added to the auth component line in your pam file for the particular service .rb "(e.g., " rlogin ). .sh examples below are some example .i /etc/host.equiv or .i \(ti/.rhosts files. .pp allow any user to log in from any host: .pp + .pp allow any user from .i host with a matching local account to log in: .pp host .pp note: the use of .i +host is never a valid syntax, including attempting to specify that any user from the host is allowed. .pp allow any user from .i host to log in: .pp host + .pp note: this is distinct from the previous example since it does not require a matching local account. .pp allow .i user from .i host to log in as any non-root user: .pp host user .pp allow all users with matching local accounts from .i host to log in except for .ir baduser : .pp host \-baduser host .pp deny all users from .ir host : .pp \-host .pp note: the use of .i "\-host\ \-user" is never a valid syntax, including attempting to specify that a particular user from the host is not trusted. .pp allow all users with matching local accounts on all hosts in a .ir netgroup : .pp +@netgroup .pp disallow all users on all hosts in a .ir netgroup : .pp \-@netgroup .pp allow all users in a .i netgroup to log in from .i host as any non-root user: .pp host +@netgroup .pp allow all users with matching local accounts on all hosts in a .i netgroup except .ir baduser : .pp +@netgroup \-baduser +@netgroup .pp note: the deny statements must always precede the allow statements because the file is processed sequentially until the first matching rule is found. .sh see also .br rhosts (5), .br rlogind (8), .br rshd (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sched_get_priority_max.2 .so man3/endian.3 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson; .\" and copyright (c) 1998 jamie lokier; .\" and copyright (c) 2002-2010, 2014 michael kerrisk; .\" and copyright (c) 2014 jeff layton .\" and copyright (c) 2014 david herrmann .\" and copyright (c) 2017 jens axboe .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1995-09-26 by andries brouwer .\" and again on 960413 and 980804 and 981223. .\" modified 1998-12-11 by jamie lokier .\" applied correction by christian ehrhardt - aeb, 990712 .\" modified 2002-04-23 by michael kerrisk .\" added note on f_setfl and o_direct .\" complete rewrite + expansion of material on file locking .\" incorporated description of f_notify, drawing on .\" stephen rothwell's notes in documentation/dnotify.txt. .\" added description of f_setlease and f_getlease .\" corrected and polished, aeb, 020527. .\" modified 2004-03-03 by michael kerrisk .\" modified description of file leases: fixed some errors of detail .\" replaced the term "lease contestant" by "lease breaker" .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" modified 2004-12-08, added o_noatime after note from martin pool .\" 2004-12-10, mtk, noted f_getown bug after suggestion from aeb. .\" 2005-04-08 jamie lokier , mtk .\" described behavior of f_setown/f_setsig in .\" multithreaded processes, and generally cleaned .\" up the discussion of f_setown. .\" 2005-05-20, johannes nicolai , .\" mtk: noted f_setown bug for socket file descriptor in linux 2.4 .\" and earlier. added text on permissions required to send signal. .\" 2009-09-30, michael kerrisk .\" note obsolete f_setown behavior with threads. .\" document f_setown_ex and f_getown_ex .\" 2010-06-17, michael kerrisk .\" document f_setpipe_sz and f_getpipe_sz. .\" 2014-07-08, david herrmann .\" document f_add_seals and f_get_seals .\" 2017-06-26, jens axboe .\" document f_{get,set}_rw_hint and f_{get,set}_file_rw_hint .\" .th fcntl 2 2021-03-22 "linux" "linux programmer's manual" .sh name fcntl \- manipulate file descriptor .sh synopsis .nf .b #include .pp .bi "int fcntl(int " fd ", int " cmd ", ... /* " arg " */ );" .fi .sh description .br fcntl () performs one of the operations described below on the open file descriptor .ir fd . the operation is determined by .ir cmd . .pp .br fcntl () can take an optional third argument. whether or not this argument is required is determined by .ir cmd . the required argument type is indicated in parentheses after each .i cmd name (in most cases, the required type is .ir int , and we identify the argument using the name .ir arg ), or .i void is specified if the argument is not required. .pp certain of the operations below are supported only since a particular linux kernel version. the preferred method of checking whether the host kernel supports a particular operation is to invoke .br fcntl () with the desired .ir cmd value and then test whether the call failed with .br einval , indicating that the kernel does not recognize this value. .ss duplicating a file descriptor .tp .br f_dupfd " (\fiint\fp)" duplicate the file descriptor .ir fd using the lowest-numbered available file descriptor greater than or equal to .ir arg . this is different from .br dup2 (2), which uses exactly the file descriptor specified. .ip on success, the new file descriptor is returned. .ip see .br dup (2) for further details. .tp .br f_dupfd_cloexec " (\fiint\fp; since linux 2.6.24)" as for .br f_dupfd , but additionally set the close-on-exec flag for the duplicate file descriptor. specifying this flag permits a program to avoid an additional .br fcntl () .b f_setfd operation to set the .b fd_cloexec flag. for an explanation of why this flag is useful, see the description of .b o_cloexec in .br open (2). .ss file descriptor flags the following commands manipulate the flags associated with a file descriptor. currently, only one such flag is defined: .br fd_cloexec , the close-on-exec flag. if the .b fd_cloexec bit is set, the file descriptor will automatically be closed during a successful .br execve (2). (if the .br execve (2) fails, the file descriptor is left open.) if the .b fd_cloexec bit is not set, the file descriptor will remain open across an .br execve (2). .tp .br f_getfd " (\fivoid\fp)" return (as the function result) the file descriptor flags; .i arg is ignored. .tp .br f_setfd " (\fiint\fp)" set the file descriptor flags to the value specified by .ir arg . .pp in multithreaded programs, using .br fcntl () .b f_setfd to set the close-on-exec flag at the same time as another thread performs a .br fork (2) plus .br execve (2) is vulnerable to a race condition that may unintentionally leak the file descriptor to the program executed in the child process. see the discussion of the .br o_cloexec flag in .br open (2) for details and a remedy to the problem. .ss file status flags each open file description has certain associated status flags, initialized by .br open (2) .\" or .\" .br creat (2), and possibly modified by .br fcntl (). duplicated file descriptors (made with .br dup (2), .br fcntl (f_dupfd), .br fork (2), etc.) refer to the same open file description, and thus share the same file status flags. .pp the file status flags and their semantics are described in .br open (2). .tp .br f_getfl " (\fivoid\fp)" return (as the function result) the file access mode and the file status flags; .i arg is ignored. .tp .br f_setfl " (\fiint\fp)" set the file status flags to the value specified by .ir arg . file access mode .rb ( o_rdonly ", " o_wronly ", " o_rdwr ) and file creation flags (i.e., .br o_creat ", " o_excl ", " o_noctty ", " o_trunc ) in .i arg are ignored. on linux, this command can change only the .br o_append , .br o_async , .br o_direct , .br o_noatime , and .b o_nonblock flags. it is not possible to change the .br o_dsync and .br o_sync flags; see bugs, below. .ss advisory record locking linux implements traditional ("process-associated") unix record locks, as standardized by posix. for a linux-specific alternative with better semantics, see the discussion of open file description locks below. .pp .br f_setlk , .br f_setlkw , and .br f_getlk are used to acquire, release, and test for the existence of record locks (also known as byte-range, file-segment, or file-region locks). the third argument, .ir lock , is a pointer to a structure that has at least the following fields (in unspecified order). .pp .in +4n .ex struct flock { ... short l_type; /* type of lock: f_rdlck, f_wrlck, f_unlck */ short l_whence; /* how to interpret l_start: seek_set, seek_cur, seek_end */ off_t l_start; /* starting offset for lock */ off_t l_len; /* number of bytes to lock */ pid_t l_pid; /* pid of process blocking our lock (set by f_getlk and f_ofd_getlk) */ ... }; .ee .in .pp the .ir l_whence ", " l_start ", and " l_len fields of this structure specify the range of bytes we wish to lock. bytes past the end of the file may be locked, but not bytes before the start of the file. .pp .i l_start is the starting offset for the lock, and is interpreted relative to either: the start of the file (if .i l_whence is .br seek_set ); the current file offset (if .i l_whence is .br seek_cur ); or the end of the file (if .i l_whence is .br seek_end ). in the final two cases, .i l_start can be a negative number provided the offset does not lie before the start of the file. .pp .i l_len specifies the number of bytes to be locked. if .i l_len is positive, then the range to be locked covers bytes .i l_start up to and including .ir l_start + l_len \-1. specifying 0 for .i l_len has the special meaning: lock all bytes starting at the location specified by .ir l_whence " and " l_start through to the end of file, no matter how large the file grows. .pp posix.1-2001 allows (but does not require) an implementation to support a negative .i l_len value; if .i l_len is negative, the interval described by .i lock covers bytes .ir l_start + l_len up to and including .ir l_start \-1. this is supported by linux since kernel versions 2.4.21 and 2.5.49. .pp the .i l_type field can be used to place a read .rb ( f_rdlck ) or a write .rb ( f_wrlck ) lock on a file. any number of processes may hold a read lock (shared lock) on a file region, but only one process may hold a write lock (exclusive lock). an exclusive lock excludes all other locks, both shared and exclusive. a single process can hold only one type of lock on a file region; if a new lock is applied to an already-locked region, then the existing lock is converted to the new lock type. (such conversions may involve splitting, shrinking, or coalescing with an existing lock if the byte range specified by the new lock does not precisely coincide with the range of the existing lock.) .tp .br f_setlk " (\fistruct flock *\fp)" acquire a lock (when .i l_type is .b f_rdlck or .br f_wrlck ) or release a lock (when .i l_type is .br f_unlck ) on the bytes specified by the .ir l_whence ", " l_start ", and " l_len fields of .ir lock . if a conflicting lock is held by another process, this call returns \-1 and sets .i errno to .b eacces or .br eagain . (the error returned in this case differs across implementations, so posix requires a portable application to check for both errors.) .tp .br f_setlkw " (\fistruct flock *\fp)" as for .br f_setlk , but if a conflicting lock is held on the file, then wait for that lock to be released. if a signal is caught while waiting, then the call is interrupted and (after the signal handler has returned) returns immediately (with return value \-1 and .i errno set to .br eintr ; see .br signal (7)). .tp .br f_getlk " (\fistruct flock *\fp)" on input to this call, .i lock describes a lock we would like to place on the file. if the lock could be placed, .br fcntl () does not actually place it, but returns .b f_unlck in the .i l_type field of .i lock and leaves the other fields of the structure unchanged. .ip if one or more incompatible locks would prevent this lock being placed, then .br fcntl () returns details about one of those locks in the .ir l_type ", " l_whence ", " l_start ", and " l_len fields of .ir lock . if the conflicting lock is a traditional (process-associated) record lock, then the .i l_pid field is set to the pid of the process holding that lock. if the conflicting lock is an open file description lock, then .i l_pid is set to \-1. note that the returned information may already be out of date by the time the caller inspects it. .pp in order to place a read lock, .i fd must be open for reading. in order to place a write lock, .i fd must be open for writing. to place both types of lock, open a file read-write. .pp when placing locks with .br f_setlkw , the kernel detects .ir deadlocks , whereby two or more processes have their lock requests mutually blocked by locks held by the other processes. for example, suppose process a holds a write lock on byte 100 of a file, and process b holds a write lock on byte 200. if each process then attempts to lock the byte already locked by the other process using .br f_setlkw , then, without deadlock detection, both processes would remain blocked indefinitely. when the kernel detects such deadlocks, it causes one of the blocking lock requests to immediately fail with the error .br edeadlk ; an application that encounters such an error should release some of its locks to allow other applications to proceed before attempting regain the locks that it requires. circular deadlocks involving more than two processes are also detected. note, however, that there are limitations to the kernel's deadlock-detection algorithm; see bugs. .pp as well as being removed by an explicit .br f_unlck , record locks are automatically released when the process terminates. .pp record locks are not inherited by a child created via .br fork (2), but are preserved across an .br execve (2). .pp because of the buffering performed by the .br stdio (3) library, the use of record locking with routines in that package should be avoided; use .br read (2) and .br write (2) instead. .pp the record locks described above are associated with the process (unlike the open file description locks described below). this has some unfortunate consequences: .ip * 3 if a process closes .i any file descriptor referring to a file, then all of the process's locks on that file are released, regardless of the file descriptor(s) on which the locks were obtained. .\" (additional file descriptors referring to the same file .\" may have been obtained by calls to .\" .br open "(2), " dup "(2), " dup2 "(2), or " fcntl ().) this is bad: it means that a process can lose its locks on a file such as .i /etc/passwd or .i /etc/mtab when for some reason a library function decides to open, read, and close the same file. .ip * the threads in a process share locks. in other words, a multithreaded program can't use record locking to ensure that threads don't simultaneously access the same region of a file. .pp open file description locks solve both of these problems. .ss open file description locks (non-posix) open file description locks are advisory byte-range locks whose operation is in most respects identical to the traditional record locks described above. this lock type is linux-specific, and available since linux 3.15. (there is a proposal with the austin group .\" fixme . review progress into posix .\" http://austingroupbugs.net/view.php?id=768 to include this lock type in the next revision of posix.1.) for an explanation of open file descriptions, see .br open (2). .pp the principal difference between the two lock types is that whereas traditional record locks are associated with a process, open file description locks are associated with the open file description on which they are acquired, much like locks acquired with .br flock (2). consequently (and unlike traditional advisory record locks), open file description locks are inherited across .br fork (2) (and .br clone (2) with .br clone_files ), and are only automatically released on the last close of the open file description, instead of being released on any close of the file. .pp conflicting lock combinations (i.e., a read lock and a write lock or two write locks) where one lock is an open file description lock and the other is a traditional record lock conflict even when they are acquired by the same process on the same file descriptor. .pp open file description locks placed via the same open file description (i.e., via the same file descriptor, or via a duplicate of the file descriptor created by .br fork (2), .br dup (2), .br fcntl () .br f_dupfd , and so on) are always compatible: if a new lock is placed on an already locked region, then the existing lock is converted to the new lock type. (such conversions may result in splitting, shrinking, or coalescing with an existing lock as discussed above.) .pp on the other hand, open file description locks may conflict with each other when they are acquired via different open file descriptions. thus, the threads in a multithreaded program can use open file description locks to synchronize access to a file region by having each thread perform its own .br open (2) on the file and applying locks via the resulting file descriptor. .pp as with traditional advisory locks, the third argument to .br fcntl (), .ir lock , is a pointer to an .ir flock structure. by contrast with traditional record locks, the .i l_pid field of that structure must be set to zero when using the commands described below. .pp the commands for working with open file description locks are analogous to those used with traditional locks: .tp .br f_ofd_setlk " (\fistruct flock *\fp)" acquire an open file description lock (when .i l_type is .b f_rdlck or .br f_wrlck ) or release an open file description lock (when .i l_type is .br f_unlck ) on the bytes specified by the .ir l_whence ", " l_start ", and " l_len fields of .ir lock . if a conflicting lock is held by another process, this call returns \-1 and sets .i errno to .br eagain . .tp .br f_ofd_setlkw " (\fistruct flock *\fp)" as for .br f_ofd_setlk , but if a conflicting lock is held on the file, then wait for that lock to be released. if a signal is caught while waiting, then the call is interrupted and (after the signal handler has returned) returns immediately (with return value \-1 and .i errno set to .br eintr ; see .br signal (7)). .tp .br f_ofd_getlk " (\fistruct flock *\fp)" on input to this call, .i lock describes an open file description lock we would like to place on the file. if the lock could be placed, .br fcntl () does not actually place it, but returns .b f_unlck in the .i l_type field of .i lock and leaves the other fields of the structure unchanged. if one or more incompatible locks would prevent this lock being placed, then details about one of these locks are returned via .ir lock , as described above for .br f_getlk . .pp in the current implementation, .\" commit 57b65325fe34ec4c917bc4e555144b4a94d9e1f7 no deadlock detection is performed for open file description locks. (this contrasts with process-associated record locks, for which the kernel does perform deadlock detection.) .\" .ss mandatory locking .ir warning : the linux implementation of mandatory locking is unreliable. see bugs below. because of these bugs, and the fact that the feature is believed to be little used, since linux 4.5, mandatory locking has been made an optional feature, governed by a configuration option .rb ( config_mandatory_file_locking ). this is an initial step toward removing this feature completely. .pp by default, both traditional (process-associated) and open file description record locks are advisory. advisory locks are not enforced and are useful only between cooperating processes. .pp both lock types can also be mandatory. mandatory locks are enforced for all processes. if a process tries to perform an incompatible access (e.g., .br read (2) or .br write (2)) on a file region that has an incompatible mandatory lock, then the result depends upon whether the .b o_nonblock flag is enabled for its open file description. if the .b o_nonblock flag is not enabled, then the system call is blocked until the lock is removed or converted to a mode that is compatible with the access. if the .b o_nonblock flag is enabled, then the system call fails with the error .br eagain . .pp to make use of mandatory locks, mandatory locking must be enabled both on the filesystem that contains the file to be locked, and on the file itself. mandatory locking is enabled on a filesystem using the "\-o mand" option to .br mount (8), or the .b ms_mandlock flag for .br mount (2). mandatory locking is enabled on a file by disabling group execute permission on the file and enabling the set-group-id permission bit (see .br chmod (1) and .br chmod (2)). .pp mandatory locking is not specified by posix. some other systems also support mandatory locking, although the details of how to enable it vary across systems. .\" .ss lost locks when an advisory lock is obtained on a networked filesystem such as nfs it is possible that the lock might get lost. this may happen due to administrative action on the server, or due to a network partition (i.e., loss of network connectivity with the server) which lasts long enough for the server to assume that the client is no longer functioning. .pp when the filesystem determines that a lock has been lost, future .br read (2) or .br write (2) requests may fail with the error .br eio . this error will persist until the lock is removed or the file descriptor is closed. since linux 3.12, .\" commit ef1820f9be27b6ad158f433ab38002ab8131db4d this happens at least for nfsv4 (including all minor versions). .pp some versions of unix send a signal .rb ( siglost ) in this circumstance. linux does not define this signal, and does not provide any asynchronous notification of lost locks. .\" .ss managing signals .br f_getown , .br f_setown , .br f_getown_ex , .br f_setown_ex , .br f_getsig , and .b f_setsig are used to manage i/o availability signals: .tp .br f_getown " (\fivoid\fp)" return (as the function result) the process id or process group id currently receiving .b sigio and .b sigurg signals for events on file descriptor .ir fd . process ids are returned as positive values; process group ids are returned as negative values (but see bugs below). .i arg is ignored. .tp .br f_setown " (\fiint\fp)" set the process id or process group id that will receive .b sigio and .b sigurg signals for events on the file descriptor .ir fd . the target process or process group id is specified in .ir arg . a process id is specified as a positive value; a process group id is specified as a negative value. most commonly, the calling process specifies itself as the owner (that is, .i arg is specified as .br getpid (2)). .ip as well as setting the file descriptor owner, one must also enable generation of signals on the file descriptor. this is done by using the .br fcntl () .b f_setfl command to set the .b o_async file status flag on the file descriptor. subsequently, a .b sigio signal is sent whenever input or output becomes possible on the file descriptor. the .br fcntl () .b f_setsig command can be used to obtain delivery of a signal other than .br sigio . .ip sending a signal to the owner process (group) specified by .b f_setown is subject to the same permissions checks as are described for .br kill (2), where the sending process is the one that employs .b f_setown (but see bugs below). if this permission check fails, then the signal is silently discarded. .ir note : the .br f_setown operation records the caller's credentials at the time of the .br fcntl () call, and it is these saved credentials that are used for the permission checks. .ip if the file descriptor .i fd refers to a socket, .b f_setown also selects the recipient of .b sigurg signals that are delivered when out-of-band data arrives on that socket. .rb ( sigurg is sent in any situation where .br select (2) would report the socket as having an "exceptional condition".) .\" the following appears to be rubbish. it doesn't seem to .\" be true according to the kernel source, and i can write .\" a program that gets a terminal-generated sigio even though .\" it is not the foreground process group of the terminal. .\" -- mtk, 8 apr 05 .\" .\" if the file descriptor .\" .i fd .\" refers to a terminal device, then sigio .\" signals are sent to the foreground process group of the terminal. .ip the following was true in 2.6.x kernels up to and including kernel 2.6.11: .rs .ip if a nonzero value is given to .b f_setsig in a multithreaded process running with a threading library that supports thread groups (e.g., nptl), then a positive value given to .b f_setown has a different meaning: .\" the relevant place in the (2.6) kernel source is the .\" 'switch' in fs/fcntl.c::send_sigio_to_task() -- mtk, apr 2005 instead of being a process id identifying a whole process, it is a thread id identifying a specific thread within a process. consequently, it may be necessary to pass .b f_setown the result of .br gettid (2) instead of .br getpid (2) to get sensible results when .b f_setsig is used. (in current linux threading implementations, a main thread's thread id is the same as its process id. this means that a single-threaded program can equally use .br gettid (2) or .br getpid (2) in this scenario.) note, however, that the statements in this paragraph do not apply to the .b sigurg signal generated for out-of-band data on a socket: this signal is always sent to either a process or a process group, depending on the value given to .br f_setown . .\" send_sigurg()/send_sigurg_to_task() bypasses .\" kill_fasync()/send_sigio()/send_sigio_to_task() .\" to directly call send_group_sig_info() .\" -- mtk, apr 2005 (kernel 2.6.11) .re .ip the above behavior was accidentally dropped in linux 2.6.12, and won't be restored. from linux 2.6.32 onward, use .br f_setown_ex to target .b sigio and .b sigurg signals at a particular thread. .tp .br f_getown_ex " (\fistruct f_owner_ex *\fp) (since linux 2.6.32)" return the current file descriptor owner settings as defined by a previous .br f_setown_ex operation. the information is returned in the structure pointed to by .ir arg , which has the following form: .ip .in +4n .ex struct f_owner_ex { int type; pid_t pid; }; .ee .in .ip the .i type field will have one of the values .br f_owner_tid , .br f_owner_pid , or .br f_owner_pgrp . the .i pid field is a positive integer representing a thread id, process id, or process group id. see .b f_setown_ex for more details. .tp .br f_setown_ex " (\fistruct f_owner_ex *\fp) (since linux 2.6.32)" this operation performs a similar task to .br f_setown . it allows the caller to direct i/o availability signals to a specific thread, process, or process group. the caller specifies the target of signals via .ir arg , which is a pointer to a .ir f_owner_ex structure. the .i type field has one of the following values, which define how .i pid is interpreted: .rs .tp .br f_owner_tid send the signal to the thread whose thread id (the value returned by a call to .br clone (2) or .br gettid (2)) is specified in .ir pid . .tp .br f_owner_pid send the signal to the process whose id is specified in .ir pid . .tp .br f_owner_pgrp send the signal to the process group whose id is specified in .ir pid . (note that, unlike with .br f_setown , a process group id is specified as a positive value here.) .re .tp .br f_getsig " (\fivoid\fp)" return (as the function result) the signal sent when input or output becomes possible. a value of zero means .b sigio is sent. any other value (including .br sigio ) is the signal sent instead, and in this case additional info is available to the signal handler if installed with .br sa_siginfo . .i arg is ignored. .tp .br f_setsig " (\fiint\fp)" set the signal sent when input or output becomes possible to the value given in .ir arg . a value of zero means to send the default .b sigio signal. any other value (including .br sigio ) is the signal to send instead, and in this case additional info is available to the signal handler if installed with .br sa_siginfo . .\" .\" the following was true only up until 2.6.11: .\" .\" additionally, passing a nonzero value to .\" .b f_setsig .\" changes the signal recipient from a whole process to a specific thread .\" within a process. .\" see the description of .\" .b f_setown .\" for more details. .ip by using .b f_setsig with a nonzero value, and setting .b sa_siginfo for the signal handler (see .br sigaction (2)), extra information about i/o events is passed to the handler in a .i siginfo_t structure. if the .i si_code field indicates the source is .br si_sigio , the .i si_fd field gives the file descriptor associated with the event. otherwise, there is no indication which file descriptors are pending, and you should use the usual mechanisms .rb ( select (2), .br poll (2), .br read (2) with .b o_nonblock set etc.) to determine which file descriptors are available for i/o. .ip note that the file descriptor provided in .i si_fd is the one that was specified during the .br f_setsig operation. this can lead to an unusual corner case. if the file descriptor is duplicated .rb ( dup (2) or similar), and the original file descriptor is closed, then i/o events will continue to be generated, but the .i si_fd field will contain the number of the now closed file descriptor. .ip by selecting a real time signal (value >= .br sigrtmin ), multiple i/o events may be queued using the same signal numbers. (queuing is dependent on available memory.) extra information is available if .b sa_siginfo is set for the signal handler, as above. .ip note that linux imposes a limit on the number of real-time signals that may be queued to a process (see .br getrlimit (2) and .br signal (7)) and if this limit is reached, then the kernel reverts to delivering .br sigio , and this signal is delivered to the entire process rather than to a specific thread. .\" see fs/fcntl.c::send_sigio_to_task() (2.4/2.6) sources -- mtk, apr 05 .pp using these mechanisms, a program can implement fully asynchronous i/o without using .br select (2) or .br poll (2) most of the time. .pp the use of .br o_async is specific to bsd and linux. the only use of .br f_getown and .b f_setown specified in posix.1 is in conjunction with the use of the .b sigurg signal on sockets. (posix does not specify the .br sigio signal.) .br f_getown_ex , .br f_setown_ex , .br f_getsig , and .b f_setsig are linux-specific. posix has asynchronous i/o and the .i aio_sigevent structure to achieve similar things; these are also available in linux as part of the gnu c library (glibc). .ss leases .b f_setlease and .b f_getlease (linux 2.4 onward) are used to establish a new lease, and retrieve the current lease, on the open file description referred to by the file descriptor .ir fd . a file lease provides a mechanism whereby the process holding the lease (the "lease holder") is notified (via delivery of a signal) when a process (the "lease breaker") tries to .br open (2) or .br truncate (2) the file referred to by that file descriptor. .tp .br f_setlease " (\fiint\fp)" set or remove a file lease according to which of the following values is specified in the integer .ir arg : .rs .tp .b f_rdlck take out a read lease. this will cause the calling process to be notified when the file is opened for writing or is truncated. .\" the following became true in kernel 2.6.10: .\" see the man-pages-2.09 changelog for further info. a read lease can be placed only on a file descriptor that is opened read-only. .tp .b f_wrlck take out a write lease. this will cause the caller to be notified when the file is opened for reading or writing or is truncated. a write lease may be placed on a file only if there are no other open file descriptors for the file. .tp .b f_unlck remove our lease from the file. .re .pp leases are associated with an open file description (see .br open (2)). this means that duplicate file descriptors (created by, for example, .br fork (2) or .br dup (2)) refer to the same lease, and this lease may be modified or released using any of these descriptors. furthermore, the lease is released by either an explicit .b f_unlck operation on any of these duplicate file descriptors, or when all such file descriptors have been closed. .pp leases may be taken out only on regular files. an unprivileged process may take out a lease only on a file whose uid (owner) matches the filesystem uid of the process. a process with the .b cap_lease capability may take out leases on arbitrary files. .tp .br f_getlease " (\fivoid\fp)" indicates what type of lease is associated with the file descriptor .i fd by returning either .br f_rdlck ", " f_wrlck ", or " f_unlck , indicating, respectively, a read lease , a write lease, or no lease. .i arg is ignored. .pp when a process (the "lease breaker") performs an .br open (2) or .br truncate (2) that conflicts with a lease established via .br f_setlease , the system call is blocked by the kernel and the kernel notifies the lease holder by sending it a signal .rb ( sigio by default). the lease holder should respond to receipt of this signal by doing whatever cleanup is required in preparation for the file to be accessed by another process (e.g., flushing cached buffers) and then either remove or downgrade its lease. a lease is removed by performing an .b f_setlease command specifying .i arg as .br f_unlck . if the lease holder currently holds a write lease on the file, and the lease breaker is opening the file for reading, then it is sufficient for the lease holder to downgrade the lease to a read lease. this is done by performing an .b f_setlease command specifying .i arg as .br f_rdlck . .pp if the lease holder fails to downgrade or remove the lease within the number of seconds specified in .ir /proc/sys/fs/lease\-break\-time , then the kernel forcibly removes or downgrades the lease holder's lease. .pp once a lease break has been initiated, .b f_getlease returns the target lease type (either .b f_rdlck or .br f_unlck , depending on what would be compatible with the lease breaker) until the lease holder voluntarily downgrades or removes the lease or the kernel forcibly does so after the lease break timer expires. .pp once the lease has been voluntarily or forcibly removed or downgraded, and assuming the lease breaker has not unblocked its system call, the kernel permits the lease breaker's system call to proceed. .pp if the lease breaker's blocked .br open (2) or .br truncate (2) is interrupted by a signal handler, then the system call fails with the error .br eintr , but the other steps still occur as described above. if the lease breaker is killed by a signal while blocked in .br open (2) or .br truncate (2), then the other steps still occur as described above. if the lease breaker specifies the .b o_nonblock flag when calling .br open (2), then the call immediately fails with the error .br ewouldblock , but the other steps still occur as described above. .pp the default signal used to notify the lease holder is .br sigio , but this can be changed using the .b f_setsig command to .br fcntl (). if a .b f_setsig command is performed (even one specifying .br sigio ), and the signal handler is established using .br sa_siginfo , then the handler will receive a .i siginfo_t structure as its second argument, and the .i si_fd field of this argument will hold the file descriptor of the leased file that has been accessed by another process. (this is useful if the caller holds leases against multiple files.) .ss file and directory change notification (dnotify) .tp .br f_notify " (\fiint\fp)" (linux 2.4 onward) provide notification when the directory referred to by .i fd or any of the files that it contains is changed. the events to be notified are specified in .ir arg , which is a bit mask specified by oring together zero or more of the following bits: .pp .rs .pd 0 .tp .b dn_access a file was accessed .rb ( read (2), .br pread (2), .br readv (2), and similar) .tp .b dn_modify a file was modified .rb ( write (2), .br pwrite (2), .br writev (2), .br truncate (2), .br ftruncate (2), and similar). .tp .b dn_create a file was created .rb ( open (2), .br creat (2), .br mknod (2), .br mkdir (2), .br link (2), .br symlink (2), .br rename (2) into this directory). .tp .b dn_delete a file was unlinked .rb ( unlink (2), .br rename (2) to another directory, .br rmdir (2)). .tp .b dn_rename a file was renamed within this directory .rb ( rename (2)). .tp .b dn_attrib the attributes of a file were changed .rb ( chown (2), .br chmod (2), .br utime (2), .br utimensat (2), and similar). .pd .re .ip (in order to obtain these definitions, the .b _gnu_source feature test macro must be defined before including .i any header files.) .ip directory notifications are normally "one-shot", and the application must reregister to receive further notifications. alternatively, if .b dn_multishot is included in .ir arg , then notification will remain in effect until explicitly removed. .ip .\" the following does seem a poor api-design choice... a series of .b f_notify requests is cumulative, with the events in .i arg being added to the set already monitored. to disable notification of all events, make an .b f_notify call specifying .i arg as 0. .ip notification occurs via delivery of a signal. the default signal is .br sigio , but this can be changed using the .b f_setsig command to .br fcntl (). (note that .b sigio is one of the nonqueuing standard signals; switching to the use of a real-time signal means that multiple notifications can be queued to the process.) in the latter case, the signal handler receives a .i siginfo_t structure as its second argument (if the handler was established using .br sa_siginfo ) and the .i si_fd field of this structure contains the file descriptor which generated the notification (useful when establishing notification on multiple directories). .ip especially when using .br dn_multishot , a real time signal should be used for notification, so that multiple notifications can be queued. .ip .b note: new applications should use the .i inotify interface (available since kernel 2.6.13), which provides a much superior interface for obtaining notifications of filesystem events. see .br inotify (7). .ss changing the capacity of a pipe .tp .br f_setpipe_sz " (\fiint\fp; since linux 2.6.35)" change the capacity of the pipe referred to by .i fd to be at least .i arg bytes. an unprivileged process can adjust the pipe capacity to any value between the system page size and the limit defined in .ir /proc/sys/fs/pipe\-max\-size (see .br proc (5)). attempts to set the pipe capacity below the page size are silently rounded up to the page size. attempts by an unprivileged process to set the pipe capacity above the limit in .ir /proc/sys/fs/pipe\-max\-size yield the error .br eperm ; a privileged process .rb ( cap_sys_resource ) can override the limit. .ip when allocating the buffer for the pipe, the kernel may use a capacity larger than .ir arg , if that is convenient for the implementation. (in the current implementation, the allocation is the next higher power-of-two page-size multiple of the requested size.) the actual capacity (in bytes) that is set is returned as the function result. .ip attempting to set the pipe capacity smaller than the amount of buffer space currently used to store data produces the error .br ebusy . .ip note that because of the way the pages of the pipe buffer are employed when data is written to the pipe, the number of bytes that can be written may be less than the nominal size, depending on the size of the writes. .tp .br f_getpipe_sz " (\fivoid\fp; since linux 2.6.35)" return (as the function result) the capacity of the pipe referred to by .ir fd . .\" .ss file sealing file seals limit the set of allowed operations on a given file. for each seal that is set on a file, a specific set of operations will fail with .b eperm on this file from now on. the file is said to be sealed. the default set of seals depends on the type of the underlying file and filesystem. for an overview of file sealing, a discussion of its purpose, and some code examples, see .br memfd_create (2). .pp currently, file seals can be applied only to a file descriptor returned by .br memfd_create (2) (if the .b mfd_allow_sealing was employed). on other filesystems, all .br fcntl () operations that operate on seals will return .br einval . .pp seals are a property of an inode. thus, all open file descriptors referring to the same inode share the same set of seals. furthermore, seals can never be removed, only added. .tp .br f_add_seals " (\fiint\fp; since linux 3.17)" add the seals given in the bit-mask argument .i arg to the set of seals of the inode referred to by the file descriptor .ir fd . seals cannot be removed again. once this call succeeds, the seals are enforced by the kernel immediately. if the current set of seals includes .br f_seal_seal (see below), then this call will be rejected with .br eperm . adding a seal that is already set is a no-op, in case .b f_seal_seal is not set already. in order to place a seal, the file descriptor .i fd must be writable. .tp .br f_get_seals " (\fivoid\fp; since linux 3.17)" return (as the function result) the current set of seals of the inode referred to by .ir fd . if no seals are set, 0 is returned. if the file does not support sealing, \-1 is returned and .i errno is set to .br einval . .pp the following seals are available: .tp .br f_seal_seal if this seal is set, any further call to .br fcntl () with .b f_add_seals fails with the error .br eperm . therefore, this seal prevents any modifications to the set of seals itself. if the initial set of seals of a file includes .br f_seal_seal , then this effectively causes the set of seals to be constant and locked. .tp .br f_seal_shrink if this seal is set, the file in question cannot be reduced in size. this affects .br open (2) with the .b o_trunc flag as well as .br truncate (2) and .br ftruncate (2). those calls fail with .b eperm if you try to shrink the file in question. increasing the file size is still possible. .tp .br f_seal_grow if this seal is set, the size of the file in question cannot be increased. this affects .br write (2) beyond the end of the file, .br truncate (2), .br ftruncate (2), and .br fallocate (2). these calls fail with .b eperm if you use them to increase the file size. if you keep the size or shrink it, those calls still work as expected. .tp .br f_seal_write if this seal is set, you cannot modify the contents of the file. note that shrinking or growing the size of the file is still possible and allowed. .\" one or more other seals are typically used with f_seal_write .\" because, given a file with the f_seal_write seal set, then, .\" while it would no longer be possible to (say) write zeros into .\" the last 100 bytes of a file, it would still be possible .\" to (say) shrink the file by 100 bytes using ftruncate(), and .\" then increase the file size by 100 bytes, which would have .\" the effect of replacing the last hundred bytes by zeros. .\" thus, this seal is normally used in combination with one of the other seals. this seal affects .br write (2) and .br fallocate (2) (only in combination with the .b falloc_fl_punch_hole flag). those calls fail with .b eperm if this seal is set. furthermore, trying to create new shared, writable memory-mappings via .br mmap (2) will also fail with .br eperm . .ip using the .b f_add_seals operation to set the .b f_seal_write seal fails with .b ebusy if any writable, shared mapping exists. such mappings must be unmapped before you can add this seal. furthermore, if there are any asynchronous i/o operations .rb ( io_submit (2)) pending on the file, all outstanding writes will be discarded. .tp .br f_seal_future_write " (since linux 5.1)" the effect of this seal is similar to .br f_seal_write , but the contents of the file can still be modified via shared writable mappings that were created prior to the seal being set. any attempt to create a new writable mapping on the file via .br mmap (2) will fail with .br eperm . likewise, an attempt to write to the file via .br write (2) will fail with .br eperm . .ip using this seal, one process can create a memory buffer that it can continue to modify while sharing that buffer on a "read-only" basis with other processes. .\" .ss file read/write hints write lifetime hints can be used to inform the kernel about the relative expected lifetime of writes on a given inode or via a particular open file description. (see .br open (2) for an explanation of open file descriptions.) in this context, the term "write lifetime" means the expected time the data will live on media, before being overwritten or erased. .pp an application may use the different hint values specified below to separate writes into different write classes, so that multiple users or applications running on a single storage back-end can aggregate their i/o patterns in a consistent manner. however, there are no functional semantics implied by these flags, and different i/o classes can use the write lifetime hints in arbitrary ways, so long as the hints are used consistently. .pp the following operations can be applied to the file descriptor, .ir fd : .tp .br f_get_rw_hint " (\fiuint64_t *\fp; since linux 4.13)" returns the value of the read/write hint associated with the underlying inode referred to by .ir fd . .tp .br f_set_rw_hint " (\fiuint64_t *\fp; since linux 4.13)" sets the read/write hint value associated with the underlying inode referred to by .ir fd . this hint persists until either it is explicitly modified or the underlying filesystem is unmounted. .tp .br f_get_file_rw_hint " (\fiuint64_t *\fp; since linux 4.13)" returns the value of the read/write hint associated with the open file description referred to by .ir fd . .tp .br f_set_file_rw_hint " (\fiuint64_t *\fp; since linux 4.13)" sets the read/write hint value associated with the open file description referred to by .ir fd . .pp if an open file description has not been assigned a read/write hint, then it shall use the value assigned to the inode, if any. .pp the following read/write hints are valid since linux 4.13: .tp .br rwh_write_life_not_set no specific hint has been set. this is the default value. .tp .br rwh_write_life_none no specific write lifetime is associated with this file or inode. .tp .br rwh_write_life_short data written to this inode or via this open file description is expected to have a short lifetime. .tp .br rwh_write_life_medium data written to this inode or via this open file description is expected to have a lifetime longer than data written with .br rwh_write_life_short . .tp .br rwh_write_life_long data written to this inode or via this open file description is expected to have a lifetime longer than data written with .br rwh_write_life_medium . .tp .br rwh_write_life_extreme data written to this inode or via this open file description is expected to have a lifetime longer than data written with .br rwh_write_life_long . .pp all the write-specific hints are relative to each other, and no individual absolute meaning should be attributed to them. .sh return value for a successful call, the return value depends on the operation: .tp .b f_dupfd the new file descriptor. .tp .b f_getfd value of file descriptor flags. .tp .b f_getfl value of file status flags. .tp .b f_getlease type of lease held on file descriptor. .tp .b f_getown value of file descriptor owner. .tp .b f_getsig value of signal sent when read or write becomes possible, or zero for traditional .b sigio behavior. .tp .br f_getpipe_sz ", " f_setpipe_sz the pipe capacity. .tp .br f_get_seals a bit mask identifying the seals that have been set for the inode referred to by .ir fd . .tp all other commands zero. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .br eacces " or " eagain operation is prohibited by locks held by other processes. .tp .b eagain the operation is prohibited because the file has been memory-mapped by another process. .tp .b ebadf .i fd is not an open file descriptor .tp .b ebadf .i cmd is .b f_setlk or .b f_setlkw and the file descriptor open mode doesn't match with the type of lock requested. .tp .br ebusy .i cmd is .br f_setpipe_sz and the new pipe capacity specified in .i arg is smaller than the amount of buffer space currently used to store data in the pipe. .tp .b ebusy .i cmd is .br f_add_seals , .ir arg includes .br f_seal_write , and there exists a writable, shared mapping on the file referred to by .ir fd . .tp .b edeadlk it was detected that the specified .b f_setlkw command would cause a deadlock. .tp .b efault .i lock is outside your accessible address space. .tp .b eintr .i cmd is .br f_setlkw or .br f_ofd_setlkw and the operation was interrupted by a signal; see .br signal (7). .tp .b eintr .i cmd is .br f_getlk , .br f_setlk , .br f_ofd_getlk , or .br f_ofd_setlk , and the operation was interrupted by a signal before the lock was checked or acquired. most likely when locking a remote file (e.g., locking over nfs), but can sometimes happen locally. .tp .b einval the value specified in .i cmd is not recognized by this kernel. .tp .b einval .i cmd is .br f_add_seals and .i arg includes an unrecognized sealing bit. .tp .br einval .i cmd is .br f_add_seals or .br f_get_seals and the filesystem containing the inode referred to by .i fd does not support sealing. .tp .b einval .i cmd is .br f_dupfd and .i arg is negative or is greater than the maximum allowable value (see the discussion of .br rlimit_nofile in .br getrlimit (2)). .tp .b einval .i cmd is .br f_setsig and .i arg is not an allowable signal number. .tp .b einval .i cmd is .br f_ofd_setlk , .br f_ofd_setlkw , or .br f_ofd_getlk , and .i l_pid was not specified as zero. .tp .b emfile .i cmd is .br f_dupfd and the per-process limit on the number of open file descriptors has been reached. .tp .b enolck too many segment locks open, lock table is full, or a remote locking protocol failed (e.g., locking over nfs). .tp .b enotdir .b f_notify was specified in .ir cmd , but .ir fd does not refer to a directory. .tp .br eperm .i cmd is .br f_setpipe_sz and the soft or hard user pipe limit has been reached; see .br pipe (7). .tp .b eperm attempted to clear the .b o_append flag on a file that has the append-only attribute set. .tp .b eperm .i cmd was .br f_add_seals , but .i fd was not open for writing or the current set of seals on the file already includes .br f_seal_seal . .sh conforming to svr4, 4.3bsd, posix.1-2001. only the operations .br f_dupfd , .br f_getfd , .br f_setfd , .br f_getfl , .br f_setfl , .br f_getlk , .br f_setlk , and .br f_setlkw are specified in posix.1-2001. .pp .br f_getown and .b f_setown are specified in posix.1-2001. (to get their definitions, define either .\" .br _bsd_source , .\" or .br _xopen_source with the value 500 or greater, or .br _posix_c_source with the value 200809l or greater.) .pp .b f_dupfd_cloexec is specified in posix.1-2008. (to get this definition, define .b _posix_c_source with the value 200809l or greater, or .b _xopen_source with the value 700 or greater.) .pp .br f_getown_ex , .br f_setown_ex , .br f_setpipe_sz , .br f_getpipe_sz , .br f_getsig , .br f_setsig , .br f_notify , .br f_getlease , and .b f_setlease are linux-specific. (define the .b _gnu_source macro to obtain these definitions.) .\" .pp .\" svr4 documents additional eio, enolink and eoverflow error conditions. .pp .br f_ofd_setlk , .br f_ofd_setlkw , and .br f_ofd_getlk are linux-specific (and one must define .br _gnu_source to obtain their definitions), but work is being done to have them included in the next version of posix.1. .pp .br f_add_seals and .br f_get_seals are linux-specific. .\" fixme . once glibc adds support, add a note about ftm requirements .sh notes the errors returned by .br dup2 (2) are different from those returned by .br f_dupfd . .\" .ss file locking the original linux .br fcntl () system call was not designed to handle large file offsets (in the .i flock structure). consequently, an .br fcntl64 () system call was added in linux 2.4. the newer system call employs a different structure for file locking, .ir flock64 , and corresponding commands, .br f_getlk64 , .br f_setlk64 , and .br f_setlkw64 . however, these details can be ignored by applications using glibc, whose .br fcntl () wrapper function transparently employs the more recent system call where it is available. .\" .ss record locks since kernel 2.0, there is no interaction between the types of lock placed by .br flock (2) and .br fcntl (). .pp several systems have more fields in .i "struct flock" such as, for example, .ir l_sysid (to identify the machine where the lock is held). .\" e.g., solaris 8 documents this field in fcntl(2), and irix 6.5 .\" documents it in fcntl(5). mtk, may 2007 .\" also, freebsd documents it (apr 2014). clearly, .i l_pid alone is not going to be very useful if the process holding the lock may live on a different machine; on linux, while present on some architectures (such as mips32), this field is not used. .pp the original linux .br fcntl () system call was not designed to handle large file offsets (in the .i flock structure). consequently, an .br fcntl64 () system call was added in linux 2.4. the newer system call employs a different structure for file locking, .ir flock64 , and corresponding commands, .br f_getlk64 , .br f_setlk64 , and .br f_setlkw64 . however, these details can be ignored by applications using glibc, whose .br fcntl () wrapper function transparently employs the more recent system call where it is available. .ss record locking and nfs before linux 3.12, if an nfsv4 client loses contact with the server for a period of time (defined as more than 90 seconds with no communication), .\" .\" neil brown: with nfsv3 the failure mode is the reverse. if .\" the server loses contact with a client then any lock stays in place .\" indefinitely ("why can't i read my mail"... i remember it well). .\" it might lose and regain a lock without ever being aware of the fact. (the period of time after which contact is assumed lost is known as the nfsv4 leasetime. on a linux nfs server, this can be determined by looking at .ir /proc/fs/nfsd/nfsv4leasetime , which expresses the period in seconds. the default value for this file is 90.) .\" .\" jeff layton: .\" note that this is not a firm timeout. the server runs a job .\" periodically to clean out expired stateful objects, and it's likely .\" that there is some time (maybe even up to another whole lease period) .\" between when the timeout expires and the job actually runs. if the .\" client gets a renew in there within that window, its lease will be .\" renewed and its state preserved. .\" this scenario potentially risks data corruption, since another process might acquire a lock in the intervening period and perform file i/o. .pp since linux 3.12, .\" commit ef1820f9be27b6ad158f433ab38002ab8131db4d if an nfsv4 client loses contact with the server, any i/o to the file by a process which "thinks" it holds a lock will fail until that process closes and reopens the file. a kernel parameter, .ir nfs.recover_lost_locks , can be set to 1 to obtain the pre-3.12 behavior, whereby the client will attempt to recover lost locks when contact is reestablished with the server. because of the attendant risk of data corruption, .\" commit f6de7a39c181dfb8a2c534661a53c73afb3081cd this parameter defaults to 0 (disabled). .sh bugs .ss f_setfl it is not possible to use .br f_setfl to change the state of the .br o_dsync and .br o_sync flags. .\" fixme . according to posix.1-2001, o_sync should also be modifiable .\" via fcntl(2), but currently linux does not permit this .\" see http://bugzilla.kernel.org/show_bug.cgi?id=5994 attempts to change the state of these flags are silently ignored. .ss f_getown a limitation of the linux system call conventions on some architectures (notably i386) means that if a (negative) process group id to be returned by .b f_getown falls in the range \-1 to \-4095, then the return value is wrongly interpreted by glibc as an error in the system call; .\" glibc source: sysdeps/unix/sysv/linux/i386/sysdep.h that is, the return value of .br fcntl () will be \-1, and .i errno will contain the (positive) process group id. the linux-specific .br f_getown_ex operation avoids this problem. .\" mtk, dec 04: some limited testing on alpha and ia64 seems to .\" indicate that any negative pgid value will cause f_getown .\" to misinterpret the return as an error. some other architectures .\" seem to have the same range check as i386. since glibc version 2.11, glibc makes the kernel .b f_getown problem invisible by implementing .b f_getown using .br f_getown_ex . .ss f_setown in linux 2.4 and earlier, there is bug that can occur when an unprivileged process uses .b f_setown to specify the owner of a socket file descriptor as a process (group) other than the caller. in this case, .br fcntl () can return \-1 with .i errno set to .br eperm , even when the owner process (group) is one that the caller has permission to send signals to. despite this error return, the file descriptor owner is set, and signals will be sent to the owner. .\" .ss deadlock detection the deadlock-detection algorithm employed by the kernel when dealing with .br f_setlkw requests can yield both false negatives (failures to detect deadlocks, leaving a set of deadlocked processes blocked indefinitely) and false positives .rb ( edeadlk errors when there is no deadlock). for example, the kernel limits the lock depth of its dependency search to 10 steps, meaning that circular deadlock chains that exceed that size will not be detected. in addition, the kernel may falsely indicate a deadlock when two or more processes created using the .br clone (2) .b clone_files flag place locks that appear (to the kernel) to conflict. .\" .ss mandatory locking the linux implementation of mandatory locking is subject to race conditions which render it unreliable: .\" http://marc.info/?l=linux-kernel&m=119013491707153&w=2 .\" .\" reconfirmed by jeff layton .\" from: jeff layton redhat.com> .\" subject: re: status of fcntl() mandatory locking .\" newsgroups: gmane.linux.file-systems .\" date: 2014-04-28 10:07:57 gmt .\" http://thread.gmane.org/gmane.linux.file-systems/84481/focus=84518 a .br write (2) call that overlaps with a lock may modify data after the mandatory lock is acquired; a .br read (2) call that overlaps with a lock may detect changes to data that were made only after a write lock was acquired. similar races exist between mandatory locks and .br mmap (2). it is therefore inadvisable to rely on mandatory locking. .sh see also .br dup2 (2), .br flock (2), .br open (2), .br socket (2), .br lockf (3), .br capabilities (7), .br feature_test_macros (7), .br lslocks (8) .pp .ir locks.txt , .ir mandatory\-locking.txt , and .i dnotify.txt in the linux kernel source directory .ir documentation/filesystems/ (on older kernels, these files are directly under the .i documentation/ directory, and .i mandatory\-locking.txt is called .ir mandatory.txt ) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getutent.3 .\" copyright 2000 sam varshavchik .\" and copyright (c) 2008 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references: rfc 2553 .th inet_pton 3 2021-03-22 "linux" "linux programmer's manual" .sh name inet_pton \- convert ipv4 and ipv6 addresses from text to binary form .sh synopsis .nf .b #include .pp .bi "int inet_pton(int " af ", const char *restrict " src \ ", void *restrict " dst ); .fi .sh description this function converts the character string .i src into a network address structure in the .i af address family, then copies the network address structure to .ir dst . the .i af argument must be either .b af_inet or .br af_inet6 . .ir dst is written in network byte order. .pp the following address families are currently supported: .tp .b af_inet .i src points to a character string containing an ipv4 network address in dotted-decimal format, "\fiddd.ddd.ddd.ddd\fp", where .i ddd is a decimal number of up to three digits in the range 0 to 255. the address is converted to a .i struct in_addr and copied to .ir dst , which must be .i sizeof(struct in_addr) (4) bytes (32 bits) long. .tp .b af_inet6 .i src points to a character string containing an ipv6 network address. the address is converted to a .i struct in6_addr and copied to .ir dst , which must be .i sizeof(struct in6_addr) (16) bytes (128 bits) long. the allowed formats for ipv6 addresses follow these rules: .rs .ip 1. 3 the preferred format is .ir x:x:x:x:x:x:x:x . this form consists of eight hexadecimal numbers, each of which expresses a 16-bit value (i.e., each .i x can be up to 4 hex digits). .ip 2. a series of contiguous zero values in the preferred format can be abbreviated to .ir :: . only one instance of .i :: can occur in an address. for example, the loopback address .i 0:0:0:0:0:0:0:1 can be abbreviated as .ir ::1 . the wildcard address, consisting of all zeros, can be written as .ir :: . .ip 3. an alternate format is useful for expressing ipv4-mapped ipv6 addresses. this form is written as .ir x:x:x:x:x:x:d.d.d.d , where the six leading .ir x s are hexadecimal values that define the six most-significant 16-bit pieces of the address (i.e., 96 bits), and the .ir d s express a value in dotted-decimal notation that defines the least significant 32 bits of the address. an example of such an address is .ir ::ffff:204.152.189.116 . .re .ip see rfc 2373 for further details on the representation of ipv6 addresses. .sh return value .br inet_pton () returns 1 on success (network address was successfully converted). 0 is returned if .i src does not contain a character string representing a valid network address in the specified address family. if .i af does not contain a valid address family, \-1 is returned and .i errno is set to .br eafnosupport . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br inet_pton () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes unlike .br inet_aton (3) and .br inet_addr (3), .br inet_pton () supports ipv6 addresses. on the other hand, .br inet_pton () accepts only ipv4 addresses in dotted-decimal notation, whereas .br inet_aton (3) and .br inet_addr (3) allow the more general numbers-and-dots notation (hexadecimal and octal number formats, and formats that don't require all four bytes to be explicitly written). for an interface that handles both ipv6 addresses, and ipv4 addresses in numbers-and-dots notation, see .br getaddrinfo (3). .sh bugs .b af_inet6 does not recognize ipv4 addresses. an explicit ipv4-mapped ipv6 address must be supplied in .i src instead. .sh examples the program below demonstrates the use of .br inet_pton () and .br inet_ntop (3). here are some example runs: .pp .in +4n .ex .rb "$" " ./a.out i6 0:0:0:0:0:0:0:0" :: .rb "$" " ./a.out i6 1:0:0:0:0:0:0:8" 1::8 .rb "$" " ./a.out i6 0:0:0:0:0:ffff:204.152.189.116" ::ffff:204.152.189.116 .ee .in .ss program source \& .ex #include #include #include #include int main(int argc, char *argv[]) { unsigned char buf[sizeof(struct in6_addr)]; int domain, s; char str[inet6_addrstrlen]; if (argc != 3) { fprintf(stderr, "usage: %s {i4|i6|} string\en", argv[0]); exit(exit_failure); } domain = (strcmp(argv[1], "i4") == 0) ? af_inet : (strcmp(argv[1], "i6") == 0) ? af_inet6 : atoi(argv[1]); s = inet_pton(domain, argv[2], buf); if (s <= 0) { if (s == 0) fprintf(stderr, "not in presentation format"); else perror("inet_pton"); exit(exit_failure); } if (inet_ntop(domain, buf, str, inet6_addrstrlen) == null) { perror("inet_ntop"); exit(exit_failure); } printf("%s\en", str); exit(exit_success); } .ee .sh see also .br getaddrinfo (3), .br inet (3), .br inet_ntop (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man3/cpu_set.3 .\" $openbsd: elf.5,v 1.12 2003/10/27 20:23:58 jmc exp $ .\"copyright (c) 1999 jeroen ruigrok van der werven .\"all rights reserved. .\" .\" %%%license_start(permissive_misc) .\"redistribution and use in source and binary forms, with or without .\"modification, are permitted provided that the following conditions .\"are met: .\"1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\"2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\"this software is provided by the author and contributors ``as is'' and .\"any express or implied warranties, including, but not limited to, the .\"implied warranties of merchantability and fitness for a particular purpose .\"are disclaimed. in no event shall the author or contributors be liable .\"for any direct, indirect, incidental, special, exemplary, or consequential .\"damages (including, but not limited to, procurement of substitute goods .\"or services; loss of use, data, or profits; or business interruption) .\"however caused and on any theory of liability, whether in contract, strict .\"liability, or tort (including negligence or otherwise) arising in any way .\"out of the use of this software, even if advised of the possibility of .\"such damage. .\" %%%license_end .\" .\" $freebsd: src/share/man/man5/elf.5,v 1.21 2001/10/01 16:09:23 ru exp $ .\" .\" slightly adapted - aeb, 2004-01-01 .\" 2005-07-15, mike frysinger , various fixes .\" 2007-10-11, mike frysinger , various fixes .\" 2007-12-08, mtk, converted from mdoc to man macros .\" .th elf 5 2021-03-22 "linux" "linux programmer's manual" .sh name elf \- format of executable and linking format (elf) files .sh synopsis .nf .\" .b #include .b #include .fi .sh description the header file .i defines the format of elf executable binary files. amongst these files are normal executable files, relocatable object files, core files, and shared objects. .pp an executable file using the elf file format consists of an elf header, followed by a program header table or a section header table, or both. the elf header is always at offset zero of the file. the program header table and the section header table's offset in the file are defined in the elf header. the two tables describe the rest of the particularities of the file. .pp .\" applications which wish to process elf binary files for their native .\" architecture only should include .\" .i .\" in their source code. .\" these applications should need to refer to .\" all the types and structures by their generic names .\" "elf_xxx" .\" and to the macros by .\" elf_xxx". .\" applications written this way can be compiled on any architecture, .\" regardless of whether the host is 32-bit or 64-bit. .\" .pp .\" should an application need to process elf files of an unknown .\" architecture, then the application needs to explicitly use either .\" "elf32_xxx" .\" or .\" "elf64_xxx" .\" type and structure names. .\" likewise, the macros need to be identified by .\" "elf32_xxx" .\" or .\" "elf64_xxx". .\" .pp this header file describes the above mentioned headers as c structures and also includes structures for dynamic sections, relocation sections and symbol tables. .\" .ss basic types the following types are used for n-bit architectures (n=32,64, .i elfn stands for .i elf32 or .ir elf64 , .i uintn_t stands for .i uint32_t or .ir uint64_t ): .pp .in +4n .ex elfn_addr unsigned program address, uintn_t elfn_off unsigned file offset, uintn_t elfn_section unsigned section index, uint16_t elfn_versym unsigned version symbol information, uint16_t elf_byte unsigned char elfn_half uint16_t elfn_sword int32_t elfn_word uint32_t elfn_sxword int64_t elfn_xword uint64_t .\" elf32_size unsigned object size .ee .in .pp (note: the *bsd terminology is a bit different. there, .i elf64_half is twice as large as .ir elf32_half , and .i elf64quarter is used for .ir uint16_t . in order to avoid confusion these types are replaced by explicit ones in the below.) .pp all data structures that the file format defines follow the "natural" size and alignment guidelines for the relevant class. if necessary, data structures contain explicit padding to ensure 4-byte alignment for 4-byte objects, to force structure sizes to a multiple of 4, and so on. .\" .ss elf header (ehdr) the elf header is described by the type .i elf32_ehdr or .ir elf64_ehdr : .pp .in +4n .ex #define ei_nident 16 typedef struct { unsigned char e_ident[ei_nident]; uint16_t e_type; uint16_t e_machine; uint32_t e_version; elfn_addr e_entry; elfn_off e_phoff; elfn_off e_shoff; uint32_t e_flags; uint16_t e_ehsize; uint16_t e_phentsize; uint16_t e_phnum; uint16_t e_shentsize; uint16_t e_shnum; uint16_t e_shstrndx; } elfn_ehdr; .ee .in .pp the fields have the following meanings: .\" .\" .tp .ir e_ident this array of bytes specifies how to interpret the file, independent of the processor or the file's remaining contents. within this array everything is named by macros, which start with the prefix .br ei_ and may contain values which start with the prefix .br elf . the following macros are defined: .rs .tp .br ei_mag0 the first byte of the magic number. it must be filled with .br elfmag0 . (0: 0x7f) .tp .br ei_mag1 the second byte of the magic number. it must be filled with .br elfmag1 . (1: \(aqe\(aq) .tp .br ei_mag2 the third byte of the magic number. it must be filled with .br elfmag2 . (2: \(aql\(aq) .tp .br ei_mag3 the fourth byte of the magic number. it must be filled with .br elfmag3 . (3: \(aqf\(aq) .tp .br ei_class the fifth byte identifies the architecture for this binary: .rs .tp 14 .pd 0 .br elfclassnone this class is invalid. .tp .br elfclass32 this defines the 32-bit architecture. it supports machines with files and virtual address spaces up to 4 gigabytes. .tp .br elfclass64 this defines the 64-bit architecture. .pd .re .tp .br ei_data the sixth byte specifies the data encoding of the processor-specific data in the file. currently, these encodings are supported: .rs 9 .tp 14 .pd 0 .br elfdatanone unknown data format. .tp .br elfdata2lsb two's complement, little-endian. .tp .br elfdata2msb two's complement, big-endian. .pd .re .tp .br ei_version the seventh byte is the version number of the elf specification: .ip .pd 0 .rs .tp 14 .br ev_none invalid version. .tp .br ev_current current version. .pd .re .\".el .tp .br ei_osabi the eighth byte identifies the operating system and abi to which the object is targeted. some fields in other elf structures have flags and values that have platform-specific meanings; the interpretation of those fields is determined by the value of this byte. for example: .rs .tp 21 .pd 0 .br elfosabi_none same as elfosabi_sysv .\" 0 .tp .br elfosabi_sysv unix system v abi .\" 0 .\" synonym: elfosabi_none .tp .br elfosabi_hpux hp-ux abi .\" 1 .tp .br elfosabi_netbsd netbsd abi .\" 2 .tp .br elfosabi_linux linux abi .\" 3 .\" .tp .\" .br elfosabi_hurd .\" hurd abi .\" 4 .\" .tp .\" .br elfosabi_86open .\" 86open common ia32 abi .\" 5 .tp .br elfosabi_solaris solaris abi .\" 6 .\" .tp .\" .br elfosabi_monterey .\" monterey project abi .\" now replaced by .\" elfosabi_aix .\" 7 .tp .br elfosabi_irix irix abi .\" 8 .tp .br elfosabi_freebsd freebsd abi .\" 9 .tp .br elfosabi_tru64 tru64 unix abi .\" 10 .\" elfosabi_modesto .\" 11 .\" elfosabi_openbsd .\" 12 .tp .br elfosabi_arm arm architecture abi .\" 97 .tp .br elfosabi_standalone stand-alone (embedded) abi .\" 255 .pd .re .tp .br ei_abiversion the ninth byte identifies the version of the abi to which the object is targeted. this field is used to distinguish among incompatible versions of an abi. the interpretation of this version number is dependent on the abi identified by the .b ei_osabi field. applications conforming to this specification use the value 0. .tp .br ei_pad start of padding. these bytes are reserved and set to zero. programs which read them should ignore them. the value for .b ei_pad will change in the future if currently unused bytes are given meanings. .\" as reported by yuri kozlov and confirmed by mike frysinger, ei_brand is .\" not in gabi (http://www.sco.com/developers/gabi/latest/ch4.eheader.html) .\" it looks to be a bsdism .\" .tp .\" .br ei_brand .\" start of architecture identification. .tp .br ei_nident the size of the .i e_ident array. .re .tp .ir e_type this member of the structure identifies the object file type: .rs .tp 16 .pd 0 .br et_none an unknown type. .tp .br et_rel a relocatable file. .tp .br et_exec an executable file. .tp .br et_dyn a shared object. .tp .br et_core a core file. .pd .re .tp .ir e_machine this member specifies the required architecture for an individual file. for example: .rs .tp 16 .pd 0 .br em_none an unknown machine .\" 0 .tp .br em_m32 at&t we 32100 .\" 1 .tp .br em_sparc sun microsystems sparc .\" 2 .tp .br em_386 intel 80386 .\" 3 .tp .br em_68k motorola 68000 .\" 4 .tp .br em_88k motorola 88000 .\" 5 .\" .tp .\" .br em_486 .\" intel 80486 .\" 6 .tp .br em_860 intel 80860 .\" 7 .tp .br em_mips mips rs3000 (big-endian only) .\" 8 .\" em_s370 .\" 9 .\" .tp .\" .br em_mips_rs4_be .\" mips rs4000 (big-endian only). deprecated .\" 10 .\" em_mips_rs3_le (mips r3000 little-endian) .\" 10 .tp .br em_parisc hp/pa .\" 15 .tp .br em_sparc32plus sparc with enhanced instruction set .\" 18 .tp .br em_ppc powerpc .\" 20 .tp .br em_ppc64 powerpc 64-bit .\" 21 .tp .br em_s390 ibm s/390 .\" 22 .tp .br em_arm advanced risc machines .\" 40 .tp .br em_sh renesas superh .\" 42 .tp .br em_sparcv9 sparc v9 64-bit .\" 43 .tp .br em_ia_64 intel itanium .\" 50 .tp .br em_x86_64 amd x86-64 .\" 62 .tp .br em_vax dec vax .\" 75 .\" em_cris .\" 76 .\" .tp .\" .br em_alpha .\" compaq [dec] alpha .\" .tp .\" .br em_alpha_exp .\" compaq [dec] alpha with enhanced instruction set .pd .re .tp .ir e_version this member identifies the file version: .rs .tp 16 .pd 0 .br ev_none invalid version .tp .br ev_current current version .pd .re .tp .ir e_entry this member gives the virtual address to which the system first transfers control, thus starting the process. if the file has no associated entry point, this member holds zero. .tp .ir e_phoff this member holds the program header table's file offset in bytes. if the file has no program header table, this member holds zero. .tp .ir e_shoff this member holds the section header table's file offset in bytes. if the file has no section header table, this member holds zero. .tp .ir e_flags this member holds processor-specific flags associated with the file. flag names take the form ef_`machine_flag'. currently, no flags have been defined. .tp .ir e_ehsize this member holds the elf header's size in bytes. .tp .ir e_phentsize this member holds the size in bytes of one entry in the file's program header table; all entries are the same size. .tp .ir e_phnum this member holds the number of entries in the program header table. thus the product of .ir e_phentsize and .ir e_phnum gives the table's size in bytes. if a file has no program header, .ir e_phnum holds the value zero. .ip if the number of entries in the program header table is larger than or equal to .\" this is a linux extension, added in linux 2.6.34. .br pn_xnum (0xffff), this member holds .br pn_xnum (0xffff) and the real number of entries in the program header table is held in the .ir sh_info member of the initial entry in section header table. otherwise, the .ir sh_info member of the initial entry contains the value zero. .rs .tp .br pn_xnum this is defined as 0xffff, the largest number .ir e_phnum can have, specifying where the actual number of program headers is assigned. .pd .re .tp .ir e_shentsize this member holds a sections header's size in bytes. a section header is one entry in the section header table; all entries are the same size. .tp .ir e_shnum this member holds the number of entries in the section header table. thus the product of .ir e_shentsize and .ir e_shnum gives the section header table's size in bytes. if a file has no section header table, .ir e_shnum holds the value of zero. .ip if the number of entries in the section header table is larger than or equal to .br shn_loreserve (0xff00), .ir e_shnum holds the value zero and the real number of entries in the section header table is held in the .ir sh_size member of the initial entry in section header table. otherwise, the .ir sh_size member of the initial entry in the section header table holds the value zero. .tp .ir e_shstrndx this member holds the section header table index of the entry associated with the section name string table. if the file has no section name string table, this member holds the value .br shn_undef . .ip if the index of section name string table section is larger than or equal to .br shn_loreserve (0xff00), this member holds .br shn_xindex (0xffff) and the real index of the section name string table section is held in the .ir sh_link member of the initial entry in section header table. otherwise, the .ir sh_link member of the initial entry in section header table contains the value zero. .\" .ss program header (phdr) an executable or shared object file's program header table is an array of structures, each describing a segment or other information the system needs to prepare the program for execution. an object file .ir segment contains one or more .ir sections . program headers are meaningful only for executable and shared object files. a file specifies its own program header size with the elf header's .ir e_phentsize and .ir e_phnum members. the elf program header is described by the type .i elf32_phdr or .i elf64_phdr depending on the architecture: .pp .in +4n .ex typedef struct { uint32_t p_type; elf32_off p_offset; elf32_addr p_vaddr; elf32_addr p_paddr; uint32_t p_filesz; uint32_t p_memsz; uint32_t p_flags; uint32_t p_align; } elf32_phdr; .ee .in .pp .in +4n .ex typedef struct { uint32_t p_type; uint32_t p_flags; elf64_off p_offset; elf64_addr p_vaddr; elf64_addr p_paddr; uint64_t p_filesz; uint64_t p_memsz; uint64_t p_align; } elf64_phdr; .ee .in .pp the main difference between the 32-bit and the 64-bit program header lies in the location of the .ir p_flags member in the total struct. .tp .ir p_type this member of the structure indicates what kind of segment this array element describes or how to interpret the array element's information. .rs 10 .tp .br pt_null the array element is unused and the other members' values are undefined. this lets the program header have ignored entries. .tp .br pt_load the array element specifies a loadable segment, described by .ir p_filesz and .ir p_memsz . the bytes from the file are mapped to the beginning of the memory segment. if the segment's memory size .ir p_memsz is larger than the file size .ir p_filesz , the "extra" bytes are defined to hold the value 0 and to follow the segment's initialized area. the file size may not be larger than the memory size. loadable segment entries in the program header table appear in ascending order, sorted on the .ir p_vaddr member. .tp .br pt_dynamic the array element specifies dynamic linking information. .tp .br pt_interp the array element specifies the location and size of a null-terminated pathname to invoke as an interpreter. this segment type is meaningful only for executable files (though it may occur for shared objects). however it may not occur more than once in a file. if it is present, it must precede any loadable segment entry. .tp .br pt_note the array element specifies the location of notes (elfn_nhdr). .tp .br pt_shlib this segment type is reserved but has unspecified semantics. programs that contain an array element of this type do not conform to the abi. .tp .br pt_phdr the array element, if present, specifies the location and size of the program header table itself, both in the file and in the memory image of the program. this segment type may not occur more than once in a file. moreover, it may occur only if the program header table is part of the memory image of the program. if it is present, it must precede any loadable segment entry. .tp .br pt_loproc ", " pt_hiproc values in the inclusive range .rb [ pt_loproc ", " pt_hiproc ] are reserved for processor-specific semantics. .tp .br pt_gnu_stack gnu extension which is used by the linux kernel to control the state of the stack via the flags set in the .ir p_flags member. .re .tp .ir p_offset this member holds the offset from the beginning of the file at which the first byte of the segment resides. .tp .ir p_vaddr this member holds the virtual address at which the first byte of the segment resides in memory. .tp .ir p_paddr on systems for which physical addressing is relevant, this member is reserved for the segment's physical address. under bsd this member is not used and must be zero. .tp .ir p_filesz this member holds the number of bytes in the file image of the segment. it may be zero. .tp .ir p_memsz this member holds the number of bytes in the memory image of the segment. it may be zero. .tp .ir p_flags this member holds a bit mask of flags relevant to the segment: .rs .tp .pd 0 .br pf_x an executable segment. .tp .br pf_w a writable segment. .tp .br pf_r a readable segment. .pd .re .ip a text segment commonly has the flags .br pf_x and .br pf_r . a data segment commonly has .br pf_w and .br pf_r . .tp .ir p_align this member holds the value to which the segments are aligned in memory and in the file. loadable process segments must have congruent values for .ir p_vaddr and .ir p_offset , modulo the page size. values of zero and one mean no alignment is required. otherwise, .ir p_align should be a positive, integral power of two, and .ir p_vaddr should equal .ir p_offset , modulo .ir p_align . .\" .ss section header (shdr) a file's section header table lets one locate all the file's sections. the section header table is an array of .i elf32_shdr or .i elf64_shdr structures. the elf header's .ir e_shoff member gives the byte offset from the beginning of the file to the section header table. .ir e_shnum holds the number of entries the section header table contains. .ir e_shentsize holds the size in bytes of each entry. .pp a section header table index is a subscript into this array. some section header table indices are reserved: the initial entry and the indices between .b shn_loreserve and .br shn_hireserve . the initial entry is used in elf extensions for .ir e_phnum , .ir e_shnum , and .ir e_shstrndx ; in other cases, each field in the initial entry is set to zero. an object file does not have sections for these special indices: .tp .br shn_undef this value marks an undefined, missing, irrelevant, or otherwise meaningless section reference. .tp .br shn_loreserve this value specifies the lower bound of the range of reserved indices. .tp .br shn_loproc ", " shn_hiproc values greater in the inclusive range .rb [ shn_loproc ", " shn_hiproc ] are reserved for processor-specific semantics. .tp .br shn_abs this value specifies the absolute value for the corresponding reference. for example, a symbol defined relative to section number .br shn_abs has an absolute value and is not affected by relocation. .tp .br shn_common symbols defined relative to this section are common symbols, such as fortran common or unallocated c external variables. .tp .br shn_hireserve this value specifies the upper bound of the range of reserved indices. the system reserves indices between .br shn_loreserve and .br shn_hireserve , inclusive. the section header table does not contain entries for the reserved indices. .pp the section header has the following structure: .pp .in +4n .ex typedef struct { uint32_t sh_name; uint32_t sh_type; uint32_t sh_flags; elf32_addr sh_addr; elf32_off sh_offset; uint32_t sh_size; uint32_t sh_link; uint32_t sh_info; uint32_t sh_addralign; uint32_t sh_entsize; } elf32_shdr; .ee .in .pp .in +4n .ex typedef struct { uint32_t sh_name; uint32_t sh_type; uint64_t sh_flags; elf64_addr sh_addr; elf64_off sh_offset; uint64_t sh_size; uint32_t sh_link; uint32_t sh_info; uint64_t sh_addralign; uint64_t sh_entsize; } elf64_shdr; .ee .in .pp no real differences exist between the 32-bit and 64-bit section headers. .tp .ir sh_name this member specifies the name of the section. its value is an index into the section header string table section, giving the location of a null-terminated string. .tp .ir sh_type this member categorizes the section's contents and semantics. .rs .tp .br sht_null this value marks the section header as inactive. it does not have an associated section. other members of the section header have undefined values. .tp .br sht_progbits this section holds information defined by the program, whose format and meaning are determined solely by the program. .tp .br sht_symtab this section holds a symbol table. typically, .br sht_symtab provides symbols for link editing, though it may also be used for dynamic linking. as a complete symbol table, it may contain many symbols unnecessary for dynamic linking. an object file can also contain a .br sht_dynsym section. .tp .br sht_strtab this section holds a string table. an object file may have multiple string table sections. .tp .br sht_rela this section holds relocation entries with explicit addends, such as type .ir elf32_rela for the 32-bit class of object files. an object may have multiple relocation sections. .tp .br sht_hash this section holds a symbol hash table. an object participating in dynamic linking must contain a symbol hash table. an object file may have only one hash table. .tp .br sht_dynamic this section holds information for dynamic linking. an object file may have only one dynamic section. .tp .br sht_note this section holds notes (elfn_nhdr). .tp .br sht_nobits a section of this type occupies no space in the file but otherwise resembles .br sht_progbits . although this section contains no bytes, the .ir sh_offset member contains the conceptual file offset. .tp .br sht_rel this section holds relocation offsets without explicit addends, such as type .ir elf32_rel for the 32-bit class of object files. an object file may have multiple relocation sections. .tp .br sht_shlib this section is reserved but has unspecified semantics. .tp .br sht_dynsym this section holds a minimal set of dynamic linking symbols. an object file can also contain a .br sht_symtab section. .tp .br sht_loproc ", " sht_hiproc values in the inclusive range .rb [ sht_loproc ", " sht_hiproc ] are reserved for processor-specific semantics. .tp .br sht_louser this value specifies the lower bound of the range of indices reserved for application programs. .tp .br sht_hiuser this value specifies the upper bound of the range of indices reserved for application programs. section types between .br sht_louser and .br sht_hiuser may be used by the application, without conflicting with current or future system-defined section types. .re .tp .ir sh_flags sections support one-bit flags that describe miscellaneous attributes. if a flag bit is set in .ir sh_flags , the attribute is "on" for the section. otherwise, the attribute is "off" or does not apply. undefined attributes are set to zero. .rs .tp .br shf_write this section contains data that should be writable during process execution. .tp .br shf_alloc this section occupies memory during process execution. some control sections do not reside in the memory image of an object file. this attribute is off for those sections. .tp .br shf_execinstr this section contains executable machine instructions. .tp .br shf_maskproc all bits included in this mask are reserved for processor-specific semantics. .re .tp .ir sh_addr if this section appears in the memory image of a process, this member holds the address at which the section's first byte should reside. otherwise, the member contains zero. .tp .ir sh_offset this member's value holds the byte offset from the beginning of the file to the first byte in the section. one section type, .br sht_nobits , occupies no space in the file, and its .ir sh_offset member locates the conceptual placement in the file. .tp .ir sh_size this member holds the section's size in bytes. unless the section type is .br sht_nobits , the section occupies .ir sh_size bytes in the file. a section of type .br sht_nobits may have a nonzero size, but it occupies no space in the file. .tp .ir sh_link this member holds a section header table index link, whose interpretation depends on the section type. .tp .ir sh_info this member holds extra information, whose interpretation depends on the section type. .tp .ir sh_addralign some sections have address alignment constraints. if a section holds a doubleword, the system must ensure doubleword alignment for the entire section. that is, the value of .ir sh_addr must be congruent to zero, modulo the value of .ir sh_addralign . only zero and positive integral powers of two are allowed. the value 0 or 1 means that the section has no alignment constraints. .tp .ir sh_entsize some sections hold a table of fixed-sized entries, such as a symbol table. for such a section, this member gives the size in bytes for each entry. this member contains zero if the section does not hold a table of fixed-size entries. .pp various sections hold program and control information: .tp .ir .bss this section holds uninitialized data that contributes to the program's memory image. by definition, the system initializes the data with zeros when the program begins to run. this section is of type .br sht_nobits . the attribute types are .br shf_alloc and .br shf_write . .tp .ir .comment this section holds version control information. this section is of type .br sht_progbits . no attribute types are used. .tp .ir .ctors this section holds initialized pointers to the c++ constructor functions. this section is of type .br sht_progbits . the attribute types are .br shf_alloc and .br shf_write . .tp .ir .data this section holds initialized data that contribute to the program's memory image. this section is of type .br sht_progbits . the attribute types are .br shf_alloc and .br shf_write . .tp .ir .data1 this section holds initialized data that contribute to the program's memory image. this section is of type .br sht_progbits . the attribute types are .br shf_alloc and .br shf_write . .tp .ir .debug this section holds information for symbolic debugging. the contents are unspecified. this section is of type .br sht_progbits . no attribute types are used. .tp .ir .dtors this section holds initialized pointers to the c++ destructor functions. this section is of type .br sht_progbits . the attribute types are .br shf_alloc and .br shf_write . .tp .ir .dynamic this section holds dynamic linking information. the section's attributes will include the .br shf_alloc bit. whether the .br shf_write bit is set is processor-specific. this section is of type .br sht_dynamic . see the attributes above. .tp .ir .dynstr this section holds strings needed for dynamic linking, most commonly the strings that represent the names associated with symbol table entries. this section is of type .br sht_strtab . the attribute type used is .br shf_alloc . .tp .ir .dynsym this section holds the dynamic linking symbol table. this section is of type .br sht_dynsym . the attribute used is .br shf_alloc . .tp .ir .fini this section holds executable instructions that contribute to the process termination code. when a program exits normally the system arranges to execute the code in this section. this section is of type .br sht_progbits . the attributes used are .br shf_alloc and .br shf_execinstr . .tp .ir .gnu.version this section holds the version symbol table, an array of .i elfn_half elements. this section is of type .br sht_gnu_versym . the attribute type used is .br shf_alloc . .tp .ir .gnu.version_d this section holds the version symbol definitions, a table of .i elfn_verdef structures. this section is of type .br sht_gnu_verdef . the attribute type used is .br shf_alloc . .tp .ir .gnu.version_r this section holds the version symbol needed elements, a table of .i elfn_verneed structures. this section is of type .br sht_gnu_versym . the attribute type used is .br shf_alloc . .tp .ir .got this section holds the global offset table. this section is of type .br sht_progbits . the attributes are processor-specific. .tp .ir .hash this section holds a symbol hash table. this section is of type .br sht_hash . the attribute used is .br shf_alloc . .tp .ir .init this section holds executable instructions that contribute to the process initialization code. when a program starts to run the system arranges to execute the code in this section before calling the main program entry point. this section is of type .br sht_progbits . the attributes used are .br shf_alloc and .br shf_execinstr . .tp .ir .interp this section holds the pathname of a program interpreter. if the file has a loadable segment that includes the section, the section's attributes will include the .br shf_alloc bit. otherwise, that bit will be off. this section is of type .br sht_progbits . .tp .ir .line this section holds line number information for symbolic debugging, which describes the correspondence between the program source and the machine code. the contents are unspecified. this section is of type .br sht_progbits . no attribute types are used. .tp .ir .note this section holds various notes. this section is of type .br sht_note . no attribute types are used. .tp .ir .note.abi\-tag this section is used to declare the expected run-time abi of the elf image. it may include the operating system name and its run-time versions. this section is of type .br sht_note . the only attribute used is .br shf_alloc . .tp .ir .note.gnu.build\-id this section is used to hold an id that uniquely identifies the contents of the elf image. different files with the same build id should contain the same executable content. see the .br \-\-build\-id option to the gnu linker (\fbld\fr (1)) for more details. this section is of type .br sht_note . the only attribute used is .br shf_alloc . .tp .ir .note.gnu\-stack this section is used in linux object files for declaring stack attributes. this section is of type .br sht_progbits . the only attribute used is .br shf_execinstr . this indicates to the gnu linker that the object file requires an executable stack. .tp .ir .note.openbsd.ident openbsd native executables usually contain this section to identify themselves so the kernel can bypass any compatibility elf binary emulation tests when loading the file. .tp .ir .plt this section holds the procedure linkage table. this section is of type .br sht_progbits . the attributes are processor-specific. .tp .ir .relname this section holds relocation information as described below. if the file has a loadable segment that includes relocation, the section's attributes will include the .br shf_alloc bit. otherwise, the bit will be off. by convention, "name" is supplied by the section to which the relocations apply. thus a relocation section for .br .text normally would have the name .br .rel.text . this section is of type .br sht_rel . .tp .ir .relaname this section holds relocation information as described below. if the file has a loadable segment that includes relocation, the section's attributes will include the .br shf_alloc bit. otherwise, the bit will be off. by convention, "name" is supplied by the section to which the relocations apply. thus a relocation section for .br .text normally would have the name .br .rela.text . this section is of type .br sht_rela . .tp .ir .rodata this section holds read-only data that typically contributes to a nonwritable segment in the process image. this section is of type .br sht_progbits . the attribute used is .br shf_alloc . .tp .ir .rodata1 this section holds read-only data that typically contributes to a nonwritable segment in the process image. this section is of type .br sht_progbits . the attribute used is .br shf_alloc . .tp .ir .shstrtab this section holds section names. this section is of type .br sht_strtab . no attribute types are used. .tp .ir .strtab this section holds strings, most commonly the strings that represent the names associated with symbol table entries. if the file has a loadable segment that includes the symbol string table, the section's attributes will include the .br shf_alloc bit. otherwise, the bit will be off. this section is of type .br sht_strtab . .tp .ir .symtab this section holds a symbol table. if the file has a loadable segment that includes the symbol table, the section's attributes will include the .br shf_alloc bit. otherwise, the bit will be off. this section is of type .br sht_symtab . .tp .ir .text this section holds the "text", or executable instructions, of a program. this section is of type .br sht_progbits . the attributes used are .br shf_alloc and .br shf_execinstr . .\" .ss string and symbol tables string table sections hold null-terminated character sequences, commonly called strings. the object file uses these strings to represent symbol and section names. one references a string as an index into the string table section. the first byte, which is index zero, is defined to hold a null byte (\(aq\e0\(aq). similarly, a string table's last byte is defined to hold a null byte, ensuring null termination for all strings. .pp an object file's symbol table holds information needed to locate and relocate a program's symbolic definitions and references. a symbol table index is a subscript into this array. .pp .in +4n .ex typedef struct { uint32_t st_name; elf32_addr st_value; uint32_t st_size; unsigned char st_info; unsigned char st_other; uint16_t st_shndx; } elf32_sym; .ee .in .pp .in +4n .ex typedef struct { uint32_t st_name; unsigned char st_info; unsigned char st_other; uint16_t st_shndx; elf64_addr st_value; uint64_t st_size; } elf64_sym; .ee .in .pp the 32-bit and 64-bit versions have the same members, just in a different order. .tp .ir st_name this member holds an index into the object file's symbol string table, which holds character representations of the symbol names. if the value is nonzero, it represents a string table index that gives the symbol name. otherwise, the symbol has no name. .tp .ir st_value this member gives the value of the associated symbol. .tp .ir st_size many symbols have associated sizes. this member holds zero if the symbol has no size or an unknown size. .tp .ir st_info this member specifies the symbol's type and binding attributes: .rs .tp .br stt_notype the symbol's type is not defined. .tp .br stt_object the symbol is associated with a data object. .tp .br stt_func the symbol is associated with a function or other executable code. .tp .br stt_section the symbol is associated with a section. symbol table entries of this type exist primarily for relocation and normally have .br stb_local bindings. .tp .br stt_file by convention, the symbol's name gives the name of the source file associated with the object file. a file symbol has .br stb_local bindings, its section index is .br shn_abs , and it precedes the other .br stb_local symbols of the file, if it is present. .tp .br stt_loproc ", " stt_hiproc values in the inclusive range .rb [ stt_loproc ", " stt_hiproc ] are reserved for processor-specific semantics. .tp .br stb_local local symbols are not visible outside the object file containing their definition. local symbols of the same name may exist in multiple files without interfering with each other. .tp .br stb_global global symbols are visible to all object files being combined. one file's definition of a global symbol will satisfy another file's undefined reference to the same symbol. .tp .br stb_weak weak symbols resemble global symbols, but their definitions have lower precedence. .tp .br stb_loproc ", " stb_hiproc values in the inclusive range .rb [ stb_loproc ", " stb_hiproc ] are reserved for processor-specific semantics. .re .ip there are macros for packing and unpacking the binding and type fields: .rs .tp .br elf32_st_bind( \fiinfo\fp ) ", " elf64_st_bind( \fiinfo\fp ) extract a binding from an .i st_info value. .tp .br elf32_st_type( \fiinfo ) ", " elf64_st_type( \fiinfo\fp ) extract a type from an .i st_info value. .tp .br elf32_st_info( \fibind\fp ", " \fitype\fp ) ", " \ elf64_st_info( \fibind\fp ", " \fitype\fp ) convert a binding and a type into an .i st_info value. .re .tp .ir st_other this member defines the symbol visibility. .rs .tp .pd 0 .br stv_default default symbol visibility rules. global and weak symbols are available to other modules; references in the local module can be interposed by definitions in other modules. .tp .br stv_internal processor-specific hidden class. .tp .br stv_hidden symbol is unavailable to other modules; references in the local module always resolve to the local symbol (i.e., the symbol can't be interposed by definitions in other modules). .tp .br stv_protected symbol is available to other modules, but references in the local module always resolve to the local symbol. .pd .pp there are macros for extracting the visibility type: .pp .br elf32_st_visibility (other) or .br elf64_st_visibility (other) .re .tp .ir st_shndx every symbol table entry is "defined" in relation to some section. this member holds the relevant section header table index. .\" .ss relocation entries (rel & rela) relocation is the process of connecting symbolic references with symbolic definitions. relocatable files must have information that describes how to modify their section contents, thus allowing executable and shared object files to hold the right information for a process's program image. relocation entries are these data. .pp relocation structures that do not need an addend: .pp .in +4n .ex typedef struct { elf32_addr r_offset; uint32_t r_info; } elf32_rel; .ee .in .pp .in +4n .ex typedef struct { elf64_addr r_offset; uint64_t r_info; } elf64_rel; .ee .in .pp relocation structures that need an addend: .pp .in +4n .ex typedef struct { elf32_addr r_offset; uint32_t r_info; int32_t r_addend; } elf32_rela; .ee .in .pp .in +4n .ex typedef struct { elf64_addr r_offset; uint64_t r_info; int64_t r_addend; } elf64_rela; .ee .in .tp .ir r_offset this member gives the location at which to apply the relocation action. for a relocatable file, the value is the byte offset from the beginning of the section to the storage unit affected by the relocation. for an executable file or shared object, the value is the virtual address of the storage unit affected by the relocation. .tp .ir r_info this member gives both the symbol table index with respect to which the relocation must be made and the type of relocation to apply. relocation types are processor-specific. when the text refers to a relocation entry's relocation type or symbol table index, it means the result of applying .br elf[32|64]_r_type or .br elf[32|64]_r_sym , respectively, to the entry's .ir r_info member. .tp .ir r_addend this member specifies a constant addend used to compute the value to be stored into the relocatable field. .\" .ss dynamic tags (dyn) the .i .dynamic section contains a series of structures that hold relevant dynamic linking information. the .i d_tag member controls the interpretation of .ir d_un . .pp .in +4n .ex typedef struct { elf32_sword d_tag; union { elf32_word d_val; elf32_addr d_ptr; } d_un; } elf32_dyn; extern elf32_dyn _dynamic[]; .ee .in .pp .in +4n .ex typedef struct { elf64_sxword d_tag; union { elf64_xword d_val; elf64_addr d_ptr; } d_un; } elf64_dyn; extern elf64_dyn _dynamic[]; .ee .in .tp .ir d_tag this member may have any of the following values: .rs .tp 12 .br dt_null marks end of dynamic section .tp .br dt_needed string table offset to name of a needed library .tp .br dt_pltrelsz size in bytes of plt relocation entries .tp .br dt_pltgot address of plt and/or got .tp .br dt_hash address of symbol hash table .tp .br dt_strtab address of string table .tp .br dt_symtab address of symbol table .tp .br dt_rela address of rela relocation table .tp .br dt_relasz size in bytes of the rela relocation table .tp .br dt_relaent size in bytes of a rela relocation table entry .tp .br dt_strsz size in bytes of string table .tp .br dt_syment size in bytes of a symbol table entry .tp .br dt_init address of the initialization function .tp .br dt_fini address of the termination function .tp .br dt_soname string table offset to name of shared object .tp .br dt_rpath string table offset to library search path (deprecated) .tp .br dt_symbolic alert linker to search this shared object before the executable for symbols .tp .br dt_rel address of rel relocation table .tp .br dt_relsz size in bytes of rel relocation table .tp .br dt_relent size in bytes of a rel table entry .tp .br dt_pltrel type of relocation entry to which the plt refers (rela or rel) .tp .br dt_debug undefined use for debugging .tp .br dt_textrel absence of this entry indicates that no relocation entries should apply to a nonwritable segment .tp .br dt_jmprel address of relocation entries associated solely with the plt .tp .br dt_bind_now instruct dynamic linker to process all relocations before transferring control to the executable .tp .br dt_runpath string table offset to library search path .tp .br dt_loproc ", " dt_hiproc values in the inclusive range .rb [ dt_loproc ", " dt_hiproc ] are reserved for processor-specific semantics .re .tp .ir d_val this member represents integer values with various interpretations. .tp .ir d_ptr this member represents program virtual addresses. when interpreting these addresses, the actual address should be computed based on the original file value and memory base address. files do not contain relocation entries to fixup these addresses. .tp .i _dynamic array containing all the dynamic structures in the .i .dynamic section. this is automatically populated by the linker. .\" gabi elf reference for note sections: .\" http://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section .\" .\" note that it implies the sizes and alignments of notes depend on the elf .\" size (e.g. 32-bit elfs have three 4-byte words and use 4-byte alignment .\" while 64-bit elfs use 8-byte words & alignment), but that is not the case .\" in the real world. notes always have three 4-byte words as can be seen .\" in the source links below (remember that elf64_word is a 32-bit quantity). .\" glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=9e59b3275917549af0cebe1f2de9ded3b7b10bf2#l1173 .\" binutils: https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=binutils/readelf.c;h=274ddd17266aef6e4ad1f67af8a13a21500ff2af#l15943 .\" linux: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/elf.h?h=v4.8#n422 .\" solaris: https://docs.oracle.com/cd/e23824_01/html/819-0690/chapter6-18048.html .\" freebsd: https://svnweb.freebsd.org/base/head/sys/sys/elf_common.h?revision=303677&view=markup#l33 .\" netbsd: https://www.netbsd.org/docs/kernel/elf-notes.html .\" openbsd: https://github.com/openbsd/src/blob/master/sys/sys/exec_elf.h#l533 .\" .ss notes (nhdr) elf notes allow for appending arbitrary information for the system to use. they are largely used by core files .ri ( e_type of .br et_core ), but many projects define their own set of extensions. for example, the gnu tool chain uses elf notes to pass information from the linker to the c library. .pp note sections contain a series of notes (see the .i struct definitions below). each note is followed by the name field (whose length is defined in \fin_namesz\fr) and then by the descriptor field (whose length is defined in \fin_descsz\fr) and whose starting address has a 4 byte alignment. neither field is defined in the note struct due to their arbitrary lengths. .pp an example for parsing out two consecutive notes should clarify their layout in memory: .pp .in +4n .ex void *memory, *name, *desc; elf64_nhdr *note, *next_note; /* the buffer is pointing to the start of the section/segment. */ note = memory; /* if the name is defined, it follows the note. */ name = note\->n_namesz == 0 ? null : memory + sizeof(*note); /* if the descriptor is defined, it follows the name (with alignment). */ desc = note\->n_descsz == 0 ? null : memory + sizeof(*note) + align_up(note\->n_namesz, 4); /* the next note follows both (with alignment). */ next_note = memory + sizeof(*note) + align_up(note\->n_namesz, 4) + align_up(note\->n_descsz, 4); .ee .in .pp keep in mind that the interpretation of .i n_type depends on the namespace defined by the .i n_namesz field. if the .i n_namesz field is not set (e.g., is 0), then there are two sets of notes: one for core files and one for all other elf types. if the namespace is unknown, then tools will usually fallback to these sets of notes as well. .pp .in +4n .ex typedef struct { elf32_word n_namesz; elf32_word n_descsz; elf32_word n_type; } elf32_nhdr; .ee .in .pp .in +4n .ex typedef struct { elf64_word n_namesz; elf64_word n_descsz; elf64_word n_type; } elf64_nhdr; .ee .in .tp .ir n_namesz the length of the name field in bytes. the contents will immediately follow this note in memory. the name is null terminated. for example, if the name is "gnu", then .i n_namesz will be set to 4. .tp .ir n_descsz the length of the descriptor field in bytes. the contents will immediately follow the name field in memory. .tp .ir n_type depending on the value of the name field, this member may have any of the following values: .rs .tp 5 .b core files (e_type = et_core) notes used by all core files. these are highly operating system or architecture specific and often require close coordination with kernels, c libraries, and debuggers. these are used when the namespace is the default (i.e., .i n_namesz will be set to 0), or a fallback when the namespace is unknown. .rs .tp 21 .pd 0 .b nt_prstatus prstatus struct .tp .b nt_fpregset fpregset struct .tp .b nt_prpsinfo prpsinfo struct .tp .b nt_prxreg prxregset struct .tp .b nt_taskstruct task structure .tp .b nt_platform string from sysinfo(si_platform) .tp .b nt_auxv auxv array .tp .b nt_gwindows gwindows struct .tp .b nt_asrs asrset struct .tp .b nt_pstatus pstatus struct .tp .b nt_psinfo psinfo struct .tp .b nt_prcred prcred struct .tp .b nt_utsname utsname struct .tp .b nt_lwpstatus lwpstatus struct .tp .b nt_lwpsinfo lwpinfo struct .tp .b nt_prfpxreg fprxregset struct .tp .b nt_siginfo siginfo_t (size might increase over time) .tp .b nt_file contains information about mapped files .tp .b nt_prxfpreg user_fxsr_struct .tp .b nt_ppc_vmx powerpc altivec/vmx registers .tp .b nt_ppc_spe powerpc spe/evr registers .tp .b nt_ppc_vsx powerpc vsx registers .tp .b nt_386_tls i386 tls slots (struct user_desc) .tp .b nt_386_ioperm x86 io permission bitmap (1=deny) .tp .b nt_x86_xstate x86 extended state using xsave .tp .b nt_s390_high_gprs s390 upper register halves .tp .b nt_s390_timer s390 timer register .tp .b nt_s390_todcmp s390 time-of-day (tod) clock comparator register .tp .b nt_s390_todpreg s390 time-of-day (tod) programmable register .tp .b nt_s390_ctrs s390 control registers .tp .b nt_s390_prefix s390 prefix register .tp .b nt_s390_last_break s390 breaking event address .tp .b nt_s390_system_call s390 system call restart data .tp .b nt_s390_tdb s390 transaction diagnostic block .tp .b nt_arm_vfp arm vfp/neon registers .tp .b nt_arm_tls arm tls register .tp .b nt_arm_hw_break arm hardware breakpoint registers .tp .b nt_arm_hw_watch arm hardware watchpoint registers .tp .b nt_arm_system_call arm system call number .pd .re .tp .b n_name = gnu extensions used by the gnu tool chain. .rs .tp .b nt_gnu_abi_tag operating system (os) abi information. the desc field will be 4 words: .ip .pd 0 .rs .ip \(bu 2 word 0: os descriptor (\fbelf_note_os_linux\fr, \fbelf_note_os_gnu\fr, and so on)` .ip \(bu word 1: major version of the abi .ip \(bu word 2: minor version of the abi .ip \(bu word 3: subminor version of the abi .re .pd .tp .b nt_gnu_hwcap synthetic hwcap information. the desc field begins with two words: .ip .pd 0 .rs .ip \(bu 2 word 0: number of entries .ip \(bu word 1: bit mask of enabled entries .re .pd .ip then follow variable-length entries, one byte followed by a null-terminated hwcap name string. the byte gives the bit number to test if enabled, (1u << bit) & bit mask. .tp .b nt_gnu_build_id unique build id as generated by the gnu .br ld (1) .br \-\-build\-id option. the desc consists of any nonzero number of bytes. .tp .b nt_gnu_gold_version the desc contains the gnu gold linker version used. .re .tp .b default/unknown namespace (e_type != et_core) these are used when the namespace is the default (i.e., .i n_namesz will be set to 0), or a fallback when the namespace is unknown. .rs .tp 12 .pd 0 .b nt_version a version string of some sort. .tp .b nt_arch architecture information. .pd .re .re .sh notes .\" openbsd .\" elf support first appeared in .\" openbsd 1.2, .\" although not all supported platforms use it as the native .\" binary file format. elf first appeared in system v. the elf format is an adopted standard. .pp the extensions for .ir e_phnum , .ir e_shnum , and .ir e_shstrndx respectively are linux extensions. sun, bsd, and amd64 also support them; for further information, look under see also. .\" .sh authors .\" the original version of this manual page was written by .\" .an jeroen ruigrok van der werven .\" .aq asmodai@freebsd.org .\" with inspiration from bsdi's .\" .bsx .\" .nm elf .\" man page. .sh see also .br as (1), .br elfedit (1), .br gdb (1), .br ld (1), .br nm (1), .br objcopy (1), .br objdump (1), .br patchelf (1), .br readelf (1), .br size (1), .br strings (1), .br strip (1), .br execve (2), .br dl_iterate_phdr (3), .br core (5), .br ld.so (8) .pp hewlett-packard, .ir "elf-64 object file format" . .pp santa cruz operation, .ir "system v application binary interface" . .pp unix system laboratories, "object files", .ir "executable and linking format (elf)" . .pp sun microsystems, .ir "linker and libraries guide" . .pp amd64 abi draft, .ir "system v application binary interface amd64 architecture processor supplement" . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" and copyright 2003,2004 andi kleen, suse labs. .\" numa_maps material copyright (c) 2005 silicon graphics incorporated. .\" christoph lameter, . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th numa 7 2021-03-22 "linux" "linux programmer's manual" .sh name numa \- overview of non-uniform memory architecture .sh description non-uniform memory access (numa) refers to multiprocessor systems whose memory is divided into multiple memory nodes. the access time of a memory node depends on the relative locations of the accessing cpu and the accessed node. (this contrasts with a symmetric multiprocessor system, where the access time for all of the memory is the same for all cpus.) normally, each cpu on a numa system has a local memory node whose contents can be accessed faster than the memory in the node local to another cpu or the memory on a bus shared by all cpus. .ss numa system calls the linux kernel implements the following numa-related system calls: .br get_mempolicy (2), .br mbind (2), .br migrate_pages (2), .br move_pages (2), and .br set_mempolicy (2). however, applications should normally use the interface provided by .ir libnuma ; see "library support" below. .ss /proc/[number]/numa_maps (since linux 2.6.14) .\" see also changelog-2.6.14 this file displays information about a process's numa memory policy and allocation. .pp each line contains information about a memory range used by the process, displaying\(emamong other information\(emthe effective memory policy for that memory range and on which nodes the pages have been allocated. .pp .i numa_maps is a read-only file. when .i /proc//numa_maps is read, the kernel will scan the virtual address space of the process and report how memory is used. one line is displayed for each unique memory range of the process. .pp the first field of each line shows the starting address of the memory range. this field allows a correlation with the contents of the .i /proc//maps file, which contains the end address of the range and other information, such as the access permissions and sharing. .pp the second field shows the memory policy currently in effect for the memory range. note that the effective policy is not necessarily the policy installed by the process for that memory range. specifically, if the process installed a "default" policy for that range, the effective policy for that range will be the process policy, which may or may not be "default". .pp the rest of the line contains information about the pages allocated in the memory range, as follows: .tp .i n= the number of pages allocated on .ir . .i includes only pages currently mapped by the process. page migration and memory reclaim may have temporarily unmapped pages associated with this memory range. these pages may show up again only after the process has attempted to reference them. if the memory range represents a shared memory area or file mapping, other processes may currently have additional pages mapped in a corresponding memory range. .tp .i file= the file backing the memory range. if the file is mapped as private, write accesses may have generated cow (copy-on-write) pages in this memory range. these pages are displayed as anonymous pages. .tp .i heap memory range is used for the heap. .tp .i stack memory range is used for the stack. .tp .i huge huge memory range. the page counts shown are huge pages and not regular sized pages. .tp .i anon= the number of anonymous page in the range. .tp .i dirty= number of dirty pages. .tp .i mapped= total number of mapped pages, if different from .ir dirty and .i anon pages. .tp .i mapmax= maximum mapcount (number of processes mapping a single page) encountered during the scan. this may be used as an indicator of the degree of sharing occurring in a given memory range. .tp .i swapcache= number of pages that have an associated entry on a swap device. .tp .i active= the number of pages on the active list. this field is shown only if different from the number of pages in this range. this means that some inactive pages exist in the memory range that may be removed from memory by the swapper soon. .tp .i writeback= number of pages that are currently being written out to disk. .sh conforming to no standards govern numa interfaces. .sh notes the linux numa system calls and .i /proc interface are available only if the kernel was configured and built with the .br config_numa option. .ss library support link with \fi\-lnuma\fp to get the system call definitions. .i libnuma and the required .i header are available in the .i numactl package. .pp however, applications should not use these system calls directly. instead, the higher level interface provided by the .br numa (3) functions in the .i numactl package is recommended. the .i numactl package is available at .ur ftp://oss.sgi.com\:/www\:/projects\:/libnuma\:/download/ .ue . the package is also included in some linux distributions. some distributions include the development library and header in the separate .i numactl\-devel package. .sh see also .br get_mempolicy (2), .br mbind (2), .br move_pages (2), .br set_mempolicy (2), .br numa (3), .br cpuset (7), .br numactl (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" and copyright (c) 2020 by alejandro colomar .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" .th circleq 3 2021-03-22 "gnu" "linux programmer's manual" .sh name circleq_empty, circleq_entry, circleq_first, circleq_foreach, circleq_foreach_reverse, circleq_head, circleq_head_initializer, circleq_init, circleq_insert_after, circleq_insert_before, circleq_insert_head, circleq_insert_tail, circleq_last, circleq_loop_next, circleq_loop_prev, circleq_next, circleq_prev, circleq_remove \- implementation of a doubly linked circular queue .sh synopsis .nf .b #include .pp .b circleq_entry(type); .pp .b circleq_head(headname, type); .bi "circleq_head circleq_head_initializer(circleq_head " head ); .bi "void circleq_init(circleq_head *" head ); .pp .bi "int circleq_empty(circleq_head *" head ); .pp .bi "void circleq_insert_head(circleq_head *" head , .bi " struct type *" elm ", circleq_entry " name ); .bi "void circleq_insert_tail(circleq_head *" head , .bi " struct type *" elm ", circleq_entry " name ); .bi "void circleq_insert_before(circleq_head *" head ", struct type *" listelm , .bi " struct type *" elm ", circleq_entry " name ); .bi "void circleq_insert_after(circleq_head *" head ", struct type *" listelm , .bi " struct type *" elm ", circleq_entry " name ); .pp .bi "struct type *circleq_first(circleq_head *" head ); .bi "struct type *circleq_last(circleq_head *" head ); .bi "struct type *circleq_prev(struct type *" elm ", circleq_entry " name ); .bi "struct type *circleq_next(struct type *" elm ", circleq_entry " name ); .bi "struct type *circleq_loop_prev(circleq_head *" head , .bi " struct type *" elm ", circleq_entry " name ); .bi "struct type *circleq_loop_next(circleq_head *" head , .bi " struct type *" elm ", circleq_entry " name ); .pp .bi "circleq_foreach(struct type *" var ", circleq_head *" head , .bi " circleq_entry " name ); .bi "circleq_foreach_reverse(struct type *" var ", circleq_head *" head , .bi " circleq_entry " name ); .pp .bi "void circleq_remove(circleq_head *" head ", struct type *" elm , .bi " circleq_entry " name ); .fi .sh description these macros define and operate on doubly linked circular queues. .pp in the macro definitions, .i type is the name of a user-defined structure, that must contain a field of type .ir circleq_entry , named .ir name . the argument .i headname is the name of a user-defined structure that must be declared using the macro .br circleq_head (). .ss creation a circular queue is headed by a structure defined by the .br circleq_head () macro. this structure contains a pair of pointers, one to the first element in the queue and the other to the last element in the queue. the elements are doubly linked so that an arbitrary element can be removed without traversing the queue. new elements can be added to the queue after an existing element, before an existing element, at the head of the queue, or at the end of the queue. a .i circleq_head structure is declared as follows: .pp .in +4 .ex circleq_head(headname, type) head; .ee .in .pp where .i struct headname is the structure to be defined, and .i struct type is the type of the elements to be linked into the queue. a pointer to the head of the queue can later be declared as: .pp .in +4 .ex struct headname *headp; .ee .in .pp (the names .i head and .i headp are user selectable.) .pp .br circleq_entry () declares a structure that connects the elements in the queue. .pp .br circleq_head_initializer () evaluates to an initializer for the queue .ir head . .pp .br circleq_init () initializes the queue referenced by .ir head . .pp .br circleq_empty () evaluates to true if there are no items on the queue. .ss insertion .br circleq_insert_head () inserts the new element .i elm at the head of the queue. .pp .br circleq_insert_tail () inserts the new element .i elm at the end of the queue. .pp .br circleq_insert_before () inserts the new element .i elm before the element .ir listelm . .pp .br circleq_insert_after () inserts the new element .i elm after the element .ir listelm . .ss traversal .br circleq_first () returns the first item on the queue. .pp .br circleq_last () returns the last item on the queue. .pp .br circleq_prev () returns the previous item on the queue, or .i &head if this item is the first one. .pp .br circleq_next () returns the next item on the queue, or .i &head if this item is the last one. .pp .br circleq_loop_prev () returns the previous item on the queue. if .i elm is the first element on the queue, the last element is returned. .pp .br circleq_loop_next () returns the next item on the queue. if .i elm is the last element on the queue, the first element is returned. .pp .br circleq_foreach () traverses the queue referenced by .i head in the forward direction, assigning each element in turn to .ir var . .i var is set to .i &head if the loop completes normally, or if there were no elements. .pp .br circleq_foreach_reverse () traverses the queue referenced by .i head in the reverse direction, assigning each element in turn to .ir var . .ss removal .br circleq_remove () removes the element .i elm from the queue. .sh return value .br circleq_empty () returns nonzero if the queue is empty, and zero if the queue contains at least one entry. .pp .br circleq_first (), .br circleq_last (), .br circleq_loop_prev (), and .br circleq_loop_next () return a pointer to the first, last, previous, or next .i type structure, respectively. .pp .br circleq_prev (), and .br circleq_next () are similar to their .br circleq_loop_* () counterparts, except that if the argument is the first or last element, respectively, they return .ir &head . .pp .br circleq_head_initializer () returns an initializer that can be assigned to the queue .ir head . .sh conforming to not in posix.1, posix.1-2001, or posix.1-2008. present on the bsds (circleq macros first appeared in 4.4bsd). .sh bugs .br circleq_foreach () and .br circleq_foreach_reverse () don't allow .i var to be removed or freed within the loop, as it would interfere with the traversal. .br circleq_foreach_safe () and .br circleq_foreach_reverse_safe (), which are present on the bsds but are not present in glibc, fix this limitation by allowing .i var to safely be removed from the list and freed from within the loop without interfering with the traversal. .sh examples .ex #include #include #include #include struct entry { int data; circleq_entry(entry) entries; /* queue */ }; circleq_head(circlehead, entry); int main(void) { struct entry *n1, *n2, *n3, *np; struct circlehead head; /* queue head */ int i; circleq_init(&head); /* initialize the queue */ n1 = malloc(sizeof(struct entry)); /* insert at the head */ circleq_insert_head(&head, n1, entries); n1 = malloc(sizeof(struct entry)); /* insert at the tail */ circleq_insert_tail(&head, n1, entries); n2 = malloc(sizeof(struct entry)); /* insert after */ circleq_insert_after(&head, n1, n2, entries); n3 = malloc(sizeof(struct entry)); /* insert before */ circleq_insert_before(&head, n2, n3, entries); circleq_remove(&head, n2, entries); /* deletion */ free(n2); /* forward traversal */ i = 0; circleq_foreach(np, &head, entries) np\->data = i++; /* reverse traversal */ circleq_foreach_reverse(np, &head, entries) printf("%i\en", np\->data); /* queue deletion */ n1 = circleq_first(&head); while (n1 != (void *)&head) { n2 = circleq_next(n1, entries); free(n1); n1 = n2; } circleq_init(&head); exit(exit_success); } .ee .sh see also .br insque (3), .br queue (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/newlocale.3 .so man3/xdr.3 .so man2/chown.2 .so man3/stailq.3 .so man3/tzset.3 .so man3/lgamma.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th ungetwc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name ungetwc \- push back a wide character onto a file stream .sh synopsis .nf .b #include .pp .bi "wint_t ungetwc(wint_t " wc ", file *" stream ); .fi .sh description the .br ungetwc () function is the wide-character equivalent of the .br ungetc (3) function. it pushes back a wide character onto .i stream and returns it. .pp if .i wc is .br weof , it returns .br weof . if .i wc is an invalid wide character, it sets .i errno to .b eilseq and returns .br weof . .pp if .i wc is a valid wide character, it is pushed back onto the stream and thus becomes available for future wide-character read operations. the file-position indicator is decremented by one or more. the end-of-file indicator is cleared. the backing storage of the file is not affected. .pp note: .i wc need not be the last wide-character read from the stream; it can be any other valid wide character. .pp if the implementation supports multiple push-back operations in a row, the pushed-back wide characters will be read in reverse order; however, only one level of push-back is guaranteed. .sh return value the .br ungetwc () function returns .i wc when successful, or .b weof upon failure. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ungetwc () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br ungetwc () depends on the .b lc_ctype category of the current locale. .sh see also .br fgetwc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1995 by jim van zandt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th tsearch 3 2021-08-27 "gnu" "linux programmer's manual" .sh name tsearch, tfind, tdelete, twalk, twalk_r, tdestroy \- manage a binary search tree .sh synopsis .nf .b #include .pp .bi "typedef enum { preorder, postorder, endorder, leaf } visit;" .pp .bi "void *tsearch(const void *" key ", void **" rootp , .bi " int (*" compar ")(const void *, const void *));" .bi "void *tfind(const void *" key ", void *const *" rootp , .bi " int (*" compar ")(const void *, const void *));" .bi "void *tdelete(const void *restrict " key ", void **restrict " rootp , .bi " int (*" compar ")(const void *, const void *));" .bi "void twalk(const void *" root , .bi " void (*" action ")(const void *" nodep ", visit " which , .bi " int " depth )); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void twalk_r(const void *" root , .bi " void (*" action ")(const void *" nodep ", visit " which , .bi " void *" closure ), .bi " void *" closure ); .bi "void tdestroy(void *" root ", void (*" free_node ")(void *" nodep )); .fi .sh description .br tsearch (), .br tfind (), .br twalk (), and .br tdelete () manage a binary search tree. they are generalized from knuth (6.2.2) algorithm t. the first field in each node of the tree is a pointer to the corresponding data item. (the calling program must store the actual data.) .i compar points to a comparison routine, which takes pointers to two items. it should return an integer which is negative, zero, or positive, depending on whether the first item is less than, equal to, or greater than the second. .pp .br tsearch () searches the tree for an item. .i key points to the item to be searched for. .i rootp points to a variable which points to the root of the tree. if the tree is empty, then the variable that .i rootp points to should be set to null. if the item is found in the tree, then .br tsearch () returns a pointer to the corresponding tree node. (in other words, .br tsearch () returns a pointer to a pointer to the data item.) if the item is not found, then .br tsearch () adds it, and returns a pointer to the corresponding tree node. .pp .br tfind () is like .br tsearch (), except that if the item is not found, then .br tfind () returns null. .pp .br tdelete () deletes an item from the tree. its arguments are the same as for .br tsearch (). .pp .br twalk () performs depth-first, left-to-right traversal of a binary tree. .i root points to the starting node for the traversal. if that node is not the root, then only part of the tree will be visited. .br twalk () calls the user function .i action each time a node is visited (that is, three times for an internal node, and once for a leaf). .ir action , in turn, takes three arguments. the first argument is a pointer to the node being visited. the structure of the node is unspecified, but it is possible to cast the pointer to a pointer-to-pointer-to-element in order to access the element stored within the node. the application must not modify the structure pointed to by this argument. the second argument is an integer which takes one of the values .br preorder , .br postorder , or .b endorder depending on whether this is the first, second, or third visit to the internal node, or the value .b leaf if this is the single visit to a leaf node. (these symbols are defined in .ir .) the third argument is the depth of the node; the root node has depth zero. .pp (more commonly, .br preorder , .br postorder , and .b endorder are known as .br preorder , .br inorder , and .br postorder : before visiting the children, after the first and before the second, and after visiting the children. thus, the choice of name .b post\%order is rather confusing.) .pp .br twalk_r () is similar to .br twalk (), but instead of the .i depth argument, the .i closure argument pointer is passed to each invocation of the action callback, unchanged. this pointer can be used to pass information to and from the callback function in a thread-safe fashion, without resorting to global variables. .pp .br tdestroy () removes the whole tree pointed to by .ir root , freeing all resources allocated by the .br tsearch () function. for the data in each tree node the function .i free_node is called. the pointer to the data is passed as the argument to the function. if no such work is necessary, .i free_node must point to a function doing nothing. .sh return value .br tsearch () returns a pointer to a matching node in the tree, or to the newly added node, or null if there was insufficient memory to add the item. .br tfind () returns a pointer to the node, or null if no match is found. if there are multiple items that match the key, the item whose node is returned is unspecified. .pp .br tdelete () returns a pointer to the parent of the node deleted, or null if the item was not found. if the deleted node was the root node, .br tdelete () returns a dangling pointer that must not be accessed. .pp .br tsearch (), .br tfind (), and .br tdelete () also return null if .i rootp was null on entry. .sh versions .br twalk_r () is available in glibc since version 2.30. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tsearch (), .br tfind (), .br tdelete () t} thread safety mt-safe race:rootp t{ .br twalk () t} thread safety mt-safe race:root t{ .br twalk_r () t} thread safety mt-safe race:root t{ .br tdestroy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4. the functions .br tdestroy () and .br twalk_r () are gnu extensions. .sh notes .br twalk () takes a pointer to the root, while the other functions take a pointer to a variable which points to the root. .pp .br tdelete () frees the memory required for the node in the tree. the user is responsible for freeing the memory for the corresponding data. .pp the example program depends on the fact that .br twalk () makes no further reference to a node after calling the user function with argument "endorder" or "leaf". this works with the gnu library implementation, but is not in the system v documentation. .sh examples the following program inserts twelve random numbers into a binary tree, where duplicate numbers are collapsed, then prints the numbers in order. .pp .ex #define _gnu_source /* expose declaration of tdestroy() */ #include #include #include #include #include static void *root = null; static void * xmalloc(size_t n) { void *p; p = malloc(n); if (p) return p; fprintf(stderr, "insufficient memory\en"); exit(exit_failure); } static int compare(const void *pa, const void *pb) { if (*(int *) pa < *(int *) pb) return \-1; if (*(int *) pa > *(int *) pb) return 1; return 0; } static void action(const void *nodep, visit which, int depth) { int *datap; switch (which) { case preorder: break; case postorder: datap = *(int **) nodep; printf("%6d\en", *datap); break; case endorder: break; case leaf: datap = *(int **) nodep; printf("%6d\en", *datap); break; } } int main(void) { int **val; srand(time(null)); for (int i = 0; i < 12; i++) { int *ptr = xmalloc(sizeof(*ptr)); *ptr = rand() & 0xff; val = tsearch(ptr, &root, compare); if (val == null) exit(exit_failure); else if (*val != ptr) free(ptr); } twalk(root, action); tdestroy(root, free); exit(exit_success); } .ee .sh see also .br bsearch (3), .br hsearch (3), .br lsearch (3), .br qsort (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th log 3 2021-03-22 "" "linux programmer's manual" .sh name log, logf, logl \- natural logarithmic function .sh synopsis .nf .b #include .pp .bi "double log(double " x ); .bi "float logf(float " x ); .bi "long double logl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br logf (), .br logl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the natural logarithm of .ir x . .sh return value on success, these functions return the natural logarithm of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is 1, the result is +0. .pp if .i x is positive infinity, positive infinity is returned. .pp if .i x is zero, then a pole error occurs, and the functions return .rb \- huge_val , .rb \- huge_valf , or .rb \- huge_vall , respectively. .pp if .i x is negative (including negative infinity), then a domain error occurs, and a nan (not a number) is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is negative .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp pole error: \fix\fp is zero .i errno is set to .br erange . a divide-by-zero floating-point exception .rb ( fe_divbyzero ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br log (), .br logf (), .br logl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh bugs in glibc 2.5 and earlier, taking the .br log () of a nan produces a bogus invalid floating-point .rb ( fe_invalid ) exception. .sh see also .br cbrt (3), .br clog (3), .br log10 (3), .br log1p (3), .br log2 (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getspnam.3 .so man2/mkdir.2 .\" copyright (c) 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)mpool.3 8.1 (berkeley) 6/4/93 .\" .th mpool 3 2021-03-22 "" "linux programmer's manual" .uc 7 .sh name mpool \- shared memory buffer pool .sh synopsis .nf .b #include .b #include .pp .bi "mpool *mpool_open(dbt *" key ", int " fd ", pgno_t " pagesize \ ", pgno_t " maxcache ); .pp .bi "void mpool_filter(mpool *" mp ", void (*pgin)(void *, pgno_t, void *)," .bi " void (*" pgout ")(void *, pgno_t, void *)," .bi " void *" pgcookie ); .pp .bi "void *mpool_new(mpool *" mp ", pgno_t *" pgnoaddr ); .bi "void *mpool_get(mpool *" mp ", pgno_t " pgno ", unsigned int " flags ); .bi "int mpool_put(mpool *" mp ", void *" pgaddr ", unsigned int " flags ); .pp .bi "int mpool_sync(mpool *" mp ); .bi "int mpool_close(mpool *" mp ); .fi .sh description .ir "note well" : this page documents interfaces provided in glibc up until version 2.1. since version 2.2, glibc no longer provides these interfaces. probably, you are looking for the apis provided by the .i libdb library instead. .pp .i mpool is the library interface intended to provide page oriented buffer management of files. the buffers may be shared between processes. .pp the function .br mpool_open () initializes a memory pool. the .i key argument is the byte string used to negotiate between multiple processes wishing to share buffers. if the file buffers are mapped in shared memory, all processes using the same key will share the buffers. if .i key is null, the buffers are mapped into private memory. the .i fd argument is a file descriptor for the underlying file, which must be seekable. if .i key is non-null and matches a file already being mapped, the .i fd argument is ignored. .pp the .i pagesize argument is the size, in bytes, of the pages into which the file is broken up. the .i maxcache argument is the maximum number of pages from the underlying file to cache at any one time. this value is not relative to the number of processes which share a file's buffers, but will be the largest value specified by any of the processes sharing the file. .pp the .br mpool_filter () function is intended to make transparent input and output processing of the pages possible. if the .i pgin function is specified, it is called each time a buffer is read into the memory pool from the backing file. if the .i pgout function is specified, it is called each time a buffer is written into the backing file. both functions are called with the .i pgcookie pointer, the page number and a pointer to the page to being read or written. .pp the function .br mpool_new () takes an .i mpool pointer and an address as arguments. if a new page can be allocated, a pointer to the page is returned and the page number is stored into the .i pgnoaddr address. otherwise, null is returned and .i errno is set. .pp the function .br mpool_get () takes an .i mpool pointer and a page number as arguments. if the page exists, a pointer to the page is returned. otherwise, null is returned and .i errno is set. the .i flags argument is not currently used. .pp the function .br mpool_put () unpins the page referenced by .ir pgaddr . .i pgaddr must be an address previously returned by .br mpool_get () or .br mpool_new (). the flag value is specified by oring any of the following values: .tp .b mpool_dirty the page has been modified and needs to be written to the backing file. .pp .br mpool_put () returns 0 on success and \-1 if an error occurs. .pp the function .br mpool_sync () writes all modified pages associated with the .i mpool pointer to the backing file. .br mpool_sync () returns 0 on success and \-1 if an error occurs. .pp the .br mpool_close () function free's up any allocated memory associated with the memory pool cookie. modified pages are .b not written to the backing file. .br mpool_close () returns 0 on success and \-1 if an error occurs. .sh errors the .br mpool_open () function may fail and set .i errno for any of the errors specified for the library routine .br malloc (3). .pp the .br mpool_get () function may fail and set .i errno for the following: .tp 15 .b einval the requested record doesn't exist. .pp the .br mpool_new () and .br mpool_get () functions may fail and set .i errno for any of the errors specified for the library routines .br read (2), .br write (2), and .br malloc (3). .pp the .br mpool_sync () function may fail and set .i errno for any of the errors specified for the library routine .br write (2). .pp the .br mpool_close () function may fail and set .i errno for any of the errors specified for the library routine .br free (3). .sh conforming to not in posix.1. present on the bsds. .sh see also .br btree (3), .br dbopen (3), .br hash (3), .br recno (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/casin.3 .so man3/cacos.3 .so man3/popen.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:08:17 1993 by rik faith (faith@cs.unc.edu) .\" modified 2002-08-25, aeb .\" modified 2004-11-12 as per suggestion by fabian kreutz/aeb .\" 2008-07-24, mtk, moved yxx() material into separate y0.3 page .\" .th j0 3 2021-03-22 "" "linux programmer's manual" .sh name j0, j0f, j0l, j1, j1f, j1l, jn, jnf, jnl \- bessel functions of the first kind .sh synopsis .nf .b #include .pp .bi "double j0(double " x ); .bi "double j1(double " x ); .bi "double jn(int " n ", double " x ); .pp .bi "float j0f(float " x ); .bi "float j1f(float " x ); .bi "float jnf(int " n ", float " x ); .pp .bi "long double j0l(long double " x ); .bi "long double j1l(long double " x ); .bi "long double jnl(int " n ", long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br j0 (), .br j1 (), .br jn (): .nf _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .pp .br j0f (), .br j0l (), .br j1f (), .br j1l (), .br jnf (), .br jnl (): .nf _xopen_source >= 600 || (_isoc99_source && _xopen_source) || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description the .br j0 () and .br j1 () functions return bessel functions of .i x of the first kind of orders 0 and 1, respectively. the .br jn () function returns the bessel function of .i x of the first kind of order .ir n . .pp the .br j0f (), .br j1f (), and .br jnf (), functions are versions that take and return .i float values. the .br j0l (), .br j1l (), and .br jnl () functions are versions that take and return .i "long double" values. .sh return value on success, these functions return the appropriate bessel value of the first kind for .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is too large in magnitude, or the result underflows, a range error occurs, and the return value is 0. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result underflow, or \fix\fp is too large in magnitude .i errno is set to .br erange . .pp these functions do not raise exceptions for .br fetestexcept (3). .\" e.g., j0(1.5e16) .\" this is intentional. .\" see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6805 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br j0 (), .br j0f (), .br j0l () t} thread safety mt-safe t{ .br j1 (), .br j1f (), .br j1l () t} thread safety mt-safe t{ .br jn (), .br jnf (), .br jnl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the functions returning .i double conform to svr4, 4.3bsd, posix.1-2001, and posix.1-2008. the others are nonstandard functions that also exist on the bsds. .sh bugs there are errors of up to 2e\-16 in the values returned by .br j0 (), .br j1 (), and .br jn () for values of .i x between \-8 and 8. .sh see also .br y0 (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified mon mar 29 22:41:16 1993, david metcalfe .\" modified sat jul 24 21:35:16 1993, rik faith (faith@cs.unc.edu) .th bsearch 3 2021-08-27 "" "linux programmer's manual" .sh name bsearch \- binary search of a sorted array .sh synopsis .nf .b #include .pp .bi "void *bsearch(const void *" key ", const void *" base , .bi " size_t " nmemb ", size_t " size , .bi " int (*" compar ")(const void *, const void *));" .fi .sh description the .br bsearch () function searches an array of .i nmemb objects, the initial member of which is pointed to by .ir base , for a member that matches the object pointed to by .ir key . the size of each member of the array is specified by .ir size . .pp the contents of the array should be in ascending sorted order according to the comparison function referenced by .ir compar . the .i compar routine is expected to have two arguments which point to the .i key object and to an array member, in that order, and should return an integer less than, equal to, or greater than zero if the .i key object is found, respectively, to be less than, to match, or be greater than the array member. .sh return value the .br bsearch () function returns a pointer to a matching member of the array, or null if no match is found. if there are multiple elements that match the key, the element returned is unspecified. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br bsearch () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh examples the example below first sorts an array of structures using .br qsort (3), then retrieves desired elements using .br bsearch (). .pp .ex #include #include #include struct mi { int nr; char *name; } months[] = { { 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" }, { 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" }, { 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" } }; #define nr_of_months (sizeof(months)/sizeof(months[0])) static int compmi(const void *m1, const void *m2) { const struct mi *mi1 = m1; const struct mi *mi2 = m2; return strcmp(mi1\->name, mi2\->name); } int main(int argc, char *argv[]) { qsort(months, nr_of_months, sizeof(months[0]), compmi); for (int i = 1; i < argc; i++) { struct mi key; struct mi *res; key.name = argv[i]; res = bsearch(&key, months, nr_of_months, sizeof(months[0]), compmi); if (res == null) printf("\(aq%s\(aq: unknown month\en", argv[i]); else printf("%s: month #%d\en", res\->name, res\->nr); } exit(exit_success); } .ee .\" this example referred to in qsort.3 .sh see also .br hsearch (3), .br lsearch (3), .br qsort (3), .br tsearch (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" this was done with the help of the glibc manual. .\" .\" 2004-10-31, aeb, corrected .th fpclassify 3 2021-03-22 "" "linux programmer's manual" .sh name fpclassify, isfinite, isnormal, isnan, isinf \- floating-point classification macros .sh synopsis .nf .b #include .pp .bi "int fpclassify(" x ); .bi "int isfinite(" x ); .bi "int isnormal(" x ); .bi "int isnan(" x ); .bi "int isinf(" x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .\" i haven't fully grokked the source to determine the ftm requirements; .\" in part, the following has been tested by experiment. .br fpclassify (), .br isfinite (), .br isnormal (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .pp .br isnan (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br isinf (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description floating point numbers can have special values, such as infinite or nan. with the macro .bi fpclassify( x ) you can find out what type .i x is. the macro takes any floating-point expression as argument. the result is one of the following values: .tp 14 .b fp_nan .i x is "not a number". .tp .b fp_infinite .i x is either positive infinity or negative infinity. .tp .b fp_zero .i x is zero. .tp .b fp_subnormal .i x is too small to be represented in normalized format. .tp .b fp_normal if nothing of the above is correct then it must be a normal floating-point number. .pp the other macros provide a short answer to some standard questions. .tp 14 .bi isfinite( x ) returns a nonzero value if .br (fpclassify(x) != fp_nan && fpclassify(x) != fp_infinite) .tp .bi isnormal( x ) returns a nonzero value if (fpclassify(x) == fp_normal) .tp .bi isnan( x ) returns a nonzero value if (fpclassify(x) == fp_nan) .tp .bi isinf( x ) returns 1 if .i x is positive infinity, and \-1 if .i x is negative infinity. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fpclassify (), .br isfinite (), .br isnormal (), .br isnan (), .br isinf () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .pp for .br isinf (), the standards merely say that the return value is nonzero if and only if the argument has an infinite value. .sh notes in glibc 2.01 and earlier, .br isinf () returns a nonzero value (actually: 1) if .i x is positive infinity or negative infinity. (this is all that c99 requires.) .sh see also .br finite (3), .br infinity (3), .br isgreater (3), .br signbit (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" (c)copyright 1999-2003 marvell(r) -- linux@syskonnect.de .\" sk98lin.4 1.1 2003/12/17 10:03:18 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual;if not, see .\" . .\" %%%license_end .\" .\" this manpage can be viewed using `groff -tascii -man sk98lin.4 | less` .\" .th sk98lin 4 2020-08-13 "linux" "linux programmer's manual" .sh name sk98lin \- marvell/syskonnect gigabit ethernet driver v6.21 .sh synopsis .b insmod sk98lin.o .rb [ speed_a=\c .ir i,j,... ] .rb [ speed_b=\c .ir i,j,... ] .rb [ autoneg_a=\c .ir i,j,... ] .rb [ autoneg_b=\c .ir i,j,... ] .rb [ dupcap_a=\c .ir i,j,... ] .rb [ dupcap_b=\c .ir i,j,... ] .rb [ flowctrl_a=\c .ir i,j,... ] .rb [ flowctrl_b=\c .ir i,j,... ] .rb [ role_a=\c .ir i,j,... ] .rb [ role_b=\c .ir i,j,... ] .rb [ contype=\c .ir i,j,... ] .rb [ moderation=\c .ir i,j,... ] .rb [ intspersec=\c .ir i,j,... ] .rb [ prefport=\c .ir i,j,... ] .rb [ rlmtmode=\c .ir i,j,... ] .sh description .ad l .hy 0 .br note : this obsolete driver was removed from the kernel in version 2.6.26. .pp .b sk98lin is the gigabit ethernet driver for marvell and syskonnect network adapter cards. it supports syskonnect sk-98xx/sk-95xx compliant gigabit ethernet adapter and any yukon compliant chipset. .pp when loading the driver using insmod, parameters for the network adapter cards might be stated as a sequence of comma separated commands. if for instance two network adapters are installed and autonegotiation on port a of the first adapter should be on, but on the port a of the second adapter switched off, one must enter: .pp insmod sk98lin.o autoneg_a=on,off .pp after .b sk98lin is bound to one or more adapter cards and the .i /proc filesystem is mounted on your system, a dedicated statistics file will be created in the folder .i /proc/net/sk98lin for all ports of the installed network adapter cards. those files are named .ir eth[x] , where .i x is the number of the interface that has been assigned to a dedicated port by the system. .pp if loading is finished, any desired ip address can be assigned to the respective .i eth[x] interface using the .br ifconfig (8) command. this causes the adapter to connect to the ethernet and to display a status message on the console saying "ethx: network connection up using port y" followed by the configured or detected connection parameters. .pp the .b sk98lin also supports large frames (also called jumbo frames). using jumbo frames can improve throughput tremendously when transferring large amounts of data. to enable large frames, the mtu (maximum transfer unit) size for an interface is to be set to a high value. the default mtu size is 1500 and can be changed up to 9000 (bytes). setting the mtu size can be done when assigning the ip address to the interface or later by using the .br ifconfig (8) command with the mtu parameter. if for instance eth0 needs an ip address and a large frame mtu size, the following two commands might be used: .pp ifconfig eth0 10.1.1.1 ifconfig eth0 mtu 9000 .pp those two commands might even be combined into one: .pp ifconfig eth0 10.1.1.1 mtu 9000 .pp note that large frames can be used only if permitted by your network infrastructure. this means, that any switch being used in your ethernet must also support large frames. quite some switches support large frames, but need to be configured to do so. most of the times, their default setting is to support only standard frames with an mtu size of 1500 (bytes). in addition to the switches inside the network, all network adapters that are to be used must also be enabled regarding jumbo frames. if an adapter is not set to receive large frames, it will simply drop them. .pp switching back to the standard ethernet frame size can be done by using the .br ifconfig (8) command again: .pp ifconfig eth0 mtu 1500 .pp the marvell/syskonnect gigabit ethernet driver for linux is able to support vlan and link aggregation according to ieee standards 802.1, 802.1q, and 802.3ad. those features are available only after installation of open source modules which can be found on the internet: .pp .ir vlan \c : .ur http://www.candelatech.com\:/\(tigreear\:/vlan.html .ue .br .i link .ir aggregation \c : .ur http://www.st.rim.or.jp\:/\(tiyumo .ue .pp note that marvell/syskonnect does not offer any support for these open source modules and does not take the responsibility for any kind of failures or problems arising when using these modules. .ss parameters .tp .bi speed_a= i,j,... this parameter is used to set the speed capabilities of port a of an adapter card. it is valid only for yukon copper adapters. possible values are: .ir 10 , .ir 100 , .ir 1000 , or .ir auto ; .i auto is the default. usually, the speed is negotiated between the two ports during link establishment. if this fails, a port can be forced to a specific setting with this parameter. .tp .bi speed_b= i,j,... this parameter is used to set the speed capabilities of port b of an adapter card. it is valid only for yukon copper adapters. possible values are: .ir 10 , .ir 100 , .ir 1000 , or .ir auto ; .i auto is the default. usually, the speed is negotiated between the two ports during link establishment. if this fails, a port can be forced to a specific setting with this parameter. .tp .bi autoneg_a= i,j,... enables or disables the use of autonegotiation of port a of an adapter card. possible values are: .ir on , .ir off , or .ir sense ; .i on is the default. the .i sense mode automatically detects whether the link partner supports auto-negotiation or not. .tp .bi autoneg_b= i,j,... enables or disables the use of autonegotiation of port b of an adapter card. possible values are: .ir on , .ir off , or .ir sense ; .i on is the default. the .i sense mode automatically detects whether the link partner supports auto-negotiation or not. .tp .bi dupcap_a= i,j,... this parameter indicates the duplex mode to be used for port a of an adapter card. possible values are: .ir half , .ir full , or .ir both ; .i both is the default. this parameter is relevant only if autoneg_a of port a is not set to .ir sense . if autoneg_a is set to .ir on , all three values of dupcap_a ( .ir half , .ir full , or .ir both ) might be stated. if autoneg_a is set to .ir off , only dupcap_a values .i full and .i half are allowed. this dupcap_a parameter is useful if your link partner does not support all possible duplex combinations. .tp .bi dupcap_b= i,j,... this parameter indicates the duplex mode to be used for port b of an adapter card. possible values are: .ir half , .ir full , or .ir both ; .i both is the default. this parameter is relevant only if autoneg_b of port b is not set to .ir sense . if autoneg_b is set to .ir on , all three values of dupcap_b ( .ir half , .ir full , or .ir both ) might be stated. if autoneg_b is set to .ir off , only dupcap_b values .i full and .i half are allowed. this dupcap_b parameter is useful if your link partner does not support all possible duplex combinations. .tp .bi flowctrl_a= i,j,... this parameter can be used to set the flow control capabilities the port reports during auto-negotiation. possible values are: .ir sym , .ir symorrem , .ir locsend , or .ir none ; .i symorrem is the default. the different modes have the following meaning: .ip .i sym = symmetric both link partners are allowed to send pause frames .br .i symorrem = symmetricorremote both or only remote partner are allowed to send pause frames .br .i locsend = localsend only local link partner is allowed to send pause frames .br .i none = none no link partner is allowed to send pause frames .ip note that this parameter is ignored if autoneg_a is set to .ir off . .tp .bi flowctrl_b= i,j,... this parameter can be used to set the flow control capabilities the port reports during auto-negotiation. possible values are: .ir sym , .ir symorrem , .ir locsend , or .ir none ; .i symorrem is the default. the different modes have the following meaning: .ip .i sym = symmetric both link partners are allowed to send pause frames .br .i symorrem = symmetricorremote both or only remote partner are allowed to send pause frames .br .i locsend = localsend only local link partner is allowed to send pause frames .br .i none = none no link partner is allowed to send pause frames .br .ip note that this parameter is ignored if autoneg_b is set to .ir off . .tp .bi role_a= i,j,... this parameter is valid only for 1000base-t adapter cards. for two 1000base-t ports to communicate, one must take the role of the master (providing timing information), while the other must be the slave. possible values are: .ir auto , .ir master , or .ir slave ; .i auto is the default. usually, the role of a port is negotiated between two ports during link establishment, but if that fails the port a of an adapter card can be forced to a specific setting with this parameter. .tp .bi role_b= i,j,... this parameter is valid only for 1000base-t adapter cards. for two 1000base-t ports to communicate, one must take the role of the master (providing timing information), while the other must be the slave. possible values are: .ir auto , .ir master , or .ir slave ; .i auto is the default. usually, the role of a port is negotiated between two ports during link establishment, but if that fails the port b of an adapter card can be forced to a specific setting with this parameter. .tp .bi contype= i,j,... this parameter is a combination of all five per-port parameters within one single parameter. this simplifies the configuration of both ports of an adapter card. the different values of this variable reflect the most meaningful combinations of port parameters. possible values and their corresponding combination of per-port parameters: .ip .ts lb lb lb lb lb lb l l l l l l. contype dupcap autoneg flowctrl role speed \fiauto\fp both on symorrem auto auto \fi100fd\fp full off none auto 100 \fi100hd\fp half off none auto 100 \fi10fd\fp full off none auto 10 \fi10hd\fp half off none auto 10 .te .ip stating any other port parameter together with this .i contype parameter will result in a merged configuration of those settings. this is due to the fact, that the per-port parameters (e.g., .ir speed_a ) have a higher priority than the combined variable .ir contype . .tp .bi moderation= i,j,... interrupt moderation is employed to limit the maximum number of interrupts the driver has to serve. that is, one or more interrupts (which indicate any transmit or receive packet to be processed) are queued until the driver processes them. when queued interrupts are to be served, is determined by the .i intspersec parameter, which is explained later below. possible moderation modes are: .ir none , .ir static , or .ir dynamic ; .i none is the default. the different modes have the following meaning: .ip .i none no interrupt moderation is applied on the adapter card. therefore, each transmit or receive interrupt is served immediately as soon as it appears on the interrupt line of the adapter card. .ip .i static interrupt moderation is applied on the adapter card. all transmit and receive interrupts are queued until a complete moderation interval ends. if such a moderation interval ends, all queued interrupts are processed in one big bunch without any delay. the term .i static reflects the fact, that interrupt moderation is always enabled, regardless how much network load is currently passing via a particular interface. in addition, the duration of the moderation interval has a fixed length that never changes while the driver is operational. .ip .i dynamic interrupt moderation might be applied on the adapter card, depending on the load of the system. if the driver detects that the system load is too high, the driver tries to shield the system against too much network load by enabling interrupt moderation. if\(emat a later time\(emthe cpu utilization decreases again (or if the network load is negligible), the interrupt moderation will automatically be disabled. .ip interrupt moderation should be used when the driver has to handle one or more interfaces with a high network load, which\(emas a consequence\(emleads also to a high cpu utilization. when moderation is applied in such high network load situations, cpu load might be reduced by 20\(en30% on slow computers. .ip note that the drawback of using interrupt moderation is an increase of the round-trip-time (rtt), due to the queuing and serving of interrupts at dedicated moderation times. .tp .bi intspersec= i,j,... this parameter determines the length of any interrupt moderation interval. assuming that static interrupt moderation is to be used, an .i intspersec parameter value of 2000 will lead to an interrupt moderation interval of 500 microseconds. possible values for this parameter are in the range of 30...40000 (interrupts per second). the default value is 2000. .ip this parameter is used only if either static or dynamic interrupt moderation is enabled on a network adapter card. this parameter is ignored if no moderation is applied. .ip note that the duration of the moderation interval is to be chosen with care. at first glance, selecting a very long duration (e.g., only 100 interrupts per second) seems to be meaningful, but the increase of packet-processing delay is tremendous. on the other hand, selecting a very short moderation time might compensate the use of any moderation being applied. .tp .bi prefport= i,j,... this parameter is used to force the preferred port to a or b (on dual-port network adapters). the preferred port is the one that is used if both ports a and b are detected as fully functional. possible values are: .i a or .ir b ; .i a is the default. .tp .bi rlmtmode= i,j,... rlmt monitors the status of the port. if the link of the active port fails, rlmt switches immediately to the standby link. the virtual link is maintained as long as at least one "physical" link is up. this parameters states how rlmt should monitor both ports. possible values are: .ir checklinkstate , .ir checklocalport , .ir checkseg , or .ir dualnet ; .i checklinkstate is the default. the different modes have the following meaning: .ip .i checklinkstate check link state only: rlmt uses the link state reported by the adapter hardware for each individual port to determine whether a port can be used for all network traffic or not. .ip .i checklocalport in this mode, rlmt monitors the network path between the two ports of an adapter by regularly exchanging packets between them. this mode requires a network configuration in which the two ports are able to "see" each other (i.e., there must not be any router between the ports). .ip .i checkseg check local port and segmentation: this mode supports the same functions as the checklocalport mode and additionally checks network segmentation between the ports. therefore, this mode is to be used only if gigabit ethernet switches are installed on the network that have been configured to use the spanning tree protocol. .ip .i dualnet in this mode, ports a and b are used as separate devices. if you have a dual port adapter, port a will be configured as .ir eth[x] and port b as .ir eth[x+1] . both ports can be used independently with distinct ip addresses. the preferred port setting is not used. rlmt is turned off. .ip note that rlmt modes .i checklocalport and .i checklinkstate are designed to operate in configurations where a network path between the ports on one adapter exists. moreover, they are not designed to work where adapters are connected back-to-back. .sh files .tp .i /proc/net/sk98lin/eth[x] the statistics file of a particular interface of an adapter card. it contains generic information about the adapter card plus a detailed summary of all transmit and receive counters. .tp .i /usr/src/linux/documentation/networking/sk98lin.txt this is the .i readme file of the .i sk98lin driver. it contains a detailed installation howto and describes all parameters of the driver. it denotes also common problems and provides the solution to them. .sh bugs report any bugs to linux@syskonnect.de .\" .sh authors .\" ralph roesler \(em rroesler@syskonnect.de .\" .br .\" mirko lindner \(em mlindner@syskonnect.de .sh see also .br ifconfig (8), .br insmod (8), .br modprobe (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_init 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_init, pthread_attr_destroy \- initialize and destroy thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_init(pthread_attr_t *" attr ); .bi "int pthread_attr_destroy(pthread_attr_t *" attr ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_init () function initializes the thread attributes object pointed to by .ir attr with default attribute values. after this call, individual attributes of the object can be set using various related functions (listed under see also), and then the object can be used in one or more .br pthread_create (3) calls that create threads. .pp calling .br pthread_attr_init () on a thread attributes object that has already been initialized results in undefined behavior. .pp when a thread attributes object is no longer required, it should be destroyed using the .br pthread_attr_destroy () function. destroying a thread attributes object has no effect on threads that were created using that object. .pp once a thread attributes object has been destroyed, it can be reinitialized using .br pthread_attr_init (). any other use of a destroyed thread attributes object has undefined results. .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors posix.1 documents an .b enomem error for .br pthread_attr_init (); on linux these functions always succeed (but portable and future-proof applications should nevertheless handle a possible error return). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_init (), .br pthread_attr_destroy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the .i pthread_attr_t type should be treated as opaque: any access to the object other than via pthreads functions is nonportable and produces undefined results. .sh examples the program below optionally makes use of .br pthread_attr_init () and various related functions to initialize a thread attributes object that is used to create a single thread. once created, the thread uses the .br pthread_getattr_np (3) function (a nonstandard gnu extension) to retrieve the thread's attributes, and then displays those attributes. .pp if the program is run with no command-line argument, then it passes null as the .i attr argument of .br pthread_create (3), so that the thread is created with default attributes. running the program on linux/x86-32 with the nptl threading implementation, we see the following: .pp .in +4n .ex .\" results from glibc 2.8, suse 11.0; oct 2008 .rb "$" " ulimit \-s" " # no stack limit ==> default stack size is 2 mb" unlimited .rb "$" " ./a.out" thread attributes: detach state = pthread_create_joinable scope = pthread_scope_system inherit scheduler = pthread_inherit_sched scheduling policy = sched_other scheduling priority = 0 guard size = 4096 bytes stack address = 0x40196000 stack size = 0x201000 bytes .ee .in .pp when we supply a stack size as a command-line argument, the program initializes a thread attributes object, sets various attributes in that object, and passes a pointer to the object in the call to .br pthread_create (3). running the program on linux/x86-32 with the nptl threading implementation, we see the following: .pp .in +4n .ex .\" results from glibc 2.8, suse 11.0; oct 2008 .rb "$" " ./a.out 0x3000000" posix_memalign() allocated at 0x40197000 thread attributes: detach state = pthread_create_detached scope = pthread_scope_system inherit scheduler = pthread_explicit_sched scheduling policy = sched_other scheduling priority = 0 guard size = 0 bytes stack address = 0x40197000 stack size = 0x3000000 bytes .ee .in .ss program source \& .ex #define _gnu_source /* to get pthread_getattr_np() declaration */ #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static void display_pthread_attr(pthread_attr_t *attr, char *prefix) { int s, i; size_t v; void *stkaddr; struct sched_param sp; s = pthread_attr_getdetachstate(attr, &i); if (s != 0) handle_error_en(s, "pthread_attr_getdetachstate"); printf("%sdetach state = %s\en", prefix, (i == pthread_create_detached) ? "pthread_create_detached" : (i == pthread_create_joinable) ? "pthread_create_joinable" : "???"); s = pthread_attr_getscope(attr, &i); if (s != 0) handle_error_en(s, "pthread_attr_getscope"); printf("%sscope = %s\en", prefix, (i == pthread_scope_system) ? "pthread_scope_system" : (i == pthread_scope_process) ? "pthread_scope_process" : "???"); s = pthread_attr_getinheritsched(attr, &i); if (s != 0) handle_error_en(s, "pthread_attr_getinheritsched"); printf("%sinherit scheduler = %s\en", prefix, (i == pthread_inherit_sched) ? "pthread_inherit_sched" : (i == pthread_explicit_sched) ? "pthread_explicit_sched" : "???"); s = pthread_attr_getschedpolicy(attr, &i); if (s != 0) handle_error_en(s, "pthread_attr_getschedpolicy"); printf("%sscheduling policy = %s\en", prefix, (i == sched_other) ? "sched_other" : (i == sched_fifo) ? "sched_fifo" : (i == sched_rr) ? "sched_rr" : "???"); s = pthread_attr_getschedparam(attr, &sp); if (s != 0) handle_error_en(s, "pthread_attr_getschedparam"); printf("%sscheduling priority = %d\en", prefix, sp.sched_priority); s = pthread_attr_getguardsize(attr, &v); if (s != 0) handle_error_en(s, "pthread_attr_getguardsize"); printf("%sguard size = %zu bytes\en", prefix, v); s = pthread_attr_getstack(attr, &stkaddr, &v); if (s != 0) handle_error_en(s, "pthread_attr_getstack"); printf("%sstack address = %p\en", prefix, stkaddr); printf("%sstack size = %#zx bytes\en", prefix, v); } static void * thread_start(void *arg) { int s; pthread_attr_t gattr; /* pthread_getattr_np() is a non\-standard gnu extension that retrieves the attributes of the thread specified in its first argument. */ s = pthread_getattr_np(pthread_self(), &gattr); if (s != 0) handle_error_en(s, "pthread_getattr_np"); printf("thread attributes:\en"); display_pthread_attr(&gattr, "\et"); exit(exit_success); /* terminate all threads */ } int main(int argc, char *argv[]) { pthread_t thr; pthread_attr_t attr; pthread_attr_t *attrp; /* null or &attr */ int s; attrp = null; /* if a command\-line argument was supplied, use it to set the stack\-size attribute and set a few other thread attributes, and set attrp pointing to thread attributes object. */ if (argc > 1) { size_t stack_size; void *sp; attrp = &attr; s = pthread_attr_init(&attr); if (s != 0) handle_error_en(s, "pthread_attr_init"); s = pthread_attr_setdetachstate(&attr, pthread_create_detached); if (s != 0) handle_error_en(s, "pthread_attr_setdetachstate"); s = pthread_attr_setinheritsched(&attr, pthread_explicit_sched); if (s != 0) handle_error_en(s, "pthread_attr_setinheritsched"); stack_size = strtoul(argv[1], null, 0); s = posix_memalign(&sp, sysconf(_sc_pagesize), stack_size); if (s != 0) handle_error_en(s, "posix_memalign"); printf("posix_memalign() allocated at %p\en", sp); s = pthread_attr_setstack(&attr, sp, stack_size); if (s != 0) handle_error_en(s, "pthread_attr_setstack"); } s = pthread_create(&thr, attrp, &thread_start, null); if (s != 0) handle_error_en(s, "pthread_create"); if (attrp != null) { s = pthread_attr_destroy(attrp); if (s != 0) handle_error_en(s, "pthread_attr_destroy"); } pause(); /* terminates when other thread calls exit() */ } .ee .sh see also .ad l .nh .br pthread_attr_setaffinity_np (3), .br pthread_attr_setdetachstate (3), .br pthread_attr_setguardsize (3), .br pthread_attr_setinheritsched (3), .br pthread_attr_setschedparam (3), .br pthread_attr_setschedpolicy (3), .br pthread_attr_setscope (3), .br pthread_attr_setsigmask_np (3), .br pthread_attr_setstack (3), .br pthread_attr_setstackaddr (3), .br pthread_attr_setstacksize (3), .br pthread_create (3), .br pthread_getattr_np (3), .br pthread_setattr_default_np (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fseek.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setsigmask_np 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setsigmask_np, pthread_attr_getsigmask_np \- set/get signal mask attribute in thread attributes object .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_attr_setsigmask_np(pthread_attr_t *" attr , .bi " const sigset_t *" sigmask ); .bi "int pthread_attr_getsigmask_np(const pthread_attr_t *" attr , .bi " sigset_t *" sigmask ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setsigmask_np () function sets the signal mask attribute of the thread attributes object referred to by .i attr to the value specified in .ir *sigmask . if .i sigmask is specified as null, then any existing signal mask attribute in .i attr is unset. .pp the .br pthread_attr_getsigmask_np () function returns the signal mask attribute of the thread attributes object referred to by .ir attr in the buffer pointed to by .ir sigmask . if the signal mask attribute is currently unset, then this function returns the special value .b pthread_attr_no_sigmask_np as its result. .sh return value the .br pthread_attr_setsigmask_np () function returns 0 on success, or a nonzero error number on failure. .pp the .br pthread_attr_getsigmask_np () function returns either 0 or .br pthread_attr_no_sigmask_np . when 0 is returned, the signal mask attribute is returned via .ir sigmask . a return value of .b pthread_attr_no_sigmask_np indicates that the signal mask attribute is not set in .ir attr . .pp on error, these functions return a positive error number. .sh errors .tp .b enomem .rb ( pthread_attr_setsigmask_np ()) could not allocate memory. .sh versions these functions are provided by glibc since version 2.32. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setsigmask_np (), .br pthread_attr_getsigmask_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh notes the signal mask attribute determines the signal mask that will be assigned to a thread created using the thread attributes object .ir attr . if this attribute is not set, then a thread created using .i attr will inherit a copy of the creating thread's signal mask. .pp for more details on signal masks, see .br sigprocmask (2). for a description of a set of macros that can be used to manipulate and inspect signal sets, see .br sigsetops (3). .pp in the absence of .br pthread_attr_setsigmask_np () it is possible to create a thread with a desired signal mask as follows: .ip \(bu 2 the creating thread uses .br pthread_sigmask (3) to save its current signal mask and set its mask to block all signals. .ip \(bu the new thread is then created using .br pthread_create (); the new thread will inherit the creating thread's signal mask. .ip \(bu the new thread sets its signal mask to the desired value using .br pthread_sigmask (3). .ip \(bu the creating thread restores its signal mask to the original value. .pp following the above steps, there is no possibility for the new thread to receive a signal before it has adjusted its signal mask to the desired value. .sh see also .br sigprocmask (2), .br pthread_attr_init (3), .br pthread_sigmask (3), .br pthreads (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 7/93 by darren senn .\" and copyright (c) 2016, michael kerrisk .\" based on a similar page copyright 1992 by rick faith .\" .\" %%%license_start(freely_redistributable) .\" may be freely distributed and modified .\" %%%license_end .\" .\" modified tue oct 22 00:22:35 edt 1996 by eric s. raymond .\" 2005-04-06 mtk, matthias lang .\" noted max_sec_in_jiffies ceiling .\" .th getitimer 2 2021-03-22 "linux" "linux programmer's manual" .sh name getitimer, setitimer \- get or set value of an interval timer .sh synopsis .nf .b #include .pp .bi "int getitimer(int " which ", struct itimerval *" curr_value ); .bi "int setitimer(int " which ", const struct itimerval *restrict " new_value , .bi " struct itimerval *restrict " old_value ); .fi .sh description these system calls provide access to interval timers, that is, timers that initially expire at some point in the future, and (optionally) at regular intervals after that. when a timer expires, a signal is generated for the calling process, and the timer is reset to the specified interval (if the interval is nonzero). .pp three types of timers\(emspecified via the .ir which argument\(emare provided, each of which counts against a different clock and generates a different signal on timer expiration: .tp .b itimer_real this timer counts down in real (i.e., wall clock) time. at each expiration, a .b sigalrm signal is generated. .tp .b itimer_virtual this timer counts down against the user-mode cpu time consumed by the process. (the measurement includes cpu time consumed by all threads in the process.) at each expiration, a .b sigvtalrm signal is generated. .tp .b itimer_prof this timer counts down against the total (i.e., both user and system) cpu time consumed by the process. (the measurement includes cpu time consumed by all threads in the process.) at each expiration, a .b sigprof signal is generated. .ip in conjunction with .br itimer_virtual , this timer can be used to profile user and system cpu time consumed by the process. .pp a process has only one of each of the three types of timers. .pp timer values are defined by the following structures: .pp .in +4n .ex struct itimerval { struct timeval it_interval; /* interval for periodic timer */ struct timeval it_value; /* time until next expiration */ }; struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ }; .ee .in .\" .ss getitimer() the function .br getitimer () places the current value of the timer specified by .ir which in the buffer pointed to by .ir curr_value . .pp the .ir it_value substructure is populated with the amount of time remaining until the next expiration of the specified timer. this value changes as the timer counts down, and will be reset to .ir it_interval when the timer expires. if both fields of .ir it_value are zero, then this timer is currently disarmed (inactive). .pp the .ir it_interval substructure is populated with the timer interval. if both fields of .ir it_interval are zero, then this is a single-shot timer (i.e., it expires just once). .ss setitimer() the function .br setitimer () arms or disarms the timer specified by .ir which , by setting the timer to the value specified by .ir new_value . if .i old_value is non-null, the buffer it points to is used to return the previous value of the timer (i.e., the same information that is returned by .br getitimer ()). .pp if either field in .ir new_value.it_value is nonzero, then the timer is armed to initially expire at the specified time. if both fields in .ir new_value.it_value are zero, then the timer is disarmed. .pp the .ir new_value.it_interval field specifies the new interval for the timer; if both of its subfields are zero, the timer is single-shot. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .ir new_value , .ir old_value , or .i curr_value is not valid a pointer. .tp .b einval .i which is not one of .br itimer_real , .br itimer_virtual , or .br itimer_prof ; or (since linux 2.6.22) one of the .i tv_usec fields in the structure pointed to by .i new_value contains a value outside the range 0 to 999999. .sh conforming to posix.1-2001, svr4, 4.4bsd (this call first appeared in 4.2bsd). posix.1-2008 marks .br getitimer () and .br setitimer () obsolete, recommending the use of the posix timers api .rb ( timer_gettime (2), .br timer_settime (2), etc.) instead. .sh notes timers will never expire before the requested time, but may expire some (short) time afterward, which depends on the system timer resolution and on the system load; see .br time (7). (but see bugs below.) if the timer expires while the process is active (always true for .br itimer_virtual ), the signal will be delivered immediately when generated. .pp a child created via .br fork (2) does not inherit its parent's interval timers. interval timers are preserved across an .br execve (2). .pp posix.1 leaves the interaction between .br setitimer () and the three interfaces .br alarm (2), .br sleep (3), and .br usleep (3) unspecified. .pp the standards are silent on the meaning of the call: .pp setitimer(which, null, &old_value); .pp many systems (solaris, the bsds, and perhaps others) treat this as equivalent to: .pp getitimer(which, &old_value); .pp in linux, this is treated as being equivalent to a call in which the .i new_value fields are zero; that is, the timer is disabled. .ir "don't use this linux misfeature" : it is nonportable and unnecessary. .sh bugs the generation and delivery of a signal are distinct, and only one instance of each of the signals listed above may be pending for a process. under very heavy loading, an .b itimer_real timer may expire before the signal from a previous expiration has been delivered. the second signal in such an event will be lost. .pp on linux kernels before 2.6.16, timer values are represented in jiffies. if a request is made set a timer with a value whose jiffies representation exceeds .b max_sec_in_jiffies (defined in .ir include/linux/jiffies.h ), then the timer is silently truncated to this ceiling value. on linux/i386 (where, since linux 2.6.13, the default jiffy is 0.004 seconds), this means that the ceiling value for a timer is approximately 99.42 days. since linux 2.6.16, the kernel uses a different internal representation for times, and this ceiling is removed. .pp on certain systems (including i386), linux kernels before version 2.6.12 have a bug which will produce premature timer expirations of up to one jiffy under some circumstances. this bug is fixed in kernel 2.6.12. .\" 4 jul 2005: it looks like this bug may remain in 2.4.x. .\" http://lkml.org/lkml/2005/7/1/165 .pp posix.1-2001 says that .br setitimer () should fail if a .i tv_usec value is specified that is outside of the range 0 to 999999. however, in kernels up to and including 2.6.21, linux does not give an error, but instead silently adjusts the corresponding seconds value for the timer. from kernel 2.6.22 onward, this nonconformance has been repaired: an improper .i tv_usec value results in an .b einval error. .\" bugzilla report 25 apr 2006: .\" http://bugzilla.kernel.org/show_bug.cgi?id=6443 .\" "setitimer() should reject noncanonical arguments" .sh see also .br gettimeofday (2), .br sigaction (2), .br signal (2), .br timer_create (2), .br timerfd_create (2), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man5/filesystems.5 .\" copyright (c) 1983, 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-10-21 by eric s. raymond .\" modified 1998-2000 by andi kleen to match linux 2.2 reality .\" modified 2002-04-23 by roger luethi .\" modified 2004-06-17 by michael kerrisk .\" 2008-12-04, mtk, add documentation of accept4() .\" .th accept 2 2021-08-27 "linux" "linux programmer's manual" .sh name accept, accept4 \- accept a connection on a socket .sh synopsis .nf .b #include .pp .bi "int accept(int " sockfd ", struct sockaddr *restrict " addr , .bi " socklen_t *restrict " addrlen ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int accept4(int " sockfd ", struct sockaddr *restrict " addr , .bi " socklen_t *restrict " addrlen ", int " flags ); .fi .sh description the .br accept () system call is used with connection-based socket types .rb ( sock_stream , .br sock_seqpacket ). it extracts the first connection request on the queue of pending connections for the listening socket, .ir sockfd , creates a new connected socket, and returns a new file descriptor referring to that socket. the newly created socket is not in the listening state. the original socket .i sockfd is unaffected by this call. .pp the argument .i sockfd is a socket that has been created with .br socket (2), bound to a local address with .br bind (2), and is listening for connections after a .br listen (2). .pp the argument .i addr is a pointer to a .i sockaddr structure. this structure is filled in with the address of the peer socket, as known to the communications layer. the exact format of the address returned .i addr is determined by the socket's address family (see .br socket (2) and the respective protocol man pages). when .i addr is null, nothing is filled in; in this case, .i addrlen is not used, and should also be null. .pp the .i addrlen argument is a value-result argument: the caller must initialize it to contain the size (in bytes) of the structure pointed to by .ir addr ; on return it will contain the actual size of the peer address. .pp the returned address is truncated if the buffer provided is too small; in this case, .i addrlen will return a value greater than was supplied to the call. .pp if no pending connections are present on the queue, and the socket is not marked as nonblocking, .br accept () blocks the caller until a connection is present. if the socket is marked nonblocking and no pending connections are present on the queue, .br accept () fails with the error .br eagain or .br ewouldblock . .pp in order to be notified of incoming connections on a socket, you can use .br select (2), .br poll (2), or .br epoll (7). a readable event will be delivered when a new connection is attempted and you may then call .br accept () to get a socket for that connection. alternatively, you can set the socket to deliver .b sigio when activity occurs on a socket; see .br socket (7) for details. .pp if .ir flags is 0, then .br accept4 () is the same as .br accept (). the following values can be bitwise ored in .ir flags to obtain different behavior: .tp 16 .b sock_nonblock set the .br o_nonblock file status flag on the open file description (see .br open (2)) referred to by the new file descriptor. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .tp .b sock_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .sh return value on success, these system calls return a file descriptor for the accepted socket (a nonnegative integer). on error, \-1 is returned, .i errno is set to indicate the error, and .i addrlen is left unchanged. .ss error handling linux .br accept () (and .br accept4 ()) passes already-pending network errors on the new socket as an error code from .br accept (). this behavior differs from other bsd socket implementations. for reliable operation the application should detect the network errors defined for the protocol after .br accept () and treat them like .b eagain by retrying. in the case of tcp/ip, these are .br enetdown , .br eproto , .br enoprotoopt , .br ehostdown , .br enonet , .br ehostunreach , .br eopnotsupp , and .br enetunreach . .sh errors .tp .br eagain " or " ewouldblock .\" actually eagain on linux the socket is marked nonblocking and no connections are present to be accepted. posix.1-2001 and posix.1-2008 allow either error to be returned for this case, and do not require these constants to have the same value, so a portable application should check for both possibilities. .tp .b ebadf .i sockfd is not an open file descriptor. .tp .b econnaborted a connection has been aborted. .tp .b efault the .i addr argument is not in a writable part of the user address space. .tp .b eintr the system call was interrupted by a signal that was caught before a valid connection arrived; see .br signal (7). .tp .b einval socket is not listening for connections, or .i addrlen is invalid (e.g., is negative). .tp .b einval .rb ( accept4 ()) invalid value in .ir flags . .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .br enobufs ", " enomem not enough free memory. this often means that the memory allocation is limited by the socket buffer limits, not by the system memory. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .tp .b eopnotsupp the referenced socket is not of type .br sock_stream . .tp .b eperm firewall rules forbid connection. .tp .b eproto protocol error. .pp in addition, network errors for the new socket and as defined for the protocol may be returned. various linux kernels can return other errors such as .br enosr , .br esocktnosupport , .br eprotonosupport , .br etimedout . the value .b erestartsys may be seen during a trace. .sh versions the .br accept4 () system call is available starting with linux 2.6.28; support in glibc is available starting with version 2.10. .sh conforming to .br accept (): posix.1-2001, posix.1-2008, svr4, 4.4bsd .rb ( accept () first appeared in 4.2bsd). .\" the bsd man page documents five possible error returns .\" (ebadf, enotsock, eopnotsupp, ewouldblock, efault). .\" posix.1-2001 documents errors .\" eagain, ebadf, econnaborted, eintr, einval, emfile, .\" enfile, enobufs, enomem, enotsock, eopnotsupp, eproto, ewouldblock. .\" in addition, susv2 documents efault and enosr. .pp .br accept4 () is a nonstandard linux extension. .pp on linux, the new socket returned by .br accept () does \finot\fp inherit file status flags such as .b o_nonblock and .b o_async from the listening socket. this behavior differs from the canonical bsd sockets implementation. .\" some testing seems to show that tru64 5.1 and hp-ux 11 also .\" do not inherit file status flags -- mtk jun 05 portable programs should not rely on inheritance or noninheritance of file status flags and always explicitly set all required flags on the socket returned from .br accept (). .sh notes there may not always be a connection waiting after a .b sigio is delivered or .br select (2), .br poll (2), or .br epoll (7) return a readability event because the connection might have been removed by an asynchronous network error or another thread before .br accept () is called. if this happens, then the call will block waiting for the next connection to arrive. to ensure that .br accept () never blocks, the passed socket .i sockfd needs to have the .b o_nonblock flag set (see .br socket (7)). .pp for certain protocols which require an explicit confirmation, such as decnet, .br accept () can be thought of as merely dequeuing the next connection request and not implying confirmation. confirmation can be implied by a normal read or write on the new file descriptor, and rejection can be implied by closing the new socket. currently, only decnet has these semantics on linux. .\" .ss the socklen_t type in the original bsd sockets implementation (and on other older systems) .\" such as linux libc4 and libc5, sunos 4, sgi the third argument of .br accept () was declared as an \fiint\ *\fp. a posix.1g draft standard wanted to change it into a \fisize_t\ *\fpc; .\" sunos 5 has 'size_t *' later posix standards and glibc 2.x have .ir "socklen_t\ * ". .sh examples see .br bind (2). .sh see also .br bind (2), .br connect (2), .br listen (2), .br select (2), .br socket (2), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" peter memishian -- meem@gnu.ai.mit.edu .\" $id: insque.3,v 1.2 1996/10/30 21:03:39 meem exp meem $ .\" and copyright (c) 2010, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code (5.4.7) .\" solaris 2.x, osf/1, and hp-ux manpages .\" curry's "unix systems programming for svr4" (o'reilly & associates 1996) .\" .\" changed to posix, 2003-08-11, aeb+wh .\" mtk, 2010-09-09: noted glibc 2.4 bug, added info on circular .\" lists, added example program .\" .th insque 3 2021-03-22 "" "linux programmer's manual" .sh name insque, remque \- insert/remove an item from a queue .sh synopsis .nf .b #include .pp .bi "void insque(void *" elem ", void *" prev ); .bi "void remque(void *" elem ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br insque (), .br remque (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source .fi .sh description the .br insque () and .br remque () functions manipulate doubly linked lists. each element in the list is a structure of which the first two elements are a forward and a backward pointer. the linked list may be linear (i.e., null forward pointer at the end of the list and null backward pointer at the start of the list) or circular. .pp the .br insque () function inserts the element pointed to by \fielem\fp immediately after the element pointed to by \fiprev\fp. .pp if the list is linear, then the call .i "insque(elem, null)" can be used to insert the initial list element, and the call sets the forward and backward pointers of .i elem to null. .pp if the list is circular, the caller should ensure that the forward and backward pointers of the first element are initialized to point to that element, and the .i prev argument of the .br insque () call should also point to the element. .pp the .br remque () function removes the element pointed to by \fielem\fp from the doubly linked list. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br insque (), .br remque () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on ancient systems, .\" e.g., sunos, linux libc4 and libc5 the arguments of these functions were of type \fistruct qelem *\fp, defined as: .pp .in +4n .ex struct qelem { struct qelem *q_forw; struct qelem *q_back; char q_data[1]; }; .ee .in .pp this is still what you will get if .b _gnu_source is defined before including \fi\fp. .pp the location of the prototypes for these functions differs among several versions of unix. the above is the posix version. some systems place them in \fi\fp. .\" linux libc4 and libc 5 placed them .\" in \fi\fp. .sh bugs in glibc 2.4 and earlier, it was not possible to specify .i prev as null. consequently, to build a linear list, the caller had to build a list using an initial call that contained the first two elements of the list, with the forward and backward pointers in each element suitably initialized. .sh examples the program below demonstrates the use of .br insque (). here is an example run of the program: .pp .in +4n .ex .rb "$ " "./a.out \-c a b c" traversing completed list: a b c that was a circular list .ee .in .ss program source \& .ex #include #include #include #include struct element { struct element *forward; struct element *backward; char *name; }; static struct element * new_element(void) { struct element *e = malloc(sizeof(*e)); if (e == null) { fprintf(stderr, "malloc() failed\en"); exit(exit_failure); } return e; } int main(int argc, char *argv[]) { struct element *first, *elem, *prev; int circular, opt, errfnd; /* the "\-c" command\-line option can be used to specify that the list is circular. */ errfnd = 0; circular = 0; while ((opt = getopt(argc, argv, "c")) != \-1) { switch (opt) { case \(aqc\(aq: circular = 1; break; default: errfnd = 1; break; } } if (errfnd || optind >= argc) { fprintf(stderr, "usage: %s [\-c] string...\en", argv[0]); exit(exit_failure); } /* create first element and place it in the linked list. */ elem = new_element(); first = elem; elem\->name = argv[optind]; if (circular) { elem\->forward = elem; elem\->backward = elem; insque(elem, elem); } else { insque(elem, null); } /* add remaining command\-line arguments as list elements. */ while (++optind < argc) { prev = elem; elem = new_element(); elem\->name = argv[optind]; insque(elem, prev); } /* traverse the list from the start, printing element names. */ printf("traversing completed list:\en"); elem = first; do { printf(" %s\en", elem\->name); elem = elem\->forward; } while (elem != null && elem != first); if (elem == first) printf("that was a circular list\en"); exit(exit_success); } .ee .sh see also .br queue (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/outb.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:54:03 1993 by rik faith (faith@cs.unc.edu) .\" fixed typo, aeb, 950823 .\" 2002-02-22, joey, mihtjel: added strtoull() .\" .th strtoul 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strtoul, strtoull, strtouq \- convert a string to an unsigned long integer .sh synopsis .nf .b #include .pp .bi "unsigned long strtoul(const char *restrict " nptr , .bi " char **restrict " endptr ", int " base ); .bi "unsigned long long strtoull(const char *restrict " nptr , .bi " char **restrict " endptr ", int " base ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strtoull (): .nf _isoc99_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description the .br strtoul () function converts the initial part of the string in .i nptr to an .i "unsigned long" value according to the given .ir base , which must be between 2 and 36 inclusive, or be the special value 0. .pp the string may begin with an arbitrary amount of white space (as determined by .br isspace (3)) followed by a single optional \(aq+\(aq or \(aq\-\(aq sign. if .i base is zero or 16, the string may then include a "0x" prefix, and the number will be read in base 16; otherwise, a zero .i base is taken as 10 (decimal) unless the next character is \(aq0\(aq, in which case it is taken as 8 (octal). .pp the remainder of the string is converted to an .i "unsigned long" value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (in bases above 10, the letter \(aqa\(aq in either uppercase or lowercase represents 10, \(aqb\(aq represents 11, and so forth, with \(aqz\(aq representing 35.) .pp if .i endptr is not null, .br strtoul () stores the address of the first invalid character in .ir *endptr . if there were no digits at all, .br strtoul () stores the original value of .i nptr in .i *endptr (and returns 0). in particular, if .i *nptr is not \(aq\e0\(aq but .i **endptr is \(aq\e0\(aq on return, the entire string is valid. .pp the .br strtoull () function works just like the .br strtoul () function but returns an .i "unsigned long long" value. .sh return value the .br strtoul () function returns either the result of the conversion or, if there was a leading minus sign, the negation of the result of the conversion represented as an unsigned value, unless the original (nonnegated) value would overflow; in the latter case, .br strtoul () returns .b ulong_max and sets .i errno to .br erange . precisely the same holds for .br strtoull () (with .b ullong_max instead of .br ulong_max ). .sh errors .tp .b einval (not in c99) the given .i base contains an unsupported value. .tp .b erange the resulting value was out of range. .pp the implementation may also set .ir errno to .b einval in case no conversion was performed (no digits seen, and 0 returned). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strtoul (), .br strtoull (), .br strtouq () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to .br strtoul (): posix.1-2001, posix.1-2008, c89, c99 svr4. .pp .br strtoull (): posix.1-2001, posix.1-2008, c99. .sh notes since .br strtoul () can legitimately return 0 or .b ulong_max .rb ( ullong_max for .br strtoull ()) on both success and failure, the calling program should set .i errno to 0 before the call, and then determine if an error occurred by checking whether .i errno has a nonzero value after the call. .pp in locales other than the "c" locale, other strings may be accepted. (for example, the thousands separator of the current locale may be supported.) .pp bsd also has .pp .in +4n .ex .bi "u_quad_t strtouq(const char *" nptr ", char **" endptr ", int " base ); .ee .in .pp with completely analogous definition. depending on the wordsize of the current architecture, this may be equivalent to .br strtoull () or to .br strtoul (). .pp negative values are considered valid input and are silently converted to the equivalent .i "unsigned long" value. .sh examples see the example on the .br strtol (3) manual page; the use of the functions described in this manual page is similar. .sh see also .br a64l (3), .br atof (3), .br atoi (3), .br atol (3), .br strtod (3), .br strtol (3), .br strtoumax (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/__ppc_yield.3 .\" copyright (c) 2017, oracle. all rights reserved. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th ioctl_getfsmap 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_getfsmap \- retrieve the physical layout of the filesystem .sh synopsis .nf .br "#include " "/* definition of " fs_ioc_getfsmap , .br " fm?_of_*" ", and " *fmr_own_* " constants */" .b #include .pp .bi "int ioctl(int " fd ", fs_ioc_getfsmap, struct fsmap_head * " arg ); .fi .sh description this .br ioctl (2) operation retrieves physical extent mappings for a filesystem. this information can be used to discover which files are mapped to a physical block, examine free space, or find known bad blocks, among other things. .pp the sole argument to this operation should be a pointer to a single .ir "struct fsmap_head" ":" .pp .in +4n .ex struct fsmap { __u32 fmr_device; /* device id */ __u32 fmr_flags; /* mapping flags */ __u64 fmr_physical; /* device offset of segment */ __u64 fmr_owner; /* owner id */ __u64 fmr_offset; /* file offset of segment */ __u64 fmr_length; /* length of segment */ __u64 fmr_reserved[3]; /* must be zero */ }; struct fsmap_head { __u32 fmh_iflags; /* control flags */ __u32 fmh_oflags; /* output flags */ __u32 fmh_count; /* # of entries in array incl. input */ __u32 fmh_entries; /* # of entries filled in (output) */ __u64 fmh_reserved[6]; /* must be zero */ struct fsmap fmh_keys[2]; /* low and high keys for the mapping search */ struct fsmap fmh_recs[]; /* returned records */ }; .ee .in .pp the two .i fmh_keys array elements specify the lowest and highest reverse-mapping key for which the application would like physical mapping information. a reverse mapping key consists of the tuple (device, block, owner, offset). the owner and offset fields are part of the key because some filesystems support sharing physical blocks between multiple files and therefore may return multiple mappings for a given physical block. .pp filesystem mappings are copied into the .i fmh_recs array, which immediately follows the header data. .\" .ss fields of struct fsmap_head the .i fmh_iflags field is a bit mask passed to the kernel to alter the output. no flags are currently defined, so the caller must set this value to zero. .pp the .i fmh_oflags field is a bit mask of flags set by the kernel concerning the returned mappings. if .b fmh_of_dev_t is set, then the .i fmr_device field represents a .i dev_t structure containing the major and minor numbers of the block device. .pp the .i fmh_count field contains the number of elements in the array being passed to the kernel. if this value is 0, .i fmh_entries will be set to the number of records that would have been returned had the array been large enough; no mapping information will be returned. .pp the .i fmh_entries field contains the number of elements in the .i fmh_recs array that contain useful information. .pp the .i fmh_reserved fields must be set to zero. .\" .ss keys the two key records in .i fsmap_head.fmh_keys specify the lowest and highest extent records in the keyspace that the caller wants returned. a filesystem that can share blocks between files likely requires the tuple .ri "(" "device" ", " "physical" ", " "owner" ", " "offset" ", " "flags" ")" to uniquely index any filesystem mapping record. classic non-sharing filesystems might be able to identify any record with only .ri "(" "device" ", " "physical" ", " "flags" ")." for example, if the low key is set to (8:0, 36864, 0, 0, 0), the filesystem will only return records for extents starting at or above 36\ kib on disk. if the high key is set to (8:0, 1048576, 0, 0, 0), only records below 1\ mib will be returned. the format of .i fmr_device in the keys must match the format of the same field in the output records, as defined below. by convention, the field .i fsmap_head.fmh_keys[0] must contain the low key and .i fsmap_head.fmh_keys[1] must contain the high key for the request. .pp for convenience, if .i fmr_length is set in the low key, it will be added to .ir fmr_block " or " fmr_offset as appropriate. the caller can take advantage of this subtlety to set up subsequent calls by copying .i fsmap_head.fmh_recs[fsmap_head.fmh_entries \- 1] into the low key. the function .i fsmap_advance (defined in .ir linux/fsmap.h ) provides this functionality. .\" .ss fields of struct fsmap the .i fmr_device field uniquely identifies the underlying storage device. if the .b fmh_of_dev_t flag is set in the header's .i fmh_oflags field, this field contains a .i dev_t from which major and minor numbers can be extracted. if the flag is not set, this field contains a value that must be unique for each unique storage device. .pp the .i fmr_physical field contains the disk address of the extent in bytes. .pp the .i fmr_owner field contains the owner of the extent. this is an inode number unless .b fmr_of_special_owner is set in the .i fmr_flags field, in which case the value is determined by the filesystem. see the section below about owner values for more details. .pp the .i fmr_offset field contains the logical address in the mapping record in bytes. this field has no meaning if the .br fmr_of_special_owner " or " fmr_of_extent_map flags are set in .ir fmr_flags "." .pp the .i fmr_length field contains the length of the extent in bytes. .pp the .i fmr_flags field is a bit mask of extent state flags. the bits are: .rs 0.4i .tp .b fmr_of_prealloc the extent is allocated but not yet written. .tp .b fmr_of_attr_fork this extent contains extended attribute data. .tp .b fmr_of_extent_map this extent contains extent map information for the owner. .tp .b fmr_of_shared parts of this extent may be shared. .tp .b fmr_of_special_owner the .i fmr_owner field contains a special value instead of an inode number. .tp .b fmr_of_last this is the last record in the data set. .re .pp the .i fmr_reserved field will be set to zero. .\" .ss owner values generally, the value of the .i fmr_owner field for non-metadata extents should be an inode number. however, filesystems are under no obligation to report inode numbers; they may instead report .b fmr_own_unknown if the inode number cannot easily be retrieved, if the caller lacks sufficient privilege, if the filesystem does not support stable inode numbers, or for any other reason. if a filesystem wishes to condition the reporting of inode numbers based on process capabilities, it is strongly urged that the .b cap_sys_admin capability be used for this purpose. .tp the following special owner values are generic to all filesystems: .rs 0.4i .tp .b fmr_own_free free space. .tp .b fmr_own_unknown this extent is in use but its owner is not known or not easily retrieved. .tp .b fmr_own_metadata this extent is filesystem metadata. .re .pp xfs can return the following special owner values: .rs 0.4i .tp .b xfs_fmr_own_free free space. .tp .b xfs_fmr_own_unknown this extent is in use but its owner is not known or not easily retrieved. .tp .b xfs_fmr_own_fs static filesystem metadata which exists at a fixed address. these are the ag superblock, the agf, the agfl, and the agi headers. .tp .b xfs_fmr_own_log the filesystem journal. .tp .b xfs_fmr_own_ag allocation group metadata, such as the free space btrees and the reverse mapping btrees. .tp .b xfs_fmr_own_inobt the inode and free inode btrees. .tp .b xfs_fmr_own_inodes inode records. .tp .b xfs_fmr_own_refc reference count information. .tp .b xfs_fmr_own_cow this extent is being used to stage a copy-on-write. .tp .b xfs_fmr_own_defective: this extent has been marked defective either by the filesystem or the underlying device. .re .pp ext4 can return the following special owner values: .rs 0.4i .tp .b ext4_fmr_own_free free space. .tp .b ext4_fmr_own_unknown this extent is in use but its owner is not known or not easily retrieved. .tp .b ext4_fmr_own_fs static filesystem metadata which exists at a fixed address. this is the superblock and the group descriptors. .tp .b ext4_fmr_own_log the filesystem journal. .tp .b ext4_fmr_own_inodes inode records. .tp .b ext4_fmr_own_blkbm block bit map. .tp .b ext4_fmr_own_inobm inode bit map. .re .sh return value on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors the error placed in .i errno can be one of, but is not limited to, the following: .tp .b ebadf .ir fd is not open for reading. .tp .b ebadmsg the filesystem has detected a checksum error in the metadata. .tp .b efault the pointer passed in was not mapped to a valid memory address. .tp .b einval the array is not long enough, the keys do not point to a valid part of the filesystem, the low key points to a higher point in the filesystem's physical storage address space than the high key, or a nonzero value was passed in one of the fields that must be zero. .tp .b enomem insufficient memory to process the request. .tp .b eopnotsupp the filesystem does not support this command. .tp .b euclean the filesystem metadata is corrupt and needs repair. .sh versions the .b fs_ioc_getfsmap operation first appeared in linux 4.12. .sh conforming to this api is linux-specific. not all filesystems support it. .sh examples see .i io/fsmap.c in the .i xfsprogs distribution for a sample program. .sh see also .br ioctl (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xdr.3 .so man2/mlock.2 .\" copyright (c) 2015, ibm corporation. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th __ppc_yield 3 2021-03-22 "gnu c library" "linux programmer's\ manual" .sh name __ppc_yield, __ppc_mdoio, __ppc_mdoom \- hint the processor to release shared resources .sh synopsis .nf .b #include .pp .b void __ppc_yield(void); .b void __ppc_mdoio(void); .b void __ppc_mdoom(void); .fi .sh description these functions provide hints about the usage of resources that are shared with other processors on the power architecture. they can be used, for example, if a program waiting on a lock intends to divert the shared resources to be used by other processors. .pp .br __ppc_yield () provides a hint that performance will probably be improved if shared resources dedicated to the executing processor are released for use by other processors. .pp .br __ppc_mdoio () provides a hint that performance will probably be improved if shared resources dedicated to the executing processor are released until all outstanding storage accesses to caching-inhibited storage have been completed. .pp .br __ppc_mdoom () provides a hint that performance will probably be improved if shared resources dedicated to the executing processor are released until all outstanding storage accesses to cacheable storage for which the data is not in the cache have been completed. .sh versions these functions first appeared in glibc in version 2.18. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br __ppc_yield (), .br __ppc_mdoio (), .br __ppc_mdoom () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions. .sh see also .br __ppc_set_ppr_med (3) .pp .ir "power isa, book\ ii - section\ 3.2 (""or"" architecture)" .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 28 11:12:17 1993 by rik faith (faith@cs.unc.edu) .\" modified mon may 13 23:08:50 1996 by martin schulze (joey@linux.de) .\" modified 11 may 1998 by joseph s. myers (jsm28@cam.ac.uk) .\" modified 990912 by aeb .\" 2007-10-10 mtk .\" added description of glob_tilde_nomatch .\" expanded the description of various flags .\" various wording fixes. .\" .th glob 3 2021-03-22 "gnu" "linux programmer's manual" .sh name glob, globfree \- find pathnames matching a pattern, free memory from glob() .sh synopsis .nf .b #include .pp .bi "int glob(const char *restrict " pattern ", int " flags , .bi " int (*" errfunc ")(const char *" epath ", int " eerrno ), .bi " glob_t *restrict " pglob ); .bi "void globfree(glob_t *" pglob ); .fi .sh description the .br glob () function searches for all the pathnames matching .i pattern according to the rules used by the shell (see .br glob (7)). no tilde expansion or parameter substitution is done; if you want these, use .br wordexp (3). .pp the .br globfree () function frees the dynamically allocated storage from an earlier call to .br glob (). .pp the results of a .br glob () call are stored in the structure pointed to by .ir pglob . this structure is of type .i glob_t (declared in .ir ) and includes the following elements defined by posix.2 (more may be present as an extension): .pp .in +4n .ex typedef struct { size_t gl_pathc; /* count of paths matched so far */ char **gl_pathv; /* list of matched pathnames. */ size_t gl_offs; /* slots to reserve in \figl_pathv\fp. */ } glob_t; .ee .in .pp results are stored in dynamically allocated storage. .pp the argument .i flags is made up of the bitwise or of zero or more the following symbolic constants, which modify the behavior of .br glob (): .tp .b glob_err return upon a read error (because a directory does not have read permission, for example). by default, .br glob () attempts carry on despite errors, reading all of the directories that it can. .tp .b glob_mark append a slash to each path which corresponds to a directory. .tp .b glob_nosort don't sort the returned pathnames. the only reason to do this is to save processing time. by default, the returned pathnames are sorted. .tp .b glob_dooffs reserve .i pglob\->gl_offs slots at the beginning of the list of strings in .ir pglob\->pathv . the reserved slots contain null pointers. .tp .b glob_nocheck if no pattern matches, return the original pattern. by default, .br glob () returns .b glob_nomatch if there are no matches. .tp .b glob_append append the results of this call to the vector of results returned by a previous call to .br glob (). do not set this flag on the first invocation of .br glob (). .tp .b glob_noescape don't allow backslash (\(aq\e\(aq) to be used as an escape character. normally, a backslash can be used to quote the following character, providing a mechanism to turn off the special meaning metacharacters. .pp .i flags may also include any of the following, which are gnu extensions and not defined by posix.2: .tp .b glob_period allow a leading period to be matched by metacharacters. by default, metacharacters can't match a leading period. .tp .b glob_altdirfunc use alternative functions .ir pglob\->gl_closedir , .ir pglob\->gl_readdir , .ir pglob\->gl_opendir , .ir pglob\->gl_lstat ", and" .i pglob\->gl_stat for filesystem access instead of the normal library functions. .tp .b glob_brace expand .br csh (1) style brace expressions of the form .br {a,b} . brace expressions can be nested. thus, for example, specifying the pattern "{foo/{,cat,dog},bar}" would return the same results as four separate .br glob () calls using the strings: "foo/", "foo/cat", "foo/dog", and "bar". .tp .b glob_nomagic if the pattern contains no metacharacters, then it should be returned as the sole matching word, even if there is no file with that name. .tp .b glob_tilde carry out tilde expansion. if a tilde (\(aq\(ti\(aq) is the only character in the pattern, or an initial tilde is followed immediately by a slash (\(aq/\(aq), then the home directory of the caller is substituted for the tilde. if an initial tilde is followed by a username (e.g., "\(tiandrea/bin"), then the tilde and username are substituted by the home directory of that user. if the username is invalid, or the home directory cannot be determined, then no substitution is performed. .tp .b glob_tilde_check this provides behavior similar to that of .br glob_tilde . the difference is that if the username is invalid, or the home directory cannot be determined, then instead of using the pattern itself as the name, .br glob () returns .br glob_nomatch to indicate an error. .tp .b glob_onlydir this is a .i hint to .br glob () that the caller is interested only in directories that match the pattern. if the implementation can easily determine file-type information, then nondirectory files are not returned to the caller. however, the caller must still check that returned files are directories. (the purpose of this flag is merely to optimize performance when the caller is interested only in directories.) .pp if .i errfunc is not null, it will be called in case of an error with the arguments .ir epath , a pointer to the path which failed, and .ir eerrno , the value of .i errno as returned from one of the calls to .br opendir (3), .br readdir (3), or .br stat (2). if .i errfunc returns nonzero, or if .b glob_err is set, .br glob () will terminate after the call to .ir errfunc . .pp upon successful return, .i pglob\->gl_pathc contains the number of matched pathnames and .i pglob\->gl_pathv contains a pointer to the list of pointers to matched pathnames. the list of pointers is terminated by a null pointer. .pp it is possible to call .br glob () several times. in that case, the .b glob_append flag has to be set in .i flags on the second and later invocations. .pp as a gnu extension, .i pglob\->gl_flags is set to the flags specified, .br or ed with .b glob_magchar if any metacharacters were found. .sh return value on successful completion, .br glob () returns zero. other possible returns are: .tp .b glob_nospace for running out of memory, .tp .b glob_aborted for a read error, and .tp .b glob_nomatch for no found matches. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br glob () t} thread safety t{ mt-unsafe race:utent env sig:alrm timer locale t} t{ .br globfree () t} thread safety mt-safe .te .hy .ad .sp 1 in the above table, .i utent in .i race:utent signifies that if any of the functions .br setutent (3), .br getutent (3), or .br endutent (3) are used in parallel in different threads of a program, then data races could occur. .br glob () calls those functions, so we use race:utent to remind users. .sh conforming to posix.1-2001, posix.1-2008, posix.2. .sh notes the structure elements .i gl_pathc and .i gl_offs are declared as .i size_t in glibc 2.1, as they should be according to posix.2, but are declared as .i int in glibc 2.0. .sh bugs the .br glob () function may fail due to failure of underlying function calls, such as .br malloc (3) or .br opendir (3). these will store their error code in .ir errno . .sh examples one example of use is the following code, which simulates typing .pp .in +4n .ex ls \-l *.c ../*.c .ee .in .pp in the shell: .pp .in +4n .ex glob_t globbuf; globbuf.gl_offs = 2; glob("*.c", glob_dooffs, null, &globbuf); glob("../*.c", glob_dooffs | glob_append, null, &globbuf); globbuf.gl_pathv[0] = "ls"; globbuf.gl_pathv[1] = "\-l"; execvp("ls", &globbuf.gl_pathv[0]); .ee .in .sh see also .br ls (1), .br sh (1), .br stat (2), .br exec (3), .br fnmatch (3), .br malloc (3), .br opendir (3), .br readdir (3), .br wordexp (3), .br glob (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/inet.3 .so man3/envz_add.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswalpha 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswalpha \- test for alphabetic wide character .sh synopsis .nf .b #include .pp .bi "int iswalpha(wint_t " wc ); .fi .sh description the .br iswalpha () function is the wide-character equivalent of the .br isalpha (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "alpha". .pp the wide-character class "alpha" is a subclass of the wide-character class "alnum", and therefore also a subclass of the wide-character class "graph" and of the wide-character class "print". .pp being a subclass of the wide-character class "print", the wide-character class "alpha" is disjoint from the wide-character class "cntrl". .pp being a subclass of the wide-character class "graph", the wide-character class "alpha" is disjoint from the wide-character class "space" and its subclass "blank". .pp being a subclass of the wide-character class "alnum", the wide-character class "alpha" is disjoint from the wide-character class "punct". .pp the wide-character class "alpha" is disjoint from the wide-character class "digit". .pp the wide-character class "alpha" contains the wide-character classes "upper" and "lower". .pp the wide-character class "alpha" always contains at least the letters \(aqa\(aq to \(aqz\(aq and \(aqa\(aq to \(aqz\(aq. .sh return value the .br iswalpha () function returns nonzero if .i wc is a wide character belonging to the wide-character class "alpha". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswalpha () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswalpha () depends on the .b lc_ctype category of the current locale. .sh see also .br isalpha (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1996 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th msync 2 2021-03-22 "linux" "linux programmer's manual" .sh name msync \- synchronize a file with a memory map .sh synopsis .nf .b #include .pp .bi "int msync(void *" addr ", size_t " length ", int " flags ); .fi .sh description .br msync () flushes changes made to the in-core copy of a file that was mapped into memory using .br mmap (2) back to the filesystem. without use of this call, there is no guarantee that changes are written back before .br munmap (2) is called. to be more precise, the part of the file that corresponds to the memory area starting at .i addr and having length .i length is updated. .pp the .i flags argument should specify exactly one of .br ms_async and .br ms_sync , and may additionally include the .b ms_invalidate bit. these bits have the following meanings: .tp .b ms_async specifies that an update be scheduled, but the call returns immediately. .tp .b ms_sync requests an update and waits for it to complete. .tp .b ms_invalidate .\" since linux 2.4, this seems to be a no-op (other than the .\" ebusy check for vm_locked). asks to invalidate other mappings of the same file (so that they can be updated with the fresh values just written). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebusy .b ms_invalidate was specified in .ir flags , and a memory lock exists for the specified address range. .tp .b einval .i addr is not a multiple of pagesize; or any bit other than .br ms_async " | " ms_invalidate " | " ms_sync is set in .ir flags ; or both .b ms_sync and .b ms_async are set in .ir flags . .tp .b enomem the indicated memory (or part of it) was not mapped. .sh conforming to posix.1-2001, posix.1-2008. .pp this call was introduced in linux 1.3.21, and then used .b efault instead of .br enomem . in linux 2.4.19, this was changed to the posix value .br enomem . .pp on posix systems on which .br msync () is available, both .b _posix_mapped_files and .b _posix_synchronized_io are defined in .i to a value greater than 0. (see also .br sysconf (3).) .\" posix.1-2001: it shall be defined to -1 or 0 or 200112l. .\" -1: unavailable, 0: ask using sysconf(). .\" glibc defines them to 1. .sh notes according to posix, either .br ms_sync or .br ms_async must be specified in .ir flags , and indeed failure to include one of these flags will cause .br msync () to fail on some systems. however, linux permits a call to .br msync () that specifies neither of these flags, with semantics that are (currently) equivalent to specifying .br ms_async . (since linux 2.6.19, .\" commit 204ec841fbea3e5138168edbc3a76d46747cc987 .br ms_async is in fact a no-op, since the kernel properly tracks dirty pages and flushes them to storage as necessary.) notwithstanding the linux behavior, portable, future-proof applications should ensure that they specify either .br ms_sync or .br ms_async in .ir flags . .sh see also .br mmap (2) .pp b.o. gallmeister, posix.4, o'reilly, pp. 128\(en129 and 389\(en391. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fpathconf.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification .\" http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th putwchar 3 2021-03-22 "gnu" "linux programmer's manual" .sh name putwchar \- write a wide character to standard output .sh synopsis .nf .b #include .pp .bi "wint_t putwchar(wchar_t " wc ); .fi .sh description the .br putwchar () function is the wide-character equivalent of the .br putchar (3) function. it writes the wide character .i wc to .ir stdout . if .i ferror(stdout) becomes true, it returns .br weof . if a wide character conversion error occurs, it sets .ir errno to .b eilseq and returns .br weof . otherwise, it returns .ir wc . .pp for a nonlocking counterpart, see .br unlocked_stdio (3). .sh return value the .br putwchar () function returns .i wc if no error occurred, or .b weof to indicate an error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br putwchar () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br putwchar () depends on the .b lc_ctype category of the current locale. .pp it is reasonable to expect that .br putwchar () will actually write the multibyte sequence corresponding to the wide character .ir wc . .sh see also .br fputwc (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2005, 2012, 2016 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under the gpl. .\" %%%license_end .\" .th fmemopen 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fmemopen \- open memory as stream .sh synopsis .nf .b #include .pp .bi "file *fmemopen(void *"buf ", size_t "size ", const char *" mode ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fmemopen (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br fmemopen () function opens a stream that permits the access specified by .ir mode . the stream allows i/o to be performed on the string or memory buffer pointed to by .ir buf . .pp the .i mode argument specifies the semantics of i/o on the stream, and is one of the following: .tp .i r the stream is opened for reading. .tp .i w the stream is opened for writing. .tp .i a append; open the stream for writing, with the initial buffer position set to the first null byte. .tp .i r+ open the stream for reading and writing. .tp .i w+ open the stream for reading and writing. the buffer contents are truncated (i.e., \(aq\e0\(aq is placed in the first byte of the buffer). .tp .i a+ append; open the stream for reading and writing, with the initial buffer position set to the first null byte. .pp the stream maintains the notion of a current position, the location where the next i/o operation will be performed. the current position is implicitly updated by i/o operations. it can be explicitly updated using .br fseek (3), and determined using .br ftell (3). in all modes other than append, the initial position is set to the start of the buffer. in append mode, if no null byte is found within the buffer, then the initial position is .ir size+1 . .pp if .i buf is specified as null, then .br fmemopen () allocates a buffer of .i size bytes. this is useful for an application that wants to write data to a temporary buffer and then read it back again. the initial position is set to the start of the buffer. the buffer is automatically freed when the stream is closed. note that the caller has no way to obtain a pointer to the temporary buffer allocated by this call (but see .br open_memstream (3)). .pp if .i buf is not null, then it should point to a buffer of at least .i len bytes allocated by the caller. .pp when a stream that has been opened for writing is flushed .rb ( fflush (3)) or closed .rb ( fclose (3)), a null byte is written at the end of the buffer if there is space. the caller should ensure that an extra byte is available in the buffer (and that .i size counts that byte) to allow for this. .pp in a stream opened for reading, null bytes (\(aq\e0\(aq) in the buffer do not cause read operations to return an end-of-file indication. a read from the buffer will indicate end-of-file only when the current buffer position advances .i size bytes past the start of the buffer. .pp write operations take place either at the current position (for modes other than append), or at the current size of the stream (for append modes). .pp attempts to write more than .i size bytes to the buffer result in an error. by default, such errors will be visible (by the absence of data) only when the .i stdio buffer is flushed. disabling buffering with the following call may be useful to detect errors at the time of an output operation: .pp setbuf(stream, null); .sh return value upon successful completion, .br fmemopen () returns a .i file pointer. otherwise, null is returned and .i errno is set to indicate the error. .sh versions .br fmemopen () was already available in glibc 1.0.x. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fmemopen (), t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function is not specified in posix.1-2001, and is not widely available on other systems. .pp posix.1-2008 specifies that \(aqb\(aq in .ir mode shall be ignored. however, technical corrigendum 1 .\" http://austingroupbugs.net/view.php?id=396 adjusts the standard to allow implementation-specific treatment for this case, thus permitting the glibc treatment of \(aqb\(aq. .sh notes there is no file descriptor associated with the file stream returned by this function (i.e., .br fileno (3) will return an error if called on the returned stream). .pp with version 2.22, binary mode (see below) was removed, many longstanding bugs in the implementation of .br fmemopen () were fixed, and a new versioned symbol was created for this interface. .\" .ss binary mode from version 2.9 to 2.21, the glibc implementation of .br fmemopen () supported a "binary" mode, enabled by specifying the letter \(aqb\(aq as the second character in .ir mode . in this mode, writes don't implicitly add a terminating null byte, and .br fseek (3) .b seek_end is relative to the end of the buffer (i.e., the value specified by the .i size argument), rather than the current string length. .pp an api bug afflicted the implementation of binary mode: to specify binary mode, the \(aqb\(aq must be the .i second character in .ir mode . thus, for example, "wb+" has the desired effect, but "w+b" does not. this is inconsistent with the treatment of .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12836 .ir mode by .br fopen (3). .pp binary mode was removed in glibc 2.22; a \(aqb\(aq specified in .i mode has no effect. .sh bugs in versions of glibc before 2.22, if .i size is specified as zero, .br fmemopen () fails with the error .br einval . .\" http://sourceware.org/bugzilla/show_bug.cgi?id=11216 it would be more consistent if this case successfully created a stream that then returned end-of-file on the first attempt at reading; since version 2.22, the glibc implementation provides that behavior. .pp in versions of glibc before 2.22, specifying append mode ("a" or "a+") for .br fmemopen () sets the initial buffer position to the first null byte, but .\" http://sourceware.org/bugzilla/show_bug.cgi?id=13152 (if the current position is reset to a location other than the end of the stream) does not force subsequent writes to append at the end of the stream. this bug is fixed in glibc 2.22. .pp in versions of glibc before 2.22, if the .i mode argument to .br fmemopen () specifies append ("a" or "a+"), and the .i size argument does not cover a null byte in .ir buf , then, according to posix.1-2008, the initial buffer position should be set to the next byte after the end of the buffer. however, in this case the glibc .\" http://sourceware.org/bugzilla/show_bug.cgi?id=13151 .br fmemopen () sets the buffer position to \-1. this bug is fixed in glibc 2.22. .pp in versions of glibc before 2.22, .\" https://sourceware.org/bugzilla/show_bug.cgi?id=14292 when a call to .br fseek (3) with a .i whence value of .b seek_end was performed on a stream created by .br fmemopen (), the .i offset was .ir subtracted from the end-of-stream position, instead of being added. this bug is fixed in glibc 2.22. .pp the glibc 2.9 addition of "binary" mode for .br fmemopen () .\" http://sourceware.org/bugzilla/show_bug.cgi?id=6544 silently changed the abi: previously, .br fmemopen () ignored \(aqb\(aq in .ir mode . .sh examples the program below uses .br fmemopen () to open an input buffer, and .br open_memstream (3) to open a dynamically sized output buffer. the program scans its input string (taken from the program's first command-line argument) reading integers, and writes the squares of these integers to the output buffer. an example of the output produced by this program is the following: .pp .in +4n .ex .rb "$" " ./a.out \(aq1 23 43\(aq" size=11; ptr=1 529 1849 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) int main(int argc, char *argv[]) { file *out, *in; int v, s; size_t size; char *ptr; if (argc != 2) { fprintf(stderr, "usage: %s \(aq...\(aq\en", argv[0]); exit(exit_failure); } in = fmemopen(argv[1], strlen(argv[1]), "r"); if (in == null) handle_error("fmemopen"); out = open_memstream(&ptr, &size); if (out == null) handle_error("open_memstream"); for (;;) { s = fscanf(in, "%d", &v); if (s <= 0) break; s = fprintf(out, "%d ", v * v); if (s == \-1) handle_error("fprintf"); } fclose(in); fclose(out); printf("size=%zu; ptr=%s\en", size, ptr); free(ptr); exit(exit_success); } .ee .sh see also .br fopen (3), .br fopencookie (3), .br open_memstream (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1996 free software foundation, inc. .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .\" 2006-02-09, some reformatting by luc van oostenryck; some .\" reformatting and rewordings by mtk .\" .th create_module 2 2021-03-22 "linux" "linux programmer's manual" .sh name create_module \- create a loadable module entry .sh synopsis .nf .b #include .pp .bi "caddr_t create_module(const char *" name ", size_t " size ); .fi .pp .ir note : no declaration of this system call is provided in glibc headers; see notes. .sh description .ir note : this system call is present only in kernels before linux 2.6. .pp .br create_module () attempts to create a loadable module entry and reserve the kernel memory that will be needed to hold the module. this system call requires privilege. .sh return value on success, returns the kernel address at which the module will reside. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eexist a module by that name already exists. .tp .b efault .i name is outside the program's accessible address space. .tp .b einval the requested size is too small even for the module header information. .tp .b enomem the kernel could not allocate a contiguous block of memory large enough for the module. .tp .b enosys .br create_module () is not supported in this version of the kernel (e.g., the kernel is version 2.6 or later). .tp .b eperm the caller was not privileged (did not have the .b cap_sys_module capability). .sh versions this system call is present on linux only up until kernel 2.4; it was removed in linux 2.6. .\" removed in linux 2.5.48 .sh conforming to .br create_module () is linux-specific. .sh notes this obsolete system call is not supported by glibc. no declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an abi for this system call. therefore, in order to employ this system call, it was sufficient to manually declare the interface in your code; alternatively, you could invoke the system call using .br syscall (2). .sh see also .br delete_module (2), .br init_module (2), .br query_module (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_attr_setstackaddr.3 .so man3/cabs.3 .so man3/rand.3 .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th fopencookie 3 2021-03-22 "linux" "linux programmer's manual" .sh name fopencookie \- opening a custom stream .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "file *fopencookie(void *restrict " cookie ", const char *restrict " mode , .bi " cookie_io_functions_t " io_funcs ); .fi .sh description the .br fopencookie () function allows the programmer to create a custom implementation for a standard i/o stream. this implementation can store the stream's data at a location of its own choosing; for example, .br fopencookie () is used to implement .br fmemopen (3), which provides a stream interface to data that is stored in a buffer in memory. .pp in order to create a custom stream the programmer must: .ip * 3 implement four "hook" functions that are used internally by the standard i/o library when performing i/o on the stream. .ip * define a "cookie" data type, a structure that provides bookkeeping information (e.g., where to store data) used by the aforementioned hook functions. the standard i/o package knows nothing about the contents of this cookie (thus it is typed as .ir "void\ *" when passed to .br fopencookie ()), but automatically supplies the cookie as the first argument when calling the hook functions. .ip * call .br fopencookie () to open a new stream and associate the cookie and hook functions with that stream. .pp the .br fopencookie () function serves a purpose similar to .br fopen (3): it opens a new stream and returns a pointer to a .i file object that is used to operate on that stream. .pp the .i cookie argument is a pointer to the caller's cookie structure that is to be associated with the new stream. this pointer is supplied as the first argument when the standard i/o library invokes any of the hook functions described below. .pp the .i mode argument serves the same purpose as for .br fopen (3). the following modes are supported: .ir r , .ir w , .ir a , .ir r+ , .ir w+ , and .ir a+ . see .br fopen (3) for details. .pp the .i io_funcs argument is a structure that contains four fields pointing to the programmer-defined hook functions that are used to implement this stream. the structure is defined as follows .pp .in +4n .ex typedef struct { cookie_read_function_t *read; cookie_write_function_t *write; cookie_seek_function_t *seek; cookie_close_function_t *close; } cookie_io_functions_t; .ee .in .pp the four fields are as follows: .tp .i cookie_read_function_t *read this function implements read operations for the stream. when called, it receives three arguments: .ip ssize_t read(void *cookie, char *buf, size_t size); .ip the .i buf and .i size arguments are, respectively, a buffer into which input data can be placed and the size of that buffer. as its function result, the .i read function should return the number of bytes copied into .ir buf , 0 on end of file, or \-1 on error. the .i read function should update the stream offset appropriately. .ip if .i *read is a null pointer, then reads from the custom stream always return end of file. .tp .i cookie_write_function_t *write this function implements write operations for the stream. when called, it receives three arguments: .ip ssize_t write(void *cookie, const char *buf, size_t size); .ip the .i buf and .i size arguments are, respectively, a buffer of data to be output to the stream and the size of that buffer. as its function result, the .i write function should return the number of bytes copied from .ir buf , or 0 on error. (the function must not return a negative value.) the .i write function should update the stream offset appropriately. .ip if .i *write is a null pointer, then output to the stream is discarded. .tp .i cookie_seek_function_t *seek this function implements seek operations on the stream. when called, it receives three arguments: .ip int seek(void *cookie, off64_t *offset, int whence); .ip the .i *offset argument specifies the new file offset depending on which of the following three values is supplied in .ir whence : .rs .tp .b seek_set the stream offset should be set .i *offset bytes from the start of the stream. .tp .b seek_cur .i *offset should be added to the current stream offset. .tp .b seek_end the stream offset should be set to the size of the stream plus .ir *offset . .re .ip before returning, the .i seek function should update .i *offset to indicate the new stream offset. .ip as its function result, the .i seek function should return 0 on success, and \-1 on error. .ip if .i *seek is a null pointer, then it is not possible to perform seek operations on the stream. .tp .i cookie_close_function_t *close this function closes the stream. the hook function can do things such as freeing buffers allocated for the stream. when called, it receives one argument: .ip int close(void *cookie); .ip the .i cookie argument is the cookie that the programmer supplied when calling .br fopencookie (). .ip as its function result, the .i close function should return 0 on success, and .b eof on error. .ip if .i *close is null, then no special action is performed when the stream is closed. .sh return value on success .br fopencookie () returns a pointer to the new stream. on error, null is returned. .\" .sh errors .\" it's not clear if errno ever gets set... .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fopencookie () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a nonstandard gnu extension. .sh examples the program below implements a custom stream whose functionality is similar (but not identical) to that available via .br fmemopen (3). it implements a stream whose data is stored in a memory buffer. the program writes its command-line arguments to the stream, and then seeks through the stream reading two out of every five characters and writing them to standard output. the following shell session demonstrates the use of the program: .pp .in +4n .ex .rb "$" " ./a.out \(aqhello world\(aq" /he/ / w/ /d/ reached end of file .ee .in .pp note that a more general version of the program below could be improved to more robustly handle various error situations (e.g., opening a stream with a cookie that already has an open stream; closing a stream that has already been closed). .ss program source \& .ex #define _gnu_source #include #include #include #include #include #define init_buf_size 4 struct memfile_cookie { char *buf; /* dynamically sized buffer for data */ size_t allocated; /* size of buf */ size_t endpos; /* number of characters in buf */ off_t offset; /* current file offset in buf */ }; ssize_t memfile_write(void *c, const char *buf, size_t size) { char *new_buff; struct memfile_cookie *cookie = c; /* buffer too small? keep doubling size until big enough. */ while (size + cookie\->offset > cookie\->allocated) { new_buff = realloc(cookie\->buf, cookie\->allocated * 2); if (new_buff == null) { return \-1; } else { cookie\->allocated *= 2; cookie\->buf = new_buff; } } memcpy(cookie\->buf + cookie\->offset, buf, size); cookie\->offset += size; if (cookie\->offset > cookie\->endpos) cookie\->endpos = cookie\->offset; return size; } ssize_t memfile_read(void *c, char *buf, size_t size) { ssize_t xbytes; struct memfile_cookie *cookie = c; /* fetch minimum of bytes requested and bytes available. */ xbytes = size; if (cookie\->offset + size > cookie\->endpos) xbytes = cookie\->endpos \- cookie\->offset; if (xbytes < 0) /* offset may be past endpos */ xbytes = 0; memcpy(buf, cookie\->buf + cookie\->offset, xbytes); cookie\->offset += xbytes; return xbytes; } int memfile_seek(void *c, off64_t *offset, int whence) { off64_t new_offset; struct memfile_cookie *cookie = c; if (whence == seek_set) new_offset = *offset; else if (whence == seek_end) new_offset = cookie\->endpos + *offset; else if (whence == seek_cur) new_offset = cookie\->offset + *offset; else return \-1; if (new_offset < 0) return \-1; cookie\->offset = new_offset; *offset = new_offset; return 0; } int memfile_close(void *c) { struct memfile_cookie *cookie = c; free(cookie\->buf); cookie\->allocated = 0; cookie\->buf = null; return 0; } int main(int argc, char *argv[]) { cookie_io_functions_t memfile_func = { .read = memfile_read, .write = memfile_write, .seek = memfile_seek, .close = memfile_close }; file *stream; struct memfile_cookie mycookie; size_t nread; char buf[1000]; /* set up the cookie before calling fopencookie(). */ mycookie.buf = malloc(init_buf_size); if (mycookie.buf == null) { perror("malloc"); exit(exit_failure); } mycookie.allocated = init_buf_size; mycookie.offset = 0; mycookie.endpos = 0; stream = fopencookie(&mycookie, "w+", memfile_func); if (stream == null) { perror("fopencookie"); exit(exit_failure); } /* write command\-line arguments to our file. */ for (int j = 1; j < argc; j++) if (fputs(argv[j], stream) == eof) { perror("fputs"); exit(exit_failure); } /* read two bytes out of every five, until eof. */ for (long p = 0; ; p += 5) { if (fseek(stream, p, seek_set) == \-1) { perror("fseek"); exit(exit_failure); } nread = fread(buf, 1, 2, stream); if (nread == 0) { if (ferror(stream) != 0) { fprintf(stderr, "fread failed\en"); exit(exit_failure); } printf("reached end of file\en"); break; } printf("/%.*s/\en", (int) nread, buf); } exit(exit_success); } .ee .sh see also .br fclose (3), .br fmemopen (3), .br fopen (3), .br fseek (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man3/rpc.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:49:27 1993 by rik faith (faith@cs.unc.edu) .\" modified fri apr 26 12:38:55 met dst 1996 by martin schulze (joey@linux.de) .\" modified 2001-11-13, aeb .\" modified 2001-12-13, joey, aeb .\" modified 2004-11-16, mtk .\" .th ctime 3 2021-03-22 "" "linux programmer's manual" .sh name asctime, ctime, gmtime, localtime, mktime, asctime_r, ctime_r, gmtime_r, localtime_r \- transform date and time to broken-down time or ascii .sh synopsis .nf .b #include .pp .bi "char *asctime(const struct tm *" tm ); .bi "char *asctime_r(const struct tm *restrict " tm ", char *restrict " buf ); .pp .bi "char *ctime(const time_t *" timep ); .bi "char *ctime_r(const time_t *restrict " timep ", char *restrict " buf ); .pp .bi "struct tm *gmtime(const time_t *" timep ); .bi "struct tm *gmtime_r(const time_t *restrict " timep , .bi " struct tm *restrict " result ); .pp .bi "struct tm *localtime(const time_t *" timep ); .bi "struct tm *localtime_r(const time_t *restrict " timep , .bi " struct tm *restrict " result ); .pp .bi "time_t mktime(struct tm *" tm ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br asctime_r (), .br ctime_r (), .br gmtime_r (), .br localtime_r (): .nf _posix_c_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br ctime (), .br gmtime (), and .br localtime () functions all take an argument of data type \fitime_t\fp, which represents calendar time. when interpreted as an absolute time value, it represents the number of seconds elapsed since the epoch, 1970-01-01 00:00:00 +0000 (utc). .pp the .br asctime () and .br mktime () functions both take an argument representing broken-down time, which is a representation separated into year, month, day, and so on. .pp broken-down time is stored in the structure \fitm\fp, which is defined in \fi\fp as follows: .pp .in +4n .ex struct tm { int tm_sec; /* seconds (0\-60) */ int tm_min; /* minutes (0\-59) */ int tm_hour; /* hours (0\-23) */ int tm_mday; /* day of the month (1\-31) */ int tm_mon; /* month (0\-11) */ int tm_year; /* year \- 1900 */ int tm_wday; /* day of the week (0\-6, sunday = 0) */ int tm_yday; /* day in the year (0\-365, 1 jan = 0) */ int tm_isdst; /* daylight saving time */ }; .ee .in .pp the members of the \fitm\fp structure are: .tp 10 .i tm_sec the number of seconds after the minute, normally in the range 0 to 59, but can be up to 60 to allow for leap seconds. .tp .i tm_min the number of minutes after the hour, in the range 0 to 59. .tp .i tm_hour the number of hours past midnight, in the range 0 to 23. .tp .i tm_mday the day of the month, in the range 1 to 31. .tp .i tm_mon the number of months since january, in the range 0 to 11. .tp .i tm_year the number of years since 1900. .tp .i tm_wday the number of days since sunday, in the range 0 to 6. .tp .i tm_yday the number of days since january 1, in the range 0 to 365. .tp .i tm_isdst a flag that indicates whether daylight saving time is in effect at the time described. the value is positive if daylight saving time is in effect, zero if it is not, and negative if the information is not available. .pp the call .bi ctime( t ) is equivalent to .bi asctime(localtime( t )) \fr. it converts the calendar time \fit\fp into a null-terminated string of the form .pp .in +4n .ex "wed jun 30 21:49:08 1993\en" .ee .in .pp the abbreviations for the days of the week are "sun", "mon", "tue", "wed", "thu", "fri", and "sat". the abbreviations for the months are "jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", and "dec". the return value points to a statically allocated string which might be overwritten by subsequent calls to any of the date and time functions. the function also sets the external variables \fitzname\fp, \fitimezone\fp, and \fidaylight\fp (see .br tzset (3)) with information about the current timezone. the reentrant version .br ctime_r () does the same, but stores the string in a user-supplied buffer which should have room for at least 26 bytes. it need not set \fitzname\fp, \fitimezone\fp, and \fidaylight\fp. .pp the .br gmtime () function converts the calendar time \fitimep\fp to broken-down time representation, expressed in coordinated universal time (utc). it may return null when the year does not fit into an integer. the return value points to a statically allocated struct which might be overwritten by subsequent calls to any of the date and time functions. the .br gmtime_r () function does the same, but stores the data in a user-supplied struct. .pp the .br localtime () function converts the calendar time \fitimep\fp to broken-down time representation, expressed relative to the user's specified timezone. the function acts as if it called .br tzset (3) and sets the external variables \fitzname\fp with information about the current timezone, \fitimezone\fp with the difference between coordinated universal time (utc) and local standard time in seconds, and \fidaylight\fp to a nonzero value if daylight savings time rules apply during some part of the year. the return value points to a statically allocated struct which might be overwritten by subsequent calls to any of the date and time functions. the .br localtime_r () function does the same, but stores the data in a user-supplied struct. it need not set \fitzname\fp, \fitimezone\fp, and \fidaylight\fp. .pp the .br asctime () function converts the broken-down time value \fitm\fp into a null-terminated string with the same format as .br ctime (). the return value points to a statically allocated string which might be overwritten by subsequent calls to any of the date and time functions. the .br asctime_r () function does the same, but stores the string in a user-supplied buffer which should have room for at least 26 bytes. .pp the .br mktime () function converts a broken-down time structure, expressed as local time, to calendar time representation. the function ignores the values supplied by the caller in the .i tm_wday and .i tm_yday fields. the value specified in the .i tm_isdst field informs .br mktime () whether or not daylight saving time (dst) is in effect for the time supplied in the .i tm structure: a positive value means dst is in effect; zero means that dst is not in effect; and a negative value means that .br mktime () should (use timezone information and system databases to) attempt to determine whether dst is in effect at the specified time. .pp the .br mktime () function modifies the fields of the .ir tm structure as follows: .i tm_wday and .i tm_yday are set to values determined from the contents of the other fields; if structure members are outside their valid interval, they will be normalized (so that, for example, 40 october is changed into 9 november); .i tm_isdst is set (regardless of its initial value) to a positive value or to 0, respectively, to indicate whether dst is or is not in effect at the specified time. calling .br mktime () also sets the external variable \fitzname\fp with information about the current timezone. .pp if the specified broken-down time cannot be represented as calendar time (seconds since the epoch), .br mktime () returns .i (time_t)\ \-1 and does not alter the members of the broken-down time structure. .sh return value on success, .br gmtime () and .br localtime () return a pointer to a .ir "struct\ tm" . .pp on success, .br gmtime_r () and .br localtime_r () return the address of the structure pointed to by .ir result . .pp on success, .br asctime () and .br ctime () return a pointer to a string. .pp on success, .br asctime_r () and .br ctime_r () return a pointer to the string pointed to by .ir buf . .pp on success, .br mktime () returns the calendar time (seconds since the epoch), expressed as a value of type .ir time_t . .pp on error, .br mktime () returns the value .ir "(time_t)\ \-1" . the remaining functions return null on error. on error, .i errno is set to indicate the error. .sh errors .tp .b eoverflow the result cannot be represented. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br asctime () t} thread safety t{ mt-unsafe race:asctime locale t} t{ .br asctime_r () t} thread safety t{ mt-safe locale t} t{ .br ctime () t} thread safety t{ mt-unsafe race:tmbuf race:asctime env locale t} t{ .br ctime_r (), .br gmtime_r (), .br localtime_r (), .br mktime () t} thread safety t{ mt-safe env locale t} t{ .br gmtime (), .br localtime () t} thread safety t{ mt-unsafe race:tmbuf env locale t} .te .hy .ad .sp 1 .sh conforming to posix.1-2001. c89 and c99 specify .br asctime (), .br ctime (), .br gmtime (), .br localtime (), and .br mktime (). posix.1-2008 marks .br asctime (), .br asctime_r (), .br ctime (), and .br ctime_r () as obsolete, recommending the use of .br strftime (3) instead. .pp posix doesn't specify the parameters of .br ctime_r () to be .ir restrict ; that is specific to glibc. .sh notes the four functions .br asctime (), .br ctime (), .br gmtime (), and .br localtime () return a pointer to static data and hence are not thread-safe. the thread-safe versions, .br asctime_r (), .br ctime_r (), .br gmtime_r (), and .br localtime_r (), are specified by susv2. .pp posix.1-2001 says: "the .br asctime (), .br ctime (), .br gmtime (), and .br localtime () functions shall return values in one of two static objects: a broken-down time structure and an array of type .ir char . execution of any of the functions may overwrite the information returned in either of these objects by any of the other functions." this can occur in the glibc implementation. .pp in many implementations, including glibc, a 0 in .i tm_mday is interpreted as meaning the last day of the preceding month. .pp the glibc version of \fistruct tm\fp has additional fields .pp .in +4n .ex long tm_gmtoff; /* seconds east of utc */ const char *tm_zone; /* timezone abbreviation */ .ee .in .pp defined when .b _bsd_source was set before including .ir . this is a bsd extension, present in 4.3bsd-reno. .pp according to posix.1-2001, .br localtime () is required to behave as though .br tzset (3) was called, while .br localtime_r () does not have this requirement. .\" see http://thread.gmane.org/gmane.comp.time.tz/2034/ for portable code, .br tzset (3) should be called before .br localtime_r (). .sh see also .br date (1), .br gettimeofday (2), .br time (2), .br utime (2), .br clock (3), .br difftime (3), .br strftime (3), .br strptime (3), .br timegm (3), .br tzset (3), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2011, hewlett-packard development company, l.p. .\" written by stephen m. cameron .\" .\" %%%license_start(gplv2_oneline) .\" licensed under gnu general public license version 2 (gplv2) .\" %%%license_end .\" .\" shorthand for double quote that works everywhere. .ds q \n'34' .th cciss 4 2021-03-22 "linux" "linux programmer's manual" .sh name cciss \- hp smart array block driver .sh synopsis .nf modprobe cciss [ cciss_allow_hpsa=1 ] .fi .sh description .\" commit 253d2464df446456c0bba5ed4137a7be0b278aa8 .br note : this obsolete driver was removed from the kernel in version 4.14, as it is superseded by the .br hpsa (4) driver in newer kernels. .pp .b cciss is a block driver for older hp smart array raid controllers. .ss options .ir "cciss_allow_hpsa=1" : this option prevents the .b cciss driver from attempting to drive any controllers that the .br hpsa (4) driver is capable of controlling, which is to say, the .b cciss driver is restricted by this option to the following controllers: .pp .nf smart array 5300 smart array 5i smart array 532 smart array 5312 smart array 641 smart array 642 smart array 6400 smart array 6400 em smart array 6i smart array p600 smart array p400i smart array e200i smart array e200 smart array e200i smart array e200i smart array e200i smart array e500 .fi .ss supported hardware the .b cciss driver supports the following smart array boards: .pp .nf smart array 5300 smart array 5i smart array 532 smart array 5312 smart array 641 smart array 642 smart array 6400 smart array 6400 u320 expansion module smart array 6i smart array p600 smart array p800 smart array e400 smart array p400i smart array e200 smart array e200i smart array e500 smart array p700m smart array p212 smart array p410 smart array p410i smart array p411 smart array p812 smart array p712m smart array p711m .fi .ss configuration details to configure hp smart array controllers, use the hp array configuration utility (either .br hpacuxe (8) or .br hpacucli (8)) or the offline rom-based configuration utility (orca) run from the smart array's option rom at boot time. .sh files .ss device nodes the device naming scheme is as follows: .pp major numbers: .pp 104 cciss0 105 cciss1 106 cciss2 105 cciss3 108 cciss4 109 cciss5 110 cciss6 111 cciss7 .pp minor numbers: .pp .ex b7 b6 b5 b4 b3 b2 b1 b0 |\-\-\-\-+\-\-\-\-| |\-\-\-\-+\-\-\-\-| | | | +\-\-\-\-\-\-\-\- partition id (0=wholedev, 1\-15 partition) | +\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- logical volume number .ee .pp the device naming scheme is: .ts li l. /dev/cciss/c0d0 controller 0, disk 0, whole device /dev/cciss/c0d0p1 controller 0, disk 0, partition 1 /dev/cciss/c0d0p2 controller 0, disk 0, partition 2 /dev/cciss/c0d0p3 controller 0, disk 0, partition 3 /dev/cciss/c1d1 controller 1, disk 1, whole device /dev/cciss/c1d1p1 controller 1, disk 1, partition 1 /dev/cciss/c1d1p2 controller 1, disk 1, partition 2 /dev/cciss/c1d1p3 controller 1, disk 1, partition 3 .te .ss files in /proc the files .i /proc/driver/cciss/cciss[0\-9]+ contain information about the configuration of each controller. for example: .pp .in +4n .ex $ \fbcd /proc/driver/cciss\fp $ \fbls \-l\fp total 0 -rw\-r\-\-r\-\- 1 root root 0 2010\-09\-10 10:38 cciss0 -rw\-r\-\-r\-\- 1 root root 0 2010\-09\-10 10:38 cciss1 -rw\-r\-\-r\-\- 1 root root 0 2010\-09\-10 10:38 cciss2 $ \fbcat cciss2\fp cciss2: hp smart array p800 controller board id: 0x3223103c firmware version: 7.14 irq: 16 logical drives: 1 current q depth: 0 current # commands on controller: 0 max q depth since init: 1 max # commands on controller since init: 2 max sg entries since init: 32 sequential access devices: 0 cciss/c2d0: 36.38gb raid 0 .ee .in .\" .ss files in /sys .tp .i /sys/bus/pci/devices//ccissx/cxdy/model displays the scsi inquiry page 0 model for logical drive .i y of controller .ir x . .tp .i /sys/bus/pci/devices//ccissx/cxdy/rev displays the scsi inquiry page 0 revision for logical drive .i y of controller .ir x . .tp .i /sys/bus/pci/devices//ccissx/cxdy/unique_id displays the scsi inquiry page 83 serial number for logical drive .i y of controller .ir x . .tp .i /sys/bus/pci/devices//ccissx/cxdy/vendor displays the scsi inquiry page 0 vendor for logical drive .i y of controller .ir x . .tp .i /sys/bus/pci/devices//ccissx/cxdy/block:cciss!cxdy a symbolic link to .ir /sys/block/cciss!cxdy . .tp .i /sys/bus/pci/devices//ccissx/rescan when this file is written to, the driver rescans the controller to discover any new, removed, or modified logical drives. .tp .i /sys/bus/pci/devices//ccissx/resettable a value of 1 displayed in this file indicates that the "reset_devices=1" kernel parameter (used by .br kdump ) is honored by this controller. a value of 0 indicates that the "reset_devices=1" kernel parameter will not be honored. some models of smart array are not able to honor this parameter. .tp .i /sys/bus/pci/devices//ccissx/cxdy/lunid displays the 8-byte lun id used to address logical drive .i y of controller .ir x . .tp .i /sys/bus/pci/devices//ccissx/cxdy/raid_level displays the raid level of logical drive .i y of controller .ir x . .tp .i /sys/bus/pci/devices//ccissx/cxdy/usage_count displays the usage count (number of opens) of logical drive .i y of controller .ir x . .ss scsi tape drive and medium changer support scsi sequential access devices and medium changer devices are supported and appropriate device nodes are automatically created (e.g., .ir /dev/st0 , .ir /dev/st1 , etc.; see .br st (4) for more details.) you must enable "scsi tape drive support for smart array 5xxx" and "scsi support" in your kernel configuration to be able to use scsi tape drives with your smart array 5xxx controller. .pp additionally, note that the driver will not engage the scsi core at init time. the driver must be directed to dynamically engage the scsi core via the .i /proc filesystem entry, which the "block" side of the driver creates as .i /proc/driver/cciss/cciss* at run time. this is because at driver init time, the scsi core may not yet be initialized (because the driver is a block driver) and attempting to register it with the scsi core in such a case would cause a hang. this is best done via an initialization script (typically in .ir /etc/init.d , but could vary depending on distribution). for example: .pp .in +4n .ex for x in /proc/driver/cciss/cciss[0\-9]* do echo "engage scsi" > $x done .ee .in .pp once the scsi core is engaged by the driver, it cannot be disengaged (except by unloading the driver, if it happens to be linked as a module.) .pp note also that if no sequential access devices or medium changers are detected, the scsi core will not be engaged by the action of the above script. .ss hot plug support for scsi tape drives hot plugging of scsi tape drives is supported, with some caveats. the .b cciss driver must be informed that changes to the scsi bus have been made. this may be done via the .i /proc filesystem. for example: .pp echo "rescan" > /proc/scsi/cciss0/1 .pp this causes the driver to: .rs .ip 1. 3 query the adapter about changes to the physical scsi buses and/or fiber channel arbitrated loop, and .ip 2. make note of any new or removed sequential access devices or medium changers. .re .pp the driver will output messages indicating which devices have been added or removed and the controller, bus, target, and lun used to address each device. the driver then notifies the scsi midlayer of these changes. .pp note that the naming convention of the .i /proc filesystem entries contains a number in addition to the driver name (e.g., "cciss0" instead of just "cciss", which you might expect). .pp note: .i only sequential access devices and medium changers are presented as scsi devices to the scsi midlayer by the .b cciss driver. specifically, physical scsi disk drives are .i not presented to the scsi midlayer. the only disk devices that are presented to the kernel are logical drives that the array controller constructs from regions on the physical drives. the logical drives are presented to the block layer (not to the scsi midlayer). it is important for the driver to prevent the kernel from accessing the physical drives directly, since these drives are used by the array controller to construct the logical drives. .ss scsi error handling for tape drives and medium changers the linux scsi midlayer provides an error-handling protocol that is initiated whenever a scsi command fails to complete within a certain amount of time (which can vary depending on the command). the .b cciss driver participates in this protocol to some extent. the normal protocol is a four-step process: .ip * 3 first, the device is told to abort the command. .ip * if that doesn't work, the device is reset. .ip * if that doesn't work, the scsi bus is reset. .ip * if that doesn't work, the host bus adapter is reset. .pp the .b cciss driver is a block driver as well as a scsi driver and only the tape drives and medium changers are presented to the scsi midlayer. furthermore, unlike more straightforward scsi drivers, disk i/o continues through the block side during the scsi error-recovery process. therefore, the .b cciss driver implements only the first two of these actions, aborting the command, and resetting the device. note also that most tape drives will not oblige in aborting commands, and sometimes it appears they will not even obey a reset command, though in most circumstances they will. if the command cannot be aborted and the device cannot be reset, the device will be set offline. .pp in the event that the error-handling code is triggered and a tape drive is successfully reset or the tardy command is successfully aborted, the tape drive may still not allow i/o to continue until some command is issued that positions the tape to a known position. typically you must rewind the tape (by issuing .i "mt \-f /dev/st0 rewind" for example) before i/o can proceed again to a tape drive that was reset. .sh see also .br hpsa (4), .br cciss_vol_status (8), .br hpacucli (8), .br hpacuxe (8) .pp .ur http://cciss.sf.net .ue , and .i documentation/blockdev/cciss.txt and .i documentation/abi/testing/sysfs\-bus\-pci\-devices\-cciss in the linux kernel source tree .\" .sh authors .\" don brace, steve cameron, chase maupin, mike miller, michael ni, .\" charles white, francis wiran .\" and probably some other people. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_mutexattr_getpshared 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_mutexattr_getpshared, pthread_mutexattr_setpshared \- get/set process-shared mutex attribute .sh synopsis .nf .b #include .pp .bi "int pthread_mutexattr_getpshared(" .bi " const pthread_mutexattr_t *restrict " attr , .bi " int *restrict " pshared ); .bi "int pthread_mutexattr_setpshared(pthread_mutexattr_t *" attr , .bi " int " pshared ); .fi .pp compile and link with \fi\-pthread\fp. .sh description these functions get and set the process-shared attribute in a mutex attributes object. this attribute must be appropriately set to ensure correct, efficient operation of a mutex created using this attributes object. .pp the process-shared attribute can have one of the following values: .tp .b pthread_process_private mutexes created with this attributes object are to be shared only among threads in the same process that initialized the mutex. this is the default value for the process-shared mutex attribute. .tp .b pthread_process_shared mutexes created with this attributes object can be shared between any threads that have access to the memory containing the object, including threads in different processes. .pp .br pthread_mutexattr_getpshared () places the value of the process-shared attribute of the mutex attributes object referred to by .ir attr in the location pointed to by .ir pshared . .pp .br pthread_mutexattr_setpshared () sets the value of the process-shared attribute of the mutex attributes object referred to by .ir attr to the value specified in .br pshared . .pp if .i attr does not refer to an initialized mutex attributes object, the behavior is undefined. .sh return value on success, these functions return 0. on error, they return a positive error number. .sh errors .br pthread_mutexattr_setpshared () can fail with the following errors: .tp .b einval the value specified in .i pshared is invalid. .tp .b enotsup .i pshared is .br pthread_process_shared but the implementation does not support process-shared mutexes. .sh conforming to posix.1-2001, posix.1-2008. .sh see also .ad l .nh .br pthread_mutexattr_init (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-3.7 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" the american national standards committee x3, on information .\" processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)stdarg.3 6.8 (berkeley) 6/29/91 .\" .\" converted for linux, mon nov 29 15:11:11 1993, faith@cs.unc.edu .\" additions, 2001-10-14, aeb .\" .th stdarg 3 2021-03-22 "" "linux programmer's manual" .sh name stdarg, va_start, va_arg, va_end, va_copy \- variable argument lists .sh synopsis .nf .b #include .pp .bi "void va_start(va_list " ap ", " last ); .ib type " va_arg(va_list " ap ", " type ); .bi "void va_end(va_list " ap ); .bi "void va_copy(va_list " dest ", va_list " src ); .fi .sh description a function may be called with a varying number of arguments of varying types. the include file .i declares a type .i va_list and defines three macros for stepping through a list of arguments whose number and types are not known to the called function. .pp the called function must declare an object of type .i va_list which is used by the macros .br va_start (), .br va_arg (), and .br va_end (). .ss va_start() the .br va_start () macro initializes .i ap for subsequent use by .br va_arg () and .br va_end (), and must be called first. .pp the argument .i last is the name of the last argument before the variable argument list, that is, the last argument of which the calling function knows the type. .pp because the address of this argument may be used in the .br va_start () macro, it should not be declared as a register variable, or as a function or an array type. .ss va_arg() the .br va_arg () macro expands to an expression that has the type and value of the next argument in the call. the argument .i ap is the .i va_list .i ap initialized by .br va_start (). each call to .br va_arg () modifies .i ap so that the next call returns the next argument. the argument .i type is a type name specified so that the type of a pointer to an object that has the specified type can be obtained simply by adding a * to .ir type . .pp the first use of the .br va_arg () macro after that of the .br va_start () macro returns the argument after .ir last . successive invocations return the values of the remaining arguments. .pp if there is no next argument, or if .i type is not compatible with the type of the actual next argument (as promoted according to the default argument promotions), random errors will occur. .pp if .i ap is passed to a function that uses .bi va_arg( ap , type ), then the value of .i ap is undefined after the return of that function. .ss va_end() each invocation of .br va_start () must be matched by a corresponding invocation of .br va_end () in the same function. after the call .bi va_end( ap ) the variable .i ap is undefined. multiple traversals of the list, each bracketed by .br va_start () and .br va_end () are possible. .br va_end () may be a macro or a function. .ss va_copy() the .br va_copy () macro copies the (previously initialized) variable argument list .i src to .ir dest . the behavior is as if .br va_start () were applied to .ir dest with the same .i last argument, followed by the same number of .br va_arg () invocations that was used to reach the current state of .ir src . .pp .\" proposal from clive@demon.net, 1997-02-28 an obvious implementation would have a .i va_list be a pointer to the stack frame of the variadic function. in such a setup (by far the most common) there seems nothing against an assignment .pp .in +4n .ex va_list aq = ap; .ee .in .pp unfortunately, there are also systems that make it an array of pointers (of length 1), and there one needs .pp .in +4n .ex va_list aq; *aq = *ap; .ee .in .pp finally, on systems where arguments are passed in registers, it may be necessary for .br va_start () to allocate memory, store the arguments there, and also an indication of which argument is next, so that .br va_arg () can step through the list. now .br va_end () can free the allocated memory again. to accommodate this situation, c99 adds a macro .br va_copy (), so that the above assignment can be replaced by .pp .in +4n .ex va_list aq; va_copy(aq, ap); \&... va_end(aq); .ee .in .pp each invocation of .br va_copy () must be matched by a corresponding invocation of .br va_end () in the same function. some systems that do not supply .br va_copy () have .b __va_copy instead, since that was the name used in the draft proposal. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br va_start (), .br va_end (), .br va_copy () t} thread safety mt-safe t{ .br va_arg () t} thread safety mt-safe race:ap .te .hy .ad .sp 1 .sh conforming to the .br va_start (), .br va_arg (), and .br va_end () macros conform to c89. c99 defines the .br va_copy () macro. .sh bugs unlike the historical .b varargs macros, the .b stdarg macros do not permit programmers to code a function with no fixed arguments. this problem generates work mainly when converting .b varargs code to .b stdarg code, but it also creates difficulties for variadic functions that wish to pass all of their arguments on to a function that takes a .i va_list argument, such as .br vfprintf (3). .sh examples the function .i foo takes a string of format characters and prints out the argument associated with each format character based on the type. .pp .ex #include #include void foo(char *fmt, ...) /* \(aq...\(aq is c syntax for a variadic function */ { va_list ap; int d; char c; char *s; va_start(ap, fmt); while (*fmt) switch (*fmt++) { case \(aqs\(aq: /* string */ s = va_arg(ap, char *); printf("string %s\en", s); break; case \(aqd\(aq: /* int */ d = va_arg(ap, int); printf("int %d\en", d); break; case \(aqc\(aq: /* char */ /* need a cast here since va_arg only takes fully promoted types */ c = (char) va_arg(ap, int); printf("char %c\en", c); break; } va_end(ap); } .ee .sh see also .br vprintf (3), .br vscanf (3), .br vsyslog (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:26:03 1993 by rik faith (faith@cs.unc.edu) .th getprotoent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getprotoent, getprotobyname, getprotobynumber, setprotoent, endprotoent \- get protocol entry .sh synopsis .nf .b #include .pp .b struct protoent *getprotoent(void); .pp .bi "struct protoent *getprotobyname(const char *" name ); .bi "struct protoent *getprotobynumber(int " proto ); .pp .bi "void setprotoent(int " stayopen ); .b void endprotoent(void); .fi .sh description the .br getprotoent () function reads the next entry from the protocols database (see .br protocols (5)) and returns a .i protoent structure containing the broken-out fields from the entry. a connection is opened to the database if necessary. .pp the .br getprotobyname () function returns a .i protoent structure for the entry from the database that matches the protocol name .ir name . a connection is opened to the database if necessary. .pp the .br getprotobynumber () function returns a .i protoent structure for the entry from the database that matches the protocol number .ir number . a connection is opened to the database if necessary. .pp the .br setprotoent () function opens a connection to the database, and sets the next entry to the first entry. if .i stayopen is nonzero, then the connection to the database will not be closed between calls to one of the .br getproto* () functions. .pp the .br endprotoent () function closes the connection to the database. .pp the .i protoent structure is defined in .i as follows: .pp .in +4n .ex struct protoent { char *p_name; /* official protocol name */ char **p_aliases; /* alias list */ int p_proto; /* protocol number */ } .ee .in .pp the members of the .i protoent structure are: .tp .i p_name the official name of the protocol. .tp .i p_aliases a null-terminated list of alternative names for the protocol. .tp .i p_proto the protocol number. .sh return value the .br getprotoent (), .br getprotobyname (), and .br getprotobynumber () functions return a pointer to a statically allocated .i protoent structure, or a null pointer if an error occurs or the end of the file is reached. .sh files .pd 0 .tp .i /etc/protocols protocol database file .pd .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getprotoent () t} thread safety t{ mt-unsafe race:protoent race:protoentbuf locale t} t{ .br getprotobyname () t} thread safety t{ mt-unsafe race:protobyname locale t} t{ .br getprotobynumber () t} thread safety t{ mt-unsafe race:protobynumber locale t} t{ .br setprotoent (), .br endprotoent () t} thread safety t{ mt-unsafe race:protoent locale t} .te .hy .ad .sp 1 in the above table, .i protoent in .i race:protoent signifies that if any of the functions .br setprotoent (), .br getprotoent (), or .br endprotoent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh see also .br getnetent (3), .br getprotoent_r (3), .br getservent (3), .br protocols (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/resolver.3 .so man3/getpwent.3 .so man3/fmin.3 .\" copyright (c) 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2007-10-23 mtk: moved the _syscalln specific material to the .\" new _syscall(2) page, and substantially enhanced and rewrote .\" the remaining material on this page. .\" .th intro 2 2021-08-27 "linux" "linux programmer's manual" .sh name intro \- introduction to system calls .sh description section 2 of the manual describes the linux system calls. a system call is an entry point into the linux kernel. usually, system calls are not invoked directly: instead, most system calls have corresponding c library wrapper functions which perform the steps required (e.g., trapping to kernel mode) in order to invoke the system call. thus, making a system call looks the same as invoking a normal library function. .pp in many cases, the c library wrapper function does nothing more than: .ip * 3 copying arguments and the unique system call number to the registers where the kernel expects them; .ip * trapping to kernel mode, at which point the kernel does the real work of the system call; .ip * setting .i errno if the system call returns an error number when the kernel returns the cpu to user mode. .pp however, in a few cases, a wrapper function may do rather more than this, for example, performing some preprocessing of the arguments before trapping to kernel mode, or postprocessing of values returned by the system call. where this is the case, the manual pages in section 2 generally try to note the details of both the (usually gnu) c library api interface and the raw system call. most commonly, the main description will focus on the c library interface, and differences for the system call are covered in the notes section. .pp for a list of the linux system calls, see .br syscalls (2). .sh return value on error, most system calls return a negative error number (i.e., the negated value of one of the constants described in .br errno (3)). the c library wrapper hides this detail from the caller: when a system call returns a negative value, the wrapper copies the absolute value into the .i errno variable, and returns \-1 as the return value of the wrapper. .pp the value returned by a successful system call depends on the call. many system calls return 0 on success, but some can return nonzero values from a successful call. the details are described in the individual manual pages. .pp in some cases, the programmer must define a feature test macro in order to obtain the declaration of a system call from the header file specified in the man page synopsis section. (where required, these feature test macros must be defined before including .i any header files.) in such cases, the required macro is described in the man page. for further information on feature test macros, see .br feature_test_macros (7). .sh conforming to certain terms and abbreviations are used to indicate unix variants and standards to which calls in this section conform. see .br standards (7). .sh notes .ss calling directly in most cases, it is unnecessary to invoke a system call directly, but there are times when the standard c library does not implement a nice wrapper function for you. in this case, the programmer must manually invoke the system call using .br syscall (2). historically, this was also possible using one of the _syscall macros described in .br _syscall (2). .ss authors and copyright conditions look at the header of the manual page source for the author(s) and copyright conditions. note that these can be different from page to page! .sh see also .ad l .nh .br _syscall (2), .br syscall (2), .br syscalls (2), .br errno (3), .br intro (3), .br capabilities (7), .br credentials (7), .br feature_test_macros (7), .br mq_overview (7), .br path_resolution (7), .br pipe (7), .br pty (7), .br sem_overview (7), .br shm_overview (7), .br signal (7), .br socket (7), .br standards (7), .br symlink (7), .br system_data_types (7), .br sysvipc (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright (c) 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th stdio_ext 3 2021-03-22 "" "linux programmer's manual" .sh name __fbufsize, __flbf, __fpending, __fpurge, __freadable, __freading, __fsetlocking, __fwritable, __fwriting, _flushlbf \- interfaces to stdio file structure .sh synopsis .nf .b #include .b #include .pp .bi "size_t __fbufsize(file *" stream ); .bi "size_t __fpending(file *" stream ); .bi "int __flbf(file *" stream ); .bi "int __freadable(file *" stream ); .bi "int __fwritable(file *" stream ); .bi "int __freading(file *" stream ); .bi "int __fwriting(file *" stream ); .bi "int __fsetlocking(file *" stream ", int " type ); .b "void _flushlbf(void);" .bi "void __fpurge(file *" stream ); .fi .sh description solaris introduced routines to allow portable access to the internals of the .i file structure, and glibc also implemented these. .pp the .br __fbufsize () function returns the size of the buffer currently used by the given stream. .pp the .br __fpending () function returns the number of bytes in the output buffer. for wide-oriented streams the unit is wide characters. this function is undefined on buffers in reading mode, or opened read-only. .pp the .br __flbf () function returns a nonzero value if the stream is line-buffered, and zero otherwise. .pp the .br __freadable () function returns a nonzero value if the stream allows reading, and zero otherwise. .pp the .br __fwritable () function returns a nonzero value if the stream allows writing, and zero otherwise. .pp the .br __freading () function returns a nonzero value if the stream is read-only, or if the last operation on the stream was a read operation, and zero otherwise. .pp the .br __fwriting () function returns a nonzero value if the stream is write-only (or append-only), or if the last operation on the stream was a write operation, and zero otherwise. .pp the .br __fsetlocking () function can be used to select the desired type of locking on the stream. it returns the current type. the .i type argument can take the following three values: .tp .b fsetlocking_internal perform implicit locking around every operation on the given stream (except for the *_unlocked ones). this is the default. .tp .b fsetlocking_bycaller the caller will take care of the locking (possibly using .br flockfile (3) in case there is more than one thread), and the stdio routines will not do locking until the state is reset to .br fsetlocking_internal . .tp .b fsetlocking_query don't change the type of locking. (only return it.) .pp the .br _flushlbf () function flushes all line-buffered streams. (presumably so that output to a terminal is forced out, say before reading keyboard input.) .pp the .br __fpurge () function discards the contents of the stream's buffer. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br __fbufsize (), .br __fpending (), .br __fpurge (), .br __fsetlocking () t} thread safety mt-safe race:stream t{ .br __flbf (), .br __freadable (), .br __freading (), .br __fwritable (), .br __fwriting (), .br _flushlbf () t} thread safety mt-safe .te .hy .ad .sp 1 .sh see also .br flockfile (3), .br fpurge (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" added note on self-signaling, aeb, 2002-06-07 .\" added note on cap_kill, mtk, 2004-06-16 .\" .th sigqueue 3 2021-03-22 "linux" "linux programmer's manual" .sh name sigqueue \- queue a signal and data to a process .sh synopsis .nf .b #include .pp .bi "int sigqueue(pid_t " pid ", int " sig ", const union sigval " value ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigqueue (): .nf _posix_c_source >= 199309l .fi .sh description .br sigqueue () sends the signal specified in .i sig to the process whose pid is given in .ir pid . the permissions required to send a signal are the same as for .br kill (2). as with .br kill (2), the null signal (0) can be used to check if a process with a given pid exists. .pp the .i value argument is used to specify an accompanying item of data (either an integer or a pointer value) to be sent with the signal, and has the following type: .pp .in +4n .ex union sigval { int sival_int; void *sival_ptr; }; .ee .in .pp if the receiving process has installed a handler for this signal using the .b sa_siginfo flag to .br sigaction (2), then it can obtain this data via the .i si_value field of the .i siginfo_t structure passed as the second argument to the handler. furthermore, the .i si_code field of that structure will be set to .br si_queue . .sh return value on success, .br sigqueue () returns 0, indicating that the signal was successfully queued to the receiving process. otherwise, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eagain the limit of signals which may be queued has been reached. (see .br signal (7) for further information.) .tp .b einval .i sig was invalid. .tp .b eperm the process does not have permission to send the signal to the receiving process. for the required permissions, see .br kill (2). .tp .b esrch no process has a pid matching .ir pid . .sh versions .br sigqueue () and the underlying .br rt_sigqueueinfo (2) system call first appeared in linux 2.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigqueue () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes if this function results in the sending of a signal to the process that invoked it, and that signal was not blocked by the calling thread, and no other threads were willing to handle this signal (either by having it unblocked, or by waiting for it using .br sigwait (3)), then at least some signal must be delivered to this thread before this function returns. .ss c library/kernel differences on linux, .br sigqueue () is implemented using the .br rt_sigqueueinfo (2) system call. the system call differs in its third argument, which is the .i siginfo_t structure that will be supplied to the receiving process's signal handler or returned by the receiving process's .br sigtimedwait (2) call. inside the glibc .br sigqueue () wrapper, this argument, .ir uinfo , is initialized as follows: .pp .in +4n .ex uinfo.si_signo = sig; /* argument supplied to sigqueue() */ uinfo.si_code = si_queue; uinfo.si_pid = getpid(); /* process id of sender */ uinfo.si_uid = getuid(); /* real uid of sender */ uinfo.si_value = val; /* argument supplied to sigqueue() */ .ee .in .sh see also .br kill (2), .br rt_sigqueueinfo (2), .br sigaction (2), .br signal (2), .br pthread_sigqueue (3), .br sigwait (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/_exit.2 .\" copyright (c) 2021 suren baghdasaryan .\" and copyright (c) 2021 minchan kim .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" commit ecb8ac8b1f146915aa6b96449b66dd48984caacc .\" .th process_madvise 2 2021-06-20 "linux" "linux programmer's manual" .sh name process_madvise \- give advice about use of memory to a process .sh synopsis .nf .br "#include " " /* definition of " madv_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .br "#include " " /* definition of " "struct iovec" " type */" .b #include .pp .bi "ssize_t syscall(sys_process_madvise, int " pidfd , .bi " const struct iovec *" iovec ", size_t " vlen \ ", int " advice , .bi " unsigned int " flags ");" .fi .pp .ir note : glibc provides no wrapper for .br process_madvise (), necessitating the use of .br syscall (2). .\" fixme: see .sh description the .br process_madvise() system call is used to give advice or directions to the kernel about the address ranges of another process or of the calling process. it provides the advice for the address ranges described by .i iovec and .ir vlen . the goal of such advice is to improve system or application performance. .pp the .i pidfd argument is a pid file descriptor (see .br pidfd_open (2)) that specifies the process to which the advice is to be applied. .pp the pointer .i iovec points to an array of .i iovec structures, defined in .ir as: .pp .in +4n .ex struct iovec { void *iov_base; /* starting address */ size_t iov_len; /* length of region */ }; .ee .in .pp the .i iovec structure describes address ranges beginning at .i iov_base address and with the size of .i iov_len bytes. .pp the .i vlen specifies the number of elements in the .i iovec structure. this value must be less than or equal to .br iov_max (defined in .i or accessible via the call .ir sysconf(_sc_iov_max) ). .pp the .i advice argument is one of the following values: .tp .br madv_cold see .br madvise (2). .tp .br madv_pageout see .br madvise (2). .pp the .i flags argument is reserved for future use; currently, this argument must be specified as 0. .pp the .i vlen and .i iovec arguments are checked before applying any advice. if .i vlen is too big, or .i iovec is invalid, then an error will be returned immediately and no advice will be applied. .pp the advice might be applied to only a part of .i iovec if one of its elements points to an invalid memory region in the remote process. no further elements will be processed beyond that point. (see the discussion regarding partial advice in return value.) .pp permission to apply advice to another process is governed by a ptrace access mode .b ptrace_mode_read_realcreds check (see .br ptrace (2)); in addition, because of the performance implications of applying the advice, the caller must have the .b cap_sys_admin capability. .sh return value on success, .br process_madvise () returns the number of bytes advised. this return value may be less than the total number of requested bytes, if an error occurred after some .i iovec elements were already processed. the caller should check the return value to determine whether a partial advice occurred. .pp on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i pidfd is not a valid pid file descriptor. .tp .b efault the memory described by .i iovec is outside the accessible address space of the process referred to by .ir pidfd . .tp .b einval .i flags is not 0. .tp .b einval the sum of the .i iov_len values of .i iovec overflows a .i ssize_t value. .tp .b einval .i vlen is too large. .tp .b enomem could not allocate memory for internal copies of the .i iovec structures. .tp .b eperm the caller does not have permission to access the address space of the process .ir pidfd . .tp .b esrch the target process does not exist (i.e., it has terminated and been waited on). .sh versions this system call first appeared in linux 5.10. .\" commit ecb8ac8b1f146915aa6b96449b66dd48984caacc support for this system call is optional, depending on the setting of the .b config_advise_syscalls configuration option. .sh conforming to the .br process_madvise () system call is linux-specific. .sh see also .br madvise (2), .br pidfd_open (2), .br process_vm_readv (2), .br process_vm_write (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sched_setaffinity.2 .so man2/llseek.2 .so man3/fpurge.3 .so man3/stdarg.3 .so man3/pthread_attr_setschedparam.3 .so man3/unlocked_stdio.3 .\" copyright (c) 2001 martin schulze .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2008-09-04, mtk, taken from debian downstream, with a few light edits .\" .th networks 5 2008-09-04 "gnu/linux" "linux system administration" .sh name networks \- network name information .sh description the file .i /etc/networks is a plain ascii file that describes known darpa networks and symbolic names for these networks. each line represents a network and has the following structure: .pp .rs .i name number aliases ... .re .pp where the fields are delimited by spaces or tabs. empty lines are ignored. the hash character (\fb#\fp) indicates the start of a comment: this character, and the remaining characters up to the end of the current line, are ignored by library functions that process the file. .pp the field descriptions are: .tp .i name the symbolic name for the network. network names can contain any printable characters except white-space characters or the comment character. .tp .i number the official number for this network in numbers-and-dots notation (see .br inet (3)). the trailing ".0" (for the host component of the network address) may be omitted. .tp .i aliases optional aliases for the network. .pp .pp this file is read by the .br route (8) and .br netstat (8) utilities. only class a, b, or c networks are supported, partitioned networks (i.e., network/26 or network/28) are not supported by this file. .sh files .tp .i /etc/networks the networks definition file. .sh see also .br getnetbyaddr (3), .br getnetbyname (3), .br getnetent (3), .br netstat (8), .br route (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1980, 1991 regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)killpg.2 6.5 (berkeley) 3/10/91 .\" .\" modified fri jul 23 21:55:01 1993 by rik faith .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .\" modified 2004-06-16 by michael kerrisk .\" added notes on cap_kill .\" modified 2004-06-21 by aeb .\" .th killpg 3 2021-03-22 "linux" "linux programmer's manual" .sh name killpg \- send signal to a process group .sh synopsis .nf .b #include .pp .bi "int killpg(int " pgrp ", int " sig ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br killpg (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source .fi .sh description .br killpg () sends the signal .i sig to the process group .ir pgrp . see .br signal (7) for a list of signals. .pp if .i pgrp is 0, .br killpg () sends the signal to the calling process's process group. (posix says: if .i pgrp is less than or equal to 1, the behavior is undefined.) .pp for the permissions required to send a signal to another process, see .br kill (2). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i sig is not a valid signal number. .tp .b eperm the process does not have permission to send the signal to any of the target processes. for the required permissions, see .br kill (2). .tp .b esrch no process can be found in the process group specified by .ir pgrp . .tp .b esrch the process group was given as 0 but the sending process does not have a process group. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd .rb ( killpg () first appeared in 4bsd). .sh notes there are various differences between the permission checking in bsd-type systems and system\ v-type systems. see the posix rationale for .br kill (3p). a difference not mentioned by posix concerns the return value .br eperm : bsd documents that no signal is sent and .b eperm returned when the permission check failed for at least one target process, while posix documents .b eperm only when the permission check failed for all target processes. .ss c library/kernel differences on linux, .br killpg () is implemented as a library function that makes the call .ir "kill(\-pgrp,\ sig)" . .sh see also .br getpgrp (2), .br kill (2), .br signal (2), .br capabilities (7), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_spin_lock.3 .so man3/endian.3 .\" copyright (c) 2019 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pidfd_open 2 2021-08-27 "linux" "linux programmer's manual" .sh name pidfd_open \- obtain a file descriptor that refers to a process .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_pidfd_open, pid_t " pid ", unsigned int " flags ); .fi .pp .ir note : glibc provides no wrapper for .br pidfd_open (), necessitating the use of .br syscall (2). .sh description the .br pidfd_open () system call creates a file descriptor that refers to the process whose pid is specified in .ir pid . the file descriptor is returned as the function result; the close-on-exec flag is set on the file descriptor. .pp the .i flags argument either has the value 0, or contains the following flag: .tp .br pidfd_nonblock " (since linux 5.10)" .\" commit 4da9af0014b51c8b015ed8c622440ef28912efe6 return a nonblocking file descriptor. if the process referred to by the file descriptor has not yet terminated, then an attempt to wait on the file descriptor using .br waitid (2) will immediately return the error .br eagain rather than blocking. .sh return value on success, .br pidfd_open () returns a file descriptor (a nonnegative integer). on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b einval .i flags is not valid. .tp .b einval .i pid is not valid. .tp .b emfile the per-process limit on the number of open file descriptors has been reached (see the description of .br rlimit_nofile in .br getrlimit (2)). .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enodev the anonymous inode filesystem is not available in this kernel. .tp .b enomem insufficient kernel memory was available. .tp .b esrch the process specified by .i pid does not exist. .sh versions .br pidfd_open () first appeared in linux 5.3. .sh conforming to .br pidfd_open () is linux specific. .sh notes the following code sequence can be used to obtain a file descriptor for the child of .br fork (2): .pp .in +4n .ex pid = fork(); if (pid > 0) { /* if parent */ pidfd = pidfd_open(pid, 0); ... } .ee .in .pp even if the child has already terminated by the time of the .br pidfd_open () call, its pid will not have been recycled and the returned file descriptor will refer to the resulting zombie process. note, however, that this is guaranteed only if the following conditions hold true: .ip \(bu 2 the disposition of .br sigchld has not been explicitly set to .br sig_ign (see .br sigaction (2)); .ip \(bu the .br sa_nocldwait flag was not specified while establishing a handler for .br sigchld or while setting the disposition of that signal to .br sig_dfl (see .br sigaction (2)); and .ip \(bu the zombie process was not reaped elsewhere in the program (e.g., either by an asynchronously executed signal handler or by .br wait (2) or similar in another thread). .pp if any of these conditions does not hold, then the child process (along with a pid file descriptor that refers to it) should instead be created using .br clone (2) with the .br clone_pidfd flag. .\" .ss use cases for pid file descriptors a pid file descriptor returned by .br pidfd_open () (or by .br clone (2) with the .br clone_pid flag) can be used for the following purposes: .ip \(bu 2 the .br pidfd_send_signal (2) system call can be used to send a signal to the process referred to by a pid file descriptor. .ip \(bu a pid file descriptor can be monitored using .br poll (2), .br select (2), and .br epoll (7). when the process that it refers to terminates, these interfaces indicate the file descriptor as readable. note, however, that in the current implementation, nothing can be read from the file descriptor .rb ( read (2) on the file descriptor fails with the error .br einval ). .ip \(bu if the pid file descriptor refers to a child of the calling process, then it can be waited on using .br waitid (2). .ip \(bu the .br pidfd_getfd (2) system call can be used to obtain a duplicate of a file descriptor of another process referred to by a pid file descriptor. .ip \(bu a pid file descriptor can be used as the argument of .br setns (2) in order to move into one or more of the same namespaces as the process referred to by the file descriptor. .ip \(bu a pid file descriptor can be used as the argument of .br process_madvise (2) in order to provide advice on the memory usage patterns of the process referred to by the file descriptor. .pp the .br pidfd_open () system call is the preferred way of obtaining a pid file descriptor for an already existing process. the alternative is to obtain a file descriptor by opening a .i /proc/[pid] directory. however, the latter technique is possible only if the .br proc (5) filesystem is mounted; furthermore, the file descriptor obtained in this way is .i not pollable and can't be waited on with .br waitid (2). .sh examples the program below opens a pid file descriptor for the process whose pid is specified as its command-line argument. it then uses .br poll (2) to monitor the file descriptor for process exit, as indicated by an .br epollin event. .\" .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include #ifndef __nr_pidfd_open #define __nr_pidfd_open 434 /* system call # on most architectures */ #endif static int pidfd_open(pid_t pid, unsigned int flags) { return syscall(__nr_pidfd_open, pid, flags); } int main(int argc, char *argv[]) { struct pollfd pollfd; int pidfd, ready; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_success); } pidfd = pidfd_open(atoi(argv[1]), 0); if (pidfd == \-1) { perror("pidfd_open"); exit(exit_failure); } pollfd.fd = pidfd; pollfd.events = pollin; ready = poll(&pollfd, 1, \-1); if (ready == \-1) { perror("poll"); exit(exit_failure); } printf("events (%#x): pollin is %sset\en", pollfd.revents, (pollfd.revents & pollin) ? "" : "not "); close(pidfd); exit(exit_success); } .ee .sh see also .br clone (2), .br kill (2), .br pidfd_getfd (2), .br pidfd_send_signal (2), .br poll (2), .br process_madvise (2), .br select (2), .br setns (2), .br waitid (2), .br epoll (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" eli zaretskii made valuable suggestions .\" .th iso_8859-8 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-8 \- iso 8859-8 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-8 encodes the characters used in modern hebrew. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-8 characters the following table displays the characters in iso 8859-8 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0 no-break space 242 162 a2 ¢ cent sign 243 163 a3 £ pound sign 244 164 a4 ¤ currency sign 245 165 a5 ¥ yen sign 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 © copyright sign 252 170 aa × multiplication sign 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ¯ macron 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ´ acute accent 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ¸ cedilla 271 185 b9 ¹ superscript one 272 186 ba ÷ division sign 273 187 bb » right-pointing double angle quotation mark 274 188 bc ¼ vulgar fraction one quarter 275 189 bd ½ vulgar fraction one half 276 190 be ¾ vulgar fraction three quarters 337 223 df ‗ double low line 340 224 e0 א hebrew letter alef 341 225 e1 ב hebrew letter bet 342 226 e2 ג hebrew letter gimel 343 227 e3 ד hebrew letter dalet 344 228 e4 ה hebrew letter he 345 229 e5 ו hebrew letter vav 346 230 e6 ז hebrew letter zayin 347 231 e7 ח hebrew letter het 350 232 e8 ט hebrew letter tet 351 233 e9 י hebrew letter yod 352 234 ea ך hebrew letter final kaf 353 235 eb כ hebrew letter kaf 354 236 ec ל hebrew letter lamed 355 237 ed ם hebrew letter final mem 356 238 ee מ hebrew letter mem 357 239 ef ן hebrew letter final nun 360 240 f0 נ hebrew letter nun 361 241 f1 ס hebrew letter samekh 362 242 f2 ע hebrew letter ayin 363 243 f3 ף hebrew letter final pe 364 244 f4 פ hebrew letter pe 365 245 f5 ץ hebrew letter final tsadi 366 246 f6 צ hebrew letter tsadi 367 247 f7 ק hebrew letter qof 370 248 f8 ר hebrew letter resh 371 249 f9 ש hebrew letter shin 372 250 fa ת hebrew letter tav 375 253 fd ‎ left-to-right mark 376 254 fe ‏ right-to-left mark .te .sh notes iso 8859-8 was also known as iso-ir-138. iso 8859-8 includes neither short vowels nor diacritical marks, and yiddish is not provided for. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sincos.3 .so man3/unlocked_stdio.3 .\" copyright (c) 1995, thomas k. dyas .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created wed aug 9 1995 thomas k. dyas .\" .th sysfs 2 2021-03-22 "linux" "linux programmer's manual" .sh name sysfs \- get filesystem type information .sh synopsis .nf .bi "int sysfs(int " option ", const char *" fsname ); .bi "int sysfs(int " option ", unsigned int " fs_index ", char *" buf ); .bi "int sysfs(int " option ); .fi .sh description .br "note" : if you are looking for information about the .b sysfs filesystem that is normally mounted at .ir /sys , see .br sysfs (5). .pp the (obsolete) .br sysfs () system call returns information about the filesystem types currently present in the kernel. the specific form of the .br sysfs () call and the information returned depends on the .i option in effect: .tp 3 .b 1 translate the filesystem identifier string .i fsname into a filesystem type index. .tp .b 2 translate the filesystem type index .i fs_index into a null-terminated filesystem identifier string. this string will be written to the buffer pointed to by .ir buf . make sure that .i buf has enough space to accept the string. .tp .b 3 return the total number of filesystem types currently present in the kernel. .pp the numbering of the filesystem type indexes begins with zero. .sh return value on success, .br sysfs () returns the filesystem index for option .br 1 , zero for option .br 2 , and the number of currently configured filesystems for option .br 3 . on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .ri "either " fsname " or " buf is outside your accessible address space. .tp .b einval .i fsname is not a valid filesystem type identifier; .i fs_index is out-of-bounds; .i option is invalid. .sh conforming to svr4. .sh notes this system-v derived system call is obsolete; don't use it. on systems with .ir /proc , the same information can be obtained via .ir /proc ; use that interface instead. .sh bugs there is no libc or glibc support. there is no way to guess how large \fibuf\fp should be. .sh see also .br proc (5), .br sysfs (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)getsockname.2 6.4 (berkeley) 3/10/91 .\" .\" modified sat jul 24 16:30:29 1993 by rik faith .\" modified tue oct 22 00:22:35 edt 1996 by eric s. raymond .\" modified sun mar 28 21:26:46 1999 by andries brouwer .\" .th getsockname 2 2021-03-22 "linux" "linux programmer's manual" .sh name getsockname \- get socket name .sh synopsis .nf .b #include .pp .bi "int getsockname(int " sockfd ", struct sockaddr *restrict " addr , .bi " socklen_t *restrict " addrlen ); .fi .sh description .br getsockname () returns the current address to which the socket .i sockfd is bound, in the buffer pointed to by .ir addr . the .i addrlen argument should be initialized to indicate the amount of space (in bytes) pointed to by .ir addr . on return it contains the actual size of the socket address. .pp the returned address is truncated if the buffer provided is too small; in this case, .i addrlen will return a value greater than was supplied to the call. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf the argument .i sockfd is not a valid file descriptor. .tp .b efault the .i addr argument points to memory not in a valid part of the process address space. .tp .b einval .i addrlen is invalid (e.g., is negative). .tp .b enobufs insufficient resources were available in the system to perform the operation. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.4bsd .rb ( getsockname () first appeared in 4.2bsd). .\" svr4 documents additional enomem .\" and enosr error codes. .sh notes for background on the .i socklen_t type, see .br accept (2). .sh see also .br bind (2), .br socket (2), .br getifaddrs (3), .br ip (7), .br socket (7), .br unix (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .so man3/max.3 .\" copyright (c), 1994, graeme w. wilford. (wilf.) .\" and copyright (c) 2010, 2015, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" fri jul 29th 12:56:44 bst 1994 wilf. .\" modified 1997-01-31 by eric s. raymond .\" modified 2002-03-09 by aeb .\" .th setgid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setgid \- set group identity .sh synopsis .nf .b #include .pp .bi "int setgid(gid_t " gid ); .fi .sh description .br setgid () sets the effective group id of the calling process. if the calling process is privileged (more precisely: has the .b cap_setgid capability in its user namespace), the real gid and saved set-group-id are also set. .pp under linux, .br setgid () is implemented like the posix version with the .b _posix_saved_ids feature. this allows a set-group-id program that is not set-user-id-root to drop all of its group privileges, do some un-privileged work, and then reengage the original effective group id in a secure manner. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval the group id specified in .i gid is not valid in this user namespace. .tp .b eperm the calling process is not privileged (does not have the \fbcap_setgid\fp capability in its user namespace), and .i gid does not match the real group id or saved set-group-id of the calling process. .sh conforming to posix.1-2001, posix.1-2008, svr4. .sh notes the original linux .br setgid () system call supported only 16-bit group ids. subsequently, linux 2.4 added .br setgid32 () supporting 32-bit ids. the glibc .br setgid () wrapper function transparently deals with the variation across kernel versions. .\" .ss c library/kernel differences at the kernel level, user ids and group ids are a per-thread attribute. however, posix requires that all threads in a process share the same credentials. the nptl threading implementation handles the posix requirements by providing wrapper functions for the various system calls that change process uids and gids. these wrapper functions (including the one for .br setgid ()) employ a signal-based technique to ensure that when one thread changes credentials, all of the other threads in the process also change their credentials. for details, see .br nptl (7). .sh see also .br getgid (2), .br setegid (2), .br setregid (2), .br capabilities (7), .br credentials (7), .br user_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/timeradd.3 .so man3/abs.3 .so man3/endian.3 .so man3/unlocked_stdio.3 .so man3/inet.3 .\" copyright 2001 andries brouwer . .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th lrint 3 2021-03-22 "" "linux programmer's manual" .sh name lrint, lrintf, lrintl, llrint, llrintf, llrintl \- round to nearest integer .sh synopsis .nf .b #include .pp .bi "long lrint(double " x ); .bi "long lrintf(float " x ); .bi "long lrintl(long double " x ); .pp .bi "long long llrint(double " x ); .bi "long long llrintf(float " x ); .bi "long long llrintl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions round their argument to the nearest integer value, using the current rounding direction (see .br fesetround (3)). .pp note that unlike the .br rint (3) family of functions, the return type of these functions differs from that of their arguments. .sh return value these functions return the rounded integer value. .pp if .i x is a nan or an infinity, or the rounded value is too large to be stored in a .i long .ri ( "long long" in the case of the .b ll* functions), then a domain error occurs, and the return value is unspecified. .\" the return value is -(long_max - 1) or -(llong_max -1) .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is a nan or infinite, or the rounded value is too large .\" .i errno .\" is set to .\" .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .pp these functions do not set .ir errno . .\" fixme . is it intentional that these functions do not set errno? .\" bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6798 .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br lrint (), .br lrintf (), .br lrintl (), .br llrint (), .br llrintf (), .br llrintl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br ceil (3), .br floor (3), .br lround (3), .br nearbyint (3), .br rint (3), .br round (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt , march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-24 by rik faith .\" modified 1996-11-04 by eric s. raymond .\" modified 2001-06-04 by aeb .\" modified 2004-05-27 by michael kerrisk .\" .th nice 2 2021-03-22 "linux" "linux programmer's manual" .sh name nice \- change process priority .sh synopsis .nf .b #include .pp .bi "int nice(int " inc ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nice (): .nf _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description .br nice () adds .i inc to the nice value for the calling thread. (a higher nice value means a lower priority.) .pp the range of the nice value is +19 (low priority) to \-20 (high priority). attempts to set a nice value outside the range are clamped to the range. .pp traditionally, only a privileged process could lower the nice value (i.e., set a higher priority). however, since linux 2.6.12, an unprivileged process can decrease the nice value of a target process that has a suitable .br rlimit_nice soft limit; see .br getrlimit (2) for details. .sh return value on success, the new nice value is returned (but see notes below). on error, \-1 is returned, and .i errno is set to indicate the error. .pp a successful call can legitimately return \-1. to detect an error, set .i errno to 0 before the call, and check whether it is nonzero after .br nice () returns \-1. .sh errors .tp .b eperm the calling process attempted to increase its priority by supplying a negative .i inc but has insufficient privileges. under linux, the .b cap_sys_nice capability is required. (but see the discussion of the .b rlimit_nice resource limit in .br setrlimit (2).) .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. however, the raw system call and (g)libc (earlier than glibc 2.2.4) return value is nonstandard, see below. .\" svr4 documents an additional .\" .b einval .\" error code. .sh notes for further details on the nice value, see .br sched (7). .pp .ir note : the addition of the "autogroup" feature in linux 2.6.38 means that the nice value no longer has its traditional effect in many circumstances. for details, see .br sched (7). .\" .ss c library/kernel differences posix.1 specifies that .br nice () should return the new nice value. however, the raw linux system call returns 0 on success. likewise, the .br nice () wrapper function provided in glibc 2.2.3 and earlier returns 0 on success. .pp since glibc 2.2.4, the .br nice () wrapper function provided by glibc provides conformance to posix.1 by calling .br getpriority (2) to obtain the new nice value, which is then returned to the caller. .sh see also .br nice (1), .br renice (1), .br fork (2), .br getpriority (2), .br getrlimit (2), .br setpriority (2), .br capabilities (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/if_nameindex.3 .so man3/circleq.3 .so man3/resolver.3 .so man3/ether_aton.3 .so man3/catan.3 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 13:35:59 1993 by rik faith .\" modified sun nov 28 17:19:01 1993 by rik faith .\" modified sat jan 13 12:58:08 1996 by michael haardt .\" .\" modified sun jul 21 18:59:33 1996 by andries brouwer .\" 2001-12-13 added remark by zack weinberg .\" 2007-06-18 mtk: .\" added details about seekable files and file offset. .\" noted that write() may write less than 'count' bytes, and .\" gave some examples of why this might occur. .\" noted what happens if write() is interrupted by a signal. .\" .th write 2 2021-03-22 "linux" "linux programmer's manual" .sh name write \- write to a file descriptor .sh synopsis .nf .b #include .pp .bi "ssize_t write(int " fd ", const void *" buf ", size_t " count ); .fi .sh description .br write () writes up to .i count bytes from the buffer starting at .i buf to the file referred to by the file descriptor .ir fd . .pp the number of bytes written may be less than .i count if, for example, there is insufficient space on the underlying physical medium, or the .b rlimit_fsize resource limit is encountered (see .br setrlimit (2)), or the call was interrupted by a signal handler after having written less than .i count bytes. (see also .br pipe (7).) .pp for a seekable file (i.e., one to which .br lseek (2) may be applied, for example, a regular file) writing takes place at the file offset, and the file offset is incremented by the number of bytes actually written. if the file was .br open (2)ed with .br o_append , the file offset is first set to the end of the file before writing. the adjustment of the file offset and the write operation are performed as an atomic step. .pp posix requires that a .br read (2) that can be proved to occur after a .br write () has returned will return the new data. note that not all filesystems are posix conforming. .pp according to posix.1, if .i count is greater than .br ssize_max , the result is implementation-defined; see notes for the upper limit on linux. .sh return value on success, the number of bytes written is returned. on error, \-1 is returned, and \fierrno\fp is set to indicate the error. .pp note that a successful .br write () may transfer fewer than .i count bytes. such partial writes can occur for various reasons; for example, because there was insufficient space on the disk device to write all of the requested bytes, or because a blocked .br write () to a socket, pipe, or similar was interrupted by a signal handler after it had transferred some, but before it had transferred all of the requested bytes. in the event of a partial write, the caller can make another .br write () call to transfer the remaining bytes. the subsequent call will either transfer further bytes or may result in an error (e.g., if the disk is now full). .pp if \ficount\fp is zero and .i fd refers to a regular file, then .br write () may return a failure status if one of the errors below is detected. if no errors are detected, or error detection is not performed, 0 is returned without causing any other effect. if \ficount\fp is zero and .i fd refers to a file other than a regular file, the results are not specified. .sh errors .tp .b eagain the file descriptor .i fd refers to a file other than a socket and has been marked nonblocking .rb ( o_nonblock ), and the write would block. see .br open (2) for further details on the .br o_nonblock flag. .tp .br eagain " or " ewouldblock .\" actually eagain on linux the file descriptor .i fd refers to a socket and has been marked nonblocking .rb ( o_nonblock ), and the write would block. posix.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities. .tp .b ebadf .i fd is not a valid file descriptor or is not open for writing. .tp .b edestaddrreq .i fd refers to a datagram socket for which a peer address has not been set using .br connect (2). .tp .b edquot the user's quota of disk blocks on the filesystem containing the file referred to by .i fd has been exhausted. .tp .b efault .i buf is outside your accessible address space. .tp .b efbig an attempt was made to write a file that exceeds the implementation-defined maximum file size or the process's file size limit, or to write at a position past the maximum allowed offset. .tp .b eintr the call was interrupted by a signal before any data was written; see .br signal (7). .tp .b einval .i fd is attached to an object which is unsuitable for writing; or the file was opened with the .b o_direct flag, and either the address specified in .ir buf , the value specified in .ir count , or the file offset is not suitably aligned. .tp .b eio a low-level i/o error occurred while modifying the inode. this error may relate to the write-back of data written by an earlier .br write (), which may have been issued to a different file descriptor on the same file. since linux 4.13, errors from write-back come with a promise that they .i may be reported by subsequent. .br write () requests, and .i will be reported by a subsequent .br fsync (2) (whether or not they were also reported by .br write ()). .\" commit 088737f44bbf6378745f5b57b035e57ee3dc4750 an alternate cause of .b eio on networked filesystems is when an advisory lock had been taken out on the file descriptor and this lock has been lost. see the .i "lost locks" section of .br fcntl (2) for further details. .tp .b enospc the device containing the file referred to by .i fd has no room for the data. .tp .b eperm the operation was prevented by a file seal; see .br fcntl (2). .tp .b epipe .i fd is connected to a pipe or socket whose reading end is closed. when this happens the writing process will also receive a .b sigpipe signal. (thus, the write return value is seen only if the program catches, blocks or ignores this signal.) .pp other errors may occur, depending on the object connected to .ir fd . .sh conforming to svr4, 4.3bsd, posix.1-2001. .\" svr4 documents additional error .\" conditions edeadlk, enolck, enolnk, enosr, enxio, or erange. .pp under svr4 a write may be interrupted and return .b eintr at any point, not just before any data is written. .sh notes the types .i size_t and .i ssize_t are, respectively, unsigned and signed integer data types specified by posix.1. .pp a successful return from .br write () does not make any guarantee that data has been committed to disk. on some filesystems, including nfs, it does not even guarantee that space has successfully been reserved for the data. in this case, some errors might be delayed until a future .br write (), .br fsync (2), or even .br close (2). the only way to be sure is to call .br fsync (2) after you are done writing all your data. .pp if a .br write () is interrupted by a signal handler before any bytes are written, then the call fails with the error .br eintr ; if it is interrupted after at least one byte has been written, the call succeeds, and returns the number of bytes written. .pp on linux, .br write () (and similar system calls) will transfer at most 0x7ffff000 (2,147,479,552) bytes, returning the number of bytes actually transferred. .\" commit e28cc71572da38a5a12c1cfe4d7032017adccf69 (this is true on both 32-bit and 64-bit systems.) .pp an error return value while performing .br write () using direct i/o does not mean the entire write has failed. partial data may be written and the data at the file offset on which the .br write () was attempted should be considered inconsistent. .sh bugs according to posix.1-2008/susv4 section xsi 2.9.7 ("thread interactions with regular file operations"): .pp .rs 4 all of the following functions shall be atomic with respect to each other in the effects specified in posix.1-2008 when they operate on regular files or symbolic links: ... .re .pp among the apis subsequently listed are .br write () and .br writev (2). and among the effects that should be atomic across threads (and processes) are updates of the file offset. however, on linux before version 3.14, this was not the case: if two processes that share an open file description (see .br open (2)) perform a .br write () (or .br writev (2)) at the same time, then the i/o operations were not atomic with respect to updating the file offset, with the result that the blocks of data output by the two processes might (incorrectly) overlap. this problem was fixed in linux 3.14. .\" http://thread.gmane.org/gmane.linux.kernel/1649458 .\" from: michael kerrisk (man-pages gmail.com> .\" subject: update of file offset on write() etc. is non-atomic with i/o .\" date: 2014-02-17 15:41:37 gmt .\" newsgroups: gmane.linux.kernel, gmane.linux.file-systems .\" commit 9c225f2655e36a470c4f58dbbc99244c5fc7f2d4 .\" author: linus torvalds .\" date: mon mar 3 09:36:58 2014 -0800 .\" .\" vfs: atomic f_pos accesses as per posix .sh see also .br close (2), .br fcntl (2), .br fsync (2), .br ioctl (2), .br lseek (2), .br open (2), .br pwrite (2), .br read (2), .br select (2), .br writev (2), .br fwrite (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ctime.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:40:51 1993 by rik faith (faith@cs.unc.edu) .\" modified sun apr 14 16:20:34 1996 by andries brouwer (aeb@cwi.nl) .th siginterrupt 3 2021-03-22 "" "linux programmer's manual" .sh name siginterrupt \- allow signals to interrupt system calls .sh synopsis .nf .b #include .pp .bi "int siginterrupt(int " sig ", int " flag ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br siginterrupt (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source .fi .sh description the .br siginterrupt () function changes the restart behavior when a system call is interrupted by the signal \fisig\fp. if the \fiflag\fp argument is false (0), then system calls will be restarted if interrupted by the specified signal \fisig\fp. this is the default behavior in linux. .pp if the \fiflag\fp argument is true (1) and no data has been transferred, then a system call interrupted by the signal \fisig\fp will return \-1 and \fierrno\fp will be set to .br eintr . .pp if the \fiflag\fp argument is true (1) and data transfer has started, then the system call will be interrupted and will return the actual amount of data transferred. .sh return value the .br siginterrupt () function returns 0 on success. it returns \-1 if the signal number .i sig is invalid, with .i errno set to indicate the error. .sh errors .tp .b einval the specified signal number is invalid. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br siginterrupt () t} thread safety t{ mt-unsafe const:sigintr t} .te .hy .ad .sp 1 .sh conforming to 4.3bsd, posix.1-2001. posix.1-2008 marks .br siginterrupt () as obsolete, recommending the use of .br sigaction (2) with the .b sa_restart flag instead. .sh see also .br signal (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getentropy 3 2021-03-22 "linux" "linux programmer's manual" .sh name getentropy \- fill a buffer with random bytes .sh synopsis .nf .b #include .pp .bi "int getentropy(void *" buffer ", size_t " length ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getentropy (): .nf _default_source .fi .sh description the .br getentropy () function writes .i length bytes of high-quality random data to the buffer starting at the location pointed to by .ir buffer . the maximum permitted value for the .i length argument is 256. .pp a successful call to .br getentropy () always provides the requested number of bytes of entropy. .sh return value on success, this function returns zero. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault part or all of the buffer specified by .i buffer and .i length is not in valid addressable memory. .tp .b eio .i length is greater than 256. .tp .b eio an unspecified error occurred while trying to overwrite .i buffer with random data. .tp .b enosys this kernel version does not implement the .br getrandom (2) system call required to implement this function. .sh versions the .br getentropy () function first appeared in glibc 2.25. .sh conforming to this function is nonstandard. it is also present on openbsd. .sh notes the .br getentropy () function is implemented using .br getrandom (2). .pp whereas the glibc wrapper makes .br getrandom (2) a cancellation point, .br getentropy () is not a cancellation point. .pp .br getentropy () is also declared in .br . (no feature test macro need be defined to obtain the declaration from that header file.) .pp a call to .br getentropy () may block if the system has just booted and the kernel has not yet collected enough randomness to initialize the entropy pool. in this case, .br getentropy () will keep blocking even if a signal is handled, and will return only once the entropy pool has been initialized. .sh see also .br getrandom (2), .br urandom (4), .br random (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strtoimax.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)fopen.3 6.8 (berkeley) 6/29/91 .\" .\" converted for linux, mon nov 29 15:22:01 1993, faith@cs.unc.edu .\" modified, aeb, 960421, 970806 .\" modified, joey, aeb, 2002-01-03 .\" .th fopen 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fopen, fdopen, freopen \- stream open functions .sh synopsis .nf .b #include .pp .bi "file *fopen(const char *restrict " pathname \ ", const char *restrict " mode ); .bi "file *fdopen(int " fd ", const char *" mode ); .bi "file *freopen(const char *restrict " pathname \ ", const char *restrict " mode , .bi " file *restrict " stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fdopen (): .nf _posix_c_source .fi .sh description the .br fopen () function opens the file whose name is the string pointed to by .i pathname and associates a stream with it. .pp the argument .i mode points to a string beginning with one of the following sequences (possibly followed by additional characters, as described below): .tp .b r open text file for reading. the stream is positioned at the beginning of the file. .tp .b r+ open for reading and writing. the stream is positioned at the beginning of the file. .tp .b w truncate file to zero length or create text file for writing. the stream is positioned at the beginning of the file. .tp .b w+ open for reading and writing. the file is created if it does not exist, otherwise it is truncated. the stream is positioned at the beginning of the file. .tp .b a open for appending (writing at end of file). the file is created if it does not exist. the stream is positioned at the end of the file. .tp .b a+ open for reading and appending (writing at end of file). the file is created if it does not exist. output is always appended to the end of the file. posix is silent on what the initial read position is when using this mode. for glibc, the initial file position for reading is at the beginning of the file, but for android/bsd/macos, the initial file position for reading is at the end of the file. .pp the .i mode string can also include the letter \(aqb\(aq either as a last character or as a character between the characters in any of the two-character strings described above. this is strictly for compatibility with c89 and has no effect; the \(aqb\(aq is ignored on all posix conforming systems, including linux. (other systems may treat text files and binary files differently, and adding the \(aqb\(aq may be a good idea if you do i/o to a binary file and expect that your program may be ported to non-unix environments.) .pp see notes below for details of glibc extensions for .ir mode . .pp any created file will have the mode .br s_irusr " | " s_iwusr " | " s_irgrp " | " s_iwgrp " | " s_iroth " | " s_iwoth (0666), as modified by the process's umask value (see .br umask (2)). .pp reads and writes may be intermixed on read/write streams in any order. note that ansi c requires that a file positioning function intervene between output and input, unless an input operation encounters end-of-file. (if this condition is not met, then a read is allowed to return the result of writes other than the most recent.) therefore it is good practice (and indeed sometimes necessary under linux) to put an .br fseek (3) or .br fgetpos (3) operation between write and read operations on such a stream. this operation may be an apparent no-op (as in \fifseek(..., 0l, seek_cur)\fp called for its synchronizing side effect). .pp opening a file in append mode (\fba\fp as the first character of .ir mode ) causes all subsequent write operations to this stream to occur at end-of-file, as if preceded the call: .pp .in +4n .ex fseek(stream, 0, seek_end); .ee .in .pp the file descriptor associated with the stream is opened as if by a call to .br open (2) with the following flags: .rs .ts allbox; lb lb c l. fopen() mode open() flags \fir\fp o_rdonly \fiw\fp o_wronly | o_creat | o_trunc \fia\fp o_wronly | o_creat | o_append \fir+\fp o_rdwr \fiw+\fp o_rdwr | o_creat | o_trunc \fia+\fp o_rdwr | o_creat | o_append .te .re .\" .ss fdopen() the .br fdopen () function associates a stream with the existing file descriptor, .ir fd . the .i mode of the stream (one of the values "r", "r+", "w", "w+", "a", "a+") must be compatible with the mode of the file descriptor. the file position indicator of the new stream is set to that belonging to .ir fd , and the error and end-of-file indicators are cleared. modes "w" or "w+" do not cause truncation of the file. the file descriptor is not dup'ed, and will be closed when the stream created by .br fdopen () is closed. the result of applying .br fdopen () to a shared memory object is undefined. .\" .ss freopen() the .br freopen () function opens the file whose name is the string pointed to by .i pathname and associates the stream pointed to by .i stream with it. the original stream (if it exists) is closed. the .i mode argument is used just as in the .br fopen () function. .pp if the .i pathname argument is a null pointer, .br freopen () changes the mode of the stream to that specified in .ir mode ; that is, .br freopen () reopens the pathname that is associated with the stream. the specification for this behavior was added in the c99 standard, which says: .pp .rs in this case, the file descriptor associated with the stream need not be closed if the call to .br freopen () succeeds. it is implementation-defined which changes of mode are permitted (if any), and under what circumstances. .re .pp the primary use of the .br freopen () function is to change the file associated with a standard text stream .ri ( stderr ", " stdin ", or " stdout ). .sh return value upon successful completion .br fopen (), .br fdopen (), and .br freopen () return a .i file pointer. otherwise, null is returned and .i errno is set to indicate the error. .sh errors .tp .b einval the .i mode provided to .br fopen (), .br fdopen (), or .br freopen () was invalid. .pp the .br fopen (), .br fdopen (), and .br freopen () functions may also fail and set .i errno for any of the errors specified for the routine .br malloc (3). .pp the .br fopen () function may also fail and set .i errno for any of the errors specified for the routine .br open (2). .pp the .br fdopen () function may also fail and set .i errno for any of the errors specified for the routine .br fcntl (2). .pp the .br freopen () function may also fail and set .i errno for any of the errors specified for the routines .br open (2), .br fclose (3), and .br fflush (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fopen (), .br fdopen (), .br freopen () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br fopen (), .br freopen (): posix.1-2001, posix.1-2008, c89, c99. .pp .br fdopen (): posix.1-2001, posix.1-2008. .sh notes .ss glibc notes the gnu c library allows the following extensions for the string specified in .ir mode : .tp .br c " (since glibc 2.3.3)" do not make the open operation, or subsequent read and write operations, thread cancellation points. this flag is ignored for .br fdopen (). .tp .br e " (since glibc 2.7)" open the file with the .b o_cloexec flag. see .br open (2) for more information. this flag is ignored for .br fdopen (). .tp .br m " (since glibc 2.3)" attempt to access the file using .br mmap (2), rather than i/o system calls .rb ( read (2), .br write (2)). currently, .\" as at glibc 2.4: use of .br mmap (2) is attempted only for a file opened for reading. .tp .b x .\" since glibc 2.0? .\" fixme . c11 specifies this flag open the file exclusively (like the .b o_excl flag of .br open (2)). if the file already exists, .br fopen () fails, and sets .i errno to .br eexist . this flag is ignored for .br fdopen (). .pp in addition to the above characters, .br fopen () and .br freopen () support the following syntax in .ir mode : .pp .bi " ,ccs=" string .pp the given .i string is taken as the name of a coded character set and the stream is marked as wide-oriented. thereafter, internal conversion functions convert i/o to and from the character set .ir string . if the .bi ,ccs= string syntax is not specified, then the wide-orientation of the stream is determined by the first file operation. if that operation is a wide-character operation, the stream is marked wide-oriented, and functions to convert to the coded character set are loaded. .sh bugs when parsing for individual flag characters in .ir mode (i.e., the characters preceding the "ccs" specification), the glibc implementation of .\" fixme . http://sourceware.org/bugzilla/show_bug.cgi?id=12685 .br fopen () and .br freopen () limits the number of characters examined in .i mode to 7 (or, in glibc versions before 2.14, to 6, which was not enough to include possible specifications such as "rb+cmxe"). the current implementation of .br fdopen () parses at most 5 characters in .ir mode . .sh see also .br open (2), .br fclose (3), .br fileno (3), .br fmemopen (3), .br fopencookie (3), .br open_memstream (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1995-2000 david engel (david@ods.com) .\" copyright 1995 rickard e. faith (faith@cs.unc.edu) .\" copyright 2000 ben collins (bcollins@debian.org) .\" redone for glibc 2.2 .\" copyright 2000 jakub jelinek (jakub@redhat.com) .\" corrected. .\" and copyright (c) 2012, 2016, michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" do not restrict distribution. .\" may be distributed under the gnu general public license .\" %%%license_end .\" .th ldd 1 2021-08-27 "" "linux programmer's manual" .sh name ldd \- print shared object dependencies .sh synopsis .nf .br ldd " [\fioption\fp]... \fifile\fp..." .fi .sh description .b ldd prints the shared objects (shared libraries) required by each program or shared object specified on the command line. an example of its use and output is the following: .pp .in +4n .ex $ \fbldd /bin/ls\fp linux\-vdso.so.1 (0x00007ffcc3563000) libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000) libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000) libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000) libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000) libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000) /lib64/ld\-linux\-x86\-64.so.2 (0x00005574bf12e000) libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000) libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000) .ee .in .pp in the usual case, .b ldd invokes the standard dynamic linker (see .br ld.so (8)) with the .b ld_trace_loaded_objects environment variable set to 1. this causes the dynamic linker to inspect the program's dynamic dependencies, and find (according to the rules described in .br ld.so (8)) and load the objects that satisfy those dependencies. for each dependency, .b ldd displays the location of the matching object and the (hexadecimal) address at which it is loaded. (the .i linux\-vdso and .i ld\-linux shared dependencies are special; see .br vdso (7) and .br ld.so (8).) .\" .ss security be aware that in some circumstances (e.g., where the program specifies an elf interpreter other than .ir ld\-linux.so ), .\" the circumstances are where the program has an interpreter .\" other than ld-linux.so. in this case, ldd tries to execute the .\" program directly with ld_trace_loaded_objects=1, with the .\" result that the program interpreter gets control, and can do .\" what it likes, or pass control to the program itself. .\" much more detail at .\" http://www.catonmat.net/blog/ldd-arbitrary-code-execution/ some versions of .b ldd may attempt to obtain the dependency information by attempting to directly execute the program, which may lead to the execution of whatever code is defined in the program's elf interpreter, and perhaps to execution of the program itself. .\" mainline glibc's ldd allows this possibility (the line .\" try_trace "$file" .\" in glibc 2.15, for example), but many distro versions of .\" ldd seem to remove that code path from the script. (in glibc versions before 2.27, .\" glibc commit eedca9772e99c72ab4c3c34e43cc764250aa3e3c the upstream .b ldd implementation did this for example, although most distributions provided a modified version that did not.) .pp thus, you should .i never employ .b ldd on an untrusted executable, since this may result in the execution of arbitrary code. a safer alternative when dealing with untrusted executables is: .pp .in +4n .ex $ \fbobjdump \-p /path/to/program | grep needed\fp .ee .in .pp note, however, that this alternative shows only the direct dependencies of the executable, while .b ldd shows the entire dependency tree of the executable. .sh options .tp .b \-\-version print the version number of .br ldd . .tp .br \-v ", " \-\-verbose print all information, including, for example, symbol versioning information. .tp .br \-u ", " \-\-unused print unused direct dependencies. (since glibc 2.3.4.) .tp .br \-d ", " \-\-data\-relocs perform relocations and report any missing objects (elf only). .tp .br \-r ", " \-\-function\-relocs perform relocations for both data objects and functions, and report any missing objects or functions (elf only). .tp .b \-\-help usage information. .\" .sh notes .\" the standard version of .\" .b ldd .\" comes with glibc2. .\" libc5 came with an older version, still present .\" on some systems. .\" the long options are not supported by the libc5 version. .\" on the other hand, the glibc2 version does not support .\" .b \-v .\" and only has the equivalent .\" .br \-\-version . .\" .lp .\" the libc5 version of this program will use the name of a library given .\" on the command line as-is when it contains a \(aq/\(aq; otherwise it .\" searches for the library in the standard locations. .\" to run it .\" on a shared library in the current directory, prefix the name with "./". .sh bugs .b ldd does not work on a.out shared libraries. .pp .b ldd does not work with some extremely old a.out programs which were built before .b ldd support was added to the compiler releases. if you use .b ldd on one of these programs, the program will attempt to run with .i argc = 0 and the results will be unpredictable. .\" .sh author .\" david engel. .\" roland mcgrath and ulrich drepper. .sh see also .br pldd (1), .br sprof (1), .br ld.so (8), .br ldconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setstack 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setstack, pthread_attr_getstack \- set/get stack attributes in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setstack(pthread_attr_t *" attr , .bi " void *" stackaddr ", size_t " stacksize ); .bi "int pthread_attr_getstack(const pthread_attr_t *restrict " attr , .bi " void **restrict " stackaddr , .bi " size_t *restrict " stacksize ); .pp compile and link with \fi\-pthread\fp. .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_attr_getstack (), .br pthread_attr_setstack (): .nf _posix_c_source >= 200112l .fi .sh description the .br pthread_attr_setstack () function sets the stack address and stack size attributes of the thread attributes object referred to by .i attr to the values specified in .ir stackaddr and .ir stacksize , respectively. these attributes specify the location and size of the stack that should be used by a thread that is created using the thread attributes object .ir attr . .pp .i stackaddr should point to the lowest addressable byte of a buffer of .i stacksize bytes that was allocated by the caller. the pages of the allocated buffer should be both readable and writable. .pp the .br pthread_attr_getstack () function returns the stack address and stack size attributes of the thread attributes object referred to by .i attr in the buffers pointed to by .ir stackaddr and .ir stacksize , respectively. .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .br pthread_attr_setstack () can fail with the following error: .tp .b einval .i stacksize is less than .br pthread_stack_min (16384) bytes. on some systems, this error may also occur if .ir stackaddr or .ir "stackaddr\ +\ stacksize" is not suitably aligned. .pp posix.1 also documents an .br eacces error if the stack area described by .i stackaddr and .i stacksize is not both readable and writable by the caller. .sh versions these functions are provided by glibc since version 2.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setstack (), .br pthread_attr_getstack () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes these functions are provided for applications that must ensure that a thread's stack is placed in a particular location. for most applications, this is not necessary, and the use of these functions should be avoided. (use .br pthread_attr_setstacksize (3) if an application simply requires a stack size other than the default.) .pp when an application employs .br pthread_attr_setstack (), it takes over the responsibility of allocating the stack. any guard size value that was set using .br pthread_attr_setguardsize (3) is ignored. if deemed necessary, it is the application's responsibility to allocate a guard area (one or more pages protected against reading and writing) to handle the possibility of stack overflow. .pp the address specified in .i stackaddr should be suitably aligned: for full portability, align it on a page boundary .ri ( sysconf(_sc_pagesize) ). .br posix_memalign (3) may be useful for allocation. probably, .ir stacksize should also be a multiple of the system page size. .pp if .i attr is used to create multiple threads, then the caller must change the stack address attribute between calls to .br pthread_create (3); otherwise, the threads will attempt to use the same memory area for their stacks, and chaos will ensue. .sh examples see .br pthread_attr_init (3). .sh see also .ad l .nh .br mmap (2), .br mprotect (2), .br posix_memalign (3), .br pthread_attr_init (3), .br pthread_attr_setguardsize (3), .br pthread_attr_setstackaddr (3), .br pthread_attr_setstacksize (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/nextafter.3 .so man3/ilogb.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setguardsize 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setguardsize, pthread_attr_getguardsize \- set/get guard size attribute in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setguardsize(pthread_attr_t *" attr \ ", size_t " guardsize ); .bi "int pthread_attr_getguardsize(const pthread_attr_t *restrict " attr , .bi " size_t *restrict " guardsize ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setguardsize () function sets the guard size attribute of the thread attributes object referred to by .i attr to the value specified in .ir guardsize . .pp if .i guardsize is greater than 0, then for each new thread created using .i attr the system allocates an additional region of at least .i guardsize bytes at the end of the thread's stack to act as the guard area for the stack (but see bugs). .pp if .i guardsize is 0, then new threads created with .i attr will not have a guard area. .pp the default guard size is the same as the system page size. .pp if the stack address attribute has been set in .i attr (using .br pthread_attr_setstack (3) or .br pthread_attr_setstackaddr (3)), meaning that the caller is allocating the thread's stack, then the guard size attribute is ignored (i.e., no guard area is created by the system): it is the application's responsibility to handle stack overflow (perhaps by using .br mprotect (2) to manually define a guard area at the end of the stack that it has allocated). .pp the .br pthread_attr_getguardsize () function returns the guard size attribute of the thread attributes object referred to by .i attr in the buffer pointed to by .ir guardsize . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors posix.1 documents an .b einval error if .i attr or .i guardsize is invalid. on linux these functions always succeed (but portable and future-proof applications should nevertheless handle a possible error return). .sh versions these functions are provided by glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setguardsize (), .br pthread_attr_getguardsize () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes a guard area consists of virtual memory pages that are protected to prevent read and write access. if a thread overflows its stack into the guard area, then, on most hard architectures, it receives a .b sigsegv signal, thus notifying it of the overflow. guard areas start on page boundaries, and the guard size is internally rounded up to the system page size when creating a thread. (nevertheless, .br pthread_attr_getguardsize () returns the guard size that was set by .br pthread_attr_setguardsize ().) .pp setting a guard size of 0 may be useful to save memory in an application that creates many threads and knows that stack overflow can never occur. .pp choosing a guard size larger than the default size may be necessary for detecting stack overflows if a thread allocates large data structures on the stack. .sh bugs as at glibc 2.8, the nptl threading implementation includes the guard area within the stack size allocation, rather than allocating extra space at the end of the stack, as posix.1 requires. (this can result in an .b einval error from .br pthread_create (3) if the guard size value is too large, leaving no space for the actual stack.) .pp the obsolete linuxthreads implementation did the right thing, allocating extra space at the end of the stack for the guard area. .\" glibc includes the guardsize within the allocated stack size, .\" which looks pretty clearly to be in violation of posix. .\" .\" filed bug, 22 oct 2008: .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6973 .\" .\" older reports: .\" https//bugzilla.redhat.com/show_bug.cgi?id=435337 .\" reportedly, linuxthreads did the right thing, allocating .\" extra space at the end of the stack: .\" http://sourceware.org/ml/libc-alpha/2008-05/msg00086.html .sh examples see .br pthread_getattr_np (3). .sh see also .br mmap (2), .br mprotect (2), .br pthread_attr_init (3), .br pthread_attr_setstack (3), .br pthread_attr_setstacksize (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fgetc.3 .so man3/termios.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th getttyent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getttyent, getttynam, setttyent, endttyent \- get ttys file entry .sh synopsis .nf .b "#include " .pp .b "struct ttyent *getttyent(void);" .bi "struct ttyent *getttynam(const char *" name ); .pp .b "int setttyent(void);" .b "int endttyent(void);" .fi .sh description these functions provide an interface to the file .b _path_ttys (e.g., .ir /etc/ttys ). .pp the function .br setttyent () opens the file or rewinds it if already open. .pp the function .br endttyent () closes the file. .pp the function .br getttynam () searches for a given terminal name in the file. it returns a pointer to a .i ttyent structure (description below). .pp the function .br getttyent () opens the file .b _path_ttys (if necessary) and returns the first entry. if the file is already open, the next entry. the .i ttyent structure has the form: .pp .in +4n .ex struct ttyent { char *ty_name; /* terminal device name */ char *ty_getty; /* command to execute, usually getty */ char *ty_type; /* terminal type for termcap */ int ty_status; /* status flags */ char *ty_window; /* command to start up window manager */ char *ty_comment; /* comment field */ }; .ee .in .pp .i ty_status can be: .pp .in +4n .ex #define tty_on 0x01 /* enable logins (start ty_getty program) */ #define tty_secure 0x02 /* allow uid 0 to login */ .ee .in .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getttyent (), .br setttyent (), .br endttyent (), .br getttynam () t} thread safety mt-unsafe race:ttyent .te .hy .ad .sp 1 .sh conforming to not in posix.1. present on the bsds, and perhaps other systems. .sh notes under linux, the file .ir /etc/ttys , and the functions described above, are not used. .sh see also .br ttyname (3), .br ttyslot (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 17:56:43 1993 by rik faith (faith@cs.unc.edu) .\" added history, aeb, 980113. .\" 2005-05-05 mtk: added strcasestr() .\" .th strstr 3 2021-08-27 "gnu" "linux programmer's manual" .sh name strstr, strcasestr \- locate a substring .sh synopsis .nf .b #include .pp .bi "char *strstr(const char *" haystack ", const char *" needle ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "char *strcasestr(const char *" haystack ", const char *" needle ); .fi .sh description the .br strstr () function finds the first occurrence of the substring .i needle in the string .ir haystack . the terminating null bytes (\(aq\e0\(aq) are not compared. .pp the .br strcasestr () function is like .br strstr (), but ignores the case of both arguments. .sh return value these functions return a pointer to the beginning of the located substring, or null if the substring is not found. .pp if .i needle is the empty string, the return value is always .i haystack itself. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strstr () t} thread safety mt-safe t{ .br strcasestr () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to .br strstr (): posix.1-2001, posix.1-2008, c89, c99. .pp the .br strcasestr () function is a nonstandard extension. .sh see also .br index (3), .br memchr (3), .br memmem (3), .br rindex (3), .br strcasecmp (3), .br strchr (3), .br string (3), .br strpbrk (3), .br strsep (3), .br strspn (3), .br strtok (3), .br wcsstr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:57:24 1993 by rik faith (faith@cs.unc.edu) .th memccpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name memccpy \- copy memory area .sh synopsis .nf .b #include .pp .bi "void *memccpy(void *restrict " dest ", const void *restrict " src , .bi " int " c ", size_t " n ); .fi .sh description the .br memccpy () function copies no more than .i n bytes from memory area .i src to memory area .ir dest , stopping when the character .i c is found. .pp if the memory areas overlap, the results are undefined. .sh return value the .br memccpy () function returns a pointer to the next character in .ir dest after .ir c , or null if .i c was not found in the first .i n characters of .ir src . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memccpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br bcopy (3), .br bstring (3), .br memcpy (3), .br memmove (3), .br strcpy (3), .br strncpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getspnam.3 .so man3/div.3 .so man3/logb.3 .\" copyright (c) 2012, cyrill gorcunov .\" and copyright (c) 2012, 2016, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" kernel commit d97b46a64674a267bc41c9e16132ee2a98c3347d .\" .th kcmp 2 2021-03-22 "linux" "linux programmer's manual" .sh name kcmp \- compare two processes to determine if they share a kernel resource .sh synopsis .nf .br "#include " " /* definition of " kcmp_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_kcmp, pid_t " pid1 ", pid_t " pid2 ", int " type , .bi " unsigned long " idx1 ", unsigned long " idx2 ); .fi .pp .ir note : glibc provides no wrapper for .br kcmp (), necessitating the use of .br syscall (2). .sh description the .br kcmp () system call can be used to check whether the two processes identified by .i pid1 and .i pid2 share a kernel resource such as virtual memory, file descriptors, and so on. .pp permission to employ .br kcmp () is governed by ptrace access mode .b ptrace_mode_read_realcreds checks against both .i pid1 and .ir pid2 ; see .br ptrace (2). .pp the .i type argument specifies which resource is to be compared in the two processes. it has one of the following values: .tp .br kcmp_file check whether a file descriptor .i idx1 in the process .i pid1 refers to the same open file description (see .br open (2)) as file descriptor .i idx2 in the process .ir pid2 . the existence of two file descriptors that refer to the same open file description can occur as a result of .br dup (2) (and similar) .br fork (2), or passing file descriptors via a domain socket (see .br unix (7)). .tp .br kcmp_files check whether the processes share the same set of open file descriptors. the arguments .i idx1 and .i idx2 are ignored. see the discussion of the .br clone_files flag in .br clone (2). .tp .br kcmp_fs check whether the processes share the same filesystem information (i.e., file mode creation mask, working directory, and filesystem root). the arguments .i idx1 and .i idx2 are ignored. see the discussion of the .br clone_fs flag in .br clone (2). .tp .br kcmp_io check whether the processes share i/o context. the arguments .i idx1 and .i idx2 are ignored. see the discussion of the .br clone_io flag in .br clone (2). .tp .br kcmp_sighand check whether the processes share the same table of signal dispositions. the arguments .i idx1 and .i idx2 are ignored. see the discussion of the .br clone_sighand flag in .br clone (2). .tp .br kcmp_sysvsem check whether the processes share the same list of system\ v semaphore undo operations. the arguments .i idx1 and .i idx2 are ignored. see the discussion of the .br clone_sysvsem flag in .br clone (2). .tp .br kcmp_vm check whether the processes share the same address space. the arguments .i idx1 and .i idx2 are ignored. see the discussion of the .br clone_vm flag in .br clone (2). .tp .br kcmp_epoll_tfd " (since linux 4.13)" .\" commit 0791e3644e5ef21646fe565b9061788d05ec71d4 check whether the file descriptor .i idx1 of the process .i pid1 is present in the .br epoll (7) instance described by .i idx2 of the process .ir pid2 . the argument .i idx2 is a pointer to a structure where the target file is described. this structure has the form: .pp .in +4n .ex struct kcmp_epoll_slot { __u32 efd; __u32 tfd; __u64 toff; }; .ee .in .pp within this structure, .i efd is an epoll file descriptor returned from .br epoll_create (2), .i tfd is a target file descriptor number, and .i toff is a target file offset counted from zero. several different targets may be registered with the same file descriptor number and setting a specific offset helps to investigate each of them. .pp note the .br kcmp () is not protected against false positives which may occur if the processes are currently running. one should stop the processes by sending .br sigstop (see .br signal (7)) prior to inspection with this system call to obtain meaningful results. .sh return value the return value of a successful call to .br kcmp () is simply the result of arithmetic comparison of kernel pointers (when the kernel compares resources, it uses their memory addresses). .pp the easiest way to explain is to consider an example. suppose that .i v1 and .i v2 are the addresses of appropriate resources, then the return value is one of the following: .rs 4 .ip 0 4 .i v1 is equal to .ir v2 ; in other words, the two processes share the resource. .ip 1 .i v1 is less than .ir v2 . .ip 2 .i v1 is greater than .ir v2 . .ip 3 .i v1 is not equal to .ir v2 , but ordering information is unavailable. .re .pp on error, \-1 is returned, and .i errno is set to indicate the error. .pp .br kcmp () was designed to return values suitable for sorting. this is particularly handy if one needs to compare a large number of file descriptors. .sh errors .tp .b ebadf .i type is .b kcmp_file and .i fd1 or .i fd2 is not an open file descriptor. .tp .b efault the epoll slot addressed by .i idx2 is outside of the user's address space. .tp .b einval .i type is invalid. .tp .b enoent the target file is not present in .br epoll (7) instance. .tp .b eperm insufficient permission to inspect process resources. the .b cap_sys_ptrace capability is required to inspect processes that you do not own. other ptrace limitations may also apply, such as .br config_security_yama , which, when .i /proc/sys/kernel/yama/ptrace_scope is 2, limits .br kcmp () to child processes; see .br ptrace (2). .tp .b esrch process .i pid1 or .i pid2 does not exist. .sh versions the .br kcmp () system call first appeared in linux 3.5. .sh conforming to .br kcmp () is linux-specific and should not be used in programs intended to be portable. .sh notes before linux 5.12, this system call is available only if the kernel is configured with .br config_checkpoint_restore , since the original purpose of the system call was for the checkpoint/restore in user space (criu) feature. (the alternative to this system call would have been to expose suitable process information via the .br proc (5) filesystem; this was deemed to be unsuitable for security reasons.) since linux 5.12, this system call is made available unconditionally. .pp see .br clone (2) for some background information on the shared resources referred to on this page. .sh examples the program below uses .br kcmp () to test whether pairs of file descriptors refer to the same open file description. the program tests different cases for the file descriptor pairs, as described in the program output. an example run of the program is as follows: .pp .in +4n .ex $ \fb./a.out\fp parent pid is 1144 parent opened file on fd 3 pid of child of fork() is 1145 compare duplicate fds from different processes: kcmp(1145, 1144, kcmp_file, 3, 3) ==> same child opened file on fd 4 compare fds from distinct open()s in same process: kcmp(1145, 1145, kcmp_file, 3, 4) ==> different child duplicated fd 3 to create fd 5 compare duplicated fds in same process: kcmp(1145, 1145, kcmp_file, 3, 5) ==> same .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static int kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2) { return syscall(sys_kcmp, pid1, pid2, type, idx1, idx2); } static void test_kcmp(char *msg, pid_t pid1, pid_t pid2, int fd_a, int fd_b) { printf("\et%s\en", msg); printf("\et\etkcmp(%jd, %jd, kcmp_file, %d, %d) ==> %s\en", (intmax_t) pid1, (intmax_t) pid2, fd_a, fd_b, (kcmp(pid1, pid2, kcmp_file, fd_a, fd_b) == 0) ? "same" : "different"); } int main(int argc, char *argv[]) { int fd1, fd2, fd3; char pathname[] = "/tmp/kcmp.test"; fd1 = open(pathname, o_creat | o_rdwr, s_irusr | s_iwusr); if (fd1 == \-1) errexit("open"); printf("parent pid is %jd\en", (intmax_t) getpid()); printf("parent opened file on fd %d\en\en", fd1); switch (fork()) { case \-1: errexit("fork"); case 0: printf("pid of child of fork() is %jd\en", (intmax_t) getpid()); test_kcmp("compare duplicate fds from different processes:", getpid(), getppid(), fd1, fd1); fd2 = open(pathname, o_creat | o_rdwr, s_irusr | s_iwusr); if (fd2 == \-1) errexit("open"); printf("child opened file on fd %d\en", fd2); test_kcmp("compare fds from distinct open()s in same process:", getpid(), getpid(), fd1, fd2); fd3 = dup(fd1); if (fd3 == \-1) errexit("dup"); printf("child duplicated fd %d to create fd %d\en", fd1, fd3); test_kcmp("compare duplicated fds in same process:", getpid(), getpid(), fd1, fd3); break; default: wait(null); } exit(exit_success); } .ee .sh see also .br clone (2), .br unshare (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getw.3 .so man7/operator.7 .so man3/rpc.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wctob 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wctob \- try to represent a wide character as a single byte .sh synopsis .nf .b #include .pp .bi "int wctob(wint_t " c ); .fi .sh description the .br wctob () function tests whether the multibyte representation of the wide character .ir c , starting in the initial state, consists of a single byte. if so, it is returned as an .ir "unsigned char" . .pp never use this function. it cannot help you in writing internationalized programs. internationalized programs must never distinguish single-byte and multibyte characters. .sh return value the .br wctob () function returns the single-byte representation of .ir c , if it exists, or .b eof otherwise. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wctob () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wctob () depends on the .b lc_ctype category of the current locale. .pp this function should never be used. internationalized programs must never distinguish single-byte and multibyte characters. use either .br wctomb (3) or the thread-safe .br wcrtomb (3) instead. .sh see also .br btowc (3), .br wcrtomb (3), .br wctomb (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:39:43 1993 by rik faith (faith@cs.unc.edu) .th strfry 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strfry \- randomize a string .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "char *strfry(char *" string ); .fi .sh description the .br strfry () function randomizes the contents of .i string by randomly swapping characters in the string. the result is an anagram of .ir string . .sh return value the .br strfry () functions returns a pointer to the randomized string. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strfry () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the .br strfry () function is unique to the gnu c library. .sh see also .br memfrob (3), .br string (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/chmod.2 .so man2/chown.2 .so man3/des_crypt.3 .so man3/sigsetops.3 .so man3/random_r.3 .\" copyright (c) 2018 by eugene syromyatnikov , .\" and copyright (c) 2018 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th address_families 7 2021-03-22 "linux" "linux programmer's manual" .sh name address_families \- socket address families (domains) .sh synopsis .nf .br "#include " " /* see notes */" .b #include .pp .bi "int socket(int " domain ", int " type ", int " protocol ); .fi .sh description the .i domain argument of the .br socket (2) specifies a communication domain; this selects the protocol family which will be used for communication. these families are defined in .ir . the formats currently understood by the linux kernel include: .tp .br af_unix ", " af_local local communication for further information, see .br unix (7). .tp .b af_inet ipv4 internet protocols. for further information, see .br ip (7). .tp .b af_ax25 amateur radio ax.25 protocol. for further information, see .br ax25 (4). .\" part of ax25-tools .tp .b af_ipx ipx \- novell protocols. .tp .b af_appletalk appletalk for further information, see .br ddp (7). .tp .b af_netrom ax.25 packet layer protocol. for further information, see .br netrom (4), .\" part of ax25-tools package .ur https://www.tldp.org/howto/ax25-howto/x61.html .i the packet radio protocols and linux .ue and the .ir ax.25 ", " net/rom ", and " "rose network programming" chapters of the .ur https://www.tldp.org/howto/ax25-howto/x2107.html .i linux amateur radio ax.25 howto .ue . .tp .b af_bridge can't be used for creating sockets; mostly used for bridge links in .br rtnetlink (7) protocol commands. .tp .b af_atmpvc access to raw atm permanent virtual circuits (pvcs). for further information, see the .ur https://www.tldp.org/howto/text/atm-linux-howto .i atm on linux howto .ue . .tp .b af_x25 itu-t x.25 / iso-8208 protocol. for further information, see .br x25 (7). .tp .b af_inet6 ipv6 internet protocols. for further information, see .br ipv6 (7). .tp .b af_rose rats (radio amateur telecommunications society) open systems environment (rose) ax.25 packet layer protocol. for further information, see the resources listed for .br af_netrom . .tp .b af_decnet decet protocol sockets. see .i documentation/networking/decnet.txt in the linux kernel source tree for details. .tp .b af_netbeui reserved for "802.2llc project"; never used. .tp .b af_security this was a short-lived (between linux 2.1.30 and 2.1.99pre2) protocol family for firewall upcalls. .tp .b af_key key management protocol, originally developed for usage with ipsec (since linux 2.1.38). this has no relation to .br keyctl (2) and the in-kernel key storage facility. see .ur https://tools.ietf.org/html/rfc2367 rfc 2367 .i pf_key key management api, version 2 .ue for details. .tp .b af_netlink kernel user interface device for further information, see .br netlink (7). .tp .b af_packet low-level packet interface. for further information, see .br packet (7). .\" .tp .\" .b af_ash .\" asynchronous serial host protocol (?) .\" notes from eugene syromyatnikov: .\" i haven't found any concrete information about this one; .\" it never was implemented in linux, at least, judging by historical .\" repos. there is also this file (and its variations): .\" https://github.com/ecki/net-tools/blob/master/lib/ash.c .\" ( https://github.com/ecki/net-tools/commits/master/lib/ash.c ) .\" it mentions "net-2 distribution" (bsd net/2?), but, again, i failed .\" to find any mentions of "ash" protocol there. .\" (for the reference: .\" ftp://pdp11.org.ru/pub/unix-archive/distributions/ucb/net2/net2.tar.gz ) .\" another source that mentions it is .\" https://www.silabs.com/documents/public/user-guides/ug101-uart-gateway-protocol-reference.pdf .\" https://www.silabs.com/documents/public/user-guides/ug115-ashv3-protocol-reference.pdf .\" but i doubt that it's related, as former files use 64-byte addresses and .\" "hamming-encode of hops", and that's barely combines with a protocol .\" that is mainly used over serial connection. .tp .b af_econet .\" commit: 349f29d841dbae854bd7367be7c250401f974f47 acorn econet protocol (removed in linux 3.5). see the .ur http://www.8bs.com/othrdnld/manuals/econet.shtml econet documentation .ue for details. .tp .b af_atmsvc access to atm switched virtual circuits (svcs) see the .ur https://www.tldp.org/howto/text/atm-linux-howto .i atm on linux howto .ue for details. .tp .b af_rds .\" commit: 639b321b4d8f4e412bfbb2a4a19bfebc1e68ace4 reliable datagram sockets (rds) protocol (since linux 2.6.30). rds over rdma has no relation to .b af_smc or .br af_xdp . for further information see .\" rds-tools: https://github.com/oracle/rds-tools/blob/master/rds.7 .\" rds-tools: https://github.com/oracle/rds-tools/blob/master/rds-rdma.7 .br rds (7), .br rds\-rdma (7), and .i documentation/networking/rds.txt in the linux kernel source tree. .tp .b af_irda .\" commits: 1ca163afb6fd569b, d64c2a76123f0300 socket interface over irda (moved to staging in linux 4.14, removed in linux 4.17). .\" irda-utils: https://sourceforge.net/p/irda/code/head/tree/tags/irdautils_0_9_18/irda-utils/man/irda.7.gz?format=raw for further information see .br irda (7). .tp .b af_pppox generic ppp transport layer, for setting up l2 tunnels (l2tp and pppoe). see .i documentation/networking/l2tp.txt in the linux kernel source tree for details. .tp .b af_wanpipe .\" commits: ce0ecd594d78710422599918a608e96dd1ee6024 legacy protocol for wide area network (wan) connectivity that was used by sangoma wan cards (called "wanpipe"); removed in linux 2.6.21. .tp .b af_llc .\" linux-history commit: 34beb106cde7da233d4df35dd3d6cf4fee937caa logical link control (ieee 802.2 llc) protocol, upper part of data link layer of iso/osi networking protocol stack (since linux 2.4); has no relation to .br af_packet . see chapter .i 13.5.3. logical link control in .i understanding linux kernel internals (o'reilly media, 2006) and .i ieee standards for local area networks: logical link control (the institute of electronics and electronics engineers, inc., new york, new york, 1985) for details. see also .ur https://wiki.linuxfoundation.org/networking/llc some historical notes .ue regarding its development. .tp .b af_ib .\" commits: 8d36eb01da5d371f..ce117ffac2e93334 infiniband native addressing (since linux 3.11). .tp .b af_mpls .\" commits: 0189197f441602acdca3f97750d392a895b778fd multiprotocol label switching (since linux 4.1); mostly used for configuring mpls routing via .br netlink (7), as it doesn't expose ability to create sockets to user space. .tp .b af_can .\" commits: 8dbde28d9711475a..5423dd67bd0108a1 controller area network automotive bus protocol (since linux 2.6.25). see .i documentation/networking/can.rst in the linux kernel source tree for details. .tp .b af_tipc .\" commits: b97bf3fd8f6a16966d4f18983b2c40993ff937d4 tipc, "cluster domain sockets" protocol (since linux 2.6.16). see .ur http://tipc.io/programming.html .i tipc programmer's guide .ue and the .ur http://tipc.io/protocol.html protocol description .ue for details. .tp .b af_bluetooth .\" commits: 8d36eb01da5d371f..ce117ffac2e93334 bluetooth low-level socket protocol (since linux 3.11). see .ur https://git.kernel.org\:/pub/scm\:/bluetooth/bluez.git\:/tree/doc/mgmt-api.txt .i bluetooth management api overview .ue and .ur https://people.csail.mit.edu/albert/bluez-intro/ .i an introduction to bluetooth programming by albert huang .ue for details. .tp .b af_iucv .\" commit: eac3731bd04c7131478722a3c148b78774553116 iucv (inter-user communication vehicle) z/vm protocol for hypervisor-guest interaction (since linux 2.6.21); has no relation to .b af_vsock and/or .br af_smc see .ur https://www.ibm.com\:/support\:/knowledgecenter\:/en/ssb27u_6.4.0\:/com.ibm.zvm.v640.hcpb4\:/iucv.htm .i iucv protocol overview .ue for details. .tp .b af_rxrpc .\" commit: 17926a79320afa9b95df6b977b40cca6d8713cea .\" http://people.redhat.com/~dhowells/rxrpc/ .\" https://www.infradead.org/~dhowells/kafs/af_rxrpc_client.html .\" http://workshop.openafs.org/afsbpw09/talks/thu_2/kafs.pdf .\" http://pages.cs.wisc.edu/~remzi/ostep/dist-afs.pdf .\" http://web.mit.edu/kolya/afs/rx/rx-spec rx, andrew file system remote procedure call protocol (since linux 2.6.22). see .i documentation/networking/rxrpc.txt in the linux kernel source tree for details. .tp .b af_isdn .\" commit: 1b2b03f8e514e4f68e293846ba511a948b80243c new "modular isdn" driver interface protocol (since linux 2.6.27). see the .ur http://www.misdn.eu/wiki/main_page/ misdn wiki .ue for details. .tp .b af_phonet .\" commit: 4b07b3f69a8471cdc142c51461a331226fef248a nokia cellular modem ipc/rpc interface (since linux 2.6.31). see .i documentation/networking/phonet.txt in the linux kernel source tree for details. .tp .b af_ieee802154 .\" commit: 9ec7671603573ede31207eb5b0b3e1aa211b2854 ieee 802.15.4 wpan (wireless personal area network) raw packet protocol (since linux 2.6.31). see .i documentation/networking/ieee802154.txt in the linux kernel source tree for details. .tp .b af_caif .\" commit: 529d6dad5bc69de14cdd24831e2a14264e93daa4 .\" https://lwn.net/articles/371017/ .\" http://read.pudn.com/downloads157/doc/comm/698729/misc/caif/com%20cpu%20to%20appl%20cpu%20interface%20description_lzn901%202002_revr1c.pdf .\" http://read.pudn.com/downloads157/doc/comm/698729/misc/caif/com%20cpu%20to%20appl%20cpu%20interface%20protocol%20specification_lzn901%201708_revr1a.pdf ericsson's communication cpu to application cpu interface (caif) protocol (since linux 2.6.36). see .i documentation/networking/caif/linux\-caif.txt in the linux kernel source tree for details. .tp .b af_alg interface to kernel crypto api (since linux 2.6.38). see .i documentation/crypto/userspace\-if.rst in the linux kernel source tree for details. .tp .b af_vsock .\" commit: d021c344051af91f42c5ba9fdedc176740cbd238 vmware vsockets protocol for hypervisor-guest interaction (since linux 3.9); has no relation to .b af_iucv and .br af_smc . for further information, see .br vsock (7). .tp .b af_kcm .\" commit: 03c8efc1ffeb6b82a22c1af8dd908af349563314 kcm (kernel connection multiplexer) interface (since linux 4.6). see .i documentation/networking/kcm.txt in the linux kernel source tree for details. .tp .b af_qipcrtr .\" commit: bdabad3e363d825ddf9679dd431cca0b2c30f881 qualcomm ipc router interface protocol (since linux 4.7). .tp .b af_smc .\" commit: f3a3e248f3f7cd9a4bed334022704d7e7fc781bf smc-r (shared memory communications over rdma) protocol (since linux 4.11), and smc-d (shared memory communications, direct memory access) protocol for intra-node z/vm quest interaction (since linux 4.19); has no relation to .br af_rds ", " af_iucv or .br af_vsock . see .ur https://tools.ietf.org/html/rfc7609 rfc 7609 .i ibm's shared memory communications over rdma (smc-r) protocol .ue for details regarding smc-r. see .ur https://www-01.ibm.com\:/software/network\:/commserver\:/smc-d/index.html .i smc-d reference information .ue for details regarding smc-d. .tp .b af_xdp .\" commit: c0c77d8fb787cfe0c3fca689c2a30d1dad4eaba7 xdp (express data path) interface (since linux 4.18). see .i documentation/networking/af_xdp.rst in the linux kernel source tree for details. .sh see also .br socket (2), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ecvt_r.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th modf 3 2021-03-22 "" "linux programmer's manual" .sh name modf, modff, modfl \- extract signed integral and fractional values from floating-point number .sh synopsis .nf .b #include .pp .bi "double modf(double " x ", double *" iptr ); .bi "float modff(float " x ", float *" iptr ); .bi "long double modfl(long double " x ", long double *" iptr ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br modff (), .br modfl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions break the argument .i x into an integral part and a fractional part, each of which has the same sign as .ir x . the integral part is stored in the location pointed to by .ir iptr . .sh return value these functions return the fractional part of .ir x . .pp if .i x is a nan, a nan is returned, and .ir *iptr is set to a nan. .pp if .i x is positive infinity (negative infinity), +0 (\-0) is returned, and .ir *iptr is set to positive infinity (negative infinity). .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br modf (), .br modff (), .br modfl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br frexp (3), .br ldexp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getegid.2 .so man3/unlocked_stdio.3 .so man3/nl_langinfo.3 .so man2/setgroups.2 .so man3/getipnodebyname.3 .so man7/system_data_types.7 .\" copyright 2001 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" aeb: some corrections .th dysize 3 2021-03-22 "gnu" "linux programmer's manual" .sh name dysize \- get number of days for a given year .sh synopsis .nf .b "#include " .pp .bi "int dysize(int " year ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br dysize (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the function returns 365 for a normal year and 366 for a leap year. the calculation for leap year is based on: .pp .in +4n .ex (year) %4 == 0 && ((year) %100 != 0 || (year) %400 == 0) .ee .in .pp the formula is defined in the macro .i __isleap(year) also found in .ir . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dysize () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function occurs in sunos 4.x. .sh notes this is a compatibility function only. don't use it in new programs. .\" the sco version of this function had a year-2000 problem. .sh see also .br strftime (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/timegm.3 .so man3/pthread_setconcurrency.3 .so man2/timer_settime.2 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2005, 2008 michael kerrisk .\" and copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-21, rik faith .\" modified 1994-08-21, michael chastain : .\" fixed typos. .\" modified 1997-01-31, eric s. raymond .\" modified 2002-09-28, aeb .\" 2009-01-12, mtk, reordered text in description and added some .\" details for dup2(). .\" 2008-10-09, mtk: add description of dup3() .\" .th dup 2 2021-03-22 "linux" "linux programmer's manual" .sh name dup, dup2, dup3 \- duplicate a file descriptor .sh synopsis .nf .b #include .pp .bi "int dup(int " oldfd ); .bi "int dup2(int " oldfd ", int " newfd ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .br "#include " " /* definition of " o_* " constants */" .b #include .pp .bi "int dup3(int " oldfd ", int " newfd ", int " flags ); .fi .sh description the .br dup () system call allocates a new file descriptor that refers to the same open file description as the descriptor .ir oldfd . (for an explanation of open file descriptions, see .br open (2).) the new file descriptor number is guaranteed to be the lowest-numbered file descriptor that was unused in the calling process. .pp after a successful return, the old and new file descriptors may be used interchangeably. since the two file descriptors refer to the same open file description, they share file offset and file status flags; for example, if the file offset is modified by using .br lseek (2) on one of the file descriptors, the offset is also changed for the other file descriptor. .pp the two file descriptors do not share file descriptor flags (the close-on-exec flag). the close-on-exec flag .rb ( fd_cloexec ; see .br fcntl (2)) for the duplicate descriptor is off. .\" .ss dup2() the .br dup2 () system call performs the same task as .br dup (), but instead of using the lowest-numbered unused file descriptor, it uses the file descriptor number specified in .ir newfd . in other words, the file descriptor .i newfd is adjusted so that it now refers to the same open file description as .ir oldfd . .pp if the file descriptor .ir newfd was previously open, it is closed before being reused; the close is performed silently (i.e., any errors during the close are not reported by .br dup2 ()). .pp the steps of closing and reusing the file descriptor .ir newfd are performed .ir atomically . this is important, because trying to implement equivalent functionality using .br close (2) and .br dup () would be subject to race conditions, whereby .i newfd might be reused between the two steps. such reuse could happen because the main program is interrupted by a signal handler that allocates a file descriptor, or because a parallel thread allocates a file descriptor. .pp note the following points: .ip * 3 if .i oldfd is not a valid file descriptor, then the call fails, and .i newfd is not closed. .ip * if .i oldfd is a valid file descriptor, and .i newfd has the same value as .ir oldfd , then .br dup2 () does nothing, and returns .ir newfd . .\" .ss dup3() .br dup3 () is the same as .br dup2 (), except that: .ip * 3 the caller can force the close-on-exec flag to be set for the new file descriptor by specifying .br o_cloexec in .ir flags . see the description of the same flag in .br open (2) for reasons why this may be useful. .ip * .\" ulrich drepper, lkml, 2008-10-09: .\" we deliberately decided on this change. otherwise, what is the .\" result of dup3(fd, fd, o_cloexec)? if .ir oldfd equals .ir newfd , then .br dup3 () fails with the error .br einval . .sh return value on success, these system calls return the new file descriptor. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i oldfd isn't an open file descriptor. .tp .b ebadf .i newfd is out of the allowed range for file descriptors (see the discussion of .br rlimit_nofile in .br getrlimit (2)). .tp .b ebusy (linux only) this may be returned by .br dup2 () or .br dup3 () during a race condition with .br open (2) and .br dup (). .tp .b eintr the .br dup2 () or .br dup3 () call was interrupted by a signal; see .br signal (7). .tp .b einval .rb ( dup3 ()) .i flags contain an invalid value. .tp .b einval .rb ( dup3 ()) .i oldfd was equal to .ir newfd . .tp .b emfile the per-process limit on the number of open file descriptors has been reached (see the discussion of .br rlimit_nofile in .br getrlimit (2)). .sh versions .br dup3 () was added to linux in version 2.6.27; glibc support is available starting with version 2.9. .sh conforming to .br dup (), .br dup2 (): posix.1-2001, posix.1-2008, svr4, 4.3bsd. .pp .br dup3 () is linux-specific. .\" svr4 documents additional .\" eintr and enolink error conditions. posix.1 adds eintr. .\" the ebusy return is linux-specific. .sh notes the error returned by .br dup2 () is different from that returned by .br fcntl( "..., " f_dupfd ", ..." ) when .i newfd is out of range. on some systems, .br dup2 () also sometimes returns .b einval like .br f_dupfd . .pp if .i newfd was open, any errors that would have been reported at .br close (2) time are lost. if this is of concern, then\(emunless the program is single-threaded and does not allocate file descriptors in signal handlers\(emthe correct approach is .i not to close .i newfd before calling .br dup2 (), because of the race condition described above. instead, code something like the following could be used: .pp .in +4n .ex /* obtain a duplicate of \(aqnewfd\(aq that can subsequently be used to check for close() errors; an ebadf error means that \(aqnewfd\(aq was not open. */ tmpfd = dup(newfd); if (tmpfd == \-1 && errno != ebadf) { /* handle unexpected dup() error. */ } /* atomically duplicate \(aqoldfd\(aq on \(aqnewfd\(aq. */ if (dup2(oldfd, newfd) == \-1) { /* handle dup2() error. */ } /* now check for close() errors on the file originally referred to by \(aqnewfd\(aq. */ if (tmpfd != \-1) { if (close(tmpfd) == \-1) { /* handle errors from close. */ } } .ee .in .sh see also .br close (2), .br fcntl (2), .br open (2), .br pidfd_getfd (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 mitchum dsouza .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" updated, aeb, 980809 .th catgets 3 2021-03-22 "" "linux programmer's manual" .sh name catgets \- get message from a message catalog .sh synopsis .nf .b #include .pp .bi "char *catgets(nl_catd " catalog ", int " set_number \ ", int " message_number , .bi " const char *" message ); .fi .sh description .br catgets () reads the message .ir message_number , in set .ir set_number , from the message catalog identified by .ir catalog , where .i catalog is a catalog descriptor returned from an earlier call to .br catopen (3). the fourth argument, .ir message , points to a default message string which will be returned by .br catgets () if the identified message catalog is not currently available. the message-text is contained in an internal buffer area and should be copied by the application if it is to be saved or modified. the return string is always terminated with a null byte (\(aq\e0\(aq). .sh return value on success, .br catgets () returns a pointer to an internal buffer area containing the null-terminated message string. on failure, .br catgets () returns the value .ir message . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br catgets () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the .br catgets () function is available only in libc.so.4.4.4c and above. the jan 1987 x/open portability guide specifies a more subtle error return: .i message is returned if the message catalog specified by .i catalog is not available, while an empty string is returned when the message catalog is available but does not contain the specified message. these two possible error returns seem to be discarded in susv2 in favor of always returning .ir message . .sh see also .br catopen (3), .br setlocale (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/clone.2 .so man3/lrint.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .\" modified, aeb, 990824 .\" .th mb_len_max 3 2015-07-23 "linux" "linux programmer's manual" .sh name mb_len_max \- maximum multibyte length of a character across all locales .sh synopsis .nf .b #include .fi .sh description the .b mb_len_max macro is the maximum number of bytes needed to represent a single wide character, in any of the supported locales. .sh return value a constant integer greater than zero. .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the entities .b mb_len_max and .i sizeof(wchar_t) are totally unrelated. in glibc, .b mb_len_max is typically 16 .\" for an explanation of why the limit was raised to 16, see .\" http://lists.gnu.org/archive/html/bug-gnulib/2015-05/msg00001.html .\" from: bruno haible .\" subject: re: why is mb_len_max so large (16) on glibc .\" date: thu, 14 may 2015 02:30:14 +0200 (6 in glibc versions earlier than 2.2), while .i sizeof(wchar_t) is 4. .sh see also .br mb_cur_max (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setbuf.3 .\" copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th erfc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name erfc, erfcf, erfcl \- complementary error function .sh synopsis .nf .b #include .pp .bi "double erfc(double " x ); .bi "float erfcf(float " x ); .bi "long double erfcl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br erfc (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br erfcf (), .br erfcl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the complementary error function of .ir x , that is, 1.0 \- erf(x). .sh return value on success, these functions return the complementary error function of .ir x , a value in the range [0,2]. .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 or \-0, 1 is returned. .pp if .i x is positive infinity, +0 is returned. .pp if .i x is negative infinity, +2 is returned. .pp if the function result underflows and produces an unrepresentable value, the return value is 0.0. .pp if the function result underflows but produces a representable (i.e., subnormal) value, .\" e.g., erfc(27) on x86-32 that value is returned, and a range error occurs. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp range error: result underflow (result is subnormal) .\" .i errno .\" is set to .\" .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .pp these functions do not set .ir errno . .\" it is intentional that these functions do not set errno for this case .\" see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br erfc (), .br erfcf (), .br erfcl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh notes the .br erfc (), .br erfcf (), and .br erfcl () functions are provided to avoid the loss accuracy that would occur for the calculation 1-erf(x) for large values of .ir x (for which the value of erf(x) approaches 1). .sh see also .br cerf (3), .br erf (3), .br exp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .so man3/remquo.3 .so man3/scanf.3 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" $id: shutdown.2,v 1.1.1.1 1999/03/21 22:52:23 freitag exp $ .\" .\" modified sat jul 24 09:57:55 1993 by rik faith .\" modified tue oct 22 22:04:51 1996 by eric s. raymond .\" modified 1998 by andi kleen .\" .th shutdown 2 2021-03-22 "linux" "linux programmer's manual" .sh name shutdown \- shut down part of a full-duplex connection .sh synopsis .nf .b #include .pp .bi "int shutdown(int " sockfd ", int " how ); .fi .sh description the .br shutdown () call causes all or part of a full-duplex connection on the socket associated with .i sockfd to be shut down. if .i how is .br shut_rd , further receptions will be disallowed. if .i how is .br shut_wr , further transmissions will be disallowed. if .i how is .br shut_rdwr , further receptions and transmissions will be disallowed. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i sockfd is not a valid file descriptor. .tp .b einval an invalid value was specified in .ir how (but see bugs). .tp .b enotconn the specified socket is not connected. .tp .b enotsock the file descriptor .i sockfd does not refer to a socket. .sh conforming to posix.1-2001, posix.1-2008, 4.4bsd .rb ( shutdown () first appeared in 4.2bsd). .sh notes the constants .br shut_rd , .br shut_wr , .b shut_rdwr have the value 0, 1, 2, respectively, and are defined in .i since glibc-2.1.91. .sh bugs checks for the validity of .i how are done in domain-specific code, and before linux 3.7 not all domains performed these checks. .\" https://bugzilla.kernel.org/show_bug.cgi?id=47111 most notably, unix domain sockets simply ignored invalid values. this problem was fixed for unix domain sockets .\" commit fc61b928dc4d72176cf4bd4d30bf1d22e599aefc .\" and for decnet sockets in commit 46b66d7077b89fb4917ceef19b3f7dd86055c94a in linux 3.7. .sh see also .br close (2), .br connect (2), .br socket (2), .br socket (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/slist.3 .\" copyright (c) 1994 jochen hein (hein@student.tu-clausthal.de) .\" copyright (c) 2008 petr baudis (pasky@suse.cz) .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2008-06-17 petr baudis .\" lc_time: describe first_weekday and first_workday .\" .th locale 5 2021-03-22 "linux" "linux user manual" .sh name locale \- describes a locale definition file .sh description the .b locale definition file contains all the information that the .br localedef (1) command needs to convert it into the binary locale database. .pp the definition files consist of sections which each describe a locale category in detail. see .br locale (7) for additional details for these categories. .ss syntax the locale definition file starts with a header that may consist of the following keywords: .tp .i escape_char is followed by a character that should be used as the escape-character for the rest of the file to mark characters that should be interpreted in a special way. it defaults to the backslash (\e). .tp .i comment_char is followed by a character that will be used as the comment-character for the rest of the file. it defaults to the number sign (#). .pp the locale definition has one part for each locale category. each part can be copied from another existing locale or can be defined from scratch. if the category should be copied, the only valid keyword in the definition is .i copy followed by the name of the locale in double quotes which should be copied. the exceptions for this rule are .b lc_collate and .b lc_ctype where a .i copy statement can be followed by locale-specific rules and selected overrides. .pp when defining a locale or a category from scratch, an existing system- provided locale definition file should be used as a reference to follow common glibc conventions. .ss locale category sections the following category sections are defined by posix: .ip * 3 .b lc_ctype .ip * .b lc_collate .ip * .b lc_messages .ip * .b lc_monetary .ip * .b lc_numeric .ip * .b lc_time .pp in addition, since version 2.2, the gnu c library supports the following nonstandard categories: .ip * 3 .b lc_address .ip * .b lc_identification .ip * .b lc_measurement .ip * .b lc_name .ip * .b lc_paper .ip * .b lc_telephone .pp see .br locale (7) for a more detailed description of each category. .ss lc_address the definition starts with the string .i lc_address in the first column. .pp the following keywords are allowed: .tp .i postal_fmt followed by a string containing field descriptors that define the format used for postal addresses in the locale. the following field descriptors are recognized: .rs .tp %n person's name, possibly constructed with the .b lc_name .i name_fmt keyword (since glibc 2.24). .tp 4 %a care of person, or organization. .tp %f firm name. .tp %d department name. .tp %b building name. .tp %s street or block (e.g., japanese) name. .tp %h house number or designation. .tp %n insert an end-of-line if the previous descriptor's value was not an empty string; otherwise ignore. .tp %t insert a space if the previous descriptor's value was not an empty string; otherwise ignore. .tp %r room number, door designation. .tp %e floor number. .tp %c country designation, from the .i country_post keyword. .tp %l local township within town or city (since glibc 2.24). .tp %z zip number, postal code. .tp %t town, city. .tp %s state, province, or prefecture. .tp %c country, as taken from data record. .pp each field descriptor may have an \(aqr\(aq after the \(aq%\(aq to specify that the information is taken from a romanized version string of the entity. .re .tp .i country_name followed by the country name in the language of the current document (e.g., "deutschland" for the .b de_de locale). .tp .i country_post followed by the abbreviation of the country (see cert_mailcodes). .tp .i country_ab2 followed by the two-letter abbreviation of the country (iso 3166). .tp .i country_ab3 followed by the three-letter abbreviation of the country (iso 3166). .tp .i country_num followed by the numeric country code (iso 3166). .tp .i country_car followed by the international license plate country code. .tp .i country_isbn followed by the isbn code (for books). .tp .i lang_name followed by the language name in the language of the current document. .tp .i lang_ab followed by the two-letter abbreviation of the language (iso 639). .tp .i lang_term followed by the three-letter abbreviation of the language (iso 639-2/t). .tp .i lang_lib followed by the three-letter abbreviation of the language for library use (iso 639-2/b). applications should in general prefer .i lang_term over .ir lang_lib . .pp the .b lc_address definition ends with the string .ir "end lc_address" . .ss lc_ctype the definition starts with the string .i lc_ctype in the first column. .pp the following keywords are allowed: .tp .i upper followed by a list of uppercase letters. the letters .b a through .b z are included automatically. characters also specified as .br cntrl , .br digit , .br punct , or .b space are not allowed. .tp .i lower followed by a list of lowercase letters. the letters .b a through .b z are included automatically. characters also specified as .br cntrl , .br digit , .br punct , or .b space are not allowed. .tp .i alpha followed by a list of letters. all character specified as either .b upper or .b lower are automatically included. characters also specified as .br cntrl , .br digit , .br punct , or .b space are not allowed. .tp .i digit followed by the characters classified as numeric digits. only the digits .b 0 through .b 9 are allowed. they are included by default in this class. .tp .i space followed by a list of characters defined as white-space characters. characters also specified as .br upper , .br lower , .br alpha , .br digit , .br graph , or .b xdigit are not allowed. the characters .br , .br , .br , .br , .br , and .b are automatically included. .tp .i cntrl followed by a list of control characters. characters also specified as .br upper , .br lower , .br alpha , .br digit , .br punct , .br graph , .br print , or .b xdigit are not allowed. .tp .i punct followed by a list of punctuation characters. characters also specified as .br upper , .br lower , .br alpha , .br digit , .br cntrl , .br xdigit , or the .b character are not allowed. .tp .i graph followed by a list of printable characters, not including the .b character. the characters defined as .br upper , .br lower , .br alpha , .br digit , .br xdigit , and .b punct are automatically included. characters also specified as .b cntrl are not allowed. .tp .i print followed by a list of printable characters, including the .b character. the characters defined as .br upper , .br lower , .br alpha , .br digit , .br xdigit , .br punct , and the .b character are automatically included. characters also specified as .b cntrl are not allowed. .tp .i xdigit followed by a list of characters classified as hexadecimal digits. the decimal digits must be included followed by one or more set of six characters in ascending order. the following characters are included by default: .b 0 through .br 9 , .b a through .br f , .b a through .br f . .tp .i blank followed by a list of characters classified as .br blank . the characters .b and .b are automatically included. .tp .i charclass followed by a list of locale-specific character class names which are then to be defined in the locale. .tp .i toupper followed by a list of mappings from lowercase to uppercase letters. each mapping is a pair of a lowercase and an uppercase letter separated with a .b , and enclosed in parentheses. .tp .i tolower followed by a list of mappings from uppercase to lowercase letters. if the keyword tolower is not present, the reverse of the toupper list is used. .tp .i map totitle followed by a list of mapping pairs of characters and letters to be used in titles (headings). .tp .i class followed by a locale-specific character class definition, starting with the class name followed by the characters belonging to the class. .tp .i charconv followed by a list of locale-specific character mapping names which are then to be defined in the locale. .tp .i outdigit followed by a list of alternate output digits for the locale. .tp .i map to_inpunct followed by a list of mapping pairs of alternate digits and separators for input digits for the locale. .tp .i map to_outpunct followed by a list of mapping pairs of alternate separators for output for the locale. .tp .i translit_start marks the start of the transliteration rules section. the section can contain the .i include keyword in the beginning followed by locale-specific rules and overrides. any rule specified in the locale file will override any rule copied or included from other files. in case of duplicate rule definitions in the locale file, only the first rule is used. .ip a transliteration rule consist of a character to be transliterated followed by a list of transliteration targets separated by semicolons. the first target which can be presented in the target character set is used, if none of them can be used the .i default_missing character will be used instead. .tp .i include in the transliteration rules section includes a transliteration rule file (and optionally a repertoire map file). .tp .i default_missing in the transliteration rules section defines the default character to be used for transliteration where none of the targets cannot be presented in the target character set. .tp .i translit_end marks the end of the transliteration rules. .pp the .b lc_ctype definition ends with the string .ir "end lc_ctype" . .ss lc_collate note that glibc does not support all posix-defined options, only the options described below are supported (as of glibc 2.23). .pp the definition starts with the string .i lc_collate in the first column. .pp the following keywords are allowed: .tp .i coll_weight_max followed by the number representing used collation levels. this keyword is recognized but ignored by glibc. .tp .i collating\-element followed by the definition of a collating-element symbol representing a multicharacter collating element. .tp .i collating\-symbol followed by the definition of a collating symbol that can be used in collation order statements. .tp .i define followed by .b string to be evaluated in an .i ifdef .b string / .i else / .i endif construct. .tp .i reorder\-after followed by a redefinition of a collation rule. .tp .i reorder\-end marks the end of the redefinition of a collation rule. .tp .i reorde\r-sections\-after followed by a script name to reorder listed scripts after. .tp .i reorder\-sections\-end marks the end of the reordering of sections. .tp .i script followed by a declaration of a script. .tp .i symbol\-equivalence followed by a collating-symbol to be equivalent to another defined collating-symbol. .pp the collation rule definition starts with a line: .tp .i order_start followed by a list of keywords chosen from .br forward , .br backward , or .br position . the order definition consists of lines that describe the collation order and is terminated with the keyword .ir order_end . .pp the .b lc_collate definition ends with the string .ir "end lc_collate" . .ss lc_identification the definition starts with the string .i lc_identification in the first column. .pp the following keywords are allowed: .tp .i title followed by the title of the locale document (e.g., "maori language locale for new zealand"). .tp .i source followed by the name of the organization that maintains this document. .tp .i address followed by the address of the organization that maintains this document. .tp .i contact followed by the name of the contact person at the organization that maintains this document. .tp .i email followed by the email address of the person or organization that maintains this document. .tp .i tel followed by the telephone number (in international format) of the organization that maintains this document. as of glibc 2.24, this keyword is deprecated in favor of other contact methods. .tp .i fax followed by the fax number (in international format) of the organization that maintains this document. as of glibc 2.24, this keyword is deprecated in favor of other contact methods. .tp .i language followed by the name of the language to which this document applies. .tp .i territory followed by the name of the country/geographic extent to which this document applies. .tp .i audience followed by a description of the audience for which this document is intended. .tp .i application followed by a description of any special application for which this document is intended. .tp .i abbreviation followed by the short name for provider of the source of this document. .tp .i revision followed by the revision number of this document. .tp .i date followed by the revision date of this document. .pp in addition, for each of the categories defined by the document, there should be a line starting with the keyword .ir category , followed by: .ip * 3 a string that identifies this locale category definition, .ip * a semicolon, and .ip * one of the .b lc_* identifiers. .pp the .b lc_identification definition ends with the string .ir "end lc_identification" . .ss lc_messages the definition starts with the string .i lc_messages in the first column. .pp the following keywords are allowed: .tp .i yesexpr followed by a regular expression that describes possible yes-responses. .tp .i noexpr followed by a regular expression that describes possible no-responses. .tp .i yesstr followed by the output string corresponding to "yes". .tp .i nostr followed by the output string corresponding to "no". .pp the .b lc_messages definition ends with the string .ir "end lc_messages" . .ss lc_measurement the definition starts with the string .i lc_measurement in the first column. .pp the following keywords are allowed: .tp .i measurement followed by number identifying the standard used for measurement. the following values are recognized: .rs .tp 4 .b 1 metric. .tp .b 2 us customary measurements. .re .pp the .b lc_measurement definition ends with the string .ir "end lc_measurement" . .ss lc_monetary the definition starts with the string .i lc_monetary in the first column. .pp the following keywords are allowed: .tp .i int_curr_symbol followed by the international currency symbol. this must be a 4-character string containing the international currency symbol as defined by the iso 4217 standard (three characters) followed by a separator. .tp .i currency_symbol followed by the local currency symbol. .tp .i mon_decimal_point followed by the single-character string that will be used as the decimal delimiter when formatting monetary quantities. .tp .i mon_thousands_sep followed by the single-character string that will be used as a group separator when formatting monetary quantities. .tp .i mon_grouping followed by a sequence of integers separated by semicolons that describe the formatting of monetary quantities. see .i grouping below for details. .tp .i positive_sign followed by a string that is used to indicate a positive sign for monetary quantities. .tp .i negative_sign followed by a string that is used to indicate a negative sign for monetary quantities. .tp .i int_frac_digits followed by the number of fractional digits that should be used when formatting with the .ir int_curr_symbol . .tp .i frac_digits followed by the number of fractional digits that should be used when formatting with the .ir currency_symbol . .tp .i p_cs_precedes followed by an integer that indicates the placement of .i currency_symbol for a nonnegative formatted monetary quantity: .rs .tp 4 .b 0 the symbol succeeds the value. .tp .b 1 the symbol precedes the value. .re .tp .i p_sep_by_space followed by an integer that indicates the separation of .ir currency_symbol , the sign string, and the value for a nonnegative formatted monetary quantity. the following values are recognized: .rs .tp 4 .b 0 no space separates the currency symbol and the value. .tp .b 1 if the currency symbol and the sign string are adjacent, a space separates them from the value; otherwise a space separates the currency symbol and the value. .tp .b 2 if the currency symbol and the sign string are adjacent, a space separates them from the value; otherwise a space separates the sign string and the value. .re .tp .i n_cs_precedes followed by an integer that indicates the placement of .i currency_symbol for a negative formatted monetary quantity. the same values are recognized as for .ir p_cs_precedes . .tp .i n_sep_by_space followed by an integer that indicates the separation of .ir currency_symbol , the sign string, and the value for a negative formatted monetary quantity. the same values are recognized as for .ir p_sep_by_space . .tp .i p_sign_posn followed by an integer that indicates where the .i positive_sign should be placed for a nonnegative monetary quantity: .rs .tp 4 .b 0 parentheses enclose the quantity and the .i currency_symbol or .ir int_curr_symbol . .tp .b 1 the sign string precedes the quantity and the .i currency_symbol or the .ir int_curr_symbol . .tp .b 2 the sign string succeeds the quantity and the .i currency_symbol or the .ir int_curr_symbol . .tp .b 3 the sign string precedes the .i currency_symbol or the .ir int_curr_symbol . .tp .b 4 the sign string succeeds the .i currency_symbol or the .ir int_curr_symbol . .re .tp .i n_sign_posn followed by an integer that indicates where the .i negative_sign should be placed for a negative monetary quantity. the same values are recognized as for .ir p_sign_posn . .tp .i int_p_cs_precedes followed by an integer that indicates the placement of .i int_curr_symbol for a nonnegative internationally formatted monetary quantity. the same values are recognized as for .ir p_cs_precedes . .tp .i int_n_cs_precedes followed by an integer that indicates the placement of .i int_curr_symbol for a negative internationally formatted monetary quantity. the same values are recognized as for .ir p_cs_precedes . .tp .i int_p_sep_by_space followed by an integer that indicates the separation of .ir int_curr_symbol , the sign string, and the value for a nonnegative internationally formatted monetary quantity. the same values are recognized as for .ir p_sep_by_space . .tp .i int_n_sep_by_space followed by an integer that indicates the separation of .ir int_curr_symbol , the sign string, and the value for a negative internationally formatted monetary quantity. the same values are recognized as for .ir p_sep_by_space . .tp .i int_p_sign_posn followed by an integer that indicates where the .i positive_sign should be placed for a nonnegative internationally formatted monetary quantity. the same values are recognized as for .ir p_sign_posn . .tp .i int_n_sign_posn followed by an integer that indicates where the .i negative_sign should be placed for a negative internationally formatted monetary quantity. the same values are recognized as for .ir p_sign_posn . .pp the .b lc_monetary definition ends with the string .ir "end lc_monetary" . .ss lc_name the definition starts with the string .i lc_name in the first column. .pp various keywords are allowed, but only .i name_fmt is mandatory. other keywords are needed only if there is common convention to use the corresponding salutation in this locale. the allowed keywords are as follows: .tp .i name_fmt followed by a string containing field descriptors that define the format used for names in the locale. the following field descriptors are recognized: .rs .tp 4 %f family name(s). .tp %f family names in uppercase. .tp %g first given name. .tp %g first given initial. .tp %l first given name with latin letters. .tp %o other shorter name. .tp %m additional given name(s). .tp %m initials for additional given name(s). .tp %p profession. .tp %s salutation, such as "doctor". .tp %s abbreviated salutation, such as "mr." or "dr.". .tp %d salutation, using the fdcc-sets conventions. .\" 1 for the name_gen .\" in glibc 2.19, %d1 is used in only: .\" /home/mtk/archive/glibc/glibc-2.19/localedata/locales/bem_zm .\" /home/mtk/archive/glibc/glibc-2.19/localedata/locales/zh_hk .\" in glibc 2.19, %d[2-5] appear to be not used at all .\" 2 for name_mr .\" 3 for name_mrs .\" 4 for name_miss .\" 5 for name_ms .tp %t if the preceding field descriptor resulted in an empty string, then the empty string, otherwise a space character. .re .tp .i name_gen followed by the general salutation for any gender. .tp .i name_mr followed by the salutation for men. .tp .i name_mrs followed by the salutation for married women. .tp .i name_miss followed by the salutation for unmarried women. .tp .i name_ms followed by the salutation valid for all women. .pp the .b lc_name definition ends with the string .ir "end lc_name" . .ss lc_numeric the definition starts with the string .i lc_numeric in the first column. .pp the following keywords are allowed: .tp .i decimal_point followed by the single-character string that will be used as the decimal delimiter when formatting numeric quantities. .tp .i thousands_sep followed by the single-character string that will be used as a group separator when formatting numeric quantities. .tp .i grouping followed by a sequence of integers separated by semicolons that describe the formatting of numeric quantities. .ip each integer specifies the number of digits in a group. the first integer defines the size of the group immediately to the left of the decimal delimiter. subsequent integers define succeeding groups to the left of the previous group. if the last integer is not \-1, then the size of the previous group (if any) is repeatedly used for the remainder of the digits. if the last integer is \-1, then no further grouping is performed. .pp the .b lc_numeric definition ends with the string .ir "end lc_numeric" . .ss lc_paper the definition starts with the string .i lc_paper in the first column. .pp the following keywords are allowed: .tp .i height followed by the height, in millimeters, of the standard paper format. .tp .i width followed by the width, in millimeters, of the standard paper format. .pp the .b lc_paper definition ends with the string .ir "end lc_paper" . .ss lc_telephone the definition starts with the string .i lc_telephone in the first column. .pp the following keywords are allowed: .tp .i tel_int_fmt followed by a string that contains field descriptors that identify the format used to dial international numbers. the following field descriptors are recognized: .rs .tp 4 %a area code without nationwide prefix (the prefix is often "00"). .tp %a area code including nationwide prefix. .tp %l local number (within area code). .tp %e extension (to local number). .tp %c country code. .tp %c alternate carrier service code used for dialing abroad. .tp %t if the preceding field descriptor resulted in an empty string, then the empty string, otherwise a space character. .re .tp .i tel_dom_fmt followed by a string that contains field descriptors that identify the format used to dial domestic numbers. the recognized field descriptors are the same as for .ir tel_int_fmt . .tp .i int_select followed by the prefix used to call international phone numbers. .tp .i int_prefix followed by the prefix used from other countries to dial this country. .pp the .b lc_telephone definition ends with the string .ir "end lc_telephone" . .ss lc_time the definition starts with the string .i lc_time in the first column. .pp the following keywords are allowed: .tp .i abday followed by a list of abbreviated names of the days of the week. the list starts with the first day of the week as specified by .i week (sunday by default). see notes. .tp .i day followed by a list of names of the days of the week. the list starts with the first day of the week as specified by .i week (sunday by default). see notes. .tp .i abmon followed by a list of abbreviated month names. .tp .i mon followed by a list of month names. .tp .i d_t_fmt followed by the appropriate date and time format (for syntax, see .br strftime (3)). .tp .i d_fmt followed by the appropriate date format (for syntax, see .br strftime (3)). .tp .i t_fmt followed by the appropriate time format (for syntax, see .br strftime (3)). .tp .i am_pm followed by the appropriate representation of the .b am and .b pm strings. this should be left empty for locales not using am/pm convention. .tp .i t_fmt_ampm followed by the appropriate time format (for syntax, see .br strftime (3)) when using 12h clock format. this should be left empty for locales not using am/pm convention. .tp .i era followed by semicolon-separated strings that define how years are counted and displayed for each era in the locale. each string has the following format: .rs .pp .ir direction ":" offset ":" start_date ":" end_date ":" era_name ":" era_format .pp the fields are to be defined as follows: .tp 4 .i direction either .b + or .br \- . .b + means the years closer to .i start_date have lower numbers than years closer to .ir end_date . .b \- means the opposite. .tp .i offset the number of the year closest to .i start_date in the era, corresponding to the .i %ey descriptor (see .br strptime (3)). .tp .i start_date the start of the era in the form of .ir yyyy/mm/dd . years prior ad 1 are represented as negative numbers. .tp .i end_date the end of the era in the form of .ir yyyy/mm/dd , or one of the two special values of .b \-* or .br +* . .b \-* means the ending date is the beginning of time. .b +* means the ending date is the end of time. .tp .i era_name the name of the era corresponding to the .i %ec descriptor (see .br strptime (3)). .tp .i era_format the format of the year in the era corresponding to the .i %ey descriptor (see .br strptime (3)). .re .tp .i era_d_fmt followed by the format of the date in alternative era notation, corresponding to the .i %ex descriptor (see .br strptime (3)). .tp .i era_t_fmt followed by the format of the time in alternative era notation, corresponding to the .i %ex descriptor (see .br strptime (3)). .tp .i era_d_t_fmt followed by the format of the date and time in alternative era notation, corresponding to the .i %ec descriptor (see .br strptime (3)). .tp .i alt_digits followed by the alternative digits used for date and time in the locale. .tp .i week followed by a list of three values separated by semicolons: the number of days in a week (by default 7), a date of beginning of the week (by default corresponds to sunday), and the minimal length of the first week in year (by default 4). regarding the start of the week, .b 19971130 shall be used for sunday and .b 19971201 shall be used for monday. see notes. .tp .ir first_weekday " (since glibc 2.2)" followed by the number of the day from the .i day list to be shown as the first day of the week in calendar applications. the default value of .b 1 corresponds to either sunday or monday depending on the value of the second .i week list item. see notes. .tp .ir first_workday " (since glibc 2.2)" followed by the number of the first working day from the .i day list. the default value is .br 2 . see notes. .tp .i cal_direction followed by a number value that indicates the direction for the display of calendar dates, as follows: .rs .tp 4 .b 1 left-right from top. .tp .b 2 top-down from left. .tp .b 3 right-left from top. .re .tp .i date_fmt followed by the appropriate date representation for .br date (1) (for syntax, see .br strftime (3)). .pp the .b lc_time definition ends with the string .ir "end lc_time" . .sh files .tp .i /usr/lib/locale/locale\-archive usual default locale archive location. .tp .i /usr/share/i18n/locales usual default path for locale definition files. .sh conforming to posix.2. .sh notes the collective gnu c library community wisdom regarding .ir abday , .ir day , .ir week , .ir first_weekday , and .i first_workday states at https://sourceware.org/glibc/wiki/locales the following: .ip * 3 the value of the second .i week list item specifies the base of the .i abday and .i day lists. .ip * .i first_weekday specifies the offset of the first day-of-week in the .i abday and .i day lists. .ip * for compatibility reasons, all glibc locales should set the value of the second .i week list item to .b 19971130 (sunday) and base the .i abday and .i day lists appropriately, and set .i first_weekday and .i first_workday to .b 1 or .br 2 , depending on whether the week and work week actually starts on sunday or monday for the locale. .\" .sh author .\" jochen hein (hein@student.tu-clausthal.de) .sh see also .br iconv (1), .br locale (1), .br localedef (1), .br localeconv (3), .br newlocale (3), .br setlocale (3), .br strftime (3), .br strptime (3), .br uselocale (3), .br charmap (5), .br charsets (7), .br locale (7), .br unicode (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th casin 3 2021-03-22 "" "linux programmer's manual" .sh name casin, casinf, casinl \- complex arc sine .sh synopsis .nf .b #include .pp .bi "double complex casin(double complex " z ); .bi "float complex casinf(float complex " z ); .bi "long double complex casinl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex arc sine of .ir z . if \fiy\ =\ casin(z)\fp, then \fiz\ =\ csin(y)\fp. the real part of .i y is chosen in the interval [\-pi/2,pi/2]. .pp one has: .pp .nf casin(z) = \-i clog(iz + csqrt(1 \- z * z)) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br casin (), .br casinf (), .br casinl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br clog (3), .br csin (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strcpy.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_unlink 3 2021-03-22 "linux" "linux programmer's manual" .sh name sem_unlink \- remove a named semaphore .sh synopsis .nf .b #include .pp .bi "int sem_unlink(const char *" name ); .fi .pp link with \fi\-pthread\fp. .sh description .br sem_unlink () removes the named semaphore referred to by .ir name . the semaphore name is removed immediately. the semaphore is destroyed once all other processes that have the semaphore open close it. .sh return value on success .br sem_unlink () returns 0; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b eacces the caller does not have permission to unlink this semaphore. .tp .b enametoolong .i name was too long. .tp .b enoent there is no semaphore with the given .ir name . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_unlink () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh see also .br sem_getvalue (3), .br sem_open (3), .br sem_post (3), .br sem_wait (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sigwaitinfo.2 .so man3/getservent.3 .so man3/csqrt.3 .\" copyright (c) 2004 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sigpause 3 2021-03-22 "linux" "linux programmer's manual" .sh name sigpause \- atomically release blocked signals and wait for interrupt .sh synopsis .nf .b #include .pp .bi "int sigpause(int " sigmask "); /* bsd (but see notes) */" .pp .bi "int sigpause(int " sig "); /* system v / unix 95 */" .fi .sh description don't use this function. use .br sigsuspend (2) instead. .pp the function .br sigpause () is designed to wait for some signal. it changes the process's signal mask (set of blocked signals), and then waits for a signal to arrive. upon arrival of a signal, the original signal mask is restored. .sh return value if .br sigpause () returns, it was interrupted by a signal and the return value is \-1 with .i errno set to .br eintr . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigpause () t} thread safety mt-safe .te .hy .ad .sp 1 .\" fixme: the marking is different from that in the glibc manual, .\" marking in glibc manual is more detailed: .\" .\" sigpause: mt-unsafe race:sigprocmask/!bsd!linux .\" .\" glibc manual says /!linux!bsd indicate the preceding marker only applies .\" when the underlying kernel is neither linux nor a bsd kernel. .\" so, it is safe in linux kernel. .sh conforming to the system v version of .br sigpause () is standardized in posix.1-2001. it is also specified in posix.1-2008, where it is marked obsolete. .sh notes .ss history the classical bsd version of this function appeared in 4.2bsd. it sets the process's signal mask to .ir sigmask . unix 95 standardized the incompatible system v version of this function, which removes only the specified signal .i sig from the process's signal mask. .\" __xpg_sigpause: unix 95, spec 1170, svid, svr4, xpg the unfortunate situation with two incompatible functions with the same name was solved by the .br \%sigsuspend (2) function, that takes a .i "sigset_t\ *" argument (instead of an .ir int ). .ss linux notes on linux, this routine is a system call only on the sparc (sparc64) architecture. .pp .\" libc4 and libc5 know only about the bsd version. .\" glibc uses the bsd version if the .b _bsd_source feature test macro is defined and none of .br _posix_source , .br _posix_c_source , .br _xopen_source , .br _gnu_source , or .b _svid_source is defined. otherwise, the system v version is used, and feature test macros must be defined as follows to obtain the declaration: .ip * 3 since glibc 2.26: _xopen_source >= 500 .\" || (_xopen_source && _xopen_source_extended) .ip * glibc 2.25 and earlier: _xopen_source .pp since glibc 2.19, only the system v version is exposed by .ir ; applications that formerly used the bsd .br sigpause () should be amended to use .br sigsuspend (2). .\" .\" for the bsd version, one usually uses a zero .\" .i sigmask .\" to indicate that no signals are to be blocked. .sh see also .br kill (2), .br sigaction (2), .br sigprocmask (2), .br sigsuspend (2), .br sigblock (3), .br sigvec (3), .br feature_test_macros (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mempcpy.3 .so man3/rpc.3 .so man3/infinity.3 .so man2/unimplemented.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th sin 3 2021-03-22 "" "linux programmer's manual" .sh name sin, sinf, sinl \- sine function .sh synopsis .nf .b #include .pp .bi "double sin(double " x ); .bi "float sinf(float " x ); .bi "long double sinl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sinf (), .br sinl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the sine of .ir x , where .i x is given in radians. .sh return value on success, these functions return the sine of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is positive infinity or negative infinity, a domain error occurs, and a nan is returned. .\" .\" posix.1 allows an optional range error for subnormal x .\" glibc 2.8 doesn't do this .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is an infinity .i errno is set to .br edom (but see bugs). an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sin (), .br sinf (), .br sinl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh bugs before version 2.10, the glibc implementation did not set .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6781 .i errno to .b edom when a domain error occurred. .sh see also .br acos (3), .br asin (3), .br atan (3), .br atan2 (3), .br cos (3), .br csin (3), .br sincos (3), .br tan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1991 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)exec.3 6.4 (berkeley) 4/19/91 .\" .\" converted for linux, mon nov 29 11:12:48 1993, faith@cs.unc.edu .\" updated more for linux, tue jul 15 11:54:18 1997, pacman@cqc.com .\" modified, 24 jun 2004, michael kerrisk .\" added note on casting null .\" .th exec 3 2021-03-22 "gnu" "linux programmer's manual" .sh name execl, execlp, execle, execv, execvp, execvpe \- execute a file .sh synopsis .nf .b #include .pp .b extern char **environ; .pp .bi "int execl(const char *" pathname ", const char *" arg ", ..." .b " /*, (char *) null */);" .bi "int execlp(const char *" file ", const char *" arg ", ..." .b " /*, (char *) null */);" .bi "int execle(const char *" pathname ", const char *" arg ", ..." .bi " /*, (char *) null, char *const " envp "[] */);" .bi "int execv(const char *" pathname ", char *const " argv "[]);" .bi "int execvp(const char *" file ", char *const " argv "[]);" .bi "int execvpe(const char *" file ", char *const " argv \ "[], char *const " envp "[]);" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br execvpe (): .nf _gnu_source .fi .sh description the .br exec () family of functions replaces the current process image with a new process image. the functions described in this manual page are layered on top of .br execve (2). (see the manual page for .br execve (2) for further details about the replacement of the current process image.) .pp the initial argument for these functions is the name of a file that is to be executed. .pp the functions can be grouped based on the letters following the "exec" prefix. .\" .ss l - execl(), execlp(), execle() the .i "const char\ *arg" and subsequent ellipses can be thought of as .ir arg0 , .ir arg1 , \&..., .ir argn . together they describe a list of one or more pointers to null-terminated strings that represent the argument list available to the executed program. the first argument, by convention, should point to the filename associated with the file being executed. the list of arguments .i must be terminated by a null pointer, and, since these are variadic functions, this pointer must be cast .ir "(char\ *) null" . .pp by contrast with the 'l' functions, the 'v' functions (below) specify the command-line arguments of the executed program as a vector. .\" .ss v - execv(), execvp(), execvpe() the .i "char\ *const argv[]" argument is an array of pointers to null-terminated strings that represent the argument list available to the new program. the first argument, by convention, should point to the filename associated with the file being executed. the array of pointers .i must be terminated by a null pointer. .ss e - execle(), execvpe() the environment of the new process image is specified via the argument .ir envp . the .i envp argument is an array of pointers to null-terminated strings and .i must be terminated by a null pointer. .pp all other .br exec () functions (which do not include 'e' in the suffix) take the environment for the new process image from the external variable .i environ in the calling process. .ss p - execlp(), execvp(), execvpe() these functions duplicate the actions of the shell in searching for an executable file if the specified filename does not contain a slash (/) character. the file is sought in the colon-separated list of directory pathnames specified in the .b path environment variable. if this variable isn't defined, the path list defaults to a list that includes the directories returned by .ir confstr(_cs_path) (which typically returns the value "/bin:/usr/bin") and possibly also the current working directory; see notes for further details. .pp .br execvpe () searches for the program using the value of .b path from the caller's environment, not from the .i envp argument. .pp if the specified filename includes a slash character, then .b path is ignored, and the file at the specified pathname is executed. .pp in addition, certain errors are treated specially. .pp if permission is denied for a file (the attempted .br execve (2) failed with the error .br eacces ), these functions will continue searching the rest of the search path. if no other file is found, however, they will return with .i errno set to .br eacces . .pp if the header of a file isn't recognized (the attempted .br execve (2) failed with the error .br enoexec ), these functions will execute the shell .ri ( /bin/sh ) with the path of the file as its first argument. (if this attempt fails, no further searching is done.) .pp all other .br exec () functions (which do not include 'p' in the suffix) take as their first argument a (relative or absolute) pathname that identifies the program to be executed. .sh return value the .br exec () functions return only if an error has occurred. the return value is \-1, and .i errno is set to indicate the error. .sh errors all of these functions may fail and set .i errno for any of the errors specified for .br execve (2). .sh versions the .br execvpe () function first appeared in glibc 2.11. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br execl (), .br execle (), .br execv () t} thread safety mt-safe t{ .br execlp (), .br execvp (), .br execvpe () t} thread safety mt-safe env .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp the .br execvpe () function is a gnu extension. .sh notes the default search path (used when the environment does not contain the variable \fbpath\fr) shows some variation across systems. it generally includes .i /bin and .ir /usr/bin (in that order) and may also include the current working directory. on some other systems, the current working is included after .i /bin and .ir /usr/bin , as an anti-trojan-horse measure. the glibc implementation long followed the traditional default where the current working directory is included at the start of the search path. however, some code refactoring during the development of glibc 2.24 .\" glibc commit 1eb8930608705702d5746e5491bab4e4429fcb83 caused the current working directory to be dropped altogether from the default search path. this accidental behavior change is considered mildly beneficial, and won't be reverted. .pp the behavior of .br execlp () and .br execvp () when errors occur while attempting to execute the file is historic practice, but has not traditionally been documented and is not specified by the posix standard. bsd (and possibly other systems) do an automatic sleep and retry if .b etxtbsy is encountered. linux treats it as a hard error and returns immediately. .pp traditionally, the functions .br execlp () and .br execvp () ignored all errors except for the ones described above and .b enomem and .br e2big , upon which they returned. they now return if any error other than the ones described above occurs. .sh bugs before glibc 2.24, .br execl () and .br execle () employed .br realloc (3) internally and were consequently not async-signal-safe, in violation of the requirements of posix.1. .\" https://sourceware.org/bugzilla/show_bug.cgi?id=19534 this was fixed in glibc 2.24. .\" .ss architecture-specific details on sparc and sparc64, .br execv () is provided as a system call by the kernel (with the prototype shown above) for compatibility with sunos. this function is .i not employed by the .br execv () wrapper function on those architectures. .sh see also .br sh (1), .br execve (2), .br execveat (2), .br fork (2), .br ptrace (2), .br fexecve (3), .br system (3), .br environ (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/clog10.3 .so man3/rcmd.3 .so man3/atoi.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th cfree 3 2021-03-22 "" "linux programmer's manual" .sh name cfree \- free allocated memory .sh synopsis .nf .pp .b "#include " .pp /* in sunos 4 */ .bi "int cfree(void *" ptr ); .pp /* in glibc or freebsd libcompat */ .bi "void cfree(void *" ptr ); .pp /* in sco openserver */ .bi "void cfree(char *" ptr ", unsigned int " num ", unsigned int " size ); .pp /* in solaris watchmalloc.so.1 */ .bi "void cfree(void *" ptr ", size_t " nelem ", size_t " elsize ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br cfree (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description this function should never be used. use .br free (3) instead. starting with version 2.26, it has been removed from glibc. .ss 1-arg cfree in glibc, the function .br cfree () is a synonym for .br free (3), "added for compatibility with sunos". .pp other systems have other functions with this name. the declaration is sometimes in .i and sometimes in .ir . .ss 3-arg cfree some sco and solaris versions have malloc libraries with a 3-argument .br cfree (), apparently as an analog to .br calloc (3). .pp if you need it while porting something, add .pp .in +4n .ex #define cfree(p, n, s) free((p)) .ee .in .pp to your file. .pp a frequently asked question is "can i use .br free (3) to free memory allocated with .br calloc (3), or do i need .br cfree ()?" answer: use .br free (3). .pp an sco manual writes: "the cfree routine is provided for compliance to the ibcse2 standard and simply calls free. the num and size arguments to cfree are not used." .sh return value the sunos version of .br cfree () (which is a synonym for .br free (3)) returns 1 on success and 0 on failure. in case of error, .i errno is set to .br einval : the value of .i ptr was not a pointer to a block previously allocated by one of the routines in the .br malloc (3) family. .sh versions the .br cfree () function was removed .\" commit 025b33ae84bb8f15b2748a1d8605dca453fce112 from glibc in version 2.26. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cfree () t} thread safety mt-safe /* in glibc */ .te .hy .ad .sp 1 .sh conforming to the 3-argument version of .br cfree () as used by sco conforms to the ibcse2 standard: intel386 binary compatibility specification, edition 2. .sh see also .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getnetent_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getnetent_r, getnetbyname_r, getnetbyaddr_r \- get network entry (reentrant) .sh synopsis .nf .b #include .pp .bi "int getnetent_r(struct netent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct netent **restrict " result , .bi " int *restrict " h_errnop ); .bi "int getnetbyname_r(const char *restrict " name , .bi " struct netent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct netent **restrict " result , .bi " int *restrict " h_errnop ); .bi "int getnetbyaddr_r(uint32_t " net ", int " type , .bi " struct netent *restrict " result_buf , .bi " char *restrict " buf ", size_t " buflen , .bi " struct netent **restrict " result , .bi " int *restrict " h_errnop ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getnetent_r (), .br getnetbyname_r (), .br getnetbyaddr_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the .br getnetent_r (), .br getnetbyname_r (), and .br getnetbyaddr_r () functions are the reentrant equivalents of, respectively, .br getnetent (3), .br getnetbyname (3), and .br getnetbynumber (3). they differ in the way that the .i netent structure is returned, and in the function calling signature and return value. this manual page describes just the differences from the nonreentrant functions. .pp instead of returning a pointer to a statically allocated .i netent structure as the function result, these functions copy the structure into the location pointed to by .ir result_buf . .pp the .i buf array is used to store the string fields pointed to by the returned .i netent structure. (the nonreentrant functions allocate these strings in static storage.) the size of this array is specified in .ir buflen . if .i buf is too small, the call fails with the error .br erange , and the caller must try again with a larger buffer. (a buffer of length 1024 bytes should be sufficient for most applications.) .\" i can find no information on the required/recommended buffer size; .\" the nonreentrant functions use a 1024 byte buffer -- mtk. .pp if the function call successfully obtains a network record, then .i *result is set pointing to .ir result_buf ; otherwise, .i *result is set to null. .pp the buffer pointed to by .i h_errnop is used to return the value that would be stored in the global variable .i h_errno by the nonreentrant versions of these functions. .\" getnetent.3 doesn't document any use of h_errno, but nevertheless .\" the nonreentrant functions no seem to set h_errno. .sh return value on success, these functions return 0. on error, they return one of the positive error numbers listed in errors. .pp on error, record not found .rb ( getnetbyname_r (), .br getnetbyaddr_r ()), or end of input .rb ( getnetent_r ()) .i result is set to null. .sh errors .tp .b enoent .rb ( getnetent_r ()) no more records in database. .tp .b erange .i buf is too small. try again with a larger buffer (and increased .ir buflen ). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getnetent_r (), .br getnetbyname_r (), .br getnetbyaddr_r () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. functions with similar names exist on some other systems, though typically with different calling signatures. .sh see also .br getnetent (3), .br networks (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-10 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-10 \- iso 8859-10 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-10 encodes the characters used in nordic languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-10 characters the following table displays the characters in iso 8859-10 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ą latin capital letter a with ogonek 242 162 a2 ē latin capital letter e with macron 243 163 a3 ģ latin capital letter g with cedilla 244 164 a4 ī latin capital letter i with macron 245 165 a5 ĩ latin capital letter i with tilde 246 166 a6 ķ latin capital letter k with cedilla 247 167 a7 § section sign 250 168 a8 ļ latin capital letter l with cedilla 251 169 a9 đ latin capital letter d with stroke 252 170 aa š latin capital letter s with caron 253 171 ab ŧ latin capital letter t with stroke 254 172 ac ž latin capital letter z with caron 255 173 ad ­ soft hyphen 256 174 ae ū latin capital letter u with macron 257 175 af ŋ latin capital letter eng 260 176 b0 ° degree sign 261 177 b1 ą latin small letter a with ogonek 262 178 b2 ē latin small letter e with macron 263 179 b3 ģ latin small letter g with cedilla 264 180 b4 ī latin small letter i with macron 265 181 b5 ĩ latin small letter i with tilde 266 182 b6 ķ latin small letter k with cedilla 267 183 b7 · middle dot 270 184 b8 ļ latin small letter l with cedilla 271 185 b9 đ latin small letter d with stroke 272 186 ba š latin small letter s with caron 273 187 bb ŧ latin small letter t with stroke 274 188 bc ž latin small letter z with caron 275 189 bd ― horizontal bar 276 190 be ū latin small letter u with macron 277 191 bf ŋ latin small letter eng 300 192 c0 ā latin capital letter a with macron 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 į latin capital letter i with ogonek 310 200 c8 č latin capital letter c with caron 311 201 c9 é latin capital letter e with acute 312 202 ca ę latin capital letter e with ogonek 312 202 cb ë latin capital letter e with diaeresis 314 204 cc ė latin capital letter e with dot above 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 ð latin capital letter eth 321 209 d1 ņ latin capital letter n with cedilla 322 210 d2 ō latin capital letter o with macron 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 ũ latin capital letter u with tilde 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ų latin capital letter u with ogonek 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ý latin capital letter y with acute 336 222 de þ latin capital letter thorn 337 223 df ß latin small letter sharp s 340 224 e0 ā latin small letter a with macron 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 į latin small letter i with ogonek 350 232 e8 č latin small letter c with caron 351 233 e9 é latin small letter e with acute 352 234 ea ę latin small letter e with ogonek 353 235 eb ë latin small letter e with diaeresis 354 236 ec ė latin small letter e with dot above 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 ð latin small letter eth 361 241 f1 ņ latin small letter n with cedilla 362 242 f2 ō latin small letter o with macron 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ũ latin small letter u with tilde 370 248 f8 ø latin small letter o with stroke 371 249 f9 ų latin small letter u with ogonek 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ý latin small letter y with acute 376 254 fe þ latin small letter thorn 377 255 ff ĸ latin small letter kra .te .sh notes iso 8859-10 is also known as latin-6. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)fseek.3 6.11 (berkeley) 6/29/91 .\" .\" converted for linux, mon nov 29 15:22:01 1993, faith@cs.unc.edu .\" .th fseek 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fgetpos, fseek, fsetpos, ftell, rewind \- reposition a stream .sh synopsis .nf .b #include .pp .bi "int fseek(file *" stream ", long " offset ", int " whence ); .bi "long ftell(file *" stream ); .pp .bi "void rewind(file *" stream ); .pp .bi "int fgetpos(file *restrict " stream ", fpos_t *restrict " pos ); .bi "int fsetpos(file *" stream ", const fpos_t *" pos ); .fi .sh description the .br fseek () function sets the file position indicator for the stream pointed to by .ir stream . the new position, measured in bytes, is obtained by adding .i offset bytes to the position specified by .ir whence . if .i whence is set to .br seek_set , .br seek_cur , or .br seek_end , the offset is relative to the start of the file, the current position indicator, or end-of-file, respectively. a successful call to the .br fseek () function clears the end-of-file indicator for the stream and undoes any effects of the .br ungetc (3) function on the same stream. .pp the .br ftell () function obtains the current value of the file position indicator for the stream pointed to by .ir stream . .pp the .br rewind () function sets the file position indicator for the stream pointed to by .i stream to the beginning of the file. it is equivalent to: .pp .rs (void) fseek(stream, 0l, seek_set) .re .pp except that the error indicator for the stream is also cleared (see .br clearerr (3)). .pp the .br fgetpos () and .br fsetpos () functions are alternate interfaces equivalent to .br ftell () and .br fseek () (with .i whence set to .br seek_set ), setting and storing the current value of the file offset into or from the object referenced by .ir pos . on some non-unix systems, an .i fpos_t object may be a complex object and these routines may be the only way to portably reposition a text stream. .sh return value the .br rewind () function returns no value. upon successful completion, .br fgetpos (), .br fseek (), .br fsetpos () return 0, and .br ftell () returns the current offset. otherwise, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b einval the .i whence argument to .br fseek () was not .br seek_set , .br seek_end , or .br seek_cur . or: the resulting file offset would be negative. .tp .b espipe the file descriptor underlying .i stream is not seekable (e.g., it refers to a pipe, fifo, or socket). .pp the functions .br fgetpos (), .br fseek (), .br fsetpos (), and .br ftell () may also fail and set .i errno for any of the errors specified for the routines .br fflush (3), .br fstat (2), .br lseek (2), and .br malloc (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fseek (), .br ftell (), .br rewind (), .br fgetpos (), .br fsetpos () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. .sh see also .br lseek (2), .br fseeko (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/gethostbyname.3 .so man3/fts.3 .so man2/brk.2 .so man7/system_data_types.7 .so man7/system_data_types.7 .so man3/getgrent_r.3 .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_send 3 2021-03-22 "linux" "linux programmer's manual" .sh name mq_send, mq_timedsend \- send a message to a message queue .sh synopsis .nf .b #include .pp .bi "int mq_send(mqd_t " mqdes ", const char *" msg_ptr , .bi " size_t " msg_len ", unsigned int " msg_prio ); .pp .b #include .b #include .pp .bi "int mq_timedsend(mqd_t " mqdes ", const char *" msg_ptr , .bi " size_t " msg_len ", unsigned int " msg_prio , .bi " const struct timespec *" abs_timeout ); .fi .pp link with \fi\-lrt\fp. .pp .ad l .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mq_timedsend (): .nf _posix_c_source >= 200112l .fi .sh description .br mq_send () adds the message pointed to by .i msg_ptr to the message queue referred to by the message queue descriptor .ir mqdes . the .i msg_len argument specifies the length of the message pointed to by .ir msg_ptr ; this length must be less than or equal to the queue's .i mq_msgsize attribute. zero-length messages are allowed. .pp the .i msg_prio argument is a nonnegative integer that specifies the priority of this message. messages are placed on the queue in decreasing order of priority, with newer messages of the same priority being placed after older messages with the same priority. see .br mq_overview (7) for details on the range for the message priority. .pp if the message queue is already full (i.e., the number of messages on the queue equals the queue's .i mq_maxmsg attribute), then, by default, .br mq_send () blocks until sufficient space becomes available to allow the message to be queued, or until the call is interrupted by a signal handler. if the .b o_nonblock flag is enabled for the message queue description, then the call instead fails immediately with the error .br eagain . .pp .br mq_timedsend () behaves just like .br mq_send (), except that if the queue is full and the .b o_nonblock flag is not enabled for the message queue description, then .i abs_timeout points to a structure which specifies how long the call will block. this value is an absolute timeout in seconds and nanoseconds since the epoch, 1970-01-01 00:00:00 +0000 (utc), specified in the following structure: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp if the message queue is full, and the timeout has already expired by the time of the call, .br mq_timedsend () returns immediately. .sh return value on success, .br mq_send () and .br mq_timedsend () return zero; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b eagain the queue was full, and the .b o_nonblock flag was set for the message queue description referred to by .ir mqdes . .tp .b ebadf the descriptor specified in .i mqdes was invalid or not opened for writing. .tp .b eintr the call was interrupted by a signal handler; see .br signal (7). .tp .b einval the call would have blocked, and .i abs_timeout was invalid, either because .i tv_sec was less than zero, or because .i tv_nsec was less than zero or greater than 1000 million. .tp .b emsgsize .i msg_len was greater than the .i mq_msgsize attribute of the message queue. .tp .b etimedout the call timed out before a message could be transferred. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mq_send (), .br mq_timedsend () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on linux, .br mq_timedsend () is a system call, and .br mq_send () is a library function layered on top of that system call. .sh see also .br mq_close (3), .br mq_getattr (3), .br mq_notify (3), .br mq_open (3), .br mq_receive (3), .br mq_unlink (3), .br mq_overview (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" 386bsd man pages .\" modified sat jul 24 18:50:48 1993 by rik faith (faith@cs.unc.edu) .\" interchanged 'needle' and 'haystack'; added history, aeb, 980113. .th memmem 3 2021-03-22 "gnu" "linux programmer's manual" .sh name memmem \- locate a substring .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void *memmem(const void *" haystack ", size_t " haystacklen , .bi " const void *" needle ", size_t " needlelen ); .fi .sh description the .br memmem () function finds the start of the first occurrence of the substring .ir needle of length .i needlelen in the memory area .i haystack of length .ir haystacklen . .sh return value the .br memmem () function returns a pointer to the beginning of the substring, or null if the substring is not found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memmem () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is not specified in posix.1, but is present on a number of other systems. .sh bugs .\" this function was broken in linux libraries up to and including libc 5.0.9; .\" there the .\" .ir needle .\" and .\" .i haystack .\" arguments were interchanged, .\" and a pointer to the end of the first occurrence of .\" .i needle .\" was returned. .\" .\" both old and new libc's have the bug that if .\" .i needle .\" is empty, .\" .i haystack\-1 .\" (instead of .\" .ir haystack ) .\" is returned. in glibc 2.0, if .i needle is empty, .br memmem () returns a pointer to the last byte of .ir haystack . this is fixed in glibc 2.1. .sh see also .br bstring (3), .br strstr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/exp.3 .so man7/iso_8859-8.7 .\" copyright (c) 2016 julia computing inc, keno fischer .\" description based on include/uapi/fuse.h and code in fs/fuse .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th fuse 4 2018-02-02 "linux" "linux programmer's manual" .sh name fuse \- filesystem in userspace (fuse) device .sh synopsis .nf .b #include .fi .sh description this device is the primary interface between the fuse filesystem driver and a user-space process wishing to provide the filesystem (referred to in the rest of this manual page as the .ir "filesystem daemon" ). this manual page is intended for those interested in understanding the kernel interface itself. those implementing a fuse filesystem may wish to make use of a user-space library such as .i libfuse that abstracts away the low-level interface. .pp at its core, fuse is a simple client-server protocol, in which the linux kernel is the client and the daemon is the server. after obtaining a file descriptor for this device, the daemon may .br read (2) requests from that file descriptor and is expected to .br write (2) back its replies. it is important to note that a file descriptor is associated with a unique fuse filesystem. in particular, opening a second copy of this device, will not allow access to resources created through the first file descriptor (and vice versa). .\" .ss the basic protocol every message that is read by the daemon begins with a header described by the following structure: .pp .in +4n .ex struct fuse_in_header { uint32_t len; /* total length of the data, including this header */ uint32_t opcode; /* the kind of operation (see below) */ uint64_t unique; /* a unique identifier for this request */ uint64_t nodeid; /* id of the filesystem object being operated on */ uint32_t uid; /* uid of the requesting process */ uint32_t gid; /* gid of the requesting process */ uint32_t pid; /* pid of the requesting process */ uint32_t padding; }; .ee .in .pp the header is followed by a variable-length data portion (which may be empty) specific to the requested operation (the requested operation is indicated by .ir opcode ). .pp the daemon should then process the request and if applicable send a reply (almost all operations require a reply; if they do not, this is documented below), by performing a .br write (2) to the file descriptor. all replies must start with the following header: .pp .in +4n .ex struct fuse_out_header { uint32_t len; /* total length of data written to the file descriptor */ int32_t error; /* any error that occurred (0 if none) */ uint64_t unique; /* the value from the corresponding request */ }; .ee .in .pp this header is also followed by (potentially empty) variable-sized data depending on the executed request. however, if the reply is an error reply (i.e., .i error is set), then no further payload data should be sent, independent of the request. .\" .ss exchanged messages this section should contain documentation for each of the messages in the protocol. this manual page is currently incomplete, so not all messages are documented. for each message, first the struct sent by the kernel is given, followed by a description of the semantics of the message. .tp .br fuse_init .ip .in +4n .ex struct fuse_init_in { uint32_t major; uint32_t minor; uint32_t max_readahead; /* since protocol v7.6 */ uint32_t flags; /* since protocol v7.6 */ }; .ee .in .ip this is the first request sent by the kernel to the daemon. it is used to negotiate the protocol version and other filesystem parameters. note that the protocol version may affect the layout of any structure in the protocol (including this structure). the daemon must thus remember the negotiated version and flags for each session. as of the writing of this man page, the highest supported kernel protocol version is .ir 7.26 . .ip users should be aware that the descriptions in this manual page may be incomplete or incorrect for older or more recent protocol versions. .ip the reply for this request has the following format: .ip .in +4n .ex struct fuse_init_out { uint32_t major; uint32_t minor; uint32_t max_readahead; /* since v7.6 */ uint32_t flags; /* since v7.6; some flags bits were introduced later */ uint16_t max_background; /* since v7.13 */ uint16_t congestion_threshold; /* since v7.13 */ uint32_t max_write; /* since v7.5 */ uint32_t time_gran; /* since v7.6 */ uint32_t unused[9]; }; .ee .in .ip if the major version supported by the kernel is larger than that supported by the daemon, the reply shall consist of only .i uint32_t major (following the usual header), indicating the largest major version supported by the daemon. the kernel will then issue a new .b fuse_init request conforming to the older version. in the reverse case, the daemon should quietly fall back to the kernel's major version. .ip the negotiated minor version is considered to be the minimum of the minor versions provided by the daemon and the kernel and both parties should use the protocol corresponding to said minor version. .tp .br fuse_getattr .ip .in +4n .ex struct fuse_getattr_in { uint32_t getattr_flags; uint32_t dummy; uint64_t fh; /* set only if (getattr_flags & fuse_getattr_fh) }; .ee .in .ip the requested operation is to compute the attributes to be returned by .br stat (2) and similar operations for the given filesystem object. the object for which the attributes should be computed is indicated either by .ir header\->nodeid or, if the .br fuse_getattr_fh flag is set, by the file handle .ir fh . the latter case of operation is analogous to .br fstat (2). .ip for performance reasons, these attributes may be cached in the kernel for a specified duration of time. while the cache timeout has not been exceeded, the attributes will be served from the cache and will not cause additional .b fuse_getattr requests. .ip the computed attributes and the requested cache timeout should then be returned in the following structure: .ip .in +4n .ex struct fuse_attr_out { /* attribute cache duration (seconds + nanoseconds) */ uint64_t attr_valid; uint32_t attr_valid_nsec; uint32_t dummy; struct fuse_attr { uint64_t ino; uint64_t size; uint64_t blocks; uint64_t atime; uint64_t mtime; uint64_t ctime; uint32_t atimensec; uint32_t mtimensec; uint32_t ctimensec; uint32_t mode; uint32_t nlink; uint32_t uid; uint32_t gid; uint32_t rdev; uint32_t blksize; uint32_t padding; } attr; }; .ee .in .tp .br fuse_access .ip .in +4n .ex struct fuse_access_in { uint32_t mask; uint32_t padding; }; .ee .in .ip if the .i default_permissions mount options is not used, this request may be used for permissions checking. no reply data is expected, but errors may be indicated as usual by setting the .i error field in the reply header (in particular, access denied errors may be indicated by returning .br \-eacces ). .tp .br fuse_open " and " fuse_opendir .in +4n .ex struct fuse_open_in { uint32_t flags; /* the flags that were passed to the open(2) */ uint32_t unused; }; .ee .in .ip the requested operation is to open the node indicated by .ir header\->nodeid . the exact semantics of what this means will depend on the filesystem being implemented. however, at the very least the filesystem should validate that the requested .i flags are valid for the indicated resource and then send a reply with the following format: .ip .in +4n .ex struct fuse_open_out { uint64_t fh; uint32_t open_flags; uint32_t padding; }; .ee .in .ip the .i fh field is an opaque identifier that the kernel will use to refer to this resource the .i open_flags field is a bit mask of any number of the flags that indicate properties of this file handle to the kernel: .rs 7 .tp 18 .br fopen_direct_io bypass page cache for this open file. .tp .br fopen_keep_cache don't invalidate the data cache on open. .tp .br fopen_nonseekable the file is not seekable. .re .tp .br fuse_read " and " fuse_readdir .ip .in +4n .ex struct fuse_read_in { uint64_t fh; uint64_t offset; uint32_t size; uint32_t read_flags; uint64_t lock_owner; uint32_t flags; uint32_t padding; }; .ee .in .ip the requested action is to read up to .i size bytes of the file or directory, starting at .ir offset . the bytes should be returned directly following the usual reply header. .tp .br fuse_interrupt .in +4n .ex struct fuse_interrupt_in { uint64_t unique; }; .ee .in .ip the requested action is to cancel the pending operation indicated by .ir unique . this request requires no response. however, receipt of this message does not by itself cancel the indicated operation. the kernel will still expect a reply to said operation (e.g., an .i eintr error or a short read). at most one .b fuse_interrupt request will be issued for a given operation. after issuing said operation, the kernel will wait uninterruptibly for completion of the indicated request. .tp .br fuse_lookup directly following the header is a filename to be looked up in the directory indicated by .ir header\->nodeid . the expected reply is of the form: .ip .in +4n .ex struct fuse_entry_out { uint64_t nodeid; /* inode id */ uint64_t generation; /* inode generation */ uint64_t entry_valid; uint64_t attr_valid; uint32_t entry_valid_nsec; uint32_t attr_valid_nsec; struct fuse_attr attr; }; .ee .in .ip the combination of .i nodeid and .i generation must be unique for the filesystem's lifetime. .ip the interpretation of timeouts and .i attr is as for .br fuse_getattr . .tp .br fuse_flush .in +4n .ex struct fuse_flush_in { uint64_t fh; uint32_t unused; uint32_t padding; uint64_t lock_owner; }; .ee .in .ip the requested action is to flush any pending changes to the indicated file handle. no reply data is expected. however, an empty reply message still needs to be issued once the flush operation is complete. .tp .br fuse_release " and " fuse_releasedir .in +4n .ex struct fuse_release_in { uint64_t fh; uint32_t flags; uint32_t release_flags; uint64_t lock_owner; }; .ee .in .ip these are the converse of .br fuse_open and .br fuse_opendir respectively. the daemon may now free any resources associated with the file handle .i fh as the kernel will no longer refer to it. there is no reply data associated with this request, but a reply still needs to be issued once the request has been completely processed. .tp .br fuse_statfs this operation implements .br statfs (2) for this filesystem. there is no input data associated with this request. the expected reply data has the following structure: .ip .in +4n .ex struct fuse_kstatfs { uint64_t blocks; uint64_t bfree; uint64_t bavail; uint64_t files; uint64_t ffree; uint32_t bsize; uint32_t namelen; uint32_t frsize; uint32_t padding; uint32_t spare[6]; }; struct fuse_statfs_out { struct fuse_kstatfs st; }; .ee .in .ip for the interpretation of these fields, see .br statfs (2). .sh errors .tp .b e2big returned from .br read (2) operations when the kernel's request is too large for the provided buffer and the request was .br fuse_setxattr . .tp .b einval returned from .br write (2) if validation of the reply failed. not all mistakes in replies will be caught by this validation. however, basic mistakes, such as short replies or an incorrect .i unique value, are detected. .tp .b eio returned from .br read (2) operations when the kernel's request is too large for the provided buffer. .ip .ir note : there are various ways in which incorrect use of these interfaces can cause operations on the provided filesystem's files and directories to fail with .br eio . among the possible incorrect uses are: .rs .ip * 3 changing .i mode & s_ifmt for an inode that has previously been reported to the kernel; or .ip * giving replies to the kernel that are shorter than what the kernel expected. .re .tp .b enodev returned from .br read (2) and .br write (2) if the fuse filesystem was unmounted. .tp .b eperm returned from operations on a .i /dev/fuse file descriptor that has not been mounted. .sh conforming to the fuse filesystem is linux-specific. .sh notes the following messages are not yet documented in this manual page: .pp .\" fixme: document the following. .in +4n .ex .br fuse_batch_forget .br fuse_bmap .br fuse_create .br fuse_destroy .br fuse_fallocate .br fuse_forget .br fuse_fsync .br fuse_fsyncdir .br fuse_getlk .br fuse_getxattr .br fuse_ioctl .br fuse_link .br fuse_listxattr .br fuse_lseek .br fuse_mkdir .br fuse_mknod .br fuse_notify_reply .br fuse_poll .br fuse_readdirplus .br fuse_readlink .br fuse_removexattr .br fuse_rename .br fuse_rename2 .br fuse_rmdir .br fuse_setattr .br fuse_setlk .br fuse_setlkw .br fuse_symlink .br fuse_unlink .br fuse_write .ee .in .sh see also .br fusermount (1), .br mount.fuse (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fputwc.3 .so man3/lgamma.3 .so man3/xcrypt.3 .so man2/mmap.2 .so man3/remainder.3 .so man3/pthread_tryjoin_np.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" based on glibc infopages .\" polished - aeb .\" .th setnetgrent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr \- handle network group entries .sh synopsis .nf .b #include .pp .bi "int setnetgrent(const char *" netgroup ); .b "void endnetgrent(void);" .pp .bi "int getnetgrent(char **restrict " host , .bi " char **restrict " user ", char **restrict " domain ); .bi "int getnetgrent_r(char **restrict " host , .bi " char **restrict " user ", char **restrict " domain , .bi " char *restrict " buf ", size_t " buflen ); .pp .bi "int innetgr(const char *" netgroup ", const char *" host , .bi " const char *" user ", const char *" domain ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .ad l .pp .nh .br setnetgrent (), .br endnetgrent (), .br getnetgrent (), .br getnetgrent_r (), .br innetgr (): .hy .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .ad .sh description the .i netgroup is a sunos invention. a netgroup database is a list of string triples .ri ( hostname ", " username ", " domainname ) or other netgroup names. any of the elements in a triple can be empty, which means that anything matches. the functions described here allow access to the netgroup databases. the file .i /etc/nsswitch.conf defines what database is searched. .pp the .br setnetgrent () call defines the netgroup that will be searched by subsequent .br getnetgrent () calls. the .br getnetgrent () function retrieves the next netgroup entry, and returns pointers in .ir host , .ir user , .ir domain . a null pointer means that the corresponding entry matches any string. the pointers are valid only as long as there is no call to other netgroup-related functions. to avoid this problem you can use the gnu function .br getnetgrent_r () that stores the strings in the supplied buffer. to free all allocated buffers use .br endnetgrent (). .pp in most cases you want to check only if the triplet .ri ( hostname ", " username ", " domainname ) is a member of a netgroup. the function .br innetgr () can be used for this without calling the above three functions. again, a null pointer is a wildcard and matches any string. the function is thread-safe. .sh return value these functions return 1 on success and 0 for failure. .sh files .i /etc/netgroup .br .i /etc/nsswitch.conf .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br setnetgrent (), .br getnetgrent_r (), .br innetgr () t} thread safety t{ mt-unsafe race:netgrent locale t} t{ .br endnetgrent () t} thread safety t{ mt-unsafe race:netgrent t} t{ .br getnetgrent () t} thread safety t{ mt-unsafe race:netgrent race:netgrentbuf locale t} .te .hy .ad .sp 1 in the above table, .i netgrent in .i race:netgrent signifies that if any of the functions .br setnetgrent (), .br getnetgrent_r (), .br innetgr (), .br getnetgrent (), or .br endnetgrent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to these functions are not in posix.1, but .br setnetgrent (), .br endnetgrent (), .br getnetgrent (), and .br innetgr () are available on most unix systems. .br getnetgrent_r () is not widely available on other systems. .\" getnetgrent_r() is on solaris 8 and aix 5.1, but not the bsds. .sh notes in the bsd implementation, .br setnetgrent () returns void. .sh see also .br sethostent (3), .br setprotoent (3), .br setservent (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 andrew morton .\" and copyright 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2006-07-05 initial creation, michael kerrisk based on .\" andrew morton's comments in fs/sync.c .\" 2010-10-09, mtk, document sync_file_range2() .\" .th sync_file_range 2 2021-03-22 "linux" "linux programmer's manual" .sh name sync_file_range \- sync a file segment with disk .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int sync_file_range(int " fd ", off64_t " offset ", off64_t " nbytes , .bi " unsigned int " flags ); .fi .sh description .br sync_file_range () permits fine control when synchronizing the open file referred to by the file descriptor .i fd with disk. .pp .i offset is the starting byte of the file range to be synchronized. .i nbytes specifies the length of the range to be synchronized, in bytes; if .i nbytes is zero, then all bytes from .i offset through to the end of file are synchronized. synchronization is in units of the system page size: .i offset is rounded down to a page boundary; .i (offset+nbytes\-1) is rounded up to a page boundary. .pp the .i flags bit-mask argument can include any of the following values: .tp .b sync_file_range_wait_before wait upon write-out of all pages in the specified range that have already been submitted to the device driver for write-out before performing any write. .tp .b sync_file_range_write initiate write-out of all dirty pages in the specified range which are not presently submitted write-out. note that even this may block if you attempt to write more than request queue size. .tp .b sync_file_range_wait_after wait upon write-out of all pages in the range after performing any write. .pp specifying .i flags as 0 is permitted, as a no-op. .ss warning this system call is extremely dangerous and should not be used in portable programs. none of these operations writes out the file's metadata. therefore, unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees that the data will be available after a crash. there is no user interface to know if a write is purely an overwrite. on filesystems using copy-on-write semantics (e.g., .ir btrfs ) an overwrite of existing allocated blocks is impossible. when writing into preallocated space, many filesystems also require calls into the block allocator, which this system call does not sync out to disk. this system call does not flush disk write caches and thus does not provide any data integrity on systems with volatile disk write caches. .ss some details .b sync_file_range_wait_before and .b sync_file_range_wait_after will detect any i/o errors or .b enospc conditions and will return these to the caller. .pp useful combinations of the .i flags bits are: .tp .b sync_file_range_wait_before | sync_file_range_write ensures that all pages in the specified range which were dirty when .br sync_file_range () was called are placed under write-out. this is a start-write-for-data-integrity operation. .tp .b sync_file_range_write start write-out of all dirty pages in the specified range which are not presently under write-out. this is an asynchronous flush-to-disk operation. this is not suitable for data integrity operations. .tp .br sync_file_range_wait_before " (or " sync_file_range_wait_after ) wait for completion of write-out of all pages in the specified range. this can be used after an earlier .b sync_file_range_wait_before | sync_file_range_write operation to wait for completion of that operation, and obtain its result. .tp .b sync_file_range_wait_before | sync_file_range_write | \ sync_file_range_wait_after this is a write-for-data-integrity operation that will ensure that all pages in the specified range which were dirty when .br sync_file_range () was called are committed to disk. .sh return value on success, .br sync_file_range () returns 0; on failure \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b einval .i flags specifies an invalid bit; or .i offset or .i nbytes is invalid. .tp .b eio i/o error. .tp .b enomem out of memory. .tp .b enospc out of disk space. .tp .b espipe .i fd refers to something other than a regular file, a block device, or a directory. .sh versions .br sync_file_range () appeared on linux in kernel 2.6.17. .sh conforming to this system call is linux-specific, and should be avoided in portable programs. .sh notes .ss sync_file_range2() some architectures (e.g., powerpc, arm) need 64-bit arguments to be aligned in a suitable pair of registers. .\" see kernel commit edd5cd4a9424f22b0fa08bef5e299d41befd5622 on such architectures, the call signature of .br sync_file_range () shown in the synopsis would force a register to be wasted as padding between the .i fd and .i offset arguments. (see .br syscall (2) for details.) therefore, these architectures define a different system call that orders the arguments suitably: .pp .in +4n .ex .bi "int sync_file_range2(int " fd ", unsigned int " flags , .bi " off64_t " offset ", off64_t " nbytes ); .ee .in .pp the behavior of this system call is otherwise exactly the same as .br sync_file_range (). .pp a system call with this signature first appeared on the arm architecture in linux 2.6.20, with the name .br arm_sync_file_range (). it was renamed in linux 2.6.22, when the analogous system call was added for powerpc. on architectures where glibc support is provided, glibc transparently wraps .br sync_file_range2 () under the name .br sync_file_range (). .sh see also .br fdatasync (2), .br fsync (2), .br msync (2), .br sync (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fgetwc.3 .so man2/lchown.2 .\" copyright (c) 2010 intel corporation, author: andi kleen .\" and copyright 2014, vivek goyal .\" and copyright (c) 2015, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th kexec_load 2 2021-03-22 "linux" "linux programmer's manual" .sh name kexec_load, kexec_file_load \- load a new kernel for later execution .sh synopsis .nf .br "#include " " /* definition of " kexec_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(sys_kexec_load, unsigned long " entry , .bi " unsigned long " nr_segments \ ", struct kexec_segment *" segments , .bi " unsigned long " flags ); .bi "long syscall(sys_kexec_file_load, int " kernel_fd ", int " initrd_fd , .bi " unsigned long " cmdline_len ", const char *" cmdline , .bi " unsigned long " flags ); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description the .br kexec_load () system call loads a new kernel that can be executed later by .br reboot (2). .pp the .i flags argument is a bit mask that controls the operation of the call. the following values can be specified in .ir flags : .tp .br kexec_on_crash " (since linux 2.6.13)" execute the new kernel automatically on a system crash. this "crash kernel" is loaded into an area of reserved memory that is determined at boot time using the .i crashkernel kernel command-line parameter. the location of this reserved memory is exported to user space via the .i /proc/iomem file, in an entry labeled "crash kernel". a user-space application can parse this file and prepare a list of segments (see below) that specify this reserved memory as destination. if this flag is specified, the kernel checks that the target segments specified in .i segments fall within the reserved region. .tp .br kexec_preserve_context " (since linux 2.6.27)" preserve the system hardware and software states before executing the new kernel. this could be used for system suspend. this flag is available only if the kernel was configured with .br config_kexec_jump , and is effective only if .i nr_segments is greater than 0. .pp the high-order bits (corresponding to the mask 0xffff0000) of .i flags contain the architecture of the to-be-executed kernel. specify (or) the constant .b kexec_arch_default to use the current architecture, or one of the following architecture constants .br kexec_arch_386 , .br kexec_arch_68k , .br kexec_arch_x86_64 , .br kexec_arch_ppc , .br kexec_arch_ppc64 , .br kexec_arch_ia_64 , .br kexec_arch_arm , .br kexec_arch_s390 , .br kexec_arch_sh , .br kexec_arch_mips , and .br kexec_arch_mips_le . the architecture must be executable on the cpu of the system. .pp the .i entry argument is the physical entry address in the kernel image. the .i nr_segments argument is the number of segments pointed to by the .i segments pointer; the kernel imposes an (arbitrary) limit of 16 on the number of segments. the .i segments argument is an array of .i kexec_segment structures which define the kernel layout: .pp .in +4n .ex struct kexec_segment { void *buf; /* buffer in user space */ size_t bufsz; /* buffer length in user space */ void *mem; /* physical address of kernel */ size_t memsz; /* physical address length */ }; .ee .in .pp the kernel image defined by .i segments is copied from the calling process into the kernel either in regular memory or in reserved memory (if .br kexec_on_crash is set). the kernel first performs various sanity checks on the information passed in .ir segments . if these checks pass, the kernel copies the segment data to kernel memory. each segment specified in .i segments is copied as follows: .ip * 3 .i buf and .i bufsz identify a memory region in the caller's virtual address space that is the source of the copy. the value in .i bufsz may not exceed the value in the .i memsz field. .ip * .i mem and .i memsz specify a physical address range that is the target of the copy. the values specified in both fields must be multiples of the system page size. .ip * .i bufsz bytes are copied from the source buffer to the target kernel buffer. if .i bufsz is less than .ir memsz , then the excess bytes in the kernel buffer are zeroed out. .pp in case of a normal kexec (i.e., the .br kexec_on_crash flag is not set), the segment data is loaded in any available memory and is moved to the final destination at kexec reboot time (e.g., when the .br kexec (8) command is executed with the .i \-e option). .pp in case of kexec on panic (i.e., the .br kexec_on_crash flag is set), the segment data is loaded to reserved memory at the time of the call, and, after a crash, the kexec mechanism simply passes control to that kernel. .pp the .br kexec_load () system call is available only if the kernel was configured with .br config_kexec . .ss kexec_file_load() the .br kexec_file_load () system call is similar to .br kexec_load (), but it takes a different set of arguments. it reads the kernel to be loaded from the file referred to by the file descriptor .ir kernel_fd , and the initrd (initial ram disk) to be loaded from file referred to by the file descriptor .ir initrd_fd . the .ir cmdline argument is a pointer to a buffer containing the command line for the new kernel. the .ir cmdline_len argument specifies size of the buffer. the last byte in the buffer must be a null byte (\(aq\e0\(aq). .pp the .ir flags argument is a bit mask which modifies the behavior of the call. the following values can be specified in .ir flags : .tp .br kexec_file_unload unload the currently loaded kernel. .tp .br kexec_file_on_crash load the new kernel in the memory region reserved for the crash kernel (as for .br kexec_on_crash ). this kernel is booted if the currently running kernel crashes. .tp .br kexec_file_no_initramfs loading initrd/initramfs is optional. specify this flag if no initramfs is being loaded. if this flag is set, the value passed in .ir initrd_fd is ignored. .pp the .br kexec_file_load () .\" see also http://lwn.net/articles/603116/ system call was added to provide support for systems where "kexec" loading should be restricted to only kernels that are signed. this system call is available only if the kernel was configured with .br config_kexec_file . .sh return value on success, these system calls returns 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eaddrnotavail .\" see kernel/kexec.::sanity_check_segment_list in the 3.19 kernel source the .b kexec_on_crash flags was specified, but the region specified by the .i mem and .i memsz fields of one of the .i segments entries lies outside the range of memory reserved for the crash kernel. .tp .b eaddrnotavail the value in a .i mem or .i memsz field in one of the .i segments entries is not a multiple of the system page size. .tp .b ebadf .i kernel_fd or .i initrd_fd is not a valid file descriptor. .tp .b ebusy another crash kernel is already being loaded or a crash kernel is already in use. .tp .b einval .i flags is invalid. .tp .b einval the value of a .i bufsz field in one of the .i segments entries exceeds the value in the corresponding .i memsz field. .tp .b einval .ir nr_segments exceeds .br kexec_segment_max (16). .tp .b einval two or more of the kernel target buffers overlap. .tp .b einval the value in .i cmdline[cmdline_len\-1] is not \(aq\e0\(aq. .tp .b einval the file referred to by .i kernel_fd or .i initrd_fd is empty (length zero). .tp .b enoexec .i kernel_fd does not refer to an open file, or the kernel can't load this file. currently, the file must be a bzimage and contain an x86 kernel that is loadable above 4\ gib in memory (see the kernel source file .ir documentation/x86/boot.txt ). .tp .b enomem could not allocate memory. .tp .b eperm the caller does not have the .br cap_sys_boot capability. .sh versions the .br kexec_load () system call first appeared in linux 2.6.13. the .br kexec_file_load () system call first appeared in linux 3.17. .sh conforming to these system calls are linux-specific. .sh see also .br reboot (2), .br syscall (2), .br kexec (8) .pp the kernel source files .ir documentation/kdump/kdump.txt and .ir documentation/admin\-guide/kernel\-parameters.txt .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" portions extracted from /usr/include/dirent.h are: .\" copyright 1991, 1992 free software foundation .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getdirentries 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getdirentries \- get directory entries in a filesystem-independent format .sh synopsis .nf .b #include .pp .bi "ssize_t getdirentries(int " fd ", char *restrict " buf ", size_t " nbytes , .bi " off_t *restrict " basep ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getdirentries (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description read directory entries from the directory specified by .i fd into .ir buf . at most .i nbytes are read. reading starts at offset .ir *basep , and .i *basep is updated with the new position after reading. .sh return value .br getdirentries () returns the number of bytes read or zero when at the end of the directory. if an error occurs, \-1 is returned, and .i errno is set to indicate the error. .sh errors see the linux library source code for details. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getdirentries () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to not in posix.1. present on the bsds, and a few other systems. use .br opendir (3) and .br readdir (3) instead. .sh see also .br lseek (2), .br open (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/csinh.3 .so man3/rpc.3 .so man3/stailq.3 .so man3/tsearch.3 .so man3/casinh.3 .so man3/drand48_r.3 .so man3/gsignal.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2003-11-15 by aeb .\" .th getgrnam 3 2021-03-22 "" "linux programmer's manual" .sh name getgrnam, getgrnam_r, getgrgid, getgrgid_r \- get group file entry .sh synopsis .nf .b #include .b #include .pp .bi "struct group *getgrnam(const char *" name ); .bi "struct group *getgrgid(gid_t " gid ); .pp .bi "int getgrnam_r(const char *restrict " name \ ", struct group *restrict " grp , .bi " char *restrict " buf ", size_t " buflen , .bi " struct group **restrict " result ); .bi "int getgrgid_r(gid_t " gid ", struct group *restrict " grp , .bi " char *restrict " buf ", size_t " buflen , .bi " struct group **restrict " result ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getgrnam_r (), .br getgrgid_r (): .nf _posix_c_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br getgrnam () function returns a pointer to a structure containing the broken-out fields of the record in the group database (e.g., the local group file .ir /etc/group , nis, and ldap) that matches the group name .ir name . .pp the .br getgrgid () function returns a pointer to a structure containing the broken-out fields of the record in the group database that matches the group id .ir gid . .pp the \figroup\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ gid_t gr_gid; /* group id */ char **gr_mem; /* null\-terminated array of pointers to names of group members */ }; .ee .in .pp for more information about the fields of this structure, see .br group (5). .pp the .br getgrnam_r () and .br getgrgid_r () functions obtain the same information as .br getgrnam () and .br getgrgid (), but store the retrieved .i group structure in the space pointed to by .ir grp . the string fields pointed to by the members of the .i group structure are stored in the buffer .i buf of size .ir buflen . a pointer to the result (in case of success) or null (in case no entry was found or an error occurred) is stored in .ir *result . .pp the call .pp sysconf(_sc_getgr_r_size_max) .pp returns either \-1, without changing .ir errno , or an initial suggested size for .ir buf . (if this size is too small, the call fails with .br erange , in which case the caller can retry with a larger buffer.) .sh return value the .br getgrnam () and .br getgrgid () functions return a pointer to a .i group structure, or null if the matching entry is not found or an error occurs. if an error occurs, .i errno is set to indicate the error. if one wants to check .i errno after the call, it should be set to zero before the call. .pp the return value may point to a static area, and may be overwritten by subsequent calls to .br getgrent (3), .br getgrgid (), or .br getgrnam (). (do not pass the returned pointer to .br free (3).) .pp on success, .br getgrnam_r () and .br getgrgid_r () return zero, and set .ir *result to .ir grp . if no matching group record was found, these functions return 0 and store null in .ir *result . in case of error, an error number is returned, and null is stored in .ir *result . .sh errors .tp .br 0 " or " enoent " or " esrch " or " ebadf " or " eperm " or ..." the given .i name or .i gid was not found. .tp .b eintr a signal was caught; see .br signal (7). .tp .b eio i/o error. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enomem .\" not in posix insufficient memory to allocate .i group structure. .\" to allocate the group structure, or to allocate buffers .tp .b erange insufficient buffer space supplied. .sh files .tp .i /etc/group local group database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getgrnam () t} thread safety t{ mt-unsafe race:grnam locale t} t{ .br getgrgid () t} thread safety t{ mt-unsafe race:grgid locale t} t{ .br getgrnam_r (), .br getgrgid_r () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes the formulation given above under "return value" is from posix.1. .\" posix.1-2001, posix.1-2008 it does not call "not found" an error, hence does not specify what value .i errno might have in this situation. but that makes it impossible to recognize errors. one might argue that according to posix .i errno should be left unchanged if an entry is not found. experiments on various unix-like systems show that lots of different values occur in this situation: 0, enoent, ebadf, esrch, ewouldblock, eperm, and probably others. .\" more precisely: .\" aix 5.1 - gives esrch .\" osf1 4.0g - gives ewouldblock .\" libc, glibc up to version 2.6, irix 6.5 - give enoent .\" glibc since version 2.7 - give 0 .\" freebsd 4.8, openbsd 3.2, netbsd 1.6 - give eperm .\" sunos 5.8 - gives ebadf .\" tru64 5.1b, hp-ux-11i, sunos 5.7 - give 0 .sh see also .br endgrent (3), .br fgetgrent (3), .br getgrent (3), .br getpwnam (3), .br setgrent (3), .br group (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sem_wait.3 .so man3/getutent.3 .so man3/remainder.3 .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th thread-keyring 7 2020-08-13 linux "linux programmer's manual" .sh name thread-keyring \- per-thread keyring .sh description the thread keyring is a keyring used to anchor keys on behalf of a process. it is created only when a thread requests it. the thread keyring has the name (description) .ir _tid . .pp a special serial number value, .br key_spec_thread_keyring , is defined that can be used in lieu of the actual serial number of the calling thread's thread keyring. .pp from the .br keyctl (1) utility, '\fb@t\fp' can be used instead of a numeric key id in much the same way, but as .br keyctl (1) is a program run after forking, this is of no utility. .pp thread keyrings are not inherited across .br clone (2) and .br fork (2) and are cleared by .br execve (2). a thread keyring is destroyed when the thread that refers to it terminates. .pp initially, a thread does not have a thread keyring. if a thread doesn't have a thread keyring when it is accessed, then it will be created if it is to be modified; otherwise the operation fails with the error .br enokey . .sh see also .ad l .nh .br keyctl (1), .br keyctl (3), .br keyrings (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getrlimit.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 21:46:57 1993 by rik faith (faith@cs.unc.edu) .\" modified 961109, 031115, aeb .\" .th getmntent 3 2021-03-22 "" "linux programmer's manual" .sh name getmntent, setmntent, addmntent, endmntent, hasmntopt, getmntent_r \- get filesystem descriptor file entry .sh synopsis .nf .b #include .b #include .pp .bi "file *setmntent(const char *" filename ", const char *" type ); .pp .bi "struct mntent *getmntent(file *" stream ); .pp .bi "int addmntent(file *restrict " stream , .bi " const struct mntent *restrict " mnt ); .pp .bi "int endmntent(file *" streamp ); .pp .bi "char *hasmntopt(const struct mntent *" mnt ", const char *" opt ); .pp /* gnu extension */ .b #include .pp .bi "struct mntent *getmntent_r(file *restrict " streamp , .bi " struct mntent *restrict " mntbuf , .bi " char *restrict " buf ", int " buflen ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getmntent_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description these routines are used to access the filesystem description file .i /etc/fstab and the mounted filesystem description file .ir /etc/mtab . .pp the .br setmntent () function opens the filesystem description file .i filename and returns a file pointer which can be used by .br getmntent (). the argument .i type is the type of access required and can take the same values as the .i mode argument of .br fopen (3). the returned stream should be closed using .br endmntent () rather than .br fclose (3). .pp the .br getmntent () function reads the next line of the filesystem description file from .i stream and returns a pointer to a structure containing the broken out fields from a line in the file. the pointer points to a static area of memory which is overwritten by subsequent calls to .br getmntent (). .pp the .br addmntent () function adds the .i mntent structure .i mnt to the end of the open .ir stream . .pp the .br endmntent () function closes the .ir stream associated with the filesystem description file. .pp the .br hasmntopt () function scans the .i mnt_opts field (see below) of the .i mntent structure .i mnt for a substring that matches .ir opt . see .i and .br mount (8) for valid mount options. .pp the reentrant .br getmntent_r () function is similar to .br getmntent (), but stores the .ir "struct mount" in the provided .i *mntbuf and stores the strings pointed to by the entries in that struct in the provided array .i buf of size .ir buflen . .pp the .i mntent structure is defined in .i as follows: .pp .in +4n .ex struct mntent { char *mnt_fsname; /* name of mounted filesystem */ char *mnt_dir; /* filesystem path prefix */ char *mnt_type; /* mount type (see mntent.h) */ char *mnt_opts; /* mount options (see mntent.h) */ int mnt_freq; /* dump frequency in days */ int mnt_passno; /* pass number on parallel fsck */ }; .ee .in .pp since fields in the mtab and fstab files are separated by whitespace, octal escapes are used to represent the characters space (\e040), tab (\e011), newline (\e012), and backslash (\e\e) in those files when they occur in one of the four strings in a .i mntent structure. the routines .br addmntent () and .br getmntent () will convert from string representation to escaped representation and back. when converting from escaped representation, the sequence \e134 is also converted to a backslash. .sh return value the .br getmntent () and .br getmntent_r () functions return a pointer to the .i mntent structure or null on failure. .pp the .br addmntent () function returns 0 on success and 1 on failure. .pp the .br endmntent () function always returns 1. .pp the .br hasmntopt () function returns the address of the substring if a match is found and null otherwise. .sh files .tp .i /etc/fstab filesystem description file .tp .i /etc/mtab mounted filesystem description file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br setmntent (), .br endmntent (), .br hasmntopt () t} thread safety mt-safe t{ .br getmntent () t} thread safety t{ mt-unsafe race:mntentbuf locale t} t{ .br addmntent () t} thread safety t{ mt-safe race:stream locale t} t{ .br getmntent_r () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to the nonreentrant functions are from sunos 4.1.3. a routine .br getmntent_r () was introduced in hp-ux 10, but it returns an .ir int . the prototype shown above is glibc-only. .sh notes system v also has a .br getmntent () function but the calling sequence differs, and the returned structure is different. under system v .i /etc/mnttab is used. 4.4bsd and digital unix have a routine .br getmntinfo (), a wrapper around the system call .br getfsstat (). .sh see also .br fopen (3), .br fstab (5), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/drand48_r.3 .so man3/rpc.3 .so man2/sigaction.2 .so man3/tailq.3 .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" based on the original comments from alexey kuznetsov, written with .\" help from matthew wilcox. .\" $id: rtnetlink.7,v 1.8 2000/01/22 01:55:04 freitag exp $ .\" .th rtnetlink 7 2021-03-22 "linux" "linux programmer's manual" .sh name rtnetlink \- linux routing socket .sh synopsis .nf .b #include .b #include .b #include .b #include .pp .bi "rtnetlink_socket = socket(af_netlink, int " socket_type ", netlink_route);" .fi .sh description rtnetlink allows the kernel's routing tables to be read and altered. it is used within the kernel to communicate between various subsystems, though this usage is not documented here, and for communication with user-space programs. network routes, ip addresses, link parameters, neighbor setups, queueing disciplines, traffic classes and packet classifiers may all be controlled through .b netlink_route sockets. it is based on netlink messages; see .br netlink (7) for more information. .\" fixme . ? all these macros could be moved to rtnetlink(3) .ss routing attributes some rtnetlink messages have optional attributes after the initial header: .pp .in +4n .ex struct rtattr { unsigned short rta_len; /* length of option */ unsigned short rta_type; /* type of option */ /* data follows */ }; .ee .in .pp these attributes should be manipulated using only the rta_* macros or libnetlink, see .br rtnetlink (3). .ss messages rtnetlink consists of these message types (in addition to standard netlink messages): .tp .br rtm_newlink ", " rtm_dellink ", " rtm_getlink create, remove, or get information about a specific network interface. these messages contain an .i ifinfomsg structure followed by a series of .i rtattr structures. .ip .ex struct ifinfomsg { unsigned char ifi_family; /* af_unspec */ unsigned short ifi_type; /* device type */ int ifi_index; /* interface index */ unsigned int ifi_flags; /* device flags */ unsigned int ifi_change; /* change mask */ }; .ee .ip .\" fixme document ifinfomsg.ifi_type .i ifi_flags contains the device flags, see .br netdevice (7); .i ifi_index is the unique interface index (since linux 3.7, it is possible to feed a nonzero value with the .b rtm_newlink message, thus creating a link with the given .ir ifindex ); .i ifi_change is reserved for future use and should be always set to 0xffffffff. .ts tab(:); c s s lb l l. routing attributes rta_type:value type:description _ ifla_unspec:-:unspecified ifla_address:hardware address:interface l2 address ifla_broadcast:hardware address:l2 broadcast address ifla_ifname:asciiz string:device name ifla_mtu:unsigned int:mtu of the device ifla_link:int:link type ifla_qdisc:asciiz string:queueing discipline ifla_stats:t{ see below t}:interface statistics .te .ip the value type for .b ifla_stats is .ir "struct rtnl_link_stats" .ri ( "struct net_device_stats" in linux 2.4 and earlier). .tp .br rtm_newaddr ", " rtm_deladdr ", " rtm_getaddr add, remove, or receive information about an ip address associated with an interface. in linux 2.2, an interface can carry multiple ip addresses, this replaces the alias device concept in 2.0. in linux 2.2, these messages support ipv4 and ipv6 addresses. they contain an .i ifaddrmsg structure, optionally followed by .i rtattr routing attributes. .ip .ex struct ifaddrmsg { unsigned char ifa_family; /* address type */ unsigned char ifa_prefixlen; /* prefixlength of address */ unsigned char ifa_flags; /* address flags */ unsigned char ifa_scope; /* address scope */ unsigned int ifa_index; /* interface index */ }; .ee .ip .i ifa_family is the address family type (currently .b af_inet or .br af_inet6 ), .i ifa_prefixlen is the length of the address mask of the address if defined for the family (like for ipv4), .i ifa_scope is the address scope, .i ifa_index is the interface index of the interface the address is associated with. .i ifa_flags is a flag word of .b ifa_f_secondary for secondary address (old alias interface), .b ifa_f_permanent for a permanent address set by the user and other undocumented flags. .ts tab(:); c s s lb l l. attributes rta_type:value type:description _ ifa_unspec:-:unspecified ifa_address:raw protocol address:interface address ifa_local:raw protocol address:local address ifa_label:asciiz string:name of the interface ifa_broadcast:raw protocol address:broadcast address ifa_anycast:raw protocol address:anycast address ifa_cacheinfo:struct ifa_cacheinfo:address information .te .\" fixme document struct ifa_cacheinfo .tp .br rtm_newroute ", " rtm_delroute ", " rtm_getroute create, remove, or receive information about a network route. these messages contain an .i rtmsg structure with an optional sequence of .i rtattr structures following. for .br rtm_getroute , setting .i rtm_dst_len and .i rtm_src_len to 0 means you get all entries for the specified routing table. for the other fields, except .i rtm_table and .ir rtm_protocol , 0 is the wildcard. .ip .ex struct rtmsg { unsigned char rtm_family; /* address family of route */ unsigned char rtm_dst_len; /* length of destination */ unsigned char rtm_src_len; /* length of source */ unsigned char rtm_tos; /* tos filter */ unsigned char rtm_table; /* routing table id; see rta_table below */ unsigned char rtm_protocol; /* routing protocol; see below */ unsigned char rtm_scope; /* see below */ unsigned char rtm_type; /* see below */ unsigned int rtm_flags; }; .ee .ts tab(:); lb l. rtm_type:route type _ rtn_unspec:unknown route rtn_unicast:a gateway or direct route rtn_local:a local interface route rtn_broadcast:t{ a local broadcast route (sent as a broadcast) t} rtn_anycast:t{ a local broadcast route (sent as a unicast) t} rtn_multicast:a multicast route rtn_blackhole:a packet dropping route rtn_unreachable:an unreachable destination rtn_prohibit:a packet rejection route rtn_throw:continue routing lookup in another table rtn_nat:a network address translation rule rtn_xresolve:t{ refer to an external resolver (not implemented) t} .te .ts tab(:); lb l. rtm_protocol:route origin _ rtprot_unspec:unknown rtprot_redirect:t{ by an icmp redirect (currently unused) t} rtprot_kernel:by the kernel rtprot_boot:during boot rtprot_static:by the administrator .te .sp 1 values larger than .b rtprot_static are not interpreted by the kernel, they are just for user information. they may be used to tag the source of a routing information or to distinguish between multiple routing daemons. see .i for the routing daemon identifiers which are already assigned. .ip .i rtm_scope is the distance to the destination: .ts tab(:); lb l. rt_scope_universe:global route rt_scope_site:t{ interior route in the local autonomous system t} rt_scope_link:route on this link rt_scope_host:route on the local host rt_scope_nowhere:destination doesn't exist .te .sp 1 the values between .b rt_scope_universe and .b rt_scope_site are available to the user. .ip the .i rtm_flags have the following meanings: .ts tab(:); lb l. rtm_f_notify:t{ if the route changes, notify the user via rtnetlink t} rtm_f_cloned:route is cloned from another route rtm_f_equalize:a multipath equalizer (not yet implemented) .te .sp 1 .i rtm_table specifies the routing table .ts tab(:); lb l. rt_table_unspec:an unspecified routing table rt_table_default:the default table rt_table_main:the main table rt_table_local:the local table .te .sp 1 the user may assign arbitrary values between .b rt_table_unspec and .br rt_table_default . .\" keep table on same page .bp +1 .ts tab(:); c s s lb2 l2 l. attributes rta_type:value type:description _ rta_unspec:-:ignored rta_dst:protocol address:route destination address rta_src:protocol address:route source address rta_iif:int:input interface index rta_oif:int:output interface index rta_gateway:protocol address:the gateway of the route rta_priority:int:priority of route rta_prefsrc:protocol address:preferred source address rta_metrics:int:route metric rta_multipath::t{ multipath nexthop data br (see below). t} rta_protoinfo::no longer used rta_flow:int:route realm rta_cacheinfo:struct rta_cacheinfo:(see linux/rtnetlink.h) rta_session::no longer used rta_mp_algo::no longer used rta_table:int:t{ routing table id; if set, .br rtm_table is ignored t} rta_mark:int: rta_mfc_stats:struct rta_mfc_stats:(see linux/rtnetlink.h) rta_via:struct rtvia:t{ gateway in different af (see below) t} rta_newdst:protocol address:t{ change packet destination address t} rta_pref:char:t{ rfc4191 ipv6 router preference (see below) t} rta_encap_type:short:t{ encapsulation type for .br lwtunnels (see below) t} rta_encap::defined by rta_encap_type rta_expires:int:t{ expire time for ipv6 routes (in seconds) t} .te .ip .b rta_multipath contains several packed instances of .i struct rtnexthop together with nested rtas .rb ( rta_gateway ): .ip .in +4n .ex struct rtnexthop { unsigned short rtnh_len; /* length of struct + length of rtas */ unsigned char rtnh_flags; /* flags (see linux/rtnetlink.h) */ unsigned char rtnh_hops; /* nexthop priority */ int rtnh_ifindex; /* interface index for this nexthop */ } .ee .in .ip there exist a bunch of .b rtnh_* macros similar to .b rta_* and .b nlhdr_* macros useful to handle these structures. .ip .in +4n .ex struct rtvia { unsigned short rtvia_family; unsigned char rtvia_addr[0]; }; .ee .in .ip .i rtvia_addr is the address, .i rtvia_family is its family type. .ip .b rta_pref may contain values .br icmpv6_router_pref_low , .br icmpv6_router_pref_medium , and .br icmpv6_router_pref_high defined incw .ir . .ip .b rta_encap_type may contain values .br lwtunnel_encap_mpls , .br lwtunnel_encap_ip , .br lwtunnel_encap_ila , or .br lwtunnel_encap_ip6 defined in .ir . .ip .b fill these values in! .tp .br rtm_newneigh ", " rtm_delneigh ", " rtm_getneigh add, remove, or receive information about a neighbor table entry (e.g., an arp entry). the message contains an .i ndmsg structure. .ip .ex struct ndmsg { unsigned char ndm_family; int ndm_ifindex; /* interface index */ __u16 ndm_state; /* state */ __u8 ndm_flags; /* flags */ __u8 ndm_type; }; struct nda_cacheinfo { __u32 ndm_confirmed; __u32 ndm_used; __u32 ndm_updated; __u32 ndm_refcnt; }; .ee .ip .i ndm_state is a bit mask of the following states: .ts tab(:); lb l. nud_incomplete:a currently resolving cache entry nud_reachable:a confirmed working cache entry nud_stale:an expired cache entry nud_delay:an entry waiting for a timer nud_probe:a cache entry that is currently reprobed nud_failed:an invalid cache entry nud_noarp:a device with no destination cache nud_permanent:a static entry .te .sp 1 valid .i ndm_flags are: .ts tab(:); lb l. ntf_proxy:a proxy arp entry ntf_router:an ipv6 router .te .sp 1 .\" fixme . .\" document the members of the struct better the .i rtattr struct has the following meanings for the .i rta_type field: .ts tab(:); lb l. nda_unspec:unknown type nda_dst:a neighbor cache n/w layer destination address nda_lladdr:a neighbor cache link layer address nda_cacheinfo:cache statistics .te .sp 1 if the .i rta_type field is .br nda_cacheinfo , then a .i struct nda_cacheinfo header follows. .tp .br rtm_newrule ", " rtm_delrule ", " rtm_getrule add, delete, or retrieve a routing rule. carries a .i struct rtmsg .tp .br rtm_newqdisc ", " rtm_delqdisc ", " rtm_getqdisc add, remove, or get a queueing discipline. the message contains a .i struct tcmsg and may be followed by a series of attributes. .ip .ex struct tcmsg { unsigned char tcm_family; int tcm_ifindex; /* interface index */ __u32 tcm_handle; /* qdisc handle */ __u32 tcm_parent; /* parent qdisc */ __u32 tcm_info; }; .ee .ts tab(:); c s s lb2 l2 l. attributes rta_type:value type:description _ tca_unspec:-:unspecified tca_kind:asciiz string:name of queueing discipline tca_options:byte sequence:qdisc-specific options follow tca_stats:struct tc_stats:qdisc statistics tca_xstats:qdisc-specific:module-specific statistics tca_rate:struct tc_estimator:rate limit .te .sp 1 in addition, various other qdisc-module-specific attributes are allowed. for more information see the appropriate include files. .tp .br rtm_newtclass ", " rtm_deltclass ", " rtm_gettclass add, remove, or get a traffic class. these messages contain a .i struct tcmsg as described above. .tp .br rtm_newtfilter ", " rtm_deltfilter ", " rtm_gettfilter add, remove, or receive information about a traffic filter. these messages contain a .i struct tcmsg as described above. .sh versions .b rtnetlink is a new feature of linux 2.2. .sh bugs this manual page is incomplete. .sh see also .br cmsg (3), .br rtnetlink (3), .br ip (7), .br netlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcscat 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcscat \- concatenate two wide-character strings .sh synopsis .nf .b #include .pp .bi "wchar_t *wcscat(wchar_t *restrict " dest \ ", const wchar_t *restrict " src ); .fi .sh description the .br wcscat () function is the wide-character equivalent of the .br strcat (3) function. it copies the wide-character string pointed to by .ir src , including the terminating null wide character (l\(aq\e0\(aq), to the end of the wide-character string pointed to by .ir dest . .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .ir wcslen(dest) + wcslen(src) +1 wide characters at .ir dest . .sh return value .br wcscat () returns .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcscat () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strcat (3), .br wcpcpy (3), .br wcscpy (3), .br wcsncat (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man4/mem.4 .so man3/bswap.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:54:45 1993 by rik faith (faith@cs.unc.edu) .th memfrob 3 2021-03-22 "gnu" "linux programmer's manual" .sh name memfrob \- frobnicate (encrypt) a memory area .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void *memfrob(void *" s ", size_t " n ); .fi .sh description the .br memfrob () function encrypts the first \fin\fp bytes of the memory area \fis\fp by exclusive-oring each character with the number 42. the effect can be reversed by using .br memfrob () on the encrypted memory area. .pp note that this function is not a proper encryption routine as the xor constant is fixed, and is suitable only for hiding strings. .sh return value the .br memfrob () function returns a pointer to the encrypted memory area. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memfrob () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the .br memfrob () function is unique to the gnu c library. .sh see also .br bstring (3), .br strfry (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_attr_setsigmask_np.3 .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th user-keyring 7 2020-08-13 linux "linux programmer's manual" .sh name user-keyring \- per-user keyring .sh description the user keyring is a keyring used to anchor keys on behalf of a user. each uid the kernel deals with has its own user keyring that is shared by all processes with that uid. the user keyring has a name (description) of the form .i _uid. where .i is the user id of the corresponding user. .pp the user keyring is associated with the record that the kernel maintains for the uid. it comes into existence upon the first attempt to access either the user keyring, the .br user\-session\-keyring (7), or the .br session\-keyring (7). the keyring remains pinned in existence so long as there are processes running with that real uid or files opened by those processes remain open. (the keyring can also be pinned indefinitely by linking it into another keyring.) .pp typically, the user keyring is created by .br pam_keyinit (8) when a user logs in. .pp the user keyring is not searched by default by .br request_key (2). when .br pam_keyinit (8) creates a session keyring, it adds to it a link to the user keyring so that the user keyring will be searched when the session keyring is. .pp a special serial number value, .br key_spec_user_keyring , is defined that can be used in lieu of the actual serial number of the calling process's user keyring. .pp from the .br keyctl (1) utility, '\fb@u\fp' can be used instead of a numeric key id in much the same way. .pp user keyrings are independent of .br clone (2), .br fork (2), .br vfork (2), .br execve (2), and .br _exit (2) excepting that the keyring is destroyed when the uid record is destroyed when the last process pinning it exits. .pp if it is necessary for a key associated with a user to exist beyond the uid record being garbage collected\(emfor example, for use by a .br cron (8) script\(emthen the .br persistent\-keyring (7) should be used instead. .pp if a user keyring does not exist when it is accessed, it will be created. .sh see also .ad l .nh .br keyctl (1), .br keyctl (3), .br keyrings (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-session\-keyring (7), .br pam_keyinit (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/printf.3 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:10:00 1993 by rik faith (faith@cs.unc.edu) .\" modified sun aug 21 17:51:50 1994 by rik faith (faith@cs.unc.edu) .\" modified sat sep 2 21:52:01 1995 by jim van zandt .\" modified mon may 27 22:55:26 1996 by martin schulze (joey@linux.de) .\" .th isalpha 3 2021-03-22 "gnu" "linux programmer's manual" .sh name isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit, isalnum_l, isalpha_l, isascii_l, isblank_l, iscntrl_l, isdigit_l, isgraph_l, islower_l, isprint_l, ispunct_l, isspace_l, isupper_l, isxdigit_l \- character classification functions .sh synopsis .nf .b #include .pp .bi "int isalnum(int " c ); .bi "int isalpha(int " c ); .bi "int iscntrl(int " c ); .bi "int isdigit(int " c ); .bi "int isgraph(int " c ); .bi "int islower(int " c ); .bi "int isprint(int " c ); .bi "int ispunct(int " c ); .bi "int isspace(int " c ); .bi "int isupper(int " c ); .bi "int isxdigit(int " c ); .pp .bi "int isascii(int " c ); .bi "int isblank(int " c ); .pp .bi "int isalnum_l(int " c ", locale_t " locale ); .bi "int isalpha_l(int " c ", locale_t " locale ); .bi "int isblank_l(int " c ", locale_t " locale ); .bi "int iscntrl_l(int " c ", locale_t " locale ); .bi "int isdigit_l(int " c ", locale_t " locale ); .bi "int isgraph_l(int " c ", locale_t " locale ); .bi "int islower_l(int " c ", locale_t " locale ); .bi "int isprint_l(int " c ", locale_t " locale ); .bi "int ispunct_l(int " c ", locale_t " locale ); .bi "int isspace_l(int " c ", locale_t " locale ); .bi "int isupper_l(int " c ", locale_t " locale ); .bi "int isxdigit_l(int " c ", locale_t " locale ); .pp .bi "int isascii_l(int " c ", locale_t " locale ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .ad l .pp .br isascii (): .nf _xopen_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source .fi .pp .br isblank (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .nh .pp .br isalnum_l (), .br isalpha_l (), .br isblank_l (), .br iscntrl_l (), .br isdigit_l (), .br isgraph_l (), .br islower_l (), .br isprint_l (), .br ispunct_l (), .br isspace_l (), .br isupper_l (), .br isxdigit_l (): .hy .nf since glibc 2.10: _xopen_source >= 700 before glibc 2.10: _gnu_source .fi .pp .br isascii_l (): .nf since glibc 2.10: _xopen_source >= 700 && (_svid_source || _bsd_source) before glibc 2.10: _gnu_source .fi .ad .sh description these functions check whether .ir c , which must have the value of an .i unsigned char or .br eof , falls into a certain character class according to the specified locale. the functions without the "_l" suffix perform the check based on the current locale. .pp the functions with the "_l" suffix perform the check based on the locale specified by the locale object .ir locale . the behavior of these functions is undefined if .i locale is the special locale object .b lc_global_locale (see .br duplocale (3)) or is not a valid locale object handle. .pp the list below explains the operation of the functions without the "_l" suffix; the functions with the "_l" suffix differ only in using the locale object .i locale instead of the current locale. .tp .br isalnum () checks for an alphanumeric character; it is equivalent to .bi "(isalpha(" c ") || isdigit(" c "))" \fr. .tp .br isalpha () checks for an alphabetic character; in the standard \fb"c"\fp locale, it is equivalent to .bi "(isupper(" c ") || islower(" c "))" \fr. in some locales, there may be additional characters for which .br isalpha () is true\(emletters which are neither uppercase nor lowercase. .tp .br isascii () checks whether \fic\fp is a 7-bit .i unsigned char value that fits into the ascii character set. .tp .br isblank () checks for a blank character; that is, a space or a tab. .tp .br iscntrl () checks for a control character. .tp .br isdigit () checks for a digit (0 through 9). .tp .br isgraph () checks for any printable character except space. .tp .br islower () checks for a lowercase character. .tp .br isprint () checks for any printable character including space. .tp .br ispunct () checks for any printable character which is not a space or an alphanumeric character. .tp .br isspace () checks for white-space characters. in the .b """c""" and .b """posix""" locales, these are: space, form-feed .rb ( \(aq\ef\(aq ), newline .rb ( \(aq\en\(aq ), carriage return .rb ( \(aq\er\(aq ), horizontal tab .rb ( \(aq\et\(aq ), and vertical tab .rb ( \(aq\ev\(aq ). .tp .br isupper () checks for an uppercase letter. .tp .br isxdigit () checks for hexadecimal digits, that is, one of .br .br "0 1 2 3 4 5 6 7 8 9 a b c d e f a b c d e f" . .sh return value the values returned are nonzero if the character .i c falls into the tested class, and zero if not. .sh versions .br isalnum_l (), .br isalpha_l (), .br isblank_l (), .br iscntrl_l (), .br isdigit_l (), .br isgraph_l (), .br islower_l (), .br isprint_l (), .br ispunct_l (), .br isspace_l (), .br isupper_l (), .br isxdigit_l (), and .br isascii_l () are available since glibc 2.3. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br isalnum (), .br isalpha (), .br isascii (), .br isblank (), .br iscntrl (), .br isdigit (), .br isgraph (), .br islower (), .br isprint (), .br ispunct (), .br isspace (), .br isupper (), .br isxdigit () t} thread safety mt-safe .te .hy .ad .sp 1 .\" fixme: need a thread-safety statement about the *_l functions .sh conforming to c89 specifies .br isalnum (), .br isalpha (), .br iscntrl (), .br isdigit (), .br isgraph (), .br islower (), .br isprint (), .br ispunct (), .br isspace (), .br isupper (), and .br isxdigit (), but not .br isascii () and .br isblank (). posix.1-2001 also specifies those functions, and also .br isascii () (as an xsi extension) and .br isblank (). c99 specifies all of the preceding functions, except .br isascii (). .pp posix.1-2008 marks .br isascii () as obsolete, noting that it cannot be used portably in a localized application. .pp posix.1-2008 specifies .br isalnum_l (), .br isalpha_l (), .br isblank_l (), .br iscntrl_l (), .br isdigit_l (), .br isgraph_l (), .br islower_l (), .br isprint_l (), .br ispunct_l (), .br isspace_l (), .br isupper_l (), and .br isxdigit_l (). .pp .br isascii_l () is a gnu extension. .sh notes the standards require that the argument .i c for these functions is either .b eof or a value that is representable in the type .ir "unsigned char" . if the argument .i c is of type .ir char , it must be cast to .ir "unsigned char" , as in the following example: .pp .in +4n .ex char c; \&... res = toupper((unsigned char) c); .ee .in .pp this is necessary because .i char may be the equivalent of .ir "signed char" , in which case a byte where the top bit is set would be sign extended when converting to .ir int , yielding a value that is outside the range of .ir "unsigned char" . .pp the details of what characters belong to which class depend on the locale. for example, .br isupper () will not recognize an a-umlaut (\(:a) as an uppercase letter in the default .b "c" locale. .sh see also .br iswalnum (3), .br iswalpha (3), .br iswblank (3), .br iswcntrl (3), .br iswdigit (3), .br iswgraph (3), .br iswlower (3), .br iswprint (3), .br iswpunct (3), .br iswspace (3), .br iswupper (3), .br iswxdigit (3), .br newlocale (3), .br setlocale (3), .br toascii (3), .br tolower (3), .br toupper (3), .br uselocale (3), .br ascii (7), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. import os import glob import random # navigate to the directory data_dir = '/media/external/man-pages-dataset/man-pages-5.13' os.chdir(data_dir) # function to preprocess the text def preprocess_text(file_path): try: with open(file_path, 'r', encoding='utf-8') as file: text = file.read() # simple preprocessing (e.g., lowercase conversion) text = text.lower() return text except exception as e: print(f'failed to process {file_path}: {e}') return none # collect and preprocess the data all_data = [] file_paths = glob.glob('**/*', recursive=true) # adjusted this line to match all files print(f'found {len(file_paths)} files.') for file_path in file_paths: preprocessed_text = preprocess_text(file_path) if preprocessed_text is not none: all_data.append(preprocessed_text) print(f'processed {len(all_data)} files.') # shuffle and split the data random.shuffle(all_data) train_size = int(0.8 * len(all_data)) train_data, val_test_data = all_data[:train_size], all_data[train_size:] val_size = int(0.5 * len(val_test_data)) val_data, test_data = val_test_data[:val_size], val_test_data[val_size:] # save the preprocessed data output_dir = os.path.join(data_dir, 'preprocessed_data') os.makedirs(output_dir, exist_ok=true) with open(os.path.join(output_dir, 'train.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(train_data)) with open(os.path.join(output_dir, 'val.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(val_data)) with open(os.path.join(output_dir, 'test.txt'), 'w', encoding='utf-8') as file: file.write('\n'.join(test_data)) print(f'data preprocessing and splitting completed. preprocessed data saved to {output_dir}') .so man2/uname.2 .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 19:53:02 1993 by rik faith (faith@cs.unc.edu) .\" .\" fixme many more values for 'name' are supported, some of which .\" are documented under 'info confstr'. .\" see for the rest. .\" these should all be added to this page. .\" see also the posix.1-2001 specification of confstr() .\" .th confstr 3 2021-03-22 "gnu" "linux programmer's manual" .sh name confstr \- get configuration dependent string variables .sh synopsis .nf .b #include .pp .bi "size_t confstr(int " "name" ", char *" buf ", size_t " len ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br confstr (): .nf _posix_c_source >= 2 || _xopen_source .fi .sh description .br confstr () gets the value of configuration-dependent string variables. .pp the .i name argument is the system variable to be queried. the following variables are supported: .tp .br _cs_gnu_libc_version " (gnu c library only; since glibc 2.3.2)" a string which identifies the gnu c library version on this system (e.g., "glibc 2.3.4"). .tp .br _cs_gnu_libpthread_version " (gnu c library only; since glibc 2.3.2)" a string which identifies the posix implementation supplied by this c library (e.g., "nptl 2.3.4" or "linuxthreads\-0.10"). .tp .b _cs_path a value for the .b path variable which indicates where all the posix.2 standard utilities can be found. .pp if .i buf is not null and .i len is not zero, .br confstr () copies the value of the string to .i buf truncated to .i len \- 1 bytes if necessary, with a null byte (\(aq\e0\(aq) as terminator. this can be detected by comparing the return value of .br confstr () against .ir len . .pp if .i len is zero and .i buf is null, .br confstr () just returns the value as defined below. .sh return value if .i name is a valid configuration variable, .br confstr () returns the number of bytes (including the terminating null byte) that would be required to hold the entire value of that variable. this value may be greater than .ir len , which means that the value in .i buf is truncated. .pp if .i name is a valid configuration variable, but that variable does not have a value, then .br confstr () returns 0. if .i name does not correspond to a valid configuration variable, .br confstr () returns 0, and .i errno is set to .br einval . .sh errors .tp .b einval the value of .i name is invalid. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br confstr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples the following code fragment determines the path where to find the posix.2 system utilities: .pp .in +4n .ex char *pathbuf; size_t n; n = confstr(_cs_path, null, (size_t) 0); pathbuf = malloc(n); if (pathbuf == null) abort(); confstr(_cs_path, pathbuf, n); .ee .in .sh see also .br getconf (1), .br sh (1), .br exec (3), .br fpathconf (3), .br pathconf (3), .br sysconf (3), .br system (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/circleq.3 .so man3/j0.3 .so man3/encrypt.3 .so man3/argz_add.3 .\" copyright (c) 2013 by michael kerrisk .\" and copyright (c) 2012 by eric w. biederman .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th pid_namespaces 7 2020-11-01 "linux" "linux programmer's manual" .sh name pid_namespaces \- overview of linux pid namespaces .sh description for an overview of namespaces, see .br namespaces (7). .pp pid namespaces isolate the process id number space, meaning that processes in different pid namespaces can have the same pid. pid namespaces allow containers to provide functionality such as suspending/resuming the set of processes in the container and migrating the container to a new host while the processes inside the container maintain the same pids. .pp pids in a new pid namespace start at 1, somewhat like a standalone system, and calls to .br fork (2), .br vfork (2), or .br clone (2) will produce processes with pids that are unique within the namespace. .pp use of pid namespaces requires a kernel that is configured with the .b config_pid_ns option. .\" .\" ============================================================ .\" .ss the namespace "init" process the first process created in a new namespace (i.e., the process created using .br clone (2) with the .br clone_newpid flag, or the first child created by a process after a call to .br unshare (2) using the .br clone_newpid flag) has the pid 1, and is the "init" process for the namespace (see .br init (1)). this process becomes the parent of any child processes that are orphaned because a process that resides in this pid namespace terminated (see below for further details). .pp if the "init" process of a pid namespace terminates, the kernel terminates all of the processes in the namespace via a .br sigkill signal. this behavior reflects the fact that the "init" process is essential for the correct operation of a pid namespace. in this case, a subsequent .br fork (2) into this pid namespace fail with the error .br enomem ; it is not possible to create a new process in a pid namespace whose "init" process has terminated. such scenarios can occur when, for example, a process uses an open file descriptor for a .i /proc/[pid]/ns/pid file corresponding to a process that was in a namespace to .br setns (2) into that namespace after the "init" process has terminated. another possible scenario can occur after a call to .br unshare (2): if the first child subsequently created by a .br fork (2) terminates, then subsequent calls to .br fork (2) fail with .br enomem . .pp only signals for which the "init" process has established a signal handler can be sent to the "init" process by other members of the pid namespace. this restriction applies even to privileged processes, and prevents other members of the pid namespace from accidentally killing the "init" process. .pp likewise, a process in an ancestor namespace can\(emsubject to the usual permission checks described in .br kill (2)\(emsend signals to the "init" process of a child pid namespace only if the "init" process has established a handler for that signal. (within the handler, the .i siginfo_t .i si_pid field described in .br sigaction (2) will be zero.) .b sigkill or .b sigstop are treated exceptionally: these signals are forcibly delivered when sent from an ancestor pid namespace. neither of these signals can be caught by the "init" process, and so will result in the usual actions associated with those signals (respectively, terminating and stopping the process). .pp starting with linux 3.4, the .br reboot (2) system call causes a signal to be sent to the namespace "init" process. see .br reboot (2) for more details. .\" .\" ============================================================ .\" .ss nesting pid namespaces pid namespaces can be nested: each pid namespace has a parent, except for the initial ("root") pid namespace. the parent of a pid namespace is the pid namespace of the process that created the namespace using .br clone (2) or .br unshare (2). pid namespaces thus form a tree, with all namespaces ultimately tracing their ancestry to the root namespace. since linux 3.7, .\" commit f2302505775fd13ba93f034206f1e2a587017929 .\" the kernel constant max_pid_ns_level the kernel limits the maximum nesting depth for pid namespaces to 32. .pp a process is visible to other processes in its pid namespace, and to the processes in each direct ancestor pid namespace going back to the root pid namespace. in this context, "visible" means that one process can be the target of operations by another process using system calls that specify a process id. conversely, the processes in a child pid namespace can't see processes in the parent and further removed ancestor namespaces. more succinctly: a process can see (e.g., send signals with .br kill (2), set nice values with .br setpriority (2), etc.) only processes contained in its own pid namespace and in descendants of that namespace. .pp a process has one process id in each of the layers of the pid namespace hierarchy in which is visible, and walking back though each direct ancestor namespace through to the root pid namespace. system calls that operate on process ids always operate using the process id that is visible in the pid namespace of the caller. a call to .br getpid (2) always returns the pid associated with the namespace in which the process was created. .pp some processes in a pid namespace may have parents that are outside of the namespace. for example, the parent of the initial process in the namespace (i.e., the .br init (1) process with pid 1) is necessarily in another namespace. likewise, the direct children of a process that uses .br setns (2) to cause its children to join a pid namespace are in a different pid namespace from the caller of .br setns (2). calls to .br getppid (2) for such processes return 0. .pp while processes may freely descend into child pid namespaces (e.g., using .br setns (2) with a pid namespace file descriptor), they may not move in the other direction. that is to say, processes may not enter any ancestor namespaces (parent, grandparent, etc.). changing pid namespaces is a one-way operation. .pp the .br ns_get_parent .br ioctl (2) operation can be used to discover the parental relationship between pid namespaces; see .br ioctl_ns (2). .\" .\" ============================================================ .\" .ss setns(2) and unshare(2) semantics calls to .br setns (2) that specify a pid namespace file descriptor and calls to .br unshare (2) with the .br clone_newpid flag cause children subsequently created by the caller to be placed in a different pid namespace from the caller. (since linux 4.12, that pid namespace is shown via the .ir /proc/[pid]/ns/pid_for_children file, as described in .br namespaces (7).) these calls do not, however, change the pid namespace of the calling process, because doing so would change the caller's idea of its own pid (as reported by .br getpid ()), which would break many applications and libraries. .pp to put things another way: a process's pid namespace membership is determined when the process is created and cannot be changed thereafter. among other things, this means that the parental relationship between processes mirrors the parental relationship between pid namespaces: the parent of a process is either in the same namespace or resides in the immediate parent pid namespace. .pp a process may call .br unshare (2) with the .b clone_newpid flag only once. after it has performed this operation, its .ir /proc/pid/ns/pid_for_children symbolic link will be empty until the first child is created in the namespace. .\" .\" ============================================================ .\" .ss adoption of orphaned children when a child process becomes orphaned, it is reparented to the "init" process in the pid namespace of its parent (unless one of the nearer ancestors of the parent employed the .br prctl (2) .b pr_set_child_subreaper command to mark itself as the reaper of orphaned descendant processes). note that because of the .br setns (2) and .br unshare (2) semantics described above, this may be the "init" process in the pid namespace that is the .i parent of the child's pid namespace, rather than the "init" process in the child's own pid namespace. .\" furthermore, by definition, the parent of the "init" process .\" of a pid namespace resides in the parent pid namespace. .\" .\" ============================================================ .\" .ss compatibility of clone_newpid with other clone_* flags in current versions of linux, .br clone_newpid can't be combined with .br clone_thread . threads are required to be in the same pid namespace such that the threads in a process can send signals to each other. similarly, it must be possible to see all of the threads of a process in the .br proc (5) filesystem. additionally, if two threads were in different pid namespaces, the process id of the process sending a signal could not be meaningfully encoded when a signal is sent (see the description of the .i siginfo_t type in .br sigaction (2)). since this is computed when a signal is enqueued, a signal queue shared by processes in multiple pid namespaces would defeat that. .pp .\" note these restrictions were all introduced in .\" 8382fcac1b813ad0a4e68a838fc7ae93fa39eda0 .\" when clone_newpid|clone_vm was disallowed in earlier versions of linux, .br clone_newpid was additionally disallowed (failing with the error .br einval ) in combination with .br clone_sighand .\" (restriction lifted in faf00da544045fdc1454f3b9e6d7f65c841de302) (before linux 4.3) as well as .\" (restriction lifted in e79f525e99b04390ca4d2366309545a836c03bf1) .br clone_vm (before linux 3.12). the changes that lifted these restrictions have also been ported to earlier stable kernels. .\" .\" ============================================================ .\" .ss /proc and pid namespaces a .i /proc filesystem shows (in the .i /proc/[pid] directories) only processes visible in the pid namespace of the process that performed the mount, even if the .i /proc filesystem is viewed from processes in other namespaces. .pp after creating a new pid namespace, it is useful for the child to change its root directory and mount a new procfs instance at .i /proc so that tools such as .br ps (1) work correctly. if a new mount namespace is simultaneously created by including .br clone_newns in the .ir flags argument of .br clone (2) or .br unshare (2), then it isn't necessary to change the root directory: a new procfs instance can be mounted directly over .ir /proc . .pp from a shell, the command to mount .i /proc is: .pp .in +4n .ex $ mount \-t proc proc /proc .ee .in .pp calling .br readlink (2) on the path .i /proc/self yields the process id of the caller in the pid namespace of the procfs mount (i.e., the pid namespace of the process that mounted the procfs). this can be useful for introspection purposes, when a process wants to discover its pid in other namespaces. .\" .\" ============================================================ .\" .ss /proc files .tp .br /proc/sys/kernel/ns_last_pid " (since linux 3.3)" .\" commit b8f566b04d3cddd192cfd2418ae6d54ac6353792 this file (which is virtualized per pid namespace) displays the last pid that was allocated in this pid namespace. when the next pid is allocated, the kernel will search for the lowest unallocated pid that is greater than this value, and when this file is subsequently read it will show that pid. .ip this file is writable by a process that has the .b cap_sys_admin or (since linux 5.9) .b cap_checkpoint_restore capability inside the user namespace that owns the pid namespace. .\" this ability is necessary to support checkpoint restore in user-space this makes it possible to determine the pid that is allocated to the next process that is created inside this pid namespace. .\" .\" ============================================================ .\" .ss miscellaneous when a process id is passed over a unix domain socket to a process in a different pid namespace (see the description of .b scm_credentials in .br unix (7)), it is translated into the corresponding pid value in the receiving process's pid namespace. .sh conforming to namespaces are a linux-specific feature. .sh examples see .br user_namespaces (7). .sh see also .br clone (2), .br reboot (2), .br setns (2), .br unshare (2), .br proc (5), .br capabilities (7), .br credentials (7), .br mount_namespaces (7), .br namespaces (7), .br user_namespaces (7), .br switch_root (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified 1993-03-29, david metcalfe .\" modified 1993-07-24, rik faith (faith@cs.unc.edu) .\" 2006-01-15, mtk, added example program. .\" modified 2012-03-08, mark r. bannister .\" and ben bacarisse .\" document qsort_r() .\" .th qsort 3 2021-03-22 "" "linux programmer's manual" .sh name qsort, qsort_r \- sort an array .sh synopsis .nf .b #include .pp .bi "void qsort(void *" base ", size_t " nmemb ", size_t " size , .bi " int (*" compar ")(const void *, const void *));" .bi "void qsort_r(void *" base ", size_t " nmemb ", size_t " size , .bi " int (*" compar ")(const void *, const void *, void *)," .bi " void *" arg ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br qsort_r (): .nf _gnu_source .fi .sh description the .br qsort () function sorts an array with \finmemb\fp elements of size \fisize\fp. the \fibase\fp argument points to the start of the array. .pp the contents of the array are sorted in ascending order according to a comparison function pointed to by \ficompar\fp, which is called with two arguments that point to the objects being compared. .pp the comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. if two members compare as equal, their order in the sorted array is undefined. .pp the .br qsort_r () function is identical to .br qsort () except that the comparison function .i compar takes a third argument. a pointer is passed to the comparison function via .ir arg . in this way, the comparison function does not need to use global variables to pass through arbitrary arguments, and is therefore reentrant and safe to use in threads. .sh return value the .br qsort () and .br qsort_r () functions return no value. .sh versions .br qsort_r () was added to glibc in version 2.8. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br qsort (), .br qsort_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br qsort (): posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes to compare c strings, the comparison function can call .br strcmp (3), as shown in the example below. .sh examples for one example of use, see the example under .br bsearch (3). .pp another example is the following program, which sorts the strings given in its command-line arguments: .pp .ex #include #include #include static int cmpstringp(const void *p1, const void *p2) { /* the actual arguments to this function are "pointers to pointers to char", but strcmp(3) arguments are "pointers to char", hence the following cast plus dereference. */ return strcmp(*(const char **) p1, *(const char **) p2); } int main(int argc, char *argv[]) { if (argc < 2) { fprintf(stderr, "usage: %s ...\en", argv[0]); exit(exit_failure); } qsort(&argv[1], argc \- 1, sizeof(char *), cmpstringp); for (int j = 1; j < argc; j++) puts(argv[j]); exit(exit_success); } .ee .sh see also .br sort (1), .br alphasort (3), .br strcmp (3), .br versionsort (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stdio_ext.3 #!/bin/sh # # remove_colophon.sh # # remove the colophon section from the man pages provided as # command-line arguments. (this is useful to remove the colophon # sections from all of the man pages in two different release trees # in order to do a "diff -run" to see the "real" differences between # the trees.) # ###################################################################### # # (c) copyright 2008 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # # for f in "$@"; do sed -i '/^\.sh colophon/,$d' "$f" done .\" copyright (c) 2018, stefan hajnoczi .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th vsock 7 2021-03-22 "linux" "linux programmer's manual" .sh name vsock \- linux vsock address family .sh synopsis .nf .b #include .b #include .pp .ib stream_socket " = socket(af_vsock, sock_stream, 0);" .ib datagram_socket " = socket(af_vsock, sock_dgram, 0);" .fi .sh description the vsock address family facilitates communication between virtual machines and the host they are running on. this address family is used by guest agents and hypervisor services that need a communications channel that is independent of virtual machine network configuration. .pp valid socket types are .b sock_stream and .br sock_dgram . .b sock_stream provides connection-oriented byte streams with guaranteed, in-order delivery. .b sock_dgram provides a connectionless datagram packet service with best-effort delivery and best-effort ordering. availability of these socket types is dependent on the underlying hypervisor. .pp a new socket is created with .pp .in +4n .ex socket(af_vsock, socket_type, 0); .ee .in .pp when a process wants to establish a connection, it calls .br connect (2) with a given destination socket address. the socket is automatically bound to a free port if unbound. .pp a process can listen for incoming connections by first binding to a socket address using .br bind (2) and then calling .br listen (2). .pp data is transmitted using the .br send (2) or .br write (2) families of system calls and data is received using the .br recv (2) or .br read (2) families of system calls. .ss address format a socket address is defined as a combination of a 32-bit context identifier (cid) and a 32-bit port number. the cid identifies the source or destination, which is either a virtual machine or the host. the port number differentiates between multiple services running on a single machine. .pp .in +4n .ex struct sockaddr_vm { sa_family_t svm_family; /* address family: af_vsock */ unsigned short svm_reserved1; unsigned int svm_port; /* port # in host byte order */ unsigned int svm_cid; /* address in host byte order */ unsigned char svm_zero[sizeof(struct sockaddr) \- sizeof(sa_family_t) \- sizeof(unsigned short) \- sizeof(unsigned int) \- sizeof(unsigned int)]; }; .ee .in .pp .i svm_family is always set to .br af_vsock . .i svm_reserved1 is always set to 0. .i svm_port contains the port number in host byte order. the port numbers below 1024 are called .ir "privileged ports" . only a process with the .b cap_net_bind_service capability may .br bind (2) to these port numbers. .i svm_zero must be zero-filled. .pp there are several special addresses: .b vmaddr_cid_any (\-1u) means any address for binding; .b vmaddr_cid_hypervisor (0) is reserved for services built into the hypervisor; .b vmaddr_cid_local (1) is the well-known address for local communication (loopback); .b vmaddr_cid_host (2) is the well-known address of the host. .pp the special constant .b vmaddr_port_any (\-1u) means any port number for binding. .ss live migration sockets are affected by live migration of virtual machines. connected .b sock_stream sockets become disconnected when the virtual machine migrates to a new host. applications must reconnect when this happens. .pp the local cid may change across live migration if the old cid is not available on the new host. bound sockets are automatically updated to the new cid. .ss ioctls the following ioctls are available on the .ir /dev/vsock device. .tp .b ioctl_vm_sockets_get_local_cid get the cid of the local machine. the argument is a pointer to an .ir "unsigned int" . .ip .in +4n .ex ioctl(fd, ioctl_vm_sockets_get_local_cid, &cid); .ee .in .ip consider using .b vmaddr_cid_any when binding instead of getting the local cid with .br ioctl_vm_sockets_get_local_cid . .ss local communication .b vmaddr_cid_local (1) directs packets to the same host that generated them. this is useful for testing applications on a single host and for debugging. .pp the local cid obtained with .br ioctl_vm_sockets_get_local_cid can be used for the same purpose, but it is preferable to use .b vmaddr_cid_local . .sh errors .tp .b eacces unable to bind to a privileged port without the .b cap_net_bind_service capability. .tp .b eaddrinuse unable to bind to a port that is already in use. .tp .b eaddrnotavail unable to find a free port for binding or unable to bind to a nonlocal cid. .tp .b einval invalid parameters. this includes: attempting to bind a socket that is already bound, providing an invalid struct .ir sockaddr_vm , and other input validation errors. .tp .b enoprotoopt invalid socket option in .br setsockopt (2) or .br getsockopt (2). .tp .b enotconn unable to perform operation on an unconnected socket. .tp .b eopnotsupp operation not supported. this includes: the .b msg_oob flag that is not implemented for the .br send (2) family of syscalls and .b msg_peek for the .br recv (2) family of syscalls. .tp .b eprotonosupport invalid socket protocol number. the protocol should always be 0. .tp .b esocktnosupport unsupported socket type in .br socket (2). only .b sock_stream and .b sock_dgram are valid. .sh versions support for vmware (vmci) has been available since linux 3.9. kvm (virtio) is supported since linux 4.8. hyper-v is supported since linux 4.14. .pp .b vmaddr_cid_local is supported since linux 5.6. .\" commit ef343b35d46667668a099655fca4a5b2e43a5dfe local communication in the guest and on the host is available since linux 5.6. previous versions supported only local communication within a guest (not on the host), and with only some transports (vmci and virtio). .sh see also .br bind (2), .br connect (2), .br listen (2), .br recv (2), .br send (2), .br socket (2), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fma.3 .\" copyright (c) 1996 andries brouwer , mon oct 31 22:13:04 1996 .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" this is combined from many sources. .\" for linux, the definitive source is of course console.c. .\" about vt100-like escape sequences in general there are .\" the iso 6429 and iso 2022 norms, the descriptions of .\" an actual vt100, and the xterm docs (ctlseqs.ms). .\" substantial portions of this text are derived from a write-up .\" by eric s. raymond . .\" .\" tiny correction, aeb, 961107. .\" .\" 2006-05-27, several corrections - thomas e. dickey .\" .th console_codes 4 2021-03-22 "linux" "linux programmer's manual" .sh name console_codes \- linux console escape and control sequences .sh description the linux console implements a large subset of the vt102 and ecma-48/iso 6429/ansi x3.64 terminal controls, plus certain private-mode sequences for changing the color palette, character-set mapping, and so on. in the tabular descriptions below, the second column gives ecma-48 or dec mnemonics (the latter if prefixed with dec) for the given function. sequences without a mnemonic are neither ecma-48 nor vt102. .pp after all the normal output processing has been done, and a stream of characters arrives at the console driver for actual printing, the first thing that happens is a translation from the code used for processing to the code used for printing. .pp if the console is in utf-8 mode, then the incoming bytes are first assembled into 16-bit unicode codes. otherwise, each byte is transformed according to the current mapping table (which translates it to a unicode value). see the \fbcharacter sets\fp section below for discussion. .pp in the normal case, the unicode value is converted to a font index, and this is stored in video memory, so that the corresponding glyph (as found in video rom) appears on the screen. note that the use of unicode (and the design of the pc hardware) allows us to use 512 different glyphs simultaneously. .pp if the current unicode value is a control character, or we are currently processing an escape sequence, the value will treated specially. instead of being turned into a font index and rendered as a glyph, it may trigger cursor movement or other control functions. see the \fblinux console controls\fp section below for discussion. .pp it is generally not good practice to hard-wire terminal controls into programs. linux supports a .br terminfo (5) database of terminal capabilities. rather than emitting console escape sequences by hand, you will almost always want to use a terminfo-aware screen library or utility such as .br ncurses (3), .br tput (1), or .br reset (1). .ss linux console controls this section describes all the control characters and escape sequences that invoke special functions (i.e., anything other than writing a glyph at the current cursor location) on the linux console. .pp .b "control characters" .pp a character is a control character if (before transformation according to the mapping table) it has one of the 14 codes 00 (nul), 07 (bel), 08 (bs), 09 (ht), 0a (lf), 0b (vt), 0c (ff), 0d (cr), 0e (so), 0f (si), 18 (can), 1a (sub), 1b (esc), 7f (del). one can set a "display control characters" mode (see below), and allow 07, 09, 0b, 18, 1a, 7f to be displayed as glyphs. on the other hand, in utf-8 mode all codes 00\(en1f are regarded as control characters, regardless of any "display control characters" mode. .pp if we have a control character, it is acted upon immediately and then discarded (even in the middle of an escape sequence) and the escape sequence continues with the next character. (however, esc starts a new escape sequence, possibly aborting a previous unfinished one, and can and sub abort any escape sequence.) the recognized control characters are bel, bs, ht, lf, vt, ff, cr, so, si, can, sub, esc, del, csi. they do what one would expect: .hp bel (0x07, \fb\(hag\fp) beeps; .hp bs (0x08, \fb\(hah\fp) backspaces one column (but not past the beginning of the line); .hp ht (0x09, \fb\(hai\fp) goes to the next tab stop or to the end of the line if there is no earlier tab stop; .hp lf (0x0a, \fb\(haj\fp), vt (0x0b, \fb\(hak\fp), and ff (0x0c, \fb\(hal\fp) all give a linefeed, and if lf/nl (new-line mode) is set also a carriage return; .hp cr (0x0d, \fb\(ham\fp) gives a carriage return; .hp so (0x0e, \fb\(han\fp) activates the g1 character set; .hp si (0x0f, \fb\(hao\fp) activates the g0 character set; .hp can (0x18, \fb\(hax\fp) and sub (0x1a, \fb\(haz\fp) abort escape sequences; .hp esc (0x1b, \fb\(ha[\fp) starts an escape sequence; .hp del (0x7f) is ignored; .hp csi (0x9b) is equivalent to esc [. .pp .b "esc- but not csi-sequences" .ad l .ts l l lx. esc c ris reset. esc d ind linefeed. esc e nel newline. esc h hts set tab stop at current column. esc m ri reverse linefeed. esc z decid t{ dec private identification. the kernel returns the string esc [ ? 6 c, claiming that it is a vt102. t} esc 7 decsc t{ save current state (cursor coordinates, attributes, character sets pointed at by g0, g1). t} esc 8 decrc t{ restore state most recently saved by esc 7. t} esc [ csi control sequence introducer esc % start sequence selecting character set esc % @ \0\0\0select default (iso 646 / iso 8859-1) esc % g \0\0\0select utf-8 esc % 8 \0\0\0select utf-8 (obsolete) esc # 8 decaln t{ dec screen alignment test \- fill screen with e's t} esc ( t{ start sequence defining g0 character set (followed by one of b, 0, u, k, as below) t} esc ( b t{ select default (iso 8859-1 mapping) t} esc ( 0 t{ select vt100 graphics mapping t} esc ( u t{ select null mapping \- straight to character rom t} esc ( k t{ select user mapping \- the map that is loaded by the utility \fbmapscrn\fp(8) t} esc ) t{ start sequence defining g1 (followed by one of b, 0, u, k, as above). t} esc > decpnm set numeric keypad mode esc = decpam set application keypad mode esc ] osc t{ (should be: operating system command) esc ] p \finrrggbb\fp: set palette, with parameter given in 7 hexadecimal digits after the final p :-(. here \fin\fp is the color (0\(en15), and \firrggbb\fp indicates the red/green/blue values (0\(en255). esc ] r: reset palette t} .te .ad .pp .b "ecma-48 csi sequences" .pp csi (or esc [) is followed by a sequence of parameters, at most npar (16), that are decimal numbers separated by semicolons. an empty or absent parameter is taken to be 0. the sequence of parameters may be preceded by a single question mark. .pp however, after csi [ (or esc [ [) a single character is read and this entire sequence is ignored. (the idea is to ignore an echoed function key.) .pp the action of a csi sequence is determined by its final character. .ad l .ts l l lx. @ ich t{ insert the indicated # of blank characters. t} a cuu t{ move cursor up the indicated # of rows. t} b cud t{ move cursor down the indicated # of rows. t} c cuf t{ move cursor right the indicated # of columns. t} d cub t{ move cursor left the indicated # of columns. t} e cnl t{ move cursor down the indicated # of rows, to column 1. t} f cpl t{ move cursor up the indicated # of rows, to column 1. t} g cha t{ move cursor to indicated column in current row. t} h cup t{ move cursor to the indicated row, column (origin at 1,1). t} j ed t{ erase display (default: from cursor to end of display). t} t{ esc [ 1 j: erase from start to cursor. t} t{ esc [ 2 j: erase whole display. t} t{ esc [ 3 j: erase whole display including scroll-back buffer (since linux 3.0). t} .\" esc [ 3 j: commit f8df13e0a901fe55631fed66562369b4dba40f8b k el t{ erase line (default: from cursor to end of line). t} t{ esc [ 1 k: erase from start of line to cursor. t} t{ esc [ 2 k: erase whole line. t} l il t{ insert the indicated # of blank lines. t} m dl t{ delete the indicated # of lines. t} p dch t{ delete the indicated # of characters on current line. t} x ech t{ erase the indicated # of characters on current line. t} a hpr t{ move cursor right the indicated # of columns. t} c da t{ answer esc [ ? 6 c: "i am a vt102". t} d vpa t{ move cursor to the indicated row, current column. t} e vpr t{ move cursor down the indicated # of rows. t} f hvp t{ move cursor to the indicated row, column. t} g tbc t{ without parameter: clear tab stop at current position. t} t{ esc [ 3 g: delete all tab stops. t} h sm set mode (see below). l rm reset mode (see below). m sgr set attributes (see below). n dsr status report (see below). q decll set keyboard leds. esc [ 0 q: clear all leds esc [ 1 q: set scroll lock led esc [ 2 q: set num lock led esc [ 3 q: set caps lock led r decstbm t{ set scrolling region; parameters are top and bottom row. t} s ? save cursor location. u ? restore cursor location. \` hpa t{ move cursor to indicated column in current row. t} .te .ad .pp .b ecma-48 select graphic rendition .pp the ecma-48 sgr sequence esc [ \fiparameters\fp m sets display attributes. several attributes can be set in the same sequence, separated by semicolons. an empty parameter (between semicolons or string initiator or terminator) is interpreted as a zero. .ad l .ts l lx. param result 0 t{ reset all attributes to their defaults t} 1 set bold 2 t{ set half-bright (simulated with color on a color display) t} 4 t{ set underscore (simulated with color on a color display) (the colors used to simulate dim or underline are set using esc ] ...) t} 5 set blink 7 set reverse video 10 t{ reset selected mapping, display control flag, and toggle meta flag (ecma-48 says "primary font"). t} 11 t{ select null mapping, set display control flag, reset toggle meta flag (ecma-48 says "first alternate font"). t} 12 t{ select null mapping, set display control flag, set toggle meta flag (ecma-48 says "second alternate font"). the toggle meta flag causes the high bit of a byte to be toggled before the mapping table translation is done. t} 21 t{ set underline; before linux 4.17, this value set normal intensity (as is done in many other terminals) t} 22 set normal intensity 24 underline off 25 blink off 27 reverse video off 30 set black foreground 31 set red foreground 32 set green foreground 33 set brown foreground 34 set blue foreground 35 set magenta foreground 36 set cyan foreground 37 set white foreground 38 t{ 256/24-bit foreground color follows, shoehorned into 16 basic colors (before linux 3.16: set underscore on, set default foreground color) t} 39 t{ set default foreground color (before linux 3.16: set underscore off, set default foreground color) t} 40 set black background 41 set red background 42 set green background 43 set brown background 44 set blue background 45 set magenta background 46 set cyan background 47 set white background 48 t{ 256/24-bit background color follows, shoehorned into 8 basic colors t} 49 set default background color 90..97 t{ set foreground to bright versions of 30..37 t} 100.107 t{ set background, same as 40..47 (bright not supported) t} .te .ad .pp commands 38 and 48 require further arguments: .ts l lx. ;5;x t{ 256 color: values 0..15 are ibgr (black, red, green, ... white), 16..231 a 6x6x6 color cube, 232..255 a grayscale ramp t} ;2;r;g;b t{ 24-bit color, r/g/b components are in the range 0..255 t} .te .pp .b ecma-48 mode switches .tp esc [ 3 h deccrm (default off): display control chars. .tp esc [ 4 h decim (default off): set insert mode. .tp esc [ 20 h lf/nl (default off): automatically follow echo of lf, vt, or ff with cr. .\" .pp .b ecma-48 status report commands .\" .tp esc [ 5 n device status report (dsr): answer is esc [ 0 n (terminal ok). .tp esc [ 6 n cursor position report (cpr): answer is esc [ \fiy\fp ; \fix\fp r, where \fix,y\fp is the cursor location. .\" .pp .b dec private mode (decset/decrst) sequences .pp .\" these are not described in ecma-48. we list the set mode sequences; the reset mode sequences are obtained by replacing the final \(aqh\(aq by \(aql\(aq. .tp esc [ ? 1 h decckm (default off): when set, the cursor keys send an esc o prefix, rather than esc [. .tp esc [ ? 3 h deccolm (default off = 80 columns): 80/132 col mode switch. the driver sources note that this alone does not suffice; some user-mode utility such as .br resizecons (8) has to change the hardware registers on the console video card. .tp esc [ ? 5 h decscnm (default off): set reverse-video mode. .tp esc [ ? 6 h decom (default off): when set, cursor addressing is relative to the upper left corner of the scrolling region. .tp esc [ ? 7 h decawm (default on): set autowrap on. in this mode, a graphic character emitted after column 80 (or column 132 of deccolm is on) forces a wrap to the beginning of the following line first. .tp esc [ ? 8 h decarm (default on): set keyboard autorepeat on. .tp esc [ ? 9 h x10 mouse reporting (default off): set reporting mode to 1 (or reset to 0)\(emsee below. .tp esc [ ? 25 h dectecm (default on): make cursor visible. .tp esc [ ? 1000 h x11 mouse reporting (default off): set reporting mode to 2 (or reset to 0)\(emsee below. .\" .pp .b linux console private csi sequences .pp .\" the following sequences are neither ecma-48 nor native vt102. they are native to the linux console driver. colors are in sgr parameters: 0 = black, 1 = red, 2 = green, 3 = brown, 4 = blue, 5 = magenta, 6 = cyan, 7 = white; 8\(en15 = bright versions of 0\(en7. .ts l lx. esc [ 1 ; \fin\fp ] t{ set color \fin\fp as the underline color. t} esc [ 2 ; \fin\fp ] t{ set color \fin\fp as the dim color. t} esc [ 8 ] t{ make the current color pair the default attributes. t} esc [ 9 ; \fin\fp ] t{ set screen blank timeout to \fin\fp minutes. t} esc [ 10 ; \fin\fp ] t{ set bell frequency in hz. t} esc [ 11 ; \fin\fp ] t{ set bell duration in msec. t} esc [ 12 ; \fin\fp ] t{ bring specified console to the front. t} esc [ 13 ] t{ unblank the screen. t} esc [ 14 ; \fin\fp ] t{ set the vesa powerdown interval in minutes. t} esc [ 15 ] t{ bring the previous console to the front (since linux 2.6.0). t} esc [ 16 ; \fin\fp ] t{ set the cursor blink interval in milliseconds (since linux 4.2). t} .\" commit bd63364caa8df38bad2b25b11b2a1b849475cce5 .te .ss character sets the kernel knows about 4 translations of bytes into console-screen symbols. the four tables are: a) latin1 \-> pc, b) vt100 graphics \-> pc, c) pc \-> pc, d) user-defined. .pp there are two character sets, called g0 and g1, and one of them is the current character set. (initially g0.) typing \fb\(han\fp causes g1 to become current, \fb\(hao\fp causes g0 to become current. .pp these variables g0 and g1 point at a translation table, and can be changed by the user. initially they point at tables a) and b), respectively. the sequences esc ( b and esc ( 0 and esc ( u and esc ( k cause g0 to point at translation table a), b), c), and d), respectively. the sequences esc ) b and esc ) 0 and esc ) u and esc ) k cause g1 to point at translation table a), b), c), and d), respectively. .pp the sequence esc c causes a terminal reset, which is what you want if the screen is all garbled. the oft-advised "echo \(hav\(hao" will make only g0 current, but there is no guarantee that g0 points at table a). in some distributions there is a program .br reset (1) that just does "echo \(ha[c". if your terminfo entry for the console is correct (and has an entry rs1=\eec), then "tput reset" will also work. .pp the user-defined mapping table can be set using .br mapscrn (8). the result of the mapping is that if a symbol c is printed, the symbol s = map[c] is sent to the video memory. the bitmap that corresponds to s is found in the character rom, and can be changed using .br setfont (8). .ss mouse tracking the mouse tracking facility is intended to return .br xterm (1)-compatible mouse status reports. because the console driver has no way to know the device or type of the mouse, these reports are returned in the console input stream only when the virtual terminal driver receives a mouse update ioctl. these ioctls must be generated by a mouse-aware user-mode application such as the .br gpm (8) daemon. .pp the mouse tracking escape sequences generated by \fbxterm\fp(1) encode numeric parameters in a single character as \fivalue\fp+040. for example, \(aq!\(aq is 1. the screen coordinate system is 1-based. .pp the x10 compatibility mode sends an escape sequence on button press encoding the location and the mouse button pressed. it is enabled by sending esc [ ? 9 h and disabled with esc [ ? 9 l. on button press, \fbxterm\fp(1) sends esc [ m \fibxy\fp (6 characters). here \fib\fp is button\-1, and \fix\fp and \fiy\fp are the x and y coordinates of the mouse when the button was pressed. this is the same code the kernel also produces. .pp normal tracking mode (not implemented in linux 2.0.24) sends an escape sequence on both button press and release. modifier information is also sent. it is enabled by sending esc [ ? 1000 h and disabled with esc [ ? 1000 l. on button press or release, \fbxterm\fp(1) sends esc [ m \fibxy\fp. the low two bits of \fib\fp encode button information: 0=mb1 pressed, 1=mb2 pressed, 2=mb3 pressed, 3=release. the upper bits encode what modifiers were down when the button was pressed and are added together: 4=shift, 8=meta, 16=control. again \fix\fp and \fiy\fp are the x and y coordinates of the mouse event. the upper left corner is (1,1). .ss comparisons with other terminals many different terminal types are described, like the linux console, as being "vt100-compatible". here we discuss differences between the linux console and the two most important others, the dec vt102 and .br xterm (1). .\" .pp .b control-character handling .pp the vt102 also recognized the following control characters: .hp nul (0x00) was ignored; .hp enq (0x05) triggered an answerback message; .hp dc1 (0x11, \fb\(haq\fp, xon) resumed transmission; .hp dc3 (0x13, \fb\(has\fp, xoff) caused vt100 to ignore (and stop transmitting) all codes except xoff and xon. .pp vt100-like dc1/dc3 processing may be enabled by the terminal driver. .pp the .br xterm (1) program (in vt100 mode) recognizes the control characters bel, bs, ht, lf, vt, ff, cr, so, si, esc. .\" .pp .b escape sequences .pp vt100 console sequences not implemented on the linux console: .ts l l l. esc n ss2 t{ single shift 2. (select g2 character set for the next character only.) t} esc o ss3 t{ single shift 3. (select g3 character set for the next character only.) t} esc p dcs t{ device control string (ended by esc \e) t} esc x sos start of string. esc \(ha pm privacy message (ended by esc \e) esc \e st string terminator esc * ... designate g2 character set esc + ... designate g3 character set .te .pp the program .br xterm (1) (in vt100 mode) recognizes esc c, esc # 8, esc >, esc =, esc d, esc e, esc h, esc m, esc n, esc o, esc p ... esc \e, esc z (it answers esc [ ? 1 ; 2 c, "i am a vt100 with advanced video option") and esc \(ha ... esc \e with the same meanings as indicated above. it accepts esc (, esc ), esc *, esc + followed by 0, a, b for the dec special character and line drawing set, uk, and us-ascii, respectively. .pp the user can configure \fbxterm\fp(1) to respond to vt220-specific control sequences, and it will identify itself as a vt52, vt100, and up depending on the way it is configured and initialized. .pp it accepts esc ] (osc) for the setting of certain resources. in addition to the ecma-48 string terminator (st), \fbxterm\fp(1) accepts a bel to terminate an osc string. these are a few of the osc control sequences recognized by \fbxterm\fp(1): .ts l l. esc ] 0 ; \fitxt\fp st t{ set icon name and window title to \fitxt\fp. t} esc ] 1 ; \fitxt\fp st set icon name to \fitxt\fp. esc ] 2 ; \fitxt\fp st set window title to \fitxt\fp. esc ] 4 ; \finum\fp; \fitxt\fp st set ansi color \finum\fp to \fitxt\fp. esc ] 10 ; \fitxt\fp st set dynamic text color to \fitxt\fp. esc ] 4 6 ; \finame\fp st t{ change log file to \finame\fp (normally disabled by a compile-time option). t} esc ] 5 0 ; \fifn\fp st set font to \fifn\fp. .te .pp it recognizes the following with slightly modified meaning (saving more state, behaving closer to vt100/vt220): .ts l l l. esc 7 decsc save cursor esc 8 decrc restore cursor .te .pp it also recognizes .ts l l lx. esc f t{ cursor to lower left corner of screen (if enabled by \fbxterm\fp(1)'s \fbhplowerleftbugcompat\fp resource) t} esc l memory lock (per hp terminals). locks memory above the cursor. esc m memory unlock (per hp terminals). esc n ls2 invoke the g2 character set. esc o ls3 invoke the g3 character set. esc | ls3r invoke the g3 character set as gr. esc } ls2r invoke the g2 character set as gr. esc \(ti ls1r invoke the g1 character set as gr. .te .pp it also recognizes esc % and provides a more complete utf-8 implementation than linux console. .\" .pp .b csi sequences .pp old versions of \fbxterm\fp(1), for example, from x11r5, interpret the blink sgr as a bold sgr. later versions which implemented ansi colors, for example, xfree86 3.1.2a in 1995, improved this by allowing the blink attribute to be displayed as a color. modern versions of xterm implement blink sgr as blinking text and still allow colored text as an alternate rendering of sgrs. stock x11r6 versions did not recognize the color-setting sgrs until the x11r6.8 release, which incorporated xfree86 xterm. all ecma-48 csi sequences recognized by linux are also recognized by .ir xterm , however \fbxterm\fp(1) implements several ecma-48 and dec control sequences not recognized by linux. .pp the \fbxterm\fp(1) program recognizes all of the dec private mode sequences listed above, but none of the linux private-mode sequences. for discussion of \fbxterm\fp(1)'s own private-mode sequences, refer to the \fixterm control sequences\fp document by edward moy, stephen gildea, and thomas e.\& dickey available with the x distribution. that document, though terse, is much longer than this manual page. for a chronological overview, .pp .rs .ur http://invisible\-island.net\:/xterm\:/xterm.log.html .ue .re .pp details changes to xterm. .pp the \fivttest\fp program .pp .rs .ur http://invisible\-island.net\:/vttest/ .ue .re .pp demonstrates many of these control sequences. the \fbxterm\fp(1) source distribution also contains sample scripts which exercise other features. .sh notes esc 8 (decrc) is not able to restore the character set changed with esc %. .sh bugs in 2.0.23, csi is broken, and nul is not ignored inside escape sequences. .pp some older kernel versions (after 2.0) interpret 8-bit control sequences. these "c1 controls" use codes between 128 and 159 to replace esc [, esc ] and similar two-byte control sequence initiators. there are fragments of that in modern kernels (either overlooked or broken by changes to support utf-8), but the implementation is incomplete and should be regarded as unreliable. .pp linux "private mode" sequences do not follow the rules in ecma-48 for private mode control sequences. in particular, those ending with ] do not use a standard terminating character. the osc (set palette) sequence is a greater problem, since \fbxterm\fp(1) may interpret this as a control sequence which requires a string terminator (st). unlike the \fbsetterm\fp(1) sequences which will be ignored (since they are invalid control sequences), the palette sequence will make \fbxterm\fp(1) appear to hang (though pressing the return-key will fix that). to accommodate applications which have been hardcoded to use linux control sequences, set the \fbxterm\fp(1) resource \fbbrokenlinuxosc\fp to true. .pp an older version of this document implied that linux recognizes the ecma-48 control sequence for invisible text. it is ignored. .sh see also .br ioctl_console (2), .br charsets (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016, michael kerrisk .\" based on an earlier version of the page where a few pieces were .\" copyright (c) 1993 by dan miner (dminer@nyx.cs.du.edu) and subsequently .\" others (see old changelog below). .\" the structure definitions are taken more or less straight from the kernel .\" source files. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .\" modified sat jul 24 12:35:12 1993 by rik faith .\" modified tue oct 22 22:29:51 1996 by eric s. raymond .\" modified mon aug 25 16:06:11 1997 by nicolás lichtmaier .\" .th sysinfo 2 2021-03-22 "linux" "linux programmer's manual" .sh name sysinfo \- return system information .sh synopsis .nf .b #include .pp .bi "int sysinfo(struct sysinfo *" info ); .fi .sh description .br sysinfo () returns certain statistics on memory and swap usage, as well as the load average. .pp until linux 2.3.16, .br sysinfo () returned information in the following structure: .pp .in +4n .ex struct sysinfo { long uptime; /* seconds since boot */ unsigned long loads[3]; /* 1, 5, and 15 minute load averages */ unsigned long totalram; /* total usable main memory size */ unsigned long freeram; /* available memory size */ unsigned long sharedram; /* amount of shared memory */ unsigned long bufferram; /* memory used by buffers */ unsigned long totalswap; /* total swap space size */ unsigned long freeswap; /* swap space still available */ unsigned short procs; /* number of current processes */ char _f[22]; /* pads structure to 64 bytes */ }; .ee .in .pp in the above structure, the sizes of the memory and swap fields are given in bytes. .pp since linux 2.3.23 (i386) and linux 2.3.48 (all architectures) the structure is: .pp .in +4n .ex struct sysinfo { long uptime; /* seconds since boot */ unsigned long loads[3]; /* 1, 5, and 15 minute load averages */ unsigned long totalram; /* total usable main memory size */ unsigned long freeram; /* available memory size */ unsigned long sharedram; /* amount of shared memory */ unsigned long bufferram; /* memory used by buffers */ unsigned long totalswap; /* total swap space size */ unsigned long freeswap; /* swap space still available */ unsigned short procs; /* number of current processes */ unsigned long totalhigh; /* total high memory size */ unsigned long freehigh; /* available high memory size */ unsigned int mem_unit; /* memory unit size in bytes */ char _f[20\-2*sizeof(long)\-sizeof(int)]; /* padding to 64 bytes */ }; .ee .in .pp in the above structure, sizes of the memory and swap fields are given as multiples of .i mem_unit bytes. .sh return value on success, .br sysinfo () returns zero. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .ir info is not a valid address. .sh versions .br sysinfo () first appeared in linux 0.98.pl6. .sh conforming to this function is linux-specific, and should not be used in programs intended to be portable. .sh notes all of the information provided by this system call is also available via .ir /proc/meminfo and .ir /proc/loadavg . .sh see also .br proc (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms(walter.harms@informatik.uni-oldenburg.de) .\" and copyright (c) 2011 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cacosh 3 2021-03-22 "" "linux programmer's manual" .sh name cacosh, cacoshf, cacoshl \- complex arc hyperbolic cosine .sh synopsis .nf .b #include .pp .bi "double complex cacosh(double complex " z ); .bi "float complex cacoshf(float complex " z ); .bi "long double complex cacoshl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex arc hyperbolic cosine of .ir z . if \fiy\ =\ cacosh(z)\fp, then \fiz\ =\ ccosh(y)\fp. the imaginary part of .i y is chosen in the interval [\-pi,pi]. the real part of .i y is chosen nonnegative. .pp one has: .pp .nf cacosh(z) = 2 * clog(csqrt((z + 1) / 2) + csqrt((z \- 1) / 2)) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cacosh (), .br cacoshf (), .br cacoshl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh examples .ex /* link with "\-lm" */ #include #include #include #include int main(int argc, char *argv[]) { double complex z, c, f; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } z = atof(argv[1]) + atof(argv[2]) * i; c = cacosh(z); printf("cacosh() = %6.3f %6.3f*i\en", creal(c), cimag(c)); f = 2 * clog(csqrt((z + 1)/2) + csqrt((z \- 1)/2)); printf("formula = %6.3f %6.3f*i\en", creal(f2), cimag(f2)); exit(exit_success); } .ee .sh see also .br acosh (3), .br cabs (3), .br ccosh (3), .br cimag (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cimag.3 .so man3/fgetc.3 .\" copyright (c) 2017 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th ioctl_iflags 2 2019-11-19 "linux" "linux programmer's manual" .sh name ioctl_iflags \- ioctl() operations for inode flags .sh description various linux filesystems support the notion of .ir "inode flags" \(emattributes that modify the semantics of files and directories. these flags can be retrieved and modified using two .br ioctl (2) operations: .pp .in +4n .ex int attr; fd = open("pathname", ...); ioctl(fd, fs_ioc_getflags, &attr); /* place current flags in \(aqattr\(aq */ attr |= fs_noatime_fl; /* tweak returned bit mask */ ioctl(fd, fs_ioc_setflags, &attr); /* update flags for inode referred to by \(aqfd\(aq */ .ee .in .pp the .br lsattr (1) and .br chattr (1) shell commands provide interfaces to these two operations, allowing a user to view and modify the inode flags associated with a file. .pp the following flags are supported (shown along with the corresponding letter used to indicate the flag by .br lsattr (1) and .br chattr (1)): .tp .br fs_append_fl " \(aqa\(aq" the file can be opened only with the .b o_append flag. (this restriction applies even to the superuser.) only a privileged process .rb ( cap_linux_immutable ) can set or clear this attribute. .tp .br fs_compr_fl " \(aqc\(aq" store the file in a compressed format on disk. this flag is .i not supported by most of the mainstream filesystem implementations; one exception is .br btrfs (5). .tp .br fs_dirsync_fl " \(aqd\(aq (since linux 2.6.0)" write directory changes synchronously to disk. this flag provides semantics equivalent to the .br mount (2) .b ms_dirsync option, but on a per-directory basis. this flag can be applied only to directories. .\" .tp .\" .br fs_extent_fl " \(aqe\(aq" .\" fixme some support on ext4? (ext4_extents_fl) .tp .br fs_immutable_fl " \(aqi\(aq" the file is immutable: no changes are permitted to the file contents or metadata (permissions, timestamps, ownership, link count, and so on). (this restriction applies even to the superuser.) only a privileged process .rb ( cap_linux_immutable ) can set or clear this attribute. .tp .br fs_journal_data_fl " \(aqj\(aq" enable journaling of file data on .br ext3 (5) and .br ext4 (5) filesystems. on a filesystem that is journaling in .i ordered or .i writeback mode, a privileged .rb ( cap_sys_resource ) process can set this flag to enable journaling of data updates on a per-file basis. .tp .br fs_noatime_fl " \(aqa\(aq" don't update the file last access time when the file is accessed. this can provide i/o performance benefits for applications that do not care about the accuracy of this timestamp. this flag provides functionality similar to the .br mount (2) .br ms_noatime flag, but on a per-file basis. .\" .tp .\" .br fs_nocomp_fl " \(aq\(aq" .\" fixme support for fs_nocomp_fl on btrfs? .tp .br fs_nocow_fl " \(aqc\(aq (since linux 2.6.39)" the file will not be subject to copy-on-write updates. this flag has an effect only on filesystems that support copy-on-write semantics, such as btrfs. see .br chattr (1) and .br btrfs (5). .tp .br fs_nodump_fl " \(aqd\(aq" don't include this file in backups made using .br dump (8). .tp .br fs_notail_fl " \(aqt\(aq" this flag is supported only on reiserfs. it disables the reiserfs tail-packing feature, which tries to pack small files (and the final fragment of larger files) into the same disk block as the file metadata. .tp .br fs_projinherit_fl " \(aqp\(aq (since linux 4.5)" .\" commit 040cb3786d9b25293b8b0b05b90da0f871e1eb9b .\" flag name was added in linux 4.4 .\" fixme not currently supported because not in fs_fl_user_modifiable? inherit the quota project id. files and subdirectories will inherit the project id of the directory. this flag can be applied only to directories. .tp .br fs_secrm_fl " \(aqs\(aq" mark the file for secure deletion. this feature is not implemented by any filesystem, since the task of securely erasing a file from a recording medium is surprisingly difficult. .tp .br fs_sync_fl " \(aqs\(aq" make file updates synchronous. for files, this makes all writes synchronous (as though all opens of the file were with the .br o_sync flag). for directories, this has the same effect as the .br fs_dirsync_fl flag. .tp .br fs_topdir_fl " \(aqt\(aq" mark a directory for special treatment under the orlov block-allocation strategy. see .br chattr (1) for details. this flag can be applied only to directories and has an effect only for ext2, ext3, and ext4. .tp .br fs_unrm_fl " \(aqu\(aq" allow the file to be undeleted if it is deleted. this feature is not implemented by any filesystem, since it is possible to implement file-recovery mechanisms outside the kernel. .pp in most cases, when any of the above flags is set on a directory, the flag is inherited by files and subdirectories created inside that directory. exceptions include .br fs_topdir_fl , which is not inheritable, and .br fs_dirsync_fl , which is inherited only by subdirectories. .sh conforming to inode flags are a nonstandard linux extension. .sh notes in order to change the inode flags of a file using the .br fs_ioc_setflags operation, the effective user id of the caller must match the owner of the file, or the caller must have the .br cap_fowner capability. .pp the type of the argument given to the .br fs_ioc_getflags and .br fs_ioc_setflags operations is .ir "int\ *" , notwithstanding the implication in the kernel source file .i include/uapi/linux/fs.h that the argument is .ir "long\ *" . .sh see also .br chattr (1), .br lsattr (1), .br mount (2), .br btrfs (5), .br ext4 (5), .br xfs (5), .br xattr (7), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/xdr.3 .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" .\" %%%license_start(bsd_oneline_cdrom) .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) .\" %%%license_end .\" .\" @(#)rpc.3n 2.4 88/08/08 4.0 rpcsrc; from 1.19 88/06/24 smi .\" .\" 2007-12-30, mtk, convert function prototypes to modern c syntax .\" .th rpc 3 2021-03-22 "" "linux programmer's manual" .sh name rpc \- library routines for remote procedure calls .sh synopsis and description these routines allow c programs to make procedure calls on other machines across the network. first, the client calls a procedure to send a data packet to the server. upon receipt of the packet, the server calls a dispatch routine to perform the requested service, and then sends back a reply. finally, the procedure call returns to the client. .\" .lp .\" we don't have an rpc_secure.3 page at the moment -- mtk, 19 sep 05 .\" routines that are used for secure rpc (des authentication) are described in .\" .br rpc_secure (3). .\" secure rpc can be used only if des encryption is available. .pp to take use of these routines, include the header file .ir "" . .pp the prototypes below make use of the following types: .pp .rs 4 .ex .bi "typedef int " bool_t ; .pp .bi "typedef bool_t (*" xdrproc_t ")(xdr *, void *, ...);" .pp .bi "typedef bool_t (*" resultproc_t ")(caddr_t " resp , .bi " struct sockaddr_in *" raddr ); .ee .re .pp see the header files for the declarations of the .ir auth , .ir client , .ir svcxprt , and .ir xdr types. .pp .nf .bi "void auth_destroy(auth *" auth ); .fi .ip a macro that destroys the authentication information associated with .ir auth . destruction usually involves deallocation of private data structures. the use of .i auth is undefined after calling .br auth_destroy (). .pp .nf .bi "auth *authnone_create(void);" .fi .ip create and return an rpc authentication handle that passes nonusable authentication information with each remote procedure call. this is the default authentication used by rpc. .pp .nf .bi "auth *authunix_create(char *" host ", uid_t " uid ", gid_t " gid , .bi " int " len ", gid_t *" aup_gids ); .fi .ip create and return an rpc authentication handle that contains authentication information. the parameter .i host is the name of the machine on which the information was created; .i uid is the user's user id; .i gid is the user's current group id; .i len and .i aup_gids refer to a counted array of groups to which the user belongs. it is easy to impersonate a user. .pp .nf .bi "auth *authunix_create_default(void);" .fi .ip calls .br authunix_create () with the appropriate parameters. .pp .nf .bi "int callrpc(char *" host ", unsigned long " prognum , .bi " unsigned long " versnum ", unsigned long " procnum , .bi " xdrproc_t " inproc ", const char *" in , .bi " xdrproc_t " outproc ", char *" out ); .fi .ip call the remote procedure associated with .ir prognum , .ir versnum , and .i procnum on the machine, .ir host . the parameter .i in is the address of the procedure's argument(s), and .i out is the address of where to place the result(s); .i inproc is used to encode the procedure's parameters, and .i outproc is used to decode the procedure's results. this routine returns zero if it succeeds, or the value of .b "enum clnt_stat" cast to an integer if it fails. the routine .br clnt_perrno () is handy for translating failure statuses into messages. .ip warning: calling remote procedures with this routine uses udp/ip as a transport; see .br clntudp_create () for restrictions. you do not have control of timeouts or authentication using this routine. .pp .nf .bi "enum clnt_stat clnt_broadcast(unsigned long " prognum , .bi " unsigned long " versnum ", unsigned long " procnum , .bi " xdrproc_t " inproc ", char *" in , .bi " xdrproc_t " outproc ", char *" out , .bi " resultproc_t " eachresult ); .fi .ip like .br callrpc (), except the call message is broadcast to all locally connected broadcast nets. each time it receives a response, this routine calls .br eachresult (), whose form is: .ip .in +4n .ex .bi "eachresult(char *" out ", struct sockaddr_in *" addr ); .ee .in .ip where .i out is the same as .i out passed to .br clnt_broadcast (), except that the remote procedure's output is decoded there; .i addr points to the address of the machine that sent the results. if .br eachresult () returns zero, .br clnt_broadcast () waits for more replies; otherwise it returns with appropriate status. .ip warning: broadcast sockets are limited in size to the maximum transfer unit of the data link. for ethernet, this value is 1500 bytes. .pp .nf .bi "enum clnt_stat clnt_call(client *" clnt ", unsigned long " procnum , .bi " xdrproc_t " inproc ", char *" in , .bi " xdrproc_t " outproc ", char *" out , .bi " struct timeval " tout ); .fi .ip a macro that calls the remote procedure .i procnum associated with the client handle, .ir clnt , which is obtained with an rpc client creation routine such as .br clnt_create (). the parameter .i in is the address of the procedure's argument(s), and .i out is the address of where to place the result(s); .i inproc is used to encode the procedure's parameters, and .i outproc is used to decode the procedure's results; .i tout is the time allowed for results to come back. .pp .nf .bi "clnt_destroy(client *" clnt ); .fi .ip a macro that destroys the client's rpc handle. destruction usually involves deallocation of private data structures, including .i clnt itself. use of .i clnt is undefined after calling .br clnt_destroy (). if the rpc library opened the associated socket, it will close it also. otherwise, the socket remains open. .pp .nf .bi "client *clnt_create(const char *" host ", unsigned long " prog , .bi " unsigned long " vers ", const char *" proto ); .fi .ip generic client creation routine. .i host identifies the name of the remote host where the server is located. .i proto indicates which kind of transport protocol to use. the currently supported values for this field are \(lqudp\(rq and \(lqtcp\(rq. default timeouts are set, but can be modified using .br clnt_control (). .ip warning: using udp has its shortcomings. since udp-based rpc messages can hold only up to 8 kbytes of encoded data, this transport cannot be used for procedures that take large arguments or return huge results. .pp .nf .bi "bool_t clnt_control(client *" cl ", int " req ", char *" info ); .fi .ip a macro used to change or retrieve various information about a client object. .i req indicates the type of operation, and .i info is a pointer to the information. for both udp and tcp, the supported values of .i req and their argument types and what they do are: .ip .in +4n .ex \fbclset_timeout\fp \fistruct timeval\fp // set total timeout \fbclget_timeout\fp \fistruct timeval\fp // get total timeout .ee .in .ip note: if you set the timeout using .br clnt_control (), the timeout parameter passed to .br clnt_call () will be ignored in all future calls. .ip .in +4n .ex \fbclget_server_addr\fp \fistruct sockaddr_in\fp // get server\(aqs address .ee .in .ip the following operations are valid for udp only: .ip .in +4n .ex \fbclset_retry_timeout\fp \fistruct timeval\fp // set the retry timeout \fbclget_retry_timeout\fp \fistruct timeval\fp // get the retry timeout .ee .in .ip the retry timeout is the time that "udp rpc" waits for the server to reply before retransmitting the request. .pp .nf .bi "clnt_freeres(client * " clnt ", xdrproc_t " outproc ", char *" out ); .fi .ip a macro that frees any data allocated by the rpc/xdr system when it decoded the results of an rpc call. the parameter .i out is the address of the results, and .i outproc is the xdr routine describing the results. this routine returns one if the results were successfully freed, and zero otherwise. .pp .nf .bi "void clnt_geterr(client *" clnt ", struct rpc_err *" errp ); .fi .ip a macro that copies the error structure out of the client handle to the structure at address .ir errp . .pp .nf .bi "void clnt_pcreateerror(const char *" s ); .fi .ip print a message to standard error indicating why a client rpc handle could not be created. the message is prepended with string .i s and a colon. used when a .br clnt_create (), .br clntraw_create (), .br clnttcp_create (), or .br clntudp_create () call fails. .pp .nf .bi "void clnt_perrno(enum clnt_stat " stat ); .fi .ip print a message to standard error corresponding to the condition indicated by .ir stat . used after .br callrpc (). .pp .nf .bi "clnt_perror(client *" clnt ", const char *" s ); .fi .ip print a message to standard error indicating why an rpc call failed; .i clnt is the handle used to do the call. the message is prepended with string .i s and a colon. used after .br clnt_call (). .pp .nf .bi "char *clnt_spcreateerror(const char *" s ); .fi .ip like .br clnt_pcreateerror (), except that it returns a string instead of printing to the standard error. .ip bugs: returns pointer to static data that is overwritten on each call. .pp .nf .bi "char *clnt_sperrno(enum clnt_stat " stat ); .fi .ip take the same arguments as .br clnt_perrno (), but instead of sending a message to the standard error indicating why an rpc call failed, return a pointer to a string which contains the message. the string ends with a newline. .ip .br clnt_sperrno () is used instead of .br clnt_perrno () if the program does not have a standard error (as a program running as a server quite likely does not), or if the programmer does not want the message to be output with .br printf (3), or if a message format different than that supported by .br clnt_perrno () is to be used. note: unlike .br clnt_sperror () and .br clnt_spcreateerror (), .br clnt_sperrno () returns pointer to static data, but the result will not get overwritten on each call. .pp .nf .bi "char *clnt_sperror(client *" rpch ", const char *" s ); .fi .ip like .br clnt_perror (), except that (like .br clnt_sperrno ()) it returns a string instead of printing to standard error. .ip bugs: returns pointer to static data that is overwritten on each call. .pp .nf .bi "client *clntraw_create(unsigned long " prognum \ ", unsigned long " versnum ); .fi .ip this routine creates a toy rpc client for the remote program .ir prognum , version .ir versnum . the transport used to pass messages to the service is actually a buffer within the process's address space, so the corresponding rpc server should live in the same address space; see .br svcraw_create (). this allows simulation of rpc and acquisition of rpc overheads, such as round trip times, without any kernel interference. this routine returns null if it fails. .pp .nf .bi "client *clnttcp_create(struct sockaddr_in *" addr , .bi " unsigned long " prognum ", unsigned long " versnum , .bi " int *" sockp ", unsigned int " sendsz \ ", unsigned int " recvsz ); .fi .ip this routine creates an rpc client for the remote program .ir prognum , version .ir versnum ; the client uses tcp/ip as a transport. the remote program is located at internet address .ir *addr . if .\"the following inline font conversion is necessary for the hyphen indicator .i addr\->sin_port is zero, then it is set to the actual port that the remote program is listening on (the remote .b portmap service is consulted for this information). the parameter .i sockp is a socket; if it is .br rpc_anysock , then this routine opens a new one and sets .ir sockp . since tcp-based rpc uses buffered i/o, the user may specify the size of the send and receive buffers with the parameters .i sendsz and .ir recvsz ; values of zero choose suitable defaults. this routine returns null if it fails. .pp .nf .bi "client *clntudp_create(struct sockaddr_in *" addr , .bi " unsigned long " prognum ", unsigned long " versnum , .bi " struct timeval " wait ", int *" sockp ); .fi .ip this routine creates an rpc client for the remote program .ir prognum , version .ir versnum ; the client uses use udp/ip as a transport. the remote program is located at internet address .ir addr . if .i addr\->sin_port is zero, then it is set to actual port that the remote program is listening on (the remote .b portmap service is consulted for this information). the parameter .i sockp is a socket; if it is .br rpc_anysock , then this routine opens a new one and sets .ir sockp . the udp transport resends the call message in intervals of .i wait time until a response is received or until the call times out. the total time for the call to time out is specified by .br clnt_call (). .ip warning: since udp-based rpc messages can hold only up to 8 kbytes of encoded data, this transport cannot be used for procedures that take large arguments or return huge results. .pp .nf .bi "client *clntudp_bufcreate(struct sockaddr_in *" addr , .bi " unsigned long " prognum ", unsigned long " versnum , .bi " struct timeval " wait ", int *" sockp , .bi " unsigned int " sendsize ", unsigned int "recosize ); .fi .ip this routine creates an rpc client for the remote program .ir prognum , on .ir versnum ; the client uses use udp/ip as a transport. the remote program is located at internet address .ir addr . if .i addr\->sin_port is zero, then it is set to actual port that the remote program is listening on (the remote .b portmap service is consulted for this information). the parameter .i sockp is a socket; if it is .br rpc_anysock , then this routine opens a new one and sets .ir sockp . the udp transport resends the call message in intervals of .i wait time until a response is received or until the call times out. the total time for the call to time out is specified by .br clnt_call (). .ip this allows the user to specify the maximum packet size for sending and receiving udp-based rpc messages. .pp .nf .bi "void get_myaddress(struct sockaddr_in *" addr ); .fi .ip stuff the machine's ip address into .ir *addr , without consulting the library routines that deal with .ir /etc/hosts . the port number is always set to .br htons(pmapport) . .pp .nf .bi "struct pmaplist *pmap_getmaps(struct sockaddr_in *" addr ); .fi .ip a user interface to the .b portmap service, which returns a list of the current rpc program-to-port mappings on the host located at ip address .ir *addr . this routine can return null. the command .ir "rpcinfo\ \-p" uses this routine. .pp .nf .bi "unsigned short pmap_getport(struct sockaddr_in *" addr , .bi " unsigned long " prognum ", unsigned long " versnum , .bi " unsigned int " protocol ); .fi .ip a user interface to the .b portmap service, which returns the port number on which waits a service that supports program number .ir prognum , version .ir versnum , and speaks the transport protocol associated with .ir protocol . the value of .i protocol is most likely .b ipproto_udp or .br ipproto_tcp . a return value of zero means that the mapping does not exist or that the rpc system failed to contact the remote .b portmap service. in the latter case, the global variable .i rpc_createerr contains the rpc status. .pp .nf .bi "enum clnt_stat pmap_rmtcall(struct sockaddr_in *" addr , .bi " unsigned long " prognum ", unsigned long " versnum , .bi " unsigned long " procnum , .bi " xdrproc_t " inproc ", char *" in , .bi " xdrproc_t " outproc ", char *" out , .bi " struct timeval " tout ", unsigned long *" portp ); .fi .ip a user interface to the .b portmap service, which instructs .b portmap on the host at ip address .i *addr to make an rpc call on your behalf to a procedure on that host. the parameter .i *portp will be modified to the program's port number if the procedure succeeds. the definitions of other parameters are discussed in .br callrpc () and .br clnt_call (). this procedure should be used for a \(lqping\(rq and nothing else. see also .br clnt_broadcast (). .pp .nf .bi "bool_t pmap_set(unsigned long " prognum ", unsigned long " versnum , .bi " int " protocol ", unsigned short " port ); .fi .ip a user interface to the .b portmap service, which establishes a mapping between the triple .ri [ prognum , versnum , protocol ] and .i port on the machine's .b portmap service. the value of .i protocol is most likely .b ipproto_udp or .br ipproto_tcp . this routine returns one if it succeeds, zero otherwise. automatically done by .br svc_register (). .pp .nf .bi "bool_t pmap_unset(unsigned long " prognum ", unsigned long " versnum ); .fi .ip a user interface to the .b portmap service, which destroys all mapping between the triple .ri [ prognum , versnum , * ] and .b ports on the machine's .b portmap service. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "int registerrpc(unsigned long " prognum ", unsigned long " versnum , .bi " unsigned long " procnum ", char *(*" procname ")(char *)," .bi " xdrproc_t " inproc ", xdrproc_t " outproc ); .fi .ip register procedure .i procname with the rpc service package. if a request arrives for program .ir prognum , version .ir versnum , and procedure .ir procnum , .i procname is called with a pointer to its parameter(s); .i procname should return a pointer to its static result(s); .i inproc is used to decode the parameters while .i outproc is used to encode the results. this routine returns zero if the registration succeeded, \-1 otherwise. .ip warning: remote procedures registered in this form are accessed using the udp/ip transport; see .br svcudp_create () for restrictions. .pp .nf .bi "struct rpc_createerr " rpc_createerr ; .fi .ip a global variable whose value is set by any rpc client creation routine that does not succeed. use the routine .br clnt_pcreateerror () to print the reason why. .pp .nf .bi "void svc_destroy(svcxprt *" xprt ); .fi .ip a macro that destroys the rpc service transport handle, .ir xprt . destruction usually involves deallocation of private data structures, including .i xprt itself. use of .i xprt is undefined after calling this routine. .pp .nf .bi "fd_set " svc_fdset ; .fi .ip a global variable reflecting the rpc service side's read file descriptor bit mask; it is suitable as a parameter to the .br select (2) system call. this is of interest only if a service implementor does their own asynchronous event processing, instead of calling .br svc_run (). this variable is read-only (do not pass its address to .br select (2)!), yet it may change after calls to .br svc_getreqset () or any creation routines. .pp .nf .bi "int " svc_fds ; .fi .ip similar to .br svc_fdset , but limited to 32 file descriptors. this interface is obsoleted by .br svc_fdset . .pp .nf .bi "svc_freeargs(svcxprt *" xprt ", xdrproc_t " inproc ", char *" in ); .fi .ip a macro that frees any data allocated by the rpc/xdr system when it decoded the arguments to a service procedure using .br svc_getargs (). this routine returns 1 if the results were successfully freed, and zero otherwise. .pp .nf .bi "svc_getargs(svcxprt *" xprt ", xdrproc_t " inproc ", char *" in ); .fi .ip a macro that decodes the arguments of an rpc request associated with the rpc service transport handle, .ir xprt . the parameter .i in is the address where the arguments will be placed; .i inproc is the xdr routine used to decode the arguments. this routine returns one if decoding succeeds, and zero otherwise. .pp .nf .bi "struct sockaddr_in *svc_getcaller(svcxprt *" xprt ); .fi .ip the approved way of getting the network address of the caller of a procedure associated with the rpc service transport handle, .ir xprt . .pp .nf .bi "void svc_getreqset(fd_set *" rdfds ); .fi .ip this routine is of interest only if a service implementor does not call .br svc_run (), but instead implements custom asynchronous event processing. it is called when the .br select (2) system call has determined that an rpc request has arrived on some rpc socket(s); .i rdfds is the resultant read file descriptor bit mask. the routine returns when all sockets associated with the value of .i rdfds have been serviced. .pp .nf .bi "void svc_getreq(int " rdfds ); .fi .ip similar to .br svc_getreqset (), but limited to 32 file descriptors. this interface is obsoleted by .br svc_getreqset (). .pp .nf .bi "bool_t svc_register(svcxprt *" xprt ", unsigned long " prognum , .bi " unsigned long " versnum , .bi " void (*" dispatch ")(struct svc_req *, svcxprt *)," .bi " unsigned long " protocol ); .fi .ip associates .i prognum and .i versnum with the service dispatch procedure, .ir dispatch . if .i protocol is zero, the service is not registered with the .b portmap service. if .i protocol is nonzero, then a mapping of the triple .ri [ prognum , versnum , protocol ] to .i xprt\->xp_port is established with the local .b portmap service (generally .i protocol is zero, .b ipproto_udp or .br ipproto_tcp ). the procedure .i dispatch has the following form: .ip .in +4n .ex dispatch(struct svc_req *request, svcxprt *xprt); .ee .in .ip the .br svc_register () routine returns one if it succeeds, and zero otherwise. .pp .nf .b "void svc_run(void);" .fi .ip this routine never returns. it waits for rpc requests to arrive, and calls the appropriate service procedure using .br svc_getreq () when one arrives. this procedure is usually waiting for a .br select (2) system call to return. .pp .nf .bi "bool_t svc_sendreply(svcxprt *" xprt ", xdrproc_t " outproc \ ", char *" out ); .fi .ip called by an rpc service's dispatch routine to send the results of a remote procedure call. the parameter .i xprt is the request's associated transport handle; .i outproc is the xdr routine which is used to encode the results; and .i out is the address of the results. this routine returns one if it succeeds, zero otherwise. .pp .nf .bi "void svc_unregister(unsigned long " prognum ", unsigned long " versnum ); .fi .ip remove all mapping of the double .ri [ prognum , versnum ] to dispatch routines, and of the triple .ri [ prognum , versnum , * ] to port number. .pp .nf .bi "void svcerr_auth(svcxprt *" xprt ", enum auth_stat " why ); .fi .ip called by a service dispatch routine that refuses to perform a remote procedure call due to an authentication error. .pp .nf .bi "void svcerr_decode(svcxprt *" xprt ); .fi .ip called by a service dispatch routine that cannot successfully decode its parameters. see also .br svc_getargs (). .pp .nf .bi "void svcerr_noproc(svcxprt *" xprt ); .fi .ip called by a service dispatch routine that does not implement the procedure number that the caller requests. .pp .nf .bi "void svcerr_noprog(svcxprt *" xprt ); .fi .ip called when the desired program is not registered with the rpc package. service implementors usually do not need this routine. .pp .nf .bi "void svcerr_progvers(svcxprt *" xprt ", unsigned long " low_vers , .bi " unsigned long " high_vers ); .fi .ip called when the desired version of a program is not registered with the rpc package. service implementors usually do not need this routine. .pp .nf .bi "void svcerr_systemerr(svcxprt *" xprt ); .fi .ip called by a service dispatch routine when it detects a system error not covered by any particular protocol. for example, if a service can no longer allocate storage, it may call this routine. .pp .nf .bi "void svcerr_weakauth(svcxprt *" xprt ); .fi .ip called by a service dispatch routine that refuses to perform a remote procedure call due to insufficient authentication parameters. the routine calls .br "svcerr_auth(xprt, auth_tooweak)" . .pp .nf .bi "svcxprt *svcfd_create(int " fd ", unsigned int " sendsize , .bi " unsigned int " recvsize ); .fi .ip create a service on top of any open file descriptor. typically, this file descriptor is a connected socket for a stream protocol such as tcp. .i sendsize and .i recvsize indicate sizes for the send and receive buffers. if they are zero, a reasonable default is chosen. .pp .nf .bi "svcxprt *svcraw_create(void);" .fi .ip this routine creates a toy rpc service transport, to which it returns a pointer. the transport is really a buffer within the process's address space, so the corresponding rpc client should live in the same address space; see .br clntraw_create (). this routine allows simulation of rpc and acquisition of rpc overheads (such as round trip times), without any kernel interference. this routine returns null if it fails. .pp .nf .bi "svcxprt *svctcp_create(int " sock ", unsigned int " send_buf_size , .bi " unsigned int " recv_buf_size ); .fi .ip this routine creates a tcp/ip-based rpc service transport, to which it returns a pointer. the transport is associated with the socket .ir sock , which may be .br rpc_anysock , in which case a new socket is created. if the socket is not bound to a local tcp port, then this routine binds it to an arbitrary port. upon completion, .i xprt\->xp_sock is the transport's socket descriptor, and .i xprt\->xp_port is the transport's port number. this routine returns null if it fails. since tcp-based rpc uses buffered i/o, users may specify the size of buffers; values of zero choose suitable defaults. .pp .nf .bi "svcxprt *svcudp_bufcreate(int " sock ", unsigned int " sendsize , .bi " unsigned int " recosize ); .fi .ip this routine creates a udp/ip-based rpc service transport, to which it returns a pointer. the transport is associated with the socket .ir sock , which may be .br rpc_anysock , in which case a new socket is created. if the socket is not bound to a local udp port, then this routine binds it to an arbitrary port. upon completion, .i xprt\->xp_sock is the transport's socket descriptor, and .i xprt\->xp_port is the transport's port number. this routine returns null if it fails. .ip this allows the user to specify the maximum packet size for sending and receiving udp-based rpc messages. .pp .nf .bi "svcxprt *svcudp_create(int " sock ); .fi .ip this call is equivalent to .i svcudp_bufcreate(sock,sz,sz) for some default size .ir sz . .pp .nf .bi "bool_t xdr_accepted_reply(xdr *" xdrs ", struct accepted_reply *" ar ); .fi .ip used for encoding rpc reply messages. this routine is useful for users who wish to generate rpc-style messages without using the rpc package. .pp .nf .bi "bool_t xdr_authunix_parms(xdr *" xdrs ", struct authunix_parms *" aupp ); .fi .ip used for describing unix credentials. this routine is useful for users who wish to generate these credentials without using the rpc authentication package. .pp .nf .bi "void xdr_callhdr(xdr *" xdrs ", struct rpc_msg *" chdr ); .fi .ip used for describing rpc call header messages. this routine is useful for users who wish to generate rpc-style messages without using the rpc package. .pp .nf .bi "bool_t xdr_callmsg(xdr *" xdrs ", struct rpc_msg *" cmsg ); .fi .ip used for describing rpc call messages. this routine is useful for users who wish to generate rpc-style messages without using the rpc package. .pp .nf .bi "bool_t xdr_opaque_auth(xdr *" xdrs ", struct opaque_auth *" ap ); .fi .ip used for describing rpc authentication information messages. this routine is useful for users who wish to generate rpc-style messages without using the rpc package. .pp .nf .bi "bool_t xdr_pmap(xdr *" xdrs ", struct pmap *" regs ); .fi .ip used for describing parameters to various .b portmap procedures, externally. this routine is useful for users who wish to generate these parameters without using the .b pmap interface. .pp .nf .bi "bool_t xdr_pmaplist(xdr *" xdrs ", struct pmaplist **" rp ); .fi .ip used for describing a list of port mappings, externally. this routine is useful for users who wish to generate these parameters without using the .b pmap interface. .pp .nf .bi "bool_t xdr_rejected_reply(xdr *" xdrs ", struct rejected_reply *" rr ); .fi .ip used for describing rpc reply messages. this routine is useful for users who wish to generate rpc-style messages without using the rpc package. .pp .nf .bi "bool_t xdr_replymsg(xdr *" xdrs ", struct rpc_msg *" rmsg ); .fi .ip used for describing rpc reply messages. this routine is useful for users who wish to generate rpc style messages without using the rpc package. .pp .nf .bi "void xprt_register(svcxprt *" xprt ); .fi .ip after rpc service transport handles are created, they should register themselves with the rpc service package. this routine modifies the global variable .ir svc_fds . service implementors usually do not need this routine. .pp .nf .bi "void xprt_unregister(svcxprt *" xprt ); .fi .ip before an rpc service transport handle is destroyed, it should unregister itself with the rpc service package. this routine modifies the global variable .ir svc_fds . service implementors usually do not need this routine. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br auth_destroy (), .br authnone_create (), .br authunix_create (), .br authunix_create_default (), .br callrpc (), .br clnt_broadcast (), .br clnt_call (), .br clnt_destroy (), .br clnt_create (), .br clnt_control (), .br clnt_freeres (), .br clnt_geterr (), .br clnt_pcreateerror (), .br clnt_perrno (), .br clnt_perror (), .br clnt_spcreateerror (), .br clnt_sperrno (), .br clnt_sperror (), .br clntraw_create (), .br clnttcp_create (), .br clntudp_create (), .br clntudp_bufcreate (), .br get_myaddress (), .br pmap_getmaps (), .br pmap_getport (), .br pmap_rmtcall (), .br pmap_set (), .br pmap_unset (), .br registerrpc (), .br svc_destroy (), .br svc_freeargs (), .br svc_getargs (), .br svc_getcaller (), .br svc_getreqset (), .br svc_getreq (), .br svc_register (), .br svc_run (), .br svc_sendreply (), .br svc_unregister (), .br svcerr_auth (), .br svcerr_decode (), .br svcerr_noproc (), .br svcerr_noprog (), .br svcerr_progvers (), .br svcerr_systemerr (), .br svcerr_weakauth (), .br svcfd_create (), .br svcraw_create (), .br svctcp_create (), .br svcudp_bufcreate (), .br svcudp_create (), .br xdr_accepted_reply (), .br xdr_authunix_parms (), .br xdr_callhdr (), .br xdr_callmsg (), .br xdr_opaque_auth (), .br xdr_pmap (), .br xdr_pmaplist (), .br xdr_rejected_reply (), .br xdr_replymsg (), .br xprt_register (), .br xprt_unregister () t} thread safety mt-safe .te .hy .ad .sp 1 .sh see also .\" we don't have an rpc_secure.3 page in the set at the moment -- mtk, 19 sep 05 .\" .br rpc_secure (3), .br xdr (3) .pp the following manuals: .rs remote procedure calls: protocol specification .br remote procedure call programming guide .br rpcgen programming guide .br .re .pp .ir "rpc: remote procedure call protocol specification" , rfc\ 1050, sun microsystems, inc., usc-isi. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcscmp 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcscmp \- compare two wide-character strings .sh synopsis .nf .b #include .pp .bi "int wcscmp(const wchar_t *" s1 ", const wchar_t *" s2 ); .fi .sh description the .br wcscmp () function is the wide-character equivalent of the .br strcmp (3) function. it compares the wide-character string pointed to by .i s1 and the wide-character string pointed to by .ir s2 . .sh return value the .br wcscmp () function returns zero if the wide-character strings at .i s1 and .i s2 are equal. it returns an integer greater than zero if at the first differing position .ir i , the corresponding wide-character .i s1[i] is greater than .ir s2[i] . it returns an integer less than zero if at the first differing position .ir i , the corresponding wide-character .i s1[i] is less than .ir s2[i] . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcscmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strcmp (3), .br wcscasecmp (3), .br wmemcmp (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright 1999 by bruno haible (haible@clisp.cons.org) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 18:20:12 1993 by rik faith (faith@cs.unc.edu) .\" modified tue jul 15 16:49:10 1997 by andries brouwer (aeb@cwi.nl) .\" modified sun jul 4 14:52:16 1999 by bruno haible (haible@clisp.cons.org) .\" modified tue aug 24 17:11:01 1999 by andries brouwer (aeb@cwi.nl) .\" modified tue feb 6 03:31:55 2001 by andries brouwer (aeb@cwi.nl) .\" .th setlocale 3 2021-03-22 "gnu" "linux programmer's manual" .sh name setlocale \- set the current locale .sh synopsis .nf .b #include .pp .bi "char *setlocale(int " category ", const char *" locale ); .fi .sh description the .br setlocale () function is used to set or query the program's current locale. .pp if .i locale is not null, the program's current locale is modified according to the arguments. the argument .i category determines which parts of the program's current locale should be modified. .ad l .nh .ts lb lb lb lx. category governs lc_all all of the locale lc_address t{ formatting of addresses and geography-related items (*) t} lc_collate string collation lc_ctype character classification lc_identification t{ metadata describing the locale (*) t} lc_measurement t{ settings related to measurements (metric versus us customary) (*) t} lc_messages t{ localizable natural-language messages t} lc_monetary t{ formatting of monetary values t} lc_name t{ formatting of salutations for persons (*) t} lc_numeric t{ formatting of nonmonetary numeric values t} lc_paper t{ settings related to the standard paper size (*) t} lc_telephone t{ formats to be used with telephone services (*) t} lc_time t{ formatting of date and time values t} .te .hy .ad .pp the categories marked with an asterisk in the above table are gnu extensions. for further information on these locale categories, see .br locale (7). .pp the argument .i locale is a pointer to a character string containing the required setting of .ir category . such a string is either a well-known constant like "c" or "da_dk" (see below), or an opaque string that was returned by another call of .br setlocale (). .pp if .i locale is an empty string, .br """""" , each part of the locale that should be modified is set according to the environment variables. the details are implementation-dependent. for glibc, first (regardless of .ir category ), the environment variable .b lc_all is inspected, next the environment variable with the same name as the category (see the table above), and finally the environment variable .br lang . the first existing environment variable is used. if its value is not a valid locale specification, the locale is unchanged, and .br setlocale () returns null. .pp the locale .b """c""" or .b """posix""" is a portable locale; it exists on all conforming systems. .pp a locale name is typically of the form .ir language "[_" territory "][." codeset "][@" modifier "]," where .i language is an iso 639 language code, .i territory is an iso 3166 country code, and .i codeset is a character set or encoding identifier like .b "iso\-8859\-1" or .br "utf\-8" . for a list of all supported locales, try "locale \-a" (see .br locale (1)). .pp if .i locale is null, the current locale is only queried, not modified. .pp on startup of the main program, the portable .b """c""" locale is selected as default. a program may be made portable to all locales by calling: .pp .in +4n .ex setlocale(lc_all, ""); .ee .in .pp after program initialization, and then: .ip \(bu 2 using the values returned from a .br localeconv (3) call for locale-dependent information; .ip \(bu using the multibyte and wide character functions for text processing if .br "mb_cur_max > 1" ; .ip \(bu using .br strcoll (3) and .br strxfrm (3) to compare strings; and .ip \(bu using .br wcscoll (3) and .br wcsxfrm (3) to compare wide-character strings. .sh return value a successful call to .br setlocale () returns an opaque string that corresponds to the locale set. this string may be allocated in static storage. the string returned is such that a subsequent call with that string and its associated category will restore that part of the process's locale. the return value is null if the request cannot be honored. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br setlocale () t} thread safety mt-unsafe const:locale env .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. .pp the c standards specify only the categories .br lc_all , .br lc_collate , .br lc_ctype , .br lc_monetary , .br lc_numeric , and .br lc_time . posix.1 adds .br lc_messages . the remaining categories are gnu extensions. .sh see also .br locale (1), .br localedef (1), .br isalpha (3), .br localeconv (3), .br nl_langinfo (3), .br rpmatch (3), .br strcoll (3), .br strftime (3), .br charsets (7), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/termios.3 .so man3/pow.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" and copyright (c) 2020 arkadiusz drabczyk .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)fread.3 6.6 (berkeley) 6/29/91 .\" .\" converted for linux, mon nov 29 15:37:33 1993, faith@cs.unc.edu .\" sun feb 19 21:26:54 1995 by faith, return values .\" modified thu apr 20 20:43:53 1995 by jim van zandt .\" modified fri may 17 10:21:51 1996 by martin schulze .\" .th fread 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fread, fwrite \- binary stream input/output .sh synopsis .nf .b #include .pp .bi "size_t fread(void *restrict " ptr ", size_t " size ", size_t " nmemb , .bi " file *restrict " stream ); .bi "size_t fwrite(const void *restrict " ptr ", size_t " size \ ", size_t " nmemb , .bi " file *restrict " stream ); .fi .sh description the function .br fread () reads .i nmemb items of data, each .i size bytes long, from the stream pointed to by .ir stream , storing them at the location given by .ir ptr . .pp the function .br fwrite () writes .i nmemb items of data, each .i size bytes long, to the stream pointed to by .ir stream , obtaining them from the location given by .ir ptr . .pp for nonlocking counterparts, see .br unlocked_stdio (3). .sh return value on success, .br fread () and .br fwrite () return the number of items read or written. this number equals the number of bytes transferred only when .i size is 1. if an error occurs, or the end of the file is reached, the return value is a short item count (or zero). .pp the file position indicator for the stream is advanced by the number of bytes successfully read or written. .pp .br fread () does not distinguish between end-of-file and error, and callers must use .br feof (3) and .br ferror (3) to determine which occurred. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fread (), .br fwrite () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89. .sh examples the program below demonstrates the use of .br fread () by parsing /bin/sh elf executable in binary mode and printing its magic and class: .pp .in +4n .ex $ \fb./a.out\fp elf magic: 0x7f454c46 class: 0x02 .ee .in .ss program source \& .ex #include #include #define array_size(arr) (sizeof(arr) / sizeof((arr)[0])) int main(void) { file *fp = fopen("/bin/sh", "rb"); if (!fp) { perror("fopen"); return exit_failure; } unsigned char buffer[4]; size_t ret = fread(buffer, sizeof(*buffer), array_size(buffer), fp); if (ret != array_size(buffer)) { fprintf(stderr, "fread() failed: %zu\en", ret); exit(exit_failure); } printf("elf magic: %#04x%02x%02x%02x\en", buffer[0], buffer[1], buffer[2], buffer[3]); ret = fread(buffer, 1, 1, fp); if (ret != 1) { fprintf(stderr, "fread() failed: %zu\en", ret); exit(exit_failure); } printf("class: %#04x\en", buffer[0]); fclose(fp); exit(exit_success); } .ee .sh see also .br read (2), .br write (2), .br feof (3), .br ferror (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th nextup 3 2021-03-22 "gnu" "linux programmer's manual" .sh name nextup, nextupf, nextupl, nextdown, nextdownf, nextdownl \- return next floating-point number toward positive/negative infinity .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "double nextup(double " x ); .bi "float nextupf(float " x ); .bi "long double nextupl(long double " x ); .pp .bi "double nextdown(double " x ); .bi "float nextdownf(float " x ); .bi "long double nextdownl(long double " x ); .fi .pp link with \fi\-lm\fp. .sh description the .br nextup (), .br nextupf (), and .br nextupl () functions return the next representable floating-point number greater than .ir x . .pp if .i x is the smallest representable negative number in the corresponding type, these functions return \-0. if .i x is 0, the returned value is the smallest representable positive number of the corresponding type. .pp if .i x is positive infinity, the returned value is positive infinity. if .i x is negative infinity, the returned value is the largest representable finite negative number of the corresponding type. .pp if .i x is nan, the returned value is nan. .pp the value returned by .ir nextdown(x) is .ir \-nextup(\-x) , and similarly for the other types. .sh return value see description. .\" .sh errors .sh versions these functions first appeared in glibc in version 2.24. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br nextup (), .br nextupf (), .br nextupl (), .br nextdown (), .br nextdownf (), .br nextdownl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are described in .ir "ieee std 754-2008 - standard for floating-point arithmetic" and .ir "iso/iec ts 18661". .sh see also .br nearbyint (3), .br nextafter (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) and .\" and copyright 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 21 aug 1994 by michael chastain : .\" removed note about old libc (pre-4.5.26) translating to 'sync'. .\" modified 15 apr 1995 by michael chastain : .\" added `see also' section. .\" modified 13 apr 1996 by markus kuhn .\" added remarks about fdatasync. .\" modified 31 jan 1997 by eric s. raymond .\" modified 18 apr 2001 by andi kleen .\" fix description to describe what it really does; add a few caveats. .\" 2006-04-28, mtk, substantial rewrite of various parts. .\" 2012-02-27 various changes by christoph hellwig .\" .th fsync 2 2021-03-22 "linux" "linux programmer's manual" .sh name fsync, fdatasync \- synchronize a file's in-core state with storage device .sh synopsis .nf .b #include .pp .bi "int fsync(int " fd ); .pp .bi "int fdatasync(int " fd ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .nf .br fsync (): glibc 2.16 and later: no feature test macros need be defined glibc up to and including 2.15: _bsd_source || _xopen_source || /* since glibc 2.8: */ _posix_c_source >= 200112l .fi .pp .br fdatasync (): .nf _posix_c_source >= 199309l || _xopen_source >= 500 .fi .sh description .br fsync () transfers ("flushes") all modified in-core data of (i.e., modified buffer cache pages for) the file referred to by the file descriptor .i fd to the disk device (or other permanent storage device) so that all changed information can be retrieved even if the system crashes or is rebooted. this includes writing through or flushing a disk cache if present. the call blocks until the device reports that the transfer has completed. .pp as well as flushing the file data, .br fsync () also flushes the metadata information associated with the file (see .br inode (7)). .pp calling .br fsync () does not necessarily ensure that the entry in the directory containing the file has also reached disk. for that an explicit .br fsync () on a file descriptor for the directory is also needed. .pp .br fdatasync () is similar to .br fsync (), but does not flush modified metadata unless that metadata is needed in order to allow a subsequent data retrieval to be correctly handled. for example, changes to .i st_atime or .i st_mtime (respectively, time of last access and time of last modification; see .br inode (7)) do not require flushing because they are not necessary for a subsequent data read to be handled correctly. on the other hand, a change to the file size .ri ( st_size , as made by say .br ftruncate (2)), would require a metadata flush. .pp the aim of .br fdatasync () is to reduce disk activity for applications that do not require all metadata to be synchronized with the disk. .sh return value on success, these system calls return zero. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid open file descriptor. .tp .b eio an error occurred during synchronization. this error may relate to data written to some other file descriptor on the same file. since linux 4.13, .\" commit 088737f44bbf6378745f5b57b035e57ee3dc4750 errors from write-back will be reported to all file descriptors that might have written the data which triggered the error. some filesystems (e.g., nfs) keep close track of which data came through which file descriptor, and give more precise reporting. other filesystems (e.g., most local filesystems) will report errors to all file descriptors that were open on the file when the error was recorded. .tp .b enospc disk space was exhausted while synchronizing. .tp .br erofs ", " einval .i fd is bound to a special file (e.g., a pipe, fifo, or socket) which does not support synchronization. .tp .br enospc ", " edquot .i fd is bound to a file on nfs or another filesystem which does not allocate space at the time of a .br write (2) system call, and some previous write failed due to insufficient storage space. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .pp on posix systems on which .br fdatasync () is available, .b _posix_synchronized_io is defined in .i to a value greater than 0. (see also .br sysconf (3).) .\" posix.1-2001: it shall be defined to -1 or 0 or 200112l. .\" -1: unavailable, 0: ask using sysconf(). .\" glibc defines them to 1. .sh notes on some unix systems (but not linux), .i fd must be a .i writable file descriptor. .pp in linux 2.2 and earlier, .br fdatasync () is equivalent to .br fsync (), and so has no performance advantage. .pp the .br fsync () implementations in older kernels and lesser used filesystems do not know how to flush disk caches. in these cases disk caches need to be disabled using .br hdparm (8) or .br sdparm (8) to guarantee safe operation. .sh see also .br sync (1), .br bdflush (2), .br open (2), .br posix_fadvise (2), .br pwritev (2), .br sync (2), .br sync_file_range (2), .br fflush (3), .br fileno (3), .br hdparm (8), .br mount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scalbln.3 .so man4/mem.4 .so man3/rpc.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" libc.info (from glibc distribution) .\" modified sat jul 24 19:12:00 1993 by rik faith .\" modified sun sep 3 20:29:36 1995 by jim van zandt .\" changed network into host byte order (for inet_network), .\" andreas jaeger , 980130. .\" 2008-06-19, mtk .\" describe the various address forms supported by inet_aton(). .\" clarify discussion of inet_lnaof(), inet_netof(), and inet_makeaddr(). .\" add discussion of classful addressing, noting that it is obsolete. .\" added an example program. .\" .th inet 3 2021-03-22 "gnu" "linux programmer's manual" .sh name inet_aton, inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof, inet_netof \- internet address manipulation routines .sh synopsis .nf .b #include .b #include .b #include .pp .bi "int inet_aton(const char *" cp ", struct in_addr *" inp ); .pp .bi "in_addr_t inet_addr(const char *" cp ); .bi "in_addr_t inet_network(const char *" cp ); .pp .bi "char *inet_ntoa(struct in_addr " in ); .pp .bi "struct in_addr inet_makeaddr(in_addr_t " net ", in_addr_t " host ); .pp .bi "in_addr_t inet_lnaof(struct in_addr " in ); .bi "in_addr_t inet_netof(struct in_addr " in ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br inet_aton (), .br inet_ntoa (): .nf since glibc 2.19: _default_source in glibc up to and including 2.19: _bsd_source || _bsd_source .fi .sh description .br inet_aton () converts the internet host address \ficp\fp from the ipv4 numbers-and-dots notation into binary form (in network byte order) and stores it in the structure that \fiinp\fp points to. .br inet_aton () returns nonzero if the address is valid, zero if not. the address supplied in .i cp can have one of the following forms: .tp 10 .i a.b.c.d each of the four numeric parts specifies a byte of the address; the bytes are assigned in left-to-right order to produce the binary address. .tp .i a.b.c parts .i a and .i b specify the first two bytes of the binary address. part .i c is interpreted as a 16-bit value that defines the rightmost two bytes of the binary address. this notation is suitable for specifying (outmoded) class b network addresses. .tp .i a.b part .i a specifies the first byte of the binary address. part .i b is interpreted as a 24-bit value that defines the rightmost three bytes of the binary address. this notation is suitable for specifying (outmoded) class a network addresses. .tp .i a the value .i a is interpreted as a 32-bit value that is stored directly into the binary address without any byte rearrangement. .pp in all of the above forms, components of the dotted address can be specified in decimal, octal (with a leading .ir 0 ), or hexadecimal, with a leading .ir 0x ). addresses in any of these forms are collectively termed .ir "ipv4 numbers-and-dots notation" . the form that uses exactly four decimal numbers is referred to as .ir "ipv4 dotted-decimal notation" (or sometimes: .ir "ipv4 dotted-quad notation" ). .pp .br inet_aton () returns 1 if the supplied string was successfully interpreted, or 0 if the string is invalid .rb ( errno is .i not set on error). .pp the .br inet_addr () function converts the internet host address \ficp\fp from ipv4 numbers-and-dots notation into binary data in network byte order. if the input is invalid, .b inaddr_none (usually \-1) is returned. use of this function is problematic because \-1 is a valid address (255.255.255.255). avoid its use in favor of .br inet_aton (), .br inet_pton (3), or .br getaddrinfo (3), which provide a cleaner way to indicate error return. .pp the .br inet_network () function converts .ir cp , a string in ipv4 numbers-and-dots notation, into a number in host byte order suitable for use as an internet network address. on success, the converted address is returned. if the input is invalid, \-1 is returned. .pp the .br inet_ntoa () function converts the internet host address \fiin\fp, given in network byte order, to a string in ipv4 dotted-decimal notation. the string is returned in a statically allocated buffer, which subsequent calls will overwrite. .pp the .br inet_lnaof () function returns the local network address part of the internet address \fiin\fp. the returned value is in host byte order. .pp the .br inet_netof () function returns the network number part of the internet address \fiin\fp. the returned value is in host byte order. .pp the .br inet_makeaddr () function is the converse of .br inet_netof () and .br inet_lnaof (). it returns an internet host address in network byte order, created by combining the network number \finet\fp with the local address \fihost\fp, both in host byte order. .pp the structure \fiin_addr\fp as used in .br inet_ntoa (), .br inet_makeaddr (), .br inet_lnaof (), and .br inet_netof () is defined in .i as: .pp .in +4n .ex typedef uint32_t in_addr_t; struct in_addr { in_addr_t s_addr; }; .ee .in .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br inet_aton (), .br inet_addr (), .br inet_network (), .br inet_ntoa () t} thread safety mt-safe locale t{ .br inet_makeaddr (), .br inet_lnaof (), .br inet_netof () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br inet_addr (), .br inet_ntoa (): posix.1-2001, posix.1-2008, 4.3bsd. .pp .br inet_aton () is not specified in posix.1, but is available on most systems. .sh notes on x86 architectures, the host byte order is least significant byte first (little endian), whereas the network byte order, as used on the internet, is most significant byte first (big endian). .pp .br inet_lnaof (), .br inet_netof (), and .br inet_makeaddr () are legacy functions that assume they are dealing with .ir "classful network addresses" . classful networking divides ipv4 network addresses into host and network components at byte boundaries, as follows: .tp 10 class a this address type is indicated by the value 0 in the most significant bit of the (network byte ordered) address. the network address is contained in the most significant byte, and the host address occupies the remaining three bytes. .tp class b this address type is indicated by the binary value 10 in the most significant two bits of the address. the network address is contained in the two most significant bytes, and the host address occupies the remaining two bytes. .tp class c this address type is indicated by the binary value 110 in the most significant three bits of the address. the network address is contained in the three most significant bytes, and the host address occupies the remaining byte. .pp classful network addresses are now obsolete, having been superseded by classless inter-domain routing (cidr), which divides addresses into network and host components at arbitrary bit (rather than byte) boundaries. .sh examples an example of the use of .br inet_aton () and .br inet_ntoa () is shown below. here are some example runs: .pp .in +4n .ex .rb "$" " ./a.out 226.000.000.037" " # last byte is in octal" 226.0.0.31 .rb "$" " ./a.out 0x7f.1 " " # first byte is in hex" 127.0.0.1 .ee .in .ss program source \& .ex #define _bsd_source #include #include #include int main(int argc, char *argv[]) { struct in_addr addr; if (argc != 2) { fprintf(stderr, "%s \en", argv[0]); exit(exit_failure); } if (inet_aton(argv[1], &addr) == 0) { fprintf(stderr, "invalid address\en"); exit(exit_failure); } printf("%s\en", inet_ntoa(addr)); exit(exit_success); } .ee .sh see also .br byteorder (3), .br getaddrinfo (3), .br gethostbyname (3), .br getnameinfo (3), .br getnetent (3), .br inet_net_pton (3), .br inet_ntop (3), .br inet_pton (3), .br hosts (5), .br networks (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/wprintf.3 .so man3/getaddrinfo.3 .\" copyright 2003 walter harms, 2004 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created 2004-10-31. text taken from a page by walter harms, 2003-09-08 .\" .th drand48_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name drand48_r, erand48_r, lrand48_r, nrand48_r, mrand48_r, jrand48_r, srand48_r, seed48_r, lcong48_r \- generate uniformly distributed pseudo-random numbers reentrantly .sh synopsis .nf .b #include .pp .bi "int drand48_r(struct drand48_data *restrict " buffer , .bi " double *restrict " result ); .bi "int erand48_r(unsigned short " xsubi [3] "," .bi " struct drand48_data *restrict "buffer , .bi " double *restrict " result ");" .pp .bi "int lrand48_r(struct drand48_data *restrict " buffer , .bi " long *restrict " result ); .bi "int nrand48_r(unsigned short " xsubi[3] "," .bi " struct drand48_data *restrict "buffer , .bi " long *restrict " result ");" .pp .bi "int mrand48_r(struct drand48_data *restrict " buffer , .bi " long *restrict " result ");" .bi "int jrand48_r(unsigned short " xsubi[3] "," .bi " struct drand48_data *restrict " buffer , .bi " long *restrict " result ");" .pp .bi "int srand48_r(long int " seedval ", struct drand48_data *" buffer ");" .bi "int seed48_r(unsigned short " seed16v[3] ", struct drand48_data *" buffer ); .bi "int lcong48_r(unsigned short " param[7] ", struct drand48_data *" buffer ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp all functions shown above: .\" .br drand48_r (), .\" .br erand48_r (), .\" .br lrand48_r (), .\" .br nrand48_r (), .\" .br mrand48_r (), .\" .br jrand48_r (), .\" .br srand48_r (), .\" .br seed48_r (), .\" .br lcong48_r (): .nf /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description these functions are the reentrant analogs of the functions described in .br drand48 (3). instead of modifying the global random generator state, they use the supplied data .ir buffer . .pp before the first use, this struct must be initialized, for example, by filling it with zeros, or by calling one of the functions .br srand48_r (), .br seed48_r (), or .br lcong48_r (). .sh return value the return value is 0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br drand48_r (), .br erand48_r (), .br lrand48_r (), .br nrand48_r (), .br mrand48_r (), .br jrand48_r (), .br srand48_r (), .br seed48_r (), .br lcong48_r () t} thread safety mt-safe race:buffer .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions and are not portable. .sh see also .br drand48 (3), .br rand (3), .br random (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) international business machines orp., 2006 .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see .\" the gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" history: .\" 2006-04-27, created by eduardo m. fleury .\" with various additions by michael kerrisk .\" .\" .th ioprio_set 2 2021-06-20 "linux" "linux programmer's manual" .sh name ioprio_get, ioprio_set \- get/set i/o scheduling class and priority .sh synopsis .nf .br "#include " "/* definition of " ioprio_* " constants */" .br "#include " "/* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_ioprio_get, int " which ", int " who ); .bi "int syscall(sys_ioprio_set, int " which ", int " who ", int " ioprio ); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description the .br ioprio_get () and .br ioprio_set () system calls get and set the i/o scheduling class and priority of one or more threads. .pp the .i which and .i who arguments identify the thread(s) on which the system calls operate. the .i which argument determines how .i who is interpreted, and has one of the following values: .tp .b ioprio_who_process .i who is a process id or thread id identifying a single process or thread. if .i who is 0, then operate on the calling thread. .tp .b ioprio_who_pgrp .i who is a process group id identifying all the members of a process group. if .i who is 0, then operate on the process group of which the caller is a member. .tp .b ioprio_who_user .i who is a user id identifying all of the processes that have a matching real uid. .\" fixme . need to document the behavior when 'who" is specified as 0 .\" see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=652443 .pp if .i which is specified as .b ioprio_who_pgrp or .b ioprio_who_user when calling .br ioprio_get (), and more than one process matches .ir who , then the returned priority will be the highest one found among all of the matching processes. one priority is said to be higher than another one if it belongs to a higher priority class .rb ( ioprio_class_rt is the highest priority class; .b ioprio_class_idle is the lowest) or if it belongs to the same priority class as the other process but has a higher priority level (a lower priority number means a higher priority level). .pp the .i ioprio argument given to .br ioprio_set () is a bit mask that specifies both the scheduling class and the priority to be assigned to the target process(es). the following macros are used for assembling and dissecting .i ioprio values: .tp .bi ioprio_prio_value( class ", " data ) given a scheduling .i class and priority .ri ( data ), this macro combines the two values to produce an .i ioprio value, which is returned as the result of the macro. .tp .bi ioprio_prio_class( mask ) given .i mask (an .i ioprio value), this macro returns its i/o class component, that is, one of the values .br ioprio_class_rt , .br ioprio_class_be , or .br ioprio_class_idle . .tp .bi ioprio_prio_data( mask ) given .i mask (an .i ioprio value), this macro returns its priority .ri ( data ) component. .pp see the notes section for more information on scheduling classes and priorities, as well as the meaning of specifying .i ioprio as 0. .pp i/o priorities are supported for reads and for synchronous .rb ( o_direct , .br o_sync ) writes. i/o priorities are not supported for asynchronous writes because they are issued outside the context of the program dirtying the memory, and thus program-specific priorities do not apply. .sh return value on success, .br ioprio_get () returns the .i ioprio value of the process with highest i/o priority of any of the processes that match the criteria specified in .i which and .ir who . on error, \-1 is returned, and .i errno is set to indicate the error. .pp on success, .br ioprio_set () returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval invalid value for .i which or .ir ioprio . refer to the notes section for available scheduler classes and priority levels for .ir ioprio . .tp .b eperm the calling process does not have the privilege needed to assign this .i ioprio to the specified process(es). see the notes section for more information on required privileges for .br ioprio_set (). .tp .b esrch no process(es) could be found that matched the specification in .i which and .ir who . .sh versions these system calls have been available on linux since kernel 2.6.13. .sh conforming to these system calls are linux-specific. .sh notes two or more processes or threads can share an i/o context. this will be the case when .br clone (2) was called with the .b clone_io flag. however, by default, the distinct threads of a process will .b not share the same i/o context. this means that if you want to change the i/o priority of all threads in a process, you may need to call .br ioprio_set () on each of the threads. the thread id that you would need for this operation is the one that is returned by .br gettid (2) or .br clone (2). .pp these system calls have an effect only when used in conjunction with an i/o scheduler that supports i/o priorities. as at kernel 2.6.17 the only such scheduler is the completely fair queuing (cfq) i/o scheduler. .pp if no i/o scheduler has been set for a thread, then by default the i/o priority will follow the cpu nice value .rb ( setpriority (2)). in linux kernels before version 2.6.24, once an i/o priority had been set using .br ioprio_set (), there was no way to reset the i/o scheduling behavior to the default. since linux 2.6.24, .\" commit 8ec680e4c3ec818efd1652f15199ed1c216ab550 specifying .i ioprio as 0 can be used to reset to the default i/o scheduling behavior. .ss selecting an i/o scheduler i/o schedulers are selected on a per-device basis via the special file .ir /sys/block//queue/scheduler . .pp one can view the current i/o scheduler via the .i /sys filesystem. for example, the following command displays a list of all schedulers currently loaded in the kernel: .pp .in +4n .ex .rb "$" " cat /sys/block/sda/queue/scheduler" noop anticipatory deadline [cfq] .ee .in .pp the scheduler surrounded by brackets is the one actually in use for the device .ri ( sda in the example). setting another scheduler is done by writing the name of the new scheduler to this file. for example, the following command will set the scheduler for the .i sda device to .ir cfq : .pp .in +4n .ex .rb "$" " su" password: .rb "#" " echo cfq > /sys/block/sda/queue/scheduler" .ee .in .\" .ss the completely fair queuing (cfq) i/o scheduler since version 3 (also known as cfq time sliced), cfq implements i/o nice levels similar to those of cpu scheduling. these nice levels are grouped into three scheduling classes, each one containing one or more priority levels: .tp .br ioprio_class_rt " (1)" this is the real-time i/o class. this scheduling class is given higher priority than any other class: processes from this class are given first access to the disk every time. thus, this i/o class needs to be used with some care: one i/o real-time process can starve the entire system. within the real-time class, there are 8 levels of class data (priority) that determine exactly how much time this process needs the disk for on each service. the highest real-time priority level is 0; the lowest is 7. in the future, this might change to be more directly mappable to performance, by passing in a desired data rate instead. .tp .br ioprio_class_be " (2)" this is the best-effort scheduling class, which is the default for any process that hasn't set a specific i/o priority. the class data (priority) determines how much i/o bandwidth the process will get. best-effort priority levels are analogous to cpu nice values (see .br getpriority (2)). the priority level determines a priority relative to other processes in the best-effort scheduling class. priority levels range from 0 (highest) to 7 (lowest). .tp .br ioprio_class_idle " (3)" this is the idle scheduling class. processes running at this level get i/o time only when no one else needs the disk. the idle class has no class data. attention is required when assigning this priority class to a process, since it may become starved if higher priority processes are constantly accessing the disk. .pp refer to the kernel source file .i documentation/block/ioprio.txt for more information on the cfq i/o scheduler and an example program. .ss required permissions to set i/o priorities permission to change a process's priority is granted or denied based on two criteria: .tp .b "process ownership" an unprivileged process may set the i/o priority only for a process whose real uid matches the real or effective uid of the calling process. a process which has the .b cap_sys_nice capability can change the priority of any process. .tp .b "what is the desired priority" attempts to set very high priorities .rb ( ioprio_class_rt ) require the .b cap_sys_admin capability. kernel versions up to 2.6.24 also required .b cap_sys_admin to set a very low priority .rb ( ioprio_class_idle ), but since linux 2.6.25, this is no longer required. .pp a call to .br ioprio_set () must follow both rules, or the call will fail with the error .br eperm . .sh bugs .\" 6 may 07: bug report raised: .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=4464 .\" ulrich drepper replied that he wasn't going to add these .\" to glibc. glibc does not yet provide a suitable header file defining the function prototypes and macros described on this page. suitable definitions can be found in .ir linux/ioprio.h . .sh see also .br ionice (1), .br getpriority (2), .br open (2), .br capabilities (7), .br cgroups (7) .pp .i documentation/block/ioprio.txt in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th utimensat 2 2021-08-27 "linux" "linux programmer's manual" .sh name utimensat, futimens \- change file timestamps with nanosecond precision .sh synopsis .nf .br "#include " " /* definition of " at_* " constants */" .b #include .pp .bi "int utimensat(int " dirfd ", const char *" pathname , .bi " const struct timespec " times "[2], int " flags ); .bi "int futimens(int " fd ", const struct timespec " times [2]); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br utimensat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .pp .br futimens (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description .br utimensat () and .br futimens () update the timestamps of a file with nanosecond precision. this contrasts with the historical .br utime (2) and .br utimes (2), which permit only second and microsecond precision, respectively, when setting file timestamps. .pp with .br utimensat () the file is specified via the pathname given in .ir pathname . with .br futimens () the file whose timestamps are to be updated is specified via an open file descriptor, .ir fd . .pp for both calls, the new file timestamps are specified in the array .ir times : .i times[0] specifies the new "last access time" (\fiatime\fp); .i times[1] specifies the new "last modification time" (\fimtime\fp). each of the elements of .i times specifies a time as the number of seconds and nanoseconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). this information is conveyed in a structure of the following form: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp updated file timestamps are set to the greatest value supported by the filesystem that is not greater than the specified time. .pp if the .i tv_nsec field of one of the .i timespec structures has the special value .br utime_now , then the corresponding file timestamp is set to the current time. if the .i tv_nsec field of one of the .i timespec structures has the special value .br utime_omit , then the corresponding file timestamp is left unchanged. in both of these cases, the value of the corresponding .i tv_sec .\" 2.6.22 was broken: it is not ignored field is ignored. .pp if .i times is null, then both timestamps are set to the current time. .\" .ss permissions requirements to set both file timestamps to the current time (i.e., .i times is null, or both .i tv_nsec fields specify .br utime_now ), either: .ip 1. 3 the caller must have write access to the file; .\" 2.6.22 was broken here -- for futimens() the check is .\" based on whether or not the file descriptor is writable, .\" not on whether the caller's effective uid has write .\" permission for the file referred to by the descriptor. .ip 2. the caller's effective user id must match the owner of the file; or .ip 3. the caller must have appropriate privileges. .pp to make any change other than setting both timestamps to the current time (i.e., .i times is not null, and neither .i tv_nsec field is .b utime_now .\" 2.6.22 was broken here: .\" both must be something other than *either* utime_omit *or* utime_now. and neither .i tv_nsec field is .br utime_omit ), either condition 2 or 3 above must apply. .pp if both .i tv_nsec fields are specified as .br utime_omit , then no file ownership or permission checks are performed, and the file timestamps are not modified, but other error conditions may still be detected. .\" .\" .ss utimensat() specifics if .i pathname is relative, then by default it is interpreted relative to the directory referred to by the open file descriptor, .ir dirfd (rather than relative to the current working directory of the calling process, as is done by .br utimes (2) for a relative pathname). see .br openat (2) for an explanation of why this can be useful. .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br utimes (2)). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp the .i flags field is a bit mask that may be 0, or include the following constant, defined in .ir : .tp .b at_symlink_nofollow if .i pathname specifies a symbolic link, then update the timestamps of the link, rather than the file to which it refers. .sh return value on success, .br utimensat () and .br futimens () return 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces .i times is null, or both .i tv_nsec values are .br utime_now , and the effective user id of the caller does not match the owner of the file, the caller does not have write access to the file, and the caller is not privileged (linux: does not have either the .b cap_fowner or the .b cap_dac_override capability). .\" but linux 2.6.22 was broken here. .\" traditionally, utime()/utimes() gives the error eacces for the case .\" where the timestamp pointer argument is null (i.e., set both timestamps .\" to the current time), and the file is owned by a user other than the .\" effective uid of the caller, and the file is not writable by the .\" effective uid of the program. utimensat() also gives this error in the .\" same case. however, in the same circumstances, when utimensat() is .\" given a 'times' array in which both tv_nsec fields are utime_now, which .\" provides equivalent functionality to specifying 'times' as null, the .\" call succeeds. it should fail with the error eacces in this case. .\" .\" posix.1-2008 has the following: .\" .tp .\" .b eacces .\" .rb ( utimensat ()) .\" .i fd .\" was not opened with .\" .b o_search .\" and the permissions of the directory to which .\" .i fd .\" refers do not allow searches. .\" ext2_immutable_fl and similar flags for other filesystems. .tp .b ebadf .rb ( futimens ()) .i fd is not a valid file descriptor. .tp .b ebadf .rb ( utimensat ()) .i pathname is relative but .i dirfd is neither .br at_fdcwd nor a valid file descriptor. .tp .b efault .i times pointed to an invalid address; or, .i dirfd was .br at_fdcwd , and .i pathname is null or an invalid address. .tp .b einval invalid value in .ir flags . .tp .b einval invalid value in one of the .i tv_nsec fields (value outside range 0 to 999,999,999, and not .b utime_now or .br utime_omit ); or an invalid value in one of the .i tv_sec fields. .tp .b einval .\" susv4 does not specify this error. .i pathname is null, .i dirfd is not .br at_fdcwd , and .i flags contains .br at_symlink_nofollow . .tp .b eloop .rb ( utimensat ()) too many symbolic links were encountered in resolving .ir pathname . .tp .b enametoolong .rb ( utimensat ()) .i pathname is too long. .tp .b enoent .rb ( utimensat ()) a component of .i pathname does not refer to an existing directory or file, or .i pathname is an empty string. .tp .b enotdir .rb ( utimensat ()) .i pathname is a relative pathname, but .i dirfd is neither .b at_fdcwd nor a file descriptor referring to a directory; or, one of the prefix components of .i pathname is not a directory. .tp .b eperm the caller attempted to change one or both timestamps to a value other than the current time, or to change one of the timestamps to the current time while leaving the other timestamp unchanged, (i.e., .i times is not null, neither .i tv_nsec field is .br utime_now , and neither .i tv_nsec field is .br utime_omit ) and either: .rs .ip * 3 the caller's effective user id does not match the owner of file, and the caller is not privileged (linux: does not have the .br cap_fowner capability); or, .ip * .\" linux 2.6.22 was broken here: .\" it was not consistent with the old utimes() implementation, .\" since the case when both tv_nsec fields are utime_now, was not .\" treated like the (times == null) case. the file is marked append-only or immutable (see .br chattr (1)). .\" ext2_immutable_fl ext_apppend_fl and similar flags for .\" other filesystems. .\" .\" why the inconsistency (which is described under notes) between .\" eacces and eperm, where only eperm tests for append-only. .\" (this was also so for the older utimes() implementation.) .re .tp .b erofs the file is on a read-only filesystem. .tp .b esrch .rb ( utimensat ()) search permission is denied for one of the prefix components of .ir pathname . .sh versions .br utimensat () was added to linux in kernel 2.6.22; glibc support was added with version 2.6. .pp support for .br futimens () first appeared in glibc 2.6. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br utimensat (), .br futimens () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br futimens () and .br utimensat () are specified in posix.1-2008. .sh notes .br utimensat () obsoletes .br futimesat (2). .pp on linux, timestamps cannot be changed for a file marked immutable, and the only change permitted for files marked append-only is to set the timestamps to the current time. (this is consistent with the historical behavior of .br utime (2) and .br utimes (2) on linux.) .pp if both .i tv_nsec fields are specified as .br utime_omit , then the linux implementation of .br utimensat () succeeds even if the file referred to by .ir dirfd and .i pathname does not exist. .ss c library/kernel abi differences on linux, .br futimens () is a library function implemented on top of the .br utimensat () system call. to support this, the linux .br utimensat () system call implements a nonstandard feature: if .i pathname is null, then the call modifies the timestamps of the file referred to by the file descriptor .i dirfd (which may refer to any type of file). using this feature, the call .i "futimens(fd,\ times)" is implemented as: .pp .in +4n .ex utimensat(fd, null, times, 0); .ee .in .pp note, however, that the glibc wrapper for .br utimensat () disallows passing null as the value for .ir pathname : the wrapper function returns the error .br einval in this case. .sh bugs several bugs afflict .br utimensat () and .br futimens () on kernels before 2.6.26. these bugs are either nonconformances with the posix.1 draft specification or inconsistencies with historical linux behavior. .ip * 3 posix.1 specifies that if one of the .i tv_nsec fields has the value .b utime_now or .br utime_omit , then the value of the corresponding .i tv_sec field should be ignored. instead, the value of the .i tv_sec field is required to be 0 (or the error .b einval results). .ip * various bugs mean that for the purposes of permission checking, the case where both .i tv_nsec fields are set to .br utime_now isn't always treated the same as specifying .i times as null, and the case where one .i tv_nsec value is .b utime_now and the other is .b utime_omit isn't treated the same as specifying .i times as a pointer to an array of structures containing arbitrary time values. as a result, in some cases: a) file timestamps can be updated by a process that shouldn't have permission to perform updates; b) file timestamps can't be updated by a process that should have permission to perform updates; and c) the wrong .i errno value is returned in case of an error. .\" below, the long description of the errors from the previous bullet .\" point (abridged because it's too much detail for a man page). .\" .ip * .\" if one of the .\" .i tv_nsec .\" fields is .\" .br utime_omit .\" and the other is .\" .br utime_now , .\" then the error .\" .b eperm .\" should occur if the process's effective user id does not match .\" the file owner and the process is not privileged. .\" instead, the call successfully changes one of the timestamps. .\" .ip * .\" if file is not writable by the effective user id of the process and .\" the process's effective user id does not match the file owner and .\" the process is not privileged, .\" and .\" .i times .\" is null, then the error .\" .b eacces .\" results. .\" this error should also occur if .\" .i times .\" points to an array of structures in which both .\" .i tv_nsec .\" fields are .\" .br utime_now . .\" instead the call succeeds. .\" .ip * .\" if a file is marked as append-only (see .\" .br chattr (1)), .\" then linux traditionally .\" (i.e., .\" .br utime (2), .\" .br utimes (2)), .\" permits a null .\" .i times .\" argument to be used in order to update both timestamps to the current time. .\" for consistency, .\" .br utimensat () .\" and .\" .br futimens () .\" should also produce the same result when given a .\" .i times .\" argument that points to an array of structures in which both .\" .i tv_nsec .\" fields are .\" .br utime_now . .\" instead, the call fails with the error .\" .br eperm . .\" .ip * .\" if a file is marked as immutable (see .\" .br chattr (1)), .\" then linux traditionally .\" (i.e., .\" .br utime (2), .\" .br utimes (2)), .\" gives an .\" .b eacces .\" error if .\" .i times .\" is null. .\" for consistency, .\" .br utimensat () .\" and .\" .br futimens () .\" should also produce the same result when given a .\" .i times .\" that points to an array of structures in which both .\" .i tv_nsec .\" fields are .\" .br utime_now . .\" instead, the call fails with the error .\" .br eperm . .ip * posix.1 says that a process that has \fiwrite access to the file\fp can make a call with .i times as null, or with .i times pointing to an array of structures in which both .i tv_nsec fields are .br utime_now , in order to update both timestamps to the current time. however, .br futimens () instead checks whether the .ir "access mode of the file descriptor allows writing" . .\" this means that a process with a file descriptor that allows .\" writing could change the timestamps of a file for which it .\" does not have write permission; .\" conversely, a process with a read-only file descriptor won't .\" be able to update the timestamps of a file, .\" even if it has write permission on the file. .sh see also .br chattr (1), .br touch (1), .br futimesat (2), .br openat (2), .br stat (2), .br utimes (2), .br futimes (3), .br inode (7), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th wcstoimax 3 2021-03-22 "" "linux programmer's manual" .sh name wcstoimax, wcstoumax \- convert wide-character string to integer .sh synopsis .nf .b #include .b #include .pp .bi "intmax_t wcstoimax(const wchar_t *restrict " nptr , .bi " wchar_t **restrict " endptr ", int " base ); .bi "uintmax_t wcstoumax(const wchar_t *restrict " nptr , .bi " wchar_t **restrict " endptr ", int " base ); .fi .sh description these functions are just like .br wcstol (3) and .br wcstoul (3), except that they return a value of type .i intmax_t and .ir uintmax_t , respectively. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcstoimax (), .br wcstoumax () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br imaxabs (3), .br imaxdiv (3), .br strtoimax (3), .br strtoumax (3), .\" fixme . the pages referred to by the following xrefs are not yet written .br wcstol (3), .br wcstoul (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/key_setsecret.3 .so man3/cbrt.3 .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th session-keyring 7 2021-03-22 linux "linux programmer's manual" .sh name session-keyring \- session shared process keyring .sh description the session keyring is a keyring used to anchor keys on behalf of a process. it is typically created by .br pam_keyinit (8) when a user logs in and a link will be added that refers to the .br user\-keyring (7). optionally, pam may revoke the session keyring on logout. (in typical configurations, pam does do this revocation.) the session keyring has the name (description) .ir _ses . .pp a special serial number value, .br key_spec_session_keyring , is defined that can be used in lieu of the actual serial number of the calling process's session keyring. .pp from the .br keyctl (1) utility, '\fb@s\fp' can be used instead of a numeric key id in much the same way. .pp a process's session keyring is inherited across .br clone (2), .br fork (2), and .br vfork (2). the session keyring is preserved across .br execve (2), even when the executable is set-user-id or set-group-id or has capabilities. the session keyring is destroyed when the last process that refers to it exits. .pp if a process doesn't have a session keyring when it is accessed, then, under certain circumstances, the .br user\-session\-keyring (7) will be attached as the session keyring and under others a new session keyring will be created. (see .br user\-session\-keyring (7) for further details.) .ss special operations the .i keyutils library provides the following special operations for manipulating session keyrings: .tp .br keyctl_join_session_keyring (3) this operation allows the caller to change the session keyring that it subscribes to. the caller can join an existing keyring with a specified name (description), create a new keyring with a given name, or ask the kernel to create a new "anonymous" session keyring with the name "_ses". (this function is an interface to the .br keyctl (2) .b keyctl_join_session_keyring operation.) .tp .br keyctl_session_to_parent (3) this operation allows the caller to make the parent process's session keyring to the same as its own. for this to succeed, the parent process must have identical security attributes and must be single threaded. (this function is an interface to the .br keyctl (2) .b keyctl_session_to_parent operation.) .pp these operations are also exposed through the .br keyctl (1) utility as: .pp .in +4n .ex keyctl session keyctl session \- [ ...] keyctl session [ ...] .ee .in .pp and: .pp .in +4n .ex keyctl new_session .ee .in .sh see also .ad l .nh .br keyctl (1), .br keyctl (3), .br keyctl_join_session_keyring (3), .br keyctl_session_to_parent (3), .br keyrings (7), .br persistent\-keyring (7), .br process\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7), .br pam_keyinit (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getgroups.2 .so man3/unlocked_stdio.3 .so man3/exec.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" parts copyright (c) 1995 nicolai langfeldt (janl@ifi.uio.no), 1/1/95 .\" and copyright (c) 2006, 2007, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-24 by rik faith .\" modified 1995-05-18 by todd larason .\" modified 1997-01-31 by eric s. raymond .\" modified 1995-01-09 by richard kettlewell .\" modified 1998-05-13 by michael haardt .\" modified 1999-07-06 by aeb & albert cahalan .\" modified 2000-01-07 by aeb .\" modified 2004-06-23 by michael kerrisk .\" 2007-06-08 mtk: added example program .\" 2007-07-05 mtk: added details on underlying system call interfaces .\" .th stat 2 2021-08-27 "linux" "linux programmer's manual" .sh name stat, fstat, lstat, fstatat \- get file status .sh synopsis .nf .b #include .pp .bi "int stat(const char *restrict " pathname , .bi " struct stat *restrict " statbuf ); .bi "int fstat(int " fd ", struct stat *" statbuf ); .bi "int lstat(const char *restrict " pathname , .bi " struct stat *restrict " statbuf ); .pp .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "int fstatat(int " dirfd ", const char *restrict " pathname , .bi " struct stat *restrict " statbuf ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br lstat (): .nf /* since glibc 2.20 */ _default_source || _xopen_source >= 500 .\" _xopen_source && _xopen_source_extended || /* since glibc 2.10: */ _posix_c_source >= 200112l || /* glibc 2.19 and earlier */ _bsd_source .fi .pp .br fstatat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description these functions return information about a file, in the buffer pointed to by .ir statbuf . no permissions are required on the file itself, but\(emin the case of .br stat (), .br fstatat (), and .br lstat ()\(emexecute (search) permission is required on all of the directories in .i pathname that lead to the file. .pp .br stat () and .br fstatat () retrieve information about the file pointed to by .ir pathname ; the differences for .br fstatat () are described below. .pp .br lstat () is identical to .br stat (), except that if .i pathname is a symbolic link, then it returns information about the link itself, not the file that the link refers to. .pp .br fstat () is identical to .br stat (), except that the file about which information is to be retrieved is specified by the file descriptor .ir fd . .\" .ss the stat structure all of these system calls return a .i stat structure, which contains the following fields: .pp .in +4n .ex struct stat { dev_t st_dev; /* id of device containing file */ ino_t st_ino; /* inode number */ mode_t st_mode; /* file type and mode */ nlink_t st_nlink; /* number of hard links */ uid_t st_uid; /* user id of owner */ gid_t st_gid; /* group id of owner */ dev_t st_rdev; /* device id (if special file) */ off_t st_size; /* total size, in bytes */ blksize_t st_blksize; /* block size for filesystem i/o */ blkcnt_t st_blocks; /* number of 512b blocks allocated */ /* since linux 2.6, the kernel supports nanosecond precision for the following timestamp fields. for the details before linux 2.6, see notes. */ struct timespec st_atim; /* time of last access */ struct timespec st_mtim; /* time of last modification */ struct timespec st_ctim; /* time of last status change */ #define st_atime st_atim.tv_sec /* backward compatibility */ #define st_mtime st_mtim.tv_sec #define st_ctime st_ctim.tv_sec }; .ee .in .pp .ir note : the order of fields in the .i stat structure varies somewhat across architectures. in addition, the definition above does not show the padding bytes that may be present between some fields on various architectures. consult the glibc and kernel source code if you need to know the details. .pp .\" background: inode attributes are modified with i_mutex held, but .\" read by stat() without taking the mutex. .ir note : for performance and simplicity reasons, different fields in the .i stat structure may contain state information from different moments during the execution of the system call. for example, if .ir st_mode or .ir st_uid is changed by another process by calling .br chmod (2) or .br chown (2), .br stat () might return the old .i st_mode together with the new .ir st_uid , or the old .i st_uid together with the new .ir st_mode . .pp the fields in the .i stat structure are as follows: .tp .i st_dev this field describes the device on which this file resides. (the .br major (3) and .br minor (3) macros may be useful to decompose the device id in this field.) .tp .i st_ino this field contains the file's inode number. .tp .i st_mode this field contains the file type and mode. see .br inode (7) for further information. .tp .i st_nlink this field contains the number of hard links to the file. .tp .i st_uid this field contains the user id of the owner of the file. .tp .i st_gid this field contains the id of the group owner of the file. .tp .i st_rdev this field describes the device that this file (inode) represents. .tp .i st_size this field gives the size of the file (if it is a regular file or a symbolic link) in bytes. the size of a symbolic link is the length of the pathname it contains, without a terminating null byte. .tp .i st_blksize this field gives the "preferred" block size for efficient filesystem i/o. .tp .i st_blocks this field indicates the number of blocks allocated to the file, in 512-byte units. (this may be smaller than .ir st_size /512 when the file has holes.) .tp .i st_atime this is the time of the last access of file data. .tp .i st_mtime this is the time of last modification of file data. .tp .i st_ctime this is the file's last status change timestamp (time of last change to the inode). .pp for further information on the above fields, see .br inode (7). .\" .ss fstatat() the .br fstatat () system call is a more general interface for accessing file information which can still provide exactly the behavior of each of .br stat (), .br lstat (), and .br fstat (). .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br stat () and .br lstat () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br stat () and .br lstat ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp .i flags can either be 0, or include one or more of the following flags ored: .tp .br at_empty_path " (since linux 2.6.39)" .\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d if .i pathname is an empty string, operate on the file referred to by .ir dirfd (which may have been obtained using the .br open (2) .b o_path flag). in this case, .i dirfd can refer to any type of file, not just a directory, and the behavior of .br fstatat () is similar to that of .br fstat (). if .i dirfd is .br at_fdcwd , the call operates on the current working directory. this flag is linux-specific; define .b _gnu_source .\" before glibc 2.16, defining _atfile_source sufficed to obtain its definition. .tp .br at_no_automount " (since linux 2.6.38)" don't automount the terminal ("basename") component of .i pathname if it is a directory that is an automount point. this allows the caller to gather attributes of an automount point (rather than the location it would mount). since linux 4.14, .\" commit 42f46148217865a545e129612075f3d828a2c4e4 also don't instantiate a nonexistent name in an on-demand directory such as used for automounter indirect maps. this flag has no effect if the mount point has already been mounted over. .ip both .br stat () and .br lstat () act as though .b at_no_automount was set. .ip the .b at_no_automount can be used in tools that scan directories to prevent mass-automounting of a directory of automount points. .ip this flag is linux-specific; define .b _gnu_source .\" before glibc 2.16, defining _atfile_source sufficed to obtain its definition. .tp .b at_symlink_nofollow if .i pathname is a symbolic link, do not dereference it: instead return information about the link itself, like .br lstat (). (by default, .br fstatat () dereferences symbolic links, like .br stat ().) .pp see .br openat (2) for an explanation of the need for .br fstatat (). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces search permission is denied for one of the directories in the path prefix of .ir pathname . (see also .br path_resolution (7).) .tp .b ebadf .i fd is not a valid open file descriptor. .tp .b ebadf .rb ( fstatat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b efault bad address. .tp .b einval .rb ( fstatat ()) invalid flag specified in .ir flags . .tp .b eloop too many symbolic links encountered while traversing the path. .tp .b enametoolong .i pathname is too long. .tp .b enoent a component of .i pathname does not exist or is a dangling symbolic link. .tp .b enoent .i pathname is an empty string and .b at_empty_path was not specified in .ir flags . .tp .b enomem out of memory (i.e., kernel memory). .tp .b enotdir a component of the path prefix of .i pathname is not a directory. .tp .b enotdir .rb ( fstatat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b eoverflow .i pathname or .i fd refers to a file whose size, inode number, or number of blocks cannot be represented in, respectively, the types .ir off_t , .ir ino_t , or .ir blkcnt_t . this error can occur when, for example, an application compiled on a 32-bit platform without .i \-d_file_offset_bits=64 calls .br stat () on a file whose size exceeds .i (1<<31)\-1 bytes. .sh versions .br fstatat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br stat (), .br fstat (), .br lstat (): svr4, 4.3bsd, posix.1-2001, posix.1.2008. .\" svr4 documents additional .\" .br fstat () .\" error conditions eintr, enolink, and eoverflow. svr4 .\" documents additional .\" .br stat () .\" and .\" .br lstat () .\" error conditions eintr, emultihop, enolink, and eoverflow. .pp .br fstatat (): posix.1-2008. .pp according to posix.1-2001, .br lstat () on a symbolic link need return valid information only in the .i st_size field and the file type of the .ir st_mode field of the .ir stat structure. posix.1-2008 tightens the specification, requiring .br lstat () to return valid information in all fields except the mode bits in .ir st_mode . .pp use of the .i st_blocks and .i st_blksize fields may be less portable. (they were introduced in bsd. the interpretation differs between systems, and possibly on a single system when nfs mounts are involved.) .sh notes .ss timestamp fields older kernels and older standards did not support nanosecond timestamp fields. instead, there were three timestamp .ri fields\(em st_atime , .ir st_mtime , and .ir st_ctime \(emtyped as .ir time_t that recorded timestamps with one-second precision. .pp since kernel 2.5.48, the .i stat structure supports nanosecond resolution for the three file timestamp fields. the nanosecond components of each timestamp are available via names of the form .ir st_atim.tv_nsec , if suitable feature test macros are defined. nanosecond timestamps were standardized in posix.1-2008, and, starting with version 2.12, glibc exposes the nanosecond component names if .br _posix_c_source is defined with the value 200809l or greater, or .br _xopen_source is defined with the value 700 or greater. up to and including glibc 2.19, the definitions of the nanoseconds components are also defined if .b _bsd_source or .b _svid_source is defined. if none of the aforementioned macros are defined, then the nanosecond values are exposed with names of the form .ir st_atimensec . .\" .ss c library/kernel differences over time, increases in the size of the .i stat structure have led to three successive versions of .br stat (): .ir sys_stat () (slot .ir __nr_oldstat ), .ir sys_newstat () (slot .ir __nr_stat ), and .i sys_stat64() (slot .ir __nr_stat64 ) on 32-bit platforms such as i386. the first two versions were already present in linux 1.0 (albeit with different names); .\" see include/asm-i386/stat.h in the linux 2.4 source code for the .\" various versions of the structure definitions the last was added in linux 2.4. similar remarks apply for .br fstat () and .br lstat (). .pp the kernel-internal versions of the .i stat structure dealt with by the different versions are, respectively: .tp .ir __old_kernel_stat the original structure, with rather narrow fields, and no padding. .tp .ir stat larger .i st_ino field and padding added to various parts of the structure to allow for future expansion. .tp .ir stat64 even larger .i st_ino field, larger .i st_uid and .i st_gid fields to accommodate the linux-2.4 expansion of uids and gids to 32 bits, and various other enlarged fields and further padding in the structure. (various padding bytes were eventually consumed in linux 2.6, with the advent of 32-bit device ids and nanosecond components for the timestamp fields.) .pp the glibc .br stat () wrapper function hides these details from applications, invoking the most recent version of the system call provided by the kernel, and repacking the returned information if required for old binaries. .\" .\" a note from andries brouwer, july 2007 .\" .\" > is the story not rather more complicated for some calls like .\" > stat(2)? .\" .\" yes and no, mostly no. see /usr/include/sys/stat.h . .\" .\" the idea is here not so much that syscalls change, but that .\" the definitions of struct stat and of the types dev_t and mode_t change. .\" this means that libc (even if it does not call the kernel .\" but only calls some internal function) must know what the .\" format of dev_t or of struct stat is. .\" the communication between the application and libc goes via .\" the include file that defines a _stat_ver and .\" _mknod_ver describing the layout of the data that user space .\" uses. each (almost each) occurrence of stat() is replaced by .\" an occurrence of xstat() where the first parameter of xstat() .\" is this version number _stat_ver. .\" .\" now, also the definitions used by the kernel change. .\" but glibc copes with this in the standard way, and the .\" struct stat as returned by the kernel is repacked into .\" the struct stat as expected by the application. .\" thus, _stat_ver and this setup cater for the application-libc .\" interface, rather than the libc-kernel interface. .\" .\" (note that the details depend on gcc being used as c compiler.) .pp on modern 64-bit systems, life is simpler: there is a single .br stat () system call and the kernel deals with a .i stat structure that contains fields of a sufficient size. .pp the underlying system call employed by the glibc .br fstatat () wrapper function is actually called .br fstatat64 () or, on some architectures, .\" strace(1) shows the name "newfstatat" on x86-64 .br newfstatat (). .sh examples the following program calls .br lstat () and displays selected fields in the returned .i stat structure. .pp .ex #include #include #include #include #include #include #include int main(int argc, char *argv[]) { struct stat sb; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } if (lstat(argv[1], &sb) == \-1) { perror("lstat"); exit(exit_failure); } printf("id of containing device: [%jx,%jx]\en", (uintmax_t) major(sb.st_dev), (uintmax_t) minor(sb.st_dev)); printf("file type: "); switch (sb.st_mode & s_ifmt) { case s_ifblk: printf("block device\en"); break; case s_ifchr: printf("character device\en"); break; case s_ifdir: printf("directory\en"); break; case s_ififo: printf("fifo/pipe\en"); break; case s_iflnk: printf("symlink\en"); break; case s_ifreg: printf("regular file\en"); break; case s_ifsock: printf("socket\en"); break; default: printf("unknown?\en"); break; } printf("i\-node number: %ju\en", (uintmax_t) sb.st_ino); printf("mode: %jo (octal)\en", (uintmax_t) sb.st_mode); printf("link count: %ju\en", (uintmax_t) sb.st_nlink); printf("ownership: uid=%ju gid=%ju\en", (uintmax_t) sb.st_uid, (uintmax_t) sb.st_gid); printf("preferred i/o block size: %jd bytes\en", (intmax_t) sb.st_blksize); printf("file size: %jd bytes\en", (intmax_t) sb.st_size); printf("blocks allocated: %jd\en", (intmax_t) sb.st_blocks); printf("last status change: %s", ctime(&sb.st_ctime)); printf("last file access: %s", ctime(&sb.st_atime)); printf("last file modification: %s", ctime(&sb.st_mtime)); exit(exit_success); } .ee .sh see also .br ls (1), .br stat (1), .br access (2), .br chmod (2), .br chown (2), .br readlink (2), .br statx (2), .br utime (2), .br capabilities (7), .br inode (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/random.3 .so man3/ecvt.3 .\" copyright (c) 2004 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th posix_openpt 3 2021-03-22 "" "linux programmer's manual" .sh name posix_openpt \- open a pseudoterminal device .sh synopsis .nf .b #include .b #include .pp .bi "int posix_openpt(int " flags ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br posix_openpt (): .nf _xopen_source >= 600 .fi .sh description the .br posix_openpt () function opens an unused pseudoterminal master device, returning a file descriptor that can be used to refer to that device. .pp the .i flags argument is a bit mask that ors together zero or more of the following flags: .tp .b o_rdwr open the device for both reading and writing. it is usual to specify this flag. .tp .b o_noctty do not make this device the controlling terminal for the process. .sh return value on success, .br posix_openpt () returns a file descriptor (a nonnegative integer) which is the lowest numbered unused file descriptor. on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors see .br open (2). .sh versions glibc support for .br posix_openpt () has been provided since version 2.2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br posix_openpt () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp .br posix_openpt () is part of the unix 98 pseudoterminal support (see .br pts (4)). .sh notes some older unix implementations that support system v (aka unix 98) pseudoterminals don't have this function, but it can be easily implemented by opening the pseudoterminal multiplexor device: .pp .in +4n .ex int posix_openpt(int flags) { return open("/dev/ptmx", flags); } .ee .in .pp calling .br posix_openpt () creates a pathname for the corresponding pseudoterminal slave device. the pathname of the slave device can be obtained using .br ptsname (3). the slave device pathname exists only as long as the master device is open. .sh see also .br open (2), .br getpt (3), .br grantpt (3), .br ptsname (3), .br unlockpt (3), .br pts (4), .br pty (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" $netbsd: fts.3,v 1.13.2.1 1997/11/14 02:09:32 mrg exp $ .\" .\" copyright (c) 1989, 1991, 1993, 1994 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)fts.3 8.5 (berkeley) 4/16/94 .\" .\" 2007-12-08, mtk, converted from mdoc to man macros .\" .th fts 3 2021-03-22 "linux" "linux programmer's manual" .sh name fts, fts_open, fts_read, fts_children, fts_set, fts_close \- \ traverse a file hierarchy .sh synopsis .nf .b #include .b #include .b #include .pp .bi "fts *fts_open(char * const *" path_argv ", int " options , .bi " int (*" compar ")(const ftsent **, const ftsent **));" .pp .bi "ftsent *fts_read(fts *" ftsp ); .pp .bi "ftsent *fts_children(fts *" ftsp ", int " instr ); .pp .bi "int fts_set(fts *" ftsp ", ftsent *" f ", int " instr ); .pp .bi "int fts_close(fts *" ftsp ); .fi .sh description the fts functions are provided for traversing file hierarchies. a simple overview is that the .br fts_open () function returns a "handle" (of type .ir "fts\ *" ) that refers to a file hierarchy "stream". this handle is then supplied to the other fts functions. the function .br fts_read () returns a pointer to a structure describing one of the files in the file hierarchy. the function .br fts_children () returns a pointer to a linked list of structures, each of which describes one of the files contained in a directory in the hierarchy. .pp in general, directories are visited two distinguishable times; in preorder (before any of their descendants are visited) and in postorder (after all of their descendants have been visited). files are visited once. it is possible to walk the hierarchy "logically" (visiting the files that symbolic links point to) or physically (visiting the symbolic links themselves), order the walk of the hierarchy or prune and/or revisit portions of the hierarchy. .pp two structures (and associated types) are defined in the include file .ir . the first type is .ir fts , the structure that represents the file hierarchy itself. the second type is .ir ftsent , the structure that represents a file in the file hierarchy. normally, an .i ftsent structure is returned for every file in the file hierarchy. in this manual page, "file" and "ftsent structure" are generally interchangeable. .pp the .i ftsent structure contains fields describing a file. the structure contains at least the following fields (there are additional fields that should be considered private to the implementation): .pp .in +4n .ex typedef struct _ftsent { unsigned short fts_info; /* flags for ftsent structure */ char *fts_accpath; /* access path */ char *fts_path; /* root path */ short fts_pathlen; /* strlen(fts_path) + strlen(fts_name) */ char *fts_name; /* filename */ short fts_namelen; /* strlen(fts_name) */ short fts_level; /* depth (\-1 to n) */ int fts_errno; /* file errno */ long fts_number; /* local numeric value */ void *fts_pointer; /* local address value */ struct _ftsent *fts_parent; /* parent directory */ struct _ftsent *fts_link; /* next file structure */ struct _ftsent *fts_cycle; /* cycle structure */ struct stat *fts_statp; /* stat(2) information */ .\" also: .\" ino_t fts_ino; /* inode (only for directories)*/ .\" dev_t fts_dev; /* device (only for directories)*/ .\" nlink_t fts_nlink; /* link count (only for directories)*/ .\" u_short fts_flags; /* private flags for ftsent structure */ .\" u_short fts_instr; /* fts_set() instructions */ } ftsent; .ee .in .pp these fields are defined as follows: .\" .bl -tag -width "fts_namelen" .tp .ir fts_info one of the following values describing the returned .i ftsent structure and the file it represents. with the exception of directories without errors .rb ( fts_d ), all of these entries are terminal, that is, they will not be revisited, nor will any of their descendants be visited. .\" .bl -tag -width fts_default .rs .tp .br fts_d a directory being visited in preorder. .tp .br fts_dc a directory that causes a cycle in the tree. (the .i fts_cycle field of the .i ftsent structure will be filled in as well.) .tp .br fts_default any .i ftsent structure that represents a file type not explicitly described by one of the other .i fts_info values. .tp .br fts_dnr a directory which cannot be read. this is an error return, and the .i fts_errno field will be set to indicate what caused the error. .tp .br fts_dot a file named "." or ".." which was not specified as a filename to .br fts_open () (see .br fts_seedot ). .tp .br fts_dp a directory being visited in postorder. the contents of the .i ftsent structure will be unchanged from when it was returned in preorder, that is, with the .i fts_info field set to .br fts_d . .tp .br fts_err this is an error return, and the .i fts_errno field will be set to indicate what caused the error. .tp .br fts_f a regular file. .tp .br fts_ns a file for which no .br stat (2) information was available. the contents of the .i fts_statp field are undefined. this is an error return, and the .i fts_errno field will be set to indicate what caused the error. .tp .br fts_nsok a file for which no .br stat (2) information was requested. the contents of the .i fts_statp field are undefined. .tp .br fts_sl a symbolic link. .tp .br fts_slnone a symbolic link with a nonexistent target. the contents of the .i fts_statp field reference the file characteristic information for the symbolic link itself. .\" .el .re .tp .ir fts_accpath a path for accessing the file from the current directory. .tp .ir fts_path the path for the file relative to the root of the traversal. this path contains the path specified to .br fts_open () as a prefix. .tp .ir fts_pathlen the sum of the lengths of the strings referenced by .ir fts_path and .ir fts_name . .tp .ir fts_name the name of the file. .tp .ir fts_namelen the length of the string referenced by .ir fts_name . .tp .ir fts_level the depth of the traversal, numbered from \-1 to n, where this file was found. the .i ftsent structure representing the parent of the starting point (or root) of the traversal is numbered \-1, and the .i ftsent structure for the root itself is numbered 0. .tp .ir fts_errno if .br fts_children () or .br fts_read () returns an .i ftsent structure whose .i fts_info field is set to .br fts_dnr , .br fts_err , or .br fts_ns , the .i fts_errno field contains the error number (i.e., the .ir errno value) specifying the cause of the error. otherwise, the contents of the .i fts_errno field are undefined. .tp .ir fts_number this field is provided for the use of the application program and is not modified by the fts functions. it is initialized to 0. .tp .ir fts_pointer this field is provided for the use of the application program and is not modified by the fts functions. it is initialized to null. .tp .ir fts_parent a pointer to the .i ftsent structure referencing the file in the hierarchy immediately above the current file, that is, the directory of which this file is a member. a parent structure for the initial entry point is provided as well, however, only the .ir fts_level , .ir fts_number , and .i fts_pointer fields are guaranteed to be initialized. .tp .ir fts_link upon return from the .br fts_children () function, the .i fts_link field points to the next structure in the null-terminated linked list of directory members. otherwise, the contents of the .i fts_link field are undefined. .tp .ir fts_cycle if a directory causes a cycle in the hierarchy (see .br fts_dc ), either because of a hard link between two directories, or a symbolic link pointing to a directory, the .i fts_cycle field of the structure will point to the .i ftsent structure in the hierarchy that references the same file as the current .i ftsent structure. otherwise, the contents of the .i fts_cycle field are undefined. .tp .ir fts_statp a pointer to .br stat (2) information for the file. .\" .el .pp a single buffer is used for all of the paths of all of the files in the file hierarchy. therefore, the .i fts_path and .i fts_accpath fields are guaranteed to be null-terminated .i only for the file most recently returned by .br fts_read (). to use these fields to reference any files represented by other .i ftsent structures will require that the path buffer be modified using the information contained in that .i ftsent structure's .i fts_pathlen field. any such modifications should be undone before further calls to .br fts_read () are attempted. the .i fts_name field is always null-terminated. .ss fts_open() the .br fts_open () function takes a pointer to an array of character pointers naming one or more paths which make up a logical file hierarchy to be traversed. the array must be terminated by a null pointer. .pp there are a number of options, at least one of which (either .br fts_logical or .br fts_physical ) must be specified. the options are selected by oring the following values: .\" .bl -tag -width "fts_physical" .tp .br fts_comfollow this option causes any symbolic link specified as a root path to be followed immediately whether or not .br fts_logical is also specified. .tp .br fts_logical this option causes the fts routines to return .i ftsent structures for the targets of symbolic links instead of the symbolic links themselves. if this option is set, the only symbolic links for which .i ftsent structures are returned to the application are those referencing nonexistent files. either .br fts_logical or .br fts_physical .i must be provided to the .br fts_open () function. .tp .br fts_nochdir as a performance optimization, the fts functions change directories as they walk the file hierarchy. this has the side-effect that an application cannot rely on being in any particular directory during the traversal. the .br fts_nochdir option turns off this optimization, and the fts functions will not change the current directory. note that applications should not themselves change their current directory and try to access files unless .br fts_nochdir is specified and absolute pathnames were provided as arguments to .br fts_open (). .tp .br fts_nostat by default, returned .i ftsent structures reference file characteristic information (the .i statp field) for each file visited. this option relaxes that requirement as a performance optimization, allowing the fts functions to set the .i fts_info field to .br fts_nsok and leave the contents of the .i statp field undefined. .tp .br fts_physical this option causes the fts routines to return .i ftsent structures for symbolic links themselves instead of the target files they point to. if this option is set, .i ftsent structures for all symbolic links in the hierarchy are returned to the application. either .br fts_logical or .br fts_physical .i must be provided to the .br fts_open () function. .tp .br fts_seedot by default, unless they are specified as path arguments to .br fts_open (), any files named "." or ".." encountered in the file hierarchy are ignored. this option causes the fts routines to return .i ftsent structures for them. .tp .br fts_xdev this option prevents fts from descending into directories that have a different device number than the file from which the descent began. .\" .el .pp the argument .br compar () specifies a user-defined function which may be used to order the traversal of the hierarchy. it takes two pointers to pointers to .i ftsent structures as arguments and should return a negative value, zero, or a positive value to indicate if the file referenced by its first argument comes before, in any order with respect to, or after, the file referenced by its second argument. the .ir fts_accpath , .ir fts_path , and .i fts_pathlen fields of the .i ftsent structures may .i never be used in this comparison. if the .i fts_info field is set to .br fts_ns or .br fts_nsok , the .i fts_statp field may not either. if the .br compar () argument is null, the directory traversal order is in the order listed in .i path_argv for the root paths, and in the order listed in the directory for everything else. .ss fts_read() the .br fts_read () function returns a pointer to an .i ftsent structure describing a file in the hierarchy. directories (that are readable and do not cause cycles) are visited at least twice, once in preorder and once in postorder. all other files are visited at least once. (hard links between directories that do not cause cycles or symbolic links to symbolic links may cause files to be visited more than once, or directories more than twice.) .pp if all the members of the hierarchy have been returned, .br fts_read () returns null and sets .i errno to 0. if an error unrelated to a file in the hierarchy occurs, .br fts_read () returns null and sets .i errno to indicate the error. if an error related to a returned file occurs, a pointer to an .i ftsent structure is returned, and .i errno may or may not have been set (see .ir fts_info ). .pp the .i ftsent structures returned by .br fts_read () may be overwritten after a call to .br fts_close () on the same file hierarchy stream, or, after a call to .br fts_read () on the same file hierarchy stream unless they represent a file of type directory, in which case they will not be overwritten until after a call to .br fts_read () after the .i ftsent structure has been returned by the function .br fts_read () in postorder. .ss fts_children() the .br fts_children () function returns a pointer to an .i ftsent structure describing the first entry in a null-terminated linked list of the files in the directory represented by the .i ftsent structure most recently returned by .br fts_read (). the list is linked through the .i fts_link field of the .i ftsent structure, and is ordered by the user-specified comparison function, if any. repeated calls to .br fts_children () will re-create this linked list. .pp as a special case, if .br fts_read () has not yet been called for a hierarchy, .br fts_children () will return a pointer to the files in the logical directory specified to .br fts_open (), that is, the arguments specified to .br fts_open (). otherwise, if the .i ftsent structure most recently returned by .br fts_read () is not a directory being visited in preorder, or the directory does not contain any files, .br fts_children () returns null and sets .i errno to zero. if an error occurs, .br fts_children () returns null and sets .i errno to indicate the error. .pp the .i ftsent structures returned by .br fts_children () may be overwritten after a call to .br fts_children (), .br fts_close (), or .br fts_read () on the same file hierarchy stream. .pp the .i instr argument is either zero or the following value: .\" .bl -tag -width fts_nameonly .tp .br fts_nameonly only the names of the files are needed. the contents of all the fields in the returned linked list of structures are undefined with the exception of the .i fts_name and .i fts_namelen fields. .\" .el .ss fts_set() the function .br fts_set () allows the user application to determine further processing for the file .i f of the stream .ir ftsp . the .br fts_set () function returns 0 on success, and \-1 if an error occurs. .pp the .i instr argument is either 0 (meaning "do nothing") or one of the following values: .\" .bl -tag -width fts_physical .tp .br fts_again revisit the file; any file type may be revisited. the next call to .br fts_read () will return the referenced file. the .i fts_stat and .i fts_info fields of the structure will be reinitialized at that time, but no other fields will have been changed. this option is meaningful only for the most recently returned file from .br fts_read (). normal use is for postorder directory visits, where it causes the directory to be revisited (in both preorder and postorder) as well as all of its descendants. .tp .br fts_follow the referenced file must be a symbolic link. if the referenced file is the one most recently returned by .br fts_read (), the next call to .br fts_read () returns the file with the .i fts_info and .i fts_statp fields reinitialized to reflect the target of the symbolic link instead of the symbolic link itself. if the file is one of those most recently returned by .br fts_children (), the .i fts_info and .i fts_statp fields of the structure, when returned by .br fts_read (), will reflect the target of the symbolic link instead of the symbolic link itself. in either case, if the target of the symbolic link does not exist, the fields of the returned structure will be unchanged and the .i fts_info field will be set to .br fts_slnone . .ip if the target of the link is a directory, the preorder return, followed by the return of all of its descendants, followed by a postorder return, is done. .tp .br fts_skip no descendants of this file are visited. the file may be one of those most recently returned by either .br fts_children () or .br fts_read (). .\" .el .ss fts_close() the .br fts_close () function closes the file hierarchy stream referred to by .i ftsp and restores the current directory to the directory from which .br fts_open () was called to open .ir ftsp . the .br fts_close () function returns 0 on success, and \-1 if an error occurs. .sh errors the function .br fts_open () may fail and set .i errno for any of the errors specified for .br open (2) and .br malloc (3). .pp the function .br fts_close () may fail and set .i errno for any of the errors specified for .br chdir (2) and .br close (2). .pp the functions .br fts_read () and .br fts_children () may fail and set .i errno for any of the errors specified for .br chdir (2), .br malloc (3), .br opendir (3), .br readdir (3), and .br stat (2). .pp in addition, .br fts_children (), .br fts_open (), and .br fts_set () may fail and set .i errno as follows: .tp .b einval .i options or .i instr was invalid. .sh versions these functions are available in linux since glibc2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fts_open (), .br fts_set (), .br fts_close () t} thread safety mt-safe t{ .br fts_read (), .br fts_children () t} thread safety mt-unsafe .te .hy .ad .sp 1 .sh conforming to 4.4bsd. .sh bugs in versions of glibc before 2.23, .\" fixed by commit 8b7b7f75d91f7bac323dd6a370aeb3e9c5c4a7d5 .\" https://sourceware.org/bugzilla/show_bug.cgi?id=15838 .\" https://sourceware.org/bugzilla/show_bug.cgi?id=11460 all of the apis described in this man page are not safe when compiling a program using the lfs apis (e.g., when compiling with .ir \-d_file_offset_bits=64 ). .\" .\" the following statement is years old, and seems no closer to .\" being true -- mtk .\" the .\" .i fts .\" utility is expected to be included in a future .\" posix.1 .\" revision. .sh see also .br find (1), .br chdir (2), .br stat (2), .br ftw (3), .br qsort (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1994 mike battersby .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by aeb, 960721 .\" 2005-11-21, mtk, added descriptions of sigisemptyset(), sigandset(), .\" and sigorset() .\" 2007-10-26 mdw added wording that a sigset_t must be initialized .\" prior to use .\" .th sigsetops 3 2021-03-22 "linux" "linux programmer's manual" .sh name sigemptyset, sigfillset, sigaddset, sigdelset, sigismember \- posix signal set operations .sh synopsis .nf .b #include .pp .bi "int sigemptyset(sigset_t *" set ); .bi "int sigfillset(sigset_t *" set ); .pp .bi "int sigaddset(sigset_t *" set ", int " signum ); .bi "int sigdelset(sigset_t *" set ", int " signum ); .pp .bi "int sigismember(const sigset_t *" set ", int " signum ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigemptyset (), .br sigfillset (), .br sigaddset (), .br sigdelset (), .br sigismember (): .nf _posix_c_source .fi .sh description these functions allow the manipulation of posix signal sets. .pp .br sigemptyset () initializes the signal set given by .i set to empty, with all signals excluded from the set. .pp .br sigfillset () initializes .i set to full, including all signals. .pp .br sigaddset () and .br sigdelset () add and delete respectively signal .i signum from .ir set . .pp .br sigismember () tests whether .i signum is a member of .ir set . .pp objects of type .i sigset_t must be initialized by a call to either .br sigemptyset () or .br sigfillset () before being passed to the functions .br sigaddset (), .br sigdelset (), and .br sigismember () or the additional glibc functions described below .rb ( sigisemptyset (), .br sigandset (), and .br sigorset ()). the results are undefined if this is not done. .sh return value .br sigemptyset (), .br sigfillset (), .br sigaddset (), and .br sigdelset () return 0 on success and \-1 on error. .pp .br sigismember () returns 1 if .i signum is a member of .ir set , 0 if .i signum is not a member, and \-1 on error. .pp on error, these functions set .i errno to indicate the error. .sh errors .tp .b einval .i signum is not a valid signal. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sigemptyset (), .br sigfillset (), .br sigaddset (), .br sigdelset (), .br sigismember (), .br sigisemptyset (), .br sigorset (), .br sigandset () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes when creating a filled signal set, the glibc .br sigfillset () function does not include the two real-time signals used internally by the nptl threading implementation. see .br nptl (7) for details. .\" .ss glibc extensions if the .b _gnu_source feature test macro is defined, then \fi\fp exposes three other functions for manipulating signal sets: .pp .nf .bi "int sigisemptyset(const sigset_t *" set ); .bi "int sigorset(sigset_t *" dest ", const sigset_t *" left , .bi " const sigset_t *" right ); .bi "int sigandset(sigset_t *" dest ", const sigset_t *" left , .bi " const sigset_t *" right ); .fi .pp .br sigisemptyset () returns 1 if .i set contains no signals, and 0 otherwise. .pp .br sigorset () places the union of the sets .i left and .i right in .ir dest . .br sigandset () places the intersection of the sets .i left and .i right in .ir dest . both functions return 0 on success, and \-1 on failure. .pp these functions are nonstandard (a few other systems provide similar functions) and their use should be avoided in portable applications. .sh see also .br sigaction (2), .br sigpending (2), .br sigprocmask (2), .br sigsuspend (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. ==================== changes in man-pages-5.13 ==================== released: 2021-08-27, christchurch ahelenia ziemiańska (наб) alan peakall alejandro colomar alexis wilke askar safin christian brauner christophe leroy christopher yeleighton cristian morales vega dan robertson darrick j. wong dominique brazziel emanueletorre eric w. biederman g. branden robinson helge kreutzmann jakub wilk james o. d. hunt jonny grant kees cook kir kolyshkin kurt kanzenbach kxuan michael kerrisk michael weiß neilbrown nora platiel pali rohár peter collingbourne richard palethorpe rodrigo campos sagar patel serge e. hallyn sergey petrakov stefan kanthak štěpán němec thomas gleixner thomas voss viet than will manley contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: apologies if i missed anyone! new and rewritten pages ----------------------- mount_setattr.2 christian brauner [alejandro colomar, michael kerrisk] new manual page documenting the mount_setattr() system call newly documented interfaces in existing pages --------------------------------------------- futex.2 kurt kanzenbach [alejandro colomar, thomas gleixner, michael kerrisk] document futex_lock_pi2 ioctl_tty.2 pali rohár [alejandro colomar, michael kerrisk] document ioctls: tcgets2, tcsets2, tcsetsw2, tcsetsf2 pidfd_open.2 michael kerrisk document pidfd_nonblock seccomp_unotify.2 rodrigo campos [alejandro colomar] document seccomp_addfd_flag_send sigaction.2 peter collingbourne [alejandro colomar, michael kerrisk] document sa_expose_tagbits and the flag support detection protocol statx.2 neilbrown document statx_mnt_id capabilities.7 user_namespaces.7 michael kerrisk, kir kolyshkin [alejandro colomar] describe cap_setfcap for mapping uid 0 mount_namespaces.7 michael kerrisk [christian brauner, eric w. biederman] more clearly explain the notion of locked mounts for a long time, this manual page has had a brief discussion of "locked" mounts, without clearly saying what this concept is, or why it exists. expand the discussion with an explanation of what locked mounts are, why mounts are locked, and some examples of the effect of locking. user_namespaces.7 michael kerrisk document /proc/pid/projid_map ld.so.8 michael kerrisk document --list-tunables option added in glibc 2.33 global changes -------------- a few pages michael kerrisk errors: correct alphabetic order a few pages michael kerrisk place see also entries in correct order a few pages michael kerrisk arrange .sh sections in correct order various pages michael kerrisk fix ebadf error description make the description of the ebadf error for invalid 'dirfd' more uniform. in particular, note that the error only occurs when the pathname is relative, and that it occurs when the 'dirfd' is neither valid *nor* has the value at_fdcwd. various pages michael kerrisk errors: combine errors into a single alphabetic list these pages split out extra errors for some apis into a separate list. probably, the pages are easier to ready if all errors are combined into a single list. note that there still remain a few pages where the errors are listed separately for different apis. for the moment, it seems best to leave those pages as is, since the error lists are largely distinct in those pages. various pages michael kerrisk terminology clean-up: "mount point" ==> "mount" many times, these pages use the terminology "mount point", where "mount" would be better. a "mount point" is the location at which a mount is attached. a "mount" is an association between a filesystem and a mount point. accept.2 access.2 getpriority.2 mlock.2 michael kerrisk errors: combine errors into a single list these pages split out errors into separate lists (perhaps per api, perhaps "may" vs "shall", perhaps "linux-specific" vs standard(??)), but there's no good reason to do this. it makes the error list harder to read, and is inconsistent with other pages. so, combine the errors into a single list. fanotify_mark.2 futimesat.2 mount_setattr.2 statx.2 symlink.2 mkfifo.3 michael kerrisk refer the reader to openat(2) for explanation of why 'dirfd' is useful various pages thomas voss [alejandro colomar] consistently use '*argv[]' changes to individual pages --------------------------- iconv.1 iconvconfig.8 michael kerrisk [christopher yeleighton] files: note that files may be under /usr/lib64 rather than /lib/64 see https://bugzilla.kernel.org/show_bug.cgi?id=214163 ldd.1 alejandro colomar [emanueletorre] fix example command add_key.2 keyctl.2 request_key.2 michael kerrisk [dominique brazziel] note that the "libkeyutils" package provides see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=992377 close_range.2 michael kerrisk, alejandro colomar glibc 2.34 has added a close_range() wrapper execve.2 michael kerrisk [nora platiel] the pathname given to interpreter is not necessarily absolute michael kerrisk see also: getauxval(3) getauxval(3) is useful background regarding execve(2). fanotify_mark.2 michael kerrisk errors: add missing ebadf error for invalid 'dirfd' ioctl_tty.2 pali rohár [alejandro colomar] update dtr example do not include unused (and incompatible) header file termios.h and include required header files for puts() and close() functions. mount.2 michael kerrisk errors: add eperm error for case where a mount is locked refer the reader to mount_namespaces(7) for details. michael kerrisk see also: add mount_setattr(2) open.2 michael kerrisk explicitly describe the ebadf error that can occur with openat() in particular, specifying an invalid file descriptor number in 'dirfd' can be used as a check that 'pathname' is absolute. michael kerrisk clarify that openat()'s dirfd must be opened with o_rdonly or o_path michael kerrisk add mount_setattr(2) to list of 'dirfd' apis open_by_handle_at.2 michael kerrisk errors: add missing ebadf error for invalid 'dirfd' readv2.2 will manley [alejandro colomar] note preadv2(..., rwf_nowait) bug in bugs section readv.2 pipe.7 michael kerrisk [наб] make text on pipe writes more general to avoid a confusion in writev(2) seccomp.2 eric w. biederman [kees cook] clarify that bad system calls kill the thread (not the process) syscalls.2 michael kerrisk add quotactl_fd(); remove quotactl_path() quotactl_path() was never wired up in linux 5.13. it was replaced instead by quotactl_fd(), michael kerrisk add system calls that are new in 5.13 umount.2 michael kerrisk errors: add einval for case where mount is locked wait.2 richard palethorpe [alejandro colomar] add esrch for when pid == int_min michael kerrisk errors: document eagain for waitid() on a pid file descriptor getaddrinfo.3 alejandro colomar [cristian morales vega] note that 'errno' is set in parallel with eai_system getauxval.3 michael kerrisk see also: add execve(2) getopt.3 james o. d. hunt [alejandro colomar] further clarification of 'optstring' pthread_setname_np.3 michael kerrisk [alexis wilke] examples: remove a bug by simplifying the code strlen.3 wcslen.3 michael kerrisk [alejandro colomar, jonny grant] recommend alternatives where input buffer might not be null-terminated strstr.3 alejandro colomar [stefan kanthak] document special case for empty needle termios.3 pali rohár [alejandro colomar] sparc architecture has 4 different bnnn constants pali rohár [alejandro colomar] add information how to set baud rate to any other value pali rohár [alejandro colomar] use bold style for bnn and extn macro constants pali rohár [alejandro colomar] document missing baud-rate constants tsearch.3 michael kerrisk name: add twalk_r wcstok.3 jakub wilk fix type mismatch in the example proc.5 michael kerrisk add /proc/pid/projid_map, referring reader to user_namespaces(7) michael kerrisk remove duplicated /proc/[pid]/gid_map entry mount_namespaces.7 michael kerrisk terminology clean-up: "mount point" ==> "mount" many times, this page uses the terminology "mount point", where "mount" would be better. a "mount point" is the location at which a mount is attached. a "mount" is an association between a filesystem and a mount point. michael kerrisk see also: add mount_setattr(2) namespaces.7 štěpán němec [alejandro colomar] fix confusion caused by text reorganization path_resolution.7 michael kerrisk [askar safin] improve description of trailing slashes see https://bugzilla.kernel.org/show_bug.cgi?id=212385 posixoptions.7 alejandro colomar [alan peakall] fix legacy functions list (s/getcwd/getwd/) user_namespaces.7 kir kolyshkin [alejandro colomar] fix a reference to a kernel document michael kerrisk [eric w. biederman] add a definition of "global root" vdso.7 michael kerrisk [christophe leroy] update clock_realtime_coarse + clock_monotonic_coarse info for powerpc alejandro colomar [christophe leroy] add y2038 compliant gettime for ppc/32 .so man3/stdarg.3 .so man3/modf.3 .so man7/system_data_types.7 .so man3/log.3 .so man2/outb.2 .so man2/outb.2 .so man4/null.4 .\" this man page is copyright (c) 1998 pawel krawczyk. .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: sendfile.2,v 1.5 1999/05/18 11:54:11 freitag exp $ .\" 2000-11-19 bert hubert : in_fd cannot be socket .\" .\" 2004-12-17, mtk .\" updated description of in_fd and out_fd for 2.6 .\" various wording and formatting changes .\" .\" 2005-03-31 martin pool mmap() improvements .\" .th sendfile 2 2021-03-22 "linux" "linux programmer's manual" .sh name sendfile \- transfer data between file descriptors .sh synopsis .nf .b #include .pp .bi "ssize_t sendfile(int" " out_fd" ", int" " in_fd" ", off_t *" \ offset ", size_t" " count" ); .\" the below is too ugly. comments about glibc versions belong .\" in the notes, not in the header. .\" .\" .b #include .\" .b #if (__glibc__==2 && __glibc_minor__>=1) || __glibc__>2 .\" .b #include .\" #else .\" .b #include .\" .b /* no system prototype before glibc 2.1. */ .\" .bi "ssize_t sendfile(int" " out_fd" ", int" " in_fd" ", off_t *" \ .\" offset ", size_t" " count" ) .\" .b #endif .\" .fi .sh description .br sendfile () copies data between one file descriptor and another. because this copying is done within the kernel, .br sendfile () is more efficient than the combination of .br read (2) and .br write (2), which would require transferring data to and from user space. .pp .i in_fd should be a file descriptor opened for reading and .i out_fd should be a descriptor opened for writing. .pp if .i offset is not null, then it points to a variable holding the file offset from which .br sendfile () will start reading data from .ir in_fd . when .br sendfile () returns, this variable will be set to the offset of the byte following the last byte that was read. if .i offset is not null, then .br sendfile () does not modify the file offset of .ir in_fd ; otherwise the file offset is adjusted to reflect the number of bytes read from .ir in_fd . .pp if .i offset is null, then data will be read from .ir in_fd starting at the file offset, and the file offset will be updated by the call. .pp .i count is the number of bytes to copy between the file descriptors. .pp the .ir in_fd argument must correspond to a file which supports .br mmap (2)-like operations (i.e., it cannot be a socket). .pp in linux kernels before 2.6.33, .i out_fd must refer to a socket. since linux 2.6.33 it can be any file. if it is a regular file, then .br sendfile () changes the file offset appropriately. .sh return value if the transfer was successful, the number of bytes written to .i out_fd is returned. note that a successful call to .br sendfile () may write fewer bytes than requested; the caller should be prepared to retry the call if there were unsent bytes. see also notes. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eagain nonblocking i/o has been selected using .b o_nonblock and the write would block. .tp .b ebadf the input file was not opened for reading or the output file was not opened for writing. .tp .b efault bad address. .tp .b einval descriptor is not valid or locked, or an .br mmap (2)-like operation is not available for .ir in_fd , or .i count is negative. .tp .b einval .i out_fd has the .b o_append flag set. this is not currently supported by .br sendfile (). .tp .b eio unspecified error while reading from .ir in_fd . .tp .b enomem insufficient memory to read from .ir in_fd . .tp .b eoverflow .i count is too large, the operation would result in exceeding the maximum size of either the input file or the output file. .tp .b espipe .i offset is not null but the input file is not seekable. .sh versions .br sendfile () first appeared in linux 2.2. the include file .i is present since glibc 2.1. .sh conforming to not specified in posix.1-2001, nor in other standards. .pp other unix systems implement .br sendfile () with different semantics and prototypes. it should not be used in portable programs. .sh notes .br sendfile () will transfer at most 0x7ffff000 (2,147,479,552) bytes, returning the number of bytes actually transferred. .\" commit e28cc71572da38a5a12c1cfe4d7032017adccf69 (this is true on both 32-bit and 64-bit systems.) .pp if you plan to use .br sendfile () for sending files to a tcp socket, but need to send some header data in front of the file contents, you will find it useful to employ the .b tcp_cork option, described in .br tcp (7), to minimize the number of packets and to tune performance. .pp in linux 2.4 and earlier, .i out_fd could also refer to a regular file; this possibility went away in the linux 2.6.x kernel series, but was restored in linux 2.6.33. .pp the original linux .br sendfile () system call was not designed to handle large file offsets. consequently, linux 2.4 added .br sendfile64 (), with a wider type for the .i offset argument. the glibc .br sendfile () wrapper function transparently deals with the kernel differences. .pp applications may wish to fall back to .br read (2)/ write (2) in the case where .br sendfile () fails with .b einval or .br enosys . .pp if .i out_fd refers to a socket or pipe with zero-copy support, callers must ensure the transferred portions of the file referred to by .i in_fd remain unmodified until the reader on the other end of .i out_fd has consumed the transferred data. .pp the linux-specific .br splice (2) call supports transferring data between arbitrary file descriptors provided one (or both) of them is a pipe. .sh see also .br copy_file_range (2), .br mmap (2), .br open (2), .br socket (2), .br splice (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ftw.3 .so man3/ctanh.3 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 21 22:40:25 1993 by rik faith .\" modified sat feb 18 15:27:48 1995 by michael haardt .\" modified sun apr 14 11:40:50 1996 by andries brouwer : .\" corrected description of effect on locks (thanks to .\" tigran aivazian ). .\" modified fri jan 31 16:21:46 1997 by eric s. raymond .\" modified 2000-07-22 by nicolás lichtmaier .\" added note about close(2) not guaranteeing that data is safe on close. .\" .th close 2 2021-03-22 "linux" "linux programmer's manual" .sh name close \- close a file descriptor .sh synopsis .nf .b #include .pp .bi "int close(int " fd ); .fi .sh description .br close () closes a file descriptor, so that it no longer refers to any file and may be reused. any record locks (see .br fcntl (2)) held on the file it was associated with, and owned by the process, are removed (regardless of the file descriptor that was used to obtain the lock). .pp if .i fd is the last file descriptor referring to the underlying open file description (see .br open (2)), the resources associated with the open file description are freed; if the file descriptor was the last reference to a file which has been removed using .br unlink (2), the file is deleted. .sh return value .br close () returns zero on success. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd isn't a valid open file descriptor. .tp .b eintr .\" though, it's in doubt whether this error can ever occur; see .\" https://lwn.net/articles/576478/ "returning eintr from close()" the .br close () call was interrupted by a signal; see .br signal (7). .tp .b eio an i/o error occurred. .tp .br enospc ", " edquot on nfs, these errors are not normally reported against the first write which exceeds the available storage space, but instead against a subsequent .br write (2), .br fsync (2), or .br close (). .pp see notes for a discussion of why .br close () should not be retried after an error. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .\" svr4 documents an additional enolink error condition. .sh notes a successful close does not guarantee that the data has been successfully saved to disk, as the kernel uses the buffer cache to defer writes. typically, filesystems do not flush buffers when a file is closed. if you need to be sure that the data is physically stored on the underlying disk, use .br fsync (2). (it will depend on the disk hardware at this point.) .pp the close-on-exec file descriptor flag can be used to ensure that a file descriptor is automatically closed upon a successful .br execve (2); see .br fcntl (2) for details. .\" .ss multithreaded processes and close() it is probably unwise to close file descriptors while they may be in use by system calls in other threads in the same process. since a file descriptor may be reused, there are some obscure race conditions that may cause unintended side effects. .\" date: tue, 4 sep 2007 13:57:35 +0200 .\" from: fredrik noring .\" one such race involves signals and erestartsys. if a file descriptor .\" in use by a system call is closed and then reused by e.g. an .\" independent open() in some unrelated thread, before the original system .\" call has restarted after erestartsys, the original system call will .\" later restart with the reused file descriptor. this is most likely a .\" serious programming error. .pp furthermore, consider the following scenario where two threads are performing operations on the same file descriptor: .ip 1. 3 one thread is blocked in an i/o system call on the file descriptor. for example, it is trying to .br write (2) to a pipe that is already full, or trying to .br read (2) from a stream socket which currently has no available data. .ip 2. another thread closes the file descriptor. .pp the behavior in this situation varies across systems. on some systems, when the file descriptor is closed, the blocking system call returns immediately with an error. .pp on linux (and possibly some other systems), the behavior is different: the blocking i/o system call holds a reference to the underlying open file description, and this reference keeps the description open until the i/o system call completes. .\" 'struct file' in kernel-speak (see .br open (2) for a discussion of open file descriptions.) thus, the blocking system call in the first thread may successfully complete after the .br close () in the second thread. .\" .ss dealing with error returns from close() a careful programmer will check the return value of .br close (), since it is quite possible that errors on a previous .br write (2) operation are reported only on the final .br close () that releases the open file description. failing to check the return value when closing a file may lead to .i silent loss of data. this can especially be observed with nfs and with disk quota. .pp note, however, that a failure return should be used only for diagnostic purposes (i.e., a warning to the application that there may still be i/o pending or there may have been failed i/o) or remedial purposes (e.g., writing the file once more or creating a backup). .pp retrying the .br close () after a failure return is the wrong thing to do, .\" the file descriptor is released early in close(); .\" close() ==> __close_fd(): .\" __put_unused_fd() ==> __clear_open_fd() .\" return filp_close(file, files); .\" .\" the errors are returned by filp_close() after the fd has been .\" cleared for re-use. since this may cause a reused file descriptor from another thread to be closed. this can occur because the linux kernel .i always releases the file descriptor early in the close operation, freeing it for reuse; the steps that may return an error, .\" filp_close() such as flushing data to the filesystem or device, occur only later in the close operation. .pp many other implementations similarly always close the file descriptor .\" freebsd documents this explicitly. from the look of the source code .\" svr4, ancient sunos, later solaris, and aix all do this. (except in the case of .br ebadf , meaning that the file descriptor was invalid) even if they subsequently report an error on return from .br close (). posix.1 is currently silent on this point, but there are plans to mandate this behavior in the next major release .\" issue 8 of the standard. .pp a careful programmer who wants to know about i/o errors may precede .br close () with a call to .br fsync (2). .pp the .b eintr error is a somewhat special case. regarding the .b eintr error, posix.1-2008 says: .pp .rs if .br close () is interrupted by a signal that is to be caught, it shall return \-1 with .i errno set to .b eintr and the state of .i fildes is unspecified. .re .pp this permits the behavior that occurs on linux and many other implementations, where, as with other errors that may be reported by .br close (), the file descriptor is guaranteed to be closed. however, it also permits another possibility: that the implementation returns an .b eintr error and keeps the file descriptor open. (according to its documentation, hp-ux's .br close () does this.) the caller must then once more use .br close () to close the file descriptor, to avoid file descriptor leaks. this divergence in implementation behaviors provides a difficult hurdle for portable applications, since on many implementations, .br close () must not be called again after an .b eintr error, and on at least one, .br close () must be called again. there are plans to address this conundrum for the next major release of the posix.1 standard. .\" fixme . for later review when issue 8 is one day released... .\" posix proposes further changes for eintr .\" http://austingroupbugs.net/tag_view_page.php?tag_id=8 .\" http://austingroupbugs.net/view.php?id=529 .\" .\" fixme . .\" review the following glibc bug later .\" https://sourceware.org/bugzilla/show_bug.cgi?id=14627 .sh see also .br close_range (2), .br fcntl (2), .br fsync (2), .br open (2), .br shutdown (2), .br unlink (2), .br fclose (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcsncat 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsncat \- concatenate two wide-character strings .sh synopsis .nf .b #include .pp .bi "wchar_t *wcsncat(wchar_t *restrict " dest \ ", const wchar_t *restrict " src , .bi " size_t " n ); .fi .sh description the .br wcsncat () function is the wide-character equivalent of the .br strncat (3) function. it copies at most .i n wide characters from the wide-character string pointed to by .i src to the end of the wide-character string pointed to by .ir dest , and adds a terminating null wide character (l\(aq\e0\(aq). .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .ir wcslen(dest) + n +1 wide characters at .ir dest . .sh return value .br wcsncat () returns .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsncat () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strncat (3), .br wcscat (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/err.3 .\" copyright 2008 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th random_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name random_r, srandom_r, initstate_r, setstate_r \- reentrant random number generator .sh synopsis .nf .b #include .pp .bi "int random_r(struct random_data *restrict " buf , .bi " int32_t *restrict " result ); .bi "int srandom_r(unsigned int " seed ", struct random_data *" buf ); .pp .bi "int initstate_r(unsigned int " seed ", char *restrict " statebuf , .bi " size_t " statelen ", struct random_data *restrict " buf ); .bi "int setstate_r(char *restrict " statebuf , .bi " struct random_data *restrict " buf ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br random_r (), .br srandom_r (), .br initstate_r (), .br setstate_r (): .nf /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description these functions are the reentrant equivalents of the functions described in .br random (3). they are suitable for use in multithreaded programs where each thread needs to obtain an independent, reproducible sequence of random numbers. .pp the .br random_r () function is like .br random (3), except that instead of using state information maintained in a global variable, it uses the state information in the argument pointed to by .ir buf , which must have been previously initialized by .br initstate_r (). the generated random number is returned in the argument .ir result . .pp the .br srandom_r () function is like .br srandom (3), except that it initializes the seed for the random number generator whose state is maintained in the object pointed to by .ir buf , which must have been previously initialized by .br initstate_r (), instead of the seed associated with the global state variable. .pp the .br initstate_r () function is like .br initstate (3) except that it initializes the state in the object pointed to by .ir buf , rather than initializing the global state variable. before calling this function, the .ir buf.state field must be initialized to null. the .br initstate_r () function records a pointer to the .i statebuf argument inside the structure pointed to by .ir buf . thus, .ir statebuf should not be deallocated so long as .ir buf is still in use. (so, .i statebuf should typically be allocated as a static variable, or allocated on the heap using .br malloc (3) or similar.) .pp the .br setstate_r () function is like .br setstate (3) except that it modifies the state in the object pointed to by .ir buf , rather than modifying the global state variable. \fistate\fp must first have been initialized using .br initstate_r () or be the result of a previous call of .br setstate_r (). .sh return value all of these functions return 0 on success. on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b einval a state array of less than 8 bytes was specified to .br initstate_r (). .tp .b einval the .i statebuf or .i buf argument to .br setstate_r () was null. .tp .b einval the .i buf or .i result argument to .br random_r () was null. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br random_r (), .br srandom_r (), .br initstate_r (), .br setstate_r () t} thread safety mt-safe race:buf .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard glibc extensions. .\" these functions appear to be on tru64, but don't seem to be on .\" solaris, hp-ux, or freebsd. .sh bugs the .br initstate_r () interface is confusing. .\" fixme . https://sourceware.org/bugzilla/show_bug.cgi?id=3662 it appears that the .ir random_data type is intended to be opaque, but the implementation requires the user to either initialize the .i buf.state field to null or zero out the entire structure before the call. .sh see also .br drand48 (3), .br rand (3), .br random (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sgetmask.2 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" .th vhangup 2 2021-03-22 "linux" "linux programmer's manual" .sh name vhangup \- virtually hangup the current terminal .sh synopsis .nf .b #include .pp .b int vhangup(void); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br vhangup (): .nf since glibc 2.21: .\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8 _default_source in glibc 2.19 and 2.20: _default_source || (_xopen_source && _xopen_source < 500) up to and including glibc 2.19: _bsd_source || (_xopen_source && _xopen_source < 500) .fi .sh description .br vhangup () simulates a hangup on the current terminal. this call arranges for other users to have a \*(lqclean\*(rq terminal at login time. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eperm the calling process has insufficient privilege to call .br vhangup (); the .b cap_sys_tty_config capability is required. .sh conforming to this call is linux-specific, and should not be used in programs intended to be portable. .sh see also .br init (1), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/sinh.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 17:03:24 1993 by rik faith (faith@cs.unc.edu) .th ttys 4 1992-12-19 "linux" "linux programmer's manual" .sh name ttys \- serial terminal lines .sh description .b ttys[0\-3] are character devices for the serial terminal lines. .pp they are typically created by: .pp .in +4n .ex mknod \-m 660 /dev/ttys0 c 4 64 # base address 0x3f8 mknod \-m 660 /dev/ttys1 c 4 65 # base address 0x2f8 mknod \-m 660 /dev/ttys2 c 4 66 # base address 0x3e8 mknod \-m 660 /dev/ttys3 c 4 67 # base address 0x2e8 chown root:tty /dev/ttys[0\-3] .ee .in .sh files .i /dev/ttys[0\-3] .sh see also .br chown (1), .br mknod (1), .br tty (4), .br agetty (8), .br mingetty (8), .br setserial (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1994 jochen hein (hein@student.tu-clausthal.de) .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th charmap 5 2020-06-09 "gnu" "linux programmer's manual" .sh name charmap \- character set description file .sh description a character set description (charmap) defines all available characters and their encodings in a character set. .br localedef (1) can use charmaps to create locale variants for different character sets. .ss syntax the charmap file starts with a header that may consist of the following keywords: .tp .ri < code_set_name > is followed by the name of the character map. .tp .ri < comment_char > is followed by a character that will be used as the comment character for the rest of the file. it defaults to the number sign (#). .tp .ri < escape_char > is followed by a character that should be used as the escape character for the rest of the file to mark characters that should be interpreted in a special way. it defaults to the backslash (\e). .tp .ri < mb_cur_max > is followed by the maximum number of bytes for a character. the default value is 1. .tp .ri < mb_cur_min > is followed by the minimum number of bytes for a character. this value must be less than or equal than .ri < mb_cur_max >. if not specified, it defaults to .ri < mb_cur_max >. .pp the character set definition section starts with the keyword .i charmap in the first column. .pp the following lines may have one of the two following forms to define the character set: .tp .ri < character >\ byte-sequence\ comment this form defines exactly one character and its byte sequence, .i comment being optional. .tp .ri < character >..< character >\ byte-sequence\ comment this form defines a character range and its byte sequence, .i comment being optional. .pp the character set definition section ends with the string .ir "end charmap" . .pp the character set definition section may optionally be followed by a section to define widths of characters. .pp the .i width_default keyword can be used to define the default width for all characters not explicitly listed. the default character width is 1. .pp the width section for individual characters starts with the keyword .i width in the first column. .pp the following lines may have one of the two following forms to define the widths of the characters: .tp .ri < character >\ width this form defines the width of exactly one character. .tp .ri < character >...< character >\ width this form defines the width for all the characters in the range. .pp the width definition section ends with the string .ir "end width" . .sh files .tp .i /usr/share/i18n/charmaps usual default character map path. .sh conforming to posix.2. .sh examples the euro sign is defined as follows in the .i utf\-8 charmap: .pp .nf /xe2/x82/xac euro sign .fi .sh see also .br iconv (1), .br locale (1), .br localedef (1), .br locale (5), .br charsets (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sem_open 3 2021-03-22 "linux" "linux programmer's manual" .sh name sem_open \- initialize and open a named semaphore .sh synopsis .nf .br "#include " " /* for o_* constants */" .br "#include " " /* for mode constants */" .b #include .pp .bi "sem_t *sem_open(const char *" name ", int " oflag ); .bi "sem_t *sem_open(const char *" name ", int " oflag , .bi " mode_t " mode ", unsigned int " value ); .fi .pp link with \fi\-pthread\fp. .sh description .br sem_open () creates a new posix semaphore or opens an existing semaphore. the semaphore is identified by .ir name . for details of the construction of .ir name , see .br sem_overview (7). .pp the .i oflag argument specifies flags that control the operation of the call. (definitions of the flags values can be obtained by including .ir .) if .b o_creat is specified in .ir oflag , then the semaphore is created if it does not already exist. the owner (user id) of the semaphore is set to the effective user id of the calling process. the group ownership (group id) is set to the effective group id of the calling process. .\" in reality the filesystem ids are used on linux. if both .b o_creat and .b o_excl are specified in .ir oflag , then an error is returned if a semaphore with the given .i name already exists. .pp if .b o_creat is specified in .ir oflag , then two additional arguments must be supplied. the .i mode argument specifies the permissions to be placed on the new semaphore, as for .br open (2). (symbolic definitions for the permissions bits can be obtained by including .ir .) the permissions settings are masked against the process umask. both read and write permission should be granted to each class of user that will access the semaphore. the .i value argument specifies the initial value for the new semaphore. if .b o_creat is specified, and a semaphore with the given .i name already exists, then .i mode and .i value are ignored. .sh return value on success, .br sem_open () returns the address of the new semaphore; this address is used when calling other semaphore-related functions. on error, .br sem_open () returns .br sem_failed , with .i errno set to indicate the error. .sh errors .tp .b eacces the semaphore exists, but the caller does not have permission to open it. .tp .b eexist both .b o_creat and .b o_excl were specified in .ir oflag , but a semaphore with this .i name already exists. .tp .b einval .i value was greater than .br sem_value_max . .tp .b einval .i name consists of just "/", followed by no other characters. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enametoolong .i name was too long. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoent the .b o_creat flag was not specified in .ir oflag and no semaphore with this .i name exists; or, .\" this error can occur if we have a name of the (nonportable) form .\" /dir/name, and the directory /dev/shm/dir does not exist. .b o_creat was specified, but .i name wasn't well formed. .tp .b enomem insufficient memory. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sem_open () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh see also .br sem_close (3), .br sem_getvalue (3), .br sem_post (3), .br sem_unlink (3), .br sem_wait (3), .br sem_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/finite.3 .so man3/circleq.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th atan 3 2021-03-22 "" "linux programmer's manual" .sh name atan, atanf, atanl \- arc tangent function .sh synopsis .nf .b #include .pp .bi "double atan(double " x ); .bi "float atanf(float " x ); .bi "long double atanl(long double " x ); .pp .fi link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br atanf (), .br atanl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions calculate the principal value of the arc tangent of .ir x ; that is the value whose tangent is .ir x . .sh return value on success, these functions return the principal value of the arc tangent of .ir x in radians; the return value is in the range [\-pi/2,\ pi/2]. .pp if .i x is a nan, a nan is returned. .pp if .i x is +0 (\-0), +0 (\-0) is returned. .pp if .i x is positive infinity (negative infinity), +pi/2 (\-pi/2) is returned. .\" .\" posix.1-2001 documents an optional range error for subnormal x; .\" glibc 2.8 does not do this. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br atan (), .br atanf (), .br atanl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br acos (3), .br asin (3), .br atan2 (3), .br carg (3), .br catan (3), .br cos (3), .br sin (3), .br tan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/atan2.3 .so man2/fstatfs.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-08-10 by walter harms (walter.harms@informatik.uni-oldenburg.de) .th copysign 3 2021-03-22 "gnu" "linux programmer's manual" .sh name copysign, copysignf, copysignl \- copy sign of a number .sh synopsis .nf .b #include .pp .bi "double copysign(double " x ", double " y ); .bi "float copysignf(float " x ", float " y ); .bi "long double copysignl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br copysign (), .br copysignf (), .br copysignl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return a value whose absolute value matches that of .ir x , but whose sign bit matches that of .ir y . .pp for example, .i "copysign(42.0,\ \-1.0)" and .i "copysign(\-42.0, \-1.0)" both return \-42.0. .sh return value on success, these functions return a value whose magnitude is taken from .i x and whose sign is taken from .ir y . .pp if .i x is a nan, a nan with the sign bit of .i y is returned. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br copysign (), .br copysignf (), .br copysignl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .\" 4.3bsd. this function is defined in iec 559 (and the appendix with recommended functions in ieee 754/ieee 854). .sh notes on architectures where the floating-point formats are not ieee 754 compliant, these functions may treat a negative zero as positive. .sh see also .br signbit (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/lgamma.3 .so man3/makedev.3 .so man3/unlocked_stdio.3 .so man3/log1p.3 .so man3/gethostbyname.3 .so man3/stdio_ext.3 .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: rtnetlink.3,v 1.2 1999/05/18 10:35:10 freitag exp $ .\" .th rtnetlink 3 2021-03-22 "gnu" "linux programmer's manual" .sh name rtnetlink \- macros to manipulate rtnetlink messages .sh synopsis .nf .b #include .b #include .b #include .b #include .pp .bi "rtnetlink_socket = socket(af_netlink, int " socket_type \ ", netlink_route);" .pp .bi "int rta_ok(struct rtattr *" rta ", int " rtabuflen ); .pp .bi "void *rta_data(struct rtattr *" rta ); .bi "unsigned int rta_payload(struct rtattr *" rta ); .pp .bi "struct rtattr *rta_next(struct rtattr *" rta \ ", unsigned int " rtabuflen ); .pp .bi "unsigned int rta_length(unsigned int " length ); .bi "unsigned int rta_space(unsigned int "length ); .fi .sh description all .br rtnetlink (7) messages consist of a .br netlink (7) message header and appended attributes. the attributes should be manipulated only using the macros provided here. .pp .bi rta_ok( rta ", " attrlen ) returns true if .i rta points to a valid routing attribute; .i attrlen is the running length of the attribute buffer. when not true then you must assume there are no more attributes in the message, even if .i attrlen is nonzero. .pp .bi rta_data( rta ) returns a pointer to the start of this attribute's data. .pp .bi rta_payload( rta ) returns the length of this attribute's data. .pp .bi rta_next( rta ", " attrlen ) gets the next attribute after .ir rta . calling this macro will update .ir attrlen . you should use .b rta_ok to check the validity of the returned pointer. .pp .bi rta_length( len ) returns the length which is required for .i len bytes of data plus the header. .pp .bi rta_space( len ) returns the amount of space which will be needed in a message with .i len bytes of data. .sh conforming to these macros are nonstandard linux extensions. .sh bugs this manual page is incomplete. .sh examples .\" fixme . ? would be better to use libnetlink in the example code here creating a rtnetlink message to set the mtu of a device: .pp .in +4n .ex #include \&... struct { struct nlmsghdr nh; struct ifinfomsg if; char attrbuf[512]; } req; struct rtattr *rta; unsigned int mtu = 1000; int rtnetlink_sk = socket(af_netlink, sock_dgram, netlink_route); memset(&req, 0, sizeof(req)); req.nh.nlmsg_len = nlmsg_length(sizeof(req.if)); req.nh.nlmsg_flags = nlm_f_request; req.nh.nlmsg_type = rtm_newlink; req.if.ifi_family = af_unspec; req.if.ifi_index = interface_index; req.if.ifi_change = 0xffffffff; /* ??? */ rta = (struct rtattr *)(((char *) &req) + nlmsg_align(req.nh.nlmsg_len)); rta\->rta_type = ifla_mtu; rta\->rta_len = rta_length(sizeof(mtu)); req.nh.nlmsg_len = nlmsg_align(req.nh.nlmsg_len) + rta_length(sizeof(mtu)); memcpy(rta_data(rta), &mtu, sizeof(mtu)); send(rtnetlink_sk, &req, req.nh.nlmsg_len, 0); .ee .in .sh see also .br netlink (3), .br netlink (7), .br rtnetlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ccos.3 .\" copyright (c) 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th bzero 3 2021-03-22 "linux" "linux programmer's manual" .sh name bzero, explicit_bzero \- zero a byte string .sh synopsis .nf .b #include .pp .bi "void bzero(void *" s ", size_t " n ); .pp .b #include .pp .bi "void explicit_bzero(void *" s ", size_t " n ); .fi .sh description the .br bzero () function erases the data in the .i n bytes of the memory starting at the location pointed to by .ir s , by writing zeros (bytes containing \(aq\e0\(aq) to that area. .pp the .br explicit_bzero () function performs the same task as .br bzero (). it differs from .br bzero () in that it guarantees that compiler optimizations will not remove the erase operation if the compiler deduces that the operation is "unnecessary". .sh return value none. .sh versions .br explicit_bzero () first appeared in glibc 2.25. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br bzero (), .br explicit_bzero () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the .br bzero () function is deprecated (marked as legacy in posix.1-2001); use .br memset (3) in new programs. posix.1-2008 removes the specification of .br bzero (). the .br bzero () function first appeared in 4.3bsd. .pp the .br explicit_bzero () function is a nonstandard extension that is also present on some of the bsds. some other implementations have a similar function, such as .br memset_explicit () or .br memset_s (). .sh notes the .br explicit_bzero () function addresses a problem that security-conscious applications may run into when using .br bzero (): if the compiler can deduce that the location to be zeroed will never again be touched by a .i correct program, then it may remove the .br bzero () call altogether. this is a problem if the intent of the .br bzero () call was to erase sensitive data (e.g., passwords) to prevent the possibility that the data was leaked by an incorrect or compromised program. calls to .br explicit_bzero () are never optimized away by the compiler. .pp the .br explicit_bzero () function does not solve all problems associated with erasing sensitive data: .ip 1. 3 the .br explicit_bzero () function does .i not guarantee that sensitive data is completely erased from memory. (the same is true of .br bzero ().) for example, there may be copies of the sensitive data in a register and in "scratch" stack areas. the .br explicit_bzero () function is not aware of these copies, and can't erase them. .ip 2. in some circumstances, .br explicit_bzero () can .i decrease security. if the compiler determined that the variable containing the sensitive data could be optimized to be stored in a register (because it is small enough to fit in a register, and no operation other than the .br explicit_bzero () call would need to take the address of the variable), then the .br explicit_bzero () call will force the data to be copied from the register to a location in ram that is then immediately erased (while the copy in the register remains unaffected). the problem here is that data in ram is more likely to be exposed by a bug than data in a register, and thus the .br explicit_bzero () call creates a brief time window where the sensitive data is more vulnerable than it would otherwise have been if no attempt had been made to erase the data. .pp note that declaring the sensitive variable with the .b volatile qualifier does .i not eliminate the above problems. indeed, it will make them worse, since, for example, it may force a variable that would otherwise have been optimized into a register to instead be maintained in (more vulnerable) ram for its entire lifetime. .pp notwithstanding the above details, for security-conscious applications, using .br explicit_bzero () is generally preferable to not using it. the developers of .br explicit_bzero () anticipate that future compilers will recognize calls to .br explicit_bzero () and take steps to ensure that all copies of the sensitive data are erased, including copies in registers or in "scratch" stack areas. .sh see also .br bstring (3), .br memset (3), .br swab (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1995 james r. van zandt .\" and copyright (c) 2006, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" changed section from 2 to 3, aeb, 950919 .\" .th mkfifo 3 2021-08-27 "gnu" "linux programmer's manual" .sh name mkfifo, mkfifoat \- make a fifo special file (a named pipe) .sh synopsis .nf .b #include .b #include .pp .bi "int mkfifo(const char *" pathname ", mode_t " mode ); .pp .br "#include " "/* definition of at_* constants */" .b #include .pp .bi "int mkfifoat(int " dirfd ", const char *" pathname ", mode_t " mode ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mkfifoat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br mkfifo () makes a fifo special file with name \fipathname\fp. \fimode\fp specifies the fifo's permissions. it is modified by the process's \fbumask\fp in the usual way: the permissions of the created file are \fb(\fp\fimode\fp\fb & \(tiumask)\fp. .pp a fifo special file is similar to a pipe, except that it is created in a different way. instead of being an anonymous communications channel, a fifo special file is entered into the filesystem by calling .br mkfifo (). .pp once you have created a fifo special file in this way, any process can open it for reading or writing, in the same way as an ordinary file. however, it has to be open at both ends simultaneously before you can proceed to do any input or output operations on it. opening a fifo for reading normally blocks until some other process opens the same fifo for writing, and vice versa. see .br fifo (7) for nonblocking handling of fifo special files. .ss mkfifoat() the .br mkfifoat () function operates in exactly the same way as .br mkfifo (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br mkfifo () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br mkfifo ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp see .br openat (2) for an explanation of the need for .br mkfifoat (). .sh return value on success .br mkfifo () and .br mkfifoat () return 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces one of the directories in \fipathname\fp did not allow search (execute) permission. .tp .b ebadf .rb ( mkfifoat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b edquot the user's quota of disk blocks or inodes on the filesystem has been exhausted. .tp .b eexist \fipathname\fp already exists. this includes the case where .i pathname is a symbolic link, dangling or not. .tp .b enametoolong either the total length of \fipathname\fp is greater than \fbpath_max\fp, or an individual filename component has a length greater than \fbname_max\fp. in the gnu system, there is no imposed limit on overall filename length, but some filesystems may place limits on the length of a component. .tp .b enoent a directory component in \fipathname\fp does not exist or is a dangling symbolic link. .tp .b enospc the directory or filesystem has no room for the new file. .tp .b enotdir a component used as a directory in \fipathname\fp is not, in fact, a directory. .tp .b enotdir .rb ( mkfifoat ()) .i pathname is a relative pathname and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b erofs \fipathname\fp refers to a read-only filesystem. .sh versions .br mkfifoat () was added to glibc in version 2.4. it is implemented using .br mknodat (2), available on linux since kernel 2.6.16. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mkfifo (), .br mkfifoat () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br mkfifo (): posix.1-2001, posix.1-2008. .pp .br mkfifoat (): posix.1-2008. .sh see also .br mkfifo (1), .br close (2), .br open (2), .br read (2), .br stat (2), .br umask (2), .br write (2), .br fifo (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2003-04-07 by michael kerrisk .\" .th tty 4 2019-03-06 "linux" "linux programmer's manual" .sh name tty \- controlling terminal .sh description the file .i /dev/tty is a character file with major number 5 and minor number 0, usually with mode 0666 and ownership root:tty. it is a synonym for the controlling terminal of a process, if any. .pp in addition to the .br ioctl (2) requests supported by the device that .b tty refers to, the .br ioctl (2) request .b tiocnotty is supported. .ss tiocnotty detach the calling process from its controlling terminal. .pp if the process is the session leader, then .b sighup and .b sigcont signals are sent to the foreground process group and all processes in the current session lose their controlling tty. .pp this .br ioctl (2) call works only on file descriptors connected to .ir /dev/tty . it is used by daemon processes when they are invoked by a user at a terminal. the process attempts to open .ir /dev/tty . if the open succeeds, it detaches itself from the terminal by using .br tiocnotty , while if the open fails, it is obviously not attached to a terminal and does not need to detach itself. .sh files .i /dev/tty .sh see also .br chown (1), .br mknod (1), .br ioctl (2), .br ioctl_console (2), .br ioctl_tty (2), .br termios (3), .br ttys (4), .br vcs (4), .br pty (7), .br agetty (8), .br mingetty (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) michael kerrisk, 2004 .\" using some material drawn from earlier man pages .\" written by thomas kuhn, copyright 1996 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th mlock 2 2021-08-27 "linux" "linux programmer's manual" .sh name mlock, mlock2, munlock, mlockall, munlockall \- lock and unlock memory .sh synopsis .nf .b #include .pp .bi "int mlock(const void *" addr ", size_t " len ); .bi "int mlock2(const void *" addr ", size_t " len ", unsigned int " flags ); .bi "int munlock(const void *" addr ", size_t " len ); .pp .bi "int mlockall(int " flags ); .b int munlockall(void); .fi .sh description .br mlock (), .br mlock2 (), and .br mlockall () lock part or all of the calling process's virtual address space into ram, preventing that memory from being paged to the swap area. .pp .br munlock () and .br munlockall () perform the converse operation, unlocking part or all of the calling process's virtual address space, so that pages in the specified virtual address range may once more to be swapped out if required by the kernel memory manager. .pp memory locking and unlocking are performed in units of whole pages. .ss mlock(), mlock2(), and munlock() .br mlock () locks pages in the address range starting at .i addr and continuing for .i len bytes. all pages that contain a part of the specified address range are guaranteed to be resident in ram when the call returns successfully; the pages are guaranteed to stay in ram until later unlocked. .pp .br mlock2 () .\" commit a8ca5d0ecbdde5cc3d7accacbd69968b0c98764e .\" commit de60f5f10c58d4f34b68622442c0e04180367f3f .\" commit b0f205c2a3082dd9081f9a94e50658c5fa906ff1 also locks pages in the specified range starting at .i addr and continuing for .i len bytes. however, the state of the pages contained in that range after the call returns successfully will depend on the value in the .i flags argument. .pp the .i flags argument can be either 0 or the following constant: .tp .b mlock_onfault lock pages that are currently resident and mark the entire range so that the remaining nonresident pages are locked when they are populated by a page fault. .pp if .i flags is 0, .br mlock2 () behaves exactly the same as .br mlock (). .pp .br munlock () unlocks pages in the address range starting at .i addr and continuing for .i len bytes. after this call, all pages that contain a part of the specified memory range can be moved to external swap space again by the kernel. .ss mlockall() and munlockall() .br mlockall () locks all pages mapped into the address space of the calling process. this includes the pages of the code, data, and stack segment, as well as shared libraries, user space kernel data, shared memory, and memory-mapped files. all mapped pages are guaranteed to be resident in ram when the call returns successfully; the pages are guaranteed to stay in ram until later unlocked. .pp the .i flags argument is constructed as the bitwise or of one or more of the following constants: .tp .b mcl_current lock all pages which are currently mapped into the address space of the process. .tp .b mcl_future lock all pages which will become mapped into the address space of the process in the future. these could be, for instance, new pages required by a growing heap and stack as well as new memory-mapped files or shared memory regions. .tp .br mcl_onfault " (since linux 4.4)" used together with .br mcl_current , .br mcl_future , or both. mark all current (with .br mcl_current ) or future (with .br mcl_future ) mappings to lock pages when they are faulted in. when used with .br mcl_current , all present pages are locked, but .br mlockall () will not fault in non-present pages. when used with .br mcl_future , all future mappings will be marked to lock pages when they are faulted in, but they will not be populated by the lock when the mapping is created. .b mcl_onfault must be used with either .b mcl_current or .b mcl_future or both. .pp if .b mcl_future has been specified, then a later system call (e.g., .br mmap (2), .br sbrk (2), .br malloc (3)), may fail if it would cause the number of locked bytes to exceed the permitted maximum (see below). in the same circumstances, stack growth may likewise fail: the kernel will deny stack expansion and deliver a .b sigsegv signal to the process. .pp .br munlockall () unlocks all pages mapped into the address space of the calling process. .sh return value on success, these system calls return 0. on error, \-1 is returned, .i errno is set to indicate the error, and no changes are made to any locks in the address space of the process. .sh errors .\"svr4 documents an additional eagain error code. .tp .b eagain .rb ( mlock (), .br mlock2 (), and .br munlock ()) some or all of the specified address range could not be locked. .tp .b einval .rb ( mlock (), .br mlock2 (), and .br munlock ()) the result of the addition .ir addr + len was less than .ir addr (e.g., the addition may have resulted in an overflow). .tp .b einval .rb ( mlock2 ()) unknown \fiflags\fp were specified. .tp .b einval .rb ( mlockall ()) unknown \fiflags\fp were specified or .b mcl_onfault was specified without either .b mcl_future or .br mcl_current . .tp .b einval (not on linux) .i addr was not a multiple of the page size. .tp .b enomem .rb ( mlock (), .br mlock2 (), and .br munlock ()) some of the specified address range does not correspond to mapped pages in the address space of the process. .tp .b enomem .rb ( mlock (), .br mlock2 (), and .br munlock ()) locking or unlocking a region would result in the total number of mappings with distinct attributes (e.g., locked versus unlocked) exceeding the allowed maximum. .\" i.e., the number of vmas would exceed the 64kb maximum (for example, unlocking a range in the middle of a currently locked mapping would result in three mappings: two locked mappings at each end and an unlocked mapping in the middle.) .tp .b enomem (linux 2.6.9 and later) the caller had a nonzero .b rlimit_memlock soft resource limit, but tried to lock more memory than the limit permitted. this limit is not enforced if the process is privileged .rb ( cap_ipc_lock ). .tp .b enomem (linux 2.4 and earlier) the calling process tried to lock more than half of ram. .\" in the case of mlock(), this check is somewhat buggy: it doesn't .\" take into account whether the to-be-locked range overlaps with .\" already locked pages. thus, suppose we allocate .\" (num_physpages / 4 + 1) of memory, and lock those pages once using .\" mlock(), and then lock the *same* page range a second time. .\" in the case, the second mlock() call will fail, since the check .\" calculates that the process is trying to lock (num_physpages / 2 + 2) .\" pages, which of course is not true. (mtk, nov 04, kernel 2.4.28) .tp .b eperm the caller is not privileged, but needs privilege .rb ( cap_ipc_lock ) to perform the requested operation. .tp .b eperm .rb ( munlockall ()) (linux 2.6.8 and earlier) the caller was not privileged .rb ( cap_ipc_lock ). .sh versions .br mlock2 () is available since linux 4.4; glibc support was added in version 2.27. .sh conforming to .br mlock (), .br munlock (), .br mlockall (), and .br munlockall (): posix.1-2001, posix.1-2008, svr4. .pp .br mlock2 () is linux specific. .pp on posix systems on which .br mlock () and .br munlock () are available, .b _posix_memlock_range is defined in \fi\fp and the number of bytes in a page can be determined from the constant .b pagesize (if defined) in \fi\fp or by calling .ir sysconf(_sc_pagesize) . .pp on posix systems on which .br mlockall () and .br munlockall () are available, .b _posix_memlock is defined in \fi\fp to a value greater than 0. (see also .br sysconf (3).) .\" posix.1-2001: it shall be defined to -1 or 0 or 200112l. .\" -1: unavailable, 0: ask using sysconf(). .\" glibc defines it to 1. .sh notes memory locking has two main applications: real-time algorithms and high-security data processing. real-time applications require deterministic timing, and, like scheduling, paging is one major cause of unexpected program execution delays. real-time applications will usually also switch to a real-time scheduler with .br sched_setscheduler (2). cryptographic security software often handles critical bytes like passwords or secret keys as data structures. as a result of paging, these secrets could be transferred onto a persistent swap store medium, where they might be accessible to the enemy long after the security software has erased the secrets in ram and terminated. (but be aware that the suspend mode on laptops and some desktop computers will save a copy of the system's ram to disk, regardless of memory locks.) .pp real-time processes that are using .br mlockall () to prevent delays on page faults should reserve enough locked stack pages before entering the time-critical section, so that no page fault can be caused by function calls. this can be achieved by calling a function that allocates a sufficiently large automatic variable (an array) and writes to the memory occupied by this array in order to touch these stack pages. this way, enough pages will be mapped for the stack and can be locked into ram. the dummy writes ensure that not even copy-on-write page faults can occur in the critical section. .pp memory locks are not inherited by a child created via .br fork (2) and are automatically removed (unlocked) during an .br execve (2) or when the process terminates. the .br mlockall () .b mcl_future and .b mcl_future | mcl_onfault settings are not inherited by a child created via .br fork (2) and are cleared during an .br execve (2). .pp note that .br fork (2) will prepare the address space for a copy-on-write operation. the consequence is that any write access that follows will cause a page fault that in turn may cause high latencies for a real-time process. therefore, it is crucial not to invoke .br fork (2) after an .br mlockall () or .br mlock () operation\(emnot even from a thread which runs at a low priority within a process which also has a thread running at elevated priority. .pp the memory lock on an address range is automatically removed if the address range is unmapped via .br munmap (2). .pp memory locks do not stack, that is, pages which have been locked several times by calls to .br mlock (), .br mlock2 (), or .br mlockall () will be unlocked by a single call to .br munlock () for the corresponding range or by .br munlockall (). pages which are mapped to several locations or by several processes stay locked into ram as long as they are locked at least at one location or by at least one process. .pp if a call to .br mlockall () which uses the .b mcl_future flag is followed by another call that does not specify this flag, the changes made by the .b mcl_future call will be lost. .pp the .br mlock2 () .b mlock_onfault flag and the .br mlockall () .b mcl_onfault flag allow efficient memory locking for applications that deal with large mappings where only a (small) portion of pages in the mapping are touched. in such cases, locking all of the pages in a mapping would incur a significant penalty for memory locking. .ss linux notes under linux, .br mlock (), .br mlock2 (), and .br munlock () automatically round .i addr down to the nearest page boundary. however, the posix.1 specification of .br mlock () and .br munlock () allows an implementation to require that .i addr is page aligned, so portable applications should ensure this. .pp the .i vmlck field of the linux-specific .i /proc/[pid]/status file shows how many kilobytes of memory the process with id .i pid has locked using .br mlock (), .br mlock2 (), .br mlockall (), and .br mmap (2) .br map_locked . .ss limits and permissions in linux 2.6.8 and earlier, a process must be privileged .rb ( cap_ipc_lock ) in order to lock memory and the .b rlimit_memlock soft resource limit defines a limit on how much memory the process may lock. .pp since linux 2.6.9, no limits are placed on the amount of memory that a privileged process can lock and the .b rlimit_memlock soft resource limit instead defines a limit on how much memory an unprivileged process may lock. .sh bugs in linux 4.8 and earlier, a bug in the kernel's accounting of locked memory for unprivileged processes (i.e., without .br cap_ipc_lock ) meant that if the region specified by .i addr and .i len overlapped an existing lock, then the already locked bytes in the overlapping region were counted twice when checking against the limit. such double accounting could incorrectly calculate a "total locked memory" value for the process that exceeded the .br rlimit_memlock limit, with the result that .br mlock () and .br mlock2 () would fail on requests that should have succeeded. this bug was fixed .\" commit 0cf2f6f6dc605e587d2c1120f295934c77e810e8 in linux 4.9. .pp in the 2.4 series linux kernels up to and including 2.4.17, a bug caused the .br mlockall () .b mcl_future flag to be inherited across a .br fork (2). this was rectified in kernel 2.4.18. .pp since kernel 2.6.9, if a privileged process calls .i mlockall(mcl_future) and later drops privileges (loses the .b cap_ipc_lock capability by, for example, setting its effective uid to a nonzero value), then subsequent memory allocations (e.g., .br mmap (2), .br brk (2)) will fail if the .b rlimit_memlock resource limit is encountered. .\" see the following lkml thread: .\" http://marc.theaimsgroup.com/?l=linux-kernel&m=113801392825023&w=2 .\" "rationale for rlimit_memlock" .\" 23 jan 2006 .sh see also .br mincore (2), .br mmap (2), .br setrlimit (2), .br shmctl (2), .br sysconf (3), .br proc (5), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/nan.3 .so man3/pthread_mutex_consistent.3 .so man2/sendfile.2 .so man3/fts.3 .so man3/xdr.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) and .\" walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th getspnam 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getspnam, getspnam_r, getspent, getspent_r, setspent, endspent, fgetspent, fgetspent_r, sgetspent, sgetspent_r, putspent, lckpwdf, ulckpwdf \- get shadow password file entry .sh synopsis .nf /* general shadow password file api */ .b #include .pp .bi "struct spwd *getspnam(const char *" name ); .b struct spwd *getspent(void); .pp .b void setspent(void); .b void endspent(void); .pp .bi "struct spwd *fgetspent(file *" stream ); .bi "struct spwd *sgetspent(const char *" s ); .pp .bi "int putspent(const struct spwd *" p ", file *" stream ); .pp .b int lckpwdf(void); .b int ulckpwdf(void); .pp /* gnu extension */ .b #include .pp .bi "int getspent_r(struct spwd *" spbuf , .bi " char *" buf ", size_t " buflen ", struct spwd **" spbufp ); .bi "int getspnam_r(const char *" name ", struct spwd *" spbuf , .bi " char *" buf ", size_t " buflen ", struct spwd **" spbufp ); .pp .bi "int fgetspent_r(file *" stream ", struct spwd *" spbuf , .bi " char *" buf ", size_t " buflen ", struct spwd **" spbufp ); .bi "int sgetspent_r(const char *" s ", struct spwd *" spbuf , .bi " char *" buf ", size_t " buflen ", struct spwd **" spbufp ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getspent_r (), .br getspnam_r (), .br fgetspent_r (), .br sgetspent_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description long ago it was considered safe to have encrypted passwords openly visible in the password file. when computers got faster and people got more security-conscious, this was no longer acceptable. julianne frances haugh implemented the shadow password suite that keeps the encrypted passwords in the shadow password database (e.g., the local shadow password file .ir /etc/shadow , nis, and ldap), readable only by root. .pp the functions described below resemble those for the traditional password database (e.g., see .br getpwnam (3) and .br getpwent (3)). .\" fixme . i've commented out the following for the .\" moment. the relationship between pam and nsswitch.conf needs .\" to be clearly documented in one place, which is pointed to by .\" the pages for the user, group, and shadow password functions. .\" (jul 2005, mtk) .\" .\" this shadow password setup has been superseded by pam .\" (pluggable authentication modules), and the file .\" .i /etc/nsswitch.conf .\" now describes the sources to be used. .pp the .br getspnam () function returns a pointer to a structure containing the broken-out fields of the record in the shadow password database that matches the username .ir name . .pp the .br getspent () function returns a pointer to the next entry in the shadow password database. the position in the input stream is initialized by .br setspent (). when done reading, the program may call .br endspent () so that resources can be deallocated. .\" some systems require a call of setspent() before the first getspent() .\" glibc does not .pp the .br fgetspent () function is similar to .br getspent () but uses the supplied stream instead of the one implicitly opened by .br setspent (). .pp the .br sgetspent () function parses the supplied string .i s into a struct .ir spwd . .pp the .br putspent () function writes the contents of the supplied struct .i spwd .i *p as a text line in the shadow password file format to .ir stream . string entries with value null and numerical entries with value \-1 are written as an empty string. .pp the .br lckpwdf () function is intended to protect against multiple simultaneous accesses of the shadow password database. it tries to acquire a lock, and returns 0 on success, or \-1 on failure (lock not obtained within 15 seconds). the .br ulckpwdf () function releases the lock again. note that there is no protection against direct access of the shadow password file. only programs that use .br lckpwdf () will notice the lock. .pp these were the functions that formed the original shadow api. they are widely available. .\" also in libc5 .\" sun doesn't have sgetspent() .ss reentrant versions analogous to the reentrant functions for the password database, glibc also has reentrant functions for the shadow password database. the .br getspnam_r () function is like .br getspnam () but stores the retrieved shadow password structure in the space pointed to by .ir spbuf . this shadow password structure contains pointers to strings, and these strings are stored in the buffer .i buf of size .ir buflen . a pointer to the result (in case of success) or null (in case no entry was found or an error occurred) is stored in .ir *spbufp . .pp the functions .br getspent_r (), .br fgetspent_r (), and .br sgetspent_r () are similarly analogous to their nonreentrant counterparts. .pp some non-glibc systems also have functions with these names, often with different prototypes. .\" sun doesn't have sgetspent_r() .ss structure the shadow password structure is defined in \fi\fp as follows: .pp .in +4n .ex struct spwd { char *sp_namp; /* login name */ char *sp_pwdp; /* encrypted password */ long sp_lstchg; /* date of last change (measured in days since 1970\-01\-01 00:00:00 +0000 (utc)) */ long sp_min; /* min # of days between changes */ long sp_max; /* max # of days between changes */ long sp_warn; /* # of days before password expires to warn user to change it */ long sp_inact; /* # of days after password expires until account is disabled */ long sp_expire; /* date when account expires (measured in days since 1970\-01\-01 00:00:00 +0000 (utc)) */ unsigned long sp_flag; /* reserved */ }; .ee .in .sh return value the functions that return a pointer return null if no more entries are available or if an error occurs during processing. the functions which have \fiint\fp as the return value return 0 for success and \-1 for failure, with .i errno set to indicate the error. .pp for the nonreentrant functions, the return value may point to static area, and may be overwritten by subsequent calls to these functions. .pp the reentrant functions return zero on success. in case of error, an error number is returned. .sh errors .tp .b eacces the caller does not have permission to access the shadow password file. .tp .b erange supplied buffer is too small. .sh files .tp .i /etc/shadow local shadow password database file .tp .i /etc/.pwd.lock lock file .pp the include file .i defines the constant .b _path_shadow to the pathname of the shadow password file. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getspnam () t} thread safety t{ mt-unsafe race:getspnam locale t} t{ .br getspent () t} thread safety t{ mt-unsafe race:getspent race:spentbuf locale t} t{ .br setspent (), .br endspent (), .br getspent_r () t} thread safety t{ mt-unsafe race:getspent locale t} t{ .br fgetspent () t} thread safety t{ mt-unsafe race:fgetspent t} t{ .br sgetspent () t} thread safety t{ mt-unsafe race:sgetspent t} t{ .br putspent (), .br getspnam_r (), .br sgetspent_r () t} thread safety t{ mt-safe locale t} t{ .br lckpwdf (), .br ulckpwdf (), .br fgetspent_r () t} thread safety t{ mt-safe t} .te .hy .ad .sp 1 in the above table, .i getspent in .i race:getspent signifies that if any of the functions .br setspent (), .br getspent (), .br getspent_r (), or .br endspent () are used in parallel in different threads of a program, then data races could occur. .sh conforming to the shadow password database and its associated api are not specified in posix.1. however, many other systems provide a similar api. .sh see also .br getgrnam (3), .br getpwnam (3), .br getpwnam_r (3), .br shadow (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .so man3/hypot.3 .so man3/cosh.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswspace 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswspace \- test for whitespace wide character .sh synopsis .nf .b #include .pp .bi "int iswspace(wint_t " wc ); .fi .sh description the .br iswspace () function is the wide-character equivalent of the .br isspace (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "space". .pp the wide-character class "space" is disjoint from the wide-character class "graph" and therefore also disjoint from its subclasses "alnum", "alpha", "upper", "lower", "digit", "xdigit", "punct". .\" note: unix98 (susv2/xbd/locale.html) says that "space" and "graph" may .\" have characters in common, except u+0020. but c99 (iso/iec 9899:1999 .\" section 7.25.2.1.10) says that "space" and "graph" are disjoint. .pp the wide-character class "space" contains the wide-character class "blank". .pp the wide-character class "space" always contains at least the space character and the control characters \(aq\ef\(aq, \(aq\en\(aq, \(aq\er\(aq, \(aq\et\(aq, \(aq\ev\(aq. .sh return value the .br iswspace () function returns nonzero if .i wc is a wide character belonging to the wide-character class "space". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswspace () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswspace () depends on the .b lc_ctype category of the current locale. .sh see also .br isspace (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sigpending.2 .so man3/circleq.3 .so man3/updwtmp.3 .so man3/fts.3 .so man3/setbuf.3 .so man3/open_memstream.3 .\" copyright (c) 2007 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th bsd_signal 3 2021-03-22 "" "linux programmer's manual" .sh name bsd_signal \- signal handling with bsd semantics .sh synopsis .nf .b #include .pp .b typedef void (*sighandler_t)(int); .pp .bi "sighandler_t bsd_signal(int " signum ", sighandler_t " handler ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br bsd_signal (): .nf since glibc 2.26: _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended && ! (_posix_c_source >= 200809l) glibc 2.25 and earlier: _xopen_source .fi .sh description the .br bsd_signal () function takes the same arguments, and performs the same task, as .br signal (2). .pp the difference between the two is that .br bsd_signal () is guaranteed to provide reliable signal semantics, that is: a) the disposition of the signal is not reset to the default when the handler is invoked; b) delivery of further instances of the signal is blocked while the signal handler is executing; and c) if the handler interrupts a blocking system call, then the system call is automatically restarted. a portable application cannot rely on .br signal (2) to provide these guarantees. .sh return value the .br bsd_signal () function returns the previous value of the signal handler, or .b sig_err on error. .sh errors as for .br signal (2). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br bsd_signal () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.2bsd, posix.1-2001. posix.1-2008 removes the specification of .br bsd_signal (), recommending the use of .br sigaction (2) instead. .sh notes use of .br bsd_signal () should be avoided; use .br sigaction (2) instead. .pp on modern linux systems, .br bsd_signal () and .br signal (2) are equivalent. but on older systems, .br signal (2) provided unreliable signal semantics; see .br signal (2) for details. .pp the use of .i sighandler_t is a gnu extension; this type is defined only if the .b _gnu_source feature test macro is defined. .sh see also .br sigaction (2), .br signal (2), .br sysv_signal (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pow10.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th csqrt 3 2021-03-22 "" "linux programmer's manual" .sh name csqrt, csqrtf, csqrtl \- complex square root .sh synopsis .nf .b #include .pp .bi "double complex csqrt(double complex " z ");" .bi "float complex csqrtf(float complex " z ");" .bi "long double complex csqrtl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex square root of .ir z , with a branch cut along the negative real axis. (that means that \ficsqrt(\-1+eps*i)\fp will be close to i while \ficsqrt(\-1\-eps*i)\fp will be close to \-i, \fiif eps\fp is a small positive real number.) .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br csqrt (), .br csqrtf (), .br csqrtl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br cexp (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) tom bjorkholm & markus kuhn, 1996 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-04-01 tom bjorkholm .\" first version written .\" 1996-04-10 markus kuhn .\" revision .\" .th sched_rr_get_interval 2 2021-03-22 "linux" "linux programmer's manual" .sh name sched_rr_get_interval \- get the sched_rr interval for the named process .sh synopsis .nf .b #include .pp .bi "int sched_rr_get_interval(pid_t " pid ", struct timespec *" tp ); .fi .sh description .br sched_rr_get_interval () writes into the .i timespec structure pointed to by .i tp the round-robin time quantum for the process identified by .ir pid . the specified process should be running under the .b sched_rr scheduling policy. .pp the .i timespec structure has the following form: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp if .i pid is zero, the time quantum for the calling process is written into .ir *tp . .\" fixme . on linux, sched_rr_get_interval() .\" returns the timeslice for sched_other processes -- this timeslice .\" is influenced by the nice value. .\" for sched_fifo processes, this always returns 0. .\" .\" the round-robin time quantum value is not alterable under linux .\" 1.3.81. .\" .sh return value on success, .br sched_rr_get_interval () returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault problem with copying information to user space. .tp .b einval invalid pid. .tp .b enosys the system call is not yet implemented (only on rather old kernels). .tp .b esrch could not find a process with the id .ir pid . .sh conforming to posix.1-2001, posix.1-2008. .sh notes posix systems on which .br sched_rr_get_interval () is available define .b _posix_priority_scheduling in .ir . .ss linux notes posix does not specify any mechanism for controlling the size of the round-robin time quantum. older linux kernels provide a (nonportable) method of doing this. the quantum can be controlled by adjusting the process's nice value (see .br setpriority (2)). assigning a negative (i.e., high) nice value results in a longer quantum; assigning a positive (i.e., low) nice value results in a shorter quantum. the default quantum is 0.1 seconds; the degree to which changing the nice value affects the quantum has varied somewhat across kernel versions. this method of adjusting the quantum was removed .\" commit a4ec24b48ddef1e93f7578be53270f0b95ad666c starting with linux 2.6.24. .pp linux 3.9 added .\" commit ce0dbbbb30aee6a835511d5be446462388ba9eee a new mechanism for adjusting (and viewing) the .br sched_rr quantum: the .i /proc/sys/kernel/sched_rr_timeslice_ms file exposes the quantum as a millisecond value, whose default is 100. writing 0 to this file resets the quantum to the default value. .\" .sh bugs .\" as of linux 1.3.81 .\" .br sched_rr_get_interval () .\" returns with error .\" enosys, because sched_rr has not yet been fully implemented and tested .\" properly. .sh see also .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005 robert love .\" and copyright (c) 2008, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2005-07-19 robert love - initial version .\" 2006-02-07 mtk, minor changes .\" 2008-10-10 mtk: add description of inotify_init1() .\" .th inotify_init 2 2020-04-11 "linux" "linux programmer's manual" .sh name inotify_init, inotify_init1 \- initialize an inotify instance .sh synopsis .nf .b #include .pp .b "int inotify_init(void);" .bi "int inotify_init1(int " flags ); .fi .sh description for an overview of the inotify api, see .br inotify (7). .pp .br inotify_init () initializes a new inotify instance and returns a file descriptor associated with a new inotify event queue. .pp if .i flags is 0, then .br inotify_init1 () is the same as .br inotify_init (). the following values can be bitwise ored in .ir flags to obtain different behavior: .tp .b in_nonblock set the .br o_nonblock file status flag on the open file description (see .br open (2)) referred to by the new file descriptor. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .tp .b in_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .sh return value on success, these system calls return a new file descriptor. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .rb ( inotify_init1 ()) an invalid value was specified in .ir flags . .tp .b emfile the user limit on the total number of inotify instances has been reached. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enomem insufficient kernel memory is available. .sh versions .br inotify_init () first appeared in linux 2.6.13; library support was added to glibc in version 2.4. .br inotify_init1 () was added in linux 2.6.27; library support was added to glibc in version 2.9. .sh conforming to these system calls are linux-specific. .sh see also .br inotify_add_watch (2), .br inotify_rm_watch (2), .br inotify (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright 1993 mitchum dsouza .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified, jmv@lucifer.dorms.spbu.ru, 1999-11-08 .\" modified, aeb, 2000-04-07 .\" updated from glibc docs, c. scott ananian, 2001-08-25 .\" modified, aeb, 2001-08-31 .\" modified, wharms 2001-11-12, remark on white space and example .\" .th strptime 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strptime \- convert a string representation of time to a time tm structure .sh synopsis .nf .br "#define _xopen_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "char *strptime(const char *restrict " s ", const char *restrict " format , .bi " struct tm *restrict " tm ); .fi .sh description the .br strptime () function is the converse of .br strftime (3); it converts the character string pointed to by .i s to values which are stored in the "broken-down time" structure pointed to by .ir tm , using the format specified by .ir format . .pp the broken-down time structure .i tm is defined in .ir as follows: .pp .in +4n .ex struct tm { int tm_sec; /* seconds (0\-60) */ int tm_min; /* minutes (0\-59) */ int tm_hour; /* hours (0\-23) */ int tm_mday; /* day of the month (1\-31) */ int tm_mon; /* month (0\-11) */ int tm_year; /* year \- 1900 */ int tm_wday; /* day of the week (0\-6, sunday = 0) */ int tm_yday; /* day in the year (0\-365, 1 jan = 0) */ int tm_isdst; /* daylight saving time */ }; .ee .in .pp for more details on the .i tm structure, see .br ctime (3). .pp the .i format argument is a character string that consists of field descriptors and text characters, reminiscent of .br scanf (3). each field descriptor consists of a .b % character followed by another character that specifies the replacement for the field descriptor. all other characters in the .i format string must have a matching character in the input string, except for whitespace, which matches zero or more whitespace characters in the input string. there should be white\%space or other alphanumeric characters between any two field descriptors. .pp the .br strptime () function processes the input string from left to right. each of the three possible input elements (whitespace, literal, or format) are handled one after the other. if the input cannot be matched to the format string, the function stops. the remainder of the format and input strings are not processed. .pp the supported input field descriptors are listed below. in case a text string (such as the name of a day of the week or a month name) is to be matched, the comparison is case insensitive. in case a number is to be matched, leading zeros are permitted but not required. .tp .b %% the .b % character. .tp .br %a " or " %a the name of the day of the week according to the current locale, in abbreviated form or the full name. .tp .br %b " or " %b " or " %h the month name according to the current locale, in abbreviated form or the full name. .tp .b %c the date and time representation for the current locale. .tp .b %c the century number (0\(en99). .tp .br %d " or " %e the day of month (1\(en31). .tp .b %d equivalent to .br %m/%d/%y . (this is the american style date, very confusing to non-americans, especially since .b %d/%m/%y is widely used in europe. the iso 8601 standard format is .br %y\-%m\-%d .) .tp .b %h the hour (0\(en23). .tp .b %i the hour on a 12-hour clock (1\(en12). .tp .b %j the day number in the year (1\(en366). .tp .b %m the month number (1\(en12). .tp .b %m the minute (0\(en59). .tp .b %n arbitrary whitespace. .tp .b %p the locale's equivalent of am or pm. (note: there may be none.) .tp .b %r the 12-hour clock time (using the locale's am or pm). in the posix locale equivalent to .br "%i:%m:%s %p" . if .i t_fmt_ampm is empty in the .b lc_time part of the current locale, then the behavior is undefined. .tp .b %r equivalent to .br %h:%m . .tp .b %s the second (0\(en60; 60 may occur for leap seconds; earlier also 61 was allowed). .tp .b %t arbitrary whitespace. .tp .b %t equivalent to .br %h:%m:%s . .tp .b %u the week number with sunday the first day of the week (0\(en53). the first sunday of january is the first day of week 1. .tp .b %w the ordinal number of the day of the week (0\(en6), with sunday = 0. .tp .b %w the week number with monday the first day of the week (0\(en53). the first monday of january is the first day of week 1. .tp .b %x the date, using the locale's date format. .tp .b %x the time, using the locale's time format. .tp .b %y the year within century (0\(en99). when a century is not otherwise specified, values in the range 69\(en99 refer to years in the twentieth century (1969\(en1999); values in the range 00\(en68 refer to years in the twenty-first century (2000\(en2068). .tp .b %y the year, including century (for example, 1991). .pp some field descriptors can be modified by the e or o modifier characters to indicate that an alternative format or specification should be used. if the alternative format or specification does not exist in the current locale, the unmodified field descriptor is used. .pp the e modifier specifies that the input string may contain alternative locale-dependent versions of the date and time representation: .tp .b %ec the locale's alternative date and time representation. .tp .b %ec the name of the base year (period) in the locale's alternative representation. .tp .b %ex the locale's alternative date representation. .tp .b %ex the locale's alternative time representation. .tp .b %ey the offset from .b %ec (year only) in the locale's alternative representation. .tp .b %ey the full alternative year representation. .pp the o modifier specifies that the numerical input may be in an alternative locale-dependent format: .tp .br %od " or " %oe the day of the month using the locale's alternative numeric symbols; leading zeros are permitted but not required. .tp .b %oh the hour (24-hour clock) using the locale's alternative numeric symbols. .tp .b %oi the hour (12-hour clock) using the locale's alternative numeric symbols. .tp .b %om the month using the locale's alternative numeric symbols. .tp .b %om the minutes using the locale's alternative numeric symbols. .tp .b %os the seconds using the locale's alternative numeric symbols. .tp .b %ou the week number of the year (sunday as the first day of the week) using the locale's alternative numeric symbols. .tp .b %ow the ordinal number of the day of the week (sunday=0), using the locale's alternative numeric symbols. .tp .b %ow the week number of the year (monday as the first day of the week) using the locale's alternative numeric symbols. .tp .b %oy the year (offset from .br %c ) using the locale's alternative numeric symbols. .sh return value the return value of the function is a pointer to the first character not processed in this function call. in case the input string contains more characters than required by the format string, the return value points right after the last consumed input character. in case the whole input string is consumed, the return value points to the null byte at the end of the string. if .br strptime () fails to match all of the format string and therefore an error occurred, the function returns null. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strptime () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2. .sh notes in principle, this function does not initialize .i tm but stores only the values specified. this means that .i tm should be initialized before the call. details differ a bit between different unix systems. the glibc implementation does not touch those fields which are not explicitly specified, except that it recomputes the .i tm_wday and .i tm_yday field if any of the year, month, or day elements changed. .\" .pp .\" this function is available since libc 4.6.8. .\" linux libc4 and libc5 includes define the prototype unconditionally; .\" glibc2 includes provide a prototype only when .\" .b _xopen_source .\" or .\" .b _gnu_source .\" are defined. .\" .pp .\" before libc 5.4.13 whitespace .\" (and the \(aqn\(aq and \(aqt\(aq specifications) was not handled, .\" no \(aqe\(aq and \(aqo\(aq locale modifier characters were accepted, .\" and the \(aqc\(aq specification was a synonym for the \(aqc\(aq specification. .pp the \(aqy\(aq (year in century) specification is taken to specify a year .\" in the 20th century by libc4 and libc5. .\" it is taken to be a year in the range 1950\(en2049 by glibc 2.0. it is taken to be a year in 1969\(en2068 since glibc 2.1. .\" in libc4 and libc5 the code for %i is broken (fixed in glibc; .\" %oi was fixed in glibc 2.2.4). .ss glibc notes for reasons of symmetry, glibc tries to support for .br strptime () the same format characters as for .br strftime (3). (in most cases, the corresponding fields are parsed, but no field in .i tm is changed.) this leads to .tp .b %f equivalent to .br %y\-%m\-%d , the iso 8601 date format. .tp .b %g the year corresponding to the iso week number, but without the century (0\(en99). .tp .b %g the year corresponding to the iso week number. (for example, 1991.) .tp .b %u the day of the week as a decimal number (1\(en7, where monday = 1). .tp .b %v the iso 8601:1988 week number as a decimal number (1\(en53). if the week (starting on monday) containing 1 january has four or more days in the new year, then it is considered week 1. otherwise, it is the last week of the previous year, and the next week is week 1. .tp .b %z an rfc-822/iso 8601 standard timezone specification. .tp .b %z the timezone name. .pp similarly, because of gnu extensions to .br strftime (3), .b %k is accepted as a synonym for .br %h , and .b %l should be accepted as a synonym for .br %i , and .b %p is accepted as a synonym for .br %p . finally .tp .b %s the number of seconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). leap seconds are not counted unless leap second support is available. .pp the glibc implementation does not require whitespace between two field descriptors. .sh examples the following example demonstrates the use of .br strptime () and .br strftime (3). .pp .ex #define _xopen_source #include #include #include #include int main(void) { struct tm tm; char buf[255]; memset(&tm, 0, sizeof(tm)); strptime("2001\-11\-12 18:31:01", "%y\-%m\-%d %h:%m:%s", &tm); strftime(buf, sizeof(buf), "%d %b %y %h:%m", &tm); puts(buf); exit(exit_success); } .ee .sh see also .br time (2), .br getdate (3), .br scanf (3), .br setlocale (3), .br strftime (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. #!/bin/sh log=/tmp/markup_check.$$ rm -f $log $log.full if test $# -eq 0; then echo 1>&2 "usage: $0 filename-or-dirname ... $#" exit 1 fi file_list=$(find $* -type f | grep '\.[1-9][a-za-z]*$') pagename_pattern='[a-z_a-z][^ ]*' ( echo "" echo "checking for page xref without space before left parenthesis:" pattern='^\.br *'"$pagename_pattern"'([1-8][^1-9]' echo " pattern: '$pattern'" grep "$pattern" $file_list | sed 's/^/ /' | tee -a $log echo "" echo "checking for .ir xrefs that should be .br" pattern='^\.ir *'"$pagename_pattern"' *([1-8][^1-9]' echo " pattern: '$pattern'" grep "$pattern" $file_list | sed 's/^/ /' | tee -a $log echo "" echo "checking for misformatted punctuation in .br xrefs" pattern='^\.br *'"$pagename_pattern"' *([1-8a-za-z]*) [^ ]' echo " pattern: '$pattern'" grep "$pattern" $file_list | sed 's/^/ /' | tee -a $log echo "" echo "checking for .b xrefs that should be .br" pattern='^\.b '"$pagename_pattern"' *([1-8a-za-z]*)' echo " pattern: '$pattern'" grep "$pattern" $file_list | sed 's/^/ /' | tee -a $log ) > $log.full if test $(cat $log | wc -l) -gt 0; then echo "" echo "markup errors!!!!!" cat $log.full exit 1 fi exit 0 .\" copyright 1995 jim van zandt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" corrected prototype and include, aeb, 990927 .th lsearch 3 2021-03-22 "gnu" "linux programmer's manual" .sh name lfind, lsearch \- linear search of an array .sh synopsis .nf .b #include .pp .bi "void *lfind(const void *" key ", const void *" base ", size_t *" nmemb , .bi " size_t " size ", int(*" compar ")(const void *, const void *));" .bi "void *lsearch(const void *" key ", void *" base ", size_t *" nmemb , .bi " size_t " size ", int(*" compar ")(const void *, const void *));" .fi .sh description .br lfind () and .br lsearch () perform a linear search for .i key in the array .ir base which has .i *nmemb elements of .i size bytes each. the comparison function referenced by .i compar is expected to have two arguments which point to the .i key object and to an array member, in that order, and which returns zero if the .i key object matches the array member, and nonzero otherwise. .pp if .br lsearch () does not find a matching element, then the .i key object is inserted at the end of the table, and .i *nmemb is incremented. in particular, one should know that a matching element exists, or that more room is available. .sh return value .br lfind () returns a pointer to a matching member of the array, or null if no match is found. .br lsearch () returns a pointer to a matching member of the array, or to the newly added member if no match is found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br lfind (), .br lsearch () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. present in libc since libc-4.6.27. .sh bugs the naming is unfortunate. .sh see also .br bsearch (3), .br hsearch (3), .br tsearch (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/log.3 .\" copyright (c) 2003 davide libenzi .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" davide libenzi .\" .th epoll 7 2021-03-22 "linux" "linux programmer's manual" .sh name epoll \- i/o event notification facility .sh synopsis .nf .b #include .fi .sh description the .b epoll api performs a similar task to .br poll (2): monitoring multiple file descriptors to see if i/o is possible on any of them. the .b epoll api can be used either as an edge-triggered or a level-triggered interface and scales well to large numbers of watched file descriptors. .pp the central concept of the .b epoll api is the .b epoll .ir instance , an in-kernel data structure which, from a user-space perspective, can be considered as a container for two lists: .ip \(bu 2 the .i interest list (sometimes also called the .b epoll set): the set of file descriptors that the process has registered an interest in monitoring. .ip \(bu the .i ready list: the set of file descriptors that are "ready" for i/o. the ready list is a subset of (or, more precisely, a set of references to) the file descriptors in the interest list. the ready list is dynamically populated by the kernel as a result of i/o activity on those file descriptors. .pp the following system calls are provided to create and manage an .b epoll instance: .ip \(bu 2 .br epoll_create (2) creates a new .b epoll instance and returns a file descriptor referring to that instance. (the more recent .br epoll_create1 (2) extends the functionality of .br epoll_create (2).) .ip \(bu interest in particular file descriptors is then registered via .br epoll_ctl (2), which adds items to the interest list of the .b epoll instance. .ip \(bu .br epoll_wait (2) waits for i/o events, blocking the calling thread if no events are currently available. (this system call can be thought of as fetching items from the ready list of the .b epoll instance.) .\" .ss level-triggered and edge-triggered the .b epoll event distribution interface is able to behave both as edge-triggered (et) and as level-triggered (lt). the difference between the two mechanisms can be described as follows. suppose that this scenario happens: .ip 1. 3 the file descriptor that represents the read side of a pipe .ri ( rfd ) is registered on the .b epoll instance. .ip 2. a pipe writer writes 2\ kb of data on the write side of the pipe. .ip 3. a call to .br epoll_wait (2) is done that will return .i rfd as a ready file descriptor. .ip 4. the pipe reader reads 1\ kb of data from .ir rfd . .ip 5. a call to .br epoll_wait (2) is done. .pp if the .i rfd file descriptor has been added to the .b epoll interface using the .b epollet (edge-triggered) flag, the call to .br epoll_wait (2) done in step .b 5 will probably hang despite the available data still present in the file input buffer; meanwhile the remote peer might be expecting a response based on the data it already sent. the reason for this is that edge-triggered mode delivers events only when changes occur on the monitored file descriptor. so, in step .b 5 the caller might end up waiting for some data that is already present inside the input buffer. in the above example, an event on .i rfd will be generated because of the write done in .b 2 and the event is consumed in .br 3 . since the read operation done in .b 4 does not consume the whole buffer data, the call to .br epoll_wait (2) done in step .b 5 might block indefinitely. .pp an application that employs the .b epollet flag should use nonblocking file descriptors to avoid having a blocking read or write starve a task that is handling multiple file descriptors. the suggested way to use .b epoll as an edge-triggered .rb ( epollet ) interface is as follows: .ip a) 3 with nonblocking file descriptors; and .ip b) by waiting for an event only after .br read (2) or .br write (2) return .br eagain . .pp by contrast, when used as a level-triggered interface (the default, when .b epollet is not specified), .b epoll is simply a faster .br poll (2), and can be used wherever the latter is used since it shares the same semantics. .pp since even with edge-triggered .br epoll , multiple events can be generated upon receipt of multiple chunks of data, the caller has the option to specify the .b epolloneshot flag, to tell .b epoll to disable the associated file descriptor after the receipt of an event with .br epoll_wait (2). when the .b epolloneshot flag is specified, it is the caller's responsibility to rearm the file descriptor using .br epoll_ctl (2) with .br epoll_ctl_mod . .pp if multiple threads (or processes, if child processes have inherited the .b epoll file descriptor across .br fork (2)) are blocked in .br epoll_wait (2) waiting on the same epoll file descriptor and a file descriptor in the interest list that is marked for edge-triggered .rb ( epollet ) notification becomes ready, just one of the threads (or processes) is awoken from .br epoll_wait (2). this provides a useful optimization for avoiding "thundering herd" wake-ups in some scenarios. .\" .ss interaction with autosleep if the system is in .b autosleep mode via .i /sys/power/autosleep and an event happens which wakes the device from sleep, the device driver will keep the device awake only until that event is queued. to keep the device awake until the event has been processed, it is necessary to use the .br epoll_ctl (2) .b epollwakeup flag. .pp when the .b epollwakeup flag is set in the .b events field for a .ir "struct epoll_event" , the system will be kept awake from the moment the event is queued, through the .br epoll_wait (2) call which returns the event until the subsequent .br epoll_wait (2) call. if the event should keep the system awake beyond that time, then a separate .i wake_lock should be taken before the second .br epoll_wait (2) call. .ss /proc interfaces the following interfaces can be used to limit the amount of kernel memory consumed by epoll: .\" following was added in 2.6.28, but them removed in 2.6.29 .\" .tp .\" .ir /proc/sys/fs/epoll/max_user_instances " (since linux 2.6.28)" .\" this specifies an upper limit on the number of epoll instances .\" that can be created per real user id. .tp .ir /proc/sys/fs/epoll/max_user_watches " (since linux 2.6.28)" this specifies a limit on the total number of file descriptors that a user can register across all epoll instances on the system. the limit is per real user id. each registered file descriptor costs roughly 90 bytes on a 32-bit kernel, and roughly 160 bytes on a 64-bit kernel. currently, .\" 2.6.29 (in 2.6.28, the default was 1/32 of lowmem) the default value for .i max_user_watches is 1/25 (4%) of the available low memory, divided by the registration cost in bytes. .ss example for suggested usage while the usage of .b epoll when employed as a level-triggered interface does have the same semantics as .br poll (2), the edge-triggered usage requires more clarification to avoid stalls in the application event loop. in this example, listener is a nonblocking socket on which .br listen (2) has been called. the function .i do_use_fd() uses the new ready file descriptor until .b eagain is returned by either .br read (2) or .br write (2). an event-driven state machine application should, after having received .br eagain , record its current state so that at the next call to .i do_use_fd() it will continue to .br read (2) or .br write (2) from where it stopped before. .pp .in +4n .ex #define max_events 10 struct epoll_event ev, events[max_events]; int listen_sock, conn_sock, nfds, epollfd; /* code to set up listening socket, \(aqlisten_sock\(aq, (socket(), bind(), listen()) omitted. */ epollfd = epoll_create1(0); if (epollfd == \-1) { perror("epoll_create1"); exit(exit_failure); } ev.events = epollin; ev.data.fd = listen_sock; if (epoll_ctl(epollfd, epoll_ctl_add, listen_sock, &ev) == \-1) { perror("epoll_ctl: listen_sock"); exit(exit_failure); } for (;;) { nfds = epoll_wait(epollfd, events, max_events, \-1); if (nfds == \-1) { perror("epoll_wait"); exit(exit_failure); } for (n = 0; n < nfds; ++n) { if (events[n].data.fd == listen_sock) { conn_sock = accept(listen_sock, (struct sockaddr *) &addr, &addrlen); if (conn_sock == \-1) { perror("accept"); exit(exit_failure); } setnonblocking(conn_sock); ev.events = epollin | epollet; ev.data.fd = conn_sock; if (epoll_ctl(epollfd, epoll_ctl_add, conn_sock, &ev) == \-1) { perror("epoll_ctl: conn_sock"); exit(exit_failure); } } else { do_use_fd(events[n].data.fd); } } } .ee .in .pp when used as an edge-triggered interface, for performance reasons, it is possible to add the file descriptor inside the .b epoll interface .rb ( epoll_ctl_add ) once by specifying .rb ( epollin | epollout ). this allows you to avoid continuously switching between .b epollin and .b epollout calling .br epoll_ctl (2) with .br epoll_ctl_mod . .ss questions and answers .ip 0. 4 what is the key used to distinguish the file descriptors registered in an interest list? .ip the key is the combination of the file descriptor number and the open file description (also known as an "open file handle", the kernel's internal representation of an open file). .ip 1. what happens if you register the same file descriptor on an .b epoll instance twice? .ip you will probably get .br eexist . however, it is possible to add a duplicate .rb ( dup (2), .br dup2 (2), .br fcntl (2) .br f_dupfd ) file descriptor to the same .b epoll instance. .\" but a file descriptor duplicated by fork(2) can't be added to the .\" set, because the [file *, fd] pair is already in the epoll set. .\" that is a somewhat ugly inconsistency. on the one hand, a child process .\" cannot add the duplicate file descriptor to the epoll set. (in every .\" other case that i can think of, file descriptors duplicated by fork have .\" similar semantics to file descriptors duplicated by dup() and friends.) on .\" the other hand, the very fact that the child has a duplicate of the .\" file descriptor means that even if the parent closes its file descriptor, .\" then epoll_wait() in the parent will continue to receive notifications for .\" that file descriptor because of the duplicated file descriptor in the child. .\" .\" see http://thread.gmane.org/gmane.linux.kernel/596462/ .\" "epoll design problems with common fork/exec patterns" .\" .\" mtk, feb 2008 this can be a useful technique for filtering events, if the duplicate file descriptors are registered with different .i events masks. .ip 2. can two .b epoll instances wait for the same file descriptor? if so, are events reported to both .b epoll file descriptors? .ip yes, and events would be reported to both. however, careful programming may be needed to do this correctly. .ip 3. is the .b epoll file descriptor itself poll/epoll/selectable? .ip yes. if an .b epoll file descriptor has events waiting, then it will indicate as being readable. .ip 4. what happens if one attempts to put an .b epoll file descriptor into its own file descriptor set? .ip the .br epoll_ctl (2) call fails .rb ( einval ). however, you can add an .b epoll file descriptor inside another .b epoll file descriptor set. .ip 5. can i send an .b epoll file descriptor over a unix domain socket to another process? .ip yes, but it does not make sense to do this, since the receiving process would not have copies of the file descriptors in the interest list. .ip 6. will closing a file descriptor cause it to be removed from all .b epoll interest lists? .ip yes, but be aware of the following point. a file descriptor is a reference to an open file description (see .br open (2)). whenever a file descriptor is duplicated via .br dup (2), .br dup2 (2), .br fcntl (2) .br f_dupfd , or .br fork (2), a new file descriptor referring to the same open file description is created. an open file description continues to exist until all file descriptors referring to it have been closed. .ip a file descriptor is removed from an interest list only after all the file descriptors referring to the underlying open file description have been closed. this means that even after a file descriptor that is part of an interest list has been closed, events may be reported for that file descriptor if other file descriptors referring to the same underlying file description remain open. to prevent this happening, the file descriptor must be explicitly removed from the interest list (using .br epoll_ctl (2) .br epoll_ctl_del ) before it is duplicated. alternatively, the application must ensure that all file descriptors are closed (which may be difficult if file descriptors were duplicated behind the scenes by library functions that used .br dup (2) or .br fork (2)). .ip 7. if more than one event occurs between .br epoll_wait (2) calls, are they combined or reported separately? .ip they will be combined. .ip 8. does an operation on a file descriptor affect the already collected but not yet reported events? .ip you can do two operations on an existing file descriptor. remove would be meaningless for this case. modify will reread available i/o. .ip 9. do i need to continuously read/write a file descriptor until .b eagain when using the .b epollet flag (edge-triggered behavior)? .ip receiving an event from .br epoll_wait (2) should suggest to you that such file descriptor is ready for the requested i/o operation. you must consider it ready until the next (nonblocking) read/write yields .br eagain . when and how you will use the file descriptor is entirely up to you. .ip for packet/token-oriented files (e.g., datagram socket, terminal in canonical mode), the only way to detect the end of the read/write i/o space is to continue to read/write until .br eagain . .ip for stream-oriented files (e.g., pipe, fifo, stream socket), the condition that the read/write i/o space is exhausted can also be detected by checking the amount of data read from / written to the target file descriptor. for example, if you call .br read (2) by asking to read a certain amount of data and .br read (2) returns a lower number of bytes, you can be sure of having exhausted the read i/o space for the file descriptor. the same is true when writing using .br write (2). (avoid this latter technique if you cannot guarantee that the monitored file descriptor always refers to a stream-oriented file.) .ss possible pitfalls and ways to avoid them .tp .b o starvation (edge-triggered) .pp if there is a large amount of i/o space, it is possible that by trying to drain it the other files will not get processed causing starvation. (this problem is not specific to .br epoll .) .pp the solution is to maintain a ready list and mark the file descriptor as ready in its associated data structure, thereby allowing the application to remember which files need to be processed but still round robin amongst all the ready files. this also supports ignoring subsequent events you receive for file descriptors that are already ready. .tp .b o if using an event cache... .pp if you use an event cache or store all the file descriptors returned from .br epoll_wait (2), then make sure to provide a way to mark its closure dynamically (i.e., caused by a previous event's processing). suppose you receive 100 events from .br epoll_wait (2), and in event #47 a condition causes event #13 to be closed. if you remove the structure and .br close (2) the file descriptor for event #13, then your event cache might still say there are events waiting for that file descriptor causing confusion. .pp one solution for this is to call, during the processing of event 47, .br epoll_ctl ( epoll_ctl_del ) to delete file descriptor 13 and .br close (2), then mark its associated data structure as removed and link it to a cleanup list. if you find another event for file descriptor 13 in your batch processing, you will discover the file descriptor had been previously removed and there will be no confusion. .sh versions the .b epoll api was introduced in linux kernel 2.5.44. .\" its interface should be finalized in linux kernel 2.5.66. support was added to glibc in version 2.3.2. .sh conforming to the .b epoll api is linux-specific. some other systems provide similar mechanisms, for example, freebsd has .ir kqueue , and solaris has .ir /dev/poll . .sh notes the set of file descriptors that is being monitored via an epoll file descriptor can be viewed via the entry for the epoll file descriptor in the process's .ir /proc/[pid]/fdinfo directory. see .br proc (5) for further details. .pp the .br kcmp (2) .b kcmp_epoll_tfd operation can be used to test whether a file descriptor is present in an epoll instance. .sh see also .br epoll_create (2), .br epoll_create1 (2), .br epoll_ctl (2), .br epoll_wait (2), .br poll (2), .br select (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/csin.3 .so man3/fenv.3 .so man3/xdr.3 .so man3/ffs.3 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 ian jackson .\" and copyright (c) 2006, 2014 michael kerrisk. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1996-09-08 by arnt gulbrandsen .\" modified 1997-01-31 by eric s. raymond .\" modified 2001-05-17 by aeb .\" modified 2004-06-23 by michael kerrisk .\" .th unlink 2 2021-08-27 "linux" "linux programmer's manual" .sh name unlink, unlinkat \- delete a name and possibly the file it refers to .sh synopsis .nf .b #include .pp .bi "int unlink(const char *" pathname ); .pp .br "#include " "/* definition of " at_* " constants */" .b #include .pp .bi "int unlinkat(int " dirfd ", const char *" pathname ", int " flags ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br unlinkat (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _atfile_source .fi .sh description .br unlink () deletes a name from the filesystem. if that name was the last link to a file and no processes have the file open, the file is deleted and the space it was using is made available for reuse. .pp if the name was the last link to a file but any processes still have the file open, the file will remain in existence until the last file descriptor referring to it is closed. .pp if the name referred to a symbolic link, the link is removed. .pp if the name referred to a socket, fifo, or device, the name for it is removed but processes which have the object open may continue to use it. .ss unlinkat() the .br unlinkat () system call operates in exactly the same way as either .br unlink () or .br rmdir (2) (depending on whether or not .i flags includes the .b at_removedir flag) except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br unlink () and .br rmdir (2) for a relative pathname). .pp if the pathname given in .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br unlink () and .br rmdir (2)). .pp if the pathname given in .i pathname is absolute, then .i dirfd is ignored. .pp .i flags is a bit mask that can either be specified as 0, or by oring together flag values that control the operation of .br unlinkat (). currently, only one such flag is defined: .tp .b at_removedir by default, .br unlinkat () performs the equivalent of .br unlink () on .ir pathname . if the .b at_removedir flag is specified, then performs the equivalent of .br rmdir (2) on .ir pathname . .pp see .br openat (2) for an explanation of the need for .br unlinkat (). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces write access to the directory containing .i pathname is not allowed for the process's effective uid, or one of the directories in .i pathname did not allow search permission. (see also .br path_resolution (7).) .tp .br ebusy the file .i pathname cannot be unlinked because it is being used by the system or another process; for example, it is a mount point or the nfs client software created it to represent an active but otherwise nameless inode ("nfs silly renamed"). .tp .b efault .i pathname points outside your accessible address space. .tp .b eio an i/o error occurred. .tp .b eisdir .i pathname refers to a directory. (this is the non-posix value returned by linux since 2.1.132.) .tp .b eloop too many symbolic links were encountered in translating .ir pathname . .tp .b enametoolong .ir pathname " was too long." .tp .b enoent a component in .i pathname does not exist or is a dangling symbolic link, or .i pathname is empty. .tp .b enomem insufficient kernel memory was available. .tp .b enotdir a component used as a directory in .i pathname is not, in fact, a directory. .tp .b eperm the system does not allow unlinking of directories, or unlinking of directories requires privileges that the calling process doesn't have. (this is the posix prescribed error return; as noted above, linux returns .b eisdir for this case.) .tp .br eperm " (linux only)" the filesystem does not allow unlinking of files. .tp .br eperm " or " eacces the directory containing .i pathname has the sticky bit .rb ( s_isvtx ) set and the process's effective uid is neither the uid of the file to be deleted nor that of the directory containing it, and the process is not privileged (linux: does not have the .b cap_fowner capability). .tp .b eperm the file to be unlinked is marked immutable or append-only. (see .br ioctl_iflags (2).) .tp .b erofs .i pathname refers to a file on a read-only filesystem. .pp the same errors that occur for .br unlink () and .br rmdir (2) can also occur for .br unlinkat (). the following additional errors can occur for .br unlinkat (): .tp .b ebadf .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b einval an invalid flag value was specified in .ir flags . .tp .b eisdir .i pathname refers to a directory, and .b at_removedir was not specified in .ir flags . .tp .b enotdir .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .sh versions .br unlinkat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br unlink (): svr4, 4.3bsd, posix.1-2001, posix.1-2008. .\" svr4 documents additional error .\" conditions eintr, emultihop, etxtbsy, enolink. .pp .br unlinkat (): posix.1-2008. .sh notes .ss glibc notes on older kernels where .br unlinkat () is unavailable, the glibc wrapper function falls back to the use of .br unlink () or .br rmdir (2). when .i pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in .ir /proc/self/fd that corresponds to the .ir dirfd argument. .sh bugs infelicities in the protocol underlying nfs can cause the unexpected disappearance of files which are still being used. .sh see also .br rm (1), .br unlink (1), .br chmod (2), .br link (2), .br mknod (2), .br open (2), .br rename (2), .br rmdir (2), .br mkfifo (3), .br remove (3), .br path_resolution (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" sd.4 .\" copyright 1992 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sd 4 2017-09-15 "linux" "linux programmer's manual" .sh name sd \- driver for scsi disk drives .sh synopsis .nf .br "#include " "/* for hdio_getgeo */" .br "#include " "/* for blkgetsize and blkrrpart */" .fi .sh configuration the block device name has the following form: .bi sd lp, where .i l is a letter denoting the physical drive, and .i p is a number denoting the partition on that physical drive. often, the partition number, .ir p , will be left off when the device corresponds to the whole drive. .pp scsi disks have a major device number of 8, and a minor device number of the form (16 * .ir drive_number ") + " partition_number , where .i drive_number is the number of the physical drive in order of detection, and .i partition_number is as follows: .ip +3 partition 0 is the whole drive .ip partitions 1\(en4 are the dos "primary" partitions .ip partitions 5\(en8 are the dos "extended" (or "logical") partitions .pp for example, .i /dev/sda will have major 8, minor 0, and will refer to all of the first scsi drive in the system; and .i /dev/sdb3 will have major 8, minor 19, and will refer to the third dos "primary" partition on the second scsi drive in the system. .pp at this time, only block devices are provided. raw devices have not yet been implemented. .sh description the following .ir ioctl s are provided: .tp .b hdio_getgeo returns the bios disk parameters in the following structure: .pp .in +4n .ex struct hd_geometry { unsigned char heads; unsigned char sectors; unsigned short cylinders; unsigned long start; }; .ee .in .ip a pointer to this structure is passed as the .br ioctl (2) parameter. .ip the information returned in the parameter is the disk geometry of the drive .i "as understood by dos!" this geometry is .i not the physical geometry of the drive. it is used when constructing the drive's partition table, however, and is needed for convenient operation of .br fdisk (1), .br efdisk (1), and .br lilo (1). if the geometry information is not available, zero will be returned for all of the parameters. .tp .b blkgetsize returns the device size in sectors. the .br ioctl (2) parameter should be a pointer to a .ir long . .tp .b blkrrpart forces a reread of the scsi disk partition tables. no parameter is needed. .ip the scsi .br ioctl (2) operations are also supported. if the .br ioctl (2) parameter is required, and it is null, then .br ioctl (2) fails with the error .br einval . .sh files .tp .i /dev/sd[a\-h] the whole device .tp .i /dev/sd[a\-h][0\-8] individual block partitions .\".sh see also .\".br scsi (4) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .so man3/rpc.3 .so man3/sin.3 .\" copyright (c) 1999 joseph samuel myers. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pread 2 2021-03-22 "linux" "linux programmer's manual" .sh name pread, pwrite \- read from or write to a file descriptor at a given offset .sh synopsis .nf .b #include .pp .bi "ssize_t pread(int " fd ", void *" buf ", size_t " count \ ", off_t " offset ); .bi "ssize_t pwrite(int " fd ", const void *" buf ", size_t " count \ ", off_t " offset ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pread (), .br pwrite (): .nf _xopen_source >= 500 || /* since glibc 2.12: */ _posix_c_source >= 200809l .fi .sh description .br pread () reads up to .i count bytes from file descriptor .i fd at offset .i offset (from the start of the file) into the buffer starting at .ir buf . the file offset is not changed. .pp .br pwrite () writes up to .i count bytes from the buffer starting at .i buf to the file descriptor .i fd at offset .ir offset . the file offset is not changed. .pp the file referenced by .i fd must be capable of seeking. .sh return value on success, .br pread () returns the number of bytes read (a return of zero indicates end of file) and .br pwrite () returns the number of bytes written. .pp note that it is not an error for a successful call to transfer fewer bytes than requested (see .br read (2) and .br write (2)). .pp on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .br pread () can fail and set .i errno to any error specified for .br read (2) or .br lseek (2). .br pwrite () can fail and set .i errno to any error specified for .br write (2) or .br lseek (2). .sh versions the .br pread () and .br pwrite () system calls were added to linux in version 2.1.60; the entries in the i386 system call table were added in 2.1.69. c library support (including emulation using .br lseek (2) on older kernels without the system calls) was added in glibc 2.1. .sh conforming to posix.1-2001, posix.1-2008. .sh notes the .br pread () and .br pwrite () system calls are especially useful in multithreaded applications. they allow multiple threads to perform i/o on the same file descriptor without being affected by changes to the file offset by other threads. .\" .ss c library/kernel differences on linux, the underlying system calls were renamed in kernel 2.6: .br pread () became .br pread64 (), and .br pwrite () became .br pwrite64 (). the system call numbers remained the same. the glibc .br pread () and .br pwrite () wrapper functions transparently deal with the change. .pp on some 32-bit architectures, the calling signature for these system calls differ, for the reasons described in .br syscall (2). .sh bugs posix requires that opening a file with the .br o_append flag should have no effect on the location at which .br pwrite () writes data. however, on linux, if a file is opened with .\" fixme . https://bugzilla.kernel.org/show_bug.cgi?id=43178 .br o_append , .br pwrite () appends data to the end of the file, regardless of the value of .ir offset . .sh see also .br lseek (2), .br read (2), .br readv (2), .br write (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_attr_setinheritsched 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_attr_setinheritsched, pthread_attr_getinheritsched \- set/get inherit-scheduler attribute in thread attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_attr_setinheritsched(pthread_attr_t *" attr , .bi " int " inheritsched ); .bi "int pthread_attr_getinheritsched(const pthread_attr_t *restrict " attr , .bi " int *restrict " inheritsched ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_attr_setinheritsched () function sets the inherit-scheduler attribute of the thread attributes object referred to by .ir attr to the value specified in .ir inheritsched . the inherit-scheduler attribute determines whether a thread created using the thread attributes object .i attr will inherit its scheduling attributes from the calling thread or whether it will take them from .ir attr . .pp the following scheduling attributes are affected by the inherit-scheduler attribute: scheduling policy .rb ( pthread_attr_setschedpolicy (3)), scheduling priority .rb ( pthread_attr_setschedparam (3)), and contention scope .rb ( pthread_attr_setscope (3)). .pp the following values may be specified in .ir inheritsched : .tp .b pthread_inherit_sched threads that are created using .i attr inherit scheduling attributes from the creating thread; the scheduling attributes in .i attr are ignored. .tp .b pthread_explicit_sched threads that are created using .i attr take their scheduling attributes from the values specified by the attributes object. .\" fixme document the defaults for scheduler settings .pp the default setting of the inherit-scheduler attribute in a newly initialized thread attributes object is .br pthread_inherit_sched . .pp the .br pthread_attr_getinheritsched () returns the inherit-scheduler attribute of the thread attributes object .ir attr in the buffer pointed to by .ir inheritsched . .sh return value on success, these functions return 0; on error, they return a nonzero error number. .sh errors .br pthread_attr_setinheritsched () can fail with the following error: .tp .b einval invalid value in .ir inheritsched . .pp posix.1 also documents an optional .b enotsup error ("attempt was made to set the attribute to an unsupported value") for .br pthread_attr_setinheritsched (). .\" .sh versions .\" available since glibc 2.0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_attr_setinheritsched (), .br pthread_attr_getinheritsched () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh bugs as at glibc 2.8, if a thread attributes object is initialized using .br pthread_attr_init (3), then the scheduling policy of the attributes object is set to .br sched_other and the scheduling priority is set to 0. however, if the inherit-scheduler attribute is then set to .br pthread_explicit_sched , then a thread created using the attribute object wrongly inherits its scheduling attributes from the creating thread. this bug does not occur if either the scheduling policy or scheduling priority attribute is explicitly set in the thread attributes object before calling .br pthread_create (3). .\" fixme . track status of the following bug: .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7007 .sh examples see .br pthread_setschedparam (3). .sh see also .ad l .nh .br pthread_attr_init (3), .br pthread_attr_setschedparam (3), .br pthread_attr_setschedpolicy (3), .br pthread_attr_setscope (3), .br pthread_create (3), .br pthread_setschedparam (3), .br pthread_setschedprio (3), .br pthreads (7), .br sched (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_cleanup_push 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_cleanup_push, pthread_cleanup_pop \- push and pop thread cancellation clean-up handlers .sh synopsis .nf .b #include .pp .bi "void pthread_cleanup_push(void (*" routine ")(void *), void *" arg ); .bi "void pthread_cleanup_pop(int " execute ); .pp compile and link with \fi\-pthread\fp. .fi .sh description these functions manipulate the calling thread's stack of thread-cancellation clean-up handlers. a clean-up handler is a function that is automatically executed when a thread is canceled (or in various other circumstances described below); it might, for example, unlock a mutex so that it becomes available to other threads in the process. .pp the .br pthread_cleanup_push () function pushes .i routine onto the top of the stack of clean-up handlers. when .i routine is later invoked, it will be given .i arg as its argument. .pp the .br pthread_cleanup_pop () function removes the routine at the top of the stack of clean-up handlers, and optionally executes it if .i execute is nonzero. .pp a cancellation clean-up handler is popped from the stack and executed in the following circumstances: .ip 1. 3 when a thread is canceled, all of the stacked clean-up handlers are popped and executed in the reverse of the order in which they were pushed onto the stack. .ip 2. when a thread terminates by calling .br pthread_exit (3), all clean-up handlers are executed as described in the preceding point. (clean-up handlers are .i not called if the thread terminates by performing a .i return from the thread start function.) .ip 3. when a thread calls .br pthread_cleanup_pop () with a nonzero .i execute argument, the top-most clean-up handler is popped and executed. .pp posix.1 permits .br pthread_cleanup_push () and .br pthread_cleanup_pop () to be implemented as macros that expand to text containing \(aq\fb{\fp\(aq and \(aq\fb}\fp\(aq, respectively. for this reason, the caller must ensure that calls to these functions are paired within the same function, and at the same lexical nesting level. (in other words, a clean-up handler is established only during the execution of a specified section of code.) .pp calling .br longjmp (3) .rb ( siglongjmp (3)) produces undefined results if any call has been made to .br pthread_cleanup_push () or .br pthread_cleanup_pop () without the matching call of the pair since the jump buffer was filled by .br setjmp (3) .rb ( sigsetjmp (3)). likewise, calling .br longjmp (3) .rb ( siglongjmp (3)) from inside a clean-up handler produces undefined results unless the jump buffer was also filled by .br setjmp (3) .rb ( sigsetjmp (3)) inside the handler. .sh return value these functions do not return a value. .sh errors there are no errors. .\" sh versions .\" available since glibc 2.0 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_cleanup_push (), .br pthread_cleanup_pop () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on linux, the .br pthread_cleanup_push () and .br pthread_cleanup_pop () functions .i are implemented as macros that expand to text containing \(aq\fb{\fp\(aq and \(aq\fb}\fp\(aq, respectively. this means that variables declared within the scope of paired calls to these functions will be visible within only that scope. .pp posix.1 .\" the text was actually added in the 2004 tc2 says that the effect of using .ir return , .ir break , .ir continue , or .ir goto to prematurely leave a block bracketed .br pthread_cleanup_push () and .br pthread_cleanup_pop () is undefined. portable applications should avoid doing this. .sh examples the program below provides a simple example of the use of the functions described in this page. the program creates a thread that executes a loop bracketed by .br pthread_cleanup_push () and .br pthread_cleanup_pop (). this loop increments a global variable, .ir cnt , once each second. depending on what command-line arguments are supplied, the main thread sends the other thread a cancellation request, or sets a global variable that causes the other thread to exit its loop and terminate normally (by doing a .ir return ). .pp in the following shell session, the main thread sends a cancellation request to the other thread: .pp .in +4n .ex $ \fb./a.out\fp new thread started cnt = 0 cnt = 1 canceling thread called clean\-up handler thread was canceled; cnt = 0 .ee .in .pp from the above, we see that the thread was canceled, and that the cancellation clean-up handler was called and it reset the value of the global variable .i cnt to 0. .pp in the next run, the main program sets a global variable that causes other thread to terminate normally: .pp .in +4n .ex $ \fb./a.out x\fp new thread started cnt = 0 cnt = 1 thread terminated normally; cnt = 2 .ee .in .pp from the above, we see that the clean-up handler was not executed (because .i cleanup_pop_arg was 0), and therefore the value of .i cnt was not reset. .pp in the next run, the main program sets a global variable that causes the other thread to terminate normally, and supplies a nonzero value for .ir cleanup_pop_arg : .pp .in +4n .ex $ \fb./a.out x 1\fp new thread started cnt = 0 cnt = 1 called clean\-up handler thread terminated normally; cnt = 0 .ee .in .pp in the above, we see that although the thread was not canceled, the clean-up handler was executed, because the argument given to .br pthread_cleanup_pop () was nonzero. .ss program source \& .ex #include #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static int done = 0; static int cleanup_pop_arg = 0; static int cnt = 0; static void cleanup_handler(void *arg) { printf("called clean\-up handler\en"); cnt = 0; } static void * thread_start(void *arg) { time_t start, curr; printf("new thread started\en"); pthread_cleanup_push(cleanup_handler, null); curr = start = time(null); while (!done) { pthread_testcancel(); /* a cancellation point */ if (curr < time(null)) { curr = time(null); printf("cnt = %d\en", cnt); /* a cancellation point */ cnt++; } } pthread_cleanup_pop(cleanup_pop_arg); return null; } int main(int argc, char *argv[]) { pthread_t thr; int s; void *res; s = pthread_create(&thr, null, thread_start, null); if (s != 0) handle_error_en(s, "pthread_create"); sleep(2); /* allow new thread to run a while */ if (argc > 1) { if (argc > 2) cleanup_pop_arg = atoi(argv[2]); done = 1; } else { printf("canceling thread\en"); s = pthread_cancel(thr); if (s != 0) handle_error_en(s, "pthread_cancel"); } s = pthread_join(thr, &res); if (s != 0) handle_error_en(s, "pthread_join"); if (res == pthread_canceled) printf("thread was canceled; cnt = %d\en", cnt); else printf("thread terminated normally; cnt = %d\en", cnt); exit(exit_success); } .ee .sh see also .br pthread_cancel (3), .br pthread_cleanup_push_defer_np (3), .br pthread_setcancelstate (3), .br pthread_testcancel (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strfromd.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcsdup 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsdup \- duplicate a wide-character string .sh synopsis .nf .b #include .pp .bi "wchar_t *wcsdup(const wchar_t *" s ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcsdup (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcsdup () function is the wide-character equivalent of the .br strdup (3) function. it allocates and returns a new wide-character string whose initial contents is a duplicate of the wide-character string pointed to by .ir s . .pp memory for the new wide-character string is obtained with .br malloc (3), and should be freed with .br free (3). .sh return value on success, .br wcsdup () returns a pointer to the new wide-character string. on error, it returns null, with .i errno set to indicate the error. .sh errors .tp .b enomem insufficient memory available to allocate duplicate string. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsdup () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. this function is not specified in posix.1-2001, and is not widely available on other systems. .\" present in libc5 and glibc 2.0 and later .sh see also .br strdup (3), .br wcscpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .so man3/malloc.3 .so man3/xdr.3 .\" from jt@hplb.hpl.hp.com thu dec 19 18:31:49 1996 .\" from: jean tourrilhes .\" address: hp labs, filton road, stoke gifford, bristol bs12 6qz, u.k. .\" jean ii - hplb - '96 .\" wavelan.c.4 .\" .\" provenance of this page is unclear. .\" .\" %%%license_start(gpl_noversion_oneline) .\" licensed under the gpl, .\" after inquiries with jean tourrilhes and bruce janson .\" (mtk, july 2006) .\" %%%license_end .\" .th wavelan 4 2021-03-22 "linux" "linux programmer's manual" .sh name wavelan \- at&t gis wavelan isa device driver .sh synopsis .nf .bi "insmod wavelan_cs.o [io=" b,b.. "] [ irq=" i,i.. "] [name=" n,n.. ] .fi .sh description .i this driver is obsolete: it was removed from the kernel in version 2.6.35. .pp .b wavelan is the low-level device driver for the ncr / at&t / lucent .b wavelan isa and digital (dec) .b roamabout ds wireless ethernet adapter. this driver is available as a module or might be compiled in the kernel. this driver supports multiple cards in both forms (up to 4) and allocates the next available ethernet device (eth0..eth#) for each card found, unless a device name is explicitly specified (see below). this device name will be reported in the kernel log file with the mac address, nwid, and frequency used by the card. .ss parameters this section applies to the module form (parameters passed on the .br insmod (8) command line). if the driver is included in the kernel, use the .i ether=irq,io,name syntax on the kernel command line. .tp .b io specify the list of base addresses where to search for wavelan cards (setting by dip switch on the card). if you don't specify any io address, the driver will scan 0x390 and 0x3e0 addresses, which might conflict with other hardware... .tp .b irq set the list of irqs that each wavelan card should use (the value is saved in permanent storage for future use). .tp .b name set the list of names to be used for each wavelan card device (name used by .br ifconfig (8)). .ss wireless extensions use .br iwconfig (8) to manipulate wireless extensions. .ss nwid (or domain) set the network id .ri [ 0 to .ir ffff ] or disable it .ri [ off ]. as the nwid is stored in the card permanent storage area, it will be reused at any further invocation of the driver. .ss frequency & channels for the 2.4\ ghz 2.00 hardware, you are able to set the frequency by specifying one of the 10 defined channels .ri ( 2.412, .i 2.422, 2.425, 2.4305, 2.432, 2.442, 2.452, 2.460, 2.462 or .ir 2.484 ) or directly as a numeric value. the frequency is changed immediately and permanently. frequency availability depends on the regulations... .ss statistics spy set a list of mac addresses in the driver (up to 8) and get the last quality of link for each of those (see .br iwspy (8)). .ss /proc/net/wireless .i status is the status reported by the modem. .i link quality reports the quality of the modulation on the air (direct sequence spread spectrum) [max = 16]. .i level and .i noise refer to the signal level and noise level [max = 64]. the .i crypt discarded packet and .i misc discarded packet counters are not implemented. .ss private ioctl you may use .br iwpriv (8) to manipulate private ioctls. .ss quality and level threshold enables you to define the quality and level threshold used by the modem (packet below that level are discarded). .ss histogram this functionality makes it possible to set a number of signal level intervals and to count the number of packets received in each of those defined intervals. this distribution might be used to calculate the mean value and standard deviation of the signal level. .ss specific notes this driver fails to detect some .b non-ncr/at&t/lucent wavelan cards. if this happens for you, you must look in the source code on how to add your card to the detection routine. .pp some of the mentioned features are optional. you may enable to disable them by changing flags in the driver header and recompile. .\" .sh author .\" bruce janson \(em bruce@cs.usyd.edu.au .\" .br .\" jean tourrilhes \(em jt@hplb.hpl.hp.com .\" .br .\" (and others; see source code for details) .\" .\" see also part .\" .sh see also .br wavelan_cs (4), .br ifconfig (8), .br insmod (8), .br iwconfig (8), .br iwpriv (8), .br iwspy (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getrpcent_r 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getrpcent_r, getrpcbyname_r, getrpcbynumber_r \- get rpc entry (reentrant) .sh synopsis .nf .b #include .pp .bi "int getrpcent_r(struct rpcent *" result_buf ", char *" buf , .bi " size_t " buflen ", struct rpcent **" result ); .bi "int getrpcbyname_r(const char *" name , .bi " struct rpcent *" result_buf ", char *" buf , .bi " size_t " buflen ", struct rpcent **" result ); .bi "int getrpcbynumber_r(int " number , .bi " struct rpcent *" result_buf ", char *" buf , .bi " size_t " buflen ", struct rpcent **" result ); .pp .fi .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getrpcent_r (), .br getrpcbyname_r (), .br getrpcbynumber_r (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source || _svid_source .fi .sh description the .br getrpcent_r (), .br getrpcbyname_r (), and .br getrpcbynumber_r () functions are the reentrant equivalents of, respectively, .br getrpcent (3), .br getrpcbyname (3), and .br getrpcbynumber (3). they differ in the way that the .i rpcent structure is returned, and in the function calling signature and return value. this manual page describes just the differences from the nonreentrant functions. .pp instead of returning a pointer to a statically allocated .i rpcent structure as the function result, these functions copy the structure into the location pointed to by .ir result_buf . .pp the .i buf array is used to store the string fields pointed to by the returned .i rpcent structure. (the nonreentrant functions allocate these strings in static storage.) the size of this array is specified in .ir buflen . if .i buf is too small, the call fails with the error .br erange , and the caller must try again with a larger buffer. (a buffer of length 1024 bytes should be sufficient for most applications.) .\" i can find no information on the required/recommended buffer size; .\" the nonreentrant functions use a 1024 byte buffer -- mtk. .pp if the function call successfully obtains an rpc record, then .i *result is set pointing to .ir result_buf ; otherwise, .i *result is set to null. .sh return value on success, these functions return 0. on error, they return one of the positive error numbers listed in errors. .pp on error, record not found .rb ( getrpcbyname_r (), .br getrpcbynumber_r ()), or end of input .rb ( getrpcent_r ()) .i result is set to null. .sh errors .tp .b enoent .rb ( getrpcent_r ()) no more records in database. .tp .b erange .i buf is too small. try again with a larger buffer (and increased .ir buflen ). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getrpcent_r (), .br getrpcbyname_r (), .br getrpcbynumber_r () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions. functions with similar names exist on some other systems, though typically with different calling signatures. .sh see also .br getrpcent (3), .br rpc (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/shm_open.3 .so man3/end.3 .\" copyright (c) 1986 the regents of the university of california. .\" all rights reserved. .\" .\" %%%license_start(permissive_misc) .\" redistribution and use in source and binary forms are permitted .\" provided that the above copyright notice and this paragraph are .\" duplicated in all such forms and that any documentation, .\" advertising materials, and other materials related to such .\" distribution and use acknowledge that the software was developed .\" by the university of california, berkeley. the name of the .\" university may not be used to endorse or promote products derived .\" from this software without specific prior written permission. .\" this software is provided ``as is'' and without any express or .\" implied warranties, including, without limitation, the implied .\" warranties of merchantability and fitness for a particular purpose. .\" %%%license_end .\" .\" @(#)resolver.5 5.9 (berkeley) 12/14/89 .\" $id: resolver.5,v 8.6 1999/05/21 00:01:02 vixie exp $ .\" .\" added ndots remark by bernhard r. link - debian bug #182886 .\" .th resolv.conf 5 2021-03-22 "" "linux programmer's manual" .uc 4 .sh name resolv.conf \- resolver configuration file .sh synopsis .nf .b /etc/resolv.conf .fi .sh description the .i resolver is a set of routines in the c library that provide access to the internet domain name system (dns). the resolver configuration file contains information that is read by the resolver routines the first time they are invoked by a process. the file is designed to be human readable and contains a list of keywords with values that provide various types of resolver information. the configuration file is considered a trusted source of dns information; see the .b trust-ad option below for details. .pp if this file does not exist, only the name server on the local machine will be queried, and the search list contains the local domain name determined from the hostname. .pp the different configuration options are: .tp \fbnameserver\fp name server ip address internet address of a name server that the resolver should query, either an ipv4 address (in dot notation), or an ipv6 address in colon (and possibly dot) notation as per rfc 2373. up to .b maxns (currently 3, see \fi\fp) name servers may be listed, one per keyword. if there are multiple servers, the resolver library queries them in the order listed. if no \fbnameserver\fp entries are present, the default is to use the name server on the local machine. (the algorithm used is to try a name server, and if the query times out, try the next, until out of name servers, then repeat trying all the name servers until a maximum number of retries are made.) .tp \fbsearch\fp search list for host-name lookup. by default, the search list contains one entry, the local domain name. it is determined from the local hostname returned by .br gethostname (2); the local domain name is taken to be everything after the first \(aq.\(aq. finally, if the hostname does not contain a \(aq.\(aq, the root domain is assumed as the local domain name. .ip this may be changed by listing the desired domain search path following the \fisearch\fp keyword with spaces or tabs separating the names. resolver queries having fewer than .i ndots dots (default is 1) in them will be attempted using each component of the search path in turn until a match is found. for environments with multiple subdomains please read .bi "options ndots:" n below to avoid man-in-the-middle attacks and unnecessary traffic for the root-dns-servers. .\" when having a resolv.conv with a line .\" search subdomain.domain.tld domain.tld .\" and doing a hostlookup, for example by .\" ping host.anothersubdomain .\" it sends dns-requests for .\" host.anothersubdomain. .\" host.anothersubdomain.subdomain.domain.tld. .\" host.anothersubdomain.domain.tld. .\" thus not only causing unnecessary traffic for the root-dns-servers .\" but broadcasting information to the outside and making man-in-the-middle .\" attacks possible. note that this process may be slow and will generate a lot of network traffic if the servers for the listed domains are not local, and that queries will time out if no server is available for one of the domains. .ip if there are multiple .b search directives, only the search list from the last instance is used. .ip in glibc 2.25 and earlier, the search list is limited to six domains with a total of 256 characters. since glibc 2.26, .\" glibc commit 3f853f22c87f0b671c0366eb290919719fa56c0e the search list is unlimited. .ip the .b domain directive is an obsolete name for the .b search directive that handles one search list entry only. .tp \fbsortlist\fp this option allows addresses returned by .br gethostbyname (3) to be sorted. a sortlist is specified by ip-address-netmask pairs. the netmask is optional and defaults to the natural netmask of the net. the ip address and optional network pairs are separated by slashes. up to 10 pairs may be specified. here is an example: .ip .in +4n sortlist 130.155.160.0/255.255.240.0 130.155.0.0 .in .tp \fboptions\fp options allows certain internal resolver variables to be modified. the syntax is .rs .ip \fboptions\fp \fioption\fp \fi...\fp .pp where \fioption\fp is one of the following: .tp \fbdebug\fp .\" since glibc 2.2? sets .br res_debug in .ir _res.options (effective only if glibc was built with debug support; see .br resolver (3)). .tp .bi ndots: n .\" since glibc 2.2 sets a threshold for the number of dots which must appear in a name given to .br res_query (3) (see .br resolver (3)) before an \fiinitial absolute query\fp will be made. the default for \fin\fp is 1, meaning that if there are any dots in a name, the name will be tried first as an absolute name before any \fisearch list\fp elements are appended to it. the value for this option is silently capped to 15. .tp .bi timeout: n .\" since glibc 2.2 sets the amount of time the resolver will wait for a response from a remote name server before retrying the query via a different name server. this may .br not be the total time taken by any resolver api call and there is no guarantee that a single resolver api call maps to a single timeout. measured in seconds, the default is .br res_timeout (currently 5, see \fi\fp). the value for this option is silently capped to 30. .tp .bi attempts: n sets the number of times the resolver will send a query to its name servers before giving up and returning an error to the calling application. the default is .br res_dflretry (currently 2, see \fi\fp). the value for this option is silently capped to 5. .tp .b rotate .\" since glibc 2.2 sets .br res_rotate in .ir _res.options , which causes round-robin selection of name servers from among those listed. this has the effect of spreading the query load among all listed servers, rather than having all clients try the first listed server first every time. .tp .b no\-check\-names .\" since glibc 2.2 sets .br res_nocheckname in .ir _res.options , which disables the modern bind checking of incoming hostnames and mail names for invalid characters such as underscore (_), non-ascii, or control characters. .tp .b inet6 .\" since glibc 2.2 sets .br res_use_inet6 in .ir _res.options . this has the effect of trying an aaaa query before an a query inside the .br gethostbyname (3) function, and of mapping ipv4 responses in ipv6 "tunneled form" if no aaaa records are found but an a record set exists. since glibc 2.25, .\" b76e065991ec01299225d9da90a627ebe6c1ac97 this option is deprecated; applications should use .br getaddrinfo (3), rather than .br gethostbyname (3). .tp .br ip6\-bytestring " (since glibc 2.3.4 to 2.24)" sets .br res_usebstring in .ir _res.options . this causes reverse ipv6 lookups to be made using the bit-label format described in rfc\ 2673; if this option is not set (which is the default), then nibble format is used. this option was removed in glibc 2.25, since it relied on a backward-incompatible dns extension that was never deployed on the internet. .tp .br ip6\-dotint / no\-ip6\-dotint " (glibc 2.3.4 to 2.24)" clear/set .br res_noip6dotint in .ir _res.options . when this option is clear .rb ( ip6\-dotint ), reverse ipv6 lookups are made in the (deprecated) .i ip6.int zone; when this option is set .rb ( no\-ip6\-dotint ), reverse ipv6 lookups are made in the .i ip6.arpa zone by default. these options are available in glibc versions up to 2.24, where .br no\-ip6\-dotint is the default. since .br ip6\-dotint support long ago ceased to be available on the internet, these options were removed in glibc 2.25. .tp .br edns0 " (since glibc 2.6)" sets .br res_use_edns0 in .ir _res.options . this enables support for the dns extensions described in rfc\ 2671. .tp .br single\-request " (since glibc 2.10)" sets .br res_snglkup in .ir _res.options . by default, glibc performs ipv4 and ipv6 lookups in parallel since version 2.9. some appliance dns servers cannot handle these queries properly and make the requests time out. this option disables the behavior and makes glibc perform the ipv6 and ipv4 requests sequentially (at the cost of some slowdown of the resolving process). .tp .br single\-request\-reopen " (since glibc 2.9)" sets .br res_snglkupreop in .ir _res.options . the resolver uses the same socket for the a and aaaa requests. some hardware mistakenly sends back only one reply. when that happens the client system will sit and wait for the second reply. turning this option on changes this behavior so that if two requests from the same port are not handled correctly it will close the socket and open a new one before sending the second request. .tp .br no\-tld\-query " (since glibc 2.14)" sets .br res_notldquery in .ir _res.options . this option causes .br res_nsearch () to not attempt to resolve an unqualified name as if it were a top level domain (tld). this option can cause problems if the site has ``localhost'' as a tld rather than having localhost on one or more elements of the search list. this option has no effect if neither res_defnames or res_dnsrch is set. .tp .br use\-vc " (since glibc 2.14)" sets .br res_usevc in .ir _res.options . this option forces the use of tcp for dns resolutions. .\" aef16cc8a4c670036d45590877d411a97f01e0cd .tp .br no\-reload " (since glibc 2.26)" sets .br res_noreload in .ir _res.options . this option disables automatic reloading of a changed configuration file. .tp .br trust\-ad " (since glibc 2.31)" .\" 446997ff1433d33452b81dfa9e626b8dccf101a4 sets .br res_trustad in .ir _res.options . this option controls the ad bit behavior of the stub resolver. if a validating resolver sets the ad bit in a response, it indicates that the data in the response was verified according to the dnssec protocol. in order to rely on the ad bit, the local system has to trust both the dnssec-validating resolver and the network path to it, which is why an explicit opt-in is required. if the .b trust\-ad option is active, the stub resolver sets the ad bit in outgoing dns queries (to enable ad bit support), and preserves the ad bit in responses. without this option, the ad bit is not set in queries, and it is always removed from responses before they are returned to the application. this means that applications can trust the ad bit in responses if the .b trust\-ad option has been set correctly. .ip in glibc version 2.30 and earlier, the ad is not set automatically in queries, and is passed through unchanged to applications in responses. .re .pp the \fisearch\fp keyword of a system's \firesolv.conf\fp file can be overridden on a per-process basis by setting the environment variable .b localdomain to a space-separated list of search domains. .pp the \fioptions\fp keyword of a system's \firesolv.conf\fp file can be amended on a per-process basis by setting the environment variable .b res_options to a space-separated list of resolver options as explained above under \fboptions\fp. .pp the keyword and value must appear on a single line, and the keyword (e.g., \fbnameserver\fp) must start the line. the value follows the keyword, separated by white space. .pp lines that contain a semicolon (;) or hash character (#) in the first column are treated as comments. .sh files .ir /etc/resolv.conf , .i .sh see also .br gethostbyname (3), .br resolver (3), .br host.conf (5), .br hosts (5), .br nsswitch.conf (5), .br hostname (7), .br named (8) .pp name server operations guide for bind .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/logb.3 .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" from: @(#)err.3 8.1 (berkeley) 6/9/93 .\" $freebsd: src/lib/libc/gen/err.3,v 1.11.2.5 2001/08/17 15:42:32 ru exp $ .\" .\" 2011-09-10, mtk, converted from mdoc to man macros .\" .th err 3 2021-03-22 "linux" "linux programmer's manual" .sh name err, verr, errx, verrx, warn, vwarn, warnx, vwarnx \- formatted error messages .sh synopsis .nf .b #include .pp .bi "noreturn void err(int " eval ", const char *" fmt ", ...);" .bi "noreturn void errx(int " eval ", const char *" fmt ", ...);" .pp .bi "void warn(const char *" fmt ", ...);" .bi "void warnx(const char *" fmt ", ...);" .pp .b #include .pp .bi "noreturn void verr(int " eval ", const char *" fmt ", va_list " args ); .bi "noreturn void verrx(int " eval ", const char *" fmt ", va_list " args ); .pp .bi "void vwarn(const char *" fmt ", va_list " args ); .bi "void vwarnx(const char *" fmt ", va_list " args ); .fi .sh description the .br err () and .br warn () family of functions display a formatted error message on the standard error output. in all cases, the last component of the program name, a colon character, and a space are output. if the .i fmt argument is not null, the .br printf (3)-like formatted error message is output. the output is terminated by a newline character. .pp the .br err (), .br verr (), .br warn (), and .br vwarn () functions append an error message obtained from .br strerror (3) based on the global variable .ir errno , preceded by another colon and space unless the .i fmt argument is null. .pp the .br errx () and .br warnx () functions do not append an error message. .pp the .br err (), .br verr (), .br errx (), and .br verrx () functions do not return, but exit with the value of the argument .ir eval . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br err (), .br errx (), .br warn (), .br warnx (), .br verr (), .br verrx (), .br vwarn (), .br vwarnx () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard bsd extensions. .\" .sh history .\" the .\" .br err () .\" and .\" .br warn () .\" functions first appeared in .\" 4.4bsd. .sh examples display the current .i errno information string and exit: .pp .in +4n .ex p = malloc(size); if (p == null) err(exit_failure, null); fd = open(file_name, o_rdonly, 0); if (fd == \-1) err(exit_failure, "%s", file_name); .ee .in .pp display an error message and exit: .pp .in +4n .ex if (tm.tm_hour < start_time) errx(exit_failure, "too early, wait until %s", start_time_string); .ee .in .pp warn of an error: .pp .in +4n .ex fd = open(raw_device, o_rdonly, 0); if (fd == \-1) warnx("%s: %s: trying the block device", raw_device, strerror(errno)); fd = open(block_device, o_rdonly, 0); if (fd == \-1) err(exit_failure, "%s", block_device); .ee .in .sh see also .br error (3), .br exit (3), .br perror (3), .br printf (3), .br strerror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-11.7 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th fmax 3 2021-03-22 "" "linux programmer's manual" .sh name fmax, fmaxf, fmaxl \- determine maximum of two floating-point numbers .sh synopsis .nf .b #include .pp .bi "double fmax(double " x ", double " y ); .bi "float fmaxf(float " x ", float " y ); .bi "long double fmaxl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fmax (), .br fmaxf (), .br fmaxl (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description these functions return the larger value of .i x and .ir y . .sh return value these functions return the maximum of .i x and .ir y . .pp if one argument is a nan, the other argument is returned. .pp if both arguments are nan, a nan is returned. .sh errors no errors occur. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fmax (), .br fmaxf (), .br fmaxl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br fdim (3), .br fmin (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcstombs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcstombs \- convert a wide-character string to a multibyte string .sh synopsis .nf .b #include .pp .bi "size_t wcstombs(char *restrict " dest ", const wchar_t *restrict " src , .bi " size_t " n ); .fi .sh description if .i dest is not null, the .br wcstombs () function converts the wide-character string .i src to a multibyte string starting at .ir dest . at most .i n bytes are written to .ir dest . the sequence of characters placed in .ir dest begins in the initial shift state. the conversion can stop for three reasons: .ip 1. 3 a wide character has been encountered that can not be represented as a multibyte sequence (according to the current locale). in this case, .i (size_t)\ \-1 is returned. .ip 2. the length limit forces a stop. in this case, the number of bytes written to .i dest is returned, but the shift state at this point is lost. .ip 3. the wide-character string has been completely converted, including the terminating null wide character (l\(aq\e0\(aq). in this case, the conversion ends in the initial shift state. the number of bytes written to .ir dest , excluding the terminating null byte (\(aq\e0\(aq), is returned. .pp the programmer must ensure that there is room for at least .i n bytes at .ir dest . .pp if .ir dest is null, .i n is ignored, and the conversion proceeds as above, except that the converted bytes are not written out to memory, and no length limit exists. .pp in order to avoid the case 2 above, the programmer should make sure .i n is greater than or equal to .ir "wcstombs(null,src,0)+1" . .sh return value the .br wcstombs () function returns the number of bytes that make up the converted part of a multibyte sequence, not including the terminating null byte. if a wide character was encountered which could not be converted, .i (size_t)\ \-1 is returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcstombs () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wcstombs () depends on the .b lc_ctype category of the current locale. .pp the function .br wcsrtombs (3) provides a better interface to the same functionality. .sh see also .br mblen (3), .br mbstowcs (3), .br mbtowc (3), .br wcsrtombs (3), .br wctomb (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcsspn 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsspn \- advance in a wide-character string, skipping any of a set of wide characters .sh synopsis .nf .b #include .pp .bi "size_t wcsspn(const wchar_t *" wcs ", const wchar_t *" accept ); .fi .sh description the .br wcsspn () function is the wide-character equivalent of the .br strspn (3) function. it determines the length of the longest initial segment of .i wcs which consists entirely of wide-characters listed in .ir accept . in other words, it searches for the first occurrence in the wide-character string .i wcs of a wide-character not contained in the wide-character string .ir accept . .sh return value the .br wcsspn () function returns the number of wide characters in the longest initial segment of .i wcs which consists entirely of wide-characters listed in .ir accept . in other words, it returns the position of the first occurrence in the wide-character string .i wcs of a wide-character not contained in the wide-character string .ir accept , or .i wcslen(wcs) if there is none. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsspn () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strspn (3), .br wcscspn (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" page by b.hubert .\" and copyright (c) 2015, thomas gleixner .\" and copyright (c) 2015, michael kerrisk .\" .\" %%%license_start(freely_redistributable) .\" may be freely modified and distributed .\" %%%license_end .\" .\" niki a. rahimi (ltc security development, narahimi@us.ibm.com) .\" added errors section. .\" .\" modified 2004-06-17 mtk .\" modified 2004-10-07 aeb, added futex_requeue, futex_cmp_requeue .\" .\" fixme still to integrate are some points from torvald riegel's mail of .\" 2015-01-23: .\" http://thread.gmane.org/gmane.linux.kernel/1703405/focus=7977 .\" .\" fixme do we need to add some text regarding torvald riegel's 2015-01-24 mail .\" http://thread.gmane.org/gmane.linux.kernel/1703405/focus=1873242 .\" .th futex 2 2021-08-27 "linux" "linux programmer's manual" .sh name futex \- fast user-space locking .sh synopsis .nf .pp .br "#include " " /* definition of " futex_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(sys_futex, uint32_t *" uaddr ", int " futex_op \ ", uint32_t " val , .bi " const struct timespec *" timeout , \ " \fr /* or: \fbuint32_t \fival2\fp */" .bi " uint32_t *" uaddr2 ", uint32_t " val3 ); .fi .pp .ir note : glibc provides no wrapper for .br futex (), necessitating the use of .br syscall (2). .sh description the .br futex () system call provides a method for waiting until a certain condition becomes true. it is typically used as a blocking construct in the context of shared-memory synchronization. when using futexes, the majority of the synchronization operations are performed in user space. a user-space program employs the .br futex () system call only when it is likely that the program has to block for a longer time until the condition becomes true. other .br futex () operations can be used to wake any processes or threads waiting for a particular condition. .pp a futex is a 32-bit value\(emreferred to below as a .ir "futex word" \(emwhose address is supplied to the .br futex () system call. (futexes are 32 bits in size on all platforms, including 64-bit systems.) all futex operations are governed by this value. in order to share a futex between processes, the futex is placed in a region of shared memory, created using (for example) .br mmap (2) or .br shmat (2). (thus, the futex word may have different virtual addresses in different processes, but these addresses all refer to the same location in physical memory.) in a multithreaded program, it is sufficient to place the futex word in a global variable shared by all threads. .pp when executing a futex operation that requests to block a thread, the kernel will block only if the futex word has the value that the calling thread supplied (as one of the arguments of the .br futex () call) as the expected value of the futex word. the loading of the futex word's value, the comparison of that value with the expected value, and the actual blocking will happen atomically and will be totally ordered with respect to concurrent operations performed by other threads on the same futex word. .\" notes from darren hart (dec 2015): .\" totally ordered with respect futex operations refers to semantics .\" of the acquire/release operations and how they impact ordering of .\" memory reads and writes. the kernel futex operations are protected .\" by spinlocks, which ensure that all operations are serialized .\" with respect to one another. .\" .\" this is a lot to attempt to define in this document. perhaps a .\" reference to linux/documentation/memory-barriers.txt as a footnote .\" would be sufficient? or perhaps for this manual, "serialized" would .\" be sufficient, with a footnote regarding "totally ordered" and a .\" pointer to the memory-barrier documentation? thus, the futex word is used to connect the synchronization in user space with the implementation of blocking by the kernel. analogously to an atomic compare-and-exchange operation that potentially changes shared memory, blocking via a futex is an atomic compare-and-block operation. .\" fixme(torvald riegel): .\" eventually we want to have some text in notes to satisfy .\" the reference in the following sentence .\" see notes for a detailed specification of .\" the synchronization semantics. .pp one use of futexes is for implementing locks. the state of the lock (i.e., acquired or not acquired) can be represented as an atomically accessed flag in shared memory. in the uncontended case, a thread can access or modify the lock state with atomic instructions, for example atomically changing it from not acquired to acquired using an atomic compare-and-exchange instruction. (such instructions are performed entirely in user mode, and the kernel maintains no information about the lock state.) on the other hand, a thread may be unable to acquire a lock because it is already acquired by another thread. it then may pass the lock's flag as a futex word and the value representing the acquired state as the expected value to a .br futex () wait operation. this .br futex () operation will block if and only if the lock is still acquired (i.e., the value in the futex word still matches the "acquired state"). when releasing the lock, a thread has to first reset the lock state to not acquired and then execute a futex operation that wakes threads blocked on the lock flag used as a futex word (this can be further optimized to avoid unnecessary wake-ups). see .br futex (7) for more detail on how to use futexes. .pp besides the basic wait and wake-up futex functionality, there are further futex operations aimed at supporting more complex use cases. .pp note that no explicit initialization or destruction is necessary to use futexes; the kernel maintains a futex (i.e., the kernel-internal implementation artifact) only while operations such as .br futex_wait , described below, are being performed on a particular futex word. .\" .ss arguments the .i uaddr argument points to the futex word. on all platforms, futexes are four-byte integers that must be aligned on a four-byte boundary. the operation to perform on the futex is specified in the .i futex_op argument; .ir val is a value whose meaning and purpose depends on .ir futex_op . .pp the remaining arguments .ri ( timeout , .ir uaddr2 , and .ir val3 ) are required only for certain of the futex operations described below. where one of these arguments is not required, it is ignored. .pp for several blocking operations, the .i timeout argument is a pointer to a .ir timespec structure that specifies a timeout for the operation. however, notwithstanding the prototype shown above, for some operations, the least significant four bytes of this argument are instead used as an integer whose meaning is determined by the operation. for these operations, the kernel casts the .i timeout value first to .ir "unsigned long", then to .ir uint32_t , and in the remainder of this page, this argument is referred to as .i val2 when interpreted in this fashion. .pp where it is required, the .ir uaddr2 argument is a pointer to a second futex word that is employed by the operation. .pp the interpretation of the final integer argument, .ir val3 , depends on the operation. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .ss futex operations the .i futex_op argument consists of two parts: a command that specifies the operation to be performed, bitwise ored with zero or more options that modify the behaviour of the operation. the options that may be included in .i futex_op are as follows: .tp .br futex_private_flag " (since linux 2.6.22)" .\" commit 34f01cc1f512fa783302982776895c73714ebbc2 this option bit can be employed with all futex operations. it tells the kernel that the futex is process-private and not shared with another process (i.e., it is being used for synchronization only between threads of the same process). this allows the kernel to make some additional performance optimizations. .\" i.e., it allows the kernel choose the fast path for validating .\" the user-space address and avoids expensive vma lookups, .\" taking reference counts on file backing store, and so on. .ip as a convenience, .i defines a set of constants with the suffix .b _private that are equivalents of all of the operations listed below, .\" except the obsolete futex_fd, for which the "private" flag was .\" meaningless but with the .br futex_private_flag ored into the constant value. thus, there are .br futex_wait_private , .br futex_wake_private , and so on. .tp .br futex_clock_realtime " (since linux 2.6.28)" .\" commit 1acdac104668a0834cfa267de9946fac7764d486 this option bit can be employed only with the .br futex_wait_bitset , .br futex_wait_requeue_pi , (since linux 4.5) .\" commit 337f13046ff03717a9e99675284a817527440a49 .br futex_wait , and (since linux 5.14) .\" commit bf22a6976897977b0a3f1aeba6823c959fc4fdae .b futex_lock_pi2 operations. .ip if this option is set, the kernel measures the .i timeout against the .b clock_realtime clock. .ip if this option is not set, the kernel measures the .i timeout against the .b clock_monotonic clock. .pp the operation specified in .i futex_op is one of the following: .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_wait " (since linux 2.6.0)" .\" strictly speaking, since some time in 2.5.x this operation tests that the value at the futex word pointed to by the address .i uaddr still contains the expected value .ir val , and if so, then sleeps waiting for a .b futex_wake operation on the futex word. the load of the value of the futex word is an atomic memory access (i.e., using atomic machine instructions of the respective architecture). this load, the comparison with the expected value, and starting to sleep are performed atomically .\" fixme: torvald, i think we may need to add some explanation of .\" "totally ordered" here. and totally ordered with respect to other futex operations on the same futex word. if the thread starts to sleep, it is considered a waiter on this futex word. if the futex value does not match .ir val , then the call fails immediately with the error .br eagain . .ip the purpose of the comparison with the expected value is to prevent lost wake-ups. if another thread changed the value of the futex word after the calling thread decided to block based on the prior value, and if the other thread executed a .br futex_wake operation (or similar wake-up) after the value change and before this .br futex_wait operation, then the calling thread will observe the value change and will not start to sleep. .ip if the .i timeout is not null, the structure it points to specifies a timeout for the wait. (this interval will be rounded up to the system clock granularity, and is guaranteed not to expire early.) the timeout is by default measured according to the .br clock_monotonic clock, but, since linux 4.5, the .br clock_realtime clock can be selected by specifying .br futex_clock_realtime in .ir futex_op . if .i timeout is null, the call blocks indefinitely. .ip .ir note : for .br futex_wait , .ir timeout is interpreted as a .ir relative value. this differs from other futex operations, where .i timeout is interpreted as an absolute value. to obtain the equivalent of .br futex_wait with an absolute timeout, employ .br futex_wait_bitset with .ir val3 specified as .br futex_bitset_match_any . .ip the arguments .i uaddr2 and .i val3 are ignored. .\" fixme . (torvald) i think we should remove this. or maybe adapt to a .\" different example. .\" .\" for .\" .br futex (7), .\" this call is executed if decrementing the count gave a negative value .\" (indicating contention), .\" and will sleep until another process or thread releases .\" the futex and executes the .\" .b futex_wake .\" operation. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_wake " (since linux 2.6.0)" .\" strictly speaking, since linux 2.5.x this operation wakes at most .i val of the waiters that are waiting (e.g., inside .br futex_wait ) on the futex word at the address .ir uaddr . most commonly, .i val is specified as either 1 (wake up a single waiter) or .br int_max (wake up all waiters). no guarantee is provided about which waiters are awoken (e.g., a waiter with a higher scheduling priority is not guaranteed to be awoken in preference to a waiter with a lower priority). .ip the arguments .ir timeout , .ir uaddr2 , and .i val3 are ignored. .\" fixme . (torvald) i think we should remove this. or maybe adapt to .\" a different example. .\" .\" for .\" .br futex (7), .\" this is executed if incrementing the count showed that .\" there were waiters, .\" once the futex value has been set to 1 .\" (indicating that it is available). .\" .\" how does "incrementing the count show that there were waiters"? .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_fd " (from linux 2.6.0 up to and including linux 2.6.25)" .\" strictly speaking, from linux 2.5.x to 2.6.25 this operation creates a file descriptor that is associated with the futex at .ir uaddr . the caller must close the returned file descriptor after use. when another process or thread performs a .br futex_wake on the futex word, the file descriptor indicates as being readable with .br select (2), .br poll (2), and .br epoll (7) .ip the file descriptor can be used to obtain asynchronous notifications: if .i val is nonzero, then, when another process or thread executes a .br futex_wake , the caller will receive the signal number that was passed in .ir val . .ip the arguments .ir timeout , .ir uaddr2 , and .i val3 are ignored. .ip because it was inherently racy, .b futex_fd has been removed .\" commit 82af7aca56c67061420d618cc5a30f0fd4106b80 from linux 2.6.26 onward. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_requeue " (since linux 2.6.0)" this operation performs the same task as .br futex_cmp_requeue (see below), except that no check is made using the value in .ir val3 . (the argument .i val3 is ignored.) .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_cmp_requeue " (since linux 2.6.7)" this operation first checks whether the location .i uaddr still contains the value .ir val3 . if not, the operation fails with the error .br eagain . otherwise, the operation wakes up a maximum of .i val waiters that are waiting on the futex at .ir uaddr . if there are more than .i val waiters, then the remaining waiters are removed from the wait queue of the source futex at .i uaddr and added to the wait queue of the target futex at .ir uaddr2 . the .i val2 argument specifies an upper limit on the number of waiters that are requeued to the futex at .ir uaddr2 . .ip .\" fixme(torvald) is the following correct? or is just the decision .\" which threads to wake or requeue part of the atomic operation? the load from .i uaddr is an atomic memory access (i.e., using atomic machine instructions of the respective architecture). this load, the comparison with .ir val3 , and the requeueing of any waiters are performed atomically and totally ordered with respect to other operations on the same futex word. .\" notes from a f2f conversation with thomas gleixner (aug 2015): ### .\" the operation is serialized with respect to operations on both .\" source and target futex. no other waiter can enqueue itself .\" for waiting and no other waiter can dequeue itself because of .\" a timeout or signal. .ip typical values to specify for .i val are 0 or 1. (specifying .br int_max is not useful, because it would make the .br futex_cmp_requeue operation equivalent to .br futex_wake .) the limit value specified via .i val2 is typically either 1 or .br int_max . (specifying the argument as 0 is not useful, because it would make the .br futex_cmp_requeue operation equivalent to .br futex_wait .) .ip the .b futex_cmp_requeue operation was added as a replacement for the earlier .br futex_requeue . the difference is that the check of the value at .i uaddr can be used to ensure that requeueing happens only under certain conditions, which allows race conditions to be avoided in certain use cases. .\" but, as rich felker points out, there remain valid use cases for .\" futex_requeue, for example, when the calling thread is requeuing .\" the target(s) to a lock that the calling thread owns .\" from: rich felker .\" date: wed, 29 oct 2014 22:43:17 -0400 .\" to: darren hart .\" cc: libc-alpha@sourceware.org, ... .\" subject: re: add futex wrapper to glibc? .ip both .br futex_requeue and .br futex_cmp_requeue can be used to avoid "thundering herd" wake-ups that could occur when using .b futex_wake in cases where all of the waiters that are woken need to acquire another futex. consider the following scenario, where multiple waiter threads are waiting on b, a wait queue implemented using a futex: .ip .in +4n .ex lock(a) while (!check_value(v)) { unlock(a); block_on(b); lock(a); }; unlock(a); .ee .in .ip if a waker thread used .br futex_wake , then all waiters waiting on b would be woken up, and they would all try to acquire lock a. however, waking all of the threads in this manner would be pointless because all except one of the threads would immediately block on lock a again. by contrast, a requeue operation wakes just one waiter and moves the other waiters to lock a, and when the woken waiter unlocks a then the next waiter can proceed. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_wake_op " (since linux 2.6.14)" .\" commit 4732efbeb997189d9f9b04708dc26bf8613ed721 .\" author: jakub jelinek .\" date: tue sep 6 15:16:25 2005 -0700 .\" fixme. (torvald) the glibc condvar implementation is currently being .\" revised (e.g., to not use an internal lock anymore). .\" it is probably more future-proof to remove this paragraph. .\" [torvald, do you have an update here?] this operation was added to support some user-space use cases where more than one futex must be handled at the same time. the most notable example is the implementation of .br pthread_cond_signal (3), which requires operations on two futexes, the one used to implement the mutex and the one used in the implementation of the wait queue associated with the condition variable. .br futex_wake_op allows such cases to be implemented without leading to high rates of contention and context switching. .ip the .br futex_wake_op operation is equivalent to executing the following code atomically and totally ordered with respect to other futex operations on any of the two supplied futex words: .ip .in +4n .ex uint32_t oldval = *(uint32_t *) uaddr2; *(uint32_t *) uaddr2 = oldval \fiop\fp \fioparg\fp; futex(uaddr, futex_wake, val, 0, 0, 0); if (oldval \ficmp\fp \ficmparg\fp) futex(uaddr2, futex_wake, val2, 0, 0, 0); .ee .in .ip in other words, .br futex_wake_op does the following: .rs .ip * 3 saves the original value of the futex word at .ir uaddr2 and performs an operation to modify the value of the futex at .ir uaddr2 ; this is an atomic read-modify-write memory access (i.e., using atomic machine instructions of the respective architecture) .ip * wakes up a maximum of .i val waiters on the futex for the futex word at .ir uaddr ; and .ip * dependent on the results of a test of the original value of the futex word at .ir uaddr2 , wakes up a maximum of .i val2 waiters on the futex for the futex word at .ir uaddr2 . .re .ip the operation and comparison that are to be performed are encoded in the bits of the argument .ir val3 . pictorially, the encoding is: .ip .in +4n .ex +---+---+-----------+-----------+ |op |cmp| oparg | cmparg | +---+---+-----------+-----------+ 4 4 12 12 <== # of bits .ee .in .ip expressed in code, the encoding is: .ip .in +4n .ex #define futex_op(op, oparg, cmp, cmparg) \e (((op & 0xf) << 28) | \e ((cmp & 0xf) << 24) | \e ((oparg & 0xfff) << 12) | \e (cmparg & 0xfff)) .ee .in .ip in the above, .i op and .i cmp are each one of the codes listed below. the .i oparg and .i cmparg components are literal numeric values, except as noted below. .ip the .i op component has one of the following values: .ip .in +4n .ex futex_op_set 0 /* uaddr2 = oparg; */ futex_op_add 1 /* uaddr2 += oparg; */ futex_op_or 2 /* uaddr2 |= oparg; */ futex_op_andn 3 /* uaddr2 &= \(tioparg; */ futex_op_xor 4 /* uaddr2 \(ha= oparg; */ .ee .in .ip in addition, bitwise oring the following value into .i op causes .ir "(1\ <<\ oparg)" to be used as the operand: .ip .in +4n .ex futex_op_arg_shift 8 /* use (1 << oparg) as operand */ .ee .in .ip the .i cmp field is one of the following: .ip .in +4n .ex futex_op_cmp_eq 0 /* if (oldval == cmparg) wake */ futex_op_cmp_ne 1 /* if (oldval != cmparg) wake */ futex_op_cmp_lt 2 /* if (oldval < cmparg) wake */ futex_op_cmp_le 3 /* if (oldval <= cmparg) wake */ futex_op_cmp_gt 4 /* if (oldval > cmparg) wake */ futex_op_cmp_ge 5 /* if (oldval >= cmparg) wake */ .ee .in .ip the return value of .br futex_wake_op is the sum of the number of waiters woken on the futex .ir uaddr plus the number of waiters woken on the futex .ir uaddr2 . .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_wait_bitset " (since linux 2.6.25)" .\" commit cd689985cf49f6ff5c8eddc48d98b9d581d9475d this operation is like .br futex_wait except that .i val3 is used to provide a 32-bit bit mask to the kernel. this bit mask, in which at least one bit must be set, is stored in the kernel-internal state of the waiter. see the description of .br futex_wake_bitset for further details. .ip if .i timeout is not null, the structure it points to specifies an absolute timeout for the wait operation. if .i timeout is null, the operation can block indefinitely. .ip the .i uaddr2 argument is ignored. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_wake_bitset " (since linux 2.6.25)" .\" commit cd689985cf49f6ff5c8eddc48d98b9d581d9475d this operation is the same as .br futex_wake except that the .i val3 argument is used to provide a 32-bit bit mask to the kernel. this bit mask, in which at least one bit must be set, is used to select which waiters should be woken up. the selection is done by a bitwise and of the "wake" bit mask (i.e., the value in .ir val3 ) and the bit mask which is stored in the kernel-internal state of the waiter (the "wait" bit mask that is set using .br futex_wait_bitset ). all of the waiters for which the result of the and is nonzero are woken up; the remaining waiters are left sleeping. .ip the effect of .br futex_wait_bitset and .br futex_wake_bitset is to allow selective wake-ups among multiple waiters that are blocked on the same futex. however, note that, depending on the use case, employing this bit-mask multiplexing feature on a futex can be less efficient than simply using multiple futexes, because employing bit-mask multiplexing requires the kernel to check all waiters on a futex, including those that are not interested in being woken up (i.e., they do not have the relevant bit set in their "wait" bit mask). .\" according to http://locklessinc.com/articles/futex_cheat_sheet/: .\" .\" "the original reason for the addition of these extensions .\" was to improve the performance of pthread read-write locks .\" in glibc. however, the pthreads library no longer uses the .\" same locking algorithm, and these extensions are not used .\" without the bitset parameter being all ones. .\" .\" the page goes on to note that the futex_wait_bitset operation .\" is nevertheless used (with a bit mask of all ones) in order to .\" obtain the absolute timeout functionality that is useful .\" for efficiently implementing pthreads apis (which use absolute .\" timeouts); futex_wait provides only relative timeouts. .ip the constant .br futex_bitset_match_any , which corresponds to all 32 bits set in the bit mask, can be used as the .i val3 argument for .br futex_wait_bitset and .br futex_wake_bitset . other than differences in the handling of the .i timeout argument, the .br futex_wait operation is equivalent to .br futex_wait_bitset with .ir val3 specified as .br futex_bitset_match_any ; that is, allow a wake-up by any waker. the .br futex_wake operation is equivalent to .br futex_wake_bitset with .ir val3 specified as .br futex_bitset_match_any ; that is, wake up any waiter(s). .ip the .i uaddr2 and .i timeout arguments are ignored. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .ss priority-inheritance futexes linux supports priority-inheritance (pi) futexes in order to handle priority-inversion problems that can be encountered with normal futex locks. priority inversion is the problem that occurs when a high-priority task is blocked waiting to acquire a lock held by a low-priority task, while tasks at an intermediate priority continuously preempt the low-priority task from the cpu. consequently, the low-priority task makes no progress toward releasing the lock, and the high-priority task remains blocked. .pp priority inheritance is a mechanism for dealing with the priority-inversion problem. with this mechanism, when a high-priority task becomes blocked by a lock held by a low-priority task, the priority of the low-priority task is temporarily raised to that of the high-priority task, so that it is not preempted by any intermediate level tasks, and can thus make progress toward releasing the lock. to be effective, priority inheritance must be transitive, meaning that if a high-priority task blocks on a lock held by a lower-priority task that is itself blocked by a lock held by another intermediate-priority task (and so on, for chains of arbitrary length), then both of those tasks (or more generally, all of the tasks in a lock chain) have their priorities raised to be the same as the high-priority task. .pp from a user-space perspective, what makes a futex pi-aware is a policy agreement (described below) between user space and the kernel about the value of the futex word, coupled with the use of the pi-futex operations described below. (unlike the other futex operations described above, the pi-futex operations are designed for the implementation of very specific ipc mechanisms.) .\" .\" quoting darren hart: .\" these opcodes paired with the pi futex value policy (described below) .\" defines a "futex" as pi aware. these were created very specifically .\" in support of pi pthread_mutexes, so it makes a lot more sense to .\" talk about a pi aware pthread_mutex, than a pi aware futex, since .\" there is a lot of policy and scaffolding that has to be built up .\" around it to use it properly (this is what a pi pthread_mutex is). .pp .\" mtk: the following text is drawn from the hart/guniguntala paper .\" (listed in see also), but i have reworded some pieces .\" significantly. .\" the pi-futex operations described below differ from the other futex operations in that they impose policy on the use of the value of the futex word: .ip * 3 if the lock is not acquired, the futex word's value shall be 0. .ip * if the lock is acquired, the futex word's value shall be the thread id (tid; see .br gettid (2)) of the owning thread. .ip * if the lock is owned and there are threads contending for the lock, then the .b futex_waiters bit shall be set in the futex word's value; in other words, this value is: .ip futex_waiters | tid .ip (note that is invalid for a pi futex word to have no owner and .br futex_waiters set.) .pp with this policy in place, a user-space application can acquire an unacquired lock or release a lock using atomic instructions executed in user mode (e.g., a compare-and-swap operation such as .i cmpxchg on the x86 architecture). acquiring a lock simply consists of using compare-and-swap to atomically set the futex word's value to the caller's tid if its previous value was 0. releasing a lock requires using compare-and-swap to set the futex word's value to 0 if the previous value was the expected tid. .pp if a futex is already acquired (i.e., has a nonzero value), waiters must employ the .b futex_lock_pi or .b futex_lock_pi2 operations to acquire the lock. if other threads are waiting for the lock, then the .b futex_waiters bit is set in the futex value; in this case, the lock owner must employ the .b futex_unlock_pi operation to release the lock. .pp in the cases where callers are forced into the kernel (i.e., required to perform a .br futex () call), they then deal directly with a so-called rt-mutex, a kernel locking mechanism which implements the required priority-inheritance semantics. after the rt-mutex is acquired, the futex value is updated accordingly, before the calling thread returns to user space. .pp it is important to note .\" tglx (july 2015): .\" if there are multiple waiters on a pi futex then a wake pi operation .\" will wake the first waiter and hand over the lock to this waiter. this .\" includes handing over the rtmutex which represents the futex in the .\" kernel. the strict requirement is that the futex owner and the rtmutex .\" owner must be the same, except for the update period which is .\" serialized by the futex internal locking. that means the kernel must .\" update the user-space value prior to returning to user space that the kernel will update the futex word's value prior to returning to user space. (this prevents the possibility of the futex word's value ending up in an invalid state, such as having an owner but the value being 0, or having waiters but not having the .b futex_waiters bit set.) .pp if a futex has an associated rt-mutex in the kernel (i.e., there are blocked waiters) and the owner of the futex/rt-mutex dies unexpectedly, then the kernel cleans up the rt-mutex and hands it over to the next waiter. this in turn requires that the user-space value is updated accordingly. to indicate that this is required, the kernel sets the .b futex_owner_died bit in the futex word along with the thread id of the new owner. user space can detect this situation via the presence of the .b futex_owner_died bit and is then responsible for cleaning up the stale state left over by the dead owner. .\" tglx (july 2015): .\" the futex_owner_died bit can also be set on uncontended futexes, where .\" the kernel has no state associated. this happens via the robust futex .\" mechanism. in that case the futex value will be set to .\" futex_owner_died. the robust futex mechanism is also available for non .\" pi futexes. .pp pi futexes are operated on by specifying one of the values listed below in .ir futex_op . note that the pi futex operations must be used as paired operations and are subject to some additional requirements: .ip * 3 .br futex_lock_pi , .br futex_lock_pi2 , and .b futex_trylock_pi pair with .br futex_unlock_pi . .b futex_unlock_pi must be called only on a futex owned by the calling thread, as defined by the value policy, otherwise the error .b eperm results. .ip * .b futex_wait_requeue_pi pairs with .br futex_cmp_requeue_pi . this must be performed from a non-pi futex to a distinct pi futex (or the error .b einval results). additionally, .i val (the number of waiters to be woken) must be 1 (or the error .b einval results). .pp the pi futex operations are as follows: .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_lock_pi " (since linux 2.6.18)" .\" commit c87e2837be82df479a6bae9f155c43516d2feebc this operation is used after an attempt to acquire the lock via an atomic user-mode instruction failed because the futex word has a nonzero value\(emspecifically, because it contained the (pid-namespace-specific) tid of the lock owner. .ip the operation checks the value of the futex word at the address .ir uaddr . if the value is 0, then the kernel tries to atomically set the futex value to the caller's tid. if the futex word's value is nonzero, the kernel atomically sets the .b futex_waiters bit, which signals the futex owner that it cannot unlock the futex in user space atomically by setting the futex value to 0. .\" tglx (july 2015): .\" the operation here is similar to the futex_wait logic. when the user .\" space atomic acquire does not succeed because the futex value was non .\" zero, then the waiter goes into the kernel, takes the kernel internal .\" lock and retries the acquisition under the lock. if the acquisition .\" does not succeed either, then it sets the futex_waiters bit, to signal .\" the lock owner that it needs to go into the kernel. here is the pseudo .\" code: .\" .\" lock(kernel_lock); .\" retry: .\" .\" /* .\" * owner might have unlocked in user space before we .\" * were able to set the waiter bit. .\" */ .\" if (atomic_acquire(futex) == success) { .\" unlock(kernel_lock()); .\" return 0; .\" } .\" .\" /* .\" * owner might have unlocked after the above atomic_acquire() .\" * attempt. .\" */ .\" if (atomic_set_waiters_bit(futex) != success) .\" goto retry; .\" .\" queue_waiter(); .\" unlock(kernel_lock); .\" block(); .\" after that, the kernel: .rs .ip 1. 3 tries to find the thread which is associated with the owner tid. .ip 2. creates or reuses kernel state on behalf of the owner. (if this is the first waiter, there is no kernel state for this futex, so kernel state is created by locking the rt-mutex and the futex owner is made the owner of the rt-mutex. if there are existing waiters, then the existing state is reused.) .ip 3. attaches the waiter to the futex (i.e., the waiter is enqueued on the rt-mutex waiter list). .re .ip if more than one waiter exists, the enqueueing of the waiter is in descending priority order. (for information on priority ordering, see the discussion of the .br sched_deadline , .br sched_fifo , and .br sched_rr scheduling policies in .br sched (7).) the owner inherits either the waiter's cpu bandwidth (if the waiter is scheduled under the .br sched_deadline policy) or the waiter's priority (if the waiter is scheduled under the .br sched_rr or .br sched_fifo policy). .\" august 2015: .\" mtk: if the realm is restricted purely to sched_other (sched_normal) .\" processes, does the nice value come into play also? .\" .\" tglx: no. sched_other/normal tasks are handled in fifo order this inheritance follows the lock chain in the case of nested locking .\" (i.e., task 1 blocks on lock a, held by task 2, .\" while task 2 blocks on lock b, held by task 3) and performs deadlock detection. .ip the .i timeout argument provides a timeout for the lock attempt. if .i timeout is not null, the structure it points to specifies an absolute timeout, measured against the .br clock_realtime clock. .\" 2016-07-07 response from thomas gleixner on lkml: .\" from: thomas gleixner .\" date: 6 july 2016 at 20:57 .\" subject: re: futex: allow futex_clock_realtime with futex_wait op .\" .\" on thu, 23 jun 2016, michael kerrisk (man-pages) wrote: .\" > on 06/23/2016 08:28 pm, darren hart wrote: .\" > > and as a follow-on, what is the reason for futex_lock_pi only using .\" > > clock_realtime? it seems reasonable to me that a user may want to wait a .\" > > specific amount of time, regardless of wall time. .\" > .\" > yes, that's another weird inconsistency. .\" .\" the reason is that phtread_mutex_timedlock() uses absolute timeouts based on .\" clock_realtime. glibc folks asked to make that the default behaviour back .\" then when we added lock_pi. if .i timeout is null, the operation will block indefinitely. .ip the .ir uaddr2 , .ir val , and .i val3 arguments are ignored. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_lock_pi2 " (since linux 5.14)" .\" commit bf22a6976897977b0a3f1aeba6823c959fc4fdae this operation is the same as .br futex_lock_pi , except that the clock against which .i timeout is measured is selectable. by default, the (absolute) timeout specified in .i timeout is measured againt the .b clock_monotonic clock, but if the .b futex_clock_realtime flag is specified in .ir futex_op , then the timeout is measured against the .b clock_realtime clock. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_trylock_pi " (since linux 2.6.18)" .\" commit c87e2837be82df479a6bae9f155c43516d2feebc this operation tries to acquire the lock at .ir uaddr . it is invoked when a user-space atomic acquire did not succeed because the futex word was not 0. .ip because the kernel has access to more state information than user space, acquisition of the lock might succeed if performed by the kernel in cases where the futex word (i.e., the state information accessible to use-space) contains stale state .rb ( futex_waiters and/or .br futex_owner_died ). this can happen when the owner of the futex died. user space cannot handle this condition in a race-free manner, but the kernel can fix this up and acquire the futex. .\" paraphrasing a f2f conversation with thomas gleixner about the .\" above point (aug 2015): ### .\" there is a rare possibility of a race condition involving an .\" uncontended futex with no owner, but with waiters. the .\" kernel-user-space contract is that if a futex is nonzero, you must .\" go into kernel. the futex was owned by a task, and that task dies .\" but there are no waiters, so the futex value is non zero. .\" therefore, the next locker has to go into the kernel, .\" so that the kernel has a chance to clean up. (cmxch on zero .\" in user space would fail, so kernel has to clean up.) .\" darren hart (oct 2015): .\" the trylock in the kernel has more state, so it can independently .\" verify the flags that user space must trust implicitly. .ip the .ir uaddr2 , .ir val , .ir timeout , and .ir val3 arguments are ignored. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_unlock_pi " (since linux 2.6.18)" .\" commit c87e2837be82df479a6bae9f155c43516d2feebc this operation wakes the top priority waiter that is waiting in .b futex_lock_pi or .b futex_lock_pi2 on the futex address provided by the .i uaddr argument. .ip this is called when the user-space value at .i uaddr cannot be changed atomically from a tid (of the owner) to 0. .ip the .ir uaddr2 , .ir val , .ir timeout , and .ir val3 arguments are ignored. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_cmp_requeue_pi " (since linux 2.6.31)" .\" commit 52400ba946759af28442dee6265c5c0180ac7122 this operation is a pi-aware variant of .br futex_cmp_requeue . it requeues waiters that are blocked via .b futex_wait_requeue_pi on .i uaddr from a non-pi source futex .ri ( uaddr ) to a pi target futex .ri ( uaddr2 ). .ip as with .br futex_cmp_requeue , this operation wakes up a maximum of .i val waiters that are waiting on the futex at .ir uaddr . however, for .br futex_cmp_requeue_pi , .i val is required to be 1 (since the main point is to avoid a thundering herd). the remaining waiters are removed from the wait queue of the source futex at .i uaddr and added to the wait queue of the target futex at .ir uaddr2 . .ip the .i val2 .\" val2 is the cap on the number of requeued waiters. .\" in the glibc pthread_cond_broadcast() implementation, this argument .\" is specified as int_max, and for pthread_cond_signal() it is 0. and .i val3 arguments serve the same purposes as for .br futex_cmp_requeue . .\" .\" the page at http://locklessinc.com/articles/futex_cheat_sheet/ .\" notes that "priority-inheritance futex to priority-inheritance .\" futex requeues are currently unsupported". however, probably .\" the page does not need to say nothing about this, since .\" thomas gleixner commented (july 2015): "they never will be .\" supported because they make no sense at all" .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .tp .br futex_wait_requeue_pi " (since linux 2.6.31)" .\" commit 52400ba946759af28442dee6265c5c0180ac7122 .\" wait on a non-pi futex at .i uaddr and potentially be requeued (via a .br futex_cmp_requeue_pi operation in another task) onto a pi futex at .ir uaddr2 . the wait operation on .i uaddr is the same as for .br futex_wait . .ip the waiter can be removed from the wait on .i uaddr without requeueing on .ir uaddr2 via a .br futex_wake operation in another task. in this case, the .br futex_wait_requeue_pi operation fails with the error .br eagain . .ip if .i timeout is not null, the structure it points to specifies an absolute timeout for the wait operation. if .i timeout is null, the operation can block indefinitely. .ip the .i val3 argument is ignored. .ip the .br futex_wait_requeue_pi and .br futex_cmp_requeue_pi were added to support a fairly specific use case: support for priority-inheritance-aware posix threads condition variables. the idea is that these operations should always be paired, in order to ensure that user space and the kernel remain in sync. thus, in the .br futex_wait_requeue_pi operation, the user-space application pre-specifies the target of the requeue that takes place in the .br futex_cmp_requeue_pi operation. .\" .\" darren hart notes that a patch to allow glibc to fully support .\" pi-aware pthreads condition variables has not yet been accepted into .\" glibc. the story is complex, and can be found at .\" https://sourceware.org/bugzilla/show_bug.cgi?id=11588 .\" darren notes that in the meantime, the patch is shipped with various .\" preempt_rt-enabled linux systems. .\" .\" related to the preceding, darren proposed that somewhere, man-pages .\" should document the following point: .\" .\" while the linux kernel, since 2.6.31, supports requeueing of .\" priority-inheritance (pi) aware mutexes via the .\" futex_wait_requeue_pi and futex_cmp_requeue_pi futex operations, .\" the glibc implementation does not yet take full advantage of this. .\" specifically, the condvar internal data lock remains a non-pi aware .\" mutex, regardless of the type of the pthread_mutex associated with .\" the condvar. this can lead to an unbounded priority inversion on .\" the internal data lock even when associating a pi aware .\" pthread_mutex with a condvar during a pthread_cond*_wait .\" operation. for this reason, it is not recommended to rely on .\" priority inheritance when using pthread condition variables. .\" .\" the problem is that the obvious location for this text is .\" the pthread_cond*wait(3) man page. however, such a man page .\" does not currently exist. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .sh return value in the event of an error (and assuming that .br futex () was invoked via .br syscall (2)), all operations return \-1 and set .i errno to indicate the error. .pp the return value on success depends on the operation, as described in the following list: .tp .b futex_wait returns 0 if the caller was woken up. note that a wake-up can also be caused by common futex usage patterns in unrelated code that happened to have previously used the futex word's memory location (e.g., typical futex-based implementations of pthreads mutexes can cause this under some conditions). therefore, callers should always conservatively assume that a return value of 0 can mean a spurious wake-up, and use the futex word's value (i.e., the user-space synchronization scheme) to decide whether to continue to block or not. .tp .b futex_wake returns the number of waiters that were woken up. .tp .b futex_fd returns the new file descriptor associated with the futex. .tp .b futex_requeue returns the number of waiters that were woken up. .tp .b futex_cmp_requeue returns the total number of waiters that were woken up or requeued to the futex for the futex word at .ir uaddr2 . if this value is greater than .ir val , then the difference is the number of waiters requeued to the futex for the futex word at .ir uaddr2 . .tp .b futex_wake_op returns the total number of waiters that were woken up. this is the sum of the woken waiters on the two futexes for the futex words at .i uaddr and .ir uaddr2 . .tp .b futex_wait_bitset returns 0 if the caller was woken up. see .b futex_wait for how to interpret this correctly in practice. .tp .b futex_wake_bitset returns the number of waiters that were woken up. .tp .b futex_lock_pi returns 0 if the futex was successfully locked. .tp .b futex_lock_pi2 returns 0 if the futex was successfully locked. .tp .b futex_trylock_pi returns 0 if the futex was successfully locked. .tp .b futex_unlock_pi returns 0 if the futex was successfully unlocked. .tp .b futex_cmp_requeue_pi returns the total number of waiters that were woken up or requeued to the futex for the futex word at .ir uaddr2 . if this value is greater than .ir val , then difference is the number of waiters requeued to the futex for the futex word at .ir uaddr2 . .tp .b futex_wait_requeue_pi returns 0 if the caller was successfully requeued to the futex for the futex word at .ir uaddr2 . .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .sh errors .tp .b eacces no read access to the memory of a futex word. .tp .b eagain .rb ( futex_wait , .br futex_wait_bitset , .br futex_wait_requeue_pi ) the value pointed to by .i uaddr was not equal to the expected value .i val at the time of the call. .ip .br note : on linux, the symbolic names .b eagain and .b ewouldblock (both of which appear in different parts of the kernel futex code) have the same value. .tp .b eagain .rb ( futex_cmp_requeue , .br futex_cmp_requeue_pi ) the value pointed to by .i uaddr is not equal to the expected value .ir val3 . .tp .b eagain .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_cmp_requeue_pi ) the futex owner thread id of .i uaddr (for .br futex_cmp_requeue_pi : .ir uaddr2 ) is about to exit, but has not yet handled the internal state cleanup. try again. .tp .b edeadlk .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_cmp_requeue_pi ) the futex word at .i uaddr is already locked by the caller. .tp .br edeadlk .\" fixme . i see that kernel/locking/rtmutex.c uses edeadlk in some .\" places, and edeadlock in others. on almost all architectures .\" these constants are synonymous. is there a reason that both .\" names are used? .\" .\" tglx (july 2015): "no. we should probably fix that." .\" .rb ( futex_cmp_requeue_pi ) while requeueing a waiter to the pi futex for the futex word at .ir uaddr2 , the kernel detected a deadlock. .tp .b efault a required pointer argument (i.e., .ir uaddr , .ir uaddr2 , or .ir timeout ) did not point to a valid user-space address. .tp .b eintr a .b futex_wait or .b futex_wait_bitset operation was interrupted by a signal (see .br signal (7)). in kernels before linux 2.6.22, this error could also be returned for a spurious wakeup; since linux 2.6.22, this no longer happens. .tp .b einval the operation in .i futex_op is one of those that employs a timeout, but the supplied .i timeout argument was invalid .ri ( tv_sec was less than zero, or .i tv_nsec was not less than 1,000,000,000). .tp .b einval the operation specified in .i futex_op employs one or both of the pointers .i uaddr and .ir uaddr2 , but one of these does not point to a valid object\(emthat is, the address is not four-byte-aligned. .tp .b einval .rb ( futex_wait_bitset , .br futex_wake_bitset ) the bit mask supplied in .i val3 is zero. .tp .b einval .rb ( futex_cmp_requeue_pi ) .i uaddr equals .i uaddr2 (i.e., an attempt was made to requeue to the same futex). .tp .b einval .rb ( futex_fd ) the signal number supplied in .i val is invalid. .tp .b einval .rb ( futex_wake , .br futex_wake_op , .br futex_wake_bitset , .br futex_requeue , .br futex_cmp_requeue ) the kernel detected an inconsistency between the user-space state at .i uaddr and the kernel state\(emthat is, it detected a waiter which waits in .b futex_lock_pi or .b futex_lock_pi2 on .ir uaddr . .tp .b einval .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_unlock_pi ) the kernel detected an inconsistency between the user-space state at .i uaddr and the kernel state. this indicates either state corruption or that the kernel found a waiter on .i uaddr which is waiting via .b futex_wait or .br futex_wait_bitset . .tp .b einval .rb ( futex_cmp_requeue_pi ) the kernel detected an inconsistency between the user-space state at .i uaddr2 and the kernel state; .\" from a conversation with thomas gleixner (aug 2015): ### .\" the kernel sees: i have non pi state for a futex you tried to .\" tell me was pi that is, the kernel detected a waiter which waits via .b futex_wait or .b futex_wait_bitset on .ir uaddr2 . .tp .b einval .rb ( futex_cmp_requeue_pi ) the kernel detected an inconsistency between the user-space state at .i uaddr and the kernel state; that is, the kernel detected a waiter which waits via .b futex_wait or .b futex_wait_bitset on .ir uaddr . .tp .b einval .rb ( futex_cmp_requeue_pi ) the kernel detected an inconsistency between the user-space state at .i uaddr and the kernel state; that is, the kernel detected a waiter which waits on .i uaddr via .b futex_lock_pi or .b futex_lock_pi2 (instead of .br futex_wait_requeue_pi ). .tp .b einval .rb ( futex_cmp_requeue_pi ) .\" this deals with the case: .\" wait_requeue_pi(a, b); .\" requeue_pi(a, c); an attempt was made to requeue a waiter to a futex other than that specified by the matching .b futex_wait_requeue_pi call for that waiter. .tp .b einval .rb ( futex_cmp_requeue_pi ) the .i val argument is not 1. .tp .b einval invalid argument. .tp .b enfile .rb ( futex_fd ) the system-wide limit on the total number of open files has been reached. .tp .b enomem .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_cmp_requeue_pi ) the kernel could not allocate memory to hold state information. .tp .b enosys invalid operation specified in .ir futex_op . .tp .b enosys the .b futex_clock_realtime option was specified in .ir futex_op , but the accompanying operation was neither .br futex_wait , .br futex_wait_bitset , .br futex_wait_requeue_pi , nor .br futex_lock_pi2 . .tp .b enosys .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_unlock_pi , .br futex_cmp_requeue_pi , .br futex_wait_requeue_pi ) a run-time check determined that the operation is not available. the pi-futex operations are not implemented on all architectures and are not supported on some cpu variants. .tp .b eperm .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_cmp_requeue_pi ) the caller is not allowed to attach itself to the futex at .i uaddr (for .br futex_cmp_requeue_pi : the futex at .ir uaddr2 ). (this may be caused by a state corruption in user space.) .tp .b eperm .rb ( futex_unlock_pi ) the caller does not own the lock represented by the futex word. .tp .b esrch .rb ( futex_lock_pi , .br futex_lock_pi2 , .br futex_trylock_pi , .br futex_cmp_requeue_pi ) the thread id in the futex word at .i uaddr does not exist. .tp .b esrch .rb ( futex_cmp_requeue_pi ) the thread id in the futex word at .i uaddr2 does not exist. .tp .b etimedout the operation in .i futex_op employed the timeout specified in .ir timeout , and the timeout expired before the operation completed. .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .sh versions futexes were first made available in a stable kernel release with linux 2.6.0. .pp initial futex support was merged in linux 2.5.7 but with different semantics from what was described above. a four-argument system call with the semantics described in this page was introduced in linux 2.5.40. a fifth argument was added in linux 2.5.70, and a sixth argument was added in linux 2.6.7. .sh conforming to this system call is linux-specific. .sh notes several higher-level programming abstractions are implemented via futexes, including posix semaphores and various posix threads synchronization mechanisms (mutexes, condition variables, read-write locks, and barriers). .\" todo fixme(torvald) above, we cite this section and claim it contains .\" details on the synchronization semantics; add the c11 equivalents .\" here (or whatever we find consensus for). .\" .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .\" .sh examples the program below demonstrates use of futexes in a program where a parent process and a child process use a pair of futexes located inside a shared anonymous mapping to synchronize access to a shared resource: the terminal. the two processes each write .ir nloops (a command-line argument that defaults to 5 if omitted) messages to the terminal and employ a synchronization protocol that ensures that they alternate in writing messages. upon running this program we see output such as the following: .pp .in +4n .ex $ \fb./futex_demo\fp parent (18534) 0 child (18535) 0 parent (18534) 1 child (18535) 1 parent (18534) 2 child (18535) 2 parent (18534) 3 child (18535) 3 parent (18534) 4 child (18535) 4 .ee .in .ss program source \& .ex /* futex_demo.c usage: futex_demo [nloops] (default: 5) demonstrate the use of futexes in a program where parent and child use a pair of futexes located inside a shared anonymous mapping to synchronize access to a shared resource: the terminal. the two processes each write \(aqnum\-loops\(aq messages to the terminal and employ a synchronization protocol that ensures that they alternate in writing messages. */ #define _gnu_source #include #include #include #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) static uint32_t *futex1, *futex2, *iaddr; static int futex(uint32_t *uaddr, int futex_op, uint32_t val, const struct timespec *timeout, uint32_t *uaddr2, uint32_t val3) { return syscall(sys_futex, uaddr, futex_op, val, timeout, uaddr2, val3); } /* acquire the futex pointed to by \(aqfutexp\(aq: wait for its value to become 1, and then set the value to 0. */ static void fwait(uint32_t *futexp) { long s; /* atomic_compare_exchange_strong(ptr, oldval, newval) atomically performs the equivalent of: if (*ptr == *oldval) *ptr = newval; it returns true if the test yielded true and *ptr was updated. */ while (1) { /* is the futex available? */ const uint32_t one = 1; if (atomic_compare_exchange_strong(futexp, &one, 0)) break; /* yes */ /* futex is not available; wait. */ s = futex(futexp, futex_wait, 0, null, null, 0); if (s == \-1 && errno != eagain) errexit("futex\-futex_wait"); } } /* release the futex pointed to by \(aqfutexp\(aq: if the futex currently has the value 0, set its value to 1 and the wake any futex waiters, so that if the peer is blocked in fwait(), it can proceed. */ static void fpost(uint32_t *futexp) { long s; /* atomic_compare_exchange_strong() was described in comments above. */ const uint32_t zero = 0; if (atomic_compare_exchange_strong(futexp, &zero, 1)) { s = futex(futexp, futex_wake, 1, null, null, 0); if (s == \-1) errexit("futex\-futex_wake"); } } int main(int argc, char *argv[]) { pid_t childpid; int nloops; setbuf(stdout, null); nloops = (argc > 1) ? atoi(argv[1]) : 5; /* create a shared anonymous mapping that will hold the futexes. since the futexes are being shared between processes, we subsequently use the "shared" futex operations (i.e., not the ones suffixed "_private"). */ iaddr = mmap(null, sizeof(*iaddr) * 2, prot_read | prot_write, map_anonymous | map_shared, \-1, 0); if (iaddr == map_failed) errexit("mmap"); futex1 = &iaddr[0]; futex2 = &iaddr[1]; *futex1 = 0; /* state: unavailable */ *futex2 = 1; /* state: available */ /* create a child process that inherits the shared anonymous mapping. */ childpid = fork(); if (childpid == \-1) errexit("fork"); if (childpid == 0) { /* child */ for (int j = 0; j < nloops; j++) { fwait(futex1); printf("child (%jd) %d\en", (intmax_t) getpid(), j); fpost(futex2); } exit(exit_success); } /* parent falls through to here. */ for (int j = 0; j < nloops; j++) { fwait(futex2); printf("parent (%jd) %d\en", (intmax_t) getpid(), j); fpost(futex1); } wait(null); exit(exit_success); } .ee .sh see also .ad l .br get_robust_list (2), .br restart_syscall (2), .br pthread_mutexattr_getprotocol (3), .br futex (7), .br sched (7) .pp the following kernel source files: .ip * 2 .i documentation/pi\-futex.txt .ip * .i documentation/futex\-requeue\-pi.txt .ip * .i documentation/locking/rt\-mutex.txt .ip * .i documentation/locking/rt\-mutex\-design.txt .ip * .i documentation/robust\-futex\-abi.txt .pp franke, h., russell, r., and kirwood, m., 2002. \fifuss, futexes and furwocks: fast userlevel locking in linux\fp (from proceedings of the ottawa linux symposium 2002), .br .ur http://kernel.org\:/doc\:/ols\:/2002\:/ols2002\-pages\-479\-495.pdf .ue .pp hart, d., 2009. \fia futex overview and update\fp, .ur http://lwn.net/articles/360699/ .ue .pp hart, d.\& and guniguntala, d., 2009. \firequeue-pi: making glibc condvars pi-aware\fp (from proceedings of the 2009 real-time linux workshop), .ur http://lwn.net/images/conf/rtlws11/papers/proc/p10.pdf .ue .pp drepper, u., 2011. \fifutexes are tricky\fp, .ur http://www.akkadia.org/drepper/futex.pdf .ue .pp futex example library, futex-*.tar.bz2 at .br .ur ftp://ftp.kernel.org\:/pub\:/linux\:/kernel\:/people\:/rusty/ .ue .\" .\" fixme(torvald) we should probably refer to the glibc code here, in .\" particular the glibc-internal futex wrapper functions that are .\" wip, and the generic pthread_mutex_t and perhaps condvar .\" implementations. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sat jul 24 16:57:14 1993 by rik faith (faith@cs.unc.edu) .th intro 4 2017-09-15 "linux" "linux programmer's manual" .sh name intro \- introduction to special files .sh description section 4 of the manual describes special files (devices). .sh files /dev/* \(em device files .sh notes .ss authors and copyright conditions look at the header of the manual page source for the author(s) and copyright conditions. note that these can be different from page to page! .sh see also .br mknod (1), .br mknod (2), .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/finite.3 .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th user-session-keyring 7 2020-08-13 linux "linux programmer's manual" .sh name user-session-keyring \- per-user default session keyring .sh description the user session keyring is a keyring used to anchor keys on behalf of a user. each uid the kernel deals with has its own user session keyring that is shared by all processes with that uid. the user session keyring has a name (description) of the form .i _uid_ses. where .i is the user id of the corresponding user. .pp the user session keyring is associated with the record that the kernel maintains for the uid. it comes into existence upon the first attempt to access either the user session keyring, the .br user\-keyring (7), or the .br session\-keyring (7). .\" davis howells: the user and user-session keyrings are managed as a pair. the keyring remains pinned in existence so long as there are processes running with that real uid or files opened by those processes remain open. (the keyring can also be pinned indefinitely by linking it into another keyring.) .pp the user session keyring is created on demand when a thread requests it or when a thread asks for its .br session\-keyring (7) and that keyring doesn't exist. in the latter case, a user session keyring will be created and, if the session keyring wasn't to be created, the user session keyring will be set as the process's actual session keyring. .pp the user session keyring is searched by .br request_key (2) if the actual session keyring does not exist and is ignored otherwise. .pp a special serial number value, .br key_spec_user_session_keyring , is defined that can be used in lieu of the actual serial number of the calling process's user session keyring. .pp from the .br keyctl (1) utility, '\fb@us\fp' can be used instead of a numeric key id in much the same way. .pp user session keyrings are independent of .br clone (2), .br fork (2), .br vfork (2), .br execve (2), and .br _exit (2) excepting that the keyring is destroyed when the uid record is destroyed when the last process pinning it exits. .pp if a user session keyring does not exist when it is accessed, it will be created. .pp rather than relying on the user session keyring, it is strongly recommended\(emespecially if the process is running as root\(emthat a .br session\-keyring (7) be set explicitly, for example by .br pam_keyinit (8). .sh notes the user session keyring was added to support situations where a process doesn't have a session keyring, perhaps because it was created via a pathway that didn't involve pam (e.g., perhaps it was a daemon started by .br inetd (8)). in such a scenario, the user session keyring acts as a substitute for the .br session\-keyring (7). .sh see also .ad l .nh .br keyctl (1), .br keyctl (3), .br keyrings (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gethostbyname.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification .\" http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th mbrtowc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mbrtowc \- convert a multibyte sequence to a wide character .sh synopsis .nf .b #include .pp .bi "size_t mbrtowc(wchar_t *restrict " pwc ", const char *restrict " s \ ", size_t " n , .bi " mbstate_t *restrict " ps ); .fi .sh description the main case for this function is when .ir s is not null and .i pwc is not null. in this case, the .br mbrtowc () function inspects at most .i n bytes of the multibyte string starting at .ir s , extracts the next complete multibyte character, converts it to a wide character and stores it at .ir *pwc . it updates the shift state .ir *ps . if the converted wide character is not l\(aq\e0\(aq (the null wide character), it returns the number of bytes that were consumed from .ir s . if the converted wide character is l\(aq\e0\(aq, it resets the shift state .i *ps to the initial state and returns 0. .pp if the .ir n bytes starting at .i s do not contain a complete multibyte character, .br mbrtowc () returns .ir "(size_t)\ \-2" . this can happen even if .i n >= .ir mb_cur_max , if the multibyte string contains redundant shift sequences. .pp if the multibyte string starting at .i s contains an invalid multibyte sequence before the next complete character, .br mbrtowc () returns .ir "(size_t)\ \-1" and sets .i errno to .br eilseq . in this case, the effects on .i *ps are undefined. .pp a different case is when .ir s is not null but .i pwc is null. in this case, the .br mbrtowc () function behaves as above, except that it does not store the converted wide character in memory. .pp a third case is when .i s is null. in this case, .ir pwc and .i n are ignored. if the conversion state represented by .i *ps denotes an incomplete multibyte character conversion, the .br mbrtowc () function returns .ir "(size_t)\ \-1" , sets .i errno to .br eilseq , and leaves .i *ps in an undefined state. otherwise, the .br mbrtowc () function puts .i *ps in the initial state and returns 0. .pp in all of the above cases, if .i ps is null, a static anonymous state known only to the .br mbrtowc () function is used instead. otherwise, .ir *ps must be a valid .i mbstate_t object. an .ir mbstate_t object .i a can be initialized to the initial state by zeroing it, for example using .pp .in +4n .ex memset(&a, 0, sizeof(a)); .ee .in .sh return value the .br mbrtowc () function returns the number of bytes parsed from the multibyte sequence starting at .ir s , if a non-l\(aq\e0\(aq wide character was recognized. it returns 0, if a l\(aq\e0\(aq wide character was recognized. it returns .i (size_t)\ \-1 and sets .i errno to .br eilseq , if an invalid multibyte sequence was encountered. it returns .i "(size_t)\ \-2" if it couldn't parse a complete multibyte character, meaning that .i n should be increased. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mbrtowc () t} thread safety mt-unsafe race:mbrtowc/!ps .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br mbrtowc () depends on the .b lc_ctype category of the current locale. .sh see also .br mbsinit (3), .br mbsrtowcs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/err.3 .so man3/slist.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt (michael@moria.de) .\" modified 1993-07-23 by rik faith (faith@cs.unc.edu) .\" modified 1994-08-21 by michael chastain (mec@shell.portal.com): .\" fixed necessary '#include' lines. .\" modified 1995-04-15 by michael chastain (mec@shell.portal.com): .\" added reference to adjtimex. .\" removed some nonsense lines pointed out by urs thuermann, .\" (urs@isnogud.escape.de), aeb, 950722. .\" modified 1997-01-14 by austin donnelly (and1000@debian.org): .\" added return values section, and bit on efault .\" added clarification on timezone, aeb, 971210. .\" removed "#include ", aeb, 010316. .\" modified, 2004-05-27 by michael kerrisk .\" added notes on capability requirement. .\" .th gettimeofday 2 2021-03-22 "linux" "linux programmer's manual" .sh name gettimeofday, settimeofday \- get / set time .sh synopsis .nf .b #include .pp .bi "int gettimeofday(struct timeval *restrict " tv , .bi " struct timezone *restrict " tz ); .bi "int settimeofday(const struct timeval *" tv , .bi " const struct timezone *" tz ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br settimeofday (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the functions .br gettimeofday () and .br settimeofday () can get and set the time as well as a timezone. .pp the .i tv argument is a .i struct timeval (as specified in .ir ): .pp .in +4n .ex struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ }; .ee .in .pp and gives the number of seconds and microseconds since the epoch (see .br time (2)). .pp the .i tz argument is a .ir "struct timezone" : .pp .in +4n .ex struct timezone { int tz_minuteswest; /* minutes west of greenwich */ int tz_dsttime; /* type of dst correction */ }; .ee .in .pp if either .i tv or .i tz is null, the corresponding structure is not set or returned. .\" fixme . the compilation warning looks to be going away in 2.17 .\" see glibc commit 4b7634a5e03b0da6f8875de9d3f74c1cf6f2a6e8 (however, compilation warnings will result if .i tv is null.) .\" the following is covered under eperm below: .\" .pp .\" only the superuser may use .\" .br settimeofday (). .pp the use of the .i timezone structure is obsolete; the .i tz argument should normally be specified as null. (see notes below.) .pp under linux, there are some peculiar "warp clock" semantics associated with the .br settimeofday () system call if on the very first call (after booting) that has a non-null .i tz argument, the .i tv argument is null and the .i tz_minuteswest field is nonzero. (the .i tz_dsttime field should be zero for this case.) in such a case it is assumed that the cmos clock is on local time, and that it has to be incremented by this amount to get utc system time. no doubt it is a bad idea to use this feature. .sh return value .br gettimeofday () and .br settimeofday () return 0 for success. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault one of .i tv or .i tz pointed outside the accessible address space. .tp .b einval .rb ( settimeofday ()): .i timezone is invalid. .tp .b einval .rb ( settimeofday ()): .i tv.tv_sec is negative or .i tv.tv_usec is outside the range [0..999,999]. .tp .br einval " (since linux 4.3)" .\" commit e1d7ba8735551ed79c7a0463a042353574b96da3 .rb ( settimeofday ()): an attempt was made to set the time to a value less than the current value of the .b clock_monotonic clock (see .br clock_gettime (2)). .tp .b eperm the calling process has insufficient privilege to call .br settimeofday (); under linux the .b cap_sys_time capability is required. .sh conforming to svr4, 4.3bsd. posix.1-2001 describes .br gettimeofday () but not .br settimeofday (). posix.1-2008 marks .br gettimeofday () as obsolete, recommending the use of .br clock_gettime (2) instead. .sh notes the time returned by .br gettimeofday () .i is affected by discontinuous jumps in the system time (e.g., if the system administrator manually changes the system time). if you need a monotonically increasing clock, see .br clock_gettime (2). .pp macros for operating on .i timeval structures are described in .br timeradd (3). .pp traditionally, the fields of .i struct timeval were of type .ir long . .\" .ss c library/kernel differences on some architectures, an implementation of .br gettimeofday () is provided in the .br vdso (7). .\" .ss the tz_dsttime field on a non-linux kernel, with glibc, the .i tz_dsttime field of .i struct timezone will be set to a nonzero value by .br gettimeofday () if the current timezone has ever had or will have a daylight saving rule applied. in this sense it exactly mirrors the meaning of .br daylight (3) for the current zone. on linux, with glibc, the setting of the .i tz_dsttime field of .i struct timezone has never been used by .br settimeofday () or .br gettimeofday (). .\" it has not .\" been and will not be supported by libc or glibc. .\" each and every occurrence of this field in the kernel source .\" (other than the declaration) is a bug. thus, the following is purely of historical interest. .pp on old systems, the field .i tz_dsttime contains a symbolic constant (values are given below) that indicates in which part of the year daylight saving time is in force. (note: this value is constant throughout the year: it does not indicate that dst is in force, it just selects an algorithm.) the daylight saving time algorithms defined are as follows: .pp .in +4n .ex \fbdst_none\fp /* not on dst */ \fbdst_usa\fp /* usa style dst */ \fbdst_aust\fp /* australian style dst */ \fbdst_wet\fp /* western european dst */ \fbdst_met\fp /* middle european dst */ \fbdst_eet\fp /* eastern european dst */ \fbdst_can\fp /* canada */ \fbdst_gb\fp /* great britain and eire */ \fbdst_rum\fp /* romania */ \fbdst_tur\fp /* turkey */ \fbdst_austalt\fp /* australian style with shift in 1986 */ .ee .in .pp of course it turned out that the period in which daylight saving time is in force cannot be given by a simple algorithm, one per country; indeed, this period is determined by unpredictable political decisions. so this method of representing timezones has been abandoned. .sh see also .br date (1), .br adjtimex (2), .br clock_gettime (2), .br time (2), .br ctime (3), .br ftime (3), .br timeradd (3), .br capabilities (7), .br time (7), .br vdso (7), .br hwclock (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getgid 2 2021-03-22 "linux" "linux programmer's manual" .sh name getgid, getegid \- get group identity .sh synopsis .nf .b #include .pp .b gid_t getgid(void); .b gid_t getegid(void); .fi .sh description .br getgid () returns the real group id of the calling process. .pp .br getegid () returns the effective group id of the calling process. .sh errors these functions are always successful and never modify .\" https://www.austingroupbugs.net/view.php?id=511 .\" 0000511: getuid and friends should not modify errno .ir errno . .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh notes the original linux .br getgid () and .br getegid () system calls supported only 16-bit group ids. subsequently, linux 2.4 added .br getgid32 () and .br getegid32 (), supporting 32-bit ids. the glibc .br getgid () and .br getegid () wrapper functions transparently deal with the variations across kernel versions. .pp on alpha, instead of a pair of .br getgid () and .br getegid () system calls, a single .br getxgid () system call is provided, which returns a pair of real and effective gids. the glibc .br getgid () and .br getegid () wrapper functions transparently deal with this. see .br syscall (2) for details regarding register mapping. .sh see also .br getresgid (2), .br setgid (2), .br setregid (2), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/argz_add.3 .so man2/rename.2 .so man3/isalpha.3 .so man3/getprotoent_r.3 .so man2/uname.2 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_getattr_np 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_getattr_np \- get attributes of created thread .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int pthread_getattr_np(pthread_t " thread ", pthread_attr_t *" attr ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_getattr_np () function initializes the thread attributes object referred to by .i attr so that it contains actual attribute values describing the running thread .ir thread . .pp the returned attribute values may differ from the corresponding attribute values passed in the .i attr object that was used to create the thread using .br pthread_create (3). in particular, the following attributes may differ: .ip * 2 the detach state, since a joinable thread may have detached itself after creation; .ip * the stack size, which the implementation may align to a suitable boundary. .ip * and the guard size, which the implementation may round upward to a multiple of the page size, or ignore (i.e., treat as 0), if the application is allocating its own stack. .pp furthermore, if the stack address attribute was not set in the thread attributes object used to create the thread, then the returned thread attributes object will report the actual stack address that the implementation selected for the thread. .pp when the thread attributes object returned by .br pthread_getattr_np () is no longer required, it should be destroyed using .br pthread_attr_destroy (3). .sh return value on success, this function returns 0; on error, it returns a nonzero error number. .sh errors .tp .b enomem .\" can happen (but unlikely) while trying to allocate memory for cpuset insufficient memory. .pp in addition, if .i thread refers to the main thread, then .br pthread_getattr_np () can fail because of errors from various underlying calls: .br fopen (3), if .ir /proc/self/maps can't be opened; and .br getrlimit (2), if the .br rlimit_stack resource limit is not supported. .sh versions this function is available in glibc since version 2.2.3. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_getattr_np () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a nonstandard gnu extension; hence the suffix "_np" (nonportable) in the name. .sh examples the program below demonstrates the use of .br pthread_getattr_np (). the program creates a thread that then uses .br pthread_getattr_np () to retrieve and display its guard size, stack address, and stack size attributes. command-line arguments can be used to set these attributes to values other than the default when creating the thread. the shell sessions below demonstrate the use of the program. .pp in the first run, on an x86-32 system, a thread is created using default attributes: .pp .in +4n .ex .rb "$" " ulimit \-s" " # no stack limit ==> default stack size is 2 mb" unlimited .rb "$" " ./a.out" attributes of created thread: guard size = 4096 bytes stack address = 0x40196000 (eos = 0x40397000) stack size = 0x201000 (2101248) bytes .ee .in .pp in the following run, we see that if a guard size is specified, it is rounded up to the next multiple of the system page size (4096 bytes on x86-32): .pp .in +4n .ex .rb "$" " ./a.out \-g 4097" thread attributes object after initializations: guard size = 4097 bytes stack address = (nil) stack size = 0x0 (0) bytes attributes of created thread: guard size = 8192 bytes stack address = 0x40196000 (eos = 0x40397000) stack size = 0x201000 (2101248) bytes .ee .in .\".in +4n .\".nf .\"$ ./a.out \-s 0x8000 .\"thread attributes object after initializations: .\" guard size = 4096 bytes .\" stack address = 0xffff8000 (eos = (nil)) .\" stack size = 0x8000 (32768) bytes .\" .\"attributes of created thread: .\" guard size = 4096 bytes .\" stack address = 0x4001e000 (eos = 0x40026000) .\" stack size = 0x8000 (32768) bytes .\".fi .\".in .pp in the last run, the program manually allocates a stack for the thread. in this case, the guard size attribute is ignored. .pp .in +4n .ex .rb "$" " ./a.out \-g 4096 \-s 0x8000 \-a" allocated thread stack at 0x804d000 thread attributes object after initializations: guard size = 4096 bytes stack address = 0x804d000 (eos = 0x8055000) stack size = 0x8000 (32768) bytes attributes of created thread: guard size = 0 bytes stack address = 0x804d000 (eos = 0x8055000) stack size = 0x8000 (32768) bytes .ee .in .ss program source \& .ex #define _gnu_source /* to get pthread_getattr_np() declaration */ #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static void display_stack_related_attributes(pthread_attr_t *attr, char *prefix) { int s; size_t stack_size, guard_size; void *stack_addr; s = pthread_attr_getguardsize(attr, &guard_size); if (s != 0) handle_error_en(s, "pthread_attr_getguardsize"); printf("%sguard size = %zu bytes\en", prefix, guard_size); s = pthread_attr_getstack(attr, &stack_addr, &stack_size); if (s != 0) handle_error_en(s, "pthread_attr_getstack"); printf("%sstack address = %p", prefix, stack_addr); if (stack_size > 0) printf(" (eos = %p)", (char *) stack_addr + stack_size); printf("\en"); printf("%sstack size = %#zx (%zu) bytes\en", prefix, stack_size, stack_size); } static void display_thread_attributes(pthread_t thread, char *prefix) { int s; pthread_attr_t attr; s = pthread_getattr_np(thread, &attr); if (s != 0) handle_error_en(s, "pthread_getattr_np"); display_stack_related_attributes(&attr, prefix); s = pthread_attr_destroy(&attr); if (s != 0) handle_error_en(s, "pthread_attr_destroy"); } static void * /* start function for thread we create */ thread_start(void *arg) { printf("attributes of created thread:\en"); display_thread_attributes(pthread_self(), "\et"); exit(exit_success); /* terminate all threads */ } static void usage(char *pname, char *msg) { if (msg != null) fputs(msg, stderr); fprintf(stderr, "usage: %s [\-s stack\-size [\-a]]" " [\-g guard\-size]\en", pname); fprintf(stderr, "\et\et\-a means program should allocate stack\en"); exit(exit_failure); } static pthread_attr_t * /* get thread attributes from command line */ get_thread_attributes_from_cl(int argc, char *argv[], pthread_attr_t *attrp) { int s, opt, allocate_stack; size_t stack_size, guard_size; void *stack_addr; pthread_attr_t *ret_attrp = null; /* set to attrp if we initialize a thread attributes object */ allocate_stack = 0; stack_size = \-1; guard_size = \-1; while ((opt = getopt(argc, argv, "ag:s:")) != \-1) { switch (opt) { case \(aqa\(aq: allocate_stack = 1; break; case \(aqg\(aq: guard_size = strtoul(optarg, null, 0); break; case \(aqs\(aq: stack_size = strtoul(optarg, null, 0); break; default: usage(argv[0], null); } } if (allocate_stack && stack_size == \-1) usage(argv[0], "specifying \-a without \-s makes no sense\en"); if (argc > optind) usage(argv[0], "extraneous command\-line arguments\en"); if (stack_size >= 0 || guard_size > 0) { ret_attrp = attrp; s = pthread_attr_init(attrp); if (s != 0) handle_error_en(s, "pthread_attr_init"); } if (stack_size >= 0) { if (!allocate_stack) { s = pthread_attr_setstacksize(attrp, stack_size); if (s != 0) handle_error_en(s, "pthread_attr_setstacksize"); } else { s = posix_memalign(&stack_addr, sysconf(_sc_pagesize), stack_size); if (s != 0) handle_error_en(s, "posix_memalign"); printf("allocated thread stack at %p\en\en", stack_addr); s = pthread_attr_setstack(attrp, stack_addr, stack_size); if (s != 0) handle_error_en(s, "pthread_attr_setstacksize"); } } if (guard_size >= 0) { s = pthread_attr_setguardsize(attrp, guard_size); if (s != 0) handle_error_en(s, "pthread_attr_setstacksize"); } return ret_attrp; } int main(int argc, char *argv[]) { int s; pthread_t thr; pthread_attr_t attr; pthread_attr_t *attrp = null; /* set to &attr if we initialize a thread attributes object */ attrp = get_thread_attributes_from_cl(argc, argv, &attr); if (attrp != null) { printf("thread attributes object after initializations:\en"); display_stack_related_attributes(attrp, "\et"); printf("\en"); } s = pthread_create(&thr, attrp, &thread_start, null); if (s != 0) handle_error_en(s, "pthread_create"); if (attrp != null) { s = pthread_attr_destroy(attrp); if (s != 0) handle_error_en(s, "pthread_attr_destroy"); } pause(); /* terminates when other thread calls exit() */ } .ee .sh see also .ad l .nh .br pthread_attr_getaffinity_np (3), .br pthread_attr_getdetachstate (3), .br pthread_attr_getguardsize (3), .br pthread_attr_getinheritsched (3), .br pthread_attr_getschedparam (3), .br pthread_attr_getschedpolicy (3), .br pthread_attr_getscope (3), .br pthread_attr_getstack (3), .br pthread_attr_getstackaddr (3), .br pthread_attr_getstacksize (3), .br pthread_attr_init (3), .br pthread_create (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/casin.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified 1993-03-29, david metcalfe .\" modified 1993-04-28, lars wirzenius .\" modified 1993-07-24, rik faith (faith@cs.unc.edu) .\" modified 1995-05-18, rik faith (faith@cs.unc.edu) to add .\" better discussion of problems with rand on other systems. .\" (thanks to esa hyyti{ (ehyytia@snakemail.hut.fi).) .\" modified 1998-04-10, nicolás lichtmaier .\" with contribution from francesco potorti .\" modified 2003-11-15, aeb, added rand_r .\" 2010-09-13, mtk, added example program .\" .th rand 3 2021-03-22 "" "linux programmer's manual" .sh name rand, rand_r, srand \- pseudo-random number generator .sh synopsis .nf .b #include .pp .b int rand(void); .bi "int rand_r(unsigned int *" seedp ); .bi "void srand(unsigned int " seed ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br rand_r (): .nf since glibc 2.24: _posix_c_source >= 199506l glibc 2.23 and earlier _posix_c_source .fi .sh description the .br rand () function returns a pseudo-random integer in the range 0 to .br rand_max inclusive (i.e., the mathematical range [0,\ \fbrand_max\fr]). .pp the .br srand () function sets its argument as the seed for a new sequence of pseudo-random integers to be returned by .br rand (). these sequences are repeatable by calling .br srand () with the same seed value. .pp if no seed value is provided, the .br rand () function is automatically seeded with a value of 1. .pp the function .br rand () is not reentrant, since it uses hidden state that is modified on each call. this might just be the seed value to be used by the next call, or it might be something more elaborate. in order to get reproducible behavior in a threaded application, this state must be made explicit; this can be done using the reentrant function .br rand_r (). .pp like .br rand (), .br rand_r () returns a pseudo-random integer in the range [0,\ \fbrand_max\fr]. the .i seedp argument is a pointer to an .ir "unsigned int" that is used to store state between calls. if .br rand_r () is called with the same initial value for the integer pointed to by .ir seedp , and that value is not modified between calls, then the same pseudo-random sequence will result. .pp the value pointed to by the .i seedp argument of .br rand_r () provides only a very small amount of state, so this function will be a weak pseudo-random generator. try .br drand48_r (3) instead. .sh return value the .br rand () and .br rand_r () functions return a value between 0 and .br rand_max (inclusive). the .br srand () function returns no value. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br rand (), .br rand_r (), .br srand () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the functions .br rand () and .br srand () conform to svr4, 4.3bsd, c89, c99, posix.1-2001. the function .br rand_r () is from posix.1-2001. posix.1-2008 marks .br rand_r () as obsolete. .sh notes the versions of .br rand () and .br srand () in the linux c library use the same random number generator as .br random (3) and .br srandom (3), so the lower-order bits should be as random as the higher-order bits. however, on older .br rand () implementations, and on current implementations on different systems, the lower-order bits are much less random than the higher-order bits. do not use this function in applications intended to be portable when good randomness is needed. (use .br random (3) instead.) .sh examples posix.1-2001 gives the following example of an implementation of .br rand () and .br srand (), possibly useful when one needs the same sequence on two different machines. .pp .in +4n .ex static unsigned long next = 1; /* rand_max assumed to be 32767 */ int myrand(void) { next = next * 1103515245 + 12345; return((unsigned)(next/65536) % 32768); } void mysrand(unsigned int seed) { next = seed; } .ee .in .pp the following program can be used to display the pseudo-random sequence produced by .br rand () when given a particular seed. .pp .in +4n .ex #include #include int main(int argc, char *argv[]) { int r, nloops; unsigned int seed; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } seed = atoi(argv[1]); nloops = atoi(argv[2]); srand(seed); for (int j = 0; j < nloops; j++) { r = rand(); printf("%d\en", r); } exit(exit_success); } .ee .in .sh see also .br drand48 (3), .br random (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tmpnam.3 .so man3/pthread_setschedparam.3 .so man3/getprotoent_r.3 .so man3/getopt.3 .so man3/inet_addr.3 .so man3/y0.3 .\" copyright (c) 2005 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthreads 7 2021-03-22 "linux" "linux programmer's manual" .sh name pthreads \- posix threads .sh description posix.1 specifies a set of interfaces (functions, header files) for threaded programming commonly known as posix threads, or pthreads. a single process can contain multiple threads, all of which are executing the same program. these threads share the same global memory (data and heap segments), but each thread has its own stack (automatic variables). .pp posix.1 also requires that threads share a range of other attributes (i.e., these attributes are process-wide rather than per-thread): .ip \- 3 process id .ip \- 3 parent process id .ip \- 3 process group id and session id .ip \- 3 controlling terminal .ip \- 3 user and group ids .ip \- 3 open file descriptors .ip \- 3 record locks (see .br fcntl (2)) .ip \- 3 signal dispositions .ip \- 3 file mode creation mask .rb ( umask (2)) .ip \- 3 current directory .rb ( chdir (2)) and root directory .rb ( chroot (2)) .ip \- 3 interval timers .rb ( setitimer (2)) and posix timers .rb ( timer_create (2)) .ip \- 3 nice value .rb ( setpriority (2)) .ip \- 3 resource limits .rb ( setrlimit (2)) .ip \- 3 measurements of the consumption of cpu time .rb ( times (2)) and resources .rb ( getrusage (2)) .pp as well as the stack, posix.1 specifies that various other attributes are distinct for each thread, including: .ip \- 3 thread id (the .i pthread_t data type) .ip \- 3 signal mask .rb ( pthread_sigmask (3)) .ip \- 3 the .i errno variable .ip \- 3 alternate signal stack .rb ( sigaltstack (2)) .ip \- 3 real-time scheduling policy and priority .rb ( sched (7)) .pp the following linux-specific features are also per-thread: .ip \- 3 capabilities (see .br capabilities (7)) .ip \- 3 cpu affinity .rb ( sched_setaffinity (2)) .ss pthreads function return values most pthreads functions return 0 on success, and an error number on failure. the error numbers that can be returned have the same meaning as the error numbers returned in .i errno by conventional system calls and c library functions. note that the pthreads functions do not set .ir errno . for each of the pthreads functions that can return an error, posix.1-2001 specifies that the function can never fail with the error .br eintr . .ss thread ids each of the threads in a process has a unique thread identifier (stored in the type .ir pthread_t ). this identifier is returned to the caller of .br pthread_create (3), and a thread can obtain its own thread identifier using .br pthread_self (3). .pp thread ids are guaranteed to be unique only within a process. (in all pthreads functions that accept a thread id as an argument, that id by definition refers to a thread in the same process as the caller.) .pp the system may reuse a thread id after a terminated thread has been joined, or a detached thread has terminated. posix says: "if an application attempts to use a thread id whose lifetime has ended, the behavior is undefined." .ss thread-safe functions a thread-safe function is one that can be safely (i.e., it will deliver the same results regardless of whether it is) called from multiple threads at the same time. .pp posix.1-2001 and posix.1-2008 require that all functions specified in the standard shall be thread-safe, except for the following functions: .pp .in +4n .ex asctime() basename() catgets() crypt() ctermid() if passed a non-null argument ctime() dbm_clearerr() dbm_close() dbm_delete() dbm_error() dbm_fetch() dbm_firstkey() dbm_nextkey() dbm_open() dbm_store() dirname() dlerror() drand48() ecvt() [posix.1-2001 only (function removed in posix.1-2008)] encrypt() endgrent() endpwent() endutxent() fcvt() [posix.1-2001 only (function removed in posix.1-2008)] ftw() gcvt() [posix.1-2001 only (function removed in posix.1-2008)] getc_unlocked() getchar_unlocked() getdate() getenv() getgrent() getgrgid() getgrnam() gethostbyaddr() [posix.1-2001 only (function removed in posix.1-2008)] gethostbyname() [posix.1-2001 only (function removed in posix.1-2008)] gethostent() getlogin() getnetbyaddr() getnetbyname() getnetent() getopt() getprotobyname() getprotobynumber() getprotoent() getpwent() getpwnam() getpwuid() getservbyname() getservbyport() getservent() getutxent() getutxid() getutxline() gmtime() hcreate() hdestroy() hsearch() inet_ntoa() l64a() lgamma() lgammaf() lgammal() localeconv() localtime() lrand48() mrand48() nftw() nl_langinfo() ptsname() putc_unlocked() putchar_unlocked() putenv() pututxline() rand() readdir() setenv() setgrent() setkey() setpwent() setutxent() strerror() strsignal() [added in posix.1-2008] strtok() system() [added in posix.1-2008] tmpnam() if passed a non-null argument ttyname() unsetenv() wcrtomb() if its final argument is null wcsrtombs() if its final argument is null wcstombs() wctomb() .ee .in .ss async-cancel-safe functions an async-cancel-safe function is one that can be safely called in an application where asynchronous cancelability is enabled (see .br pthread_setcancelstate (3)). .pp only the following functions are required to be async-cancel-safe by posix.1-2001 and posix.1-2008: .pp .in +4n .ex pthread_cancel() pthread_setcancelstate() pthread_setcanceltype() .ee .in .ss cancellation points posix.1 specifies that certain functions must, and certain other functions may, be cancellation points. if a thread is cancelable, its cancelability type is deferred, and a cancellation request is pending for the thread, then the thread is canceled when it calls a function that is a cancellation point. .pp the following functions are required to be cancellation points by posix.1-2001 and/or posix.1-2008: .pp .\" fixme .\" document the list of all functions that are cancellation points in glibc .in +4n .ex accept() aio_suspend() clock_nanosleep() close() connect() creat() fcntl() f_setlkw fdatasync() fsync() getmsg() getpmsg() lockf() f_lock mq_receive() mq_send() mq_timedreceive() mq_timedsend() msgrcv() msgsnd() msync() nanosleep() open() openat() [added in posix.1-2008] pause() poll() pread() pselect() pthread_cond_timedwait() pthread_cond_wait() pthread_join() pthread_testcancel() putmsg() putpmsg() pwrite() read() readv() recv() recvfrom() recvmsg() select() sem_timedwait() sem_wait() send() sendmsg() sendto() sigpause() [posix.1-2001 only (moves to "may" list in posix.1-2008)] sigsuspend() sigtimedwait() sigwait() sigwaitinfo() sleep() system() tcdrain() usleep() [posix.1-2001 only (function removed in posix.1-2008)] wait() waitid() waitpid() write() writev() .ee .in .pp the following functions may be cancellation points according to posix.1-2001 and/or posix.1-2008: .pp .in +4n .ex access() asctime() asctime_r() catclose() catgets() catopen() chmod() [added in posix.1-2008] chown() [added in posix.1-2008] closedir() closelog() ctermid() ctime() ctime_r() dbm_close() dbm_delete() dbm_fetch() dbm_nextkey() dbm_open() dbm_store() dlclose() dlopen() dprintf() [added in posix.1-2008] endgrent() endhostent() endnetent() endprotoent() endpwent() endservent() endutxent() faccessat() [added in posix.1-2008] fchmod() [added in posix.1-2008] fchmodat() [added in posix.1-2008] fchown() [added in posix.1-2008] fchownat() [added in posix.1-2008] fclose() fcntl() (for any value of cmd argument) fflush() fgetc() fgetpos() fgets() fgetwc() fgetws() fmtmsg() fopen() fpathconf() fprintf() fputc() fputs() fputwc() fputws() fread() freopen() fscanf() fseek() fseeko() fsetpos() fstat() fstatat() [added in posix.1-2008] ftell() ftello() ftw() futimens() [added in posix.1-2008] fwprintf() fwrite() fwscanf() getaddrinfo() getc() getc_unlocked() getchar() getchar_unlocked() getcwd() getdate() getdelim() [added in posix.1-2008] getgrent() getgrgid() getgrgid_r() getgrnam() getgrnam_r() gethostbyaddr() [posix.1-2001 only (function removed in posix.1-2008)] gethostbyname() [posix.1-2001 only (function removed in posix.1-2008)] gethostent() gethostid() gethostname() getline() [added in posix.1-2008] getlogin() getlogin_r() getnameinfo() getnetbyaddr() getnetbyname() getnetent() getopt() (if opterr is nonzero) getprotobyname() getprotobynumber() getprotoent() getpwent() getpwnam() getpwnam_r() getpwuid() getpwuid_r() gets() getservbyname() getservbyport() getservent() getutxent() getutxid() getutxline() getwc() getwchar() getwd() [posix.1-2001 only (function removed in posix.1-2008)] glob() iconv_close() iconv_open() ioctl() link() linkat() [added in posix.1-2008] lio_listio() [added in posix.1-2008] localtime() localtime_r() lockf() [added in posix.1-2008] lseek() lstat() mkdir() [added in posix.1-2008] mkdirat() [added in posix.1-2008] mkdtemp() [added in posix.1-2008] mkfifo() [added in posix.1-2008] mkfifoat() [added in posix.1-2008] mknod() [added in posix.1-2008] mknodat() [added in posix.1-2008] mkstemp() mktime() nftw() opendir() openlog() pathconf() pclose() perror() popen() posix_fadvise() posix_fallocate() posix_madvise() posix_openpt() posix_spawn() posix_spawnp() posix_trace_clear() posix_trace_close() posix_trace_create() posix_trace_create_withlog() posix_trace_eventtypelist_getnext_id() posix_trace_eventtypelist_rewind() posix_trace_flush() posix_trace_get_attr() posix_trace_get_filter() posix_trace_get_status() posix_trace_getnext_event() posix_trace_open() posix_trace_rewind() posix_trace_set_filter() posix_trace_shutdown() posix_trace_timedgetnext_event() posix_typed_mem_open() printf() psiginfo() [added in posix.1-2008] psignal() [added in posix.1-2008] pthread_rwlock_rdlock() pthread_rwlock_timedrdlock() pthread_rwlock_timedwrlock() pthread_rwlock_wrlock() putc() putc_unlocked() putchar() putchar_unlocked() puts() pututxline() putwc() putwchar() readdir() readdir_r() readlink() [added in posix.1-2008] readlinkat() [added in posix.1-2008] remove() rename() renameat() [added in posix.1-2008] rewind() rewinddir() scandir() [added in posix.1-2008] scanf() seekdir() semop() setgrent() sethostent() setnetent() setprotoent() setpwent() setservent() setutxent() sigpause() [added in posix.1-2008] stat() strerror() strerror_r() strftime() symlink() symlinkat() [added in posix.1-2008] sync() syslog() tmpfile() tmpnam() ttyname() ttyname_r() tzset() ungetc() ungetwc() unlink() unlinkat() [added in posix.1-2008] utime() [added in posix.1-2008] utimensat() [added in posix.1-2008] utimes() [added in posix.1-2008] vdprintf() [added in posix.1-2008] vfprintf() vfwprintf() vprintf() vwprintf() wcsftime() wordexp() wprintf() wscanf() .ee .in .pp an implementation may also mark other functions not specified in the standard as cancellation points. in particular, an implementation is likely to mark any nonstandard function that may block as a cancellation point. (this includes most functions that can touch files.) .pp it should be noted that even if an application is not using asynchronous cancellation, that calling a function from the above list from an asynchronous signal handler may cause the equivalent of asynchronous cancellation. the underlying user code may not expect asynchronous cancellation and the state of the user data may become inconsistent. therefore signals should be used with caution when entering a region of deferred cancellation. .\" so, scanning "cancellation point" comments in the glibc 2.8 header .\" files, it looks as though at least the following nonstandard .\" functions are cancellation points: .\" endnetgrent .\" endspent .\" epoll_pwait .\" epoll_wait .\" fcloseall .\" fdopendir .\" fflush_unlocked .\" fgetc_unlocked .\" fgetgrent .\" fgetgrent_r .\" fgetpwent .\" fgetpwent_r .\" fgets_unlocked .\" fgetspent .\" fgetspent_r .\" fgetwc_unlocked .\" fgetws_unlocked .\" fputc_unlocked .\" fputs_unlocked .\" fputwc_unlocked .\" fputws_unlocked .\" fread_unlocked .\" fwrite_unlocked .\" gai_suspend .\" getaddrinfo_a .\" getdate_r .\" getgrent_r .\" getgrouplist .\" gethostbyaddr_r .\" gethostbyname2 .\" gethostbyname2_r .\" gethostbyname_r .\" gethostent_r .\" getnetbyaddr_r .\" getnetbyname_r .\" getnetent_r .\" getnetgrent .\" getnetgrent_r .\" getprotobyname_r .\" getprotobynumber_r .\" getprotoent_r .\" getpw .\" getpwent_r .\" getservbyname_r .\" getservbyport_r .\" getservent_r .\" getspent .\" getspent_r .\" getspnam .\" getspnam_r .\" getutmp .\" getutmpx .\" getw .\" getwc_unlocked .\" getwchar_unlocked .\" initgroups .\" innetgr .\" mkostemp .\" mkostemp64 .\" mkstemp64 .\" ppoll .\" pthread_timedjoin_np .\" putgrent .\" putpwent .\" putspent .\" putw .\" putwc_unlocked .\" putwchar_unlocked .\" rcmd .\" rcmd_af .\" rexec .\" rexec_af .\" rresvport .\" rresvport_af .\" ruserok .\" ruserok_af .\" setnetgrent .\" setspent .\" sgetspent .\" sgetspent_r .\" updwtmpx .\" utmpxname .\" vfscanf .\" vfwscanf .\" vscanf .\" vsyslog .\" vwscanf .ss compiling on linux on linux, programs that use the pthreads api should be compiled using .ir "cc \-pthread" . .ss linux implementations of posix threads over time, two threading implementations have been provided by the gnu c library on linux: .tp .b linuxthreads this is the original pthreads implementation. since glibc 2.4, this implementation is no longer supported. .tp .br nptl " (native posix threads library)" this is the modern pthreads implementation. by comparison with linuxthreads, nptl provides closer conformance to the requirements of the posix.1 specification and better performance when creating large numbers of threads. nptl is available since glibc 2.3.2, and requires features that are present in the linux 2.6 kernel. .pp both of these are so-called 1:1 implementations, meaning that each thread maps to a kernel scheduling entity. both threading implementations employ the linux .br clone (2) system call. in nptl, thread synchronization primitives (mutexes, thread joining, and so on) are implemented using the linux .br futex (2) system call. .ss linuxthreads the notable features of this implementation are the following: .ip \- 3 in addition to the main (initial) thread, and the threads that the program creates using .br pthread_create (3), the implementation creates a "manager" thread. this thread handles thread creation and termination. (problems can result if this thread is inadvertently killed.) .ip \- 3 signals are used internally by the implementation. on linux 2.2 and later, the first three real-time signals are used (see also .br signal (7)). on older linux kernels, .b sigusr1 and .b sigusr2 are used. applications must avoid the use of whichever set of signals is employed by the implementation. .ip \- 3 threads do not share process ids. (in effect, linuxthreads threads are implemented as processes which share more information than usual, but which do not share a common process id.) linuxthreads threads (including the manager thread) are visible as separate processes using .br ps (1). .pp the linuxthreads implementation deviates from the posix.1 specification in a number of ways, including the following: .ip \- 3 calls to .br getpid (2) return a different value in each thread. .ip \- 3 calls to .br getppid (2) in threads other than the main thread return the process id of the manager thread; instead .br getppid (2) in these threads should return the same value as .br getppid (2) in the main thread. .ip \- 3 when one thread creates a new child process using .br fork (2), any thread should be able to .br wait (2) on the child. however, the implementation allows only the thread that created the child to .br wait (2) on it. .ip \- 3 when a thread calls .br execve (2), all other threads are terminated (as required by posix.1). however, the resulting process has the same pid as the thread that called .br execve (2): it should have the same pid as the main thread. .ip \- 3 threads do not share user and group ids. this can cause complications with set-user-id programs and can cause failures in pthreads functions if an application changes its credentials using .br seteuid (2) or similar. .ip \- 3 threads do not share a common session id and process group id. .ip \- 3 threads do not share record locks created using .br fcntl (2). .ip \- 3 the information returned by .br times (2) and .br getrusage (2) is per-thread rather than process-wide. .ip \- 3 threads do not share semaphore undo values (see .br semop (2)). .ip \- 3 threads do not share interval timers. .ip \- 3 threads do not share a common nice value. .ip \- 3 posix.1 distinguishes the notions of signals that are directed to the process as a whole and signals that are directed to individual threads. according to posix.1, a process-directed signal (sent using .br kill (2), for example) should be handled by a single, arbitrarily selected thread within the process. linuxthreads does not support the notion of process-directed signals: signals may be sent only to specific threads. .ip \- 3 threads have distinct alternate signal stack settings. however, a new thread's alternate signal stack settings are copied from the thread that created it, so that the threads initially share an alternate signal stack. (a new thread should start with no alternate signal stack defined. if two threads handle signals on their shared alternate signal stack at the same time, unpredictable program failures are likely to occur.) .ss nptl with nptl, all of the threads in a process are placed in the same thread group; all members of a thread group share the same pid. nptl does not employ a manager thread. .pp nptl makes internal use of the first two real-time signals; these signals cannot be used in applications. see .br nptl (7) for further details. .pp nptl still has at least one nonconformance with posix.1: .ip \- 3 threads do not share a common nice value. .\" fixme . bug report filed for nptl nice nonconformance .\" http://bugzilla.kernel.org/show_bug.cgi?id=6258 .\" sep 08: there is a patch by denys vlasenko to address this .\" "make setpriority posix compliant; introduce prio_thread extension" .\" monitor this to see if it makes it into mainline. .pp some nptl nonconformances occur only with older kernels: .ip \- 3 the information returned by .br times (2) and .br getrusage (2) is per-thread rather than process-wide (fixed in kernel 2.6.9). .ip \- 3 threads do not share resource limits (fixed in kernel 2.6.10). .ip \- 3 threads do not share interval timers (fixed in kernel 2.6.12). .ip \- 3 only the main thread is permitted to start a new session using .br setsid (2) (fixed in kernel 2.6.16). .ip \- 3 only the main thread is permitted to make the process into a process group leader using .br setpgid (2) (fixed in kernel 2.6.16). .ip \- 3 threads have distinct alternate signal stack settings. however, a new thread's alternate signal stack settings are copied from the thread that created it, so that the threads initially share an alternate signal stack (fixed in kernel 2.6.16). .pp note the following further points about the nptl implementation: .ip \- 3 if the stack size soft resource limit (see the description of .b rlimit_stack in .br setrlimit (2)) is set to a value other than .ir unlimited , then this value defines the default stack size for new threads. to be effective, this limit must be set before the program is executed, perhaps using the .i ulimit \-s shell built-in command .ri ( "limit stacksize" in the c shell). .ss determining the threading implementation since glibc 2.3.2, the .br getconf (1) command can be used to determine the system's threading implementation, for example: .pp .in +4n .ex bash$ getconf gnu_libpthread_version nptl 2.3.4 .ee .in .pp with older glibc versions, a command such as the following should be sufficient to determine the default threading implementation: .pp .in +4n .ex bash$ $( ldd /bin/ls | grep libc.so | awk \(aq{print $3}\(aq ) | \e egrep \-i \(aqthreads|nptl\(aq native posix threads library by ulrich drepper et al .ee .in .ss selecting the threading implementation: ld_assume_kernel on systems with a glibc that supports both linuxthreads and nptl (i.e., glibc 2.3.\fix\fp), the .b ld_assume_kernel environment variable can be used to override the dynamic linker's default choice of threading implementation. this variable tells the dynamic linker to assume that it is running on top of a particular kernel version. by specifying a kernel version that does not provide the support required by nptl, we can force the use of linuxthreads. (the most likely reason for doing this is to run a (broken) application that depends on some nonconformant behavior in linuxthreads.) for example: .pp .in +4n .ex bash$ $( ld_assume_kernel=2.2.5 ldd /bin/ls | grep libc.so | \e awk \(aq{print $3}\(aq ) | egrep \-i \(aqthreads|nptl\(aq linuxthreads\-0.10 by xavier leroy .ee .in .sh see also .ad l .nh .br clone (2), .br fork (2), .br futex (2), .br gettid (2), .br proc (5), .br attributes (7), .br futex (7), .br nptl (7), .br sigevent (7), .br signal (7) .pp various pthreads manual pages, for example: .br pthread_atfork (3), .br pthread_attr_init (3), .br pthread_cancel (3), .br pthread_cleanup_push (3), .br pthread_cond_signal (3), .br pthread_cond_wait (3), .br pthread_create (3), .br pthread_detach (3), .br pthread_equal (3), .br pthread_exit (3), .br pthread_key_create (3), .br pthread_kill (3), .br pthread_mutex_lock (3), .br pthread_mutex_unlock (3), .br pthread_mutexattr_destroy (3), .br pthread_mutexattr_init (3), .br pthread_once (3), .br pthread_spin_init (3), .br pthread_spin_lock (3), .br pthread_rwlockattr_setkind_np (3), .br pthread_setcancelstate (3), .br pthread_setcanceltype (3), .br pthread_setspecific (3), .br pthread_sigmask (3), .br pthread_sigqueue (3), and .br pthread_testcancel (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mq_notify 3 2021-03-22 "linux" "linux programmer's manual" .sh name mq_notify \- register for notification when a message is available .sh synopsis .nf .b #include .pp .bi "int mq_notify(mqd_t " mqdes ", const struct sigevent *" sevp ); .fi .pp link with \fi\-lrt\fp. .sh description .br mq_notify () allows the calling process to register or unregister for delivery of an asynchronous notification when a new message arrives on the empty message queue referred to by the message queue descriptor .ir mqdes . .pp the .i sevp argument is a pointer to a .i sigevent structure. for the definition and general details of this structure, see .br sigevent (7). .pp if .i sevp is a non-null pointer, then .br mq_notify () registers the calling process to receive message notification. the .i sigev_notify field of the .i sigevent structure to which .i sevp points specifies how notification is to be performed. this field has one of the following values: .tp .b sigev_none a "null" notification: the calling process is registered as the target for notification, but when a message arrives, no notification is sent. .\" when is sigev_none useful? .tp .b sigev_signal notify the process by sending the signal specified in .ir sigev_signo . see .br sigevent (7) for general details. the .i si_code field of the .i siginfo_t structure will be set to .br si_mesgq . in addition, .\" i don't know of other implementations that set .\" si_pid and si_uid -- mtk .i si_pid will be set to the pid of the process that sent the message, and .i si_uid will be set to the real user id of the sending process. .tp .b sigev_thread upon message delivery, invoke .i sigev_notify_function as if it were the start function of a new thread. see .br sigevent (7) for details. .pp only one process can be registered to receive notification from a message queue. .pp if .i sevp is null, and the calling process is currently registered to receive notifications for this message queue, then the registration is removed; another process can then register to receive a message notification for this queue. .pp message notification occurs only when a new message arrives and the queue was previously empty. if the queue was not empty at the time .br mq_notify () was called, then a notification will occur only after the queue is emptied and a new message arrives. .pp if another process or thread is waiting to read a message from an empty queue using .br mq_receive (3), then any message notification registration is ignored: the message is delivered to the process or thread calling .br mq_receive (3), and the message notification registration remains in effect. .pp notification occurs once: after a notification is delivered, the notification registration is removed, and another process can register for message notification. if the notified process wishes to receive the next notification, it can use .br mq_notify () to request a further notification. this should be done before emptying all unread messages from the queue. (placing the queue in nonblocking mode is useful for emptying the queue of messages without blocking once it is empty.) .sh return value on success .br mq_notify () returns 0; on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b ebadf the message queue descriptor specified in .i mqdes is invalid. .tp .b ebusy another process has already registered to receive notification for this message queue. .tp .b einval .i sevp\->sigev_notify is not one of the permitted values; or .i sevp\->sigev_notify is .b sigev_signal and .i sevp\->sigev_signo is not a valid signal number. .tp .b enomem insufficient memory. .pp posix.1-2008 says that an implementation .i may generate an .b einval .\" linux does not do this error if .i sevp is null, and the caller is not currently registered to receive notifications for the queue .ir mqdes . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mq_notify () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001. .sh notes .\" .ss c library/kernel differences in the glibc implementation, the .br mq_notify () library function is implemented on top of the system call of the same name. when .i sevp is null, or specifies a notification mechanism other than .br sigev_thread , the library function directly invokes the system call. for .br sigev_thread , much of the implementation resides within the library, rather than the kernel. (this is necessarily so, since the thread involved in handling the notification is one that must be managed by the c library posix threads implementation.) the implementation involves the use of a raw .br netlink (7) socket and creates a new thread for each notification that is delivered to the process. .sh examples the following program registers a notification request for the message queue named in its command-line argument. notification is performed by creating a thread. the thread executes a function which reads one message from the queue and then terminates the process. .ss program source .ex #include #include #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) static void /* thread start function */ tfunc(union sigval sv) { struct mq_attr attr; ssize_t nr; void *buf; mqd_t mqdes = *((mqd_t *) sv.sival_ptr); /* determine max. msg size; allocate buffer to receive msg */ if (mq_getattr(mqdes, &attr) == \-1) handle_error("mq_getattr"); buf = malloc(attr.mq_msgsize); if (buf == null) handle_error("malloc"); nr = mq_receive(mqdes, buf, attr.mq_msgsize, null); if (nr == \-1) handle_error("mq_receive"); printf("read %zd bytes from mq\en", nr); free(buf); exit(exit_success); /* terminate the process */ } int main(int argc, char *argv[]) { mqd_t mqdes; struct sigevent sev; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } mqdes = mq_open(argv[1], o_rdonly); if (mqdes == (mqd_t) \-1) handle_error("mq_open"); sev.sigev_notify = sigev_thread; sev.sigev_notify_function = tfunc; sev.sigev_notify_attributes = null; sev.sigev_value.sival_ptr = &mqdes; /* arg. to thread func. */ if (mq_notify(mqdes, &sev) == \-1) handle_error("mq_notify"); pause(); /* process will be terminated by thread function */ } .ee .sh see also .br mq_close (3), .br mq_getattr (3), .br mq_open (3), .br mq_receive (3), .br mq_send (3), .br mq_unlink (3), .br mq_overview (7), .br sigevent (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/log2.3 .\" extended attributes manual page .\" .\" copyright (c) 2000, 2002, 2007 andreas gruenbacher .\" copyright (c) 2001, 2002, 2004, 2007 silicon graphics, inc. .\" all rights reserved. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual. if not, see .\" . .\" %%%license_end .\" .th xattr 7 2020-06-09 "linux" "linux programmer's manual" .sh name xattr \- extended attributes .sh description extended attributes are name:value pairs associated permanently with files and directories, similar to the environment strings associated with a process. an attribute may be defined or undefined. if it is defined, its value may be empty or non-empty. .pp extended attributes are extensions to the normal attributes which are associated with all inodes in the system (i.e., the .br stat (2) data). they are often used to provide additional functionality to a filesystem\(emfor example, additional security features such as access control lists (acls) may be implemented using extended attributes. .pp users with search access to a file or directory may use .br listxattr (2) to retrieve a list of attribute names defined for that file or directory. .pp extended attributes are accessed as atomic objects. reading .rb ( getxattr (2)) retrieves the whole value of an attribute and stores it in a buffer. writing .rb ( setxattr (2)) replaces any previous value with the new value. .pp space consumed for extended attributes may be counted towards the disk quotas of the file owner and file group. .ss extended attribute namespaces attribute names are null-terminated strings. the attribute name is always specified in the fully qualified .ir namespace.attribute form, for example, .ir user.mime_type , .ir trusted.md5sum , .ir system.posix_acl_access , or .ir security.selinux . .pp the namespace mechanism is used to define different classes of extended attributes. these different classes exist for several reasons; for example, the permissions and capabilities required for manipulating extended attributes of one namespace may differ to another. .pp currently, the .ir security , .ir system , .ir trusted , and .ir user extended attribute classes are defined as described below. additional classes may be added in the future. .ss extended security attributes the security attribute namespace is used by kernel security modules, such as security enhanced linux, and also to implement file capabilities (see .br capabilities (7)). read and write access permissions to security attributes depend on the policy implemented for each security attribute by the security module. when no security module is loaded, all processes have read access to extended security attributes, and write access is limited to processes that have the .b cap_sys_admin capability. .ss system extended attributes system extended attributes are used by the kernel to store system objects such as access control lists. read and write access permissions to system attributes depend on the policy implemented for each system attribute implemented by filesystems in the kernel. .ss trusted extended attributes trusted extended attributes are visible and accessible only to processes that have the .b cap_sys_admin capability. attributes in this class are used to implement mechanisms in user space (i.e., outside the kernel) which keep information in extended attributes to which ordinary processes should not have access. .ss user extended attributes user extended attributes may be assigned to files and directories for storing arbitrary additional information such as the mime type, character set or encoding of a file. the access permissions for user attributes are defined by the file permission bits: read permission is required to retrieve the attribute value, and writer permission is required to change it. .pp the file permission bits of regular files and directories are interpreted differently from the file permission bits of special files and symbolic links. for regular files and directories the file permission bits define access to the file's contents, while for device special files they define access to the device described by the special file. the file permissions of symbolic links are not used in access checks. these differences would allow users to consume filesystem resources in a way not controllable by disk quotas for group or world writable special files and directories. .pp for this reason, user extended attributes are allowed only for regular files and directories, and access to user extended attributes is restricted to the owner and to users with appropriate capabilities for directories with the sticky bit set (see the .br chmod (1) manual page for an explanation of the sticky bit). .ss filesystem differences the kernel and the filesystem may place limits on the maximum number and size of extended attributes that can be associated with a file. the vfs imposes limitations that an attribute names is limited to 255 bytes and an attribute value is limited to 64\ kb. the list of attribute names that can be returned is also limited to 64\ kb (see bugs in .br listxattr (2)). .pp some filesystems, such as reiserfs (and, historically, ext2 and ext3), require the filesystem to be mounted with the .b user_xattr mount option in order for user extended attributes to be used. .pp in the current ext2, ext3, and ext4 filesystem implementations, the total bytes used by the names and values of all of a file's extended attributes must fit in a single filesystem block (1024, 2048 or 4096 bytes, depending on the block size specified when the filesystem was created). .pp in the btrfs, xfs, and reiserfs filesystem implementations, there is no practical limit on the number of extended attributes associated with a file, and the algorithms used to store extended attribute information on disk are scalable. .pp in the jfs, xfs, and reiserfs filesystem implementations, the limit on bytes used in an ea value is the ceiling imposed by the vfs. .pp in the btrfs filesystem implementation, the total bytes used for the name, value, and implementation overhead bytes is limited to the filesystem .i nodesize value (16\ kb by default). .sh conforming to extended attributes are not specified in posix.1, but some other systems (e.g., the bsds and solaris) provide a similar feature. .sh notes since the filesystems on which extended attributes are stored might also be used on architectures with a different byte order and machine word size, care should be taken to store attribute values in an architecture-independent format. .pp this page was formerly named .br attr (5). .\" .sh authors .\" andreas gruenbacher, .\" .ri < a.gruenbacher@bestbits.at > .\" and the sgi xfs development team, .\" .ri < linux-xfs@oss.sgi.com >. .sh see also .br attr (1), .br getfattr (1), .br setfattr (1), .br getxattr (2), .br ioctl_iflags (2), .br listxattr (2), .br removexattr (2), .br setxattr (2), .br acl (5), .br capabilities (7), .br selinux (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 17:28:34 1993 by rik faith .\" modified sun jun 01 17:16:34 1997 by jochen hein .\" .\" modified thu apr 25 00:43:19 2002 by bruno haible .\" .th locale 7 2021-03-22 "linux" "linux programmer's manual" .sh name locale \- description of multilanguage support .sh synopsis .nf .b #include .fi .sh description a locale is a set of language and cultural rules. these cover aspects such as language for messages, different character sets, lexicographic conventions, and so on. a program needs to be able to determine its locale and act accordingly to be portable to different cultures. .pp the header .i declares data types, functions, and macros which are useful in this task. .pp the functions it declares are .br setlocale (3) to set the current locale, and .br localeconv (3) to get information about number formatting. .pp there are different categories for locale information a program might need; they are declared as macros. using them as the first argument to the .br setlocale (3) function, it is possible to set one of these to the desired locale: .tp .br lc_address " (gnu extension, since glibc 2.2)" .\" see iso/iec technical report 14652 change settings that describe the formats (e.g., postal addresses) used to describe locations and geography-related items. applications that need this information can use .br nl_langinfo (3) to retrieve nonstandard elements, such as .b _nl_address_country_name (country name, in the language of the locale) and .b _nl_address_lang_name (language name, in the language of the locale), which return strings such as "deutschland" and "deutsch" (for german-language locales). (other element names are listed in .ir .) .tp .b lc_collate this category governs the collation rules used for sorting and regular expressions, including character equivalence classes and multicharacter collating elements. this locale category changes the behavior of the functions .br strcoll (3) and .br strxfrm (3), which are used to compare strings in the local alphabet. for example, the german sharp s is sorted as "ss". .tp .b lc_ctype this category determines the interpretation of byte sequences as characters (e.g., single versus multibyte characters), character classifications (e.g., alphabetic or digit), and the behavior of character classes. on glibc systems, this category also determines the character transliteration rules for .br iconv (1) and .br iconv (3). it changes the behavior of the character handling and classification functions, such as .br isupper (3) and .br toupper (3), and the multibyte character functions such as .br mblen (3) or .br wctomb (3). .tp .br lc_identification " (gnu extension, since glibc 2.2)" .\" see iso/iec technical report 14652 change settings that relate to the metadata for the locale. applications that need this information can use .br nl_langinfo (3) to retrieve nonstandard elements, such as .b _nl_identification_title (title of this locale document) and .b _nl_identification_territory (geographical territory to which this locale document applies), which might return strings such as "english locale for the usa" and "usa". (other element names are listed in .ir .) .tp .b lc_monetary this category determines the formatting used for monetary-related numeric values. this changes the information returned by .br localeconv (3), which describes the way numbers are usually printed, with details such as decimal point versus decimal comma. this information is internally used by the function .br strfmon (3). .tp .b lc_messages this category affects the language in which messages are displayed and what an affirmative or negative answer looks like. the gnu c library contains the .br gettext (3), .br ngettext (3), and .br rpmatch (3) functions to ease the use of this information. the gnu gettext family of functions also obey the environment variable .br language (containing a colon-separated list of locales) if the category is set to a valid locale other than .br """c""" . this category also affects the behavior of .br catopen (3). .tp .br lc_measurement " (gnu extension, since glibc 2.2)" change the settings relating to the measurement system in the locale (i.e., metric versus us customary units). applications can use .br nl_langinfo (3) to retrieve the nonstandard .b _nl_measurement_measurement element, which returns a pointer to a character that has the value 1 (metric) or 2 (us customary units). .tp .br lc_name " (gnu extension, since glibc 2.2)" .\" see iso/iec technical report 14652 change settings that describe the formats used to address persons. applications that need this information can use .br nl_langinfo (3) to retrieve nonstandard elements, such as .b _nl_name_name_mr (general salutation for men) and .b _nl_name_name_ms (general salutation for women) elements, which return strings such as "herr" and "frau" (for german-language locales). (other element names are listed in .ir .) .tp .b lc_numeric this category determines the formatting rules used for nonmonetary numeric values\(emfor example, the thousands separator and the radix character (a period in most english-speaking countries, but a comma in many other regions). it affects functions such as .br printf (3), .br scanf (3), and .br strtod (3). this information can also be read with the .br localeconv (3) function. .tp .br lc_paper " (gnu extension, since glibc 2.2)" .\" see iso/iec technical report 14652 change the settings relating to the dimensions of the standard paper size (e.g., us letter versus a4). applications that need the dimensions can obtain them by using .br nl_langinfo (3) to retrieve the nonstandard .b _nl_paper_width and .b _nl_paper_height elements, which return .i int values specifying the dimensions in millimeters. .tp .br lc_telephone " (gnu extension, since glibc 2.2)" .\" see iso/iec technical report 14652 change settings that describe the formats to be used with telephone services. applications that need this information can use .br nl_langinfo (3) to retrieve nonstandard elements, such as .b _nl_telephone_int_prefix (international prefix used to call numbers in this locale), which returns a string such as "49" (for germany). (other element names are listed in .ir .) .tp .b lc_time this category governs the formatting used for date and time values. for example, most of europe uses a 24-hour clock versus the 12-hour clock used in the united states. the setting of this category affects the behavior of functions such as .br strftime (3) and .br strptime (3). .tp .b lc_all all of the above. .pp if the second argument to .br setlocale (3) is an empty string, .ir """""" , for the default locale, it is determined using the following steps: .ip 1. 3 if there is a non-null environment variable .br lc_all , the value of .b lc_all is used. .ip 2. if an environment variable with the same name as one of the categories above exists and is non-null, its value is used for that category. .ip 3. if there is a non-null environment variable .br lang , the value of .b lang is used. .pp values about local numeric formatting is made available in a .i struct lconv returned by the .br localeconv (3) function, which has the following declaration: .pp .in +4n .ex struct lconv { /* numeric (nonmonetary) information */ char *decimal_point; /* radix character */ char *thousands_sep; /* separator for digit groups to left of radix character */ char *grouping; /* each element is the number of digits in a group; elements with higher indices are further left. an element with value char_max means that no further grouping is done. an element with value 0 means that the previous element is used for all groups further left. */ /* remaining fields are for monetary information */ char *int_curr_symbol; /* first three chars are a currency symbol from iso 4217. fourth char is the separator. fifth char is \(aq\e0\(aq. */ char *currency_symbol; /* local currency symbol */ char *mon_decimal_point; /* radix character */ char *mon_thousands_sep; /* like \fithousands_sep\fp above */ char *mon_grouping; /* like \figrouping\fp above */ char *positive_sign; /* sign for positive values */ char *negative_sign; /* sign for negative values */ char int_frac_digits; /* international fractional digits */ char frac_digits; /* local fractional digits */ char p_cs_precedes; /* 1 if currency_symbol precedes a positive value, 0 if succeeds */ char p_sep_by_space; /* 1 if a space separates currency_symbol from a positive value */ char n_cs_precedes; /* 1 if currency_symbol precedes a negative value, 0 if succeeds */ char n_sep_by_space; /* 1 if a space separates currency_symbol from a negative value */ /* positive and negative sign positions: 0 parentheses surround the quantity and currency_symbol. 1 the sign string precedes the quantity and currency_symbol. 2 the sign string succeeds the quantity and currency_symbol. 3 the sign string immediately precedes the currency_symbol. 4 the sign string immediately succeeds the currency_symbol. */ char p_sign_posn; char n_sign_posn; }; .ee .in .ss posix.1-2008 extensions to the locale api posix.1-2008 standardized a number of extensions to the locale api, based on implementations that first appeared in version 2.3 of the gnu c library. these extensions are designed to address the problem that the traditional locale apis do not mix well with multithreaded applications and with applications that must deal with multiple locales. .pp the extensions take the form of new functions for creating and manipulating locale objects .rb ( newlocale (3), .br freelocale (3), .br duplocale (3), and .br uselocale (3)) and various new library functions with the suffix "_l" (e.g., .br toupper_l (3)) that extend the traditional locale-dependent apis (e.g., .br toupper (3)) to allow the specification of a locale object that should apply when executing the function. .sh environment the following environment variable is used by .br newlocale (3) and .br setlocale (3), and thus affects all unprivileged localized programs: .tp .b locpath a list of pathnames, separated by colons (\(aq:\(aq), that should be used to find locale data. if this variable is set, only the individual compiled locale data files from .b locpath and the system default locale data path are used; any available locale archives are not used (see .br localedef (1)). the individual compiled locale data files are searched for under subdirectories which depend on the currently used locale. for example, when .i en_gb.utf\-8 is used for a category, the following subdirectories are searched for, in this order: .ir en_gb.utf\-8 , .ir en_gb.utf8 , .ir en_gb , .ir en.utf\-8 , .ir en.utf8 , and .ir en . .sh files .tp .i /usr/lib/locale/locale\-archive usual default locale archive location. .tp .i /usr/lib/locale usual default path for compiled individual locale files. .sh conforming to posix.1-2001. .\" .\" the gnu gettext functions are specified in li18nux2000. .sh see also .br iconv (1), .br locale (1), .br localedef (1), .br catopen (3), .br gettext (3), .br iconv (3), .br localeconv (3), .br mbstowcs (3), .br newlocale (3), .br ngettext (3), .br nl_langinfo (3), .br rpmatch (3), .br setlocale (3), .br strcoll (3), .br strfmon (3), .br strftime (3), .br strxfrm (3), .br uselocale (3), .br wcstombs (3), .br locale (5), .br charsets (7), .br unicode (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" rtc.4 .\" copyright 2002 urs thuermann (urs@isnogud.escape.de) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" $id: rtc.4,v 1.4 2005/12/05 17:19:49 urs exp $ .\" .\" 2006-02-08 various additions by mtk .\" 2006-11-26 cleanup, cover the generic rtc framework; david brownell .\" .th rtc 4 2021-03-22 "linux" "linux programmer's manual" .sh name rtc \- real-time clock .sh synopsis .nf #include .pp .bi "int ioctl(" fd ", rtc_" request ", " param ");" .fi .sh description this is the interface to drivers for real-time clocks (rtcs). .pp most computers have one or more hardware clocks which record the current "wall clock" time. these are called "real time clocks" (rtcs). one of these usually has battery backup power so that it tracks the time even while the computer is turned off. rtcs often provide alarms and other interrupts. .pp all i386 pcs, and acpi-based systems, have an rtc that is compatible with the motorola mc146818 chip on the original pc/at. today such an rtc is usually integrated into the mainboard's chipset (south bridge), and uses a replaceable coin-sized backup battery. .pp non-pc systems, such as embedded systems built around system-on-chip processors, use other implementations. they usually won't offer the same functionality as the rtc from a pc/at. .ss rtc vs system clock rtcs should not be confused with the system clock, which is a software clock maintained by the kernel and used to implement .br gettimeofday (2) and .br time (2), as well as setting timestamps on files, and so on. the system clock reports seconds and microseconds since a start point, defined to be the posix epoch: 1970-01-01 00:00:00 +0000 (utc). (one common implementation counts timer interrupts, once per "jiffy", at a frequency of 100, 250, or 1000 hz.) that is, it is supposed to report wall clock time, which rtcs also do. .pp a key difference between an rtc and the system clock is that rtcs run even when the system is in a low power state (including "off"), and the system clock can't. until it is initialized, the system clock can only report time since system boot ... not since the posix epoch. so at boot time, and after resuming from a system low power state, the system clock will often be set to the current wall clock time using an rtc. systems without an rtc need to set the system clock using another clock, maybe across the network or by entering that data manually. .ss rtc functionality rtcs can be read and written with .br hwclock (8), or directly with the .br ioctl (2) requests listed below. .pp besides tracking the date and time, many rtcs can also generate interrupts .ip * 3 on every clock update (i.e., once per second); .ip * at periodic intervals with a frequency that can be set to any power-of-2 multiple in the range 2 hz to 8192 hz; .ip * on reaching a previously specified alarm time. .pp each of those interrupt sources can be enabled or disabled separately. on many systems, the alarm interrupt can be configured as a system wakeup event, which can resume the system from a low power state such as suspend-to-ram (str, called s3 in acpi systems), hibernation (called s4 in acpi systems), or even "off" (called s5 in acpi systems). on some systems, the battery backed rtc can't issue interrupts, but another one can. .pp the .i /dev/rtc (or .ir /dev/rtc0 , .ir /dev/rtc1 , etc.) device can be opened only once (until it is closed) and it is read-only. on .br read (2) and .br select (2) the calling process is blocked until the next interrupt from that rtc is received. following the interrupt, the process can read a long integer, of which the least significant byte contains a bit mask encoding the types of interrupt that occurred, while the remaining 3 bytes contain the number of interrupts since the last .br read (2). .ss ioctl(2) interface the following .br ioctl (2) requests are defined on file descriptors connected to rtc devices: .tp .b rtc_rd_time returns this rtc's time in the following structure: .ip .in +4n .ex struct rtc_time { int tm_sec; int tm_min; int tm_hour; int tm_mday; int tm_mon; int tm_year; int tm_wday; /* unused */ int tm_yday; /* unused */ int tm_isdst; /* unused */ }; .ee .in .ip the fields in this structure have the same meaning and ranges as for the .i tm structure described in .br gmtime (3). a pointer to this structure should be passed as the third .br ioctl (2) argument. .tp .b rtc_set_time sets this rtc's time to the time specified by the .i rtc_time structure pointed to by the third .br ioctl (2) argument. to set the rtc's time the process must be privileged (i.e., have the .b cap_sys_time capability). .tp .br rtc_alm_read ", " rtc_alm_set read and set the alarm time, for rtcs that support alarms. the alarm interrupt must be separately enabled or disabled using the .br rtc_aie_on ", " rtc_aie_off requests. the third .br ioctl (2) argument is a pointer to an .i rtc_time structure. only the .ir tm_sec , .ir tm_min , and .i tm_hour fields of this structure are used. .tp .br rtc_irqp_read ", " rtc_irqp_set read and set the frequency for periodic interrupts, for rtcs that support periodic interrupts. the periodic interrupt must be separately enabled or disabled using the .br rtc_pie_on ", " rtc_pie_off requests. the third .br ioctl (2) argument is an .i "unsigned long\ *" or an .ir "unsigned long" , respectively. the value is the frequency in interrupts per second. the set of allowable frequencies is the multiples of two in the range 2 to 8192. only a privileged process (i.e., one having the .b cap_sys_resource capability) can set frequencies above the value specified in .ir /proc/sys/dev/rtc/max\-user\-freq . (this file contains the value 64 by default.) .tp .br rtc_aie_on ", " rtc_aie_off enable or disable the alarm interrupt, for rtcs that support alarms. the third .br ioctl (2) argument is ignored. .tp .br rtc_uie_on ", " rtc_uie_off enable or disable the interrupt on every clock update, for rtcs that support this once-per-second interrupt. the third .br ioctl (2) argument is ignored. .tp .br rtc_pie_on ", " rtc_pie_off enable or disable the periodic interrupt, for rtcs that support these periodic interrupts. the third .br ioctl (2) argument is ignored. only a privileged process (i.e., one having the .b cap_sys_resource capability) can enable the periodic interrupt if the frequency is currently set above the value specified in .ir /proc/sys/dev/rtc/max\-user\-freq . .tp .br rtc_epoch_read ", " rtc_epoch_set many rtcs encode the year in an 8-bit register which is either interpreted as an 8-bit binary number or as a bcd number. in both cases, the number is interpreted relative to this rtc's epoch. the rtc's epoch is initialized to 1900 on most systems but on alpha and mips it might also be initialized to 1952, 1980, or 2000, depending on the value of an rtc register for the year. with some rtcs, these operations can be used to read or to set the rtc's epoch, respectively. the third .br ioctl (2) argument is an .i "unsigned long\ *" or an .ir "unsigned long" , respectively, and the value returned (or assigned) is the epoch. to set the rtc's epoch the process must be privileged (i.e., have the .b cap_sys_time capability). .tp .br rtc_wkalm_rd ", " rtc_wkalm_set some rtcs support a more powerful alarm interface, using these ioctls to read or write the rtc's alarm time (respectively) with this structure: .pp .rs .in +4n .ex struct rtc_wkalrm { unsigned char enabled; unsigned char pending; struct rtc_time time; }; .ee .in .re .ip the .i enabled flag is used to enable or disable the alarm interrupt, or to read its current status; when using these calls, .br rtc_aie_on " and " rtc_aie_off are not used. the .i pending flag is used by .b rtc_wkalm_rd to report a pending interrupt (so it's mostly useless on linux, except when talking to the rtc managed by efi firmware). the .i time field is as used with .b rtc_alm_read and .b rtc_alm_set except that the .ir tm_mday , .ir tm_mon , and .i tm_year fields are also valid. a pointer to this structure should be passed as the third .br ioctl (2) argument. .sh files .tp .ir /dev/rtc ", " /dev/rtc0 ", " /dev/rtc1 ", etc." rtc special character device files. .tp .ir /proc/driver/rtc status of the (first) rtc. .sh notes when the kernel's system time is synchronized with an external reference using .br adjtimex (2) it will update a designated rtc periodically every 11 minutes. to do so, the kernel has to briefly turn off periodic interrupts; this might affect programs using that rtc. .pp an rtc's epoch has nothing to do with the posix epoch which is used only for the system clock. .pp if the year according to the rtc's epoch and the year register is less than 1970 it is assumed to be 100 years later, that is, between 2000 and 2069. .pp some rtcs support "wildcard" values in alarm fields, to support scenarios like periodic alarms at fifteen minutes after every hour, or on the first day of each month. such usage is nonportable; portable user-space code expects only a single alarm interrupt, and will either disable or reinitialize the alarm after receiving it. .pp some rtcs support periodic interrupts with periods that are multiples of a second rather than fractions of a second; multiple alarms; programmable output clock signals; nonvolatile memory; and other hardware capabilities that are not currently exposed by this api. .sh see also .br date (1), .br adjtimex (2), .br gettimeofday (2), .br settimeofday (2), .br stime (2), .br time (2), .br gmtime (3), .br time (7), .br hwclock (8) .pp .i documentation/rtc.txt in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scalbln.3 .\" copyright (c) 2000 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created, 14 dec 2000 by michael kerrisk .\" .th basename 3 2021-03-22 "gnu" "linux programmer's manual" .sh name basename, dirname \- parse pathname components .sh synopsis .nf .b #include .pp .bi "char *dirname(char *" path ); .bi "char *basename(char *" path ); .fi .sh description warning: there are two different functions .br basename (); see below. .pp the functions .br dirname () and .br basename () break a null-terminated pathname string into directory and filename components. in the usual case, .br dirname () returns the string up to, but not including, the final \(aq/\(aq, and .br basename () returns the component following the final \(aq/\(aq. trailing \(aq/\(aq characters are not counted as part of the pathname. .pp if .i path does not contain a slash, .br dirname () returns the string "." while .br basename () returns a copy of .ir path . if .i path is the string "/", then both .br dirname () and .br basename () return the string "/". if .i path is a null pointer or points to an empty string, then both .br dirname () and .br basename () return the string ".". .pp concatenating the string returned by .br dirname (), a "/", and the string returned by .br basename () yields a complete pathname. .pp both .br dirname () and .br basename () may modify the contents of .ir path , so it may be desirable to pass a copy when calling one of these functions. .pp these functions may return pointers to statically allocated memory which may be overwritten by subsequent calls. alternatively, they may return a pointer to some part of .ir path , so that the string referred to by .i path should not be modified or freed until the pointer returned by the function is no longer required. .pp the following list of examples (taken from susv2) shows the strings returned by .br dirname () and .br basename () for different paths: .rs .ts lb lb lb l l l l. path dirname basename /usr/lib /usr lib /usr/ / usr usr . usr / / / \&. . . \&.. . .. .te .re .sh return value both .br dirname () and .br basename () return pointers to null-terminated strings. (do not pass these pointers to .br free (3).) .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br basename (), .br dirname () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes there are two different versions of .br basename () - the posix version described above, and the gnu version, which one gets after .pp .in +4n .ex .br " #define _gnu_source" " /* see feature_test_macros(7) */" .b " #include " .ee .in .pp the gnu version never modifies its argument, and returns the empty string when .i path has a trailing slash, and in particular also when it is "/". there is no gnu version of .br dirname (). .pp with glibc, one gets the posix version of .br basename () when .i is included, and the gnu version otherwise. .sh bugs in the glibc implementation, the posix versions of these functions modify the .i path argument, and segfault when called with a static string such as "/usr/". .pp before glibc 2.2.1, the glibc version of .br dirname () did not correctly handle pathnames with trailing \(aq/\(aq characters, and generated a segfault if given a null argument. .sh examples the following code snippet demonstrates the use of .br basename () and .br dirname (): .in +4n .ex char *dirc, *basec, *bname, *dname; char *path = "/etc/passwd"; dirc = strdup(path); basec = strdup(path); dname = dirname(dirc); bname = basename(basec); printf("dirname=%s, basename=%s\en", dname, bname); .ee .in .sh see also .br basename (1), .br dirname (1) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2010 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th aio_init 3 2020-08-13 "linux" "linux programmer's manual" .sh name aio_init \- asynchronous i/o initialization .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b "#include " .pp .bi "void aio_init(const struct aioinit *" init ); .fi .pp link with \fi\-lrt\fp. .sh description the gnu-specific .br aio_init () function allows the caller to provide tuning hints to the glibc posix aio implementation. use of this function is optional, but to be effective, it must be called before employing any other functions in the posix aio api. .pp the tuning information is provided in the buffer pointed to by the argument .ir init . this buffer is a structure of the following form: .pp .in +4n .ex struct aioinit { int aio_threads; /* maximum number of threads */ int aio_num; /* number of expected simultaneous requests */ int aio_locks; /* not used */ int aio_usedba; /* not used */ int aio_debug; /* not used */ int aio_numusers; /* not used */ int aio_idle_time; /* number of seconds before idle thread terminates (since glibc 2.2) */ int aio_reserved; }; .ee .in .pp the following fields are used in the .i aioinit structure: .tp .i aio_threads this field specifies the maximum number of worker threads that may be used by the implementation. if the number of outstanding i/o operations exceeds this limit, then excess operations will be queued until a worker thread becomes free. if this field is specified with a value less than 1, the value 1 is used. the default value is 20. .tp .i aio_num this field should specify the maximum number of simultaneous i/o requests that the caller expects to enqueue. if a value less than 32 is specified for this field, it is rounded up to 32. .\" fixme . but, if aio_num > 32, the behavior looks strange. see .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12083 the default value is 64. .tp .i aio_idle_time this field specifies the amount of time in seconds that a worker thread should wait for further requests before terminating, after having completed a previous request. the default value is 1. .sh versions the .br aio_init () function is available since glibc 2.1. .sh conforming to this function is a gnu extension. .sh see also .br aio (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's "posix programmer's guide" (o'reilly & associates, 1991) .\" 386bsd man pages .\" .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1996-05-27 by martin schulze (joey@linux.de) .\" modified 2003-11-15 by aeb .\" 2008-11-07, mtk, added an example program for getpwnam_r(). .\" .th getpwnam 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getpwnam, getpwnam_r, getpwuid, getpwuid_r \- get password file entry .sh synopsis .nf .b #include .b #include .pp .bi "struct passwd *getpwnam(const char *" name ); .bi "struct passwd *getpwuid(uid_t " uid ); .pp .bi "int getpwnam_r(const char *restrict " name \ ", struct passwd *restrict " pwd , .bi " char *restrict " buf ", size_t " buflen , .bi " struct passwd **restrict " result ); .bi "int getpwuid_r(uid_t " uid ", struct passwd *restrict " pwd , .bi " char *restrict " buf ", size_t " buflen , .bi " struct passwd **restrict " result ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getpwnam_r (), .br getpwuid_r (): .nf _posix_c_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the .br getpwnam () function returns a pointer to a structure containing the broken-out fields of the record in the password database (e.g., the local password file .ir /etc/passwd , nis, and ldap) that matches the username .ir name . .pp the .br getpwuid () function returns a pointer to a structure containing the broken-out fields of the record in the password database that matches the user id .ir uid . .pp the \fipasswd\fp structure is defined in \fi\fp as follows: .pp .in +4n .ex struct passwd { char *pw_name; /* username */ char *pw_passwd; /* user password */ uid_t pw_uid; /* user id */ gid_t pw_gid; /* group id */ char *pw_gecos; /* user information */ char *pw_dir; /* home directory */ char *pw_shell; /* shell program */ }; .ee .in .pp see .br passwd (5) for more information about these fields. .pp the .br getpwnam_r () and .br getpwuid_r () functions obtain the same information as .br getpwnam () and .br getpwuid (), but store the retrieved .i passwd structure in the space pointed to by .ir pwd . the string fields pointed to by the members of the .i passwd structure are stored in the buffer .i buf of size .ir buflen . a pointer to the result (in case of success) or null (in case no entry was found or an error occurred) is stored in .ir *result . .pp the call .pp sysconf(_sc_getpw_r_size_max) .pp returns either \-1, without changing .ir errno , or an initial suggested size for .ir buf . (if this size is too small, the call fails with .br erange , in which case the caller can retry with a larger buffer.) .sh return value the .br getpwnam () and .br getpwuid () functions return a pointer to a .i passwd structure, or null if the matching entry is not found or an error occurs. if an error occurs, .i errno is set to indicate the error. if one wants to check .i errno after the call, it should be set to zero before the call. .pp the return value may point to a static area, and may be overwritten by subsequent calls to .br getpwent (3), .br getpwnam (), or .br getpwuid (). (do not pass the returned pointer to .br free (3).) .pp on success, .br getpwnam_r () and .br getpwuid_r () return zero, and set .ir *result to .ir pwd . if no matching password record was found, these functions return 0 and store null in .ir *result . in case of error, an error number is returned, and null is stored in .ir *result . .sh errors .tp .br 0 " or " enoent " or " esrch " or " ebadf " or " eperm " or ..." the given .i name or .i uid was not found. .tp .b eintr a signal was caught; see .br signal (7). .tp .b eio i/o error. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enomem .\" not in posix insufficient memory to allocate .i passwd structure. .\" this structure is static, allocated 0 or 1 times. no memory leak. (libc45) .tp .b erange insufficient buffer space supplied. .sh files .tp .i /etc/passwd local password database file .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br getpwnam () t} thread safety t{ mt-unsafe race:pwnam locale t} t{ .br getpwuid () t} thread safety t{ mt-unsafe race:pwuid locale t} t{ .br getpwnam_r (), .br getpwuid_r () t} thread safety t{ mt-safe locale t} .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. the .i pw_gecos field is not specified in posix, but is present on most implementations. .sh notes the formulation given above under "return value" is from posix.1-2001. it does not call "not found" an error, and hence does not specify what value .i errno might have in this situation. but that makes it impossible to recognize errors. one might argue that according to posix .i errno should be left unchanged if an entry is not found. experiments on various unix-like systems show that lots of different values occur in this situation: 0, enoent, ebadf, esrch, ewouldblock, eperm, and probably others. .\" more precisely: .\" aix 5.1 - gives esrch .\" osf1 4.0g - gives ewouldblock .\" libc, glibc up to version 2.6, irix 6.5 - give enoent .\" glibc since version 2.7 - give 0 .\" freebsd 4.8, openbsd 3.2, netbsd 1.6 - give eperm .\" sunos 5.8 - gives ebadf .\" tru64 5.1b, hp-ux-11i, sunos 5.7 - give 0 .pp the .i pw_dir field contains the name of the initial working directory of the user. login programs use the value of this field to initialize the .b home environment variable for the login shell. an application that wants to determine its user's home directory should inspect the value of .b home (rather than the value .ir getpwuid(getuid())\->pw_dir ) since this allows the user to modify their notion of "the home directory" during a login session. to determine the (initial) home directory of another user, it is necessary to use .i getpwnam("username")\->pw_dir or similar. .sh examples the program below demonstrates the use of .br getpwnam_r () to find the full username and user id for the username supplied as a command-line argument. .pp .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { struct passwd pwd; struct passwd *result; char *buf; size_t bufsize; int s; if (argc != 2) { fprintf(stderr, "usage: %s username\en", argv[0]); exit(exit_failure); } bufsize = sysconf(_sc_getpw_r_size_max); if (bufsize == \-1) /* value was indeterminate */ bufsize = 16384; /* should be more than enough */ buf = malloc(bufsize); if (buf == null) { perror("malloc"); exit(exit_failure); } s = getpwnam_r(argv[1], &pwd, buf, bufsize, &result); if (result == null) { if (s == 0) printf("not found\en"); else { errno = s; perror("getpwnam_r"); } exit(exit_failure); } printf("name: %s; uid: %jd\en", pwd.pw_gecos, (intmax_t) pwd.pw_uid); exit(exit_success); } .ee .sh see also .br endpwent (3), .br fgetpwent (3), .br getgrnam (3), .br getpw (3), .br getpwent (3), .br getspnam (3), .br putpwent (3), .br setpwent (3), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage copyright 1998 by andi kleen. .\" .\" %%%license_start(gpl_noversion_oneline) .\" subject to the gpl. .\" %%%license_end .\" .\" based on the original comments from alexey kuznetsov .\" $id: netlink.3,v 1.1 1999/05/14 17:17:24 freitag exp $ .\" .th netlink 3 2014-03-20 "gnu" "linux programmer's manual" .sh name netlink \- netlink macros .sh synopsis .nf .b #include .b #include .pp .bi "int nlmsg_align(size_t " len ); .bi "int nlmsg_length(size_t " len ); .bi "int nlmsg_space(size_t " len ); .bi "void *nlmsg_data(struct nlmsghdr *" nlh ); .bi "struct nlmsghdr *nlmsg_next(struct nlmsghdr *" nlh ", int " len ); .bi "int nlmsg_ok(struct nlmsghdr *" nlh ", int " len ); .bi "int nlmsg_payload(struct nlmsghdr *" nlh ", int " len ); .fi .sh description .i defines several standard macros to access or create a netlink datagram. they are similar in spirit to the macros defined in .br cmsg (3) for auxiliary data. the buffer passed to and from a netlink socket should be accessed using only these macros. .tp .br nlmsg_align () round the length of a netlink message up to align it properly. .tp .br nlmsg_length () given the payload length, .ir len , this macro returns the aligned length to store in the .i nlmsg_len field of the .ir nlmsghdr . .tp .br nlmsg_space () return the number of bytes that a netlink message with payload of .i len would occupy. .tp .br nlmsg_data () return a pointer to the payload associated with the passed .ir nlmsghdr . .tp .\" this is bizarre, maybe the interface should be fixed. .br nlmsg_next () get the next .i nlmsghdr in a multipart message. the caller must check if the current .i nlmsghdr didn't have the .b nlmsg_done set\(emthis function doesn't return null on end. the .i len argument is an lvalue containing the remaining length of the message buffer. this macro decrements it by the length of the message header. .tp .br nlmsg_ok () return true if the netlink message is not truncated and is in a form suitable for parsing. .tp .br nlmsg_payload () return the length of the payload associated with the .ir nlmsghdr . .sh conforming to these macros are nonstandard linux extensions. .sh notes it is often better to use netlink via .i libnetlink than via the low-level kernel interface. .sh see also .br libnetlink (3), .br netlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" and copyright (c) 2008, 2010, 2015, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified thu oct 31 12:04:29 1996 by eric s. raymond .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" 2008-05-03, mtk, expanded and rewrote parts of description and return .\" value, made style of page more consistent with man-pages style. .\" .th getgroups 2 2021-03-22 "linux" "linux programmer's manual" .sh name getgroups, setgroups \- get/set list of supplementary group ids .sh synopsis .nf .b #include .pp .bi "int getgroups(int " size ", gid_t " list []); .pp .b #include .pp .bi "int setgroups(size_t " size ", const gid_t *" list ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br setgroups (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description .br getgroups () returns the supplementary group ids of the calling process in .ir list . the argument .i size should be set to the maximum number of items that can be stored in the buffer pointed to by .ir list . if the calling process is a member of more than .i size supplementary groups, then an error results. .pp it is unspecified whether the effective group id of the calling process is included in the returned list. (thus, an application should also call .br getegid (2) and add or remove the resulting value.) .pp if .i size is zero, .i list is not modified, but the total number of supplementary group ids for the process is returned. this allows the caller to determine the size of a dynamically allocated .i list to be used in a further call to .br getgroups (). .pp .br setgroups () sets the supplementary group ids for the calling process. appropriate privileges are required (see the description of the .br eperm error, below). the .i size argument specifies the number of supplementary group ids in the buffer pointed to by .ir list . a process can drop all of its supplementary groups with the call: .pp .in +4n .ex setgroups(0, null); .ee .in .sh return value on success, .br getgroups () returns the number of supplementary group ids. on error, \-1 is returned, and .i errno is set to indicate the error. .pp on success, .br setgroups () returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i list has an invalid address. .pp .br getgroups () can additionally fail with the following error: .tp .b einval .i size is less than the number of supplementary group ids, but is not zero. .pp .br setgroups () can additionally fail with the following errors: .tp .b einval .i size is greater than .b ngroups_max (32 before linux 2.6.4; 65536 since linux 2.6.4). .tp .b enomem out of memory. .tp .b eperm the calling process has insufficient privilege (the caller does not have the .br cap_setgid capability in the user namespace in which it resides). .tp .br eperm " (since linux 3.19)" the use of .br setgroups () is denied in this user namespace. see the description of .ir /proc/[pid]/setgroups in .br user_namespaces (7). .sh conforming to .br getgroups (): svr4, 4.3bsd, posix.1-2001, posix.1-2008. .pp .br setgroups (): svr4, 4.3bsd. since .br setgroups () requires privilege, it is not covered by posix.1. .sh notes a process can have up to .b ngroups_max supplementary group ids in addition to the effective group id. the constant .b ngroups_max is defined in .ir . the set of supplementary group ids is inherited from the parent process, and preserved across an .br execve (2). .pp the maximum number of supplementary group ids can be found at run time using .br sysconf (3): .pp .in +4n .ex long ngroups_max; ngroups_max = sysconf(_sc_ngroups_max); .ee .in .pp the maximum return value of .br getgroups () cannot be larger than one more than this value. since linux 2.6.4, the maximum number of supplementary group ids is also exposed via the linux-specific read-only file, .ir /proc/sys/kernel/ngroups_max . .pp the original linux .br getgroups () system call supported only 16-bit group ids. subsequently, linux 2.4 added .br getgroups32 (), supporting 32-bit ids. the glibc .br getgroups () wrapper function transparently deals with the variation across kernel versions. .\" .ss c library/kernel differences at the kernel level, user ids and group ids are a per-thread attribute. however, posix requires that all threads in a process share the same credentials. the nptl threading implementation handles the posix requirements by providing wrapper functions for the various system calls that change process uids and gids. these wrapper functions (including the one for .br setgroups ()) employ a signal-based technique to ensure that when one thread changes credentials, all of the other threads in the process also change their credentials. for details, see .br nptl (7). .sh see also .br getgid (2), .br setgid (2), .br getgrouplist (3), .br group_member (3), .br initgroups (3), .br capabilities (7), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .\" copyright (c) 2014 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th keyrings 7 2021-03-22 linux "linux programmer's manual" .sh name keyrings \- in-kernel key management and retention facility .sh description the linux key-management facility is primarily a way for various kernel components to retain or cache security data, authentication keys, encryption keys, and other data in the kernel. .pp system call interfaces are provided so that user-space programs can manage those objects and also use the facility for their own purposes; see .br add_key (2), .br request_key (2), and .br keyctl (2). .pp a library and some user-space utilities are provided to allow access to the facility. see .br keyctl (1), .br keyctl (3), and .br keyutils (7) for more information. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss keys a key has the following attributes: .tp serial number (id) this is a unique integer handle by which a key is referred to in system calls. the serial number is sometimes synonymously referred as the key id. programmatically, key serial numbers are represented using the type .ir key_serial_t . .tp type a key's type defines what sort of data can be held in the key, how the proposed content of the key will be parsed, and how the payload will be used. .ip there are a number of general-purpose types available, plus some specialist types defined by specific kernel components. .tp description (name) the key description is a printable string that is used as the search term for the key (in conjunction with the key type) as well as a display name. during searches, the description may be partially matched or exactly matched. .tp payload (data) the payload is the actual content of a key. this is usually set when a key is created, but it is possible for the kernel to upcall to user space to finish the instantiation of a key if that key wasn't already known to the kernel when it was requested. for further details, see .br request_key (2). .ip a key's payload can be read and updated if the key type supports it and if suitable permission is granted to the caller. .tp access rights much as files do, each key has an owning user id, an owning group id, and a security label. each key also has a set of permissions, though there are more than for a normal unix file, and there is an additional category\(empossessor\(embeyond the usual user, group, and other (see .ir possession , below). .ip note that keys are quota controlled, since they require unswappable kernel memory. the owning user id specifies whose quota is to be debited. .tp expiration time each key can have an expiration time set. when that time is reached, the key is marked as being expired and accesses to it fail with the error .br ekeyexpired . if not deleted, updated, or replaced, then, after a set amount of time, an expired key is automatically removed (garbage collected) along with all links to it, and attempts to access the key fail with the error .br enokey . .tp reference count each key has a reference count. keys are referenced by keyrings, by currently active users, and by a process's credentials. when the reference count reaches zero, the key is scheduled for garbage collection. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss key types the kernel provides several basic types of key: .tp .i """keyring""" .\" note that keyrings use different fields in struct key in order to store .\" their data - index_key instead of type/description and name_link/keys .\" instead of payload. keyrings are special keys which store a set of links to other keys (including other keyrings), analogous to a directory holding links to files. the main purpose of a keyring is to prevent other keys from being garbage collected because nothing refers to them. .ip keyrings with descriptions (names) that begin with a period (\(aq.\(aq) are reserved to the implementation. .tp .i """user""" this is a general-purpose key type. the key is kept entirely within kernel memory. the payload may be read and updated by user-space applications. .ip the payload for keys of this type is a blob of arbitrary data of up to 32,767 bytes. .ip the description may be any valid string, though it is preferred that it start with a colon-delimited prefix representing the service to which the key is of interest (for instance .ir """afs:mykey""" ). .tp .ir """logon""" " (since linux 3.3)" .\" commit 9f6ed2ca257fa8650b876377833e6f14e272848b this key type is essentially the same as .ir """user""" , but it does not provide reading (i.e., the .br keyctl (2) .br keyctl_read operation), meaning that the key payload is never visible from user space. this is suitable for storing username-password pairs that should not be readable from user space. .ip the description of a .ir """logon""" key .i must start with a non-empty colon-delimited prefix whose purpose is to identify the service to which the key belongs. (note that this differs from keys of the .ir """user""" type, where the inclusion of a prefix is recommended but is not enforced.) .tp .ir """big_key""" " (since linux 3.13)" .\" commit ab3c3587f8cda9083209a61dbe3a4407d3cada10 this key type is similar to the .i """user""" key type, but it may hold a payload of up to 1\ mib in size. this key type is useful for purposes such as holding kerberos ticket caches. .ip the payload data may be stored in a tmpfs filesystem, rather than in kernel memory, if the data size exceeds the overhead of storing the data in the filesystem. (storing the data in a filesystem requires filesystem structures to be allocated in the kernel. the size of these structures determines the size threshold above which the tmpfs storage method is used.) since linux 4.8, .\" commit 13100a72f40f5748a04017e0ab3df4cf27c809ef the payload data is encrypted when stored in tmpfs, thereby preventing it from being written unencrypted into swap space. .pp there are more specialized key types available also, but they aren't discussed here because they aren't intended for normal user-space use. .pp key type names that begin with a period (\(aq.\(aq) are reserved to the implementation. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss keyrings as previously mentioned, keyrings are a special type of key that contain links to other keys (which may include other keyrings). keys may be linked to by multiple keyrings. keyrings may be considered as analogous to unix directories where each directory contains a set of hard links to files. .pp various operations (system calls) may be applied only to keyrings: .ip adding a key may be added to a keyring by system calls that create keys. this prevents the new key from being immediately deleted when the system call releases its last reference to the key. .ip linking a link may be added to a keyring pointing to a key that is already known, provided this does not create a self-referential cycle. .ip unlinking a link may be removed from a keyring. when the last link to a key is removed, that key will be scheduled for deletion by the garbage collector. .ip clearing all the links may be removed from a keyring. .ip searching a keyring may be considered the root of a tree or subtree in which keyrings form the branches and non-keyrings the leaves. this tree may be searched for a key matching a particular type and description. .pp see .br keyctl_clear (3), .br keyctl_link (3), .br keyctl_search (3), and .br keyctl_unlink (3) for more information. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss anchoring keys to prevent a key from being garbage collected, it must be anchored to keep its reference count elevated when it is not in active use by the kernel. .pp keyrings are used to anchor other keys: each link is a reference on a key. note that keyrings themselves are just keys and are also subject to the same anchoring requirement to prevent them being garbage collected. .pp the kernel makes available a number of anchor keyrings. note that some of these keyrings will be created only when first accessed. .tp process keyrings process credentials themselves reference keyrings with specific semantics. these keyrings are pinned as long as the set of credentials exists, which is usually as long as the process exists. .ip there are three keyrings with different inheritance/sharing rules: the .br session\-keyring (7) (inherited and shared by all child processes), the .br process\-keyring (7) (shared by all threads in a process) and the .br thread\-keyring (7) (specific to a particular thread). .ip as an alternative to using the actual keyring ids, in calls to .br add_key (2), .br keyctl (2), and .br request_key (2), the special keyring values .br key_spec_session_keyring , .br key_spec_process_keyring , and .br key_spec_thread_keyring can be used to refer to the caller's own instances of these keyrings. .tp user keyrings each uid known to the kernel has a record that contains two keyrings: the .br user\-keyring (7) and the .br user\-session\-keyring (7). these exist for as long as the uid record in the kernel exists. .ip as an alternative to using the actual keyring ids, in calls to .br add_key (2), .br keyctl (2), and .br request_key (2), the special keyring values .br key_spec_user_keyring and .br key_spec_user_session_keyring can be used to refer to the caller's own instances of these keyrings. .ip a link to the user keyring is placed in a new session keyring by .br pam_keyinit (8) when a new login session is initiated. .tp persistent keyrings there is a .br persistent\-keyring (7) available to each uid known to the system. it may persist beyond the life of the uid record previously mentioned, but has an expiration time set such that it is automatically cleaned up after a set time. the persistent keyring permits, for example, .br cron (8) scripts to use credentials that are left in the persistent keyring after the user logs out. .ip note that the expiration time of the persistent keyring is reset every time the persistent key is requested. .tp special keyrings there are special keyrings owned by the kernel that can anchor keys for special purposes. an example of this is the \fisystem keyring\fr used for holding encryption keys for module signature verification. .ip these special keyrings are usually closed to direct alteration by user space. .pp an originally planned "group keyring", for storing keys associated with each gid known to the kernel, is not so far implemented, is unlikely to be implemented. nevertheless, the constant .br key_spec_group_keyring has been defined for this keyring. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss possession the concept of possession is important to understanding the keyrings security model. whether a thread possesses a key is determined by the following rules: .ip (1) 4 any key or keyring that does not grant .i search permission to the caller is ignored in all the following rules. .ip (2) a thread possesses its .br session\-keyring (7), .br process\-keyring (7), and .br thread\-keyring (7) directly because those keyrings are referred to by its credentials. .ip (3) if a keyring is possessed, then any key it links to is also possessed. .ip (4) if any key a keyring links to is itself a keyring, then rule (3) applies recursively. .ip (5) if a process is upcalled from the kernel to instantiate a key (see .br request_key (2)), then it also possesses the requester's keyrings as in rule (1) as if it were the requester. .pp note that possession is not a fundamental property of a key, but must rather be calculated each time the key is needed. .pp possession is designed to allow set-user-id programs run from, say a user's shell to access the user's keys. granting permissions to the key possessor while denying them to the key owner and group allows the prevention of access to keys on the basis of uid and gid matches. .pp when it creates the session keyring, .br pam_keyinit (8) adds a link to the .br user\-keyring (7), thus making the user keyring and anything it contains possessed by default. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss access rights each key has the following security-related attributes: .ip * 3 the owning user id .ip * the id of a group that is permitted to access the key .ip * a security label .ip * a permissions mask .pp the permissions mask contains four sets of rights. the first three sets are mutually exclusive. one and only one will be in force for a particular access check. in order of descending priority, these three sets are: .ip \fiuser\fr the set specifies the rights granted if the key's user id matches the caller's filesystem user id. .ip \figroup\fr the set specifies the rights granted if the user id didn't match and the key's group id matches the caller's filesystem gid or one of the caller's supplementary group ids. .ip \fiother\fr the set specifies the rights granted if neither the key's user id nor group id matched. .pp the fourth set of rights is: .ip \fipossessor\fr the set specifies the rights granted if a key is determined to be possessed by the caller. .pp the complete set of rights for a key is the union of whichever of the first three sets is applicable plus the fourth set if the key is possessed. .pp the set of rights that may be granted in each of the four masks is as follows: .tp .i view the attributes of the key may be read. this includes the type, description, and access rights (excluding the security label). .tp .i read for a key: the payload of the key may be read. for a keyring: the list of serial numbers (keys) to which the keyring has links may be read. .tp .i write the payload of the key may be updated and the key may be revoked. for a keyring, links may be added to or removed from the keyring, and the keyring may be cleared completely (all links are removed), .tp .i search for a key (or a keyring): the key may be found by a search. for a keyring: keys and keyrings that are linked to by the keyring may be searched. .tp .i link links may be created from keyrings to the key. the initial link to a key that is established when the key is created doesn't require this permission. .tp .i setattr the ownership details and security label of the key may be changed, the key's expiration time may be set, and the key may be revoked. .pp in addition to access rights, any active linux security module (lsm) may prevent access to a key if its policy so dictates. a key may be given a security label or other attribute by the lsm; this label is retrievable via .br keyctl_get_security (3). .pp see .br keyctl_chown (3), .br keyctl_describe (3), .br keyctl_get_security (3), .br keyctl_setperm (3), and .br selinux (8) for more information. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss searching for keys one of the key features of the linux key-management facility is the ability to find a key that a process is retaining. the .br request_key (2) system call is the primary point of access for user-space applications to find a key. (internally, the kernel has something similar available for use by internal components that make use of keys.) .pp the search algorithm works as follows: .ip (1) 4 the process keyrings are searched in the following order: the thread .br thread\-keyring (7) if it exists, the .br process\-keyring (7) if it exists, and then either the .br session\-keyring (7) if it exists or the .br user\-session\-keyring (7) if that exists. .ip (2) if the caller was a process that was invoked by the .br request_key (2) upcall mechanism, then the keyrings of the original caller of .br request_key (2) will be searched as well. .ip (3) the search of a keyring tree is in breadth-first order: each keyring is searched first for a match, then the keyrings referred to by that keyring are searched. .ip (4) if a matching key is found that is valid, then the search terminates and that key is returned. .ip (5) if a matching key is found that has an error state attached, that error state is noted and the search continues. .ip (6) if no valid matching key is found, then the first noted error state is returned; otherwise, an .b enokey error is returned. .pp it is also possible to search a specific keyring, in which case only steps (3) to (6) apply. .pp see .br request_key (2) and .br keyctl_search (3) for more information. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss on-demand key creation if a key cannot be found, .br request_key (2) will, if given a .i callout_info argument, create a new key and then upcall to user space to instantiate the key. this allows keys to be created on an as-needed basis. .pp typically, this will involve the kernel creating a new process that executes the .br request\-key (8) program, which will then execute the appropriate handler based on its configuration. .pp the handler is passed a special authorization key that allows it and only it to instantiate the new key. this is also used to permit searches performed by the handler program to also search the requester's keyrings. .pp see .br request_key (2), .br keyctl_assume_authority (3), .br keyctl_instantiate (3), .br keyctl_negate (3), .br keyctl_reject (3), .br request\-key (8), and .br request\-key.conf (5) for more information. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss /proc files the kernel provides various .i /proc files that expose information about keys or define limits on key usage. .tp .ir /proc/keys " (since linux 2.6.10)" this file exposes a list of the keys for which the reading thread has .i view permission, providing various information about each key. the thread need not possess the key for it to be visible in this file. .\" david howells, dec 2016 linux-man@: .\" this [the thread need not possess the key for it to be visible in .\" this file.] is correct. see proc_keys_show() in security/keys/proc.c: .\" .\" rc = key_task_permission(key_ref, ctx.cred, key_need_view); .\" if (rc < 0) .\" return 0; .\" .\"possibly it shouldn't be, but for now it is. .\" .ip the only keys included in the list are those that grant .i view permission to the reading process (regardless of whether or not it possesses them). lsm security checks are still performed, and may filter out further keys that the process is not authorized to view. .ip an example of the data that one might see in this file (with the columns numbered for easy reference below) is the following: .ip .ex (1) (2) (3)(4) (5) (6) (7) (8) (9) 009a2028 i\-\-q\-\-\- 1 perm 3f010000 1000 1000 user krb_ccache:primary: 12 1806c4ba i\-\-q\-\-\- 1 perm 3f010000 1000 1000 keyring _pid: 2 25d3a08f i\-\-q\-\-\- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 28576bd8 i\-\-q\-\-\- 3 perm 3f010000 1000 1000 keyring _krb: 1 2c546d21 i\-\-q\-\-\- 190 perm 3f030000 1000 1000 keyring _ses: 2 30a4e0be i\-\-\-\-\-\- 4 2d 1f030000 1000 65534 keyring _persistent.1000: 1 32100fab i\-\-q\-\-\- 4 perm 1f3f0000 1000 65534 keyring _uid.1000: 2 32a387ea i\-\-q\-\-\- 1 perm 3f010000 1000 1000 keyring _pid: 2 3ce56aea i\-\-q\-\-\- 5 perm 3f030000 1000 1000 keyring _ses: 1 .ee .ip the fields shown in each line of this file are as follows: .rs .tp id (1) the id (serial number) of the key, expressed in hexadecimal. .tp flags (2) a set of flags describing the state of the key: .rs .ip i 4 .\" key_flag_instantiated the key has been instantiated. .ip r .\" key_flag_revoked the key has been revoked. .ip d .\" key_flag_dead the key is dead (i.e., the key type has been unregistered). .\" unregister_key_type() in the kernel source (a key may be briefly in this state during garbage collection.) .ip q .\" key_flag_in_quota the key contributes to the user's quota. .ip u .\" key_flag_user_construct the key is under construction via a callback to user space; see .br request\-key (2). .ip n .\" key_flag_negative the key is negatively instantiated. .ip i .\" key_flag_invalidated the key has been invalidated. .re .tp usage (3) this is a count of the number of kernel credential structures that are pinning the key (approximately: the number of threads and open file references that refer to this key). .tp timeout (4) the amount of time until the key will expire, expressed in human-readable form (weeks, days, hours, minutes, and seconds). the string .i perm here means that the key is permanent (no timeout). the string .i expd means that the key has already expired, but has not yet been garbage collected. .tp permissions (5) the key permissions, expressed as four hexadecimal bytes containing, from left to right, the possessor, user, group, and other permissions. within each byte, the permission bits are as follows: .ip .pd 0 .rs 12 .tp 0x01 .i view .tp ox02 .i read .tp 0x04 .i write .tp 0x08 .i search .tp 0x10 .i link .tp 0x20 .i setattr .re .pd .tp uid (6) the user id of the key owner. .tp gid (7) the group id of the key. the value \-1 here means that the key has no group id; this can occur in certain circumstances for keys created by the kernel. .tp type (8) the key type (user, keyring, etc.) .tp description (9) the key description (name). this field contains descriptive information about the key. for most key types, it has the form .ip name[: extra\-info] .ip the .i name subfield is the key's description (name). the optional .i extra\-info field provides some further information about the key. the information that appears here depends on the key type, as follows: .rs .tp .ir """user""" " and " """logon""" the size in bytes of the key payload (expressed in decimal). .tp .ir """keyring""" the number of keys linked to the keyring, or the string .ir empty if there are no keys linked to the keyring. .tp .ir """big_key""" the payload size in bytes, followed either by the string .ir [file] , if the key payload exceeds the threshold that means that the payload is stored in a (swappable) .br tmpfs (5) filesystem, or otherwise the string .ir [buff] , indicating that the key is small enough to reside in kernel memory. .re .ip for the .ir """.request_key_auth""" key type (authorization key; see .br request_key (2)), the description field has the form shown in the following example: .ip key:c9a9b19 pid:28880 ci:10 .ip the three subfields are as follows: .rs .tp .i key the hexadecimal id of the key being instantiated in the requesting program. .tp .i pid the pid of the requesting program. .tp .i ci the length of the callout data with which the requested key should be instantiated (i.e., the length of the payload associated with the authorization key). .re .re .tp .ir /proc/key\-users " (since linux 2.6.10)" this file lists various information for each user id that has at least one key on the system. an example of the data that one might see in this file is the following: .ip .in +4n .ex 0: 10 9/9 2/1000000 22/25000000 42: 9 9/9 8/200 106/20000 1000: 11 11/11 10/200 271/20000 .ee .in .ip the fields shown in each line are as follows: .rs .tp .i uid the user id. .tp .i usage this is a kernel-internal usage count for the kernel structure used to record key users. .tp .ir nkeys / nikeys the total number of keys owned by the user, and the number of those keys that have been instantiated. .tp .ir qnkeys / maxkeys the number of keys owned by the user, and the maximum number of keys that the user may own. .tp .ir qnbytes / maxbytes the number of bytes consumed in payloads of the keys owned by this user, and the upper limit on the number of bytes in key payloads for that user. .re .tp .ir /proc/sys/kernel/keys/gc_delay " (since linux 2.6.32)" .\" commit 5d135440faf7db8d566de0c6fab36b16cf9cfc3b the value in this file specifies the interval, in seconds, after which revoked and expired keys will be garbage collected. the purpose of having such an interval is so that there is a window of time where user space can see an error (respectively .br ekeyrevoked and .br ekeyexpired ) that indicates what happened to the key. .ip the default value in this file is 300 (i.e., 5 minutes). .tp .ir /proc/sys/kernel/keys/persistent_keyring_expiry " (since linux 3.13)" .\" commit f36f8c75ae2e7d4da34f4c908cebdb4aa42c977e this file defines an interval, in seconds, to which the persistent keyring's expiration timer is reset each time the keyring is accessed (via .br keyctl_get_persistent (3) or the .br keyctl (2) .b keyctl_get_persistent operation.) .ip the default value in this file is 259200 (i.e., 3 days). .pp the following files (which are writable by privileged processes) are used to enforce quotas on the number of keys and number of bytes of data that can be stored in key payloads: .tp .ir /proc/sys/kernel/keys/maxbytes " (since linux 2.6.26)" .\" commit 0b77f5bfb45c13e1e5142374f9d6ca75292252a4 .\" previously: keyquota_max_bytes 10000 this is the maximum number of bytes of data that a nonroot user can hold in the payloads of the keys owned by the user. .ip the default value in this file is 20,000. .tp .ir /proc/sys/kernel/keys/maxkeys " (since linux 2.6.26)" .\" commit 0b77f5bfb45c13e1e5142374f9d6ca75292252a4 .\" previously: keyquota_max_keys 100 this is the maximum number of keys that a nonroot user may own. .ip the default value in this file is 200. .tp .ir /proc/sys/kernel/keys/root_maxbytes " (since linux 2.6.26)" this is the maximum number of bytes of data that the root user (uid 0 in the root user namespace) can hold in the payloads of the keys owned by root. .ip .\"738c5d190f6540539a04baf36ce21d46b5da04bd the default value in this file is 25,000,000 (20,000 before linux 3.17). .\" commit 0b77f5bfb45c13e1e5142374f9d6ca75292252a4 .tp .ir /proc/sys/kernel/keys/root_maxkeys " (since linux 2.6.26)" .\" commit 0b77f5bfb45c13e1e5142374f9d6ca75292252a4 this is the maximum number of keys that the root user (uid 0 in the root user namespace) may own. .ip .\"738c5d190f6540539a04baf36ce21d46b5da04bd the default value in this file is 1,000,000 (200 before linux 3.17). .pp with respect to keyrings, note that each link in a keyring consumes 4 bytes of the keyring payload. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .ss users the linux key-management facility has a number of users and usages, but is not limited to those that already exist. .pp in-kernel users of this facility include: .tp network filesystems - dns the kernel uses the upcall mechanism provided by the keys to upcall to user space to do dns lookups and then to cache the results. .tp af_rxrpc and kafs - authentication the af_rxrpc network protocol and the in-kernel afs filesystem use keys to store the ticket needed to do secured or encrypted traffic. these are then looked up by network operations on af_rxrpc and filesystem operations on kafs. .tp nfs - user id mapping the nfs filesystem uses keys to store mappings of foreign user ids to local user ids. .tp cifs - password the cifs filesystem uses keys to store passwords for accessing remote shares. .tp module verification the kernel build process can be made to cryptographically sign modules. that signature is then checked when a module is loaded. .pp user-space users of this facility include: .tp kerberos key storage the mit kerberos 5 facility (libkrb5) can use keys to store authentication tokens which can be made to be automatically cleaned up a set time after the user last uses them, but until then permits them to hang around after the user has logged out so that .br cron (8) scripts can use them. .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" .sh see also .ad l .nh .br keyctl (1), .br add_key (2), .br keyctl (2), .br request_key (2), .br keyctl (3), .br keyutils (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7), .br pam_keyinit (8), .br request\-key (8) .pp the kernel source files .ir documentation/crypto/asymmetric\-keys.txt and under .ir documentation/security/keys (or, before linux 4.13, in the file .ir documentation/security/keys.txt ). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 john levon .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 2004-06-17 michael kerrisk .\" .th lookup_dcookie 2 2021-03-22 "linux" "linux programmer's manual" .sh name lookup_dcookie \- return a directory entry's path .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_lookup_dcookie, uint64_t " cookie ", char *" buffer , .bi " size_t " len ); .fi .pp .ir note : glibc provides no wrapper for .br lookup_dcookie (), necessitating the use of .br syscall (2). .sh description look up the full path of the directory entry specified by the value .ir cookie . the cookie is an opaque identifier uniquely identifying a particular directory entry. the buffer given is filled in with the full path of the directory entry. .pp for .br lookup_dcookie () to return successfully, the kernel must still hold a cookie reference to the directory entry. .sh return value on success, .br lookup_dcookie () returns the length of the path string copied into the buffer. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault the buffer was not valid. .tp .b einval the kernel has no registered cookie/directory entry mappings at the time of lookup, or the cookie does not refer to a valid directory entry. .tp .b enametoolong the name could not fit in the buffer. .tp .b enomem the kernel could not allocate memory for the temporary buffer holding the path. .tp .b eperm the process does not have the capability .b cap_sys_admin required to look up cookie values. .tp .b erange the buffer was not large enough to hold the path of the directory entry. .sh versions available since linux 2.5.43. the .b enametoolong error return was added in 2.5.70. .sh conforming to .br lookup_dcookie () is linux-specific. .sh notes .br lookup_dcookie () is a special-purpose system call, currently used only by the .br oprofile (1) profiler. it relies on a kernel driver to register cookies for directory entries. .pp the path returned may be suffixed by the string " (deleted)" if the directory entry has been removed. .sh see also .br oprofile (1) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sun jul 25 11:05:58 1993 by rik faith (faith@cs.unc.edu) .\" modified sat feb 10 16:18:03 1996 by urs thuermann (urs@isnogud.escape.de) .\" modified mon jun 16 20:02:00 1997 by nicolás lichtmaier .\" modified mon feb 6 16:41:00 1999 by nicolás lichtmaier .\" modified tue feb 8 16:46:45 2000 by chris pepper .\" modified fri sep 7 20:32:45 2001 by tammy fox .th hier 7 2021-03-22 "linux" "linux programmer's manual" .sh name hier \- description of the filesystem hierarchy .sh description a typical linux system has, among others, the following directories: .tp .i / this is the root directory. this is where the whole tree starts. .tp .i /bin this directory contains executable programs which are needed in single user mode and to bring the system up or repair it. .tp .i /boot contains static files for the boot loader. this directory holds only the files which are needed during the boot process. the map installer and configuration files should go to .i /sbin and .ir /etc . the operating system kernel (initrd for example) must be located in either .i / or .ir /boot . .tp .i /dev special or device files, which refer to physical devices. see .br mknod (1). .tp .i /etc contains configuration files which are local to the machine. some larger software packages, like x11, can have their own subdirectories below .ir /etc . site-wide configuration files may be placed here or in .ir /usr/etc . nevertheless, programs should always look for these files in .i /etc and you may have links for these files to .ir /usr/etc . .tp .i /etc/opt host-specific configuration files for add-on applications installed in .ir /opt . .tp .i /etc/sgml this directory contains the configuration files for sgml (optional). .tp .i /etc/skel when a new user account is created, files from this directory are usually copied into the user's home directory. .tp .i /etc/x11 configuration files for the x11 window system (optional). .tp .i /etc/xml this directory contains the configuration files for xml (optional). .tp .i /home on machines with home directories for users, these are usually beneath this directory, directly or not. the structure of this directory depends on local administration decisions (optional). .tp .i /lib this directory should hold those shared libraries that are necessary to boot the system and to run the commands in the root filesystem. .tp .i /lib these directories are variants of .i /lib on system which support more than one binary format requiring separate libraries (optional). .tp .i /lib/modules loadable kernel modules (optional). .tp .i /lost+found this directory contains items lost in the filesystem. these items are usually chunks of files mangled as a consequence of a faulty disk or a system crash. .tp .i /media this directory contains mount points for removable media such as cd and dvd disks or usb sticks. on systems where more than one device exists for mounting a certain type of media, mount directories can be created by appending a digit to the name of those available above starting with '0', but the unqualified name must also exist. .tp .i /media/floppy[1\-9] floppy drive (optional). .tp .i /media/cdrom[1\-9] cd-rom drive (optional). .tp .i /media/cdrecorder[1\-9] cd writer (optional). .tp .i /media/zip[1\-9] zip drive (optional). .tp .i /media/usb[1\-9] usb drive (optional). .tp .i /mnt this directory is a mount point for a temporarily mounted filesystem. in some distributions, .i /mnt contains subdirectories intended to be used as mount points for several temporary filesystems. .tp .i /opt this directory should contain add-on packages that contain static files. .tp .i /proc this is a mount point for the .i proc filesystem, which provides information about running processes and the kernel. this pseudo-filesystem is described in more detail in .br proc (5). .tp .i /root this directory is usually the home directory for the root user (optional). .tp .i /run this directory contains information which describes the system since it was booted. once this purpose was served by .ir /var/run and programs may continue to use it. .tp .i /sbin like .ir /bin , this directory holds commands needed to boot the system, but which are usually not executed by normal users. .tp .i /srv this directory contains site-specific data that is served by this system. .tp .i /sys this is a mount point for the sysfs filesystem, which provides information about the kernel like .ir /proc , but better structured, following the formalism of kobject infrastructure. .tp .i /tmp this directory contains temporary files which may be deleted with no notice, such as by a regular job or at system boot up. .tp .i /usr this directory is usually mounted from a separate partition. it should hold only shareable, read-only data, so that it can be mounted by various machines running linux. .tp .i /usr/x11r6 the x\-window system, version 11 release 6 (present in fhs 2.3, removed in fhs 3.0). .tp .i /usr/x11r6/bin binaries which belong to the x\-window system; often, there is a symbolic link from the more traditional .i /usr/bin/x11 to here. .tp .i /usr/x11r6/lib data files associated with the x\-window system. .tp .i /usr/x11r6/lib/x11 these contain miscellaneous files needed to run x; often, there is a symbolic link from .i /usr/lib/x11 to this directory. .tp .i /usr/x11r6/include/x11 contains include files needed for compiling programs using the x11 window system. often, there is a symbolic link from .i /usr/include/x11 to this directory. .tp .i /usr/bin this is the primary directory for executable programs. most programs executed by normal users which are not needed for booting or for repairing the system and which are not installed locally should be placed in this directory. .tp .i /usr/bin/mh commands for the mh mail handling system (optional). .tp .i /usr/bin/x11 this is the traditional place to look for x11 executables; on linux, it usually is a symbolic link to .ir /usr/x11r6/bin . .tp .i /usr/dict replaced by .ir /usr/share/dict . .tp .i /usr/doc replaced by .ir /usr/share/doc . .tp .i /usr/etc site-wide configuration files to be shared between several machines may be stored in this directory. however, commands should always reference those files using the .i /etc directory. links from files in .i /etc should point to the appropriate files in .ir /usr/etc . .tp .i /usr/games binaries for games and educational programs (optional). .tp .i /usr/include include files for the c compiler. .tp .i /usr/include/bsd bsd compatibility include files (optional). .tp .i /usr/include/x11 include files for the c compiler and the x\-window system. this is usually a symbolic link to .ir /usr/x11r6/include/x11 . .tp .i /usr/include/asm include files which declare some assembler functions. this used to be a symbolic link to .ir /usr/src/linux/include/asm . .tp .i /usr/include/linux this contains information which may change from system release to system release and used to be a symbolic link to .i /usr/src/linux/include/linux to get at operating-system-specific information. .ip (note that one should have include files there that work correctly with the current libc and in user space. however, linux kernel source is not designed to be used with user programs and does not know anything about the libc you are using. it is very likely that things will break if you let .i /usr/include/asm and .i /usr/include/linux point at a random kernel tree. debian systems don't do this and use headers from a known good kernel version, provided in the libc*-dev package.) .tp .i /usr/include/g++ include files to use with the gnu c++ compiler. .tp .i /usr/lib object libraries, including dynamic libraries, plus some executables which usually are not invoked directly. more complicated programs may have whole subdirectories there. .tp .i /usr/libexec directory contains binaries for internal use only and they are not meant to be executed directly by users shell or scripts. .tp .i /usr/lib these directories are variants of .i /usr/lib on system which support more than one binary format requiring separate libraries, except that the symbolic link .i /usr/lib/x11 is not required (optional). .tp .i /usr/lib/x11 the usual place for data files associated with x programs, and configuration files for the x system itself. on linux, it usually is a symbolic link to .ir /usr/x11r6/lib/x11 . .tp .i /usr/lib/gcc\-lib contains executables and include files for the gnu c compiler, .br gcc (1). .tp .i /usr/lib/groff files for the gnu groff document formatting system. .tp .i /usr/lib/uucp files for .br uucp (1). .tp .i /usr/local this is where programs which are local to the site typically go. .tp .i /usr/local/bin binaries for programs local to the site. .tp .i /usr/local/doc local documentation. .tp .i /usr/local/etc configuration files associated with locally installed programs. .tp .i /usr/local/games binaries for locally installed games. .tp .i /usr/local/lib files associated with locally installed programs. .tp .i /usr/local/lib these directories are variants of .i /usr/local/lib on system which support more than one binary format requiring separate libraries (optional). .tp .i /usr/local/include header files for the local c compiler. .tp .i /usr/local/info info pages associated with locally installed programs. .tp .i /usr/local/man man pages associated with locally installed programs. .tp .i /usr/local/sbin locally installed programs for system administration. .tp .i /usr/local/share local application data that can be shared among different architectures of the same os. .tp .i /usr/local/src source code for locally installed software. .tp .i /usr/man replaced by .ir /usr/share/man . .tp .i /usr/sbin this directory contains program binaries for system administration which are not essential for the boot process, for mounting .ir /usr , or for system repair. .tp .i /usr/share this directory contains subdirectories with specific application data, that can be shared among different architectures of the same os. often one finds stuff here that used to live in .i /usr/doc or .i /usr/lib or .ir /usr/man . .tp .i /usr/share/color contains color management information, like international color consortium (icc) color profiles (optional). .tp .i /usr/share/dict contains the word lists used by spell checkers (optional). .tp .i /usr/share/dict/words list of english words (optional). .tp .i /usr/share/doc documentation about installed programs (optional). .tp .i /usr/share/games static data files for games in .i /usr/games (optional). .tp .i /usr/share/info info pages go here (optional). .tp .i /usr/share/locale locale information goes here (optional). .tp .i /usr/share/man manual pages go here in subdirectories according to the man page sections. .tp .i /usr/share/man//man[1\-9] these directories contain manual pages for the specific locale in source code form. systems which use a unique language and code set for all manual pages may omit the substring. .tp .i /usr/share/misc miscellaneous data that can be shared among different architectures of the same os. .tp .i /usr/share/nls the message catalogs for native language support go here (optional). .tp .i /usr/share/ppd postscript printer definition (ppd) files (optional). .tp .i /usr/share/sgml files for sgml (optional). .tp .i /usr/share/sgml/docbook docbook dtd (optional). .tp .i /usr/share/sgml/tei tei dtd (optional). .tp .i /usr/share/sgml/html html dtd (optional). .tp .i /usr/share/sgml/mathtml mathml dtd (optional). .tp .i /usr/share/terminfo the database for terminfo (optional). .tp .i /usr/share/tmac troff macros that are not distributed with groff (optional). .tp .i /usr/share/xml files for xml (optional). .tp .i /usr/share/xml/docbook docbook dtd (optional). .tp .i /usr/share/xml/xhtml xhtml dtd (optional). .tp .i /usr/share/xml/mathml mathml dtd (optional). .tp .i /usr/share/zoneinfo files for timezone information (optional). .tp .i /usr/src source files for different parts of the system, included with some packages for reference purposes. don't work here with your own projects, as files below /usr should be read-only except when installing software (optional). .tp .i /usr/src/linux this was the traditional place for the kernel source. some distributions put here the source for the default kernel they ship. you should probably use another directory when building your own kernel. .tp .i /usr/tmp obsolete. this should be a link to .ir /var/tmp . this link is present only for compatibility reasons and shouldn't be used. .tp .i /var this directory contains files which may change in size, such as spool and log files. .tp .i /var/account process accounting logs (optional). .tp .i /var/adm this directory is superseded by .i /var/log and should be a symbolic link to .ir /var/log . .tp .i /var/backups reserved for historical reasons. .tp .i /var/cache data cached for programs. .tp .i /var/cache/fonts locally generated fonts (optional). .tp .i /var/cache/man locally formatted man pages (optional). .tp .i /var/cache/www www proxy or cache data (optional). .tp .i /var/cache/ package specific cache data (optional). .tp .ir /var/catman/cat[1\-9] " or " /var/cache/man/cat[1\-9] these directories contain preformatted manual pages according to their man page section. (the use of preformatted manual pages is deprecated.) .tp .i /var/crash system crash dumps (optional). .tp .i /var/cron reserved for historical reasons. .tp .i /var/games variable game data (optional). .tp .i /var/lib variable state information for programs. .tp .i /var/lib/color variable files containing color management information (optional). .tp .i /var/lib/hwclock state directory for hwclock (optional). .tp .i /var/lib/misc miscellaneous state data. .tp .i /var/lib/xdm x display manager variable data (optional). .tp .i /var/lib/ editor backup files and state (optional). .tp .i /var/lib/ these directories must be used for all distribution packaging support. .tp .i /var/lib/ state data for packages and subsystems (optional). .tp .i /var/lib/ packaging support files (optional). .tp .i /var/local variable data for .ir /usr/local . .tp .i /var/lock lock files are placed in this directory. the naming convention for device lock files is .i lck.. where .i is the device's name in the filesystem. the format used is that of hdu uucp lock files, that is, lock files contain a pid as a 10-byte ascii decimal number, followed by a newline character. .tp .i /var/log miscellaneous log files. .tp .i /var/opt variable data for .ir /opt . .tp .i /var/mail users' mailboxes. replaces .ir /var/spool/mail . .tp .i /var/msgs reserved for historical reasons. .tp .i /var/preserve reserved for historical reasons. .tp .i /var/run run-time variable files, like files holding process identifiers (pids) and logged user information .ir (utmp) . files in this directory are usually cleared when the system boots. .tp .i /var/spool spooled (or queued) files for various programs. .tp .i /var/spool/at spooled jobs for .br at (1). .tp .i /var/spool/cron spooled jobs for .br cron (8). .tp .i /var/spool/lpd spooled files for printing (optional). .tp .i /var/spool/lpd/printer spools for a specific printer (optional). .tp .i /var/spool/mail replaced by .ir /var/mail . .tp .i /var/spool/mqueue queued outgoing mail (optional). .tp .i /var/spool/news spool directory for news (optional). .tp .i /var/spool/rwho spooled files for .br rwhod (8) (optional). .tp .i /var/spool/smail spooled files for the .br smail (1) mail delivery program. .tp .i /var/spool/uucp spooled files for .br uucp (1) (optional). .tp .i /var/tmp like .ir /tmp , this directory holds temporary files stored for an unspecified duration. .tp .i /var/yp database files for nis, formerly known as the sun yellow pages (yp). .sh conforming to the filesystem hierarchy standard (fhs), version 3.0, published march 19, 2015 .ur https://refspecs.linuxfoundation.org/fhs.shtml .ue . .sh bugs this list is not exhaustive; different distributions and systems may be configured differently. .sh see also .br find (1), .br ln (1), .br proc (5), .br file\-hierarchy (7), .br mount (8) .pp the filesystem hierarchy standard .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012, vincent weaver .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" this document is based on the perf_event.h header file, the .\" tools/perf/design.txt file, and a lot of bitter experience. .\" .th perf_event_open 2 2021-08-27 "linux" "linux programmer's manual" .sh name perf_event_open \- set up performance monitoring .sh synopsis .nf .br "#include " " /* definition of " perf_* " constants */" .br "#include " " /* definition of " hw_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_perf_event_open, struct perf_event_attr *" attr , .bi " pid_t " pid ", int " cpu ", int " group_fd \ ", unsigned long " flags ); .fi .pp .ir note : glibc provides no wrapper for .br perf_event_open (), necessitating the use of .br syscall (2). .sh description given a list of parameters, .br perf_event_open () returns a file descriptor, for use in subsequent system calls .rb ( read "(2), " mmap "(2), " prctl "(2), " fcntl "(2), etc.)." .pp a call to .br perf_event_open () creates a file descriptor that allows measuring performance information. each file descriptor corresponds to one event that is measured; these can be grouped together to measure multiple events simultaneously. .pp events can be enabled and disabled in two ways: via .br ioctl (2) and via .br prctl (2). when an event is disabled it does not count or generate overflows but does continue to exist and maintain its count value. .pp events come in two flavors: counting and sampled. a .i counting event is one that is used for counting the aggregate number of events that occur. in general, counting event results are gathered with a .br read (2) call. a .i sampling event periodically writes measurements to a buffer that can then be accessed via .br mmap (2). .ss arguments the .i pid and .i cpu arguments allow specifying which process and cpu to monitor: .tp .br "pid == 0" " and " "cpu == \-1" this measures the calling process/thread on any cpu. .tp .br "pid == 0" " and " "cpu >= 0" this measures the calling process/thread only when running on the specified cpu. .tp .br "pid > 0" " and " "cpu == \-1" this measures the specified process/thread on any cpu. .tp .br "pid > 0" " and " "cpu >= 0" this measures the specified process/thread only when running on the specified cpu. .tp .br "pid == \-1" " and " "cpu >= 0" this measures all processes/threads on the specified cpu. this requires .b cap_perfmon (since linux 5.8) or .b cap_sys_admin capability or a .i /proc/sys/kernel/perf_event_paranoid value of less than 1. .tp .br "pid == \-1" " and " "cpu == \-1" this setting is invalid and will return an error. .pp when .i pid is greater than zero, permission to perform this system call is governed by .b cap_perfmon (since linux 5.9) and a ptrace access mode .b ptrace_mode_read_realcreds check on older linux versions; see .br ptrace (2). .pp the .i group_fd argument allows event groups to be created. an event group has one event which is the group leader. the leader is created first, with .ir group_fd " = \-1." the rest of the group members are created with subsequent .br perf_event_open () calls with .i group_fd being set to the file descriptor of the group leader. (a single event on its own is created with .ir group_fd " = \-1" and is considered to be a group with only 1 member.) an event group is scheduled onto the cpu as a unit: it will be put onto the cpu only if all of the events in the group can be put onto the cpu. this means that the values of the member events can be meaningfully compared\(emadded, divided (to get ratios), and so on\(emwith each other, since they have counted events for the same set of executed instructions. .pp the .i flags argument is formed by oring together zero or more of the following values: .tp .br perf_flag_fd_cloexec " (since linux 3.14)" .\" commit a21b0b354d4ac39be691f51c53562e2c24443d9e this flag enables the close-on-exec flag for the created event file descriptor, so that the file descriptor is automatically closed on .br execve (2). setting the close-on-exec flags at creation time, rather than later with .br fcntl (2), avoids potential race conditions where the calling thread invokes .br perf_event_open () and .br fcntl (2) at the same time as another thread calls .br fork (2) then .br execve (2). .tp .br perf_flag_fd_no_group this flag tells the event to ignore the .i group_fd parameter except for the purpose of setting up output redirection using the .b perf_flag_fd_output flag. .tp .br perf_flag_fd_output " (broken since linux 2.6.35)" .\" commit ac9721f3f54b27a16c7e1afb2481e7ee95a70318 this flag re-routes the event's sampled output to instead be included in the mmap buffer of the event specified by .ir group_fd . .tp .br perf_flag_pid_cgroup " (since linux 2.6.39)" .\" commit e5d1367f17ba6a6fed5fd8b74e4d5720923e0c25 this flag activates per-container system-wide monitoring. a container is an abstraction that isolates a set of resources for finer-grained control (cpus, memory, etc.). in this mode, the event is measured only if the thread running on the monitored cpu belongs to the designated container (cgroup). the cgroup is identified by passing a file descriptor opened on its directory in the cgroupfs filesystem. for instance, if the cgroup to monitor is called .ir test , then a file descriptor opened on .i /dev/cgroup/test (assuming cgroupfs is mounted on .ir /dev/cgroup ) must be passed as the .i pid parameter. cgroup monitoring is available only for system-wide events and may therefore require extra permissions. .pp the .i perf_event_attr structure provides detailed configuration information for the event being created. .pp .in +4n .ex struct perf_event_attr { __u32 type; /* type of event */ __u32 size; /* size of attribute structure */ __u64 config; /* type\-specific configuration */ union { __u64 sample_period; /* period of sampling */ __u64 sample_freq; /* frequency of sampling */ }; __u64 sample_type; /* specifies values included in sample */ __u64 read_format; /* specifies values returned in read */ __u64 disabled : 1, /* off by default */ inherit : 1, /* children inherit it */ pinned : 1, /* must always be on pmu */ exclusive : 1, /* only group on pmu */ exclude_user : 1, /* don\(aqt count user */ exclude_kernel : 1, /* don\(aqt count kernel */ exclude_hv : 1, /* don\(aqt count hypervisor */ exclude_idle : 1, /* don\(aqt count when idle */ mmap : 1, /* include mmap data */ comm : 1, /* include comm data */ freq : 1, /* use freq, not period */ inherit_stat : 1, /* per task counts */ enable_on_exec : 1, /* next exec enables */ task : 1, /* trace fork/exit */ watermark : 1, /* wakeup_watermark */ precise_ip : 2, /* skid constraint */ mmap_data : 1, /* non\-exec mmap data */ sample_id_all : 1, /* sample_type all events */ exclude_host : 1, /* don\(aqt count in host */ exclude_guest : 1, /* don\(aqt count in guest */ exclude_callchain_kernel : 1, /* exclude kernel callchains */ exclude_callchain_user : 1, /* exclude user callchains */ mmap2 : 1, /* include mmap with inode data */ comm_exec : 1, /* flag comm events that are due to exec */ use_clockid : 1, /* use clockid for time fields */ context_switch : 1, /* context switch data */ write_backward : 1, /* write ring buffer from end to beginning */ namespaces : 1, /* include namespaces data */ ksymbol : 1, /* include ksymbol events */ bpf_event : 1, /* include bpf events */ aux_output : 1, /* generate aux records instead of events */ cgroup : 1, /* include cgroup events */ text_poke : 1, /* include text poke events */ __reserved_1 : 30; union { __u32 wakeup_events; /* wakeup every n events */ __u32 wakeup_watermark; /* bytes before wakeup */ }; __u32 bp_type; /* breakpoint type */ union { __u64 bp_addr; /* breakpoint address */ __u64 kprobe_func; /* for perf_kprobe */ __u64 uprobe_path; /* for perf_uprobe */ __u64 config1; /* extension of config */ }; union { __u64 bp_len; /* breakpoint length */ __u64 kprobe_addr; /* with kprobe_func == null */ __u64 probe_offset; /* for perf_[k,u]probe */ __u64 config2; /* extension of config1 */ }; __u64 branch_sample_type; /* enum perf_branch_sample_type */ __u64 sample_regs_user; /* user regs to dump on samples */ __u32 sample_stack_user; /* size of stack to dump on samples */ __s32 clockid; /* clock to use for time fields */ __u64 sample_regs_intr; /* regs to dump on samples */ __u32 aux_watermark; /* aux bytes before wakeup */ __u16 sample_max_stack; /* max frames in callchain */ __u16 __reserved_2; /* align to u64 */ }; .ee .in .pp the fields of the .i perf_event_attr structure are described in more detail below: .tp .i type this field specifies the overall event type. it has one of the following values: .rs .tp .b perf_type_hardware this indicates one of the "generalized" hardware events provided by the kernel. see the .i config field definition for more details. .tp .b perf_type_software this indicates one of the software-defined events provided by the kernel (even if no hardware support is available). .tp .b perf_type_tracepoint this indicates a tracepoint provided by the kernel tracepoint infrastructure. .tp .b perf_type_hw_cache this indicates a hardware cache event. this has a special encoding, described in the .i config field definition. .tp .b perf_type_raw this indicates a "raw" implementation-specific event in the .ir config " field." .tp .br perf_type_breakpoint " (since linux 2.6.33)" .\" commit 24f1e32c60c45c89a997c73395b69c8af6f0a84e this indicates a hardware breakpoint as provided by the cpu. breakpoints can be read/write accesses to an address as well as execution of an instruction address. .tp dynamic pmu since linux 2.6.38, .\" commit 2e80a82a49c4c7eca4e35734380f28298ba5db19 .br perf_event_open () can support multiple pmus. to enable this, a value exported by the kernel can be used in the .i type field to indicate which pmu to use. the value to use can be found in the sysfs filesystem: there is a subdirectory per pmu instance under .ir /sys/bus/event_source/devices . in each subdirectory there is a .i type file whose content is an integer that can be used in the .i type field. for instance, .i /sys/bus/event_source/devices/cpu/type contains the value for the core cpu pmu, which is usually 4. .tp .br kprobe " and " uprobe " (since linux 4.17)" .\" commit 65074d43fc77bcae32776724b7fa2696923c78e4 .\" commit e12f03d7031a977356e3d7b75a68c2185ff8d155 .\" commit 33ea4b24277b06dbc55d7f5772a46f029600255e these two dynamic pmus create a kprobe/uprobe and attach it to the file descriptor generated by perf_event_open. the kprobe/uprobe will be destroyed on the destruction of the file descriptor. see fields .ir kprobe_func , .ir uprobe_path , .ir kprobe_addr , and .i probe_offset for more details. .re .tp .i "size" the size of the .i perf_event_attr structure for forward/backward compatibility. set this using .i sizeof(struct perf_event_attr) to allow the kernel to see the struct size at the time of compilation. .ip the related define .b perf_attr_size_ver0 is set to 64; this was the size of the first published struct. .b perf_attr_size_ver1 is 72, corresponding to the addition of breakpoints in linux 2.6.33. .\" commit cb5d76999029ae7a517cb07dfa732c1b5a934fc2 .\" this was added much later when perf_attr_size_ver2 happened .\" but the actual attr_size had increased in 2.6.33 .b perf_attr_size_ver2 is 80 corresponding to the addition of branch sampling in linux 3.4. .\" commit cb5d76999029ae7a517cb07dfa732c1b5a934fc2 .b perf_attr_size_ver3 is 96 corresponding to the addition of .i sample_regs_user and .i sample_stack_user in linux 3.7. .\" commit 1659d129ed014b715b0b2120e6fd929bdd33ed03 .b perf_attr_size_ver4 is 104 corresponding to the addition of .i sample_regs_intr in linux 3.19. .\" commit 60e2364e60e86e81bc6377f49779779e6120977f .b perf_attr_size_ver5 is 112 corresponding to the addition of .i aux_watermark in linux 4.1. .\" commit 1a5941312414c71dece6717da9a0fa1303127afa .tp .i "config" this specifies which event you want, in conjunction with the .i type field. the .i config1 and .i config2 fields are also taken into account in cases where 64 bits is not enough to fully specify the event. the encoding of these fields are event dependent. .ip there are various ways to set the .i config field that are dependent on the value of the previously described .i type field. what follows are various possible settings for .i config separated out by .ir type . .ip if .i type is .br perf_type_hardware , we are measuring one of the generalized hardware cpu events. not all of these are available on all platforms. set .i config to one of the following: .rs 12 .tp .b perf_count_hw_cpu_cycles total cycles. be wary of what happens during cpu frequency scaling. .tp .b perf_count_hw_instructions retired instructions. be careful, these can be affected by various issues, most notably hardware interrupt counts. .tp .b perf_count_hw_cache_references cache accesses. usually this indicates last level cache accesses but this may vary depending on your cpu. this may include prefetches and coherency messages; again this depends on the design of your cpu. .tp .b perf_count_hw_cache_misses cache misses. usually this indicates last level cache misses; this is intended to be used in conjunction with the .b perf_count_hw_cache_references event to calculate cache miss rates. .tp .b perf_count_hw_branch_instructions retired branch instructions. prior to linux 2.6.35, this used the wrong event on amd processors. .\" commit f287d332ce835f77a4f5077d2c0ef1e3f9ea42d2 .tp .b perf_count_hw_branch_misses mispredicted branch instructions. .tp .b perf_count_hw_bus_cycles bus cycles, which can be different from total cycles. .tp .br perf_count_hw_stalled_cycles_frontend " (since linux 3.0)" .\" commit 8f62242246351b5a4bc0c1f00c0c7003edea128a stalled cycles during issue. .tp .br perf_count_hw_stalled_cycles_backend " (since linux 3.0)" .\" commit 8f62242246351b5a4bc0c1f00c0c7003edea128a stalled cycles during retirement. .tp .br perf_count_hw_ref_cpu_cycles " (since linux 3.3)" .\" commit c37e17497e01fc0f5d2d6feb5723b210b3ab8890 total cycles; not affected by cpu frequency scaling. .re .ip if .i type is .br perf_type_software , we are measuring software events provided by the kernel. set .i config to one of the following: .rs 12 .tp .b perf_count_sw_cpu_clock this reports the cpu clock, a high-resolution per-cpu timer. .tp .b perf_count_sw_task_clock this reports a clock count specific to the task that is running. .tp .b perf_count_sw_page_faults this reports the number of page faults. .tp .b perf_count_sw_context_switches this counts context switches. until linux 2.6.34, these were all reported as user-space events, after that they are reported as happening in the kernel. .\" commit e49a5bd38159dfb1928fd25b173bc9de4bbadb21 .tp .b perf_count_sw_cpu_migrations this reports the number of times the process has migrated to a new cpu. .tp .b perf_count_sw_page_faults_min this counts the number of minor page faults. these did not require disk i/o to handle. .tp .b perf_count_sw_page_faults_maj this counts the number of major page faults. these required disk i/o to handle. .tp .br perf_count_sw_alignment_faults " (since linux 2.6.33)" .\" commit f7d7986060b2890fc26db6ab5203efbd33aa2497 this counts the number of alignment faults. these happen when unaligned memory accesses happen; the kernel can handle these but it reduces performance. this happens only on some architectures (never on x86). .tp .br perf_count_sw_emulation_faults " (since linux 2.6.33)" .\" commit f7d7986060b2890fc26db6ab5203efbd33aa2497 this counts the number of emulation faults. the kernel sometimes traps on unimplemented instructions and emulates them for user space. this can negatively impact performance. .tp .br perf_count_sw_dummy " (since linux 3.12)" .\" commit fa0097ee690693006ab1aea6c01ad3c851b65c77 this is a placeholder event that counts nothing. informational sample record types such as mmap or comm must be associated with an active event. this dummy event allows gathering such records without requiring a counting event. .re .pp .rs if .i type is .br perf_type_tracepoint , then we are measuring kernel tracepoints. the value to use in .i config can be obtained from under debugfs .i tracing/events/*/*/id if ftrace is enabled in the kernel. .re .pp .rs if .i type is .br perf_type_hw_cache , then we are measuring a hardware cpu cache event. to calculate the appropriate .i config value, use the following equation: .rs 4 .pp .in +4n .ex config = (perf_hw_cache_id) | (perf_hw_cache_op_id << 8) | (perf_hw_cache_op_result_id << 16); .ee .in .pp where .i perf_hw_cache_id is one of: .rs 4 .tp .b perf_count_hw_cache_l1d for measuring level 1 data cache .tp .b perf_count_hw_cache_l1i for measuring level 1 instruction cache .tp .b perf_count_hw_cache_ll for measuring last-level cache .tp .b perf_count_hw_cache_dtlb for measuring the data tlb .tp .b perf_count_hw_cache_itlb for measuring the instruction tlb .tp .b perf_count_hw_cache_bpu for measuring the branch prediction unit .tp .br perf_count_hw_cache_node " (since linux 3.1)" .\" commit 89d6c0b5bdbb1927775584dcf532d98b3efe1477 for measuring local memory accesses .re .pp and .i perf_hw_cache_op_id is one of: .rs 4 .tp .b perf_count_hw_cache_op_read for read accesses .tp .b perf_count_hw_cache_op_write for write accesses .tp .b perf_count_hw_cache_op_prefetch for prefetch accesses .re .pp and .i perf_hw_cache_op_result_id is one of: .rs 4 .tp .b perf_count_hw_cache_result_access to measure accesses .tp .b perf_count_hw_cache_result_miss to measure misses .re .re .pp if .i type is .br perf_type_raw , then a custom "raw" .i config value is needed. most cpus support events that are not covered by the "generalized" events. these are implementation defined; see your cpu manual (for example the intel volume 3b documentation or the amd bios and kernel developer guide). the libpfm4 library can be used to translate from the name in the architectural manuals to the raw hex value .br perf_event_open () expects in this field. .pp if .i type is .br perf_type_breakpoint , then leave .i config set to zero. its parameters are set in other places. .pp if .i type is .b kprobe or .br uprobe , set .i retprobe (bit 0 of .ir config , see .ir /sys/bus/event_source/devices/[k,u]probe/format/retprobe ) for kretprobe/uretprobe. see fields .ir kprobe_func , .ir uprobe_path , .ir kprobe_addr , and .i probe_offset for more details. .re .tp .ir kprobe_func ", " uprobe_path ", " kprobe_addr ", and " probe_offset these fields describe the kprobe/uprobe for dynamic pmus .b kprobe and .br uprobe . for .br kprobe : use .i kprobe_func and .ir probe_offset , or use .i kprobe_addr and leave .i kprobe_func as null. for .br uprobe : use .i uprobe_path and .ir probe_offset . .tp .ir sample_period ", " sample_freq a "sampling" event is one that generates an overflow notification every n events, where n is given by .ir sample_period . a sampling event has .ir sample_period " > 0." when an overflow occurs, requested data is recorded in the mmap buffer. the .i sample_type field controls what data is recorded on each overflow. .ip .i sample_freq can be used if you wish to use frequency rather than period. in this case, you set the .i freq flag. the kernel will adjust the sampling period to try and achieve the desired rate. the rate of adjustment is a timer tick. .tp .i sample_type the various bits in this field specify which values to include in the sample. they will be recorded in a ring-buffer, which is available to user space using .br mmap (2). the order in which the values are saved in the sample are documented in the mmap layout subsection below; it is not the .i "enum perf_event_sample_format" order. .rs .tp .b perf_sample_ip records instruction pointer. .tp .b perf_sample_tid records the process and thread ids. .tp .b perf_sample_time records a timestamp. .tp .b perf_sample_addr records an address, if applicable. .tp .b perf_sample_read record counter values for all events in a group, not just the group leader. .tp .b perf_sample_callchain records the callchain (stack backtrace). .tp .b perf_sample_id records a unique id for the opened event's group leader. .tp .b perf_sample_cpu records cpu number. .tp .b perf_sample_period records the current sampling period. .tp .b perf_sample_stream_id records a unique id for the opened event. unlike .b perf_sample_id the actual id is returned, not the group leader. this id is the same as the one returned by .br perf_format_id . .tp .b perf_sample_raw records additional data, if applicable. usually returned by tracepoint events. .tp .br perf_sample_branch_stack " (since linux 3.4)" .\" commit bce38cd53e5ddba9cb6d708c4ef3d04a4016ec7e this provides a record of recent branches, as provided by cpu branch sampling hardware (such as intel last branch record). not all hardware supports this feature. .ip see the .i branch_sample_type field for how to filter which branches are reported. .tp .br perf_sample_regs_user " (since linux 3.7)" .\" commit 4018994f3d8785275ef0e7391b75c3462c029e56 records the current user-level cpu register state (the values in the process before the kernel was called). .tp .br perf_sample_stack_user " (since linux 3.7)" .\" commit c5ebcedb566ef17bda7b02686e0d658a7bb42ee7 records the user level stack, allowing stack unwinding. .tp .br perf_sample_weight " (since linux 3.10)" .\" commit c3feedf2aaf9ac8bad6f19f5d21e4ee0b4b87e9c records a hardware provided weight value that expresses how costly the sampled event was. this allows the hardware to highlight expensive events in a profile. .tp .br perf_sample_data_src " (since linux 3.10)" .\" commit d6be9ad6c960f43800a6f118932bc8a5a4eadcd1 records the data source: where in the memory hierarchy the data associated with the sampled instruction came from. this is available only if the underlying hardware supports this feature. .tp .br perf_sample_identifier " (since linux 3.12)" .\" commit ff3d527cebc1fa3707c617bfe9e74f53fcfb0955 places the .b sample_id value in a fixed position in the record, either at the beginning (for sample events) or at the end (if a non-sample event). .ip this was necessary because a sample stream may have records from various different event sources with different .i sample_type settings. parsing the event stream properly was not possible because the format of the record was needed to find .br sample_id , but the format could not be found without knowing what event the sample belonged to (causing a circular dependency). .ip the .b perf_sample_identifier setting makes the event stream always parsable by putting .b sample_id in a fixed location, even though it means having duplicate .b sample_id values in records. .tp .br perf_sample_transaction " (since linux 3.13)" .\" commit fdfbbd07e91f8fe387140776f3fd94605f0c89e5 records reasons for transactional memory abort events (for example, from intel tsx transactional memory support). .ip the .i precise_ip setting must be greater than 0 and a transactional memory abort event must be measured or no values will be recorded. also note that some perf_event measurements, such as sampled cycle counting, may cause extraneous aborts (by causing an interrupt during a transaction). .tp .br perf_sample_regs_intr " (since linux 3.19)" .\" commit 60e2364e60e86e81bc6377f49779779e6120977f records a subset of the current cpu register state as specified by .ir sample_regs_intr . unlike .b perf_sample_regs_user the register values will return kernel register state if the overflow happened while kernel code is running. if the cpu supports hardware sampling of register state (i.e., pebs on intel x86) and .i precise_ip is set higher than zero then the register values returned are those captured by hardware at the time of the sampled instruction's retirement. .tp .br perf_sample_phys_addr " (since linux 4.13)" .\" commit fc7ce9c74c3ad232b084d80148654f926d01ece7 records physical address of data like in .br perf_sample_addr . .tp .br perf_sample_cgroup " (since linux 5.7)" .\" commit 96aaab686505c449e24d76e76507290dcc30e008 records (perf_event) cgroup id of the process. this corresponds to the .i id field in the .b perf_record_cgroup event. .re .tp .i read_format this field specifies the format of the data returned by .br read (2) on a .br perf_event_open () file descriptor. .rs .tp .b perf_format_total_time_enabled adds the 64-bit .i time_enabled field. this can be used to calculate estimated totals if the pmu is overcommitted and multiplexing is happening. .tp .b perf_format_total_time_running adds the 64-bit .i time_running field. this can be used to calculate estimated totals if the pmu is overcommitted and multiplexing is happening. .tp .b perf_format_id adds a 64-bit unique value that corresponds to the event group. .tp .b perf_format_group allows all counter values in an event group to be read with one read. .re .tp .i disabled the .i disabled bit specifies whether the counter starts out disabled or enabled. if disabled, the event can later be enabled by .br ioctl (2), .br prctl (2), or .ir enable_on_exec . .ip when creating an event group, typically the group leader is initialized with .i disabled set to 1 and any child events are initialized with .i disabled set to 0. despite .i disabled being 0, the child events will not start until the group leader is enabled. .tp .i inherit the .i inherit bit specifies that this counter should count events of child tasks as well as the task specified. this applies only to new children, not to any existing children at the time the counter is created (nor to any new children of existing children). .ip inherit does not work for some combinations of .ir read_format values, such as .br perf_format_group . .tp .i pinned the .i pinned bit specifies that the counter should always be on the cpu if at all possible. it applies only to hardware counters and only to group leaders. if a pinned counter cannot be put onto the cpu (e.g., because there are not enough hardware counters or because of a conflict with some other event), then the counter goes into an 'error' state, where reads return end-of-file (i.e., .br read (2) returns 0) until the counter is subsequently enabled or disabled. .tp .i exclusive the .i exclusive bit specifies that when this counter's group is on the cpu, it should be the only group using the cpu's counters. in the future this may allow monitoring programs to support pmu features that need to run alone so that they do not disrupt other hardware counters. .ip note that many unexpected situations may prevent events with the .i exclusive bit set from ever running. this includes any users running a system-wide measurement as well as any kernel use of the performance counters (including the commonly enabled nmi watchdog timer interface). .tp .i exclude_user if this bit is set, the count excludes events that happen in user space. .tp .i exclude_kernel if this bit is set, the count excludes events that happen in kernel space. .tp .i exclude_hv if this bit is set, the count excludes events that happen in the hypervisor. this is mainly for pmus that have built-in support for handling this (such as power). extra support is needed for handling hypervisor measurements on most machines. .tp .i exclude_idle if set, don't count when the cpu is running the idle task. while you can currently enable this for any event type, it is ignored for all but software events. .tp .i mmap the .i mmap bit enables generation of .b perf_record_mmap samples for every .br mmap (2) call that has .b prot_exec set. this allows tools to notice new executable code being mapped into a program (dynamic shared libraries for example) so that addresses can be mapped back to the original code. .tp .i comm the .i comm bit enables tracking of process command name as modified by the .br execve (2) and .br prctl (pr_set_name) system calls as well as writing to .ir /proc/self/comm . if the .i comm_exec flag is also successfully set (possible since linux 3.16), .\" commit 82b897782d10fcc4930c9d4a15b175348fdd2871 then the misc flag .b perf_record_misc_comm_exec can be used to differentiate the .br execve (2) case from the others. .tp .i freq if this bit is set, then .i sample_frequency not .i sample_period is used when setting up the sampling interval. .tp .i inherit_stat this bit enables saving of event counts on context switch for inherited tasks. this is meaningful only if the .i inherit field is set. .tp .i enable_on_exec if this bit is set, a counter is automatically enabled after a call to .br execve (2). .tp .i task if this bit is set, then fork/exit notifications are included in the ring buffer. .tp .i watermark if set, have an overflow notification happen when we cross the .i wakeup_watermark boundary. otherwise, overflow notifications happen after .i wakeup_events samples. .tp .ir precise_ip " (since linux 2.6.35)" .\" commit ab608344bcbde4f55ec4cd911b686b0ce3eae076 this controls the amount of skid. skid is how many instructions execute between an event of interest happening and the kernel being able to stop and record the event. smaller skid is better and allows more accurate reporting of which events correspond to which instructions, but hardware is often limited with how small this can be. .ip the possible values of this field are the following: .rs .ip 0 3 .b sample_ip can have arbitrary skid. .ip 1 .b sample_ip must have constant skid. .ip 2 .b sample_ip requested to have 0 skid. .ip 3 .b sample_ip must have 0 skid. see also the description of .br perf_record_misc_exact_ip . .re .tp .ir mmap_data " (since linux 2.6.36)" .\" commit 3af9e859281bda7eb7c20b51879cf43aa788ac2e this is the counterpart of the .i mmap field. this enables generation of .b perf_record_mmap samples for .br mmap (2) calls that do not have .b prot_exec set (for example data and sysv shared memory). .tp .ir sample_id_all " (since linux 2.6.38)" .\" commit c980d1091810df13f21aabbce545fd98f545bbf7 if set, then tid, time, id, stream_id, and cpu can additionally be included in .rb non- perf_record_sample s if the corresponding .i sample_type is selected. .ip if .b perf_sample_identifier is specified, then an additional id value is included as the last value to ease parsing the record stream. this may lead to the .i id value appearing twice. .ip the layout is described by this pseudo-structure: .ip .in +4n .ex struct sample_id { { u32 pid, tid; } /* if perf_sample_tid set */ { u64 time; } /* if perf_sample_time set */ { u64 id; } /* if perf_sample_id set */ { u64 stream_id;} /* if perf_sample_stream_id set */ { u32 cpu, res; } /* if perf_sample_cpu set */ { u64 id; } /* if perf_sample_identifier set */ }; .ee .in .tp .ir exclude_host " (since linux 3.2)" .\" commit a240f76165e6255384d4bdb8139895fac7988799 when conducting measurements that include processes running vm instances (i.e., have executed a .b kvm_run .br ioctl (2)), only measure events happening inside a guest instance. this is only meaningful outside the guests; this setting does not change counts gathered inside of a guest. currently, this functionality is x86 only. .tp .ir exclude_guest " (since linux 3.2)" .\" commit a240f76165e6255384d4bdb8139895fac7988799 when conducting measurements that include processes running vm instances (i.e., have executed a .b kvm_run .br ioctl (2)), do not measure events happening inside guest instances. this is only meaningful outside the guests; this setting does not change counts gathered inside of a guest. currently, this functionality is x86 only. .tp .ir exclude_callchain_kernel " (since linux 3.7)" .\" commit d077526485d5c9b12fe85d0b2b3b7041e6bc5f91 do not include kernel callchains. .tp .ir exclude_callchain_user " (since linux 3.7)" .\" commit d077526485d5c9b12fe85d0b2b3b7041e6bc5f91 do not include user callchains. .tp .ir mmap2 " (since linux 3.16)" .\" commit 13d7a2410fa637f450a29ecb515ac318ee40c741 .\" this is tricky; was committed during 3.12 development .\" but right before release was disabled. .\" so while you could select mmap2 starting with 3.12 .\" it did not work until 3.16 .\" commit a5a5ba72843dd05f991184d6cb9a4471acce1005 generate an extended executable mmap record that contains enough additional information to uniquely identify shared mappings. the .i mmap flag must also be set for this to work. .tp .ir comm_exec " (since linux 3.16)" .\" commit 82b897782d10fcc4930c9d4a15b175348fdd2871 this is purely a feature-detection flag, it does not change kernel behavior. if this flag can successfully be set, then, when .i comm is enabled, the .b perf_record_misc_comm_exec flag will be set in the .i misc field of a comm record header if the rename event being reported was caused by a call to .br execve (2). this allows tools to distinguish between the various types of process renaming. .tp .ir use_clockid " (since linux 4.1)" .\" commit 34f439278cef7b1177f8ce24f9fc81dfc6221d3b this allows selecting which internal linux clock to use when generating timestamps via the .i clockid field. this can make it easier to correlate perf sample times with timestamps generated by other tools. .tp .ir context_switch " (since linux 4.3)" .\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 this enables the generation of .b perf_record_switch records when a context switch occurs. it also enables the generation of .b perf_record_switch_cpu_wide records when sampling in cpu-wide mode. this functionality is in addition to existing tracepoint and software events for measuring context switches. the advantage of this method is that it will give full information even with strict .i perf_event_paranoid settings. .tp .ir write_backward " (since linux 4.6)" .\" commit 9ecda41acb971ebd07c8fb35faf24005c0baea12 this causes the ring buffer to be written from the end to the beginning. this is to support reading from overwritable ring buffer. .tp .ir namespaces " (since linux 4.11)" .\" commit e422267322cd319e2695a535e47c5b1feeac45eb this enables the generation of .b perf_record_namespaces records when a task enters a new namespace. each namespace has a combination of device and inode numbers. .tp .ir ksymbol " (since linux 5.0)" .\" commit 76193a94522f1d4edf2447a536f3f796ce56343b this enables the generation of .b perf_record_ksymbol records when new kernel symbols are registered or unregistered. this is analyzing dynamic kernel functions like ebpf. .tp .ir bpf_event " (since linux 5.0)" .\" commit 6ee52e2a3fe4ea35520720736e6791df1fb67106 this enables the generation of .b perf_record_bpf_event records when an ebpf program is loaded or unloaded. .tp .ir auxevent " (since linux 5.4)" .\" commit ab43762ef010967e4ccd53627f70a2eecbeafefb this allows normal (non-aux) events to generate data for aux events if the hardware supports it. .tp .ir cgroup " (since linux 5.7)" .\" commit 96aaab686505c449e24d76e76507290dcc30e008 this enables the generation of .b perf_record_cgroup records when a new cgroup is created (and activated). .tp .ir text_poke " (since linux 5.8)" .\" commit e17d43b93e544f5016c0251d2074c15568d5d963 this enables the generation of .b perf_record_text_poke records when there's a change to the kernel text (i.e., self-modifying code). .tp .ir wakeup_events ", " wakeup_watermark this union sets how many samples .ri ( wakeup_events ) or bytes .ri ( wakeup_watermark ) happen before an overflow notification happens. which one is used is selected by the .i watermark bit flag. .ip .i wakeup_events counts only .b perf_record_sample record types. to receive overflow notification for all .b perf_record types choose watermark and set .i wakeup_watermark to 1. .ip prior to linux 3.0, setting .\" commit f506b3dc0ec454a16d40cab9ee5d75435b39dc50 .i wakeup_events to 0 resulted in no overflow notifications; more recent kernels treat 0 the same as 1. .tp .ir bp_type " (since linux 2.6.33)" .\" commit 24f1e32c60c45c89a997c73395b69c8af6f0a84e this chooses the breakpoint type. it is one of: .rs .tp .b hw_breakpoint_empty no breakpoint. .tp .b hw_breakpoint_r count when we read the memory location. .tp .b hw_breakpoint_w count when we write the memory location. .tp .b hw_breakpoint_rw count when we read or write the memory location. .tp .b hw_breakpoint_x count when we execute code at the memory location. .pp the values can be combined via a bitwise or, but the combination of .b hw_breakpoint_r or .b hw_breakpoint_w with .b hw_breakpoint_x is not allowed. .re .tp .ir bp_addr " (since linux 2.6.33)" .\" commit 24f1e32c60c45c89a997c73395b69c8af6f0a84e this is the address of the breakpoint. for execution breakpoints, this is the memory address of the instruction of interest; for read and write breakpoints, it is the memory address of the memory location of interest. .tp .ir config1 " (since linux 2.6.39)" .\" commit a7e3ed1e470116c9d12c2f778431a481a6be8ab6 .i config1 is used for setting events that need an extra register or otherwise do not fit in the regular config field. raw offcore_events on nehalem/westmere/sandybridge use this field on linux 3.3 and later kernels. .tp .ir bp_len " (since linux 2.6.33)" .\" commit 24f1e32c60c45c89a997c73395b69c8af6f0a84e .i bp_len is the length of the breakpoint being measured if .i type is .br perf_type_breakpoint . options are .br hw_breakpoint_len_1 , .br hw_breakpoint_len_2 , .br hw_breakpoint_len_4 , and .br hw_breakpoint_len_8 . for an execution breakpoint, set this to .ir sizeof(long) . .tp .ir config2 " (since linux 2.6.39)" .\" commit a7e3ed1e470116c9d12c2f778431a481a6be8ab6 .i config2 is a further extension of the .i config1 field. .tp .ir branch_sample_type " (since linux 3.4)" .\" commit bce38cd53e5ddba9cb6d708c4ef3d04a4016ec7e if .b perf_sample_branch_stack is enabled, then this specifies what branches to include in the branch record. .ip the first part of the value is the privilege level, which is a combination of one of the values listed below. if the user does not set privilege level explicitly, the kernel will use the event's privilege level. event and branch privilege levels do not have to match. .rs .tp .b perf_sample_branch_user branch target is in user space. .tp .b perf_sample_branch_kernel branch target is in kernel space. .tp .b perf_sample_branch_hv branch target is in hypervisor. .tp .b perf_sample_branch_plm_all a convenience value that is the three preceding values ored together. .pp in addition to the privilege value, at least one or more of the following bits must be set. .tp .b perf_sample_branch_any any branch type. .tp .b perf_sample_branch_any_call any call branch (includes direct calls, indirect calls, and far jumps). .tp .b perf_sample_branch_ind_call indirect calls. .tp .br perf_sample_branch_call " (since linux 4.4)" .\" commit c229bf9dc179d2023e185c0f705bdf68484c1e73 direct calls. .tp .b perf_sample_branch_any_return any return branch. .tp .br perf_sample_branch_ind_jump " (since linux 4.2)" .\" commit c9fdfa14c3792c0160849c484e83aa57afd80ccc indirect jumps. .tp .br perf_sample_branch_cond " (since linux 3.16)" .\" commit bac52139f0b7ab31330e98fd87fc5a2664951050 conditional branches. .tp .br perf_sample_branch_abort_tx " (since linux 3.11)" .\" commit 135c5612c460f89657c4698fe2ea753f6f667963 transactional memory aborts. .tp .br perf_sample_branch_in_tx " (since linux 3.11)" .\" commit 135c5612c460f89657c4698fe2ea753f6f667963 branch in transactional memory transaction. .tp .br perf_sample_branch_no_tx " (since linux 3.11)" .\" commit 135c5612c460f89657c4698fe2ea753f6f667963 branch not in transactional memory transaction. .br perf_sample_branch_call_stack " (since linux 4.1)" .\" commit 2c44b1936bb3b135a3fac8b3493394d42e51cf70 branch is part of a hardware-generated call stack. this requires hardware support, currently only found on intel x86 haswell or newer. .re .tp .ir sample_regs_user " (since linux 3.7)" .\" commit 4018994f3d8785275ef0e7391b75c3462c029e56 this bit mask defines the set of user cpu registers to dump on samples. the layout of the register mask is architecture-specific and is described in the kernel header file .ir arch/arch/include/uapi/asm/perf_regs.h . .tp .ir sample_stack_user " (since linux 3.7)" .\" commit c5ebcedb566ef17bda7b02686e0d658a7bb42ee7 this defines the size of the user stack to dump if .b perf_sample_stack_user is specified. .tp .ir clockid " (since linux 4.1)" .\" commit 34f439278cef7b1177f8ce24f9fc81dfc6221d3b if .i use_clockid is set, then this field selects which internal linux timer to use for timestamps. the available timers are defined in .ir linux/time.h , with .br clock_monotonic , .br clock_monotonic_raw , .br clock_realtime , .br clock_boottime , and .b clock_tai currently supported. .tp .ir aux_watermark " (since linux 4.1)" .\" commit 1a5941312414c71dece6717da9a0fa1303127afa this specifies how much data is required to trigger a .b perf_record_aux sample. .tp .ir sample_max_stack " (since linux 4.8)" .\" commit 97c79a38cd454602645f0470ffb444b3b75ce574 when .i sample_type includes .br perf_sample_callchain , this field specifies how many stack frames to report when generating the callchain. .ss reading results once a .br perf_event_open () file descriptor has been opened, the values of the events can be read from the file descriptor. the values that are there are specified by the .i read_format field in the .i attr structure at open time. .pp if you attempt to read into a buffer that is not big enough to hold the data, the error .b enospc results. .pp here is the layout of the data returned by a read: .ip * 2 if .b perf_format_group was specified to allow reading all events in a group at once: .ip .in +4n .ex struct read_format { u64 nr; /* the number of events */ u64 time_enabled; /* if perf_format_total_time_enabled */ u64 time_running; /* if perf_format_total_time_running */ struct { u64 value; /* the value of the event */ u64 id; /* if perf_format_id */ } values[nr]; }; .ee .in .ip * if .b perf_format_group was .i not specified: .ip .in +4n .ex struct read_format { u64 value; /* the value of the event */ u64 time_enabled; /* if perf_format_total_time_enabled */ u64 time_running; /* if perf_format_total_time_running */ u64 id; /* if perf_format_id */ }; .ee .in .pp the values read are as follows: .tp .i nr the number of events in this file descriptor. available only if .b perf_format_group was specified. .tp .ir time_enabled ", " time_running total time the event was enabled and running. normally these values are the same. multiplexing happens if the number of events is more than the number of available pmu counter slots. in that case the events run only part of the time and the .i time_enabled and .i time running values can be used to scale an estimated value for the count. .tp .i value an unsigned 64-bit value containing the counter result. .tp .i id a globally unique value for this particular event; only present if .b perf_format_id was specified in .ir read_format . .ss mmap layout when using .br perf_event_open () in sampled mode, asynchronous events (like counter overflow or .b prot_exec mmap tracking) are logged into a ring-buffer. this ring-buffer is created and accessed through .br mmap (2). .pp the mmap size should be 1+2^n pages, where the first page is a metadata page .ri ( "struct perf_event_mmap_page" ) that contains various bits of information such as where the ring-buffer head is. .pp before kernel 2.6.39, there is a bug that means you must allocate an mmap ring buffer when sampling even if you do not plan to access it. .pp the structure of the first metadata mmap page is as follows: .pp .in +4n .ex struct perf_event_mmap_page { __u32 version; /* version number of this structure */ __u32 compat_version; /* lowest version this is compat with */ __u32 lock; /* seqlock for synchronization */ __u32 index; /* hardware counter identifier */ __s64 offset; /* add to hardware counter value */ __u64 time_enabled; /* time event active */ __u64 time_running; /* time event on cpu */ union { __u64 capabilities; struct { __u64 cap_usr_time / cap_usr_rdpmc / cap_bit0 : 1, cap_bit0_is_deprecated : 1, cap_user_rdpmc : 1, cap_user_time : 1, cap_user_time_zero : 1, }; }; __u16 pmc_width; __u16 time_shift; __u32 time_mult; __u64 time_offset; __u64 __reserved[120]; /* pad to 1 k */ __u64 data_head; /* head in the data section */ __u64 data_tail; /* user\-space written tail */ __u64 data_offset; /* where the buffer starts */ __u64 data_size; /* data buffer size */ __u64 aux_head; __u64 aux_tail; __u64 aux_offset; __u64 aux_size; } .ee .in .pp the following list describes the fields in the .i perf_event_mmap_page structure in more detail: .tp .i version version number of this structure. .tp .i compat_version the lowest version this is compatible with. .tp .i lock a seqlock for synchronization. .tp .i index a unique hardware counter identifier. .tp .i offset when using rdpmc for reads this offset value must be added to the one returned by rdpmc to get the current total event count. .tp .i time_enabled time the event was active. .tp .i time_running time the event was running. .tp .ir cap_usr_time " / " cap_usr_rdpmc " / " cap_bit0 " (since linux 3.4)" .\" commit c7206205d00ab375839bd6c7ddb247d600693c09 there was a bug in the definition of .i cap_usr_time and .i cap_usr_rdpmc from linux 3.4 until linux 3.11. both bits were defined to point to the same location, so it was impossible to know if .i cap_usr_time or .i cap_usr_rdpmc were actually set. .ip starting with linux 3.12, these are renamed to .\" commit fa7315871046b9a4c48627905691dbde57e51033 .i cap_bit0 and you should use the .i cap_user_time and .i cap_user_rdpmc fields instead. .tp .ir cap_bit0_is_deprecated " (since linux 3.12)" .\" commit fa7315871046b9a4c48627905691dbde57e51033 if set, this bit indicates that the kernel supports the properly separated .i cap_user_time and .i cap_user_rdpmc bits. .ip if not-set, it indicates an older kernel where .i cap_usr_time and .i cap_usr_rdpmc map to the same bit and thus both features should be used with caution. .tp .ir cap_user_rdpmc " (since linux 3.12)" .\" commit fa7315871046b9a4c48627905691dbde57e51033 if the hardware supports user-space read of performance counters without syscall (this is the "rdpmc" instruction on x86), then the following code can be used to do a read: .ip .in +4n .ex u32 seq, time_mult, time_shift, idx, width; u64 count, enabled, running; u64 cyc, time_offset; do { seq = pc\->lock; barrier(); enabled = pc\->time_enabled; running = pc\->time_running; if (pc\->cap_usr_time && enabled != running) { cyc = rdtsc(); time_offset = pc\->time_offset; time_mult = pc\->time_mult; time_shift = pc\->time_shift; } idx = pc\->index; count = pc\->offset; if (pc\->cap_usr_rdpmc && idx) { width = pc\->pmc_width; count += rdpmc(idx \- 1); } barrier(); } while (pc\->lock != seq); .ee .in .tp .ir cap_user_time " (since linux 3.12)" .\" commit fa7315871046b9a4c48627905691dbde57e51033 this bit indicates the hardware has a constant, nonstop timestamp counter (tsc on x86). .tp .ir cap_user_time_zero " (since linux 3.12)" .\" commit fa7315871046b9a4c48627905691dbde57e51033 indicates the presence of .i time_zero which allows mapping timestamp values to the hardware clock. .tp .i pmc_width if .ir cap_usr_rdpmc , this field provides the bit-width of the value read using the rdpmc or equivalent instruction. this can be used to sign extend the result like: .ip .in +4n .ex pmc <<= 64 \- pmc_width; pmc >>= 64 \- pmc_width; // signed shift right count += pmc; .ee .in .tp .ir time_shift ", " time_mult ", " time_offset .ip if .ir cap_usr_time , these fields can be used to compute the time delta since .i time_enabled (in nanoseconds) using rdtsc or similar. .ip .in +4n .ex u64 quot, rem; u64 delta; quot = cyc >> time_shift; rem = cyc & (((u64)1 << time_shift) \- 1); delta = time_offset + quot * time_mult + ((rem * time_mult) >> time_shift); .ee .in .ip where .ir time_offset , .ir time_mult , .ir time_shift , and .i cyc are read in the seqcount loop described above. this delta can then be added to enabled and possible running (if idx), improving the scaling: .ip .in +4n .ex enabled += delta; if (idx) running += delta; quot = count / running; rem = count % running; count = quot * enabled + (rem * enabled) / running; .ee .in .tp .ir time_zero " (since linux 3.12)" .\" commit fa7315871046b9a4c48627905691dbde57e51033 .ip if .i cap_usr_time_zero is set, then the hardware clock (the tsc timestamp counter on x86) can be calculated from the .ir time_zero , .ir time_mult , and .i time_shift values: .ip .in +4n .ex time = timestamp \- time_zero; quot = time / time_mult; rem = time % time_mult; cyc = (quot << time_shift) + (rem << time_shift) / time_mult; .ee .in .ip and vice versa: .ip .in +4n .ex quot = cyc >> time_shift; rem = cyc & (((u64)1 << time_shift) \- 1); timestamp = time_zero + quot * time_mult + ((rem * time_mult) >> time_shift); .ee .in .tp .i data_head this points to the head of the data section. the value continuously increases, it does not wrap. the value needs to be manually wrapped by the size of the mmap buffer before accessing the samples. .ip on smp-capable platforms, after reading the .i data_head value, user space should issue an rmb(). .tp .i data_tail when the mapping is .br prot_write , the .i data_tail value should be written by user space to reflect the last read data. in this case, the kernel will not overwrite unread data. .tp .ir data_offset " (since linux 4.1)" .\" commit e8c6deac69629c0cb97c3d3272f8631ef17f8f0f contains the offset of the location in the mmap buffer where perf sample data begins. .tp .ir data_size " (since linux 4.1)" .\" commit e8c6deac69629c0cb97c3d3272f8631ef17f8f0f contains the size of the perf sample region within the mmap buffer. .tp .ir aux_head ", " aux_tail ", " aux_offset ", " aux_size " (since linux 4.1)" .\" commit 45bfb2e50471abbbfd83d40d28c986078b0d24ff the aux region allows .br mmap (2)-ing a separate sample buffer for high-bandwidth data streams (separate from the main perf sample buffer). an example of a high-bandwidth stream is instruction tracing support, as is found in newer intel processors. .ip to set up an aux area, first .i aux_offset needs to be set with an offset greater than .ir data_offset + data_size and .i aux_size needs to be set to the desired buffer size. the desired offset and size must be page aligned, and the size must be a power of two. these values are then passed to mmap in order to map the aux buffer. pages in the aux buffer are included as part of the .b rlimit_memlock resource limit (see .br setrlimit (2)), and also as part of the .i perf_event_mlock_kb allowance. .ip by default, the aux buffer will be truncated if it will not fit in the available space in the ring buffer. if the aux buffer is mapped as a read only buffer, then it will operate in ring buffer mode where old data will be overwritten by new. in overwrite mode, it might not be possible to infer where the new data began, and it is the consumer's job to disable measurement while reading to avoid possible data races. .ip the .i aux_head and .i aux_tail ring buffer pointers have the same behavior and ordering rules as the previous described .i data_head and .ir data_tail . .pp the following 2^n ring-buffer pages have the layout described below. .pp if .i perf_event_attr.sample_id_all is set, then all event types will have the sample_type selected fields related to where/when (identity) an event took place (tid, time, id, cpu, stream_id) described in .b perf_record_sample below, it will be stashed just after the .i perf_event_header and the fields already present for the existing fields, that is, at the end of the payload. this allows a newer perf.data file to be supported by older perf tools, with the new optional fields being ignored. .pp the mmap values start with a header: .pp .in +4n .ex struct perf_event_header { __u32 type; __u16 misc; __u16 size; }; .ee .in .pp below, we describe the .i perf_event_header fields in more detail. for ease of reading, the fields with shorter descriptions are presented first. .tp .i size this indicates the size of the record. .tp .i misc the .i misc field contains additional information about the sample. .ip the cpu mode can be determined from this value by masking with .b perf_record_misc_cpumode_mask and looking for one of the following (note these are not bit masks, only one can be set at a time): .rs .tp .b perf_record_misc_cpumode_unknown unknown cpu mode. .tp .b perf_record_misc_kernel sample happened in the kernel. .tp .b perf_record_misc_user sample happened in user code. .tp .b perf_record_misc_hypervisor sample happened in the hypervisor. .tp .br perf_record_misc_guest_kernel " (since linux 2.6.35)" .\" commit 39447b386c846bbf1c56f6403c5282837486200f sample happened in the guest kernel. .tp .b perf_record_misc_guest_user " (since linux 2.6.35)" .\" commit 39447b386c846bbf1c56f6403c5282837486200f sample happened in guest user code. .re .pp .rs since the following three statuses are generated by different record types, they alias to the same bit: .tp .br perf_record_misc_mmap_data " (since linux 3.10)" .\" commit 2fe85427e3bf65d791700d065132772fc26e4d75 this is set when the mapping is not executable; otherwise the mapping is executable. .tp .br perf_record_misc_comm_exec " (since linux 3.16)" .\" commit 82b897782d10fcc4930c9d4a15b175348fdd2871 this is set for a .b perf_record_comm record on kernels more recent than linux 3.16 if a process name change was caused by an .br execve (2) system call. .tp .br perf_record_misc_switch_out " (since linux 4.3)" .\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 when a .b perf_record_switch or .b perf_record_switch_cpu_wide record is generated, this bit indicates that the context switch is away from the current process (instead of into the current process). .re .pp .rs in addition, the following bits can be set: .tp .b perf_record_misc_exact_ip this indicates that the content of .b perf_sample_ip points to the actual instruction that triggered the event. see also .ir perf_event_attr.precise_ip . .tp .br perf_record_misc_ext_reserved " (since linux 2.6.35)" .\" commit 1676b8a077c352085d52578fb4f29350b58b6e74 this indicates there is extended data available (currently not used). .tp .b perf_record_misc_proc_map_parse_timeout .\" commit 930e6fcd2bcce9bcd9d4aa7e755678d33f3fe6f4 this bit is not set by the kernel. it is reserved for the user-space perf utility to indicate that .i /proc/i[pid]/maps parsing was taking too long and was stopped, and thus the mmap records may be truncated. .re .tp .i type the .i type value is one of the below. the values in the corresponding record (that follows the header) depend on the .i type selected as shown. .rs .tp 4 .b perf_record_mmap the mmap events record the .b prot_exec mappings so that we can correlate user-space ips to code. they have the following structure: .ip .in +4n .ex struct { struct perf_event_header header; u32 pid, tid; u64 addr; u64 len; u64 pgoff; char filename[]; }; .ee .in .rs .tp .i pid is the process id. .tp .i tid is the thread id. .tp .i addr is the address of the allocated memory. .i len is the length of the allocated memory. .i pgoff is the page offset of the allocated memory. .i filename is a string describing the backing of the allocated memory. .re .tp .b perf_record_lost this record indicates when events are lost. .ip .in +4n .ex struct { struct perf_event_header header; u64 id; u64 lost; struct sample_id sample_id; }; .ee .in .rs .tp .i id is the unique event id for the samples that were lost. .tp .i lost is the number of events that were lost. .re .tp .b perf_record_comm this record indicates a change in the process name. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid; u32 tid; char comm[]; struct sample_id sample_id; }; .ee .in .rs .tp .i pid is the process id. .tp .i tid is the thread id. .tp .i comm is a string containing the new name of the process. .re .tp .b perf_record_exit this record indicates a process exit event. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid, ppid; u32 tid, ptid; u64 time; struct sample_id sample_id; }; .ee .in .tp .br perf_record_throttle ", " perf_record_unthrottle this record indicates a throttle/unthrottle event. .ip .in +4n .ex struct { struct perf_event_header header; u64 time; u64 id; u64 stream_id; struct sample_id sample_id; }; .ee .in .tp .b perf_record_fork this record indicates a fork event. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid, ppid; u32 tid, ptid; u64 time; struct sample_id sample_id; }; .ee .in .tp .b perf_record_read this record indicates a read event. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid, tid; struct read_format values; struct sample_id sample_id; }; .ee .in .tp .b perf_record_sample this record indicates a sample. .ip .in +4n .ex struct { struct perf_event_header header; u64 sample_id; /* if perf_sample_identifier */ u64 ip; /* if perf_sample_ip */ u32 pid, tid; /* if perf_sample_tid */ u64 time; /* if perf_sample_time */ u64 addr; /* if perf_sample_addr */ u64 id; /* if perf_sample_id */ u64 stream_id; /* if perf_sample_stream_id */ u32 cpu, res; /* if perf_sample_cpu */ u64 period; /* if perf_sample_period */ struct read_format v; /* if perf_sample_read */ u64 nr; /* if perf_sample_callchain */ u64 ips[nr]; /* if perf_sample_callchain */ u32 size; /* if perf_sample_raw */ char data[size]; /* if perf_sample_raw */ u64 bnr; /* if perf_sample_branch_stack */ struct perf_branch_entry lbr[bnr]; /* if perf_sample_branch_stack */ u64 abi; /* if perf_sample_regs_user */ u64 regs[weight(mask)]; /* if perf_sample_regs_user */ u64 size; /* if perf_sample_stack_user */ char data[size]; /* if perf_sample_stack_user */ u64 dyn_size; /* if perf_sample_stack_user && size != 0 */ u64 weight; /* if perf_sample_weight */ u64 data_src; /* if perf_sample_data_src */ u64 transaction; /* if perf_sample_transaction */ u64 abi; /* if perf_sample_regs_intr */ u64 regs[weight(mask)]; /* if perf_sample_regs_intr */ u64 phys_addr; /* if perf_sample_phys_addr */ u64 cgroup; /* if perf_sample_cgroup */ }; .ee .in .rs 4 .tp 4 .i sample_id if .b perf_sample_identifier is enabled, a 64-bit unique id is included. this is a duplication of the .b perf_sample_id .i id value, but included at the beginning of the sample so parsers can easily obtain the value. .tp .i ip if .b perf_sample_ip is enabled, then a 64-bit instruction pointer value is included. .tp .ir pid ", " tid if .b perf_sample_tid is enabled, then a 32-bit process id and 32-bit thread id are included. .tp .i time if .b perf_sample_time is enabled, then a 64-bit timestamp is included. this is obtained via local_clock() which is a hardware timestamp if available and the jiffies value if not. .tp .i addr if .b perf_sample_addr is enabled, then a 64-bit address is included. this is usually the address of a tracepoint, breakpoint, or software event; otherwise the value is 0. .tp .i id if .b perf_sample_id is enabled, a 64-bit unique id is included. if the event is a member of an event group, the group leader id is returned. this id is the same as the one returned by .br perf_format_id . .tp .i stream_id if .b perf_sample_stream_id is enabled, a 64-bit unique id is included. unlike .b perf_sample_id the actual id is returned, not the group leader. this id is the same as the one returned by .br perf_format_id . .tp .ir cpu ", " res if .b perf_sample_cpu is enabled, this is a 32-bit value indicating which cpu was being used, in addition to a reserved (unused) 32-bit value. .tp .i period if .b perf_sample_period is enabled, a 64-bit value indicating the current sampling period is written. .tp .i v if .b perf_sample_read is enabled, a structure of type read_format is included which has values for all events in the event group. the values included depend on the .i read_format value used at .br perf_event_open () time. .tp .ir nr ", " ips[nr] if .b perf_sample_callchain is enabled, then a 64-bit number is included which indicates how many following 64-bit instruction pointers will follow. this is the current callchain. .tp .ir size ", " data[size] if .b perf_sample_raw is enabled, then a 32-bit value indicating size is included followed by an array of 8-bit values of length size. the values are padded with 0 to have 64-bit alignment. .ip this raw record data is opaque with respect to the abi. the abi doesn't make any promises with respect to the stability of its content, it may vary depending on event, hardware, and kernel version. .tp .ir bnr ", " lbr[bnr] if .b perf_sample_branch_stack is enabled, then a 64-bit value indicating the number of records is included, followed by .i bnr .i perf_branch_entry structures which each include the fields: .rs .tp .i from this indicates the source instruction (may not be a branch). .tp .i to the branch target. .tp .i mispred the branch target was mispredicted. .tp .i predicted the branch target was predicted. .tp .ir in_tx " (since linux 3.11)" .\" commit 135c5612c460f89657c4698fe2ea753f6f667963 the branch was in a transactional memory transaction. .tp .ir abort " (since linux 3.11)" .\" commit 135c5612c460f89657c4698fe2ea753f6f667963 the branch was in an aborted transactional memory transaction. .tp .ir cycles " (since linux 4.3)" .\" commit 71ef3c6b9d4665ee7afbbe4c208a98917dcfc32f this reports the number of cycles elapsed since the previous branch stack update. .pp the entries are from most to least recent, so the first entry has the most recent branch. .pp support for .ir mispred , .ir predicted , and .i cycles is optional; if not supported, those values will be 0. .pp the type of branches recorded is specified by the .i branch_sample_type field. .re .tp .ir abi ", " regs[weight(mask)] if .b perf_sample_regs_user is enabled, then the user cpu registers are recorded. .ip the .i abi field is one of .br perf_sample_regs_abi_none , .br perf_sample_regs_abi_32 , or .br perf_sample_regs_abi_64 . .ip the .i regs field is an array of the cpu registers that were specified by the .i sample_regs_user attr field. the number of values is the number of bits set in the .i sample_regs_user bit mask. .tp .ir size ", " data[size] ", " dyn_size if .b perf_sample_stack_user is enabled, then the user stack is recorded. this can be used to generate stack backtraces. .i size is the size requested by the user in .i sample_stack_user or else the maximum record size. .i data is the stack data (a raw dump of the memory pointed to by the stack pointer at the time of sampling). .i dyn_size is the amount of data actually dumped (can be less than .ir size ). note that .i dyn_size is omitted if .i size is 0. .tp .i weight if .b perf_sample_weight is enabled, then a 64-bit value provided by the hardware is recorded that indicates how costly the event was. this allows expensive events to stand out more clearly in profiles. .tp .i data_src if .b perf_sample_data_src is enabled, then a 64-bit value is recorded that is made up of the following fields: .rs .tp 4 .i mem_op type of opcode, a bitwise combination of: .ip .pd 0 .rs .tp 24 .b perf_mem_op_na not available .tp .b perf_mem_op_load load instruction .tp .b perf_mem_op_store store instruction .tp .b perf_mem_op_pfetch prefetch .tp .b perf_mem_op_exec executable code .re .pd .tp .i mem_lvl memory hierarchy level hit or miss, a bitwise combination of the following, shifted left by .br perf_mem_lvl_shift : .ip .pd 0 .rs .tp 24 .b perf_mem_lvl_na not available .tp .b perf_mem_lvl_hit hit .tp .b perf_mem_lvl_miss miss .tp .b perf_mem_lvl_l1 level 1 cache .tp .b perf_mem_lvl_lfb line fill buffer .tp .b perf_mem_lvl_l2 level 2 cache .tp .b perf_mem_lvl_l3 level 3 cache .tp .b perf_mem_lvl_loc_ram local dram .tp .b perf_mem_lvl_rem_ram1 remote dram 1 hop .tp .b perf_mem_lvl_rem_ram2 remote dram 2 hops .tp .b perf_mem_lvl_rem_cce1 remote cache 1 hop .tp .b perf_mem_lvl_rem_cce2 remote cache 2 hops .tp .b perf_mem_lvl_io i/o memory .tp .b perf_mem_lvl_unc uncached memory .re .pd .tp .i mem_snoop snoop mode, a bitwise combination of the following, shifted left by .br perf_mem_snoop_shift : .ip .pd 0 .rs .tp 24 .b perf_mem_snoop_na not available .tp .b perf_mem_snoop_none no snoop .tp .b perf_mem_snoop_hit snoop hit .tp .b perf_mem_snoop_miss snoop miss .tp .b perf_mem_snoop_hitm snoop hit modified .re .pd .tp .i mem_lock lock instruction, a bitwise combination of the following, shifted left by .br perf_mem_lock_shift : .ip .pd 0 .rs .tp 24 .b perf_mem_lock_na not available .tp .b perf_mem_lock_locked locked transaction .re .pd .tp .i mem_dtlb tlb access hit or miss, a bitwise combination of the following, shifted left by .br perf_mem_tlb_shift : .ip .pd 0 .rs .tp 24 .b perf_mem_tlb_na not available .tp .b perf_mem_tlb_hit hit .tp .b perf_mem_tlb_miss miss .tp .b perf_mem_tlb_l1 level 1 tlb .tp .b perf_mem_tlb_l2 level 2 tlb .tp .b perf_mem_tlb_wk hardware walker .tp .b perf_mem_tlb_os os fault handler .re .pd .re .tp .i transaction if the .b perf_sample_transaction flag is set, then a 64-bit field is recorded describing the sources of any transactional memory aborts. .ip the field is a bitwise combination of the following values: .rs .tp .b perf_txn_elision abort from an elision type transaction (intel-cpu-specific). .tp .b perf_txn_transaction abort from a generic transaction. .tp .b perf_txn_sync synchronous abort (related to the reported instruction). .tp .b perf_txn_async asynchronous abort (not related to the reported instruction). .tp .b perf_txn_retry retryable abort (retrying the transaction may have succeeded). .tp .b perf_txn_conflict abort due to memory conflicts with other threads. .tp .b perf_txn_capacity_write abort due to write capacity overflow. .tp .b perf_txn_capacity_read abort due to read capacity overflow. .re .ip in addition, a user-specified abort code can be obtained from the high 32 bits of the field by shifting right by .b perf_txn_abort_shift and masking with the value .br perf_txn_abort_mask . .tp .ir abi ", " regs[weight(mask)] if .b perf_sample_regs_intr is enabled, then the user cpu registers are recorded. .ip the .i abi field is one of .br perf_sample_regs_abi_none , .br perf_sample_regs_abi_32 , or .br perf_sample_regs_abi_64 . .ip the .i regs field is an array of the cpu registers that were specified by the .i sample_regs_intr attr field. the number of values is the number of bits set in the .i sample_regs_intr bit mask. .tp .i phys_addr if the .b perf_sample_phys_addr flag is set, then the 64-bit physical address is recorded. .tp .i cgroup if the .b perf_sample_cgroup flag is set, then the 64-bit cgroup id (for the perf_event subsystem) is recorded. to get the pathname of the cgroup, the id should match to one in a .b perf_record_cgroup . .re .tp .b perf_record_mmap2 this record includes extended information on .br mmap (2) calls returning executable mappings. the format is similar to that of the .b perf_record_mmap record, but includes extra values that allow uniquely identifying shared mappings. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid; u32 tid; u64 addr; u64 len; u64 pgoff; u32 maj; u32 min; u64 ino; u64 ino_generation; u32 prot; u32 flags; char filename[]; struct sample_id sample_id; }; .ee .in .rs .tp .i pid is the process id. .tp .i tid is the thread id. .tp .i addr is the address of the allocated memory. .tp .i len is the length of the allocated memory. .tp .i pgoff is the page offset of the allocated memory. .tp .i maj is the major id of the underlying device. .tp .i min is the minor id of the underlying device. .tp .i ino is the inode number. .tp .i ino_generation is the inode generation. .tp .i prot is the protection information. .tp .i flags is the flags information. .tp .i filename is a string describing the backing of the allocated memory. .re .tp .br perf_record_aux " (since linux 4.1)" .\" commit 68db7e98c3a6ebe7284b6cf14906ed7c55f3f7f0 this record reports that new data is available in the separate aux buffer region. .ip .in +4n .ex struct { struct perf_event_header header; u64 aux_offset; u64 aux_size; u64 flags; struct sample_id sample_id; }; .ee .in .rs .tp .i aux_offset offset in the aux mmap region where the new data begins. .tp .i aux_size size of the data made available. .tp .i flags describes the aux update. .rs .tp .b perf_aux_flag_truncated if set, then the data returned was truncated to fit the available buffer size. .tp .b perf_aux_flag_overwrite .\" commit 2023a0d2829e521fe6ad6b9907f3f90bfbf57142 if set, then the data returned has overwritten previous data. .re .re .tp .br perf_record_itrace_start " (since linux 4.1)" .\" ec0d7729bbaed4b9d2d3fada693278e13a3d1368 this record indicates which process has initiated an instruction trace event, allowing tools to properly correlate the instruction addresses in the aux buffer with the proper executable. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid; u32 tid; }; .ee .in .rs .tp .i pid process id of the thread starting an instruction trace. .tp .i tid thread id of the thread starting an instruction trace. .re .tp .br perf_record_lost_samples " (since linux 4.2)" .\" f38b0dbb491a6987e198aa6b428db8692a6480f8 when using hardware sampling (such as intel pebs) this record indicates some number of samples that may have been lost. .ip .in +4n .ex struct { struct perf_event_header header; u64 lost; struct sample_id sample_id; }; .ee .in .rs .tp .i lost the number of potentially lost samples. .re .tp .br perf_record_switch " (since linux 4.3)" .\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 this record indicates a context switch has happened. the .b perf_record_misc_switch_out bit in the .i misc field indicates whether it was a context switch into or away from the current process. .ip .in +4n .ex struct { struct perf_event_header header; struct sample_id sample_id; }; .ee .in .tp .br perf_record_switch_cpu_wide " (since linux 4.3)" .\" commit 45ac1403f564f411c6a383a2448688ba8dd705a4 as with .b perf_record_switch this record indicates a context switch has happened, but it only occurs when sampling in cpu-wide mode and provides additional information on the process being switched to/from. the .b perf_record_misc_switch_out bit in the .i misc field indicates whether it was a context switch into or away from the current process. .ip .in +4n .ex struct { struct perf_event_header header; u32 next_prev_pid; u32 next_prev_tid; struct sample_id sample_id; }; .ee .in .rs .tp .i next_prev_pid the process id of the previous (if switching in) or next (if switching out) process on the cpu. .tp .i next_prev_tid the thread id of the previous (if switching in) or next (if switching out) thread on the cpu. .re .tp .br perf_record_namespaces " (since linux 4.11)" .\" commit e422267322cd319e2695a535e47c5b1feeac45eb this record includes various namespace information of a process. .ip .in +4n .ex struct { struct perf_event_header header; u32 pid; u32 tid; u64 nr_namespaces; struct { u64 dev, inode } [nr_namespaces]; struct sample_id sample_id; }; .ee .in .rs .tp .i pid is the process id .tp .i tid is the thread id .tp .i nr_namespace is the number of namespaces in this record .re .ip each namespace has .i dev and .i inode fields and is recorded in the fixed position like below: .rs .tp .br net_ns_index = 0 network namespace .tp .br uts_ns_index = 1 uts namespace .tp .br ipc_ns_index = 2 ipc namespace .tp .br pid_ns_index = 3 pid namespace .tp .br user_ns_index = 4 user namespace .tp .br mnt_ns_index = 5 mount namespace .tp .br cgroup_ns_index = 6 cgroup namespace .re .tp .br perf_record_ksymbol " (since linux 5.0)" .\" commit 76193a94522f1d4edf2447a536f3f796ce56343b this record indicates kernel symbol register/unregister events. .ip .in +4n .ex struct { struct perf_event_header header; u64 addr; u32 len; u16 ksym_type; u16 flags; char name[]; struct sample_id sample_id; }; .ee .in .rs .tp .i addr is the address of the kernel symbol. .tp .i len is the length of the kernel symbol. .tp .i ksym_type is the type of the kernel symbol. currently the following types are available: .rs .tp .b perf_record_ksymbol_type_bpf the kernel symbol is a bpf function. .re .tp .i flags if the .b perf_record_ksymbol_flags_unregister is set, then this event is for unregistering the kernel symbol. .re .tp .br perf_record_bpf_event " (since linux 5.0)" .\" commit 6ee52e2a3fe4ea35520720736e6791df1fb67106 this record indicates bpf program is loaded or unloaded. .ip .in +4n .ex struct { struct perf_event_header header; u16 type; u16 flags; u32 id; u8 tag[bpf_tag_size]; struct sample_id sample_id; }; .ee .in .rs .tp .i type is one of the following values: .rs .tp .b perf_bpf_event_prog_load a bpf program is loaded .tp .b perf_bpf_event_prog_unload a bpf program is unloaded .re .tp .i id is the id of the bpf program. .tp .i tag is the tag of the bpf program. currently, .b bpf_tag_size is defined as 8. .re .tp .br perf_record_cgroup " (since linux 5.7)" .\" commit 96aaab686505c449e24d76e76507290dcc30e008 this record indicates a new cgroup is created and activated. .ip .in +4n .ex struct { struct perf_event_header header; u64 id; char path[]; struct sample_id sample_id; }; .ee .in .rs .tp .i id is the cgroup identifier. this can be also retrieved by .br name_to_handle_at (2) on the cgroup path (as a file handle). .tp .i path is the path of the cgroup from the root. .re .tp .br perf_record_text_poke " (since linux 5.8)" .\" commit e17d43b93e544f5016c0251d2074c15568d5d963 this record indicates a change in the kernel text. this includes addition and removal of the text and the corresponding length is zero in this case. .ip .in +4n .ex struct { struct perf_event_header header; u64 addr; u16 old_len; u16 new_len; u8 bytes[]; struct sample_id sample_id; }; .ee .in .rs .tp .i addr is the address of the change .tp .i old_len is the old length .tp .i new_len is the new length .tp .i bytes contains old bytes immediately followed by new bytes. .re .re .ss overflow handling events can be set to notify when a threshold is crossed, indicating an overflow. overflow conditions can be captured by monitoring the event file descriptor with .br poll (2), .br select (2), or .br epoll (7). alternatively, the overflow events can be captured via sa signal handler, by enabling i/o signaling on the file descriptor; see the discussion of the .br f_setown and .br f_setsig operations in .br fcntl (2). .pp overflows are generated only by sampling events .ri ( sample_period must have a nonzero value). .pp there are two ways to generate overflow notifications. .pp the first is to set a .i wakeup_events or .i wakeup_watermark value that will trigger if a certain number of samples or bytes have been written to the mmap ring buffer. in this case, .b poll_in is indicated. .pp the other way is by use of the .b perf_event_ioc_refresh ioctl. this ioctl adds to a counter that decrements each time the event overflows. when nonzero, .b poll_in is indicated, but once the counter reaches 0 .b poll_hup is indicated and the underlying event is disabled. .pp refreshing an event group leader refreshes all siblings and refreshing with a parameter of 0 currently enables infinite refreshes; these behaviors are unsupported and should not be relied on. .\" see https://lkml.org/lkml/2011/5/24/337 .pp starting with linux 3.18, .\" commit 179033b3e064d2cd3f5f9945e76b0a0f0fbf4883 .b poll_hup is indicated if the event being monitored is attached to a different process and that process exits. .ss rdpmc instruction starting with linux 3.4 on x86, you can use the .\" commit c7206205d00ab375839bd6c7ddb247d600693c09 .i rdpmc instruction to get low-latency reads without having to enter the kernel. note that using .i rdpmc is not necessarily faster than other methods for reading event values. .pp support for this can be detected with the .i cap_usr_rdpmc field in the mmap page; documentation on how to calculate event values can be found in that section. .pp originally, when rdpmc support was enabled, any process (not just ones with an active perf event) could use the rdpmc instruction to access the counters. starting with linux 4.0, .\" 7911d3f7af14a614617e38245fedf98a724e46a9 rdpmc support is only allowed if an event is currently enabled in a process's context. to restore the old behavior, write the value 2 to .ir /sys/devices/cpu/rdpmc . .ss perf_event ioctl calls various ioctls act on .br perf_event_open () file descriptors: .tp .b perf_event_ioc_enable this enables the individual event or event group specified by the file descriptor argument. .ip if the .b perf_ioc_flag_group bit is set in the ioctl argument, then all events in a group are enabled, even if the event specified is not the group leader (but see bugs). .tp .b perf_event_ioc_disable this disables the individual counter or event group specified by the file descriptor argument. .ip enabling or disabling the leader of a group enables or disables the entire group; that is, while the group leader is disabled, none of the counters in the group will count. enabling or disabling a member of a group other than the leader affects only that counter; disabling a non-leader stops that counter from counting but doesn't affect any other counter. .ip if the .b perf_ioc_flag_group bit is set in the ioctl argument, then all events in a group are disabled, even if the event specified is not the group leader (but see bugs). .tp .b perf_event_ioc_refresh non-inherited overflow counters can use this to enable a counter for a number of overflows specified by the argument, after which it is disabled. subsequent calls of this ioctl add the argument value to the current count. an overflow notification with .b poll_in set will happen on each overflow until the count reaches 0; when that happens a notification with .b poll_hup set is sent and the event is disabled. using an argument of 0 is considered undefined behavior. .tp .b perf_event_ioc_reset reset the event count specified by the file descriptor argument to zero. this resets only the counts; there is no way to reset the multiplexing .i time_enabled or .i time_running values. .ip if the .b perf_ioc_flag_group bit is set in the ioctl argument, then all events in a group are reset, even if the event specified is not the group leader (but see bugs). .tp .b perf_event_ioc_period this updates the overflow period for the event. .ip since linux 3.7 (on arm) .\" commit 3581fe0ef37ce12ac7a4f74831168352ae848edc and linux 3.14 (all other architectures), .\" commit bad7192b842c83e580747ca57104dd51fe08c223 the new period takes effect immediately. on older kernels, the new period did not take effect until after the next overflow. .ip the argument is a pointer to a 64-bit value containing the desired new period. .ip prior to linux 2.6.36, .\" commit ad0cf3478de8677f720ee06393b3147819568d6a this ioctl always failed due to a bug in the kernel. .tp .b perf_event_ioc_set_output this tells the kernel to report event notifications to the specified file descriptor rather than the default one. the file descriptors must all be on the same cpu. .ip the argument specifies the desired file descriptor, or \-1 if output should be ignored. .tp .br perf_event_ioc_set_filter " (since linux 2.6.33)" .\" commit 6fb2915df7f0747d9044da9dbff5b46dc2e20830 this adds an ftrace filter to this event. .ip the argument is a pointer to the desired ftrace filter. .tp .br perf_event_ioc_id " (since linux 3.12)" .\" commit cf4957f17f2a89984915ea808876d9c82225b862 this returns the event id value for the given event file descriptor. .ip the argument is a pointer to a 64-bit unsigned integer to hold the result. .tp .br perf_event_ioc_set_bpf " (since linux 4.1)" .\" commit 2541517c32be2531e0da59dfd7efc1ce844644f5 this allows attaching a berkeley packet filter (bpf) program to an existing kprobe tracepoint event. you need .b cap_perfmon (since linux 5.8) or .b cap_sys_admin privileges to use this ioctl. .ip the argument is a bpf program file descriptor that was created by a previous .br bpf (2) system call. .tp .br perf_event_ioc_pause_output " (since linux 4.7)" .\" commit 86e7972f690c1017fd086cdfe53d8524e68c661c this allows pausing and resuming the event's ring-buffer. a paused ring-buffer does not prevent generation of samples, but simply discards them. the discarded samples are considered lost, and cause a .br perf_record_lost sample to be generated when possible. an overflow signal may still be triggered by the discarded sample even though the ring-buffer remains empty. .ip the argument is an unsigned 32-bit integer. a nonzero value pauses the ring-buffer, while a zero value resumes the ring-buffer. .tp .br perf_event_modify_attributes " (since linux 4.17)" .\" commit 32ff77e8cc9e66cc4fb38098f64fd54cc8f54573 this allows modifying an existing event without the overhead of closing and reopening a new event. currently this is supported only for breakpoint events. .ip the argument is a pointer to a .i perf_event_attr structure containing the updated event settings. .tp .br perf_event_ioc_query_bpf " (since linux 4.16)" .\" commit f371b304f12e31fe30207c41ca7754564e0ea4dc this allows querying which berkeley packet filter (bpf) programs are attached to an existing kprobe tracepoint. you can only attach one bpf program per event, but you can have multiple events attached to a tracepoint. querying this value on one tracepoint event returns the id of all bpf programs in all events attached to the tracepoint. you need .b cap_perfmon (since linux 5.8) or .b cap_sys_admin privileges to use this ioctl. .ip the argument is a pointer to a structure .in +4n .ex struct perf_event_query_bpf { __u32 ids_len; __u32 prog_cnt; __u32 ids[0]; }; .ee .in .ip the .i ids_len field indicates the number of ids that can fit in the provided .i ids array. the .i prog_cnt value is filled in by the kernel with the number of attached bpf programs. the .i ids array is filled with the id of each attached bpf program. if there are more programs than will fit in the array, then the kernel will return .b enospc and .i ids_len will indicate the number of program ids that were successfully copied. .\" .ss using prctl(2) a process can enable or disable all currently open event groups using the .br prctl (2) .b pr_task_perf_events_enable and .b pr_task_perf_events_disable operations. this applies only to events created locally by the calling process. this does not apply to events created by other processes attached to the calling process or inherited events from a parent process. only group leaders are enabled and disabled, not any other members of the groups. .ss perf_event related configuration files files in .i /proc/sys/kernel/ .rs 4 .tp .i /proc/sys/kernel/perf_event_paranoid the .i perf_event_paranoid file can be set to restrict access to the performance counters. .ip .pd 0 .rs .ip 2 4 allow only user-space measurements (default since linux 4.6). .\" default changed in commit 0161028b7c8aebef64194d3d73e43bc3b53b5c66 .ip 1 allow both kernel and user measurements (default before linux 4.6). .ip 0 allow access to cpu-specific data but not raw tracepoint samples. .ip \-1 no restrictions. .re .pd .ip the existence of the .i perf_event_paranoid file is the official method for determining if a kernel supports .br perf_event_open (). .tp .i /proc/sys/kernel/perf_event_max_sample_rate this sets the maximum sample rate. setting this too high can allow users to sample at a rate that impacts overall machine performance and potentially lock up the machine. the default value is 100000 (samples per second). .tp .i /proc/sys/kernel/perf_event_max_stack .\" introduced in c5dfd78eb79851e278b7973031b9ca363da87a7e this file sets the maximum depth of stack frame entries reported when generating a call trace. .tp .i /proc/sys/kernel/perf_event_mlock_kb maximum number of pages an unprivileged user can .br mlock (2). the default is 516 (kb). .re .pp files in .i /sys/bus/event_source/devices/ .pp .rs 4 since linux 2.6.34, the kernel supports having multiple pmus available for monitoring. information on how to program these pmus can be found under .ir /sys/bus/event_source/devices/ . each subdirectory corresponds to a different pmu. .tp .ir /sys/bus/event_source/devices/*/type " (since linux 2.6.38)" .\" commit abe43400579d5de0078c2d3a760e6598e183f871 this contains an integer that can be used in the .i type field of .i perf_event_attr to indicate that you wish to use this pmu. .tp .ir /sys/bus/event_source/devices/cpu/rdpmc " (since linux 3.4)" .\" commit 0c9d42ed4cee2aa1dfc3a260b741baae8615744f if this file is 1, then direct user-space access to the performance counter registers is allowed via the rdpmc instruction. this can be disabled by echoing 0 to the file. .ip as of linux 4.0 .\" a66734297f78707ce39d756b656bfae861d53f62 .\" 7911d3f7af14a614617e38245fedf98a724e46a9 the behavior has changed, so that 1 now means only allow access to processes with active perf events, with 2 indicating the old allow-anyone-access behavior. .tp .ir /sys/bus/event_source/devices/*/format/ " (since linux 3.4)" .\" commit 641cc938815dfd09f8fa1ec72deb814f0938ac33 this subdirectory contains information on the architecture-specific subfields available for programming the various .i config fields in the .i perf_event_attr struct. .ip the content of each file is the name of the config field, followed by a colon, followed by a series of integer bit ranges separated by commas. for example, the file .i event may contain the value .i config1:1,6\-10,44 which indicates that event is an attribute that occupies bits 1,6\(en10, and 44 of .ir perf_event_attr::config1 . .tp .ir /sys/bus/event_source/devices/*/events/ " (since linux 3.4)" .\" commit 641cc938815dfd09f8fa1ec72deb814f0938ac33 this subdirectory contains files with predefined events. the contents are strings describing the event settings expressed in terms of the fields found in the previously mentioned .i ./format/ directory. these are not necessarily complete lists of all events supported by a pmu, but usually a subset of events deemed useful or interesting. .ip the content of each file is a list of attribute names separated by commas. each entry has an optional value (either hex or decimal). if no value is specified, then it is assumed to be a single-bit field with a value of 1. an example entry may look like this: .ir event=0x2,inv,ldlat=3 . .tp .i /sys/bus/event_source/devices/*/uevent this file is the standard kernel device interface for injecting hotplug events. .tp .ir /sys/bus/event_source/devices/*/cpumask " (since linux 3.7)" .\" commit 314d9f63f385096580e9e2a06eaa0745d92fe4ac the .i cpumask file contains a comma-separated list of integers that indicate a representative cpu number for each socket (package) on the motherboard. this is needed when setting up uncore or northbridge events, as those pmus present socket-wide events. .re .sh return value on success, .br perf_event_open () returns the new file descriptor. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors the errors returned by .br perf_event_open () can be inconsistent, and may vary across processor architectures and performance monitoring units. .tp .b e2big returned if the .i perf_event_attr .i size value is too small (smaller than .br perf_attr_size_ver0 ), too big (larger than the page size), or larger than the kernel supports and the extra bytes are not zero. when .b e2big is returned, the .i perf_event_attr .i size field is overwritten by the kernel to be the size of the structure it was expecting. .tp .b eacces returned when the requested event requires .b cap_perfmon (since linux 5.8) or .b cap_sys_admin permissions (or a more permissive perf_event paranoid setting). some common cases where an unprivileged process may encounter this error: attaching to a process owned by a different user; monitoring all processes on a given cpu (i.e., specifying the .i pid argument as \-1); and not setting .i exclude_kernel when the paranoid setting requires it. .tp .b ebadf returned if the .i group_fd file descriptor is not valid, or, if .b perf_flag_pid_cgroup is set, the cgroup file descriptor in .i pid is not valid. .tp .br ebusy " (since linux 4.1)" .\" bed5b25ad9c8a2f5d735ef0bc746ec870c01c1b0 returned if another event already has exclusive access to the pmu. .tp .b efault returned if the .i attr pointer points at an invalid memory address. .tp .b eintr returned when trying to mix perf and ftrace handling for a uprobe. .tp .b einval returned if the specified event is invalid. there are many possible reasons for this. a not-exhaustive list: .i sample_freq is higher than the maximum setting; the .i cpu to monitor does not exist; .i read_format is out of range; .i sample_type is out of range; the .i flags value is out of range; .i exclusive or .i pinned set and the event is not a group leader; the event .i config values are out of range or set reserved bits; the generic event selected is not supported; or there is not enough room to add the selected event. .tp .b emfile each opened event uses one file descriptor. if a large number of events are opened, the per-process limit on the number of open file descriptors will be reached, and no more events can be created. .tp .b enodev returned when the event involves a feature not supported by the current cpu. .tp .b enoent returned if the .i type setting is not valid. this error is also returned for some unsupported generic events. .tp .b enospc prior to linux 3.3, if there was not enough room for the event, .\" commit aa2bc1ade59003a379ffc485d6da2d92ea3370a6 .b enospc was returned. in linux 3.3, this was changed to .br einval . .b enospc is still returned if you try to add more breakpoint events than supported by the hardware. .tp .b enosys returned if .b perf_sample_stack_user is set in .i sample_type and it is not supported by hardware. .tp .b eopnotsupp returned if an event requiring a specific hardware feature is requested but there is no hardware support. this includes requesting low-skid events if not supported, branch tracing if it is not available, sampling if no pmu interrupt is available, and branch stacks for software events. .tp .br eoverflow " (since linux 4.8)" .\" 97c79a38cd454602645f0470ffb444b3b75ce574 returned if .b perf_sample_callchain is requested and .i sample_max_stack is larger than the maximum specified in .ir /proc/sys/kernel/perf_event_max_stack . .tp .b eperm returned on many (but not all) architectures when an unsupported .ir exclude_hv ", " exclude_idle ", " exclude_user ", or " exclude_kernel setting is specified. .ip it can also happen, as with .br eacces , when the requested event requires .b cap_perfmon (since linux 5.8) or .b cap_sys_admin permissions (or a more permissive perf_event paranoid setting). this includes setting a breakpoint on a kernel address, and (since linux 3.13) setting a kernel function-trace tracepoint. .\" commit a4e95fc2cbb31d70a65beffeaf8773f881328c34 .tp .b esrch returned if attempting to attach to a process that does not exist. .sh version .br perf_event_open () was introduced in linux 2.6.31 but was called .\" commit 0793a61d4df8daeac6492dbf8d2f3e5713caae5e .br perf_counter_open (). it was renamed in linux 2.6.32. .\" commit cdd6c482c9ff9c55475ee7392ec8f672eddb7be6 .sh conforming to this .br perf_event_open () system call linux-specific and should not be used in programs intended to be portable. .sh notes the official way of knowing if .br perf_event_open () support is enabled is checking for the existence of the file .ir /proc/sys/kernel/perf_event_paranoid . .pp .b cap_perfmon capability (since linux 5.8) provides secure approach to performance monitoring and observability operations in a system according to the principal of least privilege (posix ieee 1003.1e). accessing system performance monitoring and observability operations using .b cap_perfmon rather than the much more powerful .b cap_sys_admin excludes chances to misuse credentials and makes operations more secure. .b cap_sys_admin usage for secure system performance monitoring and observability is discouraged in favor of the .b cap_perfmon capability. .sh bugs the .b f_setown_ex option to .br fcntl (2) is needed to properly get overflow signals in threads. this was introduced in linux 2.6.32. .\" commit ba0a6c9f6fceed11c6a99e8326f0477fe383e6b5 .pp prior to linux 2.6.33 (at least for x86), .\" commit b690081d4d3f6a23541493f1682835c3cd5c54a1 the kernel did not check if events could be scheduled together until read time. the same happens on all known kernels if the nmi watchdog is enabled. this means to see if a given set of events works you have to .br perf_event_open (), start, then read before you know for sure you can get valid measurements. .pp prior to linux 2.6.34, .\" fixme . cannot find a kernel commit for this one event constraints were not enforced by the kernel. in that case, some events would silently return "0" if the kernel scheduled them in an improper counter slot. .pp prior to linux 2.6.34, there was a bug when multiplexing where the wrong results could be returned. .\" commit 45e16a6834b6af098702e5ea6c9a40de42ff77d8 .pp kernels from linux 2.6.35 to linux 2.6.39 can quickly crash the kernel if "inherit" is enabled and many threads are started. .\" commit 38b435b16c36b0d863efcf3f07b34a6fac9873fd .pp prior to linux 2.6.35, .\" commit 050735b08ca8a016bbace4445fa025b88fee770b .b perf_format_group did not work with attached processes. .pp there is a bug in the kernel code between linux 2.6.36 and linux 3.0 that ignores the "watermark" field and acts as if a wakeup_event was chosen if the union has a nonzero value in it. .\" commit 4ec8363dfc1451f8c8f86825731fe712798ada02 .pp from linux 2.6.31 to linux 3.4, the .b perf_ioc_flag_group ioctl argument was broken and would repeatedly operate on the event specified rather than iterating across all sibling events in a group. .\" commit 724b6daa13e100067c30cfc4d1ad06629609dc4e .pp from linux 3.4 to linux 3.11, the mmap .\" commit fa7315871046b9a4c48627905691dbde57e51033 .i cap_usr_rdpmc and .i cap_usr_time bits mapped to the same location. code should migrate to the new .i cap_user_rdpmc and .i cap_user_time fields instead. .pp always double-check your results! various generalized events have had wrong values. for example, retired branches measured the wrong thing on amd machines until linux 2.6.35. .\" commit f287d332ce835f77a4f5077d2c0ef1e3f9ea42d2 .sh examples the following is a short example that measures the total instruction count of a call to .br printf (3). .pp .ex #include #include #include #include #include #include #include static long perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu, int group_fd, unsigned long flags) { int ret; ret = syscall(__nr_perf_event_open, hw_event, pid, cpu, group_fd, flags); return ret; } int main(int argc, char *argv[]) { struct perf_event_attr pe; long long count; int fd; memset(&pe, 0, sizeof(pe)); pe.type = perf_type_hardware; pe.size = sizeof(pe); pe.config = perf_count_hw_instructions; pe.disabled = 1; pe.exclude_kernel = 1; pe.exclude_hv = 1; fd = perf_event_open(&pe, 0, \-1, \-1, 0); if (fd == \-1) { fprintf(stderr, "error opening leader %llx\en", pe.config); exit(exit_failure); } ioctl(fd, perf_event_ioc_reset, 0); ioctl(fd, perf_event_ioc_enable, 0); printf("measuring instruction count for this printf\en"); ioctl(fd, perf_event_ioc_disable, 0); read(fd, &count, sizeof(count)); printf("used %lld instructions\en", count); close(fd); } .ee .sh see also .br perf (1), .br fcntl (2), .br mmap (2), .br open (2), .br prctl (2), .br read (2) .pp .ir documentation/admin\-guide/perf\-security.rst in the kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" written feb 1994 by steve greenland (stevegr@neosoft.com) .\" and copyright 2001, 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" updated 1999.12.19 by karl m. hegbloom .\" .\" updated 13 oct 2001, michael kerrisk .\" added description of vsyslog .\" added descriptions of log_odelay and log_nowait .\" added brief description of facility and option arguments .\" added conforming to section .\" 2001-10-13, aeb, minor changes .\" modified 13 dec 2001, martin schulze .\" modified 3 jan 2002, michael kerrisk .\" .th syslog 3 2021-03-22 "linux" "linux programmer's manual" .sh name closelog, openlog, syslog, vsyslog \- send messages to the system logger .sh synopsis .nf .b #include .pp .bi "void openlog(const char *" ident ", int " option ", int " facility ); .bi "void syslog(int " priority ", const char *" format ", ...);" .b "void closelog(void);" .pp .bi "void vsyslog(int " priority ", const char *" format ", va_list " ap ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br vsyslog (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description .ss openlog() .br openlog () opens a connection to the system logger for a program. .pp the string pointed to by .i ident is prepended to every message, and is typically set to the program name. if .i ident is null, the program name is used. (posix.1-2008 does not specify the behavior when .i ident is null.) .pp the .i option argument specifies flags which control the operation of .br openlog () and subsequent calls to .br syslog (). the .i facility argument establishes a default to be used if none is specified in subsequent calls to .br syslog (). the values that may be specified for .i option and .i facility are described below. .pp the use of .br openlog () is optional; it will automatically be called by .br syslog () if necessary, in which case .i ident will default to null. .\" .ss syslog() and vsyslog() .br syslog () generates a log message, which will be distributed by .br syslogd (8). .pp the .i priority argument is formed by oring together a .i facility value and a .i level value (described below). if no .i facility value is ored into .ir priority , then the default value set by .br openlog () is used, or, if there was no preceding .br openlog () call, a default of .br log_user is employed. .pp the remaining arguments are a .ir format , as in .br printf (3), and any arguments required by the .ir format , except that the two-character sequence .b %m will be replaced by the error message string .ir strerror ( errno ). the format string need not include a terminating newline character. .pp the function .br vsyslog () performs the same task as .br syslog () with the difference that it takes a set of arguments which have been obtained using the .br stdarg (3) variable argument list macros. .\" .ss closelog() .br closelog () closes the file descriptor being used to write to the system logger. the use of .br closelog () is optional. .\" .ss values for \fioption\fp the .i option argument to .br openlog () is a bit mask constructed by oring together any of the following values: .tp 15 .b log_cons write directly to the system console if there is an error while sending to the system logger. .tp .b log_ndelay open the connection immediately (normally, the connection is opened when the first message is logged). this may be useful, for example, if a subsequent .br chroot (2) would make the pathname used internally by the logging facility unreachable. .tp .b log_nowait don't wait for child processes that may have been created while logging the message. (the gnu c library does not create a child process, so this option has no effect on linux.) .tp .b log_odelay the converse of .br log_ndelay ; opening of the connection is delayed until .br syslog () is called. (this is the default, and need not be specified.) .tp .b log_perror (not in posix.1-2001 or posix.1-2008.) also log the message to .ir stderr . .tp .b log_pid include the caller's pid with each message. .\" .ss values for \fifacility\fp the .i facility argument is used to specify what type of program is logging the message. this lets the configuration file specify that messages from different facilities will be handled differently. .tp 15 .b log_auth security/authorization messages .tp .b log_authpriv security/authorization messages (private) .tp .b log_cron clock daemon .rb ( cron " and " at ) .tp .b log_daemon system daemons without separate facility value .tp .b log_ftp ftp daemon .tp .b log_kern kernel messages (these can't be generated from user processes) .\" log_kern has the value 0; if used as a facility, zero translates to: .\" "use the default facility". .tp .br log_local0 " through " log_local7 reserved for local use .tp .b log_lpr line printer subsystem .tp .b log_mail mail subsystem .tp .b log_news usenet news subsystem .tp .b log_syslog messages generated internally by .br syslogd (8) .tp .br log_user " (default)" generic user-level messages .tp .b log_uucp uucp subsystem .\" .ss values for \filevel\fp this determines the importance of the message. the levels are, in order of decreasing importance: .tp 15 .b log_emerg system is unusable .tp .b log_alert action must be taken immediately .tp .b log_crit critical conditions .tp .b log_err error conditions .tp .b log_warning warning conditions .tp .b log_notice normal, but significant, condition .tp .b log_info informational message .tp .b log_debug debug-level message .pp the function .br setlogmask (3) can be used to restrict logging to specified levels only. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br openlog (), .br closelog () t} thread safety mt-safe t{ .br syslog (), .br vsyslog () t} thread safety mt-safe env locale .te .hy .ad .sp 1 .sh conforming to the functions .br openlog (), .br closelog (), and .br syslog () (but not .br vsyslog ()) are specified in susv2, posix.1-2001, and posix.1-2008. .pp posix.1-2001 specifies only the .b log_user and .b log_local* values for .ir facility . however, with the exception of .b log_authpriv and .br log_ftp , the other .i facility values appear on most unix systems. .pp the .b log_perror value for .i option is not specified by posix.1-2001 or posix.1-2008, but is available in most versions of unix. .\" .sh history .\" a .\" .br syslog () .\" function call appeared in 4.2bsd. .\" 4.3bsd documents .\" .br openlog (), .\" .br syslog (), .\" .br closelog (), .\" and .\" .br setlogmask (). .\" 4.3bsd-reno also documents .\" .br vsyslog (). .\" of course early v* functions used the .\" .i .\" mechanism, which is not compatible with .\" .ir . .sh notes the argument .i ident in the call of .br openlog () is probably stored as-is. thus, if the string it points to is changed, .br syslog () may start prepending the changed string, and if the string it points to ceases to exist, the results are undefined. most portable is to use a string constant. .pp never pass a string with user-supplied data as a format, use the following instead: .pp .in +4n .ex syslog(priority, "%s", string); .ee .in .sh see also .br journalctl (1), .br logger (1), .br setlogmask (3), .br syslog.conf (5), .br syslogd (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man-page is copyright (c) 1997 john s. kallal .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" correction, aeb, 970825 .th full 4 2019-03-06 "linux" "linux programmer's manual" .sh name full \- always full device .sh configuration if your system does not have .i /dev/full created already, it can be created with the following commands: .pp .in +4n .ex mknod \-m 666 /dev/full c 1 7 chown root:root /dev/full .ee .in .sh description the file .i /dev/full has major device number 1 and minor device number 7. .pp writes to the .i /dev/full device fail with an .b enospc error. this can be used to test how a program handles disk-full errors. .pp reads from the .i /dev/full device will return \e0 characters. .pp seeks on .i /dev/full will always succeed. .sh files .i /dev/full .sh see also .br mknod (1), .br null (4), .br zero (4) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/asinh.3 .so man3/list.3 .so man3/getprotoent.3 .so man3/malloc.3 .\" copyright (c) 2009 michael kerrisk, .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_setconcurrency 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_setconcurrency, pthread_getconcurrency \- set/get the concurrency level .sh synopsis .nf .b #include .pp .bi "int pthread_setconcurrency(int " new_level ); .bi "int pthread_getconcurrency(" void ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_setconcurrency () function informs the implementation of the application's desired concurrency level, specified in .ir new_level . the implementation takes this only as a hint: posix.1 does not specify the level of concurrency that should be provided as a result of calling .br pthread_setconcurrency (). .pp specifying .i new_level as 0 instructs the implementation to manage the concurrency level as it deems appropriate. .pp .br pthread_getconcurrency () returns the current value of the concurrency level for this process. .sh return value on success, .br pthread_setconcurrency () returns 0; on error, it returns a nonzero error number. .pp .br pthread_getconcurrency () always succeeds, returning the concurrency level set by a previous call to .br pthread_setconcurrency (), or 0, if .br pthread_setconcurrency () has not previously been called. .sh errors .br pthread_setconcurrency () can fail with the following error: .tp .b einval .i new_level is negative. .pp posix.1 also documents an .br eagain error ("the value specified by .i new_level would cause a system resource to be exceeded"). .sh versions these functions are available in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_setconcurrency (), .br pthread_getconcurrency () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the default concurrency level is 0. .pp concurrency levels are meaningful only for m:n threading implementations, where at any moment a subset of a process's set of user-level threads may be bound to a smaller number of kernel-scheduling entities. setting the concurrency level allows the application to give the system a hint as to the number of kernel-scheduling entities that should be provided for efficient execution of the application. .pp both linuxthreads and nptl are 1:1 threading implementations, so setting the concurrency level has no meaning. in other words, on linux these functions merely exist for compatibility with other systems, and they have no effect on the execution of a program. .sh see also .br pthread_attr_setscope (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .so man3/rpc.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" single unix specification, version 2 .\" modified thu apr 8 15:00:12 1993, david metcalfe .\" modified sat jul 24 18:44:45 1993, rik faith (faith@cs.unc.edu) .\" modified fri feb 14 21:47:50 1997 by andries brouwer (aeb@cwi.nl) .\" modified mon oct 11 11:11:11 1999 by andries brouwer (aeb@cwi.nl) .\" modified wed nov 10 00:02:26 1999 by andries brouwer (aeb@cwi.nl) .\" modified sun may 20 22:17:20 2001 by andries brouwer (aeb@cwi.nl) .th putenv 3 2021-03-22 "gnu" "linux programmer's manual" .sh name putenv \- change or add an environment variable .sh synopsis .nf .b #include .pp .bi "int putenv(char *" string ); .\" not: const char * .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br putenv (): .nf _xopen_source || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source .fi .sh description the .br putenv () function adds or changes the value of environment variables. the argument \fistring\fp is of the form \finame\fp=\fivalue\fp. if \finame\fp does not already exist in the environment, then \fistring\fp is added to the environment. if \finame\fp does exist, then the value of \finame\fp in the environment is changed to \fivalue\fp. the string pointed to by \fistring\fp becomes part of the environment, so altering the string changes the environment. .sh return value the .br putenv () function returns zero on success. on failure, it returns a nonzero value, and .i errno is set to indicate the error. .sh errors .tp .b enomem insufficient space to allocate new environment. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br putenv () t} thread safety mt-unsafe const:env .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes the .br putenv () function is not required to be reentrant, and the one in glibc 2.0 is not, but the glibc 2.1 version is. .\" .lp .\" description for libc4, libc5, glibc: .\" if the argument \fistring\fp is of the form \finame\fp, .\" and does not contain an \(aq=\(aq character, then the variable \finame\fp .\" is removed from the environment. .\" if .\" .br putenv () .\" has to allocate a new array \fienviron\fp, .\" and the previous array was also allocated by .\" .br putenv (), .\" then it will be freed. .\" in no case will the old storage associated .\" to the environment variable itself be freed. .pp since version 2.1.2, the glibc implementation conforms to susv2: the pointer \fistring\fp given to .br putenv () is used. in particular, this string becomes part of the environment; changing it later will change the environment. (thus, it is an error to call .br putenv () with an automatic variable as the argument, then return from the calling function while \fistring\fp is still part of the environment.) however, glibc versions 2.0 to 2.1.1 differ: a copy of the string is used. on the one hand this causes a memory leak, and on the other hand it violates susv2. .pp the 4.4bsd version, like glibc 2.0, uses a copy. .pp susv2 removes the \ficonst\fp from the prototype, and so does glibc 2.1.3. .pp the gnu c library implementation provides a nonstandard extension. if .i string does not include an equal sign: .pp .in +4n .ex putenv("name"); .ee .in .pp then the named variable is removed from the caller's environment. .sh see also .br clearenv (3), .br getenv (3), .br setenv (3), .br unsetenv (3), .br environ (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/catanh.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified sat jul 24 14:13:40 1993 by rik faith .\" additions by joseph s. myers , 970909 .\" .th time 2 2021-03-22 "linux" "linux programmer's manual" .sh name time \- get time in seconds .sh synopsis .nf .b #include .pp .bi "time_t time(time_t *" tloc ); .fi .sh description .br time () returns the time as the number of seconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). .pp if .i tloc is non-null, the return value is also stored in the memory pointed to by .ir tloc . .sh return value on success, the value of time in seconds since the epoch is returned. on error, \fi((time_t)\ \-1)\fp is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i tloc points outside your accessible address space (but see bugs). .ip on systems where the c library .br time () wrapper function invokes an implementation provided by the .br vdso (7) (so that there is no trap into the kernel), an invalid address may instead trigger a .b sigsegv signal. .sh conforming to svr4, 4.3bsd, c89, c99, posix.1-2001. .\" under 4.3bsd, this call is obsoleted by .\" .br gettimeofday (2). posix does not specify any error conditions. .sh notes posix.1 defines .i seconds since the epoch using a formula that approximates the number of seconds between a specified time and the epoch. this formula takes account of the facts that all years that are evenly divisible by 4 are leap years, but years that are evenly divisible by 100 are not leap years unless they are also evenly divisible by 400, in which case they are leap years. this value is not the same as the actual number of seconds between the time and the epoch, because of leap seconds and because system clocks are not required to be synchronized to a standard reference. the intention is that the interpretation of seconds since the epoch values be consistent; see posix.1-2008 rationale a.4.15 for further rationale. .pp on linux, a call to .br time () with .i tloc specified as null cannot fail with the error .br eoverflow , even on abis where .i time_t is a signed 32-bit integer and the clock reaches or exceeds 2**31 seconds (2038-01-19 03:14:08 utc, ignoring leap seconds). (posix.1 permits, but does not require, the .b eoverflow error in the case where the seconds since the epoch will not fit in .ir time_t .) instead, the behavior on linux is undefined when the system time is out of the .i time_t range. applications intended to run after 2038 should use abis with .i time_t wider than 32 bits. .sh bugs error returns from this system call are indistinguishable from successful reports that the time is a few seconds .i before the epoch, so the c library wrapper function never sets .i errno as a result of this call. .pp the .i tloc argument is obsolescent and should always be null in new code. when .i tloc is null, the call cannot fail. .\" .ss c library/kernel differences on some architectures, an implementation of .br time () is provided in the .br vdso (7). .sh see also .br date (1), .br gettimeofday (2), .br ctime (3), .br ftime (3), .br time (7), .br vdso (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/remainder.3 .\" copyright (c) 2006, 2010 michael kerrisk .\" copyright (c) 2009 petr baudis .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sigevent 7 2021-03-22 "gnu" "linux programmer's manual" .sh name sigevent \- structure for notification from asynchronous routines .sh synopsis .nf #include .pp union sigval { /* data passed with notification */ int sival_int; /* integer value */ void *sival_ptr; /* pointer value */ }; .pp struct sigevent { int sigev_notify; /* notification method */ int sigev_signo; /* notification signal */ union sigval sigev_value; /* data passed with notification */ void (*sigev_notify_function)(union sigval); /* function used for thread notification (sigev_thread) */ void *sigev_notify_attributes; /* attributes for notification thread (sigev_thread) */ pid_t sigev_notify_thread_id; /* id of thread to signal (sigev_thread_id); linux-specific */ }; .fi .sh description the .i sigevent structure is used by various apis to describe the way a process is to be notified about an event (e.g., completion of an asynchronous request, expiration of a timer, or the arrival of a message). .pp the definition shown in the synopsis is approximate: some of the fields in the .i sigevent structure may be defined as part of a union. programs should employ only those fields relevant to the value specified in .ir sigev_notify . .pp the .i sigev_notify field specifies how notification is to be performed. this field can have one of the following values: .tp .br sigev_none a "null" notification: don't do anything when the event occurs. .tp .br sigev_signal notify the process by sending the signal specified in .ir sigev_signo . .ip if the signal is caught with a signal handler that was registered using the .br sigaction (2) .b sa_siginfo flag, then the following fields are set in the .i siginfo_t structure that is passed as the second argument of the handler: .rs .tp 10 .i si_code this field is set to a value that depends on the api delivering the notification. .tp .i si_signo this field is set to the signal number (i.e., the same value as in .ir sigev_signo ). .tp .i si_value this field is set to the value specified in .ir sigev_value . .re .ip depending on the api, other fields may also be set in the .i siginfo_t structure. .ip the same information is also available if the signal is accepted using .br sigwaitinfo (2). .tp .br sigev_thread notify the process by invoking .i sigev_notify_function "as if" it were the start function of a new thread. (among the implementation possibilities here are that each timer notification could result in the creation of a new thread, or that a single thread is created to receive all notifications.) the function is invoked with .i sigev_value as its sole argument. if .i sigev_notify_attributes is not null, it should point to a .i pthread_attr_t structure that defines attributes for the new thread (see .br pthread_attr_init (3)). .tp .br sigev_thread_id " (linux-specific)" .\" | sigev_signal vs not? currently used only by posix timers; see .br timer_create (2). .sh see also .br timer_create (2), .br aio_fsync (3), .br aio_read (3), .br aio_write (3), .br getaddrinfo_a (3), .br lio_listio (3), .br mq_notify (3), .br aio (7), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mq_receive.3 .so man3/getutent.3 .so man7/system_data_types.7 .so man3/random.3 .\" copyright (c) 2002 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sigwaitinfo 2 2021-03-22 "linux" "linux programmer's manual" .sh name sigwaitinfo, sigtimedwait, rt_sigtimedwait \- synchronously wait for queued signals .sh synopsis .nf .b #include .pp .bi "int sigwaitinfo(const sigset_t *restrict " set , .bi " siginfo_t *restrict " info ); .bi "int sigtimedwait(const sigset_t *restrict " set , .bi " siginfo_t *restrict " info , .bi " const struct timespec *restrict " timeout ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigwaitinfo (), .br sigtimedwait (): .nf _posix_c_source >= 199309l .fi .sh description .br sigwaitinfo () suspends execution of the calling thread until one of the signals in .i set is pending (if one of the signals in .i set is already pending for the calling thread, .br sigwaitinfo () will return immediately.) .pp .br sigwaitinfo () removes the signal from the set of pending signals and returns the signal number as its function result. if the .i info argument is not null, then the buffer that it points to is used to return a structure of type .i siginfo_t (see .br sigaction (2)) containing information about the signal. .pp if multiple signals in .i set are pending for the caller, the signal that is retrieved by .br sigwaitinfo () is determined according to the usual ordering rules; see .br signal (7) for further details. .pp .br sigtimedwait () operates in exactly the same way as .br sigwaitinfo () except that it has an additional argument, .ir timeout , which specifies the interval for which the thread is suspended waiting for a signal. (this interval will be rounded up to the system clock granularity, and kernel scheduling delays mean that the interval may overrun by a small amount.) this argument is of the following type: .pp .in +4n .ex struct timespec { long tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ } .ee .in .pp if both fields of this structure are specified as 0, a poll is performed: .br sigtimedwait () returns immediately, either with information about a signal that was pending for the caller, or with an error if none of the signals in .i set was pending. .sh return value on success, both .br sigwaitinfo () and .br sigtimedwait () return a signal number (i.e., a value greater than zero). on failure both calls return \-1, with .i errno set to indicate the error. .sh errors .tp .b eagain no signal in .i set became pending within the .i timeout period specified to .br sigtimedwait (). .tp .b eintr the wait was interrupted by a signal handler; see .br signal (7). (this handler was for a signal other than one of those in .ir set .) .tp .b einval .i timeout was invalid. .sh conforming to posix.1-2001, posix.1-2008. .sh notes in normal usage, the calling program blocks the signals in .i set via a prior call to .br sigprocmask (2) (so that the default disposition for these signals does not occur if they become pending between successive calls to .br sigwaitinfo () or .br sigtimedwait ()) and does not establish handlers for these signals. in a multithreaded program, the signal should be blocked in all threads, in order to prevent the signal being treated according to its default disposition in a thread other than the one calling .br sigwaitinfo () or .br sigtimedwait ()). .pp the set of signals that is pending for a given thread is the union of the set of signals that is pending specifically for that thread and the set of signals that is pending for the process as a whole (see .br signal (7)). .pp attempts to wait for .b sigkill and .b sigstop are silently ignored. .pp if multiple threads of a process are blocked waiting for the same signal(s) in .br sigwaitinfo () or .br sigtimedwait (), then exactly one of the threads will actually receive the signal if it becomes pending for the process as a whole; which of the threads receives the signal is indeterminate. .pp .br sigwaitinfo () or .br sigtimedwait (), can't be used to receive signals that are synchronously generated, such as the .br sigsegv signal that results from accessing an invalid memory address or the .br sigfpe signal that results from an arithmetic error. such signals can be caught only via signal handler. .pp posix leaves the meaning of a null value for the .i timeout argument of .br sigtimedwait () unspecified, permitting the possibility that this has the same meaning as a call to .br sigwaitinfo (), and indeed this is what is done on linux. .\" .ss c library/kernel differences on linux, .br sigwaitinfo () is a library function implemented on top of .br sigtimedwait (). .pp the glibc wrapper functions for .br sigwaitinfo () and .br sigtimedwait () silently ignore attempts to wait for the two real-time signals that are used internally by the nptl threading implementation. see .br nptl (7) for details. .pp the original linux system call was named .br sigtimedwait (). however, with the addition of real-time signals in linux 2.2, the fixed-size, 32-bit .i sigset_t type supported by that system call was no longer fit for purpose. consequently, a new system call, .br rt_sigtimedwait (), was added to support an enlarged .ir sigset_t type. the new system call takes a fourth argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the signal set in .ir set . this argument is currently required to have the value .ir sizeof(sigset_t) (or the error .b einval results). the glibc .br sigtimedwait () wrapper function hides these details from us, transparently calling .br rt_sigtimedwait () when the kernel provides it. .\" .sh see also .br kill (2), .br sigaction (2), .br signal (2), .br signalfd (2), .br sigpending (2), .br sigprocmask (2), .br sigqueue (3), .br sigsetops (3), .br sigwait (3), .br signal (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 17:46:57 1993 by rik faith (faith@cs.unc.edu) .\" modified 2001-11-17, aeb .th tmpfile 3 2021-03-22 "" "linux programmer's manual" .sh name tmpfile \- create a temporary file .sh synopsis .nf .b #include .pp .b file *tmpfile(void); .fi .sh description the .br tmpfile () function opens a unique temporary file in binary read/write (w+b) mode. the file will be automatically deleted when it is closed or the program terminates. .sh return value the .br tmpfile () function returns a stream descriptor, or null if a unique filename cannot be generated or the unique file cannot be opened. in the latter case, .i errno is set to indicate the error. .sh errors .tp .b eacces search permission denied for directory in file's path prefix. .tp .b eexist unable to generate a unique filename. .tp .b eintr the call was interrupted by a signal; see .br signal (7). .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enospc there was no room in the directory to add the new filename. .tp .b erofs read-only filesystem. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tmpfile () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd, susv2. .sh notes posix.1-2001 specifies: an error message may be written to .i stdout if the stream cannot be opened. .pp the standard does not specify the directory that .br tmpfile () will use. glibc will try the path prefix .i p_tmpdir defined in .ir , and if that fails, then the directory .ir /tmp . .sh see also .br exit (3), .br mkstemp (3), .br mktemp (3), .br tempnam (3), .br tmpnam (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) markus kuhn, 1996 .\" and copyright (c) linux foundation, 2008, written by michael kerrisk .\" .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1996-04-10 markus kuhn .\" first version written .\" modified, 2004-10-24, aeb .\" 2008-06-24, mtk .\" minor rewrites of some parts. .\" notes: describe case where clock_nanosleep() can be preferable. .\" notes: describe clock_realtime versus clock_nanosleep .\" replace crufty discussion of hz with a pointer to time(7). .th nanosleep 2 2021-03-22 "linux" "linux programmer's manual" .sh name nanosleep \- high-resolution sleep .sh synopsis .nf .b #include .pp .bi "int nanosleep(const struct timespec *" req ", struct timespec *" rem ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nanosleep (): .nf _posix_c_source >= 199309l .fi .sh description .br nanosleep () suspends the execution of the calling thread until either at least the time specified in .ir *req has elapsed, or the delivery of a signal that triggers the invocation of a handler in the calling thread or that terminates the process. .pp if the call is interrupted by a signal handler, .br nanosleep () returns \-1, sets .i errno to .br eintr , and writes the remaining time into the structure pointed to by .i rem unless .i rem is null. the value of .i *rem can then be used to call .br nanosleep () again and complete the specified pause (but see notes). .pp the structure .i timespec is used to specify intervals of time with nanosecond precision. it is defined as follows: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp the value of the nanoseconds field must be in the range 0 to 999999999. .pp compared to .br sleep (3) and .br usleep (3), .br nanosleep () has the following advantages: it provides a higher resolution for specifying the sleep interval; posix.1 explicitly specifies that it does not interact with signals; and it makes the task of resuming a sleep that has been interrupted by a signal handler easier. .sh return value on successfully sleeping for the requested interval, .br nanosleep () returns 0. if the call is interrupted by a signal handler or encounters an error, then it returns \-1, with .i errno set to indicate the error. .sh errors .tp .b efault problem with copying information from user space. .tp .b eintr the pause has been interrupted by a signal that was delivered to the thread (see .br signal (7)). the remaining sleep time has been written into .i *rem so that the thread can easily call .br nanosleep () again and continue with the pause. .tp .b einval the value in the .i tv_nsec field was not in the range 0 to 999999999 or .i tv_sec was negative. .sh conforming to posix.1-2001, posix.1-2008. .sh notes if the interval specified in .i req is not an exact multiple of the granularity underlying clock (see .br time (7)), then the interval will be rounded up to the next multiple. furthermore, after the sleep completes, there may still be a delay before the cpu becomes free to once again execute the calling thread. .pp the fact that .br nanosleep () sleeps for a relative interval can be problematic if the call is repeatedly restarted after being interrupted by signals, since the time between the interruptions and restarts of the call will lead to drift in the time when the sleep finally completes. this problem can be avoided by using .br clock_nanosleep (2) with an absolute time value. .pp posix.1 specifies that .br nanosleep () should measure time against the .b clock_realtime clock. however, linux measures the time using the .b clock_monotonic clock. .\" see also http://thread.gmane.org/gmane.linux.kernel/696854/ .\" subject: nanosleep() uses clock_monotonic, should be clock_realtime? .\" date: 2008-06-22 07:35:41 gmt this probably does not matter, since the posix.1 specification for .br clock_settime (2) says that discontinuous changes in .b clock_realtime should not affect .br nanosleep (): .rs .pp setting the value of the .b clock_realtime clock via .br clock_settime (2) shall have no effect on threads that are blocked waiting for a relative time service based upon this clock, including the .br nanosleep () function; ... consequently, these time services shall expire when the requested relative interval elapses, independently of the new or old value of the clock. .re .ss old behavior in order to support applications requiring much more precise pauses (e.g., in order to control some time-critical hardware), .br nanosleep () would handle pauses of up to 2 milliseconds by busy waiting with microsecond precision when called from a thread scheduled under a real-time policy like .b sched_fifo or .br sched_rr . this special extension was removed in kernel 2.5.39, and is thus not available in linux 2.6.0 and later kernels. .sh bugs if a program that catches signals and uses .br nanosleep () receives signals at a very high rate, then scheduling delays and rounding errors in the kernel's calculation of the sleep interval and the returned .ir remain value mean that the .ir remain value may steadily .ir increase on successive restarts of the .br nanosleep () call. to avoid such problems, use .br clock_nanosleep (2) with the .br timer_abstime flag to sleep to an absolute deadline. .pp in linux 2.4, if .br nanosleep () is stopped by a signal (e.g., .br sigtstp ), then the call fails with the error .b eintr after the thread is resumed by a .b sigcont signal. if the system call is subsequently restarted, then the time that the thread spent in the stopped state is .i not counted against the sleep interval. this problem is fixed in linux 2.6.0 and later kernels. .sh see also .br clock_nanosleep (2), .br restart_syscall (2), .br sched_setscheduler (2), .br timer_create (2), .br sleep (3), .br usleep (3), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 michael kerrisk .\" a few fragments remain from a version .\" copyright (c) 1996 free software foundation, inc. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th init_module 2 2021-03-22 "linux" "linux programmer's manual" .sh name init_module, finit_module \- load a kernel module .sh synopsis .nf .br "#include " " /* definition of " module_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_init_module, void *" module_image ", unsigned long " len , .bi " const char *" param_values ); .bi "int syscall(sys_finit_module, int " fd ", const char *" param_values , .bi " int " flags ); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description .br init_module () loads an elf image into kernel space, performs any necessary symbol relocations, initializes module parameters to values provided by the caller, and then runs the module's .i init function. this system call requires privilege. .pp the .i module_image argument points to a buffer containing the binary image to be loaded; .i len specifies the size of that buffer. the module image should be a valid elf image, built for the running kernel. .pp the .i param_values argument is a string containing space-delimited specifications of the values for module parameters (defined inside the module using .br module_param () and .br module_param_array ()). the kernel parses this string and initializes the specified parameters. each of the parameter specifications has the form: .pp .ri " " name [\c .bi = value\c .rb [ ,\c .ir value ...]] .pp the parameter .i name is one of those defined within the module using .ir module_param () (see the linux kernel source file .ir include/linux/moduleparam.h ). the parameter .i value is optional in the case of .i bool and .i invbool parameters. values for array parameters are specified as a comma-separated list. .ss finit_module() the .br finit_module () .\" commit 34e1169d996ab148490c01b65b4ee371cf8ffba2 .\" https://lwn.net/articles/519010/ system call is like .br init_module (), but reads the module to be loaded from the file descriptor .ir fd . it is useful when the authenticity of a kernel module can be determined from its location in the filesystem; in cases where that is possible, the overhead of using cryptographically signed modules to determine the authenticity of a module can be avoided. the .i param_values argument is as for .br init_module (). .pp the .i flags argument modifies the operation of .br finit_module (). it is a bit mask value created by oring together zero or more of the following flags: .\" commit 2f3238aebedb243804f58d62d57244edec4149b2 .tp .b module_init_ignore_modversions ignore symbol version hashes. .tp .b module_init_ignore_vermagic ignore kernel version magic. .pp there are some safety checks built into a module to ensure that it matches the kernel against which it is loaded. .\" http://www.tldp.org/howto/module-howto/basekerncompat.html .\" is dated, but informative these checks are recorded when the module is built and verified when the module is loaded. first, the module records a "vermagic" string containing the kernel version number and prominent features (such as the cpu type). second, if the module was built with the .b config_modversions configuration option enabled, a version hash is recorded for each symbol the module uses. this hash is based on the types of the arguments and return value for the function named by the symbol. in this case, the kernel version number within the "vermagic" string is ignored, as the symbol version hashes are assumed to be sufficiently reliable. .pp using the .b module_init_ignore_vermagic flag indicates that the "vermagic" string is to be ignored, and the .b module_init_ignore_modversions flag indicates that the symbol version hashes are to be ignored. if the kernel is built to permit forced loading (i.e., configured with .br config_module_force_load ), then loading continues, otherwise it fails with the error .b enoexec as expected for malformed modules. .sh return value on success, these system calls return 0. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .br ebadmsg " (since linux 3.7)" module signature is misformatted. .tp .b ebusy timeout while trying to resolve a symbol reference by this module. .tp .b efault an address argument referred to a location that is outside the process's accessible address space. .tp .br enokey " (since linux 3.7)" .\" commit 48ba2462ace6072741fd8d0058207d630ce93bf1 .\" commit 1d0059f3a468825b5fc5405c636a2f6e02707ffa .\" commit 106a4ee258d14818467829bf0e12aeae14c16cd7 module signature is invalid or the kernel does not have a key for this module. this error is returned only if the kernel was configured with .br config_module_sig_force ; if the kernel was not configured with this option, then an invalid or unsigned module simply taints the kernel. .tp .b enomem out of memory. .tp .b eperm the caller was not privileged (did not have the .b cap_sys_module capability), or module loading is disabled (see .ir /proc/sys/kernel/modules_disabled in .br proc (5)). .pp the following errors may additionally occur for .br init_module (): .tp .b eexist a module with this name is already loaded. .tp .b einval .i param_values is invalid, or some part of the elf image in .ir module_image contains inconsistencies. .\" .tp .\" .br einval " (linux 2.4 and earlier)" .\" some .\" .i image .\" slot is filled in incorrectly, .\" .i image\->name .\" does not correspond to the original module name, some .\" .i image\->deps .\" entry does not correspond to a loaded module, .\" or some other similar inconsistency. .tp .b enoexec the binary image supplied in .i module_image is not an elf image, or is an elf image that is invalid or for a different architecture. .pp the following errors may additionally occur for .br finit_module (): .tp .b ebadf the file referred to by .i fd is not opened for reading. .tp .b efbig the file referred to by .i fd is too large. .tp .b einval .i flags is invalid. .tp .b enoexec .i fd does not refer to an open file. .pp in addition to the above errors, if the module's .i init function is executed and returns an error, then .br init_module () or .br finit_module () fails and .i errno is set to the value returned by the .i init function. .sh versions .br finit_module () is available since linux 3.8. .sh conforming to .br init_module () and .br finit_module () are linux-specific. .sh notes the .br init_module () system call is not supported by glibc. no declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an abi for this system call. therefore, in order to employ this system call, it is (before glibc 2.23) sufficient to manually declare the interface in your code; alternatively, you can invoke the system call using .br syscall (2). .pp information about currently loaded modules can be found in .ir /proc/modules and in the file trees under the per-module subdirectories under .ir /sys/module . .pp see the linux kernel source file .i include/linux/module.h for some useful background information. .ss linux 2.4 and earlier in linux 2.4 and earlier, the .br init_module () system call was rather different: .pp .b " #include " .pp .bi " int init_module(const char *" name ", struct module *" image ); .pp (user-space applications can detect which version of .br init_module () is available by calling .br query_module (); the latter call fails with the error .br enosys on linux 2.6 and later.) .pp the older version of the system call loads the relocated module image pointed to by .i image into kernel space and runs the module's .i init function. the caller is responsible for providing the relocated image (since linux 2.6, the .br init_module () system call does the relocation). .pp the module image begins with a module structure and is followed by code and data as appropriate. since linux 2.2, the module structure is defined as follows: .pp .in +4n .ex struct module { unsigned long size_of_struct; struct module *next; const char *name; unsigned long size; long usecount; unsigned long flags; unsigned int nsyms; unsigned int ndeps; struct module_symbol *syms; struct module_ref *deps; struct module_ref *refs; int (*init)(void); void (*cleanup)(void); const struct exception_table_entry *ex_table_start; const struct exception_table_entry *ex_table_end; #ifdef __alpha__ unsigned long gp; #endif }; .ee .in .pp all of the pointer fields, with the exception of .i next and .ir refs , are expected to point within the module body and be initialized as appropriate for kernel space, that is, relocated with the rest of the module. .sh see also .br create_module (2), .br delete_module (2), .br query_module (2), .br lsmod (8), .br modprobe (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ccosh.3 .so man3/exec.3 .so man3/key_setsecret.3 .so man3/pthread_mutexattr_init.3 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_cancel 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_cancel \- send a cancellation request to a thread .sh synopsis .nf .b #include .pp .bi "int pthread_cancel(pthread_t " thread ); .pp compile and link with \fi\-pthread\fp. .fi .sh description the .br pthread_cancel () function sends a cancellation request to the thread .ir thread . whether and when the target thread reacts to the cancellation request depends on two attributes that are under the control of that thread: its cancelability .i state and .ir type . .pp a thread's cancelability state, determined by .br pthread_setcancelstate (3), can be .i enabled (the default for new threads) or .ir disabled . if a thread has disabled cancellation, then a cancellation request remains queued until the thread enables cancellation. if a thread has enabled cancellation, then its cancelability type determines when cancellation occurs. .pp a thread's cancellation type, determined by .br pthread_setcanceltype (3), may be either .ir asynchronous or .ir deferred (the default for new threads). asynchronous cancelability means that the thread can be canceled at any time (usually immediately, but the system does not guarantee this). deferred cancelability means that cancellation will be delayed until the thread next calls a function that is a .ir "cancellation point" . a list of functions that are or may be cancellation points is provided in .br pthreads (7). .pp when a cancellation requested is acted on, the following steps occur for .ir thread (in this order): .ip 1. 3 cancellation clean-up handlers are popped (in the reverse of the order in which they were pushed) and called. (see .br pthread_cleanup_push (3).) .ip 2. thread-specific data destructors are called, in an unspecified order. (see .br pthread_key_create (3).) .ip 3. the thread is terminated. (see .br pthread_exit (3).) .pp the above steps happen asynchronously with respect to the .br pthread_cancel () call; the return status of .br pthread_cancel () merely informs the caller whether the cancellation request was successfully queued. .pp after a canceled thread has terminated, a join with that thread using .br pthread_join (3) obtains .b pthread_canceled as the thread's exit status. (joining with a thread is the only way to know that cancellation has completed.) .sh return value on success, .br pthread_cancel () returns 0; on error, it returns a nonzero error number. .sh errors .tp .b esrch no thread with the id .i thread could be found. .\" .sh versions .\" available since glibc 2.0 .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pthread_cancel () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes on linux, cancellation is implemented using signals. under the nptl threading implementation, the first real-time signal (i.e., signal 32) is used for this purpose. on linuxthreads, the second real-time signal is used, if real-time signals are available, otherwise .b sigusr2 is used. .sh examples the program below creates a thread and then cancels it. the main thread joins with the canceled thread to check that its exit status was .br pthread_canceled . the following shell session shows what happens when we run the program: .pp .in +4n .ex $ ./a.out thread_func(): started; cancellation disabled main(): sending cancellation request thread_func(): about to enable cancellation main(): thread was canceled .ee .in .ss program source \& .ex #include #include #include #include #include #define handle_error_en(en, msg) \e do { errno = en; perror(msg); exit(exit_failure); } while (0) static void * thread_func(void *ignored_argument) { int s; /* disable cancellation for a while, so that we don\(aqt immediately react to a cancellation request. */ s = pthread_setcancelstate(pthread_cancel_disable, null); if (s != 0) handle_error_en(s, "pthread_setcancelstate"); printf("thread_func(): started; cancellation disabled\en"); sleep(5); printf("thread_func(): about to enable cancellation\en"); s = pthread_setcancelstate(pthread_cancel_enable, null); if (s != 0) handle_error_en(s, "pthread_setcancelstate"); /* sleep() is a cancellation point. */ sleep(1000); /* should get canceled while we sleep */ /* should never get here. */ printf("thread_func(): not canceled!\en"); return null; } int main(void) { pthread_t thr; void *res; int s; /* start a thread and then send it a cancellation request. */ s = pthread_create(&thr, null, &thread_func, null); if (s != 0) handle_error_en(s, "pthread_create"); sleep(2); /* give thread a chance to get started */ printf("main(): sending cancellation request\en"); s = pthread_cancel(thr); if (s != 0) handle_error_en(s, "pthread_cancel"); /* join with thread to see what its exit status was. */ s = pthread_join(thr, &res); if (s != 0) handle_error_en(s, "pthread_join"); if (res == pthread_canceled) printf("main(): thread was canceled\en"); else printf("main(): thread wasn\(aqt canceled (shouldn\(aqt happen!)\en"); exit(exit_success); } .ee .sh see also .ad l .nh .br pthread_cleanup_push (3), .br pthread_create (3), .br pthread_exit (3), .br pthread_join (3), .br pthread_key_create (3), .br pthread_setcancelstate (3), .br pthread_setcanceltype (3), .br pthread_testcancel (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/lround.3 .so man3/getpwnam.3 .so man2/setfsuid.2 .so man3/strcat.3 .so man3/strstr.3 .so man3/fmin.3 # spdx-license-identifier: gpl-2.0-only ######################################################################## # # (c) copyright 2020, 2021, alejandro colomar # these functions are free software; you can redistribute them and/or # modify them under the terms of the gnu general public license # as published by the free software foundation; version 2. # # these functions are distributed in the hope that they will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # ######################################################################## ######################################################################## # exit status ex_ok=0; ex_usage=64; ######################################################################## # c # sed_rm_ccomments() removes c comments. # it can't handle multiple comments in a single line correctly, # nor mixed or embedded //... and /*...*/ comments. # use as a filter (see man_lsfunc() in this file). function sed_rm_ccomments() { sed 's%/\*.*\*/%%' \ |sed -e '\%/\*%,\%\*/%{\%(\*/|/\*)%!d; s%/\*.*%%; s%.*\*/%%;}' \ |sed 's%//.*%%'; } ######################################################################## # linux kernel # grep_syscall() finds the prototype of a syscall in the kernel sources, # printing the filename, line number, and the prototype. # it should be run from the root of the linux kernel source tree. # usage example: .../linux$ grep_syscall openat2; function grep_syscall() { if (($# != 1)); then >&2 echo "usage: ${funcname[0]} "; return ${ex_usage}; fi find * -type f \ |grep '\.c$' \ |sort \ |xargs pcregrep -mn "(?s)^\w*syscall_define.\(${1},.*?\)" \ |sed -e 's/^[^:]+:[0-9]+:/&\n/'; find * -type f \ |grep '\.[ch]$' \ |sort \ |xargs pcregrep -mn "(?s)^asmlinkage\s+[\w\s]+\**sys_${1}\s*\(.*?\)" \ |sed -e 's/^[^:]+:[0-9]+:/&\n/'; } # grep_syscall_def() finds the definition of a syscall in the kernel sources, # printing the filename, line number, and the function definition. # it should be run from the root of the linux kernel source tree. # usage example: .../linux$ grep_syscall_def openat2; function grep_syscall_def() { if (($# != 1)); then >&2 echo "usage: ${funcname[0]} "; return ${ex_usage}; fi find * -type f \ |grep '\.c$' \ |sort \ |xargs pcregrep -mn "(?s)^\w*syscall_define.\(${1},.*?^}" \ |sed -e 's/^[^:]+:[0-9]+:/&\n/'; } ######################################################################## # linux man-pages # man_section() prints specific manual page sections (description, synopsis, # ...) of all manual pages in a directory (or in a single manual page file). # usage example: .../man-pages$ man_section man2 synopsis 'conforming to'; function man_section() { if (($# < 2)); then >&2 echo "usage: ${funcname[0]}
..."; return ${ex_usage}; fi local page="$1"; shift; local sect="$@"; find "${page}" -type f \ |xargs wc -l \ |grep -v -e '\b1 ' -e '\btotal\b' \ |awk '{ print $2 }' \ |sort \ |while read -r manpage; do cat \ <(<${manpage} sed -n '/^\.th/,/^\.sh/{/^\.sh/!p}') \ <(for s in ${sect}; do <${manpage} \ sed -n \ -e "/^\.sh ${s}/p" \ -e "/^\.sh ${s}/,/^\.sh/{/^\.sh/!p}"; \ done;) \ |man -p cat -l - 2>/dev/null; done; } # man_lsfunc() prints the name of all c functions declared in the synopsis # of all manual pages in a directory (or in a single manual page file). # each name is printed in a separate line # usage example: .../man-pages$ man_lsfunc man2; function man_lsfunc() { if (($# < 1)); then >&2 echo "usage: ${funcname[0]} ..."; return ${ex_usage}; fi for arg in "$@"; do man_section "${arg}" 'synopsis'; done \ |sed_rm_ccomments \ |pcregrep -mn '(?s)^ [\w ]+ \**\w+\([\w\s(,)[\]*]+?(...)?\s*\); *$' \ |grep '^[0-9]' \ |sed 's/syscall(sys_\(\w*\),/\1(/' \ |sed -e 's/^[^(]+ \**(\w+)\(.*/\1/' \ |uniq; } # man_lsvar() prints the name of all c variables declared in the synopsis # of all manual pages in a directory (or in a single manual page file). # each name is printed in a separate line # usage example: .../man-pages$ man_lsvar man3; function man_lsvar() { if (($# < 1)); then >&2 echo "usage: ${funcname[0]} ..."; return ${ex_usage}; fi for arg in "$@"; do man_section "${arg}" 'synopsis'; done \ |sed_rm_ccomments \ |pcregrep -mv '(?s)^ [\w ]+ \**\w+\([\w\s(,)[\]*]+?(...)?\s*\); *$' \ |pcregrep -mn \ -e '(?s)^ +extern [\w ]+ \**\(\*+[\w ]+\)\([\w\s(,)[\]*]+?\s*\); *$' \ -e '^ +extern [\w ]+ \**[\w ]+; *$' \ |grep '^[0-9]' \ |grep -v 'typedef' \ |sed -e 's/^[0-9]+: +extern [^(]+ \**\(\*+(\w* )?(\w+)\)\(.*/\2/' \ |sed 's/^[0-9]\+: \+extern .* \**\(\w\+\); */\1/' \ |uniq; } # pdfman() renders a manual page in pdf # usage example: .../man-pages$ pdfman man2/membarrier.2; function pdfman() { if (($# != 1)); then >&2 echo "usage: ${funcname[0]} "; return ${ex_usage}; fi; local tmp="$(mktemp -t "${1##*/}.xxxxxx")"; <${1} \ man -tps -l - \ |ps2pdf - - \ >${tmp}; xdg-open ${tmp}; } # man_gitstaged prints a list of all files with changes staged for commit # (basename only if the files are within ), separated by ", ". # usage example: .../man-pages$ git commit -m "$(man_gitstaged): msg"; function man_gitstaged() { git diff --staged --name-only \ |sed "s/$/, /" \ |sed "s%man[1-9]/%%" \ |tr -d '\n' \ |sed "s/, $//" } ######################################################################## # glibc # grep_glibc_prototype() finds a function prototype in the glibc sources, # printing the filename, line number, and the prototype. # it should be run from the root of the glibc source tree. # usage example: .../glibc$ grep_glibc_prototype printf; function grep_glibc_prototype() { if (($# != 1)); then >&2 echo "usage: ${funcname[0]} "; return ${ex_usage}; fi find * -type f \ |grep '\.h$' \ |sort \ |xargs pcregrep -mn \ "(?s)^[\w[][\w\s(,)[:\]]+\s+\**${1}\s*\([\w\s(,)[\]*]+?(...)?\)[\w\s(,)[:\]]*;" \ |sed -e 's/^[^:]+:[0-9]+:/&\n/'; } .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:46:01 1993 by rik faith (faith@cs.unc.edu) .\" modified 11 june 1995 by andries brouwer (aeb@cwi.nl) .\" 2007-07-30 ulrich drepper : document fdopendir(). .th opendir 3 2021-03-22 "gnu" "linux programmer's manual" .sh name opendir, fdopendir \- open a directory .sh synopsis .nf .b #include .b #include .pp .bi "dir *opendir(const char *" name ); .bi "dir *fdopendir(int " fd ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fdopendir (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br opendir () function opens a directory stream corresponding to the directory \finame\fp, and returns a pointer to the directory stream. the stream is positioned at the first entry in the directory. .pp the .br fdopendir () function is like .br opendir (), but returns a directory stream for the directory referred to by the open file descriptor .ir fd . after a successful call to .br fdopendir (), .i fd is used internally by the implementation, and should not otherwise be used by the application. .sh return value the .br opendir () and .br fdopendir () functions return a pointer to the directory stream. on error, null is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces permission denied. .tp .b ebadf .i fd is not a valid file descriptor opened for reading. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoent directory does not exist, or \finame\fp is an empty string. .tp .b enomem insufficient memory to complete the operation. .tp .b enotdir \finame\fp is not a directory. .sh versions .br fdopendir () is available in glibc since version 2.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br opendir (), .br fdopendir () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br opendir () is present on svr4, 4.3bsd, and specified in posix.1-2001. .br fdopendir () is specified in posix.1-2008. .sh notes filename entries can be read from a directory stream using .br readdir (3). .pp the underlying file descriptor of the directory stream can be obtained using .br dirfd (3). .pp the .br opendir () function sets the close-on-exec flag for the file descriptor underlying the .ir "dir *" . the .br fdopendir () function leaves the setting of the close-on-exec flag unchanged for the file descriptor, .ir fd . posix.1-200x leaves it unspecified whether a successful call to .br fdopendir () will set the close-on-exec flag for the file descriptor, .ir fd . .sh see also .br open (2), .br closedir (3), .br dirfd (3), .br readdir (3), .br rewinddir (3), .br scandir (3), .br seekdir (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fenv.3 .\" copyright (c) 2015 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th dlinfo 3 2021-03-22 "linux" "linux programmer's manual" .sh name dlinfo \- obtain information about a dynamically loaded object .sh synopsis .nf .b #define _gnu_source .b #include .b #include .pp .br "int dlinfo(void *restrict " handle ", int " request \ ", void *restrict " info ); .pp link with \fi\-ldl\fp. .fi .sh description the .br dlinfo () function obtains information about the dynamically loaded object referred to by .ir handle (typically obtained by an earlier call to .br dlopen (3) or .br dlmopen (3)). the .i request argument specifies which information is to be returned. the .i info argument is a pointer to a buffer used to store information returned by the call; the type of this argument depends on .ir request . .pp the following values are supported for .ir request (with the corresponding type for .ir info shown in parentheses): .tp .br rtld_di_lmid " (\filmid_t *\fp)" obtain the id of the link-map list (namespace) in which .i handle is loaded. .tp .br rtld_di_linkmap " (\fistruct link_map **\fp)" obtain a pointer to the .i link_map structure corresponding to .ir handle . the .ir info argument points to a pointer to a .i link_map structure, defined in .i as: .ip .in +4n .ex struct link_map { elfw(addr) l_addr; /* difference between the address in the elf file and the address in memory */ char *l_name; /* absolute pathname where object was found */ elfw(dyn) *l_ld; /* dynamic section of the shared object */ struct link_map *l_next, *l_prev; /* chain of loaded objects */ /* plus additional fields private to the implementation */ }; .ee .in .tp .br rtld_di_origin " (\fichar *\fp)" copy the pathname of the origin of the shared object corresponding to .ir handle to the location pointed to by .ir info . .tp .br rtld_di_serinfo " (\fidl_serinfo *\fp)" obtain the library search paths for the shared object referred to by .ir handle . the .i info argument is a pointer to a .i dl_serinfo that contains the search paths. because the number of search paths may vary, the size of the structure pointed to by .ir info can vary. the .b rtld_di_serinfosize request described below allows applications to size the buffer suitably. the caller must perform the following steps: .rs .ip 1. 3 use a .b rtld_di_serinfosize request to populate a .i dl_serinfo structure with the size .ri ( dls_size ) of the structure needed for the subsequent .b rtld_di_serinfo request. .ip 2. allocate a .i dl_serinfo buffer of the correct size .ri ( dls_size ). .ip 3. use a further .b rtld_di_serinfosize request to populate the .i dls_size and .i dls_cnt fields of the buffer allocated in the previous step. .ip 4. use a .b rtld_di_serinfo to obtain the library search paths. .re .ip the .i dl_serinfo structure is defined as follows: .ip .in +4n .ex typedef struct { size_t dls_size; /* size in bytes of the whole buffer */ unsigned int dls_cnt; /* number of elements in \(aqdls_serpath\(aq */ dl_serpath dls_serpath[1]; /* actually longer, \(aqdls_cnt\(aq elements */ } dl_serinfo; .ee .in .ip each of the .i dls_serpath elements in the above structure is a structure of the following form: .ip .in +4n .ex typedef struct { char *dls_name; /* name of library search path directory */ unsigned int dls_flags; /* indicates where this directory came from */ } dl_serpath; .ee .in .ip the .i dls_flags field is currently unused, and always contains zero. .tp .br rtld_di_serinfosize " (\fidl_serinfo *\fp)" populate the .i dls_size and .i dls_cnt fields of the .i dl_serinfo structure pointed to by .ir info with values suitable for allocating a buffer for use in a subsequent .b rtld_di_serinfo request. .tp .br rtld_di_tls_modid " (\fisize_t *\fp, since glibc 2.4)" obtain the module id of this shared object's tls (thread-local storage) segment, as used in tls relocations. if this object does not define a tls segment, zero is placed in .ir *info . .tp .br rtld_di_tls_data " (\fivoid **\fp, since glibc 2.4)" obtain a pointer to the calling thread's tls block corresponding to this shared object's tls segment. if this object does not define a pt_tls segment, or if the calling thread has not allocated a block for it, null is placed in .ir *info . .sh return value on success, .br dlinfo () returns 0. on failure, it returns \-1; the cause of the error can be diagnosed using .br dlerror (3). .sh versions .br dlinfo () first appeared in glibc 2.3.3. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dlinfo () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a nonstandard gnu extension. .sh notes this function derives from the solaris function of the same name and also appears on some other systems. the sets of requests supported by the various implementations overlaps only partially. .sh examples the program below opens a shared objects using .br dlopen (3) and then uses the .b rtld_di_serinfosize and .b rtld_di_serinfo requests to obtain the library search path list for the library. here is an example of what we might see when running the program: .pp .in +4n .ex $ \fb./a.out /lib64/libm.so.6\fp dls_serpath[0].dls_name = /lib64 dls_serpath[1].dls_name = /usr/lib64 .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include int main(int argc, char *argv[]) { void *handle; dl_serinfo serinfo; dl_serinfo *sip; if (argc != 2) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } /* obtain a handle for shared object specified on command line. */ handle = dlopen(argv[1], rtld_now); if (handle == null) { fprintf(stderr, "dlopen() failed: %s\en", dlerror()); exit(exit_failure); } /* discover the size of the buffer that we must pass to rtld_di_serinfo. */ if (dlinfo(handle, rtld_di_serinfosize, &serinfo) == \-1) { fprintf(stderr, "rtld_di_serinfosize failed: %s\en", dlerror()); exit(exit_failure); } /* allocate the buffer for use with rtld_di_serinfo. */ sip = malloc(serinfo.dls_size); if (sip == null) { perror("malloc"); exit(exit_failure); } /* initialize the \(aqdls_size\(aq and \(aqdls_cnt\(aq fields in the newly allocated buffer. */ if (dlinfo(handle, rtld_di_serinfosize, sip) == \-1) { fprintf(stderr, "rtld_di_serinfosize failed: %s\en", dlerror()); exit(exit_failure); } /* fetch and print library search list. */ if (dlinfo(handle, rtld_di_serinfo, sip) == \-1) { fprintf(stderr, "rtld_di_serinfo failed: %s\en", dlerror()); exit(exit_failure); } for (int j = 0; j < serinfo.dls_cnt; j++) printf("dls_serpath[%d].dls_name = %s\en", j, sip\->dls_serpath[j].dls_name); exit(exit_success); } .ee .sh see also .br dl_iterate_phdr (3), .br dladdr (3), .br dlerror (3), .br dlopen (3), .br dlsym (3), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/uri.7 .\" copyright 2002 dimitri papadopoulos (dpo@club-internet.fr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-9 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-9 \- iso 8859-9 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-9 encodes the characters used in turkish. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-9 characters the following table displays the characters in iso 8859-9 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ¡ inverted exclamation mark 242 162 a2 ¢ cent sign 243 163 a3 £ pound sign 244 164 a4 ¤ currency sign 245 165 a5 ¥ yen sign 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 © copyright sign 252 170 aa ª feminine ordinal indicator 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 256 174 ae ® registered sign 257 175 af ¯ macron 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ´ acute accent 265 181 b5 µ micro sign 266 182 b6 ¶ pilcrow sign 267 183 b7 · middle dot 270 184 b8 ¸ cedilla 271 185 b9 ¹ superscript one 272 186 ba º masculine ordinal indicator 273 187 bb » right-pointing double angle quotation mark 274 188 bc ¼ vulgar fraction one quarter 275 189 bd ½ vulgar fraction one half 276 190 be ¾ vulgar fraction three quarters 277 191 bf ¿ inverted question mark 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 303 195 c3 ã latin capital letter a with tilde 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 å latin capital letter a with ring above 306 198 c6 æ latin capital letter ae 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 320 208 d0 ğ latin capital letter g with breve 321 209 d1 ñ latin capital letter n with tilde 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 õ latin capital letter o with tilde 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ø latin capital letter o with stroke 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd i̇ latin capital letter i with dot above 336 222 de ş latin capital letter s with cedilla 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 343 227 e3 ã latin small letter a with tilde 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 å latin small letter a with ring above 346 230 e6 æ latin small letter ae 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 360 240 f0 ğ latin small letter g with breve 361 241 f1 ñ latin small letter n with tilde 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 õ latin small letter o with tilde 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ø latin small letter o with stroke 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ı latin small letter dotless i 376 254 fe ş latin small letter s with cedilla 377 255 ff ÿ latin small letter y with diaeresis .te .sh notes iso 8859-9 is also known as latin-5. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .\" copyright (c) 2003 nick clifford (zaf@nrc.co.nz), jan 25, 2003 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl), aug 24, 2003 .\" copyright (c) 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2003-08-23 martin schulze improvements .\" 2003-08-24 aeb, large parts rewritten .\" 2004-08-06 christoph lameter , smp note .\" .th clock_getres 2 2021-03-22 "" "linux programmer's manual" .sh name clock_getres, clock_gettime, clock_settime \- clock and time functions .sh synopsis .nf .b #include .pp .bi "int clock_getres(clockid_t " clockid ", struct timespec *" res ); .pp .bi "int clock_gettime(clockid_t " clockid ", struct timespec *" tp ); .bi "int clock_settime(clockid_t " clockid ", const struct timespec *" tp ); .fi .pp link with \fi\-lrt\fp (only for glibc versions before 2.17). .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br clock_getres (), .br clock_gettime (), .br clock_settime (): .nf _posix_c_source >= 199309l .fi .sh description the function .br clock_getres () finds the resolution (precision) of the specified clock .ir clockid , and, if .i res is non-null, stores it in the \fistruct timespec\fp pointed to by .ir res . the resolution of clocks depends on the implementation and cannot be configured by a particular process. if the time value pointed to by the argument .i tp of .br clock_settime () is not a multiple of .ir res , then it is truncated to a multiple of .ir res . .pp the functions .br clock_gettime () and .br clock_settime () retrieve and set the time of the specified clock .ir clockid . .pp the .i res and .i tp arguments are .i timespec structures, as specified in .ir : .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds */ }; .ee .in .pp the .i clockid argument is the identifier of the particular clock on which to act. a clock may be system-wide and hence visible for all processes, or per-process if it measures time only within a single process. .pp all implementations support the system-wide real-time clock, which is identified by .br clock_realtime . its time represents seconds and nanoseconds since the epoch. when its time is changed, timers for a relative interval are unaffected, but timers for an absolute point in time are affected. .pp more clocks may be implemented. the interpretation of the corresponding time values and the effect on timers is unspecified. .pp sufficiently recent versions of glibc and the linux kernel support the following clocks: .tp .b clock_realtime a settable system-wide clock that measures real (i.e., wall-clock) time. setting this clock requires appropriate privileges. this clock is affected by discontinuous jumps in the system time (e.g., if the system administrator manually changes the clock), and by the incremental adjustments performed by .br adjtime (3) and ntp. .tp .br clock_realtime_alarm " (since linux 3.0; linux-specific)" like .br clock_realtime , but not settable. see .br timer_create (2) for further details. .tp .br clock_realtime_coarse " (since linux 2.6.32; linux-specific)" .\" added in commit da15cfdae03351c689736f8d142618592e3cebc3 a faster but less precise version of .br clock_realtime . this clock is not settable. use when you need very fast, but not fine-grained timestamps. requires per-architecture support, and probably also architecture support for this flag in the .br vdso (7). .tp .br clock_tai " (since linux 3.10; linux-specific)" .\" commit 1ff3c9677bff7e468e0c487d0ffefe4e901d33f4 a nonsettable system-wide clock derived from wall-clock time but ignoring leap seconds. this clock does not experience discontinuities and backwards jumps caused by ntp inserting leap seconds as .br clock_realtime does. .ip the acronym tai refers to international atomic time. .tp .b clock_monotonic a nonsettable system-wide clock that represents monotonic time since\(emas described by posix\(em"some unspecified point in the past". on linux, that point corresponds to the number of seconds that the system has been running since it was booted. .ip the .b clock_monotonic clock is not affected by discontinuous jumps in the system time (e.g., if the system administrator manually changes the clock), but is affected by the incremental adjustments performed by .br adjtime (3) and ntp. this clock does not count time that the system is suspended. all .b clock_monotonic variants guarantee that the time returned by consecutive calls will not go backwards, but successive calls may\(emdepending on the architecture\(emreturn identical (not-increased) time values. .tp .br clock_monotonic_coarse " (since linux 2.6.32; linux-specific)" .\" added in commit da15cfdae03351c689736f8d142618592e3cebc3 a faster but less precise version of .br clock_monotonic . use when you need very fast, but not fine-grained timestamps. requires per-architecture support, and probably also architecture support for this flag in the .br vdso (7). .tp .br clock_monotonic_raw " (since linux 2.6.28; linux-specific)" .\" added in commit 2d42244ae71d6c7b0884b5664cf2eda30fb2ae68, john stultz similar to .br clock_monotonic , but provides access to a raw hardware-based time that is not subject to ntp adjustments or the incremental adjustments performed by .br adjtime (3). this clock does not count time that the system is suspended. .tp .br clock_boottime " (since linux 2.6.39; linux-specific)" .\" commit 7fdd7f89006dd5a4c702fa0ce0c272345fa44ae0 .\" commit 70a08cca1227dc31c784ec930099a4417a06e7d0 a nonsettable system-wide clock that is identical to .br clock_monotonic , except that it also includes any time that the system is suspended. this allows applications to get a suspend-aware monotonic clock without having to deal with the complications of .br clock_realtime , which may have discontinuities if the time is changed using .br settimeofday (2) or similar. .tp .br clock_boottime_alarm " (since linux 3.0; linux-specific)" like .br clock_boottime . see .br timer_create (2) for further details. .tp .br clock_process_cputime_id " (since linux 2.6.12)" this is a clock that measures cpu time consumed by this process (i.e., cpu time consumed by all threads in the process). on linux, this clock is not settable. .tp .br clock_thread_cputime_id " (since linux 2.6.12)" this is a clock that measures cpu time consumed by this thread. on linux, this clock is not settable. .pp linux also implements dynamic clock instances as described below. .ss dynamic clocks in addition to the hard-coded system-v style clock ids described above, linux also supports posix clock operations on certain character devices. such devices are called "dynamic" clocks, and are supported since linux 2.6.39. .pp using the appropriate macros, open file descriptors may be converted into clock ids and passed to .br clock_gettime (), .br clock_settime (), and .br clock_adjtime (2). the following example shows how to convert a file descriptor into a dynamic clock id. .pp .in +4n .ex #define clockfd 3 #define fd_to_clockid(fd) ((\(ti(clockid_t) (fd) << 3) | clockfd) #define clockid_to_fd(clk) ((unsigned int) \(ti((clk) >> 3)) struct timespec ts; clockid_t clkid; int fd; fd = open("/dev/ptp0", o_rdwr); clkid = fd_to_clockid(fd); clock_gettime(clkid, &ts); .ee .in .sh return value .br clock_gettime (), .br clock_settime (), and .br clock_getres () return 0 for success. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces .br clock_settime () does not have write permission for the dynamic posix clock device indicated. .tp .b efault .i tp points outside the accessible address space. .tp .b einval the .i clockid specified is invalid for one of two reasons. either the system-v style hard coded positive value is out of range, or the dynamic clock id does not refer to a valid instance of a clock object. .\" linux also gives this error on attempts to set clock_process_cputime_id .\" and clock_thread_cputime_id, when probably the proper error should be .\" eperm. .tp .b einval .rb ( clock_settime ()): .i tp.tv_sec is negative or .i tp.tv_nsec is outside the range [0..999,999,999]. .tp .b einval the .i clockid specified in a call to .br clock_settime () is not a settable clock. .tp .br einval " (since linux 4.3)" .\" commit e1d7ba8735551ed79c7a0463a042353574b96da3 a call to .br clock_settime () with a .i clockid of .b clock_realtime attempted to set the time to a value less than the current value of the .b clock_monotonic clock. .tp .b enodev the hot-pluggable device (like usb for example) represented by a dynamic .i clk_id has disappeared after its character device was opened. .tp .b enotsup the operation is not supported by the dynamic posix clock device specified. .tp .b eperm .br clock_settime () does not have permission to set the clock indicated. .sh versions these system calls first appeared in linux 2.6. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clock_getres (), .br clock_gettime (), .br clock_settime () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2. .pp on posix systems on which these functions are available, the symbol .b _posix_timers is defined in \fi\fp to a value greater than 0. the symbols .br _posix_monotonic_clock , .br _posix_cputime , .b _posix_thread_cputime indicate that .br clock_monotonic , .br clock_process_cputime_id , .b clock_thread_cputime_id are available. (see also .br sysconf (3).) .sh notes posix.1 specifies the following: .rs .pp setting the value of the .b clock_realtime clock via .br clock_settime () shall have no effect on threads that are blocked waiting for a relative time service based upon this clock, including the .br nanosleep () function; nor on the expiration of relative timers based upon this clock. consequently, these time services shall expire when the requested relative interval elapses, independently of the new or old value of the clock. .re .pp according to posix.1-2001, a process with "appropriate privileges" may set the .b clock_process_cputime_id and .b clock_thread_cputime_id clocks using .br clock_settime (). on linux, these clocks are not settable (i.e., no process has "appropriate privileges"). .\" see http://bugzilla.kernel.org/show_bug.cgi?id=11972 .\" .ss c library/kernel differences on some architectures, an implementation of .br clock_gettime () is provided in the .br vdso (7). .\" .ss historical note for smp systems before linux added kernel support for .b clock_process_cputime_id and .br clock_thread_cputime_id , glibc implemented these clocks on many platforms using timer registers from the cpus (tsc on i386, ar.itc on itanium). these registers may differ between cpus and as a consequence these clocks may return .b bogus results if a process is migrated to another cpu. .pp if the cpus in an smp system have different clock sources, then there is no way to maintain a correlation between the timer registers since each cpu will run at a slightly different frequency. if that is the case, then .i clock_getcpuclockid(0) will return .b enoent to signify this condition. the two clocks will then be useful only if it can be ensured that a process stays on a certain cpu. .pp the processors in an smp system do not start all at exactly the same time and therefore the timer registers are typically running at an offset. some architectures include code that attempts to limit these offsets on bootup. however, the code cannot guarantee to accurately tune the offsets. glibc contains no provisions to deal with these offsets (unlike the linux kernel). typically these offsets are small and therefore the effects may be negligible in most cases. .pp since glibc 2.4, the wrapper functions for the system calls described in this page avoid the abovementioned problems by employing the kernel implementation of .b clock_process_cputime_id and .br clock_thread_cputime_id , on systems that provide such an implementation (i.e., linux 2.6.12 and later). .sh examples the program below demonstrates the use of .br clock_gettime () and .br clock_getres () with various clocks. this is an example of what we might see when running the program: .pp .in +4n .ex $ \fb./clock_times x\fp clock_realtime : 1585985459.446 (18356 days + 7h 30m 59s) resolution: 0.000000001 clock_tai : 1585985496.447 (18356 days + 7h 31m 36s) resolution: 0.000000001 clock_monotonic: 52395.722 (14h 33m 15s) resolution: 0.000000001 clock_boottime : 72691.019 (20h 11m 31s) resolution: 0.000000001 .ee .in .ss program source \& .ex /* clock_times.c licensed under gnu general public license v2 or later. */ #define _xopen_source 600 #include #include #include #include #include #include #define secs_in_day (24 * 60 * 60) static void displayclock(clockid_t clock, const char *name, bool showres) { struct timespec ts; if (clock_gettime(clock, &ts) == \-1) { perror("clock_gettime"); exit(exit_failure); } printf("%\-15s: %10jd.%03ld (", name, (intmax_t) ts.tv_sec, ts.tv_nsec / 1000000); long days = ts.tv_sec / secs_in_day; if (days > 0) printf("%ld days + ", days); printf("%2dh %2dm %2ds", (int) (ts.tv_sec % secs_in_day) / 3600, (int) (ts.tv_sec % 3600) / 60, (int) ts.tv_sec % 60); printf(")\en"); if (clock_getres(clock, &ts) == \-1) { perror("clock_getres"); exit(exit_failure); } if (showres) printf(" resolution: %10jd.%09ld\en", (intmax_t) ts.tv_sec, ts.tv_nsec); } int main(int argc, char *argv[]) { bool showres = argc > 1; displayclock(clock_realtime, "clock_realtime", showres); #ifdef clock_tai displayclock(clock_tai, "clock_tai", showres); #endif displayclock(clock_monotonic, "clock_monotonic", showres); #ifdef clock_boottime displayclock(clock_boottime, "clock_boottime", showres); #endif exit(exit_success); } .ee .sh see also .br date (1), .br gettimeofday (2), .br settimeofday (2), .br time (2), .br adjtime (3), .br clock_getcpuclockid (3), .br ctime (3), .br ftime (3), .br pthread_getcpuclockid (3), .br sysconf (3), .br time (7), .br time_namespaces (7), .br vdso (7), .br hwclock (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/drand48.3 .so man3/drand48.3 .so man2/select.2 .so man3/argz_add.3 .\" copyright 1995 yggdrasil computing, incorporated. .\" and copyright 2003, 2015 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th dlsym 3 2021-03-22 "linux" "linux programmer's manual" .sh name dlsym, dlvsym \- obtain address of a symbol in a shared object or executable .sh synopsis .nf .b #include .pp .bi "void *dlsym(void *restrict " handle ", const char *restrict " symbol ); .pp .b #define _gnu_source .b #include .pp .bi "void *dlvsym(void *restrict " handle ", const char *restrict " symbol , .bi " const char *restrict " version ); .pp link with \fi\-ldl\fp. .fi .sh description the function .br dlsym () takes a "handle" of a dynamic loaded shared object returned by .br dlopen (3) along with a null-terminated symbol name, and returns the address where that symbol is loaded into memory. if the symbol is not found, in the specified object or any of the shared objects that were automatically loaded by .br dlopen (3) when that object was loaded, .br dlsym () returns null. (the search performed by .br dlsym () is breadth first through the dependency tree of these shared objects.) .pp in unusual cases (see notes) the value of the symbol could actually be null. therefore, a null return from .br dlsym () need not indicate an error. the correct way to distinguish an error from a symbol whose value is null is to call .br dlerror (3) to clear any old error conditions, then call .br dlsym (), and then call .br dlerror (3) again, saving its return value into a variable, and check whether this saved value is not null. .pp there are two special pseudo-handles that may be specified in .ir handle : .tp .b rtld_default find the first occurrence of the desired symbol using the default shared object search order. the search will include global symbols in the executable and its dependencies, as well as symbols in shared objects that were dynamically loaded with the .br rtld_global flag. .tp .br rtld_next find the next occurrence of the desired symbol in the search order after the current object. this allows one to provide a wrapper around a function in another shared object, so that, for example, the definition of a function in a preloaded shared object (see .b ld_preload in .br ld.so (8)) can find and invoke the "real" function provided in another shared object (or for that matter, the "next" definition of the function in cases where there are multiple layers of preloading). .pp the .b _gnu_source feature test macro must be defined in order to obtain the definitions of .b rtld_default and .b rtld_next from .ir . .pp the function .br dlvsym () does the same as .br dlsym () but takes a version string as an additional argument. .sh return value on success, these functions return the address associated with .ir symbol . on failure, they return null; the cause of the error can be diagnosed using .br dlerror (3). .sh versions .br dlsym () is present in glibc 2.0 and later. .br dlvsym () first appeared in glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dlsym (), .br dlvsym () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001 describes .br dlsym (). the .br dlvsym () function is a gnu extension. .sh notes there are several scenarios when the address of a global symbol is null. for example, a symbol can be placed at zero address by the linker, via a linker script or with .i \-\-defsym command-line option. undefined weak symbols also have null value. finally, the symbol value may be the result of a gnu indirect function (ifunc) resolver function that returns null as the resolved value. in the latter case, .br dlsym () also returns null without error. however, in the former two cases, the behavior of gnu dynamic linker is inconsistent: relocation processing succeeds and the symbol can be observed to have null value, but .br dlsym () fails and .br dlerror () indicates a lookup error. .\" .ss history the .br dlsym () function is part of the dlopen api, derived from sunos. that system does not have .br dlvsym (). .sh examples see .br dlopen (3). .sh see also .br dl_iterate_phdr (3), .br dladdr (3), .br dlerror (3), .br dlinfo (3), .br dlopen (3), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/j0.3 .so man3/sqrt.3 .so man3/nextafter.3 .\" this man page is copyright (c) 2000 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: ipv6.7,v 1.3 2000/12/20 18:10:31 ak exp $ .\" .\" the following socket options are undocumented .\" all of the following are from: .\" commit 333fad5364d6b457c8d837f7d05802d2aaf8a961 .\" author: yoshifuji hideaki .\" support several new sockopt / ancillary data in advanced api (rfc3542). .\" ipv6_2292pktinfo (2.6.14) .\" formerly ipv6_pktinfo .\" ipv6_2292hopopts (2.6.14) .\" formerly ipv6_hopopts, which is documented .\" ipv6_2292dstopts (2.6.14) .\" formerly ipv6_dstopts, which is documented .\" ipv6_2292rthdr (2.6.14) .\" formerly ipv6_rthdr, which is documented .\" ipv6_2292pktoptions (2.6.14) .\" formerly ipv6_pktoptions .\" ipv6_2292hoplimit (2.6.14) .\" formerly ipv6_hoplimit, which is documented .\" .\" ipv6_recvhoplimit (2.6.14) .\" ipv6_recvhopopts (2.6.14) .\" ipv6_rthdrdstopts (2.6.14) .\" ipv6_recvrthdr (2.6.14) .\" ipv6_recvdstopts (2.6.14) .\" .\" ipv6_recvpathmtu (2.6.35, flag value added in 2.6.14) .\" commit 793b14731686595a741d9f47726ad8b9a235385a .\" author: brian haley .\" ipv6_pathmtu (2.6.35, flag value added in 2.6.14) .\" commit 793b14731686595a741d9f47726ad8b9a235385a .\" author: brian haley .\" ipv6_dontfrag (2.6.35, flag value added in 2.6.14) .\" commit 793b14731686595a741d9f47726ad8b9a235385a .\" author: brian haley .\" commit 4b340ae20d0e2366792abe70f46629e576adaf5e .\" author: brian haley .\" .\" ipv6_recvtclass (2.6.14) .\" commit 41a1f8ea4fbfcdc4232f023732584aae2220de31 .\" author: yoshifuji hideaki .\" based on patch from david l stevens .\" .\" ipv6_checksum (2.2) .\" ipv6_nexthop (2.2) .\" ipv6_join_anycast (2.4.21 / 2.6) .\" ipv6_leave_anycast (2.4.21 / 2.6) .\" ipv6_flowlabel_mgr (2.2.7 / 2.4) .\" ipv6_flowinfo_send (2.2.7 / 2.4) .\" ipv6_ipsec_policy (2.6) .\" ipv6_xfrm_policy (2.6) .\" ipv6_tclass (2.6) .\" .\" ipv6_addr_preferences (2.6.26) .\" commit 7cbca67c073263c179f605bdbbdc565ab29d801d .\" author: yoshifuji hideaki .\" ipv6_minhopcount (2.6.35) .\" commit e802af9cabb011f09b9c19a82faef3dd315f27eb .\" author: stephen hemminger .\" ipv6_origdstaddr (2.6.37) .\" actually a cmsg rather than a sockopt? .\" in header file, we have ipv6_recvorigdstaddr == ipv6_origdstaddr .\" commit 6c46862280c5f55eda7750391bc65cd7e08c7535 .\" author: balazs scheidler .\" ipv6_recvorigdstaddr (2.6.37) .\" commit 6c46862280c5f55eda7750391bc65cd7e08c7535 .\" author: balazs scheidler .\" support for ipv6_recvorigdstaddr sockopt for udp sockets .\" were contributed by harry mason. .\" ipv6_transparent (2.6.37) .\" commit 6c46862280c5f55eda7750391bc65cd7e08c7535 .\" author: balazs scheidler .\" ipv6_unicast_if (3.4) .\" commit c4062dfc425e94290ac427a98d6b4721dd2bc91f .\" author: erich e. hoover .\" .th ipv6 7 2021-03-22 "linux" "linux programmer's manual" .sh name ipv6 \- linux ipv6 protocol implementation .sh synopsis .nf .b #include .b #include .pp .ib tcp6_socket " = socket(af_inet6, sock_stream, 0);" .ib raw6_socket " = socket(af_inet6, sock_raw, " protocol ");" .ib udp6_socket " = socket(af_inet6, sock_dgram, " protocol ");" .fi .sh description linux 2.2 optionally implements the internet protocol, version 6. this man page contains a description of the ipv6 basic api as implemented by the linux kernel and glibc 2.1. the interface is based on the bsd sockets interface; see .br socket (7). .pp the ipv6 api aims to be mostly compatible with the ipv4 api (see .br ip (7)). only differences are described in this man page. .pp to bind an .b af_inet6 socket to any process, the local address should be copied from the .i in6addr_any variable which has .i in6_addr type. in static initializations, .b in6addr_any_init may also be used, which expands to a constant expression. both of them are in network byte order. .pp the ipv6 loopback address (::1) is available in the global .i in6addr_loopback variable. for initializations, .b in6addr_loopback_init should be used. .pp ipv4 connections can be handled with the v6 api by using the v4-mapped-on-v6 address type; thus a program needs to support only this api type to support both protocols. this is handled transparently by the address handling functions in the c library. .pp ipv4 and ipv6 share the local port space. when you get an ipv4 connection or packet to an ipv6 socket, its source address will be mapped to v6 and it will be mapped to v6. .ss address format .in +4n .ex struct sockaddr_in6 { sa_family_t sin6_family; /* af_inet6 */ in_port_t sin6_port; /* port number */ uint32_t sin6_flowinfo; /* ipv6 flow information */ struct in6_addr sin6_addr; /* ipv6 address */ uint32_t sin6_scope_id; /* scope id (new in 2.4) */ }; struct in6_addr { unsigned char s6_addr[16]; /* ipv6 address */ }; .ee .in .pp .i sin6_family is always set to .br af_inet6 ; .i sin6_port is the protocol port (see .i sin_port in .br ip (7)); .i sin6_flowinfo is the ipv6 flow identifier; .i sin6_addr is the 128-bit ipv6 address. .i sin6_scope_id is an id depending on the scope of the address. it is new in linux 2.4. linux supports it only for link-local addresses, in that case .i sin6_scope_id contains the interface index (see .br netdevice (7)) .pp ipv6 supports several address types: unicast to address a single host, multicast to address a group of hosts, anycast to address the nearest member of a group of hosts (not implemented in linux), ipv4-on-ipv6 to address an ipv4 host, and other reserved address types. .pp the address notation for ipv6 is a group of 8 4-digit hexadecimal numbers, separated with a \(aq:\(aq. \&"::" stands for a string of 0 bits. special addresses are ::1 for loopback and ::ffff: for ipv4-mapped-on-ipv6. .pp the port space of ipv6 is shared with ipv4. .ss socket options ipv6 supports some protocol-specific socket options that can be set with .br setsockopt (2) and read with .br getsockopt (2). the socket option level for ipv6 is .br ipproto_ipv6 . a boolean integer flag is zero when it is false, otherwise true. .tp .b ipv6_addrform turn an .b af_inet6 socket into a socket of a different address family. only .b af_inet is currently supported for that. it is allowed only for ipv6 sockets that are connected and bound to a v4-mapped-on-v6 address. the argument is a pointer to an integer containing .br af_inet . this is useful to pass v4-mapped sockets as file descriptors to programs that don't know how to deal with the ipv6 api. .tp .b ipv6_add_membership, ipv6_drop_membership control membership in multicast groups. argument is a pointer to a .ir "struct ipv6_mreq" . .tp .b ipv6_mtu .br getsockopt (): retrieve the current known path mtu of the current socket. valid only when the socket has been connected. returns an integer. .ip .br setsockopt (): set the mtu to be used for the socket. the mtu is limited by the device mtu or the path mtu when path mtu discovery is enabled. argument is a pointer to integer. .tp .b ipv6_mtu_discover control path-mtu discovery on the socket. see .b ip_mtu_discover in .br ip (7) for details. .tp .b ipv6_multicast_hops set the multicast hop limit for the socket. argument is a pointer to an integer. \-1 in the value means use the route default, otherwise it should be between 0 and 255. .tp .b ipv6_multicast_if set the device for outgoing multicast packets on the socket. this is allowed only for .b sock_dgram and .b sock_raw socket. the argument is a pointer to an interface index (see .br netdevice (7)) in an integer. .tp .b ipv6_multicast_loop control whether the socket sees multicast packets that it has send itself. argument is a pointer to boolean. .tp .br ipv6_recvpktinfo " (since linux 2.6.14)" set delivery of the .b ipv6_pktinfo control message on incoming datagrams. such control messages contain a .ir "struct in6_pktinfo" , as per rfc 3542. allowed only for .b sock_dgram or .b sock_raw sockets. argument is a pointer to a boolean value in an integer. .tp .nh .b ipv6_rthdr, ipv6_authhdr, ipv6_dstopts, ipv6_hopopts, ipv6_flowinfo, ipv6_hoplimit .hy set delivery of control messages for incoming datagrams containing extension headers from the received packet. .b ipv6_rthdr delivers the routing header, .b ipv6_authhdr delivers the authentication header, .b ipv6_dstopts delivers the destination options, .b ipv6_hopopts delivers the hop options, .b ipv6_flowinfo delivers an integer containing the flow id, .b ipv6_hoplimit delivers an integer containing the hop count of the packet. the control messages have the same type as the socket option. all these header options can also be set for outgoing packets by putting the appropriate control message into the control buffer of .br sendmsg (2). allowed only for .b sock_dgram or .b sock_raw sockets. argument is a pointer to a boolean value. .tp .b ipv6_recverr control receiving of asynchronous error options. see .b ip_recverr in .br ip (7) for details. argument is a pointer to boolean. .tp .b ipv6_router_alert pass forwarded packets containing a router alert hop-by-hop option to this socket. allowed only for .b sock_raw sockets. the tapped packets are not forwarded by the kernel, it is the user's responsibility to send them out again. argument is a pointer to an integer. a positive integer indicates a router alert option value to intercept. packets carrying a router alert option with a value field containing this integer will be delivered to the socket. a negative integer disables delivery of packets with router alert options to this socket. .tp .b ipv6_unicast_hops set the unicast hop limit for the socket. argument is a pointer to an integer. \-1 in the value means use the route default, otherwise it should be between 0 and 255. .tp .br ipv6_v6only " (since linux 2.4.21 and 2.6)" .\" see rfc 3493 if this flag is set to true (nonzero), then the socket is restricted to sending and receiving ipv6 packets only. in this case, an ipv4 and an ipv6 application can bind to a single port at the same time. .ip if this flag is set to false (zero), then the socket can be used to send and receive packets to and from an ipv6 address or an ipv4-mapped ipv6 address. .ip the argument is a pointer to a boolean value in an integer. .ip the default value for this flag is defined by the contents of the file .ir /proc/sys/net/ipv6/bindv6only . the default value for that file is 0 (false). .\" flowlabel_mgr, flowinfo_send .sh errors .tp .b enodev the user tried to .br bind (2) to a link-local ipv6 address, but the .i sin6_scope_id in the supplied .i sockaddr_in6 structure is not a valid interface index. .sh versions linux 2.4 will break binary compatibility for the .i sockaddr_in6 for 64-bit hosts by changing the alignment of .i in6_addr and adding an additional .i sin6_scope_id field. the kernel interfaces stay compatible, but a program including .i sockaddr_in6 or .i in6_addr into other structures may not be. this is not a problem for 32-bit hosts like i386. .pp the .i sin6_flowinfo field is new in linux 2.4. it is transparently passed/read by the kernel when the passed address length contains it. some programs that pass a longer address buffer and then check the outgoing address length may break. .sh notes the .i sockaddr_in6 structure is bigger than the generic .ir sockaddr . programs that assume that all address types can be stored safely in a .i struct sockaddr need to be changed to use .i struct sockaddr_storage for that instead. .pp .br sol_ip , .br sol_ipv6 , .br sol_icmpv6 , and other .b sol_* socket options are nonportable variants of .br ipproto_* . see also .br ip (7). .sh bugs the ipv6 extended api as in rfc\ 2292 is currently only partly implemented; although the 2.2 kernel has near complete support for receiving options, the macros for generating ipv6 options are missing in glibc 2.1. .pp ipsec support for eh and ah headers is missing. .pp flow label management is not complete and not documented here. .pp this man page is not complete. .sh see also .br cmsg (3), .br ip (7) .pp rfc\ 2553: ipv6 basic api; linux tries to be compliant to this. rfc\ 2460: ipv6 specification. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getspnam.3 .\" copyright (c) 2016 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th cgroup_namespaces 7 2020-11-01 "linux" "linux programmer's manual" .sh name cgroup_namespaces \- overview of linux cgroup namespaces .sh description for an overview of namespaces, see .br namespaces (7). .pp cgroup namespaces virtualize the view of a process's cgroups (see .br cgroups (7)) as seen via .ir /proc/[pid]/cgroup and .ir /proc/[pid]/mountinfo . .pp each cgroup namespace has its own set of cgroup root directories. these root directories are the base points for the relative locations displayed in the corresponding records in the .ir /proc/[pid]/cgroup file. when a process creates a new cgroup namespace using .br clone (2) or .br unshare (2) with the .br clone_newcgroup flag, its current cgroups directories become the cgroup root directories of the new namespace. (this applies both for the cgroups version 1 hierarchies and the cgroups version 2 unified hierarchy.) .pp when reading the cgroup memberships of a "target" process from .ir /proc/[pid]/cgroup , the pathname shown in the third field of each record will be relative to the reading process's root directory for the corresponding cgroup hierarchy. if the cgroup directory of the target process lies outside the root directory of the reading process's cgroup namespace, then the pathname will show .i ../ entries for each ancestor level in the cgroup hierarchy. .pp the following shell session demonstrates the effect of creating a new cgroup namespace. .pp first, (as superuser) in a shell in the initial cgroup namespace, we create a child cgroup in the .i freezer hierarchy, and place a process in that cgroup that we will use as part of the demonstration below: .pp .in +4n .ex # \fbmkdir \-p /sys/fs/cgroup/freezer/sub2\fp # \fbsleep 10000 &\fp # create a process that lives for a while [1] 20124 # \fbecho 20124 > /sys/fs/cgroup/freezer/sub2/cgroup.procs\fp .ee .in .pp we then create another child cgroup in the .i freezer hierarchy and put the shell into that cgroup: .pp .in +4n .ex # \fbmkdir \-p /sys/fs/cgroup/freezer/sub\fp # \fbecho $$\fp # show pid of this shell 30655 # \fbecho 30655 > /sys/fs/cgroup/freezer/sub/cgroup.procs\fp # \fbcat /proc/self/cgroup | grep freezer\fp 7:freezer:/sub .ee .in .pp next, we use .br unshare (1) to create a process running a new shell in new cgroup and mount namespaces: .pp .in +4n .ex # \fbps1="sh2# " unshare \-cm bash\fp .ee .in .pp from the new shell started by .br unshare (1), we then inspect the .ir /proc/[pid]/cgroup files of, respectively, the new shell, a process that is in the initial cgroup namespace .ri ( init , with pid 1), and the process in the sibling cgroup .ri ( sub2 ): .pp .in +4n .ex sh2# \fbcat /proc/self/cgroup | grep freezer\fp 7:freezer:/ sh2# \fbcat /proc/1/cgroup | grep freezer\fp 7:freezer:/.. sh2# \fbcat /proc/20124/cgroup | grep freezer\fp 7:freezer:/../sub2 .ee .in .pp from the output of the first command, we see that the freezer cgroup membership of the new shell (which is in the same cgroup as the initial shell) is shown defined relative to the freezer cgroup root directory that was established when the new cgroup namespace was created. (in absolute terms, the new shell is in the .i /sub freezer cgroup, and the root directory of the freezer cgroup hierarchy in the new cgroup namespace is also .ir /sub . thus, the new shell's cgroup membership is displayed as \(aq/\(aq.) .pp however, when we look in .ir /proc/self/mountinfo we see the following anomaly: .pp .in +4n .ex sh2# \fbcat /proc/self/mountinfo | grep freezer\fp 155 145 0:32 /.. /sys/fs/cgroup/freezer ... .ee .in .pp the fourth field of this line .ri ( /.. ) should show the directory in the cgroup filesystem which forms the root of this mount. since by the definition of cgroup namespaces, the process's current freezer cgroup directory became its root freezer cgroup directory, we should see \(aq/\(aq in this field. the problem here is that we are seeing a mount entry for the cgroup filesystem corresponding to the initial cgroup namespace (whose cgroup filesystem is indeed rooted at the parent directory of .ir sub ). to fix this problem, we must remount the freezer cgroup filesystem from the new shell (i.e., perform the mount from a process that is in the new cgroup namespace), after which we see the expected results: .pp .in +4n .ex sh2# \fbmount \-\-make\-rslave /\fp # don\(aqt propagate mount events # to other namespaces sh2# \fbumount /sys/fs/cgroup/freezer\fp sh2# \fbmount \-t cgroup \-o freezer freezer /sys/fs/cgroup/freezer\fp sh2# \fbcat /proc/self/mountinfo | grep freezer\fp 155 145 0:32 / /sys/fs/cgroup/freezer rw,relatime ... .ee .in .\" .sh conforming to namespaces are a linux-specific feature. .sh notes use of cgroup namespaces requires a kernel that is configured with the .b config_cgroups option. .pp the virtualization provided by cgroup namespaces serves a number of purposes: .ip * 2 it prevents information leaks whereby cgroup directory paths outside of a container would otherwise be visible to processes in the container. such leakages could, for example, reveal information about the container framework to containerized applications. .ip * it eases tasks such as container migration. the virtualization provided by cgroup namespaces allows containers to be isolated from knowledge of the pathnames of ancestor cgroups. without such isolation, the full cgroup pathnames (displayed in .ir /proc/self/cgroups ) would need to be replicated on the target system when migrating a container; those pathnames would also need to be unique, so that they don't conflict with other pathnames on the target system. .ip * it allows better confinement of containerized processes, because it is possible to mount the container's cgroup filesystems such that the container processes can't gain access to ancestor cgroup directories. consider, for example, the following scenario: .rs 4 .ip \(bu 2 we have a cgroup directory, .ir /cg/1 , that is owned by user id 9000. .ip \(bu we have a process, .ir x , also owned by user id 9000, that is namespaced under the cgroup .ir /cg/1/2 (i.e., .i x was placed in a new cgroup namespace via .br clone (2) or .br unshare (2) with the .br clone_newcgroup flag). .re .ip in the absence of cgroup namespacing, because the cgroup directory .ir /cg/1 is owned (and writable) by uid 9000 and process .i x is also owned by user id 9000, process .i x would be able to modify the contents of cgroups files (i.e., change cgroup settings) not only in .ir /cg/1/2 but also in the ancestor cgroup directory .ir /cg/1 . namespacing process .ir x under the cgroup directory .ir /cg/1/2 , in combination with suitable mount operations for the cgroup filesystem (as shown above), prevents it modifying files in .ir /cg/1 , since it cannot even see the contents of that directory (or of further removed cgroup ancestor directories). combined with correct enforcement of hierarchical limits, this prevents process .i x from escaping the limits imposed by ancestor cgroups. .sh see also .br unshare (1), .br clone (2), .br setns (2), .br unshare (2), .br proc (5), .br cgroups (7), .br credentials (7), .br namespaces (7), .br user_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. ==================== changes in man-pages-2.00 ==================== released: 2004-12-16 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alberto bertogli anand kumria andrey kiselev andries brouwer chris green branden robinson emmanuel colbus enrico zini eric estievenart fabian kreutz florian weimer jan kuznik joey (martin) schulze johannes berg john v. belmonte karel kulhavy luis javier merino morán martin pool richard kreckel vasya pupkin apologies if i missed anyone! global changes -------------- various pages fabian kreutz many math pages had their synopses compressed, as per suggestion from fabian kreutz. various pages fabian kreutz / aeb many minor content and formatting bug fixes were made to the math pages, following suggestions from fabian kreutz (who recently translated many of the 1.70 math pages into german) and andries brouwer. various pages mtk for consistency, all instances of "super-user" were changed to the more common "superuser". various pages vasya pupkin / mtk after a note from vasya pupkin, i added to the synopsis of several section 2 pages using the _syscalln() macros. in addition: -- erroneous semicolons at the end of _syscalln() were removed on various pages. -- types such as "uint" in syscalln() declarations were changed to "unsigned int", etc. -- various other minor breakages in the synopses were fixed. the affected pages are: getdents.2 gettid.2 llseek.2 mmap2.2 modify_ldt.2 pivot_root.2 quotactl.2 readdir.2 sysctl.2 syslog.2 tkill.2 typographical or grammatical errors have been corrected in several other places. changes to individual pages --------------------------- bind.2 florian weimer added 'const' to declaration of 'my_addr' in prototype. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=239762. fcntl.2 martin pool added o_noatime to list of flags that can be changed via f_setfl. mtk/aeb noted f_getown bug after suggestion from aeb. see also: http://marc.theaimsgroup.com/?l=linux-kernel&m=108380640603164&w=2 getrlimit.2 mtk material on getrusage.2 has been separated out into its own page. rewrote discussion on rlimit_memlock to incorporate kernel 2.6.9 changes. added note on rlimit_cpu error in older kernels. added rlimit_sigpending. also made a few other minor changes. getrusage.2 mtk this page is new(ish) -- it was created by splitting getrlimit.2. repaired note on sigchld behavior to note that the posix non-conformance has been fixed in 2.6.9. kill.2 modified after suggestion from emmanuel colbus changed wording of sentence under notes describing when signals can be sent to init(1). mlock.2 munlock.2 mlockall.2 munlockall.2 these have been consolidated into a single mlock.2 page. in the process, much duplication was eliminated and new information was added about rlimit_memlock and the changes in memory locking in kernel 2.6.9, mmap.2 mtk added cross-ref to setrlimit(2) concerning memory locking limits. eric estievenart note that map_fixed replaces existing mappings msgctl.2 mtk substantial language and formatting clean-ups. added msqid_ds and ipc_perm structure definitions. msgget.2 mtk substantial language and formatting clean-ups. added notes on /proc files. msgop.2 mtk substantial language and formatting clean-ups. added notes on /proc files. open.2 martin pool added o_noatime (new in linux 2.6.8) mtk reordered list of 'flags' description alphabetically personality.2 2004-11-03 applied patch from martin schulze semctl.2 mtk substantial language and formatting clean-ups. rewrote semun text. added semid_ds and ipc_perm structure definitions. semget.2 mtk substantial language and formatting clean-ups. added notes on /proc files. rewrote bugs note about semget()'s failure to initialize semaphore values. semop.2 mtk substantial language and formatting clean-ups. added notes on /proc files. shmctl.2 mtk substantial language and formatting clean-ups. updated shmid_ds structure definitions. added information on shm_dest and shm_locked flags. noted that cap_ipc_lock is not required for shm_unlock since kernel 2.6.9. added notes on 2.6.9 rlimit_memlock changes. added rlimit_sigpending (new in linux 2.6.8) shmget.2 mtk substantial language and formatting clean-ups. added notes on /proc files. shmop.2 mtk substantial language and formatting clean-ups. changed wording and placement of sentence regarding attachment of segments marked for destruction. sigaction.2 mtk added mention of sigcont under sa_nocldstop. added sa_nocldwait. updated discussion for posix.1-2001 and sigchld and sa_flags. noted that cld_continued is supported since linux 2.6.9. added si_tkill (new in linux 2.4.19). other minor changes. signal.2 mtk removed text on ignoring sigchld; replaced with pointer to sigaction.2. sigwaitinfo.2 after bug report from andrey kiselev fixed prototype: "timeout" --> "*timeout" as per: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=222145 stat.2 enrico zini added text to clarify that s_is*() macros should be applied to st_mode field. as per: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=249698 swapon.2 after debian bug report from anand kumria added "no swap space signature" to einval error. mtk added einval error for swapoff() ("not currently a swap area"). added ebusy error for swapon(). a few formatting fixes. times.2 mtk in linux 2.6, the return value of times changed; it is no longer time since boot, but rather: boot_time + 2^32 / hz - 300 repaired note on sigchld behavior to note that the posix non-conformance has been fixed in 2.6.9. some formatting fixes. undocumented.2 after bug report from johannes berg changed .th unimplemented to: .th undocumented as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=220741 wait.2 mtk added waitid(2). added wcontinued and wifcontinued (new in 2.6.10). added text on sa_nocldstop. updated discussion of sa_nocldwait to reflect 2.6 behavior. much other text rewritten. wait4.2 mtk rewrote this page, removing much duplicated information, and replacing with pointers to wait.2. luis javier merino morán / mtk conforming to said "svr4, posix". changed to "4.3bsd" waitid.2 mtk new link to wait.2 assert.3 after bug report from branden robinson the assert() failure message goes to stderr not stdout. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=284814 ctime.3 mtk noted that 0 in tm_mday is interpreted to mean the last day of the preceding month. getnameinfo.3 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=229618 getnameinfo() does not set errno, it returns a non-zero value indicating the error. mtk added eai_overflow error killpg.3 mtk minor changes to see also and conforming to. lseek64.3 aeb new page by andries brouwer tzset.3 richard kreckel change "null" to "empty" when talking about the value of tz. http://sources.redhat.com/bugzilla/show_bug.cgi?id=601 printf.3 after bug report from jan kuznik http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=205736 fixed bad realloc() use in snprintf() example realpath.3 mtk added discussion of resolved_path == null. random.4 after bug report from john v. belmonte updated init and quit scripts to reflect kernel 2.4/2.6 reality (scripts taken from drivers/char/random.c) as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=247779 proc.5 mtk updated description of /proc/loadavg to include nr_running(), nr_threads, last_pid. rtsig-max and rtsig-nr went away in 2.6.8 updated statm, and fixed error in order of list boot.7 applied patch from martin schulze capabilities.7 mtk added o_noatime for cap_fowner netdevice.7 karel kulhavy and aeb formatting fix after note from karel kulhavy and aeb, plus a few wording fixes. signal.7 mtk /proc/sys/kernel/rtsig-* were superseded by rlimit_sigpending in kernel 2.6.8. tcp.7 mtk/aeb updated details of interaction of tcp_cork and tcp_nodelay. ==================== changes in man-pages-2.01 ==================== released: 2004-12-20 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: carsten hey johannes berg joshua kwan marek habersack martin schulze matthew dempsky matthew gregan pedro zorzenon neto tony crawford apologies if i missed anyone! global changes -------------- accept.2 close.2 send.2 setsid.2 socket.2 closedir.3 initgroups.3 mkstemp.3 opendir.3 readdir.3 telldir.3 matthew dempsky, mtk triggered by http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=283179 the wording describing how errno is set was fixed up in these pages. typographical or grammatical errors have been corrected in several other places. changes to individual pages --------------------------- sendfile.2 mtk adjusted descriptions of argument file types to be closer to 2.6 reality. wording and formatting changes. ctan.3 ctanh.3 tony crawford as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=270817 formulae on the pages should be t = s / c not t = c / s. errno.3 martin schulze, mtk removed errno declaration from prototype, added notes on historical need for this declaration. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=174175 aio_return.3 as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=224953 changed erroneous "aio_return(2)" to "aio_return(3)". posix_openpt.3 mtk new by mtk ptsname.3 mtk added description of ptsname_r(). added errors. ptsname_r.3 mtk new link to ptsname.3. shm_open.3 matthew gregan add to synopsis as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=271243 strcasecmp.3 marek habersack .sh "conforming to" -bsd 4.4 +bsd 4.4, susv3 as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=234443 strfry.3 joshua kwan added _gnu_source to prototype as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=213538 strftime.3 cartsen hey as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=276248 changed range for "%s" from 0..61 to 0..60. susv3 says 0..60. i think the manual page probably says 0..61, because that's what susv2 said. (some other implementations' man pages also say 0..61 -- e.g., solaris 8 & 9, tru64 5.1b; freebsd 5.1 says 0..60.) the glibc manual currently says 0..60. given that susv3 says 0..60, i've changed the manual page to also say this: -the second as a decimal number (range 00 to 61). +the second as a decimal number (range 00 to 60). +(the range is up to 60 to allow for occasional leap seconds.) sysconf.3 johannes berg see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=226974 -.br posix2_fort_run " - " _sc_2_fort_dev +.br posix2_fort_dev " - " _sc_2_fort_dev system.3 pedro zorzenon as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=242638 noted use of _xopen_source to get macros from for wait(2). mtk changed name of argument from 'string' to 'command' (like posix). noted that glibc does nowadays explicitly check for the existence of the shell if 'command' is null, rather than the older behavior of assuming the shell exists and always returning 1 if 'command' is null. other wording and formatting clean-ups. undocumented.3 remove some functions names that *are* documented. ==================== changes in man-pages-2.02 ==================== released: 2005-04-14 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer branden robinson colin watson david lloyd gordon jin heikki orsila jamie lokier johan walles kai makisara marko kohtala martin pool martin (joey) schulze matthias lang michael haardt michael mühlebach mike frysinger sasa stevanovic serguei leontiev apologies if i missed anyone! global changes -------------- ctime.3 tzselect.8 zdump.8 zic.8 martin (joey) schulze removed see also reference to nonexistent newctime(3). see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=236884 typographical or grammatical errors have been corrected in several other places. changes to individual pages --------------------------- clone.2 mtk noted the pid caching behavior of nptl's getpid() wrapper under bugs. added futex(2), set_thread_area(2), set_tid_address(2), tkill(2) under see also. epoll_ctl.2 epoll_create.2 marko kohtala / mtk improved various error descriptions. epoll_wait.2 david lloyd / mike frysinger, marko kohtala added eintr to errors. fcntl.2 jamie lokier / mtk improved discussion of f_setown and f_setsig with respect to multi-threaded programs. generally cleaned up the discussion of f_setown. updated conforming to to note that f_getown and f_setown are now in posix. link.2 mtk noted discrepancy between linux and posix.1 when oldpath is a symbolic link. see: http://bugs.linuxbase.org/show_bug.cgi?id=367 and: http://www.opengroup.org/austin/mailarchives/ag/msg08152.html michael haardt / mtk clarified exdev error description: it isn't possible to link across mount points, even if the mount points refer to the same file system. mincore.2 mtk, after note from gordon jin updated errors. pipe.2 as per message from serguei leontiev removed svr2, at&t, and bsd from conforming to, since a pipe on those systems is actually bidirectional. (pipes are implemented as streams on the former, and sockets on the latter.) posix_fadvise.2 mtk noted kernel version where posix_fadvise() appeared and noted bug in handling of 'len' in kernels < 2.6.6. rename.2 michael haardt clarified exdev error description: it isn't possible to rename a file across mount points, even if the mount points refer to the same file system. semop.2 mtk noted kernel version numbers for semtimedop(). setitimer.2 matthias lang, mtk noted max_sec_in_jiffies ceiling. added note about treatment of out-of-range tv_usec values. sigqueue.2 johan walles, martin (joey) schulze added sigqueue.2 to see also. times.2 mtk added notes on non-standard behavior: linux allows 'buf' to be null, but posix.1 doesn't specify this and it's non-portable. uselib.2 andries brouwer improved description; clarified distinction between eacces and enoexec. bcopy.3 heikki orsila bcopy() handles overlapping case, but memcpy() does not, so for consistency memmove() should be also mentioned. getmntent_r.3 martin (joey) schulze new link to man3/getmntent.3. memcpy.3 small wording change after suggestion from sasa stevanovic. strcasestr.3 mtk created as link to strstr.3. strftime.3 mtk noted that susv2 allowed a range of 00 to 61 for %s specifier. strstr.3 mtk added description of strcasestr(). random.4 aeb improved description of read from /dev/urandom. st.4 kai makisara substantial updates. man.7 martin schulze branden robinson colin watson mention the .url macro more verbosely. ==================== changes in man-pages-2.03 ==================== released: 2005-06-02 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer joey (martin) schulze johannes nicolai justin pryzby klaus ethgen pavel heimlich ross boylan vincent fourmond apologies if i missed anyone! global changes -------------- console.4 console_ioctl.4 mouse.4 tty.4 vcs.4 pavel heimlich change `ttys(4)' to `ttys(4)'. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- clone.2 mtk substantially enhanced discussion of clone_thread. added clone_sysvsem, clone_untraced, clone_stopped. other minor fixes. execve.2 aeb noted effect of ptracing when execing a set-uid program. fcntl.2 johannes nicolai / mtk noted f_setown bug for socket file descriptor in linux 2.4 and earlier. added text on permissions required to send signal to owner. flock.2 mtk noted that lock conversions are not atomic. getrusage.2 mtk ru_nswap has never contained useful information. kernel 2.6.6 clarified that with a patch ("[patch] eliminate nswap and cnswap"). see also: http://www.ussg.iu.edu/hypermail/linux/kernel/0404.1/0720.html kill.2 mtk clarified wording of the 'pid == -1' case. mount.2 mtk added mnt_expire, plus a few other tidy-ups. sched_setaffinity.2 mtk added text to note that sched_setaffinity() will migrate the affected process to one of the specified cpus if necessary. added a note to point out that the affinity mask is actually a per-thread attribute that can be adjusted independently for each thread in a thread group. shmctl.2 mtk noted aberrant linux behavior with respect to new attaches to a segment that has already been marked for deletion. noted changes in permissions required for shm_lock/shm_unlock. wait.2 mtk noted that the __w* flags can't be used with waitid(). confstr.3 mtk added _cs_gnu_libc_version and _cs_gnu_libpthread_version. hosts.5 ross boylan / martin schulze various changes as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=304242 proc.5 mtk minor changes to discussion of /proc/pid/stat signal fields. added 'rt_priority' and 'policy' to /proc/pid/stat. capabilities.7 mtk 1,$s/inherited/inheritable/g regex.7 vincent fourmond / joey (martin) schulze removed discussion of `[[:<:]]' and `[[:>:]]' since they do not seem to be in the glibc implementation. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=295666 tzselect.8 joey (martin) schulze / klaus ethgen the default zoneinfo directory is now /usr/share/zoneinfo. (was: /usr/local/etc/zoneinfo) as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=267471 ==================== changes in man-pages-2.04 ==================== released: 2005-06-21 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer baurjan ismagulov dave love dieter brueggemann geoff clare guido trotter kabloom kevin ryde justin pryzby mike furr olivier croquette olivier guilyardi peter cordes philipp spitzer tanaka akira thierry excoffier thomas hood vincent lefevre walter harms apologies if i missed anyone! global changes -------------- various pages mtk for consistency across pages: 1,$s/nonzero/non-zero/g typographical or grammatical errors have been corrected in several places. new pages --------- pthreads.7 mtk an overview of the linux implementations of posix threads. changes to individual pages --------------------------- _exit.2 mtk various minor changes. epoll_ctl.2 mike furr bugs: in kernels < 2.6.9, epoll_ctl_del required a non-null 'event', even though this argument is ignored. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=306517 flock.2 mtk / kevin ryde clarified semantics of relationship between flock() locks and open file entries and file descriptors. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=291121 getitimer.2 olivier croquette, thierry excoffier noted the existence of the short sleep bug (up to 1 jiffy). getrlimit.2 mtk rlimit_rss only has affect "in 2.4.x", not "in 2.4 and later". getrusage.2 geoff clare since linux 2.6, the ru_nvcsw and ru_nivcsw fields are used. nice.2 mtk / guido trotter rewrote description of return value. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=296183 open.2 walter harms o_direct needs _gnu_source. mtk o_async works for pipes and fifos in linux 2.6. various minor fixes. atexit.3 mtk various minor changes. exit.3 mtk various minor changes. getopt.3 mtk / philipp spitzer fix description of return value. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=308359 hsearch.3 mtk changed (char *) to (void *) in example. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=313607 log1p.3 justin pryzby make log(3) see also log1p(3), as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=309578 makecontext.3 tanaka akira fix description of return value for makecontext(), as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=311800 on_exit.3 mtk various minor changes. rand.3 kabloom small fix to a code example, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=194842 realpath.3 mtk / thomas hood when specifying resolved_path as null, realpath() will (still) only allocate up to path_max bytes. plus other minor changes. see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=239424 rcmd.3 dave love the required header file for these functions on linux is , as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=311680 scanf.3 olivier guilyardi arg for %p is a pointer to _a pointer to_ void, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=263109 stdin.3 vincent lefevre freopen() can change the descriptors associated with stdin/stdout/stderr, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=295859 strerror.3 baurjan ismagulov strerror_r(3) requires #define _xopen_source 600, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=290880 sysconf.3 peter cordes / mtk fix typo: "_sc_2_dev" should be "_sc_2_c_dev". proc.5 mtk added pointers under /proc/sys/net to tcp.7 and ip.7. ip.7 mtk various wording and formatting fixes. reordered /proc/sys/net/ipv4/ip_* file descriptions alphabetically. tcp.7 dieter brueggemann / mtk fixes to the discussion of siocatmark and tcp_stdurg. mtk various wording and formatting fixes. incorporated some new /proc/sys/net/ipv4/tcp_* file descriptions from the 2.6.12 source file documentation/networking/ip-sysctl.txt. ==================== changes in man-pages-2.05 ==================== released: 2005-06-27 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: a costa andries brouwer bas zoetekouw dan jacobson delian krustev dora anna volgyesi martin (joey) schulze ove kaaven apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. (special thanks to a costa.) changes to individual pages --------------------------- _exit.2 mtk / aeb reversed 2.04 introduction of the term "process termination function". close.2 mtk clarified what type of lock close() affects. minor formatting changes. dup.2 mtk consistent use of terms "open file description", "file status flags", and "file descriptor flags". removed mention of lock sharing -- it was not accurate. minor formatting fixes. fcntl.2 mtk consistent use of terms "open file description", "file status flags", and "file descriptor flags". some rewriting of discussion of file descriptor flags under f_dupfd, replaced some text duplicated in dup.2 with a cross ref to dup.2 minor wording and formatting fixes. fpclassify.3 mtk / martin (joey) schulze / bas zoetekouw the return value of isinf() changed in glibc 2.02 to differentiate positive and negative infinity. see: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=285765 getgid.2 getuid.2 delian krustev remove confusing text describing real and effective ids. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=285852 getitimer.2 mtk the short sleep bug (up to 1 jiffy) that was newly noted in man-pages-2.04 has just been fixed in 2.6.12. getpriority.2 mtk changed range documented in main text from -20..20 to -20..19. noted that the range is -20..20 on some systems. open.2 mtk / aeb clarification of term "open file description" along with explanation of what information it maintains. other wording improvements. various minor wording changes. atexit.3 mtk / aeb reversed 2.04 introduction of the term "process termination function". mtk noted use of atexit() for establishing function to be invoked on shared library unload. noted that atexit()-registered functions are not invoked on abnormal termination. formatting fixes. exit.3 mtk / aeb reversed 2.04 introduction of the term "process termination function". mtk minor rewording and formatting changes. getloadavg.3 mtk added #define _bsd_source to prototype. log2.3 martin (joey) schulze add erange error. readdir.3 mtk added definition of linux dirent structure. some formatting cleanups. strtod.3 dora anna volgyesi / mtk strtold() and strtof() need _isoc99_source or _xopen_source=600 as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=246668 tdestroy.3 mtk new link to tsearch.3. tsearch.3 mtk added tdestroy to .th line. mem.4 mtk change "chown root:mem /dev/mem" to "chown root:kmem /dev/mem". null.4 mtk change "chown root:mem /dev/null /dev/zero" to "chown root:root /dev/null /dev/zero". vcs.4 dan jacobson / martin (joey) schulze replaced "selection(1)" by "gpm(8)" under see also see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=253515 signal.7 ove kaaven sa_sigaction should be sa_siginfo as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=305369 urn.7 mtk new link to uri.7 ==================== changes in man-pages-2.06 ==================== released: 2005-07-15 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andries brouwer bhavesh p davda clau weber dov murik david lloyd frederik deweerdt justin pryzby lars wirzenius martin pool mike frysinger petter reinholdtsen steven murdoch walter harms apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. many uses of hyphens and dashes were corrected. new pages --------- canonicalize_file_name.3 walter harms / mtk removed pages ------------- sstk.2 mtk afaik, this system call has never actually done anything (other than be a stub) on any unix. changes to individual pages --------------------------- accept.2 mtk various wording and formatting fixes. bind.2 mtk minor formatting changes clone.2 mtk various minor wording improvements; some formatting fixes connect.2 mtk various wording and formatting fixes. epoll_create.2 bhavesh p davda s/positive/non-negative/ [for file descriptor] getrlimit.2 mtk documented rlimit_msgqueue limit. rlimit_rss ceased to have any effect in 2.4 in kernel 2.4.30. (it already didn't have any effect in 2.2.x and 2.6.x.) s/madvise_willneed/madv_willneed/ listen.2 mtk removed historic comment on bsd backlog ceiling. minor wording and formatting changes. semop.2 mtk added bug: in some circumstances, a process that is waiting for a semaphore to become zero is not woken up when the value does actually reach zero. http://marc.theaimsgroup.com/?l=linux-kernel&m=110260821123863&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=110261701025794&w=2 socket.2 mtk various minor wording improvements umask.2 mtk added mkdir(2) to discussion, made term "file mode creation mask" clearer. various, mostly small, wording changes errno.3 martin pool change description for estale as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=237344 fgetgrent.3 getgrent.3 getgrent_r.3 david lloyd added see also putgrent(3) see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=211336 getgrent.3 getgrnam.3 getpwent.3 getpwnam.3 lars wirzenius / mtk replace mention of /etc/{passwd,group} by references to "passwd/group database", and ldap and nis. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=316117 mtk miscellaneous wording improvements consistent description and errors wording across these pages. getnameinfo.3 mtk relocate misplaced text describing gai_strerror(). getnetent.3 petter reinholdtsen s/endservent/endnetent/ as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=316517 getspnam.3 lars wirzenius / mtk replace mention of /etc/shadow by references to "shadow password database", and ldap and nis. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=316117 mtk, claus weber miscellaneous wording improvements consistent description wording vis-a-vis getpwnam.3 etc. hsearch.3 frederik deweerdt fix hsearch_r() prototype scanf.3 justin pryzby / mtk fix description of return value as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=317037 mtk various parts substantially rewritten; added description of %n$ form; various text incorporated from the gnu c library documentation ((c) the free software foundation). shm_open.3 mtk modified details of how user and group ownership of a new object are set. various minor wording and formatting cleanups. elf.5 mike frysinger tweaked the short description to include definition of 'elf' add elfosabi_none to the elfosabi_ list tweak/add more machines to em_ list for ehdr->e_machine fix indenting to be consistent tweak the display of the elf_st_* macros document the elf_dyn structure proc.5 mtk updated discussion of /proc/stat. added text on the /proc/sys/fs/mqueue/* files. ip.7 steven murdoch change protocol in udp prototype. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=182635 tcp.7 dov murik the first sentence under notes about so_keepalive and sigpipe makes no grammatical sense (and possibly also no technical sense). it has been removed. ==================== changes in man-pages-2.07 ==================== released: 2005-07-19 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer mike frysinger apologies if i missed anyone! global changes -------------- various pages mtk the terms "set-user-id" and "set-group-id" are now used consistently (no abbreviations) across all manual pages. various pages mtk consistent use of "saved set-user-id" and "saved set-group-id" (no more "saved user id", "saved effective uid", saved group id", etc.) various pages mtk global fixes in textual descriptions: uid --> uid gid --> gid pid --> pid id --> id various pages mtk consistent use of st_atime, st_ctime, st_mtime, with explanatory text, instead of atime/ctime/mtime. various pages mtk classical bsd versions are now always named x.ybsd (formerly there was a mix of x.ybsd and bsd x.y). typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- setresuid.2 mtk some rewording. stat.2 mike frysinger improve description of st_dev and st_rdev. mtk various wording and formatting improvements. truncate.2 mtk some formatting fixes ==================== changes in man-pages-2.08 ==================== released: 2005-09-21 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: adrian bunk alain portal andrew pimlott andries brouwer baurzhan ismagulov bernhard r. link bodo stroesser david n. welton dov murik heikki orsila hasso tepper hrvoje niksic justin pryzby ludovic courtes mike frysinger nicolas françois norbert buchmuller paul brook ramiro aceves tommy pettersson walter harms apologies if i missed anyone! global changes -------------- various pages mtk rfc references are now always written as "rfc\ nnn" (not "rfc nnn" or "rfcnnn"). typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- du.1 mike frysinger to get an effect like "-h", blocksize must start with "human", not "human". time.1 mike frysinger s/standard output/standard error/ clone.2 paul brook / mtk fix small error in description of clone_parent_settid connect.2 heikki orsila add eintr error see http://lkml.org/lkml/2005/7/12/254 getpriority.2 mtk expanded discussion of relationship between user and kernel representations of the nice value. added discussion of rlimit_nice and a cross reference to getrlimit.2 under the description of the eacces error. noted 2.6.12 change in credentials checking for setpriority(). getrlimit.2 mtk added description of rlimit_rtprio added description of rlimit_nice mmap.2 mtk noted bug in map_populate for kernels before 2.6.7. mremap.2 mtk added _gnu_source to prototype. rewrote description of mremap_maymove. rewrote description of eagain error. added discussion of resizing of memory locks. added entries to see also. some formatting fixes. msgctl.2 mtk added ipc_info, msg_info, msg_stat descriptions. nanosleep.2 baurzhan ismagulov add to prototype: define _posix_c_source 199309 as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=314435 nice.2 mtk added sentence noting that range of the nice value is described in getpriority.2. added cross-reference to setrlimit(2) for discussion on rlimit_nice. outb.2 david n. welton / justin pryzby / mtk clarified the order of value and port arguments; as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=263756 pause.2 mtk added see also for sigsuspend.2 some formatting fixes. poll.2 tommy pettersson nfds should be prototyped as nfds_t as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=322934 mtk some wording and formatting improvements. prctl.2 mtk since kernel 2.6.13 pr_set_dumpable can also have the value 2. rand.3 hrvoje niksic / mtk remove misleading text describing freebsd's sranddev() function. as per debian bug 328629 readv.2 mtk / walter harms added linux notes on trickery performed by glibc when vector size exceeds iov_max. formatting clean-ups. remap_file_pages.2 mtk added text to note that start and size are both rounded downward. sched_setparam.2 mtk modified discussion of privileges; added pointer to sched_setscheduler.2 for a discussion of privileges and resource limits. sched_setscheduler.2 mtk modified discussion of privileges; added discussion of rlimit_rtprio. semctl.2 mtk added ipc_info, sem_info, sem_stat descriptions. shmctl.2 mtk added ipc_info, shm_info, shm_stat descriptions. sigaction.2 mtk split sigpending(), sigprocmask(), and sigsuspend() out into separate new pages. other minor changes mtk notes: described sa_nodefer / sa_mask bug which was present in all kernels up to and including 2.6.13. see http://marc.theaimsgroup.com/?l=linux-kernel&m=112360948603171&w=2 and http://marc.theaimsgroup.com/?l=linux-kernel&m=112362164911432&w=2 list: linux-kernel subject: signal handling possibly wrong from: bodo stroesser date: 2005-08-09 17:44:06 signal.2 mtk updated see also to reflect splitting of sigaction.2 into sigaction.2, sigsuspend.2, sigpending.2, sigprocmask.2 sigpending.2 mtk new page created by splitting out from sigaction.2 changed conforming to. sigprocmask.2 mtk new page created by splitting out from sigaction.2 added text on effect of null for 'set' argument. added text noting effect of ignoring sigbus, sigfpe, sigill, and sigsegv. noted that sigprocmask() can't be used in multithreaded process. fixed einval error diagnostic. changed conforming to. sigsuspend.2 mtk new page created by splitting out from sigaction.2 added notes on usage. added new text to description. changed conforming to. stat.2 mike frysinger improve st_blocks description. carg.3 ramiro aceves / aeb change: one has carg(z) = atan(creal(z) / cimag(z)) to: one has tan(carg(z)) = cimag(z) / creal(z) as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=326720 cmsg.3 mtk s/sol_tcp/ipproto_tcp/ (posix standard name) dlopen.3 alain portal s/-nostartupfiles/-nostartfiles/ getaddrinfo.3 mtk nowadays (since 2.3.4) glibc only sets the first ai_canonname field if ai_canonname was specified (the current behavior is all that susv3 requires). 1,$s/pf_/af_/g added descriptions of ai_all, ai_addrconfig, ai_v4mapped, and ai_numericserv. some wording and formatting fixes. getpwnam.3 bernhard r. link / mtk add notes text describing relationship of pw_dir and home and pointing out that applications should preferentially inspect home. inet.3 mike frysinger mention "little endian" and "big endian". added note about octal and hex interpretation of numbers-and-dots notation. rpc.3 mtk / ludovic courtes commented out references to rpc_secure(3) -- we don't currently have such a page in the man-pages set. in response to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=325115 setenv.3 mtk glibc 2.3.4 fixed the "name contains '='" bug. strnlen.3 mike frysinger added "#define _gnu_source" to prototype. initrd.4 norbert buchmuller / mtk added text noting that the use or real-root-dev for changing the root device is obsolete, in favor of pivot root. (however, the page still needs to be rewritten to actually describe the pivot_root method...) as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=323621 proc.5 mtk improve text describing /proc/sys/fs/mqueue/* files. describe /proc/sys/fs/suid_dumpable (new in 2.6.13). added placeholder mention of /proc/zoneinfo (new in 2.6.13). more needs to be said about this file. repaired earlier cut and paste mistake which resulted in part of the text of this page being duplicated. utmp.5 mike frysinger added text on biarch details for ut_session and ut_tv. capabilities.7 mtk added cap_audit_control and cap_audit_write. ip.7 mtk / andrew pimlott add a couple of words to make it clear that port is a 16-bit number. reformat long source lines (no text changed). s/sol_ip/ipproto_ip/ (posix standard name) hasso tepper fix discussion of ipc_recvttl / ip_ttl. signal.7 mtk updated see also to reflect splitting of sigaction.2 into sigaction.2, sigsuspend.2, sigpending.2, sigprocmask.2. socket.7 mtk clarified details of use of so_peercred. tcp.7 mtk s/sol_tcp/ipproto_tcp/ (posix standard name) s/sol_ip/ipproto_ip/ (posix standard name) udp.7 mtk added description of udp_cork socket option. s/sol_udp/ipproto_udp/ (posix standard name) s/sol_ip/ipproto_ip/ (posix standard name) ==================== changes in man-pages-2.09 ==================== released: 2005-10-13 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: justin pryzby peter chubb samuel thibault tomas pospisek trond myklebust apologies if i missed anyone! global changes -------------- ptsname.3 getpt.3 unlockpt.3 openpty.3 posix_openpt.3 grantpt.3 pts.4 tty_ioctl.4 mtk added see also for new pty.7 page. typographical or grammatical errors have been corrected in several places. new pages --------- pty.7 mtk overview of unix 98 and bsd pseudo-terminals. changes to individual pages --------------------------- ldd.1 mtk remove "-v" option (fix from fedora man-pages-2.07-7). fcntl.2 peter chubb / trond myklebust / mtk since kernel 2.6.10, a read lease can only be placed on a file descriptor that is opened read-only. see the following lkml thread of aug 2005 ("fcntl(f getlease) semantics??"): http://marc.theaimsgroup.com/?l=linux-kernel&m=112371777712197&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=112374818213000&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=112376335305284&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=112377294030092&w=2 mprotect.2 mtk add new text to enomem error. mremap.2 mtk added description of mremap_fixed and 'new_address' argument under notes. revised text of einval error. read.2 samuel thibault / mtk read() can fail with einval when using o_direct mtk added open(2) to see also. shmget.2 mtk s/int/size_t/ for type of 'size' argument (fix from fedora man-pages-2.07-7). write.2 samuel thibault / mtk write() can fail with einval when using o_direct atanh.3 mtk fix: s/acosh/atanh/ (fix from fedora man-pages-2.07-7). fopen.3 mtk improved "a+" description (fix from fedora man-pages-2.07-7). getrpcent.3 mtk s/getrpcent/setrpcent/ (fix from fedora man-pages-2.07-7). stdio.3 mtk / justin pryzby removed references to fropen() and fwopen(), which are bsdisms that don't appear in glibc. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=331174 strftime.3 mtk typo fix: %ry ==> %ey [susv3 mentions...] (fix from fedora man-pages-2.07-7). nsswitch.conf.5 mtk s/network/networks/ (fix from fedora man-pages-2.07-7). proc.5 mtk added description of /proc/sys/vm/legacy_va_layout. socket.7 mtk update description of so_rcvlowat and so_sndlowat. (fix derived from fedora man-pages-2.07-7). ==================== changes in man-pages-2.10 ==================== released: 2005-10-19 global changes -------------- the changes in this release consist *solely* of formatting fixes, with the aim bringing greater consistency to the manual pages according to the following rules: -- function name references should *always* be followed by parentheses, "()" (possibly containing a manual page section number). -- the parentheses following a function name should *not* be formatted. thus, for example, instead of: .b name() one should write: .br name () much of the change was automated using two scripts: add_parens_for_own_funcs.sh and unformat_parens.sh. for the (possible) benefit of downstream manual page maintainers and translators, i have placed these scripts in a new subdirectory 'scripts'. note the following points well: -- these scripts provide a computer-assisted solution to the above two goals. however, they are not perfect, and their output should be scanned by a human. (to see what changes the two scripts *would* make, without making them, use the "-n" command line option.) -- the scripts do not fix all instances that violate the above rules: some manual fixes are required. two further scripts are provided to help find remaining instances of function names without following "()": find_dots_no_parens.sh and find_slashes_no_parens.sh. the following changes were made: -- add_parens_for_own_funcs.sh was applied to the pages in sections 2 and 3. -- unformat_parens.sh was applied to pages in sections 2, 3, 4, and 7 (the only sections where such changes were required). -- further changes (not so very many) were performed by hand. (found places to fix with the assistance of find_dots_no_parens.sh and find_slashes_no_parens.sh). ==================== changes in man-pages-2.11 ==================== released: 2005-10-24 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal apologies if i missed anyone! global changes -------------- various pages mtk most instances of the constant "null" are not formatted (bolded) in man pages, but a few are. for consistency, formatting on "null" has been removed where it occurred. many minor formatting fixes were made. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- getrlimit.2 mtk added einval error for rlim_cur > rlim_max when calling setrlimit(). path_resolution.2 mtk repaired discussion of capabilities and file system uid, which mistakenly had involved exec() in the discussion. prctl.2 mtk removed text saying there is no library interface. there is nowadays. mkfifo.3 mtk minor change to return value text. sk98lin.4 alain portal formatting fixes. capabilities.7 mtk minor changes. ==================== changes in man-pages-2.12 ==================== released: 2005-10-31 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: akihiro motoki andries brouwer brian m. carlson herbert martin landers michael benedict apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- mlock.2 mtk reworded text around pagesize, noting also that sysconf(_sc_pagesize) can be used. path_resolution.2 mtk / aeb removed words "as well" (added in 2.11) from the phrase "and it gets these last five capabilities if its fsuid is 0 as well" since there are (unusual) situations in which fsuid can be 0 while the effective uid is not. reworked (cut down) discussion of capabilities, moving part of it into capabilities.7 setresuid.2 mtk add text to note that setresuid() always modifies the file system uid, and setresgid() likewise always modifies the file system gid. shmget.2 mtk added (brief) description of shm_hugetlb. sigaltstack.2 mtk / martin landers noted that ss_sp is automatically aligned by the kernel. byteorder.3 brian m. carlson / herbert change to in prototype; add text explaining that some systems need the former header. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=265244 capabilities.7 mtk reworked part of the discussion of exec() and capabilities. added sub-section "effect of user id changes on capabilities". reworked discussion of cap_sys_admin and file-max. ==================== changes in man-pages-2.13 ==================== released: 2005-11-03 this release consists entirely of formatting and typographical fixes. global changes -------------- typographical or grammatical errors have been corrected in several places. various pages mtk function and page cross references that were italicized were made bold (which is how the majority of function and page cross references were already done). various pages mtk instances of things like "null-terminated string" were changed to "null-terminated string". various pages mtk pathnames, structures, arguments, and that were bold were changed to italics. various pages mtk instances of the constant "null" that were bold-faced were made unformatted (which is how most instances of "null" were already formatted.) ==================== changes in man-pages-2.14 ==================== released: 2005-11-17 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: angelo avery pennarun justin pryzby martin (joey) schulze stefan brüns volker reichelt apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- rexec.3 mtk / justin pryzby this page is taken as is from the freebsd 5.4 distribution. (not checked against linux reality, but likely things are the same.) see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=336875 changes to individual pages --------------------------- arch_prctl.2 mtk updated discussion about lack of prototype in glibc. execve.2 mtk improved description of e2big error: it relates to the sum of the bytes in both environment and argument list. fcntl.2 mtk clarified parts of the discussion of file leases, noting effect of open(o_nonblock), interruption by signal handler, or termination by signal in lease breaker. in response to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=339037 stat.2 mtk / stefan brüns added linux notes describing nanosecond timestamps. frexp.3 volker reichelt / mtk fixed to point out that frexp() returns a number whose *absolute* value is >= 0.5 and < 1. amended the example program to demonstrate this. open.2 mtk / avery pennarun add ewouldblock error for file leases. in response to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=339037 putenv.3 mtk although the glibc implementation returns -1 on error (and some other man pages (e.g., the bsds) also document that value for error returns), susv3 merely says "non-zero" (and this is what manual pages on many implementations also say). posix_memalign.3 mtk formerly, the page said that all systems declare memalign() in . in fact, many declare it in . strtok.3 mtk almost a complete rewrite after angelo pointed out that the existing page was deficient. sd.4 martin schulze remove see also for nonexistent scsi.4. proc.5 mtk updated discussion of /proc/sys/kernel/pid_max. signal.7 mtk added pthreads.7 to see also. ld.so.8 mtk fix typo: s/ld_debug_output/ld_profile_output/ ==================== changes in man-pages-2.15 ==================== released: 2005-11-30 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer james vega malcolm scott senthil kumar apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- sigvec.3 -- for details, see below. sigset.3 -- for details, see below. changes to individual pages --------------------------- kill.2 mtk added text describing the 2.6.[0-7] eperm bug that occurred when sending signals to a process group. sigaction.2 mtk noted that si_signo is unused on linux. sigpending.2 mtk added bugs noting wrapper function problem that existed in glibc versions <= 2.2.1. sigpause.2 mtk moved to section 3; see also sigpause.3 below. sigsetops.3 mtk added a glibc notes section describing sigisemptyset(), sigandset(), and sigorset(). sigvec.2 sigblock.2 mtk these pages have been deleted, and replaced by a new sigvec.3 man page that more fully describes the bsd signal api. siggetmask.2 sigmask.2 sigsetmask.2 mtk these links to the now-deleted sigblock.2 have been also been deleted. they are replaced by corresponding links in section 3: sigmask.3, sigsetmask.3, siggetmask.3. sigvec.3 mtk this new page is provides a fuller description of the bsd signal api than was provided in the now-deleted sigvec.2 and sigblock.2. sigblock.3 siggetmask.3 sigmask.3 sigsetmask.3 mtk created as links to sigvec.3. sigpause.3 mtk moved here from section 2. some minor wording fixes; clarified system v origins of x/open flavor of this function. sigset.3 mtk new page describing the system v signal api: sigset(), sighold(), sigrelse(), sigignore(). strftime.3 james vega add further text clarifying that %+ specifier is not supported in glibc2. mtk added glibc notes section describing optional 'flag' and 'width' components of conversion specifiers. some wording changes to bring terminology closer to susv3. added an example program. vm86old.2 mtk / aeb add as new link to vm86.2. intro.7 mtk added a few words to reflect the fact that several of the section 7 pages provide overviews of various topics. signal.7 mtk added some see also entries. socket.7 senthil kumar / mtk added text noting that select()/poll() do not respect so_rcvlowat. udp.7 malcolm scott s/tcp_socket/udp_socket/ in example fixes http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=340927 ==================== changes in man-pages-2.16 ==================== released: 2005-12-02 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alan stern andries brouwer urs thuermann apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- howtohelp urs thuermann added instructions for finding maintainer in debian package. poll.2 mtk added notes about inftim constant provided on some other implementations. shmop.2 alan stern the -1 error return of shmat() should be cast "(void *)". strftime.3 aeb remove junk text (actually intended as source code comment in page). ip.7 urs thuermann fix a typo: s/sock_raw/sock_packet/ packet.7 urs thuermann clarification: s%sock_packet%pf_inet/sock_packet% ==================== changes in man-pages-2.17 ==================== released: 2005-12-13 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: justin pryzby michael haardt urs thuermann walter harms apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- fmemopen.3 walter harms / mtk new documentation for the glibc-specific fmemopen() and open_memstream(). based on glibc info page. pipe.7 mtk (with prompting and suggestions for improvements by michael haardt) new page providing overview of pipes and fifos. changes to individual pages --------------------------- howtohelp mtk added notes on how to write example programs for manual pages. fork.2 mtk added pointers to examples of fork() in wait.2 and pipe.2. pipe.2 mtk added an example program. added see also for new pipe.7 page. wait.2 mtk added example program demonstrating use of fork() and waitpid(). carg.3 justin pryzby delete line that should have been deleted when applying 2.08 fix for this page. getaddrinfo.3 mtk rearranged eai_* list alphabetically. inet.3 mtk added glibc notes describing feature test macros required to expose declaration of inet_aton(). open_memstream.3 mtk new link to new fmemopen.3. fifo.4 mtk added see also for new pipe.7 page. environ.5 mtk removed browser, since it seems not in fact to be common. socket.7 urs thuermann added documentation of so_timestamp. tcp.7 mtk noted 200 millisecond ceiling imposed on tcp_cork. udp.7 mtk rearranged options into something approximating alphabetical order. ==================== changes in man-pages-2.18 ==================== released: 2005-12-15 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: justin pryzby karsten sperling martin (joey) schulze mike frysinger stefan puiu apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- bind.2 mtk added mention of af_inet6 address family. added discussion of sockaddr structure and an example in the unix domain. recv.2 mtk put 'flags' list in alphabetical order. send.2 mtk added cross-reference from discussion of msg_more to udp_cork in udp(7). put 'flags' list in alphabetical order. err.3 mtk added conforming to section noting that these are non-standard bsdisms. errno.3 justin pryzby added see also for err.3. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=306867 gethostbyname.3 martin (joey) schulze / mtk added references to nsswitch.conf(5); remove cross references to resolv+(8). see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=308397 perror.3 justin pryzby added see also for err.3 . http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=306867 resolver.3 mtk / martin (joey) schulze remove cross references to resolv+(8); add cross references to resolv.conf(5). see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=214892 added see also entry for resolver(5); see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=251122 strerror.3 mtk / stefan puiu rewrote and extended the discussion of the two flavors of strerror_r(), and added some additional information on strerror(). justin pryzby added see also for err.3, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=306867 elf.5 mike frysinger fix three typos in identifier names. operator.7 karsten sperling the + operator should be in the list of unary operators. raw.7 mtk small wording changes around discussion of so_bsdcompat. fixed a couple of wording errors elsewhere. reformatted some long lines. socket.7 mtk, after a note by stefan puiu updated discussion of so_bsdcompat. reformatted some long lines. noted the linux-specific feature whereby setsockopt() doubles the value given for so_sndbuf and so_rcvbuf. noted kernel-imposed minimum values for so_sndbuf and so_rcvbuf. udp.7 mtk, after a note by stefan puiu updated discussion of so_bsdcompat. unix.7 mtk added new (un)supported features section in which it is noted that unix domain sockets do not support msg_oob or msg_more. noted details of so_snbuf and so_rcvbuf support for unix domain sockets. ==================== changes in man-pages-2.19 ==================== released: 2005-12-23 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer walter harms stefan puiu apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- howtohelp mtk minor changes. bind.2 stefan puiu / mtk remove text under einval error: "this may change in the future: see linux/unix/sock.c for details." this behavior has been unchanged for a long time, and seems unlikely to change. add eaddrinuse to errors. send.2 aeb add cmsg(3) to see also. fopen.3 walter harms / mtk added description of 'x' mode character (exclusive open). pipe.7 mtk / aeb some wording changes to description of pipes. ==================== changes in man-pages-2.20 ==================== released: 2006-01-03 global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- sigaltstack.2 mtk added some text to explain the usual scenario in which sigaltstack() is employed. getloadavg.3 mtk noted that this function is available since glibc 2.2. strcpy.3 mtk s/nulls/null bytes/ capabilities.7 mtk noted that capability bounding set appeared with kernel 2.2.11. arp.7 icmp.7 ip.7 ipv6.7 netdevice.7 packet.7 raw.7 rtnetlink.7 socket.7 tcp.7 unix.7 udp.7 mtk the only changes to these pages have been for formatting: -- structure definitions were changed to k&r style -- some long source lines were broken to fit into ~70 character lines. no changes were made to the content of these pages (yet...). ==================== changes in man-pages-2.21 ==================== released: 2006-01-16 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer falk hueffner mike frysinger senthil kumar stefan puiu apologies if i missed anyone! global changes -------------- dd.1 cp.1 truncate.2 gethostname.2 lseek.2 listxattr.2 readlink.2 sysfs.2 stat.2 ustat.2 uname.2 getdomainname.2 argz_add.3 asprintf.3 confstr.3 bstring.3 bzero.3 dlopen.3 fwide.3 gethostbyname.3 getline.3 getlogin.3 getnameinfo.3 getpass.3 hsearch.3 perror.3 printf.3 readdir.3 scanf.3 stpcpy.3 strdup.3 strfmon.3 strftime.3 string.3 strptime.3 sysconf.3 termios.3 ttyname.3 dsp56k.4 tty_ioctl.4 elf.5 proc.5 termcap.5 charsets.7 unix.7 mtk various pages use inconsistent terms for 'null byte' (which is the c99/susv3 term for the '\0' character). to rectify this the following changes were made in the above pages: replace 'zero byte' with 'null byte'. replace 'null character' with 'null byte'. replace 'nulls' with 'null bytes'. replace 'nul-terminated' by 'null-terminated'. replace 'nul' by 'null byte'. replace 'terminating nul' by 'terminating null byte'. replace 'final nul' by 'terminating null byte'. replace 'nul character' by 'null byte'. various pages mtk replace "sysv"/"sysv" by "system v". typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- capget.2 mtk noted bug that could wrongly cause eperm in unprivileged capset() with 'pid' field == getpid(). epoll_ctl.2 mtk noted that epolloneshot was added in 2.6.2. gethostname.2 mtk added glibc notes describing operation of glibc's gethostname() wrapper function. mmap.2 mtk / mike frysinger clarify relationship between mmap2(2) and mmap64(3). mtk a few other small rewordings. mmap64.3 mike frysinger new link to mmap.2. open.2 mtk added bug noting that o_async can't be enabled via open(): fcntl() must be used for this purpose. recv.2 stefan puiu relocate misplaced discussion of msg_dontwait. dlopen.3 mtk rewrote discussion of dlopen() 'flag' argument; added descriptions of rtld_noload, rtld_delete, and rtld_deepbind. noted use of atexit() to register a function that is automatically called when a library is unloaded. fmemopen.3 mtk rewrote substantial parts of the page, and relicensed under gpl. fseeko.3 mike frysinger add return value section. getopt.3 mtk noted historical use of to declare getopt(). qsort.3 mtk / falk hueffner clarify how strcmp() should be used as the 'compar' function by providing an example. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=348072 proc.5 mtk noted that /proc/mounts is pollable since kernel 2.6.15. documented /proc/pid/task. noted that the contents of /proc/pid/{cwd,exe,fd,root,task} are not available if the main thread has terminated. senthil kumar add pointer to random(4) for description of files under /proc/sys/kernel/random. udp.7 stefan puiu / mtk small rewording of discussion of so_bsdcompat (add cross-ref to socket(7)). ==================== changes in man-pages-2.22 ==================== released: 2006-02-02 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andre noll andries brouwer colin tuckley stefan puiu thomas hood thorsten kukuk walter harms global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- mmap.2 aeb / mtk noted that portable applications should specify fd as -1 when using map_anonymous. some rewriting of description of map_anonymous. rt_sigreturn.2 thorsten kukuk new link to sigreturn.2. rt_sigsuspend.2 mtk new link to sigsuspend.2. waitid.2 mtk noted that waitid() does not set infop->si_uid field on most other implementations. getopt.3 walter harms / mtk make clear that when calling getopt_long() and there are no short options, then 'optstring' should be "", not null. openpty.3 thomas hood / mtk in glibc 2.0.92, openpty() was modified to preferably open unix 98 ptys instead of bsd ptys. qsort.3 mtk small rewording under examples. strtol.3 strtoul.3 stefan puiu s/string must begin/string may begin/ proc.5 mtk documented inotify files under /proc/sys/fs/inotify: max_queued_events, max_user_instances, and max_user_watches. ==================== changes in man-pages-2.23 ==================== released: 2006-02-10 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen britton leo kerin dan jacobson justin pryzby luc van oostenryck kurt wall martin (joey) schulze matthias andree robert love samuel thibault urs thuermann apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- inotify_init.2 inotify_add_watch.2 inotify_rm_watch.2 robert love, with some additions by mtk. new pages describing the inotify api. mbind.2 get_mempolicy.2 set_mempolicy.2 andi kleen, with additional work by mtk new pages describing the numa memory allocation policy api. drawn from the set at ftp://ftp.suse.com/pub/people/ak/numa. rtc.4 urs thuermann, with additional work by mtk new page describing the real-time clock driver. inotify.7 mtk overview of the inotify api. changes to individual pages --------------------------- clone.2 andi kleen on x86, clone() should not be called through vsyscall, but directly through "int $0x80". fcntl.2 mtk small wording changes. added cross-ref to inotify.7 under the description of dnotify. kill.2 mtk / britton leo kerin small wording change under notes to clarify what happens when a process sends a signal to itself. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=350236 mlock.2 mtk / matthias andree added bugs txt on interaction between mcl_future and rlimit_memlock. see the following lkml thread: http://marc.theaimsgroup.com/?l=linux-kernel&m=113801392825023&w=2 "rationale for rlimit_memlock" msgop.2 mtk / samuel thibault rewrote declaration of 'msgp' to be "void *" in response to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=350884 various other wording fixes. open.2 mtk clarify distinction between "file creation flags" and "file status flags". read.2 justin pryzby add see also for pread(2). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=351873 sched_setaffinity.2 mtk major rewrite. select.2 mtk added return types to prototypes for fd_set(), fd_clr(), fd_zero, and fd_isset(). other minor wording changes. read.2 mtk add see also for pwrite(2). (analogous with read.2 change above.) errno.3 kurt wall / mtk add linux specific errors to this page. localeconv.3 mtk added cross-ref to locale.7 for 'struct lconv' defn. other minor wording changes. martin (joey) schulze added see also refs for nl_langinfo.3 as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=351831 scanf.3 mtk / justin pryzby minor formatting & wording fixes. setlocale.3 martin (joey) schulze added see also refs for nl_langinfo.3 as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=351831 proc.5 mtk migrated description of inotify files to the new inotify.7 page. ascii.7 dan jacobson / mtk add text describing characters 001 to 037. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=342173 locale.7 mtk minor wording and formatting changes. ==================== changes in man-pages-2.24 ==================== released: 2006-02-17 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: joerg habenicht luc van oostenryck mike frysinger samuel thibault apologies if i missed anyone! new pages --------- get_kernel_syms.2 create_module.2 delete_module.2 init_module.2 query_module.2 fsf / mtk (with assistance of luc van oostenryck) man-pages finally gets pages for these system calls, several of which are obsolete in linux 2.6. took the old gpled pages dated 1996 and made a number of clean-ups and minor additions. global changes -------------- various pages mtk change "file name" to "filename" change "path name" to "pathname" stpncpy.3 strstr.3 strcmp.3 toupper.3 strlen.3 stpcpy.3 puts.3 strdup.3 strtok.3 isalpha.3 strspn.3 gets.3 strpbrk.3 mtk after a suggestion from samuel thibault added see also pointers to wide character equivalent functions see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=351996 typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- clone.2 mtk remove duplicate clone_stopped text. commented out crufty text describing einval error for the now obsolete clone_detached flag. under clone_sighand, noted that 'flags' must also include clone_vm if clone_sighand is specified. fcntl.2 mtk under errors: separate out eagain error for locking mmaped files. inotify_add_watch.2 mtk minor wording fix. msgop.2 mtk documented the eagain error for msgrcv(). fnmatch.3 mike frysinger / mtk expand explanation of fnm_pathname. lockf.3 joerg habenicht / mtk fix up discussion of eagain/eaccess errors. ==================== changes in man-pages-2.25 ==================== released: 2006-03-02 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: james peach krzysztof benedyczak marten von gagern michael haardt michael wronksi apologies if i missed anyone! new pages --------- mq_close.3 mq_getattr.3 mq_notify.3 mq_open.3 mq_receive.3 mq_send.3 mq_unlink.3 mtk new pages describing posix message queue api. posix_fallocate.3 mtk, after a suggestion by james peach new page describing posix_fallocate(). mq_overview.7 mtk new page giving overview of the posix message queue api. changes to individual pages --------------------------- lseek.2 michael haardt add a case to the einval error text. mtk various minor wording fixes added see also referring to new posix_fallocate.3. posix_fadvise.2 mtk added "#define _xopen_source 600" to prototype. added see also referring to new posix_fallocate.3. proc.5 mtk migrated information on posix message queues to new mqueue.7 page. inotify.7 marten von gagern fix thinko: s/assuming a non-blocking/assuming a blocking/ ==================== changes in man-pages-2.26 ==================== released: 2006-03-21 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andi kleen andries brouwer christoph lameter hasso tepper justin pryzby martin (joey) schulze nicolas françois paul brook siward de groot steve beattie walter harms apologies if i missed anyone! global changes -------------- clone.2 getdents.2 gettid.2 llseek.2 mmap2.2 modify_ldt.2 pivot_root.2 quotactl.2 readdir.2 sysctl.2 syslog.2 tkill.2 mtk, aeb, steve beattie added comment in synopsis to note that syscall(2) may be preferable over _syscalln (see intro(2)). various minor formatting changes were done on a range of pages in section 7. (no content was changed.) new pages --------- openat.2 mtk new page describing openat(2), added in kernel 2.6.16, and some notes on rationale for the at*(2) system calls. mbind.2 andi kleen, christoph lameter, mtk added mpol_mf_move and mpol_mf_move_all descriptions, from numactl-0.9.2 man page. plus a few other smaller fixes. fexecve.3 mtk new page describing fexecve(3). futimes.3 mtk new page describing futimes(3). changes to individual pages --------------------------- execve.2 mtk added see also pointing to new fexecve.3. intro.2 mtk, aeb, steve beattie added some notes on syscall(2) versus _syscall. msgctl.2 msgget.2 msgop.2 mtk added see also pointing to mq_overview.7. open.2 mtk added see also pointing to new openat.2. split out part of the return value text into separate notes section. modified wording referring to raw(8) to indicate that this interface is deprecated. poll.2 mtk added discussion of ppoll(2), which is new in 2.6.16. ppoll.2 mtk new link to poll.2. recvmsg.2 sendmsg.2 mtk / paul brook added text to note that although posix says msg_controllen should be socklen_t, glibc actually uses size_t. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=356502 and the associated glibc bug report. http://sourceware.org/bugzilla/show_bug.cgi?id=2448 mtk various formatting fixes. select.2 mtk updated to reflect the fact that pselect() has been implemented in the kernel in 2.6.16; various other minor wording changes. pselect() prototype needs "#define _xopen_source 600". tempnam.3 justin pryzby clean up description of eexist error. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=357893 unlink.2 mtk added a little extra text to clarify eisdir vs eperm. utime.2 mtk added new see also entry pointing to new futimes.3 page. exec.3 mtk added see also pointing to new fexecve.3. shm_unlink.3 mtk new link to shm_open.3 (should have been made when page was originally written). swab.3 walter harms add needed "#define _xopen_source". undocumented.3 mtk updated to remove a few function names that are now documented. capabilities.7 mtk various changes to bring this page closer to current kernel versions. inotify.7 mtk noted that glibc 2.4 is required to get glibc support for inotify. mq_overview.7 mtk some rewording and added a few words about system v message queues. netlink.7 hasso tepper substantial updates to various parts of this page. mtk, alain portal minor fixes pthreads.7 mtk updated to reflect that the nptl limitation that only the main thread could call setsid() and setpgid() was removed in 2.6.16. raw.7 hasso tepper removed text implying that only in kernel 2.2 does ip_hdrincl prevent datagrams from being fragmented. socket.7 mtk documented so_sndbufforce and so_rcvbufforce socket options, new in 2.6.14. placed socket options in alphabetical order. ==================== changes in man-pages-2.27 ==================== released: 2006-03-24 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer charles p. wright christoph lameter chuck ebbert <76306.1226@compuserve.com> daniel jacobowitz ingo molnar heiko carstens janak desai paolo (blaisorblade) giarrusso stefan puiu apologies if i missed anyone! global changes -------------- man7/* mtk various minor formatting changes were done on a range of pages in section 7. (no content was changed.) new pages --------- unshare.2 mtk, with reference to documentation by janak desai new page describing unshare(2), added in kernel 2.6.16. changes to individual pages --------------------------- clone.2 fork.2 vfork.2 mtk added see also pointing to new unshare.2. mbind.2 christoph lameter mpol_mf_move_all requires cap_sys_nice not cap_sys_resource. mremap.2 mtk clarified the description of mremap_fixed and restructured the text to reflect the fact that this flag is exposed by glibc since version 2.4. ptrace.2 chuck ebbert, with assistance from daniel jacobowitz, paolo (blaisorblade) giarrusso, and charles p. wright; after a suggestion from heiko carstens. document the following ptrace requests: ptrace_setoptions (2.4.6) plus associated flags: ptrace_o_tracesysgood (2.4.6) ptrace_o_tracefork (2.5.46) ptrace_o_tracevfork (2.5.46) ptrace_o_traceclone (2.5.46) ptrace_o_traceexec (2.5.46) ptrace_o_tracevforkdone (2.5.60) ptrace_o_traceexit (2.5.60) ptrace_setsiginfo (2.3.99-pre6) ptrace_getsiginfo (2.3.99-pre6) ptrace_geteventmsg (2.5.46) ptrace_sysemu (since linux 2.6.14) ptrace_sysemu_singlestep (since linux 2.6.14) sched_get_priority_max.2 sched_setscheduler.2 sched_setparam.2 mtk, ingo molnar modified to document sched_batch policy, new in kernel 2.6.16. text describing sched_batch was added to sched_setscheduler.2, and was drawn in part from ingo molnar's description in the mail message containing the patch that implemented this policy. various other minor rewordings and formatting fixes. proc.5 mtk, using text from documentation/filesystems/proc.txt document /proc/sys/vm/drop_caches, new in kernel 2.6.16. mtk, using information from changelog-2.6.14. document /proc/pid/smaps, new in kernel 2.6.14. capabilities.7 mtk noted affect of cap_sys_nice for mbind(mpol_mf_move_all). pthreads.7 mtk kernel 2.6.16 eliminated buggy behavior with respect to the alternate signal stack. ==================== changes in man-pages-2.28 ==================== released: 2006-03-31 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: aleksandr blokhin greg johnson apologies if i missed anyone! new pages --------- sem_post.3 sem_getvalue.3 sem_close.3 sem_open.3 sem_destroy.3 sem_wait.3 sem_unlink.3 sem_init.3 sem_overview.7 mtk new pages describing the posix semaphores api. these pages supersede and provide a superset of the information in the glibc (3thr) "semaphores(3)" manual page. changes to individual pages --------------------------- ppoll.2 aleksandr blokhin fix broken link. ptrace.2 mtk wrapped long lines (no content changes). semctl.2 semget.2 semop.2 mtk add see also pointing to the new sem_overview.7 page. elf.5 greg johnson removed see also reference to nonexistent core(5). ==================== changes in man-pages-2.29 ==================== released: 2006-04-06 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: michael haardt roberto jimenoca stefan puiu apologies if i missed anyone! global changes -------------- getrlimit.2 prctl.2 sigaction.2 elf.5 signal.7 mtk added see also entry referring to new core.5 page. new pages --------- mkdirat.2 mtk new page describing mkdirat(2), new in 2.6.16. mknodat.2 mtk new page describing mknodat(2), new in 2.6.16. core.5 mtk new page describing core dump files. mkfifoat.3 mtk new page describing mkfifoat(3). changes to individual pages --------------------------- accept.2 getpeername.2 getsockname.2 michael haardt / mtk document einval error for 'len' argument < 0. fcntl.2 mtk expanded discussion of mandatory locking. getrlimit.2 mtk added bugs text on 2.6.x handling of rlimit_cpu limit of zero seconds. see http://marc.theaimsgroup.com/?l=linux-kernel&m=112256338703880&w=2 mkdir.2 mtk added see also entry referring to new mkdirat.2. mknod.2 mtk added see also entry referring to new mknodat.2. open.2 mtk / roberto jimenoca clarified discussion of file types affected by o_nonblock. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=360243 openat.2 mtk rewrote notes describing rationale for openat(). various other minor changes. recv.2 stefan puiu removed a misleading cross-ref to socket.2. shmop.2 mtk since 2.6.17-rc1, shmdt() gives the error einval in a further circumstance: if shmaddr is not aligned on a page boundary. unshare.2 mtk remove text saying that specifying invalid flags "is likely to cause compatibility problems" since the kernel now (2.6.17-rc1) contains an explicit check for invalid bits with a consequent einval error. mkfifo.3 mtk added see also entry referring to new mkfifoat.3. proc.5 mtk information on core_pattern and core_uses_pid has been migrated to the new core.5 page. ip.7 stefan puiu removed paragraph referring to obsolete ipchains / ipfw(4). sem_overview.7 mtk add see also entry referring to pthreads.7. ==================== changes in man-pages-2.30 ==================== released: 2006-04-17 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andre lehovich andries brouwer karel kulhavy stefan puiu apologies if i missed anyone! new pages --------- linkat.2 mtk new page describing linkat(), new in kernel 2.6.16 renameat.2 mtk new page describing renameat(), new in kernel 2.6.16 symlinkat.2 mtk new page describing symlinkat(), new in kernel 2.6.16 unlinkat.2 mtk new page describing unlinkat(), new in kernel 2.6.16 changes to individual pages --------------------------- link.2 mtk added see also entry pointing to new linkat.2 page. openat.2 mtk added see also entries pointing to new *at.2 pages. rename.2 mtk added see also entry pointing to new renameat.2 page. rmdir.2 mtk added see also entry pointing to new unlinkat.2 page. symlink.2 mtk added see also entry pointing to new symlinkat.2 page. unlink.2 mtk added see also entry pointing to new unlinkat.2 page. termios.3 mtk / karel kulhavy document the feature test macros required to expose various flags. karel kulhavy clarify 'speed' argument for cfsetispeed() text. karel kulhavy / mtk note that loblk is not implemented on linux. mtk clarify arguments for cfsetspeed(). various formatting changes. full.4 andre lehovich add a sentence describing the purpose of full(4). core.5 aeb / mtk rework text describing circumstances in which core dump files are not produced. mtk / stefan puiu a core dump of a multithreaded process always includes the pid in the core filename. mtk / stefan puiu eliminate some accidentally duplicated text. ==================== changes in man-pages-2.31 ==================== released: 2006-05-02 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: joshua kwan justin pryzby karel kulhavy mark glines martin (joey) schulze nishanth aravamudan reuben thomas ryan s. arnold ulrich drepper apologies if i missed anyone! page renamings -------------- the following pages have been relocated into section 7, since that is their more natural home. see also references in various other pages have been adjusted. epoll.4 fifo.4 futex.4 complex.5 environ.5 (many pages outside man-pages actually *expect* 'environ' to be in section 7.) ipc.5 renamed to svipc.7 ".so" link files have been created to link the old file locations to the new file locations. these links are added just to ensure that cross references from any other (non-man-pages) pages will remain valid; eventually these links will be removed. new pages --------- fstatat.2 mtk new page for fstatat(2), new in 2.6.16. adjtime.3 mtk new page for adjtime(3). error.3 justin pryzby / mtk new page describing error() and error_at_line() fixes http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=186307 program_invocation_name.3 mtk new page describing program_invocation_name and program_invocation_short_name variables. sockatmark.3 mtk new page for sockatmark(3). ftm.7 mtk new page describing feature test macros. time.7 mtk new page giving an overview of "time" on linux systems. global changes -------------- getgroups.2 wait4.2 chown.2 chdir.2 gettimeofday.2 initgroups.3 dirfd.3 mtk simplified wording around requirement for _bsd_source feature test macro. times.2 time.2 gettimeofday.2 getitimer.2 nanosleep.2 ctime.3 rtc.4 mtk added see also referring to new time.7. err.3 errno.3 perror.3 strerror.3 justin pryzby / mtk add see also referring to new error.3. getdate.3 printf.3 scanf.3 mtk added see also entry referring to setlocale.3. changes to individual pages --------------------------- accept.2 mark glines remove mention of sock_rdm from this page, since this socket type does not support accept()ing connections. adjtimex.2 mtk modified text referring to adjtime(); added see also for new adjtime.3 page. fsync.2 mtk, after a note by karel kulhavy rewrote most of the description, as well as some other parts the page, to clarify use and operation of, and rationale for, fsync(2) and fdatasync(2). getitimer.2 mtk updated discussion of maximum timer value to reflect the fact that the default jiffy is now 4 milliseconds. added text to note that current incorrect behavior of normalizing tv_usec >= 1000000 will be repaired in a future kernel; applications should be fixed now. gettimeofday.2 karel kulhavy point out more explicitly that 'tz' argument should normally be null. mtk various other minor edits and formatting fixes. mount.2 mtk since kernel 2.6.16, ms_noatime and ms_nodiratime are settable on a per-mount basis. detail exactly which mount flags can be changed on ms_remount. nanosleep.2 mtk / karel kulhavy clarify return value discussion. openat.2 mtk add see also reference pointing to new fstatat.2. program_invocation_short_name.3 mtk new link to new program_invocation_name.3. recv.2 mtk added see also for new sockatmark.3. rmdir.2 joshua kwan / martin (joey) schulze / mtk correct wording of ebusy case. mtk add ".." case to enotempty error select.2 karel kulhavy note more clearly that fd_set arguments can be null. mtk / karel kulhavy improve opening paragraph describing purpose of select(). mtk various other minor edits and formatting fixes. semget.2 mtk / nishanth aravamudan add text to noting that the initial values of semaphores in a new set are indeterminate. shmget.2 mtk add text noting that contents of newly created segment are zero values. sigwaitinfo.2 mtk noted that all threads should block signal being waited for. stat.2 nishanth aravamudan / mtk added note that st_size is always returned as zero for most /proc files. mtk add see also reference pointing to new fstatat.2. syscall.2 justin pryzby / mtk remove bogus bugs text. utime.2 mtk various minor changes. confstr.3 mtk rewrote return value discussion. updated conforming to. removed bugs. ctanh.3 martin (joey) schulze / mtk fix errors in description. ctime.3 mtk the range of tm_sec is 0..60 (not 0..61). error_at_line.3 error_message_count.3 error_on_per_line.3 error_print_progname.3 mtk new links to new error.3. fmemopen.3 mtk / ryan s. arnold add text noting that explicitly controlling output buffering may be useful to catch errors on output operations on an fmemopen() stream. getline.3 justin pryzby add see also pointing to getline.3. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=364772 strtod.3 strtoul.3 mtk describe correct handling of errno in order to distinguish error from success after the call. added example section which points to strtol.3 which provides an example of the use of the analogous strtol(3). strtol.3 mtk / justin pryzby add an example program. mtk describe correct handling or errno in order to distinguish error from success after the call. tmpfile.3 reuben thomas description does not need to say "temporary file name" just "temporary file", since the name is in any case unavailable to the user. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=363518 mtk in description: change /automatically deleted when the program terminates normally/ to /automatically deleted when the program terminates/ since deletion occurs on both normal and abnormal termination. ip.7 karel kulhavy / mtk various wording improvements and clarifications. signal.7 mtk / ulrich drepper add text noting that a signal's disposition is process-wide, shared by all threads. mtk add text on changing signal dispositions. add text on "signal mask and pending signals". other minor edits. time.7 mtk added see also for new adjtime.3. ld.so.8 justin pryzby remove bogus duplicate line. ==================== changes in man-pages-2.32 ==================== released: 2006-05-13 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer johannes weiner justin pryzby karel kulhavy paul brook pavel heimlich apologies if i missed anyone! new pages --------- faccessat.2 mtk new page for faccessat(2), new in 2.6.16. fchmodat.2 mtk new page for fchmodat(2), new in 2.6.16. fchownat.2 mtk new page for fchownat(2), new in 2.6.16. futimesat.2 mtk new page for futimesat(2), new in 2.6.16. changes to individual pages --------------------------- access.2 mtk add see also reference pointing to new faccessat.2 page. capget.2 mtk reworded to reflect that capabilities are per-thread. chmod.2 mtk add see also reference pointing to new fchmodat.2 page. chown.2 mtk add see also reference pointing to new fchownat.2 page. mmap.2 mtk updated discussion of map_noreserve since it is no longer restricted to map_private mappings. add reference to discussion of /proc/sys/vm/overcommit_memory in proc.5. openat.2 mtk add see also reference pointing to new faccessat.2, fchmodat.2, fchownat.2, futimesat.2 pages. shmget.2 mtk document shm_noreserve flag, new in 2.6.15. truncate.2 paul brook / mtk expand text noting that ftruncate()/truncate() may fail if asked to extend a file beyond its current length. add eperm error. utime.2 mtk add see also reference pointing to new futimesat.2 page. fopen.3 justin pryzby / mtk document 'm' (mmap) flag. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=365754 mtk document 'c' (notcancel) flag. futimes.3 mtk add see also reference pointing to new futimesat.2 page. qsort.3 johannes weiner add missing "const" qualifies to cast in example. mtk slight rewording of comments in example. termios.3 karel kulhavy clarify meaning of ixany. clarify relationship of min with vmin and time with vtime. mtk noted that cibaud, ofdel, and delecho are not implemented on linux. added explanatory paragraph for phrases "not in posix" and "xsi". capabilities.7 mtk reworded to reflect that capabilities are per-thread. add ioprio_set() to list of operations permitted by cap_sys_nice. add ioprio_set() ioprio_class_rt and ioprio_class_idle scheduling classes to list of operations permitted by cap_sys_admin. note effects of cap_sys_nice for migrate_pages(). ==================== changes in man-pages-2.33 ==================== released: 2006-05-23 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer justin pryzby martin osvald" stefan puiu apologies if i missed anyone! page renamings -------------- ftm.7 mtk / stefan puiu renamed to the more suggestive feature_test_macros.7 new pages --------- mq_getsetattr.2 mtk new page briefly describing mq_getsetattr(2), the system call that underlies mq_setattr(3) and mq_getattr(3). rpmatch.3 justin pryzby / mtk new page for rpmatch(3). changes to individual pages --------------------------- chmod.2 mtk remove mention of non-standard s_iread, s_iwrite, s_iexec. posix does now document eloop. open.2 mtk remove mention of non-standard s_iread, s_iwrite, s_iexec. mmap.2 justin pryzby add mincore(2) to see also. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=367401 msync.2 justin pryzby note that einval can also be caused by flags == ms_sync | ms_async. sched_setaffinity.2 mtk add cpu_isset, cpu_clr, cpu_set, cpu_zero to name section. select.2 mtk various minor changes. select_tut.2 mtk removed much material that is redundant with select.2. various other changes. umask.2 mtk substantial rewrite of description of 'mask'. cpu_isset.3 cpu_clr.3 cpu_set.3 cpu_zero.3 mtk new links to sched_setaffinity.2 fd_clr.3 fd_isset.3 fd_set.3 fd_zero.3 mtk new links to select.2. fts.3 justin pryzby add see also referring to ftw.3. ftw.3 justin pryzby add see also referring to fts.3. getline.3 justin pryzby various minor clarifications. mkstemp.3 mtk clarify that o_excl is an open(2) flag. mq_open.3 martin osvald fix prototype declaration for 'attr'. mq_notify.3 martin osvald s/sigev_signal/sigev_signo/ mq_setattr.3 mtk new link to mq_getattr.3. mq_timedreceive.3 mtk new link to mq_receive.3. mq_timedsend.3 mtk new link to mq_send.3. setlocale.3 justin pryzby added see also referring to rpmatch.3. sigandset.3 sigisemptyset.3 sigorset.3 mtk new links to sigsetops.3. stdio.3 justin pryzby added see also referring to unlocked_stdio.3 see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=367667 strchr.3 justin pryzby add description of strchrnul(). strchrnul.3 mtk new link to strchr.3. undocumented.3 justin pryzby / mtk updated to remove some functions that don't exist, and therefore don't need to be documented. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=367671 unlocked_stdio.3 justin pryzby added see also referring to stdio.3 see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=367667 mq_overview.7 mtk added section describing relationship between library interfaces and system calls. added see also referring to new mq_getsetattr.2. feature_test_macros.7 stefan puiu fix typo: s/_posix_c_source/_posix_source/ ==================== changes in man-pages-2.34 ==================== released: 2006-06-20 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: aristeu sergio rozanski filho bert hubert chris curtis eduardo madeira fleury joerg scheurich justin pryzby kenichi okuyama marc lehmann martin (joey) schulze mats wichmann mike frysinger peter eiserloh stefan puiu thomas dickey walter harms apologies if i missed anyone! global changes -------------- tzselect.8 zdump.8 zic.8 mtk, joey added header comment noting that these pages are in the public domain. bindresvport.3 getrpcent.3 getrpcport.3 rpc.3 xdr.3 rpc.5 mtk, aeb, joey added following to top of these pages to clarify origin and license: .\" this page was taken from the 4.4bsd-lite cdrom (bsd license) new pages --------- ioprio_set.2 eduardo madeira fleury, with edits by mtk, and review by jens axboe new page for ioprio_get(2) and ioprio_set(2), new in 2.6.13. offsetof.3 justin pryzby / mtk new page describing offsetof() macro. changes to individual pages --------------------------- _exit.2 mtk add see also referring to exit_group.2. acct.2 mtk add see also referring to acct.5. fcntl.2 mtk explicitly mention term "dnotify" in discussion of f_notify. inotify_add_watch.2 aristeu sergio rozanski filho / mtk s/// in prototypes. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=369960 mtk renamed argument from 'path' to 'pathname'. reword introductory paragraph to clarify that inotify_add_watch() may also modify an existing watch item. mtk the einval error can also occur if 'fd' is not an inotify file descriptor. mtk moved bugs section from this page to inotify.7. inotify_init.2 aristeu sergio rozanski filho / mtk s/// in prototypes. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=369960 inotify_rm_watch.2 aristeu sergio rozanski filho / mtk s/// in prototypes. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=369960 mtk the einval error can also occur if 'fd' is not an inotify file descriptor. ioprio_get.2 mtk new link to new ioprio_set.2. mmap.2 mtk add see also referring to remap_file_pages.2. mount.2 kenichi okuyama s/mnt_force/mnt_expire/ under einval error. mremap.2 mike frysinger s/unsigned long flags/int flags/ in synopsis. pipe.2 mtk add see also referring to popen.3. posix_fadvise.2 mtk add see also referring to readahead.2. read.2 mtk see also for readv should refer to section 2, not 3. readahead.2 mtk add see also referring to posix_fadvise.2. send.2 peter eiserloh fix missing arguments in statement about equivalent send() and sendto() calls. setsid.2 mtk add see also referring to tcgetsid.3. shmctl.2 mtk minor wording change at start of description. stat.2 mtk add see also referring to access.2. statfs.2 mtk relocated "note" about f_fsid. write.2 mtk see also for writev should refer to section 2, not 3. __setfpucw.3 mtk, joey added license statement (gpl) after consultation with joerg scheurich. assert_perror.3 justin pryzby add #define _gnu_source to prototype difftime.3 joey added note about time_t representation on other systems. added conforming to. ftw.3 justin pryzby / mtk a fairly major revision... document ftw_actionretval; include .sh "return value"; reorganized and rewrote much of the page added an example program. inet.3 marc lehmann fixed typo in notes. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=370277 isalpha.3 joey updated conforming to. mktemp.3 mtk updated conforming to. printf.3 walter harms add documentation of %m. readdir.3 mtk added see also referring to ftw.3. re_comp.3 mtk note that these functions are obsolete in favor of regcomp(3). justin pryzby add see also referring to regcomp.3 scandir.3 mats wichmann reworded conforming to statement on scandir() and alphasort(). strchr.3 stefan puiu fix prototype for strchrnul(). strtoul.3 stefan puiu add text clarifying treatment of strings starting with minus sign. tmpnam.3 mtk, after comments by justin pryzby add text noting the need to use open(o_excl). mtk clarify discussion of use of free(3). various other minor changes to text and formatting. tmpfile.3 mtk updated conforming to. tmpnam.3 mtk, after comments by justin pryzby add text noting the need to use open(o_excl). updated conforming to. undocumented.3 mtk remove offsetof(), which is now documented. null.4 mtk added see also referring to full.4. console_codes.4 thomas dickey various improvements and corrections. epoll.7 mtk added conforming to section mentioning freebsd kqueue and solaris /dev/poll. feature_test_macros.7 mtk added pointer to location of lfs specification. futex.7 mtk, after suggestion by joey. added license statement to page, after discussion with original author, bert hubert. mtk reformat long lines; no content changes. inotify.7 mtk 'path' argument renamed to 'pathname'. a few minor rewordings. added bugs section describing a couple of bugs. ip.7 mtk add see also referring to byteorder.3. man.7 justin pryzby add see also referring to groff_man(7). http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=369253 ==================== changes in man-pages-2.35 ==================== released: 2006-07-06 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andi kleen andrew morton bauke jan douma davide libenzi denis barbier horacio rodriguez montero johan lithander justin pryzby mike frysinger stefan puiu thorsten kukuk apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- sync_file_range.2 andrew morton / mtk new page for sync_file_range(2), new in kernel 2.6.17. changes to individual pages --------------------------- adjtime.3 mtk noted bug that occurs if 'delta' is specified as null. see http://bugzilla.kernel.org/show_bug.cgi?id=6761 bind.2 stefan puiu add eaddrnotavail error. stefan puiu / mtk make example code more complete. epoll_ctl.2 mtk / davide libenzi added epollrdhup description. mtk added see also referring to poll.2. poll.2 mtk / davide libenzi added pollrdhup description. mtk the correct header file is , not . rewrote and reformatted various other parts. readlink.2 mtk nowadays, readlink() returns 'ssize_t', as required in posix.1-2001. wavelan.4 mtk added license statement. nscd.conf.5 thorsten kukuk add documentation for various new fields. passwd.5 horacio rodriguez montero add explanation of 'x' character in 'password' field. mtk the proper name of "*" is "asterisk" not "star". tcp.7 johan lithander update rfc reference for ecn. andi kleen add sentence on "low memory" limit for tcp_mem on 32-bit systems. ==================== changes in man-pages-2.36 ==================== released: 2006-07-11 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal jens axboe justin pryzby kyle mcmartin apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- maintaining mtk how to maintain man-pages. todo mtk things that it would be nice to get done for man-pages one day. scripts/fixme_list.sh mtk this script, intended for use by manual page maintainers, displays the fixmes in the manual page source files. changes to individual pages --------------------------- fdatasync.2 fsync.2 mtk added see also referring to sync_file_range.2. sendfile.2 mtk / jens axboe fix description of 'offset' argument to explain the case where 'offset' is null. ferror.3 justin pryzby add see also referring to fdopen.3. intro.3 mtk removed information about section 3 subsections -- it doesn't reflect current reality, and probably never has. added see also referring to intro.2. tcp.7 kyle mcmartin correction: tcp_window_scaling is enabled by default. ==================== changes in man-pages-2.37 ==================== released: 2006-08-02 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal dean gaudet frank van viegen helmut grohne ivana varekova thomas huriaux ville skyttä apologies if i missed anyone! global changes -------------- thomas huriaux / mtk various formatting problems found as a result of reviewing the following command were fixed. for a in $(wc -l man?/*.?| awk '$1 > 2 {print $2}' | grep -v total); do echo $a; groff -tascii -wmac -mman $a > /dev/null; done 2>&1 | less see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=378544 typographical or grammatical errors have been corrected in several places. new pages --------- readlinkat.2 mtk (after prompting from ivana varekova) new page for readlinkat(2), new in kernel 2.6.16. changes to individual pages --------------------------- ldd.1 ville skyttä document "-u" option. chdir.2 mtk noted effect of fork() and execve() on current working directory. chroot.2 mtk noted effect of fork() and execve() on root directory. epoll_ctl.2 frank van viegen / mtk fix description of ebadf error. exevce.2 mtk add text noting that effective ids are copied to saved set-ids during execve(). see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=379297 getitimer.2 mtk noted effect of fork() and execve() on interval timers. getrlimit.2 mtk noted effect of fork() and execve() on resource limits. getpriority.2 mtk noted effect of fork() and execve(). inotify_add_watch.2 mtk some rewording; included text describing required file permissions. intro.2 mtk revised description of standards under conforming to. makecontext.3 helmut grohne / mtk point out that args following 'argc' are int. mtk added an example program. various minor wording fixes. mmap.2 mtk expand description of map_populate. mtk, after prompting by dean gaudet expand description map_nonblock. mtk various minor formatting fixes. openat.2 mtk added see also linking to readlinkat.2. nanosleep.2 mtk noted buggy behavior in linux 2.4 and earlier when nanosleep() is restarted after receiving stop+sigcont signals. nice.2 mtk very minor rewording. readlink.2 mtk added see also linking to readlinkat.2. sched_setscheduler.2 mtk noted preservation of scheduling parameters across execve(). setpgid.2 mtk noted effect of fork() and execve() on process group id. setsid.2 mtk noted effect of fork() and execve() on session id. umask.2 mtk noted effect of fork() and execve() on umask. atexit.3 mtk noted inheritance of registrations across fork(). capabilities.7 mtk added material on privileges required for move_pages(). clone_newns needs cap_sys_admin. keyctl(keyctl_chown) and keyctl(keyctl_setperm) require cap_sys_admin. ==================== changes in man-pages-2.38 ==================== released: 2006-08-03 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal apologies if i missed anyone! global changes -------------- most pages mtk there was a major reworking of the conforming to sections in most manual pages. * generally try to rationalize the names used for standards. the preferred names are now documented as the head words of the list in standards(7). for the future: there is probably no need to talk about anything more than c89, c99, posix.1-2001 (or later), xbsd, and svr4. (in particular, i've eliminated most references to xpg and svid, replacing them with references to sus or svr4.) * eliminate discussion of errors that can occur on other systems. this information exists only patchily in the manual pages, is probably of limited use, is hard to maintain, and was in some cases simply wrong (and probably always was). * tried to ensure that those interfaces specified in c99 or posix.1-2001 are marked as such in their manual pages. intro.1 intro.2 intro.3 intro.4 intro.5 intro.7 feature_test_macros.7 mtk added see also referring to new standards.7. various pages mtk changed instances of "hp ux" to "hp-ux". various pages mtk changed instances of "dg-ux to "dg/ux" typographical or grammatical errors have been corrected in several places. new pages --------- standards.7 mtk based on material taken from intro.2, but expanded to include discussion of many additional standards. changes to individual pages --------------------------- bind.2 mtk minor wording change for enotsock error. intro.2 mtk removed information on standards to new standards.7. ==================== changes in man-pages-2.39 ==================== released: 2006-08-05 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal apologies if i missed anyone! global changes -------------- various pages mtk updated conforming to and/or standards references in various pages that were missed for 2.38. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- chdir.2 mtk _xopen_source=500 also gets fchdir() prototype. standards.7 mtk added a few more standards, and expand some explanations. ==================== changes in man-pages-2.40 ==================== released: 2006-09-04 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andi kleen andries brouwer christoph hellwig chuck ebbert <76306.1226@compuserve.com> samuel thibault toralf förster apologies if i missed anyone! global changes -------------- faccessat.2 fchmodat.2 fchownat.2 fstatat.2 futimesat.2 linkat.2 mkdirat.2 mknodat.2 openat.2 readlinkat.2 renameat.2 symlinkat.2 mtk (after a note by alain portal) make naming of 'pathname' argument consistent; various minor rewordings. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- clone.2 mtk reinstate text on clone_detached, and add a few words. execve.2 mtk added list of process attributes that are not preserved on exec(). fork.2 mtk, after a suggestion by christoph hellwig greatly expanded, to describe all attributes that differ in parent and child. linkat.2 mtk document at_symlink_follow (new in 2.6.18). set_mempolicy.2 mtk / andi kleen memory policy is preserved across execve(). write.2 mtk / alain portal see also for writev should refer to section 2, not 3. (i.e., really make the change that was logged in 2.34) getcwd.3 samuel thibault / mtk fix synopsis and conforming to text for getwd() and get_current_dir(). see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=381692 proc.5 chuck ebbert document /proc/pid/auxv. capabilities.7 alain portal restore text accidentally deleted in 2.39. regex.7 mtk / alain portal change references to "1003.2" to "posix.2". ==================== changes in man-pages-2.41 ==================== released: 2006-10-12 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen andries brouwer andrew morton britton leo kerin dan jacobson guillem jover hrvoje niksic jens axboe justin pryzby kevin ryde marcel holtmann senthil kumar stefan puiu stuart macdonald trond myklebust apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- splice.2 tee.2 vmsplice.2 jens axboe / michael kerrisk see also: http://lwn.net/articles/118760/ http://lwn.net/articles/178199/ http://lwn.net/articles/179492/ http://kerneltrap.org/node/6505 http://lwn.net/articles/179434/ changes to individual pages --------------------------- ldd.1 stefan puiu note glibc version where "ldd -u" appeared. execve.2 mtk the pr_set_name setting is not preserved across an execve(). fork.2 mtk mappings marked with madvise(madv_dontfork) are not inherited by child. getdtablesize.2 mtk noted that sysconf(_sc_open_max) is preferred in portable applications. getpagesize.2 mtk noted that sysconf(_sc_page_size) is preferred in portable applications. _sc_page_size is available on most systems. madvise.2 mtk document madv_remove, new in 2.6.16. document madv_dontfork / madv_dofork, new in 2.6.16. mount.2 mtk / trond myklebust mnt_force can cause data loss. mmap.2 mtk added note on linux's old (pre-2.6.12) buggy treatment of length==0. justin pryzby / mtk added some einval errors. mremap.2 mtk remove superfluous "#include " from synopsis. msync.2 mtk added ebusy error for case where ms_invalidate is applied to a locked region. posix_fadvise.2 andrew morton since 2.6.18, posix_fadv_noreuse is a no-op. prctl.2 marcel holtmann / mtk since kernel 2.6.18, setting 2 for pr_set_dumpable is no longer possible. guillem jover updated linux versions where the options where introduced. added pr_set_timing, pr_get_timing, pr_set_name, pr_get_name, pr_set_unalign, pr_get_unalign, pr_set_fpemu, pr_get_fpemu, pr_set_fpexc, pr_get_fpexc. michael kerrisk document pr_get_endian and pr_set_endian. remap_file_pages.2 mtk add "#define _gnu_source" to synopsis. sync_file_range.2 mtk noted that sync_file_range() appeared in kernel 2.6.17. vfork.2 mtk noted interactions with fork handlers in multithreaded programs. wait4.2 mtk added feature test macros to synopsis. clog2.3 mtk / aeb / kevin ryde fix broken text in description. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=386214 clog10.3 kevin ryde fix broken text in description. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=386214 mq_receive.3 britton leo kerin fix return type in synopsis; should be "ssize_t" not "mqd_t". see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=387551 qsort.2 hrvoje niksic fix wording referring to the use of strcmp() in 'compar' function. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=391402 sendfile.2 mtk added see also referring to new splice.2 page. termios.3 mtk documented iutf8 (which was new in kernel 2.6.4). tzset.3 mtk added some tz examples. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=386087 proc.5 mtk added delayacct_blkio_ticks (new in 2.6.18) to /proc/pid/statm. ip.7 stuart macdonald / andi kleen fix discussion for tcp error queue /ip_recverr on tcp. pthreads.7 mtk noted effect of rlimit_stack resource limit for nptl. socket.7 senthil kumar place socket options in alphabetical order. ==================== changes in man-pages-2.42 ==================== released: 2006-11-24 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andrew morton chuck ebbert <76306.1226@compuserve.com> doug goldstein eduard bloch evan teran pavel heimlich petr baudis randy dunlap ulrich drepper apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- brk.2 evan teran / mtk add text describing behavior of the linux brk() system call and point out that the glibc brk() wrapper provides different behavior. mtk note that sbrk() is implemented as a library function in glibc that calls the brk() system call. futex.2 mtk futex_fd is scheduled for removal in june 2007. getaddrinfo.3 getnameinfo.3 ulrich drepper, with edits by mtk add text describing internationalized domain name extensions. open.2 mtk / eduard bloch fix description of o_largefile to mention required feature test macros. ptrace.2 chuck ebbert since linux 2.6.18, the pid of the new process is also available for ptrace_event_vforkdone. syslog.3 doug goldstein fix header file required for vsyslog() in synopsis. wcwidth.3 petr baudis fix conforming to. core.5 mtk linux 2.4.21 added core_pattern (which was already in 2.6). noted a few more reasons why a core dump file might not be produced. ==================== changes in man-pages-2.43 ==================== released: 2006-11-29 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen david brownell eduard bloch egmont koblinger reuben thomas apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- ioperm.2 mtk clarify discussion of privilege requirements. added enomem to errors. open.2 mtk / eduard bloch clarify description of o_largefile. crypt.3 egmont koblinger make description of md5 output string less ambiguous. strerror.3 reuben thomas add c99 to conforming to; see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=400634 rtc.4 david brownell update the rtc man page to reflect the new rtc class framework: - generalize ... it's not just for pc/at style rtcs, and there may be more than one rtc per system. - not all rtcs expose the same feature set as pc/at ones; most of these ioctls will be rejected by some rtcs. - be explicit about when {a,p}ie_{on,off} calls are needed. - describe the parameter to the get/set epoch request; correct the description of the get/set frequency parameter. - document rtc_wkalm_{rd,set}, which don't need aie_{on,off} and which support longer alarm periods. - hey, not all system clock implementations count timer irqs any more now that the new rt-derived clock support is merging. proc.5 mtk s/fseek(3)/lseek(2)/ under /proc/pid/mem entry. feature_test_macros.7 mtk / eduard bloch the lfs spec is now at http://opengroup.org/platform/lfs.html raw.7 udp.7 andi kleen describe the correct default for udp/raw path mtu discovery. ==================== changes in man-pages-2.44 ==================== released: 2007-04-04 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andre majorel benjamin gilbert carlo marcelo arenas belon chuck ebbert <76306.1226@compuserve.com> ivana varekova jakub jelinek john ward jorge peixoto de morais neto julien blache julien cristau justin pryzby martín ferrari mike frysinger nick piggin nick pollitt nicolas françois pádraig brady premysl hruby reuben thomas samuel thibault serge e. hallyn thomas huriaux timo sirainen val henson apologies if i missed anyone! new pages --------- termio.7 mtk, after a bit of prodding by reuben thomas a brief discussion of the old system v termio interface, with pointers to pages that will contain the information that the reader probably wants. scripts/find_repeated_words.sh mtk find consecutive duplicate words in a man page, some of which may be grammar errors. global changes -------------- various pages justin pryzby / mtk add "#define _atfile_source" to synopsis in following pages: faccessat.2 fchmodat.2 fchownat.2 fstatat.2 futimesat.2 linkat.2 mkdirat.2 mknodat.2 openat.2 readlinkat.2 renameat.2 symlinkat.2 unlinkat.2 mkfifoat.3 various pages mtk various references to "getty" were changed to "mingetty", since that is the manual page more likely to be found on current systems. various pages mtk, after a suggestion by reuben thomas updated various header pages to accurately reflect which functions are and are not part of c89. also fixed/improved a few other conforming to entries. various pages mtk s/unices/unix systems/ on the 5 pages where it appears. various pages mtk wrapped long source lines in the following files getsockopt.2 mknodat.2 io_setup.2 select_tut.2 select.2 readlinkat.2 io_cancel.2 syslog.2 wcsncat.3 getipnodebyname.3 cmsg.3 wcpncpy.3 wcsrtombs.3 wcstok.3 fgetwc.3 wmemcmp.3 wcsspn.3 div.3 modf.3 stdio_ext.3 ctermid.3 des_crypt.3 wcsncmp.3 wmemchr.3 wcsstr.3 wmemcpy.3 wprintf.3 wcsnrtombs.3 termios.3 erf.3 ceil.3 lround.3 nextafter.3 wcsncpy.3 wmemset.3 getw.3 console_ioctl.4 sk98lin.4 environ.7 unix.7 time.7 various pages mtk added a see also reference for feature_test_macros(7) to all pages where a feature test macro appears in the synopsis. various pages mtk added see also entry pointing to time.7 alarm.2 nanosleep.2 ualarm.3 usleep.3 various pages justin pryzby / mtk fixed consecutive duplicate word typos on a number of pages. typographical or grammatical errors have been corrected in several places. (special thanks to nicolas françois!) changes to individual pages --------------------------- access.2 mtk since 2.6.20, access() honors the ms_noexec mount flag. jorge peixoto de morais neto / mtk improve enoent description. clone.2 mtk added some detail to the prototype. added some notes on ia-64's clone2(). epoll_ctl.2 mtk add text to note that epollrdhup appeared in kernel 2.6.17. faccessat.2 justin pryzby various fixes as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=411177 * s/effective/real/ in description text. * added to synopsis. * various other changes. getrlimit.2 mtk / fedora downstream patches; thanks to ivana varekova added a few words to note that rlimit_nproc is really a limit on threads. io_cancel.2 io_destroy.2 io_getevents.2 io_setup.2 io_submit.2 fedora downstream patches; thanks to ivana varekova s%linux/aio.h%libaio.h% in synopsis. changed return type from "long" to "int". mbind.2 samuel thibault / mtk fix einval description. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=411777 mincore.2 nick piggin kernel 2.6.21 fixes several earlier bugs in mincore(). nick pollitt remove words "of a file" -- mincore() is describing memory residence information, not properties of a file. mtk rewrote various parts to make the page clearer. mmap.2 mtk rewrote and reorganized various parts to be clearer. taken from fedora downstream patches; thanks to ivana varekova removed text stating that mmap() never returns 0; that's not true. mount.2 mtk / val henson document ms_relatime, new in linux 2.6.20. open.2 andre majorel / mtk on linux, the error returned when opening a large file on a 32-bit system is actually efbig, not eoverflow. posix_fadvise.2 pádraig brady fix return value description: returns error number of failure. rename.2 mtk / timo sirainen various improvements to description. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=416012 semop.2 mtk if sops contains multiple operations, then these are performed in array order. all unix systems that i know of do this, and some linux applications depend on this behavior. susv3 made no explicit statement here, but susv4 will explicitly require this behavior. small rewording of explanation of "atomically". signal.2 nicolas françois fix incorrect argument name in description. mtk small wording improvement. socket.2 nicolas françois add reference to ipv6.7 page. socketcall.2 nicolas françois fix .th line. splice.2 benjamin gilbert fix inconsistent argument names in synopsis and description. statvfs.2 mtk small wording clarification. symlink.2 mtk / nicolas françois removed cryptic text under conforming to referring to "open(2) and nfs". there is no relevant text in open.2 as far as i (mtk) can see. time.2 mtk / reuben thomas remove sentence "gettimeofday() obsoleting time() on 4.3bsd". this information is old, and probably no longer relevant. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=403888 write.2 mtk, after an idea from a downstream fedora patch. clarified discussion of /count == 0/ case. ptrace.2 chuck ebbert when the parent receives an event with ptrace_event_* set, the child is not in the normal signal delivery path. this means the parent cannot do ptrace(ptrace_cont) with a signal or ptrace(ptrace_kill). kill() with a sigkill signal can be used instead to kill the child process after receiving one of these messages. sched_setaffinity.2 mtk fix glibc version number in description of 'cpusetsize' argument. vfork.2 mtk stripped some excess/outdated text from the bugs section. basename.3 mtk / jorge peixoto de morais neto add text to clarify that the pointer returned by these functions may be into some part of 'path'. dlopen.3 taken from fedora downstream patches; thanks to ivana varekova + carlo marcelo arenas belon add "#include " to example program. fclose.3 mtk complete rewrite. the existing page was hard to read, and the return value description seems to be wrong. getopt.3 mtk added getopt() example program. mtk add a few words to clarify the operation of the gnu-specific double-colon feature, which allows options to have optional arguments. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=352139 glob.3 nicolas françois fix prototype. inet_network.3 mtk, after an idea from a downstream fedora patch. clarified description of inet_network(). log.3 nicolas françois fix .th line. log10.3 nicolas françois fix .th line. malloc.3 nicolas françois small rewording to mention calloc(). posix_openpt.3 martín ferrari fix return type in synopsis; as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=400971 needs _xopen_source == 600; as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=400975 julien blache s/ptsname/posix_openpt/ in return value re_comp.3 taken from fedora downstream patches; thanks to ivana varekova add "#define _regex_re_comp" to synopsis. regex.3 nicolas françois fix .th line. termios.3 mtk added .ss headers to give some structure to this page; and a small amount of reordering. mtk added a section on canonical and non-canonical mode. mtk enhanced the discussion of "raw" mode for cfmakeraw(). mtk document cmspar. mtk make description of parodd a little clearer. reuben thomas add see also link to tty_ioctl.4 mtk add see also link to console_ioctl.4 ualarm.3 mtk removed bsd prototype from synopsis. various rewordings. usleep.3 mtk removed bsd prototype from synopsis. various rewordings. termcap.5 taken from fedora downstream patches; thanks to ivana varekova s/curses/ncurses/ under see also bootparam.7 taken from fedora downstream patches; thanks to ivana varekova documented "mem=nopentium". feature_test_macros.7 mtk the default treatment of _posix_c_source changed in glibc 2.4. mtk, after a suggestion by justin pryzby added some text warning that the "__" macros that defines internally should never be directly defined by programs. mtk, based on notes by jakub jelinek document _fortify_source (see http://gcc.gnu.org/ml/gcc-patches/2004-09/msg02055.html ) mtk document _reentrant and _thread_safe. mdoc.7 mtk / nicolas françois remove configuration section, since this does not seem to be true for linux. svipc.7 nicolas françois fix data types in associated data structures; remove nonexistent semzcnt and semncnt fields. time.7 mtk since kernel 2.6.20, the software clock can also be 300 hz. ==================== changes in man-pages-2.45 ==================== released: 2007-04-05 global changes -------------- this release consists mainly of formatting fixes (to a large number of pages) to achieve greater consistency across pages. with the exception of the few individual changes noted below, no changes were made to content. changes to individual pages --------------------------- io_destroy.2 io_getevents.2 io_setup.2 io_cancel.2 io_submit.2 mtk clarified return value text bindresvport.3 mtk rewrote prototype using modern c syntax. ==================== changes in man-pages-2.46 ==================== released: 2007-04-06 global changes -------------- this release consists mainly of formatting fixes (to a large number of pages) to achieve greater consistency across pages: * most instances of two or more consecutive blank lines in man page output were shrunk to a single line. * a number of example programs were reformatted to more closely match k&r style. * in various places (mainly code examples), the use of tabs was replaced by spaces with the exception of the few individual changes noted below, no changes were made to content. changes to individual pages --------------------------- bdflush.2 mtk add header file to synopsis. sched_rr_get_interval.2 mtk moved timespec definition from synopsis into description. select_tut.2 mtk make synopsis match select.2. ==================== changes in man-pages-2.47 ==================== released: 2007-05-04 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen john heffner apologies if i missed anyone! global changes -------------- this release consists mainly of changes to source file layout (wrapped long lines; stripped trailing white space; started new sentences on new lines). there is very little change to output formatting or content (see the notes below). changes to individual pages --------------------------- sched_rr_get_interval.2 mtk remove crufty statement that this system call is not implemented. the nice interval can be used to control the size of the round-robin quantum. corrected .th line. ip.7 john heffner / mtk document ip_pmtudisc_probe, which will be in 2.6.22. ==================== changes in man-pages-2.48 ==================== released: 2007-05-04 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: colin watson justin pryzby apologies if i missed anyone! global changes -------------- this release consists mainly of changes to source file layout (wrapped long lines; stripped trailing white space; started new sentences on new lines). there is very little change to output formatting or content (see the notes below). various pages mtk in various places where it occurred, s/nonnegative/non-negative/ various pages mtk s/wide character/wide-character/ when used attributively. changes to individual pages --------------------------- man.7 justin pryzby / colin watson / mtk .sh doesn't require quotes. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=411303 ==================== changes in man-pages-2.49 ==================== released: 2007-05-20 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: akihiro motoki bruno haible justin pryzby apologies if i missed anyone! new pages --------- bsd_signal.3 mtk documentation of bsd_signal(). euidaccess.3 mtk manual page for euidaccess() and eaccess(). getsubopt.3 mtk / justin pryzby documentation of getsubopt(). sysv_signal.3 mtk documentation of sysv_signal(). new links --------- epoll_pwait.2 mtk new link to epoll_wait.2. eaccess.3 mtk new link to new euidaccess.3, sem_timedwait.3 mtk new link to sem_wait.3. sem_trywait.3 mtk new link to sem_wait.3. global changes -------------- typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- access.3 mtk added see also ref to new euidaccess.3 page. epoll_wait.2 mtk added description of epoll_pwait(), new in kernel 2.6.19. execve.2 mtk add text noting that linux allows 'argv' and 'envp' to be null, but warning that this is non-standard and non-portable, and should be avoided in portable programs. bug filed (http://bugzilla.kernel.org/show_bug.cgi?id=8408) to get this changed, but maybe that won't be done because it is an abi change. mtk added an example program. mtk expanded the discussion of interpreter scripts and the 'optional-arg' argument of an interpreter script. for further info, see http://homepages.cwi.nl/~aeb/std/hashexclam-1.html http://www.in-ulm.de/~mascheck/various/shebang/ mtk added text noting that fd_cloexec causes record locks to be released. mtk mention effect of ms_nosuid mount(2) flag for set-user-id programs. mtk expanded description of handling of file descriptors during execve(), adding text to note that descriptors 0, 1, and 2 may be treated specially. faccessat.3 mtk added see also ref to new euidaccess.3 page. mmap.2 mtk place map_* flags list in alphabetical order. readv.2 mtk a fairly substantial rewrite, which among other things fixes the problem reported by kyle sluder in http://bugzilla.kernel.org/show_bug.cgi?id=8399 and added some example code. sigaction.2 mtk added text referring to the discussion of async-signal-safe functions in signal(7). a few other minor formatting and wording changes. signal.2 mtk moved the discussion of async-signal-safe functions to signal(7). added text referring to the discussion of async-signal-safe functions in signal(7). added see also entries referring to new bsd_signal.3 and sysv_signal.3 pages. copysign.3 bruno haible clarify discussion of negative zero. getopt.3 mtk add see also ref to new getsubopt.3. iconv_open.3 bruno haible describe the glibc/libiconv //translit and //ignore extensions for 'tocode'. iswblank.3 bruno haible update conforming to; iswblank() is in posix.1-2001. inotify.7 mtk definitions for in_dont_follow, in_mask_add, and in_onlydir were added to glibc in version 2.5. signal.7 mtk incorporated (and slightly modified) the text on async-signal-safe functions that was formerly in signal(2). added see also entries referring to new bsd_signal.3 and sysv_signal.3 pages. ==================== changes in man-pages-2.50 ==================== released: 2007-05-21 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andreas halter laird shaw mike frysinger apologies if i missed anyone! removed pages (!) ----------------- most section 1 man pages are removed mtk (with help from mike frysinger, laird shaw, andreas halter) once upon time andries added a number of section 1 manual pages to man-pages. however, since that time, those pages have not seen much maintenance, and are not in fact distributed in most distributions. instead most distributions supply the coreutils versions of these pages, which are currently maintained. in addition, man-pages provides the 1p pages, which document the portable subset of functionality of these commands. since the man1 pages are mostly unneeded, and out of date, i'm removing them. the following pages disappear: chgrp.1 chmod.1 chown.1 cp.1 dd.1 df.1 diff.1 dir.1 dircolors.1 du.1 install.1 ln.1 ls.1 mkdir.1 mkfifo.1 mknod.1 mv.1 rm.1 rmdir.1 touch.1 vdir.1 the following section 1 pages will be kept: intro.1 ldd.1 time.1 ==================== changes in man-pages-2.51 ==================== released: 2007-05-28 global changes -------------- various pages mtk (hopefully) all cross references outside a page now include a section number. this should permit better resulting output from a man2html-type conversion. various pages mtk convert function formatting of the form "\fbname\fp()" to ".br name ()". changes to individual pages --------------------------- futimesat.2 mtk s/futimes/futimesat/ in .sh name line. msgop.2 mtk put "msgrcv" and "msgsnd" in .sh name line. mount.2 mtk add "umount2" to .sh name line. wait.2 mtk add "waitid" to .sh name line. getopt.3 mtk add "getopt_long" and "getopt_long_only" in .sh name line. sem_wait.3 mtk add "sem_timedwait" and "sem_trywait" to .sh name line. stdarg.3 mtk add "va_start", "va_arg", "va_end", "va_copy" to .sh name line. ==================== changes in man-pages-2.52 ==================== released: 2007-05-29 "a foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines" ralph waldo emerson (1803-1882) "but damn it, these man pages are a mess!" global changes -------------- most of the changes below are about bringing greater consistency to manual pages, including reducing the wide range of .sh section headings. typographical or grammatical errors have been corrected in several places. various pages mtk make 'manual' component of .th line into the string "linux programmer's manual". reason: consistency. various pages mtk changed date in .th line into form yyyy-dd-mm. reason: consistency. various pages mtk some .sh header lines were made into .ss lines. (one of the aims here is to reduce the number of non-standard .sh lines.) various pages mtk change title .sh sections named "note" to "notes", in some cases also changing the location of the section within the page. reason: consistency. various pages mtk commented out .sh author sections; the right place for documentation authorship sections is usually comments at the top of the page source. various pages mtk changed .sh history to .sh versions. reason: in many cases, history was being used to describe linux/glibc version information, as was already done for versions sections in other pages. various pages mtk removed history section, or moved it as a subsection or paragraphs under another section e.g., notes. reason: there are too many arbitrary section (.sh) names, and a history section never was consistently used across linux manual pages. various pages mtk moved see also section to be last section on the page reason: consistency -- and this is where see also should be! various pages mtk relocated glibc notes as subsection under notes reason: reduce number of arbitrary section (.sh) names. various pages mtk relocated linux notes as subsection under notes reason: reduce number of arbitrary section (.sh) names. various pages mtk renamed some "availability" sections to "versions". reason: consistency. various pages mtk renamed some "diagnostics" sections to "return value". reason: consistency. getopt.3 tzselect.8 mtk s/\.sh environment variables/.sh environment/ reason: consistency. intro.2 select.2 sysctl.2 bsearch.3 dlopen.3 envz_add.3 fmtmsg.3 getgrent_r.3 getgrouplist.3 getpwent_r.3 getutent.3 hsearch.3 rtime.3 strptime.3 tsearch.3 vcs.4 wordexp.3 mtk s/return 0/exit(exit_failure)/ in main() of function example program. reason: consistency. mprotect.2 select_tut.2 dlopen.3 getgrent_r.3 getopt.3 getpwent_r.3 hsearch.3 select_tut.2 tsearch.3 mtk use symbolic constants (exit_success, exit_failure) in calls to exit(). reason: consistency. access.2 chown.2 lseek.2 open.2 read.2 utmp.5 mtk renamed restrictions section to notes, or moved text in a restrictions section under existing notes section. reason: consistency, and reduce number of arbitrary section (.sh) names. changes to individual pages --------------------------- capget.2 mtk s/\.sh further information/.sh notes/ dup.2 mtk s/\.sh warning/.sh notes/ kill.2 mtk renamed linux history section to linux notes, and relocated within page. select_tut.2 mtk relocated example program and made its .sh title "example". sigaltstack.2 mtk move code example into its own example section. sigreturn.2 mtk s/\.sh warning/.sh notes/ setuid.2 mtk s/\.sh "linux-specific remarks"/.sh linux notes/ shmget.2 mtk remove section about effect of fork()/exec()/exit(); shmop.2 contains the same text, and it only needs to be said once. shmop.2 mtk minor rewording under description. daemon.3 mtk minor wording and formatting changes. encrypt.3 mtk removed statement that glibc unconditionally exposes declarations of encrypt() and setkey(), since portable applications must use and define _xopen_source to obtain the declarations of setkey() and encrypt(). adjusted example program accordingly. mkstemp.3 mtk slight rewording. ldp.7 mtk minor wording and formatting changes. man.7 mtk substantial rewrite, revising and extending the discussion about desired conventions for writing pages. there will be further updates to this page in the next few man-pages releases. ==================== changes in man-pages-2.53 ==================== released: 2007-05-30 "a foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines" ralph waldo emerson (1803-1882) "but damn it, these man pages are a mess!" global changes -------------- many many pages mtk reordered sections to be more consistent, in some cases renaming sections or shifting paragraphs between sections. man7/* mtk in various pages in this section, .sh headings were converted to .ss. ==================== changes in man-pages-2.54 ==================== released: 2007-06-07 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: emmanuel mogenet michael berg apologies if i missed anyone! global changes -------------- various pages mtk where there is an instruction in the synopsis about linking or compiling with a certain option, the option is now marked up in italics (e.g., "\fi-lm\fp"). various pages mtk added page numbers to page cross references. a few pages mtk s/manpage/man page/, for consistency. typographical or grammatical errors have been corrected in several places. new pages --------- man-pages.7 mtk a description of the conventions that should be followed when writing pages for the man-pages package. removed pages ------------- man1/readme mtk already deleted most of the man1 pages previously, so this doesn't need to stay. ldp.7 mtk removed this page since it is out of date, and the proper place to go for up-to-date information is http://www.tldp.org/ ksoftirq.9 mtk reason: this was the only section 9 page, and it is old (linux 2.4). the man9 section never took off as an idea, and i see little point in keeping a section 9 with just a single old page. changes to individual pages --------------------------- howtohelp mtk moved some material out of here into new man-pages.7. alloc_hugepages.2 mtk minor rewrites, eliminating some duplication, and removing some outdated text. epoll_pwait.2 michael berg fix broken link path; http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=425570 fcntl.2 mtk remove misleading text about setting o_async when calling open(); one must use fcntl() f_setfl for this task. fdatasync.2 mtk converted outdated bugs note about fdatasync() being equivalent to fsync() on linux 2.2 into a notes note about this historical behavior. futex.2 mtk small rewording to fix "fails with the error ewouldblock" rather than "returns ewouldblock". see red hat bug 172828. mprotect.2 mtk, after an observation by emmanuel mogenet a much improved example program. mtk significant rewrites and additions to description. mremap.2 mtk remove text about the nonexistent bsd mremap() -- too much information, in my opinion. sched_yield.2 mtk added errors section. set_mempolicy.2 mtk moved text for "versions and library support". set_tid_address.2 mtk small rewording in return value section. sigaction.2 mtk add example section with a pointer to example in mprotect.2. sync_file_range.2 mtk fix return type in synopsis. add return value section. atexit.3 mtk small rearrangement of text under notes. bindresvport.3 mtk rewrite and substantial additional text. exec.3 mtk minor clarifications for text on execlp() and execvp(). removed files section, since it provides no useful additional info. fenv.3 mtk moved link instructions from notes to synopsis. added feenableexcept, fedisableexcept, fegetexcept to .sh name list. fputwc.3 mtk added 'putwc' to .sh name list. gethostbyname.3 mtk s/int/socklen_t/ for type of gethostbyaddr() 'len' argument, and add a few more words in notes about the type used here. login.3 mtk removed remark from notes about linking with -lutil; add text on that point to synopsis. openpty.3 mtk removed redundant remark from notes about linking with -lutil since there is text on that point under synopsis. sysconf.3 mtk added see also referring to getconf(1). unlocked_stdio.3 mtk revised .sh name section. ascii.7 mtk minor rearrangement of order of text. capabilities.7 mtk s/exec()/execve(2)/ in various places. complex.7 mtk changed "atan(1)" to "atan(1.0)" to prevent some versions of man2html(1) from mistaking that string as a page cross reference. rtnetlink.7 mtk small restructuring to avoid 'cannot adjust line' from man(1). ldconfig.8 mtk removed now very out-of-date sentence about need to link shared libraries with -lc. man.7 mtk various text was moved out of this page into the new man-pages.7. mdoc.7 mtk added see also referring to new man-pages.7. mdoc.samples.7 mtk a few changes, hopefully done right, to eliminate some errors to stderr when rendering with man(1). rtnetlink.7 mtk shorten a line in table so it fits in 80 columns. minor rewording under bugs. tzselect.8 mtk moved exit status section. ==================== changes in man-pages-2.55 ==================== released: 2007-06-10 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alexander taboriskiy joey hess john reiser julien cristau justin pryzby martin (joey) schulze mike frysinger serge van den boom ulrich drepper xose vazquez perez apologies if i missed anyone! global changes -------------- clone.2 getdents.2 gettid.2 ioprio_set.2 llseek.2 mmap2.2 modify_ldt.2 mq_getsetattr.2 pivot_root.2 quotactl.2 readdir.2 sysctl.2 syslog.2 tkill.2 mtk, after a note by mike frysinger updated to reflect the fact that the _syscalln() macros have gone away, several pages mtk change reference to path_resolution.2 to path_resolution.7. typographical or grammatical errors have been corrected in several places. moved pages ----------- path_resolution.2 has been moved to section 7, thus path_resolution.7 mtk reason: this is an overview page, not one describing as a specific system call. changes to individual pages --------------------------- maintaining mtk, after a note from xose vazquez perez added pointer to red hat man-pages bugzilla. mtk added a release philosophy note on separating out big formatting changes into their own release that contains minimal content changes. accept.2 mtk add new example section with pointer to example in bind.2. arch_prctl.2 mtk added return value section. bind.2 mtk expand example program, and move it to new example section. added text pointing to example in getaddrinfo.3. cacheflush.2 mtk convert notes section to conforming to and note that this call is linux-specific. other minor rewordings. connect.2 mtk added new example section pointing to example in getaddrinfo.3. create_module.2 mtk add enosys error. fcntl.2 flock.2 mtk small rewrite of see also text pointing to documentation/* in kernel source. get_kernel_syms.2 mtk added errors heading add enosys error. getdtablesize.2 mtk added an errors section. getsid.2 mtk added a return value section. getpid.2 mtk added an errors section (stating that the calls are always successful). ioctl_list.2 mtk add see also reference to ioctl.2. listen.2 mtk add new example section with pointer to example in bind.2. query_module.2 martin (joey) schulze add enosys error. recv.2 mtk added new example section pointing to example in getaddrinfo.3. sched_get_priority_max.2 sched_rr_get_interval.2 sched_setscheduler.2 sched_yield.2 mtk modified .th line send.2 mtk added new example section pointing to example in getaddrinfo.3. set_tid_address.2 mtk added an errors section (stating that the call is always successful). signal.2 mtk, after a note from alexander taboriskiy strengthen warning against the use of signal(). added siginterrupt(3) to see also list. mtk rewrote various parts; added an errors section. socket.2 mtk added new example section pointing to example in getaddrinfo.3. stat.2 mtk added example program. syscall.2 mtk converted to -man format; some rewrites; added an example. sysctl.2 mtk improved the example program. getnameinfo.3 mtk add text pointing to example in getaddrinfo.3. getaddrinfo.3 mtk add example programs. add getnameinfo() to see also list. memmove.3 mtk / serge van den boom clarify discussion of what happens if 'src' and 'dest' overlap. regex.3 justin pryzby add grep(1) to see also list. sigpause.3 mtk after a note from ulrich drepper clarify discussion of feature test macros that are needed to expose system v and bsd versions of this function in glibc. undocumented.3 mtk removed some functions that have been documented. wprintf.2 martin (joey) schulze remove wscanf.3 from see also list, since that page does not exist. utmp.5 joey hess removed outdated note on xdm. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=418009 martin (joey) schulze removed outdated note about debian and libc5. bootparam.7 martin (joey) schulze fix order of commands listed under 'init='. hier.7 joey hess add /media, remove /dos. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=418234 inotify.7 mtk added text describing what happens when the buffer given to read(2) is too small to return information about the next event, and noting the behavior change in 2.6.21. man-pages.7 mtk added text to note that errors list should be in alphabetical order. mdoc.7 mdoc.samples.7 mtk added see also reference to groff_mdoc(7). unix.7 mtk added example section with pointer to bind.2 example. ld.so.8 mtk simplify text describing --inhibit-rpath. mtk, after a note by john reiser describe use of $origin in rpath. ==================== changes in man-pages-2.56 ==================== released: 2007-06-11 global changes -------------- many pages mtk removed version numbers in .th lines. reason: these were only arbitrarily updated, and so impart no useful information. version information goes into a versions section nowadays, and the date in the .th line should be updated to reflect the date of the last (significant) change to the page. typographical or grammatical errors have been corrected in several places. ==================== changes in man-pages-2.57 ==================== released: 2007-06-17 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: samuel thibault apologies if i missed anyone! global changes -------------- many pages mtk fix section numbers in page cross references. changes to individual pages --------------------------- access.2 mtk minor wording fixes. small clarification of description of 'mode'. bind.2 mtk small reworking of example program. exit_group.2 mtk minor wording fixes. exit.3 mtk added more detail on exit handlers. minor wording fixes. ioctl.2 mtk remove see also reference to nonexistent mt.4. modify_ldt.2 samuel thibault / mtk in linux 2.6, the 'modify_ldt_ldt_s' structure was renamed 'user_desc'. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=378668 mtk include definition of 'user_desc' structure. minor rewordings. mprotect.2 mtk small reworking of example program. sigaction.2 mtk removed reference to nonexistent sigsend(2). a64l.3 mtk remove see also reference to nonexistent itoa.3. dysize.3 mtk removed see also reference to nonexistent time.3. encrypt.3 mtk removed see also reference to nonexistent fcrypt.3. fmemopen.3 mtk small reworking of example program. fpurge.3 mtk remove see also reference to nonexistent fclean.3. getutent.3 mtk s/ttyname(0)/ttyname(stdin_fileno)/ in program example. vcs.4 mtk s/exit(1)/exit(exit_failure)/ environ.7 mtk correct some section numbers in page cross references. man-pages.7 mtk modify requirements for example programs a little. uri.7 mtk wrapped long source lines. ==================== changes in man-pages-2.58 ==================== released: 2007-06-24 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: marc boyer mike frysinger apologies if i missed anyone! global changes -------------- various pages, as detailed below mtk added or updated versions sections. killpg.2 setuid.2 faccessat.2 fork.2 setfsuid.2 kill.2 getsid.2 wait.2 execve.2 getpid.2 setgid.2 seteuid.2 setresuid.2 setfsgid.2 access.2 initgroups.3 euidaccess.3 tcgetpgrp.3 path_resolution.7 capabilities.7 unix.7 mtk add see also link to new credentials.7. new pages --------- credentials.7 mtk an overview of linux process identifiers (pids, ppids, pgids, sids, uids, gids). changes to individual pages --------------------------- bind.2 mtk added some comments to example program. getxattr.2 mtk versions: in kernel since 2.4; glibc support since 2.3. listen.2 mtk updated discussion of somaxconn limit. listxattr.2 mtk versions: in kernel since 2.4; glibc support since 2.3. posix_fadvise.2 mtk versions: glibc support has been provided since version 2.2. readahead.2 mtk added versions section. remap_file_pages.2 mtk updated versions section with text on glibc support. removexattr.2 mtk versions: in kernel since 2.4; glibc support since 2.3. semop.2 mtk added versions section with info on semtimedop(). setxattr.2 mtk versions: in kernel since 2.4; glibc support since 2.3. dl_iterate_phdr.3 mtk versions: supported since glibc 2.2.4. getloadavg.3 mtk added versions section. posix_openpt.3 mtk versions: supported since glibc 2.2.1. printf.3 mtk after a suggestion by mike frysinger add text to the introductory part of description, about the 'size' argument of snprintf() and vsnprintf(). shm_open.3 mtk added versions section; rewrote info about linking with -lrt. strcat.3 marc boyer improve the discussion of strncat(). strcpy.3 marc boyer improve the discussion of strncpy(). proc.5 mtk added discussion of /proc/sys/net/core/somaxconn. ==================== changes in man-pages-2.59 ==================== released: 2007-06-25 global changes -------------- manual pages are now standardized on american spelling. see http://en.wikipedia.org/wiki/american_and_british_english_spelling_differences for more information on the differences. formerly, different pages (and sometimes even a single page!) employed american and british spelling conventions; best to standardize on one spelling, and american english is the standard in computer science. changes to individual pages --------------------------- man-pages.7 mtk note that man-pages has now standardized on american spelling conventions. execve.2 getxattr.2 listxattr.2 removexattr.2 setxattr.2 signal.2 syscall.2 aio_cancel.3 bindresvport.3 stdarg.3 charmap.5 bootparam.7 ipv6.7 man.7 path_resolution.7 uri.7 nscd.8 mtk corrected minor spelling/wording mistakes (i.e., changes independent of fixes for american spelling). ==================== changes in man-pages-2.60 ==================== released: 2007-06-25 global changes -------------- various pages mtk wrapped lines in some files. various pages mtk change "e.g. " to "e.g., ", or in some cases, "for example, ". various pages mtk change "i.e. " to i.e., ", or in some cases, "that is, ". various pages mtk removed authors section. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- vfork.2 mtk s/w.r.t/with respect to/ man-pages.7 mtk strengthened warning against use of authors section. ==================== changes in man-pages-2.61 ==================== released: 2007-07-01 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal benno schulenberg florian ernst ivana varekova jeff schroeder joey (martin) schulze justin pryzby loïc minier michael gehring serge van den boom stefan puiu stepan kasal apologies if i missed anyone! global changes -------------- various pages mtk substitute `\\0' by '\\0'. various pages mtk s/`/'/ when the thing being quoted is a character. accept.2 bind.2 connect.2 getsockopt.2 listen.2 socket.2 socketpair.2 mtk after a note by martin (joey) schulze add notes paragraph noting that isn't required by posix.1-2001 or linux, but was required on some implementations. accept.2 getsockname.2 recv.2 vm86.2 send.2 getgrouplist.3 memmem.3 nsswitch.conf.5 putenv.3 wprintf.3 mtk replace form `...' with \fi...\fp where the enclosed string is a pathname, type name, or argument name. a few files mtk s/process' /process's/ gets.3 qsort.3 getaddrinfo.3 rpc.3 ungetwc.3 wcsnrtombs.3 capabilities.7 mtk add section number to page cross references. time.1 bind.2 pivot_root.2 sysctl.2 mtk reordered .sh sections. full.4 mouse.4 random.4 sd.4 mtk made config/configuring heading ==> configuration time.1 console_codes.4 random.4 sk98lin.4 charmap.5 ftpusers.5 bootparam.7 charsets.7 glob.7 mq_overview.7 unicode.7 uri.7 utf-8.7 mtk reformatted headings new pages --------- backtrace.3 mtk, with input from justin pryzby and stefan puiu documents backtrace(), backtrace_symbols(), and backtrace_symbols_fd(). new links --------- backtrace_symbols.3 backtrace_symbols_fd.3 mtk links to backtrace.3. __clone.2 stepan kasal link to clone.2. changes to individual pages --------------------------- makefile serge van den boom fix setting of 'prefix' macro. eval.1p benno schulenberg fix bad text (concatenated line). chdir.2 mtk fixed description of eacces error. added sentence defining "current working directory". other minor wording changes. cfree.3 mtk added see also section. clone.2 mtk s/clone2/__clone2/. fdatasync.2 mtk minor wording changes. fork.2 alain portal fix small wording error. gethostid.2 stefan puiu / mtk add notes on what happens if gethostid() can't open /etc/hostid. idle.2 mtk made notes text into a versions section, since that's what it really describes. ioperm.2 mtk minor wording changes. intro.2 mtk rewrite to reflect the fact that the _syscalln macros are no longer available. io_cancel.2 mtk add "link with -laio" to synopsis. io_destroy.2 mtk add "link with -laio" to synopsis. io_getevents.2 mtk add "link with -laio" to synopsis. io_setup.2 mtk add "link with -laio" to synopsis. io_submit.2 ivana varekova fix include in synopsis. mtk add "link with -laio" to synopsis. ipc.2 mtk add semtimedop() to see also. note that some architectures don't have ipc(2); instead real system calls are provided for shmctl(), semctl(), etc. killpg.2 mtk minor wording changes. listen.2 mtk added to synopsis. sched_setscheduler.2 mtk add notes para about permissions required to call sched_setscheduler() on other systems. select.2 mtk noted that 'timeout' can also be changed if select() is interrupted by a signal. setup.2 mtk remove reference to _syscall0() macro. shmop.2 mtk changed text for einval error. socketcall.2 mtk add recvmsg() and sendmsg() to see also. note that some architectures don't have socketcall(2); instead real system calls are provided for socket(), bind(), etc. swapon.2 ivana varekova / mtk update text for eperm error describing the maximum number of swap files. (from downstream fedora patch.) write.2 mtk added details about seekable files and file offset. noted that write() may write less than 'count' bytes, and gave some examples of why this might occur. noted what happens if write() is interrupted by a signal. minor wording changes. __setfpucw.3 mtk added a conforming to section; other minor edits. confstr.3 mtk minor rewrites in code example. ctime.3 justin pryzby make see also refer to timegm.3 daemon.3 mtk small wording change. dl_iterate_phdr.3 michael gehring comment was missing closing "*/". dlopen.3 mtk formatting changes, and minor rewordings. mtk, after a note by serge van den boom add a comment explaining the need for the rather strange cast of the return value of dlsym(). fpclassify.3 mtk add "isinf" to name section. getgrouplist.3 mtk minor rewording. getline.3 mtk minor rewording, and note that '*n* is ignored if '*lineptr' is null. malloc.3 ivana varekova / mtk update description of malloc_check_ to include description for value 3. (from downstream fedora patch.) netlink.3 mtk added a conforming to section; other minor edits. openpty.3 mtk minor changes to synopsis. program_invocation_name.3 mtk shortened page title to invocation_name. rtnetlink.3 mtk added a conforming to section; other minor edits. scanf.3 florian ernst fix duplicated word "the". (really fix http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=412467 !) select_tut.3 mtk small wording change. setnetgrent.3 mtk added a conforming to section. sigpause.3 mtk added a conforming to section. strftime.3 just pryzby small wording fix. mtk note use of "gcc -wno-format-y2k" to avoid the "`%c' yields only last 2 digits of year in some locales" warning. strstr.3 mtk add "strcasestr" to name section. syslog.3 mtk small wording change. termios.3 mtk reformat synopsis. added a conforming to section. timegm.3 mtk small wording changes. ulimit.3 mtk remove erroneous text saying that glibc does not provide ; it does. initrd.4 mtk various reformattings. core.5 mtk added a sentence noting why core dumps named "core.pid" were useful with linuxthreads. bootparam.7 mtk fix capitalization in .ss headings. epoll.7 mtk language clean ups. feature_test_macros.7 mtk added see also section. mq_overview.7 mtk reformatted headings; minor rewrites. sem_overview.7 mtk reformatted headings; minor rewrites. socket.7 loïc minier document argument type for so_reuseaddr. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=255881 uri.7 mtk wrap long line in synopsis. ldconfig.8 mtk added see also section. ==================== changes in man-pages-2.62 ==================== released: 2007-07-09 this release consists solely of formatting fixes. there are no changes to content. contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: stepan kasal apologies if i missed anyone! global changes -------------- many many pages mtk many many formatting fixes. man[013]p/* stepan kasal add section number to .th line for posix pages in man[013]p. ==================== changes in man-pages-2.63 ==================== released: 2007-07-16 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: arnd bergmann eduardo m. fleury ivana varekova justin pryzby marc boyer martin (joey) schulze martin röhricht patrick mansfield pierre habouzit stepan kasal apologies if i missed anyone! global changes -------------- gettimeofday.2 madvise.2 msgctl.2 select.2 semctl.2 shmctl.2 syslog.2 stat.2 a64l.3 printf.3 termios.3 xdr.3 sd.4 mtk minor wording changes. obsolete.2 syscall.2 unimplemented.2 mtk added see also reference to syscalls.2. new pages --------- sgetmask.2 mtk a real man page for sgetmask(2) and ssetmask(2). (this page replaces a previous link of the same name, which linked to signal.2.) spu_create.2 arnd bergmann with additional work by eduardo m. fleury and mtk document the powerpc spu spu_create() system call. (originally taken from the kernel source file documentation/filesystems/spufs.txt.) spu_run.2 arnd bergmann with additional work by eduardo m. fleury and mtk document the powerpc spu spu_run() system call. (originally taken from the kernel source file documentation/filesystems/spufs.txt.) spufs.7 arnd bergmann with additional work by eduardo m. fleury and mtk document the powerpc spu file system. (originally taken from the kernel source file documentation/filesystems/spufs.txt.) removed pages ------------- __clone.2 mtk this file was created by accident in 2.61, as a copy of clone.2. (it should have been a link to clone.2.) obsolete.2 mtk details on this page are covered in syscalls.2 and in respective syscall man pages (stat.2, uname.2). undocumented.2 mtk this page is very out of date, and in any case difficult to maintain. information about undocumented system calls is maintained in the howtohelp file, and probably in other places soon. killpg.3 mtk this rather incomplete page seems unnecessary since there is a killpg.2. new links --------- chown32.2 fchown32.2 getegid32.2 geteuid32.2 getgid32.2 getgroups32.2 getresgid32.2 getresuid32.2 getuid32.2 lchown32.2 setfsgid32.2 setfsuid32.2 setgid32.2 setgroups32.2 setregid32.2 setresgid32.2 setresuid32.2 setreuid32.2 setuid32.2 mtk added as link to corresponding page without "32". fcntl64.2 fstat64.2 fstatat64.2 fstatfs64.2 ftruncate64.2 getdents64.2 lstat64.2 pread64.2 pwrite64.2 sendfile64.2 stat64.2 statfs64.2 truncate64.2 mtk added as link to corresponding page without "64". __clone2.2 clone2.2 mtk links to clone.2. ugetrlimit.2 mtk link to getrlimit.2. mq_notify.2 mq_open.2 mq_timedreceive.2 mq_timedsend.2 mq_unlink.2 mtk added as links to corresponding section 3 pages. fadvise64.2 fadvise64_64.2 mtk links to posix_fadvise.2. rt_sigaction.2 rt_sigpending.2 rt_sigprocmask.2 rt_sigtimedwait.2 mtk added as link to corresponding page without "rt_" prefix. rt_sigqueueinfo.2 mtk link to sigqueue.2. madvise1.2 tuxcall.2 vserver.2 mtk / ivana varekova link to unimplemented.2. changes to individual pages --------------------------- access.2 mtk fairly substantial rewrites of various parts, and a few additions. chmod.2 mtk update synopsis to reflect the fact that fchmod(2) needs either "#define _xopen_source 500" or "#define _bsd_source". chown.2 mtk update synopsis to reflect the fact that fchmod(2) and lchown(2) need either "#define _xopen_source 500" or "#define _bsd_source". added an example program. killpg.2 mtk note that killpg() is actually a library function on linux. mmap.2 mtk added note that glibc mmap() wrapper nowadays invokes mmap2(). mmap2.2 ivana varekova / mtk on most platforms the unit for 'offset' is 4096 bytes, not the system page size. mtk rewrote notes to note that glibc mmap() wrapper nowadays invokes this system call. mtk added an example program. oldfstat.2 oldlstat.2 oldstat.2 mtk changed link to point to stat.2 (instead of obsolete.2). olduname.2 oldolduname.2 mtk changed link to point to uname.2 (instead of obsolete.2). sched_setaffinity.2 martin röhricht added _gnu_source to synopsis. semctl.2 mtk remove reference discussion of ipc(2), since none of the other system v ipc pages mention ipc(2). semop.2 mtk add an example code segment. shmctl.2 mtk add svipc(7) to see also list. sigaction.2 mtk reformatted tables as lists; other minor reformattings and wording changes. sigqueue.2 mtk added info on rt_sigqueueinfo(2). sigwaitinfo.2 mtk noted that sigwaitinfo() is a library function implemented on top of sigtimedwait(). ssetmask.2 mtk make this link point to new sgetmask.2 instead of signal.2. stat.2 mtk add notes on the different system call interfaces that have appeared over time. syscalls.2 mtk a fairly substantial rewrite of this page, bringing it up to date with the current kernel version, and listing all system calls in tabular form. uname.2 mtk add notes on the different system call interfaces that have appeared over time. unimplemented.2 mtk add vserver, madvise1 to name line. removed see also reference to obsolete.2. ivana varekova add tuxcall to name line. mktemp.3 patrick mansfield fix description of return value. strcat.3 marc boyer minor fix to example program. undocumented.3 mtk add section numbers to function names; remove some functions since they are documented. proc.5 mtk update/correct text on /proc/malloc. mtk, after a note by pierre habouzit, and a few comments by justin pryzby update description of /proc/pid/stat to match 2.6.21. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=417933 inotify.7 mtk in_dont_follow and in_onlydir are only available from 2.6.15. signal.7 stepan kasal / mtk note sigrtmin value depends on glibc. mtk various rewrites and additions to the text in real-time signals. add see also reference to sgetmask.2. svipc.7 mtk add ipc(2) to see also. ==================== changes in man-pages-2.64 ==================== released: 2007-07-27 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: aleksandr koltsoff andries brouwer justin pryzby apologies if i missed anyone! global changes -------------- infinity.3 _exit.2 a64l.3 abs.3 acct.2 acosh.3 addseverity.3 adjtime.3 asinh.3 atanh.3 atoi.3 brk.2 cbrt.3 cfree.3 chdir.2 chmod.2 chown.2 clearenv.3 clock_getres.3 clone.2 confstr.3 copysign.3 ctermid.3 ctime.3 daemon.3 dirfd.3 div.3 drand48.3 drand48_r.3 dysize.3 ecvt.3 ecvt_r.3 erf.3 euidaccess.3 exp2.3 expm1.3 fdatasync.2 ferror.3 fexecve.3 fgetgrent.3 fgetpwent.3 finite.3 flockfile.3 fopen.3 fpclassify.3 fsync.2 futimes.3 fwide.3 gamma.3 gcvt.3 getcwd.3 getdate.3 getdirentries.3 getdomainname.2 getdtablesize.2 getgrent.3 getgrent_r.3 getgrouplist.3 getgroups.2 gethostbyname.3 gethostid.2 gethostname.2 getlogin.3 getmntent.3 getpagesize.2 getpw.3 getpwent.3 getpwent_r.3 getpwnam.3 getsid.2 getspnam.3 gettimeofday.2 getumask.3 getusershell.3 gsignal.3 hypot.3 inet.3 initgroups.3 insque.3 isalpha.3 iswblank.3 j0.3 kill.2 killpg.2 lgamma.3 lockf.3 log1p.3 log2.3 logb.3 longjmp.3 lrint.3 lround.3 madvise.2 mbsnrtowcs.3 memfrob.3 mincore.2 mkdtemp.3 mknod.2 mkstemp.3 mktemp.3 nan.3 nanosleep.2 nextafter.3 nice.2 on_exit.3 perror.3 posix_memalign.3 posix_openpt.3 printf.3 profil.3 psignal.3 putenv.3 putpwent.3 qecvt.3 rand.3 random.3 rcmd.3 readahead.2 readlink.2 realpath.3 remainder.3 remquo.3 rexec.3 rint.3 round.3 rpmatch.3 scalb.3 scandir.3 scanf.3 seekdir.3 select.2 sem_wait.3 semop.2 setbuf.3 setenv.3 seteuid.2 setjmp.3 setnetgrent.3 setpgid.2 setresuid.2 setreuid.2 sigaltstack.2 siginterrupt.3 significand.3 sigqueue.2 sigvec.3 sigwaitinfo.2 sockatmark.3 stat.2 stime.2 strdup.3 strerror.3 strsep.3 strtod.3 strtok.3 strtol.3 strtoul.3 symlink.2 sync.2 syscall.2 syslog.3 tcgetsid.3 telldir.3 tempnam.3 termios.3 tgamma.3 timegm.3 toascii.3 trunc.3 truncate.2 ttyslot.3 tzset.3 ualarm.3 unlocked_stdio.3 unshare.2 usleep.3 vfork.2 vhangup.2 wait.2 wait4.2 wcscasecmp.3 wcsncasecmp.3 wcsnlen.3 wcsnrtombs.3 wcswidth.3 wordexp.3 wprintf.3 mtk added/updated feature test macro requirements for glibc; see feature_test_macros.7 for details. changes to individual pages --------------------------- mq_notify.2 mq_open.2 mq_timedreceive.2 mq_timedsend.2 mq_unlink.2 mtk fix broken link setpgid.2 mtk fairly substantial changes and corrections, including adding coverage of all of the interfaces that get/set pgids. syscalls.2 mtk / aeb various rewordings; clear up some imprecisions. lgamma.3 mtk added 'signgam' to synopsis and name line. strerror.3 mtk note that the xpg version is provided since glibc 2.3.4. the page formerly said that the gnu-specific version is provided by default. that certainly isn't true nowadays, since _posix_c_source is set to 200112l by default, so that the xsi-compliant version is supplied by default. man-pages.7 mtk added note pointing to feature_test_macros.7 for a description of how feature test macro requirements should be specified in manual pages. various other minor fixes and changes. feature_test_macros.7 mtk added note about how feature test macros are specified in manual pages. many other corrections, improvements, additions, and details about differences across glibc versions. ==================== changes in man-pages-2.65 ==================== released: 2007-09-17 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: aleksandr koltsoff andi kleen anton blanchard ari entlich carsten emde françois diakhate geoff clare jon burgess julien cristau lee schermerhorn mats wichmann maxime bizon maxime vaudequin michael prokop mike frysinger nicolas françois nicolas george paul brook reuben thomas sam varshavchik samuel thibault thomas huriaux tolga dalman ulrich drepper vincent lefevre apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. various pages mtk use 'glibc' consistently to refer to gnu c library. various pages mtk order errors under errors alphabetically. various pages nicolas françois spelling and formatting fixes, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=439560 intro.2 select.2 fmtmsg.3 getgrent_r.3 envz_add.3 rtime.3 strptime.3 wordexp.3 maxime vaudequin add "#include " (to declare exit(3)) to example program. new pages --------- timeradd.3 mtk description of timeradd(), timersub(), timerclear(), timerisset(), timercmp() macros for operating on struct timeval. removed pages ------------- fdatasync.2 mtk somehow, over time, material on fdatasync(2) crept into fsync.2, and fdatasync also got added to the name section of fsync.2. all of the material in fdatasync.2 that was not already in fsync.2 has now been moved there, and the former page has been removed. in place of the content there, is now a link to fsync.2. new links --------- clock_getres.2 clock_gettime.2 clock_settime.2 mtk link to man3/clock_getres.3. fdatasync.2 mtk link to fsync.2. fdopendir.3 mtk link to opendir.3. gethostbyaddr_r.3 mats wichmann link to gethostbyaddr.3. timerclear.3 timercmp.3 timerisset.3 timersub.3 mtk links to new timeradd.3. changes to individual pages --------------------------- makefile mike frysinger make the install target of man-pages respect the standard "destdir" variable as well as check the exit status of the install command so errors aren't ignored. get_mempolicy.2 lee schermerhorn changed the "policy" parameter to "mode" through out the descriptions in an attempt to promote the concept that the memory policy is a tuple consisting of a mode and optional set of nodes. added requirement to link '-lnuma' to synopsis rewrite portions of description for clarification. added all errors currently returned by sys call. removed cautionary note that use of mpol_f_node|mpol_f_addr is not supported. this is no longer true. added mmap(2) to see also list. getitimer.2 mtk since kernel 2.6.22, linux setitimer() now conforms to posix.1, giving an einval error for a non-canonical tv_usec value. gettimeofday.2 mtk replace discussion of timer* macros with a pointer to new page timeradd.3. ioctl_list.2 nicolas george fixed argument type for blkgetsize. mbind.2 lee schermerhorn changed the "policy" parameter to "mode" throughout the descriptions in an attempt to promote the concept that the memory policy is a tuple consisting of a mode and optional set of nodes. rewrite portions of description for clarification. clarify interaction of policy with mmap()'d files and shared memory regions, including shm_huge regions. defined how "empty set of nodes" specified and what this means for mpol_preferred. mention what happens if local/target node contains no free memory. clarify semantics of multiple nodes to bind policy. note: subject to change. we'll fix the man pages when/if this happens. added all errors currently returned by sys call. added mmap(2), shmget(2), shmat(2) to see also list. mmap.2 mprotect.2 françois diakhate add text noting that prot_write may (and on x86 does) imply prot_read. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=441387 nfsservctl.2 aleksandr koltsoff fix prototype. oldfstat.2 oldlstat.2 oldstat.2 mtk fix broken link prctl.2 mtk update arches/kernel versions for pr_set_unalaign / pr_get_unalign. readahead.2 mtk removed see also reference to nonexistent fadvise.2. reboot.2 mtk place synopsis comments inside c comments (/* ... */). sched_setaffinity.2 samuel thibault note what thread is affected if 'pid' is specified as 0, or as the value returned by getpid(). sched_setscheduler.2 carsten emde add text on real-time features of mainline linux kernel. select_tut.2 mtk sync synopsis with select.2 set_mempolicy.2 lee schermerhorn changed the "policy" parameter to "mode" throughout the descriptions in an attempt to promote the concept that the memory policy is a tuple consisting of a mode and optional set of nodes. added requirement to link '-lnuma' to synopsis rewrite portions of description for clarification. clarify interaction of policy with mmap()'d files. defined how "empty set of nodes" specified and what this means for mpol_preferred. mention what happens if local/target node contains no free memory. clarify semantics of multiple nodes to bind policy. note: subject to change. we'll fix the man pages when/if this happens. added all errors currently returned by sys call. added mmap(2) to see also list. sigaction.2 mtk s/si_sign/si_errno/ in statement about which field is unused. ari entlich s/sigill/sigchld/ for paragraph describing sigchld. stat.2 mtk improve text describing underlying system calls. swapon.2 michael prokop einval also occurs if target path is on tmpfs or similar. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=435885 sync.2 mtk incorporated material from now deleted fdatasync.2. syscall.2 mtk small fix in example program. uname.2 mtk improve text describing underlying system calls. utime.2 vincent lefevre / mtk clarify utimes() behaviour when 'times' is null. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=431480 mtk other minor clarifications of description of utimes(). copysign.3 vincent lefevre s/sign/sign bit/ to remove ambiguity in description. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=435415 euidaccess.3 mtk changed notes to versions. ffsl.3 mtk add ffsl and ffsll to name line. fts.3 mtk removed statement that fts functions are expected to appear soon in posix; it's years old and has not yet come to pass. ftw.3 mtk / geoff clare fixes/improvements for example program. getdate.3 mtk add getdate_r to name section. getaddrinfo.3 mtk / geoff clare fixes/improvements for example program. gethostbyaddr.3 mats wichmann add documentation for gethostbyaddr_r(). plus a few other small fixes. gethostbyname.3 mtk add gethostbyname2, gethostbyname2_r, gethostbyname_r, gethostent_r to name line. getmntent.3 mtk fix misnamed function references. getopt.3 jon burgess fix small error in example program. getrpcent.3 mtk add setrpcent and endrpcent to name line. gsignal.3 aleksandr koltsoff fix gsignal() prototype. hsearch.3 mtk add hcreate_r, hdestroy_r, hsearch_r to name line. inet.3 maxime bizon correct definition of "struct in_addr". isatty.3 mtk minor wording fix. isgreater.3 mtk add islessequal to name line. lgamma.3 vincent lefevre fix conforming to section. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=417592 log1p.3 mtk add log1pf and log1pl to name line. longjmp.3 paul brook / mtk after a call to longjmp(), the values of modified, non-volatile variables in the function that called setjmp() are unspecified. makecontext.3 aleksandr koltsoff fix makecontext() prototype. malloc.3 mtk / tolga dalman explain what happens for malloc(0), or calloc() where one of the arguments is 0. mtk added notes on malloc()'s use of sbrk() and mmap(). mtk add mmap(2), alloca(3) to see also. mq_close.3 mq_getattr.3 mq_notify.3 mq_open.3 mq_receive.3 mq_send.3 mq_unlink.3 mtk add "link with -lrt." to synopsis. opendir.3 ulrich drepper; some edits and additional text by mtk document fdopendir(). readdir.3 mtk, after a note by andi kleen document dt_* constants for d_type. ulrich drepper / mtk rework discussion of non-standard structure fields. sem_wait.3 mtk minor improvements to example program. syslog.3 mtk add vsyslog to name section. termios.3 nicolas françois fix xcase feature test macro description. wcsspn.3 aleksandr koltsoff add return type to prototype. proc.5 mtk improve description of num_threads field under /proc/pid/stat. maxime vaudequin fix path error (s%proc/sys%proc/sys/kernel%) in mentions of /proc/sys/ostype, /proc/sys/osrelease and proc/sys/version. maxime vaudequin i noticed things to correct and to clarify in subsection "/proc/filesystems" of proc.5: - clarify filesystems listing: not only fs compiled into the kernel, also fs kernel modules currently loaded - add a reference to fs(5) - add an explanation for fs marked with "nodev" - s/mount(1)/mount(8)/, also corrected in section "see also" - clarify usage by mount: the current wording may lead to think /proc/filesystems is always used by mount when no fs is specified. so, usage of "may" which imho is more appropriate + additional explanations in mount(8) we can see: if no -t option is given, or if the auto type is specified, mount will try to guess the desired type. if mount was compiled with the blkid library, the guessing is done by this library. otherwise, mount guesses itself by probing the superblock; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. all of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g., devpts, proc and nfs). if /etc/filesystems ends in a line with a single * only, mount will read /proc/filesystems afterwards. samuel thibault since linux 2.6.11, /proc/stat has an eighth value for cpu lines: stolen time, which is the time spent in other operating systems when running in a virtualized environment. arp.7 updated bugs text referring to jiffies; refer to time.7 instead. credentials.7 mtk add words to note that file system id is linux specific. hier.7 maxime vaudequin this is some corrections for hier.7: - missing period for /media and /mnt - /mnt description is not totally correct, it is true for some distributions but in others /mnt is used as a temporary fs mount point, as it is specified by fhs: http://www.pathname.com/fhs/pub/fhs-2.3.html#mntmountpointforatemporarilymount - s/x-windows/x-window/ (3 occurrences) - section "see also": s/mount(1)/mount(8)/ man-pages.7 man.7 mdoc.7 mdoc.samples.7 mtk / nicolas françois nowadays tmac.xxx are called xxx.tmac. pthreads.7 mtk update text about modern threading implementations (nptl vs linuxthreads). socket.7 mtk, after a note by andi kleen clarify that so_sndtimeo and so_rcvtimeo only have effect for socket i/o calls; not for multiplexing system calls like select() and poll(). time.7 mtk add see also reference to new timeradd.3. ==================== changes in man-pages-2.66 ==================== released: 2007-10-01 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: amit k. arora david chinner fredrik noring mats wichmann maxime vaudequin ollie wild ulrich drepper apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- fallocate.2 david chinner, with some input from amit amora and mtk describes the fallocate() system call, new in 2.6.23. changes to individual pages --------------------------- close.2 fredrik noring add text cautioning about use of close() in multithreaded programs. execve.2 ollie wild / mtk add text describing limit on total size of argv + envp, and changes that occurred with 2.6.23. mtk add getopt(3) to see also list. open.2 mtk, acked by ulrich drepper added description of o_cloexec (new in 2.6.23) + other minor fixes for o_direct. recv.2 mtk added description of msg_cmsg_cloexec (new in 2.6.23). sysctl.2 mtk strengthened the warning against using this system call and note that it may disappear in a future kernel version. rpc.3 mats wichmann fix type definition for 'protocol' in prototypes of pmap_set() and pmap_getport(). ==================== changes in man-pages-2.67 ==================== released: 2007-10-08 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen andrew josey maxime vaudequin apologies if i missed anyone! global changes -------------- *.1p *.3p mtk, after a note by andi kleen and consultation with andrew josey. add a prolog section: this manual page is part of the posix programmer's manual. the linux implementation of this interface may differ (consult the corresponding linux manual page for details of linux behavior), or the interface may not be implemented on linux. *.0p *.1p *.3p mtk some formatting fixes, mostly to get rid of unwanted spaces before "," in formatted output. * */* mtk change all occurrences of my email address in man-pages source to my new gmail address. many many pages maxime vaudequin i noticed useless use of macros with alternating formatting (".ir" instead ".i" which suffices, ".br" instead ".b", etc.) because there is only one element. for example in ldconfig.8: -.br /sbin/ldconfig +.b /sbin/ldconfig this is not very important, it only makes the sources more tidy. to find these i used: egrep '^\.(b[ri]|r[ib]|i[rb]) ([^ ]+|\"[^\"]\+\")$' and if you want to make these changes, you can use: sed 's/^\(\.[bri]\)[bri]\( \([^ ]\+\|\"[^\"]\+\"\)\)$/\1\2/g' ==================== changes in man-pages-2.68 ==================== released: 2007-11-19 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: a. costa andrew mcdonald geoff clare heikki orsila hyokyong kim ivana varekova justin pryzby maxime vaudequin mike frysinger nicolas françois pádraig brady sam varshavchik timo juhani lindfors ulrich drepper apologies if i missed anyone! global changes -------------- faccessat.2 fchmodat.2 fchownat.2 fstatat.2 futimesat.2 linkat.2 mkdirat.2 mknodat.2 readlinkat.2 renameat.2 symlinkat.2 mkfifoat.3 mtk, after http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=445436 by timo juhani lindfors added to synopsis. typographical or grammatical errors have been corrected in several places. new pages --------- _syscall.2 mtk created as a new page, by taking the content specific to the _syscall() macros from intro(2). changes to individual pages --------------------------- readme mtk brought up to date. man-pages-*-announce mtk brought the info in here up to date. intro.1 mtk added intro paragraph about section, plus a paragraph about exit status values. move "user intro" text to notes. get_mempolicy.2 mtk reorder errors sections alphabetically intro.2 mtk pretty much a complete rewrite, covering some additional topics. moved _syscalln() material to new _syscall(2) page. mbind.2 mtk reorder errors sections alphabetically mmap.2 maxime vaudequin fix syntax error in example program. prctl.2 mtk linux 2.6.22 added support on alpha for pr_set_unalign. ptrace.2 nicolas françois / mtk s/ptrace_pokeusr/ptrace_pokeuser/ s/ptrace_peekusr/ptrace_peekuser/ read.2 mtk / geoff clare add text describing timerfd einval error for read(2). set_mempolicy.2 mtk reorder errors sections alphabetically syscall.2 mtk added _syscall(2) and intro(2) to see also section. syscalls.2 mtk added fallocate(2); removed timerfd(2). sysinfo.2 mtk removed reference to example in intro(2). dlopen.3 mtk added "link with -ldl." to synopsis. getaddrinfo.3 ulrich drepper / mtk remove references to getipnodebyname.3 and getipnodebyaddr.3. gethostbyname.3 mtk / ulrich drepper remove see also references to getipnodebyname.3 and getipnodebyaddr.3. pádraig brady / mtk / ulrich drepper point out that the functions described on this page are made obsolete by getaddrinfo(3) and getnameinfo(3). getipnodebyname.3 mtk clarify that glibc does not implement these functions. glob.3 ulrich drepper / mtk fix description of glob_onlydir. mtk added description of glob_tilde_nomatch. expanded the description of various flags. various wording fixes.. intro.3 mtk pretty much a complete rewrite, covering some additional topics. posix_fallocate.3 mtk add see also referring to fallocate.2. rpc.3 sam varshavchik add some arg declarations to prototypes; fix typos. setbuf.3 mike frysinger fix text in bugs section. sigset.3 mtk the sigset() bugs were fixed in glibc 2.5. see http://sourceware.org/bugzilla/show_bug.cgi?id=1951 intro.4 mtk minor rewrites. st.4 maxime vaudequin various small corrections, formattings and modifications. elf.5 mike frysinger document: - new p_flag: pt_gnu_stack - new sections: .gnu.version .gnu.version_d .gnu.version_r .note.gnu-stack - new structures: elfn_verdef elfn_verdaux elfn_verneed elfn_vernaux intro.5 mtk minor rewrites. proc.5 ivana varekova / mtk add text noting that since kernel 2.6.16, /proc/slabinfo is only available if config_slab is enabled. maxime vaudequin update description of /proc/pci. maxime vaudequin give italic formatting to file names in proc.5. mtk the display type of the /proc/pid/stat fields changed %lu to %u in linux 2.6.22: flags rt_priority policy slabinfo.5 ivana varekova / mtk add text noting that since kernel 2.6.16, /proc/slabinfo is only available if config_slab is enabled. intro.6 mtk minor rewrites. bootparam.7 maxime vaudequin update references to files in kernel "documentation" directory. intro.7 mtk minor rewrites. ipv6.7 andrew mcdonald fix description of ipv6_router_alert option. standards.7 mtk note online location of c99 standard. intro.8 mtk some rewrites, plus new paragraph on exit status values. ==================== changes in man-pages-2.69 ==================== released: 2007-12-03 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: adam borowski alain portal andries e. brouwer j. bruce fields david härdeman jeremy kerr luke browning mats wichmann maxime vaudequin mike frysinger reuben thomas sam varshavchik apologies if i missed anyone! global changes -------------- *.[013]p mtk many whitespace clean-ups in formatted output. mprotect.2 bind.2 mq_notify.3 makecontext.3 fmemopen.3 david härdeman / mtk rename error handling function in example program (s/die/handle_error/). typographical or grammatical errors have been corrected in several places. removed pages ------------- howtohelp maintaining mtk the content of these files is now available in html format. new links --------- cfsetspeed.3 mtk link to termios.3. changes to individual pages --------------------------- time.1 alain portal added "linux user's manual" to .th line. _syscall.2 aeb / mtk remove outdated text about pointer blocks for syscalls that have more than 5 arguments. fcntl.2 j. bruce fields add warning that mandatory locking is unreliable. j. bruce fields clarify details in description of file leases. j. bruce fields / mtk minor wording edits. j. bruce fields add f_getlease under return value. mmap.2 mtk handle errors using a custom handle_error() macro. sched_setscheduler.2 mats wichmann add bugs text noting that the return value from linux sched_setschuler() does not conform to posix. spu_create.2 jeremy kerr various updates and improvements. luke browning refinement of text describing a "gang". mtk minor edits. spu_run.2 jeremy kerr various updates and improvements. mtk minor edits. err.3 mtk remove history section. fopen.3 mike frysinger document 'e' (close-on-exec) option, new in glibc 2.7. getloadavg.3 alain portal / mtk remove history section. printf.3 andries e. brouwer / mtk fix the discussion of stdarg macros in the description of vprintf() description. sem_wait.3 mtk handle errors using a custom handle_error() macro. sigsetops.3 mats wichmann note that sigset_t objects must be initialized with sigemptyset() or sigfillset() before the other macros are employed. termios.3 mtk, after a note by alain portal added cfsetspeed() to synopsis. added text under conforming to noting that cfsetspeed() is bsd specific. ttyslot.3 alain portal various references to "getty" were changed to "mingetty", since that is the manual page more likely to be found on current systems. (completes changes that were made in man-pages-2.44.) initrd.4 mtk, after a note by alain portal move "configuration" section to top of page (like other section 4 pages) and make it a .sh section. full.4 mtk re-ordered configuration section to go before description. sk98lin.4 maxime vaudequin fix reference to kernel documentation file. elf.5 mtk renamed history section to notes, and removed bsd specific info. proc.5 maxime vaudequin mention grub(8) in same sentence as lilo(8). maxime vaudequin improve description of /proc/sys/abi and /proc/sys/kernel/modprobe. utmp.5 alain portal various references to "getty" were changed to "mingetty", since that is the manual page more likely to be found on current systems. (completes changes that were made in man-pages-2.44.) iso_8859-2.7 adam borowski reverse the 2.68 change applied by mtk in response to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=445085 that replaced "sorbian" with "serbian". (sorbian is a language of 50000 people in brandenburg.) man-pages.7 mtk added configuration to list of "standard" section names. spufs.7 jeremy kerr various updates and improvements. mtk minor edits. tcp.7 maxime vaudequin fix reference to kernel documentation file. ==================== changes in man-pages-2.70 ==================== released: 2007-12-06 global changes -------------- many pages mtk remove section numbers for page references where the reference refers to the page itself. (this stops man2html producing links from a page back to itself.) typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- get_mempolicy.2 mtk add conforming to section. io_getevents.2 mtk remove redundant see also entry. mbind.2 mtk add conforming to section. msgop.2 mtk remove redundant see also entries. sigprocmask.2 mtk remove redundant see also entry. splice.2 mtk remove redundant see also entry. add see also referring to vmsplice(2). csin.3 mtk remove redundant see also entry. add see also referring to ccos(3). gethostbyname.3 mtk add gethostbyaddr_r to name section. rint.3 mtk remove redundant see also entry. sigsetops.3 mtk minor rewording. epoll.7 mtk minor rewording. ==================== changes in man-pages-2.71 ==================== released: 2007-12-14 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal john sigler josh triplett mats wichmann pascal malaise sam varshavchik apologies if i missed anyone! global changes -------------- err.3 fts.3 getloadavg.3 queue.3 rcmd.3 rexec.3 stdin.3 elf.5 operator.7 mtk replaced the use of mdoc macros on these pages with man macros. the only pages in man-pages that still use mdoc macros are mdoc.7 and mdoc.samples.7. typographical or grammatical errors have been corrected in several places. deleted pages ------------- todo mtk this information is now on the website. changes to individual pages --------------------------- changes.old mtk reformat various change log entries to use a consistent format. expand debian bug report numbers to be urls. other minor tidy-ups. fcntl.2 mtk document the f_dupfd_cloexec operation, which is new in kernel 2.6.24. listen.2 josh triplett fix incorrect path for somaxconn. getpw.3 alain portal add enoent error to errors. sysconf.3 mats wichmann add documentation of _sc_nprocessors_conf and _sc_nprocessors_onln. tty.4 john sigler add tty_ioctl(4) to see also list. regex.7 pascal malaise separate text on back references from that describing basic regexps, as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=379829. mtk remove crufty text about word boundaries. ==================== changes in man-pages-2.72 ==================== released: 2007-12-14 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal alex tuninga bert wesarg maxime vaudequin rob weryk sam varshavchik apologies if i missed anyone! global changes -------------- various pages alain portal / mtk format include files consistently (".i <.*\.h>"). various pages alain portal / mtk format pathname in italics (.i). dbopen.3 mpool.3 recno.3 alain portal remove brackets ([]) around error names. console.4 tty.4 ttys.4 issue.5 ttytype.5 utmp.5 mtk / maxime vaudequin some systems have mingetty(8), others have agetty(8), so both should be mentioned when we are talking about getty-style programs. typographical or grammatical errors have been corrected in several places. renamed pages ------------- filesystems.5 mtk / alain portal was previously fs.5 new links --------- argz.3 bert wesarg / mtk link to argz_add.3. envz.3 bert wesarg / mtk link to envz_add.3. fs.5 mtk / alain portal link to filesystems.5. changes to individual pages --------------------------- readahead.2 rob weryk fix declaration of 'offset' in synopsis. seteuid.2 mtk s/setguid/seteuid/ in .th line. __setfpucw.3 mtk fixed include files references / formatting. abort.3 mtk, after a note by alex tuninga a fairly significant rewrite to clarify operation of abort(). argz_add.3 bert wesarg / mtk s/envz/envz_add/ in see also. basename.3 mtk s/dirname/basename/ in .th line, and swap function names in name section. envz_add.3 bert wesarg / mtk s/argz/argz_add/ in see also. flockfile.3 mtk s/lockfile/flockfile/ in .th line. getgrent_r.3 mtk s/getgrent/getgrent_r/ in .th line. stdio.3 sam varshavchik reformat function list at end of page as a proper table. ttyslot.3 maxime vaudequin revert earlier s/getty/mingetty/. this page talks about historical behavior, and that means "getty(8)". undocumented.3 mtk remove reference to "obstack stuff"; it's not clear what that is about. console_ioctl.4 mtk s/console_ioctls/console_ioctl/ in .th line. proc.5 mtk s/fs (5)/filesystems (5)/ man-pages.7 mtk / alain portal improve discussion of formatting of file names. ==================== changes in man-pages-2.73 ==================== released: 2007-12-14 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal pádraig brady reuben thomas apologies if i missed anyone! global changes -------------- various pages alain portal formatting fixes. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- mknod.2 mtk, after a report by reuben thomas clarify use of mkfifo() versus mknod(). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=455825 fgetgrent.3 mtk small rewording. fgetpwent.3 mtk small rewording. rcmd.3 mtk noted feature test macro requirements. bugs: noted that iruserok() is not declared in glibc headers. filesystems.5 mtk added reiserfs, xfs, jfs to list of file systems. ==================== changes in man-pages-2.74 ==================== released: 2007-12-20 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andrew morton david brown jeremy kerr mats wichmann sam morris sam varshavchik samuel thibault apologies if i missed anyone! global changes -------------- various pages alain portal formatting fixes. various pages mtk / alain portal s/``...''/"..."/ various pages mtk s/epoch/epoch/ various pages mtk make the standard indent for code samples, shell session logs, etc. to be ".in +4n". typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- _syscall.2 mtk nowadays there is _syscall6() also. chroot.2 mtk various minor formatting changes. epoll_wait.2 mtk fix types in structs. formatting fixes. mount.2 mtk, after a note by sam morris clarify that ms_nodiratime provides a subset of the functionality provided by ms_noatime. sched_setaffinity.2 mtk minor rearrangement of text. select_tut.2 mtk fix (my) typos in argument names. formatting fixes. spu_create.2 jeremy kerr we can use context fds for the dirfd argument to the *at() syscalls. times.2 mtk, after a note from david brown and andrew morton http://marc.info/?l=linux-kernel&m=119447727031225&w=2 rework the text describing the return value to be closer to the requirements of posix.1; move linux details to notes and add a warning not to rely on those details. add a warning about the -1 to -4095 bug which results in a 41 second window where the glibc wrapper will wrongly return -1 indicating an error. mtk remove cruft hz text. clarify text describing return value of clock(3). getw.3 mats wichmann conforming to: getw() and putw() were in susv2, but are not in posix.1-2001. hash.3 mtk / alain portal minor rewordings + formatting fixes. st.4 alain portal / mtk many formatting fixes. mtk place errors in alphabetical order. vcs.4 samuel thibault document vt_gethifontmask (new in 2.6.18) and add to example program; attribute/text characters are in the host byte order. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=456437 mtk minor edits. bootparam.7 alain portal formatting fixes. inotify.7 mtk minor heading changes and reformattings. man-pages.7 mtk note that code segments, structure definitions, shell session logs, should be indented by 4 spaces. spufs.7 jeremy kerr add a little information about the differences to mbox. ==================== changes in man-pages-2.75 ==================== released: 2008-01-08 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andi kleen andreas henriksson jeremy kerr justin pryzby phil endecott sam varshavchik thomas huriaux timo sirainen trond myklebust apologies if i missed anyone! global changes -------------- various pages mtk (grammatical) hyphenation was fixed in many places. epoll_wait.2 mbind.2 spu_run.2 ecvt.3 fmtmsg.3 getnameinfo.3 rtc.4 proc.5 charsets.7 ip.7 ipv6.7 raw.7 uri.7 justin pryzby / mtk fix incorrect usage of "a" and "an" before following vowel / consonant, by reviewing the output of the following scripts: for a in $(wc */*.? | awk '$1 > 10 {print $4}' | gv total); do echo $a manwidth=4000 man -l $a 2>/dev/null | egrep '(^| )an [^aeiou][a-z]' done | less for a in $(wc */*.? | awk '$1 > 10 {print $4}' | gv total); do echo $a manwidth=4000 man -l $a 2>/dev/null | egrep '(^| )a [aeiou][a-z]' done| less err.3 fts.3 queue.3 rcmd.3 rexec.3 stdin.3 elf.5 mtk, after a note by alain portal improve macros used in 2.71 to convert from "mdoc" to "man". _exit.2 chroot.2 getgid.2 getpid.2 getrusage.2 getsid.2 gettid.2 getuid.2 iopl.2 kill.2 personality.2 pivot_root.2 ptrace.2 sched_setparam.2 sched_setscheduler.2 sched_yield.2 seteuid.2 setgid.2 setpgid.2 setresuid.2 setreuid.2 setuid.2 unlink.2 wait.2 openpty.3 raise.3 setlogmask.3 sleep.3 ttyslot.3 ulimit.3 tty.4 tty_ioctl.4 path_resolution.7 mtk s/current process/calling process/ cacheflush.2 clone.2 fcntl.2 getitimer.2 getrlimit.2 mmap.2 mprotect.2 times.2 adjtime.3 byteorder.3 inet.3 offsetof.3 rtc.4 icmp.7 pipe.7 time.7 mtk s/x86/i386/ since that is the name used in 'arch' directories in the kernel source, and previously both i386 and x86 were both used in man pages; also nowadays 'x86' is somewhat ambiguous, since it is the name of the 'arch' directory for i386 and x86-64. conj.3 cacos.3 cacosh.3 cabs.3 carg.3 casin.3 casinh.3 catan.3 catanh.3 ccos.3 ccosh.3 cexp.3 cimag.3 clog.3 cosh.3 creal.3 csin.3 csinh.3 ctan.3 ctanh.3 sinh.3 tanh.3 mtk various reformattings. various pages alain portal formatting fixes. mlock.2 mprotect.2 mpool.3 offsetof.3 alain portal format synopsis in a manner consistent with other pages. various pages mtk / alain portal format casts so that there is a non-breaking space after the type, and remove unnecessary parentheses around the casted value. thus, for example, the following: .ir "(size_t) (\-1)" . becomes: .ir "(size_t)\ \-1" . various pages mtk / alain portal replace "-" by "\-" where a real dash is required. various pages mtk make the formatting of instances of '*varname' consistent, changing instances such as: .ri * varname to: .i *varname pciconfig_read.2 nfsservctl.2 bstring.3 cpow.3 getipnodebyname.3 getpwnam.3 getrpcent.3 lsearch.3 malloc_hook.3 mpool.3 stdin.3 strtol.3 strtoul.3 unlocked_stdio.3 regex.3 sd.4 resolv.conf.5 utmp.5 futex.7 mtk format synopsis consistently. drand48.3 drand48_r.3 flockfile.3 erf.3 sigvec.3 timeradd.3 wprintf.3 mtk, after a note by alain portal standardize sentence used under "feature test macro requirements" when referring to all functions shown in the synopsis. get_kernel_syms.2 getdents.2 getitimer.2 nanosleep.2 query_module.2 statvfs.2 clock_getres.3 getaddrinfo.3 getgrent.3 getipnodebyname.3 console_ioctl.4 tty_ioctl.4 rtnetlink.7 mtk indent structure definitions by +4n. recv.2 btree.3 dbopen.3 ether_aton.3 fts.3 hash.3 mpool.3 profil.3 rcmd.3 recno.3 rpc.3 xdr.3 console_ioctl.4 ddp.7 ip.7 ipv6.7 svipc.7 mtk use c99 standard types in declarations. s/u_long/unsigned long/ s/ulong/unsigned long/ s/u_char/unsigned char/ s/u_short/unsigned short/ s/ushort/unsigned short/ s/u_int8_t/uint8_t/ s/u_int16_t/uint16_t/ s/u_int32_t/uint32_t/ s/u_int/unsigned int/ exit_group.2 fallocate.2 getdents.2 ioctl_list.2 nfsservctl.2 sched_setaffinity.2 set_tid_address.2 ustat.2 argz_add.3 confstr.3 envz_add.3 getline.3 getpwnam.3 gets.3 getw.3 inet_ntop.3 inet_pton.3 offsetof.3 console_ioctl.4 termcap.5 ascii.7 feature_test_macros.7 netlink.7 operator.7 svipc.7 mtk fix unbalanced .nf/.fi pairs. chmod.2 getxattr.2 listxattr.2 lseek.2 removexattr.2 setxattr.2 stat.2 feature_test_macros.7 fpathconf.3 fopen.3 mtk rename argument: s/file*des/fd/ , since that is the name most commonly used on man pages for a file descriptor argument. bindresvport.3 des_crypt.3 getopt.3 getrpcent.3 realpath.3 rpc.3 xdr.3 mtk removed .sm macros. madvise.2 getdirentries.3 printf.3 sigvec.3 mtk remove extraneous .br macro before/after .sh/.ss. _syscall.2 lookup_dcookie.2 aio_cancel.3 aio_error.3 aio_fsync.3 aio_read.3 aio_return.3 aio_write.3 canonicalize_file_name.3 envz_add.3 getgrouplist.3 getttyent.3 key_setsecret.3 mtrace.3 tcgetpgrp.3 tcgetsid.3 ttyslot.3 tty_ioctl.4 mtk remove extraneous .sp macros. fcntl.2 outb.2 send.2 syscalls.2 getopt.3 proc.5 man-pages.7 standards.7 tcp.7 mtk remove/replace extraneous .sp macros. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- _syscall.2 mtk nowadays there are seven macros (see 2.74 change log also). arch_prctl.2 mtk, acked by andi kleen clarify interpretation of 'addr'; plus a few other minor edits and updates. bind.2 mtk minor rewrites. close.2 mtk clarify relationship between file descriptor and open file description. connect.2 mtk, acked by andi kleen since kernel 2.2, af_unspec for unconnecting a connected socket *is* supported. execve.2 alain portal minor rewordings. futimesat.2 alain portal remove duplicate "#include " from synopsis. getgid.2 mtk add getresgid(2) and credentials(7) to see also. getpagesize.2 mtk small rewording. getresuid.2 mtk rewrote various parts. getuid.2 mtk add getresuid(2) and credentials(7) to see also. ioctl_list.2 alain portal use proper tables for layout, and various formatting fixes. mtk various formatting fixes. listen.2 mtk rewrote various parts. mbind.2 andi kleen / mtk / alain portal modify explanation of einval 'maxnode' error. mmap.2 mtk add comma to clarify meaning of a sentence. open.2 mtk clarify initial description of o_excl. clarify description of behaviors of o_creat | o_excl for symbolic links. clarify text describing use of lockfiles without o_excl. mtk, with input from timo sirainen and trond myklebust o_excl is supported on nfsv3 and later, with linux 2.6 and later. pipe.2 mtk rename 'filedes' argument 'pipefd'. pivot_root.2 mtk s/cwd/current working directory/ seteuid.2 mtk minor changes. setpgid.2 mtk add credentials(7) to see also, and updated copyright credits, to reflect my rewrite of a few months ago. setsid.2 mtk add getsid(2) and credentials(7) to see also. spu_create.2 alain portal / mtk; acked by jeremy kerr minor formatting/wording changes. mtk put eperm in right alphabetical position in errors list. argz_add.3 mtk formatting fixes. atexit.3 mtk minor changes to example program. cerf.3 mtk these functions are still not present as at glibc 2.7. dbopen.3 alain portal / mtk various minor spelling and formatting fixes. envz_add.3 mtk formatting fixes. fexecve.3 mtk fix placement of feature test macro in synopsis. fmax.3 fmin.3 mtk small rewording. getline.3 mtk minor changes to example program. getrpcent.3 getrpcport.3 mtk use modern c prototypes in synopsis. getutent.3 alain portal / mtk formatting fixes. mbsnrtowcs.3 mbsrtowcs.3 mbstowcs.3 mtk use .ip tags to create properly formatted lists. rpc.3 mtk convert function declarations to use modern c prototypes. add text and start of page describing header files and types required by functions. reformat discussion of request under clnt_control(). xdr.3 mtk convert function declarations to use modern c prototypes. remove crufty "int empty" from xdrrec_eof() description. console_codes.4 phil endecott relocate misplaced line: "and if lf/nl (new line mode) is set also a carriage return;" as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=458338. console_ioctl.4 mtk formatting fixes. bootparam.7 mtk, after a note by alan portal fix reference to kernel documentation source file in the "the sound driver" subsection. man-pages.7 alain portal move configuration description after synopsis description. mtk / alain portal note that header files should be surrounded by angle brackets (<>). posixoptions.7 mtk minor formatting and wording fixes. rtnetlink.7 andreas henriksson fix description of rtm_f_equalize. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=458325. signal.7 mtk minor formatting and wording fixes. socket.7 mtk small rewording of discussion of o_async. spufs.7 mtk / jeremy kerr / alain portal s/spe/spu/ ==================== changes in man-pages-2.76 ==================== released: 2008-01-14 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal carlo marcelo arenas belon jeremy kerr sam varshavchik trond myklebust apologies if i missed anyone! global changes -------------- longjmp.3 printf.3 scanf.3 setbuf.3 setjmp.3 sk98lin.4 environ.7 mtk rework/remove use of ".ad" macros. ioctl_list.2 mlock.2 mprotect.2 mremap.2 syslog.2 cfree.3 mpool.3 offsetof.3 rpc.3 stdin.3 mtk fix unbalanced quotes in formatting macros. ftok.3 mtk s/i-node/inode/, for consistency with other pages and posix.1-2001. typographical or grammatical errors have been corrected in several places. changes to individual pages --------------------------- chown.2 mtk minor wording change. dup.2 mtk reordered text in description and added some details for dup2(). open.2 trond myklebust / mtk minor fix to o_excl changes in previous release. gettid.2 mtk rewrote description; noted that thread id is not the same thing as a posix thread id. pipe.2 mtk rewrote description; minor additions to example text. umask.2 mtk a few rewrites and additions. strptime.3 carlo marcelo arenas belon / mtk add "#define _xopen_source" to example program. initrd.4 mtk use quotes more consistently in formatting macros. random.4 mtk, after a report by daniel kahn gilmor add 2.6 details for /proc/sys/kernel/random/poolsize. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=459232. pthreads.7 mtk minor changes. spufs.7 mtk / jeremy kerr define abbreviation "mss". ==================== changes in man-pages-2.77 ==================== released: 2008-01-31 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: pavel heimlich phil endecott thomas huriaux vincent lefevre wang cong apologies if i missed anyone! global changes -------------- stdarg.3 bootparam.7 thomas huriaux fix broken use of single quotes at start of line, as per: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=462636 typographical or grammatical errors have been corrected in several places. new pages --------- remove_colophon.sh mtk script to remove the colophon section from the man pages provided as command-line arguments. this is useful to remove the colophon sections from all of the man pages in two different release trees in order to do a "diff -run" to see the "real" differences between the trees. changes to individual pages --------------------------- fcntl.2 mtk replace tables with .tp macros. fork.2 mtk added discussion of directory streams. removed "#include " from synopsis. changed authorship notice. futex.2 mtk add enosys error to errors. phil endecott explicitly describe return value in the event of an error. inotify_add_watch.2 mtk minor wording changes. splice.2 wang cong fix types for 2 and 4 arguments in splice prototype. wait.2 phil endecott clarify description of return value for wnohang. tkill.2 mtk rewrote description; emphasized that tkill() is obsoleted by tgkill(). alloca.3 mtk change description in name section. various rewrites and additions (including notes on longjmp() and sigsegv). mtk / vincent lefevre weaken warning against use of alloca(), and point out some cases where it can be useful; as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=461100. bootparam.7 pavel heimlich remove junk line. inotify.7 mtk replace tables with .tp macros. s/multisource synchronization/multisource synchronization (mss)/ ==================== changes in man-pages-2.78 ==================== released: 2008-02-15 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: davide libenzi greg banks michael tokarev phil endecott apologies if i missed anyone! global changes -------------- sigaction.2 signal.2 sigwaitinfo.2 signal.7 mtk add see also entry referring to new signalfd.2 page. typographical or grammatical errors have been corrected in several places. new pages --------- eventfd.2 mtk, with input and review from davide libenzi documents the eventfd() system call, new in 2.6.22. signalfd.2 mtk, with input and review from davide libenzi documents the signalfd() system call, new in 2.6.22. changes to individual pages --------------------------- futex.2 mtk / phil endecott improve wording describing error returns. open.2 greg banks greatly expand the detail on o_direct. reboot.2 mtk / michael tokarev fix return value description: in some cases reboot() does not return. mtk rename the 'flag' argument to 'cmd', since that is more meaningful, and also what is used in the kernel source. other minor wording changes. ==================== changes in man-pages-2.79 ==================== released: 2008-03-07 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries e. brouwer chris heath davide libenzi fernando luis vázquez cao heikki orsila jeremy kerr justin pryzby lasse kärkkäinen michael haardt mike frysinger ron burk sam varshavchik samuel thibault walter harms apologies if i missed anyone! global changes -------------- typographical or grammatical errors have been corrected in several places. new pages --------- timerfd_create.2 mtk, with input and review from davide libenzi documents the timerfd_create(), timerfd_settime(), and timerfd_gettime() system calls, which are new in 2.6.25. new links --------- timerfd_gettime.2 timerfd_settime.2 mtk links to new timerfd_create.2 page. eventfd_read.3 eventfd_write.3 mtk links to eventfd.2. changes to individual pages --------------------------- makefile aeb remove code relating to man1/readme, which no longer exists. execve.2 mtk clarify detail of rlimit_stack/4 limit for argv+environ. getitimer.2 mtk added see also entry referring to timerfd_create.2. getrusage.2 mtk minor rewordings. open.2 michael haardt move discussion of 'mode' argument under description of o_creat. signalfd.2 mtk fix type for 'ssi_ptr' field. see http://sources.redhat.com/ml/libc-hacker/2008-01/msg00002.html. syscalls.2 mtk add timerfd_create(), timerfd_settime(), and timerfd_gettime() to list. syslog.2 jeremy kerr add info on command type 10. add details on types 6, 7, 8, and 9. minor grammar fix. mtk update log_buf_len details. update return value section. notes capability requirements under eperm error. minor fix to description of type==3 and type==4. other minor edits. ctime.3 walter harms note that posix requires localtime() to act as though tzset() was called, but localtime_r() does not have the same requirement. see also http://thread.gmane.org/gmane.comp.time.tz/2034/ getaddrinfo.3 mtk clarify discussion of null 'hints' argument; other minor rewrites. mtk / sam varshavchik remove some duplicated text. malloc.3 lasse kärkkäinen / mike frysinger / mtk clarify description of realloc() behavior for ((size == 0) && (ptr != null)). posix_fallocate.3 samuel thibault s/stdlib.h/fcntl.h/ in synopsis. proc.5 fernando luis vázquez cao update /proc/[number]/cmdline description. it used to be true that the command line arguments were not accessible when the process had been swapped out. in ancient kernels (circa 2.0.*) the problem was that the kernel relied on get_phys_addr to access the user space buffer, which stopped working as soon as the process was swapped out. recent kernels use get_user_pages for the same purpose and thus they should not have that limitation. epoll.7 davide libenzi / mtk clarify the somewhat unintuitive behavior that occurs if a file descriptor in an epoll set is closed while other file descriptors referring to the same underlying open file description remain open. see also http://thread.gmane.org/gmane.linux.kernel/596462/. mtk clarify error that occurs if we add an epoll fd to its own set. mtk a few minor rewordings. mtk, after a note by chris heath rework q1/a1, describing what happens when adding the same file descriptor twice to an epoll set, and when adding duplicate file descriptors to the same epoll set. heikki orsila / mtk / davide libenzi clarify q9/a9 to discuss packet/token-oriented files. mtk, after comments by davide libenzi and chris heath added q0/a0, making explicit that the key for items in an epoll set is [file descriptor, open file description]. mtk, after a note by ron burk change a3, to note that when events are available, the epoll file descriptor will indicate as being readable. mtk add some further explanation to q5/a5 about why an epoll file descriptor cannot be passed across a unix domain socket. posixoptions.7 mtk add see also entry for standards(7). regex.7 mtk add grep(1) to see also. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=348552. standards.7 mtk add see also entry for posixoptions(7). time.7 mtk added see also entry referring to timerfd_create.2. ==================== changes in man-pages-2.80 ==================== released: 2008-06-05 contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: adrian bunk alain portal andreas herrmann andrew morton andries e. brouwer anoop aurelien gerome daniel burr davide libenzi felix kater folkert van heusden hamaji shinichiro heikki orsila ingo molnar justin pryzby karsten weiss martin pitt marty leisner nicolas françois nick piggin petter reinholdtsen reuben thomas sam varshavchik stuart brady theodoros v. kalamatianos thomas huriaux tim stoakes timothy baldwin tolga dalman apologies if i missed anyone! global changes -------------- bdflush.2 inotify_add_watch.2 mprotect.2 sigprocmask.2 ctime.3 getusershell.3 setbuf.3 st.4 ip.7 packet.7 mtk replace "(il)legal" by "(not) permitted" or "(in)valid". read.2 utime.2 filesystems.5 packet.7 mtk s/time stamp/timestamp/, for consistency with majority use in other pages, and in posix.1. madvise.2 mbind.2 mincore.2 mmap.2 mmap2.2 msync.2 remap_file_pages.2 mtk change name of 'start' argument to 'addr' for consistency with: * other memory-related interfaces * posix specification (for those interfaces in posix) * linux and glibc source code (in at least some cases) various pages mtk s/filesystem/file system/, for consistency with majority use in other pages, and in posix.1. various pages mtk s/zeroes/zeros/, for consistency with majority use in other pages, and in posix.1. abs.3 proc.5 mtk s/builtin/built-in/, for consistency with majority use in other pages, and in posix.1. mknod.2 ftw.3 mtk s/normal file/regular file/ various pages mtk s/nonempty/non-empty/ various pages mtk s/nonzero/non-zero/ various pages mtk s/realtime/real-time/, for consistency with majority usage. various pages mtk s/command line/command-line/ when used attributively. various pages mtk use "run time" when non-attributive, "run-time" when attributive. various pages mtk various pages that i wrote carried a slightly modified version of the "verbatim" license. in the interests of minimizing license proliferation, i've reverted the modified form so that the license is exactly the same as on other pages carrying the verbatim license. epoll_ctl.2 getitimer.2 getrlimit.2 unix.7 mtk s/since kernel x.y.z/since linux x.y.z/ wait.2 inotify.7 mtk reformat kernel version information for flags. typographical or grammatical errors have been corrected in several places. (special thanks to nicolas françois.) new pages --------- random_r.3 mtk, after a suggestion by aeb documents random_r(3), srandom_r(3), initstate_r(3), and setstate_r(3), which are the reentrant equivalents of random(3), srandom(3), initstate(3), and setstate(3). new links --------- lutimes.3 mtk link to futimes.3. initstate_r.3 setstate_r.3 srandom_r.3 mtk links to random_r.3. daylight.3 timezone.3 tzname.3 mtk links to tzset.3. isnanf.3 isnanl.3 mtk links to finite.3. encrypt_r.3 setkey_r.3 mtk links to encrypt.3. changes to individual pages --------------------------- clone.2 mtk added note that clone_stopped (which no-one uses anyway) is now deprecated. epoll_create.2 mtk add notes section pointing out that 'size' argument is unused since kernel 2.6.8. epoll_ctl.2 mtk added portability note to bugs text for epoll_ctl_del. epoll_wait.2 mtk if the 'sigmask' is null, then epoll_pwait() is equivalent to epoll_wait(). fork.2 mtk notes: since glibc 2.3.3, the glibc nptl fork() wrapper bypasses the fork() system call to invoke clone() with flags providing equivalent functionality. futex.2 mtk, after a note from adrian bunk futex_fd has been removed, as of kernel 2.6.26. futimesat.2 mtk note that this system call is made obsolete by utimensat(2). getgroups.2 petter reinholdtsen see also: add getgrouplist(3). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=479284. mtk ngroups_max increased in kernel 2.6.4. see also: add credentials(7). mtk reformat description and return value sections to be more consistent with man-pages style. add some more detail to descriptions of system calls. clarified what happens if caller of getgroups() is a member of more than 'size' supplementary groups. errors: add enomem. getpriority.2 mtk, after a note from ingo molnar add text in notes about the punchier effect of nice values in kernel 2.6.23 and later. add documentation/scheduler/sched-nice-design.txt to see also list. gettid.2 mtk added versions section noting that this system call first appeared in 2.4.11. kill.2 marty leisner / mtk add text explicitly noting that sig==0 can be used to check for the existence of a pid or pgid. mtk a few minor rewordings. mbind.2 mtk the location of the numactl package has changed. mmap.2 mtk added some .ss headings to make structure of page a little more obvious. mtk, with input from nick piggin map_populate supports both file and anonymous mappings. since 2.6.23, map_populate supports private mappings. since 2.6.23, map_nonblock causes map_populate to be a no-op. mtk notes: added details on mapping address that is selected by kernel when map_fixed is / isn't specified. mount.2 mtk the ms_remount changes in 2.4 were at 2.4.10 (not 2.4). mtk minor wording change. msgctl.2 mtk clarify that "unused" fields in msginfo structure are "unused within the kernel". msginfo.msgpool is measured in kilobytes, not bytes. minor rewordings in comments for msginfo structure. msgop.2 mtk various minor rewordings and restructurings for clarity. mtk, after a note from reuben thomas remove "msgop" from name section. mkdir.2 mtk clarify meaning of "bsd group semantics". see also: add chown(2). mknod.2 mtk see also: add chown(2) and chmod(2). mmap.2 mtk see also: add mprotect(2) and shmat(2). mprotect.2 hamaji shinichiro synopsis: s/size_t \*len/size_t len/ open.2 mtk note that o_cloexec should be in the next posix.1 revision. mtk more than just ext2 supports "mount -o bsdgroups" nowadays, so make the discussion about group ownership of new files a bit more generic. mtk see also: add chown(2) and chmod(2). poll.2 mtk if the 'sigmask' is null, then ppoll() is equivalent to poll() with respect to signal mask manipulations. posix_fadvise.2 mtk s/posix_madvise (2)/posix_madvise (3)/; (the referred-to page still doesn't exist yet, but hopefully will do sometime soon.) ptrace.2 anoop, acked by roland mcgrath. re ptrace_peekuser: the offsets and data returned might not match with the definition of struct user. see also http://lkml.org/lkml/2008/5/8/375 recv.2 felix kater / mtk improve wording for eagain error in discussion of msg_dontwait. rmdir.2 martin pitt posix.1 also allows eexist for the enotempty error condition. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=467552. sched_setscheduler.2 mtk, with input from ingo molnar add description of sched_idle policy (new in 2.6.23). tweak description of sched_batch. minor rewordings. select_tut.2 justin pryzby various wording clean-ups. semctl.2 mtk clarify that "unused" fields in seminfo structure are "unused within the kernel". minor rewordings in comments for seminfo structure. semop.2 aurelien gerome small fix in example code. setpgid.2 mtk / karsten weiss clarify description of setpgid() a little. shmctl.2 mtk clarify that "unused" fields in shminfo structure are "unused within the kernel". minor rewordings in comments for shminfo structure. shmop.2 mtk, after a note from reuben thomas remove "shmop" from name section. signalfd.2 mtk added bugs text noting that before kernel 2.6.25, the ssi_int and ssi_ptr fields are not set. added comments describing fields in signalfd_siginfo structure. update field names in example program (s/signo/ssi_signo/). various small fixes, and remove duplicated sentence. minor edits to structure definition. sigqueue.2 mtk added some comments to code in notes. stat.2 mtk minor wording change. symlink.2 mtk see also: add lchown(2). sync_file_range.2 mtk / andrew morton remove statement that (sync_file_range_wait_before | sync_file_range_write | sync_file_range_wait_after) is a traditional fdatasync(2) operation. see https://bugzilla.mozilla.org/show_bug.cgi?id=421482 comments 129 to 131. syscalls.2 mtk this page is now up to date as at kernel 2.6.25. syslog.2 mtk small tidy up of language relating to permissions/capabilities. timerfd_create.2 mtk minor change to example program. minor wording change. utime.2 reuben thomas remove unnecessary subheading for utimes(). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=477402. mtk change description in name line ("or" is not correct: these calls always change *both* timestamps). conforming to: utimes() is in posix.1-2001. mtk rename 'buf' argument of utime() to 'times' (like utimes()). clarify explanation of eacces and eperm errors. remove bugs section, since it doesn't seem to add useful information. clarified discussion of capabilities, and noted that cap_dac_override also has a role. other minor rewordings. wait.2 mtk, after a note by justin pryzby add a sentence clarifying that even though the default disposition of sigchld is "ignore", explicitly setting the disposition to sig_ign results in different treatment of zombies. aio_cancel.3 aio_error.3 aio_fsync.3 aio_read.3 aio_return.3 aio_suspend.3 aio_write.3 kevin o'gorman add "link with -lrt" to synopsis. backtrace.3 nicolas françois s/backtrace_symbols/backtrace_symbols_fd/ in one sentence. mtk fix bogus reference to variable 'strings': should be: "the array of pointers". ctime.3 mtk add warning under notes that asctime(), ctime(), gmtime(), and localtime() may each overwrite the static object returned by any of the other calls. other minor edits. dlopen.3 mtk add more detail to the description of the fields in the structure returned by dladdr(). fexecve.3 mtk clean up synopsis after work by cut-and-paste-pete: the necessary header file is not ! futimes.3 mtk add documentation of lutimes(), which appeared in glibc 2.6. mtk change description in name line ("or" is not correct: these calls always change *both* timestamps). conforming to: futimes() did not come from 4.2bsd. (it came from freebsd; see the freebsd man page.) getenv.3 mtk noted that caller must not modify returned value string. noted that getenv() is not reentrant: the buffer may be statically allocated and overwritten by later calls to getenv(), putenv(), setenv(), or unsetenv(). other minor rewrites. getgrent.3 petter reinholdtsen see also: add getgrouplist(3). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=479284. gethostbyname.3 mtk add 'h_errno' to name list. getopt.3 mtk add 'optarg', 'optind', 'opterr', and 'optopt' to name section. add subheading for getopt_long() and getopt_long_only() description. getpt.3 mtk point out that this function should be avoided in favor of posix_openpt(). add errors section referring to open(2). getsubopt.3 daniel burr synopsis: fix declaration of valuep. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=476672. malloc.3 mtk return value: note circumstances in which successful malloc() and calloc() can return null. mq_open.3 mtk, after a note by marty leisner note that is needed for o_* constants and is needed for 'mode' constants. opendir.3 mtk describe treatment of close-on-exec flag by opendir() and fdopendir(). openpty.3 mtk see also: add ttyname(3). raise.3 mtk / timothy baldwin clarify semantics of raise() when called from a multithreaded program. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=476484. mtk rewrites and additions to various parts of the page. rand.3 tolga dalman / aeb / mtk remove outdated warning in notes; encourage the use of random(3) instead. folkert van heusden clarify wording describing range of values returned by rand(). random.3 aeb / mtk / tolga dalman recommend use or random_r(3) for multithreaded applications that need independent, reproducible sequences of random numbers. move references to "the art of computer programming" and "numerical recipes", formerly in rand(3), to this page. add drand48(93) to see also list. regex.3 heikki orsila clarify description of 'rm_eo' field. sem_open.3 mtk, after a note by marty leisner note that is needed for o_* constants and is needed for 'mode' constants. sem_post.3 mtk added pointer to example in sem_wait(3). sem_close.3 sem_destroy.3 sem_getvalue.3 sem_init.3 sem_open.3 sem_post.3 sem_unlink.3 sem_wait.3 mtk, after a note from marty leisner add text to synopsis noting the need to link with "-lrt" or "-pthread". setenv.3 mtk setenv() copies 'name' and 'value' (contrast with putenv()). unsetenv() of a nonexistent variable does nothing and is considered successful. noted that setenv() and unsetenv() need not be reentrant. shm_open.3 mtk, after a note by marty leisner note that is needed for o_* constants and is needed for 'mode' constants. undocumented.3 mtk initstate_r(3), setkey_r(3), setstate_r(3) are now documented. utmp.5 nicolas françois small rewording. resolv.conf.5 nicolas françois gethostname() is in section 2, not section 3. ascii.7 stuart brady fix rendering of ' (backtick) and apostrophe (') in tables charsets.7 nicolas françois s/unicode.com/unicode.org/ credentials.7 mtk notes: pthreads requires that all threads share the same uids and gids. but the linux kernel maintains separate uids and gids for every thread. nptl does some work to ensure that credential changes by any thread are carried through to all posix threads in a process. mtk sysconf(_sc_ngroups_max) can be used to determine the number of supplementary groups that a process may belong to. clarify that supplementary group ids are specified in posix.1-2001. epoll.7 mtk, after a note from sam varshavchik for answer a2, change "not recommended" to "careful programming may be required". inotify.7 mtk document sigio feature (new in 2.6.25) for inotify file descriptors. mtk note that select()/poll()/epoll_wait() indicate a ready inotify file descriptor as readable. mtk document in_attrib in a little more detail. pthreads.7 justin pryzby grammar fix, plus fix typo in script. mtk add list of thread-safe functions. standards.7 mtk add a section on the upcoming posix revision. ld.so.8 justin pryzby / mtk various wording improvements. ==================== changes in man-pages-3.00 ==================== released: 2008-06-12, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries brouwer stuart brady apologies if i missed anyone! global changes -------------- the posix.1 man pages (sections 0p, 1p, 3p) have been moved out of this package into the separate man-pages-posix package. this made sense because those pages are seldom changed (only formatting fixes, etc.) so that it was unnecessary to redistribute them with each man-pages release. console_codes.4 random.4 dir_colors.5 proc.5 glob.7 stuart brady s/`/\`/ for backquotes used in command substitution, for proper rendering in utf-8. various pages mtk, after a note from stuart brady using /'x'/ to denote a character (string) renders poorly in utf-8, where the two ' characters render as closing single quotes. on the other hand, using /`x'/ renders nicely on utf-8, where proper opening and closing single quotes are produced by groff(1), but looks ugly when rendered in ascii. using the sequence /\\aqx\\aq/ produces a reasonable rendering ('\\aq' is a vertical "apostrophe quote") in both utf-8 and ascii. so that change is made in a number of pages. see also http://www.cl.cal.ac.uk/~mgk25/ucs/quotes.html. various pages mtk replace form /`string'/ by /"string"/, since the former renders poorly in ascii. termios.3 console_codes.4 tty_ioctl.4 termcap.5 charsets.7 mtk control character names (^x) are written boldface, without quotes. printf.3 scanf.3 proc.5 glob.7 regex.7 mtk various edits to try and bring some consistency to the use of quotes. changes to individual pages --------------------------- tty_ioctl.4 mtk small rewordings in description of packet mode. locale.7 mtk minor formatting fixes. ==================== changes in man-pages-3.01 ==================== released: 2008-06-25, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andreas herrmann andrew p andrew clayton bart van assche christian borntraeger christoph hellwig daniele giacomini dorin lazar george spelvin jason englander jeff moyer laurent vivier masatake yamoto matt mackall neil horman pavel machek peter zijlstra petr baudis petr gajdos roman zippel sam varshavchik samuel thibault stephane chazelas stuart cunningham thomas gleixner tolga dalman yao zhao wang cong apologies if i missed anyone! new and rewritten pages ----------------------- acct.5 mtk a complete rewrite of this page, now with much more detail. hostname.7 mtk a description of hostname resolution. taken from freebsd 6.2, and lightly edited for man-pages style. symlink.7 mtk a description of symbolic links. taken from freebsd 6.2, but heavily edited for linux details, improved readability, and man-pages style. newly documented interfaces in existing pages --------------------------------------------- getrlimit.2 mtk / peter zijlstra add description of rlimit_rttime limit, new in 2.6.25. mkstemp.3 mtk add description of mkostemp(), new in glibc 2.7. core.5 mtk, after a note by petr gajdos; review by neil horman document core_pattern pipe syntax, which appeared in kernel 2.6.19. add an example program demonstrating use of core_pattern pipe syntax. mtk document /proc/pid/coredump_filter, new in kernel 2.6.23. documentation was based on the text in documentation/filesystems/proc.txt, plus testing, and checking the kernel source. proc.5 mtk document /proc/pid/oom_score, which was new in kernel 2.6.11. this file displays the "badness" score of the process, which provides the basis for oom-killer decisions. mtk document /proc/pid/oom_adj, which was new in kernel 2.6.11. this file influences the oom_score of a process. mtk document /proc/pid/limits, which was new in 2.6.24. this file displays a process's resource limits. mtk document /proc/pid/fdinfo/*, which was new in 2.6.22. these files display info about each descriptor opened by the process: the current file offset, and the file access mode + file status flags as set in open() or fcntl(f_setfl). mtk document /proc/pid/mountinfo, which was new in 2.6.26. this file displays information about mount points. closely based on text from documentation/filesystems/proc.txt. mtk document /proc/pid/mountstats, which was new in 2.6.17. this file displays statistics about mount points. mtk document /proc/pid/status. samuel thibault / mtk, review by laurent vivier, christian borntraeger, and andrew p document guest (virtual cpu) time field in /proc/stat. document guest (virtual cpu) time fields in /proc/pid/stat. new links --------- mkostemp.3 mtk link to mkstemp.3. getcwd.2 mtk link to getcwd.3, which describes several interfaces, among them getcwd(), which is in fact a system call. global changes -------------- sched_setaffinity.2 sched_setscheduler.2 set_mempolicy.2 mbind.2 mtk see also: add cpuset(7). chown.2 faccessat.2 fchmodat.2 fchownat.2 fstatat.2 getxattr.2 link.2 linkat.2 listxattr.2 open.2 readlink.2 removexattr.2 rename.2 setxattr.2 stat.2 symlink.2 symlinkat.2 unlink.2 futimes.3 remove.3 path_resolution.7 mtk see also: add symlink(7). intro.1 time.1 fcntl.2 gethostbyname.3 ioctl_list.2 mtk wrap source lines so that new sentence starts on new line. addseverity.3 backtrace.3 dlopen.3 fmtmsg.3 getnameinfo.3 getpt.3 grantpt.3 makecontext.3 ptsname.3 tcgetsid.3 unlockpt.3 wordexp.3 mtk added versions section. msgctl.2 msgget.2 semget.2 semop.2 pciconfig_read.2 basename.3 cmsg.3 ftok.3 console_ioctl.4 tzfile.5 mq_overview.7 pty.7 mtk for consistency, "fix" cases where argument of .b or .i was on the following source line. adjtimex.2 getrusage.2 io_getevents.2 poll.2 select.2 semop.2 sigwaitinfo.2 aio_suspend.3 clock_getres.3 mq_receive.3 mq_send.3 sem_wait.3 proc.5 mtk see also: add time(7) typographical or grammatical errors have been corrected in several places. (special thanks to nicolas françois and alain portal.) changes to individual pages --------------------------- acct.2 mtk add a few more words to description. notes: add pointer to acct(5). alarm.2 alain portal s/process/calling process/ so as to say that the alarm signal is delivered to the calling process. brk.2 yao zhao / mtk clarify discussion of return value of sbrk(). mtk description: add some sentences giving an overview of these interfaces. add note recommending use of malloc(3). change name of brk() argument to the simpler 'addr'. add "(void *)" cast to "-1" for error return of sbrk(). removed some incorrect text about "brk(0)". note that susv2 specified the return value of sbrk(). added a detail on the glibc brk() wrapper. remove discussions of old standards (c89 and posix.1-1990); conforming to already discusses the situation with respect to more recent standards. chmod.2 mtk clarify description of chmod() and fchmod(). add further detail on s_isuid, s_isgid, and s_isvtx permissions. reformat list of permissions bits. chown.2 mtk describe rules governing ownership of new files (bsdgroups versus sysvgroups, and the effect of the parent directory's set-group-id permission bit). chroot.2 alain portal clarify description a little. s/changes the root directory/ changes the root directory of the calling process/ execve.2 mtk fix text that warns against use of null argv and envp. using a null envp does in fact seem to be portable (works on solaris and freebsd), but the linux semantics for a null argv certainly aren't consistent with other implementations. see http://bugzilla.kernel.org/show_bug.cgi?id=8408. getdents.2 mtk, after a note from george spelvin document d_type field, present since kernel 2.6.4. other minor edits. getitimer.2 mtk noted that posix.1 leaves interactions with alarm(), sleep(), and usleep() unspecified. linux 2.6.16 removed the max_sec_in_jiffies ceiling on timer values. other minor changes. io_cancel.2 io_destroy.2 io_getevents.2 io_setup.2 io_submit.2 mtk, after a note by masatake yamoto and input from jeff moyer describe the unconventional error return provided by the wrapper function in libaio (and contrast with behavior if the system call is invoked via syscall(2)). see http://thread.gmane.org/gmane.linux.ltp/4445/ alain portal / mtk re-order errors and see also entries to be alphabetical. io_getevents.2 alain portal small wording fix. io_submit.2 jeff moyer s/aio request blocks/aio control blocks/ mknod.2 mtk note that eexist applies, even if the pathname is a (possibly dangling) symbolic link. nanosleep.2 mtk, after a report from stephane chazelas remove crufty discussion of hz, and replace with a pointer to time(7). see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=485636 mtk, after some discussions with bart van assche and roman zippel notes: describe clock_realtime versus clock_nanosleep see also http://thread.gmane.org/gmane.linux.kernel/696854/ "nanosleep() uses clock_monotonic, should be clock_realtime?" mtk replace mentions of "process' by "thread". notes: describe case where clock_nanosleep() can be preferable. some minor rewrites. open.2 mtk, after a note from christoph hellwig notes: note that access mode flags are not single bits, and document the linuxism "access mode 3". see also http://thread.gmane.org/gmane.linux.kernel/653123. readdir.2 mtk minor wording fixes. recv.2 alain portal add comment to 'ee_pad' field in structure definition. sched_setscheduler.2 mtk add pointer to discussion of rlimit_rttime in getrlimit.2. mtk, after a note by andrew clayton rewrote and restructured various parts of the page for greater clarity. mtk add more detail to the rules that are applied when an unprivileged process with a non-zero rlimit_rtprio limit changes policy and priority. see also: add documentation/scheduler/sched-rt-group.txt sync_file_range.2 pavel machek sync_file_range_write can block on writes greater than request queue size. for some background, see http://thread.gmane.org/gmane.linux.kernel/687713/focus=688340 syscalls.2 mtk added system call history back to version 1.2. fix typo on kernel version for pivot_root(). syslog.2 wang cong document enosys error, which can occur if kernel was built without config_printk. utime.2 nicolas françois clarify description of 'times' array for utimes(). adjtime.3 mtk the longstanding bug that if delta was null, olddelta didn't return the outstanding clock adjustment, is now fixed (since glibc 2.8 + kernel 2.6.26). http://sourceware.org/bugzilla/show_bug?id=2449 http://bugzilla.kernel.org/show_bug.cgi?id=6761 dprintf.3 mtk note that these functions are included in the next posix revision. remove editorial discussion about what the functions should have been named. ftime.3 mtk rewrote various pieces, and added some details. getaddrinfo.3 mtk improve description or 'hints' and 'res' arguments. add details on numeric strings that can be specified for 'node'. other fairly major restructurings and rewrites to improve logical structure and clarity of the page. see also: add hostname(7). gethostbyname.3 mtk description: add reference to inet_addr(3) for dotted notation. see also: add inet(3). mtk added bugs section noting that gethostbyname() does not recognize hexadecimal components in dotted address strings; see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=482973 getmntent.3 mtk, after stuart cunningham pointed out the typo remove statement that lsb deprecates the functions "endmntent(), setmntent() [sic] and setmntent()". this doesn't seem to be true (i can't find mention of it being deprecated in any of the lsb specs). rather, lsb simply doesn't specify these functions. (lsb 1.3 had a spec of setmntent(), but not getmntent() or endmntent(), and noted that having a spec of setmntent() was of little use without also having a spec of getmntent().) see also https://lists.linux-foundation.org/pipermail/lsb-discuss/2006-october/003078.html getnameinfo.3 tolga dalman remove mention of sa_len field from example code. that field is a bsdism not present on linux. mtk various minor changes. inet.3 mtk / stephane chazelas inet_aton() is *not* in posix.1. rewrote discussion of why inet_addr() is disfavored. see also: add getaddrinfo(3). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=482979. mtk, after a note by stephane chazelas describe the various address forms supported by inet_aton(). mtk rewrite description of inet_network(). clarify discussion of inet_lnaof(), inet_netof(), and inet_makeaddr(). add discussion of classful addressing, noting that it is obsolete. added an example program. mtk relocate discussion of i386 byte order to notes. note that inet_aton() returns an address in network byte order. see also: add byteorder(3) and getnameinfo(3). inet_ntop.3 mtk remove unneeded header files from synopsis. see also: add inet(3) and getnameinfo(3). make name line more precise. move errors to an errors section. add example section pointing to inet_pton(3). inet_pton.3 mtk / stephane chazelas remove statement that inet_pton() extends inet_ntoa(); that's not really true, since inet_pton() doesn't support all of the string forms that are supported by inet_ntoa(). see also: add getaddrinfo(3). as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=482987. mtk describe ipv6 address formats. describe dotted decimal format in more detail. add an example program. mtk remove unneeded header files from synopsis. make name line more precise. make description of return value more precise. see also: add inet(3). mkfifo.3 mtk note that eexist applies, even if the pathname is a (possibly dangling) symbolic link. mkstemp.3 mtk fix discussion of o_excl flag. these functions may also fail for any of the errors described in open(2). various other rewordings. readdir.3 mtk document dt_lnk (symbolic link) for d_type field. reorder dt_ entries alphabetically. remainder.3 mtk recommend against drem(), in favor of remainder(). scanf.3 mtk, after a note from stephane chazelas add an errors section documenting at least some of the errors that may occur for scanf(). see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=487254. mtk, after a note from stephane chazelas; review by stephane chazelas document the gnu 'a' modifier for dynamically allocating strings. see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=487254. document the gnu 'm' modifier for dynamically allocating strings. strcat.3 andreas herrmann s/strcat/strncat/ (a typo that changed the semantics in description). strerror.3 mtk, after a note from daniele giacomini modify synopsis to show prototypes of both versions of strerror_r(), and make other small clarifications of the description regarding the two versions. random.4 george spelvin (taking time out from his busy broadway schedule), with some tweaks by matt mackall and mtk add a usage subsection that recommends most users to use /dev/urandom, and emphasizes parsimonious usage of /dev/random. locale.5 petr baudis lc_time: describe first_weekday and first_workday. proc.5 mtk the various cpu time fields in /proc/stat and /proc/pid/stat return time in clock ticks (user_hz, cputime_to_clock_t(), sysconf(_sc_clk_tck)). updated, clarified and expanded the description several fields in /proc/[number]/stat. mtk clarified and expanded the description of /proc/[number]/fd. mtk updated and clarified the description of /proc/[number]/statm. mtk updated and clarified the description of /proc/sys/fs/dentry-state. mtk many formatting, wording, and grammar fixes. man-pages.7 mtk enhanced description of versions section. mq_overview.7 mtk note that linux does not currently support acls for posix message queues. sem_overview.7 mtk note that linux supports acls on posix named semaphores since 2.6.19. time.7 mtk, with some suggestions from bart van assche and thomas gleixner added some details about where jiffies come into play. added section on high-resolution timers. mentioned a few other time-related interfaces at various points in the page. see http://thread.gmane.org/gmane.linux.kernel/697378. unix.7 mtk, after a note by samuel thibault provide a clear description of the three types of address that can appear in the sockaddr_un structure: pathname, unnamed, and abstract. ==================== changes in man-pages-3.02 ==================== released: 2008-07-02, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andries brouwer reuben thomas sam varshavchik stephane chazelas wang cong apologies if i missed anyone! new and rewritten pages ----------------------- clock_nanosleep.2 mtk a description of the clock_nanosleep() system call, which was added in kernel 2.6. getgrouplist.3 mtk a near complete rewrite, including additional information and a new example program. getutmp.3 mtk documents getutmp(3) and getutmpx(3). gnu_get_libc_version.3 mtk documents gnu_get_libc_version(3) and gnu_get_libc_release(3). sigwait.3 mtk documents sigwait(3). shm_overview.7 mtk an overview of the posix shared memory api. newly documented interfaces in existing pages --------------------------------------------- updwtmp.3 mtk document updwtmpx(3). new links --------- getutmpx.3 mtk link to getutmp.3. gnu_get_libc_release.3 mtk link to gnu_get_libc_version.3 updwtmpx.3 mtk link to updwtmp.3 utmpxname.3 mtk link to getutent.3. utmpx.5 mtk link to utmp.5. global changes -------------- various pages mtk s/user name/username/ various pages mtk s/host name/hostname/ changes to individual pages --------------------------- fchmodat.2 alain portal see also: add symlink.7. (3.01 changelog wrongly said this had been done.) io_setup.2 alain portal remove superfluous text from return value. mmap.2 mtk see also: add mmap(2), shm_overview(7). shmget.2 shmop.2 mtk see also: add shm_overview(7). sigreturn.2 mtk added a bit more detail on what sigreturn() actually does. signalfd.2 sigsuspend.2 mtk see also: add sigwait(3). sigwaitinfo.2 mtk describe behavior when multiple threads are blocked in sigwaitinfo()/sigtimedwait(). see also: add sigwait(3). dirfd.3 mtk return value: describe return value on success. add an errors section documenting posix.1-specified errors. getaddrinfo.3 mtk, after a note by stephane chazelas getaddrinfo() supports specifying ipv6 scope-ids. getlogin.3 mtk errors: add enotty. see also: add utmp(5). getutent.3 wang cong utmpname() does return a value. mtk add paragraph to start of description recommending use of posix.1 "utmpx" functions. conforming to: mention utmpxname(). add an errors section. there are no utmpx equivalents of the _r reentrant functions. clarify discussion of return values. add pointer to definition of utmp structure in utmp(5). clarify discussion of utmpx file on other systems (versus linux situation). getutent.3 mtk see also: add getutmp(3) inet_pton.3 stephane chazelas fix error in description of ipv6 presentation format: s/x.x.x.x.x.x.x.x/x:x:x:x:x:x:x:x/. setbuf.3 reuben thomas / mtk fix confused wording for return value of setvbuf(). fixes http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=488104. mtk other minor rewordings. shm_open.3 mtk see also: add shm_overview(7). random.4 mtk, after a note by alain portal slight rewording to make life easier for non-native english speakers. utmp.5 mtk add discussion of posix.1 utmpx specification. provide a little more detail on fields of utmp structure. added comments to macros for ut_type field. correct the description of the ut_id field. mtk consolidate duplicated information about ut_tv and ut_session on biarch platforms. mtk move some text from conforming to to notes. removed some crufty text. see also: add login(3), logout(3), logwtmp(3). ut_linesize is 32 (not 12). mtk see also: add getutmp(3) man-pages.7 mtk enhanced the discussion of font conventions. signal.7 mtk note that the delivery order of multiple pending standard signals is unspecified. see also: add sigwait(3). ==================== changes in man-pages-3.03 ==================== released: 2008-07-08, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andi kleen hidetoshi seto li zefan paul jackson sam varshavchik apologies if i missed anyone! new and rewritten pages ----------------------- getcpu.2 andi kleen, with some text and edits by mtk documents the getcpu(2) system call, introduced in linux 2.6.19. sched_getcpu.3 mtk documents sched_getcpu(3), a wrapper for getcpu(2), provided since glibc 2.6. cpuset.7 paul jackson, with review and editing by mtk, and comments by hidetoshi seto and li zefan a description of the cpuset file system, the mechanism introduced kernel 2.6.12 for confining processes to designated processors and nodes. (becomes the fourth largest page in man-pages!) newly documented interfaces in existing pages --------------------------------------------- readdir.3 mtk add documentation of readdir_r(). new links --------- updwtmpx.3 alain portal link to updwtmp.3 (3.02 changelog wrongly said this had been done). readdir_r.3 mtk link to readdir.3. global changes -------------- get_mempolicy.2 mbind.2 sched_setaffinity.2 set_mempolicy.2 mtk see also: add getcpu(2). accept.2 close.2 connect.2 dup.2 epoll_wait.2 fcntl.2 flock.2 futex.2 msgop.2 poll.2 read.2 recv.2 select.2 semop.2 send.2 sigwaitinfo.2 spu_run.2 wait.2 write.2 aio_suspend.3 mq_receive.3 mq_send.3 scanf.3 sem_wait.3 usleep.3 inotify.7 mtk errors: added reference to signal(7) in discussion of eintr. various pages mtk wrapped very long source lines. changes to individual pages --------------------------- accept.2 mtk small wording change. io_getevents.2 mtk errors: add eintr error. open.2 mtk errors: add eintr error. sigaction.2 mtk note circumstances in which each sa_* flag is meaningful. mtk describe posix specification, and linux semantics for sa_nocldwait when establishing a handler for sigchld. mtk add pointer under sa_restart to new text in signal(7) describing system call restarting. mtk other minor edits. truncate.2 mtk errors: added eintr error. a few minor rewordings. wait.2 mtk remove statement that wuntraced and wcontinued only have effect if sa_nocldstop has not been set for sigchld. that's not true. errno.3 mtk add a pointer to signal(7) for further explanation of eintr. getgrouplist.3 mtk see also: add passwd(5). readdir.3 mtk remove from synopsis; posix.1-2001 does not require it. some minor rewordings. sleep.3 mtk return value: explicitly mention interruption by signal handler. see also: add signal(7). usleep.3 mtk posix.1-2001 also only documents einval. group.5 mtk see also: add getgrent(3), getgrnam(3). passwd.5 mtk see also: add getpwent(3), getpwnam(3). proc.5 mtk add pointer to description of /proc/pid/cpuset in cpuset(7). signal.7 mtk add a section describing system call restarting, and noting which system calls are affected by sa_restart, and which system calls are never restarted. mtk describe the aberrant linux behavior whereby a stop signal plus sigcont can interrupt some system calls, even if no signal handler has been established, and note the system calls that behave this way. mtk note a few more architectures on which signal numbers are valid. see also: added a number of pages. mtk update async-signal-safe function list for posix.1-2004 (which adds sockatmark()). ==================== changes in man-pages-3.04 ==================== released: 2008-07-15, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andrea arcangeli andreas mohr andrew morgan erik bosman john brooks nikanth karthikesan pavel heimlich petr gajdos sam varshavchik serge hallyn sripathi kodi vincent lefevre apologies if i missed anyone! web site -------- licenses.html mtk a page describing the preferred licenses for new pages that are contributed to man-pages. new and rewritten pages ----------------------- utimensat.2 mtk new page documenting the utimensat() system call, new in 2.6.22, and futimens() library function. end.3 mtk documents etext, edata, and end symbols. newly documented interfaces in existing pages --------------------------------------------- memchr.3 mtk add description of rawmemchr(). proc.5 mtk document /proc/config.gz (new in kernel 2.6). mtk, based on text from documentation/vm/sysctl.txt document /proc/sys/vm/oom_kill_allocating_task (new in linux 2.6.24). document /proc/sys/vm/oom_dump_tasks (new in linux 2.6.25). document /proc/sys/vm/panic_on_oom (new in linux 2.6.18). new links --------- edata.3 etext.3 mtk links to end.3. futimens.3 mtk link to new utimensat.2. getdate_err.3 mtk link to getdate.3. h_errno.3 mtk link to gethostbyname.3. optarg.3 opterr.3 optind.3 optopt.3 mtk links to getopt.3. rawmemchr.3 mtk link to memchr.3. sys_errlist.3 sys_nerr.3 mtk links to perror.3. global changes -------------- various pages mtk s/parameter/argument/ when talking about the things given to a function call, for consistency with majority usage. various pages mtk s/unix/unix/, when not used as part of a trademark, for consistency with majority usage in pages. various pages mtk, after a note from alain portal put see also entries into alphabetical order. various pages mtk remove period at end of see also list. various pages mtk, after a note by alain portal even when the conforming to section is just a list of standards, they should be terminated by a period. getpriority.2 mb_len_max.3 mb_cur_max.3 fwide.3 mblen.3 rtime.3 st.4 proc.5 bootparam.7 man-pages.7 utf-8.7 tcp.5 mtk / alain portal small wording fixes -- express <=, <, >=, > in words when in running text. sched_setparam.2 sched_setscheduler.2 getgrent_r.3 hash.3 mtk minor rewording w.r.t. use of the term "parameter". typographical or grammatical errors have been corrected in several other places. (many, many thanks to alain portal!) changes to individual pages --------------------------- capget.2 andrew morgan update in line with addition of file capabilities and 64-bit capability sets in kernel 2.6.2[45]. clock_nanosleep.2 mtk add "link with -lrt" to synopsis. getrusage.2 sripathi kodi document rusage_thread, new in 2.6.26. mtk improve description of rusage_children. add pointer to /proc/pid/stat in proc(5). other minor clean-ups. ioprio_set.2 nikanth karthikesan since linux 2.6.25, cap_sys_admin is longer required to set a low priority (ioprio_class_idle). mount.2 mtk since linux 2.6.26, ms_rdonly honors bind mounts. openat.2 mtk see also: add utimensat(3). prctl.2 serge hallyn, with some edits/input from mtk document pr_capbset_read and pr_capbset_drop. erik bosman document pr_get_tsc and pr_set_tsc. mtk, reviewed by andrea arcangeli document pr_set_seccomp and pr_get_seccomp. mtk pr_set_keepcaps and pr_get_keepcaps operate on a per-thread setting, not a per-process setting. mtk clarify fork(2) details for pr_set_pdeathsig. mtk add description of pr_set_securebits and pr_get_securebits, as well as pointer to further info in capabilities(7). mtk pr_get_endian returns endianness info in location pointed to by arg2 (not as function result, as was implied by previous text). mtk expand description of pr_set_name and pr_get_name. mtk return value: bring up to date for various options. mtk various improvements in errors. mtk note that pr_set_timing setting of pr_timing_timestamp is not currently implemented. mtk minor changes: * clarify wording for pr_get_unalign, pr_get_fpemu, and pr_get_fpexc. * some reformatting of kernel version information. * reorder pr_get_endian and pr_set_endian entries. readlinkat.2 john brooks / mtk fix and reword erroneous return value text. recv.2 mtk noted which flags appeared in linux 2.2. sched_setaffinity.2 mtk, after a fedora downstream patch update type used for cpusetsize argument in synopsis. select.2 andreas mohr / mtk clarify "zero timeout" case. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=490868. send.2 mtk noted which flags appeared in linux 2.2. sigaction.2 mtk document si_overrun and si_tid fields of siginfo structure. add some text for si_trapno field. the si_errno field is *generally* unused. mtk put descriptions of sa_* constants in alphabetical order. signal.2 mtk rewrote and expanded portability discussion. notes: show the raw prototype of signal() (without use of sighandler_t). signalfd.2 mtk modify description of ssi_trapno field. swapon.2 mtk fix two version number typos for max_swapfiles discussion: s/2.6.10/2.4.10/ utime.2 mtk see also: add utimensat(2), futimens(3). dl_iterate_phdr.3 alain portal see also: add elf(5). crypt.3 mtk, after a fedora downstream patch describe additional encryption algorithms. see also: https://bugzilla.redhat.com/show_bug.cgi?id=428280. errno.3 mtk small rewrites in description. exec.3 mtk, after a note from alain portal small rewording. exp10.3 alain portal see also: add log10(3). exp2.3 alain portal add c99 to conforming to. fgetgrent.3 alain portal add references to group(5). mtk minor rewordings. see also: add fopen(3). fgetpwent.3 alain portal add reference to passwd(5). mtk minor rewordings. see also: add fopen(3). frexp.3 alain portal add c99 to conforming to. futimes.3 mtk see also: remove futimesat(2); add utimensat(2). getopt.3 mtk add details on initial value of optind, and note that it can be reset (to 1) to restart scanning of an argument vector. add a notes section describing the glibc-specific behavior when optind is reset to 0 (rather than 1). see http://groups.google.com/group/comp.unix.programmer/browse_thread/thread/be0d0b7a07a165fb mtk note glibc extensions under conforming to. getspnam.3 mtk improve comments on struct spwd. getpw.3 alain portal return value: note that errno is set on error. mtk add einval error. insque.3 mtk / alain portal minor rewordings. log.3 alain portal remove unnecessary sentence in errors. log10.3 mtk see also: add exp10(3). offsetof.3 alain portal small wording improvement. pow.3 alain portal remove unnecessary sentence in errors. printf.3 mtk / alain portal many small formatting fixes. proc.5 mtk remove redundant summary list of files in description of /proc/sys/kernel. make kernel version for /proc/sys/kernel/panic_on_oops more precise. make kernel version for /proc/sys/kernel/pid_max more precise. add documentation/sysctl/vm.txt to see also. other minor edits. profil.3 mtk / alain portal small wording improvement. rtime.3 mtk, after a note by alain portal clarify meaning of midnight on 1 jan 1900/1970. mtk remove netdate(1) and rdate(1) from see also, since these pages don't seem to exist on linux systems. scanf.3 vincent lefevre / mtk clarify treatment of initial white space by %% conversion specification. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=435648. mtk many small formatting fixes. stdin.3 alain portal rename considerations section to notes, and relocate to appropriate place on page. tmpfile.3 mtk, after a note by alain portal prepend "posix.1-2001 specifies that: " to the sentence stating that tmpfile() may write to stdout. (afaics, glibc's tmpfile() does not do this.) ttyname.3 alain portal remove unnecessary sentence in errors. wcsdup.3 alain portal make wording more precise: the memory allocated by wcsdup(3) *should* be freed with free(3). wordexp.3 alain portal / mtk move example into proper example section. tty_ioctl.4 mtk / petr gajdos the features in the "get and set window size" subsection require the inclusion of . capabilities.7 serge hallyn, plus a bit of work by mtk document file capabilities, per-process capability bounding set, changed semantics for cap_setpcap, and other changes in 2.6.2[45]. add cap_mac_admin, cap_mac_override, cap_setfcap. various smaller fixes. mtk, plus review by serge hallyn and andrew morgan add text detailing how cap_setpcap (theoretically) permits -- on pre-2.6.25 kernels, and 2.6.25 and later kernels with file capabilities disabled -- a thread to change the capability sets of another thread. add section describing rules for programmatically adjusting thread capability sets. add some words describing purpose of inheritable set. note existence of config_security_capabilities config option. describe rationale for capability bounding set. document securebits flags (new in 2.6.26). remove obsolete bugs section. see also: add getcap(8), setcap(8), and various libcap pages. mtk add text noting that if we set the effective flag for one file capability, then we must also set the effective flag for all other capabilities where the permitted or inheritable bit is set. mtk since linux 2.6.25, cap_sys_admin is no longer required for ioprio_set() to set ioprio_class_idle class. mtk reword discussion of cap_linux_immutable to be file-system neutral. man-pages.7 mtk a list of standards in the conforming to list should be terminated by a period. the list of pages in a see also list should not be terminated by a period. tcp.7 mtk correct a detail for sysctl_tcp_adv_win_scale. formatting fixes. ==================== changes in man-pages-3.05 ==================== released: 2008-07-23, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andries brouwer brian m. carlson fabian kreutz franck jousseaume sam varshavchik uli schlacter apologies if i missed anyone! new and rewritten pages ----------------------- matherr.3 mtk, with review by andries brouwer a description of the svid-specified mechanism for reporting math exceptions. see http://thread.gmane.org/gmane.linux.man/266. math_error.7 mtk, with review and suggested input from andries brouwer a description of how math functions report errors. see http://thread.gmane.org/gmane.linux.man/249. global changes -------------- various pages mtk s/floating point/floating-point/ when used attributively. various pages mtk for consistency with majority usage: s/plus infinity/positive infinity/ s/minus infinity/negative infinity/ typographical or grammatical errors have been corrected in several other places. changes to individual pages --------------------------- brk.2 mtk see also: add end(3). open.2 brian m. carlson / mtk remove ambiguity in description of support for o_excl on nfs. as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=491791. prctl.2 mtk place options in some semblance of alphabetical order. (no content or formatting changes were made.) cerf.3 mtk bump version number: these functions are still missing in glibc 2.8. fenv.3 mtk see also: add math_error(7). infinity.3 mtk see also: add math_error(7). nan.3 mtk remove unneeded "compile with" piece in synopsis. see also: add math_error(7). rpc.3 mtk / franck jousseaume fix errors introduced into a few prototypes when converting function declarations to use modern c prototypes in man-pages-2.75. ipv6.7 mtk, after a report from uli schlacter document the ipv6_v6only flag. ==================== changes in man-pages-3.06 ==================== released: 2008-08-05, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andreas jaeger andries brouwer fabian kreutz gernot tenchio sam varshavchik tolga dalman apologies if i missed anyone! new and rewritten pages ----------------------- erfc.3 mtk created after removing the erfc() material from erf.3. documents the complementary error function. y0.3 mtk created after removing the y*() material from j0.3. documents the bessel functions of the second kind. included errors section; noted that an exception is not raised on underflow, see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6806; and errno is not set on overflow, see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6808; included bugs section noting that errno is incorrectly set for pole error; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6807. scalbln.3 mtk created after removing the scalbln*() and scalbn*() material from scalb.3. documents scalbln() and scalbn() functions. included errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803. new and changed links --------------------- erfcf.3 erfcl.3 mtk changed these links to point to new erfc.3 page. scalblnf.3 scalblnl.3 scalbn.3 scalbnf.3 scalbnl.3 mtk changed these links to point to new scalbln.3 page. y0f.3 y0l.3 y1.3 y1f.3 y1l.3 yn.3 ynf.3 ynl.3 mtk changed these links to point to new y0.3 page. global changes -------------- various pages mtk s/floating point/floating-point/ when used attributively. typographical or grammatical errors have been corrected in several other places. changes to individual pages --------------------------- crypt.3 mtk tweak discuss text describing support for blowfish. ctime.3 mtk / gernot tenchio added some words to make clear that the string returned by ctime() and asctime() is null-terminated. math_error.7 sam varshavchik reverse order of synopsis and name sections. mtk notes: summarize the state of glibc support for exceptions and errno for error reporting. changes to individual pages (math functions) -------------------------------------------- almost all of the changes in this release relate to math man pages. very many changes were made to the math pages, including: * fixed feature test macros (ftms). often, the ftm requirements for the "float" and "long double" versions of a math function are different from the requirements for the "double" version. each math page now shows the correct ftm requirements for all three versions of the function(s) it describes. this may have required either a change to the existing ftm text (if the requirements for the "double" function were already described), or the addition of an ftm description to a synopsis where one was not previously present (typically because the "double" version of the function does not require any ftms to be defined). * conforming to: in many cases, posix.1-2001 was not mentioned. where a function is specified in posix.1-2001, this is now noted. also, statements about what other standards a function conforms to were generally clarified. (the wording about which functions conformed to c99 was previously often done as an add on sentence; now it is made part of the first sentence of the conforming to section, along with posix.1-2001.) * return value: in many cases, pages lacked descriptions of the return value when the function arguments are special values such as +0, -0, nan (not-a-number), +infinity, -infinity, etc. this has been fixed. i carried out tests on glibc 2.8 to ensure that all of these functions match the return value descriptions (and the posix.1-2001 requirements). * errors: many pages lacked a clear (or indeed any) description of how errno is set on error and what exception is raised for each error. this has been fixed. the errors sections are now generally headed up as per the posix.1 way of doing things, describing pole / range / domain errors, as applicable. i carried out tests on glibc 2.8 to ensure that all of these functions match the errors descriptions. deviations from posix.1-2001 requirements have been filed as glibc bug reports, and noted in the man pages. (the pages now describe the situation for errors as at glibc 2.8; i may eventually try and extend the text with descriptions of changes in older versions of glibc.) note: one point that has not been covered in any page is the circumstances that generate inexact (fe_inexact) exceptions. (the details for these exceptions are not specified in posix.1-2001, and i haven't gone looking for the standards that describe the details.) acos.3 mtk synopsis: added feature test macro requirements. return value: added details for special argument cases. rewrote errors section. updated conforming to. acosh.3 mtk synopsis: fixed feature test macro requirements. added return value section. rewrote errors section. updated conforming to. asin.3 mtk synopsis: added feature test macro requirements. return value: added details for special argument cases. rewrote errors section. updated conforming to. asinh.3 mtk synopsis: added feature test macro requirements. description: some rewording. return value: added details for special argument cases. added (null) errors section. updated conforming to. atan.3 mtk synopsis: added feature test macro requirements. description: some rewording. return value: added details for special argument cases. added (null) errors section. updated conforming to. atan2.3 mtk synopsis: added feature test macro requirements. description: some rewording. return value: added details for special argument cases. added (null) errors section. updated conforming to. atanh.3 mtk synopsis: fixed feature test macro requirements. added return value section. rewrote errors section. updated conforming to. added bugs section noting that pole error sets errno to edom, when it should be erange instead; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759. cbrt.3 mtk synopsis: fixed feature test macro requirements. added return value section. added (null) errors section. updated conforming to. ceil.3 mtk synopsis: added feature test macro requirements. description: enhanced. return value: added details for special argument cases. rewrote errors section. updated conforming to. notes: added some details. copysign.3 mtk added return value section. updated conforming to. cos.3 mtk synopsis: added feature test macro requirements. rewrote return value section. added errors section; noted errno is not set: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6780. updated conforming to. cosh.3 mtk synopsis: added feature test macro requirements. added return value section. added errors section. updated conforming to. erf.3 mtk removed the erfc() material (there is now a new erfc page). reason: the functions are logically separate; also their return values differ, and it would have been confusing to document them on the same page. synopsis: fixed feature test macro requirements. added return value section. added errors section; noted that errno is not set; see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785. updated conforming to. exp.3 mtk synopsis: added feature test macro requirements. added return value section. added errors section; noted that errno is not set; see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6786. updated conforming to. exp10.3 mtk synopsis: added feature test macro requirements. added return value section. added errors section; noted that errno is not set for underflow; see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6787. exp2.3 mtk added return value and errors sections. updated conforming to. expm1.3 mtk synopsis: fixed feature test macro requirements. added return value section. added errors section; noted that errno is not set for overflow; see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6788. updated conforming to. added bugs section, describing bogus underflow exception for -large, see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778; and describing bogus invalid exception for certain +large, see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814. fabs.3 mtk synopsis: added feature test macro requirements. added return value section. updated conforming to. fdim.3 mtk synopsis: added feature test macro requirements. description: some rewording. added return value section. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6796. updated conforming to. fenv.3 mtk make style of writing exception names consistent with other pages and posix.1-2001. updated conforming to. finite.3 mtk synopsis: fixed feature test macro requirements. floor.3 mtk synopsis: added feature test macro requirements. description: enhanced. return value: added details for special argument cases. rewrote errors section. updated conforming to. fma.3 mtk synopsis: added feature test macro requirements. description: some rewording. added return value section. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6801. updated conforming to. fmax.3 fmin.3 mtk name: make description clearer synopsis: added feature test macro requirements. synopsis: remove unneeded "compile with" piece. conforming to: added posix.1-2001. added return value and errors sections. fmod.3 mtk synopsis: added feature test macro requirements. return value: added details for special argument cases. rewrote errors section; noted that errno is not always set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783. updated conforming to. fpclassify.3 mtk minor wording changes. conforming to: added posix.1-2001. see also: add signbit(3). frexp.3 mtk synopsis: added feature test macro requirements. added details to return value section. added (null) errors section. conforming to: added posix.1-2001. gamma.3 mtk synopsis: fixed feature test macro requirements. added (null) return value section referring to tgamma(3). added (null) errors section referring to tgamma(3). conforming to: rewrote. hypot.3 mtk synopsis: fixed feature test macro requirements. description: note that calculation is done without causing undue overflow or underflow. added return value section. added errors section; noted that errno is not always set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6795. updated conforming to. ilogb.3 mtk synopsis: added feature test macro requirements. rewrote return value section. rewrote errors section; noted that errno is not set, and in some cases an exception is not raised; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794. conforming to: added posix.1-2001. isgreater.3 mtk name: make description clearer improve the description of isunordered(). added return value and errors sections. formatting fixes. a few wording improvements. j0.3 mtk removed material for the y*() functions to a separate y0.3 page. reason: the return values and errors/exceptions differ, and it would have been confusing to document them on the same page. added return value section. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6805. ldexp.3 mtk synopsis: added feature test macro requirements. added return value and errors sections. updated conforming to. lgamma.3 mtk note that these functions are deprecated. synopsis: fixed feature test macro requirements. added return value and errors sections referring to lgamma(3). added bugs section noting that pole error sets errno to edom, when it should be erange instead; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6777. log.3 mtk synopsis: added feature test macro requirements. added return value section. rewrote errors section. updated conforming to. log10.3 mtk synopsis: added feature test macro requirements. added return value section. rewrote errors section. updated conforming to. log1p.3 mtk synopsis: fixed feature test macro requirements. added return value section. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6792. updated conforming to. log2.3 mtk added return value section. rewrote errors section. updated conforming to. logb.3 mtk synopsis: fixed feature test macro requirements. description: added a little detail; some rewordings. return value: added details for special argument cases. rewrote errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6793. conforming to: added posix.1-2001. lrint.3 mtk description: some rewording. return value: added details for special argument cases. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6798. conforming to: added posix.1-2001. lround.3 mtk return value: added details for special argument cases. rewrote errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6797. conforming to: added posix.1-2001. modf.3 mtk synopsis: added feature test macro requirements. return value: added details for special argument cases. added (null) errors section. conforming to: added posix.1-2001. nan.3 mtk small wording changes. conforming to: added posix.1-2001. nextafter.3 mtk synopsis: fixed feature test macro requirements. return value: added details for special argument cases. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6799. conforming to: added posix.1-2001. pow.3 mtk synopsis: added feature test macro requirements. added return value section. rewrote errors section. updated conforming to. added bugs section noting that pole error sets errno to edom, when it should be erange instead; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6776. remainder.3 mtk synopsis: fixed feature test macro requirements. description: added some details. return value: added details for special argument cases. rewrote errors section; noted that errno is not always set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783. updated conforming to. added bugs section noting that remainder(nan(""), 0) wrongly causes a domain error; see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6779 remquo.3 mtk added return value section. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6801. updated conforming to. fmax.3 fmin.3 mtk name: make description clearer synopsis: added feature test macro requirements. synopsis: remove unneeded "compile with" piece. conforming to: added posix.1-2001. added return value and errors sections. fmod.3 mtk synopsis: added feature test macro requirements. return value: added details for special argument cases. rewrote errors section; noted that errno is not always set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783. updated conforming to. fpclassify.3 conforming to: added posix.1-2001. rint.3 mtk synopsis: fixed feature test macro requirements. description: added some details. return value: added details for special argument cases. errors: no errors can occur (previous text was misleading). conforming to: added posix.1-2001. notes: point out that lrint() may be preferred in some cases. round.3 mtk description: added some details. return value: added details for special argument cases. errors: no errors can occur (previous text was misleading). conforming to: added posix.1-2001. notes: point out that lround() may be preferred in some cases. scalb.3 mtk removed the scalbn() and scalbln() material to a separate scalbln.3 page. reason: scalb() is obsolete; also the exception/error conditions differ somewhat, so that it would have been confusing to document them on the same page. synopsis: fixed feature test macro requirements. description: some rewrites and added details. added return value section. added errors section; noted that errno is not set; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803 and http://sources.redhat.com/bugzilla/show_bug.cgi?id=6804. conforming to: rewrote. signbit.3 mtk synopsis: added feature test macro requirements. synopsis: remove unneeded "compile with" piece. added return value section. added (null) errors section. conforming to: added posix.1-2001. sin.3 mtk synopsis: added feature test macro requirements. added return value section. added errors section; noted errno is not set: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6781. updated conforming to. sincos.3 mtk description: added details for special argument cases. added (null) return value section. added errors section. sinh.3 mtk synopsis: added feature test macro requirements. added return value section. added errors section. updated conforming to. sqrt.3 mtk synopsis: added feature test macro requirements. added return value section. rewrote errors section. updated conforming to. tan.3 mtk synopsis: added feature test macro requirements. added return value section. added errors section. added errors section; noted errno is not set: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6782. updated conforming to. tanh.3 mtk synopsis: added feature test macro requirements. added return value section. added (null) errors section. updated conforming to. tgamma.3 mtk added return value section. rewrote errors section; noted that errno is not set / incorrectly set in some cases; see also http://sources.redhat.com/bugzilla/show_bug.cgi?id=6809 and http://sources.redhat.com/bugzilla/show_bug.cgi?id=6810. conforming to: added posix.1-2001. added notes section to hold text explaining origin of tgamma(). trunc.3 mtk return value: small rewording. conforming to: added posix.1-2001. added notes section explaining that result may be too large to store in an integer type. ==================== changes in man-pages-3.07 ==================== released: 2008-08-12, konolfingen contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alain portal andries brouwer christoph lameter cliff wickman fabian kreutz filippo santovito gerrit renker heikki orsila khalil ghorbal lee schermerhorn maxin john reuben thomas samuel thibault sam varshavchik soh kam yung stephane chazelas pavel heimlich reuben thomas apologies if i missed anyone! new and rewritten pages ----------------------- move_pages.2 christoph lameter, various edits and improvements by mtk documentation of the move_pages() system call. this page was formerly part of the numactl package, but really belongs in man-pages (since it describes a kernel interface). clock_getcpuclockid.3 mtk new page documenting the clock_getcpuclockid() library function, available since glibc 2.2. udplite.7 gerrit renker document the linux implementation of the udp-lite protocol, new in linux 2.6.20. newly documented interfaces in existing pages --------------------------------------------- proc.5 christoph lameter, minor edits and improvements by mtk documentation of the /proc/pid/numa_maps file. this material was formerly the numa_maps.5 page in the numactl package, but really belongs in man-pages (since it describes a kernel interface). global changes -------------- nanosleep.2 inet_ntop.3 inet_pton.3 scanf.3 initrd.4 mtk fix mis-ordered (.sh) sections. connect.2 socket.2 rtnetlink.3 arp.7 ddp.7 ip.7 ipv6.7 netlink.7 packet.7 raw.7 rtnetlink.7 socket.7 tcp.7 udp.7 unix.7 x25.7 mtk s/pf_/af_/ for socket family constants. reasons: the af_ and pf_ constants have always had the same values; there never has been a protocol family that had more than one address family, and posix.1-2001 only specifies the af_* constants. typographical or grammatical errors have been corrected in several other places. changes to individual pages --------------------------- execve.2 mtk the floating-point environment is reset to the default during an execve(). get_mempolicy.2 lee schermerhorn misc cleanup of get_mempolicy(2): + mention that any mode flags will be saved with mode. i don't bother to document mode flags here because we already have a pointer to set_mempolicy(2) for more info on memory policy. mode flags are discussed there. + remove some old, obsolete [imo] notes and 'roff comments. lee schermerhorn update the get_mempolicy(2) man page to add in the description of the mpol_f_mems_allowed flag, added in 2.6.23. mtk document additional einval error that occurs is mpol_f_mems_allowed is specified with either mpol_f_addr or mpol_f_node. getitimer.2 mtk conforming to: posix.1-2008 marks getitimer() and setitimer() obsolete. mbind.2 lee schermerhorn fix error conditions, now that the kernel silently ignores nodes outside the task's cpuset, as long as one valid node remains. now that cpuset man page exists, we can refer to it. remove stale comment regarding lack thereof. lee schermerhorn add brief discussion of mode flags. lee schermerhorn attempt to clarify discussion of mpol_default. mtk fix uri reference for libnuma. mprotect.2 mtk / maxin john remove efault from errors. under enomem error, note that efault was the error produced in some cases for kernels before 2.4.19. msgctl.2 mtk, after a note from filippo santovito in the ipc_perm structure definition, some fields were incorrectly named: s/key/__key/ and s/seq/__seq/. set_mempolicy.2 lee schermerhorn fix up the error return for nodemask containing nodes disallowed by the process' current cpuset. disallowed nodes are now silently ignored, as long as the nodemask contains at least one node that is on-line, allowed by the process' cpuset and has memory. now that we have a cpuset man page, we can refer to cpusets directly in the man page text. lee schermerhorn another attempt to rationalize description of mpol_default. since ~2.6.25, the system default memory policy is "local allocation". mpol_default itself is a request to remove any non-default policy and "fall back" to the surrounding context. try to say that without delving into implementation details. lee schermerhorn add discussion of mempolicy mode flags to set_mempolicy(2). this adds another reason for einval. setpgid.2 mtk conforming to: posix.1-2008 marks setpgrp() obsolete. semctl.2 mtk, after a note from filippo santovito in the ipc_perm structure definition, some fields were incorrectly named: s/key/__key/ and s/seq/__seq/. shmctl.2 filippo santovito / mtk in the ipc_perm structure definition, some fields were incorrectly named: s/key/__key/ and s/seq/__seq/. utime.2 mtk conforming to: posix.1-2008 marks utime() obsolete. conforming to: posix.1-2008 removes the posix.1-2001 legacy marking of utimes(), so mention of this point has been removed from the page. vfork.2 mtk conforming to: posix.1-2008 removes the specification of vfork(). atan2.3 fabian kreutz see also add carg(3). bcmp.3 mtk conforming to: posix.1-2008 removes the specification of bcmp(). bsd_signal.3 mtk conforming to: posix.1-2008 removes the specification ofcw bsd_signal(). bzero.3 mtk conforming to: posix.1-2008 removes the specification of bzero(). cexp2.3 mtk availability: these functions are still not in glibc as at version 2.8. clock_getres.3 mtk see also: add clock_getcpuclockid(3). clog2.3 mtk availability: these functions are still not in glibc as at version 2.8. ctime.3 mtk posix.1-2008 marks asctime(), asctime_r(), ctime(), and ctime_r() as obsolete. dprintf.3 mtk conforming to: these functions are nowadays in posix.1-2008. ecvt.3 mtk conforming to: posix.1-2008 removes the specifications of ecvt() and fcvt(). ftime.3 mtk conforming to: posix.1-2008 removes the specification of ftime(). ftw.3 mtk conforming to: posix.1-2008 marks ftw() as obsolete. gcvt.3 mtk conforming to: posix.1-2008 removes the specification of gcvt(). getcwd.3 reuben thomas / mtk clarify description of getcwd() for buf==null case; conforming to: according to posix.1, the behavior of getcwd() is unspecified for the buf==null case. mtk add an introductory paragraph giving an overview of what these functions do. fix error in description of getwd(): it does not truncate the pathname; rather, it gives an error if the pathname exceeds path_max bytes. rewrote return value section. add einval enametoolong errors for getwd(). various other clarifications and wording fixes. conforming to: posix.1-2001 does not define any errors for getwd(). conforming to: posix.1-2008 removes the specification of getwd(). gethostbyname.3 mtk conforming to: posix.1-2008 removes the specifications of gethostbyname(), gethostbyaddr(), and h_errno. gets.3 mtk conforming to: posix.1-2008 removes the specification of gets(). iconv.3 iconv_close.3 iconv_open.3 mtk versions: these functions are available in glibc since version 2.1. index.3 mtk conforming to: posix.1-2008 removes the specifications of index() and rindex(). isalpha.3 mtk conforming to: posix.1-2008 marks isalpha() as obsolete. makecontext.3 mtk conforming to: posix.1-2008 removes the specifications of makecontext() and swapcontext(). memchr.3 mtk versions: memrchr() since glibc 2.2; rawmemchr() since glibc 2.1. mempcpy.3 mtk versions: mempcpy() since glibc 2.1. mktemp.3 mtk conforming to: posix.1-2008 removes the specification of mktemp(). opendir.3 mtk conforming to: posix.1-2008 specifies fdopendir(). rand.3 mtk conforming to: posix.1-2008 marks rand_r() as obsolete. siginterrupt.3 mtk conforming to: posix.1-2008 marks siginterrupt() as obsolete. sigset.3 mtk conforming to: posix.1-2008 marks sighold(), sigignore(), sigpause(), sigrelse(), and sigset() as obsolete. strchr.3 mtk versions: strchrnul() since glibc 2.1.1. tempnam.3 mtk conforming to: posix.1-2008 marks tempnam() as obsolete. tmpnam.3 mtk conforming to: posix.1-2008 marks tmpnam() as obsolete. toascii.3 mtk conforming to: posix.1-2008 marks toascii() as obsolete. ualarm.3 mtk conforming to: posix.1-2008 removes the specification of ualarm(). ulimit.3 mtk conforming to: posix.1-2008 marks ulimit() as obsolete. usleep.3 mtk conforming to: posix.1-2008 removes the specification of usleep(). standards.7 mtk updated details for posix.1-2008, and noted that if posix.1-2001 is listed in the conforming to section of a man page, then the reader can assume that the interface is also specified in posix.1-2008, unless otherwise noted. time.7 mtk see also: add clock_getcpuclockid(3). udp.7 mtk see also: add udplite(7). changes to individual pages (math functions) -------------------------------------------- various changes here following on from the big update to the math pages in the previous release. test results going back glibc 2.3.2 (so far) allowed updates to various pages to note changes in historical behavior for error reporting by math functions. thanks to the following people for providing me with test results on various distributions and glibc versions: alain portal, andries brouwer, fabian kreutz, heikki orsila, khalil ghorbal, pavel heimlich, reuben thomas, samuel thibault, soh kam yung, and stephane chazelas cabs.3 cacos.3 cacosh.3 carg.3 casin.3 casinh.3 catan.3 catanh.3 ccos.3 ccosh.3 cexp.3 cimag.3 clog.3 clog10.3 conj.3 cpow.3 cproj.3 creal.3 csin.3 csinh.3 csqrt.3 ctan.3 ctanh.3 exp10.3 exp2.3 fdim.3 fenv.3 fma.3 fmax.3 fmin.3 log2.3 lrint.3 lround.3 nan.3 pow10.3 remquo.3 round.3 scalbln.3 sincos.3 tgamma.3 trunc.3 mtk added versions section noting that these functions first appeared in glibc in version 2.1. cosh.3 mtk bugs: in glibc 2.3.4 and earlier, an fe_overflow exception is not raised when an overflow occurs. fenv.3 mtk / fabian kreuz provide more detail in the description of rounding modes. add text describing flt_rounds (formerly in fma.3). add bugs section pointing out the flt_rounds does not reflect changes by fesetround(). fma.3 mtk remove text about flt_rounds, replacing with a cross-reference to fenv(3). fpclassify.3 mtk conforming to: note that the standards provide a weaker guarantee for the return value of isinf(). log.3 mtk bugs: in glibc 2.5 and earlier, log(nan("")) produces a bogus fe_invalid exception. lround.3 mtk add reference to fenv(3) for discussion of current rounding mode. nextafter.3 mtk bugs: in glibc 2.5 and earlier these functions do not raise an fe_underflow exception on underflow. pow.3 mtk bugs: described buggy nan return when x is negative and y is large. see also: http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866. bugs: note the bogus fe_invalid exception that occurred in glibc 2.3.2 and earlier on overflow and underflow. remainder.3 mtk add reference to fenv(3) for discussion of current rounding mode. round.3 mtk add reference to fenv(3) for discussion of current rounding mode. scalb.3 mtk conforming to: posix.1-2008 removes the specification of scalb(). tgamma.3 mtk bugs: in glibc 2.3.3, tgamma(+-0) produced a domain error instead of a pole error. y0.3 mtk in glibc 2.3.2 and earlier, these functions do not raise an fe_invalid exception for a domain error. math_error.7 mtk rewrite introductory paragraph. point out that a nan is commonly returned by functions that report a domain error. ==================== changes in man-pages-3.08 ==================== released: 2008-08-27, zurich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: gerrit renker li zefan mike bianchi sam varshavchik venkatesh srinivas vijay kumar apologies if i missed anyone! new and rewritten pages ----------------------- getnetent_r.3 mtk documents getnetent_r(), getnetbyname_r(), and getnetbyaddr_r(), the reentrant equivalents of getnetent(), getnetbyname(), and getnetbyaddr(). getprotoent_r.3 mtk documents getprotoent_r(), getprotobyname_r(), and getprotobynumber_r(), the reentrant equivalents of getprotoent(), getprotobyname(), and getprotobynumber(). getrpcent_r.3 mtk documents getrpcent_r(), getrpcbyname_r(), and getrpcbynumber_r(), the reentrant equivalents of getrpcent(), getrpcbyname(), and getrpcbynumber(). getservent_r.3 mtk documents getservent_r(), getservbyname_r(), and getservbyport_r(), the reentrant equivalents of getservent(), getservbyname(), and getservbyport(). numa.7 mtk a new page giving overview details for the linux numa interfaces. incorporates some material from mbind.2, and the description of /proc/pid/numa_maps from proc.5. newly documented interfaces in existing pages --------------------------------------------- crypt.3 mtk add description of crypt_r(). new and changed links --------------------- crypt.3 mtk new link to crypt.3. getnetbyname_r.3 getnetbyaddr_r.3 mtk new links to new getnetent_r.3. getprotobyname_r.3 getprotobynumber_r.3 mtk new links to new getprotoent_r.3. getrpcbyname_r.3 getrpcbynumber_r.3 mtk new links to new getrpcent_r.3. getservbyname_r.3 getservbyport_r.3 mtk new links to new getservent_r.3. numa_maps.5 mtk link to new numa(7) page, which incorporates the /proc/pid/numa_maps description. as part of the numactl() package, the /proc/pid/numa_maps documentation was in a numa_maps.5 page; this link ensures that "man 5 numa_maps" still works. (eventually, we may want to remove this link.) global changes -------------- get_mempolicy.2 mbind.2 move_pages.2 set_mempolicy.2 mtk add reference to numa(7) for information on library support. added a versions section. see also: add numa(7). faccessat.2 fchmodat.2 fchownat.2 fstatat.2 mkdirat.2 mknodat.2 linkat.2 openat.2 readlinkat.2 renameat.2 symlinkat.2 unlinkat.2 mkfifoat.3 psignal.3 strsignal.3 mtk these interfaces are specified in posix.1-2008. changes to individual pages --------------------------- eventfd.2 vijay kumar when an eventfd overflows, select() indicates the file as both readable and writable (not as having an exceptional condition). fcntl.2 mtk f_dupfd_cloexec is specified in posix.1-2008. getrlimit.2 mtk notes: add text mentioning the shell 'ulimit' (or 'limit') built-in command for setting resource limits. gettimeofday.2 mtk conforming to: posix.1-2008 marks gettimeofday() as obsolete. link.2 mtk note kernel version where linux stopped following symbolic links in 'oldpath'; see also http://lwn.net/articles/294667. posix.1-2008 makes it implementation-dependent whether or not 'oldpath' is dereferenced if it is a symbolic link. add a reference to linkat(2) for an interface that allows precise control of the treatment of symbolic links. mbind.2 mtk remove material on library support and numactl; that material is now in numactl.7. mmap.2 mtk add kernel version numbers for map_32bit. add some details on map_32bit (see http://lwn.net/articles/294642). move_pages.2 mtk added versions (from kernel 2.6.18) and conforming to sections. open.2 mtk o_cloexec is specified in posix.1-2008. socket.2 mtk s/d/domain/ for name of argument. add reference to socket(2) for further information on domain, type, and protocol arguments. utimensat.2 mtk conforming to: posix.1-2008 specifies utimensat() and futimens(). dirfd.3 mtk conforming to: add posix.1-2008; other minor changes. exec.3 mtk small rewording: "s/returned/failed with/ [an error]". fmemopen.3 mtk since glibc 2.7, it is possible to seek past the end of a stream created by open_memstream(). add a bugs section describing the bug in earlier glibc versions. gethostbyname.3 mtk clarify exactly which functions are obsoleted by getnameinfo() and getaddrinfo(). getnetent.3 mtk rephrase description in terms of a database, rather than a file. note that each of the get*() functions opens a connection to the database if necessary. the database connection is held open between get*() calls if 'stayopen' is non-zero (not necessarily 1). s/zero terminated list/null-terminated list/ mtk in glibc 2.2, the type of the 'net' argument for getnetbyaddr() changed from 'long' to 'uint32_t'. mtk note that the gethostbyaddr() 'net' argument is in host byte order. mtk return value: emphasize that returned pointer points to a statically allocated structure. see also: add getnetent_r.3. getprotoent.3 mtk rephrase description in terms of a database, rather than a file. note that each of the get*() functions opens a connection to the database if necessary. the database connection is held open between get*() calls if 'stayopen' is non-zero (not necessarily 1). s/zero terminated list/null-terminated list/ mtk return value: emphasize that returned pointer points to a statically allocated structure. see also: add getprotoent_r.3. getrpcent.3 mtk s/rpc/rpc/. rephrase description in terms of a database, rather than a file. note that each of the get*() functions opens a connection to the database if necessary. s/zero terminated list/null-terminated list/ mtk return value: emphasize that returned pointer points to a statically allocated structure. see also: add getrpcent_r.3. getservent.3 mtk rephrase description in terms of a database, rather than a file. note that each of the get*() functions opens a connection to the database if necessary. the database connection is held open between get*() calls if 'stayopen' is non-zero (not necessarily 1). s/zero terminated list/null-terminated list/ mtk return value: emphasize that returned pointer points to a statically allocated structure. see also: add getservent_r.3. mkdtemp.3 mtk conforming to: this function is specified in posix.1-2008. mq_notify.3 venkatesh srinivas s/sigev_notify_function/sigev_thread_function/ as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=494956. realpath.3 mtk relocate text for resolved_path==null case to description. posix.1-2001 leaves the resolved_path==null case as implementation-defined; posix.1-2008 specifies the behavior described in this man page. sem_init.3 mtk posix.1-2008 rectifies the posix.1-2001 omission, specifying that zero is returned by a successful sem_init() call. core.5 mike bianchi / mtk make the page more helpful to non-programmers by referencing the documentation of the shell's 'ulimit' command in the discussion of rlimit_core and rlimit_fsize. see also: add bash(1). mtk note that a core dump file can be used in a debugger. proc.5 mtk remove /proc/pid/numa_maps material (it is now in numa(7)). cpuset.7 mtk see also: add numa(7). inotify.7 mtk / li zefan explain bug that occurred in coalescing identical events in kernels before 2.6.25. (see commit 1c17d18e3775485bf1e0ce79575eb637a94494a2 "a potential bug in inotify_user.c" in the 2.6.25 changelog.) pthreads.7 mtk update thread-safe functions list with changes in posix.1-2008. see also: add proc(5). signal.7 mtk update list of async-signal-safe functions for posix.1-2008. ==================== changes in man-pages-3.09 ==================== released: 2008-09-10, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: bernd eckenfels bruno haible carsten emde christopher head h. peter anvin jan engelhardt joe korty marko kreen martin (joey) schulze mats wichmann michael schurter mike bianchi mike frysinger sam varshavchik suka timothy s. nelson tolga dalman török edwin apologies if i missed anyone! new and rewritten pages ----------------------- fopencookie.3 mtk document fopencookie(3), a library function that allows custom implementation of a stdio stream. networks.5 martin (joey) schulze, with a few light edits by mtk documents the /etc/networks file. global changes -------------- various pages mtk s/time zone/timezone/ for consistency across pages and with posix.1. kill.2 sigaction.2 sigpending.2 sigprocmask.2 sigsuspend.2 confstr.3 ctermid.3 ctime.3 ferror.3 flockfile.3 fopen.3 getaddrinfo.3 getgrnam.3 getnameinfo.3 getopt.3 getpwnam.3 longjmp.3 popen.3 rand.3 readdir.3 setjmp.3 sigsetops.3 sigwait.3 strtok.3 tzset.3 unlocked_stdio.3 mtk add/fix feature test macro requirements. changes to individual pages --------------------------- fcntl.2 mtk, after a note by mike bianchi more clearly and consistently describe whether or not the third argument to fcntl() is required, and what its type should be. mtk move description of negative l_len from notes, integrating it into the discussion of file locking. minor rewrites of the text on file locking. getrusage.2 bernd eckenfels see also: add clock(3), clock_gettime(3). see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=353475 ioctl_list.2 mtk remove old sentence about where to send updates for this page. add more detail on mount options that prevent updates to atime. sched_setscheduler.2 carsten emde update kernel version numbers relating to real-time support. stat.2 h. peter anvin note that lstat() will generally not trigger automounter action, whereas stat() will. clock.3 bernd eckenfels see also: add clock_gettime(3). see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=353475 clock_getres.3 tolga dalman / mtk add "link with -lrt" to synopsis; remove now redundant sentence mentioning librt from notes. getdate.3 mtk rewrite description of getdate_r() and integrate into main text (rather than describing in notes). other parts rewritten for greater clarity. make it clearer in the main text that glibc does not implement %z; remove discussion of that point from notes. added an example program. hsearch.3 mtk noted that table size as specified by 'nel' is immutable. described differences between hsearch() and hsearch_r(). added missing pieces to return value. added a number of new entries under errors. notes: added some basic advice on sizing the hash table; noted that when a table is destroyed, the caller is responsible for freeing the buffers pointed to by 'key' and 'data' fields. one of the bugs was fixed in glibc 2.3. rewrote and clarified various other pieces. rename arguments for reentrant functions, using same name as glibc headers: s/ret/retval/; s/tab/htab/. mtk, after a suggestion by timothy s. nelson integrate discussion of reentrant functions into main discussion (rather than as a short paragraph at the end). iconv.3 bruno haible describe "shift sequence" input. ptsname.3 sukadev fix return type of ptsname_r() in synopsis. readdir.3 h. peter anvin s/stat(2)/lstat(2)/ when discussing d_type (since we are talking about a case where we might be interested to whether the file itself is a symbolic link). sigsetops.3 chris head, signed-off-by: mike frysinger fix typo: s/sigdelset/sigorset/ proc.5 mats wichmann / mtk s/\[number]/[pid]/ in file names for /proc/pid files. and similar changes for task/[tid] sub-directories. mtk / mats wichmann in the description if /proc/[pid]/environ, remove reference to lilo(8)/grub(8) since there seems to be nothing in those pages that related to this /proc file. michael schurter / mtk remove sentence wrongly saying that /proc/meminfo reports info in bytes; see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=462969 mtk note that /proc/meminfo reports system-wide memory usage statistics. joe korty document new fields in /proc/interrupts that were added in linux 2.6.24. unix.7 marko kreen since glibc 2.8, _gnu_source must be defined in order to get the definition of the ucred structure from . ==================== changes in man-pages-3.10 ==================== released: 2008-09-23, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andré goddard rosa george spelvin pavel heimlich sam varshavchik john reiser apologies if i missed anyone! global changes -------------- closedir.3 dirfd.3 readdir.3 rewinddir.3 scandir.3 seekdir.3 telldir.3 mtk fix 'dir' argument name: should be 'dirp'. posix.1-2008 and glibc call this argument 'dirp' (consistent with the fact that it is a *pointer* to a dir structure). changes to individual pages --------------------------- clone.2 mtk, after a comment by john reiser clarify text describing getpid() caching bug for clone() wrapper. see also: http://sourceware.org/bugzilla/show_bug.cgi?id=6910 https://bugzilla.redhat.com/show_bug.cgi?id=417521 getpid.2 mtk, after a comment by john reiser describe getpid()'s pid caching and its consequences. timerfd_create.2 sam varshavchik s/it_interval/it_value/ when talking about timerfd_abstime. closedir.3 george spelvin clarify closedir()'s treatment of underlying file descriptor. tsearch.3 andré goddard rosa fix memory leak in example program. add use of tdestroy to example program. mtk add "#define _gnu_source" to example program. protocols.5 mtk, after a note from pavel heimlich remove see also references to nonexistent guides to yellow pages services.5 mtk remove some out-of-date bugs. mtk, after a note from pavel heimlich remove see also references to nonexistent guides to yellow pages and bind/hesiod docs. mtk remove crufty text about use of comma instead of slash to separate port and protocol. ==================== changes in man-pages-3.11 ==================== released: 2008-10-07, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andré goddard rosa eugene v. lyubimkin gergely soos kirill a. shutemov marko kreen maxin b. john maxin john michael kerrisk nicolas françois pavel heimlich ricardo catalinas jiménez sam varshavchik apologies if i missed anyone! new and rewritten pages ----------------------- umount.2 michael kerrisk create a new page for umount() and umount2() by extracting existing material from mount.2 page. new and changed links --------------------- umount2.2 michael kerrisk change link to point to new umount.2 the umount2() material migrated from mount.2 to umount.2 changes to individual pages --------------------------- execve.2 michael kerrisk _sc_arg_max is no longer necessarily constant posix.1-2001 says that the values returned by sysconf() are constant for the life of the process. but the fact that, since linux 2.6.23, arg_max is settable via rlimit_stack means _sc_arg_max is no longer constant, since it can change at each execve(). michael kerrisk linux now imposes a floor on the arg_max limit starting with linux 2.6.23, the arg_max limit became settable via (1/4 of) rlimit_stack. this broke abi compatibility if rlimit_stack was set such that arg_max was < 32 pages. document the fact that since 2.6.25 linux imposes a floor on arg_max, so that the old limit of 32 pages is guaranteed. for some background on the changes to arg_max in kernels 2.6.23 and 2.6.25, see: http://sourceware.org/bugzilla/show_bug.cgi?id=5786 http://bugzilla.kernel.org/show_bug.cgi?id=10095 http://thread.gmane.org/gmane.linux.kernel/646709/focus=648101, checked into 2.6.25 as commit a64e715fc74b1a7dcc5944f848acc38b2c4d4ee2. also some reordering/rewording of the discussion of arg_max. fallocate.2 michael kerrisk note lack of glibc wrapper; caller must use syscall(2) glibc doesn't (and quite probably won't) include a wrapper for this system call. therefore, point out that potential callers will need to use syscall(2), and rewrite the return value text to show things as they would be if syscall() is used. michael kerrisk refer reader to posix_fallocate(3) for portable interface add a para to start of page that points out that this is the low-level, linux-specific api, and point the reader to posix_fallocate(3) for the portable api. getdents.2 readdir.3 michael kerrisk d_type is currently only supported on ext[234] as at kernel 2.6.27, only ext[234] support d_type. on other file systems, d_type is always set to dt_unknown (0). getdents.2 michael kerrisk add an example program michael kerrisk comment out linux_dirent fields with varying location the location of the fields after d_name varies according to the size of d_name. we can't properly declare them in c; therefore, put those fields inside a comment. michael kerrisk the dt_* constants are defined in michael kerrisk remove header files from synopsis none of the header files provides what is needed. calls are made via syscall(2). michael kerrisk the programmer must define the linux_dirent structure point out that this structure is not defined in glibc headers. michael kerrisk s/dirent/linux_dirent/ the structure isn't currently defined in glibc headers, and the kernel name of the structure is 'linux_dirent' (as was already used in some, but not all, places in this page). getrlimit.2 michael kerrisk reword/relocate discussion of bsd's historical rlimit_ofile the old sentence sat on its own in an odd place, and anyway the modern bsds use the name rlimit_nofile. michael kerrisk refer to execve(2) for rlimit_stack's effect on arg_max refer the reader to new text in execve(2) that describes how (since linux 2.6.23) rlimit_stack determines the value of arg_max. getrusage.2 michael kerrisk rusage measures are preserved across execve(2) mlock.2 maxin john add eagain error. move_pages.2 nicolas françois make a detail of eperm error more precise mount.2 michael kerrisk add description of per-process namespaces describe per-process namespaces, including discussion of clone() and unshare clone_newns, and /proc/pid/mounts. michael kerrisk list a few other file systems that we may see in /proc/filesystems add some modern file systems to that list (xfs, jfs, ext3, reiserfs). michael kerrisk document ms_silent (and ms_verbose) mount.2 umount.2 michael kerrisk split umount*() out into a separate page the length of this page means that it's becoming difficult to parse which info is specific to mount() versus umount()/umount2(), so split the umount material out into its own page. pause.2 michael kerrisk remove mention of words "library function" this really is a system call. readdir.2 michael kerrisk the programmer must declare the old_linux_dirent structure glibc does not provide a definition of this structure. michael kerrisk s/dirent/old_linux_dirent/ nowadays, this is the name of the structure in the kernel sources. michael kerrisk remove words "which may change" these words are slightly bogus: although the interface is obsolete, for abi-compatibility reasons, the kernel folk should never be changing this interface. michael kerrisk remove header files from synopsis glibc doesn't provide any support for readdir(2), so remove these header files (which otherwise suggest that glibc does provide the required pieces). recv.2 nicolas françois move kernel version number to first mention to msg_errqueue. semop.2 kirill a. shutemov fix typo in example (the '&' before sop in the semop() call is unneeded.) send.2 michael kerrisk make kernel version for msg_confirm more precise s/2.3+ only/since linux 2.3.15/ sigaction.2 michael kerrisk refer reader to signal(7) for an overview of signals explain semantics of signal disposition during fork() and execve() refer to signal(7) for more details on signal mask. sigaltstack.2 michael kerrisk explain inheritance of alternate signal stack across fork(2) sigwaitinfo.2 michael kerrisk distinguish per-thread and process-wide signals a sentence clarifying that pending signal set is union of per-thread and process-wide pending signal sets. michael kerrisk these interfaces have per-thread semantics the page was previously fuzzy about whether these interfaces have process-wide or per-thread semantics. (e.g., now the page states that the calling *thread* (not process) is suspended until the signal is delivered.) sigpending.2 michael kerrisk explain effect of fork() and execve() for pending signal set michael kerrisk explain how thread's pending signal set is defined the pending set is the union of per-thread pending signals and process-wide pending signals. sigprocmask.2 michael kerrisk explain effects of fork() and execve() for signal mask splice.2 michael kerrisk note that splice_f_move is a no-op since kernel 2.6.21 syscall.2 michael kerrisk add more detail about wrapper functions add a few more details about work generally done by wrapper functions. note that syscall(2) performs the same steps. tkill.2 michael kerrisk einval error can also occur for invalid tgid the einval error on an invalid tgid for tgkill() was not documented; this change documents it. utimensat.2 michael kerrisk posix.1-2008 revision will likely affect ftms for futimens() make it clear that the posix.1 revision that is likely to affect the feature test macro requirements for futimens() is posix.1-2008. nicolas françois make various wordings a little more precise. the times argument point to *an array of* structures, and the man-page should say that consistently. wait4.2 michael kerrisk wait3() is a library function layered on wait4(). on linux wait3() is a library function implemented on top of wait4(). (knowing this is useful when using strace(2), for example.) atan2.3 nicolas françois fix error in description of range or return value in recent changes to the man page, mtk accidentally changed the description of the return value range to -pi/2..pi/2; the correct range is -pi..pi. cmsg.3 nicolas françois add parentheses after macro names. ctime.3 michael kerrisk clarify mktime()'s use of tm_isdst describe use of tm_isdst for input to mktime(); explain how mktime() modifies this field. (this field is left unchanged in case of error.) http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=500178 michael kerrisk clarify wording for ctime_r() and asctime_r() to indicate that the buffer must be at least 26 *bytes*. michael kerrisk minor rewording of mktime() description. floor.3 nicolas françois floor.3: fix error in description: s/smallest/largest/ hsearch.3 andré goddard rosa call hdestroy() after using hash table created by hcreate(), for the sake of completeness mq_getattr.3 michael kerrisk mq_getattr() and mq_setattr() are layered on mq_getsetattr(2) mq_getattr() and mq_setattr() are library functions layered on top of the mq_getsetattr(2) system call. (this is useful info for users of strace(1).) mq_receive.3 michael kerrisk mq_send() is a library function layered on mq_timedreceive() syscall this info is useful for users of strace(1). mq_send.3 michael kerrisk mq_send() is a library function layered on mq_timedsend() syscall this info is useful for users of strace(1). nextafter.3 nicolas françois make description more precise: s/next/largest/ readdir.3 michael kerrisk see also: add getdents(2) because readdir() is implemented on top of getdents(2). realpath.3 michael kerrisk clarify that returned pathname is null terminated also clarify that null-byte is included in path_max limit. proc.5 michael kerrisk rewrite and simplify description of /proc/mounts most of the relevant discussion is now under /proc/pid/mounts; all that needs to be here is a mention of the pre-2.4.19 system-wide namespace situation, and a reference to the discussion under /proc/pid/mounts. michael kerrisk add description of /proc/pid/mounts largely cribbed from existing /proc/mounts discussion, which is about to be rewritten. mq_overview.7 michael kerrisk add mq_notify() to list of lib. functions and syscalls in mq api signal.7 michael kerrisk improve description in name section add mention of sigaltstack(2). describe syscalls that synchronously wait for a signal, give overview of syscalls that block until a signal is caught add overview of interfaces for sending signals. michael kerrisk describe semantics w.r.t. fork() and execve() include text describing semantics of fork() and execve() for signal dispositions, signal mask, and pending signal set. ==================== changes in man-pages-3.12 ==================== released: 2008-10-29, bucaramanga contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: bert wesarg christian grigis christoph hellwig didier halesh s j.h.m. dassen (ray) jason spiro lefteris dimitroulakis michael b. trausch pierre cazenave stefan puiu apologies if i missed anyone! new and rewritten pages ----------------------- pthread_attr_init.3 michael kerrisk new page for pthread_attr_init(3) and pthread_attr_destroy(3) pthread_attr_setdetachstate.3 michael kerrisk new page for pthread_attr_setdetachstate(3) and pthread_attr_getdetachstate(3) pthread_attr_setguardsize.3 michael kerrisk new page for pthread_attr_setguardsize(3) and pthread_attr_getguardsize(3) pthread_attr_setscope.3 michael kerrisk new page for pthread_attr_setscope(3) and pthread_attr_getscope(3) pthread_attr_setstack.3 michael kerrisk new page for pthread_attr_setstack(3) and pthread_attr_getstack(3) pthread_attr_setstackaddr.3 michael kerrisk new page for pthread_attr_setstackaddr(3) and pthread_attr_getstackaddr(3) pthread_attr_setstacksize.3 michael kerrisk new page for pthread_attr_setstacksize(3) and pthread_attr_getstacksize(3) pthread_create.3 michael kerrisk new page describing pthread_create(3) pthread_detach.3 michael kerrisk new page for pthread_detach(3) pthread_equal.3 michael kerrisk new page for pthread_equal(3) pthread_exit.3 michael kerrisk new page describing pthread_exit(3) pthread_getattr_np.3 michael kerrisk new page for pthread_getattr_np(3) pthread_join.3 michael kerrisk new page for pthread_join(3) pthread_self.3 michael kerrisk new page for pthread_self(3) pthread_tryjoin_np.3 michael kerrisk new page for pthread_tryjoin_np(3) and pthread_timedjoin_np(3) newly documented interfaces in existing pages --------------------------------------------- dup.2 michael kerrisk add description of dup3() dup3() was added in kernel 2.6.27. epoll_create.2 michael kerrisk add description of new epoll_create1() the new epoll_create1() system call appeared in linux 2.6.27. eventfd.2 michael kerrisk describe eventfd2() and efd_nonblock and efd_cloexec linux 2.6.27 added eventfd(), which supports a flags argument that eventfd() did not provide. the flags so far implemented are efd_nonblock and efd_cloexec, inotify_init.2 michael kerrisk add description of inotify_init1() the inotify_init1() system call was added in linux 2.6.27. pipe.2 michael kerrisk add description of new pipe2() syscall pipe2() was added in 2.6.27. describe the o_nonblock and o_cloexec flags. signalfd.2 michael kerrisk describe signalfd4() and sfd_nonblock and sfd_cloexec linux 2.6.27 added signalfd4(), which supports a flags argument that signalfd() did not provide. the flags so far implemented are sfd_nonblock and sfd_cloexec. new and changed links --------------------- dup3.2 michael kerrisk new link to dup.2 dup.2 now contains the description of the new dup3() syscall. epoll_create1.2 michael kerrisk new link to epoll_create.2 epoll_create.2 now includes a description of the new epoll_create1() system call. eventfd2.2 michael kerrisk new link to eventfd.2 the eventfd.2 page has some details on the eventfd2() system call, which was new in linux 2.6.27. inotify_init1.2 michael kerrisk new link to inotify_init.2 inotify_init.2 now includes a description of the new inotify_init1() system call. pipe2.2 michael kerrisk new link to pipe.2 pipe(2) now contains a description of the new pipe2() syscall. pthread_attr_destroy.3 michael kerrisk new link to new pthread_attr_init.3 pthread_attr_getdetachstate.3 michael kerrisk new link to new pthread_attr_setdetachstate.3 pthread_attr_getguardsize.3 michael kerrisk new link to new pthread_attr_setguardsize.3 pthread_attr_getscope.3 michael kerrisk new link to new pthread_attr_setscope.3 pthread_attr_getstack.3 michael kerrisk new link to new pthread_attr_setstack.3 pthread_attr_getstackaddr.3 michael kerrisk new link to new pthread_attr_setstackaddr.3 pthread_attr_getstacksize.3 michael kerrisk new link to new pthread_attr_setstacksize.3 pthread_timedjoin_np.3 michael kerrisk new link to new pthread_tryjoin_np.3 signalfd4.2 michael kerrisk new link to signalfd.2 signalfd.2 now includes text describing signalfd4() system call, new in linux 2.6.27. global changes -------------- eventfd.2, getdents.2, mprotect.2, signalfd.2, timerfd_create.2, wait.2, backtrace.3, clock_getcpuclockid.3, end.3, fmemopen.3, fopencookie.3, getdate.3, getgrouplist.3, getprotoent_r.3, getservent_r.3, gnu_get_libc_version.3, inet.3, inet_pton.3, makecontext.3, matherr.3, offsetof.3, pthread_attr_init.3, pthread_create.3, pthread_getattr_np.3, sem_wait.3, strtol.3, core.5 michael kerrisk add ".ss program source" to example add ".ss program source" to clearly distinguish shell session and descriptive text from actual program code. eventfd.2, execve.2, getdents.2, ioprio_set.2, mprotect.2, signalfd.2, timerfd_create.2, wait.2, backtrace.3, clock_getcpuclockid.3, end.3, fmemopen.3, fopencookie.3, frexp.3, getdate.3, getgrouplist.3, getprotoent_r.3, getservent_r.3, gnu_get_libc_version.3, inet.3, inet_pton.3, makecontext.3, malloc.3, matherr.3, offsetof.3, pthread_attr_init.3, pthread_create.3, pthread_getattr_np.3, sem_wait.3, strftime.3, strtok.3, strtol.3, core.5, proc.5, cpuset.7, mq_overview.7 michael kerrisk format user input in shell sessions in boldface frexp.3, strftime.3, strtok.3 michael kerrisk relocate shell session above example program move the shell session text that demonstrates the use of the example program so that it precedes the actual example program. this makes the page consistent with the majority of other pages. changes to individual pages --------------------------- epoll_create.2 michael kerrisk say more about unused epoll_create() 'size' arg supply a little more explanation about why the 'size' argument of epoll_create() is nowadays ignored. eventfd.2 michael kerrisk remove crufty text relating to flags argument remove sentence saying that glibc adds a flags argument to the syscall; that was only relevant for the older eventfd() system call. getdents.2 christoph hellwig fix text relating to dt_unknown and 'd_type' support some file systems provide partial support for 'dt_type', returning dt_unknown for cases they don't support. update the discussion of 'd_type' and dt_unknown to support this. getpeername.2, getsockname.2 michael kerrisk see also: add ip(7) and unix(7) getsockopt.2 michael kerrisk einval can also occur if 'optval' is invalid in some cases, einval can occur if 'optval' is invalid. note this, and point reader to an example in ip(7). in response to: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=216092 inotify_init.2 pipe.2 timerfd_create.2 michael kerrisk clarify *_nonblock description make it clear that the nonblock flag sets an attribute in the new open file description. sched_yield.2 michael kerrisk rewrite description in terms of threads the text formerly described the operation of sched_yield() in terms of processes. it should be in terms of threads. michael kerrisk add notes text on appropriate use of sched_yield() strategic calls to sched_yield() can be used to improve performance, but unnecessary use should be avoided. sigaction.2 michael kerrisk clarify that sa_mask affects the *per-thread* signal mask the page didn't previously clearly explain the scope of the signal mask that is affected by sa_mask. signalfd.2 michael kerrisk remove crufty text relating to flags argument remove sentence saying that glibc adds a flags argument to the syscall; that was only relevant for the older signalfd() system call. sigprocmask.2 michael kerrisk clarify that sigprocmask() operates on a per-thread mask the first sentence of the page was vague on the scope of the attribute changed by sigprocmask(). reword to make this clearer and add a sentence in notes to explicitly state that the signal mask is a per-thread attribute. socket.2 michael kerrisk document sock_nonblock and sock_cloexec flags these flags, specified in the 'type' argument, are supported since linux 2.6.27. socketpair.2 michael kerrisk refer to socket(2) for sock_cloexec and sock_nonblock refer the reader to socket(2) for a description of the sock_cloexec and sock_nonblock flags, which are supported by socketpair() since linux 2.6.27. syscalls.2 michael kerrisk add new 2.6.27 system calls add pipe2(), dup3(), epoll_create1(), inotify_init1(), eventfd2(), signalfd4(). timerfd_create.2 michael kerrisk document timerfd_create() tfd_cloexec and tfd_nonblock tfd_cloexec and tfd_nonblock are supported since linux 2.6.27. vfork.2 michael kerrisk clarify meaning of "child releases the parent's memory" the man page was not explicit about how the memory used by the child is released back to the parent. ctime.3 michael kerrisk ctime_r() and localtime_r() need not set 'timezone' and 'daylight' the man page already noted that these functions need not set 'tzname', but things could be clearer: it tzset() is not called, then the other two variables also are not set. also, clarify that ctime() does set 'timezone' and 'daylight'. dlopen.3 michael kerrisk ld_library_path is inspected once, at program start-up make it clear that ld_library_path is inspected *once*, at program start-up. (verified from source and by experiment.) fmemopen.3 michael kerrisk document binary mode (mode 'b') glibc 2.9 adds support to fmemopen() for binary mode opens. binary mode is specified by inclusion of the letter 'b' in the 'mode' argument. getaddrinfo.3 michael kerrisk clarify error descriptions with some examples clarify the description of some errors by giving examples that produce the errors. (text added for eai_service and eai_socktype.) also, add an error case for eai_badflags. gethostbyname.3 michael kerrisk rationalize text on posix.1-2001 obsolete interfaces posix.1 marks gethostbyname(), gethostbyaddr(), and 'h_errno' as obsolete. the man page explained this, but with some duplication. remove the duplication, and otherwise tidy up discussion of this point. popen.3 michael kerrisk change one-line description in name s%process i/o%pipe stream to or from a process% michael kerrisk document 'e' (close-on-exec) flag glibc 2.9 implements the 'e' flag in 'type', which sets the close-on-exec flag on the underlying file descriptor. raise.3 michael kerrisk see also: add pthread_kill(3) readdir.3 christoph hellwig fix text relating to dt_unknown and 'd_type' support (this mirrors the previous change to getdents.2) some file systems provide partial support for 'dt_type', returning dt_unknown for cases they don't support. update the discussion of 'd_type' and dt_unknown to support this. strcpy.3 jason spiro strengthen warning about checking against buffer overruns http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=413940 tty_ioctl.4 michael kerrisk explain capability requirements for tioccons explain capability requirements for tioccons, and describe changes in 2.6.10 relating to capabilities. michael kerrisk explain capability requirements for various ioctls for tiocslcktrmios, tiocsctty, tiocexcl, explain the exact capability that is required (the text formerly just said "root" in each case). proc.5 michael kerrisk document /proc/sys/kernel/threads-max defines the system-wide limit on the number of threads (tasks). utmp.5 pierre cazenave it is just "other" who should not have write perms on utmp the page was vague before, saying that utmp should not be writable by any user. this isn't true: it can be, and typically is, writable by user and group. epoll.7 michael kerrisk mention epoll_create1() as part of epoll api epoll_create1() was added in linux 2.6.27, and extends the functionality of epoll_create(). inotify.7 michael kerrisk mention inotify_init1() in overview of api discuss the new inotify_init1() system call in the overview of the inotify api. ip.7 michael kerrisk detail einval error for ip_add_membership socket option in response to: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=216092 iso_8859-7.7 lefteris dimitroulakis add drachma, euro, and greek ypogegrammeni also, amend description of characters 0241 and 0242. man-pages.7 michael kerrisk example shell sessions should have user input boldfaced pthreads.7 michael kerrisk describe return value from pthreads functions describe the usual success (0) and failure (non-zero) returns, and note that posix.1-2001 specifies that pthreads functions can never fail with the error eintr. signal.7 michael kerrisk timeouts make socket interfaces non-restartable if setsockopt() is used to set a timeout on a socket(), then the various socket interfaces are not automatically restarted, even if sa_restart is specified when establishing the signal handler. analogous behavior occurs for the "stop signals" case. socket.7 michael kerrisk see also: add unix(7) ld.so.8 michael kerrisk document ld_use_load_bias drawing heavily on jakub jelinek's description in http://sources.redhat.com/ml/libc-hacker/2003-11/msg00127.html (subject: [patch] support ld_use_load_bias) --inhibit-rpath is ignored for setuid/setgid ld.so the --inhibit-rpath option is ignored if ld.so is setuid/setgid (not if the executable is setuid/setgid). michael kerrisk since glibc 2.4, setuid/setgid programs ignore ld_origin_path michael kerrisk fix description of ld_profile and ld_profile_output clarify that ld_profile is pathname or a soname, and identify name of profiling output file. fix description of ld_profile_output, which wasn't even close to the truth. (but why did it remain unfixed for so many years?) michael kerrisk since glibc 2.3.4, setuid/setgid programs ignore ld_dynamic_weak michael kerrisk since version 2.3.5, setuid/setgid programs ignore ld_show_auxv michael kerrisk reorder lists of ld_* environment variables alphabetically michael kerrisk since glibc 2.3.4, setuid/setgid programs ignore ld_debug ==================== changes in man-pages-3.13 ==================== released: 2008-11-07, bucaramanga contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: bert wesarg karsten weiss lefteris dimitroulakis olaf van der spek sam varshavchik török edwin ulrich mueller valdis kletnieks apologies if i missed anyone! new and rewritten pages ----------------------- pthread_attr_setaffinity_np.3 michael kerrisk new page for pthread_attr_setaffinity_np(3) and pthread_attr_getaffinity_np(3) pthread_attr_setschedparam.3 michael kerrisk new page for pthread_attr_setschedparam(3) and pthread_attr_getschedparam(3) pthread_attr_setschedpolicy.3 michael kerrisk new page for pthread_attr_setschedpolicy(3) and pthread_attr_getschedpolicy(3) pthread_setaffinity_np.3 michael kerrisk new page for pthread_setaffinity_np(3) and pthread_getaffinity_np(3) pthread_setschedparam.3 michael kerrisk new page for pthread_setschedparam(3) and pthread_getschedparam(3) pthread_setschedprio.3 michael kerrisk new page for pthread_setschedprio(3) new and changed links --------------------- pthread_attr_getaffinity_np.3 michael kerrisk new link to new pthread_attr_setaffinity_np.3 pthread_attr_getschedparam.3 michael kerrisk new link to new pthread_attr_setschedparam.3 pthread_attr_getschedpolicy.3 michael kerrisk new link to new pthread_attr_setschedpolicy.3 pthread_getaffinity_np.3 michael kerrisk new link to new pthread_setaffinity_np.3 pthread_getschedparam.3 michael kerrisk new link to new pthread_setschedparam.3 global changes -------------- pthread_attr_setaffinity_np.3 pthread_getattr_np.3 pthread_setaffinity_np.3 pthread_tryjoin_np.3 michael kerrisk explain _np suffix add text to conforming to explaining that the "_np" suffix is because these functions are non-portable. changes to individual pages --------------------------- sched_setaffinity.2 michael kerrisk see also: add sched_getcpu(3) sched_setaffinity.2 michael kerrisk see also: add pthread_setaffinity_np(3) sched_setaffinity.2 michael kerrisk clarify einval error for cpusetsize < kernel mask size for sched_setaffinity(), the einval error that occurs if 'cpusetsize' is smaller than the kernel cpu set size only occurs with kernels before 2.6.9. vfork.2 michael kerrisk child holds parent's memory until execve() or *termination* the page was phrased in a few places to describe the child as holding the parent's memory until the child does an execve(2) or an _exit(2). the latter case should really be the more general process termination (i.e., either _exit(2) or abnormal termination). clock_getres.3 michael kerrisk clock_process_cputime_id and clock_thread_cputime_id not settable according to posix.1-2001, the clock_process_cputime_id and clock_thread_cputime_id clocks should be settable, but currently they are not. pthread_attr_setstacksize.3 michael kerrisk, after a report by karsten weiss einval occurs on some systems if stacksize != page-size on macos x at least, pthread_attr_setstacksize(3) can fail with einval if 'stacksize' is not a multiple of the system page size. best to mention this so as to aid people writing portable programs. pthread_create.3 karsten weiss fix bug in example program the calloc() line should read like this instead: tinfo = calloc(num_threads, sizeof(struct thread_info)); pthread_exit.3 michael kerrisk bugs: thread group with a dead leader and stop signals document the bug that can occur when a stop signal is sent to a thread group whose leader has terminated. http://thread.gmane.org/gmane.linux.kernel/611611 http://marc.info/?l=linux-kernel&m=122525468300823&w=2 resolver.3 michael kerrisk fix prototype of dn_expand() the 4th argument is "char *", not "unsigned char *". http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504708 epoll.7 michael kerrisk fix error handling after accept() in example code simply continuing after an error is in most cases wrong, and can lead to infinite loops (e.g., for emfile). so handle an error by terminating. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504202 epoll.7 michael kerrisk add error handling for epoll_wait() call in example code epoll.7 michael kerrisk improve example code fill in some gaps in example code (variable declarations, adding listening socket to epoll set). give variables more meaningful names. other minor changes. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504202 iso_8859-7.7 lefteris dimitroulakis add characters for drachma and greek ypogegrammeni lines for these two characters were added in the previous patch, but the actual characters were not included in the 4th column of the table. this fixes that. pthreads.7 michael kerrisk add a section describing thread ids in particular, note that in each pthreads function that takes a thread id argument, that id by definition refers to a thread in the same process as the caller. ==================== changes in man-pages-3.14 ==================== released: 2008-11-25, bucaramanga contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andreas henriksson bert wesarg cedric le goater chris heath eric biederman eugen dedu ivana varekova jen axboe jens axboe loïc domaigne masanari iida paul evans pavel emelyanov pierre-paul paquin serge e. hallyn stefano teso stew benedict vegard nossum apologies if i missed anyone! new and rewritten pages ----------------------- cpu_set.3 michael kerrisk new page documenting cpu_* macros this page contains material moved out of sched_setscheduler(2). it overwrites a previously existing link file with the same name. michael kerrisk add description of macros for dynamically allocated cpu sets add descriptions of cpu_alloc(), cpu_alloc_size(), cpu_free(), cpu_set_s(), cpu_clr_s(), cpu_isset_s(), cpu_zero_s(), cpu_count_s(), cpu_and_s(), cpu_or_s(), cpu_xor_s(), and cpu_equal_s(). michael kerrisk add documentation of cpu_count() michael kerrisk add description of cpu_and(), cpu_or, cpu_xor(), and cpu_equal() plus a few other small clean-ups of the text michael kerrisk various improvements in description after review comments by bert wesarg: * explain that cpu_set_t is a bitset, but should be considered opaque. * a cpu set can be duplicated with memset(). * size of a cpu set is rounded up to size of long. * cpu_setsize is in bits, but the setsize argument is in bytes. michael kerrisk document cpu_alloc()/cpu_alloc_size() bug these macros return twice what they should because of thinko in glibc 2.8 and earlier. the bug is fixed for glibc 2.9. http://sourceware.org/bugzilla/show_bug.cgi?id=7029 michael kerrisk notes: discuss use of types in "prototypes" for these macros the synopsis shows types for arguments and return values, but these are really just suggestions: since the interfaces are macros, the compiler won't catch all violations of the "type rules". warn the reader of this. pthread_attr_setinheritsched.3 michael kerrisk new page for pthread_attr_setinheritsched(3) and pthread_attr_getinheritsched(3) pthread_cancel.3 michael kerrisk new page for pthread_cancel(3) pthread_cleanup_push.3 michael kerrisk new page for pthread_cleanup_push(3) and pthread_cleanup_pop(3) pthread_setcancelstate.3 michael kerrisk new page for pthread_setcancelstate(3) and pthread_setcanceltype(3) pthread_testcancel.3 michael kerrisk new page for pthread_testcancel(3) newly documented interfaces in existing pages --------------------------------------------- clone.2 jens axboe document clone_io (new in linux 2.6.25) some text also by mtk. michael kerrisk document clone_newnet michael kerrisk document clone_newuts (new in linux 2.6.19) michael kerrisk document clone_newipc flag (new in linux 2.6.19) michael kerrisk document clone_newpid flag (new in linux 2.6.24) mmap.2 michael kerrisk document map_stack flag (new in linux 2.6.27) arp.7 michael kerrisk document /proc file retrans_time_ms (new in linux 2.6.12) michael kerrisk document /proc file base_reachable_time_ms (new in linux 2.6.12) icmp.7 michael kerrisk document icmp_ignore_bogus_error_responses (new in linux 2.2) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document icmp_ratelimit and icmp_ratemask (new in linux 2.4.10) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document icmp_echo_ignore_broadcasts (new in linux 2.6.12) text taken from documentation/networking/ip-sysctl.txt tcp.7 michael kerrisk document /proc file tcp_slow_start_after_idle (new in linux 2.6.18) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_base_mss (new in linux 2.6.17) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_frto_response (new in linux 2.6.22) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_moderate_rcvbuf (new in linux 2.4.17/2.6.7) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_congestion_control (new in linux 2.4.13) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_no_metrics_save (new in linux 2.6.6) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_mtu_probing (new in linux 2.6.17) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_dma_copybreak (new in linux 2.6.24) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_tso_win_divisor (new in linux 2.6.9) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_allowed_congestion_control (new in linux 2.4.20) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_workaround_signed_windows (new in linux 2.6.26) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_available_congestion_control (new in linux 2.4.20) text taken from documentation/networking/ip-sysctl.txt michael kerrisk document /proc file tcp_abc (new in linux 2.6.15) text taken from documentation/networking/ip-sysctl.txt udp.7 michael kerrisk document /proc files udp_mem, udp_rmem_min, and udp_wmem_min all of these are new in linux 2.6.25 new and changed links --------------------- cpu_alloc.3 cpu_alloc_size.3 cpu_and.3 cpu_and_s.3 cpu_clr_s.3 cpu_count.3 cpu_count_s.3 cpu_equal.3 cpu_equal_s.3 cpu_free.3 cpu_isset_s.3 cpu_or.3 cpu_or_s.3 cpu_set_s.3 cpu_xor.3 cpu_xor_s.3 cpu_zero_s.3 michael kerrisk new link to new cpu_set.3 cpu_clr.3 cpu_isset.3 cpu_zero.3 michael kerrisk update links to point to cpu_set.3 the documentation of the cpu_* macros migrated to a new location: cpu_set.3. pthread_attr_getinheritsched.3 michael kerrisk new link to new pthread_attr_setinheritsched.3 pthread_cleanup_pop.3 michael kerrisk new link to new pthread_cleanup_push.3 pthread_setcanceltype.3 michael kerrisk new link to new pthread_setcancelstate.3 global changes -------------- clone.2 mount.2 unshare.2 proc.5 path_resolution.7 michael kerrisk global fix: s/namespace/mount-point namespace/, as appropriate in recent times, a number of other namespace flags have been added to clone(2). as such, it is no longer clear to use the generic term "namespace" to refer to the particular namespace controlled by clone_newns; instead, use the term "mount-point namespace". michael kerrisk global fix: s/mount-point namespace/mount namespace/ this is more consistent with the term "mounts namespace" used in the 2008 acm sigops paper, "virtual servers and checkpoint/restart in mainstream linux". (i avoided the "s", because using the plural strikes me as klunky english, and anyway we don't talk about the "pids namespace" or the "networks namespace", etc..) connect.2 listen.2 send.2 uname.2 cmsg.3 proc.5 arp.7 ddp.7 icmp.7 ip.7 raw.7 socket.7 tcp.7 udp.7 michael kerrisk global fix: eliminate mention of the obsolete sysctl(2) interface many pages still mention use of the obsolete sysctl(2) system call, or used the term "sysctls"; rewrite these mentions to instead be in terms of /proc interfaces. fcntl.2 signal.2 mbsnrtowcs.3 mbsrtowcs.3 mbtowc.3 wcrtomb.3 wcsnrtombs.3 wcsrtombs.3 wctomb.3 michael kerrisk global fix: s/multi-thread/multithread/ getdents.2 pthread_attr_init.3 pthread_create.3 pthread_getattr_np.3 pthread_setaffinity_np.3 pthread_setschedparam.3 pthread_tryjoin_np.3 michael kerrisk use consistent error-handling function names many older pages use a handle_error() macro to do simple error handling from system and library function calls. switch these pages to do similar. changes to individual pages --------------------------- time.1 michael kerrisk note that some shells have a 'time' built-in command therefore, to access the functionality described on this page, it may be necessary to specify the full pathname. clone.2 michael kerrisk place list of clone_* flags in alphabetical order (no content changes.) fsync.2 michael kerrisk update feature test macro requirements for fsync() since glibc 2.8, the fsync() declaration is also exposed if _posix_c_source >= 200112l sched_setaffinity.2 michael kerrisk add note on system-imposed restrictions on cpus actually used after loïc domaigne's suggestion for pthread_setaffinity_np(3), add similar text to this page noting that the system silently limits the set of cpus on which the process actually runs to the set of cpus physically present and the limits imposed by cpuset(7). sched_setaffinity.2 michael kerrisk removed discussion of cpu_* macros() these macros are now moving to a separate page. michael kerrisk refer reader to pthread_setaffinity_np(3) pthread_setaffinity_np() is preferable for setting thread cpu affinity if using the posix threads api. sysctl.2 michael kerrisk add prominent warning against using this system call this was already stated under notes, but make it even more prominent by adding a sentence at the start of the description. uname.2 michael kerrisk add c comments describing fields in utsname structure atan2.3 stefano teso fix description of range of function value return the range is not [-pi/2, pi/2], but [-pi, pi]. (mtk: this error was reported by nicolas françois, and should have been fixed in 3.11, but somewhere along the way, the fix got lost.) http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=506299 bindresvport.3 michael kerrisk since glibc 2.8, epfnosupport error is now eafnosupport glibc switched to using a posix-specified error code for this error case. http://bugs.linuxbase.org/show_bug.cgi?id=2375 clock_getres.3 michael kerrisk clock_process_cputime_id and clock_thread_cputime_id not settable according to posix.1-2001, the clock_process_cputime_id and clock_thread_cputime_id clocks should be settable, but currently they are not. getgrnam.3 michael kerrisk clarify and add more detail in return value description the page was a bit fuzzy in describing the return values for various cases. in particular, it needed to be more explicit in describing what happens for the "not found" case. this is an analogous change to the change for getpwnam.3, made after andreas henriksson's report. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504787 michael kerrisk rename arguments to getgrnam_r() and getgrgid_r() s/gbuf/grp/ and s/gbufp/result/, for consistency with posix.1 argument names. michael kerrisk clarify return value description the page was a bit fuzzy in describing the return values for various cases. in particular, it needed to be more explicit in describing what happens for the "not found" case. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504708 getpwnam.3 michael kerrisk rename arguments to getpwnam_r() and getpwuid_r() s/pwbuf/pwd/ and s/pwbufp/result/, for consistency with posix.1 argument names. michael kerrisk clarify and add more detail in return value description the page was a bit fuzzy in describing the return values for various cases. in particular, it needed to be more explicit in describing what happens for the "not found" case. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504787 michael kerrisk add an example program for getpwnam_r() inet_ntop.3 michael kerrisk rename 'cnt' argument to 'size' this is consistent with posix.1, and also a more sensible name. michael kerrisk rework text describing 'size' argument (after a suggestion by vegard nossum.) also made a few other small rewordings to in the initial paragraph. makecontext.3 michael kerrisk add text on use of pointer arguments to makecontext() passing pointer arguments to makecontext() is possible, but only on some architectures, and with no guarantees of portability. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=504699 pthread_attr_setaffinity_np.3 michael kerrisk various fixes after review by loïc domaigne reviewed-by: loïc domaigne pthread_attr_setaffinity_np.3 pthread_setaffinity_np.3 michael kerrisk update to reflect new location of cpu_*() documentation the cpu_*() macros are now documented in cpu_set.3; update to reflect that fact. michael kerrisk remove redundant text relating to cpu sets information about cpu_setsize can be found in cpu_set.3, so remove discussion of it here. pthread_attr_setschedparam.3 pthread_setschedparam.3 michael kerrisk remove text saying that only sched_priority is required by posix.1 loïc domaigne points out that if a system implements sched_sporadic (which linux does not), then other fields are also specified in sched_param. the simple solution is just to remove that phrase from the man page. pthread_cancel.3 pthread_detach.3 pthread_join.3 pthread_setaffinity_np.3 michael kerrisk make text of esrch error consistent pthread_setaffinity_np.3 michael kerrisk add text to einval error mentioning cpuset(7) michael kerrisk various improvements after review by loïc domaigne various fix-ups after loïc's review. reviewed-by: loïc domaigne pthread_setschedparam.3 michael kerrisk pthread_inherit_sched is default for inherit scheduler attribute in example, note that pthread_inherit_sched is the default for the inherit scheduler attribute. syslog.3 masanari iida log_kern messages can't be generated from user processes masanari notes that this is an faq for logger(1) and that solaris and freebsd document this point in syslog(3). the glibc info page also hides this comment in its source: internally, there is also log_kern, but log_kern == 0, which means if you try to use it here, just selects default. proc.5 ivana varekova fix reference to kernel source file use relative reference to documentation/mtrr.txt. arp.7 michael kerrisk add kernel version numbers for /proc interfaces cpuset.7 michael kerrisk see also: add cpu_set(3) epoll.7 michael kerrisk note glibc version that added epoll support icmp.7 michael kerrisk add kernel version numbers to /proc file descriptions inotify.7 vegard nossum fix description of max_user_watches it seems that inotify(7) is wrong here: "/proc/sys/fs/inotify/max_user_watches this specifies a limit on the number of watches that can be associated with each inotify instance." on my system, the default value for this variable is 8192. but i cannot create more than 8192 watches in total for the same uid even when they are on different inotify instances. so i suggest to rephrase this as: "this specifies an upper limit on the number of watches that can be created per real user id." ip.7 michael kerrisk reorder socket options alphabetically michael kerrisk added kernel version numbers for ip_* socket options michael kerrisk relocate kernel version information for ip_pmtudisc_probe michael kerrisk add kernel version numbers for /proc/sys/net/ipv4/ip_* files michael kerrisk remove mention of kernel header from description of ip_recverr looks like glibc has had this definition since about version 2.1. michael kerrisk relocate kernel version information for ip_mreqn structure michael kerrisk relocate info about linux-specific sockopts to notes also add some source comments about non-standard linux-specific options that are not yet documented. netlink.7 vegard nossum fix incorrect variable names in example code s/snl/sa/ * 2 pthreads.7 michael kerrisk add section on cancellation points this section includes a list of the functions that must and may be cancellation points. michael kerrisk rework, and fix small error in, thread-safe function list integrate the changes that occurred in posix.1-2008 into the main list (to be consistent with the list, elsewhere on this page, of functions that are cancellation points). also, fix an error that said that strerror() was added to the list in posix.1-2008. it was strsignal() that was added. (strerror() was already in the list in posix.1-2001.) michael kerrisk tweak text on sigpause() cancellation point in posix.1-2008, this function moves from the "must be" to the "may be" list. michael kerrisk add ref to signal(7) for further info on use of real-time signals signal(7) provides some further details on the use of real-time signals by the two linux threading implementations. michael kerrisk see also: add pthread_attr_init() and pthread_cancel() tcp.7 michael kerrisk update description of tcp_rmem defaults for linux 2.6 michael kerrisk add kernel version numbers for tcp_* socket options note kernel version were each socket option first appeared. michael kerrisk the tcp_bic* proc files disappeared in linux 2.6.13 michael kerrisk tcp_vegas_cong_avoid disappeared in linux 2.6.13 michael kerrisk add mention of rfc 4138 for 'tcp_frto' /proc file michael kerrisk remove mention of /proc in versions this information is not indicated for each /proc interface michael kerrisk clarify that tcp_mem measures in units of the system page size michael kerrisk update tcp_frto description for 2.6.22 changes linux 2.6.22 added a mode value 2 ("enable sack-enhanced f-rto if flow uses sack"). michael kerrisk fix alphabetical order in /proc file list a few entries were slightly out of order. michael kerrisk remove obsolete statement about /proc from versions much of the text has been updated to 2.6.27 or so, so this statement no longer applies. michael kerrisk add kernel version numbers for each /proc interface note kernel version where each /proc interface first appeared michael kerrisk tcp_westwood /proc file disappeared in linux 2.6.13 michael kerrisk update description of tcp_wmem defaults for linux 2.6 ==================== changes in man-pages-3.15 ==================== released: 2008-12-05, bucaramanga contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andre majorel andries e. brouwer chris heath drake wilson mats wichmann mel gorman michael kerrisk mike fedyk pavel machek petr baudis phil endecott rob landley sam varshavchik apologies if i missed anyone! new and rewritten pages ----------------------- makedev.3 michael kerrisk new page for makedev(), major(), and minor() macros pthread_cleanup_push_defer_np.3 michael kerrisk new page for pthread_cleanup_push_defer_np(3) and pthread_cleanup_pop_restore_np(3) newly documented interfaces in existing pages --------------------------------------------- accept.2 michael kerrisk document accept4() system call, new in linux 2.6.28 fmemopen.3 petr baudis add description of open_wmemstream(3) tcp.7 michael kerrisk document msg_trunc flag for tcp sockets new and changed links --------------------- accept4.2 michael kerrisk new link to accept.2 accept.2 now documents the new accept4() system call. open_wmemstream.3 petr baudis new link to fmemopen.3 fmemopen.3 now documents open_wmemstream(). pthread_cleanup_pop_restore_np.3 michael kerrisk new link to new pthread_cleanup_push_defer_np.3 global changes -------------- accept.2 listen.2 recv.2 getpeername.2 getsockname.2 shutdown.2 socketpair.2 michael kerrisk global fix: see also: add socket(7) bind.2 rcmd.3 capabilities.7 ip.7 michael kerrisk global fix: s/reserved port/privileged port/ some pages used one term, some pages the other term; make some consistency. connect.2 getpeername.2 getsockname.2 michael kerrisk use consistent argument names most other sockets pages are using the names 'addr' and 'addrlen'; make these pages do the same. getpeername.2 getsockname.2 getsockopt.2 recv.2 send.2 shutdown.2 sockatmark.3 socket.7 udplite.7 michael kerrisk synopsis: rename socket file descriptor argument to 'sockfd' many sockets man pages use the name 'sockfd' already. for consistency, changes the others to do so as well. gnu_dev_major.3 gnu_dev_makedev.3 gnu_dev_minor.3 major.3 minor.3 michael kerrisk new links to new makedev(3) page changes to individual pages --------------------------- _exit.2 michael kerrisk since glibc 2.3, the exit() wrapper function invokes exit_group(2) this information is useful to users of strace(1). accept.2 michael kerrisk clarify details when returned address is truncated if the returned address is truncated, the 'addrlen' argument indicates the actual size of the address, rather than a count of the number of bytes in the truncated buffer. also clarify that if 'addr' argument is null, then 'addrlen' should is unused, and should also be null. michael kerrisk reorder errors list some errors were listed under a separate "may" heading. there's probably no real need to do this; integrate those errors into the main list. exit_group.2 michael kerrisk note that since glibc 2.3, exit(2) invokes exit_group() futex.2 michael kerrisk mention that glibc provides no wrapper function for futex() get_thread_area.2 michael kerrisk note that glibc provides no wrapper for this system call getdomainname.2 michael kerrisk substantial rewrite expand description of setdomainname() and getdomainname(). note that getdomainname() is implemented as a library function in glibc. note limits on size of domain name. reorganize errors list. gethostname.2 michael kerrisk various parts rewritten write a paragraph describing sethostname(). clarify differences between glibc's gethostbyname() and the kernel gethostbyname() system calls. gethostname.2 michael kerrisk note that host_name_max is 64 on linux also note that in pre-1.0 days, the limit on hostnames was 8 bytes. getpeername.2 michael kerrisk note that returned address may be truncated if buffer is too small getsid.2 michael kerrisk simplified version information and moved to a new versions section getsockname.2 michael kerrisk note that returned address is truncated if buffer is too small mknod.2 michael kerrisk refer reader to makedev(3) to build a device id mmap.2 michael kerrisk loosen language around how 'addr' hint is interpreted mel gorman reported that in linux 2.6.27, 'addr' is rounded down to a page boundary. before kernel 2.6.26, if 'addr' was taken as a hint, it was rounded up to the next page boundary. since linux 2.6.24, it is rounded down. therefore, loosen the description of this point to say that the address is rounded to "a nearby page boundary". open.2 michael kerrisk efbig error is now eoverflow (since linux 2.6.24) when a 32-bit app opens a file whose size is too big to be represented in 31-bits, posix.1 specifies the error eoverflow. linux used to give efbig for this case, but 2.6.24 fixed this. also, add some text to describe the error scenario in more detail. pread.2 michael kerrisk note that glibc emulation for these calls uses lseek(2) (this makes it clearer that the emulated calls are not atomic.) recv.2 send.2 michael kerrisk make names of "address" and "address length" args more consistent make the names of these arguments more consistent with other sockets man pages. recv.2 michael kerrisk clarify details when returned address is truncated if the recvfrom() returned address is truncated, the 'fromlen' argument indicates the actual size of the address, rather than a count of the number of bytes in the truncated buffer. also clarify that the 'from' argument can be null, in which case 'fromlen' should is unused, and should also be null. michael kerrisk internet datagram and netlink sockets support msg_trunc for recv(2) internet datagram (since linux 2.4.27/2.6.8), and netlink (since linux 2.6.22) sockets support the msg_trunc flag for recv(2). select.2 michael kerrisk rewrote text describing feature test macros requirement for pselect() select_tut.2 michael kerrisk fix shut_fd* macros in example program add "do {} while (0)" set_thread_area.2 michael kerrisk note that glibc provides no wrapper for this system call setfsgid.2 setfsuid.2 michael kerrisk simplify version information and move to a versions section setsid.2 michael kerrisk rework return value section; add an errors section setup.2 michael kerrisk relocate some conforming to text to versions and notes stat.2 michael kerrisk document eoverflow error michael kerrisk refer reader to major() and minor() to decompose a device id syscalls.2 michael kerrisk fix version numbers for a few system calls some 2.6 system calls were wrongly mentioned as also being backported into a 2.4.x kernel. uname.2 michael kerrisk description: point reader at notes for further info on field lengths atan.3 andries e. brouwer fix return value description the correct range for the return value is [-pi/2,pi/2]. (mtk's fix in the last change to the return value text was a botch-up of a (correct) suggestion by nicolas françois.) atexit.3 michael kerrisk atexit() and on_exit(3) register functions on the same list michael kerrisk terminating registered function using longjmp() is undefined according to posix.1, using longjmp() to terminate execution of a function registered using atexit() produces undefined results. michael kerrisk calling exit(3) more than once produces undefined results if an exit handler itself calls exit(3), the results are undefined (see the posix.1-2001 specification of exit(3)). michael kerrisk the same exit handler may be registered multiple times michael kerrisk calling _exit(2) terminates processing of exit handlers michael kerrisk terminating registered function using longjmp() is undefined according to posix.1, using longjmp() to terminate execution of a function registered using atexit() produces undefined results. bindresvport.3 mats wichmann synopsis: s/\*\*/*/ in prototype michael kerrisk fix errors regarding port used, plus other rewrites glibc's bindresvport() takes no notice of sin->sin_port: it always returns an arbitrary reserved port in the anonymous range (512-1023). (reported by mats wichmann.) also: * add eaddrinuse and eacces errors. * mention use of getsockname(2). * other minor rewrites and reorderings of the text. * explicitly note that glib's bindresvport() ignores sin->sin_port. * change license there's now virtually no text remaining from the 1.70 version of this page. reviewed-by: mats wichmann reviewed-by: petr baudis dlopen.3 petr baudis describe confusing dladdr() behavior dladdr() will act unexpectedly if called from non-pic code on a compile-time-generated function pointer. fmemopen.3 michael kerrisk add versions section petr baudis see open: add fopencookie(3) fopencookie(3) is used to implement fmemopen(). fopen.3 petr baudis see also: add fmemopen(3) and fopencookie(3) fopencookie.3 petr baudis fopencookie() needs _gnu_source feature test macro getaddrinfo.3 petr baudis document results ordering and /etc/gai.conf this patch documents the order of the getaddrinfo(3) results (rfc 3484), how should the application deal with that, mentions the extremely common cause of having multiple results per query (both ipv4 and ipv6 addresses available) and mentions /etc/gai.conf. (mtk: minor tweaks, and note glibc version for /etc/gai.conf) isatty.3 michael kerrisk complete rewrite of this page, with rather more detail memmem.3 michael kerrisk remove sentence saying that libc 5.0.9 is still widely used that was a *long* time ago. on_exit.3 michael kerrisk document handling of registrations on fork(2) and execve(2) treatment in these cases is the same as for atexit(3). michael kerrisk arg given to registered function is status from *last* call to exit() it's a subtle point, but if a registered function itself calls exit(3), then subsequent functions that were registered with on_exit(3) will see the exit status given to the more recent exit(3) call. michael kerrisk note that same function may be registered multiple times setlocale.3 locale.7 michael kerrisk clean up the description of language environment variable clean up the $language description, by removing bogus comments from setlocale(3) and expanding the mention in locale(7). maybe you will decide that a more detailed description should be left to the gettext(3) documentation, but i actually care about the invisible part of the patch more since the comments have put me off the track initially ($language has nothing to do with setlocale(3) and is completely isolated to gettext, as obvious from the glibc sources). proc.5 michael kerrisk /proc/stat: s/minor/disk_idx/ in description of /proc/stat see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=225619 capabilities.7 drake wilson various minor fixes as per debian bug 471029 the relevant pieces of http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=471029 are: - delete duplicate subentry for keyctl_chown/keyctl_setperm operations in the cap_sys_admin entry. (it feels like that capability entry should be converted to a list, but i've left it in semicolon-delimited form for now.) - remove text about enfile from the text about the /proc/sys/fs/file-max limit in the cap_sys_admin entry, since this is already described in the man pages for the relevant ofile-creating system calls. - correct or clarify a few other bits of grammar and such; see the diff file itself for details. socket.7 michael kerrisk see also: add tcp(7) and udp(7) tcp.7 michael kerrisk relocate out-of-band data discussion move to a new subsection entitled "sockets api". michael kerrisk note that msg_peek can be used on out-of-band data time.7 michael kerrisk see also: add clock_gettime(3) unix.7 michael kerrisk unix domain sockets don't support the recv() msg_trunc flag michael kerrisk retitled subsection "(un)supported features" to "sockets api" this is consistent with the recent change in tcp(7). ==================== changes in man-pages-3.16 ==================== released: 2009-01-13, christchurch contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: colin watson florentin duneau petr baudis apologies if i missed anyone! new and rewritten pages ----------------------- pthread_getcpuclockid.3 michael kerrisk new page documenting pthread_getcpuclockid(3) libc.7 michael kerrisk new page giving brief overview of c libraries on linux rtld-audit.7 michael kerrisk new page documenting dynamic linker auditing api newly documented interfaces in existing pages --------------------------------------------- ld.so.8 petr baudis document ld_audit petr baudis document ld_pointer_guard new and changed links --------------------- gethostid.2 michael kerrisk new link to new page location in section 3 sethostid.2 michael kerrisk change link to point to new page location in section 3 sethostid.3 michael kerrisk new link to relocated page in section 3 glibc.7 michael kerrisk new link to new libc.7 global changes -------------- syscalls.2 feature_test_macros.7 standards.7 michael kerrisk see also: add libc(7) dlopen.3 ld.so.8 michael kerrisk see also: add rtld-audit(7) changes to individual pages --------------------------- gethostid.2 michael kerrisk move to section 3 the interfaces documented in this page are purely glibc. syscalls.2 michael kerrisk kernel 2.6.28 adds accept4() clock_getres.3 michael kerrisk see also: add pthread_getcpuclockid(3) fmemopen.3 michael kerrisk fix versions information gethostid.3 michael kerrisk before version 2.2, glibc stored the host id in /var/adm/hostid also: rewrite some text describing the /etc/hostid file, so that this location is referred to just once on the page. michael kerrisk return value: describe return value of sethostid() michael kerrisk added bugs section noting that id can't be guaranteed to be unique michael kerrisk added errors section describing errors for sethostid() michael kerrisk update section number to reflect relocation into section 3 printf.3 michael kerrisk source and destination buffers may not overlap for *s*printf() http://sourceware.org/bugzilla/show_bug.cgi?id=7075 some existing code relies on techniques like the following to append text to a buffer: $ cat s.c #include char buf[80] = "not "; main() { sprintf(buf, "%sfail", buf); puts(buf); return 0; } $ cc s.c $ ./a.out not fail however, the standards say the results are undefined if source and destination buffers overlap, and with suitable compiler options, recent changes can cause unexpected results: $ cc -v 2>&1 | grep gcc gcc version 4.3.1 20080507 (prerelease) [gcc-4_3-branch revision 135036] (suse linux) $ cc -d_fortify_source -o2 s.c $ ./a.out fail readdir.3 michael kerrisk rewrite text describing 'dirent' fields standardized in posix.1 michael kerrisk clarify text for return value/errno setting for end-of-stream case nscd.8 petr baudis correct notes section on reloading configuration files it behaved this way at least since "sun oct 18 15:02:11 1998 +0000", some four months after including the nscd implementation in glibc. but there does seem to be a short window between glibc-2.1 and glibc-2.1.3 when nscd -i was not available, i don't think it's worth muddling the point of the page with that, though. ==================== changes in man-pages-3.17 ==================== released: 2009-01-19, hobart contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: adeodato simó bastien roucaries davide libenzi lefteris dimitroulakis mads martin joergensen marc lehmann martin (joey) schulze michael kerrisk petr baudis sam varshavchik vegard nossum apologies if i missed anyone! new and rewritten pages ----------------------- endian.3 michael kerrisk new page documenting byte order conversion functions document functions (new in glibc 2.9) for conversion between host byte order and big-/little- endian byte order: htobe16(), htole16(), be16toh(), le16toh(), htobe32(), htole32(), be32toh(), le32toh(), htobe64(), htole64(), be64toh(), le64toh() getifaddrs.3 petr baudis new page documenting getifaddrs(3) and freeifaddrs(3) many edits and changes of petr's initial draft by mtk cp1251.7 lefteris dimitroulakis new page documenting cp 1251 (windows cyrillic) character set iso-8859-10.7 lefteris dimitroulakis new page documenting iso 8859-10 character set iso_8859-13.7 lefteris dimitroulakis new page documenting iso 8859-13 character set iso_8859-14.7 lefteris dimitroulakis new page documenting iso 8859-14 character set iso_8859-3.7 lefteris dimitroulakis new page documenting iso 8859-3 character set iso_8859-5.7 lefteris dimitroulakis new page documenting iso 8859-5 character set iso_8859-8.7 lefteris dimitroulakis new page documenting iso 8859-8 character set koi8-u.7 lefteris dimitroulakis new page documenting koi8-u character set newly documented interfaces in existing pages --------------------------------------------- epoll.7 michael kerrisk document /proc interfaces for limiting kernel memory usage document the following /proc files that were added in linux 2.6.28: /proc/sys/fs/epoll/max_user_instances /proc/sys/fs/epoll/max_user_watches netdevice.7 michael kerrisk document recently added interface flags iff_lower_up (since linux 2.6.17) iff_dormant (since linux 2.6.17) iff_echo (since linux 2.6.25) documentation taken from comments in new and changed links --------------------- freeifaddrs.3 michael kerrisk new link to new getifaddrs.3 htobe16.3 htole16.3 be16toh.3 le16toh.3 htobe32.3 htole32.3 be32toh.3 le32toh.3 htobe64.3 htole64.3 be64toh.3 le64toh.3 michael kerrisk new links to new endian.3 iso-8859-10.7 iso_8859_10.7 latin6.7 michael kerrisk new links to new iso_8859-10.7 iso-8859-13.7 iso_8859_13.7 latin7.7 michael kerrisk new links to new iso_8859-13.7 iso-8859-14.7 iso_8859_14.7 latin8.7 michael kerrisk new links to new iso_8859-14.7 iso-8859-3.7 iso_8859_3.7 latin3.7 michael kerrisk new links to new iso_8859-3.7 iso-8859-5.7 iso_8859_5.7 michael kerrisk new links to new iso_8859-5.7 iso-8859-8.7 iso_8859_8.7 michael kerrisk new links to new iso_8859-8.7 changes to individual pages --------------------------- bind.2 michael kerrisk see also: add getifaddrs(3) epoll_create.2 michael kerrisk document emfile error this error is encountered when the limit imposed by /proc/sys/fs/epoll/max_user_instances is encountered. michael kerrisk clarify distinction between epoll instance and epoll file descriptor reword so that the notion of an epoll instance is made clear, and made distinct from the notion of an epoll file descriptor. some other minor rewordings also. epoll_ctl.2 michael kerrisk reordered parts of the text michael kerrisk introduce notion of epoll instance introduce notion of epoll instance as distinct from epoll file descriptor. plus other wording clean-ups. michael kerrisk document enospc error (new in linux 2.6.28) this error results when the limit imposed by /proc/sys/fs/epoll/max_user_watches is encountered. epoll_wait.2 michael kerrisk introduce the notion of an epoll instance into text getdents.2 michael kerrisk before kernel < 2.6.4, 'd_type' was effectively always dt_unknown gethostid.2 michael kerrisk rename file (was misnamed gethostd.2 in previous release) getsockname.2 michael kerrisk see also: add getifaddrs(3) signalfd.2 michael kerrisk fix description of fork() semantics the page text described the semantics of the initial implementation of signalfd(). these were changed early on, but the man page wasn't updated. byteorder.3 michael kerrisk see also: add endian(3) longjmp.3 michael kerrisk clarify wording re saving/restoring signal mask michael kerrisk siglongjmp() restores signal mask iff 'savesigs' was non-zero note that siglongjmp() restores signal mask if, and only if, 'savesigs' argument of sigsetjmp() was non-zero. (previous text omitted the "and only if".) memccpy.3 michael kerrisk fix conforming to: s/c99/posix.1-2001/ michael kerrisk if the memory areas overlap, the results are undefined sethostid.3 michael kerrisk rename file (was misnamed sethostd.3 in previous release) setjmp.3 michael kerrisk clarify wording re saving/restoring signal mask michael kerrisk clarify when setjmp() provides bsd vs system v signal mask semantics strsep.3 michael kerrisk bugs: explicitly list problems afflicting strsep() previously, the page said this function suffered the same problems as strtok(), but in fact strsep() doesn't suffer from all of the same problems as strtok(), so explicitly list just the problems of strsep() in the strsep.3 page. proc.5 michael kerrisk add pointer to epoll(7) for description of epoll /proc files epoll.7 michael kerrisk various wording changes to improve clarity and consistency ==================== changes in man-pages-3.18 ==================== released: 2009-02-10, christchurch contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen bastien roucaries christian siebert christopher head florentin duneau guillem jover lefteris dimitroulakis lucio maciel michael kerrisk mike frysinger peter zijlstra petr baudis sam varshavchik satyam sharma sebastian kienzl timo sirainen vegard nossum apologies if i missed anyone! new and rewritten pages ----------------------- armscii-8.7 lefteris dimitroulakis new page documenting armscii-8 character set iso_8859-11.7 lefteris dimitroulakis new page documenting iso 8859-11 character set iso_8859-4.7 lefteris dimitroulakis new page documenting iso 8859-4 character set iso_8859-6.7 lefteris dimitroulakis new page describing iso 8859-6 character set pthread_kill.3 michael kerrisk new page documenting pthread_kill(3) pthread_kill_other_threads_np.3 michael kerrisk new page documenting pthread_kill_other_threads_np(3) pthread_sigmask.3 michael kerrisk new page documenting pthread_sigmask(3) newly documented interfaces in existing pages --------------------------------------------- clock_getres.3 michael kerrisk document clock_monotonic_raw, new in 2.6.28 new and changed links --------------------- clock_gettime.2 clock_settime.2 clock_getres.3 clock_gettime.3 clock_settime.3 michael kerrisk update links to reflect the fact that clock_* pages are now in section 2 iso-8859-11.7 iso_8859_11.7 michael kerrisk new links to new iso_8859-11.7 iso-8859-4.7 iso_8859_4.7 latin4.7 michael kerrisk new links to new iso_8859-4.7 iso-8859-6.7 iso_8859_6.7 michael kerrisk new links to new iso_8859-6.7 tis-620.7 michael kerrisk new link to new iso_8859-11.7 global changes -------------- clock_nanosleep.2 getrusage.2 timerfd_create.2 clock.3 clock_getcpuclockid.3 ftime.3 pthread_create.3 pthread_getcpuclockid.3 pthread_tryjoin_np.3 sem_wait.3 time.7 michael kerrisk global fix: fix xrefs to clock_*.? pages to reflect move to section 2 clock_nanosleep.2 execve.2 fork.2 nanosleep.2 sigaction.2 timerfd_create.2 pthread_getcpuclockid.3 ualarm.3 usleep.3 pthreads.7 time.7 michael kerrisk global fix: s/(3)/(2)/ in section number xrefs for timer_*() api the posix timers api is implemented (mostly) within the kernel, so these interfaces are system calls. although there are as yet no man pages, when they are added they should be in section 2, not 3. therefore fix those pages that currently refer to these interfaces as being in section 3. changes to individual pages --------------------------- capget.2 andi kleen add some details and relocate a paragraph while writing a little program using capset i found the capset manpage quite light on crucial details and i had to resort to rtfs. this patch improves the points i found unclear and also moves one misplaced paragraph around. clock_getres.2 michael kerrisk move page from section 3 to section 2 eventfd.2 michael kerrisk glibc eventfd() supports the use of eventfd2() since version 2.9 fork.2 michael kerrisk see also: add daemon(3) getdents.2 michael kerrisk remove unneeded have_d_type from example program since d_type will always just return dt_unknown before kernel 2.6.4, we don't need to use a conditional for determining whether we use this flag. nanosleep.2 michael kerrisk relocated misplaced bugs heading select_tut.2 michael kerrisk clean up error checking in example program (no semantic changes) michael kerrisk many parts tidied and rewritten remove some redundant text, clarify various pieces, tidy example code, etc. michael kerrisk bug fixes + rewrites in example program sebastien pointed out that the first example program wrongly thinks it can count signals. also, some further rewrites by mtk. socket.2 michael kerrisk bugs: remove discussion sock_uucp as time goes on, this sentence becomes less a piece of humor, and more a puzzle. stat.2 michael kerrisk note that open(o_noatime) also causes st_atime not to be updated timerfd_create.2 michael kerrisk add bugs noting that timerfd supports fewer clock types than timer_create() btowc.3 michael kerrisk see also: add wctob(3) clock_getcpuclockid.3 michael kerrisk see also: add pthread_getcpuclockid(3) cos.3 michael kerrisk see also: add sincos(3) fexecve.3 timo sirainen note that fexecve() depends on a mounted /proc see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 michael kerrisk conforming to: note addition of fexecve() in posix.1-2008 michael kerrisk 'fd' must be opened read-only and refer to a file that is executable fmemopen.3 michael kerrisk conforming to: note that these functions are in posix.1-2008 getifaddrs.3 lucio maciel fix memory leak in example program petr baudis various small fixes getpwnam.3 michael kerrisk see also: add getspnam(3) getumask.3 michael kerrisk updated glibc version number in notes ilogb.3 michael kerrisk see also: add significand(3) intro.3 michael kerrisk see also: add libc(7) isalpha.3 michael kerrisk fix statement that isalpa() is obsolete; should be isascii() http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=512709 michael kerrisk see also: add toascii(3) mq_notify.3 michael kerrisk add cross reference to pthread_attr_init(3) pthread_attr_setaffinity_np.3 michael kerrisk synopsis: fix declaration of 'attr' pthread_getcpuclockid.3 michael kerrisk synopsis: fix type of 'thread' qsort.3 michael kerrisk example: remove unnecessary "#include " random.3 michael kerrisk see also: add random_r(3) remainder.3 michael kerrisk see also: add div(3) scandir.3 michael kerrisk conforming to: alphasort() and scandir() are added to posix.1-2008 michael kerrisk conforming to: note that versionsort() was added to glibc in version 2.1 sem_wait.3 michael kerrisk see also: add clock_gettime(2) significand.3 michael kerrisk add conforming to noting that this function is unstandardized sigwait.3 michael kerrisk add examples section referring to pthread_sigmask(3) sin.3 michael kerrisk see also: add sincos(3) stpcpy.3 michael kerrisk add bugs section noting the possibility of buffer overruns michael kerrisk add missing pieces/fix various problems in example program michael kerrisk conforming to: stpcpy() is nowadays on the bsds michael kerrisk see also: add stpcpy.3 wcscasecmp.3 michael kerrisk conforming to: note that this function is added in posix.1-2008 wcsdup.3 michael kerrisk conforming to: note that this function was added in posix.1-2008 wcsncasecmp.3 michael kerrisk conforming to: note that this function is added in posix.1-2008 wctob.3 michael kerrisk see also: add btowc(3) proc.5 michael kerrisk remove mention of epoll/max_user_instances (since this interface appeared in 2.6.28, and then disappeared in 2.6.29.) ascii.7 michael kerrisk update see also list to include pages added in 3.17 michael kerrisk see also: add recently added iso_8859-*(7) pages epoll.7 michael kerrisk remove documentation of /proc/sys/fs/epoll/max_user_instances this /proc interface appeared in 2.6.28. but will be removed in 2.6.29. also, document change in default value of /proc/sys/fs/epoll/max_user_watches (was 1/32 of lowmem, now 1/25 of lowmem). koi8-r.7 michael kerrisk see also: add koi8-u(7); remove crufty text standards.7 michael kerrisk update to note that latest posix/sus was ratified in 2008 time.7 michael kerrisk see also: add pthread_getcpuclockid(3) ==================== changes in man-pages-3.19 ==================== released: 2009-02-20, putaruru contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: christian siebert jan engelhardt jens thoms toerring kir kolyshkin mark hills michael kerrisk parag warudkar peter zijlstra sami liedes apologies if i missed anyone! new and rewritten pages ----------------------- timer_create.2 michael kerrisk new page documenting timer_create(2) timer_delete.2 michael kerrisk new page documenting timer_delete(2) timer_getoverrun.2 michael kerrisk new page documenting timer_getoverrun(2) timer_settime.2 michael kerrisk new page documenting timer_settime(2) and timer_gettime(2) new and changed links --------------------- timer_gettime.2 michael kerrisk new link to new timer_settime.2 global changes -------------- various pages kir kolyshkin trivial punctuation fixes in see also in see also, when a few man pages are referenced, those are divided by commas. every reference is on a separate line, and all lines but the last one should end with comma. i spotted one place where there is no comma in between references, and mocked up an awk script to find similar places: for f in man*/*; do awk ' /^.sh ["]see also["]/ { sa=1; print "== " filename " =="; print; next } /^\.(pp|sh)/ { sa=0; no=0; next } /^\.br/ { if (sa==1) { print; if (no == 1) print "missing comma in " filename " +" fnr-1; no=0 } } /^\.br .*)$/ { if (sa==1) no=1; next } /\.\\"/ {next} /.*/ { if (sa==1) { print; next } } ' $f; done | fgrep 'missing comma' this patch fixes all the places found by the above script. also, there is an extra dot at the end of uri.7 "see also" section. removed as per man-pages(7) recommendation. changes to individual pages --------------------------- getitimer.2 clock_getcpuclockid.3 time.7 michael kerrisk see also: add timer_create(2) getitimer.2 michael kerrisk rename arguments for consistency with other timer pages also some other minor wording improvements splice.2 mark hills errors: add einval case for file opened o_append target file cannot be opened in append (o_append) mode in kernels prior to v2.6.27 splice() to a file in append mode is broken, and since that version it is disallowed. it is possible this behaviour may change in the future; see the kernel commit message (efc968d450e013049a662d22727cf132618dcb2f) for more information. syscalls.2 michael kerrisk note that getpmsg(2) and putmsg(2) are unimplemented see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514771 timerfd_create.2 michael kerrisk errors: add efault timerfd_create.2 michael kerrisk rename timerfd_settime() 'curr_value' arg to 'old_value' for consistency with related pages. vm86.2 parag warudkar conforming to: add 32-bit specific note that this call is only on *32-bit* intel mq_open.3 michael kerrisk errors: add enoent error for name == "/" mq_open.3 michael kerrisk errors: add eacces error for name containing > 1 slash sem_open.3 michael kerrisk errors: add einval error where name == "/" sem_open.3 jens thoms toerring add case of non-well-formed name to enoent shm_open.3 michael kerrisk clarify rules for construction of shared memory object names proc.5 michael kerrisk add description of /proc/sys/kernel/sysrq reported by: goerghe cosorea proc.5 michael kerrisk put /proc/modules entry in correct alphabetical order ascii.7 kir kolyshkin fix formatting of tables on second page to use monospaced font mq_overview.7 michael kerrisk clarify construction rules for message queue object names sem_overview.7 michael kerrisk clarify construction rules for semaphore object names see also http://groups.google.com/group/comp.os.linux.development.apps/browse_thread/thread/b4a67caa765cb65f ==================== changes in man-pages-3.20 ==================== released: 2009-03-31, christchurch contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alan curry américo wang andi kleen carlos o'donell chunming chang colin watson eelco dolstra jan engelhardt jens thoms toerring johannes stezenbach leandro a. f. pereira martin gebert michael kerrisk mike o'connor mike frysinger nikanth karthikesan reuben thomas reuben thomas roland mcgrath sam varshavchik simon gomizelj tanaka akira teddy hogeborn walter jontofsohn apologies if i missed anyone! new and rewritten pages ----------------------- cpuid.4 andi kleen new page for cpuid access device msr.4 andi kleen new page documenting x86 cpu msr access device newly documented interfaces in existing pages --------------------------------------------- proc.5 américo wang document /proc/sys/vm/swappiness michael kerrisk document /proc/sysrq-trigger global changes -------------- timer_create.2 timer_delete.2 timer_getoverrun.2 timer_settime.2 numa.7 michael kerrisk make source layout of 'link with' text consistent with other pages no actual change to formatted output, but this makes the page sources more consistent for the purpose of grepping, etc. mempcpy.3 signbit.3 significand.3 michael kerrisk global fix: acknowledge fsf in copyright these pages are heavily based on original material in glibc info pages, but the comments in the source of the pages did not acknowledge the fsf copyright on the original material. fix that. accept.2 read.2 recv.2 send.2 write.2 michael kerrisk fix discussion of eagain/ewouldblock errors for a non-blocking socket, posix.1-2001/2008 allow either eagain or ewouldblock to be returned in cases where a call would have blocked. although these constants are defined with the same value on most linux architectures (pa-risc is the exception), posix.1 does not require them to have the same value. therefore, a portable application using the sockets api should test for both errors when checking this case. (nb posix.1 only mentions ewouldblock in the context of the sockets interfaces.) change made after a note cross-posted on linux-arch@vger, http://thread.gmane.org/gmane.linux.debian.ports.hppa/5615 and a suggestion for write(2) from carlos o'donell basename.3 getgrent.3 getgrnam.3 getpwent.3 getpwnam.3 readdir.3 michael kerrisk note that returned pointer should not be given to free() armscii-8.7 cp1251.7 iso_8859-10.7 iso_8859-11.7 iso_8859-13.7 iso_8859-14.7 iso_8859-15.7 iso_8859-16.7 iso_8859-2.7 iso_8859-3.7 iso_8859-4.7 iso_8859-5.7 iso_8859-6.7 iso_8859-7.7 iso_8859-8.7 iso_8859-9.7 koi8-r.7 koi8-u.7 michael kerrisk add explicit character set encoding to first line of source nowadays mandb has provision to understand a character set encoding that is explicitly indicated in the first line of the source. as pointed out by colin watson, including such an explicit indication on pages encoded in anything other than iso 8859-1 or utf-8 is useful for man-pages that aren't shipped in utf-8. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=519209 and for some other background (responded to by colin watson in the above report): http://thread.gmane.org/gmane.comp.internationalization.linux/6040 ("man page encoding", 5 jul 2005) changes to individual pages --------------------------- fallocate.2 michael kerrisk versions: glibc support is provided since version 2.10 fcntl.2 michael kerrisk remove mention of ewouldblock from discussion of mandatory locking in the kernel, the error on encountering a mandatory lock is eagain. although eagain and ewouldblock are the same on most linux architectures, on some they are not, so don't mention ewouldblock as it is misleading. (mea culpa.) getcontext.2 michael kerrisk note that posix.1-2008 removes the specification of getcontext() getitimer.2 michael kerrisk note that posix.1-2008 recommends posix timers api instead of this api gettimeofday.2 michael kerrisk note that posix.1-2008 recommends clock_gettime() instead of this api ptrace.2 michael kerrisk note use of 'data' for ptrace_sys{call,emu} and ptrace_*_singlestep these operations use the 'data' argument as a signal number, like ptrace_cont. ptrace.2 mike frysinger only reference the kernel no longer installs linux/user.h, so update references to sys/user.h. recv.2 michael kerrisk add 'iovec' defn to defn of 'msghdr' structure the 'msghdr' structure includes a field of type 'iovec', so show the definition of that structure in this page. rename.2 michael kerrisk make enoent description consistent with posix.1-2008 timerfd_create.2 michael kerrisk errors: add einval for invalid 'flags' for timer_settime() truncate.2 michael kerrisk synopsis: fix description of feature test macro requirements after a report by arvid norlander. bcopy.3 michael kerrisk note that posix.1-2008 removes specification of bcopy() bsd_signal.3 michael kerrisk note that posix.1-2008 recommends sigaction(2) instead of this api ctime.3 michael kerrisk note that posix.1-2008 recommends strftime(3) instead of these functions ecvt.3 michael kerrisk note that posix.1-2008 recommends sprintf(3) instead of these functions gcvt.3 michael kerrisk note that posix.1-2008 recommends sprintf(3) instead of this function getcwd.3 michael kerrisk note that getcwd() should be used instead of the obsolete getwd() getgrent.3 michael kerrisk returned buffer may be statically allocated and overwritten by later calls gethostbyname.3 michael kerrisk posix.1-2008 recommends getaddrinfo(3) and getnameinfo(3) instead getnetent_r.3 michael kerrisk fix function name in text: s/getnetbynumber_r/getnetbyaddr_r/ the synopsis showed the right function name (getnetbyaddr_r), but the text repeatedly used the wrong name (getnetbynumber_r). probably, this was a cut-and-paste error. getpwent.3 michael kerrisk returned buffer may be statically allocated and overwritten by later calls index.3 michael kerrisk note that posix.1-2008 recommends strchr(3) and strrchr(3) instead isalpha.3 michael kerrisk explain why posix.1-2008 marks isascii(3) obsolete lockf.3 nikanth karthikesan update pointer to documentation in kernel source makecontext.3 michael kerrisk note that posix.1-2008 recommends the use of posix threads instead mq_notify.3 michael kerrisk document the posix.1-2008 optional einval error posix.1-2008 allows an optional einval error if notification==null and the caller is not currently registered to receive notifications. posix_fallocate.3 michael kerrisk clarify that einval also occurs of 'len' *equals* zero see http://bugzilla.kernel.org/show_bug.cgi?id=12919 posix_fallocate.3 michael kerrisk document posix.1-2001 and posix.1-2008 specifications for einval error see http://bugzilla.kernel.org/show_bug.cgi?id=12919 posix_memalign.3 michael kerrisk document handling of size==0 case for posix_memalign() pthread_exit.3 michael kerrisk fix error in description: s/pthread_create/pthread_exit/ realpath.3 michael kerrisk rework resolved_path==null discussion w.r.t. posix.1-200[18] although the page already mentioned the resolved_path==null feature, and that this feature was added in posix.1-2008, there was still some crufty text in bugs that hadn't been updated to reflect the posix.1-2008 changes. also, some other minor wording and grammar fixes. scalb.3 michael kerrisk note that posix.1-2008 recommends scalbln*(3) instead seekdir.3 michael kerrisk synopsis: fix type of 'offset' argument: s/off_t/long/ and add a notes section pointing out that 'off_t' was indeed used in glibc 2.1.1 and earlier. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=519230 sem_post.3 michael kerrisk document eoverflow error shm_open.3 michael kerrisk recast discussion on name length to exclude terminating null byte probably it's clearer to describe the length of the ipc object name as a count that excludes the null terminator. siginterrupt.3 michael kerrisk note that posix.1-2008 recommends sigaction() instead sigset.3 michael kerrisk note apis that posix.1-2008 recommends instead of these obsolete apis strftime.3 michael kerrisk small fix to description of %g see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=516677 strftime.3 michael kerrisk add details on iso 8601 week-based dates iso 8602 week-based dates are relevant for %g, %g, and %v, and the existing details on these dates are a little thin. strftime.3 michael kerrisk remove mention of year from iso 8601 standard the text mentioned the 1988 8601 standard, but there have already been two revisions of the standard since then, so simply remove mention of the year. telldir.3 michael kerrisk synopsis: fix return type: s/off_t/long/ and add a notes section pointing out that 'off_t' was indeed used in glibc 2.1.1 and earlier. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=519230 timeradd.3 michael kerrisk note that on some systems, <=, >=, == don't work for timercmp() timeradd.3 michael kerrisk synopsis: fix return types of timerisset() and timercmp() toascii.3 michael kerrisk note why posix.1-2008 marks this function obsolete console_ioctl.4 alan curry fix 'argp' type for kdgetled description see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=517485 group.5 michael kerrisk various minor rewordings and improvements resolv.conf.5 michael kerrisk document 'ip6-bytestring' option resolv.conf.5 michael kerrisk document 'edns0' option resolv.conf.5 michael kerrisk document 'ip6-dotint' / 'no-ip6-dotint' option resolv.conf.5 michael kerrisk note that maximum value of 'ndots' option is capped to 15 resolv.conf.5 michael kerrisk note that maximum value of 'timeout' option is capped to 30 hier.7 michael kerrisk add description of /srv see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=520904 ip.7 michael kerrisk fix type used to declare sin6_port the page should use the type specified by posix, rather than the (equivalent) type used in the kernel ipv6.7 teddy hogeborn fix types used to declare sin6_family and sin6_port the page should use the types specified by posix, rather than the (equivalent) types used in the kernel. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=517074 mq_overview.7 michael kerrisk recast discussion on name length to exclude terminating null byte probably it's clearer to describe the length of the ipc object name as a count that excludes the null terminator. rtld-audit.7 michael kerrisk note that multiple libraries in ld_audit doesn't work this is reportedly fixed in glibc 2.10. see http://sourceware.org/bugzilla/show_bug.cgi?id=9733 sem_overview.7 michael kerrisk fix discussion of length of semaphore names because of the "sem." prefix added by glibc to a semaphore name, the limit on the length of the name (excluding the terminating null byte) is 251 characters. ==================== changes in man-pages-3.21 ==================== released: 2009-04-15, los gatos contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: frank dana michael kerrisk roman byshko apologies if i missed anyone! new and rewritten pages ----------------------- pthread_setconcurrency.3 michael kerrisk new page documenting pthread_setconcurrency(3) and pthread_getconcurrency(3) pthread_yield.3 michael kerrisk new page documenting pthread_yield(3) new and changed links --------------------- pthread_getconcurrency.3 michael kerrisk new link to new pthread_setconcurrency(3) changes to individual pages --------------------------- initrd.4 michael kerrisk various minor wording improvements initrd.4 frank dana add missing word in description feature_test_macros.7 michael kerrisk update for glibc 2.10 changes to from glibc 2.10, understands the values 200809 for _posix_c_source and 700 for _xopen_source, and makes corresponding changes to defaults for other feature test macros. michael kerrisk add an example program this example program makes it possible to explore what feature test macros are set depending on the glibc version and the macros that are explicitly set. ldconfig.8 michael kerrisk /etc/ld.so.conf also include libraries found in /lib and /usr/lib ==================== changes in man-pages-3.22 ==================== released: 2009-07-25, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: adrian dewhurst alexander lamaison bryan østergaard christopher head doug goldstein florentin duneau gokdeniz karadag jeff moyer kosaki motohiro lucian adrian grijincu mark hills michael kerrisk mike frysinger petr baudis reimar döffinger ricardo garcia rui rlex shachar shemesh tolga dalman ku roi sobtwmxt apologies if i missed anyone! changes to individual pages --------------------------- clone.2 michael kerrisk rewrite crufty text about number of args in older version of clone() some bit rot had crept in regarding the discussion of the number of arguments in older versions of this syscall. simplify the text to just say that linux 2.4 and earlier didn't have ptid, tls, and ctid arguments. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=533868 michael kerrisk fix version number for clone_newipc it's 2.6.19, not 2.4.19. michael kerrisk fix errors in argument names in text (ptid, ctd) execve.2 mike frysinger remove erroneous statement that pending signal set is cleared on execve(2). fcntl.2 michael kerrisk the kernel source file mandatory.txt is now mandatory-locking.txt michael kerrisk the documentation/* files are now in documentation/filesystems flock.2 michael kerrisk remove unneeded reference to documentation/mandatory.txt mandatory locks are only implemented by fcntl() locking michael kerrisk the documentation/* files are now in documentation/filesystems fork.2 jeff moyer document fork() behaviour for the linux native aio io_context it was noted on lkml that the fork behaviour is documented for the posix aio calls, but not for the linux native calls. here is a patch which adds a small blurb that folks will hopefully find useful. upon fork(), the child process does not inherit the io_context_t data structures returned by io_setup, and thus cannot submit further asynchronous i/o or reap event completions for said contexts. getdents.2 michael kerrisk the d_type field is fully supported on btrfs mount.2 michael kerrisk document ms_strictatime, update description of ms_relatime starting with linux 2.6.30, the ms_relatime behavior became the default, and ms_strictatime is required to obtain the traditional semantics. poll.2 michael kerrisk remove ebadf error from errors as reported by motohiro: "man poll" describe this error code. >errors > ebadf an invalid file descriptor was given in one of the sets. but current kernel implementation ignore invalid file descriptor, not return ebadf. ... in the other hand, susv3 talk about > pollnval > the specified fd value is invalid. this flag is only valid in the > revents member; it shall ignored in the events member. and > if the value of fd is less than 0, events shall be ignored, and > ireevents shall be set to 0 in that entry on return from poll(). but, no desribe ebadf. (see http://www.opengroup.org/onlinepubs/009695399/functions/poll.html) so, i think the implementation is correct. why don't we remove ebadf description? sigaction.2 michael kerrisk expand description of si_utime and si_stime fields of siginfo_t stat.2 michael kerrisk improve wording of enotdir error syscalls.2 michael kerrisk add preadv() and pwritev(), new in kernel 2.6.30 wait.2 gokdeniz karadag document cld_dumped and cld_trapped si_code values daemon.3 michael kerrisk clarify discussion of 'noclose' and 'nochdir' arguments ffs.3 petr baudis see also: add memchr(3) fmemopen.3 petr baudis relocate bugs section to correct position petr baudis notes: there is no file descriptor associated with the returned stream alexander lamaison pointed out that this is not obvious from the documentation, citing an example with passing the file * handle to a function that tries to fstat() its fileno() in order to determine the buffer size. michael kerrisk conforming to: remove note that these functions are gnu extensions that sentence is now redundant, since these functions are added in posix.1-2008. lockf.3 michael kerrisk clarify relationship between fcntl() and lockf() locking memchr.3 petr baudis see also: add ffs(3) readdir.3 michael kerrisk the d_type field is fully supported on btrfs setjmp.3 mike frysinger fix typo and clarify return description the word "signal" was duplicated in notes, and the return section refers to setjmp() and sigsetjmp(), and mentions longjmp(), but not siglongjmp(). strcmp.3 petr baudis see also: add strverscmp(3) strcpy.3 mark hills see also: add strdup(3) complex.7 michael kerrisk add missing header file for example program reimar döffinger fix type used in example code man complex (from release 3.18) contains the following code: complex z = cexp(i * pi); reading the c99 standard, "complex" is not a valid type, and several compilers (intel icc, arm rvct) will refuse to compile. it should be double complex z = cexp(i * pi); instead. environ.7 michael kerrisk note that last element in environ array is null see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=528628 michael kerrisk wording fixes mq_overview.7 michael kerrisk note that mkdir and mount commands here need superuser privilege michael kerrisk fix example showing contents of /dev/mqueue file standards.7 michael kerrisk remove references to dated books gallmeister and lewine are rather old books. probably, there are better books to consult nowadays, and anyway, this man page isn't intended to be a bibliography. ==================== changes in man-pages-3.23 ==================== released: 2009-09-30, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: aaron gardner andrey vihrov christoph hellwig georg sauthoff leslie p. polzer marc lehmann mark hills michael kerrisk mike frysinger nicolas françois serge hallyn siward de groot rui rlex apologies if i missed anyone! changes to individual pages --------------------------- execve.2 pipe.2 tee.2 fmemopen.3 mq_notify.3 qsort.3 michael kerrisk replace use of assert() by code that checks argc see http://bugzilla.kernel.org/show_bug.cgi?id=13569 as noted by andrey: the purpose of the assert macro, defined in , is to provide a tool to check for programming mistakes or program logic errors. however, the assert macro must never be used to perform checks for run time errors, since, with the ndebug macro defined, expressions within the assert macro invocations are not evaluated/checked for, resulting in behavior that was not originally intended. ... the pages affected in the core package are execve(2) pipe(2) tee(2) fmemopen(3) mq_notify(3) qsort(3) getrusage.2 michael kerrisk ru_inblock and ru_oublock are now implemented these fields of the rusage structure are filled in since linux 2.6.22. mmap.2 michael kerrisk add brief documentation of map_hugetlb this flag is new in 2.6.32, and serves a similar purpose to the shmget() shm_hugetlb flag. open.2 christoph hellwig add some comments on o_sync and friends poll.2 michael kerrisk clarify wording describing of 'nfds' argument. reported by: rui rlex semctl.2 nicolas françois remove some redundant words setpgid.2 michael kerrisk add an explanation of orphaned process groups splice.2 tee.2 vmsplice.2 mark hills fix return type since glibc 2.7, the return type for these functions is ssize_t (formerly it was long). stat.2 nicolas françois fix small bug in example program since it is a failure, exit_failure looks more appropriate than exit_success. umount.2 michael kerrisk glibc only exposes mnt_detach and mnt_expire since version 2.11 see http://sourceware.org/bugzilla/show_bug.cgi?id=10092 exit.3 michael kerrisk add a pointer to explanation of orphaned process groups in setpgid(2) fflush.3 michael kerrisk fflush() discards buffered input ffs.3 michael kerrisk clarify that ffsl() and ffsll() are gnu extensions getaddrinfo.3 michael kerrisk note nonstandard assumed hints.ai_flags value when hints is null when hints is null, glibc assumes hints.ai_flags is ai_v4mapped|ai_addrconfig whereas posix says 0. according to ulrich drepper, glibc's behavior is better. getmntent.3 mike frysinger setmntent() argument is 'filename' not 'fp' the description of setmntent() formerly used the wrong argument name. posix_fallocate.3 nicolas françois fix reference to posix.1-2008 the sentence mentions twice posix.1-2001. i guess the second one should be posix.1-2008. this should be checked in the standard. setenv.3 michael kerrisk improve errors section add enomem error; improve einval description. also, make return value section a little more accurate in its mention of errno. strftime.3 nicolas françois fix error in description: s/monday/thursday/ proc.5 nicolas françois fix page cross reference max_user_watches is better explained in epoll(7) than inotify(7). proc.5 michael kerrisk dmesg is in section 1, not section 8 capabilities.7 michael kerrisk fs uid manipulations affect cap_linux_immutable and cap_mknod nowadays, file system uid manipulations also affect cap_linux_immutable (since 2.6.3) and cap_mknod (since 2.6.29). capabilities.7 michael kerrisk fix version number for cap_mknod in fs uid manipulations a recent patch said "since 2.6.29". it should have been "since 2.6.30". capabilities.7 nicolas françois reword a bad sentence in description of capability bounding set. mq_overview.7 michael kerrisk change documented ranges for msg_max and msgsize_max linux 2.6.28 changed the permissible ranges for these /proc files. tcp.7 udp.7 nicolas françois replace references to syctl interfaces with /proc ==================== changes in man-pages-3.24 ==================== released: 2010-02-25, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen andries e. brouwer ansgar burchardt bela lubkin bill o. gallmeister christoph hellwig colin watson dan jacobson david howells denis barbier doug manley edward welbourne fang wenqi frédéric brière garrett cooper ihar hrachyshka jann poppinga jason goldfine-middleton jason noakes jonathan nieder kevin mark hills markus peuhkuri michael kerrisk michael witten mike frysinger sam liao samy al bahra stuart kemp sunjiangangok tobias stoeckmann vlastimil babka yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- add_key.2 david howells new page documenting add_key(2) taken from keyutils-1.1 package. keyctl.2 david howells new page documenting keyctl(2) taken from keyutils-1.1 package. request_key.2 david howells new page documenting request_key(2) taken from keyutils-1.1 package. global changes -------------- various pages michael kerrisk global fix: s/non-root/unprivileged/ various pages michael kerrisk global fix: s/non-privileged/unprivileged/ various pages michael kerrisk global fix: /non-superuser/unprivileged user/ various pages michael kerrisk s/non-/non/ the tendency in english, as prescribed in style guides like chicago mos, is toward removing hyphens after prefixes like "non-" etc. various pages michael kerrisk global fix: s/re-/re/ the tendency in english, as prescribed in style guides like chicago mos, is toward removing hyphens after prefixes like "re-" etc. various pages michael kerrisk global fix: s/multi-/multi/ the tendency in english, as prescribed in style guides like chicago mos, is toward removing hyphens after prefixes like "multi-" etc. various pages michael kerrisk global fix: s/pre-/pre/ the tendency in english, as prescribed in style guides like chicago mos, is toward removing hyphens after prefixes like "pre-" etc. various pages michael kerrisk global fix: s/sub-/sub/ the tendency in english, as prescribed in style guides like chicago mos, is toward removing hyphens after prefixes like "sub-" etc. stime.2 time.2 utimensat.2 ctime.3 difftime.3 ftime.3 getspnam.3 mq_receive.3 mq_send.3 rtime.3 sem_wait.3 strftime.3 strptime.3 timeradd.3 rtc.4 core.5 proc.5 icmp.7 time.7 michael witten global fix: consistently define the epoch all definitions of the epoch have been refactored to the following: 1970-01-01 00:00:00 +0000 (utc) that form is more consistent, logical, precise, and internationally recognizable than the other variants. also, some wording has been altered as well. spu_create.2 getopt.3 passwd.5 michael kerrisk global fix: s/non-existing/nonexistent/ faccessat.2 fchmodat.2 fchownat.2 fstatat.2 futimesat.2 linkat.2 mkdirat.2 mknodat.2 openat.2 readlinkat.2 renameat.2 symlinkat.2 unlinkat.2 utimensat.2 mkfifoat.3 michael kerrisk update feature test macro requirements starting in glibc 2.10, defining _xopen_source >= 700, or _posix_c_source >= 200809 exposes the declarations of these functions. changes to individual pages --------------------------- clock_getres.2 michael kerrisk update text on nonsetabble clock_*_cputime_id clocks susv3 permits, but does not require clock_thread_cputime_id and clock_process_cputime_id to be settable. see http://bugzilla.kernel.org/show_bug.cgi?id=11972. execve.2 colin watson fix description of treatment of caught signals caught signals reset to their default on an execve() (not to being ignored). fcntl.2 michael kerrisk s/f_owner_gid/f_owner_pgrp/ peter zijlstra took the name change i suggested. michael kerrisk document f_[sg]etown_ex; update details on f_setown linux 2.6.32 adds f_setown_ex and f_getown_ex. linux 2.6.12 changed (broke) the former behavior of f_setown with respect to threads. intro.2 intro.3 michael kerrisk make subsection heading consistent with other intro.? pages these pages used "copyright terms"; the other intro.? pages used "copyright conditions". make these pages like the others. sendfile.2 michael kerrisk clarify behavior when 'offset' is null seteuid.2 michael kerrisk note unstandardized behavior for effective id posix.1 doesn't require that the effective id can be changed to the same value it currently has (a no-op). the man page should note this, since some other implementations don't permit it. setgid.2 michael kerrisk fix eperm error description s/effective group id/real group id/ this bug lived in man pages for 15 years before jason spotted it! i checked back in linux 1.0, and the behavior was as the fixed man page describes. setreuid.2 michael kerrisk add more detail on posix.1 specification for these syscalls setuid.2 michael kerrisk remove crufty statement that seteuid() is not in posix see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=569812 stime.2 strftime.3 tzset.3 zic.8 michael witten gmt -> utc (where appropriate) sync_file_range.2 christoph hellwig add some big warnings re data integrity this system call is by design completely unsuitable for any data integrity operations. make that very clear in the manpage. cpu_set.3 vlastimil babka synopsis: fix return types for cpu_count_*() these functions return 'int' not void'. confstr.3 michael kerrisk fix feature test macro requirements daemon.3 michael kerrisk fix description of 'nochdir' argument. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=554819 gethostbyname.3 michael kerrisk document feature test macro requirements for herror() and hstrerror() since glibc 2.8, one of _bsd_source, _svid_source, or _gnu_source is required. getline.3 michael kerrisk update to reflect that these functions were standardized in posix.1-2008 getnameinfo.3 michael kerrisk document feature test macros requirements for ni_maxhost and ni_maxserv since glibc 2.8, one of _bsd_source, _svid_source, or _gnu_source must be defined to obtain these definitions. getopt.3 jonathan nieder fix feature test macro requirements memchr.3 michael kerrisk add feature test macro requirements for memrchr() nextafter.3 michael kerrisk fix notable error in description. "less than y" should be "less than x". popen.3 michael kerrisk fix feature test macro requirements pthread_attr_setdetachstate.3 pthread_attr_setschedparam.3 pthread_attr_setschedpolicy.3 denis barbier argument name is 'attr' not 'thread' the function argument was misnamed in the description on these three pages. rtnetlink.3 michael kerrisk various fixes in example code edward reported a problem in the example code, where a variable seems to be misnamed. upon inspection, there seem to be a few such instances, and this patch is my best guess at how things should look. sched_getcpu.3 michael kerrisk place correct header file in synopsis sleep.3 bill o. gallmeister sleep() puts calling *thread* to sleep (not calling *process*) sleep.3 bill o. gallmeister add nanosleep(2) to see also strftime.3 michael kerrisk %z is defined in susv3 so, substitute "gnu" tag in man page by "su". strftime.3 michael witten move 822-compliant date format example to examples section the rfc 822-compliant date format given in the description of `%z' is now moved to the `examples' section (note: `example' has been renamed `examples'). furthermore, that format example is now actually rfc 822-compliant (using `%y' instead of `%y') and has been qualified as being correct only when in the context of at least an english locale. also, `%t' is used in place of `%h:%m:%s'. for completeness, an rfc 2822-compliant format example has been similarly added. strftime.3 michael witten expand introductory text strftime.3 michael witten clarification of %z specifier string.3 mark hills add stpcpy() to this list of string functions strptime.3 michael kerrisk initialize tm structure in example program undocumented.3 michael kerrisk remove pages now documented by now, the following are documented: fopencookie(3) freeifaddrs(3) rawmemchr(3) readdir_r(3) getutmp(3) getutmpx(3) utmpxname(3) http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=554819 group.5 michael kerrisk s/passwd/password/ the page inconsistently used "passwd" and "password" to refer to the same field. capabilities.7 michael kerrisk update securebits discussion to use secbit_* flags feature_test_macros.7 michael kerrisk _posix_c_source >= 200808 defines _atfile_source since glibc 2.10, _posix_c_source >= 200808 defines _atfile_source path_resolution.7 michael kerrisk add readlink(2) to see also michael kerrisk fix name line the poorly constructed part preceding "\-" causes apropos not to be able to find the subject. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=558300 signal.7 michael kerrisk fix discussion of sigunused clarify that this signal really is synonymous with sigsys. see http://bugzilla.kernel.org/show_bug.cgi?id=14449 ==================== changes in man-pages-3.25 ==================== released: 2010-06-20, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alexander e. patrakov andi kleen andrew klossner andré goddard rosa bo borgerson christian franke daisuke hatayama david sommerseth denis barbier eric blake fang wenqi francesco cosoleto gernot tenchio hugh dickins ivana hutarova varekova jan blunck jan engelhardt jan kara jeff barry manfred schwarb mark hills martin (joey) schulze michael kerrisk mihai paraschivescu mike frysinger miklos szeredi petr baudis petr gajdos petr uzel pierre habouzit reuben thomas rob landley robert wohlrab serge e. hallyn tolga dalman tom swigg walter harms yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- migrate_pages.2 andi kleen new page documenting migrate_pages(2). andi's text based on the move_pages.2 page; additional edits by mtk. migrate_pages(2) was new in linux 2.6.16. quotactl.2 jan kara major updates update the page to consolidate information from the outdated man-pages quotactl.2 page and the quotactl.2 page in the "quota-tools" package. the page in "quota-tools" has now been dropped by jan kara, so that there is just one canonical quotactl.2 page (in pan-pages). michael kerrisk various other pieces added to the page by mtk. newly documented interfaces in existing pages --------------------------------------------- fcntl.2 michael kerrisk document f_setpipe_sz and f_getpipe_sz these commands, new in kernel 2.6.35, set and get the capacity of pipes. madvise.2 andi kleen document madv_hwpoison michael kerrisk added documentation of madv_mergeable and madv_unmergeable these flags (used for kernel samepage merging, ksm) are new in 2.6.32. andi kleen document madv_soft_offline this operation was added in linux 2.6.33. mmap.2 michael kerrisk document map_uninitialized flag new in linux 2.6.33. prctl.2 andi kleen document the hwpoison prctls in 2.6.32 sched_setscheduler.2 michael kerrisk document sched_reset_on_fork new in linux 2.6.32 umount.2 michael kerrisk document umount_nofollow new in linux 2.6.34. mkstemp.3 michael kerrisk document mkstemps() and mkostemps() these functions are new in glibc 2.11. they allow the template string to include a suffix after the "xxxxxx" string. proc.5 michael kerrisk document /proc/sys/vm/memory_failure_early_kill new in 2.6.32. description based on the text in documentation/sysctl/vm.txt. michael kerrisk document /proc/sys/vm/memory_failure_recovery new in linux 2.6.32. description based on the text in documentation/sysctl/vm.txt. michael kerrisk document /proc/sys/fs/pipe-max-size socket.7 jan engelhardt document so_domain and so_protocol these read-only socket options were new in linux 2.6.32. new and changed links --------------------- fstatvfs.2 michael kerrisk adjust link to point to section 3 fstatvfs.3 statvfs.2 michael kerrisk new link to page relocated to section 3 mkstemps.3 mkostemps.3 michael kerrisk new links to mkstemp.3 mkstemp.3 now describes mkstemps(3) and mkostemps(3). timer_create.2 timer_delete.2 timer_getoverrun.2 timer_settime.2 getline.3 michael kerrisk add 'l' to constants in feature test macro specifications be consistent with posix, which uses constants such as 200809l. global changes -------------- open.2 sync_file_range.2 umount.2 michael kerrisk global fix: s/filesystem/file system/ changes to individual pages --------------------------- fcntl.2 michael kerrisk note that glibc 2.11 papers over the kernel f_getown bug since version 2.11, glibc works around the kernel limitation for process groups ids < 4096 by implementing f_getown via f_getown_ex. futex.2 michael kerrisk various fixes in see also getpriority.2 nice.2 francesco cosoleto move renice from section 8 to section 1 getrusage.2 mark hills add ru_maxrss see kernel commit 1f10206. mark hills description of maintained fields these descriptions are taken from netbsd 5.0's getrusage(2). michael kerrisk enhanced description of various fields mlock.2 michael kerrisk /proc/pid/status vmlck shows how much memory a process has locked after a note from tom swigg, it seems sensible mention vmlck here. mount.2 petr uzel fix incorrect path move_pages.2 andi kleen clarify includes/libraries mremap.2 michael kerrisk clarify existence of fifth argument. msgctl.2 semctl.2 shmctl.2 francesco cosoleto move ipcs from section 8 to section 1 open.2 michael kerrisk remove ambiguity in text on nfs and o_excl. poll.2 michael kerrisk fix discussion of ppoll() timeout argument 1. rename ppoll)(_ argument to "timeout_ts" to distinguish it from the poll() argument in the text. 2. more accurately describe the poll() call that is equivalent to ppoll(). posix_fadvise.2 michael kerrisk add sync_file_range(2) under see also prctl.2 michael kerrisk correct pr_set_keepcaps description the "keep capabilities" flag only affects the treatment of permitted capabilities, not effective capabilities. also: other improvements to make the pr_set_keepcaps text clearer. select_tut.2 michael kerrisk fix bug in example program sigaction.2 michael kerrisk add trap_branch and trap_hwbkpt to si_code values for sigtrap michael kerrisk rearrange text describing fields set by sigqueue(2) michael kerrisk add details for signals sent by posix message queue notifications michael kerrisk improve description of various siginfo_t fields michael kerrisk add some details for sigtrap and si_trapno andi kleen document hwpoison signal extensions statfs.2 michael kerrisk bring statfs struct type declarations closer to glibc reality fang wenqi add definition ext4_super_magic = 0xef53 michael kerrisk document f_frsize field. statvfs.2 michael kerrisk move this page to section 3 (since it's a library call) swapon.2 ivana hutarova varekova note effect of config_memory_failure on max_swapfiles from 2.6.32, max_swapfiles is decreased by 1 if the kernel is built with config_memory_failure. syscalls.2 michael kerrisk bring system call list up to date with linux 2.6.33 michael kerrisk fix kernel version number for utimes() cproj.3 michael kerrisk note fix for c99 conformance in glibc 2.12. crypt.3 petr baudis correct note on key portion significance as marcel moreaux notes: the linux manpage for crypt()[1] contains the following statement as the last sentence of the notes section: in the sha implementation the entire key is significant (instead of only the first 8 bytes in md5). it should probably say "des" where it says "md5" (and maybe "md5/sha" where it says "sha"), because in md5 password hashing, the entire key is significant, not just the first 8 bytes. this patch fixes the wording. fmemopen.3 michael kerrisk bug fix in example program ftw.3 michael kerrisk note that if 'fn' changes cwd, the results are undefined michael kerrisk clarify description of fpath argument as reported by pierre habouzit, 'fpath' is not relative to 'dirpath'. it is either relative to the calling process's current working directory (if 'dirpath' was relative), or it is absolute (if 'dirpath' was absolute). getaddrinfo.3 christian franke fix a field name mixup: s/ai_family/ai_flags/ getline.3 robert wohlrab remove unneeded check before free() the manpage of getline shows an example with an extra null pointer check before it calls free. this is unneeded according to free(3): if ptr is null, no operation is performed. this patch removes the "if" check. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=572508 log.3 log10.3 log2.3 jan engelhardt add cross-references to other-base logarithmic functions opendir.3 petr baudis specify feature test macro requirements for fdopendir(3) currently, there is no note on the fact that fdopendir() is posix.2008-only. openpty.3 eric blake use const as appropriate michael kerrisk note glibc version that added "const" to function arguments michael kerrisk explicitly note that these functions are not in posix resolver.3 michael kerrisk fix declaration of dn_comp() in synopsis remove the second 'exp_dn' from the calling signature. termios.3 michael kerrisk change noflsh text to speak of characters, not signals core.5 michael kerrisk update description of coredump_filter kernel 2.6.24 added mmf_dump_elf_headers. kernel 2.6.28 added mmf_dump_hugetlb_private and mmf_dump_hugetlb_shared. elf.5 daisuke hatayama document pn_xnum extension in linux-2.6.34-rc1, an elf core extension was added; user-land tools manipulating elf core dump such as gdb and binutils has already been modified before; so elf.5 needs to be modified accordingly. you can follow information on the elf extension via the lkml post: http://lkml.org/lkml/2010/1/3/103 date mon, 04 jan 2010 10:06:07 +0900 (jst) subject ... elf coredump: add extended numbering support this linux-specific extension was added in kernel 2.6.34. reviewed-by: petr baudis michael kerrisk remove ei_brand as reported by yuri kozlov and confirmed by mike frysinger, ei_brand is not in gabi (http://www.sco.com/developers/gabi/latest/ch4.eheader.html) it looks to be a bsdism michael kerrisk remove words under '.note': "described below" the existing text is broken, because there is no '"note section" format' describe below. simplest solution is to remove the words "described below". filesystems.5 jeff barry add discussion of ntfs and ext4 proc.5 michael kerrisk simplify description of /proc/sys and /proc/sys/fs in the description of these directories, there's no need to list all the files and subdirectories that they contain; that information is provided by the entries that follow. services.5 yuri kozlov remove crufty reference to nonexistent bugs section capabilities.7 michael kerrisk document cap_sys_resource and f_setpipe_sz with cap_sys_resource, a process can increase pipe capacity above /proc/sys/ps/pipe-max-size. michael kerrisk add get_robust_list() info under cap_sys_ptrace michael kerrisk add madv_hwpoison under cap_sys_admin signal.7 michael kerrisk make a clearer statement about nonportable aspect of signal(2) make a clearer statement that signal(2) is less portable for establishing a signal handler. socket.7 michael kerrisk use consistent language to describe read-only socket options udp.7 michael kerrisk add fionread warning. warn that fionread can't distinguish case of a zero-length datagram from the case where no datagrams are available. ==================== changes in man-pages-3.26 ==================== released: 2010-09-04, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: alexander shishkin brian sutin denis barbier guillem jover jianhua li linus nilsson lenaic huard mac martin schulze maxin john michael kerrisk nicholas hunt peng haitao peter stuge przemyslaw szczepaniak scott walls tan yee fan wu fengguang yitzchak gale yuri kozlov apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- eventfd.2 michael kerrisk document efd_semaphore document the efd_semaphore flag, added in kernel 2.6.30. also restructured some parts of the text to fit with the addition of the efd_semaphore text. global changes -------------- getaddrinfo.3 getipnodebyname.3 st.4 michael kerrisk s/logical or/bitwise or/ changes to individual pages --------------------------- clock_nanosleep.2 michael kerrisk fix discussion of return value when interrupted by a signal epoll_ctl.2 yuri kozlov small fix to types in data structures eventfd.2 alexander shishkin clarified close-on-exec behavior madvise.2 michael kerrisk improve discussion of madv_soft_offline mkdir.2 michael kerrisk add emlink error to errors mq_getsetattr.2 mq_close.3 mq_getattr.3 mq_notify.3 mq_send.3 mq_unlink.3 lnac huard fix return type in synopsis (s/mqd_t/int/) recv.2 send.2 michael kerrisk remove obsolete reference to glibc version in notes recv.2 send.2 nicholas hunt adjust type shown for msg_controllen to glibc reality this patch fixes the type of msg_controllen in the struct msghdr definition given in send.2 and recv.2 to match the definition in glibc and the kernel. select.2 michael kerrisk update notes on old glibc pselect() make it clear that modern glibc uses the kernel pselect() on systems where it is available. see https://bugzilla.kernel.org/show_bug.cgi?id=14411 statfs.2 guillem jover fix copy & paste error for __sword_type definition sysfs.2 michael kerrisk clarify that this syscall is obsolete. and strengthen recommendation to use /proc/filesystems instead. write.2 michael kerrisk add edestaddrreq error a64l.3 peng haitao fix error in notes, s/a64l/l64a/ error.3 linus nilsson change "perror" to "strerror" in description of error() mq_send.3 michael kerrisk fix eagain description (s/empty/full) initrd.4 yuri kozlov fix ip address in explanation of nfs example tzfile.5 michael kerrisk add information on version 2 format timezone files updated using information from the tzcode 2010l release at ftp://elsie.nci.nih.gov/pub. (it's an open question whether or not a version of tzfile.5 should live independently in man-pages. it was added to the man-pages set many years ago. for now, i'll follow a conservative course that causes least pain to downstream, by continuing to maintain a separate copy in man-pages.) see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=594219 ==================== changes in man-pages-3.27 ==================== released: 2010-09-22, nuernberg contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: caishuxian denis barbier denis silakov der mouse jan kratochvil jim belton jiri olsa kosaki motohiro mark hills matthew flaschen michael kerrisk ozgur gurcan petr baudis remi denis-courmont tanaka akira tim stoakes w. trevor king yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- sigevent.7 petr baudis, michael kerrisk new page to centralize description of sigevent structure several interfaces use this structure. best to centralize the common details in one place. content taken from the existing timerfd_create.2 and mq_open.3 pages, with additions by petr baudis and michael kerrisk. newly documented interfaces in existing pages --------------------------------------------- ip.7 jiri olsa document ip_nodefrag this option is new in linux 2.6.36 unix.7 michael kerrisk document siocinq ioctl() operation global changes -------------- _exit.2 brk.2 chdir.2 chmod.2 chown.2 chroot.2 clock_nanosleep.2 getdtablesize.2 gethostname.2 getpagesize.2 getsid.2 killpg.2 mknod.2 mknodat.2 posix_fadvise.2 pread.2 readlink.2 setpgid.2 setreuid.2 sigaltstack.2 stat.2 symlink.2 sync.2 truncate.2 vfork.2 wait.2 wait4.2 a64l.3 abs.3 acos.3 acosh.3 asin.3 asinh.3 atan.3 atan2.3 atanh.3 atoi.3 cbrt.3 ceil.3 clock_getcpuclockid.3 copysign.3 cos.3 cosh.3 dirfd.3 div.3 dprintf.3 ecvt.3 erf.3 erfc.3 exp.3 exp2.3 expm1.3 fabs.3 fdim.3 fexecve.3 ffs.3 floor.3 fma.3 fmax.3 fmemopen.3 fmin.3 fmod.3 fpclassify.3 frexp.3 fwide.3 gamma.3 gcvt.3 getcwd.3 getdate.3 getgrent.3 gethostid.3 getpass.3 getpwent.3 getsubopt.3 getw.3 hypot.3 ilogb.3 insque.3 isalpha.3 isgreater.3 iswblank.3 j0.3 j0.3 ldexp.3 lockf.3 log.3 log10.3 log1p.3 log2.3 logb.3 lrint.3 lround.3 mbsnrtowcs.3 mkdtemp.3 mkstemp.3 mktemp.3 modf.3 mq_receive.3 mq_send.3 nan.3 nextafter.3 posix_fallocate.3 posix_memalign.3 pow.3 printf.3 qecvt.3 random.3 realpath.3 remainder.3 remquo.3 rint.3 rint.3 round.3 scalb.3 scalbln.3 scanf.3 siginterrupt.3 signbit.3 sigset.3 sin.3 sinh.3 sqrt.3 stpcpy.3 stpncpy.3 strdup.3 strdup.3 strnlen.3 strsignal.3 strtod.3 strtol.3 strtoul.3 tan.3 tanh.3 tgamma.3 trunc.3 ttyslot.3 ualarm.3 usleep.3 wcpcpy.3 wcpncpy.3 wcscasecmp.3 wcsdup.3 wcsncasecmp.3 wcsnlen.3 wcsnrtombs.3 wprintf.3 michael kerrisk add/fix/update feature test macro requirements in synopsis various changes to: * update feature test requirements to note changes in recent glibc releases * correct errors in feature test macro requirements * add feature test macro requirements to pages where the requirements were not previously stated. accept.2 clone.2 dup.2 fallocate.2 pipe.2 readahead.2 sched_setaffinity.2 unshare.2 cpu_set.3 endian.3 euidaccess.3 fexecve.3 getpt.3 getpw.3 getumask.3 getutmp.3 gnu_get_libc_version.3 makedev.3 matherr.3 mbsnrtowcs.3 memfrob.3 pthread_attr_setaffinity_np.3 pthread_getattr_np.3 pthread_setaffinity_np.3 pthread_tryjoin_np.3 tcgetsid.3 wcscasecmp.3 wcsncasecmp.3 wcsnlen.3 wcsnrtombs.3 wcswidth.3 rtld-audit.7 michael kerrisk synopsis: add reference to feature_test_macros(7) these pages specify feature test macros in the function prototypes. add a reference to feature_test_macros(7), so that readers are pointed to the information that feature test macros must be defined before including *any* header file. clock_nanosleep.2 clock_getcpuclockid.3 getnetent_r.3 getprotoent_r.3 getrpcent_r.3 getservent_r.3 sigwait.3 michael kerrisk return value: note that "positive error numbers" are listed in errors fcntl.2 intro.2 open.2 poll.2 ftw.3 intro.3 matherr.3 system.3 tmpnam.3 unix.7 michael kerrisk note that feature test macros must be defined before *any* includes programmers often make the mistake of including a feature test macro only after having already included some header files. this patch adds some text at opportune places to remind programmers to do things the right way. index.3 stpcpy.3 strcasecmp.3 strcat.3 strchr.3 strcmp.3 strcoll.3 strcpy.3 strdup.3 strfry.3 strpbrk.3 strsep.3 strspn.3 strstr.3 strtok.3 strxfrm.3 michael kerrisk see also: add reference to string(3) the idea here is to provide a route to discover other string functions. armscii-8.7 cp1251.7 iso_8859-3.7 iso_8859-5.7 iso_8859-6.7 iso_8859-8.7 iso_8859-10.7 iso_8859-11.7 iso_8859-13.7 iso_8859-14.7 koi8-u.7 denis barbier fix decimal values in encoding tables octal and hexadecimal values are right, but there are some off-by one errors in decimal values. correct values are printed by this command: perl -pi -e 'if (s/^([0-7]+)\t([0-9]+)\t([0-9a-fa-f]+)//) {printf "%03o\t%d\t%s", hex($3), hex($3), $3;};' man7/*.7 changes to individual pages --------------------------- capget.2 michael kerrisk synopsis: remove unneeded "undef _posix_source" fcntl.2 michael kerrisk add feature test macro requirements for f_getown and f_setown fcntl.2 michael kerrisk note feature test macro requirements for f_dupfd_cloexec getrlimit.2 michael kerrisk document units for rlimit_rttime limit this limit is in microseconds http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=596492 lseek.2 michael kerrisk removed note about return type on ancient systems mount.2 michael kerrisk definitions of various ms_* constants only appeared in glibc 2.12 see http://sourceware.org/bugzilla/show_bug.cgi?id=11235 stat.2 michael kerrisk update information on nanosecond timestamp fields update feature test macro requirements for exposing these fields. note that these fields are specified in posix.1-2008. timer_create.2 michael kerrisk factor out generic material that was moved to new sigevent(7) page aio_fsync.3 michael kerrisk add reference to new sigevent(7) page atanh.3 michael kerrisk glibc 2.10 fixed pole error bug http://sourceware.org/bugzilla/show_bug.cgi?id=6759 was resolved. cerf.3 michael kerrisk make it clearer that this function is unimplemented cos.3 michael kerrisk errno is now correctly set to edom on a domain error http://sources.redhat.com/bugzilla/show_bug.cgi?id=6780 was (silently) resolved. expm1.3 michael kerrisk errno is now correctly set to erange on a range error http://sources.redhat.com/bugzilla/show_bug.cgi?id=6788 was (silently) resolved. fmod.3 michael kerrisk errno is now correctly set to edom for the x==inf domain error http://sources.redhat.com/bugzilla/show_bug.cgi?id=6784 was (silently) resolved. insque.3 michael kerrisk noted prev == null bug in glibc 2.4 and earlier as noted by remi denis-courmont, glibc nowadays allows 'prev' to be null, as required by posix for initializing a linear list. but in glibc 2.4 and earlier, 'prev' could not be null. add a bugs section noting this. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=551201 michael kerrisk added info on circular lists, and initializing circular lists michael kerrisk added example program lgamma.3 michael kerrisk glibc 2.10 fixed pole error bug http://sourceware.org/bugzilla/show_bug.cgi?id=6777 was (silently) resolved. log2.3 matthew flaschen log2() function does not conform to c89 log2(), log2f(), and log2l() do not conform to c89. they are defined in c99. see http://flash-gordon.me.uk/ansi.c.txt and http://www.schweikhardt.net/identifiers.html mq_notify.3 michael kerrisk factor out generic material that was moved to new sigevent(7) page pow.3 michael kerrisk errno is now correctly set to erange on a pole error http://sources.redhat.com/bugzilla/show_bug.cgi?id=6776 was (silently) resolved. pthread_kill_other_threads_np.3 michael kerrisk conforming to: note meaning of "_np" suffix rand.3 michael kerrisk clarify description of range of returned value michael kerrisk add an example program michael kerrisk expand description of rand_r() random.3 w. trevor king update initstate() return value description to match glibc readdir.3 michael kerrisk clarify that "positive error numbers" are listed in errors rexec.3 michael kerrisk synopsis: add header file and feature test macro requirements sigpause.3 michael kerrisk correct discussion of when bsd vs sysv version is used in glibc sin.3 michael kerrisk errno is now correctly set to edom on a domain error http://sources.redhat.com/bugzilla/show_bug.cgi?id=6781 was (silently) resolved. tan.3 michael kerrisk errno is now correctly set to edom on a domain error http://sources.redhat.com/bugzilla/show_bug.cgi?id=6782 was (silently) resolved. wcscasecmp.3 wcsncasecmp.3 wcsnlen.3 michael kerrisk added versions section boot.7 yuri kozlov update list of major linux distributions feature_test_macros.7 michael kerrisk make text on required placement of macros more prominent move the text that notes the requirement that feature test macros must be defined before including any header files to the top of the page, and highlight the text further, so that the reader will not miss this point. pthreads.7 signal.7 michael kerrisk add see also reference to new sigevent(7) page tcp.7 michael kerrisk clarify header file details for siocinq and siocoutq also note synonymous fionread and tiocoutq. ==================== changes in man-pages-3.28 ==================== released: 2010-10-04, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andries e. brouwer denis barbier jan kara landijk lennart poettering michael haardt michael kerrisk petr baudis sam varshavchik apologies if i missed anyone! new and rewritten pages ----------------------- getaddrinfo_a.3 petr baudis new page documenting getaddrinfo_a() the page also documents gai_suspend(), gai_cancel(), and gai_error(). aio.7 michael kerrisk new page providing an overview of posix asynchronous i/o newly documented interfaces in existing pages --------------------------------------------- exec.3 michael kerrisk document execvpe() this function was added to glibc in version 2.11. also various other small rewrites in the page. new and changed links --------------------- gai_cancel.3 gai_error.3 gai_suspend.3 petr baudis new links to new getaddrinfo_a.3 page error_one_per_line.3 michael kerrisk fix misnamed link file (was error_on_per_line.3) execvpe.3 michael kerrisk new link to exec.3 sigstack.3 michael kerrisk new link to sigaltstack.2 no new programs should use sigstack(3). point the user to the better sigaltstack(2), whose man page briefly mentions sigstack(3). vlimit.3 michael kerrisk new link to getrlimit.2 no new programs should use vlimit(3). point the user to the better setrlimit(2), whose man page briefly mentions vlimit(3). vtimes.3 michael kerrisk new link to getrusage.2 no new programs should use vtimes(3). point the user to the better getrusage(2), whose man page briefly mentions vtimes(3). global changes -------------- various pages michael kerrisk switch to american usage: "-wards" ==> "-ward" american english uses "afterward" in preference to "afterwards", and so on chdir.2 chmod.2 chown.2 gethostname.2 getsid.2 pread.2 setpgid.2 sigaltstack.2 stat.2 truncate.2 wait.2 dirfd.3 getsubopt.3 mkdtemp.3 mkstemp.3 siginterrupt.3 strdup.3 michael kerrisk simplify feature test macro requirements changes to individual pages --------------------------- getrlimit.2 michael kerrisk add mention of the ancient vlimit() function getrusage.2 michael kerrisk add mention of the ancient vtimes() function io_cancel.2 io_destroy.2 io_getevents.2 io_setup.2 io_submit.2 michael kerrisk see also: add aio(7) sched_setscheduler.2 michael kerrisk errors: note that null 'param' yields einval stat.2 michael kerrisk note feature test macro requirements for blkcnt_t and blksize_t timer_create.2 michael kerrisk standardize on name 'sevp' for sigevent argument truncate.2 michael kerrisk correct and simplify ftruncate() feature test macro requirements the glibc 2.12 feature test macro requirements for ftruncate() are buggy; see http://sourceware.org/bugzilla/show_bug.cgi?id=12037. corrected the requirements in the synopsis, and added a bugs section describing the problem in glibc 2.12. aio_cancel.3 michael kerrisk add pointer to aio(7) for example program refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section aio_error.3 michael kerrisk wording improvements in return value add pointer to aio(7) for example program refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section aio_fsync.3 michael kerrisk refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section aio_read.3 michael kerrisk various minor rewordings and additions add pointer to sigevent(7) for details of notification of i/o completion add pointer to aio(7) for example program refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section aio_return.3 michael kerrisk improve description in return value add pointer to aio(7) for example program refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section aio_suspend.3 michael kerrisk various additions and rewordings. give some arguments more meaningful names. more explicitly describe the 'nitems' argument. explicitly note that return is immediate if an i/o operation has already completed. note that aio_error(3) should be used to scan the aiocb list after a successful return. add references to other relevant pages. various other pieces rewritten. refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section aio_write.3 michael kerrisk add pointer to sigevent(7) for details of notification of i/o completion various minor rewordings and additions refer the reader to aio(7) for a description of the aiocb structure conforming to: add posix.1-2008; add versions section clearenv.3 michael kerrisk fix error in feature test macro requirements dysize.3 michael kerrisk remove crufty statement about old sco bug exec.3 michael kerrisk add feature test macro requirements for execvpe() rewrite description of path and mention _cs_path note execvp() and execlp() behavior for filename containing a slash getaddrinfo.3 michael kerrisk add see also reference to new getaddrinfo_a.3 page gethostbyname.3 michael kerrisk fix formatting of feature test macros getw.3 michael kerrisk fix feature test macros malloc.3 landijk remove editorializing comments on memory overcommitting see https://bugzilla.kernel.org/show_bug.cgi?id=19332 michael kerrisk various minor reorganizations and wording fix-ups mq_notify.3 michael kerrisk standardize on name 'sevp' for sigevent argument nl_langinfo.3 michael haardt make it clear that nl_langinfo() interacts with setlocale() add an example program posix_openpt.3 michael kerrisk fix feature test macro requirements rand.3 michael kerrisk remove duplicate #include in example program strtok.3 petr baudis add reference to strtok() example in getaddrinfo(3) inotify.7 michael kerrisk added section noting limitations and caveats of inotify sigevent.7 michael kerrisk add see also reference to new getaddrinfo_a.3 page add see also referring to new aio(7) page suffixes.7 michael kerrisk change explanation of ".rpm" to "rpm software package" ==================== changes in man-pages-3.29 ==================== released: 2010-10-19, detroit contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: balazs scheidler david prevot denis barbier guillem jover ivana varekova lennart poettering michael kerrisk sam varshavchik simon paillard stephan mueller thomas jarosch yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- subpage_prot.2 michael kerrisk new page documenting the powerpc-specific subpage_prot(2) aio_init.3 michael kerrisk new page documenting aio_init(3) newly documented interfaces in existing pages --------------------------------------------- posix_fadvise.2 michael kerrisk document the architecture-specific arm_fadvise64_64() system call this arm-specific system call fixes the argument ordering for that architecture. since linux 2.6.14. sync_file_range.2 michael kerrisk document the architecture-specific sync_file_range2() system call as described in commit edd5cd4a9424f22b0fa08bef5e299d41befd5622, the sync_file_range() argument order is broken for some architectures (powerpc, arm, tile). the remedy was a different system call using the right argument order on those architectures. psignal.3 guillem jover document psiginfo() psiginfo() was added to glibc in version 2.10. michael kerrisk add details, versions, and bugs for psiginfo() ip.7 balazs scheidler document ip_recvorigdstaddr document ip_transparent michael kerrisk document ip_freebind text based on input from lennart poettering and balazs scheidler. see https://bugzilla.kernel.org/show_bug.cgi?id=20082 new and changed links --------------------- arm_fadvise64_64.2 michael kerrisk new link to posix_fadvise.2 arm_sync_file_range.2, sync_file_range2.2 michael kerrisk new links to sync_file_range.2 arrm_fadvise.2 michael kerrisk new link to posix_fadvise.2 psiginfo.3 guillem jover new link to psignal.3 global changes -------------- many pages michael kerrisk global fix: s/unix/unix/ the man pages were rather inconsistent in the use of "unix" versus "unix". let's go with the trademark usage. various pages michael kerrisk global fix: s/pseudo-terminal/pseudoterminal/ grantpt.3, ptsname.3, unlockpt.3, pts.4 michael kerrisk global fix: s/pty/pseudoterminal/ recv.2, cmsg.3, unix.7 michael kerrisk global fix: s/unix socket/unix domain socket/ fmtmsg.3, gethostbyname.3, termios.3 michael kerrisk global fix: s/unixware/unixware/ changes to individual pages --------------------------- inotify_rm_watch.2 michael kerrisk synopsis: fix type of 'wd' argument posix_fadvise.2 michael kerrisk rewrite versions, noting that the system call is fadvise64() syscalls.2 michael kerrisk add the powerpc-specific subpage_prot() system call add sync_file_range2() truncate.2 michael kerrisk fix feature test macros aio_cancel.3 aio_error.3 aio_fsync.3 aio_read.3 aio_return.3 aio_suspend.3 aio_write.3 michael kerrisk see also: add lio_listio(3) gai_cancel.3 gai_error.3 gai_suspend.3 michael kerrisk make these into links in the previous release, these files were accidentally made copies of getaddrinfo_a.3, instead of being made as link files. getifaddrs.3 thomas jarosch prevent possible null pointer access in example program malloc.3 michael kerrisk emphasize that malloc() and realloc() do not initialize allocated memory malloc_hook.3 ivana varekova warn that these functions are deprecated strcpy.3 michael kerrisk formatting fixes in strncpy() example implementation code ip.7 michael kerrisk reword notes on linux-specific options sigevent.7 michael kerrisk see also: add aio_read(3), aio_write(3), and lio_listio(3) unix.7 michael kerrisk document the autobind feature michael kerrisk fix description of abstract socket names as reported by lennart poettering: the part about "abstract" sockets is misleading as it suggests that the sockaddr returned by getsockname() would necessarily have the size of sizeof(struct sockaddr), which however is not the case: getsockname() returns exactly the sockaddr size that was passed in on bind(). in particular, two sockets that are bound to the same sockaddr but different sizes are completely independent. see https://bugzilla.kernel.org/show_bug.cgi?id=19812 michael kerrisk fix description of "pathname" sockets as reported by lennart poettering: the part about "pathname" sockets suggests usage of sizeof(sa_family_t) + strlen(sun_path) + 1 for calculating the sockaddr size. due to alignment/padding this is probably not a good idea. instead, one should use offsetof(struct sockaddr_un, sun_path) + strlen() + 1 or something like that. see https://bugzilla.kernel.org/show_bug.cgi?id=19812 ==================== changes in man-pages-3.30 ==================== released: 2010-11-01, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen bernhard walle david prevot eric w. biederman florian lehmann jan engelhardt lucian adrian grijincu michael kerrisk paul mackerras pádraig brady reuben thomas scarlettsp yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- kexec_load.2 andi kleen new page documenting kexec_load(2) michael kerrisk add license michael kerrisk incorporate fixes from eric w. biederman eric noted that a few instances of "virtual" should be "physical" and noted: there is an expectation that at hand off from sys_kexec that virtual and physical addresses will be identity mapped. but this isn't the old alpha booting convention where you have a virtual address and then you have to parse the page table to figure out where your kernel was actually loaded. michael kerrisk additions and edits by mtk various wording and layout improvements. fixed the name of a constant: s/kexec_arch_i386/kexec_arch_386/. added return value and errors sections. added versions section note that config_kexec is needed removed details of using syscall; the reader can find them in syscall(2). added some details for kexec_preserve_context. revised the text mentioning the kernel header, since it is not yet exported, and it's not certain that it will be. lio_listio.3 michael kerrisk new page documenting lio_listio(3) newly documented interfaces in existing pages --------------------------------------------- reboot.2 andi kleen document linux_reboot_kexec some fix-ups by michael kerrisk michael kerrisk place 'cmd' values in alphabetical order. unshare.2 michael kerrisk document clone_newipc michael kerrisk document clone_newnet lucian adrian grijincu improve description of clone_newnet clone_newnet creates a new network namespace from scratch. you don't have anything from the old network namespace in the new one. even the loopback device is new. michael kerrisk document clone_sysvsem michael kerrisk document clone_newuts michael kerrisk relocate discussion of cap_sys_admin to clone_newns section and rewrite the eperm description to be more general in preparation for the new flags to be documented. global changes -------------- various pages michael kerrisk add reference to feature_test_macros(7) some pages simply list feature test macro requirements in the form: #define #gnu_source #include for these pages, add a "see feature_test_macros(7)" comment on the "#define" line. various pages michael kerrisk see also: remove redundant reference to feature_test_macros(7) various pages david prevot use greater consistency in name line (remove definite article at start of descriptive clause.) various pages michael kerrisk see also: place entries in correct order various pages michael kerrisk errors: place entries in correct order various pages michael kerrisk add section number to references to functions documented in other pages various pages michael kerrisk remove redundant section number in page references remove section number in function references that are for functions documented on this page. armscii-8.7 iso_8859-3.7 iso_8859-4.7 iso_8859-5.7 iso_8859-6.7 iso_8859-10.7 iso_8859-11.7 iso_8859-13.7 iso_8859-14.7 koi8-u.7 david prevot capitalize hexadecimal numbers changes to individual pages --------------------------- access.2 michael kerrisk note use of faccessat(2) for checking symbolic link permissions michael kerrisk give an example of a safer alternative to using access() clone.2 michael kerrisk clarify when clone_newnet implementation was completed faccessat.2 michael kerrisk note that faccessat() is racy fcntl.2 michael kerrisk return value: improve description of f_getfd and f_getfl inotify_add_watch.2 michael kerrisk document enoent error mlock.2 michael kerrisk improve wording describing /proc/pid/status /vmlck field michael kerrisk shmctl() shm_locked memory is not included in vmlck reboot.2 michael kerrisk place 'cmd' values in alphabetical order subpage_prot.2 michael kerrisk change 1-line page description michael kerrisk improvements after review by paul mackerras timer_settime.3 michael kerrisk remove redundant see also reference euidaccess.3 michael kerrisk note the use of faccessat(2) to operate on symbolic links michael kerrisk note that the use of euidaccess() is racy fenv.3 michael kerrisk clarify wording relating to glibc version getgrent.3 getgrent_r.3 getgrnam.3 michael kerrisk refer reader for group(5) for more info on group structure getopt.3 bernhard walle use constants in getopt_long() example the description of getopt_long() mentions the constants required_argument, no_argument and optional_argument. use them in the example to make the code easier to understand. getpw.3 michael kerrisk change comment describing pw_gecos getpw.3 getpwent.3 getpwent_r.3 michael kerrisk refer reader to passwd(5) for more info on the passwd structure getpwent.3 getpwnam.3 michael kerrisk note that pw_gecos is not in posix and change the comment describing this field getpwent_r.3 michael kerrisk change comment describing pw_gecos getpwnam.3 michael kerrisk some rewording and restructuring sched_getcpu.3 michael kerrisk fix feature test macro requirements strnlen.3 michael kerrisk fix feature test macro requirements group.5 michael kerrisk various minor rewordings hosts.5 protocols.5 spufs.7 termio.7 david prevot remove definite article from name section please find inline another tiny patch in order to shrink the definite article from some other pages (found with "rgrep -i ' \\\- the' man*"). passwd.5 michael kerrisk various minor rewordings proc.5 michael kerrisk add reference to mlock(2) for further info on /proc/pid/status vmlck armscii-8.7 david prevot write the character set name as armscii cp1251.7 david prevot capitalize hexadecimal numbers ip.7 david prevot fix name of socket option: s/ip_ttl/ip_transparent/ david prevot place socket options in alphabetical order koi8-r.7 david prevot fix special character names comparing to koi8-u.7, i noticed some inconsistencies in special character names. after checking with the following unicode related pages, please find inline (and gzipped attached, hopefully not messing with encoding), a patch in order to make it right, on an unicode point of view. http://www.unicode.org/charts/pdf/u2500.pdf http://www.unicode.org/charts/pdf/u25a0.pdf http://www.unicode.org/charts/pdf/u0080.pdf http://www.unicode.org/charts/pdf/u1d400.pdf david prevot fix see also reference and letter names the koi8-r(7) (russian net character set) manual page refers to iso-8859-7(7) manual page, which is the latin/greek one. i guess it should refer instead to the iso-8859-5(7) (latin/cyrillic) one. this is addressed at the end of the patch. it has also been spotted that letter names are different in this manual page and in the unicode related page [0], the first part of the page address this. 0: http://www.unicode.org/charts/pdf/u0400.pdf man-pages.7 michael kerrisk update example the old example used the chmod(2) man page, but the feature test macro requirements on that page had changed. update to use an example from a different page (acct(2), whose feature test macro requirements are probably unlikely to change in the future). ==================== changes in man-pages-3.31 ==================== released: 2010-11-12, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: andi kleen david prevot denis barbier krzysztof żelechowski michael kerrisk yuri kozlov apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- getrlimit.2 michael kerrisk added documentation of prlimit() prlimit() is new in kernel 2.6.36. inotify.7 michael kerrisk document in_excl_unlink this flag was added in linux 2.6.36. see kernel commit 8c1934c8d70b22ca8333b216aec6c7d09fdbd6a6. new and changed links --------------------- prlimit.2 michael kerrisk new link to getrlimit.2 changes to individual pages --------------------------- getrlimit.2 michael kerrisk remove unneeded text in description intro.2 michael kerrisk added various pages to see also kexec_load.2 michael kerrisk add kernel version where kexec_preserve_context first appeared added kernel version number where kexec_on_crash first appeared fix copyright make copyright in the name of intel corporation versions: fix version number kexec_load() was first implemented in 2.6.13, though the entry in the system call table was reserved starting in 2.6.7. migrate_pages.2 michael kerrisk see also: add reference to documentation/vm/page_migration sched_setaffinity.2 michael kerrisk add missing word "real" to "user id" syscalls.2 michael kerrisk fix kernel version number for kexec_load kexec_load() was first implemented in 2.6.13, though the entry in the system call table was reserved starting in 2.6.7. michael kerrisk add prlimit() to list intro.3 michael kerrisk added various pages to see also printf.3 michael kerrisk formatting fixes in example code hostname.7 michael kerrisk small improvement to description of domains see: https://bugzilla.novell.com/show_bug.cgi?id=651900 ==================== changes in man-pages-3.32 ==================== released: 2010-12-03, munich contributors ------------ the following people contributed notes, ideas, or patches that have been incorporated in changes in this release: a. costa denis barbier emil mikulic eugene kapun hugh dickins ivana hutarova varekova joern heissler lars wirzenius martin eberhard schauer michael kerrisk petr uzel roger pate török edwin yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- pthread_sigqueue.3 michael kerrisk new page documenting pthread_sigqueue() pthread_sigqueue() is new in glibc 2.11 (requires a kernel with rt_tgsigqueinfo(), added in linux 2.6.31). newly documented interfaces in existing pages --------------------------------------------- readv.2 michael kerrisk add documentation of preadv() and pwritev() the preadv() and pwritev() system calls were added in linux 2.6.30. new and changed links --------------------- preadv.2 michael kerrisk new link to readv.2 pwritev.2 michael kerrisk new link to readv.2 changes to individual pages --------------------------- chdir.2 michael kerrisk remove redundant and incorrect info on ftms from notes chown.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 clock_nanosleep.2 michael kerrisk clarify that clock_nanosleep() suspends the calling *thread* epoll_create.2 michael kerrisk note that 'size' argument must be greater than 0 see https://bugzilla.kernel.org/show_bug.cgi?id=23872 michael kerrisk added versions section epoll_ctl.2 michael kerrisk added versions section epoll_wait.2 michael kerrisk updated versions section fcntl.2 michael kerrisk add notes on fcntl64() fstatat.2 michael kerrisk add notes on fstatat64(), the name of the underlying system call getdents.2 michael kerrisk added notes on getdents64() getgid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 getgroups.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 getpagesize.2 michael kerrisk improve description of getpagesize() improve description of getpagesize() and relocate discussion of sysconf(_sc_pagesize). in part inspired by http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=537272 getresuid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 getrlimit.2 michael kerrisk add example program for prlimit() getuid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 open.2 ivana hutarova varekova o_excl can be used without o_creat for block devices since linux 2.6 there is a possibility to use o_excl without o_creat. see patch: http://lkml.org/lkml/2003/8/10/221. pread.2 michael kerrisk add notes on pread64() and pwrite64() see https://bugzilla.kernel.org/show_bug.cgi?id=23072 michael kerrisk see also: add readv(3) readv.2 michael kerrisk wording fix: readv() and writev() are system calls, not functions sendfile.2 michael kerrisk add notes on sendfile64() setfsgid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 setfsuid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 setgid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 setresuid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 setreuid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 setuid.2 michael kerrisk add notes explaining 32-bit system calls added in linux 2.4 sigqueue.2 pthreads.7 signal.7 michael kerrisk see also: add pthread_sigqueue(3) stat.2 michael kerrisk fix eoverflow error description 2<<31 should read 1<<31 (which equals 2^31). statfs.2 michael kerrisk add notes on statfs64() and fstatfs64() swapon.2 hugh dickins document swap_flag_discard and discarding of swap pages truncate.2 michael kerrisk add notes on truncate64() and ftruncate64() memcpy.3 michael kerrisk change "should not overlap" to "must not overlap" glibc 2.12 changed things so that applications that use memcpy() on overlapping regions will encounter problems. (the standards have long said that the behaviors is undefined if the memory areas overlap.) see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=603144 in reference of http://lwn.net/articles/414467/ and http://article.gmane.org/gmane.comp.lib.glibc.alpha/15278 usleep.3 petr uzel usleep() suspends calling thread, not process core.5 michael kerrisk change single quote to double quote in shell session example the example section has a sample shell session containing: echo '|$pwd/core_pattern_pipe_test %p uid=%u gid=%g sig=%s' but $pwd won't be expanded in single quotes. it should be double quotes around the entire argument or some other form. pthreads.7 michael kerrisk added description of async-cancel-safe functions unix.7 michael kerrisk reworded the text of various errors michael kerrisk added enoent error ==================== changes in man-pages-3.33 ==================== released: 2011-09-16, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes and ideas that have been incorporated in changes in this release: akira fujita alexander schuch andries brouwer brian m. carlson dan jacobson folkert van heusden graham gower hendrik jan thomassen jan engelhardt joey adams johannes laire jon grant josh triplett konstantin ritt luis javier merino michael kerrisk mike frysinger mikel ward nick black paul evans petr pisar przemyslaw pawelczyk regid ichira reuben thomas richard b. kreckel ryan mullen sebastian geiger sebastian unger seonghun lim serge e. hallyn simon cross simon paillard stan sieler timmy lee tolga dalman tomislav jonjic yuri kozlov wei luosheng apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- sync.2 michael kerrisk added new syncfs() system call syncfs() was added in linux 2.6.39. new and changed links --------------------- syncfs.2 michael kerrisk new link for sync(2). global changes -------------- various pages simon paillard global fix: properly escape minus sign changes to individual pages --------------------------- clone.2 michael kerrisk note that clone_stopped was removed in 2.6.38 execve.2 michael kerrisk [sebastian geiger] note that the first argv[] value should contain name of executable fcntl.2 michael kerrisk [reuben thomas] note that f_getfl also retrieves file access mode getrlimit.2 michael kerrisk [ryan mullen] remove mention of kernel versions in discussion of rlimit_cpu michael kerrisk [seonghun lim] fix example program and add _file_offset_bits requirement mlock.2 michael kerrisk [brian m. carlson] clarify einval error see http://bugs.debian.org/cgi-bin/bugreport.cgi?625747 michael kerrisk [seonghun lim] simplify and correct text for eperm error mprotect.2 seonghun lim fix off-by-one error in a memory range seonghun lim fix small bug in example program the description of the example program says that it makes the third page "read-only". thus use prot_read instead of prot_none. open.2 folkert van heusden remove text describing o_cloexec as linux-specific o_cloexec is specified in posix.1-2008, as noted elsewhere in the page. readlink.2 michael kerrisk [dan jacobson] see also: add readlink(1) sendfile.2 akira fujita since 2.6.33, 'out_fd' can refer to any file type linux kernel commit cc56f7de7f00d188c7c4da1e9861581853b9e92f meant sendfile(2) can work with any output file. michael kerrisk shift text on falling back to read()/write() to notes michael kerrisk [tolga dalman] remove mention of kernel version for 'in_fd' argument tolga dalman add an explicit reference to splice(2) unlike sendfile(), splice() can transfer data between a pair of sockets. sigaction.2 michael kerrisk [tolga dalman] add a little info about ucontext_t stat.2 michael kerrisk [jon grant] small rewording of enametoolong error sync.2 michael kerrisk some rewrites to description of sync() syscalls.2 michael kerrisk added fanotify_init() and fanotify_mark() to syscall list michael kerrisk added new 2.6.39 system calls michael kerrisk updated for linux 3.0 system calls michael kerrisk update kernel version at head of syscall list michael kerrisk update to mention 3.x kernel series syslog.2 michael kerrisk [serge e. hallyn] update for kernel 2.6.37 changes document /proc/sys/kernel/dmesg_restrict. document cap_syslog. time.2 michael kerrisk [alexander schuch] notes: fix description of "seconds since the epoch" timerfd_create.2 michael kerrisk [josh triplett] note behavior when timerfd_settime() old_value is null see http://bugs.debian.org/cgi-bin/bugreport.cgi?641513 tomislav jonjic fix small error in description of timerfd_settime() truncate.2 seonghun lim remove redundant eintr description unlink.2 hendrik jan thomassen improve ebusy description cacos.3 cacosh.3 catan.3 catanh.3 michael kerrisk [richard b. kreckel, andries brouwer] fix formula describing function the man pages for cacos(), cacosh(), catan(), catanh() contain incorrect formulae describing the functions. cacos.3 michael kerrisk add example program cacosh.3 michael kerrisk add example program cacosh.3 casinh.3 catan.3 catanh.3 michael kerrisk see also: add reference to inverse function catan.3 michael kerrisk add example program catanh.3 michael kerrisk add example program ccos.3 ccosh.3 csin.3 csinh.3 ctan.3 ctanh.3 michael kerrisk see also add reference to "arc" inverse function cexp.3 michael kerrisk see also: add cexp(3) clog.3 michael kerrisk see also: add reference to clog(2) crypt.3 michael kerrisk [jan engelhardt] fix header file and feature test macro requirements for crypt_r() err.3 seonghun lim clean up description of error message source in the second paragraph of description section, one of the sources of error messages is incorrect: the four functions obtain error message only from errno, and "a code" is just relevant with errc() and warnc(), which are not present on linux. see http://www.unix.com/man-page/freebsd/3/err/ . then, the third paragraph becomes a duplicate. fflush.3 regid ichira fix wording error see http://bugs.debian.org/cgi-bin/bugreport.cgi?614021 hsearch.3 seonghun lim update errors section einval can occur for hdestroy_r(). einval can't occur for hcreate(). other minor fixes. lockf.3 michael kerrisk [mikel ward] errors: ebadf can also occur for nonwritable file descriptor as noted in the description, the file descriptor must be writable in order to place a lock. malloc.3 seonghun lim reorder prototypes in synopsis calloc() comes before realloc() in the other sections, so should do in synopsis, too. mbstowcs.3 michael kerrisk see also: add reference to wcstombs(3) memcmp.3 michael kerrisk [sebastian unger] clarify that comparison interprets bytes as "unsigned char" realpath.3 michael kerrisk [seonghun lim] fix einval error since glibc 2.3, resolved_path can be non-null (with the semantics already documented in the page). scandir(3) mike frysinger add enoent/enotdir errors siginterrupt.3 michael kerrisk [luis javier merino] remove misleading sentence about signal(2) and system call interruption strlen.3 michael kerrisk [jon grant] see also: add strnlen(3) strnlen.3 michael kerrisk [jon grant] conforming to: note that strnlen() is in posix.1-2008 strtoul.3 michael kerrisk [tolga dalman] fix notes section constants termios.3 michael kerrisk use "terminal special characters" consistently throughout page michael kerrisk [paul evans] add documentation of _posix_vdisable see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=627841 michael kerrisk add a description of status character michael kerrisk added description of swtch character michael kerrisk add names of terminal special characters michael kerrisk list terminal special characters in alphabetical order wcstombs.3 michael kerrisk see also: add mbstowcs(3) console_codes.4 petr pisar add esc [ 3 j linux 3.0 (commit f8df13e0a901fe55631fed66562369b4dba40f8b) implements \e[3j to allow scrambling content of console including scroll-back buffer (http://thread.gmane.org/gmane.linux.kernel/1125792). proc.5 michael kerrisk [stan sieler] add description of 'ppid' field of /proc/pid/status michael kerrisk [stan sieler] add description of 'sigq' field of /proc/pid/status capabilities.7 michael kerrisk [serge e. hallyn] document cap_syslog and related changes in linux 2.6.37 michael kerrisk file capabilities are no longer optional starting with linux 2.6.33, the config_security_file_capabilities has been removed, and file capabilities are always part of the kernel. complex.7 michael kerrisk updated see also list to include all complex math functions ipv6.7 michael kerrisk [simon cross] fix description of address notation: "8 4-digit hexadecimal numbers" signal.7 seonghun lim remove crufty repeated info about linuxthreads unix.7 michael kerrisk add pointer to cmsg(3) for an example of the use of scm_rights ==================== changes in man-pages-3.34 ==================== released: 2011-09-23, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes and ideas that have been incorporated in changes in this release: alan curry benjamin poirier brian m. carlson david howells david prévot denis barbier doug goldstein eric blake guillem jover jon grant michael kerrisk neil horman paul pluzhnikov reuben thomas stefan puiu stephan mueller stephen cameron sunil mushran apologies if i missed anyone! new and rewritten pages ----------------------- rt_sigqueueinfo.2 michael kerrisk [stephan mueller] new page for rt_sigqueueinfo(2) and rt_tgsigqueueinfo(2) this replaces the previous '.so' man page link file for rt_sigqueueinfo.2, which linked to this sigqueue() man page. cciss.4 stephen m. cameron new man page for cciss driver i obtained the information in this man page as a consequence of having worked on the cciss driver for the past several years, and having written considerable portions of it. michael kerrisk copyedit by mtk hpsa.4 stephen m. cameron new man page for the hpsa driver i obtained the information in this man page as a consequence of being the main author of the hpsa driver. michael kerrisk copyedits my mtk newly documented interfaces in existing pages --------------------------------------------- fstatat.2 michael kerrisk [david howells] document at_no_automount this flag was added in linux 2.6.38. lseek.2 michael kerrisk [eric blake, sunil mushran] document seek_hole and seek_data these flags, designed for discovering holes in a file, were added in linux 3.1. included comments from eric blake and sunil mushran. madvise.2 doug goldstein add madv_hugepage and madv_nohugepage document the madv_hugepage and madv_nohugepage flags added to madvise() in linux 2.6.38. new and changed links --------------------- rt_tgsigqueueinfo.2 michael kerrisk new link to new rt_sigqueueinfo.2 page sigqueue.2 michael kerrisk create link to page that was relocated to section 3 global changes -------------- various pages michael kerrisk change reference to "sigqueue(2)" to "sigqueue(3)" changes to individual pages --------------------------- fallocate.2 michael kerrisk errors: add eperm and espipe errors lseek.2 michael kerrisk [alan curry, reuben thomas] remove suspect note about 'whence' being incorrect english prctl.2 paul pluzhnikov pr_set_dumpable makes process non-ptrace-attachable readlink.2 guillem jover document using st_size to allocate the buffer michael kerrisk added copyright text + changelog note for guillem jover's patch sched_setscheduler.2 michael kerrisk document 2.6.39 changes to rules governing changes from sched_idle policy since linux 2.6.39, unprivileged processes under the sched_idle policy can switch to another nonrealtime policy if their nice value falls within the range permitted by their rlimit_nice limit. tkill.2 michael kerrisk see also: add rt_sigqueueinfo (2) btowc.3, wctob.3 michael kerrisk [brian m. carlson] add pointers to better, thread-safe alternative functions see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=606899 fwide.3 michael kerrisk add _isoc95_source to feature test macro requirements since glibc 2.12, _isoc95_source can also be used to expose prototype of this function. index.3 michael kerrisk [jon grant] fix text mentioning terminating null pthread_sigqueue.3 michael kerrisk replace explicit mention of rt_tgsigqueueinfo() with see also reference sigqueue.3 michael kerrisk move this page to section 3 now that the underlying system call rt_sigqueueinfo(2) is properly documented, move sigqueue() to section 3, since it is really a library function. michael kerrisk update text in line with existence of new rt_sigqueueinfo.2 page wcsnlen.3 jon grant improve description of 'maxlen' argument it's worth clarifying 'maxlen' is in wide-char units, not bytes. wprintf.3 michael kerrisk add _isoc95_source to feature test macro requirements since glibc 2.12, _isoc95_source can also be used to expose prototype of these functions. feature_test_macros.7 michael kerrisk document _isoc95_source _isoc95_source was added in glibc 2.12 as a means to expose c90 amendment 1 definitions. ip.7 benjamin poirier [neil horman] improve description of ip_mtu_discover signal.7 michael kerrisk see also: add rt_sigqueueinfo(2) ==================== changes in man-pages-3.35 ==================== released: 2011-10-04, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes and ideas that have been incorporated in changes in this release: andi kleen david prévot denis barbier eric w. biederman guillem jover jon grant kevin lyda michael kerrisk mike frysinger reuben thomas apologies if i missed anyone! new and rewritten pages ----------------------- recvmmsg.2 andi kleen, michael kerrisk new man page for recvmmsg(2) setns.2 eric w. biederman new manual page for setns(2) michael kerrisk various improvements global changes -------------- various pages michael kerrisk global fix: remove spaces around em-dash normal english typographical convention is not to have spaces around em dashes. various pages michael kerrisk global fix: s/null pointer/null pointer/ various pages michael kerrisk global fix: use oring use "oring", not "or'ing", nor an italic ".ir or ing". various pages michael kerrisk global fix: consistent use of "null wide character" bring more consistency to the discussion of "[terminating] null wide character" by writing (at least in the initial use in a page) "[terminating] null wide character (l'\0')". various pages michael kerrisk global fix: consistent use of "null byte" bring more consistency to the discussion of "[terminating] null byte" by writing (at least in the initial use in a page) "[terminating] null byte ('\0')". mount.2, prctl.2 michael kerrisk s/task/thread/ for consistency with other pages changes to individual pages --------------------------- lseek.2 guillem jover conforming to: note other systems that have seek_hole+seek_data recv.2 michael kerrisk add mention of recvmmsg(2) recvmmsg.2 michael kerrisk see also: add sendmmsg(2) send.2 michael kerrisk conforming to: posix.1-2008 adds msg_nosignal sigwaitinfo.2 michael kerrisk note that attempts to wait for sigkill and sigstop are silently ignored stat.2 michael kerrisk note posix.1-2001 and posix.1-2008 requirements for lstat() michael kerrisk regarding automounter action, add a reference to fstatat(2) michael kerrisk clean up text describing which posix describes s_if* constants aio_cancel.3 michael kerrisk [jon grant] clarify meaning of "return status" and "error status" gets.3 michael kerrisk posix.1-2008 marks gets() obsolescent the page formerly erroneously stated that posix.1-2008 removed the specification of this function. mbsnrtowcs.3 michael kerrisk conforming to: add posix.1-2008 this function is specified in the posix.1-2008 revision. regex.3 michael kerrisk [reuben thomas] change "terminating null" to "terminating null byte" stpcpy.3 stpncpy.3 mike frysinger note that these functions are in posix.1-2008 update the "conforming to" sections of these functions to note that they are now part of the posix.1-2008 standard. stpncpy.3 michael kerrisk change "terminating null" to "terminating null byte" strcpy.3 mike frysinger see also: add stpncpy(3) strdup.3 michael kerrisk conforming to: strndup() is in posix.1-2008 wcpcpy.3 wcpncpy.3 wcsnlen.3 wcsnrtombs.3 michael kerrisk conforming to: add posix.1-2008 these functions are specified in the posix.1-2008 revision. proc.5 eric w. biederman document /proc/[pid]/ns/ michael kerrisk some edit's to eric biederman's /proc/[pid]/ns/ additions capabilities.7 michael kerrisk list setns(2) as an operation allowed by cap_sys_admin ==================== changes in man-pages-3.36 ==================== released: 2012-02-27, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes and ideas that have been incorporated in changes in this release: alain benedetti carado christoph hellwig clemens ladisch david prévot elie de brauwer guillem jover jessica mckellar josef bacik junjiro okajima lucian adrian grijincu michael kerrisk mike frysinger pat pannuto salvo tomaselli simone piccardi slaven rezic starlight stephan mueller vijay rao walter haidinger walter harms yang yang apologies if i missed anyone! new and rewritten pages ----------------------- sendmmsg.2 michael kerrisk [stephan mueller] new page for sendmmsg(2) some pieces inspired by an initial attempt by stephan mueller. newly documented interfaces in existing pages --------------------------------------------- fallocate.2 lucian adrian grijincu document falloc_fl_punch_hole falloc_fl_punch_hole was added in linux 2.6.38, for punching holes in the allocated space in a file. changes to individual pages --------------------------- dup.2 michael kerrisk synopsis: add "#include " for o_* constants fallocate.2 michael kerrisk substantial restructuring of description the addition of a second class of operation ("hole punching") to the man page made it clear that some significant restructuring is required. so i substantially reworked the page, including the preexisting material on the default "file allocation" operation. michael kerrisk [josef bacik] add further details for falloc_fl_punch_hole michael kerrisk errors: add eperm error case for falloc_fl_punch_hole fork.2 michael kerrisk notes: describe clone() call equivalent to fork() fsync.2 christoph hellwig various improvements - explain the situation with disk caches better - remove the duplicate fdatasync() explanation in the notes section - remove an incorrect note about fsync() generally requiring two writes - remove an obsolete ext2 example note - fsync() works on any file descriptor (doesn't need to be writable); correct the ebadf error code explanation michael kerrisk [guillem jover] note that some systems require a writable file descriptor an edited version of guillem jover's comments: [while the file descriptor does not need to be writable on linux] that's not a safe portable assumption to make on posix in general as that behavior is not specified and as such is implementation-specific. some unix systems do actually fail on read-only file descriptors, for example [hp-ux and aix]. mount.2 michael kerrisk [junjiro okajima] removed erroneous statement about ms_rdonly and bind mounts open.2 jessica mckellar fix grammar in o_direct description some small grammar fixes to the o_direct description. pipe.2 michael kerrisk [salvo tomaselli] synopsis: add "#include " for o_* constants see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=659750 sched_rr_get_interval.2 clemens ladisch update notes on modifying quantum since linux 2.6.24, it is no longer possible to modify the sched_rr quantum using setpriority(2). (slight edits to clemens' patch by mtk.) michael kerrisk reordered various pieces of text michael kerrisk reworded text of esrch error send.2 michael kerrisk add mention of sendmmsg(2) sync.2 michael kerrisk [simone piccardi] prototype: fix return type of syncfs() vfork.2 michael kerrisk [starlight] clarify what is duplicated in the child add some words to make it clear to the reader that vfork(), like fork(), creates duplicates of process attributes in the child. michael kerrisk note clone() flags equivalent to vfork() michael kerrisk [starlight, mike frysinger] add some notes on reasons why vfork() still exists michael kerrisk [starlight] clarify that calling *thread* is suspended during vfork() michael kerrisk conforming to: note that posix.1-2001 marked vfork() obsolete gets.3 michael kerrisk document c11 and glibc 2.16 changes affecting gets() pthread_sigmask.3 michael kerrisk [pat pannuto] fix comment that was inconsistent with code in example program sem_wait.3 walter harms example: remove extraneous line of output from shell session wcsnrtombs.3 wcsrtombs.3 wcstombs.3 michael kerrisk fix-ups for e9c23bc636426366d659809bc99cd84661e86464 core.5 michael kerrisk [junjiro okajima] document %e specifier for core_pattern passwd.5 michael kerrisk [walter haidinger] s/asterisk/asterisk (*)/ to improve clarity michael kerrisk correct note on passwd field value when shadowing is enabled when password shadowing is enabled, the password field contains an 'x' (not "*'). proc.5 elie de brauwer fix description of fourth field of /proc/loadavg signed-off-by: elie de brauwer resolv.conf.5 michael kerrisk [slaven rezic] describe syntax used for comments see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=656994 feature_test_macros.7 michael kerrisk document _isoc11_source inotify.7 michael kerrisk [yang yang] note that 'cookie' field is set to zero when unused man.7 michael kerrisk various fixes for description of name section as noted by reporter: * the code sample given for the name section is incomplete because the actual content sample is not given. * additionally, the description assumes that the item described is a command, which need not be the case. * the command makewhatis is not present on my system; the documented tool to create the whatis database is called mandb. * the description on .sh name in man(7) should either copy the relevant paragraph of lexgrog(1) or refer to it. ==================== changes in man-pages-3.37 ==================== released: 2012-03-06, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes and ideas that have been incorporated in changes in this release: denys vlasenko mark r. bannister michael kerrisk oleg nesterov tejun heo apologies if i missed anyone! new and rewritten pages ----------------------- getent.1 mark r. bannister new page to document 'getent' binary provided by glibc changes to individual pages --------------------------- bdflush.2 michael kerrisk note that bdflush() is deprecated, and does nothing nfsservctl.2 michael kerrisk note that this system call was removed in linux 3.1 ptrace.2 denys vlasenko [oleg nesterov, tejun heo] add extended description of various ptrace quirks changes include: s/parent/tracer/g, s/child/tracee/g - ptrace interface now is sufficiently cleaned up to not treat tracing process as parent. deleted several outright false statements: - pid 1 can be traced - tracer is not shown as parent in ps output - ptrace_attach is not "the same behavior as if tracee had done a ptrace_traceme": ptrace_attach delivers a sigstop. - sigstop _can_ be injected. - removed mentions of sunos and solaris as irrelevant. - added a few more known bugs. added a large block of text in description which doesn't focus on mechanical description of each flag and operation, but rather tries to describe a bigger picture. the targeted audience is a person which is reasonably knowledgeable in unix but did not spend years working with ptrace, and thus may be unaware of its quirks. this text went through several iterations of review by oleg nesterov and tejun heo. this block of text intentionally uses as little markup as possible, otherwise future modifications to it will be very hard to make. michael kerrisk global clean-up of page * wording and formatting fixes to existing text and denys vlasenko's new text. * various technical amendments and improvements to denys vlasenko's new text. * added fixme for various problems with the current text. michael kerrisk integrated changes after further review from denys vlasenko syscalls.2 michael kerrisk note that nfsservctl(2) was removed in linux 3.1 note that bdflush(2) is deprecated capabilities.7 michael kerrisk add cap_wake_alarm michael kerrisk add various operations under cap_sys_admin add perf_event_open(2) to cap_sys_admin add vm86_request_irq vm86(2) command to cap_sys_admin update cap_net_admin with notes from include/linux/capability.h add nfsservctl(2) to cap_sys_admin michael kerrisk add ioctl(fibmap) under cap_sys_rawio michael kerrisk add virtual terminal ioctl()s under cap_sys_tty_config michael kerrisk update cap_net_raw with notes from include/linux/capability.h michael kerrisk add f_setpipe_sz case to cap_sys_resource add posix messages queues queues_max case to cap_sys_resource update cap_sys_resource with notes from include/linux/capability.h michael kerrisk see also: add libcap(3) ld.so.8 michael kerrisk add --audit command-line option ==================== changes in man-pages-3.38 ==================== released: 2012-03-25, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: akihiro motoki artyom pervukhin beňas petr ben bacarisse bjarni ingi gislason david prévot denis barbier denys vlasenko eric blake iain fraser justin t pryzby kirill brilliantov mark r bannister matthew gregan michael kerrisk nix peter schiffer sergei zhirikov apologies if i missed anyone! new and rewritten pages ----------------------- get_nprocs_conf.3 beňas petr new page documenting get_nprocs_conf(3) and get_nprocs(3) michael kerrisk some additions and improvements malloc_get_state.3 michael kerrisk new page documenting malloc_get_state(3) and malloc_set_state(3) mallopt.3 michael kerrisk new man page for mallopt(3) mtrace.3 michael kerrisk complete rewrite of page, adding much more detail scandirat.3 mark r bannister new page for scandirat(3) (new in glibc 2.15) newly documented interfaces in existing pages --------------------------------------------- posix_memalign.3 michael kerrisk document aligned_alloc(3) aligned_alloc() is new in c11. michael kerrisk document pvalloc(3) qsort.3 mark r bannister add documentation of qsort_r(3) ben bacarisse improvements to mark r bannister's qsort_r() patch michael kerrisk add versions section for qsort_r() new and changed links --------------------- aligned_alloc.3 michael kerrisk new link to posix_memalign.3 get_nprocs.3 beňas petr link to new get_nprocs_conf.3 page malloc_set_state.3 michael kerrisk link to new malloc_get_state.3 page pvalloc.3 michael kerrisk new link to posix_memalign.3 global changes -------------- various pages michael kerrisk global formatting fix: balance .nf/.fi pairs various pages michael kerrisk global fix: place sections in correct order various pages michael kerrisk [justin t pryzby] global fix: remove duplicated words remove instances of duplicate words found using justin's grep-fu: for f in man?/*.[1-9]; do grep -he ' ([[:alpha:]]{2,} +)\1' "$f" | grep -evw '(proc|hugetlbfs|xxx*|root|long) *\1'; done | grep -e --colo ' ([[:alpha:]]{2,} +)\1' various pages michael kerrisk correct order of see also entries changes to individual pages --------------------------- futimesat.2 michael kerrisk prototype: correct header file and feature test macro requirements keyctl.2 bjarni ingi gislason strip trailing tabs from source line see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=664688 ptrace.2 denys vlasenko document ptrace_geteventmsg for ptrace_event_exec denys vlasenko various fixes to recent updates of this page symlinkat.2 michael kerrisk [eric blake] prototype: correct header file syscalls.2 michael kerrisk remove unimplemented system calls from main syscall list the unimplemented system calls are in any case noted lower down in the page. also: rearrange the text describing the unimplemented system calls. michael kerrisk note a few system calls that were removed in linux 2.6 michael kerrisk add process_vm_readv(2) and process_vm_writev(2) unlinkat.2 michael kerrisk [eric blake] prototype: correct header file michael kerrisk prototype: add for at_* constants utimensat.2 michael kerrisk prototype: add for at_* constants copysign.3 michael kerrisk [tolga dalman] description: add a couple of examples malloc.3 michael kerrisk notes: add a short discussion of arenas michael kerrisk replace discussion of malloc_check_ with pointer to mallopt(3) michael kerrisk see also: add mtrace(3) see also: add malloc_get_state(3) posix_memalign.3 michael kerrisk rename memalign() argument rename "boundary" to "alignment" for consistency with posix_memalign(). michael kerrisk improve discussion of feature test macros and header files for valloc(3) rtnetlink.3 kirill brilliantov [sergei zhirikov] fix example code, rta_len assignment should use rta_length() see also http://bugs.debian.org/655088 scandir.3 mark r bannister see also: add scandirat(3) sigqueue.3 nix remove rt_sigqueueinfo from th line rt_sigqueueinfo() now has its own manual page, so should not be listed in the .th line of this page. tzset.3 peter schiffer correct description for julian 'n' date format the julian 'n' date format counts starting from 0, not 1. michael kerrisk add some clarifying remarks to discussion of julian day formats packet.7 michael kerrisk [iain fraser] fix comment on 'sll_hatype' field tcp.7 michael kerrisk [artyom pervukhin] correct rfc for time_wait assassination hazards ==================== changes in man-pages-3.39 ==================== released: 2012-04-17, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: abhijith das alexander kruppa andreas jaeger armin rigo cyrill gorcunov denys vlasenko eric blake felix jak jeff mahoney jesus otero jonathan nieder kevin o'gorman mark r bannister michael kerrisk michael welsh duggan mike frysinger petr gajdos regid ichira reuben thomas ricardo catalinas jiménez simone piccardi tetsuo handa apologies if i missed anyone! new and rewritten pages ----------------------- malloc_trim.3 michael kerrisk new man page for malloc_trim(3) malloc_usable_size.3 michael kerrisk new man page for malloc_usable_size(3) newly documented interfaces in existing pages --------------------------------------------- prctl.2 cyrill gorcunov document pr_set_mm (new in linux 3.3) michael kerrisk various edits and improvements to cyrill's patch changes to individual pages --------------------------- epoll_create.2 michael kerrisk rework discussion of 'size' argument michael kerrisk add .ss for description of epoll_create1() epoll_wait.2 michael kerrisk [armin rigo] another thread can add to epoll instance while epoll_wait is blocked see https://bugzilla.kernel.org/show_bug.cgi?id=43072 michael kerrisk clarify that epoll_pwait() blocks calling *thread* a few wording improvements fchmodat.2 michael kerrisk [mike frysinger] note difference between glibc wrapper and underlying system call the wrapper function has a 'flags' argument (which currently serves no purpose), while the underlying system call does not. fcntl.2 abhijith das explain behaviour of f_getlease during lease break michael kerrisk [eric blake] change type of arg from "long" to "int" various fcntl(2) commands require an integral 'arg'. the man page said it must be "long" in all such cases. however, for the cases covered by posix, there is an explicit requirement that these arguments be "int". update the man page to reflect. probably, all of the other "long" cases (not specified in posix) should be "int", and this patch makes them so. based on a note fromeric blake, relating to f_dupfd_cloexec. gettimeofday.2 michael kerrisk reorganize content the main change is to move the historical information about the 'tz_dsttime' to notes. michael kerrisk [felix] note that compiler issues warnings if 'tv' is null mmap.2 michael kerrisk [kevin o'gorman] clarify that this system call should not be invoked directly see https://bugzilla.kernel.org/show_bug.cgi?id=42892 michael kerrisk clarify notes discussion of mmap() versus mmap2() poll.2 michael kerrisk [michael welsh duggan] document negative value in 'fd' field michael kerrisk document semantics of passing zero in 'events' field ptrace.2 denys vlasenko various fixes for some reason, the ptrace_traceme paragraph talks about some general aspects of ptraced process behavior. it repeats the "tracee stops on every signal" information even though that was already explained just a few paragraphs before. then it describes legacy sigtrap on execve(). this patch deletes the first part, and moves the second part up, into the general ptrace description. it also adds "if ptrace_o_traceexec option is not in effect" to the description of the legacy sigtrap on execve(). the patch also amends the part which says "for requests other than ptrace_kill, the tracee must be stopped." - ptrace_attach also doesn't require that. sigaction.2 michael kerrisk [andreas jaeger, ] clarify that the use of si_sigio is for linux 2.2 only see also http://sourceware.org/bugzilla/show_bug.cgi?id=6745 sigprocmask.2 mike frysinger errors: add efault times.2 michael kerrisk [simone piccardi] errors: add efault div.3 michael kerrisk [reuben thomas] conforming to: add c99 fread.3 regid ichira clarify further that return value is number of items, not bytes see also http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=665780 getaddrinfo.3 michael kerrisk [jak] correct type of ai_addrlen field malloc.3 michael kerrisk see also: add malloc_usable_size(3) see also: add malloc_trim(3) mallopt.3 michael kerrisk fix text describing m_perturb and free() see also: add malloc_trim(3) memchr.3 michael kerrisk [reuben thomas] remove mention of terminating null in description of rawmemchr() perror.3 michael kerrisk [jesus otero] note that use of 'sys_errlist' is deprecated rcmd.3 michael kerrisk glibc eventually added a declaration of iruserok() in version 2.12 sysconf.3 michael kerrisk [ricardo catalinas jiménez] add mention of _sc_symloop_max nologin.5 michael kerrisk [tetsuo handa] nologin must not only exist, but *be readable* to be effective nsswitch.conf.5 mark r bannister significant rewrites and improvements this patch applies to nsswitch.conf.5 in man-pages-3.36. my changes almost completely rewrite large sections of the man page. they are needed to add clarity, correct grammar, reduce confusion, and bring up-to-date with the latest glibc. i have checked the man page against the nss source code in glibc 2.14.90. historical notes are demoted to the footer. the rewrite makes the man page much clearer to understand, more authoratitive, and easier to read. michael kerrisk light edits to mark bannister's changes capabilities.7 michael kerrisk add prctl(pr_set_mm) to cap_sys_resource epoll.7 michael kerrisk some minor clarifications at start of description netlink.7 jeff mahoney [petr gajdos] note cases where nonprivileged users can use netlink multicast groups see also https://bugzilla.novell.com/show_bug.cgi?id=754611 unix.7 michael kerrisk [tetsuo handa] add a detail on autobind feature ld.so.8 jonathan nieder [reuben thomas] document effect of hwcaps on search path wording by aurelien jarno from debian glibc's r4701 (2011-06-04). addresses http://bugs.debian.org/622385 ==================== changes in man-pages-3.40 ==================== released: 2012-04-27, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexey toptygin bernhard walle brian f. g. bidulock brian m. carlson christopher yeoh daniel j blueman eric blake eugen dedu james hunt john sullivan jon grant lepton marcel holtmann michael kerrisk mike frysinger petr baudis simon paillard stefan puiu ulrich drepper vadim mikhailov apologies if i missed anyone! new and rewritten pages ----------------------- process_vm_readv.2 mike frysinger, christopher yeoh, michael kerrisk new page for process_vm_readv(2) and process_vm_writev(2) mcheck.3 michael kerrisk new man page for mcheck(3) and related functions also describes mcheck_check_all(3), mcheck_pedantic(3), and mprobe(3) newly documented interfaces in existing pages --------------------------------------------- rcmd.3 michael kerrisk document "_af" variants of these functions document rcmd_af(), rresvport_af(), iruserok_af(), ruserok_af(). also some restructuring and other clarifications. rexec.3 michael kerrisk document rexec_af() new and changed links --------------------- iruserok_af.3 rcmd_af.3 rresvport_af.3 ruserok_af.3 michael kerrisk new links to rcmd.3 rexec_af.3 michael kerrisk new link to rexec.3 changes to individual pages --------------------------- clock_getres.2 michael kerrisk clarify difference between clock_monotonic and clock_monotonic_raw note interactions of these two clocks with discontinuous adjustments to the system time and ntp/adjtime(2). fallocate.2 michael kerrisk [john sullivan] fix description of enosys and eopnotsup errors as reported in https://bugzilla.redhat.com/show_bug.cgi?id=680214 fchmodat.2 michael kerrisk [mike frysinger] improve discussion of difference between wrapper and underlying syscall gettimeofday.2 michael kerrisk gettimeofday() is affected by discontinuous jumps in the system time advise reader to use clock_gettime(2), if they need a monotonically increasing time source. michael kerrisk see also: add clock_gettime(2) prctl.2 michael kerrisk add pr_task_perf_events_disable and pr_task_perf_events_enable add some basic documentation of these operations, with a pointer to tools/perf/design.txt for more information. michael kerrisk [marcel holtmann] amend details of pr_set_pdeathsig ptrace.2 michael kerrisk [mike frysinger] note sparc deviation with respect to get/set regs sparc reverses the use of 'addr' and 'data' for ptrace_getregs, ptrace_getfpregs, ptrace_setregs, and ptrace_setfpregs. send.2 stefan puiu document eacces error case for udp sigaction.2 michael kerrisk remove mention of raise(3) for si_user for a long time now, glibc's raise(3) didn't yield si_user for the signal receiver, so remove mention of raise(3) here. the user can deduce the details, if needed, by looking at the recently updated raise(3) page. aio_cancel.3 michael kerrisk [jon grant] rewrite return value section to be clearer aio_init.3 michael kerrisk [jon grant] remove extraneous "posix" from name section btree.3 dbopen.3 hash.3 mpool.3 recno.3 michael kerrisk [brian m. carlson] note that glibc no longer provides these interfaces glibc stopped providing these interfaces with v2.2. nowadays, the user that finds these pages probably wants the libdb api, so note this in the page. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=337581 fopen.3 michael kerrisk bugs: note limitation on number of flag characters parsed in 'mode' michael kerrisk note that 'c' and 'e' flags are ignored for fdopen() determined from reading libio/iofdopen.c. michael kerrisk document ",ccs=string" feature of 'mode' for fopen()/freopen() getgrnam.3 michael kerrisk [ulrich drepper] fix discussion of _sc_getgr_r_size_max the value is not meant to be a maximum (as was specified in susv3) but an initial guess at the required size (as specified in susv4). getpwnam.3 michael kerrisk [ulrich drepper] fix discussion of _sc_getpw_r_size_max the value is not meant to be a maximum (as was specified in susv3) but an initial guess at the required size (as specified in susv4). malloc.3 mallopt.3 mtrace.3 michael kerrisk see also: add mcheck(3) memchr.3 michael kerrisk clarify description, omitting mention of "strings" and "characters" the existing text slipped into talking about characters and strings, which could mislead readers into thing that, for example, searches for the byte '\0' are treated specially. therefore, rewrite in terms of "bytes" and "memory areas". at the same time, make a few source file clean-ups. mkstemp.3 michael kerrisk add "mkstemps" and "mkostemps" to name line posix_openpt.3 michael kerrisk [vadim mikhailov] add some details on use of the slave pathname an explicit pointer to ptsname(3) is useful, as is a note of the fact that the slave device pathname exists only as long as the master device is held open. raise.3 michael kerrisk add some notes on underlying system call that is used rcmd.3 michael kerrisk add some details of the rresvport() 'port' argument resolver.3 petr baudis note that many options are documented in resolv.conf(5) scandir.3 michael kerrisk [daniel j blueman] improve example source code: s/0/null/ in scandir() call strchr.3 james hunt explain behavior when searching for '\0' strerror.3 eric blake [stefan puiu] improve strerror_r() description posix requires that perror() not modify the static storage returned by strerror(). posix 2008 and c99 both require that strerror() never return null (a strerror() that always returns "" for all inputs is valid for c99, but not for posix). http://sourceware.org/bugzilla/show_bug.cgi?id=12204 documents glibc's change to come into compliance with posix regarding strerror_r() return value. the gnu strerror_r() use of 'buf' was confusing - i ended up writing a test program that proves that 'buf' is unused for valid 'errnum', but contains truncated "unknown message" for out-of-range 'errnum'. see also http://austingroupbugs.net/view.php?id=382 bernhard walle correct description of error return for xsi strerror_r() michael kerrisk [eric blake] note how to use 'errno' to detect errors when calling strerror() michael kerrisk [jon grant] add an example of the kind of string returned by strerror() resolv.conf.5 petr baudis document "single-request" option inotify.7 michael kerrisk note buffer size that guarantees being able to read at least one event james hunt correct description of size of inotify_event structure iso_8859-1.7 eugen dedu add "-" for soft hyphen see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=156154 netdevice.7 brian f. g. bidulock document some sioc configuration ioctls this patch adds common but missing sioc configuration ioctls to the netdevice.7 manual pages that are not documented anywhere else. siocsifpflags and siocgifpflags are linux-specific. flag values come from linux 2.6.25 kernel headers for sockios. the others are standard bsd ioctls that have always been implemented by linux and were verified from inspecting netdevice.c kernel code. socket.7 michael kerrisk [alexey toptygin] correct description of so_broadcast tcp.7 lepton correct description for tcp_maxseg on modern kernel ==================== changes in man-pages-3.41 ==================== released: 2012-05-11, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: akihiro motoki andries e. brouwer angelo borsotti bjarni ingi gislason brian m. carlson casper dik david prévot d. barbier eric blake hugh dickins ivana varekova jakub jelinek jan kara jason baron jean-michel vourgère jeff moyer josh triplett kasper dupont kosaki motohiro lauri kasanen mel gorman michael kerrisk mike frysinger nick piggin paul pluzhnikov petr baudis ralph corderoy rich felker simone piccardi simon paillard stefan puiu stephen hemminger vincent lefevre yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- get_robust_list.2 ivana varekova [michael kerrisk] new page documenting get_robust_list(2) and set_robust_list(2) mallinfo.3 michael kerrisk [kosaki motohiro, paul pluzhnikov] new page for mallinfo(3) malloc_info.3 michael kerrisk [jakub jelinek] new page for malloc_info(3) malloc_stats.3 michael kerrisk [kosaki motohiro] new man page for malloc_stats(3) newly documented interfaces in existing pages --------------------------------------------- madvise.2 jason baron document madv_dontdump and madv_dodump new and changed links --------------------- set_robust_list.2 michael kerrisk new link to new get_robust_list.2 page list_entry.3 list_head.3 list_init.3 list_insert_after.3 list_insert_head.3 list_remove.3 tailq_entry.3 tailq_head.3 tailq_init.3 tailq_insert_after.3 tailq_insert_head.3 tailq_insert_tail.3 tailq_remove.3 circleq_entry.3 circleq_head.3 circleq_init.3 circleq_insert_after.3 circleq_insert_before.3 circleq_insert_head.3 circleq_insert_tail.3 circleq_remove.3 michael kerrisk new link to queue.3 the queue(3) page documents these macros, so it makes sense to have links for the names. des_failed.3 michael kerrisk new link to des_crypt.3 the des_crypt(3) page documents this macro, so it makes sense to have a link for the name. qsort_r.3 michael kerrisk new link to qsort.3 overlooked to add this link in 3.38, when documentation of qsort_r() was added to the qsort.3 page. global changes -------------- faccessat.2 fchmodat.2 fchownat.2 fstatat.2 futimesat.2 inotify_init.2 linkat.2 mkdirat.2 mknodat.2 openat.2 readlinkat.2 renameat.2 setns.2 splice.2 symlinkat.2 sync.2 tee.2 unlinkat.2 vmsplice.2 michael kerrisk [lauri kasanen] global fix: note glibc version that added library support confstr.3 strcasecmp.3 strcat.3 strcmp.3 strcpy.3 strdup.3 strftime.3 strlen.3 strnlen.3 strpbrk.3 strspn.3 strtok.3 strxfrm.3 michael kerrisk [andries e. brouwer] clarify that these functions operate on bytes, not (wide) characters change 'character(s)' to 'byte(s)' to make clear that these functions operate on bytes, not wide / utf8 characters. (posix uses 'byte(s)' similarly, to make this point.) icmp.7 ipv6.7 packet.7 raw.7 rtnetlink.7 unix.7 x25.7 michael kerrisk remove names of constants from name line some of the sockets/network protocol pages included names of the corresponding address family constants in the name line, but this wasn't done consistently across all pages, and probably it adds little value in those pages that did do this. so, remove these constants from those pages that have them in the name section. changes to individual pages --------------------------- clock_getres.2 michael kerrisk [josh triplett] expand description of clock_realtime make it clear that this clock may be discontinuous, and is affected my incremental ntp and clock-adjtime(2) adjustments. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=540872 epoll_wait.2 michael kerrisk clarify that 'timeout' is a *minimum* interval make it clear that 'timeout' is a minimum interval; the actual interval will be rounded up to the system clock granularity, and may overrun because of kernel scheduling delays. execve.2 michael kerrisk rewording to deemphasize libc5 details fork.2 mike frysinger errors: add enosys can occur on, for example, non-mmu hardware. getcpu.2 mike frysinger add return value and errors sections michael kerrisk refer reader to notes for more info about 'tcache' michael kerrisk description: reword a sentence to be clearer io_cancel.2 io_destroy.2 io_getevents.2 io_setup.2 io_submit.2 michael kerrisk rewrite to focus on system call api rewrite to focus on the system call interface, adding some notes on the libaio wrapper differences. see the following mail: 2012-05-07 "aio manuals", linux-man@vger http://thread.gmane.org/gmane.linux.man/1935/focus=2910 other minor rewrites. mount.2 michael kerrisk comment out an old linux libc detail open.2 nick piggin [kosaki motohiro, jan kara, hugh dickins] describe race of direct i/o and fork() rework 04cd7f64, which didn't capture the details correctly. see the april/may 2012 linux-man@ mail thread "[patch] describe race of direct read and fork for unaligned buffers" http://thread.gmane.org/gmane.linux.kernel.mm/77571 poll.2 michael kerrisk clarify that 'timeout' is a *minimum* interval make it clear that 'timeout' is a minimum interval; the actual interval will be rounded up to the system clock granularity, and may overrun because of kernel scheduling delays. michael kerrisk clarify discussion of wrapper function emulation clarify that glibc (as well as old libc) provides emulation using select(2) on older kernels that don't have a poll() system call. michael kerrisk make the meaning of a zero timeout explicit clarify that timeout==0 causes an immediate return, even if no file descriptors are ready. pread.2 michael kerrisk [kasper dupont] bugs: note o_append + pwrite() does the wrong thing see https://bugzilla.kernel.org/show_bug.cgi?id=43178 recvmmsg.2 michael kerrisk clarify that 'timeout' is a *minimum* interval make it clear that 'timeout' interval will be rounded up to the system clock granularity, and may overrun because of kernel scheduling delays. select.2 michael kerrisk clarify that 'timeout' is a *minimum* interval make it clear that 'timeout' is a minimum interval; the actual interval will be rounded up to the system clock granularity, and may overrun because of kernel scheduling delays. michael kerrisk expand description of the self-pipe trick michael kerrisk add further details on pselect6() system call that underlies pselect() semop.2 michael kerrisk clarify that 'timeout' of semtimedop() is a *minimum* interval make it clear that 'timeout' interval will be rounded up to the system clock granularity, and may overrun because of kernel scheduling delays. signal.2 michael kerrisk note that 'sig_t' requires _bsd_source also remove some old linux libc details sigwaitinfo.2 michael kerrisk clarify that 'timeout' of sigtimedwait() is a *minimum* interval make it clear that 'timeout' is a minimum interval; the actual interval will be rounded up to the system clock granularity, and may overrun because of kernel scheduling delays. stat.2 bjarni ingi gislason formatting fixes from "groff -ww" (or "man --warnings=w ..."): warning: around line 442: table wider than line width gnu man uses line length of 78. use text blocks. two spaces between sentences or better: start each sentence in a new line. syscalls.2 bjarni ingi gislason formatting fixes from "groff -ww ..." (or "man --warnings=w ..."): warning: around line 157: table wider than line width have to use text blocks. move some text to its correct column. split text to two columns to avoid hyphenation. sysinfo.2 michael kerrisk remove reference to obsolete libc5 syslog.2 michael kerrisk remove some details about obsolete linux libc aio_cancel.3 aio_error.3 aio_fsync.3 aio_read.3 aio_return.3 aio_suspend.3 aio_write.3 michael kerrisk errors: add/update enosys error aio_cancel.3 michael kerrisk clarify what happens when a request isn't successfully canceled michael kerrisk add pointers to aio(7) and sigevent(7) dbopen.3 michael kerrisk synopsis: add header file upstreamed from debian, and consistent with freebsd dbopen(3) man page. fmemopen.3 michael kerrisk note details of posix.1-2008 specification of 'b' in 'mode' michael kerrisk [rich felker] bugs: fmemopen() doesn't correctly set file position in some cases if 'mode' is append, but 'size' does not cover a null byte in 'buf', then fmemopen() incorrectly sets the initial file position to -1, rather than the next byte after the end of the buffer. see http://sourceware.org/bugzilla/show_bug.cgi?id=13151 michael kerrisk bugs: fmemopen() incorrectly handles size==0 case if size is zero, fmemopen() fails, this is surprising behavior, and not specified in posix.1-2008. see http://sourceware.org/bugzilla/show_bug.cgi?id=11216 reported-by; alex shinn michael kerrisk bugs: note silent abi change for fmemopen() in glibc 2.9 michael kerrisk [rich felker] bugs: append mode does not force writes to append append mode correctly sets the initial offset but does not force subsequent writes to append at end of stream. see http://sourceware.org/bugzilla/show_bug.cgi?id=13152 michael kerrisk [eric blake] bugs: note inconsistent treatment of 'b' in 'mode' fopen() permits, for example, both "w+b" and "wb+", but only the latter is meaningful to fmemopen(). see http://sourceware.org/bugzilla/show_bug.cgi?id=12836 fopencookie.3 michael kerrisk [petr baudis] correct description of return for user-supplied 'write' function see http://sourceware.org/bugzilla/show_bug.cgi?id=2074 getaddrinfo.3 jean-michel vourgère note that ai_addrconfig is not affected by loopback addresses see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=660479 iconv.3 michael kerrisk upstream useful note from debian warn the reader that the pointer arguments can't be interpreted as c style strings. also, note possible alignment requirements for the referenced bytes sequences, michael kerrisk write a better paragraph introducing iconv() and its arguments isgreater.3 michael kerrisk [vincent lefevre] clarify that the arguments to these macros must be real-floating see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=609033 lio_listio.3 michael kerrisk clarify that async notification occurs when *all* i/os complete makedev.3 michael kerrisk synopsis: correct return types of major() and minor() see https://bugzilla.redhat.com/show_bug.cgi?id=754188 reported-by; zdenek kabelac malloc.3 michael kerrisk see also: add malloc_info(3) malloc_get_state.3 michael kerrisk fix wordos in function names in name line mallopt.3 michael kerrisk fix example program the example code was a version that was not consistent with the shell output shown on the page. reported-by: simon paillard michael kerrisk restore accidentally omitted line in shell session michael kerrisk see also: add malloc_stats(3) mmap64.3 michael kerrisk change target of link to mmap.2 (was mmap2.2) upstreamed from red hat / fedora realpath.3 michael kerrisk [casper dik] remove note about solaris possibly returning a relative path syslog.3 michael kerrisk [ralph corderoy] document behavior when 'ident' argument to openlog() is null see https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/382096 michael kerrisk update conforming to for posix.1-2008 posix.1-2008 doesn't change any details, but make that more explicit. undocumented.3 michael kerrisk remove some functions that have been documented sd.4 michael kerrisk remove reference to nonexistent scsi(4) page upstreamed from redhat / fedora sk98lin.4 michael kerrisk [stephen hemminger] note that this driver was removed in 2.6.28 see https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/528020 passwd.5 michael kerrisk upstream pieces from red hat/fedora note mention of empty password field. add description of "*np*" in password field. michael kerrisk various minor fixes and improvements proc.5 michael kerrisk note that cap_sys_admin processes can override file-max upstreamed from red hat / fedora michael kerrisk document /proc/[pid]/cgroup upstreamed from red hat / fedora resolv.conf.5 michael kerrisk take a debian improvement into upstream tzfile.5 michael kerrisk mention timezone directories in description note that timezone files are usually in /usr/lib/zoneinfo or /usr/share/zoneinfo. michael kerrisk drop synopsis the synopsis doesn't correspond to a user-visible file. michael kerrisk see also: add pointer to glibc source file timezone/tzfile.h michael kerrisk see also: add tzset(3) and tzselect(8) ascii.7 bjarni ingi gislason indent for "troff" makes table too wide fix following from "groff -t -ww ...": warning: around line 53: table wider than line width extra indent for "troff" makes the table look misplaced (default "ps" output). cp1251.7 bjarni ingi gislason table too wide from "nroff -ww -t ...": warning: around line 44: table wider than line width columns are made narrower (column gutter decreased). ipv6.7 stefan puiu add enodev error for bind() to link-local ipv6 address signal.7 michael kerrisk [simone piccardi] clarify that siglost is unused michael kerrisk comment out crufty bugs text on siglost it must be a very long time since the statement there about siglost was true. (the text seems to date back to 1996.) michael kerrisk update architectures for tables of signal numbers utf-8.7 brian m. carlson two clarifications this patch clarifies that 0xc0 and 0xc1 are not valid in any utf-8 encoding[0], and it also references rfc 3629 instead of rfc 2279. [0] in order to have 0xc0, you'd have to have a two-byte encoding with all the data bits zero in the first byte (and thus only six bits of data), which would be an ascii character encoded in the non-shortest form. similarly with 0xc1. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=538641 ldconfig.8 nscd.8 michael kerrisk remove path prefix from name line command names shown in name are normally just the basename, not the full pathname of the command. ==================== changes in man-pages-3.42 ==================== released: 2012-08-14, konolfingen contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: aaron peschel adrian dabrowski akihiro motoki alan curry bjarni ingi gislason christoph lameter colin mccabe daniel zingaro david prévot denys vlasenko henry hu herbert xu jan engelhardt jim hill joonsoo kim kalle olavi niemitalo martin h michael kerrisk michael s. tsirkin rasmus villemoes sami kerola sam varshavchik shawn landden simon paillard tolga dalman ulrich drepper марк коренберг apologies if i missed anyone! global changes -------------- various pages sami kerola global fix: use ur macro where applicable the syntax .ur http://example.com paired with .ue will create links which one can interact, if the pager allows that. one way to see the effect is ask the man(1) command to use browser display, e.g.: man -h man7/uri.7 ("\:" is optional groff syntax to permit hyphenless line breaks.) changes to individual pages --------------------------- ldd.1 michael kerrisk add security note on untrusted executables see also http://www.catonmat.net/blog/ldd-arbitrary-code-execution/ and http://tldp.org/howto/program-library-howto/shared-libraries.html clone.2 michael kerrisk rewrite discussion of sys_clone futex.2 марк коренберг consolidate error descriptions to errors michael kerrisk various wording fix-ups michael kerrisk fix description of einval error the current text seems incorrect. replace with a more general description. getdents.2 select_tut.2 atof.3 atoi.3 pthread_create.3 pthread_sigmask.3 rtime.3 setbuf.3 tsearch.3 netlink.7 michael kerrisk [jan engelhardt] remove unneeded casts get_robust_list.2 get_thread_area.2 getcpu.2 getdents.2 gettid.2 io_cancel.2 io_destroy.2 io_getevents.2 io_setup.2 io_submit.2 ioprio_set.2 kexec_load.2 llseek.2 modify_ldt.2 mq_getsetattr.2 pivot_root.2 readdir.2 rt_sigqueueinfo.2 set_thread_area.2 sgetmask.2 spu_create.2 spu_run.2 subpage_prot.2 sysctl.2 tkill.2 michael kerrisk add note to synopsis that there is no glibc wrapper for system call reduce the chance that the reader may be misled into thinking that there is a wrapper function for this system call by noting explicitly in the synopsis that there is no glibc wrapper and pointing the reader to notes for further details. ioprio_set.2 colin mccabe clarify the multithreaded behavior of ioprio_set(2) michael kerrisk [марк коренберг, kalle olavi niemitalo] document who==0 for ioprio_who_process and ioprio_who_pgrp for ioprio_who_process, who==0 means operate on the caller. for ioprio_who_pgrp, who==0 means operate on the caller's process group. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=652443 migrate_pages.2 michael kerrisk [christoph lameter, joonsoo kim] fix description of return value mount.2 michael kerrisk for ms_remount, source is ignored mprotect.2 michael kerrisk [rasmus villemoes] 'addr' argument is not const as reported by rasmus: both my system's man-pages (3.22) and the latest online (3.41) show: int mprotect(const void *addr, size_t len, int prot); as the prototype for mprotect(2). however, posix [1] and the actual sys/mman.h (on all the systems i checked) do not have the const qualifier on the first argument. msgctl.2 semctl.2 shmctl.2 svipc.7 michael kerrisk don't mention that ipc_perm is defined in there's no need to mention that the 'ipc_perm' structure is defined in . that's an implementation detail, and furthermore is itself included by the other system v ipc header files. the current text might lead the reader to conclude that they must include , which is not the case (it is required neither on linux, nor by the standards). msgctl.2 msgget.2 msgop.2 semctl.2 semget.2 semop.2 shmctl.2 shmget.2 michael kerrisk notes: and aren't strictly needed add text to notes to say that the and header files aren't required by linux or the standards, but may be needed for portability to old systems. ptrace.2 denys vlasenko explain wnohang behavior and eintr bug i didn't like the "sigkill operates similarly, with exceptions" phrase (if it's different, then it's not "similar", right?), and now i got around to changing it. now it says simply: "sigkill does not generate signal-delivery-stop and therefore the tracer can't suppress it." replaced "why wnohang is not reliable" example with a more realistic one (the one which actually inspired to add this information to man page in the first place): we got esrch - process is gone! - but waitpid(wnohang) can still confusingly return 0 "no processes to wait for". replaced "this means that unneeded trailing arguments may be omitted" part with a much better recommendation to never do that and to supply zero arguments instead. (the part about "undocumentedness" of gcc behavior was bogus, btw - deleted). expanded bugs section with the explanation and an example of visible strace behavior on the buggy syscalls which exit with eintr on ptrace attach. i hope this will lead to people submitting better bug reports to lkml about such syscalls. seteuid.2 michael kerrisk note glibc version where setegid() implementation changed in glibc 2.2/2.3, setegid() switched from setregid() to setresgid(). set_tid_address.2 michael kerrisk rename 'ctid' argument for consistency with clone(2) page michael kerrisk some rewordings and minor clarifications sigwaitinfo.2 michael kerrisk [daniel zingaro] some wording clarifications mainly rewording things like "is delivered" to "becomes pending", which is more accurate terminology. syscall.2 michael kerrisk add some more details to the description of syscall(2) and add another example of using syscall() to the program example. syscalls.2 michael kerrisk add kcmp(2) michael kerrisk move discussion of set_zone_reclaim(2) out of main table this system call was never visible to user space, so it makes sense to move it out of the main table of system calls into the notes below the table. getifaddrs.3 michael kerrisk [adrian dabrowski] note that ifa_addr and ifa_netmask can be null readdir.3 michael kerrisk [jan engelhardt] handle -1 error from pathconf() in example code snippet improve the example demonstrating allocation of a buffer for readdir_r() to handle -1 error return from pathconf(). otherwise, naive readers may think that pathconf() return value can be used without checking. realpath.3 shawn landden use past tense with ancient history (libc4, libc5) regex.3 michael kerrisk correct see also reference to glibc manual "regex" section rtime.3 michael kerrisk [jan engelhardt] fix broken pointer cast in example code sem_close.3 sem_destroy.3 sem_getvalue.3 sem_init.3 sem_open.3 sem_post.3 sem_unlink.3 sem_wait.3 sem_overview.7 michael kerrisk note that "cc -pthread" is required; "-lrt" no longer works see https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/874418 sigwait.3 michael kerrisk reword "is delivered" to "becomes pending" strcat.3 michael kerrisk add some text to emphasize the dangers of buffer overruns michael kerrisk notes: add discussion of strlcat() strcpy.3 michael kerrisk note that info is lost when strncpy() doesn't null terminate michael kerrisk add some text to emphasize possibility of buffer runs with strcpy() michael kerrisk notes: add a discussion of strlcpy() inspired by https://lwn.net/articles/506530/ michael kerrisk fix description of the null-byte padding performed by strncpy() tsearch.3 michael kerrisk notes: remove redundant discussion of unorthodox use of term "postorder" this point is already covered at greater length in the main text of the page (see the piece "more commonly, ..."). michael kerrisk clarify use for first argument to the twalk() 'action' function there's a number of details in posix that are omitted in the current version of this page. michael kerrisk some wording fixes core.5 michael kerrisk note effect of madvise(2) madv_dontdump flag capabilities.7 michael kerrisk document cap_block_suspend glob.7 bjarni ingi gislason change 8 bit characters to 7 bit representation fixes rendering errors for accented 'a' characters. michael kerrisk [aaron peschel] update bash(1) command used to obtain classical globbing behavior the man page formerly noted the bash(1) v1 command to do this. iso_8859-1.7 bjarni ingi gislason explanation of soft hyphen and the code for it :89: warning: can't find special character `shc' this is the only "iso_8859-*.7" file that has this (now) undefined character. the code in column four in "iso_8859-1.7" is "0x2d" ("hyphen, minus sign" or "hyphen-minus") instead of "0xad". see debian bug 156154 (or package "manpages"). there should be an explanation for this graphic character and the code should be 0xad in iso_8859-1.7 (as in all others), even though "[gn]roff" does not display a "hyphen" in that position of the table. the line with "soft hyphen" gets a footnote and a short explanation. mdoc.7 bjarni ingi gislason fixing a warning and a table fis warning from "groff -ww ..." (or "man --warnings=w ..."): :294: warning: tab character in unquoted macro argument in one table the distance between columns is too small in the "ps" output. (bug in the groff "doc.tmac" macro?) mdoc.samples.7 bjarni ingi gislason fix warnings from [ng]roff, corrections from "man -ww ..." (groff -ww ...): :541: warning: tab character in unquoted macro argument [+3 similar warnings] :813: warning: macro `pu' not defined usage: .rv -std in sections 2 and 3 only (#1669) mdoc warning: a .bl directive has no matching .el (#1821) string "pu" defined as a row of punctuation characters. ".bl" and ".el" fixed. some arguments, that start with a period or are the name of a macro, protected with "\&". variable name for macro ".rv" corrected. netdevice.7 bjarni ingi gislason line in table too long fix warning from "man ..." ("nroff -ww ..."): nroff: netdevice.7: warning: around line 98: table wider than line width fix: no right adjustment in text blocks in tables. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=673873 netlink.7 bjarni ingi gislason line in table is too long fix warning from "man ..." ("nroff -ww ..."): nroff: netlink.7: warning: around line 195: table wider than line width horizontal line incorporated into table. no right adjustment of text blocks in tables. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=673875 simon paillard [herbert xu] change description of "*_pid" fields to "port id" as reported by herbert xu, these should not be considered as pids. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=383296 rtnetlink.7 bjarni ingi gislason line in table too long fix warning from "man ..." ("nroff -ww ..."): nroff: rtnetlink.7: warning: around line 415: table wider than line width column gutter reduced to fit line length. right adjustment in text blocks removed in tables. some header made centered in tables. one table put on same page. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=674051 socket.7 martin h document so_mark socket option commit 4a19ec5800fc3bb64e2d87c4d9fdd9e636086fe0 in jan 2008 added the new so_mark socket option. this patch is based on text from the commit message. see https://bugzilla.kernel.org/show_bug.cgi?id=16461. svipc.7 michael kerrisk synopsis: remove include of and including and isn't needed on linux and isn't really relevant for the explanation on this page. ==================== changes in man-pages-3.43 ==================== released: 2012-10-05, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adrian bunk anatoli klassen andreas schwab bjarni ingi gislason david prévot eric dumazet florian weimer frédéric brière fredrik arnerup guillem jover jan engelhardt michael kerrisk simon josefsson stephane fillod trevor woerner yuri kozlov apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- getenv.3 michael kerrisk [florian weimer, andreas schwab] document secure_getenv(3) new and changed links --------------------- phys.2 michael kerrisk new link to unimplemented.2 secure_getenv.3 michael kerrisk new link to getenv.3 global changes -------------- various pages michael kerrisk global fix: s/-/\\-/ when real hyphen is required (e.g., in code) various pages david prévot [michael kerrisk] global fix: various consistency fixes for see also various pages michael kerrisk global fix: use "linux kernel source" consistently rather than "kernel source". various pages michael kerrisk global fix: disable justification and hyphenation in see also for a better visual result, disable justification and hyphenation in see also where page names are long. syscalls.2 uname.2 boot.7 michael kerrisk global fix: s/os/operating system/ changes to individual pages --------------------------- epoll_wait.2 michael kerrisk [fredrik arnerup] describe timeout limitation in kernels < 2.6.37 as reported by fredrik (and as far as i can tell the problem went back to 2.6.0): the timeout argument has an upper limit. any values above that limit are treated the same as -1, i.e. to wait indefinitely. the limit is given by: #define ep_max_mstimeo min(1000ull * max_schedule_timeout / hz, \ (long_max - 999ull) / hz) that is, the limit depends on the size of a long and the timer frequency. assuming the long is never smaller than 32 bits and hz never larger than 1000, the worst case is 35 minutes. i think this should be mentioned under "bugs". although this is likely to be fixed in the future (http://lkml.org/lkml/2010/8/8/144), the problem exists in at least 2.6.14 - 2.6.35. i don't know if select(2) and poll(2) are affected. https://bugzilla.kernel.org/show_bug.cgi?id=20762 michael kerrisk add pointer to select(2) for discussion of close in another thread getitimer.2 michael kerrisk [trevor woerner] note linux's odd handling of the new_value==null case michael kerrisk [trevor woerner] fix types used to declare fields in timeval struct keyctl.2 david prévot reorder see also, without .br poll.2 michael kerrisk add pointer to select(2) for discussion of close in another thread select.2 michael kerrisk [stephane fillod] note behavior if monitored file descriptor is closed in another thread executive summary: a sane application can't rely on any particular behavior if another thread closes a file descriptor being monitored by select(). see https://bugzilla.kernel.org/show_bug.cgi?id=40852 michael kerrisk clarify equivalent pselect() code in terms of threads s/sigprogmask/pthread_sigmask/ semop.2 michael kerrisk recast discussion of blocking behavior in terms of threads semop() blocks the calling thread, not the process. michael kerrisk see also: add clone(2) give reader a clue about clone_sysvsem. shutdown.2 michael kerrisk [eric dumazet] document einval error (and associated bug) eric dumazet noted that einval was not documented. some further digging shows that it's also not diagnosed consistently. see https://bugzilla.kernel.org/show_bug.cgi?id=47111. sigaction.2 michael kerrisk tweak sa_resethand description timer_settime.2 michael kerrisk small rewording around discussion of pointer arguments wait4.2 adrian bunk note that these functions are nonstandard and recommend alternatives some edits to adrian's patch by mtk. michael kerrisk conforming to: note sus details for wait3() gnu_get_libc_version.3 michael kerrisk remove unneeded "#define _gnu_source" from synopsis pthread_kill.3 pthread_sigqueue.3 michael kerrisk remove wording "another" writing "another thread" in these pages implies that these functions can't be used to send a signal to the calling thread itself, which is of course untrue. sigvec.3 michael kerrisk add "int" arg to sv_handler definition in sigvec structure michael kerrisk fix small error in discussion of blocking of signals the signal that causes the handler to be invoked is blocked, but saying "by default" implies that this can be changed via the api. it cannot. (one needs sigaction(2) for that.) syslog.3 simon josefsson remove (apparently bogus) text claiming log_auth is deprecated log_auth is in posix, and widely available. there seems to be no basis to the claim it is deprecated. quoting simon: i cannot find any other source that claim log_auth is deprecated in any way. log_auth is distinct from log_authpriv. the gnu c library manual only documents log_auth. the header files contains both without any comment. common systems like debian appear to refer to both auth and authpriv facilities in syslog configurations. popular daemons appear to use both facilities. both facilities are discussed in several rfcs. see https://bugzilla.kernel.org/show_bug.cgi?id=46091 ttyname.3 michael kerrisk see also: add ctermid(3) proc.5 michael kerrisk clarify header file related to 'flags' field of /proc/pid/stat michael kerrisk [frédéric brière] update description of 'starttime' field of /proc/pid/stat the unit of measurement changed from jiffies to clock ticks in linux 2.6. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=675891 michael kerrisk document /proc/sys/kernel/kptr_restrict michael kerrisk [kees cook] document /proc/sys/fs/protected_symlinks based on text in documentation/sysctl/fs.txt by kees cook michael kerrisk [kees cook] document /proc/sys/fs/protected_hardlinks based on text in documentation/sysctl/fs.txt by kees cook capabilities.7 michael kerrisk document interaction of cap_syslog and /proc/sys/kernel/kptr_restrict ip.7 michael kerrisk see also: add ipv6(7) see also: add icmp(7) man-pages.7 michael kerrisk add some advice about disabling hyphenation in see also ld.so.8 michael kerrisk describe interpretation of slashes in dependency strings michael kerrisk repeat note that ld_library_path is ignored in privileged programs this point is already noted when discussing search order for libraries, but it's worth repeating under the specific discussion of ld_library_path further down the page. michael kerrisk add some details for ld_preload note that ld_preload list separator can be space or colon ==================== changes in man-pages-3.44 ==================== released: 2012-11-07, barcelona contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: bert hubert david prévot james youngman kees cook lars wirzenius lucas de marchi michael kerrisk rusty russell simon paillard thomas habets apologies if i missed anyone! new and rewritten pages ----------------------- delete_module.2 michael kerrisk rewrite to linux 2.6+ reality michael kerrisk change license and copyright there is now nothing left of the original fsf-copyrighted page. so, change the copyright and license. michael kerrisk [lucas de marchi, rusty russell] substantial reorganization after comments from rusty russell rusty notes that o_nonblock is almost always used in practice. therefore, it would be better to reorganize the page to consider that "the default". init_module.2 michael kerrisk rewrite to linux 2.6+ reality michael kerrisk change copyright and license little of the original page now remains. change copyright and license michael kerrisk [rusty russell] changes after review comments from rusty russell kees cook add various pieces describing linux 2.6+ behavior pieces take from, or inspired by, a patch sent by kees. getauxval.3 michael kerrisk document getauxval() function added in glibc 2.16 global changes -------------- various pages michael kerrisk global fix: use consistent capitalization in name section the line(s) in the name section should only use capitals where english usage dictates that. otherwise, use lowercase throughout. various pages michael kerrisk global fix: "userspace" ==> "user space" or "user-space" existing pages variously use "userspace or "user space". but, "userspace" is not quite an english word. so change "userspace" to "user space" or, when used attributively, "user-space". changes to individual pages --------------------------- clock_getres.2 clock_nanosleep.2 michael kerrisk linking with -lrt is no longer needed from glibc 2.17 onward create_module.2 michael kerrisk note that this system call is present only in kernels before 2.6 michael kerrisk note that enosys probably indicates kernel 2.6+ execve.2 michael kerrisk document treatment of pr_set_pdeathsig on execve() michael kerrisk document treatment of secbit_keep_caps securebits flag on execve() fork.2 michael kerrisk note treatment of default timer slack value on fork() getdomainname.2 simon paillard [lars wirzenius] point out that these calls relate to nis, not dns see http://bugs.debian.org/295635 get_kernel_syms.2 michael kerrisk note that this system call is present only in kernels before 2.6 ipc.2 michael kerrisk update note on architectures that don't have ipc() replace mention of ia64 with x86-64 and arm. link.2 michael kerrisk add eperm error triggered by /proc/sys/fs/protected_hardlink prctl.2 michael kerrisk mention documentation/prctl/no_new_privs.txt for pr_set_no_new_privs kees cook update seccomp sections for mode 2 (bpf) this adds a short summary of the arguments used for "mode 2" (bpf) seccomp. michael kerrisk small improvements to pr_set_seccomp discussion note type of 'arg3' for seccomp_mode_filter. add pointer to documentation/prctl/seccomp_filter.txt. michael kerrisk note 'seccomp' semantics with respect to fork(), execve(), and prctl() michael kerrisk document pr_set_timerslack and pr_get_timerslack michael kerrisk reword pr_set_name and pr_get_name in terms of threads plus tfix kees cook document pr_set_no_new_privs, pr_get_no_new_privs this adds a short description of the no_new_privs bit, as described in documentation/prctl/no_new_privs.txt. ptrace.2 michael kerrisk clarify that some operations are not present on all architectures ptrace_getregs, ptrace_setgrefs, ptrace_getfpregs, and ptrace_getspregs are not present on all architectures. ptrace_sysemu and ptrace_sysemu_singlestep are present only on x86. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=122383 query_module.2 michael kerrisk add a few words clarifying reference to /sys/module michael kerrisk note that this system call is present only in kernels before 2.6 michael kerrisk note that enosys probably indicates kernel 2.6+ michael kerrisk see also: add modinfo(8) and lsinfo(8) michael kerrisk move some information in notes to versions socketcall.2 michael kerrisk update note on architectures that don't have socketcall() replace mention of ia64 with x86-64 and arm. times.2 thomas habets recommend clock_gettime(2) as alternative to times(2) clock_getcpuclockid.3 michael kerrisk linking with -lrt is no longer needed from glibc 2.17 onward fts.3 simon paillard [james youngman] improve description of physical vs. logical tree walking see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=633505 getenv.3 michael kerrisk see also: add getauxval(3) proc.5 michael kerrisk document /proc/meminfo info mostly taken from documentation/filesystems/proc.txt and documentation/vm/hugetlbpage.txt. michael kerrisk default for /proc/sys/fs/protected_{hardlinks,symlinks} is now 0 the default setting of 1 in/proc/sys/fs/protected_hardlinks and /proc/sys/fs/protected_symlinks caused one too many breakages for linus's taste, so commit 561ec64ae67e changed the default for both files to 0. note system call error yielded by /proc/sys/fs/protected_symlinks note that violating 'protected_symlinks' restrictions causes system calls to fail with the error eacces. michael kerrisk since linux 2.6.27, /proc/sys/kernel/modprobe depends on config_modules ipv6.7 bert hubert document ipv6_recvpktinfo man-pages.7 michael kerrisk note rules for capitalization in name section time.7 michael kerrisk add a subsection on timer slack ld.so.8 michael kerrisk see also: add getauxval(3) ==================== changes in man-pages-3.45 ==================== released: 2012-12-21, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andi kleen cyril hrubis david prévot elie de brauwer eric dumazet felipe pena florian weimer gao feng jan glauber jim paris jon grant julien cristau michael kerrisk mike frysinger rens van der heijden simon paillard thierry vignaud trevor woerner yoshifuji hideaki apologies if i missed anyone! new and rewritten pages ----------------------- s390_runtime_instr.2 jan glauber new page for s390-specific s390_runtime_instr(2) if_nameindex.3 yoshifuji hideaki document if_nameindex(3) and if_freenameindex(3) michael kerrisk edits, improvements and corrections to hideaki's page michael kerrisk add an example program if_nametoindex.3 yoshifuji hideaki new page documenting if_nametoindex(3) and if_indextoname(3) new and changed links --------------------- if_freenameindex.3 michael kerrisk new link to if_nameindex.3 if_indextoname.3 michael kerrisk new link to if_nametoindex.3 global changes -------------- sysconf.3 cciss.4 michael kerrisk global fix: s/runtime/run time/ changes to individual pages --------------------------- clone.2 michael kerrisk since 2.6.30, clone_newipc also supports posix message queues delete_module.2 michael kerrisk small rewording of description of effect of o_trunc getrlimit.2 michael kerrisk [trevor woerner] document linux's nonstandard treatment or rlimit_cpu soft limit upon encountering the rlimit_cpu soft limit when a sigxcpu handler has been installed, linux invokes the signal handler *and* raises the soft limit by one second. this behavior repeats until the limit is encountered. no other implementation that i tested (solaris 10, freebsd 9.0, openbsd 5.0) does this, and it seems unlikely to be posix-conformant. the (linux-specific) rlimit_rttime soft limit exhibits similar behavior. michael kerrisk point reader at discussion of /proc/[pid]/limits in proc(5) io_getevents.2 michael kerrisk io_getevents() may cause segfault when called with invalid ctx_id for reference see: http://marc.info/?l=linux-aio&m=130089887002435&w=2 recv.2 michael kerrisk [eric dumazet] unix domain sockets support msg_trunc since 3.4 sendmmsg.2 elie de brauwer add example program for sendmmsg() stat.2 simon paillard clarify description of eoverflow error the eoverflow error is not only for st_size, but also inode and block size fields. see glibc source file sysdeps/unix/sysv/linux/xstatconv.c and kernel source file fs/stat.c. also, fix bit/byte confusion see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=604928 syscalls.2 michael kerrisk update various references to "i386" to "x86" michael kerrisk add s390_runtime_instr(2) sysctl.2 michael kerrisk mention config_sysctl_syscall michael kerrisk calls to sysctl() log warnings to the kernel log since 2.6.24 syslog.2 michael kerrisk substantially reorganize discussion of commands make the layout of the discussion of the commands more readable. michael kerrisk add kernel symbolic 'type' names michael kerrisk clarify syslog_action_size_unread semantics syslog_action_size_unread returns the number of bytes available for reading via syslog_action_read. michael kerrisk clarify where syslog_action_read_all places data it reads michael kerrisk clarify semantics of syslog_action_clear the syslog_action_clear command (5) does not really clear the ring buffer; rather it affects the semantics of what is returned by commands 3 (syslog_action_read_all) and 4 (syslog_action_read_clear). michael kerrisk clarify discussion of privileges for commands 3 and 10 michael kerrisk add mention of config_log_buf_shift wait.2 michael kerrisk bugs: document odd waitid() behavior when 'infop' is null getifaddrs.3 michael kerrisk [julien cristau] update description of ifa_data to linux 2.6+ reality see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=526778 memcmp.3 michael kerrisk [jon grant] enhance return value text and remove redundant text from description note that sign of result equals sign of difference between first two bytes that differ (treated as "unsigned char")." mkstemp.3 michael kerrisk [florian weimer] deemphasize discussion of mode 066 in glibc 2.0.6 glibc 2.0.6 is now so ld that the discussion of details of that version can be deemphasized placing just under notes. see https://bugzilla.kernel.org/show_bug.cgi?id=51811 strcmp.3 michael kerrisk [jon grant] enhance return value text and remove redundant text from description note that sign of result equals sign of difference between first two bytes that differ (treated as "unsigned char")." ttyname.3 michael kerrisk fix confused text in errors the existing text suggested that the errors applied only for ttyname_r(). however, 2 of the 3 errors can occur for ttyname(). undocumented.3 michael kerrisk remove some now documented functions proc.5 michael kerrisk [jim paris] correct description of swapfree in /proc/meminfo michael kerrisk note change of /proc/[pid]/limits file permissions in 2.6.36 resolv.conf.5 simon paillard document ipv6 format for nameserver see: http://bugs.debian.org/610036 capabilities.7 michael kerrisk [rens van der heijden] correct url for posix.1e draft ipv6.7 gao feng add description of getsockopt() for ipv6_mtu in ipv4,ip_mtu is only supported by getsockopt. in ipv6, we can use ipv6_mtu to set socket's mtu, but the return value of getsockopt() is the path mtu. rtnetlink.7 michael kerrisk [julien cristau] update description of ifla_stats to linux 2.6+ reality see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=526778 socket.7 michael kerrisk [yoshifuji hideaki] document 'sockaddr' and 'sockaddr_storage' types andi kleen explain effect of so_sndtimeo for connect() when so_sndtimeo is set before connect(), then connect() may return ewouldblock when the timeout fires. ==================== changes in man-pages-3.46 ==================== released: 2013-01-27, canberra contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andrew perepechko cédric boutillier cyrill gorcunov daan spitz david prévot elie de brauwer garrett cooper james noble justin lebar kees cook lucas de marchi mark hills maxin b. john michael kerrisk michal gorny peter budny peter lekeynstein rusty russell samuel thibault sam varshavchik shawn landden simon paillard starlight theodore ts'o wolfgang rohdewald zsbán ambrus apologies if i missed anyone! new and rewritten pages ----------------------- kcmp.2 cyrill gorcunov, michael kerrisk new page for kcmp(2) newly documented interfaces in existing pages --------------------------------------------- init_module.2 michael kerrisk [kees cook, rusty russell, lucas de marchi] document finit_module(2) rusty russell [lucas de marchi, kees cook] document finit_module() 'flags' argument document module_init_ignore_modversions and module_init_ignore_vermagic. (some edits by mtk.) new and changed links --------------------- finit_module.2 michael kerrisk new link to init_module.2 __after_morecore_hook.3 __free_hook.3 __malloc_initialize_hook.3 __memalign_hook.3 __realloc_hook.3 michael kerrisk new link to malloc_hook.3 global changes -------------- various pages michael kerrisk global fix: s/tty/terminal/ changes to individual pages --------------------------- clone.2 michael kerrisk add kernel versions for various clone_* constants michael kerrisk clone_newipc governs mechanisms that don't have filesystem pathnames michael kerrisk clone_newipc doesn't mount the posix mq file system michael kerrisk add an example program (clone_newuts) michael kerrisk some reworking of clone_newipc text no substantial content changes. michael kerrisk see also: add kcmp(2) see also: add setns(2) fallocate.2 michael kerrisk falloc_fl_* flags are defined in glibc only since 2.18 getxattr.2 removexattr.2 setxattr.2 michael kerrisk [andrew perepechko, ] note that enoattr is a synonym for enodata various people have pointed out that strace(1) shows enodata for the case where the named attribute does not exist, or the process has no access to this attribute. enodata and enoattr are in fact defined as synonyms. point this out in the man page, so that people understand the strace(1) info. see https://bugzilla.kernel.org/show_bug.cgi?id=51871 getxattr.2 listxattr.2 removexattr.2 setxattr.2 michael kerrisk put errors under errors section the errno values on these pages were listed in a nonstandard way under the return value section. put them in errors sections. init_module.2 michael kerrisk [rusty russell] errors: add errors for module signatures (ebadmsg, enokey) link.2 mkdir.2 mknod.2 open.2 rename.2 symlink.2 write.2 mkfifo.3 mark hills document edquot error the return error edquot is not documented in open(2), write(2), symlink(2) etc. whether inodes or disk blocks are required for each function is something i based on received wisdom and bsd documentation, rather than tracing the code to the kernel. for symlink(2) this certainly depends on the file system type. listxattr.2 michael kerrisk [theodore ts'o] fix return value description on success, 0 may be returned, so change wording from "positive number" to "nonnegative number". outb.2 michael kerrisk add synopsis prctl.2 kees cook document pr_set_ptracer document the yama lsm's prctl handler that allows processes to declare ptrace restriction exception relationships via pr_set_ptracer. michael kerrisk make it explicit that pr_set_ptracer replaces previous setting the attribute is a scalar, not a list. shawn landden document einval error for pr_set_ptracer michael kerrisk document pr_get_tid_address ptrace.2 michael kerrisk document ptrace_o_exitkill michael kerrisk place ptrace_setoptions list in alphabetical order query_module.2 michael kerrisk must be called using syscall(2) yes, the call is way obsolete, but add this info for completeness. recvmmsg.2 elie de brauwer add/correct kernel version info for recvmmsg() and msg_waitfornone this patch isolates the since/version related fixes as requested. this change introduces the following delta: * the page states it was added in 2.6.32 but it is only added 2.6.33 (ref: http://kernelnewbies.org/linux_2_6_33) * the msg_waitforone flag was in turn only added in 2.6.34 (ref: http://kernelnewbies.org/linux_2_6_34) elie de brauwer add an example program setns.2 michael kerrisk add example program sigaction.2 michael kerrisk [zsbán ambrus] note feature test macro requirements for 'siginfo_t' see https://bugzilla.kernel.org/show_bug.cgi?id=52931 syscalls.2 michael kerrisk add kern_features(2) michael kerrisk add utrap_install(2) sparc-specific, present since ancient times michael kerrisk add finit_module(2) sysctl.2 michael kerrisk [garrett cooper] errors: eacces as a synonym for eprm see https://bugzilla.kernel.org/show_bug.cgi?id=46731 and http://thread.gmane.org/gmane.linux.ltp/11413/focus=957635 from: garrett cooper gmail.com> subject: re: [ltp] [patch] sysctl03: sysctl returns eacces after 2.6.33-rc1 newsgroups: gmane.linux.kernel, gmane.linux.ltp date: 2010-03-04 18:35:33 gmt unshare.2 michael kerrisk update notes on unimplemented flags michael kerrisk fix text problems in description of clone_fs michael kerrisk see also: add kcmp(2) see also: add setns(2) michael kerrisk reorder clone_newuts entry in list difftime.3 michael kerrisk [michal gorny] remove crufty text about 'time_t' on "other systems" back in 2006, some text came in via debian patches that seems crufty. remove it. see https://bugzilla.kernel.org/show_bug.cgi?id=46731 getaddrinfo.3 getnameinfo.3 michael kerrisk [peter budny] fix some confused references to function names see https://bugzilla.kernel.org/show_bug.cgi?id=52741 getspnam.3 michael kerrisk [wolfgang rohdewald] errors: add eacces see https://bugzilla.kernel.org/show_bug.cgi?id=52681 __setfpucw.3 michael kerrisk add proper page cross refs for alternate functions core.5 proc.5 kees cook clarify suid_dumpable versus core_pattern in linux 3.6, additional requirements were placed on core_pattern when suid_dumpable is set to 2. document this and include commit references. justin lebar statm's "shared" field refers to pages backed by files i noticed that statm's "shared" field doesn't match the sum of all the "shared" entries in smaps [1]. the kernel docs explain that statm's "shared" field is "number of pages that are shared (i.e. backed by a file)" [2]. smaps appears to call a page shared if it's mapped by at least two processes, which explains this discrepancy. i'm not a kernel hacker, but it appears to me they do mean "i.e." and not "e.g." in the statm description: in fs/proc/task_mmu.c::task_statm, i see *shared = get_mm_counter(mm, mm_filepages); here's a patch which updates the man page to match the (hopefully correct) kernel docs. [1] https://bugzilla.mozilla.org/show_bug.cgi?id=807181 [2] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=documentation/filesystems/proc.txt;h=a1793d670cd01bd374eddf54ffdfc768504291ff;hb=head proc.5 kees cook put /proc/sys/kernel/hotplug in alphabetical order kees cook document /proc/sys/kernel/dmesg_restrict kees cook linux 3.4 changed permissions needed to change kptr_restrict michael kerrisk [samuel thibault, simon paillard] add field numbers for /proc/pid/stat see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=553413 add numbering to /proc/stat "cpu" fields see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=553413 michael kerrisk reorganize text describing /proc/stat "cpu" fields michael kerrisk rewording of suid_dumpable text after comments from kees cook michael kerrisk [samuel thibault, simon paillard] add field numbers for /proc/[pid]/statm see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=553413 michael kerrisk document /proc/stat "cpu" "nice_guest" field info taken from commit ce0e7b28fb75cb003cfc8d0238613aaf1c55e797 michael kerrisk [peter lekeynstein] document /prod/[pid]/oom_score_adj text taken directly from documentation/filesystems/proc.txt, with some light editing. see https://bugzilla.kernel.org/show_bug.cgi?id=50421 shells.5 michael kerrisk add /etc/bash to list of example shells ttytype.5 michael kerrisk add proper xref for termcap and terminfo pages capabilities.7 michael kerrisk add kcmp(2) under cap_sys_ptrace man-pages.7 michael kerrisk update description of section 7 ==================== changes in man-pages-3.47 ==================== released: 2013-02-12, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: david prévot d. barbier lennart poettering michael kerrisk mike frysinger peter schiffer radek pazdera reuben thomas shawn landden simon paillard vince weaver apologies if i missed anyone! new and rewritten pages ----------------------- perf_event_open.2 vincent weaver new page documenting perf_event_open(2) pthread_setname_np.3 chandan apsangi, michael kerrisk new page for pthread_setname_np(3) and pthread_getname_np(3) sln.8 michael kerrisk [peter schiffer] new page documenting the 'sln' command provided by glibc inspired by a red hat downstream page, but with rather more detail. newly documented interfaces in existing pages --------------------------------------------- prctl.2 michael kerrisk [shawn landden, lennart poettering] document pr_set_child_subreaper and pr_get_child_subreaper ip.7 radek pazdera add source-specific multicast sockopts this patch adds documentation of several source-specific multicast socket options that were added to kernel with implementation of igmpv3 in 2.5.68. the following socket options were added: ip_add_source_membership ip_drop_source_membership ip_block_source ip_unblock_source ip_msfilter pages moved across sections --------------------------- getcontext.3 michael kerrisk this page really belongs in section 3 (moved from section 2) getdtablesize.3 michael kerrisk move from section 2 new and changed links --------------------- getcontext.2 michael kerrisk make link to page moved into section 3 getdtablesize.2 michael kerrisk link to renamed getdtablesize.3 setcontext.2 michael kerrisk modify link to point to section 3 pthread_getname_np.3 michael kerrisk new link to new pthread_setname_np.3 setcontext.3 michael kerrisk link to getcontext page renamed into section 3 changes to individual pages --------------------------- fallocate.2 michael kerrisk see also: add fallocate(1) flock.2 michael kerrisk see also: add flock(1) fork.2 michael kerrisk see also: add exit(2) getpriority.2 michael kerrisk bugs: note that nice value is per-thread on linux getrlimit.2 michael kerrisk see also: add prlimit(1) gettid.2 michael kerrisk see also: add various system calls that use thread ids ioprio_set.2 michael kerrisk see also: add ionice(1) sched_setaffinity.2 michael kerrisk see also: add taskset(1) sched_setparam.2 michael kerrisk scheduling policy and parameters are per-thread on linux direct the reader to the discussion in sched_setscheduler(2). sched_setscheduler.2 michael kerrisk scheduling policy and parameters are per-thread on linux michael kerrisk see also: add chrt(1) setsid.2 michael kerrisk see also: add setsid(1) shmop.2 michael kerrisk [peter schiffer] errors: add eidrm taken from red hat downstream patch sigaction.2 makecontext.3 michael kerrisk change getcontext/setcontext page ref to section 3 signal.2 michael kerrisk [reuben thomas] clarify system v vs bsd semantics for signal() syscalls.2 michael kerrisk the list on this page is not just syscalls common to all platforms michael kerrisk add perfctr(2) add ppc_rtas(2) michael kerrisk add kernel version number of utrap_install(2) unimplemented.2 michael kerrisk [peter schiffer] remove mention of kernel version number in description inet.3 michael kerrisk [peter schiffer] fix error in example using inet_aton() see https://bugzilla.redhat.com/show_bug.cgi?id=837090 patch taken from red hat downstream. posix_fallocate.3 michael kerrisk see also: add fallocate(1) regex.3 reuben thomas clarify details of matching the first is that it's far from clear that the end points of the complete string match are stored in the zero'th element of the regmatch_t array; secondly, the phrase "next largest substring match" is positively misleading, implying some sort of size ordering, whereas in fact they are ordered according to their appearance in the regex pattern. scanf.3 michael kerrisk clarify meaning of "string conversions" for 'm' modifier mike frysinger update %a vs %m documentation posix.1-2008 adopted the 'm' flag for dynamic allocation. update page to cover it and relegate the glibc-specific 'a' flag to notes. strtol.3 michael kerrisk [peter schiffer] replace some bogus text about "thousands separator" see https://bugzilla.redhat.com/show_bug.cgi?id=652870 sysconf.3 michael kerrisk [peter schiffer] use "_sc_pagesize" consistently on page s/_sc_page_size/_sc_pagesize/ in one instance. from red hat downstream patch. nscd.conf.5 peter schiffer add max-db-size and auto-propagate descriptions, default values, + misc * added missing valid services (services and netgroup) * added many default values for options * reordered options according to the nscd.conf file (logical order) * added 2 missing options: max-db-size and auto-propagate nsswitch.conf.5 peter schiffer mention initgroups db proc.5 michael kerrisk document /proc/profile michael kerrisk [peter schiffer] update /proc/sys/fs/file-nr to include linux 2.6 details michael kerrisk clarify relationship between file-max and file-nr the third value in /proc/sys/fs/file-nr is the same as the value in /proc/sys/fs/file-max. michael kerrisk note message written to kernel log when file-max limit is hit info from documentation/sysctl/fs.txt. michael kerrisk mention lscpu(1) under discussion of /proc/cpuinfo resolv.conf.5 michael kerrisk [peter schiffer] document "single-request-reopen" option taken from red hat downstream patch see https://bugzilla.redhat.com/show_bug.cgi?id=717770 see http://thread.gmane.org/gmane.linux.man/3161 utmp.5 michael kerrisk see also: add utmpdump(1) cpuset.7 simon paillard add missing 'cpuset.' prefix for some flags see kernel commit e21a05cb408bb9f244f11a0813d4b355dad0822e svipc.7 michael kerrisk see also: add ipcmk(1), ipcrm(1), ipcs(1) termio.7 michael kerrisk see also: add reset(1), setterm(1), stty(1), tty(4) ld.so.8 michael kerrisk [peter schiffer] ld_verbose does not work with ld.so --list and --verify from red hat downstream patch see https://bugzilla.redhat.com/show_bug.cgi?id=532629 michael kerrisk see also: add sln(8) zdump.8 michael kerrisk [peter schiffer] bring up to date with zdump --help patch taken from red hat downstream. ==================== changes in man-pages-3.48 ==================== released: 2013-03-05, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andrey vagin aristeu rozanski colin walters cyril hrubis cyrill gorcunov daniel p. berrange david prévot d. barbier denys vlasenko flavio leitner graham gower ivana varekova kai kunschke marcela maslanova marc lehmann marshel abraham michael kerrisk nathan stratton treadway pavel emelyanov peter schiffer simon heimberg simon paillard török edwin ulrich drepper zack weinberg apologies if i missed anyone! new and rewritten pages ----------------------- getunwind.2 marcela maslanova new page documenting getunwind(2) taken from red hat downstream man pages set michael kerrisk much rewriting some text taken from arch/ia64/kernel/unwind.c. perfmonctl.2 ivana varekova new page documenting ia-64-specific perfmonctl(2) taken from red hat downstream man pages michael kerrisk rework discussion of pfm_create_context add versions and conforming to note that there is no glibc wrapper remove pfm_create_evtsets, pfm_delete_evtsets, pfm_getinfo_evtsets these don't exist, and it appears they never have. fix argument types for pfm_write_pmcs, pfm_write_pmds, pfm_read_pmds the types that were being used don't exist! briefly document pfm_get_features, pfm_debug, pfm_get_pmc_reset_val gai.conf.5 ulrich drepper new page documenting gai.conf taken from red hat downstream pages nss.5 ulrich drepper new page describing nss.conf newly documented interfaces in existing pages --------------------------------------------- clock_getres.2 cyril hrubis document clock_realtime_coarse and clock_monotonic_coarse cyril hrubis document clock_boottime michael kerrisk some improvements to clock_boottime description ptrace.2 denys vlasenko document ptrace_getregset, ptrace_setregset, ptrace_seize, and friends document ptrace_getregset, ptrace_setregset, ptrace_seize, ptrace_interrupt, and ptrace_listen. new and changed links --------------------- fattach.2 fdetach.2 getmsg.2 isastream.2 putmsg.2 michael kerrisk [peter schiffer] new link to unimplemented.2 taken from red hat downstream. see https://bugzilla.redhat.com/show_bug.cgi?id=436407 global changes -------------- many pages michael kerrisk global fix: remove unneeded double quotes in .sh headings many pages michael kerrisk global fix: remove unneeded double quotes in .ss headings many pages michael kerrisk global fix: use consistent capitalization in .ss headings capitalization in .ss sections across pages (and sometimes even within a single page) is wildly inconsistent. make it consistent. capitalize first word in heading, but otherwise use lower case, except where english usage (e.g., proper nouns) or programming language requirements (e.g., identifier names) dictate otherwise. many pages michael kerrisk [denys vlasenko] remove double blank lines in output various pages michael kerrisk fix order of sh sections changes to individual pages --------------------------- accept.2 michael kerrisk name: add "accept4" access.2 colin walters note that access() may also fail for fuse since in some cases (e.g. libguestfs's guestmount) it also has the semantics where files can appear owned by root, but are actually mutable by the user, despite what one might infer from the unix permissions. getpeername.2 michael kerrisk [kai kunschke] clarify semantics of getpeername() for datagram sockets see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=674034 getuid.2 michael kerrisk remove duplicate section heading mmap.2 cyril hrubis add note about partial page in bugs section this adds a note about linux behavior with partial page at the end of the object. the problem here is that a page that contains only part of a file (because the file size is not multiple of page_size) stays in page cache even after the mapping is unmapped and the file is closed. so if some process dirties such page, other mappings will see the changes rather than zeroes. michael kerrisk [török edwin] some 'flags' values require a feature test macro to be defined add text to notes noting that some map_* constants are defined only if a suitable feature test macro is defined. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=542601 cyril hrubis document eoverflow error open.2 michael kerrisk clarify list of file creation flags posix.1-2008 tc1 clarified this, so that o_cloexec, o_directory, and o_nofollow are also in this list. prctl.2 cyrill gorcunov add some details for pr_get_tid_address read.2 michael kerrisk [zack weinberg] clarify interaction of count==0 and error checking posix deliberately leaves this case open, so the man page should be less specific about what happens. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=533232 michael kerrisk [marc lehmann] remove crufty text about o_nonblock on files see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=700529 michael kerrisk clarify details for seekable files unimplemented.2 michael kerrisk [peter schiffer] add various streams interfaces to name taken from red hat downstream. see https://bugzilla.redhat.com/show_bug.cgi?id=436407 cexp2.3 michael kerrisk still does not exist in glibc 2.17 exit.3 michael kerrisk note that a call to execve() clears exit handler registrations getaddrinfo.3 michael kerrisk see also: add gai.conf(5) malloc_trim.3 michael kerrisk remove duplicate section title printf.3 marshel abraham [graham gower, graham gower] fix error handling in example code see https://bugzilla.kernel.org/show_bug.cgi?id=23282 pthread_yield.3 michael kerrisk [aristeu rozanski] add _gnu_source feature test macro to synopsis resolver.3 resolv.conf.5 michael kerrisk [nathan stratton treadway, simon heimberg] res_debug is only available if glibc is compiled with debug support see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=692136 and https://bugzilla.kernel.org/show_bug.cgi?id=43061 strtol.3 michael kerrisk [peter schiffer] remove crufty text from previous fix core.5 michael kerrisk document config_coredump capabilities.7 andrey vagin nonexistent bits are no longer shown as set in /proc/pid/status cap* inotify.7 michael kerrisk a monitoring process can't easily distinguish events triggered by itself ip.7 flavio leitner [peter schiffer] improve explanation about calling listen() or connect() man-pages.7 michael kerrisk describe rules for capitalization in .ss headings rtnetlink.7 pavel emelyanov add info about ability to create links with given index since kernel v3.7 the rtm_newlink message now accepts nonzero values in ifi_index field. mention this fact in the respective rtnetlink.7 section. socket.7 pavel emelyanov so_bindtodevice is now readable so_bindtodevice is readable since kernel 3.8. ==================== changes in man-pages-3.49 ==================== released: 2013-03-10, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: michael kerrisk global changes -------------- the goal of the changes below to consistently format copyright and license information in the comments in the page source at the top of each page. this allows for easy scripting to extract that information. following these changes the comments the top of the page source should now consistently have the form: .\" .\" .\" %%%license_start() .\" .\" %%%license_end .\" note that the 'license-type' is merely descriptive. its purpose is to simplify scripting for the purpose of gathering statistics on types of licenses used in man-pages. it is not a statement about the actual licensing of the page; that license is contain inside the license_start...license_end clause. all pages michael kerrisk add a license_start()...license_end clause in source at top of each page that encapsulates the license text. michael kerrisk put copyright info at top of page, followed by blank line and license various pages michael kerrisk update info in source comments on where to get a copy of the gpl various pages michael kerrisk remove "hey emacs" comment in page source only certain pages have this; there is no consistency, so remove it from all pages michael kerrisk remove "-*- nroff -*-" comment at top of source ==================== changes in man-pages-3.50 ==================== released: 2013-03-15, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andrey vagin bernhard kuemel elie de brauwer erik saule florian weimer friedrich delgado friedrichs jonathan nieder jose luis domingo lopez mark r bannister michael kerrisk sam varshavchik simon paillard apologies if i missed anyone! new and rewritten pages ----------------------- canonicalize_file_name.3 michael kerrisk rewrite page, adding much more detail global changes -------------- various pages michael kerrisk global fix: s/end_license/license_end/ various pages michael kerrisk global fix: s/bitmask/bit mask/ changes to individual pages --------------------------- getent.1 mark r bannister netgroup description incorrectly refers to initgroups capget.2 michael kerrisk update url for libcap fork.2 michael kerrisk port access permission bits (ioperm()) are turned off in the child futex.2 michael kerrisk 'timeout' is a minimum duration that the call will wait, not a maximum ioperm.2 michael kerrisk note that iopl() level of 3 is needed to access ports michael kerrisk 'num' is *bits* not bytes! michael kerrisk linux 2.6.8 lifted the port limit to 65,536 see http://article.gmane.org/gmane.linux.kernel/202624/ from: stas sergeev aknet.ru> subject: [patch][rfc] larger io bitmap date: 2004-05-07 19:55:03 gmt michael kerrisk ioperm() operates on the calling *thread* (not process) michael kerrisk clarify meaning of 'turn_on' argument plus form formatting fixes. michael kerrisk clarify that default state of permission bits in child is off michael kerrisk notes: add mention of /proc/ioports michael kerrisk see also: add outb(2) iopl.2 michael kerrisk cap_sys_rawio is required to *raise* the i/o privilege level michael kerrisk clarify that the two least significant bits of 'level' are what matter michael kerrisk see also: add outb(2) syscalls.2 michael kerrisk add version information for all (other) syscalls michael kerrisk add perfmonctl(2) futimes.3 michael kerrisk [jonathan nieder] errors: add enosys for lutimes() see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=620746 getpass.3 michael kerrisk [erik saule] suggest use of the echo flag as an alternative see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=644261 realpath.3 michael kerrisk document gnu extensions for eacces and enoent errors stdarg.3 michael kerrisk [friedrich delgado friedrichs] describe va_copy() see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=575077 termios.3 michael kerrisk [bernhard kuemel] mention that noncanonical mode does not do input processing see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=643854 random.4 elie de brauwer document write and document the ioctl interface of /dev/random the update consists out of two parts: - a minor thing which just documents what happens if a write to /dev/(u)random is performed, which is used in the example script but not explicitly mentioned. - the other (biggest) part is the documentation of the ioctl() interface which /dev/(u)random exposes. this ioctl() lives in drivers/char/random.c and the primitives can be found in include/linux/random.h one comment remains, there used to be an rndgetpool ioctl() which disappeared in v2.6.9. i found two patches on the net: - http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.8.1/2.6.8.1-mm4/broken-out/dev-random-remove-rndgetpool-ioctl.patch - https://lkml.org/lkml/2004/3/25/168 but as far as i can tell the first one got applied but the 2nd one seems more correct. the result is that even today one can still find traces of the rndgetpool ioctl() in the header files. is this there for historical reasons or because it might break userspace, even though using it will just give an einval. bootparam.7 jose luis domingo lopez document 'rootfstype' option see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=182014 capabilities.7 michael kerrisk add various pieces under cap_sys_rawio info obtained by grepping the kernel source. michael kerrisk add cap_sys_resource /proc/pid/oom_score_adj case netlink.7 andrey vagin add a note about broadcast messages to multiple groups socket.7 michael kerrisk [florian weimer] define _gnu_source to obtain the definition of 'struct ucred' see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=572210 ==================== changes in man-pages-3.51 ==================== released: 2013-04-17, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andreas jaeger andrew clayton brian m. carlson changhee han cyril hrubis damien grassart david prévot denis barbier jeff moyer krzysztof konopko kyle mcmartin mark h weaver michael kerrisk mike frysinger nicolas hillegeer pavel emelyanov peter schiffer radek pazdera ralph loader simon paillard the wanderer apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- sched_rr_get_interval.2 michael kerrisk document /proc/sys/kernel/sched_rr_timeslice_ms proc.5 pavel emelyanov document /proc/[pid]/map_files directory this directory was added in linux v3.3 and provides info about files being mmap-ed in a way very similar to how /proc/[pid]/fd works. v2: added examples of how links look like and noted dependency on kernel config option config_checkpoint_restore. michael kerrisk document /proc/sys/kernel/shm_rmid_forced capabilities.7 michael kerrisk document /proc/sys/kernel/cap_last_cap global changes -------------- various pages michael kerrisk global fix: fix placement of word "only" various pages simon paillard license headers: consistent format various pages michael kerrisk global fix: s/since kernel/since linux/ various system v ipc pages in section 2 michael kerrisk add "system v" to .th line and text make it clear that these pages relate to system v ipc, not posix ipc. changes to individual pages --------------------------- access.2 michael kerrisk [the wanderer] clarify return value for f_ok see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=705293 alarm.2 michael kerrisk correct the description of behavior when 'seconds' is 0 clone.2 michael kerrisk [peter schiffer] add prototype for syscall to synopsis and further clarify the distinction between the system call and the wrapper function in the introductory text. michael kerrisk update feature test macro requirements the requirements quietly changed in glibc 2.14 see also http://www.sourceware.org/bugzilla/show_bug.cgi?id=4749 michael kerrisk [mike frysinger] clarify differences between clone2() syscall and wrapper function michael kerrisk [mike frysinger] note those architectures where the sys_clone argument order differs michael kerrisk [mike frysinger] add short subsection noting that blackfin, m68k, and sparc are different michael kerrisk move clone2() text to subsection in description the description of ia64 clone2() should follow the discussion of the raw system call interface. michael kerrisk change subhead for ia64 discussion getcpu.2 michael kerrisk recommend that 'tcache' should be specified as null nowadays io_cancel.2 jeff moyer, michael kerrisk [cyril hrubis] improve description io_destroy.2 jeff moyer improve description the description was rather vague, citing a "list of i/o contexts" and stating that it "can" cancel outstanding requests. this update makes things more concrete so that the reader knows exactly what's going on. io_getevents.2 jeff moyer the 'timeout' argument is not updated i looked back through the kernel code, and the timeout was never updated in any case. i've submitted a patch upstream to change the comment above io_getevents. io_setup.2 jeff moyer clarify nr_events nr_events is technically the number of completion events that can be stored in the completion ring. the wording of the man page: "capable of receiving at least nr_events" seems dubious to me, only because i worry that folks might interpret that to mean 'nr_events' total, instead of 'nr_events' concurrently. further, i've added information on where to find the per-user limit on 'nr_events', /proc/sys/fs/aio-max-nr. let me know if you think that is not relevant. listxattr.2 michael kerrisk explain use of 'size' argument lseek.2 michael kerrisk [andreas jaeger] _gnu_source must be defined to get seek_data and seek_hole definitions see http://sourceware.org/bugzilla/show_bug.cgi?id=15312 mmap.2 michael kerrisk add pointers to relevant /proc files described in proc(5) posix_fadvise.2 pread.2 readahead.2 sync_file_range.2 truncate.2 michael kerrisk refer to syscall(2) for abi semantics on certain 32-bit architectures also: in sync_file_range.2 and posix_fadvise.2 remove description of conventional calling signature as flawed, and in posix_fadvise.2, de-emphasize focus on arm, and rather phrase as a more general discussion of certain architectures. readdir.2 michael kerrisk readdir(2) doesn't exist on x86-64 semop.2 michael kerrisk clarify the discussion of 'semadj' shmctl.2 michael kerrisk refer to proc(5) for description of /proc/sys/kernel/shm_rmid_forced syscall.2 changhee han add notes that caution users when passing arguments to syscall() for example, passing 'long long' on arm-32 requires special treatment. mike frysinger [michael kerrisk] document the exact calling convention for architecture system calls mike frysinger [kyle mcmartin] add pa-risc details under calling conventions michael kerrisk [mike frysinger] refine discussion of arm and other abis syscalls.2 michael kerrisk update kernel version number at start of list umask.2 michael kerrisk see also: add acl(5) unshare.2 michael kerrisk update feature test macro requirements the requirements quietly changed in glibc 2.14 see also http://www.sourceware.org/bugzilla/show_bug.cgi?id=4749 fopencookie.3 michael kerrisk [ralph loader] correct definition of cookie_io_functions_t pthread_setname_np.3 andrew clayton the thread argument is passed in by value readir.3 seekdir.3 telldir.3 michael kerrisk eliminate the implication that these functions deal with "offsets" the directory position dealt with by the readdir() and friends is not a simple file offset in modern file systems. typically, it is some kind of cookie value. add text and make other changes to these pages to eliminate the implication that this is an offset, and warn the reader that directory positions should be treated strictly as opaque values. in the process, rename the 'offset' argument of seekdir(3) to 'loc', and add some text to readdir(3) to note that the 'd_off' field is the same value returned by telldir(3) at the current directory position. see also https://lwn.net/articles/544298/ scalb.3 mark h weaver fix prototypes for scalbf() and scalbl() sched_getcpu.3 michael kerrisk update feature test macro requirements the requirements quietly changed in glibc 2.14 see also http://www.sourceware.org/bugzilla/show_bug.cgi?id=4749 ualarm.3 michael kerrisk [nicolas hillegeer] add note on the behavior when 'usecs' is zero posix.1-2001 does not specify the behavior in this case and no other system that i checked documented the behavior. probably, most or all systems do what linux does in this case: cancel any pending alarm, just as alarm(0) does. add that info in notes. elf.5 mike frysinger add byte positions for all ei_xxx fields when describing e_ident, most of the ei_xxx defines mention the exact byte number. this is useful when manually hacking an elf with a hex editor. however, the last few fields don't do this, which means you have to count things up yourself. add a single word to each so you don't have to do that. proc.5 michael kerrisk refer to sched_rr_get_interval(2) for info on sched_rr_timeslice_ms since linux 3.9, /proc/sys/kernel/sched_rr_timeslice_ms can be used to change the sched_rr quantum. michael kerrisk see also: add sysctl(8) krzysztof konopko simplify the example of printing out environ the binutils package contains a very handy utility to print out null-byte delimited strings from a file. this can replace a rather complex expression with cat(1) provided as an example for printing out /proc/[pid]/environ. michael kerrisk update /proc/pid/maps example update to 64-bit example that includes "[heap]", "[stack], and "[vdso]" michael kerrisk formatting fixes for /proc/pid/maps mike frysinger document the "pathname" field of /proc/pid/maps michael kerrisk add reference to capabilities(7) for /proc/sys/kernel/cap_last_cap michael kerrisk /proc/pid/maps: add a reference to mmap(2) ip.7 radek pazdera document ip_multicast_all this commit adds documentation for the ip_multicast_all socket option. the option was added to the linux kernel in 2.6.31: author nivedita singhvi commit f771bef98004d9d141b085d987a77d06669d4f4f the description is based on a previous one [3] posted by the original author of the code -- nivedita, but it is slightly re-worded. i tested it myself and it works as described. references: [1] http://lxr.free-electrons.com/source/net/ipv4/ip_sockglue.c#l972 [2] http://lxr.free-electrons.com/source/net/ipv4/igmp.c#l2267 [3] http://patchwork.ozlabs.org/patch/28902/ units.7 brian m. carlson units should use an actual µ the units(7) man page uses an ascii u in place of the actual greek letter mu. since we're in the twenty-first century, with utf-8-compatible terminals and terminal emulators, we should use the actual letter µ instead of an ascii approximation. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=704787 ==================== changes in man-pages-3.52 ==================== released: 2013-07-04, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adrian bunk andrea remondini anthony foiani brian norris cyril hrubis dan jacobson david prévot eric s. raymond georg sauthoff jeff moyer jérémie galarneau jon grant manuel traut марк коренберг michael kerrisk mike frysinger pavel emelyanov peng haitao peter ladow petr gajdos regid siddhesh poyarekar simone piccardi simon paillard vince weaver yuri kozlov apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- perf_event_open.2 vince weaver add perf_ioc_flag_group documentation the perf_event_open() enable/disable/reset ioctls can take an argument, perf_ioc_flag_group. this wasn't documented at all until about a year ago (despite the support being there from the beginning) so i missed this when initially writing the man page. socket.7 pavel emelyanov, michael kerrisk document so_peek_off option since linux 3.4 there appeared an ability to specify the offset in bytes from which the data will be msg_peek-ed. describe this socket option in the socket(7) page, where all the other socket options are described. global changes -------------- various pages michael kerrisk convert inline formatting (\fx...\fp) to dot-directive formatting readdir.2 asprintf. getline.3 getlogin.3 pthread_setname_np.3 readdir.3 strerror.3 michael kerrisk [jon grant] clarify that terminating null byte is '\0' changes to individual pages --------------------------- execve.2 peter ladow add envp to the linux notes about null pointers during the review of static analysis results, we discovered a functional, but non-portable, use of execve(). for example: char *cmd[] = { "/path/to/some/file", null }; execve(cmd[0], cmd, null); the call succeeds. yet, the static analysis tool (rightly) pointed out that envp could be dereferenced. but digging into glibc and the kernel, it appears that like argv, envp when null is treated as if it were an empty list. so, to clear things up, i'm submitting this patch to update the man page to indicate that envp is treated like argv. fallocate.2 michael kerrisk return value: mention that 'errno' is set on error io_setup.2 cyril hrubis [jeff moyer] clarify the nr_events parameter currently the io_setup.2 man page describes what the kernel really does, i.e., that the resulting context may be able to hold more than the 'nr_event's operations because the memory allocated in kernel is rounded to be multiple of page size. it is better not to expose this implementation detail and simply state that the resulting context is suitable for 'nr_events' operations. perf_event_open.2 vince weaver clarify the perf_event_open() wakeup_events/wakeup_watermark fields clarify the perf_event_open() wakeup_events/wakeup_watermark fields a bit, based on info from kernel commit cfeb1d90a1b1. vince weaver update to match the linux 3.10 release this patch updates the perf_event_open() documentation to include new interfaces added in the 3.10 kernel. it also documents a few [to be documented] instances left over from the 3.7 kernel. vince weaver small correction to description of 'flags' argument prctl.2 michael kerrisk note equivalents of pr_set_name pthread_setname_np() and pthread_getname_np() and /proc/self/task/tid/comm provide access to the same attribute. pread.2 michael kerrisk [марк коренберг] pread() and pwrite() are especially useful in multithreaded applications recv.2 michael kerrisk return value: mention that 'errno' is set on error semctl.2 michael kerrisk [simone piccardi] 'sem_nsems' is 'unsigned long' since linux 2.4 shmget.2 michael kerrisk rewrite return value and mention that 'errno' is set on error sigaction.2 michael kerrisk [brian norris] return value: mention that 'errno' is set on error signal.2 michael kerrisk return value: mention that 'errno' is set on error sigpending.2 michael kerrisk return value: mention that 'errno' is set on error sigprocmask.2 michael kerrisk return value: mention that 'errno' is set on error sigsuspend.2 michael kerrisk return value: mention that 'errno' is set on error syscall.2 mike frysinger document s390/s390x calling convention a64l.3 peng haitao attributes: note function that is not thread-safe the function l64a() is not thread safe. abs.3 peng haitao attributes: note functions that are thread-safe the functions abs(), labs(), llabs() and imaxabs() are thread-safe. aio_error.3 peng haitao attributes: note function that is thread-safe the function aio_error() is thread safe. aio_return.3 peng haitao attributes: note function that is thread-safe the function aio_return() is thread safe. alloca.3 adrian bunk correct information on getting non-inlined version with gcc+glibc - remove the incorrect information that -fno-builtin would help - add -std=c11 to the list of strict options - emphasize more that both the gcc option and not including alloca.h are needed - add the #ifdef from the glibc alloca.h to make the situation clearer bindresvport.3 peng haitao attributes: note function that is thread-safe before glibc 2.17, bindresvport() is not thread-safe. since glibc 2.17, it is thread-safe, the patch can refer to url: http://sourceware.org/git/?p=glibc.git;a=commit;h=f6da27e53695ad1cc0e2a9490358decbbfdff5e5 canonicalize_file_name.3 michael kerrisk put conforming to section in right location catgets.3 michael kerrisk [jon grant] clarify that null byte is '\0' ceil.3 peng haitao attributes: note functions that are thread-safe the functions ceil(), ceilf() and ceill() are thread safe. cimag.3 peng haitao attributes: note functions that are thread-safe the functions cimag(), cimagf() and cimagl() are thread safe. clock_getcpuclockid.3 peng haitao attributes: note function that is thread-safe the function clock_getcpuclockid() is thread safe. conj.3 peng haitao attributes: note functions that are thread-safe the functions conj(), conjf() and conjl() are thread safe. crypt.3 peng haitao attributes: note function that is not thread-safe the function crypt() is not thread safe. ctermid.3 peng haitao attributes: note function that is thread safe with exceptions the function ctermid() is thread safe with exceptions. dirfd.3 michael kerrisk return value: mention that 'errno' is set on error drand48.3 peng haitao attributes: note functions that are not thread-safe the functions drand48(), erand48(), lrand48(), nrand48(), mrand48(), jrand48(), srand48(), seed48() and lcong48() are not thread safe. ecvt.3 peng haitao attributes: note functions that are not thread-safe the functions ecvt() and fcvt() return a string located in a static buffer which is overwritten by the next call to the functions, so they are not thread-safe. encrypt.3 peng haitao attributes: note functions that are not thread-safe the functions encrypt() and setkey() are not thread safe. ether_aton.3 peng haitao attributes: note functions that are not thread-safe the functions ether_aton() and ether_ntoa() are not thread safe. fcloseall.3 peng haitao attributes: note function that is not thread-safe the function fcloseall() is not thread safe. ferror.3 peng haitao attributes: note functions that are thread-safe the functions ferror(), clearerr(), feof() and fileno() are thread safe. fgetgrent.3 michael kerrisk return value: mention that 'errno' is set on error fgetpwent.3 michael kerrisk return value: mention that 'errno' is set on error fgetwc.3 michael kerrisk return value: mention that 'errno' is set on error fmtmsg.3 peng haitao attributes: note function that is thread-safe before glibc 2.16, fmtmsg() is not thread-safe. since glibc 2.16, it is thread-safe, the patch can refer to url: http://sourceware.org/git/?p=glibc.git;a=commit;h=7724defcf8873116fe4efab256596861eef21a94 fputwc.3 michael kerrisk return value: mention that 'errno' is set on error getdate.3 peng haitao attributes: note functions that are and aren't thread-safe getgrent.3 peng haitao attributes: note function that is not thread-safe the function getgrent() is not thread safe. getgrnam.3 peng haitao attributes: note functions that are and aren't thread-safe getline.3 michael kerrisk return value: mention that 'errno' is set on error getlogin.3 peng haitao attributes: note function that is not thread-safe the function getlogin() is not thread safe. the function cuserid() is thread-safe with exceptions. michael kerrisk return value: mention that 'errno' is set on error getpass.3 peng haitao attributes: note functions that are not thread-safe getpwent.3 peng haitao attributes: note function that is not thread-safe the function getpwent() is not thread safe. getpwnam.3 peng haitao attributes: note functions that are and aren't thread-safe getspnam.3 michael kerrisk return value: mention that 'errno' is set on error getttyent.3 peng haitao attributes: note functions that are not thread-safe getusershell.3 peng haitao attributes: note functions that are not thread-safe the functions getusershell(), setusershell() and endusershell() are not thread safe. getutent.3 michael kerrisk return value: mention that 'errno' is set on error hsearch.3 michael kerrisk return value: mention that 'errno' is set on error hsearch.3 peng haitao attributes: note functions that are not thread-safe the functions hsearch(), hcreate() and hdestroy() are not thread-safe. localeconv.3 peng haitao attributes: note functions that are not thread-safe the function localeconv() returns a pointer to a structure which might be overwritten by subsequent calls to localeconv() or by calls to setlocale(), so it is not thread-safe. peng haitao add return value section malloc_info.3 michael kerrisk return value: mention that 'errno' is set on error mblen.3 peng haitao attributes: note function that is not thread-safe the function mblen() is not thread safe. mbrlen.3 peng haitao attributes: note function that is thread safe with exceptions the function mbrlen() is thread safe with exceptions. mbrtowc.3 peng haitao attributes: note function that is thread safe with exceptions the function mbrtowc() is thread safe with exceptions. mktemp.3 michael kerrisk return value: mention that 'errno' is set on error modf.3 peng haitao attributes: note functions that are thread-safe the functions modf(), modff() and modfl() are thread safe. popen.3 michael kerrisk return value: mention that 'errno' is set on error pthread_attr_setinheritsched.3 michael kerrisk note the scheduling attributes affected by this function pthread_attr_setschedparam.3 pthread_attr_setschedpolicy.3 pthread_attr_setscope.3 michael kerrisk [manuel traut, siddhesh poyarekar] the inherit-scheduler attribute must be set to pthread_explicit_sched in order for the attributes set by these functions to have an effect, the caller must use pthread_attr_setinheritsched(3) to set the inherit-scheduler attribute of the attributes object to pthread_explicit_sched. ptsname.3 peng haitao attributes: note function that is not thread-safe the function ptsname() is not thread safe. putenv.3 michael kerrisk return value: mention that 'errno' is set on error putpwent.3 michael kerrisk return value: mention that 'errno' is set on error qecvt.3 peng haitao attributes: note functions that are not thread-safe the functions qecvt() and qfcvt() are not thread-safe. random.3 michael kerrisk return value: mention that 'errno' is set on error michael kerrisk add einval error for setstate() michael kerrisk bugs: initstate() does not return null on error http://sourceware.org/bugzilla/show_bug.cgi?id=15380 random_r.3 michael kerrisk return value: mention that 'errno' is set on error readdir.3 peng haitao attributes: note functions that are not thread-safe the data returned by readdir() may be overwritten by subsequent calls to readdir() for the same directory stream, so it is not thread-safe. re_comp.3 peng haitao attributes: note functions that are not thread-safe the functions re_comp() and re_exec() are not thread safe. rexec.3 peng haitao attributes: note functions that are not thread-safe the functions rexec() and rexec_af() are not thread safe. round.3 peng haitao attributes: note functions that are thread-safe the functions round(), roundf() and roundl() are thread safe. scalbln.3 peng haitao attributes: note functions that are thread-safe the functions scalbn(), scalbnf(), scalbnl(), scalbln(), scalblnf() and scalblnl() are thread safe. scandir.3 michael kerrisk return value: mention that 'errno' is set on error siginterrupt.3 michael kerrisk return value: mention that 'errno' is set on error signbit.3 peng haitao attributes: note macro that is thread-safe the macro signbit() is thread safe. sigsetops.3 michael kerrisk return value: mention that 'errno' is set on error stdio_ext.3 peng haitao attributes: note functions that are not thread-safe the functions __fbufsize(), __fpending(), __fpurge() and __fsetlocking() are not thread safe. strdup.3 michael kerrisk return value: mention that 'errno' is set on error strerror.3 peng haitao attributes: note function that is not thread-safe the function strerror() is not thread safe. strftime.3 michael kerrisk clarify details of return value michael kerrisk bugs: 'errno' is not set if the result string would exceed 'max' bytes strtok.3 peng haitao attributes: note function that is not thread-safe the function strtok() is not thread safe. michael kerrisk [georg sauthoff] add more detail on the operation of strtok() add a number of missing details on the operation of strtok() tempnam.3 michael kerrisk return value: mention that 'errno' is set on error timegm.3 jérémie galarneau copy the string returned by getenv() the example of a portable version of timegm() uses the string returned by getenv() after calling setenv() on the same environment variable. the tz string may be invalid as per getenv.3: "the string pointed to by the return value of getenv() may be statically allocated, and can be modified by a subsequent call to getenv(), putenv(3), setenv(3), or unsetenv(3)." tmpnam.3 peng haitao attributes: note function that is thread safe with exceptions the function tmpnam() is thread safe with exceptions. trunc.3 peng haitao attributes: note functions that are thread-safe the functions trunc(), truncf() and truncl() are thread safe. ttyname.3 michael kerrisk attributes: note functions that are and aren't thread-safe ttyslot.3 michael kerrisk attributes: note functions that are not thread-safe usleep.3 michael kerrisk return value: mention that 'errno' is set on error wcsdup.3 michael kerrisk return value: mention that 'errno' is set on error core.5 michael kerrisk implicitly adding the pid to a core filename was dropped in 2.6.27 proc.5 michael kerrisk document /proc/[pid]/fd/ anon_inode symlinks mike frysinger document /proc/[pid]/fd/ symlinks a bit more describe the type:[inode] syntax used in this dir bootparam.7 michael kerrisk [dan jacobson] remove outdated text on lilo and loadlin strike the discussion of lilo and loadlin, which are long obsolete, and make a brief mention of grub. see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=604019 regid remove mention of the deprecated rdev(8) the deprecated rdev(8) command was removed from util-linux in 2010. see https://git.kernel.org/?p=utils/util-linux/util-linux.git;a=commit;h=a3e40c14651fccf18e7954f081e601389baefe3fo andrea remondini document the 'resume' boot parameter inotify.7 michael kerrisk [jon grant] clarify that null byte is '\0' iso_8859-2.7 eric s. raymond remove incorrect reference to nonexistent groff glyph \[shc] the reference incorrectly attempted to duplicate an actual soft hyphen (hex 0xad) just before it in the file. man-pages.7 peng haitao add description of "attributes" "attributes" section can mention thread safety, cancellation safety, and async-cancel-safety. socket.7 michael kerrisk note that 'optval' for socket options is an 'int' in most cases tcp.7 michael kerrisk note that 'optval' for socket options is an 'int' in most cases udp.7 michael kerrisk note that 'optval' for socket options is an 'int' in most cases ==================== changes in man-pages-3.53 ==================== released: 2013-07-31, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: al viro andrey vagin benjamin poirier chris heath chuck coffing david prévot denys vlasenko dmitry v. levin felix schulte graud michael kerrisk oleg nesterov peng haitao peter schiffer simon paillard vince weaver apologies if i missed anyone! new and rewritten pages ----------------------- restart_syscall.2 michael kerrisk new page for restart_syscall(2) system call newly documented interfaces in existing pages --------------------------------------------- fchownat.2 michael kerrisk document at_empty_path fstatat.2 michael kerrisk document at_empty_path linkat.2 michael kerrisk document at_empty_path open.2 michael kerrisk [al viro] document o_path see also https://bugzilla.redhat.com/show_bug.cgi?id=885740 changes to individual pages --------------------------- clock_nanosleep.2 futex.2 nanosleep.2 poll.2 sigaction.2 sigreturn.2 signal.7 michael kerrisk see also: add restart_syscall(2) open.2 michael kerrisk [geoffrey thomas] remove warning that o_directory is only for use with opendir(3) o_directory can also be used with, for example, o_path. perf_event_open.2 vince weaver improve perf_sample_branch_stack documentation vince weaver fix indentation of the mmap layout section the indentation of the mmap layout section wasn't quite right. i think this improves things but i admit i'm not an expert at the low-level indentation directives. vince weaver update perf_ioc_flag_group info it turns out perf_ioc_flag_group was broken from 75f937f24bd9 (in linux 2.6.31, the initial perf_event release) until 724b6daa1 (linux 3.4). i've done some extensive kernel source code digging plus running tests of various kernels and i hope the info presented is accurate now. (patch edited somewhat by mtk.) vince weaver improve sysfs files documentation this improves the documentation of the various perf_event_open()-related sysfs files. ptrace.2 denys vlasenko [oleg nesterov, dmitry v. levin] if seize was used, initial auto-attach stop is event_stop for every ptrace_o_tracefoo option, mention that old-style sigstop is replaced by ptrace_event_stop if ptrace_seize attach was used. mention the same thing again in the description of ptrace_event_stop. denys vlasenko [oleg nesterov, dmitry v. levin] mention that ptrace_peek* libc api and kernel api are different denys vlasenko [oleg nesterov, dmitry v. levin] clarify ptrace_interrupt, ptrace_listen, and group-stop behavior readlink.2 michael kerrisk document use of empty 'pathname' argument michael kerrisk change error check in example program from "< 0" to "== -1" chuck coffing fix possible race condition in readlink.2 example i noticed that the example in the readlink.2 man pages does error checking for a race condition that would cause the value of the symbolic link to get larger. however, it doesn't handle the opposite case, in which the value gets shorter. (the null terminator is always set at the old, longer offset.) this could cause the program to operate on uninitialized data. setpgid.2 michael kerrisk [graud] s/sigtstp/sigttin/ when discussing reads from terminal see https://bugzilla.kernel.org/show_bug.cgi?id=60504 clog2.3 michael kerrisk note that these functions are still not present in glibc 2.17 dirfd.3 peng haitao attributes: note function that is thread-safe the function dirfd() is thread safe. div.3 peng haitao attributes: note functions that are thread-safe the functions div(), ldiv(), lldiv() and imaxdiv() are thread safe. fabs.3 peng haitao attributes: note functions that are thread-safe the functions fabs(), fabsf() and fabsl() are thread safe. fdim.3 peng haitao attributes: note functions that are thread-safe the functions fdim(), fdimf() and fdiml() are thread safe. fflush.3 peng haitao attributes: note function that is thread-safe the function fflush() is thread safe. finite.3 peng haitao attributes: note functions that are thread-safe the functions finite(), finitef(), finitel(), isinf(), isinff(), isinfl(), isnan(), isnanf() and isnanl() are thread safe. flockfile.3 peng haitao attributes: note functions that are thread-safe the functions flockfile(), ftrylockfile() and funlockfile() are thread safe. floor.3 peng haitao attributes: note functions that are thread-safe the functions floor(), floorf() and floorl() are thread safe. resolv.conf.5 simon paillard explain how to set empty domain see http://bugs.debian.org/463575 capabilities.7 michael kerrisk add open_by_handle_at(2) under cap_dac_read_search inotify.7 michael kerrisk [felix schulte] clarify description of in_moved_from and in_moved_to man-pages.7 michael kerrisk description should note versions for new interface features or behavior udp.7 benjamin poirier add missing #include directive using the udp_cork socket option documented in udp.7 requires including . ld.so.8 michael kerrisk rework rpath token expansion text michael kerrisk describe $platform rpath token michael kerrisk describe $lib rpath token michael kerrisk document ld_bind_not michael kerrisk [simon paillard] add reference to pthreads(7) in discussion of ld_assume_kernel ==================== changes in man-pages-3.54 ==================== released: 2013-09-17, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: a. costa akihiro motoki andreas wiese andrew hunter chen gang christopher hall christos tsopokis david prévot d. barbier doug goldstein elie de brauwer eugen dedu felix janda g.raud hannes landeholm j. bruce fields j. bruce fields johan erlandsson jon grant magnus reftel marko myllynen michael kerrisk oleg nesterov peng haitao peter schiffer robert harris rodrigo campos simon paillard stas vince weaver will newton zdenek pavlas zsbán ambrus apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- ioctl_list.2 zsbán ambrus document fat_ioctl_get_attributes the attached patch adds four ioctls from linux/msdos_fs.h to the ioctl_list(2) manpage. the ioctl fat_ioctl_get_attributes reads fat attributes of a file a mounted vfat file system. i tested this on linux 2.6.33, an example script can be found at http://www.perlmonks.com/?node_id=832623 global changes -------------- various pages michael kerrisk global fix: s/file system/filesystem/ notwithstanding 24d01c530c5a3f75217543d02bf6712395e5f90c, "filesystem" is the form used by the great majority of man pages outside the man-pages project and in a number of other sources, so let's go with that. changes to individual pages --------------------------- access.2 j. bruce fields fix outdated nfs information note that nfs versions since version 3 support an "access" call so that the client doesn't have to guess permissions or id mapping on its own. (see rfc 1813 sections 1.7 and 3.3.4.) adjtimex.2 michael kerrisk see also: add adjtimex(8) clock_getres.2 michael kerrisk [rodrigo campos] note circumstances in which "smp" note applies. michael kerrisk add kernel version for clock_*_cputime_id clock_process_cputime_id and clock_thread_cputime_id appeared in 2.6.12. michael kerrisk add versions section futex.2 michael kerrisk the 'timeout' can be rounded upwards by clock granularity and also overrun kill.2 michael kerrisk small improvements to text on historical rules for permissions nfsservctl.2 michael kerrisk note commands that were only in linux 2.4.x and earlier open.2 robert harris add mmap(2) to list of calls that fail when given an o_path descriptor doug goldstein add einval to errors list einval can be returned by open(2) when the underlying filesystem doesn't support o_direct. it is documented in the notes section but this patch adds it to the list of possible errors. perf_event_open.2 vince weaver perf_sample_branch_stack updates this started out as just adding the new perf_event_open features from linux 3.11 (which was the addition of transactional memory defines for perf_sample_branch_stack samples) but turned into a general cleanup of the perf_sample_branch_stack documentation. the main clarification is that at least one of the non-privilege values must be set or else perf_event_open() will return an einval error. michael kerrisk reorder text describing fields of 'perf_event_header' structure place the fields with the shorter descriptions first, to make the information easier to read. poll.2 michael kerrisk clarify wording of 'timeout' as a "minimum" interval sched_setaffinity.2 michael kerrisk [christos tsopokis] clarify that these system calls affect a per-thread attribute sched_setparam.2 michael kerrisk clarify that this system call applies to threads (not processes) sched_setscheduler.2 michael kerrisk clarify that this system call applies to threads (not processes) select.2 michael kerrisk [g.raud] clarify wording of 'timeout' as a "minimum" interval setfsgid.2 michael kerrisk [oleg nesterov] clarify description of return value more clearly describe the weirdness in the return value of this system call, and note the problems it creates in bugs michael kerrisk correct header file in synopsis michael kerrisk refer to setfsuid(2) for an explanation of why setfsgid() is obsolete michael kerrisk wording improvements setfsuid.2 michael kerrisk [oleg nesterov] clarify description of return value more clearly describe the weirdness in the return value of this system call, and note the problems it creates in bugs michael kerrisk [chen gang] clarify historical details and note that setfsuid() is obsolete michael kerrisk wording improvements michael kerrisk correct header file in synopsis sigwaitinfo.2 michael kerrisk clarify wording of 'timeout' as a "minimum" interval syscall.2 johan erlandsson add missing argument in example johan erlandsson correct registers for arm/eabi registers was off by one. reference: http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=3105/4 see also: http://peterdn.com/post/e28098hello-world!e28099-in-arm-assembly.aspx https://wiki.debian.org/armeabiport http://en.wikipedia.org/wiki/calling_convention#arm wait.2 michael kerrisk [hannes landeholm] add details on the fifth argument provided by raw waitid() system call see https://bugzilla.kernel.org/show_bug.cgi?id=60744 clock.3 michael kerrisk clock() switched from using times(2) to clock_gettime() in glibc 2.18 drand48_r.3 peng haitao attributes: note functions that are thread-safe the functions drand48_r(), erand48_r(), lrand48_r(), nrand48_r(), mrand48_r(), jrand48_r(), srand48_r(), seed48_r(), and lcong48_r() are thread safe. fma.3 peng haitao attributes: note functions that are thread-safe the functions fma(), fmaf() and fmal() are thread safe. fmax.3 peng haitao attributes: note functions that are thread-safe the functions fmax(), fmaxf() and fmaxl() are thread safe. fmin.3 peng haitao attributes: note functions that are thread-safe the functions fmin(), fminf() and fminl() are thread safe. fpclassify.3 peng haitao attributes: note functions that are thread-safe the functions fpclassify(), isfinite(), isnormal(), isnan(), and isinf() are thread safe. frexp.3 peng haitao attributes: note functions that are thread-safe the functions frexp(), frexpf() and frexpl() are thread safe. gethostbyname.3 michael kerrisk [jon grant] gai_strerror() is the modern replacement for herror() and hstrerror() michael kerrisk update feature test macro requirements for herror() and hstrerror() michael kerrisk add feature test macro requirements for h_errno ilogb.3 peng haitao attributes: note functions that are thread-safe the functions ilogb(), ilogbf() and ilogbl() are thread safe. ldexp.3 peng haitao attributes: note functions that are thread-safe the functions ldexp(), ldexpf() and ldexpl() are thread safe. lrint.3 peng haitao attributes: note functions that are thread-safe the functions lrint(), lrintf(), lrintl(), llrint(), llrintf(), and llrintl() are thread safe. lround.3 peng haitao attributes: note functions that are thread-safe the functions lround(), lroundf(), lroundl(), llround(), llroundf() and llroundl() are thread safe. lseek64.3 peng haitao attributes: note function that is thread-safe the function lseek64() is thread safe. mbsinit.3 peng haitao attributes: note function that is thread-safe the function mbsinit() is thread safe. nextafter.3 peng haitao attributes: note functions that are thread-safe the functions nextafter(), nextafterf(), nextafterl(), nexttoward(), nexttowardf() and nexttowardl() are thread safe. posix_memalign.3 michael kerrisk [will newton] 'errno" is indeterminate after a call to posix_memalign() michael kerrisk [will newton] clarify wording on "return value" when size==0 printf.3 christopher hall correctly describe the meaning of a negative precision the printf(3) manpage says that a negative precision is taken to be zero, whereas printf(3p) says that a negative precision is taken as if the precision were omitted. glibc agrees with the latter (posix) specification. test code: printf("%f\n",42.0); // "42.000000" printf("%.*f\n",0,42.0); // "42" printf("%.*f\n",-1,42.0); // "42.000000" this patch corrects the explanation to match what actually happens. rewinddir.3 peng haitao attributes: note function that is thread-safe the function rewinddir() is thread safe. rint.3 peng haitao attributes: note functions that are thread-safe the functions nearbyint(), nearbyintf(), nearbyintl(), rint(), rintf() and rintl() are thread safe. seekdir.3 peng haitao attributes: note function that is thread-safe the function seekdir() is thread safe. telldir.3 peng haitao attributes: note function that is thread-safe the function telldir() is thread safe. wctomb.3 peng haitao attributes: note function that is not thread-safe the function wctomb() is not thread safe. wavelan.4 michael kerrisk [elie de brauwer] this driver disappeared in 2.56.35 dir_colors.5 michael kerrisk [stas] add various synonyms see http://bugs.debian.org/553477 simon paillard [stas] add keywords suid, sgid, sticky, sticky_other_writable, other_writable see http://bugs.debian.org/553477 see ls.c and dircolors.c in coreutils proc.5 peter schiffer document /proc/[pid]/io file attempt to document fields in the /proc/[pid]/io file, based on the documentation/filesystems/proc.txt. the text will probably need some grammar corrections. michael kerrisk [marko myllynen] /proc/sys/fs/inode-max went away in linux 2.4 also, the 'preshrink' field in /proc/sys/fs/inode-state became a dummy value in linux 2.4. see https://bugzilla.kernel.org/show_bug.cgi?id=60836 michael kerrisk [a. costa] note block size used by /proc/partitions see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=666972 michael kerrisk add rationale on drop_caches and note that it can hurt performance see also http://lwn.net/articles/562211/ bootparam.7 michael kerrisk [eugen dedu] remove "lilo" entries from see also see http://bugs.debian.org/604019 inotify.7 michael kerrisk see also: add inotifywait(1) and inotifywatch(1) ip.7 simon paillard ip_multicast_if setsockopt recognizes struct mreq (compatibility) kernel added compatibility only recently in 3a084ddb4bf299a6e898a9a07c89f3917f0713f7 see: http://bugs.debian.org/607979 standards.7 michael kerrisk add mention of susv4-tc1 (posix.1-2013) ==================== changes in man-pages-3.55 ==================== released: 2013-12-12, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alfred agrell andreas sandberg christoph hellwig david gibson david prévot fabrice bauzac greg price jon grant kosaki motohiro liu jiaming maxin b. john michael kerrisk paolo bonzini peng haitao robert p. j. day rodrigo campos shawn landden trevor bramwell vince weaver yang yang yuanhang zheng yuri kozlov janh apologies if i missed anyone! global changes -------------- assert.3 assert_perror.3 rexec.3 rpc.3 michael kerrisk [jon grant] reword a sentence to use more gender-neutral language changes to individual pages --------------------------- execve.2 michael kerrisk 'arg...' for interpreter scripts starts with argv[1] fallocate.2 christoph hellwig clarify the zeroing behavior fallocate() zeroes only space that did not previously contain data, but leaves existing data untouched. futex.2 rodrigo campos fix link to rusty's futex example library when i asked to webmaster@kernel.org, konstantin ryabitsev answered that the ".nl." is "an obsolete scheme and really should be changed to just ftp.kernel.org". getgroups.2 michael kerrisk note that ngroups_max is defined in michael kerrisk clarify that sysconf(_sc_ngroups_max) is a run-time technique michael kerrisk document /proc/sys/kernel/ngroups_max ioctl.2 michael kerrisk [kosaki motohiro, david gibson] 'request' argument is typed as 'unsigned long' in glibc see https://bugzilla.kernel.org/show_bug.cgi?id=42705 perf_event_open.2 vince weaver linux 3.12 rdpmc/mmap it turns out that the perf_event mmap page rdpmc/time setting was broken, dating back to the introduction of the feature. due to a mistake with a bitfield, two different values mapped to the same feature bit. a new somewhat backwards compatible interface was introduced in linux 3.12. a much longer report on the issue can be found here: https://lwn.net/articles/567894/ vince weaver linux 3.12 adds perf_sample_identifier a new perf_sample_identifier sample type was added in linux 3.12. vince weaver e2big documentation the following documents the e2big error return for perf_event_open(). i actually ran into this error the hard way and it took me half a day to figure out why my ->size value was changing. vince weaver linux 3.12 adds perf_event_ioc_id a new perf_event related ioctl, perf_event_ioc_id, was added in linux 3.12. vince weaver perf_count_sw_dummy support support for the perf_count_sw_dummy event type was added in linux 3.12. vince weaver [andreas sandberg] perf_event_ioc_period update the perf_event_ioc_period ioctl was broken until 2.6.36, and it turns out that the arm architecture has some differing behavior too. pipe.2 trevor bramwell fix error in example program poll.2 michael kerrisk [paolo bonzini] clarify meaning of events==0 events==0 does not mean that revents is always returned as zero. the "output only" events (pollhup, pollerr, pollnval) can still be returned. see https://bugzilla.kernel.org/show_bug.cgi?id=61911 readlink.2 michael kerrisk [yuanhang zheng] fix typo in error message in example program recv.2 michael kerrisk remove out-of-date statement that unix domain does not support msg_trunc should have removed that sentence as part of commit a25601b48b822eb1882ae336574b8d062a17e564 sched_get_priority_max.2 michael kerrisk add sched_idle to discussion send.2 michael kerrisk return value: these calls return number of bytes (not characters) sent setreuid.2 michael kerrisk small clarification to description of when saved set-user-id is set sigpending.2 michael kerrisk note treatment of signals that are blocked *and* ignored stat.2 michael kerrisk note filesystem support for nanosecond timestamps add some detail on which native filesystems do and don't support nanosecond timestamps. michael kerrisk cosmetic reworking of timestamp discussion in notes michael kerrisk [yang yang] update discussion of nanosecond timestamps the existing text describes the timestamp fields as 'time_t' and delegates discussion of nanosecond timestamps under notes. nanosecond timestamps have been around for a while now, and are in posix.1-2008, so reverse the orientation of the discussion, putting the nanosecond fields into description and detailing the historical situation under notes. symlink.2 michael kerrisk further fine tuning of argument names follow-up to f2ae6dde0c68448bec986d12fe32268a2c98bfd9 see https://sourceware.org/bugzilla/show_bug.cgi?id=16073 michael kerrisk [fabrice bauzac] give arguments of symlink() more meaningful names adjtime.3 peng haitao attributes: note function that is thread-safe the function adjtime() is thread safe. alloca.3 peng haitao attributes: note function that is thread-safe the function alloca() is thread safe. asinh.3 peng haitao attributes: note functions that are thread-safe the functions asinh(), asinhf() and asinhl() are thread safe. atan.3 peng haitao attributes: note functions that are thread-safe the functions atan(), atanf() and atanl() are thread safe. atof.3 peng haitao attributes: note function that is thread safe with exceptions the function atof() is thread safe with exceptions. atoi.3 peng haitao attributes: note functions that are thread safe with exceptions the functions atoi(), atol() and atoll() are thread safe with exceptions. bcmp.3 peng haitao attributes: note function that is thread-safe the function bcmp() is thread safe. bcopy.3 peng haitao attributes: note function that is thread-safe the function bcopy() is thread safe. bsd_signal.3 peng haitao attributes: note function that is thread-safe the function bsd_signal() is thread safe. bzero.3 peng haitao attributes: note function that is thread-safe the function bzero() is thread safe. cbrt.3 peng haitao attributes: note functions that are thread-safe the functions cbrt(), cbrtf() and cbrtl() are thread safe. copysign.3 peng haitao attributes: note functions that are thread-safe the functions copysign(), copysignf() and copysignl() are thread safe. cos.3 peng haitao attributes: note functions that are thread-safe the functions cos(), cosf() and cosl() are thread safe. cproj.3 peng haitao attributes: note functions that are thread-safe the functions cproj(), cprojf() and cprojl() are thread safe. creal.3 peng haitao attributes: note functions that are thread-safe the functions creal(), crealf() and creall() are thread safe. daemon.3 peng haitao attributes: note function that is thread-safe the function daemon() is thread safe. des_crypt.3 peng haitao attributes: note functions that are thread-safe the functions ecb_crypt(), cbc_crypt() and des_setparity() are thread safe. difftime.3 peng haitao attributes: note function that is thread-safe the function difftime() is thread safe. dysize.3 peng haitao attributes: note function that is thread-safe the function dysize() is thread safe. erf.3 peng haitao attributes: note functions that are thread-safe the functions erf(), erff() and erfl() are thread safe. erfc.3 peng haitao attributes: note functions that are thread-safe the functions erfc(), erfcf() and erfcl() are thread safe. euidaccess.3 peng haitao attributes: note functions that are thread-safe the functions euidaccess() and eaccess() are thread safe. expm1.3 peng haitao attributes: note functions that are thread-safe the functions expm1(), expm1f() and expm1l() are thread safe. fexecve.3 michael kerrisk posix.1-2008 specifies fexecve() michael kerrisk explain the use and rationale of fexecve() ftime.3 peng haitao attributes: note function that is thread-safe the function ftime() is thread safe. ftok.3 peng haitao attributes: note function that is thread-safe the function ftok() is thread safe. ftw.3 michael kerrisk nftw() visits directories with ftw_d if ftw_depth was not specified michael kerrisk explain probable cause of ftw_ns futimes.3 peng haitao attributes: note functions that are thread-safe the functions futimes() and lutimes() are thread safe. getaddrinfo.3 michael kerrisk explain one use case for ai_addrconfig michael kerrisk highlight difference in ai_flags when hints==null notes already described how glibc differs from posix. add a pointer to that text from the point in description where hints==null is discussed. kcmp.3 shawn landden reword slightly awkward section malloc.3 greg price scale back promises of alignment it's not true that the return value is suitably aligned for "any variable"; for example, it's unsuitable for a variable like float *x __attribute__ ((__vector_size__ (32))); which requires 32-byte alignment. types like this are defined in , and with 16-byte alignment in and , so the application programmer need not even know that a vector_size attribute has been applied. on an x86 architecture, a program that loads from or stores to a pointer with this type derived from malloc can crash because gcc generates an aligned load/store, like movdqa. the c99 standard (tc3, as of n1256) does say the return value is suitably aligned for "any type of object". the c11 standard (as of n1570) revises this to any type with "fundamental alignment", which means an alignment "supported by the implementation in all contexts", which i suppose tautologically includes aligning malloc/realloc return values. the actual behavior of current glibc malloc is to align to the greater of 2 * sizeof(size_t) and __alignof__ (long double), which may be one bit greater than this commit promises. mq_receive.3 michael kerrisk [janh] msg_len must be greater than *or equal to* mq_msgsize see https://bugzilla.kernel.org/show_bug.cgi?id=64571 setenv.3 michael kerrisk clarify that setenv() returns success in the overwrite==0 case sigsetops.3 michael kerrisk [robert p. j. day] add 'const' to sigisemptyset(), sigorset(), sigandset() declarations michael kerrisk rework text describing sigisemptyset(), sigorset(), and sigandset() statvfs.3 peng haitao attributes: note functions that are thread-safe the functions statvfs() and fstatvfs() are thread safe. stdarg.3 peng haitao attributes: note macros that are thread-safe the macros va_start(), va_arg(), va_end() and va_copy() are thread safe. termios.3 peng haitao attributes: note functions that are thread-safe the functions tcgetattr(), tcsetattr(), tcsendbreak(), tcdrain(), tcflush(), tcflow(), cfmakeraw(), cfgetispeed(), cfgetospeed(), cfsetispeed(), cfsetospeed() and cfsetspeed() are thread safe. ungetwc.3 peng haitao attributes: note function that is thread-safe the function ungetwc() is thread safe. unlockpt.3 peng haitao attributes: note function that is thread-safe the function unlockpt() is thread safe. usleep.3 peng haitao attributes: note function that is thread-safe the function usleep() is thread safe. wcpcpy.3 peng haitao attributes: note function that is thread-safe the function wcpcpy() is thread safe. wcscasecmp.3 peng haitao attributes: note function that is thread safe with exceptions the function wcscasecmp() is thread safe with exceptions. wcscat.3 peng haitao attributes: note function that is thread-safe the function wcscat() is thread safe. wcschr.3 peng haitao attributes: note function that is thread-safe the function wcschr() is thread safe. wcscmp.3 peng haitao attributes: note function that is thread-safe the function wcscmp() is thread safe. wcscpy.3 peng haitao attributes: note function that is thread-safe the function wcscpy() is thread safe. wcscspn.3 peng haitao attributes: note function that is thread-safe the function wcscspn() is thread safe. wcslen.3 peng haitao attributes: note function that is thread-safe the function wcslen() is thread safe. wcsncasecmp.3 peng haitao attributes: note function that is thread safe with exceptions the function wcsncasecmp() is thread safe with exceptions. wcsncat.3 peng haitao attributes: note function that is thread-safe the function wcsncat() is thread safe. wcsncmp.3 peng haitao attributes: note function that is thread-safe the function wcsncmp() is thread safe. wcsncpy.3 peng haitao attributes: note function that is thread-safe the function wcsncpy() is thread safe. wcsnlen.3 peng haitao attributes: note function that is thread-safe the function wcsnlen() is thread safe. wcspbrk.3 peng haitao attributes: note function that is thread-safe the function wcspbrk() is thread safe. wcsrchr.3 peng haitao attributes: note function that is thread-safe the function wcsrchr() is thread safe. wcsspn.3 peng haitao attributes: note function that is thread-safe the function wcsspn() is thread safe. wcsstr.3 peng haitao attributes: note function that is thread-safe the function wcsstr() is thread safe. wcstoimax.3 peng haitao attributes: note functions that are thread safe with exceptions the functions wcstoimax() and wcstoumax() are thread safe with exceptions. wcstok.3 peng haitao attributes: note function that is thread-safe the function wcstok() is thread safe. wcswidth.3 peng haitao attributes: note function that is thread safe with exceptions the function wcswidth() is thread safe with exceptions. wctrans.3 peng haitao attributes: note function that is thread safe with exceptions the function wctrans() is thread safe with exceptions. wctype.3 peng haitao attributes: note function that is thread safe with exceptions the function wctype() is thread safe with exceptions. wcwidth.3 peng haitao attributes: note function that is thread safe with exceptions the function wcwidth() is thread safe with exceptions. wmemchr.3 peng haitao attributes: note function that is thread-safe the function wmemchr() is thread safe. wmemcmp.3 peng haitao attributes: note function that is thread-safe the function wmemcmp() is thread safe. wmemcpy.3 peng haitao attributes: note function that is thread-safe the function wmemcpy() is thread safe. wmemmove.3 peng haitao attributes: note function that is thread-safe the function wmemmove() is thread safe. wmemset.3 peng haitao attributes: note function that is thread-safe the function wmemset() is thread safe. tty_ioctl.4 michael kerrisk [liu jiaming] note that 'arg' should be 0 in the usual case when using tiocsctty michael kerrisk rework text on root to discuss just in terms of capabilities proc.5 michael kerrisk document /proc/sys/kernel/ngroups_max capabilities.7 michael kerrisk fix 2 version numbers under "effect of user id changes on capabilities" feature_test_macros.7 michael kerrisk add _isoc11_source to example program tcp.7 michael kerrisk fix (nontrivial) wordo in discussion of msg_trunc s/msg_peek/msg_trunc/ ld.so.8 michael kerrisk [alfred agrell] fix crufty wording in one sentence ==================== changes in man-pages-3.56 ==================== released: 2014-01-11, christchurch in memory of doris church (1939-2013) contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andre majorel arif zaman bert wesarg daniel borkmann david malcolm david prévot dongsheng song elie de brauwer james smith janne blomqvist joseph s. myers luke hutchison marco dione mathieu desnoyers mathieu malaterre matthias klose michael kerrisk mike frysinger moritz 'morty' strübe nadav har'el ondřej bílka prádraig brady peng haitao raphael geissert shawn landden simon paillard stephen kell sudhanshu goswami sworddragon2 vince weaver willem de bruijn yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- fgetc.3 gets.3 david malcolm split gets(3) to isolate unsafe gets(3) to a page on its own currently man3/gets.3 documents various safe i/o functions, along with the toxic "gets" function. at the risk of being melodramatic, this strikes me as akin to storing rat poison in a food cabinet, in the same style of packaging as the food, but with a post-it note on it saying "see warnings below". i think such "never use this" functions should be quarantined into their own manpages, rather than listing them alongside sane functions. the attached patch does this for "gets", moving the documentation of the good functions from man3/gets.3 into man3/fgetc.3, updating the so links in the relevant functions to point at the latter. it then rewrites man3/gets.3 to spell out that "gets" is toxic and should never be used (with a link to cwe-242 for good measure). michael kerrisk [andre majorel] tweaks to david malcolm's patch vdso.7 mike frysinger new page documenting the vdso mapped into each process by the kernel newly documented interfaces in existing pages --------------------------------------------- reboot.2 elie de brauwer document linux_reboot_sw_suspend new and changed links --------------------- fgets.3 getc.3 getchar.3 ungetc.3 michael kerrisk adjust links to gets(3) to point to fgetc(3) global changes -------------- various pages michael kerrisk global fix of "null pointer" change "null pointer" to "null" or null pointer". posix uses the term "null pointer", not "null pointer". various pages michael kerrisk stylistic changes to code example for ease of reading, don't embed assignments inside if(). various pages michael kerrisk replace uses of "i.e.," in main text with "that is" or similar usual man-pages style is to use "i.e." only within parenthetical expressions. various pages michael kerrisk replace uses of "e.g." in main text with "for example" or similar usual man-pages style is to use "e.g." only within parenthetical expressions. various pages michael kerrisk add "program source" subheading under example various pages michael kerrisk add "static" to global variables and functions in example program changes to individual pages --------------------------- clock_getres.2 michael kerrisk [nadav har'el] improve description of clock_process_cputime_id see https://bugzilla.kernel.org/show_bug.cgi?id=67291 close.2 michael kerrisk [p?draig brady] note that errors from close() should be used only for diagnosis in particular, retrying after eintr is a bad idea. see http://austingroupbugs.net/view.php?id=529 see http://thread.gmane.org/gmane.comp.lib.glibc.alpha/37702 subject: [rfc][bz #14627] make linux close errno to einprogress when interrupted in signal. execve.2 michael kerrisk [marco dione] add further cases to efault error see https://sourceware.org/bugzilla/show_bug.cgi?id=16402 perf_event_open.2 vince weaver [sudhanshu goswami] clarify issues with the disabled bit clarify the perf_event_open behavior with respect to the disabled bit and creating event groups. vince weaver [sudhanshu goswami] clarify issues with the exclusive bit warn that using the perf_event_open "exclusive" bit, while it might seem like a good idea, might lead to all 0 results in some common usage cases. reboot.2 elie de brauwer mention rb_power_off the manpage did not mention rb_power_off which is the glibc symbolic name for linux_reboot_cmd_power_off. $ cd /usr/include $ cat x86_64-linux-gnu/sys/reboot.h | grep power_off define rb_power_off 0x4321fedc elie de brauwer add "linux" to kernel version numbers michael kerrisk add rb_sw_suspend synonym michael kerrisk add rb_kexec synonym setpgid.2 michael kerrisk [joseph s. myers] bsd getpgrp() and setpgrp() go away in glibc 2.19 socket.2 michael kerrisk [dongsheng song] remove crufty statement that af_inet does not support sock_seqpacket linux af_inet supports sock_seqpacket via sctp. syscall.2 mike frysinger fix ia64 registers the original list of registers was created by confusing strace source code--this is for parsing legacy 32-bit code (which is dead and no one cares). update the list to reflect native ia64 syscall interface. syscall.2 syscalls.2 getauxval.3 mike frysinger add references to new vdso(7) page utimensat.2 michael kerrisk small wording improvement for times!=null case dlopen.3 michael kerrisk [mike frysinger] update remarks on cast needed when assigning dlsym() return value posix.1-2013 eases life when casting the dlsym() return value to a function pointer michael kerrisk [stephen kell] fix description of dli_sname see https://sourceware.org/bugzilla/show_bug.cgi?id=16262 getline.3 michael kerrisk [luke hutchison] correct description of how '*n' is used when '*lineptr' == null see https://sourceware.org/bugzilla/show_bug.cgi?id=5468 michael kerrisk remove see also reference to unsafe gets(3) mcheck.3 simon paillard [raphael geissert] typo in compiler flag see http://bugs.debian.org/732464 mkstemp.3 michael kerrisk [janne blomqvist] better describe 'flags' that can be specified for mkostemp() printf.3 michael kerrisk [arif zaman] fix memory leak in snprintf() example see http://stackoverflow.com/questions/19933479/snprintf-man-page-example-memory-leak pthread_kill.3 michael kerrisk [mathieu desnoyers] posix.1-2008 removes esrch posix.1-2001 mistakenly documented an esrch error, and posix.1-2008 removes this error. glibc does return this error in cases where it can determine that a thread id is invalid, but equally, the use of an invalid thread id can cause a segmentation fault. puts.3 michael kerrisk see also: replace reference to gets(3) with fgets(3) scanf.3 michael kerrisk [ondřej bílka] improve discussion of obsolete 'a' dynamic allocation modifier setjmp.3 michael kerrisk [joseph s. myers] bsd setjmp() semantics go away in glibc 2.19 sigpause.3 michael kerrisk [joseph s. myers] bsd sigpause() goes away in glibc 2.19 michael kerrisk correct feature text macro requirements peng haitao attributes: note function that is thread-safe the function sigpause() is thread safe. sigqueue.3 peng haitao attributes: note function that is thread-safe the function sigqueue() is thread safe. sigwait.3 peng haitao attributes: note function that is thread-safe the function sigwait() is thread safe. sin.3 peng haitao attributes: note functions that are thread-safe the functions sin(), sinf() and sinl() are thread safe. sincos.3 peng haitao attributes: note functions that are thread-safe the functions sincos(), sincosf() and sincosl() are thread safe. string.3 moritz 'morty' strübe add short description of the functions it is helpful to have a short description about what the different functions in string.h do. michael kerrisk fixes and enhancements to moritz strübe's patch strptime.3 michael kerrisk [mathieu malaterre, simon paillard] add number ranges to comments in 'tm' structure see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=729570 michael kerrisk point to ctime(3) for more details on 'tm' structure michael kerrisk some rewording and reorganization strsep.3 michael kerrisk clarify description the use of "symbols" in the existing description is confusing; it's "bytes". other fixes as well. strspn.3 michael kerrisk [mathieu malaterre] improve description in name see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=723659 strstr.3 michael kerrisk clarify return value: s/substring/located substring/ sysv_signal.3 peng haitao attributes: note function that is thread-safe the function sysv_signal() is thread safe. tan.3 peng haitao attributes: note functions that are thread-safe the functions tan(), tanf() and tanl() are thread safe. tanh.3 peng haitao attributes: note functions that are thread-safe the functions tanh(), tanhf() and tanhl() are thread safe. toascii.3 peng haitao attributes: note function that is thread-safe the function toascii() is thread safe. toupper.3 peng haitao attributes: note functions that are thread safe with exceptions the functions toupper() and tolower() are thread safe with exceptions. towctrans.3 peng haitao attributes: note function that is thread-safe the function towctrans() is thread safe. towlower.3 peng haitao attributes: note function that is thread safe with exceptions the function towlower() is thread safe with exceptions. towupper.3 peng haitao attributes: note function that is thread safe with exceptions the function towupper() is thread safe with exceptions. ualarm.3 peng haitao attributes: note function that is thread-safe the function ualarm() is thread safe. wcpncpy.3 peng haitao attributes: note function that is thread-safe the function wcpncpy() is thread safe. proc.5 michael kerrisk [sworddragon2] fix formula for commitlimit under /proc/meminfo see https://bugzilla.kernel.org/show_bug.cgi?id=60991 credentials.7 michael kerrisk list apis that operate on process groups michael kerrisk add details on controlling terminal and foreground/background jobs feature_test_macros.7 michael kerrisk document _default_source michael kerrisk [joseph s. myers] from glibc 2.19, _bsd_source no longer causes __favor_bsd starting with glibc 2.19, _bsd_source no longer causes bsd definitions to be favored in cases where standards conflict. libc.7 mike frysinger see also: add various entries man-pages.7 michael kerrisk [mike frysinger] add style guide section incorporate some of the existing material in the page into the style guide, and add a lot more material, mainly drawn from the "global changes" sections in the release changelogs. michael kerrisk add historical note on reason for use of american spelling michael kerrisk [mike frysinger] various improvements to style guide packet.7 willem de bruijn [daniel borkmann] document fanout, ring, and auxiliary options this patch adds descriptions of the common packet socket options packet_auxdata, packet_fanout, packet_rx_ring, packet_statistics, packet_tx_ring and the ring-specific options packet_loss, packet_reserve, packet_timestamp, packet_version michael kerrisk add kernel version numbers for packet_version and packet_timestamp ld.so.8 michael kerrisk [matthias klose] default output file for d_debug is stderr not stdout see https://sourceware.org/bugzilla/show_bug.cgi?id=6874 ==================== changes in man-pages-3.57 ==================== released: 2014-01-24, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andi kleen andre majorel andrey vagin andy lutomirski axel beckert bernhard walle brandon edens eliezer tamir gioele barabucci ian abbott jerry chu jonas jonsson marc lehmann michael kerrisk mike frysinger peng haitao reuben thomas simone piccardi simon paillard thomas posch tilman schmidt vince weaver yuri kozlov марк коренберг apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- msgop.2 michael kerrisk document msg_copy open.2 michael kerrisk, andy lutomirski document o_tmpfile o_tmpfile is new in linux 3.11 perf_event_open.2 vince weaver [andi kleen] perf_sample_transaction support in linux 3.13 the following patch adds descriptions of the new perf_event_open.2 perf_sample_transaction sample type as added in linux 3.13. the descriptions are based on information provided by andi kleen, both in the e-mail [patch 1/6] perf, core: add generic transaction flags v5 sent to the linux-kernel list as well as an e-mail [patch] document transaction flags in perf_event_open manpage sent to the linux-man list. the implementation is based heavily on the intel haswell processor. documentation can be found at this page: http://software.intel.com/en-us/blogs/2013/05/03/intelr-transactional-synchronization-extensions-intelr-tsx-profiling-with-linux-0 as well as in section 18.11.5.1 of volume 3 of the intel 64 and ia-32 architecture software developer's manual. ptrace.2 andrey vagin add description for ptrace_peeksiginfo retrieve signals without removing them from a queue. andrey vagin add description for ptrace_getsigmask and ptrace_setsigmask these two commands allow to examine and change mask of blocked signals. socket.7 eliezer tamir add description for so_busy_poll add description for the so_busy_poll socket option. tcp.7 michael kerrisk [jerry chu] document tcp_user_timeout text slightly adapted from jerry chu's (excellent) commit message (commit dca43c75e7e545694a9dd6288553f55c53e2a3a3). michael kerrisk document tcp_congestion global changes -------------- various pages michael kerrisk reword to avoid use of "etc." various pages peng haitao [andre majorel] make wording around thread-safety and setlocale() more precise getdate.3 strptime.3 locale.5 michael kerrisk replace "weekday" with less ambiguous language notwithstanding posix's use of the term "weekday", in everyday english, "weekday" is commonly understood to mean a day in the set [monday..friday] (vs one of the "weekend" days). changes to individual pages --------------------------- epoll_wait.2 michael kerrisk [jonas jonsson] clarify wording of eintr error see https://bugzilla.kernel.org/show_bug.cgi?id=66571 faccessat.2 michael kerrisk note that the system call takes only three arguments fallocate.2 michael kerrisk note filesystems that support falloc_fl_punch_hole operation fcntl.2 michael kerrisk bugs: the o_sync and o_dsync flags are not modifiable using f_setfl michael kerrisk add subsections under bugs there's several bugs listed. it's helpful to mark them separately. michael kerrisk posix.1 specifies f_setown and f_getown for sockets/sigurg getrlimit.2 michael kerrisk [марк коренберг] note that rlim_cur can be set lower than current resource consumption getsockopt.2 michael kerrisk see also: add ip(7) and udp(7) keyctl.2 michael kerrisk see also: mention documentation/security/keys.txt linkat.2 michael kerrisk add enoent for o_tmpfile created with o_excl michael kerrisk errors: add einval lseek.2 michael kerrisk note which filesystems support seek_hole/seek_data msgop.2 michael kerrisk note that msg_except is linux-specific open.2 michael kerrisk update conforming to add posix.1-2008. add mention of o_tmpfile. update text on various flags that were added in posix.1-2008, and whose definitions can, since glibc 2.12, be obtained by suitably defining _posix_c_source or _xopen_source michael kerrisk add pointer in description to bugs, for o_async limitation michael kerrisk remove crufty duplicate text on modifying file status flags ptrace.2 michael kerrisk add details to descriptions of ptrace_getsigmask and ptrace_setsigmask select.2 michael kerrisk [marc lehmann] return value: fix discussion of treatment of file descriptor sets see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=574370 syscalls.2 michael kerrisk remove madvise1() from main list madvise1() is one of the system calls that was never implemented, and listed toward the bottom of the page. timer_create.2 michael kerrisk add pointer to proc(5) for info on /proc/[pid]/timers unlinkat.2 michael kerrisk [mike frysinger:] errors: add eisdir see https://bugzilla.kernel.org/show_bug.cgi?id=29702 ferror.3 michael kerrisk clearerr(), feof(), and ferror() are also posix-conformant michael kerrisk [reuben thomas] conforming to: add fileno() gets.3 ian abbott see also: add fgets(3) mq_receive.3 mq_send.3 michael kerrisk [simone piccardi] synopsis: s/unsigned/unsigned int/ printf.3 michael kerrisk small reorganization of text in example rand.3 michael kerrisk s/unsigned/unsigned int/ in example stpcpy.3 peng haitao attributes: note function that is thread-safe the function stpcpy() is thread safe. stpncpy.3 peng haitao attributes: note function that is thread-safe the function stpncpy() is thread safe. strcat.3 peng haitao attributes: note functions that are thread-safe the functions strcat() and strncat() are thread safe. strchr.3 peng haitao attributes: note functions that are thread-safe the functions strchr(), strrchr() and strchrnul() are thread safe. strcmp.3 peng haitao attributes: note functions that are thread-safe the functions strcmp() and strncmp() are thread safe. strftime.3 brandon edens change "week day" to "day of week" see https://bugzilla.kernel.org/show_bug.cgi?id=68861 strstr.3 peng haitao attributes: note function that is thread safe with exceptions the function strstr() is thread safe. the function strcasestr() is thread safe with exceptions. strtod.3 peng haitao attributes: note functions that are thread safe with exceptions the functions strtod(), strtof() and strtold() are thread safe with exceptions. strtoimax.3 peng haitao attributes: note functions that are thread safe with exceptions the functions strtoimax() and strtoumax() are thread safe with exceptions. strtol.3 peng haitao attributes: note functions that are thread safe with exceptions the functions strtol(), strtoll() and strtoq() are thread safe with exceptions. tcgetpgrp.3 peng haitao attributes: note functions that are thread-safe the functions tcgetpgrp() and tcsetpgrp() are thread safe. tcgetsid.3 peng haitao attributes: note function that is thread-safe the function tcgetsid() is thread safe. core.5 bernhard walle mention that %e exists since linux 3.0 '%e' in the 'core_pattern' has been introduced in kernel commit 57cc083ad9e1bfeeb4a0ee831e7bb008c8865bf0 which was included in version 3.0. add that information to the manual page. filesystems.5 michael kerrisk [axel beckert] add reference to proc(5) for more details on /proc/filesystems see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=735590 locale.5 michael kerrisk see also: add locale(7) proc.5 michael kerrisk document /proc/[pid]/timers michael kerrisk update discussion of wchan remove crufty reference to /etc/psdatabase in /proc/pid/stat. add /proc/pid/wchan. see https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/737452 environ.7 michael kerrisk [gioele barabucci] correct reference to locale(7) (not locale(5)) locale(7) is the right place for details of the lc_* environment variables. see http://bugs.debian.org/638186 michael kerrisk improve references for discussion of locale environment variables michael kerrisk see also: add catopen(3) michael kerrisk see also: add locale(5) man-pages.7 michael kerrisk prefer "usable" over "useable" netdevice.7 tilman schmidt document siocgifconf case ifc_req==null add the missing description of the possibility to call siocgifconf with ifc_req==null to determine the needed buffer size, as described in http://lkml.indiana.edu/hypermail/linux/kernel/0110.1/0506.html and verified against source files net/core/dev_ioctl.c and net/ipv4/devinet.c in the current kernel git tree. this functionality has been present since the beginning of the 2.6 series. it's about time it gets documented. while i'm at it, also generally clarify the section on siocgifconf. standards.7 michael kerrisk enhance description of v7 michael kerrisk add c11 tcp.7 michael kerrisk describe format of tcp_*_congestion_control /proc files describe format of tcp_allowed_congestion_control and tcp_available_congestion_control. ==================== changes in man-pages-3.58 ==================== released: 2014-02-11, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: cyril hrubis daniel borkmann david prévot fabrice bauzac michael kerrisk mike frysinger network nut ola olsson peng haitao peter schiffer simone piccardi simon paillard yuri kozlov марк коренберг 未卷起的浪 apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- pipe.2 michael kerrisk document the pipe2() o_direct flag added in linux 3.4 packet.7 daniel borkmann document packet_qdisc_bypass new in linux 3.14. global changes -------------- various pages simon paillard formatting fix: add space between function and () if br or ir detected through the regex: git grep -p '^\.(br|ir) [\w]*\([\d]*\)$' various pages simon paillard formatting fix: add space between word and punctuation if br or ir detected through the regex: git grep -p '^\.(br|ir) [^ ]*[,\.]$' could probably be extended to match more cases and fix in perl. various pages michael kerrisk use oxford comma gettid.2 restart_syscall.2 passwd.5 socket.7 michael kerrisk fix order of see also entries changes to individual pages --------------------------- epoll_wait.2 michael kerrisk [network nut] remove word "minimum" from the description of 'timeout' epoll_wait.2 poll.2 select.2 michael kerrisk go into more detail on timeout and when call will cease blocking getxattr.2 listxattr.2 removexattr.2 setxattr.2 michael kerrisk [fabrice bauzac] correct header file is (not ) see https://bugzilla.kernel.org/show_bug.cgi?id=70141 msgctl.2 cyril hrubis add note about ignored arg to ipc_rmid prctl.2 michael kerrisk [марк коренберг] pr_set_pdeathsig value is preserved across execve(2) recv.2 michael kerrisk rework and reorganize the text in various parts of the page. isolate details specific to recv() vs recvfrom() vs recvmsg() place details specific to each system call under a separate subheading. rework discussion of 'src_addr' and 'addrlen' for recvfrom() add description of 'buf' and 'len' in recvfrom() section 'addrlen' should be 0 (*not* null) when 'src_addr' is null improve text describing recvfrom() call that is equivalent to recv() michael kerrisk [未卷起的浪] describe the various cases where the return value can be 0 shmctl.2 michael kerrisk note that 'buf' is ignored for ipc_rmid symlinkat.2 michael kerrisk make argument names consistent with symlink(2) page isalpha.3 peng haitao attributes: note functions that are thread-safe the functions isalnum(), isalpha(), isascii(), isblank(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper() and isxdigit() are thread safe. isatty.3 peng haitao attributes: note function that is thread-safe the function isatty() is thread safe. isgreater.3 peng haitao attributes: note macros that are thread-safe the macros isgreater(), isgreaterequal(), isless(), islessequal(), islessgreater() and isunordered() are thread safe. iswalnum.3 peng haitao attributes: note function that is thread safe with exceptions the function iswalnum() is thread safe with exceptions. iswalpha.3 peng haitao attributes: note function that is thread safe with exceptions the function iswalpha() is thread safe with exceptions. iswblank.3 peng haitao attributes: note function that is thread safe with exceptions the function iswblank() is thread safe with exceptions. iswcntrl.3 peng haitao attributes: note function that is thread safe with exceptions the function iswcntrl() is thread safe with exceptions. lockf.3 michael kerrisk [simone piccardi] fix incorrect argument mentioned under einval error pthread_kill.3 michael kerrisk add feature test macro requirements pthread_sigmask.3 michael kerrisk add feature test macro requirements strtoul.3 peng haitao attributes: note functions that are thread safe with exceptions the functions strtoul(), strtoull() and strtouq() are thread safe with exceptions. nscd.conf.5 peter schiffer add note about default values proc.5 michael kerrisk see also: add some further kernel documentation/sysctl files man-pages.7 michael kerrisk attributes sections come after versions peng haitao has consistently ordered the attributes after versions, so adjust the text in man-pages.7 vdso.7 michael kerrisk add words "virtual dynamic shared object" in description ==================== changes in man-pages-3.59 ==================== released: 2014-02-16, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: michael kerrisk peter schiffer weizhou pan apologies if i missed anyone! global changes -------------- various pages peter schiffer, michael kerrisk [weizhou pan] convert pages containing non-ascii in source code comments to use utf-8 done using a slightly modified version of peter schiffer's convert_to_utf_8.sh script. the script was modified so as *not* a "coding:" marker to the groff source. for now, we'll only put that marker on pages that contain non-ascii characters in the rendered text. see https://bugzilla.kernel.org/show_bug.cgi?id=60807 armscii-8.7 cp1251.7 iso_8859-1.7 iso_8859-10.7 iso_8859-11.7 iso_8859-13.7 iso_8859-14.7 iso_8859-15.7 iso_8859-16.7 iso_8859-2.7 iso_8859-3.7 iso_8859-4.7 iso_8859-5.7 iso_8859-6.7 iso_8859-7.7 iso_8859-8.7 iso_8859-9.7 koi8-r.7 koi8-u.7 peter schiffer, michael kerrisk [weizhou pan] convert pages containing non-ascii to use utf-8 done using peter schiffer's convert_to_utf_8.sh script. these pages containing non-ascii in the rendered characters, and so the script inserts a "coding:" marker into the groff source. see https://bugzilla.kernel.org/show_bug.cgi?id=60807 ==================== changes in man-pages-3.60 ==================== released: 2014-02-18, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: david prévot d. barbier kalle olavi niemitalo michael kerrisk simon paillard apologies if i missed anyone! changes to individual pages --------------------------- sigvec.3 michael kerrisk [kalle olavi niemitalo] fix error in code snippet s/sigpause/sigmask/ armscii-8.7 cp1251.7 iso_8859-1.7 iso_8859-10.7 iso_8859-11.7 iso_8859-13.7 iso_8859-14.7 iso_8859-15.7 iso_8859-16.7 iso_8859-2.7 iso_8859-3.7 iso_8859-4.7 iso_8859-5.7 iso_8859-6.7 iso_8859-7.7 iso_8859-8.7 iso_8859-9.7 koi8-u.7 michael kerrisk [simon paillard] remove comment that glyphs in column 4 may not display correctly with the conversion to utf-8, the glyphs in column 4 of the tables in these pages will display regardless of whether the environment is configured for the corresponding character set. iso_8859-11.7 iso_8859-13.7 d. barbier [simon paillard] fix encoding mistakes in 5f7f4042b8848127d852c6fa7c02e31ccfaeeae5 fixed via: for f in iso_8859-11 iso_8859-13; do cp man7/$f.7 $f iconv -f utf8 -t latin1 $f | iconv -f iso-${f#iso_} -t utf8 > man7/$f.7 done ==================== changes in man-pages-3.61 ==================== released: 2014-02-26, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andrew hunter carlos o'donell christoph hellwig daniel borkmann duncan de wet kir kolyshkin kosaki motohiro michael kerrisk neil horman peng haitao simon paillard sulaiman mustafa xiawei chen apologies if i missed anyone! new and rewritten pages ----------------------- a note from christoph hellwig prompted me to perform a task that has been queued for a while: merging the text of the man pages for the *at([23]) ("directory file descriptor") apis into their corresponding traditional pages. when the *at([23]) pages were originally written (mostly in 2006), the apis were not part of posix and (in most cases) were not available on other systems. so, it made some sense to wall them off into their own separate pages. eight years later, with the apis now all in posix (except scandirat()), it is much more sensible to document the newer apis alongside their traditional counterparts, so that the newer apis are not "hidden", and the reader can more easily see the differences between the apis. thus, the text of 14 pairs of pages has been merged, and the "merged from" pages have been converted to links to the "merged to" pages. along the way, a few other fixes were made to the pages, as noted below. one page that did not undergo such a change was utimensat(2), which is different enough from utime(2) that it warrants a separate page. unlike the other *at() pages, the utimensat(2) page was also already self-contained, rather than defining itself in terms of differences from utime(2) as the other *at() pages did. access.2 michael kerrisk merge text from faccessat(2) michael kerrisk remove faccessat() race warning that point is already covered in existing text in this page. michael kerrisk access() also conforms to posix.1-2008 chmod.2 michael kerrisk merge text from fchmodat(2) michael kerrisk use argument name 'pathname' throughout page (some apis were using 'path' while others used 'pathname') michael kerrisk conforming to: chmod() and fchmod() are also in posix.1-2008 chown.2 michael kerrisk merge text of fchownat(2) michael kerrisk at_empty_path is linux-specific and requires _gnu_source michael kerrisk use argument name 'pathname' throughout page (some apis were using 'path' while others used 'pathname') michael kerrisk remove sentence that fchownat() is present on solaris that point was only really relevant before fchownat() was standardized in posix.1.2008. michael kerrisk conforming to: chown(), fchown(), lchown() are in posix.1-2008 link.2 michael kerrisk merge text of linkat(2) michael kerrisk conforming to: link() is in posix.1-2008 michael kerrisk at_empty_path is linux-specific and requires _gnu_source mkdir.2 michael kerrisk merge text of mkdirat(2) michael kerrisk conforming to: mkdir() is in posix.1-2008 mknod.2 michael kerrisk merge text of mknodat(2) michael kerrisk conforming to: mknod(2) is in posix.1-2008 open.2 michael kerrisk merge text from openat(2) michael kerrisk remove sentence that openat() is present on solaris that point was only really relevant before openat() was standardized in posix.1.2008. readlink.2 michael kerrisk merge text of readlinkat(2) michael kerrisk conforming to: readlink() is in posix.1-2008. michael kerrisk use argument name 'pathname' throughout page (some apis were using 'path' while others used 'pathname') rename.2 michael kerrisk merge text of renameat(2) michael kerrisk conforming to: rename(2) is in posix.1-2008 stat.2 michael kerrisk merge text from fstatat(2) michael kerrisk at_empty_path and at_no_automount are linux-specific these flags require _gnu_source. michael kerrisk use argument name 'pathname' throughout page (some apis were using 'path' while others used 'pathname') michael kerrisk remove sentence that fstatat() is present on solaris that point was only really relevant before fstatat() was standardized in posix.1.2008. michael kerrisk conforming to: stat(), fstat(), lstat() are specified in posix.1-2008 symlink.2 michael kerrisk merge text of symlinkat(2) michael kerrisk conforming to: symlink() is in posix.1-2008 unlink.2 michael kerrisk merge text of unlinkat(2) michael kerrisk remove sentence that unlinkat() is present on solaris that point was only really relevant before unlinkat() was standardized in posix.1.2008. michael kerrisk conforming to: unlink() is in posix.1-2008 mkfifo.3 michael kerrisk merge text of mkfifoat(3) michael kerrisk conforming to: mkfifo() is in posix.1-2008 scandir.3 michael kerrisk merge text of scandirat(3) michael kerrisk update feature test macro requirements the ftm requirements changed in glibc 2.10. michael kerrisk remove libc4/libc5 note under conforming to no-one much cares about linux libc these days. michael kerrisk put detail about alphasort under a notes heading this text was under conforming to, which made no sense. michael kerrisk rework conforming to text newly documented interfaces in existing pages --------------------------------------------- prctl.2 kir kolyshkin document pr_set_mm options in linux 3.5 some of the pr_set_mm options were merged to vanilla kernel later, and appeared in linux 3.5. those are: - pr_set_mm_arg_start - pr_set_mm_arg_end - pr_set_mm_env_start - pr_set_mm_env_end - pr_set_mm_auxv - pr_set_mm_exe_file socket.7 neil horman document the so_rxq_ovfl socket option michael kerrisk add kernel version number for so_rxq_ovfl new and changed links --------------------- faccessat.2 michael kerrisk convert to link to access.2 fchmodat.2 michael kerrisk convert to link to chmod.2 fchownat.2 michael kerrisk convert to link to chown.2 fstatat.2 michael kerrisk convert to link to stat.2 linkat.2 michael kerrisk convert to link to link.2 mkdirat.2 michael kerrisk convert to link to mkdir.2 mknodat.2 michael kerrisk convert to link to mknod.2 openat.2 michael kerrisk convert to link to open.2 readlinkat.2 michael kerrisk convert to link to symlink.2 renameat.2 michael kerrisk convert to link rename.2 symlinkat.2 michael kerrisk convert to link to symlink.2 unlinkat.2 michael kerrisk convert to link to unlink.2 mkfifoat.3 michael kerrisk convert to link to mkfifo.3 scandirat.3 michael kerrisk convert to link to scandir.3 changes to individual pages --------------------------- alarm.2 michael kerrisk note semantics of alarm with respect to fork() and execve() fcntl.2 michael kerrisk warn that f_getlk info may already be out of date when the call returns intro.2 michael kerrisk describe policy on documenting differences between syscall and glibc api mmap2.2 michael kerrisk reword note on glibc mmap() wrapper invocation of mmap2() michael kerrisk this system call does not exist on x86-64 msgctl.2 michael kerrisk errors: add eperm for unprivileged attempt to set msg_qbytes > msgmnb prctl.2 michael kerrisk [xiawei chen] clarify that pr_get_timerslack is returned as the function result michael kerrisk clarify that pr_get_seccomp is returned as function result michael kerrisk clarify that pr_get_no_new_privs is returned as function result ptrace.2 michael kerrisk [andrew hunter] make it clearer that glibc and syscall apis differ for ptrace_peek* thanks to denys vlasenko's additions in 78686915aed6bd12 this page does note that the glibc api for ptrace_peek* differs from the raw syscall interface. but, as the report at https://bugzilla.kernel.org/show_bug.cgi?id=70801 shows, this information could be more obvious. this patch makes its so. sgetmask.2 michael kerrisk note that these system calls don't exist on x86-64 swapon.2 michael kerrisk split einval cases into separate entries under errors michael kerrisk add einval error for invalid flags to swapon() syscalls.2 michael kerrisk see also: add intro(2) umount.2 michael kerrisk split einval cases into separate items michael kerrisk errors: add einval case that was new in 2.6.34 utime.2 michael kerrisk add note that modern applications probably want utimensat(2) etc. crypt.3 michael kerrisk [kosaki motohiro] errors: add einval and eperm errors see https://bugzilla.kernel.org/show_bug.cgi?id=69771 getifaddrs.3 michael kerrisk enhance example program print statistics for af_packet interfaces. add missing feature test macro definition. reformat output. iswctype.3 peng haitao attributes: note function that is thread-safe the function iswctype() is thread safe. sem_post.3 peng haitao attributes: note function that is thread-safe the function sem_post() is thread safe. sem_unlink.3 peng haitao attributes: note function that is thread-safe the function sem_unlink() is thread safe. sem_wait.3 peng haitao attributes: note functions that are thread-safe the functions sem_wait(), sem_trywait() and sem_timedwait() are thread safe. setbuf.3 peng haitao attributes: note functions that are thread-safe the functions setbuf(), setbuffer(), setlinebuf() and setvbuf() are thread safe. strlen.3 peng haitao attributes: note function that is thread-safe the function strlen() is thread safe. strnlen.3 peng haitao attributes: note function that is thread-safe the function strnlen() is thread safe. strpbrk.3 peng haitao attributes: note function that is thread-safe the function strpbrk() is thread safe. strsep.3 peng haitao attributes: note function that is thread-safe the function strsep() is thread safe. swab.3 peng haitao attributes: note function that is thread-safe the function swab() is thread safe. resolv.conf.5 carlos o'donell description: mention that the data is trusted in a recent discussion about dnssec it was brought to my attention that not all system administrators may understand that the information in /etc/resolv.conf is fully trusted. the resolver implementation in glibc treats /etc/resolv.conf as a fully trusted source of dns information and passes on the ad-bit for dnssec as trusted. this patch adds a clarifying sentence to make it absolutely clear that indeed this source of information is trusted. ascii.7 michael kerrisk [sulaiman mustafa] fix rendering of single quote (decimal character 39) michael kerrisk see also: add utf-8(7) michael kerrisk [duncan de wet] remove mention of iso 8859-1 as being the default encoding on linux packet.7 neil horman document packet_fanout_qm fanout mode michael kerrisk add kernel version for packet_fanout_qm daniel borkmann improve packet_qdisc_bypass description socket.7 michael kerrisk add kernel version number for so_busy_poll ==================== changes in man-pages-3.62 ==================== released: 2014-03-11, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: cyril hrubis joseph s. myers marius gaubas michael kerrisk mike frysinger peng haitao rick stanley simon paillard apologies if i missed anyone! new and rewritten pages ----------------------- locale.1 michael kerrisk [review from mike frysinger] new page describing locale(1) newly documented interfaces in existing pages --------------------------------------------- locale.5 michael kerrisk document lc_address michael kerrisk document lc_identification michael kerrisk document lc_measurement michael kerrisk document lc_name michael kerrisk document lc_paper michael kerrisk document lc_telephone removed pages ------------- sync.8 michael kerrisk [christoph hellwig, pádraig brady] sometime in the 20th century (before my watch), a sync(8) page into man-pages. it documents the sync command from "fileutils", which long ago become coreutils, and the piece under notes note some behavior of sync(2) that ceased to be true many years ago. the man-pages project generally focuses on only linux kernel and (g)libc interfaces, so this sync(8) page doesn't really belong. furthermore, coreutils has a sync(1) page which covers the same command. after discussions on the coreutils list, i've decided to retire this page from man-pages. changes to individual pages --------------------------- clone.2 michael kerrisk note that clone_thread also in effect requires clone_vm stat.2 michael kerrisk [marius gaubas] warn the reader that the 'stat' structure definition is not precise padding fields aren't shown, and the order of fields varies somewhat across architectures. gethostbyname.3 michael kerrisk remove redundant ftm requirements _gnu_source implies _svid_source and _bsd_source, so _bsd_source || _svid_source || _gnu_source is the same as _bsd_source || _svid_source getutmp.3 michael kerrisk see also: add utmpdump(1) log1p.3 peng haitao attributes: note functions that are thread-safe the functions log1p(), log1pf() and log1pl() are thread safe. logb.3 peng haitao attributes: note functions that are thread-safe the functions logb(), logbf() and logbl() are thread safe. memccpy.3 peng haitao attributes: note function that is thread-safe the function memccpy() is thread safe. memchr.3 peng haitao attributes: note functions that are thread-safe the functions memchr(), memrchr() and rawmemchr() are thread safe. mktemp.3 michael kerrisk make warning not to use this function more prominent qecvt.3 michael kerrisk [joseph s. myers] recommend snprintf(3) not sprintf(3) raise.3 peng haitao attributes: note function that is thread-safe the function raise() is thread safe. remove.3 peng haitao attributes: note function that is thread-safe the function remove() is thread safe. sem_destroy.3 peng haitao attributes: note function that is thread-safe the function sem_destroy() is thread safe. sem_getvalue.3 peng haitao attributes: note function that is thread-safe the function sem_getvalue() is thread safe. sem_init.3 peng haitao attributes: note function that is thread-safe the function sem_init() is thread safe. sockatmark.3 peng haitao attributes: note function that is thread-safe the function sockatmark() is thread safe. strcpy.3 peng haitao attributes: note functions that are thread-safe the functions strcpy() and strncpy() are thread safe. michael kerrisk [rick stanley] fix a bug, and improve discussion of forcing termination with strncpy() strspn.3 peng haitao attributes: note functions that are thread-safe the functions strspn() and strcspn() are thread safe. tempnam.3 michael kerrisk make warning not to use this function more prominent tmpnam.3 michael kerrisk recommend use mkstemp(3) or tmpfile(3) instead locale.5 michael kerrisk add intro section that lists all of the lc categories michael kerrisk 'p_cs_precedes' is for *positive* values michael kerrisk clarify 'p_sign_posn' and 'n_sign_posn'; simplify 'n_sign_posn' add initial sentence for 'p_sign_posn' and 'n_sign_posn'. remove repeated list for 'n_sign_posn'. michael kerrisk document lc_messages 'yesstr' and 'nostr' michael kerrisk clarify lc_monetary 'n_cs_precedes' michael kerrisk lc_monetary: document 'int_p_sign_posn' and 'int_n_sign_posn' michael kerrisk clarify/rework 'p_cs_precedes' and 'n_cs_precedes' michael kerrisk lc_monetary: document 'int_p_sep_by_space' and 'int_n_sep_by_space' michael kerrisk remove crufty reference to posix.2 michael kerrisk lc_monetary: document 'int_p_cs_precedes' and 'int_n_cs_precedes' michael kerrisk clarify/simplify 'n_sep_by_space' michael kerrisk lc_time: document 'cal_direction' and 'date_fmt' michael kerrisk clarify 'p_sep_by_space' feature_test_macros.7 michael kerrisk _bsd_source and _svid_source are deprecated in glibc 2.20 michael kerrisk _gnu_source implicitly defines other macros saying that _gnu_source has the "effects of" other macros is not quite precise. michael kerrisk reword glibc version for _isoc95_source michael kerrisk _isoc99_source also exposes c95 definitions michael kerrisk _isoc11_source implies the effects of _isoc99_source michael kerrisk note version number for _posix_c_source >= 200112l implies c99/c95 _posix_c_source >= 200112l causes c95 definitions to be exposed only since glibc 2.12 and c99 definitions only since 2.10. michael kerrisk _xopen_source may implicitly define _posix_source and _posix_c_source michael kerrisk reword glibc version for _isoc99_source michael kerrisk rework discussion of _isoc99_source michael kerrisk improve discussion of _default_source michael kerrisk _posix_c_source >= 200112l implies c95 and c95 features ==================== changes in man-pages-3.63 ==================== released: 2014-03-18, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: carlos o'donell christoph hellwig corrado zoccolo gregory p. smith joseph s. myers michael kerrisk mike frysinger peng haitao phillip susi robert p. j. day stefan puiu zhu yanhai apologies if i missed anyone! new and rewritten pages ----------------------- duplocale.3 michael kerrisk new page documenting duplocale(3) newlocale.3 michael kerrisk [mike frysinger] new page documenting newlocale(3) and freelocale(3) towlower.3 michael kerrisk largely rewrite description of towlower() to be simpler and clearer towupper.3 michael kerrisk largely rewrite description of towupper() to be simpler and clearer uselocale.3 michael kerrisk new page documenting uselocale(3) newly documented interfaces in existing pages --------------------------------------------- open.2 michael kerrisk document o_dsync and rewrite discussion of o_sync isalpha.3 michael kerrisk document the "_l" locale apis the gnu c library v2.3 added some locale apis, most of which were later specified in posix.1-2008, namely: isalnum_l() isalpha_l() isblank_l() iscntrl_l() isdigit_l() isgraph_l() islower_l() isprint_l() ispunct_l() isspace_l() isupper_l() isxdigit_l() isascii_l() also update and correct various pieces in conforming to (and remove a few crufty old pieces there). strerror.3 michael kerrisk document strerror_l() toupper.3 michael kerrisk document toupper_l() and tolower_l() towlower.3 michael kerrisk document towlower_l() towupper.3 michael kerrisk document towupper_l() proc.5 michael kerrisk document /proc/sys/kernel/random/uuid locale.7 michael kerrisk document lc_address document lc_identification document lc_measurement document lc_name document lc_paper document lc_telephone new and changed links --------------------- freelocale.3 michael kerrisk new link to new newlocale.3 page isalnum_l.3 isascii_l.3 isblank_l.3 iscntrl_l.3 isdigit_l.3 isgraph_l.3 islower_l.3 isprint_l.3 ispunct_l.3 isspace_l.3 isupper_l.3 isxdigit_l.3 michael kerrisk new links to isalpha.3 tolower_l.3 toupper_l.3 michael kerrisk new links to toupper.3 towlower_l.3 michael kerrisk new link to towlower.3 towupper_l.3 michael kerrisk new link to towupper.3 global changes -------------- various pages michael kerrisk global change: "upper case" ==> "uppercase", "lower case" ==> lowercase" changes to individual pages --------------------------- mount.2 michael kerrisk see also: add blkid(1) msgop.2 michael kerrisk document two msg_copy failure modes since linux 3.14, the kernel now diagnoses two errors when using msgrcv() msg_copy: * msg_copy must be specified with ipc_nowait * msg_copy can't be specified with msg_except open.2 michael kerrisk organize some material under additional subheadings in notes there's an amorphous mass of material under notes. structure it with some subheadings, and do a little reorganizing. michael kerrisk add other system calls and functions that are like openat() fanotify_mark(2), name_to_handle_at(2), and scandirat(3) have a directory file descriptor argument for the same reason as openat(). also: reword the rationale for the *at() functions somewhat. michael kerrisk clarify eloop error interaction with o_path readahead.2 phillip susi [corrado zoccolo, gregory p. smith, zhu yanhai, michael kerrisk, christoph hellwig] don't claim the call blocks until all data has been read the readahead(2) man page was claiming that the call blocks until all data has been read into the cache. this is incorrect. see https://bugzilla.kernel.org/show_bug.cgi?id=54271 stat.2 michael kerrisk see also: add ls(1) and stat(1) fts.3 christoph hellwig [michael kerrisk] the fts(3) api does not work with lfs builds as pointed out during a recent discussion on libc-hacker the fts(3) apis can't be used with large file offsets: https://sourceware.org/bugzilla/show_bug.cgi?id=15838 mbrtowc.3 mbsnrtowcs.3 mbsrtowcs.3 mbtowc.3 michael kerrisk add entries in see also mainly inspired by the posix pages. mbsinit.3 michael kerrisk see also: add mbrlen(3), mbrtowc(3), and wcrtomb(3) mbsrtowcs.3 wcsrtombs.3 michael kerrisk see also: add mbsinit(3) mbstowcs.3 michael kerrisk [stefan puiu] add example program and add some see also entries memcmp.3 peng haitao attributes: note function that is thread-safe the function memcmp() is thread safe. memcpy.3 peng haitao attributes: note function that is thread-safe the function memcpy() is thread safe. memfrob.3 peng haitao attributes: note function that is thread-safe the function memfrob() is thread safe. memmem.3 peng haitao attributes: note function that is thread-safe the function memmem() is thread safe. memmove.3 peng haitao attributes: note function that is thread-safe the function memmove() is thread safe. mempcpy.3 peng haitao attributes: note functions that are thread-safe the functions mempcpy() and wmempcpy() are thread safe. memset.3 peng haitao attributes: note function that is thread-safe the function memset() is thread safe. strerror.3 michael kerrisk conforming to: strerror() and strerror_r() are in posix.1-2008 michael kerrisk add ss heading for strerror_r() toupper.3 michael kerrisk rewrite to more explicitly bring locales into the discussion michael kerrisk retitle bugs section to notes these are not really bugs, just background info. wcrtomb.3 wcsnrtombs.3 wcsrtombs.3 wcstombs.3 wctomb.3 michael kerrisk see also: add various entries mainly inspired by posix core.5 mike frysinger [michael kerrisk] document core_pattern %d specifier document %p core_pattern specifier michael kerrisk rearrange core_pattern specifiers alphabetically locale.5 michael kerrisk see also: add newlocale(3) + duplocale(3) feature_test_macros.7 michael kerrisk [joseph s. myers] remove mention of bogus _isoc95_source macro the _isoc95_source macro is defined in , but it does nothing. so remove discussion of it, and move some of the discussion of c95 under the _isoc99_source subhead. michael kerrisk [carlos o'donell] add packaging note for _bsd_source/_svid_source/_default_source to compile warning-free across glibc < 2.20 and glibc >= 2.20 code may been to define both _default_source and either _bsd_source or _svid_source. michael kerrisk reword description of c90 locale.7 michael kerrisk add subsection on posix.1-2008 (originally gnu) extensions to locale api michael kerrisk remove reference to li18nux2000 li18nux2000 is difficult to even find these days, and in any case this page does not document gettext(), so notes about gettext() in the conforming to section here make no sense. michael kerrisk see also: add mbstowcs(3) and wcstombs(3) see also: add newlocale(3) + duplocale(3) man-pages.7 michael kerrisk add preferred term "superblock" michael kerrisk add preferred terms "uppercase" and "lowercase" ==================== changes in man-pages-3.64 ==================== released: 2014-04-06, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: abhay sachan alexey samsonov andrey vagin aneesh kumar k.v christoph hellwig david prévot eric dumazet eric w. biederman jan kara kir kolyshkin michael kerrisk mike frysinger neilbrown peng haitao peter hurley petr gajdos robert p. j. day vince weaver yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- open_by_handle_at.2 michael kerrisk [mike frysinger, neil brown, aneesh kumar k.v, christoph hellwig] new page describing name_to_handle_at(2) and open_by_handle_at(2) inotify.7 michael kerrisk rewrite introductory section reorganize "limitations and caveats" subsection michael kerrisk further describe the race when adding a watch to a new subtree michael kerrisk directory renames may invalidate multiple paths cached by application michael kerrisk add paragraph on cache consistency checking michael kerrisk mention cache rebuilding to handle overflow events michael kerrisk moving an object to another filesystem generates in_delete_self michael kerrisk [jan kara] add text on dealing with rename() events michael kerrisk note rationale and consequences of event coalescing michael kerrisk [eric w. biederman] inotify doesn't work for remote and pseudo filesystems michael kerrisk add some examples of events generated by various system calls michael kerrisk bugs: in_oneshot does now cause in_ignored when the watch is dropped a silent change as a result of the fanotify work in kernel 2.6.36. michael kerrisk note that in_delete_self will be followed by in_ignored michael kerrisk note that in_unmount will be followed by an in_ignored event michael kerrisk inotify does not report events for mmap(2) and msync(2) michael kerrisk add examples of syscalls that trigger in_attrib michael kerrisk add some examples of syscalls that trigger in_modify michael kerrisk execve(2) also generates in_access michael kerrisk add examples of syscalls that trigger in_create newly documented interfaces in existing pages --------------------------------------------- perf_event_open.2 vince weaver [michael kerrisk] document the perf_flag_fd_cloexec flag the linux 3.14 release adds support for the perf_flag_fd_cloexec flag. feature_test_macros.7 michael kerrisk document _largefile_source tcp.7 michael kerrisk [eric dumazet] document /proc/sys/net/ipv4/tcp_autocorking text heavily based on documentation/networking/ip-sysctl.txt new and changed links --------------------- name_to_handle_at.2 michael kerrisk new link to new open_by_handle_at(2) page global changes -------------- fmemopen.3 getaddrinfo.3 mq_notify.3 offsetof.3 aio.7 michael kerrisk print size_t/ssize_t values using %z printf() modifier there are fewer and fewer systems these days that don't support the %z specifier mandated in c99. so replace the use of %ld/%lu + (long) cast with %zd/%zu. changes to individual pages --------------------------- bdflush.2 fsync.2 sync.2 kir kolyshkin see also: remove update(8) reference remove reference to update(8) man page, since there is no such page. this is an ancient bsd leftover i believe. chown.2 michael kerrisk note that 'dirfd' can be at_fdcwd when at_empty_path is used getxattr.2 abhay sachan fix return value description a ea can have length zero. inotify_add_watch.2 michael kerrisk errors: add enametoolong inotify_init.2 michael kerrisk add pointer to inotify(7) link.2 michael kerrisk when at_empty_path is specified, 'olddirfd' must not refer to a directory mmap.2 andrey vagin the file descriptor for a file mapping must be readable there is no difference between map_shared and map_private. open.2 michael kerrisk see also: add open_by_name_at(2) perf_event_open.2 vince weaver document perf_event_ioc_period behavior change linux 3.14 (in commit bad7192b842c83e580747ca57104dd51fe08c223) changes the perf_event perf_event_ioc_period ioctl() behavior on all architectures to update immediately, to match the behavior found on arm. stat.2 michael kerrisk note that 'dirfd' can be at_fdcwd when at_empty_path is used syscalls.2 michael kerrisk add sched_getattr() and sched_setattr() and update kernel version to 3.14 abort.3 peng haitao attributes: note function that is thread-safe the function abort() is thread safe. confstr.3 michael kerrisk see also: add getconf(1), fpathconf(3), sysconf(3), pathconf(3) exit.3 peng haitao attributes: note function that is not thread-safe the function exit() is not thread safe. fenv.3 peng haitao attributes: note functions that are thread-safe the functions feclearexcept(), fegetexceptflag(), feraiseexcept(), fesetexceptflag(), fetestexcept(), fegetround(), fesetround(), fegetenv(), feholdexcept(), fesetenv(), feupdateenv(), feenableexcept(), fedisableexcept() and fegetexcept() are thread safe. fpathconf.3 michael kerrisk see also: add confstr(3) fseek.3 michael kerrisk [petr gajdos] document einval error for negative file offset fseeko.3 michael kerrisk add feature test macro requirements fts.3 michael kerrisk [mike frysinger] remove mention of "32-bit systems" in bugs fwide.3 wprintf.3 michael kerrisk [robert p. j. day] remove mention of bogus _isoc95_source feature test macro getline.3 alexey samsonov caller should free the allocated buffer even if getline() failed relevant discussion in glibc bugzilla: https://sourceware.org/bugzilla/show_bug.cgi?id=5666 getloadavg.3 peng haitao attributes: note function that is thread-safe the function getloadavg() is thread safe. getpt.3 peng haitao attributes: note function that is thread-safe the function getpt() is thread safe. if_nametoindex.3 peng haitao attributes: note functions that are thread-safe the functions if_nametoindex() and if_indextoname() are thread safe. index.3 peng haitao attributes: note functions that are thread-safe the functions index() and rindex() are thread safe. mkfifo.3 peng haitao attributes: note functions that are thread-safe the functions mkfifo() and mkfifoat() are thread safe. netlink.3 michael kerrisk see also: make the reference for libnetlink the libnetlink(3) man page random.3 peng haitao attributes: note functions that are thread-safe the functions random(), srandom(), initstate() and setstate() are thread safe. random_r.3 peng haitao attributes: note functions that are thread-safe the functions random_r(), srandom_r(), initstate_r() and setstate_r() are thread safe. sigvec.3 peng haitao attributes: note functions that are thread-safe the functions sigvec(), sigblock(), sigsetmask() and siggetmask() are thread safe. the macro sigmask() is thread safe. sysconf.3 michael kerrisk see also: add confstr(3) termios.3 michael kerrisk [peter hurley] fix error in discussion of min > 0, time == 0 noncanonical mode as reported by peter hurley, for the min > 0, time == 0 case: read() may unblock when min bytes are available but return up to the 'count' parameter if more input arrives in between waking and copying into the user buffer. ... read() may also _not_ return until min bytes have been received, even if 'count' bytes have been received. michael kerrisk add a note on interaction of o_nonblock with noncanonical min/time posix leaves the behavior open. michael kerrisk clarify termination conditions for min > 0, time > 0 michael kerrisk clarify behavior if data is available before noncanonical read() michael kerrisk add descriptive titles to noncanonical read() cases symlink.7 michael kerrisk add subsection on opening a symbolic link with o_path michael kerrisk name_to_handle_at(2) and open_by_handle_at(2) optionally follow symlinks michael kerrisk mention use of readlink(2) to read contents of a symlink ==================== changes in man-pages-3.65 ==================== released: 2014-04-20, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alex thorlton ashish sangwan christopher covington christoph hellwig craig mcqueen dave chinner david prévot greg troxel matthew dempsky michael kerrisk mike frysinger namjae jeon peng haitao petr gajdos richard hansen simon paillard steven stewart-gallus vince weaver yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- inet_net_pton.3 michael kerrisk new page describing inet_net_pton(3) and inet_net_ntop(3) newly documented interfaces in existing pages --------------------------------------------- fallocate.2 michael kerrisk, namjae jeon [christoph hellwig, dave chinner] document falloc_fl_collapse_range prctl.2 michael kerrisk [alex thorlton] document pr_set_thp_disable and pr_get_thp_disable proc.5 michael kerrisk document /proc/[pid]/stack michael kerrisk document /proc/[pid]/clear_refs new and changed links --------------------- inet_net_ntop.3 michael kerrisk new link to new inet_net_pton.3 changes to individual pages --------------------------- fcntl.2 michael kerrisk note the race when o_cloexec is used at same time as fork()+execve() madvise.2 michael kerrisk see also: see prctl(2) because of pr_set_thp_disable. mlock.2 michael kerrisk describe treatment of mcl_future during fork(2) and execve(2) msync.2 michael kerrisk [richard hansen, greg troxel] warn that one of ms_sync or ms_async is required open.2 michael kerrisk add more detail on the race that o_cloexec is designed to avoid michael kerrisk [matthew dempsky] remove crufty text stating that o_directory is linux-specific michael kerrisk note which filesystems support o_tmpfile perf_event_open.2 vince weaver [michael kerrisk] clarify eacces and eperm errors clarify the reasons for eacces and eperm errors. vince weaver [michael kerrisk] make the errors section more comprehensive. determined both by code inspection and by writing a large number of test programs. personality.2 michael kerrisk available execution domains are listed in michael kerrisk fix discussion of return value prctl.2 michael kerrisk errors: document einval for pr_get_no_new_privs errors: document einval for pr_set_pdeathsig errors: document einval for pr_set_timing errors: document einval for pr_set_dumpable errors: document einval for pr_set_no_new_privs shmget.2 michael kerrisk rewrite description of shmmni default value michael kerrisk note default value of shmmax note default value for shmall byteorder.3 peng haitao attributes: note functions that are thread-safe the functions htonl(), htons(), ntohl() and ntohs() are thread safe. fexecve.3 michael kerrisk [steven stewart-gallus] if 'fd' is a close-on-exec file descriptor for a script, fexecve() fails see https://bugzilla.kernel.org/show_bug.cgi?id=74481 ffs.3 peng haitao attributes: note functions that are thread-safe the functions ffs(), ffsl() and ffsll() are thread safe. getauxval.3 peng haitao attributes: note function that is thread-safe the function getauxval() is thread safe. getcontext.3 peng haitao attributes: note functions that are thread-safe the functions getcontext() and setcontext() are thread safe. getsubopt.3 peng haitao attributes: note function that is thread-safe the function getsubopt() is thread safe. getutmp.3 peng haitao attributes: note functions that are thread-safe the functions getutmp() and getutmpx() are thread safe. inet.3 michael kerrisk note success and error return for inet_aton() inet.3 michael kerrisk [craig mcqueen] the form 'a.b' if is suitable for class a addresses (not class c) michael kerrisk see also: add inet_net_pton(3) makecontext.3 peng haitao attributes: note functions that are thread-safe the functions makecontext() and swapcontext() are thread safe. pthread_attr_setdetachstate.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setdetachstate() and pthread_attr_getdetachstate() are thread safe. pthread_attr_setguardsize.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setguardsize() and pthread_attr_getguardsize() are thread safe. sigsetops.3 peng haitao attributes: note functions that are thread-safe the functions sigemptyset(), sigfillset(), sigaddset(), sigdelset(), sigismember(), sigisemptyset(), sigorset() and sigandset() are thread safe. proc.5 petr gajdos improve /proc/[pid]/smaps entries description michael kerrisk /proc/pid/smaps is present only if config_proc_page_monitor michael kerrisk note kernel version for /proc/sys/kernel/{shmall,shmmax} michael kerrisk note kernel version for /proc/sys/kernel/{msgmax,msgmnb} capabilities.7 michael kerrisk see also: add capsh(1) libc.7 michael kerrisk add musl libc ==================== changes in man-pages-3.66 ==================== released: 2014-05-08, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alan curry carsten andrich daniel borkmann david prévot eric siegerman heinrich schuchardt jan kara jan moskyto matejka john marshall lukáš czerner manfred spraul michael kerrisk miklos szeredi neil horman peng haitao peter schiffer randy dunlap silvan jegen simon paillard stefan puiu steven stewart-gallus stijn hinterding willem de bruijn yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- fanotify_init.2 heinrich schuchardt, michael kerrisk new page documenting fanotify_init(2) fanotify_mark.2 heinrich schuchardt, michael kerrisk new page documenting fanotify_mark(2) sched_setscheduler.2 michael kerrisk page rewritten stripped out the general scheduling material, which moved to sched(7), and rewrote much of the remainder. changed copyright and license since pretty much all of the content was or is written by mtk. fanotify.7 heinrich schuchardt, michael kerrisk new page providing overview of the fanotify api sched.7 michael kerrisk new page providing an overview of the scheduling apis most of this content derives from sched_setscheduler(2). in preparation for adding a sched_setattr(2) page, it makes sense to isolate out this general content to a separate page that is referred to by the other scheduling pages. newly documented interfaces in existing pages --------------------------------------------- fallocate.2 lukas czerner [michael kerrisk] document falloc_fl_zero_range falloc_fl_zero_range was added in linux 3.14, for zeroing ranges in the allocated space in a file. rename.2 miklos szeredi [michael kerrisk] document renameat2() system call added in linux 3.15 shmop.2 michael kerrisk document shm_exec changes to individual pages --------------------------- flock.2 michael kerrisk employ term "open file description" in description and include reference to open(2) for an explanation of the term. getpriority.2 michael kerrisk see also: add sched(7) getsockopt.2 carsten andrich see also: add packet(7) link.2 michael kerrisk [steven stewart-gallus] document enoent error for linkat() see https://bugzilla.kernel.org/show_bug.cgi?id=73301 msgget.2 michael kerrisk reword eexist error msgop.2 michael kerrisk note capability required to raise mq size beyond msgmnb msync.2 michael kerrisk [heinrich schuchardt] s/flushes... back to disk/flushes... back to filesystem/ nice.2 michael kerrisk see also: add sched(7) open.2 peter schiffer update note on alignment of user buffer and file offset for o_direct the sentence in open(2) man page in notes for o_direct flag: "under linux 2.6, alignment to 512-byte boundaries suffices." is not universally correct. the alignment is a property of the storage, for example, 4k-sector drives with no 512 byte sector emulation will be unable to perform 512-byte direct i/o. michael kerrisk note some of the various synonyms for "open file description" michael kerrisk remove repetitious text on use of fcntl() to change file status flags open_by_handle_at.2 michael kerrisk mention freebsd analogs posix_fadvise.2 michael kerrisk [eric siegerman] fix wording error under "architecture-specific variants" see https://bugzilla.kernel.org/show_bug.cgi?id=75431 process_vm_readv.2 michael kerrisk [stijn hinterding] add feature test macro requirements the _gnu_source ftm must be defined. read.2 michael kerrisk bugs: detail nonatomicity bug with respect to file offset updates this bug was fixed in linux 3.14, with commit 9c225f2655e36a470c4f58dbbc99244c5fc7f2d4 see also http://thread.gmane.org/gmane.linux.kernel/1649458 sched_get_priority_max.2 michael kerrisk small changes consistent with migration of content to sched(7) sched_rr_get_interval.2 michael kerrisk small changes consistent with migration of content to sched(7) sched_setaffinity.2 michael kerrisk small changes consistent with migration of content to sched(7) sched_setparam.2 michael kerrisk small changes consistent with migration of content to sched(7) sched_yield.2 michael kerrisk small changes consistent with migration of content to sched(7) semget.2 michael kerrisk consolidate discussion on noninitialization of semaphores the fact that semget() does not initialize the semaphores in a new set was covered in two places (in description and bugs). consolidate these into one place (in notes) and also point out that posix.1-2008 says that a future version of the standard may require an implementation to initialize the semaphores to 0. michael kerrisk clarify semmns versus semmsl*semmni michael kerrisk rework einval text a little michael kerrisk clarify wording for eexist error shmget.2 manfred spraul clarify shmall the default for shmall is a limit of 8 gb, regardless of page_size. the current documentation does not mention that and is therefore more difficult to understand than necessary. manfred spraul correct math error 2097152 is 2^21, not 2^20. michael kerrisk reword eexist error michael kerrisk clarify one of the einval cases michael kerrisk note that shm_noreserve is a linux extension michael kerrisk [simon paillard] fix kernel version numbers in discussion of shmall michael kerrisk rework einval text michael kerrisk move and rework discussion of mode bits michael kerrisk reword description of o_excl shmop.2 michael kerrisk move fork(2), execve(2), _exit(2) discussion to notes michael kerrisk add subheads for shmat() and shmdt() michael kerrisk rework discussion of shm_rdonly and shm_remap into list format michael kerrisk structure the attach cases as a list sigaction.2 alan curry fix bad cross reference (times(2) not time(2)) the system call that reports child cpu usage is times(2), not time(2). symlink.2 michael kerrisk [steven stewart-gallus] document enoent error for symlinkat() see https://bugzilla.kernel.org/show_bug.cgi?id=73301 syscalls.2 michael kerrisk add renameat2() and bump kernel version. write.2 michael kerrisk bugs: detail nonatomicity bug with respect to file offset updates this bug was fixed in linux 3.14, with commit 9c225f2655e36a470c4f58dbbc99244c5fc7f2d4 see also http://thread.gmane.org/gmane.linux.kernel/1649458 pthread_attr_setinheritsched.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setinheritsched() and pthread_attr_getinheritsched() are thread safe. pthread_attr_setschedparam.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setschedparam() and pthread_attr_getschedparam() are thread safe. pthread_attr_setschedpolicy.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setschedpolicy() and pthread_attr_getschedpolicy() are thread safe. pthread_attr_setscope.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setscope() and pthread_attr_getscope() are thread safe. pthread_attr_setstack.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setstack() and pthread_attr_getstack() are thread safe. sched_getcpu.3 michael kerrisk see also: add sched(7) termios.3 michael kerrisk [yuri kozlov] rework intro text for 'c_oflag' michael kerrisk ofdel is in posix.1-2001, so remove "(not in posix)" text proc.5 jan moskyto matejka [randy dunlap] improve description of /proc/stat 'intr' field the sum at the beginning of line "intr" includes also unnumbered interrupts. packet.7 carsten andrich [neil horman] improve sockopt documentation for packet sockets carsten andrich [willem de bruijn] packet_loss has inverse meaning stefan puiu [daniel borkmann, carsten andrich] status in packet_rx_ring is actually a bit mask michael kerrisk [carsten andrich] see also: add /tools/testing/selftests/net/psock_tpacket.c ==================== changes in man-pages-3.67 ==================== released: 2014-05-21, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andy lutomirski aurelien jarno bill allombert christoph hellwig davidlohr bueso heinrich schuchardt ingo schwarze jan kara jon grant juri lelli lucas de marchi michael kerrisk peng haitao peter zijlstra rasmus villemoes sam varshavchik simon paillard steven stewart-gallus török edwin william morriss yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- sched_setattr.2 michael kerrisk, peter zijlstra [juri lelli] new page describing sched_setattr(2) and sched_getattr(2) system.3 michael kerrisk rewrote large parts of the page and added a number of details newly documented interfaces in existing pages --------------------------------------------- sched.7 peter zijlstra, michael kerrisk [juri lelli] document sched_deadline new and changed links --------------------- renameat2.2 michael kerrisk new link to rename.2 sched_getattr.2 michael kerrisk new link to new sched_setattr changes to individual pages --------------------------- bind.2 michael kerrisk errors: add eaddrinuse for ephemeral port range exhaustion chown.2 michael kerrisk notes: add some subheadings connect.2 michael kerrisk [william morriss] errors: add eaddrnotavail for ephemeral port range exhaustion verified from testing and the kernel source. see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=745775 michael kerrisk remove mention of ip_local_port_range under eagain error create_module.2 delete_module.2 init_module.2 query_module.2 michael kerrisk [lucas de marchi] clarify glibc header file declaration/abi wrapper details create_module(), delete_module(), init_module(), and query_module() are not declared in header files, but through an accident of history glibc provides an abi for them that it continues to maintain, for compatibility reasons. execve.2 michael kerrisk [steven stewart-gallus] note sigkill case when execve() fails beyond the point of no return michael kerrisk notes: add a subheading and reorder paragraphs fanotify_init.2 heinrich schuchardt [michael kerrisk] document range of permitted flags for event_f_flags with a new patch included in the mm tree, event_f_flags is checked for allowable values. fcntl.2 michael kerrisk add "file locking" subheading under notes fork.2 michael kerrisk errors: sched_deadline tasks can fail with eagain sched_deadline tasks can fail with eagain unless the reset-on-fork flag is set. futex.2 michael kerrisk note that there is no glibc wrapper getpriority.2 rasmus villemoes fix prototypes for getpriority() and setpriority() the who argument has type id_t (which happens to be u32 on linux). get_robust_list.2 rasmus villemoes add to synopsis of get_robust_list() if one were to implement wrappers for [gs]et_robust_list() using the given prototypes, one would also have to include sys/types.h to get a definition of size_t. getrusage.2 michael kerrisk [bill allombert] _gnu_source must be defined to obtain rusage_thread definition see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=746569 link.2 open.2 andy lutomirski [michael kerrisk] update at_empty_path and o_path documentation listen.2 michael kerrisk errors: add eaddrinuse for ephemeral port range exhaustion mbind.2 rasmus villemoes fix prototype for mbind(2) the nmask argument is const. the return type in numaif.h is long. (well, at least says nmask is const. the current kernel does not define it as a const argument, but sys_mbind() only passes it to get_nodes(), which does treat it as const.) msgop.2 davidlohr bueso [michael kerrisk] enhance description of "full queue" criteria poll.2 rasmus villemoes add to synopsis for ppoll() one needs to #include to get the definition of the type (sigset_t) of the mask argument to ppoll(). readlink.2 rasmus villemoes fix return type of readlinkat() recv.2 michael kerrisk clarify details of msg_name and msg_namelen fields recvmmsg.2 michael kerrisk describe timeout bug see https://bugzilla.kernel.org/show_bug.cgi?id=75371 and http://thread.gmane.org/gmane.linux.man/5677 remap_file_pages.2 andy lutomirski [christoph hellwig, andy lutomirski] remap_file_pages() has no benefit for real files linux commit 3ee6dafc677a68e461a7ddafc94a580ebab80735 caused remap_file_pages to be emulated when used on real file. sched_get_priority_max.2 michael kerrisk 'policy' can also be sched_deadline sched_setaffinity.2 rasmus villemoes fix prototype for sched_setaffinity() the mask argument is const. sched_setparam.2 michael kerrisk errors: mark errors that apply just for sched_setparam() michael kerrisk errors: add einval for invalid arguments michael kerrisk see also: add sched_setattr(2) sched_setscheduler.2 michael kerrisk errors: mark errors that apply just to sched_setscheduler() michael kerrisk errors: add einval case for pid < 0 michael kerrisk errors: separate out einval cases semget.2 michael kerrisk notes: add subheadings and reorder paragraphs semop.2 rasmus villemoes fix prototypes for semop() and semtimedop() the nsops arguments have type size_t, not unsigned, and the timeout argument of semtimedop() is const. michael kerrisk notes: add a subheading send.2 michael kerrisk add details on various 'msghdr' fields michael kerrisk errors: add eagain for ephemeral port range exhaustion michael kerrisk add some subheadings under description shmget.2 michael kerrisk notes: add a subheading stat.2 michael kerrisk [aurelien jarno] describe feature test macro requirements for file type test macros see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=728240 michael kerrisk update ftm requirements for lstat() michael kerrisk split discussion of 'st_mode' fields into type and permissions michael kerrisk move text on s_i*() macros to follow text on s_i* macros that ordering is more logical stime.2 rasmus villemoes fix prototype for stime() the argument is const, both according to the actual header files and according to . syscall.2 rasmus villemoes fix prototype for syscall() the first argument and the return value of syscall() has type long, not int. getopt.3 michael kerrisk example: add subheadings to distinguish the two example programs malloc.3 michael kerrisk reword text referring to mallopt(3) linux libc is no longer "recent"; drop mention of it. pthread_attr_setinheritsched.3 pthread_attr_setschedparam.3 pthread_attr_setschedpolicy.3 pthread_setaffinity_np.3 pthread_setschedparam.3 pthread_setschedprio.3 pthread_yield.3 pthreads.7 michael kerrisk change references to "sched_setscheduler(2)" to "sched(7)" change consistent with the fact that the scheduling overview page is now sched(7) not sched_setscheduler(2). pthread_attr_setstackaddr.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setstackaddr() and pthread_attr_getstackaddr() are thread safe. pthread_attr_setstacksize.3 peng haitao attributes: note functions that are thread-safe the functions pthread_attr_setstacksize() and pthread_attr_getstacksize() are thread safe. pthread_kill.3 peng haitao attributes: note function that is thread-safe the function pthread_kill() is thread safe. pthread_kill_other_threads_np.3 peng haitao attributes: note function that is thread-safe the function pthread_kill_other_threads_np() is thread safe. pthread_self.3 peng haitao attributes: note function that is thread-safe the function pthread_self() is thread safe. pthread_setcancelstate.3 michael kerrisk add paragraph breaks to "asynchronous cancelability" subsection pthread_setcancelstate.3 peng haitao attributes: note functions that are thread-safe the functions pthread_setcancelstate() and pthread_setcanceltype() are thread safe. michael kerrisk notes: add some subheadings pthread_setschedparam.3 peng haitao attributes: note functions that are thread-safe the functions pthread_setschedparam() and pthread_getschedparam() are thread safe. pthread_setschedprio.3 peng haitao attributes: note function that is thread-safe the function pthread_setschedprio() is thread safe. pthread_sigmask.3 peng haitao attributes: note function that is thread-safe the function pthread_sigmask() is thread safe. pthread_sigqueue.3 peng haitao attributes: note function that is thread-safe the function pthread_sigqueue() is thread safe. pthread_testcancel.3 peng haitao attributes: note function that is thread-safe the function pthread_testcancel() is thread safe. pthread_yield.3 peng haitao attributes: note function that is thread-safe the function pthread_yield() is thread safe. remquo.3 peng haitao attributes: note functions that are thread-safe the functions remquo(), remquof() and remquol() are thread safe. rtime.3 peng haitao attributes: note function that is thread-safe the function rtime() is thread safe. sched_getcpu.3 peng haitao attributes: note function that is thread-safe the function sched_getcpu() is thread safe. stpcpy.3 ingo schwarze note some history of stpcpy() quoting ingo: i just noticed that the stpcpy(3) manual contains a speculation that appears to be untrue on closer investigation: that function did not originate in ms dos, but in lattice c on amigados. here is a patch against the git master head to fix that, and add some more historical information. to provide some background and allow you to more easily verify the correctness of the patch, i'm appending my mail to , where i'm giving some more details about the history and pointing to some primary sources. that mail also contains the (similar, but shorter) patch i just committed to the openbsd manual page. strcasecmp.3 michael kerrisk [aurelien jarno, török edwin] explain why strcasecmp()+strncasecmp() are also declared in see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=729436 strcpy.3 michael kerrisk notes: add a subheading fd.4 michael kerrisk [sam varshavchik] fix floppy disk device names the naming convention shown in the page was ancient. now, the page is consistent with documentation/devices.txt (where it is noted that "the use of the capital letters d, h and e for the 3.5" models have been deprecated, since the drive type is insignificant for these devices" proc.5 michael kerrisk document /proc/timer_stats michael kerrisk (briefly) document /proc/timer_list michael kerrisk add /proc/sys/kernel/{sched_rt_period_us,sched_rt_runtime_us} reference sched(7) for an explanation of these two files capabilities.7 michael kerrisk mention sched_setattr(2) under cap_sys_nice cpuset.7 michael kerrisk see also: add sched(7) credentials.7 michael kerrisk mention sched_getattr() as a place where credentials are checked fanotify.7 heinrich schuchardt [jan kara] bugs: error events can be lost when reading from fanotify fd michael kerrisk [heinrich schuchardt] fix description of fan_event_next() fan_event_next() does not update 'meta'; rather, it returns a pointer to the next metadata structure. in addition, generally rework the description to be a bit clearer and more detailed. heinrich schuchardt document fan_event_metadata_len ip.7 michael kerrisk note cases where an ephemeral port is used michael kerrisk remove bugs text on glibc failing to declare in_pktinfo michael kerrisk clarify 'ip_local_port_range' and mention the term "ephemeral ports" michael kerrisk note some more details about assignment of ephemeral ports michael kerrisk bugs: ephemeral port range exhaustion is diagnosed inconsistently different system calls use different 'errno' values to diagnose exhaustion of the ephemeral port range. sched.7 michael kerrisk document sched_rt_period_us and sched_rt_runtime_us /proc files and rework and relocate the text on dealing with runaway real-time processes. michael kerrisk mention sched_setattr(2) in list of apis that can change policies michael kerrisk sched_setattr(2) can also be used to set 'nice' value michael kerrisk remove mention of sched_setscheduler() when talking about sched_priority there are nowadays multiple ways to set sched_priority (and in fact there always were, since we also had sched_setparam(2)). michael kerrisk see also: add documentation/scheduler/sched-design-cfs.txt michael kerrisk don't mention sched_setscheduler(2) in discussions of setting policies in a couple of places, sched_setscheduler(2) is mentioned as the way of setting policies. but now there is sched_setattr(2) as well, rewrite the text in a more generic way. michael kerrisk rework summary text describing sched_setattr(2) and sched_getattr(2) note that these apis are a superset of sched_setscheduler(2) and sched_getscheduler(2). michael kerrisk remove crufty text relating to sched_setscheduler() all of the removed text is in sched_setscheduler(2) and should have been trimmed from this page. michael kerrisk see also: mention more files in documentation/scheduler/ directory ==================== changes in man-pages-3.68 ==================== released: 2014-05-28, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alastair mckinstry carsten grohmann colin williams heinrich schuchardt lars wirzenius marko myllynen michael kerrisk peng haitao rasmus villemoes richard braakman simon paillard apologies if i missed anyone! new and rewritten pages ----------------------- localedef.1 marko myllynen, richard braakman, alastair mckinstry, lars wirzenius new page for localedef(1) add new page based on debian localedef(1) page. new and changed links --------------------- procfs.5 new link to proc.5 since the term "procfs" is widely used, it seems reasonable to have a link from that name to proc(5). changes to individual pages --------------------------- locale.1 marko myllynen provide a step-by-step example of how to use a custom locale marko myllynen use lc_telephone instead of lc_messages in the example yesstr/nostr in lc_messages are planned to be changed at some point [1], so it's better to provide an example which won't be obsoleted by that change. [1] https://sourceware.org/bugzilla/show_bug.cgi?id=16975 adjtimex.2 michael kerrisk add feature test macro requirements clone.2 michael kerrisk errors: add cross-reference to fork(2) for explanation of eagain fork.2 michael kerrisk errors: add pid_max and threads-max to eagain and rewrite text to be the same as pthread_create(3). getrlimit.2 michael kerrisk rlimit_nproc is not enforced if cap_sys_admin or cap_sys_resource remap_file_pages.2 rasmus villemoes fix prototype the pgoff argument has type size_t, not ssize_t (and in the kernel it is unsigned long). set_mempolicy.2 rasmus villemoes fix prototype for set_mempolicy(2) the nodemask argument is const. the return type in numaif.h is long. swapon.2 rasmus villemoes remove header from synopsis the header is not readily available, and the comment seems to indicate that it is for getting page_size. but it is never mentioned why one would need to know that, and it is in any case better obtained using sysconf(), provided by . a64l.3 rasmus villemoes fix prototype for a64l() the argument is const, both according to posix and the glibc headers. adjtime.3 rasmus villemoes add required header the prototype for adjtime(3) is declared in . argz_add.3 rasmus villemoes fix prototypes update the prototypes of argz_{delete,extract,next} to agree with glibc headers and manual. bstring.3 rasmus villemoes fix prototypes the length parameter n has type size_t in bcmp(), bcopy() and bzero(). envz_add.3 rasmus villemoes fix prototypes the envz_len parameters for envz_entry() and envz_get() are not passed by reference. fpathconf.3 rasmus villemoes fix prototype the path argument to pathconf() is const. fseek.3 rasmus villemoes fix prototype the pos argument to fsetpos() is const. gcvt.3 rasmus villemoes fix prototype the ndigit parameter to gcvt() has type int. getaddrinfo_a.3 rasmus villemoes fix prototype the pointer arguments to gai_suspend() are const. getauxval.3 rasmus villemoes fix permissions there doesn't seem to be any reason for getauxval.3 to be executable... getnameinfo.3 rasmus villemoes fix prototype the hostlen and servlen parameters have type socklen_t. (the types changed in glibc 2.2) michael kerrisk note types of 'hostlen'; and 'servlen' in glibc < 2.2 getrpcent.3 rasmus villemoes fix prototype the argument to getrpcbyname() is const. getrpcport.3 rasmus villemoes add #include and fix prototype the prototype for getrpcport() is obtained by #include'ing . also, update its prototype. getspnam.3 rasmus villemoes fix prototype the struct spwd argument to putspent() is const. getutent.3 rasmus villemoes fix prototypes the arguments to getutid(), getutline(), and pututline() are const. inet.3 rasmus villemoes fix prototype the parameters to inet_makeaddr have type in_addr_t. inet_net_pton.3 rasmus villemoes srcfix, cfix use a consistent style throughout the man-pages. key_setsecret.3 rasmus villemoes fix prototypes remove const qualifiers from arguments to key_decryptsession, key_encryptsession, and key_setsecret. makecontext.3 rasmus villemoes fix prototype the second argument to swapcontext() is const. makedev.3 rasmus villemoes fix prototype gnu_dev_makedev, and hence its trivial macro wrapper makedev, takes two unsigned int parameters; this is consistent with it being the inverse of (gnu_dev_)major/minor, which return unsigned int. malloc_trim.3 rasmus villemoes fix prototype as mentioned further down, malloc_trim returns an integer. mq_getattr.3 rasmus villemoes fix prototype the newattr parameter to mq_setattr is const. newlocale.3 marko myllynen list all available category masks michael kerrisk add lc_all_mask description nl_langinfo.3 marko myllynen expand the example code a bit better illustrate querying elements from different categories. perror.3 rasmus villemoes fix declaration the elements of the array sys_errlist are also const. pthread_attr_setaffinity_np.3 pthread_attr_setdetachstate.3 pthread_attr_setguardsize.3 pthread_attr_setinheritsched.3 pthread_attr_setschedparam.3 pthread_attr_setschedpolicy.3 pthread_attr_setscope.3 pthread_attr_setstack.3 pthread_attr_setstackaddr.3 pthread_attr_setstacksize.3 rasmus villemoes constify parameters each of the pthread_attr_get* functions extract some piece of information from a pthread_attr_t, which is passed by const reference. add the const keyword to the prototypes of these functions. pthread_cleanup_push_defer_np.3 michael kerrisk [rasmus villemoes] add feature test macro requirements pthread_create.3 michael kerrisk [carsten grohmann] add pid_max limit to eagain error cases pthread_equal.3 peng haitao attributes: note function that is thread-safe the function pthread_equal() is thread safe. pthread_exit.3 peng haitao attributes: note function that is thread-safe the function pthread_exit() is thread safe. pthread_getcpuclockid.3 peng haitao attributes: note function that is thread-safe the function pthread_getcpuclockid() is thread safe. pthread_setaffinity_np.3 peng haitao attributes: note functions that are thread-safe the functions pthread_setaffinity_np() and pthread_getaffinity_np() are thread safe. pthread_setconcurrency.3 peng haitao attributes: note functions that are thread-safe the functions pthread_setconcurrency() and pthread_getconcurrency() are thread safe. pthread_setname_np.3 rasmus villemoes fix prototype the name parameter of pthread_getname_np is an output parameter and hence not const. pthread_setschedparam.3 rasmus villemoes fix prototypes add return type for pthread_{s,g}etschedparam. pthread_setschedprio.3 rasmus villemoes fix prototype add return type for pthread_setschedprio. pthread_sigqueue.3 rasmus villemoes add missing #include rcmd.3 rasmus villemoes fix prototypes unlike the bsds, the second argument of rcmd() and rcmd_af() has type unsigned short. the first argument of iruserok_af() has type const void*. re_comp.3 rasmus villemoes fix prototypes re_comp and re_exec take const char* arguments. resolver.3 rasmus villemoes fix prototypes and extern-declaration fix const- and signedness of various char* parameters. also, there is no "struct state", but _res is a struct __res_state. (actually, _res is errno-like in that it is really a macro expanding to (*__res_state()).) rexec.3 rasmus villemoes fix prototypes the user, passwd and cmd arguments to rexec and rexec_af are all const. rtime.3 rasmus villemoes replace header the header does not provide rtime(); does, as is also implied in both the notes and example sections. scandir.3 rasmus villemoes fix prototypes the alphasort and versionsort functions take arguments of type const struct dirent **, not const void *. setlocale.3 michael kerrisk [marko myllynen] simplify locale category listing and add gnu-specific locale categories some information that was here will move to locale(7). marko myllynen remove now obsolete notes section setnetgrent.3 rasmus villemoes fix prototype the buflen argument to getnetgrent_r has type size_t. sigvec.3 rasmus villemoes fix prototype the vec argument to sigvec is const. tsearch.3 rasmus villemoes fix prototype the rootp argument to tfind is "void * const *", not "const void **". core.5 michael kerrisk core dump files are nowadays core.pid by default locale.5 marko myllynen document mon_grouping and grouping properly michael kerrisk note default value for 'first_workday' michael kerrisk [marko myllynen] add brief descriptions of collating-element and collating-symbol marko myllynen t_fmt_ampm is needed only for locales that employ am/pm convention michael kerrisk [marko myllynen] remove crufty reference to /usr/lib/nls/src that file is nowhere to be found marko myllynen clarify lc_time/am_pm and lc_name keywords usage am_pm should be defined only if am/pm convention is used to signal applications they should not try to print them when using them in unwanted. same for all lc_name keywords expect for name_fmt which should be always defined. marko myllynen clarify lang_term / lang_lib as noted by keld simonsen in the lib-locales@sourceware mailing list: https://sourceware.org/ml/libc-locales/2014-q2/msg00008.html from: keld simonsen to: marko myllynen date: tue, 29 apr 2014 17:02:09 +0200 lang_term reflects iso 639-2/t (terminology) codes, while lang_lib reflects iso 639-2/b (bibliographic) codes. lang_term is preferred over lang_lib codes for locale names. there are 20 specific iso 639-2/b codes. marko myllynen correct the files section proc.5 michael kerrisk 'pid_max' is a system-wide limit on number of threads and processes since pids > /proc/sys/kernel/pid_max are not allocated, this file thus also imposes a system-wide limit on the number of threads and processes. capabilities.7 michael kerrisk cap_sys_admin allows overriding rlimit_nproc michael kerrisk cap_sys_ptrace allows process_vm_readv(2) and process_vm_writev(2) charsets.7 michael kerrisk [marko myllynen] remove crufty statement that romanian may be switching to iso 8859-16 michael kerrisk remove ancient paragraph on charsets supported in glibc 2.3.2 that test is rather ancient, and probably of little use. fanotify.7 heinrich schuchardt fix to example program: fanotify read() should use aligned buffer inotify.7 heinrich schuchardt add example program this example of the usage of the inotify api shows the usage of inotify_init1(2) and inotify_add_watch(2) as well as polling and reading from the inotify file descriptor. heinrich schuchardt munmap() does not generate inotify events locale.7 marko myllynen [michael kerrisk] document the locpath environment variable michael kerrisk add further details on various categories ==================== changes in man-pages-3.69 ==================== released: 2014-06-14, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: cyril hrubis jan chaloupka jeff layton kirill a. shutemov kosaki motohiro marko myllynen michael kerrisk neilbrown peng haitao petr gajdos qian lei rasmus villemoes vasiliy kulikov walter harms yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- iconv.1 marko myllynen [michael kerrisk] new page for the iconv(1) command iconvconfig.8 marko myllynen new page for iconvconfig(8) newly documented interfaces in existing pages --------------------------------------------- fcntl.2 jeff layton, michael kerrisk document open file description locks as provided by the fcntl() operations f_ofd_setlk, f_ofd_setlkw, and f_ofd_getlk changes to individual pages --------------------------- locale.1 marko myllynen add files section, add charmap(5) reference marko myllynen align with recent charmap(5) / repertoiremap(5) changes execve.2 michael kerrisk [neilbrown] before kernel 2.6.0, rlimit_nproc had no effect for set*uid() michael kerrisk [vasiliy kulikov] rlimit_nproc is checked only if preceded by set*uid() michael kerrisk [vasiliy kulikov, neilbrown, kosaki motohiro] document eagain error see also https://bugzilla.kernel.org/show_bug.cgi?id=42704 fcntl.2 michael kerrisk detail the limitations of traditional (process-associated) locks michael kerrisk [jeff layton] describe how to check whether the kernel supports a particular command michael kerrisk errors: add einval for invalid 'cmd' michael kerrisk add para introducing advisory locks and noting existence of ofd locks michael kerrisk [jeff layton] add notes on f_setlkw deadlock detection and its limitations michael kerrisk add an explicit note that mandatory locking is not in posix michael kerrisk rewrite introductory paragraphs on mandatory locking make the structure more logical, and also explicitly mention ofd locks. michael kerrisk [jeff layton] reword discussion of mandatory lock bug a little jeff layton confirmed that the bug remains even in modern kernels. michael kerrisk explain posix background to eacces/eagain error for f_getlk michael kerrisk add notes subhead for record locking and nfs michael kerrisk [neilbrown] note treatment of locks when an nfs client loses contact with the server michael kerrisk [jeff layton] nfsv4leasetime controls the "contact lost" interval for nfsv4 flock.2 michael kerrisk in some modern bsds, fcntl() and flock() locks do interact so, reword and extend the discussion of this topic in notes. michael kerrisk move notes text describing implementation of flock() michael kerrisk [neilbrown] add more details on nfs, including linux 2.6.37 changes also: move notes text describing interaction of fcntl() and flock() locks. fork.2 michael kerrisk add notes on inheritance of flock() and ofd locks across fork() lseek.2 michael kerrisk add reference to open(2) for discussion of file descriptors and ofds open.2 michael kerrisk rework and extend the discussion of open file descriptions open_by_handle_at.2 rasmus villemoes add reference to feature_test_macros(7) recvmmsg.2 rasmus villemoes add reference to feature_test_macros(7) remap_file_pages.2 michael kerrisk [kirill a. shutemov] note that remap_file_pages() is deprecated sendmmsg.2 rasmus villemoes add reference to feature_test_macros(7) seteuid.2 michael kerrisk seteuid() and setegid() are implemented as library functions michael kerrisk error checking should always be performed, even when caller is uid 0 setresuid.2 michael kerrisk document eagain error that can occur after kernel alloc_uid() failure michael kerrisk since linux 3.1, the eagain case for rlimit_nproc no longer occurs michael kerrisk correct the description of the eagain error michael kerrisk error checking should always be performed, even when caller is uid 0 setreuid.2 michael kerrisk document eagain error that can occur after kernel alloc_uid() failure michael kerrisk error checking should always be performed, even when caller is uid 0 michael kerrisk add eagain error for hitting rlimit_nproc limit michael kerrisk since linux 3.1, the eagain case for rlimit_nproc no longer occurs setuid.2 michael kerrisk document eagain error that can occur after kernel alloc_uid() failure michael kerrisk correct the description of the eagain error michael kerrisk error checking should always be performed, even when caller is uid 0 michael kerrisk since linux 3.1, the eagain case for rlimit_nproc no longer occurs statfs.2 cyril hrubis update magic constants most of the updates are taken from /usr/include/linux/magic.h, some were found by grepping the linux source code. cyril hrubis [michael kerrisk] fstatfs(2) was broken on file descriptors from pipe(2) syscalls.2 michael kerrisk note that remap_file_pages() is deprecated basename.3 peng haitao attributes: note functions that are thread-safe the functions basename() and dirname() are thread safe. catgets.3 peng haitao attributes: note function that is thread-safe the function catgets() is thread safe. getdate.3 rasmus villemoes use blank definition of _gnu_source in example program getdirentries.3 peng haitao attributes: note function that is thread-safe the function getdirentries() is thread safe. getdtablesize.3 peng haitao attributes: note function that is thread-safe the function getdtablesize() is thread safe. iconv.3 qian lei [peng haitao] attributes: note function that is thread-safe the function iconv() is thread safe. michael kerrisk see also: add iconvconfig(8) lockf.3 qian lei [peng haitao] attributes: note function that is thread-safe the function lockf() is thread safe. malloc_get_state.3 rasmus villemoes synopsis: use correct header the nonstandard functions malloc_set_state() and malloc_get_state() are provided by not . malloc_usable_size.3 qian lei attributes: note function that is thread-safe the function malloc_usable_size() is thread safe. matherr.3 qian lei [peng haitao] attributes: note function that is thread-safe the function matherr() is thread safe. mkdtemp.3 peng haitao attributes: note function that is thread-safe the function mkdtemp() is thread safe. mkstemp.3 peng haitao attributes: note functions that are thread-safe the functions mkstemp(), mkostemp(), mkstemps() and mkostemps() are thread safe. mq_close.3 qian lei attributes: note function that is thread-safe the function mq_close() is thread safe. mq_getattr.3 qian lei attributes: note function that is thread-safe the functions mq_getattr() and mq_setattr() are thread safe. mq_open.3 peng haitao attributes: note function that is thread-safe the function mq_open() is thread safe. mq_receive.3 peng haitao attributes: note functions that are thread-safe the functions mq_receive() and mq_timedreceive() are thread safe. mq_send.3 peng haitao attributes: note functions that are thread-safe the functions mq_send() and mq_timedsend() are thread safe. mq_unlink.3 qian lei attributes: note function that is thread-safe the function mq_unlink() is thread safe. posix_fallocate.3 peng haitao attributes: note function that is thread-safe the function posix_fallocate() is thread safe. posix_openpt.3 peng haitao attributes: note function that is thread-safe the function posix_openpt() is thread safe. siginterrupt.3 peng haitao attributes: note function that is not thread-safe the function siginterrupt() is not thread safe. system.3 peng haitao attributes: note function that is thread-safe the function system() is thread safe. charmap.5 marko myllynen update to match current glibc charmap(5) was outdated, bring it to closer to reality by fixing syntax descriptions to match current glibc code and practices, adding missing options, removing obsolete comments and references, and removing now incorrect examples. locale.5 marko myllynen clarify am/pm settings a bit localedef(1) complains if really undefined, should be empty instead. also: add some see also references. marko myllynen document glibc conventions regarding days and week based on existing practice and glibc community wiki page at https://sourceware.org/glibc/wiki/locales proc.5 michael kerrisk [jan chaloupka, walter harms] add a brief description of /proc/fs repertoiremap.5 marko myllynen new page for repertoiremap(5) rather obsolete feature but localedef(1) refers to repertoiremaps. bootparam.7 petr gajdos describe 'rootflags' and 'rootdelay' kernel parameters patch based on text from documentation/kernel-parameters.txt charsets.7 marko myllynen update to reflect past developments rewrite the introduction to make unicode's prominence more obvious. reformulate parts of the text to reflect current unicode world. minor clarification for ascii/iso sections, some other minor fixes. marko myllynen list cjk encodings in the order of c, j, k environ.7 michael kerrisk see also: add env(1), printenv(1), ld.so(8) locale.7 marko myllynen add some see also references man-pages.7 michael kerrisk note that .th 'date' field is nowadays automatically updated by scripts signal.7 michael kerrisk describe eintr semantics for recvmmsg(2) michael kerrisk clarify text describing eintr semantics for socket interfaces unicode.7 marko myllynen update to reflect past developments the unicode(7) page will look more modern with few small changes: - drop old bugs section, editors cope with utf-8 ok these days, and perhaps the state-of-the-art is better described elsewhere anyway than in a man page - drop old suggestion about avoiding combined characters - refer to lanana for linux zone, add registry file reference - drop a reference to an inactive/dead mailing list - update some reference urls utf-8.7 marko myllynen drop an old comment about utf-8 replacing iso 8859 and add locale(1) under see also. ==================== changes in man-pages-3.70 ==================== released: 2014-07-08, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: carlos o'donell elie de brauwer florian weimer heinrich schuchardt marko myllynen michael kerrisk nadav har'el neilbrown rich felker robert p. j. day simon paillard tomi salminen walter harms yuri kozlov кирилл apologies if i missed anyone! new and rewritten pages ----------------------- sprof.1 michael kerrisk [marko myllynen] new page for the glibc sprof(1) command newly documented interfaces in existing pages --------------------------------------------- epoll_ctl.2 neilbrown document epollwakeup epoll.7 neilbrown document epollwakeup changes to individual pages --------------------------- iconv.1 iconvconfig.8 marko myllynen clarify gconv file terminology a bit ldd.1 michael kerrisk see also: add sprof(1) connect.2 michael kerrisk errors: add eprototype see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=708394 dup.2 michael kerrisk [rich felker] fix erroneous discussion regarding closing 'newfd' before calling dup2() and propose a workaround if the caller cares about catching close() time errors. see http://stackoverflow.com/questions/23440216/race-condition-when-using-dup2#comment36888604_23444465 and http://austingroupbugs.net/view.php?id=411 michael kerrisk rework and enhance discussion of dup2() in particular, note that dup2() performs the steps of closing and reusing 'newfd' atomically. michael kerrisk add subhead for dup3() epoll_ctl.2 michael kerrisk bugs: epollwakeup is silently ignored without cap_block_suspend if the caller does not have cap_block_suspend, then epollwakeup is silently ignored. fcntl.2 michael kerrisk [tomi salminen] the return value for f_setpipe_sz is the pipe capacity michael kerrisk errors: document enotdir error for f_notify michael kerrisk use proper page cross-references in f_notify discussion michael kerrisk suggest the use of real-time signals with f_notify getitimer.2 michael kerrisk rewrite a few pieces to clarify some details inotify_add_watch.2 michael kerrisk clarify that the target of a watch is an i-node the target of a watch is an i-node, not a pathname. clarify the text to prevent the reader possibly misunderstanding that establishing watches by two different links to the same file might create different watch descriptors. open.2 michael kerrisk [кирилл] o_cloexec is also one the flags not ignored when o_path is specified pipe.2 elie de brauwer pipe_buf is defined in limits.h to make use of pipe_buf in an application one should include . adding a reference to this inclusion. poll.2 michael kerrisk [nadav har'el] the negate-fd-to-ignore technique does not work for file descriptor 0 see https://bugzilla.kernel.org/show_bug.cgi?id=79411 set_tid_address.2 michael kerrisk [rich felker] use "thread" rather than "process" in description michael kerrisk see also: add gettid(2) shmop.2 michael kerrisk explain shmlba in much more detail splice.2 michael kerrisk document eagain error see https://bugzilla.kernel.org/show_bug.cgi?id=48641 syscalls.2 carlos o'donell add prlimit64(2) while trying to reconcile the new features in glibc with the documented entries in the linux kernel man pages i noticed that glibc exports prlimit64 for use by 32-bit applications (as does the linux kernel), but that prlimit64 was not defined in the syscalls list or in the prlimit-related page. this is not the complete fix for this, but i don't have the time to explain why and when prlimit64 should be used (or how it should be used safely). therefore i'm just patching the syscalls.2 list to show that prlimit64 exists and was added in 2.6.36 (verified with git by checking out the tags before and after). syslog.2 michael kerrisk rework introductory paragraph michael kerrisk [robert p. j. day] rework text describing loglevels the kernel header file mentioned in the discussion of the kern_* constants has morphed and is no longer exported inside glibc. and the definitions of the constants themselves changed subtly with kernel commit 04d2c8c83d0e3ac5f78aeede51babb3236200112. so, rewrite the description of the constants to be a bit more abstract. michael kerrisk rewrite parts of the page, and import /proc/sys/kernel/printk * move /proc/sys/kernel/printk from proc(5) to this page, and correct various details in the discussion of that file. * rewrite and correct various other details on the page. * clean out some crufty text. * miscellaneous minor fixes. michael kerrisk update syslog_action_console_off + syslog_action_console_on description details changed in linux 2.6.32 tee.2 michael kerrisk document eagain error see https://bugzilla.kernel.org/show_bug.cgi?id=48641 vmsplice.2 michael kerrisk document eagain error see https://bugzilla.kernel.org/show_bug.cgi?id=48641 ether_aton.3 michael kerrisk make description of ether_line() bug a little more informative mallopt.3 michael kerrisk [florian weimer] malloc_mmap_threshold_ and malloc_mmap_max_ *do* work in setgid programs my testing on this point was bogus, overlooking details of strace(1)'s behavior with setuid programs. see https://sourceware.org/bugzilla/show_bug.cgi?id=12155 printf.3 michael kerrisk [rich felker] remove libc4 and libc5 details rich felker noted that "scare text" in the man page warned about the use of snprintf() on libc, and that some people had cited this as a reason not to use snprintf(). linux libc is now ancient history, so there is no real need to keep that text. but, while we're at it, we may as well clear out all of the other ancient libc4 and libc5 pieces in the page. they are nowadays more clutter than help. michael kerrisk susv3 and later agree with c99 for the snprintf() return value determined by inspection of the susv3 and susv4 specifications. michael kerrisk remove some old text about glibc 2.0 changes we probably don't now need such ancient info. michael kerrisk update references to standards for c and s conversion specifiers profil.3 michael kerrisk see also: add sprof(1) charmap.5 marko myllynen various minor updates and improvements - more precise title - extend description a bit - document previously omitted width_default marko myllynen remove accidental iso c compliance reference glibc refers in locale/programs/charmap.c to iso c 99 section 7.17.(2) and iso c 99 section 5.2.1.(3) that if a character map is not ascii compatible then the locale using it is not iso c compliant. this does not state anything about the character set itself. proc.5 michael kerrisk replace /proc/sys/kernel/printk discussion with reference to syslog(2) it makes more sense to have the /proc/sys/kernel/printk with the related material in syslog(2). michael kerrisk rewrite /proc/sys/kernel/printk description inotify.7 michael kerrisk clarify which events are generated for watched directories really, with respect to watched directories, events fall into three classes (not two, as was shown): * events that can be generated only for the watched directory. * events that can be generated only for objects that are inside the watched directory. * events that can be generated both for the watched directory and for objects inside the directory. so, mark these three classes more clearly in the list of inotify events. heinrich schuchardt [michael kerrisk] bugs: note possible bug triggered by watch descriptor reuse watch descriptor ids are returned by inotify_add_watch(). when calling inotify_rm_watch() an in_ignored is placed on the inotify queue pointing to the id of the removed watch. inotify_add_watch() should not return a watch descriptor id for which events are still on the queue but should return an unused id. unfortunately, the existing kernel code does not provide such a guarantee. actually, in rare cases watch descriptor ids are returned by inotify_add_watch() for which events are still on the inotify queue. see https://bugzilla.kernel.org/show_bug.cgi?id=77111 michael kerrisk add further detail to the watch descriptor reuse bug as well as inotify_rm_watch(), file deletion and unmounting a filesystem can also cause a watch descriptor to be deleted. michael kerrisk the watch descriptor reuse bug may be hard to hit in practice explain the circumstances in detail, indicating that the bug may be very unlikely to occur in practice. michael kerrisk clarify description of in_excl_unlink clarify the text a little, in particular making it clearer that the target of a watch is an i-node (not a pathname). michael kerrisk clarify in_oneshot explanation make it clearer that the target of monitoring is an i-node, not a pathname. michael kerrisk make comment on 'mask' field more accurate libc.7 michael kerrisk clarify man-pages policy on documenting c libraries other than glibc michael kerrisk use absolute dates in discussion of libc vs glibc pipe.7 elie de brauwer add reference that the pipe capacity can be changed in fcntl(2) f_setpipe_sz, f_getpipe_sz and /proc/sys/fs/pipe-max-size are defined, however pipe(7) still defines the pipe capacity as being a static entity. adding a reference to fcntl(2). michael kerrisk [walter harms] clarify that since 2.6.35, 65535 bytes is the default pipe capacity ld.so.8 michael kerrisk clarify that ld_profile can specify just a single shared object michael kerrisk clarify that ld_profile output is appended to target file the ld_profile output is appended to any existing contents of the target file. michael kerrisk see also: add sprof(1) ==================== changes in man-pages-3.71 ==================== released: 2014-08-17, chicago contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adrian bunk damir nedzibovic david prévot d. barbier jakub wilk jan chaloupka marko myllynen michael kerrisk mike frysinger neilbrown paul jackson peng haitao rahul bedarkar rob landley ryan hammonds simon paillard ville ylenius vince weaver yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- group_member.3 michael kerrisk new page documenting group_member(3) isfdtype.3 michael kerrisk new page documenting isfdtype(3) newly documented interfaces in existing pages --------------------------------------------- perf_event_open.2 vince weaver document new comm_exec flag linux 3.16 (more specifically, commit 82b897782d10fcc4 ) added support for differentiating between process renames caused by exec versus those caused by other methods. vince weaver document new mmap2 record type linux 3.16 (more specifically, commit a5a5ba72843dd05f9 ) enabled the enhanced mmap2 record support. the interface was added in linux 3.12 but disabled until linux 3.16. vince weaver document perf_sample_branch_cond linux 3.16 (more specifically, commit bac52139f0b7ab31330 ) adds support for gathering perf_sample_branch_cond conditional branch values when doing perf_sample_branch_stack sampling. proc.5 michael kerrisk document /proc/pid/comm michael kerrisk document /proc/pid/pagemap michael kerrisk document /proc/pid/personality michael kerrisk document /proc/pid/syscall michael kerrisk document /proc/kpagecount michael kerrisk document /proc/kpageflags michael kerrisk document /proc/sys/vm/overcommit_kbytes capabilities.7 michael kerrisk add cap_audit_read cap_audit_read is new in linux 3.16. global changes -------------- ldd.1 clone.2 execve.2 getpagesize.2 ioperm.2 msgop.2 readv.2 recv.2 select.2 send.2 seteuid.2 shmop.2 signal.2 sync.2 sysinfo.2 utime.2 abs.3 atoi.3 catopen.3 clearenv.3 ctime.3 des_crypt.3 ecvt.3 flockfile.3 fseeko.3 ftime.3 ftok.3 ftw.3 getcwd.3 getdtablesize.3 getline.3 getpass.3 getpass.3 getutent.3 glob.3 insque.3 lseek64.3 memmem.3 mkstemp.3 mktemp.3 on_exit.3 openpty.3 putenv.3 putenv.3 qecvt.3 realpath.3 realpath.3 remove.3 setbuf.3 sigpause.3 strftime.3 strptime.3 tzset.3 xcrypt.3 utmp.5 environ.7 ipv6.7 packet.7 michael kerrisk remove ancient linux libc details access.2 brk.2 chmod.2 eventfd.2 gethostname.2 getpriority.2 mmap.2 poll.2 ptrace.2 readv.2 sched_setaffinity.2 select.2 seteuid.2 signalfd.2 sync_file_range.2 timer_create.2 uname.2 wait.2 michael kerrisk notes: add "c library/kernel abi differences" subheading changes to individual pages --------------------------- access.2 michael kerrisk glibc falls back to using access() on kernels that lack faccessat() bdflush.2 fsync.2 sync.2 proc.5 adrian bunk change "sync(1)" to "sync(8)" bind.2 michael kerrisk [ryan hammonds] correct einval error description as pointed out by ryan: my application is trying to bind an ipv4 udp socket to an address. i've found that passing an invalid address length to bind() causes bind to return einval. according to the bind(2) manpage, this should only occur when using unix domain sockets (which i am not). chmod.2 michael kerrisk glibc falls back to chmod() on kernels that don't support fchmodat() michael kerrisk glibc falls back to chown()/lchown() on kernels that lack fchownat() epoll_wait.2 michael kerrisk notes: describe raw epoll_pwait() system call differences getgroups.2 michael kerrisk see also: add group_member(3) getpriority.2 michael kerrisk enhance discussion of kernel nice range versus user-space nice range michael kerrisk move text describing nice range on other systems getrlimit.2 michael kerrisk add cross reference to core(5) in discussion of rlimit_core michael kerrisk describe the "large" resource limit bug on 32-bit platforms see https://bugzilla.kernel.org/show_bug.cgi?id=5042. michael kerrisk glibc's setrlimit() and getrlimit() are implemented using prlimit() kexec_load.2 michael kerrisk note limit of 16 for 'nr_segments' michael kerrisk clarify the 'flags' bits that contain the architecture michael kerrisk add kexec_arch_68k to list of architectures for 'flags' michael kerrisk reword description of 'flags' a little link.2 michael kerrisk glibc falls back to link() on kernels that lack linkat() unless 'flags' contains at_symlink_follow. mkdir.2 michael kerrisk glibc falls back to mkdir() on kernels that don't support mkdirat() perf_event_open.2 vince weaver clarify perf_sample_stack_user usage this clarifies the perf_sample_stack_user section. i found these issue while implementing some code that uses the option. the important change is fixing the name of the sample_stack_user parameter, the rest is just some wording fixes and minor clarifications. vince weaver clarify perf_sample_data_src usage when checking the fields in the perf_sample_data_src type samples you need to shift the masks before doing the compare. although the value you are checking (perf_mem_data_src) is specified as a bitfield so this might all fall apart if trying to access the field in a cross-endian way. the power people were working on this issue, not sure if they resolved it. poll.2 michael kerrisk describe fifth argument (sigsetsize) of raw ppoll() system call process_vm_readv.2 michael kerrisk [ville ylenius] fix typo in example program readlink.2 michael kerrisk glibc falls back to readlink() on kernels that lack readlinkat() recv.2 michael kerrisk 'addrlen' should be null (not 0) if we don't need sender address rename.2 michael kerrisk glibc falls back to rename() when the kernel doesn't have renameat() sigwaitinfo.2 michael kerrisk the raw sigtimedwait() system call has a fifth argument symlink.2 michael kerrisk glibc falls back to symlink() on kernels that lack symlinkat() sysinfo.2 michael kerrisk add versions section unlink.2 michael kerrisk glibc falls back to unlink() or rmdir() on kernels that lack unlinkat() atoi.3 michael kerrisk downgrade discussion of atoq() remove most references to atoq() in this page, since this function was present only in linux libc (not glibc). cerf.3 cexp2.3 clog2.3 michael kerrisk update version number on "not yet in glibc" sentence fgetgrent.3 getgrent.3 getgrent_r.3 getgrnam.3 michael kerrisk [rob landley] clarify that 'gr_mem' is a null-terminated array of pointers fseeko.3 michael kerrisk add versions section ftw.3 michael kerrisk add versions section getauxval.3 michael kerrisk document enoent error and add an entry to bugs explaining the ambiguity that was present before the addition of this error. getgrouplist.3 michael kerrisk see also: add group_member(3) getline.3 rahul bedarkar close opened file at end of example program memmem.3 michael kerrisk rewrite text of glibc 2.0 bug printf.3 michael kerrisk [jakub wilk] clarify details of the %n conversion specifier see http://bugs.debian.org/756602 michael kerrisk [jakub wilk] note use of 'j', 'z', and 't' length modifiers for '%n' see http://bugs.debian.org/756602 michael kerrisk update with some susv3 details setbuf.3 michael kerrisk remove ancient linux libc and 4.x bsd details strstr.3 michael kerrisk remove discussion of linux libc bugs linux libc is old enough that we needn't care any longer. strtod.3 michael kerrisk explain nan(n-char-sequence) strtod.3 michael kerrisk see also: add nan(3), nanf(3), nanl(3) updwtmp.3 michael kerrisk replace availability section with note to link logwtmp() using -lutil linux libc details are no longer needed these days. core.5 rahul bedarkar close opened file in example program proc.5 michael kerrisk fix kernel version numbers for /proc/pid/stat fields proc.5 jan chaloupka add missing proc stats fields adding missing proc stats fields from https://www.kernel.org/doc/documentation/filesystems/proc.txt michael kerrisk [simon paillard] remove crufty text under 'timer_stats' michael kerrisk update /proc/pid/stat 'state' field documentation michael kerrisk improve description of /proc/pid/stat fields added in linux 3.3 and 3.5 michael kerrisk refer to getauxval(3) in discussion of /proc/pid/auxv michael kerrisk rework formatting of /proc/pid/stat list make the field numbers more prominent. michael kerrisk note that /proc/pid/cmdline is read-only michael kerrisk rework discussion of commitlimit and /proc/sys/vm/overcommit_memory michael kerrisk improve discussion of /proc/sys/vm/overcommit_ratio charsets.7 david prévot [marko myllynen] tidy up list remove german from main list, to be consistent with earlier removal of dutch and french (in commit a8ed5f7430e0d1). inotify.7 michael kerrisk note that in_only_dir can be used to avoid races michael kerrisk note that insertion of in_moved_from+in_moved_to pair is not atomic michael kerrisk mention use of timeout when reading in_moved_to after in_moved_from man-pages.7 michael kerrisk add description of "c library/kernel abi differences" subsection michael kerrisk rework text describing sections (stylistic improvements) vdso.7 mike frysinger add new i386 vdso symbols in linux 3.15 michael kerrisk note kernel version that exports new i386 symbols (linux 3.15) ==================== changes in man-pages-3.72 ==================== released: 2014-09-07, mountain view contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: christian von roques holger hans peter freyther michael haardt michael kerrisk mike frysinger peter schiffer rusty russell sorin dumitru apologies if i missed anyone! new and rewritten pages ----------------------- memusage.1 peter schiffer, michael kerrisk [jan chaloupka] new page for glibc memusage(1) command memusagestat.1 peter schiffer [jan chaloupka, michael kerrisk] new page for glibc memusagestat(1) command mtrace.1 peter schiffer [jan chaloupka] new page describing the glibc mtrace(1) command changes to individual pages --------------------------- connect.2 michael haardt note that a new socket should be used if connect() fails fcntl.2 michael kerrisk one must define _gnu_source to get the f_ofd_* definitions poll.2, select.2 rusty russell fix erroneous description of "available for write". posix says: "pollout normal data may be written without blocking.". this "may" is misleading, see the posix write page: write requests to a pipe or fifo shall be handled in the same way as a regular file with the following exceptions: ... if the o_nonblock flag is clear, a write request may cause the thread to block, but on normal completion it shall return nbyte. ... when attempting to write to a file descriptor (other than a pipe or fifo) that supports non-blocking writes and cannot accept the data immediately: if the o_nonblock flag is clear, write() shall block the calling thread until the data can be accepted. if the o_nonblock flag is set, write() shall not block the thread. if some data can be written without blocking the thread, write() shall write what it can and return the number of bytes written. otherwise, it shall return -1 and set errno to [eagain]. the net result is that write() of more than 1 byte on a socket, pipe or fifo which is "ready" may block: write() (unlike read!) will attempt to write the entire buffer and only return a short write under exceptional circumstances. indeed, this is the behaviour we see in linux: https://github.com/rustyrussell/ccan/commit/897626152d12d7fd13a8feb36989eb5c8c1f3485 https://plus.google.com/103188246877163594460/posts/bktgtmhdfgz errno.3 michael kerrisk see also: add errno(1) rtnetlink.3 holger hans peter freyther fix parameters for the send() call in the example inotify.7 michael kerrisk in_open and in_close_nowrite can also occur for directories michael kerrisk in_close_write occurs only for files (not monitored directory) michael kerrisk in_modify is generated for files only (not monitored directories) michael kerrisk in_access occurs only for files inside directories in_access does not occur for monitored directory. packet.7 sorin dumitru fix include file it looks like most of the socket options from this man pages are not defined in . they are defined in so we should include that one. ==================== changes in man-pages-3.73 ==================== released: 2014-09-21, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: david prévot eric w. biederman j. bruce fields justin cormack lorenzo beretta michael kerrisk rob landley serge e. hallyn serge hallyn vasily kulikov vincent lefevre vitaly rybnikov yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- namespaces.7 michael kerrisk [eric w. biederman] new page providing overview of linux namespaces pid_namespaces.7 michael kerrisk [eric w. biederman, vasily kulikov, rob landley, serge hallyn] new page describing pid namespaces user_namespaces.7 michael kerrisk [eric w. biederman, andy lutomirski, serge hallyn] new page describing user namespaces. newly documented interfaces in existing pages --------------------------------------------- clone.2 eric w. biederman [michael kerrisk] document clone_newuser for creating a new user namespace setns.2 eric w. biederman, michael kerrisk document the pid, user, and mount namespace support document clone_newpid, clone_newuser, and clone_newns flags. unshare.2 michael kerrisk [eric w. biederman] document clone_newpid michael kerrisk [eric w. biederman] document clone_newuser michael kerrisk document clone_thread, clone_sighand, and clone_vm changes to individual pages --------------------------- clone.2 michael kerrisk move some clone_newnet text to namespaces.7 michael kerrisk move some clone_newuts text 2 to namespaces.7 michael kerrisk move some clone_newipc text to namespaces.7 michael kerrisk reword discussion of clone_newns, removing text also in namespaces(7) michael kerrisk standardize text on clone_new* flags and cap_sys_admin michael kerrisk einval if (clone_newuser|clone_newpid) && (clone_thread|clone_parent) michael kerrisk add more detail on the meaning of clone_sysvsem flock.2 michael kerrisk [j. bruce fields] don't mention "classical bsd" in discussion of fcntl()/flock interaction the noninteraction of flock(2) and fcntl(2) locks does not seem to be classical bsd semantics (at least, checking the 4.4bsd sources suggest that the lock types do interact, although there have been other systems also where fcntl() and flock() locks do not interact). so, fix the text discussing "classical bsd" lock semantics. getunwind.2 michael kerrisk [yuri kozlov] fix description of return value s/size of unwind table/size of the unwind data/ mount.2 eric w. biederman clarify use of 'mountflags' and 'data' for ms_remount reboot.2 michael kerrisk [justin cormack, eric w. biederman] document effect of reboot() inside pid namespaces semop.2 michael kerrisk refer to clone(2) for semantics of clone_sysvsem and semadj lists seteuid.2 setgid.2 setresuid.2 setreuid.2 setuid.2 michael kerrisk einval can occur if uid/gid is not valid in caller's user namespace setns.2 michael kerrisk [eric w. biederman] clarify capabilities required for reassociating with a mount namespace michael kerrisk specify kernel version on each clone_new* flag and remove text on flags from versions. unshare.2 michael kerrisk add an example program michael kerrisk clarify semantics of clone_sysvsem michael kerrisk clone_sysvsem does not require cap_sys_admin michael kerrisk note flags implied by clone_thread and clone_vm clock.3 michael kerrisk [vincent lefevre] the implementation uses clock_gettime() was to improve *accuracy* (the man page text mistakenly used the word "precision".) drand48.3 michael kerrisk [lorenzo beretta] remove crufty text about svid 3 marking drand48() obsolete see http://bugs.debian.org/758293 proc.5 michael kerrisk move /proc/[pid]/mounts text to namespaces.7 michael kerrisk move /proc/[pid]/mountstats text to namespaces.7 capabilities.7 michael kerrisk refer reader to user_namespaces(7) for a discussion of capabilities michael kerrisk document cap_setuid and cap_setgid for user namespace mappings michael kerrisk setns() needs cap_sys_admin in the *target* namespace michael kerrisk since linux 3.8, user namespaces no longer require cap_sys_admin mq_overview.7 michael kerrisk refer to namespaces(7) for info on posix mqs and ipc namespaces svipc.7 michael kerrisk refer to namespaces(7) for info on system v ipc and ipc namespaces ==================== changes in man-pages-3.74 ==================== released: 2014-10-03, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: arto bendiken ben hutchings benjamin herr c. alex north-keys carlos o'donell cyril hrubis davidlohr bueso doug ledford elie de brauwer heinrich schuchardt jonny grant lanchon manfred spraul marko myllynen michael kerrisk shriramana sharma thomas mack wieland hoffmann apologies if i missed anyone! new and rewritten pages ----------------------- pldd.1 michael kerrisk new page for pldd(1) command added to glibc in version 2.15 cp1252.7 marko myllynen new page documenting cp 1252 cp 1252 is probably one of the most used windows code pages so let's add a page for it alongside with the already provided cp 1251 page. table generated from /usr/share/i18n/charmaps/cp1252. newly documented interfaces in existing pages --------------------------------------------- mq_overview.7 michael kerrisk document /proc/sys/fs/mqueue/msgsize_default michael kerrisk document /proc/sys/fs/mqueue/msg_default changes to individual pages --------------------------- ldd.1 michael kerrisk see also: add pldd(1) execve.2 michael kerrisk [c. alex north-keys] remove unneeded ".sh" extension in interpreter script example see https://bugzilla.kernel.org/show_bug.cgi?id=84701 fanotify_init.2 heinrich schuchardt bugs: o_cloexec is ignored michael kerrisk [heinrich schuchardt] the 'event_f_flags' failure to check invalid flags was fixed in 3.15 fanotify_mark.2 michael kerrisk note that various bugs were fixed in linux 3.16 getrlimit.2 michael kerrisk [doug ledford] since linux 3.5, the accounting formula for rlimit_msgqueue has changed open.2 michael kerrisk [shriramana sharma] fix number and formula in description of eoverflow error readlink.2 michael kerrisk [ben hutchings] fix description of readlinkat() with empty 'pathname' michael kerrisk see also: add realpath(3) sched_setattr.2 sched_setscheduler.2 michael kerrisk see also: add chrt(1) shmget.2 manfred spraul [michael kerrisk, davidlohr bueso] update for increase of shmall and shmmax the default values of shmall and shmmax have been increased. syscalls.2 michael kerrisk add 3 new system calls added in linux 3.17 vmsplice.2 cyril hrubis vmsplice() does not fail when nr_segs==0 this nr_segs==0 case is no-op; the call succeeds and no einval error is returned. dlopen.3 michael kerrisk see also: add pldd(1) fseeko.3 michael kerrisk [thomas mack] _file_offset_bits must be defined before including any header file getgrent.3 carlos o'donell add enoent and eagain to error list mq_getattr.3 michael kerrisk add an example program the example program can be used to discover the default 'mq_maxmsg' and 'mq_msgsize' values used to create a queue with a mq_open(3) call in which 'attr' is null. mq_open.3 michael kerrisk two /proc files control the defaults for the attrp==null case refer the reader to the discussion in mq_overview(7) for a discussion of these files, which exist since linux 3.5. realpath.3 michael kerrisk see also: add realpath(1) proc.5 elie de brauwer document /proc/buddyinfo this patch adds a short description about the contents of /proc/buddyinfo and how this file can be used to assist in checking for memory fragmentation issues. michael kerrisk mention pmap(1) in discussion of /proc/pid/smaps armscii-8.7 marko myllynen charset pages unification, minor cleanups ascii.7 marko myllynen charset pages unification, minor cleanups this and [the related *.7] patches will provide unification of charset pages, minor cleanups, and some unifying cosmetic changes. references are adjusted so that all pages include a reference to charsets(7), which contains a description of these sets, stray comments are removed, some obsolete statements (like iso 8859-1 being the de-facto ascii replacement) are removed, and some minor reformatting to minimize diff's between the pages are done. the actual substance, the character tables, remain unchanged. this series changes the following pages (under man7): ascii, armscii, cp1251, koi8-r, koi8-u, and all of iso_8859-*. cp1251.7 marko myllynen charset pages unification, minor cleanups iso_8859-10.7 marko myllynen charset pages unification, minor cleanups iso_8859-11.7 marko myllynen charset pages unification, minor cleanups iso_8859-13.7 marko myllynen charset pages unification, minor cleanups iso_8859-14.7 marko myllynen charset pages unification, minor cleanups iso_8859-15.7 marko myllynen charset pages unification, minor cleanups iso_8859-16.7 marko myllynen charset pages unification, minor cleanups iso_8859-1.7 marko myllynen charset pages unification, minor cleanups iso_8859-2.7 marko myllynen charset pages unification, minor cleanups iso_8859-3.7 marko myllynen charset pages unification, minor cleanups iso_8859-4.7 marko myllynen charset pages unification, minor cleanups iso_8859-5.7 marko myllynen charset pages unification, minor cleanups iso_8859-6.7 marko myllynen charset pages unification, minor cleanups iso_8859-7.7 marko myllynen charset pages unification, minor cleanups iso_8859-8.7 marko myllynen charset pages unification, minor cleanups iso_8859-9.7 marko myllynen charset pages unification, minor cleanups koi8-r.7 marko myllynen charset pages unification, minor cleanups - remove stray comments, streamline description (charsets(7) and wikipedia provide more detailed and up-to-date description) - list differences between koi8-r.7 vs koi8-u.7 koi8-u.7 marko myllynen charset pages unification, minor cleanups - remove stray comments, streamline description (charsets(7) and wikipedia provide more detailed and up-to-date description) - list differences between koi8-r.7 vs koi8-u.7 mq_overview.7 michael kerrisk update queues_max details for linux 3.14 and in general rework the text a little. michael kerrisk update discussion of hard_msgmax the limit has changed in 2.6.33 and then again in 3.5. michael kerrisk [arto bendiken] update details for 'queues_max' limit things changed in linux 3.5. see https://bugs.launchpad.net/bugs/1155695 michael kerrisk update details on defaults and ceiling for 'msgsize_max' limit michael kerrisk rework discussion of hard_msgmax michael kerrisk [davidlohr bueso] various fixes after review from davidlohr bueso sched.7 michael kerrisk see also: add taskset(1) ld.so.8 michael kerrisk see also: add pldd(1) michael kerrisk see also: add dlopen(3) michael kerrisk see also: add ld(1) ==================== changes in man-pages-3.75 ==================== released: 2014-10-15, düsseldorf contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: jonny grant michael kerrisk robert schweikert tetsuo handa walter harms apologies if i missed anyone! new and rewritten pages ----------------------- pthread_rwlockattr_setkind_np.3 robert schweikert [michael kerrisk] new page documenting pthread_rwlockattr_[sg]etkind_np(3) documents pthread_rwlockattr_setkind_np(3) and pthread_rwlockattr_getkind_np(3). new and changed links --------------------- pthread_rwlockattr_getkind_np.3 robert schweikert new link to pthread_rwlockattr_setkind_np(3) changes to individual pages --------------------------- readlink.2 michael kerrisk [jonny grant] add free() call to example program readv.2 michael kerrisk the raw preadv() and pwritev() syscalls split 'offset' into 2 arguments signal.7 michael kerrisk pthread_mutex_lock() and pthread_cond_wait() are restartable pthread_mutex_lock(, pthread_cond_wait(), and related apis are automatically restarted if interrupted by a signal handler. unix.7 michael kerrisk [carlos o'donell, david miller, tetsuo handa] various additions and rewordings notable changes: * clarify some details for pathname sockets. * add some advice on portably coding with pathname sockets. * note the "buggy" behavior for pathname sockets when the supplied pathname is 108 bytes (after a report by tetsuo handa). ==================== changes in man-pages-3.76 ==================== released: 2014-12-31, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam jiang andrea balboni andreas schwab bernhard walle carlos o'donell david wragg florian westphal heinrich schuchardt huxiaoxiang jan chaloupka jonathan wakely jonny grant josh triplett kamezawa hiroyuki laurent georget manuel lópez-ibáñez marko myllynen ma shimiao mel gorman michael gehring michael haardt michael kerrisk mike frysinger rasmus villemoes richard weinberger rich felker scott harvey siddhesh poyarekar simon newton simon paillard sven hoexter tobias werth weijie yang will newton yuri kozlov 刘湃 尹杰 apologies if i missed anyone! new and rewritten pages ----------------------- adjtimex.2 laurent georget add fields in struct timex description this patch updates the man page with the new fields added in struct timex since last edition of the man page. laurent georget [michael kerrisk] document adj_tai michael kerrisk improve description of adj_offset_singleshot michael kerrisk add brief documentation of adj_micro and adj_nano michael kerrisk reformat return value list and remove numeric values, since they're not needed michael kerrisk other 'modes' bits are ignored on adj_offset_* other bits in 'modes' are ignored if modes contains adj_offset_singleshot or adj_offset_ss_read. michael kerrisk add nanosecond details fixes https://bugzilla.kernel.org/show_bug.cgi?id=61171. michael kerrisk document adj_offset_ss_read michael kerrisk reformat 'times' flags as list and remove numeric values, since they're not needed. michael kerrisk note effect of adj_nano for adj_setoffset michael kerrisk add comment noting that timex structure contains padding bytes michael kerrisk add more details to description of 'tai' field michael kerrisk note meaning of "pll" abbreviation michael kerrisk clarify which 'timex' field is used by each 'modes' bit michael kerrisk document timex 'status' bits michael kerrisk clarify treatment of other 'modes' bits for adj_offset_* michael kerrisk update rfc number: rfc 5905 obsoletes rfc 1305 michael kerrisk briefly document adj_setoffset michael kerrisk note pps (pulse per second) fields in timex structure sigreturn.2 michael kerrisk add (a lot) more detail on the signal trampoline and rewrite much of the page. newly documented interfaces in existing pages --------------------------------------------- proc.5 bernhard walle document /proc/thread-self /proc/thread-self has been introduced in linux 3.17 with commit 0097875bd41528922fb3bb5f348c53f17e00e2fd. sven hoexter [michael kerrisk, kamezawa hiroyuki] document "vmswap" field of /proc/[pid]/status florian westphal document /proc/net/netfilter/nfnetlink_queue changes to individual pages --------------------------- localedef.1 marko myllynen mention default path for compiled files clock_nanosleep.2 michael kerrisk note that 'clock_id' can also be a cpu clock id epoll_ctl.2 michael kerrisk regular files and directories can't be monitored with epoll_ctl() ioctl.2 heinrich schuchardt rename 'd' argument to 'fd' in text in most other manpages file descriptors are called 'fd'. this patches renames attribute 'd' to 'fd'. madvise.2 michael kerrisk versions: support for madvise() is now configurable support for this system call now depends on the config_advise_syscalls configuration option. open.2 michael kerrisk enhance rationale discussion for openat() and friends posix_fadvise.2 mel gorman document the behavior of partial page discard requests it is not obvious from the interface that "partial page discard" requests are ignored. it should be spelled out. michael kerrisk [weijie yang] errors: since 2.6.16, the kernel correctly deals with the espipe case michael kerrisk support for fadvise64() is now configurable support for this system call now depends on the config_advise_syscalls configuration option. prctl.2 andreas schwab correct description of null-termination in pr_get_name and pr_set_name the size of the process name has always been at most 16 byte _including_ the null terminator. this also means that the name returned by pr_get_name is always null-terminated. michael kerrisk pr_set_name silently truncates strings that exceed 16 bytes restart_syscall.2 michael kerrisk add some text explaining why restart_syscall() exists sched_setaffinity.2 michael kerrisk notes: add paragraph on how to discover set of cpus available on system michael kerrisk see also: add nproc(1) and lscpu(1) select.2 michael kerrisk see also: add restart_syscall(2) semop.2 michael kerrisk add note that interrupted semtimedop() returns 'timeout' unchanged michael kerrisk remove information about semtimedop() eagain that is repeated elsewhere michael kerrisk add subsection head for semtimedop() setsid.2 michael kerrisk rewrite some pieces and add some details among other changes, add an explanation of why setsid() can't be called from a process group leader sgetmask.2 michael kerrisk since 3.16, support for these system calls is configurable support for these calls is now dependent on the setting of the config_sgetmask_syscall option. sigaction.2 michael kerrisk document sa_restorer michael kerrisk add some detail on the sa_restorer field michael kerrisk see also: add sigreturn(2) splice.2 michael kerrisk reformat description of 'fd_in' and 'off_in' to improve readability syscall.2 michael kerrisk see also: add errno(3) syscalls.2 michael kerrisk see also: add errno(3) michael kerrisk 3.19 adds execveat() michael kerrisk add bpf(2) to list tee.2 michael kerrisk add shell session demonstrating use of the example program tkill.2 michael kerrisk [rich felker] remove bogus text saying tgid==-1 makes tgkill() equivalent to tkill() abort.3 michael kerrisk note that sigabrt is raised as though raise(3) is called also note that abort() is posix.1-2008 compliant. cmsg.3 david wragg ensure buf is suitably aligned in sending example inspection of the definition of cmsg_firsthdr (both in glibc and the suggested definition in rfc3542) shows that it yields the msg_control field. so when sending, the pointer placed in msg_control should be suitably aligned as a struct cmsghdr. in the sending example, buf was declared as a bare char array, and so is not necessarily suitably aligned. the solution here involves placing buf inside a union, and is based on the sockets/scm_rights_send.c sample from the linux programming interface "dist" source code collection. exp10.3 michael kerrisk before glibc 2.19, exp() did not give erange error on underflow http://sources.redhat.com/bugzilla/show_bug.cgi?id=6787 ftw.3 michael kerrisk ftw_chdir has no effect on the 'fpath' argument passed to fn() getopt.3 michael kerrisk [jonny grant] ensure that 'nsecs' is used ilogb.3 michael kerrisk [will newton] since glibc 2.16, ilogb() does correctly diagnose domain errors memcmp.3 michael haardt document return value for n==0 case michael haardt warn against use of memcmp() for comparing security-critical data mq_open.3 michael kerrisk document the o_cloexec flag michael kerrisk place 'flags' constants in alphabetical order pow.3 manuel lópez-ibáñez add note on performance characteristics of pow() pthread_setschedparam.3 simon newton fix logic error in example program the example program will crash if -a is used, since 'attr' is uninitialized. $ ./a.out -a *** error in `./a.out': free(): invalid pointer: 0xb779c3c4 *** aborted (core dumped) 刘湃 small fixes to example program sigvec.3 michael kerrisk starting with version 2.21, glibc no longer exports sigvec() sysconf.3 josh triplett document _sc_ngroups_max already documented in getgroups(2), but not in sysconf(3). termios.3 michael kerrisk see also: add tset(1) tgamma.3 michael kerrisk since glibc 2.18, errno is correctly set to edom when (x == -infinity)) wordexp.3 carlos o'donell make it clear that wrde_nocmd prevents command substitution the use of wrde_nocmd prevents command substitution. if the flag wrde_nocmd is set then no command substitution shall occur and the error wrde_cmdsub will be returned if such substitution is requested when processing the words. the manual page as-is makes it seem like the command substitution occurs, and an error is returned *after* the substitution. this patch clarifies that. locale.5 marko myllynen describe the formats of values locale(5) describes what a locale should define but doesn't spell out how (in what format). the patch attempts to address this, it also has few trivial additional enhancements. * reference to locale(7) for category descriptions. * clarify first_workday in notes a bit. * add upstream bz reference for two missing lc_address fields. marko myllynen fix miscoded character resolv.conf.5 jan chaloupka add missing no-tld-query option based on commit [1], the no-tld-query option exists for resolv.conf configuration file. description of this option is provided in [2]. this patch just copies this option into resolv.conf.5 man page. plus changes 'a' member into 'an' before 'unqualified name as if it ...' on the third line of [2]. based on [3], this option was added in glibc 2.14 as solving [4] bug. [1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=f87dfb1f11c01f2ccdc40d81e134cd06b32e28e8 [2] http://www.daemon-systems.org/man/resolv.conf.5.html man page. [3] https://sourceware.org/git/?p=glibc.git;a=blob;f=news;h=952f32af17e7fb49c4c1a305de673a13075bfaf5;hb=f87dfb1f11c01f2ccdc40d81e134cd06b32e28e8 [4] https://sourceware.org/bugzilla/show_bug.cgi?id=12734 credentials.7 josh triplett cross-reference getgroups(2) since credentials.7 discusses supplementary gids, it should reference getgroups(2). fanotify.7 heinrich schuchardt allow relative paths in example the current example code requires passing an absolute path to the mount to be watched. by passing at_fdcwd to fanotify_mark it can use both absolute and relative paths. heinrich schuchardt fallocate(2) creates no events fallocate(2) should create fan_modify events but does not. heinrich schuchardt [michael kerrisk] fanotify notifies only events generated on the same mount unfortunately, fanotify does not inform listeners for all paths under which a touched filesystem object is visible, but only the listener using the same path as the process touching the filesystem object. heinrich schuchardt update bugs to note bugs still not fixed in 3.17 i bumped the linux version number in the bugs section to 3.17. inotify.7 heinrich schuchardt fallocate(2) does not trigger inotify events calling fallocate(2) does not result in inotify events. locale.7 marko myllynen improve locpath description locpath is ignored by privileged programs. add locale archive references. add files section. man-pages.7 michael kerrisk [laurent georget] clarify that see also entries may refer to pages from other projects signal.7 michael kerrisk mention other "slow devices" reads from eventfd(2), signalfd(2), timerfd(2), inotify(7), and fanotify(7) file descriptors are also slow operations that are restartable. michael kerrisk fix so_recvtimeo/ so_sendtimeo confusion in text michael kerrisk since linux 3.8, reads on inotify(7) file descriptors are restartable michael kerrisk inotify(7) reads no longer show the odd eintr error after sigcont since kernel 3.7, reads from inotify(7) file descriptors no longer show the (linux oddity) behavior of failing with eintr when the process resumes after a stop signal + sigcont. michael kerrisk see also: add sigreturn(2) unix.7 michael kerrisk [scott harvey] fix buglet in code snippet in bugs section ld.so.8 carlos o'donell add --inhibit-cache option the dynamic loader has 6 options, only 5 are documented. this patch documents the sixth option i.e. `--inhibit-cache`. jonathan wakely [siddhesh poyarekar] correct documentation of $origin as noted by siddhesh: the ld.so man page says: $origin (or equivalently ${origin}) this expands to the directory containing the application executable. thus, an application located in somedir/app could be compiled with this is incorrect since it expands to the directory containing the dso and not the application executable. this seems like deliberate behaviour in dl-object.c, so it needs to be fixed in the man page. see http://stackoverflow.com/questions/26280738/what-is-the-equivalent-of-loader-path-for-rpath-specification-on-linux/26281226#26281226 ==================== changes in man-pages-3.77 ==================== released: 2015-01-10, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: akihiro motoki alexandre bique andre majorel andy lutomirski daniel borkmann dave hansen elie de brauwer heinrich schuchardt ignat loskutov jeff epler jérôme pouiller kees cook laurent georget masanari iida michael haardt michael kerrisk mike frysinger richard cochran stephan mueller troy davis vince weaver will drewry apologies if i missed anyone! new and rewritten pages ----------------------- seccomp.2 kees cook, michael kerrisk, will drewry [andy lutomirski] new page documenting seccomp(2) combines documentation from prctl, in-kernel seccomp_filter.txt and dropper.c, along with details specific to the new system call. newly documented interfaces in existing pages --------------------------------------------- netlink.7 stephan mueller [michael kerrisk] add netlink_crypto changes to individual pages --------------------------- adjtimex.2 laurent georget [richard cochran, jeff epler] clarify the 'ppm scaling' used in struct timex this patch makes explicit and clarifies the unit used for the fields "freq", "ppsfreq" and "stabil" in struct timex. michael kerrisk [masanari iida] note that time_error is the modern synonym for time_bad perf_event_open.2 vince weaver clarify the perf_flag_fd_* flags this change clarifies the behavior of the perf_flag_fd_output and perf_flag_fd_no_group flags to perf_event_open(), and removes the related fixme comments. while writing tests to validate the behavior of these flags i discovered that perf_flag_fd_output has been broken since the 2.6.35 kernel release. prctl.2 dave hansen [michael kerrisk] add description of intel mpx calls the 3.19 kernel will have support for intel mpx, including a pair of new prctl() calls (pr_mpx_enable_management and pr_mpx_disable_management) for enabling and disabling the kernel's management of the "bounds tables". add a descriptions of the interface. michael kerrisk add mention of seccomp(2) under pr_set_seccomp michael kerrisk suggest /proc/pid/status "seccomp" as alternative to pr_get_seccomp michael kerrisk sigkill can also occur pr_get_seccomp in seccomp_mode_filter mode kees cook [andy lutomirski] document seccomp_mode_filter vs efault this notes the distinction made between einval and efault when attempting to use seccomp_mode_filter with pr_set_seccomp. setns.2 pid_namespaces.7 mike frysinger elaborate discussion of the pid namespace descendant limitation the setns(2) man page already mentions that clone_newpid may only be used with descendant namespaces, but this nuance could be listed in a few more places so it is not missed. shmget.2 michael kerrisk [akihiro motoki] make wording of shmall description a little clearer sigaction.2 michael kerrisk add siginfo_t fields for seccomp_ret_trap memchr.3 strstr.3 alexandre bique reference memmem(3) in see also section memcmp.3 michael kerrisk [michael haardt] notes: add some detail on avoiding memcmp() of cryptographic data wording largely based on comments from michael haardt. pthread_tryjoin_np.3 jérôme pouiller [michael kerrisk] document einval error for pthread_timedjoin_np() mem.4 elie de brauwer /dev/kmem depends on config_devkmem elie de brauwer correct /dev/port group in example mem.4 mentions that group for /dev/port should be set to 'mem' however, all other files (/dev/mem and /dev/kmem) use the kmem group in their examples and on my system /dev/port belongs to kmem. hence the 'mem' group was probably a typo: elie de brauwer add config_strict_devmem since 2.6.26 the config_nonpromisc_devmem options limits the physical addresses which can be accessed through /dev/mem. random.4 heinrich schuchardt describe handling of o_nonblock /dev/random and /dev/urandom treat o_nonblock differently. this should be described in the manpage. heinrich schuchardt mention prng used by urandom /dev/urandom uses a pseudo-random number generator to replace missing entropy. proc.5 michael kerrisk document "seccomp" field of /proc/pid/status epoll.7 michael kerrisk [ignat loskutov] use epoll_create1() rather than epoll_create() in the code example epoll_create1() is more or less the preferred api for new applications, since it allows for some flags and avoids the misdesigned epoll_create() argument, and so it seems sensible to use that in the example, rather than epoll_create(). tcp.7 troy davis clarify tcp_tw_recycle on internet-facing hosts clarify that tcp_tw_recycle will break communication with many general-purpose remote internet hosts (namely, remote nat devices) even when the linux device itself is not behind nat. ==================== changes in man-pages-3.78 ==================== released: 2015-01-22, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: akihiro motoki alexey ishchuk carlos o'donell christian seiler daniel j blueman david drysdale david herrmann elie de brauwer elliot hughes jessica mckellar kees cook michael hayes michael kerrisk rich felker vince weaver apologies if i missed anyone! new and rewritten pages ----------------------- execveat.2 david drysdale, michael kerrisk [rich felker] new page for execveat(2) memfd_create.2 michael kerrisk, david herrmann new page for memfd_create() system call including notes about file sealing s390_pci_mmio_write.2 alexey ishchuk new page for s390 s390_pci_mmio_write() and s390_pci_mmio_read() new manual page for the new pci mmio memory access system calls, s390_pci_mmio_write() and s390_pci_mmio_read(), added for the s390 platform. newly documented interfaces in existing pages --------------------------------------------- fcntl.2 david herrmann [michael kerrisk] document f_add_seals and f_get_seals commands proc.5 elie de brauwer document /proc/sys/vm/compact_memory michael kerrisk document /proc/sys/fs/nr_open new and changed links --------------------- s390_pci_mmio_read.2 michael kerrisk new link to new s390_pci_mmio_write(2) page changes to individual pages --------------------------- dup.2 michael kerrisk add reference to rlimit_nofile for emfile error michael kerrisk add reference to rlimit_nofile for ebadf error on 'newfd'. execve.2 fexecve.3 michael kerrisk see also: add execveat(2) fallocate.2 mmap.2 open.2 truncate.2 write.2 michael kerrisk errors: add eperm for operation denied by file seal fcntl.2 michael kerrisk errors: add ebusy case for f_setpipe_sz michael kerrisk add reference to rlimit_nofile for f_dupfd einval error on 'arg'. michael kerrisk errors: add open file description lock error cases getrlimit.2 michael kerrisk update text on rlimit_nofile ceiling to refer to /proc/sys/fs/file-max mbind.2 michael kerrisk [daniel j blueman] clarify efault text mmap.2 shmget.2 shm_open.3 michael kerrisk see also: add memfd_create(2) open.2 michael kerrisk refer to rlimit_nofile for explanation of emfile error michael kerrisk add execveat(2) in system call list under "rationale for openat()" perf_event_open.2 vince weaver clarify description of overflow events update the perf_event_open manpage to be more consistent when discussing overflow events. it merges the discussion of poll-type notifications with those generated by sigio signal handlers. this addresses the remaining fixmes is the document. vince weaver remove inaccurate paragraph describing attr.config remove an inaccurate paragraph about values in the attr.config field. this information was never true in any released kernel; it somehow snuck into the manpage because it is still described this way in tools/perf/design.txt in the kernel source tree. michael kerrisk correct the kernel version number for perf_count_hw_cache_node michael kerrisk add some kernel version numbers to various fields and constants ptrace.2 sigaction.2 seccomp.2 kees cook ptrace and siginfo details while writing some additional seccomp tests, i realized ptrace_event_seccomp wasn't documented yet. fixed this, and added additional notes related to ptrace events sigtrap details. readv.2 michael kerrisk update details on glibc readv()/writev() wrapper behavior and add a historical detail about linux 2.0. select.2 michael kerrisk mention rlimit_nofile as a possible cause of einval error syscall.2 kees cook add arm64 and mips add mips and arm64 to tables, along with some further details on these architectures, syscalls.2 michael kerrisk add s390_pci_mmio_read(2) and s390_pci_mmio_write(2) michael kerrisk note kernel() version that introduced get_kernel_syms() note kernel version that introduced ppc_rtas() note kernel version that introduced create_module() note kernel version that added setup() michael kerrisk remove some details for sync_file_range2() make the table a bit simpler. the details can anyway be found in the system call man page. utimensat.2 michael kerrisk [elliot hughes] if both tv_sec fields are utime_omit, the file need not exist as noted by elliot, if both tv_sec fields are utime_omit, utimensat() will return success even if the file does not exist. errno.3 michael kerrisk the rlimit_nofile resource limit is a common cause of emfile exec.3 michael kerrisk see also: add execveat(2) fclose.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument harmonize all the manual pages to use "stream" for file* instead of randomly using "fp" or "stream." choosing something and being consistent helps users scan the man pages quickly and understand what they are looking at. fexecve.3 michael kerrisk rewrite the script+close-on-exec problem as a bug also, add one or two details about this scenario. michael kerrisk the natural idiom when using fexecve() is to use the close-on-exec flag fmemopen.3 michael kerrisk consistency fix: use "stream" as name for "file *" argument fopencookie.3 michael kerrisk consistency fix: use "stream" as name for "file *" argument getgrent_r.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument getline.3 michael kerrisk consistency fix: use "stream" as name for "file *" argument getmntent.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument getpw.3 michael kerrisk [carlos o'donell] describe return value when 'uid' is not found getpwent_r.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument getspnam.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument malloc_info.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument posix_fallocate.3 michael kerrisk note that posix_fallocate() is implemented using fallocate(2) putgrent.3 carlos o'donell consistency fix: use "stream" as name for "file *" argument harmonize all the manual pages to use "stream" for file* instead of randomly using "fp" or "stream." choosing something and being consistent helps users scan the man pages quickly and understand what they are looking at. locale.5 akihiro motoki correct variable name proc.5 michael kerrisk remove bogus statement about nr_open being a ceiling for file-max ==================== changes in man-pages-3.79 ==================== released: 2015-02-01, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: akihiro motoki heinrich schuchardt j william piggott masanari iida michael kerrisk scot doyle sergey v. zubkov stephan mueller vince weaver vivek goyal apologies if i missed anyone! new and rewritten pages ----------------------- getrandom.2 heinrich schuchardt, theodore t'so, michael kerrisk new page documenting getrandom(2) kernel 3.17 introduces a new system call getrandom(2). kexec_load.2 vivek goyal, michael kerrisk add documentation of kexec_file_load(2) michael kerrisk, vivek goyal rewrite and extend documentation of kexec_load(). new and changed links --------------------- kexec_file_load.2 michael kerrisk new link to kexec_load.2 changes to individual pages --------------------------- personality.2 michael kerrisk see also: add setarch(8) prctl.2 michael kerrisk unused arguments of pr_mpx_(en,dis}able_management must be zero reboot.2 michael kerrisk see also: add kexec_load(2) socket.2 stephan mueller document af_alg add a reference to the af_alg protocol accessible via socket(2). fflush.3 michael kerrisk [sergey v. zubkov] clarify that flushing of input streams occurs only for seekable files see https://bugzilla.kernel.org/show_bug.cgi?id=91931 michael kerrisk [sergey v. zubkov] posix.1-2008 specifies the behavior when flushing input streams posix.1-2001 did not have a specification for input streams, but posix.1-2008 added one. getopt.3 michael kerrisk see also: add getopt(1) random.3 heinrich schuchardt see also: add getrandom(2) termios.3 michael kerrisk see also: add reset(1), setterm(1), tput(1) tzset.3 j william piggott document behavior when tz filespec omits the colon if the tz filespec omits the leading colon, glibc will parse it for any valid format, i.e., it will still work. j william piggott add description for posixrules file j william piggott correct system timezone file path j william piggott there are only two tz formats tzset(3) currently states that there are three tz formats. the first two it lists are actually variations of the posix-style tz format, of which there are at least five variations. this patch corrects this to match the posix specification of tz having only two formats. j william piggott filespec omitted incorrect paragraph three of the description section says that when tz is set, but empty, then utc is used. later it says if the tz filespec is omitted then the file /usr/share/zoneinfo/localtime is used. this is incorrect, it will use utc in that case as well. j william piggott fix incorrect tz string representation the tz string representation indicates that the start/end rules are required; this is incorrect. j william piggott add environment section + other rearrangements files section was overly verbose and included environment variables. added environment section, removing env vars from the files section. random.4 heinrich schuchardt see also: add getrandom(2) passwd.5 michael kerrisk see also: add chfn(1), chsh(1) capabilities.7 michael kerrisk see also: add setpriv(1) signal.7 michael kerrisk add getrandom(2) to list of restartable system calls michael kerrisk add f_ofd_setlkw to list of restartable operations ==================== changes in man-pages-3.80 ==================== released: 2015-02-21, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: akihiro motoki andy lutomirski bill mcconnaughey chris mayo christophe blaess david wilson denys vlasenko doug goldstein eric wong heinrich schuchardt j william piggott james hunt jan chaloupka jan stancek jeff layton jens thoms toerring kevin easton luke faraone mark seaborn mathieu malaterre michael kerrisk michal hocko minchan kim patrick horgan peng haitao ralf baechle rob somers simon paillard stephen smalley tao ma tobias herzke vince weaver vlastimil babka zbigniew brzeziński apologies if i missed anyone! new and rewritten pages ----------------------- ioctl_fat.2 heinrich schuchardt [michael kerrisk] new man page for the ioctl(2) fat api the ioctl(2) system call may be used to retrieve information about the fat file system and to set file attributes. madvise.2 michael kerrisk summary: this page has been significantly reorganised and rewritten michael kerrisk recast discussion of 'advice' into two groups of values madvise() is one of those system calls that has congealed over time, as has the man page. it's helpful to split the discussion of 'advice' into those flags into two groups: * those flags that are (1) widespread across implementations; (2) have counterparts in posix_madvise(3); and (3) were present in the initial linux madvise implementation. * the rest, which are values that (1) may not have counterparts in other implementations; (2) have no counterparts in posix_madvise(3); and (3) were added to linux in more recent times. michael kerrisk explicitly list the five flags provided by posix_fadvise() over time, bit rot has afflicted this page. since the original text was written many new linux-specific flags have been added. so, now it's better to explicitly list the flags that correspond to the posix analog of madvise(). jan chaloupka [hugh dickins, michael kerrisk] starting with linux 3.5, more file systems support madv_remove michael kerrisk split einval error into separate cases michael kerrisk explain madv_remove in terms of file hole punching michael kerrisk madv_remove can be applied only to shared writable mappings michael kerrisk madv_remove cannot be applied to locked or huge tlb pages michael kerrisk [vlastimil babka] clarify that madv_dontneed has effect on pages only if it succeeds michael kerrisk [vlastimil babka] clarifications for madv_dontneed michael kerrisk [michal hocko] improve madv_dontneed description michael kerrisk madv_dontneed cannot be applied to huge tlb or locked pages michael kerrisk [vlastimil babka] remove mention of "shared pages" as a cause of einval for madv_dontneed michael kerrisk [vlastimil babka] note huge tlb as a cause of einval for madv_dontneed michael kerrisk [minchan kim] add mention of vm_pfnmap in discussion of madv_dontneed and madv_remove michael kerrisk drop sentence saying that kernel may ignore 'advice' the sentence creates misunderstandings, and does not really add information. michael kerrisk note that some linux-specific 'advice' change memory-access semantics michael kerrisk notes: remove crufty text about "command" versus "advice" the point made in this fairly ancient text is more or less evident from the description, and it's not clear what "standard" is being referred to. michael kerrisk mention posix.1-2008 addition of posix_madv_noreuse michael kerrisk remove "posix.1b" from conforming to michael kerrisk move mention of posix_fadvise() from conforming to to see also michael kerrisk errors: add eperm error case for madv_hwpoison michael kerrisk note that madvise() is nonstandard, but widespread newly documented interfaces in existing pages --------------------------------------------- proc.5 michael kerrisk (briefly) document /proc/pid/attr/socketcreate michael kerrisk (briefly) document /proc/pid/attr/keycreate michael kerrisk [stephen smalley] document /proc/pid/attr/{current,exec,fscreate,prev} heavily based on stephen smalley's text in https://lwn.net/articles/28222/ from: stephen smalley to: lkml and others subject: [rfc][patch] process attribute api for security modules date: 08 apr 2003 16:17:52 -0400 michael kerrisk document /proc/sys/kernel/auto_msgmni socket.7 david wilson [michael kerrisk] document so_reuseport socket option new and changed links --------------------- get_thread_area.2 andy lutomirski make get_thread_area.2 a link to rewritten set_thread_area.2 page changes to individual pages --------------------------- time.1 michael kerrisk make option argument formatting consistent with other pages access.2 denys vlasenko explain how access() check treats capabilities we have users who are terribly confused why their binaries with cap_dac_override capability see eaccess from access() calls, but are able to read the file. the reason is access() isn't the "can i read/write/execute this file?" question, it is the "(assuming that i'm a setuid binary,) can *the user who invoked me* read/write/execute this file?" question. that's why it uses real uids as documented, and why it ignores capabilities when capability-endorsed binaries are run by non-root (this patch adds this information). to make users more likely to notice this less-known detail, the patch expands the explanation with rationale for this logic into a separate paragraph. arch_prctl.2 set_thread_area.2 get_thread_area.2 andy lutomirski improve tls documentation the documentation for set_thread_area was very vague. this improves it, accounts for recent kernel changes, and merges it with get_thread_area.2. get_thread_area.2 now becomes a link. while i'm at it, clarify the related arch_prctl.2 man page. cacheflush.2 ralf baechle update some portability details and bugs michael kerrisk refer reader to bugs in discussion of einval error capget.2 michael kerrisk document v3 capabilities constants michael kerrisk rewrite discussion of kernel versions that support file capabilities file capabilities ceased to be optional in linux 2.6.33. clone.2 peng haitao fix description of clone_parent_settid clone_parent_settid only stores child thread id in parent memory. clone.2 execve.2 kevin easton document interaction of execve(2) with clone_files this patch the fact that a successful execve(2) in a process that is sharing a file descriptor table results in unsharing the table. i discovered this through testing and verified it by source inspection - there is a call to unshare_files() early in do_execve_common(). fcntl.2 michael kerrisk [jeff layton] clarify cases of conflict between traditional record and ofd locks verified by experiment on linux 3.15 and 3.19rc4. fork.2 michal hocko eagain is not reported when task allocation fails i am not sure why we have: "eagain fork() cannot allocate sufficient memory to copy the parent's page tables and allocate a task structure or the child." the text seems to be there from the time when man-pages were moved to git so there is no history for it. and it doesn't reflect reality: the kernel reports both dup_task_struct and dup_mm failures as enomem to the userspace. this seems to be the case from early 2.x times so let's simply remove this part. heinrich schuchardt child and parent run in separate memory spaces fork.2 should clearly point out that child and parent process run in separate memory spaces. michael kerrisk notes: add "c library/kernel abi differences" subheading getpid.2 michael kerrisk notes: add "c library/kernel abi differences" subheading getxattr.2 michael kerrisk various rewordings plus one or two details clarified michael kerrisk add pointer to example in listxattr(2) killpg.2 michael kerrisk notes: add "c library/kernel abi differences" subheading listxattr.2 heinrich schuchardt provide example program michael kerrisk reword discussion of size==0 case michael kerrisk add note on handling increases in sizes of keys or values michael kerrisk remove mention of which filesystems implement acls such a list will only become outdated (as it already was). migrate_pages.2 jan stancek document efault and einval errors i encountered these errors while writing testcase for migrate_pages syscall for ltp (linux test project). i checked stable kernel tree 3.5 to see which paths return these. both can be returned from get_nodes(), which is called from: syscall_define4(migrate_pages, pid_t, pid, unsigned long, maxnode, const unsigned long __user *, old_nodes, const unsigned long __user *, new_nodes) the testcase does following: efault a) old_nodes/new_nodes is area mmaped with prot_none b) old_nodes/new_nodes is area not mmapped in process address space, -1 or area that has been just munmmaped einval a) maxnodes overflows kernel limit b) new_nodes contain node, which has no memory or does not exist or is not returned for get_mempolicy(mpol_f_mems_allowed). modify_ldt.2 andy lutomirski overhaul the documentation this clarifies the behavior and documents all four functions. andy lutomirski clarify the lm bit's behavior the lm bit should never have existed in the first place. sigh. mprotect.2 mark seaborn mention effect of read_implies_exec personality flag i puzzled over mprotect()'s effect on /proc/*/maps for a while yesterday -- it was setting "x" without prot_exec being specified. here is a patch to add some explanation. msgget.2 michael kerrisk add details of msgmni default value msgop.2 michael kerrisk clarify wording of msgmax and msgmnb limits perf_event_open.2 vince weaver clarify perf_event_ioc_refresh behavior currently the perf_event_ioc_refresh ioctl, when applied to a group leader, will refresh all children. also if a refresh value of 0 is chosen then the refresh becomes infinite (never runs out). back in 2011 papi was relying on these behaviors but i was told that both were unsupported and subject to being removed at any time. (see https://lkml.org/lkml/2011/5/24/337 ) however the behavior has not been changed. this patch updates the manpage to still list the behavior as unsupported, but removes the inaccurate description of it only being a problem with 2.6 kernels. prctl.2 michael kerrisk [bill mcconnaughey] mention file capabilities in discussion of pr_set_dumpable michael kerrisk greatly expand discussion of "dumpable" flag in particular, detail the interactions with /proc/sys/fs/suid_dumpable. michael kerrisk reorder paragraphs describing pr_set_dumpable michael kerrisk mention suid_dump_disable and suid_dump_user under pr_set_dumpable michael kerrisk executing a file with capabilities also resets the parent death signal ptrace.2 james hunt explain behaviour should ptrace tracer call execve(2) this behaviour was verified by reading the kernel source and confirming the behaviour using a test program. denys vlasenko add information on ptrace_seize versus ptrace_attach differences extend description of ptrace_seize with the short summary of its differences from ptrace_attach. the following paragraph: ptrace_event_stop stop induced by ptrace_interrupt command, or group-stop, or ini- tial ptrace-stop when a new child is attached (only if attached using ptrace_seize), or ptrace_event_stop if ptrace_seize was used. has an editing error (the part after last comma makes no sense). removing it. mention that legacy post-execve sigtrap is disabled by ptrace_seize. sched_setattr.2 michael kerrisk [christophe blaess] synopsis: remove 'const' from 'attr' sched_getattr() argument semget.2 michael kerrisk note default value for semmni and semmsl semop.2 michael kerrisk note defaults for semopm and warn against increasing > 1000 sendfile.2 eric wong caution against modifying sent pages setxattr.2 michael kerrisk errors: add enotsup for invalid namespace prefix michael kerrisk remove redundant text under enotsup error michael kerrisk note that zero-length attribute values are permitted michael kerrisk rework text describing 'flags' argument stat.2 michael kerrisk notes: add "c library/kernel abi differences" subheading statfs.2 michael kerrisk [jan chaloupka] document the 'f_flags' field added in linux 2.6.36 michael kerrisk clarify that 'statfs' structure has some padding bytes the number of padding bytes has changed over time, as some bytes are used, so describe this aspect of the structure less explicitly. tao ma add ocfs2_super_magic michael kerrisk use __fsword_t in statfs structure definition this more closely matches modern glibc reality. michael kerrisk add a note on the __fsword_t type michael kerrisk document 'f_spare' more vaguely wait.2 michael kerrisk note that waitpid() is a wrapper for wait4() michael kerrisk note that wait() is a library function implemented via wait4() wait4.2 michael kerrisk notes: add "c library/kernel abi differences" subheading encrypt.3 rob somers improve code example i (and some others) found that the original example code did not seem to work as advertised. the new code (used by permission of the original author, jens thoms toerring) was found on comp.os.linux.development. mktemp.3 luke faraone description reference to bugs corrected mktemp(3)'s description referenced notes, but no such section exists. corrected to refer to bugs. pthread_attr_setschedparam.3 tobias herzke describe einval in errors resolver.3 host.conf.5 simon paillard host.conf 'order' option deprecated, replaced by nsswitch.conf(5) http://www.sourceware.org/bugzilla/show_bug.cgi?id=2389 http://repo.or.cz/w/glibc.git/commit/b9c65d0902e5890c4f025b574725154032f8120a reported at http://bugs.debian.org/270368, http://bugs.debian.org/396633, and http://bugs.debian.org/344233. statvfs.3 michael kerrisk document missing 'f_flag' bit values and reorganize information relating to which flags are in posix.1. michael kerrisk [jan chaloupka] statvfs() now populates 'f_flag' from statfs()'s f_flag field these changes came with glibc 2.13, and the kernel's addition of a 'f_flags' field in linux 2.6.36. syslog.3 michael kerrisk [doug goldstein] remove unneeded vsyslog() does not need this. tzset.3 j william piggott add offset format tzset.3 does not illustrate the posix offset format. specifically, there is no indication in the manual what the optional components of it are. random.4 michael kerrisk note maximum number of bytes returned by read(2) on /dev/random michael kerrisk [mathieu malaterre] since linux 3.16, reads from /dev/urandom return at most 32 mb see https://bugs.debian.org/775328 and https://bugzilla.kernel.org/show_bug.cgi?id=80981#c9 core.5 michael kerrisk [bill mcconnaughey] executing a file that has capabilities also prevents core dumps michael kerrisk document "%i" and "%i" core_pattern specifiers intro.5 michael kerrisk remove words "and protocols" there are no protocol descriptions in section 5. protocols are in section 7. proc.5 michael kerrisk add reference to prctl(2) in discussion of /proc/sys/fs/suid_dumpable and note that /proc/sys/fs/suid_dumpable defines the value assigned to the process "dumpable" flag in certain circumstances. michael kerrisk note that cap_sys_admin is required to list /proc/pid/map_files this might however change in the future; see the jan 2015 lkml thread: re: [rfc][patch v2] procfs: always expose /proc//map_files/ and make it readable resolv.conf.5 michael kerrisk see also: add nsswitch.conf(5) capabilities.7 michael kerrisk mention secbit_keep_caps as an alternative to prctl() pr_set_keepcaps chris mayo notes: add last kernel versions for obsolete options the config_security_capabilities option was removed by commit 5915eb53861c5776cfec33ca4fcc1fd20d66dd27 the config_security_file_capabilities option removed in linux 2.6.33 as already mentioned in description. pthreads.7 michael kerrisk see also: add fork(2) unix.7 jan chaloupka mention sock_stream socket for ioctl_type of ioctl() from https://bugzilla.redhat.com/show_bug.cgi?id=1110401. unix.7 is not clear about socket type of ioctl_type argument of ioctl() function. the description of siocinq is applicable only for sock_stream socket. for sock_dgram, udp(7) man page gives correct description of siocinq ldconfig.8 michael kerrisk place options in alphabetical order michael kerrisk note glibc version number for '-l' option michael kerrisk document -c/--format option michael kerrisk add long form of some options michael kerrisk [patrick horgan] ld.so.conf uses only newlines as delimiters mtk: confirmed by reading source of parse_conf() in elf/ldconfig.c. michael kerrisk document -v/--version option michael kerrisk document -i/--ignore-aux-cache option ld.so.8 michael kerrisk relocate "hardware capabilities" to be a subsection under notes this is more consistent with standard man-pages headings and layout. michael kerrisk (briefly) document ld_trace_prelinking michael kerrisk remove duplicate description of ld_bind_not ==================== changes in man-pages-3.81 ==================== released: 2015-03-02, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexandre oliva carlos o'donell ma shimiao michael kerrisk peng haitao apologies if i missed anyone! new and rewritten pages ----------------------- attributes.7 alexandre oliva, michael kerrisk [carlos o'donell] new page describing posix safety concepts global changes -------------- many pages peng haitao, michael kerrisk reformat existing thread-safety information to use a tabular format, rather than plain text. changes to individual pages --------------------------- mmap.2 ma shimiao attributes: note functions that are thread-safe the function mmap() and munmap() are thread safe. a64l.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. acos.3 ma shimiao attributes: note functions that are thread-safe the function acos(), acosf() and acosl() are thread safe. acosh.3 ma shimiao attributes: note functions that are thread-safe the function acosh(), acoshf() and acoshl() are thread safe. addseverity.3 ma shimiao attributes: note function is thread-safe the function addseverity() is thread safe. aio_cancel.3 ma shimiao attributes: note function that is thread-safe the function aio_cancel() is thread safe. aio_fsync.3 ma shimiao attributes: note function that is thread-safe the function aio_fsync() is thread safe. aio_read.3 ma shimiao attributes: note function that is thread-safe the function aio_read() is thread safe. aio_suspend.3 ma shimiao attributes: note function that is thread-safe the function aio_suspend() is thread safe. aio_write.3 ma shimiao attributes: note function that is thread-safe the function aio_write() is thread safe. argz_add.3 ma shimiao attributes: note functions that are thread-safe asin.3 ma shimiao attributes: note functions that are thread-safe the function asin(), asinf() and asinl() are thread safe. assert.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. assert_perror.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. atan2.3 ma shimiao attributes: note functions that are thread-safe the function atan2(), atan2f() and atan2l() are thread safe. atanh.3 ma shimiao attributes: note functions that are thread-safe the function atanh(), atanhf() and atanhl() are thread safe. backtrace.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. btowc.3 ma shimiao attributes: note function that is thread-safe the function btowc() in glibc is thread safe. its marking matches glibc marking. cabs.3 ma shimiao attributes: note functions that are thread-safe the function cabs(), cabsf() and cabsl() are thread safe. cacos.3 ma shimiao attributes: note functions that are thread-safe the function cacos(), cacosf() and cacosl() are thread safe. cacosh.3 ma shimiao attributes: note functions that are thread-safe the functions cacosh(), cacoshf() and cacoshl() in glibc are thread safe. its markings match glibc markings. canonicalize_file_name.3 ma shimiao attributes: note function that is thread-safe the functions canonicalize_file_name() in glibc is thread safe. its marking matches glibc marking. carg.3 ma shimiao attributes: note functions that are thread-safe the function carg(), cargf() and cargl() are thread safe. casin.3 ma shimiao attributes: note functions that are thread-safe the functions casin(), casinf() and casinl() are thread safe. their markings match glibc markings. casinh.3 ma shimiao attributes: note functions that are thread-safe the functions casinh(), casinhf() and casinhl() in glibc are thread safe. its markings match glibc markings. catan.3 ma shimiao attributes: note functions that are thread-safe the functions catan(), catanf() and catanl() are thread safe. their markings match glibc markings. catanh.3 ma shimiao attributes: note functions that are thread-safe the functions catanh(), catanhf() and catanhl() in glibc are thread safe. its markings match glibc markings. catopen.3 peng haitao attributes: note functions that are thread-safe the functions catopen() and catclose() are thread safe. cfree.3 ma shimiao attributes: note function that is thread-safe the function cfree() in glibc is thread safe. its marking matches glibc marking. clog10.3 ma shimiao attributes: note functions that are thread-safe the functions clog10(), clog10f() and clog10l() in glibc are thread safe. its markings match glibc markings. clog.3 ma shimiao attributes: note functions that are thread-safe the function clog(), clogf() and clogl() are thread safe. closedir.3 ma shimiao attributes: note function that is thread-safe the function closedir() in glibc is thread safe. its marking matches glibc marking. confstr.3 ma shimiao attributes: note function that is thread-safe the function confstr() is thread safe. cosh.3 ma shimiao attributes: note functions that are thread-safe the functions cosh(), coshf() and coshl() in glibc are thread safe. its markings match glibc markings. cpow.3 ma shimiao attributes: note functions that are thread-safe the functions cpow(), cpowf() and cpowl() in glibc are thread safe. its markings match glibc markings. crypt.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. ctermid.3 ma shimiao modify thread-safety information according to the change of source code, ctermid's level has been changed from mt-unsafe to mt-safe. after modifying, the marking matches the glibc marking. drand48.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. drand48_r.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. ecvt.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be same as glibc manual. ecvt_r.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. encrypt.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. envz_add.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. exec.3 peng haitao attributes: note functions that are thread-safe the functions execl(), execlp(), execle(), execv(), execvp() and execvpe() are thread safe. exit.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. exp10.3 ma shimiao attributes: note functions that are thread-safe exp2.3 ma shimiao attributes: note functions that are thread-safe the function exp2(), exp2f() and exp2l() are thread safe. exp.3 ma shimiao attributes: note functions that are thread-safe the function exp(), expf() and expl() are thread safe. fclose.3 ma shimiao attributes: note function that is thread-safe the function fclose() is thread safe. its marking matches glibc marking. fcloseall.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. fgetc.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. fgetwc.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. fgetws.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. fmod.3 ma shimiao attributes: note functions that are thread-safe the function fmod(), fmodf() and fmodl() are thread safe. fnmatch.3 peng haitao attributes: note function that is thread safe with exceptions the function fnmatch() is thread safe with exceptions. fopen.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. fopencookie.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. fread.3 peng haitao attributes: note functions that are thread-safe the functions fread() and fwrite() are thread safe. gamma.3 peng haitao attributes: note functions that are not thread-safe the functions gamma(), gammaf() and gammal() are not thread safe. ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getcontext.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getcwd.3 peng haitao attributes: note functions that are thread-safe the functions getcwd(), getwd() and get_current_dir_name() are thread safe. getdate.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getenv.3 peng haitao attributes: note functions that are thread-safe the functions getenv() and secure_getenv() are thread safe. getfsent.3 peng haitao attributes: note functions that are not thread-safe the functions setfsent(), getfsent(), endfsent(), getfsspec() and getfsfile() are not thread safe. ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getgrent.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getgrnam.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getgrouplist.3 peng haitao attributes: note function that is thread safe with exceptions the function getgrouplist() is thread safe with exceptions. getlogin.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getopt.3 peng haitao attributes: note functions that are not thread-safe the functions getopt(), getopt_long() and getopt_long_only() are not thread safe. ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getpass.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getpwent.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. getpwnam.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. gets.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. getw.3 peng haitao attributes: note functions that are thread-safe the functions getw() and putw() are thread safe. gnu_get_libc_version.3 peng haitao attributes: note functions that are thread-safe the functions gnu_get_libc_version() and gnu_get_libc_release() are thread safe. hsearch.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. iconv.3 peng haitao modify thread-safety information inet.3 peng haitao attributes: note functions that are thread safe with exceptions the functions inet_aton() and inet_addr() are thread safe with exceptions. the functions inet_network(), inet_ntoa(), inet_makeaddr(), inet_lnaof() and inet_netof() are thread safe. modify thread-safety information after researching and talking, we think inet_network() and inet_ntoa() should be marked with locale. after changing, the markings match glbc markings. inet_pton.3 peng haitao attributes: note function that is thread safe with exceptions the function inet_pton() is thread safe with exceptions. iswdigit.3 peng haitao attributes: note function that is thread safe with exceptions the function iswdigit() is thread safe with exceptions. iswgraph.3 peng haitao attributes: note function that is thread safe with exceptions the function iswgraph() is thread safe with exceptions. iswlower.3 peng haitao attributes: note function that is thread safe with exceptions the function iswlower() is thread safe with exceptions. iswprint.3 peng haitao attributes: note function that is thread safe with exceptions the function iswprint() is thread safe with exceptions. iswpunct.3 peng haitao attributes: note function that is thread safe with exceptions the function iswpunct() is thread safe with exceptions. iswspace.3 peng haitao attributes: note function that is thread safe with exceptions the function iswspace() is thread safe with exceptions. iswupper.3 peng haitao attributes: note function that is thread safe with exceptions the function iswupper() is thread safe with exceptions. iswxdigit.3 peng haitao attributes: note function that is thread safe with exceptions the function iswxdigit() is thread safe with exceptions. j0.3 ma shimiao attributes: note functions that are thread-safe the function j0(), j1f() jnl() and so on are thread safe. lio_listio.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. log10.3 ma shimiao attributes: note functions that are thread-safe the function log10(), log10f() and log10l() are thread safe. log2.3 ma shimiao attributes: note functions that are thread-safe the function log2(), log2f() and log2l() are thread safe. log.3 ma shimiao attributes: note functions that are thread-safe the function log(), logf() and logl() are thread safe. makecontext.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. makedev.3 peng haitao attributes: note macros that are thread-safe the macros makedev(), major() and minor() are thread safe. malloc.3 ma shimiao attributes: note functions that are thread-safe the function malloc(), free(), calloc() and realloc() are thread safe. mblen.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. mbstowcs.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. mbtowc.3 peng haitao attributes: note function that is not thread-safe the function mbtowc() is not thread safe. ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. mktemp.3 peng haitao attributes: note function that is thread-safe the function mktemp() is thread safe. mtrace.3 peng haitao attributes: note functions that are not thread-safe the functions mtrace() and muntrace() are not thread safe. nan.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. nl_langinfo.3 peng haitao attributes: note function that is thread safe with exceptions the function nl_langinfo() is thread safe with exceptions. opendir.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. pow10.3 ma shimiao attributes: note functions that are thread-safe the function pow10(), pow10f() and pow10l() are thread safe. pow.3 ma shimiao attributes: note functions that are thread-safe the function pow(), powf() and powl() are thread safe. pthread_setcancelstate.3 michael kerrisk add async-signal-safety information ptsname.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. putenv.3 ma shimiao attributes: note function that is thread-unsafe the function putenv() is thread unsafe. puts.3 peng haitao attributes: note functions that are thread-safe the functions fputc(), fputs(), putc(), putchar() and puts() are thread safe. putwchar.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. qecvt.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be same as glibc manual. rand.3 peng haitao attributes: note macros that are thread-safe the functions rand(), rand_r() and srand() are thread safe. random_r.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. readdir.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be same as glibc manual. realpath.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. regex.3 peng haitao attributes: note functions that are thread safe with exceptions the functions regcomp() and regexec() are thread safe with exceptions. the functions regerror() and regfree() are thread safe. remainder.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. scalb.3 ma shimiao attributes: note functions that are thread-safe the function scalb(), scalbf() and scalbl() are thread safe. setenv.3 ma shimiao attributes: note functions that are thread-unsafe the function setenv() and unsetenv() are thread unsafe. siginterrupt.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. sigset.3 peng haitao attributes: note macros that are thread-safe the functions sigset(), sighold(), sigrelse() and sigignore() are thread safe. sinh.3 ma shimiao attributes: note functions that are thread-safe the function sinh(), sinhf() and sinhl() are thread safe. sqrt.3 ma shimiao attributes: note functions that are thread-safe the function sqrt(), sqrtf() and sqrtl() are thread safe. stdarg.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. stdio_ext.3 ma shimiao modify thread-safety information change the thread safety information to be the same as glibc. strcasecmp.3 peng haitao attributes: note functions that are thread safe with exceptions the functions strcasecmp() and strncasecmp() are thread safe with exceptions. strerror.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. strfmon.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. strfry.3 peng haitao attributes: note function that is thread-safe the function strfry() is thread safe. strftime.3 peng haitao attributes: note function that is thread safe with exceptions the function strftime() is thread safe with exceptions. strptime.3 peng haitao attributes: note function that is thread safe with exceptions the function strptime() is thread safe with exceptions. strtok.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. strverscmp.3 peng haitao attributes: note function that is thread-safe the function strverscmp() is thread safe. strxfrm.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. syslog.3 peng haitao attributes: note functions that are thread safe with exceptions the functions openlog() and closelog() are thread safe. the functions syslog() and vsyslog() are thread safe with exceptions. tempnam.3 peng haitao attributes: note function that is thread-safe the function tempnam() is thread safe. termios.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. ma shimiao modify thread-safety information as this is man page for linux, we don't need thread safety information for bsd tgamma.3 ma shimiao attributes: note functions that are thread-safe the functions tgamma(), tgammaf() and tgammal() in glibc are thread safe. its markings match glibc markings. timegm.3 peng haitao attributes: note functions that are thread safe with exceptions the functions timelocal() and timegm() are thread safe with exceptions. tmpfile.3 ma shimiao attributes: note function that is thread-safe its markings match glibc markings. tmpnam.3 peng haitao modify thread-safety information when the argument s is null, tmpnam() should be mt-unsafe. toupper.3 ma shimiao modify thread-safety information after researching and talking, we think toupper() and tolower() should not be marked with locale. after changing, the markings match glbc markings. tsearch.3 ma shimiao attributes: note functions that are thread-safe the functions' markings match glibc markings. ttyname.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be same as glibc manual. tzset.3 peng haitao attributes: note function that is thread safe with exceptions the function tzset() is thread safe with exceptions. wcsdup.3 ma shimiao attributes: note function that is thread-safe its marking matches glibc marking. wctomb.3 ma shimiao modify thread-safety information as annotation in glibc manual is more detailed, change the thread-safety information to be the same as glibc manual. y0.3 ma shimiao attributes: note functions that are thread-safe the function y0(), y1f() ynl() and so on are thread safe. man-pages.7 michael kerrisk refer reader to attributes(7) for details of attributes section michael kerrisk see also: add attributes(7) pthreads.7 michael kerrisk see also: add attributes(7) standards.7 michael kerrisk see also: add attributes(7) ==================== changes in man-pages-3.82 ==================== released: 2015-03-29, paris contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alban crequy andy lutomirski bert wesarg bill pemberton chris delozier david madore dmitry deshevoy eric w. biederman heinrich schuchardt jakub wilk jann horn jason vas dias josh triplett j william piggott kees cook konstantin shemyak ma shimiao matt turner michael kerrisk michael witten mikael pettersson namhyung kim nicolas francois paul e condon peter adkins scot doyle shawn landden stéphane aulery stephen smalley taisuke yamada torvald riegel vincent lefevre yuri kozlov apologies if i missed anyone! new and rewritten pages ----------------------- nptl.7 michael kerrisk new page with details of the nptl posix threads implementation newly documented interfaces in existing pages --------------------------------------------- user_namespaces.7 eric w. biederman [michael kerrisk] document /proc/[pid]/setgroups changes to individual pages --------------------------- intro.1 stéphane aulery prompt is not % but $ stéphane aulery various improvements - add reference to other common shells dash(1), ksh(1) - add a reference to stdout(3) - separate cp and mv descriptions - add examples of special cases of cd - add su(1) and shutdown(8) references for section logout and poweroff - move control-d to section logout and poweroff - fix some little formatting errors stéphane aulery add cross references cited stéphane aulery order see also section clone.2 josh triplett document that clone() silently ignores clone_pid and clone_stopped normally, system calls return einval for flags they don't support. explicitly document that clone does *not* produce an error for these two obsolete flags. michael kerrisk small rewording of explanation of clone() wrt threads clone has so many effects that it's an oversimplification to say that the *main* use of clone is to create a thread. (in fact, the use of clone() to create new processes may well be more common, since glibc's fork() is a wrapper that calls clone().) getgroups.2 michael kerrisk [shawn landden] add discussion of nptl credential-changing mechanism at the kernel level, credentials (uids and gids) are a per-thread attribute. nptl uses a signal-based mechanism to ensure that when one thread changes its credentials, all other threads change credentials to the same values. by this means, the nptl implementation conforms to the posix requirement that the threads in a process share credentials. michael kerrisk errors: add eperm for the case where /proc/pid/setgroups is "deny" michael kerrisk note capability associated with eperm error for setgroups(2) michael kerrisk refer reader to user_namespaces(7) for discussion of /proc/pid/setgroups the discussion of /proc/pid/setgroups has moved from proc(5) to user_namespaces(7). getpid.2 michael kerrisk note that getppid() returns 0 if parent is in different pid namespace getsockopt.2 konstantin shemyak note return value details when netfilter is involved ioctl_list.2 heinrich schuchardt see also ioctl_fat.2 add fat_ioctl_get_volume_id see also ioctl_fat.2 heinrich schuchardt include/linux/ext2_fs.h include linux/ext2_fs.h does not contain any ioctl definitions anymore. request codes ext2_ioc* have been replaced by fs_ioc* in linux/fs.h. some definitions of fs_ioc_* use long* but the actual code expects int* (see fs/ext2/ioctl.c). msgop.2 bill pemberton remove eagain as msgrcv() errno the list of errnos for msgrcv() lists both eagain and enomsg as the errno for no message available with the ipc_nowait flag. enomsg is the errno that will be set. bill pemberton add an example program open.2 michael kerrisk [jason vas dias] mention blocking semantics for fifo opens see https://bugzilla.kernel.org/show_bug.cgi?id=95191 seccomp.2 jann horn [kees cook, mikael pettersson, andy lutomirski] add note about alarm(2) not being sufficient to limit runtime jann horn explain blacklisting problems, expand example michael kerrisk [kees cook] add mention of libseccomp setgid.2 michael kerrisk clarify that setgid() changes all gids when caller has cap_setgid michael kerrisk [shawn landden] add discussion of nptl credential-changing mechanism at the kernel level, credentials (uids and gids) are a per-thread attribute. nptl uses a signal-based mechanism to ensure that when one thread changes its credentials, all other threads change credentials to the same values. by this means, the nptl implementation conforms to the posix requirement that the threads in a process share credentials. setresuid.2 michael kerrisk [shawn landden] add discussion of nptl credential-changing mechanism at the kernel level, credentials (uids and gids) are a per-thread attribute. nptl uses a signal-based mechanism to ensure that when one thread changes its credentials, all other threads change credentials to the same values. by this means, the nptl implementation conforms to the posix requirement that the threads in a process share credentials. setreuid.2 michael kerrisk [shawn landden] add discussion of nptl credential-changing mechanism at the kernel level, credentials (uids and gids) are a per-thread attribute. nptl uses a signal-based mechanism to ensure that when one thread changes its credentials, all other threads change credentials to the same values. by this means, the nptl implementation conforms to the posix requirement that the threads in a process share credentials. michael kerrisk see also: add credentials(7) setuid.2 michael kerrisk clarify that setuid() changes all uids when caller has cap_setuid michael kerrisk [shawn landden] add discussion of nptl credential-changing mechanism at the kernel level, credentials (uids and gids) are a per-thread attribute. nptl uses a signal-based mechanism to ensure that when one thread changes its credentials, all other threads change credentials to the same values. by this means, the nptl implementation conforms to the posix requirement that the threads in a process share credentials. sigaction.2 michael kerrisk add discussion of rt_sigaction(2) michael kerrisk note treatment of signals used internally by nptl the glibc wrapper gives an einval error on attempts to change the disposition of either of the two real-time signals used by nptl. sigpending.2 michael kerrisk add discussion of rt_sigpending(2) sigprocmask.2 michael kerrisk add discussion of rt_sigprocmask(2) michael kerrisk note treatment of signals used internally by nptl the glibc wrapper silently ignores attempts to block the two real-time signals used by nptl. sigreturn.2 michael kerrisk add discussion of rt_sigreturn(2) sigsuspend.2 michael kerrisk add discussion of rt_sigsuspend(2) sigwaitinfo.2 michael kerrisk note treatment of signals used internally by nptl the glibc wrappers silently ignore attempts to wait for signals used by nptl. michael kerrisk add discussion of rt_sigtimedwait(2) socket.2 heinrich schuchardt see also close(2) the description mentions close(2). hence it should also be referenced in the see also section. syscall.2 jann horn add x32 abi umount.2 eric w. biederman document the effect of shared subtrees on umount(2) eric w. biederman correct the description of mnt_detach i recently realized that i had been reasoning improperly about what umount(mnt_detach) did based on an insufficient description in the umount.2 man page, that matched my intuition but not the implementation. when there are no submounts, mnt_detach is essentially harmless to applications. where there are submounts, mnt_detach changes what is visible to applications using the detach directories. michael kerrisk move "shared mount + umount" text to a subsection in notes aio_return.3 stéphane aulery document the return value on error reported by alexander holler clock.3 stéphane aulery clocks_per_sec = 1000000 is required by xsi, not posix debian bug #728213 reported by tanaka akira see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=728213 dlopen.3 michael kerrisk amend error in description of dlclose() behavior the current text says that unloading depends on whether the reference count falls to zero *and no other libraries are using symbols in this library*. that latter text has been there since man-pages-1.29, but it seems rather dubious. how could the implementation know whether other libraries are still using symbols in this library? furthermore, no other implementation's man page mentions this point. seems best to drop this point. michael kerrisk add some details for rtld_default michael kerrisk add some details on rtld_next and preloading michael kerrisk rtld_next works for symbols generally, not just functions the common use case is for functions, but rtld_next also applies to variable symbols. michael kerrisk dlclose() recursively closes dependent libraries note that dlclose() recursively closes dependent libraries that were loaded by dlopen() michael kerrisk rename second dlopen() argument from "flag" to "flags" this is more consistent with other such arguments michael kerrisk reformat text on rtld_default and rtld_next fmemopen.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. fpathconf.3 ma shimiao attributes: note functions that are thread-safe the marking matches glibc marking. fputwc.3 ma shimiao attributes: note functions that are thread-safe the marking matches glibc marking. fputws.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. fseek.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. fseeko.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. gcvt.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. getline.3 ma shimiao attributes: note functions that are thread-safe the marking matches glibc marking. getwchar.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. hypot.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. iconv_open.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. if_nameindex.3 ma shimiao attributes: note functions that are thread-safe the markings match glibc markings. initgroups.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. mq_open.3 torvald riegel add einval error case for invalid name this behavior is implementation-defined by posix. if the name doesn't start with a '/', glibc returns einval without attempting the syscall. popen.3 ma shimiao attributes: note functions that are thread-safe the marking matches glibc marking. pthread_kill.3 michael kerrisk note treatment of signals used internally by nptl the glibc pthread_kill() function gives an error on attempts to send either of the real-time signals used by nptl. pthread_sigmask.3 michael kerrisk note treatment of signals used internally by nptl the glibc implementation silently ignores attempts to block the two real-time signals used by nptl. pthread_sigqueue.3 michael kerrisk note treatment of signals used internally by nptl the glibc pthread_sigqueue() function gives an error on attempts to send either of the real-time signals used by nptl. resolver.3 stéphane aulery [jakub wilk] document missing options used by _res structure indicate defaults missing options: res_insecure1, res_insecure2, res_noaliases, use_inet6, rotate, nocheckname, res_keeptsig, blast, usebstring, noip6dotint, use_edns0, snglkup, snglkupreop, res_use_dnssec, notldquery, default written from the glibc source and resolv.conf.5. see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=527136 stéphane aulery res_igntc is implemented rint.3 matt turner document that halfway cases are rounded to even per ieee-754 rounding rules. the round(3) page describes the behavior of rint and nearbyint in the halfway cases by saying: these functions round x to the nearest integer, but round halfway cases away from zero [...], instead of to the nearest even integer like rint(3) sigqueue.3 michael kerrisk notes: add "c library/kernel abi differences" subheading michael kerrisk clarify version info (mention rt_sigqueueinfo()) sigsetops.3 michael kerrisk note treatment of signals used internally by nptl the glibc sigfillset() function excludes the two real-time signals used by nptl. sigwait.3 michael kerrisk note treatment of signals used internally by nptl the glibc sigwait() silently ignore attempts to wait for signals used by nptl. strcoll.3 ma shimiao attributes: note function that is thread-safe the markings match glibc markings. strdup.3 ma shimiao attributes: note functions that are thread-safe the marking matches glibc marking. tzset.3 j william piggott add 'std' quoting information ulimit.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. wcstombs.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. wctob.3 ma shimiao attributes: note function that is thread-safe the marking matches glibc marking. xdr.3 taisuke yamada clarified incompatibility and correct usage of xdr api see http://bugs.debian.org/628099 console_codes.4 scot doyle add console private csi sequence 15 an undocumented escape sequence in drivers/tty/vt/vt.c brings the previously accessed virtual terminal to the foreground. mtk: patch misattributed to taisuke yamada in git commit because of a muck up on my part. michael kerrisk add kernel version number for csi sequence 15 random.4 michael kerrisk fix permissions shown for the devices these days, the devices are rw for everyone. filesystems.5 michael kerrisk remove dubious claim about comparative performance of ext2 perhaps it was the best filesystem performance-wise in the 20th century, when that text was written. that probably ceased to be true quite a long time ago, though. stéphane aulery add cross references for ext filesystems stéphane aulery specifies the scope of this list and its limits. host.conf.5 hosts.5 resolv.conf.5 stéphane aulery [paul e condon] cross references of these pages. see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=298259 host.conf.5 stéphane aulery rework discussion of nospoof, spoofalert, spoof and resolv_spoof_check the keywords and environment variables "nospoof", "spoofalert", "spoof" and resolv_spoof_check were added to glibc 2.0.7 but never implemented move descriptions to historical section and reorder it for clarity see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=773443 hosts.5 stéphane aulery [vincent lefevre] mention 127.0.1.1 for fqdn and ipv6 examples see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=562890 proc.5 taisuke yamada document /proc/pid/status vmpin field see https://bugs.launchpad.net/bugs/1071746 michael kerrisk document (the obsolete) /proc/pid/seccomp michael kerrisk replace description of 'uid_map' with a reference to user_namespaces(7) all of the information in proc(5) was also present in user_namespaces(7), but the latter was more detailed and up to date. taisuke yamada fix selinux /proc/pid/attr/current example since the /proc/pid/attr api was added to the kernel, there have been a couple of changes to the selinux handling of /proc/pid/attr/current. fix the selinux /proc/pid/attr/current example text to reflect these changes and note which kernel versions first included the changes. securetty.5 stéphane aulery [nicolas francois] note that the pam_securetty module also uses this file see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=528015 this patch is a modified version of the one proposed without parts specific to debian. boot.7 michael witten copy edit while a lot of the changes are issues of presentation, there are also issues of grammar and punctuation. michael witten mention `systemd(1)' and its related `bootup(7)' it's important that the reader receive contemporary information. credentials.7 michael kerrisk see also: add pthreads(7) michael kerrisk add reference to nptl(7) feature_test_macros.7 michael kerrisk update discussion of _fortify_source since the initial implementation a lot more checks were added. describe all the checks would be too verbose (and would soon fall out of date as more checks are added). so instead, describe the kinds of checks that are done more generally. also a few other minor edits to the text. hier.7 stéphane aulery first patch of a series to achieve compliance with fhs 2.3 stéphane aulery sgml and xml directories are separated in fhs 2.3 stéphane aulery add missing directories defined by fhs 2.3 stéphane aulery identify which directories are optional stéphane aulery document /initrd, /lost+found and /sys ubuntu bug #70094 reported by brian beck https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/70094 stéphane aulery explain yp, which is not obvious ipv6.7 stéphane aulery [david madore] sol_ipv6 and other sol_* options socket are not portable see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=472447 man-pages.7 michael kerrisk [bill pemberton] add indent(1) command that produces desired formatting for example code stéphane aulery improve description of sections in accordance with intro pages packet.7 michael kerrisk rework description of fanout algorithms as list michael kerrisk remove mention of needing uid 0 to create packet socket the existing text makes no sense. the check is based purely on a capability check. (kernel function net/packet/af_packet.c::packet_create() michael kerrisk remove text about ancient glibc not defining sol_packet this was fixed in glibc 2.1.1, which is a long while ago. and in any case, there is nothing special about this case; it's just one of those times when glibc lags. michael kerrisk rework description of 'sockaddr_ll' fields as a list michael kerrisk various minor edits pthreads.7 michael kerrisk add references to nptl(7) raw.7 michael kerrisk rephrase "linux 2.2" language to "linux 2.2 or later" the man page was written in the linux 2.2 timeframe, and some phrasing was not future-proof. signal.7 michael kerrisk note when linux added realtime signals michael kerrisk correct the range of realtime signals michael kerrisk summarize 2.2 system call changes that resulted from larger signal sets michael kerrisk see also: add nptl(7) tcp.7 peter adkins document removal of tcp_synq_hsize looking over the man page for 'tcp' i came across a reference to tuning the 'tcp_synq_hsize' parameter when increasing 'tcp_max_syn_backlog' above 1024. however, this static sizing was removed back in linux 2.6.20 in favor of dynamic scaling - as part of commit 72a3effaf633bcae9034b7e176bdbd78d64a71db. user_namespaces.7 eric w. biederman update the documentation to reflect the fixes for negative groups files with access permissions such as rwx---rwx give fewer permissions to their group then they do to everyone else. which means dropping groups with setgroups(0, null) actually grants a process privileges. the unprivileged setting of gid_map turned out not to be safe after this change. privileged setting of gid_map can be interpreted as meaning yes it is ok to drop groups. [ eric additionally noted: setting of gid_map with privilege has been clarified to mean that dropping groups is ok. this allows existing programs that set gid_map with privilege to work without changes. that is, newgidmap(1) continues to work unchanged.] to prevent this problem and future problems, user namespaces were changed in such a way as to guarantee a user can not obtain credentials without privilege that they could not obtain without the help of user namespaces. this meant testing the effective user id and not the filesystem user id, as setresuid(2) and setregid(2) allow setting any process uid or gid (except the supplementary groups) to the effective id. furthermore, to preserve in some form the useful applications that have been setting gid_map without privilege, the file /proc/[pid]/setgroups was added to allow disabling setgroups(2). with setgroups(2) permanently disabled in a user namespace, it again becomes safe to allow writes to gid_map without privilege. michael kerrisk rework some text describing permission rules for updating map files no (intentional) change to the facts, but this restructuring should make the meaning easier to grasp. michael kerrisk update kernel version associated with 5-line limit for map files as at linux 3.18, the limit is still five lines, so mention the more recent kernel version in the text. michael kerrisk [alban crequy] handle /proc/pid/setgroups in the example program michael kerrisk rework text describing restrictions on updating /proc/pid/setgroups no (intentional) changes to factual description, but the restructured text is hopefully easier to grasp. michael kerrisk explain why the /proc/pid/setgroups file was added ldconfig.8 michael kerrisk note use of /lib64 and /usr/lib64 on some 64-bit architectures ld.so.8 michael kerrisk note the use of /lib64 and /usr/lib64 on some 64-bit architectures ==================== changes in man-pages-3.83 ==================== released: 2015-04-19, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andreas baak andreas dilger cdlscpmv cyrill gorcunov darrick j. wong david rientjes dima tisnek eric sandeen fabien pichot felix sedlmeier gleb fotengauer-malinovskiy heinrich schuchardt jann horn jon grant jonny grant kees cook masanari iida ma shimiao michael kerrisk nikos mavrogiannopoulos omar sandoval pierre chifflier robin h. johnson rob landley theodore ts'o vlastimil babka walter harms william woodruff yoshifuji hideaki zeng linggang apologies if i missed anyone! new and rewritten pages ----------------------- posix_madvise.3 michael kerrisk new page documenting posix_madvise(3) ftw.3 michael kerrisk reorganize the page to give primacy to nftw() nftw() is the better api, and posix.1-2008 marks ftw() obsolete. newly documented interfaces in existing pages --------------------------------------------- getdents.2 michael kerrisk [dima tisnek] document getdents64() see https://bugzilla.kernel.org/show_bug.cgi?id=14795 mount.2 michael kerrisk, theodore ts'o [eric sandeen, andreas dilger, omar sandoval, darrick j. wong] document ms_lazytime proc.5 michael kerrisk document /proc/sys/kernel/randomize_va_space michael kerrisk document /proc/pid/fdinfo epoll format michael kerrisk describe /proc/pid/fdinfo eventfd format michael kerrisk document /proc/pid/fdinfo signalfd format new and changed links --------------------- newfstatat.2 michael kerrisk new link to fstatat64.2 prlimit64.2 michael kerrisk new link to getrlimit.2 global changes -------------- various section 3 math pages michael kerrisk note that these functions are also in posix.1-2001 and posix.1-2008 changes to individual pages --------------------------- getent.1 robin h. johnson document options the options to getent are now documented, after being around for nearly a decade without changes. michael kerrisk document help and version options fallocate.2 michael kerrisk fix kernel version number for falloc_fl_zero_range falloc_fl_zero_range was added in 3.15, not 3.14. michael kerrisk note that smb3 added falloc_fl_zero_range support in linux 3.17 getrlimit.2 michael kerrisk note that the underlying system call for prlimit() is prlimit64() michael kerrisk remove "_file_offset_bits == 64" from prlimit() ftm requirements "_file_offset_bits == 64" is not needed to get the prlimit() declaration. ioctl_list.2 nikos mavrogiannopoulos siocaddrt accepts in6_rtmsg in inet6 protocol heinrich schuchardt tfd_ioc_set_ticks timerfd_create.2 mentions tfd_ioc_set_ticks. we should add it to ioctl_list.2, too. llseek.2 michael kerrisk advise reader to use lseek(2) instead michael kerrisk llseek() exists on 32-bit platforms to support seeking to large offsets madvise.2 david rientjes specify madv_remove returns einval for hugetlbfs madvise(2) actually returns with error einval for madv_remove when used for hugetlb vmas, not eopnotsupp, and this has been the case since madv_remove was introduced in commit f6b3ec238d12 ("madvise(madv_remove): remove pages from tmpfs shm backing store"). specify the exact behavior. michael kerrisk see also: add posix_madvise(2) poll.2 michael kerrisk [andreas baak] see also: add epoll(7) posix_fadvise.2 michael kerrisk add "c library/kernel abi differences" subsection pread.2 michael kerrisk add "c library/kernel abi differences" subsection seccomp.2 michael kerrisk [pierre chifflier, kees cook] note that seccomp_data is read-only stat.2 michael kerrisk add some details on various "stat" versions three versions of "stat" appeared on 32-bit systems, dealing with structures of different (increasing) sizes. explain some of the details, and also note that the situation is simpler on modern 64-bit architectures. michael kerrisk add mention of newfstatat() the underlying system call for fstatat() is newfstatat() on some architectures. symlink.2 michael kerrisk [jonny grant] errors: add linkpath=="" case for enoent syscalls.2 michael kerrisk remove prlimit() there really is only the prlimit64() system call. michael kerrisk add some details about the "multiple versions of system calls" the multiple-system-call-version phenomenon is particularly a feature of older 32-bit platforms. hint at that fact in the text. timerfd_create.2 cyrill gorcunov [michael kerrisk] document tfd_ioc_set_ticks ioctl() operation michael kerrisk add some details to c library/kernel abi differences unshare.2 michael kerrisk [fabien pichot] remove mention of "system v" from discussion of clone_newipc these days, clone_newipc also affects posix message queues. asprintf.3 zeng linggang attributes: note functions that are thread-safe carg.3 michael kerrisk add introductory sentence explaining what these functions calculate ccos.3 ma shimiao attributes: note functions that are thread-safe michael kerrisk add introductory sentence explaining what these functions calculate ccosh.3 michael kerrisk add introductory sentence explaining what these functions calculate cexp.3 ma shimiao attributes: note functions that are thread-safe clock.3 ma shimiao attributes: note functions that is thread-safe clog.3 michael kerrisk add introductory sentence explaining what these functions calculate csin.3 ma shimiao attributes: note functions that are thread-safe michael kerrisk add introductory sentence explaining what these functions calculate csinh.3 ma shimiao attributes: note functions that are thread-safe michael kerrisk add introductory sentence explaining what these functions calculate csqrt.3 ma shimiao attributes: note functions that are thread-safe michael kerrisk simplify description of what these functions calculate ctan.3 ma shimiao attributes: note functions that are thread-safe michael kerrisk add introductory sentence explaining what these functions calculate ctanh.3 ma shimiao attributes: note functions that are thread-safe michael kerrisk add introductory sentence explaining what these functions calculate ctime.3 zeng linggang attributes: note functions that aren't thread-safe exec.3 michael kerrisk synopsis: clarify calling signature for execl() and execlp() michael kerrisk [andreas baak] correct prototype for execle() make the prototype shown into correct c. ftw.3 michael kerrisk [felix sedlmeier] ftw() and nftw() differ for the non-stat-able symlink case the posix specification of ftw() says that an un-stat-able symlink may yield either ftw_ns or ftw_sl. the specification of nftw() does not carry this statement. michael kerrisk conforming to: add posix.1-2008 michael kerrisk update posix version references in notes getcwd.3 jann horn [michael kerrisk] note behavior for unreachable current working directory michael kerrisk add enomem error gethostbyname.3 michael kerrisk [jonny grant] clarify that no_address and no_data are synonyms michael kerrisk add some detail for no_data text consistent with posix and freebsd's gethostbyname() man page. zeng linggang attributes: note functions that aren't thread-safe getnetent.3 zeng linggang attributes: note functions that aren't thread-safe get_nprocs_conf.3 zeng linggang attributes: note functions that are thread-safe getutent.3 zeng linggang attributes: note functions that aren't thread-safe glob.3 zeng linggang attributes: note functions that aren't thread-safe insque.3 ma shimiao attributes: note functions that are thread-safe login.3 zeng linggang attributes: note functions that aren't thread-safe lseek64.3 michael kerrisk clarify details with respect to 32-bit and 64-bit systems malloc.3 michael kerrisk add enomem error mbsnrtowcs.3 zeng linggang attributes: note function that isn't thread-safe mbsrtowcs.3 zeng linggang attributes: note function that isn't thread-safe mq_notify.3 michael kerrisk add "c library/kernel abi differences" subsection mq_open.3 michael kerrisk [fabien pichot] notes: explain differences from the underlying system call the check for the slash at the start of a pathname is done in glibc openpty.3 zeng linggang attributes: note functions that aren't thread-safe perror.3 zeng linggang attributes: note function that is thread-safe posix_memalign.3 zeng linggang attributes: note functions that aren't thread-safe printf.3 zeng linggang attributes: note functions that are thread-safe walter harms [michael kerrisk] simplify the example code qsort.3 michael kerrisk [rob landley] alphasort() and versionsort() are not suitable for 'compar' in glibc 2.10, the prototypes of alphasort() and versionsort() were changed so that the arguments switched from 'const void *' to 'const struct dirent **', to match the posix.1-2008 specification of alphasort(). as such, compiler warnings will result if these functions are used as the arguments of qsort(). warning: passing argument 4 of 'qsort' from incompatible pointer type expected '__compar_fn_t' but argument is of type 'int (*)(const struct dirent **, const struct dirent **)' therefore, remove the ancient notes text suggesting that alphasort() and versionsort() can be used as suitable 'compar' arguments for qsort(). realpath.3 michael kerrisk [jon grant] add enomem error scandir.3 michael kerrisk glibc 2.10 changed the argument types for alphasort() and versionsort() zeng linggang attributes: note functions that are thread-safe scanf.3 zeng linggang attributes: note functions that are thread-safe setnetgrent.3 zeng linggang attributes: note functions that aren't thread-safe significand.3 ma shimiao attributes: note functions that are thread-safe strcasecmp.3 michael kerrisk [jonny grant] clarify that strcasecmp() does a byte-wise comparison michael kerrisk conforming to: add posix.1-2008 unlocked_stdio.3 zeng linggang attributes: note functions that aren't thread-safe updwtmp.3 zeng linggang attributes: note functions that aren't thread-safe wcrtomb.3 zeng linggang attributes: note function that isn't thread-safe wcsnrtombs.3 zeng linggang attributes: note function that isn't thread-safe wcsrtombs.3 zeng linggang attributes: note function that isn't thread-safe wordexp.3 zeng linggang attributes: note functions that aren't thread-safe wprintf.3 zeng linggang attributes: note functions that are thread-safe proc.5 michael kerrisk describe "mnt_id" field of /proc/pid/fdinfo michael kerrisk note that abstract sockets are included in /proc/net/unix michael kerrisk update description /proc/sys/unix 'type' field the existing text was very crufty. unix domain sockets support more than sock_stream for a _very_ long time now. michael kerrisk add some detail to /proc/pid/timers michael kerrisk [vlastimil babka] enhance discussion of /proc/pid/status 'vmswap' field epoll.7 michael kerrisk see also: add poll(2) and select(2) icmp.7 yoshifuji hideaki/吉藤英明 document net.ipv4.ping_group_range knob nptl.7 michael kerrisk add reference to timer_create(2) ==================== changes in man-pages-4.00 ==================== released: 2015-05-07, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: advait dixi alain kalker andi kleen andreas gruenbacher andreas heiduk askar safin brice goglin cameron norman carlos o'donell chris metcalf christophe lohr christopher head christoph hellwig david wilcox denis du egmont koblinger filipe brandenburger filipus klutiero florian weimer frédéric maria gleb fotengauer-malinovskiy graham shaw gregor jasny guillem jover guy harris heinrich schuchardt ian pilcher jann horn jason newton j. bruce fields jiri pirko joachim wuttke joern heissler jonathan nieder joonas salo jussi lehtola kirill a. shutemov kosaki motohiro laurence gonsalves magnus reftel michael kerrisk neilbrown regid ichira sam varshavchik steinar h. gunderson stéphane aulery stephane fillod tetsuo handa thomas hood urs thuermann vasiliy kulikov vegard nossum weijie yang william woodruff zeng linggang apologies if i missed anyone! new and rewritten pages ----------------------- get_phys_pages.3 william woodruff document get_phys_pages() and get_avphys_pages() loop.4 urs thuermann, michael kerrisk new page documenting the loop device xattr.7 andreas gruenbacher import attr(5) man page from the 'attr' project after discussions with andreas gruenbacher, it makes sense to move this page into man-pages, since it mostly relates to kernel details. since this is an overview page, we'll move it to section 7. michael kerrisk rename page "xattr" is a more meaningful name than "attr" (it resonates with the names of the system calls), so as long as we are moving the page to a new section, we'll change the name as well, and retain an acl(5) link so that old references remain valid. newly documented interfaces in existing pages --------------------------------------------- mmap.2 michael kerrisk [andi kleen] document map_huge_2mb, map_huge_1gb, and map_huge_shift shmget.2 michael kerrisk [andi kleen] document shm_huge_2mb, shm_huge_1gb, and shm_huge_shift resolver.3 michael kerrisk [jonathan nieder] add descriptions of some other resolver functions add res_ninit(), res_nquery(), res_nsearch(), and res_nquerydomain(), res_nmkquery(), res_nsend(). tty_ioctl.4 frédéric maria [stephane fillod, andreas heiduk] document tiocmiwait and tiocgicount michael kerrisk document tiocgexcl michael kerrisk document tiogcpkt michael kerrisk document tiocsptlck michael kerrisk document tiocgptlck new and changed links --------------------- cmsg_data.3 michael kerrisk new link to cmsg(3) cmsg_len.3 michael kerrisk new link to cmsg(3) dprintf.3 michael kerrisk convert to a link to printf.3 get_avphys_pages.3 william woodruff new link to new get_phys_pages.3 page res_ninit.3 res_nmkquery.3 res_nquery.3 res_nquerydomain.3 res_nsearch.3 res_nsend.3 michael kerrisk new links to resolver(3) man page loop-control.4 michael kerrisk new link to loop.4 attr.5 michael kerrisk new link to xattr(7) global changes -------------- chown.2 execve.2 prctl.2 truncate.2 proc.5 capabilities.7 ld.so.8 michael kerrisk tighter wording: 'mode bit' rather than 'permission bit' for sticky, set-uid, and set-gid mode bits (as used in posix). changes to individual pages --------------------------- add_key.2 keyctl.2 request_key.2 michael kerrisk see also: add keyrings(7) add_key.2 request_key.2 michael kerrisk see also: add keyctl(3) epoll_ctl.2 michael kerrisk after epollhup, eof will be seen only after all data has been consumed epoll_wait.2 michael kerrisk clarify that signal mask treatment in epoll_pwait() is per-thread s/sigprocmask()/pthread_sigmask()/ fcntl.2 michael kerrisk [vegard nossum] note an f_setsig corner case get_mempolicy.2, set_mempolicy brice goglin policy is per thread, not per process getxattr.2 listxattr.2 removexattr.2 setxattr.2 capabilities.7 michael kerrisk adjust "attr(5)" references to "xattr(7)" ioctl.2 michael kerrisk see also: add console_ioctl(2) and tty_ioctl(2) listxattr.2 xattr.7 michael kerrisk describe listxattr(2) e2big error and document it as a bug mkdir.2 michael kerrisk wording fixes + point reader at stat(2) for explanation of file mode michael kerrisk [andreas grünbacher] further tweaks to text on s_isvtx and 'mode' argument mknod.2 michael kerrisk rewordings + point reader at stat(2) for details of mode bits mmap.2 michael kerrisk remove text that implies that munmap() syncs map_shared mapping to file the existing text in this page: map_shared share this mapping. updates to the mapping are visible to other processes that map this file, and are carried through to the underly‐ ing file. the file may not actually be updated until msync(2) or munmap() is called. implies that munmap() will sync the mapping to the underlying file. posix doesn't require this, and some light reading of the code and some light testing (fsync() after munmap() of a large file) also indicates that linux doesn't do this. msync.2 michael kerrisk rework text of description rewrite the text somewhat, for easier comprehension. no (intentional) changes to factual content nfsservctl.2 michael kerrisk [j. bruce fields] note that nfsservctl() was replaced by files in nfsd filesystem open.2 michael kerrisk [andreas gruenbacher] open() honors the s_isvtx, s_isuid, and s_isgid bits in 'mode' michael kerrisk tighten wording: use 'mode bit' rather than 'permission bit' michael kerrisk [neilbrown] bugs: o_creat | o_directory succeeds if pathname does not exist poll.2 michael kerrisk [ian pilcher] clarify that signal mask treatment in ppoll() is per-thread s/sigprocmask()/pthread_sigmask()/ michael kerrisk [sam varshavchik] after pollhup, eof will be seen only after all data has been consumed michael kerrisk make it clearer which bits are ignored in 'events' prctl.2 michael kerrisk [david wilcox, filipe brandenburger] note that "parent" for purposes of pr_set_deathsig is a *thread* see https://bugzilla.kernel.org/show_bug.cgi?id=43300 sendfile.2 michael kerrisk [jason newton] note that sendfile does not support o_append for 'out_fd' see https://bugzilla.kernel.org/show_bug.cgi?id=82841 michael kerrisk [gregor jasny] return value: note the possibility of "short sends" see https://bugzilla.kernel.org/show_bug.cgi?id=97491 michael kerrisk [askar safin] clarify text on 'out_fd' and regular files in linux 2.4 see https://bugzilla.kernel.org/show_bug.cgi?id=86001 shutdown.2 michael kerrisk [stéphane aulery] bugs: unix domain sockets now detect invalid 'how' values bug fixed in linux 3.7. see https://bugzilla.kernel.org/show_bug.cgi?id=47111 sigaction.2 michael kerrisk refer the reader to fcntl(2) f_setsig for further details on si_fd stat.2 jann horn add note about stat() being racy andreas gruenbacher improve description of some mode constants michael kerrisk [andreas grünbacher] remove excessive leading zeros on some constants michael kerrisk add text on posix terms "file mode bits" and "file permission bits" recent changes to various pages employ this distinction. michael kerrisk tighten wording: use 'mode bit' rather than 'permission bit' according to posix, the 9 ugo*rwx bits are permissions, and 'mode' is used to refer to collectively to those bits plus sticky, set-uid, and set_gid bits. syslog.2 michael kerrisk see also: add dmesg(1) umask.2 open.2 mknod.2 mkdir.2 andreas gruenbacher explain what default acls do explain the effect that default acls have (instead of the umask) in umask.2. mention that default acls can have an affect in open.2, mknod.2, and mkdir.2. unshare.2 michael kerrisk [florian weimer] give the reader a hint that unshare() works on processes or threads see https://bugzilla.kernel.org/show_bug.cgi?id=59281 atexit.3 zeng linggang attributes: note function that is thread-safe bsearch.3 zeng linggang attributes: note function that is thread-safe cmsg.3 michael kerrisk [christopher head] fix error in scm_rights code sample remove erroneous second initialization of msg.msg_controllen in the example code for scm_rights. see https://bugzilla.kernel.org/show_bug.cgi?id=15952 cpu_set.3 chris metcalf clarify language about "available" cpus the cpu_set.3 man page uses the adjective "available" when explaining what the argument to cpu_set() means. this is confusing, since "available" isn't well-defined. the kernel has a set of adjectives (possible, present, online, and active) that qualify cpus, but normally none of these are what the cpu_set_t bit index means: it's just "which cpu", using the kernel's internal numbering system, even if that cpu isn't possible or present. this change removes the word "available" and adds a sentence warning that cpu sets may not be contiguous due to dynamic cpu hotplug, etc. err.3 zeng linggang attributes: note functions that are thread-safe ftw.3 zeng linggang attributes: note functions that are thread-safe gethostbyname.3 carlos o'donell nss plugins searched first carlos o'donell "order" is obsolete gethostid.3 zeng linggang attributes: note functions that are/aren't thread-safe getmntent.3 zeng linggang attributes: note functions that are/aren't thread-safe get_nprocs_conf.3 michael kerrisk use exit() rather than return in main() getopt.3 michael kerrisk [guy harris] remove crufty bugs section see https://bugzilla.kernel.org/show_bug.cgi?id=90261 iconv_close.3 zeng linggang attributes: note function that is thread-safe inet_ntop.3 zeng linggang attributes: note function that is thread-safe longjmp.3 zeng linggang attributes: note functions that are thread-safe lsearch.3 zeng linggang attributes: note functions that are thread-safe mcheck.3 zeng linggang attributes: note functions that aren't thread-safe on_exit.3 zeng linggang attributes: note function that is thread-safe printf.3 michael kerrisk [egmont koblinger] merge dprintf() and vdprintf() discussion into this page michael kerrisk see also: add puts(3) michael kerrisk move return value discussion to proper return value section putpwent.3 zeng linggang attributes: note function that is thread-safe qsort.3 zeng linggang attributes: note functions that are thread-safe regex.3 michael kerrisk [laurence gonsalves] fix error in description of 'cflags' 'cflags' is a bit mask of *zero* (not one) or more flags. resolver.3 stéphane aulery add info about res_insecure1 and res_insecure2 option in debug mode scanf.3 joern heissler improve description of %n specifier setjmp.3 zeng linggang attributes: note functions that are thread-safe setlocale.3 zeng linggang attributes: note function that isn't thread-safe setlogmask.3 zeng linggang attributes: note function that isn't thread-safe sleep.3 zeng linggang attributes: note function that isn't thread-safe strsignal.3 zeng linggang attributes: note function that isn't thread-safe sysconf.3 zeng linggang attributes: note function that is thread-safe undocumented.3 william woodruff remove documented functions tty_ioctl.4 michael kerrisk [denis du] fix error in code example proc.5 michael kerrisk [cameron norman, vasiliy kulikov] document /proc mount options document the 'hidepid' and 'gid' mount options that were added in linux 3.3. see https://bugzilla.kernel.org/show_bug.cgi?id=90641 based on text by vasiliy kulikov in documentation/filesystems/proc.txt. michael kerrisk [kirill a. shutemov] improve description of /proc/pid/status guillem jover document /proc/pid/exe behaviour on unlinked pathnames michael kerrisk [weijie yang] document /proc/pid/status vmpmd resolv.conf.5 stéphane aulery [thomas hood] document use-vc option added to glibc 2.14 fix ubuntu bug #1110781: https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/1110781 stéphane aulery [thomas hood] document res_snglkupreop fix ubuntu bug #1110781: https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/1110781 tzfile.5 sam varshavchik add various details on version 2 format aio.7 michael kerrisk add details and update url for ols 2003 paper on aio bootparam.7 michael kerrisk [alain kalker] update discussion of 'debug' option see https://bugzilla.kernel.org/show_bug.cgi?id=97161 michael kerrisk summary of multiple changes: remove cruft from this page. much of the detail on hardware specifics in this page dates from the 20th century. (the last major update to this page was in man-pages-1.14!) it's hugely out of date now (many of these devices disappeared from the kernel years ago.) so, i've taken a large scythe to the page to remove anything that looks seriously dated. in the process, the page has shrunk to less than 50% of its previous size. michael kerrisk remove "buff=" details this seems to have gone away in linux 2.2. michael kerrisk remove crufty "mouse drivers" options michael kerrisk remove crufty "general non-device-specific boot arguments" options michael kerrisk remove crufty "hard disks" options michael kerrisk remove crufty "mem=" details michael kerrisk remove crufty details on ibm mca bus devices michael kerrisk remove 'swap=" details this seems to have gone away in linux 2.2, michael kerrisk remove crufty floppy disk driver options in the specific case of floppy drives: the drivers still exist, but it's been a while since most of saw these devices in the wild. so, just refer the reader to the kernel source file for details. (the detail in this man page was after all originally drawn from that file.) remove crufty "isdn drivers" options michael kerrisk remove crufty "line printer driver" options michael kerrisk remove crufty "serial port drivers" options michael kerrisk remove crufty reference to config_bugi386 that option disappeared in linux 2.4. michael kerrisk remove crufty text "bootsetups array" dates from linux 2.0. michael kerrisk remove crufty "video hardware" options michael kerrisk remove crufty scsi device driver options fanotify.7 michael kerrisk [heinrich schuchardt] since linux 3.19, fallocate(2) generates fan_modify events inotify.7 michael kerrisk [heinrich schuchardt] since linux 3.19, fallocate(2) generates in_modify events ip.7 michael kerrisk explain how ip_add_membership determines its argument type michael kerrisk [jiri pirko, magnus reftel] clarify details of the ip_multicast_if socket option michael kerrisk [advait dixi] remove dubious text that says that so_priority sets ip tos see https://bugzilla.kernel.org/show_bug.cgi?id=35852 michael kerrisk relocate misplaced text describing enoprotoopt error packet.7 graham shaw add sll_protocol to list of required fields for outbound packets pthreads.7 michael kerrisk [kosaki motohiro] using thread ids whose lifetime has expired gives undefined behavior see https://bugzilla.kernel.org/show_bug.cgi?id=53061 raw.7 michael kerrisk [tetsuo handa] for incoming datagrams, sin_port is set to zero michael kerrisk mention sendto(), recvfrom(), and so on when discussing address format this gives the reader a little context for the following discussion of 'sin_port'. michael kerrisk remove crufty reference to michael kerrisk replace reference to rfc 1700 with pointer to iana protocol number list signal.7 michael kerrisk [steinar h. gunderson] clarify that i/o operations on disks are not interrupted by signals see https://bugzilla.kernel.org/show_bug.cgi?id=97721 unix.7 michael kerrisk [christophe lohr] remove mention of unix_path_max this kernel constant is not exposed to user space. michael kerrisk note the 108 bytes for sun_path is how things are done on linux and refer the reader to notes for discussion of portability. xattr.7 michael kerrisk document ea limits for btrfs michael kerrisk document vfs-imposed limits on eas vfs imposes a 255-byte limit on ea names, and a 64kb limit on ea values. michael kerrisk the ext[234] block limitation applies to sum of all eas it is not a per-ea limit. michael kerrisk clarify permissions required to work with 'user' eas michael kerrisk ext2 and ext3 no longer need mounting with 'user_xattr' for user eas michael kerrisk add various relevant pages to see also michael kerrisk add conforming to section michael kerrisk modify headings to man-pages norms michael kerrisk btrfs also supports extended attributes michael kerrisk file capabilities are implemented using *security* attributes not *system* attributes michael kerrisk describe limit on ea values for jfs, xfs, and reiserfs michael kerrisk explicitly mention some of the xattr system calls in description naming the system calls helps to orient the reader nscd.8 michael kerrisk add mention of 'services' and 'netgroup' databases this makes the page consistent with nscd.conf(5). ==================== changes in man-pages-4.01 ==================== released: 2015-07-23, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexei starovoitov andries e. brouwer arjun shankar ashish sangwan ben woodard carlos o'donell christoph thompson cortland setlow daniel borkmann david leppik dilyan palauzov doug klima eric b munson florian weimer hack ndo jann horn jens axboe jian wen joerg roedel julian orth kees cook laszlo ersek marko myllynen mehdi aqadjani memar michael kerrisk michal hocko mike frysinger mike hayward miklos szeredi namhyung kim namjae jeon nathan lynch neilbrown pádraig brady pavel machek peter hurley sam varshavchik scot doyle stephan mueller tobias stoeckmann tulio magno quites machado filho uwe kleine-könig vegard nossum ville skyttä vince weaver zeng linggang 文剑 apologies if i missed anyone! new and rewritten pages ----------------------- bpf.2 alexei starovoitov, michael kerrisk [daniel borkmann] new page documenting bpf(2) __ppc_get_timebase.3 tulio magno quites machado filho new page documenting __ppc_get_timebase() and __ppc_get_timebase_freq() glibc 2.16 was released with a new function for the power architecture that can read its time base register. glibc 2.17 adds a function to read the frequency at which the time base register of power processors is updated. queue.3 michael kerrisk [david leppik, doug klima] reimport from latest freebsd page long ago, doug klima noted that many macros were not documented in the queue(3) page. fix by reimporting from latest [1] freebsd man page. [1] revision 263142, modified fri mar 14 03:07:51 2014 utc this also fixes https://sourceware.org/bugzilla/show_bug.cgi?id=1506 this time, i'll learn from past mistakes and not convert from 'mdoc' to 'man' macros. michael kerrisk use subsections in description michael kerrisk remove see also reference to nonexistent tree(3) michael kerrisk use real hyphens in code samples michael kerrisk comment out text for functions not in glibc michael kerrisk replace history with conforming to newly documented interfaces in existing pages --------------------------------------------- rename.2 michael kerrisk [miklos szeredi] document rename_whiteout heavily based on text by miklos szeredi. new and changed links --------------------- __ppc_get_timebase_freq.3 tulio magno quites machado filho new link to new __ppc_get_timebase(3) page list_empty.3 list_first.3 list_foreach.3 list_head_initializer.3 list_insert_before.3 list_next.3 slist_empty.3 slist_entry.3 slist_first.3 slist_foreach.3 slist_head.3 slist_head_initializer.3 slist_init.3 slist_insert_after.3 slist_insert_head.3 slist_next.3 slist_remove.3 slist_remove_head.3 stailq_concat.3 stailq_empty.3 stailq_entry.3 stailq_first.3 stailq_foreach.3 stailq_head.3 stailq_head_initializer.3 stailq_init.3 stailq_insert_after.3 stailq_insert_head.3 stailq_insert_tail.3 stailq_next.3 stailq_remove.3 stailq_remove_head.3 tailq_concat.3 tailq_empty.3 tailq_first.3 tailq_foreach.3 tailq_foreach_reverse.3 tailq_head_initializer.3 tailq_insert_before.3 tailq_last.3 tailq_next.3 tailq_prev.3 tailq_swap.3 michael kerrisk new links to queue.3 global changes -------------- various pages michael kerrisk [andries e. brouwer] remove "abi" from "c library/kernel abi differences" subheadings the "abi" doesn't really convey anything significant in the title. these subsections are about describing differences between the kernel and (g)libc interfaces. changes to individual pages --------------------------- intro.1 michael kerrisk [andries e. brouwer] drop intro paragraph on '$?' shell variable as andries notes, this piece of text is rather out of place in a page that was intended to provide a tutorial introduction for beginners logging in on a linux system. locale.1 marko myllynen a minor output format clarification a minor clarification for the locale output format which was brought up at https://sourceware.org/bugzilla/show_bug.cgi?id=18516. for reference, see https://sourceware.org/bugzilla/show_bug.cgi?id=18516 http://pubs.opengroup.org/onlinepubs/9699919799/utilities/locale.html add conforming to section capget.2 julian orth clarify that hdrp->pid==0 is equivalent gettid() not getpid() chroot.2 jann horn chroot() is not intended for security; document attack it is unfortunate that this discourages this use of chroot(2) without pointing out alternative solutions - for example, openssh and vsftpd both still rely on chroot(2) for security. bind mounts should theoretically be usable as a replacement, but currently, they have a similar problem (cve-2015-2925) that hasn't been fixed in ~6 months, so i'd rather not add it to the manpage as a solution before a fix lands. clock_getres.2 zeng linggang attributes: note functions that are thread-safe eventfd.2 zeng linggang attributes: note function that is thread-safe execve.2 michael kerrisk elaborate on envp/argv as null behavior _exit.2 michael kerrisk open stdio frames are not flushed, temporary files are deleted many years ago, text was added to the page saying that it is implementation-dependent whether stdio streams are flushed and whether temporary are removed. in part, this change appears to be because posix.1-2001 added text related to this point. however, that seems to have been an error in posix, and the text was subsequently removed for posix.1-2008. see https://collaboration.opengroup.org/austin/interps/documents/9984/ai-085.txt austin group interpretation reference 1003.1-2001 #085 fallocate.2 namjae jeon [michael kerrisk] document falloc_fl_insert_range michael kerrisk since linux 4.2, ext4 supports falloc_fl_insert_range fcntl.2 michael kerrisk ofd locks are proposed for inclusion in the next posix revision getrlimit.2 zeng linggang attributes: note functions that are thread-safe getrusage.2 zeng linggang attributes: note function that is thread-safe gettid.2 michael kerrisk note that for a thread group leader, gettid() == getpid() iopl.2 michael kerrisk remove some historical libc5 and glibc 1 details these details are ancient, and long ago ceased to be relevant. ioprio_set.2 michael kerrisk [jens axboe] document meaning of ioprio==0 mlock.2 michael kerrisk [mehdi aqadjani memar] document another enomem error case enomem can occur if locking/unlocking in the middle of a region would increase the number of vmas beyond the system limit (64k). mmap.2 michal hocko [eric b munson] clarify map_populate david rientjes has noticed that map_populate wording might promise much more than the kernel actually provides and intends to provide. the primary usage of the flag is to pre-fault the range. there is no guarantee that no major faults will happen later on. the pages might have been reclaimed by the time the process tries to access them. michal hocko [eric b munson] clarify map_locked semantics map_locked had a subtly different semantic from mmap(2)+mlock(2) since it has been introduced. mlock(2) fails if the memory range cannot get populated to guarantee that no future major faults will happen on the range. mmap(map_locked) on the other hand silently succeeds even if the range was populated only partially. fixing this subtle difference in the kernel is rather awkward because the memory population happens after mm locks have been dropped and so the cleanup before returning failure (munlock) could operate on something else than the originally mapped area. e.g. speculative userspace page fault handler catching segv and doing mmap(fault_addr, map_fixed|map_locked) might discard portion of a racing mmap and lead to lost data. although it is not clear whether such a usage would be valid, mmap page doesn't explicitly describe requirements for threaded applications so we cannot exclude this possibility. this patch makes the semantic of map_locked explicit and suggests using mmap + mlock as the only way to guarantee no later major page faults. michael kerrisk errors: point out that enomem can occur even for munmap() mprotect.2 michael kerrisk note enomem error that can occur when we reach limit on maximum vmas open.2 read.2 write.2 michael kerrisk [mike hayward] clarify that o_nonblock is a no-op for regular files and block devices perf_event_open.2 vince weaver [joerg roedel] exclude_host/exclude_guest clarification this patch relates to the exclude_host and exclude_guest bits added by the following commit: exclude_host, exclude_guest; linux 3.2 commit a240f76165e6255384d4bdb8139895fac7988799 author: joerg roedel date: wed oct 5 14:01:16 2011 +0200 perf, core: introduce attrs to count in either host or guest mode the updated manpage text clarifies that the "exclude_host" and "exclude_guest" perf_event_open() attr bits only apply in the context of a kvm environment and are currently x86 only. vince weaver document perf_sample_regs_intr this patch relates to the addition of perf_sample_regs_intr support added in the following commit: perf_sample_regs_intr; linux 3.19 commit 60e2364e60e86e81bc6377f49779779e6120977f author: stephane eranian perf: add ability to sample machine state on interrupt the primary difference between perf_sample_regs_intr and the existing perf_sample_regs_user is that the new support will return kernel register values. also if precise_ip is set higher than 0 then the pebs register state will be returned rather than the saved interrupt state. this patch incorporates feedback from stephane eranian and andi kleen. prctl.2 seccomp.2 michael kerrisk clarify that seccomp_set_mode_strict disallows exit_group(2) these days, glibc implements _exit() as a wrapper around exit_group(2). (when seccomp was originally introduced, this was not the case.) give the reader a clue that, despite what glibc is doing, what seccomp_set_mode_strict permits is the true _exit(2) system call, and not exit_group(2). pread.2 read.2 readv.2 sendfile.2 write.2 michael kerrisk clarify that linux limits transfers to a maximum of 0x7ffff000 bytes see https://bugs.debian.org/629994 and https://bugs.debian.org/630029. pread.2 michael kerrisk rewrite return value section (also drop the text on pwrite() returning zero; that seems bogus.) ptrace.2 michael kerrisk [vegard nossum] ptrace_o_traceexit clarification readv.2 michael kerrisk remove bugs heading the text on mixing i/o syscalls and stdio is a general point of behavior. it's not a bug as such. recv.2 send.2 michael kerrisk explain some subtleties of msg_dontwait versus o_nonblock rename.2 michael kerrisk michael kerrisk note that rename_noreplace can't be employed with rename_exchange sched_setaffinity.2 michael kerrisk add an example program michael kerrisk [florian weimer] explain how to deal with 1024-cpu limitation of glibc's cpu_set_t type michael kerrisk mention the use of the 'isolcpus' kernel boot option sched_setattr.2 julian orth remove a const attribute the attr argument of sched_setattr was documented as const but the kernel will modify the size field of this struct if it contains an invalid value. see the documentation of the size field for details. seccomp.2 michael kerrisk see also: add bpf(2) send.2 michael kerrisk expand on subtleties of msg_nosignal versus ignoring sigpipe sigaltstack.2 zeng linggang attributes: note function that is thread-safe socket.2 stephan mueller update documentation reference for af_alg truncate.2 michael kerrisk errors: ftruncate() can fail if the file descriptor is not writable utimensat.2 zeng linggang attributes: note functions that are thread-safe after research, we think utimensat() and futimens() are thread-safe. but, there are not markings of utimensat() and futimens() in glibc document. clearenv.3 zeng linggang attributes: note function that is not thread-safe dl_iterate_phdr.3 zeng linggang attributes: note function that is thread-safe error.3 zeng linggang attributes: note functions that are/aren't thread-safe fexecve.3 zeng linggang attributes: note function that is thread-safe fpurge.3 zeng linggang attributes: note function that is thread-safe fread.3 andries e. brouwer clarify terminology in the "return value" section the word item is in italics as if it were one of the function parameters. but the word "item" occurs here for the first time, earlier the text uses "element". [patch improves this.] fts.3 zeng linggang attributes: note functions that are/aren't thread-safe getaddrinfo.3 zeng linggang attributes: note functions that are thread-safe getaddrinfo_a.3 zeng linggang attributes: note functions that are thread-safe getauxval.3 michael kerrisk file capabilities also trigger at_secure michael kerrisk (briefly) document at_hwcap2 getgrent_r.3 zeng linggang attributes: note functions that are/aren't thread-safe gethostbyname.3 michael kerrisk [laszlo ersek] remove mention of ipv6 addresses, which are not supported as reported by laszlo ersek: gethostbyname(3) fails to resolve the ipv6 address "::1", but the manual page says: "if name is an ipv4 or ipv6 address, no lookup is performed and gethostbyname() simply copies name into the h_name field [...]". debian bug report: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=455762 glibc bug report: http://sourceware.org/bugzilla/show_bug.cgi?id=5479 susv3 link for gethostbyname(3): http://www.opengroup.org/onlinepubs/000095399/functions/gethostbyname.html it seems that the glibc behavior is conformant, and the manual page is in error. getifaddrs.3 zeng linggang attributes: note functions that are thread-safe getnameinfo.3 zeng linggang attributes: note function that is thread-safe getnetent_r.3 zeng linggang attributes: note functions that are thread-safe getprotoent.3 zeng linggang attributes: note functions that aren't thread-safe getprotoent_r.3 zeng linggang attributes: note functions that are thread-safe getpw.3 zeng linggang attributes: note function that is thread-safe getpwent_r.3 zeng linggang attributes: note functions that are/aren't thread-safe getrpcent.3 zeng linggang attributes: note functions that are/aren't thread-safe getrpcent_r.3 zeng linggang attributes: note functions that are thread-safe getrpcport.3 zeng linggang attributes: note function that is thread-safe getservent.3 zeng linggang attributes: note functions that aren't thread-safe getservent_r.3 zeng linggang attributes: note functions that are thread-safe gsignal.3 zeng linggang attributes: note functions that are thread-safe key_setsecret.3 zeng linggang attributes: note functions that are thread-safe malloc_get_state.3 zeng linggang attributes: note functions that are thread-safe malloc_info.3 zeng linggang attributes: note function that is thread-safe malloc_stats.3 zeng linggang attributes: note function that is thread-safe malloc_trim.3 zeng linggang attributes: note function that is thread-safe mb_len_max.3 michael kerrisk clarify meaning of mb_len_max michael kerrisk [pádraig brady] mb_len_max is 16 in modern glibc versions memcpy.3 michael kerrisk notes: describe the glibc 2.13 changes that revealed buggy applications adding a note on this point seems worthwhile as a way of emphasizing the point that the buffers must not overlap. mq_notify.3 zeng linggang attributes: note function that is thread-safe perror.3 michael kerrisk some wording improvements and clarifications profil.3 zeng linggang attributes: note function that is not thread-safe psignal.3 zeng linggang attributes: note functions that are thread-safe pthread_attr_init.3 zeng linggang attributes: note functions that are thread-safe michael kerrisk use "%zd" for printing size_t in example code pthread_attr_setaffinity_np.3 zeng linggang attributes: note functions that are thread-safe pthread_cancel.3 zeng linggang attributes: note function that is thread-safe pthread_cleanup_push.3 zeng linggang attributes: note functions that are thread-safe pthread_create.3 zeng linggang attributes: note function that is thread-safe pthread_detach.3 zeng linggang attributes: note function that is thread-safe pthread_getattr_np.3 zeng linggang attributes: note function that is thread-safe pthread_join.3 zeng linggang attributes: note function that is thread-safe pthread_setname_np.3 zeng linggang attributes: note functions that are thread-safe pthread_tryjoin_np.3 zeng linggang attributes: note functions that are thread-safe putgrent.3 zeng linggang attributes: note function that is thread-safe rcmd.3 zeng linggang attributes: note functions that are/aren't thread-safe resolver.3 zeng linggang attributes: note functions that are thread-safe rpc.3 zeng linggang attributes: note functions that are thread-safe rpmatch.3 zeng linggang attributes: note function that is thread-safe sem_close.3 zeng linggang attributes: note function that is thread-safe sem_open.3 zeng linggang attributes: note function that is thread-safe setaliasent.3 zeng linggang attributes: note functions that are/aren't thread-safe setlocale.3 marko myllynen update conforming to http://pubs.opengroup.org/onlinepubs/9699919799/functions/setlocale.html setlocale.3 marko myllynen tweak c/posix locale portability description as discussed earlier, the current description might be a little bit too stringent, let's avoid the issue by describing the portability aspect on a slightly higher level. references: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/v1_chap06.html http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/v1_chap07.html http://pubs.opengroup.org/onlinepubs/9699919799/functions/setlocale.html shm_open.3 zeng linggang attributes: note functions that are thread-safe strfmon.3 marko myllynen document strfmon_l(3) describe strfmon_l(3). http://pubs.opengroup.org/onlinepubs/9699919799/functions/strfmon.html marko myllynen fix conforming to afaics strfmon(3) is now defined in posix and the glibc implementation is as specified there. http://pubs.opengroup.org/onlinepubs/9699919799/functions/strfmon.html marko myllynen rewrite the example i think the example is more accurate when we use the exact locale names and also the euro sign where appropriate. xcrypt.3 zeng linggang attributes: note functions that are thread-safe xdr.3 zeng linggang attributes: note functions that are thread-safe console_codes.4 scot doyle [pavel machek, michael kerrisk] add csi sequence for cursor blink interval add a console private csi sequence to specify the current console's cursor blink interval. the interval is specified as a number of milliseconds until the next cursor display state toggle, from 50 to 65535. null.4 michael kerrisk note that reads from /dev/zero are interruptible since linux 2.6.31 core.5 michael kerrisk mention 'coredump_filter' boot option host.conf.5 michael kerrisk wording fix: s/resolv+/the resolver library/ the term "resolv+" seems to be historical cruft. hosts.equiv.5 carlos o'donell fix format, clarify idm needs, and provide examples. in some recent work with a red hat customer i had the opportunity to discuss the fine nuances of the ruserok() function and related api which are used to implement rlogin and rsh. it came to my attention after working with qe on some automated internal testing that there were no good examples in the hosts.equiv manual page showing how the format was supposed to work for this file and for ~/.rhosts, worse the "format" line showed that there should be spaces between arguments when that would clearly lead to incorrect behaviour. in addition some things that the format allows you to write are just wrong like "-host -user" which makes no sense since the host is already rejected, and should be written as "host -user" instead. i added notes in the example to make it clear that "-host -user" is invalid. i fixed three things: (a) the format line. - either +, or [-]hostname, or +@netgrp or -@netgrp. - either +, or [-]username, or +@netgrp or -@netgrp. - you must specify something in the hostname portion so remove optional brackets. (b) clarify language around credentials - if the host is not trusted you must provide credentials to the login system and that could be anything really and it depends on your configuration e.g. pam or whatever idm you have. (c) provide real-world examples - provide several real world examples and some corner case examples for how you would write something. hopefully others can add examples as they see fit. michael kerrisk [carlos o'donell, arjun shankar] improve explanation in example locale.5 marko myllynen document map to_inpunct, map to_outpunct see e.g. fa_ir for reference. marko myllynen document class in lc_ctype see e.g. the locale zh_cn and http://en.cppreference.com/w/cpp/string/wide/towctrans http://en.cppreference.com/w/cpp/string/wide/wctrans marko myllynen add iconv(1) reference marko myllynen document character transliteration see e.g. da_dk for reference. (not sure should we actually provide an example here?) marko myllynen document era keywords this patch completes the lc_time section - since these era keywords are so tightly coupled, i'm providing them as a single patch. based on http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap07.html http://www.open-std.org/jtc1/sc22/wg20/docs/n972-14652ft.pdf marko myllynen document default_missing marko myllynen document outdigit and alt_digits see e.g. fa_ir for reference. marko myllynen refer to locale(7) more prominently it's probably a good idea to refer to locale(7) so that a reader can check what a category is about before describing them in detail. marko myllynen document charclass and charconv see e.g. the locales ja_jp and ko_kr and http://en.cppreference.com/w/cpp/string/wide/towctrans http://en.cppreference.com/w/cpp/string/wide/wctrans marko myllynen copy is not exclusive in lc_ctype and lc_collate see e.g. da_dk for reference. marko myllynen remove the fixme for timezone the timezone of lc_time is not in posix, only 6 (out of ~300) glibc locales define it, the glibc code comment below from glibc.git/programs/ld-time.c seems to suggest it's not a good idea, and there's been a proposal in upstream [1] to remove the existing timezone definitions from glibc locales so i think it's actually better to leave this one undocumented: /* xxx we don't perform any tests on the timezone value since this is simply useless, stupid $&$!@... */ 1) https://sourceware.org/ml/libc-alpha/2015-06/msg00098.html move the remaining lc_collate fixmes together while at it. marko myllynen fix country_isbn format both plain numbers and unicode code points are used in glibc locales but checking the code reveals that country_isbn is handled like the rest of its category expect for country_num which was clarified earlier. marko myllynen sort according to the standard sort the options so that those defined in posix are listed first, then followed by those defined in iso/iec tr 14652 in the order of common convention in many widely used glibc locales. actual descriptions are unchanged. http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/v1_chap07.html marko myllynen refer to strftime(3) where appropriate the relationship between the locale time format syntax and strftime() cannot be considered as obvious. marko myllynen document map "totitle" see e.g. locales/i18n for reference. michael kerrisk [marko myllynen] remove bugs section saying man page is not complete to some degree, this is true of many pages. and anyway, this page is much better after recent work by marko. proc.5 michael kerrisk list /proc/vmstat fields michael kerrisk tweak /proc/vmstat text michael kerrisk add /proc/crypto entry with a pointer to further information michael kerrisk [kees cook] document /proc/sys/kernel/sysctl_writes_strict based on text in documentation/sysctl/kernel.txt. michael kerrisk move misordered /proc/[pid]/timers entry michael kerrisk refer to bpf(2) for explanation of /proc/sys/net/core/bpf_jit_enable repertoiremap.5 marko myllynen symbolic names aka mnemonics a long time ago in glibc, repertoire maps were used (but they were removed already in 2000), those mapping files were named as mnemonics, so "mnemonic" is a term that would almost certainly come up if somebody studies glibc side (perhaps even the related standards like iso 9945 [which i don't have access to]) so i thought it's worth to mention to term in the man page to make sure we're talking about the same thing, otherwise someone might wonder is that something different or not. iow, symbolic names and mnemonics are often used interchangeably, let's mention the other often used term in the page, too. capabilities.7 michael kerrisk cap_sys_admin allows calling bpf(2) locale.7 marko myllynen lc_ctype determines transliteration rules on glibc systems packet.7 文剑 [cortland setlow] fix description of binding a packet socket to an interface pty.7 neilbrown [peter hurley] clarify asynchronous nature of pty i/o a pty is not like a pipe - there may be delayed between data being written at one end and it being available at the other. this became particularly apparent after commit f95499c3030f ("n_tty: don't wait for buffer work in read() loop") in linux 3.12 see also the mail thread at https://lkml.org/lkml/2015/5/1/35 date mon, 04 may 2015 12:32:04 -0400 from peter hurley <> subject re: [patch bisected regression] input_available_p() sometimes says 'no' when it should say 'yes' rtld-audit.7 ben woodard use correct printf() specifier for pointer types in the example code you used %x rather than %p in the example code for an audit library. the problem is that it truncates the pointers on 64b platforms. so you get something like: la_symbind64(): symname = strrchr sym->st_value = 0x7f4b8a3f8960 ndx = 222 flags = 0x0 refcook = 8b53e5c8 defcook = 8b537e30 rather than: la_symbind64(): symname = fclose sym->st_value = 0x7fa452dd49b0 ndx = 1135 flags = 0x0 refcook = 0x7fa453f395c8 defcook = 0x7fa453f32e30 this has bitten me a handful of times when playing around with audit test libraries to investigate its behavior. sched.7 michael kerrisk remove ancient, wildly optimistic prediction about future of rt patches it seems the patches were not merged by 2.6.30... socket.7 michael kerrisk see also: add bpf(2) vdso.7 nathan lynch [mike frysinger] update for arm the 32-bit arm architecture in linux has gained a vdso as of the 4.1 release. (i was the primary author.) document the symbols exported by the arm vdso. accepted kernel submission: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-march/332573.html ==================== changes in man-pages-4.02 ==================== released: 2015-08-08, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: carlos o'donell daniel borkmann david rientjes dilyan palauzov gabriel f. t. gomes gleb fotengauer-malinovskiy goswin von brederlow heinrich schuchardt jonathan david amery michael kerrisk mike frysinger mike kravetz nicholas miell nikola forró sam varshavchik yaarit zeng linggang apologies if i missed anyone! new and rewritten pages ----------------------- dladdr.3 michael kerrisk new page documenting dladdr() and dladdr1() relocate/rewrite dladdr() text formerly contained in dlopen(3). add documentation of dladdr1(). zeng linggang attributes: note functions that are thread-safe dlerror.3 michael kerrisk migrate dlerror(3) to new separate man page michael kerrisk note that the returned message may be in a statically allocated buffer michael kerrisk note that the returned string does not include a trailing newline zeng linggang attributes: note function that is thread-safe dlinfo.3 michael kerrisk new page describing dlinfo(3) zeng linggang attributes: note function that is thread-safe dlopen.3 michael kerrisk this page was substantially rewritten and enhanced. notably: * the dladdr(), dlsym, dlvsym(), and dlerror() content were moved to separate new pages; * documentation for dlmopen was added; * and other changes as noted below. zeng linggang attributes: note functions that are thread-safe michael kerrisk move atexit() discussion under "initialization and finalization" michael kerrisk move discussion of _init() and _fini() to notes michael kerrisk rework the discussion of initialization and finalization functions deemphasize the obsolete _init/_fini and give more prominence to gcc constructors/destructors. michael kerrisk dlclose() will unload the object when all references have been released michael kerrisk example: remove mention of "-rdynamic" that option isn't needed for compiling and running this program. michael kerrisk remove reference to ld.so info page the command "info ld.so" simply shows the man page... michael kerrisk add versions section michael kerrisk reorganize conformance information for 'flags' dlsysm.3 michael kerrisk move dlsym() and dlvsym() content to new separate page zeng linggang attributes: note functions that are thread-safe newly documented interfaces in existing pages --------------------------------------------- dlopen.3 michael kerrisk, carlos o'donell document dlmopen(3) nl_langinfo.3 sam varshavchik, michael kerrisk add documentation for nl_langinfo_l(3) __ppc_set_ppr_med.3 gabriel f. t. gomes document ppc functions providing access to ppr gnu c library 2.18 adds functions (__ppc_set_ppr_low(3), __ppc_set_ppr_med(3), __ppc_set_ppr_med_low(3)) that provide access to the program priority register (ppr). __ppc_yield.3 gabriel f. t. gomes document ppc performance-hint functions gnu c library 2.18 adds functions __ppc_yield(3), __ppc_mdoio(3), and __ppc_mdoom(3) that can be used provide a hint that performance could be improved if shared resources are released for use by other processors. new and changed links --------------------- dladdr1.3 michael kerrisk new link to (new) dladdr(3) page dlmopen.3 michael kerrisk new link to dlopen.3 dlvsym.3 michael kerrisk adjust link to point to new self-contained dlsym(3) page nl_langinfo_l.3 michael kerrisk new link to nl_langinfo.3 __ppc_mdoio.3 gabriel f. t. gomes new link to __ppc_yield.3 __ppc_mdoom.3 gabriel f. t. gomes new link to __ppc_yield.3 __ppc_set_ppr_low.3 gabriel f. t. gomes new link to __ppc_set_ppr_med.3 __ppc_set_ppr_med_low.3 gabriel f. t. gomes new link to __ppc_set_ppr_med.3 global changes -------------- very many pages michael kerrisk update conforming to section to reflect posix.1-2001 and posix.1-2008 details. (by now, i believe all pages should be up to date with respect to appropriately mentioning posix.1-2001 and posix.1-2008.) ldd.1 sprof.1 execve.2 dlopen.3 ld.so.8 michael kerrisk prefer "shared object" over "shared library" the man pages variously use "shared library" or "shared object". try to more consistently use one term ("shared object"), while also pointing out on a few pages that the terms are synonymous. changes to individual pages --------------------------- accept.2 michael kerrisk add mention of posix.1-2008 regarding eagain vs ewouldblock bpf.2 daniel borkmann various updates/follow-ups to address some fixmes a couple of follow-ups to the bpf(2) man-page, besides others: * description of map data types * explanation on ebpf tail calls and program arrays * paragraph on tc holding ref of the ebpf program in the kernel * updated ascii image with tc ingress and egress invocations * __sync_fetch_and_add() and example usage mentioned on arrays * minor reword on the licensing and other minor fixups execve.2 michael kerrisk reword text on posix and #! io_getevents.2 michael kerrisk note return value on interruption by a signal handler michael kerrisk clarify details of return value for timeout-expired case michael kerrisk clarify and extend discussion of 'timeout' argument mmap.2 michael kerrisk note that 'length' need not be a page-size multiple for munmap() michael kerrisk [david rientjes, david rientjes, mike kravetz] describe mmap()/munmap() argument requirements for huge-page mappings michael kerrisk move discussion of timestamps to notes a straight move; no changes to the content. this content is better placed in notes. seccomp.2 michael kerrisk see also: mention libseccomp pages see also: add scmp_sys_resolver(1) sigaction.2 michael kerrisk correct the list of flags that were added in posix.1-2001 socketpair.2 michael kerrisk [goswin von brederlow] clarify use of sock_* flags in 'type' argument see http://bugs.debian.org/794217 atexit.3 michael kerrisk see also: add dlopen(3) clock_getcpuclockid.3 michael kerrisk improve wording of eperm error it's imprecise to say that this is an "optional" error in posix.1. dl_iterate_phdr.3 michael kerrisk note that 'size' allows callback() to discover structure extensions michael kerrisk see also: add dladdr(3) michael kerrisk conforming to: note that this function appears on some other systems fseeko.3 michael kerrisk remove crufty notes section this ancient system v detail is unneeded. getutent.3 michael kerrisk mention posix.1-2008 for the "utmpx" functions iconv_close.3 iconv_open.3 michael kerrisk conforming to: change "unix98" to "susv2" malloc.3 michael kerrisk change "unix 98" to "susv2" mktemp.3 gleb fotengauer-malinovskiy reference mkdtemp(3) in addition to mkstemp(3) mention mkdtemp(3) as another secure alternative to mktemp(3). see also https://sourceware.org/bugzilla/show_bug.cgi?id=2898. mq_receive.3 mq_send.3 michael kerrisk clarify discussion of 'timeout' in particular, remove the word 'ceiling', which falsely suggests that the call might return prematurely. nl_langinfo.3 michael kerrisk explicitly describe the return value on success michael kerrisk posix specifies that the caller may not modify the returned string michael kerrisk enhance return value description note some further cases where returned string may be invalidated or overwritten. perror.3 michael kerrisk reformat conforming to information michael kerrisk note that 'sys_errlist' and 'sys_nerr' are not in posix.1 posix_openpt.3 michael kerrisk reword text regarding systems that don't have posix_openpt() printf.3 michael kerrisk conforming to: update details for dprintf() and vdprintf() setlogmask.3 michael kerrisk remove useless statement in conforming to saying that the description in psox.1-2001 is flawed, without saying what the fla is, is not helpful. (and no, i don't know what the flaw is.) shm_open.3 michael kerrisk add posix.1-2008 details regarding group id of new shared memory object strfmon.3 michael kerrisk fix erroneous conforming to strfmon() is in posix.1. fanotify.7 heinrich schuchardt clarify effects of file moves if files or directories are moved to other mounts, the inode is deleted. fanotify marks are lost. mq_overview.7 michael kerrisk remove unneeded conforming to section nptl.7 michael kerrisk [nicholas miell] note that i386 and x86-64 binaries can't share mutexes sched.7 nikola forró fix descriptions of sched_get_priority_max() / sched_get_priority_min() sem_overview.7 michael kerrisk remove unneeded conforming to section shm_overview.7 michael kerrisk remove unneeded conforming to section sigevent.7 michael kerrisk remove unneeded conforming to section symlink.7 michael kerrisk update with posix.1-2008 details for link(2) ld.so.8 michael kerrisk [jonathan david amery] items in ld_library_path can also be delimited by semicolons see http://bugs.debian.org/794559. ==================== changes in man-pages-4.03 ==================== released: 2015-12-05, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexander shishkin alexei starovoitov andy lutomirski arto bendiken carlos o'donell casper ti. vector daniel borkmann david drysdale eric b munson florian weimer gabriel f. t. gomes heinrich schuchardt ingo molnar jakub wilk johannes stüttgen jonathan wakely jonny grant kees cook maria guseva masami hiramatsu meikun wang michael kerrisk michal hocko mike frysinger namhyung kim nikola forró olivier tartrou peter hurley peter zijlstra (intel) ross zwisler serge hallyn silvan jegen stefan tauner steven rostedt tobias stoeckmann tycho andersen ville skyttä vince weaver zeng linggang apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- perf_event_open.2 vince weaver 4.1 adds aux sample support vince weaver 4.1 data_offset and data_size fields vince weaver [alexander shishkin] document aux_{head,tail,offset,size} support vince weaver 4.0 update rdpmc documentation vince weaver 4.1 adds perf_record_itrace_start vince weaver document 4.1 clockid support vince weaver [steven rostedt, masami hiramatsu] 4.1 perf_event_ioc_set_bpf support vince weaver 4.1 adds aux_flag_overwrite support vince weaver 4.1 perf_sample_branch_call_stack vince weaver 4.1 adds aux_watermark vince weaver add possibility of ebusy error prctl.2 andy lutomirski [kees cook, serge hallyn] document operations for ambient capabilities michael kerrisk rework pr_cap_ambient text note that arg4 and arg5 must be zero for cap_ambient return value: add pr_cap_ambient + pr_cap_ambient_is_set case errors: document pr_cap_ambient error cases __ppc_set_ppr_med.3 gabriel f. t. gomes document ppc functions providing access to ppr gnu c library commit 1747fcda4902a3b46183d93fb16ed9b436b2608b extends the priorities that can be set to the program priority register (ppr), with the functions: __ppc_set_ppr_very_low(3) and __ppc_set_ppr_med_high(3). capabilities.7 andy lutomirski [kees cook, serge hallyn] document ambient capabilities michael kerrisk various additions and reworkings for ambient capability text new and changed links --------------------- __ppc_set_ppr_med_high.3 gabriel f. t. gomes new link to __ppc_set_ppr_med.3 __ppc_set_ppr_very_low.3 gabriel f. t. gomes new link to __ppc_set_ppr_med.3 changes to individual pages --------------------------- mremap.2 eric b munson [michal hocko] add note about mremap() with locked areas when mremap() is used to move or expand a mapping that is locked with mlock() or equivalent it will attempt to populate the new area. however, like mmap(map_locked), mremap() will not fail if the area cannot be populated. also like mmap(map_locked) this might come as a surprise to users and should be noted. open.2 michael kerrisk [david drysdale] remove accidental mention of o_tty_init an earlier edit mentioned o_tty_init as a file creation flag. that's true, according posix, but linux does not implement this flag, so remove mention of it. pipe.2 michael kerrisk see also: add splice(2) prctl.2 michael kerrisk reorder options alphabetically employ a pseudo-alphabetical order, ordering options after removal of any "pr_", "pr_set_", or "pr_get" prefix. michael kerrisk fix alphabetical misplacements in errors ptrace.2 tycho andersen document ptrace_o_suspend_seccomp flag michael kerrisk document /proc/sys/kernel/yama/ptrace_scope michael kerrisk note that ptrace_attach cannot be applied to nondumpable processes michael kerrisk see also: add prctl(2) reboot.2 casper ti. vector 1-argument reboot() is also provided by alternative libc seccomp.2 michael kerrisk describe use of 'instruction_pointer' data field michael kerrisk [kees cook] note why all filters in a set are executed even after seccomp_ret_kill signalfd.2 michael kerrisk describe semantics with respect to scm_rights syscalls.2 michael kerrisk add mlock(2) michael kerrisk add userfaultfd() daemon.3 michael kerrisk [johannes stüttgen] note that daemon() is buggy with respect to controlling tty acquisition dirfd.3 jonathan wakely remove outdated notes as stated in the synopsis, since glibc 2.10 this function is also declared by the relevant x/open and posix macros. dlopen.3 michael kerrisk make it more explicit that ld_bind_now overrides rtld_lazy michael kerrisk [florian weimer] correct the pathname used in example quoting florian: this does not work because libm.so can be a linker script: handle = dlopen("libm.so", rtld_lazy); the proper way to do this is to include and use libm_so. see https://bugzilla.kernel.org/show_bug.cgi?id=108821 michael kerrisk include a shell session showing build/run in example michael kerrisk change arguments to main() to "void" in example fgetgrent.3 zeng linggang attributes: note function that is not thread-safe fgetpwent.3 zeng linggang attributes: note function that is not thread-safe getauxval.3 michael kerrisk add some details for at_secure getspnam.3 zeng linggang attributes: note functions that are/aren't thread-safe mallinfo.3 zeng linggang attributes: note function that is not thread-safe mallopt.3 carlos o'donell document m_arena_test and m_arena_max posix_fallocate.3 michael kerrisk clarify text relating to mt-safety carlos o'donell mention glibc emulation caveats termios.3 olivier tartrou add missing details on behaviour of parmrk for a serial terminal, with a specific configuration, input bytes with value 0377 are passed to the program as two bytes, 0377 0377. tty_ioctl.4 michael kerrisk [peter hurley] note that tiocttygstruct went away in linux 2.5.67 core.5 ross zwisler add info about dax coredump filtering flags kernel 4.4 added two new core dump filtering flags, mmf_dump_dax_private and mmf_dump_dax_shared. these flags allow us to explicitly filter dax mappings. this is desirable because dax mappings, like hugetlb mappings, have the potential to be very large. nsswitch.conf.5 nikola forró add list of files being read when "files" service is used this is not mentioned anywhere. users can assume that the file being read is something like /etc/$database, but that's not always the case. it's better to explicitly specify which file is read for each respective database. the list of files was acquired from glibc source code. proc.5 heinrich schuchardt [michael kerrisk] add details for threads-max add detail information for threads-max. the checks for minimum and maximum values exist since kernel 4.1. https://lkml.org/lkml/2015/3/15/96 heinrich schuchardt /proc/sys: describe whitespace characters michael kerrisk document 'capamb' in /proc/pid/status michael kerrisk add reference to ptrace(2) for /proc/sys/kernel/yama/ptrace_scope aio.7 michael kerrisk [meikun wang] add missing include file, , to example program mq_overview.7 michael kerrisk [arto bendiken] document qsize bug that appeared in 3.5 and was fixed in 4.2 path_resolution.7 michael kerrisk clarify recursive resolution of symlinks and note limits pipe.7 michael kerrisk see also: add splice(2) rtld-audit.7 namhyung kim fix (typo) error in la_pltenter() description s/la_pltenter()/la_pltexit()/ la_pltenter() is called regardless of the value of framesizep but la_pltexit() is called only if la_pltenter() returns with non-zero framesizep set. i spent long time to figure out why la_pltexit() is not called at all. signal.7 michael kerrisk [michael hocko] note async-signal-safe functions added by posix.1-2008 tc1 tcp.7 daniel borkmann [michael kerrisk] improve paragraphs on tcp_ecn and add tcp_ecn_fallback bullet improve description of tcp_ecn, fix the rfc number and it's not a boolean anymore since long time, and add a description for tcp_ecn_fallback. see also kernel doc under documentation/networking/ip-sysctl.txt on tcp_ecn and tcp_ecn_fallback. ld.so.8 michael kerrisk ld_pointer_guard has been removed in glibc 2.23 michael kerrisk describe secure-execution mode michael kerrisk [maria guseva] replace mentions of set-uid/set-gid programs with secure-execution mode inspired by a patch from maria guseva. maria guseva [silvan jegen] ld_debug is effective in secure-execution mode if /etc/suid-debug exists ==================== changes in man-pages-4.04 ==================== released: 2015-12-29, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexander monakov andries e. brouwer archie cobbs carlos o'donell colin rice darren hart davidlohr bueso dmitry v. levin eric b munson heinrich schuchardt h.j. lu jakub wilk jonathan wakely jonny grant laurent georget lennart poettering mathieu desnoyers michael kerrisk michal hocko mike frysinger pádraig brady paul eggert pavel machek phil blundell richard voigt rich felker rusty russell thomas gleixner tom gundersen torvald riegel vincent lefevre vlastimil babka walter harms zack weinberg apologies if i missed anyone! new and rewritten pages ----------------------- futex.2 michael kerrisk, thomas gleixner, torvald riegel [davidlohr bueso, heinrich schuchardt, darren hart, rusty russell, pavel machek, rich felker] rewrite and massively expand page membarrier.2 mathieu desnoyers [michael kerrisk] new page documenting membarrier() system call newly documented interfaces in existing pages --------------------------------------------- mlock.2 eric b munson [michal hocko, vlastimil babka, michael kerrisk] document mlock2(2) and mcl_onfault new and changed links --------------------- mlock2.2 eric b munson new link to mlock.2 global changes -------------- various pages michael kerrisk errors: standardize text for emfile error various pages michael kerrisk errors: standardize error text for enotsock error various pages michael kerrisk errors: standardize text for enfile error changes to individual pages --------------------------- clock_getres.2 michael kerrisk see also: add vdso(7) epoll_create.2 michael kerrisk errors: add another emfile error case fanotify_init.2 michael kerrisk errors: add an emfile error case fork.2 michael kerrisk child of mt-process is restricted to async-signal-safe functions getcpu.2 michael kerrisk see also: add vdso(7) getrlimit.2 michael kerrisk [lennart poettering] the init of measurement for rlimit_rss is bytes, not pages get_robust_list.2 michael kerrisk reword einval error text gettimeofday.2 carlos o'donell expand on the historical meaning of tz_dsttime michael kerrisk see also: add vdso(7) inotify_init.2 michael kerrisk errors: add an emfile error case personality.2 dmitry v. levin note kernel and glibc versions that introduced this system call poll.2 richard voigt timeout_ts is a pointer, so use -> not . for member access michael kerrisk shorten name of timeout argument for ppoll() the name is overly long, and does not hint at the fact that this argument is a pointer. fix this by renaming: s/timeout_ts/tmo_p/ sendfile.2 laurent georget document more errors sigreturn.2 michael kerrisk see also: add vdso(7) socketcall.2 michael kerrisk since linux 4.3, x86-32 provides direct system calls for the sockets api time.2 zack weinberg explain why the glibc time() wrapper never sets 'errno' michael kerrisk [h.j. lu] where time() is provided by vdso, an invalid address may give sigsegv michael kerrisk [paul eggert] describe eoverflow details michael kerrisk see also: add vdso(7) michael kerrisk rename 't' argument to 'tloc' dlerror.3 michael kerrisk [jonny grant] clarify that the string returned by dlerror() is null terminated dlopen.3 michael kerrisk include a shell session showing build/run in example michael kerrisk change arguments to main() to "void" in example drand48.3 michael kerrisk [vincent lefevre] correct descriptions of ranges returned by these functions see http://bugs.debian.org/803459 errno.3 michael kerrisk note probable cause of enfile error fnmatch.3 pádraig brady describe the fnm_extmatch flag and pattern syntax iconv.3 andries e. brouwer notes: describe correct usage for flushing partially buffered input random_r.3 michael kerrisk [archie cobbs] clarify need to use initstate_r() tzset.3 carlos o'donell clarify "daylight" and remove erroneous note random.4 michael kerrisk [tom gundersen] rework example scripts to assume 'poolsize' unit is bits, not bytes michael kerrisk [walter harms] use modern command substitution syntax in shell session log proc.5 michael kerrisk reaching /proc/sys/fs/file-max limit normally produces an enfile error futex.7 heinrich schuchardt see also updates michael kerrisk note some other locking primitives that are built with futexes heinrich schuchardt nptl, avoid abbreviation michael kerrisk note that a futex is 4 bytes on all platforms vdso.7 michael kerrisk add note on strace(1) and vdso ld.so.8 h.j. lu [michael kerrisk] document ld_prefer_map_32bit_exec michael kerrisk clarify setting of ld_bind_not michael kerrisk clarify setting of ld_dynamic_weak michael kerrisk clarify setting of ld_trace_prelinking michael kerrisk clarify some details for ld_show_auxv ==================== changes in man-pages-4.05 ==================== released: 2016-03-15, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adhemerval zanella akihiro suda alan aversa alan cox alec leamas alex henrie alexander miller andreas gruenbacher andreas schwab anna schumaker askar safin bill o. gallmeister carlos o'donell chris pick christoph hellwig craig gallek darrick j. wong davidlohr bueso dmitry v. levin dr. tobias quathamer eric blake eric dumazet florian weimer gabriel corona heinrich schuchardt ivan shapovalov jakub wilk jason baron jason vas dias jérémie galarneau jeremy harris joachim wuttke joe stein john stultz josh triplett kondo, naoya krzysztof adamski manfred spraul marianne chevrot marko myllynen mark post martin gebert mats wichmann matt zimmerman michael kerrisk ` mike frysinger minchan kim naoya kondo naresh kamboju nikola forró nikos mavrogiannopoulos orion poplawski pakin yury patrick donnelly paul eggert paul pluzhnikov peter hurley peter wu petr gajdos philip semanchuk rasmus villemoes rich felker simon que stephan bergmann stéphane aulery stephen hurd vincent bernat william preston yuri kozlov zefram apologies if i missed anyone! new and rewritten pages ----------------------- copy_file_range.2 anna schumaker [darrick j. wong, christoph hellwig, michael kerrisk] new page documenting copy_file_range() copy_file_range() is a new system call for copying ranges of data completely in the kernel. this gives filesystems an opportunity to implement some kind of "copy acceleration", such as reflinks or server-side-copy (in the case of nfs). personality.2 michael kerrisk this page has been greatly expanded, to add descriptions of personality domains. fmemopen.3 michael kerrisk [adhemerval zanella] significant reworking of this page: * rework discussion of the (obsolete) binary mode * split open_memstream(3) description into a separate page. * note various fmemopen() bugs that were fixed in glibc 2.22 * greatly expand description of 'mode' argument * rework description of 'buf' and 'len' arguments * expand discussion of "current position" for fmemopen() stream ntp_gettime.3 michael kerrisk new page describing ntp_gettime(3) and ntp_gettimex(3) open_memstream.3 michael kerrisk new page created by split of fmemopen(3). at the same time, add and rework a few details in the text. posix_spawn.3 bill o. gallmeister, michael kerrisk new man page documenting posix_spawn(3) and posix_spawnp(3) readdir.3 michael kerrisk [florian weimer] split readdir_r() content into separate page as suggested by florian weimer: it may make sense to move this documentation to a separate manual page, specific to readdir_r. this will keep the readdir() documentation nice and crisp. most programmers will never have to consult all these details. michael kerrisk near complete restructuring of the page and add some further details michael kerrisk [florian weimer, rich felker, paul eggert] add a lot more detail on portable use of the 'd_name' field readdir_r.3 michael kerrisk [florian weimer] new page created after split of readdir(3). michael kerrisk [florian weimer] explain why readdir_r() is deprecated and readdir() is preferred michael kerrisk [florian weimer] remove misleading code example using pathconf() lirc.4 alec leamas new page documenting lirc device driver newly documented interfaces in existing pages --------------------------------------------- adjtimex.2 michael kerrisk document ntp_adjtime(3) epoll_ctl.2 michael kerrisk [jason baron] document epollexclusive madvise.2 minchan kim [michael kerrisk] document madv_free document the madv_free flag added to madvise() in linux 4.5. proc.5 michael kerrisk document cmatotal and cmafree fields of /proc/meminfo michael kerrisk document additional /proc/meminfo fields document directmap4k, directmap4m, directmap2m, directmap1g michael kerrisk document memavailable /proc/meminfo field michael kerrisk document inotify /proc/pid/fdinfo entries michael kerrisk document fanotify /proc/pid/fdinfo entries michael kerrisk add some kernel version numbers for /proc/pid/fdinfo entries michael kerrisk [patrick donnelly] /proc/pid/fdinfo displays the setting of the close-on-exec flag note also the pre-3.1 bug in the display of this info. socket.7 craig gallek [michael kerrisk, vincent bernat] document some bpf-related socket options document the behavior and the first kernel version for each of the following socket options: so_attach_filter so_attach_bpf so_attach_reuseport_cbpf so_attach_reuseport_ebpf so_detach_filter so_detach_bpf so_lock_filter new and changed links --------------------- isalpha_l.3 michael kerrisk new link to isalpha.3 longjmp.3 michael kerrisk replace page with link to setjmp(3), which now incorporates longjmp() ntp_adjtime.3 michael kerrisk new link to adjtimex(2) ntp_gettimex.3 michael kerrisk new link to ntp_gettime.3 open_wmemstream.3 michael kerrisk update link to point to new open_memstream(2) page posix_spawnp.3 michael kerrisk new link to new posix_spawn.3 page siglongjmp.3 michael kerrisk rewire link to point to setjmp(3) strerror_l.3 michael kerrisk new link to strerror.3 fix missing link global changes -------------- various pages michael kerrisk update ftm requirements (_default_source) michael kerrisk update feature test macro requirements update to use _default_source, and also changes brought by glibc commit 266865c0e7b79d4196e2cc393693463f03c90bd8. various pages michael kerrisk simplify ftm requirements looking at (or feature_test_macros(7)), one can see that when _xopen_source is defined with the value 700 (or greater), then _posix_c_source is defined with the value 200809l (or greater). therefore, terms in the man pages such as _xopen_source\ >=\ 700 || _posix_c_source\ >=\ 200809l can be simplified to: _posix_c_source\ >=\ 200809l various pages michael kerrisk simplify ftm requirements looking at (or feature_test_macros(7)), one can see that when _xopen_source is defined with the value 600 (or greater), then _posix_c_source is defined with the value 200112l (or greater). therefore, terms in the man pages such as _xopen_source\ >=\ 600 || _posix_c_source\ >=\ 200112l can be simplified to: _posix_c_source\ >=\ 200112l various pages michael kerrisk simplify ftm requirements _xopen_source implies _posix_c_source >=2, so simplify ftm requirements in various pages. various pages michael kerrisk remove "or 'cc -std=c99'" from synopsis under the ftm requirements all of these pages document the requirement for _isoc99_source. and feature_test_macros(7) now documents that "cc -std=c99" produces the same effect as defining _isoc99_source. so, all of these pages don't additionally need to specify "or 'cc -std=c99'" under the ftm requirements in the synopsis. removing that redundant text also simplifies the synopsis a little. various pages michael kerrisk simplify ftm requirements looking at (or feature_test_macros(7)), one can see that when _xopen_source is defined with the value 600 (or greater), then _posix_c_source is defined with the value 200112l (or greater). therefore, terms in the man pages such as _xopen_source\ >=\ 600 || _posix_c_source\ >=\ 200112l can be simplified to: _posix_c_source\ >=\ 200112l various pages michael kerrisk remove references to _xopen_source_extended in synopsis _xopen_source_extended is obsolete (it existed in susv1, but not subsequent standards). _xopen_source >= 500 produces the same effects as (_xopen_source && _xopen_source_extended). modifying the synopsis of various ages that contain: _xopen_source\ >=\ 500 || _xopen_source\ &&\ _xopen_source_extended to just: _xopen_source\ >=\ 500 this has the following benefits: a) simplifying the synopsis by removing ancient historical information. b) preventing users from being misled into using _xopen_source_extended in new source code. various pages michael kerrisk remove mention of the obsolete _posix_source macro from synopsis _posix_source was a posix.1-1990 creation that was soon made obsolete by _posix_c_source. retaining mention of it in the feature test macro requirements section of the synopsis doesn't contain important information, and may mislead readers into actually trying to use this macro. a few mentions of it are maintained in a some pages where defining _posix_source inhibits some behavior. various sockets-related pages michael kerrisk [carlos o'donell] use consistent argument/variable names for socket addresses and lengths as noted by carlos, there's quite a bit of inconsistency across pages. use 'addr' and 'addrlen' consistently in variables and function arguments. various pages michael kerrisk wording fix: "current file offset" ==> "file offset" "file offset" is the preferred posix terminology. various pages michael kerrisk word "descriptor" more precisely use either "file descriptor" or "message queue descriptor". various pages michael kerrisk errors: add reference to signal(7) in description of eintr changes to individual pages --------------------------- locale.1 marko myllynen add "locale -c charmap" as an example addresses https://bugzilla.kernel.org/show_bug.cgi?id=104511. localedef.1 marko myllynen add hint on purpose of --no-archive indicate why using --no-archive might be a good idea. the issue is that if you create a custom locale with localedef(1) and put it to the locale archive then during the next glibc upgrade the locale archive is updated as well and your custom locale is gone.) accept.2 michael kerrisk errors: improve description for ebadf adjtimex.2 michael kerrisk [john stultz] various improvements after feedback from john stultz michael kerrisk remove ftm requirements it seems that adjtimex() never needed _bsd_source (and my earlier commit 5918743bc8b02b was simply a blunder). michael kerrisk split einval error cases michael kerrisk note treatment of out-of-range buf.offset michael kerrisk don't refer reader to adjtime(3) probably, it's not wise to suggest adjtime(3) as the more portable api. rather, ntp_adjtime(3) should be used. michael kerrisk [naresh kamboju] update details of buf.offset einval error michael kerrisk see also: add ntp_gettime(3) michael kerrisk improve description of some pps timex fields michael kerrisk add attributes section william preston [petr gajdos] update a detail in adjtimex return value description michael kerrisk note range constraints and clamping for adj_frequency bdflush.2 michael kerrisk note that glibc support for this system call went away in version 2.23 bind.2 michael kerrisk improve description of enoent error bpf.2 michael kerrisk document close-on-exec semantics the close-on-exec file descriptor flag is automatically enabled for fds returned by bpf(). chmod.2 michael kerrisk clarify terminology (file mode versus file permission bits) chown.2 michael kerrisk errors: improve ebadf description clone.2 unshare.2 michael kerrisk remove mention of _bsd_source and _svid_source the right way to expose declarations for these linux-specific system calls was always _gnu_source. mentioning the historical use of _bsd_source and _svid_source just clouds the issue. connect.2 michael kerrisk errors: improve ebadf description create_module.2 michael kerrisk glibc 2.23 removed last vestiges of support for this system call delete_module.2 michael kerrisk glibc 2.23 removed last vestiges of support for this system call epoll_ctl.2 michael kerrisk document eloop error for circular monitoring loops eventfd.2 michael kerrisk note that eventfd info is available in /proc/pid/fdinfo execve.2 michael kerrisk [krzysztof adamski] add eperm error for capabilities check of capability-dumb binaries michael kerrisk add reference to ld-linux.so(8) michael kerrisk see also: add system(3) fanotify_init.2 michael kerrisk note kernel version that allowed o_cloexec for event_f_flags fcntl.2 flock.2 michael kerrisk see also: add lslocks(8) fcntl.2 michael kerrisk [jason vas dias] rework description of f_setown as suggested by jason, make it clearer that i/o signalling requires the use of both f_setown and o_async. while we're at, make a few other cleanups to the text. michael kerrisk remove mention of _bsd_source to get definition of f_setown/f_getown this usage went away in glibc 2.20, and the simplest remedy is just to omit mention of it. futex.2 michael kerrisk futex_clock_realtime can now be used with futex_wait get_kernel_syms.2 michael kerrisk note that glibc does not support this system call init_module.2 michael kerrisk glibc 2.23 removed last vestiges of support for this system call ioctl_list.2 heinrich schuchardt include uapi/linux/wireless.h add the list of wireless ioctls. heinrich schuchardt path to sockios.h sockios.h is now in include/uapi heinrich schuchardt add reference to netdevice.7 netdevice.7 describes most of the ioctls of sockios.h heinrich schuchardt transfer structure (wireless.h ioctls) the sole parameter to be passed to the wireless.h ioctls is of type struct iwreq *. ioperm.2 michael kerrisk [alex henrie] ioperm.2: permissions are inherited across fork(2) see https://bugzilla.kernel.org/show_bug.cgi?id=99911 iopl.2 michael kerrisk [alex henrie] permissions are not inherited across fork(2) or preserved on execve(2) see https://bugzilla.kernel.org/show_bug.cgi?id=99901 lseek.2 michael kerrisk fuse now supports seek_hole and seek_data michael kerrisk nfs supports seek_hole and seek_data michael kerrisk see also: add open(2) madvise.2 michael kerrisk clarify madv_hwpoison wording to say that it applies to a page range mknod.2 michael kerrisk see also: add mknod(1) mount.2 michael kerrisk see also: add findmnt(8) open.2 michael kerrisk notes: mention existence of proc/pid/fd and /proc/pid/fdinfo mark post [petr gajdos] o_tmpfile support is now provided bt btrfs pipe.2 michael kerrisk [eric blake] note treatment of 'pipefd' on error poll.2 michael kerrisk [josh triplett] document spurious eagain error that can occur on other systems light reworking of text proposed by josh triplett. readlink.2 michael kerrisk clarify einval error description recv.2 heinrich schuchardt equivalence to read() describe the recv(2)-read(2) and the recvfrom(2)-recv(2) equivalences for zero-valued arguments. michael kerrisk msg_waitall has no effect for datagram sockets recv.2 cmsg.3 nikola forró fix type of cmsg_len member of cmsghdr structure the type shown for cmsg_len member of cmsghdr structure is socklen_t, but the actual type used by glibc and the kernel is size_t. the information was obtained from glibc source code: http://bit.ly/21m1rmp michael kerrisk note that cmsg_len is typed as socklen_t in posix.1 sched_setaffinity.2 michael kerrisk [florian weimer, florian weimer] warn that cpu_alloc() may allocate a slightly cpu set than requested michael kerrisk [florian weimer] add reference to cpu_alloc(3) sched_setattr.2 michael kerrisk [akihiro suda] eperm depends on affinity mask of target thread, not calling thread select.2 michael kerrisk [josh triplett] document spurious eagain error that can occur on other systems light reworking of text proposed by josh triplett. nikos mavrogiannopoulos mention the 'fd_set' size limitation early and refer to poll(2) change this because of the serious limitation of select() imposing a limit on the range of file descriptors that can be monitored. this is currently mentioned too late in the documentation (in the notes section). the man page should warn early and refer to poll(2) as soon as possible. michael kerrisk add details on the glibc fixed-size fd_set limitation no modern application should use select() on linux. select_tut.2 michael kerrisk some readability fixes to example program michael kerrisk better variable names in example program michael kerrisk simplify 'if' logic in example program michael kerrisk use correct type (socklen_t) for addrlen semctl.2 michael kerrisk [davidlohr bueso, manfred spraul, philip semanchuk] notes: note when 'sempid' is set on various implementations see https://bugzilla.kernel.org/show_bug.cgi?id=112271 and http://thread.gmane.org/gmane.linux.kernel/2162754/ subject: [patch] don't set sempid in semctl syscall. date: 2016-02-26 12:21:38 gmt semop.2 michael kerrisk tweak comment describing 'sempid' sendfile.2 askar safin fix incorrect description in text referring to splice(2) michael kerrisk see also: add copy_file_range(2) setpgid.2 michael kerrisk correct/simplify ftm requirements for bsd setpgrp() and getpgrp() signalfd.2 michael kerrisk note that signalfd info is available in /proc/pid/fdinfo sigprocmask.2 michael kerrisk [mike frysinger] explicitly refer the reader to sigsetops(3) this man page did not make it obvious which functions should be used for manipulating signals sets, nor where those functions were documented. socketpair.2 michael kerrisk [eric blake] note treatment of 'sv' on error splice.2 askar safin improve description of 0 return value. see https://bugzilla.kernel.org/show_bug.cgi?id=90911 statfs.2 michael kerrisk [jakub wilk] use consistent case for hex constants sync.2 christoph hellwig clarify description and document the linux data integrity guarantees syscall.2 mike frysinger add more architectures and improve error documentation move the error register documentation into the main table rather than listing them in sentences after the fact. add sparc error return details. add details for alpha/arc/m68k/microblaze/nios2/powerpc/superh/ tile/xtensa. syscalls.2 michael kerrisk add copy_file_range(2) times.2 kondo, naoya fix an incorrect description in notes the text has an incorrect description in notes, it says that (2^32/hz) - 300 is about 429 million. it is correct only if hz=10 which does not look common today. so just removing "(i.e., about 429 million)" is good enough. truncate.2 michael kerrisk see also: add truncate(1) uselib.2 michael kerrisk mention config_uselib michael kerrisk note that glibc does not support this (obsolete) system call wait.2 wait4.2 michael kerrisk rename the "status" argument to "wstatus" the fact that exit(3)/_exit(2) has an argument called "status" and the same name is used in the arguments to the wait*() calls can a little too easily lead the user into thinking that the two arguments hold the same information, when of course they don't. so, use a different name for the argument of the wait*() functions, to reduce the chances of such confusion. backtrace.3 michael kerrisk [martin gebert] small fixes to example program clearenv.3 michael kerrisk [matt zimmerman] clarify the use and effect of clearenv() see http://bugs.debian.org/679323 michael kerrisk variables can be added to the environment after calling clearenv() clog10.3 michael kerrisk show an alternative equivalence for clog10() michael kerrisk update conforming to fix grammar error and add c11. dl_iterate_phdr.3 michael kerrisk [paul pluzhnikov] describe 'struct dl_phdr_info' fields added in glibc 2.4 see https://bugzilla.kernel.org/show_bug.cgi?id=103011 michael kerrisk [simon que] note that first object visited by 'callback' is the main program see https://bugzilla.kernel.org/show_bug.cgi?id=94141 errno.3 michael kerrisk add some explanation of enoent error exec.3 michael kerrisk see also: add system(3) exp.3 michael kerrisk [joachim wuttke] see also: add expm1(3) fopen.3 michael kerrisk see also: add open_memstream(3) fts.3 michael kerrisk bugs: glibc-2.23 now has lfs support for the fts functions gamma.3 michael kerrisk [alan cox] gamma() was documented in svid 2 getaddrinfo.3 michael kerrisk [andreas schwab, orion poplawski] update ftm requirements for glibc 2.22 since glibc 2.22 getaddrinfo() etc. are only declared for posix.1-2001 or later. getcwd.3 michael kerrisk see also: add pwd(1) opendir.3 michael kerrisk help the reader by explicitly mentioning the use of readdir(3) perror.3 michael kerrisk suggest use of strerror(3) in place of deprecated 'sys_errlist' posix_fallocate.3 jérémie galarneau errors: add eintr the glibc implementation of posix_fallocate(), which calls fallocate(), may be interrupted. the fallocate() emulation also makes use of pread()/pwrite(), which may also be interrupted. posix_memalign.3 michael kerrisk [eric blake] note posix_memalign()'s treatment of 'memptr' on error pthread_setaffinity_np.3 michael kerrisk see also: add cpu_set(3) queue.3 dr. tobias quathamer remove double conforming to section rcmd.3 nikola forró add missing condition concerning .rhosts file the list of conditions determining if iruserok() and ruserok() functions automatically fail is incomplete. according to glibc source code, the functions also fail if the .rhosts file is hard linked anywhere. setbuf.3 michael kerrisk see also: add stdbuf(1) setjmp.3 michael kerrisk rewrite and merge longjmp()/siglongjmp() discussion into this page the discussion of nonlocal gotos is much easier to read if setjmp() and longjmp() are discussed in the same page. while we're at it, rework almost the entire text and add several more details. michael kerrisk note the interactions of longjmp() and non-async-signal-safe functions posix.1-2008 tc2 adds explicit text on this point. see http://austingroupbugs.net/view.php?id=516#c1195 michael kerrisk explain why nonlocal gotos make code harder to maintain michael kerrisk reword warning on longjmp() to function that has already returned michael kerrisk remove reference to obsolete _xopen_source_extended sleep.3 michael kerrisk see also: add sleep(1) strftime.3 michael kerrisk [jeremy harris] note which 'tm' fields are used to calculate each output string see https://bugzilla.redhat.com/show_bug.cgi?id=1162218 strlen.3 michael kerrisk [alan aversa] conforming to: add c11 system.3 michael kerrisk see also: add execve(2) termios.3 dr. tobias quathamer document line length in canonical mode see https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/n_tty.c#n1673 see https://bugs.debian.org/797479 michael kerrisk see also: add tty(1) michael kerrisk [peter hurley] further improvements to recent tweaks of canonical mode 4096 char limit timegm.3 michael kerrisk [stephen hurd, mats wichmann] remove sample implementation of timegm() stephen and mats both question the wisdom of showing a portable *non-thread-safe* implementation of timegm(), and i find it hard to disagree. so, remove this code. see https://bugzilla.kernel.org/show_bug.cgi?id=103701 michael kerrisk expand description a little st4.4 dr. tobias quathamer remove spurious copyright section tty_ioctl.4 michael kerrisk see also: add ldattach(1) elf.5 michael kerrisk [gabriel corona, mike frysinger] fix description of stv_protected michael kerrisk improve description of stv_default michael kerrisk improve description of stv_hidden chris pick remove erroneous, duplicate shn_* section michael kerrisk [chris pick] reword discussion of range values a little gai.conf.5 michael kerrisk add versions section group.5 michael kerrisk see also: add groups(2) see also: add gpasswd(1) see also: add sg(1) se also: add gshadow(5) see also: add chgrp(1) locale.5 marko myllynen [mike frysinger] tel + fax are deprecated nsswitch.conf.5 nikola forró update nss compatibility mode description utmp.5 michael kerrisk see also: add lslogins(1) aio.7 andreas gruenbacher improve example when aio_sigevent.sigev_notify is set to sigev_signal, signal handlers called for asynchronous i/o operations will have si->si_code set to si_asyncio. check to make sure that si->si_value.sival_ptr is defined. capabilities.7 michael kerrisk explain safety check for capability-dumb binaries michael kerrisk see also: add sg(1), su(1) see also: add id(1), group(5), passwd(5) credentials.7 michael kerrisk see also: add groups(2) environ.7 michael kerrisk describe the bourne "name=value command" syntax michael kerrisk add some details describing hos shell's environment is initialized michael kerrisk note that child of fork(2) inherits copy of parent's environment michael kerrisk see also: add pam_env(3) epoll.7 michael kerrisk mention that epoll info is available via /proc/pid/fdinfo fanotify.7 michael kerrisk refer reader to proc(5) for info on /proc/pid/fdinfo fanotify entries feature_test_macros.7 michael kerrisk add a summary of some ftm key points michael kerrisk give an early hint about some macros being defined by default michael kerrisk clarify relation between _xopen_source >=500 and _xopen_source_extended emphasize that defining _xopen_source >=500 produces same effects as defining _xopen_source_extended. michael kerrisk note that man pages don't mention _xopen_source_extended as per previous commit, mention of _xopen_source_extended has generally been removed from the man pages. michael kerrisk note effects of "cc -std=c99" and "cc -std=c11" michael kerrisk clarify some _isoc99_source / _default_source details michael kerrisk clarify that _xopen_source_extended is obsolete since susv2, _xopen_source_extended is no longer specified in the standard. inotify.7 michael kerrisk refer reader to proc(5) for info on /proc/pid/fdinfo inotify entries ip.7 eric dumazet document ip_bind_address_no_port socket option mq_overview.7 michael kerrisk note that the close-on-exec flag is automatically set on mq descriptors namespaces.7 michael kerrisk see also: add lsns(1) lsns(1) was recently added in util-linux, probably to appear in next release (2.28?). pipe.7 michael kerrisk [jason vas dias] clarify that i/o signalling requires use of both f_setown and o_async michael kerrisk see also: add mkfifo(1) signal.7 michael kerrisk note the interactions of longjmp() and non-async-signal-safe functions see http://austingroupbugs.net/view.php?id=516#c1195. socket.7 michael kerrisk see also: add pcap(3) see also: add wireshark(1) and tcpdump(8) standards.7 michael kerrisk add posix.1-2008 tc2 (posix.1-2016) svipc.7 michael kerrisk tweak description of 'sempid' michael kerrisk see also: add lsipc(1) symlink.7 michael kerrisk [zefram] some "magic" symlinks have permissions other than 0777 see https://bugs.debian.org/743525 time.7 michael kerrisk see also: add timeout(1) see also: add ntp_adjtime(3) and ntp_gettime(3) unicode.7 dr. tobias quathamer document private use areas see https://bugs.debian.org/285444 unix.7 heinrich schuchardt add example a complete example demonstrating the usage of sockets for local interprocess communication is added. michael kerrisk introduce term "sequenced-packet" for sock_seqpacket michael kerrisk some wording improvements ==================== changes in man-pages-4.06 ==================== released: 2016-05-09, oslo contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexander miller alon bar-lev benjamin poirier christoph hellwig colin ian king dr. tobias quathamer ed avis georg sauthoff heinrich schuchardt jakub wilk jordan birks marko myllynen michael kerrisk mike frysinger nikola forró rasmus villemoes serge e. hallyn serge hallyn valery reznic zubair lutfullah kakakhel apologies if i missed anyone! new and rewritten pages ----------------------- cgroups.7 serge hallyn, michael kerrisk new page documenting cgroups cgroup_namespaces.7 michael kerrisk [serge hallyn] new page describing cgroup namespaces newly documented interfaces in existing pages --------------------------------------------- clone.2 michael kerrisk document clone_newcgroup readv.2 christoph hellwig document preadv2() and pwritev2() setns.2 michael kerrisk document clone_newcgroup unshare.2 michael kerrisk document clone_newcgroup changes to individual pages --------------------------- clock_getres.2 michael kerrisk [rasmus villemoes] note that coarse clocks need architecture and vdso support clone.2 fork.2 nikola forró document erestartnointr error code clone.2 michael kerrisk [colin ian king] errors: add einval for improperly aligned 'child_stack' value execve.2 michael kerrisk [valery reznic] since linux 2.6.28, recursive script interpretation is supported fcntl.2 michael kerrisk note that mandatory locking is now governed by a configuration option fsync.2 michael kerrisk [georg sauthoff] give some examples of files where sync can fail with einval getrlimit.2 michael kerrisk see also: add cgroups(7) ioctl_fat.2 heinrich schuchardt use %04x to print volume id leading zeroes should be used when display a fat volume id. ioprio_set.2 michael kerrisk see also: add cgroups(7) lseek.2 michael kerrisk note that 'off_t' is an integer data type defined by posix memfd_create.2 michael kerrisk note that memfd_create() does not have a glibc wrapper mount.2 michael kerrisk ms_mandlock requires cap_sys_admin (since linux 4.5) quotactl.2 michael kerrisk document q_getnextquota and q_xgetnextquota michael kerrisk rework/reorder errors list make into a single alphabetically ordered list michael kerrisk note kernel version that removed q_getstats michael kerrisk add kernel version for g_getinfo, q_setinfo, and q_getfmt readv.2 michael kerrisk clarify that 'size_t' and 'ssize_t' are integer types specified in posix semctl.2 michael kerrisk from kernel 4.6, linux now updates 'sempid' on setall operations sigaction.2 michael kerrisk document segv_bnderr michael kerrisk document segv_pkuerr syscalls.2 michael kerrisk add preadv2() and pwritev2() write.2 michael kerrisk clarify that 'size_t' and 'ssize_t' are integer types specified in posix makedev.3 mike frysinger use in synopsis defining these functions via causes problems for some folk. as noted by zack wein: libstdc++ force-enables _gnu_source, which means people writing in c++ _can't_ avoid these nonstandard macros by using a strict conformance mode. since glibc has basically always used , update the docs to have people include that instead. michael kerrisk notes: mention that may also define these macros popen.3 nikola forró return value: describe successful case reference: http://pubs.opengroup.org/onlinepubs/9699919799/functions/popen.html http://pubs.opengroup.org/onlinepubs/9699919799/functions/pclose.html strtod.3 michael kerrisk [ed avis] improve a detail in return value core.5 michael kerrisk document /proc/sys/kernel/core_pipe_limit locale.5 marko myllynen adjust lc_identification / abbreviation tiny tweak to locale.5 based on iso/iec tr 14652: http://www.open-std.org/jtc1/sc22/wg20/docs/n972-14652ft.pdf marko myllynen update lc_address after glibc change this patch updates locale.5 to match the recent glibc change in commit a837257199ffab76237385b830cc7b6179fc2f18 marko myllynen complete lc_collate here's the first attempt to (almost) complete the locale.5 manual page by documenting all (but perhaps one) of the missing lc_collate keywords. mike frysinger country_car: add a better description nsswitch.conf.5 marko myllynen document group merging document the recently merged glibc group merge support. glibc commit ced8f8933673f4efda1d666d26a1a949602035ed https://sourceware.org/glibc/wiki/proposals/groupmerging proc.5 michael kerrisk move /proc/pid/cgroup discussion to cgroups(7) page michael kerrisk add some background on why /proc/pid/mountinfo was added michael kerrisk improve description of /proc/pid/mountinfo 'root' field michael kerrisk add pointer to cgroups(7) for documentation of /proc/cgroups michael kerrisk add reference to core(5) for info on /proc/sys/kernel/core_pipe_limit cpuset.7 michael kerrisk see also: add cgroups(7) ip.7 benjamin poirier fix incorrect sockopt name "ip_leave_group" does not exist. it was perhaps a confusion with mcast_leave_group. change the text to ip_drop_membership which has the same function as mcast_leave_group and is documented in the ip.7 man page. reference: linux kernel net/ipv4/ip_sockglue.c do_ip_setsockopt() namespaces.7 michael kerrisk see also: add cgroups(7), cgroup_namespaces(7) vdso.7 zubair lutfullah kakakhel [mike frysinger] update for mips document the symbols exported by the mips vdso. vdso support was added from kernel 4.4 onwards. see https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/log/arch/mips/vdso michael kerrisk [rasmus villemoes] the __kernel_clock_* interfaces don't support *_coarse clocks on powerpc ld.so.8 michael kerrisk [alon bar-lev] document use of $origin, $lib, and $platform in environment variables these strings are meaningful in ld_library_path and ld_preload. ==================== changes in man-pages-4.07 ==================== released: 2016-07-17, ulm contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alec leamas andrey vagin andy lutomirski carsten grohmann chris gassib christoph hellwig darren hart darrick j. wong élie bouttier eric biggers eric w. biederman florian weimer håkon sandsmark iustin pop jacob willoughby jakub wilk james h cownie jann horn john wiersba jörn engel josh triplett kai mäkisara kees cook keno fischer li peng marko kevac marko myllynen michael kerrisk michał zegan miklos szeredi mitch walker neven sajko nikos mavrogiannopoulos omar sandoval ori avtalion rahul bedarkar robin kuzmin rob landley shawn landden stefan puiu stephen smalley szabolcs nagy thomas gleixner tobias stoeckmann tom callaway tom gundersen vince weaver w. trevor king "yuming ma(马玉明)" apologies if i missed anyone! new and rewritten pages ----------------------- ioctl_fideduperange.2 darrick j. wong [christoph hellwig, michael kerrisk] new page documenting the fideduperange ioctl document the fideduperange ioctl, formerly known as btrfs_ioc_extent_same. ioctl_ficlonerange.2 darrick j. wong [christoph hellwig, michael kerrisk] new page documenting ficlone and ficlonerange ioctls document the ficlone and ficlonerange ioctls, formerly known as the btrfs_ioc_clone and btrfs_ioc_clone_range ioctls. nextup.3 michael kerrisk new page documenting nextup(), nextdown(), and related functions mount_namespaces.7 michael kerrisk [michael kerrisk] new page describing mount namespaces newly documented interfaces in existing pages --------------------------------------------- mount.2 michael kerrisk document flags used to set propagation type document ms_shared, ms_private, ms_slave, and ms_unbindable. michael kerrisk document the ms_rec flag ptrace.2 michael kerrisk [kees cook, jann horn, eric w. biederman, stephen smalley] document ptrace access modes proc.5 michael kerrisk document /proc/[pid]/timerslack_ns michael kerrisk document /proc/pid/status 'ngid' field michael kerrisk document /proc/pid/status fields: 'nstgid', 'nspid', 'nspgid', 'nssid' michael kerrisk document /proc/pid/status 'umask' field new and changed links --------------------- preadv2.2 pwritev2.2 michael kerrisk new links to readv(2) nextdown.3 nextdownf.3 nextdownl.3 nextupf.3 nextupl.3 michael kerrisk new links to nextup(3) changes to individual pages --------------------------- ldd.1 michael kerrisk add a little more detail on why ldd is unsafe with untrusted executables michael kerrisk add more detail on the output of ldd localedef.1 marko myllynen drop --old-style description the glibc upstream decided to drop localedef(1) --old-style option [1] altogether, i think we can do the same with localedef(1), the option hasn't done anything in over 16 years and i doubt anyone uses it. add_key.2 mitch walker empty payloads are not allowed in user-defined keys chroot.2 michael kerrisk see also: add pivot_root(2) clone.2 michael kerrisk add reference to mount_namespaces(7) under clone_newns description fork.2 michael kerrisk add enomem error for pid namespace where "init" has died futex.2 michael kerrisk correct an enosys error description since linux 4.5, futex_clock_realtime is allowed with futex_wait. michael kerrisk [darren hart] remove crufty text about futex_wait_bitset interpretation of timeout since linux 4.5, futex_wait also understands futex_clock_realtime. michael kerrisk [thomas gleixner] explain how to get equivalent of futex_wait with an absolute timeout michael kerrisk describe futex_bitset_match_any describe futex_bitset_match_any and futex_wait and futex_wake equivalences. michael kerrisk note that at least one bit must be set in mask for bitset operations at least one bit must be set in the 'val3' mask supplied for the futex_wait_bitset and futex_wake_bitset operations. michael kerrisk [thomas gleixner, darren hart] fix descriptions of various timeouts michael kerrisk clarify clock default and choices for futex_wait getitimer.2 michael kerrisk substantial rewrites to various parts of the page michael kerrisk [tom callaway] change license to note that page may be modified the page as originally written carried text that said the page may be freely distributed but made no statement about modification. in the 20+ years since it was first written, the page has in fact seen repeated, sometimes substantial, modifications, and only a small portion of the original text remains. one could i suppose rewrite the last few pieces that remain from the original, but as the largest contributor to the pages existing text, i'm just going to relicense it to explicitly note that modification is permitted. (i presume the failure by the original author to grant permission to modify was simply an oversight; certainly, the large number of people who have changed the page have taken that to be the case.) see also https://bugzilla.kernel.org/show_bug.cgi?id=118311 get_mempolicy.2 michael kerrisk [jörn engel] correct rounding to 'maxnodes' (bits, not bytes) michael kerrisk [jörn engel] fix prototype for get_mempolicy() in numaif.h, 'addr' is typed as 'void *' getpriority.2 michael kerrisk make discussion of rlimit_nice more prominent the discussion of rlimit_nice was hidden under the eperm error, where it was difficult to find. place some relevant text in description. michael kerrisk note that getpriority()/setpriority deal with same attribute as nice(2) michael kerrisk [robin kuzmin] clarify equivalence between lower nice value and higher priority get_robust_list.2 michael kerrisk get_robust_list() is governed by ptrace_mode_read_realcreds ioctl.2 michael kerrisk see also: add ioctl_fideduperange(2) and ioctl_ficlonerange(2) kcmp.2 michael kerrisk kcmp() is governed by ptrace_mode_read_realcreds shawn landden note about security_yama kill.2 michael kerrisk [john wiersba] clarify the meaning if sig==0 lookup_dcookie.2 michael kerrisk see also: add oprofile(1) mmap.2 michael kerrisk [rahul bedarkar] example: for completeness, add munmap() and close() calls mount.2 michael kerrisk restructure discussion of 'mountflags' into functional groups the existing text makes no differentiation between different "classes" of mount flags. however, certain flags such as ms_remount, ms_bind, ms_move, etc. determine the general type of operation that mount() performs. furthermore, the choice of which class of operation to perform is performed in a certain order, and that order is significant if multiple flags are specified. restructure and extend the text to reflect these details. michael kerrisk relocate text on multimounting and mount stacking to notes the text was somewhat out of place in its previous location; notes is a better location. michael kerrisk remove version numbers attached to flags that are modifiable on remount this information was simply bogus. mea culpa. michael kerrisk refer reader to mount_namespaces(7) for details on propagation types michael kerrisk see also: s/namespaces(7)/mount_namespaces(7)/ omar sandoval ms_bind still ignores mountflags this is clear from the do_mount() function in the kernel as of v4.6. michael kerrisk note the default treatment of atime flags during ms_remount the behavior changed in linux 3.17. michael kerrisk clarify that ms_move ignores remaining bits in 'mountflags' michael kerrisk note kernel version that added ms_move michael kerrisk ms_nosuid also disables file capabilities michael kerrisk relocate/demote/rework text on ms_mgc_val the use of this constant has not been needed for 15 years now. michael kerrisk clarify that 'source' and 'target' are pathnames, and can refer to files michael kerrisk update example list of filesystem types put more modern examples in; remove many older examples. michael kerrisk ms_lazytime and ms_relatime can be changed on remount michael kerrisk explicitly note that ms_dirsync setting cannot be changed on remount michael kerrisk move text describing 'data' argument higher up in page in preparation for other reworking. michael kerrisk since linux 2.6.26, bind mounts can be made read-only open.2 eric biggers refer to correct functions in description of o_tmpfile pciconfig_read.2 michael kerrisk [tom callaway] change license to note that page may be modified niki rahimi, the author of this page, has agreed that it's okay to change the license to note that the page can be modified. see https://bugzilla.kernel.org/show_bug.cgi?id=118311 perf_event_open.2 michael kerrisk if pid > 0, the operation is governed by ptrace_mode_read_realcreds jann horn document new perf_event_paranoid default keno fischer [vince weaver] add a note that dyn_size is omitted if size == 0 the perf_output_sample_ustack in kernel/events/core.c only writes a single 64 bit word if it can't dump the user registers. from the current version of the man page, i would have expected two 64 bit words (one for size, one for dyn_size). change the man page to make this behavior explicit. prctl.2 michael kerrisk some wording improvements in timer slack description michael kerrisk refer reader to discussion of /proc/[pid]/timerslack_ns under discussion of pr_set_timerslack, refer the reader to the /proc/[pid]/timerslack_ns file, documented in proc(5). process_vm_readv.2 michael kerrisk rephrase permission rules in terms of a ptrace access mode check ptrace.2 michael kerrisk [jann horn] update yama ptrace_scope documentation reframe the discussion in terms of ptrace_mode_attach checks, and make a few other minor tweaks and additions. michael kerrisk, jann horn note that user namespaces can be used to bypass yama protections michael kerrisk note that ptrace_seize is subject to a ptrace access mode check michael kerrisk rephrase ptrace_attach permissions in terms of ptrace access mode check quotactl.2 michael kerrisk [jacob willoughby] 'dqb_curspace' is in bytes, not blocks this error appears to have been injected into glibc when copying some headers from bsd. see https://bugs.debian.org/825548 recv.2 michael kerrisk [tom gundersen] with pending 0-length datagram read() and recv() with flags == 0 differ setfsgid.2 setfsuid.2 jann horn [michael kerrisk] fix note about errors from the syscall wrapper see sysdeps/unix/sysv/linux/i386/setfsuid.c in glibc-2.2.1. (this code is not present in modern glibc anymore.) michael kerrisk move glibc wrapper notes to "c library/kernel differences" subsection sysinfo.2 michael kerrisk rewrite and update various pieces umask.2 michael kerrisk notes: mention /proc/pid/status 'umask' field umount.2 michael kerrisk see also: add mount_namespaces(7) unshare.2 michael kerrisk add reference to mount_namespaces(7) under clone_newns description utimensat.2 michael kerrisk [rob landley] note that the glibc wrapper disallows pathname==null wait.2 michael kerrisk since linux 4.7, __wall is implied if child being ptraced michael kerrisk waitid() now (since linux 4.7) also supports __wnothread/__wclone/__wall assert.3 nikos mavrogiannopoulos improved description removed text referring to text not being helpful to users. provide the error text instead to allow the reader to determine whether it is helpful. recommend against using ndebug for programs to exhibit deterministic behavior. moved description ahead of recommendations. michael kerrisk clarify details of message printed by assert() fmax.3 fmin.3 michael kerrisk see also: add fdim(3) getauxval.3 cownie, james h correct at_hwcap result description inet_pton.3 stefan puiu mention byte order malloc_hook.3 michael kerrisk glibc 2.24 removes __malloc_initialize_hook memmem.3 michael kerrisk [shawn landden] note that memmem() is present on some other systems mkdtemp.3 mktemp.3 michael kerrisk see also: add mktemp(1) printf.3 michael kerrisk [shawn landden] note support in other c libraries for %m and %n strcasecmp.3 michael kerrisk [ori avtalion] make details of strncasecmp() comparison clearer strcat.3 michael kerrisk add a program that shows the performance characteristics of strcat() in honor of joel spolksy's visit to munich, let's start educating schlemiel the painter. strtoul.3 michael kerrisk see also: add a64l(3) strxfrm.3 michael kerrisk [florian weimer] remove notes section strxfrm() and strncpy() are not precisely equivalent in the posix locale, so this notes section was not really correct. see https://bugzilla.kernel.org/show_bug.cgi?id=104221 console_codes.4 console_ioctl.4 tty.4 vcs.4 charsets.7 marko myllynen remove console(4) references 0f9e647 removed the obsolete console(4) page but we still have few references to it. the patch below removes them or converts to refs to console_ioctl(4) where appropriate. console_ioctl.4 michael kerrisk [chris gassib] the argument to kdgetmode is an 'int' lirc.4 alec leamas update after upstreamed lirc.h, bugfixes. st.4 kai mäkisara fix description of read() when block is larger than request kai mäkisara update mtmkpart for kernels >= 4.6 update the description of the mtmkpart operation of mtioctop to match the changes in kernel version 4.6. charmap.5 marko myllynen clarify keyword syntax updates charmap(5) to match the syntax all the glibc charmap files are using currently. elf.5 michael kerrisk see also: add readelf(1) locale.5 marko myllynen document missing keywords, minor updates marko myllynen clarify keyword syntax marko myllynen adjust conformance proc.5 namespaces.7 michael kerrisk move /proc/pid/mounts information to proc(5) there was partial duplication, and some extra information in namespaces(7). move everything to proc(5). proc.5 michael kerrisk /proc/pid/fd/* are governed by ptrace_mode_read_fscreds permission to dereference/readlink /proc/pid/fd/* symlinks is governed by a ptrace_mode_read_fscreds ptrace access mode check. michael kerrisk /proc/pid/timerslack_ns is governed by ptrace_mode_attach_fscreds permission to access /proc/pid/timerslack_ns is governed by a ptrace_mode_attach_fscreds ptrace access mode check. michael kerrisk document /proc/pid/{maps,mem,pagemap} access mode checks permission to access /proc/pid/{maps,pagemap} is governed by a ptrace_mode_read_fscreds ptrace access mode check. permission to access /proc/pid/mem is governed by a ptrace_mode_attach_fscreds ptrace access mode check. michael kerrisk note /proc/pid/stat fields that are governed by ptrace_mode_read_fscreds michael kerrisk /proc/pid/{cwd,exe,root} are governed by ptrace_mode_read_fscreds permission to dereference/readlink /proc/pid/{cwd,exe,root} is governed by a ptrace_mode_read_fscreds ptrace access mode check. michael kerrisk /proc/pid/io is governed by ptrace_mode_read_fscreds permission to access /proc/pid/io is governed by a ptrace_mode_read_fscreds ptrace access mode check. michael kerrisk /proc/pid/{personality,stack,syscall} are governed by ptrace_mode_attach_fscreds permission to access /proc/pid/{personality,stack,syscall} is governed by a ptrace_mode_attach_fscreds ptrace access mode check. michael kerrisk /proc/pid/{auxv,environ,wchan} are governed by ptrace_mode_read_fscreds permission to access /proc/pid/{auxv,environ,wchan} is governed by a ptrace_mode_read_fscreds ptrace access mode check. michael kerrisk move shared subtree /proc/pid/mountinfo fields to mount_namespaces(7) move information on shared subtree fields in /proc/pid/mountinfo to mount_namespaces(7). michael kerrisk ["yuming ma(马玉明)"] note that /proc/net is now virtualized per network namespace michael kerrisk add references to mount_namespaces(7) repertoiremap.5 marko myllynen clarify keyword syntax utmp.5 michael kerrisk see also: add logname(1) capabilities.7 michael kerrisk [andy lutomirski] note on secure_no_cap_ambient_raise for capabilities-only environment michael kerrisk add a detail on use of securebits cgroup_namespaces.7 michael kerrisk see also: add namespaces(7) cgroups.7 michael kerrisk errors: add mount(2) ebusy error cp1251.7 cp1252.7 iso_8859-1.7 iso_8859-15.7 iso_8859-5.7 koi8-r.7 koi8-u.7 marko myllynen add some charset references add some references to related charsets here and there. credentials.7 michael kerrisk see also: add runuser(1) see also: add newgrp(1) see also: add sudo(8) feature_test_macros.7 michael kerrisk emphasize that applications should not directly include man-pages.7 michael kerrisk clarify which sections man-pages provides man pages for michael kerrisk [josh triplett] add a few more details on formatting conventions add some more details for section 1 and 8 formatting. separate out formatting discussion into commands, functions, and "general". namespaces.7 michael kerrisk /proc/pid/ns/* are governed by ptrace_mode_read_fscreds permission to dereference/readlink /proc/pid/ns/* symlinks is governed by a ptrace_mode_read_fscreds ptrace access mode check. michael kerrisk nowadays, file changes in /proc/pid/mounts are notified differently exceptional condition for select(), (e)pollpri for (e)poll michael kerrisk remove /proc/pid/mountstats description this is a duplicate of information in proc(5). michael kerrisk refer to new mount_namespaces(7) for information on mount namespaces netlink.7 andrey vagin describe netlink socket options michael kerrisk rework version information (no changes in technical details.) pid_namespaces.7 michael kerrisk see also: add namespaces(7) unix.7 michael kerrisk move discussion on pathname socket permissions to description michael kerrisk expand discussion of socket permissions michael kerrisk fix statement about permissions needed to connect to a unix domain socket read permission is not required (verified by experiment). michael kerrisk clarify ownership and permissions assigned during socket creation michael kerrisk [carsten grohmann] update text on socket permissions on other systems at least some of the modern bsds seem to check for write permission on a socket. (i tested openbsd 5.9.) on solaris 10, some light testing suggested that write permission is still not checked on that system. michael kerrisk note that umask / permissions have no effect for abstract sockets w. trevor king fix example code: 'ret' check after accept populates 'data_socket' michael kerrisk move some abstract socket details to a separate subsection michael kerrisk note that abstract sockets automatically disappear when fds are closed user_namespaces.7 michael kerrisk [michał zegan] clarify meaning of privilege in a user namespace having privilege in a user ns only allows privileged operations on resources governed by that user ns. many privileged operations relate to resources that have no association with any namespace type, and only processes with privilege in the initial user ns can perform those operations. see https://bugzilla.kernel.org/show_bug.cgi?id=120671 michael kerrisk [michał zegan] list the mount operations permitted by cap_sys_admin list the mount operations permitted by cap_sys_admin in a noninitial userns. see https://bugzilla.kernel.org/show_bug.cgi?id=120671 michael kerrisk [michał zegan] cap_sys_admin allows mounting cgroup filesystems see https://bugzilla.kernel.org/show_bug.cgi?id=120671 michael kerrisk clarify details of cap_sys_admin and cgroup v1 mounts with respect to cgroups version 1, cap_sys_admin in the user namespace allows only *named* hierarchies to be mounted (and not hierarchies that have a controller). michael kerrisk clarify cap_sys_admin details for mounting fs_userns_mount filesystems michael kerrisk correct user namespace rules for mounting /proc michael kerrisk describe a concrete example of capability checking add a concrete example of how the kernel checks capabilities in an associated user namespace when a process attempts a privileged operation. michael kerrisk correct kernel version where xfs added support for user namespaces linux 3.12, not 3.11. michael kerrisk see also: add ptrace(2) see also: add cgroup_namespaces(7) utf-8.7: shawn landden include rfc 3629 and clarify endianness which is left ambiguous the endianness is suggested by the order the bytes are displayed, but the text is ambiguous. ==================== changes in man-pages-4.08 ==================== released: 2016-10-08, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: arnaud gaillard bill pemberton carlos o'donell christoph hellwig david turner dr. tobias quathamer elliott hughes eugene syromyatnikov heinrich schuchardt hu keping igor liferenko ivan kharpalev jakub wilk jann horn josh triplett keno fischer laurent georget local lembke mats wichmann michael kerrisk mike crowe mike frysinger namhyung kim nikola forró patrick mclean peter wu petr cermak quentin rameau ray bellis rich felker ruben kerkhof sam varshavchik sebastian andrzej siewior siward de groot sloane bernstein stefan tauner tim savannah ursache vladimir zefram 王守堰 apologies if i missed anyone! new and rewritten pages ----------------------- quotactl.2 eugene syromyatnikov [michael kerrisk] updated information regarding disk quota flags added information regarding dqf_sys_file flag; updated definition of v1_dqf_rsquash, which has been defined privately and defined publicly as dqf_root_squash. eugene syromyatnikov updated information regarding xfs-specific quotactl subcommands added information regarding structure definitions used for xfs-specific subcommands, updated flag constants, added information regarding ignored syscall arguments, added notes on usage of kernel uapi header. eugene syromyatnikov additions regarding project quotas added information regarding presence of project quotas. bswap.3 michael kerrisk new page documenting bswap_16(), bswap_32(), and bswap_64() cgroups.7 michael kerrisk substantial rewrites, additions, and corrections. newly documented interfaces in existing pages --------------------------------------------- readv.2 michael kerrisk document the pwritev2() rwf_sync and rwf_dsync flags proc.5 michael kerrisk document /proc/pid/seccomp jann horn document /proc/[pid]/task/[tid]/children document the /proc/[pid]/task/[tid]/children interface from criu, and more importantly, document why it's usually not a good interface. new and changed links --------------------- bswap_16.3 bswap_32.3 bswap_64.3 new link to new bswap.3 global changes -------------- various pages michael kerrisk fix section ordering various pages had sections in an order different from that prescribed in man-pages(7). various pages michael kerrisk [mike frysinger] consistently use /proc/[pid] (not /proc/pid) various pages michael kerrisk fix order of see also entries entries should be ordered first by section, and then alphabetically within the section. various pages michael kerrisk order errors alphabetically various pages michael kerrisk remove section number from page self reference fix places where pages refer to the function that they describe and include a section number in that reference. such references cause some html-rendering tools to create self-references in the page. a few pages michael kerrisk eliminate groff "cannot adjust line" warnings changes to individual pages --------------------------- pldd.1 michael kerrisk [carlos o'donell] note gdb(1) command that can be used as a replacement for pldd taken from carlos o'donnell's suggestion in https://sourceware.org/bugzilla/show_bug.cgi?id=18035#c2 michael kerrisk bugs: pldd has not worked since glibc 2.19 accept.2 michael kerrisk mention epoll(7) alongside poll()/select() michael kerrisk demote discussion of decnet to notes decnet ceased to be important long ago... adjtimex.2 nikola forró fix kernel version references chroot.2 michael kerrisk note user namespace requirements for cap_sys_chroot clone.2 keno fischer [josh triplett] adjust syscall prototype and expand clone_settls description michael kerrisk [josh triplett, josh triplett] document raw syscall interfaces on various other architectures michael kerrisk change types for 'ptid' and 'ctid' in syscall prototypes these types changed from 'void *' to 'int *' back in linux 3.8. michael kerrisk einval is generated by glibc wrapper for null 'fn' or 'child_stack' clarify that this error is produced by the wrapper function, not the underlying system call. in particular, the point is that the raw system call can accommodate a null pointer for 'child_stack'. michael kerrisk [elliott hughes] make the implications of clone_files more explicit if clone_files is not set, the duplicated fds nevertheless share file offset and status flags via the open file description. michael kerrisk mention kcmp() under notes close.2 michael kerrisk add mention of the close-on-exec flag michael kerrisk clarify discussion noting that close() does not flush buffer cache epoll_wait.2 mike crowe clarify that the timeout is measured against clock_monotonic execve.2 michael kerrisk mention use of 'environ' to access environment list michael kerrisk note that real uid, real gid, and supplementary gids are unchanged fanotify_init.2 heinrich schuchardt update bugs information fcntl.2 michael kerrisk note an important detail of f_setown permission rules for signals f_setown records the caller's credentials at the time of the fcntl() call, and it is these saved credentials that are used for subsequent permission checks. michael kerrisk make the description of the effect of close-on-exec a little clearer michael kerrisk clarify that f_getfd and f_getfl return flags via the function result fork.2 michael kerrisk pid of new process also does not match any existing session id fsync.2 michael kerrisk see also: add pwritev(2) since linux 4.7, pwritev() has flags related to i/o integrity completion. getdomainname.2 michael kerrisk note user namespace requirements for cap_sys_admin getgroups.2 michael kerrisk note user namespace requirements for cap_setgid gethostname.2 michael kerrisk note user namespace requirements for cap_sys_admin getrlimit.2 michael kerrisk note user namespace semantics for cap_sys_resource getsid.2 michael kerrisk rework description to be somewhat clearer michael kerrisk correct the definition of "session id" getunwind.2 michael kerrisk simplify text referring to vdso(7) the detail given here is redundant, since this info is also in vdso(7). kcmp.2 michael kerrisk add an example program kill.2 michael kerrisk note the user namespace requirement for cap_kill killpg.2 michael kerrisk refer reader to kill(2) for signal permission rules mlock.2 sebastian andrzej siewior document that fork() after mlock() may be a bad idea in a rt process mmap.2 jann horn describe treatment of 'offset' for map_anonymous michael kerrisk [siward de groot] small improvement to description of map_shared see https://sourceware.org/bugzilla/show_bug.cgi?id=6887 msgctl.2 msgget.2 msgop.2 semctl.2 semget.2 semop.2 shmctl.2 shmget.2 shmop.2 michael kerrisk note the user namespace requirements for cap_ipc_owner open.2 michael kerrisk clarify user namespace capability requirements for o_noatime michael kerrisk notes: kcmp() can be used to test if two fds refer to the same ofd michael kerrisk f2fs support for o_tmpfile was added in linux 3.16 michael kerrisk clarify the rules about how the group id of a new file is determined prctl.2 michael kerrisk refer to proc(5) for effects of dumpability on ownership of /proc/pid/* michael kerrisk errors: add eacces error for pr_set_seccomp-seccomp_mode_filter michael kerrisk simplify list of cases where "dumpable" attribute is reset michael kerrisk note user namespace requirements for pr_capbset_drop cap_setpcap readlink.2 michael kerrisk [ursache vladimir] make example program handle links that report a size of zero some "magic" symlinks created by the kernel (e.g., those under /proc and /sys) report 'st_size' as zero. modify the example program to handle that possibility. michael kerrisk emphasize that truncation of returned buffer generates no error readv.2 michael kerrisk [christoph hellwig] clarify that rwf_dsync and rwf_sync apply only to data being written michael kerrisk add preadv2() and pwritev2() to name line reboot.2 michael kerrisk note user namespace requirements around cap_sys_boot rename.2 michael kerrisk [tim savannah] clarify that errors may cause rename to fail (not to be nonatomic) sched_setaffinity.2 michael kerrisk note user namespace requirements for cap_sys_nice seccomp.2 michael kerrisk cap_sys_admin is required only in caller's user namespace select_tut.2 peter wu fix various issues in example program seteuid.2 michael kerrisk note user namespace requirements for cap_setuid and cap_setgid setgid.2 michael kerrisk note user namespace requirements for cap_setgid setpgid.2 michael kerrisk add a reference to credentials(7) setpgid.2 setsid.2 michael kerrisk relocate some text on sessions and sessions leaders some text that was in setpgid(2) is better placed in setsid(2). setresuid.2 michael kerrisk note user namespace requirements for cap_setuid setreuid.2 michael kerrisk note user namespace requirements for cap_setuid and cap_setgid setsid.2 michael kerrisk refer to credentials(7) for details for details on controlling terminal refer to credentials(7) for details of how a session obtains a controlling terminal. set_thread_area.2 michael kerrisk add get_thread_area() to name setuid.2 michael kerrisk note user namespace requirements for cap_setuid sigprocmask.2 keno fischer expand/clarify libc/kernel sigset_t difference stat.2 michael kerrisk [ursache vladimir, mats wichmann] improve discussion of 'st_size' for /proc and /sys files michael kerrisk _bsd_source and _svid_source no longer expose nanosecond timestamps umask.2 michael kerrisk provide a rationale for the existence of /proc/pid/status 'umask' field wait.2 michael kerrisk remove erroneous statement that waitpid() is implemented via wait4() there is a fallback to wait4(), but only if the kernel does not provide a waitpid() system call. bindresvport.3 rcmd.3 ip.7 michael kerrisk note user namespace requirements for cap_net_bind_service byteorder.3 michael kerrisk see also: add bswap(3) dlopen.3 michael kerrisk dlmopen() is still broken in glibc 2.24 endian.3 michael kerrisk see also: add bswap(3) ffs.3 michael kerrisk [stefan tauner] correct feature test macro requirements fmemopen.3 michael kerrisk [rich felker] remove bogus suggestion to use setbuffer() getlogin.3 michael kerrisk update feature test macro requirements for cuserid() getumask.3 michael kerrisk note that getumask() is still unavailable in glibc 2.24 michael kerrisk point to umask(2) for a thread-safe way to discover process's umask mkstemp.3 quentin rameau fix _posix_c_source value for mkstemp() the correct _posix_c_source value has always been 200809l, not 200112l. pthread_join.3 michael kerrisk [mats wichmann] note that the caller might do clean up after joining with a thread michael kerrisk [王守堰] clarify use of 'retval' pointer resolver.3 ray bellis correct arguments to res_ninit(res_state statep) strverscmp.3 michael kerrisk add an example program wcstombs.3 michael kerrisk [igor liferenko] wcsrtombs() does not provide thread-safe interface to same functionality see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=741360 core.5 mike frysinger [michael kerrisk] add more details for output paths and the crash handler people sometimes assume that the crash handler runs in the same context as the crashing process. they would be incorrect :). proc.5 mike frysinger clarify the root symlink and mount namespaces if the target process is in a different mount namespace, the root symlink actually shows that view of the filesystem. michael kerrisk [mike frysinger] expand discussion of /proc/[pid]/root add a shell example showing that /proc/[pid]/root is more than a symlink. based on an example provided by mike frysinger in an earlier commit message. michael kerrisk explain rules determining ownership of /proc/pid/* files describe the effect of the "dumpable" attribute on ownership of /proc/pid files. michael kerrisk note effect of 'suid_dumpable' on ownership of /proc/pid files michael kerrisk refer to ptrace(2) for info on effect of suid_dumpable on ptraceability michael kerrisk add reference to core(5) in discussion of 'suid_dumpable' michael kerrisk note that 'suid_dumpable' mode 1 is insecure michael kerrisk document /proc/meminfo '+shmemhugepages' and 'shmempmdmapped' fields michael kerrisk document /proc/pid/status 'rssanon', 'rssfile', and 'rssshmem' fields michael kerrisk document /proc/pid/status 'hugetlbpages' field michael kerrisk [zefram] clarify that /proc/pid/statm 'shared' field counts *resident* pages see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=741360 michael kerrisk add reference to umask(2) in discussion of /proc/pid/status 'umask' michael kerrisk clarify user namespace requirements for /proc/sys/fs/protected_hardlinks michael kerrisk note changes to config option governing /proc/[pid]/task/[tid]/children michael kerrisk clarify description of /proc/pid/statm 'lib' and 'dt' fields these fields are always zero since linux 2.6. namhyung kim [petr cermak] add description of clear_refs_mm_hiwater_rss michael kerrisk update example vm values in /proc/pid/status capabilities.7 michael kerrisk add note about nosuid to file capabilities section michael kerrisk see also: add proc(5) michael kerrisk see also: add setsid(2) and setpgid(2) glob.7 michael kerrisk [arnaud gaillard] clarify that syntactically incorrect patterns are left unchanged packet.7 michael kerrisk clarify user namespace requirements for cap_net_raw pipe.7 michael kerrisk [patrick mclean] document fionread raw.7 michael kerrisk clarify user namespace requirements for cap_net_raw also remove mention of uid 0 as a method or creating a raw socket. as far as i can tell from reading the kernel source (net/ipv4/af_inet.c), this is not true. socket.7 michael kerrisk siocspgrp: refer to fcntl(2) f_setown for correct permission rules the permission rules described for sioccpgrp are wrong. rather than repeat the rules here, just refer the reader to fcntl(2), where the rules are described for f_setown. unix.7 michael kerrisk [laurent georget, ivan kharpalev] remove mention of recvmsg() from discussion of epipe error see https://bugzilla.kernel.org/show_bug.cgi?id=137351 ld.so.8 michael kerrisk expand description of ld_debug provide a list of the categories, and note that multiple categories can be specified. michael kerrisk add glibc version for ld_use_load_bias michael kerrisk clarify text describing whether secure-mode programs preload libraries michael kerrisk remove discussion of environment variables understood by libc5 libc5 disappeared long ago, so cease cluttering up this page with those ancient details. thus, remove discussion of the following environment variables: ld_aout_library_path, ld_aout_preload, ld_keepdir, ld_nowarn, and ldd_argv0. michael kerrisk remove text with ancient libc4 and linux libc details michael kerrisk remove mention of "elf only" drawing a distinction between elf-only features versus a,out ceased to be relevant long ago, so cluttering the page with "elf-only" serves no purpose. ==================== changes in man-pages-4.09 ==================== released: 2016-12-12, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: afzal mohammed andrew clayton carlos o'donell christoph lameter daniel baluta daniel berrange daniel wagner darrick j. wong dave hansen dmitry v. levin dr. tobias quathamer elliott hughes eric w. biederman eugene syromyatnikov florian weimer heinrich schuchardt igor liferenko jakub wilk jann horn jeremy harris kees cook keno fischer laurent georget laurent georget marcos mello michael hausenblas michael kerrisk mike frysinger mike galbraith miroslav koskar nikos mavrogiannopoulos omar sandoval pavel emelyanov piotr kwapulinski siddhesh poyarekar theodore ts'o vegard nossum vincent lefevre vince weaver wainer dos santos moschetta wang long willy tarreau zack weinberg apologies if i missed anyone! new and rewritten pages ----------------------- pkey_alloc.2 dave hansen [michael kerrisk] new page documenting pkey_alloc(2) and pkey_free(2) pthread_getattr_default_np.3 michael kerrisk new page documenting pthread_getattr_default_np(3) and pthread_setattr_default_np(3) strfromd.3 wainer dos santos moschetta new page documenting strfromd(3), strfromf(3), and strfroml(3) the iso/iec ts 18661-1 specifies the strfrom() class of functions that convert a float-point value to string. fuse.4 keno fischer [michael kerrisk] new page describing /dev/fuse this is my writeup of a basic description of /dev/fuse after playing with it for a few hours today. it is of course woefully incomplete, and since i neither have a use case nor am working on this code, i will not be in a position to expand it in the near future. however, i'm hoping this could still serve as a handy reference for others looking at this interface. [mtk: notwithstanding the incompleteness of this page, it's a good base for future extension.] tmpfs.5 michael kerrisk new page documenting the tmpfs filesystem pkeys.7 dave hansen [michael kerrisk] new page with overview of memory protection keys random.7 michael kerrisk [theodore ts'o, nikos mavrogiannopoulos, laurent georget] new page providing an overview of interfaces for obtaining randomness contains material extracted from getrandom(2) and random(4), as well as new material. sock_diag.7 pavel emelyanov, dmitry v. levin new page documenting netlink_sock_diag interface close.2 getpriority.2 nice.2 timer_create.2 timerfd_create.2 random.4 elf.5 proc.5 sched.7 various authors these pages also saw substantial updates, as described under "changes to individual pages". newly documented interfaces in existing pages --------------------------------------------- mmap.2 michael kerrisk add (much) more detail on map_growsdown mprotect.2 dave hansen document the new pkey_mprotect() system call eugene syromyatnikov document prot_sem, prot_sao, prot_growsup, and prot_growsdown prctl.2 eugene syromyatnikov document pr_set_fp_mode and pr_get_fp_mode perf_event_open.2 vince weaver perf_record_switch support linux 4.3 introduced two new record types for recording context switches: perf_record_switch and perf_record_switch_cpu_wide. vince weaver add perf_sample_branch_call branch sample type vince weaver perf_sample_branch_ind_jump branch_sample_type linux 4.2 added a new branch_sample_type: perf_sample_branch_ind_jump vince weaver document perf_record_misc_proc_map_parse_timeout vince weaver document sample_max_stack and /proc/sys/kernel/perf_event_max_stack linux 4.8 added a new sample_max_stack parameter, as well as /proc/sys/kernel/perf_event_max_stack which limits it and a new eoverflow error return. dave hansen perf_record_lost_samples record type linux 4.2 added a new record type: perf_record_lost_samples it is generated when hardware samples (currently only intel pebs) are lost. ptrace.2 michael kerrisk document ptrace_seccomp_get_filter michael kerrisk document ptrace_get_thread_area and ptrace_set_thread_area namespaces.7 michael kerrisk [eric w. biederman] document the ns_get_userns and ns_get_parent ioctl() operations sched.7 michael kerrisk [mike galbraith] document the autogroup feature includes documenting autogroup nice value michael kerrisk autogrouping breaks traditional semantics of nice in many cases when autogrouping is enabled (the default in many distros) there are many traditional use cases where the nice value ceases to have any effect. michael kerrisk add a subsection on nice value and group scheduling new and changed links --------------------- killpg.2 michael kerrisk new link to relocated killpg(3) page pkey_free.2 michael kerrisk new link to new pkey_alloc(2) page pkey_mprotect.2 michael kerrisk new link to mprotect(2) pthread_setattr_default_np.3 michael kerrisk new link to new pthread_getattr_default_np.3 strfromf.3 wainer dos santos moschetta new link to strfromd(3) strfroml.3 wainer dos santos moschetta new link to strfromd(3) global changes -------------- various pages michael kerrisk remove ancient libc4 and libc5 details it's nearly 20 years now since linux libc went away. remove some ancient details from the pages. various pages michael kerrisk add cross references to new tmpfs(5) page various pages michael kerrisk change section number from 2 to 3 in killpg() references changes to individual pages --------------------------- accept.2 michael kerrisk remove editorializing comments about 'socklen_t' michael kerrisk simplify the discussion of 'socklen_t' we don't really need to list the old oses in this discussion. adjtimex.2 clock_getres.2 gettimeofday.2 michael kerrisk see also: add hwclock(8) bind.2 connect.2 getpeername.2 getsockname.2 getsockopt.2 michael kerrisk replace discussion of 'socklen_t' with reference to accept(2) the discussion of 'socklen_t' editorializes and is repeated across several pages. replace it with a reference to accept(2), where some details about this type are provided. chmod.2 michael kerrisk see also: add chmod(1) chown.2 michael kerrisk see also: add chgrp(1) and chown(1) chroot.2 michael kerrisk see also: add chroot(1) clone.2 michael kerrisk the clone_*_settid operations store tid before return to user space clone_parent_settid and clone_child_settid store the new tid before clone() returns to user space close.2 michael kerrisk [daniel wagner] rework and greatly extend discussion of error handling further clarify that an error return should be used only for diagnostic or remedial purposes. michael kerrisk other unix implementations also close the fd, even if reporting an error looking at some historical source code suggests that the "close() always closes regardless of error return" behavior has a long history, predating even posix.1-1990. michael kerrisk note that future posix plans to require that the fd is closed on error see http://austingroupbugs.net/view.php?id=529#c1200. michael kerrisk clarify the variation in eintr behavior per posix and other systems fallocate.2 darrick j. wong document behavior with shared blocks note that falloc_fl_unshare may use cow to unshare blocks to guarantee that a disk write won't fail with enospc. fanotify_mark.2 heinrich schuchardt mention fan_q_overflow to receive overflow events it is necessary to set this bit in fanotify_mark(). fcntl.2 michael kerrisk f_getpipe_sz allocates next power-of-2 multiple of requested size add some detail about current implementation, since this helps the user understand the effect of the user pipe limits added in linux 4.5 (described in pipe(7)). michael kerrisk add eperm that occurs for f_setpipe_sz when user pipe limit is reached fideduperange.2 darrick j. wong [omar sandoval] fix the discussion of maximum sizes fix the discussion of the limitations on the dest_count and src_length parameters to the fideduperange ioctl() to reflect what's actually in the kernel. fsync.2 michael kerrisk see also: add fileno(3) fileno(3) is useful if one is combining fflush(3)/fclose(3) and fsync(2). michael kerrisk see also: add fflush(3) getgroups.2 andrew clayton ftm requirements fix for setgroups(2) gethostname.2 michael kerrisk see also: add hostname(1) get_mempolicy.2 michael kerrisk note that 'addr' must be null when 'flags' is 0 getpriority.2 michael kerrisk warn that autogrouping voids the effect of 'nice' in many cases refer the reader to sched(7) for the details. michael kerrisk expand discussion of getpriority() return value michael kerrisk the nice value supplied to setpriority() is clamped note that the nice value supplied to setpriority() is clamped to the permitted range. michael kerrisk improve description of setpriority() return value getpriority.2 sched.7 michael kerrisk move nice value details from getpriority(2) to sched(7) centralizing these details in sched(7) is more logical. getrandom.2 random.4 michael kerrisk consolidate and improve discussion on usage of randomness currently, recommendations on how to consume randomness are spread across both getrandom(2) and random(4) and the general opinion seems to be that the text in getrandom(2) does a somewhat better job. consolidate the discussion to a single page (getrandom(2)) and address some of the concerns expressed about the existing text in random(4). [some of this text ultimately made its way into the new random(7) page.] getrandom.2 michael kerrisk remove material incorporated into random(7) michael kerrisk note advantages of fact that getrandom() doesn't use file descriptors michael kerrisk clarify that getrandom() is not "reading" from /dev/{random,urandom} getrlimit.2 michael kerrisk refer to sched(7) in discussion of rlimit_rtprio and rlimit_rttime michael kerrisk describe the range of the rlimit_nice limit michael kerrisk refer to sched(7) in the discussion of rlimit_nice michael kerrisk see also: add credentials(7) ioctl_ficlonerange.2 ioctl_fideduperange.2 darrick j. wong clarify the behavior of the fideduperange ioctl kill.2 michael kerrisk see also: add kill(1) mbind.2 michael kerrisk [christoph lameter] memory policy is a per-thread attribute, not a per-process attribute mbind.2 set_mempolicy.2 piotr kwapulinski [christoph lameter, michael kerrisk] add mpol_local numa memory policy documentation mount.2 michael kerrisk see also: add mountpoint(1) mprotect.2 michael kerrisk conforming to: note that pkey_mprotect() is linux-specific nice.2 michael kerrisk warn that autogrouping voids the effect of 'nice' in many cases michael kerrisk conforming to: remove an ancient svr4 detail on errno values michael kerrisk rework discussion of nice() return value and standards conformance make the text a little clearer. in particular, clarify that the raw system call (still) returns 0 on success. michael kerrisk clarify the range of the nice value, and note that it is clamped michael kerrisk add mention of rlimit_nice michael kerrisk move discussion of handling the -1 success return to return value this detail was rather hidden in notes. also, rework the text a little. michael kerrisk clarify that nice() changes the nice value of the calling *thread* michael kerrisk add "c library/kernel differences" subsection heading michael kerrisk add reference to sched(7) for further details on the nice value open.2 michael kerrisk ubifs supports o_tmpfile starting with linux 4.9 michael kerrisk document enomem that occurs when opening fifo because of pipe hard limit perf_event_open.2 vince weaver add cycles field in lbr records linux 4.3 added a cycles field to the perf_sample_branch_stack last branch records. vince weaver update time_shift sample code linux 4.3 improved the accuracy of the clock/ns conversion routines. michael kerrisk clarify the use of signals for capturing overflow events pipe.2 michael kerrisk add enfile error for user pipe hard limit reached prctl.2 eugene syromyatnikov some additional details regarding the pr_get_unaligned operation eugene syromyatnikov note the output buffer size for pr_get_tid_address operation on x32/n32 michael kerrisk remove numeric definitions of pr_fp_mode_fr and pr_fp_mode_fre bits ptrace.2 keno fischer document the behavior of ptrace_sysemu stops keno fischer expand documentation ptrace_event_seccomp traps in linux 4.8, the order of ptrace_event_seccomp and syscall-entry-stops was reversed. document both behaviors and their interaction with the various forms of restart. quotactl.2 eugene syromyatnikov describe q_xquotasync, which is present but no-op in recent kernels reboot.2 wang long note errors for invalid commands inside a pid namespace sched_setattr.2 michael kerrisk fix cross reference for further info on the nice value the information moved from getpriority(2) to sched(7). sched_setscheduler.2 michael kerrisk [daniel berrange] mention sched_deadline give the reader a clue that there is another policy available that can't be set via sched_setscheduler(2). seccomp.2 jann horn document changed interaction with ptrace before kernel 4.8, the seccomp check will not be run again after the tracer is notified. fixed in kernel 4.9. michael kerrisk notes: mention ptrace(ptrace_seccomp_get_filter) to dump seccomp filters set_mempolicy.2 michael kerrisk reformat list of modes setsid.2 michael kerrisk improve wording of text on calling setsid() after fork()+_exit() michael kerrisk see also: add sched(7) list sched(7), because setsid(2) is part of the machinery of autogrouping. sigaction.2 dave hansen further documentation of segv_pkuerr signalfd.2 michael kerrisk document ssi_addr_lsb field of signalfd_siginfo symlink.2 michael kerrisk see also: add namei(1) sync_file_range.2 michael kerrisk fix description for espipe error a file descriptor can't refer to a symbolic link. syscalls.2 michael kerrisk add pkey_alloc(), pkey_free(), and pkey_mprotect() new system calls in linux 4.9. michael kerrisk add ppc_swapcontext(2) timer_create.2 michael kerrisk document clock_boottime michael kerrisk document clock_realtime_alarm and clock_boottime_alarm timerfd_create.2 michael kerrisk document clock_boottime, clock_realtime_alarm, and clock_boottime_alarm michael kerrisk document tfd_timer_cancel_on_set michael kerrisk rework discussion on relative and absolute timers unlink.2 michael kerrisk see also: add unlink(2) utime.2 utimensat.2 michael kerrisk see also: add touch(1) wait.2 michael kerrisk on some architectures, waitpid() is a wrapper that calls wait4(). atof.3 wainer dos santos moschetta see also: add strfromd(3) ctime.3 michael kerrisk add errors section michael kerrisk return value: describe return values more explicitly errno.3 michael kerrisk [igor liferenko] add glibc error text for eilseq fclose.3 fflush.3 michael kerrisk see also: add fileno(2) getlogin.3 michael kerrisk remove deprecated _reentrant from ftm requirements for getlogin_r() michael kerrisk see also: add logname(1) isalpha.3 michael kerrisk note circumstances where 'c' must be cast to 'unsigned char' killpg.3 michael kerrisk move killpg.2 from section to section 3 mallopt.3 michael kerrisk [siddhesh poyarekar] document 0 as default value of m_arena_max and explain its meaning michael kerrisk improve description of m_arena_test michael kerrisk document default value for m_arena_test michael kerrisk note default value of m_perturb mbsnrtowcs.3 michael kerrisk [igor liferenko] note behavior of mbsnrtowcs() for an incomplete character note the behavior of mbsnrtowcs() when an incomplete character is found at end of the input buffer. mbstowcs.3 wcstombs.3 michael kerrisk [igor liferenko] improve language relating to "initial state" see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=839705 mbstowcs.3 michael kerrisk [igor liferenko] add missing include to example program see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=845172 mq_close.3 michael kerrisk description: add reference to mq_notify(3) mq_open.3 eugene syromyatnikov clarification regarding usage of mq_flags attribute in mq_open() mq_receive.3 mq_send.3 eugene syromyatnikov clarification regarding reasons behind ebadf printf.3 wainer dos santos moschetta see also: add strfromd(3) pthread_attr_init.3 michael kerrisk see also: add pthread_setattr_default_np(3) pthread_create.3 michael kerrisk see also: add pthread_setattr_default_np(3) ptsname.3 michael kerrisk note that ptsname_r() is proposed for future inclusion in posix.1 michael kerrisk conforming to:: clarify that only ptsname() is standardized (so far) remainder.3 michael kerrisk note fix to remainder(nan(""), 0) handling the bug https://www.sourceware.org/bugzilla/show_bug.cgi?id=6779 has been fixed in glibc 2.15. michael kerrisk document fixes for edom handling for range errors the bug http://sources.redhat.com/bugzilla/show_bug.cgi?id=6783 was fixed in glibc 2.15. setjmp.3 michael kerrisk _bsd_source must be *explicitly* defined to get bsd setjmp() semantics strtod.3 wainer dos santos moschetta see also: add strfromd(3) tgamma.3 michael kerrisk document fixes to give erange for underflow range error the bug https://www.sourceware.org/bugzilla/show_bug.cgi?id=6810 was fixed in glibc 2.19. timegm.3 michael kerrisk add errors section michael kerrisk [vincent lefevre] add return value section tmpnam.3 michael kerrisk properly document tmpnam_r(3) toupper.3 michael kerrisk note circumstances where 'c' must be cast to 'unsigned char' ttyname.3 michael kerrisk see also: add tty(1) console_ioctl.4 michael kerrisk add brief descriptive text for kdgkbmode modes miroslav koskar add k_off keyboard mode random.4 michael kerrisk add reference to new random(7) page michael kerrisk rework formatting of /proc interfaces make the information easier to parse by formatting the file descriptions as hanging lists. no significant content changes. nikos mavrogiannopoulos [laurent georget] provide a more accurate description of /dev/urandom this documents the "property" of /dev/urandom of being able to serve numbers prior to pool being initialized, and removes any suggested usages of /dev/random which are disputable (i.e., one-time pad). document the fact /dev/random is only suitable for applications which can afford indeterminate delays since very few applications can do so. smooth the alarming language about a theoretical attack, and mention that its security depends on the cryptographic primitives used by the kernel, as well as the total entropy gathered. michael kerrisk [laurent georget, theodore ts'o] improve discussion of /dev/urandom, blocking reads, and signals the text currently states that o_nonblock has no effect for /dev/urandom, which is true. it also says that reads from /dev/urandom are nonblocking. this is at the least confusing. if one attempts large reads (say 10mb) from /dev/urandom there is an appreciable delay, and interruption by a signal handler will result in a short read. amend the text to reflect this. elf.5 mike frysinger add subsection headers at major points the current pages dumps all the content into one big description with no real visual break up between logically independent sections. add some subsection headers to make it easier to read and scan. mike frysinger document notes document the elf{32,64}_nhdr structure, the sections/segments that contain notes, and how to interpret them. i've been lazy and only included the gnu extensions here, especially as others are not defined in the elf.h header file as shipped by glibc. filesystems.5 michael kerrisk see also: add fuse(4) proc.5 dave hansen describe new protectionkey 'smaps' field michael kerrisk add example protectionkey output for 'smaps' file michael kerrisk add pointers to sched(7) for autogroup files sched(7) describes /proc/sys/kernel/sched_autogroup_enabled and /proc/pid/autogroup. michael kerrisk add /proc/sys/fs/pipe-user-pages-{hard,soft} entries michael kerrisk improve description of the kernelpagesize and mmupagesize 'smaps' fields michael kerrisk rework 'smaps' protectionkey text and add some details michael kerrisk mention lslocks(8) in discussion of /proc/locks michael kerrisk describe shmem field of /proc/meminfo michael kerrisk rework 'smaps' vmflags text, and add kernel version and example output proc.5 pipe.7 michael kerrisk move /proc/sys/fs/pipe-max-size content from proc(5) to pipe(7) resolv.conf.5 carlos o'donell [florian weimer] timeout does not map to resolver api calls utmp.5 michael kerrisk see also: add users(1) capabilities.7 michael kerrisk cap_sys_admin governs ptrace(2) ptrace_seccomp_get_filter michael kerrisk cap_sys_admin allows privileged ioctl() operations on /dev/random cgroups.7 michael kerrisk add details on 'cpu' cfs bandwidth control credentials.7 michael kerrisk see also: add setpriv(1) michael kerrisk see also: add shadow(5) feature_test_macros.7 michael kerrisk [zack weinberg] note that _reentrant and _thread_safe are now deprecated michael kerrisk note that "cc -pthread" defines _reentrant inotify.7 michael kerrisk note a subtlety of event generation when monitoring a directory libc.7 michael kerrisk add a note on why glibc 2.x uses the soname libc.so.6 michael kerrisk add a few historical details on linux libc4 and libc5 just for historical interest. details taken from http://www.linux-m68k.org/faq/glibcinfo.html. mdoc.7 michael kerrisk add a cross-reference to groff_mdoc(7) mount_namespaces.7 michael kerrisk see also: add user_namespaces(7) mount_namespaces.7 user_namespaces.7 michael kerrisk migrate subsection on mount restrictions to mount_namespaces(7) this section material in the user_namespaces(7) page was written before the creation of the mount_namespaces(7) manual page. nowadays, this material properly belongs in the newer page. netlink.7 dmitry v. levin document netlink_inet_diag rename to netlink_sock_diag dmitry v. levin add references to sock_diag(7) pid_namespaces.7 michael kerrisk refer to namespaces(7) for information about ns_get_parent pipe.7 michael kerrisk, vegard nossum [vegard nossum] document /proc files controlling memory usage by pipes document /proc/sys/fs/pipe-max-size and /proc/sys/fs/pipe-user-pages-{soft,hard}. michael kerrisk document pre-linux 4.9 bugs in pipe limit checking sched.7 michael kerrisk add a new introductory paragraph describing the nice value michael kerrisk add more precise details on cfs's treatment of the nice value michael kerrisk mention rlimit_nice in the discussion of the nice value michael kerrisk notes: mention cgroups cpu controller michael kerrisk add introductory sentence mentioning cfs scheduler michael kerrisk add nice(2), getpriority(2), and setpriority(2) to api list michael kerrisk make it clearer that sched_other is always scheduled below real-time michael kerrisk give the page a more generic name the page isn't just about apis. standards.7 michael kerrisk posix.1-2016 (posix.1-2008 tc2) has now been released symlink.7 michael kerrisk see also: add namei(1) uri.7 jakub wilk use "example.com" as example domain user_namespaces.7 michael kerrisk add reference to namespaces(7) for ns_get_userns operation michael kerrisk add reference to namespaces(7) for ns_get_parent operation ==================== changes in man-pages-4.10 ==================== released: 2017-03-13, paris contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam martindale alex anders thulin andreas gruenbacher brian masney casey schaufler david howells erik kline erik roland van der meer eugene syromyatnikov fabjan sukalia heinrich schuchardt helmut eller hugo guiroux ian jackson jakub wilk jann horn jan ziak <0xe2.0x9a.0x9b@gmail.com> john wiersba jon jensen kai noda kasaki motohiro keno fischer kent fredic krzysztof kulakowski maik zumstrull mat martineau michael kerrisk mike frysinger nadav har'el namhyung kim nicolas biscos omar sandoval paul fee reverend homer rob landley sergey polovko steven luo tadeusz struk vincent bernat vivenzio pagliari wainer dos santos moschetta willy tarreau apologies if i missed anyone! new and rewritten pages ----------------------- add_key.2 michael kerrisk [eugene syromyatnikov, david howells] major improvements and additions the page has doubled in length. ioctl_iflags.2 michael kerrisk new page describing inode flags and ioctl() operations ioctl_ns.2 michael kerrisk new page created by splitting ioctl(2) operations out of namespaces(7) keyctl.2 michael kerrisk, eugene syromyatnikov [david howells, mat martineau] a vast number of additions and improvements the page has gone from somewhat over 100 lines to well over 1000 lines and now more or less documents the complete interface provided by this system call. getentropy.3 michael kerrisk new page documenting getentropy(3) getentropy(3) is added to glibc in version 2.25. keyrings.7 david howells new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk [eugene syromyatnikov, david howells] very many additions and improvements michael kerrisk document /proc/keys michael kerrisk document /proc/sys/kernel/keys/persistent_keyring_expiry michael kerrisk document /proc/key-users michael kerrisk document /proc/sys/kernel/keys/gc_delay michael kerrisk document /proc files that define key quotas persistent-keyring.7 michael kerrisk new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk various clean-ups and additions process-keyring.7 michael kerrisk new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk various additions and improvements request_key.2 michael kerrisk, eugene syromyatnikov [david howells] very many additions and improvements the page is now three times its former length. session-keyring.7 michael kerrisk new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk various reworking and additions signal-safety.7 michael kerrisk new page created by migrating the signal-safety discussion from signal(7). along the way some more details got added. michael kerrisk [kasaki motohiro] note async-signal-safety problems caused by pthread_atfork() see https://bugzilla.kernel.org/show_bug.cgi?id=25292 michael kerrisk [kasaki motohiro] note glibc deviations from posix requirements see https://bugzilla.kernel.org/show_bug.cgi?id=25292 thread-keyring.7 michael kerrisk new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk various rewordings and additions user-keyring.7 michael kerrisk new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk various reworking and improvements user-session-keyring.7 michael kerrisk new page (written by david howells) adopted from keyutils since this page documents kernel-user-space interfaces, it makes sense to have it as part of man-pages, rather than the keyutils package. michael kerrisk various rewordings and additions newly documented interfaces in existing pages --------------------------------------------- bzero.3 michael kerrisk document explicit_bzero() (new in glibc 2.25) also, reword the description of bzero somewhat. proc.5 michael kerrisk document /proc/sys/vm/user_reserve_kbytes michael kerrisk document /proc/sys/vm/admin_reserve_kbytes michael kerrisk document /proc/sys/fs/mount-max michael kerrisk document /proc/pid/status 'nonewprivs' field new and changed links --------------------- explicit_bzero.3 michael kerrisk new link to bzero.3 changes to individual pages --------------------------- chmod.2 michael kerrisk errors: add eperm error for immutable/append-only file chown.2 michael kerrisk errors: add eperm error for immutable/append-only file chroot.2 michael kerrisk see also: add switch_root(8) clock_getres.2 michael kerrisk note posix.1 requirements re relative time services and clock_realtime clone.2 michael kerrisk clone() does not execute fork handlers execve.2 michael kerrisk rework text describing when effective ids aren't transformed by execve() michael kerrisk file capabilities can be ignored for the same reasons as set-uid/set-gid michael kerrisk the 'no_new_privs' bit inhibits transformations of the effective ids fork.2 michael kerrisk cgroup pids controller may also be trigger for eagain error fsync.2 michael kerrisk see also: add posix_fadvise(2) getrandom.2 michael kerrisk remove getentropy(3) details and defer to new getentropy(3) page michael kerrisk starting with glibc 2.25, getrandom() is now declared in michael kerrisk glibc support was added in version 2.25 getrlimit.2 michael kerrisk document role of rlimit_nofile for fd passing over unix sockets getxattr.2 listxattr.2 andreas gruenbacher document e2big errors inotify_add_watch.2 michael kerrisk note "inode" as a synonym for "filesystem object" consistent with clarifications just made in inotify(7). ioctl.2 michael kerrisk see also: add ioctl_ns(2), ioctl_iflags(2) ioctl_fat.2 brian masney correctly reference volume id instead of volume label kcmp.2 michael kerrisk mention the clone(2) flags relating to various kcmp() 'type' values michael kerrisk kcmp_file: note reasons why fds may refer to same open file description link.2 michael kerrisk when using linkat() at_empty_path, 'olddirfd' must not be a directory michael kerrisk errors: add eperm for immutable/append-only files michael kerrisk note limits where emlink is encountered on ext4 and btrfs listxattr.2 michael kerrisk eliminate extra e2big error text andreas' patch added a second description of e2big that was (mostly) more detailed than the existing text. combine the two texts. lseek.2 michael kerrisk o_append overrides the effect of lseek() when doing file writes michael kerrisk remove ancient info about whence values and return values on old systems michael kerrisk remove slightly bogus advice about race conditions the page already (by now) contains a reference to open(2) for a discussion of open file descriptions. leave it at that, since the reader can then deduce how things work. madvise.2 michael kerrisk note that madvise() is generally about improving performance mbind.2 krzysztof kulakowski [michael kerrisk] update mpol_bind description the behavior of mpol_bind changed in linux 2.6.26. mincore.2 michael kerrisk see also: add madvise(2), posix_fadvise(2), posix_madvise(3) mlock.2 michael kerrisk note pre-4.9 bug in rlimit_memlock accounting for overlapping locks michael kerrisk see also: add mincore(2) mmap.2 michael kerrisk mincore(2) can be used to discover which pages of a mapping are resident mount.2 michael kerrisk [rob landley] refer to mount_namespaces(7) for details of default propagation type nanosleep.2 michael kerrisk describe "creeping sleep" problem nanosleep() has a problem if used in a program that catches signals and those signals are delivered at a very high rate. describe the problem, and note that clock_nanosleep(2) provides a solution. michael kerrisk bugs: explicitly note that the linux 2.4 bug was fixed in linux 2.6 open.2 michael kerrisk make it clear that o_append implies atomicity michael kerrisk clarify distinction between file creation flags and file status flags michael kerrisk note ambiguity of eloop error when using o_nofollow michael kerrisk restructure o_nofollow text for easier parsing michael kerrisk clarify that o_nofollow is now in posix poll.2 select.2 nicolas biscos add a reference to the sigset discussion in sigprocmask(2) a little while back, i added a note to sigprocmask.2 that discussed the difference between the libc's and the kernel's sigset_t structures. i added that note, because i saw this being done wrong in a tool tracing system calls (causing subtle bugs). as it turns out, the same bugs existed for ppoll and pselect, for the same reason. i'm hoping by adding the reference here, future writers of similar tools will find that discussion and not make the same mistake. posix_fadvise.2 michael kerrisk mention /proc/sys/vm/drop_caches it may be helpful for the reader of this page to know about /proc/sys/vm/drop_caches. michael kerrisk reorganize some text details for various flags were hidden under notes. move them to description, to make the details more obvious. michael kerrisk one can use open(2) + mmap(2) + mincore(2) as a 'fincore' note that open(2) + mmap(2) + mincore(2) can be used to get a view of which pages of a file are currently cached. michael kerrisk [maik zumstrull] note that posix_fadv_dontneed *may* try to write back dirty pages michael kerrisk see also: mincore(2) prctl.2 michael kerrisk clarify that the ambient capability set is per-thread keno fischer be more precise in what causes dumpable to reset michael kerrisk the no_new_privs setting is per-thread (not per-process) michael kerrisk mention /proc/pid/status 'nonewprivs' field michael kerrisk add reference to seccomp(2) in discussion of pr_set_no_new_privs ptrace.2 omar sandoval clarify description of ptrace_o_exitkill read.2 michael kerrisk [kai noda] rework text in description that talks about limits for 'count' see https://bugzilla.kernel.org/show_bug.cgi?id=86061 michael kerrisk [steven luo] remove crufty text about eintr and partial read remove bogus text saying that posix permits partial read to return -1/eintr on interrupt by a signal handler. that statement already ceased to be true in susv1 (1995)! see https://bugzilla.kernel.org/show_bug.cgi?id=193111 readv.2 michael kerrisk remove generic advice about mixing stdio and syscalls on same file there is nothing specific to readv()/writev() about this advice. recv.2 michael kerrisk [vincent bernat] remove duplicate paragraph man-pages-1.34 included changes that duplicated an existing paragraph. remove that duplicate. michael kerrisk see also: add ip(7), ipv6(7), tcp(7), udp(7), unix(7) remap_file_pages.2 michael kerrisk remap_file_pages() has been replaced by a slower in-kernel emulation send.2 michael kerrisk see also: add ipv6(7), socket(7), unix(7) setxattr.2 michael kerrisk errors: add eperm for immutable/append-only files signalfd.2 michael kerrisk signalfd() doesn't play well with helper programs spawned by libraries see https://lwn.net/articles/415684/. michael kerrisk signalfd can't be used to receive synchronously generated signals signals such as the sigsegv that results from an invalid memory access can be caught only with a handler. stat.2 michael kerrisk example: extend program to also show id of the containing device michael kerrisk notes: mention fstatat() at_no_automount in discussion of automounting statfs.2 namhyung kim add more filesystem types add missing magic numbers from /usr/include/linux/magic.h syscall.2 mike frysinger add endian details with 64-bit splitting architectures that split 64-bit values across register pairs usually do so according to their c abi calling convention (which means endianness). add some notes to that effect, and change the readahead example to show a little endian example (since that is way more common than big endian). also start a new list of syscalls that this issue does not apply to. mike frysinger note parisc handling of aligned register pairs while parisc would normally have the same behavior as arm/powerpc, they decide to write shim syscall stubs to unpack/realign rather than expose the padding to userspace. tkill.2 jann horn document eagain error for real-time signals truncate.2 michael kerrisk note use of ftruncate() for posix shared memory objects unlink.2 michael kerrisk errors: add eperm error for immutable/read-only files vfork.2 michael kerrisk explain why the child should not call exit(3) michael kerrisk another reason to use vfork() is to avoid overcommitting memory michael kerrisk note some caveats re the use of vfork() inspired by rich felker's post at http://ewontfix.com/7/. see also https://sourceware.org/bugzilla/show_bug.cgi?id=14749 and see also https://sourceware.org/bugzilla/show_bug.cgi?id=14750. michael kerrisk see also: add _exit(2) write.2 michael kerrisk [kai noda] alert the reader that there is a limit on 'count' see https://bugzilla.kernel.org/show_bug.cgi?id=86061 aio_suspend.3 michael kerrisk note that the glibc implementation is not async-signal-safe see https://sourceware.org/bugzilla/show_bug.cgi?id=13172 backtrace.3 michael kerrisk see also: add addr2line(1) and gdb(1) bcmp.3 bcopy.3 bzero.3 memccpy.3 memchr.3 memcmp.3 memcpy.3 memfrob.3 memmem.3 memmove.3 memset.3 michael kerrisk see also: add bstring(3) exec.3 michael kerrisk execl() and execle() were not async-signal-safe before glibc 2.24 fopen.3 michael kerrisk [helmut eller] describe freopen() behavior for null pathname argument see https://bugzilla.kernel.org/show_bug.cgi?id=191261 michael kerrisk note the open(2) flags that correspond to the 'mode' argument michael kerrisk change argument name: 'path' to 'pathname' for consistency with open(2). michael kerrisk add subsection headings for each function fts.3 michael kerrisk use better argument name for fts_children() and fts_set() michael kerrisk fix minor error in ftsent structure definition michael kerrisk improve explanation of 'fts_errno' michael kerrisk give a hint that there are further fields in the ftsent structure michael kerrisk clarify meaning of zero as 'instr' value for fts_set() ftw.3 michael kerrisk correctly handle use of stat info for ftw_ns in example program michael kerrisk clarify that stat buffer is undefined for ftw_ns getline.3 michael kerrisk example: better error handling michael kerrisk [kent fredic] example: handle null bytes in input jann horn document enomem error case see the error handling in libio/iogetdelim.c michael kerrisk example: specify file to be opened as command-line argument michael kerrisk use better variable name in example program getmntent.3 michael kerrisk [anders thulin] prefer '\\' as the escape to get a backslash see https://bugzilla.kernel.org/show_bug.cgi?id=191611 getopt.3 michael kerrisk reword discussion of error handling and reporting the existing description was hard to understand. break it into a bullet list that separates out the details in a manner that is easier to parse. michael kerrisk correct details of use of to get getopt() declaration michael kerrisk [john wiersba] remove some redundant text mq_open.3 michael kerrisk [adam martindale] include definition of the 'mq_attr' structure in this man page make the reader's life a little easier by saving them from having to refer to mq_getattr(3). mq_send.3 michael kerrisk [adam martindale] refer to mq_overview(7) for details on range of message priority __ppc_set_ppr_med.3 wainer dos santos moschetta note need for _arch_pwr8 macro the _arch_pwr8 macro must be defined to get the __ppc_set_ppr_very_low() and __ppc_set_ppr_med_high() definitions. printf.3 michael kerrisk document nonstandard 'z' modifier michael kerrisk document 'q' length modifier michael kerrisk [erik roland van der meer] fix a small bug in example code move the second call to va_end(ap) to above the if-block that precedes it, so that the va_list 'ap' will be cleaned up in all cases. michael kerrisk [nadav har'el] as a nonstandard extension, gnu treats 'll' and 'l' as synonyms see https://bugzilla.kernel.org/show_bug.cgi?id=190341. michael kerrisk add references to setlocale(3) in discussions of locales michael kerrisk see also: remove bogus self reference (dprintf(3)) random.3 michael kerrisk relocate information of "optimal" value of initstate() 'n' argument the information was a bit hidden in notes. random_r.3 michael kerrisk [jan ziak] 'buf.state' must be initialized to null before calling initstate_r() see https://bugzilla.kernel.org/show_bug.cgi?id=192801. michael kerrisk add some usage notes for setstate_r() michael kerrisk note that 'buf' records a pointer to 'statebuf' see https://sourceware.org/bugzilla/show_bug.cgi?id=3662. michael kerrisk add bugs section pointing out the weirdness of the initstate_r() api resolver.3 michael kerrisk res_aaonly, res_primary, res_nocheckname, res_keeptsig are deprecated these options were never implemented; since glibc 2.25, they are deprecated. michael kerrisk the res_noip6dotint is removed in glibc 2.25 michael kerrisk note that res_blast was unimplemented and is now deprecated michael kerrisk res_use_inet6 is deprecated since glibc 2.25 michael kerrisk res_usebstring was removed in glibc 2.25 resolver.3 resolv.conf.5 michael kerrisk note that res_usebstring defaults to off scandir.3 michael kerrisk [ian jackson] fix errors in example program see http://bugs.debian.org/848231. michael kerrisk improve logic of the example program scanf.3 michael kerrisk document the quote (') modifier for decimal conversions sem_post.3 setjmp.3 michael kerrisk see also: add signal-safety(7) sem_wait.3 michael kerrisk [fabjan sukalia] remove statement that sa_restart does not cause restarting this has not been true since linux 2.6.22. the description of eintr maintains a reference to signal(7), which explains the historical details. see https://bugzilla.kernel.org/show_bug.cgi?id=192071 sleep.3 michael kerrisk [mike frysiner] note that sleep() is implemented via nanosleep(2) see https://bugzilla.kernel.org/show_bug.cgi?id=73371. michael kerrisk [mike frysinger] note that sleep() sleeps for a real-time number of seconds see https://bugzilla.kernel.org/show_bug.cgi?id=73371. michael kerrisk convert bugs text to "portability notes" subsection the existing text is not a bug, as such. michael kerrisk description: minor reworking strerror.3 heinrich schuchardt indicate reasonable buffer size for strerror_r() and strerror_l() add a hint which buffer size is needed for strerror_r() and strerror_l(). strverscmp.3 michael kerrisk [vivenzio pagliari] fix comparison error in example program system.3 michael kerrisk in the glibc implementation, fork handlers are not executed by system() random.4 michael kerrisk [jon jensen] note that entropy_avail will be a number in the range 0..4096 core.5 michael kerrisk clarify that dumping program's initial cwd is root directory michael kerrisk the target of core dump piping can also be a script filesystems.5 michael kerrisk see also: add btrfs(5), nfs(5), tmpfs(5) intro.5 michael kerrisk document the reality that by now section 5 also covers filesystems there are by now, from various filesystem projects, various pages in section 5 that document different filesystems. change intro(5) to reflect that. documented after following: http://bugs.debian.org/847998 proc.5 mike frysinger [michael kerrisk] clarify /proc/pid/environ behavior /proc/pid/environ reflects process environment at *start* of program execution; it is set at time of execve(2) michael kerrisk add reference to slabinfo(5) in discussion of /proc/meminfo 'slab' field michael kerrisk add entries for "keys" files that refer reader to keyrings(7) michael kerrisk remove duplicate /proc/[pid]/seccomp entry michael kerrisk mention other system calls that create 'anon_inode' file descriptors mention a few other system calls that create file descriptors that display an 'anon_inode' symlink in /proc/pid/fd michael kerrisk add some detail on overcommit_memory value 1 michael kerrisk add reference to vdso(7) in discussion of /proc/pid/maps resolv.conf.5 michael kerrisk ip6-bytestring was removed in glibc 2.25 michael kerrisk the ipc-dotint and no-ip6-dotint options were removed in glibc 2.25 michael kerrisk the 'inet6' option is deprecated since glibc 2.25 slabinfo.5 michael kerrisk see also: add slabtop(1) capabilities.7 michael kerrisk [casey schaufler] add subsection with notes to kernel developers provide some notes to kernel developers considering how to choose which capability should govern a new kernel feature. michael kerrisk further enhance the recommendation against new uses of cap_sys_admin michael kerrisk explicitly point from cap_sys_admin to "notes for kernel developers" michael kerrisk add another case for cap_dac_read_search michael kerrisk refer to execve(2) for the reasons that file capabilities may be ignored michael kerrisk document a new use of cap_sys_resource michael kerrisk add some more operations governed by cap_sys_admin michael kerrisk adjust references to chattr(1) to point to ioctl_iflags(2) environ.7 michael kerrisk mention prctl(2) pr_set_mm_env_start and pr_set_mm_env_end operations inotify.7 michael kerrisk point out that inotify monitoring is inode based ip.7 michael kerrisk see also: add ip(8) man.7 uri.7 jakub wilk use "www.kernel.org" in example urls apparently www.kernelnotes.org is now a spam site. mount_namespaces.7 michael kerrisk [rob landley] rework the discussion of defaults for mount propagation types add rather more detail. in particular, note the cases where the default propagation type is ms_private vs ms_shared. namespaces.7 michael kerrisk example: fix an error in shell session michael kerrisk example: rename the example program use a more generic name, since this program may be expanded in various ways in the future. michael kerrisk see also: add ip-netns(8) michael kerrisk remove content split out into ioctl_ns(2) netlink.7 michael kerrisk netlink_ip6_fw went away in linux 3.5 michael kerrisk netlink_w1 went away in linux 2.6.18 michael kerrisk add netlink_scsitransport to list michael kerrisk add netlink_rdma to list michael kerrisk netlink_firewall was removed in linux 3.5 michael kerrisk netlink_nflog was removed in linux 3.17 jakub wilk update libnl homepage url the original url is 404. pid_namespaces.7 user_namespaces.7 michael kerrisk adjust references to namespaces(7) to ioctl_ns(2) pid_namespaces.7 keno fischer clone_sighand|clone_vm|clone_newpid is no longer disallowed pipe.7 michael kerrisk since linux 4.9, pipe-max-size is ceiling for the default pipe capacity michael kerrisk clarify that default pipe capacity is 16 pages the statement that the default pipe capacity is 65536 bytes is accurate only on systems where the page size is 4096b. see the use of pipe_def_buffers in the kernel source. random.7 michael kerrisk mention getentropy(3) michael kerrisk see also: add getentropy(3) michael kerrisk see also: add getauxval(3) a small hint to the reader that some random bytes arrive in the auxiliary vector. signal.7 michael kerrisk sigsys: add reference to seccomp(2) michael kerrisk change description of sigsys to "bad system call" this is the more typical definition. michael kerrisk sigpipe: add reference to pipe(7) michael kerrisk sigxfsz: add reference to setrlimit(2) michael kerrisk add a name for sigemt michael kerrisk sigxcpu: add reference to setrlimit(2) michael kerrisk migrated signal-safety discussion to new signal-safety(7) page unix.7 michael kerrisk [sergey polovko] since linux 3.4, unix domain sockets support msg_trunc this was correctly noted in recv(2), but the unix(7) page was not correspondingly updated for the linux 3.4 change. michael kerrisk [willy tarreau] document etoomanyrefs for scm_rights send exceeding rlimit_nofile limit user_namespaces.7 michael kerrisk change page cross reference: keyctl(2) ==> keyrings(7) ld.so.8 michael kerrisk ld_bind_not has effect only for function symbols michael kerrisk describe use of ld_debug with ld_bind_not michael kerrisk in secure mode, ld_audit restricts the libraries that it will load michael kerrisk ld_audit understands $origin, $lib, and $platform ==================== changes in man-pages-4.11 ==================== released: 2017-05-03, baden, switzerland contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alexander alemayhu alexander miller andrea arcangeli andreas dilger andrew clayton arnd bergmann ben dog carlos o'donell chema gonzalez christian brauner cyril hrubis david howells dmitry v. levin florian weimer francois saint-jacques frank theile georg sauthoff ian abbott jakub wilk jan heberer marcin ślusarz marko myllynen matthew wilcox michael kerrisk mike frysinger mike rapoport nicolas biscos nicolas iooss nikos mavrogiannopoulos nominal animal silvan jegen stephan bergmann walter harms zack weinberg 丁贵强 apologies if i missed anyone! new and rewritten pages ----------------------- ioctl_userfaultfd.2 michael kerrisk, mike rapoport new page describing ioctl(2) operations for userfaultfd statx.2 david howells, michael kerrisk [andreas dilger] new page describing statx(2) system call added in linux 4.11 userfaultfd.2 mike rapoport, michael kerrisk [andrea arcangeli] new page describing userfaultfd(2) system call. pthread_atfork.3 michael kerrisk new page describing pthread_atfork(3) slabinfo.5 michael kerrisk rewrite to try to bring the content close to current reality there's still gaps to fill in, but the existing page was in any case hugely out of date. inode.7 michael kerrisk new page with information about inodes david howells provided a statx(2) page that duplicated much of the information from stat(2). avoid such duplication by moving the common information in stat(2) and statx(2) to a new page. renamed pages -------------- ioctl_console.2 michael kerrisk renamed from console_ioctl.4 most ioctl() man pages are in section 2, so move this one there for consistency. michael kerrisk note type of 'argp' for a various operations for some commands, there was no clear statement about the type of the 'argp' argument. ioctl_tty.2 michael kerrisk renamed from tty_ioctl(4) all other ioctl(2) pages are in section 2. make this page consistent. michael kerrisk packet mode state change events give pollpri events for poll(2) newly documented interfaces in existing pages --------------------------------------------- ioctl_ns.2 michael kerrisk document the ns_get_nstype operation added in linux 4.11 michael kerrisk document the ns_get_owner_uid operation added in linux 4.11 proc.5 michael kerrisk document /proc/sys/kernel/sched_child_runs_first namespaces.7 michael kerrisk document the /proc/sys/user/* files added in linux 4.9 socket.7 francois saint-jacques, michael kerrisk document so_incoming_cpu new and changed links --------------------- console_ioctl.4 michael kerrisk link for old name of ioctl_console(2) page tty_ioctl.4 michael kerrisk link for old name of ioctl_tty(2) page global changes -------------- various pages michael kerrisk change page cross-references from tty_ioctl(4) to ioctl_tty(2) michael kerrisk change page cross-references for console_ioctl(4) to ioctl_console(2) changes to individual pages --------------------------- alarm.2 michael kerrisk see also: add timer_create(2) and timerfd_create(2) chmod.2 fsync.2 mkdir.2 mknod.2 open.2 truncate.2 umask.2 utime.2 utimensat.2 michael kerrisk add/replace references to inode(7) clone.2 michael kerrisk clone_newcgroup by an unprivileged process also causes an eperm error clone.2 unshare.2 michael kerrisk exceeding one of the limits in /proc/sys/user/* can cause enospc michael kerrisk clone_newpid yields enospc if nesting limit of pid namespaces is reached michael kerrisk exceeding the maximum nested user namespace limit now gives enospc formerly, if the limit of 32 nested user namespaces was exceeded, the error eusers resulted. starting with linux 4.9, the error is enospc. epoll_ctl.2 michael kerrisk defer to poll(2) for an explanation of epollin michael kerrisk [nicolas biscos] epollerr is also set on write end of a pipe when the read end is closed michael kerrisk [nicolas biscos] give the reader a clue that the 'events' field can be zero 'events' specified as zero still allows epollhup and epollerr to be reported. _exit.2 michael kerrisk on exit, child processes may be inherited by a "subreaper" it is no longer necessarily true that orphaned processes are inherited by pid 1. michael kerrisk only the least significant byte of exit status is passed to the parent fcntl.2 michael kerrisk mention memfd_create() in the discussion of file seals give the reader a clue about what kinds of objects can be employed with file seals. michael kerrisk file seals are not generally applicable to tmpfs(5) files as far as i can see, file seals can be applied only to memfd_create(2) file descriptors. this was checked by experiment and by reading mm/shmem.c::shmem_get_inode((), where one finds the following line that applies to all new shmem files: info->seals = f_seal_seal; only in the code of the memfd_create() system call is this setting reversed (in mm/shmem.c::memfd_create): if (flags & mfd_allow_sealing) info->seals &= ~f_seal_seal; fork.2 michael kerrisk see also: add pthread_atfork(3) getdents.2 open.2 stat.2 statx.2 michael kerrisk see also: add inode(7) getdtablesize.2 attr.5 alexander miller move .so directive to first line improves compatibility with the man and other dumb tools that process man page files. getpid.2 michael kerrisk mention init(1) and "subreapers" in discussion of parent pid ioctl_list.2 cyril hrubis [arnd bergmann] blkraset/blkraget take unsigned long ioctl_ns.2 michael kerrisk errors: document enotty kexec_load.2 sched_setaffinity.2 bootparam.7 michael kerrisk documentation/kernel-parameters.txt is now in documentation/admin-guide/ lseek.2 michael kerrisk see also: add fallocate(2) both of these pages discuss file holes. mincore.2 michael kerrisk see also: add fincore(1) mmap.2 michael kerrisk remove ancient reference to flags that appear on some other systems map_autogrow, map_autoresrv, map_copy, and map_local may have appeared on some systems many years ago, but the discussion here mentions no details and the systems and flags probably ceased to be relevant long ago. so, remove this text. michael kerrisk see also: add userfaultfd(2) open.2 michael kerrisk add statx() to list of "at" calls in rationale discussion poll.2 michael kerrisk expand discussion of pollpri michael kerrisk [nicolas biscos] pollerr is also set on write end of a pipe when the read end is closed posix_fadvise.2 michael kerrisk see also: add fincore(1) prctl.2 mike frysinger pr_set_mm: refine config_checkpoint_restore requirement the linux 3.10 release dropped the c/r requirement and opened it up to all users. mike frysinger pr_set_mm: document new pr_set_mm_map{,_size} helpers mike frysinger pr_set_mm: document arg4/arg5 zero behavior the kernel will immediately reject calls where arg4/arg5 are not zero. see kernel/sys.c:prctl_set_mm(). michael kerrisk explain rationale for use of subreaper processes michael kerrisk note semantics of child_subreaper setting on fork() and exec() michael kerrisk improve description of pr_set_child_subreaper rename.2 michael kerrisk [georg sauthoff] note that there is no glibc wrapper for renameat2() sched_setaffinity.2 michael kerrisk see also: add get_nprocs(3) select.2 michael kerrisk [matthew wilcox, carlos o'donell] linux select() is buggy wrt posix in its check for ebadf errors michael kerrisk show correspondence between select() and poll() readiness notifications michael kerrisk give a hint that sets must be reinitialized if using select() in a loop michael kerrisk refer to pollpri in poll(2) for info on exceptional conditions michael kerrisk move mislocated text describing the self-pipe text from bugs to notes sigaction.2 michael kerrisk show the prototype of an sa_siginfo signal handler signalfd.2 michael kerrisk sigkill and sigstop are silently ignored in 'mask' sigprocmask.2 dmitry v. levin do not specify an exact value of rt_sigprocmask's 4th argument as sizeof(kernel_sigset_t) is not the same for all architectures, it would be better not to mention any numbers as its value. michael kerrisk 'set' and 'oldset' can both be null sigwaitinfo.2 michael kerrisk sigwaitinfo() can't be used to accept synchronous signals socketcall.2 mike frysinger document call argument stat.2 michael kerrisk remove information migrated to inode(7) page michael kerrisk restructure field descriptions as a hanging list michael kerrisk remove "other systems" subsection these details about other systems were added in 1999, and were probably of limited use then, and even less today. however, they do clutter the page, so remove them. michael kerrisk description: add list entries for 'st_uid' and 'st_gid' michael kerrisk add some subsection headings to ease readability david howells errors: correct description of enoent michael kerrisk give 'struct stat' argument a more meaningful name ('statbuf') marcin ślusarz tweak description of at_empty_path currently it says when dirfd is at_fdcwd it can be something other than directory, which doesn't make much sense. just swap the order of sentences. michael kerrisk add slightly expanded description of 'st_ino' field michael kerrisk description: add a list entry for 'st_ino' michael kerrisk description: add a list entry for 'st_nlinks' field syscalls.2 michael kerrisk add membarrier(2) michael kerrisk fix kernel version for userfaultfd(2) michael kerrisk linux 4.11 added statx() michael kerrisk include deprecated getunwind(2) in list wait.2 michael kerrisk orphaned children may be adopted by a "subreaper", rather by than pd 1 bzero.3 michael kerrisk [zack weinberg] add correct header file for explicit_bzero() cfree.3 michael kerrisk cfree() is removed from glibc in version 2.26 exit.3 michael kerrisk improve discussion of zombie processes getentropy.3 nikos mavrogiannopoulos [michael kerrisk, florian weimer] correct header file michael kerrisk [frank theile] synopsis: add missing return type for getentropy() declaration grantpt.3 michael kerrisk tell a more nuanced story about what grantpt() does or does not do insque.3 michael kerrisk see also: add queue(3) queue.3 michael kerrisk see also: add insque(3) shm_open.3 michael kerrisk clarify that posix shared memory uses tmpfs(5) syslog.3 michael kerrisk [ian abbott, walter harms] reorganize page text for easier parsing and better readability michael kerrisk various rewordings and improvements michael kerrisk note default value for 'facility' when calling openlog() michael kerrisk see also: add journalctl(1) ttyname.3 dmitry v. levin document enodev error code christian brauner notes: warn about a confusing case that may occur with mount namespaces wcsdup.3 jan heberer return value: fix error in return value description return value for failure was accidentally changed from null to -1 in man-pages commit 572acb41c48b6b8e690d50edff367d8b8b01702a. elf.5 michael kerrisk see also: add elfedit(1), nm(1), size(1), strings(1), and strip(1) nsswitch.conf.5 florian weimer mention sudoers it turns out that sudo drops things into nsswitch.conf, too. proc.5 michael kerrisk refer to namespaces(7) for discussion of /proc/sys/user/* files michael kerrisk simplify /proc/slabinfo entry don't repeat (out-of-date) info from slabinfo(5); just defer to that page. tmpfs.5 michael kerrisk tmpfs supports extended attributes, but not 'user' extended attributes environ.7 jakub wilk fix name of function that honors tmpdir tempnam() takes the tmpdir environment variable into account, unlike tmpnam(), which always creates pathnames within /tmp. hostname.7 marko myllynen use lower case for hostname example marko myllynen use generic names in examples marko myllynen describe accepted characters for hostname inotify.7 michael kerrisk [nicolas iooss] mounting a filesystem on top of a monitored directory causes no event man-pages.7 michael kerrisk note preferred approach for 'duplicate' errors pid_namespaces.7 michael kerrisk the maximum nesting depth for pid namespaces is 32 user_namespaces.7 stephan bergmann fixes to example while toying around with the userns_child_exec example program on the user_namespaces(7) man page, i noticed two things: * in the example section, we need to mount the new /proc before looking at /proc/$$/status, otherwise the latter will print information about the outer namespace's pid 1 (i.e., the real init). so the two paragraphs need to be swapped. * in the program source, make sure to close pipe_fd[0] in the child before exec'ing. pthreads.7 michael kerrisk see also: add pthread_rwlockattr_setkind_np(3) pty.7 michael kerrisk mention a couple of other applications of pseudoterminals sem_overview.7 michael kerrisk see also: add shm_overview(7) signal.7 michael kerrisk see also: add sigreturn(2) tcp.7 michael kerrisk note indications for oob data given by select(2) and poll(2) chema gonzalez tcp_abc was removed in 3.9 xattr.7 michael kerrisk see also: add ioctl_iflags(2) people sometimes confuse xattrs and inode flags. provide a link to the page that describes inode flags to give them a tip. ld.so.8 michael kerrisk mention quoting when using "rpath tokens" in ld_audit and ld_preload michael kerrisk expand description of /etc/ld.so.preload michael kerrisk mention ldconfig(8) in discussion of /etc/ld.so.cache zdump.8 jakub wilk add options section heading ==================== changes in man-pages-4.12 ==================== released: 2017-07-13, london contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alex henrie andi kleen arjun shankar brad bendily cameron wright carlos o'donell darrick j. wong david lewis dj delorie douglas caetano dos santos dr. tobias quathamer eric biggers ferdinand thiessen g. branden robinson heinrich schuchardt henry bent jakub wilk janne snabb joe brown jorge nerin kirill tkhai lilydjwg long wang michael kerrisk mike frysinger nadav har'el neilbrown pavel tikhomirov quentin rameau ruben kerkhof sulit 石井大貴 apologies if i missed anyone! new and rewritten pages ----------------------- ioctl_getfsmap.2 darrick j. wong document the getfsmap ioctl document the new getfsmap ioctl that returns the physical layout of a (disk-based) filesystem. newly documented interfaces in existing pages --------------------------------------------- namespaces.7 kirill tkhai [michael kerrisk] document the /proc/[pid]/ns/pid_for_children file changes to individual pages --------------------------- ldd.1 michael kerrisk 'objdump -p prog | grep needed' doesn't give quite same info as 'ldd' chmod.2 michael kerrisk put fchmod() feature test macro requirements in a more readable format michael kerrisk note glibc 2.24 feature test macro requirements changes for fchmod() chown.2 michael kerrisk when file owner or group is changed, file capabilities are cleared michael kerrisk changes to file owner by root also clear set-uid and set-gid bits clone.2 michael kerrisk update bugs to reflect fact that pid caching was removed in glibc 2.25 epoll_wait.2 michael kerrisk clarify semantics of returned 'data' field the returned 'data' is the 'data' most recently set via epoll_ctl(). get_mempolicy.2 michael kerrisk [nadav har'el, andi kleen] synopsis: fix return type of get_mempolicy() see https://bugzilla.kernel.org/show_bug.cgi?id=97051 getpid.2 carlos o'donell, michael kerrisk note that pid caching is removed as of glibc 2.25 since glibc 2.25 the pid cache is removed. rationale given in the release notes: https://sourceware.org/glibc/wiki/release/2.25#pid_cache_removal ioctl.2 michael kerrisk see also: add ioctl_getfsmap(2) ioctl_getfsmap.2 michael kerrisk fix ordering of sections michael kerrisk add versions section michael kerrisk errors: order alphabetically madvise.2 michael kerrisk remove bogus text re posix_madv_noreuse there is a posix_fadv_noreuse for posix_fadvise(), but no posix_madv_noreuse for any api in posix. membarrier.2 michael kerrisk add enosys error for 'nohz_full' cpu setting mount.2 neilbrown revise description of ms_remount | ms_bind ms_remount|ms_bind affects all per-mount-point flag. ms_rdonly is only special because it, uniquely, is both a per-mount-point flag *and* a per-filesystem flag. so the sections of per-mount-point flags and ms_remount can usefully be clarified. open.2 michael kerrisk note some further advantages of the *at() apis pipe.2 michael kerrisk see also: add tee(2) and vmsplice(2) readv.2 michael kerrisk glibc 2.26 adds library support for preadv2() and pwritev2() sched_setaffinity.2 michael kerrisk mention cpuset cgroups as a cause of einval error seccomp.2 mike frysinger expand seccomp_ret_kill documentation sigaction.2 michael kerrisk note feature test macro requirements for 'si_code' constants michael kerrisk add a subheading for the description of 'si_code' michael kerrisk trap_branch and trap_hwbkpt are present only on ia64 sigaltstack.2 michael kerrisk note that specifying ss_onstack in ss.ss_flags decreases portability in the illumos source (which presumably mirrors its solaris ancestry), there is this check in the sigaltstack() implementation: if (ss.ss_flags & ~ss_disable) return (set_errno(einval)); and in the freebsd source we find similar: if ((ss->ss_flags & ~ss_disable) != 0) return (einval); michael kerrisk note buggy addition of ss.ss_flags==ss_onstack note buggy addition of ss.ss_flags==ss_onstack as a synonym for ss_flags==0. no other implementation does this, afaik. and it was not needed :-(. michael kerrisk specifying 'ss' returns the current settings without changing them michael kerrisk give 'oss' argument a more meaningful name: 'old_ss' michael kerrisk some minor reworking of the text michael kerrisk errors: update description of einval error splice.2 tee.2 vmsplice.2 michael kerrisk see also: add pipe(7) splice.2 michael kerrisk errors: split einval error cases michael kerrisk errors: add einval for case where both descriptors refer to same pipe timer_create.2 michael kerrisk document the config_posix_timers option added in linux 4.10 wait.2 michael kerrisk note glibc 2.26 changes to feature test macro requirements for waitid() acosh.3 asinh.3 atanh.3 alex henrie remove c89 designation. see https://bugzilla.kernel.org/show_bug.cgi?id=196319 bsd_signal.3 michael kerrisk note feature test macro requirements changes for glibc 2.26 dl_iterate_phdr.3 michael kerrisk dl_iterate_phdr() shows the order in which objects were loaded dl_iterate_phdr() tells us not just which objects are loaded, but also the order in which they are loaded (the "link-map order"). since the order is relevant for understanding symbol resolution, give the reader this clue. michael kerrisk expand the code example, and show sample output michael kerrisk list values for the 'p_type' field dlsym.3 michael kerrisk _gnu_source is needed to get rtld_default and rtld_next definitions flockfile.3 michael kerrisk note glibc 2.24 feature test macro requirement changes fpathconf.3 michael kerrisk rework return value description to add more detail michael kerrisk add an errors section michael kerrisk largely rewrite the description of _pc_chown_restricted michael kerrisk rewrite description of _pc_pipe_buf the existing description was not accurate, and lacked details. ftw.3 michael kerrisk bugs: document a probable glibc regression in ftw_sln case see https://bugzilla.redhat.com/show_bug.cgi?id=1422736 and http://austingroupbugs.net/view.php?id=1121. getaddrinfo.3 quentin rameau fix _posix_c_source value for getaddrinfo() the correct _posix_c_source value is 200112l, not 201112l in features.h. getcontext.3 carlos o'donell exemplar structure should use 'ucontext_t'. getgrent.3 michael kerrisk note glibc 2.22 changes for feature test macro requirements grantpt.3 ptsname.3 unlockpt.3 ferdinand thiessen [michael kerrisk] update feature test macro-requirements for glibc 2.24 if_nametoindex.3 douglas caetano dos santos add enodev error for if_nametoindex() malloc.3 michael kerrisk document the reallocarray() added in glibc 2.26 nl_langinfo.3 michael kerrisk note feature test macro requirements for nl_langinfo_l() posix_madvise.3 dr. tobias quathamer remove paragraph about posix_fadv_noreuse posix_fadv_noreuse is documented for posix_fadvise, and a corresponding posix_madv_noreuse flag is not specified by posix. see https://bugs.debian.org/865699 ptsname.3 michael kerrisk [arjun shankar] since glibc 2.26, ptsname_r() no longer gives einval for buf==null rand.3 michael kerrisk note glibc 2.24 feature test macro requirement changes for rand_r() resolver.3 michael kerrisk add basic notes on 'op' argument of res_nmkquery() and res_mkquery() sigpause.3 michael kerrisk note glibc 2.26 changes to feature test macro requirements sigwait.3 michael kerrisk note glibc 2.26 feature test macro changes strtol.3 heinrich schuchardt mention 0x prefix the prefix 0x may be capitalized as 0x. see iso/iec 9899:1999. sysconf.3 michael kerrisk [pavel tikhomirov] rework return value description to add more detail make the discussion clearer, and add a few details. also, fix the problem report from pavel tikhomirov who noted that the man page falsely said that errno is not changed on a successful return. addresses https://bugzilla.kernel.org/show_bug.cgi?id=195955 michael kerrisk add errors section ttyslot.3 michael kerrisk fix error in feature test macro requirements michael kerrisk note feature test macro requirements changes in glibc 2.24 michael kerrisk clarify details of use of file unlocked_stdio.3 michael kerrisk note glibc 2.24 feature test macro requirement changes elf.5 michael kerrisk see also: add dl_iterate_phdr(3) nsswitch.conf.5 dj delorie clarify group merge rules this minor patch clarifies when merging is not done, and how duplicate entries are merged. proc.5 michael kerrisk document that 'iowait' field of /proc/stat is unreliable text taken from chao fan's kernel commit 9c240d757658a3ae996. slabinfo.5 michael kerrisk [jorge nerin] see also: add some references to relevant kernel source files tmpfs.5 michael kerrisk see also: add memfd_create(2), mmap(2), shm_open(3) capabilities.7 michael kerrisk clarify the effect on process capabilities when uid 0 does execve(2) michael kerrisk note effect on capabilities when a process with uid != 0 does execve(2) michael kerrisk [david lewis] fix reversed descriptions of cap_mac_override and cap_mac_admin michael kerrisk see also: add filecap(8), netcap(8), pscap(8) cgroup_namespaces.7 michael kerrisk add some further explanation of the example shell session michael kerrisk fix a bug in shell session example inode.7 michael kerrisk note glibc 2.24 feature test macro changes for s_ifsock and s_issock() man.7 g. branden robinson undocument "url" macro in man(7) in favor .ur+.ue pid_namespaces.7 michael kerrisk mention /proc/[pid]/ns/pid_for_children pipe.7 michael kerrisk see also: add tee(2) and vmsplice(2) sigevent.7 michael kerrisk mention signal.h header file signal.7 michael kerrisk [lilydjwg] since linux 3.8, read(2) on an inotify fd is restartable with sa_restart see https://bugzilla.kernel.org/show_bug.cgi?id=195711 michael kerrisk read() from an inotify fd is no longer interrupted by a stop signal (change was in linux 3.8.) tcp.7 michael kerrisk document value '2' for tcp_timestamps since linux 4.10, the value '2' is meaningful for tcp_timestamps ruben kerkhof change default value of tcp_frto the default changed in c96fd3d461fa495400df24be3b3b66f0e0b152f9 (linux 2.6.24). ld.so.8 michael kerrisk greatly expand the explanation of ld_dynamic_weak carlos o'donell expand dt_runpath details. ld.so.8: expand dt_runpath details. every 3 years we get asked why dt_runpath doesn't work like dt_rpath. the most recent question was here: https://www.sourceware.org/ml/libc-help/2017-06/msg00013.html we need to expand the description of dt_runpath to cover this situation and explain that the dt_runpath entries apply only to the immediate dt_needed, not that of another, say dlopen'd child object. michael kerrisk since glibc 2.2.5, ld_profile is ignored in secure-execution mode michael kerrisk make notes on secure-execute mode more prominent place each note on secure-execution mode in a separate paragraph, to make it more obvious. michael kerrisk note that libraries in standard directories are not normally set-uid in secure mode, ld_preload loads only libraries from standard directories that are marked set-uid. note that it is unusual for a library to be marked in this way. michael kerrisk see also: add elf(5) michael kerrisk note version where secure-execution started ignoring ld_use_load_bias michael kerrisk correct glibc version that ignores ld_show_auxv in secure-execution mode ignored since 2.3.4 (not 2.3.5). michael kerrisk rewrite ld_debug_output description and note that .pid is appended ==================== changes in man-pages-4.13 ==================== released: 2017-09-15, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: aleksa sarai alex henrie benjamin peterson bjarni ingi gislason cyrill gorcunov darrick j. wong david wilder dennis knorr don brace douglas caetano dos santos elliott hughes eugene syromyatnikov fabio scotoni florian weimer jakub wilk jason noakes jens axboe jonas grabber kees cook konstantin shemyak li zhijian marko myllynen mark wielaard meelis roos michael kerrisk mike rapoport neilbrown otto ebeling paul eggert rick jones sage weil sam varshavchik sergey z. shrikant giridhar stephan müller sukadev bhattiprolu tej chajed thiago jung bauermann vincent bernat yubin ruan ильдар низамов apologies if i missed anyone! new and rewritten pages ----------------------- pthread_mutex_consistent.3 yubin ruan, michael kerrisk new page documenting pthread_mutex_consistent(3) pthread_mutexattr_getpshared.3 michael kerrisk new page for pthread_mutexattr_getpshared(3) and pthread_mutexattr_setpshared(3) pthread_mutexattr_init.3 michael kerrisk new page for pthread_mutexattr_init(3) and pthread_mutexattr_destroy(3) pthread_mutexattr_setrobust.3 yubin ruan, michael kerrisk new page for pthread_mutexattr_setrobust(3) and pthread_mutexattr_getrobust(3) sysfs.5 michael kerrisk [mark wielaard] new page documenting the sysfs filesystem just a skeleton page so far, but perhaps it will be filled out over time. newly documented interfaces in existing pages --------------------------------------------- fcntl.2 jens axboe, michael kerrisk describe the set/get write hints commands that are added in linux 4.13 document f_get_rw_hint, f_set_rw_hint, f_get_file_rw_hint, and f_set_file_rw_hint. ioctl_tty.2 aleksa sarai, michael kerrisk add tiocgptpeer documentation kcmp.2 cyrill gorcunov add kcmp_epoll_tfd description keyctl.2 eugene syromyatnikov document the keyctl_restrict_keyring operation eugene syromyatnikov [stephan müller] document the ability to provide kdf parameters in keyctl_dh_compute new and changed links --------------------- pthread_mutexattr_destroy.3 michael kerrisk new link to new pthread_mutexattr_init.3 page pthread_mutexattr_getrobust.3 pthread_mutexattr_getrobust_np.3 pthread_mutexattr_setrobust_np.3 michael kerrisk new links to new pthread_mutexattr_setrobust.3 page pthread_mutexattr_setpshared.3 michael kerrisk new link to new pthread_mutexattr_getpshared.3 page global changes -------------- various pages michael kerrisk use .ex/.ee for example programs various pages michael kerrisk use consistent markup for code snippets change .nf/.fi to .ex/.ee various pages michael kerrisk use consistent markup for code snippets the preferred form is .pp/.ip .in +4n .ex .ee .in .pp/.ip various pages michael kerrisk formatting fix: replace blank lines with .pp/.ip blank lines shouldn't generally appear in *roff source (other than in code examples), since they create large vertical spaces between text blocks. various pages michael kerrisk [bjarni ingi gislason] add a non-breaking space between a number and a unit (prefix) based on a patch by bjarni ingi gislason. various pages michael kerrisk [bjarni ingi gislason] use en-dash for ranges based on a patch by bjarni ingi gislason. a few pages michael kerrisk fix misordering of sections michael kerrisk fix order of see also entries changes to individual pages --------------------------- ldd.1 michael kerrisk add more detail on ldd security implications, noting glibc 2.27 changes add_key.2 backtrace.3 syslog.3 michael kerrisk fix misordered see also entries add_key.2 request_key.2 keyrings.7 eugene syromyatnikov update linux documentation pointers chown.2 michael kerrisk update kernel version in note on support for grpid/nogrpid mount options there has been no change since linux 2.6.25, so update the kernel version to 4.12. execve.2 michael kerrisk see also: add get_robust_list(2) getrandom.2 michael kerrisk [fabio scotoni] synopsis: make return type of getrandom() 'ssize_t' this accords with glibc headers and the linux kernel source. getrlimit.2 thiago jung bauermann mention unit used by rlimit_core and rlimit_fsize michael kerrisk note that rlimit_as and rlimit_data are rounded down to system page size michael kerrisk mention unit for rlimit_data getrlimit.2 mmap.2 malloc.3 jonas grabber rlimit_data affects mmap(2) since linux 4.7 get_robust_list.2 michael kerrisk detail the operation of robust futex lists michael kerrisk since linux 2.6.28, robust futex lists also have an effect for execve(2) michael kerrisk clarify that "thread id" means "kernel thread id" michael kerrisk see also: add pthread_mutexattr_setrobust(3) ioctl_getfsmap.2 darrick j. wong correct semantics of fmr_of_last flag ioctl_userfaultfd.2 mike rapoport document replacement of enospc with esrch mike rapoport update uffdio_api.features description there is no requirement that uffdio_api.features must be zero for newer kernels. this field actually defines what features space would like to enable. io_submit.2 sage weil acknowledge possibility of short return note that the return value may be a value less than 'nr' if not all iocbs were queued at once. ipc.2 michael kerrisk see also: add svipc(7) keyctl.2 eugene syromyatnikov mention keyctl_dh_compute(3) and keyctl_dh_compute_alloc (3) these functions have been added in keyutils 1.5.10 eugene syromyatnikov mention enomem in errors eugene syromyatnikov update kernel documentation path reference move_pages.2 otto ebeling [michael kerrisk] note permission changes that occurred in linux 4.13 mprotect.2 michael kerrisk [shrikant giridhar] add warning about the use of printf() in the example code open.2 neilbrown improve o_path documentation - fstatfs is now permitted. - ioctl isn't, and is worth listing explicitly - o_path allows an automount point to be opened with triggering the mount. prctl.2 seccomp.2 eugene syromyatnikov update pointer to in-kernel seccomp documentation prctl.2 ptrace.2 eugene syromyatnikov update pointer to in-kernel yama documentation prctl.2 eugene syromyatnikov update pointer to in-kernel no_new_privs flag documentation readlink.2 michael kerrisk [jason noakes] fix an off-by-one error in example code seccomp.2 kees cook clarify seccomp_ret_kill kills tasks not processes select_tut.2 michael kerrisk [sergey z.] clarify an ambiguity with respect to select() and eagain see https://bugzilla.kernel.org/show_bug.cgi?id=196345 set_tid_address.2 elliott hughes note that there's no glibc wrapper for set_tid_address() socket.2 michael kerrisk [yubin ruan] socket() uses the lowest available file descriptor _syscall.2 michael kerrisk remove redundant comment from example a discussion of the nroff source of the manual page isn't very useful... sysfs.2 michael kerrisk add a pointer to sysfs(5) to help possibly confused readers michael kerrisk make it clearer near the start of the page that sysfs(2) is obsolete timer_create.2 michael kerrisk strengthen the warning about use of printf() in the example program michael kerrisk update cross reference: signal(7) should be signal-safety(7) umount.2 neilbrown revise mnt_force description mnt_force does not allow a busy filesystem to be unmounted. only mnt_detach allows that. mnt_force only tries to abort pending transactions, in the hope that might help umount not to block, also, other filesystems than nfs support mnt_force. unshare.2 eugene syromyatnikov update pointer to in-kernel unshare documentation wait.2 michael kerrisk [ильдар низамов] posix.1-2008 tc1 clarifies treatment of 'si_pid' for waitid() wnohang cmsg.3 sukadev bhattiprolu add a scatter/gather buffer to sample code michael kerrisk reorganize the text somewhat (no content changes) crypt.3 konstantin shemyak [michael kerrisk] add description of previously undocumented 'rounds' parameter konstantin shemyak encryption isn't done with sha-xxx, but with a function based on sha-xxx konstantin shemyak clarify that ending of the salt string with '$' is optional exit.3 michael kerrisk mention the prctl(2) pr_set_pdeathsig operation michael kerrisk see also: add get_robust_list(2) michael kerrisk add a heading to delimit discussion of signals sent to other processes exp2.3 alex henrie remove c89 designation log1p.3 alex henrie document fixes to give edom or erange on error matherr.3 michael kerrisk note that glibc 2.27 removes the 'matherr' mechanism michael kerrisk remove crufty feature test macro requirements pow10.3 michael kerrisk note that pow10() is now obsolete in favor of exp10() also, the pow10() functions are no longer supported by glibc, starting with version 2.27. sincos.3 michael kerrisk note that sincos() is intended to be more efficient than sin() + cos() cciss.4 hpsa.4 eugene syromyatnikov [don brace, meelis roos] mention cciss removal in linux 4.14 during the linux 4.13 development cycle, the cciss driver has been removed in favor of the hpsa driver, which has been amended with some legacy board support. initrd.4 proc.5 bootparam.7 eugene syromyatnikov update pointer to in-kernel initrd documentation initrd.4 eugene syromyatnikov update pointer to in-kernel root over nfs documentation intro.4 michael kerrisk see also: add mknod(1) and mknod(2) host.conf.5 michael kerrisk add cross-reference to hosts(5) locale.5 marko myllynen refer to existing locales for encoding details since i don't think it would make sense to try to have different explanation for each glibc version on the locale(5) man page, i'm proposing that we apply the below patch so that we refer to existing locale definition files in general and not spell out the exact format or any certain locale as a definitive guideline. nologin.5 michael kerrisk add a sentence explaining why nologin is useful proc.5 eugene syromyatnikov document removal of htab-reclaim sysctl file this ppc-specific sysctl option has been removed in linux 2.4.9.2, according to historic linux repository commit log. eugene syromyatnikov add description for cpun lines in /proc/stat eugene syromyatnikov add description for softirq line in /proc/stat eugene syromyatnikov document removal of timer_stats file michael kerrisk note linux 4.9 changes to privileges for /proc/[pid]/timerslack_ns michael kerrisk show command used to mount /proc michael kerrisk explicitly note in intro that some /proc files are writable eugene syromyatnikov update pointer to in-kernel sysrq documentation michael kerrisk see also: add sysfs(5) eugene syromyatnikov update pointer to in-kernel security keys documentation benjamin peterson fix path to binfmt_misc docs eugene syromyatnikov update pointer to in-kernel mtrr documentation eugene syromyatnikov update reference to kernel's crypto api documentation tzfile.5 paul eggert sync from tzdb upstream this makes tzfile.5 a copy of the tzdb version, except that the tzdb version's first line is replaced by man-pages boilerplate. the new version documents version 3 format, among other things. also, it removes the "summary of the timezone information file format" section, which should no longer be needed due to improvements in the part of the man page. capabilities.7 michael kerrisk note semantics for a program that is set-uid-root and has capabilities note semantics for a program that is both set-user-id-root and has file capabilities. michael kerrisk [dennis knorr] note that a set-uid-root program may have an empty file capability set cgroups.7 michael kerrisk see also: systemd-cgls(1) cpuset.7 eugene syromyatnikov update pointer to in-kernel cpusets documentation keyrings.7 eugene syromyatnikov document description restriction for logon keys "logon" type has additional check that enforces colon-separated prefix in key descriptions. eugene syromyatnikov add pointers to kernel's documentation mostly because of asymmetric-keys.txt, which is outside security/keys for some reason. man-pages.7 michael kerrisk expand the guidance on formatting code snippets netlink.7 david wilder change buffer size in example code about reading netlink message michael kerrisk [rick jones] add a comment on 8192 buffer size in example code pthreads.7 michael kerrisk see also: add pthread_mutexattr_destroy(3) and pthread_mutexattr_init(3) signal.7 michael kerrisk since glibc 2.26, sigunused is no longer defined tcp.7 vincent bernat tcp_tw_recycle is removed from linux 4.12 and it is completely broken. unicode.7 eugene syromyatnikov update pointer to in-kernel unicode terminal support documentation ==================== changes in man-pages-4.14 ==================== released: 2017-11-27, paris contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adhemerval zanella adrian bunk ahmad fatoum andrea arcangeli bastien roucaries breno leitao carlos o'donell christian brauner christoph hellwig colm maccárthaigh craig ringer cristian rodríguez david eckardt don brace elliot hughes eric w. biederman fabio scotoni fangrui song florian weimer g. branden robinson goldwyn rodrigues grégory vander schueren jakub wilk jann horn jeff layton jens axboe jonny grant julien gomes kees cook křištof želechovski lennart poettering lucas werkmeister marcus folkesson marin h. mathieu desnoyers matthew wilcox michael kerrisk michal hocko michał zegan mihir mehta mike frysinger mike kravetz mike rapoport miklos szeredi neilbrown oliver ebert pedro alves per böhlin peter zijlstra petr malat petr uzel prakash sangappa raghavendra d prabhu rahul bedarkar ram pai richard knutsson rik van riel scott vokes seonghun lim stas sergeev stefan puiu thomas gleixner tobias klausmann tomas pospisek tyler hicks victor porton walter harms wesley aptekar-cassels yubin ruan zack weinberg дилян палаузов apologies if i missed anyone! new and rewritten pages ----------------------- pthread_spin_init.3 michael kerrisk [peter zijlstra, thomas gleixner, zack weinberg, florian weimer] new page describing pthread_spin_init(3) and pthread_spin_destroy(3) pthread_spin_lock.3 michael kerrisk [carlos o'donell] new page describing functions that lock and unlock spin locks add a page describing pthread_spin_lock(3), pthread_spin_unlock(3), and pthread_spin_trylock(3). smartpqi.4 don brace [michael kerrisk, g. branden robinson] document the smartpqi scsi driver veth.4 tomáš pospíšek, eric biederman, michael kerrisk new page documenting veth virtual ethernet devices based on a page from tomáš pospíšek, with some clean-ups by mtk. removed pages ------------- infnan.3: michael kerrisk this function was in libc4 and libc5, but never part of glibc. it ceased to be relevant nearly 20 years ago. time to remove the man page. newly documented interfaces in existing pages --------------------------------------------- ioctl_userfaultfd.2 userfaultfd.2 prakash sangappa [andrea arcangeli, mike rapoport] add description for uffd_feature_sigbus madvise.2 rik van riel [colm maccárthaigh, michael kerrisk] document madv_wipeonfork and madv_keeponfork michael kerrisk note fork() and execve() semantics for wipe-on-fork setting membarrier.2 mathieu desnoyers update membarrier manpage for 4.14 add documentation for these new membarrier() commands: membarrier_cmd_private_expedited membarrier_cmd_register_private_expedited memfd_create.2 mike kravetz add description of mfd_hugetlb (hugetlbfs) support hugetlbfs support for memfd_create() was recently merged by linus and should be in the linux 4.14 release. to request hugetlbfs support a new memfd_create() flag (mfd_hugetlb) was added. readv.2 christoph hellwig document rwf_nowait added in linux 4.14 seccomp.2 tyler hicks document the seccomp_get_action_avail operation added in linux 4.14 tyler hicks document the seccomp_filter_flag_log flag added in linux 4.14 tyler hicks document the seccomp_ret_log action added in linux 4.14 michael kerrisk [kees cook] add description of seccomp_ret_kill_process michael kerrisk add seccomp_ret_kill_thread description and rework seccomp_ret_kill text michael kerrisk document the seccomp audit logging feature added in linux 4.14 seccomp.2 proc.5 tyler hicks document the seccomp /proc interfaces added in linux 4.14 document the seccomp /proc interfaces in linux 4.14: /proc/sys/kernel/seccomp/actions_avail and /proc/sys/kernel/seccomp/actions_logged. sigaltstack.2 michael kerrisk [stas sergeev] document the ss_autodisarm flag added in linux 4.7 proc.5 michael kerrisk document /proc/locks oliver ebert document /proc/kpagecgroup oliver ebert add kpf_balloon, kpf_zero_page, and kpf_idle for /proc/kpageflags pid_namespaces.7 michael kerrisk document /proc/sys/kernel/ns_last_pid new and changed links --------------------- pthread_spin_destroy.3 michael kerrisk new link to new pthread_spin_init.3 page pthread_spin_trylock.3 pthread_spin_unlock.3 michael kerrisk new links to new pthread_spin_lock.3 page global changes -------------- various pages michael kerrisk consistently use "x86-64", not "x86_64" when referring to the architecture, consistently use "x86-64", not "x86_64". hitherto, there was a mixture of usages, with "x86-64" predominant. various pages g. branden robinson replace incorrect uses of latin abbreviation "cf.". people seem to be using "cf." ("conferre"), which means "compare", to mean "see" instead, for which the latin abbreviation would be "q.v." ("quod vide" -> "which see"). in some cases "cf." might actually be the correct term but it's still not clear what specific aspects of a function/system call one is supposed to be comparing. changes to individual pages --------------------------- capget.2 michael kerrisk clarify discussion of kernels that have no vfs capability support clock_getres.2 michael kerrisk clock_gettime() may be implemented in the vdso clone.2 michael kerrisk warn that the clone() wrapper modifies child_stack in the parent michael kerrisk rework the discussion of the historical clone_pid for clarity michael kerrisk add notes heading michael kerrisk add a reference to new veth(4) page michael kerrisk eliminate some redundant phrasing in discussion of "fn()" michael kerrisk combine redundant paragraphs describing child_stack==null michael kerrisk note that child_stack can be null when using the raw system call michael kerrisk remove a redundant paragraph connect.2 michael kerrisk clarify that econnrefused is for stream sockets fcntl.2 michael kerrisk [jens axboe] inode read-write hints persist only until the filesystem is unmounted flock.2 michael kerrisk move nfs details to a headed subsection michael kerrisk [petr uzel] placing an exclusive lock over nfs requires the file is open for writing fork.2 rik van riel [colm maccárthaigh, michael kerrisk] document effect of madv_wipeonfork fork.2 getsid.2 setpgid.2 setsid.2 ahmad fatoum include in synopsis to obtain declaration of pid_t fsync.2 craig ringer errors: add enospc getcpu.2 michael kerrisk getcpu() may have an implementation in the vdso getpid.2 michael kerrisk mention that pid == tgid, and note contrast with tid michael kerrisk see also: add gettid(2) getrandom.2 michael kerrisk [fabio scotoni] errors: add enosys getrlimit.2 michael kerrisk [scott vokes] make it clear rlimit_nproc is a limit on current number of processes https://twitter.com/silentbicycle/status/893849097903505409 gettid.2 michael kerrisk see also: add getpid(2) gettimeofday.2 michael kerrisk note that gettimeofday() may be implemented in the vdso ioctl_userfaultfd.2 michael kerrisk rework version information for feature bits io_submit.2 goldwyn rodrigues add iocb details to io_submit add more information about the iocb structure. explains the fields of the i/o control block structure which is passed to the io_submit() call. michael kerrisk add cross-reference to io_getevents(2) michael kerrisk cross reference pwritev(2) in discussion of rwf_sync and rwf_dsync membarrier.2 mathieu desnoyers update example to take tso into account the existing example given specifically states that it focus on x86 (tso memory model), but gives a read-read vs write-write ordering example, even though this scenario does not require explicit barriers on tso. so either we change the example architecture to a weakly-ordered architecture, or we change the example to a scenario requiring barriers on x86. let's stay on x86, but provide a dekker as example instead. mathieu desnoyers adapt the membarrier_cmd_shared return value documentation to reflect that it now returns -einval when issued on a system configured for nohz_full. memfd_create.2 michael kerrisk note the limit for size of 'name' mkdir.2 michael kerrisk [raghavendra d prabhu] errors: document einval error for invalid filename mmap.2 michael kerrisk add explicit text noting that 'length' must be greater than 0 currently, this detail is hidden in errors. make it clear in the main text. michael kerrisk see also: add ftruncate(2) mremap.2 mike kravetz [florian weimer, jann horn] add description of old_size == 0 functionality since at least the 2.6 time frame, mremap() would create a new mapping of the same pages if 'old_size == 0'. it would also leave the original mapping. this was used to create a 'duplicate mapping'. a recent change was made to mremap() so that an attempt to create a duplicate a private mapping will fail. michael kerrisk [michal hocko, mike kravetz] bugs: describe older behavior for old_size==0 on private mappings explain the older behavior, and why it changed. this is a follow-up to mike kravetz's patch documenting the behavior for old_size==0 with shared mappings. michael kerrisk reformat einval errors as a list open.2 michael kerrisk by contrast with o_rdonly, no file permissions are required for o_path note one of the significant advantages of o_path: many of the operations applied to o_path file descriptors don't require read permission, so there's no reason why the open() itself should require read permission. michael kerrisk note use of o_path to provide o_exec functionality michael kerrisk mention o_path file descriptor use with fexecve(3) michael kerrisk errors: document einval error for invalid filename michael kerrisk clarify that o_tmpfile creates a *regular* file michael kerrisk make it explicit that o_creat creates a regular file michael kerrisk since glibc 2.26, the open() wrapper always uses the openat() syscall michael kerrisk change pathname used in discussion of rationale for openat() /path/to/file is a little confusing as a pathname michael kerrisk make the purpose of open() a little clearer at the start of the page open_by_handle_at.2 neilbrown clarifications needed due to nfs reexport neilbrown [lennart poettering] clarify max_handle_sz as hinted in the kernel source, max_handle_sz is a hint rather than a promise. pipe.2 michael kerrisk [marin h.] since linux 4.5, fcntl() can be used to set o_direct for a pipe see https://bugzilla.kernel.org/show_bug.cgi?id=197917 pivot_root.2 michael kerrisk see also: add switch_root(8) pkey_alloc.2 breno leitao fix argument order currently pkey_alloc() syscall has two arguments, and the very first argument is still not supported and should be set to zero. the second argument is the one that should specify the page access rights. ptrace.2 michael kerrisk see also: add ltrace(1) reboot.2 michael kerrisk [michał zegan] fix bogus description of reboot() from non-initial pid namespace the current text was confused (mea culpa). no signal is sent to the init() process. rather, depending on the 'cmd' given to reboot(), the 'group_exit_code' value will set to either sighup or sigint, with the effect that one of those signals is reported to wait() in the parent process. see https://bugzilla.kernel.org/show_bug.cgi?id=195899 michael kerrisk see also: remove reboot(8) (synonym for halt(8)); add shutdown(8) michael kerrisk see also: add systemctl(1), systemd(1) recvmmsg.2 sendmmsg.2 elliot hughes type fixes in synopsis [mtk: the raw system calls use "unsigned int", but the glibc wrappers have "int" for the 'flags' argument.] sched_setaffinity.2 michael kerrisk see also: add numactl(8) sched_yield.2 michael kerrisk [peter zijlstra] sched_yield() is intended for use with real-time scheduling policies seccomp.2 michael kerrisk [adhemerval zanella, florian weimer, kees cook] add some caveats regarding the use of seccomp filters michael kerrisk document the "default" filter return action the kernel defaults to either seccomp_ret_kill_process or seccomp_ret_kill_thread for unrecognized filter return action values. michael kerrisk [kees cook] change seccomp_ret_action to seccomp_ret_action_full in linux 4.14, the action component of the return value switched from being 15 bits to being 16 bits. a new macro, seccomp_ret_action_full, that masks the 16 bits was added, to replace the older seccomp_ret_action. michael kerrisk explicitly note that other threads survive seccomp_ret_kill_thread michael kerrisk see also: add strace(1) send.2 grégory vander schueren add ealready to errors setns.2 michael kerrisk see also: add nsenter(1) shmop.2 yubin ruan note that return value of shmat() is page-aligned sigaction.2 michael kerrisk rework discussion of sa_siginfo handler arguments expand and rework the text a little, in particular adding a reference to sigreturn(2) as a source of further information about the ucontext argument. michael kerrisk mention that libc sets the act.sa_restorer field sigaltstack.2 michael kerrisk [walter harms] reword bugs text to be a little clearer michael kerrisk add explicit error handling to example code michael kerrisk add use of sigaction() to example code sigreturn.2 michael kerrisk make it a little clearer that a stack frame is created by the kernel michael kerrisk glibc has a simple wrapper for sigreturn() that returns enosys splice.2 michael kerrisk since linux 2.6.31,'fd_in' and 'fd_out' may both refer to pipes stat.2 michael kerrisk [richard knutsson] use lstat() instead of stat() it's more logical to use lstat() in the example code, since one can then experiment with symbolic links, and also the s_iflnk case can also occur. neilbrown correct at_no_automount text and general revisions expand on the relationship between fstatat() and the other three functions, and improve the description of at_no_automount. specifically, both stat() and lstat() act the same way with respect to automounts, and that behavior matches fstatat() with the at_no_automount flag. statfs.2 michael kerrisk add some comments noting filesystems that are no longer current michael kerrisk add comments describing a few filesystem types time.2 michael kerrisk note that time() may be implemented in the vdso michael kerrisk [victor porton] language fix-up: clarify that "tasks" means "work" see https://bugzilla.kernel.org/show_bug.cgi?id=197183 userfaultfd.2 mike rapoport bugs: document spurious uffd_event_fork write.2 fsync.2 close.2 neilbrown [jeff layton] update description of error codes since 4.13, errors from writeback are more reliably reported to all file descriptors that might be relevant. add notes to this effect, and also add detail about enospc and edquot which can be delayed in a similar many to eio - for nfs in particular. abort.3 michael kerrisk starting with glibc 2.27, abort() does not attempt to flush streams michael kerrisk see also: add assert(3) backtrace_symbols_fd(3) stefan puiu [walter harms] backtrace_symbols_fd() can trigger a call to malloc() daemon.3 michael kerrisk see also: add daemon(7), logrotate(8) errno.3 michael kerrisk note use of errno(1) to look up error names and numbers michael kerrisk update error list for posix.1-2008 posix.1-2008 specified a couple of new errors not present in posix.1-2001. michael kerrisk [walter harms] note the use of perror(3) and strerror(3) michael kerrisk recast the advice against manually declaring 'errno' recast the advice against manually declaring 'errno' to a more modern perspective. it's 13 years since the original text was added, and even then it was describing old behavior. cast the description to be about behavior further away in time, and note more clearly that manual declaration will cause problems with modern c libraries. michael kerrisk add some missing errors michael kerrisk error numbers are positive values (rather than nonzero values) posix.1-2008 noted the explicitly the change (to align with the c standards) that error numbers are positive, rather than nonzero. michael kerrisk reorganize the text and add some subheadings restructure the text and add some subheadings for better readability. no (intentional) content changes. michael kerrisk [wesley aptekar-cassels] note that error numbers vary somewhat across architectures added after a patch from wesley aptekar-cassels that proposed to add error numbers to the text. michael kerrisk note the also provides the symbolic error names michael kerrisk [walter harms] explicitly note that error numbers vary also across unix systems exec.3 michael kerrisk glibc 2.24 dropped cwd from the default path document the glibc 2.24 change that dropped cwd from the default search path employed by execlp(), execvp() and execvpe() when path is not defined. fexecve.3 michael kerrisk o_path file descriptors are also usable with fexecve() cristian rodríguez fexecve() is now implemented with execveat(2), where available michael kerrisk add some detail on the glibc implementation of fexecve() via execveat(2) ffs.3 michael kerrisk glibc 2.27 relaxes the ftm requirements for ffsl() and ffsll() get_nprocs_conf.3 michael kerrisk see also: add nproc(1) lround.3 michael kerrisk [david eckardt] clarify that lround() rounds *halfway cases" away from zero see https://bugzilla.kernel.org/show_bug.cgi?id=194601 makedev.3 adrian bunk glibc has deprecated exposing the definitions via mallinfo.3 jakub wilk fix the example remove reference to non-standard "tlpi_hdr.h" and replace calls to functions that were declared in this header. malloc.3 michael kerrisk see also: add valgrind(1) popen.3 michael kerrisk add a cross reference to caveats in system(3) all of the same risks regarding system() also apply to popen(). pthread_detach.3 michael kerrisk [rahul bedarkar] improve sentence describing freeing of resources on process termination as reported by rahul, the existing sentence could be read as meaning that resources of joined and terminated detached threads are freed only at process termination. eliminate that possible misreading. pthread_yield.3 michael kerrisk [peter zijlstra] pthread_yield() is intended for use with real-time scheduling policies setlocale.3 michael kerrisk [křištof želechovski] the standards do not specify all of the locale categories sockatmark.3 seonghun lim fix cruft in code example stdio.3 michael kerrisk use proper section cross references in function list michael kerrisk remove crufty reference to pc(1) sysconf.3 michael kerrisk mention get_nprocs_conf(3) mention get_nprocs_conf(3) in discussion of _sc_nprocessors_conf and _sc_nprocessors_onln. system.3 michael kerrisk [bastien roucaries] create a "caveats" subsection to hold warnings about the use of system() see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=882222 michael kerrisk [bastien roucaries] mention path explicitly in discussion of system() and set-uid programs michael kerrisk [bastien roucaries] note that user input for system() should be carefully sanitized michael kerrisk mention file capabilities in discussion of privileged programs michael kerrisk correctly note which shell debian uses as (noninteractive) /bin/sh core.5 michael kerrisk add some notes on systemd and core dumps michael kerrisk dumps are not produced if core_pattern is empty and core_uses_pid is 0 michael kerrisk [per böhlin] rlimit_core is not enforced when piping core dump to a program michael kerrisk see also: add systemd-coredump(8) michael kerrisk see also: add coredumpctl(1) filesystems.5 michael kerrisk [jonny grant] replace crufty url reference for 'smb' with up-to-date url michael kerrisk [jonny grant] refer to vfat as an extended fat (not dos) filesystem proc.5 michael kerrisk [miklos szered, ram pai] correct the description of the parent mount id for /proc/pid/mountinfo oliver ebert add mmap-exclusive bit for /proc/[pid]/pagemap marcus folkesson update description of /proc//oom_score lucas werkmeister clarify permissions in /proc/[pid]/fd/ michael kerrisk add reference to pid_namespaces(7) for /proc/sys/kernel/ns_last_pid shells.5 michael kerrisk see also: add pam_shells(8) sysfs.5 michael kerrisk add a brief explanation of /sys/kernel michael kerrisk add a brief description of /sys/class/net michael kerrisk add a brief description of /sys/kernel/mm michael kerrisk add brief description of /sys/kernel/debug/tracing michael kerrisk add a description of /sys/kernel/mm/hugepages arp.7 michael kerrisk see also: add arpd(8) capabilities.7 michael kerrisk add a reference to xattr(7) in the discussion of extended attributes michael kerrisk see also: add captest(8) epoll.7 michael kerrisk note existence of kcmp() kcmp_epoll_tfd operation fifo.7 michael kerrisk refer reader to pipe(7) for details of i/o semantics of fifos hier.7 michael kerrisk see also: add file-hierarchy(7) icmp.7 michael kerrisk see also: add rdisc(8) man-pages.7 michael kerrisk note that "x86-64" is generally preferred over "x86_64" g. branden robinson add a use case for real minus character namespaces.7 michael kerrisk add a reference to new veth(4) page michael kerrisk example: refer also to example in clone(2) pid_namespaces.7 michael kerrisk see also: add reboot(2) add because reboot(2) has special semantics for non-initial pid namespaces. pthreads.7 michael kerrisk see also: add pthread_spin_init(3) and pthread_spin_lock(3) socket.7 michael kerrisk [petr malat, tobias klausmann] correct the description of so_rxq_ovfl standards.7 michael kerrisk see also: add getconf(1), confstr(3), pathconf(3), sysconf(3) user_namespaces.7 christian brauner [michael kerrisk] document new 340 line idmap limit ld.so.8 michael kerrisk [yubin ruan] simplify language around conferring capabilities the statement "conferring permitted or effective capabilities" to the process is somewhat redundant. binaries with capabilities confer capabilities only to those process capability sets, so it's simpler to just say "confers capabilities to the process". ==================== changes in man-pages-4.15 ==================== released: 2018-02-02, palo alto contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam liddell andrea parri andries e. brouwer elie roudninski eric benton florian weimer g. branden robinson jakub wilk joel williamson john hubbard jorgen hansen keno fischer michael kerrisk michal hocko neilbrown nikola forró nikolay borisov pradeep kumar qingfeng hao ricardo biehl pasquali roblabla roman gushchin shawn landden stefan hajnoczi stefan raspl tejun heo apologies if i missed anyone! new and rewritten pages ----------------------- s390_sthyi.2 qingfeng hao [michael kerrisk] new page for s390-specific s390_sthyi(2) network_namespaces.7 michael kerrisk new page describing network namespaces based on content moved from namespaces(7) vsock.7 stefan hajnoczi [jorgen hansen, michael kerrisk] document the vsock socket address family newly documented interfaces in existing pages --------------------------------------------- cgroups.7 michael kerrisk [tejun heo] document cgroups v2 "thread mode" michael kerrisk [tejun heo] document cgroup v2 delegation via the 'nsdelegate' mount option michael kerrisk document the cgroup.max.depth and cgroup.max.descendants files michael kerrisk document 'release_agent' mount option michael kerrisk [roman gushchin] document /sys/kernel/cgroup/delegate michael kerrisk [roman gushchin] document /sys/kernel/cgroup/features michael kerrisk [roman gushchin] document cgroups v2 cgroup.stat file global changes -------------- various pages g. branden robinson standardize on "nonzero" also add this term to the style guide in man-pages(7). changes to individual pages --------------------------- bpf.2 nikolay borisov sync list of supported map types with 4.14 kernel copy_file_range.2 michael kerrisk library support was added in glibc 2.27 shawn landden glibc provides a user-space emulation where the system call is absent florian weimer efbig errors are possible, similar to write(2) michael kerrisk errors: add eisdir michael kerrisk order errors alphabetically michael kerrisk add comment to code example explaining use of syscall(2) fcntl.2 read.2 write.2 neilbrown document "lost locks" as cause for eio. if an advisory lock is lost, then read/write requests on any affected file descriptor can return eio - for nfsv4 at least. memfd_create.2 michael kerrisk glibc support for memfd_create() was added in version 2.27 mlock.2 michael kerrisk make details for mlock_onfault a little more explicit michael kerrisk glibc support for mlock2() is added in version 2.27 mmap.2 john hubbard [michael hocko] map_fixed is no longer discouraged map_fixed has been widely used for a very long time, yet the man page still claims that "the use of this option is discouraged". john hubbard map_fixed updated documentation -- expand the documentation to discuss the hazards in enough detail to allow avoiding them. -- mention the upcoming map_fixed_safe flag. -- enhance the alignment requirement slightly. mount.2 keno fischer [michael kerrisk] add einval error condition when ms_binding mnt_locked submounts mprotect.2 pkey_alloc.2 michael kerrisk glibc support for memory protection keys was added in version 2.27 perf_event_open.2 michael kerrisk see also: add perf(1) pkey_alloc.2 michael kerrisk clarify description of pkey_alloc() 'flags' argument prctl.2 michael kerrisk defer to capabilities(7) for discussion of the "keep capabilities" flag recvmmsg.2 sendmmsg.2 nikola forró point out that error handling is unreliable seccomp.2 michael kerrisk clarify that seccomp_ret_trap sigsys signal is thread-directed syscalls.2 michael kerrisk add s390-specific s390_sthyi(2) to syscall list unshare.2 michael kerrisk clarify that eusers occurred only until kernel 4.8 errno.3 michael kerrisk 'errno -s' can be used to search for errors by string in description michael kerrisk add linux error text corresponding to enomem fgetpwent.3 michael kerrisk add missing attributes preamble fts.3 michael kerrisk [pradeep kumar] fts_pathlen = strlen(fts_path) + strlen(fts_name) fuse.4 michael kerrisk places errors in alphabetical order (no content changes) veth.4 michael kerrisk add network_namespaces(7) sysfs.5 michael kerrisk refer to cgroups(7) for information about files in /sys/kernel/cgroup capabilities.7 michael kerrisk note which capability sets are affected by secbit_no_setuid_fixup note explicitly that secbit_no_setuid_fixup is relevant for the permitted, effective, and ambient capability sets. michael kerrisk deemphasize the ancient prctl(2) pr_set_keepcaps command the modern approach is secbits_keep_caps. michael kerrisk clarify effect of cap_setfcap make it clear that cap_setfcap allows setting arbitrary capabilities on a file. michael kerrisk clarify which capability sets are effected by secbit_keep_caps this flag has relevance only for the process permitted and effective sets. michael kerrisk rephrase cap_setpcap description * mention kernel versions. * place current kernel behavior first michael kerrisk secbit_keep_caps is ignored if secbit_no_setuid_fixup is set michael kerrisk ambient set is also cleared when uids are set to nonzero value cgroups.7 michael kerrisk add a more complete description of cgroup v1 named hierarchies michael kerrisk add a section on unmounting cgroup v1 filesystems michael kerrisk add subsection describing cgroups v2 subtree delegation michael kerrisk mention enoent error that can occur when writing to subtree_control file michael kerrisk add list of currently available version 2 controllers nikolay borisov add information about rdma controller michael kerrisk rewrite the description of cgroup v2 subtree control michael kerrisk [tejun heo] note linux 4.11 changes to cgroup v2 delegation containment rules michael kerrisk systemd(1) nowadays automatically mounts the cgroup2 filesystem michael kerrisk clarify that cgroup.controllers is read-only michael kerrisk elaborate a little on problems of splitting threads across cgroups in v1 michael kerrisk [tejun heo] tweak the description of delegation of cgroup.subtree_control ip.7 ricardo biehl pasquali inaddr_* values cannot be assigned directly to 's_addr' michael kerrisk s/inaddr_any/inaddr_loopback/ in discussion of htonl() inaddr_loopback is a better example, since it is not byte-order neutral. namespaces.7 network_namespaces.7 michael kerrisk move content from namespaces(7) to network_namespaces(7) pid_namespaces.7 michael kerrisk see also: add mount_namespaces(7) sched.7 michael kerrisk [andrea parri] correctly describe effect of priority changes for rt threads the placement of a thread in the run queue for its new priority depends on the direction of movement in priority. (this appears to contradict posix, except in the case of pthread_setschedprio().) user_namespaces.7 michael kerrisk mention ns_get_owner_uid ioctl() operation ==================== changes in man-pages-4.16 ==================== released: 2018-04-30, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam borowski andy owen carlos o'donell carsten grohmann elvira khabirova enrique garcia frederic brault heinrich schuchardt howard johnson jakub wilk jan kara jann horn john hubbard jürg billeter konstantin grinemayer konstantin khlebnikov martin mares mathieu desnoyers mattias andrée michael kerrisk michal hocko mike frysinger nikos mavrogiannopoulos robin kuzmin ross zwisler rusty russell serge e. hallyn song liu tomi salminen apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- membarrier.2 mathieu desnoyers [michael kerrisk] document new membarrier commands introduced in linux 4.16 document the following membarrier commands introduced in linux 4.16: membarrier_cmd_global_expedited (the old enum label membarrier_cmd_shared is now an alias to preserve header backward compatibility) membarrier_cmd_register_global_expedited membarrier_cmd_private_expedited_sync_core membarrier_cmd_register_private_expedited_sync_core mmap.2 jan kara [ross zwisler, michael kerrisk] add description of map_shared_validate and map_sync michal hocko [john hubbard, michael kerrisk, jann horn] document new map_fixed_noreplace flag 4.17+ kernels offer a new map_fixed_noreplace flag which allows the caller to atomically probe for a given address range. readv.2 io_submit.2 jürg billeter document rwf_append added in linux 4.16 capabilities.7 michael kerrisk describe file capability versioning michael kerrisk [serge e. hallyn] document namespaced-file capabilities [there's still more work to be done on this new text] changes to individual pages --------------------------- bpf.2 michael kerrisk update list of architectures that support jited ebpf and note kernel version numbers where support is added. michael kerrisk kernel 4.15 added config_bpf_jit_always_on this causes the jit compiler to be always on and forces bpf_jit_enable to 1. execve.2 michael kerrisk note that describing execve as "executing a new process" is misleading this misdescription is so common that it's worth calling it out explicitly. michael kerrisk more explicitly describe effect of execve() in the opening paragraph fallocate.2 michael kerrisk since linux 4.16, btrfs supports falloc_fl_zero_range getrlimit.2 michael kerrisk cap_sys_resource capability is required in *initial user namespace* io_submit.2 michael kerrisk add kernel version numbers for various 'aio_rw_flags' flags michael kerrisk place 'aio_rw_flags' in alphabetical order mmap.2 jann horn map_fixed is okay if the address range has been reserved clarify that map_fixed is appropriate if the specified address range has been reserved using an existing mapping, but shouldn't be used otherwise. michael kerrisk move the text on map_fixed to notes this text has become rather long, making it somewhat unwieldy in the discussion of the mmap() flags. therefore, move it to notes, with a pointer in description referring the reader to notes. michael kerrisk [heinrich schuchardt] clarify that when addr==null, address chosen by kernel is page-aligned michael kerrisk add a little historical detail on the obsolete map_denywrite mount.2 michael kerrisk errors: add ebusy for the case of trying to stack same mount twice michael kerrisk remove a couple of obsolete ebusy errors as far as i can tell, these ebusy errors disappeared with the addition of stackable mounts in linux 2.4. msgget.2 semget.2 shmget.2 michael kerrisk the purpose of "flags" == 0 is to obtain id of an existing ipc object this was implied in these pages, but the meaning of "flags" == 0 could be more explicit, as indicated by questions such as https://stackoverflow.com/questions/49833569/flag-value-of-semget-function open.2 jann horn document more -etxtbsy conditions jakub wilk add missing argument for snprintf() in example code perf_event_open.2 song liu add type kprobe and uprobe two new types kprobe and uprobe are being added to perf_event_open(), which allow creating kprobe or uprobe with perf_event_open. this patch adds information about these types. ptrace.2 jann horn copy retval info for seccomp_get_filter to right section the "return value" section made a claim that was incorrect for ptrace_seccomp_get_filter. explicitly describe the behavior of ptrace_seccomp_get_filter in the "return value" section (as usual), but leave the now duplicate description in the section describing ptrace_seccomp_get_filter, since the ptrace_seccomp_get_filter section would otherwise probably become harder to understand. readv.2 michael kerrisk remove redundant sentence seccomp.2 michael kerrisk note that execve() may change syscall numbers during life of process on a multiarch/multi-abi platform such as modern x86, each architecture/abi (x86-64, x32, i386)has its own syscall numbers, which means a seccomp() filter may see different syscall numbers over the life of the process if that process uses execve() to execute programs that has a different architectures/abis. michael kerrisk note which architectures support seccomp bpf michael kerrisk in example, clearly note that x32 syscalls are >= x32_syscall_bit shutdown.2 carsten grohmann see also: add close(2) syscall.2 adam borowski add riscv wait.2 michael kerrisk [robin kuzmin] wait() and waitpid() block the calling thread (not process) wait4.2 michael kerrisk [martin mares] soften the warning against the use of wait3()/wait4() these functions are nonstandard, but there is no replacement. see https://bugzilla.kernel.org/show_bug.cgi?id=199215 crypt.3 encrypt.3 carlos o'donell [michael kerrisk] add notes about _xopen_crypt the distribution may choose not to support _xopen_crypt in the case that the distribution has transitioned from glibc crypt to libxcrypt. fseek.3 michael kerrisk [andy owen] errors: ebadf should be espipe michael kerrisk improve epipe error text getcwd.3 carlos o'donell mention that "(unreachable)" is no longer returned for glibc >= 2.27. makedev.3 michael kerrisk since glibc 2.28, no longer defines these macros pthread_create.3 frederic brault note default thread stack size for several architectures tsearch.3 jann horn clarify items vs nodes the manpage claimed that tsearch() returns a pointer to a data item. this is incorrect; tsearch() returns a pointer to the corresponding tree node, which can also be interpreted as a pointer to a pointer to the data item. since this api is quite unintuitive, also add a clarifying sentence. jann horn tdelete() can return dangling pointers posix says that deleting the root node must cause tdelete() to return some unspecified non-null pointer. glibc implements it by returning a dangling pointer to the (freed) root node. therefore, explicitly note that tdelete() may return bad pointers that must not be accessed. elf.5 michael kerrisk see also: add patchelf(1) filesystems.5 michael kerrisk add an entry for tmpfs(5) group.5 michael kerrisk see also: add vigr(8) passwd.5 michael kerrisk see also: add vipw(8) sysfs.5 michael kerrisk add brief note on /sys/fs/smackfs tmpfs.5 mike frysinger document current mount options some of this content is moved from the mount(8) man page. style was based on proc(5) sections. michael kerrisk remove reference to mount(8) for discussion of mount options the mount options are now described in this page. michael kerrisk see also: add documentation/vm/transhuge.txt michael kerrisk reformat 'huge' and 'mpol' mount option values as lists michael kerrisk describe 'mpol' mount options based on text from documentation/filesystems/tmpfs.txt. michael kerrisk document 'huge' mount options based on text from documentation/vm/transhuge.txt. michael kerrisk see also: add set_mempolicy(2) michael kerrisk document mpol=local mount option capabilities.7 michael kerrisk remove redundant mention of ptrace_seccomp_get_filter cgroups.7 michael kerrisk cgroup.events transitions generate pollerr as well as pollpri mount_namespaces.7 michael kerrisk note another case where shared "peer groups" are formed namespaces.7 michael kerrisk [konstantin khlebnikov] mention that device id should also be checked when comparing ns symlinks when comparing two namespaces symlinks to see if they refer to the same namespace, both the inode number and the device id should be compared. this point was already made clear in ioctl_ns(2), but was missing from this page. michael kerrisk note an idiosyncrasy of /proc/[pid]/ns/pid_for_children /proc/[pid]/ns/pid_for_children has a value only after first child is created in pid namespace. verified by experiment. network_namespaces.7 michael kerrisk network namespaces isolate the unix domain abstract socket namespace michael kerrisk add cross reference to unix(7) for further information on unix domain abstract sockets. posixoptions.7 carlos o'donell expand xsi options groups we define in detail the x/open system interfaces i.e. _xopen_unix and all of the x/open system interfaces (xsi) options groups. the xsi options groups include encryption, realtime, advanced realtime, realtime threads, advanced realtime threads, tracing, streams, and legacy interfaces. michael kerrisk use a more consistent, less cluttered layout for option lists michael kerrisk make function lists more consistent and less cluttered use more consistent layout for lists of functions, and remove punctuation from the lists to make them less cluttered. socket.7 michael kerrisk [tomi salminen] fix error in so_incoming_cpu code snippet the last argument is passed by value, not reference. time.7 michael kerrisk [enrique garcia] mention clock_gettime()/clock_settime() rather than [gs]ettimeofday() gettimeofday() is declared obsolete by posix. mention instead the modern apis for working with the realtime clock. see https://bugzilla.kernel.org/show_bug.cgi?id=199049 unix.7 michael kerrisk [rusty russell] errors: add ebadf for sending closed file descriptor with scm_rights vdso.7 michael kerrisk vdso symbols (system calls) are not visible to seccomp(2) filters xattr.7 michael kerrisk see also: add selinux(8) ld.so.8 mike frysinger make lack of separator escaping explicit make it clear that the delimiters in ld_preload, ld_library_path, and ld_audit cannot be escaped so people don't try various methods (such as \:) to workaround it. michael kerrisk remove unneeded mention of path in discussion of ld_library_path this brief sentence doesn't add value to the text. ==================== changes in man-pages-5.00 ==================== released: 2019-03-06, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam manzanares alan jenkins alec leamas alessandro vesely alexander e. patrakov allison randal amir goldstein anatoly borodin andreas gruenbacher andreas westfeld andrei vagin andrew price anthony iliopoulos antonio chirizzi antonio ospite arkadiusz drabczyk balbir singh benjamin peterson bernd petrovitsch bert hubert bjarni ingi gislason burkhard lück carlos o'donell claudio scordino daniel borkmann daniel kamil kozar davidlohr bueso davidlohr bueso david newall dmitry v. levin elliot hughes elvira khabirova emil fihlman enrico scholz eric benton eric sanchis eugene syromiatnikov eugene syromyatnikov felipe gasper florian weimer frank theile g. branden robinson goldwyn rodrigues goldwyn rodrigues göran häggsjö harry mallon heinrich schuchardt heiko carstens helge deller henry wilson hiroya ito howard johnson ian turner ignat loskutov ingo schwarze jakub wilk james weigle jann horn jann horn jason a. donenfeld jeff moyer jens thoms toerring joe lawrence johannes altmanninger johannes liebermann jonny grant joseph c. sible joseph sible josh gao josh triplett kees cook keith thompson keno fischer konrad rzeszutek wilk konst mayer leah hanson lucas de marchi lucas werkmeister luka macan marc-andré lureau marcus gelderie marcus gelderie marko myllynen mark schott matthew bobrowski matthew kilgore mattias engdegård mauro carvalho chehab michael becker michael kerrisk michael witten michal hocko mihir mehta mike frysinger mike frysinger mike rapoport mike weilgart nadav har'el nick gregory niklas hambüchen nikola forró nixiaoming oded elisha paul eggert paul millar philip dumont pierre chifflier quentin monnet radostin stoyanov robert o'callahan robert p. j. day robin kuzmin ruschein sam varshavchik sean young shawn landden simone piccardi snyh solal pirelli stan schwertly stephan knauss szabolcs nagy thomas posch tobias klauser troy engel tycho andersen tycho kirchner vince weaver wang nan william kucharski xiao yang apologies if i missed anyone! new and rewritten pages ----------------------- s390_guarded_storage.2 eugene syromyatnikov new page documenting s390_guarded_storage(2) s390-specific system call address_families.7 michael kerrisk [eugene syromyatnikov] new page that contains details of socket address families there is too much detail in socket(2). move most of it into a new page instead. bpf-helpers.7 michael kerrisk [daniel borkmann, quentin monnet] add new man page for ebpf helper functions (autogenerated from kernel source files) removed pages ------------- mdoc.7 mdoc.samples.7 michael kerrisk [ingo schwarze] remove mdoc(7) and mdoc.samples(7) groff_mdoc(7) from the groff project provides a better equivalent of mdoc.samples(7) and the 'mandoc' project provides a better mdoc(7). and nowadays, there are virtually no pages in "man-pages" that use mdoc markup. newly documented interfaces in existing pages --------------------------------------------- fanotify_init.2 fanotify.7 nixiaoming [amir goldstein, michael kerrisk] document fan_report_tid fanotify_init.2: add new flag fan_report_tid fanotify.7: update description of member pid in struct fanotify_event_metadata amir goldstein document fan_mark_filesystem monitor fanotify events on the entire filesystem. matthew bobrowski [amir goldstein] document fan_open_exec and fan_open_exec_perm io_submit.2 adam manzanares document iocb_flag_ioprio msgctl.2 semctl.2 shmctl.2 davidlohr bueso [joe lawrence, michael kerrisk] document stat_any commands prctl.2 konrad rzeszutek wilk [michael kerrisk] document pr_set_speculation_ctrl and pr_get_speculation_ctrl sched_setattr.2 claudio scordino [michael kerrisk] document sched_flag_dl_overrun and sched_flag_reclaim socket.2 tobias klauser document af_xdp document af_xdp added in linux 4.18. inotify.7 henry wilson document in_mask_create unix.7 michael kerrisk document so_passsec michael kerrisk document scm_security ancillary data new and changed links --------------------- reallocarray.3 michael kerrisk new link to malloc(3) precedence.7 josh triplett add as a redirect to operator.7 global changes -------------- various pages michael kerrisk [g. branden robinson] use '\e' rather than '\\' to get a backslash various pages michael kerrisk [bjarni ingi gislason, g. branden robinson] use zero‐width space in appropriate locations various pages michael kerrisk clarify the distinction between "file descriptor" and "file description" various pages mike rapoport update paths for in-kernel memory management documentation files a few pages michael kerrisk change references to '2.6.0-test*' series kernels to just '2.6.0' changes to individual pages --------------------------- iconv.1 marko myllynen see also: add uconv(1) localedef.1 howard johnson note that -f and -c, are reversed from what you might expect time.1 michael kerrisk [johannes altmanninger] document the -q/--quiet option jakub wilk update bug reporting address bpf.2 tobias klauser update jit support list for linux 4.18 jit support for x86-32 was during the linux 4.18 release cycle. also correct the entry for mips (only mips64 is supported). oded elisha fix bug in example quentin monnet see also: add bpf-helpers(7) capget.2 michael kerrisk remove crufty sentence suggesting use of deprecated functions remove crufty sentence suggesting use of deprecated capsetp(3) and capgetp(3); the manual page for those functions has long (at least as far back as 2007) noted that they are deprecated. michael kerrisk remove first paragraph, which repeats details from capabilities(7) chroot.2 michael kerrisk mention /proc/[pid]/root clock_getres.2 michael kerrisk [jens thoms toerring] clock_monotonic_raw does not count while the system is suspended michael kerrisk [jens thoms toerring] on linux clock_monotonic counts time that the system has run since boot michael kerrisk [jens thoms toerring] clock_monotonic does not count while the system is suspended michael kerrisk errors: add einval error for noncanonical clock_settime() value clone.2 michael kerrisk rework discussion of threads and signals the discussion is phrased in terms of signals sent using kill(2), but applies equally to a signal sent by the kernel. jann horn pending clone_newpid prevents thread creation michael kerrisk clarify the discussion of threads and signals and explicitly introduce the terms "process-directed" and "thread-directed" signals. eugene syromyatnikov add information about clone and clone2 on ia-64 michael kerrisk errors: einval occurs with clone_newuser if !config_user_ns connect.2 benjamin peterson document error semantics of nonblocking unix domain sockets epoll_ctl.2 michael kerrisk use the term "interest list" consistently epoll_wait.2 michael kerrisk clarify the behavior when epoll_wait()-ing on an empty interest list michael kerrisk note that epoll_wait() round robins through the set of ready descriptors eventfd.2 michael kerrisk move text noting that eventfd() creates a fd earlier in the page fcntl.2 michael kerrisk actual pipe capacity may in practice be less than nominal capacity the number of bytes that can be written to the pipe may be less (sometimes substantially less) than the nominal capacity. eugene syromyatnikov mention that l_sysid is not used even if present michael kerrisk briefly explain the meaning of the 'l_sysid' field in 'struct flock' futex.2 benjamin peterson make the example use c11 atomics rather than gcc builtins getcpu.2 tobias klauser [michael kerrisk] getcpu() now has a glibc wrapper; remove mention of syscall(2) the glibc wrapper was added in glibc 2.29, release on 1 feb 2019. getgid.2 getpid.2 getuid.2 pipe.2 syscall.2 eugene syromiatnikov [michael kerrisk] describe 2nd return value peculiarity some architectures (ab)use second return value register for additional return value in some system calls. let's describe this. getgroups.2 michael kerrisk note that a process can drop all groups with: setgroups(0, null) getrlimit.2 eugene syromyatnikov note that setrlimit(rlimit_cpu) doesn't fail michael kerrisk resource limits are process-wide attributes shared by all threads this was already noted in pthreads(7), but bears repeating here. eugene syromyatnikov correct information about large limits on 32-bit architectures gettid.2 michael kerrisk glibc provides a wrapper since version 2.30 gettimeofday.2 michael kerrisk errors: add einval for noncanonical 'tv' argument to settimeofday() gettimeofday.2 clock_getres.2 michael kerrisk [jens thoms toerring] errors: einval can occur if new real time is less than monotonic clock getxattr.2 removexattr.2 setxattr.2 michael kerrisk [andreas gruenbacher, enrico scholz] errors: replace enoattr with enodata see also https://bugzilla.kernel.org/show_bug.cgi?id=201995 inotify_add_watch.2 paul millar add in_onlydir based error henry wilson note errors that can occur for in_mask_create io_submit.2 jeff moyer fix the description of aio_data aio_data is not a kernel-internal field. madvise.2 michal hocko [niklas hambüchen] madv_free clarify swapless behavior memfd_create.2 marc-andré lureau update hugetlb file-sealing support lucas de marchi fix header for memfd_create() joseph c. sible _gnu_source is required mmap.2 elliott hughes explicitly state that the fd can be closed jann horn [michal hocko, william kucharski] fix description of treatment of the hint the current manpage reads as if the kernel will always pick a free space close to the requested address, but that's not the case. mount.2 michael kerrisk clearly distinguish per-mount-point vs per-superblock mount flags michael kerrisk ms_silent is ignored when changing propagation type michael kerrisk attempts to change ms_silent setting during remount are silently ignored michael kerrisk [harry mallon] document erofs for read-only filesystems see https://bugzilla.kernel.org/show_bug.cgi?id=200649 michael kerrisk clarify that per-superblock flags are shared during remount michael kerrisk remove crufty sentence about ms_bind + ms_remount michael kerrisk mention /proc/pid/mountinfo many people are unaware of the /proc/pid/mountinfo file. provide a helpful clue here. michael kerrisk mandatory locking also now requires config_mandatory_file_locking michael kerrisk [simone piccardi] add ms_strictatime to list of flags that can be used in remount michael kerrisk eacces: note some reasons why a filesystem may be read-only michael kerrisk see also: add ioctl_iflags(2) msgop.2 michael kerrisk correct the capability description for msgsnd() eaccess error nfsservctl.2 michael kerrisk add versions section noting that this system call no longer exists open.2 lucas werkmeister document enxio for sockets michael kerrisk clarify a special use case of o_nonblock for devices eugene syromiatnikov mention presence of unused o_rsync definition o_rsync is defined in on hp pa-risc, but is not used anyway. eugene syromiatnikov document fasync usage in linux uapi headers andrew price remove o_direct-related quotation remove a section that adds no benefit to the discussion of o_direct. michael kerrisk [robin kuzmin] clarify that o_nonblock has no effect on poll/epoll/select perf_event_open.2 vince weaver [wang nan] document the perf_event_ioc_pause_output ioctl the perf_event_ioc_pause_output ioctl was introduced in linux 4.7. vince weaver fix wording in multiplexing description vince weaver clarify exclude_idle vince weaver document the perf_event_ioc_query_bpf ioctl vince weaver document the perf_event_ioc_modify_attributes ioctl vince weaver fix prctl behavior description pivot_root.2 elvira khabirova explain the initramfs case and point to switch_root(8) joseph sible [joseph c. sible] document einval if root is rootfs pkey_alloc.2 michael kerrisk [szabolcs nagy] switch to glibc prototype in synopsis poll.2 michael kerrisk note that poll() and ppoll() are not affected by o_nonblock posix_fadvise.2 eugene syromyatnikov describe the difference between fadvise64/fadvise64_64 prctl.2 benjamin peterson pr_set_mm_exe_file may now be used as many times as desired michael kerrisk add some further historical details on pr_set_mm_exe_file michael kerrisk [jann horn] explain the circumstances in which the parent-death signal is sent michael kerrisk rework the pr_set_pdeathsig description a little, for easier readability michael kerrisk add additional info on pr_set_pdeathsig the signal is process directed and the siginfo_t->si_pid filed contains the pid of the terminating parent. michael kerrisk note libcap(3) apis for operating on ambient capability set (however, the libcap apis do not yet seem to have manual pages...) michael kerrisk mention libcap apis for operating on capability bounding set ptrace.2 dmitry v. levin do not say that ptrace_o_tracesysgood may not work jann horn bugs: ptrace() may set errno to zero readdir.2 eugene syromyatnikov fix struct old_linux_dirent in accordance with current definition readv.2 xiao yang [florian weimer] fix wrong errno for an unknown flag rename.2 michael kerrisk glibc 2.28 adds library support for renameat2() tobias klauser add feature test macro for renameat2() the glibc wrapper for renameat2() was added in glibc 2.28 and requires _gnu_source. eugene syromiatnikov some additional notes regarding rename_whiteout lucas werkmeister [michael kerrisk] add kernel versions for rename_noreplace support michael kerrisk rework list of supported filesystems for rename_noreplace tobias klauser renameat2() now has a glibc wrapper; remove mention of syscall(2) s390_runtime_instr.2 eugene syromyatnikov add a note about runtime_instr.h availability s390_sthyi.2 eugene syromyatnikov [heiko carstens] some minor additions sched_setattr.2 michael kerrisk add a bit more detail for sched_deadline sched_setparam.2 michael kerrisk clarify that scheduling parameters are per-thread (not per-process) seccomp.2 michael kerrisk (briefly) document seccomp_filter_flag_spec_allow michael kerrisk see also: add bpfc(1) select.2 michael kerrisk bugs: the use of value-result arguments is a design bug michael kerrisk [robin kuzmin] note that select() and pselect() are not affected by o_nonblock select_tut.2 michael kerrisk [antonio chirizzi] diagnose inet_aton() errors with simple fprintf() (not perror()) setgid.2 michael kerrisk clarify eperm capability requirements with respect to user namespaces setns.2 michael kerrisk when joining a user namespace, it must be a descendant user namespace michael kerrisk note capability requirements for changing pid namespace note capability requirements for changing network, ipc, or uts namespace note capability requirements for changing cgroup namespace michael kerrisk some text restructuring and reordering set_thread_area.2 eugene syromyatnikov mention related prctl() requests in see also eugene syromyatnikov mention that get_thread_area() is also linux-specific eugene syromyatnikov describe set_thread_area()/get_thread_area() on m68k/mips setuid.2 michael kerrisk clarify eperm capability requirements with respect to user namespaces sigaction.2 eugene syromyatnikov [michael kerrisk] describe obsolete usage of struct sigcontext as signal handler argument sigsuspend.2 michael kerrisk clarify that sigsuspend() suspends the calling *thread* socket.2 michael kerrisk remove references to external docs this information is all in the new address_families(7) michael kerrisk add cross reference to address_families(7) eugene syromyatnikov reinstate af_vsock mention michael kerrisk simplify list of address families remove many of the details that are in address_families(7) nikola forró remove notes concerning af_alg and af_xdp all address families are now documented in address_families.7. michael kerrisk remove some more obscure protocols from address family list the list of address families in this page is still overwhelmingly long. so let's shorten it. the removed entries are all in address_families(7). michael kerrisk remove a few obsolete protocols documentation for these remains in address_families(7) socketpair.2 eugene syromyatnikov note that af_tipc also supports socketpair(2) introduced by linux commit v4.12-rc1~64^3~304^2~1. stat.2 michael kerrisk [alessandro vesely] errors: enoent can occur where a path component is a dangling symlink see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=909789 benjamin peterson see also: add statx(2) statx.2 tobias klauser [michael kerrisk] statx() now has a glibc wrapper; remove mention of syscall(2) syscall.2 eugene syromyatnikov [michael kerrisk] elaborate x32 abi specifics snyh fix wrong retval register number in alpha architecture helge deller parisc needs care with syscall parameters michael kerrisk rework table to render within 80 columns syscalls.2 eugene syromyatnikov change example of a thin syscall wrapper to chdir() as truncate(3) should dispatch between truncate/truncate64, as noted later in the page. eugene syromyatnikov [michael kerrisk] update syscall table added: arc_gettls, arc_settls, arc_usr_cmpxchg, arch_prctl, atomic_barrier, atomic_cmpxchg_32, bfin_spinlock, breakpoint, clone2, cmpxchg, cmpxchg_badaddr, dma_memcpy, execv, get_tls, getdomainname, getdtablesize, gethostname, getxgid, getxpid, getxuid, metag_get_tls, metag_set_fpu_flags,metag_set_tls, metag_set_global_bit, newfstatat, old_adjtimex, oldumount, or1k_atomic, pread, pwrite, riscv_flush_icache, sched_get_affinity, sched_set_affinity, set_tls, setaltroot, sethae, setpgrp, spill, sram_alloc, sram_free, swapcontext, switch_endian, sys_debug_setcontext, syscall, sysmips, timerfd, usr26, usr32, xtensa. uncommented: memory_ordering renamed: ppc_rtas to rtas (__nr_rtas), ppc_swapcontext to swapcontext (__nr_swapcontext). eugene syromyatnikov note about s390x and old_mmap michael kerrisk add s390_guarded_storage(2) michael kerrisk update syscall list for linux 4.18 eugene syromyatnikov note that not all architectures return errno negated helge deller parisc linux does not any longer emulate hp-ux michael kerrisk comment out details of a few system calls that only ever briefly existed unshare.2 michael kerrisk [shawn landden] same einval errors as for clone(2) can also occur with unshare(2) tycho andersen note einval when unsharing pid ns twice the kernel doesn't allow unsharing a pid ns if it has previously been unshared. ustat.2 michael kerrisk starting with version 2.28, glibc no longer provides a wrapper function vmsplice.2 andrei vagin note that vmsplice can splice pages from pipe to memory wait.2 michael kerrisk add some cross references to core(5) write.2 michael kerrisk [nadav har'el] return value: clarify details of partial write and https://bugzilla.kernel.org/show_bug.cgi?id=197961 goldwyn rodrigues add details on partial direct i/o writes alloca.3 michael kerrisk [robin kuzmin] prevent any misunderstanding about when allocated memory is released bsd_signal.3 xiao yang fix the wrong version of _posix_c_source bstring.3 michael kerrisk [emil fihlman] correct argument list for memmem() prototype cmsg.3 michael kerrisk explain zero-initialization requirement for cmsg_nxthdr() michael kerrisk remove out of place mention of msg_ctrunc this detail is covered in recvmsg(2), and now also in unix(7). michael kerrisk note that cmsg_firsthdr can return null michael kerrisk remove unnecessary 'fdptr' intermediate variable in example code des_crypt.3 encrypt.3 michael kerrisk the functions described in these pages are removed in glibc 2.28 dlsym.3 michael kerrisk describe a case where a symbol value may be null errno.3 michael kerrisk [robert p. j. day] mention that errno(1) is part of the 'moreutils' package exec.3 michael kerrisk [eugene syromyatnikov] note that sparc provides an execv() system call exit.3 mike frysinger note wider sysexits.h availability ferror.3 elliot hughes warn about closing the result of fileno() fnmatch.3 elliott hughes clarify "shell wildcard pattern" getaddrinfo.3 michael kerrisk [eric sanchis] fix off-by-one error in example client program getcwd.3 michael kerrisk rework text on use of getcwd() system call make it clear that all of the library functions described on this page will use the getcwd() system call if it is present. michael kerrisk add details on the getcwd() syscall and how it used by libc functions michael kerrisk reorder the text describing "(unreachable)" being returned by getcwd() getmntent.3 elliot hughes clarify that endmntent() should be used rather than fclose() isatty.3 michael kerrisk [jakub wilk] most non-tty files nowadays result in the error enotty historically, at least fifos and pipes yielded the error einval. lockf.3 ian turner errors: add eintr malloc.3 michael kerrisk add reference to glibc mallocinternals wiki michael kerrisk note that calloc() detects overflow when multiplying its arguments michael kerrisk since glibc 2.29, reallocarray() is exposed by defining _default_source info gleaned from glibc news file. pthread_attr_init.3 michael kerrisk [göran häggsjö, jakub wilk] use correct printf() specifier for "size_t" in example program pthread_rwlockattr_setkind_np.3 carlos o'donell remove bug notes pthread_setname_np.3 jakub wilk explain _np suffix add text to conforming to explaining that the "_np" suffix is because these functions are non-portable. putenv.3 michael kerrisk note a glibc extension: putenv("name") removes an environment variable resolver.3 michael becker add documentation of res_nclose() strcmp.3 heinrich schuchardt clarify that strcmp() is not locale aware strcpy.3 matthew kilgore fix example code for strncpy, which could pass an incorrect length michael kerrisk [frank theile] use "destination" consistently (instead of "target" sometimes) strfry.3 keith thompson remove incorrect reference to rand(3) string.3 strlen.3 strnlen.3 michael kerrisk [jakub wilk] use 'bytes' not 'characters' this is in line with posix terminology. system.3 michael kerrisk [jonny grant] use '(char *) null' rather than '(char *) 0' michael kerrisk note that system() can fail for the same reasons as fork(2) arkadiusz drabczyk mention that 'errno' is set on error termios.3 eugene syromyatnikov note an xtabs alpha issue trunc.3 michael kerrisk [eric benton, g. branden robinson] make the description a little clearer michael kerrisk emphasize that the return value is a floating-point number xcrypt.3 jason a. donenfeld warn folks not to use these functions lirc.4 sean young fix broken link sean young document error returns more explicitly sean young lirc.h include file is in /usr/include/linux/lirc.h sean young [alec leamas, mauro carvalho chehab] remove ioctls and feature bits which were never implemented sean young unsupported ioctl() operations always return enotty sean young lirc_mode_lirccode has been replaced by lirc_mode_scancode sean young document remaining ioctl (lirc_get_rec_timeout) now all ioctls are documented. sean young timeout reports are enabled by default sean young some devices are send only sean young update see also sean young lirc_can_set_rec_duty_cycle_range was never supported no driver ever supported such a thing. michael kerrisk clarify the description lirc_set_rec_timeout tty.4 michael witten add `vcs(4)' and `pty(7)' to the `see also' section vcs.4 mattias engdegård [michael witten] fix broken example code core.5 michael kerrisk add cross reference to vdso(7) where "virtual dso" is mentioned filesystems.5 eugene syromyatnikov mention sysfs(2) host.conf.5 nikola forró clarify glibc versions in which spoof options were removed proc.5 michael kerrisk [philip dumont] document /proc/[tid] see also https://bugzilla.kernel.org/show_bug.cgi?id=201441 michael kerrisk add an overview section describing the groups of files under /proc keno fischer [robert o'callahan] correct description of nstgid lucas werkmeister document fdinfo format for timerfd stephan knauss mention /proc/uptime includes time spent in suspend michael kerrisk reword /proc/pid/fdinfo timerfd field descriptions as a hanging list michael kerrisk see also: add htop(1) and pstree(1) fs/proc/uptime.c:uptime_proc_show() fetches time using ktime_get_boottime which includes the time spent in suspend. michael kerrisk document /proc/pid/status coredumping field michael kerrisk mention choom(1) in discussion of /proc/[pid]/oom_score_adj michael kerrisk add a few details on /proc/pid/fdinfo timerfd michael kerrisk document /proc/meminfo kreclaimable field michael kerrisk explain how to determine top-most mount in /proc/pid/mountinfo explain how to determine the top-most mount at a particular location by inspecting /proc/pid/mountinfo. michael kerrisk [jakub wilk] remove bogus suggestion to use cat(1) to read files containing '\0' michael kerrisk refer to mount(2) for explanation of mount vs superblock options michael kerrisk fix description of /proc/pid/* ownership to account for user namespaces elvira khabirova describe ambiguities in /proc//maps michael kerrisk [nick gregory] since linux 4.5, "stack:" is no longer shown in /proc/pid/maps nikola forró document /proc/[pid]/status speculation_store_bypass field alan jenkins vmalloc information is no longer calculated (linux 4.4) michael kerrisk [alexander e. patrakov, jakub wilk, michael kerrisk] use 'tr '\000' '\n' to display contents of /proc/pid/environ michael kerrisk setting dumpable to 1 reverts ownership of /proc/pid/* to effective ids michael kerrisk document /proc/meminfo lazyfree field michael kerrisk fix kernel source pathname for soft-dirty documentation michael kerrisk /proc/[pid]/status vmpmd field was removed in linux 4.15 resolv.conf.5 nikola forró document no-reload (res_npreload) option tzfile.5 paul eggert sync from tzdb upstream capabilities.7 michael kerrisk fix some imprecisions in discussion of namespaced file capabilities the file uid does not come into play when creating a v3 security.capability extended attribute. michael kerrisk note that v3 security.attributes are transparently created/retrieved michael kerrisk improve the discussion of when file capabilities are ignored the text stated that the execve() capability transitions are not performed for the same reasons that setuid and setgid mode bits may be ignored (as described in execve(2)). but, that's not quite correct: rather, the file capability sets are treated as empty for the purpose of the capability transition calculations. michael kerrisk rework bounding set as per-thread set in transformation rules michael kerrisk substantially rework "capabilities and execution of programs by root" rework for improved clarity, and also to include missing details on the case where (1) the binary that is being executed has capabilities attached and (2) the real user id of the process is not 0 (root) and (3) the effective user id of the process is 0 (root). marcus gelderie add details about secbit_keep_caps the description of secbit_keep_caps is misleading about the effects on the effective capabilities of a process during a switch to nonzero uids. the effective set is cleared based on the effective uid switching to a nonzero value, even if secbit_keep_caps is set. however, with this bit set, the effective and permitted sets are not cleared if the real and saved set-user-id are set to nonzero values. marcus gelderie mention header for secbit constants mention that the named constants (secbit_keep_caps and others) are available only if the linux/securebits.h user-space header is included. michael kerrisk add text introducing bounding set along with other capability sets michael kerrisk [allison randal] update url for location of posix.1e draft standard michael kerrisk cap_sys_chroot allows use of setns() to change the mount namespace michael kerrisk [pierre chifflier] ambient capabilities do not trigger secure-execution mode michael kerrisk add a subsection on per-user-namespace "set-user-id-root" programs michael kerrisk rework discussion of exec and uid 0, correcting a couple of details clarify the "capabilities and execution of programs by root" section, and correct a couple of details: * if a process with ruid == 0 && euid != 0 does an exec, the process will nevertheless gain effective capabilities if the file effective bit is set. * set-uid-root programs only confer a full set of capabilities if the binary does not also have attached capabilities. michael kerrisk update url for libcap tarballs the previous location does not seem to be getting updated. (for example, at the time of this commit, libcap-2.26 had been out for two months, but was not present at http://www.kernel.org/pub/linux/libs/security/linux-privs. michael kerrisk clarify which capability sets capset(2) and capget(2) apply to capset(2) and capget(2) apply operate only on the permitted, effective, and inheritable process capability sets. michael kerrisk correct the description of secbit_keep_caps michael kerrisk add background details on capability transformations during execve(2) add background details on ambient and bounding set when discussing capability transformations during execve(2). michael kerrisk document the 'no_file_caps' kernel command-line option cgroup_namespaces.7 michael kerrisk [troy engel] clarify the example by making an implied detail more explicit. see https://bugzilla.kernel.org/show_bug.cgi?id=201047 cgroups.7 michael kerrisk add more detail on v2 'cpu' controller and realtime threads explicitly note the scheduling policies that are relevant for the v2 'cpu' controller. michael kerrisk document the use of 'cgroup_no_v1=named' to disable v1 named hierarchies this feature was added in linux 5.0. michael kerrisk [mike weilgart] complete partial sentence re kernel boot options and 'nsdelegate' https://bugzilla.kernel.org/show_bug.cgi?id=201029 michael kerrisk reframe the text on delegation to include more details about cgroups v1 michael kerrisk [leah hanson] rework discussion of writing to cgroup.type file in particular, it is possible to write "threaded" to a cgroup.type file if the current type is "domain threaded". previously, the text had implied that this was not possible. michael kerrisk [balbir singh, marcus gelderie] soften the discussion about delegation in cgroups v1 balbir pointed out that v1 delegation was not an accidental feature. epoll.7 michael kerrisk introduce the terms "interest list" and "ready list" michael kerrisk consistently use the term "interest list" rather than "epoll set" michael kerrisk reformat q&a list michael kerrisk note that edge-triggered notification wakes up only one waiter note a useful performance benefit of epollet: ensuring that only one of multiple waiters (in epoll_wait()) is woken up when a file descriptor becomes ready. michael kerrisk expand the discussion of the implications of file descriptor duplication in particular, note that it may be difficult for an application to know about the existence of duplicate file descriptors. feature_test_macros.7 michael kerrisk [andreas westfeld] add more detail on why ftms must be defined before including any header inotify.7 michael kerrisk [paul millar] note enotdir error that can occur for in_onlydir note enotdir error that occurs when requesting a watch on a nondirectory with in_onlydir. ip.7 bert hubert ip_recvttl error fixed i need to get the ttl of udp datagrams from userspace, so i set the ip_recvttl socket option. and as promised by ip.7, i then get ip_ttl messages from recvfrom. however, unlike what the manpage promises, the ttl field gets passed as a 32 bit integer. man.7 michael kerrisk see also: remove mdoc.samples(7) mount_namespaces.7 michael kerrisk see also: add findmnt(8) namespaces.7 michael kerrisk list factors that may pin a namespace into existence various factors may pin a namespace into existence, even when it has no member processes. michael kerrisk [tycho kirchner] briefly explain why cap_sys_admin is needed to create nonuser namespaces michael kerrisk mention ioctl(2) in discussion of namespaces apis michael kerrisk see also: add pam_namespace(8) pid_namespaces.7 michael kerrisk clarify the semantics for the adoption of orphaned processes because of setns() semantics, the parent of a process may reside in the outer pid namespace. if that parent terminates, then the child is adopted by the "init" in the outer pid namespace (rather than the "init" of the pid namespace of the child). michael kerrisk note a detail of /proc/pid/ns/pid_for_children behavior after clone(clone_newpid), /proc/pid/ns/pid_for_children is empty until the first child is created. verified by experiment. michael kerrisk note that a process can do unshare(clone_newpid) only once sched.7 michael kerrisk [eugene syromyatnikov] in the kernel source sched_other is actually called sched_normal michael kerrisk see also: add ps(1) and top(1) michael kerrisk see also: add chcpu(1), lscpu(1) signal.7 michael kerrisk [robin kuzmin] clarify that sigsuspend() and pause() suspend the calling *thread* helge deller add signal numbers for parisc michael kerrisk unify signal lists into a signal table that embeds standards info having the signals listed in three different tables reduces readability, and would require more table splits if future standards specify other signals. michael kerrisk reorder the architectures in the signal number lists x86 and arm are the most common architectures, but currently are in the second subfield in the signal number lists. instead, swap that info with subfield 1, so the most common architectures are first in the list. michael kerrisk place signal numbers in a separate table the current tables of signal information are unwieldy, as they try to cram in too much information. michael kerrisk insert standards info into tables michael kerrisk see also: add clone(2) socket.7 michael kerrisk refer reader to unix(7) for information on so_passsec michael kerrisk see also: add address_families(7) socket.7 unix.7 michael kerrisk move text describing so_peercred from socket(7) to unix(7) this is, afaik, an option specific to unix domain sockets, so place it in unix(7). tcp.7 udp.7 michael kerrisk add a reference to socket(7) noting existence of further socket options unix.7 michael kerrisk enhance the description of scm_rights the existing description is rather thin. more can be said. michael kerrisk there is a limit on the size of the file descriptor array for scm_rights the limit is defined in the kernel as scm_max_fd (253). michael kerrisk rework so_peercred text for greater clarity michael kerrisk [felipe gasper] clarify so_passcred behavior michael kerrisk explicitly note that so_passcred provides scm_credentials messages michael kerrisk if the buffer to receive scm_rights fds is too small, fds are closed michael kerrisk one must send at least one byte of real data with ancillary data michael kerrisk ancillary data forms a barrier when receiving on a stream socket michael kerrisk when sending ancillary data, only one item of each type may be sent michael kerrisk improve wording describing socket option argument/return values michael kerrisk clarify treatment of incoming ancillary data if 'msg_control' is null michael kerrisk note behavior if buffer to receive ancillary data is too small michael kerrisk fix a minor imprecision in description of scm_credentials michael kerrisk refer reader to socket(7) for information about so_peek_off user_namespaces.7 michael kerrisk rework terminology describing ownership of nonuser namespaces prefer the word "owns" rather than "associated with" when describing the relationship between user namespaces and non-user namespaces. the existing text used a mix of the two terms, with "associated with" being predominant, but to my ear, describing the relationship as "ownership" is more comprehensible. vdso.7 helge deller fix parisc gateway page description ld.so.8 michael kerrisk [florian weimer, david newall] document the --preload command-line option added in glibc 2.30 michael kerrisk note delimiters for 'list' in --audit and --inhibit-rpath michael kerrisk place options in alphabetical order michael kerrisk ld_preload-ed objects are added to link map in left-to-right order zdump.8 paul eggert sync from tzdb upstream zic.8 paul eggert sync from tzdb upstream ==================== changes in man-pages-5.01 ==================== released: 2019-05-09, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: abhinav upadhyay andreas korb anisse astier brice goglin carlos o'donell dr. jürgen sauermann egmont koblinger elias benali elliot hughes florian weimer hugues evrard jakub nowak jakub wilk keegan saunders lucas werkmeister marcus huewe michael kerrisk michael witten seth troisi slavomir kaslev vincent lefevre wladimir mutel apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- tsearch.3 florian weimer [michael kerrisk] document the twalk_r() function added in glibc 2.30 new and changed links --------------------- twalk_r.3 michael kerrisk new link to twalk(3) page changes to individual pages --------------------------- accept.2 michael kerrisk note that 'addrlen' is left unchanged in the event of an error see http://austingroupbugs.net/view.php?id=836. bpf.2 michael kerrisk update kernel version info for jit compiler clone.2 michael kerrisk [jakub nowak] clone_child_settid has effect before clone() returns *in the child* clone_child_settid may not have had effect by the time clone() returns in the parent, which could be relevant if the clone_vm flag is employed. the relevant kernel code is in schedule_tail(), which is called in ret_from_fork() in the child. see https://bugzilla.kernel.org/show_bug.cgi?id=203105 execve.2 exec.3 michael kerrisk [dr. jürgen sauermann] consistently use the term 'pathname' (not 'path') execve.2 michael kerrisk note that stack+environ size is also limited to 3/4 of _stk_lim in fs/exec.c::prepare_arg_pages(), we have: limit = _stk_lim / 4 * 3; limit = min(limit, bprm->rlim_stack.rlim_cur / 4); michael kerrisk [dr. jürgen sauermann] see also: refer to exec(3) (rather than execl(3)) pipe.2 michael kerrisk note that 'pipefd' is left unchanged in the event of an error see http://austingroupbugs.net/view.php?id=467. sched_setaffinity.2 michael kerrisk [brice goglin] correct details of return value of sched_getaffinity() syscall setfsgid.2 michael kerrisk rewrite for improved clarity and defer to setfsuid() for details rewrite for improved clarity and defer to setfsuid(2) for the rationale of the fsgid rather than repeating the same details in this page. setfsuid.2 michael kerrisk rewrite for improved clarity and to hint history more explicitly the current text reads somewhat clumsily. rewrite it to introduce the euid and fsuid in parallel, and more clearly hint at the historical rationale for the fsuid, which is detailed lower in the page. socketpair.2 michael kerrisk clarify that 'sv' is left unchanged in the event of an error see also http://austingroupbugs.net/view.php?id=483. splice.2 slavomir kaslev eagain can occur when called on nonblocking file descriptors syscalls.2 michael kerrisk [andreas korb] remove crufty text about i386 syscall dispatch table the removed text long ago ceased to be accurate. nowadays, the dispatch table is autogenerated when building the kernel (via the kernel makefile, arch/x86/entry/syscalls/makefile). tee.2 slavomir kaslev eagain can occur when called on nonblocking file descriptors fopen.3 elliot hughes explain bsd vs glibc "a+" difference where is the initial read position for an "a+" stream? posix leaves this unspecified. most bsd man pages are silent, and macos has the ambiguous "the stream is positioned at the end of the file", not differentiating between reads and writes other than to say that fseek(3) does not affect writes. glibc's documentation explicitly specifies that the initial read position is the beginning of the file. mallinfo.3 elliott hughes further discourage use of mallinfo() the bugs section already explains why you need to be cautious about using mallinfo, but given the number of bug reports we see on android, it seems not many people are reading that far. call it out up front. malloc_trim.3 carlos o'donell update trimming information since glibc 2.8, commit 68631c8eb92, the malloc_trim function has iterated over all arenas and free'd back to the os all page runs that were free. this allows an application to call malloc_trim to consolidate fragmented chunks and free back any pages it can to potentially reduce rss usage. posix_memalign.3 elliot hughes some functions set errno true of bionic, glibc, and musl. (i didn't check elsewhere.) resolver.3 michael kerrisk [wladimir mutel] mention that some functions set 'h_errno' stdarg.3 michael kerrisk [vincent lefevre] remove the notes section describing the ancient varargs macros stdarg.h is now 30 years old, and gcc long ago (2004) ceased to implement . there seems little value in keeping this text. see https://bugzilla.kernel.org/show_bug.cgi?id=202907 michael kerrisk [egmont koblinger] add a note that "..." in function signature means a variadic function egmont suggested adding this, because the string "..." appears at several other points in the page, but just to indicate that some text is omitted from example code. strerror.3 jakub wilk don't discuss buffer size for strerror_l() unlike strerror_r(), strerror_l() doesn't take buffer length as an argument. strtol.3 strtoul.3 jakub wilk see also: add strtoimax(3), strtoumax(3) sysconf.3 michael kerrisk [hugues evrard] clearly note that _sc_pagesize and _sc_page_size are synonyms tsearch.3 florian weimer do not use const arguments in twalk() callback the const specifier is not part of the prototype (it only applies to the implementation), so showing it here confuses the reader. michael kerrisk synopsis: add missing definition of 'visit' type michael kerrisk reformat twalk() and twalk_r() prototypes for easier readability console_codes.4 jakub wilk document that \e[1;n] and \e[2;n] support 16 colors source: setterm_command() in drivers/tty/vt/vt.c elf.5 michael kerrisk [keegan saunders] a data segment does not have pf_x proc.5 michael witten [anisse astier] add missing inode field to /proc/net/unix hostname.7 florian weimer hostaliases/search path processing is dns-specific other nss modules do not necessarily honor these settings. inode.7 michael kerrisk note that timestamp fields measure time starting at the epoch michael kerrisk timestamp fields are structures that include a nanosecond component michael kerrisk add references to execve(2) to describe set-uid/set-gid behaviors ==================== changes in man-pages-5.02 ==================== released: 2019-08-02, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alan stern alexey izbyshev amir goldstein cyrill gorcunov eric sanchis eugene syromyatnikov finn o'leary florian weimer g. branden robinson guillaume laporte jakub wilk jan kara kumar chaudhary, naveen mark wielaard matthew bobrowski matthew kenigsberg matthias hertel michael kerrisk michal sekletar oleg nesterov palmer dabbelt petr vaněk sami kerola shawn landden thorsten glaser tobias klauser tomas skäre yang xu apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- fanotify.7 fanotify_init.2 fanotify_mark.2 matthew bobrowski [amir goldstein, jan kara] document fan_report_fid and directory modification events vdso.7 tobias klauser [palmer dabbelt] document vdso for riscv renamed pages ------------- sysvipc.7 svipc(7) is renamed to sysvipc(7). the name sysvipc is a bit more natural, and is the name used in /proc/sysvipc. new and changed links --------------------- svipc.7 michael kerrisk add old name of sysvipc(7) page as a link global changes -------------- various pages michael kerrisk change reference to svipc(7) to sysvipc(7) changes to individual pages --------------------------- pldd.1 g. branden robinson [michael kerrisk] document glibc's unbreakage of tool after a longstanding breakage, pldd now works again (glibc 2.30). bpf.2 michael kerrisk correct kernel version for jit support on s390 chdir.2 michael kerrisk add enotdir error for fchdir() execve.2 michael kerrisk [eugene syromyatnikov] since linux 5.1, the limit on the #! line is 255 chars (rather than 127) shawn landden [michael kerrisk] add more detail about shebangs michael kerrisk linux is not alone in ignoring the set-uid and set-gid bits for scripts mount.2 michael kerrisk errors: add a couple of einval errors for ms_move michael kerrisk see also: add chroot(2) and pivot_root(2) mprotect.2 mark wielaard pkey_mprotect() acts like mprotect() if pkey is set to -1, not 0 mprotect.2 pkey_alloc.2 mark wielaard [florian weimer] _gnu_source is required for the pkey functions. pivot_root.2 michael kerrisk errors: einval occurs if 'new_root' or its parent has shared propagation michael kerrisk 'new_root' must be a mount point it appears that 'new_root' may not have needed to be a mount point on ancient kernels, but already in linux 2.4.5 this changed. michael kerrisk 'put_old' can't be a mount point with ms_shared propagation michael kerrisk see also: add mount(2) poll.2 michael kerrisk [alan stern] note that poll() equivalent code for ppoll() is not quite equivalent prctl.2 yang xu [cyrill gorcunov] correct some details for pr_set_timerslack setxattr.2 finn o'leary [michael kerrisk] add erange to 'errors' section tkill.2 michael kerrisk glibc 2.30 provides a wrapper for tgkill() dlopen.3 michael kerrisk clarify the rules for symbol resolution in a dlopen'ed object the existing text wrongly implied that symbol look up first occurred in the object and then in main, and did not mention whether dependencies of main where used for symbol resolution. michael kerrisk clarify when an executable's symbols can be used for symbol resolution the --export-dynamic linker option is not the only way that main's global symbols may end up in the dynamic symbol table and thus be used to satisfy symbol reference in a shared object. a symbol may also be placed into the dynamic symbol table if ld(1) notices a dependency in another object during the static link. michael kerrisk an object opened with rtld_local can be promoted to rtld_global michael kerrisk note that symbol use might keep a dlclose'd object in memory michael kerrisk on dlclose(), destructors are called when reference count falls to 0 michael kerrisk make it clear that rtld_nodelete also affects global variables michael kerrisk clarify that constructors are called only when library is first loaded exec.3 matthew kenigsberg explain function groupings i've found the exec man page quite difficult to read when trying to find the behavior for a specific function. since the names of the functions are inline and the order of the descriptions isn't clear, it's hard to find which paragraphs apply to each function. i thought it would be much easier to read if the grouping based on letters is stated. getutent.3 michael kerrisk [thorsten glaser] fix missing include file in example see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=932382 on_exit.3 michael kerrisk [sami kerola] stack variables may be out of scope when exit handler is invoked strcat.3 michael kerrisk [eric sanchis] fix off-by-one error in example code cpuid.4 michael kerrisk see also: add cpuid(1) elf.5 michael kerrisk see also: add ld.so(8) proc.5 michael kerrisk correct description of /proc/pid/status 'shdpnd' and 'sigpnd' fields these fields are signal masks, not counters. michael kerrisk clarify that various mask fields in /proc/pid/status are in hexadecimal capabilities.7 michael kerrisk add a note about using strace on binaries that have capabilities michael kerrisk add pivot_root(2) to cap_sys_admin list michael kerrisk cap_fowner also allows modifying user xattrs on sticky directories cgroup_namespaces.7 michael kerrisk some wording fixes to improve clarity michael kerrisk in the example shell session, give second shell a different prompt credentials.7 michael kerrisk note that /proc/pid/status shows a process's credentials michael kerrisk see also: add tcgetsid(3) fanotify.7 matthew bobrowski reword fan_report_fid data structure inclusion semantics michael kerrisk clarify logic in estale check michael kerrisk reorder text in example michael kerrisk reformat program output to fit in 80 columns mount_namespaces.7 michael kerrisk clarify implications for other ns if mount point is removed in one ns if a mount point is deleted or renamed or removed in one mount namespace, this will cause an object that is mounted at that location in another mount namespace to be unmounted (as verified by experiment). this was implied by the existing text, but it is better to make this detail explicit. michael kerrisk see also: add pivot_root(2), pivot_root(8) namespaces.7 michael kerrisk note initial values of hostname and domainname in a new uts namespace sched.7 michael kerrisk see also: add pthread_getschedparam(3) signal.7 michal sekletar [oleg nesterov, michael kerrisk] clarify that siginfo_t isn't changed on coalescing michael kerrisk various fields in /proc/pid/status show signal-related information michael kerrisk add subsection on queuing and delivery semantics for standard signals socket.7 michael kerrisk select()/poll()/epoll honor so_rcvlowat since linux 2.6.28 unix.7 michael kerrisk note scm_rights interaction with rlimit_nofile if the file descriptors received in scm_rights would cause the process to its exceed rlimit_nofile limit, the excess fds are discarded. user_namespaces.7 michael kerrisk describe the effect of file-related capabilities inside user namespaces michael kerrisk describe how kernel treats uids/gids when a process accesses files vdso.7 tobias klauser mention removal of blackfin port in linux 4.17 ld.so.8 michael kerrisk [matthias hertel] note some further details of secure-execution mode note some further details of the treatment of environment variables in secure execution mode. in particular (as noted by matthias hertel), note that ignored environment variables are also stripped from the environment. furthermore, there are some other variables, not used by the dynamic linker itself, that are also treated in this way (see the glibc source file sysdeps/generic/unsecvars.h). ==================== changes in man-pages-5.03 ==================== released: 2019-10-11, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam borowski aleksa sarai alexey budankov amir goldstein andrew clayton carlos o'donell christian brauner christopher m. riedl daniel colascione dave carroll dave chinner дилян палаузов dmitry v. levin don brace eponymous alias eric biggers eric w. biederman florian weimer florin blanaru gilbert wu ingo schwarze jakub wilk kevin barnett marko myllynen matti moell matti möll matt perricone michael kerrisk mike frysinger murthy bhat nikola forró nilsocket paul wise philipp wendler raphael moreira zinsly rasmus villemoes reid priedhorsky rick stanley rob landley scott benesh scott teel shawn anastasio simone piccardi vincent lefevre yang xu apologies if i missed anyone! new and rewritten pages ----------------------- pidfd_open.2 michael kerrisk [christian brauner, florian weimer, daniel colascione] new page documenting pidfd_open(2) pidfd_send_signal.2 michael kerrisk [florian weimer, christian brauner] new page documenting pidfd_send_signal(2) pivot_root.2 michael kerrisk [eric w. biederman, reid priedhorsky, philipp wendler] this page has been completely rewritten, adding a lot of missing details (including the use of pivot_root(".", ".")) and an example program. in addition, the text prevaricating on whether or not pivot_root() might change the root and current working directories has been eliminated, and replaced with a simple description of the behavior of the system call, which has not changed for 19 years, and will not change in the future. many longstanding errors in the old version of the page have also been corrected. ipc_namespaces.7 michael kerrisk new page with content migrated from namespaces(7) uts_namespaces.7 michael kerrisk new page with content migrated from namespaces(7) newly documented interfaces in existing pages --------------------------------------------- clone.2 christian brauner, michael kerrisk document clone_pidfd add an entry for clone_pidfd. this flag is available starting with kernel 5.2. if specified, a process file descriptor ("pidfd") referring to the child process will be returned in the ptid argument. fanotify_mark.2 jakub wilk document fan_move_self ptrace.2 dmitry v. levin [michael kerrisk] document ptrace_get_syscall_info regex.3 rob landley document reg_startend new and changed links --------------------- res_nclose.3 michael kerrisk add new link to resolver.3 global changes -------------- various pages michael kerrisk see also: correct list order various pages michael kerrisk remove section number from references to function in its own page various pages michael kerrisk errors: correct alphabetical order changes to individual pages --------------------------- localedef.1 marko myllynen describe recently added options describe few recently added options (present in glibc-2.29). clone.2 michael kerrisk see also: add pidfd_open(2) copy_file_range.2 amir goldstein [dave chinner] kernel v5.3 updates fanotify_mark.2 jakub wilk add kernel version numbers for some fan_* constants getdomainname.2 michael kerrisk add mention of uts namespaces gethostname.2 michael kerrisk [jakub wilk] mention uts namespaces io_submit.2 matti moell [matti möll] fix kernel version numbers for 'aio_rw_flags' flags kill.2 michael kerrisk see also: add pidfd_send_signal(2) mmap.2 nikola forró fix einval conditions since introduction of map_shared_validate, in case flags contain both map_private and map_shared, mmap() doesn't fail with einval, it succeeds. the reason for that is that map_shared_validate is in fact equal to map_private | map_shared. mount.2 michael kerrisk [reid priedhorsky] describe the concept of "parent mounts" michael kerrisk notes: add subsection heading for /proc/[pid]/{mounts,mountinfo} michael kerrisk rework the text on mount namespaces a little eliminate the term "per-process namespaces" and add a reference to mount_namespaces(7). move_pages.2 yang xu [michael kerrisk] mark e2big as deprecated e2big was removed in 2.6.29, we should mark it as deprecated. perf_event_open.2 michael kerrisk [alexey budankov] see also: add documentation/admin-guide/perf-security.rst prctl.2 michael kerrisk clarify that pr_get_speculation_ctrl returns value as function result michael kerrisk clarify that pr_mce_kill_get returns value via function result michael kerrisk clarify that pr_get_fp_mode returns value as function result michael kerrisk return value: add some missing entries note success return for pr_get_speculation_ctrl and pr_get_fp_mode. rt_sigqueueinfo.2 michael kerrisk note that 'si_code' can't be specified as si_kernel michael kerrisk the rules for 'si_code' don't apply when sending a signal to oneself the restriction on what values may be specified in 'si_code' apply only when sending a signal to a process other than the caller itself. michael kerrisk rename 'uinfo' argument to 'info' this is more consistent with the naming in other pages that refer to a 'siginfo_t' structure. michael kerrisk see also: add pidfd_send_signal(2) sched_setaffinity.2 michael kerrisk return value: sched_getaffinity() syscall differs from the wrapper setns.2 mike frysinger fix clone_newns restriction info sigaction.2 michael kerrisk see also: add pidfd_send_signal(2) signalfd.2 andrew clayton, michael kerrisk note about interactions with epoll & fork statx.2 michael kerrisk [simone piccardi] clarify details of a case where an invalid 'mask' value may be rejected syscall.2 shawn anastasio add information for powerpc64 michael kerrisk [adam borowski, florin blanaru] update name of syscall instruction for riscv syscalls.2 michael kerrisk add fsconfig(), fsmount(), fsopen(), fspick(), move_mount(), open_tree() michael kerrisk [(), michael(), kerrisk(),] add new syscalls in 5.1 add io_uring_enter(), io_uring_register(), io_uring_setup(), and pidfd_send_signal(). michael kerrisk add clone3() and pidfd_open() uname.2 michael kerrisk replace reference to namespaces(7) with reference to uts_namespaces(7) errno.3 rasmus villemoes add some comments on eagain/ewouldblock and edeadlk/edeadlock fexecve.3 michael kerrisk [simone piccardi] enosys occurs only if the kernel provides no execveat() syscall michael kerrisk [simone piccardi] errors: add enoent getauxval.3 raphael moreira zinsly add new cache geometry entries printf.3 vincent lefevre add detail on the first digit with the %e format pthread_setcancelstate.3 pthreads.7 signal-safety.7 carlos o'donell describe issues with cancellation points in signal handlers strtok.3 michael kerrisk [eponymous alias] correct description of use of 'saveptr' argument in strtok_r() michael kerrisk [eponymous alias] the caller should not modify 'saveptr' between strtok_r() calls michael kerrisk add portability note for strtok_r() '*saveptr' value on some implementations, '*saveptr' must be null on first call to strtok_r(). smartpqi.4 murthy bhat [don brace, kevin barnett, matt perricone, scott benesh] add sysfs entries gilbert wu [don brace, kevin barnett, matt perricone, scott benesh] add module param expose ld first dave carroll [don brace, kevin barnett, matt perricone, scott benesh] add module param to hide vsep core.5 paul wise explain the new situation with argument splitting things changed in linux v5.3-rc3 commit 315c69261dd3 from splitting after template expansion to splitting beforehand. resolv.conf.5 nikola forró update information about search list since glibc 2.26, the number of domains in the search list is no longer limited. man-pages.7 michael kerrisk relocate and enhance the text on semantic newlines michael kerrisk [paul wise] paragraphs should not be separated by blank lines mount_namespaces.7 michael kerrisk explain how a namespace's mount point list is initialized provide a more detailed explanation of the initialization of the mount point list in a new mount namespace. michael kerrisk [eric w. biederman] clarify description of "less privileged" mount namespaces michael kerrisk see also: refer to example in pivot_root(2) michael kerrisk [eric w. biederman] it may be desirable to disable propagation after creating a namespace after creating a new mount namespace, it may be desirable to disable mount propagation. give the reader a more explicit hint about this. mq_overview.7 sysvipc.7 michael kerrisk adjust references to namespaces(7) to ipc_namespaces(7) namespaces.7 michael kerrisk remove content migrated to new ipc_namespaces(7) page michael kerrisk remove content migrated to uts_namespaces(7) michael kerrisk include manual page references in the summary table of namespace types make the page more compact by removing the stub subsections that list the manual pages for the namespace types. and while we're here, add an explanation of the table columns. operator.7 michael kerrisk [rick stanley] prefix and postfix ++/-- have different precedences harbison and steele also agree on this. signal.7 michael kerrisk enhance the text on process-directed and thread-directed signals clone(2) has a good description of these concepts; borrow from it liberally. michael kerrisk see also: add pidfd_send_signal(2) user_namespaces.7 michael kerrisk improve explanation of meaning of ownership of nonuser namespaces ==================== changes in man-pages-5.04 ==================== released: 2019-11-19, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: andrew price christian brauner florian weimer jakub wilk jan kara jann horn kenigbolo meya stephen marko myllynen michael kerrisk mikael magnusson robert edmonds silviu popescu torin carey witold baryluk yang xu apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- clone.2 michael kerrisk [christian brauner, jakub wilk] document clone3() wait.2 michael kerrisk add p_pidfd for waiting on a child referred to by a pid file descriptor bpf-helpers.7 michael kerrisk refresh against kernel v5.4-rc7 new and changed links --------------------- clone3.2 michael kerrisk new link to clone(2) changes to individual pages --------------------------- clone.2 michael kerrisk rename arguments for consistency with clone3() make the names of the clone() arguments the same as the fields in the clone3() 'args' struct: ctid ==> child_pid ptid ==> parent_tid newtls ==> tld child_stack ==> stack michael kerrisk consistently order paragraphs for clone_new* flags sometimes the descriptions of these flags mentioned the corresponding section 7 namespace manual page and then the required capabilities, and sometimes the order was the was the reverse. make it consistent. michael kerrisk [christian brauner, jann horn] example: allocate child's stack using mmap(2) rather than malloc(3) christian brauner suggested mmap(map_stack), rather than malloc(), as the canonical way of allocating a stack for the child of clone(), and jann horn noted some reasons why (map_stack exists elsewhere, and mmap() returns a page-aligned block of memory, which is useful if we want to set up a guard page at the end of the stack). michael kerrisk [christian brauner] tidy up the description of clone_detached the obsolete clone_detached flag has never been properly documented, but now the discussion clone_pidfd also requires mention of clone_detached. so, properly document clone_detached, and mention its interactions with clone_pidfd. michael kerrisk [christian brauner] give the introductory paragraph a new coat of paint change the text in the introductory paragraph (which was written 20 years ago) to reflect the fact that clone*() does more things nowadays. michael kerrisk remove wording that suggests clone_new* flags are for containers these flags are used for implementing many other interesting things by now. michael kerrisk remove various details that are already covered in namespaces pages remove details of uts, ipc, and network namespaces that are already covered in the corresponding namespaces pages in section 7. clone.2 proc.5 michael kerrisk adjust references to namespaces(7) adjust references to namespaces(7) to be references to pages describing specific namespace types. fallocate.2 andrew price add gfs2 to the list of punch hole-capable filesystems ioctl_iflags.2 michael kerrisk [robert edmonds] emphasize that fs_ioc_getflags and fs_ioc_setflags argument is 'int *' ioctl_list.2 michael kerrisk add reference to ioctl(2) see also section the referenced section lists various pages that document ioctls. mmap.2 michael kerrisk note that map_stack exists on some other systems michael kerrisk some rewording of the description of map_stack reword a little to allow for the fact that there are now *two* reasons to consider using this flag. pidfd_open.2 michael kerrisk note the waitid() use case for pid file descriptors michael kerrisk add a subsection header "use cases for pid file descriptors" michael kerrisk make it a little more explicit the clone_pidfd returns a pid fd pivot_root.2 michael kerrisk example: allocate stack using mmap() map_stack rather than malloc() quotactl.2 yang xu [jan kara] add some details about q_quotaon seccomp.2 cgroups.7 michael kerrisk switch to "considerate language" select.2 michael kerrisk pollin_set/pollout_set/pollex_set are now defined in terms of epoll* since kernel commit a9a08845e9acbd224e4ee466f5c1275ed50054e8, the equivalence between select() and poll()/epoll is defined in terms of the epoll* constants, rather than the poll* constants. wait.2 michael kerrisk waitid() can be used to wait on children in same process group as caller since linux 5.4, idtype == p_pgid && id == 0 can be used to wait on children in same process group as caller. michael kerrisk clarify semantics of waitpid(0, ...) as noted in kernel commit 821cc7b0b205c0df64cce59aacc330af251fa8f7, threads create an ambiguity: what if the calling process's pgid is changed by another thread while waitpid(0, ...) is blocked? so, clarify that waitpid(0, ...) means wait for children whose pgid matches the caller's pgid at the time of the call to waitpid(). getauxval.3 michael kerrisk [witold baryluk] clarify that at_base_platform and at_execfn return pointers to strings see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=942207 resolv.conf.5 florian weimer attempt clarify domain/search interaction the domain directive is historic at this point; it should not be used. netdevice.7 michael kerrisk [silviu popescu] small wording fix in description of siocgifconf siocgifconf returns "network layer" addresses (not "transport layer"). uts_namespaces.7 michael kerrisk add a little more detail on scope of uts namespaces ==================== changes in man-pages-5.05 ==================== released: 2020-02-09, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: adam borowski adrian reber andy lutomirski antonin décimo benjamin peterson brennan vincent christian brauner colin ian king cyril hrubis daniel colascione denys vlasenko dj delorie dmitry v. levin jakub wilk jashank jeremy joel fernandes john hubbard john jones joseph c. sible kevin sztern marko myllynen markus t metzger michael kerrisk michal hocko mike frysinger mike salvatore mikhail golubev nick shipp nikola forró peter gajdos petr vorel ponnuvel palaniyappan rich felker robin kuzmin samuel thibault sam varshavchik vegard nossum weitian li will yang xu yu jian wu apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- clone.2 adrian reber [christian brauner, michael kerrisk] add clone3() set_tid information michael kerrisk document clone_clear_sighand fcntl.2 joel fernandes [michael kerrisk] update manpage with new memfd f_seal_future_write seal memfd_create.2 joel fernandes update manpage with new memfd f_seal_future_write seal loop.4 yang xu document loop_set_block_size yang xu document loop_set_direct_io proc.5 michael kerrisk document /proc/sys/vm/unprivileged_userfaultfd changes to individual pages --------------------------- capget.2 michael kerrisk [yang xu] add missing details in eperm error for setting inheritable capabilities clone.2 michael kerrisk note that clone_thread causes similar behavior to clone_parent the introductory paragraphs note that "the calling process" is normally synonymous with the "the parent process", except in the case of clone_parent. the same is also true of clone_thread. christian brauner [michael kerrisk] mention that clone_parent is off-limits for inits michael kerrisk [colin ian king] add old einval error for aarch64 michael kerrisk errors: add einval for use of clone_parent by an init process futex.2 ponnuvel palaniyappan fix a bug in the example listen.2 michael kerrisk [peter gajdos] the 'somaxconn' default value has increased to 4096 modify_ldt.2 set_thread_area.2 andy lutomirski [markus t metzger] fix type of base_addr move_pages.2 john hubbard [michal hocko] remove enoent from the list of possible return values open.2 adam borowski no need for /proc to make an o_tmpfile file permanent in the example snippet, we already have the fd, thus there's no need to refer to the file by name. and, /proc/ might be not mounted or not accessible. michael kerrisk [joseph c. sible] in o_tmpfile example, describe alternative linkat() call this was already shown in an earlier version of the page, but adam borowski's patch replaced it with an alternative. probably, it is better to show both possibilities. perf_event_open.2 daniel colascione mention eintr for perf_event_open ptrace.2 denys vlasenko ptrace_event_stop does not always report sigtrap quotactl.2 michael kerrisk don't show numeric values of q_xquotaon xfs_quota_?dq_* flags the programmer should not need to care about the numeric values, and their inclusion is verbosity. yang xu [michael kerrisk] add einval error of q_xquotarm operation stime.2 michael kerrisk note that stime() is deprecated syscall.2 petr vorel [cyril hrubis] update feature test macro requirements sysctl.2 michael kerrisk this system call was removed in linux 5.5; adjust the page accordingly userfaultfd.2 yang xu [michael kerrisk] add eperm error cmsg.3 rich felker clarify alignment issues and correct method of accessing cmsg_data() from an email by rich felker: it came to my attention while reviewing possible breakage with move to 64-bit time_t that some applications are dereferencing data in socket control messages (particularly scm_timestamp*) in-place as the message type, rather than memcpy'ing it to appropriate storage. this necessarily does not work and is not supportable if the message contains data with greater alignment requirement than the header. in particular, on 32-bit archs, cmsghdr has size 12 and alignment 4, but struct timeval and timespec may have alignment requirement 8. michael kerrisk [rich felker] modify cmsg_data() example to use memcpy() see previous patch to this page for rationale exit.3 benjamin peterson [mike frysinger] use hex for the status mask ftime.3 michael kerrisk note that this function is deprecated getpt.3 samuel thibault remove mention of o_noctty the glibc implementation of getpt has actually never been setting malloc.3 vegard nossum clarify realloc() return value petr vorel remove duplicate _gnu_source console_codes.4 adam borowski document \e[90m to 97, 100 to 107 adam borowski \e[21m is now underline since 65d9982d7e523a1a8e7c9af012da0d166f72fc56 (4.17), it follows xterm rather than common sense and consistency, being the only command 1..9 where n+20 doesn't undo what n did. as libvte 0.51.90 got changed the same way, this behaviour will probably stay. adam borowski update \e[38m and \e[48m supported since cec5b2a97a11ade56a701e83044d0a2a984c67b4 (3.16). cgroups.7 michael kerrisk the v2 freezer controller was added in linux 5.2 michael kerrisk split discussion of cgroups.events file and v2 release notification in preparation for adding a description of the "frozen" key. michael kerrisk describe the cgroup.events "frozen" key michael kerrisk improve the discussion of the advantages of v2 release notification inotify.7 nick shipp merge late perror() into fprintf() in example code netlink.7 antonin décimo fix alignment issue in example packet.7 kevin sztern [michael kerrisk] add missing tpacket_auxdata field (tp_vlan_tpid) rtnetlink.7 antonin décimo ifa_index is an unsigned int tcp.7 michael kerrisk tcp_low_latency is ignored since linux 4.14 unix.7 michael kerrisk the pid sent with scm_credentials must match an existing process vsock.7 mikhail golubev [michael kerrisk] add missing structure element the structure 'struct sockaddr_vm' has additional element 'unsigned char svm_zero[]' since version v3.9-rc1. ldconfig.8 dj delorie document file filter and symlink pattern expectations ==================== changes in man-pages-5.06 ==================== released: 2020-04-11, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alejandro colomar aleksa sarai alexander miller andrea arcangeli andré almeida andrei vagin andrew micallef bart van assche benjamin peterson bjarni ingi gislason christian brauner devi r.k dmitry safonov eric biggers eric dumazet eric rannaud eugene syromyatnikov heinrich schuchardt helge deller jakub wilk jorgen hansen julia suvorova keno fischer krzysztof małysa marc lehmann matthew bobrowski matthew wilcox michael galassi michael kerrisk michal hocko mike christie mike frysinger pablo m. ronchi ricardo biehl pasquali stefan hajnoczi stefano garzarella thomas gleixner walter harms zack weinberg apologies if i missed anyone! new and rewritten pages ----------------------- openat2.2 aleksa sarai [michael kerrisk] document new openat2(2) syscall pidfd_getfd.2 michael kerrisk [christian brauner] new manual page documenting the pidfd_getfd() system call select.2 michael kerrisk rewrite description improve structure and readability, at the same time incorporating text and details that were formerly in select_tut(2). also move a few details in other parts of the page into description. michael kerrisk consolidate the discussion of pselect into a headed subsection michael kerrisk consolidate historical glibc pselect() details under one subhead michael kerrisk consolidate info on usleep() emulation in one place michael kerrisk place the discussion of the self-pipe technique in a headed subsection michael kerrisk note that fd_set() and fd_clr() do not return errors michael kerrisk remove details of historical #include requirements the posix situation has been the norm for a long time now, and including ancient details overcomplicates the page. michael kerrisk remove some ancient information about pre-posix types for 'timeout' select_tut.2 michael kerrisk eliminate duplication of info across select_tut.2 and select2 there was a lot of a duplication of info in synopsis, description return value, and see also. move all of the info to one place: the select(2) page. sysvipc.7 michael kerrisk rewrite this page as just a summary of the system v ipc apis all of the other details in this page have by now been moved into the relevant *ctl(2) pages. time_namespaces.7 michael kerrisk [andrei vagin, dmitry safonov, thomas gleixner] new page documenting time namespaces newly documented interfaces in existing pages --------------------------------------------- arch_prctl.2 keno fischer add arch_set_cpuid subcommand clock_getres.2 benjamin peterson document clock_tai michael kerrisk add clock_realtime_alarm and clock_boottime_alarm prctl.2 mike christie [michal hocko, michael kerrisk, bart van assche] document pr_setio_flusher/get_io_flusher setns.2 michael kerrisk document clone_newtime statx.2 eric biggers document statx_attr_verity unshare.2 michael kerrisk document clone_newtime socket.7 ricardo biehl pasquali, michael kerrisk add description of so_select_err_queue alejandro colomar [michael kerrisk] document so_timestampns global changes -------------- various pages michael kerrisk remove a few mentions of the ancient "linux libc" various pages michael kerrisk global formatting fix: disfavor nonstandard .tp indents in many cases, these don't improve readability, and (when stacked) they sometimes have the side effect of sometimes forcing text to be justified within a narrow column range. various pages michael kerrisk [christian brauner] fix clumsy wording around "nonnegative file descriptors" changes to individual pages --------------------------- clock_getres.2 helge deller [michael kerrisk] consecutive calls for clock_monotonic may return same value consecutive calls to clock_gettime(clock_monotonic) are guaranteed to return monotonic values, which means that they either return the *same* time value like the last call, or a later (higher) time value. eric rannaud dynamic posix clock devices can return other errors michael kerrisk improve description of cpu-time clocks michael kerrisk add an example program michael kerrisk clock_realtime_coarse is not settable michael kerrisk note that cpu-time clocks are not settable. explicitly note that clock_process_cputime_id and clock_process_cputime_id are not settable. michael kerrisk clarify that clock_tai is nonsettable michael kerrisk clarify that clock_monotonic is system-wide michael kerrisk errors: add einval for attempt to set a nonsettable clock michael kerrisk move text in bugs to notes the fact that clock_process_cputime_id and clock_process_cputime_id are not settable isn't a bug, since posix does allow the possibility that these clocks are not settable. michael kerrisk see also: add time_namespaces(7) clock_nanosleep.2 michael kerrisk clock_nanosleep() can also sleep against clock_tai michael kerrisk clock_nanosleep() also supports clock_boottime presumably (and from a quick glance at the source code) since linux 2.6.39, when clock_boottime was introduced. clock_nanosleep.2 timer_create.2 timerfd_create.2 michael kerrisk add various missing errors mostly verified by testing and reading the code. there is unfortunately quite a bit of inconsistency across api~s: clock_gettime clock_settime clock_nanosleep timer_create timerfd_create clock_boottime y n (einval) y y y clock_boottime_alarm y n (einval) y [1] y [1] y [1] clock_monotonic y n (einval) y y y clock_monotonic_coarse y n (einval) n (enotsup) n (enotsup) n (einval) clock_monotonic_raw y n (einval) n (enotsup) n (enotsup) n (einval) clock_realtime y y y y y clock_realtime_alarm y n (einval) y [1] y [1] y [1] clock_realtime_coarse y n (einval) n (enotsup) n (enotsup) n (einval) clock_tai y n (einval) y y n (einval) clock_process_cputime_id y n (einval) y y n (einval) clock_thread_cputime_id y n (einval) n (einval [2]) y n (einval) pthread_getcpuclockid() y n (einval) y y n (einval) [1] the caller must have cap_wake_alarm, or the error eperm results. [2] this error is generated in the glibc wrapper. connect.2 michael kerrisk [eric dumazet] update the details on af_unspec update the details on af_unspec and circumstances in which socket can be reconnected. dup.2 michael kerrisk see also: add pidfd_getfd(2) epoll_ctl.2 michael kerrisk various minor additions and clarifications epoll_wait.2 michael kerrisk a few minor additions and rewrites execve.2 michael kerrisk add a subhead for the discussion of effect on process attributes michael kerrisk explicitly note that argv[argc] == null in the new program michael kerrisk errors: enoent does not occur for missing shared libraries see http://sourceware.org/bugzilla/show_bug.cgi?id=12241. _exit.2 michael kerrisk clarify that raw _exit() system call terminates only the calling thread inotify_add_watch.2 michael kerrisk example: add reference to example in inotify(7) io_submit.2 julia suvorova add iocb_cmd_poll opcode lseek.2 michael kerrisk [matthew wilcox] errors: enxio can also occur seek_data in middle of hole at end of file madvise.2 michael kerrisk [andrea arcangeli] incorporate some (ancient) comments about madv_hugepage back in 2011, a mail from andrea arcangeli noted some details that i never got round to incorporating into the manual page. mmap.2 michael kerrisk add a subhead for the 'flags' argument michael kerrisk move some text hidden at the end of description to notes msgctl.2 michael kerrisk add information on permission bits (based on sysvipc(7) text) michael kerrisk copy information on 'msqid_ds' fields from sysvipc(7) open.2 michael kerrisk clarify that o_nofollow is relevant (only) for basename of 'pathname' aleksa sarai add references to new openat2(2) page michael kerrisk note einval error for invalid character in basename of 'pathname' pidfd_open.2 michael kerrisk mention pidfd_getfd(2) poll.2 michael kerrisk add an example program michael kerrisk mention epoll(7) in the introductory paragraph michael kerrisk improve description of efault error michael kerrisk fix description of enomem error select_tut.2 michael kerrisk adjust header file includes in example employ , rather than the historical header files. semctl.2 michael kerrisk copy information on 'semid_ds' fields from sysvipc(7) michael kerrisk add a reference to the example in shmop(2) michael kerrisk add information on permission bits (based on sysvipc(7) text) semget.2 michael kerrisk example: add an example program semop.2 michael kerrisk add a reference to the semop(2) example in shmop(2) shmctl.2 michael kerrisk add information on permission bits (based on sysvipc(7) text) michael kerrisk note that execute permission is not needed for shmat() shm_exec michael kerrisk copy information on 'shmid_ds' fields from sysvipc(7) michael kerrisk some small improvements to the description of the 'shmid_ds' structure shmget.2 michael kerrisk add a reference to the example in shmop(2) shmop.2 michael kerrisk example: add a pair of example programs add example programs demonstrating usage of shmget(2), shmat(2), semget(2), semctl(2), and semop(2). sigaction.2 signal.7 zack weinberg document kernel bugs in delivery of signals from cpu exceptions stat.2 michael kerrisk clarify definitions of timestamp fields in particular, make it clear that atime and mtime relate to the file *data*. syscalls.2 michael kerrisk add new linux 5.6 system calls michael kerrisk note that the 5.x series followed 4.20 timer_create.2 michael kerrisk timer_create(2) also supports clock_tai michael kerrisk mention clock_getres(2) for further details on the various clocks timerfd_create.2 michael kerrisk [thomas gleixner] note a case where timerfd_settime() can fail with ecanceled michael kerrisk [devi r.k, thomas gleixner] negative changes to clock_realtime may cause read() to return 0 michael kerrisk rework text for einval for invalid clock id michael kerrisk refer reader to clock_getres(2) for further details on the clocks unshare.2 michael kerrisk add clone_newcgroup and clone_newtime to example program exit.3 michael kerrisk [walter harms] small improvement to the discussion of 'status' argument ftok.3 michael kerrisk example: add a reference to the example in semget(2) getifaddrs.3 michael kerrisk [michael galassi] example: remove unneeded loop variable nl_langinfo.3 eugene syromyatnikov document era-related locale elements eugene syromyatnikov add information about am/pm time format locale elements eugene syromyatnikov mention the respective strftime(3) conversion specifications sem_init.3 michael kerrisk add references to example code in shm_open(3) and sem_wait(3) sem_post.3 michael kerrisk add a reference to code example code in shm_open(3) shm_open.3 michael kerrisk example: add some example programs strcmp.3 michael kerrisk add an example program michael kerrisk [andrew micallef, walter harms] rework text describing return value to be clearer michael kerrisk note that the comparison is done using unsigned char michael kerrisk see also: add ascii(7) strftime.3 eugene syromyatnikov [michael kerrisk] refer to the relevant nl_langinfo(3) items eugene syromyatnikov expand %e and %o description eugene syromyatnikov consistently document fall-back format string proc.5 mike frysinger clarify /proc/[pid]/cmdline mutability cgroups.7 michael kerrisk update list of cgroups v2 controllers update the list of cgroups v2 controllers (several controllers were missing). michael kerrisk add a subsection on cgroup v2 mount options and include 'nsdelegate' michael kerrisk document the cgroups v2 'memory_localevents' mount option michael kerrisk see also: add documentation/admin-guide/cgroup-v2.rst namespaces.7 michael kerrisk add time namespaces information michael kerrisk eliminate some superfluous info from display of /proc/pid/ns links path_resolution.7 aleksa sarai update to mention openat2(2) features socket.7 michael kerrisk note scm message types for so_timestamp and so_timestampns tcp.7 michael kerrisk see also: mention documentation/networking/ip-sysctl.txt time.7 michael kerrisk add small subsection on clocks and time namespaces unix.7 heinrich schuchardt correct example vsock.7 stefano garzarella [jorgen hansen, stefan hajnoczi] add vmaddr_cid_local description ==================== changes in man-pages-5.07 ==================== released: 2020-06-09, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: achilles gaikwad adhemerval zanella aleksa sarai alexander monakov alexander morozov alexopo seid amir goldstein andi kleen andrea galbusera arnd bergmann branden robinson brian geffon bruno haible chris lamb christian brauner dave hansen dave martin david adam devin j. pohly dmitry v. levin eric hopper eric sandeen eugene syromyatnikov fabien siron florian weimer gary perkins geoff clare goldwyn rodrigues heiko carstens heinrich schuchardt helge kreutzmann ian rogers idan katz jakub wilk jan kara jan moskyto matejka jason etherton jeff moyer john marshall jonny grant joseph c. sible jürgen sauermann kai mäkisara keno fischer kirill a. shutemov kirill smelkov kir kolyshkin léo stefanesco li xinhai lokesh gidra lukas czerner manfred spraul marco curreli marcus gelderie martin doucha matthew bobrowski michael kerrisk michal hocko nikola forró olivier gayot ondrej slamecka paul eggert peter schiffer peter wu petr vorel piotr caban ricardo castano richard cochran richard palethorpe russell king stefan puiu thierry lelegard thomas piekarski tobias stoeckmann urs thuermann vincent lefèvre vlad vrafaeli@msn.com walter harms will deacon yang shi yunqiang su apologies if i missed anyone! new and rewritten pages ----------------------- ioctl_fslabel.2 eric sandeen new page documenting filesystem get/set label ioctl(2) operations removed pages ------------- ioctl_list.2 michael kerrisk [heinrich schuchardt, eugene syromyatnikov] this page was first added more than 20 years ago. since that time it has seen hardly any update, and is by now very much out of date, as reported by heinrich schuchardt and confirmed by eugene syromyatnikov. as heinrich says: man-pages like netdevices.7 or ioctl_fat.2 are what is needed to help a user who does not want to read through the kernel code. if ioctl_list.2 has not been reasonably maintained since linux 1.3.27 and hence is not a reliable source of information, shouldn't it be dropped? my answer is, yes (but let's move a little info into ioctl(2)). newly documented interfaces in existing pages --------------------------------------------- adjtimex.2 arnd bergmann [richard cochran, michael kerrisk] document clock_adjtime(2) clock_getres.2 richard cochran [michael kerrisk] explain dynamic clocks clone.2 christian brauner, michael kerrisk document the clone3() clone_into_cgroup flag mremap.2 brian geffon, michael kerrisk [lokesh gidra] document mremap_dontunmap open.2 joseph c. sible [michael kerrisk] document fs.protected_fifos and fs.protected_regular prctl.2 dave martin add pr_spec_indirect_branch for speculation_ctrl prctls dave martin add pr_spec_disable_noexec for speculation_ctrl prctls dave martin add pr_pac_reset_keys (arm64) ptrace.2 joseph c. sible document ptrace_set_syscall proc.5 michael kerrisk document /proc/sys/fs/protected_regular michael kerrisk document /proc/sys/fs/protected_fifos michael kerrisk document /proc/sys/fs/aio-max-nr and /proc/sys/fs/aio-nr new and changed links --------------------- clock_adjtime.2 arnd bergmann new link to adjtimex(2) global changes -------------- various pages michael kerrisk retitle example section heading to examples examples appears to be the wider majority usage across various projects' manual pages, and is also what is used in the posix manual pages. various pages michael kerrisk correct bogus posix.1 standards names posix.1-2003 ==> posix.1-2001 tc1 posix.1-2004 ==> posix.1-2001 tc2 posix.1-2013 ==> posix.1-2008 tc1 posix.1-2016 ==> posix.1-2008 tc2 various pages michael kerrisk add section number in page cross-reference. various pages kir kolyshkin add missing commas in see also various pages michael kerrisk remove availability section heading in the few pages where this heading (which is "nonstandard" within man-pages) is used, it always immediately follows conforming to and generally contains information related to standards. remove the section heading, thus incorporating availability into conforming to. various pages michael kerrisk remove section number in page self-references various pages michael kerrisk put see also entries in alphabetical order various pages michael kerrisk place sh sections in standard order fix various pages that deviated from the norm described in man-pages(7). various "aio" pages michael kerrisk [andi kleen, jeff moyer] change uses of aio_context_t to io_context_t changes to individual pages --------------------------- bpf.2 peter wu update enum bpf_map_type and enum bpf_prog_type richard palethorpe change note on unprivileged access the kernel now allows calls to bpf() without cap_sys_admin under some circumstances. clone.2 michael kerrisk add kernel version numbers for clone_args fields michael kerrisk combine separate notes sections close.2 michael kerrisk [lukas czerner, peter schiffer, thierry lelegard] note behavior when close() happens in a parallel thread if one thread is blocked in an i/o system call on a file descriptor that is closed in another thread, then the blocking system call does not return immediately, but rather when the i/o operation completes. this surprises some people, but is longstanding behavior. connect.2 stefan puiu can return eacces because of selinux execve.2 michael kerrisk [eric hopper] changes to the "dumpable" flag may change ownership of /proc/pid files michael kerrisk improve/correct discussion of changes to dumpable flag during execve(2) the details were not quite accurate. defer to prctl(2) for the more complete picture. nikola forró clarify signal sent to the process on late failure michael kerrisk see also: add capabilities(7) fanotify_init.2 amir goldstein [matthew bobrowski] move out of place entry fan_report_fid it was inserted in the middle of the fan_class_ multi flags bit and broke the multi flag documentation. michael kerrisk [alexander morozov, amir goldstein, jan kara] remove mention of fan_q_overflow as an input value in 'mask' see https://bugzilla.kernel.org/show_bug.cgi?id=198569. amir goldstein [jan kara, matthew bobrowski] clarification about fan_event_on_child and new events amir goldstein [jan kara, matthew bobrowski] clarification about fan_mark_mount and fan_report_fid getdents.2 petr vorel [michael kerrisk] mention glibc support for getdents64() support was added in glibc 2.30. chris lamb correct linux_dirent definition in example code it is "unsigned long" earlier up in the file gettid.2 michael kerrisk [joseph c. sible] document header file and feature test macro requirements for gettid() ioctl.2 michael kerrisk see also: add ioctl_fslabel(2) michael kerrisk remove mentions of ioctl_list(2) michael kerrisk move subsection on "ioctl structure" from ioctl_list(2) to ioctl(2) io_setup.2 michael kerrisk tweak description of /proc/sys/fs/aio-max-nr mbind.2 li xinhai [michael kerrisk] remove note about mpol_mf_strict been ignored mmap.2 michael kerrisk [heinrich schuchardt] don't mark map_anon as deprecated move_pages.2 yang shi [michal hocko] returning positive value is a new error case mremap.2 michael kerrisk remove mention of "segmentation fault" in efault text "segmentation fault" (sigsegv) is not exactly the same thing as efault. michael kerrisk reorder some paragraphs in notes michael kerrisk move a paragraph from description to notes msgctl.2 michael kerrisk correct description of 'msg_ctime' field verified by inspecting kernel source. nfsservctl.2 michael kerrisk see also: add nfsd(7) open.2 michael kerrisk some '*at' apis have functionality that isn't in conventional apis note that another reason to use the *at() apis is to access 'flags' functionality that is not available in the corresponding conventional apis. michael kerrisk add a few more apis to list in "rationale for openat()..." there have been a few more dirfd apis added in recent times. michael kerrisk explain ways in which a 'directory file descriptor' can be obtained michael kerrisk add openat2() to list of apis that take a 'dirfd' argument openat2.2 michael kerrisk [aleksa sarai] various changes after feedback from aleksa sarai poll.2 michael kerrisk add license to example program prctl.2 dave martin sort prctls into alphabetical order dave martin clarify that prctl can apply to threads the current synopsis for prctl(2) misleadingly claims that prctl operates on a process. rather, some (in fact, most) prctls operate dave martin [dave hansen] document removal of intel mpx prctls dave martin fix mis-description of thread id values in procfs dave martin work around bogus constant "maxsig" in pr_set_pdeathsig michael kerrisk add reference to proc(5) for /proc/self/task/[tid]/comm dave martin [michael kerrisk] add health warning dave martin clarify the unsupported hardware case of einval rename.2 michael kerrisk see also: add rename(1) s390_runtime_instr.2 heiko carstens [eugene syromyatnikov, michael kerrisk] document signum argument behavior change document that the signum argument is ignored in newer kernels, but that user space should pass a valid real-time signal number for backwards compatibility. semctl.2 michael kerrisk [manfred spraul] correct description of sem_ctime field semget.2 michael kerrisk add license to example program shmctl.2 michael kerrisk correct 'shm_ctime' description shmop.2 michael kerrisk add license to example programs statfs.2 michael kerrisk [david adam] add smb2 constant to filesystem types list syscall.2 dave martin [will deacon] arm64: fix syscall number register size dave martin [russell king] arm: use real register names for arm/oabi sysfs.2 michael kerrisk see also: add proc(5) and sysfs(5) utimensat.2 goldwyn rodrigues immutable flag returns eperm linux kernel commit 337684a1746f "fs: return eperm on immutable inode" changed the return value of the utimensat(2) from -eacces to -eperm in case of an immutable flag. wait4.2 michael kerrisk update wait3() feature test macro requirements for changes in glibc 2.26 cexp2.3 michael kerrisk still not present in glibc 2.31 cmsg.3 michael kerrisk conforming to: note which cmsg_* apis are in current and upcoming posix dirfd.3 michael kerrisk see also: add openat(2) dlsym.3 alexander monakov extend discussion of null symbol values avoid implying that use of ifunc is the only way to produce a symbol with null value. give more scenarios how a symbol may get null value, but explain that in those scenarios dlsym() will fail with glibc's ld.so due to an implementation inconsistency. err.3 michael kerrisk examples: use exit_failure rather than 1 as exit status expm1.3 michael kerrisk the expm1() bogus underflow floating-point exception has been fixed see https://www.sourceware.org/bugzilla/show_bug.cgi?id=6778 michael kerrisk the bogus invalid floating-point exception bug has been fixed https://www.sourceware.org/bugzilla/show_bug.cgi?id=6814. fdim.3 michael kerrisk bugs: these functions did not set errno on some architectures https://www.sourceware.org/bugzilla/show_bug.cgi?id=6796 ftw.3 michael kerrisk glibc eventually fixed a regression in ftw_sln behavior for details, see: https://bugzilla.redhat.com/show_bug.cgi?id=1422736 http://austingroupbugs.net/view.php?id=1121 https://bugzilla.redhat.com/show_bug.cgi?id=1422736 getauxval.3 yunqiang su mips, at_base_platform passes isa level getdtablesize.3 michael kerrisk remove redundant statement that getdtablesize() is a library function malloc.3 michael kerrisk add 'reallocarray' in name michael kerrisk add versions section noting when reallocarray() was added to glibc newlocale.3 michael kerrisk [piotr caban] fix a valgrind issue in example program see https://bugzilla.kernel.org/show_bug.cgi?id=202977. nextafter.3 michael kerrisk since glibc 2.23, these functions do set errno see https://www.sourceware.org/bugzilla/show_bug.cgi?id=6799. posix_spawn.3 olivier gayot [adhemerval zanella] clarify by using name of steps rather than syscalls olivier gayot [adhemerval zanella] document implementation using clone() since glibc 2.24 olivier gayot [adhemerval zanella] document posix_spawn_usevfork added a few lines about posix_spawn_usevfork so that it appears clearly that since glibc 2.24, the flag has no effect. olivier gayot [adhemerval zanella] document the posix_spawn_setsid attribute pow.3 michael kerrisk bugs: pow() performance problem for some (rare) inputs has been fixed see https://sourceware.org/bugzilla/show_bug.cgi?id=13932 michael kerrisk several bugs in glibc's pow() implementation were fixed in glibc 2.16 see https://www.sourceware.org/bugzilla/show_bug.cgi?id=3866. michael kerrisk add a subheading to mark off historical bugs that are now fixed printf.3 tobias stoeckmann prevent signed integer overflow in example ptsname.3 bruno haible fix description of failure behaviour of ptsname_r() random.3 john marshall change "rand_max" tp "2^31-1" scalb.3 michael kerrisk these functions now correctly set errno for the edom and erange cases see https://www.sourceware.org/bugzilla/show_bug.cgi?id=6803 and https://www.sourceware.org/bugzilla/show_bug.cgi?id=6804 scalbln.3 michael kerrisk these functions now correctly set errno for the erange case see https://www.sourceware.org/bugzilla/show_bug.cgi?id=6803 scanf.3 michael kerrisk [jürgen sauermann] clarify that 'x' specifier allows a 0x/0x prefix in input string sem_getvalue.3 michael kerrisk [andrea galbusera] note that glibc's sem_getvalue() doesn't return einval errors see https://bugzilla.kernel.org/show_bug.cgi?id=204273 setlogmask.3 michael kerrisk note that log_upto() is included in the next posix release shm_open.3 michael kerrisk add license to example programs sincos.3 michael kerrisk the glibc implementation does now give edom for a domain error see https://www.sourceware.org/bugzilla/show_bug.cgi?id=15467 stdarg.3 michael kerrisk see also: add vprintf(3), vscanf(3), vsyslog(3) strcmp.3 michael kerrisk add license to example programs strftime.3 urs thuermann iso week number can be 52, add example y0.3 michael kerrisk these functions now correctly diagnose a pole error https://sourceware.org/bugzilla/show_bug.cgi?id=6807 michael kerrisk errno is now correctly set to erange on underflow https://www.sourceware.org/bugzilla/show_bug.cgi?id=6808 loop.4 michael kerrisk [vlad] 'lo_flags' is nowadays "r/w" see https://bugzilla.kernel.org/show_bug.cgi?id=203417 veth.4 devin j. pohly add a more direct example iproute2 allows you to specify the netns for either side of a veth interface at creation time. add an example of this to veth(4) so it doesn't sound like you have to move the interfaces in a separate step. core.5 michael kerrisk [jonny grant] mention 'sysctl -w' as a way of changing core_pattern setting michael kerrisk [jonny grant] note that not dumping core of an unreadable binary is a security measure michael kerrisk [jonny grant] explain that core_pattern %e is process/thread 'comm' value the 'comm' value is typically the same as the (possibly truncated) executable name, but may be something different. filesystems.5 michael kerrisk see also: add sysfs(5) and xfs(5) locale.5 michael kerrisk [helge kreutzmann] improve description of 'first_weekday' proc.5 michael kerrisk note kernel version for /proc/pid/smaps vmflags "wf" flag michael kerrisk add "um" and "uw" to vmflags in /proc/[pid]/smaps michael kerrisk add "mp" to vmflags in /proc/[pid]/smaps michael kerrisk note kernel version that removed /proc/pid/smaps vmflags "nl" flag ian rogers add "wf" to vmflags in /proc/[pid]/smaps michael kerrisk note kernel version for /proc/pid/smaps vmflags "dd" flag michael kerrisk add "sf" to vmflags in /proc/[pid]/smaps michael kerrisk [kirill a. shutemov] remove "mp" under vmflags in /proc/[pid]/smaps michael kerrisk [eric hopper] alert the reader that uid/gid changes can reset the "dumpable" attribute keno fischer fix an outdated note about map_files the restriction to cap_sys_admin was removed from map_files in 2015. michael kerrisk [helge kreutzmann] better explanation of some /proc/ide fields michael kerrisk task_comm_len limit includes the terminating '\0' clarify this detail in the discussion of /proc/[pid]/comm. michael kerrisk add a detail to /proc/[pid]/comm note the connection to the "%e" specifier in /proc/sys/kernel/core_pattern. securetty.5 michael kerrisk [helge kreutzmann] improve wording of .sh one-line description tzfile.5 michael kerrisk sync to 2020a tzdb release from https://www.iana.org/time-zones, version 2020a. michael kerrisk explain ut abbreviation ascii.7 michael kerrisk [helge kreutzmann] see also: fix sort order in entries bpf-helpers.7 michael kerrisk resync against kernel 5.7 cgroups.7 marcus gelderie mention cgroup.sane_behavior file the cgroup.sane_behavior file returns the hard-coded value "0" and is kept for legacy purposes. mention this in the man-page. michael kerrisk note the existence of the clone3() clone_into_cgroup flag credentials.7 michael kerrisk alert reader that uid/gid changes can affect process capabilities michael kerrisk changes to process uids/gids can effect the "dumpable" attribute michael kerrisk add a list of the apis that change a process's credentials fanotify.7 amir goldstein [jan kara, matthew bobrowski] fix fanotify_fid.c example michael kerrisk wrap some long lines in example program fanotify.7 fanotify_mark.2 amir goldstein [matthew bobrowski] clarify fan_ondir in output mask fan_ondir was an input only flag before introducing fan_report_fid. since the introduction of fan_report_fid, it can also be in output mask. hier.7 thomas piekarski [gary perkins] updating from fhs 2.3 to 3.0 see https://bugzilla.kernel.org/show_bug.cgi?id=206693 inotify.7 michael kerrisk [jason etherton] add missing #include in example program ip.7 michael kerrisk [martin doucha] note a few more valid 'protocol' values see https://bugzilla.kernel.org/show_bug.cgi?id=204981 michael kerrisk see also: add netdevice(7) man-pages.7 michael kerrisk rename example to examples michael kerrisk describe copyright section man-pages doesn't use copyright sections in manual pages, but various projects do. make some recommendations about placement of the section. michael kerrisk add reporting bugs section man-pages doesn't have a reporting bugs section in manual pages, but many other projects do. make some recommendations about placement of that section. michael kerrisk mention authors in summary section list although man-pages doesn't use authors sections, many projects do use an authors section in their manual pages, so mention it in man-pages to suggest some guidance on the position at which to place that section. mount_namespaces.7 michael kerrisk see also: add mount(8), umount(8) namespaces.7 michael kerrisk document /proc/sys/user/max_time_namespaces netlink.7 michael kerrisk [idan katz] update path for netlink_connector docs in kernel source tree michael kerrisk [fabien siron] note that netlink_sock_diag is preferred over netlink_inet_diag pid_namespaces.7 michael kerrisk note that /proc/sys/kernel/ns_last_pid is virtualized per pid ns michael kerrisk correct capability requirements for write to /proc/sys/kernel/ns_last_pid cap_sys_admin is needed in the user ns that owns the pid ns. rtnetlink.7 jan moskyto matejka [michael kerrisk] add missing rta_* attributes standards.7 michael kerrisk [geoff clare] add some more standards add: susv4 2016 edition, posix.1-2017, and susv4 2018 edition michael kerrisk remove mention of bogus "posix" names the terms posix.1-{2003,2004,2013,2016} were inventions of my imagination, as confirmed by consulting geoff clare of the open group. remove these names. symlink.7 michael kerrisk describe differences in the treatment of symlinks in the dirname describe differences in the treatment of symlinks in the dirname part of pathname. tcp.7 michael kerrisk [vrafaeli@msn.com] update info on tcp_syn_retries default value see https://bugzilla.kernel.org/show_bug.cgi?id=202885. user_namespaces.7 michael kerrisk [léo stefanesco] clarify that "system time" means "calendar time" xattr.7 achilles gaikwad add attr(1) as relevant page to see also ldconfig.8 florian weimer mention new default for --format in glibc 2.32 zdump.8 michael kerrisk [marco curreli, paul eggert] update to latest upstream tz release look under "latest version", which is 2020a. ==================== changes in man-pages-5.08 ==================== released: 2020-08-13, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alejandro colomar aleksa sarai alyssa ross andrew price andy lutomirski arkadiusz drabczyk benjamin peterson bjarni ingi gislason bruno haible carlos o'donell catalin marinas dan kenigsberg dave martin diogo miguel ferreira rodrigues florian weimer g. branden robinson geoff clare helge kreutzmann jakub wilk jeff layton john scott kumar kartikeya dwivedi michael kerrisk mike frysinger oleksandr kravchuk philip adams rich felker saikiran madugula stephen hemminger sven hoexter thomas bartelsmeier thomas piekarski victorm007@yahoo.com apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- prctl.2 dave martin add sve prctls (arm64) add documentation for the pr_sve_set_vl and pr_sve_get_vl prctls added in linux 4.15 for arm64. dave martin [catalin marinas] add tagged address abi control prctls (arm64) add documentation for the pr_set_tagged_addr_ctrl and pr_get_tagged_addr_ctrl prctls added in linux 5.4 for arm64. setns.2 michael kerrisk document the use of pid file descriptors with setns() starting with linux 5.8, setns() can take a pid file descriptor as an argument, and move the caller into or more of the namespaces of the thread referred to by that descriptor. capabilities.7 michael kerrisk document cap_bpf michael kerrisk add cap_perfmon symlink.7 aleksa sarai document magic links more completely global changes -------------- a few pages michael kerrisk use \` rather than ` \` produces better rendering in pdf. various pages michael kerrisk [geoff clare] use "\(ti" instead of "~" a naked tilde ("~") renders poorly in pdf. instead use "\(ti", which renders better in a pdf, and produces the same glyph when rendering on a terminal. various pages michael kerrisk [geoff clare] use "\(ha" rather than "^" in code this renders better in pdf. various pages mike frysinger drop "coding: utf-8" header this header is used inconsistently -- man pages are utf-8 encoded but not setting this marker. it's only respected by the man-db package, and seems a bit anachronistic at this point when utf-8 is the standard default nowadays. various pages mike frysinger trim leading blank comment line very few pages do this, so trim them. various pages mike frysinger use standard .\" comment style the \" comment produces blank lines. use the .\" that the vast majority of the codebase uses instead. various pages mike frysinger [g. branden robinson] various pages: drop t comment header historically, a comment of the following form at the top of a manual page was used to indicate too man(1) that the use of tbl(1) was required in order to process tables: '\" t however, at least as far back as 2001 (according to branden), man-db's man(1) automatically uses tbl(1) as needed, rendering this comment unnecessary. and indeed many existing pages in man-pages that have tables don't have this comment at the top of the file. so, drop the comment from those files where it is present. changes to individual pages --------------------------- ioctl_tty.2 michael kerrisk fix a confusing wording error in description of tiocsptlck iopl.2 thomas piekarski [victorm007@yahoo.com] updating description of permissions and disabling interrupts update description of permissions for port-mapped i/o set per-thread and not per-process. mention that iopl() can not disable interrupts since linux 5.5 anymore and is in general deprecated and only provided for legacy x servers. see https://bugzilla.kernel.org/show_bug.cgi?id=205317 keyctl.2 oleksandr kravchuk declare auth_key to fix a compilation error in example code lseek.2 andrew price list gfs2 support for seek_hole/seek_data mount.2 michael kerrisk errors: add einval for bind mount of mount namespace inode open.2 michael kerrisk say a bit more about what happens when 'mode' is wrongly omitted pidfd_open.2 michael kerrisk add the setns(2) use case for pid file descriptors michael kerrisk close the pidfd in example close the pid file descriptor in the example program, to hint to the reader that like every other kind of file descriptor, a pid fd should be closed. prctl.2 michael kerrisk the parent death signal is cleared on some credential changes see kernel/cred.c::commit_creds() in the linux 5.6 source code. seccomp.2 andy lutomirski improve x32 and nr truncation notes send.2 recv.2 alyssa ross add msg_iovlen posix note msg_iovlen is incorrectly typed (according to posix) in addition to msg_controllen, but unlike msg_controllen, this wasn't mentioned for msg_iovlen. setns.2 michael kerrisk example: use o_cloexec when opening namespace file descriptor michael kerrisk it is possible to setns() to the caller's current pid namespace the page currently incorrectly says that 'fd' must refer to a descendant pid namespace. however, 'fd' can also refer to the caller's current pid namespace. verified by experiment, and also comments in kernel/pid_namespace.c (linux 5.8-rc1). sync.2 jeff layton syncfs() now returns errors if writeback fails a patch has been merged for v5.8 that changes how syncfs() reports errors. change the sync() manpage accordingly. syscalls.2 michael kerrisk add faccessat2(), added in linux 5.8 sysctl.2 michael kerrisk glibc removed support for sysctl() starting in version 2.32 atoi.3 arkadiusz drabczyk explain disadvantages of atoi() michael kerrisk relocate bugs section michael kerrisk add notes section explaining 0 return value on error and note that this is not specified by posix. fread.3 arkadiusz drabczyk add example arkadiusz drabczyk explain that file position is moved after calling fread()/fwrite() corresponding manpage on freebsd already contains that information. getpt.3 posix_openpt.3 pts.4 michael kerrisk use the term "pseudoterminal multiplexor device" for /dev/ptmx let's use some consistent terminology for this device. posix_memalign.3 bruno haible clarify how to free the result of posix_memalign pthread_rwlockattr_setkind_np.3 carlos o'donell [kumar kartikeya dwivedi] clarify a pthread_rwlock_prefer_writer_np detail queue.3 alejandro colomar remove wrong code from example alejandro colomar comment out text for functions not in glibc (related: 6559169cac) pts.4 michael kerrisk remove notes on bsd pseudoterminals this information is already covered better in pty(7). no need to mention it again here. hosts.5 thomas bartelsmeier clarify capability for ipv6 outside of examples resolves https://bugzilla.kernel.org/show_bug.cgi?id=208279 proc.5 jakub wilk use "pwd -p" for printing cwd "/bin/pwd" happens to work with the gnu coreutils implementation, which has -p as the default, contrary to posix requirements. use "pwd -p" instead, which is shorter, easier to type, and should work everywhere. arkadiusz drabczyk inform that comm in /proc/pid/{stat,status} might also be truncated pgrep for example searches for a process name in /proc/pid/status resolv.conf.5 michael kerrisk [helge kreutzmann] clarify that ip6-bytestring was removed in 2.25 capabilities.7 dan kenigsberg clarify that cap_sys_nice relates to *lowering* the nice value saikiran madugula cap_sys_resource: add two more items for posix message queues cap_sys_resource also allows overriding /proc/sys/fs/mqueue/msg_max and /proc/sys/fs/mqueue/msgsize_max. michael kerrisk [dan kenigsberg] clarify wording around increasing process nice value michael kerrisk see also: add getpcaps(8) cgroups.7 cpuset.7 sven hoexter update kernel cgroup documentation references cgroups-v1/v2 documentation got moved to the "admin-guide" subfolder and converted from .txt files to .rst ip.7 michael kerrisk [stephen hemminger] remove mention of ipfw(4) which was in long obsolete ipchains project man-pages.7 michael kerrisk add some notes on generating optimal glyphs getting nice renderings of ^ ` and ~ requires special steps in the page source. pty.7 michael kerrisk explicitly mention config_legacy_ptys explicitly mention config_legacy_ptys, and note that it is disabled by default since linux 2.6.30. michael kerrisk relocate a paragraph to notes standards.7 michael kerrisk add an entry for posix.1-1988 michael kerrisk [geoff clare] correct various details in the explanation of xpg/posix/sus ld.so.8 florian weimer [michael kerrisk] list more places in which dynamic string tokens are expanded this happens for more than just dt_rpath/dt_runpath. arkadiusz drabczyk explain that empty entry in ld_library_path means cwd zic.8 michael kerrisk sync to 2020a tzdb release from https://www.iana.org/time-zones, version 2020a. ==================== changes in man-pages-5.09 ==================== released: 2020-11-01, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alejandro colomar aleksa sarai alexey budankov amir goldstein carlos o'donell dave martin david howells david laight dmitry v. levin érico rolim florian weimer g. branden robinson hauke fath heinrich schuchardt henrik@optoscale.no ira weiny jakub wilk jan kara jann horn jing peng jonathan wakely jonny grant konstantin bukin mark mossberg marko hrastovec matthew bobrowski michael kerrisk mike frysinger paul eggert paul moore rich felker samanta navarro serge hallyn simon mcvittie sridhar samudrala stephen smalley steve hilder thomas piekarski tony may tycho andersen yang xu apologies if i missed anyone! new and rewritten pages ----------------------- circleq.3 alejandro colomar new page with 'circleq' content extracted from queue(3) list.3 alejandro colomar new page with 'list' content extracted from queue(3) pthread_attr_setsigmask_np.3 michael kerrisk new page for pthread_attr_setsigmask_np() + pthread_attr_getsigmask_np() add a page documenting the pthread_attr_setsigmask_np(3) and pthread_attr_getsigmask_np(3) functions added in glibc 2.32. slist.3 alejandro colomar new page with 'slist' content extracted from queue(3) stailq.3 alejandro colomar new page with 'stailq' content extracted from queue(3) tailq.3 alejandro colomar new page with 'tailq' content extracted from queue(3) system_data_types.7 alejandro colomar, michael kerrisk a new page documenting a wide range of system data types. kernel_lockdown.7 david howells, heinrich schuchardt [michael kerrisk] new page documenting the kernel lockdown feature queue.7 alejandro colomar create summary page for 'queue' apis the former queue(3) page was rather unwieldy, as it attempted to describe too many apis. after splitting that content out into a number of smaller pages ( circleq.3, list.3, slist.3, stailq.3, and tailq.3) move the much-reduced queue(3) page, which is now essentially a summary of those apis, from section 3 to section 7. newly documented interfaces in existing pages --------------------------------------------- fanotify_init.2 fanotify.7 amir goldstein [jan kara, matthew bobrowski] document fan_report_dir_fid fanotify_init.2 fanotify.7 amir goldstein [jan kara, matthew bobrowski] document fan_report_name statx.2 ira weiny add statx_attr_dax strerror.3 michael kerrisk document strerrorname_np() and strerrordesc_np() strerrorname_np() and strerrordesc_np() were added in glibc 2.32. strsignal.3 michael kerrisk document sigabbrev_np() and sigdescr_np(). sigabbrev_np() and sigdescr_np() were added in glibc 2.32. loop.4 yang xu document loop_configure ioctl yang xu document lo_flags_direct_io flag capabilities.7 michael kerrisk document the cap_checkpoint_restore capability added in linux 5.9 ip.7 stephen smalley [paul moore] document ip_passsec for udp sockets ip.7 socket.7 stephen smalley document so_peersec for af_inet sockets sridhar samudrala document so_incoming_napi_id socket.7 unix.7 stephen smalley [serge hallyn, simon mcvittie] add initial description for so_peersec new and changed links --------------------- aiocb.3 clock_t.3 clockid_t.3 dev_t.3 div_t.3 double_t.3 fenv_t.3 fexcept_t.3 file.3 float_t.3 gid_t.3 id_t.3 imaxdiv_t.3 int8_t.3 int16_t.3 int32_t.3 int64_t.3 intn_t.3 intmax_t.3 intptr_t.3 lconv.3 ldiv_t.3 lldiv_t.3 off_t.3 pid_t.3 ptrdiff_t.3 regex_t.3 regmatch_t.3 regoff_t.3 siginfo_t.3 sigset_t.3 sigval.3 size_t.3 ssize_t.3 suseconds_t.3 time_t.3 timer_t.3 timespec.3 timeval.3 uid_t.3 uint8_t.3 uint16_t.3 uint32_t.3 uint64_t.3 uintn_t.3 uintptr_t.3 va_list.3 void.3 alejandro colomar, michael kerrisk new links to system_data_types(7) circleq_entry.3 circleq_head.3 circleq_init.3 circleq_insert_after.3 circleq_insert_before.3 circleq_insert_head.3 circleq_insert_tail.3 circleq_remove.3 alejandro colomar link to the new circleq(3) page instead of queue(3) list_empty.3 list_entry.3 list_first.3 list_foreach.3 list_head.3 list_head_initializer.3 list_init.3 list_insert_after.3 list_insert_before.3 list_insert_head.3 list_next.3 list_remove.3 alejandro colomar link to the new list.3 page instead of queue.3 slist_empty.3 slist_entry.3 slist_first.3 slist_foreach.3 slist_head.3 slist_head_initializer.3 slist_init.3 slist_insert_after.3 slist_insert_head.3 slist_next.3 slist_remove.3 slist_remove_head.3 alejandro colomar link to the new slist(3) page instead of queue(3) stailq_concat.3 stailq_empty.3 stailq_entry.3 stailq_first.3 stailq_foreach.3 stailq_head.3 stailq_head_initializer.3 stailq_init.3 stailq_insert_after.3 stailq_insert_head.3 stailq_insert_tail.3 stailq_next.3 stailq_remove.3 stailq_remove_head.3 alejandro colomar link to the new stailq(3) page instead of queue(3) tailq_concat.3 tailq_empty.3 tailq_entry.3 tailq_first.3 tailq_foreach.3 tailq_foreach_reverse.3 tailq_head.3 tailq_head_initializer.3 tailq_init.3 tailq_insert_after.3 tailq_insert_before.3 tailq_insert_head.3 tailq_insert_tail.3 tailq_last.3 tailq_next.3 tailq_prev.3 tailq_remove.3 tailq_swap.3 alejandro colomar link to the new tailq(3) page instead of queue(3) getcwd.2 mq_notify.2 mq_open.2 mq_timedreceive.2 mq_timedsend.2 mq_unlink.2 michael kerrisk reinstate links to section 3 pages that document system calls some of the links removed in commit 247c654385128fd0748 should have been kept, because in some cases there are real system calls whose wrapper functions are documented in section 3. queue.3 alejandro colomar link to queue(7) sigabbrev_np.3 michael kerrisk new link to strsignal.3 sigdescr_np.3 michael kerrisk new link to strsignal.3 strerrordesc_np.3 michael kerrisk new link to strerror(3) strerrorname_np.3 michael kerrisk new link to strerror(3) sys_siglist.3 michael kerrisk new link to strsignal(3) global changes -------------- various pages alejandro colomar use ``sizeof`` consistently through all the examples in the following way: - use the name of the variable instead of its type as argument for ``sizeof``. various pages alejandro colomar use sizeof() to get buffer size (instead of hardcoding macro name) various pages michael kerrisk use \(aq instead of ' inside monospace fonts use \(aq to get an unslanted single quote inside monospace code blocks. using a simple ' results in a slanted quote inside pdfs. various pages michael kerrisk, alejandro colomar use c99 style to declare loop counter variables rather than: sometype x; for (x = ....; ...) use for (sometype x = ...; ...) this brings the declaration and use closer together (thus aiding readability) and also clearly indicates the scope of the loop counter variable. various pages alejandro colomar switch printf() casts to use [u]intmax_t + %ju / %jd let's move to the 21st century. instead of casting system data types to long/long long/etc. in printf() calls, instead cast to intmax_t or uintmax_t, the largest available signed/unsigned integer types. various pages alejandro colomar omit 'int' keyword for 'short', 'long' and 'long long' types various pages alejandro colomar remove unneeded casts various pages alejandro colomar in printf(): s/0x%/%#/ except when followed by x instead of x use printf()'s '#' flag character to prepend the string "0x". however, when the number is printed in uppercase, and the prefix is in lowercase, the string "0x" needs to be manually written. various pages michael kerrisk use c99-style declarations for readability rather than writing things such as: struct sometype *x; ... x = malloc(sizeof(*x)); let's use c99 style so that the type info is in the same line as the allocation: struct sometype *x = malloc(sizeof(*x)); various pages alejandro colomar cast to 'unsigned long' rather than 'long' when printing with "%lx" stdarg.3 alejandro colomar declare variables with different types in different lines in particular, don's mix a variable and a pointer declaration on the same line: type x, *p; changes to individual pages --------------------------- memusage.1 michael kerrisk examples: remove doubled calculations the same calculations are repeated in malloc() and printf() calls. for better readability, do the calculations once. michael kerrisk use %zu rather than %zd when printing 'size_t' values clock_getres.2 alejandro colomar examples: use 'const' when appropriate alejandro colomar [jakub wilk] cast 'time_t' to 'int' for printf() and fix the length modifiers michael kerrisk [tony may] fix type and variable name in dynamic clock code example clone.2 michael kerrisk cap_checkpoint_restore can now be used to employ 'set_tid' epoll_ctl.2 michael kerrisk epoll instances can be nested to a maximum depth of 5 this limit appears to be an off-by-one count against ep_max_nests (4). michael kerrisk move some version info from conforming to to versions eventfd.2 alejandro colomar use 'prixn' macros when printing c99 fixed-width integer types futex.2 alejandro colomar use appropriate types getdents.2 alejandro colomar synopsis: add missing header and feature test macro intro.2 intro.3 credentials.7 feature_test_macros.7 standards.7 michael kerrisk see also: add system_data_types(7) ioctl_ns.2 stat.2 alejandro colomar [konstantin bukin] fix signedness of printf specifiers membarrier.2 alejandro colomar note that glibc does not provide a wrapper mprotect.2 alejandro colomar use "%p" rather than casting to 'long' when printing pointer values mq_getsetattr.2 alejandro colomar use 'const' when appropriate msgop.2 yang xu add restriction on enosys error open.2 michael kerrisk [henrik@optoscale.no] errors: add ebusy openat.2 alejandro colomar synopsis: return long the linux kernel uses long as the return type for this syscall. as glibc provides no wrapper, use the same type the kernel uses. open_by_handle_at.2 alejandro colomar use "%u" rather than "%d" when printing 'unsigned int' values perf_event_open.2 alexey budankov update the man page with cap_perfmon related information recv.2 send.2 michael kerrisk add cross references to pages with further info about ancillary data sched_getattr.2 aleksa sarai update to include changed size semantics seccomp.2 michael kerrisk [jann horn] warn reader that seccomp_ret_trace can be overridden highlight to the reader that if another filter returns a higher-precedence action value, then the ptracer will not be notified. michael kerrisk [rich felker] warn against the use of seccomp_ret_kill_thread killing a thread with seccomp_ret_kill_thread is very likely to leave the rest of the process in a broken state. michael kerrisk [rich felker] examples: use seccomp_ret_kill_process rather than seccomp_ret_kill alejandro colomar use array_size() macro instead of raw sizeof division setns.2 michael kerrisk correct the version for time namespace support sigaction.2 michael kerrisk [alejandro colomar] use correct posix type for siginfo_t.si_value syscalls.2 michael kerrisk move system calls from discontinued ports out of main syscall list various ports that had their own indigenous system calls have been discontinued. remove those system calls (none of which had manual pages!) to a separate part of the page, to avoid cluttering the main list of system calls. michael kerrisk add close_range (linux 5.9) timerfd_create.2 alejandro colomar use 'prixn' macros when printing c99 fixed-width integer types userfaultfd.2 michael kerrisk use a better type (uint64_t) for 'len' in examples alejandro colomar use 'prix64' rather than "%llx" when printing 64-bit fixed-width types argz_add.3 envz_add.3 michael kerrisk [jonny grant] point out that 'error_t' is an integer type bsearch.3 alejandro colomar fix intermediate type and remove unneeded casts bswap.3 jakub wilk use strtoull() for parsing 64-bit numbers dlopen.3 michael kerrisk clarify dt_runpath/dt_rpath details it is the dt_runpath/dt_rpath of the calling object (not the executable) that is relevant for the library search. verified by experiment. errno.3 michael kerrisk [alejandro colomar] note that the pthreads apis do not set errno fopencookie.3 alejandro colomar printf()'s .* expects an int; cast accordingly alejandro colomar fix bugs in example fread.3 alejandro colomar move array_size logic into macro freeaddrinfo.3 marko hrastovec fix memory leaks in freeaddrinfo() examples getline.3 alejandro colomar use %zd rather than %zu when printing 'ssize_t' values lseek64.3 michael kerrisk since glibc 2.28. the 'llseek' symbol is no longer available mallinfo.3 michael kerrisk the 'usmblks' field is nowadays always 0 offsetof.3 alejandro colomar use "%zu" rather than "%zd" when printing 'size_t' values perror.3 michael kerrisk sys_errlist and sys_nerr are no longer exposed by the change came with the release of glibc 2.32. posix_fallocate.3 érico rolim add eopnotsupp error code. psignal.3 strsignal.3 michael kerrisk consolidate information on 'sys_siglist' in one page (strsignal(3)) pthread_attr_init.3 michael kerrisk see also: add pthread_attr_init(3) pthread_attr_init.3 pthread_create.3 pthread_getattr_np.3 michael kerrisk use correct type (size_t) for some variables pthread_getattr_np.3 alejandro colomar use "%zu" and "%zx" when printing 'size_t' values pthread_sigmask.3 michael kerrisk see also: add pthread_attr_setsigmask_np(3) qsort.3 alejandro colomar fix casts alejandro colomar synopsis: move code from queue.3 to stailq.3 regex.3 alejandro colomar add example program alejandro colomar remove unnecessary include strsignal.3 michael kerrisk [hauke fath] note that starting with v2.32, glibc no longer exports 'sys_siglist' michael kerrisk further addition on version range for sys_siglist michael kerrisk note that 'sys_siglist' is nonstandard strtod.3 jonathan wakely fix return value for underflow strtol.3 alejandro colomar examples: simplify errno checking alejandro colomar examples: as the default base, use special value 0 alejandro colomar examples: delimit output string using "" tsearch.3 alejandro colomar simplify type usage and remove unneeded casts alejandro colomar use size_t for malloc() argument loop.4 yang xu add some details about lo_flags core.5 alejandro colomar use adequate type locale.5 florian weimer decimal points, thousands separators must be one character proc.5 michael kerrisk update capability requirements for accessing /proc/[pid]/map_files jann horn [mark mossberg] document inaccurate rss due to split_rss_counting michael kerrisk note "open file description" as (better) synonym for "file handle" resolv.5 florian weimer document the trust-ad option aio.7 alejandro colomar use perror() directly bpf-helpers.7 michael kerrisk [jakub wilk] resync with current kernel source capabilities.7 michael kerrisk under cap_sys_admin, group "sub-capabilities" together cap_bpf, cap_perfmon, and cap_checkpoint_restore have all been added to split out the power of cap_sys_admin into weaker pieces. group all of these capabilities together in the list under cap_sys_admin, to make it clear that there is a pattern to these capabilities. michael kerrisk cap_sys_admin implies cap_checkpoint_restore but the latter, weaker capability is preferred. michael kerrisk add kernel doc reference for cap_perfmon fanotify.7 alejandro colomar pass array to read(2) directly instead of a pointer to it fanotify.7 fanotify_mark.2 amir goldstein [jan kara, matthew bobrowski] generalize documentation of fan_report_fid feature_test_macros.7 jakub wilk update list of macros that inhibit default definitions man.7 michael kerrisk [g. branden robinson] clarify that alternating typeface macros print arguments without spaces man-pages.7 michael kerrisk add some more requests re code examples michael kerrisk soften the statement that ideal programs should be short namespaces.7 michael kerrisk a 'time_for_children' symlink can also pin a namespace pid_namespaces.7 michael kerrisk update capability requirements for /proc/sys/kernel/ns_last_pid pthreads.7 michael kerrisk explicitly note that pthreads apis return an errno-style value on error rtld-audit.7 florian weimer [carlos o'donell] clarify la_version handshake returning its argument without further checks is almost always wrong for la_version. alejandro colomar use "%u" rather than "%d" when printing 'unsigned int' values sigevent.7 michael kerrisk note that 'sigev_notify_thread_id' is linux-specific socket.7 michael kerrisk see also: add ipv6(7) ==================== changes in man-pages-5.10 ==================== released: 2020-12-21, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: ahelenia ziemiańska alejandro colomar amir goldstein arusekk baruch siach bill allombert colin ian king dave martin davide giorgio heinrich schuchardt jan kara jing peng john a. leuenhagen mathias rav michael kerrisk mike crowe namhyung kim peter oskolkov philip rowlands rob landley ross zwisler sebastian kirmayer наб apologies if i missed anyone! newly documented interfaces in existing pages --------------------------------------------- access.2 michael kerrisk document faccessat2() faccessat2() was added in linux 5.8 and enables a fix to longstanding bugs in the faccessat() wrapper function. membarrier.2 peter oskolkov [alejandro colomar] update for linux 5.10 linux kernel commit 2a36ab717e8fe678d98f81c14a0b124712719840 (part of 5.10 release) changed sys_membarrier prototype/parameters and added two new commands [membarrier_cmd_private_expedited_rseq and membarrier_cmd_register_private_expedited_rseq]. mount.2 statfs.2 ross zwisler add nosymfollow flags to mount(2) and statfs(2) new and changed links --------------------- faccessat2.2 michael kerrisk new link to access.2 circleq_empty.3 circleq_first.3 circleq_foreach.3 circleq_foreach_reverse.3 circleq_head_initializer.3 circleq_last.3 circleq_loop_next.3 circleq_loop_prev.3 circleq_next.3 circleq_prev.3 michael kerrisk add missing links to circleq.3 pthread_attr_getsigmask_np.3 michael kerrisk new link to pthread_attr_setsigmask_np.3 global changes -------------- various pages alejandro colomar use oxford comma changes to individual pages --------------------------- access.2 michael kerrisk bugs: note that faccessat() wrapper function emulation ignores acls bpf.2 michael kerrisk place examples section in correct location cacheflush.2 alejandro colomar document architecture-specific variants alejandro colomar [heinrich schuchardt] document __builtin___clear_cache() as a more portable alternative chroot.2 memfd_create.2 tailq.3 michael kerrisk [alejandro colomar] fix unbalanced .nf/.fi clock_getres.2 michael kerrisk place errors in alphabetical order clone.2 sigaltstack.2 michael kerrisk clone(clone_vm) disables the alternate signal stack getrlimit.2 michael kerrisk state more precisely the range of kernel versions that had rlimit_locks getrusage.2 michael kerrisk note that the 'vtimes' symbol exists only up to glibc 2.32 io_cancel.2 io_destroy.2 io_getevents.2 io_setup.2 io_submit.2 alejandro colomar synopsis: s/io_context_t/aio_context_t/ linux uses aio_context_t for these syscalls, and it's the type provided by . use it in the synopsis. libaio uses 'io_context_t', but that difference is already noted in notes. io_setup.2 alejandro colomar synopsis: return long link.2 mathias rav errors: add enoent when target is deleted linux kernel commit aae8a97d3ec30788790d1720b71d76fd8eb44b73 (part of kernel release v2.6.39) added a check to disallow creating a hard link to an unlinked file. llseek.2 michael kerrisk note size of 'loff_t' type michael kerrisk point the reader to lseek64(3) for info about llseek(3) michael kerrisk some mild rewriting to ease reading of the info in this page mmap.2 michael kerrisk clarify sigbus text and treatment of partial page at end of a mapping msgctl.2 michael kerrisk make comments in 'msqid_ds' definition more compact michael kerrisk place list of field descriptions in same order as structure definition michael kerrisk use field name "msg_cbytes" rather than "__msg_cbytes" michael kerrisk add description of 'msg_cbytes' field openat.2 colin ian king fix include path, should be linux/openat2.h perf_event_open.2 namhyung kim [alejandro colomar] update man page with recent kernel changes alejandro colomar assign calculated value explicitly to 'config' restart_syscall.2 alejandro colomar synopsis: fix restart_syscall() return type set_tid_address.2 alejandro colomar synopsis: fix set_tid_address() return type shmctl.2 michael kerrisk place list of field descriptions in same order as structure definition sigaction.2 michael kerrisk clarify description of sa_nodefer clarify description of sa_nodefer, and note interaction with act.sa_mask. michael kerrisk add a cross-reference to signal(7) for further info on 'ucontext_t' sigaltstack.2 michael kerrisk clarify that the alternate signal stack is per-thread clarify that the alternate signal stack is per-thread (rather than process-wide). spu_create.2 michael kerrisk add kernel version numbers for spu_create_affinity_spu/_mem michael kerrisk relocate paragraph on 'mode' argument michael kerrisk [alejandro colomar] clarify that spu_create() now has 4 arguments but once had only 3 subpage_prot.2 alejandro colomar synopsis: fix return type: s/long/int/ syscalls.2 michael kerrisk add process_madvise() michael kerrisk note that sysctl() was removed in linux 5.5 timer_getoverrun.2 michael kerrisk timer_getoverrun() now clamps the overrun count to delaytimer_max see https://bugzilla.kernel.org/show_bug.cgi?id=12665. uselib.2 posix_memalign.3 profil.3 rtime.3 michael kerrisk remove some text about libc/libc5 with this change, there remain almost no vestiges of information about the long defunct linux libc. errno.3 michael kerrisk note another possible cause of the emfile error getcontext.3 michael kerrisk mention sa_siginfo flag when talking about 3-argument signal handler michael kerrisk see also: add signal(7) list.3 michael kerrisk name: remove list_prev, which is not documented in this page lseek64.3 michael kerrisk remove section numbers from interface list michael kerrisk remove sentence saying lseek64() is an alias for llseek() michael kerrisk notes: describe the origin of lseek64() in lfs nextafter.3 michael kerrisk remove duplicate "bugs" section heading pthread_tryjoin_np.3 michael kerrisk [mike crowe] note that pthread_timedjoin_np() uses clock_realtime, but there's a bug rcmd.3 michael kerrisk see also: remove intro(2) strnlen.3 michael kerrisk [heinrich schuchardt] fix a small inconsistency in the text elf.5 michael kerrisk see also: add objcopy(1) filesystems.5 ahelenia ziemiańska [alejandro colomar] fix link to user space tooling for ncpfs ahelenia ziemiańska [alejandro colomar] note ncpfs removal from kernel attributes.7 michael kerrisk see also: add signal-safety(7) fanotify.7 amir goldstein [jan kara] fix outdated description kernel_lockdown.7 michael kerrisk remove unneeded quotes packet.7 baruch siach [alejandro colomar] update references to kernel documentation pthreads.7 michael kerrisk rephrase function list in terms of posix rather than sus the list was using an inconsistent mixture of "posix" and "sus". signal.7 michael kerrisk [heinrich schuchardt, dave martin] add some details on the execution of signal handlers add a "big picture" of what happens when a signal handler is invoked. michael kerrisk add pidfd_send_signal() to list of apis for sending signals michael kerrisk mention 'ucontext_t' in the discussion of signal handler execution michael kerrisk see also: add swapcontext(3) signal-safety.7 michael kerrisk note async-signal-safety details for errno standards.7 michael kerrisk add url for posix.1-2008/susv4 michael kerrisk add lfs (large file summit) michael kerrisk [rob landley] fix some urls for locations of the standards michael kerrisk relocate the discussion on posix manual pages tcp.7 alejandro colomar [philip rowlands] tcp_syncookies: it is now an integer [0, 2] since linux kernel 3.12, tcp_syncookies can have the value 2, which sends out cookies unconditionally. ==================== changes in man-pages-5.11 ==================== released: 2021-03-21, munich contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: alejandro colomar alessandro bono alyssa ross bastien roucariès bruno haible christian brauner ciprian dorin craciun dmitry v. levin dmitry vorobev edef enke chen gabriel krisman bertazi ganimedes colomar jakub wilk jan kara jens axboe johannes pfister johannes wellhöfer john morris jonathan wakely jonny grant manfred spraul michael kerrisk michal hocko minchan kim pádraig brady pali rohár palmer dabbelt paran lee peter h. froehlich philipp schuster stephen kitt steve grubb suren baghdasaryan szunti valentin kettner vincent lefevre walter franzini walter harms willem de bruijn yang xu zack weinberg apologies if i missed anyone! new and rewritten pages ----------------------- close_range.2 stephen kitt, michael kerrisk [christian brauner] new page documenting close_range(2) process_madvise.2 suren baghdasaryan, minchan kim [michal hocko, alejandro colomar, michael kerrisk] document process_madvise(2) fileno.3 michael kerrisk split fileno(3) content out of ferror(3) into new page fileno(3) differs from the other functions in various ways. for example, it is governed by different standards, and can set 'errno'. conversely, the other functions are about examining the status of a stream, while fileno(3) simply obtains the underlying file descriptor. furthermore, splitting this function out allows for some cleaner upcoming changes in ferror(3). newly documented interfaces in existing pages --------------------------------------------- epoll_wait.2 willem de bruijn [dmitry v. levin] add documentation of epoll_pwait2() expand the epoll_wait() page with epoll_pwait2(), an epoll_wait() variant that takes a struct timespec to enable nanosecond resolution timeout. fanotify_init.2 fanotify.7 jan kara [steve grubb] document fan_audit flag and fan_enable_audit madvise.2 michael kerrisk add descriptions of madv_cold and madv_pageout taken from process_madvise(2). openat2.2 jens axboe add resolve_cached prctl.2 gabriel krisman bertazi document syscall user dispatch mallinfo.3 michael kerrisk document mallinfo2() and note that mallinfo() is deprecated document the mallinfo2() function added in glibc 2.33. update example program to use mallinfo2() system_data_types.7 alejandro colomar add off64_t to system_data_types(7) ld.so.8 michael kerrisk document the --argv0 option added in glibc 2.33 new and changed links --------------------- epoll_pwait2.2 dmitry v. levin new link to epoll_wait(2) mallinfo2.3 michael kerrisk new link to mallinfo(3) off64_t.3 alejandro colomar new link to system_data_types(7) global changes -------------- various pages alejandro colomar synopsis: use 'restrict' in prototypes this change has been completed for *all* relevant pages (around 135 pages in total). various pages alejandro colomar [zack weinberg] remove unused the manual pages are already inconsistent in which headers need to be included. right now, not all of the types used by a function have their required header included in the synopsis. if we were to add the headers required by all of the types used by functions, the synopsis would grow too much. not only it would grow too much, but the information there would be less precise. having system_data_types(7) document each type with all the information about required includes is much more precise, and the info is centralized so that it's much easier to maintain. so let's document only the include required for the function prototype, and also the ones required for the macros needed to call the function. only defines types, not functions or constants, so it doesn't belong to man[23] (function) pages at all. i ignore if some old systems had headers that required you to include *before* them (incomplete headers), but if so, those implementations would be broken, and those headers should probably provide some kind of warning. i hope this is not the case. [mtk: already in 2001, posix.1 removed the requirement to include for many apis, so this patch seems well past due.] a few pages alejandro colomar add notes about missing glibc wrappers _exit.2 abort.3 err.3 exit.3 pthread_exit.3 setjmp.3 alejandro colomar synopsis: use 'noreturn' in prototypes use standard c11 'noreturn' in these manual page for functions that do not return. various pages ganimedes colomar [alejandro colomar] normalize synopsis notes about nonexistent glibc wrappers to easily distinguish documentation about glibc wrappers from documentation about kernel syscalls, let's have a normalized 'note' in the synopsis, and a further explanation in the page body (notes in most of them), as already happened in many (but not all) of the manual pages for syscalls without a wrapper. furthermore, let's normalize the messages, following membarrier.2 (because it's already quite extended), so that it's easy to use grep to find those pages. normalize notes about nonexistent glibc wrappers this commit normalizes texts under sections other than synopsis (most of them in notes). global changes (formatting fixes and minor edits) ------------------------------------------------- various pages michael kerrisk errors: remove redundant statement that 'errno' is set this is implied in every other manual page. there is no need to state it explicitly in these pages. various pages michael kerrisk use periods more consistently inside code comments in general, complete sentences in free-standing comments should be terminated by periods. a few pages michael kerrisk better table formatting in particular, allow for rendering in widths different from (especially less than) 80 columns. various pages michael kerrisk consistency fix-up in ftms generally, place '||' at start of a line, rather than the end of the previous line. rationale: this placement clearly indicates that each piece is an alternative. various pages michael kerrisk [alejandro colomar] bring more whitespace consistency in synopsis the use of vertical white space in the synopsis sections is rather inconsistent. make it more consistent, subject to the following heuristics: * prefer no blank lines between function signatures by default. * where many functions are defined in the synopsis, add blank lines where needed to improve readability, possibly by using blank lines to separate logical groups of functions. various pages alejandro colomar consistently use 'unsigned int' most pages use 'unsigned int' (and the kernel too). make them all do so. various pages michael kerrisk various improvements in wording in return value various pages michael kerrisk s/glibc versions . clone.2 valentin kettner fix types in clone_args a file descriptor is an int so it should be stored through an int pointer while parent_tid should have the same type as child_tid which is pid_t pointer. close.2 michael kerrisk see also: add close_range(2) copy_file_range.2 alejandro colomar document glibc wrapper instead of kernel syscall glibc uses 'off64_t' instead of 'loff_t'. delete_module.2 alejandro colomar synopsis: fix prototype parameter types the linux kernel uses 'unsigned int' instead of 'int' for the 'flags' parameter. as glibc provides no wrapper, use the same type the kernel uses. epoll_create.2 michael kerrisk conforming to: mention that epoll_create1() is linux-specific epoll_wait.2 michael kerrisk conforming to: mention that epoll_pwait() is linux-specific execve.2 palmer dabbelt correct the versions of linux that don't have arg_max argv/envp size execveat.2 alejandro colomar fix prototype it's been 6 years since execveat(2) was added to the kernel, and there's still no glibc wrapper. let's document the kernel syscall prototype. getcpu.2 michael kerrisk [alejandro colomar] rewrite page to describe glibc wrapper function since glibc 2.29, there is a wrapper for getcpu(2). the wrapper has only 2 arguments, omitting the unused third system call argument. rework the manual page to reflect this. getgid.2 getuid.2 michael kerrisk note that these interfaces never modify 'errno' see https://www.austingroupbugs.net/view.php?id=511 and the posix.1-2008 specifications of the interfaces. gethostname.2 michael kerrisk update ftm requirements for gethostname() getpagesize.2 getdtablesize.3 michael kerrisk update/correct ftm requirements getrusage.2 michael kerrisk starting in 2.33, glibc no longer provides vtimes() ioctl_tty.2 michael kerrisk reformat argument type information the current mark-up renders poorly. to resolve this, move the type information into a separate line. ipc.2 alejandro colomar fix prototype parameter types kcmp.2 michael kerrisk since linux 5.12, kcmp() availability is unconditional kcmp() is no longer dependent on config_checkpoint_restore. keyctl.2 alejandro colomar synopsis: fix prototype parameter types the linux kernel uses 'unsigned long'. there's no reason to use the typedef '__kernel_ulong_t'. lookup_dcookie.2 alejandro colomar use standard types: u64 -> uint64_t madvise.2 michael kerrisk see also: add process_madvise(2) mlock.2 alejandro colomar mlock2(): fix prototype parameter types the documented prototype for mlock2() was a mix of the glibc wrapper prototype and the kernel syscall prototype. let's document the glibc wrapper prototype, which is shown below. michael kerrisk conforming to: note more explicitly which apis are in the standards mmap2.2 alejandro colomar fix prototype parameter types there are many slightly different prototypes for this syscall, but none of them is like the documented one. of all the different prototypes, let's document the asm-generic one. mount.2 michael kerrisk note that the 'data' argument can be null move_pages.2 alejandro colomar add notes about missing glibc wrappers open.2 rename.2 alyssa ross refer to tmpfs rather than shmem if i'm understanding correctly, tmpfs is a filesystem built on shmem, so i think it's more correct (and probably much more widely understandable) to refer to tmpfs here. pciconfig_read.2 alejandro colomar synopsis: fix prototype parameter types use the glibc prototypes instead of the kernel ones. exception: use 'int' instead of 'enum'. pidfd_open.2 michael kerrisk note the process_madvise(2) use case for pid file descriptors readlink.2 michael kerrisk [jonny grant] emphasize that the returned buffer is not null-terminated s390_pci_mmio_write.2 alejandro colomar synopsis: add 'const' qualifier s390_pci_mmio_write() uses 'const void *' instead of 'void *'. sched_setattr.2 alejandro colomar add note about missing glibc wrappers semctl.2 yang xu [alejandro colomar, manfred spraul] correct sem_stat_any description socketcall.2 alejandro colomar add note about missing glibc wrapper splice.2 alejandro colomar use 'off64_t' instead of 'loff_t' the kernel syscall uses 'loff_t', but the glibc wrapper uses 'off64_t'. let's document the wrapper prototype, as in other pages. spu_create.2 alejandro colomar synopsis: fix prototype parameter type the 'flags' parameter of spu_create() uses 'unsigned int'. spu_run.2 alejandro colomar synopsis: fix prototype parameter types the 2nd and 3rd parameters of spu_run() use 'uint32_t *'. stat.2 jonathan wakely [alejandro colomar] remove from synopsis there seems to be no reason is shown here, so remove it. michael kerrisk move the obsolete _bsd_source ftm to the end of the ftm info syscall.2 peter h. froehlich update superh syscall convention syscalls.2 michael kerrisk add epoll_pwait2() tkill.2 alejandro colomar synopsis: fix prototype parameter types all but the last parameters of t[g]kill() use 'pid_t', both in the kernel and glibc. vmsplice.2 alejandro colomar synopsis: fix prototype parameter type the 3rd parameter of vmsplice() uses 'size_t' in glibc. bstring.3 michael kerrisk see also: add string(3) circleq.3 list.3 slist.3 stailq.3 tailq.3 alejandro colomar improve readability, especially in synopsis circleq.3 alejandro colomar fix circleq_loop_*() return type crypt.3 michael kerrisk reformat ftm info (in preparation for next patch) michael kerrisk update crypt() ftm requirements to note glibc 2.28 changes ecvt.3 gcvt.3 michael kerrisk update ftm requirements error.3 michael kerrisk [alejandro colomar, walter harms] clarify the meaning of 'status==0' for error(3) ferror.3 michael kerrisk remove fileno(3) content that was migrated to new fileno(3) page michael kerrisk add a return value section michael kerrisk posix.1-2008: these functions won't change 'errno' if 'stream' is valid see https://www.austingroupbugs.net/view.php?id=401. fread.3 alessandro bono examples: swap size and nmemb params it works both ways, but this one feels more right. we are reading four elements sizeof(*buffer) bytes each. fseeko.3 michael kerrisk move info about obsolete ftm from synopsis to notes this makes the synopsis more consistent with other pages. ftime.3 michael kerrisk glibc 2.33 has removed ftime() ftw.3 alejandro colomar synopsis: remove duplicate header gethostbyname.3 michael kerrisk move mention of from synopsis to description the functions are all declared in . is only needed for the af_* constants. gethostid.3 michael kerrisk update ftm requirements for gethostid() get_phys_pages.3 alejandro colomar [jakub wilk] glibc gets the info from sysinfo(2) since 2.23 grantpt.3 ptsname.3 unlockpt.3 michael kerrisk remove mention of _xopen_source_extended ftm this rather ancient ftm is not mentioned in other pages for reasons discussed in feature_test_macros(7). remove this ftm from the three pages where it does appear. malloc.3 alejandro colomar [johannes pfister] document that realloc(p, 0) is specific to glibc and nonportable malloc_hook.3 alejandro colomar synopsis: use 'volatile' in prototypes malloc_trim.3 dmitry vorobev remove mention of free() call 'malloc_trim' was and is never called from the 'free' function. pthread_create.3 michael kerrisk [paran lee] fix undeclared variable error in example program michael kerrisk fix a signedness error in the example code puts.3 michael kerrisk reorder functions more logically (group related functions together) qecvt.3 michael kerrisk update feature test macro requirements setbuf.3 michael kerrisk posix doesn't require errno to be unchanged after successful setbuf() see https://www.austingroupbugs.net/view.php?id=397#c799 setlocale.3 michael kerrisk [alejandro colomar, bruno haible] restructure a particularly difficult sentence simpleq.3 stailq.3 queue.7 simpleq_*.3 alejandro colomar document simpleq_*() as an alias to stailq_*() macros strerror.3 alejandro colomar strerrorname_np() and strerrordesc_np() first appeared on glibc 2.32 string.3 michael kerrisk see also: add bstring(3) system.3 alejandro colomar [ciprian dorin craciun] document bug and workaround when the command name starts with a hyphen environ.7 bastien roucariès reorder the text move the text describing how to set environment variable before the list(s) of variables in order to improve readability. bastien roucariès document convention of string in environ document the name=value system and that nul byte is forbidden. bastien roucariès document that home, logname, shell, user are set at login time and point to the su(1) manual page. bastien roucariès add see also ld.so(8) for ld_ variables michael kerrisk [bastien roucariès] improve the description of path add more details of how path is used, and mention the legacy use of an empty prefix. bastien roucariès [alejandro colomar, bastien roucaries, vincent lefevre] document valid values of pathnames for shell, pager and editor/visual michael kerrisk [bastien roucariès] note the default if pager is not defined michael kerrisk be a little more precise when discussing 'exec' say "execve(2)" instead of "exec(3)", and note that this step starts a new program (not a new process!). michael kerrisk [bastien roucariès] relocate and reword the mention of _gnu_source man-pages.7 michael kerrisk document "acknowledgement" as the preferred spelling michael kerrisk add some notes on comments in example code michael kerrisk add a formatting and wording conventions section in man-pages-5.11, a large number of pages were edited to achieve greater consistency in the synopsis, return value and attributes sections. to avoid future inconsistencies, try to capture some of the preferred conventions in text in man-pages(7). michael kerrisk note some rationale for the use of real minus signs netdevice.7 pali rohár [alejandro colomar] update documentation for siocgifaddr siocsifaddr siocdifaddr netlink.7 pali rohár [alejandro colomar] fix minimal linux version for netlink_cap_ack netlink_cap_ack option was introduced in commit 0a6a3a23ea6e which first appeared in linux version 4.3 and not 4.2. pali rohár [alejandro colomar] remove ipv4 from description rtnetlink is not only used for ipv4 philipp schuster clarify details of netlink error responses make it clear that netlink error responses (i.e., messages with type nlmsg_error (0x2)), can be longer than sizeof(struct nlmsgerr). in certain circumstances, the payload can be longer. shm_overview.7 michael kerrisk see also: add memfd_create(2) sock_diag.7 pali rohár [alejandro colomar] fix recvmsg() usage in the example tcp.7 enke chen documentation revision for tcp_user_timeout uri.7 michael kerrisk note that 'logical' quoting is the norm in europe ==================== changes in man-pages-5.12 ==================== released: 2021-06-20, christchurch contributors ------------ the following people contributed patches/fixes or (noted in brackets in the changelog below) reports, notes, and ideas that have been incorporated in changes in this release: ahelenia ziemiańska akihiro motoki alejandro colomar alyssa ross aurelien aptel borislav petkov bruce merry chris keilbart christian brauner christoph anton mitterer dann frazier dmitry v. levin florian weimer huang ying jakub wilk james o. d. hunt jann horn johannes berg jon murphy josh triplett katsuhiro numata kees cook mark kettenis mathieu desnoyers michael kerrisk mike rapoport peter xu sargun dhillon stefan puiu štěpán němec thomasavoss topi miettinen tycho andersen utkarsh singh vishwajith k walter harms yang xu zhiheng li наб apologies if i missed anyone! new and rewritten pages ----------------------- seccomp_unotify.2 michael kerrisk [tycho andersen, jann horn, kees cook, christian brauner sargun dhillon] new page documenting the seccomp user-space notification mechanism max.3 alejandro colomar new page to document max() and min() newly documented interfaces in existing pages --------------------------------------------- seccomp.2 tycho andersen [michaelkerrisk] document seccomp_get_notif_sizes tycho andersen document seccomp_filter_flag_new_listener [michael kerrisk] tycho andersen document seccomp_ret_user_notif [michael kerrisk] set_mempolicy.2 huang ying [alejandro colomar, "huang, ying"] add mode flag mpol_f_numa_balancing userfaultfd.2 peter xu [alejandro colomar, mike rapoport] add uffd_feature_thread_id docs peter xu [alejandro colomar, mike rapoport] add write-protect mode docs proc.5 michael kerrisk document /proc/sys/vm/sysctl_hugetlb_shm_group system_data_types.7 alejandro colomar add 'blksize_t' alejandro colomar add 'blkcnt_t' alejandro colomar add 'mode_t' alejandro colomar add 'struct sockaddr' alejandro colomar add 'cc_t' alejandro colomar add 'socklen_t' new and changed links --------------------- blkcnt_t.3 alejandro colomar new link to system_data_types(7) blksize_t.3 alejandro colomar new link to system_data_types(7) cc_t.3 alejandro colomar new link to system_data_types(7) min.3 michael kerrisk new link to min.3 mode_t.3 alejandro colomar new link to system_data_types(7) sockaddr.3 alejandro colomar new link to system_data_types(7) socklen_t.3 alejandro colomar new link to system_data_types(7) global changes -------------- many pages alejandro colomar synopsis: use syscall(sys_...); for system calls without a wrapper many pages alejandro colomar synopsis: document why each header is required many pages alejandro colomar synopsis: remove unused includes various pages alejandro colomar add note about the use of syscall(2) various pages alejandro colomar synopsis: miscellaneous fixes to includes a few pages alejandro colomar synopsis: add missing 'const' changes to individual pages --------------------------- dup.2 michael kerrisk rewrite the description of dup() somewhat as can be seen by any number of stackoverflow questions, people persistently misunderstand what dup() does, and the existing manual page text, which talks of "copying" a file descriptor doesn't help. rewrite the text a little to try to prevent some of these misunderstandings, in particular noting at the start that dup() allocates a new file descriptor. michael kerrisk clarify what silent closing means alejandro colomar synopsis: use consistent comments through pages epoll_wait.2 alejandro colomar move misplaced subsection to notes from bugs execveat.2 michael kerrisk library support has been added in glibc 2.34 _exit.2 michael kerrisk add a little more detail on the raw _exit() system cal exit_group.2 alejandro colomar use 'noreturn' in prototypes flock.2 aurelien aptel [alejandro colomar] add cifs details cifs flock() locks behave differently than the standard. give an overview of those differences. ioperm.2 alejandro colomar remove obvious comment memfd_create.2 mmap.2 shmget.2 michael kerrisk [yang xu] document the eperm error for huge page allocations this error can occur if the caller is does not have cap_ipc_lock and is not a member of the sysctl_hugetlb_shm_group. mmap.2 bruce merry clarify that map_populate is best-effort mount.2 topi miettinen document selinux use of ms_nosuid mount flag open.2 alejandro colomar [walter harms] fix bug in linkat(2) call example at_empty_path works with empty strings (""), but not with null (or at least it's not obvious). michael kerrisk make it clearer that an fd is an index into the process's fd table sometimes people are confused, thinking a file descriptor is just a number.... perfmonctl.2 michael kerrisk this system call was removed in linux 5.10 pipe.2 alejandro colomar synopsis: fix incorrect prototype michael kerrisk rearrange synopsis so that minority version pipe() is at end ptrace.2 dmitry v. levin [alejandro colomar, mathieu desnoyers] mention ptrace_get_syscall_info in return value section seccomp.2 michael kerrisk reorder list of seccomp_set_mode_filter flags alphabetically (no content changes.) michael kerrisk see also: add seccomp_unotify(2) select.2 michael kerrisk strengthen the warning regarding the low value of fd_setsize all modern code should avoid select(2) in favor of poll(2) or epoll(7). michael kerrisk relocate sentence about the fd_set value-result arguments to bugs syscalls.2 michael kerrisk perfmonctl(2) was removed in linux 5.10 bswap.3 alejandro colomar bswap_*() are implemented using functions even though it's true that they are macros, it's transparent to the user. the user will see their results casted to unsigned types after the conversion due to the underlying functions, so it's better to document these as the underlying functions, specifying the types. cmsg.3 unix.7 michael kerrisk refer to seccomp_unotify(2) for an example of scm_rights usage cpow.3 alejandro colomar use 'complex' after the type consistently ctime.3 michael kerrisk [katsuhiro numata] restore documentation of 'tm_gmtoff' field errno.3 alejandro colomar [florian weimer, mark kettenis] fix enodata text enodata is an xsi streams extension (not base posix). exec.3 josh triplett [alejandro colomar] clarify that execvpe() uses path from the caller, not envp josh triplett [alejandro colomar] fix description of 'e' variants the envp argument specifies the environment of the new process image, not "the environment of the caller". fflush.3 alejandro colomar see also: add fpurge(3) getline.3 наб [ahelenia ziemiańska, alejandro colomar] !*lineptr is sufficient no implementation or spec requires *n to be 0 to allocate a new buffer. getopt.3 james o. d. hunt [alejandro colomar] clarify behaviour printf.3 utkarsh singh [alejandro colomar] add overall structure of format string pthread_attr_setinheritsched.3 pthread_attr_setschedparam.3 alejandro colomar synopsis: use 'restrict' in prototypes pthread_mutexattr_setrobust.3 michael kerrisk note that the *_np() apis are deprecated since glibc 2.34 alejandro colomar synopsis: remove incorrect 'const' pthread_mutex_consistent.3 michael kerrisk note that pthread_mutexattr_setrobust() is now deprecated pthread_yield.3 michael kerrisk note that this function is deprecated since glibc 2.34 rpc.3 alejandro colomar synopsis: fix prototypes (misc.) scanf.3 alyssa ross [alejandro colomar] clarify that %n supports type modifiers xdr.3 alejandro colomar synopsis: fix prototype types use the same types glibc uses, and add a missing 'const'. capabilities.7 michael kerrisk cap_ipc_lock also governs memory allocation using huge pages environ.7 josh triplett [alejandro colomar] remove obsolete admonishment of the gzip environment variable kernel_lockdown.7 dann frazier [alejandro colomar] remove description of lifting via sysrq (not upstream) the patch that implemented lockdown lifting via sysrq ended up getting dropped[*] before the feature was merged upstream. having the feature documented but unsupported has caused some confusion for our users. mount_namespaces.7 namespaces.7 michael kerrisk relocate reference to pam_namespace(8) from namespaces.7 to mount_namespaces.7. signal.7 michael kerrisk add reference to seccomp_unotify(2) the seccomp user-space notification feature can cause changes in the semantics of sa_restart with respect to system calls that would never normally be restarted. point the reader to the page that provide further details. vsock.7 alyssa ross ioctls are on /dev/vsock, not sockets .\" copyright (c) 2003 free software foundation, inc. .\" and copyright (c) 2017 goldwyn rodrigues .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .th io_submit 2 2021-03-22 "linux" "linux programmer's manual" .sh name io_submit \- submit asynchronous i/o blocks for processing .sh synopsis .nf .br "#include " " /* defines needed types */" .pp .bi "int io_submit(aio_context_t " ctx_id ", long " nr \ ", struct iocb **" iocbpp ); .fi .pp .ir note : there is no glibc wrapper for this system call; see notes. .sh description .ir note : this page describes the raw linux system call interface. the wrapper function provided by .i libaio uses a different type for the .i ctx_id argument. see notes. .pp the .br io_submit () system call queues \finr\fp i/o request blocks for processing in the aio context \fictx_id\fp. the .i iocbpp argument should be an array of \finr\fp aio control blocks, which will be submitted to context \fictx_id\fp. .pp the .i iocb (i/o control block) structure defined in .ir linux/aio_abi.h defines the parameters that control the i/o operation. .pp .in +4n .ex #include struct iocb { __u64 aio_data; __u32 padded(aio_key, aio_rw_flags); __u16 aio_lio_opcode; __s16 aio_reqprio; __u32 aio_fildes; __u64 aio_buf; __u64 aio_nbytes; __s64 aio_offset; __u64 aio_reserved2; __u32 aio_flags; __u32 aio_resfd; }; .ee .in .pp the fields of this structure are as follows: .tp .i aio_data this data is copied into the .i data field of the .i io_event structure upon i/o completion (see .br io_getevents (2)). .tp .i aio_key this is an internal field used by the kernel. do not modify this field after an .br io_submit () call. .tp .i aio_rw_flags this defines the r/w flags passed with structure. the valid values are: .rs .tp .br rwf_append " (since linux 4.16)" .\" commit e1fc742e14e01d84d9693c4aca4ab23da65811fb append data to the end of the file. see the description of the flag of the same name in .br pwritev2 (2) as well as the description of .b o_append in .br open (2). the .i aio_offset field is ignored. the file offset is not changed. .tp .br rwf_dsync " (since linux 4.13)" write operation complete according to requirement of synchronized i/o data integrity. see the description of the flag of the same name in .br pwritev2 (2) as well the description of .b o_dsync in .br open (2). .tp .br rwf_hipri " (since linux 4.13)" high priority request, poll if possible .tp .br rwf_nowait " (since linux 4.14)" don't wait if the i/o will block for operations such as file block allocations, dirty page flush, mutex locks, or a congested block device inside the kernel. if any of these conditions are met, the control block is returned immediately with a return value of .b \-eagain in the .i res field of the .i io_event structure (see .br io_getevents (2)). .tp .br rwf_sync " (since linux 4.13)" write operation complete according to requirement of synchronized i/o file integrity. see the description of the flag of the same name in .br pwritev2 (2) as well the description of .b o_sync in .br open (2). .re .tp .i aio_lio_opcode this defines the type of i/o to be performed by the .i iocb structure. the valid values are defined by the enum defined in .ir linux/aio_abi.h : .ip .in +4n .ex enum { iocb_cmd_pread = 0, iocb_cmd_pwrite = 1, iocb_cmd_fsync = 2, iocb_cmd_fdsync = 3, iocb_cmd_poll = 5, iocb_cmd_noop = 6, iocb_cmd_preadv = 7, iocb_cmd_pwritev = 8, }; .ee .in .tp .i aio_reqprio this defines the requests priority. .tp .i aio_fildes the file descriptor on which the i/o operation is to be performed. .tp .i aio_buf this is the buffer used to transfer data for a read or write operation. .tp .i aio_nbytes this is the size of the buffer pointed to by .ir aio_buf . .tp .i aio_offset this is the file offset at which the i/o operation is to be performed. .tp .i aio_flags this is the set of flags associated with the .i iocb structure. the valid values are: .rs .tp .br iocb_flag_resfd asynchronous i/o control must signal the file descriptor mentioned in .i aio_resfd upon completion. .tp .br iocb_flag_ioprio " (since linux 4.18)" .\" commit d9a08a9e616beeccdbd0e7262b7225ffdfa49e92 interpret the .i aio_reqprio field as an .b ioprio_value as defined by .ir linux/ioprio.h . .re .tp .i aio_resfd the file descriptor to signal in the event of asynchronous i/o completion. .sh return value on success, .br io_submit () returns the number of \fiiocb\fps submitted (which may be less than \finr\fp, or 0 if \finr\fp is zero). for the failure return, see notes. .sh errors .tp .b eagain insufficient resources are available to queue any \fiiocb\fps. .tp .b ebadf the file descriptor specified in the first \fiiocb\fp is invalid. .tp .b efault one of the data structures points to invalid data. .tp .b einval the aio context specified by \fictx_id\fp is invalid. \finr\fp is less than 0. the \fiiocb\fp at .i *iocbpp[0] is not properly initialized, the operation specified is invalid for the file descriptor in the \fiiocb\fp, or the value in the .i aio_reqprio field is invalid. .tp .b enosys .br io_submit () is not implemented on this architecture. .tp .b eperm the .i aio_reqprio field is set with the class .br ioprio_class_rt , but the submitting context does not have the .b cap_sys_admin capability. .sh versions the asynchronous i/o system calls first appeared in linux 2.5. .sh conforming to .br io_submit () is linux-specific and should not be used in programs that are intended to be portable. .sh notes glibc does not provide a wrapper for this system call. you could invoke it using .br syscall (2). but instead, you probably want to use the .br io_submit () wrapper function provided by .\" http://git.fedorahosted.org/git/?p=libaio.git .ir libaio . .pp note that the .i libaio wrapper function uses a different type .ri ( io_context_t ) .\" but glibc is confused, since uses 'io_context_t' to declare .\" the system call. for the .i ctx_id argument. note also that the .i libaio wrapper does not follow the usual c library conventions for indicating errors: on error it returns a negated error number (the negative of one of the values listed in errors). if the system call is invoked via .br syscall (2), then the return value follows the usual conventions for indicating an error: \-1, with .i errno set to a (positive) value that indicates the error. .sh see also .br io_cancel (2), .br io_destroy (2), .br io_getevents (2), .br io_setup (2), .br aio (7) .\" .sh author .\" kent yoder. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getnetent.3 .\" copyright (c) 2004 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th set_tid_address 2 2021-06-20 "linux" "linux programmer's manual" .sh name set_tid_address \- set pointer to thread id .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "pid_t syscall(sys_set_tid_address, int *" tidptr ); .fi .pp .ir note : glibc provides no wrapper for .br set_tid_address (), necessitating the use of .br syscall (2). .sh description for each thread, the kernel maintains two attributes (addresses) called .i set_child_tid and .ir clear_child_tid . these two attributes contain the value null by default. .tp .i set_child_tid if a thread is started using .br clone (2) with the .b clone_child_settid flag, .i set_child_tid is set to the value passed in the .i ctid argument of that system call. .ip when .i set_child_tid is set, the very first thing the new thread does is to write its thread id at this address. .tp .i clear_child_tid if a thread is started using .br clone (2) with the .b clone_child_cleartid flag, .i clear_child_tid is set to the value passed in the .i ctid argument of that system call. .pp the system call .br set_tid_address () sets the .i clear_child_tid value for the calling thread to .ir tidptr . .pp when a thread whose .i clear_child_tid is not null terminates, then, if the thread is sharing memory with other threads, then 0 is written at the address specified in .i clear_child_tid and the kernel performs the following operation: .pp futex(clear_child_tid, futex_wake, 1, null, null, 0); .pp the effect of this operation is to wake a single thread that is performing a futex wait on the memory location. errors from the futex wake operation are ignored. .sh return value .br set_tid_address () always returns the caller's thread id. .sh errors .br set_tid_address () always succeeds. .sh versions this call is present since linux 2.5.48. details as given here are valid since linux 2.5.49. .sh conforming to this system call is linux-specific. .sh see also .br clone (2), .br futex (2), .br gettid (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getcwd.3 .\" because getcwd(3) is layered on a system call of the same name .so man3/xdr.3 .so man3/posix_memalign.3 .so man3/key_setsecret.3 .so man3/rpc.3 .so man3/getservent_r.3 .\" copyright (c) michael haardt (michael@cantor.informatik.rwth-aachen.de), .\" sun jan 15 19:16:33 1995 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified, sun feb 26 15:02:58 1995, faith@cs.unc.edu .th lp 4 2021-03-22 "linux" "linux programmer's manual" .sh name lp \- line printer devices .sh synopsis .nf .b #include .fi .sh configuration \fblp\fp[0\(en2] are character devices for the parallel line printers; they have major number 6 and minor number 0\(en2. the minor numbers correspond to the printer port base addresses 0x03bc, 0x0378, and 0x0278. usually they have mode 220 and are owned by user .i root and group .ir lp . you can use printer ports either with polling or with interrupts. interrupts are recommended when high traffic is expected, for example, for laser printers. for typical dot matrix printers, polling will usually be enough. the default is polling. .sh description the following .br ioctl (2) calls are supported: .ip "\fbint ioctl(int \fp\fifd\fp\fb, lptime, int \fp\fiarg\fp\fb)\fp" sets the amount of time that the driver sleeps before rechecking the printer when the printer's buffer appears to be filled to .ir arg . if you have a fast printer, decrease this number; if you have a slow printer, then increase it. this is in hundredths of a second, the default 2 being 0.02 seconds. it influences only the polling driver. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpchar, int \fp\fiarg\fp\fb)\fp" sets the maximum number of busy-wait iterations which the polling driver does while waiting for the printer to get ready for receiving a character to .ir arg . if printing is too slow, increase this number; if the system gets too slow, decrease this number. the default is 1000. it influences only the polling driver. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpabort, int \fp\fiarg\fp\fb)\fp" if .i arg is 0, the printer driver will retry on errors, otherwise it will abort. the default is 0. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpabortopen, int \fp\fiarg\fp\fb)\fp" if .i arg is 0, .br open (2) will be aborted on error, otherwise error will be ignored. the default is to ignore it. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpcareful, int \fp\fiarg\fp\fb)\fp" if .i arg is 0, then the out-of-paper, offline, and error signals are required to be false on all writes, otherwise they are ignored. the default is to ignore them. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpwait, int \fp\fiarg\fp\fb)\fp" sets the number of busy waiting iterations to wait before strobing the printer to accept a just-written character, and the number of iterations to wait before turning the strobe off again, to .ir arg . the specification says this time should be 0.5 microseconds, but experience has shown the delay caused by the code is already enough. for that reason, the default value is 0. .\" fixme . actually, since linux 2.2, the default is 1 this is used for both the polling and the interrupt driver. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpsetirq, int \fp\fiarg\fp\fb)\fp" this .br ioctl (2) requires superuser privileges. it takes an .i int containing the new irq as argument. as a side effect, the printer will be reset. when .i arg is 0, the polling driver will be used, which is also default. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpgetirq, int *\fp\fiarg\fp\fb)\fp" stores the currently used irq in .ir arg . .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpgetstatus, int *\fp\fiarg\fp\fb)\fp" stores the value of the status port in .ir arg . the bits have the following meaning: .ts l l. lp_pbusy inverted busy input, active high lp_pack unchanged acknowledge input, active low lp_poutpa unchanged out-of-paper input, active high lp_pselecd unchanged selected input, active high lp_perrorp unchanged error input, active low .te .ip refer to your printer manual for the meaning of the signals. note that undocumented bits may also be set, depending on your printer. .ip "\fbint ioctl(int \fp\fifd\fp\fb, lpreset)\fp" resets the printer. no argument is used. .sh files .i /dev/lp* .\" .sh authors .\" the printer driver was originally written by jim weigand and linus .\" torvalds. .\" it was further improved by michael k.\& johnson. .\" the interrupt code was written by nigel gamble. .\" alan cox modularized it. .\" lpcareful, lpabort, lpgetstatus were added by chris metcalf. .sh see also .br chmod (1), .br chown (1), .br mknod (1), .br lpcntl (8), .br tunelp (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:41:34 1993 by rik faith (faith@cs.unc.edu) .\" modified wed oct 17 01:12:26 2001 by john levon .th strdup 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strdup, strndup, strdupa, strndupa \- duplicate a string .sh synopsis .nf .b #include .pp .bi "char *strdup(const char *" s ); .pp .bi "char *strndup(const char *" s ", size_t " n ); .bi "char *strdupa(const char *" s ); .bi "char *strndupa(const char *" s ", size_t " n ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strdup (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br strndup (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .pp .br strdupa (), .br strndupa (): .nf _gnu_source .fi .sh description the .br strdup () function returns a pointer to a new string which is a duplicate of the string .ir s . memory for the new string is obtained with .br malloc (3), and can be freed with .br free (3). .pp the .br strndup () function is similar, but copies at most .i n bytes. if .i s is longer than .ir n , only .i n bytes are copied, and a terminating null byte (\(aq\e0\(aq) is added. .pp .br strdupa () and .br strndupa () are similar, but use .br alloca (3) to allocate the buffer. they are available only when using the gnu gcc suite, and suffer from the same limitations described in .br alloca (3). .sh return value on success, the .br strdup () function returns a pointer to the duplicated string. it returns null if insufficient memory was available, with .i errno set to indicate the error. .sh errors .tp .b enomem insufficient memory available to allocate duplicate string. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strdup (), .br strndup (), .br strdupa (), .br strndupa () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .\" 4.3bsd-reno, not (first) 4.3bsd. .br strdup () conforms to svr4, 4.3bsd, posix.1-2001. .br strndup () conforms to posix.1-2008. .br strdupa () and .br strndupa () are gnu extensions. .sh see also .br alloca (3), .br calloc (3), .br free (3), .br malloc (3), .br realloc (3), .br string (3), .br wcsdup (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/vm86.2 .so man2/pciconfig_read.2 .so man3/hsearch.3 .\" copyright (c) 2014 kees cook .\" and copyright (c) 2012 will drewry .\" and copyright (c) 2008, 2014,2017 michael kerrisk .\" and copyright (c) 2017 tyler hicks .\" and copyright (c) 2020 tycho andersen .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th seccomp 2 2021-08-27 "linux" "linux programmer's manual" .sh name seccomp \- operate on secure computing state of the process .sh synopsis .nf .br "#include " " /* definition of " seccomp_* " constants */" .br "#include " " /* definition of " "struct sock_fprog" " */" .br "#include " " /* definition of " audit_* " constants */" .br "#include " " /* definition of " sig* " constants */" .br "#include " " /* definition of " ptrace_* " constants */" .\" kees cook noted: anything that uses seccomp_ret_trace returns will .\" need .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_seccomp, unsigned int " operation ", unsigned int " flags , .bi " void *" args ); .fi .pp .ir note : glibc provides no wrapper for .br seccomp (), necessitating the use of .br syscall (2). .sh description the .br seccomp () system call operates on the secure computing (seccomp) state of the calling process. .pp currently, linux supports the following .ir operation values: .tp .br seccomp_set_mode_strict the only system calls that the calling thread is permitted to make are .br read (2), .br write (2), .br _exit (2) (but not .br exit_group (2)), and .br sigreturn (2). other system calls result in the termination of the calling thread, or termination of the entire process with the .br sigkill signal when there is only one thread. strict secure computing mode is useful for number-crunching applications that may need to execute untrusted byte code, perhaps obtained by reading from a pipe or socket. .ip note that although the calling thread can no longer call .br sigprocmask (2), it can use .br sigreturn (2) to block all signals apart from .br sigkill and .br sigstop . this means that .br alarm (2) (for example) is not sufficient for restricting the process's execution time. instead, to reliably terminate the process, .br sigkill must be used. this can be done by using .br timer_create (2) with .br sigev_signal and .ir sigev_signo set to .br sigkill , or by using .br setrlimit (2) to set the hard limit for .br rlimit_cpu . .ip this operation is available only if the kernel is configured with .br config_seccomp enabled. .ip the value of .ir flags must be 0, and .ir args must be null. .ip this operation is functionally identical to the call: .ip .in +4n .ex prctl(pr_set_seccomp, seccomp_mode_strict); .ee .in .tp .br seccomp_set_mode_filter the system calls allowed are defined by a pointer to a berkeley packet filter (bpf) passed via .ir args . this argument is a pointer to a .ir "struct\ sock_fprog" ; it can be designed to filter arbitrary system calls and system call arguments. if the filter is invalid, .br seccomp () fails, returning .br einval in .ir errno . .ip if .br fork (2) or .br clone (2) is allowed by the filter, any child processes will be constrained to the same system call filters as the parent. if .br execve (2) is allowed, the existing filters will be preserved across a call to .br execve (2). .ip in order to use the .br seccomp_set_mode_filter operation, either the calling thread must have the .br cap_sys_admin capability in its user namespace, or the thread must already have the .i no_new_privs bit set. if that bit was not already set by an ancestor of this thread, the thread must make the following call: .ip .in +4n .ex prctl(pr_set_no_new_privs, 1); .ee .in .ip otherwise, the .br seccomp_set_mode_filter operation fails and returns .br eacces in .ir errno . this requirement ensures that an unprivileged process cannot apply a malicious filter and then invoke a set-user-id or other privileged program using .br execve (2), thus potentially compromising that program. (such a malicious filter might, for example, cause an attempt to use .br setuid (2) to set the caller's user ids to nonzero values to instead return 0 without actually making the system call. thus, the program might be tricked into retaining superuser privileges in circumstances where it is possible to influence it to do dangerous things because it did not actually drop privileges.) .ip if .br prctl (2) or .br seccomp () is allowed by the attached filter, further filters may be added. this will increase evaluation time, but allows for further reduction of the attack surface during execution of a thread. .ip the .br seccomp_set_mode_filter operation is available only if the kernel is configured with .br config_seccomp_filter enabled. .ip when .ir flags is 0, this operation is functionally identical to the call: .ip .in +4n .ex prctl(pr_set_seccomp, seccomp_mode_filter, args); .ee .in .ip the recognized .ir flags are: .rs .tp .br seccomp_filter_flag_log " (since linux 4.14)" .\" commit e66a39977985b1e69e17c4042cb290768eca9b02 all filter return actions except .br seccomp_ret_allow should be logged. an administrator may override this filter flag by preventing specific actions from being logged via the .ir /proc/sys/kernel/seccomp/actions_logged file. .tp .br seccomp_filter_flag_new_listener " (since linux 5.0)" .\" commit 6a21cc50f0c7f87dae5259f6cfefe024412313f6 after successfully installing the filter program, return a new user-space notification file descriptor. (the close-on-exec flag is set for the file descriptor.) when the filter returns .br seccomp_ret_user_notif a notification will be sent to this file descriptor. .ip at most one seccomp filter using the .br seccomp_filter_flag_new_listener flag can be installed for a thread. .ip see .br seccomp_unotify (2) for further details. .tp .br seccomp_filter_flag_spec_allow " (since linux 4.17)" .\" commit 00a02d0c502a06d15e07b857f8ff921e3e402675 disable speculative store bypass mitigation. .tp .br seccomp_filter_flag_tsync when adding a new filter, synchronize all other threads of the calling process to the same seccomp filter tree. a "filter tree" is the ordered list of filters attached to a thread. (attaching identical filters in separate .br seccomp () calls results in different filters from this perspective.) .ip if any thread cannot synchronize to the same filter tree, the call will not attach the new seccomp filter, and will fail, returning the first thread id found that cannot synchronize. synchronization will fail if another thread in the same process is in .br seccomp_mode_strict or if it has attached new seccomp filters to itself, diverging from the calling thread's filter tree. .re .tp .br seccomp_get_action_avail " (since linux 4.14)" .\" commit d612b1fd8010d0d67b5287fe146b8b55bcbb8655 test to see if an action is supported by the kernel. this operation is helpful to confirm that the kernel knows of a more recently added filter return action since the kernel treats all unknown actions as .br seccomp_ret_kill_process . .ip the value of .ir flags must be 0, and .ir args must be a pointer to an unsigned 32-bit filter return action. .tp .br seccomp_get_notif_sizes " (since linux 5.0)" .\" commit 6a21cc50f0c7f87dae5259f6cfefe024412313f6 get the sizes of the seccomp user-space notification structures. since these structures may evolve and grow over time, this command can be used to determine how much memory to allocate for sending and receiving notifications. .ip the value of .ir flags must be 0, and .ir args must be a pointer to a .ir "struct seccomp_notif_sizes" , which has the following form: .ip .ex struct seccomp_notif_sizes __u16 seccomp_notif; /* size of notification structure */ __u16 seccomp_notif_resp; /* size of response structure */ __u16 seccomp_data; /* size of \(aqstruct seccomp_data\(aq */ }; .ee .ip see .br seccomp_unotify (2) for further details. .\" .ss filters when adding filters via .br seccomp_set_mode_filter , .ir args points to a filter program: .pp .in +4n .ex struct sock_fprog { unsigned short len; /* number of bpf instructions */ struct sock_filter *filter; /* pointer to array of bpf instructions */ }; .ee .in .pp each program must contain one or more bpf instructions: .pp .in +4n .ex struct sock_filter { /* filter block */ __u16 code; /* actual filter code */ __u8 jt; /* jump true */ __u8 jf; /* jump false */ __u32 k; /* generic multiuse field */ }; .ee .in .pp when executing the instructions, the bpf program operates on the system call information made available (i.e., use the .br bpf_abs addressing mode) as a (read-only) .\" quoting kees cook: .\" if bpf even allows changing the data, it's not copied back to .\" the syscall when it runs. anything wanting to do things like .\" that would need to use ptrace to catch the call and directly .\" modify the registers before continuing with the call. buffer of the following form: .pp .in +4n .ex struct seccomp_data { int nr; /* system call number */ __u32 arch; /* audit_arch_* value (see ) */ __u64 instruction_pointer; /* cpu instruction pointer */ __u64 args[6]; /* up to 6 system call arguments */ }; .ee .in .pp because numbering of system calls varies between architectures and some architectures (e.g., x86-64) allow user-space code to use the calling conventions of multiple architectures (and the convention being used may vary over the life of a process that uses .br execve (2) to execute binaries that employ the different conventions), it is usually necessary to verify the value of the .ir arch field. .pp it is strongly recommended to use an allow-list approach whenever possible because such an approach is more robust and simple. a deny-list will have to be updated whenever a potentially dangerous system call is added (or a dangerous flag or option if those are deny-listed), and it is often possible to alter the representation of a value without altering its meaning, leading to a deny-list bypass. see also .ir caveats below. .pp the .ir arch field is not unique for all calling conventions. the x86-64 abi and the x32 abi both use .br audit_arch_x86_64 as .ir arch , and they run on the same processors. instead, the mask .br __x32_syscall_bit is used on the system call number to tell the two abis apart. .\" as noted by dave drysdale in a note at the end of .\" https://lwn.net/articles/604515/ .\" one additional detail to point out for the x32 abi case: .\" the syscall number gets a high bit set (__x32_syscall_bit), .\" to mark it as an x32 call. .\" .\" if x32 support is included in the kernel, then __syscall_mask .\" will have a value that is not all-ones, and this will trigger .\" an extra instruction in system_call to mask off the extra bit, .\" so that the syscall table indexing still works. .pp this means that a policy must either deny all syscalls with .br __x32_syscall_bit or it must recognize syscalls with and without .br __x32_syscall_bit set. a list of system calls to be denied based on .ir nr that does not also contain .ir nr values with .br __x32_syscall_bit set can be bypassed by a malicious program that sets .br __x32_syscall_bit . .pp additionally, kernels prior to linux 5.4 incorrectly permitted .ir nr in the ranges 512-547 as well as the corresponding non-x32 syscalls ored with .br __x32_syscall_bit . for example, .ir nr == 521 and .ir nr == (101 | .br __x32_syscall_bit ) would result in invocations of .br ptrace (2) with potentially confused x32-vs-x86_64 semantics in the kernel. policies intended to work on kernels before linux 5.4 must ensure that they deny or otherwise correctly handle these system calls. on linux 5.4 and newer, .\" commit 6365b842aae4490ebfafadfc6bb27a6d3cc54757 such system calls will fail with the error .br enosys , without doing anything. .pp the .i instruction_pointer field provides the address of the machine-language instruction that performed the system call. this might be useful in conjunction with the use of .i /proc/[pid]/maps to perform checks based on which region (mapping) of the program made the system call. (probably, it is wise to lock down the .br mmap (2) and .br mprotect (2) system calls to prevent the program from subverting such checks.) .pp when checking values from .ir args , keep in mind that arguments are often silently truncated before being processed, but after the seccomp check. for example, this happens if the i386 abi is used on an x86-64 kernel: although the kernel will normally not look beyond the 32 lowest bits of the arguments, the values of the full 64-bit registers will be present in the seccomp data. a less surprising example is that if the x86-64 abi is used to perform a system call that takes an argument of type .ir int , the more-significant half of the argument register is ignored by the system call, but visible in the seccomp data. .pp a seccomp filter returns a 32-bit value consisting of two parts: the most significant 16 bits (corresponding to the mask defined by the constant .br seccomp_ret_action_full ) contain one of the "action" values listed below; the least significant 16-bits (defined by the constant .br seccomp_ret_data ) are "data" to be associated with this return value. .pp if multiple filters exist, they are \fiall\fp executed, in reverse order of their addition to the filter tree\(emthat is, the most recently installed filter is executed first. (note that all filters will be called even if one of the earlier filters returns .br seccomp_ret_kill . this is done to simplify the kernel code and to provide a tiny speed-up in the execution of sets of filters by avoiding a check for this uncommon case.) .\" from an aug 2015 conversation with kees cook where i asked why *all* .\" filters are applied even if one of the early filters returns .\" seccomp_ret_kill: .\" .\" it's just because it would be an optimization that would only speed up .\" the ret_kill case, but it's the uncommon one and the one that doesn't .\" benefit meaningfully from such a change (you need to kill the process .\" really quickly?). we would speed up killing a program at the (albeit .\" tiny) expense to all other filtered programs. best to keep the filter .\" execution logic clear, simple, and as fast as possible for all .\" filters. the return value for the evaluation of a given system call is the first-seen action value of highest precedence (along with its accompanying data) returned by execution of all of the filters. .pp in decreasing order of precedence, the action values that may be returned by a seccomp filter are: .tp .br seccomp_ret_kill_process " (since linux 4.14)" .\" commit 4d3b0b05aae9ee9ce0970dc4cc0fb3fad5e85945 .\" commit 0466bdb99e8744bc9befa8d62a317f0fd7fd7421 this value results in immediate termination of the process, with a core dump. the system call is not executed. by contrast with .br seccomp_ret_kill_thread below, all threads in the thread group are terminated. (for a discussion of thread groups, see the description of the .br clone_thread flag in .br clone (2).) .ip the process terminates .i "as though" killed by a .b sigsys signal. even if a signal handler has been registered for .br sigsys , the handler will be ignored in this case and the process always terminates. to a parent process that is waiting on this process (using .br waitpid (2) or similar), the returned .i wstatus will indicate that its child was terminated as though by a .br sigsys signal. .tp .br seccomp_ret_kill_thread " (or " seccomp_ret_kill ) this value results in immediate termination of the thread that made the system call. the system call is not executed. other threads in the same thread group will continue to execute. .ip the thread terminates .i "as though" killed by a .b sigsys signal. see .br seccomp_ret_kill_process above. .ip .\" see these commits: .\" seccomp: dump core when using seccomp_ret_kill .\" (b25e67161c295c98acda92123b2dd1e7d8642901) .\" seccomp: only dump core when single-threaded .\" (d7276e321ff8a53106a59c85ca46d03e34288893) before linux 4.11, any process terminated in this way would not trigger a coredump (even though .b sigsys is documented in .br signal (7) as having a default action of termination with a core dump). since linux 4.11, a single-threaded process will dump core if terminated in this way. .ip with the addition of .br seccomp_ret_kill_process in linux 4.14, .br seccomp_ret_kill_thread was added as a synonym for .br seccomp_ret_kill , in order to more clearly distinguish the two actions. .ip .br note : the use of .br seccomp_ret_kill_thread to kill a single thread in a multithreaded process is likely to leave the process in a permanently inconsistent and possibly corrupt state. .tp .br seccomp_ret_trap this value results in the kernel sending a thread-directed .br sigsys signal to the triggering thread. (the system call is not executed.) various fields will be set in the .i siginfo_t structure (see .br sigaction (2)) associated with signal: .rs .ip * 3 .i si_signo will contain .br sigsys . .ip * .ir si_call_addr will show the address of the system call instruction. .ip * .ir si_syscall and .ir si_arch will indicate which system call was attempted. .ip * .i si_code will contain .br sys_seccomp . .ip * .i si_errno will contain the .br seccomp_ret_data portion of the filter return value. .re .ip the program counter will be as though the system call happened (i.e., the program counter will not point to the system call instruction). the return value register will contain an architecture\-dependent value; if resuming execution, set it to something appropriate for the system call. (the architecture dependency is because replacing it with .br enosys could overwrite some useful information.) .tp .br seccomp_ret_errno this value results in the .b seccomp_ret_data portion of the filter's return value being passed to user space as the .ir errno value without executing the system call. .tp .br seccomp_ret_user_notif " (since linux 5.0)" .\" commit 6a21cc50f0c7f87dae5259f6cfefe024412313f6 forward the system call to an attached user-space supervisor process to allow that process to decide what to do with the system call. if there is no attached supervisor (either because the filter was not installed with the .br seccomp_filter_flag_new_listener flag or because the file descriptor was closed), the filter returns .br enosys (similar to what happens when a filter returns .br seccomp_ret_trace and there is no tracer). see .br seccomp_unotify (2) for further details. .ip note that the supervisor process will not be notified if another filter returns an action value with a precedence greater than .br seccomp_ret_user_notif . .tp .br seccomp_ret_trace when returned, this value will cause the kernel to attempt to notify a .br ptrace (2)-based tracer prior to executing the system call. if there is no tracer present, the system call is not executed and returns a failure status with .i errno set to .br enosys . .ip a tracer will be notified if it requests .br ptrace_o_traceseccomp using .ir ptrace(ptrace_setoptions) . the tracer will be notified of a .br ptrace_event_seccomp and the .br seccomp_ret_data portion of the filter's return value will be available to the tracer via .br ptrace_geteventmsg . .ip the tracer can skip the system call by changing the system call number to \-1. alternatively, the tracer can change the system call requested by changing the system call to a valid system call number. if the tracer asks to skip the system call, then the system call will appear to return the value that the tracer puts in the return value register. .ip .\" this was changed in ce6526e8afa4. .\" a related hole, using ptrace_syscall instead of seccomp_ret_trace, was .\" changed in arch-specific commits, e.g. 93e35efb8de4 for x86 and .\" 0f3912fd934c for arm. before kernel 4.8, the seccomp check will not be run again after the tracer is notified. (this means that, on older kernels, seccomp-based sandboxes .b "must not" allow use of .br ptrace (2)\(emeven of other sandboxed processes\(emwithout extreme care; ptracers can use this mechanism to escape from the seccomp sandbox.) .ip note that a tracer process will not be notified if another filter returns an action value with a precedence greater than .br seccomp_ret_trace . .tp .br seccomp_ret_log " (since linux 4.14)" .\" commit 59f5cf44a38284eb9e76270c786fb6cc62ef8ac4 this value results in the system call being executed after the filter return action is logged. an administrator may override the logging of this action via the .ir /proc/sys/kernel/seccomp/actions_logged file. .tp .br seccomp_ret_allow this value results in the system call being executed. .pp if an action value other than one of the above is specified, then the filter action is treated as either .br seccomp_ret_kill_process (since linux 4.14) .\" commit 4d3b0b05aae9ee9ce0970dc4cc0fb3fad5e85945 or .br seccomp_ret_kill_thread (in linux 4.13 and earlier). .\" .ss /proc interfaces the files in the directory .ir /proc/sys/kernel/seccomp provide additional seccomp information and configuration: .tp .ir actions_avail " (since linux 4.14)" .\" commit 8e5f1ad116df6b0de65eac458d5e7c318d1c05af a read-only ordered list of seccomp filter return actions in string form. the ordering, from left-to-right, is in decreasing order of precedence. the list represents the set of seccomp filter return actions supported by the kernel. .tp .ir actions_logged " (since linux 4.14)" .\" commit 0ddec0fc8900201c0897b87b762b7c420436662f a read-write ordered list of seccomp filter return actions that are allowed to be logged. writes to the file do not need to be in ordered form but reads from the file will be ordered in the same way as the .ir actions_avail file. .ip it is important to note that the value of .ir actions_logged does not prevent certain filter return actions from being logged when the audit subsystem is configured to audit a task. if the action is not found in the .ir actions_logged file, the final decision on whether to audit the action for that task is ultimately left up to the audit subsystem to decide for all filter return actions other than .br seccomp_ret_allow . .ip the "allow" string is not accepted in the .ir actions_logged file as it is not possible to log .br seccomp_ret_allow actions. attempting to write "allow" to the file will fail with the error .br einval . .\" .ss audit logging of seccomp actions .\" commit 59f5cf44a38284eb9e76270c786fb6cc62ef8ac4 since linux 4.14, the kernel provides the facility to log the actions returned by seccomp filters in the audit log. the kernel makes the decision to log an action based on the action type, whether or not the action is present in the .i actions_logged file, and whether kernel auditing is enabled (e.g., via the kernel boot option .ir audit=1 ). .\" or auditing could be enabled via the netlink api (audit_set) the rules are as follows: .ip * 3 if the action is .br seccomp_ret_allow , the action is not logged. .ip * otherwise, if the action is either .br seccomp_ret_kill_process or .br seccomp_ret_kill_thread , and that action appears in the .ir actions_logged file, the action is logged. .ip * otherwise, if the filter has requested logging (the .br seccomp_filter_flag_log flag) and the action appears in the .ir actions_logged file, the action is logged. .ip * otherwise, if kernel auditing is enabled and the process is being audited .rb ( autrace (8)), the action is logged. .ip * otherwise, the action is not logged. .sh return value on success, .br seccomp () returns 0. on error, if .br seccomp_filter_flag_tsync was used, the return value is the id of the thread that caused the synchronization failure. (this id is a kernel thread id of the type returned by .br clone (2) and .br gettid (2).) on other errors, \-1 is returned, and .ir errno is set to indicate the error. .sh errors .br seccomp () can fail for the following reasons: .tp .br eacces the caller did not have the .br cap_sys_admin capability in its user namespace, or had not set .ir no_new_privs before using .br seccomp_set_mode_filter . .tp .br ebusy while installing a new filter, the .br seccomp_filter_flag_new_listener flag was specified, but a previous filter had already been installed with that flag. .tp .br efault .ir args was not a valid address. .tp .br einval .ir operation is unknown or is not supported by this kernel version or configuration. .tp .b einval the specified .ir flags are invalid for the given .ir operation . .tp .br einval .i operation included .br bpf_abs , but the specified offset was not aligned to a 32-bit boundary or exceeded .ir "sizeof(struct\ seccomp_data)" . .tp .br einval .\" see kernel/seccomp.c::seccomp_may_assign_mode() in 3.18 sources a secure computing mode has already been set, and .i operation differs from the existing setting. .tp .br einval .i operation specified .br seccomp_set_mode_filter , but the filter program pointed to by .i args was not valid or the length of the filter program was zero or exceeded .b bpf_maxinsns (4096) instructions. .tp .br enomem out of memory. .tp .br enomem .\" enomem in kernel/seccomp.c::seccomp_attach_filter() in 3.18 sources the total length of all filter programs attached to the calling thread would exceed .b max_insns_per_path (32768) instructions. note that for the purposes of calculating this limit, each already existing filter program incurs an overhead penalty of 4 instructions. .tp .br eopnotsupp .i operation specified .br seccomp_get_action_avail , but the kernel does not support the filter return action specified by .ir args . .tp .br esrch another thread caused a failure during thread sync, but its id could not be determined. .sh versions the .br seccomp () system call first appeared in linux 3.17. .\" fixme . add glibc version .sh conforming to the .br seccomp () system call is a nonstandard linux extension. .sh notes rather than hand-coding seccomp filters as shown in the example below, you may prefer to employ the .i libseccomp library, which provides a front-end for generating seccomp filters. .pp the .ir seccomp field of the .ir /proc/[pid]/status file provides a method of viewing the seccomp mode of a process; see .br proc (5). .pp .br seccomp () provides a superset of the functionality provided by the .br prctl (2) .br pr_set_seccomp operation (which does not support .ir flags ). .pp since linux 4.4, the .br ptrace (2) .b ptrace_seccomp_get_filter operation can be used to dump a process's seccomp filters. .\" .ss architecture support for seccomp bpf architecture support for seccomp bpf filtering .\" check by grepping for have_arch_seccomp_filter in kconfig files in .\" kernel source. last checked in linux 4.16-rc source. is available on the following architectures: .ip * 3 x86-64, i386, x32 (since linux 3.5) .pd 0 .ip * arm (since linux 3.8) .ip * s390 (since linux 3.8) .ip * mips (since linux 3.16) .ip * arm-64 (since linux 3.19) .ip * powerpc (since linux 4.3) .ip * tile (since linux 4.3) .ip * pa-risc (since linux 4.6) .\" user mode linux since linux 4.6 .pd .\" .ss caveats there are various subtleties to consider when applying seccomp filters to a program, including the following: .ip * 3 some traditional system calls have user-space implementations in the .br vdso (7) on many architectures. notable examples include .br clock_gettime (2), .br gettimeofday (2), and .br time (2). on such architectures, seccomp filtering for these system calls will have no effect. (however, there are cases where the .br vdso (7) implementations may fall back to invoking the true system call, in which case seccomp filters would see the system call.) .ip * seccomp filtering is based on system call numbers. however, applications typically do not directly invoke system calls, but instead call wrapper functions in the c library which in turn invoke the system calls. consequently, one must be aware of the following: .rs .ip \(bu 3 the glibc wrappers for some traditional system calls may actually employ system calls with different names in the kernel. for example, the .br exit (2) wrapper function actually employs the .br exit_group (2) system call, and the .br fork (2) wrapper function actually calls .br clone (2). .ip \(bu the behavior of wrapper functions may vary across architectures, according to the range of system calls provided on those architectures. in other words, the same wrapper function may invoke different system calls on different architectures. .ip \(bu finally, the behavior of wrapper functions can change across glibc versions. for example, in older versions, the glibc wrapper function for .br open (2) invoked the system call of the same name, but starting in glibc 2.26, the implementation switched to calling .br openat (2) on all architectures. .re .pp the consequence of the above points is that it may be necessary to filter for a system call other than might be expected. various manual pages in section 2 provide helpful details about the differences between wrapper functions and the underlying system calls in subsections entitled .ir "c library/kernel differences" . .pp furthermore, note that the application of seccomp filters even risks causing bugs in an application, when the filters cause unexpected failures for legitimate operations that the application might need to perform. such bugs may not easily be discovered when testing the seccomp filters if the bugs occur in rarely used application code paths. .\" .ss seccomp-specific bpf details note the following bpf details specific to seccomp filters: .ip * 3 the .b bpf_h and .b bpf_b size modifiers are not supported: all operations must load and store (4-byte) words .rb ( bpf_w ). .ip * to access the contents of the .i seccomp_data buffer, use the .b bpf_abs addressing mode modifier. .ip * the .b bpf_len addressing mode modifier yields an immediate mode operand whose value is the size of the .ir seccomp_data buffer. .sh examples the program below accepts four or more arguments. the first three arguments are a system call number, a numeric architecture identifier, and an error number. the program uses these values to construct a bpf filter that is used at run time to perform the following checks: .ip [1] 4 if the program is not running on the specified architecture, the bpf filter causes system calls to fail with the error .br enosys . .ip [2] if the program attempts to execute the system call with the specified number, the bpf filter causes the system call to fail, with .i errno being set to the specified error number. .pp the remaining command-line arguments specify the pathname and additional arguments of a program that the example program should attempt to execute using .br execv (3) (a library function that employs the .br execve (2) system call). some example runs of the program are shown below. .pp first, we display the architecture that we are running on (x86-64) and then construct a shell function that looks up system call numbers on this architecture: .pp .in +4n .ex $ \fbuname \-m\fp x86_64 $ \fbsyscall_nr() { cat /usr/src/linux/arch/x86/syscalls/syscall_64.tbl | \e awk \(aq$2 != "x32" && $3 == "\(aq$1\(aq" { print $1 }\(aq }\fp .ee .in .pp when the bpf filter rejects a system call (case [2] above), it causes the system call to fail with the error number specified on the command line. in the experiments shown here, we'll use error number 99: .pp .in +4n .ex $ \fberrno 99\fp eaddrnotavail 99 cannot assign requested address .ee .in .pp in the following example, we attempt to run the command .br whoami (1), but the bpf filter rejects the .br execve (2) system call, so that the command is not even executed: .pp .in +4n .ex $ \fbsyscall_nr execve\fp 59 $ \fb./a.out\fp usage: ./a.out [] hint for : audit_arch_i386: 0x40000003 audit_arch_x86_64: 0xc000003e $ \fb./a.out 59 0xc000003e 99 /bin/whoami\fp execv: cannot assign requested address .ee .in .pp in the next example, the bpf filter rejects the .br write (2) system call, so that, although it is successfully started, the .br whoami (1) command is not able to write output: .pp .in +4n .ex $ \fbsyscall_nr write\fp 1 $ \fb./a.out 1 0xc000003e 99 /bin/whoami\fp .ee .in .pp in the final example, the bpf filter rejects a system call that is not used by the .br whoami (1) command, so it is able to successfully execute and produce output: .pp .in +4n .ex $ \fbsyscall_nr preadv\fp 295 $ \fb./a.out 295 0xc000003e 99 /bin/whoami\fp cecilia .ee .in .ss program source .ex #include #include #include #include #include #include #include #include #include #define x32_syscall_bit 0x40000000 #define array_size(arr) (sizeof(arr) / sizeof((arr)[0])) static int install_filter(int syscall_nr, int t_arch, int f_errno) { unsigned int upper_nr_limit = 0xffffffff; /* assume that audit_arch_x86_64 means the normal x86\-64 abi (in the x32 abi, all system calls have bit 30 set in the \(aqnr\(aq field, meaning the numbers are >= x32_syscall_bit). */ if (t_arch == audit_arch_x86_64) upper_nr_limit = x32_syscall_bit \- 1; struct sock_filter filter[] = { /* [0] load architecture from \(aqseccomp_data\(aq buffer into accumulator. */ bpf_stmt(bpf_ld | bpf_w | bpf_abs, (offsetof(struct seccomp_data, arch))), /* [1] jump forward 5 instructions if architecture does not match \(aqt_arch\(aq. */ bpf_jump(bpf_jmp | bpf_jeq | bpf_k, t_arch, 0, 5), /* [2] load system call number from \(aqseccomp_data\(aq buffer into accumulator. */ bpf_stmt(bpf_ld | bpf_w | bpf_abs, (offsetof(struct seccomp_data, nr))), /* [3] check abi \- only needed for x86\-64 in deny\-list use cases. use bpf_jgt instead of checking against the bit mask to avoid having to reload the syscall number. */ bpf_jump(bpf_jmp | bpf_jgt | bpf_k, upper_nr_limit, 3, 0), /* [4] jump forward 1 instruction if system call number does not match \(aqsyscall_nr\(aq. */ bpf_jump(bpf_jmp | bpf_jeq | bpf_k, syscall_nr, 0, 1), /* [5] matching architecture and system call: don\(aqt execute the system call, and return \(aqf_errno\(aq in \(aqerrno\(aq. */ bpf_stmt(bpf_ret | bpf_k, seccomp_ret_errno | (f_errno & seccomp_ret_data)), /* [6] destination of system call number mismatch: allow other system calls. */ bpf_stmt(bpf_ret | bpf_k, seccomp_ret_allow), /* [7] destination of architecture mismatch: kill process. */ bpf_stmt(bpf_ret | bpf_k, seccomp_ret_kill_process), }; struct sock_fprog prog = { .len = array_size(filter), .filter = filter, }; if (seccomp(seccomp_set_mode_filter, 0, &prog)) { perror("seccomp"); return 1; } return 0; } int main(int argc, char *argv[]) { if (argc < 5) { fprintf(stderr, "usage: " "%s []\en" "hint for : audit_arch_i386: 0x%x\en" " audit_arch_x86_64: 0x%x\en" "\en", argv[0], audit_arch_i386, audit_arch_x86_64); exit(exit_failure); } if (prctl(pr_set_no_new_privs, 1, 0, 0, 0)) { perror("prctl"); exit(exit_failure); } if (install_filter(strtol(argv[1], null, 0), strtol(argv[2], null, 0), strtol(argv[3], null, 0))) exit(exit_failure); execv(argv[4], &argv[4]); perror("execv"); exit(exit_failure); } .ee .sh see also .br bpfc (1), .br strace (1), .br bpf (2), .br prctl (2), .br ptrace (2), .br seccomp_unotify (2), .br sigaction (2), .br proc (5), .br signal (7), .br socket (7) .pp various pages from the .i libseccomp library, including: .br scmp_sys_resolver (1), .br seccomp_export_bpf (3), .br seccomp_init (3), .br seccomp_load (3), and .br seccomp_rule_add (3). .pp the kernel source files .ir documentation/networking/filter.txt and .ir documentation/userspace\-api/seccomp_filter.rst .\" commit c061f33f35be0ccc80f4b8e0aea5dfd2ed7e01a3 (or .ir documentation/prctl/seccomp_filter.txt before linux 4.13). .pp mccanne, s.\& and jacobson, v.\& (1992) .ir "the bsd packet filter: a new architecture for user-level packet capture" , proceedings of the usenix winter 1993 conference .ur http://www.tcpdump.org/papers/bpf\-usenix93.pdf .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .so man7/iso_8859-2.7 .\" written by mike frysinger .\" .\" %%%license_start(public_domain) .\" this page is in the public domain. .\" %%%license_end .\" .\" useful background: .\" http://articles.manugarg.com/systemcallinlinux2_6.html .\" https://lwn.net/articles/446528/ .\" http://www.linuxjournal.com/content/creating-vdso-colonels-other-chicken .\" http://www.trilithium.com/johan/2005/08/linux-gate/ .\" .th vdso 7 2021-08-27 "linux" "linux programmer's manual" .sh name vdso \- overview of the virtual elf dynamic shared object .sh synopsis .nf .b #include .pp .b void *vdso = (uintptr_t) getauxval(at_sysinfo_ehdr); .fi .sh description the "vdso" (virtual dynamic shared object) is a small shared library that the kernel automatically maps into the address space of all user-space applications. applications usually do not need to concern themselves with these details as the vdso is most commonly called by the c library. this way you can code in the normal way using standard functions and the c library will take care of using any functionality that is available via the vdso. .pp why does the vdso exist at all? there are some system calls the kernel provides that user-space code ends up using frequently, to the point that such calls can dominate overall performance. this is due both to the frequency of the call as well as the context-switch overhead that results from exiting user space and entering the kernel. .pp the rest of this documentation is geared toward the curious and/or c library writers rather than general developers. if you're trying to call the vdso in your own application rather than using the c library, you're most likely doing it wrong. .ss example background making system calls can be slow. in x86 32-bit systems, you can trigger a software interrupt .ri ( "int $0x80" ) to tell the kernel you wish to make a system call. however, this instruction is expensive: it goes through the full interrupt-handling paths in the processor's microcode as well as in the kernel. newer processors have faster (but backward incompatible) instructions to initiate system calls. rather than require the c library to figure out if this functionality is available at run time, the c library can use functions provided by the kernel in the vdso. .pp note that the terminology can be confusing. on x86 systems, the vdso function used to determine the preferred method of making a system call is named "__kernel_vsyscall", but on x86-64, the term "vsyscall" also refers to an obsolete way to ask the kernel what time it is or what cpu the caller is on. .pp one frequently used system call is .br gettimeofday (2). this system call is called both directly by user-space applications as well as indirectly by the c library. think timestamps or timing loops or polling\(emall of these frequently need to know what time it is right now. this information is also not secret\(emany application in any privilege mode (root or any unprivileged user) will get the same answer. thus the kernel arranges for the information required to answer this question to be placed in memory the process can access. now a call to .br gettimeofday (2) changes from a system call to a normal function call and a few memory accesses. .ss finding the vdso the base address of the vdso (if one exists) is passed by the kernel to each program in the initial auxiliary vector (see .br getauxval (3)), via the .b at_sysinfo_ehdr tag. .pp you must not assume the vdso is mapped at any particular location in the user's memory map. the base address will usually be randomized at run time every time a new process image is created (at .br execve (2) time). this is done for security reasons, to prevent "return-to-libc" attacks. .pp for some architectures, there is also an .b at_sysinfo tag. this is used only for locating the vsyscall entry point and is frequently omitted or set to 0 (meaning it's not available). this tag is a throwback to the initial vdso work (see .ir history below) and its use should be avoided. .ss file format since the vdso is a fully formed elf image, you can do symbol lookups on it. this allows new symbols to be added with newer kernel releases, and allows the c library to detect available functionality at run time when running under different kernel versions. oftentimes the c library will do detection with the first call and then cache the result for subsequent calls. .pp all symbols are also versioned (using the gnu version format). this allows the kernel to update the function signature without breaking backward compatibility. this means changing the arguments that the function accepts as well as the return value. thus, when looking up a symbol in the vdso, you must always include the version to match the abi you expect. .pp typically the vdso follows the naming convention of prefixing all symbols with "__vdso_" or "__kernel_" so as to distinguish them from other standard symbols. for example, the "gettimeofday" function is named "__vdso_gettimeofday". .pp you use the standard c calling conventions when calling any of these functions. no need to worry about weird register or stack behavior. .sh notes .ss source when you compile the kernel, it will automatically compile and link the vdso code for you. you will frequently find it under the architecture-specific directory: .pp find arch/$arch/ \-name \(aq*vdso*.so*\(aq \-o \-name \(aq*gate*.so*\(aq .\" .ss vdso names the name of the vdso varies across architectures. it will often show up in things like glibc's .br ldd (1) output. the exact name should not matter to any code, so do not hardcode it. .if t \{\ .ft cw \} .ts l l. user abi vdso name _ aarch64 linux\-vdso.so.1 arm linux\-vdso.so.1 ia64 linux\-gate.so.1 mips linux\-vdso.so.1 ppc/32 linux\-vdso32.so.1 ppc/64 linux\-vdso64.so.1 riscv linux\-vdso.so.1 s390 linux\-vdso32.so.1 s390x linux\-vdso64.so.1 sh linux\-gate.so.1 i386 linux\-gate.so.1 x86-64 linux\-vdso.so.1 x86/x32 linux\-vdso.so.1 .te .if t \{\ .in .ft p \} .ss strace(1), seccomp(2), and the vdso when tracing systems calls with .br strace (1), symbols (system calls) that are exported by the vdso will .i not appear in the trace output. those system calls will likewise not be visible to .br seccomp (2) filters. .sh architecture-specific notes the subsections below provide architecture-specific notes on the vdso. .pp note that the vdso that is used is based on the abi of your user-space code and not the abi of the kernel. thus, for example, when you run an i386 32-bit elf binary, you'll get the same vdso regardless of whether you run it under an i386 32-bit kernel or under an x86-64 64-bit kernel. therefore, the name of the user-space abi should be used to determine which of the sections below is relevant. .ss arm functions .\" see linux/arch/arm/vdso/vdso.lds.s .\" commit: 8512287a8165592466cb9cb347ba94892e9c56a5 the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __vdso_gettimeofday linux_2.6 (exported since linux 4.1) __vdso_clock_gettime linux_2.6 (exported since linux 4.1) .te .if t \{\ .in .ft p \} .pp .\" see linux/arch/arm/kernel/entry-armv.s .\" see linux/documentation/arm/kernel_user_helpers.txt additionally, the arm port has a code page full of utility functions. since it's just a raw page of code, there is no elf information for doing symbol lookups or versioning. it does provide support for different versions though. .pp for information on this code page, it's best to refer to the kernel documentation as it's extremely detailed and covers everything you need to know: .ir documentation/arm/kernel_user_helpers.txt . .ss aarch64 functions .\" see linux/arch/arm64/kernel/vdso/vdso.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_rt_sigreturn linux_2.6.39 __kernel_gettimeofday linux_2.6.39 __kernel_clock_gettime linux_2.6.39 __kernel_clock_getres linux_2.6.39 .te .if t \{\ .in .ft p \} .ss bfin (blackfin) functions (port removed in linux 4.17) .\" see linux/arch/blackfin/kernel/fixed_code.s .\" see http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:fixed-code as this cpu lacks a memory management unit (mmu), it doesn't set up a vdso in the normal sense. instead, it maps at boot time a few raw functions into a fixed location in memory. user-space applications then call directly into that region. there is no provision for backward compatibility beyond sniffing raw opcodes, but as this is an embedded cpu, it can get away with things\(emsome of the object formats it runs aren't even elf based (they're bflt/flat). .pp for information on this code page, it's best to refer to the public documentation: .br http://docs.blackfin.uclinux.org/doku.php?id=linux\-kernel:fixed\-code .ss mips functions .\" see linux/arch/mips/vdso/vdso.ld.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_gettimeofday linux_2.6 (exported since linux 4.4) __kernel_clock_gettime linux_2.6 (exported since linux 4.4) .te .if t \{\ .in .ft p \} .ss ia64 (itanium) functions .\" see linux/arch/ia64/kernel/gate.lds.s .\" also linux/arch/ia64/kernel/fsys.s and linux/documentation/ia64/fsys.txt the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_sigtramp linux_2.5 __kernel_syscall_via_break linux_2.5 __kernel_syscall_via_epc linux_2.5 .te .if t \{\ .in .ft p \} .pp the itanium port is somewhat tricky. in addition to the vdso above, it also has "light-weight system calls" (also known as "fast syscalls" or "fsys"). you can invoke these via the .i __kernel_syscall_via_epc vdso helper. the system calls listed here have the same semantics as if you called them directly via .br syscall (2), so refer to the relevant documentation for each. the table below lists the functions available via this mechanism. .if t \{\ .ft cw \} .ts l. function _ clock_gettime getcpu getpid getppid gettimeofday set_tid_address .te .if t \{\ .in .ft p \} .ss parisc (hppa) functions .\" see linux/arch/parisc/kernel/syscall.s .\" see linux/documentation/parisc/registers the parisc port has a code page with utility functions called a gateway page. rather than use the normal elf auxiliary vector approach, it passes the address of the page to the process via the sr2 register. the permissions on the page are such that merely executing those addresses automatically executes with kernel privileges and not in user space. this is done to match the way hp-ux works. .pp since it's just a raw page of code, there is no elf information for doing symbol lookups or versioning. simply call into the appropriate offset via the branch instruction, for example: .pp ble (%sr2, %r0) .if t \{\ .ft cw \} .ts l l. offset function _ 00b0 lws_entry (cas operations) 00e0 set_thread_pointer (used by glibc) 0100 linux_gateway_entry (syscall) .te .if t \{\ .in .ft p \} .ss ppc/32 functions .\" see linux/arch/powerpc/kernel/vdso32/vdso32.lds.s the table below lists the symbols exported by the vdso. the functions marked with a .i * are available only when the kernel is a powerpc64 (64-bit) kernel. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_clock_getres linux_2.6.15 __kernel_clock_gettime linux_2.6.15 __kernel_clock_gettime64 linux_5.11 __kernel_datapage_offset linux_2.6.15 __kernel_get_syscall_map linux_2.6.15 __kernel_get_tbfreq linux_2.6.15 __kernel_getcpu \fi*\fr linux_2.6.15 __kernel_gettimeofday linux_2.6.15 __kernel_sigtramp_rt32 linux_2.6.15 __kernel_sigtramp32 linux_2.6.15 __kernel_sync_dicache linux_2.6.15 __kernel_sync_dicache_p5 linux_2.6.15 .te .if t \{\ .in .ft p \} .pp in kernel versions before linux 5.6, .\" commit 654abc69ef2e69712e6d4e8a6cb9292b97a4aa39 the .b clock_realtime_coarse and .b clock_monotonic_coarse clocks are .i not supported by the .i __kernel_clock_getres and .i __kernel_clock_gettime interfaces; the kernel falls back to the real system call. .ss ppc/64 functions .\" see linux/arch/powerpc/kernel/vdso64/vdso64.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_clock_getres linux_2.6.15 __kernel_clock_gettime linux_2.6.15 __kernel_datapage_offset linux_2.6.15 __kernel_get_syscall_map linux_2.6.15 __kernel_get_tbfreq linux_2.6.15 __kernel_getcpu linux_2.6.15 __kernel_gettimeofday linux_2.6.15 __kernel_sigtramp_rt64 linux_2.6.15 __kernel_sync_dicache linux_2.6.15 __kernel_sync_dicache_p5 linux_2.6.15 .te .if t \{\ .in .ft p \} .pp in kernel versions before linux 4.16, .\" commit 5c929885f1bb4b77f85b1769c49405a0e0f154a1 the .b clock_realtime_coarse and .b clock_monotonic_coarse clocks are .i not supported by the .i __kernel_clock_getres and .i __kernel_clock_gettime interfaces; the kernel falls back to the real system call. .ss riscv functions .\" see linux/arch/riscv/kernel/vdso/vdso.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_rt_sigreturn linux_4.15 __kernel_gettimeofday linux_4.15 __kernel_clock_gettime linux_4.15 __kernel_clock_getres linux_4.15 __kernel_getcpu linux_4.15 __kernel_flush_icache linux_4.15 .te .if t \{\ .in .ft p \} .ss s390 functions .\" see linux/arch/s390/kernel/vdso32/vdso32.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_clock_getres linux_2.6.29 __kernel_clock_gettime linux_2.6.29 __kernel_gettimeofday linux_2.6.29 .te .if t \{\ .in .ft p \} .ss s390x functions .\" see linux/arch/s390/kernel/vdso64/vdso64.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_clock_getres linux_2.6.29 __kernel_clock_gettime linux_2.6.29 __kernel_gettimeofday linux_2.6.29 .te .if t \{\ .in .ft p \} .ss sh (superh) functions .\" see linux/arch/sh/kernel/vsyscall/vsyscall.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_rt_sigreturn linux_2.6 __kernel_sigreturn linux_2.6 __kernel_vsyscall linux_2.6 .te .if t \{\ .in .ft p \} .ss i386 functions .\" see linux/arch/x86/vdso/vdso32/vdso32.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __kernel_sigreturn linux_2.5 __kernel_rt_sigreturn linux_2.5 __kernel_vsyscall linux_2.5 .\" added in 7a59ed415f5b57469e22e41fc4188d5399e0b194 and updated .\" in 37c975545ec63320789962bf307f000f08fabd48. __vdso_clock_gettime linux_2.6 (exported since linux 3.15) __vdso_gettimeofday linux_2.6 (exported since linux 3.15) __vdso_time linux_2.6 (exported since linux 3.15) .te .if t \{\ .in .ft p \} .ss x86-64 functions .\" see linux/arch/x86/vdso/vdso.lds.s the table below lists the symbols exported by the vdso. all of these symbols are also available without the "__vdso_" prefix, but you should ignore those and stick to the names below. .if t \{\ .ft cw \} .ts l l. symbol version _ __vdso_clock_gettime linux_2.6 __vdso_getcpu linux_2.6 __vdso_gettimeofday linux_2.6 __vdso_time linux_2.6 .te .if t \{\ .in .ft p \} .ss x86/x32 functions .\" see linux/arch/x86/vdso/vdso32.lds.s the table below lists the symbols exported by the vdso. .if t \{\ .ft cw \} .ts l l. symbol version _ __vdso_clock_gettime linux_2.6 __vdso_getcpu linux_2.6 __vdso_gettimeofday linux_2.6 __vdso_time linux_2.6 .te .if t \{\ .in .ft p \} .ss history the vdso was originally just a single function\(emthe vsyscall. in older kernels, you might see that name in a process's memory map rather than "vdso". over time, people realized that this mechanism was a great way to pass more functionality to user space, so it was reconceived as a vdso in the current format. .sh see also .br syscalls (2), .br getauxval (3), .br proc (5) .pp the documents, examples, and source code in the linux source code tree: .pp .in +4n .ex documentation/abi/stable/vdso documentation/ia64/fsys.txt documentation/vdso/* (includes examples of using the vdso) find arch/ \-iname \(aq*vdso*\(aq \-o \-iname \(aq*gate*\(aq .ee .in .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/resolver.3 .so man3/setjmp.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cabs 3 2021-03-22 "" "linux programmer's manual" .sh name cabs, cabsf, cabsl \- absolute value of a complex number .sh synopsis .nf .b #include .pp .bi "double cabs(double complex " z ); .bi "float cabsf(float complex " z ); .bi "long double cabsl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions return the absolute value of the complex number .ir z . the result is a real number. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cabs (), .br cabsf (), .br cabsl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes the function is actually an alias for .i "hypot(a,\ b)" (or, equivalently, .ir "sqrt(a*a\ +\ b*b)" ). .sh see also .br abs (3), .br cimag (3), .br hypot (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th fwide 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fwide \- set and determine the orientation of a file stream .sh synopsis .nf .b #include .pp .bi "int fwide(file *" stream ", int " mode ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fwide (): .nf _xopen_source >= 500 || _isoc99_source || _posix_c_source >= 200112l .fi .sh description when \fimode\fp is zero, the .br fwide () function determines the current orientation of \fistream\fp. it returns a positive value if \fistream\fp is wide-character oriented, that is, if wide-character i/o is permitted but char i/o is disallowed. it returns a negative value if \fistream\fp is byte oriented\(emthat is, if char i/o is permitted but wide-character i/o is disallowed. it returns zero if \fistream\fp has no orientation yet; in this case the next i/o operation might change the orientation (to byte oriented if it is a char i/o operation, or to wide-character oriented if it is a wide-character i/o operation). .pp once a stream has an orientation, it cannot be changed and persists until the stream is closed. .pp when \fimode\fp is nonzero, the .br fwide () function first attempts to set \fistream\fp's orientation (to wide-character oriented if \fimode\fp is greater than 0, or to byte oriented if \fimode\fp is less than 0). it then returns a value denoting the current orientation, as above. .sh return value the .br fwide () function returns the stream's orientation, after possibly changing it. a positive return value means wide-character oriented. a negative return value means byte oriented. a return value of zero means undecided. .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes wide-character output to a byte oriented stream can be performed through the .br fprintf (3) function with the .b %lc and .b %ls directives. .pp char oriented output to a wide-character oriented stream can be performed through the .br fwprintf (3) function with the .b %c and .b %s directives. .sh see also .br fprintf (3), .br fwprintf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006, 2008, michael kerrisk .\" (a few fragments remain from an earlier (1992) version written in .\" 1992 by drew eckhardt .) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified sat jul 24 12:51:53 1993 by rik faith .\" modified tue oct 22 22:39:04 1996 by eric s. raymond .\" modified thu may 1 06:05:54 utc 1997 by nicolás lichtmaier .\" with lars wirzenius suggestion .\" 2006-05-13, mtk, substantial rewrite of description of 'mask' .\" 2008-01-09, mtk, a few rewrites and additions. .th umask 2 2021-03-22 "linux" "linux programmer's manual" .sh name umask \- set file mode creation mask .sh synopsis .nf .b #include .pp .bi "mode_t umask(mode_t " mask ); .fi .sh description .br umask () sets the calling process's file mode creation mask (umask) to .i mask & 0777 (i.e., only the file permission bits of .i mask are used), and returns the previous value of the mask. .pp the umask is used by .br open (2), .br mkdir (2), and other system calls that create files .\" e.g., mkfifo(), creat(), mknod(), sem_open(), mq_open(), shm_open() .\" but not the system v ipc *get() calls to modify the permissions placed on newly created files or directories. specifically, permissions in the umask are turned off from the .i mode argument to .br open (2) and .br mkdir (2). .pp alternatively, if the parent directory has a default acl (see .br acl (5)), the umask is ignored, the default acl is inherited, the permission bits are set based on the inherited acl, and permission bits absent in the .i mode argument are turned off. for example, the following default acl is equivalent to a umask of 022: .pp u::rwx,g::r-x,o::r-x .pp combining the effect of this default acl with a .i mode argument of 0666 (rw-rw-rw-), the resulting file permissions would be 0644 (rw-r--r--). .pp the constants that should be used to specify .i mask are described in .br inode (7). .pp the typical default value for the process umask is .i s_iwgrp\ |\ s_iwoth (octal 022). in the usual case where the .i mode argument to .br open (2) is specified as: .pp .in +4n .ex s_irusr | s_iwusr | s_irgrp | s_iwgrp | s_iroth | s_iwoth .ee .in .pp (octal 0666) when creating a new file, the permissions on the resulting file will be: .pp .in +4n .ex s_irusr | s_iwusr | s_irgrp | s_iroth .ee .in .pp (because 0666 & \(ti022 = 0644; i.e., rw\-r\-\-r\-\-). .sh return value this system call always succeeds and the previous value of the mask is returned. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes a child process created via .br fork (2) inherits its parent's umask. the umask is left unchanged by .br execve (2). .pp it is impossible to use .br umask () to fetch a process's umask without at the same time changing it. a second call to .br umask () would then be needed to restore the umask. the nonatomicity of these two steps provides the potential for races in multithreaded programs. .pp since linux 4.7, the umask of any process can be viewed via the .i umask field of .ir /proc/[pid]/status . inspecting this field in .ir /proc/self/status allows a process to retrieve its umask without at the same time changing it. .pp the umask setting also affects the permissions assigned to posix ipc objects .rb ( mq_open (3), .br sem_open (3), .br shm_open (3)), fifos .rb ( mkfifo (3)), and unix domain sockets .rb ( unix (7)) created by the process. the umask does not affect the permissions assigned to system\ v ipc objects created by the process (using .br msgget (2), .br semget (2), .br shmget (2)). .sh see also .br chmod (2), .br mkdir (2), .br open (2), .br stat (2), .br acl (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/mlock.2 .\" copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_mutexattr_init 3 2019-10-10 "linux" "linux programmer's manual" .sh name pthread_mutexattr_init, pthread_mutexattr_destroy \- initialize and destroy a mutex attributes object .sh synopsis .nf .b #include .pp .bi "int pthread_mutexattr_init(pthread_mutexattr_t *" attr ");" .bi "int pthread_mutexattr_destroy(pthread_mutexattr_t *" attr ");" .fi .pp compile and link with \fi\-pthread\fp. .sh description the .br pthread_mutexattr_init () function initializes the mutex attributes object pointed to by .i attr with default values for all attributes defined by the implementation. .pp the results of initializing an already initialized mutex attributes object are undefined. .pp the .br pthread_mutexattr_destroy () function destroys a mutex attribute object (making it uninitialized). once a mutex attributes object has been destroyed, it can be reinitialized with .br pthread_mutexattr_init (). .pp the results of destroying an uninitialized mutex attributes object are undefined. .sh return value on success, these functions return 0. on error, they return a positive error number. .sh conforming to posix.1-2001, posix.1-2008. .sh notes subsequent changes to a mutex attributes object do not affect mutex that have already been initialized using that object. .sh see also .ad l .nh .br pthread_mutex_init (3), .br pthread_mutexattr_getpshared (3), .br pthread_mutexattr_getrobust (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/stailq.3 .so man2/utime.2 .\" copyright (c) 1993 rickard e. faith .\" and copyright (c) 1994 andries e. brouwer .\" and copyright (c) 2002, 2005 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2008-10-06, mtk: created this as a new page by splitting .\" umount/umount2 material out of mount.2 .\" .th umount 2 2021-08-27 "linux" "linux programmer's manual" .sh name umount, umount2 \- unmount filesystem .sh synopsis .nf .b "#include " .pp .bi "int umount(const char *" target ); .bi "int umount2(const char *" target ", int " flags ); .fi .sh description .br umount () and .br umount2 () remove the attachment of the (topmost) filesystem mounted on .ir target . .\" note: the kernel naming differs from the glibc naming .\" umount2 is the glibc name for what the kernel now calls umount .\" and umount is the glibc name for oldumount .pp appropriate privilege (linux: the .b cap_sys_admin capability) is required to unmount filesystems. .pp linux 2.1.116 added the .br umount2 () system call, which, like .br umount (), unmounts a target, but allows additional .i flags controlling the behavior of the operation: .tp .br mnt_force " (since linux 2.1.116)" ask the filesystem to abort pending requests before attempting the unmount. this may allow the unmount to complete without waiting for an inaccessible server, but could cause data loss. if, after aborting requests, some processes still have active references to the filesystem, the unmount will still fail. as at linux 4.12, .br mnt_force is supported only on the following filesystems: 9p (since linux 2.6.16), ceph (since linux 2.6.34), cifs (since linux 2.6.12), fuse (since linux 2.6.16), lustre (since linux 3.11), and nfs (since linux 2.1.116). .tp .br mnt_detach " (since linux 2.4.11)" perform a lazy unmount: make the mount unavailable for new accesses, immediately disconnect the filesystem and all filesystems mounted below it from each other and from the mount table, and actually perform the unmount when the mount ceases to be busy. .tp .br mnt_expire " (since linux 2.6.8)" mark the mount as expired. if a mount is not currently in use, then an initial call to .br umount2 () with this flag fails with the error .br eagain , but marks the mount as expired. the mount remains expired as long as it isn't accessed by any process. a second .br umount2 () call specifying .b mnt_expire unmounts an expired mount. this flag cannot be specified with either .b mnt_force or .br mnt_detach . .tp .br umount_nofollow " (since linux 2.6.34)" .\" later added to 2.6.33-stable don't dereference .i target if it is a symbolic link. this flag allows security problems to be avoided in set-user-id-\firoot\fp programs that allow unprivileged users to unmount filesystems. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors the error values given below result from filesystem type independent errors. each filesystem type may have its own special errors and its own special behavior. see the linux kernel source code for details. .tp .b eagain a call to .br umount2 () specifying .b mnt_expire successfully marked an unbusy filesystem as expired. .tp .b ebusy .i target could not be unmounted because it is busy. .tp .b efault .i target points outside the user address space. .tp .b einval .i target is not a mount point. .tp .b einval .i target is locked; see .br mount_namespaces (7). .tp .b einval .br umount2 () was called with .b mnt_expire and either .b mnt_detach or .br mnt_force . .tp .br einval " (since linux 2.6.34)" .br umount2 () was called with an invalid flag value in .ir flags . .tp .b enametoolong a pathname was longer than .br maxpathlen . .tp .b enoent a pathname was empty or had a nonexistent component. .tp .b enomem the kernel could not allocate a free page to copy filenames or data into. .tp .b eperm the caller does not have the required privileges. .sh versions .br mnt_detach and .br mnt_expire .\" http://sourceware.org/bugzilla/show_bug.cgi?id=10092 are available in glibc since version 2.11. .sh conforming to these functions are linux-specific and should not be used in programs intended to be portable. .sh notes .ss umount() and shared mounts shared mounts cause any mount activity on a mount, including .br umount () operations, to be forwarded to every shared mount in the peer group and every slave mount of that peer group. this means that .br umount () of any peer in a set of shared mounts will cause all of its peers to be unmounted and all of their slaves to be unmounted as well. .pp this propagation of unmount activity can be particularly surprising on systems where every mount is shared by default. on such systems, recursively bind mounting the root directory of the filesystem onto a subdirectory and then later unmounting that subdirectory with .br mnt_detach will cause every mount in the mount namespace to be lazily unmounted. .pp to ensure .br umount () does not propagate in this fashion, the mount may be remounted using a .br mount (2) call with a .i mount_flags argument that includes both .br ms_rec and .br ms_private prior to .br umount () being called. .ss historical details the original .br umount () function was called as \fiumount(device)\fp and would return .b enotblk when called with something other than a block device. in linux 0.98p4, a call \fiumount(dir)\fp was added, in order to support anonymous devices. in linux 2.3.99-pre7, the call \fiumount(device)\fp was removed, leaving only \fiumount(dir)\fp (since now devices can be mounted in more than one place, so specifying the device does not suffice). .sh see also .br mount (2), .br mount_namespaces (7), .br path_resolution (7), .br mount (8), .br umount (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/readv.2 .\" copyright (c) 2009 bill o. gallmeister (bgallmeister@gmail.com) .\" and copyright 2010 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux glibc source code .\" posix 1003.1-2004 documentation .\" (http://www.opengroup.org/onlinepubs/009695399) .\" .th posix_spawn 3 2021-03-22 "gnu" "linux programmer's manual" .sh name posix_spawn, posix_spawnp \- spawn a process .sh synopsis .nf .b #include .pp .bi "int posix_spawn(pid_t *restrict " pid ", const char *restrict " path , .bi " const posix_spawn_file_actions_t *restrict " file_actions , .bi " const posix_spawnattr_t *restrict " attrp , .bi " char *const " argv [restrict], .bi " char *const " envp [restrict]); .bi "int posix_spawnp(pid_t *restrict " pid ", const char *restrict " file , .bi " const posix_spawn_file_actions_t *restrict " file_actions , .bi " const posix_spawnattr_t *restrict " attrp , .bi " char *const " argv [restrict], .bi " char *const " envp [restrict]); .fi .sh description the .br posix_spawn () and .br posix_spawnp () functions are used to create a new child process that executes a specified file. these functions were specified by posix to provide a standardized method of creating new processes on machines that lack the capability to support the .br fork (2) system call. these machines are generally small, embedded systems lacking mmu support. .pp the .br posix_spawn () and .br posix_spawnp () functions provide the functionality of a combined .br fork (2) and .br exec (3), with some optional housekeeping steps in the child process before the .br exec (3). these functions are not meant to replace the .br fork (2) and .br execve (2) system calls. in fact, they provide only a subset of the functionality that can be achieved by using the system calls. .pp the only difference between .br posix_spawn () and .br posix_spawnp () is the manner in which they specify the file to be executed by the child process. with .br posix_spawn (), the executable file is specified as a pathname (which can be absolute or relative). with .br posix_spawnp (), the executable file is specified as a simple filename; the system searches for this file in the list of directories specified by .br path (in the same way as for .br execvp (3)). for the remainder of this page, the discussion is phrased in terms of .br posix_spawn (), with the understanding that .br posix_spawnp () differs only on the point just described. .pp the remaining arguments to these two functions are as follows: .ip * 3 the .i pid argument points to a buffer that is used to return the process id of the new child process. .ip * the .i file_actions argument points to a .i "spawn file actions object" that specifies file-related actions to be performed in the child between the .br fork (2) and .br exec (3) steps. this object is initialized and populated before the .br posix_spawn () call using .br posix_spawn_file_actions_init (3) and the .br posix_spawn_file_actions_* () functions. .ip * the .i attrp argument points to an .i attributes objects that specifies various attributes of the created child process. this object is initialized and populated before the .br posix_spawn () call using .br posix_spawnattr_init (3) and the .br posix_spawnattr_* () functions. .ip * the .i argv and .i envp arguments specify the argument list and environment for the program that is executed in the child process, as for .br execve (2). .pp below, the functions are described in terms of a three-step process: the .br fork () step, the .rb pre- exec () step (executed in the child), and the .br exec () step (executed in the child). .ss fork() step since glibc 2.24, the .br posix_spawn () function commences by calling .br clone (2) with .br clone_vm and .br clone_vfork flags. older implementations use .br fork (2), or possibly .br vfork (2) (see below). .pp the pid of the new child process is placed in .ir *pid . the .br posix_spawn () function then returns control to the parent process. .pp subsequently, the parent can use one of the system calls described in .br wait (2) to check the status of the child process. if the child fails in any of the housekeeping steps described below, or fails to execute the desired file, it exits with a status of 127. .pp before glibc 2.24, the child process is created using .br vfork (2) instead of .br fork (2) when either of the following is true: .ip * 3 the .i spawn-flags element of the attributes object pointed to by .i attrp contains the gnu-specific flag .br posix_spawn_usevfork ; or .ip * .i file_actions is null and the .i spawn-flags element of the attributes object pointed to by .i attrp does \finot\fp contain .br posix_spawn_setsigmask , .br posix_spawn_setsigdef , .br posix_spawn_setschedparam , .br posix_spawn_setscheduler , .br posix_spawn_setpgroup , or .br posix_spawn_resetids . .pp in other words, .br vfork (2) is used if the caller requests it, or if there is no cleanup expected in the child before it .br exec (3)s the requested file. .ss pre-exec() step: housekeeping in between the .br fork() and the .br exec() steps, a child process may need to perform a set of housekeeping actions. the .br posix_spawn () and .br posix_spawnp () functions support a small, well-defined set of system tasks that the child process can accomplish before it executes the executable file. these operations are controlled by the attributes object pointed to by .ir attrp and the file actions object pointed to by .ir file_actions . in the child, processing is done in the following sequence: .ip 1. 3 process attribute actions: signal mask, signal default handlers, scheduling algorithm and parameters, process group, and effective user and group ids are changed as specified by the attributes object pointed to by .ir attrp . .ip 2. file actions, as specified in the .i file_actions argument, are performed in the order that they were specified using calls to the .br posix_spawn_file_actions_add* () functions. .ip 3. file descriptors with the .b fd_cloexec flag set are closed. .pp all process attributes in the child, other than those affected by attributes specified in the object pointed to by .ir attrp and the file actions in the object pointed to by .ir file_actions , will be affected as though the child was created with .br fork (2) and it executed the program with .br execve (2). .pp the process attributes actions are defined by the attributes object pointed to by .ir attrp . the .i spawn-flags attribute (set using .br posix_spawnattr_setflags (3)) controls the general actions that occur, and other attributes in the object specify values to be used during those actions. .pp the effects of the flags that may be specified in .ir spawn-flags are as follows: .tp .b posix_spawn_setsigmask set the signal mask to the signal set specified in the .i spawn-sigmask attribute .\" fixme . .\" (see .\" .br posix_spawnattr_setsigmask (3)) of the object pointed to by .ir attrp . if the .b posix_spawn_setsigmask flag is not set, then the child inherits the parent's signal mask. .tp .b posix_spawn_setsigdef reset the disposition of all signals in the set specified in the .i spawn-sigdefault attribute .\" fixme . .\" (see .\" .br posix_spawnattr_setsigdefault (3)) of the object pointed to by .ir attrp to the default. for the treatment of the dispositions of signals not specified in the .i spawn-sigdefault attribute, or the treatment when .b posix_spawn_setsigdef is not specified, see .br execve (2). .tp .b posix_spawn_setschedparam .\" (posix_priority_scheduling only) if this flag is set, and the .b posix_spawn_setscheduler flag is not set, then set the scheduling parameters to the parameters specified in the .i spawn-schedparam attribute .\" fixme . .\" (see .\" .br posix_spawnattr_setschedparam (3)) of the object pointed to by .ir attrp . .tp .b posix_spawn_setscheduler set the scheduling policy algorithm and parameters of the child, as follows: .rs .ip * 3 the scheduling policy is set to the value specified in the .i spawn-schedpolicy attribute .\" fixme . .\" (see .\" .br posix_spawnattr_setpolicy (3)) of the object pointed to by .ir attrp . .ip * the scheduling parameters are set to the value specified in the .i spawn-schedparam attribute .\" fixme . .\" (see .\" .br posix_spawnattr_setschedparam (3)) of the object pointed to by .ir attrp (but see bugs). .pp if the .b posix_spawn_setschedparam and .b posix_spawn_setschedpolicy flags are not specified, the child inherits the corresponding scheduling attributes from the parent. .re .tp .b posix_spawn_resetids if this flag is set, reset the effective uid and gid to the real uid and gid of the parent process. if this flag is not set, then the child retains the effective uid and gid of the parent. in either case, if the set-user-id and set-group-id permission bits are enabled on the executable file, their effect will override the setting of the effective uid and gid (se .br execve (2)). .tp .b posix_spawn_setpgroup set the process group to the value specified in the .i spawn-pgroup attribute .\" fixme . .\" (see .\" .br posix_spawnattr_setpgroup (3)) of the object pointed to by .ir attrp . if the .i spawn-pgroup attribute has the value 0, the child's process group id is made the same as its process id. if the .b posix_spawn_setpgroup flag is not set, the child inherits the parent's process group id. .tp .b posix_spawn_usevfork since glibc 2.24, this flag has no effect. on older implementations, setting this flag forces the .br fork() step to use .br vfork (2) instead of .br fork (2). the .b _gnu_source feature test macro must be defined to obtain the definition of this constant. .tp .br posix_spawn_setsid " (since glibc 2.26)" if this flag is set, the child process shall create a new session and become the session leader. the child process shall also become the process group leader of the new process group in the session (see .br setsid (2)). the .b _gnu_source feature test macro must be defined to obtain the definition of this constant. .\" this flag has been accepted in posix, see: .\" http://austingroupbugs.net/view.php?id=1044 .\" and has been implemented in glibc since version 2.26 .\" commit daeb1fa2e1b33323e719015f5f546988bd4cc73b .pp if .i attrp is null, then the default behaviors described above for each flag apply. .\" mtk: i think we probably don't want to say the following, since it .\" could lead people to do the wrong thing .\" the posix standard tells you to call .\" this function to de-initialize the attributes object pointed to by .\" .i attrp .\" when you are done with it; .\" however, on linux systems this operation is a no-op. .pp the .i file_actions argument specifies a sequence of file operations that are performed in the child process after the general processing described above, and before it performs the .br exec (3). if .i file_actions is null, then no special action is taken, and standard .br exec (3) semantics apply\(emfile descriptors open before the exec remain open in the new process, except those for which the .b fd_cloexec flag has been set. file locks remain in place. .pp if .i file_actions is not null, then it contains an ordered set of requests to .br open (2), .br close (2), and .br dup2 (2) files. these requests are added to the .i file_actions by .br posix_spawn_file_actions_addopen (3), .br posix_spawn_file_actions_addclose (3), and .br posix_spawn_file_actions_adddup2 (3). the requested operations are performed in the order they were added to .ir file_actions . .\" fixme . i think the following is best placed in the .\" posix_spawn_file_actions_adddup2(3) page, and a similar statement is .\" also needed in posix_spawn_file_actions_addclose(3) .\" note that you can specify file descriptors in .\" .i posix_spawn_file_actions_adddup2 (3) .\" which would not be usable if you called .\" .br dup2 (2) .\" at that time--i.e., file descriptors that are opened or .\" closed by the earlier operations .\" added to .\" .i file_actions . .pp if any of the housekeeping actions fails (due to bogus values being passed or other reasons why signal handling, process scheduling, process group id functions, and file descriptor operations might fail), the child process exits with exit value 127. .ss exec() step once the child has successfully forked and performed all requested pre-exec steps, the child runs the requested executable. .pp the child process takes its environment from the .i envp argument, which is interpreted as if it had been passed to .br execve (2). the arguments to the created process come from the .i argv argument, which is processed as for .br execve (2). .sh return value upon successful completion, .br posix_spawn () and .br posix_spawnp () place the pid of the child process in .ir pid , and return 0. if there is an error during the .br fork() step, then no child is created, the contents of .ir *pid are unspecified, and these functions return an error number as described below. .pp even when these functions return a success status, the child process may still fail for a plethora of reasons related to its pre-\fbexec\fr() initialization. in addition, the .br exec (3) may fail. in all of these cases, the child process will exit with the exit value of 127. .sh errors the .br posix_spawn () and .br posix_spawnp () functions fail only in the case where the underlying .br fork (2), .br vfork (2), or .br clone (2) call fails; in these cases, these functions return an error number, which will be one of the errors described for .br fork (2), .br vfork (2), or .br clone (2). .pp in addition, these functions fail if: .tp .b enosys function not supported on this system. .sh versions the .br posix_spawn () and .br posix_spawnp () functions are available since glibc 2.2. .sh conforming to posix.1-2001, posix.1-2008. .\" fixme . this piece belongs in spawnattr_setflags(3) .\" the .\" .b posix_spawn_usevfork .\" flag is a gnu extension; the .\" .b _gnu_source .\" feature test macro must be defined (before including any header files) .\" to obtain the definition of this constant. .sh notes the housekeeping activities in the child are controlled by the objects pointed to by .i attrp (for non-file actions) and .i file_actions in posix parlance, the .i posix_spawnattr_t and .i posix_spawn_file_actions_t data types are referred to as objects, and their elements are not specified by name. portable programs should initialize these objects using only the posix-specified functions. (in other words, although these objects may be implemented as structures containing fields, portable programs must avoid dependence on such implementation details.) .pp according to posix, it is unspecified whether fork handlers established with .br pthread_atfork (3) are called when .br posix_spawn () is invoked. since glibc 2.24, the fork handlers are not executed in any case. .\" tested on glibc 2.12 on older implementations, fork handlers are called only if the child is created using .br fork (2). .pp there is no "posix_fspawn" function (i.e., a function that is to .br posix_spawn () as .br fexecve (3) is to .br execve (2)). however, this functionality can be obtained by specifying the .i path argument as one of the files in the caller's .ir /proc/self/fd directory. .sh bugs posix.1 says that when .b posix_spawn_setscheduler is specified in .ir spawn-flags , then the .b posix_spawn_setschedparam (if present) is ignored. however, before glibc 2.14, calls to .br posix_spawn () failed with an error if .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12052 .br posix_spawn_setscheduler was specified without also specifying .br posix_spawn_setschedparam . .sh examples the program below demonstrates the use of various functions in the posix spawn api. the program accepts command-line attributes that can be used to create file actions and attributes objects. the remaining command-line arguments are used as the executable name and command-line arguments of the program that is executed in the child. .pp in the first run, the .br date (1) command is executed in the child, and the .br posix_spawn () call employs no file actions or attributes objects. .pp .in +4n .ex $ \fb./a.out date\fp pid of child: 7634 tue feb 1 19:47:50 cest 2011 child status: exited, status=0 .ee .in .pp in the next run, the .i \-c command-line option is used to create a file actions object that closes standard output in the child. consequently, .br date (1) fails when trying to perform output and exits with a status of 1. .pp .in +4n .ex $ \fb./a.out \-c date\fp pid of child: 7636 date: write error: bad file descriptor child status: exited, status=1 .ee .in .pp in the next run, the .i \-s command-line option is used to create an attributes object that specifies that all (blockable) signals in the child should be blocked. consequently, trying to kill child with the default signal sent by .br kill (1) (i.e., .br sigterm ) fails, because that signal is blocked. therefore, to kill the child, .br sigkill is necessary .rb ( sigkill can't be blocked). .pp .in +4n .ex $ \fb./a.out \-s sleep 60 &\fp [1] 7637 $ pid of child: 7638 $ \fbkill 7638\fp $ \fbkill \-kill 7638\fp $ child status: killed by signal 9 [1]+ done ./a.out \-s sleep 60 .ee .in .pp when we try to execute a nonexistent command in the child, the .br exec (3) fails and the child exits with a status of 127. .pp .in +4n .ex $ \fb./a.out xxxxx pid of child: 10190 child status: exited, status=127 .ee .in .ss program source \& .ex #include #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); \e exit(exit_failure); } while (0) #define errexiten(en, msg) \e do { errno = en; perror(msg); \e exit(exit_failure); } while (0) char **environ; int main(int argc, char *argv[]) { pid_t child_pid; int s, opt, status; sigset_t mask; posix_spawnattr_t attr; posix_spawnattr_t *attrp; posix_spawn_file_actions_t file_actions; posix_spawn_file_actions_t *file_actionsp; /* parse command\-line options, which can be used to specify an attributes object and file actions object for the child. */ attrp = null; file_actionsp = null; while ((opt = getopt(argc, argv, "sc")) != \-1) { switch (opt) { case \(aqc\(aq: /* \-c: close standard output in child */ /* create a file actions object and add a "close" action to it. */ s = posix_spawn_file_actions_init(&file_actions); if (s != 0) errexiten(s, "posix_spawn_file_actions_init"); s = posix_spawn_file_actions_addclose(&file_actions, stdout_fileno); if (s != 0) errexiten(s, "posix_spawn_file_actions_addclose"); file_actionsp = &file_actions; break; case \(aqs\(aq: /* \-s: block all signals in child */ /* create an attributes object and add a "set signal mask" action to it. */ s = posix_spawnattr_init(&attr); if (s != 0) errexiten(s, "posix_spawnattr_init"); s = posix_spawnattr_setflags(&attr, posix_spawn_setsigmask); if (s != 0) errexiten(s, "posix_spawnattr_setflags"); sigfillset(&mask); s = posix_spawnattr_setsigmask(&attr, &mask); if (s != 0) errexiten(s, "posix_spawnattr_setsigmask"); attrp = &attr; break; } } /* spawn the child. the name of the program to execute and the command\-line arguments are taken from the command\-line arguments of this program. the environment of the program execed in the child is made the same as the parent\(aqs environment. */ s = posix_spawnp(&child_pid, argv[optind], file_actionsp, attrp, &argv[optind], environ); if (s != 0) errexiten(s, "posix_spawn"); /* destroy any objects that we created earlier. */ if (attrp != null) { s = posix_spawnattr_destroy(attrp); if (s != 0) errexiten(s, "posix_spawnattr_destroy"); } if (file_actionsp != null) { s = posix_spawn_file_actions_destroy(file_actionsp); if (s != 0) errexiten(s, "posix_spawn_file_actions_destroy"); } printf("pid of child: %jd\en", (intmax_t) child_pid); /* monitor status of the child until it terminates. */ do { s = waitpid(child_pid, &status, wuntraced | wcontinued); if (s == \-1) errexit("waitpid"); printf("child status: "); if (wifexited(status)) { printf("exited, status=%d\en", wexitstatus(status)); } else if (wifsignaled(status)) { printf("killed by signal %d\en", wtermsig(status)); } else if (wifstopped(status)) { printf("stopped by signal %d\en", wstopsig(status)); } else if (wifcontinued(status)) { printf("continued\en"); } } while (!wifexited(status) && !wifsignaled(status)); exit(exit_success); } .ee .sh see also .nh \" disable hyphenation .ad l .br close (2), .br dup2 (2), .br execl (2), .br execlp (2), .br fork (2), .br open (2), .br sched_setparam (2), .br sched_setscheduler (2), .br setpgid (2), .br setuid (2), .br sigaction (2), .br sigprocmask (2), .br posix_spawn_file_actions_addclose (3), .br posix_spawn_file_actions_adddup2 (3), .br posix_spawn_file_actions_addopen (3), .br posix_spawn_file_actions_destroy (3), .br posix_spawn_file_actions_init (3), .br posix_spawnattr_destroy (3), .br posix_spawnattr_getflags (3), .br posix_spawnattr_getpgroup (3), .br posix_spawnattr_getschedparam (3), .br posix_spawnattr_getschedpolicy (3), .br posix_spawnattr_getsigdefault (3), .br posix_spawnattr_getsigmask (3), .br posix_spawnattr_init (3), .br posix_spawnattr_setflags (3), .br posix_spawnattr_setpgroup (3), .br posix_spawnattr_setschedparam (3), .br posix_spawnattr_setschedpolicy (3), .br posix_spawnattr_setsigdefault (3), .br posix_spawnattr_setsigmask (3), .br pthread_atfork (3), .ir , base definitions volume of posix.1-2001, .i http://www.opengroup.org/unix/online.html .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getaddrinfo_a.3 .so man3/unlocked_stdio.3 .\" copyright (c) 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th fpurge 3 2021-03-22 "" "linux programmer's manual" .sh name fpurge, __fpurge \- purge a stream .sh synopsis .nf /* unsupported */ .b #include .pp .bi "int fpurge(file *" stream ); .pp /* supported */ .b #include .b #include .pp .bi "void __fpurge(file *" stream ); .fi .sh description the function .br fpurge () clears the buffers of the given stream. for output streams this discards any unwritten output. for input streams this discards any input read from the underlying object but not yet obtained via .br getc (3); this includes any text pushed back via .br ungetc (3). see also .br fflush (3). .pp the function .br __fpurge () does precisely the same, but without returning a value. .sh return value upon successful completion .br fpurge () returns 0. on error, it returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b ebadf .i stream is not an open stream. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br __fpurge () t} thread safety mt-safe race:stream .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard and not portable. the function .br fpurge () was introduced in 4.4bsd and is not available under linux. the function .br __fpurge () was introduced in solaris, and is present in glibc 2.1.95 and later. .sh notes usually it is a mistake to want to discard input buffers. .sh see also .\" .br fclean (3), .br fflush (3), .br setbuf (3), .br stdio_ext (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th repertoiremap 5 2020-06-09 "gnu" "linux user manual" .sh name repertoiremap \- map symbolic character names to unicode code points .sh description a repertoire map defines mappings between symbolic character names (mnemonics) and unicode code points when compiling a locale with .br localedef (1). using a repertoire map is optional, it is needed only when symbolic names are used instead of now preferred unicode code points. .ss syntax the repertoiremap file starts with a header that may consist of the following keywords: .tp .i comment_char is followed by a character that will be used as the comment character for the rest of the file. it defaults to the number sign (#). .tp .i escape_char is followed by a character that should be used as the escape character for the rest of the file to mark characters that should be interpreted in a special way. it defaults to the backslash (\e). .pp the mapping section starts with the keyword .i charids in the first column. .pp the mapping lines have the following form: .tp .i comment this defines exactly one mapping, .i comment being optional. .pp the mapping section ends with the string .ir "end charids" . .sh files .tp .i /usr/share/i18n/repertoiremaps usual default repertoire map path. .sh conforming to posix.2. .sh notes repertoire maps are deprecated in favor of unicode code points. .sh examples a mnemonic for the euro sign can be defined as follows: .pp .nf euro sign .fi .sh see also .br locale (1), .br localedef (1), .br charmap (5), .br locale (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:01:24 1993 by rik faith (faith@cs.unc.edu) .th strpbrk 3 2021-03-22 "" "linux programmer's manual" .sh name strpbrk \- search a string for any of a set of bytes .sh synopsis .nf .b #include .pp .bi "char *strpbrk(const char *" s ", const char *" accept ); .fi .sh description the .br strpbrk () function locates the first occurrence in the string .i s of any of the bytes in the string .ir accept . .sh return value the .br strpbrk () function returns a pointer to the byte in .i s that matches one of the bytes in .ir accept , or null if no such byte is found. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strpbrk () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh see also .br index (3), .br memchr (3), .br rindex (3), .br strchr (3), .br string (3), .br strsep (3), .br strspn (3), .br strstr (3), .br strtok (3), .br wcspbrk (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/isalpha.3 .\" copyright (c) 1996 free software foundation, inc. .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .\" 2006-02-09, some reformatting by luc van oostenryck; some .\" reformatting and rewordings by mtk .\" .th query_module 2 2021-03-22 "linux" "linux programmer's manual" .sh name query_module \- query the kernel for various bits pertaining to modules .sh synopsis .nf .b #include .pp .bi "int query_module(const char *" name ", int " which ", void *" buf , .bi " size_t " bufsize ", size_t *" ret ); .fi .pp .ir note : no declaration of this system call is provided in glibc headers; see notes. .sh description .ir note : this system call is present only in kernels before linux 2.6. .pp .br query_module () requests information from the kernel about loadable modules. the returned information is placed in the buffer pointed to by .ir buf . the caller must specify the size of .i buf in .ir bufsize . the precise nature and format of the returned information depend on the operation specified by .ir which . some operations require .i name to identify a currently loaded module, some allow .i name to be null, indicating the kernel proper. .pp the following values can be specified for .ir which : .tp .b 0 returns success, if the kernel supports .br query_module (). used to probe for availability of the system call. .tp .b qm_modules returns the names of all loaded modules. the returned buffer consists of a sequence of null-terminated strings; .i ret is set to the number of modules. .\" ret is set on enospc .tp .b qm_deps returns the names of all modules used by the indicated module. the returned buffer consists of a sequence of null-terminated strings; .i ret is set to the number of modules. .\" ret is set on enospc .tp .b qm_refs returns the names of all modules using the indicated module. this is the inverse of .br qm_deps . the returned buffer consists of a sequence of null-terminated strings; .i ret is set to the number of modules. .\" ret is set on enospc .tp .b qm_symbols returns the symbols and values exported by the kernel or the indicated module. the returned buffer is an array of structures of the following form .\" ret is set on enospc .ip .in +4n .ex struct module_symbol { unsigned long value; unsigned long name; }; .ee .in .ip followed by null-terminated strings. the value of .i name is the character offset of the string relative to the start of .ir buf ; .i ret is set to the number of symbols. .tp .b qm_info returns miscellaneous information about the indicated module. the output buffer format is: .ip .in +4n .ex struct module_info { unsigned long address; unsigned long size; unsigned long flags; }; .ee .in .ip where .i address is the kernel address at which the module resides, .i size is the size of the module in bytes, and .i flags is a mask of .br mod_running , .br mod_autoclean , and so on, that indicates the current status of the module (see the linux kernel source file .ir include/linux/module.h ). .i ret is set to the size of the .i module_info structure. .sh return value on success, zero is returned. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault at least one of .ir name , .ir buf , or .i ret was outside the program's accessible address space. .tp .b einval invalid .ir which ; or .i name is null (indicating "the kernel"), but this is not permitted with the specified value of .ir which . .\" not permitted with qm_deps, qm_refs, or qm_info. .tp .b enoent no module by that .i name exists. .tp .b enospc the buffer size provided was too small. .i ret is set to the minimum size needed. .tp .b enosys .br query_module () is not supported in this version of the kernel (e.g., the kernel is version 2.6 or later). .sh versions this system call is present on linux only up until kernel 2.4; it was removed in linux 2.6. .\" removed in linux 2.5.48 .sh conforming to .br query_module () is linux-specific. .sh notes some of the information that was formerly available via .br query_module () can be obtained from .ir /proc/modules , .ir /proc/kallsyms , and the files under the directory .ir /sys/module . .pp the .br query_module () system call is not supported by glibc. no declaration is provided in glibc headers, but, through a quirk of history, glibc does export an abi for this system call. therefore, in order to employ this system call, it is sufficient to manually declare the interface in your code; alternatively, you can invoke the system call using .br syscall (2). .sh see also .br create_module (2), .br delete_module (2), .br get_kernel_syms (2), .br init_module (2), .br lsmod (8), .br modinfo (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswctype 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswctype \- wide-character classification .sh synopsis .nf .b #include .pp .bi "int iswctype(wint_t " wc ", wctype_t " desc ); .fi .sh description if .i wc is a wide character having the character property designated by .i desc (or in other words: belongs to the character class designated by .ir desc ), the .br iswctype () function returns nonzero. otherwise, it returns zero. if .i wc is .br weof , zero is returned. .pp .i desc must be a character property descriptor returned by the .br wctype (3) function. .sh return value the .br iswctype () function returns nonzero if the .i wc has the designated property. otherwise, it returns 0. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswctype () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswctype () depends on the .b lc_ctype category of the current locale. .sh see also .br iswalnum (3), .br iswalpha (3), .br iswblank (3), .br iswcntrl (3), .br iswdigit (3), .br iswgraph (3), .br iswlower (3), .br iswprint (3), .br iswpunct (3), .br iswspace (3), .br iswupper (3), .br iswxdigit (3), .br wctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page is copyright (c) 1999 matthew wilcox . .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" modified june 1999 andi kleen .\" $id: arp.7,v 1.10 2000/04/27 19:31:38 ak exp $ .\" .th arp 7 2020-08-13 "linux" "linux programmer's manual" .sh name arp \- linux arp kernel module. .sh description this kernel protocol module implements the address resolution protocol defined in rfc\ 826. it is used to convert between layer2 hardware addresses and ipv4 protocol addresses on directly connected networks. the user normally doesn't interact directly with this module except to configure it; instead it provides a service for other protocols in the kernel. .pp a user process can receive arp packets by using .br packet (7) sockets. there is also a mechanism for managing the arp cache in user-space by using .br netlink (7) sockets. the arp table can also be controlled via .br ioctl (2) on any .b af_inet socket. .pp the arp module maintains a cache of mappings between hardware addresses and protocol addresses. the cache has a limited size so old and less frequently used entries are garbage-collected. entries which are marked as permanent are never deleted by the garbage-collector. the cache can be directly manipulated by the use of ioctls and its behavior can be tuned by the .i /proc interfaces described below. .pp when there is no positive feedback for an existing mapping after some time (see the .i /proc interfaces below), a neighbor cache entry is considered stale. positive feedback can be gotten from a higher layer; for example from a successful tcp ack. other protocols can signal forward progress using the .b msg_confirm flag to .br sendmsg (2). when there is no forward progress, arp tries to reprobe. it first tries to ask a local arp daemon .b app_solicit times for an updated mac address. if that fails and an old mac address is known, a unicast probe is sent .b ucast_solicit times. if that fails too, it will broadcast a new arp request to the network. requests are sent only when there is data queued for sending. .pp linux will automatically add a nonpermanent proxy arp entry when it receives a request for an address it forwards to and proxy arp is enabled on the receiving interface. when there is a reject route for the target, no proxy arp entry is added. .ss ioctls three ioctls are available on all .b af_inet sockets. they take a pointer to a .i struct arpreq as their argument. .pp .in +4n .ex struct arpreq { struct sockaddr arp_pa; /* protocol address */ struct sockaddr arp_ha; /* hardware address */ int arp_flags; /* flags */ struct sockaddr arp_netmask; /* netmask of protocol address */ char arp_dev[16]; }; .ee .in .pp .br siocsarp ", " siocdarp " and " siocgarp respectively set, delete, and get an arp mapping. setting and deleting arp maps are privileged operations and may be performed only by a process with the .b cap_net_admin capability or an effective uid of 0. .pp .i arp_pa must be an .b af_inet address and .i arp_ha must have the same type as the device which is specified in .ir arp_dev . .i arp_dev is a zero-terminated string which names a device. .rs .ts tab(:) allbox; c s l l. \fiarp_flags\fr flag:meaning atf_com:lookup complete atf_perm:permanent entry atf_publ:publish entry atf_usetrailers:trailers requested atf_netmask:use a netmask atf_dontpub:don't answer .te .re .pp if the .b atf_netmask flag is set, then .i arp_netmask should be valid. linux 2.2 does not support proxy network arp entries, so this should be set to 0xffffffff, or 0 to remove an existing proxy arp entry. .b atf_usetrailers is obsolete and should not be used. .ss /proc interfaces arp supports a range of .i /proc interfaces to configure parameters on a global or per-interface basis. the interfaces can be accessed by reading or writing the .i /proc/sys/net/ipv4/neigh/*/* files. each interface in the system has its own directory in .ir /proc/sys/net/ipv4/neigh/ . the setting in the "default" directory is used for all newly created devices. unless otherwise specified, time-related interfaces are specified in seconds. .tp .ir anycast_delay " (since linux 2.2)" .\" precisely: 2.1.79 the maximum number of jiffies to delay before replying to a ipv6 neighbor solicitation message. anycast support is not yet implemented. defaults to 1 second. .tp .ir app_solicit " (since linux 2.2)" .\" precisely: 2.1.79 the maximum number of probes to send to the user space arp daemon via netlink before dropping back to multicast probes (see .ir mcast_solicit ). defaults to 0. .tp .ir base_reachable_time " (since linux 2.2)" .\" precisely: 2.1.79 once a neighbor has been found, the entry is considered to be valid for at least a random value between .ir base_reachable_time "/2 and 3*" base_reachable_time /2. an entry's validity will be extended if it receives positive feedback from higher level protocols. defaults to 30 seconds. this file is now obsolete in favor of .ir base_reachable_time_ms . .tp .ir base_reachable_time_ms " (since linux 2.6.12)" as for .ir base_reachable_time , but measures time in milliseconds. defaults to 30000 milliseconds. .tp .ir delay_first_probe_time " (since linux 2.2)" .\" precisely: 2.1.79 delay before first probe after it has been decided that a neighbor is stale. defaults to 5 seconds. .tp .ir gc_interval " (since linux 2.2)" .\" precisely: 2.1.79 how frequently the garbage collector for neighbor entries should attempt to run. defaults to 30 seconds. .tp .ir gc_stale_time " (since linux 2.2)" .\" precisely: 2.1.79 determines how often to check for stale neighbor entries. when a neighbor entry is considered stale, it is resolved again before sending data to it. defaults to 60 seconds. .tp .ir gc_thresh1 " (since linux 2.2)" .\" precisely: 2.1.79 the minimum number of entries to keep in the arp cache. the garbage collector will not run if there are fewer than this number of entries in the cache. defaults to 128. .tp .ir gc_thresh2 " (since linux 2.2)" .\" precisely: 2.1.79 the soft maximum number of entries to keep in the arp cache. the garbage collector will allow the number of entries to exceed this for 5 seconds before collection will be performed. defaults to 512. .tp .ir gc_thresh3 " (since linux 2.2)" .\" precisely: 2.1.79 the hard maximum number of entries to keep in the arp cache. the garbage collector will always run if there are more than this number of entries in the cache. defaults to 1024. .tp .ir locktime " (since linux 2.2)" .\" precisely: 2.1.79 the minimum number of jiffies to keep an arp entry in the cache. this prevents arp cache thrashing if there is more than one potential mapping (generally due to network misconfiguration). defaults to 1 second. .tp .ir mcast_solicit " (since linux 2.2)" .\" precisely: 2.1.79 the maximum number of attempts to resolve an address by multicast/broadcast before marking the entry as unreachable. defaults to 3. .tp .ir proxy_delay " (since linux 2.2)" .\" precisely: 2.1.79 when an arp request for a known proxy-arp address is received, delay up to .i proxy_delay jiffies before replying. this is used to prevent network flooding in some cases. defaults to 0.8 seconds. .tp .ir proxy_qlen " (since linux 2.2)" .\" precisely: 2.1.79 the maximum number of packets which may be queued to proxy-arp addresses. defaults to 64. .tp .ir retrans_time " (since linux 2.2)" .\" precisely: 2.1.79 the number of jiffies to delay before retransmitting a request. defaults to 1 second. this file is now obsolete in favor of .ir retrans_time_ms . .tp .ir retrans_time_ms " (since linux 2.6.12)" the number of milliseconds to delay before retransmitting a request. defaults to 1000 milliseconds. .tp .ir ucast_solicit " (since linux 2.2)" .\" precisely: 2.1.79 the maximum number of attempts to send unicast probes before asking the arp daemon (see .ir app_solicit ). defaults to 3. .tp .ir unres_qlen " (since linux 2.2)" .\" precisely: 2.1.79 the maximum number of packets which may be queued for each unresolved address by other network layers. defaults to 3. .sh versions the .i struct arpreq changed in linux 2.0 to include the .i arp_dev member and the ioctl numbers changed at the same time. support for the old ioctls was dropped in linux 2.2. .pp support for proxy arp entries for networks (netmask not equal 0xffffffff) was dropped in linux 2.2. it is replaced by automatic proxy arp setup by the kernel for all reachable hosts on other interfaces (when forwarding and proxy arp is enabled for the interface). .pp the .i neigh/* interfaces did not exist before linux 2.2. .sh bugs some timer settings are specified in jiffies, which is architecture- and kernel version-dependent; see .br time (7). .pp there is no way to signal positive feedback from user space. this means connection-oriented protocols implemented in user space will generate excessive arp traffic, because ndisc will regularly reprobe the mac address. the same problem applies for some kernel protocols (e.g., nfs over udp). .pp this man page mashes together functionality that is ipv4-specific with functionality that is shared between ipv4 and ipv6. .sh see also .br capabilities (7), .br ip (7), .br arpd (8) .pp rfc\ 826 for a description of arp. rfc\ 2461 for a description of ipv6 neighbor discovery and the base algorithms used. linux 2.2+ ipv4 arp uses the ipv6 algorithms when applicable. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/argz_add.3 .so man7/iso_8859-4.7 .so man2/readv.2 .\" copyright (c) 1996 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" written 11 april 1996 by andries brouwer .\" 960412: added comments from stephen tweedie .\" modified tue oct 22 22:28:41 1996 by eric s. raymond .\" modified mon jan 5 20:31:04 1998 by aeb. .\" .th sysctl 2 2021-03-22 "linux" "linux programmer's manual" .sh name sysctl \- read/write system parameters .sh synopsis .nf .b #include .b #include .pp .bi "int _sysctl(struct __sysctl_args *" args ); .fi .sh description .b this system call no longer exists on current kernels! see notes. .pp the .br _sysctl () call reads and/or writes kernel parameters. for example, the hostname, or the maximum number of open files. the argument has the form .pp .in +4n .ex struct __sysctl_args { int *name; /* integer vector describing variable */ int nlen; /* length of this vector */ void *oldval; /* 0 or address where to store old value */ size_t *oldlenp; /* available room for old value, overwritten by actual size of old value */ void *newval; /* 0 or address of new value */ size_t newlen; /* size of new value */ }; .ee .in .pp this call does a search in a tree structure, possibly resembling a directory tree under .ir /proc/sys , and if the requested item is found calls some appropriate routine to read or modify the value. .sh return value upon successful completion, .br _sysctl () returns 0. otherwise, a value of \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .br eacces ", " eperm no search permission for one of the encountered "directories", or no read permission where .i oldval was nonzero, or no write permission where .i newval was nonzero. .tp .b efault the invocation asked for the previous value by setting .i oldval non-null, but allowed zero room in .ir oldlenp . .tp .b enotdir .i name was not found. .sh versions this system call first appeared in linux 1.3.57. it was removed in linux 5.5; glibc support was removed in version 2.32. .sh conforming to this call is linux-specific, and should not be used in programs intended to be portable. it originated in 4.4bsd. only linux has the .i /proc/sys mirror, and the object naming schemes differ between linux and 4.4bsd, but the declaration of the .br sysctl () function is the same in both. .sh notes use of this system call was long discouraged: since linux 2.6.24, uses of this system call result in warnings in the kernel log, and in linux 5.5, the system call was finally removed. use the .i /proc/sys interface instead. .pp note that on older kernels where this system call still exists, it is available only if the kernel was configured with the .b config_sysctl_syscall option. furthermore, glibc does not provide a wrapper for this system call, necessitating the use of .br syscall (2). .sh bugs the object names vary between kernel versions, making this system call worthless for applications. .pp not all available objects are properly documented. .pp it is not yet possible to change operating system by writing to .ir /proc/sys/kernel/ostype . .sh examples .ex #define _gnu_source #include #include #include #include #include #include int _sysctl(struct __sysctl_args *args ); #define osnamesz 100 int main(void) { struct __sysctl_args args; char osname[osnamesz]; size_t osnamelth; int name[] = { ctl_kern, kern_ostype }; memset(&args, 0, sizeof(args)); args.name = name; args.nlen = sizeof(name)/sizeof(name[0]); args.oldval = osname; args.oldlenp = &osnamelth; osnamelth = sizeof(osname); if (syscall(sys__sysctl, &args) == \-1) { perror("_sysctl"); exit(exit_failure); } printf("this machine is running %*s\en", osnamelth, osname); exit(exit_success); } .ee .sh see also .br proc (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mkstemp.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)scanf.3 6.14 (berkeley) 1/8/93 .\" .\" converted for linux, mon nov 29 15:22:01 1993, faith@cs.unc.edu .\" modified to resemble the gnu libio setup used in the linux libc .\" used in versions 4.x (x>4) and 5 helmut.geyer@iwr.uni-heidelberg.de .\" modified, aeb, 970121 .\" 2005-07-14, mtk, added description of %n$ form; various text .\" incorporated from the gnu c library documentation ((c) the .\" free software foundation); other parts substantially rewritten. .\" .\" 2008-06-23, mtk .\" add errors section. .\" document the 'a' and 'm' modifiers for dynamic string allocation. .\" .th scanf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name scanf, fscanf, sscanf, vscanf, vsscanf, vfscanf \- input format conversion .sh synopsis .nf .b #include .pp .bi "int scanf(const char *restrict " format ", ...);" .bi "int fscanf(file *restrict " stream , .bi " const char *restrict " format ", ...);" .bi "int sscanf(const char *restrict " str , .bi " const char *restrict " format ", ...);" .pp .b #include .pp .bi "int vscanf(const char *restrict " format ", va_list " ap ); .bi "int vfscanf(file *restrict " stream , .bi " const char *restrict " format ", va_list " ap ); .bi "int vsscanf(const char *restrict " str , .bi " const char *restrict " format ", va_list " ap ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br vscanf (), .br vsscanf (), .br vfscanf (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description the .br scanf () family of functions scans input according to .i format as described below. this format may contain .ir "conversion specifications" ; the results from such conversions, if any, are stored in the locations pointed to by the .i pointer arguments that follow .ir format . each .i pointer argument must be of a type that is appropriate for the value returned by the corresponding conversion specification. .pp if the number of conversion specifications in .i format exceeds the number of .i pointer arguments, the results are undefined. if the number of .i pointer arguments exceeds the number of conversion specifications, then the excess .i pointer arguments are evaluated, but are otherwise ignored. .pp the .br scanf () function reads input from the standard input stream .ir stdin , .br fscanf () reads input from the stream pointer .ir stream , and .br sscanf () reads its input from the character string pointed to by .ir str . .pp the .br vfscanf () function is analogous to .br vfprintf (3) and reads input from the stream pointer .i stream using a variable argument list of pointers (see .br stdarg (3). the .br vscanf () function scans a variable argument list from the standard input and the .br vsscanf () function scans it from a string; these are analogous to the .br vprintf (3) and .br vsprintf (3) functions respectively. .pp the .i format string consists of a sequence of .i directives which describe how to process the sequence of input characters. if processing of a directive fails, no further input is read, and .br scanf () returns. a "failure" can be either of the following: .ir "input failure" , meaning that input characters were unavailable, or .ir "matching failure" , meaning that the input was inappropriate (see below). .pp a directive is one of the following: .tp \(bu a sequence of white-space characters (space, tab, newline, etc.; see .br isspace (3)). this directive matches any amount of white space, including none, in the input. .tp \(bu an ordinary character (i.e., one other than white space or \(aq%\(aq). this character must exactly match the next character of input. .tp \(bu a conversion specification, which commences with a \(aq%\(aq (percent) character. a sequence of characters from the input is converted according to this specification, and the result is placed in the corresponding .i pointer argument. if the next item of input does not match the conversion specification, the conversion fails\(emthis is a .ir "matching failure" . .pp each .i conversion specification in .i format begins with either the character \(aq%\(aq or the character sequence "\fb%\fp\fin\fp\fb$\fp" (see below for the distinction) followed by: .tp \(bu an optional \(aq*\(aq assignment-suppression character: .br scanf () reads input as directed by the conversion specification, but discards the input. no corresponding .i pointer argument is required, and this specification is not included in the count of successful assignments returned by .br scanf (). .tp \(bu for decimal conversions, an optional quote character (\(aq). this specifies that the input number may include thousands' separators as defined by the .br lc_numeric category of the current locale. (see .br setlocale (3).) the quote character may precede or follow the \(aq*\(aq assignment-suppression character. .tp \(bu an optional \(aqm\(aq character. this is used with string conversions .ri ( %s , .ir %c , .ir %[ ), and relieves the caller of the need to allocate a corresponding buffer to hold the input: instead, .br scanf () allocates a buffer of sufficient size, and assigns the address of this buffer to the corresponding .i pointer argument, which should be a pointer to a .i "char\ *" variable (this variable does not need to be initialized before the call). the caller should subsequently .br free (3) this buffer when it is no longer required. .tp \(bu an optional decimal integer which specifies the .ir "maximum field width" . reading of characters stops either when this maximum is reached or when a nonmatching character is found, whichever happens first. most conversions discard initial white space characters (the exceptions are noted below), and these discarded characters don't count toward the maximum field width. string input conversions store a terminating null byte (\(aq\e0\(aq) to mark the end of the input; the maximum field width does not include this terminator. .tp \(bu an optional .ir "type modifier character" . for example, the .b l type modifier is used with integer conversions such as .b %d to specify that the corresponding .i pointer argument refers to a .i "long" rather than a pointer to an .ir int . .tp \(bu a .i "conversion specifier" that specifies the type of input conversion to be performed. .pp the conversion specifications in .i format are of two forms, either beginning with \(aq%\(aq or beginning with "\fb%\fp\fin\fp\fb$\fp". the two forms should not be mixed in the same .i format string, except that a string containing "\fb%\fp\fin\fp\fb$\fp" specifications can include .b %% and .br %* . if .i format contains \(aq%\(aq specifications, then these correspond in order with successive .i pointer arguments. in the "\fb%\fp\fin\fp\fb$\fp" form (which is specified in posix.1-2001, but not c99), .i n is a decimal integer that specifies that the converted input should be placed in the location referred to by the .ir n -th .i pointer argument following .ir format . .ss conversions the following .i "type modifier characters" can appear in a conversion specification: .tp .b h indicates that the conversion will be one of \fbd\fp, \fbi\fp, \fbo\fp, \fbu\fp, \fbx\fp, \fbx\fp, or \fbn\fp and the next pointer is a pointer to a .i short or .i unsigned short (rather than .ir int ). .tp .b hh as for .br h , but the next pointer is a pointer to a .i signed char or .ir "unsigned char" . .tp .b j as for .br h , but the next pointer is a pointer to an .i intmax_t or a .ir uintmax_t . this modifier was introduced in c99. .tp .b l indicates either that the conversion will be one of \fbd\fp, \fbi\fp, \fbo\fp, \fbu\fp, \fbx\fp, \fbx\fp, or \fbn\fp and the next pointer is a pointer to a .i long or .i unsigned long (rather than .ir int ), or that the conversion will be one of \fbe\fp, \fbf\fp, or \fbg\fp and the next pointer is a pointer to .i double (rather than .ir float ). specifying two .b l characters is equivalent to .br l . if used with .b %c or .br %s , the corresponding parameter is considered as a pointer to a wide character or wide-character string respectively. .\" this use of l was introduced in amendment 1 to iso c90. .tp .b l indicates that the conversion will be either \fbe\fp, \fbf\fp, or \fbg\fp and the next pointer is a pointer to .i "long double" or the conversion will be \fbd\fp, \fbi\fp, \fbo\fp, \fbu\fp, or \fbx\fp and the next pointer is a pointer to .ir "long long" . .\" mtk, jul 05: the following is no longer true for modern .\" ansi c (i.e., c99): .\" (note that long long is not an .\" ansi c .\" type. any program using this will not be portable to all .\" architectures). .tp .b q equivalent to .br l . this specifier does not exist in ansi c. .tp .b t as for .br h , but the next pointer is a pointer to a .ir ptrdiff_t . this modifier was introduced in c99. .tp .b z as for .br h , but the next pointer is a pointer to a .ir size_t . this modifier was introduced in c99. .pp the following .i "conversion specifiers" are available: .tp .b % matches a literal \(aq%\(aq. that is, .b %\&% in the format string matches a single input \(aq%\(aq character. no conversion is done (but initial white space characters are discarded), and assignment does not occur. .tp .b d matches an optionally signed decimal integer; the next pointer must be a pointer to .ir int . .\" .tp .\" .b d .\" equivalent to .\" .ir ld ; .\" this exists only for backward compatibility. .\" (note: thus only in libc4 .\" in libc5 and glibc the .\" .b %d .\" is silently ignored, causing old programs to fail mysteriously.) .tp .b i matches an optionally signed integer; the next pointer must be a pointer to .ir int . the integer is read in base 16 if it begins with .i 0x or .ir 0x , in base 8 if it begins with .ir 0 , and in base 10 otherwise. only characters that correspond to the base are used. .tp .b o matches an unsigned octal integer; the next pointer must be a pointer to .ir "unsigned int" . .tp .b u matches an unsigned decimal integer; the next pointer must be a pointer to .ir "unsigned int" . .tp .b x matches an unsigned hexadecimal integer (that may optionally begin with a prefix of .i 0x or .ir 0x , which is discarded); the next pointer must be a pointer to .ir "unsigned int" . .tp .b x equivalent to .br x . .tp .b f matches an optionally signed floating-point number; the next pointer must be a pointer to .ir float . .tp .b e equivalent to .br f . .tp .b g equivalent to .br f . .tp .b e equivalent to .br f . .tp .b a (c99) equivalent to .br f . .tp .b s matches a sequence of non-white-space characters; the next pointer must be a pointer to the initial element of a character array that is long enough to hold the input sequence and the terminating null byte (\(aq\e0\(aq), which is added automatically. the input string stops at white space or at the maximum field width, whichever occurs first. .tp .b c matches a sequence of characters whose length is specified by the .i maximum field width (default 1); the next pointer must be a pointer to .ir char , and there must be enough room for all the characters (no terminating null byte is added). the usual skip of leading white space is suppressed. to skip white space first, use an explicit space in the format. .tp .b \&[ matches a nonempty sequence of characters from the specified set of accepted characters; the next pointer must be a pointer to .ir char , and there must be enough room for all the characters in the string, plus a terminating null byte. the usual skip of leading white space is suppressed. the string is to be made up of characters in (or not in) a particular set; the set is defined by the characters between the open bracket .b [ character and a close bracket .b ] character. the set .i excludes those characters if the first character after the open bracket is a circumflex .rb ( \(ha ). to include a close bracket in the set, make it the first character after the open bracket or the circumflex; any other position will end the set. the hyphen character .b \- is also special; when placed between two other characters, it adds all intervening characters to the set. to include a hyphen, make it the last character before the final close bracket. for instance, .b [\(ha]0\-9\-] means the set "everything except close bracket, zero through nine, and hyphen". the string ends with the appearance of a character not in the (or, with a circumflex, in) set or when the field width runs out. .tp .b p matches a pointer value (as printed by .b %p in .br printf (3)); the next pointer must be a pointer to a pointer to .ir void . .tp .b n nothing is expected; instead, the number of characters consumed thus far from the input is stored through the next pointer, which must be a pointer to .ir int , or variant whose size matches the (optionally) supplied integer length modifier. this is .i not a conversion and does .i not increase the count returned by the function. the assignment can be suppressed with the .b * assignment-suppression character, but the effect on the return value is undefined. therefore .b %*n conversions should not be used. .sh return value on success, these functions return the number of input items successfully matched and assigned; this can be fewer than provided for, or even zero, in the event of an early matching failure. .pp the value .b eof is returned if the end of input is reached before either the first successful conversion or a matching failure occurs. .b eof is also returned if a read error occurs, in which case the error indicator for the stream (see .br ferror (3)) is set, and .i errno is set to indicate the error. .sh errors .tp .b eagain the file descriptor underlying .i stream is marked nonblocking, and the read operation would block. .tp .b ebadf the file descriptor underlying .i stream is invalid, or not open for reading. .tp .b eilseq input byte sequence does not form a valid character. .tp .b eintr the read operation was interrupted by a signal; see .br signal (7). .tp .b einval not enough arguments; or .i format is null. .tp .b enomem out of memory. .tp .b erange the result of an integer conversion would exceed the size that can be stored in the corresponding integer type. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br scanf (), .br fscanf (), .br sscanf (), .br vscanf (), .br vsscanf (), .br vfscanf () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to the functions .br fscanf (), .br scanf (), and .br sscanf () conform to c89 and c99 and posix.1-2001. these standards do not specify the .b erange error. .pp the .b q specifier is the 4.4bsd notation for .ir "long long" , while .b ll or the usage of .b l in integer conversions is the gnu notation. .pp the linux version of these functions is based on the .i gnu .i libio library. take a look at the .i info documentation of .i gnu .i libc (glibc-1.08) for a more concise description. .sh notes .ss the 'a' assignment-allocation modifier originally, the gnu c library supported dynamic allocation for string inputs (as a nonstandard extension) via the .b a character. (this feature is present at least as far back as glibc 2.0.) thus, one could write the following to have .br scanf () allocate a buffer for an input string, with a pointer to that buffer being returned in .ir *buf : .pp char *buf; scanf("%as", &buf); .pp the use of the letter .b a for this purpose was problematic, since .b a is also specified by the iso c standard as a synonym for .b f (floating-point input). posix.1-2008 instead specifies the .b m modifier for assignment allocation (as documented in description, above). .pp note that the .b a modifier is not available if the program is compiled with .i "gcc \-std=c99" or .ir "gcc \-d_isoc99_source" (unless .b _gnu_source is also specified), in which case the .b a is interpreted as a specifier for floating-point numbers (see above). .pp support for the .b m modifier was added to glibc starting with version 2.7, and new programs should use that modifier instead of .br a . .pp as well as being standardized by posix, the .b m modifier has the following further advantages over the use of .br a: .ip * 2 it may also be applied to .b %c conversion specifiers (e.g., .br %3mc ). .ip * it avoids ambiguity with respect to the .b %a floating-point conversion specifier (and is unaffected by .ir "gcc \-std=c99" etc.). .sh bugs all functions are fully c89 conformant, but provide the additional specifiers .b q and .b a as well as an additional behavior of the .b l and .b l specifiers. the latter may be considered to be a bug, as it changes the behavior of specifiers defined in c89. .pp some combinations of the type modifiers and conversion specifiers defined by ansi c do not make sense (e.g., .br "%ld" ). while they may have a well-defined behavior on linux, this need not to be so on other architectures. therefore it usually is better to use modifiers that are not defined by ansi c at all, that is, use .b q instead of .b l in combination with \fbd\fp, \fbi\fp, \fbo\fp, \fbu\fp, \fbx\fp, and \fbx\fp conversions or .br ll . .pp the usage of .b q is not the same as on 4.4bsd, as it may be used in float conversions equivalently to .br l . .sh examples to use the dynamic allocation conversion specifier, specify .b m as a length modifier (thus .b %ms or \fb%m[\fp\firange\fp\fb]\fp). the caller must .br free (3) the returned string, as in the following example: .pp .in +4n .ex char *p; int n; errno = 0; n = scanf("%m[a\-z]", &p); if (n == 1) { printf("read: %s\en", p); free(p); } else if (errno != 0) { perror("scanf"); } else { fprintf(stderr, "no matching characters\en"); } .ee .in .pp as shown in the above example, it is necessary to call .br free (3) only if the .br scanf () call successfully read a string. .sh see also .br getc (3), .br printf (3), .br setlocale (3), .br strtod (3), .br strtol (3), .br strtoul (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 rickard e. faith (faith@cs.unc.edu) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" historical remark, aeb, 2004-06-05 .th getuid 2 2021-03-22 "linux" "linux programmer's manual" .sh name getuid, geteuid \- get user identity .sh synopsis .nf .b #include .pp .b uid_t getuid(void); .b uid_t geteuid(void); .fi .sh description .br getuid () returns the real user id of the calling process. .pp .br geteuid () returns the effective user id of the calling process. .sh errors these functions are always successful and never modify .\" https://www.austingroupbugs.net/view.php?id=511 .\" 0000511: getuid and friends should not modify errno .ir errno . .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd. .sh notes .ss history in unix\ v6 the .br getuid () call returned .ir "(euid << 8) + uid" . unix\ v7 introduced separate calls .br getuid () and .br geteuid (). .pp the original linux .br getuid () and .br geteuid () system calls supported only 16-bit user ids. subsequently, linux 2.4 added .br getuid32 () and .br geteuid32 (), supporting 32-bit ids. the glibc .br getuid () and .br geteuid () wrapper functions transparently deal with the variations across kernel versions. .pp on alpha, instead of a pair of .br getuid () and .br geteuid () system calls, a single .br getxuid () system call is provided, which returns a pair of real and effective uids. the glibc .br getuid () and .br geteuid () wrapper functions transparently deal with this. see .br syscall (2) for details regarding register mapping. .sh see also .br getresuid (2), .br setreuid (2), .br setuid (2), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/err.3 .so man2/sched_setparam.2 .\" copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_cleanup_push_defer_np 3 2021-03-22 "linux" "linux programmer's manual" .sh name pthread_cleanup_push_defer_np, pthread_cleanup_pop_restore_np \- push and pop thread cancellation clean-up handlers while saving cancelability type .sh synopsis .nf .b #include .pp .bi "void pthread_cleanup_push_defer_np(void (*" routine ")(void *), void *" arg ); .bi "void pthread_cleanup_pop_restore_np(int " execute ); .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_cleanup_push_defer_np (), .br pthread_cleanup_pop_defer_np (): .nf _gnu_source .fi .sh description these functions are the same as .br pthread_cleanup_push (3) and .br pthread_cleanup_pop (3), except for the differences noted on this page. .pp like .br pthread_cleanup_push (3), .br pthread_cleanup_push_defer_np () pushes .i routine onto the thread's stack of cancellation clean-up handlers. in addition, it also saves the thread's current cancelability type, and sets the cancelability type to "deferred" (see .br pthread_setcanceltype (3)); this ensures that cancellation clean-up will occur even if the thread's cancelability type was "asynchronous" before the call. .pp like .br pthread_cleanup_pop (3), .br pthread_cleanup_pop_restore_np () pops the top-most clean-up handler from the thread's stack of cancellation clean-up handlers. in addition, it restores the thread's cancelability type to its value at the time of the matching .br pthread_cleanup_push_defer_np (). .pp the caller must ensure that calls to these functions are paired within the same function, and at the same lexical nesting level. other restrictions apply, as described in .br pthread_cleanup_push (3). .pp this sequence of calls: .pp .in +4n .ex pthread_cleanup_push_defer_np(routine, arg); pthread_cleanup_pop_restore_np(execute); .ee .in .pp is equivalent to (but shorter and more efficient than): .pp .\" as far as i can see, linuxthreads reverses the two substeps .\" in the push and pop below. .in +4n .ex int oldtype; pthread_cleanup_push(routine, arg); pthread_setcanceltype(pthread_cancel_deferred, &oldtype); \&... pthread_setcanceltype(oldtype, null); pthread_cleanup_pop(execute); .ee .in .\" sh versions .\" available since glibc 2.0 .sh conforming to these functions are nonstandard gnu extensions; hence the suffix "_np" (nonportable) in the names. .sh see also .br pthread_cancel (3), .br pthread_cleanup_push (3), .br pthread_setcancelstate (3), .br pthread_testcancel (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/fmax.3 .\" copyright (c) 2010 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th aio 7 2021-03-22 "linux" "linux programmer's manual" .sh name aio \- posix asynchronous i/o overview .sh description the posix asynchronous i/o (aio) interface allows applications to initiate one or more i/o operations that are performed asynchronously (i.e., in the background). the application can elect to be notified of completion of the i/o operation in a variety of ways: by delivery of a signal, by instantiation of a thread, or no notification at all. .pp the posix aio interface consists of the following functions: .tp .br aio_read (3) enqueue a read request. this is the asynchronous analog of .br read (2). .tp .br aio_write (3) enqueue a write request. this is the asynchronous analog of .br write (2). .tp .br aio_fsync (3) enqueue a sync request for the i/o operations on a file descriptor. this is the asynchronous analog of .br fsync (2) and .br fdatasync (2). .tp .br aio_error (3) obtain the error status of an enqueued i/o request. .tp .br aio_return (3) obtain the return status of a completed i/o request. .tp .br aio_suspend (3) suspend the caller until one or more of a specified set of i/o requests completes. .tp .br aio_cancel (3) attempt to cancel outstanding i/o requests on a specified file descriptor. .tp .br lio_listio (3) enqueue multiple i/o requests using a single function call. .pp the .i aiocb ("asynchronous i/o control block") structure defines parameters that control an i/o operation. an argument of this type is employed with all of the functions listed above. this structure has the following form: .pp .in +4n .ex #include struct aiocb { /* the order of these fields is implementation\-dependent */ int aio_fildes; /* file descriptor */ off_t aio_offset; /* file offset */ volatile void *aio_buf; /* location of buffer */ size_t aio_nbytes; /* length of transfer */ int aio_reqprio; /* request priority */ struct sigevent aio_sigevent; /* notification method */ int aio_lio_opcode; /* operation to be performed; lio_listio() only */ /* various implementation\-internal fields not shown */ }; /* operation codes for \(aqaio_lio_opcode\(aq: */ enum { lio_read, lio_write, lio_nop }; .ee .in .pp the fields of this structure are as follows: .tp .i aio_fildes the file descriptor on which the i/o operation is to be performed. .tp .i aio_offset this is the file offset at which the i/o operation is to be performed. .tp .i aio_buf this is the buffer used to transfer data for a read or write operation. .tp .i aio_nbytes this is the size of the buffer pointed to by .ir aio_buf . .tp .i aio_reqprio this field specifies a value that is subtracted from the calling thread's real-time priority in order to determine the priority for execution of this i/o request (see .br pthread_setschedparam (3)). the specified value must be between 0 and the value returned by .ir sysconf(_sc_aio_prio_delta_max) . this field is ignored for file synchronization operations. .tp .i aio_sigevent this field is a structure that specifies how the caller is to be notified when the asynchronous i/o operation completes. possible values for .ir aio_sigevent.sigev_notify are .br sigev_none , .br sigev_signal , and .br sigev_thread . see .br sigevent (7) for further details. .tp .i aio_lio_opcode the type of operation to be performed; used only for .br lio_listio (3). .pp in addition to the standard functions listed above, the gnu c library provides the following extension to the posix aio api: .tp .br aio_init (3) set parameters for tuning the behavior of the glibc posix aio implementation. .sh errors .tp .b einval the .i aio_reqprio field of the .i aiocb structure was less than 0, or was greater than the limit returned by the call .ir sysconf(_sc_aio_prio_delta_max) . .sh versions the posix aio interfaces are provided by glibc since version 2.1. .sh conforming to posix.1-2001, posix.1-2008. .sh notes it is a good idea to zero out the control block buffer before use (see .br memset (3)). the control block buffer and the buffer pointed to by .i aio_buf must not be changed while the i/o operation is in progress. these buffers must remain valid until the i/o operation completes. .pp simultaneous asynchronous read or write operations using the same .i aiocb structure yield undefined results. .pp the current linux posix aio implementation is provided in user space by glibc. this has a number of limitations, most notably that maintaining multiple threads to perform i/o operations is expensive and scales poorly. work has been in progress for some time on a kernel state-machine-based implementation of asynchronous i/o (see .br io_submit (2), .br io_setup (2), .br io_cancel (2), .br io_destroy (2), .br io_getevents (2)), but this implementation hasn't yet matured to the point where the posix aio implementation can be completely reimplemented using the kernel system calls. .\" http://lse.sourceforge.net/io/aio.html .\" http://lse.sourceforge.net/io/aionotes.txt .\" http://lwn.net/articles/148755/ .sh examples the program below opens each of the files named in its command-line arguments and queues a request on the resulting file descriptor using .br aio_read (3). the program then loops, periodically monitoring each of the i/o operations that is still in progress using .br aio_error (3). each of the i/o requests is set up to provide notification by delivery of a signal. after all i/o requests have completed, the program retrieves their status using .br aio_return (3). .pp the .b sigquit signal (generated by typing control-\e) causes the program to request cancellation of each of the outstanding requests using .br aio_cancel (3). .pp here is an example of what we might see when running this program. in this example, the program queues two requests to standard input, and these are satisfied by two lines of input containing "abc" and "x". .pp .in +4n .ex $ \fb./a.out /dev/stdin /dev/stdin\fp opened /dev/stdin on descriptor 3 opened /dev/stdin on descriptor 4 aio_error(): for request 0 (descriptor 3): in progress for request 1 (descriptor 4): in progress \fbabc\fp i/o completion signal received aio_error(): for request 0 (descriptor 3): i/o succeeded for request 1 (descriptor 4): in progress aio_error(): for request 1 (descriptor 4): in progress \fbx\fp i/o completion signal received aio_error(): for request 1 (descriptor 4): i/o succeeded all i/o requests completed aio_return(): for request 0 (descriptor 3): 4 for request 1 (descriptor 4): 2 .ee .in .ss program source \& .ex #include #include #include #include #include #include #include #define buf_size 20 /* size of buffers for read operations */ #define errexit(msg) do { perror(msg); exit(exit_failure); } while (0) struct iorequest { /* application\-defined structure for tracking i/o requests */ int reqnum; int status; struct aiocb *aiocbp; }; static volatile sig_atomic_t gotsigquit = 0; /* on delivery of sigquit, we attempt to cancel all outstanding i/o requests */ static void /* handler for sigquit */ quithandler(int sig) { gotsigquit = 1; } #define io_signal sigusr1 /* signal used to notify i/o completion */ static void /* handler for i/o completion signal */ aiosighandler(int sig, siginfo_t *si, void *ucontext) { if (si\->si_code == si_asyncio) { write(stdout_fileno, "i/o completion signal received\en", 31); /* the corresponding iorequest structure would be available as struct iorequest *ioreq = si\->si_value.sival_ptr; and the file descriptor would then be available via ioreq\->aiocbp\->aio_fildes */ } } int main(int argc, char *argv[]) { struct sigaction sa; int s; int numreqs; /* total number of queued i/o requests */ int openreqs; /* number of i/o requests still in progress */ if (argc < 2) { fprintf(stderr, "usage: %s ...\en", argv[0]); exit(exit_failure); } numreqs = argc \- 1; /* allocate our arrays. */ struct iorequest *iolist = calloc(numreqs, sizeof(*iolist)); if (iolist == null) errexit("calloc"); struct aiocb *aiocblist = calloc(numreqs, sizeof(*aiocblist)); if (aiocblist == null) errexit("calloc"); /* establish handlers for sigquit and the i/o completion signal. */ sa.sa_flags = sa_restart; sigemptyset(&sa.sa_mask); sa.sa_handler = quithandler; if (sigaction(sigquit, &sa, null) == \-1) errexit("sigaction"); sa.sa_flags = sa_restart | sa_siginfo; sa.sa_sigaction = aiosighandler; if (sigaction(io_signal, &sa, null) == \-1) errexit("sigaction"); /* open each file specified on the command line, and queue a read request on the resulting file descriptor. */ for (int j = 0; j < numreqs; j++) { iolist[j].reqnum = j; iolist[j].status = einprogress; iolist[j].aiocbp = &aiocblist[j]; iolist[j].aiocbp\->aio_fildes = open(argv[j + 1], o_rdonly); if (iolist[j].aiocbp\->aio_fildes == \-1) errexit("open"); printf("opened %s on descriptor %d\en", argv[j + 1], iolist[j].aiocbp\->aio_fildes); iolist[j].aiocbp\->aio_buf = malloc(buf_size); if (iolist[j].aiocbp\->aio_buf == null) errexit("malloc"); iolist[j].aiocbp\->aio_nbytes = buf_size; iolist[j].aiocbp\->aio_reqprio = 0; iolist[j].aiocbp\->aio_offset = 0; iolist[j].aiocbp\->aio_sigevent.sigev_notify = sigev_signal; iolist[j].aiocbp\->aio_sigevent.sigev_signo = io_signal; iolist[j].aiocbp\->aio_sigevent.sigev_value.sival_ptr = &iolist[j]; s = aio_read(iolist[j].aiocbp); if (s == \-1) errexit("aio_read"); } openreqs = numreqs; /* loop, monitoring status of i/o requests. */ while (openreqs > 0) { sleep(3); /* delay between each monitoring step */ if (gotsigquit) { /* on receipt of sigquit, attempt to cancel each of the outstanding i/o requests, and display status returned from the cancellation requests. */ printf("got sigquit; canceling i/o requests: \en"); for (int j = 0; j < numreqs; j++) { if (iolist[j].status == einprogress) { printf(" request %d on descriptor %d:", j, iolist[j].aiocbp\->aio_fildes); s = aio_cancel(iolist[j].aiocbp\->aio_fildes, iolist[j].aiocbp); if (s == aio_canceled) printf("i/o canceled\en"); else if (s == aio_notcanceled) printf("i/o not canceled\en"); else if (s == aio_alldone) printf("i/o all done\en"); else perror("aio_cancel"); } } gotsigquit = 0; } /* check the status of each i/o request that is still in progress. */ printf("aio_error():\en"); for (int j = 0; j < numreqs; j++) { if (iolist[j].status == einprogress) { printf(" for request %d (descriptor %d): ", j, iolist[j].aiocbp\->aio_fildes); iolist[j].status = aio_error(iolist[j].aiocbp); switch (iolist[j].status) { case 0: printf("i/o succeeded\en"); break; case einprogress: printf("in progress\en"); break; case ecanceled: printf("canceled\en"); break; default: perror("aio_error"); break; } if (iolist[j].status != einprogress) openreqs\-\-; } } } printf("all i/o requests completed\en"); /* check status return of all i/o requests. */ printf("aio_return():\en"); for (int j = 0; j < numreqs; j++) { ssize_t s; s = aio_return(iolist[j].aiocbp); printf(" for request %d (descriptor %d): %zd\en", j, iolist[j].aiocbp\->aio_fildes, s); } exit(exit_success); } .ee .sh see also .ad l .nh .br io_cancel (2), .br io_destroy (2), .br io_getevents (2), .br io_setup (2), .br io_submit (2), .br aio_cancel (3), .br aio_error (3), .br aio_init (3), .br aio_read (3), .br aio_return (3), .br aio_write (3), .br lio_listio (3) .pp "asynchronous i/o support in linux 2.5", bhattacharya, pratt, pulavarty, and morgan, proceedings of the linux symposium, 2003, .ur https://www.kernel.org/doc/ols/2003/ols2003\-pages\-351\-366.pdf .ue .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 28 11:12:07 1993 by rik faith (faith@cs.unc.edu) .\" modified fri sep 8 15:48:13 1995 by andries brouwer (aeb@cwi.nl) .th fgetc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fgetc, fgets, getc, getchar, ungetc \- input of characters and strings .sh synopsis .nf .b #include .pp .bi "int fgetc(file *" stream ); .bi "int getc(file *" stream ); .b "int getchar(void);" .pp .bi "char *fgets(char *restrict " s ", int " size ", file *restrict " stream ); .pp .bi "int ungetc(int " c ", file *" stream ); .fi .sh description .br fgetc () reads the next character from .i stream and returns it as an .i unsigned char cast to an .ir int , or .b eof on end of file or error. .pp .br getc () is equivalent to .br fgetc () except that it may be implemented as a macro which evaluates .i stream more than once. .pp .br getchar () is equivalent to .bi "getc(" stdin ) \fr. .pp .br fgets () reads in at most one less than .i size characters from .i stream and stores them into the buffer pointed to by .ir s . reading stops after an .b eof or a newline. if a newline is read, it is stored into the buffer. a terminating null byte (\(aq\e0\(aq) is stored after the last character in the buffer. .pp .br ungetc () pushes .i c back to .ir stream , cast to .ir "unsigned char" , where it is available for subsequent read operations. pushed-back characters will be returned in reverse order; only one pushback is guaranteed. .pp calls to the functions described here can be mixed with each other and with calls to other input functions from the .i stdio library for the same input stream. .pp for nonlocking counterparts, see .br unlocked_stdio (3). .sh return value .br fgetc (), .br getc (), and .br getchar () return the character read as an .i unsigned char cast to an .i int or .b eof on end of file or error. .pp .br fgets () returns .i s on success, and null on error or when end of file occurs while no characters have been read. .pp .br ungetc () returns .i c on success, or .b eof on error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fgetc (), .br fgets (), .br getc (), .br getchar (), .br ungetc () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99. .pp it is not advisable to mix calls to input functions from the .i stdio library with low-level calls to .br read (2) for the file descriptor associated with the input stream; the results will be undefined and very probably not what you want. .sh see also .br read (2), .br write (2), .br ferror (3), .br fgetwc (3), .br fgetws (3), .br fopen (3), .br fread (3), .br fseek (3), .br getline (3), .br gets (3), .br getwchar (3), .br puts (3), .br scanf (3), .br ungetwc (3), .br unlocked_stdio (3), .br feature_test_macros (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/floor.3 .so man3/cpu_set.3 .\" copyright (c) 1995 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2012, 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" written 11 june 1995 by andries brouwer .\" 2008-02-15, jeremy kerr .\" add info on command type 10; add details on types 6, 7, 8, & 9. .\" 2008-02-15, michael kerrisk .\" update log_buf_len details; update return value section. .\" .th syslog 2 2021-03-22 "linux" "linux programmer's manual" .sh name syslog, klogctl \- read and/or clear kernel message ring buffer; set console_loglevel .sh synopsis .nf .br "#include " " /* definition of " syslog_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_syslog, int " type ", char *" bufp ", int " len ); .pp /* the glibc interface */ .b #include .pp .bi "int klogctl(int " type ", char *" bufp ", int " len ); .fi .sh description .ir note : probably, you are looking for the c library function .br syslog (), which talks to .br syslogd (8); see .br syslog (3) for details. .pp this page describes the kernel .br syslog () system call, which is used to control the kernel .ir printk () buffer; the glibc wrapper function for the system call is called .br klogctl (). .ss the kernel log buffer the kernel has a cyclic buffer of length .b log_buf_len in which messages given as arguments to the kernel function .br printk () are stored (regardless of their log level). in early kernels, .b log_buf_len had the value 4096; from kernel 1.3.54, it was 8192; from kernel 2.1.113, it was 16384; since kernel 2.4.23/2.6, the value is a kernel configuration option .rb ( config_log_buf_shift , default value dependent on the architecture). .\" under "general setup" ==> "kernel log buffer size" .\" for 2.6, precisely the option seems to have appeared in 2.5.55. since linux 2.6.6, the size can be queried with command type 10 (see below). .ss commands the \fitype\fp argument determines the action taken by this function. the list below specifies the values for .ir type . the symbolic names are defined in the kernel source, but are not exported to user space; you will either need to use the numbers, or define the names yourself. .tp .br syslog_action_close " (0)" close the log. currently a nop. .tp .br syslog_action_open " (1)" open the log. currently a nop. .tp .br syslog_action_read " (2)" read from the log. the call waits until the kernel log buffer is nonempty, and then reads at most \filen\fp bytes into the buffer pointed to by .ir bufp . the call returns the number of bytes read. bytes read from the log disappear from the log buffer: the information can be read only once. this is the function executed by the kernel when a user program reads .ir /proc/kmsg . .tp .br syslog_action_read_all " (3)" read all messages remaining in the ring buffer, placing them in the buffer pointed to by .ir bufp . the call reads the last \filen\fp bytes from the log buffer (nondestructively), but will not read more than was written into the buffer since the last "clear ring buffer" command (see command 5 below)). the call returns the number of bytes read. .tp .br syslog_action_read_clear " (4)" read and clear all messages remaining in the ring buffer. the call does precisely the same as for a .i type of 3, but also executes the "clear ring buffer" command. .tp .br syslog_action_clear " (5)" the call executes just the "clear ring buffer" command. the .i bufp and .i len arguments are ignored. .ip this command does not really clear the ring buffer. rather, it sets a kernel bookkeeping variable that determines the results returned by commands 3 .rb ( syslog_action_read_all ) and 4 .rb ( syslog_action_read_clear ). this command has no effect on commands 2 .rb ( syslog_action_read ) and 9 .rb ( syslog_action_size_unread ). .tp .br syslog_action_console_off " (6)" the command saves the current value of .i console_loglevel and then sets .i console_loglevel to .ir minimum_console_loglevel , so that no messages are printed to the console. before linux 2.6.32, .\" commit 1aaad49e856ce41adc07d8ae0c8ef35fc4483245 the command simply sets .i console_loglevel to .ir minimum_console_loglevel . see the discussion of .ir /proc/sys/kernel/printk , below. .ip the .i bufp and .i len arguments are ignored. .tp .br syslog_action_console_on " (7)" if a previous .b syslog_action_console_off command has been performed, this command restores .i console_loglevel to the value that was saved by that command. before linux 2.6.32, .\" commit 1aaad49e856ce41adc07d8ae0c8ef35fc4483245 this command simply sets .i console_loglevel to .ir default_console_loglevel . see the discussion of .ir /proc/sys/kernel/printk , below. .ip the .i bufp and .i len arguments are ignored. .tp .br syslog_action_console_level " (8)" the call sets .i console_loglevel to the value given in .ir len , which must be an integer between 1 and 8 (inclusive). the kernel silently enforces a minimum value of .ir minimum_console_loglevel for .ir len . see the .ir "log level" section for details. the .i bufp argument is ignored. .tp .br syslog_action_size_unread " (9) (since linux 2.4.10)" the call returns the number of bytes currently available to be read from the kernel log buffer via command 2 .rb ( syslog_action_read ). the .i bufp and .i len arguments are ignored. .tp .br syslog_action_size_buffer " (10) (since linux 2.6.6)" this command returns the total size of the kernel log buffer. the .i bufp and .i len arguments are ignored. .pp all commands except 3 and 10 require privilege. in linux kernels before 2.6.37, command types 3 and 10 are allowed to unprivileged processes; since linux 2.6.37, these commands are allowed to unprivileged processes only if .ir /proc/sys/kernel/dmesg_restrict has the value 0. before linux 2.6.37, "privileged" means that the caller has the .br cap_sys_admin capability. since linux 2.6.37, "privileged" means that the caller has either the .br cap_sys_admin capability (now deprecated for this purpose) or the (new) .br cap_syslog capability. .\" .\" .ss /proc/sys/kernel/printk .i /proc/sys/kernel/printk is a writable file containing four integer values that influence kernel .i printk() behavior when printing or logging error messages. the four values are: .tp .i console_loglevel only messages with a log level lower than this value will be printed to the console. the default value for this field is .b default_console_loglevel (7), but it is set to 4 if the kernel command line contains the word "quiet",\" since linux 2.4 10 if the kernel command line contains the word "debug", and to 15 in case of a kernel fault (the 10 and 15 are just silly, and equivalent to 8). the value of .ir console_loglevel can be set (to a value in the range 1\(en8) by a .br syslog () call with a .i type of 8. .tp .i default_message_loglevel this value will be used as the log level for .ir printk() messages that do not have an explicit level. up to and including linux 2.6.38, the hard-coded default value for this field was 4 .rb ( kern_warning ); since linux 2.6.39, .\" commit 5af5bcb8d37f99ba415a1adc6da71051b84f93a5 the default value is a defined by the kernel configuration option .br config_default_message_loglevel , which defaults to 4. .tp .i minimum_console_loglevel the value in this field is the minimum value to which .i console_loglevel can be set. .tp .i default_console_loglevel this is the default value for .ir console_loglevel . .\" .\" .ss the log level every .ir printk () message has its own log level. if the log level is not explicitly specified as part of the message, it defaults to .ir default_message_loglevel . the conventional meaning of the log level is as follows: .ts lb lb lb lb c l. kernel constant level value meaning kern_emerg 0 system is unusable kern_alert 1 t{ action must be taken immediately t} kern_crit 2 critical conditions kern_err 3 error conditions kern_warning 4 warning conditions kern_notice 5 t{ normal but significant condition t} kern_info 6 informational kern_debug 7 debug-level messages .te .sp 1 the kernel .ir printk() routine will print a message on the console only if it has a log level less than the value of .ir console_loglevel . .sh return value for \fitype\fp equal to 2, 3, or 4, a successful call to .br syslog () returns the number of bytes read. for \fitype\fp 9, .br syslog () returns the number of bytes currently available to be read on the kernel log buffer. for \fitype\fp 10, .br syslog () returns the total size of the kernel log buffer. for other values of \fitype\fp, 0 is returned on success. .pp in case of error, \-1 is returned, and \fierrno\fp is set to indicate the error. .sh errors .tp .b einval bad arguments (e.g., bad .ir type ; or for .i type 2, 3, or 4, .i buf is null, or .i len is less than zero; or for .i type 8, the .i level is outside the range 1 to 8). .tp .b enosys this .br syslog () system call is not available, because the kernel was compiled with the .br config_printk kernel-configuration option disabled. .tp .b eperm an attempt was made to change .i console_loglevel or clear the kernel message ring buffer by a process without sufficient privilege (more precisely: without the .b cap_sys_admin or .br cap_syslog capability). .tp .b erestartsys system call was interrupted by a signal; nothing was read. (this can be seen only during a trace.) .sh conforming to this system call is linux-specific and should not be used in programs intended to be portable. .sh notes from the very start, people noted that it is unfortunate that a system call and a library routine of the same name are entirely different animals. .\" in libc4 and libc5 the number of this call was defined by .\" .br sys_klog . .\" in glibc 2.0 the syscall is baptized .\" .br klogctl (). .sh see also .br dmesg (1), .br syslog (3), .br capabilities (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this man page is copyright (c) 1999 andi kleen . .\" .\" %%%license_start(verbatim_one_para) .\" permission is granted to distribute possibly modified copies .\" of this page provided the header is included verbatim, .\" and in case of nontrivial modification author and date .\" of the modification is added to the header. .\" %%%license_end .\" .\" $id: netdevice.7,v 1.10 2000/08/17 10:09:54 ak exp $ .\" .\" modified, 2004-11-25, mtk, formatting and a few wording fixes .\" .\" modified, 2011-11-02, , added many basic .\" but missing ioctls, such as siocgifaddr. .\" .th netdevice 7 2021-03-22 "linux" "linux programmer's manual" .sh name netdevice \- low-level access to linux network devices .sh synopsis .nf .b "#include " .b "#include " .fi .sh description this man page describes the sockets interface which is used to configure network devices. .pp linux supports some standard ioctls to configure network devices. they can be used on any socket's file descriptor regardless of the family or type. most of them pass an .i ifreq structure: .pp .in +4n .ex struct ifreq { char ifr_name[ifnamsiz]; /* interface name */ union { struct sockaddr ifr_addr; struct sockaddr ifr_dstaddr; struct sockaddr ifr_broadaddr; struct sockaddr ifr_netmask; struct sockaddr ifr_hwaddr; short ifr_flags; int ifr_ifindex; int ifr_metric; int ifr_mtu; struct ifmap ifr_map; char ifr_slave[ifnamsiz]; char ifr_newname[ifnamsiz]; char *ifr_data; }; }; .ee .in .pp .b af_inet6 is an exception. it passes an .i in6_ifreq structure: .pp .in +4n .ex struct in6_ifreq { struct in6_addr ifr6_addr; u32 ifr6_prefixlen; int ifr6_ifindex; /* interface index */ }; .ee .in .pp normally, the user specifies which device to affect by setting .i ifr_name to the name of the interface or .i ifr6_ifindex to the index of the interface. all other members of the structure may share memory. .ss ioctls if an ioctl is marked as privileged, then using it requires an effective user id of 0 or the .b cap_net_admin capability. if this is not the case, .b eperm will be returned. .tp .b siocgifname given the .ir ifr_ifindex , return the name of the interface in .ir ifr_name . this is the only ioctl which returns its result in .ir ifr_name . .tp .b siocgifindex retrieve the interface index of the interface into .ir ifr_ifindex . .tp .br siocgifflags ", " siocsifflags get or set the active flag word of the device. .i ifr_flags contains a bit mask of the following values: .\" do not right adjust text blocks in tables .na .ts tab(:); c s l l. device flags iff_up:interface is running. iff_broadcast:valid broadcast address set. iff_debug:internal debugging flag. iff_loopback:interface is a loopback interface. iff_pointopoint:interface is a point-to-point link. iff_running:resources allocated. iff_noarp:t{ no arp protocol, l2 destination address not set. t} iff_promisc:interface is in promiscuous mode. iff_notrailers:avoid use of trailers. iff_allmulti:receive all multicast packets. iff_master:master of a load balancing bundle. iff_slave:slave of a load balancing bundle. iff_multicast:supports multicast iff_portsel:is able to select media type via ifmap. iff_automedia:auto media selection active. iff_dynamic:t{ the addresses are lost when the interface goes down. t} iff_lower_up:driver signals l1 up (since linux 2.6.17) iff_dormant:driver signals dormant (since linux 2.6.17) iff_echo:echo sent packets (since linux 2.6.25) .te .ad .pp setting the active flag word is a privileged operation, but any process may read it. .tp .br siocgifpflags ", " siocsifpflags get or set extended (private) flags for the device. .i ifr_flags contains a bit mask of the following values: .ts tab(:); c s l l. private flags iff_802_1q_vlan:interface is 802.1q vlan device. iff_ebridge:interface is ethernet bridging device. iff_slave_inactive:interface is inactive bonding slave. iff_master_8023ad:interface is 802.3ad bonding master. iff_master_alb:interface is balanced-alb bonding master. iff_bonding:interface is a bonding master or slave. iff_slave_needarp:interface needs arps for validation. iff_isatap:interface is rfc4214 isatap interface. .te .pp setting the extended (private) interface flags is a privileged operation. .tp .br siocgifaddr ", " siocsifaddr ", " siocdifaddr get, set, or delete the address of the device using .ir ifr_addr , or .i ifr6_addr with .ir ifr6_prefixlen . setting or deleting the interface address is a privileged operation. for compatibility, .b siocgifaddr returns only .b af_inet addresses, .b siocsifaddr accepts .b af_inet and .b af_inet6 addresses, and .b siocdifaddr deletes only .b af_inet6 addresses. a .b af_inet address can be deleted by setting it to zero via .br siocsifaddr . .tp .br siocgifdstaddr ", " siocsifdstaddr get or set the destination address of a point-to-point device using .ir ifr_dstaddr . for compatibility, only .b af_inet addresses are accepted or returned. setting the destination address is a privileged operation. .tp .br siocgifbrdaddr ", " siocsifbrdaddr get or set the broadcast address for a device using .ir ifr_brdaddr . for compatibility, only .b af_inet addresses are accepted or returned. setting the broadcast address is a privileged operation. .tp .br siocgifnetmask ", " siocsifnetmask get or set the network mask for a device using .ir ifr_netmask . for compatibility, only .b af_inet addresses are accepted or returned. setting the network mask is a privileged operation. .tp .br siocgifmetric ", " siocsifmetric get or set the metric of the device using .ir ifr_metric . this is currently not implemented; it sets .i ifr_metric to 0 if you attempt to read it and returns .b eopnotsupp if you attempt to set it. .tp .br siocgifmtu ", " siocsifmtu get or set the mtu (maximum transfer unit) of a device using .ir ifr_mtu . setting the mtu is a privileged operation. setting the mtu to too small values may cause kernel crashes. .tp .br siocgifhwaddr ", " siocsifhwaddr get or set the hardware address of a device using .ir ifr_hwaddr . the hardware address is specified in a struct .ir sockaddr . .i sa_family contains the arphrd_* device type, .i sa_data the l2 hardware address starting from byte 0. setting the hardware address is a privileged operation. .tp .b siocsifhwbroadcast set the hardware broadcast address of a device from .ir ifr_hwaddr . this is a privileged operation. .tp .br siocgifmap ", " siocsifmap get or set the interface's hardware parameters using .ir ifr_map . setting the parameters is a privileged operation. .ip .in +4n .ex struct ifmap { unsigned long mem_start; unsigned long mem_end; unsigned short base_addr; unsigned char irq; unsigned char dma; unsigned char port; }; .ee .in .ip the interpretation of the ifmap structure depends on the device driver and the architecture. .tp .br siocaddmulti ", " siocdelmulti add an address to or delete an address from the device's link layer multicast filters using .ir ifr_hwaddr . these are privileged operations. see also .br packet (7) for an alternative. .tp .br siocgiftxqlen ", " siocsiftxqlen get or set the transmit queue length of a device using .ir ifr_qlen . setting the transmit queue length is a privileged operation. .tp .b siocsifname changes the name of the interface specified in .i ifr_name to .ir ifr_newname . this is a privileged operation. it is allowed only when the interface is not up. .tp .b siocgifconf return a list of interface (network layer) addresses. this currently means only addresses of the .b af_inet (ipv4) family for compatibility. unlike the others, this ioctl passes an .i ifconf structure: .ip .in +4n .ex struct ifconf { int ifc_len; /* size of buffer */ union { char *ifc_buf; /* buffer address */ struct ifreq *ifc_req; /* array of structures */ }; }; .ee .in .ip if .i ifc_req is null, .b siocgifconf returns the necessary buffer size in bytes for receiving all available addresses in .ir ifc_len . otherwise, .i ifc_req contains a pointer to an array of .i ifreq structures to be filled with all currently active l3 interface addresses. .i ifc_len contains the size of the array in bytes. within each .i ifreq structure, .i ifr_name will receive the interface name, and .i ifr_addr the address. the actual number of bytes transferred is returned in .ir ifc_len . .ip if the size specified by .i ifc_len is insufficient to store all the addresses, the kernel will skip the exceeding ones and return success. there is no reliable way of detecting this condition once it has occurred. it is therefore recommended to either determine the necessary buffer size beforehand by calling .b siocgifconf with .i ifc_req set to null, or to retry the call with a bigger buffer whenever .i ifc_len upon return differs by less than .i sizeof(struct ifreq) from its original value. .ip if an error occurs accessing the .i ifconf or .i ifreq structures, .b efault will be returned. .\" slaving isn't supported in 2.2 .\" . .\" .tp .\" .br siocgifslave ", " siocsifslave .\" get or set the slave device using .\" .ir ifr_slave . .\" setting the slave device is a privileged operation. .\" .pp .\" fixme . add amateur radio stuff. .pp most protocols support their own ioctls to configure protocol-specific interface options. see the protocol man pages for a description. for configuring ip addresses, see .br ip (7). .pp in addition, some devices support private ioctls. these are not described here. .sh notes .b siocgifconf and the other ioctls that accept or return only .b af_inet socket addresses are ip-specific and perhaps should rather be documented in .br ip (7). .pp the names of interfaces with no addresses or that don't have the .b iff_running flag set can be found via .ir /proc/net/dev . .pp .b af_inet6 ipv6 addresses can be read from .i /proc/net/if_inet6 or via .br rtnetlink (7). adding a new ipv6 address and deleting an existing ipv6 address can be done via .b siocsifaddr and .b siocdifaddr or via .br rtnetlink (7). retrieving or changing destination ipv6 addresses of a point-to-point interface is possible only via .br rtnetlink (7). .sh bugs glibc 2.1 is missing the .i ifr_newname macro in .ir . add the following to your program as a workaround: .pp .in +4n .ex #ifndef ifr_newname #define ifr_newname ifr_ifru.ifru_slave #endif .ee .in .sh see also .br proc (5), .br capabilities (7), .br ip (7), .br rtnetlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .so man3/round.3 .so man3/conj.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright (c) 2008 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified mon apr 12 12:49:57 1993, david metcalfe .\" modified sat jul 24 18:56:22 1993, rik faith (faith@cs.unc.edu) .\" modified wed feb 20 21:09:36 2002, ian redfern (redferni@logica.com) .\" 2008-07-09, mtk, add rawmemchr() .\" .th memchr 3 2021-03-22 "" "linux programmer's manual" .sh name memchr, memrchr, rawmemchr \- scan memory for a character .sh synopsis .nf .b #include .pp .bi "void *memchr(const void *" s ", int " c ", size_t " n ); .bi "void *memrchr(const void *" s ", int " c ", size_t " n ); .bi "void *rawmemchr(const void *" s ", int " c ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br memrchr (), .br rawmemchr (): .nf _gnu_source .fi .sh description the .br memchr () function scans the initial .i n bytes of the memory area pointed to by .i s for the first instance of .ir c . both .i c and the bytes of the memory area pointed to by .i s are interpreted as .ir "unsigned char" . .pp the .br memrchr () function is like the .br memchr () function, except that it searches backward from the end of the .i n bytes pointed to by .i s instead of forward from the beginning. .pp the .br rawmemchr () function is similar to .br memchr (): it assumes (i.e., the programmer knows for certain) that an instance of .i c lies somewhere in the memory area starting at the location pointed to by .ir s , and so performs an optimized search for .ir c (i.e., no use of a count argument to limit the range of the search). if an instance of .i c is not found, the results are unpredictable. the following call is a fast means of locating a string's terminating null byte: .pp .in +4n .ex char *p = rawmemchr(s,\ \(aq\e0\(aq); .ee .in .sh return value the .br memchr () and .br memrchr () functions return a pointer to the matching byte or null if the character does not occur in the given memory area. .pp the .br rawmemchr () function returns a pointer to the matching byte, if one is found. if no matching byte is found, the result is unspecified. .sh versions .br rawmemchr () first appeared in glibc in version 2.1. .pp .br memrchr () first appeared in glibc in version 2.2. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br memchr (), .br memrchr (), .br rawmemchr () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br memchr (): posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .pp the .br memrchr () function is a gnu extension, available since glibc 2.1.91. .pp the .br rawmemchr () function is a gnu extension, available since glibc 2.1. .sh see also .br bstring (3), .br ffs (3), .br index (3), .br memmem (3), .br rindex (3), .br strchr (3), .br strpbrk (3), .br strrchr (3), .br strsep (3), .br strspn (3), .br strstr (3), .br wmemchr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/stat.2 .so man3/wprintf.3 .\" copyright (c) 2005 michael kerrisk .\" based on earlier work by faith@cs.unc.edu and .\" mike battersby .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2005-09-15, mtk, created new page by splitting off from sigaction.2 .\" .th sigsuspend 2 2021-03-22 "linux" "linux programmer's manual" .sh name sigsuspend, rt_sigsuspend \- wait for a signal .sh synopsis .nf .b #include .pp .bi "int sigsuspend(const sigset_t *" mask ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sigsuspend (): .nf _posix_c_source .fi .sh description .br sigsuspend () temporarily replaces the signal mask of the calling thread with the mask given by .i mask and then suspends the thread until delivery of a signal whose action is to invoke a signal handler or to terminate a process. .pp if the signal terminates the process, then .br sigsuspend () does not return. if the signal is caught, then .br sigsuspend () returns after the signal handler returns, and the signal mask is restored to the state before the call to .br sigsuspend (). .pp it is not possible to block .b sigkill or .br sigstop ; specifying these signals in .ir mask , has no effect on the thread's signal mask. .sh return value .br sigsuspend () always returns \-1, with .i errno set to indicate the error (normally, .br eintr ). .sh errors .tp .b efault .i mask points to memory which is not a valid part of the process address space. .tp .b eintr the call was interrupted by a signal; .br signal (7). .sh conforming to posix.1-2001, posix.1-2008. .sh notes normally, .br sigsuspend () is used in conjunction with .br sigprocmask (2) in order to prevent delivery of a signal during the execution of a critical code section. the caller first blocks the signals with .br sigprocmask (2). when the critical code has completed, the caller then waits for the signals by calling .br sigsuspend () with the signal mask that was returned by .br sigprocmask (2) (in the .i oldset argument). .pp see .br sigsetops (3) for details on manipulating signal sets. .\" .ss c library/kernel differences the original linux system call was named .br sigsuspend (). however, with the addition of real-time signals in linux 2.2, the fixed-size, 32-bit .ir sigset_t type supported by that system call was no longer fit for purpose. consequently, a new system call, .br rt_sigsuspend (), was added to support an enlarged .ir sigset_t type. the new system call takes a second argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the signal set in .ir mask . this argument is currently required to have the value .ir sizeof(sigset_t) (or the error .b einval results). the glibc .br sigsuspend () wrapper function hides these details from us, transparently calling .br rt_sigsuspend () when the kernel provides it. .\" .sh see also .br kill (2), .br pause (2), .br sigaction (2), .br signal (2), .br sigprocmask (2), .br sigwaitinfo (2), .br sigsetops (3), .br sigwait (3), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1999 andries brouwer (aeb@cwi.nl) .\" .\" earlier versions of this page influenced the present text. .\" it was derived from a berkeley page with version .\" @(#)printf.3 6.14 (berkeley) 7/30/91 .\" converted for linux by faith@cs.unc.edu, updated by .\" helmut.geyer@iwr.uni-heidelberg.de, agulbra@troll.no and bruno haible. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 1999-11-25 aeb - rewritten, using susv2 and c99. .\" 2000-07-26 jsm28@hermes.cam.ac.uk - three small fixes .\" 2000-10-16 jsm28@hermes.cam.ac.uk - more fixes .\" .th printf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name printf, fprintf, dprintf, sprintf, snprintf, vprintf, vfprintf, vdprintf, vsprintf, vsnprintf \- formatted output conversion .sh synopsis .nf .b #include .pp .bi "int printf(const char *restrict " format ", ...);" .bi "int fprintf(file *restrict " stream , .bi " const char *restrict " format ", ...);" .bi "int dprintf(int " fd , .bi " const char *restrict " format ", ...);" .bi "int sprintf(char *restrict " str , .bi " const char *restrict " format ", ...);" .bi "int snprintf(char *restrict " str ", size_t " size , .bi " const char *restrict " format ", ...);" .pp .b #include .pp .bi "int vprintf(const char *restrict " format ", va_list " ap ); .bi "int vfprintf(file *restrict " stream , .bi " const char *restrict " format ", va_list " ap ); .bi "int vdprintf(int " fd , .bi " const char *restrict " format ", va_list " ap ); .bi "int vsprintf(char *restrict " str , .bi " const char *restrict " format ", va_list " ap ); .bi "int vsnprintf(char *restrict " str ", size_t " size , .bi " const char *restrict " format ", va_list " ap ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br snprintf (), .br vsnprintf (): .nf _xopen_source >= 500 || _isoc99_source || /* glibc <= 2.19: */ _bsd_source .fi .pp .br dprintf (), .br vdprintf (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the functions in the .br printf () family produce output according to a .i format as described below. the functions .br printf () and .br vprintf () write output to .ir stdout , the standard output stream; .br fprintf () and .br vfprintf () write output to the given output .ir stream ; .br sprintf (), .br snprintf (), .br vsprintf (), and .br vsnprintf () write to the character string .ir str . .pp the function .br dprintf () is the same as .br fprintf () except that it outputs to a file descriptor, .ir fd , instead of to a .br stdio (3) stream. .pp the functions .br snprintf () and .br vsnprintf () write at most .i size bytes (including the terminating null byte (\(aq\e0\(aq)) to .ir str . .pp the functions .br vprintf (), .br vfprintf (), .br vdprintf (), .br vsprintf (), .br vsnprintf () are equivalent to the functions .br printf (), .br fprintf (), .br dprintf (), .br sprintf (), .br snprintf (), respectively, except that they are called with a .i va_list instead of a variable number of arguments. these functions do not call the .i va_end macro. because they invoke the .i va_arg macro, the value of .i ap is undefined after the call. see .br stdarg (3). .pp all of these functions write the output under the control of a .i format string that specifies how subsequent arguments (or arguments accessed via the variable-length argument facilities of .br stdarg (3)) are converted for output. .pp c99 and posix.1-2001 specify that the results are undefined if a call to .br sprintf (), .br snprintf (), .br vsprintf (), or .br vsnprintf () would cause copying to take place between objects that overlap (e.g., if the target string array and one of the supplied input arguments refer to the same buffer). see notes. .ss format of the format string the format string is a character string, beginning and ending in its initial shift state, if any. the format string is composed of zero or more directives: ordinary characters (not .br % ), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments. each conversion specification is introduced by the character .br % , and ends with a .ir "conversion specifier" . in between there may be (in this order) zero or more .ir flags , an optional minimum .ir "field width" , an optional .i precision and an optional .ir "length modifier" . .pp the overall syntax of a conversion specification is: .pp .in +4n .nf %[$][flags][width][.precision][length modifier]conversion .fi .in .pp the arguments must correspond properly (after type promotion) with the conversion specifier. by default, the arguments are used in the order given, where each \(aq*\(aq (see .i "field width" and .i precision below) and each conversion specifier asks for the next argument (and it is an error if insufficiently many arguments are given). one can also specify explicitly which argument is taken, at each place where an argument is required, by writing "%m$" instead of \(aq%\(aq and "*m$" instead of \(aq*\(aq, where the decimal integer \fim\fp denotes the position in the argument list of the desired argument, indexed starting from 1. thus, .pp .in +4n .ex printf("%*d", width, num); .ee .in .pp and .pp .in +4n .ex printf("%2$*1$d", width, num); .ee .in .pp are equivalent. the second style allows repeated references to the same argument. the c99 standard does not include the style using \(aq$\(aq, which comes from the single unix specification. if the style using \(aq$\(aq is used, it must be used throughout for all conversions taking an argument and all width and precision arguments, but it may be mixed with "%%" formats, which do not consume an argument. there may be no gaps in the numbers of arguments specified using \(aq$\(aq; for example, if arguments 1 and 3 are specified, argument 2 must also be specified somewhere in the format string. .pp for some numeric conversions a radix character ("decimal point") or thousands' grouping character is used. the actual character used depends on the .b lc_numeric part of the locale. (see .br setlocale (3).) the posix locale uses \(aq.\(aq as radix character, and does not have a grouping character. thus, .pp .in +4n .ex printf("%\(aq.2f", 1234567.89); .ee .in .pp results in "1234567.89" in the posix locale, in "1234567,89" in the nl_nl locale, and in "1.234.567,89" in the da_dk locale. .ss flag characters the character % is followed by zero or more of the following flags: .tp .b # the value should be converted to an "alternate form". for .b o conversions, the first character of the output string is made zero (by prefixing a 0 if it was not zero already). for .b x and .b x conversions, a nonzero result has the string "0x" (or "0x" for .b x conversions) prepended to it. for .br a , .br a , .br e , .br e , .br f , .br f , .br g , and .b g conversions, the result will always contain a decimal point, even if no digits follow it (normally, a decimal point appears in the results of those conversions only if a digit follows). for .b g and .b g conversions, trailing zeros are not removed from the result as they would otherwise be. for other conversions, the result is undefined. .tp .b \&0 the value should be zero padded. for .br d , .br i , .br o , .br u , .br x , .br x , .br a , .br a , .br e , .br e , .br f , .br f , .br g , and .b g conversions, the converted value is padded on the left with zeros rather than blanks. if the .b \&0 and .b \- flags both appear, the .b \&0 flag is ignored. if a precision is given with a numeric conversion .rb ( d , .br i , .br o , .br u , .br x , and .br x ), the .b \&0 flag is ignored. for other conversions, the behavior is undefined. .tp .b \- the converted value is to be left adjusted on the field boundary. (the default is right justification.) the converted value is padded on the right with blanks, rather than on the left with blanks or zeros. a .b \- overrides a .b \&0 if both are given. .tp .b \(aq \(aq (a space) a blank should be left before a positive number (or empty string) produced by a signed conversion. .tp .b + a sign (+ or \-) should always be placed before a number produced by a signed conversion. by default, a sign is used only for negative numbers. a .b + overrides a space if both are used. .pp the five flag characters above are defined in the c99 standard. the single unix specification specifies one further flag character. .tp .b \(aq for decimal conversion .rb ( i , .br d , .br u , .br f , .br f , .br g , .br g ) the output is to be grouped with thousands' grouping characters if the locale information indicates any. (see .br setlocale (3).) note that many versions of .br gcc (1) cannot parse this option and will issue a warning. (susv2 did not include \fi%\(aqf\fp, but susv3 added it.) .pp glibc 2.2 adds one further flag character. .tp .b i for decimal integer conversion .rb ( i , .br d , .br u ) the output uses the locale's alternative output digits, if any. for example, since glibc 2.2.3 this will give arabic-indic digits in the persian ("fa_ir") locale. .\" outdigits keyword in locale file .ss field width an optional decimal digit string (with nonzero first digit) specifying a minimum field width. if the converted value has fewer characters than the field width, it will be padded with spaces on the left (or right, if the left-adjustment flag has been given). instead of a decimal digit string one may write "*" or "*m$" (for some decimal integer \fim\fp) to specify that the field width is given in the next argument, or in the \fim\fp-th argument, respectively, which must be of type .ir int . a negative field width is taken as a \(aq\-\(aq flag followed by a positive field width. in no case does a nonexistent or small field width cause truncation of a field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result. .ss precision an optional precision, in the form of a period (\(aq.\(aq) followed by an optional decimal digit string. instead of a decimal digit string one may write "*" or "*m$" (for some decimal integer \fim\fp) to specify that the precision is given in the next argument, or in the \fim\fp-th argument, respectively, which must be of type .ir int . if the precision is given as just \(aq.\(aq, the precision is taken to be zero. a negative precision is taken as if the precision were omitted. this gives the minimum number of digits to appear for .br d , .br i , .br o , .br u , .br x , and .b x conversions, the number of digits to appear after the radix character for .br a , .br a , .br e , .br e , .br f , and .b f conversions, the maximum number of significant digits for .b g and .b g conversions, or the maximum number of characters to be printed from a string for .b s and .b s conversions. .ss length modifier here, "integer conversion" stands for .br d , .br i , .br o , .br u , .br x , or .b x conversion. .tp .b hh a following integer conversion corresponds to a .i signed char or .i unsigned char argument, or a following .b n conversion corresponds to a pointer to a .i signed char argument. .tp .b h a following integer conversion corresponds to a .i short or .i unsigned short argument, or a following .b n conversion corresponds to a pointer to a .i short argument. .tp .b l (ell) a following integer conversion corresponds to a .i long or .i unsigned long argument, or a following .b n conversion corresponds to a pointer to a .i long argument, or a following .b c conversion corresponds to a .i wint_t argument, or a following .b s conversion corresponds to a pointer to .i wchar_t argument. .tp .b ll (ell-ell). a following integer conversion corresponds to a .i long long or .i unsigned long long argument, or a following .b n conversion corresponds to a pointer to a .i long long argument. .tp .b q a synonym for .br ll . this is a nonstandard extension, derived from bsd; avoid its use in new code. .tp .b l a following .br a , .br a , .br e , .br e , .br f , .br f , .br g , or .b g conversion corresponds to a .i long double argument. (c99 allows %lf, but susv2 does not.) .tp .b j a following integer conversion corresponds to an .i intmax_t or .i uintmax_t argument, or a following .b n conversion corresponds to a pointer to an .i intmax_t argument. .tp .b z a following integer conversion corresponds to a .i size_t or .i ssize_t argument, or a following .b n conversion corresponds to a pointer to a .i size_t argument. .tp .b z a nonstandard synonym for .br z that predates the appearance of .br z . do not use in new code. .tp .b t a following integer conversion corresponds to a .i ptrdiff_t argument, or a following .b n conversion corresponds to a pointer to a .i ptrdiff_t argument. .pp susv3 specifies all of the above, except for those modifiers explicitly noted as being nonstandard extensions. susv2 specified only the length modifiers .b h (in .br hd , .br hi , .br ho , .br hx , .br hx , .br hn ) and .b l (in .br ld , .br li , .br lo , .br lx , .br lx , .br ln , .br lc , .br ls ) and .b l (in .br le , .br le , .br lf , .br lg , .br lg ). .pp as a nonstandard extension, the gnu implementations treats .b ll and .b l as synonyms, so that one can, for example, write .br llg (as a synonym for the standards-compliant .br lg ) and .br ld (as a synonym for the standards compliant .br lld ). such usage is nonportable. .\" .ss conversion specifiers a character that specifies the type of conversion to be applied. the conversion specifiers and their meanings are: .tp .br d ", " i the .i int argument is converted to signed decimal notation. the precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros. the default precision is 1. when 0 is printed with an explicit precision 0, the output is empty. .tp .br o ", " u ", " x ", " x the .i "unsigned int" argument is converted to unsigned octal .rb ( o ), unsigned decimal .rb ( u ), or unsigned hexadecimal .rb ( x and .br x ) notation. the letters .b abcdef are used for .b x conversions; the letters .b abcdef are used for .b x conversions. the precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros. the default precision is 1. when 0 is printed with an explicit precision 0, the output is empty. .tp .br e ", " e the .i double argument is rounded and converted in the style .rb [\-]d \&. ddd e \(+-dd where there is one digit (which is nonzero if the argument is nonzero) before the decimal-point character and the number of digits after it is equal to the precision; if the precision is missing, it is taken as 6; if the precision is zero, no decimal-point character appears. an .b e conversion uses the letter .b e (rather than .br e ) to introduce the exponent. the exponent always contains at least two digits; if the value is zero, the exponent is 00. .tp .br f ", " f the .i double argument is rounded and converted to decimal notation in the style .rb [\-]ddd \&. ddd, where the number of digits after the decimal-point character is equal to the precision specification. if the precision is missing, it is taken as 6; if the precision is explicitly zero, no decimal-point character appears. if a decimal point appears, at least one digit appears before it. .ip (susv2 does not know about .b f and says that character string representations for infinity and nan may be made available. susv3 adds a specification for .br f . the c99 standard specifies "[\-]inf" or "[\-]infinity" for infinity, and a string starting with "nan" for nan, in the case of .b f conversion, and "[\-]inf" or "[\-]infinity" or "nan" in the case of .b f conversion.) .tp .br g ", " g the .i double argument is converted in style .b f or .b e (or .b f or .b e for .b g conversions). the precision specifies the number of significant digits. if the precision is missing, 6 digits are given; if the precision is zero, it is treated as 1. style .b e is used if the exponent from its conversion is less than \-4 or greater than or equal to the precision. trailing zeros are removed from the fractional part of the result; a decimal point appears only if it is followed by at least one digit. .tp .br a ", " a (c99; not in susv2, but added in susv3) for .b a conversion, the .i double argument is converted to hexadecimal notation (using the letters abcdef) in the style .rb [\-] 0x h \&. hhhh p \(+-d; for .b a conversion the prefix .br 0x , the letters abcdef, and the exponent separator .b p is used. there is one hexadecimal digit before the decimal point, and the number of digits after it is equal to the precision. the default precision suffices for an exact representation of the value if an exact representation in base 2 exists and otherwise is sufficiently large to distinguish values of type .ir double . the digit before the decimal point is unspecified for nonnormalized numbers, and nonzero but otherwise unspecified for normalized numbers. the exponent always contains at least one digit; if the value is zero, the exponent is 0. .tp .b c if no .b l modifier is present, the .i int argument is converted to an .ir "unsigned char" , and the resulting character is written. if an .b l modifier is present, the .i wint_t (wide character) argument is converted to a multibyte sequence by a call to the .br wcrtomb (3) function, with a conversion state starting in the initial state, and the resulting multibyte string is written. .tp .b s if no .b l modifier is present: the .i "const char\ *" argument is expected to be a pointer to an array of character type (pointer to a string). characters from the array are written up to (but not including) a terminating null byte (\(aq\e0\(aq); if a precision is specified, no more than the number specified are written. if a precision is given, no null byte need be present; if the precision is not specified, or is greater than the size of the array, the array must contain a terminating null byte. .ip if an .b l modifier is present: the .i "const wchar_t\ *" argument is expected to be a pointer to an array of wide characters. wide characters from the array are converted to multibyte characters (each by a call to the .br wcrtomb (3) function, with a conversion state starting in the initial state before the first wide character), up to and including a terminating null wide character. the resulting multibyte characters are written up to (but not including) the terminating null byte. if a precision is specified, no more bytes than the number specified are written, but no partial multibyte characters are written. note that the precision determines the number of .i bytes written, not the number of .i wide characters or .ir "screen positions" . the array must contain a terminating null wide character, unless a precision is given and it is so small that the number of bytes written exceeds it before the end of the array is reached. .tp .b c (not in c99 or c11, but in susv2, susv3, and susv4.) synonym for .br lc . don't use. .tp .b s (not in c99 or c11, but in susv2, susv3, and susv4.) synonym for .br ls . don't use. .tp .b p the .i "void\ *" pointer argument is printed in hexadecimal (as if by .b %#x or .br %#lx ). .tp .b n the number of characters written so far is stored into the integer pointed to by the corresponding argument. that argument shall be an .ir "int\ *" , or variant whose size matches the (optionally) supplied integer length modifier. no argument is converted. (this specifier is not supported by the bionic c library.) the behavior is undefined if the conversion specification includes any flags, a field width, or a precision. .tp .b m (glibc extension; supported by uclibc and musl.) print output of .ir strerror(errno) . no argument is required. .tp .b % a \(aq%\(aq is written. no argument is converted. the complete conversion specification is \(aq%%\(aq. .sh return value upon successful return, these functions return the number of characters printed (excluding the null byte used to end output to strings). .pp the functions .br snprintf () and .br vsnprintf () do not write more than .i size bytes (including the terminating null byte (\(aq\e0\(aq)). if the output was truncated due to this limit, then the return value is the number of characters (excluding the terminating null byte) which would have been written to the final string if enough space had been available. thus, a return value of .i size or more means that the output was truncated. (see also below under notes.) .pp if an output error is encountered, a negative value is returned. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br printf (), .br fprintf (), .br sprintf (), .br snprintf (), .br vprintf (), .br vfprintf (), .br vsprintf (), .br vsnprintf () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to .br fprintf (), .br printf (), .br sprintf (), .br vprintf (), .br vfprintf (), .br vsprintf (): posix.1-2001, posix.1-2008, c89, c99. .pp .br snprintf (), .br vsnprintf (): posix.1-2001, posix.1-2008, c99. .pp the .br dprintf () and .br vdprintf () functions were originally gnu extensions that were later standardized in posix.1-2008. .pp concerning the return value of .br snprintf (), susv2 and c99 contradict each other: when .br snprintf () is called with .ir size =0 then susv2 stipulates an unspecified return value less than 1, while c99 allows .i str to be null in this case, and gives the return value (as always) as the number of characters that would have been written in case the output string has been large enough. posix.1-2001 and later align their specification of .br snprintf () with c99. .\" .pp .\" linux libc4 knows about the five c standard flags. .\" it knows about the length modifiers \fbh\fp, \fbl\fp, \fbl\fp, .\" and the conversions .\" \fbc\fp, \fbd\fp, \fbe\fp, \fbe\fp, \fbf\fp, \fbf\fp, .\" \fbg\fp, \fbg\fp, \fbi\fp, \fbn\fp, \fbo\fp, \fbp\fp, .\" \fbs\fp, \fbu\fp, \fbx\fp, and \fbx\fp, .\" where \fbf\fp is a synonym for \fbf\fp. .\" additionally, it accepts \fbd\fp, \fbo\fp, and \fbu\fp as synonyms .\" for \fbld\fp, \fblo\fp, and \fblu\fp. .\" (this is bad, and caused serious bugs later, when .\" support for \fb%d\fp disappeared.) .\" no locale-dependent radix character, .\" no thousands' separator, no nan or infinity, no "%m$" and "*m$". .\" .pp .\" linux libc5 knows about the five c standard flags and the \(aq flag, .\" locale, "%m$" and "*m$". .\" it knows about the length modifiers \fbh\fp, \fbl\fp, \fbl\fp, .\" \fbz\fp, and \fbq\fp, but accepts \fbl\fp and \fbq\fp .\" both for \filong double\fp and for \filong long\fp (this is a bug). .\" it no longer recognizes \fbf\fp, \fbd\fp, \fbo\fp, and \fbu\fp, .\" but adds the conversion character .\" .br m , .\" which outputs .\" .ir strerror(errno) . .\" .pp .\" glibc 2.0 adds conversion characters \fbc\fp and \fbs\fp. .pp glibc 2.1 adds length modifiers \fbhh\fp, \fbj\fp, \fbt\fp, and \fbz\fp and conversion characters \fba\fp and \fba\fp. .pp glibc 2.2 adds the conversion character \fbf\fp with c99 semantics, and the flag character \fbi\fp. .sh notes some programs imprudently rely on code such as the following .pp sprintf(buf, "%s some further text", buf); .pp to append text to .ir buf . however, the standards explicitly note that the results are undefined if source and destination buffers overlap when calling .br sprintf (), .br snprintf (), .br vsprintf (), and .br vsnprintf (). .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7075 depending on the version of .br gcc (1) used, and the compiler options employed, calls such as the above will .b not produce the expected results. .pp the glibc implementation of the functions .br snprintf () and .br vsnprintf () conforms to the c99 standard, that is, behaves as described above, since glibc version 2.1. until glibc 2.0.6, they would return \-1 when the output was truncated. .\" .sh history .\" unix v7 defines the three routines .\" .br printf (), .\" .br fprintf (), .\" .br sprintf (), .\" and has the flag \-, the width or precision *, the length modifier l, .\" and the conversions doxfegcsu, and also d,o,u,x as synonyms for ld,lo,lu,lx. .\" this is still true for 2.9.1bsd, but 2.10bsd has the flags .\" #, + and and no longer mentions d,o,u,x. .\" 2.11bsd has .\" .br vprintf (), .\" .br vfprintf (), .\" .br vsprintf (), .\" and warns not to use d,o,u,x. .\" 4.3bsd reno has the flag 0, the length modifiers h and l, .\" and the conversions n, p, e, g, x (with current meaning) .\" and deprecates d,o,u. .\" 4.4bsd introduces the functions .\" .br snprintf () .\" and .\" .br vsnprintf (), .\" and the length modifier q. .\" freebsd also has functions .\" .br asprintf () .\" and .\" .br vasprintf (), .\" that allocate a buffer large enough for .\" .br sprintf (). .\" in glibc there are functions .\" .br dprintf () .\" and .\" .br vdprintf () .\" that print to a file descriptor instead of a stream. .sh bugs because .br sprintf () and .br vsprintf () assume an arbitrarily long string, callers must be careful not to overflow the actual space; this is often impossible to assure. note that the length of the strings produced is locale-dependent and difficult to predict. use .br snprintf () and .br vsnprintf () instead (or .br asprintf (3) and .br vasprintf (3)). .\" .pp .\" linux libc4.[45] does not have a .\" .br snprintf (), .\" but provides a libbsd that contains an .\" .br snprintf () .\" equivalent to .\" .br sprintf (), .\" that is, one that ignores the .\" .i size .\" argument. .\" thus, the use of .\" .br snprintf () .\" with early libc4 leads to serious security problems. .pp code such as .bi printf( foo ); often indicates a bug, since .i foo may contain a % character. if .i foo comes from untrusted user input, it may contain \fb%n\fp, causing the .br printf () call to write to memory and creating a security hole. .\" .pp .\" some floating-point conversions under early libc4 .\" caused memory leaks. .sh examples to print .i pi to five decimal places: .pp .in +4n .ex #include #include fprintf(stdout, "pi = %.5f\en", 4 * atan(1.0)); .ee .in .pp to print a date and time in the form "sunday, july 3, 10:02", where .i weekday and .i month are pointers to strings: .pp .in +4n .ex #include fprintf(stdout, "%s, %s %d, %.2d:%.2d\en", weekday, month, day, hour, min); .ee .in .pp many countries use the day-month-year order. hence, an internationalized version must be able to print the arguments in an order specified by the format: .pp .in +4n .ex #include fprintf(stdout, format, weekday, month, day, hour, min); .ee .in .pp where .i format depends on locale, and may permute the arguments. with the value: .pp .in +4n .ex "%1$s, %3$d. %2$s, %4$d:%5$.2d\en" .ee .in .pp one might obtain "sonntag, 3. juli, 10:02". .pp to allocate a sufficiently large string and print into it (code correct for both glibc 2.0 and glibc 2.1): .pp .ex #include #include #include char * make_message(const char *fmt, ...) { int n = 0; size_t size = 0; char *p = null; va_list ap; /* determine required size. */ va_start(ap, fmt); n = vsnprintf(p, size, fmt, ap); va_end(ap); if (n < 0) return null; size = (size_t) n + 1; /* one extra byte for \(aq\e0\(aq */ p = malloc(size); if (p == null) return null; va_start(ap, fmt); n = vsnprintf(p, size, fmt, ap); va_end(ap); if (n < 0) { free(p); return null; } return p; } .ee .pp if truncation occurs in glibc versions prior to 2.0.6, this is treated as an error instead of being handled gracefully. .sh see also .br printf (1), .br asprintf (3), .br puts (3), .br scanf (3), .br setlocale (3), .br strfromd (3), .br wcrtomb (3), .br wprintf (3), .br locale (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification .\" http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th getwchar 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getwchar \- read a wide character from standard input .sh synopsis .nf .b #include .pp .b "wint_t getwchar(void);" .fi .sh description the .br getwchar () function is the wide-character equivalent of the .br getchar (3) function. it reads a wide character from .i stdin and returns it. if the end of stream is reached, or if .i ferror(stdin) becomes true, it returns .br weof . if a wide-character conversion error occurs, it sets .i errno to .b eilseq and returns .br weof . .pp for a nonlocking counterpart, see .br unlocked_stdio (3). .sh return value the .br getwchar () function returns the next wide-character from standard input, or .br weof . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getwchar () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br getwchar () depends on the .b lc_ctype category of the current locale. .pp it is reasonable to expect that .br getwchar () will actually read a multibyte sequence from standard input and then convert it to a wide character. .sh see also .br fgetwc (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2006 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sun jul 25 10:53:39 1993 by rik faith (faith@cs.unc.edu) .\" added correction due to nsd@bbc.com (nick duffek) - aeb, 950610 .th strtol 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strtol, strtoll, strtoq \- convert a string to a long integer .sh synopsis .nf .b #include .pp .bi "long strtol(const char *restrict " nptr , .bi " char **restrict " endptr ", int " base ); .bi "long long strtoll(const char *restrict " nptr , .bi " char **restrict " endptr ", int " base ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br strtoll (): .nf _isoc99_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description the .br strtol () function converts the initial part of the string in .i nptr to a long integer value according to the given .ir base , which must be between 2 and 36 inclusive, or be the special value 0. .pp the string may begin with an arbitrary amount of white space (as determined by .br isspace (3)) followed by a single optional \(aq+\(aq or \(aq\-\(aq sign. if .i base is zero or 16, the string may then include a "0x" or "0x" prefix, and the number will be read in base 16; otherwise, a zero .i base is taken as 10 (decimal) unless the next character is \(aq0\(aq, in which case it is taken as 8 (octal). .pp the remainder of the string is converted to a .i long value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (in bases above 10, the letter \(aqa\(aq in either uppercase or lowercase represents 10, \(aqb\(aq represents 11, and so forth, with \(aqz\(aq representing 35.) .pp if .i endptr is not null, .br strtol () stores the address of the first invalid character in .ir *endptr . if there were no digits at all, .br strtol () stores the original value of .i nptr in .i *endptr (and returns 0). in particular, if .i *nptr is not \(aq\e0\(aq but .i **endptr is \(aq\e0\(aq on return, the entire string is valid. .pp the .br strtoll () function works just like the .br strtol () function but returns a .i long long integer value. .sh return value the .br strtol () function returns the result of the conversion, unless the value would underflow or overflow. if an underflow occurs, .br strtol () returns .br long_min . if an overflow occurs, .br strtol () returns .br long_max . in both cases, .i errno is set to .br erange . precisely the same holds for .br strtoll () (with .b llong_min and .b llong_max instead of .b long_min and .br long_max ). .sh errors .tp .b einval (not in c99) the given .i base contains an unsupported value. .tp .b erange the resulting value was out of range. .pp the implementation may also set .ir errno to .b einval in case no conversion was performed (no digits seen, and 0 returned). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strtol (), .br strtoll (), .br strtoq () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to .br strtol (): posix.1-2001, posix.1-2008, c89, c99 svr4, 4.3bsd. .pp .br strtoll (): posix.1-2001, posix.1-2008, c99. .sh notes since .br strtol () can legitimately return 0, .br long_max , or .b long_min .rb ( llong_max or .b llong_min for .br strtoll ()) on both success and failure, the calling program should set .i errno to 0 before the call, and then determine if an error occurred by checking whether .i errno has a nonzero value after the call. .pp according to posix.1, in locales other than "c" and "posix", these functions may accept other, implementation-defined numeric strings. .pp bsd also has .pp .in +4n .ex .bi "quad_t strtoq(const char *" nptr ", char **" endptr ", int " base ); .ee .in .pp with completely analogous definition. depending on the wordsize of the current architecture, this may be equivalent to .br strtoll () or to .br strtol (). .sh examples the program shown below demonstrates the use of .br strtol (). the first command-line argument specifies a string from which .br strtol () should parse a number. the second (optional) argument specifies the base to be used for the conversion. (this argument is converted to numeric form using .br atoi (3), a function that performs no error checking and has a simpler interface than .br strtol ().) some examples of the results produced by this program are the following: .pp .in +4n .ex .rb "$" " ./a.out 123" strtol() returned 123 .rb "$" " ./a.out \(aq 123\(aq" strtol() returned 123 .rb "$" " ./a.out 123abc" strtol() returned 123 further characters after number: "abc" .rb "$" " ./a.out 123abc 55" strtol: invalid argument .rb "$" " ./a.out \(aq\(aq" no digits were found .rb "$" " ./a.out 4000000000" strtol: numerical result out of range .ee .in .ss program source \& .ex #include #include #include #include int main(int argc, char *argv[]) { int base; char *endptr, *str; long val; if (argc < 2) { fprintf(stderr, "usage: %s str [base]\en", argv[0]); exit(exit_failure); } str = argv[1]; base = (argc > 2) ? atoi(argv[2]) : 0; errno = 0; /* to distinguish success/failure after call */ val = strtol(str, &endptr, base); /* check for various possible errors. */ if (errno != 0) { perror("strtol"); exit(exit_failure); } if (endptr == str) { fprintf(stderr, "no digits were found\en"); exit(exit_failure); } /* if we got here, strtol() successfully parsed a number. */ printf("strtol() returned %ld\en", val); if (*endptr != \(aq\e0\(aq) /* not necessarily an error... */ printf("further characters after number: \e"%s\e"\en", endptr); exit(exit_success); } .ee .sh see also .br atof (3), .br atoi (3), .br atol (3), .br strtod (3), .br strtoimax (3), .br strtoul (3), .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/setgid.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:08:17 1993 by rik faith (faith@cs.unc.edu) .\" modified 2002-08-25, aeb .\" modified 2004-11-12 as per suggestion by fabian kreutz/aeb .\" 2008-07-24, mtk, created this page, based on material from j0.3. .\" .th y0 3 2021-03-22 "" "linux programmer's manual" .sh name y0, y0f, y0l, y1, y1f, y1l, yn, ynf, ynl \- bessel functions of the second kind .sh synopsis .nf .b #include .pp .bi "double y0(double " x ); .bi "double y1(double " x ); .bi "double yn(int " n ", double " x ); .pp .bi "float y0f(float " x ); .bi "float y1f(float " x ); .bi "float ynf(int " n ", float " x ); .pp .bi "long double y0l(long double " x ); .bi "long double y1l(long double " x ); .bi "long double ynl(int " n ", long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br y0 (), .br y1 (), .br yn (): .nf _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .pp .br y0f (), .br y0l (), .br y1f (), .br y1l (), .br ynf (), .br ynl (): .nf _xopen_source >= 600 || (_isoc99_source && _xopen_source) || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source .fi .sh description the .br y0 () and .br y1 () functions return bessel functions of .i x of the second kind of orders 0 and 1, respectively. the .br yn () function returns the bessel function of .i x of the second kind of order .ir n . .pp the value of .i x must be positive. .pp the .br y0f (), .br y1f (), and .br ynf () functions are versions that take and return .i float values. the .br y0l (), .br y1l (), and .br ynl () functions are versions that take and return .i "long double" values. .sh return value on success, these functions return the appropriate bessel value of the second kind for .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is negative, a domain error occurs, and the functions return .rb \- huge_val , .rb \- huge_valf , or .rb \- huge_vall , respectively. (posix.1-2001 also allows a nan return for this case.) .pp if .i x is 0.0, a pole error occurs, and the functions return .rb \- huge_val , .rb \- huge_valf , or .rb \- huge_vall , respectively. .pp if the result underflows, a range error occurs, and the functions return 0.0 .pp if the result overflows, a range error occurs, and the functions return .rb \- huge_val , .rb \- huge_valf , or .rb \- huge_vall , respectively. (posix.1-2001 also allows a 0.0 return for this case.) .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is negative .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp pole error: \fix\fp is 0.0 .\" before posix.1-2001 tc2, this was (inconsistently) specified .\" as a range error. .i errno is set to .br erange and an .b fe_divbyzero exception is raised (but see bugs). .tp range error: result underflow .\" e.g., y0(1e33) on glibc 2.8/x86-32 .i errno is set to .br erange . no .b fe_underflow exception is returned by .\" this is intended behavior .\" see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6806 .br fetestexcept (3) for this case. .tp range error: result overflow .\" e.g., yn(10, 1e-40) on glibc 2.8/x86-32 .i errno is set to .br erange (but see bugs). an overflow floating-point exception .rb ( fe_overflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br y0 (), .br y0f (), .br y0l () t} thread safety mt-safe t{ .br y1 (), .br y1f (), .br y1l () t} thread safety mt-safe t{ .br yn (), .br ynf (), .br ynl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the functions returning .i double conform to svr4, 4.3bsd, posix.1-2001, posix.1-2008. the others are nonstandard functions that also exist on the bsds. .sh bugs before glibc 2.19, .\" http://sourceware.org/bugzilla/show_bug.cgi?id=6807 these functions misdiagnosed pole errors: .i errno was set to .br edom , instead of .br erange and no .b fe_divbyzero exception was raised. .pp before glibc 2.17, .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6808 did not set .i errno for "range error: result underflow". .pp in glibc version 2.3.2 and earlier, .\" actually, 2.3.2 is the earliest test result i have; so yet .\" to confirm if this error occurs only in 2.3.2. these functions do not raise an invalid floating-point exception .rb ( fe_invalid ) when a domain error occurs. .sh see also .br j0 (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-16.7 .\" copyright (c) 1999 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2003-11-15, aeb, added tmpnam_r .\" .th tmpnam 3 2021-03-22 "" "linux programmer's manual" .sh name tmpnam, tmpnam_r \- create a name for a temporary file .sh synopsis .nf .b #include .pp .bi "char *tmpnam(char *" s ); .bi "char *tmpnam_r(char *" s ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br tmpnam_r () .nf since glibc 2.19: _default_source up to and including glibc 2.19: _bsd_source || _svid_source .fi .sh description .b note: avoid using these functions; use .br mkstemp (3) or .br tmpfile (3) instead. .pp the .br tmpnam () function returns a pointer to a string that is a valid filename, and such that a file with this name did not exist at some point in time, so that naive programmers may think it a suitable name for a temporary file. if the argument .i s is null, this name is generated in an internal static buffer and may be overwritten by the next call to .br tmpnam (). if .i s is not null, the name is copied to the character array (of length at least .ir l_tmpnam ) pointed to by .i s and the value .i s is returned in case of success. .pp the created pathname has a directory prefix .ir p_tmpdir . (both .i l_tmpnam and .i p_tmpdir are defined in .ir , just like the .b tmp_max mentioned below.) .pp the .br tmpnam_r () function performs the same task as .br tmpnam (), but returns null (to indicate an error) if .i s is null. .sh return value these functions return a pointer to a unique temporary filename, or null if a unique name cannot be generated. .sh errors no errors are defined. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tmpnam () t} thread safety mt-unsafe race:tmpnam/!s t{ .br tmpnam_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br tmpnam (): svr4, 4.3bsd, c89, c99, posix.1-2001. posix.1-2008 marks .br tmpnam () as obsolete. .pp .br tmpnam_r () is a nonstandard extension that is also available .\" appears to be on solaris on a few other systems. .sh notes the .br tmpnam () function generates a different string each time it is called, up to .b tmp_max times. if it is called more than .b tmp_max times, the behavior is implementation defined. .pp although these functions generate names that are difficult to guess, it is nevertheless possible that between the time that the pathname is returned and the time that the program opens it, another program might create that pathname using .br open (2), or create it as a symbolic link. this can lead to security holes. to avoid such possibilities, use the .br open (2) .b o_excl flag to open the pathname. or better yet, use .br mkstemp (3) or .br tmpfile (3). .pp portable applications that use threads cannot call .br tmpnam () with a null argument if either .b _posix_threads or .b _posix_thread_safe_functions is defined. .sh bugs never use these functions. use .br mkstemp (3) or .br tmpfile (3) instead. .sh see also .br mkstemp (3), .br mktemp (3), .br tempnam (3), .br tmpfile (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcswidth 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcswidth \- determine columns needed for a fixed-size wide-character string .sh synopsis .nf .br "#define _xopen_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int wcswidth(const wchar_t *" s ", size_t " n ); .fi .sh description the .br wcswidth () function returns the number of columns needed to represent the wide-character string pointed to by .ir s , but at most .i n wide characters. if a nonprintable wide character occurs among these characters, \-1 is returned. .sh return value the .br wcswidth () function returns the number of column positions for the wide-character string .ir s , truncated to at most length .ir n . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcswidth () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes the behavior of .br wcswidth () depends on the .b lc_ctype category of the current locale. .sh see also .br iswprint (3), .br wcwidth (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th complex 7 2021-03-22 "" "linux programmer's manual" .sh name complex \- basics of complex mathematics .sh synopsis .nf .b #include .fi .sh description complex numbers are numbers of the form z = a+b*i, where a and b are real numbers and i = sqrt(\-1), so that i*i = \-1. .pp there are other ways to represent that number. the pair (a,b) of real numbers may be viewed as a point in the plane, given by x- and y-coordinates. this same point may also be described by giving the pair of real numbers (r,phi), where r is the distance to the origin o, and phi the angle between the x-axis and the line oz. now z = r*exp(i*phi) = r*(cos(phi)+i*sin(phi)). .pp the basic operations are defined on z = a+b*i and w = c+d*i as: .tp .b addition: z+w = (a+c) + (b+d)*i .tp .b multiplication: z*w = (a*c \- b*d) + (a*d + b*c)*i .tp .b division: z/w = ((a*c + b*d)/(c*c + d*d)) + ((b*c \- a*d)/(c*c + d*d))*i .pp nearly all math function have a complex counterpart but there are some complex-only functions. .sh examples your c-compiler can work with complex numbers if it supports the c99 standard. link with \fi\-lm\fp. the imaginary unit is represented by i. .pp .ex /* check that exp(i * pi) == \-1 */ #include /* for atan */ #include #include int main(void) { double pi = 4 * atan(1.0); double complex z = cexp(i * pi); printf("%f + %f * i\en", creal(z), cimag(z)); } .ee .sh see also .br cabs (3), .br cacos (3), .br cacosh (3), .br carg (3), .br casin (3), .br casinh (3), .br catan (3), .br catanh (3), .br ccos (3), .br ccosh (3), .br cerf (3), .br cexp (3), .br cexp2 (3), .br cimag (3), .br clog (3), .br clog10 (3), .br clog2 (3), .br conj (3), .br cpow (3), .br cproj (3), .br creal (3), .br csin (3), .br csinh (3), .br csqrt (3), .br ctan (3), .br ctanh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1998, 1999 thorsten kukuk (kukuk@vt.uni-paderborn.de) .\" copyright (c) 2011, mark r. bannister .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th nsswitch.conf 5 2017-05-03 "linux" "linux programmer's manual" .sh name nsswitch.conf \- name service switch configuration file .sh description the name service switch (nss) configuration file, .ir /etc/nsswitch.conf , is used by the gnu c library and certain other applications to determine the sources from which to obtain name-service information in a range of categories, and in what order. each category of information is identified by a database name. .pp the file is plain ascii text, with columns separated by spaces or tab characters. the first column specifies the database name. the remaining columns describe the order of sources to query and a limited set of actions that can be performed by lookup result. .pp the following databases are understood by the gnu c library: .tp 12 .b aliases mail aliases, used by .br getaliasent (3) and related functions. .tp .b ethers ethernet numbers. .tp .b group groups of users, used by .br getgrent (3) and related functions. .tp .b hosts host names and numbers, used by .br gethostbyname (3) and related functions. .tp .b initgroups supplementary group access list, used by .br getgrouplist (3) function. .tp .b netgroup network-wide list of hosts and users, used for access rules. c libraries before glibc 2.1 supported netgroups only over nis. .tp .b networks network names and numbers, used by .br getnetent (3) and related functions. .tp .b passwd user passwords, used by .br getpwent (3) and related functions. .tp .b protocols network protocols, used by .br getprotoent (3) and related functions. .tp .b publickey public and secret keys for secure_rpc used by nfs and nis+. .tp .b rpc remote procedure call names and numbers, used by .br getrpcbyname (3) and related functions. .tp .b services network services, used by .br getservent (3) and related functions. .tp .b shadow shadow user passwords, used by .br getspnam (3) and related functions. .pp the gnu c library ignores databases with unknown names. some applications use this to implement special handling for their own databases. for example, .br sudo (8) consults the .b sudoers database. .pp here is an example .i /etc/nsswitch.conf file: .pp .in +4n .ex passwd: compat group: compat shadow: compat hosts: dns [!unavail=return] files networks: nis [notfound=return] files ethers: nis [notfound=return] files protocols: nis [notfound=return] files rpc: nis [notfound=return] files services: nis [notfound=return] files .ee .in .pp the first column is the database name. the remaining columns specify: .ip * 3 one or more service specifications, for example, "files", "db", or "nis". the order of the services on the line determines the order in which those services will be queried, in turn, until a result is found. .ip * optional actions to perform if a particular result is obtained from the preceding service, for example, "[notfound=return]". .pp the service specifications supported on your system depend on the presence of shared libraries, and are therefore extensible. libraries called .ib /lib/libnss_service.so. x will provide the named .ir service . on a standard installation, you can use "files", "db", "nis", and "nisplus". for the .b hosts database, you can additionally specify "dns". for the .br passwd , .br group , and .b shadow databases, you can additionally specify "compat" (see .b "compatibility mode" below). the version number .b x may be 1 for glibc 2.0, or 2 for glibc 2.1 and later. on systems with additional libraries installed, you may have access to further services such as "hesiod", "ldap", "winbind", and "wins". .pp an action may also be specified following a service specification. the action modifies the behavior following a result obtained from the preceding data source. action items take the general form: .pp .rs 4 .ri [ status = action ] .br .ri [! status = action ] .re .pp where .pp .rs 4 .i status => .b success | .b notfound | .b unavail | .b tryagain .br .i action => .b return | .b continue | .b merge .re .pp the ! negates the test, matching all possible results except the one specified. the case of the keywords is not significant. .pp the .i status value is matched against the result of the lookup function called by the preceding service specification, and can be one of: .rs 4 .tp 12 .b success no error occurred and the requested entry is returned. the default action for this condition is "return". .tp .b notfound the lookup succeeded, but the requested entry was not found. the default action for this condition is "continue". .tp .b unavail the service is permanently unavailable. this can mean either that the required file cannot be read, or, for network services, that the server is not available or does not allow queries. the default action for this condition is "continue". .tp .b tryagain the service is temporarily unavailable. this could mean a file is locked or a server currently cannot accept more connections. the default action for this condition is "continue". .re .pp the .i action value can be one of: .rs 4 .tp 12 .b return return a result now. do not call any further lookup functions. however, for compatibility reasons, if this is the selected action for the .b group database and the .b notfound status, and the configuration file does not contain the .b initgroups line, the next lookup function is always called, without affecting the search result. .tp .b continue call the next lookup function. .tp .b merge .i [success=merge] is used between two database entries. when a group is located in the first of the two group entries, processing will continue on to the next one. if the group is also found in the next entry (and the group name and gid are an exact match), the member list of the second entry will be added to the group object to be returned. available since glibc 2.24. note that merging will not be done for .br getgrent (3) nor will duplicate members be pruned when they occur in both entries being merged. .re .ss compatibility mode (compat) the nss "compat" service is similar to "files" except that it additionally permits special entries in corresponding files for granting users or members of netgroups access to the system. the following entries are valid in this mode: .rs 4 .pp for .b passwd and .b shadow databases: .rs 4 .tp 12 .bi + user include the specified .i user from the nis passwd/shadow map. .tp .bi +@ netgroup include all users in the given .ir netgroup . .tp .bi \- user exclude the specified .i user from the nis passwd/shadow map. .tp .bi \-@ netgroup exclude all users in the given .ir netgroup . .tp .b + include every user, except previously excluded ones, from the nis passwd/shadow map. .re .pp for .b group database: .rs 4 .tp 12 .bi + group include the specified .i group from the nis group map. .tp .bi \- group exclude the specified .i group from the nis group map. .tp .b + include every group, except previously excluded ones, from the nis group map. .re .re .pp by default, the source is "nis", but this may be overridden by specifying any nss service except "compat" itself as the source for the pseudo-databases .br passwd_compat , .br group_compat , and .br shadow_compat . .sh files a service named .i service is implemented by a shared object library named .ib libnss_service.so. x that resides in .ir /lib . .rs 4 .tp 25 .pd 0 .i /etc/nsswitch.conf nss configuration file. .tp .ib /lib/libnss_compat.so. x implements "compat" source. .tp .ib /lib/libnss_db.so. x implements "db" source. .tp .ib /lib/libnss_dns.so. x implements "dns" source. .tp .ib /lib/libnss_files.so. x implements "files" source. .tp .ib /lib/libnss_hesiod.so. x implements "hesiod" source. .tp .ib /lib/libnss_nis.so. x implements "nis" source. .tp .ib /lib/libnss_nisplus.so. x implements "nisplus" source. .pd .re .pp the following files are read when "files" source is specified for respective databases: .rs 4 .tp 12 .pd 0 .b aliases .i /etc/aliases .tp .b ethers .i /etc/ethers .tp .b group .i /etc/group .tp .b hosts .i /etc/hosts .tp .b initgroups .i /etc/group .tp .b netgroup .i /etc/netgroup .tp .b networks .i /etc/networks .tp .b passwd .i /etc/passwd .tp .b protocols .i /etc/protocols .tp .b publickey .i /etc/publickey .tp .b rpc .i /etc/rpc .tp .b services .i /etc/services .tp .b shadow .i /etc/shadow .pd .re .sh notes within each process that uses .br nsswitch.conf , the entire file is read only once. if the file is later changed, the process will continue using the old configuration. .pp traditionally, there was only a single source for service information, often in the form of a single configuration file (e.g., \fi/etc/passwd\fp). however, as other name services, such as the network information service (nis) and the domain name service (dns), became popular, a method was needed that would be more flexible than fixed search orders coded into the c library. the name service switch mechanism, which was based on the mechanism used by sun microsystems in the solaris 2 c library, introduced a cleaner solution to the problem. .sh see also .br getent (1), .br nss (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 2014, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th group_member 3 2021-03-22 "gnu" "linux programmer's manual" .sh name group_member \- test whether a process is in a group .sh synopsis .nf .b #include .pp .bi "int group_member(gid_t " gid ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br group_member (): .nf _gnu_source .fi .sh description the .br group_member () function tests whether any of the caller's supplementary group ids (as returned by .br getgroups (2)) matches .ir gid . .sh return value the .br group_member () function returns nonzero if any of the caller's supplementary group ids matches .ir gid , and zero otherwise. .sh conforming to this function is a nonstandard gnu extension. .sh see also .br getgid (2), .br getgroups (2), .br getgrouplist (3), .br group (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/expm1.3 .so man2/outb.2 .so man3/isgreater.3 .\" copyright (c) 2008, 2016 michael kerrisk .\" and copyright (c) 2016 florian weimer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th readdir_r 3 2021-03-22 "" "linux programmer's manual" .sh name readdir_r \- read a directory .sh synopsis .nf .b #include .pp .bi "int readdir_r(dir *restrict " dirp ", struct dirent *restrict " entry , .bi " struct dirent **restrict " result ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br readdir_r (): .nf _posix_c_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description this function is deprecated; use .br readdir (3) instead. .pp the .br readdir_r () function was invented as a reentrant version of .br readdir (3). it reads the next directory entry from the directory stream .ir dirp , and returns it in the caller-allocated buffer pointed to by .ir entry . for details of the .ir dirent structure, see .br readdir (3). .pp a pointer to the returned buffer is placed in .ir *result ; if the end of the directory stream was encountered, then null is instead returned in .ir *result . .pp it is recommended that applications use .br readdir (3) instead of .br readdir_r (). furthermore, since version 2.24, glibc deprecates .br readdir_r (). the reasons are as follows: .ip * 3 on systems where .br name_max is undefined, calling .br readdir_r () may be unsafe because the interface does not allow the caller to specify the length of the buffer used for the returned directory entry. .ip * on some systems, .br readdir_r () can't read directory entries with very long names. when the glibc implementation encounters such a name, .br readdir_r () fails with the error .b enametoolong .ir "after the final directory entry has been read" . on some other systems, .br readdir_r () may return a success status, but the returned .ir d_name field may not be null terminated or may be truncated. .ip * in the current posix.1 specification (posix.1-2008), .br readdir (3) is not required to be thread-safe. however, in modern implementations (including the glibc implementation), concurrent calls to .br readdir (3) that specify different directory streams are thread-safe. therefore, the use of .br readdir_r () is generally unnecessary in multithreaded programs. in cases where multiple threads must read from the same directory stream, using .br readdir (3) with external synchronization is still preferable to the use of .br readdir_r (), for the reasons given in the points above. .ip * it is expected that a future version of posix.1 .\" fixme . .\" http://www.austingroupbugs.net/view.php?id=696 will make .br readdir_r () obsolete, and require that .br readdir (3) be thread-safe when concurrently employed on different directory streams. .sh return value the .br readdir_r () function returns 0 on success. on error, it returns a positive error number (listed under errors). if the end of the directory stream is reached, .br readdir_r () returns 0, and returns null in .ir *result . .sh errors .tp .b ebadf invalid directory stream descriptor \fidirp\fp. .tp .b enametoolong a directory entry whose name was too long to be read was encountered. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br readdir_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh see also .br readdir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswalnum 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswalnum \- test for alphanumeric wide character .sh synopsis .nf .b #include .pp .bi "int iswalnum(wint_t " wc ); .fi .sh description the .br iswalnum () function is the wide-character equivalent of the .br isalnum (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "alnum". .pp the wide-character class "alnum" is a subclass of the wide-character class "graph", and therefore also a subclass of the wide-character class "print". .pp being a subclass of the wide-character class "print", the wide-character class "alnum" is disjoint from the wide-character class "cntrl". .pp being a subclass of the wide-character class "graph", the wide-character class "alnum" is disjoint from the wide-character class "space" and its subclass "blank". .pp the wide-character class "alnum" is disjoint from the wide-character class "punct". .pp the wide-character class "alnum" is the union of the wide-character classes "alpha" and "digit". as such, it also contains the wide-character class "xdigit". .pp the wide-character class "alnum" always contains at least the letters \(aqa\(aq to \(aqz\(aq, \(aqa\(aq to \(aqz\(aq and the digits \(aq0\(aq to \(aq9\(aq. .sh return value the .br iswalnum () function returns nonzero if .i wc is a wide character belonging to the wide-character class "alnum". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswalnum () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswalnum () depends on the .b lc_ctype category of the current locale. .sh see also .br isalnum (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getttyent.3 the files in this directory are scripts for man-pages maintenance tasks. they may be useful for downstream man-pages package maintainers or for man-pages translators. this directory does not contain any files that need to be installed in order to use the manual pages. .so man3/rpc.3 .so man3/strtol.3 .so man3/wprintf.3 man-pages|linux kernel and c library user-space interface documentation|https://www.kernel.org/doc/man-pages/|repo|git|https://www.kernel.org/doc/man-pages/index.html|https://www.kernel.org/doc/man-pages/reporting_bugs.html|2021-08-27 .\" copyright (c) 2006, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th sockatmark 3 2021-03-22 "linux" "linux programmer's manual" .sh name sockatmark \- determine whether socket is at out-of-band mark .sh synopsis .nf .b #include .pp .bi "int sockatmark(int " sockfd ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br sockatmark (): .nf _posix_c_source >= 200112l .fi .sh description .br sockatmark () returns a value indicating whether or not the socket referred to by the file descriptor .i sockfd is at the out-of-band mark. if the socket is at the mark, then 1 is returned; if the socket is not at the mark, 0 is returned. this function does not remove the out-of-band mark. .sh return value a successful call to .br sockatmark () returns 1 if the socket is at the out-of-band mark, or 0 if it is not. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i sockfd is not a valid file descriptor. .tp .b einval .\" posix.1 says enotty for this case .i sockfd is not a file descriptor to which .br sockatmark () can be applied. .sh versions .br sockatmark () was added to glibc in version 2.2.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br sockatmark () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes if .br sockatmark () returns 1, then the out-of-band data can be read using the .b msg_oob flag of .br recv (2). .pp out-of-band data is supported only on some stream socket protocols. .pp .br sockatmark () can safely be called from a handler for the .b sigurg signal. .pp .br sockatmark () is implemented using the .b siocatmark .br ioctl (2) operation. .sh bugs prior to glibc 2.4, .br sockatmark () did not work. .sh examples the following code can be used after receipt of a .b sigurg signal to read (and discard) all data up to the mark, and then read the byte of data at the mark: .pp .ex char buf[buf_len]; char oobdata; int atmark, s; for (;;) { atmark = sockatmark(sockfd); if (atmark == \-1) { perror("sockatmark"); break; } if (atmark) break; s = read(sockfd, buf, buf_len); if (s == \-1) perror("read"); if (s <= 0) break; } if (atmark == 1) { if (recv(sockfd, &oobdata, 1, msg_oob) == \-1) { perror("recv"); ... } } .ee .sh see also .br fcntl (2), .br recv (2), .br send (2), .br tcp (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tgamma.3 .\" copyright 1993 giorgio ciucci (giorgio@crcc.it) .\" and copyright 2004, 2005 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .\" modified sun feb 18 01:59:29 2001 by andries e. brouwer .\" modified, 27 may 2004, michael kerrisk .\" added notes on cap_ipc_owner requirement .\" modified, 17 jun 2004, michael kerrisk .\" added notes on cap_sys_admin requirement for ipc_set and ipc_rmid .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" added msqid_ds and ipc_perm structure definitions .\" 2005-08-02, mtk: added ipc_info, msg_info, msg_stat descriptions .\" 2018-03-20, dbueso: added msg_stat_any description. .\" .th msgctl 2 2021-03-22 "linux" "linux programmer's manual" .sh name msgctl \- system v message control operations .sh synopsis .nf .b #include .pp .bi "int msgctl(int " msqid ", int " cmd ", struct msqid_ds *" buf ); .fi .sh description .br msgctl () performs the control operation specified by .i cmd on the system\ v message queue with identifier .ir msqid . .pp the .i msqid_ds data structure is defined in \fi\fp as follows: .pp .in +4n .ex struct msqid_ds { struct ipc_perm msg_perm; /* ownership and permissions */ time_t msg_stime; /* time of last msgsnd(2) */ time_t msg_rtime; /* time of last msgrcv(2) */ time_t msg_ctime; /* time of creation or last modification by msgctl() */ unsigned long msg_cbytes; /* # of bytes in queue */ msgqnum_t msg_qnum; /* # number of messages in queue */ msglen_t msg_qbytes; /* maximum # of bytes in queue */ pid_t msg_lspid; /* pid of last msgsnd(2) */ pid_t msg_lrpid; /* pid of last msgrcv(2) */ }; .ee .in .pp the fields of the .i msgid_ds structure are as follows: .tp 11 .i msg_perm this is an .i ipc_perm structure (see below) that specifies the access permissions on the message queue. .tp .i msg_stime time of the last .br msgsnd (2) system call. .tp .i msg_rtime time of the last .br msgrcv (2) system call. .tp .i msg_ctime time of creation of queue or time of last .br msgctl () .br ipc_set operation. .tp .i msg_cbytes number of bytes in all messages currently on the message queue. this is a nonstandard linux extension that is not specified in posix. .tp .i msg_qnum number of messages currently on the message queue. .tp .i msg_qbytes maximum number of bytes of message text allowed on the message queue. .tp .i msg_lspid id of the process that performed the last .br msgsnd (2) system call. .tp .i msg_lrpid id of the process that performed the last .br msgrcv (2) system call. .pp the .i ipc_perm structure is defined as follows (the highlighted fields are settable using .br ipc_set ): .pp .in +4n .ex struct ipc_perm { key_t __key; /* key supplied to msgget(2) */ uid_t \fbuid\fp; /* effective uid of owner */ gid_t \fbgid\fp; /* effective gid of owner */ uid_t cuid; /* effective uid of creator */ gid_t cgid; /* effective gid of creator */ unsigned short \fbmode\fp; /* permissions */ unsigned short __seq; /* sequence number */ }; .ee .in .pp the least significant 9 bits of the .i mode field of the .i ipc_perm structure define the access permissions for the message queue. the permission bits are as follows: .ts l l. 0400 read by user 0200 write by user 0040 read by group 0020 write by group 0004 read by others 0002 write by others .te .pp bits 0100, 0010, and 0001 (the execute bits) are unused by the system. .pp valid values for .i cmd are: .tp .b ipc_stat copy information from the kernel data structure associated with .i msqid into the .i msqid_ds structure pointed to by .ir buf . the caller must have read permission on the message queue. .tp .b ipc_set write the values of some members of the .i msqid_ds structure pointed to by .i buf to the kernel data structure associated with this message queue, updating also its .i msg_ctime member. .ip the following members of the structure are updated: .ir msg_qbytes , .ir msg_perm.uid , .ir msg_perm.gid , and (the least significant 9 bits of) .ir msg_perm.mode . .ip the effective uid of the calling process must match the owner .ri ( msg_perm.uid ) or creator .ri ( msg_perm.cuid ) of the message queue, or the caller must be privileged. appropriate privilege (linux: the .b cap_sys_resource capability) is required to raise the .i msg_qbytes value beyond the system parameter .br msgmnb . .tp .b ipc_rmid immediately remove the message queue, awakening all waiting reader and writer processes (with an error return and .i errno set to .br eidrm ). the calling process must have appropriate privileges or its effective user id must be either that of the creator or owner of the message queue. the third argument to .br msgctl () is ignored in this case. .tp .br ipc_info " (linux-specific)" return information about system-wide message queue limits and parameters in the structure pointed to by .ir buf . this structure is of type .i msginfo (thus, a cast is required), defined in .i if the .b _gnu_source feature test macro is defined: .ip .in +4n .ex struct msginfo { int msgpool; /* size in kibibytes of buffer pool used to hold message data; unused within kernel */ int msgmap; /* maximum number of entries in message map; unused within kernel */ int msgmax; /* maximum number of bytes that can be written in a single message */ int msgmnb; /* maximum number of bytes that can be written to queue; used to initialize msg_qbytes during queue creation (msgget(2)) */ int msgmni; /* maximum number of message queues */ int msgssz; /* message segment size; unused within kernel */ int msgtql; /* maximum number of messages on all queues in system; unused within kernel */ unsigned short msgseg; /* maximum number of segments; unused within kernel */ }; .ee .in .ip the .ir msgmni , .ir msgmax , and .i msgmnb settings can be changed via .i /proc files of the same name; see .br proc (5) for details. .tp .br msg_info " (linux-specific)" return a .i msginfo structure containing the same information as for .br ipc_info , except that the following fields are returned with information about system resources consumed by message queues: the .i msgpool field returns the number of message queues that currently exist on the system; the .i msgmap field returns the total number of messages in all queues on the system; and the .i msgtql field returns the total number of bytes in all messages in all queues on the system. .tp .br msg_stat " (linux-specific)" return a .i msqid_ds structure as for .br ipc_stat . however, the .i msqid argument is not a queue identifier, but instead an index into the kernel's internal array that maintains information about all message queues on the system. .tp .br msg_stat_any " (linux-specific, since linux 4.17)" return a .i msqid_ds structure as for .br msg_stat . however, .i msg_perm.mode is not checked for read access for .ir msqid meaning that any user can employ this operation (just as any user may read .ir /proc/sysvipc/msg to obtain the same information). .sh return value on success, .br ipc_stat , .br ipc_set , and .b ipc_rmid return 0. a successful .b ipc_info or .b msg_info operation returns the index of the highest used entry in the kernel's internal array recording information about all message queues. (this information can be used with repeated .b msg_stat or .b msg_stat_any operations to obtain information about all queues on the system.) a successful .b msg_stat or .b msg_stat_any operation returns the identifier of the queue whose index was given in .ir msqid . .pp on failure, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces the argument .i cmd is equal to .b ipc_stat or .br msg_stat , but the calling process does not have read permission on the message queue .ir msqid , and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b efault the argument .i cmd has the value .b ipc_set or .br ipc_stat , but the address pointed to by .i buf isn't accessible. .tp .b eidrm the message queue was removed. .tp .b einval invalid value for .i cmd or .ir msqid . or: for a .b msg_stat operation, the index value specified in .i msqid referred to an array slot that is currently unused. .tp .b eperm the argument .i cmd has the value .b ipc_set or .br ipc_rmid , but the effective user id of the calling process is not the creator (as found in .ir msg_perm.cuid ) or the owner (as found in .ir msg_perm.uid ) of the message queue, and the caller is not privileged (linux: does not have the .b cap_sys_admin capability). .tp .b eperm an attempt .rb ( ipc_set ) was made to increase .i msg_qbytes beyond the system parameter .br msgmnb , but the caller is not privileged (linux: does not have the .b cap_sys_resource capability). .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svid does not document the eidrm error condition. .sh notes the .br ipc_info , .br msg_stat , and .b msg_info operations are used by the .br ipcs (1) program to provide information on allocated resources. in the future these may modified or moved to a .i /proc filesystem interface. .pp various fields in the \fistruct msqid_ds\fp were typed as .i short under linux 2.2 and have become .i long under linux 2.4. to take advantage of this, a recompilation under glibc-2.1.91 or later should suffice. (the kernel distinguishes old and new calls by an .b ipc_64 flag in .ir cmd .) .sh see also .br msgget (2), .br msgrcv (2), .br msgsnd (2), .br capabilities (7), .br mq_overview (7), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getmntent.3 .so man3/tailq.3 .\" copyright 2000 nicolás lichtmaier .\" created 2000-07-22 00:52-0300 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 2002-07-23 19:21:35 cest 2002 walter harms .\" .\" .\" modified 2003-04-04, aeb .\" .th encrypt 3 2021-03-22 "" "linux programmer's manual" .sh name encrypt, setkey, encrypt_r, setkey_r \- encrypt 64-bit messages .sh synopsis .nf .br "#define _xopen_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void encrypt(char " block "[64], int " edflag ); .pp .br "#define _xopen_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "void setkey(const char *" key ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b "#include " .pp .bi "void setkey_r(const char *" key ", struct crypt_data *" data ); .bi "void encrypt_r(char *" block ", int " edflag \ ", struct crypt_data *" data ); .fi .pp each of these requires linking with \fi\-lcrypt\fp. .sh description these functions encrypt and decrypt 64-bit messages. the .br setkey () function sets the key used by .br encrypt (). the .i key argument used here is an array of 64 bytes, each of which has numerical value 1 or 0. the bytes key[n] where n=8*i-1 are ignored, so that the effective key length is 56 bits. .pp the .br encrypt () function modifies the passed buffer, encoding if .i edflag is 0, and decoding if 1 is being passed. like the .i key argument, also .i block is a bit vector representation of the actual value that is encoded. the result is returned in that same vector. .pp these two functions are not reentrant, that is, the key data is kept in static storage. the functions .br setkey_r () and .br encrypt_r () are the reentrant versions. they use the following structure to hold the key data: .pp .in +4n .ex struct crypt_data { char keysched[16 * 8]; char sb0[32768]; char sb1[32768]; char sb2[32768]; char sb3[32768]; char crypt_3_buf[14]; char current_salt[2]; long current_saltbits; int direction; int initialized; }; .ee .in .pp before calling .br setkey_r () set .i data\->initialized to zero. .sh return value these functions do not return any value. .sh errors set .i errno to zero before calling the above functions. on success, .i errno is unchanged. .tp .b enosys the function is not provided. (for example because of former usa export restrictions.) .sh versions because they employ the des block cipher, which is no longer considered secure, .br crypt (), .br crypt_r (), .br setkey (), and .br setkey_r () were removed in glibc 2.28. applications should switch to a modern cryptography library, such as .br libgcrypt . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br encrypt (), .br setkey () t} thread safety mt-unsafe race:crypt t{ .br encrypt_r (), .br setkey_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br encrypt (), .br setkey (): posix.1-2001, posix.1-2008, sus, svr4. .pp the functions .br encrypt_r () and .br setkey_r () are gnu extensions. .sh notes .ss availability in glibc see .br crypt (3). .ss features in glibc in glibc 2.2, these functions use the des algorithm. .sh examples .ex #define _xopen_source #include #include #include #include int main(void) { char key[64]; char orig[9] = "eggplant"; char buf[64]; char txt[9]; for (int i = 0; i < 64; i++) { key[i] = rand() & 1; } for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { buf[i * 8 + j] = orig[i] >> j & 1; } setkey(key); } printf("before encrypting: %s\en", orig); encrypt(buf, 0); for (int i = 0; i < 8; i++) { for (int j = 0, txt[i] = \(aq\e0\(aq; j < 8; j++) { txt[i] |= buf[i * 8 + j] << j; } txt[8] = \(aq\e0\(aq; } printf("after encrypting: %s\en", txt); encrypt(buf, 1); for (int i = 0; i < 8; i++) { for (int j = 0, txt[i] = \(aq\e0\(aq; j < 8; j++) { txt[i] |= buf[i * 8 + j] << j; } txt[8] = \(aq\e0\(aq; } printf("after decrypting: %s\en", txt); exit(exit_success); } .ee .sh see also .br cbc_crypt (3), .br crypt (3), .br ecb_crypt (3), .\" .br fcrypt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2001 richard braakman .\" copyright (c) 2004 alastair mckinstry .\" copyright (c) 2005 lars wirzenius .\" copyright (c) 2014 marko myllynen .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" this manual page was initially written by richard braakman .\" on behalf of the debian gnu/linux project and anyone else .\" who wants it. it was amended by alastair mckinstry to .\" explain new iso 14652 elements, and amended further by .\" lars wirzenius to document new functionality (as of gnu .\" c library 2.3.5). .\" .th localedef 1 2021-03-22 "linux" "linux user manual" .sh name localedef \- compile locale definition files .sh synopsis .ad l .nh .b localedef .ri [ options ] .i outputpath .br .b "localedef \-\-add\-to\-archive" .ri [ options ] .i compiledpath .br .b "localedef \-\-delete\-from\-archive" .ri [ options ] .ir localename " ..." .br .b "localedef \-\-list\-archive" .ri [ options ] .br .b "localedef \-\-help" .br .b "localedef \-\-usage" .br .b "localedef \-\-version" .ad b .hy .sh description the .b localedef program reads the indicated .i charmap and .i input files, compiles them to a binary form quickly usable by the locale functions in the c library .rb ( setlocale (3), .br localeconv (3), etc.), and places the output in .ir outputpath . .pp the .i outputpath argument is interpreted as follows: .ip * 3 if .i outputpath contains a slash character ('/'), it is interpreted as the name of the directory where the output definitions are to be stored. in this case, there is a separate output file for each locale category .ri ( lc_time , .ir lc_numeric , and so on). .ip * if the .b \-\-no\-archive option is used, .i outputpath is the name of a subdirectory in .i /usr/lib/locale where per-category compiled files are placed. .ip * otherwise, .i outputpath is the name of a locale and the compiled locale data is added to the archive file .ir /usr/lib/locale/locale\-archive . a locale archive is a memory-mapped file which contains all the system-provided locales; it is used by all localized programs when the environment variable .b locpath is not set. .pp in any case, .b localedef aborts if the directory in which it tries to write locale files has not already been created. .pp if no .i charmapfile is given, the value .i ansi_x3.4\-1968 (for ascii) is used by default. if no .i inputfile is given, or if it is given as a dash (\-), .b localedef reads from standard input. .sh options .ss operation-selection options a few options direct .b localedef to do something other than compile locale definitions. only one of these options should be used at a time. .tp .b \-\-add\-to\-archive add the .i compiledpath directories to the locale archive file. the directories should have been created by previous runs of .br localedef , using .br \-\-no\-archive . .tp .b \-\-delete\-from\-archive delete the named locales from the locale archive file. .tp .b \-\-list\-archive list the locales contained in the locale archive file. .ss other options some of the following options are sensible only for certain operations; generally, it should be self-evident which ones. notice that .b \-f and .b \-c are reversed from what you might expect; that is, .b \-f is not the same as .br \-\-force . .tp .bi \-f " charmapfile" "\fr, \fp\-\-charmap=" charmapfile specify the file that defines the character set that is used by the input file. if .i charmapfile contains a slash character ('/'), it is interpreted as the name of the character map. otherwise, the file is sought in the current directory and the default directory for character maps. if the environment variable .b i18npath is set, .i $i18npath/charmaps/ and .i $i18npath/ are also searched after the current directory. the default directory for character maps is printed by .br "localedef \-\-help" . .tp .bi \-i " inputfile" "\fr, \fp\-\-inputfile=" inputfile specify the locale definition file to compile. the file is sought in the current directory and the default directory for locale definition files. if the environment variable .b i18npath is set, .i $i18npath/locales/ and .i $i18npath are also searched after the current directory. the default directory for locale definition files is printed by .br "localedef \-\-help" . .tp .bi \-u " repertoirefile" "\fr, \fp\-\-repertoire\-map=" repertoirefile read mappings from symbolic names to unicode code points from .ir repertoirefile . if .i repertoirefile contains a slash character ('/'), it is interpreted as the pathname of the repertoire map. otherwise, the file is sought in the current directory and the default directory for repertoire maps. if the environment variable .b i18npath is set, .i $i18npath/repertoiremaps/ and .i $i18npath are also searched after the current directory. the default directory for repertoire maps is printed by .br "localedef \-\-help" . .tp .bi \-a " aliasfile" "\fr, \fp\-\-alias\-file=" aliasfile use .i aliasfile to look up aliases for locale names. there is no default aliases file. .tp .br \-c ", " \-\-force write the output files even if warnings were generated about the input file. .tp .br \-v ", " \-\-verbose generate extra warnings about errors that are normally ignored. .tp .b \-\-big\-endian generate big-endian output. .tp .b \-\-little\-endian generate little-endian output. .tp .b \-\-no\-archive do not use the locale archive file, instead create .i outputpath as a subdirectory in the same directory as the locale archive file, and create separate output files for locale categories in it. this is helpful to prevent system locale archive updates from overwriting custom locales created with .br localedef . .tp .b \-\-no\-hard\-links do not create hard links between installed locales. .tp .bi \-\-no\-warnings= warnings comma-separated list of warnings to disable. supported warnings are .i ascii and .ir intcurrsym . .tp .b \-\-posix conform strictly to posix. implies .br \-\-verbose . this option currently has no other effect. posix conformance is assumed if the environment variable .b posixly_correct is set. .tp .bi \-\-prefix= pathname set the prefix to be prepended to the full archive pathname. by default, the prefix is empty. setting the prefix to .ir foo , the archive would be placed in .ir foo/usr/lib/locale/locale\-archive . .tp .b \-\-quiet suppress all notifications and warnings, and report only fatal errors. .tp .b \-\-replace replace a locale in the locale archive file. without this option, if the locale is in the archive file already, an error occurs. .tp .bi \-\-warnings= warnings comma-separated list of warnings to enable. supported warnings are .i ascii and .ir intcurrsym . .tp .br \-? ", " \-\-help print a usage summary and exit. also prints the default paths used by .br localedef . .tp .b "\-\-usage" print a short usage summary and exit. .tp .br \-v ", " \-\-version print the version number, license, and disclaimer of warranty for .br localedef . .sh exit status one of the following exit values can be returned by .br localedef : .tp .b 0 command completed successfully. .tp .b 1 warnings or errors occurred, output files were written. .tp .b 4 errors encountered, no output created. .sh environment .tp .b posixly_correct the .b \-\-posix flag is assumed if this environment variable is set. .tp .b i18npath a colon-separated list of search directories for files. .sh files .tp .i /usr/share/i18n/charmaps usual default character map path. .tp .i /usr/share/i18n/locales usual default path for locale definition files. .tp .i /usr/share/i18n/repertoiremaps usual default repertoire map path. .tp .i /usr/lib/locale/locale\-archive usual default locale archive location. .tp .i /usr/lib/locale usual default path for compiled individual locale data files. .tp .i outputpath/lc_address an output file that contains information about formatting of addresses and geography-related items. .tp .i outputpath/lc_collate an output file that contains information about the rules for comparing strings. .tp .i outputpath/lc_ctype an output file that contains information about character classes. .tp .i outputpath/lc_identification an output file that contains metadata about the locale. .tp .i outputpath/lc_measurement an output file that contains information about locale measurements (metric versus us customary). .tp .i outputpath/lc_messages/sys_lc_messages an output file that contains information about the language messages should be printed in, and what an affirmative or negative answer looks like. .tp .i outputpath/lc_monetary an output file that contains information about formatting of monetary values. .tp .i outputpath/lc_name an output file that contains information about salutations for persons. .tp .i outputpath/lc_numeric an output file that contains information about formatting of nonmonetary numeric values. .tp .i outputpath/lc_paper an output file that contains information about settings related to standard paper size. .tp .i outputpath/lc_telephone an output file that contains information about formats to be used with telephone services. .tp .i outputpath/lc_time an output file that contains information about formatting of data and time values. .sh conforming to posix.1-2008. .sh examples compile the locale files for finnish in the utf\-8 character set and add it to the default locale archive with the name .br fi_fi.utf\-8 : .pp .in +4n .ex localedef \-f utf\-8 \-i fi_fi fi_fi.utf\-8 .ee .in .pp the next example does the same thing, but generates files into the .i fi_fi.utf\-8 directory which can then be used by programs when the environment variable .b locpath is set to the current directory (note that the last argument must contain a slash): .pp .in +4n .ex localedef \-f utf\-8 \-i fi_fi ./fi_fi.utf\-8 .ee .in .sh see also .br locale (1), .br charmap (5), .br locale (5), .br repertoiremap (5), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswgraph 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswgraph \- test for graphic wide character .sh synopsis .nf .b #include .pp .bi "int iswgraph(wint_t " wc ); .fi .sh description the .br iswgraph () function is the wide-character equivalent of the .br isgraph (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "graph". .pp the wide-character class "graph" is a subclass of the wide-character class "print". .pp being a subclass of the wide-character class "print", the wide-character class "graph" is disjoint from the wide-character class "cntrl". .pp the wide-character class "graph" is disjoint from the wide-character class "space" and therefore also disjoint from its subclass "blank". .\" note: unix98 (susv2/xbd/locale.html) says that "graph" and "space" may .\" have characters in common, except u+0020. but c99 (iso/iec 9899:1999 .\" section 7.25.2.1.10) says that "space" and "graph" are disjoint. .pp the wide-character class "graph" contains all the wide characters from the wide-character class "print" except the space character. it therefore contains the wide-character classes "alnum" and "punct". .sh return value the .br iswgraph () function returns nonzero if .i wc is a wide character belonging to the wide-character class "graph". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswgraph () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswgraph () depends on the .b lc_ctype category of the current locale. .sh see also .br isgraph (3), .br iswctype (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th casinh 3 2021-03-22 "" "linux programmer's manual" .sh name casinh, casinhf, casinhl \- complex arc sine hyperbolic .sh synopsis .nf .b #include .pp .bi "double complex casinh(double complex " z ); .bi "float complex casinhf(float complex " z ); .bi "long double complex casinhl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex arc hyperbolic sine of .ir z . if \fiy\ =\ casinh(z)\fp, then \fiz\ =\ csinh(y)\fp. the imaginary part of .i y is chosen in the interval [\-pi/2,pi/2]. .pp one has: .pp .nf casinh(z) = clog(z + csqrt(z * z + 1)) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br casinh (), .br casinhf (), .br casinhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br asinh (3), .br cabs (3), .br cimag (3), .br csinh (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright ibm corp. 2017 .\" author: qingfeng hao .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th s390_sthyi 2 2021-03-22 "linux programmer's manual" .sh name s390_sthyi \- emulate sthyi instruction .sh synopsis .nf .br "#include " " /* definition of " sthyi_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_s390_sthyi, unsigned long " function_code , .bi " void *" resp_buffer ", uint64_t *" return_code , .bi " unsigned long " flags ); .fi .pp .ir note : glibc provides no wrapper for .br s390_sthyi (), necessitating the use of .br syscall (2). .sh description the .br s390_sthyi () system call emulates the sthyi (store hypervisor information) instruction. it provides hardware resource information for the machine and its virtualization levels. this includes cpu type and capacity, as well as the machine model and other metrics. .pp the .i function_code argument indicates which function to perform. the following code(s) are supported: .tp .b sthyi_fc_cp_ifl_cap return cp (central processor) and ifl (integrated facility for linux) capacity information. .pp the .i resp_buffer argument specifies the address of a response buffer. when the .i function_code is .br sthyi_fc_cp_ifl_cap , the buffer must be one page (4k) in size. if the system call returns 0, the response buffer will be filled with cpu capacity information. otherwise, the response buffer's content is unchanged. .pp the .i return_code argument stores the return code of the sthyi instruction, using one of the following values: .tp 0 success. .tp 4 unsupported function code. .pp for further details about .ir return_code , .ir function_code , and .ir resp_buffer , see the reference given in notes. .pp the .i flags argument is provided to allow for future extensions and currently must be set to 0. .sh return value on success (that is: emulation succeeded), the return value of .br s390_sthyi () matches the condition code of the sthyi instructions, which is a value in the range [0..3]. a return value of 0 indicates that cpu capacity information is stored in .ir *resp_buffer . a return value of 3 indicates "unsupported function code" and the content of .ir *resp_buffer is unchanged. the return values 1 and 2 are reserved. .pp on error, \-1 is returned, and .ir errno is set to indicate the error. .sh errors .tp .b efault the value specified in .i resp_buffer or .i return_code is not a valid address. .tp .b einval the value specified in .i flags is nonzero. .tp .b enomem allocating memory for handling the cpu capacity information failed. .tp .b eopnotsupp the value specified in .i function_code is not valid. .sh versions this system call is available since linux 4.15. .sh conforming to this linux-specific system call is available only on the s390 architecture. .sh notes for details of the sthyi instruction, see .ur https://www.ibm.com\:/support\:/knowledgecenter\:/ssb27u_6.3.0\:/com.ibm.zvm.v630.hcpb4\:/hcpb4sth.htm the documentation page .ue . .pp when the system call interface is used, the response buffer doesn't have to fulfill alignment requirements described in the sthyi instruction definition. .pp the kernel caches the response (for up to one second, as of linux 4.16). subsequent system call invocations may return the cached response. .sh see also .br syscall (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 by thomas koenig (ig25@rz.uni-karlsruhe.de) .\" and copyright (c) 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 28 11:12:26 1993 by rik faith (faith@cs.unc.edu) .\" .\" fixme probably all of the following should be documented: .\" _pc_sync_io, .\" _pc_async_io, .\" _pc_prio_io, .\" _pc_sock_maxbuf, .\" _pc_filesizebits, .\" _pc_rec_incr_xfer_size, .\" _pc_rec_max_xfer_size, .\" _pc_rec_min_xfer_size, .\" _pc_rec_xfer_align, .\" _pc_alloc_size_min, .\" _pc_symlink_max, .\" _pc_2_symlinks .\" .th fpathconf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name fpathconf, pathconf \- get configuration values for files .sh synopsis .nf .b #include .pp .bi "long fpathconf(int " fd ", int " name ); .bi "long pathconf(const char *" path ", int " name ); .fi .sh description .br fpathconf () gets a value for the configuration option .i name for the open file descriptor .ir fd . .pp .br pathconf () gets a value for configuration option .i name for the filename .ir path . .pp the corresponding macros defined in .i are minimum values; if an application wants to take advantage of values which may change, a call to .br fpathconf () or .br pathconf () can be made, which may yield more liberal results. .pp setting .i name equal to one of the following constants returns the following configuration options: .tp .b _pc_link_max the maximum number of links to the file. if .i fd or .i path refer to a directory, then the value applies to the whole directory. the corresponding macro is .br _posix_link_max . .tp .b _pc_max_canon the maximum length of a formatted input line, where .i fd or .i path must refer to a terminal. the corresponding macro is .br _posix_max_canon . .tp .b _pc_max_input the maximum length of an input line, where .i fd or .i path must refer to a terminal. the corresponding macro is .br _posix_max_input . .tp .b _pc_name_max the maximum length of a filename in the directory .i path or .ir fd that the process is allowed to create. the corresponding macro is .br _posix_name_max . .tp .b _pc_path_max the maximum length of a relative pathname when .i path or .i fd is the current working directory. the corresponding macro is .br _posix_path_max . .tp .b _pc_pipe_buf the maximum number of bytes that can be written atomically to a pipe of fifo. for .br fpathconf (), .i fd should refer to a pipe or fifo. for .br fpathconf (), .i path should refer to a fifo or a directory; in the latter case, the returned value corresponds to fifos created in that directory. the corresponding macro is .br _posix_pipe_buf . .tp .b _pc_chown_restricted this returns a positive value if the use of .br chown (2) and .br fchown (2) for changing a file's user id is restricted to a process with appropriate privileges, and changing a file's group id to a value other than the process's effective group id or one of its supplementary group ids is restricted to a process with appropriate privileges. according to posix.1, this variable shall always be defined with a value other than \-1. the corresponding macro is .br _posix_chown_restricted . .ip if .i fd or .i path refers to a directory, then the return value applies to all files in that directory. .tp .b _pc_no_trunc this returns nonzero if accessing filenames longer than .b _posix_name_max generates an error. the corresponding macro is .br _posix_no_trunc . .tp .b _pc_vdisable this returns nonzero if special character processing can be disabled, where .i fd or .i path must refer to a terminal. .sh return value the return value of these functions is one of the following: .ip * 3 on error, \-1 is returned and .i errno is set to indicate the error (for example, .br einval , indicating that .i name is invalid). .ip * if .i name corresponds to a maximum or minimum limit, and that limit is indeterminate, \-1 is returned and .i errno is not changed. (to distinguish an indeterminate limit from an error, set .i errno to zero before the call, and then check whether .i errno is nonzero when \-1 is returned.) .ip * if .i name corresponds to an option, a positive value is returned if the option is supported, and \-1 is returned if the option is not supported. .ip * otherwise, the current value of the option or limit is returned. this value will not be more restrictive than the corresponding value that was described to the application in .i or .i when the application was compiled. .sh errors .tp .b eacces .rb ( pathconf ()) search permission is denied for one of the directories in the path prefix of .ir path . .tp .b ebadf .rb ( fpathconf ()) .i fd is not a valid file descriptor. .tp .b einval .i name is invalid. .tp .b einval the implementation does not support an association of .i name with the specified file. .tp .b eloop .rb ( pathconf ()) too many symbolic links were encountered while resolving .ir path . .tp .b enametoolong .rb ( pathconf ()) .i path is too long. .tp .b enoent .rb ( pathconf ()) a component of .i path does not exist, or .i path is an empty string. .tp .b enotdir .rb ( pathconf ()) a component used as a directory in .i path is not in fact a directory. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fpathconf (), .br pathconf () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh notes files with name lengths longer than the value returned for .i name equal to .b _pc_name_max may exist in the given directory. .pp some returned values may be huge; they are not suitable for allocating memory. .sh see also .br getconf (1), .br open (2), .br statfs (2), .br confstr (3), .br sysconf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt (michael@moria.de) .\" modified sat jul 24 14:29:17 1993 by rik faith (faith@cs.unc.edu) .\" modified 961203 and 001211 and 010326 by aeb@cwi.nl .\" modified 001213 by michael haardt (michael@moria.de) .\" modified 13 jun 02, michael kerrisk .\" added note on nonstandard behavior when sigchld is ignored. .\" modified 2004-11-16, mtk, noted that the nonconformance when .\" sigchld is being ignored is fixed in 2.6.9; other minor changes .\" modified 2004-12-08, mtk, in 2.6 times() return value changed .\" 2005-04-13, mtk .\" added notes on nonstandard behavior: linux allows 'buf' to .\" be null, but posix.1 doesn't specify this and it's nonportable. .\" .th times 2 2021-03-22 "linux" "linux programmer's manual" .sh name times \- get process times .sh synopsis .nf .b #include .pp .bi "clock_t times(struct tms *" buf ); .fi .sh description .br times () stores the current process times in the .i "struct tms" that .i buf points to. the .i struct tms is as defined in .ir : .pp .in +4n .ex struct tms { clock_t tms_utime; /* user time */ clock_t tms_stime; /* system time */ clock_t tms_cutime; /* user time of children */ clock_t tms_cstime; /* system time of children */ }; .ee .in .pp the .i tms_utime field contains the cpu time spent executing instructions of the calling process. the .i tms_stime field contains the cpu time spent executing inside the kernel while performing tasks on behalf of the calling process. .pp the .i tms_cutime field contains the sum of the .i tms_utime and .i tms_cutime values for all waited-for terminated children. the .i tms_cstime field contains the sum of the .i tms_stime and .i tms_cstime values for all waited-for terminated children. .pp times for terminated children (and their descendants) are added in at the moment .br wait (2) or .br waitpid (2) returns their process id. in particular, times of grandchildren that the children did not wait for are never seen. .pp all times reported are in clock ticks. .sh return value .br times () returns the number of clock ticks that have elapsed since an arbitrary point in the past. the return value may overflow the possible range of type .ir clock_t . on error, \fi(clock_t)\ \-1\fp is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i tms points outside the process's address space. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes the number of clock ticks per second can be obtained using: .pp .in +4n .ex sysconf(_sc_clk_tck); .ee .in .pp in posix.1-1996 the symbol \fbclk_tck\fp (defined in .ir ) is mentioned as obsolescent. it is obsolete now. .pp in linux kernel versions before 2.6.9, if the disposition of .b sigchld is set to .br sig_ign , then the times of terminated children are automatically included in the .i tms_cstime and .i tms_cutime fields, although posix.1-2001 says that this should happen only if the calling process .br wait (2)s on its children. this nonconformance is rectified in linux 2.6.9 and later. .\" see the description of times() in xsh, which says: .\" the times of a terminated child process are included... when wait() .\" or waitpid() returns the process id of this terminated child. .pp on linux, the .i buf argument can be specified as null, with the result that .br times () just returns a function result. however, posix does not specify this behavior, and most other unix implementations require a non-null value for .ir buf . .pp note that .br clock (3) also returns a value of type .ir clock_t , but this value is measured in units of .br clocks_per_sec , not the clock ticks used by .br times (). .pp on linux, the "arbitrary point in the past" from which the return value of .br times () is measured has varied across kernel versions. on linux 2.4 and earlier, this point is the moment the system was booted. since linux 2.6, this point is \fi(2^32/hz) \- 300\fp seconds before system boot time. this variability across kernel versions (and across unix implementations), combined with the fact that the returned value may overflow the range of .ir clock_t , means that a portable application would be wise to avoid using this value. to measure changes in elapsed time, use .br clock_gettime (2) instead. .\" .pp .\" on older systems the number of clock ticks per second is given .\" by the variable hz. .ss historical svr1-3 returns .i long and the struct members are of type .i time_t although they store clock ticks, not seconds since the epoch. v7 used .i long for the struct members, because it had no type .i time_t yet. .sh bugs a limitation of the linux system call conventions on some architectures (notably i386) means that on linux 2.6 there is a small time window (41 seconds) soon after boot when .br times () can return \-1, falsely indicating that an error occurred. the same problem can occur when the return value wraps past the maximum value that can be stored in .br clock_t . .\" the problem is that a syscall return of -4095 to -1 .\" is interpreted by glibc as an error, and the wrapper converts .\" the return value to -1. .\" http://marc.info/?l=linux-kernel&m=119447727031225&w=2 .\" "compat_sys_times() bogus until jiffies >= 0" .\" november 2007 .sh see also .br time (1), .br getrusage (2), .br wait (2), .br clock (3), .br sysconf (3), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/dbopen.3 .\" copyright (c) 2016 pavel emelyanov .\" copyright (c) 2016 dmitry v. levin .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th sock_diag 7 2021-03-22 "linux" "linux programmer's manual" .sh name sock_diag \- obtaining information about sockets .sh synopsis .nf .b #include .b #include .br "#include " " /* for unix domain sockets */" .br "#include " " /* for ipv4 and ipv6 sockets */" .pp .bi "diag_socket = socket(af_netlink, " socket_type ", netlink_sock_diag);" .fi .sh description the sock_diag netlink subsystem provides a mechanism for obtaining information about sockets of various address families from the kernel. this subsystem can be used to obtain information about individual sockets or request a list of sockets. .pp in the request, the caller can specify additional information it would like to obtain about the socket, for example, memory information or information specific to the address family. .pp when requesting a list of sockets, the caller can specify filters that would be applied by the kernel to select a subset of sockets to report. for now, there is only the ability to filter sockets by state (connected, listening, and so on.) .pp note that sock_diag reports only those sockets that have a name; that is, either sockets bound explicitly with .br bind (2) or sockets that were automatically bound to an address (e.g., by .br connect (2)). this is the same set of sockets that is available via .ir /proc/net/unix , .ir /proc/net/tcp , .ir /proc/net/udp , and so on. .\" .ss request the request starts with a .i "struct nlmsghdr" header described in .br netlink (7) with .i nlmsg_type field set to .br sock_diag_by_family . it is followed by a header specific to the address family that starts with a common part shared by all address families: .pp .in +4n .ex struct sock_diag_req { __u8 sdiag_family; __u8 sdiag_protocol; }; .ee .in .pp the fields of this structure are as follows: .tp .i sdiag_family an address family. it should be set to the appropriate .b af_* constant. .tp .i sdiag_protocol depends on .ir sdiag_family . it should be set to the appropriate .b ipproto_* constant for .b af_inet and .br af_inet6 , and to 0 otherwise. .pp if the .i nlmsg_flags field of the .i "struct nlmsghdr" header has the .br nlm_f_dump flag set, it means that a list of sockets is being requested; otherwise it is a query about an individual socket. .\" .ss response the response starts with a .i "struct nlmsghdr" header and is followed by an array of objects specific to the address family. the array is to be accessed with the standard .b nlmsg_* macros from the .br netlink (3) api. .pp each object is the nla (netlink attributes) list that is to be accessed with the .b rta_* macros from .br rtnetlink (3) api. .\" .ss unix domain sockets for unix domain sockets the request is represented in the following structure: .pp .in +4n .ex struct unix_diag_req { __u8 sdiag_family; __u8 sdiag_protocol; __u16 pad; __u32 udiag_states; __u32 udiag_ino; __u32 udiag_show; __u32 udiag_cookie[2]; }; .ee .in .pp the fields of this structure are as follows: .tp .i sdiag_family the address family; it should be set to .br af_unix . .pp .i sdiag_protocol .pd 0 .tp .pd .i pad these fields should be set to 0. .tp .i udiag_states this is a bit mask that defines a filter of sockets states. only those sockets whose states are in this mask will be reported. ignored when querying for an individual socket. supported values are: .pp .rs 12 1 << .b tcp_established .pp 1 << .b tcp_listen .re .tp .i udiag_ino this is an inode number when querying for an individual socket. ignored when querying for a list of sockets. .tp .i udiag_show this is a set of flags defining what kind of information to report. each requested kind of information is reported back as a netlink attribute as described below: .rs .tp .b udiag_show_name the attribute reported in answer to this request is .br unix_diag_name . the payload associated with this attribute is the pathname to which the socket was bound (a sequence of bytes up to .b unix_path_max length). .tp .b udiag_show_vfs the attribute reported in answer to this request is .br unix_diag_vfs . the payload associated with this attribute is represented in the following structure: .ip .in +4n .ex struct unix_diag_vfs { __u32 udiag_vfs_dev; __u32 udiag_vfs_ino; }; .ee .in .ip the fields of this structure are as follows: .rs .tp .i udiag_vfs_dev the device number of the corresponding on-disk socket inode. .tp .i udiag_vfs_ino the inode number of the corresponding on-disk socket inode. .re .tp .b udiag_show_peer the attribute reported in answer to this request is .br unix_diag_peer . the payload associated with this attribute is a __u32 value which is the peer's inode number. this attribute is reported for connected sockets only. .tp .b udiag_show_icons the attribute reported in answer to this request is .br unix_diag_icons . the payload associated with this attribute is an array of __u32 values which are inode numbers of sockets that has passed the .br connect (2) call, but hasn't been processed with .br accept (2) yet. this attribute is reported for listening sockets only. .tp .b udiag_show_rqlen the attribute reported in answer to this request is .br unix_diag_rqlen . the payload associated with this attribute is represented in the following structure: .ip .in +4n .ex struct unix_diag_rqlen { __u32 udiag_rqueue; __u32 udiag_wqueue; }; .ee .in .ip the fields of this structure are as follows: .rs .tp .i udiag_rqueue for listening sockets: the number of pending connections. the length of the array associated with the .b unix_diag_icons response attribute is equal to this value. .ip for established sockets: the amount of data in incoming queue. .tp .i udiag_wqueue for listening sockets: the backlog length which equals to the value passed as the second argument to .br listen (2). .ip for established sockets: the amount of memory available for sending. .re .tp .b udiag_show_meminfo the attribute reported in answer to this request is .br unix_diag_meminfo . the payload associated with this attribute is an array of __u32 values described below in the subsection "socket memory information". .pp the following attributes are reported back without any specific request: .tp .br unix_diag_shutdown the payload associated with this attribute is __u8 value which represents bits of .br shutdown (2) state. .re .tp .i udiag_cookie this is an array of opaque identifiers that could be used along with .i udiag_ino to specify an individual socket. it is ignored when querying for a list of sockets, as well as when all its elements are set to \-1. .pp the response to a query for unix domain sockets is represented as an array of .pp .in +4n .ex struct unix_diag_msg { __u8 udiag_family; __u8 udiag_type; __u8 udiag_state; __u8 pad; __u32 udiag_ino; __u32 udiag_cookie[2]; }; .ee .in .pp followed by netlink attributes. .pp the fields of this structure are as follows: .tp .i udiag_family this field has the same meaning as in .ir "struct unix_diag_req" . .tp .i udiag_type this is set to one of .br sock_packet , .br sock_stream , or .br sock_seqpacket . .tp .i udiag_state this is set to one of .br tcp_listen or .br tcp_established . .tp .i pad this field is set to 0. .tp .i udiag_ino this is the socket inode number. .tp .i udiag_cookie this is an array of opaque identifiers that could be used in subsequent queries. .\" .ss ipv4 and ipv6 sockets for ipv4 and ipv6 sockets, the request is represented in the following structure: .pp .in +4n .ex struct inet_diag_req_v2 { __u8 sdiag_family; __u8 sdiag_protocol; __u8 idiag_ext; __u8 pad; __u32 idiag_states; struct inet_diag_sockid id; }; .ee .in .pp where .i "struct inet_diag_sockid" is defined as follows: .pp .in +4n .ex struct inet_diag_sockid { __be16 idiag_sport; __be16 idiag_dport; __be32 idiag_src[4]; __be32 idiag_dst[4]; __u32 idiag_if; __u32 idiag_cookie[2]; }; .ee .in .pp the fields of .i "struct inet_diag_req_v2" are as follows: .tp .i sdiag_family this should be set to either .b af_inet or .b af_inet6 for ipv4 or ipv6 sockets respectively. .tp .i sdiag_protocol this should be set to one of .br ipproto_tcp , .br ipproto_udp , or .br ipproto_udplite . .tp .i idiag_ext this is a set of flags defining what kind of extended information to report. each requested kind of information is reported back as a netlink attribute as described below: .rs .tp .b inet_diag_tos the payload associated with this attribute is a __u8 value which is the tos of the socket. .tp .b inet_diag_tclass the payload associated with this attribute is a __u8 value which is the tclass of the socket. ipv6 sockets only. for listen and close sockets, this is followed by .b inet_diag_skv6only attribute with associated __u8 payload value meaning whether the socket is ipv6-only or not. .tp .b inet_diag_meminfo the payload associated with this attribute is represented in the following structure: .ip .in +4n .ex struct inet_diag_meminfo { __u32 idiag_rmem; __u32 idiag_wmem; __u32 idiag_fmem; __u32 idiag_tmem; }; .ee .in .ip the fields of this structure are as follows: .rs .tp 12 .i idiag_rmem the amount of data in the receive queue. .tp .i idiag_wmem the amount of data that is queued by tcp but not yet sent. .tp .i idiag_fmem the amount of memory scheduled for future use (tcp only). .tp .i idiag_tmem the amount of data in send queue. .re .tp .b inet_diag_skmeminfo the payload associated with this attribute is an array of __u32 values described below in the subsection "socket memory information". .tp .b inet_diag_info the payload associated with this attribute is specific to the address family. for tcp sockets, it is an object of type .ir "struct tcp_info" . .tp .b inet_diag_cong the payload associated with this attribute is a string that describes the congestion control algorithm used. for tcp sockets only. .re .tp .i pad this should be set to 0. .tp .i idiag_states this is a bit mask that defines a filter of socket states. only those sockets whose states are in this mask will be reported. ignored when querying for an individual socket. .tp .i id this is a socket id object that is used in dump requests, in queries about individual sockets, and is reported back in each response. unlike unix domain sockets, ipv4 and ipv6 sockets are identified using addresses and ports. all values are in network byte order. .pp the fields of .i "struct inet_diag_sockid" are as follows: .tp .i idiag_sport the source port. .tp .i idiag_dport the destination port. .tp .i idiag_src the source address. .tp .i idiag_dst the destination address. .tp .i idiag_if the interface number the socket is bound to. .tp .i idiag_cookie this is an array of opaque identifiers that could be used along with other fields of this structure to specify an individual socket. it is ignored when querying for a list of sockets, as well as when all its elements are set to \-1. .pp the response to a query for ipv4 or ipv6 sockets is represented as an array of .pp .in +4n .ex struct inet_diag_msg { __u8 idiag_family; __u8 idiag_state; __u8 idiag_timer; __u8 idiag_retrans; struct inet_diag_sockid id; __u32 idiag_expires; __u32 idiag_rqueue; __u32 idiag_wqueue; __u32 idiag_uid; __u32 idiag_inode; }; .ee .in .pp followed by netlink attributes. .pp the fields of this structure are as follows: .tp .i idiag_family this is the same field as in .ir "struct inet_diag_req_v2" . .tp .i idiag_state this denotes socket state as in .ir "struct inet_diag_req_v2" . .tp .i idiag_timer for tcp sockets, this field describes the type of timer that is currently active for the socket. it is set to one of the following constants: .ip .pd 0 .rs 12 .tp .b 0 no timer is active .tp .b 1 a retransmit timer .tp .b 2 a keep-alive timer .tp .b 3 a time_wait timer .tp .b 4 a zero window probe timer .re .pd .ip for non-tcp sockets, this field is set to 0. .tp .i idiag_retrans for .i idiag_timer values 1, 2, and 4, this field contains the number of retransmits. for other .i idiag_timer values, this field is set to 0. .tp .i idiag_expires for tcp sockets that have an active timer, this field describes its expiration time in milliseconds. for other sockets, this field is set to 0. .tp .i idiag_rqueue for listening sockets: the number of pending connections. .ip for other sockets: the amount of data in the incoming queue. .tp .i idiag_wqueue for listening sockets: the backlog length. .ip for other sockets: the amount of memory available for sending. .tp .i idiag_uid this is the socket owner uid. .tp .i idiag_inode this is the socket inode number. .\" .ss socket memory information the payload associated with .b unix_diag_meminfo and .br inet_diag_skmeminfo netlink attributes is an array of the following __u32 values: .tp .b sk_meminfo_rmem_alloc the amount of data in receive queue. .tp .b sk_meminfo_rcvbuf the receive socket buffer as set by .br so_rcvbuf . .tp .b sk_meminfo_wmem_alloc the amount of data in send queue. .tp .b sk_meminfo_sndbuf the send socket buffer as set by .br so_sndbuf . .tp .b sk_meminfo_fwd_alloc the amount of memory scheduled for future use (tcp only). .tp .b sk_meminfo_wmem_queued the amount of data queued by tcp, but not yet sent. .tp .b sk_meminfo_optmem the amount of memory allocated for the socket's service needs (e.g., socket filter). .tp .b sk_meminfo_backlog the amount of packets in the backlog (not yet processed). .sh versions .b netlink_inet_diag was introduced in linux 2.6.14 and supported .b af_inet and .b af_inet6 sockets only. in linux 3.3, it was renamed to .b netlink_sock_diag and extended to support .b af_unix sockets. .pp .b unix_diag_meminfo and .br inet_diag_skmeminfo were introduced in linux 3.6. .sh conforming to the netlink_sock_diag api is linux-specific. .sh examples the following example program prints inode number, peer's inode number, and name of all unix domain sockets in the current namespace. .pp .ex #include #include #include #include #include #include #include #include #include #include static int send_query(int fd) { struct sockaddr_nl nladdr = { .nl_family = af_netlink }; struct { struct nlmsghdr nlh; struct unix_diag_req udr; } req = { .nlh = { .nlmsg_len = sizeof(req), .nlmsg_type = sock_diag_by_family, .nlmsg_flags = nlm_f_request | nlm_f_dump }, .udr = { .sdiag_family = af_unix, .udiag_states = \-1, .udiag_show = udiag_show_name | udiag_show_peer } }; struct iovec iov = { .iov_base = &req, .iov_len = sizeof(req) }; struct msghdr msg = { .msg_name = &nladdr, .msg_namelen = sizeof(nladdr), .msg_iov = &iov, .msg_iovlen = 1 }; for (;;) { if (sendmsg(fd, &msg, 0) < 0) { if (errno == eintr) continue; perror("sendmsg"); return \-1; } return 0; } } static int print_diag(const struct unix_diag_msg *diag, unsigned int len) { if (len < nlmsg_length(sizeof(*diag))) { fputs("short response\en", stderr); return \-1; } if (diag\->udiag_family != af_unix) { fprintf(stderr, "unexpected family %u\en", diag\->udiag_family); return \-1; } unsigned int rta_len = len \- nlmsg_length(sizeof(*diag)); unsigned int peer = 0; size_t path_len = 0; char path[sizeof(((struct sockaddr_un *) 0)\->sun_path) + 1]; for (struct rtattr *attr = (struct rtattr *) (diag + 1); rta_ok(attr, rta_len); attr = rta_next(attr, rta_len)) { switch (attr\->rta_type) { case unix_diag_name: if (!path_len) { path_len = rta_payload(attr); if (path_len > sizeof(path) \- 1) path_len = sizeof(path) \- 1; memcpy(path, rta_data(attr), path_len); path[path_len] = \(aq\e0\(aq; } break; case unix_diag_peer: if (rta_payload(attr) >= sizeof(peer)) peer = *(unsigned int *) rta_data(attr); break; } } printf("inode=%u", diag\->udiag_ino); if (peer) printf(", peer=%u", peer); if (path_len) printf(", name=%s%s", *path ? "" : "@", *path ? path : path + 1); putchar(\(aq\en\(aq); return 0; } static int receive_responses(int fd) { long buf[8192 / sizeof(long)]; struct sockaddr_nl nladdr; struct iovec iov = { .iov_base = buf, .iov_len = sizeof(buf) }; int flags = 0; for (;;) { struct msghdr msg = { .msg_name = &nladdr, .msg_namelen = sizeof(nladdr), .msg_iov = &iov, .msg_iovlen = 1 }; ssize_t ret = recvmsg(fd, &msg, flags); if (ret < 0) { if (errno == eintr) continue; perror("recvmsg"); return \-1; } if (ret == 0) return 0; if (nladdr.nl_family != af_netlink) { fputs("!af_netlink\en", stderr); return \-1; } const struct nlmsghdr *h = (struct nlmsghdr *) buf; if (!nlmsg_ok(h, ret)) { fputs("!nlmsg_ok\en", stderr); return \-1; } for (; nlmsg_ok(h, ret); h = nlmsg_next(h, ret)) { if (h\->nlmsg_type == nlmsg_done) return 0; if (h\->nlmsg_type == nlmsg_error) { const struct nlmsgerr *err = nlmsg_data(h); if (h\->nlmsg_len < nlmsg_length(sizeof(*err))) { fputs("nlmsg_error\en", stderr); } else { errno = \-err\->error; perror("nlmsg_error"); } return \-1; } if (h\->nlmsg_type != sock_diag_by_family) { fprintf(stderr, "unexpected nlmsg_type %u\en", (unsigned) h\->nlmsg_type); return \-1; } if (print_diag(nlmsg_data(h), h\->nlmsg_len)) return \-1; } } } int main(void) { int fd = socket(af_netlink, sock_raw, netlink_sock_diag); if (fd < 0) { perror("socket"); return 1; } int ret = send_query(fd) || receive_responses(fd); close(fd); return ret; } .ee .sh see also .br netlink (3), .br rtnetlink (3), .br netlink (7), .br tcp (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/sysvipc.7 .\" copyright 2003,2004 andi kleen, suse labs. .\" and copyright 2007 lee schermerhorn, hewlett packard .\" .\" %%%license_start(verbatim_prof) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2006-02-03, mtk, substantial wording changes and other improvements .\" 2007-08-27, lee schermerhorn .\" more precise specification of behavior. .\" .th set_mempolicy 2 2021-06-20 linux "linux programmer's manual" .sh name set_mempolicy \- set default numa memory policy for a thread and its children .sh synopsis .nf .b "#include " .pp .bi "long set_mempolicy(int " mode ", const unsigned long *" nodemask , .bi " unsigned long " maxnode ); .pp link with \fi\-lnuma\fp. .fi .sh description .br set_mempolicy () sets the numa memory policy of the calling thread, which consists of a policy mode and zero or more nodes, to the values specified by the .ir mode , .ir nodemask , and .i maxnode arguments. .pp a numa machine has different memory controllers with different distances to specific cpus. the memory policy defines from which node memory is allocated for the thread. .pp this system call defines the default policy for the thread. the thread policy governs allocation of pages in the process's address space outside of memory ranges controlled by a more specific policy set by .br mbind (2). the thread default policy also controls allocation of any pages for memory-mapped files mapped using the .br mmap (2) call with the .b map_private flag and that are only read (loaded) from by the thread and of memory-mapped files mapped using the .br mmap (2) call with the .b map_shared flag, regardless of the access type. the policy is applied only when a new page is allocated for the thread. for anonymous memory this is when the page is first touched by the thread. .pp the .i mode argument must specify one of .br mpol_default , .br mpol_bind , .br mpol_interleave , .br mpol_preferred , or .br mpol_local (which are described in detail below). all modes except .b mpol_default require the caller to specify the node or nodes to which the mode applies, via the .i nodemask argument. .pp the .i mode argument may also include an optional .ir "mode flag" . the supported .i "mode flags" are: .tp .br mpol_f_numa_balancing " (since linux 5.12)" .\" commit bda420b985054a3badafef23807c4b4fa38a3dff when .i mode is .br mpol_bind , enable the kernel numa balancing for the task if it is supported by the kernel. if the flag isn't supported by the kernel, or is used with .i mode other than .br mpol_bind , \-1 is returned and .i errno is set to .br einval . .tp .br mpol_f_relative_nodes " (since linux 2.6.26)" a nonempty .i nodemask specifies node ids that are relative to the set of node ids allowed by the process's current cpuset. .tp .br mpol_f_static_nodes " (since linux 2.6.26)" a nonempty .i nodemask specifies physical node ids. linux will not remap the .i nodemask when the process moves to a different cpuset context, nor when the set of nodes allowed by the process's current cpuset context changes. .pp .i nodemask points to a bit mask of node ids that contains up to .i maxnode bits. the bit mask size is rounded to the next multiple of .ir "sizeof(unsigned long)" , but the kernel will use bits only up to .ir maxnode . a null value of .i nodemask or a .i maxnode value of zero specifies the empty set of nodes. if the value of .i maxnode is zero, the .i nodemask argument is ignored. .pp where a .i nodemask is required, it must contain at least one node that is on-line, allowed by the process's current cpuset context, (unless the .b mpol_f_static_nodes mode flag is specified), and contains memory. if the .b mpol_f_static_nodes is set in .i mode and a required .i nodemask contains no nodes that are allowed by the process's current cpuset context, the memory policy reverts to .ir "local allocation" . this effectively overrides the specified policy until the process's cpuset context includes one or more of the nodes specified by .ir nodemask . .pp the .i mode argument must include one of the following values: .tp .b mpol_default this mode specifies that any nondefault thread memory policy be removed, so that the memory policy "falls back" to the system default policy. the system default policy is "local allocation"\(emthat is, allocate memory on the node of the cpu that triggered the allocation. .i nodemask must be specified as null. if the "local node" contains no free memory, the system will attempt to allocate memory from a "near by" node. .tp .b mpol_bind this mode defines a strict policy that restricts memory allocation to the nodes specified in .ir nodemask . if .i nodemask specifies more than one node, page allocations will come from the node with the lowest numeric node id first, until that node contains no free memory. allocations will then come from the node with the next highest node id specified in .i nodemask and so forth, until none of the specified nodes contain free memory. pages will not be allocated from any node not specified in the .ir nodemask . .tp .b mpol_interleave this mode interleaves page allocations across the nodes specified in .i nodemask in numeric node id order. this optimizes for bandwidth instead of latency by spreading out pages and memory accesses to those pages across multiple nodes. however, accesses to a single page will still be limited to the memory bandwidth of a single node. .\" note: the following sentence doesn't make sense in the context .\" of set_mempolicy() -- no memory area specified. .\" to be effective the memory area should be fairly large, .\" at least 1 mb or bigger. .tp .b mpol_preferred this mode sets the preferred node for allocation. the kernel will try to allocate pages from this node first and fall back to "near by" nodes if the preferred node is low on free memory. if .i nodemask specifies more than one node id, the first node in the mask will be selected as the preferred node. if the .i nodemask and .i maxnode arguments specify the empty set, then the policy specifies "local allocation" (like the system default policy discussed above). .tp .br mpol_local " (since linux 3.8)" .\" commit 479e2802d09f1e18a97262c4c6f8f17ae5884bd8 .\" commit f2a07f40dbc603c15f8b06e6ec7f768af67b424f this mode specifies "local allocation"; the memory is allocated on the node of the cpu that triggered the allocation (the "local node"). the .i nodemask and .i maxnode arguments must specify the empty set. if the "local node" is low on free memory, the kernel will try to allocate memory from other nodes. the kernel will allocate memory from the "local node" whenever memory for this node is available. if the "local node" is not allowed by the process's current cpuset context, the kernel will try to allocate memory from other nodes. the kernel will allocate memory from the "local node" whenever it becomes allowed by the process's current cpuset context. .pp the thread memory policy is preserved across an .br execve (2), and is inherited by child threads created using .br fork (2) or .br clone (2). .sh return value on success, .br set_mempolicy () returns 0; on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b efault part of all of the memory range specified by .i nodemask and .i maxnode points outside your accessible address space. .tp .b einval .i mode is invalid. or, .i mode is .b mpol_default and .i nodemask is nonempty, or .i mode is .b mpol_bind or .b mpol_interleave and .i nodemask is empty. or, .i maxnode specifies more than a page worth of bits. or, .i nodemask specifies one or more node ids that are greater than the maximum supported node id. or, none of the node ids specified by .i nodemask are on-line and allowed by the process's current cpuset context, or none of the specified nodes contain memory. or, the .i mode argument specified both .b mpol_f_static_nodes and .br mpol_f_relative_nodes . or, the .b mpol_f_numa_balancing isn't supported by the kernel, or is used with .i mode other than .br mpol_bind . .tp .b enomem insufficient kernel memory was available. .sh versions the .br set_mempolicy () system call was added to the linux kernel in version 2.6.7. .sh conforming to this system call is linux-specific. .sh notes memory policy is not remembered if the page is swapped out. when such a page is paged back in, it will use the policy of the thread or memory range that is in effect at the time the page is allocated. .pp for information on library support, see .br numa (7). .sh see also .br get_mempolicy (2), .br getcpu (2), .br mbind (2), .br mmap (2), .br numa (3), .br cpuset (7), .br numa (7), .br numactl (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/copysign.3 .so man2/msgop.2 .so man3/pthread_mutexattr_setrobust.3 .so man3/cmsg.3 .\" copyright 1993 giorgio ciucci (giorgio@crcc.it) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified 1996-10-22, eric s. raymond .\" modified 2002-01-08, michael kerrisk .\" modified 2003-04-28, ernie petrides .\" modified 2004-05-27, michael kerrisk .\" modified, 11 nov 2004, michael kerrisk .\" language and formatting clean-ups .\" added notes on /proc files .\" 2005-04-08, mtk, noted kernel version numbers for semtimedop() .\" 2007-07-09, mtk, added an example code segment. .\" .th semop 2 2021-03-22 "linux" "linux programmer's manual" .sh name semop, semtimedop \- system v semaphore operations .sh synopsis .nf .b #include .pp .bi "int semop(int " semid ", struct sembuf *" sops ", size_t " nsops ); .bi "int semtimedop(int " semid ", struct sembuf *" sops ", size_t " nsops , .bi " const struct timespec *" timeout ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br semtimedop (): .nf _gnu_source .fi .sh description each semaphore in a system\ v semaphore set has the following associated values: .pp .in +4n .ex unsigned short semval; /* semaphore value */ unsigned short semzcnt; /* # waiting for zero */ unsigned short semncnt; /* # waiting for increase */ pid_t sempid; /* pid of process that last .ee .in .pp .br semop () performs operations on selected semaphores in the set indicated by .ir semid . each of the .i nsops elements in the array pointed to by .i sops is a structure that specifies an operation to be performed on a single semaphore. the elements of this structure are of type .ir "struct sembuf" , containing the following members: .pp .in +4n .ex unsigned short sem_num; /* semaphore number */ short sem_op; /* semaphore operation */ short sem_flg; /* operation flags */ .ee .in .pp flags recognized in .i sem_flg are .b ipc_nowait and .br sem_undo . if an operation specifies .br sem_undo , it will be automatically undone when the process terminates. .pp the set of operations contained in .i sops is performed in .ir "array order" , and .ir atomically , that is, the operations are performed either as a complete unit, or not at all. the behavior of the system call if not all operations can be performed immediately depends on the presence of the .b ipc_nowait flag in the individual .i sem_flg fields, as noted below. .pp each operation is performed on the .ir sem_num \-th semaphore of the semaphore set, where the first semaphore of the set is numbered 0. there are three types of operation, distinguished by the value of .ir sem_op . .pp if .i sem_op is a positive integer, the operation adds this value to the semaphore value .ri ( semval ). furthermore, if .b sem_undo is specified for this operation, the system subtracts the value .i sem_op from the semaphore adjustment .ri ( semadj ) value for this semaphore. this operation can always proceed\(emit never forces a thread to wait. the calling process must have alter permission on the semaphore set. .pp if .i sem_op is zero, the process must have read permission on the semaphore set. this is a "wait-for-zero" operation: if .i semval is zero, the operation can immediately proceed. otherwise, if .b ipc_nowait is specified in .ir sem_flg , .br semop () fails with .i errno set to .b eagain (and none of the operations in .i sops is performed). otherwise, .i semzcnt (the count of threads waiting until this semaphore's value becomes zero) is incremented by one and the thread sleeps until one of the following occurs: .ip \(bu 2 .i semval becomes 0, at which time the value of .i semzcnt is decremented. .ip \(bu the semaphore set is removed: .br semop () fails, with .i errno set to .br eidrm . .ip \(bu the calling thread catches a signal: the value of .i semzcnt is decremented and .br semop () fails, with .i errno set to .br eintr . .pp if .i sem_op is less than zero, the process must have alter permission on the semaphore set. if .i semval is greater than or equal to the absolute value of .ir sem_op , the operation can proceed immediately: the absolute value of .i sem_op is subtracted from .ir semval , and, if .b sem_undo is specified for this operation, the system adds the absolute value of .i sem_op to the semaphore adjustment .ri ( semadj ) value for this semaphore. if the absolute value of .i sem_op is greater than .ir semval , and .b ipc_nowait is specified in .ir sem_flg , .br semop () fails, with .i errno set to .b eagain (and none of the operations in .i sops is performed). otherwise, .i semncnt (the counter of threads waiting for this semaphore's value to increase) is incremented by one and the thread sleeps until one of the following occurs: .ip \(bu 2 .i semval becomes greater than or equal to the absolute value of .ir sem_op : the operation now proceeds, as described above. .ip \(bu the semaphore set is removed from the system: .br semop () fails, with .i errno set to .br eidrm . .ip \(bu the calling thread catches a signal: the value of .i semncnt is decremented and .br semop () fails, with .i errno set to .br eintr . .pp on successful completion, the .i sempid value for each semaphore specified in the array pointed to by .i sops is set to the caller's process id. in addition, the .i sem_otime .\" and .\" .i sem_ctime is set to the current time. .ss semtimedop() .br semtimedop () behaves identically to .br semop () except that in those cases where the calling thread would sleep, the duration of that sleep is limited by the amount of elapsed time specified by the .i timespec structure whose address is passed in the .i timeout argument. (this sleep interval will be rounded up to the system clock granularity, and kernel scheduling delays mean that the interval may overrun by a small amount.) if the specified time limit has been reached, .br semtimedop () fails with .i errno set to .b eagain (and none of the operations in .i sops is performed). if the .i timeout argument is null, then .br semtimedop () behaves exactly like .br semop (). .pp note that if .br semtimedop () is interrupted by a signal, causing the call to fail with the error .br eintr , the contents of .ir timeout are left unchanged. .sh return value on success, .br semop () and .br semtimedop () return 0. on failure, they return \-1, and set .i errno to indicate the error. .sh errors .tp .b e2big the argument .i nsops is greater than .br semopm , the maximum number of operations allowed per system call. .tp .b eacces the calling process does not have the permissions required to perform the specified semaphore operations, and does not have the .b cap_ipc_owner capability in the user namespace that governs its ipc namespace. .tp .b eagain an operation could not proceed immediately and either .b ipc_nowait was specified in .i sem_flg or the time limit specified in .i timeout expired. .tp .b efault an address specified in either the .i sops or the .i timeout argument isn't accessible. .tp .b efbig for some operation the value of .i sem_num is less than 0 or greater than or equal to the number of semaphores in the set. .tp .b eidrm the semaphore set was removed. .tp .b eintr while blocked in this system call, the thread caught a signal; see .br signal (7). .tp .b einval the semaphore set doesn't exist, or .i semid is less than zero, or .i nsops has a nonpositive value. .tp .b enomem the .i sem_flg of some operation specified .b sem_undo and the system does not have enough memory to allocate the undo structure. .tp .b erange for some operation .i sem_op+semval is greater than .br semvmx , the implementation dependent maximum value for .ir semval . .sh versions .br semtimedop () first appeared in linux 2.5.52, and was subsequently backported into kernel 2.4.22. glibc support for .br semtimedop () first appeared in version 2.3.3. .sh conforming to posix.1-2001, posix.1-2008, svr4. .\" svr4 documents additional error conditions einval, efbig, enospc. .sh notes the .i sem_undo structures of a process aren't inherited by the child produced by .br fork (2), but they are inherited across an .br execve (2) system call. .pp .br semop () is never automatically restarted after being interrupted by a signal handler, regardless of the setting of the .b sa_restart flag when establishing a signal handler. .pp a semaphore adjustment .ri ( semadj ) value is a per-process, per-semaphore integer that is the negated sum of all operations performed on a semaphore specifying the .b sem_undo flag. each process has a list of .i semadj values\(emone value for each semaphore on which it has operated using .br sem_undo . when a process terminates, each of its per-semaphore .i semadj values is added to the corresponding semaphore, thus undoing the effect of that process's operations on the semaphore (but see bugs below). when a semaphore's value is directly set using the .b setval or .b setall request to .br semctl (2), the corresponding .i semadj values in all processes are cleared. the .br clone (2) .b clone_sysvsem flag allows more than one process to share a .i semadj list; see .br clone (2) for details. .pp the \fisemval\fp, \fisempid\fp, \fisemzcnt\fp, and \fisemnct\fp values for a semaphore can all be retrieved using appropriate .br semctl (2) calls. .ss semaphore limits the following limits on semaphore set resources affect the .br semop () call: .tp .b semopm maximum number of operations allowed for one .br semop () call. before linux 3.19, .\" commit e843e7d2c88b7db107a86bd2c7145dc715c058f4 the default value for this limit was 32. since linux 3.19, the default value is 500. on linux, this limit can be read and modified via the third field of .ir /proc/sys/kernel/sem . .\" this /proc file is not available in linux 2.2 and earlier -- mtk .ir note : this limit should not be raised above 1000, .\" see comment in linux 3.19 source file include/uapi/linux/sem.h because of the risk of that .br semop () fails due to kernel memory fragmentation when allocating memory to copy the .ir sops array. .tp .b semvmx maximum allowable value for .ir semval : implementation dependent (32767). .pp the implementation has no intrinsic limits for the adjust on exit maximum value .rb ( semaem ), the system wide maximum number of undo structures .rb ( semmnu ) and the per-process maximum number of undo entries system parameters. .sh bugs when a process terminates, its set of associated .i semadj structures is used to undo the effect of all of the semaphore operations it performed with the .b sem_undo flag. this raises a difficulty: if one (or more) of these semaphore adjustments would result in an attempt to decrease a semaphore's value below zero, what should an implementation do? one possible approach would be to block until all the semaphore adjustments could be performed. this is however undesirable since it could force process termination to block for arbitrarily long periods. another possibility is that such semaphore adjustments could be ignored altogether (somewhat analogously to failing when .b ipc_nowait is specified for a semaphore operation). linux adopts a third approach: decreasing the semaphore value as far as possible (i.e., to zero) and allowing process termination to proceed immediately. .pp in kernels 2.6.x, x <= 10, there is a bug that in some circumstances prevents a thread that is waiting for a semaphore value to become zero from being woken up when the value does actually become zero. this bug is fixed in kernel 2.6.11. .\" the bug report: .\" http://marc.theaimsgroup.com/?l=linux-kernel&m=110260821123863&w=2 .\" the fix: .\" http://marc.theaimsgroup.com/?l=linux-kernel&m=110261701025794&w=2 .sh examples the following code segment uses .br semop () to atomically wait for the value of semaphore 0 to become zero, and then increment the semaphore value by one. .pp .in +4n .ex struct sembuf sops[2]; int semid; /* code to set \fisemid\fp omitted */ sops[0].sem_num = 0; /* operate on semaphore 0 */ sops[0].sem_op = 0; /* wait for value to equal 0 */ sops[0].sem_flg = 0; sops[1].sem_num = 0; /* operate on semaphore 0 */ sops[1].sem_op = 1; /* increment value by one */ sops[1].sem_flg = 0; if (semop(semid, sops, 2) == \-1) { perror("semop"); exit(exit_failure); } .ee .in .pp a further example of the use of .br semop () can be found in .br shmop (2). .sh see also .br clone (2), .br semctl (2), .br semget (2), .br sigaction (2), .br capabilities (7), .br sem_overview (7), .br sysvipc (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-10.7 .so man3/wcstoimax.3 .so man7/system_data_types.7 .so man7/iso_8859-15.7 .so man2/setxattr.2 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 18:08:52 1993 by rik faith (faith@cs.unc.edu) .\" modified 2001-08-31, aeb .\" .th strcmp 3 2021-03-22 "" "linux programmer's manual" .sh name strcmp, strncmp \- compare two strings .sh synopsis .nf .b #include .pp .bi "int strcmp(const char *" s1 ", const char *" s2 ); .bi "int strncmp(const char *" s1 ", const char *" s2 ", size_t " n ); .fi .sh description the .br strcmp () function compares the two strings .i s1 and .ir s2 . the locale is not taken into account (for a locale-aware comparison, see .br strcoll (3)). the comparison is done using unsigned characters. .pp .br strcmp () returns an integer indicating the result of the comparison, as follows: .ip \(bu 2 0, if the .i s1 and .i s2 are equal; .ip \(bu a negative value if .i s1 is less than .ir s2 ; .ip \(bu a positive value if .i s1 is greater than .ir s2 . .pp the .br strncmp () function is similar, except it compares only the first (at most) .ir n bytes of .i s1 and .ir s2 . .sh return value the .br strcmp () and .br strncmp () functions return an integer less than, equal to, or greater than zero if .i s1 (or the first .i n bytes thereof) is found, respectively, to be less than, to match, or be greater than .ir s2 . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strcmp (), .br strncmp () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .sh notes posix.1 specifies only that: .rs .pp the sign of a nonzero return value shall be determined by the sign of the difference between the values of the first pair of bytes (both interpreted as type .ir "unsigned char" ) that differ in the strings being compared. .re .pp in glibc, as in most other implementations, the return value is the arithmetic result of subtracting the last compared byte in .i s2 from the last compared byte in .ir s1 . (if the two characters are equal, this difference is 0.) .sh examples the program below can be used to demonstrate the operation of .br strcmp () (when given two arguments) and .br strncmp () (when given three arguments). first, some examples using .br strcmp (): .pp .in +4n .ex $ \fb./string_comp abc abc\fp and are equal $ \fb./string_comp abc ab\fp # \(aqc\(aq is ascii 67; \(aqc\(aq \- \(aq\e0\(aq = 67 is greater than (67) $ \fb./string_comp aba abz\fp # \(aqa\(aq is ascii 65; \(aqz\(aq is ascii 90 is less than (\-25) $ \fb./string_comp abj abc\fp is greater than (7) $ .\fb/string_comp $\(aq\e201\(aq a\fp # 0201 \- 0101 = 0100 (or 64 decimal) is greater than (64) .ee .in .pp the last example uses .br bash (1)-specific syntax to produce a string containing an 8-bit ascii code; the result demonstrates that the string comparison uses unsigned characters. .pp and then some examples using .br strncmp (): .pp .in +4n .ex $ \fb./string_comp abc ab 3\fp is greater than (67) $ \fb./string_comp abc ab 2\fp and are equal in the first 2 bytes .ee .in .ss program source \& .ex /* string_comp.c licensed under gnu general public license v2 or later. */ #include #include #include int main(int argc, char *argv[]) { int res; if (argc < 3) { fprintf(stderr, "usage: %s []\en", argv[0]); exit(exit_failure); } if (argc == 3) res = strcmp(argv[1], argv[2]); else res = strncmp(argv[1], argv[2], atoi(argv[3])); if (res == 0) { printf(" and are equal"); if (argc > 3) printf(" in the first %d bytes\en", atoi(argv[3])); printf("\en"); } else if (res < 0) { printf(" is less than (%d)\en", res); } else { printf(" is greater than (%d)\en", res); } exit(exit_success); } .ee .sh see also .br bcmp (3), .br memcmp (3), .br strcasecmp (3), .br strcoll (3), .br string (3), .br strncasecmp (3), .br strverscmp (3), .br wcscmp (3), .br wcsncmp (3), .br ascii (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strcmp.3 .so man3/xdr.3 .\" copyright (c) 2009, linux foundation, written by michael kerrisk .\" .\" a few pieces remain from an earlier version .\" copyright (c) 2008, nanno langstraat .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th endian 3 2021-03-22 "gnu" "linux programmer's manual" .sh name htobe16, htole16, be16toh, le16toh, htobe32, htole32, be32toh, le32toh, htobe64, htole64, be64toh, le64toh \- convert values between host and big-/little-endian byte order .sh synopsis .nf .b #include .pp .bi "uint16_t htobe16(uint16_t " host_16bits ); .bi "uint16_t htole16(uint16_t " host_16bits ); .bi "uint16_t be16toh(uint16_t " big_endian_16bits ); .bi "uint16_t le16toh(uint16_t " little_endian_16bits ); .pp .bi "uint32_t htobe32(uint32_t " host_32bits ); .bi "uint32_t htole32(uint32_t " host_32bits ); .bi "uint32_t be32toh(uint32_t " big_endian_32bits ); .bi "uint32_t le32toh(uint32_t " little_endian_32bits ); .pp .bi "uint64_t htobe64(uint64_t " host_64bits ); .bi "uint64_t htole64(uint64_t " host_64bits ); .bi "uint64_t be64toh(uint64_t " big_endian_64bits ); .bi "uint64_t le64toh(uint64_t " little_endian_64bits ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .ad l .pp .br htobe16 (), .br htole16 (), .br be16toh (), .br le16toh (), .br htobe32 (), .br htole32 (), .br be32toh (), .br le32toh (), .br htobe64 (), .br htole64 (), .br be64toh (), .br le64toh (): .nf since glibc 2.19: _default_source in glibc up to and including 2.19: _bsd_source .fi .ad .sh description these functions convert the byte encoding of integer values from the byte order that the current cpu (the "host") uses, to and from little-endian and big-endian byte order. .pp the number, .ir nn , in the name of each function indicates the size of integer handled by the function, either 16, 32, or 64 bits. .pp the functions with names of the form "htobe\finn\fp" convert from host byte order to big-endian order. .pp the functions with names of the form "htole\finn\fp" convert from host byte order to little-endian order. .pp the functions with names of the form "be\finn\fptoh" convert from big-endian order to host byte order. .pp the functions with names of the form "le\finn\fptoh" convert from little-endian order to host byte order. .sh versions these functions were added to glibc in version 2.9. .sh conforming to these functions are nonstandard. similar functions are present on the bsds, where the required header file is .i instead of .ir . unfortunately, netbsd, freebsd, and glibc haven't followed the original openbsd naming convention for these functions, whereby the .i nn component always appears at the end of the function name (thus, for example, in netbsd, freebsd, and glibc, the equivalent of openbsds "betoh32" is "be32toh"). .sh notes these functions are similar to the older .br byteorder (3) family of functions. for example, .br be32toh () is identical to .br ntohl (). .pp the advantage of the .br byteorder (3) functions is that they are standard functions available on all unix systems. on the other hand, the fact that they were designed for use in the context of tcp/ip means that they lack the 64-bit and little-endian variants described in this page. .sh examples the program below display the results of converting an integer from host byte order to both little-endian and big-endian byte order. since host byte order is either little-endian or big-endian, only one of these conversions will have an effect. when we run this program on a little-endian system such as x86-32, we see the following: .pp .in +4n .ex $ \fb./a.out\fp x.u32 = 0x44332211 htole32(x.u32) = 0x44332211 htobe32(x.u32) = 0x11223344 .ee .in .ss program source \& .ex #include #include #include #include int main(int argc, char *argv[]) { union { uint32_t u32; uint8_t arr[4]; } x; x.arr[0] = 0x11; /* lowest\-address byte */ x.arr[1] = 0x22; x.arr[2] = 0x33; x.arr[3] = 0x44; /* highest\-address byte */ printf("x.u32 = %#x\en", x.u32); printf("htole32(x.u32) = %#x\en", htole32(x.u32)); printf("htobe32(x.u32) = %#x\en", htobe32(x.u32)); exit(exit_success); } .ee .sh see also .br bswap (3), .br byteorder (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2004 andries brouwer . .\" and copyright (c) 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th lseek64 3 2021-03-22 "linux" "linux programmer's manual" .sh name lseek64 \- reposition 64-bit read/write file offset .sh synopsis .nf .br "#define _largefile64_source" " /* see feature_test_macros(7) */" .b #include .b #include .pp .bi "off64_t lseek64(int " fd ", off64_t " offset ", int " whence ); .fi .sh description the .br lseek () family of functions reposition the offset of the open file associated with the file descriptor .i fd to .i offset bytes relative to the start, current position, or end of the file, when .i whence has the value .br seek_set , .br seek_cur , or .br seek_end , respectively. .pp for more details, return value, and errors, see .br lseek (2). .pp four interfaces are available: .br lseek (), .br lseek64 (), .br llseek (), and .br _llseek (). .\" .\" for some background details, see: .\" https://lore.kernel.org/linux-man/cakgnakhnswr3uyhyyaxx74fzfj3jrpfaapvrk0afk_caousbdg@mail.gmail.com/ .\" .ss lseek() prototype: .pp .in +4n .ex .bi "off_t lseek(int " fd ", off_t " offset ", int " whence ); .ee .in .pp the c library's .br lseek () wrapper function uses the type .ir off_t . this is a 32-bit signed type on 32-bit architectures, unless one compiles with .pp .in +4n .ex #define _file_offset_bits 64 .ee .in .pp in which case it is a 64-bit signed type. .ss lseek64() prototype: .pp .in +4n .ex .bi "off64_t lseek64(int " fd ", off64_t " offset ", int " whence ); .ee .in .pp the .br lseek64 () library function uses a 64-bit type even when .i off_t is a 32-bit type. its prototype (and the type .ir off64_t ) is available only when one compiles with .pp .in +4n .ex #define _largefile64_source .ee .in .pp the function .br lseek64 () .\" in glibc 2.0.94, not in 2.0.6 is available since glibc 2.1. .\" .ss llseek() prototype: .pp .in +4n .ex .bi "loff_t llseek(int " fd ", loff_t " offset ", int " whence ); .ee .in .pp the type .i loff_t is a 64-bit signed type. the .br llseek () library function is available in glibc and works without special defines. however, the glibc headers do not provide a prototype. users should add the above prototype, or something equivalent, to their own source. when users complained about data loss caused by a miscompilation of .br e2fsck (8), glibc 2.1.3 added the link-time warning .pp .in +4n "the \`llseek\' function may be dangerous; use \`lseek64\' instead." .in .pp this makes this function unusable if one desires a warning-free compilation. .pp since glibc 2.28, .\" glibc commit 5c5c0dd747070db624c8e2c43691cec854f114ef this function symbol is no longer available to newly linked applications. .\" .ss _llseek() on 32-bit architectures, this is the system call that is used (by the c library wrapper functions) to implement all of the above functions. the prototype is: .pp .in +4n .ex .bi "int _llseek(int " fd ", off_t " offset_hi ", off_t " offset_lo , .bi " loff_t *" result ", int " whence ); .ee .in .pp for more details, see .br llseek (2). .pp 64-bit systems don't need an .br _llseek () system call. instead, they have an .br lseek (2) system call that supports 64-bit file offsets. .\" in arch/x86/entry/syscalls/syscall_32.tbl, .\" we see the following line: .\" .\" 140 i386 _llseek sys_llseek .\" .\" this is essentially telling us that 'sys_llseek' (the name generated .\" by syscall_define5(llseek...)) is exposed to user-space as system call .\" number 140, and that system call number will (iiuc) be exposed in .\" autogenerated headers with the name "__nr__llseek" (i.e., "_llseek"). .\" the "i386" is telling us that this happens in i386 (32-bit intel). .\" there is nothing equivalent on x86-64, because 64 bit systems don't .\" need an _llseek system call. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br lseek64 () t} thread safety mt-safe .te .hy .ad .sp 1 .sh notes .br lseek64 () is one of the functions that was specified in the large file summit (lfs) specification that was completed in 1996. the purpose of the specification was to provide transitional support that allowed applications on 32-bit systems to access files whose size exceeds that which can be represented with a 32-bit .ir off_t type. as noted above, this symbol is exposed by header files if the .b _largefile64_source feature test macro is defined. alternatively, on a 32-bit system, the symbol .i lseek is aliased to .i lseek64 if the macro .b _file_offset_bits is defined with the value 64. .sh see also .br llseek (2), .br lseek (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 yoshifuji hideaki .\" and copyright (c) 2012 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume .\" no responsibility for errors or omissions, or for damages resulting .\" from the use of the information contained herein. the author(s) may .\" not have taken the same level of care in the production of this .\" manual, which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th if_nameindex 3 2021-03-22 "gnu" "linux programmer's manual" .sh name if_nameindex, if_freenameindex \- get network interface names and indexes .sh synopsis .nf .b #include .pp .bi "struct if_nameindex *if_nameindex(" void ); .bi "void if_freenameindex(struct if_nameindex *" "ptr" ); .fi .sh description the .br if_nameindex () function returns an array of .i if_nameindex structures, each containing information about one of the network interfaces on the local system. the .i if_nameindex structure contains at least the following entries: .pp .in +4n .ex unsigned int if_index; /* index of interface (1, 2, ...) */ char *if_name; /* null\-terminated name ("eth0", etc.) */ .ee .in .pp the .i if_index field contains the interface index. the .i if_name field points to the null-terminated interface name. the end of the array is indicated by entry with .i if_index set to zero and .i if_name set to null. .pp the data structure returned by .br if_nameindex () is dynamically allocated and should be freed using .br if_freenameindex () when no longer needed. .sh return value on success, .br if_nameindex () returns pointer to the array; on error, null is returned, and .i errno is set to indicate the error. .sh errors .br if_nameindex () may fail and set .i errno if: .tp .b enobufs insufficient resources available. .pp .br if_nameindex () may also fail for any of the errors specified for .br socket (2), .br bind (2), .br ioctl (2), .br getsockname (2), .br recvmsg (2), .br sendto (2), or .br malloc (3). .sh versions the .br if_nameindex () function first appeared in glibc 2.1, but before glibc 2.3.4, the implementation supported only interfaces with ipv4 addresses. support of interfaces that don't have ipv4 addresses is available only on kernels that support netlink. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br if_nameindex (), .br if_freenameindex () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, rfc\ 3493. .pp this function first appeared in bsdi. .sh examples the program below demonstrates the use of the functions described on this page. an example of the output this program might produce is the following: .pp .in +4n .ex $ \fb./a.out\fi 1: lo 2: wlan0 3: em1 .ee .in .ss program source .ex #include #include #include #include int main(int argc, char *argv[]) { struct if_nameindex *if_ni, *i; if_ni = if_nameindex(); if (if_ni == null) { perror("if_nameindex"); exit(exit_failure); } for (i = if_ni; ! (i\->if_index == 0 && i\->if_name == null); i++) printf("%u: %s\en", i\->if_index, i\->if_name); if_freenameindex(if_ni); exit(exit_success); } .ee .sh see also .br getsockopt (2), .br setsockopt (2), .br getifaddrs (3), .br if_indextoname (3), .br if_nametoindex (3), .br ifconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pipe 7 2021-08-27 "linux" "linux programmer's manual" .sh name pipe \- overview of pipes and fifos .sh description pipes and fifos (also known as named pipes) provide a unidirectional interprocess communication channel. a pipe has a .i read end and a .ir "write end" . data written to the write end of a pipe can be read from the read end of the pipe. .pp a pipe is created using .br pipe (2), which creates a new pipe and returns two file descriptors, one referring to the read end of the pipe, the other referring to the write end. pipes can be used to create a communication channel between related processes; see .br pipe (2) for an example. .pp a fifo (short for first in first out) has a name within the filesystem (created using .br mkfifo (3)), and is opened using .br open (2). any process may open a fifo, assuming the file permissions allow it. the read end is opened using the .b o_rdonly flag; the write end is opened using the .b o_wronly flag. see .br fifo (7) for further details. .ir note : although fifos have a pathname in the filesystem, i/o on fifos does not involve operations on the underlying device (if there is one). .ss i/o on pipes and fifos the only difference between pipes and fifos is the manner in which they are created and opened. once these tasks have been accomplished, i/o on pipes and fifos has exactly the same semantics. .pp if a process attempts to read from an empty pipe, then .br read (2) will block until data is available. if a process attempts to write to a full pipe (see below), then .br write (2) blocks until sufficient data has been read from the pipe to allow the write to complete. nonblocking i/o is possible by using the .br fcntl (2) .b f_setfl operation to enable the .b o_nonblock open file status flag. .pp the communication channel provided by a pipe is a .ir "byte stream" : there is no concept of message boundaries. .pp if all file descriptors referring to the write end of a pipe have been closed, then an attempt to .br read (2) from the pipe will see end-of-file .rb ( read (2) will return 0). if all file descriptors referring to the read end of a pipe have been closed, then a .br write (2) will cause a .b sigpipe signal to be generated for the calling process. if the calling process is ignoring this signal, then .br write (2) fails with the error .br epipe . an application that uses .br pipe (2) and .br fork (2) should use suitable .br close (2) calls to close unnecessary duplicate file descriptors; this ensures that end-of-file and .br sigpipe / epipe are delivered when appropriate. .pp it is not possible to apply .br lseek (2) to a pipe. .ss pipe capacity a pipe has a limited capacity. if the pipe is full, then a .br write (2) will block or fail, depending on whether the .b o_nonblock flag is set (see below). different implementations have different limits for the pipe capacity. applications should not rely on a particular capacity: an application should be designed so that a reading process consumes data as soon as it is available, so that a writing process does not remain blocked. .pp in linux versions before 2.6.11, the capacity of a pipe was the same as the system page size (e.g., 4096 bytes on i386). since linux 2.6.11, the pipe capacity is 16 pages (i.e., 65,536 bytes in a system with a page size of 4096 bytes). since linux 2.6.35, the default pipe capacity is 16 pages, but the capacity can be queried and set using the .br fcntl (2) .br f_getpipe_sz and .br f_setpipe_sz operations. see .br fcntl (2) for more information. .pp the following .br ioctl (2) operation, which can be applied to a file descriptor that refers to either end of a pipe, places a count of the number of unread bytes in the pipe in the .i int buffer pointed to by the final argument of the call: .pp ioctl(fd, fionread, &nbytes); .pp the .b fionread operation is not specified in any standard, but is provided on many implementations. .\" .ss /proc files on linux, the following files control how much memory can be used for pipes: .tp .ir /proc/sys/fs/pipe\-max\-pages " (only in linux 2.6.34)" .\" commit b492e95be0ae672922f4734acf3f5d35c30be948 an upper limit, in pages, on the capacity that an unprivileged user (one without the .br cap_sys_resource capability) can set for a pipe. .ip the default value for this limit is 16 times the default pipe capacity (see above); the lower limit is two pages. .ip this interface was removed in linux 2.6.35, in favor of .ir /proc/sys/fs/pipe\-max\-size . .tp .ir /proc/sys/fs/pipe\-max\-size " (since linux 2.6.35)" .\" commit ff9da691c0498ff81fdd014e7a0731dab2337dac the maximum size (in bytes) of individual pipes that can be set .\" this limit is not checked on pipe creation, where the capacity is .\" always pipe_def_bufs, regardless of pipe-max-size by users without the .b cap_sys_resource capability. the value assigned to this file may be rounded upward, to reflect the value actually employed for a convenient implementation. to determine the rounded-up value, display the contents of this file after assigning a value to it. .ip the default value for this file is 1048576 (1\ mib). the minimum value that can be assigned to this file is the system page size. attempts to set a limit less than the page size cause .br write (2) to fail with the error .br einval . .ip since linux 4.9, .\" commit 086e774a57fba4695f14383c0818994c0b31da7c the value on this file also acts as a ceiling on the default capacity of a new pipe or newly opened fifo. .tp .ir /proc/sys/fs/pipe\-user\-pages\-hard " (since linux 4.5)" .\" commit 759c01142a5d0f364a462346168a56de28a80f52 the hard limit on the total size (in pages) of all pipes created or set by a single unprivileged user (i.e., one with neither the .b cap_sys_resource nor the .b cap_sys_admin capability). so long as the total number of pages allocated to pipe buffers for this user is at this limit, attempts to create new pipes will be denied, and attempts to increase a pipe's capacity will be denied. .ip when the value of this limit is zero (which is the default), no hard limit is applied. .\" the default was chosen to avoid breaking existing applications that .\" make intensive use of pipes (e.g., for splicing). .tp .ir /proc/sys/fs/pipe\-user\-pages\-soft " (since linux 4.5)" .\" commit 759c01142a5d0f364a462346168a56de28a80f52 the soft limit on the total size (in pages) of all pipes created or set by a single unprivileged user (i.e., one with neither the .b cap_sys_resource nor the .b cap_sys_admin capability). so long as the total number of pages allocated to pipe buffers for this user is at this limit, individual pipes created by a user will be limited to one page, and attempts to increase a pipe's capacity will be denied. .ip when the value of this limit is zero, no soft limit is applied. the default value for this file is 16384, which permits creating up to 1024 pipes with the default capacity. .pp before linux 4.9, some bugs affected the handling of the .ir pipe\-user\-pages\-soft and .ir pipe\-user\-pages\-hard limits; see bugs. .\" .ss pipe_buf posix.1 says that writes of less than .b pipe_buf bytes must be atomic: the output data is written to the pipe as a contiguous sequence. writes of more than .b pipe_buf bytes may be nonatomic: the kernel may interleave the data with data written by other processes. posix.1 requires .b pipe_buf to be at least 512 bytes. (on linux, .b pipe_buf is 4096 bytes.) the precise semantics depend on whether the file descriptor is nonblocking .rb ( o_nonblock ), whether there are multiple writers to the pipe, and on .ir n , the number of bytes to be written: .tp \fbo_nonblock\fp disabled, \fin\fp <= \fbpipe_buf\fp all .i n bytes are written atomically; .br write (2) may block if there is not room for .i n bytes to be written immediately .tp \fbo_nonblock\fp enabled, \fin\fp <= \fbpipe_buf\fp if there is room to write .i n bytes to the pipe, then .br write (2) succeeds immediately, writing all .i n bytes; otherwise .br write (2) fails, with .i errno set to .br eagain . .tp \fbo_nonblock\fp disabled, \fin\fp > \fbpipe_buf\fp the write is nonatomic: the data given to .br write (2) may be interleaved with .br write (2)s by other process; the .br write (2) blocks until .i n bytes have been written. .tp \fbo_nonblock\fp enabled, \fin\fp > \fbpipe_buf\fp if the pipe is full, then .br write (2) fails, with .i errno set to .br eagain . otherwise, from 1 to .i n bytes may be written (i.e., a "partial write" may occur; the caller should check the return value from .br write (2) to see how many bytes were actually written), and these bytes may be interleaved with writes by other processes. .ss open file status flags the only open file status flags that can be meaningfully applied to a pipe or fifo are .b o_nonblock and .br o_async . .pp setting the .b o_async flag for the read end of a pipe causes a signal .rb ( sigio by default) to be generated when new input becomes available on the pipe. the target for delivery of signals must be set using the .br fcntl (2) .b f_setown command. on linux, .b o_async is supported for pipes and fifos only since kernel 2.6. .ss portability notes on some systems (but not linux), pipes are bidirectional: data can be transmitted in both directions between the pipe ends. posix.1 requires only unidirectional pipes. portable applications should avoid reliance on bidirectional pipe semantics. .ss bugs before linux 4.9, some bugs affected the handling of the .ir pipe\-user\-pages\-soft and .ir pipe\-user\-pages\-hard limits when using the .br fcntl (2) .br f_setpipe_sz operation to change a pipe's capacity: .\" these bugs where remedied by a series of patches, in particular, .\" commit b0b91d18e2e97b741b294af9333824ecc3fadfd8 and .\" commit a005ca0e6813e1d796a7422a7e31d8b8d6555df1 .ip (1) 5 when increasing the pipe capacity, the checks against the soft and hard limits were made against existing consumption, and excluded the memory required for the increased pipe capacity. the new increase in pipe capacity could then push the total memory used by the user for pipes (possibly far) over a limit. (this could also trigger the problem described next.) .ip starting with linux 4.9, the limit checking includes the memory required for the new pipe capacity. .ip (2) the limit checks were performed even when the new pipe capacity was less than the existing pipe capacity. this could lead to problems if a user set a large pipe capacity, and then the limits were lowered, with the result that the user could no longer decrease the pipe capacity. .ip starting with linux 4.9, checks against the limits are performed only when increasing a pipe's capacity; an unprivileged user can always decrease a pipe's capacity. .ip (3) the accounting and checking against the limits were done as follows: .ip .rs .pd 0 .ip (a) 4 test whether the user has exceeded the limit. .ip (b) make the new pipe buffer allocation. .ip (c) account new allocation against the limits. .pd .re .ip this was racey. multiple processes could pass point (a) simultaneously, and then allocate pipe buffers that were accounted for only in step (c), with the result that the user's pipe buffer allocation could be pushed over the limit. .ip starting with linux 4.9, the accounting step is performed before doing the allocation, and the operation fails if the limit would be exceeded. .pp before linux 4.9, bugs similar to points (1) and (3) could also occur when the kernel allocated memory for a new pipe buffer; that is, when calling .br pipe (2) and when opening a previously unopened fifo. .sh see also .br mkfifo (1), .br dup (2), .br fcntl (2), .br open (2), .br pipe (2), .br poll (2), .br select (2), .br socketpair (2), .br splice (2), .br stat (2), .br tee (2), .br vmsplice (2), .br mkfifo (3), .br epoll (7), .br fifo (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt, march 28, 1992 .\" and copyright (c) 2002 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2004-11-16 -- mtk: the getrlimit.2 page, which formerly included .\" coverage of getrusage(2), has been split, so that the latter is .\" now covered in its own getrusage.2. for older details of change .\" history, etc., see getrlimit.2 .\" .\" modified 2004-11-16, mtk, noted that the nonconformance .\" when sigchld is being ignored is fixed in 2.6.9. .\" 2008-02-22, sripathi kodi : document rusage_thread .\" 2008-05-25, mtk, clarify rusage_children + other clean-ups. .\" 2010-05-24, mark hills : description of fields, .\" document ru_maxrss .\" 2010-05-24, mtk, enhanced description of various fields .\" .th getrusage 2 2021-03-22 "linux" "linux programmer's manual" .sh name getrusage \- get resource usage .sh synopsis .nf .b #include .pp .bi "int getrusage(int " who ", struct rusage *" usage ); .fi .sh description .br getrusage () returns resource usage measures for .ir who , which can be one of the following: .tp .b rusage_self return resource usage statistics for the calling process, which is the sum of resources used by all threads in the process. .tp .b rusage_children return resource usage statistics for all children of the calling process that have terminated and been waited for. these statistics will include the resources used by grandchildren, and further removed descendants, if all of the intervening descendants waited on their terminated children. .tp .br rusage_thread " (since linux 2.6.26)" return resource usage statistics for the calling thread. the .b _gnu_source feature test macro must be defined (before including .i any header file) in order to obtain the definition of this constant from .ir . .pp the resource usages are returned in the structure pointed to by .ir usage , which has the following form: .pp .in +4n .ex struct rusage { struct timeval ru_utime; /* user cpu time used */ struct timeval ru_stime; /* system cpu time used */ long ru_maxrss; /* maximum resident set size */ long ru_ixrss; /* integral shared memory size */ long ru_idrss; /* integral unshared data size */ long ru_isrss; /* integral unshared stack size */ long ru_minflt; /* page reclaims (soft page faults) */ long ru_majflt; /* page faults (hard page faults) */ long ru_nswap; /* swaps */ long ru_inblock; /* block input operations */ long ru_oublock; /* block output operations */ long ru_msgsnd; /* ipc messages sent */ long ru_msgrcv; /* ipc messages received */ long ru_nsignals; /* signals received */ long ru_nvcsw; /* voluntary context switches */ long ru_nivcsw; /* involuntary context switches */ }; .ee .in .pp not all fields are completed; unmaintained fields are set to zero by the kernel. (the unmaintained fields are provided for compatibility with other systems, and because they may one day be supported on linux.) the fields are interpreted as follows: .tp .i ru_utime this is the total amount of time spent executing in user mode, expressed in a .i timeval structure (seconds plus microseconds). .tp .i ru_stime this is the total amount of time spent executing in kernel mode, expressed in a .i timeval structure (seconds plus microseconds). .tp .ir ru_maxrss " (since linux 2.6.32)" this is the maximum resident set size used (in kilobytes). for .br rusage_children , this is the resident set size of the largest child, not the maximum resident set size of the process tree. .tp .ir ru_ixrss " (unmaintained)" this field is currently unused on linux. .\" on some systems, .\" this is the integral of the text segment memory consumption, .\" expressed in kilobyte-seconds. .tp .ir ru_idrss " (unmaintained)" this field is currently unused on linux. .\" on some systems, this is the integral of the data segment memory consumption, .\" expressed in kilobyte-seconds. .tp .ir ru_isrss " (unmaintained)" this field is currently unused on linux. .\" on some systems, this is the integral of the stack memory consumption, .\" expressed in kilobyte-seconds. .tp .i ru_minflt the number of page faults serviced without any i/o activity; here i/o activity is avoided by \*(lqreclaiming\*(rq a page frame from the list of pages awaiting reallocation. .tp .i ru_majflt the number of page faults serviced that required i/o activity. .tp .ir ru_nswap " (unmaintained)" this field is currently unused on linux. .\" on some systems, this is the number of swaps out of physical memory. .tp .ir ru_inblock " (since linux 2.6.22)" the number of times the filesystem had to perform input. .tp .ir ru_oublock " (since linux 2.6.22)" the number of times the filesystem had to perform output. .tp .ir ru_msgsnd " (unmaintained)" this field is currently unused on linux. .\" on freebsd 6.2, this appears to measure messages sent over sockets .\" on some systems, .\" this field records the number of messages sent over sockets. .tp .ir ru_msgrcv " (unmaintained)" this field is currently unused on linux. .\" on freebsd 6.2, this appears to measure messages received over sockets .\" on some systems, .\" this field records the number of messages received over sockets. .tp .ir ru_nsignals " (unmaintained)" this field is currently unused on linux. .\" on some systems, this field records the number of signals received. .tp .ir ru_nvcsw " (since linux 2.6)" the number of times a context switch resulted due to a process voluntarily giving up the processor before its time slice was completed (usually to await availability of a resource). .tp .ir ru_nivcsw " (since linux 2.6)" the number of times a context switch resulted due to a higher priority process becoming runnable or because the current process exceeded its time slice. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i usage points outside the accessible address space. .tp .b einval .i who is invalid. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getrusage () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. posix.1 specifies .br getrusage (), but specifies only the fields .i ru_utime and .ir ru_stime . .pp .b rusage_thread is linux-specific. .sh notes resource usage metrics are preserved across an .br execve (2). .pp in linux kernel versions before 2.6.9, if the disposition of .b sigchld is set to .b sig_ign then the resource usages of child processes are automatically included in the value returned by .br rusage_children , although posix.1-2001 explicitly prohibits this. this nonconformance is rectified in linux 2.6.9 and later. .\" see the description of getrusage() in xsh. .\" a similar statement was also in susv2. .pp the structure definition shown at the start of this page was taken from 4.3bsd reno. .pp ancient systems provided a .br vtimes () function with a similar purpose to .br getrusage (). for backward compatibility, glibc (up until version 2.32) also provides .br vtimes (). all new applications should be written using .br getrusage (). (since version 2.33, glibc no longer provides an .br vtimes () implementation.) .pp see also the description of .ir /proc/[pid]/stat in .br proc (5). .sh see also .br clock_gettime (2), .br getrlimit (2), .br times (2), .br wait (2), .br wait4 (2), .br clock (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .\" copyright (c) 2001 andries brouwer . .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2007-07-05 mtk: added details on underlying system call interfaces .\" .th uname 2 2021-03-22 "linux" "linux programmer's manual" .sh name uname \- get name and information about current kernel .sh synopsis .nf .b #include .pp .bi "int uname(struct utsname *" buf ); .fi .sh description .br uname () returns system information in the structure pointed to by .ir buf . the .i utsname struct is defined in .ir : .pp .in +4n .ex struct utsname { char sysname[]; /* operating system name (e.g., "linux") */ char nodename[]; /* name within "some implementation\-defined network" */ char release[]; /* operating system release (e.g., "2.6.28") */ char version[]; /* operating system version */ char machine[]; /* hardware identifier */ #ifdef _gnu_source char domainname[]; /* nis or yp domain name */ #endif }; .ee .in .pp the length of the arrays in a .i struct utsname is unspecified (see notes); the fields are terminated by a null byte (\(aq\e0\(aq). .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i buf is not valid. .sh conforming to posix.1-2001, posix.1-2008, svr4. there is no .br uname () call in 4.3bsd. .pp the .i domainname member (the nis or yp domain name) is a gnu extension. .sh notes this is a system call, and the operating system presumably knows its name, release, and version. it also knows what hardware it runs on. so, four of the fields of the struct are meaningful. on the other hand, the field .i nodename is meaningless: it gives the name of the present machine in some undefined network, but typically machines are in more than one network and have several names. moreover, the kernel has no way of knowing about such things, so it has to be told what to answer here. the same holds for the additional .i domainname field. .pp to this end, linux uses the system calls .br sethostname (2) and .br setdomainname (2). note that there is no standard that says that the hostname set by .br sethostname (2) is the same string as the .i nodename field of the struct returned by .br uname () (indeed, some systems allow a 256-byte hostname and an 8-byte nodename), but this is true on linux. the same holds for .br setdomainname (2) and the .i domainname field. .pp the length of the fields in the struct varies. some operating systems or libraries use a hardcoded 9 or 33 or 65 or 257. other systems use .b sys_nmln or .b _sys_nmln or .b utslen or .br _utsname_length . clearly, it is a bad idea to use any of these constants; just use sizeof(...). often 257 is chosen in order to have room for an internet hostname. .pp part of the utsname information is also accessible via .ir /proc/sys/kernel/ { ostype , .ir hostname , .ir osrelease , .ir version , .ir domainname }. .ss c library/kernel differences over time, increases in the size of the .i utsname structure have led to three successive versions of .br uname (): .ir sys_olduname () (slot .ir __nr_oldolduname ), .ir sys_uname () (slot .ir __nr_olduname ), and .ir sys_newuname () (slot .ir __nr_uname) . the first one .\" that was back before linux 1.0 used length 9 for all fields; the second .\" that was also back before linux 1.0 used 65; the third also uses 65 but adds the .i domainname field. the glibc .br uname () wrapper function hides these details from applications, invoking the most recent version of the system call provided by the kernel. .sh see also .br uname (1), .br getdomainname (2), .br gethostname (2), .br uts_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified mon apr 12 12:51:24 1993, david metcalfe .\" 2006-05-19, justin pryzby .\" document strchrnul(3). .\" .th strchr 3 2021-03-22 "gnu" "linux programmer's manual" .sh name strchr, strrchr, strchrnul \- locate character in string .sh synopsis .nf .b #include .pp .bi "char *strchr(const char *" s ", int " c ); .bi "char *strrchr(const char *" s ", int " c ); .pp .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "char *strchrnul(const char *" s ", int " c ); .fi .sh description the .br strchr () function returns a pointer to the first occurrence of the character .i c in the string .ir s . .pp the .br strrchr () function returns a pointer to the last occurrence of the character .i c in the string .ir s . .pp the .br strchrnul () function is like .br strchr () except that if .i c is not found in .ir s , then it returns a pointer to the null byte at the end of .ir s , rather than null. .pp here "character" means "byte"; these functions do not work with wide or multibyte characters. .sh return value the .br strchr () and .br strrchr () functions return a pointer to the matched character or null if the character is not found. the terminating null byte is considered part of the string, so that if .i c is specified as \(aq\e0\(aq, these functions return a pointer to the terminator. .pp the .br strchrnul () function returns a pointer to the matched character, or a pointer to the null byte at the end of .i s (i.e., .ir "s+strlen(s)" ) if the character is not found. .sh versions .br strchrnul () first appeared in glibc in version 2.1.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strchr (), .br strrchr (), .br strchrnul () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br strchr (), .br strrchr (): posix.1-2001, posix.1-2008, c89, c99, svr4, 4.3bsd. .pp .br strchrnul () is a gnu extension. .sh see also .br index (3), .br memchr (3), .br rindex (3), .br string (3), .br strlen (3), .br strpbrk (3), .br strsep (3), .br strspn (3), .br strstr (3), .br strtok (3), .br wcschr (3), .br wcsrchr (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1996 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 5 oct 2002, modified by michael kerrisk .\" updated for posix.1 2001 .\" 2004-12-17 martin schulze , mtk .\" removed errno declaration prototype, added notes .\" 2006-02-09 kurt wall, mtk .\" added non-posix errors .\" .th errno 3 2021-03-22 "" "linux programmer's manual" .sh name errno \- number of last error .sh synopsis .nf .b #include .\".pp .\".bi "extern int " errno ; .fi .sh description the .i header file defines the integer variable .ir errno , which is set by system calls and some library functions in the event of an error to indicate what went wrong. .\" .ss errno the value in .i errno is significant only when the return value of the call indicated an error (i.e., \-1 from most system calls; \-1 or null from most library functions); a function that succeeds .i is allowed to change .ir errno . the value of .i errno is never set to zero by any system call or library function. .pp for some system calls and library functions (e.g., .br getpriority (2)), \-1 is a valid return on success. in such cases, a successful return can be distinguished from an error return by setting .i errno to zero before the call, and then, if the call returns a status that indicates that an error may have occurred, checking to see if .i errno has a nonzero value. .pp .i errno is defined by the iso c standard to be a modifiable lvalue of type .ir int , and must not be explicitly declared; .i errno may be a macro. .i errno is thread-local; setting it in one thread does not affect its value in any other thread. .\" .ss error numbers and names valid error numbers are all positive numbers. the .i header file defines symbolic names for each of the possible error numbers that may appear in .ir errno . .pp all the error names specified by posix.1 must have distinct values, with the exception of .b eagain and .br ewouldblock , which may be the same. on linux, these two have the same value on all architectures. .pp the error numbers that correspond to each symbolic name vary across unix systems, and even across different architectures on linux. therefore, numeric values are not included as part of the list of error names below. the .br perror (3) and .br strerror (3) functions can be used to convert these names to corresponding textual error messages. .pp on any particular linux system, one can obtain a list of all symbolic error names and the corresponding error numbers using the .br errno (1) command (part of the .i moreutils package): .pp .in +4n .ex $ \fberrno \-l\fp eperm 1 operation not permitted enoent 2 no such file or directory esrch 3 no such process eintr 4 interrupted system call eio 5 input/output error \&... .ee .in .pp the .br errno (1) command can also be used to look up individual error numbers and names, and to search for errors using strings from the error description, as in the following examples: .pp .in +4n .ex $ \fberrno 2\fp enoent 2 no such file or directory $ \fberrno esrch\fp esrch 3 no such process $ \fberrno \-s permission\fp eacces 13 permission denied .ee .in .\".pp .\" posix.1 (2001 edition) lists the following symbolic error names. of .\" these, \fbedom\fp and \fberange\fp are in the iso c standard. iso c .\" amendment 1 defines the additional error number \fbeilseq\fp for .\" coding errors in multibyte or wide characters. .\" .ss list of error names in the list of the symbolic error names below, various names are marked as follows: .ip * 3 .ir posix.1-2001 : the name is defined by posix.1-2001, and is defined in later posix.1 versions, unless otherwise indicated. .ip * .ir posix.1-2008 : the name is defined in posix.1-2008, but was not present in earlier posix.1 standards. .ip * .ir c99 : the name is defined by c99. .pp below is a list of the symbolic error names that are defined on linux: .tp 16 .b e2big argument list too long (posix.1-2001). .tp .b eacces permission denied (posix.1-2001). .tp .b eaddrinuse address already in use (posix.1-2001). .tp .b eaddrnotavail address not available (posix.1-2001). .\" eadv is only an error on hurd(?) .tp .b eafnosupport address family not supported (posix.1-2001). .tp .b eagain resource temporarily unavailable (may be the same value as .br ewouldblock ) (posix.1-2001). .tp .b ealready connection already in progress (posix.1-2001). .tp .b ebade invalid exchange. .tp .b ebadf bad file descriptor (posix.1-2001). .tp .b ebadfd file descriptor in bad state. .tp .b ebadmsg bad message (posix.1-2001). .tp .b ebadr invalid request descriptor. .tp .b ebadrqc invalid request code. .tp .b ebadslt invalid slot. .\" ebfont is defined but appears not to be used by kernel or glibc. .tp .b ebusy device or resource busy (posix.1-2001). .tp .b ecanceled operation canceled (posix.1-2001). .tp .b echild no child processes (posix.1-2001). .tp .b echrng channel number out of range. .tp .b ecomm communication error on send. .tp .b econnaborted connection aborted (posix.1-2001). .tp .b econnrefused connection refused (posix.1-2001). .tp .b econnreset connection reset (posix.1-2001). .tp .b edeadlk resource deadlock avoided (posix.1-2001). .tp .b edeadlock on most architectures, a synonym for .br edeadlk . on some architectures (e.g., linux mips, powerpc, sparc), it is a separate error code "file locking deadlock error". .tp .b edestaddrreq destination address required (posix.1-2001). .tp .b edom mathematics argument out of domain of function (posix.1, c99). .\" edotdot is defined but appears to be unused .tp .b edquot .\" posix just says "reserved" disk quota exceeded (posix.1-2001). .tp .b eexist file exists (posix.1-2001). .tp .b efault bad address (posix.1-2001). .tp .b efbig file too large (posix.1-2001). .tp .b ehostdown host is down. .tp .b ehostunreach host is unreachable (posix.1-2001). .tp .b ehwpoison memory page has hardware error. .tp .b eidrm identifier removed (posix.1-2001). .tp .b eilseq invalid or incomplete multibyte or wide character (posix.1, c99). .ip the text shown here is the glibc error description; in posix.1, this error is described as "illegal byte sequence". .tp .b einprogress operation in progress (posix.1-2001). .tp .b eintr interrupted function call (posix.1-2001); see .br signal (7). .tp .b einval invalid argument (posix.1-2001). .tp .b eio input/output error (posix.1-2001). .tp .b eisconn socket is connected (posix.1-2001). .tp .b eisdir is a directory (posix.1-2001). .tp .b eisnam is a named type file. .tp .b ekeyexpired key has expired. .tp .b ekeyrejected key was rejected by service. .tp .b ekeyrevoked key has been revoked. .tp .b el2hlt level 2 halted. .tp .b el2nsync level 2 not synchronized. .tp .b el3hlt level 3 halted. .tp .b el3rst level 3 reset. .tp .b elibacc cannot access a needed shared library. .tp .b elibbad accessing a corrupted shared library. .tp .b elibmax attempting to link in too many shared libraries. .tp .b elibscn \&.lib section in a.out corrupted .tp .b elibexec cannot exec a shared library directly. .tp .b elnrange .\" elnrng appears to be used by a few drivers link number out of range. .tp .b eloop too many levels of symbolic links (posix.1-2001). .tp .b emediumtype wrong medium type. .tp .b emfile too many open files (posix.1-2001). commonly caused by exceeding the .br rlimit_nofile resource limit described in .br getrlimit (2). can also be caused by exceeding the limit specified in .ir /proc/sys/fs/nr_open . .tp .b emlink too many links (posix.1-2001). .tp .b emsgsize message too long (posix.1-2001). .tp .b emultihop .\" posix says "reserved" multihop attempted (posix.1-2001). .tp .b enametoolong filename too long (posix.1-2001). .\" enavail is defined, but appears not to be used .tp .b enetdown network is down (posix.1-2001). .tp .b enetreset connection aborted by network (posix.1-2001). .tp .b enetunreach network unreachable (posix.1-2001). .tp .b enfile too many open files in system (posix.1-2001). on linux, this is probably a result of encountering the .ir /proc/sys/fs/file\-max limit (see .br proc (5)). .tp .b enoano .\" enoano appears to be used by a few drivers no anode. .tp .b enobufs no buffer space available (posix.1 (xsi streams option)). .\" enocsi is defined but appears to be unused. .tp .b enodata the named attribute does not exist, or the process has no access to this attribute; see .br xattr (7). .ip in posix.1-2001 (xsi streams option), this error was described as "no message is available on the stream head read queue". .tp .b enodev no such device (posix.1-2001). .tp .b enoent no such file or directory (posix.1-2001). .ip typically, this error results when a specified pathname does not exist, or one of the components in the directory prefix of a pathname does not exist, or the specified pathname is a dangling symbolic link. .tp .b enoexec exec format error (posix.1-2001). .tp .b enokey required key not available. .tp .b enolck no locks available (posix.1-2001). .tp .b enolink .\" posix says "reserved" link has been severed (posix.1-2001). .tp .b enomedium no medium found. .tp .b enomem not enough space/cannot allocate memory (posix.1-2001). .tp .b enomsg no message of the desired type (posix.1-2001). .tp .b enonet machine is not on the network. .tp .b enopkg package not installed. .tp .b enoprotoopt protocol not available (posix.1-2001). .tp .b enospc no space left on device (posix.1-2001). .tp .b enosr no stream resources (posix.1 (xsi streams option)). .tp .b enostr not a stream (posix.1 (xsi streams option)). .tp .b enosys function not implemented (posix.1-2001). .tp .b enotblk block device required. .tp .b enotconn the socket is not connected (posix.1-2001). .tp .b enotdir not a directory (posix.1-2001). .tp .b enotempty directory not empty (posix.1-2001). .\" enotnam is defined but appears to be unused. .tp .b enotrecoverable state not recoverable (posix.1-2008). .tp .b enotsock not a socket (posix.1-2001). .tp .b enotsup operation not supported (posix.1-2001). .tp .b enotty inappropriate i/o control operation (posix.1-2001). .tp .b enotuniq name not unique on network. .tp .b enxio no such device or address (posix.1-2001). .tp .b eopnotsupp operation not supported on socket (posix.1-2001). .ip .rb ( enotsup and .b eopnotsupp have the same value on linux, but according to posix.1 these error values should be distinct.) .tp .b eoverflow value too large to be stored in data type (posix.1-2001). .tp .b eownerdead .\" used at least by the user-space side of rubost mutexes owner died (posix.1-2008). .tp .b eperm operation not permitted (posix.1-2001). .tp .b epfnosupport protocol family not supported. .tp .b epipe broken pipe (posix.1-2001). .tp .b eproto protocol error (posix.1-2001). .tp .b eprotonosupport protocol not supported (posix.1-2001). .tp .b eprototype protocol wrong type for socket (posix.1-2001). .tp .b erange result too large (posix.1, c99). .tp .b eremchg remote address changed. .tp .b eremote object is remote. .tp .b eremoteio remote i/o error. .tp .b erestart interrupted system call should be restarted. .tp .b erfkill .\" erfkill appears to be used by various drivers operation not possible due to rf-kill. .tp .b erofs read-only filesystem (posix.1-2001). .tp .b eshutdown cannot send after transport endpoint shutdown. .tp .b espipe invalid seek (posix.1-2001). .tp .b esocktnosupport socket type not supported. .tp .b esrch no such process (posix.1-2001). .\" esrmnt is defined but appears not to be used .tp .b estale stale file handle (posix.1-2001). .ip this error can occur for nfs and for other filesystems. .tp .b estrpipe streams pipe error. .tp .b etime timer expired (posix.1 (xsi streams option)). .ip (posix.1 says "stream .br ioctl (2) timeout".) .tp .b etimedout connection timed out (posix.1-2001). .tp .b etoomanyrefs .\" etoomanyrefs seems to be used in net/unix/af_unix.c too many references: cannot splice. .tp .b etxtbsy text file busy (posix.1-2001). .tp .b euclean structure needs cleaning. .tp .b eunatch protocol driver not attached. .tp .b eusers too many users. .tp .b ewouldblock operation would block (may be same value as .br eagain ) (posix.1-2001). .tp .b exdev improper link (posix.1-2001). .tp .b exfull exchange full. .sh notes a common mistake is to do .pp .in +4n .ex if (somecall() == \-1) { printf("somecall() failed\en"); if (errno == ...) { ... } } .ee .in .pp where .i errno no longer needs to have the value it had upon return from .ir somecall () (i.e., it may have been changed by the .br printf (3)). if the value of .i errno should be preserved across a library call, it must be saved: .pp .in +4n .ex if (somecall() == \-1) { int errsv = errno; printf("somecall() failed\en"); if (errsv == ...) { ... } } .ee .in .pp note that the posix threads apis do .i not set .i errno on error. instead, on failure they return an error number as the function result. these error numbers have the same meanings as the error numbers returned in .i errno by other apis. .pp on some ancient systems, .i was not present or did not declare .ir errno , so that it was necessary to declare .i errno manually (i.e., .ir "extern int errno" ). .br "do not do this" . it long ago ceased to be necessary, and it will cause problems with modern versions of the c library. .sh see also .br errno (1), \" in the moreutils package .br err (3), .br error (3), .br perror (3), .br strerror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th btowc 3 2021-03-22 "gnu" "linux programmer's manual" .sh name btowc \- convert single byte to wide character .sh synopsis .nf .b #include .pp .bi "wint_t btowc(int " c ); .fi .sh description the .br btowc () function converts \fic\fp, interpreted as a multibyte sequence of length 1, starting in the initial shift state, to a wide character and returns it. if \fic\fp is .b eof or not a valid multibyte sequence of length 1, the .br btowc () function returns .br weof . .sh return value the .br btowc () function returns the wide character converted from the single byte \fic\fp. if \fic\fp is .b eof or not a valid multibyte sequence of length 1, it returns .br weof . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br btowc () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br btowc () depends on the .b lc_ctype category of the current locale. .pp this function should never be used. it does not work for encodings which have state, and unnecessarily treats single bytes differently from multibyte sequences. use either .br mbtowc (3) or the thread-safe .br mbrtowc (3) instead. .sh see also .br mbrtowc (3), .br mbtowc (3), .br wctob (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/geteuid.2 #!/bin/sh # # fixme_list.sh # # display fixme segments from man-pages source files # # (c) copyright 2007 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # ###################################################################### # # (c) copyright 2006 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # # show_all="n" while getopts "a" optname; do case "$optname" in a) # "all" # even show fixmes that aren't generally interesting. (typically # these fixmes are notes to the maintainer to reverify something # at a future date.) show_all="y" ;; *) echo "unknown option: $optarg" exit 1 ;; esac done shift $(( $optind - 1 )) if test $# -eq 0; then echo "usage: $0 [-a] pathname..." 1>&2 exit 1; fi for dir in "$@"; do for page in $(find "$dir" -type f -name '*.[1-9]' \ -exec grep -l fixme {} \; | sort) do cat "$page" | awk -v show_all=$show_all -v page_name="$page" \ ' begin { page_fixme_cnt = 0; } /fixme/ { # /.\" fixme . / ==> do not display this fixme, unless # -a command-line option was supplied if ($0 ~ /^\.\\" fixme \./ ) fixme_type = "hidden" else if ($0 ~ /^\.\\" fixme *\?/ ) fixme_type = "question" else fixme_type = "normal"; if (fixme_type == "normal" || show_all == "y") { if (page_fixme_cnt == 0) { print "=========="; print page_name; } page_fixme_cnt++; finished = 0; do { print $0; # implicit end of fixme is end-of-file or a line # that is not a comment if (getline == 0) finished = 1; if (!($0 ~ /^.\\"/)) finished = 1; # /.\" .$/ ==> explicit end of fixme if ($0 ~ /^.\\" \.$/) finished = 1; } while (!finished); print ""; } } ' done | sed -e 's/^\.\\"/ /' | sed -e 's/ *$//' | cat -s done .so man3/stailq.3 .\" copyright (c) 2017 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th inode 7 2021-03-22 "linux" "linux programmer's manual" .sh name inode \- file inode information .sh description each file has an inode containing metadata about the file. an application can retrieve this metadata using .br stat (2) (or related calls), which returns a .i stat structure, or .br statx (2), which returns a .i statx structure. .pp the following is a list of the information typically found in, or associated with, the file inode, with the names of the corresponding structure fields returned by .br stat (2) and .br statx (2): .tp device where inode resides \fistat.st_dev\fp; \fistatx.stx_dev_minor\fp and \fistatx.stx_dev_major\fp .ip each inode (as well as the associated file) resides in a filesystem that is hosted on a device. that device is identified by the combination of its major id (which identifies the general class of device) and minor id (which identifies a specific instance in the general class). .tp inode number \fistat.st_ino\fp; \fistatx.stx_ino\fp .ip each file in a filesystem has a unique inode number. inode numbers are guaranteed to be unique only within a filesystem (i.e., the same inode numbers may be used by different filesystems, which is the reason that hard links may not cross filesystem boundaries). this field contains the file's inode number. .tp file type and mode \fistat.st_mode\fp; \fistatx.stx_mode\fp .ip see the discussion of file type and mode, below. .tp link count \fistat.st_nlink\fp; \fistatx.stx_nlink\fp .ip this field contains the number of hard links to the file. additional links to an existing file are created using .br link (2). .tp user id .i st_uid \fistat.st_uid\fp; \fistatx.stx_uid\fp .ip this field records the user id of the owner of the file. for newly created files, the file user id is the effective user id of the creating process. the user id of a file can be changed using .br chown (2). .tp group id \fistat.st_gid\fp; \fistatx.stx_gid\fp .ip the inode records the id of the group owner of the file. for newly created files, the file group id is either the group id of the parent directory or the effective group id of the creating process, depending on whether or not the set-group-id bit is set on the parent directory (see below). the group id of a file can be changed using .br chown (2). .tp device represented by this inode \fistat.st_rdev\fp; \fistatx.stx_rdev_minor\fp and \fistatx.stx_rdev_major\fp .ip if this file (inode) represents a device, then the inode records the major and minor id of that device. .tp file size \fistat.st_size\fp; \fistatx.stx_size\fp .ip this field gives the size of the file (if it is a regular file or a symbolic link) in bytes. the size of a symbolic link is the length of the pathname it contains, without a terminating null byte. .tp preferred block size for i/o \fistat.st_blksize\fp; \fistatx.stx_blksize\fp .ip this field gives the "preferred" blocksize for efficient filesystem i/o. (writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.) .tp number of blocks allocated to the file \fistat.st_blocks\fp; \fistatx.stx_size\fp .ip this field indicates the number of blocks allocated to the file, 512-byte units, (this may be smaller than .ir st_size /512 when the file has holes.) .ip the posix.1 standard notes .\" rationale for sys/stat.h in posix.1-2008 that the unit for the .i st_blocks member of the .i stat structure is not defined by the standard. on many implementations it is 512 bytes; on a few systems, a different unit is used, such as 1024. furthermore, the unit may differ on a per-filesystem basis. .tp last access timestamp (atime) \fistat.st_atime\fp; \fistatx.stx_atime\fp .ip this is the file's last access timestamp. it is changed by file accesses, for example, by .br execve (2), .br mknod (2), .br pipe (2), .br utime (2), and .br read (2) (of more than zero bytes). other interfaces, such as .br mmap (2), may or may not update the atime timestamp .ip some filesystem types allow mounting in such a way that file and/or directory accesses do not cause an update of the atime timestamp. (see .ir noatime , .ir nodiratime , and .i relatime in .br mount (8), and related information in .br mount (2).) in addition, the atime timestamp is not updated if a file is opened with the .br o_noatime flag; see .br open (2). .tp file creation (birth) timestamp (btime) (not returned in the \fistat\fp structure); \fistatx.stx_btime\fp .ip the file's creation timestamp. this is set on file creation and not changed subsequently. .ip the btime timestamp was not historically present on unix systems and is not currently supported by most linux filesystems. .\" fixme is it supported on ext4 and xfs? .tp last modification timestamp (mtime) \fistat.st_mtime\fp; \fistatx.stx_mtime\fp .ip this is the file's last modification timestamp. it is changed by file modifications, for example, by .br mknod (2), .br truncate (2), .br utime (2), and .br write (2) (of more than zero bytes). moreover, the mtime timestamp of a directory is changed by the creation or deletion of files in that directory. the mtime timestamp is .i not changed for changes in owner, group, hard link count, or mode. .tp last status change timestamp (ctime) \fistat.st_ctime\fp; \fistatx.stx_ctime\fp .ip this is the file's last status change timestamp. it is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.). .pp the timestamp fields report time measured with a zero point at the .ir epoch , 1970-01-01 00:00:00 +0000, utc (see .br time (7)). .pp nanosecond timestamps are supported on xfs, jfs, btrfs, and ext4 (since linux 2.6.23). .\" commit ef7f38359ea8b3e9c7f2cae9a4d4935f55ca9e80 nanosecond timestamps are not supported in ext2, ext3, and reiserfs. in order to return timestamps with nanosecond precision, the timestamp fields in the .i stat and .i statx structures are defined as structures that include a nanosecond component. see .br stat (2) and .br statx (2) for details. on filesystems that do not support subsecond timestamps, the nanosecond fields in the .i stat and .i statx structures are returned with the value 0. .\" .ss the file type and mode the .i stat.st_mode field (for .br statx (2), the .i statx.stx_mode field) contains the file type and mode. .pp posix refers to the .i stat.st_mode bits corresponding to the mask .b s_ifmt (see below) as the .ir "file type" , the 12 bits corresponding to the mask 07777 as the .ir "file mode bits" and the least significant 9 bits (0777) as the .ir "file permission bits" . .pp the following mask values are defined for the file type: .in +4n .ts lb l l. s_ifmt 0170000 bit mask for the file type bit field s_ifsock 0140000 socket s_iflnk 0120000 symbolic link s_ifreg 0100000 regular file s_ifblk 0060000 block device s_ifdir 0040000 directory s_ifchr 0020000 character device s_ififo 0010000 fifo .te .in .pp thus, to test for a regular file (for example), one could write: .pp .in +4n .ex stat(pathname, &sb); if ((sb.st_mode & s_ifmt) == s_ifreg) { /* handle regular file */ } .ee .in .pp because tests of the above form are common, additional macros are defined by posix to allow the test of the file type in .i st_mode to be written more concisely: .rs 4 .tp 1.2i .br s_isreg (m) is it a regular file? .tp .br s_isdir (m) directory? .tp .br s_ischr (m) character device? .tp .br s_isblk (m) block device? .tp .br s_isfifo (m) fifo (named pipe)? .tp .br s_islnk (m) symbolic link? (not in posix.1-1996.) .tp .br s_issock (m) socket? (not in posix.1-1996.) .re .pp the preceding code snippet could thus be rewritten as: .pp .in +4n .ex stat(pathname, &sb); if (s_isreg(sb.st_mode)) { /* handle regular file */ } .ee .in .pp the definitions of most of the above file type test macros are provided if any of the following feature test macros is defined: .br _bsd_source (in glibc 2.19 and earlier), .br _svid_source (in glibc 2.19 and earlier), or .br _default_source (in glibc 2.20 and later). in addition, definitions of all of the above macros except .br s_ifsock and .br s_issock () are provided if .br _xopen_source is defined. .pp the definition of .br s_ifsock can also be exposed either by defining .br _xopen_source with a value of 500 or greater or (since glibc 2.24) by defining both .br _xopen_source and .br _xopen_source_extended . .pp the definition of .br s_issock () is exposed if any of the following feature test macros is defined: .br _bsd_source (in glibc 2.19 and earlier), .br _default_source (in glibc 2.20 and later), .br _xopen_source with a value of 500 or greater, .br _posix_c_source with a value of 200112l or greater, or (since glibc 2.24) by defining both .br _xopen_source and .br _xopen_source_extended . .pp the following mask values are defined for the file mode component of the .i st_mode field: .in +4n .nh .ad l .ts lb l lx. s_isuid 04000 t{ set-user-id bit (see \fbexecve\fp(2)) t} s_isgid 02000 t{ set-group-id bit (see below) t} s_isvtx 01000 t{ sticky bit (see below) t} s_irwxu 00700 t{ owner has read, write, and execute permission t} s_irusr 00400 t{ owner has read permission t} s_iwusr 00200 t{ owner has write permission t} s_ixusr 00100 t{ owner has execute permission t} s_irwxg 00070 t{ group has read, write, and execute permission t} s_irgrp 00040 t{ group has read permission t} s_iwgrp 00020 t{ group has write permission t} s_ixgrp 00010 t{ group has execute permission t} s_irwxo 00007 t{ others (not in group) have read, write, and execute permission t} s_iroth 00004 t{ others have read permission t} s_iwoth 00002 t{ others have write permission t} s_ixoth 00001 t{ others have execute permission t} .te .ad .hy .in .pp the set-group-id bit .rb ( s_isgid ) has several special uses. for a directory, it indicates that bsd semantics are to be used for that directory: files created there inherit their group id from the directory, not from the effective group id of the creating process, and directories created there will also get the .b s_isgid bit set. for an executable file, the set-group-id bit causes the effective group id of a process that executes the file to change as described in .br execve (2). for a file that does not have the group execution bit .rb ( s_ixgrp ) set, the set-group-id bit indicates mandatory file/record locking. .pp the sticky bit .rb ( s_isvtx ) on a directory means that a file in that directory can be renamed or deleted only by the owner of the file, by the owner of the directory, and by a privileged process. .sh conforming to if you need to obtain the definition of the .ir blkcnt_t or .ir blksize_t types from .ir , then define .br _xopen_source with the value 500 or greater (before including .i any header files). .pp posix.1-1990 did not describe the .br s_ifmt , .br s_ifsock , .br s_iflnk , .br s_ifreg , .br s_ifblk , .br s_ifdir , .br s_ifchr , .br s_ififo , and .b s_isvtx constants, but instead specified the use of the macros .br s_isdir () and so on. the .br s_if* constants are present in posix.1-2001 and later. .pp the .br s_islnk () and .br s_issock () macros were not in posix.1-1996, but both are present in posix.1-2001; the former is from svid 4, the latter from susv2. .pp unix\ v7 (and later systems) had .br s_iread , .br s_iwrite , .br s_iexec , and where posix prescribes the synonyms .br s_irusr , .br s_iwusr , and .br s_ixusr . .sh notes for pseudofiles that are autogenerated by the kernel, the file size (\fistat.st_size\fp; \fistatx.stx_size\fp) reported by the kernel is not accurate. for example, the value 0 is returned for many files under the .i /proc directory, while various files under .ir /sys report a size of 4096 bytes, even though the file content is smaller. for such files, one should simply try to read as many bytes as possible (and append \(aq\e0\(aq to the returned buffer if it is to be interpreted as a string). .sh see also .br stat (1), .br stat (2), .br statx (2), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/setfsgid.2 .\" michael haardt (michael@cantor.informatik.rwth.aachen.de) .\" sat sep 3 22:00:30 met dst 1994 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" sun feb 19 21:32:25 1995, faith@cs.unc.edu edited details away .\" .\" to do: this manual page should go more into detail how des is perturbed, .\" which string will be encrypted, and what determines the repetition factor. .\" is a simple repetition using ecb used, or something more advanced? i hope .\" the presented explanations are at least better than nothing, but by no .\" means enough. .\" .\" added _xopen_source, aeb, 970705 .\" added gnu md5 stuff, aeb, 011223 .\" .th crypt 3 2021-03-22 "" "linux programmer's manual" .sh name crypt, crypt_r \- password and data encryption .sh synopsis .nf .b #include .pp .bi "char *crypt(const char *" key ", const char *" salt ); .pp .b #include .pp .bi "char *crypt_r(const char *" key ", const char *" salt , .bi " struct crypt_data *restrict " data ); .fi .pp link with \fi\-lcrypt\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br crypt (): .nf since glibc 2.28: _default_source glibc 2.27 and earlier: _xopen_source .fi .br .pp .br crypt_r (): .nf _gnu_source .fi .sh description .br crypt () is the password encryption function. it is based on the data encryption standard algorithm with variations intended (among other things) to discourage use of hardware implementations of a key search. .pp .i key is a user's typed password. .pp .i salt is a two-character string chosen from the set [\fba\-za\-z0\-9./\fp]. this string is used to perturb the algorithm in one of 4096 different ways. .pp by taking the lowest 7 bits of each of the first eight characters of the .ir key , a 56-bit key is obtained. this 56-bit key is used to encrypt repeatedly a constant string (usually a string consisting of all zeros). the returned value points to the encrypted password, a series of 13 printable ascii characters (the first two characters represent the salt itself). the return value points to static data whose content is overwritten by each call. .pp warning: the key space consists of .if t 2\s-2\u56\s0\d .if n 2**56 equal 7.2e16 possible values. exhaustive searches of this key space are possible using massively parallel computers. software, such as .br crack (1), is available which will search the portion of this key space that is generally used by humans for passwords. hence, password selection should, at minimum, avoid common words and names. the use of a .br passwd (1) program that checks for crackable passwords during the selection process is recommended. .pp the des algorithm itself has a few quirks which make the use of the .br crypt () interface a very poor choice for anything other than password authentication. if you are planning on using the .br crypt () interface for a cryptography project, don't do it: get a good book on encryption and one of the widely available des libraries. .pp .br crypt_r () is a reentrant version of .br crypt (). the structure pointed to by .i data is used to store result data and bookkeeping information. other than allocating it, the only thing that the caller should do with this structure is to set .i data\->initialized to zero before the first call to .br crypt_r (). .sh return value on success, a pointer to the encrypted password is returned. on error, null is returned. .sh errors .tp .b einval .i salt has the wrong format. .tp .b enosys the .br crypt () function was not implemented, probably because of u.s.a. export restrictions. .\" this level of detail is not necessary in this man page. . . .\" .pp .\" when encrypting a plain text p using des with the key k results in the .\" encrypted text c, then the complementary plain text p' being encrypted .\" using the complementary key k' will result in the complementary encrypted .\" text c'. .\" .pp .\" weak keys are keys which stay invariant under the des key transformation. .\" the four known weak keys 0101010101010101, fefefefefefefefe, .\" 1f1f1f1f0e0e0e0e and e0e0e0e0f1f1f1f1 must be avoided. .\" .pp .\" there are six known half weak key pairs, which keys lead to the same .\" encrypted data. keys which are part of such key clusters should be .\" avoided. .\" sorry, i could not find out what they are. .\"" .\" .pp .\" heavily redundant data causes trouble with des encryption, when used in the .\" .i codebook .\" mode that .\" .br crypt () .\" implements. the .\" .br crypt () .\" interface should be used only for its intended purpose of password .\" verification, and should not be used as part of a data encryption tool. .\" .pp .\" the first and last three output bits of the fourth s-box can be .\" represented as function of their input bits. empiric studies have .\" shown that s-boxes partially compute the same output for similar input. .\" it is suspected that this may contain a back door which could allow the .\" nsa to decrypt des encrypted data. .\" .pp .\" making encrypted data computed using crypt() publicly available has .\" to be considered insecure for the given reasons. .tp .b eperm .i /proc/sys/crypto/fips_enabled has a nonzero value, and an attempt was made to use a weak encryption type, such as des. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br crypt () t} thread safety mt-unsafe race:crypt t{ .br crypt_r () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to .br crypt (): posix.1-2001, posix.1-2008, svr4, 4.3bsd. .br crypt_r () is a gnu extension. .sh notes .ss availability in glibc the .br crypt (), .br encrypt (3), and .br setkey (3) functions are part of the posix.1-2008 xsi options group for encryption and are optional. if the interfaces are not available, then the symbolic constant .br _xopen_crypt is either not defined, or it is defined to \-1 and availability can be checked at run time with .br sysconf (3). this may be the case if the downstream distribution has switched from glibc crypt to .ir libxcrypt . when recompiling applications in such distributions, the programmer must detect if .br _xopen_crypt is not available and include .i for the function prototypes; otherwise .i libxcrypt is an abi-compatible drop-in replacement. .ss features in glibc the glibc version of this function supports additional encryption algorithms. .pp if .i salt is a character string starting with the characters "$\fiid\fp$" followed by a string optionally terminated by "$", then the result has the form: .rs .pp $\fiid\fp$\fisalt\fp$\fiencrypted\fp .re .pp .i id identifies the encryption method used instead of des and this then determines how the rest of the password string is interpreted. the following values of .i id are supported: .rs .ts lb lb l lx. id method _ 1 md5 2a t{ blowfish (not in mainline glibc; added in some linux distributions) t} .\" opensuse has blowfish, but afaics, this option is not supported .\" natively by glibc -- mtk, jul 08 .\" .\" md5 | sun md5 .\" glibc doesn't appear to natively support sun md5; i don't know .\" if any distros add the support. 5 sha-256 (since glibc 2.7) 6 sha-512 (since glibc 2.7) .te .re .pp thus, $5$\fisalt\fp$\fiencrypted\fp and $6$\fisalt\fp$\fiencrypted\fp contain the password encrypted with, respectively, functions based on sha-256 and sha-512. .pp "\fisalt\fp" stands for the up to 16 characters following "$\fiid\fp$" in the salt. the "\fiencrypted\fp" part of the password string is the actual computed password. the size of this string is fixed: .rs .ts lb l. md5 22 characters sha-256 43 characters sha-512 86 characters .te .re .pp the characters in "\fisalt\fp" and "\fiencrypted\fp" are drawn from the set [\fba\-za\-z0\-9./\fp]. in the md5 and sha implementations the entire .i key is significant (instead of only the first 8 bytes in des). .pp since glibc 2.7, .\" glibc commit 9425cb9eea6a62fc21d99aafe8a60f752b934b05 the sha-256 and sha-512 implementations support a user-supplied number of hashing rounds, defaulting to 5000. if the "$\fiid\fp$" characters in the salt are followed by "rounds=\fixxx\fp$", where \fixxx\fp is an integer, then the result has the form .rs .pp $\fiid\fp$\firounds=yyy\fp$\fisalt\fp$\fiencrypted\fp .re .pp where \fiyyy\fp is the number of hashing rounds actually used. the number of rounds actually used is 1000 if .i xxx is less than 1000, 999999999 if .i xxx is greater than 999999999, and is equal to .i xxx otherwise. .sh see also .br login (1), .br passwd (1), .br encrypt (3), .br getpass (3), .br passwd (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt (michael@moria.de) .\" modified sat jul 24 14:48:00 1993 by rik faith (faith@cs.unc.edu) .\" modified 1995 by mike battersby (mib@deakin.edu.au) .\" modified 2000 by aeb, following michael kerrisk .\" .th pause 2 2021-03-22 "linux" "linux programmer's manual" .sh name pause \- wait for signal .sh synopsis .nf .b #include .pp .b int pause(void); .fi .sh description .br pause () causes the calling process (or thread) to sleep until a signal is delivered that either terminates the process or causes the invocation of a signal-catching function. .sh return value .br pause () returns only when a signal was caught and the signal-catching function returned. in this case, .br pause () returns \-1, and .i errno is set to .\" .br erestartnohand . .br eintr . .sh errors .tp .b eintr a signal was caught and the signal-catching function returned. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br kill (2), .br select (2), .br signal (2), .br sigsuspend (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sched_setattr.2 .\" copyright (c) 1993 by thomas koenig .\" and copyright (c) 2004 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified sat jul 24 13:30:06 1993 by rik faith .\" modified sun aug 21 17:42:42 1994 by rik faith .\" (thanks to koen holtman ) .\" modified wed may 17 15:54:12 1995 by rik faith .\" to remove *'s from status in macros (thanks to michael shields). .\" modified as suggested by nick duffek , aeb, 960426 .\" modified mon jun 23 14:09:52 1997 by aeb - add eintr. .\" modified thu nov 26 02:12:45 1998 by aeb - add sigchld stuff. .\" modified mon jul 24 21:37:38 2000 by david a. wheeler .\" - noted thread issues. .\" modified 26 jun 01 by michael kerrisk .\" added __wclone, __wall, and __wnothread descriptions .\" modified 2001-09-25, aeb .\" modified 26 jun 01 by michael kerrisk, .\" updated notes on setting disposition of sigchld to sig_ign .\" 2004-11-11, mtk .\" added waitid(2); added wcontinued and wifcontinued() .\" added text on sa_nocldstop .\" updated discussion of sa_nocldwait to reflect 2.6 behavior .\" much other text rewritten .\" 2005-05-10, mtk, __w* flags can't be used with waitid() .\" 2008-07-04, mtk, removed erroneous text about sa_nocldstop .\" .th wait 2 2021-08-27 "linux" "linux programmer's manual" .sh name wait, waitpid, waitid \- wait for process to change state .sh synopsis .nf .b #include .pp .bi "pid_t wait(int *" "wstatus" ); .bi "pid_t waitpid(pid_t " pid ", int *" wstatus ", int " options ); .pp .bi "int waitid(idtype_t " idtype ", id_t " id \ ", siginfo_t *" infop ", int " options ); /* this is the glibc and posix interface; see notes for information on the raw system call. */ .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br waitid (): .nf since glibc 2.26: _xopen_source >= 500 || _posix_c_source >= 200809l .\" (_xopen_source && _xopen_source_extended) glibc 2.25 and earlier: _xopen_source || /* since glibc 2.12: */ _posix_c_source >= 200809l || /* glibc <= 2.19: */ _bsd_source .fi .sh description all of these system calls are used to wait for state changes in a child of the calling process, and obtain information about the child whose state has changed. a state change is considered to be: the child terminated; the child was stopped by a signal; or the child was resumed by a signal. in the case of a terminated child, performing a wait allows the system to release the resources associated with the child; if a wait is not performed, then the terminated child remains in a "zombie" state (see notes below). .pp if a child has already changed state, then these calls return immediately. otherwise, they block until either a child changes state or a signal handler interrupts the call (assuming that system calls are not automatically restarted using the .b sa_restart flag of .br sigaction (2)). in the remainder of this page, a child whose state has changed and which has not yet been waited upon by one of these system calls is termed .ir waitable . .ss wait() and waitpid() the .br wait () system call suspends execution of the calling thread until one of its children terminates. the call .i wait(&wstatus) is equivalent to: .pp .in +4n .ex waitpid(\-1, &wstatus, 0); .ee .in .pp the .br waitpid () system call suspends execution of the calling thread until a child specified by .i pid argument has changed state. by default, .br waitpid () waits only for terminated children, but this behavior is modifiable via the .i options argument, as described below. .pp the value of .i pid can be: .ip "< \-1" meaning wait for any child process whose process group id is equal to the absolute value of .ir pid . .ip \-1 meaning wait for any child process. .ip 0 meaning wait for any child process whose process group id is equal to that of the calling process at the time of the call to .br waitpid (). .ip "> 0" meaning wait for the child whose process id is equal to the value of .ir pid . .pp the value of .i options is an or of zero or more of the following constants: .tp .b wnohang return immediately if no child has exited. .tp .b wuntraced also return if a child has stopped (but not traced via .br ptrace (2)). status for .i traced children which have stopped is provided even if this option is not specified. .tp .br wcontinued " (since linux 2.6.10)" also return if a stopped child has been resumed by delivery of .br sigcont . .pp (for linux-only options, see below.) .pp if .i wstatus is not null, .br wait () and .br waitpid () store status information in the \fiint\fp to which it points. this integer can be inspected with the following macros (which take the integer itself as an argument, not a pointer to it, as is done in .br wait () and .br waitpid ()!): .tp .bi wifexited( wstatus ) returns true if the child terminated normally, that is, by calling .br exit (3) or .br _exit (2), or by returning from main(). .tp .bi wexitstatus( wstatus ) returns the exit status of the child. this consists of the least significant 8 bits of the .i status argument that the child specified in a call to .br exit (3) or .br _exit (2) or as the argument for a return statement in main(). this macro should be employed only if .b wifexited returned true. .tp .bi wifsignaled( wstatus ) returns true if the child process was terminated by a signal. .tp .bi wtermsig( wstatus ) returns the number of the signal that caused the child process to terminate. this macro should be employed only if .b wifsignaled returned true. .tp .bi wcoredump( wstatus ) returns true if the child produced a core dump (see .br core (5)). this macro should be employed only if .b wifsignaled returned true. .ip this macro is not specified in posix.1-2001 and is not available on some unix implementations (e.g., aix, sunos). therefore, enclose its use inside .ir "#ifdef wcoredump ... #endif" . .tp .bi wifstopped( wstatus ) returns true if the child process was stopped by delivery of a signal; this is possible only if the call was done using .b wuntraced or when the child is being traced (see .br ptrace (2)). .tp .bi wstopsig( wstatus ) returns the number of the signal which caused the child to stop. this macro should be employed only if .b wifstopped returned true. .tp .bi wifcontinued( wstatus ) (since linux 2.6.10) returns true if the child process was resumed by delivery of .br sigcont . .ss waitid() the .br waitid () system call (available since linux 2.6.9) provides more precise control over which child state changes to wait for. .pp the .i idtype and .i id arguments select the child(ren) to wait for, as follows: .ip "\fiidtype\fp == \fbp_pid\fp" wait for the child whose process id matches .ir id . .ip "\fiidtype\fp == \fbp_pidfd\fp (since linux 5.4)" .\" commit 3695eae5fee0605f316fbaad0b9e3de791d7dfaf wait for the child referred to by the pid file descriptor specified in .ir id . (see .br pidfd_open (2) for further information on pid file descriptors.) .ip "\fiidtype\fp == \fbp_pgid\fp" wait for any child whose process group id matches .ir id . since linux 5.4, .\" commit 821cc7b0b205c0df64cce59aacc330af251fa8f7 if .i id is zero, then wait for any child that is in the same process group as the caller's process group at the time of the call. .ip "\fiidtype\fp == \fbp_all\fp" wait for any child; .i id is ignored. .pp the child state changes to wait for are specified by oring one or more of the following flags in .ir options : .tp .b wexited wait for children that have terminated. .tp .b wstopped wait for children that have been stopped by delivery of a signal. .tp .b wcontinued wait for (previously stopped) children that have been resumed by delivery of .br sigcont . .pp the following flags may additionally be ored in .ir options : .tp .b wnohang as for .br waitpid (). .tp .b wnowait leave the child in a waitable state; a later wait call can be used to again retrieve the child status information. .pp upon successful return, .br waitid () fills in the following fields of the .i siginfo_t structure pointed to by .ir infop : .tp \fisi_pid\fp the process id of the child. .tp \fisi_uid\fp the real user id of the child. (this field is not set on most other implementations.) .tp \fisi_signo\fp always set to .br sigchld . .tp \fisi_status\fp either the exit status of the child, as given to .br _exit (2) (or .br exit (3)), or the signal that caused the child to terminate, stop, or continue. the .i si_code field can be used to determine how to interpret this field. .tp \fisi_code\fp set to one of: .b cld_exited (child called .br _exit (2)); .b cld_killed (child killed by signal); .b cld_dumped (child killed by signal, and dumped core); .b cld_stopped (child stopped by signal); .b cld_trapped (traced child has trapped); or .b cld_continued (child continued by .br sigcont ). .pp if .b wnohang was specified in .i options and there were no children in a waitable state, then .br waitid () returns 0 immediately and the state of the .i siginfo_t structure pointed to by .i infop depends on the implementation. to (portably) distinguish this case from that where a child was in a waitable state, zero out the .i si_pid field before the call and check for a nonzero value in this field after the call returns. .pp posix.1-2008 technical corrigendum 1 (2013) adds the requirement that when .b wnohang is specified in .i options and there were no children in a waitable state, then .br waitid () should zero out the .i si_pid and .i si_signo fields of the structure. on linux and other implementations that adhere to this requirement, it is not necessary to zero out the .i si_pid field before calling .br waitid (). however, not all implementations follow the posix.1 specification on this point. .\" posix.1-2001 leaves this possibility unspecified; most .\" implementations (including linux) zero out the structure .\" in this case, but at least one implementation (aix 5.1) .\" does not -- mtk nov 04 .sh return value .br wait (): on success, returns the process id of the terminated child; on failure, \-1 is returned. .pp .br waitpid (): on success, returns the process id of the child whose state has changed; if .b wnohang was specified and one or more child(ren) specified by .i pid exist, but have not yet changed state, then 0 is returned. on failure, \-1 is returned. .pp .br waitid (): returns 0 on success or if .b wnohang was specified and no child(ren) specified by .i id has yet changed state; on failure, \-1 is returned. .\" fixme as reported by vegard nossum, if infop is null, then waitid() .\" returns the pid of the child. either this is a bug, or it is intended .\" behavior that needs to be documented. see my jan 2009 lkml mail .\" "waitid() return value strangeness when infop is null". .pp on failure, each of these calls sets .i errno to indicate the error. .sh errors .tp .b eagain the pid file descriptor specified in .i id is nonblocking and the process that it refers to has not terminated. .tp .b echild (for .br wait ()) the calling process does not have any unwaited-for children. .tp .b echild (for .br waitpid () or .br waitid ()) the process specified by .i pid .rb ( waitpid ()) or .i idtype and .i id .rb ( waitid ()) does not exist or is not a child of the calling process. (this can happen for one's own child if the action for .b sigchld is set to .br sig_ign . see also the \filinux notes\fp section about threads.) .tp .b eintr .b wnohang was not set and an unblocked signal or a .b sigchld was caught; see .br signal (7). .tp .b einval the .i options argument was invalid. .tp .b esrch (for .br wait () or .br waitpid ()) .i pid is equal to .br int_min . .sh conforming to svr4, 4.3bsd, posix.1-2001. .sh notes a child that terminates, but has not been waited for becomes a "zombie". the kernel maintains a minimal set of information about the zombie process (pid, termination status, resource usage information) in order to allow the parent to later perform a wait to obtain information about the child. as long as a zombie is not removed from the system via a wait, it will consume a slot in the kernel process table, and if this table fills, it will not be possible to create further processes. if a parent process terminates, then its "zombie" children (if any) are adopted by .br init (1), (or by the nearest "subreaper" process as defined through the use of the .br prctl (2) .b pr_set_child_subreaper operation); .br init (1) automatically performs a wait to remove the zombies. .pp posix.1-2001 specifies that if the disposition of .b sigchld is set to .b sig_ign or the .b sa_nocldwait flag is set for .b sigchld (see .br sigaction (2)), then children that terminate do not become zombies and a call to .br wait () or .br waitpid () will block until all children have terminated, and then fail with .i errno set to .br echild . (the original posix standard left the behavior of setting .b sigchld to .b sig_ign unspecified. note that even though the default disposition of .b sigchld is "ignore", explicitly setting the disposition to .b sig_ign results in different treatment of zombie process children.) .pp linux 2.6 conforms to the posix requirements. however, linux 2.4 (and earlier) does not: if a .br wait () or .br waitpid () call is made while .b sigchld is being ignored, the call behaves just as though .b sigchld were not being ignored, that is, the call blocks until the next child terminates and then returns the process id and status of that child. .ss linux notes in the linux kernel, a kernel-scheduled thread is not a distinct construct from a process. instead, a thread is simply a process that is created using the linux-unique .br clone (2) system call; other routines such as the portable .br pthread_create (3) call are implemented using .br clone (2). before linux 2.4, a thread was just a special case of a process, and as a consequence one thread could not wait on the children of another thread, even when the latter belongs to the same thread group. however, posix prescribes such functionality, and since linux 2.4 a thread can, and by default will, wait on children of other threads in the same thread group. .pp the following linux-specific .i options are for use with children created using .br clone (2); they can also, since linux 4.7, .\" commit 91c4e8ea8f05916df0c8a6f383508ac7c9e10dba be used with .br waitid (): .tp .b __wclone .\" since 0.99pl10 wait for "clone" children only. if omitted, then wait for "non-clone" children only. (a "clone" child is one which delivers no signal, or a signal other than .b sigchld to its parent upon termination.) this option is ignored if .b __wall is also specified. .tp .br __wall " (since linux 2.4)" .\" since patch-2.3.48 wait for all children, regardless of type ("clone" or "non-clone"). .tp .br __wnothread " (since linux 2.4)" .\" since patch-2.4.0-test8 do not wait for children of other threads in the same thread group. this was the default before linux 2.4. .pp since linux 4.7, .\" commit bf959931ddb88c4e4366e96dd22e68fa0db9527c .\" prevents cases where an unreapable zombie is created if .\" /sbin/init doesn't use __wall. the .b __wall flag is automatically implied if the child is being ptraced. .ss c library/kernel differences .br wait () is actually a library function that (in glibc) is implemented as a call to .br wait4 (2). .pp on some architectures, there is no .br waitpid () system call; .\" e.g., i386 has the system call, but not x86-64 instead, this interface is implemented via a c library wrapper function that calls .br wait4 (2). .pp the raw .br waitid () system call takes a fifth argument, of type .ir "struct rusage\ *" . if this argument is non-null, then it is used to return resource usage information about the child, in the same manner as .br wait4 (2). see .br getrusage (2) for details. .sh bugs according to posix.1-2008, an application calling .br waitid () must ensure that .i infop points to a .i siginfo_t structure (i.e., that it is a non-null pointer). on linux, if .i infop is null, .br waitid () succeeds, and returns the process id of the waited-for child. applications should avoid relying on this inconsistent, nonstandard, and unnecessary feature. .sh examples .\" fork.2 refers to this example program. the following program demonstrates the use of .br fork (2) and .br waitpid (). the program creates a child process. if no command-line argument is supplied to the program, then the child suspends its execution using .br pause (2), to allow the user to send signals to the child. otherwise, if a command-line argument is supplied, then the child exits immediately, using the integer supplied on the command line as the exit status. the parent process executes a loop that monitors the child using .br waitpid (), and uses the w*() macros described above to analyze the wait status value. .pp the following shell session demonstrates the use of the program: .pp .in +4n .ex .rb "$" " ./a.out &" child pid is 32360 [1] 32359 .rb "$" " kill \-stop 32360" stopped by signal 19 .rb "$" " kill \-cont 32360" continued .rb "$" " kill \-term 32360" killed by signal 15 [1]+ done ./a.out $ .ee .in .ss program source \& .ex #include #include #include #include #include int main(int argc, char *argv[]) { pid_t cpid, w; int wstatus; cpid = fork(); if (cpid == \-1) { perror("fork"); exit(exit_failure); } if (cpid == 0) { /* code executed by child */ printf("child pid is %jd\en", (intmax_t) getpid()); if (argc == 1) pause(); /* wait for signals */ _exit(atoi(argv[1])); } else { /* code executed by parent */ do { w = waitpid(cpid, &wstatus, wuntraced | wcontinued); if (w == \-1) { perror("waitpid"); exit(exit_failure); } if (wifexited(wstatus)) { printf("exited, status=%d\en", wexitstatus(wstatus)); } else if (wifsignaled(wstatus)) { printf("killed by signal %d\en", wtermsig(wstatus)); } else if (wifstopped(wstatus)) { printf("stopped by signal %d\en", wstopsig(wstatus)); } else if (wifcontinued(wstatus)) { printf("continued\en"); } } while (!wifexited(wstatus) && !wifsignaled(wstatus)); exit(exit_success); } } .ee .sh see also .br _exit (2), .br clone (2), .br fork (2), .br kill (2), .br ptrace (2), .br sigaction (2), .br signal (2), .br wait4 (2), .br pthread_create (3), .br core (5), .br credentials (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/timerfd_create.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcsnrtombs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsnrtombs \- convert a wide-character string to a multibyte string .sh synopsis .nf .b #include .pp .bi "size_t wcsnrtombs(char *restrict " dest ", const wchar_t **restrict " src , .bi " size_t " nwc ", size_t " len \ ", mbstate_t *restrict " ps ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br wcsnrtombs (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br wcsnrtombs () function is like the .br wcsrtombs (3) function, except that the number of wide characters to be converted, starting at .ir *src , is limited to .ir nwc . .pp if .i dest is not null, the .br wcsnrtombs () function converts at most .i nwc wide characters from the wide-character string .i *src to a multibyte string starting at .ir dest . at most .i len bytes are written to .ir dest . the shift state .i *ps is updated. the conversion is effectively performed by repeatedly calling .ir "wcrtomb(dest, *src, ps)" , as long as this call succeeds, and then incrementing .i dest by the number of bytes written and .i *src by one. the conversion can stop for three reasons: .ip 1. 3 a wide character has been encountered that can not be represented as a multibyte sequence (according to the current locale). in this case, .i *src is left pointing to the invalid wide character, .i (size_t)\ \-1 is returned, and .i errno is set to .br eilseq . .ip 2. .i nwc wide characters have been converted without encountering a null wide character (l\(aq\e0\(aq), or the length limit forces a stop. in this case, .i *src is left pointing to the next wide character to be converted, and the number of bytes written to .i dest is returned. .ip 3. the wide-character string has been completely converted, including the terminating null wide character (which has the side effect of bringing back .i *ps to the initial state). in this case, .i *src is set to null, and the number of bytes written to .ir dest , excluding the terminating null byte (\(aq\e0\(aq), is returned. .pp if .ir dest is null, .i len is ignored, and the conversion proceeds as above, except that the converted bytes are not written out to memory, and that no destination length limit exists. .pp in both of the above cases, if .i ps is null, a static anonymous state known only to the .br wcsnrtombs () function is used instead. .pp the programmer must ensure that there is room for at least .i len bytes at .ir dest . .sh return value the .br wcsnrtombs () function returns the number of bytes that make up the converted part of multibyte sequence, not including the terminating null byte. if a wide character was encountered which could not be converted, .i (size_t)\ \-1 is returned, and .i errno set to .br eilseq . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br wcsnrtombs () t} thread safety t{ mt-unsafe race:wcsnrtombs/!ps t} .te .hy .ad .sp 1 .sh conforming to posix.1-2008. .sh notes the behavior of .br wcsnrtombs () depends on the .b lc_ctype category of the current locale. .pp passing null as .i ps is not multithread safe. .sh see also .br iconv (3), .br mbsinit (3), .br wcsrtombs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/regex.3 .\" copyright (c) 2001 markus kuhn .\" and copyright (c) 2015 sam varshavchik .\" and copyright (c) 2015 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 manual .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .\" corrected prototype, 2002-10-18, aeb .\" .th nl_langinfo 3 2021-03-22 "gnu" "linux programmer's manual" .sh name nl_langinfo, nl_langinfo_l \- query language and locale information .sh synopsis .nf .b #include .pp .bi "char *nl_langinfo(nl_item " item ); .bi "char *nl_langinfo_l(nl_item " item ", locale_t " locale ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nl_langinfo_l (): .nf since glibc 2.24: _posix_c_source >= 200809l glibc 2.23 and earlier: _posix_c_source >= 200112l .fi .sh description the .br nl_langinfo () and .br nl_langinfo_l () functions provide access to locale information in a more flexible way than .br localeconv (3). .br nl_langinfo () returns a string which is the value corresponding to \fiitem\fp in the program's current global locale. .br nl_langinfo_l () returns a string which is the value corresponding to \fiitem\fp for the locale identified by the locale object \filocale\fp, which was previously created by .br newlocale (3). individual and additional elements of the locale categories can be queried. .pp examples for the locale elements that can be specified in \fiitem\fp using the constants defined in \fi\fp are: .tp .br codeset \ (lc_ctype) return a string with the name of the character encoding used in the selected locale, such as "utf-8", "iso-8859-1", or "ansi_x3.4-1968" (better known as us-ascii). this is the same string that you get with "locale charmap". for a list of character encoding names, try "locale \-m" (see .br locale (1)). .tp .br d_t_fmt \ (lc_time) return a string that can be used as a format string for .br strftime (3) to represent time and date in a locale-specific way .rb ( %c conversion specification). .tp .br d_fmt \ (lc_time) return a string that can be used as a format string for .br strftime (3) to represent a date in a locale-specific way .rb ( %x conversion specification). .tp .br t_fmt \ (lc_time) return a string that can be used as a format string for .br strftime (3) to represent a time in a locale-specific way .rb ( %x conversion specification). .tp .br am_str \ (lc_time) return a string that represents affix for ante meridiem (before noon, "am") time. (used in .b %p .br strftime (3) conversion specification.) .tp .br pm_str \ (lc_time) return a string that represents affix for post meridiem (before midnight, "pm") time. (used in .b %p .br strftime (3) conversion specification.) .tp .br t_fmt_ampm \ (lc_time) return a string that can be used as a format string for .br strftime (3) to represent a time in a.m. or p.m. notation in a locale-specific way .rb ( %r conversion specification). .tp .br era \ (lc_time) return era description, which contains information about how years are counted and displayed for each era in a locale. each era description segment shall have the format: .rs .ip .ir direction : offset : start_date : end_date : era_name : era_format .re .ip according to the definitions below: .rs .tp 12 .i direction either a .rb \[dq] + "\[dq] or a \[dq]" - \[dq] character. the .rb \[dq] + \[dq] means that years increase from the .i start_date towards the .ir end_date , .rb \[dq] - \[dq] means the opposite. .tp .i offset the epoch year of the .ir start_date . .tp .i start_date a date in the form .ir yyyy / mm / dd , where .ir yyyy ", " mm ", and " dd are the year, month, and day numbers respectively of the start of the era. .tp .i end_date the ending date of the era, in the same format as the .ir start_date , or one of the two special values .rb \[dq] -* \[dq] (minus infinity) or .rb \[dq] +* \[dq] (plus infinity). .tp .i era_name the name of the era, corresponding to the .b %ec .br strftime (3) conversion specification. .tp .i era_format the format of the year in the era, corresponding to the .b %ey .br strftime (3) conversion specification. .re .ip era description segments are separated by semicolons. most locales do not define this value. examples of locales that do define this value are the japanese and thai locales. .tp .br era_d_t_fmt \ (lc_time) return a string that can be used as a format string for .br strftime (3) for alternative representation of time and date in a locale-specific way .rb ( %ec conversion specification). .tp .br era_d_fmt \ (lc_time) return a string that can be used as a format string for .br strftime (3) for alternative representation of a date in a locale-specific way .rb ( %ex conversion specification). .tp .br era_t_fmt \ (lc_time) return a string that can be used as a format string for .br strftime (3) for alternative representation of a time in a locale-specific way .rb ( %ex conversion specification). .tp .br day_ "{1\(en7} (lc_time)" return name of the \fin\fp-th day of the week. [warning: this follows the us convention day_1 = sunday, not the international convention (iso 8601) that monday is the first day of the week.] (used in .b %a .br strftime (3) conversion specification.) .tp .br abday_ "{1\(en7} (lc_time)" return abbreviated name of the \fin\fp-th day of the week. (used in .b %a .br strftime (3) conversion specification.) .tp .br mon_ "{1\(en12} (lc_time)" return name of the \fin\fp-th month. (used in .b %b .br strftime (3) conversion specification.) .tp .br abmon_ "{1\(en12} (lc_time)" return abbreviated name of the \fin\fp-th month. (used in .b %b .br strftime (3) conversion specification.) .tp .br radixchar \ (lc_numeric) return radix character (decimal dot, decimal comma, etc.). .tp .br thousep \ (lc_numeric) return separator character for thousands (groups of three digits). .tp .br yesexpr \ (lc_messages) return a regular expression that can be used with the .br regex (3) function to recognize a positive response to a yes/no question. .tp .br noexpr \ (lc_messages) return a regular expression that can be used with the .br regex (3) function to recognize a negative response to a yes/no question. .tp .br crncystr \ (lc_monetary) return the currency symbol, preceded by "\-" if the symbol should appear before the value, "+" if the symbol should appear after the value, or "." if the symbol should replace the radix character. .pp the above list covers just some examples of items that can be requested. for a more detailed list, consult .ir "the gnu c library reference manual" . .sh return value on success, these functions return a pointer to a string which is the value corresponding to .i item in the specified locale. .pp if no locale has been selected by .br setlocale (3) for the appropriate category, .br nl_langinfo () return a pointer to the corresponding string in the "c" locale. the same is true of .br nl_langinfo_l () if .i locale specifies a locale where .i langinfo data is not defined. .pp if \fiitem\fp is not valid, a pointer to an empty string is returned. .pp the pointer returned by these functions may point to static data that may be overwritten, or the pointer itself may be invalidated, by a subsequent call to .br nl_langinfo (), .br nl_langinfo_l (), or .br setlocale (3). the same statements apply to .br nl_langinfo_l () if the locale object referred to by .i locale is freed or modified by .br freelocale (3) or .br newlocale (3). .pp posix specifies that the application may not modify the string returned by these functions. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br nl_langinfo () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, susv2. .sh notes the behavior of .br nl_langinfo_l () is undefined if .i locale is the special locale object .br lc_global_locale or is not a valid locale object handle. .sh examples the following program sets the character type and the numeric locale according to the environment and queries the terminal character set and the radix character. .pp .ex #include #include #include #include int main(int argc, char *argv[]) { setlocale(lc_ctype, ""); setlocale(lc_numeric, ""); printf("%s\en", nl_langinfo(codeset)); printf("%s\en", nl_langinfo(radixchar)); exit(exit_success); } .ee .sh see also .br locale (1), .br localeconv (3), .br setlocale (3), .br charsets (7), .br locale (7) .pp the gnu c library reference manual .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sigprocmask.2 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cproj 3 2021-03-22 "" "linux programmer's manual" .sh name cproj, cprojf, cprojl \- project into riemann sphere .sh synopsis .nf .b #include .pp .bi "double complex cproj(double complex " z ");" .bi "float complex cprojf(float complex " z ");" .bi "long double complex cprojl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions project a point in the plane onto the surface of a riemann sphere, the one-point compactification of the complex plane. each finite point .i z projects to .i z itself. every complex infinite value is projected to a single infinite value, namely to positive infinity on the real axis. .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br cproj (), .br cprojf (), .br cprojl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh notes in glibc 2.11 and earlier, the implementation does something different (a .i stereographic projection onto a riemann sphere). .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=10401 .sh see also .br cabs (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/setnetgrent.3 .\" copyright (c) 2001 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" text fragments inspired by martin schulze . .\" .th asprintf 3 2021-03-22 "gnu" "linux programmer's manual" .sh name asprintf, vasprintf \- print to allocated string .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int asprintf(char **restrict " strp ", const char *restrict " fmt ", ...);" .bi "int vasprintf(char **restrict " strp ", const char *restrict " fmt , .bi " va_list " ap ); .fi .sh description the functions .br asprintf () and .br vasprintf () are analogs of .br sprintf (3) and .br vsprintf (3), except that they allocate a string large enough to hold the output including the terminating null byte (\(aq\e0\(aq), and return a pointer to it via the first argument. this pointer should be passed to .br free (3) to release the allocated storage when it is no longer needed. .sh return value when successful, these functions return the number of bytes printed, just like .br sprintf (3). if memory allocation wasn't possible, or some other error occurs, these functions will return \-1, and the contents of .i strp are undefined. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br asprintf (), .br vasprintf () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to these functions are gnu extensions, not in c or posix. they are also available under *bsd. the freebsd implementation sets .i strp to null on error. .sh see also .br free (3), .br malloc (3), .br printf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strtok.3 .\" copyright (c) 1990, 1991 the regents of the university of california. .\" and copyright (c) 2021 michael kerrisk .\" all rights reserved. .\" .\" this code is derived from software contributed to berkeley by .\" chris torek and the american national standards committee x3, .\" on information processing systems. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)ferror.3 6.8 (berkeley) 6/29/91 .\" .\" .\" converted for linux, mon nov 29 14:24:40 1993, faith@cs.unc.edu .\" .th ferror 3 2021-03-22 "" "linux programmer's manual" .sh name clearerr, feof, ferror \- check and reset stream status .sh synopsis .nf .b #include .pp .bi "void clearerr(file *" stream ); .bi "int feof(file *" stream ); .bi "int ferror(file *" stream ); .fi .sh description the function .br clearerr () clears the end-of-file and error indicators for the stream pointed to by .ir stream . .pp the function .br feof () tests the end-of-file indicator for the stream pointed to by .ir stream , returning nonzero if it is set. the end-of-file indicator can be cleared only by the function .br clearerr (). .pp the function .br ferror () tests the error indicator for the stream pointed to by .ir stream , returning nonzero if it is set. the error indicator can be reset only by the .br clearerr () function. .pp for nonlocking counterparts, see .br unlocked_stdio (3). .sh return value the .br feof () function returns nonzero if the end-of-file indicator is set for .ir stream ; otherwise, it returns zero. .pp the .br ferror () function returns nonzero if the error indicator is set for .ir stream ; otherwise, it returns zero. .sh errors these functions should not fail and do not set .ir errno . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br clearerr (), .br feof (), .br ferror () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to the functions .br clearerr (), .br feof (), and .br ferror () conform to c89, c99, posix.1-2001, and posix.1-2008. .sh notes posix.1-2008 specifies .\"https://www.austingroupbugs.net/view.php?id=401 that these functions shall not change the value of .i errno if .i stream is valid. .sh see also .br open (2), .br fdopen (3), .br fileno (3), .br stdio (3), .br unlocked_stdio (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2005 robert love .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2005-07-19 robert love - initial version .\" 2006-02-07 mtk, minor changes .\" .th inotify_rm_watch 2 2021-03-22 "linux" "linux programmer's manual" .sh name inotify_rm_watch \- remove an existing watch from an inotify instance .sh synopsis .nf .b #include .pp .bi "int inotify_rm_watch(int " fd ", int " wd ); .\" before glibc 2.10, the second argument was types as uint32_t. .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=7040 .fi .sh description .br inotify_rm_watch () removes the watch associated with the watch descriptor .i wd from the inotify instance associated with the file descriptor .ir fd . .pp removing a watch causes an .b in_ignored event to be generated for this watch descriptor. (see .br inotify (7).) .sh return value on success, .br inotify_rm_watch () returns zero. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b einval the watch descriptor .i wd is not valid; or .i fd is not an inotify file descriptor. .sh versions inotify was merged into the 2.6.13 linux kernel. .sh conforming to this system call is linux-specific. .sh see also .br inotify_add_watch (2), .br inotify_init (2), .br inotify (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .\" copyright (c) 1994, 1995 by daniel quinlan (quinlan@yggdrasil.com) .\" and copyright (c) 2002-2008,2017 michael kerrisk .\" with networking additions from alan cox (a.cox@swansea.ac.uk) .\" and scsi additions from michael neuffer (neuffer@mail.uni-mainz.de) .\" and sysctl additions from andries brouwer (aeb@cwi.nl) .\" and system v ipc (as well as various other) additions from .\" michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1995-05-17 by faith@cs.unc.edu .\" minor changes by aeb and marty leisner (leisner@sdsp.mc.xerox.com). .\" modified 1996-04-13, 1996-07-22 by aeb@cwi.nl .\" modified 2001-12-16 by rwhron@earthlink.net .\" modified 2002-07-13 by jbelton@shaw.ca .\" modified 2002-07-22, 2003-05-27, 2004-04-06, 2004-05-25 .\" by michael kerrisk .\" 2004-11-17, mtk -- updated notes on /proc/loadavg .\" 2004-12-01, mtk, rtsig-max and rtsig-nr went away in 2.6.8 .\" 2004-12-14, mtk, updated 'statm', and fixed error in order of list .\" 2005-05-12, mtk, updated 'stat' .\" 2005-07-13, mtk, added /proc/sys/fs/mqueue/* .\" 2005-09-16, mtk, added /proc/sys/fs/suid_dumpable .\" 2005-09-19, mtk, added /proc/zoneinfo .\" 2005-03-01, mtk, moved /proc/sys/fs/mqueue/* material to mq_overview.7. .\" 2008-06-05, mtk, added /proc/[pid]/oom_score, /proc/[pid]/oom_adj, .\" /proc/[pid]/limits, /proc/[pid]/mountinfo, /proc/[pid]/mountstats, .\" and /proc/[pid]/fdinfo/*. .\" 2008-06-19, mtk, documented /proc/[pid]/status. .\" 2008-07-15, mtk, added /proc/config.gz .\" .\" fixme cross check against documentation/filesystems/proc.txt .\" to see what information could be imported from that file .\" into this file. .\" .th proc 5 2021-08-27 "linux" "linux programmer's manual" .sh name proc \- process information pseudo-filesystem .sh description the .b proc filesystem is a pseudo-filesystem which provides an interface to kernel data structures. it is commonly mounted at .ir /proc . typically, it is mounted automatically by the system, but it can also be mounted manually using a command such as: .pp .in +4n .ex mount \-t proc proc /proc .ee .in .pp most of the files in the .b proc filesystem are read-only, but some files are writable, allowing kernel variables to be changed. .\" .ss mount options the .b proc filesystem supports the following mount options: .tp .br hidepid "=\fin\fp (since linux 3.3)" .\" commit 0499680a42141d86417a8fbaa8c8db806bea1201 this option controls who can access the information in .ir /proc/[pid] directories. the argument, .ir n , is one of the following values: .rs .tp 4 0 everybody may access all .ir /proc/[pid] directories. this is the traditional behavior, and the default if this mount option is not specified. .tp 1 users may not access files and subdirectories inside any .ir /proc/[pid] directories but their own (the .ir /proc/[pid] directories themselves remain visible). sensitive files such as .ir /proc/[pid]/cmdline and .ir /proc/[pid]/status are now protected against other users. this makes it impossible to learn whether any user is running a specific program (so long as the program doesn't otherwise reveal itself by its behavior). .\" as an additional bonus, since .\" .ir /proc/[pid]/cmdline .\" is inaccessible for other users, .\" poorly written programs passing sensitive information via .\" program arguments are now protected against local eavesdroppers. .tp 2 as for mode 1, but in addition the .ir /proc/[pid] directories belonging to other users become invisible. this means that .ir /proc/[pid] entries can no longer be used to discover the pids on the system. this doesn't hide the fact that a process with a specific pid value exists (it can be learned by other means, for example, by "kill \-0 $pid"), but it hides a process's uid and gid, which could otherwise be learned by employing .br stat (2) on a .ir /proc/[pid] directory. this greatly complicates an attacker's task of gathering information about running processes (e.g., discovering whether some daemon is running with elevated privileges, whether another user is running some sensitive program, whether other users are running any program at all, and so on). .re .tp .br gid "=\figid\fp (since linux 3.3)" .\" commit 0499680a42141d86417a8fbaa8c8db806bea1201 specifies the id of a group whose members are authorized to learn process information otherwise prohibited by .br hidepid (i.e., users in this group behave as though .i /proc was mounted with .ir hidepid=0 ). this group should be used instead of approaches such as putting nonroot users into the .br sudoers (5) file. .\" .ss overview underneath .ir /proc , there are the following general groups of files and subdirectories: .tp .ir /proc/[pid] " subdirectories" each one of these subdirectories contains files and subdirectories exposing information about the process with the corresponding process id. .ip underneath each of the .i /proc/[pid] directories, a .i task subdirectory contains subdirectories of the form .ir task/[tid] , which contain corresponding information about each of the threads in the process, where .i tid is the kernel thread id of the thread. .ip the .i /proc/[pid] subdirectories are visible when iterating through .i /proc with .br getdents (2) (and thus are visible when one uses .br ls (1) to view the contents of .ir /proc ). .tp .ir /proc/[tid] " subdirectories" each one of these subdirectories contains files and subdirectories exposing information about the thread with the corresponding thread id. the contents of these directories are the same as the corresponding .ir /proc/[pid]/task/[tid] directories. .ip the .i /proc/[tid] subdirectories are .i not visible when iterating through .i /proc with .br getdents (2) (and thus are .i not visible when one uses .br ls (1) to view the contents of .ir /proc ). .tp .i /proc/self when a process accesses this magic symbolic link, it resolves to the process's own .i /proc/[pid] directory. .tp .i /proc/thread\-self when a thread accesses this magic symbolic link, it resolves to the process's own .i /proc/self/task/[tid] directory. .tp .i /proc/[a\-z]* various other files and subdirectories under .i /proc expose system-wide information. .pp all of the above are described in more detail below. .\" .ss files and directories the following list provides details of many of the files and directories under the .i /proc hierarchy. .tp .i /proc/[pid] there is a numerical subdirectory for each running process; the subdirectory is named by the process id. each .i /proc/[pid] subdirectory contains the pseudo-files and directories described below. .ip the files inside each .i /proc/[pid] directory are normally owned by the effective user and effective group id of the process. however, as a security measure, the ownership is made .ir root:root if the process's "dumpable" attribute is set to a value other than 1. .ip before linux 4.11, .\" commit 68eb94f16227336a5773b83ecfa8290f1d6b78ce .ir root:root meant the "global" root user id and group id (i.e., uid 0 and gid 0 in the initial user namespace). since linux 4.11, if the process is in a noninitial user namespace that has a valid mapping for user (group) id 0 inside the namespace, then the user (group) ownership of the files under .i /proc/[pid] is instead made the same as the root user (group) id of the namespace. this means that inside a container, things work as expected for the container "root" user. .ip the process's "dumpable" attribute may change for the following reasons: .rs .ip * 3 the attribute was explicitly set via the .br prctl (2) .b pr_set_dumpable operation. .ip * the attribute was reset to the value in the file .ir /proc/sys/fs/suid_dumpable (described below), for the reasons described in .br prctl (2). .re .ip resetting the "dumpable" attribute to 1 reverts the ownership of the .ir /proc/[pid]/* files to the process's effective uid and gid. note, however, that if the effective uid or gid is subsequently modified, then the "dumpable" attribute may be reset, as described in .br prctl (2). therefore, it may be desirable to reset the "dumpable" attribute .i after making any desired changes to the process's effective uid or gid. .tp .i /proc/[pid]/attr .\" https://lwn.net/articles/28222/ .\" from: stephen smalley .\" to: lkml and others .\" subject: [rfc][patch] process attribute api for security modules .\" date: 08 apr 2003 16:17:52 -0400 .\" .\" http://www.nsa.gov/research/_files/selinux/papers/module/x362.shtml .\" the files in this directory provide an api for security modules. the contents of this directory are files that can be read and written in order to set security-related attributes. this directory was added to support selinux, but the intention was that the api be general enough to support other security modules. for the purpose of explanation, examples of how selinux uses these files are provided below. .ip this directory is present only if the kernel was configured with .br config_security . .tp .ir /proc/[pid]/attr/current " (since linux 2.6.0)" the contents of this file represent the current security attributes of the process. .ip in selinux, this file is used to get the security context of a process. prior to linux 2.6.11, this file could not be used to set the security context (a write was always denied), since selinux limited process security transitions to .br execve (2) (see the description of .ir /proc/[pid]/attr/exec , below). since linux 2.6.11, selinux lifted this restriction and began supporting "set" operations via writes to this node if authorized by policy, although use of this operation is only suitable for applications that are trusted to maintain any desired separation between the old and new security contexts. .ip prior to linux 2.6.28, selinux did not allow threads within a multithreaded process to set their security context via this node as it would yield an inconsistency among the security contexts of the threads sharing the same memory space. since linux 2.6.28, selinux lifted this restriction and began supporting "set" operations for threads within a multithreaded process if the new security context is bounded by the old security context, where the bounded relation is defined in policy and guarantees that the new security context has a subset of the permissions of the old security context. .ip other security modules may choose to support "set" operations via writes to this node. .tp .ir /proc/[pid]/attr/exec " (since linux 2.6.0)" this file represents the attributes to assign to the process upon a subsequent .br execve (2). .ip in selinux, this is needed to support role/domain transitions, and .br execve (2) is the preferred point to make such transitions because it offers better control over the initialization of the process in the new security label and the inheritance of state. in selinux, this attribute is reset on .br execve (2) so that the new program reverts to the default behavior for any .br execve (2) calls that it may make. in selinux, a process can set only its own .i /proc/[pid]/attr/exec attribute. .tp .ir /proc/[pid]/attr/fscreate " (since linux 2.6.0)" this file represents the attributes to assign to files created by subsequent calls to .br open (2), .br mkdir (2), .br symlink (2), and .br mknod (2) .ip selinux employs this file to support creation of a file (using the aforementioned system calls) in a secure state, so that there is no risk of inappropriate access being obtained between the time of creation and the time that attributes are set. in selinux, this attribute is reset on .br execve (2), so that the new program reverts to the default behavior for any file creation calls it may make, but the attribute will persist across multiple file creation calls within a program unless it is explicitly reset. in selinux, a process can set only its own .ir /proc/[pid]/attr/fscreate attribute. .tp .ir /proc/[pid]/attr/keycreate " (since linux 2.6.18)" .\" commit 4eb582cf1fbd7b9e5f466e3718a59c957e75254e if a process writes a security context into this file, all subsequently created keys .rb ( add_key (2)) will be labeled with this context. for further information, see the kernel source file .i documentation/security/keys/core.rst (or file .\" commit b68101a1e8f0263dbc7b8375d2a7c57c6216fb76 .i documentation/security/keys.txt on linux between 3.0 and 4.13, or .\" commit d410fa4ef99112386de5f218dd7df7b4fca910b4 .i documentation/keys.txt before linux 3.0). .tp .ir /proc/[pid]/attr/prev " (since linux 2.6.0)" this file contains the security context of the process before the last .br execve (2); that is, the previous value of .ir /proc/[pid]/attr/current . .tp .ir /proc/[pid]/attr/socketcreate " (since linux 2.6.18)" .\" commit 42c3e03ef6b298813557cdb997bd6db619cd65a2 if a process writes a security context into this file, all subsequently created sockets will be labeled with this context. .tp .ir /proc/[pid]/autogroup " (since linux 2.6.38)" .\" commit 5091faa449ee0b7d73bc296a93bca9540fc51d0a see .br sched (7). .tp .ir /proc/[pid]/auxv " (since 2.6.0)" .\" precisely: linux 2.6.0-test7 this contains the contents of the elf interpreter information passed to the process at exec time. the format is one \fiunsigned long\fp id plus one \fiunsigned long\fp value for each entry. the last entry contains two zeros. see also .br getauxval (3). .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .ir /proc/[pid]/cgroup " (since linux 2.6.24)" see .br cgroups (7). .tp .ir /proc/[pid]/clear_refs " (since linux 2.6.22)" .\" commit b813e931b4c8235bb42e301096ea97dbdee3e8fe (2.6.22) .\" commit 398499d5f3613c47f2143b8c54a04efb5d7a6da9 (2.6.32) .\" commit 040fa02077de01c7e08fa75be6125e4ca5636011 (3.11) .\" .\" "clears page referenced bits shown in smaps output" .\" write-only, writable only by the owner of the process .ip this is a write-only file, writable only by owner of the process. .ip the following values may be written to the file: .rs .tp 1 (since linux 2.6.22) .\" internally: clear_refs_all reset the pg_referenced and accessed/young bits for all the pages associated with the process. (before kernel 2.6.32, writing any nonzero value to this file had this effect.) .tp 2 (since linux 2.6.32) .\" internally: clear_refs_anon reset the pg_referenced and accessed/young bits for all anonymous pages associated with the process. .tp 3 (since linux 2.6.32) .\" internally: clear_refs_mapped reset the pg_referenced and accessed/young bits for all file-mapped pages associated with the process. .re .ip clearing the pg_referenced and accessed/young bits provides a method to measure approximately how much memory a process is using. one first inspects the values in the "referenced" fields for the vmas shown in .ir /proc/[pid]/smaps to get an idea of the memory footprint of the process. one then clears the pg_referenced and accessed/young bits and, after some measured time interval, once again inspects the values in the "referenced" fields to get an idea of the change in memory footprint of the process during the measured interval. if one is interested only in inspecting the selected mapping types, then the value 2 or 3 can be used instead of 1. .ip further values can be written to affect different properties: .rs .tp 4 (since linux 3.11) clear the soft-dirty bit for all the pages associated with the process. .\" internally: clear_refs_soft_dirty this is used (in conjunction with .ir /proc/[pid]/pagemap ) by the check-point restore system to discover which pages of a process have been dirtied since the file .ir /proc/[pid]/clear_refs was written to. .tp 5 (since linux 4.0) .\" internally: clear_refs_mm_hiwater_rss reset the peak resident set size ("high water mark") to the process's current resident set size value. .re .ip writing any value to .ir /proc/[pid]/clear_refs other than those listed above has no effect. .ip the .ir /proc/[pid]/clear_refs file is present only if the .b config_proc_page_monitor kernel configuration option is enabled. .tp .i /proc/[pid]/cmdline this read-only file holds the complete command line for the process, unless the process is a zombie. .\" in 2.3.26, this also used to be true if the process was swapped out. in the latter case, there is nothing in this file: that is, a read on this file will return 0 characters. the command-line arguments appear in this file as a set of strings separated by null bytes (\(aq\e0\(aq), with a further null byte after the last string. .ip if, after an .br execve (2), the process modifies its .i argv strings, those changes will show up here. this is not the same thing as modifying the .i argv array. .ip furthermore, a process may change the memory location that this file refers via .br prctl (2) operations such as .br pr_set_mm_arg_start . .ip think of this file as the command line that the process wants you to see. .tp .ir /proc/[pid]/comm " (since linux 2.6.33)" .\" commit 4614a696bd1c3a9af3a08f0e5874830a85b889d4 this file exposes the process's .i comm value\(emthat is, the command name associated with the process. different threads in the same process may have different .i comm values, accessible via .ir /proc/[pid]/task/[tid]/comm . a thread may modify its .i comm value, or that of any of other thread in the same thread group (see the discussion of .b clone_thread in .br clone (2)), by writing to the file .ir /proc/self/task/[tid]/comm . strings longer than .b task_comm_len (16) characters (including the terminating null byte) are silently truncated. .ip this file provides a superset of the .br prctl (2) .b pr_set_name and .b pr_get_name operations, and is employed by .br pthread_setname_np (3) when used to rename threads other than the caller. the value in this file is used for the .i %e specifier in .ir /proc/sys/kernel/core_pattern ; see .br core (5). .tp .ir /proc/[pid]/coredump_filter " (since linux 2.6.23)" see .br core (5). .tp .ir /proc/[pid]/cpuset " (since linux 2.6.12)" .\" and/proc/[pid]/task/[tid]/cpuset see .br cpuset (7). .tp .i /proc/[pid]/cwd this is a symbolic link to the current working directory of the process. to find out the current working directory of process 20, for instance, you can do this: .ip .in +4n .ex .rb "$" " cd /proc/20/cwd; pwd \-p" .ee .in .ip .\" the following was still true as at kernel 2.6.13 in a multithreaded process, the contents of this symbolic link are not available if the main thread has already terminated (typically by calling .br pthread_exit (3)). .ip permission to dereference or read .rb ( readlink (2)) this symbolic link is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .i /proc/[pid]/environ this file contains the initial environment that was set when the currently executing program was started via .br execve (2). the entries are separated by null bytes (\(aq\e0\(aq), and there may be a null byte at the end. thus, to print out the environment of process 1, you would do: .ip .in +4n .ex .rb "$" " cat /proc/1/environ | tr \(aq\e000\(aq \(aq\en\(aq" .ee .in .ip if, after an .br execve (2), the process modifies its environment (e.g., by calling functions such as .br putenv (3) or modifying the .br environ (7) variable directly), this file will .i not reflect those changes. .ip furthermore, a process may change the memory location that this file refers via .br prctl (2) operations such as .br pr_set_mm_env_start . .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .i /proc/[pid]/exe under linux 2.2 and later, this file is a symbolic link containing the actual pathname of the executed command. this symbolic link can be dereferenced normally; attempting to open it will open the executable. you can even type .i /proc/[pid]/exe to run another copy of the same executable that is being run by process [pid]. if the pathname has been unlinked, the symbolic link will contain the string \(aq(deleted)\(aq appended to the original pathname. .\" the following was still true as at kernel 2.6.13 in a multithreaded process, the contents of this symbolic link are not available if the main thread has already terminated (typically by calling .br pthread_exit (3)). .ip permission to dereference or read .rb ( readlink (2)) this symbolic link is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .ip under linux 2.0 and earlier, .i /proc/[pid]/exe is a pointer to the binary which was executed, and appears as a symbolic link. a .br readlink (2) call on this file under linux 2.0 returns a string in the format: .ip [device]:inode .ip for example, [0301]:1502 would be inode 1502 on device major 03 (ide, mfm, etc. drives) minor 01 (first partition on the first drive). .ip .br find (1) with the .i \-inum option can be used to locate the file. .tp .i /proc/[pid]/fd/ this is a subdirectory containing one entry for each file which the process has open, named by its file descriptor, and which is a symbolic link to the actual file. thus, 0 is standard input, 1 standard output, 2 standard error, and so on. .ip for file descriptors for pipes and sockets, the entries will be symbolic links whose content is the file type with the inode. a .br readlink (2) call on this file returns a string in the format: .ip type:[inode] .ip for example, .i socket:[2248868] will be a socket and its inode is 2248868. for sockets, that inode can be used to find more information in one of the files under .ir /proc/net/ . .ip for file descriptors that have no corresponding inode (e.g., file descriptors produced by .br bpf (2), .br epoll_create (2), .br eventfd (2), .br inotify_init (2), .br perf_event_open (2), .br signalfd (2), .br timerfd_create (2), and .br userfaultfd (2)), the entry will be a symbolic link with contents of the form .ip anon_inode: .ip in many cases (but not all), the .i file-type is surrounded by square brackets. .ip for example, an epoll file descriptor will have a symbolic link whose content is the string .ir "anon_inode:[eventpoll]" . .ip .\"the following was still true as at kernel 2.6.13 in a multithreaded process, the contents of this directory are not available if the main thread has already terminated (typically by calling .br pthread_exit (3)). .ip programs that take a filename as a command-line argument, but don't take input from standard input if no argument is supplied, and programs that write to a file named as a command-line argument, but don't send their output to standard output if no argument is supplied, can nevertheless be made to use standard input or standard output by using .ir /proc/[pid]/fd files as command-line arguments. for example, assuming that .i \-i is the flag designating an input file and .i \-o is the flag designating an output file: .ip .in +4n .ex .rb "$" " foobar \-i /proc/self/fd/0 \-o /proc/self/fd/1 ..." .ee .in .ip and you have a working filter. .\" the following is not true in my tests (mtk): .\" note that this will not work for .\" programs that seek on their files, as the files in the fd directory .\" are not seekable. .ip .i /proc/self/fd/n is approximately the same as .i /dev/fd/n in some unix and unix-like systems. most linux makedev scripts symbolically link .i /dev/fd to .ir /proc/self/fd , in fact. .ip most systems provide symbolic links .ir /dev/stdin , .ir /dev/stdout , and .ir /dev/stderr , which respectively link to the files .ir 0 , .ir 1 , and .ir 2 in .ir /proc/self/fd . thus the example command above could be written as: .ip .in +4n .ex .rb "$" " foobar \-i /dev/stdin \-o /dev/stdout ..." .ee .in .ip permission to dereference or read .rb ( readlink (2)) the symbolic links in this directory is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .ip note that for file descriptors referring to inodes (pipes and sockets, see above), those inodes still have permission bits and ownership information distinct from those of the .i /proc/[pid]/fd entry, and that the owner may differ from the user and group ids of the process. an unprivileged process may lack permissions to open them, as in this example: .ip .in +4n .ex .rb "$" " echo test | sudo \-u nobody cat" test .rb "$" " echo test | sudo \-u nobody cat /proc/self/fd/0" cat: /proc/self/fd/0: permission denied .ee .in .ip file descriptor 0 refers to the pipe created by the shell and owned by that shell's user, which is not .ir nobody , so .b cat does not have permission to create a new file descriptor to read from that inode, even though it can still read from its existing file descriptor 0. .tp .ir /proc/[pid]/fdinfo/ " (since linux 2.6.22)" this is a subdirectory containing one entry for each file which the process has open, named by its file descriptor. the files in this directory are readable only by the owner of the process. the contents of each file can be read to obtain information about the corresponding file descriptor. the content depends on the type of file referred to by the corresponding file descriptor. .ip for regular files and directories, we see something like: .ip .in +4n .ex .rb "$" " cat /proc/12015/fdinfo/4" pos: 1000 flags: 01002002 mnt_id: 21 .ee .in .ip the fields are as follows: .rs .tp .i pos this is a decimal number showing the file offset. .tp .i flags this is an octal number that displays the file access mode and file status flags (see .br open (2)). if the close-on-exec file descriptor flag is set, then .i flags will also include the value .br o_cloexec . .ip before linux 3.1, .\" commit 1117f72ea0217ba0cc19f05adbbd8b9a397f5ab7 this field incorrectly displayed the setting of .b o_cloexec at the time the file was opened, rather than the current setting of the close-on-exec flag. .tp .i .i mnt_id this field, present since linux 3.15, .\" commit 49d063cb353265c3af701bab215ac438ca7df36d is the id of the mount containing this file. see the description of .ir /proc/[pid]/mountinfo . .re .ip for eventfd file descriptors (see .br eventfd (2)), we see (since linux 3.8) .\" commit cbac5542d48127b546a23d816380a7926eee1c25 the following fields: .ip .in +4n .ex pos: 0 flags: 02 mnt_id: 10 eventfd\-count: 40 .ee .in .ip .i eventfd\-count is the current value of the eventfd counter, in hexadecimal. .ip for epoll file descriptors (see .br epoll (7)), we see (since linux 3.8) .\" commit 138d22b58696c506799f8de759804083ff9effae the following fields: .ip .in +4n .ex pos: 0 flags: 02 mnt_id: 10 tfd: 9 events: 19 data: 74253d2500000009 tfd: 7 events: 19 data: 74253d2500000007 .ee .in .ip each of the lines beginning .i tfd describes one of the file descriptors being monitored via the epoll file descriptor (see .br epoll_ctl (2) for some details). the .ir tfd field is the number of the file descriptor. the .i events field is a hexadecimal mask of the events being monitored for this file descriptor. the .i data field is the data value associated with this file descriptor. .ip for signalfd file descriptors (see .br signalfd (2)), we see (since linux 3.8) .\" commit 138d22b58696c506799f8de759804083ff9effae the following fields: .ip .in +4n .ex pos: 0 flags: 02 mnt_id: 10 sigmask: 0000000000000006 .ee .in .ip .i sigmask is the hexadecimal mask of signals that are accepted via this signalfd file descriptor. (in this example, bits 2 and 3 are set, corresponding to the signals .b sigint and .br sigquit ; see .br signal (7).) .ip for inotify file descriptors (see .br inotify (7)), we see (since linux 3.8) the following fields: .ip .in +4n .ex pos: 0 flags: 00 mnt_id: 11 inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle\-bytes:8 fhandle\-type:1 f_handle:2af87e00220ffd73 inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle\-bytes:8 fhandle\-type:1 f_handle:27261900802dfd73 .ee .in .ip each of the lines beginning with "inotify" displays information about one file or directory that is being monitored. the fields in this line are as follows: .rs .tp .i wd a watch descriptor number (in decimal). .tp .i ino the inode number of the target file (in hexadecimal). .tp .i sdev the id of the device where the target file resides (in hexadecimal). .tp .i mask the mask of events being monitored for the target file (in hexadecimal). .re .ip if the kernel was built with exportfs support, the path to the target file is exposed as a file handle, via three hexadecimal fields: .ir fhandle\-bytes , .ir fhandle\-type , and .ir f_handle . .ip for fanotify file descriptors (see .br fanotify (7)), we see (since linux 3.8) the following fields: .ip .in +4n .ex pos: 0 flags: 02 mnt_id: 11 fanotify flags:0 event\-flags:88002 fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle\-bytes:8 fhandle\-type:1 f_handle:4f261900a82dfd73 .ee .in .ip the fourth line displays information defined when the fanotify group was created via .br fanotify_init (2): .rs .tp .i flags the .i flags argument given to .br fanotify_init (2) (expressed in hexadecimal). .tp .i event\-flags the .i event_f_flags argument given to .br fanotify_init (2) (expressed in hexadecimal). .re .ip each additional line shown in the file contains information about one of the marks in the fanotify group. most of these fields are as for inotify, except: .rs .tp .i mflags the flags associated with the mark (expressed in hexadecimal). .tp .i mask the events mask for this mark (expressed in hexadecimal). .tp .i ignored_mask the mask of events that are ignored for this mark (expressed in hexadecimal). .re .ip for details on these fields, see .br fanotify_mark (2). .ip for timerfd file descriptors (see .br timerfd (2)), we see (since linux 3.17) .\" commit af9c4957cf212ad9cf0bee34c95cb11de5426e85 the following fields: .ip .in +4n .ex pos: 0 flags: 02004002 mnt_id: 13 clockid: 0 ticks: 0 settime flags: 03 it_value: (7695568592, 640020877) it_interval: (0, 0) .ee .in .rs .tp .i clockid this is the numeric value of the clock id (corresponding to one of the .b clock_* constants defined via .ir ) that is used to mark the progress of the timer (in this example, 0 is .br clock_realtime ). .tp .i ticks this is the number of timer expirations that have occurred, (i.e., the value that .br read (2) on it would return). .tp .i settime flags this field lists the flags with which the timerfd was last armed (see .br timerfd_settime (2)), in octal (in this example, both .b tfd_timer_abstime and .b tfd_timer_cancel_on_set are set). .tp .i it_value this field contains the amount of time until the timer will next expire, expressed in seconds and nanoseconds. this is always expressed as a relative value, regardless of whether the timer was created using the .b tfd_timer_abstime flag. .tp .i it_interval this field contains the interval of the timer, in seconds and nanoseconds. (the .i it_value and .i it_interval fields contain the values that .br timerfd_gettime (2) on this file descriptor would return.) .re .tp .ir /proc/[pid]/gid_map " (since linux 3.5)" see .br user_namespaces (7). .tp .ir /proc/[pid]/io " (since kernel 2.6.20)" .\" commit 7c3ab7381e79dfc7db14a67c6f4f3285664e1ec2 this file contains i/o statistics for the process, for example: .ip .in +4n .ex .rb "#" " cat /proc/3828/io" rchar: 323934931 wchar: 323929600 syscr: 632687 syscw: 632675 read_bytes: 0 write_bytes: 323932160 cancelled_write_bytes: 0 .ee .in .ip the fields are as follows: .rs .tp .ir rchar ": characters read" the number of bytes which this task has caused to be read from storage. this is simply the sum of bytes which this process passed to .br read (2) and similar system calls. it includes things such as terminal i/o and is unaffected by whether or not actual physical disk i/o was required (the read might have been satisfied from pagecache). .tp .ir wchar ": characters written" the number of bytes which this task has caused, or shall cause to be written to disk. similar caveats apply here as with .ir rchar . .tp .ir syscr ": read syscalls" attempt to count the number of read i/o operations\(emthat is, system calls such as .br read (2) and .br pread (2). .tp .ir syscw ": write syscalls" attempt to count the number of write i/o operations\(emthat is, system calls such as .br write (2) and .br pwrite (2). .tp .ir read_bytes ": bytes read" attempt to count the number of bytes which this process really did cause to be fetched from the storage layer. this is accurate for block-backed filesystems. .tp .ir write_bytes ": bytes written" attempt to count the number of bytes which this process caused to be sent to the storage layer. .tp .ir cancelled_write_bytes : the big inaccuracy here is truncate. if a process writes 1 mb to a file and then deletes the file, it will in fact perform no writeout. but it will have been accounted as having caused 1 mb of write. in other words: this field represents the number of bytes which this process caused to not happen, by truncating pagecache. a task can cause "negative" i/o too. if this task truncates some dirty pagecache, some i/o which another task has been accounted for (in its .ir write_bytes ) will not be happening. .re .ip .ir note : in the current implementation, things are a bit racy on 32-bit systems: if process a reads process b's .i /proc/[pid]/io while process b is updating one of these 64-bit counters, process a could see an intermediate result. .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .ir /proc/[pid]/limits " (since linux 2.6.24)" this file displays the soft limit, hard limit, and units of measurement for each of the process's resource limits (see .br getrlimit (2)). up to and including linux 2.6.35, this file is protected to allow reading only by the real uid of the process. since linux 2.6.36, .\" commit 3036e7b490bf7878c6dae952eec5fb87b1106589 this file is readable by all users on the system. .\" fixme describe /proc/[pid]/loginuid .\" added in 2.6.11; updating requires cap_audit_control .\" config_auditsyscall .tp .ir /proc/[pid]/map_files/ " (since kernel 3.3)" .\" commit 640708a2cff7f81e246243b0073c66e6ece7e53e this subdirectory contains entries corresponding to memory-mapped files (see .br mmap (2)). entries are named by memory region start and end address pair (expressed as hexadecimal numbers), and are symbolic links to the mapped files themselves. here is an example, with the output wrapped and reformatted to fit on an 80-column display: .ip .in +4n .ex .rb "#" " ls \-l /proc/self/map_files/" lr\-\-\-\-\-\-\-\-. 1 root root 64 apr 16 21:31 3252e00000\-3252e20000 \-> /usr/lib64/ld\-2.15.so \&... .ee .in .ip although these entries are present for memory regions that were mapped with the .br map_file flag, the way anonymous shared memory (regions created with the .b map_anon | map_shared flags) is implemented in linux means that such regions also appear on this directory. here is an example where the target file is the deleted .i /dev/zero one: .ip .in +4n .ex lrw\-\-\-\-\-\-\-. 1 root root 64 apr 16 21:33 7fc075d2f000\-7fc075e6f000 \-> /dev/zero (deleted) .ee .in .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .ip until kernel version 4.3, .\" commit bdb4d100afe9818aebd1d98ced575c5ef143456c this directory appeared only if the .b config_checkpoint_restore kernel configuration option was enabled. .ip capabilities are required to read the contents of the symbolic links in this directory: before linux 5.9, the reading process requires .br cap_sys_admin in the initial user namespace; since linux 5.9, the reading process must have either .br cap_sys_admin or .br cap_checkpoint_restore in the user namespace where it resides. .tp .i /proc/[pid]/maps a file containing the currently mapped memory regions and their access permissions. see .br mmap (2) for some further information about memory mappings. .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .ip the format of the file is: .ip .in +4n .ex .i "address perms offset dev inode pathname" 00400000\-00452000 r\-xp 00000000 08:02 173521 /usr/bin/dbus\-daemon 00651000\-00652000 r\-\-p 00051000 08:02 173521 /usr/bin/dbus\-daemon 00652000\-00655000 rw\-p 00052000 08:02 173521 /usr/bin/dbus\-daemon 00e03000\-00e24000 rw\-p 00000000 00:00 0 [heap] 00e24000\-011f7000 rw\-p 00000000 00:00 0 [heap] \&... 35b1800000\-35b1820000 r\-xp 00000000 08:02 135522 /usr/lib64/ld\-2.15.so 35b1a1f000\-35b1a20000 r\-\-p 0001f000 08:02 135522 /usr/lib64/ld\-2.15.so 35b1a20000\-35b1a21000 rw\-p 00020000 08:02 135522 /usr/lib64/ld\-2.15.so 35b1a21000\-35b1a22000 rw\-p 00000000 00:00 0 35b1c00000\-35b1dac000 r\-xp 00000000 08:02 135870 /usr/lib64/libc\-2.15.so 35b1dac000\-35b1fac000 \-\-\-p 001ac000 08:02 135870 /usr/lib64/libc\-2.15.so 35b1fac000\-35b1fb0000 r\-\-p 001ac000 08:02 135870 /usr/lib64/libc\-2.15.so 35b1fb0000\-35b1fb2000 rw\-p 001b0000 08:02 135870 /usr/lib64/libc\-2.15.so \&... f2c6ff8c000\-7f2c7078c000 rw\-p 00000000 00:00 0 [stack:986] \&... 7fffb2c0d000\-7fffb2c2e000 rw\-p 00000000 00:00 0 [stack] 7fffb2d48000\-7fffb2d49000 r\-xp 00000000 00:00 0 [vdso] .ee .in .ip the .i address field is the address space in the process that the mapping occupies. the .i perms field is a set of permissions: .ip .in +4n .ex r = read w = write x = execute s = shared p = private (copy on write) .ee .in .ip the .i offset field is the offset into the file/whatever; .i dev is the device (major:minor); .i inode is the inode on that device. 0 indicates that no inode is associated with the memory region, as would be the case with bss (uninitialized data). .ip the .i pathname field will usually be the file that is backing the mapping. for elf files, you can easily coordinate with the .i offset field by looking at the offset field in the elf program headers .ri ( "readelf\ \-l" ). .ip there are additional helpful pseudo-paths: .rs .tp .ir [stack] the initial process's (also known as the main thread's) stack. .tp .ir [stack:] " (from linux 3.4 to 4.4)" .\" commit b76437579d1344b612cf1851ae610c636cec7db0 (added) .\" commit 65376df582174ffcec9e6471bf5b0dd79ba05e4a (removed) a thread's stack (where the .ir is a thread id). it corresponds to the .ir /proc/[pid]/task/[tid]/ path. this field was removed in linux 4.5, since providing this information for a process with large numbers of threads is expensive. .tp .ir [vdso] the virtual dynamically linked shared object. see .br vdso (7). .tp .ir [heap] the process's heap. .in .re .ip if the .i pathname field is blank, this is an anonymous mapping as obtained via .br mmap (2). there is no easy way to coordinate this back to a process's source, short of running it through .br gdb (1), .br strace (1), or similar. .ip .i pathname is shown unescaped except for newline characters, which are replaced with an octal escape sequence. as a result, it is not possible to determine whether the original pathname contained a newline character or the literal .i \e012 character sequence. .ip if the mapping is file-backed and the file has been deleted, the string " (deleted)" is appended to the pathname. note that this is ambiguous too. .ip under linux 2.0, there is no field giving pathname. .tp .i /proc/[pid]/mem this file can be used to access the pages of a process's memory through .br open (2), .br read (2), and .br lseek (2). .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_attach_fscreds check; see .br ptrace (2). .tp .ir /proc/[pid]/mountinfo " (since linux 2.6.26)" .\" this info adapted from documentation/filesystems/proc.txt .\" commit 2d4d4864ac08caff5c204a752bd004eed4f08760 this file contains information about mounts in the process's mount namespace (see .br mount_namespaces (7)). it supplies various information (e.g., propagation state, root of mount for bind mounts, identifier for each mount and its parent) that is missing from the (older) .ir /proc/[pid]/mounts file, and fixes various other problems with that file (e.g., nonextensibility, failure to distinguish per-mount versus per-superblock options). .ip the file contains lines of the form: .ip .ex 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 \- ext3 /dev/root rw,errors=continue (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) .ee .ip the numbers in parentheses are labels for the descriptions below: .rs 7 .tp 5 (1) mount id: a unique id for the mount (may be reused after .br umount (2)). .tp (2) parent id: the id of the parent mount (or of self for the root of this mount namespace's mount tree). .ip if a new mount is stacked on top of a previous existing mount (so that it hides the existing mount) at pathname p, then the parent of the new mount is the previous mount at that location. thus, when looking at all the mounts stacked at a particular location, the top-most mount is the one that is not the parent of any other mount at the same location. (note, however, that this top-most mount will be accessible only if the longest path subprefix of p that is a mount point is not itself hidden by a stacked mount.) .ip if the parent mount lies outside the process's root directory (see .br chroot (2)), the id shown here won't have a corresponding record in .i mountinfo whose mount id (field 1) matches this parent mount id (because mounts that lie outside the process's root directory are not shown in .ir mountinfo ). as a special case of this point, the process's root mount may have a parent mount (for the initramfs filesystem) that lies .\" miklos szeredi, nov 2017: the hidden one is the initramfs, i believe .\" mtk: in the initial mount namespace, this hidden id has the value 0 outside the process's root directory, and an entry for that mount will not appear in .ir mountinfo . .tp (3) major:minor: the value of .i st_dev for files on this filesystem (see .br stat (2)). .tp (4) root: the pathname of the directory in the filesystem which forms the root of this mount. .tp (5) mount point: the pathname of the mount point relative to the process's root directory. .tp (6) mount options: per-mount options (see .br mount (2)). .tp (7) optional fields: zero or more fields of the form "tag[:value]"; see below. .tp (8) separator: the end of the optional fields is marked by a single hyphen. .tp (9) filesystem type: the filesystem type in the form "type[.subtype]". .tp (10) mount source: filesystem-specific information or "none". .tp (11) super options: per-superblock options (see .br mount (2)). .re .ip currently, the possible optional fields are .ir shared , .ir master , .ir propagate_from , and .ir unbindable . see .br mount_namespaces (7) for a description of these fields. parsers should ignore all unrecognized optional fields. .ip for more information on mount propagation see: .i documentation/filesystems/sharedsubtree.txt in the linux kernel source tree. .tp .ir /proc/[pid]/mounts " (since linux 2.4.19)" this file lists all the filesystems currently mounted in the process's mount namespace (see .br mount_namespaces (7)). the format of this file is documented in .br fstab (5). .ip since kernel version 2.6.15, this file is pollable: after opening the file for reading, a change in this file (i.e., a filesystem mount or unmount) causes .br select (2) to mark the file descriptor as having an exceptional condition, and .br poll (2) and .br epoll_wait (2) mark the file as having a priority event .rb ( pollpri ). (before linux 2.6.30, a change in this file was indicated by the file descriptor being marked as readable for .br select (2), and being marked as having an error condition for .br poll (2) and .br epoll_wait (2).) .tp .ir /proc/[pid]/mountstats " (since linux 2.6.17)" this file exports information (statistics, configuration information) about the mounts in the process's mount namespace (see .br mount_namespaces (7)). lines in this file have the form: .ip .in +4n .ex device /dev/sda7 mounted on /home with fstype ext3 [stats] ( 1 ) ( 2 ) (3 ) ( 4 ) .ee .in .ip the fields in each line are: .rs 7 .tp 5 (1) the name of the mounted device (or "nodevice" if there is no corresponding device). .tp (2) the mount point within the filesystem tree. .tp (3) the filesystem type. .tp (4) optional statistics and configuration information. currently (as at linux 2.6.26), only nfs filesystems export information via this field. .re .ip this file is readable only by the owner of the process. .tp .ir /proc/[pid]/net " (since linux 2.6.25)" see the description of .ir /proc/net . .tp .ir /proc/[pid]/ns/ " (since linux 3.0)" .\" see commit 6b4e306aa3dc94a0545eb9279475b1ab6209a31f this is a subdirectory containing one entry for each namespace that supports being manipulated by .br setns (2). for more information, see .br namespaces (7). .tp .ir /proc/[pid]/numa_maps " (since linux 2.6.14)" see .br numa (7). .tp .ir /proc/[pid]/oom_adj " (since linux 2.6.11)" this file can be used to adjust the score used to select which process should be killed in an out-of-memory (oom) situation. the kernel uses this value for a bit-shift operation of the process's .ir oom_score value: valid values are in the range \-16 to +15, plus the special value \-17, which disables oom-killing altogether for this process. a positive score increases the likelihood of this process being killed by the oom-killer; a negative score decreases the likelihood. .ip the default value for this file is 0; a new process inherits its parent's .i oom_adj setting. a process must be privileged .rb ( cap_sys_resource ) to update this file. .ip since linux 2.6.36, use of this file is deprecated in favor of .ir /proc/[pid]/oom_score_adj . .tp .ir /proc/[pid]/oom_score " (since linux 2.6.11)" .\" see mm/oom_kill.c::badness() in pre 2.6.36 sources .\" see mm/oom_kill.c::oom_badness() after 2.6.36 .\" commit a63d83f427fbce97a6cea0db2e64b0eb8435cd10 this file displays the current score that the kernel gives to this process for the purpose of selecting a process for the oom-killer. a higher score means that the process is more likely to be selected by the oom-killer. the basis for this score is the amount of memory used by the process, with increases (+) or decreases (\-) for factors including: .\" see mm/oom_kill.c::badness() in pre 2.6.36 sources .\" see mm/oom_kill.c::oom_badness() after 2.6.36 .\" commit a63d83f427fbce97a6cea0db2e64b0eb8435cd10 .rs .ip * 2 whether the process is privileged (\-). .\" more precisely, if it has cap_sys_admin or (pre 2.6.36) cap_sys_resource .re .ip before kernel 2.6.36 the following factors were also used in the calculation of oom_score: .rs .ip * 2 whether the process creates a lot of children using .br fork (2) (+); .ip * whether the process has been running a long time, or has used a lot of cpu time (\-); .ip * whether the process has a low nice value (i.e., > 0) (+); and .ip * whether the process is making direct hardware access (\-). .\" more precisely, if it has cap_sys_rawio .re .ip the .i oom_score also reflects the adjustment specified by the .i oom_score_adj or .i oom_adj setting for the process. .tp .ir /proc/[pid]/oom_score_adj " (since linux 2.6.36)" .\" text taken from 3.7 documentation/filesystems/proc.txt this file can be used to adjust the badness heuristic used to select which process gets killed in out-of-memory conditions. .ip the badness heuristic assigns a value to each candidate task ranging from 0 (never kill) to 1000 (always kill) to determine which process is targeted. the units are roughly a proportion along that range of allowed memory the process may allocate from, based on an estimation of its current memory and swap use. for example, if a task is using all allowed memory, its badness score will be 1000. if it is using half of its allowed memory, its score will be 500. .ip there is an additional factor included in the badness score: root processes are given 3% extra memory over other tasks. .ip the amount of "allowed" memory depends on the context in which the oom-killer was called. if it is due to the memory assigned to the allocating task's cpuset being exhausted, the allowed memory represents the set of mems assigned to that cpuset (see .br cpuset (7)). if it is due to a mempolicy's node(s) being exhausted, the allowed memory represents the set of mempolicy nodes. if it is due to a memory limit (or swap limit) being reached, the allowed memory is that configured limit. finally, if it is due to the entire system being out of memory, the allowed memory represents all allocatable resources. .ip the value of .i oom_score_adj is added to the badness score before it is used to determine which task to kill. acceptable values range from \-1000 (oom_score_adj_min) to +1000 (oom_score_adj_max). this allows user space to control the preference for oom-killing, ranging from always preferring a certain task or completely disabling it from oom-killing. the lowest possible value, \-1000, is equivalent to disabling oom-killing entirely for that task, since it will always report a badness score of 0. .ip consequently, it is very simple for user space to define the amount of memory to consider for each task. setting an .i oom_score_adj value of +500, for example, is roughly equivalent to allowing the remainder of tasks sharing the same system, cpuset, mempolicy, or memory controller resources to use at least 50% more memory. a value of \-500, on the other hand, would be roughly equivalent to discounting 50% of the task's allowed memory from being considered as scoring against the task. .ip for backward compatibility with previous kernels, .i /proc/[pid]/oom_adj can still be used to tune the badness score. its value is scaled linearly with .ir oom_score_adj . .ip writing to .ir /proc/[pid]/oom_score_adj or .ir /proc/[pid]/oom_adj will change the other with its scaled value. .ip the .br choom (1) program provides a command-line interface for adjusting the .i oom_score_adj value of a running process or a newly executed command. .tp .ir /proc/[pid]/pagemap " (since linux 2.6.25)" this file shows the mapping of each of the process's virtual pages into physical page frames or swap area. it contains one 64-bit value for each virtual page, with the bits set as follows: .rs .tp 63 if set, the page is present in ram. .tp 62 if set, the page is in swap space .tp 61 (since linux 3.5) the page is a file-mapped page or a shared anonymous page. .tp 60\(en57 (since linux 3.11) zero .\" not quite true; see commit 541c237c0923f567c9c4cabb8a81635baadc713f .tp 56 (since linux 4.2) .\" commit 77bb499bb60f4b79cca7d139c8041662860fcf87 .\" commit 83b4b0bb635eee2b8e075062e4e008d1bc110ed7 the page is exclusively mapped. .tp 55 (since linux 3.11) pte is soft-dirty (see the kernel source file .ir documentation/admin\-guide/mm/soft\-dirty.rst ). .tp 54\(en0 if the page is present in ram (bit 63), then these bits provide the page frame number, which can be used to index .ir /proc/kpageflags and .ir /proc/kpagecount . if the page is present in swap (bit 62), then bits 4\(en0 give the swap type, and bits 54\(en5 encode the swap offset. .re .ip before linux 3.11, bits 60\(en55 were used to encode the base-2 log of the page size. .ip to employ .ir /proc/[pid]/pagemap efficiently, use .ir /proc/[pid]/maps to determine which areas of memory are actually mapped and seek to skip over unmapped regions. .ip the .ir /proc/[pid]/pagemap file is present only if the .b config_proc_page_monitor kernel configuration option is enabled. .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .ir /proc/[pid]/personality " (since linux 2.6.28)" .\" commit 478307230810d7e2a753ed220db9066dfdf88718 this read-only file exposes the process's execution domain, as set by .br personality (2). the value is displayed in hexadecimal notation. .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_attach_fscreds check; see .br ptrace (2). .tp .i /proc/[pid]/root unix and linux support the idea of a per-process root of the filesystem, set by the .br chroot (2) system call. this file is a symbolic link that points to the process's root directory, and behaves in the same way as .ir exe , and .ir fd/* . .ip note however that this file is not merely a symbolic link. it provides the same view of the filesystem (including namespaces and the set of per-process mounts) as the process itself. an example illustrates this point. in one terminal, we start a shell in new user and mount namespaces, and in that shell we create some new mounts: .ip .in +4n .ex $ \fbps1=\(aqsh1# \(aq unshare \-urnm\fp sh1# \fbmount \-t tmpfs tmpfs /etc\fp # mount empty tmpfs at /etc sh1# \fbmount \-\-bind /usr /dev\fp # mount /usr at /dev sh1# \fbecho $$\fp 27123 .ee .in .ip in a second terminal window, in the initial mount namespace, we look at the contents of the corresponding mounts in the initial and new namespaces: .ip .in +4n .ex $ \fbps1=\(aqsh2# \(aq sudo sh\fp sh2# \fbls /etc | wc \-l\fp # in initial ns 309 sh2# \fbls /proc/27123/root/etc | wc \-l\fp # /etc in other ns 0 # the empty tmpfs dir sh2# \fbls /dev | wc \-l\fp # in initial ns 205 sh2# \fbls /proc/27123/root/dev | wc \-l\fp # /dev in other ns 11 # actually bind # mounted to /usr sh2# \fbls /usr | wc \-l\fp # /usr in initial ns 11 .ee .in .ip .\" the following was still true as at kernel 2.6.13 in a multithreaded process, the contents of the .i /proc/[pid]/root symbolic link are not available if the main thread has already terminated (typically by calling .br pthread_exit (3)). .ip permission to dereference or read .rb ( readlink (2)) this symbolic link is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .ir /proc/[pid]/projid_map " (since linux 3.7)" .\" commit f76d207a66c3a53defea67e7d36c3eb1b7d6d61d see .br user_namespaces (7). .tp .ir /proc/[pid]/seccomp " (linux 2.6.12 to 2.6.22)" this file can be used to read and change the process's secure computing (seccomp) mode setting. it contains the value 0 if the process is not in seccomp mode, and 1 if the process is in strict seccomp mode (see .br seccomp (2)). writing 1 to this file places the process irreversibly in strict seccomp mode. (further attempts to write to the file fail with the .b eperm error.) .ip in linux 2.6.23, this file went away, to be replaced by the .br prctl (2) .br pr_get_seccomp and .br pr_set_seccomp operations (and later by .br seccomp (2) and the .i seccomp field in .ir /proc/[pid]/status ). .\" fixme describe /proc/[pid]/sessionid .\" commit 1e0bd7550ea9cf474b1ad4c6ff5729a507f75fdc .\" config_auditsyscall .\" added in 2.6.25; read-only; only readable by real uid .\" .\" fixme describe /proc/[pid]/sched .\" added in 2.6.23 .\" config_sched_debug, and additional fields if config_schedstats .\" displays various scheduling parameters .\" this file can be written, to reset stats .\" the set of fields exposed by this file have changed .\" significantly over time. .\" commit 43ae34cb4cd650d1eb4460a8253a8e747ba052ac .\" .\" fixme describe /proc/[pid]/schedstats and .\" /proc/[pid]/task/[tid]/schedstats .\" added in 2.6.9 .\" config_schedstats .tp .ir /proc/[pid]/setgroups " (since linux 3.19)" see .br user_namespaces (7). .tp .ir /proc/[pid]/smaps " (since linux 2.6.14)" this file shows memory consumption for each of the process's mappings. (the .br pmap (1) command displays similar information, in a form that may be easier for parsing.) for each mapping there is a series of lines such as the following: .ip .in +4n .ex 00400000\-0048a000 r\-xp 00000000 fd:03 960637 /bin/bash size: 552 kb rss: 460 kb pss: 100 kb shared_clean: 452 kb shared_dirty: 0 kb private_clean: 8 kb private_dirty: 0 kb referenced: 460 kb anonymous: 0 kb anonhugepages: 0 kb shmemhugepages: 0 kb shmempmdmapped: 0 kb swap: 0 kb kernelpagesize: 4 kb mmupagesize: 4 kb kernelpagesize: 4 kb mmupagesize: 4 kb locked: 0 kb protectionkey: 0 vmflags: rd ex mr mw me dw .ee .in .ip the first of these lines shows the same information as is displayed for the mapping in .ir /proc/[pid]/maps . the following lines show the size of the mapping, the amount of the mapping that is currently resident in ram ("rss"), the process's proportional share of this mapping ("pss"), the number of clean and dirty shared pages in the mapping, and the number of clean and dirty private pages in the mapping. "referenced" indicates the amount of memory currently marked as referenced or accessed. "anonymous" shows the amount of memory that does not belong to any file. "swap" shows how much would-be-anonymous memory is also used, but out on swap. .ip the "kernelpagesize" line (available since linux 2.6.29) is the page size used by the kernel to back the virtual memory area. this matches the size used by the mmu in the majority of cases. however, one counter-example occurs on ppc64 kernels whereby a kernel using 64 kb as a base page size may still use 4 kb pages for the mmu on older processors. to distinguish the two attributes, the "mmupagesize" line (also available since linux 2.6.29) reports the page size used by the mmu. .ip the "locked" indicates whether the mapping is locked in memory or not. .ip the "protectionkey" line (available since linux 4.9, on x86 only) contains the memory protection key (see .br pkeys (7)) associated with the virtual memory area. this entry is present only if the kernel was built with the .b config_x86_intel_memory_protection_keys configuration option (since linux 4.6). .ip the "vmflags" line (available since linux 3.8) represents the kernel flags associated with the virtual memory area, encoded using the following two-letter codes: .ip rd - readable wr - writable ex - executable sh - shared mr - may read mw - may write me - may execute ms - may share gd - stack segment grows down pf - pure pfn range dw - disabled write to the mapped file lo - pages are locked in memory io - memory mapped i/o area sr - sequential read advise provided rr - random read advise provided dc - do not copy area on fork de - do not expand area on remapping ac - area is accountable nr - swap space is not reserved for the area ht - area uses huge tlb pages sf - perform synchronous page faults (since linux 4.15) nl - non-linear mapping (removed in linux 4.0) ar - architecture specific flag wf - wipe on fork (since linux 4.14) dd - do not include area into core dump sd - soft-dirty flag (since linux 3.13) mm - mixed map area hg - huge page advise flag nh - no-huge page advise flag mg - mergeable advise flag um - userfaultfd missing pages tracking (since linux 4.3) uw - userfaultfd wprotect pages tracking (since linux 4.3) .ip the .ir /proc/[pid]/smaps file is present only if the .b config_proc_page_monitor kernel configuration option is enabled. .tp .ir /proc/[pid]/stack " (since linux 2.6.29)" .\" 2ec220e27f5040aec1e88901c1b6ea3d135787ad this file provides a symbolic trace of the function calls in this process's kernel stack. this file is provided only if the kernel was built with the .b config_stacktrace configuration option. .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_attach_fscreds check; see .br ptrace (2). .tp .i /proc/[pid]/stat status information about the process. this is used by .br ps (1). it is defined in the kernel source file .ir fs/proc/array.c "." .ip the fields, in order, with their proper .br scanf (3) format specifiers, are listed below. whether or not certain of these fields display valid information is governed by a ptrace access mode .br ptrace_mode_read_fscreds " | " ptrace_mode_noaudit check (refer to .br ptrace (2)). if the check denies access, then the field value is displayed as 0. the affected fields are indicated with the marking [pt]. .rs .tp (1) \fipid\fp \ %d .br the process id. .tp (2) \ficomm\fp \ %s the filename of the executable, in parentheses. strings longer than .b task_comm_len (16) characters (including the terminating null byte) are silently truncated. this is visible whether or not the executable is swapped out. .tp (3) \fistate\fp \ %c one of the following characters, indicating process state: .rs .ip r 3 running .ip s sleeping in an interruptible wait .ip d waiting in uninterruptible disk sleep .ip z zombie .ip t stopped (on a signal) or (before linux 2.6.33) trace stopped .ip t .\" commit 44d90df6b757c59651ddd55f1a84f28132b50d29 tracing stop (linux 2.6.33 onward) .ip w paging (only before linux 2.6.0) .ip x dead (from linux 2.6.0 onward) .ip x .\" commit 44d90df6b757c59651ddd55f1a84f28132b50d29 dead (linux 2.6.33 to .\" commit 74e37200de8e9c4e09b70c21c3f13c2071e77457 3.13 only) .ip k .\" commit 44d90df6b757c59651ddd55f1a84f28132b50d29 wakekill (linux 2.6.33 to .\" commit 74e37200de8e9c4e09b70c21c3f13c2071e77457 3.13 only) .ip w .\" commit 44d90df6b757c59651ddd55f1a84f28132b50d29 waking (linux 2.6.33 to .\" commit 74e37200de8e9c4e09b70c21c3f13c2071e77457 3.13 only) .ip p .\" commit f2530dc71cf0822f90bb63ea4600caaef33a66bb parked (linux 3.9 to .\" commit 74e37200de8e9c4e09b70c21c3f13c2071e77457 3.13 only) .re .tp (4) \fippid\fp \ %d the pid of the parent of this process. .tp (5) \fipgrp\fp \ %d the process group id of the process. .tp (6) \fisession\fp \ %d the session id of the process. .tp (7) \fitty_nr\fp \ %d the controlling terminal of the process. (the minor device number is contained in the combination of bits 31 to 20 and 7 to 0; the major device number is in bits 15 to 8.) .tp (8) \fitpgid\fp \ %d .\" this field and following, up to and including wchan added 0.99.1 the id of the foreground process group of the controlling terminal of the process. .tp (9) \fiflags\fp \ %u the kernel flags word of the process. for bit meanings, see the pf_* defines in the linux kernel source file .ir include/linux/sched.h . details depend on the kernel version. .ip the format for this field was %lu before linux 2.6. .tp (10) \fiminflt\fp \ %lu the number of minor faults the process has made which have not required loading a memory page from disk. .tp (11) \ficminflt\fp \ %lu the number of minor faults that the process's waited-for children have made. .tp (12) \fimajflt\fp \ %lu the number of major faults the process has made which have required loading a memory page from disk. .tp (13) \ficmajflt\fp \ %lu the number of major faults that the process's waited-for children have made. .tp (14) \fiutime\fp \ %lu amount of time that this process has been scheduled in user mode, measured in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). this includes guest time, \figuest_time\fp (time spent running a virtual cpu, see below), so that applications that are not aware of the guest time field do not lose that time from their calculations. .tp (15) \fistime\fp \ %lu amount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). .tp (16) \ficutime\fp \ %ld amount of time that this process's waited-for children have been scheduled in user mode, measured in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). (see also .br times (2).) this includes guest time, \ficguest_time\fp (time spent running a virtual cpu, see below). .tp (17) \ficstime\fp \ %ld amount of time that this process's waited-for children have been scheduled in kernel mode, measured in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). .tp (18) \fipriority\fp \ %ld (explanation for linux 2.6) for processes running a real-time scheduling policy .ri ( policy below; see .br sched_setscheduler (2)), this is the negated scheduling priority, minus one; that is, a number in the range \-2 to \-100, corresponding to real-time priorities 1 to 99. for processes running under a non-real-time scheduling policy, this is the raw nice value .rb ( setpriority (2)) as represented in the kernel. the kernel stores nice values as numbers in the range 0 (high) to 39 (low), corresponding to the user-visible nice range of \-20 to 19. .ip before linux 2.6, this was a scaled value based on the scheduler weighting given to this process. .\" and back in kernel 1.2 days things were different again. .tp (19) \finice\fp \ %ld the nice value (see .br setpriority (2)), a value in the range 19 (low priority) to \-20 (high priority). .\" back in kernel 1.2 days things were different. .\" .tp .\" \ficounter\fp %ld .\" the current maximum size in jiffies of the process's next timeslice, .\" or what is currently left of its current timeslice, if it is the .\" currently running process. .\" .tp .\" \fitimeout\fp %u .\" the time in jiffies of the process's next timeout. .\" timeout was removed sometime around 2.1/2.2 .tp (20) \finum_threads\fp \ %ld number of threads in this process (since linux 2.6). before kernel 2.6, this field was hard coded to 0 as a placeholder for an earlier removed field. .tp (21) \fiitrealvalue\fp \ %ld the time in jiffies before the next .b sigalrm is sent to the process due to an interval timer. since kernel 2.6.17, this field is no longer maintained, and is hard coded as 0. .tp (22) \fistarttime\fp \ %llu the time the process started after system boot. in kernels before linux 2.6, this value was expressed in jiffies. since linux 2.6, the value is expressed in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). .ip the format for this field was %lu before linux 2.6. .tp (23) \fivsize\fp \ %lu virtual memory size in bytes. .tp (24) \firss\fp \ %ld resident set size: number of pages the process has in real memory. this is just the pages which count toward text, data, or stack space. this does not include pages which have not been demand-loaded in, or which are swapped out. this value is inaccurate; see .i /proc/[pid]/statm below. .tp (25) \firsslim\fp \ %lu current soft limit in bytes on the rss of the process; see the description of .b rlimit_rss in .br getrlimit (2). .tp (26) \fistartcode\fp \ %lu \ [pt] the address above which program text can run. .tp (27) \fiendcode\fp \ %lu \ [pt] the address below which program text can run. .tp (28) \fistartstack\fp \ %lu \ [pt] the address of the start (i.e., bottom) of the stack. .tp (29) \fikstkesp\fp \ %lu \ [pt] the current value of esp (stack pointer), as found in the kernel stack page for the process. .tp (30) \fikstkeip\fp \ %lu \ [pt] the current eip (instruction pointer). .tp (31) \fisignal\fp \ %lu the bitmap of pending signals, displayed as a decimal number. obsolete, because it does not provide information on real-time signals; use .i /proc/[pid]/status instead. .tp (32) \fiblocked\fp \ %lu the bitmap of blocked signals, displayed as a decimal number. obsolete, because it does not provide information on real-time signals; use .i /proc/[pid]/status instead. .tp (33) \fisigignore\fp \ %lu the bitmap of ignored signals, displayed as a decimal number. obsolete, because it does not provide information on real-time signals; use .i /proc/[pid]/status instead. .tp (34) \fisigcatch\fp \ %lu the bitmap of caught signals, displayed as a decimal number. obsolete, because it does not provide information on real-time signals; use .i /proc/[pid]/status instead. .tp (35) \fiwchan\fp \ %lu \ [pt] this is the "channel" in which the process is waiting. it is the address of a location in the kernel where the process is sleeping. the corresponding symbolic name can be found in .ir /proc/[pid]/wchan . .tp (36) \finswap\fp \ %lu .\" nswap was added in 2.0 number of pages swapped (not maintained). .tp (37) \ficnswap\fp \ %lu .\" cnswap was added in 2.0 cumulative \finswap\fp for child processes (not maintained). .tp (38) \fiexit_signal\fp \ %d \ (since linux 2.1.22) signal to be sent to parent when we die. .tp (39) \fiprocessor\fp \ %d \ (since linux 2.2.8) cpu number last executed on. .tp (40) \firt_priority\fp \ %u \ (since linux 2.5.19) real-time scheduling priority, a number in the range 1 to 99 for processes scheduled under a real-time policy, or 0, for non-real-time processes (see .br sched_setscheduler (2)). .tp (41) \fipolicy\fp \ %u \ (since linux 2.5.19) scheduling policy (see .br sched_setscheduler (2)). decode using the sched_* constants in .ir linux/sched.h . .ip the format for this field was %lu before linux 2.6.22. .tp (42) \fidelayacct_blkio_ticks\fp \ %llu \ (since linux 2.6.18) aggregated block i/o delays, measured in clock ticks (centiseconds). .tp (43) \figuest_time\fp \ %lu \ (since linux 2.6.24) guest time of the process (time spent running a virtual cpu for a guest operating system), measured in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). .tp (44) \ficguest_time\fp \ %ld \ (since linux 2.6.24) guest time of the process's children, measured in clock ticks (divide by .ir sysconf(_sc_clk_tck) ). .tp (45) \fistart_data\fp \ %lu \ (since linux 3.3) \ [pt] .\" commit b3f7f573a20081910e34e99cbc91831f4f02f1ff address above which program initialized and uninitialized (bss) data are placed. .tp (46) \fiend_data\fp \ %lu \ (since linux 3.3) \ [pt] .\" commit b3f7f573a20081910e34e99cbc91831f4f02f1ff address below which program initialized and uninitialized (bss) data are placed. .tp (47) \fistart_brk\fp \ %lu \ (since linux 3.3) \ [pt] .\" commit b3f7f573a20081910e34e99cbc91831f4f02f1ff address above which program heap can be expanded with .br brk (2). .tp (48) \fiarg_start\fp \ %lu \ (since linux 3.5) \ [pt] .\" commit 5b172087f99189416d5f47fd7ab5e6fb762a9ba3 address above which program command-line arguments .ri ( argv ) are placed. .tp (49) \fiarg_end\fp \ %lu \ (since linux 3.5) \ [pt] .\" commit 5b172087f99189416d5f47fd7ab5e6fb762a9ba3 address below program command-line arguments .ri ( argv ) are placed. .tp (50) \fienv_start\fp \ %lu \ (since linux 3.5) \ [pt] .\" commit 5b172087f99189416d5f47fd7ab5e6fb762a9ba3 address above which program environment is placed. .tp (51) \fienv_end\fp \ %lu \ (since linux 3.5) \ [pt] .\" commit 5b172087f99189416d5f47fd7ab5e6fb762a9ba3 address below which program environment is placed. .tp (52) \fiexit_code\fp \ %d \ (since linux 3.5) \ [pt] .\" commit 5b172087f99189416d5f47fd7ab5e6fb762a9ba3 the thread's exit status in the form reported by .br waitpid (2). .re .tp .i /proc/[pid]/statm provides information about memory usage, measured in pages. the columns are: .ip .in +4n .ex size (1) total program size (same as vmsize in \fi/proc/[pid]/status\fp) resident (2) resident set size (inaccurate; same as vmrss in \fi/proc/[pid]/status\fp) shared (3) number of resident shared pages (i.e., backed by a file) (inaccurate; same as rssfile+rssshmem in \fi/proc/[pid]/status\fp) text (4) text (code) .\" (not including libs; broken, includes data segment) lib (5) library (unused since linux 2.6; always 0) data (6) data + stack .\" (including libs; broken, includes library text) dt (7) dirty pages (unused since linux 2.6; always 0) .ee .in .ip .\" see split_rss_counting in the kernel. .\" inaccuracy is bounded by task_rss_events_thresh. some of these values are inaccurate because of a kernel-internal scalability optimization. if accurate values are required, use .i /proc/[pid]/smaps or .i /proc/[pid]/smaps_rollup instead, which are much slower but provide accurate, detailed information. .tp .i /proc/[pid]/status provides much of the information in .i /proc/[pid]/stat and .i /proc/[pid]/statm in a format that's easier for humans to parse. here's an example: .ip .in +4n .ex .rb "$" " cat /proc/$$/status" name: bash umask: 0022 state: s (sleeping) tgid: 17248 ngid: 0 pid: 17248 ppid: 17200 tracerpid: 0 uid: 1000 1000 1000 1000 gid: 100 100 100 100 fdsize: 256 groups: 16 33 100 nstgid: 17248 nspid: 17248 nspgid: 17248 nssid: 17200 vmpeak: 131168 kb vmsize: 131168 kb vmlck: 0 kb vmpin: 0 kb vmhwm: 13484 kb vmrss: 13484 kb rssanon: 10264 kb rssfile: 3220 kb rssshmem: 0 kb vmdata: 10332 kb vmstk: 136 kb vmexe: 992 kb vmlib: 2104 kb vmpte: 76 kb vmpmd: 12 kb vmswap: 0 kb hugetlbpages: 0 kb # 4.4 coredumping: 0 # 4.15 threads: 1 sigq: 0/3067 sigpnd: 0000000000000000 shdpnd: 0000000000000000 sigblk: 0000000000010000 sigign: 0000000000384004 sigcgt: 000000004b813efb capinh: 0000000000000000 capprm: 0000000000000000 capeff: 0000000000000000 capbnd: ffffffffffffffff capamb: 0000000000000000 nonewprivs: 0 seccomp: 0 speculation_store_bypass: vulnerable cpus_allowed: 00000001 cpus_allowed_list: 0 mems_allowed: 1 mems_allowed_list: 0 voluntary_ctxt_switches: 150 nonvoluntary_ctxt_switches: 545 .ee .in .ip the fields are as follows: .rs .tp .ir name command run by this process. strings longer than .b task_comm_len (16) characters (including the terminating null byte) are silently truncated. .tp .ir umask process umask, expressed in octal with a leading zero; see .br umask (2). (since linux 4.7.) .tp .ir state current state of the process. one of "r (running)", "s (sleeping)", "d (disk sleep)", "t (stopped)", "t (tracing stop)", "z (zombie)", or "x (dead)". .tp .ir tgid thread group id (i.e., process id). .tp .ir ngid numa group id (0 if none; since linux 3.13). .tp .ir pid thread id (see .br gettid (2)). .tp .ir ppid pid of parent process. .tp .ir tracerpid pid of process tracing this process (0 if not being traced). .tp .ir uid ", " gid real, effective, saved set, and filesystem uids (gids). .tp .ir fdsize number of file descriptor slots currently allocated. .tp .ir groups supplementary group list. .tp .ir nstgid thread group id (i.e., pid) in each of the pid namespaces of which .i [pid] is a member. the leftmost entry shows the value with respect to the pid namespace of the process that mounted this procfs (or the root namespace if mounted by the kernel), followed by the value in successively nested inner namespaces. .\" commit e4bc33245124db69b74a6d853ac76c2976f472d5 (since linux 4.1.) .tp .ir nspid thread id in each of the pid namespaces of which .i [pid] is a member. the fields are ordered as for .ir nstgid . (since linux 4.1.) .tp .ir nspgid process group id in each of the pid namespaces of which .i [pid] is a member. the fields are ordered as for .ir nstgid . (since linux 4.1.) .tp .ir nssid descendant namespace session id hierarchy session id in each of the pid namespaces of which .i [pid] is a member. the fields are ordered as for .ir nstgid . (since linux 4.1.) .tp .ir vmpeak peak virtual memory size. .tp .ir vmsize virtual memory size. .tp .ir vmlck locked memory size (see .br mlock (2)). .tp .ir vmpin pinned memory size .\" commit bc3e53f682d93df677dbd5006a404722b3adfe18 (since linux 3.2). these are pages that can't be moved because something needs to directly access physical memory. .tp .ir vmhwm peak resident set size ("high water mark"). this value is inaccurate; see .i /proc/[pid]/statm above. .tp .ir vmrss resident set size. note that the value here is the sum of .ir rssanon , .ir rssfile , and .ir rssshmem . this value is inaccurate; see .i /proc/[pid]/statm above. .tp .ir rssanon size of resident anonymous memory. .\" commit bf9683d6990589390b5178dafe8fd06808869293 (since linux 4.5). this value is inaccurate; see .i /proc/[pid]/statm above. .tp .ir rssfile size of resident file mappings. .\" commit bf9683d6990589390b5178dafe8fd06808869293 (since linux 4.5). this value is inaccurate; see .i /proc/[pid]/statm above. .tp .ir rssshmem size of resident shared memory (includes system v shared memory, mappings from .br tmpfs (5), and shared anonymous mappings). .\" commit bf9683d6990589390b5178dafe8fd06808869293 (since linux 4.5). .tp .ir vmdata ", " vmstk ", " vmexe size of data, stack, and text segments. this value is inaccurate; see .i /proc/[pid]/statm above. .tp .ir vmlib shared library code size. .tp .ir vmpte page table entries size (since linux 2.6.10). .tp .ir vmpmd .\" commit dc6c9a35b66b520cf67e05d8ca60ebecad3b0479 size of second-level page tables (added in linux 4.0; removed in linux 4.15). .tp .ir vmswap .\" commit b084d4353ff99d824d3bc5a5c2c22c70b1fba722 swapped-out virtual memory size by anonymous private pages; shmem swap usage is not included (since linux 2.6.34). this value is inaccurate; see .i /proc/[pid]/statm above. .tp .ir hugetlbpages size of hugetlb memory portions .\" commit 5d317b2b6536592a9b51fe65faed43d65ca9158e (since linux 4.4). .tp .ir coredumping contains the value 1 if the process is currently dumping core, and 0 if it is not .\" commit c643401218be0f4ab3522e0c0a63016596d6e9ca (since linux 4.15). this information can be used by a monitoring process to avoid killing a process that is currently dumping core, which could result in a corrupted core dump file. .tp .ir threads number of threads in process containing this thread. .tp .ir sigq this field contains two slash-separated numbers that relate to queued signals for the real user id of this process. the first of these is the number of currently queued signals for this real user id, and the second is the resource limit on the number of queued signals for this process (see the description of .br rlimit_sigpending in .br getrlimit (2)). .tp .ir sigpnd ", " shdpnd mask (expressed in hexadecimal) of signals pending for thread and for process as a whole (see .br pthreads (7) and .br signal (7)). .tp .ir sigblk ", " sigign ", " sigcgt masks (expressed in hexadecimal) indicating signals being blocked, ignored, and caught (see .br signal (7)). .tp .ir capinh ", " capprm ", " capeff masks (expressed in hexadecimal) of capabilities enabled in inheritable, permitted, and effective sets (see .br capabilities (7)). .tp .ir capbnd capability bounding set, expressed in hexadecimal (since linux 2.6.26, see .br capabilities (7)). .tp .ir capamb ambient capability set, expressed in hexadecimal (since linux 4.3, see .br capabilities (7)). .tp .ir nonewprivs .\" commit af884cd4a5ae62fcf5e321fecf0ec1014730353d value of the .i no_new_privs bit (since linux 4.10, see .br prctl (2)). .tp .ir seccomp .\" commit 2f4b3bf6b2318cfaa177ec5a802f4d8d6afbd816 seccomp mode of the process (since linux 3.8, see .br seccomp (2)). 0 means .br seccomp_mode_disabled ; 1 means .br seccomp_mode_strict ; 2 means .br seccomp_mode_filter . this field is provided only if the kernel was built with the .br config_seccomp kernel configuration option enabled. .tp .ir speculation_store_bypass .\" commit fae1fa0fc6cca8beee3ab8ed71d54f9a78fa3f64 speculation flaw mitigation state (since linux 4.17, see .br prctl (2)). .tp .ir cpus_allowed hexadecimal mask of cpus on which this process may run (since linux 2.6.24, see .br cpuset (7)). .tp .ir cpus_allowed_list same as previous, but in "list format" (since linux 2.6.26, see .br cpuset (7)). .tp .ir mems_allowed mask of memory nodes allowed to this process (since linux 2.6.24, see .br cpuset (7)). .tp .ir mems_allowed_list same as previous, but in "list format" (since linux 2.6.26, see .br cpuset (7)). .tp .ir voluntary_ctxt_switches ", " nonvoluntary_ctxt_switches number of voluntary and involuntary context switches (since linux 2.6.23). .re .tp .ir /proc/[pid]/syscall " (since linux 2.6.27)" .\" commit ebcb67341fee34061430f3367f2e507e52ee051b this file exposes the system call number and argument registers for the system call currently being executed by the process, followed by the values of the stack pointer and program counter registers. the values of all six argument registers are exposed, although most system calls use fewer registers. .ip if the process is blocked, but not in a system call, then the file displays \-1 in place of the system call number, followed by just the values of the stack pointer and program counter. if process is not blocked, then the file contains just the string "running". .ip this file is present only if the kernel was configured with .br config_have_arch_tracehook . .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_attach_fscreds check; see .br ptrace (2). .tp .ir /proc/[pid]/task " (since linux 2.6.0)" .\" precisely: linux 2.6.0-test6 this is a directory that contains one subdirectory for each thread in the process. the name of each subdirectory is the numerical thread id .ri ( [tid] ) of the thread (see .br gettid (2)). .ip within each of these subdirectories, there is a set of files with the same names and contents as under the .i /proc/[pid] directories. for attributes that are shared by all threads, the contents for each of the files under the .i task/[tid] subdirectories will be the same as in the corresponding file in the parent .i /proc/[pid] directory (e.g., in a multithreaded process, all of the .i task/[tid]/cwd files will have the same value as the .i /proc/[pid]/cwd file in the parent directory, since all of the threads in a process share a working directory). for attributes that are distinct for each thread, the corresponding files under .i task/[tid] may have different values (e.g., various fields in each of the .i task/[tid]/status files may be different for each thread), .\" in particular: "children" :/ or they might not exist in .i /proc/[pid] at all. .ip .\" the following was still true as at kernel 2.6.13 in a multithreaded process, the contents of the .i /proc/[pid]/task directory are not available if the main thread has already terminated (typically by calling .br pthread_exit (3)). .tp .ir /proc/[pid]/task/[tid]/children " (since linux 3.5)" .\" commit 818411616baf46ceba0cff6f05af3a9b294734f7 a space-separated list of child tasks of this task. each child task is represented by its tid. .ip .\" see comments in get_children_pid() in fs/proc/array.c this option is intended for use by the checkpoint-restore (criu) system, and reliably provides a list of children only if all of the child processes are stopped or frozen. it does not work properly if children of the target task exit while the file is being read! exiting children may cause non-exiting children to be omitted from the list. this makes this interface even more unreliable than classic pid-based approaches if the inspected task and its children aren't frozen, and most code should probably not use this interface. .ip until linux 4.2, the presence of this file was governed by the .b config_checkpoint_restore kernel configuration option. since linux 4.2, .\" commit 2e13ba54a2682eea24918b87ad3edf70c2cf085b it is governed by the .b config_proc_children option. .tp .ir /proc/[pid]/timers " (since linux 3.10)" .\" commit 5ed67f05f66c41e39880a6d61358438a25f9fee5 .\" commit 48f6a7a511ef8823fdff39afee0320092d43a8a0 a list of the posix timers for this process. each timer is listed with a line that starts with the string "id:". for example: .ip .in +4n .ex id: 1 signal: 60/00007fff86e452a8 notify: signal/pid.2634 clockid: 0 id: 0 signal: 60/00007fff86e452a8 notify: signal/pid.2634 clockid: 1 .ee .in .ip the lines shown for each timer have the following meanings: .rs .tp .i id the id for this timer. this is not the same as the timer id returned by .br timer_create (2); rather, it is the same kernel-internal id that is available via the .i si_timerid field of the .ir siginfo_t structure (see .br sigaction (2)). .tp .i signal this is the signal number that this timer uses to deliver notifications followed by a slash, and then the .i sigev_value value supplied to the signal handler. valid only for timers that notify via a signal. .tp .i notify the part before the slash specifies the mechanism that this timer uses to deliver notifications, and is one of "thread", "signal", or "none". immediately following the slash is either the string "tid" for timers with .b sigev_thread_id notification, or "pid" for timers that notify by other mechanisms. following the "." is the pid of the process (or the kernel thread id of the thread) that will be delivered a signal if the timer delivers notifications via a signal. .tp .i clockid this field identifies the clock that the timer uses for measuring time. for most clocks, this is a number that matches one of the user-space .br clock_* constants exposed via .ir . .b clock_process_cputime_id timers display with a value of \-6 in this field. .b clock_thread_cputime_id timers display with a value of \-2 in this field. .re .ip this file is available only when the kernel was configured with .br config_checkpoint_restore . .tp .ir /proc/[pid]/timerslack_ns " (since linux 4.6)" .\" commit da8b44d5a9f8bf26da637b7336508ca534d6b319 .\" commit 5de23d435e88996b1efe0e2cebe242074ce67c9e this file exposes the process's "current" timer slack value, expressed in nanoseconds. the file is writable, allowing the process's timer slack value to be changed. writing 0 to this file resets the "current" timer slack to the "default" timer slack value. for further details, see the discussion of .br pr_set_timerslack in .br prctl (2). .ip initially, permission to access this file was governed by a ptrace access mode .b ptrace_mode_attach_fscreds check (see .br ptrace (2)). however, this was subsequently deemed too strict a requirement (and had the side effect that requiring a process to have the .b cap_sys_ptrace capability would also allow it to view and change any process's memory). therefore, since linux 4.9, .\" commit 7abbaf94049914f074306d960b0f968ffe52e59f only the (weaker) .b cap_sys_nice capability is required to access this file. .tp .ir /proc/[pid]/uid_map " (since linux 3.5)" see .br user_namespaces (7). .tp .ir /proc/[pid]/wchan " (since linux 2.6.0)" the symbolic name corresponding to the location in the kernel where the process is sleeping. .ip permission to access this file is governed by a ptrace access mode .b ptrace_mode_read_fscreds check; see .br ptrace (2). .tp .ir /proc/[tid] there is a numerical subdirectory for each running thread that is not a thread group leader (i.e., a thread whose thread id is not the same as its process id); the subdirectory is named by the thread id. each one of these subdirectories contains files and subdirectories exposing information about the thread with the thread id .ir tid . the contents of these directories are the same as the corresponding .ir /proc/[pid]/task/[tid] directories. .ip the .i /proc/[tid] subdirectories are .i not visible when iterating through .i /proc with .br getdents (2) (and thus are .i not visible when one uses .br ls (1) to view the contents of .ir /proc ). however, the pathnames of these directories are visible to (i.e., usable as arguments in) system calls that operate on pathnames. .tp .i /proc/apm advanced power management version and battery information when .b config_apm is defined at kernel compilation time. .tp .i /proc/buddyinfo this file contains information which is used for diagnosing memory fragmentation issues. each line starts with the identification of the node and the name of the zone which together identify a memory region. this is then followed by the count of available chunks of a certain order in which these zones are split. the size in bytes of a certain order is given by the formula: .ip (2^order)\ *\ page_size .ip the binary buddy allocator algorithm inside the kernel will split one chunk into two chunks of a smaller order (thus with half the size) or combine two contiguous chunks into one larger chunk of a higher order (thus with double the size) to satisfy allocation requests and to counter memory fragmentation. the order matches the column number, when starting to count at zero. .ip for example on an x86-64 system: .rs -12 .ex node 0, zone dma 1 1 1 0 2 1 1 0 1 1 3 node 0, zone dma32 65 47 4 81 52 28 13 10 5 1 404 node 0, zone normal 216 55 189 101 84 38 37 27 5 3 587 .ee .re .ip in this example, there is one node containing three zones and there are 11 different chunk sizes. if the page size is 4 kilobytes, then the first zone called .i dma (on x86 the first 16 megabyte of memory) has 1 chunk of 4 kilobytes (order 0) available and has 3 chunks of 4 megabytes (order 10) available. .ip if the memory is heavily fragmented, the counters for higher order chunks will be zero and allocation of large contiguous areas will fail. .ip further information about the zones can be found in .ir /proc/zoneinfo . .tp .i /proc/bus contains subdirectories for installed busses. .tp .i /proc/bus/pccard subdirectory for pcmcia devices when .b config_pcmcia is set at kernel compilation time. .tp .i /proc/bus/pccard/drivers .tp .i /proc/bus/pci contains various bus subdirectories and pseudo-files containing information about pci busses, installed devices, and device drivers. some of these files are not ascii. .tp .i /proc/bus/pci/devices information about pci devices. they may be accessed through .br lspci (8) and .br setpci (8). .tp .ir /proc/cgroups " (since linux 2.6.24)" see .br cgroups (7). .tp .i /proc/cmdline arguments passed to the linux kernel at boot time. often done via a boot manager such as .br lilo (8) or .br grub (8). .tp .ir /proc/config.gz " (since linux 2.6)" this file exposes the configuration options that were used to build the currently running kernel, in the same format as they would be shown in the .i .config file that resulted when configuring the kernel (using .ir "make xconfig" , .ir "make config" , or similar). the file contents are compressed; view or search them using .br zcat (1) and .br zgrep (1). as long as no changes have been made to the following file, the contents of .i /proc/config.gz are the same as those provided by: .ip .in +4n .ex cat /lib/modules/$(uname \-r)/build/.config .ee .in .ip .i /proc/config.gz is provided only if the kernel is configured with .br config_ikconfig_proc . .tp .i /proc/crypto a list of the ciphers provided by the kernel crypto api. for details, see the kernel .i "linux kernel crypto api" documentation available under the kernel source directory .i documentation/crypto/ .\" commit 3b72c814a8e8cd638e1ba0da4dfce501e9dff5af (or .i documentation/docbook before 4.10; the documentation can be built using a command such as .ir "make htmldocs" in the root directory of the kernel source tree). .tp .i /proc/cpuinfo this is a collection of cpu and system architecture dependent items, for each supported architecture a different list. two common entries are \fiprocessor\fp which gives cpu number and \fibogomips\fp; a system constant that is calculated during kernel initialization. smp machines have information for each cpu. the .br lscpu (1) command gathers its information from this file. .tp .i /proc/devices text listing of major numbers and device groups. this can be used by makedev scripts for consistency with the kernel. .tp .ir /proc/diskstats " (since linux 2.5.69)" this file contains disk i/o statistics for each disk device. see the linux kernel source file .i documentation/iostats.txt for further information. .tp .i /proc/dma this is a list of the registered \fiisa\fp dma (direct memory access) channels in use. .tp .i /proc/driver empty subdirectory. .tp .i /proc/execdomains list of the execution domains (abi personalities). .tp .i /proc/fb frame buffer information when .b config_fb is defined during kernel compilation. .tp .i /proc/filesystems a text listing of the filesystems which are supported by the kernel, namely filesystems which were compiled into the kernel or whose kernel modules are currently loaded. (see also .br filesystems (5).) if a filesystem is marked with "nodev", this means that it does not require a block device to be mounted (e.g., virtual filesystem, network filesystem). .ip incidentally, this file may be used by .br mount (8) when no filesystem is specified and it didn't manage to determine the filesystem type. then filesystems contained in this file are tried (excepted those that are marked with "nodev"). .tp .i /proc/fs .\" fixme much more needs to be said about /proc/fs .\" contains subdirectories that in turn contain files with information about (certain) mounted filesystems. .tp .i /proc/ide this directory exists on systems with the ide bus. there are directories for each ide channel and attached device. files include: .ip .in +4n .ex cache buffer size in kb capacity number of sectors driver driver version geometry physical and logical geometry identify in hexadecimal media media type model manufacturer\(aqs model number settings drive settings smart_thresholds ide disk management thresholds (in hex) smart_values ide disk management values (in hex) .ee .in .ip the .br hdparm (8) utility provides access to this information in a friendly format. .tp .i /proc/interrupts this is used to record the number of interrupts per cpu per io device. since linux 2.6.24, for the i386 and x86-64 architectures, at least, this also includes interrupts internal to the system (that is, not associated with a device as such), such as nmi (nonmaskable interrupt), loc (local timer interrupt), and for smp systems, tlb (tlb flush interrupt), res (rescheduling interrupt), cal (remote function call interrupt), and possibly others. very easy to read formatting, done in ascii. .tp .i /proc/iomem i/o memory map in linux 2.4. .tp .i /proc/ioports this is a list of currently registered input-output port regions that are in use. .tp .ir /proc/kallsyms " (since linux 2.5.71)" this holds the kernel exported symbol definitions used by the .br modules (x) tools to dynamically link and bind loadable modules. in linux 2.5.47 and earlier, a similar file with slightly different syntax was named .ir ksyms . .tp .i /proc/kcore this file represents the physical memory of the system and is stored in the elf core file format. with this pseudo-file, and an unstripped kernel .ri ( /usr/src/linux/vmlinux ) binary, gdb can be used to examine the current state of any kernel data structures. .ip the total length of the file is the size of physical memory (ram) plus 4\ kib. .tp .ir /proc/keys " (since linux 2.6.10)" see .br keyrings (7). .tp .ir /proc/key\-users " (since linux 2.6.10)" see .br keyrings (7). .tp .i /proc/kmsg this file can be used instead of the .br syslog (2) system call to read kernel messages. a process must have superuser privileges to read this file, and only one process should read this file. this file should not be read if a syslog process is running which uses the .br syslog (2) system call facility to log kernel messages. .ip information in this file is retrieved with the .br dmesg (1) program. .tp .ir /proc/kpagecgroup " (since linux 4.3)" .\" commit 80ae2fdceba8313b0433f899bdd9c6c463291a17 this file contains a 64-bit inode number of the memory cgroup each page is charged to, indexed by page frame number (see the discussion of .ir /proc/[pid]/pagemap ). .ip the .ir /proc/kpagecgroup file is present only if the .b config_memcg kernel configuration option is enabled. .tp .ir /proc/kpagecount " (since linux 2.6.25)" this file contains a 64-bit count of the number of times each physical page frame is mapped, indexed by page frame number (see the discussion of .ir /proc/[pid]/pagemap ). .ip the .ir /proc/kpagecount file is present only if the .b config_proc_page_monitor kernel configuration option is enabled. .tp .ir /proc/kpageflags " (since linux 2.6.25)" this file contains 64-bit masks corresponding to each physical page frame; it is indexed by page frame number (see the discussion of .ir /proc/[pid]/pagemap ). the bits are as follows: .ip 0 - kpf_locked 1 - kpf_error 2 - kpf_referenced 3 - kpf_uptodate 4 - kpf_dirty 5 - kpf_lru 6 - kpf_active 7 - kpf_slab 8 - kpf_writeback 9 - kpf_reclaim 10 - kpf_buddy 11 - kpf_mmap (since linux 2.6.31) 12 - kpf_anon (since linux 2.6.31) 13 - kpf_swapcache (since linux 2.6.31) 14 - kpf_swapbacked (since linux 2.6.31) 15 - kpf_compound_head (since linux 2.6.31) 16 - kpf_compound_tail (since linux 2.6.31) 17 - kpf_huge (since linux 2.6.31) 18 - kpf_unevictable (since linux 2.6.31) 19 - kpf_hwpoison (since linux 2.6.31) 20 - kpf_nopage (since linux 2.6.31) 21 - kpf_ksm (since linux 2.6.32) 22 - kpf_thp (since linux 3.4) 23 - kpf_balloon (since linux 3.18) .\" kpf_balloon: commit 09316c09dde33aae14f34489d9e3d243ec0d5938 24 - kpf_zero_page (since linux 4.0) .\" kpf_zero_page: commit 56873f43abdcd574b25105867a990f067747b2f4 25 - kpf_idle (since linux 4.3) .\" kpf_idle: commit f074a8f49eb87cde95ac9d040ad5e7ea4f029738 .ip for further details on the meanings of these bits, see the kernel source file .ir documentation/admin\-guide/mm/pagemap.rst . before kernel 2.6.29, .\" commit ad3bdefe877afb47480418fdb05ecd42842de65e .\" commit e07a4b9217d1e97d2f3a62b6b070efdc61212110 .br kpf_writeback , .br kpf_reclaim , .br kpf_buddy , and .br kpf_locked did not report correctly. .ip the .ir /proc/kpageflags file is present only if the .b config_proc_page_monitor kernel configuration option is enabled. .tp .ir /proc/ksyms " (linux 1.1.23\(en2.5.47)" see .ir /proc/kallsyms . .tp .i /proc/loadavg the first three fields in this file are load average figures giving the number of jobs in the run queue (state r) or waiting for disk i/o (state d) averaged over 1, 5, and 15 minutes. they are the same as the load average numbers given by .br uptime (1) and other programs. the fourth field consists of two numbers separated by a slash (/). the first of these is the number of currently runnable kernel scheduling entities (processes, threads). the value after the slash is the number of kernel scheduling entities that currently exist on the system. the fifth field is the pid of the process that was most recently created on the system. .tp .i /proc/locks this file shows current file locks .rb ( flock "(2) and " fcntl (2)) and leases .rb ( fcntl (2)). .ip an example of the content shown in this file is the following: .ip .in +4n .ex 1: posix advisory read 5433 08:01:7864448 128 128 2: flock advisory write 2001 08:01:7864554 0 eof 3: flock advisory write 1568 00:2f:32388 0 eof 4: posix advisory write 699 00:16:28457 0 eof 5: posix advisory write 764 00:16:21448 0 0 6: posix advisory read 3548 08:01:7867240 1 1 7: posix advisory read 3548 08:01:7865567 1826 2335 8: ofdlck advisory write \-1 08:01:8713209 128 191 .ee .in .ip the fields shown in each line are as follows: .rs .ip (1) 4 the ordinal position of the lock in the list. .ip (2) the lock type. values that may appear here include: .rs .tp .b flock this is a bsd file lock created using .br flock (2). .tp .b ofdlck this is an open file description (ofd) lock created using .br fcntl (2). .tp .b posix this is a posix byte-range lock created using .br fcntl (2). .re .ip (3) among the strings that can appear here are the following: .rs .tp .b advisory this is an advisory lock. .tp .b mandatory this is a mandatory lock. .re .ip (4) the type of lock. values that can appear here are: .rs .tp .b read this is a posix or ofd read lock, or a bsd shared lock. .tp .b write this is a posix or ofd write lock, or a bsd exclusive lock. .re .ip (5) the pid of the process that owns the lock. .ip because ofd locks are not owned by a single process (since multiple processes may have file descriptors that refer to the same open file description), the value \-1 is displayed in this field for ofd locks. (before kernel 4.14, .\" commit 9d5b86ac13c573795525ecac6ed2db39ab23e2a8 a bug meant that the pid of the process that initially acquired the lock was displayed instead of the value \-1.) .ip (6) three colon-separated subfields that identify the major and minor device id of the device containing the filesystem where the locked file resides, followed by the inode number of the locked file. .ip (7) the byte offset of the first byte of the lock. for bsd locks, this value is always 0. .ip (8) the byte offset of the last byte of the lock. .b eof in this field means that the lock extends to the end of the file. for bsd locks, the value shown is always .ir eof . .re .ip since linux 4.9, .\" commit d67fd44f697dff293d7cdc29af929241b669affe the list of locks shown in .i /proc/locks is filtered to show just the locks for the processes in the pid namespace (see .br pid_namespaces (7)) for which the .i /proc filesystem was mounted. (in the initial pid namespace, there is no filtering of the records shown in this file.) .ip the .br lslocks (8) command provides a bit more information about each lock. .tp .ir /proc/malloc " (only up to and including linux 2.2)" .\" it looks like this only ever did something back in 1.0 days this file is present only if .b config_debug_malloc was defined during compilation. .tp .i /proc/meminfo this file reports statistics about memory usage on the system. it is used by .br free (1) to report the amount of free and used memory (both physical and swap) on the system as well as the shared memory and buffers used by the kernel. each line of the file consists of a parameter name, followed by a colon, the value of the parameter, and an option unit of measurement (e.g., "kb"). the list below describes the parameter names and the format specifier required to read the field value. except as noted below, all of the fields have been present since at least linux 2.6.0. some fields are displayed only if the kernel was configured with various options; those dependencies are noted in the list. .rs .tp .ir memtotal " %lu" total usable ram (i.e., physical ram minus a few reserved bits and the kernel binary code). .tp .ir memfree " %lu" the sum of .ir lowfree + highfree . .tp .ir memavailable " %lu (since linux 3.14)" an estimate of how much memory is available for starting new applications, without swapping. .tp .ir buffers " %lu" relatively temporary storage for raw disk blocks that shouldn't get tremendously large (20 mb or so). .tp .ir cached " %lu" in-memory cache for files read from the disk (the page cache). doesn't include .ir swapcached . .tp .ir swapcached " %lu" memory that once was swapped out, is swapped back in but still also is in the swap file. (if memory pressure is high, these pages don't need to be swapped out again because they are already in the swap file. this saves i/o.) .tp .ir active " %lu" memory that has been used more recently and usually not reclaimed unless absolutely necessary. .tp .ir inactive " %lu" memory which has been less recently used. it is more eligible to be reclaimed for other purposes. .tp .ir active(anon) " %lu (since linux 2.6.28)" [to be documented.] .tp .ir inactive(anon) " %lu (since linux 2.6.28)" [to be documented.] .tp .ir active(file) " %lu (since linux 2.6.28)" [to be documented.] .tp .ir inactive(file) " %lu (since linux 2.6.28)" [to be documented.] .tp .ir unevictable " %lu (since linux 2.6.28)" (from linux 2.6.28 to 2.6.30, \fbconfig_unevictable_lru\fp was required.) [to be documented.] .tp .ir mlocked " %lu (since linux 2.6.28)" (from linux 2.6.28 to 2.6.30, \fbconfig_unevictable_lru\fp was required.) [to be documented.] .tp .ir hightotal " %lu" (starting with linux 2.6.19, \fbconfig_highmem\fp is required.) total amount of highmem. highmem is all memory above \(ti860 mb of physical memory. highmem areas are for use by user-space programs, or for the page cache. the kernel must use tricks to access this memory, making it slower to access than lowmem. .tp .ir highfree " %lu" (starting with linux 2.6.19, \fbconfig_highmem\fp is required.) amount of free highmem. .tp .ir lowtotal " %lu" (starting with linux 2.6.19, \fbconfig_highmem\fp is required.) total amount of lowmem. lowmem is memory which can be used for everything that highmem can be used for, but it is also available for the kernel's use for its own data structures. among many other things, it is where everything from .i slab is allocated. bad things happen when you're out of lowmem. .tp .ir lowfree " %lu" (starting with linux 2.6.19, \fbconfig_highmem\fp is required.) amount of free lowmem. .tp .ir mmapcopy " %lu (since linux 2.6.29)" .rb ( config_mmu is required.) [to be documented.] .tp .ir swaptotal " %lu" total amount of swap space available. .tp .ir swapfree " %lu" amount of swap space that is currently unused. .tp .ir dirty " %lu" memory which is waiting to get written back to the disk. .tp .ir writeback " %lu" memory which is actively being written back to the disk. .tp .ir anonpages " %lu (since linux 2.6.18)" non-file backed pages mapped into user-space page tables. .tp .ir mapped " %lu" files which have been mapped into memory (with .br mmap (2)), such as libraries. .tp .ir shmem " %lu (since linux 2.6.32)" amount of memory consumed in .br tmpfs (5) filesystems. .tp .ir kreclaimable " %lu (since linux 4.20)" kernel allocations that the kernel will attempt to reclaim under memory pressure. includes .i sreclaimable (below), and other direct allocations with a shrinker. .tp .ir slab " %lu" in-kernel data structures cache. (see .br slabinfo (5).) .tp .ir sreclaimable " %lu (since linux 2.6.19)" part of .ir slab , that might be reclaimed, such as caches. .tp .ir sunreclaim " %lu (since linux 2.6.19)" part of .ir slab , that cannot be reclaimed on memory pressure. .tp .ir kernelstack " %lu (since linux 2.6.32)" amount of memory allocated to kernel stacks. .tp .ir pagetables " %lu (since linux 2.6.18)" amount of memory dedicated to the lowest level of page tables. .tp .ir quicklists " %lu (since linux 2.6.27)" (\fbconfig_quicklist\fp is required.) [to be documented.] .tp .ir nfs_unstable " %lu (since linux 2.6.18)" nfs pages sent to the server, but not yet committed to stable storage. .tp .ir bounce " %lu (since linux 2.6.18)" memory used for block device "bounce buffers". .tp .ir writebacktmp " %lu (since linux 2.6.26)" memory used by fuse for temporary writeback buffers. .tp .ir commitlimit " %lu (since linux 2.6.10)" this is the total amount of memory currently available to be allocated on the system, expressed in kilobytes. this limit is adhered to only if strict overcommit accounting is enabled (mode 2 in .ir /proc/sys/vm/overcommit_memory ). the limit is calculated according to the formula described under .ir /proc/sys/vm/overcommit_memory . for further details, see the kernel source file .ir documentation/vm/overcommit\-accounting.rst . .tp .ir committed_as " %lu" the amount of memory presently allocated on the system. the committed memory is a sum of all of the memory which has been allocated by processes, even if it has not been "used" by them as of yet. a process which allocates 1 gb of memory (using .br malloc (3) or similar), but touches only 300 mb of that memory will show up as using only 300 mb of memory even if it has the address space allocated for the entire 1 gb. .ip this 1 gb is memory which has been "committed" to by the vm and can be used at any time by the allocating application. with strict overcommit enabled on the system (mode 2 in .ir /proc/sys/vm/overcommit_memory ), allocations which would exceed the .i commitlimit will not be permitted. this is useful if one needs to guarantee that processes will not fail due to lack of memory once that memory has been successfully allocated. .tp .ir vmalloctotal " %lu" total size of vmalloc memory area. .tp .ir vmallocused " %lu" amount of vmalloc area which is used. since linux 4.4, .\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0 this field is no longer calculated, and is hard coded as 0. see .ir /proc/vmallocinfo . .tp .ir vmallocchunk " %lu" largest contiguous block of vmalloc area which is free. since linux 4.4, .\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0 this field is no longer calculated and is hard coded as 0. see .ir /proc/vmallocinfo . .tp .ir hardwarecorrupted " %lu (since linux 2.6.32)" (\fbconfig_memory_failure\fp is required.) [to be documented.] .tp .ir lazyfree " %lu (since linux 4.12)" shows the amount of memory marked by .br madvise (2) .br madv_free . .tp .ir anonhugepages " %lu (since linux 2.6.38)" (\fbconfig_transparent_hugepage\fp is required.) non-file backed huge pages mapped into user-space page tables. .tp .ir shmemhugepages " %lu (since linux 4.8)" (\fbconfig_transparent_hugepage\fp is required.) memory used by shared memory (shmem) and .br tmpfs (5) allocated with huge pages. .tp .ir shmempmdmapped " %lu (since linux 4.8)" (\fbconfig_transparent_hugepage\fp is required.) shared memory mapped into user space with huge pages. .tp .ir cmatotal " %lu (since linux 3.1)" total cma (contiguous memory allocator) pages. (\fbconfig_cma\fp is required.) .tp .ir cmafree " %lu (since linux 3.1)" free cma (contiguous memory allocator) pages. (\fbconfig_cma\fp is required.) .tp .ir hugepages_total " %lu" (\fbconfig_hugetlb_page\fp is required.) the size of the pool of huge pages. .tp .ir hugepages_free " %lu" (\fbconfig_hugetlb_page\fp is required.) the number of huge pages in the pool that are not yet allocated. .tp .ir hugepages_rsvd " %lu (since linux 2.6.17)" (\fbconfig_hugetlb_page\fp is required.) this is the number of huge pages for which a commitment to allocate from the pool has been made, but no allocation has yet been made. these reserved huge pages guarantee that an application will be able to allocate a huge page from the pool of huge pages at fault time. .tp .ir hugepages_surp " %lu (since linux 2.6.24)" (\fbconfig_hugetlb_page\fp is required.) this is the number of huge pages in the pool above the value in .ir /proc/sys/vm/nr_hugepages . the maximum number of surplus huge pages is controlled by .ir /proc/sys/vm/nr_overcommit_hugepages . .tp .ir hugepagesize " %lu" (\fbconfig_hugetlb_page\fp is required.) the size of huge pages. .tp .ir directmap4k " %lu (since linux 2.6.27)" number of bytes of ram linearly mapped by kernel in 4 kb pages. (x86.) .tp .ir directmap4m " %lu (since linux 2.6.27)" number of bytes of ram linearly mapped by kernel in 4 mb pages. (x86 with .br config_x86_64 or .br config_x86_pae enabled.) .tp .ir directmap2m " %lu (since linux 2.6.27)" number of bytes of ram linearly mapped by kernel in 2 mb pages. (x86 with neither .br config_x86_64 nor .br config_x86_pae enabled.) .tp .ir directmap1g " %lu (since linux 2.6.27)" (x86 with .br config_x86_64 and .b config_x86_direct_gbpages enabled.) .re .tp .i /proc/modules a text list of the modules that have been loaded by the system. see also .br lsmod (8). .tp .i /proc/mounts before kernel 2.4.19, this file was a list of all the filesystems currently mounted on the system. with the introduction of per-process mount namespaces in linux 2.4.19 (see .br mount_namespaces (7)), this file became a link to .ir /proc/self/mounts , which lists the mounts of the process's own mount namespace. the format of this file is documented in .br fstab (5). .tp .i /proc/mtrr memory type range registers. see the linux kernel source file .i documentation/x86/mtrr.txt .\" commit 7225e75144b9718cbbe1820d9c011c809d5773fd (or .i documentation/mtrr.txt before linux 2.6.28) for details. .tp .i /proc/net this directory contains various files and subdirectories containing information about the networking layer. the files contain ascii structures and are, therefore, readable with .br cat (1). however, the standard .br netstat (8) suite provides much cleaner access to these files. .ip with the advent of network namespaces, various information relating to the network stack is virtualized (see .br network_namespaces (7)). thus, since linux 2.6.25, .\" commit e9720acd728a46cb40daa52c99a979f7c4ff195c .ir /proc/net is a symbolic link to the directory .ir /proc/self/net , which contains the same files and directories as listed below. however, these files and directories now expose information for the network namespace of which the process is a member. .tp .i /proc/net/arp this holds an ascii readable dump of the kernel arp table used for address resolutions. it will show both dynamically learned and preprogrammed arp entries. the format is: .ip .in +4n .ex ip address hw type flags hw address mask device 192.168.0.50 0x1 0x2 00:50:bf:25:68:f3 * eth0 192.168.0.250 0x1 0xc 00:00:00:00:00:00 * eth0 .ee .in .ip here "ip address" is the ipv4 address of the machine and the "hw type" is the hardware type of the address from rfc\ 826. the flags are the internal flags of the arp structure (as defined in .ir /usr/include/linux/if_arp.h ) and the "hw address" is the data link layer mapping for that ip address if it is known. .tp .i /proc/net/dev the dev pseudo-file contains network device status information. this gives the number of received and sent packets, the number of errors and collisions and other basic statistics. these are used by the .br ifconfig (8) program to report device status. the format is: .ip .ex inter\-| receive | transmit face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed lo: 2776770 11307 0 0 0 0 0 0 2776770 11307 0 0 0 0 0 0 eth0: 1215645 2751 0 0 0 0 0 0 1782404 4324 0 0 0 427 0 0 ppp0: 1622270 5552 1 0 0 0 0 0 354130 5669 0 0 0 0 0 0 tap0: 7714 81 0 0 0 0 0 0 7714 81 0 0 0 0 0 0 .ee .\" .tp .\" .i /proc/net/ipx .\" no information. .\" .tp .\" .i /proc/net/ipx_route .\" no information. .tp .i /proc/net/dev_mcast defined in .ir /usr/src/linux/net/core/dev_mcast.c : .ip .in +4n .ex indx interface_name dmi_u dmi_g dmi_address 2 eth0 1 0 01005e000001 3 eth1 1 0 01005e000001 4 eth2 1 0 01005e000001 .ee .in .tp .i /proc/net/igmp internet group management protocol. defined in .ir /usr/src/linux/net/core/igmp.c . .tp .i /proc/net/rarp this file uses the same format as the .i arp file and contains the current reverse mapping database used to provide .br rarp (8) reverse address lookup services. if rarp is not configured into the kernel, this file will not be present. .tp .i /proc/net/raw holds a dump of the raw socket table. much of the information is not of use apart from debugging. the "sl" value is the kernel hash slot for the socket, the "local_address" is the local address and protocol number pair. \&"st" is the internal status of the socket. the "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of kernel memory usage. the "tr", "tm\->when", and "rexmits" fields are not used by raw. the "uid" field holds the effective uid of the creator of the socket. .\" .tp .\" .i /proc/net/route .\" no information, but looks similar to .\" .br route (8). .tp .i /proc/net/snmp this file holds the ascii data needed for the ip, icmp, tcp, and udp management information bases for an snmp agent. .tp .i /proc/net/tcp holds a dump of the tcp socket table. much of the information is not of use apart from debugging. the "sl" value is the kernel hash slot for the socket, the "local_address" is the local address and port number pair. the "rem_address" is the remote address and port number pair (if connected). \&"st" is the internal status of the socket. the "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of kernel memory usage. the "tr", "tm\->when", and "rexmits" fields hold internal information of the kernel socket state and are useful only for debugging. the "uid" field holds the effective uid of the creator of the socket. .tp .i /proc/net/udp holds a dump of the udp socket table. much of the information is not of use apart from debugging. the "sl" value is the kernel hash slot for the socket, the "local_address" is the local address and port number pair. the "rem_address" is the remote address and port number pair (if connected). "st" is the internal status of the socket. the "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of kernel memory usage. the "tr", "tm\->when", and "rexmits" fields are not used by udp. the "uid" field holds the effective uid of the creator of the socket. the format is: .ip .ex sl local_address rem_address st tx_queue rx_queue tr rexmits tm\->when uid 1: 01642c89:0201 0c642c89:03ff 01 00000000:00000001 01:000071ba 00000000 0 1: 00000000:0801 00000000:0000 0a 00000000:00000000 00:00000000 6f000100 0 1: 00000000:0201 00000000:0000 0a 00000000:00000000 00:00000000 00000000 0 .ee .tp .i /proc/net/unix lists the unix domain sockets present within the system and their status. the format is: .ip .ex num refcount protocol flags type st inode path 0: 00000002 00000000 00000000 0001 03 42 1: 00000001 00000000 00010000 0001 01 1948 /dev/printer .ee .ip the fields are as follows: .rs .tp 10 .ir num : the kernel table slot number. .tp .ir refcount : the number of users of the socket. .tp .ir protocol : currently always 0. .tp .ir flags : the internal kernel flags holding the status of the socket. .tp .ir type : the socket type. for .br sock_stream sockets, this is 0001; for .br sock_dgram sockets, it is 0002; and for .br sock_seqpacket sockets, it is 0005. .tp .ir st : the internal state of the socket. .tp .ir inode : the inode number of the socket. .tp .ir path : the bound pathname (if any) of the socket. sockets in the abstract namespace are included in the list, and are shown with a .i path that commences with the character '@'. .re .tp .i /proc/net/netfilter/nfnetlink_queue this file contains information about netfilter user-space queueing, if used. each line represents a queue. queues that have not been subscribed to by user space are not shown. .ip .in +4n .ex 1 4207 0 2 65535 0 0 0 1 (1) (2) (3)(4) (5) (6) (7) (8) .ee .in .ip the fields in each line are: .rs 7 .tp 5 (1) the id of the queue. this matches what is specified in the .b \-\-queue\-num or .b \-\-queue\-balance options to the .br iptables (8) nfqueue target. see .br iptables\-extensions (8) for more information. .tp (2) the netlink port id subscribed to the queue. .tp (3) the number of packets currently queued and waiting to be processed by the application. .tp (4) the copy mode of the queue. it is either 1 (metadata only) or 2 (also copy payload data to user space). .tp (5) copy range; that is, how many bytes of packet payload should be copied to user space at most. .tp (6) queue dropped. number of packets that had to be dropped by the kernel because too many packets are already waiting for user space to send back the mandatory accept/drop verdicts. .tp (7) queue user dropped. number of packets that were dropped within the netlink subsystem. such drops usually happen when the corresponding socket buffer is full; that is, user space is not able to read messages fast enough. .tp (8) sequence number. every queued packet is associated with a (32-bit) monotonically increasing sequence number. this shows the id of the most recent packet queued. .re .ip the last number exists only for compatibility reasons and is always 1. .tp .i /proc/partitions contains the major and minor numbers of each partition as well as the number of 1024-byte blocks and the partition name. .tp .i /proc/pci this is a listing of all pci devices found during kernel initialization and their configuration. .ip this file has been deprecated in favor of a new .i /proc interface for pci .ri ( /proc/bus/pci ). it became optional in linux 2.2 (available with .b config_pci_old_proc set at kernel compilation). it became once more nonoptionally enabled in linux 2.4. next, it was deprecated in linux 2.6 (still available with .b config_pci_legacy_proc set), and finally removed altogether since linux 2.6.17. .\" fixme document /proc/sched_debug (since linux 2.6.23) .\" see also /proc/[pid]/sched .tp .ir /proc/profile " (since linux 2.4)" this file is present only if the kernel was booted with the .i profile=1 command-line option. it exposes kernel profiling information in a binary format for use by .br readprofile (1). writing (e.g., an empty string) to this file resets the profiling counters; on some architectures, writing a binary integer "profiling multiplier" of size .ir sizeof(int) sets the profiling interrupt frequency. .tp .i /proc/scsi a directory with the .i scsi mid-level pseudo-file and various scsi low-level driver directories, which contain a file for each scsi host in this system, all of which give the status of some part of the scsi io subsystem. these files contain ascii structures and are, therefore, readable with .br cat (1). .ip you can also write to some of the files to reconfigure the subsystem or switch certain features on or off. .tp .i /proc/scsi/scsi this is a listing of all scsi devices known to the kernel. the listing is similar to the one seen during bootup. scsi currently supports only the \fiadd\-single\-device\fp command which allows root to add a hotplugged device to the list of known devices. .ip the command .ip .in +4n .ex echo \(aqscsi add\-single\-device 1 0 5 0\(aq > /proc/scsi/scsi .ee .in .ip will cause host scsi1 to scan on scsi channel 0 for a device on id 5 lun 0. if there is already a device known on this address or the address is invalid, an error will be returned. .tp .i /proc/scsi/[drivername] \fi[drivername]\fp can currently be ncr53c7xx, aha152x, aha1542, aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000, pas16, qlogic, scsi_debug, seagate, t128, u15\-24f, ultrastore, or wd7000. these directories show up for all drivers that registered at least one scsi hba. every directory contains one file per registered host. every host-file is named after the number the host was assigned during initialization. .ip reading these files will usually show driver and host configuration, statistics, and so on. .ip writing to these files allows different things on different hosts. for example, with the \filatency\fp and \finolatency\fp commands, root can switch on and off command latency measurement code in the eata_dma driver. with the \filockup\fp and \fiunlock\fp commands, root can control bus lockups simulated by the scsi_debug driver. .tp .i /proc/self this directory refers to the process accessing the .i /proc filesystem, and is identical to the .i /proc directory named by the process id of the same process. .tp .i /proc/slabinfo information about kernel caches. see .br slabinfo (5) for details. .tp .i /proc/stat kernel/system statistics. varies with architecture. common entries include: .rs .tp .i cpu 10132153 290696 3084719 46828483 16683 0 25195 0 175628 0 .tq .i cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0 the amount of time, measured in units of user_hz (1/100ths of a second on most architectures, use .ir sysconf(_sc_clk_tck) to obtain the right value), .\" 1024 on alpha and ia64 that the system ("cpu" line) or the specific cpu ("cpu\fin\fr" line) spent in various states: .rs .tp .i user (1) time spent in user mode. .tp .i nice (2) time spent in user mode with low priority (nice). .tp .i system (3) time spent in system mode. .tp .i idle (4) time spent in the idle task. .\" fixme . actually, the following info about the /proc/stat 'cpu' field .\" does not seem to be quite right (at least in 2.6.12 or 3.6): .\" the idle time in /proc/uptime does not quite match this value this value should be user_hz times the second entry in the .i /proc/uptime pseudo-file. .tp .ir iowait " (since linux 2.5.41)" (5) time waiting for i/o to complete. this value is not reliable, for the following reasons: .\" see kernel commit 9c240d757658a3ae9968dd309e674c61f07c7f48 .rs .ip 1. 3 the cpu will not wait for i/o to complete; iowait is the time that a task is waiting for i/o to complete. when a cpu goes into idle state for outstanding task i/o, another task will be scheduled on this cpu. .ip 2. on a multi-core cpu, the task waiting for i/o to complete is not running on any cpu, so the iowait of each cpu is difficult to calculate. .ip 3. the value in this field may .i decrease in certain conditions. .re .tp .ir irq " (since linux 2.6.0)" .\" precisely: linux 2.6.0-test4 (6) time servicing interrupts. .tp .ir softirq " (since linux 2.6.0)" .\" precisely: linux 2.6.0-test4 (7) time servicing softirqs. .tp .ir steal " (since linux 2.6.11)" (8) stolen time, which is the time spent in other operating systems when running in a virtualized environment .tp .ir guest " (since linux 2.6.24)" (9) time spent running a virtual cpu for guest operating systems under the control of the linux kernel. .\" see changelog entry for 5e84cfde51cf303d368fcb48f22059f37b3872de .tp .ir guest_nice " (since linux 2.6.33)" .\" commit ce0e7b28fb75cb003cfc8d0238613aaf1c55e797 (10) time spent running a niced guest (virtual cpu for guest operating systems under the control of the linux kernel). .re .tp \fipage 5741 1808\fp the number of pages the system paged in and the number that were paged out (from disk). .tp \fiswap 1 0\fp the number of swap pages that have been brought in and out. .tp .\" fixme . the following is not the full picture for the 'intr' of .\" /proc/stat on 2.6: \fiintr 1462898\fp this line shows counts of interrupts serviced since boot time, for each of the possible system interrupts. the first column is the total of all interrupts serviced including unnumbered architecture specific interrupts; each subsequent column is the total for that particular numbered interrupt. unnumbered interrupts are not shown, only summed into the total. .tp \fidisk_io: (2,0):(31,30,5764,1,2) (3,0):\fp... (major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written) .br (linux 2.4 only) .tp \fictxt 115315\fp the number of context switches that the system underwent. .tp \fibtime 769041601\fp boot time, in seconds since the epoch, 1970-01-01 00:00:00 +0000 (utc). .tp \fiprocesses 86031\fp number of forks since boot. .tp \fiprocs_running 6\fp number of processes in runnable state. (linux 2.5.45 onward.) .tp \fiprocs_blocked 2\fp number of processes blocked waiting for i/o to complete. (linux 2.5.45 onward.) .tp .i softirq 229245889 94 60001584 13619 5175704 2471304 28 51212741 59130143 0 51240672 .\" commit d3d64df21d3d0de675a0d3ffa7c10514f3644b30 this line shows the number of softirq for all cpus. the first column is the total of all softirqs and each subsequent column is the total for particular softirq. (linux 2.6.31 onward.) .re .tp .i /proc/swaps swap areas in use. see also .br swapon (8). .tp .i /proc/sys this directory (present since 1.3.57) contains a number of files and subdirectories corresponding to kernel variables. these variables can be read and in some cases modified using the \fi/proc\fp filesystem, and the (deprecated) .br sysctl (2) system call. .ip string values may be terminated by either \(aq\e0\(aq or \(aq\en\(aq. .ip integer and long values may be written either in decimal or in hexadecimal notation (e.g., 0x3fff). when writing multiple integer or long values, these may be separated by any of the following whitespace characters: \(aq\ \(aq, \(aq\et\(aq, or \(aq\en\(aq. using other separators leads to the error .br einval . .tp .ir /proc/sys/abi " (since linux 2.4.10)" this directory may contain files with application binary information. .\" on some systems, it is not present. see the linux kernel source file .i documentation/sysctl/abi.txt for more information. .tp .i /proc/sys/debug this directory may be empty. .tp .i /proc/sys/dev this directory contains device-specific information (e.g., .ir dev/cdrom/info ). on some systems, it may be empty. .tp .i /proc/sys/fs this directory contains the files and subdirectories for kernel variables related to filesystems. .tp .ir /proc/sys/fs/aio\-max\-nr " and " /proc/sys/fs/aio\-nr " (since linux 2.6.4)" .i aio\-nr is the running total of the number of events specified by .br io_setup (2) calls for all currently active aio contexts. if .i aio\-nr reaches .ir aio\-max\-nr , then .br io_setup (2) will fail with the error .br eagain . raising .i aio\-max\-nr does not result in the preallocation or resizing of any kernel data structures. .tp .i /proc/sys/fs/binfmt_misc documentation for files in this directory can be found in the linux kernel source in the file .ir documentation/admin\-guide/binfmt\-misc.rst (or in .ir documentation/binfmt_misc.txt on older kernels). .tp .ir /proc/sys/fs/dentry\-state " (since linux 2.2)" this file contains information about the status of the directory cache (dcache). the file contains six numbers, .ir nr_dentry ", " nr_unused ", " age_limit " (age in seconds)," .i want_pages (pages requested by system) and two dummy values. .rs .ip * 2 .i nr_dentry is the number of allocated dentries (dcache entries). this field is unused in linux 2.2. .ip * .i nr_unused is the number of unused dentries. .ip * .i age_limit .\" looks like this is unused in kernels 2.2 to 2.6 is the age in seconds after which dcache entries can be reclaimed when memory is short. .ip * .i want_pages .\" looks like this is unused in kernels 2.2 to 2.6 is nonzero when the kernel has called shrink_dcache_pages() and the dcache isn't pruned yet. .re .tp .i /proc/sys/fs/dir\-notify\-enable this file can be used to disable or enable the .i dnotify interface described in .br fcntl (2) on a system-wide basis. a value of 0 in this file disables the interface, and a value of 1 enables it. .tp .i /proc/sys/fs/dquot\-max this file shows the maximum number of cached disk quota entries. on some (2.4) systems, it is not present. if the number of free cached disk quota entries is very low and you have some awesome number of simultaneous system users, you might want to raise the limit. .tp .i /proc/sys/fs/dquot\-nr this file shows the number of allocated disk quota entries and the number of free disk quota entries. .tp .ir /proc/sys/fs/epoll " (since linux 2.6.28)" this directory contains the file .ir max_user_watches , which can be used to limit the amount of kernel memory consumed by the .i epoll interface. for further details, see .br epoll (7). .tp .i /proc/sys/fs/file\-max this file defines a system-wide limit on the number of open files for all processes. system calls that fail when encountering this limit fail with the error .br enfile . (see also .br setrlimit (2), which can be used by a process to set the per-process limit, .br rlimit_nofile , on the number of files it may open.) if you get lots of error messages in the kernel log about running out of file handles (open file descriptions) (look for "vfs: file\-max limit reached"), try increasing this value: .ip .in +4n .ex echo 100000 > /proc/sys/fs/file\-max .ee .in .ip privileged processes .rb ( cap_sys_admin ) can override the .i file\-max limit. .tp .i /proc/sys/fs/file\-nr this (read-only) file contains three numbers: the number of allocated file handles (i.e., the number of open file descriptions; see .br open (2)); the number of free file handles; and the maximum number of file handles (i.e., the same value as .ir /proc/sys/fs/file\-max ). if the number of allocated file handles is close to the maximum, you should consider increasing the maximum. before linux 2.6, the kernel allocated file handles dynamically, but it didn't free them again. instead the free file handles were kept in a list for reallocation; the "free file handles" value indicates the size of that list. a large number of free file handles indicates that there was a past peak in the usage of open file handles. since linux 2.6, the kernel does deallocate freed file handles, and the "free file handles" value is always zero. .tp .ir /proc/sys/fs/inode\-max " (only present until linux 2.2)" this file contains the maximum number of in-memory inodes. this value should be 3\(en4 times larger than the value in .ir file\-max , since \fistdin\fp, \fistdout\fp and network sockets also need an inode to handle them. when you regularly run out of inodes, you need to increase this value. .ip starting with linux 2.4, there is no longer a static limit on the number of inodes, and this file is removed. .tp .i /proc/sys/fs/inode\-nr this file contains the first two values from .ir inode\-state . .tp .i /proc/sys/fs/inode\-state this file contains seven numbers: .ir nr_inodes , .ir nr_free_inodes , .ir preshrink , and four dummy values (always zero). .ip .i nr_inodes is the number of inodes the system has allocated. .\" this can be slightly more than .\" .i inode\-max .\" because linux allocates them one page full at a time. .i nr_free_inodes represents the number of free inodes. .ip .i preshrink is nonzero when the .i nr_inodes > .i inode\-max and the system needs to prune the inode list instead of allocating more; since linux 2.4, this field is a dummy value (always zero). .tp .ir /proc/sys/fs/inotify " (since linux 2.6.13)" this directory contains files .ir max_queued_events ", " max_user_instances ", and " max_user_watches , that can be used to limit the amount of kernel memory consumed by the .i inotify interface. for further details, see .br inotify (7). .tp .i /proc/sys/fs/lease\-break\-time this file specifies the grace period that the kernel grants to a process holding a file lease .rb ( fcntl (2)) after it has sent a signal to that process notifying it that another process is waiting to open the file. if the lease holder does not remove or downgrade the lease within this grace period, the kernel forcibly breaks the lease. .tp .i /proc/sys/fs/leases\-enable this file can be used to enable or disable file leases .rb ( fcntl (2)) on a system-wide basis. if this file contains the value 0, leases are disabled. a nonzero value enables leases. .tp .ir /proc/sys/fs/mount\-max " (since linux 4.9)" .\" commit d29216842a85c7970c536108e093963f02714498 the value in this file specifies the maximum number of mounts that may exist in a mount namespace. the default value in this file is 100,000. .tp .ir /proc/sys/fs/mqueue " (since linux 2.6.6)" this directory contains files .ir msg_max ", " msgsize_max ", and " queues_max , controlling the resources used by posix message queues. see .br mq_overview (7) for details. .tp .ir /proc/sys/fs/nr_open " (since linux 2.6.25)" .\" commit 9cfe015aa424b3c003baba3841a60dd9b5ad319b this file imposes a ceiling on the value to which the .br rlimit_nofile resource limit can be raised (see .br getrlimit (2)). this ceiling is enforced for both unprivileged and privileged process. the default value in this file is 1048576. (before linux 2.6.25, the ceiling for .br rlimit_nofile was hard-coded to the same value.) .tp .ir /proc/sys/fs/overflowgid " and " /proc/sys/fs/overflowuid these files allow you to change the value of the fixed uid and gid. the default is 65534. some filesystems support only 16-bit uids and gids, although in linux uids and gids are 32 bits. when one of these filesystems is mounted with writes enabled, any uid or gid that would exceed 65535 is translated to the overflow value before being written to disk. .tp .ir /proc/sys/fs/pipe\-max\-size " (since linux 2.6.35)" see .br pipe (7). .tp .ir /proc/sys/fs/pipe\-user\-pages\-hard " (since linux 4.5)" see .br pipe (7). .tp .ir /proc/sys/fs/pipe\-user\-pages\-soft " (since linux 4.5)" see .br pipe (7). .tp .ir /proc/sys/fs/protected_fifos " (since linux 4.19)" the value in this file is/can be set to one of the following: .rs .tp 4 0 writing to fifos is unrestricted. .tp 1 don't allow .b o_creat .br open (2) on fifos that the caller doesn't own in world-writable sticky directories, unless the fifo is owned by the owner of the directory. .tp 2 as for the value 1, but the restriction also applies to group-writable sticky directories. .re .ip the intent of the above protections is to avoid unintentional writes to an attacker-controlled fifo when a program expected to create a regular file. .tp .ir /proc/sys/fs/protected_hardlinks " (since linux 3.6)" .\" commit 800179c9b8a1e796e441674776d11cd4c05d61d7 when the value in this file is 0, no restrictions are placed on the creation of hard links (i.e., this is the historical behavior before linux 3.6). when the value in this file is 1, a hard link can be created to a target file only if one of the following conditions is true: .rs .ip * 3 the calling process has the .br cap_fowner capability in its user namespace and the file uid has a mapping in the namespace. .ip * the filesystem uid of the process creating the link matches the owner (uid) of the target file (as described in .br credentials (7), a process's filesystem uid is normally the same as its effective uid). .ip * all of the following conditions are true: .rs 4 .ip \(bu 3 the target is a regular file; .ip \(bu the target file does not have its set-user-id mode bit enabled; .ip \(bu the target file does not have both its set-group-id and group-executable mode bits enabled; and .ip \(bu the caller has permission to read and write the target file (either via the file's permissions mask or because it has suitable capabilities). .re .re .ip the default value in this file is 0. setting the value to 1 prevents a longstanding class of security issues caused by hard-link-based time-of-check, time-of-use races, most commonly seen in world-writable directories such as .ir /tmp . the common method of exploiting this flaw is to cross privilege boundaries when following a given hard link (i.e., a root process follows a hard link created by another user). additionally, on systems without separated partitions, this stops unauthorized users from "pinning" vulnerable set-user-id and set-group-id files against being upgraded by the administrator, or linking to special files. .tp .ir /proc/sys/fs/protected_regular " (since linux 4.19)" the value in this file is/can be set to one of the following: .rs .tp 4 0 writing to regular files is unrestricted. .tp 1 don't allow .b o_creat .br open (2) on regular files that the caller doesn't own in world-writable sticky directories, unless the regular file is owned by the owner of the directory. .tp 2 as for the value 1, but the restriction also applies to group-writable sticky directories. .re .ip the intent of the above protections is similar to .ir protected_fifos , but allows an application to avoid writes to an attacker-controlled regular file, where the application expected to create one. .tp .ir /proc/sys/fs/protected_symlinks " (since linux 3.6)" .\" commit 800179c9b8a1e796e441674776d11cd4c05d61d7 when the value in this file is 0, no restrictions are placed on following symbolic links (i.e., this is the historical behavior before linux 3.6). when the value in this file is 1, symbolic links are followed only in the following circumstances: .rs .ip * 3 the filesystem uid of the process following the link matches the owner (uid) of the symbolic link (as described in .br credentials (7), a process's filesystem uid is normally the same as its effective uid); .ip * the link is not in a sticky world-writable directory; or .ip * the symbolic link and its parent directory have the same owner (uid) .re .ip a system call that fails to follow a symbolic link because of the above restrictions returns the error .br eacces in .ir errno . .ip the default value in this file is 0. setting the value to 1 avoids a longstanding class of security issues based on time-of-check, time-of-use races when accessing symbolic links. .tp .ir /proc/sys/fs/suid_dumpable " (since linux 2.6.13)" .\" the following is based on text from documentation/sysctl/kernel.txt the value in this file is assigned to a process's "dumpable" flag in the circumstances described in .br prctl (2). in effect, the value in this file determines whether core dump files are produced for set-user-id or otherwise protected/tainted binaries. the "dumpable" setting also affects the ownership of files in a process's .ir /proc/[pid] directory, as described above. .ip three different integer values can be specified: .rs .tp \fi0\ (default)\fp .\" in kernel source: suid_dump_disable this provides the traditional (pre-linux 2.6.13) behavior. a core dump will not be produced for a process which has changed credentials (by calling .br seteuid (2), .br setgid (2), or similar, or by executing a set-user-id or set-group-id program) or whose binary does not have read permission enabled. .tp \fi1\ ("debug")\fp .\" in kernel source: suid_dump_user all processes dump core when possible. (reasons why a process might nevertheless not dump core are described in .br core (5).) the core dump is owned by the filesystem user id of the dumping process and no security is applied. this is intended for system debugging situations only: this mode is insecure because it allows unprivileged users to examine the memory contents of privileged processes. .tp \fi2\ ("suidsafe")\fp .\" in kernel source: suid_dump_root any binary which normally would not be dumped (see "0" above) is dumped readable by root only. this allows the user to remove the core dump file but not to read it. for security reasons core dumps in this mode will not overwrite one another or other files. this mode is appropriate when administrators are attempting to debug problems in a normal environment. .ip additionally, since linux 3.6, .\" 9520628e8ceb69fa9a4aee6b57f22675d9e1b709 .i /proc/sys/kernel/core_pattern must either be an absolute pathname or a pipe command, as detailed in .br core (5). warnings will be written to the kernel log if .i core_pattern does not follow these rules, and no core dump will be produced. .\" 54b501992dd2a839e94e76aa392c392b55080ce8 .re .ip for details of the effect of a process's "dumpable" setting on ptrace access mode checking, see .br ptrace (2). .tp .i /proc/sys/fs/super\-max this file controls the maximum number of superblocks, and thus the maximum number of mounted filesystems the kernel can have. you need increase only .i super\-max if you need to mount more filesystems than the current value in .i super\-max allows you to. .tp .i /proc/sys/fs/super\-nr this file contains the number of filesystems currently mounted. .tp .i /proc/sys/kernel this directory contains files controlling a range of kernel parameters, as described below. .tp .i /proc/sys/kernel/acct this file contains three numbers: .ir highwater , .ir lowwater , and .ir frequency . if bsd-style process accounting is enabled, these values control its behavior. if free space on filesystem where the log lives goes below .i lowwater percent, accounting suspends. if free space gets above .i highwater percent, accounting resumes. .i frequency determines how often the kernel checks the amount of free space (value is in seconds). default values are 4, 2, and 30. that is, suspend accounting if 2% or less space is free; resume it if 4% or more space is free; consider information about amount of free space valid for 30 seconds. .tp .ir /proc/sys/kernel/auto_msgmni " (linux 2.6.27 to 3.18)" .\" commit 9eefe520c814f6f62c5d36a2ddcd3fb99dfdb30e (introduces feature) .\" commit 0050ee059f7fc86b1df2527aaa14ed5dc72f9973 (rendered redundant) from linux 2.6.27 to 3.18, this file was used to control recomputing of the value in .ir /proc/sys/kernel/msgmni upon the addition or removal of memory or upon ipc namespace creation/removal. echoing "1" into this file enabled .i msgmni automatic recomputing (and triggered a recomputation of .i msgmni based on the current amount of available memory and number of ipc namespaces). echoing "0" disabled automatic recomputing. (automatic recomputing was also disabled if a value was explicitly assigned to .ir /proc/sys/kernel/msgmni .) the default value in .i auto_msgmni was 1. .ip since linux 3.19, the content of this file has no effect (because .ir msgmni .\" fixme must document the 3.19 'msgmni' changes. defaults to near the maximum value possible), and reads from this file always return the value "0". .tp .ir /proc/sys/kernel/cap_last_cap " (since linux 3.2)" see .br capabilities (7). .tp .ir /proc/sys/kernel/cap\-bound " (from linux 2.2 to 2.6.24)" this file holds the value of the kernel .i "capability bounding set" (expressed as a signed decimal number). this set is anded against the capabilities permitted to a process during .br execve (2). starting with linux 2.6.25, the system-wide capability bounding set disappeared, and was replaced by a per-thread bounding set; see .br capabilities (7). .tp .i /proc/sys/kernel/core_pattern see .br core (5). .tp .i /proc/sys/kernel/core_pipe_limit see .br core (5). .tp .i /proc/sys/kernel/core_uses_pid see .br core (5). .tp .i /proc/sys/kernel/ctrl\-alt\-del this file controls the handling of ctrl-alt-del from the keyboard. when the value in this file is 0, ctrl-alt-del is trapped and sent to the .br init (1) program to handle a graceful restart. when the value is greater than zero, linux's reaction to a vulcan nerve pinch (tm) will be an immediate reboot, without even syncing its dirty buffers. note: when a program (like dosemu) has the keyboard in "raw" mode, the ctrl-alt-del is intercepted by the program before it ever reaches the kernel tty layer, and it's up to the program to decide what to do with it. .tp .ir /proc/sys/kernel/dmesg_restrict " (since linux 2.6.37)" the value in this file determines who can see kernel syslog contents. a value of 0 in this file imposes no restrictions. if the value is 1, only privileged users can read the kernel syslog. (see .br syslog (2) for more details.) since linux 3.4, .\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8 only users with the .br cap_sys_admin capability may change the value in this file. .tp .ir /proc/sys/kernel/domainname " and " /proc/sys/kernel/hostname can be used to set the nis/yp domainname and the hostname of your box in exactly the same way as the commands .br domainname (1) and .br hostname (1), that is: .ip .in +4n .ex .rb "#" " echo \(aqdarkstar\(aq > /proc/sys/kernel/hostname" .rb "#" " echo \(aqmydomain\(aq > /proc/sys/kernel/domainname" .ee .in .ip has the same effect as .ip .in +4n .ex .rb "#" " hostname \(aqdarkstar\(aq" .rb "#" " domainname \(aqmydomain\(aq" .ee .in .ip note, however, that the classic darkstar.frop.org has the hostname "darkstar" and dns (internet domain name server) domainname "frop.org", not to be confused with the nis (network information service) or yp (yellow pages) domainname. these two domain names are in general different. for a detailed discussion see the .br hostname (1) man page. .tp .i /proc/sys/kernel/hotplug this file contains the pathname for the hotplug policy agent. the default value in this file is .ir /sbin/hotplug . .tp .\" removed in commit 87f504e5c78b910b0c1d6ffb89bc95e492322c84 (tglx/history.git) .ir /proc/sys/kernel/htab\-reclaim " (before linux 2.4.9.2)" (powerpc only) if this file is set to a nonzero value, the powerpc htab .\" removed in commit 1b483a6a7b2998e9c98ad985d7494b9b725bd228, before 2.6.28 (see kernel file .ir documentation/powerpc/ppc_htab.txt ) is pruned each time the system hits the idle loop. .tp .ir /proc/sys/kernel/keys/* this directory contains various files that define parameters and limits for the key-management facility. these files are described in .br keyrings (7). .tp .ir /proc/sys/kernel/kptr_restrict " (since linux 2.6.38)" .\" 455cd5ab305c90ffc422dd2e0fb634730942b257 the value in this file determines whether kernel addresses are exposed via .i /proc files and other interfaces. a value of 0 in this file imposes no restrictions. if the value is 1, kernel pointers printed using the .i %pk format specifier will be replaced with zeros unless the user has the .br cap_syslog capability. if the value is 2, kernel pointers printed using the .i %pk format specifier will be replaced with zeros regardless of the user's capabilities. the initial default value for this file was 1, but the default was changed .\" commit 411f05f123cbd7f8aa1edcae86970755a6e2a9d9 to 0 in linux 2.6.39. since linux 3.4, .\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8 only users with the .br cap_sys_admin capability can change the value in this file. .tp .i /proc/sys/kernel/l2cr (powerpc only) this file contains a flag that controls the l2 cache of g3 processor boards. if 0, the cache is disabled. enabled if nonzero. .tp .i /proc/sys/kernel/modprobe this file contains the pathname for the kernel module loader. the default value is .ir /sbin/modprobe . the file is present only if the kernel is built with the .b config_modules .rb ( config_kmod in linux 2.6.26 and earlier) option enabled. it is described by the linux kernel source file .i documentation/kmod.txt (present only in kernel 2.4 and earlier). .tp .ir /proc/sys/kernel/modules_disabled " (since linux 2.6.31)" .\" 3d43321b7015387cfebbe26436d0e9d299162ea1 .\" from documentation/sysctl/kernel.txt a toggle value indicating if modules are allowed to be loaded in an otherwise modular kernel. this toggle defaults to off (0), but can be set true (1). once true, modules can be neither loaded nor unloaded, and the toggle cannot be set back to false. the file is present only if the kernel is built with the .b config_modules option enabled. .tp .ir /proc/sys/kernel/msgmax " (since linux 2.2)" this file defines a system-wide limit specifying the maximum number of bytes in a single message written on a system v message queue. .tp .ir /proc/sys/kernel/msgmni " (since linux 2.4)" this file defines the system-wide limit on the number of message queue identifiers. see also .ir /proc/sys/kernel/auto_msgmni . .tp .ir /proc/sys/kernel/msgmnb " (since linux 2.2)" this file defines a system-wide parameter used to initialize the .i msg_qbytes setting for subsequently created message queues. the .i msg_qbytes setting specifies the maximum number of bytes that may be written to the message queue. .tp .ir /proc/sys/kernel/ngroups_max " (since linux 2.6.4)" this is a read-only file that displays the upper limit on the number of a process's group memberships. .tp .ir /proc/sys/kernel/ns_last_pid " (since linux 3.3)" see .br pid_namespaces (7). .tp .ir /proc/sys/kernel/ostype " and " /proc/sys/kernel/osrelease these files give substrings of .ir /proc/version . .tp .ir /proc/sys/kernel/overflowgid " and " /proc/sys/kernel/overflowuid these files duplicate the files .i /proc/sys/fs/overflowgid and .ir /proc/sys/fs/overflowuid . .tp .i /proc/sys/kernel/panic this file gives read/write access to the kernel variable .ir panic_timeout . if this is zero, the kernel will loop on a panic; if nonzero, it indicates that the kernel should autoreboot after this number of seconds. when you use the software watchdog device driver, the recommended setting is 60. .tp .ir /proc/sys/kernel/panic_on_oops " (since linux 2.5.68)" this file controls the kernel's behavior when an oops or bug is encountered. if this file contains 0, then the system tries to continue operation. if it contains 1, then the system delays a few seconds (to give klogd time to record the oops output) and then panics. if the .i /proc/sys/kernel/panic file is also nonzero, then the machine will be rebooted. .tp .ir /proc/sys/kernel/pid_max " (since linux 2.5.34)" this file specifies the value at which pids wrap around (i.e., the value in this file is one greater than the maximum pid). pids greater than this value are not allocated; thus, the value in this file also acts as a system-wide limit on the total number of processes and threads. the default value for this file, 32768, results in the same range of pids as on earlier kernels. on 32-bit platforms, 32768 is the maximum value for .ir pid_max . on 64-bit systems, .i pid_max can be set to any value up to 2^22 .rb ( pid_max_limit , approximately 4 million). .\" prior to 2.6.10, pid_max could also be raised above 32768 on 32-bit .\" platforms, but this broke /proc/[pid] .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=109513010926152&w=2 .tp .ir /proc/sys/kernel/powersave\-nap " (powerpc only)" this file contains a flag. if set, linux-ppc will use the "nap" mode of powersaving, otherwise the "doze" mode will be used. .tp .i /proc/sys/kernel/printk see .br syslog (2). .tp .ir /proc/sys/kernel/pty " (since linux 2.6.4)" this directory contains two files relating to the number of unix 98 pseudoterminals (see .br pts (4)) on the system. .tp .i /proc/sys/kernel/pty/max this file defines the maximum number of pseudoterminals. .\" fixme document /proc/sys/kernel/pty/reserve .\" new in linux 3.3 .\" commit e9aba5158a80098447ff207a452a3418ae7ee386 .tp .i /proc/sys/kernel/pty/nr this read-only file indicates how many pseudoterminals are currently in use. .tp .i /proc/sys/kernel/random this directory contains various parameters controlling the operation of the file .ir /dev/random . see .br random (4) for further information. .tp .ir /proc/sys/kernel/random/uuid " (since linux 2.4)" each read from this read-only file returns a randomly generated 128-bit uuid, as a string in the standard uuid format. .tp .ir /proc/sys/kernel/randomize_va_space " (since linux 2.6.12)" .\" some further details can be found in documentation/sysctl/kernel.txt select the address space layout randomization (aslr) policy for the system (on architectures that support aslr). three values are supported for this file: .rs .ip 0 3 turn aslr off. this is the default for architectures that don't support aslr, and when the kernel is booted with the .i norandmaps parameter. .ip 1 make the addresses of .br mmap (2) allocations, the stack, and the vdso page randomized. among other things, this means that shared libraries will be loaded at randomized addresses. the text segment of pie-linked binaries will also be loaded at a randomized address. this value is the default if the kernel was configured with .br config_compat_brk . .ip 2 (since linux 2.6.25) .\" commit c1d171a002942ea2d93b4fbd0c9583c56fce0772 also support heap randomization. this value is the default if the kernel was not configured with .br config_compat_brk . .re .tp .i /proc/sys/kernel/real\-root\-dev this file is documented in the linux kernel source file .i documentation/admin\-guide/initrd.rst .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/initrd.txt before linux 4.10). .tp .ir /proc/sys/kernel/reboot\-cmd " (sparc only)" this file seems to be a way to give an argument to the sparc rom/flash boot loader. maybe to tell it what to do after rebooting? .tp .i /proc/sys/kernel/rtsig\-max (only in kernels up to and including 2.6.7; see .br setrlimit (2)) this file can be used to tune the maximum number of posix real-time (queued) signals that can be outstanding in the system. .tp .i /proc/sys/kernel/rtsig\-nr (only in kernels up to and including 2.6.7.) this file shows the number of posix real-time signals currently queued. .tp .ir /proc/[pid]/sched_autogroup_enabled " (since linux 2.6.38)" .\" commit 5091faa449ee0b7d73bc296a93bca9540fc51d0a see .br sched (7). .tp .ir /proc/sys/kernel/sched_child_runs_first " (since linux 2.6.23)" if this file contains the value zero, then, after a .br fork (2), the parent is first scheduled on the cpu. if the file contains a nonzero value, then the child is scheduled first on the cpu. (of course, on a multiprocessor system, the parent and the child might both immediately be scheduled on a cpu.) .tp .ir /proc/sys/kernel/sched_rr_timeslice_ms " (since linux 3.9)" see .br sched_rr_get_interval (2). .tp .ir /proc/sys/kernel/sched_rt_period_us " (since linux 2.6.25)" see .br sched (7). .tp .ir /proc/sys/kernel/sched_rt_runtime_us " (since linux 2.6.25)" see .br sched (7). .tp .ir /proc/sys/kernel/seccomp " (since linux 4.14)" .\" commit 8e5f1ad116df6b0de65eac458d5e7c318d1c05af this directory provides additional seccomp information and configuration. see .br seccomp (2) for further details. .tp .ir /proc/sys/kernel/sem " (since linux 2.4)" this file contains 4 numbers defining limits for system v ipc semaphores. these fields are, in order: .rs .ip semmsl 8 the maximum semaphores per semaphore set. .ip semmns 8 a system-wide limit on the number of semaphores in all semaphore sets. .ip semopm 8 the maximum number of operations that may be specified in a .br semop (2) call. .ip semmni 8 a system-wide limit on the maximum number of semaphore identifiers. .re .tp .i /proc/sys/kernel/sg\-big\-buff this file shows the size of the generic scsi device (sg) buffer. you can't tune it just yet, but you could change it at compile time by editing .i include/scsi/sg.h and changing the value of .br sg_big_buff . however, there shouldn't be any reason to change this value. .tp .ir /proc/sys/kernel/shm_rmid_forced " (since linux 3.1)" .\" commit b34a6b1da371ed8af1221459a18c67970f7e3d53 .\" see also documentation/sysctl/kernel.txt if this file is set to 1, all system v shared memory segments will be marked for destruction as soon as the number of attached processes falls to zero; in other words, it is no longer possible to create shared memory segments that exist independently of any attached process. .ip the effect is as though a .br shmctl (2) .b ipc_rmid is performed on all existing segments as well as all segments created in the future (until this file is reset to 0). note that existing segments that are attached to no process will be immediately destroyed when this file is set to 1. setting this option will also destroy segments that were created, but never attached, upon termination of the process that created the segment with .br shmget (2). .ip setting this file to 1 provides a way of ensuring that all system v shared memory segments are counted against the resource usage and resource limits (see the description of .b rlimit_as in .br getrlimit (2)) of at least one process. .ip because setting this file to 1 produces behavior that is nonstandard and could also break existing applications, the default value in this file is 0. set this file to 1 only if you have a good understanding of the semantics of the applications using system v shared memory on your system. .tp .ir /proc/sys/kernel/shmall " (since linux 2.2)" this file contains the system-wide limit on the total number of pages of system v shared memory. .tp .ir /proc/sys/kernel/shmmax " (since linux 2.2)" this file can be used to query and set the run-time limit on the maximum (system v ipc) shared memory segment size that can be created. shared memory segments up to 1 gb are now supported in the kernel. this value defaults to .br shmmax . .tp .ir /proc/sys/kernel/shmmni " (since linux 2.4)" this file specifies the system-wide maximum number of system v shared memory segments that can be created. .tp .ir /proc/sys/kernel/sysctl_writes_strict " (since linux 3.16)" .\" commit f88083005ab319abba5d0b2e4e997558245493c8 .\" commit 2ca9bb456ada8bcbdc8f77f8fc78207653bbaa92 .\" commit f4aacea2f5d1a5f7e3154e967d70cf3f711bcd61 .\" commit 24fe831c17ab8149413874f2fd4e5c8a41fcd294 the value in this file determines how the file offset affects the behavior of updating entries in files under .ir /proc/sys . the file has three possible values: .rs .tp 4 \-1 this provides legacy handling, with no printk warnings. each .br write (2) must fully contain the value to be written, and multiple writes on the same file descriptor will overwrite the entire value, regardless of the file position. .tp 0 (default) this provides the same behavior as for \-1, but printk warnings are written for processes that perform writes when the file offset is not 0. .tp 1 respect the file offset when writing strings into .i /proc/sys files. multiple writes will .i append to the value buffer. anything written beyond the maximum length of the value buffer will be ignored. writes to numeric .i /proc/sys entries must always be at file offset 0 and the value must be fully contained in the buffer provided to .br write (2). .\" fixme . .\" with /proc/sys/kernel/sysctl_writes_strict==1, writes at an .\" offset other than 0 do not generate an error. instead, the .\" write() succeeds, but the file is left unmodified. .\" this is surprising. the behavior may change in the future. .\" see thread.gmane.org/gmane.linux.man/9197 .\" from: michael kerrisk (man-pages .\" subject: sysctl_writes_strict documentation + an oddity? .\" newsgroups: gmane.linux.man, gmane.linux.kernel .\" date: 2015-05-09 08:54:11 gmt .re .tp .i /proc/sys/kernel/sysrq this file controls the functions allowed to be invoked by the sysrq key. by default, the file contains 1 meaning that every possible sysrq request is allowed (in older kernel versions, sysrq was disabled by default, and you were required to specifically enable it at run-time, but this is not the case any more). possible values in this file are: .rs .tp 5 0 disable sysrq completely .tp 1 enable all functions of sysrq .tp > 1 bit mask of allowed sysrq functions, as follows: .pd 0 .rs .tp 5 \ \ 2 enable control of console logging level .tp \ \ 4 enable control of keyboard (sak, unraw) .tp \ \ 8 enable debugging dumps of processes etc. .tp \ 16 enable sync command .tp \ 32 enable remount read-only .tp \ 64 enable signaling of processes (term, kill, oom-kill) .tp 128 allow reboot/poweroff .tp 256 allow nicing of all real-time tasks .re .pd .re .ip this file is present only if the .b config_magic_sysrq kernel configuration option is enabled. for further details see the linux kernel source file .i documentation/admin\-guide/sysrq.rst .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/sysrq.txt before linux 4.10). .tp .i /proc/sys/kernel/version this file contains a string such as: .ip #5 wed feb 25 21:49:24 met 1998 .ip the "#5" means that this is the fifth kernel built from this source base and the date following it indicates the time the kernel was built. .tp .ir /proc/sys/kernel/threads\-max " (since linux 2.3.11)" .\" the following is based on documentation/sysctl/kernel.txt this file specifies the system-wide limit on the number of threads (tasks) that can be created on the system. .ip since linux 4.1, .\" commit 230633d109e35b0a24277498e773edeb79b4a331 the value that can be written to .i threads\-max is bounded. the minimum value that can be written is 20. the maximum value that can be written is given by the constant .b futex_tid_mask (0x3fffffff). if a value outside of this range is written to .ir threads\-max , the error .b einval occurs. .ip the value written is checked against the available ram pages. if the thread structures would occupy too much (more than 1/8th) of the available ram pages, .i threads\-max is reduced accordingly. .tp .ir /proc/sys/kernel/yama/ptrace_scope " (since linux 3.5)" see .br ptrace (2). .tp .ir /proc/sys/kernel/zero\-paged " (powerpc only)" this file contains a flag. when enabled (nonzero), linux-ppc will pre-zero pages in the idle loop, possibly speeding up get_free_pages. .tp .i /proc/sys/net this directory contains networking stuff. explanations for some of the files under this directory can be found in .br tcp (7) and .br ip (7). .tp .i /proc/sys/net/core/bpf_jit_enable see .br bpf (2). .tp .i /proc/sys/net/core/somaxconn this file defines a ceiling value for the .i backlog argument of .br listen (2); see the .br listen (2) manual page for details. .tp .i /proc/sys/proc this directory may be empty. .tp .i /proc/sys/sunrpc this directory supports sun remote procedure call for network filesystem (nfs). on some systems, it is not present. .tp .ir /proc/sys/user " (since linux 4.9)" see .br namespaces (7). .tp .i /proc/sys/vm this directory contains files for memory management tuning, buffer, and cache management. .tp .ir /proc/sys/vm/admin_reserve_kbytes " (since linux 3.10)" .\" commit 4eeab4f5580d11bffedc697684b91b0bca0d5009 this file defines the amount of free memory (in kib) on the system that should be reserved for users with the capability .br cap_sys_admin . .ip the default value in this file is the minimum of [3% of free pages, 8mib] expressed as kib. the default is intended to provide enough for the superuser to log in and kill a process, if necessary, under the default overcommit 'guess' mode (i.e., 0 in .ir /proc/sys/vm/overcommit_memory ). .ip systems running in "overcommit never" mode (i.e., 2 in .ir /proc/sys/vm/overcommit_memory ) should increase the value in this file to account for the full virtual memory size of the programs used to recover (e.g., .br login (1) .br ssh (1), and .br top (1)) otherwise, the superuser may not be able to log in to recover the system. for example, on x86-64 a suitable value is 131072 (128mib reserved). .ip changing the value in this file takes effect whenever an application requests memory. .tp .ir /proc/sys/vm/compact_memory " (since linux 2.6.35)" when 1 is written to this file, all zones are compacted such that free memory is available in contiguous blocks where possible. the effect of this action can be seen by examining .ir /proc/buddyinfo . .ip present only if the kernel was configured with .br config_compaction . .tp .ir /proc/sys/vm/drop_caches " (since linux 2.6.16)" writing to this file causes the kernel to drop clean caches, dentries, and inodes from memory, causing that memory to become free. this can be useful for memory management testing and performing reproducible filesystem benchmarks. because writing to this file causes the benefits of caching to be lost, it can degrade overall system performance. .ip to free pagecache, use: .ip echo 1 > /proc/sys/vm/drop_caches .ip to free dentries and inodes, use: .ip echo 2 > /proc/sys/vm/drop_caches .ip to free pagecache, dentries, and inodes, use: .ip echo 3 > /proc/sys/vm/drop_caches .ip because writing to this file is a nondestructive operation and dirty objects are not freeable, the user should run .br sync (1) first. .tp .ir /proc/sys/vm/sysctl_hugetlb_shm_group " (since linux 2.6.7)" this writable file contains a group id that is allowed to allocate memory using huge pages. if a process has a filesystem group id or any supplementary group id that matches this group id, then it can make huge-page allocations without holding the .br cap_ipc_lock capability; see .br memfd_create (2), .br mmap (2), and .br shmget (2). .tp .ir /proc/sys/vm/legacy_va_layout " (since linux 2.6.9)" .\" the following is from documentation/filesystems/proc.txt if nonzero, this disables the new 32-bit memory-mapping layout; the kernel will use the legacy (2.4) layout for all processes. .tp .ir /proc/sys/vm/memory_failure_early_kill " (since linux 2.6.32)" .\" the following is based on the text in documentation/sysctl/vm.txt control how to kill processes when an uncorrected memory error (typically a 2-bit error in a memory module) that cannot be handled by the kernel is detected in the background by hardware. in some cases (like the page still having a valid copy on disk), the kernel will handle the failure transparently without affecting any applications. but if there is no other up-to-date copy of the data, it will kill processes to prevent any data corruptions from propagating. .ip the file has one of the following values: .rs .ip 1: 4 kill all processes that have the corrupted-and-not-reloadable page mapped as soon as the corruption is detected. note that this is not supported for a few types of pages, such as kernel internally allocated data or the swap cache, but works for the majority of user pages. .ip 0: 4 unmap the corrupted page from all processes and kill a process only if it tries to access the page. .re .ip the kill is performed using a .b sigbus signal with .i si_code set to .br bus_mceerr_ao . processes can handle this if they want to; see .br sigaction (2) for more details. .ip this feature is active only on architectures/platforms with advanced machine check handling and depends on the hardware capabilities. .ip applications can override the .i memory_failure_early_kill setting individually with the .br prctl (2) .b pr_mce_kill operation. .ip present only if the kernel was configured with .br config_memory_failure . .tp .ir /proc/sys/vm/memory_failure_recovery " (since linux 2.6.32)" .\" the following is based on the text in documentation/sysctl/vm.txt enable memory failure recovery (when supported by the platform). .rs .ip 1: 4 attempt recovery. .ip 0: 4 always panic on a memory failure. .re .ip present only if the kernel was configured with .br config_memory_failure . .tp .ir /proc/sys/vm/oom_dump_tasks " (since linux 2.6.25)" .\" the following is from documentation/sysctl/vm.txt enables a system-wide task dump (excluding kernel threads) to be produced when the kernel performs an oom-killing. the dump includes the following information for each task (thread, process): thread id, real user id, thread group id (process id), virtual memory size, resident set size, the cpu that the task is scheduled on, oom_adj score (see the description of .ir /proc/[pid]/oom_adj ), and command name. this is helpful to determine why the oom-killer was invoked and to identify the rogue task that caused it. .ip if this contains the value zero, this information is suppressed. on very large systems with thousands of tasks, it may not be feasible to dump the memory state information for each one. such systems should not be forced to incur a performance penalty in oom situations when the information may not be desired. .ip if this is set to nonzero, this information is shown whenever the oom-killer actually kills a memory-hogging task. .ip the default value is 0. .tp .ir /proc/sys/vm/oom_kill_allocating_task " (since linux 2.6.24)" .\" the following is from documentation/sysctl/vm.txt this enables or disables killing the oom-triggering task in out-of-memory situations. .ip if this is set to zero, the oom-killer will scan through the entire tasklist and select a task based on heuristics to kill. this normally selects a rogue memory-hogging task that frees up a large amount of memory when killed. .ip if this is set to nonzero, the oom-killer simply kills the task that triggered the out-of-memory condition. this avoids a possibly expensive tasklist scan. .ip if .i /proc/sys/vm/panic_on_oom is nonzero, it takes precedence over whatever value is used in .ir /proc/sys/vm/oom_kill_allocating_task . .ip the default value is 0. .tp .ir /proc/sys/vm/overcommit_kbytes " (since linux 3.14)" .\" commit 49f0ce5f92321cdcf741e35f385669a421013cb7 this writable file provides an alternative to .ir /proc/sys/vm/overcommit_ratio for controlling the .i commitlimit when .ir /proc/sys/vm/overcommit_memory has the value 2. it allows the amount of memory overcommitting to be specified as an absolute value (in kb), rather than as a percentage, as is done with .ir overcommit_ratio . this allows for finer-grained control of .ir commitlimit on systems with extremely large memory sizes. .ip only one of .ir overcommit_kbytes or .ir overcommit_ratio can have an effect: if .ir overcommit_kbytes has a nonzero value, then it is used to calculate .ir commitlimit , otherwise .ir overcommit_ratio is used. writing a value to either of these files causes the value in the other file to be set to zero. .tp .i /proc/sys/vm/overcommit_memory this file contains the kernel virtual memory accounting mode. values are: .rs .ip 0: heuristic overcommit (this is the default) .br 1: always overcommit, never check .br 2: always check, never overcommit .re .ip in mode 0, calls of .br mmap (2) with .b map_noreserve are not checked, and the default check is very weak, leading to the risk of getting a process "oom-killed". .ip in mode 1, the kernel pretends there is always enough memory, until memory actually runs out. one use case for this mode is scientific computing applications that employ large sparse arrays. in linux kernel versions before 2.6.0, any nonzero value implies mode 1. .ip in mode 2 (available since linux 2.6), the total virtual address space that can be allocated .ri ( commitlimit in .ir /proc/meminfo ) is calculated as .ip commitlimit = (total_ram \- total_huge_tlb) * overcommit_ratio / 100 + total_swap .ip where: .rs 12 .ip * 3 .i total_ram is the total amount of ram on the system; .ip * .i total_huge_tlb is the amount of memory set aside for huge pages; .ip * .i overcommit_ratio is the value in .ir /proc/sys/vm/overcommit_ratio ; and .ip * .i total_swap is the amount of swap space. .re .ip for example, on a system with 16 gb of physical ram, 16 gb of swap, no space dedicated to huge pages, and an .i overcommit_ratio of 50, this formula yields a .i commitlimit of 24 gb. .ip since linux 3.14, if the value in .i /proc/sys/vm/overcommit_kbytes is nonzero, then .i commitlimit is instead calculated as: .ip commitlimit = overcommit_kbytes + total_swap .ip see also the description of .ir /proc/sys/vm/admin_reserve_kbytes and .ir /proc/sys/vm/user_reserve_kbytes . .tp .ir /proc/sys/vm/overcommit_ratio " (since linux 2.6.0)" this writable file defines a percentage by which memory can be overcommitted. the default value in the file is 50. see the description of .ir /proc/sys/vm/overcommit_memory . .tp .ir /proc/sys/vm/panic_on_oom " (since linux 2.6.18)" .\" the following is adapted from documentation/sysctl/vm.txt this enables or disables a kernel panic in an out-of-memory situation. .ip if this file is set to the value 0, the kernel's oom-killer will kill some rogue process. usually, the oom-killer is able to kill a rogue process and the system will survive. .ip if this file is set to the value 1, then the kernel normally panics when out-of-memory happens. however, if a process limits allocations to certain nodes using memory policies .rb ( mbind (2) .br mpol_bind ) or cpusets .rb ( cpuset (7)) and those nodes reach memory exhaustion status, one process may be killed by the oom-killer. no panic occurs in this case: because other nodes' memory may be free, this means the system as a whole may not have reached an out-of-memory situation yet. .ip if this file is set to the value 2, the kernel always panics when an out-of-memory condition occurs. .ip the default value is 0. 1 and 2 are for failover of clustering. select either according to your policy of failover. .tp .ir /proc/sys/vm/swappiness .\" the following is from documentation/sysctl/vm.txt the value in this file controls how aggressively the kernel will swap memory pages. higher values increase aggressiveness, lower values decrease aggressiveness. the default value is 60. .tp .ir /proc/sys/vm/user_reserve_kbytes " (since linux 3.10)" .\" commit c9b1d0981fcce3d9976d7b7a56e4e0503bc610dd specifies an amount of memory (in kib) to reserve for user processes. this is intended to prevent a user from starting a single memory hogging process, such that they cannot recover (kill the hog). the value in this file has an effect only when .ir /proc/sys/vm/overcommit_memory is set to 2 ("overcommit never" mode). in this case, the system reserves an amount of memory that is the minimum of [3% of current process size, .ir user_reserve_kbytes ]. .ip the default value in this file is the minimum of [3% of free pages, 128mib] expressed as kib. .ip if the value in this file is set to zero, then a user will be allowed to allocate all free memory with a single process (minus the amount reserved by .ir /proc/sys/vm/admin_reserve_kbytes ). any subsequent attempts to execute a command will result in "fork: cannot allocate memory". .ip changing the value in this file takes effect whenever an application requests memory. .tp .ir /proc/sys/vm/unprivileged_userfaultfd " (since linux 5.2)" .\" cefdca0a86be517bc390fc4541e3674b8e7803b0 this (writable) file exposes a flag that controls whether unprivileged processes are allowed to employ .br userfaultfd (2). if this file has the value 1, then unprivileged processes may use .br userfaultfd (2). if this file has the value 0, then only processes that have the .b cap_sys_ptrace capability may employ .br userfaultfd (2). the default value in this file is 1. .tp .ir /proc/sysrq\-trigger " (since linux 2.4.21)" writing a character to this file triggers the same sysrq function as typing alt-sysrq- (see the description of .ir /proc/sys/kernel/sysrq ). this file is normally writable only by .ir root . for further details see the linux kernel source file .i documentation/admin\-guide/sysrq.rst .\" commit 9d85025b0418163fae079c9ba8f8445212de8568 (or .i documentation/sysrq.txt before linux 4.10). .tp .i /proc/sysvipc subdirectory containing the pseudo-files .ir msg ", " sem " and " shm "." these files list the system v interprocess communication (ipc) objects (respectively: message queues, semaphores, and shared memory) that currently exist on the system, providing similar information to that available via .br ipcs (1). these files have headers and are formatted (one ipc object per line) for easy understanding. .br sysvipc (7) provides further background on the information shown by these files. .tp .ir /proc/thread\-self " (since linux 3.17)" .\" commit 0097875bd41528922fb3bb5f348c53f17e00e2fd this directory refers to the thread accessing the .i /proc filesystem, and is identical to the .i /proc/self/task/[tid] directory named by the process thread id .ri ( [tid] ) of the same thread. .tp .ir /proc/timer_list " (since linux 2.6.21)" .\" commit 289f480af87e45f7a6de6ba9b4c061c2e259fe98 this read-only file exposes a list of all currently pending (high-resolution) timers, all clock-event sources, and their parameters in a human-readable form. .tp .ir /proc/timer_stats " (from linux 2.6.21 until linux 4.10)" .\" commit 82f67cd9fca8c8762c15ba7ed0d5747588c1e221 .\" date: fri feb 16 01:28:13 2007 -0800 .\" text largely derived from documentation/timers/timer_stats.txt .\" removed in commit dfb4357da6ddbdf57d583ba64361c9d792b0e0b1 .\" date: wed feb 8 11:26:59 2017 -0800 this is a debugging facility to make timer (ab)use in a linux system visible to kernel and user-space developers. it can be used by kernel and user-space developers to verify that their code does not make undue use of timers. the goal is to avoid unnecessary wakeups, thereby optimizing power consumption. .ip if enabled in the kernel .rb ( config_timer_stats ), but not used, it has almost zero run-time overhead and a relatively small data-structure overhead. even if collection is enabled at run time, overhead is low: all the locking is per-cpu and lookup is hashed. .ip the .i /proc/timer_stats file is used both to control sampling facility and to read out the sampled information. .ip the .i timer_stats functionality is inactive on bootup. a sampling period can be started using the following command: .ip .in +4n .ex # echo 1 > /proc/timer_stats .ee .in .ip the following command stops a sampling period: .ip .in +4n .ex # echo 0 > /proc/timer_stats .ee .in .ip the statistics can be retrieved by: .ip .in +4n .ex $ cat /proc/timer_stats .ee .in .ip while sampling is enabled, each readout from .i /proc/timer_stats will see newly updated statistics. once sampling is disabled, the sampled information is kept until a new sample period is started. this allows multiple readouts. .ip sample output from .ir /proc/timer_stats : .ip .in +4n .ex .rb $ " cat /proc/timer_stats" timer stats version: v0.3 sample period: 1.764 s collection: active 255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer) 71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer) 58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer) 4, 1694 gnome\-shell mod_delayed_work_on (delayed_work_timer_fn) 17, 7 rcu_sched rcu_gp_kthread (process_timeout) \&... 1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn) 1d, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn) 1029 total events, 583.333 events/sec .ee .in .ip the output columns are: .rs .ip * 3 a count of the number of events, optionally (since linux 2.6.23) followed by the letter \(aqd\(aq .\" commit c5c061b8f9726bc2c25e19dec227933a13d1e6b7 deferrable timers if this is a deferrable timer; .ip * the pid of the process that initialized the timer; .ip * the name of the process that initialized the timer; .ip * the function where the timer was initialized; and .ip * (in parentheses) the callback function that is associated with the timer. .re .ip during the linux 4.11 development cycle, this file was removed because of security concerns, as it exposes information across namespaces. furthermore, it is possible to obtain the same information via in-kernel tracing facilities such as ftrace. .tp .i /proc/tty subdirectory containing the pseudo-files and subdirectories for tty drivers and line disciplines. .tp .i /proc/uptime this file contains two numbers (values in seconds): the uptime of the system (including time spent in suspend) and the amount of time spent in the idle process. .tp .i /proc/version this string identifies the kernel version that is currently running. it includes the contents of .ir /proc/sys/kernel/ostype , .ir /proc/sys/kernel/osrelease , and .ir /proc/sys/kernel/version . for example: .ip .in +4n .ex linux version 1.0.9 (quinlan@phaze) #1 sat may 14 01:51:54 edt 1994 .ee .in .\" fixme 2.6.13 seems to have /proc/vmcore implemented; document this .\" see documentation/kdump/kdump.txt .\" commit 666bfddbe8b8fd4fd44617d6c55193d5ac7edb29 .\" needs config_vmcore .\" .tp .ir /proc/vmstat " (since linux 2.6.0)" this file displays various virtual memory statistics. each line of this file contains a single name-value pair, delimited by white space. some lines are present only if the kernel was configured with suitable options. (in some cases, the options required for particular files have changed across kernel versions, so they are not listed here. details can be found by consulting the kernel source code.) the following fields may be present: .\" fixme we need explanations for each of the following fields... .rs .tp .ir nr_free_pages " (since linux 2.6.31)" .\" commit d23ad42324cc4378132e51f2fc5c9ba6cbe75182 .tp .ir nr_alloc_batch " (since linux 3.12)" .\" commit 81c0a2bb515fd4daae8cab64352877480792b515 .tp .ir nr_inactive_anon " (since linux 2.6.28)" .\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db .tp .ir nr_active_anon " (since linux 2.6.28)" .\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db .tp .ir nr_inactive_file " (since linux 2.6.28)" .\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db .tp .ir nr_active_file " (since linux 2.6.28)" .\" commit 4f98a2fee8acdb4ac84545df98cccecfd130f8db .tp .ir nr_unevictable " (since linux 2.6.28)" .\" commit 7b854121eb3e5ba0241882ff939e2c485228c9c5 .tp .ir nr_mlock " (since linux 2.6.28)" .\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820 .tp .ir nr_anon_pages " (since linux 2.6.18)" .\" commit f3dbd34460ff54962d3e3244b6bcb7f5295356e6 .tp .ir nr_mapped " (since linux 2.6.0)" .tp .ir nr_file_pages " (since linux 2.6.18)" .\" commit 347ce434d57da80fd5809c0c836f206a50999c26 .tp .ir nr_dirty " (since linux 2.6.0)" .tp .ir nr_writeback " (since linux 2.6.0)" .tp .ir nr_slab_reclaimable " (since linux 2.6.19)" .\" commit 972d1a7b140569084439a81265a0f15b74e924e0 .\" linux 2.6.0 had nr_slab .tp .ir nr_slab_unreclaimable " (since linux 2.6.19)" .\" commit 972d1a7b140569084439a81265a0f15b74e924e0 .tp .ir nr_page_table_pages " (since linux 2.6.0)" .tp .ir nr_kernel_stack " (since linux 2.6.32)" .\" commit c6a7f5728a1db45d30df55a01adc130b4ab0327c amount of memory allocated to kernel stacks. .tp .ir nr_unstable " (since linux 2.6.0)" .tp .ir nr_bounce " (since linux 2.6.12)" .\" commit edfbe2b0038723e5699ab22695ccd62b5542a5c1 .tp .ir nr_vmscan_write " (since linux 2.6.19)" .\" commit e129b5c23c2b471d47f1c5d2b8b193fc2034af43 .tp .ir nr_vmscan_immediate_reclaim " (since linux 3.2)" .\" commit 49ea7eb65e7c5060807fb9312b1ad4c3eab82e2c .tp .ir nr_writeback_temp " (since linux 2.6.26)" .\" commit fc3ba692a4d19019387c5acaea63131f9eab05dd .tp .ir nr_isolated_anon " (since linux 2.6.32)" .\" commit a731286de62294b63d8ceb3c5914ac52cc17e690 .tp .ir nr_isolated_file " (since linux 2.6.32)" .\" commit a731286de62294b63d8ceb3c5914ac52cc17e690 .tp .ir nr_shmem " (since linux 2.6.32)" .\" commit 4b02108ac1b3354a22b0d83c684797692efdc395 pages used by shmem and .br tmpfs (5). .tp .ir nr_dirtied " (since linux 2.6.37)" .\" commit ea941f0e2a8c02ae876cd73deb4e1557248f258c .tp .ir nr_written " (since linux 2.6.37)" .\" commit ea941f0e2a8c02ae876cd73deb4e1557248f258c .tp .ir nr_pages_scanned " (since linux 3.17)" .\" commit 0d5d823ab4e608ec7b52ac4410de4cb74bbe0edd .tp .ir numa_hit " (since linux 2.6.18)" .\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5 .\" present only if the kernel was configured with .\" .br config_numa . .tp .ir numa_miss " (since linux 2.6.18)" .\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5 .\" present only if the kernel was configured with .\" .br config_numa . .tp .ir numa_foreign " (since linux 2.6.18)" .\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5 .\" present only if the kernel was configured with .\" .br config_numa . .tp .ir numa_interleave " (since linux 2.6.18)" .\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5 .\" present only if the kernel was configured with .\" .br config_numa . .tp .ir numa_local " (since linux 2.6.18)" .\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5 .\" present only if the kernel was configured with .\" .br config_numa . .tp .ir numa_other " (since linux 2.6.18)" .\" commit ca889e6c45e0b112cb2ca9d35afc66297519b5d5 .\" present only if the kernel was configured with .\" .br config_numa . .tp .ir workingset_refault " (since linux 3.15)" .\" commit a528910e12ec7ee203095eb1711468a66b9b60b0 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir workingset_activate " (since linux 3.15)" .\" commit a528910e12ec7ee203095eb1711468a66b9b60b0 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir workingset_nodereclaim " (since linux 3.15)" .\" commit 449dd6984d0e47643c04c807f609dd56d48d5bcc .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir nr_anon_transparent_hugepages " (since linux 2.6.38)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir nr_free_cma " (since linux 3.7)" .\" commit d1ce749a0db12202b711d1aba1d29e823034648d number of free cma (contiguous memory allocator) pages. .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir nr_dirty_threshold " (since linux 2.6.37)" .\" commit 79da826aee6a10902ef411bc65864bd02102fa83 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir nr_dirty_background_threshold " (since linux 2.6.37)" .\" commit 79da826aee6a10902ef411bc65864bd02102fa83 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgpgin " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgpgout " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pswpin " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pswpout " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgalloc_dma " (since linux 2.6.5)" .\" linux 2.6.0 had pgalloc .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgalloc_dma32 " (since linux 2.6.16)" .\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgalloc_normal " (since linux 2.6.5)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgalloc_high " (since linux 2.6.5)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_highmem . .tp .ir pgalloc_movable " (since linux 2.6.23)" .\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgfree " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgactivate " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgdeactivate " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgfault " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgmajfault " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgrefill_dma " (since linux 2.6.5)" .\" linux 2.6.0 had pgrefill .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgrefill_dma32 " (since linux 2.6.16)" .\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgrefill_normal " (since linux 2.6.5)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgrefill_high " (since linux 2.6.5)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_highmem . .tp .ir pgrefill_movable " (since linux 2.6.23)" .\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .\" formerly there were .\" pgsteal_high .\" pgsteal_normal .\" pgsteal_dma32 .\" pgsteal_dma .\" these were split out into pgsteal_kswapd* and pgsteal_direct* .\" in commit 904249aa68010c8e223263c922fcbb840a3f42e4 .tp .ir pgsteal_kswapd_dma " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" linux 2.6.0 had pgsteal .\" present only if the kernel was configured with .\" .\" .br config_vm_event_counters . .tp .ir pgsteal_kswapd_dma32 " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgsteal_kswapd_normal " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgsteal_kswapd_high " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_highmem . .tp .ir pgsteal_kswapd_movable " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgsteal_direct_dma .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgsteal_direct_dma32 " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgsteal_direct_normal " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgsteal_direct_high " (since linux 3.4)" .\" commit 904249aa68010c8e223263c922fcbb840a3f42e4 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_highmem . .tp .ir pgsteal_direct_movable " (since linux 2.6.23)" .\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_kswapd_dma .\" linux 2.6.0 had pgscan .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_kswapd_dma32 " (since linux 2.6.16)" .\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_kswapd_normal " (since linux 2.6.5)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_kswapd_high .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_highmem . .tp .ir pgscan_kswapd_movable " (since linux 2.6.23)" .\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_direct_dma .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_direct_dma32 " (since linux 2.6.16)" .\" commit 9328b8faae922e52073785ed6c1eaa8565648a0e .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_direct_normal .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_direct_high .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_highmem . .tp .ir pgscan_direct_movable " (since linux 2.6.23)" .\" commit 2a1e274acf0b1c192face19a4be7c12d4503eaaf .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgscan_direct_throttle " (since linux 3.6)" .\" commit 68243e76ee343d63c6cf76978588a885951e2818 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir zone_reclaim_failed " (since linux 2.6.31)" .\" commit 24cf72518c79cdcda486ed26074ff8151291cf65 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_numa . .tp .ir pginodesteal " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir slabs_scanned " (since linux 2.6.5)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir kswapd_inodesteal " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir kswapd_low_wmark_hit_quickly " (since 2.6.33)" .\" commit bb3ab596832b920c703d1aea1ce76d69c0f71fb7 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir kswapd_high_wmark_hit_quickly " (since 2.6.33)" .\" commit bb3ab596832b920c703d1aea1ce76d69c0f71fb7 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pageoutrun " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir allocstall " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir pgrotated " (since linux 2.6.0)" .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir drop_pagecache " (since linux 3.15)" .\" commit 5509a5d27b971a90b940e148ca9ca53312e4fa7a .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir drop_slab " (since linux 3.15)" .\" commit 5509a5d27b971a90b940e148ca9ca53312e4fa7a .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir numa_pte_updates " (since linux 3.8)" .\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_numa_balancing . .tp .ir numa_huge_pte_updates " (since linux 3.13)" .\" commit 72403b4a0fbdf433c1fe0127e49864658f6f6468 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_numa_balancing . .tp .ir numa_hint_faults " (since linux 3.8)" .\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_numa_balancing . .tp .ir numa_hint_faults_local " (since linux 3.8)" .\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_numa_balancing . .tp .ir numa_pages_migrated " (since linux 3.8)" .\" commit 03c5a6e16322c997bf8f264851bfa3f532ad515f .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_numa_balancing .\" and .\" .br config_numa_balancing . .tp .ir pgmigrate_success " (since linux 3.8)" .\" commit 5647bc293ab15f66a7b1cda850c5e9d162a6c7c2 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_migration . .tp .ir pgmigrate_fail " (since linux 3.8)" .\" commit 5647bc293ab15f66a7b1cda850c5e9d162a6c7c2 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_migration . .tp .ir compact_migrate_scanned " (since linux 3.8)" .\" commit 397487db696cae0b026a474a5cd66f4e372995e6 .\" linux 3.8 dropped compact_blocks_moved, compact_pages_moved, and .\" compact_pagemigrate_failed .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_compaction . .tp .ir compact_free_scanned " (since linux 3.8)" .\" commit 397487db696cae0b026a474a5cd66f4e372995e6 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_compaction . .tp .ir compact_isolated " (since linux 3.8)" .\" commit 397487db696cae0b026a474a5cd66f4e372995e6 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_compaction . .tp .ir compact_stall " (since linux 2.6.35)" .\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_compaction . .tp .ir compact_fail " (since linux 2.6.35)" .\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_compaction . .tp .ir compact_success " (since linux 2.6.35)" .\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_compaction . .tp .ir htlb_buddy_alloc_success " (since linux 2.6.26)" .\" commit 3b1163006332302117b1b2acf226d4014ff46525 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_hugetlb_page . .tp .ir htlb_buddy_alloc_fail " (since linux 2.6.26)" .\" commit 3b1163006332302117b1b2acf226d4014ff46525 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_hugetlb_page . .tp .ir unevictable_pgs_culled " (since linux 2.6.28)" .\" commit bbfd28eee9fbd73e780b19beb3dc562befbb94fa .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir unevictable_pgs_scanned " (since linux 2.6.28)" .\" commit bbfd28eee9fbd73e780b19beb3dc562befbb94fa .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir unevictable_pgs_rescued " (since linux 2.6.28)" .\" commit bbfd28eee9fbd73e780b19beb3dc562befbb94fa .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir unevictable_pgs_mlocked " (since linux 2.6.28)" .\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir unevictable_pgs_munlocked " (since linux 2.6.28)" .\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir unevictable_pgs_cleared " (since linux 2.6.28)" .\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .tp .ir unevictable_pgs_stranded " (since linux 2.6.28)" .\" commit 5344b7e648980cc2ca613ec03a56a8222ff48820 .\" present only if the kernel was configured with .\" .br config_vm_event_counters . .\" linux 3.7 removed unevictable_pgs_mlockfreed .tp .ir thp_fault_alloc " (since linux 2.6.39)" .\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir thp_fault_fallback " (since linux 2.6.39)" .\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir thp_collapse_alloc " (since linux 2.6.39)" .\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir thp_collapse_alloc_failed " (since linux 2.6.39)" .\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir thp_split " (since linux 2.6.39)" .\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir thp_zero_page_alloc " (since linux 3.8)" .\" commit d8a8e1f0da3d29d7268b3300c96a059d63901b76 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir thp_zero_page_alloc_failed " (since linux 3.8)" .\" commit d8a8e1f0da3d29d7268b3300c96a059d63901b76 see the kernel source file .ir documentation/admin\-guide/mm/transhuge.rst . .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_transparent_hugepage . .tp .ir balloon_inflate " (since linux 3.18)" .\" commit 09316c09dde33aae14f34489d9e3d243ec0d5938 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_memory_balloon . .tp .ir balloon_deflate " (since linux 3.18)" .\" commit 09316c09dde33aae14f34489d9e3d243ec0d5938 .\" present only if the kernel was configured with .\" .br config_vm_event_counters .\" and .\" .br config_memory_balloon . .tp .ir balloon_migrate " (since linux 3.18)" .\" commit 09316c09dde33aae14f34489d9e3d243ec0d5938 .\" present only if the kernel was configured with .\" .br config_vm_event_counters , .\" .br config_memory_balloon , .\" and .\" .br config_balloon_compaction . .tp .ir nr_tlb_remote_flush " (since linux 3.12)" .\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211 .\" present only if the kernel was configured with .\" .br config_debug_tlbflush .\" and .\" .br config_smp . .tp .ir nr_tlb_remote_flush_received " (since linux 3.12)" .\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211 .\" present only if the kernel was configured with .\" .br config_debug_tlbflush .\" and .\" .br config_smp . .tp .ir nr_tlb_local_flush_all " (since linux 3.12)" .\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211 .\" present only if the kernel was configured with .\" .br config_debug_tlbflush . .tp .ir nr_tlb_local_flush_one " (since linux 3.12)" .\" commit 9824cf9753ecbe8f5b47aa9b2f218207defea211 .\" present only if the kernel was configured with .\" .br config_debug_tlbflush . .tp .ir vmacache_find_calls " (since linux 3.16)" .\" commit 4f115147ff802267d0aa41e361c5aa5bd933d896 .\" present only if the kernel was configured with .\" .br config_debug_vm_vmacache . .tp .ir vmacache_find_hits " (since linux 3.16)" .\" commit 4f115147ff802267d0aa41e361c5aa5bd933d896 .\" present only if the kernel was configured with .\" .br config_debug_vm_vmacache . .tp .ir vmacache_full_flushes " (since linux 3.19)" .\" commit f5f302e21257ebb0c074bbafc37606c26d28cc3d .\" present only if the kernel was configured with .\" .br config_debug_vm_vmacache . .re .tp .ir /proc/zoneinfo " (since linux 2.6.13)" this file displays information about memory zones. this is useful for analyzing virtual memory behavior. .\" fixme more should be said about /proc/zoneinfo .sh notes many files contain strings (e.g., the environment and command line) that are in the internal format, with subfields terminated by null bytes (\(aq\e0\(aq). when inspecting such files, you may find that the results are more readable if you use a command of the following form to display them: .pp .in +4n .ex .rb "$" " cat \fifile\fp | tr \(aq\e000\(aq \(aq\en\(aq" .ee .in .pp this manual page is incomplete, possibly inaccurate, and is the kind of thing that needs to be updated very often. .\" .sh acknowledgements .\" the material on /proc/sys/fs and /proc/sys/kernel is closely based on .\" kernel source documentation files written by rik van riel. .sh see also .br cat (1), .br dmesg (1), .br find (1), .br free (1), .br htop (1), .br init (1), .br ps (1), .br pstree (1), .br tr (1), .br uptime (1), .br chroot (2), .br mmap (2), .br readlink (2), .br syslog (2), .br slabinfo (5), .br sysfs (5), .br hier (7), .br namespaces (7), .br time (7), .br arp (8), .br hdparm (8), .br ifconfig (8), .br lsmod (8), .br lspci (8), .br mount (8), .br netstat (8), .br procinfo (8), .br route (8), .br sysctl (8) .pp the linux kernel source files: .ir documentation/filesystems/proc.txt , .ir documentation/sysctl/fs.txt , .ir documentation/sysctl/kernel.txt , .ir documentation/sysctl/net.txt , and .ir documentation/sysctl/vm.txt . .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tcgetpgrp.3 .so man3/getfsent.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_return 3 2021-03-22 "" "linux programmer's manual" .sh name aio_return \- get return status of asynchronous i/o operation .sh synopsis .nf .b "#include " .pp .bi "ssize_t aio_return(struct aiocb *" aiocbp ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_return () function returns the final return status for the asynchronous i/o request with control block pointed to by .ir aiocbp . (see .br aio (7) for a description of the .i aiocb structure.) .pp this function should be called only once for any given request, after .br aio_error (3) returns something other than .br einprogress . .sh return value if the asynchronous i/o operation has completed, this function returns the value that would have been returned in case of a synchronous .br read (2), .br write (2), .br fsync (2), or .br fdatasync (2), call. on error, \-1 is returned, and \fierrno\fp is set to indicate the error. .pp if the asynchronous i/o operation has not yet completed, the return value and effect of .br aio_return () are undefined. .sh errors .tp .b einval .i aiocbp does not point at a control block for an asynchronous i/o request of which the return status has not been retrieved yet. .tp .b enosys .br aio_return () is not implemented. .sh versions the .br aio_return () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_return () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples see .br aio (7). .sh see also .br aio_cancel (3), .br aio_error (3), .br aio_fsync (3), .br aio_read (3), .br aio_suspend (3), .br aio_write (3), .br lio_listio (3), .br aio (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/stat.2 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" and copyright (c) 2011 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th catan 3 2021-03-22 "" "linux programmer's manual" .sh name catan, catanf, catanl \- complex arc tangents .sh synopsis .nf .b #include .pp .bi "double complex catan(double complex " z ); .bi "float complex catanf(float complex " z ); .bi "long double complex catanl(long double complex " z ); .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex arc tangent of .ir z . if \fiy\ =\ catan(z)\fp, then \fiz\ =\ ctan(y)\fp. the real part of y is chosen in the interval [\-pi/2,pi/2]. .pp one has: .pp .nf catan(z) = (clog(1 + i * z) \- clog(1 \- i * z)) / (2 * i) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br catan (), .br catanf (), .br catanl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh examples .ex /* link with "\-lm" */ #include #include #include #include int main(int argc, char *argv[]) { double complex z, c, f; double complex i = i; if (argc != 3) { fprintf(stderr, "usage: %s \en", argv[0]); exit(exit_failure); } z = atof(argv[1]) + atof(argv[2]) * i; c = catan(z); printf("catan() = %6.3f %6.3f*i\en", creal(c), cimag(c)); f = (clog(1 + i * z) \- clog(1 \- i * z)) / (2 * i); printf("formula = %6.3f %6.3f*i\en", creal(f2), cimag(f2)); exit(exit_success); } .ee .sh see also .br ccos (3), .br clog (3), .br ctan (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/endian.3 .so man2/setuid.2 .so man3/cpu_set.3 .\" copyright (c) 2007, michael kerrisk .\" and copyright (c) 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2007-05-31, mtk: rewrite and substantial additional text. .\" 2008-12-03, mtk: rewrote some pieces and fixed some errors .\" .th bindresvport 3 2021-03-22 "" "linux programmer's manual" .sh name bindresvport \- bind a socket to a privileged ip port .sh synopsis .nf .b #include .b #include .pp .bi "int bindresvport(int " sockfd ", struct sockaddr_in *" sin ); .fi .sh description .br bindresvport () is used to bind the socket referred to by the file descriptor .i sockfd to a privileged anonymous ip port, that is, a port number arbitrarily selected from the range 512 to 1023. .\" glibc actually starts searching with a port # in the range 600 to 1023 .pp if the .br bind (2) performed by .br bindresvport () is successful, and .i sin is not null, then .i sin\->sin_port returns the port number actually allocated. .pp .i sin can be null, in which case .i sin\->sin_family is implicitly taken to be .br af_inet . however, in this case, .br bindresvport () has no way to return the port number actually allocated. (this information can later be obtained using .br getsockname (2).) .sh return value .br bindresvport () returns 0 on success; otherwise \-1 is returned and .i errno is set to indicate the error. .sh errors .br bindresvport () can fail for any of the same reasons as .br bind (2). in addition, the following errors may occur: .tp .br eacces the calling process was not privileged (on linux: the calling process did not have the .b cap_net_bind_service capability in the user namespace governing its network namespace). .tp .b eaddrinuse all privileged ports are in use. .tp .br eafnosupport " (" epfnosupport " in glibc 2.7 and earlier)" .i sin is not null and .i sin\->sin_family is not .br af_inet . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br bindresvport () t} thread safety t{ glibc\ >=\ 2.17: mt-safe; .\" commit f6da27e53695ad1cc0e2a9490358decbbfdff5e5 glibc\ <\ 2.17: mt-unsafe t} .te .hy .ad .sp 1 .pp the .br bindresvport () function uses a static variable that was not protected by a lock before glibc 2.17, rendering the function mt-unsafe. .sh conforming to not in posix.1. present on the bsds, solaris, and many other systems. .sh notes unlike some .br bindresvport () implementations, the glibc implementation ignores any value that the caller supplies in .ir sin\->sin_port . .sh see also .br bind (2), .br getsockname (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1995 by jim van zandt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getw 3 2021-03-22 "gnu" "linux programmer's manual" .sh name getw, putw \- input and output of words (ints) .sh synopsis .nf .b #include .pp .bi "int getw(file *" stream ); .bi "int putw(int " w ", file *" stream ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br getw (), .br putw (): .nf since glibc 2.3.3: _xopen_source && ! (_posix_c_source >= 200112l) || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source before glibc 2.3.3: _svid_source || _bsd_source || _xopen_source .fi .sh description .br getw () reads a word (that is, an \fiint\fp) from \fistream\fp. it's provided for compatibility with svr4. we recommend you use .br fread (3) instead. .pp .br putw () writes the word \fiw\fp (that is, an \fiint\fp) to \fistream\fp. it is provided for compatibility with svr4, but we recommend you use .br fwrite (3) instead. .sh return value normally, .br getw () returns the word read, and .br putw () returns 0. on error, they return \fbeof\fp. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br getw (), .br putw () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to svr4, susv2. not present in posix.1. .sh bugs the value returned on error is also a legitimate data value. .br ferror (3) can be used to distinguish between the two cases. .sh see also .br ferror (3), .br fread (3), .br fwrite (3), .br getc (3), .br putc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 19:42:04 1993 by rik faith (faith@cs.unc.edu) .\" added fabsl, fabsf, aeb, 2001-06-07 .\" .th fabs 3 2021-03-22 "" "linux programmer's manual" .sh name fabs, fabsf, fabsl \- absolute value of floating-point number .sh synopsis .nf .b #include .pp .bi "double fabs(double " x ); .bi "float fabsf(float " x ); .bi "long double fabsl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br fabsf (), .br fabsl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the absolute value of the floating-point number .ir x . .sh return value these functions return the absolute value of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is \-0, +0 is returned. .pp if .i x is negative infinity or positive infinity, positive infinity is returned. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br fabs (), .br fabsf (), .br fabsl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br abs (3), .br cabs (3), .br ceil (3), .br floor (3), .br labs (3), .br rint (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th path_resolution 7 2021-08-27 "linux" "linux programmer's manual" .sh name path_resolution \- how a pathname is resolved to a file .sh description some unix/linux system calls have as parameter one or more filenames. a filename (or pathname) is resolved as follows. .ss step 1: start of the resolution process if the pathname starts with the \(aq/\(aq character, the starting lookup directory is the root directory of the calling process. a process inherits its root directory from its parent. usually this will be the root directory of the file hierarchy. a process may get a different root directory by use of the .br chroot (2) system call, or may temporarily use a different root directory by using .br openat2 (2) with the .b resolve_in_root flag set. .pp a process may get an entirely private mount namespace in case it\(emor one of its ancestors\(emwas started by an invocation of the .br clone (2) system call that had the .b clone_newns flag set. this handles the \(aq/\(aq part of the pathname. .pp if the pathname does not start with the \(aq/\(aq character, the starting lookup directory of the resolution process is the current working directory of the process \(em or in the case of .br openat (2)-style system calls, the .i dfd argument (or the current working directory if .b at_fdcwd is passed as the .i dfd argument). the current working directory is inherited from the parent, and can be changed by use of the .br chdir (2) system call. .pp pathnames starting with a \(aq/\(aq character are called absolute pathnames. pathnames not starting with a \(aq/\(aq are called relative pathnames. .ss step 2: walk along the path set the current lookup directory to the starting lookup directory. now, for each nonfinal component of the pathname, where a component is a substring delimited by \(aq/\(aq characters, this component is looked up in the current lookup directory. .pp if the process does not have search permission on the current lookup directory, an .b eacces error is returned ("permission denied"). .pp if the component is not found, an .b enoent error is returned ("no such file or directory"). .pp if the component is found, but is neither a directory nor a symbolic link, an .b enotdir error is returned ("not a directory"). .pp if the component is found and is a directory, we set the current lookup directory to that directory, and go to the next component. .pp if the component is found and is a symbolic link (symlink), we first resolve this symbolic link (with the current lookup directory as starting lookup directory). upon error, that error is returned. if the result is not a directory, an .b enotdir error is returned. if the resolution of the symbolic link is successful and returns a directory, we set the current lookup directory to that directory, and go to the next component. note that the resolution process here can involve recursion if the prefix ('dirname') component of a pathname contains a filename that is a symbolic link that resolves to a directory (where the prefix component of that directory may contain a symbolic link, and so on). in order to protect the kernel against stack overflow, and also to protect against denial of service, there are limits on the maximum recursion depth, and on the maximum number of symbolic links followed. an .b eloop error is returned when the maximum is exceeded ("too many levels of symbolic links"). .pp .\" .\" presently: max recursion depth during symlink resolution: 5 .\" max total number of symbolic links followed: 40 .\" _posix_symloop_max is 8 as currently implemented on linux, the maximum number .\" maxsymlinks is 40 of symbolic links that will be followed while resolving a pathname is 40. in kernels before 2.6.18, the limit on the recursion depth was 5. starting with linux 2.6.18, this limit .\" max_nested_links was raised to 8. in linux 4.2, .\" commit 894bc8c4662ba9daceafe943a5ba0dd407da5cd3 the kernel's pathname-resolution code was reworked to eliminate the use of recursion, so that the only limit that remains is the maximum of 40 resolutions for the entire pathname. .pp the resolution of symbolic links during this stage can be blocked by using .br openat2 (2), with the .b resolve_no_symlinks flag set. .ss step 3: find the final entry the lookup of the final component of the pathname goes just like that of all other components, as described in the previous step, with two differences: (i) the final component need not be a directory (at least as far as the path resolution process is concerned\(emit may have to be a directory, or a nondirectory, because of the requirements of the specific system call), and (ii) it is not necessarily an error if the component is not found\(emmaybe we are just creating it. the details on the treatment of the final entry are described in the manual pages of the specific system calls. .ss . and .. by convention, every directory has the entries "." and "..", which refer to the directory itself and to its parent directory, respectively. .pp the path resolution process will assume that these entries have their conventional meanings, regardless of whether they are actually present in the physical filesystem. .pp one cannot walk up past the root: "/.." is the same as "/". .ss mount points after a "mount dev path" command, the pathname "path" refers to the root of the filesystem hierarchy on the device "dev", and no longer to whatever it referred to earlier. .pp one can walk out of a mounted filesystem: "path/.." refers to the parent directory of "path", outside of the filesystem hierarchy on "dev". .pp traversal of mount points can be blocked by using .br openat2 (2), with the .b resolve_no_xdev flag set (though note that this also restricts bind mount traversal). .ss trailing slashes if a pathname ends in a \(aq/\(aq, that forces resolution of the preceding component as in step 2: the component preceding the slash either exists and resolves to a directory or it names a directory that is to be created immediately after the pathname is resolved. otherwise, a trailing \(aq/\(aq is ignored. .ss final symlink if the last component of a pathname is a symbolic link, then it depends on the system call whether the file referred to will be the symbolic link or the result of path resolution on its contents. for example, the system call .br lstat (2) will operate on the symlink, while .br stat (2) operates on the file pointed to by the symlink. .ss length limit there is a maximum length for pathnames. if the pathname (or some intermediate pathname obtained while resolving symbolic links) is too long, an .b enametoolong error is returned ("filename too long"). .ss empty pathname in the original unix, the empty pathname referred to the current directory. nowadays posix decrees that an empty pathname must not be resolved successfully. linux returns .b enoent in this case. .ss permissions the permission bits of a file consist of three groups of three bits; see .br chmod (1) and .br stat (2). the first group of three is used when the effective user id of the calling process equals the owner id of the file. the second group of three is used when the group id of the file either equals the effective group id of the calling process, or is one of the supplementary group ids of the calling process (as set by .br setgroups (2)). when neither holds, the third group is used. .pp of the three bits used, the first bit determines read permission, the second write permission, and the last execute permission in case of ordinary files, or search permission in case of directories. .pp linux uses the fsuid instead of the effective user id in permission checks. ordinarily the fsuid will equal the effective user id, but the fsuid can be changed by the system call .br setfsuid (2). .pp (here "fsuid" stands for something like "filesystem user id". the concept was required for the implementation of a user space nfs server at a time when processes could send a signal to a process with the same effective user id. it is obsolete now. nobody should use .br setfsuid (2).) .pp similarly, linux uses the fsgid ("filesystem group id") instead of the effective group id. see .br setfsgid (2). .\" fixme . say something about filesystem mounted read-only ? .ss bypassing permission checks: superuser and capabilities on a traditional unix system, the superuser .ri ( root , user id 0) is all-powerful, and bypasses all permissions restrictions when accessing files. .\" (but for exec at least one x bit must be set) -- aeb .\" but there is variation across systems on this point: for .\" example, hp-ux and tru64 are as described by aeb. however, .\" on some implementations (e.g., solaris, freebsd), .\" access(x_ok) by superuser will report success, regardless .\" of the file's execute permission bits. -- mtk (oct 05) .pp on linux, superuser privileges are divided into capabilities (see .br capabilities (7)). two capabilities are relevant for file permissions checks: .b cap_dac_override and .br cap_dac_read_search . (a process has these capabilities if its fsuid is 0.) .pp the .b cap_dac_override capability overrides all permission checking, but grants execute permission only when at least one of the file's three execute permission bits is set. .pp the .b cap_dac_read_search capability grants read and search permission on directories, and read permission on ordinary files. .\" fixme . say something about immutable files .\" fixme . say something about acls .sh see also .br readlink (2), .br capabilities (7), .br credentials (7), .br symlink (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th csin 3 2021-03-22 "" "linux programmer's manual" .sh name csin, csinf, csinl \- complex sine function .sh synopsis .nf .b #include .pp .bi "double complex csin(double complex " z ");" .bi "float complex csinf(float complex " z ); .bi "long double complex csinl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex sine of .ir z . .pp the complex sine function is defined as: .pp .nf csin(z) = (exp(i * z) \- exp(\-i * z)) / (2 * i) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br csin (), .br csinf (), .br csinl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br casin (3), .br ccos (3), .br ctan (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gethostbyname.3 .so man3/drand48.3 .\" copyright (c) 2014 google, inc., written by david drysdale .\" and copyright (c) 2015, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th execveat 2 2021-08-27 "linux" "linux programmer's manual" .sh name execveat \- execute program relative to a directory file descriptor .sh synopsis .nf .br "#include " " /* definition of " at_* " constants */" .b #include .pp .bi "int execveat(int " dirfd ", const char *" pathname , .bi " const char *const " argv "[], const char *const " envp [], .bi " int " flags ); .fi .sh description .\" commit 51f39a1f0cea1cacf8c787f652f26dfee9611874 the .br execveat () system call executes the program referred to by the combination of .i dirfd and .ir pathname . it operates in exactly the same way as .br execve (2), except for the differences described in this manual page. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br execve (2) for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br execve (2)). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp if .i pathname is an empty string and the .br at_empty_path flag is specified, then the file descriptor .i dirfd specifies the file to be executed (i.e., .ir dirfd refers to an executable file, rather than a directory). .pp the .i flags argument is a bit mask that can include zero or more of the following flags: .tp .br at_empty_path if .i pathname is an empty string, operate on the file referred to by .ir dirfd (which may have been obtained using the .br open (2) .b o_path flag). .tp .b at_symlink_nofollow if the file identified by .i dirfd and a non-null .i pathname is a symbolic link, then the call fails with the error .br eloop . .sh return value on success, .br execveat () does not return. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors the same errors that occur for .br execve (2) can also occur for .br execveat (). the following additional errors can occur for .br execveat (): .tp .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b einval invalid flag specified in .ir flags . .tp .b eloop .i flags includes .br at_symlink_nofollow and the file identified by .i dirfd and a non-null .i pathname is a symbolic link. .tp .b enoent the program identified by .i dirfd and .i pathname requires the use of an interpreter program (such as a script starting with "#!"), but the file descriptor .i dirfd was opened with the .b o_cloexec flag, with the result that the program file is inaccessible to the launched interpreter. see bugs. .tp .b enotdir .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .sh versions .br execveat () was added to linux in kernel 3.19. library support was added to glibc in version 2.34. .sh conforming to the .br execveat () system call is linux-specific. .sh notes in addition to the reasons explained in .br openat (2), the .br execveat () system call is also needed to allow .br fexecve (3) to be implemented on systems that do not have the .i /proc filesystem mounted. .pp when asked to execute a script file, the .ir argv[0] that is passed to the script interpreter is a string of the form .ir /dev/fd/n or .ir /dev/fd/n/p , where .i n is the number of the file descriptor passed via the .ir dirfd argument. a string of the first form occurs when .br at_empty_path is employed. a string of the second form occurs when the script is specified via both .ir dirfd and .ir pathname ; in this case, .ir p is the value given in .ir pathname . .pp for the same reasons described in .br fexecve (3), the natural idiom when using .br execveat () is to set the close-on-exec flag on .ir dirfd . (but see bugs.) .sh bugs the .b enoent error described above means that it is not possible to set the close-on-exec flag on the file descriptor given to a call of the form: .pp execveat(fd, "", argv, envp, at_empty_path); .pp however, the inability to set the close-on-exec flag means that a file descriptor referring to the script leaks through to the script itself. as well as wasting a file descriptor, this leakage can lead to file-descriptor exhaustion in scenarios where scripts recursively employ .br execveat (). .\" for an example, see michael kerrisk's 2015-01-10 reply in this lkml .\" thread (http://thread.gmane.org/gmane.linux.kernel/1836105/focus=20229): .\" .\" subject: [patchv10 man-pages 5/5] execveat.2: initial man page.\" for execveat(2 .\" date: mon, 24 nov 2014 11:53:59 +0000 .sh see also .br execve (2), .br openat (2), .br fexecve (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th timer_getoverrun 2 2021-03-22 linux "linux programmer's manual" .sh name timer_getoverrun \- get overrun count for a posix per-process timer .sh synopsis .nf .b #include .pp .bi "int timer_getoverrun(timer_t " timerid ); .fi .pp link with \fi\-lrt\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br timer_getoverrun (): .nf _posix_c_source >= 199309l .fi .sh description .br timer_getoverrun () returns the "overrun count" for the timer referred to by .ir timerid . an application can use the overrun count to accurately calculate the number of timer expirations that would have occurred over a given time interval. timer overruns can occur both when receiving expiration notifications via signals .rb ( sigev_signal ), and via threads .rb ( sigev_thread ). .pp when expiration notifications are delivered via a signal, overruns can occur as follows. regardless of whether or not a real-time signal is used for timer notifications, the system queues at most one signal per timer. (this is the behavior specified by posix.1. the alternative, queuing one signal for each timer expiration, could easily result in overflowing the allowed limits for queued signals on the system.) because of system scheduling delays, or because the signal may be temporarily blocked, there can be a delay between the time when the notification signal is generated and the time when it is delivered (e.g., caught by a signal handler) or accepted (e.g., using .br sigwaitinfo (2)). in this interval, further timer expirations may occur. the timer overrun count is the number of additional timer expirations that occurred between the time when the signal was generated and when it was delivered or accepted. .pp timer overruns can also occur when expiration notifications are delivered via invocation of a thread, since there may be an arbitrary delay between an expiration of the timer and the invocation of the notification thread, and in that delay interval, additional timer expirations may occur. .sh return value on success, .br timer_getoverrun () returns the overrun count of the specified timer; this count may be 0 if no overruns have occurred. on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i timerid is not a valid timer id. .sh versions this system call is available since linux 2.6. .sh conforming to posix.1-2001, posix.1-2008. .sh notes when timer notifications are delivered via signals .rb ( sigev_signal ), on linux it is also possible to obtain the overrun count via the .i si_overrun field of the .i siginfo_t structure (see .br sigaction (2)). this allows an application to avoid the overhead of making a system call to obtain the overrun count, but is a nonportable extension to posix.1. .pp posix.1 discusses timer overruns only in the context of timer notifications using signals. .\" fixme . austin bug filed, 11 feb 09 .\" https://www.austingroupbugs.net/view.php?id=95 .sh bugs posix.1 specifies that if the timer overrun count is equal to or greater than an implementation-defined maximum, .br delaytimer_max , then .br timer_getoverrun () should return .br delaytimer_max . however, before linux 4.19, .\" http://bugzilla.kernel.org/show_bug.cgi?id=12665 if the timer overrun value exceeds the maximum representable integer, the counter cycles, starting once more from low values. since linux 4.19, .\" commit 78c9c4dfbf8c04883941445a195276bb4bb92c76 .br timer_getoverrun () returns .b delaytimer_max (defined as .b int_max in .ir ) in this case (and the overrun value is reset to 0). .sh examples see .br timer_create (2). .sh see also .br clock_gettime (2), .br sigaction (2), .br signalfd (2), .br sigwaitinfo (2), .br timer_create (2), .br timer_delete (2), .br timer_settime (2), .br signal (7), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/puts.3 .so man3/resolver.3 .\" copyright (c) 2006 justin pryzby .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(permissive_misc) .\" permission is hereby granted, free of charge, to any person obtaining .\" a copy of this software and associated documentation files (the .\" "software"), to deal in the software without restriction, including .\" without limitation the rights to use, copy, modify, merge, publish, .\" distribute, sublicense, and/or sell copies of the software, and to .\" permit persons to whom the software is furnished to do so, subject to .\" the following conditions: .\" .\" the above copyright notice and this permission notice shall be .\" included in all copies or substantial portions of the software. .\" .\" the software is provided "as is", without warranty of any kind, .\" express or implied, including but not limited to the warranties of .\" merchantability, fitness for a particular purpose and noninfringement. .\" in no event shall the authors or copyright holders be liable for any .\" claim, damages or other liability, whether in an action of contract, .\" tort or otherwise, arising from, out of or in connection with the .\" software or the use or other dealings in the software. .\" %%%license_end .\" .\" references: .\" glibc manual and source .th error 3 2021-03-22 "gnu" "linux programmer's manual" .sh name error, error_at_line, error_message_count, error_one_per_line, error_print_progname \- glibc error reporting functions .sh synopsis .nf .b #include .pp .bi "void error(int " status ", int " errnum ", const char *" format ", ...);" .bi "void error_at_line(int " status ", int " errnum ", const char *" filename , .bi " unsigned int " linenum ", const char *" format ", ...);" .pp .bi "extern unsigned int " error_message_count ; .bi "extern int " error_one_per_line ; .pp .bi "extern void (*" error_print_progname ")(void);" .fi .sh description .br error () is a general error-reporting function. it flushes .ir stdout , and then outputs to .i stderr the program name, a colon and a space, the message specified by the .br printf (3)-style format string \fiformat\fp, and, if \fierrnum\fp is nonzero, a second colon and a space followed by the string given by .ir strerror(errnum) . any arguments required for .i format should follow .i format in the argument list. the output is terminated by a newline character. .pp the program name printed by .br error () is the value of the global variable .br program_invocation_name (3). .i program_invocation_name initially has the same value as .ir main ()'s .ir argv[0] . the value of this variable can be modified to change the output of .br error (). .pp if \fistatus\fp has a nonzero value, then .br error () calls .br exit (3) to terminate the program using the given value as the exit status; otherwise it returns after printing the error message. .pp the .br error_at_line () function is exactly the same as .br error (), except for the addition of the arguments .i filename and .ir linenum . the output produced is as for .br error (), except that after the program name are written: a colon, the value of .ir filename , a colon, and the value of .ir linenum . the preprocessor values \fb__line__\fp and \fb__file__\fp may be useful when calling .br error_at_line (), but other values can also be used. for example, these arguments could refer to a location in an input file. .pp if the global variable \fierror_one_per_line\fp is set nonzero, a sequence of .br error_at_line () calls with the same value of \fifilename\fp and \filinenum\fp will result in only one message (the first) being output. .pp the global variable \fierror_message_count\fp counts the number of messages that have been output by .br error () and .br error_at_line (). .pp if the global variable \fierror_print_progname\fp is assigned the address of a function (i.e., is not null), then that function is called instead of prefixing the message with the program name and colon. the function should print a suitable string to .ir stderr . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br error () t} thread safety mt-safe locale t{ .br error_at_line () t} thread safety t{ mt-unsafe\ race: error_at_line/\:error_one_per_line locale t} .te .hy .ad .sp 1 .pp the internal .i error_one_per_line variable is accessed (without any form of synchronization, but since it's an .i int used once, it should be safe enough) and, if .i error_one_per_line is set nonzero, the internal static variables (not exposed to users) used to hold the last printed filename and line number are accessed and modified without synchronization; the update is not atomic and it occurs before disabling cancellation, so it can be interrupted only after one of the two variables is modified. after that, .br error_at_line () is very much like .br error (). .sh conforming to these functions and variables are gnu extensions, and should not be used in programs intended to be portable. .sh see also .br err (3), .br errno (3), .br exit (3), .br perror (3), .br program_invocation_name (3), .br strerror (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/drand48_r.3 .so man7/iso_8859-7.7 .\" copyright (c) international business machines corp., 2006 .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see .\" the gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" history: .\" 2005-09-28, created by arnd bergmann , .\" mark nutter and .\" ulrich weigand .\" 2006-06-16, revised by eduardo m. fleury .\" 2007-07-10, quite a lot of polishing by mtk .\" 2007-09-28, updates for newer kernels by jeremy kerr .\" .th spufs 7 2021-03-22 linux "linux programmer's manual" .sh name spufs \- spu filesystem .sh description the spu filesystem is used on powerpc machines that implement the cell broadband engine architecture in order to access synergistic processor units (spus). .pp the filesystem provides a name space similar to posix shared memory or message queues. users that have write permissions on the filesystem can use .br spu_create (2) to establish spu contexts under the .b spufs root directory. .pp every spu context is represented by a directory containing a predefined set of files. these files can be used for manipulating the state of the logical spu. users can change permissions on the files, but can't add or remove files. .ss mount options .tp .b uid= set the user owning the mount point; the default is 0 (root). .tp .b gid= set the group owning the mount point; the default is 0 (root). .tp .b mode= set the mode of the top-level directory in .br spufs , as an octal mode string. the default is 0775. .ss files the files in .b spufs mostly follow the standard behavior for regular system calls like .br read (2) or .br write (2), but often support only a subset of the operations supported on regular filesystems. this list details the supported operations and the deviations from the standard behavior described in the respective man pages. .pp all files that support the .br read (2) operation also support .br readv (2) and all files that support the .br write (2) operation also support .br writev (2). all files support the .br access (2) and .br stat (2) family of operations, but for the latter call, the only fields of the returned .i stat structure that contain reliable information are .ir st_mode , .ir st_nlink , .ir st_uid , and .ir st_gid . .pp all files support the .br chmod (2)/ fchmod (2) and .br chown (2)/ fchown (2) operations, but will not be able to grant permissions that contradict the possible operations (e.g., read access on the .i wbox file). .pp the current set of files is: .tp .i /capabilities contains a comma-delimited string representing the capabilities of this spu context. possible capabilities are: .rs .tp .b sched this context may be scheduled. .tp .b step this context can be run in single-step mode, for debugging. .pp new capabilities flags may be added in the future. .re .tp .i /mem the contents of the local storage memory of the spu. this can be accessed like a regular shared memory file and contains both code and data in the address space of the spu. the possible operations on an open .i mem file are: .rs .tp .br read "(2), " pread "(2), " write "(2), " pwrite "(2), " lseek (2) these operate as usual, with the exception that .br lseek (2), .br write (2), and .br pwrite (2) are not supported beyond the end of the file. the file size is the size of the local storage of the spu, which is normally 256 kilobytes. .tp .br mmap (2) mapping .i mem into the process address space provides access to the spu local storage within the process address space. only .b map_shared mappings are allowed. .re .tp .i /regs contains the saved general-purpose registers of the spu context. this file contains the 128-bit values of each register, from register 0 to register 127, in order. this allows the general-purpose registers to be inspected for debugging. .ip reading to or writing from this file requires that the context is scheduled out, so use of this file is not recommended in normal program operation. .ip the .i regs file is not present on contexts that have been created with the .b spu_create_nosched flag. .tp .i /mbox the first spu-to-cpu communication mailbox. this file is read-only and can be read in units of 4 bytes. the file can be used only in nonblocking mode \- even .br poll (2) cannot be used to block on this file. the only possible operation on an open .i mbox file is: .rs .tp .br read (2) if .i count is smaller than four, .br read (2) returns \-1 and sets .i errno to .br einval . if there is no data available in the mailbox (i.e., the spu has not sent a mailbox message), the return value is set to \-1 and .i errno is set to .br eagain . when data has been read successfully, four bytes are placed in the data buffer and the value four is returned. .re .tp .i /ibox the second spu-to-cpu communication mailbox. this file is similar to the first mailbox file, but can be read in blocking i/o mode, thus calling .br read (2) on an open .i ibox file will block until the spu has written data to its interrupt mailbox channel (unless the file has been opened with .br o_nonblock , see below). also, .br poll (2) and similar system calls can be used to monitor for the presence of mailbox data. .ip the possible operations on an open .i ibox file are: .rs .tp .br read (2) if .i count is smaller than four, .br read (2) returns \-1 and sets .i errno to .br einval . if there is no data available in the mailbox and the file descriptor has been opened with .br o_nonblock , the return value is set to \-1 and .i errno is set to .br eagain . .ip if there is no data available in the mailbox and the file descriptor has been opened without .br o_nonblock , the call will block until the spu writes to its interrupt mailbox channel. when data has been read successfully, four bytes are placed in the data buffer and the value four is returned. .tp .br poll (2) poll on the .i ibox file returns .i "(pollin | pollrdnorm)" whenever data is available for reading. .re .tp .i /wbox the cpu-to-spu communication mailbox. it is write-only and can be written in units of four bytes. if the mailbox is full, .br write (2) will block, and .br poll (2) can be used to block until the mailbox is available for writing again. the possible operations on an open .i wbox file are: .rs .tp .br write (2) if .i count is smaller than four, .br write (2) returns \-1 and sets .i errno to .br einval . if there is no space available in the mailbox and the file descriptor has been opened with .br o_nonblock , the return value is set to \-1 and .i errno is set to .br eagain . .ip if there is no space available in the mailbox and the file descriptor has been opened without .br o_nonblock , the call will block until the spu reads from its ppe (powerpc processing element) mailbox channel. when data has been written successfully, the system call returns four as its function result. .tp .br poll (2) a poll on the .i wbox file returns .i "(pollout | pollwrnorm)" whenever space is available for writing. .re .tp .ir /mbox_stat ", " /ibox_stat ", " /wbox_stat these are read-only files that contain the length of the current queue of each mailbox\(emthat is, how many words can be read from .ir mbox " or " ibox or how many words can be written to .i wbox without blocking. the files can be read only in four-byte units and return a big-endian binary integer number. the only possible operation on an open .i *box_stat file is: .rs .tp .br read (2) if .i count is smaller than four, .br read (2) returns \-1 and sets .i errno to .br einval . otherwise, a four-byte value is placed in the data buffer. this value is the number of elements that can be read from (for .ir mbox_stat and .ir ibox_stat ) or written to (for .ir wbox_stat ) the respective mailbox without blocking or returning an .br eagain error. .re .tp .ir /npc ", " /decr ", " /decr_status ", " /spu_tag_mask ", " \ /event_mask ", " /event_status ", " /srr0 ", " /lslr internal registers of the spu. these files contain an ascii string representing the hex value of the specified register. reads and writes on these files (except for .ir npc , see below) require that the spu context be scheduled out, so frequent access to these files is not recommended for normal program operation. .ip the contents of these files are: .rs .tp 16 .i npc next program counter \- valid only when the spu is in a stopped state. .tp .i decr spu decrementer .tp .i decr_status decrementer status .tp .i spu_tag_mask mfc tag mask for spu dma .tp .i event_mask event mask for spu interrupts .tp .i event_status number of spu events pending (read-only) .tp .i srr0 interrupt return address register .tp .i lslr local store limit register .re .ip the possible operations on these files are: .rs .tp .br read (2) reads the current register value. if the register value is larger than the buffer passed to the .br read (2) system call, subsequent reads will continue reading from the same buffer, until the end of the buffer is reached. .ip when a complete string has been read, all subsequent read operations will return zero bytes and a new file descriptor needs to be opened to read a new value. .tp .br write (2) a .br write (2) operation on the file sets the register to the value given in the string. the string is parsed from the beginning until the first nonnumeric character or the end of the buffer. subsequent writes to the same file descriptor overwrite the previous setting. .ip except for the .i npc file, these files are not present on contexts that have been created with the .b spu_create_nosched flag. .re .tp .ir /fpcr this file provides access to the floating point status and control register (fcpr) as a binary, four-byte file. the operations on the .i fpcr file are: .rs .tp .br read (2) if .i count is smaller than four, .br read (2) returns \-1 and sets .i errno to .br einval . otherwise, a four-byte value is placed in the data buffer; this is the current value of the .i fpcr register. .tp .br write (2) if .i count is smaller than four, .br write (2) returns \-1 and sets .i errno to .br einval . otherwise, a four-byte value is copied from the data buffer, updating the value of the .i fpcr register. .re .tp .ir /signal1 ", " /signal2 the files provide access to the two signal notification channels of an spu. these are read-write files that operate on four-byte words. writing to one of these files triggers an interrupt on the spu. the value written to the signal files can be read from the spu through a channel read or from host user space through the file. after the value has been read by the spu, it is reset to zero. the possible operations on an open .i signal1 or .i signal2 file are: .rs .tp .br read (2) if .i count is smaller than four, .br read (2) returns \-1 and sets .i errno to .br einval . otherwise, a four-byte value is placed in the data buffer; this is the current value of the specified signal notification register. .tp .br write (2) if .i count is smaller than four, .br write (2) returns \-1 and sets .i errno to .br einval . otherwise, a four-byte value is copied from the data buffer, updating the value of the specified signal notification register. the signal notification register will either be replaced with the input data or will be updated to the bitwise or operation of the old value and the input data, depending on the contents of the .ir signal1_type or .ir signal2_type files respectively. .re .tp .ir /signal1_type ", " /signal2_type these two files change the behavior of the .ir signal1 and .ir signal2 notification files. they contain a numeric ascii string which is read as either "1" or "0". in mode 0 (overwrite), the hardware replaces the contents of the signal channel with the data that is written to it. in mode 1 (logical or), the hardware accumulates the bits that are subsequently written to it. the possible operations on an open .i signal1_type or .i signal2_type file are: .rs .tp .br read (2) when the count supplied to the .br read (2) call is shorter than the required length for the digit (plus a newline character), subsequent reads from the same file descriptor will complete the string. when a complete string has been read, all subsequent read operations will return zero bytes and a new file descriptor needs to be opened to read the value again. .tp .br write (2) a .br write (2) operation on the file sets the register to the value given in the string. the string is parsed from the beginning until the first nonnumeric character or the end of the buffer. subsequent writes to the same file descriptor overwrite the previous setting. .re .tp .ir /mbox_info ", " /ibox_info ", " /wbox_info ", " /dma_into ", " /proxydma_info read-only files that contain the saved state of the spu mailboxes and dma queues. this allows the spu status to be inspected, mainly for debugging. the .i mbox_info and .i ibox_info files each contain the four-byte mailbox message that has been written by the spu. if no message has been written to these mailboxes, then contents of these files is undefined. the .ir mbox_stat , .ir ibox_stat , and .i wbox_stat files contain the available message count. .ip the .i wbox_info file contains an array of four-byte mailbox messages, which have been sent to the spu. with current cbea machines, the array is four items in length, so up to 4 * 4 = 16 bytes can be read from this file. if any mailbox queue entry is empty, then the bytes read at the corresponding location are undefined. .ip the .i dma_info file contains the contents of the spu mfc dma queue, represented as the following structure: .ip .in +4n .ex struct spu_dma_info { uint64_t dma_info_type; uint64_t dma_info_mask; uint64_t dma_info_status; uint64_t dma_info_stall_and_notify; uint64_t dma_info_atomic_command_status; struct mfc_cq_sr dma_info_command_data[16]; }; .ee .in .ip the last member of this data structure is the actual dma queue, containing 16 entries. the .i mfc_cq_sr structure is defined as: .ip .in +4n .ex struct mfc_cq_sr { uint64_t mfc_cq_data0_rw; uint64_t mfc_cq_data1_rw; uint64_t mfc_cq_data2_rw; uint64_t mfc_cq_data3_rw; }; .ee .in .ip the .i proxydma_info file contains similar information, but describes the proxy dma queue (i.e., dmas initiated by entities outside the spu) instead. the file is in the following format: .ip .in +4n .ex struct spu_proxydma_info { uint64_t proxydma_info_type; uint64_t proxydma_info_mask; uint64_t proxydma_info_status; struct mfc_cq_sr proxydma_info_command_data[8]; }; .ee .in .ip accessing these files requires that the spu context is scheduled out - frequent use can be inefficient. these files should not be used for normal program operation. .ip these files are not present on contexts that have been created with the .b spu_create_nosched flag. .tp .ir /cntl this file provides access to the spu run control and spu status registers, as an ascii string. the following operations are supported: .rs .tp .br read (2) reads from the .i cntl file will return an ascii string with the hex value of the spu status register. .tp .br write (2) writes to the .i cntl file will set the context's spu run control register. .re .tp .i /mfc provides access to the memory flow controller of the spu. reading from the file returns the contents of the spu's mfc tag status register, and writing to the file initiates a dma from the mfc. the following operations are supported: .rs .tp .br write (2) writes to this file need to be in the format of a mfc dma command, defined as follows: .ip .in +4n .ex struct mfc_dma_command { int32_t pad; /* reserved */ uint32_t lsa; /* local storage address */ uint64_t ea; /* effective address */ uint16_t size; /* transfer size */ uint16_t tag; /* command tag */ uint16_t class; /* class id */ uint16_t cmd; /* command opcode */ }; .ee .in .ip writes are required to be exactly .i sizeof(struct mfc_dma_command) bytes in size. the command will be sent to the spu's mfc proxy queue, and the tag stored in the kernel (see below). .tp .br read (2) reads the contents of the tag status register. if the file is opened in blocking mode (i.e., without .br o_nonblock ), then the read will block until a dma tag (as performed by a previous write) is complete. in nonblocking mode, the mfc tag status register will be returned without waiting. .tp .br poll (2) calling .br poll (2) on the .i mfc file will block until a new dma can be started (by checking for .br pollout ) or until a previously started dma (by checking for .br pollin ) has been completed. .ip .i /mss provides access to the mfc multisource synchronization (mss) facility. by .br mmap (2)-ing this file, processes can access the mss area of the spu. .ip the following operations are supported: .tp .br mmap (2) mapping .b mss into the process address space gives access to the spu mss area within the process address space. only .b map_shared mappings are allowed. .re .tp .i /psmap provides access to the whole problem-state mapping of the spu. applications can use this area to interface to the spu, rather than writing to individual register files in .br spufs . .ip the following operations are supported: .rs .tp .br mmap (2) mapping .b psmap gives a process a direct map of the spu problem state area. only .b map_shared mappings are supported. .re .tp .i /phys\-id read-only file containing the physical spu number that the spu context is running on. when the context is not running, this file contains the string "\-1". .ip the physical spu number is given by an ascii hex string. .tp .i /object\-id allows applications to store (or retrieve) a single 64-bit id into the context. this id is later used by profiling tools to uniquely identify the context. .rs .tp .br write (2) by writing an ascii hex value into this file, applications can set the object id of the spu context. any previous value of the object id is overwritten. .tp .br read (2) reading this file gives an ascii hex string representing the object id for this spu context. .re .sh examples .tp .ir /etc/fstab " entry" none /spu spufs gid=spu 0 0 .\" .sh authors .\" arnd bergmann , mark nutter , .\" ulrich weigand , jeremy kerr .sh see also .br close (2), .br spu_create (2), .br spu_run (2), .br capabilities (7) .pp .i the cell broadband engine architecture (cbea) specification .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1993 michael haardt (michael@moria.de) .\" and copyright (c) 1999 andries brouwer (aeb@cwi.nl) .\" and copyright (c) 2006 justin pryzby .\" and copyright (c) 2006 michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sun jul 25 11:02:22 1993 by rik faith (faith@cs.unc.edu) .\" 2006-05-24, justin pryzby .\" document ftw_actionretval; include .sh return value; .\" 2006-05-24, justin pryzby and .\" michael kerrisk .\" reorganized and rewrote much of the page .\" 2006-05-24, michael kerrisk .\" added an example program. .\" .th ftw 3 2021-03-22 "linux" "linux programmer's manual" .sh name ftw, nftw \- file tree walk .sh synopsis .nf .b #include .pp .bi "int nftw(const char *" dirpath , .bi " int (*" fn ")(const char *" fpath ", const struct stat *" sb , .bi " int " typeflag ", struct ftw *" ftwbuf ), .bi " int " nopenfd ", int " flags ); .pp .bi "int ftw(const char *" dirpath , .bi " int (*" fn ")(const char *" fpath ", const struct stat *" sb , .bi " int " typeflag ), .bi " int " nopenfd ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br nftw (): .nf _xopen_source >= 500 .fi .sh description .br nftw () walks through the directory tree that is located under the directory \fidirpath\fp, and calls \fifn\fp() once for each entry in the tree. by default, directories are handled before the files and subdirectories they contain (preorder traversal). .pp to avoid using up all of the calling process's file descriptors, \finopenfd\fp specifies the maximum number of directories that .br nftw () will hold open simultaneously. when the search depth exceeds this, .br nftw () will become slower because directories have to be closed and reopened. .br nftw () uses at most one file descriptor for each level in the directory tree. .pp for each entry found in the tree, .br nftw () calls \fifn\fp() with four arguments: .ir fpath , .ir sb , .ir typeflag , and .ir ftwbuf . .i fpath is the pathname of the entry, and is expressed either as a pathname relative to the calling process's current working directory at the time of the call to .br nftw (), if .ir dirpath was expressed as a relative pathname, or as an absolute pathname, if .i dirpath was expressed as an absolute pathname. .i sb is a pointer to the .i stat structure returned by a call to .br stat (2) for .ir fpath . .pp the .i typeflag argument passed to .ir fn () is an integer that has one of the following values: .tp .b ftw_f .i fpath is a regular file. .tp .b ftw_d .i fpath is a directory. .tp .b ftw_dnr .i fpath is a directory which can't be read. .tp .b ftw_dp .i fpath is a directory, and \fbftw_depth\fp was specified in \fiflags\fp. (if .b ftw_depth was not specified in .ir flags , then directories will always be visited with .i typeflag set to .br ftw_d .) all of the files and subdirectories within \fifpath\fp have been processed. .tp .b ftw_ns the .br stat (2) call failed on .ir fpath , which is not a symbolic link. the probable cause for this is that the caller had read permission on the parent directory, so that the filename .i fpath could be seen, but did not have execute permission, so that the file could not be reached for .br stat (2). the contents of the buffer pointed to by .i sb are undefined. .tp .b ftw_sl .i fpath is a symbolic link, and \fbftw_phys\fp was set in \fiflags\fp. .\" to obtain the definition of this constant from .\" .ir , .\" either .\" .b _bsd_source .\" must be defined, or .\" .br _xopen_source .\" must be defined with a value of 500 or more. .tp .b ftw_sln .i fpath is a symbolic link pointing to a nonexistent file. (this occurs only if \fbftw_phys\fp is not set.) in this case the .i sb argument passed to .ir fn () contains information returned by performing .br lstat (2) on the "dangling" symbolic link. (but see bugs.) .pp the fourth argument .ri ( ftwbuf ) that .br nftw () supplies when calling \fifn\fp() is a pointer to a structure of type \fiftw\fp: .pp .in +4n .ex struct ftw { int base; int level; }; .ee .in .pp .i base is the offset of the filename (i.e., basename component) in the pathname given in .ir fpath . .i level is the depth of .i fpath in the directory tree, relative to the root of the tree .ri ( dirpath , which has depth 0). .pp to stop the tree walk, \fifn\fp() returns a nonzero value; this value will become the return value of .br nftw (). as long as \fifn\fp() returns 0, .br nftw () will continue either until it has traversed the entire tree, in which case it will return zero, or until it encounters an error (such as a .br malloc (3) failure), in which case it will return \-1. .pp because .br nftw () uses dynamic data structures, the only safe way to exit out of a tree walk is to return a nonzero value from \fifn\fp(). to allow a signal to terminate the walk without causing a memory leak, have the handler set a global flag that is checked by \fifn\fp(). \fidon't\fp use .br longjmp (3) unless the program is going to terminate. .pp the \fiflags\fp argument of .br nftw () is formed by oring zero or more of the following flags: .tp .br ftw_actionretval " (since glibc 2.3.3)" if this glibc-specific flag is set, then .br nftw () handles the return value from .ir fn () differently. .ir fn () should return one of the following values: .rs .tp .b ftw_continue instructs .br nftw () to continue normally. .tp .b ftw_skip_siblings if \fifn\fp() returns this value, then siblings of the current entry will be skipped, and processing continues in the parent. .\" if \fbftw_depth\fp .\" is set, the entry's parent directory is processed next (with .\" \fiflag\fp set to \fbftw_dp\fp). .tp .b ftw_skip_subtree if \fifn\fp() is called with an entry that is a directory (\fitypeflag\fp is \fbftw_d\fp), this return value will prevent objects within that directory from being passed as arguments to \fifn\fp(). .br nftw () continues processing with the next sibling of the directory. .tp .b ftw_stop causes .br nftw () to return immediately with the return value \fbftw_stop\fp. .pp other return values could be associated with new actions in the future; \fifn\fp() should not return values other than those listed above. .pp the feature test macro .b _gnu_source must be defined (before including .i any header files) in order to obtain the definition of \fbftw_actionretval\fp from \fi\fp. .re .tp .b ftw_chdir if set, do a .br chdir (2) to each directory before handling its contents. this is useful if the program needs to perform some action in the directory in which \fifpath\fp resides. (specifying this flag has no effect on the pathname that is passed in the .i fpath argument of .ir fn .) .tp .b ftw_depth if set, do a post-order traversal, that is, call \fifn\fp() for the directory itself \fiafter\fp handling the contents of the directory and its subdirectories. (by default, each directory is handled \fibefore\fp its contents.) .tp .b ftw_mount if set, stay within the same filesystem (i.e., do not cross mount points). .tp .b ftw_phys if set, do not follow symbolic links. (this is what you want.) if not set, symbolic links are followed, but no file is reported twice. .ip if \fbftw_phys\fp is not set, but \fbftw_depth\fp is set, then the function .ir fn () is never called for a directory that would be a descendant of itself. .ss ftw() .br ftw () is an older function that offers a subset of the functionality of .br nftw (). the notable differences are as follows: .ip * 3 .br ftw () has no .ir flags argument. it behaves the same as when .br nftw () is called with .i flags specified as zero. .ip * the callback function, .ir fn (), is not supplied with a fourth argument. .ip * the range of values that is passed via the .i typeflag argument supplied to .ir fn () is smaller: just .br ftw_f , .br ftw_d , .br ftw_dnr , .br ftw_ns , and (possibly) .br ftw_sl . .sh return value these functions return 0 on success, and \-1 if an error occurs. .pp if \fifn\fp() returns nonzero, then the tree walk is terminated and the value returned by \fifn\fp() is returned as the result of .br ftw () or .br nftw (). .pp if .br nftw () is called with the \fbftw_actionretval\fp flag, then the only nonzero value that should be used by \fifn\fp() to terminate the tree walk is \fbftw_stop\fp, and that value is returned as the result of .br nftw (). .sh versions .br nftw () is available under glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br nftw () t} thread safety mt-safe cwd t{ .br ftw () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, susv1. posix.1-2008 marks .br ftw () as obsolete. .sh notes posix.1-2008 notes that the results are unspecified if .i fn does not preserve the current working directory. .pp the function .br nftw () and the use of \fbftw_sl\fp with .br ftw () were introduced in susv1. .pp in some implementations (e.g., glibc), .br ftw () will never use \fbftw_sl\fp, on other systems \fbftw_sl\fp occurs only for symbolic links that do not point to an existing file, and again on other systems .br ftw () will use \fbftw_sl\fp for each symbolic link. if .i fpath is a symbolic link and .br stat (2) failed, posix.1-2008 states that it is undefined whether \fbftw_ns\fp or \fbftw_sl\fp is passed in .ir typeflag . for predictable results, use .br nftw (). .sh bugs according to posix.1-2008, when the .ir typeflag argument passed to .ir fn () contains .br ftw_sln , the buffer pointed to by .i sb should contain information about the dangling symbolic link (obtained by calling .br lstat (2) on the link). early glibc versions correctly followed the posix specification on this point. however, as a result of a regression introduced in glibc 2.4, the contents of the buffer pointed to by .i sb were undefined when .b ftw_sln is passed in .ir typeflag . (more precisely, the contents of the buffer were left unchanged in this case.) this regression was eventually fixed in glibc 2.30, .\" https://bugzilla.redhat.com/show_bug.cgi?id=1422736 .\" http://austingroupbugs.net/view.php?id=1121 .\" glibc commit 6ba205b2c35e3e024c8c12d2ee1b73363e84da87 .\" https://sourceware.org/bugzilla/show_bug.cgi?id=23501 so that the glibc implementation (once more) follows the posix specification. .sh examples the following program traverses the directory tree under the path named in its first command-line argument, or under the current directory if no argument is supplied. it displays various information about each file. the second command-line argument can be used to specify characters that control the value assigned to the \fiflags\fp argument when calling .br nftw (). .ss program source \& .ex #define _xopen_source 500 #include #include #include #include #include static int display_info(const char *fpath, const struct stat *sb, int tflag, struct ftw *ftwbuf) { printf("%\-3s %2d ", (tflag == ftw_d) ? "d" : (tflag == ftw_dnr) ? "dnr" : (tflag == ftw_dp) ? "dp" : (tflag == ftw_f) ? "f" : (tflag == ftw_ns) ? "ns" : (tflag == ftw_sl) ? "sl" : (tflag == ftw_sln) ? "sln" : "???", ftwbuf\->level); if (tflag == ftw_ns) printf("\-\-\-\-\-\-\-"); else printf("%7jd", (intmax_t) sb\->st_size); printf(" %\-40s %d %s\en", fpath, ftwbuf\->base, fpath + ftwbuf\->base); return 0; /* to tell nftw() to continue */ } int main(int argc, char *argv[]) { int flags = 0; if (argc > 2 && strchr(argv[2], \(aqd\(aq) != null) flags |= ftw_depth; if (argc > 2 && strchr(argv[2], \(aqp\(aq) != null) flags |= ftw_phys; if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags) == \-1) { perror("nftw"); exit(exit_failure); } exit(exit_success); } .ee .sh see also .br stat (2), .br fts (3), .br readdir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/resolver.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcsncpy 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsncpy \- copy a fixed-size string of wide characters .sh synopsis .nf .b #include .pp .bi "wchar_t *wcsncpy(wchar_t *restrict " dest \ ", const wchar_t *restrict " src , .bi " size_t " n ); .fi .sh description the .br wcsncpy () function is the wide-character equivalent of the .br strncpy (3) function. it copies at most .i n wide characters from the wide-character string pointed to by .ir src , including the terminating null wide character (l\(aq\e0\(aq), to the array pointed to by .ir dest . exactly .i n wide characters are written at .ir dest . if the length \fiwcslen(src)\fp is smaller than .ir n , the remaining wide characters in the array pointed to by .i dest are filled with null wide characters. if the length \fiwcslen(src)\fp is greater than or equal to .ir n , the string pointed to by .i dest will not be terminated by a null wide character. .pp the strings may not overlap. .pp the programmer must ensure that there is room for at least .i n wide characters at .ir dest . .sh return value .br wcsncpy () returns .ir dest . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcsncpy () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh see also .br strncpy (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/malloc_hook.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-25 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th acosh 3 2021-03-22 "" "linux programmer's manual" .sh name acosh, acoshf, acoshl \- inverse hyperbolic cosine function .sh synopsis .nf .b #include .pp .bi "double acosh(double " x ); .bi "float acoshf(float " x ); .bi "long double acoshl(long double " x ); .pp .fi link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br acosh (): .nf _isoc99_source || _posix_c_source >= 200112l || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br acoshf (), .br acoshl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions calculate the inverse hyperbolic cosine of .ir x ; that is the value whose hyperbolic cosine is .ir x . .sh return value on success, these functions return the inverse hyperbolic cosine of .ir x . .pp if .i x is a nan, a nan is returned. .pp if .i x is +1, +0 is returned. .pp if .i x is positive infinity, positive infinity is returned. .pp if .i x is less than 1, a domain error occurs, and the functions return a nan. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is less than 1 .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br acosh (), .br acoshf (), .br acoshl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd. .sh see also .br asinh (3), .br atanh (3), .br cacosh (3), .br cosh (3), .br sinh (3), .br tanh (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/infinity.3 .\" copyright (c) 2000 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th strfmon 3 2021-03-22 "linux" "linux programmer's manual" .sh name strfmon, strfmon_l \- convert monetary value to a string .sh synopsis .nf .b #include .pp .bi "ssize_t strfmon(char *restrict " s ", size_t " max , .bi " const char *restrict " format ", ...);" .bi "ssize_t strfmon_l(char *restrict " s ", size_t " max ", locale_t " locale , .bi " const char *restrict " format ", ...);" .fi .sh description the .br strfmon () function formats the specified monetary amount according to the current locale and format specification .i format and places the result in the character array .i s of size .ir max . .pp the .br strfmon_l () function performs the same task, but uses the locale specified by .ir locale . the behavior of .br strfmon_l () is undefined if .i locale is the special locale object .br lc_global_locale (see .br duplocale (3)) or is not a valid locale object handle. .pp ordinary characters in .i format are copied to .i s without conversion. conversion specifiers are introduced by a \(aq%\(aq character. immediately following it there can be zero or more of the following flags: .tp .bi = f the single-byte character .i f is used as the numeric fill character (to be used with a left precision, see below). when not specified, the space character is used. .tp .b \(ha do not use any grouping characters that might be defined for the current locale. by default, grouping is enabled. .tp .br ( " or " + the ( flag indicates that negative amounts should be enclosed between parentheses. the + flag indicates that signs should be handled in the default way, that is, amounts are preceded by the locale's sign indication, for example, nothing for positive, "\-" for negative. .tp .b ! omit the currency symbol. .tp .b \- left justify all fields. the default is right justification. .pp next, there may be a field width: a decimal digit string specifying a minimum field width in bytes. the default is 0. a result smaller than this width is padded with spaces (on the left, unless the left-justify flag was given). .pp next, there may be a left precision of the form "#" followed by a decimal digit string. if the number of digits left of the radix character is smaller than this, the representation is padded on the left with the numeric fill character. grouping characters are not counted in this field width. .pp next, there may be a right precision of the form "." followed by a decimal digit string. the amount being formatted is rounded to the specified number of digits prior to formatting. the default is specified in the .i frac_digits and .i int_frac_digits items of the current locale. if the right precision is 0, no radix character is printed. (the radix character here is determined by .br lc_monetary , and may differ from that specified by .br lc_numeric .) .pp finally, the conversion specification must be ended with a conversion character. the three conversion characters are .tp .b % (in this case, the entire specification must be exactly "%%".) put a \(aq%\(aq character in the result string. .tp .b i one argument of type .i double is converted using the locale's international currency format. .tp .b n one argument of type .i double is converted using the locale's national currency format. .sh return value the .br strfmon () function returns the number of characters placed in the array .ir s , not including the terminating null byte, provided the string, including the terminating null byte, fits. otherwise, it sets .i errno to .br e2big , returns \-1, and the contents of the array is undefined. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br strfmon () t} thread safety mt-safe locale t{ .br strfmon_l () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples the call .pp .in +4n .ex strfmon(buf, sizeof(buf), "[%\(ha=*#6n] [%=*#6i]", 1234.567, 1234.567); .ee .in .pp outputs .pp .in +4n .ex [€ **1234,57] [eur **1 234,57] .ee .in .pp in the .i nl_nl locale. the .ir de_de , .ir de_ch , .ir en_au , and .i en_gb locales yield .pp .in +4n .ex [ **1234,57 €] [ **1.234,57 eur] [ fr. **1234.57] [ chf **1\(aq234.57] [ $**1234.57] [ aud**1,234.57] [ £**1234.57] [ gbp**1,234.57] .ee .in .sh see also .br duplocale (3), .br setlocale (3), .br sprintf (3), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/system_data_types.7 .\" copyright 1999 suse gmbh nuernberg, germany .\" author: thorsten kukuk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of the .\" license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the gnu .\" general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified, 6 may 2002, michael kerrisk, .\" change listed order of /usr/lib and /lib .th ldconfig 8 2021-03-22 "gnu" "linux programmer's manual" .sh name ldconfig \- configure dynamic linker run-time bindings .sh synopsis .br /sbin/ldconfig " [" \-nnvxv "] [" \-f " \ficonf\fp] [" \-c " \ficache\fp] [" \-r " \firoot\fp]" .ir directory \... .pd 0 .pp .pd .b /sbin/ldconfig .b \-l .rb [ \-v ] .ir library \... .pd 0 .pp .pd .b /sbin/ldconfig .b \-p .sh description .b ldconfig creates the necessary links and cache to the most recent shared libraries found in the directories specified on the command line, in the file .ir /etc/ld.so.conf , and in the trusted directories, .i /lib and .ir /usr/lib (on some 64-bit architectures such as x86-64, .i /lib and .ir /usr/lib are the trusted directories for 32-bit libraries, while .i /lib64 and .ir /usr/lib64 are used for 64-bit libraries). .pp the cache is used by the run-time linker, .i ld.so or .ir ld\-linux.so . .b ldconfig checks the header and filenames of the libraries it encounters when determining which versions should have their links updated. .pp .b ldconfig will attempt to deduce the type of elf libraries (i.e., libc5 or libc6/glibc) based on what c libraries, if any, the library was linked against. .\" the following sentence looks suspect .\" (perhaps historical cruft) -- mtk, jul 2005 .\" therefore, when making dynamic libraries, .\" it is wise to explicitly link against libc (use \-lc). .pp some existing libraries do not contain enough information to allow the deduction of their type. therefore, the .i /etc/ld.so.conf file format allows the specification of an expected type. this is used .i only for those elf libraries which we can not work out. the format is "dirname=type", where type can be libc4, libc5, or libc6. (this syntax also works on the command line.) spaces are .i not allowed. also see the .b \-p option. .b ldconfig should normally be run by the superuser as it may require write permission on some root owned directories and files. .pp note that .b ldconfig will only look at files that are named .i lib*.so* (for regular shared objects) or .i ld\-*.so* (for the dynamic loader itself). other files will be ignored. also, .b ldconfig expects a certain pattern to how the symlinks are set up, like this example, where the middle file .rb ( libfoo.so.1 here) is the soname for the library: .pp .in +4n .ex libfoo.so \-> libfoo.so.1 \-> libfoo.so.1.12 .ee .in .pp failure to follow this pattern may result in compatibility issues after an upgrade. .sh options .tp .br \-c " \fifmt\fp, " \-\-format=\fifmt\fp (since glibc 2.2) cache format to use: .ir old , .ir new , or .ir compat . since glibc 2.32, the default is .ir new . .\" commit cad64f778aced84efdaa04ae64f8737b86f063ab before that, it was .ir compat . .tp .bi "\-c " cache use .i cache instead of .ir /etc/ld.so.cache . .tp .bi "\-f " conf use .i conf instead of .ir /etc/ld.so.conf . .\" fixme glibc 2.7 added -i .tp .br \-i ", " \-\-ignore\-aux\-cache (since glibc 2.7) .\" commit 27d9ffda17df4d2388687afd12897774fde39bcc ignore auxiliary cache file. .tp .b \-l (since glibc 2.2) library mode. manually link individual libraries. intended for use by experts only. .tp .b \-n process only the directories specified on the command line. don't process the trusted directories, nor those specified in .ir /etc/ld.so.conf . implies .br \-n . .tp .b \-n don't rebuild the cache. unless .b \-x is also specified, links are still updated. .tp .br \-p ", " \-\-print\-cache print the lists of directories and candidate libraries stored in the current cache. .tp .bi "\-r " root change to and use .i root as the root directory. .tp .br \-v ", " \-\-verbose verbose mode. print current version number, the name of each directory as it is scanned, and any links that are created. overrides quiet mode. .tp .br \-v ", " \-\-version print program version. .tp .b \-x don't update links. unless .b \-n is also specified, the cache is still rebuilt. .sh files .\" fixme since glibc-2.3.4, "include" directives are supported in ld.so.conf .\" .\" fixme since glibc-2.4, "hwcap" directives are supported in ld.so.conf .pd 0 .tp .i /lib/ld.so run-time linker/loader. .tp .i /etc/ld.so.conf file containing a list of directories, one per line, in which to search for libraries. .tp .i /etc/ld.so.cache file containing an ordered list of libraries found in the directories specified in .ir /etc/ld.so.conf , as well as those found in the trusted directories. .pd .sh see also .br ldd (1), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/truncate.2 .so man3/slist.3 .\" copyright (c) 2012, ibm corporation. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th __ppc_get_timebase 3 2021-03-22 "gnu c library" "linux programmer's\ manual" .sh name __ppc_get_timebase, __ppc_get_timebase_freq \- get the current value of the time base register on power architecture and its frequency. .sh synopsis .nf .b #include .pp .bi "uint64_t __ppc_get_timebase(void);" .bi "uint64_t __ppc_get_timebase_freq(void);" .fi .sh description .br __ppc_get_timebase () reads the current value of the time base register and returns its value, while .br __ppc_get_timebase_freq () returns the frequency in which the time base register is updated. .pp the time base register is a 64-bit register provided by power architecture processors. it stores a monotonically incremented value that is updated at a system-dependent frequency that may be different from the processor frequency. .sh return value .br __ppc_get_timebase () returns a 64-bit unsigned integer that represents the current value of the time base register. .pp .br __ppc_get_timebase_freq () returns a 64-bit unsigned integer that represents the frequency at which the time base register is updated. .sh versions gnu c library support for .\" commit d9dc34cd569bcfe714fe8c708e58c028106e8b2e .br __ppc_get_timebase () has been provided since version 2.16 and .\" commit 8ad11b9a9cf1de82bd7771306b42070b91417c11 .br __ppc_get_timebase_freq () has been available since version 2.17. .sh conforming to both functions are nonstandard gnu extensions. .sh examples the following program will calculate the time, in microseconds, spent between two calls to .br __ppc_get_timebase (). .ss program source \& .ex #include #include #include #include #include /* maximum value of the time base register: 2\(ha60 \- 1. source: power isa. */ #define max_tb 0xfffffffffffffff int main(void) { uint64_t tb1, tb2, diff; uint64_t freq = __ppc_get_timebase_freq(); printf("time base frequency = %"priu64" hz\en", freq); tb1 = __ppc_get_timebase(); // do some stuff... tb2 = __ppc_get_timebase(); if (tb2 > tb1) { diff = tb2 \- tb1; } else { /* treat time base register overflow. */ diff = (max_tb \- tb2) + tb1; } printf("elapsed time = %1.2f usecs\en", (double) diff * 1000000 / freq ); exit(exit_success); } .ee .sh see also .br time (2), .br usleep (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/wait4.2 .so man3/ferror.3 .so man2/mlock.2 .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th locale 1 2021-03-22 "linux" "linux user manual" .sh name locale \- get locale-specific information .sh synopsis .nf .br locale " [\fioption\fp]" .br locale " [\fioption\fp] " \-a .br locale " [\fioption\fp] " \-m .br locale " [\fioption\fp] \finame\fp..." .fi .sh description the .b locale command displays information about the current locale, or all locales, on standard output. .pp when invoked without arguments, .b locale displays the current locale settings for each locale category (see .br locale (5)), based on the settings of the environment variables that control the locale (see .br locale (7)). values for variables set in the environment are printed without double quotes, implied values are printed with double quotes. .pp if either the .b \-a or the .b \-m option (or one of their long-format equivalents) is specified, the behavior is as follows: .tp .br \-a ", " \-\-all\-locales display a list of all available locales. the .b \-v option causes the .b lc_identification metadata about each locale to be included in the output. .tp .br \-m ", " \-\-charmaps display the available charmaps (character set description files). to display the current character set for the locale, use \fblocale \-c charmap\fr. .pp the .b locale command can also be provided with one or more arguments, which are the names of locale keywords (for example, .ir date_fmt , .ir ctype\-class\-names , .ir yesexpr , or .ir decimal_point ) or locale categories (for example, .b lc_ctype or .br lc_time ). for each argument, the following is displayed: .ip * 3 for a locale keyword, the value of that keyword to be displayed. .ip * for a locale category, the values of all keywords in that category are displayed. .pp when arguments are supplied, the following options are meaningful: .tp .br \-c ", " \-\-category\-name for a category name argument, write the name of the locale category on a separate line preceding the list of keyword values for that category. .ip for a keyword name argument, write the name of the locale category for this keyword on a separate line preceding the keyword value. .ip this option improves readability when multiple name arguments are specified. it can be combined with the .b \-k option. .tp .br \-k ", " \-\-keyword\-name for each keyword whose value is being displayed, include also the name of that keyword, so that the output has the format: .ip \fikeyword\fp="\fivalue\fp" .pp the .b locale command also knows about the following options: .tp .br \-v ", " \-\-verbose display additional information for some command-line option and argument combinations. .tp .br \-? ", " \-\-help display a summary of command-line options and arguments and exit. .tp .b \-\-usage display a short usage message and exit. .tp .br \-v ", " \-\-version display the program version and exit. .sh files .tp .i /usr/lib/locale/locale\-archive usual default locale archive location. .tp .i /usr/share/i18n/locales usual default path for locale definition files. .sh conforming to posix.1-2001, posix.1-2008. .sh examples .ex $ \fblocale\fp lang=en_us.utf\-8 lc_ctype="en_us.utf\-8" lc_numeric="en_us.utf\-8" lc_time="en_us.utf\-8" lc_collate="en_us.utf\-8" lc_monetary="en_us.utf\-8" lc_messages="en_us.utf\-8" lc_paper="en_us.utf\-8" lc_name="en_us.utf\-8" lc_address="en_us.utf\-8" lc_telephone="en_us.utf\-8" lc_measurement="en_us.utf\-8" lc_identification="en_us.utf\-8" lc_all= $ \fblocale date_fmt\fp %a %b %e %h:%m:%s %z %y $ \fblocale \-k date_fmt\fp date_fmt="%a %b %e %h:%m:%s %z %y" $ \fblocale \-ck date_fmt\fp lc_time date_fmt="%a %b %e %h:%m:%s %z %y" $ \fblocale lc_telephone\fp +%c (%a) %l (%a) %l 11 1 utf\-8 $ \fblocale \-k lc_telephone\fp tel_int_fmt="+%c (%a) %l" tel_dom_fmt="(%a) %l" int_select="11" int_prefix="1" telephone\-codeset="utf\-8" .ee .pp the following example compiles a custom locale from the .i ./wrk directory with the .br localedef (1) utility under the .i $home/.locale directory, then tests the result with the .br date (1) command, and then sets the environment variables .b locpath and .b lang in the shell profile file so that the custom locale will be used in the subsequent user sessions: .pp .ex $ \fbmkdir \-p $home/.locale\fp $ \fbi18npath=./wrk/ localedef \-f utf\-8 \-i fi_se $home/.locale/fi_se.utf\-8\fp $ \fblocpath=$home/.locale lc_all=fi_se.utf\-8 date\fp $ \fbecho "export locpath=\e$home/.locale" >> $home/.bashrc\fp $ \fbecho "export lang=fi_se.utf\-8" >> $home/.bashrc\fp .ee .sh see also .br localedef (1), .br charmap (5), .br locale (5), .br locale (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th ctanh 3 2021-03-22 "" "linux programmer's manual" .sh name ctanh, ctanhf, ctanhl \- complex hyperbolic tangent .sh synopsis .nf .b #include .pp .bi "double complex ctanh(double complex " z ");" .bi "float complex ctanhf(float complex " z ); .bi "long double complex ctanhl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex hyperbolic tangent of .ir z . .pp the complex hyperbolic tangent function is defined mathematically as: .pp .nf ctanh(z) = csinh(z) / ccosh(z) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ctanh (), .br ctanhf (), .br ctanhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br catanh (3), .br ccosh (3), .br csinh (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/sync_file_range.2 .so man3/unlocked_stdio.3 .\" copyright (c) 2003 free software foundation, inc. .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .th io_getevents 2 2021-03-22 "linux" "linux programmer's manual" .sh name io_getevents \- read asynchronous i/o events from the completion queue .sh synopsis .nf .br "#include " " /* definition of " *io_* " types */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_io_getevents, aio_context_t " ctx_id , .bi " long " min_nr ", long " nr ", struct io_event *" events , .bi " struct timespec *" timeout ); .fi .pp .ir note : glibc provides no wrapper for .br io_getevents (), necessitating the use of .br syscall (2). .sh description .ir note : this page describes the raw linux system call interface. the wrapper function provided by .i libaio uses a different type for the .i ctx_id argument. see notes. .pp the .br io_getevents () system call attempts to read at least \fimin_nr\fp events and up to \finr\fp events from the completion queue of the aio context specified by \fictx_id\fp. .pp the \fitimeout\fp argument specifies the amount of time to wait for events, and is specified as a relative timeout in a structure of the following form: .pp .in +4n .ex struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* nanoseconds [0 .. 999999999] */ }; .ee .in .pp the specified time will be rounded up to the system clock granularity and is guaranteed not to expire early. .pp specifying .i timeout as null means block indefinitely until at least .i min_nr events have been obtained. .sh return value on success, .br io_getevents () returns the number of events read. this may be 0, or a value less than .ir min_nr , if the .i timeout expired. it may also be a nonzero value less than .ir min_nr , if the call was interrupted by a signal handler. .pp for the failure return, see notes. .sh errors .tp .b efault either \fievents\fp or \fitimeout\fp is an invalid pointer. .tp .b eintr interrupted by a signal handler; see .br signal (7). .tp .b einval \fictx_id\fp is invalid. \fimin_nr\fp is out of range or \finr\fp is out of range. .tp .b enosys .br io_getevents () is not implemented on this architecture. .sh versions the asynchronous i/o system calls first appeared in linux 2.5. .sh conforming to .br io_getevents () is linux-specific and should not be used in programs that are intended to be portable. .sh notes you probably want to use the .br io_getevents () wrapper function provided by .\" http://git.fedorahosted.org/git/?p=libaio.git .ir libaio . .pp note that the .i libaio wrapper function uses a different type .ri ( io_context_t ) .\" but glibc is confused, since uses 'io_context_t' to declare .\" the system call. for the .i ctx_id argument. note also that the .i libaio wrapper does not follow the usual c library conventions for indicating errors: on error it returns a negated error number (the negative of one of the values listed in errors). if the system call is invoked via .br syscall (2), then the return value follows the usual conventions for indicating an error: \-1, with .i errno set to a (positive) value that indicates the error. .sh bugs an invalid .ir ctx_id may cause a segmentation fault instead of generating the error .br einval . .sh see also .br io_cancel (2), .br io_destroy (2), .br io_setup (2), .br io_submit (2), .br aio (7), .br time (7) .\" .sh author .\" kent yoder. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strtod.3 .so man3/setaliasent.3 .so man2/alloc_hugepages.2 .so man3/getutent.3 .\" copyright (c) 1995 michael chastain (mec@shell.portal.com), 15 april 1995. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified tue oct 22 08:11:14 edt 1996 by eric s. raymond .th ipc 2 2021-03-22 "linux" "linux programmer's manual" .sh name ipc \- system v ipc system calls .sh synopsis .nf .br "#include " " /* definition of needed constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_ipc, unsigned int " call ", int " first , .bi " unsigned long " second ", unsigned long " third \ ", void *" ptr , .bi " long " fifth ); .fi .pp .ir note : glibc provides no wrapper for .br ipc (), necessitating the use of .br syscall (2). .sh description .br ipc () is a common kernel entry point for the system\ v ipc calls for messages, semaphores, and shared memory. .i call determines which ipc function to invoke; the other arguments are passed through to the appropriate call. .pp user-space programs should call the appropriate functions by their usual names. only standard library implementors and kernel hackers need to know about .br ipc (). .sh conforming to .br ipc () is linux-specific, and should not be used in programs intended to be portable. .sh notes on some architectures\(emfor example x86-64 and arm\(emthere is no .br ipc () system call; instead, .br msgctl (2), .br semctl (2), .br shmctl (2), and so on really are implemented as separate system calls. .sh see also .br msgctl (2), .br msgget (2), .br msgrcv (2), .br msgsnd (2), .br semctl (2), .br semget (2), .br semop (2), .br semtimedop (2), .br shmat (2), .br shmctl (2), .br shmdt (2), .br shmget (2), .br sysvipc (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2014 marko myllynen .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iconv 1 2021-08-27 "gnu" "linux user manual" .sh name iconv \- convert text from one character encoding to another .sh synopsis .b iconv .ri [ options ] .ri "[\-f " from-encoding "]" .ri "[\-t " to-encoding "]" .ri [ inputfile ]... .sh description the .b iconv program reads in text in one encoding and outputs the text in another encoding. if no input files are given, or if it is given as a dash (\-), .b iconv reads from standard input. if no output file is given, .b iconv writes to standard output. .pp if no .i from-encoding is given, the default is derived from the current locale's character encoding. if no .i to-encoding is given, the default is derived from the current locale's character encoding. .sh options .tp .bi \-f " from-encoding" "\fr, \fp\-\-from\-code=" from-encoding use .i from-encoding for input characters. .tp .bi \-t " to-encoding" "\fr, \fp\-\-to\-code=" to-encoding use .i to-encoding for output characters. .ip if the string .b //ignore is appended to .ir to-encoding , characters that cannot be converted are discarded and an error is printed after conversion. .ip if the string .b //translit is appended to .ir to-encoding , characters being converted are transliterated when needed and possible. this means that when a character cannot be represented in the target character set, it can be approximated through one or several similar looking characters. characters that are outside of the target character set and cannot be transliterated are replaced with a question mark (?) in the output. .tp .br \-l ", " \-\-list list all known character set encodings. .tp .b "\-c" silently discard characters that cannot be converted instead of terminating when encountering such characters. .tp .bi \-o " outputfile" "\fr, \fp\-\-output=" outputfile use .i outputfile for output. .tp .br \-s ", " \-\-silent this option is ignored; it is provided only for compatibility. .tp .b "\-\-verbose" print progress information on standard error when processing multiple files. .tp .br \-? ", " \-\-help print a usage summary and exit. .tp .b "\-\-usage" print a short usage summary and exit. .tp .br \-v ", " \-\-version print the version number, license, and disclaimer of warranty for .br iconv . .sh exit status zero on success, nonzero on errors. .sh environment internally, the .b iconv program uses the .br iconv (3) function which in turn uses .i gconv modules (dynamically loaded shared libraries) to convert to and from a character set. before calling .br iconv (3), the .b iconv program must first allocate a conversion descriptor using .br iconv_open (3). the operation of the latter function is influenced by the setting of the .b gconv_path environment variable: .ip * 3 if .b gconv_path is not set, .br iconv_open (3) loads the system gconv module configuration cache file created by .br iconvconfig (8) and then, based on the configuration, loads the gconv modules needed to perform the conversion. if the system gconv module configuration cache file is not available then the system gconv module configuration file is used. .ip * if .b gconv_path is defined (as a colon-separated list of pathnames), the system gconv module configuration cache is not used. instead, .br iconv_open (3) first tries to load the configuration files by searching the directories in .b gconv_path in order, followed by the system default gconv module configuration file. if a directory does not contain a gconv module configuration file, any gconv modules that it may contain are ignored. if a directory contains a gconv module configuration file and it is determined that a module needed for this conversion is available in the directory, then the needed module is loaded from that directory, the order being such that the first suitable module found in .b gconv_path is used. this allows users to use custom modules and even replace system-provided modules by providing such modules in .b gconv_path directories. .sh files .tp .i /usr/lib/gconv usual default gconv module path. .tp .i /usr/lib/gconv/gconv\-modules usual system default gconv module configuration file. .tp .i /usr/lib/gconv/gconv\-modules.cache usual system gconv module configuration cache. .pp depending on the architecture, the above files may instead be located at directories with the path prefix .ir /usr/lib64 . .sh conforming to posix.1-2001. .sh examples convert text from the iso 8859-15 character encoding to utf-8: .pp .in +4n .ex $ \fbiconv \-f iso\-8859\-15 \-t utf\-8 < input.txt > output.txt\fp .ee .in .pp the next example converts from utf-8 to ascii, transliterating when possible: .pp .in +4n .ex $ \fbecho abc ß α € àḃç | iconv \-f utf\-8 \-t ascii//translit\fp abc ss ? eur abc .ee .in .sh see also .br locale (1), .br uconv (1), .br iconv (3), .br nl_langinfo (3), .br charsets (7), .br iconvconfig (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th cexp2 3 2021-03-22 "" "linux programmer's manual" .sh name cexp2, cexp2f, cexp2l \- base-2 exponent of a complex number .sh synopsis .nf .b #include .pp .bi "double complex cexp2(double complex " z ");" .bi "float complex cexp2f(float complex " z ");" .bi "long double complex cexp2l(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description the function returns 2 raised to the power of .ir z . .sh conforming to these function names are reserved for future use in c99. .pp as at version 2.31, these functions are not provided in glibc. .\" but reserved in namespace. .sh see also .br cabs (3), .br cexp (3), .br clog10 (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. #!/bin/sh # # convert_to_utf_8.sh # # find man pages with encoding other than us-ascii, and convert them # to the utf-8 encoding. # # example usage: # # cd man-pages-x.yy # sh convert_to_utf_8.sh man?/* # ###################################################################### # # (c) copyright 2013, peter schiffer # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # if [[ $# -lt 2 ]]; then echo "usage: ${0} man?/*" 1>&2 exit 1 fi out_dir="$1" shift enc_line="" for f in "$@"; do enc=$(file -bi "$f" | cut -d = -f 2) if [[ $enc != "us-ascii" ]]; then dirn=$(dirname "$f") basen=$(basename "$f") new_dir="${out_dir}/${dirn}" if [[ ! -e "$new_dir" ]]; then mkdir -p "$new_dir" fi case "$basen" in armscii-8.7 | cp1251.7 | iso_8859-*.7 | koi8-?.7) # iconv does not understand some encoding names that # start "iso_", but does understand the corresponding # forms that start with "iso-" from_enc="$(echo $basen | sed 's/\.7$//;s/iso_/iso-/')" ;; *) echo "null transform: $f" from_enc=$enc ;; esac printf "converting %-23s from %s\n" "$f" "$from_enc" echo "$enc_line" > "${new_dir}/${basen}" iconv -f "$from_enc" -t utf-8 "$f" \ | sed "/.*-\*- coding:.*/d;/.\\\" t$/d" >> "${new_dir}/${basen}" fi done exit 0 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th ctan 3 2021-03-22 "" "linux programmer's manual" .sh name ctan, ctanf, ctanl \- complex tangent function .sh synopsis .nf .b #include .pp .bi "double complex ctan(double complex " z ");" .bi "float complex ctanf(float complex " z ); .bi "long double complex ctanl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex tangent of .ir z . .pp the complex tangent function is defined as: .pp .nf ctan(z) = csin(z) / ccos(z) .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br ctan (), .br ctanf (), .br ctanl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br catan (3), .br ccos (3), .br csin (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getpwnam.3 .\" copyright andries brouwer, 2000 .\" some fragments of text came from the time-1.7 info file. .\" inspired by kromjx@crosswinds.net. .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th time 1 2019-03-06 "" "linux user's manual" .sh name time \- time a simple command or give resource usage .sh synopsis .b time \c .ri [ options ] " command " [ arguments... ] .sh description the .b time command runs the specified program .i command with the given arguments. when .i command finishes, .b time writes a message to standard error giving timing statistics about this program run. these statistics consist of (i) the elapsed real time between invocation and termination, (ii) the user cpu time (the sum of the .i tms_utime and .i tms_cutime values in a .i "struct tms" as returned by .br times (2)), and (iii) the system cpu time (the sum of the .i tms_stime and .i tms_cstime values in a .i "struct tms" as returned by .br times (2)). .pp note: some shells (e.g., .br bash (1)) have a built-in .b time command that provides similar information on the usage of time and possibly other resources. to access the real command, you may need to specify its pathname (something like .ir /usr/bin/time ). .sh options .tp .b \-p when in the posix locale, use the precise traditional format .ip .in +4n .ex "real %f\enuser %f\ensys %f\en" .ee .in .ip (with numbers in seconds) where the number of decimals in the output for %f is unspecified but is sufficient to express the clock tick accuracy, and at least one. .sh exit status if .i command was invoked, the exit status is that of .ir command . otherwise, it is 127 if .i command could not be found, 126 if it could be found but could not be invoked, and some other nonzero value (1\(en125) if something else went wrong. .sh environment the variables .br lang , .br lc_all , .br lc_ctype , .br lc_messages , .br lc_numeric , and .b nlspath are used for the text and formatting of the output. .b path is used to search for .ir command . .sh gnu version below a description of the gnu 1.7 version of .br time . disregarding the name of the utility, gnu makes it output lots of useful information, not only about time used, but also on other resources like memory, i/o and ipc calls (where available). the output is formatted using a format string that can be specified using the .i \-f option or the .b time environment variable. .pp the default format string is: .pp .in +4n .ex %uuser %ssystem %eelapsed %pcpu (%xtext+%ddata %mmax)k %iinputs+%ooutputs (%fmajor+%rminor)pagefaults %wswaps .ee .in .pp when the .i \-p option is given, the (portable) output format is used: .pp .in +4n .ex real %e user %u sys %s .ee .in .\" .ss the format string the format is interpreted in the usual printf-like way. ordinary characters are directly copied, tab, newline, and backslash are escaped using \et, \en, and \e\e, a percent sign is represented by %%, and otherwise % indicates a conversion. the program .b time will always add a trailing newline itself. the conversions follow. all of those used by .br tcsh (1) are supported. .pp .b "time" .tp .b %e elapsed real time (in [hours:]minutes:seconds). .tp .b %e (not in .br tcsh (1).) elapsed real time (in seconds). .tp .b %s total number of cpu-seconds that the process spent in kernel mode. .tp .b %u total number of cpu-seconds that the process spent in user mode. .tp .b %p percentage of the cpu that this job got, computed as (%u + %s) / %e. .pp .b "memory" .tp .b %m maximum resident set size of the process during its lifetime, in kbytes. .tp .b %t (not in .br tcsh (1).) average resident set size of the process, in kbytes. .tp .b %k average total (data+stack+text) memory use of the process, in kbytes. .tp .b %d average size of the process's unshared data area, in kbytes. .tp .b %p (not in .br tcsh (1).) average size of the process's unshared stack space, in kbytes. .tp .b %x average size of the process's shared text space, in kbytes. .tp .b %z (not in .br tcsh (1).) system's page size, in bytes. this is a per-system constant, but varies between systems. .tp .b %f number of major page faults that occurred while the process was running. these are faults where the page has to be read in from disk. .tp .b %r number of minor, or recoverable, page faults. these are faults for pages that are not valid but which have not yet been claimed by other virtual pages. thus the data in the page is still valid but the system tables must be updated. .tp .b %w number of times the process was swapped out of main memory. .tp .b %c number of times the process was context-switched involuntarily (because the time slice expired). .tp .b %w number of waits: times that the program was context-switched voluntarily, for instance while waiting for an i/o operation to complete. .pp .b "i/o" .tp .b %i number of filesystem inputs by the process. .tp .b %o number of filesystem outputs by the process. .tp .b %r number of socket messages received by the process. .tp .b %s number of socket messages sent by the process. .tp .b %k number of signals delivered to the process. .tp .b %c (not in .br tcsh (1).) name and command-line arguments of the command being timed. .tp .b %x (not in .br tcsh (1).) exit status of the command. .ss gnu options .tp .bi "\-f " format ", \-\-format=" format specify output format, possibly overriding the format specified in the environment variable time. .tp .b "\-p, \-\-portability" use the portable output format. .tp .bi "\-o " file ", \-\-output=" file do not send the results to .ir stderr , but overwrite the specified file. .tp .b "\-a, \-\-append" (used together with \-o.) do not overwrite but append. .tp .b "\-v, \-\-verbose" give very verbose output about all the program knows about. .tp .b "\-q, \-\-quiet" don't report abnormal program termination (where .i command is terminated by a signal) or nonzero exit status. .\" .ss gnu standard options .tp .b "\-\-help" print a usage message on standard output and exit successfully. .tp .b "\-v, \-\-version" print version information on standard output, then exit successfully. .tp .b "\-\-" terminate option list. .sh bugs not all resources are measured by all versions of unix, so some of the values might be reported as zero. the present selection was mostly inspired by the data provided by 4.2 or 4.3bsd. .pp gnu time version 1.7 is not yet localized. thus, it does not implement the posix requirements. .pp the environment variable .b time was badly chosen. it is not unusual for systems like .br autoconf (1) or .br make (1) to use environment variables with the name of a utility to override the utility to be used. uses like more or time for options to programs (instead of program pathnames) tend to lead to difficulties. .pp it seems unfortunate that .i \-o overwrites instead of appends. (that is, the .i \-a option should be the default.) .pp mail suggestions and bug reports for gnu .b time to .ir bug\-time@gnu.org . please include the version of .br time , which you can get by running .pp .in +4n .ex time \-\-version .ee .in .pp and the operating system and c compiler you used. .\" .sh authors .\" .tp .\" .ip "david keppel" .\" original version .\" .ip "david mackenzie" .\" posixization, autoconfiscation, gnu getoptization, .\" documentation, other bug fixes and improvements. .\" .ip "arne henrik juul" .\" helped with portability .\" .ip "francois pinard" .\" helped with portability .sh see also .br bash (1), .br tcsh (1), .br times (2), .br wait3 (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_attr_setscope.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2001-04-01 by aeb .\" modified 2003-07-23 by aeb .\" .th usleep 3 2021-03-22 "" "linux programmer's manual" .sh name usleep \- suspend execution for microsecond intervals .sh synopsis .nf .b "#include " .pp .bi "int usleep(useconds_t " usec ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br usleep (): .nf since glibc 2.12: (_xopen_source >= 500) && ! (_posix_c_source >= 200809l) || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source before glibc 2.12: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description the .br usleep () function suspends execution of the calling thread for (at least) \fiusec\fp microseconds. the sleep may be lengthened slightly by any system activity or by the time spent processing the call or by the granularity of system timers. .sh return value the .br usleep () function returns 0 on success. on error, \-1 is returned, with .i errno set to indicate the error. .sh errors .tp .b eintr interrupted by a signal; see .br signal (7). .tp .b einval \fiusec\fp is greater than or equal to 1000000. (on systems where that is considered an error.) .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br usleep () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to 4.3bsd, posix.1-2001. posix.1-2001 declares this function obsolete; use .br nanosleep (2) instead. posix.1-2008 removes the specification of .br usleep (). .pp on the original bsd implementation, and in glibc before version 2.2.2, the return type of this function is .ir void . the posix version returns .ir int , and this is also the prototype used since glibc 2.2.2. .pp only the .b einval error return is documented by susv2 and posix.1-2001. .sh notes the type .i useconds_t is an unsigned integer type capable of holding integers in the range [0,1000000]. programs will be more portable if they never mention this type explicitly. use .pp .in +4n .ex #include \&... unsigned int usecs; \&... usleep(usecs); .ee .in .pp the interaction of this function with the .b sigalrm signal, and with other timer functions such as .br alarm (2), .br sleep (3), .br nanosleep (2), .br setitimer (2), .br timer_create (2), .br timer_delete (2), .br timer_getoverrun (2), .br timer_gettime (2), .br timer_settime (2), .br ualarm (3) is unspecified. .sh see also .br alarm (2), .br getitimer (2), .br nanosleep (2), .br select (2), .br setitimer (2), .br sleep (3), .br ualarm (3), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getservent_r.3 .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .\" modified 2003-11-18, aeb: historical remarks .\" .th gamma 3 2021-03-22 "gnu" "linux programmer's manual" .sh name gamma, gammaf, gammal \- (logarithm of the) gamma function .sh synopsis .nf .b #include .pp .bi "double gamma(double " x ");" .bi "float gammaf(float " x ");" .bi "long double gammal(long double " x ");" .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br gamma (): .nf _xopen_source || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .pp .br gammaf (), .br gammal (): .nf _xopen_source >= 600 || (_xopen_source && _isoc99_source) || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions are deprecated: instead, use either the .br tgamma (3) or the .br lgamma (3) functions, as appropriate. .pp for the definition of the gamma function, see .br tgamma (3). .ss *bsd version the libm in 4.4bsd and some versions of freebsd had a .br gamma () function that computes the gamma function, as one would expect. .ss glibc version glibc has a .br gamma () function that is equivalent to .br lgamma (3) and computes the natural logarithm of the gamma function. .sh return value see .br lgamma (3). .sh errors see .br lgamma (3). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br gamma (), .br gammaf (), .br gammal () t} thread safety mt-unsafe race:signgam .te .hy .ad .sp 1 .sh conforming to because of historical variations in behavior across systems, this function is not specified in any recent standard. it was documented in svid 2. .sh notes .ss history 4.2bsd had a .br gamma () that computed .ri ln(|gamma(| x |)|), leaving the sign of .ri gamma(| x |) in the external integer .ir signgam . in 4.3bsd the name was changed to .br lgamma (3), and the man page promises .pp .in +4n "at some time in the future the name gamma will be rehabilitated and used for the gamma function" .in .pp this did indeed happen in 4.4bsd, where .br gamma () computes the gamma function (with no effect on .ir signgam ). however, this came too late, and we now have .br tgamma (3), the "true gamma" function. .\" the freebsd man page says about gamma() that it is like lgamma() .\" except that is does not set signgam. .\" also, that 4.4bsd has a gamma() that computes the true gamma function. .sh see also .br lgamma (3), .br signgam (3), .br tgamma (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/pthread_setcancelstate.3 .so man2/posix_fadvise.2 .so man2/stat.2 .so man3/towlower.3 .\" copyright (c) 1993 michael haardt (michael@moria.de) .\" fri apr 2 11:32:09 met dst 1993 .\" copyright (c) 2006-2015, michael kerrisk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 1993-07-24 by rik faith .\" modified 1995-02-25 by jim van zandt .\" modified 1995-09-02 by jim van zandt .\" moved to man3, aeb, 950919 .\" modified 2001-09-22 by michael kerrisk .\" modified 2001-12-17, aeb .\" modified 2004-10-31, aeb .\" 2006-12-28, mtk: .\" added .ss headers to give some structure to this page; and a .\" small amount of reordering. .\" added a section on canonical and noncanonical mode. .\" enhanced the discussion of "raw" mode for cfmakeraw(). .\" document cmspar. .\" .th termios 3 2021-08-27 "linux" "linux programmer's manual" .sh name termios, tcgetattr, tcsetattr, tcsendbreak, tcdrain, tcflush, tcflow, cfmakeraw, cfgetospeed, cfgetispeed, cfsetispeed, cfsetospeed, cfsetspeed \- get and set terminal attributes, line control, get and set baud rate .sh synopsis .nf .b #include .b #include .pp .bi "int tcgetattr(int " fd ", struct termios *" termios_p ); .bi "int tcsetattr(int " fd ", int " optional_actions , .bi " const struct termios *" termios_p ); .pp .bi "int tcsendbreak(int " fd ", int " duration ); .bi "int tcdrain(int " fd ); .bi "int tcflush(int " fd ", int " queue_selector ); .bi "int tcflow(int " fd ", int " action ); .pp .bi "void cfmakeraw(struct termios *" termios_p ); .pp .bi "speed_t cfgetispeed(const struct termios *" termios_p ); .bi "speed_t cfgetospeed(const struct termios *" termios_p ); .pp .bi "int cfsetispeed(struct termios *" termios_p ", speed_t " speed ); .bi "int cfsetospeed(struct termios *" termios_p ", speed_t " speed ); .bi "int cfsetspeed(struct termios *" termios_p ", speed_t " speed ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br cfsetspeed (), .br cfmakeraw (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _bsd_source .fi .sh description the termios functions describe a general terminal interface that is provided to control asynchronous communications ports. .ss the termios structure many of the functions described here have a \fitermios_p\fp argument that is a pointer to a \fitermios\fp structure. this structure contains at least the following members: .pp .in +4n .ex tcflag_t c_iflag; /* input modes */ tcflag_t c_oflag; /* output modes */ tcflag_t c_cflag; /* control modes */ tcflag_t c_lflag; /* local modes */ cc_t c_cc[nccs]; /* special characters */ .ee .in .pp the values that may be assigned to these fields are described below. in the case of the first four bit-mask fields, the definitions of some of the associated flags that may be set are exposed only if a specific feature test macro (see .br feature_test_macros (7)) is defined, as noted in brackets ("[]"). .pp in the descriptions below, "not in posix" means that the value is not specified in posix.1-2001, and "xsi" means that the value is specified in posix.1-2001 as part of the xsi extension. .pp \fic_iflag\fp flag constants: .tp .b ignbrk ignore break condition on input. .tp .b brkint if \fbignbrk\fp is set, a break is ignored. if it is not set but \fbbrkint\fp is set, then a break causes the input and output queues to be flushed, and if the terminal is the controlling terminal of a foreground process group, it will cause a \fbsigint\fp to be sent to this foreground process group. when neither \fbignbrk\fp nor \fbbrkint\fp are set, a break reads as a null byte (\(aq\e0\(aq), except when \fbparmrk\fp is set, in which case it reads as the sequence \e377 \e0 \e0. .tp .b ignpar ignore framing errors and parity errors. .tp .b parmrk if this bit is set, input bytes with parity or framing errors are marked when passed to the program. this bit is meaningful only when \fbinpck\fp is set and \fbignpar\fp is not set. the way erroneous bytes are marked is with two preceding bytes, \e377 and \e0. thus, the program actually reads three bytes for one erroneous byte received from the terminal. if a valid byte has the value \e377, and \fbistrip\fp (see below) is not set, the program might confuse it with the prefix that marks a parity error. therefore, a valid byte \e377 is passed to the program as two bytes, \e377 \e377, in this case. .ip if neither \fbignpar\fp nor \fbparmrk\fp is set, read a character with a parity error or framing error as \e0. .tp .b inpck enable input parity checking. .tp .b istrip strip off eighth bit. .tp .b inlcr translate nl to cr on input. .tp .b igncr ignore carriage return on input. .tp .b icrnl translate carriage return to newline on input (unless \fbigncr\fp is set). .tp .b iuclc (not in posix) map uppercase characters to lowercase on input. .tp .b ixon enable xon/xoff flow control on output. .tp .b ixany (xsi) typing any character will restart stopped output. (the default is to allow just the start character to restart output.) .tp .b ixoff enable xon/xoff flow control on input. .tp .b imaxbel (not in posix) ring bell when input queue is full. linux does not implement this bit, and acts as if it is always set. .tp .br iutf8 " (since linux 2.6.4)" (not in posix) input is utf8; this allows character-erase to be correctly performed in cooked mode. .pp .i c_oflag flag constants: .tp .b opost enable implementation-defined output processing. .tp .b olcuc (not in posix) map lowercase characters to uppercase on output. .tp .b onlcr (xsi) map nl to cr-nl on output. .tp .b ocrnl map cr to nl on output. .tp .b onocr don't output cr at column 0. .tp .b onlret don't output cr. .tp .b ofill send fill characters for a delay, rather than using a timed delay. .tp .b ofdel fill character is ascii del (0177). if unset, fill character is ascii nul (\(aq\e0\(aq). (not implemented on linux.) .tp .b nldly newline delay mask. values are \fbnl0\fp and \fbnl1\fp. [requires .b _bsd_source or .b _svid_source or .br _xopen_source ] .tp .b crdly carriage return delay mask. values are \fbcr0\fp, \fbcr1\fp, \fbcr2\fp, or \fbcr3\fp. [requires .b _bsd_source or .b _svid_source or .br _xopen_source ] .tp .b tabdly horizontal tab delay mask. values are \fbtab0\fp, \fbtab1\fp, \fbtab2\fp, \fbtab3\fp (or \fbxtabs\fp, but see the .b bugs section). a value of tab3, that is, xtabs, expands tabs to spaces (with tab stops every eight columns). [requires .b _bsd_source or .b _svid_source or .br _xopen_source ] .tp .b bsdly backspace delay mask. values are \fbbs0\fp or \fbbs1\fp. (has never been implemented.) [requires .b _bsd_source or .b _svid_source or .br _xopen_source ] .tp .b vtdly vertical tab delay mask. values are \fbvt0\fp or \fbvt1\fp. .tp .b ffdly form feed delay mask. values are \fbff0\fp or \fbff1\fp. [requires .b _bsd_source or .b _svid_source or .br _xopen_source ] .pp \fic_cflag\fp flag constants: .tp .b cbaud (not in posix) baud speed mask (4+1 bits). [requires .b _bsd_source or .br _svid_source ] .tp .b cbaudex (not in posix) extra baud speed mask (1 bit), included in .br cbaud . [requires .b _bsd_source or .br _svid_source ] .ip (posix says that the baud speed is stored in the .i termios structure without specifying where precisely, and provides .br cfgetispeed () and .br cfsetispeed () for getting at it. some systems use bits selected by .b cbaud in .ir c_cflag , other systems use separate fields, for example, .i sg_ispeed and .ir sg_ospeed .) .tp .b csize character size mask. values are \fbcs5\fp, \fbcs6\fp, \fbcs7\fp, or \fbcs8\fp. .tp .b cstopb set two stop bits, rather than one. .tp .b cread enable receiver. .tp .b parenb enable parity generation on output and parity checking for input. .tp .b parodd if set, then parity for input and output is odd; otherwise even parity is used. .tp .b hupcl lower modem control lines after last process closes the device (hang up). .tp .b clocal ignore modem control lines. .tp .b loblk (not in posix) block output from a noncurrent shell layer. for use by \fbshl\fp (shell layers). (not implemented on linux.) .tp .b cibaud (not in posix) mask for input speeds. the values for the .b cibaud bits are the same as the values for the .b cbaud bits, shifted left .b ibshift bits. [requires .b _bsd_source or .br _svid_source ] (not implemented on linux.) .tp .b cmspar (not in posix) use "stick" (mark/space) parity (supported on certain serial devices): if .b parodd is set, the parity bit is always 1; if .b parodd is not set, then the parity bit is always 0. [requires .b _bsd_source or .br _svid_source ] .tp .b crtscts (not in posix) enable rts/cts (hardware) flow control. [requires .b _bsd_source or .br _svid_source ] .pp \fic_lflag\fp flag constants: .tp .b isig when any of the characters intr, quit, susp, or dsusp are received, generate the corresponding signal. .tp .b icanon enable canonical mode (described below). .tp .b xcase (not in posix; not supported under linux) if \fbicanon\fp is also set, terminal is uppercase only. input is converted to lowercase, except for characters preceded by \e. on output, uppercase characters are preceded by \e and lowercase characters are converted to uppercase. [requires .b _bsd_source or .b _svid_source or .br _xopen_source ] .\" glibc is probably now wrong to allow .\" define .\" .b _xopen_source .\" to expose .\" .br xcase . .tp .b echo echo input characters. .tp .b echoe if \fbicanon\fp is also set, the erase character erases the preceding input character, and werase erases the preceding word. .tp .b echok if \fbicanon\fp is also set, the kill character erases the current line. .tp .b echonl if \fbicanon\fp is also set, echo the nl character even if echo is not set. .tp .b echoctl (not in posix) if \fbecho\fp is also set, terminal special characters other than tab, nl, start, and stop are echoed as \fb\(hax\fp, where x is the character with ascii code 0x40 greater than the special character. for example, character 0x08 (bs) is echoed as \fb\(hah\fp. [requires .b _bsd_source or .br _svid_source ] .tp .b echoprt (not in posix) if \fbicanon\fp and \fbecho\fp are also set, characters are printed as they are being erased. [requires .b _bsd_source or .br _svid_source ] .tp .b echoke (not in posix) if \fbicanon\fp is also set, kill is echoed by erasing each character on the line, as specified by \fbechoe\fp and \fbechoprt\fp. [requires .b _bsd_source or .br _svid_source ] .tp .b defecho (not in posix) echo only when a process is reading. (not implemented on linux.) .tp .b flusho (not in posix; not supported under linux) output is being flushed. this flag is toggled by typing the discard character. [requires .b _bsd_source or .br _svid_source ] .tp .b noflsh disable flushing the input and output queues when generating signals for the int, quit, and susp characters. .\" stevens lets susp only flush the input queue .tp .b tostop send the .b sigttou signal to the process group of a background process which tries to write to its controlling terminal. .tp .b pendin (not in posix; not supported under linux) all characters in the input queue are reprinted when the next character is read. .rb ( bash (1) handles typeahead this way.) [requires .b _bsd_source or .br _svid_source ] .tp .b iexten enable implementation-defined input processing. this flag, as well as \fbicanon\fp must be enabled for the special characters eol2, lnext, reprint, werase to be interpreted, and for the \fbiuclc\fp flag to be effective. .pp the \fic_cc\fp array defines the terminal special characters. the symbolic indices (initial values) and meaning are: .tp .b vdiscard (not in posix; not supported under linux; 017, si, ctrl-o) toggle: start/stop discarding pending output. recognized when .b iexten is set, and then not passed as input. .tp .b vdsusp (not in posix; not supported under linux; 031, em, ctrl-y) delayed suspend character (dsusp): send .b sigtstp signal when the character is read by the user program. recognized when .b iexten and .b isig are set, and the system supports job control, and then not passed as input. .tp .b veof (004, eot, ctrl-d) end-of-file character (eof). more precisely: this character causes the pending tty buffer to be sent to the waiting user program without waiting for end-of-line. if it is the first character of the line, the .br read (2) in the user program returns 0, which signifies end-of-file. recognized when .b icanon is set, and then not passed as input. .tp .b veol (0, nul) additional end-of-line character (eol). recognized when .b icanon is set. .tp .b veol2 (not in posix; 0, nul) yet another end-of-line character (eol2). recognized when .b icanon is set. .tp .b verase (0177, del, rubout, or 010, bs, ctrl-h, or also #) erase character (erase). this erases the previous not-yet-erased character, but does not erase past eof or beginning-of-line. recognized when .b icanon is set, and then not passed as input. .tp .b vintr (003, etx, ctrl-c, or also 0177, del, rubout) interrupt character (intr). send a .b sigint signal. recognized when .b isig is set, and then not passed as input. .tp .b vkill (025, nak, ctrl-u, or ctrl-x, or also @) kill character (kill). this erases the input since the last eof or beginning-of-line. recognized when .b icanon is set, and then not passed as input. .tp .b vlnext (not in posix; 026, syn, ctrl-v) literal next (lnext). quotes the next input character, depriving it of a possible special meaning. recognized when .b iexten is set, and then not passed as input. .tp .b vmin minimum number of characters for noncanonical read (min). .tp .b vquit (034, fs, ctrl-\e) quit character (quit). send .b sigquit signal. recognized when .b isig is set, and then not passed as input. .tp .b vreprint (not in posix; 022, dc2, ctrl-r) reprint unread characters (reprint). recognized when .b icanon and .b iexten are set, and then not passed as input. .tp .b vstart (021, dc1, ctrl-q) start character (start). restarts output stopped by the stop character. recognized when .b ixon is set, and then not passed as input. .tp .b vstatus (not in posix; not supported under linux; status request: 024, dc4, ctrl-t). status character (status). display status information at terminal, including state of foreground process and amount of cpu time it has consumed. also sends a .b siginfo signal (not supported on linux) to the foreground process group. .tp .b vstop (023, dc3, ctrl-s) stop character (stop). stop output until start character typed. recognized when .b ixon is set, and then not passed as input. .tp .b vsusp (032, sub, ctrl-z) suspend character (susp). send .b sigtstp signal. recognized when .b isig is set, and then not passed as input. .tp .b vswtch (not in posix; not supported under linux; 0, nul) switch character (swtch). used in system v to switch shells in .ir "shell layers" , a predecessor to shell job control. .tp .b vtime timeout in deciseconds for noncanonical read (time). .tp .b vwerase (not in posix; 027, etb, ctrl-w) word erase (werase). recognized when .b icanon and .b iexten are set, and then not passed as input. .pp an individual terminal special character can be disabled by setting the value of the corresponding .i c_cc element to .br _posix_vdisable . .pp the above symbolic subscript values are all different, except that .br vtime , .b vmin may have the same value as .br veol , .br veof , respectively. in noncanonical mode the special character meaning is replaced by the timeout meaning. for an explanation of .b vmin and .br vtime , see the description of noncanonical mode below. .ss retrieving and changing terminal settings .br tcgetattr () gets the parameters associated with the object referred by \fifd\fp and stores them in the \fitermios\fp structure referenced by \fitermios_p\fp. this function may be invoked from a background process; however, the terminal attributes may be subsequently changed by a foreground process. .pp .br tcsetattr () sets the parameters associated with the terminal (unless support is required from the underlying hardware that is not available) from the \fitermios\fp structure referred to by \fitermios_p\fp. \fioptional_actions\fp specifies when the changes take effect: .ip \fbtcsanow\fp the change occurs immediately. .ip \fbtcsadrain\fp the change occurs after all output written to .i fd has been transmitted. this option should be used when changing parameters that affect output. .ip \fbtcsaflush\fp the change occurs after all output written to the object referred by .i fd has been transmitted, and all input that has been received but not read will be discarded before the change is made. .ss canonical and noncanonical mode the setting of the .b icanon canon flag in .i c_lflag determines whether the terminal is operating in canonical mode .rb ( icanon set) or noncanonical mode .rb ( icanon unset). by default, .b icanon is set. .pp in canonical mode: .ip * 2 input is made available line by line. an input line is available when one of the line delimiters is typed (nl, eol, eol2; or eof at the start of line). except in the case of eof, the line delimiter is included in the buffer returned by .br read (2). .ip * 2 line editing is enabled (erase, kill; and if the .b iexten flag is set: werase, reprint, lnext). a .br read (2) returns at most one line of input; if the .br read (2) requested fewer bytes than are available in the current line of input, then only as many bytes as requested are read, and the remaining characters will be available for a future .br read (2). .ip * 2 the maximum line length is 4096 chars (including the terminating newline character); lines longer than 4096 chars are truncated. after 4095 characters, input processing (e.g., .b isig and .b echo* processing) continues, but any input data after 4095 characters up to (but not including) any terminating newline is discarded. this ensures that the terminal can always receive more input until at least one line can be read. .pp in noncanonical mode input is available immediately (without the user having to type a line-delimiter character), no input processing is performed, and line editing is disabled. the read buffer will only accept 4095 chars; this provides the necessary space for a newline char if the input mode is switched to canonical. the settings of min .ri ( c_cc[vmin] ) and time .ri ( c_cc[vtime] ) determine the circumstances in which a .br read (2) completes; there are four distinct cases: .tp min == 0, time == 0 (polling read) if data is available, .br read (2) returns immediately, with the lesser of the number of bytes available, or the number of bytes requested. if no data is available, .br read (2) returns 0. .tp min > 0, time == 0 (blocking read) .br read (2) blocks until min bytes are available, and returns up to the number of bytes requested. .tp min == 0, time > 0 (read with timeout) time specifies the limit for a timer in tenths of a second. the timer is started when .br read (2) is called. .br read (2) returns either when at least one byte of data is available, or when the timer expires. if the timer expires without any input becoming available, .br read (2) returns 0. if data is already available at the time of the call to .br read (2), the call behaves as though the data was received immediately after the call. .tp min > 0, time > 0 (read with interbyte timeout) time specifies the limit for a timer in tenths of a second. once an initial byte of input becomes available, the timer is restarted after each further byte is received. .br read (2) returns when any of the following conditions is met: .rs .ip * 3 min bytes have been received. .ip * the interbyte timer expires. .ip * the number of bytes requested by .br read (2) has been received. (posix does not specify this termination condition, and on some other implementations .\" e.g., solaris .br read (2) does not return in this case.) .re .ip because the timer is started only after the initial byte becomes available, at least one byte will be read. if data is already available at the time of the call to .br read (2), the call behaves as though the data was received immediately after the call. .pp posix .\" posix.1-2008 xbd 11.1.7 does not specify whether the setting of the .b o_nonblock file status flag takes precedence over the min and time settings. if .b o_nonblock is set, a .br read (2) in noncanonical mode may return immediately, regardless of the setting of min or time. furthermore, if no data is available, posix permits a .br read (2) in noncanonical mode to return either 0, or \-1 with .i errno set to .br eagain . .ss raw mode .br cfmakeraw () sets the terminal to something like the "raw" mode of the old version 7 terminal driver: input is available character by character, echoing is disabled, and all special processing of terminal input and output characters is disabled. the terminal attributes are set as follows: .pp .in +4n .ex termios_p\->c_iflag &= \(ti(ignbrk | brkint | parmrk | istrip | inlcr | igncr | icrnl | ixon); termios_p\->c_oflag &= \(tiopost; termios_p\->c_lflag &= \(ti(echo | echonl | icanon | isig | iexten); termios_p\->c_cflag &= \(ti(csize | parenb); termios_p\->c_cflag |= cs8; .ee .in .\" .ss line control .br tcsendbreak () transmits a continuous stream of zero-valued bits for a specific duration, if the terminal is using asynchronous serial data transmission. if \fiduration\fp is zero, it transmits zero-valued bits for at least 0.25 seconds, and not more than 0.5 seconds. if \fiduration\fp is not zero, it sends zero-valued bits for some implementation-defined length of time. .pp if the terminal is not using asynchronous serial data transmission, .br tcsendbreak () returns without taking any action. .pp .br tcdrain () waits until all output written to the object referred to by .i fd has been transmitted. .pp .br tcflush () discards data written to the object referred to by .i fd but not transmitted, or data received but not read, depending on the value of .ir queue_selector : .ip \fbtciflush\fp flushes data received but not read. .ip \fbtcoflush\fp flushes data written but not transmitted. .ip \fbtcioflush\fp flushes both data received but not read, and data written but not transmitted. .pp .br tcflow () suspends transmission or reception of data on the object referred to by .ir fd , depending on the value of .ir action : .ip \fbtcooff\fp suspends output. .ip \fbtcoon\fp restarts suspended output. .ip \fbtcioff\fp transmits a stop character, which stops the terminal device from transmitting data to the system. .ip \fbtcion\fp transmits a start character, which starts the terminal device transmitting data to the system. .pp the default on open of a terminal file is that neither its input nor its output is suspended. .ss line speed the baud rate functions are provided for getting and setting the values of the input and output baud rates in the \fitermios\fp structure. the new values do not take effect until .br tcsetattr () is successfully called. .pp setting the speed to \fbb0\fp instructs the modem to "hang up". the actual bit rate corresponding to \fbb38400\fp may be altered with .br setserial (8). .pp the input and output baud rates are stored in the \fitermios\fp structure. .pp .br cfgetospeed () returns the output baud rate stored in the \fitermios\fp structure pointed to by .ir termios_p . .pp .br cfsetospeed () sets the output baud rate stored in the \fitermios\fp structure pointed to by \fitermios_p\fp to \fispeed\fp, which must be one of these constants: .pp .nf .ft b b0 b50 b75 b110 b134 b150 b200 b300 b600 b1200 b1800 b2400 b4800 b9600 b19200 b38400 b57600 b115200 b230400 b460800 b500000 b576000 b921600 b1000000 b1152000 b1500000 b2000000 .ft p .fi .pp these constants are additionally supported on the sparc architecture: .pp .nf .ft b b76800 b153600 b307200 b614400 .ft p .fi .pp these constants are additionally supported on non-sparc architectures: .pp .nf .ft b b2500000 b3000000 b3500000 b4000000 .ft p .fi .pp due to differences between architectures, portable applications should check if a particular .bi b nnn constant is defined prior to using it. .pp the zero baud rate, .br b0 , is used to terminate the connection. if b0 is specified, the modem control lines shall no longer be asserted. normally, this will disconnect the line. .b cbaudex is a mask for the speeds beyond those defined in posix.1 (57600 and above). thus, .br b57600 " & " cbaudex is nonzero. .pp setting the baud rate to a value other than those defined by .bi b nnn constants is possible via the .b tcsets2 ioctl; see .br ioctl_tty (2). .pp .br cfgetispeed () returns the input baud rate stored in the .i termios structure. .pp .br cfsetispeed () sets the input baud rate stored in the .i termios structure to .ir speed , which must be specified as one of the .bi b nnn constants listed above for .br cfsetospeed (). if the input baud rate is set to zero, the input baud rate will be equal to the output baud rate. .pp .br cfsetspeed () is a 4.4bsd extension. it takes the same arguments as .br cfsetispeed (), and sets both input and output speed. .sh return value .br cfgetispeed () returns the input baud rate stored in the \fitermios\fp structure. .pp .br cfgetospeed () returns the output baud rate stored in the \fitermios\fp structure. .pp all other functions return: .ip 0 on success. .ip \-1 on failure and set .i errno to indicate the error. .pp note that .br tcsetattr () returns success if \fiany\fp of the requested changes could be successfully carried out. therefore, when making multiple changes it may be necessary to follow this call with a further call to .br tcgetattr () to check that all changes have been performed successfully. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .nh .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br tcgetattr (), .br tcsetattr (), .br tcdrain (), .br tcflush (), .br tcflow (), .br tcsendbreak (), .br cfmakeraw (), .br cfgetispeed (), .br cfgetospeed (), .br cfsetispeed (), .br cfsetospeed (), .br cfsetspeed () t} thread safety mt-safe .te .hy .ad .sp 1 .\" fixme: the markings are different from that in the glibc manual. .\" markings in glibc manual are more detailed: .\" .\" tcsendbreak: mt-unsafe race:tcattr(filedes)/bsd .\" tcflow: mt-unsafe race:tcattr(filedes)/bsd .\" .\" glibc manual says /bsd indicate the preceding marker only applies .\" when the underlying kernel is a bsd kernel. .\" so, it is safety in linux kernel. .hy .sh conforming to .br tcgetattr (), .br tcsetattr (), .br tcsendbreak (), .br tcdrain (), .br tcflush (), .br tcflow (), .br cfgetispeed (), .br cfgetospeed (), .br cfsetispeed (), and .br cfsetospeed () are specified in posix.1-2001. .pp .br cfmakeraw () and .br cfsetspeed () are nonstandard, but available on the bsds. .sh notes unix\ v7 and several later systems have a list of baud rates where after the values .br b0 through .b b9600 one finds the two constants .br exta , .b extb ("external a" and "external b"). many systems extend the list with much higher baud rates. .pp the effect of a nonzero \fiduration\fp with .br tcsendbreak () varies. sunos specifies a break of .i "duration\ *\ n" seconds, where \fin\fp is at least 0.25, and not more than 0.5. linux, aix, du, tru64 send a break of .i duration milliseconds. freebsd and netbsd and hp-ux and macos ignore the value of .ir duration . under solaris and unixware, .br tcsendbreak () with nonzero .i duration behaves like .br tcdrain (). .\" libc4 until 4.7.5, glibc for sysv: einval for duration > 0. .\" libc4.7.6, libc5, glibc for unix: duration in ms. .\" glibc for bsd: duration in us .\" glibc for sunos4: ignore duration .sh bugs .\" kernel 77e5bff1640432f28794a00800955e646dcd7455 .\" glibc 573963e32ffac46d9891970ddebde2ac3212c5c0 on the alpha architecture before linux 4.16 (and glibc before 2.28), the .b xtabs value was different from .b tab3 and it was ignored by the .b n_tty line discipline code of the terminal driver as a result (because as it wasn't part of the .b tabdly mask). .sh see also .br reset (1), .br setterm (1), .br stty (1), .br tput (1), .br tset (1), .br tty (1), .br ioctl_console (2), .br ioctl_tty (2), .br setserial (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cacosh.3 #!/bin/sh # # find_slashes_no_parens.sh # # look for function names inside \f[bi]...\f[pb] that aren't # followed by "()". # # this script is designed to help with "by hand" tidy-ups after # the automated changes made by add_parens_for_own_funcs.sh. # # the first argument to this script names a manual page directory where # 'man2' and 'man3' subdirectories can be found. the pages names in # these directories are used to generate a series of regular expressions # that can be used to search the manual page files that are named in # the remaining command-line arguments. # # example usage: # # cd man-pages-x.yy # sh find_slashes_no_parens.sh . man?/*.? > matches.log # ###################################################################### # # (c) copyright 2005 & 2013, michael kerrisk # this program is free software; you can redistribute it and/or # modify it under the terms of the gnu general public license # as published by the free software foundation; either version 2 # of the license, or (at your option) any later version. # # this program is distributed in the hope that it will be useful, # but without any warranty; without even the implied warranty of # merchantability or fitness for a particular purpose. see the # gnu general public license for more details # (http://www.gnu.org/licenses/gpl-2.0.html). # if test $# -lt 2; then echo "usage: $0 man-page-root-dir file file..." 1>&2 exit 1 fi dir=$1 if ! test -d $dir/man2 || ! test -d $dir/man3; then echo "can't find man2 and man3 under $dir" 1>&2 exit 1 fi shift 1 echo "this will probably take a few minutes..." 1>&2 regexp_file=tmp.$0.regexp rm -f $regexp_file # we grep out a few page names that are likely to generate false # positives... for page in $( find $dir/man2/* $dir/man3/* -type f -name '*.[23]' | egrep -v '/(stderr|stdin|stdout|errno|termios|string)\..$'); do base=$(basename $page | sed -e 's/\.[23]$//') echo "\\\\f[bi]$base\\\\f[pb][^(]" >> $regexp_file echo "\\\\f[bi]$base\\\\f[pb]\$" >> $regexp_file done sort -o $regexp_file $regexp_file # not really needed echo "built regexp file; now about to grep..." 1>&2 grep -f $regexp_file $* rm -f $regexp_file exit 0 .\" copyright (c) 2016 intel corporation .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pkeys 7 2021-03-22 "linux" "linux programmer's manual" .sh name pkeys \- overview of memory protection keys .sh description memory protection keys (pkeys) are an extension to existing page-based memory permissions. normal page permissions using page tables require expensive system calls and tlb invalidations when changing permissions. memory protection keys provide a mechanism for changing protections without requiring modification of the page tables on every permission change. .pp to use pkeys, software must first "tag" a page in the page tables with a pkey. after this tag is in place, an application only has to change the contents of a register in order to remove write access, or all access to a tagged page. .pp protection keys work in conjunction with the existing .br prot_read / .br prot_write / .br prot_exec permissions passed to system calls such as .br mprotect (2) and .br mmap (2), but always act to further restrict these traditional permission mechanisms. .pp if a process performs an access that violates pkey restrictions, it receives a .br sigsegv signal. see .br sigaction (2) for details of the information available with that signal. .pp to use the pkeys feature, the processor must support it, and the kernel must contain support for the feature on a given processor. as of early 2016 only future intel x86 processors are supported, and this hardware supports 16 protection keys in each process. however, pkey 0 is used as the default key, so a maximum of 15 are available for actual application use. the default key is assigned to any memory region for which a pkey has not been explicitly assigned via .br pkey_mprotect (2). .pp protection keys have the potential to add a layer of security and reliability to applications. but they have not been primarily designed as a security feature. for instance, wrpkru is a completely unprivileged instruction, so pkeys are useless in any case that an attacker controls the pkru register or can execute arbitrary instructions. .pp applications should be very careful to ensure that they do not "leak" protection keys. for instance, before calling .br pkey_free (2), the application should be sure that no memory has that pkey assigned. if the application left the freed pkey assigned, a future user of that pkey might inadvertently change the permissions of an unrelated data structure, which could impact security or stability. the kernel currently allows in-use pkeys to have .br pkey_free (2) called on them because it would have processor or memory performance implications to perform the additional checks needed to disallow it. implementation of the necessary checks is left up to applications. applications may implement these checks by searching the .ir /proc/[pid]/smaps file for memory regions with the pkey assigned. further details can be found in .br proc (5). .pp any application wanting to use protection keys needs to be able to function without them. they might be unavailable because the hardware that the application runs on does not support them, the kernel code does not contain support, the kernel support has been disabled, or because the keys have all been allocated, perhaps by a library the application is using. it is recommended that applications wanting to use protection keys should simply call .br pkey_alloc (2) and test whether the call succeeds, instead of attempting to detect support for the feature in any other way. .pp although unnecessary, hardware support for protection keys may be enumerated with the .i cpuid instruction. details of how to do this can be found in the intel software developers manual. the kernel performs this enumeration and exposes the information in .ir /proc/cpuinfo under the "flags" field. the string "pku" in this field indicates hardware support for protection keys and the string "ospke" indicates that the kernel contains and has enabled protection keys support. .pp applications using threads and protection keys should be especially careful. threads inherit the protection key rights of the parent at the time of the .br clone (2), system call. applications should either ensure that their own permissions are appropriate for child threads at the time when .br clone (2) is called, or ensure that each child thread can perform its own initialization of protection key rights. .\" .ss signal handler behavior each time a signal handler is invoked (including nested signals), the thread is temporarily given a new, default set of protection key rights that override the rights from the interrupted context. this means that applications must re-establish their desired protection key rights upon entering a signal handler if the desired rights differ from the defaults. the rights of any interrupted context are restored when the signal handler returns. .pp this signal behavior is unusual and is due to the fact that the x86 pkru register (which stores protection key access rights) is managed with the same hardware mechanism (xsave) that manages floating-point registers. the signal behavior is the same as that of floating-point registers. .\" .ss protection keys system calls the linux kernel implements the following pkey-related system calls: .br pkey_mprotect (2), .br pkey_alloc (2), and .br pkey_free (2). .pp the linux pkey system calls are available only if the kernel was configured and built with the .br config_x86_intel_memory_protection_keys option. .sh examples the program below allocates a page of memory with read and write permissions. it then writes some data to the memory and successfully reads it back. after that, it attempts to allocate a protection key and disallows access to the page by using the wrpkru instruction. it then tries to access the page, which we now expect to cause a fatal signal to the application. .pp .in +4n .ex .rb "$" " ./a.out" buffer contains: 73 about to read buffer again... segmentation fault (core dumped) .ee .in .ss program source \& .ex #define _gnu_source #include #include #include #include static inline void wrpkru(unsigned int pkru) { unsigned int eax = pkru; unsigned int ecx = 0; unsigned int edx = 0; asm volatile(".byte 0x0f,0x01,0xef\en\et" : : "a" (eax), "c" (ecx), "d" (edx)); } int pkey_set(int pkey, unsigned long rights, unsigned long flags) { unsigned int pkru = (rights << (2 * pkey)); return wrpkru(pkru); } int pkey_mprotect(void *ptr, size_t size, unsigned long orig_prot, unsigned long pkey) { return syscall(sys_pkey_mprotect, ptr, size, orig_prot, pkey); } int pkey_alloc(void) { return syscall(sys_pkey_alloc, 0, 0); } int pkey_free(unsigned long pkey) { return syscall(sys_pkey_free, pkey); } #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) int main(void) { int status; int pkey; int *buffer; /* * allocate one page of memory. */ buffer = mmap(null, getpagesize(), prot_read | prot_write, map_anonymous | map_private, \-1, 0); if (buffer == map_failed) errexit("mmap"); /* * put some random data into the page (still ok to touch). */ *buffer = __line__; printf("buffer contains: %d\en", *buffer); /* * allocate a protection key: */ pkey = pkey_alloc(); if (pkey == \-1) errexit("pkey_alloc"); /* * disable access to any memory with "pkey" set, * even though there is none right now. */ status = pkey_set(pkey, pkey_disable_access, 0); if (status) errexit("pkey_set"); /* * set the protection key on "buffer". * note that it is still read/write as far as mprotect() is * concerned and the previous pkey_set() overrides it. */ status = pkey_mprotect(buffer, getpagesize(), prot_read | prot_write, pkey); if (status == \-1) errexit("pkey_mprotect"); printf("about to read buffer again...\en"); /* * this will crash, because we have disallowed access. */ printf("buffer contains: %d\en", *buffer); status = pkey_free(pkey); if (status == \-1) errexit("pkey_free"); exit(exit_success); } .ee .sh see also .br pkey_alloc (2), .br pkey_free (2), .br pkey_mprotect (2), .br sigaction (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gethostbyname.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_fsync 3 2021-03-22 "" "linux programmer's manual" .sh name aio_fsync \- asynchronous file synchronization .sh synopsis .nf .b "#include " .pp .bi "int aio_fsync(int " op ", struct aiocb *" aiocbp ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_fsync () function does a sync on all outstanding asynchronous i/o operations associated with .ir aiocbp\->aio_fildes . (see .br aio (7) for a description of the .i aiocb structure.) .pp more precisely, if .i op is .br o_sync , then all currently queued i/o operations shall be completed as if by a call of .br fsync (2), and if .i op is .br o_dsync , this call is the asynchronous analog of .br fdatasync (2). .pp note that this is a request only; it does not wait for i/o completion. .pp apart from .ir aio_fildes , the only field in the structure pointed to by .i aiocbp that is used by this call is the .i aio_sigevent field (a .i sigevent structure, described in .br sigevent (7)), which indicates the desired type of asynchronous notification at completion. all other fields are ignored. .sh return value on success (the sync request was successfully queued) this function returns 0. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eagain out of resources. .tp .b ebadf .i aio_fildes is not a valid file descriptor open for writing. .tp .b einval synchronized i/o is not supported for this file, or .i op is not .b o_sync or .br o_dsync . .tp .b enosys .br aio_fsync () is not implemented. .sh versions the .br aio_fsync () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_fsync () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh see also .br aio_cancel (3), .br aio_error (3), .br aio_read (3), .br aio_return (3), .br aio_suspend (3), .br aio_write (3), .br lio_listio (3), .br aio (7), .br sigevent (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getgroups.2 .\" copyright (c) 2009 linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th timer_delete 2 2021-03-22 linux "linux programmer's manual" .sh name timer_delete \- delete a posix per-process timer .sh synopsis .nf .b #include .pp .bi "int timer_delete(timer_t " timerid ); .fi .pp link with \fi\-lrt\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br timer_delete (): .nf _posix_c_source >= 199309l .fi .sh description .br timer_delete () deletes the timer whose id is given in .ir timerid . if the timer was armed at the time of this call, it is disarmed before being deleted. the treatment of any pending signal generated by the deleted timer is unspecified. .sh return value on success, .br timer_delete () returns 0. on failure, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i timerid is not a valid timer id. .sh versions this system call is available since linux 2.6. .sh conforming to posix.1-2001, posix.1-2008. .sh see also .br clock_gettime (2), .br timer_create (2), .br timer_getoverrun (2), .br timer_settime (2), .br time (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th posix_fallocate 3 2021-03-22 "gnu" "linux programmer's manual" .sh name posix_fallocate \- allocate file space .sh synopsis .nf .b #include .pp .bi "int posix_fallocate(int " fd ", off_t " offset ", off_t " len ); .fi .pp .ad l .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br posix_fallocate (): .nf _posix_c_source >= 200112l .fi .sh description the function .br posix_fallocate () ensures that disk space is allocated for the file referred to by the file descriptor .i fd for the bytes in the range starting at .i offset and continuing for .i len bytes. after a successful call to .br posix_fallocate (), subsequent writes to bytes in the specified range are guaranteed not to fail because of lack of disk space. .pp if the size of the file is less than .ir offset + len , then the file is increased to this size; otherwise the file size is left unchanged. .sh return value .br posix_fallocate () returns zero on success, or an error number on failure. note that .i errno is not set. .sh errors .tp .b ebadf .i fd is not a valid file descriptor, or is not opened for writing. .tp .b efbig .i offset+len exceeds the maximum file size. .tp .b eintr a signal was caught during execution. .tp .b einval .i offset was less than 0, or .i len was less than or equal to 0, or the underlying filesystem does not support the operation. .tp .b enodev .i fd does not refer to a regular file. .tp .b enospc there is not enough space left on the device containing the file referred to by .ir fd . .tp .b eopnotsupp the filesystem containing the file referred to by .i fd does not support this operation. this error code can be returned by c libraries that don't perform the emulation shown in notes, such as musl libc. .tp .b espipe .i fd refers to a pipe. .sh versions .br posix_fallocate () is available since glibc 2.1.94. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br posix_fallocate () t} thread safety t{ mt-safe (but see notes) t} .te .hy .ad .sp 1 .sh conforming to posix.1-2001. .pp posix.1-2008 says that an implementation .i shall give the .b einval error if .i len was 0, or .i offset was less than 0. posix.1-2001 says that an implementation .i shall give the .b einval error if .i len is less than 0, or .i offset was less than 0, and .i may give the error if .i len equals zero. .sh notes in the glibc implementation, .br posix_fallocate () is implemented using the .br fallocate (2) system call, which is mt-safe. if the underlying filesystem does not support .br fallocate (2), then the operation is emulated with the following caveats: .ip * 2 the emulation is inefficient. .ip * there is a race condition where concurrent writes from another thread or process could be overwritten with null bytes. .ip * there is a race condition where concurrent file size increases by another thread or process could result in a file whose size is smaller than expected. .ip * if .i fd has been opened with the .b o_append or .b o_wronly flags, the function fails with the error .br ebadf . .pp in general, the emulation is not mt-safe. on linux, applications may use .br fallocate (2) if they cannot tolerate the emulation caveats. in general, this is only recommended if the application plans to terminate the operation if .b eopnotsupp is returned, otherwise the application itself will need to implement a fallback with all the same problems as the emulation provided by glibc. .sh see also .br fallocate (1), .br fallocate (2), .br lseek (2), .br posix_fadvise (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt .\" and copyright (c) 1993,1994 ian jackson .\" and copyright (c) 2006, 2014, michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" you may distribute it under the terms of the gnu general .\" public license. it comes with no warranty. .\" %%%license_end .\" .\" modified 1996-08-18 by urs .\" modified 2003-04-23 by michael kerrisk .\" modified 2004-06-23 by michael kerrisk .\" .th mknod 2 2021-08-27 "linux" "linux programmer's manual" .sh name mknod, mknodat \- create a special or ordinary file .sh synopsis .nf .b #include .pp .bi "int mknod(const char *" pathname ", mode_t " mode ", dev_t " dev ); .pp .br "#include " "/* definition of at_* constants */" .b #include .pp .bi "int mknodat(int " dirfd ", const char *" pathname ", mode_t " mode \ ", dev_t " dev ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br mknod (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description the system call .br mknod () creates a filesystem node (file, device special file, or named pipe) named .ir pathname , with attributes specified by .i mode and .ir dev . .pp the .i mode argument specifies both the file mode to use and the type of node to be created. it should be a combination (using bitwise or) of one of the file types listed below and zero or more of the file mode bits listed in .br inode (7). .pp the file mode is modified by the process's .i umask in the usual way: in the absence of a default acl, the permissions of the created node are .ri ( mode " & \(ti" umask ). .pp the file type must be one of .br s_ifreg , .br s_ifchr , .br s_ifblk , .br s_ififo , or .b s_ifsock .\" (s_ifsock since linux 1.2.4) to specify a regular file (which will be created empty), character special file, block special file, fifo (named pipe), or unix domain socket, respectively. (zero file type is equivalent to type .br s_ifreg .) .pp if the file type is .b s_ifchr or .br s_ifblk , then .i dev specifies the major and minor numbers of the newly created device special file .rb ( makedev (3) may be useful to build the value for .ir dev ); otherwise it is ignored. .pp if .i pathname already exists, or is a symbolic link, this call fails with an .b eexist error. .pp the newly created node will be owned by the effective user id of the process. if the directory containing the node has the set-group-id bit set, or if the filesystem is mounted with bsd group semantics, the new node will inherit the group ownership from its parent directory; otherwise it will be owned by the effective group id of the process. .\" .\" .ss mknodat() the .br mknodat () system call operates in exactly the same way as .br mknod (), except for the differences described here. .pp if the pathname given in .i pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor .i dirfd (rather than relative to the current working directory of the calling process, as is done by .br mknod () for a relative pathname). .pp if .i pathname is relative and .i dirfd is the special value .br at_fdcwd , then .i pathname is interpreted relative to the current working directory of the calling process (like .br mknod ()). .pp if .i pathname is absolute, then .i dirfd is ignored. .pp see .br openat (2) for an explanation of the need for .br mknodat (). .sh return value .br mknod () and .br mknodat () return zero on success. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces the parent directory does not allow write permission to the process, or one of the directories in the path prefix of .i pathname did not allow search permission. (see also .br path_resolution (7).) .tp .b ebadf .br ( mknodat ()) .i pathname is relative but .i dirfd is neither .b at_fdcwd nor a valid file descriptor. .tp .b edquot the user's quota of disk blocks or inodes on the filesystem has been exhausted. .tp .b eexist .i pathname already exists. this includes the case where .i pathname is a symbolic link, dangling or not. .tp .b efault .ir pathname " points outside your accessible address space." .tp .b einval .i mode requested creation of something other than a regular file, device special file, fifo or socket. .tp .b eloop too many symbolic links were encountered in resolving .ir pathname . .tp .b enametoolong .ir pathname " was too long." .tp .b enoent a directory component in .i pathname does not exist or is a dangling symbolic link. .tp .b enomem insufficient kernel memory was available. .tp .b enospc the device containing .i pathname has no room for the new node. .tp .b enotdir a component used as a directory in .i pathname is not, in fact, a directory. .tp .b enotdir .br ( mknodat ()) .i pathname is relative and .i dirfd is a file descriptor referring to a file other than a directory. .tp .b eperm .i mode requested creation of something other than a regular file, fifo (named pipe), or unix domain socket, and the caller is not privileged (linux: does not have the .b cap_mknod capability); .\" for unix domain sockets and regular files, eperm is returned only in .\" linux 2.2 and earlier; in linux 2.4 and later, unprivileged can .\" use mknod() to make these files. also returned if the filesystem containing .i pathname does not support the type of node requested. .tp .b erofs .i pathname refers to a file on a read-only filesystem. .sh versions .br mknodat () was added to linux in kernel 2.6.16; library support was added to glibc in version 2.4. .sh conforming to .br mknod (): svr4, 4.4bsd, posix.1-2001 (but see below), posix.1-2008. .\" the linux version differs from the svr4 version in that it .\" does not require root permission to create pipes, also in that no .\" emultihop, enolink, or eintr error is documented. .pp .br mknodat (): posix.1-2008. .sh notes posix.1-2001 says: "the only portable use of .br mknod () is to create a fifo-special file. if .i mode is not .b s_ififo or .i dev is not 0, the behavior of .br mknod () is unspecified." however, nowadays one should never use .br mknod () for this purpose; one should use .br mkfifo (3), a function especially defined for this purpose. .pp under linux, .br mknod () cannot be used to create directories. one should make directories with .br mkdir (2). .\" and one should make unix domain sockets with socket(2) and bind(2). .pp there are many infelicities in the protocol underlying nfs. some of these affect .br mknod () and .br mknodat (). .sh see also .br mknod (1), .br chmod (2), .br chown (2), .br fcntl (2), .br mkdir (2), .br mount (2), .br socket (2), .br stat (2), .br umask (2), .br unlink (2), .br makedev (3), .br mkfifo (3), .br acl (5), .br path_resolution (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1989, 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)operator.7 8.1 (berkeley) 6/9/93 .\" .\" copied shamelessly from freebsd with minor changes. 2003-05-21 .\" brian m. carlson .\" .\" restored automatic formatting from freebsd. 2003-08-24 .\" martin schulze .\" .\" 2007-12-08, mtk, converted from mdoc to man macros .\" .th operator 7 2020-08-13 "linux" "linux programmer's manual" .sh name operator \- c operator precedence and order of evaluation .sh description this manual page lists c operators and their precedence in evaluation. .pp .ts lb lb lb l l l. operator associativity notes () [] \-> . ++ \-\- left to right [1] ! \(ti ++ \-\- + \- (type) * & sizeof right to left [2] * / % left to right + \- left to right << >> left to right < <= > >= left to right == != left to right & left to right \(ha left to right | left to right && left to right || left to right ?: right to left = += \-= *= /= %= <<= >>= &= \(ha= |= right to left , left to right .te .pp the following notes provide further information to the above table: .pp .pd 0 .ip [1] 4 the ++ and \-\- operators at this precedence level are the postfix flavors of the operators. .ip [2] the ++ and \-\- operators at this precedence level are the prefix flavors of the operators. .pd .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" written by david howells (dhowells@redhat.com) .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_onepara) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license .\" as published by the free software foundation; either version .\" 2 of the license, or (at your option) any later version. .\" %%%license_end .\" .th add_key 2 2021-08-27 linux "linux key management calls" .sh name add_key \- add a key to the kernel's key management facility .sh synopsis .nf .b #include .pp .bi "key_serial_t add_key(const char *" type ", const char *" description , .bi " const void *" payload ", size_t " plen , .bi " key_serial_t " keyring ");" .fi .pp .ir note : there is no glibc wrapper for this system call; see notes. .sh description .br add_key () creates or updates a key of the given .i type and .ir description , instantiates it with the .i payload of length .ir plen , attaches it to the nominated .ir keyring , and returns the key's serial number. .pp the key may be rejected if the provided data is in the wrong format or it is invalid in some other way. .pp if the destination .i keyring already contains a key that matches the specified .ir type and .ir description , then, if the key type supports it, .\" fixme the aforementioned phrases begs the question: .\" which key types support this? that key will be updated rather than a new key being created; if not, a new key (with a different id) will be created and it will displace the link to the extant key from the keyring. .\" fixme perhaps elaborate the implications here? namely, the new .\" key will have a new id, and if the old key was a keyring that .\" is consequently unlinked, then keys that it was anchoring .\" will have their reference count decreased by one (and may .\" consequently be garbage collected). is this all correct? .pp the destination .i keyring serial number may be that of a valid keyring for which the caller has .i write permission. alternatively, it may be one of the following special keyring ids: .\" fixme . perhaps have a separate page describing special keyring ids? .tp .b key_spec_thread_keyring this specifies the caller's thread-specific keyring .rb ( thread\-keyring (7)). .tp .b key_spec_process_keyring this specifies the caller's process-specific keyring .rb ( process\-keyring (7)). .tp .b key_spec_session_keyring this specifies the caller's session-specific keyring .rb ( session\-keyring (7)). .tp .b key_spec_user_keyring this specifies the caller's uid-specific keyring .rb ( user\-keyring (7)). .tp .b key_spec_user_session_keyring this specifies the caller's uid-session keyring .rb ( user\-session\-keyring (7)). .ss key types the key .i type is a string that specifies the key's type. internally, the kernel defines a number of key types that are available in the core key management code. among the types that are available for user-space use and can be specified as the .i type argument to .br add_key () are the following: .tp .i """keyring""" keyrings are special key types that may contain links to sequences of other keys of any type. if this interface is used to create a keyring, then .i payload should be null and .i plen should be zero. .tp .ir """user""" this is a general purpose key type whose payload may be read and updated by user-space applications. the key is kept entirely within kernel memory. the payload for keys of this type is a blob of arbitrary data of up to 32,767 bytes. .tp .ir """logon""" " (since linux 3.3)" .\" commit 9f6ed2ca257fa8650b876377833e6f14e272848b this key type is essentially the same as .ir """user""" , but it does not permit the key to read. this is suitable for storing payloads that you do not want to be readable from user space. .pp this key type vets the .i description to ensure that it is qualified by a "service" prefix, by checking to ensure that the .i description contains a ':' that is preceded by other characters. .tp .ir """big_key""" " (since linux 3.13)" .\" commit ab3c3587f8cda9083209a61dbe3a4407d3cada10 this key type is similar to .ir """user""" , but may hold a payload of up to 1\ mib. if the key payload is large enough, then it may be stored encrypted in tmpfs (which can be swapped out) rather than kernel memory. .pp for further details on these key types, see .br keyrings (7). .sh return value on success, .br add_key () returns the serial number of the key it created or updated. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b eacces the keyring wasn't available for modification by the user. .tp .b edquot the key quota for this user would be exceeded by creating this key or linking it to the keyring. .tp .b efault one or more of .ir type , .ir description , and .i payload points outside process's accessible address space. .tp .b einval the size of the string (including the terminating null byte) specified in .i type or .i description exceeded the limit (32 bytes and 4096 bytes respectively). .tp .b einval the payload data was invalid. .tp .b einval .ir type was .ir """logon""" and the .i description was not qualified with a prefix string of the form .ir """service:""" . .tp .b ekeyexpired the keyring has expired. .tp .b ekeyrevoked the keyring has been revoked. .tp .b enokey the keyring doesn't exist. .tp .b enomem insufficient memory to create a key. .tp .b eperm the .i type started with a period (\(aq.\(aq). key types that begin with a period are reserved to the implementation. .tp .b eperm .i type was .i """keyring""" and the .i description started with a period (\(aq.\(aq). keyrings with descriptions (names) that begin with a period are reserved to the implementation. .sh versions this system call first appeared in linux 2.6.10. .sh conforming to this system call is a nonstandard linux extension. .sh notes glibc does not provide a wrapper for this system call. a wrapper is provided in the .ir libkeyutils library. (the accompanying package provides the .i header file.) when employing the wrapper in that library, link with .ir \-lkeyutils . .sh examples the program below creates a key with the type, description, and payload specified in its command-line arguments, and links that key into the session keyring. the following shell session demonstrates the use of the program: .pp .in +4n .ex $ \fb./a.out user mykey "some payload"\fp key id is 64a4dca $ \fbgrep \(aq64a4dca\(aq /proc/keys\fp 064a4dca i\-\-q\-\-\- 1 perm 3f010000 1000 1000 user mykey: 12 .ee .in .ss program source \& .ex #include #include #include #include #include #include int main(int argc, char *argv[]) { key_serial_t key; if (argc != 4) { fprintf(stderr, "usage: %s type description payload\en", argv[0]); exit(exit_failure); } key = add_key(argv[1], argv[2], argv[3], strlen(argv[3]), key_spec_session_keyring); if (key == \-1) { perror("add_key"); exit(exit_failure); } printf("key id is %jx\en", (uintmax_t) key); exit(exit_success); } .ee .sh see also .ad l .nh .br keyctl (1), .br keyctl (2), .br request_key (2), .br keyctl (3), .br keyrings (7), .br keyutils (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user\-session\-keyring (7) .pp the kernel source files .ir documentation/security/keys/core.rst and .ir documentation/keys/request\-key.rst (or, before linux 4.13, in the files .\" commit b68101a1e8f0263dbc7b8375d2a7c57c6216fb76 .ir documentation/security/keys.txt and .\" commit 3db38ed76890565772fcca3279cc8d454ea6176b .ir documentation/security/keys\-request\-key.txt ). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/scanf.3 .so man7/iso_8859-2.7 .so man3/fenv.3 .so man3/makedev.3 .\" copyright (c) ibm corp. 2015 .\" author: alexey ishchuk .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th s390_pci_mmio_write 2 2021-03-22 "linux programmer's manual" .sh name s390_pci_mmio_write, s390_pci_mmio_read \- transfer data to/from pci mmio memory page .sh synopsis .nf .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_s390_pci_mmio_write, unsigned long " mmio_addr , .bi " const void *" user_buffer ", size_t " length ); .bi "int syscall(sys_s390_pci_mmio_read, unsigned long " mmio_addr , .bi " void *" user_buffer ", size_t " length ); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description the .br s390_pci_mmio_write () system call writes .ir length bytes of data from the user-space buffer .ir user_buffer to the pci mmio memory location specified by .ir mmio_addr . the .br s390_pci_mmio_read () system call reads .i length bytes of data from the pci mmio memory location specified by .ir mmio_addr to the user-space buffer .ir user_buffer . .pp these system calls must be used instead of the simple assignment or data-transfer operations that are used to access the pci mmio memory areas mapped to user space on the linux system z platform. the address specified by .ir mmio_addr must belong to a pci mmio memory page mapping in the caller's address space, and the data being written or read must not cross a page boundary. the .ir length value cannot be greater than the system page size. .sh return value on success, .br s390_pci_mmio_write () and .br s390_pci_mmio_read () return 0. on failure, \-1 is returned and .ir errno is set to indicate the error. .sh errors .tp .b efault the address in .i mmio_addr is invalid. .tp .b efault .ir user_buffer does not point to a valid location in the caller's address space. .tp .b einval invalid .i length argument. .tp .b enodev pci support is not enabled. .tp .b enomem insufficient memory. .sh versions these system calls are available since linux 3.19. .sh conforming to this linux-specific system call is available only on the s390 architecture. the required pci support is available beginning with system z ec12. .sh see also .br syscall (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-9.7 .so man3/stdio_ext.3 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" .th wcwidth 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcwidth \- determine columns needed for a wide character .sh synopsis .nf .br "#define _xopen_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int wcwidth(wchar_t " c ); .fi .sh description the .br wcwidth () function returns the number of columns needed to represent the wide character .ir c . if .i c is a printable wide character, the value is at least 0. if .i c is null wide character (l\(aq\e0\(aq), the value is 0. otherwise, \-1 is returned. .sh return value the .br wcwidth () function returns the number of column positions for .ir c . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcwidth () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp note that glibc before 2.2.5 used the prototype .pp .nf .bi "int wcwidth(wint_t " c ); .fi .sh notes the behavior of .br wcwidth () depends on the .b lc_ctype category of the current locale. .sh see also .br iswprint (3), .br wcswidth (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/drand48_r.3 .so man3/xcrypt.3 .so man3/fenv.3 .so man3/rint.3 .so man3/tailq.3 .\" copyright (c) 2001 by john levon .\" based in part on gnu libc documentation. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" 2001-10-11, 2003-08-22, aeb, added some details .\" 2012-03-23, michael kerrisk .\" document pvalloc() and aligned_alloc() .th posix_memalign 3 2021-03-22 "gnu" "linux programmer's manual" .sh name posix_memalign, aligned_alloc, memalign, valloc, pvalloc \- allocate aligned memory .sh synopsis .nf .b #include .pp .bi "int posix_memalign(void **" memptr ", size_t " alignment ", size_t " size ); .bi "void *aligned_alloc(size_t " alignment ", size_t " size ); .bi "void *valloc(size_t " size ); .pp .b #include .pp .bi "void *memalign(size_t " alignment ", size_t " size ); .bi "void *pvalloc(size_t " size ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br posix_memalign (): .nf _posix_c_source >= 200112l .fi .pp .br aligned_alloc (): .nf _isoc11_source .fi .pp .br valloc (): .nf since glibc 2.12: (_xopen_source >= 500) && !(_posix_c_source >= 200112l) || /* glibc since 2.19: */ _default_source || /* glibc <= 2.19: */ _svid_source || _bsd_source before glibc 2.12: _bsd_source || _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended .fi .sh description the function .br posix_memalign () allocates .i size bytes and places the address of the allocated memory in .ir "*memptr" . the address of the allocated memory will be a multiple of .ir "alignment" , which must be a power of two and a multiple of .ir "sizeof(void\ *)" . this address can later be successfully passed to .br free (3). if .i size is 0, then the value placed in .ir "*memptr" is either null .\" glibc does this: or a unique pointer value. .pp the obsolete function .br memalign () allocates .i size bytes and returns a pointer to the allocated memory. the memory address will be a multiple of .ir alignment , which must be a power of two. .\" the behavior of memalign() for size==0 is as for posix_memalign() .\" but no standards govern this. .pp the function .br aligned_alloc () is the same as .br memalign (), except for the added restriction that .i size should be a multiple of .ir alignment . .pp the obsolete function .br valloc () allocates .i size bytes and returns a pointer to the allocated memory. the memory address will be a multiple of the page size. it is equivalent to .ir "memalign(sysconf(_sc_pagesize),size)" . .pp the obsolete function .br pvalloc () is similar to .br valloc (), but rounds the size of the allocation up to the next multiple of the system page size. .pp for all of these functions, the memory is not zeroed. .sh return value .br aligned_alloc (), .br memalign (), .br valloc (), and .br pvalloc () return a pointer to the allocated memory on success. on error, null is returned, and \fierrno\fp is set to indicate the error. .pp .br posix_memalign () returns zero on success, or one of the error values listed in the next section on failure. the value of .i errno is not set. on linux (and other systems), .br posix_memalign () does not modify .i memptr on failure. a requirement standardizing this behavior was added in posix.1-2008 tc2. .\" http://austingroupbugs.net/view.php?id=520 .sh errors .tp .b einval the .i alignment argument was not a power of two, or was not a multiple of .ir "sizeof(void\ *)" . .tp .b enomem there was insufficient memory to fulfill the allocation request. .sh versions the functions .br memalign (), .br valloc (), and .br pvalloc () have been available since at least glibc 2.0. .pp the function .br aligned_alloc () was added to glibc in version 2.16. .pp the function .br posix_memalign () is available since glibc 2.1.91. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aligned_alloc (), .br memalign (), .br posix_memalign () t} thread safety mt-safe t{ .br valloc (), .br pvalloc () t} thread safety mt-unsafe init .te .hy .ad .sp 1 .sh conforming to the function .br valloc () appeared in 3.0bsd. it is documented as being obsolete in 4.3bsd, and as legacy in susv2. it does not appear in posix.1. .pp the function .br pvalloc () is a gnu extension. .pp the function .br memalign () appears in sunos 4.1.3 but not in 4.4bsd. .pp the function .br posix_memalign () comes from posix.1d and is specified in posix.1-2001 and posix.1-2008. .pp the function .br aligned_alloc () is specified in the c11 standard. .\" .ss headers everybody agrees that .br posix_memalign () is declared in \fi\fp. .pp on some systems .br memalign () is declared in \fi\fp instead of \fi\fp. .pp according to susv2, .br valloc () is declared in \fi\fp. .\" libc4,5 and glibc declares it in \fi\fp, and also in \fi\fp if suitable feature test macros are defined (see above). .sh notes on many systems there are alignment restrictions, for example, on buffers used for direct block device i/o. posix specifies the .i "pathconf(path,_pc_rec_xfer_align)" call that tells what alignment is needed. now one can use .br posix_memalign () to satisfy this requirement. .pp .br posix_memalign () verifies that .i alignment matches the requirements detailed above. .br memalign () may not check that the .i alignment argument is correct. .pp posix requires that memory obtained from .br posix_memalign () can be freed using .br free (3). some systems provide no way to reclaim memory allocated with .br memalign () or .br valloc () (because one can pass to .br free (3) only a pointer obtained from .br malloc (3), while, for example, .br memalign () would call .br malloc (3) and then align the obtained value). .\" other systems allow passing the result of .\" .ir valloc () .\" to .\" .ir free (3), .\" but not to .\" .ir realloc (3). the glibc implementation allows memory obtained from any of these functions to be reclaimed with .br free (3). .pp the glibc .br malloc (3) always returns 8-byte aligned memory addresses, so these functions are needed only if you require larger alignment values. .sh see also .br brk (2), .br getpagesize (2), .br free (3), .br malloc (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/unimplemented.2 .so man7/system_data_types.7 .so man3/endian.3 .\" copyright (c) 1996 free software foundation, inc. .\" .\" %%%license_start(gpl_noversion_oneline) .\" this file is distributed according to the gnu general public license. .\" %%%license_end .\" .\" 2006-02-09, some reformatting by luc van oostenryck; some .\" reformatting and rewordings by mtk .\" .th get_kernel_syms 2 2021-03-22 "linux" "linux programmer's manual" .sh name get_kernel_syms \- retrieve exported kernel and module symbols .sh synopsis .nf .b #include .pp .bi "int get_kernel_syms(struct kernel_sym *" table ); .fi .pp .ir note : no declaration of this system call is provided in glibc headers; see notes. .sh description .br note : this system call is present only in kernels before linux 2.6. .pp if .i table is null, .br get_kernel_syms () returns the number of symbols available for query. otherwise, it fills in a table of structures: .pp .in +4n .ex struct kernel_sym { unsigned long value; char name[60]; }; .ee .in .pp the symbols are interspersed with magic symbols of the form .bi # module-name with the kernel having an empty name. the value associated with a symbol of this form is the address at which the module is loaded. .pp the symbols exported from each module follow their magic module tag and the modules are returned in the reverse of the order in which they were loaded. .sh return value on success, returns the number of symbols copied to .ir table . on error, \-1 is returned and .i errno is set to indicate the error. .sh errors there is only one possible error return: .tp .b enosys .br get_kernel_syms () is not supported in this version of the kernel. .sh versions this system call is present on linux only up until kernel 2.4; it was removed in linux 2.6. .\" removed in linux 2.5.48 .sh conforming to .br get_kernel_syms () is linux-specific. .sh notes this obsolete system call is not supported by glibc. no declaration is provided in glibc headers, but, through a quirk of history, glibc versions before 2.23 did export an abi for this system call. therefore, in order to employ this system call, it was sufficient to manually declare the interface in your code; alternatively, you could invoke the system call using .br syscall (2). .sh bugs there is no way to indicate the size of the buffer allocated for .ir table . if symbols have been added to the kernel since the program queried for the symbol table size, memory will be corrupted. .pp the length of exported symbol names is limited to 59 characters. .pp because of these limitations, this system call is deprecated in favor of .br query_module (2) (which is itself nowadays deprecated in favor of other interfaces described on its manual page). .sh see also .br create_module (2), .br delete_module (2), .br init_module (2), .br query_module (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" this manpage is copyright (c) 2001 paul sheer. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" very minor changes, aeb .\" .\" modified 5 june 2002, michael kerrisk .\" 2006-05-13, mtk, removed much material that is redundant with select.2 .\" various other changes .\" 2008-01-26, mtk, substantial changes and rewrites .\" .th select_tut 2 2021-03-22 "linux" "linux programmer's manual" .sh name select, pselect \- synchronous i/o multiplexing .sh synopsis see .br select (2) .sh description the .br select () and .br pselect () system calls are used to efficiently monitor multiple file descriptors, to see if any of them is, or becomes, "ready"; that is, to see whether i/o becomes possible, or an "exceptional condition" has occurred on any of the file descriptors. .pp this page provides background and tutorial information on the use of these system calls. for details of the arguments and semantics of .br select () and .br pselect (), see .br select (2). .\" .ss combining signal and data events .br pselect () is useful if you are waiting for a signal as well as for file descriptor(s) to become ready for i/o. programs that receive signals normally use the signal handler only to raise a global flag. the global flag will indicate that the event must be processed in the main loop of the program. a signal will cause the .br select () (or .br pselect ()) call to return with \fierrno\fp set to \fbeintr\fp. this behavior is essential so that signals can be processed in the main loop of the program, otherwise .br select () would block indefinitely. .pp now, somewhere in the main loop will be a conditional to check the global flag. so we must ask: what if a signal arrives after the conditional, but before the .br select () call? the answer is that .br select () would block indefinitely, even though an event is actually pending. this race condition is solved by the .br pselect () call. this call can be used to set the signal mask to a set of signals that are to be received only within the .br pselect () call. for instance, let us say that the event in question was the exit of a child process. before the start of the main loop, we would block \fbsigchld\fp using .br sigprocmask (2). our .br pselect () call would enable .b sigchld by using an empty signal mask. our program would look like: .pp .ex static volatile sig_atomic_t got_sigchld = 0; static void child_sig_handler(int sig) { got_sigchld = 1; } int main(int argc, char *argv[]) { sigset_t sigmask, empty_mask; struct sigaction sa; fd_set readfds, writefds, exceptfds; int r; sigemptyset(&sigmask); sigaddset(&sigmask, sigchld); if (sigprocmask(sig_block, &sigmask, null) == \-1) { perror("sigprocmask"); exit(exit_failure); } sa.sa_flags = 0; sa.sa_handler = child_sig_handler; sigemptyset(&sa.sa_mask); if (sigaction(sigchld, &sa, null) == \-1) { perror("sigaction"); exit(exit_failure); } sigemptyset(&empty_mask); for (;;) { /* main loop */ /* initialize readfds, writefds, and exceptfds before the pselect() call. (code omitted.) */ r = pselect(nfds, &readfds, &writefds, &exceptfds, null, &empty_mask); if (r == \-1 && errno != eintr) { /* handle error */ } if (got_sigchld) { got_sigchld = 0; /* handle signalled event here; e.g., wait() for all terminated children. (code omitted.) */ } /* main body of program */ } } .ee .ss practical so what is the point of .br select ()? can't i just read and write to my file descriptors whenever i want? the point of .br select () is that it watches multiple descriptors at the same time and properly puts the process to sleep if there is no activity. unix programmers often find themselves in a position where they have to handle i/o from more than one file descriptor where the data flow may be intermittent. if you were to merely create a sequence of .br read (2) and .br write (2) calls, you would find that one of your calls may block waiting for data from/to a file descriptor, while another file descriptor is unused though ready for i/o. .br select () efficiently copes with this situation. .ss select law many people who try to use .br select () come across behavior that is difficult to understand and produces nonportable or borderline results. for instance, the above program is carefully written not to block at any point, even though it does not set its file descriptors to nonblocking mode. it is easy to introduce subtle errors that will remove the advantage of using .br select (), so here is a list of essentials to watch for when using .br select (). .tp 4 1. you should always try to use .br select () without a timeout. your program should have nothing to do if there is no data available. code that depends on timeouts is not usually portable and is difficult to debug. .tp 2. the value \finfds\fp must be properly calculated for efficiency as explained above. .tp 3. no file descriptor must be added to any set if you do not intend to check its result after the .br select () call, and respond appropriately. see next rule. .tp 4. after .br select () returns, all file descriptors in all sets should be checked to see if they are ready. .tp 5. the functions .br read (2), .br recv (2), .br write (2), and .br send (2) do \finot\fp necessarily read/write the full amount of data that you have requested. if they do read/write the full amount, it's because you have a low traffic load and a fast stream. this is not always going to be the case. you should cope with the case of your functions managing to send or receive only a single byte. .tp 6. never read/write only in single bytes at a time unless you are really sure that you have a small amount of data to process. it is extremely inefficient not to read/write as much data as you can buffer each time. the buffers in the example below are 1024 bytes although they could easily be made larger. .tp 7. calls to .br read (2), .br recv (2), .br write (2), .br send (2), and .br select () can fail with the error \fbeintr\fp, and calls to .br read (2), .br recv (2) .br write (2), and .br send (2) can fail with .i errno set to \fbeagain\fp (\fbewouldblock\fp). these results must be properly managed (not done properly above). if your program is not going to receive any signals, then it is unlikely you will get \fbeintr\fp. if your program does not set nonblocking i/o, you will not get \fbeagain\fp. .\" nonetheless, you should still cope with these errors for completeness. .tp 8. never call .br read (2), .br recv (2), .br write (2), or .br send (2) with a buffer length of zero. .tp 9. if the functions .br read (2), .br recv (2), .br write (2), and .br send (2) fail with errors other than those listed in \fb7.\fp, or one of the input functions returns 0, indicating end of file, then you should \finot\fp pass that file descriptor to .br select () again. in the example below, i close the file descriptor immediately, and then set it to \-1 to prevent it being included in a set. .tp 10. the timeout value must be initialized with each new call to .br select (), since some operating systems modify the structure. .br pselect () however does not modify its timeout structure. .tp 11. since .br select () modifies its file descriptor sets, if the call is being used in a loop, then the sets must be reinitialized before each call. .\" "i have heard" does not fill me with confidence, and doesn't .\" belong in a man page, so i've commented this point out. .\" .tp .\" 11. .\" i have heard that the windows socket layer does not cope with oob data .\" properly. .\" it also does not cope with .\" .br select () .\" calls when no file descriptors are set at all. .\" having no file descriptors set is a useful .\" way to sleep the process with subsecond precision by using the timeout. .\" (see further on.) .sh return value see .br select (2). .sh notes generally speaking, all operating systems that support sockets also support .br select (). .br select () can be used to solve many problems in a portable and efficient way that naive programmers try to solve in a more complicated manner using threads, forking, ipcs, signals, memory sharing, and so on. .pp the .br poll (2) system call has the same functionality as .br select (), and is somewhat more efficient when monitoring sparse file descriptor sets. it is nowadays widely available, but historically was less portable than .br select (). .pp the linux-specific .br epoll (7) api provides an interface that is more efficient than .br select (2) and .br poll (2) when monitoring large numbers of file descriptors. .sh examples here is an example that better demonstrates the true utility of .br select (). the listing below is a tcp forwarding program that forwards from one tcp port to another. .pp .ex #include #include #include #include #include #include #include #include #include #include static int forward_port; #undef max #define max(x,y) ((x) > (y) ? (x) : (y)) static int listen_socket(int listen_port) { struct sockaddr_in addr; int lfd; int yes; lfd = socket(af_inet, sock_stream, 0); if (lfd == \-1) { perror("socket"); return \-1; } yes = 1; if (setsockopt(lfd, sol_socket, so_reuseaddr, &yes, sizeof(yes)) == \-1) { perror("setsockopt"); close(lfd); return \-1; } memset(&addr, 0, sizeof(addr)); addr.sin_port = htons(listen_port); addr.sin_family = af_inet; if (bind(lfd, (struct sockaddr *) &addr, sizeof(addr)) == \-1) { perror("bind"); close(lfd); return \-1; } printf("accepting connections on port %d\en", listen_port); listen(lfd, 10); return lfd; } static int connect_socket(int connect_port, char *address) { struct sockaddr_in addr; int cfd; cfd = socket(af_inet, sock_stream, 0); if (cfd == \-1) { perror("socket"); return \-1; } memset(&addr, 0, sizeof(addr)); addr.sin_port = htons(connect_port); addr.sin_family = af_inet; if (!inet_aton(address, (struct in_addr *) &addr.sin_addr.s_addr)) { fprintf(stderr, "inet_aton(): bad ip address format\en"); close(cfd); return \-1; } if (connect(cfd, (struct sockaddr *) &addr, sizeof(addr)) == \-1) { perror("connect()"); shutdown(cfd, shut_rdwr); close(cfd); return \-1; } return cfd; } #define shut_fd1 do { \e if (fd1 >= 0) { \e shutdown(fd1, shut_rdwr); \e close(fd1); \e fd1 = \-1; \e } \e } while (0) #define shut_fd2 do { \e if (fd2 >= 0) { \e shutdown(fd2, shut_rdwr); \e close(fd2); \e fd2 = \-1; \e } \e } while (0) #define buf_size 1024 int main(int argc, char *argv[]) { int h; int fd1 = \-1, fd2 = \-1; char buf1[buf_size], buf2[buf_size]; int buf1_avail = 0, buf1_written = 0; int buf2_avail = 0, buf2_written = 0; if (argc != 4) { fprintf(stderr, "usage\en\etfwd " " \en"); exit(exit_failure); } signal(sigpipe, sig_ign); forward_port = atoi(argv[2]); h = listen_socket(atoi(argv[1])); if (h == \-1) exit(exit_failure); for (;;) { int ready, nfds = 0; ssize_t nbytes; fd_set readfds, writefds, exceptfds; fd_zero(&readfds); fd_zero(&writefds); fd_zero(&exceptfds); fd_set(h, &readfds); nfds = max(nfds, h); if (fd1 > 0 && buf1_avail < buf_size) fd_set(fd1, &readfds); /* note: nfds is updated below, when fd1 is added to exceptfds. */ if (fd2 > 0 && buf2_avail < buf_size) fd_set(fd2, &readfds); if (fd1 > 0 && buf2_avail \- buf2_written > 0) fd_set(fd1, &writefds); if (fd2 > 0 && buf1_avail \- buf1_written > 0) fd_set(fd2, &writefds); if (fd1 > 0) { fd_set(fd1, &exceptfds); nfds = max(nfds, fd1); } if (fd2 > 0) { fd_set(fd2, &exceptfds); nfds = max(nfds, fd2); } ready = select(nfds + 1, &readfds, &writefds, &exceptfds, null); if (ready == \-1 && errno == eintr) continue; if (ready == \-1) { perror("select()"); exit(exit_failure); } if (fd_isset(h, &readfds)) { socklen_t addrlen; struct sockaddr_in client_addr; int fd; addrlen = sizeof(client_addr); memset(&client_addr, 0, addrlen); fd = accept(h, (struct sockaddr *) &client_addr, &addrlen); if (fd == \-1) { perror("accept()"); } else { shut_fd1; shut_fd2; buf1_avail = buf1_written = 0; buf2_avail = buf2_written = 0; fd1 = fd; fd2 = connect_socket(forward_port, argv[3]); if (fd2 == \-1) shut_fd1; else printf("connect from %s\en", inet_ntoa(client_addr.sin_addr)); /* skip any events on the old, closed file descriptors. */ continue; } } /* nb: read oob data before normal reads. */ if (fd1 > 0 && fd_isset(fd1, &exceptfds)) { char c; nbytes = recv(fd1, &c, 1, msg_oob); if (nbytes < 1) shut_fd1; else send(fd2, &c, 1, msg_oob); } if (fd2 > 0 && fd_isset(fd2, &exceptfds)) { char c; nbytes = recv(fd2, &c, 1, msg_oob); if (nbytes < 1) shut_fd2; else send(fd1, &c, 1, msg_oob); } if (fd1 > 0 && fd_isset(fd1, &readfds)) { nbytes = read(fd1, buf1 + buf1_avail, buf_size \- buf1_avail); if (nbytes < 1) shut_fd1; else buf1_avail += nbytes; } if (fd2 > 0 && fd_isset(fd2, &readfds)) { nbytes = read(fd2, buf2 + buf2_avail, buf_size \- buf2_avail); if (nbytes < 1) shut_fd2; else buf2_avail += nbytes; } if (fd1 > 0 && fd_isset(fd1, &writefds) && buf2_avail > 0) { nbytes = write(fd1, buf2 + buf2_written, buf2_avail \- buf2_written); if (nbytes < 1) shut_fd1; else buf2_written += nbytes; } if (fd2 > 0 && fd_isset(fd2, &writefds) && buf1_avail > 0) { nbytes = write(fd2, buf1 + buf1_written, buf1_avail \- buf1_written); if (nbytes < 1) shut_fd2; else buf1_written += nbytes; } /* check if write data has caught read data. */ if (buf1_written == buf1_avail) buf1_written = buf1_avail = 0; if (buf2_written == buf2_avail) buf2_written = buf2_avail = 0; /* one side has closed the connection, keep writing to the other side until empty. */ if (fd1 < 0 && buf1_avail \- buf1_written == 0) shut_fd2; if (fd2 < 0 && buf2_avail \- buf2_written == 0) shut_fd1; } exit(exit_success); } .ee .pp the above program properly forwards most kinds of tcp connections including oob signal data transmitted by \fbtelnet\fp servers. it handles the tricky problem of having data flow in both directions simultaneously. you might think it more efficient to use a .br fork (2) call and devote a thread to each stream. this becomes more tricky than you might suspect. another idea is to set nonblocking i/o using .br fcntl (2). this also has its problems because you end up using inefficient timeouts. .pp the program does not handle more than one simultaneous connection at a time, although it could easily be extended to do this with a linked list of buffers\(emone for each connection. at the moment, new connections cause the current connection to be dropped. .sh see also .br accept (2), .br connect (2), .br poll (2), .br read (2), .br recv (2), .br select (2), .br send (2), .br sigprocmask (2), .br write (2), .br epoll (7) .\" .sh authors .\" this man page was written by paul sheer. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .\" copyright (c) 2008 michael kerrisk .\" starting from a version by davide libenzi .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th signalfd 2 2021-03-22 linux "linux programmer's manual" .sh name signalfd \- create a file descriptor for accepting signals .sh synopsis .nf .b #include .pp .bi "int signalfd(int " fd ", const sigset_t *" mask ", int " flags ); .fi .sh description .br signalfd () creates a file descriptor that can be used to accept signals targeted at the caller. this provides an alternative to the use of a signal handler or .br sigwaitinfo (2), and has the advantage that the file descriptor may be monitored by .br select (2), .br poll (2), and .br epoll (7). .pp the .i mask argument specifies the set of signals that the caller wishes to accept via the file descriptor. this argument is a signal set whose contents can be initialized using the macros described in .br sigsetops (3). normally, the set of signals to be received via the file descriptor should be blocked using .br sigprocmask (2), to prevent the signals being handled according to their default dispositions. it is not possible to receive .b sigkill or .b sigstop signals via a signalfd file descriptor; these signals are silently ignored if specified in .ir mask . .pp if the .i fd argument is \-1, then the call creates a new file descriptor and associates the signal set specified in .i mask with that file descriptor. if .i fd is not \-1, then it must specify a valid existing signalfd file descriptor, and .i mask is used to replace the signal set associated with that file descriptor. .pp starting with linux 2.6.27, the following values may be bitwise ored in .ir flags to change the behavior of .br signalfd (): .tp 14 .b sfd_nonblock set the .br o_nonblock file status flag on the open file description (see .br open (2)) referred to by the new file descriptor. using this flag saves extra calls to .br fcntl (2) to achieve the same result. .tp .b sfd_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .pp in linux up to version 2.6.26, the .i flags argument is unused, and must be specified as zero. .pp .br signalfd () returns a file descriptor that supports the following operations: .tp .br read (2) if one or more of the signals specified in .i mask is pending for the process, then the buffer supplied to .br read (2) is used to return one or more .i signalfd_siginfo structures (see below) that describe the signals. the .br read (2) returns information for as many signals as are pending and will fit in the supplied buffer. the buffer must be at least .i "sizeof(struct signalfd_siginfo)" bytes. the return value of the .br read (2) is the total number of bytes read. .ip as a consequence of the .br read (2), the signals are consumed, so that they are no longer pending for the process (i.e., will not be caught by signal handlers, and cannot be accepted using .br sigwaitinfo (2)). .ip if none of the signals in .i mask is pending for the process, then the .br read (2) either blocks until one of the signals in .i mask is generated for the process, or fails with the error .b eagain if the file descriptor has been made nonblocking. .tp .br poll "(2), " select "(2) (and similar)" the file descriptor is readable (the .br select (2) .i readfds argument; the .br poll (2) .b pollin flag) if one or more of the signals in .i mask is pending for the process. .ip the signalfd file descriptor also supports the other file-descriptor multiplexing apis: .br pselect (2), .br ppoll (2), and .br epoll (7). .tp .br close (2) when the file descriptor is no longer required it should be closed. when all file descriptors associated with the same signalfd object have been closed, the resources for object are freed by the kernel. .ss the signalfd_siginfo structure the format of the .i signalfd_siginfo structure(s) returned by .br read (2)s from a signalfd file descriptor is as follows: .pp .in +4n .ex struct signalfd_siginfo { uint32_t ssi_signo; /* signal number */ int32_t ssi_errno; /* error number (unused) */ int32_t ssi_code; /* signal code */ uint32_t ssi_pid; /* pid of sender */ uint32_t ssi_uid; /* real uid of sender */ int32_t ssi_fd; /* file descriptor (sigio) */ uint32_t ssi_tid; /* kernel timer id (posix timers) uint32_t ssi_band; /* band event (sigio) */ uint32_t ssi_overrun; /* posix timer overrun count */ uint32_t ssi_trapno; /* trap number that caused signal */ .\" ssi_trapno is unused on most arches int32_t ssi_status; /* exit status or signal (sigchld) */ int32_t ssi_int; /* integer sent by sigqueue(3) */ uint64_t ssi_ptr; /* pointer sent by sigqueue(3) */ uint64_t ssi_utime; /* user cpu time consumed (sigchld) */ uint64_t ssi_stime; /* system cpu time consumed (sigchld) */ uint64_t ssi_addr; /* address that generated signal (for hardware\-generated signals) */ uint16_t ssi_addr_lsb; /* least significant bit of address (sigbus; since linux 2.6.37) */ .\" ssi_addr_lsb: commit b8aeec34175fc8fe8b0d40efea4846dfc1ba663e uint8_t pad[\fix\fp]; /* pad size to 128 bytes (allow for additional fields in the future) */ }; .ee .in .pp each of the fields in this structure is analogous to the similarly named field in the .i siginfo_t structure. the .i siginfo_t structure is described in .br sigaction (2). not all fields in the returned .i signalfd_siginfo structure will be valid for a specific signal; the set of valid fields can be determined from the value returned in the .i ssi_code field. this field is the analog of the .i siginfo_t .i si_code field; see .br sigaction (2) for details. .ss fork(2) semantics after a .br fork (2), the child inherits a copy of the signalfd file descriptor. a .br read (2) from the file descriptor in the child will return information about signals queued to the child. .ss semantics of file descriptor passing as with other file descriptors, signalfd file descriptors can be passed to another process via a unix domain socket (see .br unix (7)). in the receiving process, a .br read (2) from the received file descriptor will return information about signals queued to that process. .ss execve(2) semantics just like any other file descriptor, a signalfd file descriptor remains open across an .br execve (2), unless it has been marked for close-on-exec (see .br fcntl (2)). any signals that were available for reading before the .br execve (2) remain available to the newly loaded program. (this is analogous to traditional signal semantics, where a blocked signal that is pending remains pending across an .br execve (2).) .ss thread semantics the semantics of signalfd file descriptors in a multithreaded program mirror the standard semantics for signals. in other words, when a thread reads from a signalfd file descriptor, it will read the signals that are directed to the thread itself and the signals that are directed to the process (i.e., the entire thread group). (a thread will not be able to read signals that are directed to other threads in the process.) .\" .ss epoll(7) semantics if a process adds (via .br epoll_ctl (2)) a signalfd file descriptor to an .br epoll (7) instance, then .br epoll_wait (2) returns events only for signals sent to that process. in particular, if the process then uses .br fork (2) to create a child process, then the child will be able to .br read (2) signals that are sent to it using the signalfd file descriptor, but .br epoll_wait (2) will .b not indicate that the signalfd file descriptor is ready. in this scenario, a possible workaround is that after the .br fork (2), the child process can close the signalfd file descriptor that it inherited from the parent process and then create another signalfd file descriptor and add it to the epoll instance. alternatively, the parent and the child could delay creating their (separate) signalfd file descriptors and adding them to the epoll instance until after the call to .br fork (2). .sh return value on success, .br signalfd () returns a signalfd file descriptor; this is either a new file descriptor (if .i fd was \-1), or .i fd if .i fd was a valid signalfd file descriptor. on error, \-1 is returned and .i errno is set to indicate the error. .sh errors .tp .b ebadf the .i fd file descriptor is not a valid file descriptor. .tp .b einval .i fd is not a valid signalfd file descriptor. .\" or, the .\" .i sizemask .\" argument is not equal to .\" .ir sizeof(sigset_t) ; .tp .b einval .i flags is invalid; or, in linux 2.6.26 or earlier, .i flags is nonzero. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enodev could not mount (internal) anonymous inode device. .tp .b enomem there was insufficient memory to create a new signalfd file descriptor. .sh versions .br signalfd () is available on linux since kernel 2.6.22. working support is provided in glibc since version 2.8. .\" signalfd() is in glibc 2.7, but reportedly does not build the .br signalfd4 () system call (see notes) is available on linux since kernel 2.6.27. .sh conforming to .br signalfd () and .br signalfd4 () are linux-specific. .sh notes a process can create multiple signalfd file descriptors. this makes it possible to accept different signals on different file descriptors. (this may be useful if monitoring the file descriptors using .br select (2), .br poll (2), or .br epoll (7): the arrival of different signals will make different file descriptors ready.) if a signal appears in the .i mask of more than one of the file descriptors, then occurrences of that signal can be read (once) from any one of the file descriptors. .pp attempts to include .b sigkill and .b sigstop in .i mask are silently ignored. .pp the signal mask employed by a signalfd file descriptor can be viewed via the entry for the corresponding file descriptor in the process's .ir /proc/[pid]/fdinfo directory. see .br proc (5) for further details. .\" .ss limitations the signalfd mechanism can't be used to receive signals that are synchronously generated, such as the .br sigsegv signal that results from accessing an invalid memory address or the .br sigfpe signal that results from an arithmetic error. such signals can be caught only via signal handler. .pp as described above, in normal usage one blocks the signals that will be accepted via .br signalfd (). if spawning a child process to execute a helper program (that does not need the signalfd file descriptor), then, after the call to .br fork (2), you will normally want to unblock those signals before calling .br execve (2), so that the helper program can see any signals that it expects to see. be aware, however, that this won't be possible in the case of a helper program spawned behind the scenes by any library function that the program may call. in such cases, one must fall back to using a traditional signal handler that writes to a file descriptor monitored by .br select (2), .br poll (2), or .br epoll (7). .\" .ss c library/kernel differences the underlying linux system call requires an additional argument, .ir "size_t sizemask" , which specifies the size of the .i mask argument. the glibc .br signalfd () wrapper function does not include this argument, since it provides the required value for the underlying system call. .pp there are two underlying linux system calls: .br signalfd () and the more recent .br signalfd4 (). the former system call does not implement a .i flags argument. the latter system call implements the .i flags values described above. starting with glibc 2.9, the .br signalfd () wrapper function will use .br signalfd4 () where it is available. .sh bugs in kernels before 2.6.25, the .i ssi_ptr and .i ssi_int fields are not filled in with the data accompanying a signal sent by .br sigqueue (3). .\" the fix also was put into 2.6.24.5 .sh examples the program below accepts the signals .b sigint and .b sigquit via a signalfd file descriptor. the program terminates after accepting a .b sigquit signal. the following shell session demonstrates the use of the program: .pp .in +4n .ex .rb "$" " ./signalfd_demo" .br "\(hac" " # control\-c generates sigint" got sigint .b \(hac got sigint \fb\(ha\e\fp # control\-\e generates sigquit got sigquit $ .ee .in .ss program source \& .ex #include #include #include #include #include #define handle_error(msg) \e do { perror(msg); exit(exit_failure); } while (0) int main(int argc, char *argv[]) { sigset_t mask; int sfd; struct signalfd_siginfo fdsi; ssize_t s; sigemptyset(&mask); sigaddset(&mask, sigint); sigaddset(&mask, sigquit); /* block signals so that they aren\(aqt handled according to their default dispositions. */ if (sigprocmask(sig_block, &mask, null) == \-1) handle_error("sigprocmask"); sfd = signalfd(\-1, &mask, 0); if (sfd == \-1) handle_error("signalfd"); for (;;) { s = read(sfd, &fdsi, sizeof(fdsi)); if (s != sizeof(fdsi)) handle_error("read"); if (fdsi.ssi_signo == sigint) { printf("got sigint\en"); } else if (fdsi.ssi_signo == sigquit) { printf("got sigquit\en"); exit(exit_success); } else { printf("read unexpected signal\en"); } } } .ee .sh see also .br eventfd (2), .br poll (2), .br read (2), .br select (2), .br sigaction (2), .br sigprocmask (2), .br sigwaitinfo (2), .br timerfd_create (2), .br sigsetops (3), .br sigwait (3), .br epoll (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/byteorder.3 .\" copyright (c) 2016, ibm corporation. .\" written by mike rapoport .\" and copyright (c) 2016 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th ioctl_userfaultfd 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_userfaultfd \- create a file descriptor for handling page faults in user space .sh synopsis .nf .br "#include " " /* definition of " uffd* " constants */" .b #include .pp .bi "int ioctl(int " fd ", int " cmd ", ...);" .fi .sh description various .br ioctl (2) operations can be performed on a userfaultfd object (created by a call to .br userfaultfd (2)) using calls of the form: .pp .in +4n .ex ioctl(fd, cmd, argp); .ee .in in the above, .i fd is a file descriptor referring to a userfaultfd object, .i cmd is one of the commands listed below, and .i argp is a pointer to a data structure that is specific to .ir cmd . .pp the various .br ioctl (2) operations are described below. the .br uffdio_api , .br uffdio_register , and .br uffdio_unregister operations are used to .i configure userfaultfd behavior. these operations allow the caller to choose what features will be enabled and what kinds of events will be delivered to the application. the remaining operations are .ir range operations. these operations enable the calling application to resolve page-fault events. .\" .ss uffdio_api (since linux 4.3.) enable operation of the userfaultfd and perform api handshake. .pp the .i argp argument is a pointer to a .ir uffdio_api structure, defined as: .pp .in +4n .ex struct uffdio_api { __u64 api; /* requested api version (input) */ __u64 features; /* requested features (input/output) */ __u64 ioctls; /* available ioctl() operations (output) */ }; .ee .in .pp the .i api field denotes the api version requested by the application. .pp the kernel verifies that it can support the requested api version, and sets the .i features and .i ioctls fields to bit masks representing all the available features and the generic .br ioctl (2) operations available. .pp for linux kernel versions before 4.11, the .i features field must be initialized to zero before the call to .br uffdio_api , and zero (i.e., no feature bits) is placed in the .i features field by the kernel upon return from .br ioctl (2). .pp starting from linux 4.11, the .i features field can be used to ask whether particular features are supported and explicitly enable userfaultfd features that are disabled by default. the kernel always reports all the available features in the .i features field. .pp to enable userfaultfd features the application should set a bit corresponding to each feature it wants to enable in the .i features field. if the kernel supports all the requested features it will enable them. otherwise it will zero out the returned .i uffdio_api structure and return .br einval . .\" fixme add more details about feature negotiation and enablement .pp the following feature bits may be set: .tp .br uffd_feature_event_fork " (since linux 4.11)" when this feature is enabled, the userfaultfd objects associated with a parent process are duplicated into the child process during .br fork (2) and a .b uffd_event_fork event is delivered to the userfaultfd monitor .tp .br uffd_feature_event_remap " (since linux 4.11)" if this feature is enabled, when the faulting process invokes .br mremap (2), the userfaultfd monitor will receive an event of type .br uffd_event_remap . .tp .br uffd_feature_event_remove " (since linux 4.11)" if this feature is enabled, when the faulting process calls .br madvise (2) with the .b madv_dontneed or .b madv_remove advice value to free a virtual memory area the userfaultfd monitor will receive an event of type .br uffd_event_remove . .tp .br uffd_feature_event_unmap " (since linux 4.11)" if this feature is enabled, when the faulting process unmaps virtual memory either explicitly with .br munmap (2), or implicitly during either .br mmap (2) or .br mremap (2), the userfaultfd monitor will receive an event of type .br uffd_event_unmap . .tp .br uffd_feature_missing_hugetlbfs " (since linux 4.11)" if this feature bit is set, the kernel supports registering userfaultfd ranges on hugetlbfs virtual memory areas .tp .br uffd_feature_missing_shmem " (since linux 4.11)" if this feature bit is set, the kernel supports registering userfaultfd ranges on shared memory areas. this includes all kernel shared memory apis: system v shared memory, .br tmpfs (5), shared mappings of .ir /dev/zero , .br mmap (2) with the .b map_shared flag set, .br memfd_create (2), and so on. .tp .br uffd_feature_sigbus " (since linux 4.14)" .\" commit 2d6d6f5a09a96cc1fec7ed992b825e05f64cb50e if this feature bit is set, no page-fault events .rb ( uffd_event_pagefault ) will be delivered. instead, a .b sigbus signal will be sent to the faulting process. applications using this feature will not require the use of a userfaultfd monitor for processing memory accesses to the regions registered with userfaultfd. .tp .br uffd_feature_thread_id " (since linux 4.14)" if this feature bit is set, .i uffd_msg.pagefault.feat.ptid will be set to the faulted thread id for each page-fault message. .pp the returned .i ioctls field can contain the following bits: .\" fixme this user-space api seems not fully polished. why are there .\" not constants defined for each of the bit-mask values listed below? .tp .b 1 << _uffdio_api the .b uffdio_api operation is supported. .tp .b 1 << _uffdio_register the .b uffdio_register operation is supported. .tp .b 1 << _uffdio_unregister the .b uffdio_unregister operation is supported. .tp .b 1 << _uffdio_writeprotect the .b uffdio_writeprotect operation is supported. .pp this .br ioctl (2) operation returns 0 on success. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .tp .b efault .i argp refers to an address that is outside the calling process's accessible address space. .tp .b einval the userfaultfd has already been enabled by a previous .br uffdio_api operation. .tp .b einval the api version requested in the .i api field is not supported by this kernel, or the .i features field passed to the kernel includes feature bits that are not supported by the current kernel version. .\" fixme in the above error case, the returned 'uffdio_api' structure is .\" zeroed out. why is this done? this should be explained in the manual page. .\" .\" mike rapoport: .\" in my understanding the uffdio_api .\" structure is zeroed to allow the caller .\" to distinguish the reasons for -einval. .\" .ss uffdio_register (since linux 4.3.) register a memory address range with the userfaultfd object. the pages in the range must be "compatible". .pp up to linux kernel 4.11, only private anonymous ranges are compatible for registering with .br uffdio_register . .pp since linux 4.11, hugetlbfs and shared memory ranges are also compatible with .br uffdio_register . .pp the .i argp argument is a pointer to a .i uffdio_register structure, defined as: .pp .in +4n .ex struct uffdio_range { __u64 start; /* start of range */ __u64 len; /* length of range (bytes) */ }; struct uffdio_register { struct uffdio_range range; __u64 mode; /* desired mode of operation (input) */ __u64 ioctls; /* available ioctl() operations (output) */ }; .ee .in .pp the .i range field defines a memory range starting at .i start and continuing for .i len bytes that should be handled by the userfaultfd. .pp the .i mode field defines the mode of operation desired for this memory region. the following values may be bitwise ored to set the userfaultfd mode for the specified range: .tp .b uffdio_register_mode_missing track page faults on missing pages. .tp .b uffdio_register_mode_wp track page faults on write-protected pages. .pp if the operation is successful, the kernel modifies the .i ioctls bit-mask field to indicate which .br ioctl (2) operations are available for the specified range. this returned bit mask is as for .br uffdio_api . .pp this .br ioctl (2) operation returns 0 on success. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .\" fixme is the following error list correct? .\" .tp .b ebusy a mapping in the specified range is registered with another userfaultfd object. .tp .b efault .i argp refers to an address that is outside the calling process's accessible address space. .tp .b einval an invalid or unsupported bit was specified in the .i mode field; or the .i mode field was zero. .tp .b einval there is no mapping in the specified address range. .tp .b einval .i range.start or .i range.len is not a multiple of the system page size; or, .i range.len is zero; or these fields are otherwise invalid. .tp .b einval there as an incompatible mapping in the specified address range. .\" mike rapoport: .\" enomem if the process is exiting and the .\" mm_struct has gone by the time userfault grabs it. .ss uffdio_unregister (since linux 4.3.) unregister a memory address range from userfaultfd. the pages in the range must be "compatible" (see the description of .br uffdio_register .) .pp the address range to unregister is specified in the .ir uffdio_range structure pointed to by .ir argp . .pp this .br ioctl (2) operation returns 0 on success. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .tp .b einval either the .i start or the .i len field of the .i ufdio_range structure was not a multiple of the system page size; or the .i len field was zero; or these fields were otherwise invalid. .tp .b einval there as an incompatible mapping in the specified address range. .tp .b einval there was no mapping in the specified address range. .\" .ss uffdio_copy (since linux 4.3.) atomically copy a continuous memory chunk into the userfault registered range and optionally wake up the blocked thread. the source and destination addresses and the number of bytes to copy are specified by the .ir src ", " dst ", and " len fields of the .i uffdio_copy structure pointed to by .ir argp : .pp .in +4n .ex struct uffdio_copy { __u64 dst; /* destination of copy */ __u64 src; /* source of copy */ __u64 len; /* number of bytes to copy */ __u64 mode; /* flags controlling behavior of copy */ __s64 copy; /* number of bytes copied, or negated error */ }; .ee .in .pp the following value may be bitwise ored in .ir mode to change the behavior of the .b uffdio_copy operation: .tp .b uffdio_copy_mode_dontwake do not wake up the thread that waits for page-fault resolution .tp .b uffdio_copy_mode_wp copy the page with read-only permission. this allows the user to trap the next write to the page, which will block and generate another write-protect userfault message. this is used only when both .b uffdio_register_mode_missing and .b uffdio_register_mode_wp modes are enabled for the registered range. .pp the .i copy field is used by the kernel to return the number of bytes that was actually copied, or an error (a negated .ir errno -style value). .\" fixme above: why is the 'copy' field used to return error values? .\" this should be explained in the manual page. if the value returned in .i copy doesn't match the value that was specified in .ir len , the operation fails with the error .br eagain . the .i copy field is output-only; it is not read by the .b uffdio_copy operation. .pp this .br ioctl (2) operation returns 0 on success. in this case, the entire area was copied. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .tp .b eagain the number of bytes copied (i.e., the value returned in the .i copy field) does not equal the value that was specified in the .i len field. .tp .b einval either .i dst or .i len was not a multiple of the system page size, or the range specified by .ir src and .ir len or .ir dst and .ir len was invalid. .tp .b einval an invalid bit was specified in the .ir mode field. .tp .br enoent " (since linux 4.11)" the faulting process has changed its virtual memory layout simultaneously with an outstanding .b uffdio_copy operation. .tp .br enospc " (from linux 4.11 until linux 4.13)" the faulting process has exited at the time of a .b uffdio_copy operation. .tp .br esrch " (since linux 4.13)" the faulting process has exited at the time of a .b uffdio_copy operation. .\" .ss uffdio_zeropage (since linux 4.3.) zero out a memory range registered with userfaultfd. .pp the requested range is specified by the .i range field of the .i uffdio_zeropage structure pointed to by .ir argp : .pp .in +4n .ex struct uffdio_zeropage { struct uffdio_range range; __u64 mode; /* flags controlling behavior of copy */ __s64 zeropage; /* number of bytes zeroed, or negated error */ }; .ee .in .pp the following value may be bitwise ored in .ir mode to change the behavior of the .b uffdio_zeropage operation: .tp .b uffdio_zeropage_mode_dontwake do not wake up the thread that waits for page-fault resolution. .pp the .i zeropage field is used by the kernel to return the number of bytes that was actually zeroed, or an error in the same manner as .br uffdio_copy . .\" fixme why is the 'zeropage' field used to return error values? .\" this should be explained in the manual page. if the value returned in the .i zeropage field doesn't match the value that was specified in .ir range.len , the operation fails with the error .br eagain . the .i zeropage field is output-only; it is not read by the .b uffdio_zeropage operation. .pp this .br ioctl (2) operation returns 0 on success. in this case, the entire area was zeroed. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .tp .b eagain the number of bytes zeroed (i.e., the value returned in the .i zeropage field) does not equal the value that was specified in the .i range.len field. .tp .b einval either .i range.start or .i range.len was not a multiple of the system page size; or .i range.len was zero; or the range specified was invalid. .tp .b einval an invalid bit was specified in the .ir mode field. .tp .br esrch " (since linux 4.13)" the faulting process has exited at the time of a .b uffdio_zeropage operation. .\" .ss uffdio_wake (since linux 4.3.) wake up the thread waiting for page-fault resolution on a specified memory address range. .pp the .b uffdio_wake operation is used in conjunction with .br uffdio_copy and .br uffdio_zeropage operations that have the .br uffdio_copy_mode_dontwake or .br uffdio_zeropage_mode_dontwake bit set in the .i mode field. the userfault monitor can perform several .br uffdio_copy and .br uffdio_zeropage operations in a batch and then explicitly wake up the faulting thread using .br uffdio_wake . .pp the .i argp argument is a pointer to a .i uffdio_range structure (shown above) that specifies the address range. .pp this .br ioctl (2) operation returns 0 on success. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .tp .b einval the .i start or the .i len field of the .i ufdio_range structure was not a multiple of the system page size; or .i len was zero; or the specified range was otherwise invalid. .ss uffdio_writeprotect (since linux 5.7) write-protect or write-unprotect a userfaultfd-registered memory range registered with mode .br uffdio_register_mode_wp . .pp the .i argp argument is a pointer to a .i uffdio_range structure as shown below: .pp .in +4n .ex struct uffdio_writeprotect { struct uffdio_range range; /* range to change write permission*/ __u64 mode; /* mode to change write permission */ }; .ee .in .pp there are two mode bits that are supported in this structure: .tp .b uffdio_writeprotect_mode_wp when this mode bit is set, the ioctl will be a write-protect operation upon the memory range specified by .ir range . otherwise it will be a write-unprotect operation upon the specified range, which can be used to resolve a userfaultfd write-protect page fault. .tp .b uffdio_writeprotect_mode_dontwake when this mode bit is set, do not wake up any thread that waits for page-fault resolution after the operation. this can be specified only if .b uffdio_writeprotect_mode_wp is not specified. .pp this .br ioctl (2) operation returns 0 on success. on error, \-1 is returned and .i errno is set to indicate the error. possible errors include: .tp .b einval the .i start or the .i len field of the .i ufdio_range structure was not a multiple of the system page size; or .i len was zero; or the specified range was otherwise invalid. .tp .b eagain the process was interrupted; retry this call. .tp .b enoent the range specified in .i range is not valid. for example, the virtual address does not exist, or not registered with userfaultfd write-protect mode. .tp .b efault encountered a generic fault during processing. .sh return value see descriptions of the individual operations, above. .sh errors see descriptions of the individual operations, above. in addition, the following general errors can occur for all of the operations described above: .tp .b efault .i argp does not point to a valid memory address. .tp .b einval (for all operations except .br uffdio_api .) the userfaultfd object has not yet been enabled (via the .br uffdio_api operation). .sh conforming to these .br ioctl (2) operations are linux-specific. .sh bugs in order to detect available userfault features and enable some subset of those features the userfaultfd file descriptor must be closed after the first .br uffdio_api operation that queries features availability and reopened before the second .br uffdio_api operation that actually enables the desired features. .sh examples see .br userfaultfd (2). .sh see also .br ioctl (2), .br mmap (2), .br userfaultfd (2) .pp .ir documentation/admin\-guide/mm/userfaultfd.rst in the linux kernel source tree .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c), 1995, graeme w. wilford. (wilf.) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" wed jun 14 16:10:28 bst 1995 wilf. (g.wilford@ee.surrey.ac.uk) .\" tiny change in formatting - aeb, 950812 .\" modified 8 may 1998 by joseph s. myers (jsm28@cam.ac.uk) .\" .\" show the synopsis section nicely .th regex 3 2021-03-22 "gnu" "linux programmer's manual" .sh name regcomp, regexec, regerror, regfree \- posix regex functions .sh synopsis .nf .b #include .pp .bi "int regcomp(regex_t *restrict " preg ", const char *restrict " regex , .bi " int " cflags ); .bi "int regexec(const regex_t *restrict " preg \ ", const char *restrict " string , .bi " size_t " nmatch ", regmatch_t " pmatch "[restrict]\ , int " eflags ); .pp .bi "size_t regerror(int " errcode ", const regex_t *restrict " preg , .bi " char *restrict " errbuf ", size_t " errbuf_size ); .bi "void regfree(regex_t *" preg ); .fi .sh description .ss posix regex compiling .br regcomp () is used to compile a regular expression into a form that is suitable for subsequent .br regexec () searches. .pp .br regcomp () is supplied with .ir preg , a pointer to a pattern buffer storage area; .ir regex , a pointer to the null-terminated string and .ir cflags , flags used to determine the type of compilation. .pp all regular expression searching must be done via a compiled pattern buffer, thus .br regexec () must always be supplied with the address of a .br regcomp ()-initialized pattern buffer. .pp .i cflags is the .rb bitwise- or of zero or more of the following: .tp .b reg_extended use .b posix extended regular expression syntax when interpreting .ir regex . if not set, .b posix basic regular expression syntax is used. .tp .b reg_icase do not differentiate case. subsequent .br regexec () searches using this pattern buffer will be case insensitive. .tp .b reg_nosub do not report position of matches. the .i nmatch and .i pmatch arguments to .br regexec () are ignored if the pattern buffer supplied was compiled with this flag set. .tp .b reg_newline match-any-character operators don't match a newline. .ip a nonmatching list .rb ( [\(ha...] ) not containing a newline does not match a newline. .ip match-beginning-of-line operator .rb ( \(ha ) matches the empty string immediately after a newline, regardless of whether .ir eflags , the execution flags of .br regexec (), contains .br reg_notbol . .ip match-end-of-line operator .rb ( $ ) matches the empty string immediately before a newline, regardless of whether .i eflags contains .br reg_noteol . .ss posix regex matching .br regexec () is used to match a null-terminated string against the precompiled pattern buffer, .ir preg . .i nmatch and .i pmatch are used to provide information regarding the location of any matches. .i eflags is the .rb bitwise- or of zero or more of the following flags: .tp .b reg_notbol the match-beginning-of-line operator always fails to match (but see the compilation flag .b reg_newline above). this flag may be used when different portions of a string are passed to .br regexec () and the beginning of the string should not be interpreted as the beginning of the line. .tp .b reg_noteol the match-end-of-line operator always fails to match (but see the compilation flag .b reg_newline above). .tp .b reg_startend use .i pmatch[0] on the input string, starting at byte .i pmatch[0].rm_so and ending before byte .ir pmatch[0].rm_eo . this allows matching embedded nul bytes and avoids a .br strlen (3) on large strings. it does not use .i nmatch on input, and does not change .b reg_notbol or .b reg_newline processing. this flag is a bsd extension, not present in posix. .ss byte offsets unless .b reg_nosub was set for the compilation of the pattern buffer, it is possible to obtain match addressing information. .i pmatch must be dimensioned to have at least .i nmatch elements. these are filled in by .br regexec () with substring match addresses. the offsets of the subexpression starting at the .ir i th open parenthesis are stored in .ir pmatch[i] . the entire regular expression's match addresses are stored in .ir pmatch[0] . (note that to return the offsets of .i n subexpression matches, .i nmatch must be at least .ir n+1 .) any unused structure elements will contain the value \-1. .pp the .i regmatch_t structure which is the type of .i pmatch is defined in .ir . .pp .in +4n .ex typedef struct { regoff_t rm_so; regoff_t rm_eo; } regmatch_t; .ee .in .pp each .i rm_so element that is not \-1 indicates the start offset of the next largest substring match within the string. the relative .i rm_eo element indicates the end offset of the match, which is the offset of the first character after the matching text. .ss posix error reporting .br regerror () is used to turn the error codes that can be returned by both .br regcomp () and .br regexec () into error message strings. .pp .br regerror () is passed the error code, .ir errcode , the pattern buffer, .ir preg , a pointer to a character string buffer, .ir errbuf , and the size of the string buffer, .ir errbuf_size . it returns the size of the .i errbuf required to contain the null-terminated error message string. if both .i errbuf and .i errbuf_size are nonzero, .i errbuf is filled in with the first .i "errbuf_size \- 1" characters of the error message and a terminating null byte (\(aq\e0\(aq). .ss posix pattern buffer freeing supplying .br regfree () with a precompiled pattern buffer, .i preg will free the memory allocated to the pattern buffer by the compiling process, .br regcomp (). .sh return value .br regcomp () returns zero for a successful compilation or an error code for failure. .pp .br regexec () returns zero for a successful match or .b reg_nomatch for failure. .sh errors the following errors can be returned by .br regcomp (): .tp .b reg_badbr invalid use of back reference operator. .tp .b reg_badpat invalid use of pattern operators such as group or list. .tp .b reg_badrpt invalid use of repetition operators such as using \(aq*\(aq as the first character. .tp .b reg_ebrace un-matched brace interval operators. .tp .b reg_ebrack un-matched bracket list operators. .tp .b reg_ecollate invalid collating element. .tp .b reg_ectype unknown character class name. .tp .b reg_eend nonspecific error. this is not defined by posix.2. .tp .b reg_eescape trailing backslash. .tp .b reg_eparen un-matched parenthesis group operators. .tp .b reg_erange invalid use of the range operator; for example, the ending point of the range occurs prior to the starting point. .tp .b reg_esize compiled regular expression requires a pattern buffer larger than 64\ kb. this is not defined by posix.2. .tp .b reg_espace the regex routines ran out of memory. .tp .b reg_esubreg invalid back reference to a subexpression. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br regcomp (), .br regexec () t} thread safety mt-safe locale t{ .br regerror () t} thread safety mt-safe env t{ .br regfree () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples .ex #include #include #include #include #define array_size(arr) (sizeof((arr)) / sizeof((arr)[0])) static const char *const str = "1) john driverhacker;\en2) john doe;\en3) john foo;\en"; static const char *const re = "john.*o"; int main(void) { static const char *s = str; regex_t regex; regmatch_t pmatch[1]; regoff_t off, len; if (regcomp(®ex, re, reg_newline)) exit(exit_failure); printf("string = \e"%s\e"\en", str); printf("matches:\en"); for (int i = 0; ; i++) { if (regexec(®ex, s, array_size(pmatch), pmatch, 0)) break; off = pmatch[0].rm_so + (s \- str); len = pmatch[0].rm_eo \- pmatch[0].rm_so; printf("#%d:\en", i); printf("offset = %jd; length = %jd\en", (intmax_t) off, (intmax_t) len); printf("substring = \e"%.*s\e"\en", len, s + pmatch[0].rm_so); s += pmatch[0].rm_eo; } exit(exit_success); } .ee .sh see also .br grep (1), .br regex (7) .pp the glibc manual section, .i "regular expressions" .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/unlocked_stdio.3 .so man3/rpc.3 .\" copyright 2015-2017 mathieu desnoyers .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th membarrier 2 2021-08-27 "linux" "linux programmer's manual" .sh name membarrier \- issue memory barriers on a set of threads .sh synopsis .nf .pp .br "#include " \ " /* definition of " membarrier_* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_membarrier, int " cmd ", unsigned int " flags \ ", int " cpu_id ); .fi .pp .ir note : glibc provides no wrapper for .br membarrier (), necessitating the use of .br syscall (2). .sh description the .br membarrier () system call helps reducing the overhead of the memory barrier instructions required to order memory accesses on multi-core systems. however, this system call is heavier than a memory barrier, so using it effectively is .i not as simple as replacing memory barriers with this system call, but requires understanding of the details below. .pp use of memory barriers needs to be done taking into account that a memory barrier always needs to be either matched with its memory barrier counterparts, or that the architecture's memory model doesn't require the matching barriers. .pp there are cases where one side of the matching barriers (which we will refer to as "fast side") is executed much more often than the other (which we will refer to as "slow side"). this is a prime target for the use of .br membarrier (). the key idea is to replace, for these matching barriers, the fast-side memory barriers by simple compiler barriers, for example: .pp .in +4n .ex asm volatile ("" : : : "memory") .ee .in .pp and replace the slow-side memory barriers by calls to .br membarrier (). .pp this will add overhead to the slow side, and remove overhead from the fast side, thus resulting in an overall performance increase as long as the slow side is infrequent enough that the overhead of the .br membarrier () calls does not outweigh the performance gain on the fast side. .pp the .i cmd argument is one of the following: .tp .br membarrier_cmd_query " (since linux 4.3)" query the set of supported commands. the return value of the call is a bit mask of supported commands. .br membarrier_cmd_query , which has the value 0, is not itself included in this bit mask. this command is always supported (on kernels where .br membarrier () is provided). .tp .br membarrier_cmd_global " (since linux 4.16)" ensure that all threads from all processes on the system pass through a state where all memory accesses to user-space addresses match program order between entry to and return from the .br membarrier () system call. all threads on the system are targeted by this command. .tp .br membarrier_cmd_global_expedited " (since linux 4.16)" execute a memory barrier on all running threads of all processes that previously registered with .br membarrier_cmd_register_global_expedited . .ip upon return from the system call, the calling thread has a guarantee that all running threads have passed through a state where all memory accesses to user-space addresses match program order between entry to and return from the system call (non-running threads are de facto in such a state). this guarantee is provided only for the threads of processes that previously registered with .br membarrier_cmd_register_global_expedited . .ip given that registration is about the intent to receive the barriers, it is valid to invoke .br membarrier_cmd_global_expedited from a process that has not employed .br membarrier_cmd_register_global_expedited . .ip the "expedited" commands complete faster than the non-expedited ones; they never block, but have the downside of causing extra overhead. .tp .br membarrier_cmd_register_global_expedited " (since linux 4.16)" register the process's intent to receive .br membarrier_cmd_global_expedited memory barriers. .tp .br membarrier_cmd_private_expedited " (since linux 4.14)" execute a memory barrier on each running thread belonging to the same process as the calling thread. .ip upon return from the system call, the calling thread has a guarantee that all its running thread siblings have passed through a state where all memory accesses to user-space addresses match program order between entry to and return from the system call (non-running threads are de facto in such a state). this guarantee is provided only for threads in the same process as the calling thread. .ip the "expedited" commands complete faster than the non-expedited ones; they never block, but have the downside of causing extra overhead. .ip a process must register its intent to use the private expedited command prior to using it. .tp .br membarrier_cmd_register_private_expedited " (since linux 4.14)" register the process's intent to use .br membarrier_cmd_private_expedited . .tp .br membarrier_cmd_private_expedited_sync_core " (since linux 4.16)" in addition to providing the memory ordering guarantees described in .br membarrier_cmd_private_expedited , upon return from system call the calling thread has a guarantee that all its running thread siblings have executed a core serializing instruction. this guarantee is provided only for threads in the same process as the calling thread. .ip the "expedited" commands complete faster than the non-expedited ones, they never block, but have the downside of causing extra overhead. .ip a process must register its intent to use the private expedited sync core command prior to using it. .tp .br membarrier_cmd_register_private_expedited_sync_core " (since linux 4.16)" register the process's intent to use .br membarrier_cmd_private_expedited_sync_core . .tp .br membarrier_cmd_private_expedited_rseq " (since linux 5.10)" ensure the caller thread, upon return from system call, that all its running thread siblings have any currently running rseq critical sections restarted if .i flags parameter is 0; if .i flags parameter is .br membarrier_cmd_flag_cpu , then this operation is performed only on cpu indicated by .ir cpu_id . this guarantee is provided only for threads in the same process as the calling thread. .ip rseq membarrier is only available in the "private expedited" form. .ip a process must register its intent to use the private expedited rseq command prior to using it. .tp .br membarrier_cmd_register_private_expedited_rseq " (since linux 5.10)" register the process's intent to use .br membarrier_cmd_private_expedited_rseq . .tp .br membarrier_cmd_shared " (since linux 4.3)" this is an alias for .br membarrier_cmd_global that exists for header backward compatibility. .pp the .i flags argument must be specified as 0 unless the command is .br membarrier_cmd_private_expedited_rseq , in which case .i flags can be either 0 or .br membarrier_cmd_flag_cpu . .pp the .i cpu_id argument is ignored unless .i flags is .br membarrier_cmd_flag_cpu , in which case it must specify the cpu targeted by this membarrier command. .pp all memory accesses performed in program order from each targeted thread are guaranteed to be ordered with respect to .br membarrier (). .pp if we use the semantic .i barrier() to represent a compiler barrier forcing memory accesses to be performed in program order across the barrier, and .i smp_mb() to represent explicit memory barriers forcing full memory ordering across the barrier, we have the following ordering table for each pairing of .ir barrier() , .br membarrier (), and .ir smp_mb() . the pair ordering is detailed as (o: ordered, x: not ordered): .pp barrier() smp_mb() membarrier() barrier() x x o smp_mb() x o o membarrier() o o o .sh return value on success, the .b membarrier_cmd_query operation returns a bit mask of supported commands, and the .br membarrier_cmd_global , .br membarrier_cmd_global_expedited , .br membarrier_cmd_register_global_expedited , .br membarrier_cmd_private_expedited , .br membarrier_cmd_register_private_expedited , .br membarrier_cmd_private_expedited_sync_core , and .b membarrier_cmd_register_private_expedited_sync_core operations return zero. on error, \-1 is returned, and .i errno is set to indicate the error. .pp for a given command, with .i flags set to 0, this system call is guaranteed to always return the same value until reboot. further calls with the same arguments will lead to the same result. therefore, with .i flags set to 0, error handling is required only for the first call to .br membarrier (). .sh errors .tp .b einval .i cmd is invalid, or .i flags is nonzero, or the .br membarrier_cmd_global command is disabled because the .i nohz_full cpu parameter has been set, or the .br membarrier_cmd_private_expedited_sync_core and .br membarrier_cmd_register_private_expedited_sync_core commands are not implemented by the architecture. .tp .b enosys the .br membarrier () system call is not implemented by this kernel. .tp .b eperm the current process was not registered prior to using private expedited commands. .sh versions the .br membarrier () system call was added in linux 4.3. .pp before linux 5.10, the prototype for .br membarrier () was: .pp .in +4n .ex .bi "int membarrier(int " cmd ", int " flags ); .ee .in .sh conforming to .br membarrier () is linux-specific. .\" .sh see also .\" fixme see if the following syscalls make it into linux 4.15 or later .\" .br cpu_opv (2), .\" .br rseq (2) .sh notes a memory barrier instruction is part of the instruction set of architectures with weakly ordered memory models. it orders memory accesses prior to the barrier and after the barrier with respect to matching barriers on other cores. for instance, a load fence can order loads prior to and following that fence with respect to stores ordered by store fences. .pp program order is the order in which instructions are ordered in the program assembly code. .pp examples where .br membarrier () can be useful include implementations of read-copy-update libraries and garbage collectors. .sh examples assuming a multithreaded application where "fast_path()" is executed very frequently, and where "slow_path()" is executed infrequently, the following code (x86) can be transformed using .br membarrier (): .pp .in +4n .ex #include static volatile int a, b; static void fast_path(int *read_b) { a = 1; asm volatile ("mfence" : : : "memory"); *read_b = b; } static void slow_path(int *read_a) { b = 1; asm volatile ("mfence" : : : "memory"); *read_a = a; } int main(int argc, char *argv[]) { int read_a, read_b; /* * real applications would call fast_path() and slow_path() * from different threads. call those from main() to keep * this example short. */ slow_path(&read_a); fast_path(&read_b); /* * read_b == 0 implies read_a == 1 and * read_a == 0 implies read_b == 1. */ if (read_b == 0 && read_a == 0) abort(); exit(exit_success); } .ee .in .pp the code above transformed to use .br membarrier () becomes: .pp .in +4n .ex #define _gnu_source #include #include #include #include #include static volatile int a, b; static int membarrier(int cmd, unsigned int flags, int cpu_id) { return syscall(__nr_membarrier, cmd, flags, cpu_id); } static int init_membarrier(void) { int ret; /* check that membarrier() is supported. */ ret = membarrier(membarrier_cmd_query, 0, 0); if (ret < 0) { perror("membarrier"); return \-1; } if (!(ret & membarrier_cmd_global)) { fprintf(stderr, "membarrier does not support membarrier_cmd_global\en"); return \-1; } return 0; } static void fast_path(int *read_b) { a = 1; asm volatile ("" : : : "memory"); *read_b = b; } static void slow_path(int *read_a) { b = 1; membarrier(membarrier_cmd_global, 0, 0); *read_a = a; } int main(int argc, char *argv[]) { int read_a, read_b; if (init_membarrier()) exit(exit_failure); /* * real applications would call fast_path() and slow_path() * from different threads. call those from main() to keep * this example short. */ slow_path(&read_a); fast_path(&read_b); /* * read_b == 0 implies read_a == 1 and * read_a == 0 implies read_b == 1. */ if (read_b == 0 && read_a == 0) abort(); exit(exit_success); } .ee .in .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/list.3 .\" copyright (c) 1993 .\" the regents of the university of california. all rights reserved. .\" and copyright (c) 2020 by alejandro colomar .\" .\" %%%license_start(bsd_3_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" .th stailq 3 2021-08-27 "gnu" "linux programmer's manual" .sh name .\"simpleq_concat, simpleq_empty, simpleq_entry, simpleq_first, simpleq_foreach, .\"simpleq_foreach_from, .\"simpleq_foreach_from_safe, .\"simpleq_foreach_safe, simpleq_head, simpleq_head_initializer, simpleq_init, simpleq_insert_after, simpleq_insert_head, simpleq_insert_tail, .\"simpleq_last, simpleq_next, simpleq_remove, .\"simpleq_remove_after, simpleq_remove_head, .\"simpleq_swap, stailq_concat, stailq_empty, stailq_entry, stailq_first, stailq_foreach, .\"stailq_foreach_from, .\"stailq_foreach_from_safe, .\"stailq_foreach_safe, stailq_head, stailq_head_initializer, stailq_init, stailq_insert_after, stailq_insert_head, stailq_insert_tail, .\"stailq_last, stailq_next, stailq_remove, .\"stailq_remove_after, stailq_remove_head, .\"stailq_swap \- implementation of a singly linked tail queue .sh synopsis .nf .b #include .pp .b stailq_entry(type); .pp .b stailq_head(headname, type); .bi "stailq_head stailq_head_initializer(stailq_head " head ); .bi "void stailq_init(stailq_head *" head ); .pp .bi "int stailq_empty(stailq_head *" head ); .pp .bi "void stailq_insert_head(stailq_head *" head , .bi " struct type *" elm ", stailq_entry " name ); .bi "void stailq_insert_tail(stailq_head *" head , .bi " struct type *" elm ", stailq_entry " name ); .bi "void stailq_insert_after(stailq_head *" head ", struct type *" listelm , .bi " struct type *" elm ", stailq_entry " name ); .pp .bi "struct type *stailq_first(stailq_head *" head ); .\" .bi "struct type *stailq_last(stailq_head *" head ", struct type *" elm , .\" .bi " stailq_entry " name ); .bi "struct type *stailq_next(struct type *" elm ", stailq_entry " name ); .pp .bi "stailq_foreach(struct type *" var ", stailq_head *" head ", stailq_entry " name ); .\" .bi "stailq_foreach_from(struct type *" var ", stailq_head *" head , .\" .bi " stailq_entry " name ); .\" .pp .\" .bi "stailq_foreach_safe(struct type *" var ", stailq_head *" head , .\" .bi " stailq_entry " name ", struct type *" temp_var ); .\" .bi "stailq_foreach_from_safe(struct type *" var ", stailq_head *" head , .\" .bi " stailq_entry " name ", struct type *" temp_var ); .pp .bi "void stailq_remove(stailq_head *" head ", struct type *" elm ", type," .bi " stailq_entry " name ); .bi "void stailq_remove_head(stailq_head *" head , .bi " stailq_entry " name ); .\" .bi "void stailq_remove_after(stailq_head *" head ", struct type *" elm , .\" .bi " stailq_entry " name ); .pp .bi "void stailq_concat(stailq_head *" head1 ", stailq_head *" head2 ); .\" .bi "void stailq_swap(stailq_head *" head1 ", stailq_head *" head2 , .\" .bi " stailq_entry " name ); .fi .ir note : identical macros prefixed with simpleq instead of stailq exist; see notes. .sh description these macros define and operate on singly linked tail queues. .pp in the macro definitions, .i type is the name of a user-defined structure, that must contain a field of type .ir stailq_entry , named .ir name . the argument .i headname is the name of a user-defined structure that must be declared using the macro .br stailq_head (). .ss creation a singly linked tail queue is headed by a structure defined by the .br stailq_head () macro. this structure contains a pair of pointers, one to the first element in the tail queue and the other to the last element in the tail queue. the elements are singly linked for minimum space and pointer manipulation overhead at the expense of o(n) removal for arbitrary elements. new elements can be added to the tail queue after an existing element, at the head of the tail queue, or at the end of the tail queue. a .i stailq_head structure is declared as follows: .pp .in +4 .ex stailq_head(headname, type) head; .ee .in .pp where .i struct headname is the structure to be defined, and .i struct type is the type of the elements to be linked into the tail queue. a pointer to the head of the tail queue can later be declared as: .pp .in +4 .ex struct headname *headp; .ee .in .pp (the names .i head and .i headp are user selectable.) .pp .br stailq_entry () declares a structure that connects the elements in the tail queue. .pp .br stailq_head_initializer () evaluates to an initializer for the tail queue .ir head . .pp .br stailq_init () initializes the tail queue referenced by .ir head . .pp .br stailq_empty () evaluates to true if there are no items on the tail queue. .ss insertion .br stailq_insert_head () inserts the new element .i elm at the head of the tail queue. .pp .br stailq_insert_tail () inserts the new element .i elm at the end of the tail queue. .pp .br stailq_insert_after () inserts the new element .i elm after the element .ir listelm . .ss traversal .br stailq_first () returns the first item on the tail queue or null if the tail queue is empty. .\" .pp .\" .br stailq_last () .\" returns the last item on the tail queue. .\" if the tail queue is empty the return value is null . .pp .br stailq_next () returns the next item on the tail queue, or null this item is the last. .pp .br stailq_foreach () traverses the tail queue referenced by .i head in the forward direction, assigning each element in turn to .ir var . .\" .pp .\" .br stailq_foreach_from () .\" behaves identically to .\" .br stailq_foreach () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found stailq element and begins the loop at .\" .i var .\" instead of the first element in the stailq referenced by .\" .ir head . .\" .pp .\" .br stailq_foreach_safe () .\" traverses the tail queue referenced by .\" .i head .\" in the forward direction, assigning each element .\" in turn to .\" .ir var . .\" however, unlike .\" .br stailq_foreach () .\" here it is permitted to both remove .\" .i var .\" as well as free it from within the loop safely without interfering with the .\" traversal. .\" .pp .\" .br stailq_foreach_from_safe () .\" behaves identically to .\" .br stailq_foreach_safe () .\" when .\" .i var .\" is null, else it treats .\" .i var .\" as a previously found stailq element and begins the loop at .\" .i var .\" instead of the first element in the stailq referenced by .\" .ir head . .ss removal .br stailq_remove () removes the element .i elm from the tail queue. .pp .br stailq_remove_head () removes the element at the head of the tail queue. for optimum efficiency, elements being removed from the head of the tail queue should use this macro explicitly rather than the generic .br stailq_remove () macro. .\" .pp .\" .br stailq_remove_after () .\" removes the element after .\" .i elm .\" from the tail queue. .\" unlike .\" .br stailq_remove (), .\" this macro does not traverse the entire tail queue. .ss other features .br stailq_concat () concatenates the tail queue headed by .i head2 onto the end of the one headed by .i head1 removing all entries from the former. .\" .pp .\" .br stailq_swap () .\" swaps the contents of .\" .i head1 .\" and .\" .ir head2 . .sh return value .br stailq_empty () returns nonzero if the queue is empty, and zero if the queue contains at least one entry. .pp .br stailq_first (), and .br stailq_next () return a pointer to the first or next .i type structure, respectively. .pp .br stailq_head_initializer () returns an initializer that can be assigned to the queue .ir head . .sh conforming to not in posix.1, posix.1-2001, or posix.1-2008. present on the bsds (stailq macros first appeared in 4.4bsd). .sh notes some bsds provide simpleq instead of stailq. they are identical, but for historical reasons they were named differently on different bsds. stailq originated on freebsd, and simpleq originated on netbsd. for compatibility reasons, some systems provide both sets of macros. glibc provides both stailq and simpleq, which are identical except for a missing simpleq equivalent to .br stailq_concat (). .sh bugs .br stailq_foreach () doesn't allow .i var to be removed or freed within the loop, as it would interfere with the traversal. .br stailq_foreach_safe (), which is present on the bsds but is not present in glibc, fixes this limitation by allowing .i var to safely be removed from the list and freed from within the loop without interfering with the traversal. .sh examples .ex #include #include #include #include struct entry { int data; stailq_entry(entry) entries; /* singly linked tail queue */ }; stailq_head(stailhead, entry); int main(void) { struct entry *n1, *n2, *n3, *np; struct stailhead head; /* singly linked tail queue head */ stailq_init(&head); /* initialize the queue */ n1 = malloc(sizeof(struct entry)); /* insert at the head */ stailq_insert_head(&head, n1, entries); n1 = malloc(sizeof(struct entry)); /* insert at the tail */ stailq_insert_tail(&head, n1, entries); n2 = malloc(sizeof(struct entry)); /* insert after */ stailq_insert_after(&head, n1, n2, entries); stailq_remove(&head, n2, entry, entries); /* deletion */ free(n2); n3 = stailq_first(&head); stailq_remove_head(&head, entries); /* deletion from the head */ free(n3); n1 = stailq_first(&head); n1\->data = 0; for (int i = 1; i < 5; i++) { n1 = malloc(sizeof(struct entry)); stailq_insert_head(&head, n1, entries); n1\->data = i; } /* forward traversal */ stailq_foreach(np, &head, entries) printf("%i\en", np\->data); /* tailq deletion */ n1 = stailq_first(&head); while (n1 != null) { n2 = stailq_next(n1, entries); free(n1); n1 = n2; } stailq_init(&head); exit(exit_success); } .ee .sh see also .br insque (3), .br queue (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/exec.3 .so man3/resolver.3 .\" copyright (c) 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified sat jul 24 21:25:52 1993 by rik faith (faith@cs.unc.edu) .\" modified 11 june 1995 by andries brouwer (aeb@cwi.nl) .th closedir 3 2021-03-22 "" "linux programmer's manual" .sh name closedir \- close a directory .sh synopsis .nf .b #include .b #include .pp .bi "int closedir(dir *" dirp ); .fi .sh description the .br closedir () function closes the directory stream associated with .ir dirp . a successful call to .br closedir () also closes the underlying file descriptor associated with .ir dirp . the directory stream descriptor .i dirp is not available after this call. .sh return value the .br closedir () function returns 0 on success. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b ebadf invalid directory stream descriptor .ir dirp . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br closedir () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh see also .br close (2), .br opendir (3), .br readdir (3), .br rewinddir (3), .br scandir (3), .br seekdir (3), .br telldir (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cmsg.3 .so man3/getspnam.3 .so man3/key_setsecret.3 .so man3/getcwd.3 .\" copyright (c) 2014 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" .th sched_setscheduler 2 2021-03-22 "linux" "linux programmer's manual" .sh name sched_setscheduler, sched_getscheduler \- set and get scheduling policy/parameters .sh synopsis .nf .b #include .pp .bi "int sched_setscheduler(pid_t " pid ", int " policy , .bi " const struct sched_param *" param ); .bi "int sched_getscheduler(pid_t " pid ); .fi .sh description the .br sched_setscheduler () system call sets both the scheduling policy and parameters for the thread whose id is specified in \fipid\fp. if \fipid\fp equals zero, the scheduling policy and parameters of the calling thread will be set. .pp the scheduling parameters are specified in the .i param argument, which is a pointer to a structure of the following form: .pp .in +4n .ex struct sched_param { ... int sched_priority; ... }; .ee .in .pp in the current implementation, the structure contains only one field, .ir sched_priority . the interpretation of .i param depends on the selected policy. .pp currently, linux supports the following "normal" (i.e., non-real-time) scheduling policies as values that may be specified in .ir policy : .tp 14 .br sched_other the standard round-robin time-sharing policy; .\" in the 2.6 kernel sources, sched_other is actually called .\" sched_normal. .tp .br sched_batch for "batch" style execution of processes; and .tp .br sched_idle for running .i very low priority background jobs. .pp for each of the above policies, .ir param\->sched_priority must be 0. .pp various "real-time" policies are also supported, for special time-critical applications that need precise control over the way in which runnable threads are selected for execution. for the rules governing when a process may use these policies, see .br sched (7). the real-time policies that may be specified in .ir policy are: .tp 14 .br sched_fifo a first-in, first-out policy; and .tp .br sched_rr a round-robin policy. .pp for each of the above policies, .ir param\->sched_priority specifies a scheduling priority for the thread. this is a number in the range returned by calling .br sched_get_priority_min (2) and .br sched_get_priority_max (2) with the specified .ir policy . on linux, these system calls return, respectively, 1 and 99. .pp since linux 2.6.32, the .b sched_reset_on_fork flag can be ored in .i policy when calling .br sched_setscheduler (). as a result of including this flag, children created by .br fork (2) do not inherit privileged scheduling policies. see .br sched (7) for details. .pp .br sched_getscheduler () returns the current scheduling policy of the thread identified by \fipid\fp. if \fipid\fp equals zero, the policy of the calling thread will be retrieved. .sh return value on success, .br sched_setscheduler () returns zero. on success, .br sched_getscheduler () returns the policy for the thread (a nonnegative integer). on error, both calls return \-1, and .i errno is set to indicate the error. .sh errors .tp .b einval invalid arguments: .i pid is negative or .i param is null. .tp .b einval .rb ( sched_setscheduler ()) .i policy is not one of the recognized policies. .tp .b einval .rb ( sched_setscheduler ()) .i param does not make sense for the specified .ir policy . .tp .b eperm the calling thread does not have appropriate privileges. .tp .b esrch the thread whose id is \fipid\fp could not be found. .sh conforming to posix.1-2001, posix.1-2008 (but see bugs below). the \fbsched_batch\fp and \fbsched_idle\fp policies are linux-specific. .sh notes further details of the semantics of all of the above "normal" and "real-time" scheduling policies can be found in the .br sched (7) manual page. that page also describes an additional policy, .br sched_deadline , which is settable only via .br sched_setattr (2). .pp posix systems on which .br sched_setscheduler () and .br sched_getscheduler () are available define .b _posix_priority_scheduling in \fi\fp. .pp posix.1 does not detail the permissions that an unprivileged thread requires in order to call .br sched_setscheduler (), and details vary across systems. for example, the solaris 7 manual page says that the real or effective user id of the caller must match the real user id or the save set-user-id of the target. .pp the scheduling policy and parameters are in fact per-thread attributes on linux. the value returned from a call to .br gettid (2) can be passed in the argument .ir pid . specifying .i pid as 0 will operate on the attributes of the calling thread, and passing the value returned from a call to .br getpid (2) will operate on the attributes of the main thread of the thread group. (if you are using the posix threads api, then use .br pthread_setschedparam (3), .br pthread_getschedparam (3), and .br pthread_setschedprio (3), instead of the .br sched_* (2) system calls.) .sh bugs posix.1 says that on success, .br sched_setscheduler () should return the previous scheduling policy. linux .br sched_setscheduler () does not conform to this requirement, since it always returns 0 on success. .sh see also .ad l .nh .br chrt (1), .br nice (2), .br sched_get_priority_max (2), .br sched_get_priority_min (2), .br sched_getaffinity (2), .br sched_getattr (2), .br sched_getparam (2), .br sched_rr_get_interval (2), .br sched_setaffinity (2), .br sched_setattr (2), .br sched_setparam (2), .br sched_yield (2), .br setpriority (2), .br capabilities (7), .br cpuset (7), .br sched (7) .ad .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/getdate.3 .so man3/y0.3 .so man3/getgrent.3 .so man7/system_data_types.7 .so man3/scanf.3 .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-3 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-3 \- iso 8859-3 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-3 encodes the characters used in certain southeast european languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-3 characters the following table displays the characters in iso 8859-3 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ħ latin capital letter h with stroke 242 162 a2 ˘ breve 243 163 a3 £ pound sign 244 164 a4 ¤ currency sign 246 166 a6 ĥ latin capital letter h with circumflex 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 i̇ latin capital letter i with dot above 252 170 aa ş latin capital letter s with cedilla 253 171 ab ğ latin capital letter g with breve 254 172 ac ĵ latin capital letter j with circumflex 255 173 ad ­ soft hyphen 257 175 af ż latin capital letter z with dot above 260 176 b0 ° degree sign 261 177 b1 ħ latin small letter h with stroke 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ´ acute accent 265 181 b5 µ micro sign 266 182 b6 ĥ latin small letter h with circumflex 267 183 b7 · middle dot 270 184 b8 ¸ cedilla 271 185 b9 ı latin small letter dotless i 272 186 ba ş latin small letter s with cedilla 273 187 bb ğ latin small letter g with breve 274 188 bc ĵ latin small letter j with circumflex 275 189 bd ½ vulgar fraction one half 277 191 bf ż latin small letter z with dot above 300 192 c0 à latin capital letter a with grave 301 193 c1 á latin capital letter a with acute 302 194 c2 â latin capital letter a with circumflex 304 196 c4 ä latin capital letter a with diaeresis 305 197 c5 ċ latin capital letter c with dot above 306 198 c6 ĉ latin capital letter c with circumflex 307 199 c7 ç latin capital letter c with cedilla 310 200 c8 è latin capital letter e with grave 311 201 c9 é latin capital letter e with acute 312 202 ca ê latin capital letter e with circumflex 313 203 cb ë latin capital letter e with diaeresis 314 204 cc ì latin capital letter i with grave 315 205 cd í latin capital letter i with acute 316 206 ce î latin capital letter i with circumflex 317 207 cf ï latin capital letter i with diaeresis 321 209 d1 ñ latin capital letter n with tilde 322 210 d2 ò latin capital letter o with grave 323 211 d3 ó latin capital letter o with acute 324 212 d4 ô latin capital letter o with circumflex 325 213 d5 ġ latin capital letter g with dot above 326 214 d6 ö latin capital letter o with diaeresis 327 215 d7 × multiplication sign 330 216 d8 ĝ latin capital letter g with circumflex 331 217 d9 ù latin capital letter u with grave 332 218 da ú latin capital letter u with acute 333 219 db û latin capital letter u with circumflex 334 220 dc ü latin capital letter u with diaeresis 335 221 dd ŭ latin capital letter u with breve 336 222 de ŝ latin capital letter s with circumflex 337 223 df ß latin small letter sharp s 340 224 e0 à latin small letter a with grave 341 225 e1 á latin small letter a with acute 342 226 e2 â latin small letter a with circumflex 344 228 e4 ä latin small letter a with diaeresis 345 229 e5 ċ latin small letter c with dot above 346 230 e6 ĉ latin small letter c with circumflex 347 231 e7 ç latin small letter c with cedilla 350 232 e8 è latin small letter e with grave 351 233 e9 é latin small letter e with acute 352 234 ea ê latin small letter e with circumflex 353 235 eb ë latin small letter e with diaeresis 354 236 ec ì latin small letter i with grave 355 237 ed í latin small letter i with acute 356 238 ee î latin small letter i with circumflex 357 239 ef ï latin small letter i with diaeresis 361 241 f1 ñ latin small letter n with tilde 362 242 f2 ò latin small letter o with grave 363 243 f3 ó latin small letter o with acute 364 244 f4 ô latin small letter o with circumflex 365 245 f5 ġ latin small letter g with dot above 366 246 f6 ö latin small letter o with diaeresis 367 247 f7 ÷ division sign 370 248 f8 ĝ latin small letter g with circumflex 371 249 f9 ù latin small letter u with grave 372 250 fa ú latin small letter u with acute 373 251 fb û latin small letter u with circumflex 374 252 fc ü latin small letter u with diaeresis 375 253 fd ŭ latin small letter u with breve 376 254 fe ŝ latin small letter s with circumflex 377 255 ff ˙ dot above .te .sh notes iso 8859-3 is also known as latin-3. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" written sat mar 8 10:35:08 mez 1997 by .\" j. "mufti" scheurich (mufti@csv.ica.uni-stuttgart.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" this page is licensed under the gnu general public license .\" %%%license_end .\" .th __setfpucw 3 2021-03-22 "linux" "linux programmer's manual" .sh name __setfpucw \- set fpu control word on i386 architecture (obsolete) .sh synopsis .nf .b #include .pp .bi "void __setfpucw(unsigned short " control_word ); .fi .sh description .br __setfpucw () transfers .i control_word to the registers of the fpu (floating-point unit) on the i386 architecture. this was used to control floating-point precision, rounding and floating-point exceptions. .sh conforming to this function was a nonstandard gnu extension. .sh notes as of glibc 2.1 this function does not exist anymore. there are new functions from c99, with prototypes in .ir , to control fpu rounding modes, like .br fegetround (3), .br fesetround (3), and the floating-point environment, like .br fegetenv (3), .br feholdexcept (3), .br fesetenv (3), .br feupdateenv (3), and fpu exception handling, like .br feclearexcept (3), .br fegetexceptflag (3), .br feraiseexcept (3), .br fesetexceptflag (3), and .br fetestexcept (3). .pp if direct access to the fpu control word is still needed, the .b _fpu_getcw and .b _fpu_setcw macros from .i can be used. .sh examples .b __setfpucw(0x1372) .pp set fpu control word on the i386 architecture to \- extended precision \- rounding to nearest \- exceptions on overflow, zero divide and nan .sh see also .br feclearexcept (3) .pp .i .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2006 michael kerrisk .\" a few fragments remain from an earlier (1992) page by .\" drew eckhardt (drew@cs.colorado.edu), .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt (michael@moria.de) .\" modified sat jul 24 13:22:07 1993 by rik faith (faith@cs.unc.edu) .\" modified 21 aug 1994 by michael chastain (mec@shell.portal.com): .\" referenced 'clone(2)'. .\" modified 1995-06-10, 1996-04-18, 1999-11-01, 2000-12-24 .\" by andries brouwer (aeb@cwi.nl) .\" modified, 27 may 2004, michael kerrisk .\" added notes on capability requirements .\" 2006-09-04, michael kerrisk .\" greatly expanded, to describe all attributes that differ .\" parent and child. .\" .th fork 2 2021-03-22 "linux" "linux programmer's manual" .sh name fork \- create a child process .sh synopsis .nf .b #include .pp .b pid_t fork(void); .fi .sh description .br fork () creates a new process by duplicating the calling process. the new process is referred to as the .i child process. the calling process is referred to as the .i parent process. .pp the child process and the parent process run in separate memory spaces. at the time of .br fork () both memory spaces have the same content. memory writes, file mappings .rb ( mmap (2)), and unmappings .rb ( munmap (2)) performed by one of the processes do not affect the other. .pp the child process is an exact duplicate of the parent process except for the following points: .ip * 3 the child has its own unique process id, and this pid does not match the id of any existing process group .rb ( setpgid (2)) or session. .ip * the child's parent process id is the same as the parent's process id. .ip * the child does not inherit its parent's memory locks .rb ( mlock (2), .br mlockall (2)). .ip * process resource utilizations .rb ( getrusage (2)) and cpu time counters .rb ( times (2)) are reset to zero in the child. .ip * the child's set of pending signals is initially empty .rb ( sigpending (2)). .ip * the child does not inherit semaphore adjustments from its parent .rb ( semop (2)). .ip * the child does not inherit process-associated record locks from its parent .rb ( fcntl (2)). (on the other hand, it does inherit .br fcntl (2) open file description locks and .br flock (2) locks from its parent.) .ip * the child does not inherit timers from its parent .rb ( setitimer (2), .br alarm (2), .br timer_create (2)). .ip * the child does not inherit outstanding asynchronous i/o operations from its parent .rb ( aio_read (3), .br aio_write (3)), nor does it inherit any asynchronous i/o contexts from its parent (see .br io_setup (2)). .pp the process attributes in the preceding list are all specified in posix.1. the parent and child also differ with respect to the following linux-specific process attributes: .ip * 3 the child does not inherit directory change notifications (dnotify) from its parent (see the description of .b f_notify in .br fcntl (2)). .ip * the .br prctl (2) .b pr_set_pdeathsig setting is reset so that the child does not receive a signal when its parent terminates. .ip * the default timer slack value is set to the parent's current timer slack value. see the description of .br pr_set_timerslack in .br prctl (2). .ip * memory mappings that have been marked with the .br madvise (2) .b madv_dontfork flag are not inherited across a .br fork (). .ip * memory in address ranges that have been marked with the .br madvise (2) .b madv_wipeonfork flag is zeroed in the child after a .br fork (). (the .b madv_wipeonfork setting remains in place for those address ranges in the child.) .ip * the termination signal of the child is always .b sigchld (see .br clone (2)). .ip * the port access permission bits set by .br ioperm (2) are not inherited by the child; the child must turn on any bits that it requires using .br ioperm (2). .pp note the following further points: .ip * 3 the child process is created with a single thread\(emthe one that called .br fork (). the entire virtual address space of the parent is replicated in the child, including the states of mutexes, condition variables, and other pthreads objects; the use of .br pthread_atfork (3) may be helpful for dealing with problems that this can cause. .ip * after a .br fork () in a multithreaded program, the child can safely call only async-signal-safe functions (see .br signal\-safety (7)) until such time as it calls .br execve (2). .ip * the child inherits copies of the parent's set of open file descriptors. each file descriptor in the child refers to the same open file description (see .br open (2)) as the corresponding file descriptor in the parent. this means that the two file descriptors share open file status flags, file offset, and signal-driven i/o attributes (see the description of .b f_setown and .b f_setsig in .br fcntl (2)). .ip * the child inherits copies of the parent's set of open message queue descriptors (see .br mq_overview (7)). each file descriptor in the child refers to the same open message queue description as the corresponding file descriptor in the parent. this means that the two file descriptors share the same flags .ri ( mq_flags ). .ip * the child inherits copies of the parent's set of open directory streams (see .br opendir (3)). posix.1 says that the corresponding directory streams in the parent and child .i may share the directory stream positioning; on linux/glibc they do not. .sh return value on success, the pid of the child process is returned in the parent, and 0 is returned in the child. on failure, \-1 is returned in the parent, no child process is created, and .i errno is set to indicate the error. .sh errors .tp .b eagain .\" note! the following should match the description in pthread_create(3) a system-imposed limit on the number of threads was encountered. there are a number of limits that may trigger this error: .rs .ip * 3 the .br rlimit_nproc soft resource limit (set via .br setrlimit (2)), which limits the number of processes and threads for a real user id, was reached; .ip * the kernel's system-wide limit on the number of processes and threads, .ir /proc/sys/kernel/threads\-max , was reached (see .br proc (5)); .ip * the maximum number of pids, .ir /proc/sys/kernel/pid_max , was reached (see .br proc (5)); or .ip * the pid limit .ri ( pids.max ) imposed by the cgroup "process number" (pids) controller was reached. .re .tp .b eagain the caller is operating under the .br sched_deadline scheduling policy and does not have the reset-on-fork flag set. see .br sched (7). .tp .b enomem .br fork () failed to allocate the necessary kernel structures because memory is tight. .tp .b enomem an attempt was made to create a child process in a pid namespace whose "init" process has terminated. see .br pid_namespaces (7). .tp .b enosys .br fork () is not supported on this platform (for example, .\" e.g., arm (optionally), blackfin, c6x, frv, h8300, microblaze, xtensa hardware without a memory-management unit). .tp .br erestartnointr " (since linux 2.6.17)" .\" commit 4a2c7a7837da1b91468e50426066d988050e4d56 system call was interrupted by a signal and will be restarted. (this can be seen only during a trace.) .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. .sh notes under linux, .br fork () is implemented using copy-on-write pages, so the only penalty that it incurs is the time and memory required to duplicate the parent's page tables, and to create a unique task structure for the child. .ss c library/kernel differences since version 2.3.3, .\" nptl/sysdeps/unix/sysv/linux/fork.c rather than invoking the kernel's .br fork () system call, the glibc .br fork () wrapper that is provided as part of the nptl threading implementation invokes .br clone (2) with flags that provide the same effect as the traditional system call. (a call to .br fork () is equivalent to a call to .br clone (2) specifying .i flags as just .br sigchld .) the glibc wrapper invokes any fork handlers that have been established using .br pthread_atfork (3). .\" and does some magic to ensure that getpid(2) returns the right value. .sh examples see .br pipe (2) and .br wait (2). .sh see also .br clone (2), .br execve (2), .br exit (2), .br setrlimit (2), .br unshare (2), .br vfork (2), .br wait (2), .br daemon (3), .br pthread_atfork (3), .br capabilities (7), .br credentials (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 1995-08-14 by arnt gulbrandsen .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .th pow 3 2021-03-22 "" "linux programmer's manual" .sh name pow, powf, powl \- power functions .sh synopsis .nf .b #include .pp .bi "double pow(double " x ", double " y ); .bi "float powf(float " x ", float " y ); .bi "long double powl(long double " x ", long double " y ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br powf (), .br powl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions return the value of .i x raised to the power of .ir y . .sh return value on success, these functions return the value of .i x to the power of .ir y . .pp if .i x is a finite value less than 0, and .i y is a finite noninteger, a domain error occurs, .\" the domain error is generated at least as far back as glibc 2.4 and a nan is returned. .pp if the result overflows, a range error occurs, .\" the range error is generated at least as far back as glibc 2.4 and the functions return .br huge_val , .br huge_valf , or .br huge_vall , respectively, with the mathematically correct sign. .pp if result underflows, and is not representable, a range error occurs, and 0.0 is returned. .\" posix.1 does not specify the sign of the zero, .\" but http://sources.redhat.com/bugzilla/show_bug.cgi?id=2678 .\" points out that the zero has the wrong sign in some cases. .pp except as specified below, if .i x or .i y is a nan, the result is a nan. .pp if .i x is +1, the result is 1.0 (even if .i y is a nan). .pp if .i y is 0, the result is 1.0 (even if .i x is a nan). .pp if .i x is +0 (\-0), and .i y is an odd integer greater than 0, the result is +0 (\-0). .pp if .i x is 0, and .i y greater than 0 and not an odd integer, the result is +0. .pp if .i x is \-1, and .i y is positive infinity or negative infinity, the result is 1.0. .pp if the absolute value of .i x is less than 1, and .i y is negative infinity, the result is positive infinity. .pp if the absolute value of .i x is greater than 1, and .i y is negative infinity, the result is +0. .pp if the absolute value of .i x is less than 1, and .i y is positive infinity, the result is +0. .pp if the absolute value of .i x is greater than 1, and .i y is positive infinity, the result is positive infinity. .pp if .i x is negative infinity, and .i y is an odd integer less than 0, the result is \-0. .pp if .i x is negative infinity, and .i y less than 0 and not an odd integer, the result is +0. .pp if .i x is negative infinity, and .i y is an odd integer greater than 0, the result is negative infinity. .pp if .i x is negative infinity, and .i y greater than 0 and not an odd integer, the result is positive infinity. .pp if .i x is positive infinity, and .i y less than 0, the result is +0. .pp if .i x is positive infinity, and .i y greater than 0, the result is positive infinity. .pp if .i x is +0 or \-0, and .i y is an odd integer less than 0, a pole error occurs and .br huge_val , .br huge_valf , or .br huge_vall , is returned, with the same sign as .ir x . .pp if .i x is +0 or \-0, and .i y is less than 0 and not an odd integer, a pole error occurs and .\" the pole error is generated at least as far back as glibc 2.4 .rb + huge_val , .rb + huge_valf , or .rb + huge_vall , is returned. .sh errors .\" fixme . review status of this error .\" longstanding bug report for glibc: .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=369 .\" for negative x, and -large and +large y, glibc 2.8 gives incorrect .\" results .\" pow(-0.5,-dbl_max)=nan .\" edom fe_invalid nan; fail-errno fail-except fail-result; .\" fail (expected: range-error-overflow (erange, fe_overflow); +inf) .\" .\" pow(-1.5,-dbl_max)=nan .\" edom fe_invalid nan; fail-errno fail-except fail-result; .\" fail (expected: range-error-underflow (erange, fe_underflow); +0) .\" .\" pow(-0.5,dbl_max)=nan .\" edom fe_invalid nan; fail-errno fail-except fail-result; .\" fail (expected: range-error-underflow (erange, fe_underflow); +0) .\" .\" pow(-1.5,dbl_max)=nan .\" edom fe_invalid nan; fail-errno fail-except fail-result; .\" fail (expected: range-error-overflow (erange, fe_overflow); +inf) see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is negative, and \fiy\fp is a finite noninteger .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .tp pole error: \fix\fp is zero, and \fiy\fp is negative .i errno is set to .br erange (but see bugs). a divide-by-zero floating-point exception .rb ( fe_divbyzero ) is raised. .tp range error: the result overflows .i errno is set to .br erange . an overflow floating-point exception .rb ( fe_overflow ) is raised. .tp range error: the result underflows .i errno is set to .br erange . an underflow floating-point exception .rb ( fe_underflow ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br pow (), .br powf (), .br powl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh bugs .ss historical bugs (now fixed) before glibc 2.28, .\" https://sourceware.org/bugzilla/show_bug.cgi?id=13932 on some architectures (e.g., x86-64) .br pow () may be more than 10,000 times slower for some inputs than for other nearby inputs. this affects only .br pow (), and not .br powf () nor .br powl (). this problem was fixed .\" commit c3d466cba1692708a19c6ff829d0386c83a0c6e5 in glibc 2.28. .pp a number of bugs .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866 in the glibc implementation of .br pow () were fixed in glibc version 2.16. .pp in glibc 2.9 and earlier, .\" .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6776 when a pole error occurs, .i errno is set to .br edom instead of the posix-mandated .br erange . since version 2.10, .\" or possibly 2.9, i haven't found the source code change .\" and i don't have a 2.9 system to test glibc does the right thing. .pp in version 2.3.2 and earlier, .\" actually, 2.3.2 is the earliest test result i have; so yet .\" to confirm if this error occurs only in 2.3.2. when an overflow or underflow error occurs, glibc's .br pow () generates a bogus invalid floating-point exception .rb ( fe_invalid ) in addition to the overflow or underflow exception. .sh see also .br cbrt (3), .br cpow (3), .br sqrt (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2003 andries e. brouwer (aeb@cwi.nl) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th alloc_hugepages 2 2021-03-22 "linux" "linux programmer's manual" .sh name alloc_hugepages, free_hugepages \- allocate or free huge pages .sh synopsis .nf .bi "void *syscall(sys_alloc_hugepages, int " key ", void *" addr \ ", size_t " len , .bi " int " prot ", int " flag ); .\" asmlinkage unsigned long sys_alloc_hugepages(int key, unsigned long addr, .\" unsigned long len, int prot, int flag); .bi "int syscall(sys_free_hugepages, void *" addr ); .\" asmlinkage int sys_free_hugepages(unsigned long addr); .fi .pp .ir note : glibc provides no wrappers for these system calls, necessitating the use of .br syscall (2). .sh description the system calls .br alloc_hugepages () and .br free_hugepages () were introduced in linux 2.5.36 and removed again in 2.5.54. they existed only on i386 and ia64 (when built with .br config_hugetlb_page ). in linux 2.4.20, the syscall numbers exist, but the calls fail with the error .br enosys . .pp on i386 the memory management hardware knows about ordinary pages (4\ kib) and huge pages (2 or 4\ mib). similarly ia64 knows about huge pages of several sizes. these system calls serve to map huge pages into the process's memory or to free them again. huge pages are locked into memory, and are not swapped. .pp the .i key argument is an identifier. when zero the pages are private, and not inherited by children. when positive the pages are shared with other applications using the same .ir key , and inherited by child processes. .pp the .i addr argument of .br free_hugepages () tells which page is being freed: it was the return value of a call to .br alloc_hugepages (). (the memory is first actually freed when all users have released it.) the .i addr argument of .br alloc_hugepages () is a hint, that the kernel may or may not follow. addresses must be properly aligned. .pp the .i len argument is the length of the required segment. it must be a multiple of the huge page size. .pp the .i prot argument specifies the memory protection of the segment. it is one of .br prot_read , .br prot_write , .br prot_exec . .pp the .i flag argument is ignored, unless .i key is positive. in that case, if .i flag is .br ipc_creat , then a new huge page segment is created when none with the given key existed. if this flag is not set, then .b enoent is returned when no segment with the given key exists. .sh return value on success, .br alloc_hugepages () returns the allocated virtual address, and .br free_hugepages () returns zero. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b enosys the system call is not supported on this kernel. .sh files .tp .i /proc/sys/vm/nr_hugepages number of configured hugetlb pages. this can be read and written. .tp .i /proc/meminfo gives info on the number of configured hugetlb pages and on their size in the three variables hugepages_total, hugepages_free, hugepagesize. .sh conforming to these extinct system calls were specific to linux on intel processors. .sh notes these system calls are gone; they existed only in linux 2.5.36 through to 2.5.54. now the hugetlbfs filesystem can be used instead. memory backed by huge pages (if the cpu supports them) is obtained by using .br mmap (2) to map files in this virtual filesystem. .pp the maximal number of huge pages can be specified using the .b hugepages= boot parameter. .\".pp .\" requires config_hugetlb_page (under "processor type and features") .\" and config_hugetlbfs (under "filesystems"). .\" mount \-t hugetlbfs hugetlbfs /huge .\" shm_hugetlb .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/printf.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-27 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th frexp 3 2021-03-22 "" "linux programmer's manual" .sh name frexp, frexpf, frexpl \- convert floating-point number to fractional and integral components .sh synopsis .nf .b #include .pp .bi "double frexp(double " x ", int *" exp ); .bi "float frexpf(float " x ", int *" exp ); .bi "long double frexpl(long double " x ", int *" exp ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br frexpf (), .br frexpl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions are used to split the number .i x into a normalized fraction and an exponent which is stored in .ir exp . .sh return value these functions return the normalized fraction. if the argument .i x is not zero, the normalized fraction is .i x times a power of two, and its absolute value is always in the range 1/2 (inclusive) to 1 (exclusive), that is, [0.5,1). .pp if .i x is zero, then the normalized fraction is zero and zero is stored in .ir exp . .pp if .i x is a nan, a nan is returned, and the value of .i *exp is unspecified. .pp if .i x is positive infinity (negative infinity), positive infinity (negative infinity) is returned, and the value of .i *exp is unspecified. .sh errors no errors occur. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br frexp (), .br frexpf (), .br frexpl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh examples the program below produces results such as the following: .pp .in +4n .ex .rb "$" " ./a.out 2560" frexp(2560, &e) = 0.625: 0.625 * 2\(ha12 = 2560 .rb "$" " ./a.out \-4" frexp(\-4, &e) = \-0.5: \-0.5 * 2\(ha3 = \-4 .ee .in .ss program source \& .ex #include #include #include #include int main(int argc, char *argv[]) { double x, r; int exp; x = strtod(argv[1], null); r = frexp(x, &exp); printf("frexp(%g, &e) = %g: %g * %d\(ha%d = %g\en", x, r, r, flt_radix, exp, x); exit(exit_success); } .ee .sh see also .br ldexp (3), .br modf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .so man2/setreuid.2 .so man2/pciconfig_read.2 .\" copyright (c) 2017, yubin ruan .\" and copyright (c) 2017, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th pthread_mutex_consistent 3 2021-08-27 "linux" "linux programmer's manual" .sh name pthread_mutex_consistent \- make a robust mutex consistent .sh synopsis .nf .b #include .pp .bi "int pthread_mutex_consistent(pthread_mutex_t *" mutex ");" .fi .pp compile and link with \fi\-pthread\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br pthread_mutex_consistent (): .nf _posix_c_source >= 200809l .fi .sh description this function makes a robust mutex consistent if it is in an inconsistent state. a mutex can be left in an inconsistent state if its owner terminates while holding the mutex, in which case the next owner who acquires the mutex will succeed and be notified by a return value of .br eownerdead from a call to .br pthread_mutex_lock (). .sh return value on success, .ir pthread_mutex_consistent () returns 0. otherwise, it returns a positive error number to indicate the error. .sh errors .tp .b einval the mutex is either not robust or is not in an inconsistent state. .sh versions .br pthread_mutex_consistent () was added to glibc in version 2.12. .sh conforming to posix.1-2008. .sh notes .br pthread_mutex_consistent () simply informs the implementation that the state (shared data) guarded by the mutex has been restored to a consistent state and that normal operations can now be performed with the mutex. it is the application's responsibility to ensure that the shared data has been restored to a consistent state before calling .br pthread_mutex_consistent (). .pp before the addition of .br pthread_mutex_consistent () to posix, glibc defined the following equivalent nonstandard function if .br _gnu_source was defined: .pp .nf .bi "int pthread_mutex_consistent_np(const pthread_mutex_t *" mutex ); .fi .pp this gnu-specific api, which first appeared in glibc 2.4, is nowadays obsolete and should not be used in new programs; since glibc 2.34 it has been marked as deprecated. .sh examples see .br pthread_mutexattr_setrobust (3). .sh see also .ad l .nh .br pthread_mutex_lock (3), .br pthread_mutexattr_getrobust (3), .br pthread_mutexattr_init (3), .br pthread_mutexattr_setrobust (3), .br pthreads (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/xdr.3 .\" copyright (c) 2016, oracle. all rights reserved. .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .th ioctl_fideduperange 2 2021-03-22 "linux" "linux programmer's manual" .sh name ioctl_fideduperange \- share some the data of one file with another file .sh synopsis .nf .br "#include " " /* definition of " fideduperange " and .br " file_dedupe_* " constants */ .b #include .pp .bi "int ioctl(int " src_fd ", fideduperange, struct file_dedupe_range *" arg ); .fi .sh description if a filesystem supports files sharing physical storage between multiple files, this .br ioctl (2) operation can be used to make some of the data in the .b src_fd file appear in the .b dest_fd file by sharing the underlying storage if the file data is identical ("deduplication"). both files must reside within the same filesystem. this reduces storage consumption by allowing the filesystem to store one shared copy of the data. if a file write should occur to a shared region, the filesystem must ensure that the changes remain private to the file being written. this behavior is commonly referred to as "copy on write". .pp this ioctl performs the "compare and share if identical" operation on up to .ir src_length bytes from file descriptor .ir src_fd at offset .ir src_offset . this information is conveyed in a structure of the following form: .pp .in +4n .ex struct file_dedupe_range { __u64 src_offset; __u64 src_length; __u16 dest_count; __u16 reserved1; __u32 reserved2; struct file_dedupe_range_info info[0]; }; .ee .in .pp deduplication is atomic with regards to concurrent writes, so no locks need to be taken to obtain a consistent deduplicated copy. .pp the fields .ir reserved1 " and " reserved2 must be zero. .pp destinations for the deduplication operation are conveyed in the array at the end of the structure. the number of destinations is given in .ir dest_count , and the destination information is conveyed in the following form: .pp .in +4n .ex struct file_dedupe_range_info { __s64 dest_fd; __u64 dest_offset; __u64 bytes_deduped; __s32 status; __u32 reserved; }; .ee .in .pp each deduplication operation targets .ir src_length bytes in file descriptor .ir dest_fd at offset .ir dest_offset . the field .ir reserved must be zero. during the call, .ir src_fd must be open for reading and .ir dest_fd must be open for writing. the combined size of the struct .ir file_dedupe_range and the struct .ir file_dedupe_range_info array must not exceed the system page size. the maximum size of .ir src_length is filesystem dependent and is typically 16\ mib. this limit will be enforced silently by the filesystem. by convention, the storage used by .ir src_fd is mapped into .ir dest_fd and the previous contents in .ir dest_fd are freed. .pp upon successful completion of this ioctl, the number of bytes successfully deduplicated is returned in .ir bytes_deduped and a status code for the deduplication operation is returned in .ir status . if even a single byte in the range does not match, the deduplication request will be ignored and .ir status set to .br file_dedupe_range_differs . the .ir status code is set to .b file_dedupe_range_same for success, a negative error code in case of error, or .b file_dedupe_range_differs if the data did not match. .sh return value on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors possible errors include (but are not limited to) the following: .tp .b ebadf .ir src_fd is not open for reading; .ir dest_fd is not open for writing or is open for append-only writes; or the filesystem which .ir src_fd resides on does not support deduplication. .tp .b einval the filesystem does not support deduplicating the ranges of the given files. this error can also appear if either file descriptor represents a device, fifo, or socket. disk filesystems generally require the offset and length arguments to be aligned to the fundamental block size. neither btrfs nor xfs support overlapping deduplication ranges in the same file. .tp .b eisdir one of the files is a directory and the filesystem does not support shared regions in directories. .tp .b enomem the kernel was unable to allocate sufficient memory to perform the operation or .ir dest_count is so large that the input argument description spans more than a single page of memory. .tp .b eopnotsupp this can appear if the filesystem does not support deduplicating either file descriptor, or if either file descriptor refers to special inodes. .tp .b eperm .ir dest_fd is immutable. .tp .b etxtbsy one of the files is a swap file. swap files cannot share storage. .tp .b exdev .ir dest_fd " and " src_fd are not on the same mounted filesystem. .sh versions this ioctl operation first appeared in linux 4.5. it was previously known as .b btrfs_ioc_file_extent_same and was private to btrfs. .sh conforming to this api is linux-specific. .sh notes because a copy-on-write operation requires the allocation of new storage, the .br fallocate (2) operation may unshare shared blocks to guarantee that subsequent writes will not fail because of lack of disk space. .pp some filesystems may limit the amount of data that can be deduplicated in a single call. .sh see also .br ioctl (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcrtomb 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcrtomb \- convert a wide character to a multibyte sequence .sh synopsis .nf .b #include .pp .bi "size_t wcrtomb(char *restrict " s ", wchar_t " wc \ ", mbstate_t *restrict " ps ); .fi .sh description the main case for this function is when .i s is not null and .i wc is not a null wide character (l\(aq\e0\(aq). in this case, the .br wcrtomb () function converts the wide character .i wc to its multibyte representation and stores it at the beginning of the character array pointed to by .ir s . it updates the shift state .ir *ps , and returns the length of said multibyte representation, that is, the number of bytes written at .ir s . .pp a different case is when .i s is not null, but .i wc is a null wide character (l\(aq\e0\(aq). in this case, the .br wcrtomb () function stores at the character array pointed to by .i s the shift sequence needed to bring .i *ps back to the initial state, followed by a \(aq\e0\(aq byte. it updates the shift state .i *ps (i.e., brings it into the initial state), and returns the length of the shift sequence plus one, that is, the number of bytes written at .ir s . .pp a third case is when .i s is null. in this case, .i wc is ignored, and the function effectively returns .pp wcrtomb(buf, l\(aq\e0\(aq, ps) .pp where .i buf is an internal anonymous buffer. .pp in all of the above cases, if .i ps is null, a static anonymous state known only to the .br wcrtomb () function is used instead. .sh return value the .br wcrtomb () function returns the number of bytes that have been or would have been written to the byte array at .ir s . if .i wc can not be represented as a multibyte sequence (according to the current locale), .i (size_t)\ \-1 is returned, and .i errno set to .br eilseq . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br wcrtomb () t} thread safety mt-unsafe race:wcrtomb/!ps .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wcrtomb () depends on the .b lc_ctype category of the current locale. .pp passing null as .i ps is not multithread safe. .sh see also .br mbsinit (3), .br wcsrtombs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1992 drew eckhardt (drew@cs.colorado.edu), march 28, 1992 .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified by michael haardt .\" modified 1993-07-24 by rik faith .\" modified 1995-06-10 by andries brouwer .\" modified 2004-06-23 by michael kerrisk .\" modified 2004-10-10 by andries brouwer .\" .th utime 2 2021-03-22 "linux" "linux programmer's manual" .sh name utime, utimes \- change file last access and modification times .sh synopsis .nf .b #include .pp .bi "int utime(const char *" filename ", const struct utimbuf *" times ); .pp .b #include .pp .bi "int utimes(const char *" filename ", const struct timeval " times [2]); .fi .sh description .b note: modern applications may prefer to use the interfaces described in .br utimensat (2). .pp the .br utime () system call changes the access and modification times of the inode specified by .i filename to the .ir actime " and " modtime fields of .i times respectively. .pp if .i times is null, then the access and modification times of the file are set to the current time. .pp changing timestamps is permitted when: either the process has appropriate privileges, or the effective user id equals the user id of the file, or .i times is null and the process has write permission for the file. .pp the .i utimbuf structure is: .pp .in +4n .ex struct utimbuf { time_t actime; /* access time */ time_t modtime; /* modification time */ }; .ee .in .pp the .br utime () system call allows specification of timestamps with a resolution of 1 second. .pp the .br utimes () system call is similar, but the .i times argument refers to an array rather than a structure. the elements of this array are .i timeval structures, which allow a precision of 1 microsecond for specifying timestamps. the .i timeval structure is: .pp .in +4n .ex struct timeval { long tv_sec; /* seconds */ long tv_usec; /* microseconds */ }; .ee .in .pp .i times[0] specifies the new access time, and .i times[1] specifies the new modification time. if .i times is null, then analogously to .br utime (), the access and modification times of the file are set to the current time. .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces search permission is denied for one of the directories in the path prefix of .i path (see also .br path_resolution (7)). .tp .b eacces .i times is null, the caller's effective user id does not match the owner of the file, the caller does not have write access to the file, and the caller is not privileged (linux: does not have either the .b cap_dac_override or the .b cap_fowner capability). .tp .b enoent .i filename does not exist. .tp .b eperm .i times is not null, the caller's effective uid does not match the owner of the file, and the caller is not privileged (linux: does not have the .b cap_fowner capability). .tp .b erofs .i path resides on a read-only filesystem. .sh conforming to .br utime (): svr4, posix.1-2001. posix.1-2008 marks .br utime () as obsolete. .pp .br utimes (): 4.3bsd, posix.1-2001. .sh notes linux does not allow changing the timestamps on an immutable file, or setting the timestamps to something other than the current time on an append-only file. .\" .\" in libc4 and libc5, .\" .br utimes () .\" is just a wrapper for .\" .br utime () .\" and hence does not allow a subsecond resolution. .sh see also .br chattr (1), .br touch (1), .br futimesat (2), .br stat (2), .br utimensat (2), .br futimens (3), .br futimes (3), .br inode (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2003 davide libenzi .\" davide libenzi .\" and copyright 2007, 2012, 2014, 2018 michael kerrisk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" 2007-04-30: mtk, added description of epoll_pwait() .\" .th epoll_wait 2 2021-03-22 "linux" "linux programmer's manual" .sh name epoll_wait, epoll_pwait, epoll_pwait2 \- wait for an i/o event on an epoll file descriptor .sh synopsis .nf .b #include .pp .bi "int epoll_wait(int " epfd ", struct epoll_event *" events , .bi " int " maxevents ", int " timeout ); .bi "int epoll_pwait(int " epfd ", struct epoll_event *" events , .bi " int " maxevents ", int " timeout , .bi " const sigset_t *" sigmask ); .bi "int epoll_pwait2(int " epfd ", struct epoll_event *" events , .bi " int " maxevents ", const struct timespec *" timeout , .bi " const sigset_t *" sigmask ); .\" fixme: check if glibc has added a wrapper for epoll_pwait2(), .\" and if so, check the prototype. .\" https://sourceware.org/bugzilla/show_bug.cgi?id=27359 .fi .sh description the .br epoll_wait () system call waits for events on the .br epoll (7) instance referred to by the file descriptor .ir epfd . the buffer pointed to by .i events is used to return information from the ready list about file descriptors in the interest list that have some events available. up to .i maxevents are returned by .br epoll_wait (). the .i maxevents argument must be greater than zero. .pp the .i timeout argument specifies the number of milliseconds that .br epoll_wait () will block. time is measured against the .b clock_monotonic clock. .pp a call to .br epoll_wait () will block until either: .ip \(bu 2 a file descriptor delivers an event; .ip \(bu the call is interrupted by a signal handler; or .ip \(bu the timeout expires. .pp note that the .i timeout interval will be rounded up to the system clock granularity, and kernel scheduling delays mean that the blocking interval may overrun by a small amount. specifying a .i timeout of \-1 causes .br epoll_wait () to block indefinitely, while specifying a .i timeout equal to zero cause .br epoll_wait () to return immediately, even if no events are available. .pp the .i struct epoll_event is defined as: .pp .in +4n .ex typedef union epoll_data { void *ptr; int fd; uint32_t u32; uint64_t u64; } epoll_data_t; struct epoll_event { uint32_t events; /* epoll events */ epoll_data_t data; /* user data variable */ }; .ee .in .pp the .i data field of each returned .i epoll_event structure contains the same data as was specified in the most recent call to .br epoll_ctl (2) .rb ( epoll_ctl_add ", " epoll_ctl_mod ) for the corresponding open file descriptor. .pp the .i events field is a bit mask that indicates the events that have occurred for the corresponding open file description. see .br epoll_ctl (2) for a list of the bits that may appear in this mask. .\" .ss epoll_pwait() the relationship between .br epoll_wait () and .br epoll_pwait () is analogous to the relationship between .br select (2) and .br pselect (2): like .br pselect (2), .br epoll_pwait () allows an application to safely wait until either a file descriptor becomes ready or until a signal is caught. .pp the following .br epoll_pwait () call: .pp .in +4n .ex ready = epoll_pwait(epfd, &events, maxevents, timeout, &sigmask); .ee .in .pp is equivalent to .i atomically executing the following calls: .pp .in +4n .ex sigset_t origmask; pthread_sigmask(sig_setmask, &sigmask, &origmask); ready = epoll_wait(epfd, &events, maxevents, timeout); pthread_sigmask(sig_setmask, &origmask, null); .ee .in .pp the .i sigmask argument may be specified as null, in which case .br epoll_pwait () is equivalent to .br epoll_wait (). .\" .ss epoll_pwait2() the .br epoll_pwait2 () system call is equivalent to .br epoll_pwait () except for the .i timeout argument. it takes an argument of type .i timespec to be able to specify nanosecond resolution timeout. this argument functions the same as in .br pselect (2) and .br ppoll (2). if .i timeout is null, then .br epoll_pwait2 () can block indefinitely. .sh return value on success, .br epoll_wait () returns the number of file descriptors ready for the requested i/o, or zero if no file descriptor became ready during the requested .i timeout milliseconds. on failure, .br epoll_wait () returns \-1 and .i errno is set to indicate the error. .sh errors .tp .b ebadf .i epfd is not a valid file descriptor. .tp .b efault the memory area pointed to by .i events is not accessible with write permissions. .tp .b eintr the call was interrupted by a signal handler before either (1) any of the requested events occurred or (2) the .i timeout expired; see .br signal (7). .tp .b einval .i epfd is not an .b epoll file descriptor, or .i maxevents is less than or equal to zero. .sh versions .br epoll_wait () was added to the kernel in version 2.6. .\" to be precise: kernel 2.5.44. .\" the interface should be finalized by linux kernel 2.5.66. library support is provided in glibc starting with version 2.3.2. .pp .br epoll_pwait () was added to linux in kernel 2.6.19. library support is provided in glibc starting with version 2.6. .pp .br epoll_pwait2 () was added to linux in kernel 5.11. .sh conforming to .br epoll_wait (), .br epoll_pwait (), and .br epoll_pwait2 () are linux-specific. .sh notes while one thread is blocked in a call to .br epoll_wait (), it is possible for another thread to add a file descriptor to the waited-upon .b epoll instance. if the new file descriptor becomes ready, it will cause the .br epoll_wait () call to unblock. .pp if more than .i maxevents file descriptors are ready when .br epoll_wait () is called, then successive .br epoll_wait () calls will round robin through the set of ready file descriptors. this behavior helps avoid starvation scenarios, where a process fails to notice that additional file descriptors are ready because it focuses on a set of file descriptors that are already known to be ready. .pp note that it is possible to call .br epoll_wait () on an .b epoll instance whose interest list is currently empty (or whose interest list becomes empty because file descriptors are closed or removed from the interest in another thread). the call will block until some file descriptor is later added to the interest list (in another thread) and that file descriptor becomes ready. .ss c library/kernel differences the raw .br epoll_pwait () and .br epoll_pwait2 () system calls have a sixth argument, .ir "size_t sigsetsize" , which specifies the size in bytes of the .ir sigmask argument. the glibc .br epoll_pwait () wrapper function specifies this argument as a fixed value (equal to .ir sizeof(sigset_t) ). .sh bugs in kernels before 2.6.37, a .i timeout value larger than approximately .i long_max / hz milliseconds is treated as \-1 (i.e., infinity). thus, for example, on a system where .i sizeof(long) is 4 and the kernel .i hz value is 1000, this means that timeouts greater than 35.79 minutes are treated as infinity. .sh see also .br epoll_create (2), .br epoll_ctl (2), .br epoll (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" %%%license_start(public_domain) .\" this page is in the public domain. - aeb .\" %%%license_end .\" .th unlockpt 3 2021-03-22 "" "linux programmer's manual" .sh name unlockpt \- unlock a pseudoterminal master/slave pair .sh synopsis .nf .b #define _xopen_source .b #include .pp .bi "int unlockpt(int " fd ");" .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br unlockpt (): .nf since glibc 2.24: _xopen_source >= 500 .\" || (_xopen_source && _xopen_source_extended) glibc 2.23 and earlier: _xopen_source .fi .sh description the .br unlockpt () function unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by the file descriptor .ir fd . .pp .br unlockpt () should be called before opening the slave side of a pseudoterminal. .sh return value when successful, .br unlockpt () returns 0. otherwise, it returns \-1 and sets .i errno to indicate the error. .sh errors .tp .b ebadf the .i fd argument is not a file descriptor open for writing. .tp .b einval the .i fd argument is not associated with a master pseudoterminal. .sh versions .br unlockpt () is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br unlockpt () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh see also .br grantpt (3), .br posix_openpt (3), .br ptsname (3), .br pts (4), .br pty (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man7/iso_8859-10.7 .so man3/getutent.3 .so man3/strerror.3 .\" copyright (c) 2003 andries brouwer (aeb@cwi.nl) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th aio_cancel 3 2021-03-22 "" "linux programmer's manual" .sh name aio_cancel \- cancel an outstanding asynchronous i/o request .sh synopsis .nf .b "#include " .pp .bi "int aio_cancel(int " fd ", struct aiocb *" aiocbp ); .pp link with \fi\-lrt\fp. .fi .sh description the .br aio_cancel () function attempts to cancel outstanding asynchronous i/o requests for the file descriptor .ir fd . if .i aiocbp is null, all such requests are canceled. otherwise, only the request described by the control block pointed to by .i aiocbp is canceled. (see .br aio (7) for a description of the .i aiocb structure.) .pp normal asynchronous notification occurs for canceled requests (see .br aio (7) and .br sigevent (7)). the request return status .rb ( aio_return (3)) is set to \-1, and the request error status .rb ( aio_error (3)) is set to .br ecanceled . the control block of requests that cannot be canceled is not changed. .pp if the request could not be canceled, then it will terminate in the usual way after performing the i/o operation. (in this case, .br aio_error (3) will return the status .br einprogresss .) .pp if .i aiocbp is not null, and .i fd differs from the file descriptor with which the asynchronous operation was initiated, unspecified results occur. .pp which operations are cancelable is implementation-defined. .\" freebsd: not those on raw disk devices. .sh return value the .br aio_cancel () function returns one of the following values: .tp .b aio_canceled all requests were successfully canceled. .tp .b aio_notcanceled at least one of the requests specified was not canceled because it was in progress. in this case, one may check the status of individual requests using .br aio_error (3). .tp .b aio_alldone all requests had already been completed before the call. .tp \-1 an error occurred. the cause of the error can be found by inspecting .ir errno . .sh errors .tp .b ebadf .i fd is not a valid file descriptor. .tp .b enosys .br aio_cancel () is not implemented. .sh versions the .br aio_cancel () function is available since glibc 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br aio_cancel () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .sh examples see .br aio (7). .sh see also .br aio_error (3), .br aio_fsync (3), .br aio_read (3), .br aio_return (3), .br aio_suspend (3), .br aio_write (3), .br lio_listio (3), .br aio (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/catan.3 .\" copyright (c) 1999, 2000 suse gmbh nuernberg, germany .\" author: thorsten kukuk .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of the .\" license, or (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the gnu .\" general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th nscd.conf 5 2020-12-21 "gnu" "linux programmer's manual" .sh name nscd.conf \- name service cache daemon configuration file .sh description the file .i /etc/nscd.conf is read from .br nscd (8) at startup. each line specifies either an attribute and a value, or an attribute, service, and a value. fields are separated either by space or tab characters. a \(aq#\(aq (number sign) indicates the beginning of a comment; following characters, up to the end of the line, are not interpreted by nscd. .pp valid services are \fipasswd\fp, \figroup\fp, \fihosts\fp, \fiservices\fp, or \finetgroup\fp. .pp .b logfile .i debug-file-name .rs specifies name of the file to which debug info should be written. .re .pp .b debug\-level .i value .rs sets the desired debug level. the default is 0. .re .pp .b threads .i number .rs this is the number of threads that are started to wait for requests. at least five threads will always be created. .re .pp .b max\-threads .i number .rs specifies the maximum number of threads. the default is 32. .re .pp .b server\-user .i user .rs if this option is set, nscd will run as this user and not as root. if a separate cache for every user is used (\-s parameter), this option is ignored. .re .pp .b stat\-user .i user .rs specifies the user who is allowed to request statistics. .re .pp .b reload\-count unlimited | .i number .rs limit on the number of times a cached entry gets reloaded without being used before it gets removed. the default is 5. .re .pp .b paranoia .i .rs enabling paranoia mode causes nscd to restart itself periodically. the default is no. .re .pp .b restart\-interval .i time .rs sets the restart interval to .i time seconds if periodic restart is enabled by enabling .b paranoia mode. the default is 3600. .re .pp .b enable\-cache .i service .i .rs enables or disables the specified .i service cache. the default is no. .re .pp .b positive\-time\-to\-live .i service .i value .rs sets the ttl (time-to-live) for positive entries (successful queries) in the specified cache for .ir service . .i value is in seconds. larger values increase cache hit rates and reduce mean response times, but increase problems with cache coherence. .re .pp .b negative\-time\-to\-live .i service .i value .rs sets the ttl (time-to-live) for negative entries (unsuccessful queries) in the specified cache for .ir service . .i value is in seconds. can result in significant performance improvements if there are several files owned by uids (user ids) not in system databases (for example untarring the linux kernel sources as root); should be kept small to reduce cache coherency problems. .re .pp .b suggested\-size .i service .i value .rs this is the internal hash table size, .i value should remain a prime number for optimum efficiency. the default is 211. .re .pp .b check\-files .i service .i .rs enables or disables checking the file belonging to the specified .i service for changes. the files are .ir /etc/passwd , .ir /etc/group , .ir /etc/hosts , .ir /etc/services , and .ir /etc/netgroup . the default is yes. .re .pp .b persistent .i service .i .rs keep the content of the cache for .i service over server restarts; useful when .b paranoia mode is set. the default is no. .re .pp .b shared .i service .i .rs the memory mapping of the nscd databases for .i service is shared with the clients so that they can directly search in them instead of having to ask the daemon over the socket each time a lookup is performed. the default is no. .re .pp .b max\-db\-size .i service .i bytes .rs the maximum allowable size, in bytes, of the database files for the .ir service . the default is 33554432. .re .pp .b auto\-propagate .i service .i .rs when set to .i no for .i passwd or .i group service, then the .i .byname requests are not added to .i passwd.byuid or .i group.bygid cache. this can help with tables containing multiple records for the same id. the default is yes. this option is valid only for services .i passwd and .ir group . .re .sh notes the default values stated in this manual page originate from the source code of .br nscd (8) and are used if not overridden in the configuration file. the default values used in the configuration file of your distribution might differ. .sh see also .br nscd (8) .\" .sh author .\" .b nscd .\" was written by thorsten kukuk and ulrich drepper. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/asin.3 .so man7/system_data_types.7 .\" copyright (c) 2002 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th intro 1 2020-08-13 "linux" "linux user's manual" .sh name intro \- introduction to user commands .sh description section 1 of the manual describes user commands and tools, for example, file manipulation tools, shells, compilers, web browsers, file and image viewers and editors, and so on. .sh notes linux is a flavor of unix, and as a first approximation all user commands under unix work precisely the same under linux (and freebsd and lots of other unix-like systems). .pp under linux, there are guis (graphical user interfaces), where you can point and click and drag, and hopefully get work done without first reading lots of documentation. the traditional unix environment is a cli (command line interface), where you type commands to tell the computer what to do. that is faster and more powerful, but requires finding out what the commands are. below a bare minimum, to get started. .ss login in order to start working, you probably first have to open a session by giving your username and password. the program .br login (1) now starts a .i shell (command interpreter) for you. in case of a graphical login, you get a screen with menus or icons and a mouse click will start a shell in a window. see also .br xterm (1). .ss the shell one types commands to the .ir shell , the command interpreter. it is not built-in, but is just a program and you can change your shell. everybody has their own favorite one. the standard one is called .ir sh . see also .br ash (1), .br bash (1), .br chsh (1), .br csh (1), .br dash (1), .br ksh (1), .br zsh (1). .pp a session might go like: .pp .in +4n .ex .rb "knuth login: " aeb .rb "password: " ******** .rb "$ " date tue aug 6 23:50:44 cest 2002 .rb "$ " cal august 2002 su mo tu we th fr sa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 .rb "$ " ls bin tel .rb "$ " "ls \-l" total 2 drwxrwxr\-x 2 aeb 1024 aug 6 23:51 bin \-rw\-rw\-r\-\- 1 aeb 37 aug 6 23:52 tel .rb "$ " "cat tel" maja 0501\-1136285 peter 0136\-7399214 .rb "$ " "cp tel tel2" .rb "$ " "ls \-l" total 3 drwxr\-xr\-x 2 aeb 1024 aug 6 23:51 bin \-rw\-r\-\-r\-\- 1 aeb 37 aug 6 23:52 tel \-rw\-r\-\-r\-\- 1 aeb 37 aug 6 23:53 tel2 .rb "$ " "mv tel tel1" .rb "$ " "ls \-l" total 3 drwxr\-xr\-x 2 aeb 1024 aug 6 23:51 bin \-rw\-r\-\-r\-\- 1 aeb 37 aug 6 23:52 tel1 \-rw\-r\-\-r\-\- 1 aeb 37 aug 6 23:53 tel2 .rb "$ " "diff tel1 tel2" .rb "$ " "rm tel1" .rb "$ " "grep maja tel2" maja 0501\-1136285 $ .ee .in .pp here typing control-d ended the session. .pp the .b $ here was the command prompt\(emit is the shell's way of indicating that it is ready for the next command. the prompt can be customized in lots of ways, and one might include stuff like username, machine name, current directory, time, and so on. an assignment ps1="what next, master? " would change the prompt as indicated. .pp we see that there are commands .i date (that gives date and time), and .i cal (that gives a calendar). .pp the command .i ls lists the contents of the current directory\(emit tells you what files you have. with a .i \-l option it gives a long listing, that includes the owner and size and date of the file, and the permissions people have for reading and/or changing the file. for example, the file "tel" here is 37 bytes long, owned by aeb and the owner can read and write it, others can only read it. owner and permissions can be changed by the commands .i chown and .ir chmod . .pp the command .i cat will show the contents of a file. (the name is from "concatenate and print": all files given as parameters are concatenated and sent to "standard output" (see .br stdout (3)), here the terminal screen.) .pp the command .i cp (from "copy") will copy a file. .pp the command .i mv (from "move"), on the other hand, only renames it. .pp the command .i diff lists the differences between two files. here there was no output because there were no differences. .pp the command .i rm (from "remove") deletes the file, and be careful! it is gone. no wastepaper basket or anything. deleted means lost. .pp the command .i grep (from "g/re/p") finds occurrences of a string in one or more files. here it finds maja's telephone number. .ss pathnames and the current directory files live in a large tree, the file hierarchy. each has a .i "pathname" describing the path from the root of the tree (which is called .ir / ) to the file. for example, such a full pathname might be .ir /home/aeb/tel . always using full pathnames would be inconvenient, and the name of a file in the current directory may be abbreviated by giving only the last component. that is why .i /home/aeb/tel can be abbreviated to .i tel when the current directory is .ir /home/aeb . .pp the command .i pwd prints the current directory. .pp the command .i cd changes the current directory. .pp try alternatively .i cd and .i pwd commands and explore .i cd usage: "cd", "cd .", "cd ..", "cd /", and "cd \(ti". .ss directories the command .i mkdir makes a new directory. .pp the command .i rmdir removes a directory if it is empty, and complains otherwise. .pp the command .i find (with a rather baroque syntax) will find files with given name or other properties. for example, "find . \-name tel" would find the file .i tel starting in the present directory (which is called .ir . ). and "find / \-name tel" would do the same, but starting at the root of the tree. large searches on a multi-gb disk will be time-consuming, and it may be better to use .br locate (1). .ss disks and filesystems the command .i mount will attach the filesystem found on some disk (or floppy, or cdrom or so) to the big filesystem hierarchy. and .i umount detaches it again. the command .i df will tell you how much of your disk is still free. .ss processes on a unix system many user and system processes run simultaneously. the one you are talking to runs in the .ir foreground , the others in the .ir background . the command .i ps will show you which processes are active and what numbers these processes have. the command .i kill allows you to get rid of them. without option this is a friendly request: please go away. and "kill \-9" followed by the number of the process is an immediate kill. foreground processes can often be killed by typing control-c. .ss getting information there are thousands of commands, each with many options. traditionally commands are documented on .ir "man pages" , (like this one), so that the command "man kill" will document the use of the command "kill" (and "man man" document the command "man"). the program .i man sends the text through some .ir pager , usually .ir less . hit the space bar to get the next page, hit q to quit. .pp in documentation it is customary to refer to man pages by giving the name and section number, as in .br man (1). man pages are terse, and allow you to find quickly some forgotten detail. for newcomers an introductory text with more examples and explanations is useful. .pp a lot of gnu/fsf software is provided with info files. type "info info" for an introduction on the use of the program .ir info . .pp special topics are often treated in howtos. look in .i /usr/share/doc/howto/en and use a browser if you find html files there. .\" .\" actual examples? separate section for each of cat, cp, ...? .\" gzip, bzip2, tar, rpm .sh see also .br ash (1), .br bash (1), .br chsh (1), .br csh (1), .br dash (1), .br ksh (1), .br locate (1), .br login (1), .br man (1), .br xterm (1), .br zsh (1), .br wait (2), .br stdout (3), .br man\-pages (7), .br standards (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/cpu_set.3 .\" copyright (c) 2015 michael kerrisk .\" and copyright (c) 2008 petr baudis (dladdr caveat) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th dladdr 3 2021-03-22 "linux" "linux programmer's manual" .sh name dladdr, dladdr1 \- translate address to symbolic information .sh synopsis .nf .b #define _gnu_source .b #include .pp .bi "int dladdr(const void *" addr ", dl_info *" info ); .bi "int dladdr1(const void *" addr ", dl_info *" info ", void **" extra_info , .bi " int " flags ); .pp link with \fi\-ldl\fp. .fi .sh description the function .br dladdr () determines whether the address specified in .ir addr is located in one of the shared objects loaded by the calling application. if it is, then .br dladdr () returns information about the shared object and symbol that overlaps .ir addr . this information is returned in a .i dl_info structure: .pp .in +4n .ex typedef struct { const char *dli_fname; /* pathname of shared object that contains address */ void *dli_fbase; /* base address at which shared object is loaded */ const char *dli_sname; /* name of symbol whose definition overlaps \fiaddr\fp */ void *dli_saddr; /* exact address of symbol named in \fidli_sname\fp */ } dl_info; .ee .in .pp if no symbol matching .i addr could be found, then .i dli_sname and .i dli_saddr are set to null. .pp the function .br dladdr1 () is like .br dladdr (), but returns additional information via the argument .ir extra_info . the information returned depends on the value specified in .ir flags , which can have one of the following values: .tp .b rtld_dl_linkmap obtain a pointer to the link map for the matched file. the .ir extra_info argument points to a pointer to a .i link_map structure (i.e., .ir "struct link_map\ **" ), defined in .i as: .ip .in +4n .ex struct link_map { elfw(addr) l_addr; /* difference between the address in the elf file and the address in memory */ char *l_name; /* absolute pathname where object was found */ elfw(dyn) *l_ld; /* dynamic section of the shared object */ struct link_map *l_next, *l_prev; /* chain of loaded objects */ /* plus additional fields private to the implementation */ }; .ee .in .tp .b rtld_dl_syment obtain a pointer to the elf symbol table entry of the matching symbol. the .ir extra_info argument is a pointer to a symbol pointer: .ir "const elfw(sym) **" . the .ir elfw () macro definition turns its argument into the name of an elf data type suitable for the hardware architecture. for example, on a 64-bit platform, .i elfw(sym) yields the data type name .ir elf64_sym , which is defined in .ir as: .ip .in +4n .ex typedef struct { elf64_word st_name; /* symbol name */ unsigned char st_info; /* symbol type and binding */ unsigned char st_other; /* symbol visibility */ elf64_section st_shndx; /* section index */ elf64_addr st_value; /* symbol value */ elf64_xword st_size; /* symbol size */ } elf64_sym; .ee .in .ip the .i st_name field is an index into the string table. .ip the .i st_info field encodes the symbol's type and binding. the type can be extracted using the macro .br elf64_st_type(st_info) (or .br elf32_st_type() on 32-bit platforms), which yields one of the following values: .in +4n .ts lb lb lb l. value description stt_notype symbol type is unspecified stt_object symbol is a data object stt_func symbol is a code object stt_section symbol associated with a section stt_file symbol's name is filename stt_common symbol is a common data object stt_tls symbol is thread-local data object stt_gnu_ifunc symbol is indirect code object .te .in .ip the symbol binding can be extracted from the .i st_info field using the macro .br elf64_st_bind(st_info) (or .br elf32_st_bind() on 32-bit platforms), which yields one of the following values: .in +4n .ts lb lb lb l. value description stb_local local symbol stb_global global symbol stb_weak weak symbol stb_gnu_unique unique symbol .te .in .ip the .i st_other field contains the symbol's visibility, which can be extracted using the macro .br elf64_st_visibility(st_info) (or .br elf32_st_visibility() on 32-bit platforms), which yields one of the following values: .in +4n .ts lb lb lb l. value description stv_default default symbol visibility rules stv_internal processor-specific hidden class stv_hidden symbol unavailable in other modules stv_protected not preemptible, not exported .te .in .sh return value on success, these functions return a nonzero value. if the address specified in .i addr could be matched to a shared object, but not to a symbol in the shared object, then the .i info\->dli_sname and .i info\->dli_saddr fields are set to null. .pp if the address specified in .i addr could not be matched to a shared object, then these functions return 0. in this case, an error message is .i not .\" according to the freebsd man page, dladdr1() does signal an .\" error via dlerror() for this case. available via .br dlerror (3). .sh versions .br dladdr () is present in glibc 2.0 and later. .br dladdr1 () first appeared in glibc 2.3.3. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br dladdr (), .br dladdr1 () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to these functions are nonstandard gnu extensions that are also present on solaris. .sh bugs sometimes, the function pointers you pass to .br dladdr () may surprise you. on some architectures (notably i386 and x86-64), .i dli_fname and .i dli_fbase may end up pointing back at the object from which you called .br dladdr (), even if the function used as an argument should come from a dynamically linked library. .pp the problem is that the function pointer will still be resolved at compile time, but merely point to the .i plt (procedure linkage table) section of the original object (which dispatches the call after asking the dynamic linker to resolve the symbol). to work around this, you can try to compile the code to be position-independent: then, the compiler cannot prepare the pointer at compile time any more and .br gcc (1) will generate code that just loads the final symbol address from the .i got (global offset table) at run time before passing it to .br dladdr (). .sh see also .br dl_iterate_phdr (3), .br dlinfo (3), .br dlopen (3), .br dlsym (3), .br ld.so (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2018 eugene syromyatnikov .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th s390_guarded_storage 2 2021-03-22 "linux programmer's manual" .sh name s390_guarded_storage \- operations with z/architecture guarded storage facility .sh synopsis .nf .br "#include " "/* definition of " gs_* " constants */" .br "#include " \ "/* definition of " sys_* " constants */" .b #include .pp .bi "int syscall(sys_s390_guarded_storage, int " command , .bi " struct gs_cb *" gs_cb ); .fi .pp .ir note : glibc provides no wrapper for .br s390_guarded_storage (), necessitating the use of .br syscall (2). .sh description the .br s390_guarded_storage () system call enables the use of the guarded storage facility (a z/architecture-specific feature) for user-space processes. .pp .\" the description is based on .\" http://www-05.ibm.com/de/linux-on-z-ws-us/agenda/pdfs/8_-_linux_whats_new_-_stefan_raspl.pdf .\" and "z/architecture principles of operation" obtained from .\" http://publibfi.boulder.ibm.com/epubs/pdf/dz9zr011.pdf the guarded storage facility is a hardware feature that allows marking up to 64 memory regions (as of z14) as guarded; reading a pointer with a newly introduced "load guarded" (lgg) or "load logical and shift guarded" (llgfsg) instructions will cause a range check on the loaded value and invoke a (previously set up) user-space handler if one of the guarded regions is affected. .pp the .\" the command description is copied from v4.12-rc1~139^2~56^2 commit message .i command argument indicates which function to perform. the following commands are supported: .tp .b gs_enable enable the guarded storage facility for the calling task. the initial content of the guarded storage control block will be all zeros. after enablement, user-space code can use the "load guarded storage controls" (lgsc) instruction (or the .br load_gs_cb () function wrapper provided in the .i asm/guarded_storage.h header) to load an arbitrary control block. while a task is enabled, the kernel will save and restore the calling content of the guarded storage registers on context switch. .tp .b gs_disable disables the use of the guarded storage facility for the calling task. the kernel will cease to save and restore the content of the guarded storage registers, the task-specific content of these registers is lost. .tp .b gs_set_bc_cb set a broadcast guarded storage control block to the one provided in the .i gs_cb argument. this is called per thread and associates a specific guarded storage control block with the calling task. this control block will be used in the broadcast command .br gs_broadcast . .tp .b gs_clear_bc_cb clears the broadcast guarded storage control block. the guarded storage control block will no longer have the association established by the .b gs_set_bc_cb command. .tp .b gs_broadcast sends a broadcast to all thread siblings of the calling task. every sibling that has established a broadcast guarded storage control block will load this control block and will be enabled for guarded storage. the broadcast guarded storage control block is consumed; a second broadcast without a refresh of the stored control block with .b gs_set_bc_cb will not have any effect. .pp the .i gs_cb argument specifies the address of a guarded storage control block structure and is currently used only by the .b gs_set_bc_cb command; all other aforementioned commands ignore this argument. .sh return value on success, the return value of .br s390_guarded_storage () is 0. .pp on error, \-1 is returned, and .ir errno is set to indicate the error. .sh errors .tp .b efault .i command was .br gs_set_bc_cb and the copying of the guarded storage control block structure pointed by the .i gs_cb argument has failed. .tp .b einval the value provided in the .i command argument was not valid. .tp .b enomem .i command was one of .br gs_enable " or " gs_set_bc_cb , and the allocation of a new guarded storage control block has failed. .tp .b eopnotsupp the guarded storage facility is not supported by the hardware. .sh versions .\" 916cda1aa1b412d7cf2991c3af7479544942d121, v4.12-rc1~139^2~56^2 this system call is available since linux 4.12. .sh conforming to this linux-specific system call is available only on the s390 architecture. .pp the guarded storage facility is available beginning with system z14. .sh notes the description of the guarded storage facility along with related instructions and guarded storage control block and guarded storage event parameter list structure layouts is available in "z/architecture principles of operations" beginning from the twelfth edition. .pp the .i gs_cb structure has a field .i gsepla (guarded storage event parameter list address), which is a user-space pointer to a guarded storage event parameter list structure (that contains the address of the aforementioned event handler in the .i gseha field), and its layout is available as a .b gs_epl structure type definition in the .i asm/guarded_storage.h header. .\" .pp .\" for the example of using the guarded storage facility, see .\" .ur https://developer.ibm.com/javasdk/2017/09/25/concurrent-scavenge-using-guarded-storage-facility-works/ .\" the article with the description of its usage in the java garbage collection .\" .ue .sh see also .br syscall (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2016 michael kerrisk .\" and copyright (c) 2016 eugene syromyatnikov .\" a very few fragments remain from an earlier version of this page .\" written by david howells (dhowells@redhat.com) .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th keyctl 2 2021-08-27 linux "linux key management calls" .sh name keyctl \- manipulate the kernel's key management facility .sh synopsis .nf .br "#include " " /* definition of " key* " constants */" .br "#include " " /* definition of " sys_* " constants */" .b #include .pp .bi "long syscall(sys_keyctl, int " operation ", unsigned long " arg2 , .bi " unsigned long " arg3 ", unsigned long " arg4 , .bi " unsigned long " arg5 ); .fi .pp .ir note : glibc provides no wrapper for .br keyctl (), necessitating the use of .br syscall (2). .sh description .br keyctl () allows user-space programs to perform key manipulation. .pp the operation performed by .br keyctl () is determined by the value of the .i operation argument. each of these operations is wrapped by the .i libkeyutils library (provided by the .i keyutils package) into individual functions (noted below) to permit the compiler to check types. .pp the permitted values for .i operation are: .tp .br keyctl_get_keyring_id " (since linux 2.6.10)" map a special key id to a real key id for this process. .ip this operation looks up the special key whose id is provided in .i arg2 (cast to .ir key_serial_t ). if the special key is found, the id of the corresponding real key is returned as the function result. the following values may be specified in .ir arg2 : .rs .tp .b key_spec_thread_keyring this specifies the calling thread's thread-specific keyring. see .br thread\-keyring (7). .tp .b key_spec_process_keyring this specifies the caller's process-specific keyring. see .br process\-keyring (7). .tp .b key_spec_session_keyring this specifies the caller's session-specific keyring. see .br session\-keyring (7). .tp .b key_spec_user_keyring this specifies the caller's uid-specific keyring. see .br user\-keyring (7). .tp .b key_spec_user_session_keyring this specifies the caller's uid-session keyring. see .br user\-session\-keyring (7). .tp .br key_spec_reqkey_auth_key " (since linux 2.6.16)" .\" commit b5f545c880a2a47947ba2118b2509644ab7a2969 this specifies the authorization key created by .br request_key (2) and passed to the process it spawns to generate a key. this key is available only in a .br request\-key (8)-style program that was passed an authorization key by the kernel and ceases to be available once the requested key has been instantiated; see .br request_key (2). .tp .br key_spec_requestor_keyring " (since linux 2.6.29)" .\" commit 8bbf4976b59fc9fc2861e79cab7beb3f6d647640 this specifies the key id for the .br request_key (2) destination keyring. this keyring is available only in a .br request\-key (8)-style program that was passed an authorization key by the kernel and ceases to be available once the requested key has been instantiated; see .br request_key (2). .re .ip the behavior if the key specified in .i arg2 does not exist depends on the value of .i arg3 (cast to .ir int ). if .i arg3 contains a nonzero value, then\(emif it is appropriate to do so (e.g., when looking up the user, user-session, or session key)\(ema new key is created and its real key id returned as the function result. .\" the keyctl_get_keyring_id.3 page says that a new key .\" "will be created *if it is appropriate to do so**. what is the .\" determiner for appropriate? .\" david howells: some special keys such as key_spec_reqkey_auth_key .\" wouldn't get created but user/user-session/session keyring would .\" be created. otherwise, the operation fails with the error .br enokey . .ip if a valid key id is specified in .ir arg2 , and the key exists, then this operation simply returns the key id. if the key does not exist, the call fails with error .br enokey . .ip the caller must have .i search permission on a keyring in order for it to be found. .ip the arguments .ir arg4 and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_get_keyring_id (3). .tp .br keyctl_join_session_keyring " (since linux 2.6.10)" replace the session keyring this process subscribes to with a new session keyring. .\" this may be useful in conjunction with some sort of .\" session management framework that is employed by the application. .ip if .i arg2 is null, an anonymous keyring with the description "_ses" is created and the process is subscribed to that keyring as its session keyring, displacing the previous session keyring. .ip otherwise, .i arg2 (cast to .ir "char\ *" ) is treated as the description (name) of a keyring, and the behavior is as follows: .rs .ip * 3 if a keyring with a matching description exists, the process will attempt to subscribe to that keyring as its session keyring if possible; if that is not possible, an error is returned. in order to subscribe to the keyring, the caller must have .i search permission on the keyring. .ip * if a keyring with a matching description does not exist, then a new keyring with the specified description is created, and the process is subscribed to that keyring as its session keyring. .re .ip the arguments .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_join_session_keyring (3). .tp .br keyctl_update " (since linux 2.6.10)" update a key's data payload. .ip the .i arg2 argument (cast to .ir key_serial_t ) specifies the id of the key to be updated. the .i arg3 argument (cast to .ir "void\ *" ) points to the new payload and .i arg4 (cast to .ir size_t ) contains the new payload size in bytes. .ip the caller must have .i write permission on the key specified and the key type must support updating. .ip a negatively instantiated key (see the description of .br keyctl_reject ) can be positively instantiated with this operation. .ip the .i arg5 argument is ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_update (3). .tp .br keyctl_revoke " (since linux 2.6.10)" revoke the key with the id provided in .i arg2 (cast to .ir key_serial_t ). the key is scheduled for garbage collection; it will no longer be findable, and will be unavailable for further operations. further attempts to use the key will fail with the error .br ekeyrevoked . .ip the caller must have .ir write or .ir setattr permission on the key. .\" keys with the key_flag_keep bit set cause an eperm .\" error for keyctl_revoke. does this need to be documented? .\" david howells: no significance for user space. .ip the arguments .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_revoke (3). .tp .br keyctl_chown " (since linux 2.6.10)" change the ownership (user and group id) of a key. .ip the .i arg2 argument (cast to .ir key_serial_t ) contains the key id. the .i arg3 argument (cast to .ir uid_t ) contains the new user id (or \-1 in case the user id shouldn't be changed). the .i arg4 argument (cast to .ir gid_t ) contains the new group id (or \-1 in case the group id shouldn't be changed). .ip the key must grant the caller .i setattr permission. .ip for the uid to be changed, or for the gid to be changed to a group the caller is not a member of, the caller must have the .b cap_sys_admin capability (see .br capabilities (7)). .ip if the uid is to be changed, the new user must have sufficient quota to accept the key. the quota deduction will be removed from the old user to the new user should the uid be changed. .ip the .i arg5 argument is ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_chown (3). .tp .br keyctl_setperm " (since linux 2.6.10)" change the permissions of the key with the id provided in the .i arg2 argument (cast to .ir key_serial_t ) to the permissions provided in the .i arg3 argument (cast to .ir key_perm_t ). .ip if the caller doesn't have the .b cap_sys_admin capability, it can change permissions only for the keys it owns. (more precisely: the caller's filesystem uid must match the uid of the key.) .ip the key must grant .i setattr permission to the caller .ir regardless of the caller's capabilities. .\" fixme above, is it really intended that a privileged process can't .\" override the lack of the 'setattr' permission? .ip the permissions in .ir arg3 specify masks of available operations for each of the following user categories: .rs .tp .ir possessor " (since linux 2.6.14)" .\" commit 664cceb0093b755739e56572b836a99104ee8a75 this is the permission granted to a process that possesses the key (has it attached searchably to one of the process's keyrings); see .br keyrings (7). .tp .ir user this is the permission granted to a process whose filesystem uid matches the uid of the key. .tp .ir group this is the permission granted to a process whose filesystem gid or any of its supplementary gids matches the gid of the key. .tp .ir other this is the permission granted to other processes that do not match the .ir user and .ir group categories. .re .ip the .ir user , .ir group , and .ir other categories are exclusive: if a process matches the .ir user category, it will not receive permissions granted in the .ir group category; if a process matches the .i user or .ir group category, then it will not receive permissions granted in the .ir other category. .ip the .i possessor category grants permissions that are cumulative with the grants from the .ir user , .ir group , or .ir other category. .ip each permission mask is eight bits in size, with only six bits currently used. the available permissions are: .rs .tp .ir view this permission allows reading attributes of a key. .ip this permission is required for the .br keyctl_describe operation. .ip the permission bits for each category are .br key_pos_view , .br key_usr_view , .br key_grp_view , and .br key_oth_view . .tp .ir read this permission allows reading a key's payload. .ip this permission is required for the .br keyctl_read operation. .ip the permission bits for each category are .br key_pos_read , .br key_usr_read , .br key_grp_read , and .br key_oth_read . .tp .ir write this permission allows update or instantiation of a key's payload. for a keyring, it allows keys to be linked and unlinked from the keyring, .ip this permission is required for the .br keyctl_update , .br keyctl_revoke , .br keyctl_clear , .br keyctl_link , and .br keyctl_unlink operations. .ip the permission bits for each category are .br key_pos_write , .br key_usr_write , .br key_grp_write , and .br key_oth_write . .tp .ir search this permission allows keyrings to be searched and keys to be found. searches can recurse only into nested keyrings that have .i search permission set. .ip this permission is required for the .br keyctl_get_keyring_id , .br keyctl_join_session_keyring , .br keyctl_search , and .br keyctl_invalidate operations. .ip the permission bits for each category are .br key_pos_search , .br key_usr_search , .br key_grp_search , and .br key_oth_search . .tp .ir link this permission allows a key or keyring to be linked to. .ip this permission is required for the .br keyctl_link and .br keyctl_session_to_parent operations. .ip the permission bits for each category are .br key_pos_link , .br key_usr_link , .br key_grp_link , and .br key_oth_link . .tp .ir setattr " (since linux 2.6.15)." this permission allows a key's uid, gid, and permissions mask to be changed. .ip this permission is required for the .br keyctl_revoke , .br keyctl_chown , and .br keyctl_setperm operations. .ip the permission bits for each category are .br key_pos_setattr , .br key_usr_setattr , .br key_grp_setattr , and .br key_oth_setattr . .re .ip as a convenience, the following macros are defined as masks for all of the permission bits in each of the user categories: .br key_pos_all , .br key_usr_all , .br key_grp_all , and .br key_oth_all . .ip the .ir arg4 " and " arg5 arguments are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_setperm (3). .tp .br keyctl_describe " (since linux 2.6.10)" obtain a string describing the attributes of a specified key. .ip the id of the key to be described is specified in .i arg2 (cast to .ir key_serial_t ). the descriptive string is returned in the buffer pointed to by .i arg3 (cast to .ir "char\ *" ); .i arg4 (cast to .ir size_t ) specifies the size of that buffer in bytes. .ip the key must grant the caller .i view permission. .ip the returned string is null-terminated and contains the following information about the key: .ip .in +4n .ir type ; uid ; gid ; perm ; description .in .ip in the above, .ir type and .ir description are strings, .ir uid and .ir gid are decimal strings, and .i perm is a hexadecimal permissions mask. the descriptive string is written with the following format: .ip %s;%d;%d;%08x;%s .ip .br "note: the intention is that the descriptive string should" .br "be extensible in future kernel versions". in particular, the .ir description field will not contain semicolons; .\" fixme but, the kernel does not enforce the requirement .\" that the key description contains no semicolons! .\" so, user space has no guarantee here?? .\" either something more needs to be said here, .\" or a kernel fix is required. it should be parsed by working backwards from the end of the string to find the last semicolon. this allows future semicolon-delimited fields to be inserted in the descriptive string in the future. .ip writing to the buffer is attempted only when .ir arg3 is non-null and the specified buffer size is large enough to accept the descriptive string (including the terminating null byte). .\" function commentary says it copies up to buflen bytes, but see the .\" (buffer && buflen >= ret) condition in keyctl_describe_key() in .\" security/keyctl.c in order to determine whether the buffer size was too small, check to see if the return value of the operation is greater than .ir arg4 . .ip the .i arg5 argument is ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_describe (3). .tp .b keyctl_clear clear the contents of (i.e., unlink all keys from) a keyring. .ip the id of the key (which must be of keyring type) .\" or the error enotdir results is provided in .i arg2 (cast to .ir key_serial_t ). .\" according to documentation/security/keys.txt: .\" this function can also be used to clear special kernel keyrings if they .\" are appropriately marked if the user has cap_sys_admin capability. the .\" dns resolver cache keyring is an example of this. .ip the caller must have .i write permission on the keyring. .ip the arguments .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_clear (3). .tp .br keyctl_link " (since linux 2.6.10)" create a link from a keyring to a key. .ip the key to be linked is specified in .ir arg2 (cast to .ir key_serial_t ); the keyring is specified in .ir arg3 (cast to .ir key_serial_t ). .ip if a key with the same type and description is already linked in the keyring, then that key is displaced from the keyring. .ip before creating the link, the kernel checks the nesting of the keyrings and returns appropriate errors if the link would produce a cycle or if the nesting of keyrings would be too deep (the limit on the nesting of keyrings is determined by the kernel constant .br keyring_search_max_depth , defined with the value 6, and is necessary to prevent overflows on the kernel stack when recursively searching keyrings). .ip the caller must have .i link permission on the key being added and .i write permission on the keyring. .ip the arguments .ir arg4 and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_link (3). .tp .br keyctl_unlink " (since linux 2.6.10)" unlink a key from a keyring. .ip the id of the key to be unlinked is specified in .i arg2 (cast to .ir key_serial_t ); the id of the keyring from which it is to be unlinked is specified in .i arg3 (cast to .ir key_serial_t ). .ip if the key is not currently linked into the keyring, an error results. .ip the caller must have .i write permission on the keyring from which the key is being removed. .ip if the last link to a key is removed, then that key will be scheduled for destruction. .ip the arguments .ir arg4 and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_unlink (3). .tp .br keyctl_search " (since linux 2.6.10)" search for a key in a keyring tree, returning its id and optionally linking it to a specified keyring. .ip the tree to be searched is specified by passing the id of the head keyring in .ir arg2 (cast to .ir key_serial_t ). the search is performed breadth-first and recursively. .ip the .i arg3 and .i arg4 arguments specify the key to be searched for: .i arg3 (cast as .ir "char\ *" ) contains the key type (a null-terminated character string up to 32 bytes in size, including the terminating null byte), and .i arg4 (cast as .ir "char\ *" ) contains the description of the key (a null-terminated character string up to 4096 bytes in size, including the terminating null byte). .ip the source keyring must grant .i search permission to the caller. when performing the recursive search, only keyrings that grant the caller .i search permission will be searched. only keys with for which the caller has .i search permission can be found. .ip if the key is found, its id is returned as the function result. .ip if the key is found and .i arg5 (cast to .ir key_serial_t ) is nonzero, then, subject to the same constraints and rules as .br keyctl_link , the key is linked into the keyring whose id is specified in .ir arg5 . if the destination keyring specified in .i arg5 already contains a link to a key that has the same type and description, then that link will be displaced by a link to the key found by this operation. .ip instead of valid existing keyring ids, the source .ri ( arg2 ) and destination .ri ( arg5 ) keyrings can be one of the special keyring ids listed under .br keyctl_get_keyring_id . .ip this operation is exposed by .i libkeyutils via the function .br keyctl_search (3). .tp .br keyctl_read " (since linux 2.6.10)" read the payload data of a key. .ip the id of the key whose payload is to be read is specified in .i arg2 (cast to .ir key_serial_t ). this can be the id of an existing key, or any of the special key ids listed for .br keyctl_get_keyring_id . .\" including key_spec_reqkey_auth_key .ip the payload is placed in the buffer pointed by .i arg3 (cast to .ir "char\ *" ); the size of that buffer must be specified in .i arg4 (cast to .ir size_t ). .ip the returned data will be processed for presentation according to the key type. for example, a keyring will return an array of .i key_serial_t entries representing the ids of all the keys that are linked to it. the .ir "user" key type will return its data as is. if a key type does not implement this function, the operation fails with the error .br eopnotsupp . .ip if .i arg3 is not null, as much of the payload data as will fit is copied into the buffer. on a successful return, the return value is always the total size of the payload data. to determine whether the buffer was of sufficient size, check to see that the return value is less than or equal to the value supplied in .ir arg4 . .ip the key must either grant the caller .i read permission, or grant the caller .i search permission when searched for from the process keyrings (i.e., the key is possessed). .ip the .i arg5 argument is ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_read (3). .tp .br keyctl_instantiate " (since linux 2.6.10)" (positively) instantiate an uninstantiated key with a specified payload. .ip the id of the key to be instantiated is provided in .i arg2 (cast to .ir key_serial_t ). .ip the key payload is specified in the buffer pointed to by .i arg3 (cast to .ir "void\ *"); the size of that buffer is specified in .i arg4 (cast to .ir size_t ). .ip the payload may be a null pointer and the buffer size may be 0 if this is supported by the key type (e.g., it is a keyring). .ip the operation may be fail if the payload data is in the wrong format or is otherwise invalid. .ip if .i arg5 (cast to .ir key_serial_t ) is nonzero, then, subject to the same constraints and rules as .br keyctl_link , the instantiated key is linked into the keyring whose id specified in .ir arg5 . .ip the caller must have the appropriate authorization key, and once the uninstantiated key has been instantiated, the authorization key is revoked. in other words, this operation is available only from a .br request\-key (8)-style program. see .br request_key (2) for an explanation of uninstantiated keys and key instantiation. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_instantiate (3). .tp .br keyctl_negate " (since linux 2.6.10)" negatively instantiate an uninstantiated key. .ip this operation is equivalent to the call: .ip keyctl(keyctl_reject, arg2, arg3, enokey, arg4); .ip the .i arg5 argument is ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_negate (3). .tp .br keyctl_set_reqkey_keyring " (since linux 2.6.13)" set the default keyring to which implicitly requested keys will be linked for this thread, and return the previous setting. implicit key requests are those made by internal kernel components, .\" i.e., calls to the kernel's internal request_key() interface, .\" which is distinct from the request_key(2) system call (which .\" ultimately employs the kernel-internal interface). such as can occur when, for example, opening files on an afs or nfs filesystem. setting the default keyring also has an effect when requesting a key from user space; see .br request_key (2) for details. .ip the .i arg2 argument (cast to .ir int ) should contain one of the following values, to specify the new default keyring: .rs .tp .br key_reqkey_defl_no_change don't change the default keyring. this can be used to discover the current default keyring (without changing it). .tp .br key_reqkey_defl_default this selects the default behaviour, which is to use the thread-specific keyring if there is one, otherwise the process-specific keyring if there is one, otherwise the session keyring if there is one, otherwise the uid-specific session keyring, otherwise the user-specific keyring. .tp .br key_reqkey_defl_thread_keyring use the thread-specific keyring .rb ( thread\-keyring (7)) as the new default keyring. .tp .br key_reqkey_defl_process_keyring use the process-specific keyring .rb ( process\-keyring (7)) as the new default keyring. .tp .br key_reqkey_defl_session_keyring use the session-specific keyring .rb ( session\-keyring (7)) as the new default keyring. .tp .br key_reqkey_defl_user_keyring use the uid-specific keyring .rb ( user\-keyring (7)) as the new default keyring. .tp .br key_reqkey_defl_user_session_keyring use the uid-specific session keyring .rb ( user\-session\-keyring (7)) as the new default keyring. .tp .br key_reqkey_defl_requestor_keyring " (since linux 2.6.29)" .\" 8bbf4976b59fc9fc2861e79cab7beb3f6d647640 use the requestor keyring. .\" fixme the preceding explanation needs to be expanded. .\" is the following correct: .\" .\" the requestor keyring is the dest_keyring that .\" was supplied to a call to request_key(2)? .\" .\" david howells said: to be checked .re .ip all other values are invalid. .\" (including the still-unsupported key_reqkey_defl_group_keyring) .ip the arguments .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip the setting controlled by this operation is inherited by the child of .br fork (2) and preserved across .br execve (2). .ip this operation is exposed by .i libkeyutils via the function .br keyctl_set_reqkey_keyring (3). .tp .br keyctl_set_timeout " (since linux 2.6.16)" set a timeout on a key. .ip the id of the key is specified in .i arg2 (cast to .ir key_serial_t ). the timeout value, in seconds from the current time, is specified in .i arg3 (cast to .ir "unsigned int" ). the timeout is measured against the realtime clock. .ip specifying the timeout value as 0 clears any existing timeout on the key. .ip the .i /proc/keys file displays the remaining time until each key will expire. (this is the only method of discovering the timeout on a key.) .ip the caller must either have the .i setattr permission on the key or hold an instantiation authorization token for the key (see .br request_key (2)). .ip the key and any links to the key will be automatically garbage collected after the timeout expires. subsequent attempts to access the key will then fail with the error .br ekeyexpired . .ip this operation cannot be used to set timeouts on revoked, expired, or negatively instantiated keys. .ip the arguments .ir arg4 and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_set_timeout (3). .tp .br keyctl_assume_authority " (since linux 2.6.16)" assume (or divest) the authority for the calling thread to instantiate a key. .ip the .i arg2 argument (cast to .ir key_serial_t ) specifies either a nonzero key id to assume authority, or the value 0 to divest authority. .ip if .i arg2 is nonzero, then it specifies the id of an uninstantiated key for which authority is to be assumed. that key can then be instantiated using one of .br keyctl_instantiate , .br keyctl_instantiate_iov , .br keyctl_reject , or .br keyctl_negate . once the key has been instantiated, the thread is automatically divested of authority to instantiate the key. .ip authority over a key can be assumed only if the calling thread has present in its keyrings the authorization key that is associated with the specified key. (in other words, the .br keyctl_assume_authority operation is available only from a .br request\-key (8)-style program; see .br request_key (2) for an explanation of how this operation is used.) the caller must have .i search permission on the authorization key. .ip if the specified key has a matching authorization key, then the id of that key is returned. the authorization key can be read .rb ( keyctl_read ) to obtain the callout information passed to .br request_key (2). .ip if the id given in .i arg2 is 0, then the currently assumed authority is cleared (divested), and the value 0 is returned. .ip the .br keyctl_assume_authority mechanism allows a program such as .br request\-key (8) to assume the necessary authority to instantiate a new uninstantiated key that was created as a consequence of a call to .br request_key (2). for further information, see .br request_key (2) and the kernel source file .ir documentation/security/keys\-request\-key.txt . .ip the arguments .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_assume_authority (3). .tp .br keyctl_get_security " (since linux 2.6.26)" .\" commit 70a5bb72b55e82fbfbf1e22cae6975fac58a1e2d get the lsm (linux security module) security label of the specified key. .ip the id of the key whose security label is to be fetched is specified in .i arg2 (cast to .ir key_serial_t ). the security label (terminated by a null byte) will be placed in the buffer pointed to by .i arg3 argument (cast to .ir "char\ *" ); the size of the buffer must be provided in .i arg4 (cast to .ir size_t ). .ip if .i arg3 is specified as null or the buffer size specified in .ir arg4 is too small, the full size of the security label string (including the terminating null byte) is returned as the function result, and nothing is copied to the buffer. .ip the caller must have .i view permission on the specified key. .ip the returned security label string will be rendered in a form appropriate to the lsm in force. for example, with selinux, it may look like: .ip unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 .ip if no lsm is currently in force, then an empty string is placed in the buffer. .ip the .i arg5 argument is ignored. .ip this operation is exposed by .i libkeyutils via the functions .br keyctl_get_security (3) and .br keyctl_get_security_alloc (3). .tp .br keyctl_session_to_parent " (since linux 2.6.32)" .\" commit ee18d64c1f632043a02e6f5ba5e045bb26a5465f replace the session keyring to which the .i parent of the calling process subscribes with the session keyring of the calling process. .\" what is the use case for keyctl_session_to_parent? .\" david howells: the process authentication groups people requested this, .\" but then didn't use it; maybe there are no users. .ip the keyring will be replaced in the parent process at the point where the parent next transitions from kernel space to user space. .ip the keyring must exist and must grant the caller .i link permission. the parent process must be single-threaded and have the same effective ownership as this process and must not be set-user-id or set-group-id. the uid of the parent process's existing session keyring (f it has one), as well as the uid of the caller's session keyring much match the caller's effective uid. .ip the fact that it is the parent process that is affected by this operation allows a program such as the shell to start a child process that uses this operation to change the shell's session keyring. (this is what the .br keyctl (1) .b new_session command does.) .ip the arguments .ir arg2 , .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_session_to_parent (3). .tp .br keyctl_reject " (since linux 2.6.39)" .\" commit fdd1b94581782a2ddf9124414e5b7a5f48ce2f9c mark a key as negatively instantiated and set an expiration timer on the key. this operation provides a superset of the functionality of the earlier .br keyctl_negate operation. .ip the id of the key that is to be negatively instantiated is specified in .i arg2 (cast to .ir key_serial_t ). the .i arg3 (cast to .ir "unsigned int" ) argument specifies the lifetime of the key, in seconds. the .i arg4 argument (cast to .ir "unsigned int" ) specifies the error to be returned when a search hits this key; typically, this is one of .br ekeyrejected , .br ekeyrevoked , or .br ekeyexpired . .ip if .i arg5 (cast to .ir key_serial_t ) is nonzero, then, subject to the same constraints and rules as .br keyctl_link , the negatively instantiated key is linked into the keyring whose id is specified in .ir arg5 . .ip the caller must have the appropriate authorization key. in other words, this operation is available only from a .br request\-key (8)-style program. see .br request_key (2). .ip the caller must have the appropriate authorization key, and once the uninstantiated key has been instantiated, the authorization key is revoked. in other words, this operation is available only from a .br request\-key (8)-style program. see .br request_key (2) for an explanation of uninstantiated keys and key instantiation. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_reject (3). .tp .br keyctl_instantiate_iov " (since linux 2.6.39)" .\" commit ee009e4a0d4555ed522a631bae9896399674f063 instantiate an uninstantiated key with a payload specified via a vector of buffers. .ip this operation is the same as .br keyctl_instantiate , but the payload data is specified as an array of .ir iovec structures: .ip .in +4n .ex struct iovec { void *iov_base; /* starting address of buffer */ size_t iov_len; /* size of buffer (in bytes) */ }; .ee .in .ip the pointer to the payload vector is specified in .ir arg3 (cast as .ir "const struct iovec\ *" ). the number of items in the vector is specified in .ir arg4 (cast as .ir "unsigned int" ). .ip the .i arg2 (key id) and .i arg5 (keyring id) are interpreted as for .br keyctl_instantiate . .ip this operation is exposed by .i libkeyutils via the function .br keyctl_instantiate_iov (3). .tp .br keyctl_invalidate " (since linux 3.5)" .\" commit fd75815f727f157a05f4c96b5294a4617c0557da mark a key as invalid. .ip the id of the key to be invalidated is specified in .i arg2 (cast to .ir key_serial_t ). .ip to invalidate a key, the caller must have .i search permission on the key. .\" cap_sys_admin is permitted to invalidate certain special keys .ip this operation marks the key as invalid and schedules immediate garbage collection. the garbage collector removes the invalidated key from all keyrings and deletes the key when its reference count reaches zero. after this operation, the key will be ignored by all searches, even if it is not yet deleted. .ip keys that are marked invalid become invisible to normal key operations immediately, though they are still visible in .i /proc/keys (marked with an 'i' flag) until they are actually removed. .ip the arguments .ir arg3 , .ir arg4 , and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_invalidate (3). .tp .br keyctl_get_persistent " (since linux 3.13)" .\" commit f36f8c75ae2e7d4da34f4c908cebdb4aa42c977e get the persistent keyring .rb ( persistent\-keyring (7)) for a specified user and link it to a specified keyring. .ip the user id is specified in .i arg2 (cast to .ir uid_t ). if the value \-1 is specified, the caller's real user id is used. the id of the destination keyring is specified in .i arg3 (cast to .ir key_serial_t ). .ip the caller must have the .br cap_setuid capability in its user namespace in order to fetch the persistent keyring for a user id that does not match either the real or effective user id of the caller. .ip if the call is successful, a link to the persistent keyring is added to the keyring whose id was specified in .ir arg3 . .ip the caller must have .i write permission on the keyring. .ip the persistent keyring will be created by the kernel if it does not yet exist. .ip each time the .b keyctl_get_persistent operation is performed, the persistent keyring will have its expiration timeout reset to the value in: .ip .in +4n .ex /proc/sys/kernel/keys/persistent_keyring_expiry .ee .in .ip should the timeout be reached, the persistent keyring will be removed and everything it pins can then be garbage collected. .ip persistent keyrings were added to linux in kernel version 3.13. .ip the arguments .ir arg4 and .ir arg5 are ignored. .ip this operation is exposed by .i libkeyutils via the function .br keyctl_get_persistent (3). .tp .br keyctl_dh_compute " (since linux 4.7)" .\" commit ddbb41148724367394d0880c516bfaeed127b52e compute a diffie-hellman shared secret or public key, optionally applying key derivation function (kdf) to the result. .ip the .i arg2 argument is a pointer to a set of parameters containing serial numbers for three .ir """user""" keys used in the diffie-hellman calculation, packaged in a structure of the following form: .ip .in +4n .ex struct keyctl_dh_params { int32_t private; /* the local private key */ int32_t prime; /* the prime, known to both parties */ int32_t base; /* the base integer: either a shared generator or the remote public key */ }; .ee .in .ip each of the three keys specified in this structure must grant the caller .i read permission. the payloads of these keys are used to calculate the diffie-hellman result as: .ip base \(ha private mod prime .ip if the base is the shared generator, the result is the local public key. if the base is the remote public key, the result is the shared secret. .ip the .i arg3 argument (cast to .ir "char\ *" ) points to a buffer where the result of the calculation is placed. the size of that buffer is specified in .i arg4 (cast to .ir size_t ). .ip the buffer must be large enough to accommodate the output data, otherwise an error is returned. if .i arg4 is specified zero, in which case the buffer is not used and the operation returns the minimum required buffer size (i.e., the length of the prime). .ip diffie-hellman computations can be performed in user space, but require a multiple-precision integer (mpi) library. moving the implementation into the kernel gives access to the kernel mpi implementation, and allows access to secure or acceleration hardware. .ip adding support for dh computation to the .br keyctl () system call was considered a good fit due to the dh algorithm's use for deriving shared keys; it also allows the type of the key to determine which dh implementation (software or hardware) is appropriate. .\" commit f1c316a3ab9d24df6022682422fe897492f2c0c8 .ip if the .i arg5 argument is .br null , then the dh result itself is returned. otherwise (since linux 4.12), it is a pointer to a structure which specifies parameters of the kdf operation to be applied: .ip .in +4n .ex struct keyctl_kdf_params { char *hashname; /* hash algorithm name */ char *otherinfo; /* sp800\-56a otherinfo */ __u32 otherinfolen; /* length of otherinfo data */ __u32 __spare[8]; /* reserved */ }; .ee .in .ip the .i hashname field is a null-terminated string which specifies a hash name (available in the kernel's crypto api; the list of the hashes available is rather tricky to observe; please refer to the .ur https://www.kernel.org\:/doc\:/html\:/latest\:/crypto\:/architecture.html "kernel crypto api architecture" .ue documentation for the information regarding how hash names are constructed and your kernel's source and configuration regarding what ciphers and templates with type .b crypto_alg_type_shash are available) to be applied to dh result in kdf operation. .ip the .i otherinfo field is an .i otherinfo data as described in sp800-56a section 5.8.1.2 and is algorithm-specific. this data is concatenated with the result of dh operation and is provided as an input to the kdf operation. its size is provided in the .i otherinfolen field and is limited by .b keyctl_kdf_max_oi_len constant that defined in .i security/keys/internal.h to a value of 64. .ip the .b __spare field is currently unused. .\" commit 4f9dabfaf8df971f8a3b6aa324f8f817be38d538 it was ignored until linux 4.13 (but still should be user-addressable since it is copied to the kernel), and should contain zeros since linux 4.13. .ip the kdf implementation complies with sp800-56a as well as with sp800-108 (the counter kdf). .ip .\" keyutils commit 742c9d7b94051d3b21f9f61a73ed6b5f3544cb82 .\" keyutils commit d68a981e5db41d059ac782071c35d1e8f3aaf61c this operation is exposed by .i libkeyutils (from version 1.5.10 onwards) via the functions .br keyctl_dh_compute (3) and .br keyctl_dh_compute_alloc (3). .tp .br keyctl_restrict_keyring " (since linux 4.12)" .\" commit 6563c91fd645556c7801748f15bc727c77fcd311 .\" commit 7228b66aaf723a623e578aa4db7d083bb39546c9 apply a key-linking restriction to the keyring with the id provided in .ir arg2 (cast to .ir key_serial_t ). the caller must have .ir setattr permission on the key. if .i arg3 is null, any attempt to add a key to the keyring is blocked; otherwise it contains a pointer to a string with a key type name and .i arg4 contains a pointer to string that describes the type-specific restriction. as of linux 4.12, only the type "asymmetric" has restrictions defined: .rs .tp .b builtin_trusted allows only keys that are signed by a key linked to the built-in keyring (".builtin_trusted_keys"). .tp .b builtin_and_secondary_trusted allows only keys that are signed by a key linked to the secondary keyring (".secondary_trusted_keys") or, by extension, a key in a built-in keyring, as the latter is linked to the former. .tp .bi key_or_keyring: key .tq .bi key_or_keyring: key :chain if .i key specifies the id of a key of type "asymmetric", then only keys that are signed by this key are allowed. .ip if .i key specifies the id of a keyring, then only keys that are signed by a key linked to this keyring are allowed. .ip if ":chain" is specified, keys that are signed by a keys linked to the destination keyring (that is, the keyring with the id specified in the .i arg2 argument) are also allowed. .re .ip note that a restriction can be configured only once for the specified keyring; once a restriction is set, it can't be overridden. .ip the argument .i arg5 is ignored. .\" fixme document keyctl_restrict_keyring, added in linux 4.12 .\" commit 6563c91fd645556c7801748f15bc727c77fcd311 .\" author: mat martineau .\" see documentation/security/keys.txt .sh return value for a successful call, the return value depends on the operation: .tp .b keyctl_get_keyring_id the id of the requested keyring. .tp .b keyctl_join_session_keyring the id of the joined session keyring. .tp .b keyctl_describe the size of the description (including the terminating null byte), irrespective of the provided buffer size. .tp .b keyctl_search the id of the key that was found. .tp .b keyctl_read the amount of data that is available in the key, irrespective of the provided buffer size. .tp .b keyctl_set_reqkey_keyring the id of the previous default keyring to which implicitly requested keys were linked (one of .br key_reqkey_defl_user_* ). .tp .b keyctl_assume_authority either 0, if the id given was 0, or the id of the authorization key matching the specified key, if a nonzero key id was provided. .tp .b keyctl_get_security the size of the lsm security label string (including the terminating null byte), irrespective of the provided buffer size. .tp .b keyctl_get_persistent the id of the persistent keyring. .tp .b keyctl_dh_compute the number of bytes copied to the buffer, or, if .i arg4 is 0, the required buffer size. .tp all other operations zero. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eacces the requested operation wasn't permitted. .tp .b eagain .i operation was .b keyctl_dh_compute and there was an error during crypto module initialization. .tp .b edeadlk .i operation was .br keyctl_link and the requested link would result in a cycle. .tp .b edeadlk .i operation was .br keyctl_restrict_keyring and the requested keyring restriction would result in a cycle. .tp .b edquot the key quota for the caller's user would be exceeded by creating a key or linking it to the keyring. .tp .b eexist .i operation was .br keyctl_restrict_keyring and keyring provided in .i arg2 argument already has a restriction set. .tp .b efault .i operation was .b keyctl_dh_compute and one of the following has failed: .rs .ip \(bu 3 copying of the .ir "struct keyctl_dh_params" , provided in the .i arg2 argument, from user space; .ip \(bu copying of the .ir "struct keyctl_kdf_params" , provided in the non-null .i arg5 argument, from user space (in case kernel supports performing kdf operation on dh operation result); .ip \(bu copying of data pointed by the .i hashname field of the .i "struct keyctl_kdf_params" from user space; .ip \(bu copying of data pointed by the .i otherinfo field of the .i struct keyctl_kdf_params from user space if the .i otherinfolen field was nonzero; .ip \(bu copying of the result to user space. .re .tp .b einval .i operation was .b keyctl_setperm and an invalid permission bit was specified in .ir arg3 . .tp .b einval .i operation was .br keyctl_search and the size of the description in .ir arg4 (including the terminating null byte) exceeded 4096 bytes. .tp .b einval size of the string (including the terminating null byte) specified in .i arg3 (the key type) or .i arg4 (the key description) exceeded the limit (32 bytes and 4096 bytes respectively). .tp .br einval " (linux kernels before 4.12)" .i operation was .br keyctl_dh_compute , argument .i arg5 was non-null. .tp .b einval .i operation was .b keyctl_dh_compute and the digest size of the hashing algorithm supplied is zero. .tp .b einval .i operation was .b keyctl_dh_compute and the buffer size provided is not enough to hold the result. provide 0 as a buffer size in order to obtain the minimum buffer size. .tp .b einval .i operation was .b keyctl_dh_compute and the hash name provided in the .i hashname field of the .i struct keyctl_kdf_params pointed by .i arg5 argument is too big (the limit is implementation-specific and varies between kernel versions, but it is deemed big enough for all valid algorithm names). .tp .b einval .\" commit 4f9dabfaf8df971f8a3b6aa324f8f817be38d538 .i operation was .b keyctl_dh_compute and the .i __spare field of the .i struct keyctl_kdf_params provided in the .i arg5 argument contains nonzero values. .tp .b ekeyexpired an expired key was found or specified. .tp .b ekeyrejected a rejected key was found or specified. .tp .b ekeyrevoked a revoked key was found or specified. .tp .b eloop .i operation was .br keyctl_link and the requested link would cause the maximum nesting depth for keyrings to be exceeded. .tp .b emsgsize .i operation was .b keyctl_dh_compute and the buffer length exceeds .b keyctl_kdf_max_output_len (which is 1024 currently) or the .i otherinfolen field of the .i struct keyctl_kdf_parms passed in .i arg5 exceeds .b keyctl_kdf_max_oi_len (which is 64 currently). .tp .br enfile " (linux kernels before 3.13)" .ir operation was .br keyctl_link and the keyring is full. (before linux 3.13, .\" commit b2a4df200d570b2c33a57e1ebfa5896e4bc81b69 the available space for storing keyring links was limited to a single page of memory; since linux 3.13, there is no fixed limit.) .tp .b enoent .i operation was .b keyctl_unlink and the key to be unlinked isn't linked to the keyring. .tp .b enoent .i operation was .b keyctl_dh_compute and the hashing algorithm specified in the .i hashname field of the .i struct keyctl_kdf_params pointed by .i arg5 argument hasn't been found. .tp .b enoent .i operation was .b keyctl_restrict_keyring and the type provided in .i arg3 argument doesn't support setting key linking restrictions. .tp .b enokey no matching key was found or an invalid key was specified. .tp .b enokey the value .b keyctl_get_keyring_id was specified in .ir operation , the key specified in .i arg2 did not exist, and .i arg3 was zero (meaning don't create the key if it didn't exist). .tp .b enomem one of kernel memory allocation routines failed during the execution of the syscall. .tp .b enotdir a key of keyring type was expected but the id of a key with a different type was provided. .tp .b eopnotsupp .i operation was .b keyctl_read and the key type does not support reading (e.g., the type is .ir """login""" ). .tp .b eopnotsupp .i operation was .b keyctl_update and the key type does not support updating. .tp .b eopnotsupp .i operation was .br keyctl_restrict_keyring , the type provided in .i arg3 argument was "asymmetric", and the key specified in the restriction specification provided in .i arg4 has type other than "asymmetric" or "keyring". .tp .b eperm .i operation was .br keyctl_get_persistent , .i arg2 specified a uid other than the calling thread's real or effective uid, and the caller did not have the .b cap_setuid capability. .tp .b eperm .i operation was .br keyctl_session_to_parent and either: all of the uids (gids) of the parent process do not match the effective uid (gid) of the calling process; the uid of the parent's existing session keyring or the uid of the caller's session keyring did not match the effective uid of the caller; the parent process is not single-thread; or the parent process is .br init (1) or a kernel thread. .tp .b etimedout .i operation was .b keyctl_dh_compute and the initialization of crypto modules has timed out. .sh versions this system call first appeared in linux 2.6.10. .sh conforming to this system call is a nonstandard linux extension. .sh notes a wrapper is provided in the .ir libkeyutils library. (the accompanying package provides the .i header file.) when employing the wrapper in that library, link with .ir \-lkeyutils . however, rather than using this system call directly, you probably want to use the various library functions mentioned in the descriptions of individual operations above. .sh examples the program below provide subset of the functionality of the .br request\-key (8) program provided by the .i keyutils package. for informational purposes, the program records various information in a log file. .pp as described in .br request_key (2), the .br request\-key (8) program is invoked with command-line arguments that describe a key that is to be instantiated. the example program fetches and logs these arguments. the program assumes authority to instantiate the requested key, and then instantiates that key. .pp the following shell session demonstrates the use of this program. in the session, we compile the program and then use it to temporarily replace the standard .br request\-key (8) program. (note that temporarily disabling the standard .br request\-key (8) program may not be safe on some systems.) while our example program is installed, we use the example program shown in .br request_key (2) to request a key. .pp .in +4n .ex $ \fbcc \-o key_instantiate key_instantiate.c \-lkeyutils\fp $ \fbsudo mv /sbin/request\-key /sbin/request\-key.backup\fp $ \fbsudo cp key_instantiate /sbin/request\-key\fp $ \fb./t_request_key user mykey somepayloaddata\fp key id is 20d035bf $ \fbsudo mv /sbin/request\-key.backup /sbin/request\-key\fp .ee .in .pp looking at the log file created by this program, we can see the command-line arguments supplied to our example program: .pp .in +4n .ex $ \fbcat /tmp/key_instantiate.log\fp time: mon nov 7 13:06:47 2016 command line arguments: argv[0]: /sbin/request\-key operation: create key_to_instantiate: 20d035bf uid: 1000 gid: 1000 thread_keyring: 0 process_keyring: 0 session_keyring: 256e6a6 key description: user;1000;1000;3f010000;mykey auth key payload: somepayloaddata destination keyring: 256e6a6 auth key description: .request_key_auth;1000;1000;0b010000;20d035bf .ee .in .pp the last few lines of the above output show that the example program was able to fetch: .ip * 3 the description of the key to be instantiated, which included the name of the key .ri ( mykey ); .ip * the payload of the authorization key, which consisted of the data .ri ( somepayloaddata ) passed to .br request_key (2); .ip * the destination keyring that was specified in the call to .br request_key (2); and .ip * the description of the authorization key, where we can see that the name of the authorization key matches the id of the key that is to be instantiated .ri ( 20d035bf ). .pp the example program in .br request_key (2) specified the destination keyring as .br key_spec_session_keyring . by examining the contents of .ir /proc/keys , we can see that this was translated to the id of the destination keyring .ri ( 0256e6a6 ) shown in the log output above; we can also see the newly created key with the name .ir mykey and id .ir 20d035bf . .pp .in +4n .ex $ \fbcat /proc/keys | egrep \(aqmykey|256e6a6\(aq\fp 0256e6a6 i\-\-q\-\-\- 194 perm 3f030000 1000 1000 keyring _ses: 3 20d035bf i\-\-q\-\-\- 1 perm 3f010000 1000 1000 user mykey: 16 .ee .in .ss program source \& .ex /* key_instantiate.c */ #include #include #include #include #include #include #include #include #include #include #ifndef key_spec_requestor_keyring #define key_spec_requestor_keyring \-8 #endif int main(int argc, char *argv[]) { file *fp; time_t t; char *operation; key_serial_t key_to_instantiate, dest_keyring; key_serial_t thread_keyring, process_keyring, session_keyring; uid_t uid; gid_t gid; char dbuf[256]; char auth_key_payload[256]; int akp_size; /* size of auth_key_payload */ int auth_key; fp = fopen("/tmp/key_instantiate.log", "w"); if (fp == null) exit(exit_failure); setbuf(fp, null); t = time(null); fprintf(fp, "time: %s\en", ctime(&t)); /* * the kernel passes a fixed set of arguments to the program * that it execs; fetch them. */ operation = argv[1]; key_to_instantiate = atoi(argv[2]); uid = atoi(argv[3]); gid = atoi(argv[4]); thread_keyring = atoi(argv[5]); process_keyring = atoi(argv[6]); session_keyring = atoi(argv[7]); fprintf(fp, "command line arguments:\en"); fprintf(fp, " argv[0]: %s\en", argv[0]); fprintf(fp, " operation: %s\en", operation); fprintf(fp, " key_to_instantiate: %jx\en", (uintmax_t) key_to_instantiate); fprintf(fp, " uid: %jd\en", (intmax_t) uid); fprintf(fp, " gid: %jd\en", (intmax_t) gid); fprintf(fp, " thread_keyring: %jx\en", (uintmax_t) thread_keyring); fprintf(fp, " process_keyring: %jx\en", (uintmax_t) process_keyring); fprintf(fp, " session_keyring: %jx\en", (uintmax_t) session_keyring); fprintf(fp, "\en"); /* * assume the authority to instantiate the key named in argv[2]. */ if (keyctl(keyctl_assume_authority, key_to_instantiate) == \-1) { fprintf(fp, "keyctl_assume_authority failed: %s\en", strerror(errno)); exit(exit_failure); } /* * fetch the description of the key that is to be instantiated. */ if (keyctl(keyctl_describe, key_to_instantiate, dbuf, sizeof(dbuf)) == \-1) { fprintf(fp, "keyctl_describe failed: %s\en", strerror(errno)); exit(exit_failure); } fprintf(fp, "key description: %s\en", dbuf); /* * fetch the payload of the authorization key, which is * actually the callout data given to request_key(). */ akp_size = keyctl(keyctl_read, key_spec_reqkey_auth_key, auth_key_payload, sizeof(auth_key_payload)); if (akp_size == \-1) { fprintf(fp, "keyctl_read failed: %s\en", strerror(errno)); exit(exit_failure); } auth_key_payload[akp_size] = \(aq\e0\(aq; fprintf(fp, "auth key payload: %s\en", auth_key_payload); /* * for interest, get the id of the authorization key and * display it. */ auth_key = keyctl(keyctl_get_keyring_id, key_spec_reqkey_auth_key); if (auth_key == \-1) { fprintf(fp, "keyctl_get_keyring_id failed: %s\en", strerror(errno)); exit(exit_failure); } fprintf(fp, "auth key id: %jx\en", (uintmax_t) auth_key); /* * fetch key id for the request_key(2) destination keyring. */ dest_keyring = keyctl(keyctl_get_keyring_id, key_spec_requestor_keyring); if (dest_keyring == \-1) { fprintf(fp, "keyctl_get_keyring_id failed: %s\en", strerror(errno)); exit(exit_failure); } fprintf(fp, "destination keyring: %jx\en", (uintmax_t) dest_keyring); /* * fetch the description of the authorization key. this * allows us to see the key type, uid, gid, permissions, * and description (name) of the key. among other things, * we will see that the name of the key is a hexadecimal * string representing the id of the key to be instantiated. */ if (keyctl(keyctl_describe, key_spec_reqkey_auth_key, dbuf, sizeof(dbuf)) == \-1) { fprintf(fp, "keyctl_describe failed: %s\en", strerror(errno)); exit(exit_failure); } fprintf(fp, "auth key description: %s\en", dbuf); /* * instantiate the key using the callout data that was supplied * in the payload of the authorization key. */ if (keyctl(keyctl_instantiate, key_to_instantiate, auth_key_payload, akp_size + 1, dest_keyring) == \-1) { fprintf(fp, "keyctl_instantiate failed: %s\en", strerror(errno)); exit(exit_failure); } exit(exit_success); } .ee .sh see also .ad l .nh .br keyctl (1), .br add_key (2), .br request_key (2), .\" .br find_key_by_type_and_name (3) .\" there is a man page, but this function seems not to exist .br keyctl (3), .br keyctl_assume_authority (3), .br keyctl_chown (3), .br keyctl_clear (3), .br keyctl_describe (3), .br keyctl_describe_alloc (3), .br keyctl_dh_compute (3), .br keyctl_dh_compute_alloc (3), .br keyctl_get_keyring_id (3), .br keyctl_get_persistent (3), .br keyctl_get_security (3), .br keyctl_get_security_alloc (3), .br keyctl_instantiate (3), .br keyctl_instantiate_iov (3), .br keyctl_invalidate (3), .br keyctl_join_session_keyring (3), .br keyctl_link (3), .br keyctl_negate (3), .br keyctl_read (3), .br keyctl_read_alloc (3), .br keyctl_reject (3), .br keyctl_revoke (3), .br keyctl_search (3), .br keyctl_session_to_parent (3), .br keyctl_set_reqkey_keyring (3), .br keyctl_set_timeout (3), .br keyctl_setperm (3), .br keyctl_unlink (3), .br keyctl_update (3), .br recursive_key_scan (3), .br recursive_session_key_scan (3), .br capabilities (7), .br credentials (7), .br keyrings (7), .br keyutils (7), .br persistent\-keyring (7), .br process\-keyring (7), .br session\-keyring (7), .br thread\-keyring (7), .br user\-keyring (7), .br user_namespaces (7), .br user\-session\-keyring (7), .br request\-key (8) .pp the kernel source files under .ir documentation/security/keys/ (or, before linux 4.13, in the file .ir documentation/security/keys.txt ). .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/slist.3 .so man3/lround.3 .so man3/nextup.3 .\" copyright (c) 2003 davide libenzi .\" and copyright 2008, 2009, 2012 michael kerrisk .\" davide libenzi .\" .\" %%%license_start(gplv2+_sw_3_para) .\" this program is free software; you can redistribute it and/or modify .\" it under the terms of the gnu general public license as published by .\" the free software foundation; either version 2 of the license, or .\" (at your option) any later version. .\" .\" this program is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified 2004-06-17 by michael kerrisk .\" modified 2005-04-04 by marko kohtala .\" 2008-10-10, mtk: add description of epoll_create1() .\" .th epoll_create 2 2021-03-22 "linux" "linux programmer's manual" .sh name epoll_create, epoll_create1 \- open an epoll file descriptor .sh synopsis .nf .b #include .pp .bi "int epoll_create(int " size ); .bi "int epoll_create1(int " flags ); .fi .sh description .br epoll_create () creates a new .br epoll (7) instance. since linux 2.6.8, the .i size argument is ignored, but must be greater than zero; see notes. .pp .br epoll_create () returns a file descriptor referring to the new epoll instance. this file descriptor is used for all the subsequent calls to the .b epoll interface. when no longer required, the file descriptor returned by .br epoll_create () should be closed by using .br close (2). when all file descriptors referring to an epoll instance have been closed, the kernel destroys the instance and releases the associated resources for reuse. .ss epoll_create1() if .i flags is 0, then, other than the fact that the obsolete .i size argument is dropped, .br epoll_create1 () is the same as .br epoll_create (). the following value can be included in .ir flags to obtain different behavior: .tp .b epoll_cloexec set the close-on-exec .rb ( fd_cloexec ) flag on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .sh return value on success, these system calls return a file descriptor (a nonnegative integer). on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval .i size is not positive. .tp .b einval .rb ( epoll_create1 ()) invalid value specified in .ir flags . .tp .b emfile the per-user limit on the number of epoll instances imposed by .i /proc/sys/fs/epoll/max_user_instances was encountered. see .br epoll (7) for further details. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enomem there was insufficient memory to create the kernel object. .sh versions .br epoll_create () was added to the kernel in version 2.6. library support is provided in glibc starting with version 2.3.2. .pp .\" to be precise: kernel 2.5.44. .\" the interface should be finalized by linux kernel 2.5.66. .br epoll_create1 () was added to the kernel in version 2.6.27. library support is provided in glibc starting with version 2.9. .sh conforming to .br epoll_create () and .br epoll_create1 () are linux-specific. .sh notes in the initial .br epoll_create () implementation, the .i size argument informed the kernel of the number of file descriptors that the caller expected to add to the .b epoll instance. the kernel used this information as a hint for the amount of space to initially allocate in internal data structures describing events. (if necessary, the kernel would allocate more space if the caller's usage exceeded the hint given in .ir size .) nowadays, this hint is no longer required (the kernel dynamically sizes the required data structures without needing the hint), but .i size must still be greater than zero, in order to ensure backward compatibility when new .b epoll applications are run on older kernels. .sh see also .br close (2), .br epoll_ctl (2), .br epoll_wait (2), .br epoll (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/catanh.3 .\" copyright 2005, 2012, 2016 michael kerrisk .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under the gpl. .\" %%%license_end .\" .\" 2008-12-04, petr baudis : document open_wmemstream() .\" .th open_memstream 3 2021-03-22 "gnu" "linux programmer's manual" .sh name open_memstream, open_wmemstream \- open a dynamic memory buffer stream .sh synopsis .nf .b #include .pp .bi "file *open_memstream(char **" ptr ", size_t *" sizeloc ); .pp .b #include .pp .bi "file *open_wmemstream(wchar_t **" ptr ", size_t *" sizeloc ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br open_memstream (), .br open_wmemstream (): .nf since glibc 2.10: _posix_c_source >= 200809l before glibc 2.10: _gnu_source .fi .sh description the .br open_memstream () function opens a stream for writing to a memory buffer. the function dynamically allocates the buffer, and the buffer automatically grows as needed. initially, the buffer has a size of zero. after closing the stream, the caller should .br free (3) this buffer. .pp the locations pointed to by .ir ptr and .i sizeloc are used to report, respectively, the current location and the size of the buffer. the locations referred to by these pointers are updated each time the stream is flushed .rb ( fflush (3)) and when the stream is closed .rb ( fclose (3)). these values remain valid only as long as the caller performs no further output on the stream. if further output is performed, then the stream must again be flushed before trying to access these values. .pp a null byte is maintained at the end of the buffer. this byte is .i not included in the size value stored at .ir sizeloc . .pp the stream maintains the notion of a current position, which is initially zero (the start of the buffer). each write operation implicitly adjusts the buffer position. the stream's buffer position can be explicitly changed with .br fseek (3) or .br fseeko (3). moving the buffer position past the end of the data already written fills the intervening space with null characters. .pp the .br open_wmemstream () is similar to .br open_memstream (), but operates on wide characters instead of bytes. .sh return value upon successful completion, .br open_memstream () and .br open_wmemstream () return a .i file pointer. otherwise, null is returned and .i errno is set to indicate the error. .sh versions .br open_memstream () was already available in glibc 1.0.x. .br open_wmemstream () is available since glibc 2.4. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br open_memstream (), .br open_wmemstream () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to posix.1-2008. these functions are not specified in posix.1-2001, and are not widely available on other systems. .sh notes there is no file descriptor associated with the file stream returned by these functions (i.e., .br fileno (3) will return an error if called on the returned stream). .sh bugs in glibc before version 2.7, seeking past the end of a stream created by .br open_memstream () does not enlarge the buffer; instead the .br fseek (3) call fails, returning \-1. .\" http://sourceware.org/bugzilla/show_bug.cgi?id=1996 .sh examples see .br fmemopen (3). .sh see also .br fmemopen (3), .br fopen (3), .br setbuf (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/strchr.3 .so man3/unlocked_stdio.3 .so man3/unlocked_stdio.3 .\" copyright 2003 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th putgrent 3 2021-03-22 "gnu" "linux programmer's manual" .sh name putgrent \- write a group database entry to a file .sh synopsis .nf .br "#define _gnu_source" " /* see feature_test_macros(7) */" .b #include .pp .bi "int putgrent(const struct group *restrict " grp \ ", file *restrict " stream ); .fi .sh description the .br putgrent () function is the counterpart for .br fgetgrent (3). the function writes the content of the provided .ir "struct group" into the .ir stream . the list of group members must be null-terminated or null-initialized. .pp the .ir "struct group" is defined as follows: .pp .in +4n .ex struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ gid_t gr_gid; /* group id */ char **gr_mem; /* group members */ }; .ee .in .sh return value the function returns zero on success, and a nonzero value on error. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br putgrent () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is a gnu extension. .sh see also .br fgetgrent (3), .br getgrent (3), .br group (5) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/gethostbyname.3 .\" copyright (c) 2014, theodore ts'o .\" copyright (c) 2014,2015 heinrich schuchardt .\" copyright (c) 2015, michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th getrandom 2 2021-03-22 "linux" "linux programmer's manual" .sh name getrandom \- obtain a series of random bytes .sh synopsis .nf .b #include .pp .bi "ssize_t getrandom(void *"buf ", size_t " buflen ", unsigned int " flags ); .fi .sh description the .br getrandom () system call fills the buffer pointed to by .i buf with up to .i buflen random bytes. these bytes can be used to seed user-space random number generators or for cryptographic purposes. .pp by default, .br getrandom () draws entropy from the .i urandom source (i.e., the same source as the .ir /dev/urandom device). this behavior can be changed via the .i flags argument. .pp if the .i urandom source has been initialized, reads of up to 256 bytes will always return as many bytes as requested and will not be interrupted by signals. no such guarantees apply for larger buffer sizes. for example, if the call is interrupted by a signal handler, it may return a partially filled buffer, or fail with the error .br eintr . .pp if the .i urandom source has not yet been initialized, then .br getrandom () will block, unless .b grnd_nonblock is specified in .ir flags . .pp the .i flags argument is a bit mask that can contain zero or more of the following values ored together: .tp .b grnd_random if this bit is set, then random bytes are drawn from the .i random source (i.e., the same source as the .ir /dev/random device) instead of the .i urandom source. the .i random source is limited based on the entropy that can be obtained from environmental noise. if the number of available bytes in the .i random source is less than requested in .ir buflen , the call returns just the available random bytes. if no random bytes are available, the behavior depends on the presence of .b grnd_nonblock in the .i flags argument. .tp .b grnd_nonblock by default, when reading from the .ir random source, .br getrandom () blocks if no random bytes are available, and when reading from the .ir urandom source, it blocks if the entropy pool has not yet been initialized. if the .b grnd_nonblock flag is set, then .br getrandom () does not block in these cases, but instead immediately returns \-1 with .i errno set to .br eagain . .sh return value on success, .br getrandom () returns the number of bytes that were copied to the buffer .ir buf . this may be less than the number of bytes requested via .i buflen if either .br grnd_random was specified in .ir flags and insufficient entropy was present in the .ir random source or the system call was interrupted by a signal. .pp on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b eagain the requested entropy was not available, and .br getrandom () would have blocked if the .b grnd_nonblock flag was not set. .tp .b efault the address referred to by .i buf is outside the accessible address space. .tp .b eintr the call was interrupted by a signal handler; see the description of how interrupted .br read (2) calls on "slow" devices are handled with and without the .b sa_restart flag in the .br signal (7) man page. .tp .b einval an invalid flag was specified in .ir flags . .tp .b enosys the glibc wrapper function for .br getrandom () determined that the underlying kernel does not implement this system call. .sh versions .br getrandom () was introduced in version 3.17 of the linux kernel. support was added to glibc in version 2.25. .sh conforming to this system call is linux-specific. .sh notes for an overview and comparison of the various interfaces that can be used to obtain randomness, see .br random (7). .pp unlike .ir /dev/random and .ir /dev/urandom , .br getrandom () does not involve the use of pathnames or file descriptors. thus, .br getrandom () can be useful in cases where .br chroot (2) makes .i /dev pathnames invisible, and where an application (e.g., a daemon during start-up) closes a file descriptor for one of these files that was opened by a library. .\" .ss maximum number of bytes returned as of linux 3.19 the following limits apply: .ip * 3 when reading from the .ir urandom source, a maximum of 33554431 bytes is returned by a single call to .br getrandom () on systems where .i int has a size of 32 bits. .ip * when reading from the .ir random source, a maximum of 512 bytes is returned. .ss interruption by a signal handler when reading from the .i urandom source .rb ( grnd_random is not set), .br getrandom () will block until the entropy pool has been initialized (unless the .br grnd_nonblock flag was specified). if a request is made to read a large number of bytes (more than 256), .br getrandom () will block until those bytes have been generated and transferred from kernel memory to .ir buf . when reading from the .i random source .rb ( grnd_random is set), .br getrandom () will block until some random bytes become available (unless the .br grnd_nonblock flag was specified). .pp the behavior when a call to .br getrandom () that is blocked while reading from the .i urandom source is interrupted by a signal handler depends on the initialization state of the entropy buffer and on the request size, .ir buflen . if the entropy is not yet initialized, then the call fails with the .b eintr error. if the entropy pool has been initialized and the request size is large .ri ( buflen "\ >\ 256)," the call either succeeds, returning a partially filled buffer, or fails with the error .br eintr . if the entropy pool has been initialized and the request size is small .ri ( buflen "\ <=\ 256)," then .br getrandom () will not fail with .br eintr . instead, it will return all of the bytes that have been requested. .pp when reading from the .ir random source, blocking requests of any size can be interrupted by a signal handler (the call fails with the error .br eintr ). .pp using .br getrandom () to read small buffers (<=\ 256 bytes) from the .i urandom source is the preferred mode of usage. .pp the special treatment of small values of .i buflen was designed for compatibility with openbsd's .br getentropy (3), which is nowadays supported by glibc. .pp the user of .br getrandom () .i must always check the return value, to determine whether either an error occurred or fewer bytes than requested were returned. in the case where .b grnd_random is not specified and .i buflen is less than or equal to 256, a return of fewer bytes than requested should never happen, but the careful programmer will check for this anyway! .sh bugs as of linux 3.19, the following bug exists: .\" fixme patch proposed https://lkml.org/lkml/2014/11/29/16 .ip * 3 depending on cpu load, .br getrandom () does not react to interrupts before reading all bytes requested. .sh see also .br getentropy (3), .br random (4), .br urandom (4), .br random (7), .br signal (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" adapted glibc info page .\" .\" polished a little, aeb .th addseverity 3 2021-03-22 "gnu" "linux programmer's manual" .sh name addseverity \- introduce new severity classes .sh synopsis .nf .pp .b #include .pp .bi "int addseverity(int " severity ", const char *" s ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br addseverity (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description this function allows the introduction of new severity classes which can be addressed by the .i severity argument of the .br fmtmsg (3) function. by default, that function knows only how to print messages for severity 0-4 (with strings (none), halt, error, warning, info). this call attaches the given string .i s to the given value .ir severity . if .i s is null, the severity class with the numeric value .i severity is removed. it is not possible to overwrite or remove one of the default severity classes. the severity value must be nonnegative. .sh return value upon success, the value .b mm_ok is returned. upon error, the return value is .br mm_notok . possible errors include: out of memory, attempt to remove a nonexistent or default severity class. .sh versions .br addseverity () is provided in glibc since version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br addseverity () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to this function is not specified in the x/open portability guide although the .br fmtmsg (3) function is. it is available on system v systems. .sh notes new severity classes can also be added by setting the environment variable .br sev_level . .sh see also .br fmtmsg (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 1990, 1993 .\" the regents of the university of california. all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)hash.3 8.6 (berkeley) 8/18/94 .\" .th hash 3 2017-09-15 "" "linux programmer's manual" .uc 7 .sh name hash \- hash database access method .sh synopsis .nf .ft b #include #include .ft r .fi .sh description .ir "note well" : this page documents interfaces provided in glibc up until version 2.1. since version 2.2, glibc no longer provides these interfaces. probably, you are looking for the apis provided by the .i libdb library instead. .pp the routine .br dbopen (3) is the library interface to database files. one of the supported file formats is hash files. the general description of the database access methods is in .br dbopen (3), this manual page describes only the hash-specific information. .pp the hash data structure is an extensible, dynamic hashing scheme. .pp the access-method-specific data structure provided to .br dbopen (3) is defined in the .i include file as follows: .pp .in +4n .ex typedef struct { unsigned int bsize; unsigned int ffactor; unsigned int nelem; unsigned int cachesize; uint32_t (*hash)(const void *, size_t); int lorder; } hashinfo; .ee .in .pp the elements of this structure are as follows: .tp 10 .i bsize defines the hash table bucket size, and is, by default, 256 bytes. it may be preferable to increase the page size for disk-resident tables and tables with large data items. .tp .i ffactor indicates a desired density within the hash table. it is an approximation of the number of keys allowed to accumulate in any one bucket, determining when the hash table grows or shrinks. the default value is 8. .tp .i nelem is an estimate of the final size of the hash table. if not set or set too low, hash tables will expand gracefully as keys are entered, although a slight performance degradation may be noticed. the default value is 1. .tp .i cachesize is the suggested maximum size, in bytes, of the memory cache. this value is .ir "only advisory" , and the access method will allocate more memory rather than fail. .tp .i hash is a user-defined hash function. since no hash function performs equally well on all possible data, the user may find that the built-in hash function does poorly on a particular data set. a user-specified hash functions must take two arguments (a pointer to a byte string and a length) and return a 32-bit quantity to be used as the hash value. .tp .i lorder is the byte order for integers in the stored database metadata. the number should represent the order as an integer; for example, big endian order would be the number 4,321. if .i lorder is 0 (no order is specified), the current host order is used. if the file already exists, the specified value is ignored and the value specified when the tree was created is used. .pp if the file already exists (and the .b o_trunc flag is not specified), the values specified for .ir bsize , .ir ffactor , .ir lorder , and .i nelem are ignored and the values specified when the tree was created are used. .pp if a hash function is specified, .i hash_open attempts to determine if the hash function specified is the same as the one with which the database was created, and fails if it is not. .pp backward-compatible interfaces to the routines described in .br dbm (3), and .br ndbm (3) are provided, however these interfaces are not compatible with previous file formats. .sh errors the .i hash access method routines may fail and set .i errno for any of the errors specified for the library routine .br dbopen (3). .sh bugs only big and little endian byte order are supported. .sh see also .br btree (3), .br dbopen (3), .br mpool (3), .br recno (3) .pp .ir "dynamic hash tables" , per-ake larson, communications of the acm, april 1988. .pp .ir "a new hash package for unix" , margo seltzer, usenix proceedings, winter 1991. .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2002, 2020 michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th shm_open 3 2021-03-22 "linux" "linux programmer's manual" .sh name shm_open, shm_unlink \- create/open or unlink posix shared memory objects .sh synopsis .nf .b #include .br "#include " " /* for mode constants */" .br "#include " " /* for o_* constants */" .pp .bi "int shm_open(const char *" name ", int " oflag ", mode_t " mode ); .bi "int shm_unlink(const char *" name ); .fi .pp link with \fi\-lrt\fp. .sh description .br shm_open () creates and opens a new, or opens an existing, posix shared memory object. a posix shared memory object is in effect a handle which can be used by unrelated processes to .br mmap (2) the same region of shared memory. the .br shm_unlink () function performs the converse operation, removing an object previously created by .br shm_open (). .pp the operation of .br shm_open () is analogous to that of .br open (2). .i name specifies the shared memory object to be created or opened. for portable use, a shared memory object should be identified by a name of the form .ir /somename ; that is, a null-terminated string of up to .bi name_max (i.e., 255) characters consisting of an initial slash, .\" glibc allows the initial slash to be omitted, and makes .\" multiple initial slashes equivalent to a single slash. .\" this differs from the implementation of posix message queues. followed by one or more characters, none of which are slashes. .\" glibc allows subdirectory components in the name, in which .\" case the subdirectory must exist under /dev/shm, and allow the .\" required permissions if a user wants to create a shared memory .\" object in that subdirectory. .pp .i oflag is a bit mask created by oring together exactly one of .b o_rdonly or .b o_rdwr and any of the other flags listed here: .tp .b o_rdonly open the object for read access. a shared memory object opened in this way can be .br mmap (2)ed only for read .rb ( prot_read ) access. .tp .b o_rdwr open the object for read-write access. .tp .b o_creat create the shared memory object if it does not exist. the user and group ownership of the object are taken from the corresponding effective ids of the calling process, .\" in truth it is actually the filesystem ids on linux, but these .\" are nearly always the same as the effective ids. (mtk, jul 05) and the object's permission bits are set according to the low-order 9 bits of .ir mode , except that those bits set in the process file mode creation mask (see .br umask (2)) are cleared for the new object. a set of macro constants which can be used to define .i mode is listed in .br open (2). (symbolic definitions of these constants can be obtained by including .ir .) .ip a new shared memory object initially has zero length\(emthe size of the object can be set using .br ftruncate (2). the newly allocated bytes of a shared memory object are automatically initialized to 0. .tp .b o_excl if .b o_creat was also specified, and a shared memory object with the given .i name already exists, return an error. the check for the existence of the object, and its creation if it does not exist, are performed atomically. .tp .b o_trunc if the shared memory object already exists, truncate it to zero bytes. .pp definitions of these flag values can be obtained by including .ir . .pp on successful completion .br shm_open () returns a new file descriptor referring to the shared memory object. this file descriptor is guaranteed to be the lowest-numbered file descriptor not previously opened within the process. the .b fd_cloexec flag (see .br fcntl (2)) is set for the file descriptor. .pp the file descriptor is normally used in subsequent calls to .br ftruncate (2) (for a newly created object) and .br mmap (2). after a call to .br mmap (2) the file descriptor may be closed without affecting the memory mapping. .pp the operation of .br shm_unlink () is analogous to .br unlink (2): it removes a shared memory object name, and, once all processes have unmapped the object, deallocates and destroys the contents of the associated memory region. after a successful .br shm_unlink (), attempts to .br shm_open () an object with the same .i name fail (unless .b o_creat was specified, in which case a new, distinct object is created). .sh return value on success, .br shm_open () returns a file descriptor (a nonnegative integer). on success, .br shm_unlink () returns 0. on failure, both functions return \-1 and set .i errno to indicate the error. .sh errors .tp .b eacces permission to .br shm_unlink () the shared memory object was denied. .tp .b eacces permission was denied to .br shm_open () .i name in the specified .ir mode , or .b o_trunc was specified and the caller does not have write permission on the object. .tp .b eexist both .b o_creat and .b o_excl were specified to .br shm_open () and the shared memory object specified by .i name already exists. .tp .b einval the .i name argument to .br shm_open () was invalid. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enametoolong the length of .i name exceeds .br path_max . .tp .b enfile the system-wide limit on the total number of open files has been reached. .tp .b enoent an attempt was made to .br shm_open () a .i name that did not exist, and .b o_creat was not specified. .tp .b enoent an attempt was to made to .br shm_unlink () a .i name that does not exist. .sh versions these functions are provided in glibc 2.2 and later. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br shm_open (), .br shm_unlink () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008. .pp posix.1-2001 says that the group ownership of a newly created shared memory object is set to either the calling process's effective group id or "a system default group id". posix.1-2008 says that the group ownership may be set to either the calling process's effective group id or, if the object is visible in the filesystem, the group id of the parent directory. .sh notes posix leaves the behavior of the combination of .b o_rdonly and .b o_trunc unspecified. on linux, this will successfully truncate an existing shared memory object\(emthis may not be so on other unix systems. .pp the posix shared memory object implementation on linux makes use of a dedicated .br tmpfs (5) filesystem that is normally mounted under .ir /dev/shm . .sh examples the programs below employ posix shared memory and posix unnamed semaphores to exchange a piece of data. the "bounce" program (which must be run first) raises the case of a string that is placed into the shared memory by the "send" program. once the data has been modified, the "send" program then prints the contents of the modified shared memory. an example execution of the two programs is the following: .pp .in +4n .ex $ \fb./pshm_ucase_bounce /myshm &\fp [1] 270171 $ \fb./pshm_ucase_send /myshm hello\fp hello .ee .in .pp further detail about these programs is provided below. .\" .ss program source: pshm_ucase.h the following header file is included by both programs below. its primary purpose is to define a structure that will be imposed on the memory object that is shared between the two programs. .pp .in +4n .ex #include #include #include #include #include #include #include #define errexit(msg) do { perror(msg); exit(exit_failure); \e } while (0) #define buf_size 1024 /* maximum size for exchanged string */ /* define a structure that will be imposed on the shared memory object */ struct shmbuf { sem_t sem1; /* posix unnamed semaphore */ sem_t sem2; /* posix unnamed semaphore */ size_t cnt; /* number of bytes used in \(aqbuf\(aq */ char buf[buf_size]; /* data being transferred */ }; .ee .in .\" .ss program source: pshm_ucase_bounce.c the "bounce" program creates a new shared memory object with the name given in its command-line argument and sizes the object to match the size of the .i shmbuf structure defined in the header file. it then maps the object into the process's address space, and initializes two posix semaphores inside the object to 0. .pp after the "send" program has posted the first of the semaphores, the "bounce" program upper cases the data that has been placed in the memory by the "send" program and then posts the second semaphore to tell the "send" program that it may now access the shared memory. .pp .in +4n .ex /* pshm_ucase_bounce.c licensed under gnu general public license v2 or later. */ #include #include "pshm_ucase.h" int main(int argc, char *argv[]) { if (argc != 2) { fprintf(stderr, "usage: %s /shm\-path\en", argv[0]); exit(exit_failure); } char *shmpath = argv[1]; /* create shared memory object and set its size to the size of our structure. */ int fd = shm_open(shmpath, o_creat | o_excl | o_rdwr, s_irusr | s_iwusr); if (fd == \-1) errexit("shm_open"); if (ftruncate(fd, sizeof(struct shmbuf)) == \-1) errexit("ftruncate"); /* map the object into the caller\(aqs address space. */ struct shmbuf *shmp = mmap(null, sizeof(*shmp), prot_read | prot_write, map_shared, fd, 0); if (shmp == map_failed) errexit("mmap"); /* initialize semaphores as process\-shared, with value 0. */ if (sem_init(&shmp\->sem1, 1, 0) == \-1) errexit("sem_init\-sem1"); if (sem_init(&shmp\->sem2, 1, 0) == \-1) errexit("sem_init\-sem2"); /* wait for \(aqsem1\(aq to be posted by peer before touching shared memory. */ if (sem_wait(&shmp\->sem1) == \-1) errexit("sem_wait"); /* convert data in shared memory into upper case. */ for (int j = 0; j < shmp\->cnt; j++) shmp\->buf[j] = toupper((unsigned char) shmp\->buf[j]); /* post \(aqsem2\(aq to tell the peer that it can now access the modified data in shared memory. */ if (sem_post(&shmp\->sem2) == \-1) errexit("sem_post"); /* unlink the shared memory object. even if the peer process is still using the object, this is okay. the object will be removed only after all open references are closed. */ shm_unlink(shmpath); exit(exit_success); } .ee .in .\" .ss program source: pshm_ucase_send.c the "send" program takes two command-line arguments: the pathname of a shared memory object previously created by the "bounce" program and a string that is to be copied into that object. .pp the program opens the shared memory object and maps the object into its address space. it then copies the data specified in its second argument into the shared memory, and posts the first semaphore, which tells the "bounce" program that it can now access that data. after the "bounce" program posts the second semaphore, the "send" program prints the contents of the shared memory on standard output. .pp .in +4n .ex /* pshm_ucase_send.c licensed under gnu general public license v2 or later. */ #include #include "pshm_ucase.h" int main(int argc, char *argv[]) { if (argc != 3) { fprintf(stderr, "usage: %s /shm\-path string\en", argv[0]); exit(exit_failure); } char *shmpath = argv[1]; char *string = argv[2]; size_t len = strlen(string); if (len > buf_size) { fprintf(stderr, "string is too long\en"); exit(exit_failure); } /* open the existing shared memory object and map it into the caller\(aqs address space. */ int fd = shm_open(shmpath, o_rdwr, 0); if (fd == \-1) errexit("shm_open"); struct shmbuf *shmp = mmap(null, sizeof(*shmp), prot_read | prot_write, map_shared, fd, 0); if (shmp == map_failed) errexit("mmap"); /* copy data into the shared memory object. */ shmp\->cnt = len; memcpy(&shmp\->buf, string, len); /* tell peer that it can now access shared memory. */ if (sem_post(&shmp\->sem1) == \-1) errexit("sem_post"); /* wait until peer says that it has finished accessing the shared memory. */ if (sem_wait(&shmp\->sem2) == \-1) errexit("sem_wait"); /* write modified data in shared memory to standard output. */ write(stdout_fileno, &shmp\->buf, len); write(stdout_fileno, "\en", 1); exit(exit_success); } .ee .in .sh see also .br close (2), .br fchmod (2), .br fchown (2), .br fcntl (2), .br fstat (2), .br ftruncate (2), .br memfd_create (2), .br mmap (2), .br open (2), .br umask (2), .br shm_overview (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/ether_aton.3 .so man3/strtod.3 .\" copyright (c) 2006 red hat, inc. all rights reserved. .\" and copyright (c) 2013 michael kerrisk .\" written by ivana varekova .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th perfmonctl 2 2021-03-22 linux "linux programmer's manual" .sh name perfmonctl \- interface to ia-64 performance monitoring unit .sh synopsis .nf .b #include .b #include .pp .bi "long perfmonctl(int " fd ", int " cmd ", void *" arg ", int " narg ");" .fi .pp .ir note : there is no glibc wrapper for this system call; see notes. .sh description the ia-64-specific .br perfmonctl () system call provides an interface to the pmu (performance monitoring unit). the pmu consists of pmd (performance monitoring data) registers and pmc (performance monitoring control) registers, which gather hardware statistics. .pp .br perfmonctl () applies the operation .i cmd to the input arguments specified by .ir arg . the number of arguments is defined by \finarg\fr. the .i fd argument specifies the perfmon context to operate on. .pp supported values for .i cmd are: .tp .b pfm_create_context .nf .bi "perfmonctl(int " fd ", pfm_create_context, pfarg_context_t *" ctxt ", 1);" .fi set up a context. .ip the .i fd parameter is ignored. a new perfmon context is created as specified in .i ctxt and its file descriptor is returned in \fictxt->ctx_fd\fr. .ip the file descriptor can be used in subsequent calls to .br perfmonctl () and can be used to read event notifications (type .ir pfm_msg_t ) using .br read (2). the file descriptor is pollable using .br select (2), .br poll (2), and .br epoll (7). .ip the context can be destroyed by calling .br close (2) on the file descriptor. .tp .b pfm_write_pmcs .\" pfm_write_pmcs() .nf .bi "perfmonctl(int " fd ", pfm_write_pmcs, pfarg_reg_t *" pmcs ", n);" .fi set pmc registers. .tp .b pfm_write_pmds .nf .bi "perfmonctl(int " fd ", pfm_write_pmds, pfarg_reg_t *" pmds ", n);" .fi .\" pfm_write_pmds() set pmd registers. .tp .b pfm_read_pmds .\" pfm_read_pmds() .nf .bi "perfmonctl(int " fd ", pfm_read_pmds, pfarg_reg_t *" pmds ", n);" .fi read pmd registers. .tp .b pfm_start .\" pfm_start() .nf .\" .bi "perfmonctl(int " fd ", pfm_start, arg, 1); .bi "perfmonctl(int " fd ", pfm_start, null, 0);" .fi start monitoring. .tp .b pfm_stop .\" pfm_stop() .nf .bi "perfmonctl(int " fd ", pfm_stop, null, 0);" .fi stop monitoring. .tp .b pfm_load_context .\" pfm_context_load() .nf .bi "perfmonctl(int " fd ", pfm_load_context, pfarg_load_t *" largs ", 1);" .fi attach the context to a thread. .tp .b pfm_unload_context .\" pfm_context_unload() .nf .bi "perfmonctl(int " fd ", pfm_unload_context, null, 0);" .fi detach the context from a thread. .tp .b pfm_restart .\" pfm_restart() .nf .bi "perfmonctl(int " fd ", pfm_restart, null, 0);" .fi restart monitoring after receiving an overflow notification. .tp .b pfm_get_features .\" pfm_get_features() .nf .bi "perfmonctl(int " fd ", pfm_get_features, pfarg_features_t *" arg ", 1);" .fi .tp .b pfm_debug .\" pfm_debug() .nf .bi "perfmonctl(int " fd ", pfm_debug, " val ", 0);" .fi if .i val is nonzero, enable debugging mode, otherwise disable. .tp .b pfm_get_pmc_reset_val .\" pfm_get_pmc_reset() .nf .bi "perfmonctl(int " fd ", pfm_get_pmc_reset_val, pfarg_reg_t *" req ", n);" .fi reset pmc registers to default values. .\" .\" .\" .tp .\" .b pfm_create_evtsets .\" .\" create or modify event sets .\" .nf .\" .bi "perfmonctl(int " fd ", pfm_create_evtsets, pfarg_setdesc_t *desc , n); .\" .fi .\" .tp .\" .b pfm_delete_evtsets .\" delete event sets .\" .nf .\" .bi "perfmonctl(int " fd ", pfm_delete_evtset, pfarg_setdesc_t *desc , n); .\" .fi .\" .tp .\" .b pfm_getinfo_evtsets .\" get information about event sets .\" .nf .\" .bi "perfmonctl(int " fd ", pfm_getinfo_evtsets, pfarg_setinfo_t *info, n); .\" .fi .sh return value .br perfmonctl () returns zero when the operation is successful. on error, \-1 is returned and .i errno is set to indicate the error. .sh versions .br perfmonctl () was added in linux 2.4; .\" commit ecf5b72d5f66af843f189dfe9ce31598c3e48ad7 it was removed in linux 5.10. .sh conforming to .br perfmonctl () is linux-specific and is available only on the ia-64 architecture. .sh notes this system call was broken for many years, and ultimately removed in linux 5.10. .pp glibc does not provide a wrapper for this system call; on kernels where it exists, call it using .br syscall (2). .sh see also .br gprof (1) .pp the perfmon2 interface specification .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/random.3 .so man2/sched_setscheduler.2 .so man2/statfs.2 .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th iswupper 3 2021-03-22 "gnu" "linux programmer's manual" .sh name iswupper \- test for uppercase wide character .sh synopsis .nf .b #include .pp .bi "int iswupper(wint_t " wc ); .fi .sh description the .br iswupper () function is the wide-character equivalent of the .br isupper (3) function. it tests whether .i wc is a wide character belonging to the wide-character class "upper". .pp the wide-character class "upper" is a subclass of the wide-character class "alpha", and therefore also a subclass of the wide-character class "alnum", of the wide-character class "graph" and of the wide-character class "print". .pp being a subclass of the wide-character class "print", the wide-character class "upper" is disjoint from the wide-character class "cntrl". .pp being a subclass of the wide-character class "graph", the wide-character class "upper" is disjoint from the wide-character class "space" and its subclass "blank". .pp being a subclass of the wide-character class "alnum", the wide-character class "upper" is disjoint from the wide-character class "punct". .pp being a subclass of the wide-character class "alpha", the wide-character class "upper" is disjoint from the wide-character class "digit". .pp the wide-character class "upper" contains at least those characters .i wc which are equal to .i towupper(wc) and different from .ir towlower(wc) . .pp the wide-character class "upper" always contains at least the letters \(aqa\(aq to \(aqz\(aq. .sh return value the .br iswupper () function returns nonzero if .i wc is a wide character belonging to the wide-character class "upper". otherwise, it returns zero. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br iswupper () t} thread safety mt-safe locale .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br iswupper () depends on the .b lc_ctype category of the current locale. .pp this function is not very appropriate for dealing with unicode characters, because unicode knows about three cases: upper, lower, and title case. .sh see also .br isupper (3), .br iswctype (3), .br towupper (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2002 walter harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" %%%license_start(gpl_noversion_oneline) .\" distributed under gpl .\" %%%license_end .\" .th csinh 3 2021-03-22 "" "linux programmer's manual" .sh name csinh, csinhf, csinhl \- complex hyperbolic sine .sh synopsis .nf .b #include .pp .bi "double complex csinh(double complex " z ");" .bi "float complex csinhf(float complex " z ");" .bi "long double complex csinhl(long double complex " z ");" .pp link with \fi\-lm\fp. .fi .sh description these functions calculate the complex hyperbolic sine of .ir z . .pp the complex hyperbolic sine function is defined as: .pp .nf csinh(z) = (exp(z)\-exp(\-z))/2 .fi .sh versions these functions first appeared in glibc in version 2.1. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br csinh (), .br csinhf (), .br csinhl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .sh see also .br cabs (3), .br casinh (3), .br ccosh (3), .br ctanh (3), .br complex (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) bruno haible .\" .\" %%%license_start(gplv2+_doc_onepara) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" %%%license_end .\" .\" references consulted: .\" gnu glibc-2 source code and manual .\" dinkumware c library reference http://www.dinkumware.com/ .\" opengroup's single unix specification http://www.unix-systems.org/online.html .\" iso/iec 9899:1999 .\" .th wcsrtombs 3 2021-03-22 "gnu" "linux programmer's manual" .sh name wcsrtombs \- convert a wide-character string to a multibyte string .sh synopsis .nf .b #include .pp .bi "size_t wcsrtombs(char *restrict " dest ", const wchar_t **restrict " src , .bi " size_t " len ", mbstate_t *restrict " ps ); .fi .sh description if .i dest is not null, the .br wcsrtombs () function converts the wide-character string .i *src to a multibyte string starting at .ir dest . at most .i len bytes are written to .ir dest . the shift state .i *ps is updated. the conversion is effectively performed by repeatedly calling .ir "wcrtomb(dest, *src, ps)" , as long as this call succeeds, and then incrementing .i dest by the number of bytes written and .i *src by one. the conversion can stop for three reasons: .ip 1. 3 a wide character has been encountered that can not be represented as a multibyte sequence (according to the current locale). in this case, .i *src is left pointing to the invalid wide character, .i (size_t)\ \-1 is returned, and .i errno is set to .br eilseq . .ip 2. the length limit forces a stop. in this case, .i *src is left pointing to the next wide character to be converted, and the number of bytes written to .i dest is returned. .ip 3. the wide-character string has been completely converted, including the terminating null wide character (l\(aq\e0\(aq), which has the side effect of bringing back .i *ps to the initial state. in this case, .i *src is set to null, and the number of bytes written to .ir dest , excluding the terminating null byte (\(aq\e0\(aq), is returned. .pp if .ir dest is null, .i len is ignored, and the conversion proceeds as above, except that the converted bytes are not written out to memory, and that no length limit exists. .pp in both of the above cases, if .i ps is null, a static anonymous state known only to the .br wcsrtombs () function is used instead. .pp the programmer must ensure that there is room for at least .i len bytes at .ir dest . .sh return value the .br wcsrtombs () function returns the number of bytes that make up the converted part of multibyte sequence, not including the terminating null byte. if a wide character was encountered which could not be converted, .i (size_t)\ \-1 is returned, and .i errno set to .br eilseq . .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lb lb lbx l l l. interface attribute value t{ .br wcsrtombs () t} thread safety t{ mt-unsafe race:wcsrtombs/!ps t} .te .hy .ad .sp 1 .sh conforming to posix.1-2001, posix.1-2008, c99. .sh notes the behavior of .br wcsrtombs () depends on the .b lc_ctype category of the current locale. .pp passing null as .i ps is not multithread safe. .sh see also .br iconv (3), .br mbsinit (3), .br wcrtomb (3), .br wcsnrtombs (3), .br wcstombs (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 1999 dimitri papadopoulos (dpo@club-internet.fr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-7 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-7 \- iso 8859-7 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-7 encodes the characters used in modern monotonic greek. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-7 characters the following table displays the characters in iso 8859-7 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ‘ left single quotation mark 242 162 a2 ’ right single quotation mark 243 163 a3 £ pound sign 244 164 a4 € euro sign 245 165 a5 ₯ drachma sign 246 166 a6 ¦ broken bar 247 167 a7 § section sign 250 168 a8 ¨ diaeresis 251 169 a9 © copyright sign 252 170 aa ͺ greek ypogegrammeni 253 171 ab « left-pointing double angle quotation mark 254 172 ac ¬ not sign 255 173 ad ­ soft hyphen 257 175 af ― horizontal bar 260 176 b0 ° degree sign 261 177 b1 ± plus-minus sign 262 178 b2 ² superscript two 263 179 b3 ³ superscript three 264 180 b4 ΄ greek tonos 265 181 b5 ΅ greek dialytika tonos 266 182 b6 ά greek capital letter alpha with tonos 267 183 b7 · middle dot 270 184 b8 έ greek capital letter epsilon with tonos 271 185 b9 ή greek capital letter eta with tonos 272 186 ba ί greek capital letter iota with tonos 273 187 bb » right-pointing double angle quotation mark 274 188 bc ό greek capital letter omicron with tonos 275 189 bd ½ vulgar fraction one half 276 190 be ύ greek capital letter upsilon with tonos 277 191 bf ώ greek capital letter omega with tonos 300 192 c0 ΐ t{ greek small letter iota with .br dialytika and tonos t} 301 193 c1 α greek capital letter alpha 302 194 c2 β greek capital letter beta 303 195 c3 γ greek capital letter gamma 304 196 c4 δ greek capital letter delta 305 197 c5 ε greek capital letter epsilon 306 198 c6 ζ greek capital letter zeta 307 199 c7 η greek capital letter eta 310 200 c8 θ greek capital letter theta 311 201 c9 ι greek capital letter iota 312 202 ca κ greek capital letter kappa 313 203 cb λ greek capital letter lambda 314 204 cc μ greek capital letter mu 315 205 cd ν greek capital letter nu 316 206 ce ξ greek capital letter xi 317 207 cf ο greek capital letter omicron 320 208 d0 π greek capital letter pi 321 209 d1 ρ greek capital letter rho 323 211 d3 σ greek capital letter sigma 324 212 d4 τ greek capital letter tau 325 213 d5 υ greek capital letter upsilon 326 214 d6 φ greek capital letter phi 327 215 d7 χ greek capital letter chi 330 216 d8 ψ greek capital letter psi 331 217 d9 ω greek capital letter omega 332 218 da ϊ greek capital letter iota with dialytika 333 219 db ϋ greek capital letter upsilon with dialytika 334 220 dc ά greek small letter alpha with tonos 335 221 dd έ greek small letter epsilon with tonos 336 222 de ή greek small letter eta with tonos 337 223 df ί greek small letter iota with tonos 340 224 e0 ΰ t{ greek small letter upsilon with dialytika and tonos t} 341 225 e1 α greek small letter alpha 342 226 e2 β greek small letter beta 343 227 e3 γ greek small letter gamma 344 228 e4 δ greek small letter delta 345 229 e5 ε greek small letter epsilon 346 230 e6 ζ greek small letter zeta 347 231 e7 η greek small letter eta 350 232 e8 θ greek small letter theta 351 233 e9 ι greek small letter iota 352 234 ea κ greek small letter kappa 353 235 eb λ greek small letter lambda 354 236 ec μ greek small letter mu 355 237 ed ν greek small letter nu 356 238 ee ξ greek small letter xi 357 239 ef ο greek small letter omicron 360 240 f0 π greek small letter pi 361 241 f1 ρ greek small letter rho 362 242 f2 ς greek small letter final sigma 363 243 f3 σ greek small letter sigma 364 244 f4 τ greek small letter tau 365 245 f5 υ greek small letter upsilon 366 246 f6 φ greek small letter phi 367 247 f7 χ greek small letter chi 370 248 f8 ψ greek small letter psi 371 249 f9 ω greek small letter omega 372 250 fa ϊ greek small letter iota with dialytika 373 251 fb ϋ greek small letter upsilon with dialytika 374 252 fc ό greek small letter omicron with tonos 375 253 fd ύ greek small letter upsilon with tonos 376 254 fe ώ greek small letter omega with tonos .te .sh notes iso 8859-7 was formerly known as elot-928 or ecma-118:1986. .sh see also .br ascii (7), .br charsets (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man2/getxattr.2 .\" this manpage is copyright (c) 1992 drew eckhardt; .\" and copyright (c) 1993 michael haardt, ian jackson. .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" modified wed jul 21 23:02:38 1993 by rik faith .\" modified 2001-11-17, aeb .\" .th _exit 2 2021-03-22 "linux" "linux programmer's manual" .sh name _exit, _exit \- terminate the calling process .sh synopsis .nf .b #include .pp .bi "noreturn void _exit(int " status ); .pp .b #include .pp .bi "noreturn void _exit(int " status ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br _exit (): .nf _isoc99_source || _posix_c_source >= 200112l .fi .sh description .br _exit () terminates the calling process "immediately". any open file descriptors belonging to the process are closed. any children of the process are inherited by .br init (1) (or by the nearest "subreaper" process as defined through the use of the .br prctl (2) .b pr_set_child_subreaper operation). the process's parent is sent a .b sigchld signal. .pp the value .i "status & 0xff" is returned to the parent process as the process's exit status, and can be collected by the parent using one of the .br wait (2) family of calls. .pp the function .br _exit () is equivalent to .br _exit (). .sh return value these functions do not return. .sh conforming to posix.1-2001, posix.1-2008, svr4, 4.3bsd. the function .br _exit () was introduced by c99. .sh notes for a discussion on the effects of an exit, the transmission of exit status, zombie processes, signals sent, and so on, see .br exit (3). .pp the function .br _exit () is like .br exit (3), but does not call any functions registered with .br atexit (3) or .br on_exit (3). open .br stdio (3) streams are not flushed. on the other hand, .br _exit () does close open file descriptors, and this may cause an unknown delay, waiting for pending output to finish. if the delay is undesired, it may be useful to call functions like .br tcflush (3) before calling .br _exit (). whether any pending i/o is canceled, and which pending i/o may be canceled upon .br _exit (), is implementation-dependent. .ss c library/kernel differences in glibc up to version 2.3, the .br _exit () wrapper function invoked the kernel system call of the same name. since glibc 2.3, the wrapper function invokes .br exit_group (2), in order to terminate all of the threads in a process. .pp the raw .br _exit () system call terminates only the calling thread, and actions such as reparenting child processes or sending .b sigchld to the parent process are performed only if this is the last thread in the thread group. .\" _exit() is used by pthread_exit() to terminate the calling thread .sh see also .br execve (2), .br exit_group (2), .br fork (2), .br kill (2), .br wait (2), .br wait4 (2), .br waitpid (2), .br atexit (3), .br exit (3), .br on_exit (3), .br termios (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/div.3 .so man3/rpc.3 .\" copyright (c) 1995, thomas k. dyas .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" created 1995-08-09 thomas k. dyas .\" modified 1997-01-31 by eric s. raymond .\" modified 2001-03-22 by aeb .\" modified 2003-08-04 by aeb .\" .th ustat 2 2021-03-22 "linux" "linux programmer's manual" .sh name ustat \- get filesystem statistics .sh synopsis .nf .b #include .br "#include " " /* libc[45] */" .br "#include " " /* glibc2 */" .pp .bi "int ustat(dev_t " dev ", struct ustat *" ubuf ); .fi .sh description .br ustat () returns information about a mounted filesystem. .i dev is a device number identifying a device containing a mounted filesystem. .i ubuf is a pointer to a .i ustat structure that contains the following members: .pp .in +4n .ex daddr_t f_tfree; /* total free blocks */ ino_t f_tinode; /* number of free inodes */ char f_fname[6]; /* filsys name */ char f_fpack[6]; /* filsys pack name */ .ee .in .pp the last two fields, .i f_fname and .ir f_fpack , are not implemented and will always be filled with null bytes (\(aq\e0\(aq). .sh return value on success, zero is returned and the .i ustat structure pointed to by .i ubuf will be filled in. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b efault .i ubuf points outside of your accessible address space. .tp .b einval .i dev does not refer to a device containing a mounted filesystem. .tp .b enosys the mounted filesystem referenced by .i dev does not support this operation, or any version of linux before 1.3.16. .sh versions since version 2.28, glibc no longer provides a wrapper for this system call. .sh conforming to svr4. .\" svr4 documents additional error conditions enolink, ecomm, and eintr .\" but has no enosys condition. .sh notes .br ustat () is deprecated and has been provided only for compatibility. all new programs should use .br statfs (2) instead. .ss hp-ux notes the hp-ux version of the .i ustat structure has an additional field, .ir f_blksize , that is unknown elsewhere. hp-ux warns: for some filesystems, the number of free inodes does not change. such filesystems will return \-1 in the field .ir f_tinode . .\" some software tries to use this in order to test whether the .\" underlying filesystem is nfs. for some filesystems, inodes are dynamically allocated. such filesystems will return the current number of free inodes. .sh see also .br stat (2), .br statfs (2) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright 2009 lefteris dimitroulakis (edimitro@tee.gr) .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .th iso_8859-5 7 2020-08-13 "linux" "linux programmer's manual" .sh name iso_8859-5 \- iso 8859-5 character set encoded in octal, decimal, and hexadecimal .sh description the iso 8859 standard includes several 8-bit extensions to the ascii character set (also known as iso 646-irv). iso 8859-5 encodes the cyrillic characters used in many east european languages. .ss iso 8859 alphabets the full set of iso 8859 alphabets includes: .ts l l. iso 8859-1 west european languages (latin-1) iso 8859-2 central and east european languages (latin-2) iso 8859-3 southeast european and miscellaneous languages (latin-3) iso 8859-4 scandinavian/baltic languages (latin-4) iso 8859-5 latin/cyrillic iso 8859-6 latin/arabic iso 8859-7 latin/greek iso 8859-8 latin/hebrew iso 8859-9 latin-1 modification for turkish (latin-5) iso 8859-10 lappish/nordic/eskimo languages (latin-6) iso 8859-11 latin/thai iso 8859-13 baltic rim languages (latin-7) iso 8859-14 celtic (latin-8) iso 8859-15 west european languages (latin-9) iso 8859-16 romanian (latin-10) .te .ss iso 8859-5 characters the following table displays the characters in iso 8859-5 that are printable and unlisted in the .br ascii (7) manual page. .ts l l l c lp-1. oct dec hex char description _ 240 160 a0   no-break space 241 161 a1 ё cyrillic capital letter io 242 162 a2 ђ cyrillic capital letter dje 243 163 a3 ѓ cyrillic capital letter gje 244 164 a4 є cyrillic capital letter ukrainian ie 245 165 a5 ѕ cyrillic capital letter dze 246 166 a6 і t{ cyrillic capital letter .br byelorussian-ukrainian i t} 247 167 a7 ї cyrillic capital letter yi 250 168 a8 ј cyrillic capital letter je 251 169 a9 љ cyrillic capital letter lje 252 170 aa њ cyrillic capital letter nje 253 171 ab ћ cyrillic capital letter tshe 254 172 ac ќ cyrillic capital letter kje 255 173 ad ­ soft hyphen 256 174 ae ў cyrillic capital letter short u 257 175 af џ cyrillic capital letter dzhe 260 176 b0 а cyrillic capital letter a 261 177 b1 б cyrillic capital letter be 262 178 b2 в cyrillic capital letter ve 263 179 b3 г cyrillic capital letter ghe 264 180 b4 д cyrillic capital letter de 265 181 b5 е cyrillic capital letter ie 266 182 b6 ж cyrillic capital letter zhe 267 183 b7 з cyrillic capital letter ze 270 184 b8 и cyrillic capital letter i 271 185 b9 й cyrillic capital letter short i 272 186 ba к cyrillic capital letter ka 273 187 bb л cyrillic capital letter el 274 188 bc м cyrillic capital letter em 275 189 bd н cyrillic capital letter en 276 190 be о cyrillic capital letter o 277 191 bf п cyrillic capital letter pe 300 192 c0 р cyrillic capital letter er 301 193 c1 с cyrillic capital letter es 302 194 c2 т cyrillic capital letter te 303 195 c3 у cyrillic capital letter u 304 196 c4 ф cyrillic capital letter ef 305 197 c5 х cyrillic capital letter ha 306 198 c6 ц cyrillic capital letter tse 307 199 c7 ч cyrillic capital letter che 310 200 c8 ш cyrillic capital letter sha 311 201 c9 щ cyrillic capital letter shcha 312 202 ca ъ cyrillic capital letter hard sign 313 203 cb ы cyrillic capital letter yeru 314 204 cc ь cyrillic capital letter soft sign 315 205 cd э cyrillic capital letter e 316 206 ce ю cyrillic capital letter yu 317 207 cf я cyrillic capital letter ya 320 208 d0 а cyrillic small letter a 321 209 d1 б cyrillic small letter be 322 210 d2 в cyrillic small letter ve 323 211 d3 г cyrillic small letter ghe 324 212 d4 д cyrillic small letter de 325 213 d5 е cyrillic small letter ie 326 214 d6 ж cyrillic small letter zhe 327 215 d7 з cyrillic small letter ze 330 216 d8 и cyrillic small letter i 331 217 d9 й cyrillic small letter short i 332 218 da к cyrillic small letter ka 333 219 db л cyrillic small letter el 334 220 dc м cyrillic small letter em 335 221 dd н cyrillic small letter en 336 222 de о cyrillic small letter o 337 223 df п cyrillic small letter pe 340 224 e0 р cyrillic small letter er 341 225 e1 с cyrillic small letter es 342 226 e2 т cyrillic small letter te 343 227 e3 у cyrillic small letter u 344 228 e4 ф cyrillic small letter ef 345 229 e5 х cyrillic small letter ha 346 230 e6 ц cyrillic small letter tse 347 231 e7 ч cyrillic small letter che 350 232 e8 ш cyrillic small letter sha 351 233 e9 щ cyrillic small letter shcha 352 234 ea ъ cyrillic small letter hard sign 353 235 eb ы cyrillic small letter yeru 354 236 ec ь cyrillic small letter soft sign 355 237 ed э cyrillic small letter e 356 238 ee ю cyrillic small letter yu 357 239 ef я cyrillic small letter ya 360 240 f0 № numero sign 361 241 f1 ё cyrillic small letter io 362 242 f2 ђ cyrillic small letter dje 363 243 f3 ѓ cyrillic small letter gje 364 244 f4 є cyrillic small letter ukrainian ie 365 245 f5 ѕ cyrillic small letter dze 366 246 f6 і cyrillic small letter byelorussian-ukrainian i 367 247 f7 ї cyrillic small letter yi 370 248 f8 ј cyrillic small letter je 371 249 f9 љ cyrillic small letter lje 372 250 fa њ cyrillic small letter nje 373 251 fb ј cyrillic small letter tshe 374 252 fc ќ cyrillic small letter kje 375 253 fd § section sign 376 254 fe ў cyrillic small letter short u 377 255 ff џ cyrillic small letter dzhe .te .sh see also .br ascii (7), .br charsets (7), .br cp1251 (7), .br koi8\-r (7), .br koi8\-u (7), .br utf\-8 (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/atan.3 .\" copyright (c) 1993 michael haardt (michael@moria.de), .\" fri apr 2 11:32:09 met dst 1993 .\" .\" %%%license_start(gplv2+_doc_full) .\" this is free documentation; you can redistribute it and/or .\" modify it under the terms of the gnu general public license as .\" published by the free software foundation; either version 2 of .\" the license, or (at your option) any later version. .\" .\" the gnu general public license's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" this manual is distributed in the hope that it will be useful, .\" but without any warranty; without even the implied warranty of .\" merchantability or fitness for a particular purpose. see the .\" gnu general public license for more details. .\" .\" you should have received a copy of the gnu general public .\" license along with this manual; if not, see .\" . .\" %%%license_end .\" .\" modified sun jul 25 11:06:34 1993 by rik faith (faith@cs.unc.edu) .\" corrected mon oct 21 17:47:19 edt 1996 by eric s. raymond (esr@thyrsus.com) .th nologin 5 2017-09-15 "linux" "linux programmer's manual" .sh name nologin \- prevent unprivileged users from logging into the system .sh description if the file \fi/etc/nologin\fp exists and is readable, .br login (1) will allow access only to root. other users will be shown the contents of this file and their logins will be refused. this provides a simple way of temporarily disabling all unprivileged logins. .sh files .i /etc/nologin .sh see also .br login (1), .br shutdown (8) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/erfc.3 \" copyright (c) 2013, heinrich schuchardt .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of .\" this manual under the conditions for verbatim copying, provided that .\" the entire resulting derived work is distributed under the terms of .\" a permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume. .\" no responsibility for errors or omissions, or for damages resulting. .\" from the use of the information contained herein. the author(s) may. .\" not have taken the same level of care in the production of this. .\" manual, which is licensed free of charge, as they might when working. .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .th fanotify_init 2 2021-03-22 "linux" "linux programmer's manual" .sh name fanotify_init \- create and initialize fanotify group .sh synopsis .nf .br "#include " " /* definition of " o_* " constants */" .b #include .pp .bi "int fanotify_init(unsigned int " flags ", unsigned int " event_f_flags ); .fi .sh description for an overview of the fanotify api, see .br fanotify (7). .pp .br fanotify_init () initializes a new fanotify group and returns a file descriptor for the event queue associated with the group. .pp the file descriptor is used in calls to .br fanotify_mark (2) to specify the files, directories, mounts, or filesystems for which fanotify events shall be created. these events are received by reading from the file descriptor. some events are only informative, indicating that a file has been accessed. other events can be used to determine whether another application is permitted to access a file or directory. permission to access filesystem objects is granted by writing to the file descriptor. .pp multiple programs may be using the fanotify interface at the same time to monitor the same files. .pp in the current implementation, the number of fanotify groups per user is limited to 128. this limit cannot be overridden. .pp calling .br fanotify_init () requires the .b cap_sys_admin capability. this constraint might be relaxed in future versions of the api. therefore, certain additional capability checks have been implemented as indicated below. .pp the .i flags argument contains a multi-bit field defining the notification class of the listening application and further single bit fields specifying the behavior of the file descriptor. .pp if multiple listeners for permission events exist, the notification class is used to establish the sequence in which the listeners receive the events. .pp only one of the following notification classes may be specified in .ir flags : .tp .b fan_class_pre_content this value allows the receipt of events notifying that a file has been accessed and events for permission decisions if a file may be accessed. it is intended for event listeners that need to access files before they contain their final data. this notification class might be used by hierarchical storage managers, for example. .tp .b fan_class_content this value allows the receipt of events notifying that a file has been accessed and events for permission decisions if a file may be accessed. it is intended for event listeners that need to access files when they already contain their final content. this notification class might be used by malware detection programs, for example. .tp .b fan_class_notif this is the default value. it does not need to be specified. this value only allows the receipt of events notifying that a file has been accessed. permission decisions before the file is accessed are not possible. .pp listeners with different notification classes will receive events in the order .br fan_class_pre_content , .br fan_class_content , .br fan_class_notif . the order of notification for listeners in the same notification class is undefined. .pp the following bits can additionally be set in .ir flags : .tp .b fan_cloexec set the close-on-exec flag .rb ( fd_cloexec ) on the new file descriptor. see the description of the .b o_cloexec flag in .br open (2). .tp .b fan_nonblock enable the nonblocking flag .rb ( o_nonblock ) for the file descriptor. reading from the file descriptor will not block. instead, if no data is available, .br read (2) fails with the error .br eagain . .tp .b fan_unlimited_queue remove the limit of 16384 events for the event queue. use of this flag requires the .b cap_sys_admin capability. .tp .b fan_unlimited_marks remove the limit of 8192 marks. use of this flag requires the .b cap_sys_admin capability. .tp .br fan_report_tid " (since linux 4.20)" .\" commit d0a6a87e40da49cfc7954c491d3065a25a641b29 report thread id (tid) instead of process id (pid) in the .i pid field of the .i "struct fanotify_event_metadata" supplied to .br read (2) (see .br fanotify (7)). .tp .br fan_enable_audit " (since linux 4.15)" .\" commit de8cd83e91bc3ee212b3e6ec6e4283af9e4ab269 enable generation of audit log records about access mediation performed by permission events. the permission event response has to be marked with the .b fan_audit flag for an audit log record to be generated. .tp .br fan_report_fid " (since linux 5.1)" .\" commit a8b13aa20afb69161b5123b4f1acc7ea0a03d360 this value allows the receipt of events which contain additional information about the underlying filesystem object correlated to an event. an additional record of type .br fan_event_info_type_fid encapsulates the information about the object and is included alongside the generic event metadata structure. the file descriptor that is used to represent the object correlated to an event is instead substituted with a file handle. it is intended for applications that may find the use of a file handle to identify an object more suitable than a file descriptor. additionally, it may be used for applications monitoring a directory or a filesystem that are interested in the directory entry modification events .br fan_create , .br fan_delete , and .br fan_move , or in events such as .br fan_attrib , .br fan_delete_self , and .br fan_move_self . all the events above require an fanotify group that identifies filesystem objects by file handles. note that for the directory entry modification events the reported file handle identifies the modified directory and not the created/deleted/moved child object. the use of .br fan_class_content or .br fan_class_pre_content is not permitted with this flag and will result in the error .br einval . see .br fanotify (7) for additional details. .tp .br fan_report_dir_fid " (since linux 5.9)" events for fanotify groups initialized with this flag will contain (see exceptions below) additional information about a directory object correlated to an event. an additional record of type .br fan_event_info_type_dfid encapsulates the information about the directory object and is included alongside the generic event metadata structure. for events that occur on a non-directory object, the additional structure includes a file handle that identifies the parent directory filesystem object. note that there is no guarantee that the directory filesystem object will be found at the location described by the file handle information at the time the event is received. when combined with the flag .br fan_report_fid , two records may be reported with events that occur on a non-directory object, one to identify the non-directory object itself and one to identify the parent directory object. note that in some cases, a filesystem object does not have a parent, for example, when an event occurs on an unlinked but open file. in that case, with the .br fan_report_fid flag, the event will be reported with only one record to identify the non-directory object itself, because there is no directory associated with the event. without the .br fan_report_fid flag, no event will be reported. see .br fanotify (7) for additional details. .tp .br fan_report_name " (since linux 5.9)" events for fanotify groups initialized with this flag will contain additional information about the name of the directory entry correlated to an event. this flag must be provided in conjunction with the flag .br fan_report_dir_fid . providing this flag value without .br fan_report_dir_fid will result in the error .br einval . this flag may be combined with the flag .br fan_report_fid . an additional record of type .br fan_event_info_type_dfid_name , which encapsulates the information about the directory entry, is included alongside the generic event metadata structure and substitutes the additional information record of type .br fan_event_info_type_dfid . the additional record includes a file handle that identifies a directory filesystem object followed by a name that identifies an entry in that directory. for the directory entry modification events .br fan_create , .br fan_delete , and .br fan_move , the reported name is that of the created/deleted/moved directory entry. for other events that occur on a directory object, the reported file handle is that of the directory object itself and the reported name is '.'. for other events that occur on a non-directory object, the reported file handle is that of the parent directory object and the reported name is the name of a directory entry where the object was located at the time of the event. the rationale behind this logic is that the reported directory file handle can be passed to .br open_by_handle_at (2) to get an open directory file descriptor and that file descriptor along with the reported name can be used to call .br fstatat (2). the same rule that applies to record type .br fan_event_info_type_dfid also applies to record type .br fan_event_info_type_dfid_name : if a non-directory object has no parent, either the event will not be reported or it will be reported without the directory entry information. note that there is no guarantee that the filesystem object will be found at the location described by the directory entry information at the time the event is received. see .br fanotify (7) for additional details. .tp .b fan_report_dfid_name this is a synonym for .rb ( fan_report_dir_fid | fan_report_name ). .pp the .i event_f_flags argument defines the file status flags that will be set on the open file descriptions that are created for fanotify events. for details of these flags, see the description of the .i flags values in .br open (2). .i event_f_flags includes a multi-bit field for the access mode. this field can take the following values: .tp .b o_rdonly this value allows only read access. .tp .b o_wronly this value allows only write access. .tp .b o_rdwr this value allows read and write access. .pp additional bits can be set in .ir event_f_flags . the most useful values are: .tp .b o_largefile enable support for files exceeding 2\ gb. failing to set this flag will result in an .b eoverflow error when trying to open a large file which is monitored by an fanotify group on a 32-bit system. .tp .br o_cloexec " (since linux 3.18)" .\" commit 0b37e097a648aa71d4db1ad108001e95b69a2da4 enable the close-on-exec flag for the file descriptor. see the description of the .b o_cloexec flag in .br open (2) for reasons why this may be useful. .pp the following are also allowable: .br o_append , .br o_dsync , .br o_noatime , .br o_nonblock , and .br o_sync . specifying any other flag in .i event_f_flags yields the error .b einval (but see bugs). .sh return value on success, .br fanotify_init () returns a new file descriptor. on error, \-1 is returned, and .i errno is set to indicate the error. .sh errors .tp .b einval an invalid value was passed in .i flags or .ir event_f_flags . .b fan_all_init_flags (deprecated since linux kernel version 4.20) .\" commit 23c9deeb3285d34fd243abb3d6b9f07db60c3cf4 defines all allowable bits for .ir flags . .tp .b emfile the number of fanotify groups for this user exceeds 128. .tp .b emfile the per-process limit on the number of open file descriptors has been reached. .tp .b enomem the allocation of memory for the notification group failed. .tp .b enosys this kernel does not implement .br fanotify_init (). the fanotify api is available only if the kernel was configured with .br config_fanotify . .tp .b eperm the operation is not permitted because the caller lacks the .b cap_sys_admin capability. .sh versions .br fanotify_init () was introduced in version 2.6.36 of the linux kernel and enabled in version 2.6.37. .sh conforming to this system call is linux-specific. .sh bugs the following bug was present in linux kernels before version 3.18: .ip * 3 .\" fixed by commit 0b37e097a648aa71d4db1ad108001e95b69a2da4 the .b o_cloexec is ignored when passed in .ir event_f_flags . .pp the following bug was present in linux kernels before version 3.14: .ip * 3 .\" fixed by commit 48149e9d3a7e924010a0daab30a6197b7d7b6580 the .i event_f_flags argument is not checked for invalid flags. flags that are intended only for internal use, such as .br fmode_exec , can be set, and will consequently be set for the file descriptors returned when reading from the fanotify file descriptor. .sh see also .br fanotify_mark (2), .br fanotify (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .\" copyright (c) 2012 by michael kerrisk .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .th mtrace 3 2021-03-22 "gnu" "linux programmer's manual" .sh name mtrace, muntrace \- malloc tracing .sh synopsis .nf .b "#include " .pp .b "void mtrace(void);" .b "void muntrace(void);" .fi .sh description the .br mtrace () function installs hook functions for the memory-allocation functions .rb ( malloc (3), .br realloc (3) .br memalign (3), .br free (3)). these hook functions record tracing information about memory allocation and deallocation. the tracing information can be used to discover memory leaks and attempts to free nonallocated memory in a program. .pp the .br muntrace () function disables the hook functions installed by .br mtrace (), so that tracing information is no longer recorded for the memory-allocation functions. if no hook functions were successfully installed by .br mtrace (), .br muntrace () does nothing. .pp when .br mtrace () is called, it checks the value of the environment variable .br malloc_trace , which should contain the pathname of a file in which the tracing information is to be recorded. if the pathname is successfully opened, it is truncated to zero length. .pp if .br malloc_trace is not set, or the pathname it specifies is invalid or not writable, then no hook functions are installed, and .br mtrace () has no effect. in set-user-id and set-group-id programs, .br malloc_trace is ignored, and .br mtrace () has no effect. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br mtrace (), .br muntrace () t} thread safety mt-unsafe .te .hy .ad .sp 1 .\" fixme: the marking is different from that in the glibc manual, .\" markings in glibc manual are more detailed: .\" .\" mtrace: mt-unsafe env race:mtrace const:malloc_hooks init .\" muntrace: mt-unsafe race:mtrace const:malloc_hooks locale .\" .\" but there is something wrong in glibc manual, for example: .\" glibc manual says muntrace should have marking locale because it calls .\" fprintf(), but muntrace does not execute area which cause locale problem. .sh conforming to these functions are gnu extensions. .sh notes in normal usage, .br mtrace () is called once at the start of execution of a program, and .br muntrace () is never called. .pp the tracing output produced after a call to .br mtrace () is textual, but not designed to be human readable. the gnu c library provides a perl script, .br mtrace (1), that interprets the trace log and produces human-readable output. for best results, the traced program should be compiled with debugging enabled, so that line-number information is recorded in the executable. .pp the tracing performed by .br mtrace () incurs a performance penalty (if .b malloc_trace points to a valid, writable pathname). .sh bugs the line-number information produced by .br mtrace (1) is not always precise: the line number references may refer to the previous or following (nonblank) line of the source code. .sh examples the shell session below demonstrates the use of the .br mtrace () function and the .br mtrace (1) command in a program that has memory leaks at two different locations. the demonstration uses the following program: .pp .in +4n .ex .rb "$ " "cat t_mtrace.c" #include #include #include int main(int argc, char *argv[]) { mtrace(); for (int j = 0; j < 2; j++) malloc(100); /* never freed\-\-a memory leak */ calloc(16, 16); /* never freed\-\-a memory leak */ exit(exit_success); } .ee .in .pp when we run the program as follows, we see that .br mtrace () diagnosed memory leaks at two different locations in the program: .pp .in +4n .ex .rb "$ " "cc \-g t_mtrace.c \-o t_mtrace" .rb "$ " "export malloc_trace=/tmp/t" .rb "$ " "./t_mtrace" .rb "$ " "mtrace ./t_mtrace $malloc_trace" memory not freed: -\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- address size caller 0x084c9378 0x64 at /home/cecilia/t_mtrace.c:12 0x084c93e0 0x64 at /home/cecilia/t_mtrace.c:12 0x084c9448 0x100 at /home/cecilia/t_mtrace.c:16 .ee .in .pp the first two messages about unfreed memory correspond to the two .br malloc (3) calls inside the .i for loop. the final message corresponds to the call to .br calloc (3) (which in turn calls .br malloc (3)). .sh see also .br mtrace (1), .br malloc (3), .br malloc_hook (3), .br mcheck (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/rpc.3 .\" copyright 1993 david metcalfe (david@prism.demon.co.uk) .\" and copyright 2008, linux foundation, written by michael kerrisk .\" .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" references consulted: .\" linux libc source code .\" lewine's _posix programmer's guide_ (o'reilly & associates, 1991) .\" 386bsd man pages .\" modified 1993-07-24 by rik faith (faith@cs.unc.edu) .\" modified 2002-07-25 by walter harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .th acos 3 2021-03-22 "" "linux programmer's manual" .sh name acos, acosf, acosl \- arc cosine function .sh synopsis .nf .b #include .pp .bi "double acos(double " x ); .bi "float acosf(float " x ); .bi "long double acosl(long double " x ); .fi .pp link with \fi\-lm\fp. .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br acosf (), .br acosl (): .nf _isoc99_source || _posix_c_source >= 200112l || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source || _svid_source .fi .sh description these functions calculate the arc cosine of .ir x ; that is the value whose cosine is .ir x . .sh return value on success, these functions return the arc cosine of .ir x in radians; the return value is in the range [0,\ pi]. .pp if .i x is a nan, a nan is returned. .pp if .i x is +1, +0 is returned. .pp if .i x is positive infinity or negative infinity, a domain error occurs, and a nan is returned. .pp if .i x is outside the range [\-1,\ 1], a domain error occurs, and a nan is returned. .sh errors see .br math_error (7) for information on how to determine whether an error has occurred when calling these functions. .pp the following errors can occur: .tp domain error: \fix\fp is outside the range [\-1,\ 1] .i errno is set to .br edom . an invalid floating-point exception .rb ( fe_invalid ) is raised. .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br acos (), .br acosf (), .br acosl () t} thread safety mt-safe .te .hy .ad .sp 1 .sh conforming to c99, posix.1-2001, posix.1-2008. .pp the variant returning .i double also conforms to svr4, 4.3bsd, c89. .sh see also .br asin (3), .br atan (3), .br atan2 (3), .br cacos (3), .br cos (3), .br sin (3), .br tan (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/tailq.3 .\" copyright (c) 1983, 1991 the regents of the university of california. .\" and copyright (c) 2009, 2010, 2014, 2015, michael kerrisk .\" all rights reserved. .\" .\" %%%license_start(bsd_4_clause_ucb) .\" redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. all advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" this product includes software developed by the university of .\" california, berkeley and its contributors. .\" 4. neither the name of the university nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" this software is provided by the regents and contributors ``as is'' and .\" any express or implied warranties, including, but not limited to, the .\" implied warranties of merchantability and fitness for a particular purpose .\" are disclaimed. in no event shall the regents or contributors be liable .\" for any direct, indirect, incidental, special, exemplary, or consequential .\" damages (including, but not limited to, procurement of substitute goods .\" or services; loss of use, data, or profits; or business interruption) .\" however caused and on any theory of liability, whether in contract, strict .\" liability, or tort (including negligence or otherwise) arising in any way .\" out of the use of this software, even if advised of the possibility of .\" such damage. .\" %%%license_end .\" .\" @(#)setregid.2 6.4 (berkeley) 3/10/91 .\" .\" modified sat jul 24 09:08:49 1993 by rik faith .\" portions extracted from linux/kernel/sys.c: .\" copyright (c) 1991, 1992 linus torvalds .\" may be distributed under the gnu general public license .\" changes: 1994-07-29 by wilf .\" 1994-08-02 by wilf due to change in kernel. .\" 2004-07-04 by aeb .\" 2004-05-27 by michael kerrisk .\" .th setreuid 2 2021-03-22 "linux" "linux programmer's manual" .sh name setreuid, setregid \- set real and/or effective user or group id .sh synopsis .nf .b #include .pp .bi "int setreuid(uid_t " ruid ", uid_t " euid ); .bi "int setregid(gid_t " rgid ", gid_t " egid ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br setreuid (), .br setregid (): .nf _xopen_source >= 500 .\" || _xopen_source && _xopen_source_extended || /* since glibc 2.19: */ _default_source || /* glibc <= 2.19: */ _bsd_source .fi .sh description .br setreuid () sets real and effective user ids of the calling process. .pp supplying a value of \-1 for either the real or effective user id forces the system to leave that id unchanged. .pp unprivileged processes may only set the effective user id to the real user id, the effective user id, or the saved set-user-id. .pp unprivileged users may only set the real user id to the real user id or the effective user id. .pp if the real user id is set (i.e., .i ruid is not \-1) or the effective user id is set to a value not equal to the previous real user id, the saved set-user-id will be set to the new effective user id. .pp completely analogously, .br setregid () sets real and effective group id's of the calling process, and all of the above holds with "group" instead of "user". .sh return value on success, zero is returned. on error, \-1 is returned, and .i errno is set to indicate the error. .pp .ir note : there are cases where .br setreuid () can fail even when the caller is uid 0; it is a grave security error to omit checking for a failure return from .br setreuid (). .sh errors .tp .b eagain the call would change the caller's real uid (i.e., .i ruid does not match the caller's real uid), but there was a temporary failure allocating the necessary kernel data structures. .tp .b eagain .i ruid does not match the caller's real uid and this call would bring the number of processes belonging to the real user id .i ruid over the caller's .b rlimit_nproc resource limit. since linux 3.1, this error case no longer occurs (but robust applications should check for this error); see the description of .b eagain in .br execve (2). .tp .b einval one or more of the target user or group ids is not valid in this user namespace. .tp .b eperm the calling process is not privileged (on linux, does not have the necessary capability in its user namespace: .b cap_setuid in the case of .br setreuid (), or .b cap_setgid in the case of .br setregid ()) and a change other than (i) swapping the effective user (group) id with the real user (group) id, or (ii) setting one to the value of the other or (iii) setting the effective user (group) id to the value of the saved set-user-id (saved set-group-id) was specified. .sh conforming to posix.1-2001, posix.1-2008, 4.3bsd .rb ( setreuid () and .br setregid () first appeared in 4.2bsd). .sh notes setting the effective user (group) id to the saved set-user-id (saved set-group-id) is possible since linux 1.1.37 (1.1.38). .pp posix.1 does not specify all of the uid changes that linux permits for an unprivileged process. for .br setreuid (), the effective user id can be made the same as the real user id or the saved set-user-id, and it is unspecified whether unprivileged processes may set the real user id to the real user id, the effective user id, or the saved set-user-id. for .br setregid (), the real group id can be changed to the value of the saved set-group-id, and the effective group id can be changed to the value of the real group id or the saved set-group-id. the precise details of what id changes are permitted vary across implementations. .pp posix.1 makes no specification about the effect of these calls on the saved set-user-id and saved set-group-id. .pp the original linux .br setreuid () and .br setregid () system calls supported only 16-bit user and group ids. subsequently, linux 2.4 added .br setreuid32 () and .br setregid32 (), supporting 32-bit ids. the glibc .br setreuid () and .br setregid () wrapper functions transparently deal with the variations across kernel versions. .\" .ss c library/kernel differences at the kernel level, user ids and group ids are a per-thread attribute. however, posix requires that all threads in a process share the same credentials. the nptl threading implementation handles the posix requirements by providing wrapper functions for the various system calls that change process uids and gids. these wrapper functions (including those for .br setreuid () and .br setregid ()) employ a signal-based technique to ensure that when one thread changes credentials, all of the other threads in the process also change their credentials. for details, see .br nptl (7). .sh see also .br getgid (2), .br getuid (2), .br seteuid (2), .br setgid (2), .br setresuid (2), .br setuid (2), .br capabilities (7), .br credentials (7), .br user_namespaces (7) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/. .so man3/mkstemp.3 .\" copyright (c) 2002 andries brouwer .\" .\" %%%license_start(verbatim) .\" permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" since the linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. the author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. the author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%license_end .\" .\" this replaces an earlier man page written by walter harms .\" . .th gsignal 3 2021-03-22 "" "linux programmer's manual" .sh name gsignal, ssignal \- software signal facility .sh synopsis .nf .b #include .pp .b typedef void (*sighandler_t)(int); .pp .bi "int gsignal(int " signum ); .pp .bi "sighandler_t ssignal(int " signum ", sighandler_t " action ); .fi .pp .rs -4 feature test macro requirements for glibc (see .br feature_test_macros (7)): .re .pp .br gsignal (), .br ssignal (): .nf since glibc 2.19: _default_source glibc 2.19 and earlier: _svid_source .fi .sh description don't use these functions under linux. due to a historical mistake, under linux these functions are aliases for .br raise (3) and .br signal (2), respectively. .pp elsewhere, on system v-like systems, these functions implement software signaling, entirely independent of the classical .br signal (2) and .br kill (2) functions. the function .br ssignal () defines the action to take when the software signal with number .i signum is raised using the function .br gsignal (), and returns the previous such action or .br sig_dfl . the function .br gsignal () does the following: if no action (or the action .br sig_dfl ) was specified for .ir signum , then it does nothing and returns 0. if the action .b sig_ign was specified for .ir signum , then it does nothing and returns 1. otherwise, it resets the action to .b sig_dfl and calls the action function with argument .ir signum , and returns the value returned by that function. the range of possible values .i signum varies (often 1\(en15 or 1\(en17). .sh attributes for an explanation of the terms used in this section, see .br attributes (7). .ad l .nh .ts allbox; lbx lb lb l l l. interface attribute value t{ .br gsignal () t} thread safety mt-safe t{ .br ssignal () t} thread safety mt-safe sigintr .te .hy .ad .sp 1 .sh conforming to these functions are available under aix, dg/ux, hp-ux, sco, solaris, tru64. they are called obsolete under most of these systems, and are broken under .\" linux libc and glibc. some systems also have .br gsignal_r () and .br ssignal_r (). .sh see also .br kill (2), .br signal (2), .br raise (3) .sh colophon this page is part of release 5.13 of the linux .i man-pages project. a description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.